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11,755,005 | https://en.wikipedia.org/wiki/Ovulitis%20azaleae | Ovulitis azaleae is a plant pathogen affecting azaleas and rhododendrons.
See also
List of azalea diseases
List of rhododendron diseases
References
External links
Index Fungorum
USDA ARS Fungal Database
Fungal plant pathogens and diseases
Ornamental plant pathogens and diseases
Sclerotiniaceae
Fungus species | Ovulitis azaleae | [
"Biology"
] | 72 | [
"Fungi",
"Fungus species"
] |
11,755,082 | https://en.wikipedia.org/wiki/Pestalotia%20rhododendri | Pestalotia rhododendri is a fungal plant pathogen infecting azaleas and rhododendrons.
Important diseases: Pestalotiopsis tip blight of conifers, Gray leaf spot
Pestalotia is primarily a secondary pathogen. It is saprophytic on dead and dying tissues and is weakly parasitic infecting wounds under moist conditions.
Tips of conifer branches particularly Leyland cypress, arborvitae and juniper turn brown to grayish in color. Infected bark may be covered in fungal fruiting structures giving the tissue a black sooty appearance. Leaf spots tend to be tan to gray and are often the result of previous damage such as freeze injury, scorching or mechanical wounds.
Dark, disc or cushion-shaped acervuli are formed under the plant epidermis which then splits open revealing the fruiting structures. Conidia are produced on short simple conidiophores within the acervulus.
Conidia are multi-celled with usually three darkly pigmented center cells and clear pointed end cells. Conidia are ellipsoid or fusoid (football-shaped). A diagnostic feature is the two or more clear, whisker-like appendages arising from the end cell
References
External links
USDA ARS Fungal Database
Fungal plant pathogens and diseases
Ornamental plant pathogens and diseases
Xylariales
Fungus species | Pestalotia rhododendri | [
"Biology"
] | 285 | [
"Fungi",
"Fungus species"
] |
11,755,283 | https://en.wikipedia.org/wiki/Airflow%20Sciences%20Corporation | Airflow Sciences Corporation (ASC) is an engineering consulting company based in Livonia, Michigan, USA that specializes in the design and optimization of equipment and processes involving flow, heat transfer, combustion, and mass transfer. Engineering techniques include Computational Fluid Dynamics (CFD) modeling, experimental laboratory testing, and field measurements at client sites. ASC works for a wide range of industries world-wide, including power generation, manufacturing, aerospace, HVAC, food processing, biomedical, pollution control, oil and gas, rail, legal, and automotive.
In addition to engineering consulting, ASC has a test equipment division that manufactures flow measurement equipment such as data loggers, pressure/flow/temperature instrumentation, wind tunnels, and online flow systems.
ASC is the parent company of Azore Software, LLC, which develops and sells the commercial simulation software AzoreCFD. This advanced polyhedral-based CFD software use widely used for flow and heat transfer analysis and design.
History
The company was founded in 1975 by Robert Gielow and James Paul, two Professional Engineers with backgrounds in the aerospace industry. They quickly realized that the analysis techniques they applied to projects such as the Apollo program Moon rockets and commercial aircraft design could be used to advance a wide variety of other industries. Early years of the company were focused on aerodynamic optimization of vehicles such as cars, tractor trailers, and rail cars to minimize drag and fuel consumption. This work involved both wind tunnel testing and numerical simulation.
In the 1970s and 1980s, ASC developed a range of simulation software for potential flow and viscous flow analysis, writing its own CFD solver (VISCOUS). The capabilities of this cartesian-based CFD software eventually included advanced physics such as combustion, particulate transport and drying simulations, time-dependence, and convection/conduction/radiation heat transfer. In the 1990s and early 2000s, ASC personnel developed a new CFD software package, AzoreCFD, featuring a modern, polyhedral based solver in order to analyze highly complex geometries and physics. Azore development continues with new features and simulations capabilities incorporated to allow more unique flow problems to be analyzed.
In addition to simulation of flow and heat transfer, ASC has advanced its field testing capabilities on a regular basis over the years. Many of the tests ASC is requested to perform are new or unique, requiring development and fabrication of custom flow measurement equipment. Today's testing capabilities include velocity, temperature, pressure, particulate sampling, gas species and emissions, and more.
Problems solved by ASC
ASC works with its customer's to solve problems involving the flow of fluids (gases or liquids) in or around a wide variety of equipment or goods. Some problems include simply the flow itself. These include such things as reducing pressure drop, eliminating flow induced vibrations, or ensuring uniform flow through an equipment that processes elements of the flow. Since fluid flow carries energy, heat transfer problems such as improving thermal mixing or heating/cooling characteristics are often solved. Similarly, ASC undertakes many problems involving the pneumatic transport of particulate and droplets. The chemical reactions in a flowing gas or liquid are also the subject of ASC studies. Methods used to solve these problems include: Numerical simulation (including Computational fluid dynamics), Wind tunnel testing, Laboratory modeling (including Scale models), and Flow measurement/Field testing.
Customer base
ASC customers include manufacturing and processing firms from a wide variety of industries, including:
Electricity / power generation
Renewable energy
Food processing
Manufacturing
Metals processing / heat treating
Heating, Ventilation, and Air Conditioning (HVAC) of buildings
Cement and mineral production and mining
Pulp and paper
Sporting equipment Aerodynamics
Steel producers
Automotive industry and auto racing companies
Class I railroads and railcar manufacturers
Biotechnology firms
ASC has performed over 4000 engineering studies worldwide since 1975.
External links
Airflow Sciences Corporation web site
Airflow Sciences Equipment Division web site
Azore CFD Software web site
ASC YouTube page
Airflow Sciences Equipment YouTube page
Azore YouTube page
ASC LinkedIn
Fluid dynamics
Companies based in Wayne County, Michigan
Engineering companies of the United States
Technology companies established in 1975 | Airflow Sciences Corporation | [
"Chemistry",
"Engineering"
] | 833 | [
"Piping",
"Chemical engineering",
"Fluid dynamics"
] |
11,755,914 | https://en.wikipedia.org/wiki/Polish%20Aero%20Club | The Polish Aero Club (Aeroklub Polski, AP) is the Polish central association of persons practising air sports or recreational flying. It was founded in 1921 and is a member of the Fédération Aéronautique Internationale. It has a headquarters in Warsaw.
History
Aviation organizations could be founded in Poland only after regaining independence in 1918. The first such organization was Aeroklub Polski w Poznaniu (PAC in Poznań), founded on 30 October 1919 and admitted to the FAI in 1920. In June 1920 there was founded Aeroklub Polski w Warszawie (PAC in Warsaw). On 18 January 1921 both Aero Clubs formed a central federation Aeroklub Rzeczypospolitej Polskiej (ARP; Aero Club of the Polish Republic). By 1939, there were created several other regional aero clubs, including some university aero clubs.
Before the World War II, members of the ARP took active part in world's aviation sports. The first major international event was the Challenge 1930 touring planes contest. The Poles enjoyed success in the Challenge 1932 and several Gordon Bennett Cup in ballooning contests. The ARP organized the Challenge 1934 international contest and the Gordon Bennett Cup in ballooning in 1934–1936, also successful for the Polish pilots.
Just after the World War II, in 1945 the association was renewed and more regional aero clubs were created. In 1957–1990 it was named Aeroklub Polskiej Rzeczpospolitej Ludowej (APRL; Aero Club of the Polish People's Republic). At the time of communist Poland, the membership in aero club was practically the only chance for private persons to fly. The ARP/APRL was supported by the government and supplied with trainer and auxiliary aircraft withdrawn from the Polish Air Force, distributed to regional aero clubs.
Present
In 1990, after a fall of communism, the organization was renamed to its current name Aeroklub Polski, referring to the first historical organization of that type.
Aeroklub Polski is the national governing and coordinating body of air sport and recreational flying. Organizational units of the Aeroklub Polski are regional aero clubs; members of regional aero clubs are also members of AP. Currently there are 58 regional aero clubs in Poland (as of 2007).
Goals of AP are, among others: a propagation and development of the aviation in Poland, an organization of air sports and air recreation, a representation of Polish air sports abroad, a training of aviators. It is also a sports association.
See also
Włocławek Aero Club (1959), regional branch of The Polish Aero Club
References
Historia AP on Aeroklub Polski official site (in Polish) [retrieved 2-3-2015]
External links
Official site
Flying clubs
Sports clubs and teams in Poland
Aviation in Poland
Fédération Aéronautique Internationale | Polish Aero Club | [
"Engineering"
] | 579 | [
"Fédération Aéronautique Internationale",
"Aeronautics organizations"
] |
11,756,393 | https://en.wikipedia.org/wiki/Stearamidopropyl%20dimethylamine | Stearamidopropyl dimethylamine is an ingredient in some types of hair conditioner. It has antistatic, emulsifying, hair conditioning, and surfactant properties. It is water soluble, readily biodegradable, and mildly toxic to aquatic life.
References
External links
Fatty acid amides
Cosmetics chemicals
Dimethylamino compounds | Stearamidopropyl dimethylamine | [
"Chemistry"
] | 74 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
11,756,462 | https://en.wikipedia.org/wiki/Hybrid%20cryptosystem | In cryptography, a hybrid cryptosystem is one which combines the convenience of a public-key cryptosystem with the efficiency of a symmetric-key cryptosystem. Public-key cryptosystems are convenient in that they do not require the sender and receiver to share a common secret in order to communicate securely. However, they often rely on complicated mathematical computations and are thus generally much more inefficient than comparable symmetric-key cryptosystems. In many applications, the high cost of encrypting long messages in a public-key cryptosystem can be prohibitive. This is addressed by hybrid systems by using a combination of both.
A hybrid cryptosystem can be constructed using any two separate cryptosystems:
a key encapsulation mechanism, which is a public-key cryptosystem
a data encapsulation scheme, which is a symmetric-key cryptosystem
The hybrid cryptosystem is itself a public-key system, whose public and private keys are the same as in the key encapsulation scheme.
Note that for very long messages the bulk of the work in encryption/decryption is done by the more efficient symmetric-key scheme, while the inefficient public-key scheme is used only to encrypt/decrypt a short key value.
All practical implementations of public key cryptography today employ the use of a hybrid system. Examples include the TLS protocol and the SSH protocol, that use a public-key mechanism for key exchange (such as Diffie-Hellman) and a symmetric-key mechanism for data encapsulation (such as AES). The OpenPGP file format and the PKCS#7 file format are other examples.
Hybrid Public Key Encryption (HPKE, published as RFC 9180) is a modern standard for generic hybrid encryption. HPKE is used within multiple IETF protocols, including MLS and TLS Encrypted Hello.
Envelope encryption is an example of a usage of hybrid cryptosystems in cloud computing. In a cloud context, hybrid cryptosystems also enable centralized key management.
Example
To encrypt a message addressed to Alice in a hybrid cryptosystem, Bob does the following:
Obtains Alice's public key.
Generates a fresh symmetric key for the data encapsulation scheme.
Encrypts the message under the data encapsulation scheme, using the symmetric key just generated.
Encrypts the symmetric key under the key encapsulation scheme, using Alice's public key.
Sends both of these ciphertexts to Alice.
To decrypt this hybrid ciphertext, Alice does the following:
Uses her private key to decrypt the symmetric key contained in the key encapsulation segment.
Uses this symmetric key to decrypt the message contained in the data encapsulation segment.
Security
If both the key encapsulation and data encapsulation schemes in a hybrid cryptosystem are secure against adaptive chosen ciphertext attacks, then the hybrid scheme inherits that property as well. However, it is possible to construct a hybrid scheme secure against adaptive chosen ciphertext attacks even if the key encapsulation has a slightly weakened security definition (though the security of the data encapsulation must be slightly stronger).
Envelope encryption
Envelope encryption is term used for encrypting with a hybrid cryptosystem used by all major cloud service providers, often as part of a centralized key management system in cloud computing.
Envelope encryption gives names to the keys used in hybrid encryption: Data Encryption Keys (abbreviated DEK, and used to encrypt data) and Key Encryption Keys (abbreviated KEK, and used to encrypt the DEKs). In a cloud environment, encryption with envelope encryption involves generating a DEK locally, encrypting one's data using the DEK, and then issuing a request to wrap (encrypt) the DEK with a KEK stored in a potentially more secure service. Then, this wrapped DEK and encrypted message constitute a ciphertext for the scheme. To decrypt a ciphertext, the wrapped DEK is unwrapped (decrypted) via a call to a service, and then the unwrapped DEK is used to decrypt the encrypted message. In addition to the normal advantages of a hybrid cryptosystem, using asymmetric encryption for the KEK in a cloud context provides easier key management and separation of roles, but can be slower.
In cloud systems, such as Google Cloud Platform and Amazon Web Services, a key management system (KMS) can be available as a service. In some cases, the key management system will store keys in hardware security modules, which are hardware systems that protect keys with hardware features like intrusion resistance. This means that KEKs can also be more secure because they are stored on secure specialized hardware. Envelope encryption makes centralized key management easier because a centralized key management system only needs to store KEKs, which occupy less space, and requests to the KMS only involve sending wrapped and unwrapped DEKs, which use less bandwidth than transmitting entire messages. Since one KEK can be used to encrypt many DEKs, this also allows for less storage space to be used in the KMS. This also allows for centralized auditing and access control at one point of access.
See also
Transport Layer Security
Secure Shell
Key Encapsulation Mechanism
References
Cryptography | Hybrid cryptosystem | [
"Mathematics",
"Engineering"
] | 1,154 | [
"Applied mathematics",
"Cryptography",
"Cybersecurity engineering"
] |
11,757,070 | https://en.wikipedia.org/wiki/Phomopsis%20elaeagni | Phomopsis elaeagni is a fungal plant pathogen infecting black walnuts.
References
External links
USDA ARS Fungal Database
Fungal tree pathogens and diseases
Walnut tree diseases
elaeagni
Fungus species | Phomopsis elaeagni | [
"Biology"
] | 42 | [
"Fungi",
"Fungus species"
] |
11,757,250 | https://en.wikipedia.org/wiki/CH2N2 | {{DISPLAYTITLE:CH2N2}}
CH2N2 may refer to:
Cyanamide, an organic compound
Diazirine, class of organic molecules with a cyclopropene-like ring, 3H-diazirene
Diazomethane, chemical compound discovered in 1894
Isodiazomethane, parent compound of a class of derivatives of general formula R2N–NC
Nitrilimine, class of organic compounds sharing a common functional group with the general structure R-CN-NR | CH2N2 | [
"Chemistry"
] | 108 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
11,757,262 | https://en.wikipedia.org/wiki/Ascospora%20ruborum | Ascospora ruborum is a species of anamorphic ascomycete fungus. It is a plant pathogen that causes cane spot and dieback of raspberry and dewberry.
References
Fungi described in 1894
Fungal plant pathogens and diseases
Small fruit diseases
Enigmatic Ascomycota taxa
Fungus species | Ascospora ruborum | [
"Biology"
] | 64 | [
"Fungi",
"Fungus species"
] |
11,757,346 | https://en.wikipedia.org/wiki/CH3NO | {{DISPLAYTITLE:CH3NO}}
The molecular formula CH3NO (molar mass: 45.04 g/mol, exact mass: 45.0215 u) may refer to:
Formaldoxime
Formamide, or methanamide
Oxaziridine | CH3NO | [
"Chemistry"
] | 61 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
11,757,349 | https://en.wikipedia.org/wiki/Mycosphaerella%20rubi | Mycosphaerella rubi is a fungal plant pathogen.
See also
List of Mycosphaerella species
References
Fungal plant pathogens and diseases
rubi
Fungi described in 1921
Fungus species | Mycosphaerella rubi | [
"Biology"
] | 40 | [
"Fungi",
"Fungus species"
] |
11,757,364 | https://en.wikipedia.org/wiki/CH4N2O | {{DISPLAYTITLE:CH4N2O}}
The molecular formula CH4N2O (molar mass: 60.06 g/mol, exact mass: 60.03236 u) may refer to:
Urea, or carbamide
Ammonium cyanate
Formylhydrazine | CH4N2O | [
"Chemistry"
] | 67 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
11,757,365 | https://en.wikipedia.org/wiki/CH4N2S | {{DISPLAYTITLE:CH4N2S}}
The molecular formula CH4N2S (molar mass: 76.12 g/mol, exact mass: 76.0095 u) may refer to:
Ammonium thiocyanate
Thiourea | CH4N2S | [
"Chemistry"
] | 61 | [
"Isomerism",
"Set index articles on molecular formulas"
] |
11,757,410 | https://en.wikipedia.org/wiki/Phragmidium%20rubi-idaei | Phragmidium rubi-idaei is a plant pathogen infecting caneberries, Rubus spp.
References
Fungal plant pathogens and diseases
Small fruit diseases
Pucciniales
Taxa named by Augustin Pyramus de Candolle
Fungi described in 1815
Fungus species | Phragmidium rubi-idaei | [
"Biology"
] | 57 | [
"Fungi",
"Fungus species"
] |
11,757,516 | https://en.wikipedia.org/wiki/Alternaria%20dianthi | Alternaria dianthi, sometimes known as carnation blight, is a fungal pathogen of the genus Dianthus. Alternaria dianthi infections begin as small circular or ovular spots on leaves and stems, which can be red, purple, brown, yellow or gray.
This pathogen has been found in carnation and other Dianthus cultures worldwide, including in India, the United States, New Zealand, the Canary Islands, and Egypt. Fourteen gene sequences of Alternaria dianthi have been published as of April 11, 2014
Symptoms
Alternaria dianthi can infect healthy plants, and favors humid, warm environments. The multicolored circular spots can grow to infect entire plants, resulting in wilting or death. These spots tend to be smaller than one centimeter, but can be larger, especially around stems. The cankers formed by A. dianthi spread through the stomata of leaf cells, and generally lead to yellowing, wilting, and death of the leaves of infected plants.
Life cycle
Alternaria dianthi reproduces asexually, forming row-like spores off of hyphae. Spores are formed on blisters on the host as well as within the mycelium. The thin, globular spores are spread through water. Spore production and infection decreases over winter, and has been observed to be highest in rainy summer months.
The spores of A. dianthi germinate optimally around 24 °C (75 °F), and cannot germinate below 4 °C (40 °F) or above 32 °C (90 °F). The fungus has been cultured on simple media such as potato dextrose agar, and does not need Dianthus tissue to germinate. Spores come into contact with healthy leaf and stem tissue of Dianthus plants through wind, rain, and contact with infected tissue. The host plant must be wet or moist for spores to germinate. Moderate to high humidity is also a requirement, and one study found that spores would not germinate under 55% humidity. The life cycle takes about four days from germination to the production of new conidia.
Spores produced by Alternaria species are black, and can persist on dead tissue, in soil, and on hard surfaces such as those found in greenhouses.
No observations of pathogens of Alternaria dianthi have been published.
Impact
Alternaria dianthi was first recorded in the scientific literature by F.L. Stevens and J.G. Hall in 1909, from florists in the United States. The fungus, along with other members of the genus Alternaria, is effectively controlled by the commercial fungicide mancozeb, as well as dithiocarbamates, chlorothalonil, and iprodione. Although A. dianthi has been found in wild and commercial varieties of Dianthus plants worldwide, no studies of the economic impacts or losses due to the disease have been published.
References
External links
USDA ARS Fungal Database
dianthi
Fungal plant pathogens and diseases
Fungi described in 1909
Fungi of New Zealand
Fungus species | Alternaria dianthi | [
"Biology"
] | 649 | [
"Fungi",
"Fungus species"
] |
11,757,559 | https://en.wikipedia.org/wiki/Alternaria%20saponariae | Alternaria saponariae is a fungal plant pathogen.
References
saponariae
Fungal plant pathogens and diseases
Fungi described in 1938
Fungus species | Alternaria saponariae | [
"Biology"
] | 32 | [
"Fungi",
"Fungus species"
] |
11,757,586 | https://en.wikipedia.org/wiki/Davidiella%20dianthi | Davidiella dianthi is a fungal plant pathogen infecting carnations.
References
External links
Index Fungorum
USDA ARS Fungal Database
Fungal plant pathogens and diseases
Ornamental plant pathogens and diseases
Davidiellaceae
Fungi described in 2003
Fungus species | Davidiella dianthi | [
"Biology"
] | 54 | [
"Fungi",
"Fungus species"
] |
11,757,634 | https://en.wikipedia.org/wiki/Sclerotinia%20minor | Sclerotinia minor (white mold) is a plant pathogen infecting Chicory, Radicchio, carrots, tomatoes, sunflowers, peanuts and lettuce.
References
External links
Index Fungorum
USDA ARS Fungal Database
Fungal plant pathogens and diseases
Carrot diseases
Tomato diseases
Lettuce diseases
Sclerotiniaceae
Fungi described in 1920
Fungus species | Sclerotinia minor | [
"Biology"
] | 77 | [
"Fungi",
"Fungus species"
] |
11,757,851 | https://en.wikipedia.org/wiki/Podosphaera%20fusca | Podosphaera fusca is a fungus that parasitically infects plants (a phytopathogen). It is one cause of powdery mildew in melons and gourds.
Some sources suggest that P. fusca should be considered synonymous with P. xanthii, while others maintain they are separate species in the subsection Magnicellulata of the section Sphaerotheca of the genus Podosphaera, , based on the size of chasmothecia, and on the thin-walled portion of the asci (oculus).
References
Fungal fruit diseases
Fungal plant pathogens and diseases
fusca
Vegetable diseases
Fungi described in 1829
Taxa named by Elias Magnus Fries
Fungus species | Podosphaera fusca | [
"Biology"
] | 148 | [
"Fungi",
"Fungus species"
] |
11,757,994 | https://en.wikipedia.org/wiki/Yamabe%20problem | The Yamabe problem refers to a conjecture in the mathematical field of differential geometry, which was resolved in the 1980s. It is a statement about the scalar curvature of Riemannian manifolds:
By computing a formula for how the scalar curvature of relates to that of , this statement can be rephrased in the following form:
The mathematician Hidehiko Yamabe, in the paper , gave the above statements as theorems and provided a proof; however, discovered an error in his proof. The problem of understanding whether the above statements are true or false became known as the Yamabe problem. The combined work of Yamabe, Trudinger, Thierry Aubin, and Richard Schoen provided an affirmative resolution to the problem in 1984.
It is now regarded as a classic problem in geometric analysis, with the proof requiring new methods in the fields of differential geometry and partial differential equations. A decisive point in Schoen's ultimate resolution of the problem was an application of the positive energy theorem of general relativity, which is a purely differential-geometric mathematical theorem first proved (in a provisional setting) in 1979 by Schoen and Shing-Tung Yau.
There has been more recent work due to Simon Brendle, Marcus Khuri, Fernando Codá Marques, and Schoen, dealing with the collection of all positive and smooth functions such that, for a given Riemannian manifold , the metric has constant scalar curvature. Additionally, the Yamabe problem as posed in similar settings, such as for complete noncompact Riemannian manifolds, is not yet fully understood.
The Yamabe problem in special cases
Here, we refer to a "solution of the Yamabe problem" on a Riemannian manifold as a Riemannian metric on for which there is a positive smooth function with
On a closed Einstein manifold
Let be a smooth Riemannian manifold. Consider a positive smooth function so that is an arbitrary element of the smooth conformal class of A standard computation shows
Taking the -inner product with results in
If is assumed to be Einstein, then the left-hand side vanishes. If is assumed to be closed, then one can do an integration by parts, recalling the Bianchi identity to see
If has constant scalar curvature, then the right-hand side vanishes. The consequent vanishing of the left-hand side proves the following fact, due to Obata (1971):
Obata then went on to prove that, except in the case of the standard sphere with its usual constant-sectional-curvature metric, the only constant-scalar-curvature metrics in the conformal class of an Einstein metric (on a closed manifold) are constant multiples of the given metric. The proof proceeds by showing that the gradient of the conformal factor is actually a conformal Killing field. If the conformal factor is not constant, following flow lines of this gradient field, starting at a minimum of the conformal factor, then allows one to show that the manifold is conformally related to the cylinder , and hence has vanishing Weyl curvature.
The non-compact case
A closely related question is the so-called "non-compact Yamabe problem", which asks: Is it true that on every smooth complete Riemannian manifold which is not compact, there exists a metric that is conformal to g, has constant scalar curvature and is also complete? The answer is no, due to counterexamples given by . Various additional criteria under which a solution to the Yamabe problem for a non-compact manifold can be shown to exist are known (for example ); however, obtaining a full understanding of when the problem can be solved in the non-compact case remains a topic of research.
See also
Yamabe flow
Yamabe invariant
References
Research articles
.
Textbooks
Aubin, Thierry. Some nonlinear problems in Riemannian geometry. Springer Monographs in Mathematics. Springer-Verlag, Berlin, 1998. xviii+395 pp.
Schoen, R.; Yau, S.-T. Lectures on differential geometry. Lecture notes prepared by Wei Yue Ding, Kung Ching Chang [Gong Qing Zhang], Jia Qing Zhong and Yi Chao Xu. Translated from the Chinese by Ding and S. Y. Cheng. With a preface translated from the Chinese by Kaising Tso. Conference Proceedings and Lecture Notes in Geometry and Topology, I. International Press, Cambridge, MA, 1994. v+235 pp.
Struwe, Michael. Variational methods. Applications to nonlinear partial differential equations and Hamiltonian systems. Fourth edition. Ergebnisse der Mathematik und ihrer Grenzgebiete. 3. Folge. A Series of Modern Surveys in Mathematics [Results in Mathematics and Related Areas. 3rd Series. A Series of Modern Surveys in Mathematics], 34. Springer-Verlag, Berlin, 2008. xx+302 pp.
Riemannian geometry
Mathematical problems | Yamabe problem | [
"Mathematics"
] | 1,013 | [
"Mathematical problems"
] |
9,266,475 | https://en.wikipedia.org/wiki/Architectural%20determinism | Architectural determinism (also sometimes referred to as environmental determinism though that term has a broader meaning) is a theory employed in urbanism, sociology and environmental psychology which claims the built environment is the chief or even sole determinant of social behaviour. A. S. Baum defines the notion thus "In its most extreme form, this position argues that the environment causes certain behaviours, denying any interaction between environment and behaviour. Architectural determinism poses the idea that people can adapt to any arrangement of space and that behaviour in a given environment is caused entirely by the characteristics of the environment."
The origins of the concept may be traced in Jeremy Bentham's Panopticon and in the Enlightenment bienfaisance as expressed in the institutional reform of prisons and hospitals. However the notion only gained generally currency and universal applicability with the rise of behaviourism, functionalism and the utopian social programme of the Modernist architectural movement. The term was first coined by Maurice Broady in his 1966 paper Social theory in Architectural Design which also roundly criticised the authoritarian nature of this belief. Few architects have espoused the view that design can control behaviour but it has long been an assumption amongst urbanists and architects that architecture can limit and channel behaviour in a predictable manner. This weaker, positivist view was articulated by Adolf Behne when he asserted "you can kill a man with a building just as easily as with an axe." The determinist belief was a contributory factor in the numerous slum clearances of the post-War industrialised world (see Herbert J. Gans). Despite being a widely held, if not always articulated, theory the premise was not sustained by social research, for example the "Hawthorne experiments" by Mayo at Harvard found no direct correlation between work environment and output. The determinist hypothesis as an explanation of social conduct is now most often referred to in the literature as discredited, yet is still to be found as an argument for urban renewal.
See also
Identity safety cues
Proxemics
Social condenser
References
Paul-Alan Johnson, The Theory of Architecture: Concepts, Themes, and Practices, 1994.
Architectural theory
Determinism
Environmental psychology | Architectural determinism | [
"Engineering",
"Environmental_science"
] | 449 | [
"Environmental psychology",
"Environmental social science",
"Architectural theory",
"Architecture"
] |
9,266,554 | https://en.wikipedia.org/wiki/Volume%20testing | Volume testing belongs to the group of non-functional tests, which are a group of tests often misunderstood and/or used interchangeably. Volume testing refers to testing a software application with a certain amount of data to assert the system performance with a certain amount of data in the database. Volume testing is regarded by some as a type of capacity testing, and is often deemed necessary as other types of tests normally don't use large amounts of data, but rather typically use small amounts of data. It is the only type of test which checks the ability of a system to handle large pools of data. For example, the test can be used to stress the database to its maximum limit. While the amount can, in generic terms, be the database size, it could also be the size of an interface file that is the subject of volume testing. For example, if one wants to volume test an application with a specific database size, the database will be expanded to that size and the application's performance will then be tested on it. Another example could be when there is a requirement for the application to interact with an interface file (could be any file such as .dat, .xml); this interaction could be reading and/or writing on to/from the file. A sample file of an intended size can then be created and used to test the application's functionality in order to test the performance.
References
Software testing | Volume testing | [
"Engineering"
] | 286 | [
"Software engineering",
"Software testing"
] |
9,266,740 | https://en.wikipedia.org/wiki/Non-functional%20testing | Non-functional testing is testing software for its non-functional requirements: the way a system operates, rather than specific behaviors of that system. This is in contrast to functional testing, which tests against functional requirements that describe the functions of a system and its components.
Non-functional testing includes:
Accessibility testing
Baseline testing
Compliance testing
Documentation testing
Endurance testing or reliability testing
Load testing
Localization testing and Internationalization testing
Performance testing
Recovery testing
Resilience testing
Security testing
Scalability testing
Stress testing
Usability testing
Volume testing
References
Software testing | Non-functional testing | [
"Engineering"
] | 105 | [
"Software engineering",
"Software testing"
] |
9,266,795 | https://en.wikipedia.org/wiki/Scalability%20testing | Scalability testing is the testing of a software application to measure its capability to scale up or scale out in terms of any of its non-functional capability.
Performance, scalability and reliability testing are usually grouped together by software quality analysts.
The main goals of scalability testing are to determine the user limit for the web application and ensure end user experience, under a high load, is not compromised. One example is if a web page can be accessed in a timely fashion with a limited delay in response. Another goal is to check if the server can cope i.e. Will the server crash if it is under a heavy load?
Dependent on the application that is being tested, different parameters are tested. If a webpage is being tested, the highest possible number of simultaneous users would be tested. Also dependent on the application being tested is the attributes that are tested - these can include CPU usage, network usage or user experience.
Successful testing will project most of the issues which could be related to the network, database or hardware/software.
Creating a scalability test
When creating a new application, it is difficult to accurately predict the number of users in 1, 2 or even 5 years. Although an estimate can be made, it is not a definite number. An issue with an increasing number of users is that it can create new areas of failure. For example, if you have 100,000 new visitors, it's not just access to the application that could be a problem; you might also experience issues with the database where you need to store all the data of these new customers.
Increment loads
This is why when creating a scalability test, it is important to scale up in increments. These steps can be split into small, medium and high loads.
We must scale up in increments as each stage tests a different aspect. Small loads ensure the system functions as it should on a basic level. Medium loads test the system can function at its expected level. High loads test the system can cope with a high load.
Test environment
The environment should be constant throughout testing in order to provide accurate and reliable results. If the testing is a success, we should see a proportional change in performance. For example, if we double the users on the system, we should see a drop in performance of 50%.
Alternatively, if measuring system statistics such as memory or CPU usage over time, this may have a different graph that is not proportional as users are not being plotted on either axis.
Outcomes of scalability testing
Once data from all stages is collected, we can proceed to plot the results using various graphs tailored to the specific variables and metrics being analyzed. The type of graphs chosen will depend on the nature of the data and the objectives of the analysis.
Unproportional outcome
In Figure 1, we can see a graph showing a resources usage (in this case, memory) over time. The graph is not proportionate but can still be considered a passed test as initially there is a ramp up phase as the system begins to run, however, as more users are added, there is little change in memory usage. This means that the current memory capacity can cope with all 3 stages of the test.
Proportional outcome
In figure 2, we can see a more proportional increase, comparing the number of users to the time taken to execute a report. With a low load of 20 users, the average time is 5.5 seconds, as we increase the load to medium (40 users) and a high load (60 users), the average time increases to 9.5 and 18 seconds respectively.
In some cases, there may be changes that have to be made to the server software or hardware. Once the necessary upgrades have been made, we must re-run the tests to ensure the upgrades have been effective in addressing the issues previously raised.
When we have a proportional outcome, there are no bottlenecks as we scale up and increase the load the system is placed under.
Vertical and horizontal scaling
As a result of scalability testing, upgrades can be required to software and hardware. These upgrades can be split into vertical or horizontal scaling.
Vertical scaling, also known as scaling up, is the process of replacing a component with a device that is generally more powerful or improved. For example, replacing a processor with a faster one. Horizontal scaling, also known as scaling out is setting up another server for example to run in parallel with the original so they share the workload.
Advantages and disadvantages
There are advantages and disadvantages to both methods of scaling. Although scaling up may be simpler, the addition of hardware resources can result in diminishing returns. This means that every time we upgrade the processor for example, we do not always get the same level of benefits as the previous change.
However, horizontal scaling can be extremely expensive, not only the cost of entire systems such as servers, but we must also take into account their regular maintenance costs .
References
External links
Designing Distributed Applications with Visual Studio .NET: Scalability
Software testing | Scalability testing | [
"Engineering"
] | 1,011 | [
"Software engineering",
"Software testing"
] |
9,268,925 | https://en.wikipedia.org/wiki/Boundary%20scan%20description%20language | Boundary scan description language (BSDL) is a hardware description language for electronics testing using JTAG. It has been added to the IEEE Std. 1149.1, and BSDL files are increasingly well supported by JTAG tools for boundary scan applications, and by test case generators.
BSDL overview
BSDL was a subset of VHDL. However, since IEEE 1149.1-2013, it is no longer a "proper" subset of VHDL but it is considered based on VHDL. It is formally defined in IEEE Standard 1149.1 Annex B. Each BSDL file describes one version of an IC and has many package pin maps as are available for a particular die. This is necessary because, for example, two different BGA packages will have different balls; even if the ball has the same name it may be bonded to a different signal on the other package, and sometimes bondings change between revisions.
Each digital signal (pin or ball) on the package is defined, as are the registers and opcodes used in an IEEE 1149.1, IEEE 1149.6, IEEE 1149.8.1, IEEE 1532 and IEEE 1149.4 compliant IC. There is one instruction register, a minimum of a 1-bit bypass register, one boundary scan register and optionally a 32 bit device_id register. The registers other than the instruction register are called TDRs or Test Data Registers. The boundary scan register (BSR) is unique as it is the register which is also mapped to the I/O of the device. Many of the BSDL definitions are sets of single long string constants.
Note that registers not involved in boundary scan are often not defined. Instructions that are not publicly defined are included in the INSTRUCTION_PRIVATE section. Microprocessor register descriptions in BSDL typically do not include enough information to aid in building a 1149.1 based emulator or debugger.
References
External links
Free BSDL Compiler - Validates Grammar, Semantics and Syntax according to IEEE standard rules
Free public library of BSDL files for many devices
BSDL Tutorial
BSDL Files
BSDL & SVF file formats, functions and features
Electronics manufacturing
Hardware testing
Printed circuit board manufacturing | Boundary scan description language | [
"Engineering"
] | 454 | [
"Electrical engineering",
"Electronic engineering",
"Electronics manufacturing",
"Printed circuit board manufacturing"
] |
9,269,065 | https://en.wikipedia.org/wiki/Precision%20tests%20of%20QED | Quantum electrodynamics (QED), a relativistic quantum field theory of electrodynamics, is among the most stringently tested theories in physics. The most precise and specific tests of QED consist of measurements of the electromagnetic fine-structure constant, α, in various physical systems. Checking the consistency of such measurements tests the theory.
Tests of a theory are normally carried out by comparing experimental results to theoretical predictions. In QED, there is some subtlety in this comparison, because theoretical predictions require as input an extremely precise value of α, which can only be obtained from another precision QED experiment. Because of this, the comparisons between theory and experiment are usually quoted as independent determinations of α. QED is then confirmed to the extent that these measurements of α from different physical sources agree with each other.
The agreement found this way is to within ten parts in a billion (10−8), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements as described below. This makes QED one of the most accurate physical theories constructed thus far.
Besides these independent measurements of the fine-structure constant, many other predictions of QED have been tested as well.
Measurements of the fine-structure constant using different systems
Precision tests of QED have been performed in low-energy atomic physics experiments, high-energy collider experiments, and condensed matter systems. The value of α is obtained in each of these experiments by fitting an experimental measurement to a theoretical expression (including higher-order radiative corrections) that includes α as a parameter. The uncertainty in the extracted value of α includes both experimental and theoretical uncertainties. This program thus requires both high-precision measurements and high-precision theoretical calculations. Unless noted otherwise, all results below are taken from.
Low-energy measurements
Anomalous magnetic dipole moments
The most precise measurement of α comes from the anomalous magnetic dipole moment, or g−2 (pronounced "g minus 2"), of the electron. To make this measurement, two ingredients are needed:
A precise measurement of the anomalous magnetic dipole moment, and
A precise theoretical calculation of the anomalous magnetic dipole moment in terms of α.
As of February 2007, the best measurement of the anomalous magnetic dipole moment of the electron was made by the group of Gerald Gabrielse at Harvard University, using a single electron caught in a Penning trap. The difference between the electron's cyclotron frequency and its spin precession frequency in a magnetic field is proportional to g−2. An extremely high precision measurement of the quantized energies of the cyclotron orbits, or Landau levels, of the electron, compared to the quantized energies of the electron's two possible spin orientations, gives a value for the electron's spin g-factor:
g/2 = ,
a precision of better than one part in a trillion. (The digits in parentheses indicate the standard uncertainty in the last listed digits of the measurement.)
The current state-of-the-art theoretical calculation of the anomalous magnetic dipole moment of the electron includes QED diagrams with up to four loops. Combining this with the experimental measurement of g yields the most precise value of α:
α−1 = ,
a precision of better than a part in a billion. This uncertainty is ten times smaller than the nearest rival method involving atom-recoil measurements.
A value of α can also be extracted from the anomalous magnetic dipole moment of the muon. The g-factor of the muon is extracted using the same physical principle as for the electron above – namely, that the difference between the cyclotron frequency and the spin precession frequency in a magnetic field is proportional to g−2. The most precise measurement comes from Brookhaven National Laboratory's muon g−2 experiment, in which polarized muons are stored in a cyclotron and their spin orientation is measured by the direction of their decay electrons. As of February 2007, the current world average muon g-factor measurement is,
g/2 = ,
a precision of better than one part in a billion. The difference between the g-factors of the muon and the electron is due to their difference in mass. Because of the muon's larger mass, contributions to the theoretical calculation of its anomalous magnetic dipole moment from Standard Model weak interactions and from contributions involving hadrons are important at the current level of precision, whereas these effects are not important for the electron. The muon's anomalous magnetic dipole moment is also sensitive to contributions from new physics beyond the Standard Model, such as supersymmetry. For this reason, the muon's anomalous magnetic moment is normally used as a probe for new physics beyond the Standard Model rather than as a test of QED.
See muon g–2 for current efforts to refine the measurement.
Atom-recoil measurements
This is an indirect method of measuring α, based on measurements of the masses of the electron, certain atoms, and the Rydberg constant. The Rydberg constant is known to seven parts in a trillion. The mass of the electron relative to that of caesium and rubidium atoms is also known with extremely high precision. If the mass of the electron can be measured with sufficiently high precision, then α can be found from the Rydberg constant according to
To get the mass of the electron, this method actually measures the mass of an 87Rb atom by measuring the recoil speed of the atom after it emits a photon of known wavelength in an atomic transition. Combining this with the ratio of electron to 87Rb atom, the result for α is,
α−1 = .
Because this measurement is the next-most-precise after the measurement of α from the electron's anomalous magnetic dipole moment described above, their comparison provides the most stringent test of QED: the value of α obtained here is within one standard deviation of that found from the electron's anomalous magnetic dipole moment, an agreement to within ten parts in a billion.
Neutron Compton wavelength
This method of measuring α is very similar in principle to the atom-recoil method. In this case, the accurately known mass ratio of the electron to the neutron is used. The neutron mass is measured with high precision through a very precise measurement of its Compton wavelength. This is then combined with the value of the Rydberg constant to extract α. The result is,
α−1 = .
Hyperfine splitting
Hyperfine splitting is a splitting in the energy levels of an atom caused by the interaction between the magnetic moment of the nucleus and the combined spin and orbital magnetic moment of the electron. The hyperfine splitting in hydrogen, measured using Ramsey's hydrogen maser, is known with great precision. Unfortunately, the influence of the proton's internal structure limits how precisely the splitting can be predicted theoretically. This leads to the extracted value of α being dominated by theoretical uncertainty:
α−1 = .
The hyperfine splitting in muonium, an "atom" consisting of an electron and an antimuon, provides a more precise measurement of α because the muon has no internal structure:
α−1 = .
Lamb shift
The Lamb shift is a small difference in the energies of the 2 S1/2 and 2 P1/2 energy levels of hydrogen, which arises from a one-loop effect in quantum electrodynamics. The Lamb shift is proportional to α5 and its measurement yields the extracted value:
α−1 = .
Positronium
Positronium is an "atom" consisting of an electron and a positron. Whereas the calculation of the energy levels of ordinary hydrogen is contaminated by theoretical uncertainties from the proton's internal structure, the particles that make up positronium have no internal structure so precise theoretical calculations can be performed. The measurement of the splitting between the 2 3S1 and the 1 3S1 energy levels of positronium yields
α−1 = .
Measurements of α can also be extracted from the positronium decay rate. Positronium decays through the annihilation of the electron and the positron into two or more gamma-ray photons. The decay rate of the singlet ("para-positronium") 1S0 state yields
α−1 = ,
and the decay rate of the triplet ("ortho-positronium") 3S1 state yields
α−1 = .
This last result is the only serious discrepancy among the numbers given here, but there is some evidence that uncalculated higher-order quantum corrections give a large correction to the value quoted here.
High-energy QED processes
The cross sections of higher-order QED reactions at high-energy electron-positron colliders provide a determination of α. In order to compare the extracted value of α with the low-energy results, higher-order QED effects including the running of α due to vacuum polarization must be taken into account. These experiments typically achieve only percent-level accuracy, but their results are consistent with the precise measurements available at lower energies.
The cross section for e e → e e e e yields
α−1 = ,
and the cross section for e e → e e μ μ yields
α−1 = .
Condensed matter systems
The quantum Hall effect and the AC Josephson effect are exotic quantum interference phenomena in condensed matter systems. These two effects provide a standard electrical resistance and a standard frequency, respectively, which measure the charge of the electron with corrections that are strictly zero for macroscopic systems.
The quantum Hall effect yields
α−1 = ,
and the AC Josephson effect yields
α−1 = .
Other tests
QED predicts that the photon is a massless particle. A variety of highly sensitive tests have proven that the photon mass is either zero, or else extraordinarily small. One type of these tests, for example, works by checking Coulomb's law at high accuracy, as the photon's mass would be nonzero if Coulomb's law were modified. See .
QED predicts that when electrons get very close to each other, they behave as if they had a higher electric charge, due to vacuum polarization. This prediction was experimentally verified in 1997 using the TRISTAN particle accelerator in Japan.
QED effects like vacuum polarization and self-energy influence the electrons bound to a nucleus in a heavy atom due to extreme electromagnetic fields. A recent experiment on the ground state hyperfine splitting in 209Bi80+ and 209Bi82+ ions revealed a deviation from the theory by more than 7 standard uncertainties. Indications show that this deviation may originate from a wrong value of the nuclear magnetic moment of 209Bi.
See also
QED vacuum
Eötvös experiment, another very high accuracy test, of gravitation
References
External links
Particle Data Group (PDG)
PDG Review of the Muon Anomalous Magnetic Moment as of July 2007
PDG 2007 Listing of particle properties for electron
PDG 2007 Listing of particle properties for muon
Quantum electrodynamics
Electrodynamics | Precision tests of QED | [
"Mathematics"
] | 2,276 | [
"Electrodynamics",
"Dynamical systems"
] |
9,269,176 | https://en.wikipedia.org/wiki/Bill%20Wakeham |
Sir William Arnot Wakeham FREng (born 25 September 1944) is a British chemical engineer. From 2001 to 2009 he was Vice-Chancellor of the University of Southampton.
Education
Wakeham received his undergraduate and graduate degrees in physics at Exeter University.
Career
He served as a research associate at Brown University, in Providence, Rhode Island. In 1971 he was appointed lecturer in the Department of Chemical Engineering and Chemical Technology at Imperial College, London. He was successively Reader in 1979, Professor of Chemical Physics in 1985, and head of the Department of Chemical Engineering in 1988.
His academic specialty is thermodynamics, particularly the thermophysical properties of fluids and intermolecular forces.
In 1996 he was appointed Pro-Rector (Research) and subsequently also Deputy Rector and Pro-Rector (Resources) at Imperial College, holding these positions simultaneously. He oversaw the college's medical school formation in 1997 from the merger of St Mary's Hospital Medical School, Charing Cross and Westminster Medical School (formerly Charing Cross Hospital Medical School and Westminster Hospital Medical School), the Royal Postgraduate Medical School and the National Heart and Lung Institute.
In 2007 the then Secretary of State for Innovation, Universities and Skills, Rt. Hon. John Denham MP invited him to chair a review of UK physics which reported in October 2008.
He is a visiting professor at Imperial College. He is a member of the Engineering and Physical Sciences Research Council (EPSRC) and chairs their Resource Audit Committee. He is
a member of the South East England Development Agency (SEEDA) Board. He is a member of the European Union expert panel on philanthropy and universities. He is UK Chair of the British-Italian Partnership Programme.
Honours
He was knighted in the 2009 Birthday Honours. He was President of the Institution of Chemical Engineers 2011–2. He is a Chartered Engineer, Chartered Physicist and Fellow of the Royal Academy of Engineering, the Institution of Chemical Engineers, the Institution of Electrical Engineers, the Institute of Physics and Imperial College London. He is a Touloukian Medal holder from the American Society of Mechanical Engineers (1997) and holds honorary degrees from Universidade Nova de Lisboa, Exeter University, Loughborough University
Personal life
He married Christina Marjorie Stone in 1969 and they had one son. They divorced in 1974. He married second Sylvia Frances Tolley in 1978 and they had two sons.
See also
List of University of Southampton people
External links
University of Southampton page announcing Wakeham's knighthood and summarising his career
References
British chemical engineers
Chemical engineering academics
Vice-chancellors of the University of Southampton
Living people
1944 births
Fellows of the Royal Academy of Engineering
Fellows of the Institute of Physics
Fellows of the Institution of Electrical Engineers
Knights Bachelor
Alumni of the University of Exeter
Academics of Imperial College London
Fellows of the Institution of Chemical Engineers | Bill Wakeham | [
"Chemistry"
] | 567 | [
"Chemical engineering academics",
"Chemical engineers"
] |
9,269,357 | https://en.wikipedia.org/wiki/Oxidative%20deamination | Oxidative deamination is a form of deamination that generates α-keto acids and other oxidized products from amine-containing compounds, and occurs primarily in the liver. Oxidative deamination is stereospecific, meaning it contains different stereoisomers as reactants and products; this process is either catalyzed by L or D- amino acid oxidase and L-amino acid oxidase is present only in the liver and kidney. Oxidative deamination is an important step in the catabolism of amino acids, generating a more metabolizable form of the amino acid, and also generating ammonia as a toxic byproduct. The ammonia generated in this process can then be neutralized into urea via the urea cycle.
Much of the oxidative deamination occurring in cells involves the amino acid glutamate, which can be oxidatively deaminated by the enzyme glutamate dehydrogenase (GDH), using NAD or NADP as a coenzyme. This reaction generates α-ketoglutarate (α-KG) and ammonia. Glutamate can then be regenerated from α-KG via the action of transaminases or aminotransferase, which catalyze the transfer of an amino group from an amino acid to an α-keto acid. In this manner, an amino acid can transfer its amine group to glutamate, after which GDH can then liberate ammonia via oxidative deamination. This is a common pathway during amino acid catabolism.
Another enzyme responsible for oxidative deamination is monoamine oxidase, which catalyzes the deamination of monoamines via addition of oxygen. This generates the corresponding ketone- or aldehyde-containing form of the molecule, and generates ammonia. Monoamine oxidases MAO-A and MAO-B play vital roles in the degradation and inactivation of monoamine neurotransmitters such as serotonin and epinephrine. Monoamine oxidases are important drug targets, targeted by MAO inhibitors (MAOIs) such as selegiline. Glutamate dehydrogenase play an important role in oxidative deamination.
References
External links
Diagram from Elmhurst
Metabolism
Protein catabolism | Oxidative deamination | [
"Chemistry",
"Biology"
] | 496 | [
"Biotechnology stubs",
"Biochemistry stubs",
"Cellular processes",
"Biochemistry",
"Metabolism"
] |
9,269,429 | https://en.wikipedia.org/wiki/Adaptive%20hypermedia | Adaptive hypermedia (AH) uses hypermedia which is adaptive according to a user model. In contrast to regular hypermedia, where all users are offered the same set of hyperlinks, adaptive hypermedia (AH) tailors what the user is offered based on a model of the user's goals, preferences and knowledge, thus providing links or content most appropriate to the current user.
Background
Adaptive hypermedia is used in educational hypermedia, on-line information and help systems, as well as institutional information systems. Adaptive educational hypermedia tailors what the learner sees to that learner's goals, abilities, needs, interests, and knowledge of the subject, by providing hyperlinks that are most relevant to the user in an effort to shape the user's cognitive load. The teaching tools "adapt" to the learner. On-line information systems provide reference access to information for users with a different knowledge level of the subject.
An adaptive hypermedia system should satisfy three criteria: it should be a hypertext or hypermedia system, it should have a user model and it should be able to adapt the hypermedia using the model.
A semantic distinction is made between adaptation, referring to system-driven changes for personalisation, and adaptability, referring to user-driven changes. One way of looking at this is that adaptation is automatic, whereas adaptability is not. From an epistemic point of view, adaptation can be described as analytic, a-priori, whereas adaptability is synthetic, a-posteriori. In other words, any adaptable system, as it "contains" a human, is by default "intelligent", whereas an adaptive system that presents "intelligence" is more surprising and thus more interesting.
Architecture
The system categories in which user modelling and adaptivity have been deployed by various researchers in the field share an underlying architecture. The conceptual structure for adaptive systems generally consists of interdependent components: a user model, a domain model and an interaction model.
User model
The user model is a representation of the knowledge and preferences which the system 'believes' a user (which may be an individual, a group of people or non-human agents) possesses. It is a knowledge source which is separable by the system from the rest of its knowledge and contains explicit assumptions about the user. Knowledge for the user model can be acquired implicitly by making inferences about users from their interaction with the system, by carrying out some form of test, or from assigning users to generic user categories usually called 'stereotypes'. The student model consists of a personal profile (which includes static data, e.g., name and password), cognitive profile (adaptable data such as preferences), and a student knowledge profile. Systems may adapt, depending on user features such as:
goals (a feature related with the context of a user's work in hypermedia)
knowledge (knowledge of the subject represented in the hyperspace)
background ( all the information related to the user's previous experience outside the subject of the hypermedia system which is relevant enough to be considered)
hyperspace experience (how familiar is the user with the structure of the hyperspace and how easily can the user navigate it)
preferences (the user can prefer some nodes and links over others and some parts of a page over others).
Domain model
The domain model defines the aspects of the application which can be adapted or which are otherwise required for the operation of the adaptive system. The domain model contains several concepts that stand as the backbone for the content of the system. Other terms which have been used for this concept include content model, application model, system model, device model and task model. It describes educational content such as information pages, examples, and problems. The simplest content model relates every content item to exactly one domain concept (in this model, this concept is frequently referred to as a domain topic). More advanced content models use multi-concept indexing for each content item and sometimes use roles to express the nature of item-concept relationship.
A cognitively valid domain model should capture descriptions of the application at three levels, namely:
The task level which makes the user aware of the system purpose.
The logical level which describes how something works.
The physical level which describes how to do something.
Each content concept has a set of topics. Topics represent individual pieces of knowledge for each domain and the size of each topic varies in relation to the particular domain. Additionally, topics are linked to each other forming a semantic network. This network is the structure of the knowledge domain.
Interaction model
The interaction or adaptation model contains everything which is concerned with the relationships which exist between the representation of the users (the user model) and the representation of the application (the domain model). It displays information to the user based on his or her cognitive preferences. For instance, the module will divide a page's content into chunks with conditions set to only display to certain users or preparing two variants of a single concept page with a similar condition.
The two main aspects to the interaction model are capturing the appropriate raw data and representing the inferences, adaptations and evaluations which may occur.
Content-level and link-level adaptation are distinguished as two different classes of hypermedia adaptation; the first is termed adaptive presentation and the second, adaptive navigation support.
Adaptive presentation
The idea of various adaptive presentation techniques is to adapt the content of a page accessed by a particular user to current knowledge, goals, and other characteristics of the user.
For example, a qualified user can be provided with more detailed and deep information while a novice can receive additional explanations.
Adaptive text presentation is the most studied technology of hypermedia adaptation.
There are a number of different techniques for adaptive text presentation.
Adaptive navigation support
The idea of adaptive navigation support techniques is to help users to find their paths in hyperspace by adapting the way of presenting links to goals, knowledge, and other characteristics of an individual user.
This area of research is newer than adaptive presentation, a number of interesting techniques have been already suggested and implemented.
We distinguish four kinds of link presentation which are different from the point of what can be altered and adapted:
Local non-contextual links – This type includes all kinds of links on regular hypermedia pages which are independent from the content of the page.
Contextual links or "real hypertext" links – This type comprises "hotwords" in texts, "hot spots" in pictures, and other kinds of links which are embedded in the context of the page content and cannot be removed from it.
Links from index and content pages – An index or a content page can be considered as a special kind of page which contains only links.
Links on local maps and links on global hyperspace maps – Maps usually graphically represent a hyperspace or a local area of hyperspace as a network of nodes connected by arrows.
Methods
Adaptation methods are defined as generalizations of existing adaptation techniques. Each method is based on a clear adaptation idea which can be presented at the conceptual level.
Content adaptation
additional explanations – hides parts of information about a particular concept which are not relevant to the user's level of knowledge about this concept,
prerequisite explanations – before presenting an explanation of a concept the system inserts explanations of all its prerequisite concepts which are not sufficiently known to the user,
comparative explanations – if a concept similar to the concept being presented is known, the user gets a comparative explanation which stress similarities and differences between the current concept and the related one,
explanation variants – assumes that showing or hiding some portion of the content is not always sufficient for the adaptation because different users may need essentially different information,
sorting – fragments of information about the concept are sorted from information which is most relevant to user's background and knowledge to information which is least relevant.
Link adaptation
global guidance – the system suggests navigation paths on a global scale,
local guidance – the system suggests the next step to take, for instance through a "next" or "continue" button,
local orientation support – the system presents an overview of a part of the (link) structure of the hyperspace,
global orientation support – the system presents an overview of the whole (link) structure of the hyperspace,
managing personalized views in information spaces – each view may be a list of links to all pages or sub-parts of the whole hyperspace which are relevant for a particular working goal.
Techniques
Adaptation techniques refer to methods of providing adaptation in existing AH systems.
Content adaptation
conditional text – with this technique, all possible information about a concept is divided into several chunks of texts. Each chunk is associated with a condition on the level of user knowledge represented in the user model. When presenting the information about the concept, the system presents only the chunks where the condition is true.
stretchtext – turns off and on different parts of the content according to the user knowledge level.
page variants – the most simple adaptive presentation technique. With this technique, a system keeps two or more variants of the same page with different presentations of the same content.
fragment variants – The system stores several variants of explanations for each concept and the user gets the page which includes variants corresponding to his or her knowledge about the concepts presented in the page
frame-based techniques – With this technique all the information about a particular concept is represented in form of a frame. Slots of a frame can contain several explanation variants of the concept, links to other frames, examples, etc. Special presentation rules are used to decide which slots should be presented to a particular user and in which order.
Link adaptation
direct guidance – the "next best" node for the user to visit is shown, e.g. through a "next" or "continue" button,
link sorting – all the links on a particular page are sorted according to the user model and to some goal-oriented criteria: the more towards the top of the page, the more relevant the link is,
link hiding – hiding links to "non-relevant" pages by changing the color of the anchors to that of normal text,
link annotation – to augment the link with some form of comment which tells the user more about the current state of the pages to which the annotated links refer,
link disabling – the "link functionality" of a link is removed,
link removal – link anchors for undesired links (non-relevant or not yet ready to read) are removed,
map adaptation – the content and presentation of a map of the link structure of the hyperspace is adapted.
Authoring adaptive hypermedia
Authoring adaptive hypermedia uses designing and creation processes for content, usually in the form of a resource collection and domain model, and adaptive behaviour, usually in the form of IF-THEN rules. Recently, adaptation languages have been proposed for increased generality. As adaptive hypermedia adapts at least to the user, authoring of AH comprises at least a user model, and may also include other aspects.
Issues
Authoring of adaptive hypermedia was long considered as secondary to adaptive hypermedia delivery. This was not surprising in the early stages of adaptive hypermedia, when the focus was on research and expansion. Now that adaptive hypermedia itself has reached a certain maturity, the issue is to bring it out to the community and let the various stakeholders reap the benefits. However, authoring and creation of hypermedia is not trivial. Unlike in traditional authoring for hypermedia and the web, a linear storyline is not enough. Instead, various alternatives have to be created for the given material. For example, if a course should be delivered both to visual and verbal learners, there should be created at least two perfectly equivalent versions of the material in visual and in verbal form, respectively. Moreover, an adaptation strategy should be created that states that the visual content should be delivered to visual learners, whereas the verbal content should be delivered to the verbal learners. Thus, authors should not only be able to create different versions of their content, but be able to specify (and in some cases, design from scratch) adaptation strategies of delivery of contents. Issues with which authoring of adaptive hypermedia is confronted are:
creation of exchange language for the content (some early examples are the CAM language),
creation of exchange language for adaptation (with the LAG language and the LAG-XLS language as examples),
creation of a framework for adaptation (see, e.g., the LAG framework),
standardization of adaptation processes.
AH authoring frameworks
There already exist some approaches to help authors to build adaptive-hypermedia-based systems. However, there is a strong need for high-level approaches, formalisms and tools that support and facilitate the description of reusable adaptive hypermedia and websites. Such models started appearing (see, e.g., the AHAM model of adaptive hypermedia, or the LAOS framework for authoring of adaptive hypermedia). Moreover, recently have we noticed a shift in interest, as it became clearer that the implementation-oriented approach would forever keep adaptive hypermedia away from the 'layman' author. The creator of adaptive hypermedia cannot be expected to know all facets of the process as described above. Still, he/she can be reasonably trusted to be an expert in one of these facets. For instance, it is reasonable to expect that there are content experts (such as, e.g., experts in chemistry, for instance). It is reasonable to expect, for adaptive educational hypermedia that there are experts in pedagogy, who are able to add pedagogical metadata to the content created by content experts. Finally, it is reasonable to expect that adaptation experts will be the one creating the implementation of adaptation strategies, and descriptions (metadata) of such nature that they can be understood and applied by laymen authors. This type of division of work determines the different authoring personas that should be expected to collaborate in the creation process of adaptive hypermedia. Moreover, the contributions of these various personas correspond to the different modules that are to be expected in adaptive hypermedia systems.
AH authoring systems
MOT (My Online Teacher)
TANGOW
History
By the early 1990s, the two main parent areas – hypertext and user modeling – had achieved a level of maturity that allowed for the research in these areas to be explored together. Many researchers had recognized the problems of static hypertext in different application areas, and explored various ways to adapt the output and behavior of hypertext systems to suit the needs of individual users. Several early papers on adaptive hypermedia were published in the User Modeling and User-Adapted Interaction (UMUAI) journal; the first workshop on adaptive hypermedia was held during a user modeling conference; and a special issue of UMUAI on adaptive hypermedia was published in 1996. Several innovative adaptive hypermedia techniques had been developed, and several research-level adaptive hypermedia systems had been built and evaluated.
After 1996, adaptive hypermedia grew rapidly. Research teams commenced projects in adaptive hypermedia, and many students selected the subject area for their PhD theses. A book on adaptive hypermedia, and a special issue of the New Review of Hypermedia and Multimedia (1998) were published. Two main factors accounted for this growth. Due a diverse audience, the internet boosted research into adaptivity. Almost all the papers published before 1996 describe classic pre-Web hypertext and hypermedia; the majority of papers published since 1996 are devoted to Web-based adaptive hypermedia systems. The second factor was the accumulation and consolidation of research experience in the field. Early papers provided few references to similar work in adaptive hypermedia, and described original laboratory systems developed to demonstrate and explore innovative ideas. After 1996, papers cite earlier work, and usually suggest either real world systems, or research systems developed for real world settings by elaborating or an extending techniques suggested earlier. This is indicative of the relative maturity of adaptive hypermedia as a research direction.
Research
Adaptive hypermedia and user modeling continue to be actively researched, with results published in several journals and conferences such as:
User Modeling and User-Adapted Interaction (UMUAI)
Adaptive Hypermedia
See also
Adaptive learning
Attentive user interface
Simulation
User modeling
References
Cristea, A. (2005). Authoring of Adaptive Hypermedia. Educational Technology & Society, 8 (3), 6-8. ()
A. Cristea and L. Aroyo, Adaptive Authoring of Adaptive Educational Hypermedia, AH 2002, Adaptive Hypermedia and Adaptive Web-Based Systems, LNCS 2347, Springer, 122-132
External links
A3H@AH'08;
A3H@UM'07;
A3H@AH'06;
A3H@AIED'05;
A3H@AH'04;
A3H@WBE'04
Hypertext
Hypermedia
Learning
Educational technology | Adaptive hypermedia | [
"Technology"
] | 3,404 | [
"Multimedia",
"Hypermedia"
] |
9,269,515 | https://en.wikipedia.org/wiki/Pivalamide | Pivalamide (2,2-dimethylpropanamide, or NDEPA), a simple amide substituted with a tert-butyl group having the chemical formula: tBu-CO-NH2. It is the amide of pivalic acid.
N-Pivalamide, is a functional group having the following chemical formula: tBu-CO-NH-R
References
Carboxamides
Tert-butyl compounds | Pivalamide | [
"Chemistry"
] | 97 | [
"Organic compounds",
"Organic compound stubs",
"Organic chemistry stubs"
] |
9,269,527 | https://en.wikipedia.org/wiki/Urine%20specific%20gravity | Specific gravity, in the context of clinical pathology, is a urinalysis parameter commonly used in the evaluation of kidney function and can aid in the diagnosis of various renal diseases.
Background
One of the main roles of the kidneys in humans and other mammals is to aid in the clearance of various water-soluble molecules, including toxins, toxicants, and metabolic waste. The body excretes some of these waste molecules via urination, and the role of the kidney is to concentrate the urine, such that waste molecules can be excreted with minimal loss of water and nutrients. The concentration of the excreted molecules determines the urine's specific gravity. In adult humans, normal specific gravity values range from 1.010 to 1.030.
Specific gravity and disease
Adults generally have a specific gravity in the range of 1.010 to 1.030. Increases in specific gravity (hypersthenuria, i.e. increased concentration of solutes in the urine) may be associated with dehydration, diarrhea, emesis, excessive sweating, urinary tract/bladder infection, glucosuria, renal artery stenosis, hepatorenal syndrome, decreased blood flow to the kidney (especially as a result of heart failure), and an excess of antidiuretic hormone caused by the syndrome of inappropriate antidiuretic hormone secretion. A specific gravity greater than 1.035 is consistent with frank dehydration. In neonates, normal urine specific gravity is 1.003. Hypovolemic patients usually have a specific gravity >1.015.
Decreased specific gravity (hyposthenuria, i.e. decreased concentration of solutes in urine) may be associated with renal failure, pyelonephritis, diabetes insipidus, acute tubular necrosis, interstitial nephritis, and excessive fluid intake (e.g., psychogenic polydipsia).
Osmolality is normally used for more detailed analysis, but USG remains popular for its convenience.
References
Urine tests
Laboratory techniques | Urine specific gravity | [
"Chemistry"
] | 434 | [
"nan"
] |
9,269,802 | https://en.wikipedia.org/wiki/Teotl | Teōtl () is a Nahuatl term for sacredness or divinity that is sometimes translated as "god". For the Aztecs was the metaphysical omnipresence upon which their religious philosophy was based.
As described by James Maffie, "is essentially power: continually active, actualized, and actualizing energy-in-motion... It is an ever-continuing process, like a flowing river... It continually and continuously generates and regenerates as well as permeates, encompasses and shapes reality as part of an endless process. It creates the cosmos and all its contents from within itself as well as out of itself."
This is conceptualized in a kind of monistic pantheism as manifest in the supreme god , as well as a large pantheon of lesser gods and idealizations of natural phenomena such as stars and fire.
Similar concepts to existed elsewhere in Mesoamerica at the time of the conquest, such as in the Zapotec term or the Maya or . Such immaterial energy can also be compared to the Polynesian concept of Mana. In Pipil mythology (Nawat cognate of Teotl) is known as the creator and father of life.
The gods in the Aztec pantheon, themselves each referred to as a (plural ), were active elements in the world that could manifest in natural phenomena, in abstract art, and as summoned or even embodied by priests during rituals – all these could be called .
Molly Bassett identifies major characteristics of as the term is used in the Florentine Codex to get further insight on Aztec religion as described in other codices.
Whereas in most Nahuatl translations of the Bible and Christian texts, "God" () is translated with the Spanish word "", in modern translations by the Catholic Church in the 21st century, the word "", which is a combination of and the reverential suffix -tzin, is used officially for "God".
References
Sources
External links
Discussion on the Internet Encyclopedia of Philosophy
Aztec mythology and religion
Vitalism
Aztec philosophy | Teotl | [
"Biology"
] | 418 | [
"Non-Darwinian evolution",
"Vitalism",
"Biology theories"
] |
9,269,819 | https://en.wikipedia.org/wiki/Serial%20Vector%20Format | Serial Vector Format (SVF) is a file format that contains boundary scan vectors to be sent to an electronic circuit using a JTAG interface. Boundary scan vectors consist of the following data:
Stimulus data: This is data to be sent to a device or electronic circuit
Expected response: This is the data the device or circuit is expected to send back if there is no error
Mask data: Defines which bits in the expected response are valid; other bits of the device's response are unknown and must be ignored when comparing the expected response and the data returned from the circuit
Additional information on how to send the data (e.g. maximum clock frequency)
The SVF standard was jointly developed by companies Texas Instruments and Teradyne. Control over the format has been handed off to boundary-scan solution provider ASSET InterTech. The most recent revision is Revision E.
SVF files are used to transfer boundary scan data between tools. As an example a VHDL compiler may create an SVF file that is read by a tool for programming CPLDs.
The SVF file is defined as an ASCII file that consists of a set of SVF statements. The maximum number of characters allowed on a line is 256, although one SVF statement can span more than one line. Each statement consists of a command and associated parameters. Each SVF statement is terminated by a semicolon. SVF is not case sensitive. Comments can be inserted into a SVF file after an exclamation point ‘!’ or a pair of slashes ‘//’. Either ‘//’ or ‘!’ will comment out the remainder of the line.
SVF commands
ENDDR: Specifies default end state for DR scan operations.
ENDIR: Specifies default end state for IR scan operations.
FREQUENCY: Specifies maximum test clock frequency for IEEE 1149.1 bus operations.
HDR: (Header Data Register) Specifies a header pattern that is prepended to the beginning of subsequent DR scan operations.
HIR: (Header Instruction Register) Specifies a header pattern that is prepended to the beginning of subsequent IR scan operations.
PIO: (Parallel Input/Output) Specifies a parallel test pattern.
PIOMAP: (Parallel Input/Output Map) Maps PIO column positions to a logical pin.
RUNTEST: Forces the IEEE 1149.1 bus to a run state for a specified number of clocks or a specified time period.
SDR: (Scan Data Register) Performs an IEEE 1149.1 Data Register scan.
SIR: (Scan Instruction Register) Performs an IEEE 1149.1 Instruction Register scan.
STATE: Forces the IEEE 1149.1 bus to a specified stable state.
TDR: (Trailer Data Register) Specifies a trailer pattern that is appended to the end of subsequent DR scan operations.
TIR: (Trailer Instruction Register) Specifies a trailer pattern that is appended to the end of subsequent IR scan operations.
TRST: (Test ReSeT) Controls the optional Test Reset line.
References
The In-System Configuration Handbook: A Designer's Guide to ISC, Neil G. Jacobson,
External links
Serial Vector Format Specification latest version available - Revision E
SVF and XSVF File Formats for Xilinx Devices specifies XSVF, a binary version of SVF
Electronics manufacturing
Computer file formats | Serial Vector Format | [
"Engineering"
] | 675 | [
"Electronic engineering",
"Electronics manufacturing"
] |
9,270,416 | https://en.wikipedia.org/wiki/Talarian | Talarian was a provider of real-time infrastructure software. Now part of TIBCO, it was a veteran provider of message-oriented middleware.
Talarian was a member of the Business Integration Group (BIG), the Internet Protocol Multicast Initiative (IPMI), the Securities Industry Middleware Council (SIMC), the Object Management Group (OMG), and the Internet Engineering Task Force (IETF).
SmartSockets
SmartSockets was the main product of Talarian. It is a real-time message-oriented middleware (MOM) which is scalable and fault tolerant. Its programming model is built specifically to offer high-speed interprocess communication (IPC) for multiprocessor architecture, scalability and reliability.
It supports a variety of communication paradigms including publish-subscribe, adaptive multicast, redundant connections, peer-to-peer, and RPC.
Included as part of the SmartSockets package are graphical tools for monitoring and debugging applications.
It is supported on a wide range of platforms:
HP-UX
AIX
Linux
Compaq NSK/OSS
Tru64
OpenVMS
Windows
Solaris
Irix
VxWorks
Applications using SmartSockets can be developed with the following languages:
C API
C++ Class Libraries
ActiveX Components
Java Class Library
SmartSockets is now a product of TIBCO. See acquisition below.
Acquisition by TIBCO
In January 2002 TIBCO acquired Talarian for approximately $115 million. It was its primary competitor in the delivery of high-performance messaging solutions.
TIBCO paid $5.30 per share, half in stock and half in cash, for each of Talarian's outstanding shares.
Customers
Talarian customers were large end-users, OEMs and systems integrators in need of solutions where real-time data flow supports high-information volumes.
List of Famous Customers:
Boeing
AT&T
Hewlett-Packard
Cisco
MTR
New York Stock Exchange
NASA's ground control station for the Hubble Space Telescope
References
Talarian : Everything You Need To Know About Middleware
2002 mergers and acquisitions
Middleware
Software companies based in California
Defunct software companies of the United States
Software companies established in 1989
Software companies disestablished in 2002 | Talarian | [
"Technology",
"Engineering"
] | 467 | [
"Software engineering",
"Middleware",
"IT infrastructure"
] |
9,270,430 | https://en.wikipedia.org/wiki/List%20of%20semiconductor%20IP%20core%20vendors | The following is a list of notable vendors in the business of licensing IP cores.
Artificial Intelligence / Machine Learning / GEMM Accelerators
Akeana
Analog-to-digital converters (ADC)
Cadence Design Systems
Cosmic Circuits
Dolphin Integration
S3 Group
Synopsys
Broadband modem and error correction
Cadence Design Systems
CEVA, Inc.
IMEC
On2 Technologies (through acquisition of Hantro)
Synopsys (through acquisition of Virage Logic)
Tensilica (now part of Cadence Design Systems)
Digital-to-analog converters (DAC)
Cadence Design Systems
Cosmic Circuits (now part of Cadence Design Systems)
Dolphin Integration
S3 Group
Digital signal processors (DSP)
Synopsys - ARC
Tensilica - Xtensa (now part of Cadence Design Systems)
DRAM
DRAM controllers
Actel
Altera
Arm Holdings
Barco Silex
Cadence Design Systems (through acquisition of Denali Software)
Faraday Technology
Lattice Semiconductor
Rambus
Synopsys
Xilinx (acquired by AMD)
DRAM PHYs
Arm Holdings
Cadence Design Systems (through acquisition of Denali Software)
Synopsys (through acquisition of Virage Logic)
High-bandwidth memory - HBM PHYs
eSilicon
Rambus
Synopsys
Hybrid memory cube - HMC Controllers
Open-Silicon
University of Heidelberg
Communication IP
Network-on-chip (NoC) / On-chip interconnect
Akeana
Arteris IP
Arm Holdings
Bluetooth SW stack, link layer, and PHY
Arm Holdings (through acquisition of Dicentric and Sunrise Micro Devices)
Ethernet PHY
Arm Holdings (through acquisition of Artisan Components)
Cadence Design Systems
V-by-One
Socionext - HV Series
General-purpose microprocessors
Akeana
Andes Technology, Codasip, SiFive, and others - RISC-V
Arm Holdings - Arm Cortex and Neoverse processor cores
CEVA, Inc. - CEVA-X DSP
Dolphin Integration - 8051, 80251
eSi-RISC - eSi-RISC
Freescale and others - ColdFire
IBM and others - PowerPC/Power ISA
Infineon Technologies - TricoreA
MIPS Technologies - MIPS architecture
OpenCores - OpenRISC
Renesas - SuperH
Socionext - Fujitsu FR
Sun Microsystems and others - OpenSPARC
Synopsys - ARC
Tensilica - Xtensa (now part of Cadence Design Systems)
Western Design Center - 6502, 65816, 65xx
Xilinx (acquired by AMD) - MicroBlaze
Graphics processing units (GPU)
AMD
Arm Holdings
Imagination Technologies
Intel
NVidia
FPGA
Altera
Xilinx (acquired by AMD)
Embedded FPGA (eFPGA)
Menta SAS
HDMI
Silicon Image
Synopsys
ISP
Silicon Image
Socionext - Milbeaut
I/O pad libraries
Arm Holdings (through acquisition of Artisan Components)
Faraday Technology
Synopsys
TSMC
On-chip SRAMs
Arm Holdings (through acquisition of Artisan Components)
Dolphin Integration
eSilicon
Synopsys (through acquisition of Virage Logic)
Phase-locked loops (PLL)
Arm Holdings (through acquisition of Artisan Components)
Cadence Design Systems
CEVA, Inc.
Cosmic Circuits
S3 Group
TSMC
Power management
S3 Group
Cosmic Circuits
Dolphin Integration
SiliconGate Lda
Serial ATA (SATA) controllers
CEVA, Inc.
Synopsys Inc.
Standard cell libraries
Arm Holdings (through acquisition of Artisan Components)
Faraday Technology
NanGate
Silvaco (through acquisition of Dolphin Integration's libraries)
Synopsys
Video processors and computer graphics
Arm Holdings (through acquisition of Falanx and Logipard)
CEVA, Inc.
Chips&Media Specializes in video codecs, image signal processing, and deep learning-based computer vision system (super-resolution).
Google (through acquisition of On2 Technologies)
Imagination Technologies
intoPIX - Specializes in lightweight low latency image, video and sensor compression, including JPEG XS IP, TicoRAW IP and others.
Silicon Image
Socionext - HEVC/H.265, SEERIS 2.5D Graphics IP
Vivante Corporation (offers GPU IP solutions for applications in the mobile, consumer, automotive, embedded, real time/mission critical, and home entertainment markets.)
References
Electronic design
Semiconductor IP cores | List of semiconductor IP core vendors | [
"Engineering"
] | 883 | [
"Electronic design",
"Electronic engineering",
"Design"
] |
9,270,702 | https://en.wikipedia.org/wiki/Stream%20ripping | Stream ripping (also called stream recording) is the process of saving data streams to a file. The process is sometimes referred to as destreaming.
Stream ripping is most often referred in the context of saving audio or video from streaming media websites and services such as YouTube outside of the officially-provided means of offline playback (if any) using unsanctioned software and tools. This is often prohibited under each respective website or service's Terms of Use.
Legality
The Recording Industry Association of America (RIAA) has taken stances against tools that are, in particular, used to rip content from YouTube, citing that their use to download music from the website and convert them to audio formats constitutes a violation of their members' copyrights. The RIAA has targeted various stream ripping websites (including the websites themselves, and listings for them via search engines) under the anti-circumvention provisions of the U.S. Digital Millennium Copyright Act (DMCA), under its claim that a "rolling cipher" used by YouTube to generate the URL for the video file itself constitutes a technical protection measure, since it is "intended to inhibit direct access to the underlying YouTube video files, thereby preventing or inhibiting the downloading, copying, or distribution of the video files". Unlike the more common forms of takedowns performed under the Online Copyright Infringement Liability Limitation Act, there is no scheme of counter-notices for such takedowns. These actions have faced criticism, noting that there are legitimate uses for these services beyond ripping music, such as downloading video content needed to utilize one's right to fair use, or explicit rights of reuse (such as free content licenses) granted by a content creator.
In October 2020, the RIAA similarly issued takedowns to code hosting service GitHub targeting youtube-dl, an open source tool for similar purposes, also citing circumvention of the aforementioned "rolling cipher", as well as usage examples in its readme file that "expressly suggests" its use with copyrighted works.
On November 16, 2020, GitHub later reinstated youtube-dl and subsequently released a related blog post with more information on the status of the takedown.
On February 9, 2023, GitHub and the Electronic Frontier Foundation filed amicus curiae contesting the ruling against a stream ripping service, Yout, concerning that the ruling could render many software that add features or customize user experience as a circumvention violation, and arguing that lacking features such as a download button is not a technical protection measure because youtube allowed any browser to access its videos including browsers that allow users to customize them.
See also
Comparison of YouTube downloaders
Protection of Broadcasts and Broadcasting Organizations Treaty
References
External links
StreamRecorder.NET
Digital television
Film and video technology
Internet broadcasting
Internet radio
Streaming television
Ripping
Streaming media systems
Video on demand | Stream ripping | [
"Technology"
] | 588 | [
"Internet radio",
"Computer systems",
"Streaming media systems",
"Telecommunications systems",
"Streaming television",
"Multimedia"
] |
9,270,946 | https://en.wikipedia.org/wiki/Calcium%20aluminates | Calcium aluminates are a range of materials obtained by heating calcium oxide and aluminium oxide together at high temperatures. They are encountered in the manufacture of refractories and cements.
The stable phases shown in the phase diagram (formed at atmospheric pressure under an atmosphere of normal humidity) are:
Tricalcium aluminate, 3CaO·Al2O3 ()
Dodecacalcium hepta-aluminate, 12CaO·7Al2O3 () (once known as mayenite)
Monocalcium aluminate, CaO·Al2O3 (CA) (occurring in nature as krotite and dmitryivanovite – two polymorphs)
Monocalcium dialuminate, CaO·2Al2O3 () (occurring in nature as grossite )
Monocalcium hexa-aluminate, CaO·6Al2O3 () (occurring in nature as hibonite, a representative of magnetoplumbite group)
In addition, other phases include:
Dicalcium aluminate, 2CaO·Al2O3 (), which exists only at pressures above 2500 MPa. The crystal is orthorhombic, with density 3480 kg·m−3. The natural dicalcium aluminate, brownmillerite, may form at normal pressure but elevated temperature in pyrometamorphic zones, e.g., in burning coal-mining heaps.
Pentacalcium trialuminate, 5CaO·3Al2O3 (), forms only under an anhydrous and oxygen free atmosphere. The crystal is orthorhombic, with a density of 3067 kg·m−3. It reacts rapidly with water.
Tetracalcium trialuminate, 4CaO·3Al2O3 (), is a metastable phase formed by dehydrating 4CaO·3Al2O3·3H2O ().
Hydration reaction
In contrast to Portland cements, calcium aluminates do not release calcium hydroxide () portlandite or lime during their hydration.
See also
Calcium aluminate cements
Cement
Cement chemist notation (CCN)in which the following abbreviations for calcium and aluminium oxides are defined as:
C = CaO
A =
Hydrocalumite
Mayenite
Ye'elimite, , a rare natural anhydrous calcium sulfoaluminate
References
Further reading
Aluminates
Calcium compounds
Cement
Ceramic materials
Refractory materials | Calcium aluminates | [
"Physics",
"Engineering"
] | 526 | [
"Refractory materials",
"Materials",
"Ceramic materials",
"Ceramic engineering",
"Matter"
] |
9,271,528 | https://en.wikipedia.org/wiki/The%20Spaceguard%20Foundation | The Spaceguard Foundation (SGF) is a private organization based in Frascati, Italy, whose purpose is to study, discover and observe near-Earth objects (NEO) and protect the Earth from the possible threat of their collision. The foundation is non-partisan, non-political and non-profit, and acts as the international organization grouping together the spaceguard organizations in various countries, as well as individual astronomers and organizations interested in the foundation's activities.
The foundation was established in Rome in 1996. Since then, it has moved into the ESA Centre for Earth Observation (ESRIN) at Frascati. , Italian astronomer Andrea Carusi heads the foundation.
The Spaceguard System
The Spaceguard System is a collection of observatories engaging in near-Earth objects (NEO) observations. The Spaceguard Central Node—the website of the foundation—manages the collection and provides the observatories with services which would optimize the international coordination of NEO followups. The individual observatories in the system participate in these services on a volunteer basis. , all the observatories in the system are ground-based.
Related organizations
Spaceguard Croatia (Croatia)
Spaceguard Foundation e.V. (Germany)
Japan Spaceguard Association (Japan)
Spaceguard UK (United Kingdom)
See also
B612 Foundation
Chelyabinsk meteor
Tunguska event
References
External links
The Spaceguard Central Node
Mirror site: The Spaceguard Central Node
The Spaceguard System
ESA's page on the Spaceguard Central Node
Astronomical surveys
Scientific research foundations
Foundations based in Italy
Organizations established in 1996
Planetary defense organizations | The Spaceguard Foundation | [
"Astronomy"
] | 328 | [
"Planetary defense organizations",
"Astronomical surveys",
"Works about astronomy",
"Astronomy organizations",
"Astronomical objects"
] |
9,271,651 | https://en.wikipedia.org/wiki/Solution%20precursor%20plasma%20spray | Solution precursor plasma spray (SPPS) is a thermal spray process where a feedstock solution is heated and then deposited onto a substrate. Basic properties of the process are fundamentally similar to other plasma spraying processes. However, instead of injecting a powder into the plasma plume, a liquid precursor is used. The benefits of utilizing the SPPS process include the ability to create unique nanometer sized microstructures without the injection feed problems normally associated with powder systems and flexible, rapid exploration of novel precursor compositions.
Background
The use of a solution precursor was first reported as a coating technology by Karthikeyan et al. In that work, Karthikeyan showed that the use of a solution precursor was in fact feasible; however, well adhered coatings could not be generated. Further work was reported in 2001, which refined the process to produce thermal barrier coatings, YAG films, and silicon ceramic coatings. Since then, extensive research on the technology has been explored in large part by the University of Connecticut and Inframat Corporation.
Process
The precursor solution is formulated by dissolving salts (commonly zirconium and yttrium when used to formulate thermal barrier coatings) in a solvent. Once dissolved, the solution is then injected via a pressurized feed system. As with other thermal spray processes, feedstock material is melted and then deposited onto a substrate. Typically, the SPPS process sees material injected into a plasma plume or high velocity oxygen fuel (HVOF) combustion flame. Once the solution is injected, the droplets go through several chemical and physical changes and can arrive at the substrate in several different states, from fully melted to unpyrolized. The deposition state can be manipulated through spray parameters and can be used to significantly control coating properties, such as density and strength.
Thermal barrier coatings
Most current research on SPPS has examined is application to create thermal barrier coatings (TBCs). These complex ceramic/metallic material systems are used to protect components in hot sections of gas turbine and diesel engines. The SPPS process lends itself particularly well to the creation of these TBCs. Studies report the generation of coatings demonstrating superior durability and mechanical properties. Superior durability is imparted by the creation of controlled through thickness vertical cracks. These cracks only slightly increase coating conductivity while allowing for strain relief of stress generated by the CTE mismatch between the coating and the substrate during cyclic heating. The generation of these through thickness cracks was systematically explored and found to be caused by the depositing a controlled portion of unpyrolized material in the coating. Superior mechanical properties such as bond strength and in-plane toughness result from the nanometer sized microstructure that are created by the SPPS process.
Other studies have shown that engineered coatings can reduce thermal conductivity to some of the lowest reported values for TBCs. These low thermal conductivities were achieved through the generation of an alternating high-porosity, low-porosity microstructure or the synthesis of a low-conductivity precursor composition with rare-earth dopants.
Costs
The SPPS process is adapted to existing thermal spray systems. Application costs are significantly less than EB-PVD coatings and slightly higher than Air Plasma Spray coatings.
References
Plasma processing
Coatings | Solution precursor plasma spray | [
"Chemistry"
] | 673 | [
"Coatings"
] |
9,272,422 | https://en.wikipedia.org/wiki/Specific%20ultraviolet%20absorbance | Specific ultraviolet absorbance (SUVA) is the absorbance of ultraviolet light in a water sample at a specified wavelength that is normalized for dissolved organic carbon (DOC) concentration. Specific UV absorbance (SUVA) wavelengths have analytical uses to measure the aromatic character of dissolved organic matter by detecting density of electron conjugation which is associated with aromatic bonds.
Derivation
To derive SUVA, first, UVC light (UV spectrum subtypes) at 254 nm or 280 nm, is measured in units of absorbance per meter of path length, often the sample must be diluted with ultrapure water because absorbance can be high. As increasing dissolved organic carbon concentration increases absorbance in the UV range, the UV light has to be normalized to the concentration of dissolved organic carbon in mg per L to ascertain differences in the aromatic quality of the water.
Aromatic character is used in the study of dissolved organic matter, from mineral soils, or organic soils, to use as an assay to whether or not dissolved organic carbon in the water is labile, a ready source of energy, or is from a relatively old source of carbon (recalcitrant). However, although a good indicator of aromaticity, caution must be used with determination of reactivity.
Measures of water purity often rely on measuring turbidity, not aromaticity.
References
Further reading
Water chemistry
Spectroscopy | Specific ultraviolet absorbance | [
"Physics",
"Chemistry"
] | 282 | [
"Molecular physics",
"Spectrum (physical sciences)",
"Instrumental analysis",
"nan",
"Spectroscopy"
] |
9,272,650 | https://en.wikipedia.org/wiki/Universal%20waste | Universal waste is a category of waste materials designated as "hazardous waste", but containing materials that are very common. It is defined in , by the United States Environmental Protection Agency but states may also have corollary regulations regarding these materials.
Universal waste includes:
Batteries; lithium, Silver ion, nickel cadmium (Ni-Cad), mercury-oxide, or sealed lead-acid. Spent Lead-Acid Batteries being reclaimed do not need to be managed as universal waste.
Pesticides; Stocks of a suspended and canceled pesticide that are part of a voluntary or mandatory recall
Mercury Containing Equipment; a device or part of a device (including thermostats) that contains elemental mercury integral to its function.
Lamps; include, but are not limited to, fluorescent, high intensity discharge, neon, mercury vapor, high pressure sodium, and metal halide lamps.
Aerosol cans: a non-refillable receptacle containing a compressed gas, liquid, or solution under pressure for expelling a liquid, paste, or powder. These include, but are not limited to spray paints, lubricants, solvents, adhesives.
Businesses and other generators of such waste are required to provide for their proper disposal.
References
Waste | Universal waste | [
"Physics"
] | 252 | [
"Materials",
"Waste",
"Matter"
] |
9,272,721 | https://en.wikipedia.org/wiki/Kinematic%20diagram | In mechanical engineering, a kinematic diagram or kinematic scheme (also called a joint map or skeleton diagram) illustrates the connectivity of links and joints of a mechanism or machine rather than the dimensions or shape of the parts. Often links are presented as geometric objects, such as lines, triangles or squares, that support schematic versions of the joints of the mechanism or machine.
For example, the figures show the kinematic diagrams (i) of the slider-crank that forms a piston and crank-shaft in an engine, and (ii) of the first three joints for a PUMA manipulator.
|- style="text-align:center;"
| ||
|- style="text-align:center;"
| PUMA robot || and its kinematic diagram
Linkage graph
A kinematic diagram can be formulated as a graph by representing the joints of the mechanism as vertices and the links as edges of the graph. This version of the kinematic diagram has proven effective in enumerating kinematic structures in the process of machine design.
An important consideration in this design process is the degree of freedom of the system of links and joints, which is determined using the Chebychev–Grübler–Kutzbach criterion.
Elements of machines
Elements of kinematics diagrams include the frame, which is the frame of reference for all the moving components, as well as links (kinematic pairs), and joints. Primary Joints include pins, sliders and other elements that allow pure rotation or pure linear motion. Higher order joints also exist that allow a combination of rotation or linear motion. Kinematic diagrams also include points of interest, and other important components.
See also
Free body diagram
Kinematic synthesis
Left-hand–right-hand activity chart
References
Mechanisms (engineering)
Diagrams
Classical mechanics | Kinematic diagram | [
"Physics",
"Engineering"
] | 378 | [
"Mechanics",
"Classical mechanics",
"Mechanical engineering",
"Mechanisms (engineering)"
] |
9,273,845 | https://en.wikipedia.org/wiki/Audiokinetic%20Wwise | Wwise (Wave Works Interactive Sound Engine) is Audiokinetic's software for interactive media and video games, available for free to non-commercial users and under license for commercial video game developers. It features an audio authoring tool and a cross-platform sound engine.
Description
The Wwise authoring application uses a graphical interface to centralize all aspects of audio creation. The functionality in this interface allows sound designers to:
Import audio files for use in video games
Apply audio plug-in effects
Mix in real-time
Define game states
Simulate audio environments
Manage sound integration
Apply the Windows Spatial Audio API, or Dolby Atmos.
Wwise allows for on-the-fly audio authoring directly in game. Over a local network, users can create, audition, and tweak sound effects and subtle sound behaviors while the game is being played on another host.
Wwise also includes the following components:
Cross-platform sound engine (Wwise Authoring)
Multichannel Creator (allows creation of multichannel audio)
Plug-in architecture for source, effect, and source control plug-ins, part of Wwise Launcher
SoundFrame API
Wave Viewer (allows for sampling of WAV audio files)
Supported operating systems
Wwise supports the following platforms:
Adoption by video games
Titles which have used Audiokinetic include:
Commercial game engine integration
Wwise is intended to be compatible with proprietary and commercial engines.
Unreal Engine 3
Unreal Engine 4
Unity
Cocos2d-x
CryEngine
Orochi 3
Gamebryo
Fox Engine
Autodesk Stingray
Open 3D Engine (which superseded Amazon Lumberyard)
Theatre
One play has used Wwise and its Interactive Music capabilities for live performance:
Dom Duardos by Gil Vicente, co-produced by Companhia Contigo Teatro and Grupo de Mímica e Teatro Oficina Versus, with music by Pedro Macedo Camacho
See also
FMOD
OpenAL
Sound design
Video game development
References
External links
Alexander Brandon, "Audio Middleware, Part 2: More Contenders in the Emerging Field" Mix Magazine, 04-01-2007. Retrieved on 04-13-2007.
Audio libraries
Middleware
Video game development software
Video game development software for Linux
Video game music technology | Audiokinetic Wwise | [
"Technology",
"Engineering"
] | 445 | [
"Software engineering",
"Middleware",
"IT infrastructure"
] |
9,274,067 | https://en.wikipedia.org/wiki/Marangoni%20number | The Marangoni number (Ma) is, as usually defined, the dimensionless number that compares the rate of transport due to Marangoni flows, with the rate of transport of diffusion. The Marangoni effect is flow of a liquid due to gradients in the surface tension of the liquid. Diffusion is of whatever is creating the gradient in the surface tension. Thus as the Marangoni number compares flow and diffusion timescales it is a type of Péclet number.
The Marangoni number is defined as:
A common example is surface tension gradients caused by temperature gradients. Then the relevant diffusion process is that of thermal energy (heat). Another is surface gradients caused by variations in the concentration of surfactants, where the diffusion is now that of surfactant molecules.
The number is named after Italian scientist Carlo Marangoni, although its use dates from the 1950s and it was neither discovered nor used by Carlo Marangoni.
The Marangoni number for a simple liquid of viscosity with a surface tension change over a distance parallel to the surface, can be estimated as follows. Note that we assume that is the only length scale in the problem, which in practice implies that the liquid be at least deep. The transport rate is usually estimated using the equations of Stokes flow, where the fluid velocity is obtained by equating the stress gradient to the viscous dissipation. A surface tension is a force per unit length, so the resulting stress must scale as , while the viscous stress scales as , for the speed of the Marangoni flow. Equating the two we have a flow speed . As Ma is a type of Péclet number, it is a velocity times a length, divided by a diffusion constant, , Here this is the diffusion constant of whatever is causing the surface tension difference. So,
Marangoni number due to thermal gradients
A common application is to a layer of liquid, such as water, when there is a temperature difference across this layer. This could be due to the liquid evaporating or being heated from below. There is a surface tension at the surface of a liquid that depends on temperature, typically as the temperature increases the surface tension decreases. Thus if due to a small fluctuation temperature, one part of the surface is hotter than another, there will be flow from the hotter part to the colder part, driven by this difference in surface tension, this flow is called the Marangoni effect. This flow will transport thermal energy, and the Marangoni number compares the rate at which thermal energy is transported by this flow to the rate at which thermal energy diffuses.
For a liquid layer of thickness , viscosity and thermal diffusivity , with a surface tension which changes with temperature at a rate , the Marangoni number can be calculated using the following formula:
When Ma is small thermal diffusion dominates and there is no flow, but for large Ma, flow (convection) occurs, driven by the gradients in the surface tension. This is called Bénard-Marangoni convection.
References
Dimensionless numbers of fluid mechanics
Dimensionless numbers of thermodynamics
Fluid dynamics | Marangoni number | [
"Physics",
"Chemistry",
"Engineering"
] | 647 | [
"Thermodynamic properties",
"Physical quantities",
"Dimensionless numbers of thermodynamics",
"Chemical engineering",
"Piping",
"Fluid dynamics"
] |
975,309 | https://en.wikipedia.org/wiki/Cementation%20process | The cementation process is an obsolete technology for making steel by carburization of iron. Unlike modern steelmaking, it increased the amount of carbon in the iron. It was apparently developed before the 17th century. Derwentcote Steel Furnace, built in 1720, is the earliest surviving example of a cementation furnace. Another example in the UK is the cementation furnace in Doncaster Street, Sheffield.
Origins
The process was described in a treatise published in Prague in 1574. It was invented by Johann Nussbaum of Magdeburg, who began operations at Nuremberg (with partners) in 1601. The process was patented in England by William Ellyot and Mathias Meysey in 1614. At that date, the "invention" could consist merely of the introduction of a new industry or product, or even a mere monopoly. They evidently soon transferred the patent to Sir Basil Brooke, but he was forced to surrender it in 1619. A clause in the patent prohibiting the import of steel was found to be undesirable because he could not supply as much good steel as was needed. Brooke's furnaces were probably in his manor of Madeley at Coalbrookdale (which certainly existed before the English Civil War) where two cementation furnaces have been excavated.<ref>P. Belford and R. A. Ross, 'English steelmaking in the seventeenth century: excavation of two cementation furnaces at Coalbrookdale' Historical Metallurgy 41(2) (2007), 105-123.</ref> He probably used bar iron from the Forest of Dean, where he was a partner in farming the King's ironworks in two periods.
By 1631, it was recognised that Swedish iron was the best raw material and then or later particularly certain marks (brands) such as double bullet (so called from the mark OO) from Österby and hoop L from Leufsta (now Lövsta), whose mark consisted of an L in a circle, both belonging to Louis De Geer and his descendants. These were among the first ironworks in Sweden to use the Walloon process of fining iron, producing what was known in England as oregrounds iron. It was so called from the Swedish port of Öregrund, north of Stockholm, in whose hinterland most of the ironworks lay. The ore used came ultimately from the Dannemora mine.
Process
The process begins with wrought iron and charcoal. It uses one or more long stone pots inside a furnace. Typically, in Sheffield, each pot was 14 feet by 4 feet and 3.5 feet deep. Iron bars and charcoal are packed in alternating layers, with a top layer of charcoal and then refractory matter to make the pot or "coffin" airtight. Some manufacturers used a mixture of powdered charcoal, soot and mineral salts, called cement powder. In larger works, up to 16 tons of iron were treated in each cycle, though it can be done on a small scale, such as in a small furnace or blacksmith's forge.
Depending on the thickness of the iron bars, the pots were then heated from below for a week or more. Bars were regularly examined and when the correct condition was reached the heat was withdrawn and the pots were left until cool—usually around fourteen days. The iron had gained a little over 1% in mass from the carbon in the charcoal, and had become heterogeneous bars of blister steel.
The bars were then shortened, bound, heated and forge welded together to become shear steel. It would be cut and re welded multiple times, with each new weld producing a more homogeneous, higher quality steel. This would be done at most 3-4 times, as more is unnecessary and could potentially cause carbon loss from the steel.
Alternatively they could be broken up and melted in a crucible using a crucible furnace with a flux to become crucible steel (at the time also called cast steel), a process devised by Benjamin Huntsman in Sheffield in the 1740s.
Similar processes
Brass production
In the early modern period, brass, an alloy of copper and zinc, was usually produced by a cementation process in which metallic copper was heated with calamine, a zinc ore, to make calamine brass.
Notes
References
K. C. Barraclough, Steel before Bessemer I: Blister Steel: The Birth of an Industry (1985).
K. C. Barraclough, "Swedish Iron and Sheffield Steel", History of Technology 12 (1990), 1–39.
Dorian Gerhold, "The steel industry in England, 1614-1740", in R.W. Hoyle (ed.), "Histories of people and landscape: essays on the Sheffield region in memory of David Hey" (2021), 65-86
P. W. King, "The Cartel in Oregrounds Iron", Journal of Industrial History 6 (2003), 25–48.
R. J. MacKenzie and J. A Whiteman, "Why pay more? An archaeometallurgical examination of 19th century Swedish Wrought iron and Sheffield blister steel", Historical Metallurgy'' 40(2) (2006), 138–49.
Steelmaking
Metallurgical processes
Obsolete technologies | Cementation process | [
"Chemistry",
"Materials_science"
] | 1,080 | [
"Metallurgical processes",
"Steelmaking",
"Metallurgy"
] |
975,347 | https://en.wikipedia.org/wiki/Data%20manipulation%20language | A data manipulation language (DML) is a computer programming language used for adding (inserting), deleting, and modifying (updating) data in a database. A DML is often a sublanguage of a broader database language such as SQL, with the DML comprising some of the operators in the language. Read-only selecting of data is sometimes distinguished as being part of a separate data query language (DQL), but it is closely related and sometimes also considered a component of a DML; some operators may perform both selecting (reading) and writing.
A popular data manipulation language is that of Structured Query Language (SQL), which is used to retrieve and manipulate data in a relational database. Other forms of DML are those used by IMS/DLI, CODASYL databases, such as IDMS and others.
SQL
In SQL, the data manipulation language comprises the SQL-data change statements, which modify stored data but not the schema or database objects. Manipulation of persistent database objects, e.g., tables or stored procedures, via the SQL schema statements, rather than the data stored within them, is considered to be part of a separate data definition language (DDL). In SQL these two categories are similar in their detailed syntax, data types, expressions etc., but distinct in their overall function.
The SQL-data change statements are a subset of the SQL-data statements; this also contains the SELECT query statement, which strictly speaking is part of the DQL, not the DML. In common practice though, this distinction is not made and SELECT is widely considered to be part of DML, so the DML consists of all SQL-data statements, not only the SQL-data change statements. The SELECT ... INTO ... form combines both selection and manipulation, and thus is strictly considered to be DML because it manipulates (i.e. modifies) data.
Data manipulation languages have their functional capability organized by the initial word in a statement, which is almost always a verb. In the case of SQL, these verbs are:
SELECT ... FROM ... WHERE ... (strictly speaking DQL)
SELECT ... INTO ...
INSERT INTO ... VALUES ...
UPDATE ... SET ... WHERE ...
DELETE FROM ... WHERE ...
For example, the command to insert a row into table employees:
INSERT INTO employees (first_name, last_name, fname) VALUES ('John', 'Capita', 'xcapit00');
Variants
Most SQL database implementations extend their SQL capabilities by providing imperative, i.e. procedural languages. Examples of these are Oracle's PL/SQL and IBM Db2's SQL_PL.
Data manipulation languages tend to have many different flavors and capabilities between database vendors. There have been a number of standards established for SQL by ANSI, but vendors still provide their own extensions to the standard while not implementing the entire standard.
Data manipulation languages are divided into two types, procedural programming and declarative programming.
Data manipulation languages were initially only used within computer programs, but with the advent of SQL have come to be used interactively by database administrators.
See also
CRUD
Statements
Select (SQL)
Insert (SQL)
Update (SQL)
Delete (SQL)
Related languages
Data control language
Data definition language
Data query language
References
External links
DML Commands in Oracle
Data modeling
SQL
Articles with example SQL code | Data manipulation language | [
"Engineering"
] | 715 | [
"Data modeling",
"Data engineering"
] |
975,447 | https://en.wikipedia.org/wiki/Toxidrome | A toxidrome (a portmanteau of toxic and syndrome, coined in 1970 by Mofenson and Greensher) is a syndrome caused by a dangerous level of toxins in the body. It is often the consequence of a drug overdose. Common symptoms include dizziness, disorientation, nausea, vomiting and oscillopsia. It may indicate a medical emergency requiring treatment at a poison control center. Aside from poisoning, a systemic infection may also lead to one. Classic toxidromes are presented below, which are variable or obscured by co-ingestion of multiple drugs.
A common tool for assessing for the presence of toxidrome in the United Kingdom is the CRESS tool.
Anticholinergic
The symptoms of an anticholinergic toxidrome include blurred vision, coma, decreased bowel sounds, delirium, dry skin, fever, flushing, hallucinations, ileus, memory loss, mydriasis (dilated pupils), myoclonus, psychosis, seizures and urinary retention. Complications include hypertension, hyperthermia and tachycardia. Substances that may cause this toxidrome include antihistamines, antipsychotics, antidepressants, antiparkinsonian drugs, atropine, benztropine, datura, diphenhydramine and scopolamine.
Cholinergic
The symptoms of a cholinergic toxidrome include bronchorrhea, confusion, defecation, diaphoresis, diarrhea, emesis, lacrimation, miosis, muscle fasciculations, salivation, seizures, urination and weakness. Complications include bradycardia, hypothermia and tachypnea. Substances that may cause this toxidrome include carbamates, mushrooms and organophosphates.
Hallucinogenic
The symptoms of a hallucinogenic toxidrome include disorientation, hallucinations, hyperactive bowel sounds, panic and seizures. Complications include hypertension, tachycardia and tachypnea. Substances that may cause this toxidrome include substituted amphetamines, cocaine and phencyclidine.
Opiate
The symptoms of an opiate toxidrome include the classic triad of coma, pinpoint pupils and respiratory depression as well as altered mental states, shock, pulmonary edema and unresponsiveness. Complications include bradycardia, hypotension and hypothermia. Substances that may cause this toxidrome are opioids.
Sedative/hypnotic
The symptoms of sedative/hypnotic toxidrome include ataxia, blurred vision, coma, confusion, delirium, deterioration of central nervous system functions, diplopia, dysesthesias, hallucinations, nystagmus, paresthesias, sedation, slurred speech and stupor. Apnea is a potential complication. Substances that may cause it include anticonvulsants, barbiturates, benzodiazepines, gamma-Hydroxybutyric acid, Methaqualone and ethanol. While most sedative-hypnotics are anticonvulsant, some such as GHB and methaqualone instead lower the seizure threshold, so can cause paradoxical seizures in overdose.
Sympathomimetic
The symptoms of a sympathomimetic toxidrome include anxiety, delusions, diaphoresis, hyperreflexia, mydriasis, paranoia, piloerection and seizures. Complications include hypertension and tachycardia. Substances that may cause this toxidrome include cocaine, amphetamine and compounds based upon amphetamine's structure such as ephedrine (Ma Huang), methamphetamine, phenylpropanolamine and pseudoephedrine. The bronchodilator salbutamol may also cause this toxidrome. It may appear very similar to the anticholinergic toxidrome, but is distinguished by hyperactive bowel sounds and sweating.
References
Further reading
Medical emergencies
Medical terminology
Toxicology
Substance intoxication
Medical mnemonics | Toxidrome | [
"Environmental_science"
] | 868 | [
"Toxicology"
] |
975,450 | https://en.wikipedia.org/wiki/Argument%20of%20periapsis | The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ω (omega), is one of the orbital elements of an orbiting body. Parametrically, ω is the angle from the body's ascending node to its periapsis, measured in the direction of motion.
For specific types of orbits, terms such as argument of perihelion (for heliocentric orbits), argument of perigee (for geocentric orbits), argument of periastron (for orbits around stars), and so on, may be used (see apsis for more information).
An argument of periapsis of 0° means that the orbiting body will be at its closest approach to the central body at the same moment that it crosses the plane of reference from South to North. An argument of periapsis of 90° means that the orbiting body will reach periapsis at its northmost distance from the plane of reference.
Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis. However, especially in discussions of binary stars and exoplanets, the terms "longitude of periapsis" or "longitude of periastron" are often used synonymously with "argument of periapsis".
Calculation
In astrodynamics the argument of periapsis ω can be calculated as follows:
If ez < 0 then ω → 2 − ω.
where:
n is a vector pointing towards the ascending node (i.e. the z-component of n is zero),
e is the eccentricity vector (a vector pointing towards the periapsis).
In the case of equatorial orbits (which have no ascending node), the argument is strictly undefined. However, if the convention of setting the longitude of the ascending node Ω to 0 is followed, then the value of ω follows from the two-dimensional case:
If the orbit is clockwise (i.e. (r × v)z < 0) then ω → 2 − ω.
where:
ex and ey are the x- and y-components of the eccentricity vector e.
In the case of circular orbits it is often assumed that the periapsis is placed at the ascending node and therefore ω = 0. However, in the professional exoplanet community, ω = 90° is more often assumed for circular orbits, which has the advantage that the time of a planet's inferior conjunction (which would be the time the planet would transit if the geometry were favorable) is equal to the time of its periastron.
See also
Apsidal precession
Kepler orbit
Orbital mechanics
Orbital node
References
External links
Argument Of Perihelion in Swinburne University Astronomy Website
Orbits
Angle | Argument of periapsis | [
"Physics"
] | 572 | [
"Geometric measurement",
"Scalar physical quantities",
"Physical quantities",
"Wikipedia categories named after physical quantities",
"Angle"
] |
975,599 | https://en.wikipedia.org/wiki/311%20%28number%29 | 311 (three hundred [and] eleven) is the natural number following 310 and preceding 312.
311 is the 64th prime; a twin prime with 313; an irregular prime; an emirp, an Eisenstein prime with no imaginary part and real part of the form ; a Gaussian prime with no imaginary part and real part of the form ; and a permutable prime with 113 and 131.
It can be expressed as a sum of consecutive primes in four different ways: as a sum of three consecutive primes (101 + 103 + 107), as a sum of five consecutive primes (53 + 59 + 61 + 67 + 71), as a sum of seven consecutive primes (31 + 37 + 41 + 43 + 47 + 53 + 59), and as a sum of eleven consecutive primes (11 + 13 + 17 + 19 + 23 + 29 + 31 + 37 + 41 + 43 + 47).
311 is a strictly non-palindromic number, as it is not palindromic in any base between base 2 and base 309.
311 is the smallest positive integer d such that the imaginary quadratic field Q() has class number = 19.
4311 - 3311 is prime
References
Integers | 311 (number) | [
"Mathematics"
] | 256 | [
"Elementary mathematics",
"Integers",
"Mathematical objects",
"Numbers"
] |
975,637 | https://en.wikipedia.org/wiki/Moustache%20wax | Moustache wax is a stiff pomade applied to a moustache as a grooming aid to hold the hairs in place, especially at the extremities. The required product strength (or stiffness) is based on whisker length and the desired style. It can also have restorative properties, which become more important as the hair length increases. The wax is usually scented and sometimes pigmented with dyes; high end products utilize various combinations of iron oxide to create darker shades.
Generally less than a fingernail of wax is used when applied. More sophisticated recipes may include gum arabic and a soap, scent and colouring may also be added if desired, to either strengthen the hold or for comfort.
Common ingredients
Beeswax
Coconut oil or shea nut butter (or any saturated vegetable oil, solid at room temperature, and not prone to rancidity)
Lanolin
Petroleum jelly (Vaseline)
Gum arabic or pine resin
Scented oils
Tallow
In addition to the wax itself, more-experienced "waxers" use a moustache wax remover and conditioner. The reason for this is that warm soapy water (used by the novice) removes wax build-up but damages the bristles by stripping them of natural oils, so an oilbased moustache wax remover, that may double as a leavein conditioner, is preferred by some.
Notes
References
See also
Hair wax
Moustache
Waxes | Moustache wax | [
"Physics"
] | 293 | [
"Materials",
"Matter",
"Waxes"
] |
976,020 | https://en.wikipedia.org/wiki/Gaper | A gaper (Dutch pronunciation: [ˈɣaːpər]) is a stone or wooden figurehead, often depicting a Moor, Muslim, or North African. The figurehead first appeared in the late 16th century as a hangout sign used outside the storefronts of drug stores in the Netherlands. The meaning of gaper is the same in English; the figurehead is always displayed with an open mouth, sometimes with a pill resting on his tongue.
The gaper's gaping tongue could represent the intake of medicine and grimace represents the bitter taste of the medicine. The gaper takes on various appearances that are symbolic of the origin for the pharmacist’s practice or medicinal ingredients. There are stories of the gaper as a symbol of the pharmacist’s traveling "quack" or helper. Recently, gaper figureheads have been stolen or removed from storefronts. Now, few remain within public view in the city of Amsterdam. Outside museum collections, fewer than 50 can be seen on buildings. Some have now lent their names to cafes, such as De Vergulde Gaper in Amsterdam.
Origin
Turkish fashion, Japonerie, and Chinoiserie are said to be a source of inspiration for creating the gapers. The origin of the gaper, mostly Southern or exotic, symbolizes the origin of the ingredients used in the drugstore's medicines. During the 17th century, Western European trade with continents such as Asia and Africa introduced new spices from far and unknown places. Many exotic medicine components entered Europe through trade with the Ottoman Empire. Europeans traded with the Ottomans for senna leaves, opium, saffron, turmeric, and various resins, gums, and minerals, incense, myrrh, and bitumen. The spices and ingredients were brought back to Europe and later dried and sold by a chemist.
Design, style, and symbolism
Each gaper is hand cut and painted using a stone or wood base. They are usually displayed with an open mouth or with their tongues sticking out. Recent research indicates that the open mouth originates from the way the chemist's customers gaped with astonishment when they saw the enormous variety of exotic substances inside. Gapers have facial expressions ranging from innocent to humorous to suffering. Gapers takes on various appearances with each instance being unique. Their individual designs are claimed to be specific to the specialties of the drugstore.
The oriental gapers are categorized between two identities: the Muslim and the Moor, both referring to people from the Maghreb in North-West Africa. Gapers with dark brown or black skin were used to represent the moors. The common oriental gaper often wore a turban with gold earrings. The turban confirmed an exotic origin that suggested the origin of the medicines to customers.
There are also many white gapers, often looking very ill with a pale skin color or having a facial expression of suffering and pain. These symbolize the patients of the chemist.
There were also 'golden' gapers, gapers with a crown and gapers with a monkey on their shoulder. Although women have taken up the chemist's profession since 1950, in Holland, few gapers depict a female. Before 1950, the profession of chemist was an exclusively male preserve. A law of 1865 prohibited women from following education to become a chemist. The first female chemist in the Netherlands (also one of the first female retailers) was Mia Ranke, who opened her chemist's shop in 1934. The gaper referring to illness or a sick patient commonly wore a hat with a hanging point with a tassel or pom-pom attached to it. Some gapers were depicted in uniform, as a fire brigade, police or a Roman soldier. In the French era (1795-1813) there was a push towards a national policy on medicine sales. The gapers in uniform were introduced during the second half of the 19th century after the government extended authority on the sale of medicines.
The gaper had several identities that suggest background information or a story to the onlooker. The gaper as a jester would "refer to the helper of the traveling person or quack". The helper acted as a patient who, for example, would picture the miracle provided and instantly healed his illness. This whole play was accompanied by many theatrical gestures and grimaces. Then the quack called everyone who wanted to hear how well the treatment worked, to pull in as many customers as possible. The traveling quack would settle in a store with a wooden sign of the trusted helper placed by the store’s front door. As a symbol for the jester or help, the gaper would perform silly acts outside the store or in privacy to entertain customers and bring in more business. The Oriental dressed gaper possibly refers to the use of ingredients such as aloe vera, opium and gum arabic in medicines. It would "reference to the origin of the opium that is in the store sold in the form of sleeping dumplings." It is difficult to say if all the different types of gapers have been around since the beginning. It is also possible that most of the different characters were a later development.
Use
The gaper in the late 16th-century functioned as a hangout out sign on the street. Not only did the figurehead communicate information about the origin of the medicines, but it was also a tool for luring in customers. In this period there were no house numbers. The gaper served as a hangout known as a recognizable point for business. Pharmacies often decorated their storefronts with 'rarities' to invoke customer curiosities. Exotic items such as a stuffed crocodile or tortoise, ostrich eggs, deer antlers, narwhal teeth, sawfish teeth, elk legs, and peacock feathers were popular decorations. Some say that the gaper was used to taunt non-buying bystanders in the street. The gaper could have also served as a mirror image of the drugstore's pharmacist. Historical images show that the cap with a hanging point and tassel, similar to some hats depicted on gapers, was regularly worn by the 16th-century pharmacists.
Saturated market
Beginning in 1840, the demand for medicine quickly became unbalanced. This caused many drugstores to close, taking the gaper figureheads with them. The Act on the Exercise of Medicine in 1865 declared that the pharmacy had to be separate from the drugstore. Pharmacists were required to have a diploma, if not, then they were no longer considered a chemist. This caused the drug stores to change their appearance. The pharmacy displayed the mortar as a symbol for the ability to prepare medicines, while the druggists continued to use the gaper as a symbol. This caused a large decline in the numbers of gapers left in the cities.
Controversy
Recently, gaper figureheads have been stolen from storefronts. However, some have been later returned to new locations throughout the Netherlands. The gaper on the facade of Wijde Heisteeg 4 was stolen and delivered back in 2004 on the sidewalk outside the Municipal Archive on the Amsteldijk. There are stories of gapers being vandalized and used for jokes. A gaper from the Wolvenstraat in Amsterdam was pushed off of its platform by pranksters in March 1960. In 1830, a gaper was stuffed with gunpowder by a group of students and then blown up in the middle of the street. In 1895, the gaper on Heiligeweg 42 was given a large piece of liver sausage in its mouth. The gaper at this address also disappeared in 2008, there is still no clarity as to where it has gone. The reasoning for theft and associating the gaper with jokes are also unclear.
There is speculation that the disappearance of the gaper figureheads is caused by the weather. The gapers are hung outside storefronts and exposed to rain for long periods of time. This has caused many wooden gaper figureheads to rot or split. This is clearly visible with some preserved figureheads in museum archives. The decaying or splitting causes the gaper to fall completely apart over time. Some gapers were protected with a layer of lead-mix and flaxseed oil over the paint. Others received a lead plate on top of their hats so the rain did not end up directly on the wood.
Some gapers disappeared during the Second World War. The gaper that was hanging on Lange Delft in Middelburg was lost in 1940 during a bombing. Made in 1693, it was the oldest preserved gaper in the Netherlands. The gaper on the corner of Gasthuisstraat in Gorinchem disappeared one morning during the war. It is speculated that it was taken as a war booty, or maybe for wood in someone's stove.
There is still uncertainty about the origin and historical reasoning for the gaper. According to folklore, people used to hang monsters with their tongue sticking out off of buildings to ward off evil spirits. Some researchers explore the gaper in connection to certain medieval folklore stories. However, there still isn't much solid evidence as to why certain types of gapers were depicted and why the gaper became the figurehead of pharmacists drug supply.
Conservation
The gaper is now a historical collector’s item. The Royal Archeology Society in Amsterdam received a gaper in both 1882 and 1883. Meanwhile, the Museum of Antiquities in Groningen was given a gaper in 1891 and 1892. Also, Oudheidkundige Vereniging Flehite in Amersfoort received a gaper in 1893. The Haarlem chemist Anton van Os (1889-1982), for example, gathered at least 50 gapers from all over the country from the 1930s until his death. Now about 120 copies from before 1925 have been retained.
See also
Dutch architecture
Figureheads
History of The Netherlands
References
External links
Architectural elements
Architecture in the Netherlands
Outdoor sculptures | Gaper | [
"Technology",
"Engineering"
] | 2,060 | [
"Building engineering",
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976,183 | https://en.wikipedia.org/wiki/Optimized%20Link%20State%20Routing%20Protocol | The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad hoc networks, which can also be used on other wireless ad hoc networks. OLSR is a proactive link-state routing protocol, which uses hello and topology control (TC) messages to discover and then disseminate link state information throughout the mobile ad hoc network. Individual nodes use this topology information to compute next hop destinations for all nodes in the network using shortest hop forwarding paths.
Features specific to OLSR
Link-state routing protocols such as Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS) elect a designated router on every link to perform flooding of topology information. In wireless ad hoc networks, there is different notion of a link, packets can and do go out the same interface; hence, a different approach is needed in order to optimize the flooding process. Using Hello messages the OLSR protocol at each node discovers 2-hop neighbor information and performs a distributed election of a set of multipoint relays (MPRs). Nodes select MPRs such that there exists a path to each of its 2-hop neighbors via a node selected as an MPR. These MPR nodes then source and forward TC messages that contain the MPR selectors. This functioning of MPRs makes OLSR unique from other link state routing protocols in a few different ways: The forwarding path for TC messages is not shared among all nodes but varies depending on the source, only a subset of nodes source link state information, not all links of a node are advertised but only those that represent MPR selections.
Since link-state routing requires the topology database to be synchronized across the network, OSPF and IS-IS perform topology flooding using a reliable algorithm. Such an algorithm is very difficult to design for ad hoc wireless networks, so OLSR doesn't bother with reliability; it simply floods topology data often enough to make sure that the database does not remain unsynchronized for extended periods of time.
Multipoint relays
Multipoint relays (MPRs) relay messages between nodes. They also have the main role in routing and selecting the proper route from any source to any desired destination node.
MPRs advertise link-state information for their MPR selectors (a node selected as a MPR) periodically in their control messages. MPRs are also used to form a route from a given node to any destination in route calculation. Each node periodically broadcasts a Hello message for the link sensing, neighbor detection and MPR selection processes.
Benefits
Being a proactive protocol, routes to all destinations within the network are known and maintained before use. Having the routes available within the standard routing table can be useful for some systems and network applications as there is no route discovery delay associated with finding a new route.
The routing overhead generated, while generally greater than that of a reactive protocol, does not increase with the number of routes being created.
Default and network routes can be injected into the system by Host and Network Association (HNA) messages allowing for connection to the internet or other networks within the OLSR MANET cloud. Network routes are something reactive protocols do not currently execute well.
Timeout values and validity information is contained within the messages conveying information allowing for differing timer values to be used at differing nodes.
Criticisms
The original definition of OLSR does not include any provisions for sensing of link quality; it simply assumes that a link is up if a number of hello packets have been received recently. This assumes that links are bi-modal (either working or failed), which is not necessarily the case on wireless networks, where links often exhibit intermediate rates of packet loss. Implementations such as the open source OLSRd (commonly used on Linux-based mesh routers) have been extended (as of v. 0.4.8) with link quality sensing.
Being a proactive protocol, OLSR uses power and network resources in order to propagate data about possibly unused routes. While this is not a problem for wired access points, and laptops, it makes OLSR unsuitable for sensor networks that try to sleep most of the time.
For small scale wired access points with low CPU power, the open source OLSRd project showed that large scale mesh networks can run with OLSRd on thousands of nodes with very little CPU power on embedded devices.
Being a link-state protocol, OLSR requires a reasonably large amount of bandwidth and CPU power to compute optimal paths in the network. In the typical networks where OLSR is used (which rarely exceed a few hundreds of nodes), this does not appear to be a problem.
By only using MPRs to flood topology information, OLSR removes some of the redundancy of the flooding process, which may be a problem in networks with moderate to large packet loss rates – however the MPR mechanism is self-pruning (which means that in case of packet losses, some nodes that would not have retransmitted a packet, may do so).
Messages
OLSR makes use of "Hello" messages to find its one hop neighbors and its two hop neighbors through their responses. The sender can then select its multipoint relays (MPR) based on the one hop node that offers the best routes to the two hop nodes. Each node has also an MPR selector set, which enumerates nodes that have selected it as an MPR node. OLSR uses topology control (TC) messages along with MPR forwarding to disseminate neighbor information throughout the network. Host and network association (HNA) messages are used by OLSR to disseminate network route advertisements in the same way TC messages advertise host routes.
Hello
Topology control (TC)
Other approaches
The problem of routing in ad hoc wireless networks is actively being researched, and OLSR is but one of several proposed solutions. To many, it is not clear whether a whole new protocol is needed, or whether OSPF could be extended with support for wireless interfaces.
In bandwidth- and power-starved environments, it is interesting to keep the network silent when there is no traffic to be routed. Reactive routing protocols do not maintain routes, but build them on demand. As link-state protocols require database synchronisation, such protocols typically use the distance vector approach, as in AODV and DSDV, or more ad hoc approaches that do not necessarily build optimal paths, such as Dynamic Source Routing.
For more information see the list of ad hoc routing protocols.
OLSR version 2
OLSRv2 was published by the IETF in April 2014 as a standards-track protocol. It maintains many of the key features of the original including MPR selection and dissemination. Key differences are the flexibility and modular design using shared components: packet format packetbb, and neighborhood discovery protocol NHDP. These components are being designed to be common among next generation IETF MANET protocols. Differences in the handling of multiple address and interface enabled nodes is also present between OLSR and OLSRv2.
Implementations
OLSR.ORG – Downloadable code for OLSR on Linux, Windows, Mac OS X, FreeBSD, NetBSD and OpenBSD systems. Features a great deal of documentation, including an informative survey of related work.
NRL-OLSR – Open source code of NRL-OLSR. Works on Windows, MacOS, Linux, and various embedded PDA systems such as Arm/Zaurus and PocketPC as well as simulation environments ns2 and OPNET., http://cs.itd.nrl.navy.mil/focus/
SOURCEFORGE.NET-OLSR – Created by MOVIQUITY and based on studies within the project Workpad, it offers a code in C# to deploy a MANET (Ad Hoc, Meshnet) with protocol OLSR. Developed for WM 6, Win XP and can be adapted to other platforms using .Net Framework and Compact. http://sourceforge.net/projects/wmolsr/
See also
B.A.T.M.A.N., Better Approach To Mobile Adhoc Networking
IEEE 802.1aq
TRILL, Transparent Interconnection of Lots of Links
References
External links
IETF Home Page The Internet Engineering Task Force standards body
olsr.funkfeuer.at currently advancing the olsr.org implementation to improve scalability
Optimized Link State Routing, which includes this Flash Demo.
Pyramid Linux – an embedded distro for embedded x86 boards with OLSR, web interface, etc. Primarily used in Community Networks.
NRL's Networks and Communication Systems Branch – includes project information and open source networking tools and software developed by the U.S. Naval Research Lab.
Wireless networking
Routing
Routing algorithms
Ad hoc routing protocols
Routing protocols | Optimized Link State Routing Protocol | [
"Technology",
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976,344 | https://en.wikipedia.org/wiki/Wienerberger | Wienerberger AG is an Austrian brick maker which is Europe's leading manufacturer of roof tiles and the world’s largest producer of bricks.
In addition to clay products, the company is one of the leading suppliers of plastic pipe in Europe. With its over 200 production sites, the Wienerberger Group generated revenues of €4,224 million and EBITDA of €783,3 million in 2023. It is based in Vienna, Austria. Founded in 1819, the company's shares have been listed on the Vienna Stock Exchange since 1869 and currently have a free float of 100%.
History
In 1819 Wienerberger was founded in Vienna by Alois Miesbach and got its start making use of clay deposits in the Wienerberg area of Vienna. The company embraced innovations such as circular kiln designs, allowing it to have near-continuous production and achieve early success. Miesbach continued to increase manufacturing capacity as the business grew, and by the time of his death in 1857 the company had nine factories, a clay plant, and multiple coal mines. Miesbach's nephew, Heinrich Drasche, took over the company and maintained its dominant position. Starting in 1869 the company traded on the Vienna Stock Exchange.
For the next hundred years Wienerberger was the market leader in Austria. They branched into other related industries, such as ornamental sculptures, roof tiles, and architectural terracotta. After World War One and the fall of the Austro-Hungarian Empire Wienerberger lost many of its foreign operations and rebuilt around its core Austrian businesses.
The company began using mechanical presses for brick production around the 1920s, allowing them to produce perforated bricks. Advanced tunnel kilns were adopted starting in the 1950s, leading to increased manufacturing efficiency. They purchased Bramac, a concrete roof tile manufacturer, in 1972.
Starting with its purchase of Germany's Oltmanns-Gruppe company in 1986, Wienerberger expanded into other regions of Europe and entered the plastic pipe business. In 1999 the company acquired General Shale in the United States and became the world's leading manufacturer of bricks.
The company continued to undertake numerous international acquisitions, including Baggeridge PLC in 2007, Semmelrock in 2010, and Tondach Gleinstätten and Keymer Tiles in 2014. In 2021 the company's American branch, General Shale, acquired Meridian Brick of Georgia, doubling revenues in the United States.
Wienerberger finalized its purchase of French tile manufacturer Terreal in 2024, dramatically expanding its presence throughout Europe and giving it ownership of Creaton and Ludowici Roof Tile. Around the same time General Shale completed its purchase of Summitville Tile, an Ohio floor tile and facing brick manufacturer.
References
External links
Vienna Stock Exchange: Market Data Wienerberger AG
Manufacturing companies based in Vienna
Companies based in Vienna
Companies listed on the Wiener Börse
Companies in the Austrian Traded Index
Brick manufacturers
Roof tiles
Manufacturer of architectural terracotta
Austrian brands | Wienerberger | [
"Engineering"
] | 591 | [
"Manufacturer of architectural terracotta",
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976,365 | https://en.wikipedia.org/wiki/Divided%20differences | In mathematics, divided differences is an algorithm, historically used for computing tables of logarithms and trigonometric functions. Charles Babbage's difference engine, an early mechanical calculator, was designed to use this algorithm in its operation.
Divided differences is a recursive division process. Given a sequence of data points , the method calculates the coefficients of the interpolation polynomial of these points in the Newton form.
Definition
Given n + 1 data points
where the are assumed to be pairwise distinct, the forward divided differences are defined as:
To make the recursive process of computation clearer, the divided differences can be put in tabular form, where the columns correspond to the value of j above, and each entry in the table is computed from the difference of the entries to its immediate lower left and to its immediate upper left, divided by a difference of corresponding x-values:
Notation
Note that the divided difference depends on the values and , but the notation hides the dependency on the x-values. If the data points are given by a function f,
one sometimes writes the divided difference in the notation
Other notations for the divided difference of the function ƒ on the nodes x0, ..., xn are:
Example
Divided differences for and the first few values of :
Thus, the table corresponding to these terms upto two columns has the following form:
Properties
Linearity
Leibniz rule
Divided differences are symmetric: If is a permutation then
Polynomial interpolation in the Newton form: if is a polynomial function of degree , and is the divided difference, then
If is a polynomial function of degree , then
Mean value theorem for divided differences: if is n times differentiable, then for a number in the open interval determined by the smallest and largest of the 's.
Matrix form
The divided difference scheme can be put into an upper triangular matrix:
Then it holds
if is a scalar
This follows from the Leibniz rule. It means that multiplication of such matrices is commutative. Summarised, the matrices of divided difference schemes with respect to the same set of nodes x form a commutative ring.
Since is a triangular matrix, its eigenvalues are obviously .
Let be a Kronecker delta-like function, that is Obviously , thus is an eigenfunction of the pointwise function multiplication. That is is somehow an "eigenmatrix" of : . However, all columns of are multiples of each other, the matrix rank of is 1. So you can compose the matrix of all eigenvectors of from the -th column of each . Denote the matrix of eigenvectors with . Example The diagonalization of can be written as
Polynomials and power series
The matrix
contains the divided difference scheme for the identity function with respect to the nodes , thus contains the divided differences for the power function with exponent .
Consequently, you can obtain the divided differences for a polynomial function by applying to the matrix : If
and
then
This is known as Opitz' formula.
Now consider increasing the degree of to infinity, i.e. turn the Taylor polynomial into a Taylor series.
Let be a function which corresponds to a power series.
You can compute the divided difference scheme for by applying the corresponding matrix series to :
If
and
then
Alternative characterizations
Expanded form
With the help of the polynomial function this can be written as
Peano form
If and , the divided differences can be expressed as
where is the -th derivative of the function and is a certain B-spline of degree for the data points , given by the formula
This is a consequence of the Peano kernel theorem; it is called the Peano form of the divided differences and is the Peano kernel for the divided differences, all named after Giuseppe Peano.
Forward and backward differences
When the data points are equidistantly distributed we get the special case called forward differences. They are easier to calculate than the more general divided differences.
Given n+1 data points
with
the forward differences are defined as
whereas the backward differences are defined as:
Thus the forward difference table is written as:whereas the backwards difference table is written as:
The relationship between divided differences and forward differences is
whereas for backward differences:
See also
Difference quotient
Neville's algorithm
Polynomial interpolation
Mean value theorem for divided differences
Nörlund–Rice integral
Pascal's triangle
References
External links
An implementation in Haskell.
Finite differences
de:Polynominterpolation#Bestimmung der Koeffizienten: Schema der dividierten Differenzen | Divided differences | [
"Mathematics"
] | 926 | [
"Mathematical analysis",
"Finite differences"
] |
976,516 | https://en.wikipedia.org/wiki/Sergei%20Bernstein | Sergei Natanovich Bernstein (, sometimes Romanized as ; 5 March 1880 – 26 October 1968) was a Ukrainian and Soviet mathematician of Jewish origin known for contributions to partial differential equations, differential geometry, probability theory, and approximation theory.
Life
Bernstein was born into the Jewish family of prominent Ukrainian physiologist Nathaniel Bernstein in Odessa. Sergei was brought up in Odessa but his father died on 4 February 1891 just before he was eleven years old. He graduated from high school in 1898. After this, following his mother's wishes, he went with his elder sister to Paris. Bernstein's sister studied biology in Paris and did not return to Ukraine but worked at the Pasteur Institute.
After one year studying mathematics at the Sorbonne, Bernstein decided that he would rather become an engineer and entered the École supérieure d'électricité. However, he continued to be interested in mathematics and spent three terms at the University of Göttingen, beginning in the autumn of 1902, where his studies were supervised by David Hilbert.
Bernstein returned to Paris and submitted his doctoral dissertation "Sur la nature analytique des solutions des équations aux dérivées partielles du second ordre" to the Sorbonne in the spring of 1904. He returned to Russia in 1905 and taught at Kharkiv University from 1908 to 1933. He was made an ordinary professor in 1920. Bernstein later worked at the Mathematical Institute of the USSR Academy of Sciences in Leningrad, and also taught at the University and Polytechnic Institute. From January 1939, Bernstein also worked also at Moscow University. He and his wife were evacuated to Borovoe, Kazakhstan in 1941. From 1943 he worked at the Mathematical Institute in Moscow, and edited Chebyshev’s complete works. In 1947 he was dismissed from the university and became head of the Department of Constructive Function Theory at the Steklov Institute. He died in Moscow in 1968.
Work
Partial differential equations
In his doctoral dissertation, submitted in 1904 to the Sorbonne, Bernstein solved Hilbert's nineteenth problem on the analytic solution of elliptic differential equations. His later work was devoted to Dirichlet's boundary problem for non-linear equations of elliptic type, where, in particular, he introduced a priori estimates.
Probability theory
In 1917, Bernstein suggested the first axiomatic foundation of probability theory, based on the underlying algebraic structure. It was later superseded by the measure-theoretic approach of Kolmogorov.
In the 1920s, he introduced a method for proving limit theorems for sums of dependent random variables.
Approximation theory
Through his application of Bernstein polynomials, he laid the foundations of constructive function theory, a field studying the connection between smoothness properties of a function and its approximations by polynomials. In particular, he proved the Weierstrass approximation theorem and Bernstein's theorem (approximation theory). Bernstein polynomials also form the mathematical basis for Bézier curves, which later became important in computer graphics.
International Congress of Mathematicians
Bernstein was an invited speaker at the International Congress of Mathematicians (ICM) in Cambridge, England in 1912 and in Bologna in 1928 and a plenary speaker at the ICM in Zurich. His plenary address Sur les liaisons entre quantités aléatoires was read by Bohuslav Hostinsky.
Honors and awards
Academician of the Academy of Sciences of the Soviet Union (1929)
Member of the German Mathematical Society (1926)
Member of the French Mathematical Society (1944)
Honorary Doctor of Science of the University of Algiers (1944)
Honorary Doctor of Science of the University of Paris (1945)
Foreign member of the French Academy of Sciences (1955)
Stalin Prize (1942)
Order of Lenin (1945)
Order of the Red Banner of Labour (1944)
Publications
S. N. Bernstein, Collected Works (Russian):
vol. 1, The Constructive Theory of Functions (1905–1930), translated: Atomic Energy Commission, Springfield, Va, 1958
vol. 2, The Constructive Theory of Functions (1931–1953)
vol. 3, Differential equations, calculus of variations and geometry (1903–1947)
vol. 4, Theory of Probability. Mathematical statistics (1911–1946)
S. N. Bernstein, The Theory of Probabilities (Russian), Moscow, Leningrad, 1946
See also
A priori estimate
Bernstein algebra
Bernstein's inequality (mathematical analysis)
Bernstein inequalities in probability theory
Bernstein polynomial
Bernstein's problem
Bernstein's theorem (approximation theory)
Bernstein's theorem on monotone functions
Bernstein–von Mises theorem
Stone–Weierstrass theorem
Notes
References
External links
Sergei Natanovich Bernstein and history of approximation theory from Technion — Israel Institute of Technology
Author profile in the database zbMATH
1880 births
1968 deaths
Scientists from Odesa
People from Odessky Uyezd
Odesa Jews
Soviet mathematicians
Approximation theorists
Mathematical analysts
PDE theorists
Probability theorists
19th-century mathematicians from the Russian Empire
20th-century Russian mathematicians
Expatriates from the Russian Empire in France
University of Paris alumni
Academic staff of Moscow State University
Academic staff of the National University of Kharkiv
Corresponding Members of the Russian Academy of Sciences (1917–1925)
Full Members of the USSR Academy of Sciences
Full Members of the All-Ukrainian Academy of Sciences
Recipients of the Stalin Prize
Recipients of the Order of Lenin
Recipients of the Order of the Red Banner of Labour
Burials at Novodevichy Cemetery
Russian scientists | Sergei Bernstein | [
"Mathematics"
] | 1,076 | [
"Mathematical analysis",
"Mathematical analysts"
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976,586 | https://en.wikipedia.org/wiki/Shuttle%E2%80%93Mir%20program | The Shuttle–Mir program () was a collaborative space program between Russia and the United States that involved American Space Shuttles visiting the Russian space station Mir, Russian cosmonauts flying on the Shuttle, and an American astronaut flying aboard a Soyuz spacecraft to allow American astronauts to engage in long-duration expeditions aboard Mir.
The project, sometimes called "Phase One", was intended to allow the United States to learn from Russian experience with long-duration spaceflight and to foster a spirit of cooperation between the two nations and their space agencies, the National Aeronautics and Space Administration (NASA) and the Russian Space Agency (PKA). The project helped to prepare the way for further cooperative space ventures; specifically, "Phase Two" of the joint project, the construction of the International Space Station (ISS). The program was announced in 1993, the first mission started in 1994 and the project continued until its scheduled completion in 1998. Eleven Space Shuttle missions, a joint Soyuz flight and almost 1,000 cumulative days in space for American astronauts occurred over the course of seven long-duration expeditions. In addition to Space Shuttle launches to Mir the United States also fully funded and equipped with scientific equipment the Spektr module (launched in 1995) and the Priroda module (launched in 1996), making them de facto U.S. modules during the duration of the Shuttle-Mir program.
During the four-year program, many firsts in spaceflight were achieved by the two nations, including the first American astronaut to launch aboard a Soyuz spacecraft, the largest spacecraft ever to have been assembled at that time in history, and the first American spacewalk using a Russian Orlan spacesuit.
The program was marred by various concerns, notably the safety of Mir following a fire, a Russian spacecraft colliding with Spektr rendering it uninhabitable, financial issues with the cash-strapped Russian space program and worries from astronauts about the attitudes of the program administrators. Nevertheless, a large amount of science, expertise in space station construction and knowledge in working in a cooperative space venture was gained from the combined operations, allowing the construction of the ISS to proceed much more smoothly than would have otherwise been the case.
Background
The origins of the Shuttle–Mir program can be traced back to the 1975 Apollo–Soyuz Test Project, that resulted in a joint US/Soviet mission during the détente period of the Cold War and the docking between a US Apollo spacecraft and a Soviet Soyuz spacecraft. This was followed by the talks between NASA and Intercosmos in the 1970s about a "Shuttle–Salyut" program to fly Space Shuttle missions to a Salyut space station, with later talks in the 1980s even considering flights of the future Soviet shuttles from the Buran programme to a future US space station – this "Shuttle–Salyut" program never materialized however during the existence of the Soviet Intercosmos program.
This changed after the Dissolution of the Soviet Union: the end of Cold War and Space Race resulted in funding for the US modular space station (originally named Freedom), which was planned since the early 1980s, being slashed.
Similar budgetary difficulties were being faced by other nations with space station projects, prompting American government officials to start negotiations with partners in Europe, Russia, Japan, and Canada in the early 1990s to begin a collaborative, multi-national, space station project.
In the Russian Federation, as the successor to much of the Soviet Union and its space program, the deteriorating economic situation in the post-Soviet economic chaos led to growing financial problems of the now Russian space station program. The construction of the Mir-2 space station as a replacement for the aging Mir became illusionary, though only after its base block, DOS-8, had been built. These developments resulted in bringing the former adversaries together with the Shuttle–Mir Program, which would pave the way to the International Space Station, a joint project with several international partners.
In June 1992, American President George H. W. Bush and Russian president Boris Yeltsin agreed to co-operate on space exploration by signing the Agreement between the United States of America and the Russian Federation Concerning Cooperation in the Exploration and Use of Outer Space for Peaceful Purposes. This agreement called for setting up a short, joint space project, during which one American astronaut would board the Russian space station Mir and two Russian cosmonauts would board a Space Shuttle.
In September 1993, American Vice-President Al Gore Jr., and Russian Prime Minister Viktor Chernomyrdin announced plans for a new space station, which eventually became the International Space Station. They also agreed, in preparation for this new project, that the United States would be heavily involved in the Mir project in the years ahead, under the code name "Phase One" (the construction of the ISS being "Phase Two").
The first Space Shuttle flight to Mir was a rendezvous mission without docking on STS-63. This was followed during the course of the project by nine Shuttle–Mir docking missions, from STS-71 to STS-91. The Shuttle rotated crews and delivered supplies, and one mission, STS-74, carried a docking module and a pair of solar arrays to Mir. Various scientific experiments were also conducted, both on shuttle flights and long-term aboard the station. The project also saw the launch of two new modules, Spektr and Priroda, to Mir, which were used by American astronauts as living quarters and laboratories to conduct the majority of their science aboard the station. These missions allowed NASA and Roscosmos to learn a great deal about how best to work with international partners in space and how to minimize the risks associated with assembling a large space station in orbit, as would have to be done with the ISS.
The project also served as a political ruse on the part of the American government, providing a diplomatic channel for NASA to take part in the funding of the cripplingly under-funded Russian space program. This in turn allowed the newly fledged Russian government to keep Mir operating, in addition to the Russian space program as a whole, ensuring the Russian government remained friendly towards the United States.
Increments
In addition to the flights of the Shuttle to Mir, Phase One also featured seven "Increments" aboard the station, long-duration flights aboard Mir by American astronauts. The seven astronauts who took part in the Increments, Norman Thagard, Shannon Lucid, John Blaha, Jerry Linenger, Michael Foale, David Wolf and Andrew Thomas, were each flown in turn to Star City, Russia, to undergo training in various aspects of the operation of Mir and the Soyuz spacecraft used for transport to and from the Station. The astronauts also received practice in carrying out spacewalks outside Mir and lessons in the Russian language, which would be used throughout their missions to talk with the other cosmonauts aboard the station and Mission Control in Russia, the TsUP.
During their expeditions aboard Mir, the astronauts carried out various experiments, including growth of crops and crystals, and took hundreds of photographs of the Earth. They also assisted in the maintenance and repair of the aging station, following various incidents with fires, collisions, power losses, uncontrolled spins and toxic leaks. In all, the American astronauts would spend almost a thousand days aboard Mir, allowing NASA to learn a great deal about long-duration spaceflight, particularly in the areas of astronaut psychology and how best to arrange experiment schedules for crews aboard space stations.
Mir
Mir was constructed between 1986 and 1996 and was the world's first modular space station. It was the first consistently inhabited long-term research station in space, and previously held the record for longest continuous human presence in space, at eight days short of ten years. Mir purpose was to provide a large and habitable scientific laboratory in space, and, through a number of collaborations, including Intercosmos and Shuttle–Mir, was made internationally accessible to cosmonauts and astronauts of many different countries. The station existed until March 23, 2001, at which point it was deliberately deorbited, and broke apart during atmospheric re-entry.
Mir was based upon the Salyut series of space stations previously launched by the Soviet Union (seven Salyut space stations had been launched since 1971), and was mainly serviced by Russian-crewed Soyuz spacecraft and Progress cargo ships. The Buran space shuttle was anticipated to visit Mir, but its program was canceled after its first uncrewed spaceflight. Visiting US Space Shuttles used an Androgynous Peripheral Attach System docking collar originally designed for Buran, mounted on a bracket originally designed for use with the American Space Station Freedom.
With the Space Shuttle docked to Mir, the temporary enlargements of living and working areas amounted to a complex that was the world's largest spacecraft at that time, with a combined mass of .
Space Shuttle
The Space Shuttle was a partially reusable low Earth orbital spacecraft system that was operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft of which it was the only item funded for development. The first of four orbital test flights occurred in 1981, leading to operational flights beginning in 1982. In addition to the prototype, whose completion was cancelled, five complete Shuttle systems were built and used on a total of 135 missions from 1981 to 2011, launched from the Kennedy Space Center (KSC) in Florida. The Shuttle fleet's total mission time was 1322 days, 19 hours, 21 minutes and 23 seconds.
The Space Shuttle carried large payloads to various orbits, and, during the Shuttle–Mir and ISS programs, provided crew rotation and carried various supplies, modules and pieces of equipment to the stations. Each Shuttle was designed for a projected lifespan of 100 launches or 10 years' operational life.
Nine docking missions were flown to Mir, from 1995 to 1997 during "Phase One": Space Shuttle docked seven times to Mir, with and each flying one docking mission to Mir. As Space Shuttle was the oldest and heaviest of the fleet, it was not suited for efficient operations at Mir (and later the ISS's) 51.6-degree inclination – Columbia was therefore not retrofitted with the necessary external airlock and Orbital Docking System, and never flew to a space station.
Timeline
New cooperation begins (1994)
Phase One of the Shuttle–Mir program began on February 3, 1994, with the launch of Space Shuttle Discovery on its 18th mission, STS-60. The eight-day mission was the first shuttle flight of that year, the first flight of a Russian cosmonaut, Sergei Krikalev, aboard the American shuttle, and marked the start of increased cooperation in space for the two nations, 37 years after the Space Race began. Part of an international agreement on human space flight, the mission was the second flight of the Spacehab pressurized module and marked the hundredth "Getaway Special" payload to fly in space. The primary payload for the mission was the Wake Shield Facility (or WSF), a device designed to generate new semiconductor films for advanced electronics. The WSF was flown at the end of Discovery robotic arm over the course of the flight. During the mission, the astronauts aboard Discovery also carried out various experiments aboard the Spacehab module in the Orbiter's payload bay, and took part in a live bi-directional audio and downlink video hookup between themselves and the three cosmonauts on board Mir, Valeri Polyakov, Viktor Afanasyev and Yury Usachev (flying Mir expeditions LD-4 and EO-15).
America arrives at Mir (1995)
1995 began with the launch of the Space Shuttle Discovery on February 3. Discovery's mission, STS-63, was the second Space Shuttle flight in the program and the first flight of the shuttle with a female pilot, Eileen Collins. Referred to as the "near-Mir" mission, the eight-day flight saw the first rendezvous of a Space Shuttle with Mir, as Russian cosmonaut Vladimir Titov and the rest of Discovery crew approached within of Mir. Following the rendezvous, Collins performed a flyaround of the station. The mission, a dress rehearsal for the first docked mission in the program, STS-71, also carried out testing of various techniques and pieces of equipment that would be used during the docking missions that followed.
Five weeks after Discovery flight, the March 14 launch of Soyuz TM-21 carried expedition EO-18 to Mir. The crew consisted of cosmonauts Vladimir Dezhurov and Gennady Strekalov and NASA astronaut Norman Thagard, who became the first American to fly into space aboard the Soyuz spacecraft. During the course of their 115-day expedition, the Spektr science module (which served as living and working space for American astronauts) was launched aboard a Proton rocket and docked to Mir. Spektr carried more than of research equipment from America and other nations. The expedition's crew returned to Earth aboard Space Shuttle Atlantis following the first Shuttle–Mir docking during mission STS-71.
The primary objectives of STS-71, launched on June 27, called for the Space Shuttle Atlantis to rendezvous and perform the first docking between an American Space Shuttle and the station. On June 29, Atlantis successfully docked with Mir, becoming the first US spacecraft to dock with a Russian spacecraft since the Apollo-Soyuz Test Project in 1975. Atlantis delivered cosmonauts Anatoly Solovyev and Nikolai Budarin, who would form the expedition EO-19 crew, and retrieved astronaut Norman Thagard and cosmonauts Vladimir Dezhurov and Gennady Strekalov of the expedition EO-18 crew. Atlantis also carried out on-orbit joint US-Russian life sciences investigations aboard a Spacelab module and performed a logistical resupply of the station.
The final Shuttle flight of 1995, STS-74, began with the November 12 launch of Space Shuttle Atlantis, and delivered the Russian-built Docking Module to Mir, along with a new pair of solar arrays and other hardware upgrades for the station. The Docking Module was designed to provide more clearance for Shuttles in order to prevent any collisions with Mir solar arrays during docking, a problem which had been overcome during STS-71 by relocating the station's Kristall module to a different location on the station. The module, attached to Kristall docking port, prevented the need for this procedure on further missions. During the course of the flight, nearly of water were transferred to Mir and experiment samples including blood, urine and saliva were moved to Atlantis for return to Earth.
Priroda (1996)
Continuous US presence aboard Mir started in 1996 with the March 22 launch of Atlantis on mission STS-76, when the Second Increment astronaut Shannon Lucid was transferred to the station. STS-76 was the third docking mission to Mir, which also demonstrated logistics capabilities through deployment of a Spacehab module, and placed experiment packages aboard Mir docking module, which marked the first spacewalk which occurred around docked vehicles. The spacewalks, carried out from Atlantis crew cabin, provided valuable experience for astronauts in order to prepare for later assembly missions to the International Space Station.
Lucid became the first American woman to live on station, and, following a six-week extension to her Increment due to issues with Shuttle Solid Rocket Boosters, her 188-day mission set the US single spaceflight record. During Lucid's time aboard Mir, the Priroda module, with about of US science hardware, was docked to Mir. Lucid made use of both Priroda and Spektr to carry out 28 different science experiments and as living quarters.
Her stay aboard Mir ended with the flight of Atlantis on STS-79, which launched on September 16. STS-79 was the first Shuttle mission to carry a double Spacehab module. More than of supplies were transferred to Mir, including water generated by Atlantis fuel cells, and experiments that included investigations into superconductors, cartilage development, and other biology studies. About of experiment samples and equipment were also transferred back from Mir to Atlantis, making the total transfer the most extensive yet.
This, the fourth docking, also saw John Blaha transferring onto Mir to take his place as resident Increment astronaut. His stay on the station improved operations in several areas, including transfer procedures for a docked space shuttle, "hand-over" procedures for long-duration American crew members and "Ham" amateur radio communications.
Two spacewalks were carried out during his time aboard. Their aim was to remove electrical power connectors from a 12-year-old solar power array on the base block and reconnect the cables to the more efficient new solar power arrays. In all, Blaha spent four months with the Mir-22 cosmonaut crew conducting material science, fluid science, and life science research, before returning to Earth the next year aboard Atlantis on STS-81.
Fire and collision (1997)
In 1997 STS-81 replaced Increment astronaut John Blaha with Jerry Linenger, after Blaha's 118-day stay aboard Mir. During this fifth shuttle docking, the crew of Atlantis moved supplies to the station and returned to Earth the first plants to complete a life cycle in space; a crop of wheat planted by Shannon Lucid. During five days of mated operations, the crews transferred nearly of logistics to Mir, and transferred of materials back to Atlantis (the most materials transferred between the two spacecraft to that date).
The STS-81 crew also tested the Shuttle Treadmill Vibration Isolation and Stabilization System (TVIS), designed for use in the Zvezda module of the International Space Station. The shuttle's small vernier jet thrusters were fired during the mated operations to gather engineering data for "reboosting" the ISS. After undocking, Atlantis performed a fly-around of Mir, leaving Linenger aboard the station.
During his Increment, Linenger became the first American to conduct a spacewalk from a foreign space station and the first to test the Russian-built Orlan-M spacesuit alongside Russian cosmonaut Vasili Tsibliyev. All three crewmembers of expedition EO-23 performed a "fly-around" in the Soyuz spacecraft, first undocking from one docking port of the station, then manually flying to and redocking the capsule at a different location. This made Linenger the first American to undock from a space station aboard two different spacecraft (Space Shuttle and Soyuz).
Linenger and his Russian crewmates Vasili Tsibliyev and Aleksandr Lazutkin faced several difficulties during the mission. These included the most severe fire aboard an orbiting spacecraft (caused by a backup oxygen-generating device), failures of various on board systems, a near collision with a Progress resupply cargo ship during a long-distance manual docking system test and a total loss of station electrical power. The power failure also caused a loss of attitude control, which led to an uncontrolled "tumble" through space.
The next NASA astronaut to stay on Mir was Michael Foale. Foale and Russian mission specialist Elena Kondakova boarded Mir from Atlantis on mission STS-84. The STS-84 crew transferred 249 items between the two spacecraft, along with water, experiment samples, supplies and hardware. One of the first items transferred to Mir was an Elektron oxygen-generating unit. Atlantis was stopped three times while backing away during the undocking sequence on May 21. The aim was to collect data from a European sensor device designed for future rendezvous of ESA's Automated Transfer Vehicle (ATV) with the International Space Station.
Foale's Increment proceeded fairly normally until June 25, when a resupply ship collided with solar arrays on the Spektr module during the second test of the Progress manual docking system, TORU. The module's outer shell was hit and holed, which caused the station to lose pressure. This was the first on-orbit depressurization in the history of spaceflight. The crew quickly cut cables leading to the module and closed Spektr hatch in order to prevent the need to abandon the station in their Soyuz lifeboat. Their efforts stabilized the station's air pressure, whilst the pressure in Spektr, containing many of Foale's experiments and personal effects, dropped to a vacuum. Fortunately, food, water and other vital supplies were stored in other modules, and salvage and replanning effort by Foale and the science community minimized the loss of research data and capability.
In an effort to restore some of the power and systems lost following the isolation of Spektr and to attempt to locate the leak, Mir new commander Anatoly Solovyev and flight engineer Pavel Vinogradov carried out a salvage operation later in the mission. They entered the empty module during a so-called "IVA" spacewalk, inspecting the condition of hardware and running cables through a special hatch from Spektr systems to the rest of the station. Following these first investigations, Foale and Solovyev conducted a 6-hour EVA on the surface of Spektr to inspect the damaged module.
After these incidents, the US Congress and NASA considered whether to abandon the program out of concern for astronauts' safety but NASA administrator Daniel Goldin decided to continue the program. The next flight to Mir, STS-86, brought Increment astronaut David Wolf to the station.
STS-86 performed the seventh Shuttle–Mir docking, the last of 1997. During Atlantis stay crew members Titov and Parazynski conducted the first joint US–Russian extravehicular activity during a Shuttle mission, and the first in which a Russian wore a US spacesuit. During the five-hour spacewalk, the pair affixed a Solar Array Cap to the Docking Module, for a future attempt by crew members to seal off the leak in Spektr hull. The mission returned Foale to Earth, along with samples, hardware, and an old Elektron oxygen generator, and dropped Wolf off on the Station ready for his 128-day Increment. Wolf had originally been scheduled to be the final Mir astronaut, but was chosen to go on the Increment instead of astronaut Wendy Lawrence. Lawrence was deemed ineligible for flight because of a change in Russian requirements after the Progress supply vehicle collision. The new rules required that all Mir crew members should be trained and ready for spacewalks, but a Russian spacesuit could not be prepared for Lawrence in time for launch.
Phase One closes down (1998)
The final year of Phase One began with the flight of Space Shuttle Endeavour on STS-89. The mission delivered cosmonaut Salizhan Sharipov to Mir and replaced David Wolf with Andy Thomas, following Wolf's 119-day Increment.
During his Increment, the last of the program, Thomas worked on 27 science investigations into areas of advanced technology, Earth sciences, human life sciences, microgravity research, and ISS risk mitigation. His stay on Mir, considered the smoothest of the entire Phase One program, featured weekly "Letters from the Outpost" from Thomas and passed two milestones for length of spaceflight—815 consecutive days in space by American astronauts since the launch of Shannon Lucid on the STS-76 mission in March 1996, and 907 days of Mir occupancy by American astronauts dating back to Norman Thagard's trip to Mir in March 1995.
Thomas returned to Earth on the final Shuttle–Mir mission, STS-91. The mission closed out Phase One, with the EO-25 and STS-91 crews transferring water to Mir and exchanging almost of cargo experiments and supplies between the two spacecraft. Long-term American experiments that had been on board Mir were also moved into Discovery. Hatches were closed for undocking at 9:07 a.m. Eastern Daylight Time (EDT) on June 8 and the spacecraft separated at 12:01 p.m. EDT that day.
Phases Two and Three: ISS (1998–present)
With the landing of Discovery on June 12, 1998, the Phase One program concluded. Techniques and equipment developed during the program assisted the development of Phase Two: initial assembly of the International Space Station (ISS). The arrival of the Destiny Laboratory Module in 2001 marked the end of Phase Two and the start of Phase Three, the final outfitting of the station, completed in 2012.
In 2015, a reconfiguration of the American segment was completed to allow its docking ports to accommodate NASA-sponsored commercial crew vehicles, that were expected to start visiting the ISS in 2018.
, the ISS has a pressurized volume of , and its pressurized modules total in length, plus a large truss structure that spans , making it the largest spacecraft ever assembled. The completed station consists of five laboratories and is able to support six crew members. With over of habitable volume and a mass of the completed station is almost twice the size of the combined Shuttle–Mir spacecraft.
Phases Two and Three are intended to continue both international cooperation in space and zero-gravity scientific research, particularly regarding long-duration spaceflight. By spring 2015, Roscosmos, NASA, and the Canadian Space Agency (CSA) have agreed to extend the ISS's mission from 2020 to 2024.
In 2018 that was then extended out to 2030. The results of this research will provide considerable information for long-duration expeditions to the Moon and flights to Mars.
Following the intentional deorbiting of Mir on 23 March 2001, the ISS became the only space station in orbit around Earth. It retained that distinction until the launch of Chinese Tiangong-1 space laboratory on 29 September 2011.
Mir legacy lives on in the station, bringing together five space agencies in the cause of exploration and allowing those space agencies to prepare for their next leap into space, to the Moon, Mars and beyond.
Complete list of Shuttle–Mir missions
Controversy
Safety and scientific return
Criticism of the program was primarily concerned with the safety of the aging Mir, particularly following the fire aboard the station and collision with the Progress supply vessel in 1997.
The fire, caused by the malfunction of a backup solid-fuel oxygen generator (SFOG), burned for, according to various sources, between 90 seconds and 14 minutes, and produced large amounts of toxic smoke that filled the station for around 45 minutes. This forced the crew to don respirators, but some of the respirator masks initially worn were broken. Fire extinguishers mounted on the walls of the modules were immovable. The fire occurred during a crew rotation, and as such there were six men aboard the station rather than the usual three. Access to one of the docked Soyuz lifeboats was blocked, which would have prevented escape by half of the crew. A similar incident had occurred on an earlier Mir expedition, although in that case the SFOG burned for only a few seconds.
The near-miss and collision incidents presented further safety issues. Both were caused by failure of the same piece of equipment, the TORU manual docking system, which was undergoing tests at the time. The tests were called in order to gauge the performance of long-distance docking in order to enable the cash-strapped Russians to remove the expensive Kurs automatic docking system from the Progress ships.
In the wake of the collision NASA and the Russian Space Agency instigated numerous safety councils who were to determine the cause of the accident. As their investigations progressed, the two space agencies results began moving in different directions. NASA's results blamed the TORU docking system, as it required the astronaut or cosmonaut in charge to dock the Progress without the aide of any sort of telemetry or guidance. However, the Russian Space Agency's results blamed the accident on crew error, accusing their own cosmonaut of miscalculating the distance between the Progress and the space station. The Russian Space Agency's results were heavily criticized, even by their own cosmonaut Tsibliyev, on whom they were placing the blame. During his first press conference following his return to Earth, the cosmonaut expressed his anger and disapproval by declaring, "It has been a long tradition here in Russia to look for scapegoats."
The accidents also added to the increasingly vocal criticism of the aging station's reliability. Astronaut Blaine Hammond claimed that his safety concerns about Mir were ignored by NASA officials, and that records of safety meetings "disappeared from a locked vault". Mir was originally designed to fly for five years but eventually flew for three times that length of time. During Phase One and afterward, the station was showing her age—constant computer crashes, loss of power, uncontrolled tumbles through space and leaking pipes were an ever-present concern for crews. Various breakdowns of Mir Elektron oxygen-generating system were also a concern. These breakdowns led crews to become increasingly reliant on the SFOG systems that caused the fire in 1997. SFOG systems continue to be a problem aboard the ISS.
Another issue of controversy was the scale of its actual scientific return, particularly following the loss of the Spektr science module. Astronauts, managers and various members of the press all complained that the benefits of the program were outweighed by the risks associated with it, especially considering the fact that most of the US science experiments had been contained within the holed module. As such, a large amount of American research was inaccessible, reducing the science that could be performed. The safety issues caused NASA to reconsider the future of the program at various times. The agency eventually decided to continue and came under fire from various areas of the press regarding that decision.
Attitudes
Attitudes of the Russian space program and NASA towards Phase One were also of concern to the astronauts involved. Because of Russia's financial issues, many workers at the TsUP felt that the mission hardware and continuation of Mir was more important than the lives of the cosmonauts aboard the station. As such the program was run very differently compared to American programs: cosmonauts had their days being planned for them to the minute, actions (such as docking) which would be performed manually by shuttle pilots were all carried out automatically, and cosmonauts had their pay docked if they made any errors during their flights. Americans learned aboard Skylab and earlier space missions that this level of control was not productive and had since made mission plans more flexible. The Russians, however, would not budge, and many felt that significant work time was lost because of this.
Following the two accidents in 1997, astronaut Jerry Linenger felt that the Russian authorities attempted a cover-up to downplay the significance of the incidents, fearing that the Americans would back out of the partnership. A large part of this "cover-up" was the seeming impression that the American astronauts were not in fact "partners" aboard the station, but were instead "guests". NASA staff did not find out for several hours about the fire and collision and found themselves kept out of decision-making processes. NASA became more involved when Russian mission controllers intended to place blame for the accident entirely on Vasily Tsibliyev. It was only after the application of significant pressure from NASA that this stance was changed.
At various times during the program, NASA managers and personnel found themselves limited in terms of resources and manpower, particularly as Phase Two geared up, and had a hard time getting anywhere with NASA administration. One particular area of contention was with crew assignments to missions. Many astronauts allege that the method of selection prevented the most skilled people from performing roles they were best-suited for.
Finances
Since the breakup of the Soviet Union a few years earlier, the Russian economy had been slowly collapsing and the budget for space exploration was reduced by around 80%. Before and after Phase One, a great deal of Russia's space finances came from flights of astronauts from Europe and other countries, with one Japanese TV station paying $9.5 million to have one of their reporters, Toyohiro Akiyama, flown aboard Mir. By the start of Phase One, cosmonauts regularly found their missions extended to save money on launchers, the six-yearly flights of the Progress had been reduced to three, and there was a distinct possibility of Mir being sold for around $500 million.
Critics argued that the $325 million contract NASA had with Russia was the only thing keeping the Russian space program alive, and only the Space Shuttle was keeping Mir aloft. NASA also had to pay hefty fees for training manuals and equipment used by astronauts training at Star City. Problems came to a head when ABC's Nightline revealed that there was a distinct possibility of embezzlement of American finances by the Russian authorities in order to build a suite of new cosmonaut houses in Moscow, or else that the building projects were being funded by the Russian Mafia. NASA administrator Goldin was invited onto Nightline to defend the homes but he refused to comment. NASA's office for external affairs was quoted as saying, "What Russia does with its own money is their business."
See also
List of heaviest spacecraft
Skylab 4
References
External links
History of Shuttle–Mir (NASA)
Diary of Linenger Increment (NASA)
Shuttle–Mir Lessons for the International Space Station James Oberg, Contributing Editor, SPECTRUM magazine June 1998, pp. 28–37
Human spaceflight programs
Mir
Space Shuttle missions
NASA programs
Russia–United States relations | Shuttle–Mir program | [
"Engineering"
] | 6,844 | [
"Space programs",
"Human spaceflight programs"
] |
976,642 | https://en.wikipedia.org/wiki/Multiplication%20operator | In operator theory, a multiplication operator is an operator defined on some vector space of functions and whose value at a function is given by multiplication by a fixed function . That is,
for all in the domain of , and all in the domain of (which is the same as the domain of ).
Multiplication operators generalize the notion of operator given by a diagonal matrix. More precisely, one of the results of operator theory is a spectral theorem that states that every self-adjoint operator on a Hilbert space is unitarily equivalent to a multiplication operator on an L2 space.
These operators are often contrasted with composition operators, which are similarly induced by any fixed function . They are also closely related to Toeplitz operators, which are compressions of multiplication operators on the circle to the Hardy space.
Properties
A multiplication operator on , where is -finite, is bounded if and only if is in . In this case, its operator norm is equal to .
The adjoint of a multiplication operator is , where is the complex conjugate of . As a consequence, is self-adjoint if and only if is real-valued.
The spectrum of a bounded multiplication operator is the essential range of ; outside of this spectrum, the inverse of is the multiplication operator
Two bounded multiplication operators and on are equal if and are equal almost everywhere.
Example
Consider the Hilbert space of complex-valued square integrable functions on the interval . With , define the operator
for any function in . This will be a self-adjoint bounded linear operator, with domain all of and with norm . Its spectrum will be the interval (the range of the function defined on ). Indeed, for any complex number , the operator is given by
It is invertible if and only if is not in , and then its inverse is
which is another multiplication operator.
This example can be easily generalized to characterizing the norm and spectrum of a multiplication operator on any Lp space.
See also
Translation operator
Shift operator
Transfer operator
Decomposition of spectrum (functional analysis)
References
Functional analysis | Multiplication operator | [
"Mathematics"
] | 412 | [
"Functions and mappings",
"Mathematical relations",
"Mathematical objects",
"Linear operators"
] |
976,663 | https://en.wikipedia.org/wiki/Industrial%20and%20multiphase%20power%20plugs%20and%20sockets | Industrial and multiphase plugs and sockets provide a connection to the electrical mains rated at higher voltages and currents than household plugs and sockets. They are generally used in polyphase systems, with high currents, or when protection from environmental hazards is required. Industrial outlets may have weatherproof covers, waterproofing sleeves, or may be interlocked with a switch to prevent accidental disconnection of an energized plug. Some types of connectors are approved for hazardous areas such as coal mines or petrochemical plants, where flammable gas may be present.
Almost all three-phase power plugs have an earth (ground) connection, but may not have a neutral because three-phase loads such as motors do not need the neutral. Such plugs have only four prongs (earth, and the three phases). An example of a socket with neutral is the L21-30 (30 A) and the L21-20 (20 A) both of which have five pins (earth, neutral, and X, Y, Z phases).
While some forms of power plugs and sockets are set by international standards, countries may have their own different standards and regulations. For example, the colour-coding of wires may not be the same as for small mains plugs.
Concepts and terminology
Generally the plug is the movable connector attached to an electrically operated device's mains cable, and the socket is fixed on equipment or a building structure and connected to an energised electrical circuit. The plug has protruding pins or, in US terminology, blades (referred to as male) that fit into matching slots or holes (called female) in the sockets. A plug is defined in IEC 60050 as an accessory having pins designed to engage with the contacts of a socket-outlet, also incorporating means for the electrical connection and mechanical retention of flexible cables or cords, a plug does not contain components which modify the electrical output from the electrical input (except where a switch or fuse is provided as a means of disconnecting the output from input). In this article, the term 'plug' is used in the sense defined by IEC 60050. Sockets are designed to prevent exposure of bare energised contacts.
To reduce the risk of users accidentally touching energized conductors and thereby experiencing electric shock, plug and socket systems often incorporate safety features in addition to the recessed slots or holes of the energized socket. These may include plugs with insulated sleeves, recessed sockets, sockets with blocking shutters, and sockets designed to accept only compatible plugs inserted in the correct orientation.
The term plug is in general and technical use in all forms of English, common alternatives being power plug,
electric plug,
and (in the UK) plug top.
The normal technical term (in both British and International English) for an AC power socket is socket-outlet,
but in non-technical common use a number of other terms are used.
In British English the general term is socket, but there are numerous common alternatives, including power point, plug socket,
wall socket,
and wall plug.
In American English receptacle and outlet are common, sometimes with qualifiers such as wall outlet, electrical outlet and electrical receptacle, all of these sometimes to be found in the same document.
Electrical sockets for industrial, commercial and domestic purposes generally provide two or more current carrying (live) connections to the supply conductors. These connections are classified as poles. A pole will be either a neutral connection or a line
Neutral is usually very near to earth potential, usually being earthed either at the distribution board or at the substation. Line (also known as phase or hot, and commonly, but technically incorrectly, as live) carries the full supply voltage relative to the neutral (and to earth).
Single phase sockets are classified as two pole (2P) and provide a single line contact and a neutral contact. In addition, a protective earth (Ground in American terminology) contact is usually, but not always, present, in which case the socket is classified as two pole and earth(2P+E).
Three phase sockets provide three line contacts, they may also include either or both of a neutral and protective earth contact. The designations of the three contacts may vary. The IEC standards use the Line designations L1, L2 and L3. NEMA standards use the Phase designations X, Y and Z.
Sockets intended for use with the American split Phase distribution system may have two line contacts and neutral. In this case the line designators X and Y are used. They may also include a protective earth contact.
Europe
IEC 60309 system
In Europe, the most common range of heavy commercial and industrial connectors are made to IEC 60309 (formerly IEC 309) and various standards based on it (including BS 4343 and BS EN 60309-2). These are often referred to in the UK as CEE industrial, CEEform or simply CEE plugs, or as "Commando connectors" (after the MK Commando brand name for these connectors).
The maximum voltage rating of IEC 60309 connectors is 1000 V DC or AC; the maximum current rating is 800 A; and the maximum frequency 500 Hz. Plugs are available in P+N+E (unbalanced single phase with neutral), 2P+E (balanced single phase), 3P+E (3 phase without neutral), and 3P+N+E (three phase with neutral). Current ratings available include 16 A, 32 A, 63 A, 125 A and 200 A.
Voltage rating and other characteristics are represented by a colour code (in three-phase plugs the stated voltage is the phase-phase voltage, not the phase-neutral voltage). Plugs have the earth pin of a larger diameter than the others, and located in different places depending on the voltage rating, making it impossible to mate, for instance, a blue plug with a yellow socket. Since the different current ratings have different overall sizes, it is also not possible to mate different pin configurations or current ratings. For example, a 16 A 3P+E 400 V plug will not mate with a 16 A 3P+N+E 400 V socket and a 16 A P+N+E 230 V plug will not mate with a 32 A P+N+E 230 V socket.
Yellow 2P+E, blue P+N+E, yellow 3P+E, red 3P+E, and red 3P+N+E are by far the most common arrangements. Blue P+N+E sockets (generally 16 A, although 32 A is becoming more common) are used as standard by British and Danish campsites and yacht marinas to provide 240 V domestic mains power to frame-tents, trailer-tents, caravans, and boats; they are also used elsewhere in Europe for the same purpose, though in some countries the local domestic plug is also widely used. Static caravans generally use the similar 32 A version because of the requirement to power electrical cooking and heating appliances. The blue P+N+E 16 A version carrying 240 V is also used in shopping malls and their peripherals to power 'temporary' stalls not incorporated within a lock-up shop, there is also use in domestic gardens within Britain to power garden equipment, barbecues, and temporary lighting. The yellow 2P+E 16 A version carrying 115 V is used extensively on the London Underground railway system to power temporary usage of heavy-duty fans; it is also frequently used by tradesmen within the UK, built into a portable transformer box that is powered from a standard 13 A 240 V mains supply, to run heavy-duty power-tools designed to operate at 115 V.
A small number of marinas provide 230 V single-phase power through a red three-phase connector (breaking the relevant standards in the process). This goes some way to ensuring that only boats that have paid the required fee (and thus obtained an appropriately made-up adaptor cable) are able to use the electricity.
For more detailed information, see the main article IEC 60309.
Entertainment industry
Throughout Europe, a common use of industrial power connectors is in the entertainment and broadcast industries.
In this industry the above-mentioned IEC 60309 connectors are referred to as CEEform (or just CEE) connectors. 230 V single-phase (blue) and 400 V three-phase (red) connectors between 16 A and 125 A ratings are used.
Where more current carrying capacity is required, such as between generator sets and distribution boards, VEAM Powerlocks or Cam-Loks may be used. These connectors are single pole so five are required to accommodate all three phases, neutral and ground. Powerlocks have a rating of 400 A or 660 A at 1 kV. Cam-Lok E1016 Series are rated at 600 V 400 A.
Powerlocks are identified with the European harmonized colour code, they are also annotated as follows:
Cam-Loks are also available in these colours.
Where it is necessary to run separate feeds through multicable, the Socapex 19-pin connector is often encountered on theatre and studio lighting rigs.
UK: Lewden plugs
Lewden plugs and sockets are metal bodied waterproof plugs and sockets made by Lewden. The pin arrangements of the smaller single phase varieties are the same as BS 1363 and BS 546 plugs and sockets. These plugs and sockets will mate with normal plugs and sockets of the same pin arrangement but they are only waterproof when a Lewden plug is used in a Lewden socket and the screw ring is properly tightened (sockets have a metal cover that screws on to waterproof them when not in use).
UK: BS 196
In 1930, the BS 196 standard for industrial plugs and sockets was introduced. The plugs are available in 5 A, 15 A and 30 A variants, with various configurations of keyways and pins to cater for different voltages. BS 196 plugs have now been superseded by BS 4343 (CEE type) connectors in most modern applications.
Sweden, Germany and Netherlands: Perilex plugs
Perilex plugs and sockets are 5-pin 3-phase connectors. The system provides 400 V 3P+N+PE and exists in 16 A and 25 A versions. In Sweden, the 16 A is generally used for stoves and to some extent for other heating devices in kitchens.
In the Netherlands, Perilex is also used to connect fans with wired speed control (Switched L2 and L3 pins), but fans may not use three phase power
Sweden: Semko 17 plugs
Semko 17 were 3/4-pin 3-phase connectors, with (4-pin) or without (3-pin) a neutral connector. Earth were provided via the shield. The connectors were available in different sizes, 16 A with rounded corners; 25 A and 63 A were rectangular. These connectors were used mainly in industrial and agricultural installations. Manufacturing and selling of Semko-17 connectors with metal shells was prohibited in 1989. A few years later manufacturing and selling of all Semko-17 connectors were prohibited. Existing connectors may be used but not by any employee (prohibited by "Arbetsmiljöverket"). The reason for the prohibition is that Semko-17 had several safety issues. The ground connection can become oxidized and when the shells are made of metal any ground fault goes right through the hands of a person connecting/disconnecting a male and a female cable connector (unless the person wears insulating gloves). Incorrect use of the ground connector as a neutral was not uncommon. Perhaps the worst issue is that in some connectors the ground screw could rust so severely that the ground wire comes loose and in the worst case make contact with a line (phase) wire nearby.
Switzerland: SN 441011
The Swiss standard SN 441011 (until 2019 SEV 1011) Plugs and socket-outlets for household and similar purposes. defines a hierarchical system of plugs and sockets including both single and three phase connectors. Sockets will accept plugs with the same or fewer number of pins and the same or lower ratings. Single phase Swiss plugs and sockets are described in the main article SN 441011.
The type 15 plug and socket has 3 round pins of 4 mm diameter, plus 2 flat pins (for L2 and L3). It is designed for three phase applications and is rated at 10 A, 250 V/440 V. The socket will also accept types 11 and 12 plugs, and the Europlug.
The type 25 plug and socket has 3 rectangular pins, 4 mm x 5 mm, plus 2 flat pins (for L2 and L3). It is designed for three phase applications and is rated at 16 A, 250 V/440 V. The socket will accept types 11, 12, 21, and 23 single phase plugs, the Europlug, and types 15 and 25 three phase plugs.
Former Yugoslavia
This type of three phase plug and sockets are mainly used in households in former Yugoslavian countries, they are 5-pin 3-phase connectors, rated at 16 A, 380 V. Industrial 3-phase connectors are same as European IEC 60309.
North America
Pin and sleeve
In North America, there are two types of pin and sleeve products that are used:
NEMA
The American pin and sleeve circular connectors are not compatible with the newer IEC 60309 type. Current ratings are 30, 60, 100, 200, and 400 A. All are rated for voltages up to 250 V DC or 600 V AC. Contact arrangements are from 2 to 4 pins. There are two styles depending on the treatment of the ground. Style 1 grounds only on the shell. Style 2 uses one of the contacts as well as the shell, internally connected together. They are not strongly typed for specific circuits and voltages as the IEC 309 are. One insert rotation option is available to prevent mating of similar connectors with different voltages.
The contacts in the plug are simple cylinders (sleeves), while the pin contacts in the receptacle have the spring arrangement to hold contact pressure, the reverse of the IEC 60309 type connectors. All contacts are the same diameter. Originally metal construction was used, but now they are also made with plastic shells. Since only keying in the connector shell is used, and since the keys can be damaged in industrial use, it is possible to mis-match worn connectors.
IEC
IEC 60309 Series II (North American) pin and sleeve connectors have gained significant traction in North America over the course of the last 30 years . Series II current ratings are 20, 30, 60, 100, 200, 300, 350, 500 and 600 amps. The voltage ratings go up to 1000 V AC. These have been replacing the American-style for some time and are much more likely to be found in food processing, data centers, healthcare, entertainment, and other industries.
NEMA connectors
NEMA devices are not exclusively industrial devices, and some types are found in nearly all buildings in the United States. "Industrial-grade" connectors are constructed to meet or exceed the requirements of more stringent industry testing standards, and are more heavily built to withstand damage than residential and light commercial connectors of the same type. Industrial devices may also be constructed to be dust or water-tight. NEMA wiring devices are made in current ratings from 15–60 A, and voltage ratings from 125–600 V.
There are two basic configurations of NEMA plug and socket: straight-blade and locking. Numbers prefixed by L are twist-lock, others are straight blade. Locking type connectors are found mostly in industrial applications and are not common in residential and light commercial use.
Twist-locking connectors
Twist-locking connectors were first invented by Harvey Hubbell III in 1938 and Twist-Lock remains a registered trademark of Hubbell Incorporated to this day, although the term tends to be used generically to refer to NEMA twist-locking connectors manufactured by any company. Twist-locking connectors all use curved blades that have shapes that conform to portions of the circumference of a circle. Once pushed into the receptacle, the plug is twisted and its now-rotated prongs latch into the receptacle. To unlatch the plug, the rotation is reversed. The locking coupling makes for a very reliable connection in commercial and industrial settings.
Like non-locking connectors, these come in a variety of standardized configurations and follow the same general naming scheme except that they all begin with an L for locking. The connector families are designed so that 120 V connectors, 208/240 V connectors, and various other, higher-voltage connectors can not be accidentally intermated.
Stage pin connectors
A stage pin connector (SPC), or grounded stage pin (GSP), is a connector used primarily in the theatre industry for stage lighting applications in the United States. Stage pin connectors are generally used for conducting dimmed power from a dimmer to stage lighting instruments, although occasionally they can power other equipment.
The primary advantage of the stage pin connector over the NEMA 5-15 connector (commonly known as an Edison connector in the theatre industry) is its increased durability and resistance to damage due to its more robust construction and the ability to compensate for wear with a pin splitter. Having a distinct connector designated for dimmable power also helps prevent confusion of dimmed and non-dimmed circuits which could lead to equipment damage. Even the smallest stage pin connectors are rated for 20 A, which translates to 2.4 kW at 120 V, compared to the 15 A and 1.8 kW of the NEMA 5-15. In applications where cables are on the floor, the low profile of the connector allows for connections that are only slightly higher than the cables they connect.
California 50 A Connector
In North America for moderate current requirements the 50 A California-style connector, also known as CS6364 and CS6365 is commonly used. It features a twist-lock design with a metal sleeve full protecting the blades on the male connector and a center ground spike on the female connector to aid in centering.
California connectors are commonly used at outdoor events, shows and conventions and at construction sites. The connector gets its name from being developed as a safer connector during the early days of Hollywood film studios in California. The first high-current connectors used in the studios were stage pin (also referred to as "paddle plugs") used in theaters, which were not grounded. The California plug, however, is grounded by the outer steel shroud. This also helped protect the male contact pins from damage from the constant dragging of cables around a set throughout the day. The grounded shroud helps absorb the arc-flash if the connector is plugged or unplugged while energized. The original paddle plugs were known for dangerous arc-flashes, especially in the older DC-powered theaters in the early years of electrical stage lighting.
For example, a three phase plug which requires a neutral connection cannot be inserted into a socket outlet which does not provide for such a connection. However, a plug which does not require a neutral connection can be inserted into a socket outlet which provides such a connection, although the neutral connection would not be utilized in that situation.
For stage lighting use, a common plug is the 32-A 5-pin connector with a neutral pin. Motor loads that don't need the neutral use a four-pin connector. Larger requirements may use powerlock or camlock connectors. In the IT industry, the IEC 60309 system is sometimes used.
Australia
In Australia, New Zealand and many associated South Pacific island nations, the AS/NZS 3123 standard is used. In this series, multiple sizes of three-phase round-pin socket are standardized by current rating and neutral circuit. Each socket within a group accepts plugs in the same group up to its rating, but excludes plugs with a higher current rating, from a different group, or with a neutral pin (if there is not one in the socket). Multiphase plugs and sockets are rated at up to 500 V and all include an earth connection. These plugs and sockets are usually IP56 rated if fitted correctly. A screw collar helps hold plug and socket together.
In the single-phase standard AS/NZS 3112 used in residential environments, plugs of lower current rating may be inserted into single phase socket outlets of higher current rating but not vice versa. While this feature is somewhat reflected with multiphase sockets, it is further limited to only plugs within the same group. For example, there is one group that consists of 32 A, 40 A and 50 A connectors, and another group of 50 A, 63 A and 80 A connectors. The 32 A plug can be connected to any of the 32 A, 40 A or 50 A sockets in the first group, however it cannot be connected to any of the 50 A, 63 A or 80 A sockets in the second group. The standard notes that there are two different, incompatible 50 A connectors that are not interchangeable as they are physically different sizes.
Compatibility is grouped like this, such that larger sockets in one group can take the same plug or any smaller plugs from that group only:
Each of the three phase plugs and sockets are available as 4-pin (without neutral) or 5-pin (with neutral). A plug without a neutral pin can be inserted into a socket carrying neutral, but the reverse is not possible as the neutral pin blocks insertion into a socket that does not have a hole for the neutral conductor.
From this it can be seen that, for example, installing a 32 A, 250 V socket will only be compatible with a 32 A plug and it will not be possible to insert 10 A or 20 A plugs.
Within each size group, the plugs and sockets are keyed with certain "lugs" protruding on the outside of the plugs. Higher current plugs have more lugs to prevent them from being inserted into a lower current socket outlet, while still allowing them to be inserted into a socket outlet of the same size group rated for a higher current. For example, a 32 A 4-pin plug without neutral can plug into a 50 A 5-pin socket with neutral available.
However a 10 A 5-pin plug cannot fit a 32 A 5-pin socket, as the plugs are in different groups and not only are their diameters different, but the position of the conductors also varies by a few degrees (for example the group 7/8 32 A plug has its L and N pins at 9 o'clock and 3 o'clock, while the group 1/2 20 A plug has its L and N pins at 10 o'clock and 2 o'clock instead.)
There are also metal clad plugs and sockets that go up to 63 A ratings, at a significantly higher cost.
See also
Domestic AC power plugs and sockets
Double insulated
Electricity
Electrical power
Ground and neutral
Protective multiple earthing
SAE J1772 - Single phase AC and optional DC Electric Vehicle charging
Type 2 connector - Three phase AC and optional DC Electric Vehicle charging
References
External links
Mains power connectors
Electrical wiring | Industrial and multiphase power plugs and sockets | [
"Physics",
"Engineering"
] | 4,814 | [
"Electrical systems",
"Building engineering",
"Physical systems",
"Electrical engineering",
"Electrical wiring"
] |
976,666 | https://en.wikipedia.org/wiki/Monomial%20basis | In mathematics the monomial basis of a polynomial ring is its basis (as a vector space or free module over the field or ring of coefficients) that consists of all monomials. The monomials form a basis because every polynomial may be uniquely written as a finite linear combination of monomials (this is an immediate consequence of the definition of a polynomial).
One indeterminate
The polynomial ring of univariate polynomials over a field is a -vector space, which has
as an (infinite) basis. More generally, if is a ring then is a free module which has the same basis.
The polynomials of degree at most form also a vector space (or a free module in the case of a ring of coefficients), which has as a basis.
The canonical form of a polynomial is its expression on this basis:
or, using the shorter sigma notation:
The monomial basis is naturally totally ordered, either by increasing degrees
or by decreasing degrees
Several indeterminates
In the case of several indeterminates a monomial is a product
where the are non-negative integers. As an exponent equal to zero means that the corresponding indeterminate does not appear in the monomial; in particular is a monomial.
Similar to the case of univariate polynomials, the polynomials in form a vector space (if the coefficients belong to a field) or a free module (if the coefficients belong to a ring), which has the set of all monomials as a basis, called the monomial basis.
The homogeneous polynomials of degree form a subspace which has the monomials of degree as a basis. The dimension of this subspace is the number of monomials of degree , which is
where is a binomial coefficient.
The polynomials of degree at most form also a subspace, which has the monomials of degree at most as a basis. The number of these monomials is the dimension of this subspace, equal to
In contrast to the univariate case, there is no natural total order of the monomial basis in the multivariate case. For problems which require choosing a total order, such as Gröbner basis computations, one generally chooses an admissible monomial order – that is, a total order on the set of monomials such that
and for every monomial
See also
Horner's method
Polynomial sequence
Newton polynomial
Lagrange polynomial
Legendre polynomial
Bernstein form
Chebyshev form
Algebra
Polynomials | Monomial basis | [
"Mathematics"
] | 511 | [
"Polynomials",
"Algebra"
] |
976,673 | https://en.wikipedia.org/wiki/Hilbert%E2%80%93Schmidt%20operator | In mathematics, a Hilbert–Schmidt operator, named after David Hilbert and Erhard Schmidt, is a bounded operator that acts on a Hilbert space and has finite Hilbert–Schmidt norm
where is an orthonormal basis. The index set need not be countable. However, the sum on the right must contain at most countably many non-zero terms, to have meaning. This definition is independent of the choice of the orthonormal basis.
In finite-dimensional Euclidean space, the Hilbert–Schmidt norm is identical to the Frobenius norm.
‖·‖ is well defined
The Hilbert–Schmidt norm does not depend on the choice of orthonormal basis. Indeed, if and are such bases, then
If then As for any bounded operator, Replacing with in the first formula, obtain The independence follows.
Examples
An important class of examples is provided by Hilbert–Schmidt integral operators.
Every bounded operator with a finite-dimensional range (these are called operators of finite rank) is a Hilbert–Schmidt operator.
The identity operator on a Hilbert space is a Hilbert–Schmidt operator if and only if the Hilbert space is finite-dimensional.
Given any and in , define by , which is a continuous linear operator of rank 1 and thus a Hilbert–Schmidt operator;
moreover, for any bounded linear operator on (and into ), .
If is a bounded compact operator with eigenvalues of , where each eigenvalue is repeated as often as its multiplicity, then is Hilbert–Schmidt if and only if , in which case the Hilbert–Schmidt norm of is .
If , where is a measure space, then the integral operator with kernel is a Hilbert–Schmidt operator and .
Space of Hilbert–Schmidt operators
The product of two Hilbert–Schmidt operators has finite trace-class norm; therefore, if A and B are two Hilbert–Schmidt operators, the Hilbert–Schmidt inner product can be defined as
The Hilbert–Schmidt operators form a two-sided *-ideal in the Banach algebra of bounded operators on .
They also form a Hilbert space, denoted by or , which can be shown to be naturally isometrically isomorphic to the tensor product of Hilbert spaces
where is the dual space of .
The norm induced by this inner product is the Hilbert–Schmidt norm under which the space of Hilbert–Schmidt operators is complete (thus making it into a Hilbert space).
The space of all bounded linear operators of finite rank (i.e. that have a finite-dimensional range) is a dense subset of the space of Hilbert–Schmidt operators (with the Hilbert–Schmidt norm).
The set of Hilbert–Schmidt operators is closed in the norm topology if, and only if, is finite-dimensional.
Properties
Every Hilbert–Schmidt operator is a compact operator.
A bounded linear operator is Hilbert–Schmidt if and only if the same is true of the operator , in which case the Hilbert–Schmidt norms of T and |T| are equal.
Hilbert–Schmidt operators are nuclear operators of order 2, and are therefore compact operators.
If and are Hilbert–Schmidt operators between Hilbert spaces then the composition is a nuclear operator.
If is a bounded linear operator then we have .
is a Hilbert–Schmidt operator if and only if the trace of the nonnegative self-adjoint operator is finite, in which case .
If is a bounded linear operator on and is a Hilbert–Schmidt operator on then , , and . In particular, the composition of two Hilbert–Schmidt operators is again Hilbert–Schmidt (and even a trace class operator).
The space of Hilbert–Schmidt operators on is an ideal of the space of bounded operators that contains the operators of finite-rank.
If is a Hilbert–Schmidt operator on then where is an orthonormal basis of H, and is the Schatten norm of for . In Euclidean space, is also called the Frobenius norm.
See also
References
Linear operators
Operator theory | Hilbert–Schmidt operator | [
"Mathematics"
] | 796 | [
"Mathematical objects",
"Functions and mappings",
"Mathematical relations",
"Linear operators"
] |
976,723 | https://en.wikipedia.org/wiki/Soffit | A soffit is an exterior architectural feature, generally the horizontal, aloft underside of the roof edge. Its archetypal form, sometimes incorporating or implying the projection of rafters or trusses over the exterior of supporting walls, is the underside of eaves (to connect a supporting wall to projecting edge(s) of the roof). The vertical band at the edge of the roof is called a fascia. A soffit of an arch is frequently called an intrados.
Etymology
The term soffit is from , formed as a ceiling; and directly from suffictus for suffixus, , to fix underneath).
Soffits in homes and offices
In architecture, soffit is the underside (but not base) of any construction element.
Examples include:
Under the eaves of a roof
In foremost use soffit is the first definition in the table above. In spatial analysis, it is one of the two necessary planes of any (3-dimensional) optionally built area, eaves, which projects, for such area to be within the building's space.
In two-dimensional face analysis it is a discrete face almost always parallel with the ground that bridges the gap(s) between a building's siding (walls) and either: their parallel extraneous plane (fascia) where such exists; or where no such plane, a point along (or the abrupt end of) the roof's outer projection (overhang). Soffits and fascias are archetypally screwed or nailed to rafters known as lookout rafters or lookouts for short, their repair being often undertaken simultaneously. A parapet wall or cornice tend to preclude eaves, as an alternate design, both favouring flat roofs and weather-proof walls. Very pronounced overhangs (eaves) are characteristic to European architecture to shield the walls from rain, sleet and snow such as Swiss chalet style, Dutch, Romanian, and Tudor architecture.
Soffit exposure profile (from wall to fascia) on a building's exterior can vary from a few centimetres (2–3 inches) to 3 feet or more, depending on construction. It can be non-ventilated or ventilated, to prevent condensation. A grill that covers the venting opening on the bottom of the soffit is called a soffit vent. A soffit joist can be added to the framework instead of or in addition to lookouts.
References
Ceilings
Roofs | Soffit | [
"Technology",
"Engineering"
] | 513 | [
"Structural system",
"Ceilings",
"Structural engineering",
"Roofs"
] |
976,730 | https://en.wikipedia.org/wiki/Safe%20operating%20area | For power semiconductor devices (such as BJT, MOSFET, thyristor or IGBT), the safe operating area (SOA) is defined as the voltage and current conditions over which the device can be expected to operate without self-damage.
SOA is usually presented in transistor datasheets as a graph with VCE (collector-emitter voltage) on the abscissa and ICE (collector-emitter current) on the ordinate; the safe 'area' referring to the area under the curve. The SOA specification combines the various limitations of the device — maximum voltage, current, power, junction temperature, secondary breakdown — into one curve, allowing simplified design of protection circuitry.
Often, in addition to the continuous rating, separate SOA curves are also plotted for short duration pulse conditions (1 ms pulse, 10 ms pulse, etc.).
The safe operating area curve is a graphical representation of the power handling capability of the device under various conditions. The SOA curve takes into account the wire bond current carrying capability, transistor junction temperature, internal power dissipation and secondary breakdown limitations.
Limits of the safe operating area
Where both current and voltage are plotted on logarithmic scales, the borders of the SOA are straight lines:
{|
| 1. || IC || = ICmax || — current limit
|-
| 2. || VCE || = VCEmax || — voltage limit
|-
| 3. || IC·VCE || = Pmax || — dissipation limit, thermal breakdown
|-
| 4. || IC·VCEα || = const || — this is the limit given by the secondary breakdown (bipolar junction transistors only)
|}
SOA specifications are useful to the design engineer working on power circuits such as amplifiers and power supplies as they allow quick assessment of the limits of device performance, the design of appropriate protection circuitry, or selection of a more capable device. SOA curves are also important in the design of foldback circuits.
Secondary breakdown
For a device that makes use of the secondary breakdown effect see Avalanche transistor
Secondary breakdown is a failure mode in bipolar power transistors. In a power transistor with a large junction area, under certain conditions of current and voltage, the current concentrates in a small spot of the base-emitter junction. This causes local heating, progressing into a short between collector and emitter. This often leads to the destruction of the transistor. Secondary breakdown can occur both with forward and reverse base drive. Except at low collector-emitter voltages, the secondary breakdown limit restricts the collector current more than the steady-state power dissipation of the device. Older power MOSFETs did not exhibit secondary breakdown, with their safe operating area being limited only by maximum current (the capacity of the bonding wires), maximum power dissipation and maximum voltage. This has changed in more recent devices as detailed in the next section. However, power MOSFETs have parasitic PN and BJT elements within the structure, which can cause more complex localized failure modes resembling secondary breakdown.
MOSFET thermal runaway in linear mode
In their early history, MOSFETs became known for their absence of secondary breakdown. This benefit was due to the fact that ON-resistance increases with increasing temperature, so that part of the MOSFET which is running hotter (e.g. due to irregularities in the die-attachment, etc.) will carry a lower current density, tending to even out any temperature variation and prevent hot spots. Recently, MOSFETs with very high transconductance, optimised for switching operation, have become available. When operated in linear mode, especially at high drain-source voltages and low drain currents, the gate-source voltage tends to be very close to the threshold voltage. Unfortunately the threshold voltage decreases as temperature increases, so that if there are any slight temperature variations across the chip, then the hotter regions will tend to carry more current than the cooler regions when Vgs is very close to Vth. This can lead to thermal runaway and the destruction of the MOSFET even when it is operating within its Vds, Id and Pd ratings. Some (usually expensive) MOSFETs are specified for operation in the linear region and include DC SOA diagrams, e.g. IXYS IXTK8N150L.
Reverse bias safe operating area
Transistors require some time to turn off, due to effects such as minority carrier storage time and capacitance. While turning off, they may be damaged depending on how the load responds (especially with poorly snubbed inductive loads). The reverse bias safe operating area (or RBSOA) is the SOA during the brief time before turning the device into the off state—during the short time when the base current bias is reversed. As long as the collector voltage and collector current stay within the RBSOA during the entire turnoff, the transistor will be undamaged. Typically the RBSOA will be specified for a variety of turn-off conditions, such as shorting the base to the emitter, but also faster turn-off protocols where the base-emitter voltage bias is reversed.
The RBSOA shows distinct dependencies compared to the normal SOA. For example in IGBTs the high-current, high-voltage corner of the RBSOA is cut out when the collector voltage increases too quickly. Since the RBSOA is associated with a very brief turn-off process, it is not constrained by the continuous power dissipation limit.
The ordinary safe operating area (when the device is in the on state) may be referred to as the Forward bias safe operating area (or FBSOA) when it is possible to confuse it with the RBSOA.
Protection
The most common form of SOA protection used with bipolar junction transistors senses the collector-emitter current with a low-value series resistor. The voltage across this resistor is applied to a small auxiliary transistor that progressively 'steals' base current from the power device as it passes excess collector current.
Another style of protection is to measure the temperature of the outside of the transistor, as an estimate of junction temperature, and reduce drive to the device or switch it off if the temperature is too high. If multiple transistors are used in parallel, only a few need to be monitored for case temperature to protect all parallel devices.
This approach is effective but not bullet-proof. In practice, it is very difficult to design a protection circuit that will work under all conditions, and it is left up to the design engineer to weigh the likely fault conditions against the complexity and cost of the protection.
See also
Derating
References
H. A. Schafft, J. C. French, Secondary Breakdown in Transistors, IRE Trans. Electron Devices ED-9, 129-136 (1962). online
Michaël Bairanzade, Understanding Power Transistors Breakdown Parameters, OnSemi application node AN1628/D online
Apex technical document on operating power opamps within SOA
Power electronics
Electronic engineering | Safe operating area | [
"Technology",
"Engineering"
] | 1,487 | [
"Electrical engineering",
"Electronic engineering",
"Computer engineering",
"Power electronics"
] |
976,740 | https://en.wikipedia.org/wiki/Neptunbrunnen%20%28Berlin%29 | The Neptune Fountain () in Berlin was built in 1891 and was designed by Reinhold Begas. The Roman god Neptune is in the center. The four women around him represent the four main rivers of Prussia at the time the fountain was constructed: the Elbe (with the allegorical figure holding fruits and ears of corn), Rhine (fishnet and grapes), Vistula (wooden blocks, symbols of forestry), and Oder (goats and animal skins). The Vistula is now entirely in Poland, while the Oder forms the border between Germany and Poland.
The fountain was removed from its original location at the Schlossplatz in 1951, when the former Berliner Schloss (Berlin Palace) there was demolished. Eventually, after being restored, the fountain was moved in 1969 to its present location between the St Mary's Church and the Rotes Rathaus.
The diameter is 18 m (59 ft), the height is 10 m (33 ft).
There was another well-known in Breslau (nicknamed "Gabeljürge" or "Georgie Fork" by the locals), but it was destroyed during World War II and the city was later transferred to Poland.
Events
In 2013, a member of the Berlin Police Force shot an armed man before the fountain. The 31-year-old man was nude, holding a knife, and was believed to be mentally disturbed.
References
External links
1891 sculptures
Allegorical sculptures in Germany
Buildings and structures in Berlin
Fountains in Germany
Outdoor sculptures in Berlin
Sculptures of men in Germany
Sculptures of Neptune
Sculptures of women in Germany
Statues in Germany
Personifications of rivers | Neptunbrunnen (Berlin) | [
"Physics",
"Mathematics"
] | 329 | [
"Quantity",
"Colossal statues",
"Physical quantities",
"Size"
] |
976,840 | https://en.wikipedia.org/wiki/True%20longitude | In celestial mechanics, true longitude is the ecliptic longitude at which an orbiting body could actually be found if its inclination were zero. Together with the inclination and the ascending node, the true longitude can tell us the precise direction from the central object at which the body would be located at a particular time.
Calculation
The true longitude can be calculated as follows:
where:
is the orbit's true anomaly,
is the longitude of orbit's periapsis,
is the argument of periapsis, and
is the longitude of the orbit's ascending node,
References
Orbits
Equations of astronomy | True longitude | [
"Physics",
"Astronomy"
] | 119 | [
"Concepts in astronomy",
"Astronomy stubs",
"Astrophysics",
"Astrophysics stubs",
"Equations of astronomy"
] |
976,897 | https://en.wikipedia.org/wiki/Cone%20Nebula | The Cone Nebula is an H II region in the constellation of Monoceros. It was discovered by William Herschel on December 26, 1785, at which time he designated it H V.27. The nebula is located about 830 parsecs or 2,700 light-years from Earth. The Cone Nebula forms part of the nebulosity surrounding the Christmas Tree Cluster. The designation of NGC 2264 in the New General Catalogue refers to both objects and not the nebula alone.
Description
The diffuse Cone Nebula, so named because of its apparent shape, lies in the southern part of NGC 2264, the northern part being the magnitude-3.9 Christmas Tree Cluster. It is in the northern part of Monoceros, just north of the midpoint of a line from Procyon to Betelgeuse.
The cone's shape comes from a dark absorption nebula consisting of cold molecular hydrogen and dust in front of a faint emission nebula containing hydrogen ionized by S Monocerotis, the brightest star of NGC 2264. The faint nebula is approximately seven light-years long (with an apparent length of 10 arcminutes), and is 2,700 light-years from Earth.
The nebula is part of a much larger star-forming complex—the Hubble Space Telescope was used to capture images of forming stars in 1997.
See also
Perceptions of religious imagery in natural phenomena
Notes and references
External links
Cone Nebula pictures from ESA-Hubble
Hubble image of Cone Nebula
NGC 2264
Dark nebulae
Diffuse nebulae
Monoceros
H II regions
Astronomical objects discovered in 1785
Perceptions of religious imagery in natural phenomena | Cone Nebula | [
"Astronomy"
] | 330 | [
"Monoceros",
"Constellations"
] |
977,092 | https://en.wikipedia.org/wiki/Naxos%20radar%20detector | The Naxos radar warning receiver was a World War II German countermeasure to S band microwave radar produced by a cavity magnetron. Introduced in September 1943, it replaced Metox, which was incapable of detecting centimetric radar. Two versions were widely used, the FuG 350 Naxos Z that allowed night fighters to home in on H2S radars carried by RAF Bomber Command aircraft, and the FuMB 7 Naxos U for U-boats, offering early warning of the approach of RAF Coastal Command patrol aircraft equipped with ASV Mark III radar. A later model, Naxos ZR, provided warning of the approach of RAF night fighters equipped with AI Mk. VIII radar.
Background
Prior to the introduction of the cavity magnetron, radar systems used traditional vacuum tube electronics and were limited to about 1.5 m wavelength in UK use, and as low as 50 cm in German systems. Both could receive the transmissions of their opposing radar systems and radar warning receivers were widely used by both sides in a number of roles.
By 1942, the UK had made enough progress on the magnetron to begin introducing new radars using it, including the AI Mk. VIII radar for night fighters, ASV Mk. III radar for sea-surface search (anti-submarine) and the H2S radar for bomber guidance. None of the existing German receivers could operate at the magnetron's 10 cm wavelength, and the introduction of the ASV Mk. III, in particular, led to significant losses among the U-boat fleet during the summer of 1943.
Before the magnetron had been deployed operationally, there was a great debate in the UK over whether or not Bomber Command should be allowed to use it. Unlike other types of tube electronics of the era, which are quite fragile, the main component of the magnetron is a large block of copper. If an aircraft carrying one were shot down and recovered, there was a very good chance the block would survive, at which point the secret would be revealed to anyone familiar with microwave techniques. This is precisely what occurred on the night of 2/3 February 1943, when the second mission to attempt to use H2S led to one of the Short Stirling bombers carrying it being shot down near Rotterdam. The magnetron was recovered and this Rotterdam Gerät (gadget, or device) led to the rapid formation of a study group to exploit it.
The group first met at the Telefunken offices in Berlin on 22 February. Although the possibility of developing radars using it was considered, the much more pressing need was the development of countermeasures to this now-undetectable radar. This effect was hampered by the industry's recent decision to give up on microwave research, considering it to be a dead-end, as had British engineers before the introduction of the magnetron. Adding to their problems was the lack of a suitable rugged crystal detector, which was the only system able to reliably detect these high frequency signals. Enormous effort was expended to address these problems, and prototype units were available by the summer.
Aircraft use
The first operational use was in a Junkers Ju 88 on 2 September 1943. The unit, and others that were delivered during this time, proved extremely difficult to keep working. Even when they did work, their angle accuracy was limited, and it did not provide elevation or range information of any sort. Operators found it useful for finding the bomber stream, at ranges as great as , but could not use it to home in on individual aircraft. The Naxos Z system's rotating antenna for airborne use was driven by a DC motor, and comprised what appear to be a pair of vacuum tubes laid flat on a circular rotating carriage, which would be enclosed within a radome of either hemispherical shape for single-engine fighter use, or in a more aerodynamic "teardrop" shape for placement atop a twin-engined night fighter's canopy.
News of the device made its way to England, where some level of panic broke out when it was suggested that the H2S could be leading to the aircraft's demise. Arguments over the use of H2S by bomber command started anew. These were finally put to rest in July 1944 when a Naxos-equipped Ju 88 night fighter became lost and landed in the UK. The crew described the operation of Naxos as being of little overall use, while another device, Flensburg was able to home in on individual aircraft's Monica radar. Monica was removed from service and H2S was allowed to continue throughout the war.
When it was clear that the magnetron was known to the Germans, the RAF released its night fighter version, AI Mk. VIII radar, for use over Europe. This radar provided a significant advantage to the RAF over the older systems used by the Germans, and for the first time the RAF was able to seriously disrupt German night fighter operations by attacking them directly. Aircraft that did survive reported that there was no warning of the attack, and it was quickly surmised that the RAF had introduced a new microwave AI radar. This led to the rapid introduction of the Naxos ZR, tuned to the Mk. VIII's frequency and equipped with rearward facing antennas.
Altogether, about 700 Naxos Z and ZR's were produced.
Submarine use
Given the concerns over the possibility of losing a magnetron to the Germans, for some time through the summer of 1942 the RAF limited future deliveries to Coastal Command aircraft for anti-submarine duties, where the possibility of capture was remote. However, Bomber Command fought this decision and by the time deliveries started late in the year they received all of the units. This was reconsidered once again when it was becoming clear the U-boats had been equipped with some sort of detector for the existing ASV Mk. II radar, as they could be seen disappearing on the radar as the aircraft approached, and this was put to fearsome use in early 1943. A new agreement was reached where Coastal and Bomber Command would split the deliveries about 65/35.
When the first of these ASV Mk. III radar systems began reaching service in early 1943, the effects were profound. Once again British aircraft could attack submarines with no warning until the last seconds when the Leigh light was illuminated, far too late for the submarine to take defensive action. A new phase started where British aircraft pressed into the Bay of Biscay and German submarines were told to remain on the surface and fight it out in daylight rather than risk almost certain death at night. This led to a crash program to equip their fleet with a variation of Naxos that could detect the new radar.
The resulting Naxos U initially proved to have very short detection range, too short to be really useful. This led to a series of new antenna designs before the final Fliege (fly) semi-parabolic system was introduced. This had the distinct disadvantage that it was not waterproof and had to be removed from its mounting and taken inside in order to dive. Even with this antenna, warning times were on the order of one minute. An even later version, Naxos ZM, spun the antenna at 1,300 RPM to display the angle directly on a cathode-ray tube display in the submarine. This was still under development when the war ended.
Although Naxos was useful against ASV Mk. III, by 1944 the British and US were already well on their way to introducing newer magnetron-based radar systems, like the American H2X, operating at even higher frequencies in the 3 cm band. The first of these ASV Mk. VI radars were being introduced to service just as Naxos was being fitted. As a result, Naxos never had as great a success as the Metox it replaced.
Other developments
Experiments with a ground-based version of Naxos using directional antennas had been carried out under the name Corfu. Some effort was made to develop this into an airborne version, FuG 351 Corfu Z, but this never entered service.
An attempt to address the limited resolution of Naxos was undertaken in the Korfu, which had a better antenna system and more sensitive receiver.
Naxos receivers were also combined with the parabolic antennas from Würzburg radar systems to produce a long-range receiver tuned to the British Oboe radio navigation system. The system later used a Domeyer receiver and became the Naxburg system. Oboe broadcast pulses from the aircraft that needed to be powerful enough to be received by ground stations in the UK. This made them relatively easy to pick out at short ranges, as long as the receiver was tuned to a suitable frequency. When such a signal was detected, false pulses identical to those received from the aircraft were re-broadcast from the ground. Stations in the UK thus received two or more signals for every signal they sent out, which confused the detectors.
See also
H2X, the American X-band bombing radar immune to detection from the Naxos detecting device.
References
World War II German electronics
Radar warning receivers
Military equipment introduced from 1940 to 1944 | Naxos radar detector | [
"Technology"
] | 1,859 | [
"Warning systems",
"Radar warning receivers"
] |
977,139 | https://en.wikipedia.org/wiki/Joist | A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the subfloor sheathing, allowing it to function as a horizontal diaphragm. Joists are often doubled or tripled, placed side by side, where conditions warrant, such as where wall partitions require support.
Joists are either made of wood, engineered wood, or steel, each of which has unique characteristics. Typically, wood joists have the cross section of a plank with the longer faces positioned vertically. However, engineered wood joists may have a cross section resembling the Roman capital letter ""; these joists are referred to as -joists. Steel joists can take on various shapes, resembling the Roman capital letters "C", "", "L" and "S".
Wood joists were also used in old-style timber framing. The invention of the circular saw for use in modern sawmills has made it possible to fabricate wood joists as dimensional lumber.
Strength characteristics
Joists must exhibit the strength to support the anticipated load over a long period of time. In many countries, the fabrication and installation of all framing members including joists must meet building code standards. Considering the cross section of a typical joist, the overall depth of the joist is critical in establishing a safe and stable floor or ceiling system. The wider the spacing between the joists, the deeper the joist needs to be to limit stress and deflection under load. Lateral support called dwang, blocking, or strutting increases its stability, preventing the joist from buckling under load. There are approved formulas for calculating the depth required and reducing the depth as needed; however, a rule of thumb for calculating the depth of a wooden floor joist for a residential property is to take half the span in feet, add two, and use the resulting number as the depth in inches; for example, the joist depth required for a span is . Many steel joist manufacturers supply load tables to allow designers to select the proper joist sizes for their projects.
Standard dimensional lumber joists have their limitations due to the limits of what farmed lumber can provide. Engineered wood products such as I-joists gain strength from expanding the overall depth of the joist, as well as by providing high-quality engineered wood for both the bottom and the top chords of the joist. A common saying regarding structural design is that "deeper is cheaper", referring to the more cost-effective design of a given structure by using deeper but more expensive joists, because fewer joists are needed and longer spans are achieved, which more than makes up for the added cost of deeper joists.
Types
In traditional timber framing there may be a single set of joists which carry both a floor and ceiling called a single floor (single joist floor, single framed floor) or two sets of joists, one carrying the floor and another carrying the ceiling called a double floor (double framed floor). The term binding joist is sometimes used to describe beams at floor level running perpendicular to the ridge of a gable roof and joined to the intermediate posts. Joists which land on a binding joist are called bridging joists. A large beam in the ceiling of a room carrying joists is a summer beam. A ceiling joist may be installed flush with the bottom of the beam or sometimes below the beam. Joists left exposed and visible from below are called "naked flooring" or "articulated" (a modern U.S. term) and were typically planed smooth (wrought) and sometimes chamfered or beaded.
Connections to supporting beams
Joists may join to their supporting beams in many ways: joists resting on top of the supporting beams are said to be "lodged"; dropped in using a butt cog joint (a type of lap joint), half-dovetail butt cog, or a half-dovetail lap joint. Joists may also be tenoned in during the raising with a soffit tenon or a tusk tenon (possibly with a housing). Joists can also be joined by being slipped into mortises after the beams are in place such as a chase mortise (pulley mortise), L-mortise, or "short joist". Also, in some Dutch-American work, ground level joists are placed on a foundation and then a sill placed on top of the joists such as what timber frame builder Jack Sobon called an "inverted sill" or with a "plank sill".
Joists can have different joints on either ends such as being tenoned on one end and lodged on the other end.
A reduction in the under-side of cogged joist-ends may be square, sloped or curved. Typically joists do not tie the beams together, but sometimes they are pinned or designed to hold under tension. Joists on the ground floor were sometimes a pole (pole joist, half-round joist, log joist. A round timber with one flat surface) and in barns long joists were sometimes supported on a sleeper (a timber not joined to but supporting other beams).
Joists left out of an area form an opening called a "well" as in a stairwell or chimney-well. The joists forming the well are the heading joist (header) and trimming joist (trimmer). Trimmers take the name of the feature such as hearth trimmer, stair trimmer, etc.
Shortened joists are said to be crippled. The term rim joist is rare before the 1940s in America; it forms the edge of a floor. The outermost joist in half timber construction may be of a more durable species than the interior joists. In a barn, loose poles above the drive floor are called a scaffold. Between the joists, the area called a joist-bay, and above the ceiling in some old houses is material called pugging, which was used to deaden sound, insulate, and resist the spread of fire.
In platform framing, the joists may be connected to the rim joist with toenailing or by using a joist hanger.
See also
Beam (structure)
Framing (construction)
Girder
Purlin
Rafter
Truss
References
Ceilings
Structural system
Carpentry
Building engineering
Floors
Roofing materials | Joist | [
"Technology",
"Engineering"
] | 1,328 | [
"Structural engineering",
"Building engineering",
"Floors",
"Structural system",
"Civil engineering",
"Ceilings",
"Architecture"
] |
977,193 | https://en.wikipedia.org/wiki/Halocarbon | Halocarbon compounds are chemical compounds in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (fluorine, chlorine, bromine or iodine – ) resulting in the formation of organofluorine compounds, organochlorine compounds, organobromine compounds, and organoiodine compounds. Chlorine halocarbons are the most common and are called organochlorides.
Many synthetic organic compounds such as plastic polymers, and a few natural ones, contain halogen atoms; they are known as halogenated compounds or organohalogens. Organochlorides are the most common industrially used organohalides, although the other organohalides are used commonly in organic synthesis. Except for extremely rare cases, organohalides are not produced biologically, but many pharmaceuticals are organohalides. Notably, many pharmaceuticals such as Prozac have trifluoromethyl groups.
For information on inorganic halide chemistry, see halide.
Chemical families
Halocarbons are typically classified in the same ways as the similarly structured organic compounds that have hydrogen atoms occupying the molecular sites of the halogen atoms in halocarbons. Among the chemical families are:
haloalkanes—compounds with carbon atoms linked by single bonds
haloalkenes—compounds with one or more double bonds between carbon atoms
haloaromatics—compounds with carbons linked in one or more aromatic rings with a delocalised donut shaped pi cloud.
The halogen atoms in halocarbon molecules are often called "substituents," as though those atoms had been substituted for hydrogen atoms. However halocarbons are prepared in many ways that do not involve direct substitution of halogens for hydrogens.
History and context
A few halocarbons are produced in massive amounts by microorganisms. For example, several million tons of methyl bromide are estimated to be produced by marine organisms annually. Most of the halocarbons encountered in everyday life – solvents, medicines, plastics – are man-made. The first synthesis of halocarbons was achieved in the early 1800s. Production began accelerating when their useful properties as solvents and anesthetics were discovered. Development of plastics and synthetic elastomers has led to greatly expanded scale of production. A substantial percentage of drugs are halocarbons.
Natural halocarbons
A large amount of the naturally occurring halocarbons, such as dioxine, are created by wood fire and volcanic activity. A third major source is marine algae, which produce several chlorinated methane and ethane containing compounds. Several thousand complex halocarbons are known to be produced mainly by marine species. Although chlorine compounds are the majority of the discovered compounds, bromides, iodides and fluorides have also been found in nature. Tyrian purple is a bromide and is produced by certain sea snails. Thyroxine is secreted by the thyroid gland and is an iodide. The highly toxic fluoroacetate is one of the rare natural organofluorides and is produced by certain plants.
Organoiodine compounds, including biological derivatives
Organoiodine compounds, called organic iodides, are similar in structure to organochlorine and organobromine compounds, but the C-I bond is weaker. Many organic iodides are known, but few are of major industrial importance. Iodide compounds are mainly produced as nutritional supplements.
The thyroxin hormones are essential for human health, hence the usefulness of iodized salt.
Six mg of iodide a day can be used to treat patients with hyperthyroidism due to its ability to inhibit the organification process in thyroid hormone synthesis, the so-called Wolff–Chaikoff effect. Prior to 1940, iodides were the predominant antithyroid agents. In large doses, iodides inhibit proteolysis of thyroglobulin, which permits TH to be synthesized and stored in colloid, but not released into the bloodstream. This mechanism is referred to as Plummer effect.
This treatment is seldom used today as a stand-alone therapy despite the rapid improvement of patients immediately following administration. The major disadvantage of iodide treatment lies in the fact that excessive stores of TH accumulate, slowing the onset of action of thioamides (TH synthesis blockers). In addition, the functionality of iodides fades after the initial treatment period. An "escape from block" is also a concern, as extra stored TH may spike following discontinuation of treatment.
Uses
The first halocarbon commercially used was Tyrian purple, a natural organobromide of the Murex brandaris marine snail.
Common uses for halocarbons have been as solvents, pesticides, refrigerants, fire-resistant oils, ingredients of elastomers, adhesives and sealants, electrically insulating coatings, plasticizers, and plastics. Many halocarbons have specialized uses in industry. One halocarbon, sucralose, is a sweetener.
Before they became strictly regulated, the general public often encountered haloalkanes as paint and cleaning solvents such as trichloroethane (1,1,1-trichloroethane) and carbon tetrachloride (tetrachloromethane), pesticides like 1,2-dibromoethane (EDB, ethylene dibromide), and refrigerants like Freon-22 (duPont trademark for chlorodifluoromethane). Some haloalkanes are still widely used for industrial cleaning, such as methylene chloride (dichloromethane), and as refrigerants, such as R-134a (1,1,1,2-tetrafluoroethane).
Haloalkenes have also been used as solvents, including perchloroethylene (Perc, tetrachloroethene), widespread in dry cleaning, and trichloroethylene (TCE, 1,1,2-trichloroethene). Other haloalkenes have been chemical building blocks of plastics such as polyvinyl chloride ("vinyl" or PVC, polymerized chloroethene) and Teflon (duPont trademark for polymerized tetrafluoroethene, PTFE).
Haloaromatics include the former Aroclors (Monsanto Company trademark for polychlorinated biphenyls, PCBs), once widely used in power transformers and capacitors and in building caulk, the former Halowaxes (Union Carbide trademark for polychlorinated naphthalenes, PCNs), once used for electrical insulation, and the chlorobenzenes and their derivatives, used for disinfectants, pesticides such as dichloro-diphenyl-trichloroethane (DDT, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane), herbicides such as 2,4-D (2,4-dichlorophenoxyacetic acid), askarel dielectrics (mixed with PCBs, no longer used in most countries), and chemical feedstocks.
A few halocarbons, including acid halides like acetyl chloride, are highly reactive; these are rarely found outside chemical processing. The widespread uses of halocarbons were often driven by observations that most of them were more stable than other substances. They may be less affected by acids or alkalis; they may not burn as readily; they may not be attacked by bacteria or molds; or they may not be affected as much by sun exposure.
Hazards
The stability of halocarbons tended to encourage beliefs that they were mostly harmless, although in the mid-1920s physicians reported workers in polychlorinated naphthalene (PCN) manufacturing suffering from chloracne , and by the late 1930s it was known that workers exposed to PCNs could die from liver disease and that DDT would kill mosquitos and other insects . By the 1950s, there had been several reports and investigations of workplace hazards. In 1956, for example, after testing hydraulic oils containing polychlorinated biphenyl (PCB)s, the U.S. Navy found that skin contact caused fatal liver disease in animals and rejected them as "too toxic for use in a submarine" .
In 1962 a book by U.S. biologist Rachel Carson started a storm of concerns about environmental pollution, first focused on DDT and other pesticides, some of them also halocarbons. These concerns were amplified when in 1966 Danish chemist Soren Jensen reported widespread residues of PCBs among Arctic and sub-Arctic fish and birds . In 1974, Mexican chemist Mario Molina and U.S. chemist Sherwood Rowland predicted that common halocarbon refrigerants, the chlorofluorocarbons (CFCs), would accumulate in the upper atmosphere and destroy protective ozone . Within a few years, ozone depletion was being observed above Antarctica, leading to bans on production and use of chlorofluorocarbons in many countries. In 2007, the Intergovernmental Panel on Climate Change (IPCC) said halocarbons were a direct cause of global warming.
Since the 1970s there have been longstanding, unresolved controversies over potential health hazards of trichloroethylene (TCE) and other halocarbon solvents that had been widely used for industrial cleaning . More recently perfluorooctanoic acid (PFOA), a precursor in the most common manufacturing process for Teflon and also used to make coatings for fabrics and food packaging, became a health and environmental concern starting in 2006 , suggesting that halocarbons, though thought to be among the most inert, may also present hazards.
Halocarbons, including those that might not be hazards in themselves, can present waste disposal issues. Because they do not readily degrade in natural environments, halocarbons tend to accumulate. Incineration and accidental fires can create corrosive byproducts such as hydrochloric acid and hydrofluoric acid, and poisons like halogenated dioxins and furans. Species of Desulfitobacterium are being investigated for their potential in the bioremediation of halogenic organic compounds.
See also
Halogenation
Carbon–fluorine bond
Fluorinated gases
List of refrigerants
Notes
References
, settled between the parties, reviewed in
, cited in Chemical Industry Archives, Anniston Case , by Environmental Working Group, Washington, DC, 2002
External links | Halocarbon | [
"Chemistry"
] | 2,227 | [
"Organohalides",
"Organic compounds",
"Functional groups"
] |
977,206 | https://en.wikipedia.org/wiki/Stabilator | A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer (which is fixed) and elevator (which is adjustable). Apart from reduced drag, particularly at high Mach numbers, it is a useful device for changing the aircraft balance within wide limits, and for reducing stick forces.
Stabilator is a portmanteau of stabilizer and elevator. It is also known as an all-moving tailplane (British English), all-movable tail(plane), all-moving stabilizer, all-flying tail (American English), all-flying horizontal tail, full-flying stabilizer, and slab tailplane.
General aviation
Because it involves a moving balanced surface, a stabilator can allow the pilot to generate a given pitching moment with a lower control force. Due to the high forces involved in tail balancing loads, stabilators are designed to pivot about their aerodynamic center (near the tail's mean quarter-chord). This is the point at which the pitching moment is constant regardless of the angle of attack, and thus any movement of the stabilator can be made without added pilot effort. However, to be certified by the appropriate regulatory agency, an airplane must show an increasing resistance to an increasing pilot input (movement). To provide this resistance, stabilators on small aircraft contain an anti-servo tab (usually acting also as a trim tab) that deflects in the same direction as the stabilator, thus providing an aerodynamic force resisting the pilot's input. General aviation aircraft with stabilators include the Piper Cherokee and the Cessna 177. The Glaser-Dirks DG-100 glider initially used a stabilator without an anti-servo tab to increase resistance: as a result, the pitch movement of the glider is very sensitive. Later models used a conventional stabilizer and elevator.
Military
All-flying tailplanes were used on many pioneer aircraft and the popular Morane-Saulnier G, H and L monoplanes from France as well as the early Fokker Eindecker monoplane and Halberstadt D.II biplane fighters from Germany all flew with them, although at the cost of stability: none of these aircraft, with the possible exception of the biplane Halberstadts, could be flown hands-off.
Stabilators were developed to achieve adequate pitch control in supersonic flight, and are almost universal on modern military combat aircraft.
The British wartime Miles M.52 supersonic project was designed with stabilators. Though the design only flew as a scale rocket, its all-flying tail was tested on the Miles Falcon. The contemporary American supersonic project, the Bell X-1, used separately-adjustable horizontal stabilizer and elevators allowing movement as a single surface or elevator deflection at a fixed tailplane setting.
Entering service in 1951, the Boeing B-47 Stratojet was the world's first purposely built jet bomber to include one piece stabilator design. A stabilator was considered for the Boeing B-52 Stratofortress but rejected due to the unreliability of hydraulics at the time.
The North American F-86 Sabre, the first U.S. Air Force aircraft which could go supersonic (although in a shallow dive) was introduced with a conventional horizontal stabilizer with elevators, which was eventually replaced with a stabilator.
When stabilators can move differentially to perform the roll control function of ailerons, as they do on many modern fighter aircraft they are known as elevons or rolling tails. A canard surface, looking like a stabilator but not stabilizing like a tailplane, can also be mounted in front of the main wing in a canard configuration (Curtiss-Wright XP-55 Ascender).
Stabilators on military aircraft have the same problem of too light control forces (inducing overcontrol) as general aviation aircraft. Unlike light aircraft, supersonic aircraft are not fitted with anti-servo tabs, which would add unacceptable drag. In older jet fighter aircraft, a resisting force was generated within the control system, either by springs or a resisting hydraulic force, rather than by an external anti-servo tab. For example, the North American F-100 Super Sabre, used gearing and a variable stiffness spring attached to the control stick to provide an acceptable resistance to pilot input. In modern fighters, control inputs are processed by computers ("fly by wire"), and there is no direct connection between the pilot's stick and the stabilator.
Airliners
Most modern airliners do not have a stabilator. Instead they have an adjustable horizontal stabilizer and a separate elevator control. The movable horizontal stabilizer is adjusted to keep the pitch axis in trim during flight as the speed changes, or as fuel is burned and the center of gravity moves. These adjustments are commanded by the autopilot when it is engaged, or by the human pilot if the plane is being flown manually. Adjustable stabilizers are not the same as stabilators: a stabilator is controlled by the pilot's control yoke or stick, whereas an adjustable stabilizer is controlled by the trim system.
In the Boeing 737, the adjustable stabilizer trim system is powered by an electrically operated jackscrew.
One example of an airliner with a genuine stabilator used for flight control is the Lockheed L-1011.
See also
Canard
Index of aviation articles
References
External links
Stabilators (NASA) – Includes Java applet
Aerodynamics
Aircraft controls
Aircraft wing design
ja:スタビレーター | Stabilator | [
"Chemistry",
"Engineering"
] | 1,173 | [
"Aerospace engineering",
"Aerodynamics",
"Fluid dynamics"
] |
977,244 | https://en.wikipedia.org/wiki/Substituent | In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms substituent and functional group, as well as side chain and pendant group, are used almost interchangeably to describe those branches from the parent structure, though certain distinctions are made in polymer chemistry. In polymers, side chains extend from the backbone structure. In proteins, side chains are attached to the alpha carbon atoms of the amino acid backbone.)
The suffix -yl is used when naming organic compounds that contain a single bond replacing one hydrogen; -ylidene and -ylidyne are used with double bonds and triple bonds, respectively. In addition, when naming hydrocarbons that contain a substituent, positional numbers are used to indicate which carbon atom the substituent attaches to when such information is needed to distinguish between isomers. Substituents can be a combination of the inductive effect and the mesomeric effect. Such effects are also described as electron-rich and electron withdrawing. Additional steric effects result from the volume occupied by a substituent.
The phrases most-substituted and least-substituted are frequently used to describe or compare molecules that are products of a chemical reaction. In this terminology, methane is used as a reference of comparison. Using methane as a reference, for each hydrogen atom that is replaced or "substituted" by something else, the molecule can be said to be more highly substituted. For example:
Markovnikov's rule predicts that the hydrogen atom is added to the carbon of the alkene functional group which has the greater number of hydrogen atoms (fewer alkyl substituents).
Zaitsev's rule predicts that the major reaction product is the alkene with the more highly substituted (more stable) double bond.
Nomenclature
The suffix -yl is used in organic chemistry to form names of radicals, either separate species (called free radicals) or chemically bonded parts of molecules (called moieties). It can be traced back to the old name of methanol, "methylene" (from , 'wine' and , 'wood', 'forest'), which became shortened to "methyl" in compound names, from which -yl was extracted. Several reforms of chemical nomenclature eventually generalized the use of the suffix to other organic substituents.
The use of the suffix is determined by the number of hydrogen atoms that the substituent replaces on a parent compound (and also, usually, on the substituent). According to the 1993 IUPAC recommendations:
-yl means that one hydrogen is replaced.
-ylidene means that two hydrogens are replaced by a double bond between parent and substituent.
-ylidyne means that three hydrogens are replaced by a triple bond between parent and substituent.
The suffix -ylidine is encountered sporadically, and appears to be a variant spelling of "-ylidene"; it is not mentioned in the IUPAC guidelines.
For multiple bonds of the same type, which link the substituent to the parent group, the infixes -di-, -tri-, -tetra-, etc., are used: -diyl (two single bonds), -triyl (three single bonds), -tetrayl (four single bonds), -diylidene (two double bonds).
For multiple bonds of different types, multiple suffixes are concatenated: -ylylidene (one single and one double), -ylylidyne (one single and one triple), -diylylidene (two single and one double).
The parent compound name can be altered in two ways:
For many common compounds the substituent is linked at one end (the 1 position) and historically not numbered in the name. The IUPAC 2013 Rules however do require an explicit locant for most substituents in a preferred IUPAC name. The substituent name is modified by stripping -ane (see alkane) and adding the appropriate suffix. This is "recommended only for saturated acyclic and monocyclic hydrocarbon substituent groups and for the mononuclear parent hydrides of silicon, germanium, tin, lead, and boron". Thus, if there is a carboxylic acid called "X-ic acid", an alcohol ending "X-anol" (or "X-yl alcohol"), or an alkane called "X-ane", then "X-yl" typically denotes the same carbon chain lacking these groups but modified by attachment to some other parent molecule.
The more general method omits only the terminal "e" of the substituent name, but requires explicit numbering of each yl prefix, even at position 1 (except for -ylidyne, which as a triple bond must terminate the substituent carbon chain). Pentan-1-yl is an example of a name by this method, and is synonymous with pentyl from the previous guideline.
Note that some popular terms such as "vinyl" (when used to mean "polyvinyl") represent only a portion of the full chemical name.
Methane substituents
According to the above rules, a carbon atom in a molecule, considered as a substituent, has the following names depending on the number of hydrogens bound to it, and the type of bonds formed with the remainder of the molecule:
Notation
In a chemical structural formula, an organic substituent such as methyl, ethyl, or aryl can be written as R (or R1, R2, etc.) It is a generic placeholder, the R derived from radical or rest, which may replace any portion of the formula as the author finds convenient. The first to use this symbol was Charles Frédéric Gerhardt in 1844.
The symbol X is often used to denote electronegative substituents such as the halides.
Statistical distribution
One cheminformatics study identified 849,574 unique substituents up to 12 non-hydrogen atoms large and containing only carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, selenium, and the halogens in a set of 3,043,941 molecules. Fifty substituents can be considered common as they are found in more than 1% of this set, and 438 are found in more than 0.1%. 64% of the substituents are found in only one molecule. The top 5 most common are the methyl, phenyl, chlorine, methoxy, and hydroxyl substituents. The total number of organic substituents in organic chemistry is estimated at 3.1 million, creating a total of 6.7×1023 molecules. An infinite number of substituents can be obtained simply by increasing carbon chain length. For instance, the substituents methyl (-CH3) and pentyl (-C5H11).
See also
Functional groups are a subset of substituents
References
Organic chemistry
Chemical nomenclature | Substituent | [
"Chemistry"
] | 1,522 | [
"Substituents",
"nan"
] |
977,364 | https://en.wikipedia.org/wiki/National%20Lift%20Tower | The National Lift Tower (previously called the Express Lift Tower) is a lift-testing tower built by the Express Lift Company (a lifts division of the General Electric Company) off Weedon Road in Northampton, England. The structure was commissioned in 1978 with construction commencing in 1980 and was officially opened by Queen Elizabeth II on 12 November 1982. It has been a Grade II Listed Building since 1997.
The tower can be viewed from Arbury Hill, the highest point in Northamptonshire.
Background
The site
The tower is in St James End, west of Northampton town centre. The area is named after Northampton Abbey, an Augustinian monastery dedicated to St James, which was founded in 1104–1105. When the former Express Lift factory, which included the lift-testing tower, was redeveloped for housing in 1999–2000, excavations were carried out to determine the location and remains of any parts of the abbey. A cemetery of burials was excavated during winter 2000–2001. The bones were analyzed to determine the health and burial practices in the late-medieval population of Northampton.
Construction
Designed by architect Maurice Walton of Stimpson Walton Bond, the tower is tall, in diameter at the base and tapers to at the top. The only lift-testing tower in Britain, and one of only two in Europe, it was granted Grade II listed building status on 30 October 1997, making it the youngest listed building in the UK at the time. The building's small, obround shaped windows were a design motif of the Express Lift Company, whose lift control panels featured control buttons and floor indicators of the same shape.
In January 1997, the tower fell out of use after Express was taken over by Otis (who typically used its test facilities in the United States). In 1999, the tower and surrounding land was sold to Wilcon Homes for development.
From the time it was built, one shaft was specifically used by the British Standards Institution (BSI) for type testing of lift safety components at the time under the BS 5655 and BS EN81 standards. Safety Gear testing involved putting the lift cars (frame) into free fall conditions with rated mass at tripping speeds as required by the designers of the safety gear to ensure the lift cars decelerated and stopped within the requirements of the standard. Buffer testing involved impacting them with the maximum and minimum mass at tripping speeds to ensure decelerations were within that requirement by the standard in both cases the aim was to ensure if the lift ever went into free fall or uncontrolled downward movement the safety components stopped the lift without causing any serious injury to the occupant. BSI ceased using the test tower soon after the site was acquired for housing in 1997–1998.
The building is now privately owned and has been renamed the National Lift Tower. Following extensive renovation and repairs, the tower was re-opened for business in October 2009. The tower is used by lift companies for research, development, testing and marketing. As well as being a resource for the lift industry, the building is also available to companies requiring tall vertical spaces, for example companies wishing to test working-at-height safety devices.
There are six lift shafts of varying heights and speeds, including a high-speed shaft with a travel of and a theoretical maximum speed of .
The tower's renovation was officially completed in July 2010. Further building work was planned with planning permission being sought to build a visitor's centre incorporating a 100-seater auditorium and cafe. However, permission for this structure was denied by Northampton Borough Council in March 2012.
Abseiling at the tower has been going on since May 2011 with over £140,000 having been raised for charity in the period to May 2012. Northampton Borough Council has now granted approval for it to be used up to 24 times a year for abseiling.
As of 2015, the tower was being used as the world's tallest drainage-testing facility.
Local radio broadcasting
The tower once housed a transmitter on the top of it, for broadcasting community radio station Revolution Radio on FM 96.1 MHz, which launched on 12 June 2021.
Mentions
The tower featured prominently in a 1993 episode of the Channel 4 educational programme The Secret Life of Machines (Series 3, Episode 1), in which Tim Hunkin demonstrates the operation of the high-speed lift in the tower.
The tower was lampooned by broadcaster Terry Wogan as the "Northampton lighthouse". He wrote a section of the book Icons of Northamptonshire (2014) about it.
The Northampton Chronicle & Echo published an article for April Fools' Day 2008, claiming that the lift tower would be pulled down. Comments were made on the paper's website regarding the lack of respect of the local council for not publicly announcing it. Another April Fools' Day story in the same paper suggested the tower would be redeveloped as a mooring station for airships.
The Lift Tower is featured in the science fiction novel Time to Repair by Mark Gallard.
See also
List of towers
Express Lifts history booklet from 1982 includes internal diagrams of the tower
References
External links
Official Website
Abseiling at the tower website
BBC Legacies: Northampton's "Lighthouse"
Architectural details
Risky Buildings: Express Lift Tower
BBC: 360 degree panorama from tower
Wilcon Homes Limited
Northampton lift tower back on the up and up...
Northampton lift tower set for new lease of life
New name for Northampton's lift tower
British Standards Institution (BSI)
Towers in Northamptonshire
Grade II listed buildings in Northamptonshire
Towers completed in 1982
Elevators
1982 establishments in England
Elevator test towers | National Lift Tower | [
"Engineering"
] | 1,117 | [
"Building engineering",
"Elevators"
] |
977,463 | https://en.wikipedia.org/wiki/Net.art | net.art refers to a group of artists who have worked in the medium of Internet art since 1994. Some of the early adopters and main members of this movement include Vuk Ćosić, Jodi.org, Alexei Shulgin, Olia Lialina, Heath Bunting, Daniel García Andújar, and Rachel Baker. Although this group was formed as a parody of avant garde movements by writers such as Tilman Baumgärtel, Josephine Bosma, Hans Dieter Huber and Pit Schultz, their individual works have little in common.
The term "net.art" is also used as a synonym for net art or Internet art and covers a much wider range of artistic practices. In this wider definition, net.art means art that uses the Internet as its medium and that cannot be experienced in any other way. Typically net.art has the Internet and the specific socio-culture that it spawned as its subject matter but this is not required.
The German critic Tilman Baumgärtel - building on the ideas of American critic Clement Greenberg - has frequently argued for a "media specificity" of net.art in his writings. According to the introduction to his book "net.art. Materialien zur Netzkunst", the specific qualities of net.art are "connectivity, global reach, multimediality, immateriality, interactivity and egality".
History of the net.art movement
The net.art movement arose in the context of the wider development of Internet art. As such, net.art is more of a movement and a critical and political landmark in Internet art history, than a specific genre. Early precursors of the net.art movement include the international fluxus (Nam June Paik) and avant-pop (Mark Amerika) movements. The avant-pop movement particularly became widely recognized in Internet circles from 1993, largely via the popular Alt-X site.
In 1995, the term "net.art" was used by nettime initiator Pit Schultz as a title for an exhibition in Berlin in 1995, in which Vuk Cosic and Alexei Shulgin both showed their work. It was later used with regard to the "net.art per se" meeting of artists and theorists in Trieste in May 1996, and referred to a group of artists who worked together closely in the first half of the 1990s. These meetings gave birth to the website net.art per se, a fake CNN website "commemorating" the event. The term "net.art" has been wrongly attributed to artist Vuk Cosic in 1997, after Alexei Shulgin wrote about the origin of the term in a prank mail to the nettime mailinglist. According to Shulgin's mail net.art stemmed from "conjoined phrases in an email bungled by a technical glitch (a morass of alphanumeric junk, its only legible term 'net.art')".
Online social networks
net.artists have built digital art communities through an active practice of web hosting and web art curating. net.artists have defined themselves through an international and networked mode of communication, an interplay of exchanges, collaborative and cooperative work . They have a large presence on several mailing lists such as Rhizome, File festival, Electronic Language International Festival, Nettime, Syndicate and Eyebeam. The identity of the net.artists is defined by both their digital works and their critical involvement in the digital art community, as the polemical discussion led by Olia Lialina that occurred on Nettime in early 2006 on the "New Media" Wikipedia entry shows
net.artists like Jodi developed a particular form of e-mail art, or spam mail art, through text reprocessing and ASCII art. The term "spam art" was coined by net critique and net art practitioner Frederic Madre to describe all such forms of disruptive interventions in mailing-lists, where seemingly nonsensical texts were generated by simple scripts, online forms or typed by hand.
A connection can be made to the e-mail interventions of "Codeworks" artists such as Mez or mi ga or robots like Mailia which analyze emails and reply to them. "Codeworks" is a term coined by poet Alan Sondheim to define the textual experiments of artists playing with faux-code and non-executable script or mark-up languages.
Tactical media net art
net.art developed in a context of cultural crisis in Eastern Europe in the beginning of the 1990s after the end of the Soviet Union and the fall of the Berlin Wall. The artists involved in net.art experiments are associated with the idea of a "social responsibility" that would answer the idea of democracy as a modern capitalist myth. The Internet, often promoted as the democratic tool par excellence, but largely participating in the rules of vested interests, is targeted by the net.artists who claimed that "a space where you can buy is a space where you can steal, but also where you can distribute". net.artists focus on finding new ways of sharing public space.
By questioning structures such as the navigation window and challenging their functionality, net.artists have shown that what is considered to be natural by most Internet users is actually highly constructed, even controlled, by corporations. Company browsers like Netscape Navigator or Internet Explorer display user-friendly structures (the "navigation", the "exploration" are landmarks of social practices) to provide the user with a familiar environment; net.artists try to break this familiarity. Olia Lialina, in My Boyfriend Came Back From The War or the duo Jodi, with their series of pop-up interventions and browser crashing applets, have engaged the materiality of navigation in their work. Their experiments have given birth to what could be called "browser art", which has been expanded by the British collective I/O/D's experimental navigator WebStalker.
Alexei Shulgin and Heath Bunting have played with the structure of advertisement portals by establishing lists of keywords unlikely to be searched for but nonetheless existing on the web as URLs or metadata components: they use this relational data to enmesh paths of navigation in order to create new readable texts . The user is not exploring one art website that has its own meaning and aesthetic significance within itself, but rather they are exposed to the entire network as a collection of socioeconomic forces and political stances that are not always visible.
Rachel Greene has associated net.art with tactical media as a form of Detournement. Greene writes: "The subversion of corporate websites shares a blurry border with hacking and agitprop practices that would become an important field of net art, often referred to as 'tactical media'."
Hacker culture
The Jodi collective works with the aesthetics of computer errors, which has a lot in common, on both the aesthetic and pragmatic levels, with hacker culture. Questioning and disturbing the browsing experience with hacks, code tricks, faux-code, and faux-virus, critically investigates the context in which they are agents. In turn, the digital environment becomes concerned with its own internal structure. The collective 0100101110101101.org expands the idea of "art hacktivism" by performing code interventions and perturbations in art festivals such as the Venice Biennale. On the other hand, the collective irational.org expands the idea of "art hacktivism" by performing interventions and perturbations in the real world, acting on it as on a possible ground for social reengineering.
"We can point to a superficial difference between most net.art and hacking: hackers have an obsession with getting inside other computer systems and having an agency there, whereas the 404 errors in the JTDDS (for example) only engage other systems in an intentionally wrong manner in order to store a 'secret' message in their error logs. It's nice to think of artists as hackers who endeavour to get inside cultural systems and make them do things they were never intended to do: artists as culture hackers.".
A networking expert hacked into DNS servers to have the traceroute Linux command reveal the history of star wars IV. This deep technical repurposing for the sake of enchantment and fun can be considered as a net.art performance.
Computer worms can be intentionally good and positive when they are repurposed for large-scale ephemeral art that uses the whole Internet as a canvas.
Critique of the art world
During the heyday of net.art developments, particularly during the rise of global dot.com capitalism, the first series of critical columns appeared in German and English in the online publication Telepolis. Edited by writer and artist Armin Medosch, the work published at Telepolis featured American artist and net theorist Mark Amerika's "Amerika Online" columns. These columns satirized the way self-effacing net.artists (himself included) took themselves too seriously. In response, European net.artists impersonated Amerika in faux emails to deconstruct his demystification of the marketing schemes most net.artists employed to achieve art world legitimacy. It was suggested that "the duplicitous dispatches were meant to raise US awareness of electronic artists in Europe, and may even contain an element of jealousy."
Many of these net.art interventions also tackled the issue of art as business and investigated mainstream cultural institutions such as the Tate Modern. Harwood, a member of the Mongrel collective, in his work Uncomfortable Proximity (the first on-line project commissioned by Tate) mirrors the Tate's own website, and offers new images and ideas, collaged from his own experiences, his readings of Tate works, and publicity materials that inform his interest in the Tate website.
net.artists have actively participated in the debate over the definition of net.art within the context of the art market. net.art promoted the modernist idea of the work of art as a process, as opposed to a conception of art as object making . Alexander R. Galloway, in an e-flux article entitled "Jodi's Infrastructure" argues that Jodi's approach to net.art, which involves the very structures that govern coding, is uniquely modernist: the form and content converge in the artwork. The presentation of this process within the art world—whether it should be sold in the market, or shown in the institutional art environment, is problematic for digital works created for the Internet. The web, as marketable as it is, cannot be restricted to the ideological dimensions of the legitimate field of art, the institution of legitimation for art value, that is both ideological and economical . All for Sale by Aliona is an early net.art experiment addressing such issues. The WWWArt Award competition initiated by Alexei Shulgin in 1995 suggests rewarding found Internet works with what he calls an "art feeling."
Some projects, such as Joachim Schmid's Archiv, Hybrids, or Copies by Eva & Franco Mattes (under the pseudonym of 0100101110101101.org), are examples of how to store art-related or documentary data on a website. Cloning, plagiarizing, and collective creation are provided as alternative answers, such as in the Refresh Project.
Olia Lialina has addressed the issue of digital curating via her web platform Teleportacia.org, an online gallery to promote and sell net.art works. Each piece of net.art has its originality protected by a guarantee constituted by its URL, which acts as a barrier against reproducibility and/or forgery. Lialina claimed that this allowed the buyer of the piece to own it as they wished: controlling the location address as a means of controlling access to the piece. This attempt at giving net.art an economic identity and a legitimation within the art world was questioned even within the net.art sphere, though the project was often understood as a satire. On the other hand, Teo Spiller really sold a web art project Megatronix to Ljubljana Municipal Museum in May 1999, calling the whole project of selling the net.art.trade.
Teleportacia.org became an ambiguous experiment on the notion of originality in the age of extreme digital reproduction and remix culture. The guarantee of originality protected by the URL was quickly challenged by Eva & Franco Mattes, who, under the pseudonym of 0100101110101101.org, cloned the content and produced an unauthorized mirror-site, showing the net.art works in the same context and the same quality as the original. The Last Real Net Art Museum is another example of Olia Lialina's attempt to deal with the issue.
Online social networks experiments, such as the Poietic Generator, which existed before the net.art movement, was involved in it, and still exist after it, may show that the fashion scheme of net.art may have forgotten some deep theoretical questions.
See also
Digital culture
History of the Internet
Internet art
Glitch art
Net-poetry
Surfing club
References
Bibliography
Baranski Sandrine, La musique en réseau, une musique de la complexité ?, Éditions universitaires européennes, 2010 La musique en réseau
Bosma, Josephine, Nettitudes Let's Talk Net Art, Nai010 publishers, Rotterdam, 2011,
Martín Prada, Juan, Prácticas artísticas e Internet en la época de las redes sociales, Editorial AKAL, Madrid, 2012,
External links
Thomas Dreher: History of Computer Art, chap. VI.3 Net Art in the Web Munich 2014
Thomas Dreher: IASLonline Lessons in NetArt.
Internet culture
Art websites
Multimedia
New media art | Net.art | [
"Technology"
] | 2,840 | [
"Multimedia",
"Net.artists"
] |
977,489 | https://en.wikipedia.org/wiki/M101%20Group | The M101 Group is a loose group of galaxies located in the constellation Ursa Major. The group is named after the brightest galaxy in the group, the Pinwheel Galaxy (M101). Most of the other members of the group are companions of the Pinwheel Galaxy. The group itself is one of many located within the Virgo Supercluster (i.e. the Local Supercluster).
Members
The table below lists galaxies that have been consistently identified as group members in the Nearby Galaxies Catalog, the survey of Fouque et al., the Lyons Groups of Galaxies (LGG) Catalog, and the three group lists created from the Nearby Optical Galaxy sample of Giuricin et al.
Other possible members galaxies (galaxies listed in only one or two of the lists from the above references) include the irregular galaxies NGC 5238 and UGC 8508.
Nearby groups
The M51 Group, which includes the Whirlpool Galaxy (M51) and the Sunflower Galaxy (M63), is located to the southeast of the M101 Group, and the NGC 5866 Group is located to the northwest. The distances to these three groups (as determined from the distances to the individual member galaxies) are similar, which suggests that the M51 Group, the M101 Group, and the NGC 5866 Group are actually part of a single large, loose, elongated group. However, most group identification methods (including those used by the references cited above) identify these three groups as separate entities.
See also
Virgo Cluster
References
Virgo Supercluster
Ursa Major | M101 Group | [
"Astronomy"
] | 324 | [
"Ursa Major",
"Constellations"
] |
977,522 | https://en.wikipedia.org/wiki/Rocket-powered%20aircraft | A rocket-powered aircraft or rocket plane is an aircraft that uses a rocket engine for propulsion, sometimes in addition to airbreathing jet engines. Rocket planes can achieve much higher speeds than similarly sized jet aircraft, but typically for at most a few minutes of powered operation, followed by a gliding flight. Unhindered by the need for oxygen from the atmosphere, they are suitable for very high-altitude flight. They are also capable of delivering much higher acceleration and shorter takeoffs. Many rocket aircraft may be drop launched from transport planes, as take-off from ground may leave them with insufficient time to reach high altitudes.
Rockets have been used simply to assist the main propulsion in the form of jet assisted take off (JATO) also known as rocket-assisted takeoff (RATO or RATOG). Not all rocket planes are of the conventional takeoff like "normal" aircraft. Some types have been air-launched from another plane, while other types have taken off vertically – nose in the air and tail to the ground ("tail-sitters").
Because of the use of heavy propellants and other practical difficulties of operating rockets, the majority of rocket planes have been built for experimental or research use, as interceptor fighters and space aircraft.
History
Background
Peruvian polymath Pedro Paulet conceptualized the Avión Torpedo in 1902 – a liquid-propellant rocket-powered aircraft that featured a canopy fixed to a delta tiltwing – spending decades seeking donors for the aircraft while serving as a diplomat in Europe and Latin America. Paulet's concept of using liquid-propellant was decades ahead of rocket engineers at the time who utilized black powder as a propellant. Reports of Paulet's rocket aircraft concept first appeared in 1927 after Charles Lindbergh crossed the Atlantic Ocean in an aircraft. Paulet publicly criticized Austrian rocket pioneer Max Valier's proposal about a rocket-powered aircraft completing the journey faster using black powder, arguing that his liquid-propellant rocket aircraft from thirty years earlier would be a better option.
Paulet would go on to visit the German rocket association Verein für Raumschiffahrt (VfR) and on March 15, 1928, Valier applauded Paulet's liquid-propelled rocket design in the VfR publication Die Rakete, saying the engine had "amazing power". In May 1928, Paulet was present to observe the demonstration of a rocket car of the Opel RAK program of Fritz von Opel and Max Valier, and after meeting with the German rocket enthusiasts. VfR members began to view black powder as a hindrance for rocket propulsion, with Valier himself believing that Paulet's engine was necessary for future rocket development. Paulet would soon be approached by Nazi Germany to help develop rocket technology, though he refused to assist and never shared the formula for his propellant. The Nazi government would then appropriate Paulet's work while a Soviet spy in the VfR, Alexander Boris Scherchevsky, possibly shared plans with the Soviet Union.
On 11 June 1928, as part of the Opel RAK program of Fritz von Opel and Max Valier, Lippisch Ente became the first aircraft to fly under rocket power. During the following year, the Opel RAK.1 became the first purpose-built rocket plane to fly with Fritz von Opel himself as the pilot. The Opel RAK.1 flight is also considered the world's first public flight of a manned rocket plane since it took place before a large crowd and with world media in attendance.
On 28 June 1931, another ground-breaking rocket flight was conducted by the Italian aviator and inventor Ettore Cattaneo, who created another privately built rocket plane. It flew and landed without particular problems. Following this flight, the King of Italy Victor Emmanuel III appointed Cattaneo count of Taliedo; due to his pioneering role in rocket flight, his likeness is displayed in the Space Museum of Saint Petersburg as well as in the Museum of Science and Tech of Milan.
World War II
The Heinkel He 176 was the world's first aircraft to be propelled solely by a liquid-propellant rocket engine. It performed its first powered flight on 20 June 1939 with Erich Warsitz at the controls. The He 176, while demonstrated to the Reich Air Ministry did not attract much official support, leading to Heinkel abandoning its rocket propulsion endeavours; the sole aircraft was briefly displayed at the Berlin Air Museum and was destroyed by an Allied bombing raid in 1943.
The first rocket plane ever to be mass-produced was the Messerschmitt Me 163 Komet interceptor, introduced by Germany towards the final years of the conflict as one of several efforts to develop effective rocket-powered aircraft. The Luftwaffe's first dedicated Me 163 fighter wing, Jagdgeschwader 400 (JG 400) was established in 1944, and was principally tasked with providing additional protection for the manufacturing plants producing synthetic gasoline, which were prominent targets for Allied air raids. It was planned to station further defensive units of rocket fighters around Berlin, the Ruhr and the German Bight.
A typical Me 163 tactic was to fly vertically upward through the bombers at , climb to , then dive through the formation again, firing as they went. This approach afforded the pilot two brief chances to fire a few rounds from his cannons before gliding back to his airfield. It was often difficult to supply the needed fuel for operating the rocket motors. In the final days of the Third Reich, the Me 163 was withdrawn in favor of the more successful Messerschmitt Me 262, which used jet propulsion instead.
Other German rocket-powered aircraft were pursued as well, including the Bachem Ba 349 "Natter", a vertical takeoff manned rocket interceptor aircraft that flew in prototype form. Further projects never even reached the prototype stage, such as the Zeppelin Rammer, the Fliegende Panzerfaust and the Focke-Wulf Volksjäger. Having a much larger size than any other rocket-powered endeavor of the conflict, the Silbervogel antipodal bomber spaceplane was planned by the Germans, however, later calculations showed that design would not have worked, instead being destroyed during reentry. The Me 163 Komet is the only type of rocket-powered fighter to see combat in history, and one of only two types of rocket-powered aircraft seeing any combat.
Japan, who was allied to Nazi Germany, secured the design schematics of the Me 163 Komet. After considerable effort, it successfully established its own production capability, which was used to produce a limited number of its own copies, known as the Mitsubishi J8M, which performed its first powered flight on 7 July 1945. Furthermore, Japan attempted to develop its own domestically designed rocket-powered interceptor, the Mizuno Shinryu; neither the J8M or the Shinryu ever saw combat. The Japanese also produced approximately 850 Yokosuka MXY-7 Ohka rocket-powered suicide attack aircraft during the Second World War, a number were deployed in the Battle of Okinawa. Postwar analysis concluded that the Ohkas impact was negligible, and that no U.S. Navy capital ships had been hit during the attacks due to the effective defensive tactics that were employed.
Other experimental aircraft included the Soviet Bereznyak-Isayev BI-1 that flew in 1942 while the Northrop XP-79 was originally planned with rocket engines but switched to jet engines for its first and only flight in 1945. A rocket-assisted P-51D Mustang was developed by North American Aviation that could attain . The engine ran on fumaric acid and aniline which was stored in two under wing drop tanks. The plane was tested in flight in April 1945. The rocket engine could run for about a minute. Similarly, the Messerschmitt Me 262 "Heimatschützer" series used a combination of rocket and jet propulsion to allow for shorter take-offs, faster climb rate, and even greater speeds.
Cold War era
During 1946, the Soviet Mikoyan-Gurevich I-270 was constructed in response to a Soviet Air Forces requirement issued during the previous year for a rocket-powered interceptor aircraft in the point-defence role. The design of the I-270 incorporated several pieces of technology that had been developed by Sergei Korolev between 1932 and 1943.
During 1947, a key milestone in aviation history was reached by the rocket-powered Bell X-1, which became the first aircraft to break the speed of sound in level flight, and would be the first of a series of NACA/NASA rocket-powered aircraft. Amongst these experimental aircraft were the North American X-15 and X-15A2 designs, which were operated for around a decade and eventually attained a maximum speed of Mach 6.7 as well as a peak altitude in excess of 100 km, setting new records in the process.
During the 1950s, the British developed several mixed power designs to cover the performance gap that existed in then-current turbojet designs. The rocket was the main engine for delivering the speed and height required for high speed interception of high level bombers and the turbojet gave increased fuel economy in other parts of flight, most notably to ensure that the aircraft was able to make a powered landing rather than risking an unpredictable gliding return. One design was the Avro 720, which was primarily propelled by an 8,000 lbf (36 kN) Armstrong Siddeley Screamer rocket engine that ran on kerosene fuel mixed with liquid oxygen as the oxidizing agent. Work on the Avro 720 was abandoned shortly after the Air Ministry's decision to terminate development of the Screamer rocket engine, allegedly due to official concerns regarding the practicality of using liquid oxygen, which boils at -183 °C (90 K) and is a fire hazard, within an operational environment.
Work reached a more advanced stage with the Avro 720's rival, the Saunders-Roe SR.53. The propulsion system of this aircraft used hydrogen peroxide as a combined fuel and oxidiser, which was viewed as less problematic than the Avro 720's liquid oxygen. On 16 May 1957, Squadron Leader John Booth DFC was at the controls of XD145 for the first test flight, following up with the maiden flight of the second prototype XD151, on 6 December 1957. During the subsequent flight test programme, these two prototypes flew 56 separate test flights, during which a maximum speed of Mach 1.33 was recorded. Furthermore, since late 1953, Saunders-Roe had worked upon a derivative of the SR.53, which was separately designated as the SR.177; the principal change was the presence of an onboard radar, lacking on the SR.53 and the Avro 720 as it not being a requirement of the specification, but left the pilot dependent on his own vision other than radio-based directions supplied from ground-based radar control.
Both the SR.53 and its SR.177 cousin were relatively close to attain production status when wider political factors bore down upon the programme. During 1957, a massive re-thinking of air defence philosophy in Britain occurred, which was embodied in the 1957 Defence White Paper. This paper called for manned combat aircraft to be replaced by missiles, and thus the prospects of an order from the RAF evaporated overnight. While both the Royal Navy and Germany remained potential customers for the SR.177, the confidence of both parties was shaken by the move. Further factors, such as the Lockheed bribery scandals to compel overseas nations to order the Lockheed F-104 Starfighter, also served to undermine the sale prospects of the SR.177, costing potential customers such as Germany and Japan.
Throughout the late 1940s and 1950s, the French Air Staff also had considerable interest in rocket-powered aircraft. According to author Michel van Pelt, French Air Force officials were against a pure rocket-powered flight but favoured a mixed-propulsion approach, using a combination of rocket and turbojet engines. While the Société d'Etudes pour la Propulsion par Réaction (SEPR) set about developing France's own domestic rocket engines, the French aircraft manufacturer SNCASE was aware of the French Air Force's keenness for a capable point defence interceptor aircraft, and thus begun work on the SNCASE SE.212 Durandal. In comparison to other French mixed-power experimental aircraft, such as the competing SNCASO Trident prototype interceptor, it was a heavier aircraft, intended to fly primarily on its jet engine rather than its rocket motor. A pair of prototype aircraft were constructed; on 20 April 1956, the first performed its maiden flight, initially flying only using jet power. It was the second prototype that first made use of the rocket motor during April 1957. During flight testing, a maximum speed of was attained at an altitude of, even without using the extra power of the rocket motor; this rose to 1667 km/h at 11,800 m while the rocket was active. A total of 45 test flights were performed prior to work on the programme being terminated.
At the request of the French Air Staff, the French aircraft company SNCASO also developed its own point defence interceptor, the SNCASO Trident. It was primarily powered by a single SEPR-built rocket engine and augmented with a set of wing-tip mounted turbojet engines; operationally, both rocket and turbojet engines were to be used to perform a rapid climb and interception at high altitudes, while the jet engines alone would be used to return to base. On 2 March 1953, the first prototype Trident I conducted the type's maiden flight; flown by test pilot Jacques Guignard, the aircraft used the entire length of the runway to get airborne, being powered only by its turbojet engines. On 1 September 1953, second Trident I prototype crashed during its first flight after struggling to gain altitude after takeoff and colliding with an electricity pylon. Despite the loss, the French Air Force were impressed by the Trident's performance and were keen to have an improved model into service. On 21 May 1957, the first Trident II, 001, was destroyed during a test flight out of Centre d'Essais en Vol (Flight Test Center); caused when highly volatile rocket fuel and oxidiser, Furaline ( C13H12N2O) and Nitric acid (HNO3) respectively, accidentally mixed and exploded, resulting in the death of test pilot Charles Goujon. Two months later, all work was halted on the programme.
The advancement of the turbojet engine output, the advent of missiles, and advances in radar had made a return to mixed power unnecessary.
The development of Soviet rockets and satellites was the driving force behind the development of NASA's space program. In the early 1960s, American research into the Boeing X-20 Dyna-Soar spaceplane was cancelled due to lack of purpose; later the studies contributed to the Space Shuttle, which in turn motivated the Soviet Buran. Another similar program was ISINGLASS which was to be a rocket plane launched from a Boeing B-52 Stratofortress carrier, which was intended to achieve Mach 22, but this was never funded. ISINGLASS was intended to overfly the USSR. No images of the vehicle configuration have been released.
The Lunar Landing Research Vehicle was a mixed powered vehicle- a jet engine cancelled 5/6 of the force due to gravity, and the rocket power was able to simulate the Apollo lunar lander.
Various versions of the Reaction Motors XLR11 rocket engine powered the X-1 and X-15, but also the Martin Marietta X-24A, Martin Marietta X-24B, Northrop HL-10, Northrop M2-F2, Northrop M2-F3, and the Republic XF-91 Thunderceptor, either as a primary or auxiliary engine.
The Northrop HL-10, Northrop M2-F2 and Northrop M2-F3 were examples of a lifting body, which are aircraft which have very little if any wing and simply obtain lift from the body of the vehicle. Another example is backslider rockets in amateur rocketry.
Post Cold War era
The EZ-Rocket research and test airplane was first flown in 2001. After evaluating the EZ-Rocket, the Rocket Racing League developed three separate rocket racer aircraft over the following decade.
During 2003, another privately developed rocket-powered aircraft performed its first flight. SpaceShipOne functions both as a rocket-powered aircraft—with wings and aerodynamic control surfaces—as well as a spaceplane—with RCS thrusters for control in the vacuum of space. For their work, the SpaceShipOne team were awarded the Space Achievement Award.
In April 2019, the Chinese company Space Transportation carried out a test of a 3,700-kilogram technology demonstrator named Jiageng-1. The 8.7-meter-long plane has a wingspan of 2.5 meters and it is a part of development of the larger, future Tianxing-I-1 vertical takeoff, horizontal landing reusable launch vehicle.
Planned rocket-powered aircraft
Aerial Regional-scale Environmental Survey
Skylon (spacecraft)
XCOR Lynx
Zero Emission Hyper Sonic Transport
See also
List of rocket aircraft
List of vehicle speed records
Rocket Racing League (RRL)
Zero-length launch, launching air-breathing aircraft with rockets
References
Citations
Bibliography
"Armstrong Siddeley Screamer". Flight, No. 2478, Vol 70, 27 July 1956. pp. 160–164.
Bachem, Erich. "Einige grundsätzliche Probleme des Senkrechstarts. Probleme aus der Astronautischen Grundlagenforschung" (in German). Proceedings of the Third International Congress on Astronautics. Stuttgart: Gesellschaft für Weltraumforschung, September 1952.
Bille, Matt and Erika Lishock. The First Space Race: Launching the World's First Satellites. College Station, Texas: Texas A&M University Press, 2004. .
"Cancelled Projects:The list Up-Dated". Flight, 17 August 1967, p. 262.
Caidin, Martin. Wings into Space: The History and Future of Winged Space Flight. New York: Holt, Rinehart and Winston Inc., 1964.
Dornberger, Walter R. "The Rocket-Propelled Commercial Airliner". Dyna-Soar: Hypersonic Strategic Weapons System, Research Report No 135.. Minneapolis, Minnesota: University of Minnesota, Institute of Technology, 1956.
Galland, Adolf. The First and the Last. New York: Ballantine Books, 1957.
Geiger, Clarence J. History of the X-20A Dyna-Soar. Vol. 1: AFSC Historical Publications Series 63-50-I, Document ID ASD-TR-63-50-I. Wright-Patterson AFB, Ohio: Aeronautical Systems Division Information Office, 1963.
Godwin, Robert, ed. Dyna-Soar: Hypersonic Strategic Weapons System. Burlington, ON: Apogee Books, 2003. .
Gunston, Bill. Fighters of the Fifties. Cambridge, England: Patrick Stephens Limited, 1981. .
Jackson, A. J. Avro Aircraft since 1908. London:Putnam, 1990. .
Jackson, Robert. "Combat Aircraft Prototypes since 1945", New York: Arco/Prentice Hall Press, 1986, LCCN 85-18725, .
Jones, Barry. "Saro's Mixed-Power Saga". Aeroplane Monthly, November 1994. London:IPC. ISSN 0143-7240. pp. 32–39.
Lommel, Horst. Der erste bemannte Raketenstart der Welt (2nd ed.) (in German). Stuttgart: Motorbuch Verlag, 1998. .
London, Pete. "Saunders-Roe's Rocket Fighters." Aircraft, Vol. 43, no. 7, July 2010.
Mason, Francis K. The British Fighter since 1912. Annapolis, Maryland, USA:Naval Institute Press, 1992. .
"Mixed-Power Interceptor". Flight, 24 May 1957, pp. 697–700.
Pelt, Michel van. Rocketing into the Future: The History and Technology of Rocket Planes. Springer Science & Business Media, 2012. .
Späte, Wolfgang. Top Secret Bird: Luftwaffe's Me-163 Komet. Missoula, Montana: Pictorial Histories Publishing Co., 1989. .
Winchester, Jim. "TSR.2." Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. Kent, UK: Grange Books plc., 2005. .
Wood, Derek. Project Cancelled: The Disaster of Britain's Abandoned Aircraft Projects. London, UK: Jane's, 2nd edition, 1986. .
Yenne, Bill. The Encyclopedia of US Spacecraft. London: Bison Books, 1985. .
External links
The official Erich Warsitz website (world’s first jet pilot) about the world’s first liquid-fuelled rocket aircraft, the legendary Heinkel He 176
Aircraft configurations
German inventions
Vehicles introduced in 1928 | Rocket-powered aircraft | [
"Engineering"
] | 4,301 | [
"Aircraft configurations",
"Aerospace engineering"
] |
977,527 | https://en.wikipedia.org/wiki/Truncated%20power%20function | In mathematics, the truncated power function with exponent is defined as
In particular,
and interpret the exponent as conventional power.
Relations
Truncated power functions can be used for construction of B-splines.
is the Heaviside function.
where is the indicator function.
Truncated power functions are refinable.
See also
Macaulay brackets
External links
Truncated Power Function on MathWorld
References
Numerical analysis | Truncated power function | [
"Mathematics"
] | 79 | [
"Computational mathematics",
"Mathematical relations",
"Approximations",
"Numerical analysis"
] |
977,559 | https://en.wikipedia.org/wiki/Castillo%20de%20San%20Marcos | The Castillo de San Marcos (Spanish for “St. Mark’s Castle”) is the oldest masonry fort in the continental United States; it is located on the western shore of Matanzas Bay in St. Augustine, Florida.
It was designed by the Spanish engineer Ignacio Daza, with construction beginning in 1672, 107 years after the city's founding by Spanish Admiral and conquistador Pedro Menéndez de Avilés, when Florida was part of the Spanish Empire. The fort's construction was ordered by Governor Francisco de la Guerra y de la Vega after a raid by the English privateer Robert Searles in 1668 that destroyed much of St. Augustine and damaged the existing wooden fort. Work proceeded under the administration of Guerra's successor, Manuel de Cendoya in 1671, and the first coquina stones were laid in 1672. The construction of the core of the current fortress was completed in 1695, although it would undergo many alterations and renovations over the centuries.
When Britain gained control of Florida in 1763 pursuant to the Treaty of Paris, St. Augustine became the capital of British East Florida, and the fort was renamed Fort St. Mark until the Peace of Paris (1783) when Florida was transferred back to Spain and the fort's original name restored. In 1819, Spain signed the Adams–Onís Treaty which ceded Florida to the United States in 1821; consequently, the fort was designated a United States Army base and renamed Fort Marion, in honor of American Revolutionary War hero Francis Marion. The fort was declared a National Monument in 1924, and after 251 years of continuous military possession, was deactivated in 1933. The site was subsequently turned over to the United States National Park Service. In 1942 the original name, Castillo de San Marcos, was restored by an Act of Congress.
Castillo de San Marcos was attacked several times and twice besieged: first by English colonial forces led by Carolina Colony Governor James Moore in 1702, and then by English Georgia colonial Governor James Oglethorpe in 1740. However, possession of the fort has changed five times, all peaceful, among four different governments: Spain, 1695–1763 and 1783–1821, Kingdom of Great Britain, 1763–1783, and the United States, 1821–date (during 1861–1865, under control of the Confederate States of America). Owing to its strategic cannon placement and star-shaped design, the fort was never breached or taken by force throughout its various stages of sovereign ownership.
Under United States control the fort was used as a military prison to incarcerate members of Native American tribes starting with the Seminole—including the famous war chief, Osceola, in the Second Seminole War—and members of western tribes, including Geronimo's band of Chiricahua Apache. The Native American art form known as Ledger Art had its origins at the fort during the imprisonment of members of the Plains tribes such as Howling Wolf of the southern Cheyenne.
Although built in part by African slaves owned by the Spanish, the fort later served as one of the first entry points of fugitive slaves from British North America into Spanish Florida, where they were freed by the Spanish colonial authorities. This quickly led to the first free Black settlement in the future United States (Fort Mose, formed just north of St Augustine).
Ownership of the Castillo was transferred to the National Park Service in 1933, and, along with the nearby St. Augustine Historic District, has been a popular tourist destination ever since.
Structure
The European city of St. Augustine was founded by the admiral Pedro Menéndez de Avilés for the Spanish Crown in 1565 on the site of a former Native American village called Seloy.
The need for fortifications was recognized after it was attacked by Sir Francis Drake and his fleet of 22 ships in 1586, and over the next 80 years, a succession of nine wooden forts were built in various locations along the coastline. After an attack in 1668 by the English pirate Robert Searle, however, during which the town of St. Augustine was burned to the ground, wooden forts were deemed inadequate, and Mariana, Queen Regent of Spain, approved the construction of a masonry fortification to protect the city.
The Castillo is a masonry star fort made of a stone called coquina (Spanish for "small shells"), which consists of ancient shells that have bonded together to form a sedimentary rock similar to limestone. Native Americans from Spain's nearby missions did most of the labor, with additional skilled workers brought in from Havana, Cuba. The coquina was quarried from the 'King's Quarry' on Anastasia Island in what is today Anastasia State Park across Matanzas Bay from the Castillo, and ferried across to the construction site. Construction began on and lasted twenty-three years, with completion in 1695.
The fort has four bastions named San Pedro, San Agustín, San Carlos, and San Pablo, with a ravelin protecting the sally port. On the two landward sides, a large glacis was constructed which would force any attackers to advance upward toward the fort's cannon and allow the cannon shot to proceed downslope for greater efficiency in hitting multiple targets. Also, the artificial mound of the glacis in front of the walls helped to protect them from direct cannon fire attempting to breach them in a siege. Immediately surrounding the fort was a moat which was usually kept dry, but that could be flooded with seawater to a depth of about in case of attack by land.
Multiple embrasures were built into the curtain wall along the top of the fort as well as into the bastions for the deployment of a cannon of various calibers. Infantry embrasures were also built into the walls below the level of the terreplein for the deployment of muskets by the fort's defenders. It was through one of these embrasures that twenty Seminoles held as prisoners would escape in 1837.
History
First English siege
In 1670, Charles Town (modern-day Charleston, South Carolina) was founded by English colonists. As it was just two days' sail from St. Augustine, the English settlement and encroachment of English traders into Spanish territory spurred the Spanish in their construction of a fort.
Slaves from the Carolina colony began escaping to St Augustine in 1687, where the Spanish agreed to free (and employ) them if they converted to Catholicism. When an English major from Carolina attempted to retrieve escapees in 1688, the Spanish Governor Diego de Quiroga refused. Charles II of Spain issued an official policy in 1693, cementing the informal practice.
In 1702, English colonial forces under the command of Carolina Governor James Moore Sr. embarked on an expedition to capture St. Augustine early in Queen Anne's War. The English laid siege to St. Augustine in November 1702. About 1,500 town residents and soldiers were crammed into the fort during the two-month siege. The small English cannons had little effect on the walls of the fort, because the coquina masonry was very effective at absorbing the impact of cannonballs causing them to sink into the walls, rather than shattering or puncturing them.
The siege was broken when the Spanish fleet from Havana arrived, trapping some English vessels in the bay. The English decided to burn their ships to prevent them from falling under Spanish control, and then marched overland back to Carolina. The town of St. Augustine was destroyed, in part by the Spanish and in part by the English, as a result of the siege.
Second period of construction
Beginning in 1738, under the supervision of Spanish engineer Pedro Ruiz de Olano, the interior of the fort was redesigned and rebuilt. Interior rooms were made deeper, and vaulted ceilings replaced the original wooden ones. The vaulted ceilings allowed for better protection from bombardments and allowed for cannon to be placed along the gun deck, not just at the corner bastions. The new ceilings required the height of the exterior wall to be increased from 26 to .
Second British siege
Spain and Britain were rivals in Europe, and since the two countries had both founded empires in the New World, their rivalry continued there as well. In 1733, the British merchantmen Rebecca, commanded by Captain Robert Jenkins, was seized in the Caribbean by the Spanish coast guard. Suspecting that Rebecca had been trading illegally with Spanish colonies (which was forbidden by both Spain and Britain), the Spanish searched the ship. A fight broke out between the Spanish and British sailors. In the skirmish, Jenkins had his ear cut off by a Spanish officer, who picked it up and said "Take this to your king and tell him that if he were here I would serve him in the same manner!" When Jenkins reported the incident to British authorities, they used it as a casus belli to declare war on Spain in 1739. The war was called the War of Jenkins' Ear.
After British Admiral Edward Vernon won a significant victory at Portobelo, General James Oglethorpe, the founder of Georgia, was quick to imitate him in North America. In June 1740, Oglethorpe and a British fleet of seven ships appeared off St. Augustine. As in the 1702 siege, three hundred soldiers and 1,300 residents found refuge within the Castillo's walls. For 27 days the British bombarded the Castillo and St. Augustine. Realizing his cannon were not affecting the Castillo's walls of coquina, Oglethorpe decided to starve the people of St. Augustine into submission by blockading the inlet at the Matanzas River and all roads into St. Augustine. However, some supplies were able to reach the city via the river, and with morale and supplies low for the British forces, Oglethorpe had to retreat. In order to protect the city from future blockades and sieges, the Spanish built Fort Matanzas to guard the river, which could be used as a rear entrance to avoid St. Augustine's primary defense system.
British occupation
In 1763, the British managed to take control of the Castillo but not by force. As a provision of the Treaty of Paris (1763) after the Seven Years' War, Britain gained all of Spanish Florida in exchange for returning Havana and Manila to Spain. On July 21, 1763, the Spanish governor turned the Castillo over to the British, who established St. Augustine as the capital of the province of East Florida, established by the Royal Proclamation of 1763.
The British made some changes to the fort, and renamed it Fort St. Mark. As Great Britain was the dominant power in North America, they were not worried about keeping the fort in top condition. This attitude prevailed until the outbreak of the American Revolutionary War. The fort was used as a military prison during the war. Among those imprisoned was Christopher Gadsden, the Lieutenant governor of South Carolina. He was also a delegate to the Continental Congress and a brigadier general in the Continental Army during the war. He was released after 11 months.
Improvements were begun on the fort, in keeping with its new role as a base of operations for the British in the South. The gates and walls were repaired, and second floors were added to several rooms to increase the housing capacity of the fort. The Castillo saw action during the American Revolution mainly as a prison, although St. Augustine was targeted by several aborted expeditions from Georgia. Several revolutionary fighters who had been captured in Charleston were held there when it was taken by the British, including three Founding Fathers; Thomas Heyward Jr., Arthur Middleton, and Edward Rutledge. The Spanish declared war on Britain in 1779, drawing off forces from Fort St. Mark and keeping the British occupied. Bernardo de Gálvez, governor of Spanish Louisiana, attacked several British-held cities in West Florida, capturing all of them. The only major British operation that used troops from St. Augustine was the poorly coordinated but successful capture of Savannah, Georgia; the city was taken by troops from New York before those from St. Augustine arrived.
At the end of the war, the Peace of Paris (1783) called for the return of Florida to Spain. On July 12, 1784, Spanish troops returned to St. Augustine.
Second Spanish period
When Spain regained control over Florida they found a much-changed territory. Many Spaniards had left Florida after the handover to Britain, and many British citizens stayed after it was returned to Spain. Many border problems arose between Spanish Florida and the new United States. Spain changed the name of the fort back to the Castillo de San Marcos, and continued to build upon the improvements that Britain had made to the fort in an effort to strengthen Spain's hold on the territory. However, due to increased pressure from the United States and several other factors, in 1819 Spain signed the Adams–Onís Treaty, ceding Florida to the United States, which was transferred in 1821.
First United States period
Upon receiving the fort from Spain, the Americans changed its name to Fort Marion. It was named to honor General Francis Marion, an American Revolutionary War hero nicknamed "The Swamp Fox." Structurally, the Americans made few changes to the fort during this time. Many storerooms were converted to prison cells on account of their heavy doors and barred windows. Also, part of the moat was filled in and transformed into an artillery battery as part of the American coastal defense system. The original Spanish seawall was dismantled to ground level and a new seawall constructed immediately adjacent to the seaward side of the original. At this time a hotshot furnace was also built in the filled-in section of the moat behind the newly built water battery. Cannonballs were heated in the furnace to fire at wooden enemy ships.
In October 1837, during the Second Seminole War, Seminole chief Osceola was taken prisoner by the Americans while attending a peace conference near Fort Peyton under a flag of truce. He was imprisoned in Fort Marion along with his followers, including Uchee Billy, King Philip and his son Coacoochee (Wild Cat), and then transported to Fort Moultrie on Sullivan's Island in Charleston's harbor. Uchee Billy was captured on September 10, 1837, and he died at the fort on November 29. His skull was kept as a curio by Frederick Weedon. The doctor also decapitated Osceola after his death in Fort Moultrie and kept the head in preservative.
On November 19, 1837, Coacoochee and nineteen other Seminole, including two women, escaped from Fort Marion. Coacoochee, known for fabricating entertaining stories, later said that only he and his friend Talmus Hadjo had escaped - by squeezing through the eight-inch (203 mm) opening of the embrasure located high in their cell and sliding down a makeshift rope into the dry moat. Hadjo, however, was not on the official list of prisoners. However the Seminole escaped, they made their way to their band's encampment at the headwaters of the Tomoka River, about forty miles south of St. Augustine. Because of their having been poorly treated, they vowed to continue fighting, and the war was prolonged for four more years. The cell from which Coacoochee escaped was long part of the official lore of the fort.
Confederate States period
In January 1861, Florida seceded from the United States in the opening months of the American Civil War. Union troops had withdrawn from the fort, leaving only one man behind as caretaker. On January 7, 1861, three days before Florida seceded, 125 militiamen marched on the fort by the order of Governor Madison S. Perry. The Union soldier manning the fort refused to surrender it unless he was given a receipt for it from the Confederacy. He was given the receipt, and the fort was taken by the Confederacy without a shot. General Robert E. Lee, then in command of the coastal defenses of South Carolina, Georgia, and East Florida, ordered that most of the artillery in the fort be sent to other, more strategic, forts. This left only five cannons in the water battery to defend Fort Marion.
The Saint Augustine Blues, a militia unit formed in St. Augustine, were enrolled into the Confederate Army at Ft. Marion on August 5, 1861. They were assigned to the recently organized Third Florida Infantry as its Company B. More than a dozen former members of the St. Augustine Blues are buried in a row at the city's Tolomato Cemetery. Men from the unit were most likely part of the force that originally occupied the fort on January 7, 1861.
The fort, along with the rest of the city of St. Augustine, was reoccupied by Union troops after acting mayor Cristobal Bravo officially surrendered the city to Union Navy fleet commander Christopher Raymond Perry Rodgers on March 11, 1862. The Confederate forces left the city the previous evening in anticipation of the arrival of the Union fleet under the command of Commodore Dupont.
Second United States period
The fort was taken back by Union forces on March 11, 1862, when the USS Wabash entered the bay, finding the city evacuated by Confederate troops. The city leaders were willing to surrender in order to preserve the town, and the city and the fort were retaken without firing a shot. Throughout the rest of the fort's operational history, it was used as a military prison.
Beginning in 1875, numerous Native American prisoners were held at the fort in the aftermath of the Indian Wars in the west. Many would die at the fort. Among the captives were Chief White Horse of the Kiowa, and Chief Grey Beard of the southern Cheyenne.
During this period, Richard Henry Pratt, a Civil War veteran, supervised the prisoners and upgraded the conditions for them. He removed the prisoners' shackles and allowed them out of the casemates where they had been confined. He developed ways to give the men more autonomy and attempted to organize educational and cultural programs for them. They became a center of interest to northerners vacationing in St. Augustine, who included teachers and missionaries. Pratt recruited volunteers to teach the Indian prisoners English, the Christian religion, and elements of American culture. He and most US officials believed that such assimilation was needed for the Indians' survival in the changing society.
The men were also encouraged to make art; they created hundreds of drawings. Some of the collection of Ledger Art by Fort Marion artists is held by the Smithsonian Institution. It may be viewed online.
Encouraged by the men's progress in education, residents and visitors to St. Augustine raised funds for scholarships to support nearly 20 of the former prisoners in college after they were released from Ft. Marion. Seventeen men attended the Hampton Institute, a historically black college established in 1868 for freedmen by the American Missionary Association.
Others were sponsored and educated in New York State at private colleges. Among the latter were David Pendleton Oakerhater, as he became known, who was sponsored by US Senator George H. Pendleton (D-OH) and his wife. Oakerhater studied and later was ordained as an Episcopal priest. He returned to the West to work as a missionary with Indian tribes. He was later recognized by the Episcopal Church as a saint.
Pratt's experiences at Fort Marion were the basis for his campaign to create American Indian boarding schools. He was authorized to found the Carlisle Indian Industrial School in 1879, which became a model for other government-funded boarding schools established by the Bureau of Indian Affairs. It operated until 1918. At their peak, some 350-450 schools were established, and only 25 were off-reservation.
From 1886 to 1887, approximately 491 Apaches were held prisoner at Fort Marion; many were of the Chiricahua and Warm Springs Apache bands from Arizona. There were 82 men and the rest were women and children. Among the men, 14, including Chatto, had previously been paid scouts for the US Army. Among the Chiricahua were members of the notable chief Geronimo's band, including his wife. Geronimo was sent to Fort Pickens, in violation of his agreed terms of surrender. While at the fort, many of the prisoners had to camp in tents, as there was not sufficient space for them. At least 24 Apache died as prisoners and were buried in North Beach.
In 1898, over 200 deserters from the Spanish–American War were imprisoned at the fort. This marked one of the last uses of the fort as an operational base. In 1900, the fort was taken off the active duty rolls after 205 years of service under five different flags.
Preservation
In 1924, Fort Marion was designated as a National Monument. In 1933 it was transferred to the National Park Service from the War Department.
In 1942, in honor of its Spanish heritage, Congress authorized renaming the fort as Castillo de San Marcos.
In 1964 the Castillo figured in the civil rights movement, when the "Freedom Tree" on the fort green became a gathering place for demonstrators who were not welcome across the street on what was state or private property in the age of segregation. The demonstrations in St. Augustine, led by Robert Hayling, Hosea Williams, and Martin Luther King played an important role in bringing about passage of the landmark Civil Rights Act of 1964, one of the two great legislative accomplishments of the movement.
As a historic property of the National Park Service, the National Monument was listed on the National Register of Historic Places (NRHP) on October 15, 1966. The National Park Service manages the Castillo together with Fort Matanzas National Monument. In 1975, the Castillo was designated an Historic Civil Engineering Landmark by the American Society of Civil Engineers.
Since being transferred to the Park Service, the Castillo has become a popular tourist attraction. It occupies in downtown St. Augustine, Florida.
In popular culture
The fort has been featured on many television shows including Monumental Mysteries and Ghost Adventures, as well as the 1951 film Distant Drums.
Gallery
See also
List of national monuments of the United States
References
Further reading
Diane Glancy, Fort Marion Prisoners and the Trauma of Native Education. Lincoln, NE: University of Nebraska Press, 2014.
External links
Description of "Fort Marion" from an 1867 travelers guide
Castillo's Historic Civil Engineering Landmark information
Detailed history of the Castillo
Take a 3D Tour of the Castillo, right in your browser
Pictorial history of Fort Marion, 1925
1695 establishments in the Spanish Empire
American Civil War forts in Florida
San Marcos
San Marcos
Florida in the American Civil War
Historic Civil Engineering Landmarks
Military and war museums in Florida
Museums in St. Augustine, Florida
Parks in St. Johns County, Florida
Protected areas established in 1924
Tourist attractions in St. Augustine, Florida
Historic American Buildings Survey in Florida
Star forts
Spanish Florida
Second Seminole War fortifications | Castillo de San Marcos | [
"Engineering"
] | 4,558 | [
"Civil engineering",
"Historic Civil Engineering Landmarks"
] |
977,584 | https://en.wikipedia.org/wiki/NGC%203982 | NGC 3982 (also known as UGC 6918) is an intermediate spiral galaxy approximately 68 million light-years away in the constellation Ursa Major. It was discovered by William Herschel on April 14, 1789, and misclassified as a planetary nebula. NGC 3982 is a part of the M109 Group.
At an apparent magnitude of 12.0, NGC 3982 needs a telescope to be viewed. Using small telescopes, the galaxy appears as a very faint, diffuse patch of light, with its central region appearing as a slightly brighter diffuse ball.
General
NGC 3982 is a Seyfert 2 galaxy that spans about 30,000 light-years, about one-third of the size of our Milky Way galaxy. The galaxy is receding from us at about 1,109 km/s. The galaxy is a typical spiral galaxy, similar to our Milky Way. It harbors a supermassive black hole at its core and has massive regions of star formation in the bright blue knots in the spiral arms. Supernovae are likely to be found within these regions.
NGC 3982 has a high rate of star birth within its arms, which are lined by pink star-forming regions of glowing hydrogen and newborn blue star clusters. Its bright nucleus is home to older populations of stars, which grow more densely packed toward the center. The galaxy also has active star formation in the circumnuclear region, estimated at /year. The HST image of NGC 3982 shows a mini-spiral between the circumnuclear star-forming region and the galaxy's nucleus, which could be the channel through which gas is transported to the supermassive black hole from the star-forming region.
NGC 3982 is a member of the M109 Group, a group of galaxies located in the constellation Ursa Major that may contain over 50 galaxies. The group was named after the brightest galaxy in the group, the spiral galaxy M109.
Astronomers are interested in studying this galaxy as it can help in measuring extragalactic distances. It is helpful because it possesses two tools used to estimate astronomical distances: supernovae and Cepheid variable stars.
Supernova 1998aq
In 1998, the light from a supernova in NGC 3982 (later called ) reached Earth and was discovered by British amateur astronomer Mark Armstrong. It was discovered when it had an apparent magnitude of 14.9, and had grown considerably brighter by two days after its initial sighting (it reached maximum magnitude 14.0).
The supernova explosion resulted from a binary system in which a white dwarf star was capturing mass from its companion star. When the white dwarf had gathered enough mass and was no longer able to support itself, the star detonated in a violent and extremely bright explosion.
Since a supernova occurs in a typical spiral galaxy (roughly) once every 100 years, astronomers have software continuously monitor high-resolution automatic survey camera images of galaxies like NGC 3982, for early detection of supernova explosions.
References
External links
Spiral Galaxy NGC 3982 @ SEDS NGC objects pages
NGC 3982 at ESA/Hubble
Circumnuclear Star Forming Activity in NGC 3982
Intermediate spiral galaxies
M109 Group
Ursa Major
3982
06918
037520
17890414 | NGC 3982 | [
"Astronomy"
] | 680 | [
"Ursa Major",
"Constellations"
] |
977,725 | https://en.wikipedia.org/wiki/Semi-local%20ring | In mathematics, a semi-local ring is a ring for which R/J(R) is a semisimple ring, where J(R) is the Jacobson radical of R.
The above definition is satisfied if R has a finite number of maximal right ideals (and finite number of maximal left ideals). When R is a commutative ring, the converse implication is also true, and so the definition of semi-local for commutative rings is often taken to be "having finitely many maximal ideals".
Some literature refers to a commutative semi-local ring in general as a
quasi-semi-local ring, using semi-local ring to refer to a Noetherian ring with finitely many maximal ideals.
A semi-local ring is thus more general than a local ring, which has only one maximal (right/left/two-sided) ideal.
Examples
Any right or left Artinian ring, any serial ring, and any semiperfect ring is semi-local.
The quotient is a semi-local ring. In particular, if is a prime power, then is a local ring.
A finite direct sum of fields is a semi-local ring.
In the case of commutative rings with unity, this example is prototypical in the following sense: the Chinese remainder theorem shows that for a semi-local commutative ring R with unit and maximal ideals m1, ..., mn
.
(The map is the natural projection). The right hand side is a direct sum of fields. Here we note that ∩i mi=J(R), and we see that R/J(R) is indeed a semisimple ring.
The classical ring of quotients for any commutative Noetherian ring is a semilocal ring.
The endomorphism ring of an Artinian module is a semilocal ring.
Semi-local rings occur for example in algebraic geometry when a (commutative) ring R is localized with respect to the multiplicatively closed subset S = ∩ (R \ pi), where the pi are finitely many prime ideals.
Textbooks
Ring theory
Localization (mathematics) | Semi-local ring | [
"Mathematics"
] | 445 | [
"Fields of abstract algebra",
"Ring theory"
] |
977,778 | https://en.wikipedia.org/wiki/Circinus%20Galaxy | The Circinus Galaxy (ESO 97-G13) is a Seyfert galaxy in the constellation of Circinus. It is located 4 degrees below the Galactic plane, and, at a distance of , is one of the closest major galaxies to the Milky Way. The galaxy is undergoing tumultuous changes, as rings of gas are likely being ejected from the galaxy. Its outermost ring is 1400 light-years across while the inner ring is 260 light-years across. Although the Circinus galaxy can be seen using a small telescope, it was not noticed until 1977 because it lies close to the plane of the Milky Way and is obscured by galactic dust. The Circinus Galaxy is a Type II Seyfert galaxy and is one of the closest known active galaxies to the Milky Way, though it is probably slightly farther away than Centaurus A.
Circinus Galaxy produced supernova SN 1996cr, which was identified over a decade after it exploded. This supernova event was first observed during 2001 as a bright, variable object in a Chandra X-ray Observatory image, but it was not confirmed as a supernova until years later.
The Circinus Galaxy is one of twelve large galaxies in the "Council of Giants" surrounding the Local Group in the Local Sheet. One object is possibly a satellite of the Circinus Galaxy, known as HIZOA J1353-58. HIZOA J1353-58 was discovered in a survey of neutral hydrogen (H I) and is located within the Zone of Avoidance.
NuSTAR detected a ULX at the edge of this galaxy, a black hole about 100 times the mass of the Sun.
Notes
References
External links
Chandra X observatory Examines Black Holes Large and Small in Nearby Galaxy
The Hubble European Space Agency picture and information
Local Sheet
Circinus
Seyfert galaxies
50779
97-G13 | Circinus Galaxy | [
"Astronomy"
] | 387 | [
"Circinus",
"Constellations"
] |
977,799 | https://en.wikipedia.org/wiki/HCG%2087 | HCG 87 is a compact group of galaxies listed in the Hickson Compact Group Catalogue. This group is about 400 million light-years away in the constellation Capricornus.
The group distinguishes itself as one of the most compact groups of galaxies, hosting two active galactic nuclei and a starburst among its three members, all of which show signs of interaction. This interaction, which astronomers have called visually, and scientifically, intriguing is being examined to understand the influence of active nuclei on star formation histories.
Members
External links
Astronomy Picture of the Day
Galaxy Group HCG 87 – 2003 July 31
HCG 87: A Small Group of Galaxies – 2010 July 6
Close-ups of HCG 87
Galactic Clusters
Studies of Hickson Compact Groups
References
87
Galaxy clusters
Capricornus | HCG 87 | [
"Astronomy"
] | 157 | [
"Galaxy clusters",
"Galaxy stubs",
"Capricornus",
"Astronomy stubs",
"Constellations",
"Astronomical objects"
] |
977,804 | https://en.wikipedia.org/wiki/Nikoloz%20Muskhelishvili | Nikoloz (Niko) Muskhelishvili (; – 15 July 1976) was a Soviet Georgian mathematician, physicist and engineer who was one of the founders and first President (1941–1972) of the Georgian SSR Academy of Sciences (now Georgian National Academy of Sciences).
Life and career
Muskhelishvili was born on in Tbilisi, then part of the Russian Empire into a family of engineers. He graduated from local grammar school in 1909 and afterwards from the Physics and Mathematics Faculty of Saint Petersburg in 1914. Immediately after his graduation he became head of Applied Mathematics of the same faculty and in 1918 passed the exam for the master's degree. His first scientific magazine was published already earlier in 1915 containing a number of issues on elasticity theory. From 1917 to 1920 he worked as assistant director of the Petrograd University and also taught mathematics in other institutions in Saint Petersburg. At request of the short-lived Democratic Republic of Georgia he moved back to his native country in 1920 in order to organize the establishment of a national scientific school. There Muskhelishvili conducted lessons in the Tbilisi State University and Polytechnic Institute as an assistant professor and from 1922 to 1938 as head professor. After the Soviet invasion of Georgia in 1921, Muskhelishvili was allowed to carry on his works in the Transcaucasian Soviet Academy of Sciences and since 1933 was corresponding member of the USSR Academy of Sciences. He became a member of the CPSU in 1940.
In 1941 based on the former Georgian Academy of Sciences a new USSR Academy of Sciences was established by the Georgian SSR and Muskhelishvili got elected as its first president and academician. Simultaneously he also became director of the Tbilisi Mathematics Institute named after AM Rasmadze, and held that position until his death in 1976.
From 1956 to 1976 Muskhelishvili was chairman of the National Committee of the USSR on Theoretical and Applied Mechanics (established by the Decree of the Presidium of the Academy of Sciences). Since 1957 he was also member of the Presidium of the Academy of Sciences. In 1972 due to health problems the professor resigned from the post of president of the Georgian SSR Academy of Sciences but in recognition for his outstanding achievements and services was elected honorary president of the academy. He was also an academician and honorary professor of the Academies of Sciences of the Armenian and Azerbaijani SSRs since 1961. Muskhelishvili was an honorary member of the Bulgarian Academy of Sciences since 1952, Polish Academy of Sciences since 1960 and the Berlin Academy of Sciences since 1967. He also held the position of deputy chairman of the Supreme Soviet of the Soviet Union in eight convocations from 1937 to 1974.
Nikoloz Muskhelishvili died on 15 July 1976 in Tbilisi and is buried in the Mtatsminda Pantheon.
Contributions to science
Muskhelishvili conducted fundamental research on the theories of physical elasticity, Integral equations, Boundary value problems and other. He was one of the first to apply the theory of functions of complex variables to the problems of elasticity theories, proposing a number of techniques that have been successfully implemented in numerous areas of mathematics, theoretical physics and mechanics. His works solved all major problems of the Plane Elasticity Theory opening a wide class of domains reducing the plane problem to finite systems of linear algebraic equations c singular kernels. He is also credited with major contributions to the theory of linear boundary value problems for analytic functions and one-dimensional integral equations. Muskhelishvili is the author of various scientific articles, monographs and textbooks on mathematics which have been used by universities since their publishing. Highest regarded ones are the monographs "Some basic problems of the mathematical theory of elasticity" (1933) and "Singular Integral Equations" (1947).
Involvement in military research
During World War II Muskhelishvili was responsible for retargeting the preoccupation of the Academy of Science to national defense. He completed a series of research, experimental and theoretical work in different areas of applied mathematics, physics and mechanics, which all had great practical importance and decisive impact on the development of a range of military hardware during and after the war. However, the exact scale is unknown and classified. His achievements and involvement in the defense sphere earned him several awards, including the Medal "For the Defence of the Caucasus". He got also awarded for the launch of the world's first artificial satellite into space in 1961 on which development he had contributed as well. Muskhelishvili was a renowned specialist in engineering able to apply a lot of his theories and solutions, including torsion bar suspension for tracked vehicles such as tanks. Most of his research, theories, and ideas were considered and implemented for the development of certain vehicles during the Cold War, some of which already originated from his earlier theoretical work during World War II, on the elasticity of specific material under specific circumstances such as different temperature, weight, composition etc. His work practically applied to anything from land-based vehicles to aircraft, rockets, and satellites.
Membership in scientific academies
Corresponding Member of the USSR Academy of Sciences
Academician of the USSR Academy of Sciences
Academician of Academy of Sciences of the Georgian SSR
Honorary Academician of Armenian Academy of Sciences
Honorary Academician of Azerbaijan Academy of Sciences
Foreign Member of Bulgarian Academy of Sciences
Foreign Member of Polish Academy of Sciences
Foreign Member of German (Berlin) Academy of Sciences
Notable awards
Hero of Socialist Labour (1945)
Stalin Prize (1941), (1947)
Order of Lenin (1941), (1945), (1952), (1961), (1966), (1975)
Order of the October Revolution (1970)
Order of the Red Banner of Labour (1944)
Gold Medal of the Turin Academy of Sciences (1969)
Gold Medal of the Slovak Academy of Sciences (1970)
Cyril and Methodius I degree (1970)
Lomonosov Gold Medal (1972)
The Georgian Academy of Sciences established a prize named after Nikoloz Muskhelishvili.
Main publications
"On the equilibrium of elastic circular disks under the influence of stresses applied at the points of their encirclement and acting in their domains". (Russian), Izv. Electrotekhnich. Inst., Petrograd, 12 (1915), 39–55 (jointly with G. V. Kolosov).
"On thermal stresses in the plane problem of the theory of elasticity". (Russian), Izv. Electrotekhnich. Inst., Petrograd, 13 (1916), 23–37.
"On defining a harmonic function by conditions given on the contour". (Russian) Zh. Fiz.-mat.ob-va, Perm Univ., 1918, (1919), Issue I, 89–93.
"Applications des intégrales analogues à celles de Cauchy et quelques problèmes de la physique mathématique". - Tiflis, Edition de l'Université de Tiflis, Imprimerie de l'Etat, 1922.
"On periodic orbits in closed geodesic lines (abstract)". (Russian) Trans. All-Russian Math. Congr. Moscow, April 27–May 4, 1927, Moscow-Leningrad, 1928,189.
"On some contour problems of plane hydrodynamics".(Russian) Proc.of All-Russian Math. Congr. Moscow-Leningrad, 1928, 262.
"Zum Problem der Torsion der homogenen isotropen Prismen". Izv. Tiflis. polit.in-ta, 1 (1929), part 1, 1-–20.
"Nouvelle méthode de rèduction du problème biharmonique fondamental à une equation de Fredholm". C. R. Acad. Sci.,192 (1931), No. 2, 77–79.
"Théorèmes d'existence relatifs au problème biharmonique et aux problèmes d'élasticité a deux dimensions". C. R. Acad. Sci., 192 (1931), No. 4, 221–223.
"To the problem of torsion and bending of elastic bars composed of various materials. (Russian). Izv. AN SSSR, OMEN, 1932, iss.7, 907–945.
"To the problem of torsion and bending of composite elastic beams". (Russian) Izv. Inzh. Inst. Gruzii, 1932, iss. I, 123–127.
"Some basic problems of the mathematical theory of elasticity. Basic Equations, the plane problem, torsion and bending (Foreword by Acad. A. N. Krilov)". (Russian) Acad. Sci. USSR, Leningrad, 1933.
"Singular integral equations, boundary value problems of the function theory and some of their applications to mathematical physics (Russian)", Moscow -Leningrad, 1946.
"Sur le problème de torsion des poutres élastiques composées". C. R. Acad. Sci., 194 (1932), No. 17, 1435–1437.
"Recherches sur des problèmes aux limites relatifs à l'équation biharmonique et aux équations de l'élasticité à deux dimensions". Math. Ann., 1932, Bd. 107, No. 2, 282–312.
"Solution of a plane problem of the theory of elasticity for a solid ellipse". (Russian) PMM, I (1933), is. I, 5–12.
"Praktische Lösung der fundamentalen Randwertaufgaben der Elastizitätstheorie in der Ebene fur einige Berandungsformen". Z. Angew. Math. und Mech., 1933, Bd. 13, No. 14, 264–282.
"Sur l'équivalence de deux méthodes de reduction du problème plan biharmonique à une équation intégrale". C. R. Acad. Sci., 196 (1933), No. 26, 1947–1948 (avec V. Fock).
"A new general method of the solution of the basic boundary value problems of the plane theory of elasticity". (Russian) DAN SSSR, 3 (1934), No. 1, 7–11.
"Investigation of new integral equations of the plane theory of elasticity". (Russian) DAN SSSR, 3 (1934), No. 2, 73–77.
"On a new boundary value problem of the theory of elasticity". (Russian) DAN SSSR, 3 (1934),141–144.
"A new method of the solution of plane problems of the theory of elasticity". (Russian) Bull. II All-Union Math. Congr. in Leningrad, June 24–30, Leningrad, 1934, 68 (Abstract).
"Solution of the basic mixed problem of the theory of elasticity for half-plane". (Russian) DAN SSSR, 3(1935), No. 2, 51-–53.
"Theory of elasticity". (Russian) Big Soviet Encycl., 56 (1936), 147–158.
"A new method of solution of plane problems of the theory of elasticity (Abstract)". (Russian) Trans. II All-Union Math. Congr. in Leningrad, June 24–30, 2 (1934), Leningrad-Moscow, 1936, 345–346.
"On the numerical solution of a plane problem of the theory of elasticity". (Georgian). Trans. Tbil. Math. Inst., 1 (1937), 83–87.
Transl. editing: Chapters 7–9. In the book by F. Frank and R. Mizes "Differential and Integral equations of Mathematical Physics". Part 2. Transl. edited by L. E. Gurevich. Leningrad-Moscow, 1937, 224–346.
"On the solution of the basic boundary value problems of the theory of Newtonean potential". (Russian) PMM, 4 (1940), iss. 4, 3–26.
"On the solution of the basic contour problems of the logarithmic potential theory". (Russian). Trans. Tbil. Math. Inst., 7 (1939), 1–24 (jointly with L. Z. Avazashvili).
"On the solution of the Dirichlet problem on a plane". (Russian) Bull. Georgian Branch USSR Acad. Sci., 1 (1940), No. 2, 99–106.
"Remarks on the basic boundary value problems of the potential theory". (Russian) Bull. Georgian Branch USSR Acad. Sci., 1 (1940), No. 3, 169–170. Amendments to the Paper, ditto, No. 7, 567.
"Application of integrals of the Cauchy type to one class of singular integral equations". (Russian) Trans. Tbil. Mat. Inst., 10 (1941), 1–43, 161–162.
"On the basic mixed boundary value problem of the logarithmic potential theory for multiply connected domains". (Russian) Bull. Acad. Sci. Georgian SSR,2(1941), No. 4, 309–313.
"Basic boundary value problems of the theory of elasticity for a half-plane". (Russian) Bull Acad. Sci. Georgian SSR, 2 (1941), No. 10, 873–880.
"Singular integral equations with a Cauchy type kernel on open contours". (Russian) Trans. Tbil. Math. Inst. Acad. Sci. Georgian SSR, 2 (1942), 141–172 (jointly with D. A. Kveselava).
"Basic boundary value problems of the theory of elasticity for a plane with rectilinear cuts". (Russian) Bull. Acad. Sci. Georgian SSR, 3 (1942), No. 2, 103–110.
"To the problem of equilibrium of a rigid punch at the boundary of an elastic half-plane in the presence of friction". (Russian) Bull. Acad. Sci. Georgian SSR,43(1942), No. 5, 413–418.
"Systems of singular integral equations with Cauchy type kernels". (Russian) Bull. Acad. Sci. Georgian SSR, 3 (1942), No. 10, 987–984.
"Riemann boundary value problem for several unknown functions and its applications to systems of singular integral equations". (Russian) Trans. Tbil. math. Inst., 12(1943), 1–46 (jointly with N. P. Vekua).
"Applications of the theory of analytic functions to the theory of elasticity". (Russian) All-Union Congr. on theoretical and Applied Mechanics. Report Abstracts. Moscow, 1960, 142–143 (jointly with I. N. Vekua).
"Methods of the theory of analytic functions in the theory of elasticity". (Russian) Trans. All-Union Congr. on Theoretical and Applied Mechanics (1960). Moscow-Leningrad, USSR Acad. Sci. Publ., 1962, 310-388 (jointly with I. N. Vekua).
"Applications of the theory of functions of a complex variable to the theory of elasticity". In the book: "Application of the theory of functions in solid medium mechanics". (Russian) v. VII, Nauka, Moscow, 1965, 32–55. Ditto in English: 56–75.
References
Bibliography
Muskhelishvili, Nikoloz. Poggendorff's biographischliterarisches Handwörterbuch. Bd. 6. 1923–1931. 3. L-R. Berlin, Verlag Chemie, 1938, S.1811.
Ali Kheiralla, . Muskhelishvili, N.I.Some Basic problems of the mathematical theory of elasticity. Third revis. and augmented ed. Moscow,1949, Groningen, P.Noordhoff, Ltd., 1953.-J.Appl. Mech.,21(1954), No 4, 417–418.
Bogoliubov, N. N., Medvedev, B. V. and Tavkhelidze, A.N. The application of the methods of N.I. Muskhelishvili to the solution of singular integral equations in quantum field theory. Problems of continuum mechanics. Contributions in honor of the seventieth birthday of academician N.I. Muskhelishvili. 16 February 1961. Philadelphia, Pa, Soc. Industrial and Appl. Math.,(1961), 39–55.
Brandstatter, J.J. Muskhelishvili N.I. Some basic problems of the mathematical theory of elasticity. Third revis.and augmented ed., Moscow,1949. Groningen, P. Noordhoff, Ltd., 1953. Appl.Mech.Rev., 7(1954), No 7, 293–294.
Hill, R. A landmark in the theory of elasticity.[Muskhelishvili, N. I. Singular integral equations. Ed. 2. Moscow, 1946. Groningen, P. Noordhoff, N.V.,1953; Muskhelishvili, N.I. Some basic problems of the mathematical theory of elastisity.Third revised and augmented ed. Moscow,1949.Groningen, P. Noordhoff, N. V.,1953]. Nature, 174(1954), No 4433, 713–714.
.
Scott, E.J. Muskhelishvili, N. I. Singular integral equations. 2nd ed. Groningen, P. Noordhoff, Ltd., 1953. Appl. Mech. Rev.,7(1954), No 10, 424–425.
Nikolai Ivanovich Muskhelishvili. (Russian) Materiali k bibliografii uchenych v SSSR, Seria "Matematika". Foreword by I.Vekua. Bibliography by A. Epifanova. Nauka, Moscow, 1967.
Niko Muskhelishvili (Biobibliographical Series "Georgian Scientists"; Foreword by A. Bitsadze and B. Khvedelidze). (Georgian) Metsniereba, Tbilisi,1980.
N. Vekua. Niko Muskhelishvili. (Georgian) Metsniereba, Tbilisi, 1989.
I.Vekua. Academician Nikolai Ivanovich Muskhelishvili.[Dedic. to the 70th birthday]. Short Biography and Survey of Scientific Works. (Georgian) Georgian Academy of Sciences, Tbilisi, 1961.
I. Vekua. Academician N. Muskhelishvili. Short Biography and Survey of Scientific Works.(Georgian) Metniereba, Tbilisi, 1991, 60 pp.
I. Vekua. Academician N. Muskhelishvili. Short Biography and Survey of Scientific Works.(Russian) Metsniereba, Tbilisi, 1991.
I. Vekua. Academician N. Muskhelishvili. Short Biography and Survey of Scientific Works. Metsniereba, Tbilisi, 1991.
G. K. Mikhailov, J.R.M. Radok. On N.I. Muskhelishvili's place in the world of science and mathematics. Proc. of the Intern.Sympos. Dedic. to the Cent.of Academ. N. Muskhelishvili. Tbilisi, Rep.of Georgia, June 6–11, 1991.
B. Khvedelidze, G. Manjavidze. A. Survey of N.I. Muskhelishvili's scientific heritage. Proc. of the Intern.Sympos. Dedic.to the Centenary of Acad. N. Muskhelishvili. Tbilisi, Rep. of Georgia, 6–11 June 1991.
Muskhelishvili, Mikola Ivanovich. (Ukrainian) Ukr.rad.enc.9(1962), 441.
See also
List of Georgians
Torsion bar suspension
Elasticity (physics)
Science and technology in the Soviet Union
1891 births
1976 deaths
Scientists from Tbilisi
Academic staff of Tbilisi State University
Foreign members of the Bulgarian Academy of Sciences
Full Members of the USSR Academy of Sciences
Members of the German Academy of Sciences at Berlin
First convocation members of the Supreme Soviet of the Soviet Union
Second convocation members of the Supreme Soviet of the Soviet Union
Third convocation members of the Supreme Soviet of the Soviet Union
Fourth convocation members of the Supreme Soviet of the Soviet Union
Fifth convocation members of the Supreme Soviet of the Soviet Union
Sixth convocation members of the Supreme Soviet of the Soviet Union
Seventh convocation members of the Supreme Soviet of the Soviet Union
Eighth convocation members of the Supreme Soviet of the Soviet Union
Members of the Central Committee of the 20th Congress of the Communist Party of the Soviet Union
Members of the Central Committee of the 22nd Congress of the Communist Party of the Soviet Union
Members of the Central Committee of the 23rd Congress of the Communist Party of the Soviet Union
Members of the Central Committee of the 24th Congress of the Communist Party of the Soviet Union
Heroes of Socialist Labour
Recipients of the Lomonosov Gold Medal
Recipients of the Order of Lenin
Recipients of the Order of the October Revolution
Recipients of the Order of the Red Banner of Labour
Recipients of the Stalin Prize
People of World War II from Georgia (country)
20th-century mathematicians from Georgia (country)
Physicists from Georgia (country)
20th-century scientists from Georgia (country)
Soviet mathematicians
Soviet scientists
Burials at Mtatsminda Pantheon | Nikoloz Muskhelishvili | [
"Technology"
] | 4,531 | [
"Science and technology awards",
"Recipients of the Lomonosov Gold Medal"
] |
977,873 | https://en.wikipedia.org/wiki/His%20Majesty%27s%20Railway%20Inspectorate | Established in 1840, His Majesty's Railway Inspectorate (HMRI) is the organisation responsible for overseeing safety on Britain's railways and tramways. It was previously a separate non-departmental public body, but from 1990 to April 2006 it was part of the Health and Safety Executive. It was then transferred to the Office of Rail and Road and ceased to exist by that name in May 2009 when it was renamed the Safety Directorate. However, in summer 2015 its name was re-established as the safety arm of ORR.
Modern HMRI inspectorate
The modern HMRI within the Office of Road and Rail (ORR) identifies as "The Railway Inspectorate". HMRI works in tandem with the rest of the ORR, and as such may be consulted on matters effecting industry efficiency.
Internally, most of HMRI's inspectors are part of the Railway Safety Directorate (RSD) of the ORR, although some Railway Performance and Planning (RPP) engineers have some more limited powers as warranted HMRI individuals.
HMRI's role and powers largely mirror the HSE which is the safety regulator in other non-railway industries. HMRI has powers to enter a railway under section 20 of the Health and Safety at Work etc. Act 1974. It also issues licensing and drivers' licences under the Railways and Other Guided Transport Systems (Safety) Regulations 2006 (ROGS).
HMRI's individuals are drawn from within industry and experienced HSE inspectors. Commonly, individuals are professional engineers or time-served safety professionals. All inspectors are issued a warrant by the chief inspector to that effect. Normally an inspector will use the industry Personal Track Safety (PTS) card. However, inspectors have the right, in reasonable circumstances, not to do so.
History
First fifty years
Establishment
The body originated in 1840, as a result of the Railway Regulation Act 1840 ('Lord Seymour's Act'), when Inspecting Officers of Railways were first appointed by the Board of Trade (BoT).
Britain's railways at that time were private companies; the 1840 Act required them to report to the BoT all accidents which had caused personal injury: it also gave the inspectorate powers to inspect any railway, and hence from its formation the inspectorate was used to investigate serious railway accidents and report upon them to the BoT.
Inspection of new lines
They were tasked with inspecting new lines, and commenting on their suitability for carrying passenger traffic.
However, the inspectorate had no powers to require changes until the Railway Regulation Act 1842 ('An Act for the better Regulation of Railways and for the Conveyance of Troops') gave the BoT powers to delay opening of new lines if the inspectorate was concerned about "Incompleteness of the Works or permanent Way, or the Insufficiency of the Establishment" for working the line.
Crash investigation
Their first investigation was of the Howden rail crash on 7 August 1840, which had killed five passengers (although the inspector's report said four, three passengers were killed instantly, two dying later of their injuries) as a result of the derailment of a train caused by the fall of a large casting from a wagon on a passenger train.
The inspectorate's reports of their accident investigations were made to the BoT alone, but eventually published as part of the BoT's annual report to Parliament.
Competence
Until the late 1960s HMRI's inspecting officers were all recruited from the Corps of Royal Engineers. In the early years of the inspectorate, their competence to adjudicate on civil engineering structures was questioned by critics, sometimes with good reason.
A reorganisation of the inspectorate in November 1846 abolished the post of inspector-general, and led to the departure of Major-General Charles Pasley, the incumbent, and one of his subordinates.
Pasley had come under criticism after the bridges and earthworks of the North British Railway's line from Edinburgh to Berwick – approved by Pasley in June 1846 – failed to withstand heavy rain in September 1846, with nineteen miles of track being rendered unusable. Temporary works were undertaken to restore a service, Pasley approved them (orally), but some of the new work then proved faulty.
In 1849 the Manchester, Sheffield and Lincolnshire Railway's Torksey viaduct across the River Trent was not initially accepted by the railway inspector Lintorn Simmons because he was unhappy with its novel (tubular girder) design by John Fowler.
This decision (and also the basic premise that a bridge designed by a member of the Institution of Civil Engineers (ICE) which had passed all practical tests could be rejected by a railway inspector because he was uncomfortable with its novel design) was criticised by the ICE:
Threatened with a call for a parliamentary enquiry should approval continue to be withheld, the inspectorate reconsidered and approved the bridge un-modified.
Subsequently, and consequently, the BoT took the view that (as it explained in defending itself from criticism that the defects in the Tay Bridge should have been seen and acted upon by the inspectorate):
Critics at the end of the 1850s also noted that during the Crimean War, the Grand Crimean Central Railway had been built to forward supplies from Balaclava to British siege lines not by the Royal Engineers, but by a consortium of civilian railway contractors. If the government turned to civilians as best fitted to build a military railway, was it not anomalous that it thought military engineers best fitted to inspect new railway lines?
Extension and formalisation of powers
The inspectorate's powers were extended and formalised by the Railway Regulation Act 1871 ('An Act to amend the Law respecting the Inspection and Regulation of Railways'). Paragraph 4 extended the power to inspect to give inspectors explicit powers to require the production of persons and papers by a company being inspected. Paragraph 5 meant new works on existing lines were liable to the same inspection regime as new lines. The BoT could now set up a formal court of inquiry to investigate an accident, taking evidence on oath in public hearings. Inspectors investigating an accident were now required to make a formal report to the BoT, which was now empowered to publish reports (from an inspector or from a court of inquiry) directly.
Subsequent public inquiries under the new powers included those into the Shipton-on-Cherwell train crash in 1874 (chaired by an inspector William Yolland), and into the Tay Bridge disaster of 1879. However, the procedure fell into abeyance after the failure of the three-man board (of which Yolland, by now chief inspecting officer, was a member) of the Tay Bridge inquiry to arrive at an agreed report.
For many years in the mid-19th century the Railway Inspectorate advocated in its accident returns and otherwise three safety measures it saw as vital to ensure passenger safety:
"lock" Interlocking of points and signals, so that conflicting signal indications are prevented;
"block" A space-interval or absolute block system of signalling, where one train is not allowed to enter a physical section until the preceding one had left it; and
"brake" Continuous brakes, to put at the command of the engine driver adequate braking power; this requirement being increased as the technology made it reasonable to 'automatic' (in modern parlance 'fail-safe') continuous brakes which had to be 'held off' by vacuum or compressed air and would be applied automatically if that supply was lost (e.g. if a train were divided).
The Board of Trade got as far and as fast as it could by persuasion, but had no powers to enforce its views on often reluctant railway managements of existing lines.
Inspectors disagreed as to whether the board should be given powers to require changes. Yolland's official report on an 1867 accident (in which eight people died at a junction unaltered since an 1862 fatal accident, despite an inspector having urged improvements) pressed for such powers:
Tyler himself supported the view taken by successive governments: that to take such powers would remove the clarity of existing arrangements, where responsibility for passenger safety lay with the railway companies alone.
The death of 80 people on a Sunday school outing in the Armagh rail disaster of 1889 brought a reversal of this policy on the three key issues: within two months of the accident Parliament had enacted the Regulation of Railways Act 1889, which authorised the Board of Trade to require the use of continuous automatic brakes on passenger railways, along with the block system of signalling and the interlocking of all points and signals. This is often taken as the beginning of the modern era in UK rail safety: "the old happy-go-lucky days of railway working" came to an end.
Modern era
The chief inspecting officer from 1916 to 1929 was Colonel John Wallace Pringle, responsible for investigating many accidents. It was during his tenure, in 1919, that the office became part of the newly created Ministry of Transport.
The last chief inspecting officer with a Royal Engineers background, Major Rose, retired in 1988 and he was replaced by an appointee from the Health and Safety Executive (HSE).
Since then, inspecting officers have been recruited from the HSE or as mid-career railway employees from the former British Rail.
List of chief inspecting officers / HM Chief Inspectors of Railways
Original twin functions of the HMRI
The function of HMRI was to inspect and approve all new (or modified) railway works and to investigate railway accidents.
Accident investigations were inquisitorial, generally not open to the public, and aimed to determine the causes behind the accident (both the immediate cause and contributory factors) and to make recommendations to avoid re-occurrence. Until the 1860s, in the first instance, accident reports were internal and only published in the accident returns made from time to time by the Board of Trade to Parliament. For fatal accidents, a coroner's inquest would also be held, which inspectors might attend to hear the evidence, to assist the coroner, or to give evidence themselves of what their investigation had found. In the absence of input from the inspectorate, inquests rarely went beyond the immediate cause; hence, said one inspector in 1870:
Coroner's inquests were public and their proceedings and verdicts widely reported in the press.
In later years, accident reports were published directly, widely circulated within the railway industry, and reported upon by the press.
Recent history
The HMRI became part of the Department of Transport and remained so until 1990, when it was transferred to the Health and Safety Executive (HSE). About this time HMRI expanded its scope and recruited additional staff, Railway Employment Officers. It was their job to monitor the workplace safety and health of railway employees.
After the move to the HSE, (newsworthy) train crash investigations tended to be held as public inquiries presided over by a High Court judge; and the findings published. These inquiries tended to be more adversarial; with the aim of identifying the guilty parties. In some cases criminal prosecution of these parties has occurred in parallel with the public inquiry, delaying the inquiry until the criminal prosecutions have been completed.
The transfer to the HSE was unpopular with many in the industry, and as part of its rail review in 2004 the government announced that the Railway Inspectorate would be transferred from the HSE to merge with the Office of Rail Regulation (now the Office of Rail and Road). The transfer took place on 2 April 2006.
The inspectorate oversaw both operational safety and the initial integrity of new and modified works. As a result of the legislative change, which transferred them to the Office of Rail Regulation, the scope of HMRI enforcement no longer covered guided bus, trolleybus and most cable-hauled transport systems.
In May 2009 the legal entity known as "HM Railway Inspectorate" ceased to exist when a single rail regulatory body covering both safety and economic issues, the Safety Directorate, was created, but the 180 individual inspectors will continue to be known as His Majesty's Railway Inspectors.
A summary of government bodies overseeing HM Railway Inspectorate are shown in the table. Several changes reflect wider government re-organisations.
See also
Rail Accident Investigation Branch
Notes
Citations
References
speaker at columns 1136–1138 is repeating criticisms by George Parker Bidder
: pages cited give the affair plus Fowler's subsequent views
Further reading
Describes many key investigations made by the Inspectorate.
Describes the early history of the Inspectorate.
External links
Rail Accident Investigation Branch - Current investigatory body for rail accidents in the UK
Railways Archive - Accident Archive - contains facsimiles of reports of many HMRI accident investigations (accident returns for older investigations, accident reports more recently).
Occupational safety and health organizations
History of rail transport in the United Kingdom
Rail accident investigators
Organizations established in 1840
Defunct public bodies of the United Kingdom
Safety organisations based in the United Kingdom
1840 establishments in the United Kingdom | His Majesty's Railway Inspectorate | [
"Technology"
] | 2,573 | [
"Railway accidents and incidents",
"Rail accident investigators"
] |
977,983 | https://en.wikipedia.org/wiki/Charge%20qubit | In quantum computing, a charge qubit (also known as Cooper-pair box) is a qubit whose basis states are charge states (i.e. states which represent the presence or absence of excess Cooper pairs in the island). In superconducting quantum computing, a charge qubit is formed by a tiny superconducting island coupled by a Josephson junction (or practically, superconducting tunnel junction) to a superconducting reservoir (see figure). The state of the qubit is determined by the number of Cooper pairs that have tunneled across the junction. In contrast with the charge state of an atomic or molecular ion, the charge states of such an "island" involve a macroscopic number of conduction electrons of the island. The quantum superposition of charge states can be achieved by tuning the gate voltage U that controls the chemical potential of the island. The charge qubit is typically read-out by electrostatically coupling the island to an extremely sensitive electrometer such as the radio-frequency single-electron transistor.
Typical T2 coherence times for a charge qubit are on the order of 1–2 μs. Recent work has shown T2 times approaching 100 μs using a type of charge qubit known as a transmon inside a three-dimensional superconducting cavity. Understanding the limits of T2 is an active area of research in the field of superconducting quantum computing.
Fabrication
Charge qubits are fabricated using techniques similar to those used for microelectronics. The devices are usually made on silicon or sapphire wafers using electron beam lithography (different from phase qubit, which uses photolithography) and metallic thin film evaporation processes. To create Josephson junctions, a technique known as shadow evaporation is normally used; this involves evaporating the source metal alternately at two angles through the lithography defined mask in the electron beam resist. This results in two overlapping layers of the superconducting metal, in between which a thin layer of insulator (normally aluminum oxide) is deposited.
Hamiltonian
If the Josephson junction has a junction capacitance , and the gate capacitor , then the charging (Coulomb) energy of one Cooper pair is:
If denotes the number of excess Cooper pairs in the island (i.e. its net charge is ), then the Hamiltonian is:
where is a control parameter known as effective offset charge ( is the gate voltage), and the Josephson energy of the tunneling junction.
At low temperature and low gate voltage, one can limit the analysis to only the lowest and states, and therefore obtain a two-level quantum system (a.k.a. qubit).
Note that some recent papers adopt a different notation, and define the charging energy as that of one electron:
and then the corresponding Hamiltonian is:
Benefits
To-date, the realizations of qubits that have had the most success are ion traps and NMR, with Shor's algorithm even being implemented using NMR. However, it is hard to see these two methods being scaled to the hundreds, thousands, or millions of qubits necessary to create a quantum computer. Solid-state representations of qubits are much more easily scalable, but they themselves have their own problem: decoherence. Superconductors, however, have the advantage of being more easily scaled, and they are more coherent than normal solid-state systems.
Experimental progresses
The implementation of Superconducting charge qubits have been progressing quickly since 1996. Design was theoretically described in 1997 by Shnirman, while the evidence of quantum coherence of the charge in a Cooper pair box was published in February 1997 by Vincent Bouchiat et al. In 1999, coherent oscillations in the charge Qubit were first observed by Nakamura et al. Manipulation of the quantum states and full realization of the charge qubit was observed 2 years later. In 2007, a more advanced device known as Transmon showing enhanced coherence times due to its reduced sensitivity to charge noise was developed at Yale University by Robert J. Schoelkopf, Michel Devoret, Steven M. Girvin and their colleagues .
References
Quantum information science
Quantum electronics
Superconductivity | Charge qubit | [
"Physics",
"Materials_science",
"Engineering"
] | 884 | [
"Physical quantities",
"Quantum electronics",
"Superconductivity",
"Quantum mechanics",
"Materials science",
"Condensed matter physics",
"Nanotechnology",
"Electrical resistance and conductance"
] |
978,035 | https://en.wikipedia.org/wiki/Remote%20broadcast | In broadcast engineering, a remote broadcast (usually just called a remote or a live remote, or in news parlance, a live shot) is broadcasting done from a location away from a formal television or radio studio and is considered an electronic field production (EFP). A remote pickup unit (RPU) is usually used to transmit the audio and/or video back to the broadcast station, where it joins the normal airchain. Other methods include satellite trucks, production trucks and even regular telephone lines if necessary.
History
The first airing of a remote broadcast came in 1924, when Loew's Theater publicist and WHN (New York City) station manager Nils Granlund leased telegraph lines from Western Union to provide the first link in what became called cabaret broadcasting." By early 1925, Granlund had established remote lines between WHN and more than thirty New York City jazz nightclubs, including the Silver Slipper, The Parody Club, the Cotton Club, the Strand Roof, and Club Moritz. These big band remotes would become a staple of the old-time radio era, lasting well into the 1950s.
Nils T. Granlund cited the 1925 WHN airing of Senator James J. Walker's announcement of his New York City mayoral candidacy through a remote broadcast from the New York Press Club as the first such remote link for a political forum.
In Latin America on 27 October 1920, Dr Sussini made the first remote transmission in Argentina from the theatre El Coliseo in Buenos Aires. In Mexico on 27 September 1921, Adolfo Gomez Fernandez made a transmission from the Teatro Ideal, Mexico DF
The very first live remote broadcast to the nation was by the Canadian Broadcasting Corporation in 1938 when Frank Willis reported on the Moose River Gold Mine disaster in Nova Scotia http://archives.cbc.ca/economy_business/natural_resources/clips/3860/
On 11 June 1955, NBC, The National Broadcasting Company, provided the 1st live remote broadcast to the nation from Niagara Falls, New York.
Radio
In radio, remotes are often used for special events, such as concerts or sporting events, where either the entire event or advertisements for the event are broadcast on location. The cost of personnel and equipment is usually paid for by the host at each performance. However, if the event is recurring, such as a weekly broadcast from a nightclub, then dedicated lines are usually installed by the local telephone company in order to save on costs. With low range radio stations, and at events with no telephone lines, several radio stations will call into the studio request line with a cell phone and microphone setup. From there, another DJ in the studio will put them on-location live on the air via the studio request line. Some stations use this method when doing live broadcasts in areas where the signal is weak.
Originally, analog audio broadcasts were sent through telephone hybrids, which, although low quality, were found to be acceptable for voice broadcasts. Later, frequency extenders were developed that used additional lines, shifting higher treble audio frequencies down on one end and back up on the other, providing a reasonable reproduction of the original sound. Currently, digital lines, such as ISDN or DSL, are used to send compressed digital audio back to the studio. In addition, modern remote pickup units have become extremely portable and can transmit single-channel monophonic FM-quality audio over regular telephone lines using built-in modems and advanced compression algorithms (MPEG-4, etc.). See POTS codec.
Television
In TV, live television remotes are an almost daily part of television news broadcasts in the U.S. As a part of electronic news gathering (ENG), remotes are meant to bring the audience to the scene of the action.
To get to the scene quickly, a live remote may be done from a helicopter.
Live television remotes may often be used in a manner similar to radio remotes (and vice versa) as well.
See also
Remote recording
Remote integration model
References
Broadcast engineering | Remote broadcast | [
"Engineering"
] | 811 | [
"Broadcast engineering",
"Electronic engineering"
] |
978,045 | https://en.wikipedia.org/wiki/Comparison%20of%20web%20browsers | This is a comparison of both historical and current web browsers based on developer, engine, platform(s), releases, license, and cost.
General information
Basic general information about the browsers. Browsers listed on a light purple background are discontinued. Platforms with a yellow background have limited support.
Operating system support
Browsers are compiled to run on certain operating systems, without emulation.
This list is not exhaustive, but rather reflects the most common OSes today (e.g. Netscape Navigator was also developed for OS/2 at a time when macOS 10 did not exist) but does not include the growing appliance segment (for example, the Opera web browser has gained a leading role for use in mobile phones, smartphones, the Nintendo DS and Wii, and Personal Digital Assistants, and is also used in some smart TVs).
Both the web browser and OS means most recent version, example: Windows 11 with Internet Explorer 11.
Browser features
Information about what common browser features are implemented natively (without third-party add-ons).
Accessibility features
Information about what common accessibility features are implemented natively (without third-party add-ons). Browsers that do not support pop-ups have no need for pop-up blocking abilities, so that field is marked as N/A.
Accessibility features (continued)
Information about what common accessibility features are implemented natively (without third-party add-ons).
Web technology support
Information about what web standards, and technologies the browsers support, except for JavaScript. External links lead to information about support in future versions of the browsers or extensions that provide such functionality.
Plugins and syndicated content support
Information about what web standards, and technologies the browsers support. External links lead to information about support in future versions of the browsers or extensions that provide such functionality.
JavaScript support
Information about what JavaScript technologies the browsers support. Note that although XPath is used by XSLT, it is only considered here if it can be accessed using JavaScript. External links lead to information about support in future versions of the browsers or extensions that provide such functionality, e.g., Babel.
See what parts of DOM your browser supports
Protocol support
Information about what Internet protocols the browsers support (in addition to HTTP that all (modern) browser should and do fully support). External links lead to information about support in future versions of the browsers or extensions that provide such functionality.
More than half of web traffic from Chrome to Google's servers is handled by QUIC protocol, not TCP (or HTTP/1). Chrome, Opera, and Firefox have support for QUIC, and HTTP/3, while Safari is testing it for a subset of users.
Image format support
Information about what image formats the browsers support. External links lead to information about support in future versions of the browsers or extensions that provide such functionality.
Internationalization
Most browsers are available in more than one language.
See also
History of the web browser
List of web browsers
Comparison of browser engines
Comparison of lightweight web browsers
Version history for TLS/SSL support in web browsers
Usage share of web browsers
Comparison of download managers
Browser security
Browser wars
HTML video browser support
HTML audio supported audio coding formats
References
Web browser comparisons
Online services comparisons | Comparison of web browsers | [
"Technology"
] | 679 | [
"Online services comparisons",
"Computing comparisons"
] |
978,101 | https://en.wikipedia.org/wiki/Wallpaper%20%28computing%29 | A wallpaper or background (also known as a desktop background, desktop picture or desktop image on computers) is a digital image (photo, drawing etc.) used as a decorative background of a graphical user interface on the screen of a computer, smartphone or other electronic device. On a computer, wallpapers are generally used on the desktop, while on a mobile phone they serve as the background for the home screen. Though most devices include a default background image, modern devices usually allow users to manually change the background image.
The term "wallpaper" was used in Microsoft Windows before Windows XP (In Windows XP and later, it is called the "desktop background"). Meanwhile, macOS refers to it as "desktop picture". On older systems that allowed small repeated patterns to be set as background images, the term desktop pattern was used.
History
The X Window System was one of the earliest systems to include support for an arbitrary image as wallpaper via the xsetroot program, which at least as early as the X10R3 release in 1985 could tile the screen with any solid color or any binary-image X BitMap file. In 1989, a free software program called was released that allowed an arbitrary color GIF image to be used as wallpaper, and in the same year the free xloadimage program was released which could display a variety of image formats (including color images in Sun Rasterfile format) as the desktop background. Subsequently, a number of programs were released that added wallpaper support for additional image formats and other features, such as the xpmroot program (released in 1993 as part of fvwm) and the xv software (released in 1994).
The original Macintosh operating system only allowed a selection of 8×8-pixel binary-image tiled patterns; the ability to use small color patterns was added in System 5 in 1987. Mac OS 8 in 1997 was the first Macintosh version to include built-in support for using arbitrary images as desktop pictures, rather than small repeating patterns.
Windows 3.0 in 1990 was the first version of Microsoft Windows to feature support for wallpaper customization, and used the term "wallpaper" for this feature. Although Windows 3.0 only came with 7 small patterns (2 black-and-white and 5 16-color), the user could supply other images in the BMP file format with up to 8-bit color (although the system was theoretically capable of handling 24-bit color images, it did so by dithering them to an 8-bit palette) to provide similar wallpaper features otherwise lacking in those systems. A wallpaper feature was added in a beta release of OS/2 2.0 in 1991.
Due to the widespread use of personal computers, some wallpapers have become immensely recognizable and gained iconic cultural status. Bliss, the default wallpaper of Windows XP, has become the most viewed photograph of the 2000s.
Animated backgrounds
Animated backgrounds (sometimes referred to as live backgrounds or dynamic backgrounds) refers to wallpapers which feature a moving image or a 2D / 3D scene as an operating system background rather than a static image, it may also refer to wallpapers being cycled in a playlist, often with certain transition effects. Some operating systems, such as Android, provide native support for animated wallpapers.
Microsoft Windows
Active Desktop, which is included in Windows 95 OSR 2.5 through Windows XP, allows web apps to run as desktop background and deliver live contents. Animation is one of the possibilities.
In the Ultimate edition of Windows Vista, Windows DreamScene allows videos of any supported format (including animated GIFs) as wallpapers.
Starting with Windows 7, the OS can cycle through pictures from a folder at regular intervals. While the OS no longer supports animated backgrounds, it enables third-party software to fill that gap. This degree of extensibility is unique to Windows.
Android
Live wallpapers have been introduced in Android 2.0 Eclair to provide native support for animated wallpapers. From a technical point of view, live wallpapers are software applications that provide a moving background image and may allow for user interaction or utilize other hardware and software features within the device (accelerometer, GPS, network access, etc.).
macOS and iOS
macOS has built-in support, via the Desktop & Screen Saver panel in its System Preferences/Settings, for cycling through a folder collection of images on a timed interval or when logging in or waking from sleep. Since macOS Mojave, the user can also select a "Dynamic Desktop" that automatically updates to visually match the time of the day.
Additionally, macOS has the native ability to run a screen saver on the desktop; in this configuration, the screen saver appears beneath the desktop icons in place of the system wallpaper. However, macOS does not feature a built-in interface to do this; it must be done through Terminal commands or various third-party applications.
Dynamically animated backgrounds have also been introduced in iOS 7 and later versions, however they are restricted to the ones provided by Apple. Jailbroken iOS devices can download other dynamic backgrounds.
Linux distros
Linux distributions usually provides their own original backgrounds. For example:
Debian puts many alternative backgrounds under the /usr/share/backgrounds directory.
GNOME 2 can be set to cycle through pictures from a folder at regular intervals, similarly to Windows 7.
MATE provides various wallpapers, usually in the /usr/share/backgrounds/mate directory.
KDE version 4 and later provide various dynamic wallpapers, including a slideshow, and other options provided by plugins, such as fractals and Earth map.
Enlightenment v17 supports image sequences, animated and interactive desktop backgrounds in its default configuration.
See also
Wallpaper group
References
Graphical user interface elements
Desktop environments | Wallpaper (computing) | [
"Technology"
] | 1,195 | [
"Components",
"Graphical user interface elements"
] |
978,171 | https://en.wikipedia.org/wiki/Ramrod | A ramrod (or scouring stick) is a metal or wooden device used with muzzleloading firearms to push the projectile up against the propellant (mainly blackpowder). The ramrod was used with weapons such as muskets and cannons and was usually held in a notch underneath the barrel.
Use in firearms
Bullets that did not fit snugly in the barrel were often secured in place by a wad of paper or cloth, but either way, ramming was necessary to place the bullet securely at the rear of the barrel. Ramming was also needed to tamp the powder so that it would explode properly instead of fizzle (this was a leading cause of misfires).
In some pistols from the 17th century, the ramrod is folded up in a small compartment at the end of the pommel.
The ramrod could also be fitted with tools for various tasks such as cleaning the weapon, or retrieving a stuck bullet.
Caplock revolvers
Cap and ball revolvers were loaded a bit like muzzleloaders—powder was poured into each chamber of the cylinder from the muzzle end, and a bullet was then squeezed in. Such handguns usually had a ramming mechanism built into the frame. The user pulled a lever underneath the barrel of the pistol, which pushed a rammer into the aligned chamber.
Caplock revolvers mostly had mechanical devices with ramrods mounted on the frame of the revolver, which rammed the ball into the chamber of the cylinder by pulling a lever that was connected to the ramrod in various ways (by hinge, screw or lever). These mechanisms are called rammers or loading-levers. The most popular rammers used in caplock revolvers were the Colt, Adams and Kerr systems.
Colt's rammer
Colt's rammer, patented by Samuel Colt about 1839, is a straight lever hinged under the barrel, with a triangular plate on its back end. The back corner of the triangle is hinged under the barrel, while the bottom corner is hinged to a short ramrod below and behind it. Pulling the lever down pushes the rod into the lowest chamber of the cylinder. This system was used on Colt revolvers from 1839 until 1873, when the Colt Peacemaker with metallic cartridges was introduced, as well as on Remington and Webley revolvers.
Adams rammer
Adams rammer, patented by Robert Adams in 1853, a straight or slightly downward-curving lever mounted on the left or right side of the frame with a screw at the front end and resting under the cylinder on the side of the stock when not in use. The lever pivots around a pin at the front end (on the frame of the revolver in front of and below the cylinder), and has a short ramrod in the middle, facing down in a fixed position. To use, the lever must be manually rotated down and forward for 270°, until the lever is in front of the cylinder and the rod enters one of the chambers, pressing the ball in. This mechanism was used on older Adams revolvers (on the left side of the revolver) and Webley Longspur revolvers (on the right side of the revolver).
Kerr's rammer
Kerr rammer, patented by James Kerr in 1855, a bent lever (bent downwards at a right or obtuse angle, with a short ramrod on the lower arm) which pivots about a pin on the front of the revolver frame in front of the cylinder and rests on the left side of the barrel when not in use. The lever must be turned up 90° to push the rod into the chamber. This mechanism was used in the Beaumont-Adams and Tranter revolvers, as well as the newer Adams and Webley Longspur revolvers.
Artillery
Naval artillery began as muzzle-loading cannon and these too required ramming. Large muzzle loading guns continued into the 1880s, using wooden staffs worked by several sailors as ramrods. Manual ramming was replaced with hydraulic powered ramming with trials on from 1874.
Other uses
indicates the term is also a used to describe a trail or ranch foreman, particularly one on cattle drives. It is also used as a verb to describe spurring or forcing a thing, such as a piece of legislation, forward. Similar to v. “spearhead”.
References
Literature
External links
Firearm components | Ramrod | [
"Technology"
] | 886 | [
"Firearm components",
"Components"
] |
978,322 | https://en.wikipedia.org/wiki/Noranda%20Mines | Noranda Inc. was a mining and metallurgy company originally from Rouyn-Noranda, Quebec, Canada. It was listed on the TSX under the symbol NRD.LV. After eventually acquiring a large interest in rival mining company Falconbridge, it merged with that company in 2005. The combined company continued under the name Falconbridge Limited, ending the Noranda name. Only one year later in 2006 Falconbridge was acquired by the Swiss-based mining company Xstrata. On 2 May 2013 ownership of Xstrata was fully acquired by mining behemoth Glencore.
History and operations
Noranda was incorporated in 1922 as Noranda Mines under the leadership of James Y. Murdoch to exploit the Horne deposit, discovered by Edmond Henry Horne on mineral claims he staked in 1920 near Rouyn-Noranda, Quebec. Extraction of copper began on 17 December 1927. Although extraction was originally predicted to last for only three years, additional reserves (the gigantic "Giant H Orebody") were quickly discovered; the mine would form the backbone of Noranda's operations until reserves were exhausted in 1976.
Beginning in 1930, Noranda diversified by acquiring holdings in the forestry, oil, manufacturing, and automotive industries. In 1931, the company opened the CCR refinery in Montréal-Est, which processes all the copper produced by the Horne Smelter.
Noranda gained its first international property in 1938 with the purchase of the Empresa Minera de Nicaragua gold mine in Nicaragua.
The company gained a large interest in Kerr Addison Gold Mines in 1945.
In 1955 it opened the Gaspé Copper Mines, and in 1963 Canadian Electrolytic Zinc (CEZ), in which Noranda held a large stake, began production.
In 1967, Noranda divested itself at $80 per share of its holdings in Denison Mines, which it had purchased in 1964 for $12 to $18 per share. A sum of $80mn was devoted to Potash mines in Saskatchewan, while $50mn purchased a 51% stake in the Brunswick Mining and Smelting Corporation earlier that year, as well as an investment in Pacific Coast Company, an aluminum products manufacturer based in Cleveland, Ohio.
Following the 1973 Chilean coup d'état, Noranda reclaimed its 49% share in its subsidiary Chile Canadian Mines. The company then invested $600,000 of new capital in its Chilean mines, the first major mining investment after the coup, securing the right to the Andacollo copper reserves in northern Chile in 1976. The year 1973 also saw the company expand into aluminum with the opening of an aluminum smelter in New Madrid, Missouri, and the oil business with the formation of Canadian Hunter.
Asset management companies Brascan and Caisse de Dépôt gained effective control of Noranda with a $1 billion CAD investment in 1981.
In 1984 Noranda Mines changed its name to Noranda Inc., as a reflection of its wide diversification. Also in 1984, the company became a large player in the electronics scrap and recycling business by purchasing Micro Metallics Corp.
In 1995 Noranda gained full control of Brunswick Mining and Smelting, a zinc mine and smelting company in New Brunswick; they opened a battery recycling facility one year later. Also in 1995 Noranda entered Latin America with the purchase of a 25% stake in the Refimet smelter outside of Antofagasta, Chile. Noranda obtained 100% control in 1998 and ownership of that site aided later expansion into Latin America.
Noranda announced that it would divest itself from all industries unrelated to mining and metals in 1997, and completed the transition the following year, removing itself from the forestry and oil and gas industries.
In August 2000, Noranda was the top miner in Canada.
The company gained a 34% stake in the huge Antamina copper-zinc mine in Peru, which opened in 2001.
In 2002 Noranda opened a large aluminum foil plant in Tennessee.
It expanded its recycling business with the opening of an electronic hardware recycling facility in Brampton, Ontario in 2003.
Noranda expanded its aluminum business in 2004 by gaining a 50% interest in the Gramercy alumina refinery in Louisiana and associated Jamaican bauxite deposits.
By 2005, the company had operations in 18 countries.
Merger
Noranda had bought 19.9% of rival mining company Falconbridge in 1988, which was raised to a 58.4% stake in 2002. In 2005 China Minmetals was rumoured to be interested in buying Noranda, which caused the Canadian federal government to review its foreign investment policy. In June 2005 Noranda completed a merger with Falconbridge, essentially purchasing Falconbridge outright. However, the combined company continued under the name Falconbridge Limited, ending the Noranda name as a large mining company. Brascan reduced its stake in the new company to 20%.
Less than a year after completing its merger with Falconbridge, the new company was acquired by Xstrata. The Noranda name continues for companies with Noranda Aluminum, which was the spun off by Xstrata, and the Noranda Income Fund which is a large zinc refinery in Salaberry-de-Valleyfield, Quebec.
Scotland and Wales
Noranda Mines also operated in the UK in the early 70's with active exploration programs in Scotland and north Wales. The exploration program consisted of soil and stream sampling and limited Induced Polarisation and fluxgate magnetometer surveys. These programs were sufficiently advanced to give rise to drilling programs in Snowdonia (Hafod y llan) either side of the Watkin path, and also in Wester Ross just outside Locharron. Copper mineralisation was encountered in the Welsh drilling program but essentially nothing in Wester Ross.
Drilling in Snowdonia was with a hand portable x-ray rig capable of reaching approximately 100 ft and in Wester Ross with a Boyles Bros. rotary rig drilling to approximately 1000 ft.
Leadership
President
James Young Murdoch, 1922–1956
John Ross Bradfield, 1956–1964
Richard Valentine Porritt, 1964–1968
Alfred Powis, 1968–1982
Adam Hartley Zimmerman, 1982–1987
David Wylie Kerr, 1987–1995
Edward Courtney Pratt, 1995–1997
David Wylie Kerr, 1997–2001
Derek George Pannell, 2001–2005
Chairman of the Board
James Young Murdoch, 1956–1962
John Ross Bradfield, 1964–1974
William Stanley Row, 1974–1977
Alfred Powis, 1977–1995
David Wylie Kerr, 1995–1997
Edward Courtney Pratt, 1997–1998
Robert James Harding, 1998–2001
David Wylie Kerr, 2001–2002
See also
Alumysa, a suspended aluminium smelter project by Noranda in Patagonia
Noranda Caldera
Edper Investments, which controlled Noranda from 1981 through its ownership of Brascan.
References
External links
Former website (April 15, 2005 snapshot from the Internet Archive)
Flash presentation See "About us", "History and Milestones" Retrieved 26 June 2008.
Companies formerly listed on the Toronto Stock Exchange
Defunct mining companies of Canada
Copper mining companies of Canada
Zinc mining companies
Companies based in Toronto
Defunct companies of Ontario
Non-renewable resource companies established in 1922
Non-renewable resource companies disestablished in 2005
Canadian companies established in 1922
Apollo Global Management companies
Rouyn-Noranda
Xstrata
Private equity portfolio companies
Canadian companies disestablished in 2005
1922 establishments in Quebec
2005 disestablishments in Ontario | Noranda Mines | [
"Chemistry"
] | 1,495 | [
"Metallurgical industry of Canada",
"Metallurgical industry by country"
] |
978,611 | https://en.wikipedia.org/wiki/Joint%20quantum%20entropy | The joint quantum entropy generalizes the classical joint entropy to the context of quantum information theory. Intuitively, given two quantum states and , represented as density operators that are subparts of a quantum system, the joint quantum entropy is a measure of the total uncertainty or entropy of the joint system. It is written or , depending on the notation being used for the von Neumann entropy. Like other entropies, the joint quantum entropy is measured in bits, i.e. the logarithm is taken in base 2.
In this article, we will use for the joint quantum entropy.
Background
In information theory, for any classical random variable , the classical Shannon entropy is a measure of how uncertain we are about the outcome of . For example, if is a probability distribution concentrated at one point, the outcome of is certain and therefore its entropy . At the other extreme, if is the uniform probability distribution with possible values, intuitively one would expect is associated with the most uncertainty. Indeed, such uniform probability distributions have maximum possible entropy .
In quantum information theory, the notion of entropy is extended from probability distributions to quantum states, or density matrices. For a state , the von Neumann entropy is defined by
Applying the spectral theorem, or Borel functional calculus for infinite dimensional systems, we see that it generalizes the classical entropy. The physical meaning remains the same. A maximally mixed state, the quantum analog of the uniform probability distribution, has maximum von Neumann entropy. On the other hand, a pure state, or a rank one projection, will have zero von Neumann entropy. We write the von Neumann entropy (or sometimes .
Definition
Given a quantum system with two subsystems A and B, the term joint quantum entropy simply refers to the von Neumann entropy of the combined system. This is to distinguish from the entropy of the subsystems.
In symbols, if the combined system is in state ,
the joint quantum entropy is then
Each subsystem has its own entropy. The state of the subsystems are given by the partial trace operation.
Properties
The classical joint entropy is always at least equal to the entropy of each individual system. This is not the case for the joint quantum entropy. If the quantum state exhibits quantum entanglement, then the entropy of each subsystem may be larger than the joint entropy. This is equivalent to the fact that the conditional quantum entropy may be negative, while the classical conditional entropy may never be.
Consider a maximally entangled state such as a Bell state. If is a Bell state, say,
then the total system is a pure state, with entropy 0, while each individual subsystem is a maximally mixed state, with maximum von Neumann entropy . Thus the joint entropy of the combined system is less than that of subsystems. This is because for entangled states, definite states cannot be assigned to subsystems, resulting in positive entropy.
Notice that the above phenomenon cannot occur if a state is a separable pure state. In that case, the reduced states of the subsystems are also pure. Therefore, all entropies are zero.
Relations to other entropy measures
The joint quantum entropy can be used to define of the conditional quantum entropy:
and the quantum mutual information:
These definitions parallel the use of the classical joint entropy to define the conditional entropy and mutual information.
See also
Quantum relative entropy
Quantum mutual information
References
Nielsen, Michael A. and Isaac L. Chuang, Quantum Computation and Quantum Information. Cambridge University Press, 2000.
Quantum mechanical entropy
Quantum information theory | Joint quantum entropy | [
"Physics"
] | 707 | [
"Quantum mechanical entropy",
"Entropy",
"Physical quantities"
] |
978,650 | https://en.wikipedia.org/wiki/Triple%20product | In geometry and algebra, the triple product is a product of three 3-dimensional vectors, usually Euclidean vectors. The name "triple product" is used for two different products, the scalar-valued scalar triple product and, less often, the vector-valued vector triple product.
Scalar triple product
The scalar triple product (also called the mixed product, box product, or triple scalar product) is defined as the dot product of one of the vectors with the cross product of the other two.
Geometric interpretation
Geometrically, the scalar triple product
is the (signed) volume of the parallelepiped defined by the three vectors given.
Properties
The scalar triple product is unchanged under a circular shift of its three operands (a, b, c):
Swapping the positions of the operators without re-ordering the operands leaves the triple product unchanged. This follows from the preceding property and the commutative property of the dot product:
Swapping any two of the three operands negates the triple product. This follows from the circular-shift property and the anticommutativity of the cross product:
The scalar triple product can also be understood as the determinant of the matrix that has the three vectors either as its rows or its columns (a matrix has the same determinant as its transpose):
If the scalar triple product is equal to zero, then the three vectors a, b, and c are coplanar, since the parallelepiped defined by them would be flat and have no volume.
If any two vectors in the scalar triple product are equal, then its value is zero:
Also:
The simple product of two triple products (or the square of a triple product), may be expanded in terms of dot products:This restates in vector notation that the product of the determinants of two 3×3 matrices equals the determinant of their matrix product. As a special case, the square of a triple product is a Gram determinant.
The ratio of the triple product and the product of the three vector norms is known as a polar sine:which ranges between −1 and 1.
Scalar or pseudoscalar
Although the scalar triple product gives the volume of the parallelepiped, it is the signed volume, the sign depending on the orientation of the frame or the parity of the permutation of the vectors. This means the product is negated if the orientation is reversed, for example by a parity transformation, and so is more properly described as a pseudoscalar if the orientation can change.
This also relates to the handedness of the cross product; the cross product transforms as a pseudovector under parity transformations and so is properly described as a pseudovector. The dot product of two vectors is a scalar but the dot product of a pseudovector and a vector is a pseudoscalar, so the scalar triple product (of vectors) must be pseudoscalar-valued.
If T is a proper rotation then
but if T is an improper rotation then
Scalar or scalar density
Strictly speaking, a scalar does not change at all under a coordinate transformation. (For example, the factor of 2 used for doubling a vector does not change if the vector is in spherical vs. rectangular coordinates.) However, if each vector is transformed by a matrix then the triple product ends up being multiplied by the determinant of the transformation matrix, which could be quite arbitrary for a non-rotation. That is, the triple product is more properly described as a scalar density.
As an exterior product
In exterior algebra and geometric algebra the exterior product of two vectors is a bivector, while the exterior product of three vectors is a trivector. A bivector is an oriented plane element and a trivector is an oriented volume element, in the same way that a vector is an oriented line element.
Given vectors a, b and c, the product
is a trivector with magnitude equal to the scalar triple product, i.e.
,
and is the Hodge dual of the scalar triple product. As the exterior product is associative brackets are not needed as it does not matter which of or is calculated first, though the order of the vectors in the product does matter. Geometrically the trivector a ∧ b ∧ c corresponds to the parallelepiped spanned by a, b, and c, with bivectors , and matching the parallelogram faces of the parallelepiped.
As a trilinear function
The triple product is identical to the volume form of the Euclidean 3-space applied to the vectors via interior product. It also can be expressed as a contraction of vectors with a rank-3 tensor equivalent to the form (or a pseudotensor equivalent to the volume pseudoform); see below.
Vector triple product
The vector triple product is defined as the cross product of one vector with the cross product of the other two. The following relationship holds:
.
This is known as triple product expansion, or Lagrange's formula, although the latter name is also used for several other formulas. Its right hand side can be remembered by using the mnemonic "ACB − ABC", provided one keeps in mind which vectors are dotted together. A proof is provided below. Some textbooks write the identity as such that a more familiar mnemonic "BAC − CAB" is obtained, as in “back of the cab”.
Since the cross product is anticommutative, this formula may also be written (up to permutation of the letters) as:
From Lagrange's formula it follows that the vector triple product satisfies:
which is the Jacobi identity for the cross product. Another useful formula follows:
These formulas are very useful in simplifying vector calculations in physics. A related identity regarding gradients and useful in vector calculus is Lagrange's formula of vector cross-product identity:
This can be also regarded as a special case of the more general Laplace–de Rham operator .
Proof
The component of is given by:
Similarly, the and components of are given by:
By combining these three components we obtain:
Using geometric algebra
If geometric algebra is used the cross product b × c of vectors is expressed as their exterior product b∧c, a bivector. The second cross product cannot be expressed as an exterior product, otherwise the scalar triple product would result. Instead a left contraction can be used, so the formula becomes
The proof follows from the properties of the contraction. The result is the same vector as calculated using a × (b × c).
Interpretations
Tensor calculus
In tensor notation, the triple product is expressed using the Levi-Civita symbol:
and
referring to the -th component of the resulting vector. This can be simplified by performing a contraction on the Levi-Civita symbols,
where is the Kronecker delta function ( when and when ) and is the generalized Kronecker delta function. We can reason out this identity by recognizing that the index will be summed out leaving only and . In the first term, we fix and thus . Likewise, in the second term, we fix and thus .
Returning to the triple cross product,
Vector calculus
Consider the flux integral of the vector field across the parametrically-defined surface : . The unit normal vector to the surface is given by , so the integrand is a scalar triple product.
See also
Quadruple product
Vector algebra relations
Notes
References
External links
Khan Academy video of the proof of the triple product expansion
Articles containing proofs
Mathematical identities
Multilinear algebra
Operations on vectors
Ternary operations | Triple product | [
"Mathematics"
] | 1,562 | [
"Mathematical problems",
"Articles containing proofs",
"Mathematical identities",
"Mathematical theorems",
"Algebra"
] |
978,717 | https://en.wikipedia.org/wiki/Orbital%20node | An orbital node is either of the two points where an orbit intersects a plane of reference to which it is inclined. A non-inclined orbit, which is contained in the reference plane, has no nodes.
Planes of reference
Common planes of reference include the following:
For a geocentric orbit, Earth's equatorial plane. In this case, non-inclined orbits are called equatorial.
For a heliocentric orbit, the ecliptic or invariable plane. In this case, non-inclined orbits are called ecliptic.
For an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary (called the plane of the sky).
Node distinction
If a reference direction from one side of the plane of reference to the other is defined, the two nodes can be distinguished. For geocentric and heliocentric orbits, the ascending node (or north node) is where the orbiting object moves north through the plane of reference, and the descending node (or south node) is where it moves south through the plane. In the case of objects outside the Solar System, the ascending node is the node where the orbiting secondary passes away from the observer, and the descending node is the node where it moves towards the observer., p. 137.
The position of the node may be used as one of a set of parameters, called orbital elements, which describe the orbit. This is done by specifying the longitude of the ascending node (or, sometimes, the longitude of the node.)
The line of nodes is the straight line resulting from the intersection of the object's orbital plane with the plane of reference; it passes through the two nodes.
Symbols and nomenclature
The symbol of the ascending node is (Unicode: U+260A, ☊), and the symbol of the descending node is (Unicode: U+260B, ☋).
In medieval and early modern times, the ascending and descending nodes of the Moon in the ecliptic plane were called the "dragon's head" (, ) and "dragon's tail" (), respectively. These terms originally referred to the times when the Moon crossed the apparent path of the sun in the sky (as in a solar eclipse). Also, corruptions of the Arabic term such as ganzaar, genzahar, geuzaar and zeuzahar were used in the medieval West to denote either of the nodes.
The Koine Greek terms and were also used for the ascending and descending nodes, giving rise to the English terms anabibazon and catabibazon.
Lunar nodes
For the orbit of the Moon around Earth, the plane is taken to be the ecliptic, not the equatorial plane. The gravitational pull of the Sun upon the Moon causes its nodes to gradually precess westward, completing a cycle in approximately 18.6 years.
Use in astrology
The image of the ascending and descending orbital nodes as the head and tail of a dragon, 180 degrees apart in the sky, goes back to the Chaldeans; it was used by the Zoroastrians, and then by Arabic astronomers and astrologers. In Middle Persian, its head and tail were respectively called and ; in Arabic, and — or in the case of the Moon, ___ . Among the arguments against astrologers made by Ibn Qayyim al-Jawziyya (1292–1350), in his Miftah Dar al-SaCadah: "Why is it that you have given an influence to [the head] and [the tail], which are two imaginary points [ascending and descending nodes]?"
See also
Eclipse
Euler angles
Longitude of the ascending node
References
Technical factors of astrology
Orbits
Point (geometry) | Orbital node | [
"Mathematics"
] | 764 | [
"Point (geometry)"
] |
978,720 | https://en.wikipedia.org/wiki/Gefitinib | Gefitinib, sold under the brand name Iressa, is a medication used for certain breast, lung and other cancers. Gefitinib is an EGFR inhibitor, like erlotinib, which interrupts signaling through the epidermal growth factor receptor (EGFR) in target cells. Therefore, it is only effective in cancers with mutated and overactive EGFR, but resistances to gefitinib can arise through other mutations. It is marketed by AstraZeneca and Teva.
It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication.
Mechanism of action
Gefitinib is the first selective inhibitor of epidermal growth factor receptor's (EGFR) tyrosine kinase domain. Thus gefitinib is an EGFR inhibitor. The target protein (EGFR) is a member of a family of receptors (ErbB) which includes Her1(EGFR), Her2(erb-B2), Her3(erb-B3) and Her4 (Erb-B4).
EGFR is overexpressed in the cells of certain types of human carcinomas - for example in lung and breast cancers. This leads to inappropriate activation of the anti-apoptotic Ras signalling cascade, eventually leading to uncontrolled cell proliferation. Research on gefitinib-sensitive non-small cell lung cancers has shown that a mutation in the EGFR tyrosine kinase domain is responsible for activating anti-apoptotic pathways. These mutations tend to confer increased sensitivity to tyrosine kinase inhibitors such as gefitinib and erlotinib. Of the types of non-small cell lung cancer histologies, adenocarcinoma is the type that most often harbors these mutations. These mutations are more commonly seen in Asians, women, and non-smokers (who also tend to more often have adenocarcinoma).
Gefitinib inhibits EGFR tyrosine kinase by binding to the adenosine triphosphate (ATP)-binding site of the enzyme. Thus the function of the EGFR tyrosine kinase in activating the anti-apoptotic Ras signal transduction cascade is inhibited, and malignant cells are inhibited.
Clinical uses
Gefitinib is marketed in many countries.
Iressa was approved and marketed in July 2002, in Japan, making it the first country to import the drug.
The FDA approved gefitinib in May 2003, for non-small cell lung cancer (NSCLC). It was approved as monotherapy for the treatment of people with locally advanced or metastatic NSCLC after failure of both platinum-based and docetaxel chemotherapies.
In June 2005, the FDA withdrew approval for use in new patients due to lack of evidence that it extended life.
In the European Union, gefitinib is indicated since 2009 in advanced NSCLC in all lines of treatment for patients harbouring EGFR mutations. This label was granted after gefitinib demonstrated as a first-line treatment to significantly improve progression-free survival vs. a platinum doublet regime in patients harbouring such mutations. IPASS has been the first of four phase III trials to have confirmed gefitinib superiority in this patient population.
In most of the other countries where gefitinib is marketed it is approved for people with advanced NSCLC who had received at least one previous chemotherapy regime. However, applications to expand its label as a first-line treatment in patients harbouring EGFR mutations is currently in process based on the latest scientific evidence. As at August 2012 New Zealand has approved gefitinib as first-line treatment for patients with EGFR mutation for naive locally advanced or metastatic, unresectable NSCLC. This is publicly funded for an initial four-month term and renewal if no progression.
In July 2015, the FDA approved gefitinib as a first-line treatment for NSCLC.
Experimental uses
In August 2013, the BBC reported that researchers in Edinburgh and Melbourne found, in a small-scale trial of 12 patients, that the effectiveness of Methotrexate for treating ectopic pregnancy was improved when Gefitinib was also administered.
Studies
IPASS (IRESSA Pan-Asia Study) was a randomized, large-scale, double-blinded study which compared gefitinib vs. carboplatin/ paclitaxel as a first-line treatment in advanced NSCLC.
IPASS studied 1,217 patients with confirmed adenocarcinoma histology who were former or never smokers. A pre-planned sub-group analyses showed that progression-free survival (PFS) was significantly longer for gefitinib than chemotherapy in patients with EGFR mutation positive tumours (HR 0.48, 95 per cent CI 0.36 to 0.64, p less than 0.0001), and significantly longer for chemotherapy than gefitinib in patients with EGFR mutation negative tumours (HR 2.85, 95 per cent CI 2.05 to 3.98, p less than 0.0001).
This, in 2009, was the first time a targeted monotherapy has demonstrated significantly longer PFS than doublet chemotherapy.
EGFR diagnostic tests
Roche Diagnostics, Genzyme, QIAGEN, Argenomics S.A. & other companies make tests to detect EGFR mutations, designed to help predict which lung cancer patients may respond best to some therapies, including gefitinib and erlotinib.
The tests examine the genetics of tumors removed for biopsy for mutations that make them susceptible to treatment.
The EGFR mutation test may also help AstraZeneca win regulatory approval for use of their drugs as initial therapies. Currently the TK inhibitors are approved for use only after other drugs fail. In the case of gefitinib, the drug works only in about 10% of patients with advanced non-small cell lung cancer, the most common type of lung cancer.
Adverse effects
As gefitinib is a selective chemotherapeutic agent, its tolerability profile is better than previous cytotoxic agents. Adverse drug reactions (ADRs) are acceptable for a potentially fatal disease.
Acne-like rash is reported very commonly. Other common adverse effects (≥1% of patients) include: diarrhoea, nausea, vomiting, anorexia, stomatitis, dehydration, skin reactions, paronychia, asymptomatic elevations of liver enzymes, asthenia, conjunctivitis, blepharitis.
Infrequent adverse effects (0.1–1% of patients) include: interstitial lung disease, corneal erosion, aberrant eyelash and hair growth.
Resistance
Gefitinib and other first-generation EGFR inhibitors reversibly bind to the receptor protein, effectively competing for the ATP binding pocket. Secondary mutations can arise that alter the binding site, the most common mutation being T790M, where a threonine is replaced by a methionine at amino acid position 790, which is in the ligand-binding domain that typically binds ATP. Threonine 790 is the gatekeeper residue, meaning it is key in determining specificity in the binding pocket. When it is mutated into a methionine, researchers originally hypothesized that it caused drug inhibition due to the steric hindrance of the bulkier methionine that selected for the binding of ATP instead of gefitinib. As of 2008, the current hypothesized mechanism is that resistance to gefitinib is conveyed by increasing the ATP affinity of EGFR on an enzymatic level, meaning that the protein preferentially binds ATP over gefitinib.
In order to combat this acquired resistance to gefitinib and other first-generation inhibitors, researchers have used irreversible EGFR inhibitors like neratinib or dacomitinib, called tyrosine kinase inhibitors (TKIs). These new drugs covalently bind to the ATP binding pocket, so when they are attached to EGFR, they cannot be displaced by ATP. Even if the mutated versions of EGFR have a higher affinity for ATP, they will eventually use the irreversible inhibitors as ligands, which effectively shuts down their activity. When enough irreversible ligands have bound to EGFR, proliferation will be halted and apoptosis will be triggered through multiple pathways; for example, Bim can be activated after it is no longer inhibited by ERK, one of the kinases in the EGFR signaling pathway. Even with gefitinib halting progression of NSCLC, the development of the cancer progresses after 9 to 13 months due to acquired resistances like the T790M mutation. These TKIs like dacomitinib extended overall survival by close to a year.
References
External links
Receptor tyrosine kinase inhibitors
4-Morpholinyl compounds
Quinazolines
Chlorobenzene derivatives
Fluorobenzene derivatives
Amines
Phenol ethers
Drugs developed by AstraZeneca
Antineoplastic drugs | Gefitinib | [
"Chemistry"
] | 1,954 | [
"Amines",
"Bases (chemistry)",
"Functional groups"
] |
978,840 | https://en.wikipedia.org/wiki/Cryostat | A cryostat (from cryo meaning cold and stat meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various refrigeration methods, most commonly using cryogenic fluid bath such as liquid helium. Hence it is usually assembled into a vessel, similar in construction to a vacuum flask or Dewar. Cryostats have numerous applications within science, engineering, and medicine.
Types
Closed-cycle cryostats
Closed-cycle cryostats consist of a chamber through which cold helium vapour is pumped. An external mechanical refrigerator extracts the warmer helium exhaust vapour, which is cooled and recycled. Closed-cycle cryostats consume a relatively large amount of electrical power, but need not be refilled with helium and can run continuously for an indefinite period. Objects may be cooled by attaching them to a metallic cold plate inside a vacuum chamber which is in thermal contact with the helium vapour chamber.
Continuous-flow cryostats
Continuous-flow cryostats are cooled by liquid cryogens (typically liquid helium or nitrogen) from a storage dewar. As the cryogen boils within the cryostat, it is continuously replenished by a steady flow from the storage dewar. Temperature control of the sample within the cryostat is typically performed by controlling the flow rate of cryogen into the cryostat together with a heating wire attached to a PID temperature control loop. The length of time over which cooling may be maintained is dictated by the volume of cryogens available.
Owing to the scarcity of liquid helium, some laboratories have facilities to capture and recover helium as it escapes from the cryostat, although these facilities are also costly to operate.
Bath cryostats
Bath cryostats are similar in construction to vacuum flasks filled with liquid helium. A cold plate is placed in thermal contact with the liquid helium bath. The liquid helium may be replenished as it boils away, at intervals between a few hours and several months, depending on the volume and construction of the cryostat. The boil-off rate is minimised by shielding the bath with either cold helium vapour, or vacuum shield with walls constructed from super insulator material. The helium vapour which boils away from the bath very effectively cools thermal shields around the outside of the bath. In the older designs there may be additional liquid nitrogen bath, or several concentric layers of shielding, with gradually increasing temperatures. However, the invention of super insulator materials has made this technology obsolete.
Multistage cryostats
In order to achieve temperatures lower than liquid helium at atmospheric pressure, additional cooler stages may be added to the cryostat. Temperatures down to 1 K can be reached by attaching the cold plate to a 1-K pot, which is a container of the He-4 isotope that may be pumped to low vapor pressure via a vacuum pump. Temperatures just below 0.300 K may be achieved using He-3, the rare isotope of helium, as the working fluid in a helium pot.
Temperatures down to 1 mK can be reached by employing dilution refrigerator or dry dilution refrigerator typically in addition to the main stage and 1 K pot. Temperatures below that can be reached using magnetic refrigeration.
Applications
Magnetic resonance imaging and research magnet types
Cryostats used in MRI machines are designed to hold a cryogen, typically helium, in a liquid state with minimal evaporation (boil-off). The liquid helium bath is designed to keep the superconducting magnet's bobbin of superconductive wire in its superconductive state. In this state, the wire has no electrical resistance and very large currents are maintained with low power input. To maintain superconductivity, the bobbin must be kept below its transition temperature by being immersed in the liquid helium. If, for any reason, the wire becomes resistive, i.e. loses superconductivity, a condition known as a "quench", the liquid helium evaporates, instantly raising pressure within the vessel. A burst disk, usually made of carbon, is placed within the chimney or vent pipe so that during a pressure excursion, the gaseous helium can be safely vented out of the MRI suite. Modern MRI cryostats use a mechanical refrigerator (cryocooler) to re-condense the helium gas and return it to the bath, to maintain cryogenic conditions and to conserve helium.
Typically cryostats are manufactured with two vessels, one inside the other. The outer vessel is evacuated with the vacuum acting as a thermal insulator. The inner vessel contains the cryogen and is supported within the outer vessel by structures made from low-conductivity materials. An intermediate shield between the outer and inner vessels intercepts the heat radiated from the outer vessel. This heat is removed by a cryocooler. Older helium cryostats used a liquid nitrogen vessel as this radiation shield and had the liquid helium in an inner, third, vessel. Nowadays few units using multiple cryogens are made with the trend being towards 'cryogen-free' cryostats in which all heat loads are removed by cryocoolers.
Biological microtome type
Cryostats are used in medicine to cut histological slides. They are usually used in a process called frozen section histology (see Frozen section procedure). The cryostat is essentially an ultrafine "deli-slicer", called a microtome, placed in a freezer. The cryostat is usually a stationary upright freezer, with an external wheel for rotating the microtome. The temperature can be varied, depending on the tissue being cut usually from −20 °C to −30 °C. The freezer is either powered by electricity, or by a refrigerant like liquid nitrogen. Small portable cryostats are available and can run off generators or vehicle inverters. To minimize unnecessary warming all necessary mechanical movements of the microtome can be achieved by hand via a wheel mounted outside the chamber. Newer microtomes have electric push button advancement of the tissue. The precision of the cutting is in micrometres. Tissue are sectioned as thin as 1 micrometre. Usual histology slides are mounted with a thickness of about 7 micrometres. Specimens that are soft at room temperature are mounted on a cutting medium (often made of egg white) on a metal "chuck", and frozen to cutting temperature (for example at −20 °C). Once frozen, the specimen on the chuck is mounted on the microtome. The crank is rotated and the specimen advances toward the cutting blade. Once the specimen is cut to a satisfactory quality, it is mounted on a warm (room temperature) clear glass slide, where it will instantaneously melt and adhere. The glass slide and specimen is dried with a dryer or air dried, and stained. The entire process from mounting to reading the slide takes from 10 to 20 minutes, allowing rapid diagnosis in the operating room, for the surgical excision of cancer. The cryostat can be used to cut histology and tissue slide (e.g., for enzyme localization) outside of medicine, but the quality of the section is poor compared to standard fixed section wax mounted histology.
See also
Lambda point refrigerator
References
Containers
Cryogenics
Vacuum flasks | Cryostat | [
"Physics"
] | 1,518 | [
"Applied and interdisciplinary physics",
"Vacuum flasks",
"Vacuum",
"Cryogenics",
"Matter"
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978,913 | https://en.wikipedia.org/wiki/Brittleness | A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Breaking is often accompanied by a sharp snapping sound.
When used in materials science, it is generally applied to materials that fail when there is little or no plastic deformation before failure. One proof is to match the broken halves, which should fit exactly since no plastic deformation has occurred.
Brittleness in different materials
Polymers
Mechanical characteristics of polymers can be sensitive to temperature changes near room temperatures. For example, poly(methyl methacrylate) is extremely brittle at temperature 4˚C, but experiences increased ductility with increased temperature.
Amorphous polymers are polymers that can behave differently at different temperatures. They may behave like a glass at low temperatures (the glassy region), a rubbery solid at intermediate temperatures (the leathery or glass transition region), and a viscous liquid at higher temperatures (the rubbery flow and viscous flow region). This behavior is known as viscoelastic behavior. In the glassy region, the amorphous polymer will be rigid and brittle. With increasing temperature, the polymer will become less brittle.
Metals
Some metals show brittle characteristics due to their slip systems. The more slip systems a metal has, the less brittle it is, because plastic deformation can occur along many of these slip systems. Conversely, with fewer slip systems, less plastic deformation can occur, and the metal will be more brittle. For example, HCP (hexagonal close packed) metals have few active slip systems, and are typically brittle.
Ceramics
Ceramics are generally brittle due to the difficulty of dislocation motion, or slip. There are few slip systems in crystalline ceramics that a dislocation is able to move along, which makes deformation difficult and makes the ceramic more brittle.
Ceramic materials generally exhibit ionic bonding. Because of the ions’ electric charge and their repulsion of like-charged ions, slip is further restricted.
Changing brittle materials
Materials can be changed to become more brittle or less brittle.
Toughening
When a material has reached the limit of its strength, it usually has the option of either deformation or fracture. A naturally malleable metal can be made stronger by impeding the mechanisms of plastic deformation (reducing grain size, precipitation hardening, work hardening, etc.), but if this is taken to an extreme, fracture becomes the more likely outcome, and the material can become brittle. Improving material toughness is, therefore, a balancing act.
Naturally brittle materials, such as glass, are not difficult to toughen effectively. Most such techniques involve one of two mechanisms: to deflect or absorb the tip of a propagating crack or to create carefully controlled residual stresses so that cracks from certain predictable sources will be forced closed. The first principle is used in laminated glass where two sheets of glass are separated by an interlayer of polyvinyl butyral. The polyvinyl butyral, as a viscoelastic polymer, absorbs the growing crack. The second method is used in toughened glass and pre-stressed concrete. A demonstration of glass toughening is provided by Prince Rupert's Drop. Brittle polymers can be toughened by using metal particles to initiate crazes when a sample is stressed, a good example being high-impact polystyrene or HIPS. The least brittle structural ceramics are silicon carbide (mainly by virtue of its high strength) and transformation-toughened zirconia.
A different philosophy is used in composite materials, where brittle glass fibers, for example, are embedded in a ductile matrix such as polyester resin. When strained, cracks are formed at the glass–matrix interface, but so many are formed that much energy is absorbed and the material is thereby toughened. The same principle is used in creating metal matrix composites.
Effect of pressure
Generally, the brittle strength of a material can be increased by pressure. This happens as an example in the brittle–ductile transition zone at an approximate depth of in the Earth's crust, at which rock becomes less likely to fracture, and more likely to deform ductilely (see rheid).
Crack growth
Supersonic fracture is crack motion faster than the speed of sound in a brittle material. This phenomenon was first discovered by scientists from the Max Planck Institute for Metals Research in Stuttgart (Markus J. Buehler and Huajian Gao) and IBM Almaden Research Center in San Jose, California (Farid F. Abraham).
See also
Charpy impact test
Ductility
Forensic engineering
Fractography
Izod impact strength test
Strengthening mechanisms of materials
Toughness
References
Continuum mechanics
Materials science
Physical properties | Brittleness | [
"Physics",
"Materials_science",
"Engineering"
] | 959 | [
"Physical phenomena",
"Applied and interdisciplinary physics",
"Continuum mechanics",
"Classical mechanics",
"Materials science",
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"Physical properties"
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978,916 | https://en.wikipedia.org/wiki/Customer%20service | Customer service is the assistance and advice provided by a company through phone, online chat, mail, and e-mail to those who buy or use its products or services. Each industry requires different levels of customer service, but towards the end, the idea of a well-performed service is that of increasing revenues. The perception of success of the customer service interactions is dependent on employees "who can adjust themselves to the personality of the customer". Customer service is often practiced in a way that reflects the strategies and values of a firm. Good quality customer service is usually measured through customer retention.
Customer service for some firms is part of the firm’s intangible assets and can differentiate it from others in the industry. One good customer service experience can change the entire perception a customer holds towards the organization. It is expected that AI-based chatbots will significantly impact customer service and call centre roles and will increase productivity substantially. Many organisations have already adopted AI chatbots to improve their customer service experience.
The evolution in the service industry has identified the needs of consumers. Companies usually create policies or standards to guide their personnel to follow their particular service package. A service package is a combination of tangible and intangible characteristics a firm uses to take care of its clients.
Customer support
Customer support is a range of consumer services to assist customers in making cost-effective and correct use of a product. It includes assistance in planning, installation, training, troubleshooting, maintenance, upgrading, and disposal of a product. These services may even be provided at the place in which the customer makes use of the product or service. In this case, it is called "at home customer service" or "at home customer support." Customer support is an effective strategy that ensures that the customer's needs have been attended to. Customer support helps ensure that the products and services that have been provided to the customer meet their expectations. Given an effective and efficient customer support experience, customers tend to be loyal to the organization, which creates a competitive advantage over its competitors. Organizations should ensure that any complaints from customers about customer support have been dealt with effectively.
Automation and productivity increase
Customer service may be provided in person (e.g. sales / service representative), or by automated means, such as kiosks, websites, and apps. An advantage of automation is that it can provide service 24 hours a day which can complement face-to-face customer service. There is also economic benefit to the firm. Through the evolution of technology, automated services become less expensive over time. This helps provide services to more customers for a fraction of the cost of employees' wages. Automation can facilitate customer service or replace it entirely.
A popular type of automated customer service is done through artificial intelligence (AI). The customer benefit of AI is the feel for chatting with a live agent through improved speech technologies while giving customers the self-service benefit. AI can learn through interaction to give a personalized service. The exchange the Internet of Things (IoT) facilitates within devices, lets us transfer data when we need it, where we need it. Each gadget catches the information it needs while it maintains communication with other devices. This is also done through advances in hardware and software technology. Another form of automated customer service is touch-tone phone, which usually involves IVR (Interactive Voice Response) a main menu and the use of a keypad as options (e.g. "Press 1 for English, Press 2 for Spanish").
In the Internet era, a challenge is to maintain and/or enhance the personal experience while making use of the efficiencies of online commerce. "Online customers are literally invisible to you (and you to them), so it's easy to shortchange them emotionally. But this lack of visual and tactile presence makes it even more crucial to create a sense of personal, human-to-human connection in the online arena."
Examples of customer service by artificial means are automated online assistants that can be seen as avatars on websites, which enterprises can use to reduce operating and training costs. These are driven by chatbots, and a major underlying technology to such systems is natural language processing.
Metrics
The two primary methods of gathering feedback are customer surveys and Net Promoter Score measurement, used for calculating the loyalty that exists between a provider and a consumer.
Instant feedback
Many outfits have implemented feedback loops that allow them to capture feedback at point of experience. For example, National Express in the UK has invited passengers to send text messages while riding the bus. This has been shown to be useful, as it allows companies to improve their customer service before the customer defects, thus making it far more likely that the customer will return next time.
See also
Automated attendant
Customer experience management
Customer relationship management
Customer satisfaction
Customer Service Assurance
Customer service representative
Customer service training
Demand chain
Interactive voice response
Live support software
Privacy policy
Professional services automation
Public Services
Sales
Sales process engineering
Sales territory
Service climate
Service system
Social skills
Support automation
Technical support
Help desk software
References
Further reading
Krishnan, C., Gupta, A., Gupta, A., Singh, G. (2022). Impact of Artificial Intelligence-Based Chatbots on Customer Engagement and Business Growth. In: Hong, TP., Serrano-Estrada, L., Saxena, A., Biswas, A. (eds) Deep Learning for Social Media Data Analytics. Studies in Big Data, vol 113. Springer, Cham.
Adam, M., Wessel, M. & Benlian, A. AI-based chatbots in customer service and their effects on user compliance. Electron Markets 31, 427–445 (2021).
Hardalov, M., Koychev, I., Nakov, P. (2018). Towards Automated Customer Support. In: Agre, G., van Genabith, J., Declerck, T. (eds) Artificial Intelligence: Methodology, Systems, and Applications. AIMSA 2018. Lecture Notes in Computer Science(), vol 11089. Springer, Cham.
Roberts, C. and Maier, T. (2024), "The evolution of service toward automated customer assistance: there is a difference", International Journal of Contemporary Hospitality Management, Vol. 36 No. 6, pp. 1914-1925.
Suendermann, D., Liscombe, J., Pieraccini, R., Evanini, K. (2010). “How am I Doing?”: A New Framework to Effectively Measure the Performance of Automated Customer Care Contact Centers. In: Neustein, A. (eds) Advances in Speech Recognition. Springer, Boston, MA.
Computer telephony integration
Services marketing
Interactive narrative
Email
Online chat
Telephony | Customer service | [
"Technology"
] | 1,374 | [
"Information technology",
"Computer telephony integration"
] |
978,951 | https://en.wikipedia.org/wiki/Record%20linkage | Record linkage (also known as data matching, data linkage, entity resolution, and many other terms) is the task of finding records in a data set that refer to the same entity across different data sources (e.g., data files, books, websites, and databases). Record linkage is necessary when joining different data sets based on entities that may or may not share a common identifier (e.g., database key, URI, National identification number), which may be due to differences in record shape, storage location, or curator style or preference. A data set that has undergone RL-oriented reconciliation may be referred to as being cross-linked.
Naming conventions
"Record linkage" is the term used by statisticians, epidemiologists, and historians, among others, to describe the process of joining records from one data source with another that describe the same entity. However, many other terms are used for this process. Unfortunately, this profusion of terminology has led to few cross-references between these research communities.
Computer scientists often refer to it as "data matching" or as the "object identity problem". Commercial mail and database applications refer to it as "merge/purge processing" or "list washing". Other names used to describe the same concept include: "coreference/entity/identity/name/record resolution", "entity disambiguation/linking", "fuzzy matching", "duplicate detection", "deduplication", "record matching", "(reference) reconciliation", "object identification", "data/information integration" and "conflation".
While they share similar names, record linkage and Linked Data are two separate approaches to processing and structuring data. Although both involve identifying matching entities across different data sets, record linkage standardly equates "entities" with human individuals; by contrast, Linked Data is based on the possibility of interlinking any web resource across data sets, using a correspondingly broader concept of identifier, namely a URI.
History
The initial idea of record linkage goes back to Halbert L. Dunn in his 1946 article titled "Record Linkage" published in the American Journal of Public Health.
Howard Borden Newcombe then laid the probabilistic foundations of modern record linkage theory in a 1959 article in Science. These were formalized in 1969 by Ivan Fellegi and Alan Sunter, in their pioneering work "A Theory For Record Linkage", where they proved that the probabilistic decision rule they described was optimal when the comparison attributes were conditionally independent. In their work they recognized the growing interest in applying advances in computing and automation to large collections of administrative data, and the Fellegi-Sunter theory remains the mathematical foundation for many record linkage applications.
Since the late 1990s, various machine learning techniques have been developed that can, under favorable conditions, be used to estimate the conditional probabilities required by the Fellegi-Sunter theory. Several researchers have reported that the conditional independence assumption of the Fellegi-Sunter algorithm is often violated in practice; however, published efforts to explicitly model the conditional dependencies among the comparison attributes have not resulted in an improvement in record linkage quality. On the other hand, machine learning or neural network algorithms that do not rely on these assumptions often provide far higher accuracy, when sufficient labeled training data is available.
Record linkage can be done entirely without the aid of a computer, but the primary reasons computers are often used to complete record linkages are to reduce or eliminate manual review and to make results more easily reproducible. Computer matching has the advantages of allowing central supervision of processing, better quality control, speed, consistency, and better reproducibility of results.
Methods
Data preprocessing
Record linkage is highly sensitive to the quality of the data being linked, so all data sets under consideration (particularly their key identifier fields) should ideally undergo a data quality assessment prior to record linkage. Many key identifiers for the same entity can be presented quite differently between (and even within) data sets, which can greatly complicate record linkage unless understood ahead of time. For example, key identifiers for a man named William J. Smith might appear in three different data sets as so:
In this example, the different formatting styles lead to records that look different but in fact all refer to the same entity with the same logical identifier values. Most, if not all, record linkage strategies would result in more accurate linkage if these values were first normalized or standardized into a consistent format (e.g., all names are "Surname, Given name", and all dates are "YYYY/MM/DD"). Standardization can be accomplished through simple rule-based data transformations or more complex procedures such as lexicon-based tokenization and probabilistic hidden Markov models. Several of the packages listed in the Software Implementations section provide some of these features to simplify the process of data standardization.
Entity resolution
Entity resolution is an operational intelligence process, typically powered by an entity resolution engine or middleware, whereby organizations can connect disparate data sources with a view to understanding possible entity matches and non-obvious relationships across multiple data silos. It analyzes all of the information relating to individuals and/or entities from multiple sources of data, and then applies likelihood and probability scoring to determine which identities are a match and what, if any, non-obvious relationships exist between those identities.
Entity resolution engines are typically used to uncover risk, fraud, and conflicts of interest, but are also useful tools for use within customer data integration (CDI) and master data management (MDM) requirements. Typical uses for entity resolution engines include terrorist screening, insurance fraud detection, USA Patriot Act compliance, organized retail crime ring detection and applicant screening.
For example: Across different data silos – employee records, vendor data, watch lists, etc. – an organization may have several variations of an entity named ABC, which may or may not be the same individual. These entries may, in fact, appear as ABC1, ABC2, or ABC3 within those data sources. By comparing similarities between underlying attributes such as address, date of birth, or social security number, the user can eliminate some possible matches and confirm others as very likely matches.
Entity resolution engines then apply rules, based on common sense logic, to identify hidden relationships across the data. In the example above, perhaps ABC1 and ABC2 are not the same individual, but rather two distinct people who share common attributes such as address or phone number.
Data matching
While entity resolution solutions include data matching technology, many data matching offerings do not fit the definition of entity resolution. Here are four factors that distinguish entity resolution from data matching, according to John Talburt, director of the UALR Center for Advanced Research in Entity Resolution and Information Quality:
Works with both structured and unstructured records, and it entails the process of extracting references when the sources are unstructured or semi-structured
Uses elaborate business rules and concept models to deal with missing, conflicting, and corrupted information
Utilizes non-matching, asserted linking (associate) information in addition to direct matching
Uncovers non-obvious relationships and association networks (i.e. who's associated with whom)
In contrast to data quality products, more powerful identity resolution engines also include a rules engine and workflow process, which apply business intelligence to the resolved identities and their relationships. These advanced technologies make automated decisions and impact business processes in real time, limiting the need for human intervention.
Deterministic record linkage
The simplest kind of record linkage, called deterministic or rules-based record linkage, generates links based on the number of individual identifiers that match among the available data sets. Two records are said to match via a deterministic record linkage procedure if all or some identifiers (above a certain threshold) are identical. Deterministic record linkage is a good option when the entities in the data sets are identified by a common identifier, or when there are several representative identifiers (e.g., name, date of birth, and sex when identifying a person) whose quality of data is relatively high.
As an example, consider two standardized data sets, Set A and Set B, that contain different bits of information about patients in a hospital system. The two data sets identify patients using a variety of identifiers: Social Security Number (SSN), name, date of birth (DOB), sex, and ZIP code (ZIP). The records in two data sets (identified by the "#" column) are shown below:
The most simple deterministic record linkage strategy would be to pick a single identifier that is assumed to be uniquely identifying, say SSN, and declare that records sharing the same value identify the same person while records not sharing the same value identify different people. In this example, deterministic linkage based on SSN would create entities based on A1 and A2; A3 and B1; and A4. While A1, A2, and B2 appear to represent the same entity, B2 would not be included into the match because it is missing a value for SSN.
Handling exceptions such as missing identifiers involves the creation of additional record linkage rules. One such rule in the case of missing SSN might be to compare name, date of birth, sex, and ZIP code with other records in hopes of finding a match. In the above example, this rule would still not match A1/A2 with B2 because the names are still slightly different: standardization put the names into the proper (Surname, Given name) format but could not discern "Bill" as a nickname for "William". Running names through a phonetic algorithm such as Soundex, NYSIIS, or metaphone, can help to resolve these types of problems. However, they may still stumble over surname changes as the result of marriage or divorce, but then B2 would be matched only with A1 since the ZIP code in A2 is different. Thus, another rule would need to be created to determine whether differences in particular identifiers are acceptable (such as ZIP code) and which are not (such as date of birth).
As this example demonstrates, even a small decrease in data quality or small increase in the complexity of the data can result in a very large increase in the number of rules necessary to link records properly. Eventually, these linkage rules will become too numerous and interrelated to build without the aid of specialized software tools. In addition, linkage rules are often specific to the nature of the data sets they are designed to link together. One study was able to link the Social Security Death Master File with two hospital registries from the Midwestern United States using SSN, NYSIIS-encoded first name, birth month, and sex, but these rules may not work as well with data sets from other geographic regions or with data collected on younger populations. Thus, continuous maintenance testing of these rules is necessary to ensure they continue to function as expected as new data enter the system and need to be linked. New data that exhibit different characteristics than was initially expected could require a complete rebuilding of the record linkage rule set, which could be a very time-consuming and expensive endeavor.
Probabilistic record linkage
Probabilistic record linkage, sometimes called fuzzy matching (also probabilistic merging or fuzzy merging in the context of merging of databases), takes a different approach to the record linkage problem by taking into account a wider range of potential identifiers, computing weights for each identifier based on its estimated ability to correctly identify a match or a non-match, and using these weights to calculate the probability that two given records refer to the same entity. Record pairs with probabilities above a certain threshold are considered to be matches, while pairs with probabilities below another threshold are considered to be non-matches; pairs that fall between these two thresholds are considered to be "possible matches" and can be dealt with accordingly (e.g., human reviewed, linked, or not linked, depending on the requirements). Whereas deterministic record linkage requires a series of potentially complex rules to be programmed ahead of time, probabilistic record linkage methods can be "trained" to perform well with much less human intervention.
Many probabilistic record linkage algorithms assign match/non-match weights to identifiers by means of two probabilities called and . The probability is the probability that an identifier in two non-matching records will agree purely by chance. For example, the probability for birth month (where there are twelve values that are approximately uniformly distributed) is ; identifiers with values that are not uniformly distributed will have different probabilities for different values (possibly including missing values). The probability is the probability that an identifier in matching pairs will agree (or be sufficiently similar, such as strings with low Jaro-Winkler or Levenshtein distance). This value would be in the case of perfect data, but given that this is rarely (if ever) true, it can instead be estimated. This estimation may be done based on prior knowledge of the data sets, by manually identifying a large number of matching and non-matching pairs to "train" the probabilistic record linkage algorithm, or by iteratively running the algorithm to obtain closer estimations of the probability. If a value of were to be estimated for the probability, then the match/non-match weights for the birth month identifier would be:
The same calculations would be done for all other identifiers under consideration to find their match/non-match weights. Then, every identifier of one record would be compared with the corresponding identifier of another record to compute the total weight of the pair: the match weight is added to the running total whenever a pair of identifiers agree, while the non-match weight is added (i.e. the running total decreases) whenever the pair of identifiers disagrees. The resulting total weight is then compared to the aforementioned thresholds to determine whether the pair should be linked, non-linked, or set aside for special consideration (e.g. manual validation).
Blocking
Determining where to set the match/non-match thresholds is a balancing act between obtaining an acceptable sensitivity (or recall, the proportion of truly matching records that are linked by the algorithm) and positive predictive value (or precision, the proportion of records linked by the algorithm that truly do match). Various manual and automated methods are available to predict the best thresholds, and some record linkage software packages have built-in tools to help the user find the most acceptable values. Because this can be a very computationally demanding task, particularly for large data sets, a technique known as blocking is often used to improve efficiency. Blocking attempts to restrict comparisons to just those records for which one or more particularly discriminating identifiers agree, which has the effect of increasing the positive predictive value (precision) at the expense of sensitivity (recall). For example, blocking based on a phonetically coded surname and ZIP code would reduce the total number of comparisons required and would improve the chances that linked records would be correct (since two identifiers already agree), but would potentially miss records referring to the same person whose surname or ZIP code was different (due to marriage or relocation, for instance). Blocking based on birth month, a more stable identifier that would be expected to change only in the case of data error, would provide a more modest gain in positive predictive value and loss in sensitivity, but would create only twelve distinct groups which, for extremely large data sets, may not provide much net improvement in computation speed. Thus, robust record linkage systems often use multiple blocking passes to group data in various ways in order to come up with groups of records that should be compared to each other.
Machine learning
In recent years, a variety of machine learning techniques have been used in record linkage. It has been recognized that the classic Fellegi-Sunter algorithm for probabilistic record linkage outlined above is equivalent to the Naive Bayes algorithm in the field of machine learning, and suffers from the same assumption of the independence of its features (an assumption that is typically not true). Higher accuracy can often be achieved by using various other machine learning techniques, including a single-layer perceptron, random forest, and SVM. In conjunction with distributed technologies, accuracy and scale for record linkage can be improved further.
Human-machine hybrid record linkage
High quality record linkage often requires a human–machine hybrid system to safely manage uncertainty in the ever changing streams of chaotic big data. Recognizing that linkage errors propagate into the linked data and its analysis, interactive record linkage systems have been proposed. Interactive record linkage is defined as people iteratively fine tuning the results from the automated methods and managing the uncertainty and its propagation to subsequent analyses. The main objectives of interactive record linkage systems is to manually resolve uncertain linkages and validate the results until it is at acceptable levels for the given application. Variations of interactive record linkage that enhance privacy during the human interaction steps have also been proposed.
Privacy-preserving record linkage
Record linkage is increasingly required across databases held by different organisations, where the complementary data held by these organisations can, for example, help to identify patients that are susceptible to certain adverse drug reactions (linking hospital, doctor, pharmacy databases). In many such applications, however, the databases to be linked contain sensitive information about people which cannot be shared between the organisations.
Privacy-preserving record linkage (PPRL) methods have been developed with the aim to link databases without the need of sharing the original sensitive values between the organisations that participate in a linkage. In PPRL, generally the attribute values of records to be compared are encoded or encrypted in some form. A popular such encoding technique used are Bloom filter, which allows approximate similarities to be calculated between encoded values without the need for sharing the corresponding sensitive plain-text values. At the end of the PPRL process only limited information about the record pairs classified as matches is revealed to the organisations that participate in the linkage process. The techniques used in PPRL must guarantee that no participating organisation, nor any external adversary, can compromise the privacy of the entities that are represented by records in the databases being linked.
Mathematical model
In an application with two files, A and B, denote the rows (records) by in file A and in file B. Assign characteristics to each record. The set of records that represent identical entities is defined by
and the complement of set , namely set representing different entities is defined as
.
A vector, is defined, that contains the coded agreements and disagreements on each characteristic:
where is a subscript for the characteristics (sex, age, marital status, etc.) in the files. The conditional probabilities of observing a specific vector given , are defined as
and
respectively.
Applications
Master data management
Most Master data management (MDM) products use a record linkage process to identify records from different sources representing the same real-world entity. This linkage is used to create a "golden master record" containing the cleaned, reconciled data about the entity. The techniques used in MDM are the same as for record linkage generally. MDM expands this matching not only to create a "golden master record" but to infer relationships also. (i.e. a person has a same/similar surname and same/similar address, this might imply they share a household relationship).
Data warehousing and business intelligence
Record linkage plays a key role in data warehousing and business intelligence. Data warehouses serve to combine data from many different operational source systems into one logical data model, which can then be subsequently fed into a business intelligence system for reporting and analytics. Each operational source system may have its own method of identifying the same entities used in the logical data model, so record linkage between the different sources becomes necessary to ensure that the information about a particular entity in one source system can be seamlessly compared with information about the same entity from another source system. Data standardization and subsequent record linkage often occur in the "transform" portion of the extract, transform, load (ETL) process.
Historical research
Record linkage is important to social history research since most data sets, such as census records and parish registers were recorded long before the invention of National identification numbers. When old sources are digitized, linking of data sets is a prerequisite for longitudinal study. This process is often further complicated by lack of standard spelling of names, family names that change according to place of dwelling, changing of administrative boundaries, and problems of checking the data against other sources. Record linkage was among the most prominent themes in the History and computing field in the 1980s, but has since been subject to less attention in research.
Medical practice and research
Record linkage is an important tool in creating data required for examining the health of the public and of the health care system itself. It can be used to improve data holdings, data collection, quality assessment, and the dissemination of information. Data sources can be examined to eliminate duplicate records, to identify under-reporting and missing cases (e.g., census population counts), to create person-oriented health statistics, and to generate disease registries and health surveillance systems. Some cancer registries link various data sources (e.g., hospital admissions, pathology and clinical reports, and death registrations) to generate their registries. Record linkage is also used to create health indicators. For example, fetal and infant mortality is a general indicator of a country's socioeconomic development, public health, and maternal and child services. If infant death records are matched to birth records, it is possible to use birth variables, such as birth weight and gestational age, along with mortality data, such as cause of death, in analyzing the data. Linkages can help in follow-up studies of cohorts or other groups to determine factors such as vital status, residential status, or health outcomes. Tracing is often needed for follow-up of industrial cohorts, clinical trials, and longitudinal surveys to obtain the cause of death and/or cancer. An example of a successful and long-standing record linkage system allowing for population-based medical research is the Rochester Epidemiology Project based in Rochester, Minnesota.
Criticism of existing software implementations
The main reasons cited are:
Project costs: costs typically in the hundreds of thousands of dollars
Time: lack of enough time to deal with large-scale data cleansing software
Security: concerns over sharing information, giving an application access across systems, and effects on legacy systems
Scalability: Due to the absence of unique identifiers in records, record linkage is computationally expensive and difficult to scale.
Accuracy: Changing business data and capturing of all rules for linking is a tough and extensive exercise
See also
Capacity optimization
Content-addressable storage
Data deduplication
Delta encoding
Entity linking
Entity-attribute-value model
Identity resolution
Linked data
Named-entity recognition
Open data
Schema matching
Single-instance storage
Author Name Disambiguation
Notes and references
External links
Data Linkage Project at Penn State, USA
Stanford Entity Resolution Framework
Dedoop - Deduplication with Hadoop
Privacy Enhanced Interactive Record Linkage at Texas A&M University
An Overview Of Data Matching
Data management | Record linkage | [
"Technology"
] | 4,825 | [
"Data management",
"Data"
] |
978,997 | https://en.wikipedia.org/wiki/Gilead%20Sciences | Gilead Sciences, Inc. () is an American biopharmaceutical company headquartered in Foster City, California, that focuses on researching and developing antiviral drugs used in the treatment of HIV/AIDS, hepatitis B, hepatitis C, influenza, and COVID-19, including ledipasvir/sofosbuvir and sofosbuvir. Gilead is a member of the Nasdaq-100 and the S&P 100.
Gilead was founded in 1987 under the name Oligogen by Michael L. Riordan. The original name was a reference to oligonucleotides, small strands of DNA used to target genetic sequences. Gilead held its initial public offering in 1992, and successfully developed drugs like Tamiflu and Vistide that decade.
In the 2000s, Gilead received approval for drugs including Viread and Hepsera, among others. It began evolving from a biotechnology company into a pharmaceutical company, acquiring several subsidiaries, though it still relied heavily on contracting to manufacture its drugs.
The company continued its growth in the 2010s. However, it came under heavy scrutiny over its business practices, including extremely high pricing of drugs such as Sovaldi and Truvada in the United States relative to production cost and cost in the developing world.
History
Foundation
In June 1987, Gilead Sciences was originally founded under the name Oligogen by Michael L. Riordan, a medical doctor. Riordan graduated from Washington University in St. Louis, the Johns Hopkins School of Medicine, and the Harvard Business School. The idea for Gilead began as a research project at Menlo Ventures, where Michael was an associate. Three scientific advisers worked with Riordan to create the company: Peter Dervan of Caltech, Doug Melton of Harvard, and Harold M. Weintraub of the Fred Hutchinson Cancer Research Center, along with H. Dubose Montgomery, one of Menlo Ventures founders. Riordan served as CEO from the company's founding until 1996. Menlo Ventures subsequently made the first investment in Gilead of $2 million. Riordan also recruited scientific advisers, including Harold Varmus, a Nobel laureate who later became Director of the National Institutes of Health, and Jack Szostak, recipient of the Nobel Prize for Physiology or Medicine in 2009.
The company's primary therapeutic focus was in antiviral medicines, a field that piqued Riordan's interest after he contracted dengue fever. Riordan recruited Donald Rumsfeld to join the board of directors in 1988, followed by Benno C. Schmidt, Sr., Gordon Moore, and George P. Shultz. Riordan tried to recruit Warren Buffett as an investor and board member but was unsuccessful.
The company focused its early research on making small strands of DNA (oligomers, or more particularly, oligonucleotides) to target specific genetic code sequences – that is, antisense therapy, a form of gene therapy. According to Riordan, he had always wanted to use the name Gilead Sciences all along. Still, he used Oligogen as a temporary name because he needed to deal with a trademark clearance issue with a California nonprofit organization that was already using the word Gilead in its name. He had first heard of the Balm of Gilead when he read Lanford Wilson's play Balm in Gilead while in medical school, then learned that naturally occurring acetylsalicylic acid (aspirin) had been found in modern times in a willow tree species from that part of that world, and was therefore inspired to name his company Gilead. After founding Oligogen, he contacted the nonprofit about the naming issue and secured the right to use the Gilead Sciences name in exchange for a $1,000 donation.
By 1988, the company had moved its headquarters to Foster City's Vintage Park neighborhood, where it has been based ever since. The company began to develop small molecule antiviral therapeutics in 1991, when the company in-licensed a group of nucleotide compounds including tenofovir.
Riordan later recalled that Gilead's first decade as a startup was an extremely stressful experience for him, as a young venture capitalist serving for the first time as the founder, chairman, and chief executive officer of his own biotech company. The new company had no products and very little income, and narrowly escaped going out of business on several occasions: "It was touch and go for a long time". Finding a way for Gilead to make money was Riordan's top priority "every second of the day for eight years".
1990–1999: IPO
Gilead's antisense intellectual property portfolio was sold to Ionis Pharmaceuticals. Gilead debuted on the NASDAQ in January 1992. Its initial public offering raised $86.25 million in proceeds.
In June 1996, Gilead launched Vistide (cidofovir injection) for the treatment of cytomegalovirus (CMV) retinitis in patients with AIDS.
In January 1997, Donald Rumsfeld was appointed chairman, but left the board in January 2001 when he was appointed United States Secretary of Defense during George W. Bush's first term as president.
In March 1999, Gilead acquired NeXstar Pharmaceuticals of Boulder, Colorado. At the time, NeXstar's annual sales of $130 million was three times Gilead's sales; it sold AmBisome, an injectable fungal treatment, and DaunoXome, an oncology drug taken by HIV patients. That same year, Roche announced FDA approval of Tamiflu (oseltamivir) for the treatment of influenza. Tamiflu was originally discovered by Gilead and licensed to Roche for late-phase development and marketing.
One reason for entering into the Tamiflu licensing agreement was that with only 350 employees, Gilead still did not yet have the capability to sell its drugs directly to overseas buyers. To avoid having to license future drugs in order to access international markets, Gilead simply acquired the 480-employee NeXstar, which had already built its own sales force in Europe to market AmBisome there.
2000 to 2009
Viread (tenofovir) achieved first approval in 2001 for the treatment of HIV.
In 2002, Gilead changed its corporate strategy to focus exclusively on antivirals, and sold its cancer assets to OSI Pharmaceuticals for $200 million.
In December 2002, Gilead and Triangle Pharmaceuticals announced that Gilead would acquire Triangle for around $464 million; Triangle's lead drug was emtricitabine that was near FDA approval, and it had two other antivirals in its pipeline. The company also announced its first full year of profitability. Later that year, Hepsera (adefovir) was approved for the treatment of chronic hepatitis B, and Emtriva (emtricitabine) for the treatment of HIV.
During this era, Gilead completed its gradual evolution from a biotech startup into a pharmaceutical company. The San Francisco Chronicle noted that by 2003, the Gilead corporate campus in Foster City had expanded to "seven low-slung sand-colored buildings around a tiny lake on which ducks happily paddle." Like many startups, Gilead originally leased its space, but in 2004, the company paid $123 million to buy all its headquarters buildings from its landlords. However, even as Gilead developed its ability to distribute and sell its own drugs, it remained distinct from most pharmaceutical companies in terms of its strong reliance on subcontracting most of its manufacturing to contract manufacturing organizations.
In 2004, during the Avian flu pandemic scare, Gilead Sciences' revenue from Tamiflu almost quadrupled to $44.6m as more than 60 national governments stockpiled the antiviral drug, though the firm had made a loss in 2003 before concern about the flu started. As stocks soared, US Defense Secretary and Pentagon chief Donald Rumsfeld sold shares of the company, receiving more than $5 million in capital gains, while still maintaining up to $25m-worth of shares by the end of the year. Sales of Tamiflu almost quadrupled again in 2005, to $161.6m, during which time the share price tripled. A 2005 report showed that, in all, Rumsfeld owned shares worth up to $95.9m, from which he got an income of up to $13m.
In 2006, the company acquired Corus Pharma, Inc. for $365 million. The acquisition of Corus signaled Gilead's entry into the respiratory arena. Corus was developing aztreonam lysine for the treatment of patients with cystic fibrosis who are infected with Pseudomonas aeruginosa.
In July 2006, the U.S. Food and Drug Administration (FDA) approved Atripla, a once a day single tablet regimen for HIV, combining Sustiva (efavirenz), a Bristol-Myers Squibb product, and Truvada (emtricitabine and tenofovir disoproxil), a Gilead product.
Gilead purchased Raylo Chemicals, Inc. in November 2006, for a price of . Raylo Chemical, based in Edmonton, Alberta, was a wholly-owned subsidiary of Degussa AG, a German company. Raylo Chemical was a custom manufacturer of active pharmaceutical ingredients and advanced intermediates for the pharmaceutical and biopharmaceutical industries.
Later in the same year, Gilead acquired Myogen, Inc. for $2.5 billion (then its largest acquisition). With two drugs in development (ambrisentan and darusentan), and one marketed product (Flolan) for pulmonary diseases, the acquisition of Myogen has solidified Gilead's position in this therapeutic arena. Under an agreement with GlaxoSmithKline, Myogen marketed Flolan (epoprostenol sodium) in the United States for the treatment of primary pulmonary hypertension. Additionally, Myogen was developing (in Phase 3 studies) darusentan, also an endothelin receptor antagonist, for the potential treatment of resistant hypertension.
Gilead expanded its move into respiratory therapeutics in 2007 by entering into a licensing agreement with Parion for an epithelial sodium channel inhibitor for the treatment of pulmonary diseases, including cystic fibrosis, chronic obstructive pulmonary disease and bronchiectasis.
In 2009, the company acquired CV Therapeutics, Inc. for $1.4 billion, bringing Ranexa and Lexiscan into Gilead. Ranexa is a cardiovascular drug used to treat chest pain related to coronary artery disease, with both of these products and pipeline building out Gilead's cardiovascular franchise. Later that year, the company was named one of the Fastest Growing Companies by Fortune.
2010 to 2019
In 2010, the company acquired CGI Pharmaceuticals for $120 million, expanding Gilead's research expertise into kinase biology and chemistry. Later that year, the company acquired Arresto Biosciences, Inc. for $225 million, obtaining developmental-stage research for treating fibrotic diseases and cancer.
In February 2011, the company acquired Calistoga Pharmaceuticals for ($225 million plus milestone payments). The acquisition boosted Gilead's oncology and inflammation areas. Later that year, Gilead made its most important acquisition – and by then most expensive – with the purchase of Pharmasset, Inc. This transaction helped cement Gilead as the leader in treatment of the hepatitis C virus by giving it control of sofosbuvir (see below).
In October 2011, Gilead broke ground on a massive multi-year expansion of its 17-building headquarters campus in Foster City. By replacing eight one or two-story buildings with seven new structures ranging as tall as 10 stories, Gilead nearly doubled its headquarters real estate footprint from about 620,000 square feet to about 1.2 million square feet.
On July 16, 2012, the FDA approved Gilead's Truvada for prevention of HIV infection (it was already approved for treating HIV). The pill was a preventive measure (PrEP) for people at high risk of getting HIV through sexual activity.
In 2013, the company acquired YM Biosciences, Inc. for $510 million. The acquisition brings drug candidate CYT387, an orally-administered, once-daily, selective inhibitor of the Janus kinase (JAK) family, specifically JAK1 and JAK2, into Gilead's oncology pipeline. The JAK enzymes have been implicated in myeloproliferative diseases, inflammatory disorders, and certain cancers.
In 2015, the company made a trio of acquisitions:
It bought Phenex Pharmaceuticals for $470 million. Its Farnesoid X receptor (FXR) program used small-molecule FXR agonists in the treatment of liver diseases such as non-alcoholic steatohepatitis.
It bought EpiTherapeutics for $65 million. This acquisition gave Gilead first-in-class small molecule inhibitors of histone demethylases involved in regulating gene transcription in cancer.
It paid $425 million for a 15% equity stake in Galapagos NV, with additional payments for Gilead to license the experimental anti-inflammatory drug filgotinib, which may treat rheumatoid arthritis, ulcerative colitis, and Crohn's disease.
In 2016, the company acquired Nimbus Apollo, Inc. for $400 million, giving Gilead control of the compound NDI-010976 (an ACC inhibitor) and other preclinical ACC inhibitors for the treatment of non-alcoholic steatohepatitis and for the potential treatment of hepatocellular carcinoma. Also in 2016, the company was named the most generous company on the 2016 Fortune list of The Most Generous Companies of the Fortune 500. Charitable donations to HIV/AIDS and liver disease organizations totaled over 440 million in 2015.
In August 2017, the company announced it would acquire Kite Pharma for $11.9 billion, equating to $180 cash per share, a 29% premium over the closing price of the shares. The deal was Gilead's entry into the cell therapy market and added a chimeric antigen receptor T cell (CAR-T) therapy candidate to the company's portfolio. By 2022 this acquisition had led to two marketed products for lymphoma: Yescarta and Tecartus. In November, the company announced it will acquire Cell Design Labs for up to $567 million, after it indirectly acquired a stake of 12.2% via the Kite Pharma deal.
On May 9, 2019, the U.S. Department of Health and Human Services announced that Gilead Sciences will donate Truvada, the only drug approved to prevent infection with H.I.V., for free to 200,000 patients annually for 11 years. On December 3, 2019, HHS explained how the government would distribute the donated drugs. HHS Secretary Alex Azar explained that the U.S. government will pay Gilead $200 per bottle for 30 pills for costs associated with getting the drug from factories into the eventual hands of patients.
2020 onwards
In March 2020, the company announced it would acquire Forty Seven Inc. for $95.50 a share ($4.9 billion in total). On April 7, 2020, Gilead completed acquisition of Forty Seven, Inc. for "$95.50 per share, net to the seller in cash, without interest, or approximately $4.9 billion in the aggregate."
In June 2020, Bloomberg reported that AstraZeneca Plc had made a preliminary approach to Gilead for a potential merger, worth almost $240 billion. In the same month, the company announced it would acquire a 49.9% stake in privately held Pionyr Immunotherapeutics Inc for $275 million.
In September 2020, Gilead announced it had reached a deal to acquire Immunomedics for $21 billion ($88 per share), gaining control of the cancer treatment Trodelvy (Sacituzumab govitecan-hziy) – a first-in-class Trop-2 antibody-drug conjugate. In December, the business announced it would acquire German biotech, MYR GmbH, for €1.15 billion plus up to a further €300 million. MYR focuses on the treatment of chronic hepatitis delta virus.
On August 11, 2021, U.S. Senator Rand Paul disclosed that his wife Kelley Paul had purchased a stake in Gilead Sciences on February 26, 2020.
In November 2021, the company was added to the Dow Jones Sustainability World Index.
In January 2022, Gilead pulled its cancer drug Zydelig (idelalisib) from its accelerated approval in relapsed follicular B-cell non-Hodgkin lymphoma (FL) and relapsed small lymphocytic leukemia (SLL). In September, the company completed its acquisition of MiroBio for $405 million.
In February 2023, the business, through Kite Pharma completed its acquisition of Tmunity Therapeutics In May, the business announced it would acquire XinThera and its small molecule inhibitors.
In February 2024, the company acquired CymaBay Therapeutics, and in September, paid Genesis Therapeutics $35 million for AI-based drug discovery work.
Acquisition history
Gilead Sciences
NeXstar Pharmaceuticals (Acq 1999)
Triangle Pharmaceuticals (Acq 2003)
Myogen, Inc. (Acq 2006)
Corus Pharma, Inc (Acq 2006)
Raylo Chemicals (Acq 2006)
CV Therapeutics, Inc. (Acq 2009)
CGI Pharmaceuticals (Acq 2010)
Calistoga Pharmaceuticals (Acq 2011)
Pharmasset Inc (Acq 2011)
Phenex Pharmaceuticals (Acq 2015)
EpiTherapeutics (Acq 2015)
Galapagos NV (Acq 2015)
Nimbus Apollo, Inc. (Acq 2016)
Kite Pharma (Acq 2017)
Cell Design Labs (Acq 2017)
Tmunity Therapeutics (Acq 2023)
Forty Seven (Acq 2020)
Immunomedics (Acq 2020)
MYR GmbH (Acq 2020)
MiroBio (Acq 2022)
CymaBay Therapeutics (Acq 2024)
Treatments for hepatitis C
The drug sofosbuvir had been part of the 2011 acquisition of Pharmasset. In 2013, the FDA approved this drug, under the trade name Sovaldi, as a treatment for the hepatitis C virus. Forbes magazine ranked Gilead its number 4 drug company, citing a market capitalization of US$113 billion and stock appreciation of 100%, and describing their 2011 purchase of Pharmasset for $11 billion as "one of the best pharma acquisitions ever". Deutsche Bank estimated Sovaldi sales in the year's final quarter would be $53 million, and Barron's noted the FDA approval and subsequent strong sales of the "potentially revolutionary" drug as a positive indicator for the stock.
On July 11, 2014, the United States Senate Committee on Finance investigated Sovaldi's high price ($1,000 per pill; $84,000 for the full 12-week regimen). Senators questioned the extent to which the market was operating "efficiently and rationally", and committee chairman Ron Wyden (D-Oregon) and ranking minority member Chuck Grassley (R-Iowa) wrote to CEO John C. Martin asking Gilead to justify the price for this drug. The committee hearings did not result in new law, but in 2014 and 2015, due to negotiated and mandated discounts, Sovaldi was sold well below the list price. For poorer countries, Gilead licensed multiple companies to produce generic versions of Sovaldi; in India, a pill's price was as low as $4.29.
Gilead later combined Sovaldi with other antivirals in single-pill combinations. First, Sovaldi was combined with ledipasvir and marketed as Harvoni. This treatment for hepatitis C cures the patient in 94% to 99% of cases (HCV genotype 1). By 2017, Gilead was reporting drastic drops in Sovaldi revenue from year to year, not only because of pricing pressure but because the number of suitable patients decreased. Later single-pill combinations were Epclusa (with velpatasvir) and Vosevi (with velpatasvir and voxilaprevir).
Finances
For the fiscal year 2017, Gilead Sciences reported earnings of US$4.628 billion and annual revenue of US$26.107 billion, a decline of 14.1% over the previous fiscal cycle. Gilead Sciences's shares traded at over $70 per share, and its market capitalization was valued at US$93.4 billion in October 2018.
Prospects for the future
As of 2017, Gilead's challenge is to develop or acquire new blockbuster drugs before its current revenue-producers wane or their patent protection expires. Gilead benefited from the expansion of Medicaid in the ACA; Leerink analyst Geoffrey Porges wrote that Gilead's HIV drugs could face funding pressure under reform proposals. Gilead has $32 billion in cash, but $27.4 billion is outside the U.S. and is unavailable for acquisitions unless Gilead pays U.S. tax on it, though it could borrow against it. Gilead would benefit from proposals to let companies repatriate offshore capital with minimal further taxation.
Gilead's Entospletinib has shown a 90% complete response rate for MLL type acute myeloid leukaemia (AML).
Criticisms
TAF development delays
Several mass tort lawsuits have been filed against Gilead alleging that the company deliberately delayed development of antiretroviral drugs based on tenofovir alafenamide fumarate (TAF) in order to maximize profits from previous-generation medications containing tenofovir disoproxil fumarate (TDF). Plaintiffs allege that Gilead suspended TAF in 2004 despite clear evidence indicating that TAF-based medications were safer than TDF, a compound whose long-term use was associated with adverse side effects such as nephrotoxicity and bone density loss.
Gilead's first TAF medication, marketed under the trade name Genvoya, came out in 2015. Lawsuits allege that in the interim period, many HIV patients who continuously took Gilead's older TDF-based drugs suffered severe side effects, including nephrotoxicity.
Pricing
Sovaldi
Gilead came under intense criticism for its high pricing of its patented drug sofosbuvir (sold under the brand name Sovaldi), used to treat hepatitis C. In the US, for instance, it was launched at $1,000 per pill or $84,000 for the standard 84-day course, but it was drastically cheaper in the developing world; in India, it dropped as low as $4.29 per pill. While Sovaldi represented a significant improvement over contemporary treatments, the controversy surrounding its price ignited a national debate in the US, according to Reuters.
The United States Senate Committee on Finance launched an 18-month investigation of Gilead's Sovaldi pricing, and argued in its 2015 report that Gilead set prices high in disregard of the human cost and in order to set the stage for a higher eventual price for Sovaldi's successor, Harvoni. The committee's investigation, based in part on internal documents obtained from Gilead, revealed that the company had considered prices ranging from $50,000 to $115,000 per year, trying to strike a balance between revenue and predicted activist and public relations blowback, with little regard to research and development costs.
The high prices forced state Medicaid programs to ration treatment to patients, delaying treatment of less advanced hepatitis C cases. In Oregon, for example, 10,000 Medicaid patients were deemed good candidates for Sovaldi therapy, but the Oregon Health Authority estimated that treating half of these patients would more than double the state's total drug expenditures. The state thus opted to limit treatment to 500 patients per year.
Truvada and Descovy
Truvada was introduced to the market by Gilead in 2004 to treat HIV infections. In the following years, the United States government conducted research demonstrating that Truvada was able to prevent HIV infection. The US Centers for Disease Control holds the patent for this use of Truvada as pre-exposure prophylaxis (PreP).
Gilead introduced Truvada for PreP in 2012, at which point a prescription cost approximately $1,200 per month in the United States. By 2018, this price had increased to up to $2,000, despite generally costing less than $100 outside the U.S. Gilead made over $3 billion in sales of Truvada in 2018.
The high price drew the ire of activist groups such as ACT UP and was the subject of a Congressional hearing in May 2019. Gilead's CEO defended its pricing in the hearing by noting the large sums the company spends on HIV/AIDS research. Activists pressured the US government to enforce its patent on Truvada in order to combat the high prices set by Gilead.
In May 2019, Gilead announced it would donate enough Truvada to treat up to 200,000 patients annually for up to 11 years, the result of discussions with the Department of Health and Human Services under Trump. Dr. Rochelle Walensky noted that the donations still covered less than one-fifth of the people who need the drug, and argued it was possibly a move to help the company market Descovy, a more advanced successor drug. Walensky led a 2020 study that concluded the high costs of Descovy would on the whole negate any comparative advantage of prescribing it over a generic Truvada alternative.
In July 2021, Gilead announced it would decrease 340B Drug Pricing Program reimbursements to clinics serving primarily low-income communities; clinics argued this severely hinders their ability to provide HIV/AIDS prevention and treatment services among vulnerable populations.
Anticompetitive behavior
Gilead has also been accused of stifling competition. A lawsuit filed in the United States in 2019 alleged that the company entered "pay for delay" agreements with other manufacturers, wherein the manufacturers agreed to delay releasing generic versions of Truvada. In 2021, CVS Pharmacy and RiteAid filed a lawsuit on similar grounds against Gilead, Bristol-Myers Squibb, and Teva Pharmaceuticals in 2021.
In response to criticisms over the price of Sovaldi, Gilead began licensing the rights to produce generic versions of the drug to select producers in India in 2015. Included in the licensing agreements were 'anti-diversion' provisions, designed to prevent the drug from being exported back to developed countries where the cheaper, generic alternatives were still unavailable. (In India, a one-month treatment cost approximately US$300, versus $1,000 per pill in the United States.) Gilead required the Indian producers to screen patients to determine who could buy Sovaldi, which was criticized by Médecins Sans Frontières since it could lead to the exclusion of vulnerable groups like refugees and migrants from accessing the medicines. In response to the criticism, Gilead eventually relaxed these requirements.
Tax structures and tax avoidance
Gilead has been criticized for tax avoidance. Tax avoidance, as opposed to tax evasion, is the use of legal means to shift tax burdens from the one jurisdiction to overseas affiliates that pay a lower tax rate, even if revenue is primarily generated outside the overseas jurisdiction.
A 2016 report by the liberal think tank Americans for Tax Fairness argued that Gilead was able to avoid up to $10 billion in taxes on U.S. sales through mechanisms such as transfer pricing, the sale of assets between affiliated entities. In particular, Gilead sells intellectual property to an Irish subsidiary, which then sells the finished products, such as Sovaldi, in the United States and elsewhere, paying the low Irish tax rate on profits. The practice is common among multinational pharmaceutical companies like Gilead.
On December 26, 2018, The Times reported that Gilead had used the Double Irish arrangement to avoid U.S. corporate taxes on global profits, stating that the firm "used a controversial tax loophole arrangement to shift almost in profits through an Irish entity in just two years" without paying Irish taxes. The company repatriated a portion of the Irish subsidiary's holdings, $28 billion, to the United States in 2018 following reductions of the corporate tax rate. For this it paid an estimated $5.5 billion in tax.
Remdesivir
Gilead sought and obtained orphan drug designation for remdesivir from the US Food and Drug Administration (FDA) on March 23, 2020. This designation is intended to encourage the development of drugs affecting fewer than 200,000 Americans by granting strengthened and extended legal monopoly rights to the manufacturer, along with waivers on taxes and government fees.
Remdesivir became a candidate for treating COVID-19; at the time the status was granted, fewer than 200,000 Americans had COVID-19, but numbers were climbing rapidly as the COVID-19 pandemic reached the US, and crossing the threshold soon was considered inevitable. Gilead retains 20-year remdesivir patents in more than 70 countries.
In 2021, remdesivir (tradename Veklury) generated more than $4.5 billion in annual revenues, and was Gilead's highest selling product.
COVID-19
Emergency use authorization for remdesivir was granted in the U.S. on May 1, 2020, for people hospitalized with severe COVID-19. In September 2020 following a review of the evidence, the WHO issued guidance not to use remdesivir for people with COVID-19, as there was no good evidence of benefit. However, over 2020–22 with further clinical research, remdesivir had been approved for treatment of hospitalized people with COVID-19 in the United States, European Union, and multiple other countries. In 2022, the Canadian component of the WHO international Solidarity Trial reported that in-hospital people with COVID-19 treated with remdesivir had lower death rates (by about 4%) and reduced need for oxygen and mechanical ventilation compared to people receiving standard-of-care treatments.
Regulatory approval
Veklury received approval from the US Food and Drug Administration (FDA) in October 2020 use in hospitalized adults and children 12 years and older for treatment of severe COVID-19 infections. In January 2022, the FDA gave regulatory approval to Veklury for use in adults and children (12 years of age and older who weigh at least and are positive for COVID-19, not hospitalized, and are ill having high risk for developing severe COVID-19, including hospitalization or death.
The FDA also provided Emergency Use Authorization for Veklury treatment of children under age 12 who are COVID-positive and not hospitalized, but have mild-to-moderate COVID-19 with high risk of developing severe COVID-19, including hospitalization or death.
References
External links
American companies established in 1987
1987 establishments in California
1992 initial public offerings
Biopharmaceutical companies
Biotechnology companies established in 1987
Biotechnology companies of the United States
Companies based in Foster City, California
Life sciences industry
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Specialty drugs | Gilead Sciences | [
"Biology"
] | 6,582 | [
"Specialty drugs",
"Life sciences industry"
] |
979,149 | https://en.wikipedia.org/wiki/Address | An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along with other identifiers such as house or apartment numbers and organization name. Some addresses also contain special codes, such as a postal code, to make identification easier and aid in the routing of mail.
Addresses provide a means of physically locating a building. They are used in identifying buildings as the end points of a postal system and as parameters in statistics collection, especially in census-taking and the insurance industry. Address formats are different in different places, and unlike latitude and longitude coordinates, there is no simple mapping from an address to a location.
History
Until the 18th and 19th centuries, most houses and buildings were not numbered.
In London, one of the first recorded instances of a street being numbered was Prescot Street in Goodman’s Fields in 1708. Street naming and numbering began under the age of Enlightenment, also as part of campaigns for census and military conscription, such as in the dominions of Maria Theresa in the mid 18th century. Numbering allowed the efficient delivery of mail, as the postal system evolved in the 18th and 19th centuries to reach widespread usage.
In London, house numbering was not regulated until the Metropolitan Management Act of 1855, which granted the newly formed Board of Works the power to control street naming and numbering. Under pressure from the Post Office, the Board began simplifying addresses in 1857, tackling the most confusing streets and assigning district codes, like EC (Eastern Central) and WC (Western Central), which laid the foundation for the postcode system. Postcodes, as we know them, were only introduced in the 1960s-1970s. Despite some public resistance to changing street names and numbers, by 1871, over 4,800 street names had been altered, and 100,000 houses renumbered in London. Though house numbering took time to become widely accepted, it eventually became firmly established.
Comprehensive addressing of all buildings is still incomplete, even in developed countries. For example, the Navajo Nation in the United States was still assigning rural addresses as of 2015 and the lack of addresses can be used for voter disenfranchisement in the USA. In many cities in Asia, most minor streets were never named, and this is still the case today in much of Japan. Over a third of addresses in Ireland shared their address with at least one other property at the time of the Eircode's introduction in 2015.
Land registration systems, known as Cadastres, helped manage property ownership in Ancient Rome, especially as Rome expanded. The city was divided into 14 regions (regiones) by Emperor Augustus to streamline administration, which became the foundation for locating properties.
Current addressing schemes
House numbering or naming
In most English-speaking countries, the usual method of house numbering is an alternating numbering scheme progressing in each direction along a street, with odd numbers on one side (often west or south or the left-hand side leading away from a main road) and even numbers on the other side, although there is significant variation on this basic pattern. Many older towns and cities in the UK have "up and down" numbering where the numbers progress sequentially along one side of the road, and then sequentially back down the other side. Cities in North America, particularly those planned on a grid plan, often incorporate block numbers, quadrants (explained below), and cardinal directions into their street numbers, so that in many such cities, addresses roughly follow a Cartesian coordinate system. Some other cities around the world have their own schemes.
Although house numbering is the principal identification scheme in many parts of the world, it is also common for houses in the United Kingdom and Ireland to be identified by name, rather than number, especially in villages. In these cases, the street name will usually follow the house name. Such an address might read: "Smith Cottage, Frog Lane, Barchester, Barsetshire, BZ9 9BA" or "Dunroamin, Emo, Co. Laois, Ireland" (fictional examples).
Quadrants
In cities with Cartesian-coordinate-based addressing systems, the streets that form the north–south and east–west dividing lines constitute the x and y axes of a Cartesian coordinate plane and thus divide the city into quadrants. The quadrants are typically identified in the street names, although the manner of doing so varies from city to city. For example, in one city, all streets in the northeast quadrant may have "NE" prefixed or suffixed to their street names, while in another, the intersection of North Calvert Street and East 27th Street can be only in the northeast quadrant.
Street-naming conventions
Street names may follow a variety of themes. In many North American cities, such as San Francisco, USA, and Edmonton, Alberta and Vancouver, British Columbia, streets are simply numbered sequentially across the street grid. Numbered streets originated in the United States in Philadelphia by Thomas Holme who laid out the original plan for the city in 1683. Washington, D.C. has its numbered streets running north–south and lettered or alphabetically named streets running east–west, while diagonal avenues are typically named after states. In Salt Lake City, and many other Utah cities, streets are in a large grid and are numbered in increments of 100 based on their location relative to the center of the city in blocks. A similar system is in use in Detroit with the Mile Road System. In some housing developments in North America and elsewhere, street names may all follow the same theme (for example, bird species), or start with the same letter. Streets in Continental Europe, the Middle East, and Latin America are often named after famous people or significant dates.
Postal codes
Postal codes are a relatively recent development in addressing, designed to speed the sorting and processing of mail by assigning unique numeric or alphanumeric codes to each geographical locality.
Postal alternatives to physical addresses
For privacy and other purposes, postal services have made it possible to receive mail without revealing one's physical address or even having a fixed physical address. Examples are post office boxes, service addresses and poste restante (general delivery).
Address format
In most of the world, addresses are written in order from most specific to general, i.e. finest to coarsest information, starting with the addressee and ending with the largest geographical unit. For example:
In English-speaking countries, the postal code usually comes last. In much of Europe, the code precedes the town name, thus: "1010 Lausanne". Sometimes, the ISO 3166 country code is placed in front of the postal code: "CH-1010 Lausanne".
If a house number is provided, it is written on the same line as the street name; a house name is written on the previous line. When addresses are written inline, line breaks are replaced by commas. Conventions on the placing of house numbers differ: either before or after the street name. Similarly, there are differences in the placement of postal codes: in the UK, they are written on a separate line at the end of the address; in Australia, Canada and the United States, they usually appear immediately after the state or province, on the same line; in Austria, Belgium, France, Germany and The Netherlands they appear before the city, on the same line.
East Asian addressing systems, including Chinese, Japanese, Korean, and Taiwanese addressing systems, when written in their native scripts, use the big-endian order, from the largest geographical area to the smallest geographical area, followed by the recipient's name. However, both have the same order as western countries when written in the Latin script. The Hungarian system also goes from large to small units, except that the name of the addressee is put into the first line.
The Universal Postal Convention strongly recommends the following:
"The addressee's address shall be worded in a precise and complete manner. It shall be written very legibly in roman letters and Arabic numerals. If other letters and numerals are used in the country of destination, it shall be recommended that the address be given also in these letters and numerals. The name of the place of destination and the name of the country of destination shall be written in capital letters together with the correct postcode number or delivery zone number or post office box number, if any. The name of the country of destination shall be written preferably in the language of the country of origin. To avoid any difficulty in the countries of transit, it is desirable for the name of the country of destination to be added in an internationally known language. Designated operators may recommend that, on items addressed to countries where the recommended position of the postcode is in front of the name of the location of destination, the postcode should be preceded by the EN ISO 3166-1 alpha-2 country code followed by a hyphen. This shall in no way detract from the requirement for the name of the destination country to be printed in full."
Format by country and area
Argentina
In Argentina, an address must be mailed this way:
The postal code has been changed from a four digit format to an eight digit format, which is shown in the example. The new format adds a district or province letter code at the beginning, which allows it to be identified. As the system has been changed recently, the four digit format can still be used: in that case it is necessary to add the name of the province or district.
Australia
In common with the rest of the English-speaking world, addresses in Australia put the street number—which may be a range—before the street name, and the placename before the postcode. Unlike addresses in most other comparable places, the city is not included in the address, but rather a much more fine-grained locality is used, usually referred to in Australia as a suburb or locality – although these words are understood in a different way than in other countries. Because the suburb or town serves to locate the street or delivery type, the postcode serves only as routing information rather than to distinguish previous other parts of an address. As an example, there are around 8,000 localities in Victoria (cf. List of localities in Victoria and List of Melbourne suburbs), yet around 700 unique geographic postcodes. For certain large volume receivers or post offices, the "locality" may be an institution or street name. It is always considered incorrect to include the city or metropolis name in an address (unless this happens to be the name of the suburb), and doing so may delay delivery.
Australia Post recommends that the last line of the address should be set in capital letters. In Australia, subunits are essential and should be separated from the street by two spaces; apartments, flats and units are typically separated with a forward slash (/) instead.
Apartment, flat and unit numbers, if necessary, are shown immediately prior to the street number (which might be a range), and, as noted above, are separated from the street number by a forward slash. These conventions can cause confusion. To clarify, 3/17 Adam Street would mean Apartment 3 (before the slash) at 17 Adam Street (in the case of a residential address) or Unit 3 at 17 Adam St (in the case of a business park). On the other hand, 3–17 Adam Street would specify a large building (or cluster of related buildings) occupying the lots spanning street numbers 3 to 17 on one side of Adam St (without specifying any particular place within the buildings). These forms can be combined, so 3/5–9 Eve Street signifies Apartment 3 (before the slash) in a building which spans street numbers 5 to 9 on one side of Eve Street.
As in the US, the state/territory is crucial information as many placenames are reused in different states/territories; it is usually separated from the suburb with two spaces and abbreviated. In printed matter, the postcode follows after two spaces; in handwritten matter, the postcode should be written in the boxes provided.
In addition to PO Boxes, other delivery types (which are typically abbreviated) may include:
Australian Post Addressing Guidelines
In rural areas, "Property numbers are worked out based on the distance from the start of the road to the entrance of the property. That distance (in metres) is divided by ten. Even numbers are on the right and odd numbers are on the left. For example: the entrance to a property 5,080 metres from the start of the road on the right hand side becomes number 508. The start of the road is determined as the fastest and safest road accessed from the nearest major road or town. Rural road maps are being drawn up to define the name, the start point and direction of every rural road."
Austria
In Austria, the address is generally formatted as follows:
The postal code always consists of four digits.
Bangladesh
In Bangladesh, the format used for rural and urban addresses is different.
Urban Addresses
The postal code always consists of four digits.
Rural Addresses
Belarus
In Belarus, some neighbourhoods may be planned in such a way that some, or most, apartment buildings don't face a named street. In this case, a number of expedients can be used. In older neighbourhoods, a "main" building may have the same number as one or more "subsidiary" buildings accessible via driveways behind the main building. They will be addressed as vul. Lenina, d. 123 (123 Lenin St) An address may also cover one or more subsidiary buildings behind the main building, addressed as vul. Lenina, d. 123, bud. 2 (123 Lenin St, unit 2, where bud. (abbreviation for ) means a '(subsidiary) building'). In newer areas with more regular street plans, apartment buildings that do not face a named street may be designated with Cyrillic letters appended to the building number, e.g. 123-а, 123-б, etc., in Cyrillic alphabetical order.
In some microraion neighbourhoods, with few, if any, buildings facing named streets, the name (or more likely number of the microraion (planned housing development)) would be used instead of the street name; thus someone may live at 4-th microrayon, d. 123, kv. 56, i.e. 123 – 4th Microraion, apt. 56.
Source: Belposhta
Belgium
In Belgium, the address starts with the most specific information (addressee individual identification) and ends with the most general information (postcode and town for domestic mail or country for cross border mail.)
Spatial information of a physical address (including building, wing, stairwell, floor and door) may be useful for internal path of delivery, but is not allowed in the delivery point location line (i.e. the line containing street, number and box number). If needed, this information will appear on a line above the delivery point location line.
The street number is placed after the thoroughfare name (unlike in France), separated by a space. Separators such as punctuation (point, comma or other signs) or "nº", or "nr" are not allowed. Extension designation (box numbers), if present, appears in the delivery point location line, preceded by the word for "box" ( in Dutch, in French). Symbols such as b, Bt, #, -, / are not allowed as separators between the street number element and the box number element.
Examples of a correctly formatted postal address:
The Belgian addressing guidelines are registered with the Universal Postal Union (UPU and see the link Universal Postal Union – Postal addressing systems in member countries). These guidelines indicate exactly how to combine the various address components in order to obtain a correctly formatted postal address.
The complete set of addressing guidelines can be found on the website of the Belgian postal operator (bpost). The correct representation of an address is not limited to the correct structure of address components but also relates to the content of addresses and their position on envelopes (see bpost – Lettres & cartes – Envoi – Comment addresser ? (in French)).
It is also possible to validate a Belgian postal address on bpost's website and to receive feedback on the content and the format of an address.
Brazil
In Brazil, an address must be written this way:
States can have their name written in full, abbreviated in some way, or totally abbreviated to two letters (SP = São Paulo, RJ = Rio de Janeiro, etc.).
Only towns with 60,000 inhabitants and above have postal codes individualized for streets, roads, avenues, etc. One street can have several postal codes (by odd/even numbers side or by segment). These postcodes range from -000 to -899. Other towns have only a generic postcode with the suffix -000. Recipients of bulk mail (large companies, condos, etc.) have specific postcodes, with a suffix ranging from -900 to -959. P.O. boxes are mailed to offices, with suffixes ranging from -970 to -979. Some rural settlements have community postboxes with suffix -990.
Bulgaria
Similar to Belgium and most other European countries, in Bulgaria the address starts with the most specific information (addressee individual identification) and ends with the most general information (town and postcode for domestic mail or country for cross border (international) mail.)
Spatial information of a physical address (including building, wing, stairwell, floor and door) may be useful for internal path of delivery, but is not allowed in the delivery point location line (i.e. the line containing street, number and box number). If needed, this information will appear on a line above the delivery point location line.
The street number is placed after the thoroughfare name (unlike in France), separated by a space and the symbol 'No. '. Separators such as punctuation (point, comma or other signs) are allowed if needed. Extension designation (box numbers), if present, appears in the delivery point location line, preceded by the word for "box" (" {numeral}", " {numeral}", or " {numeral}"). Symbols such as #, -, / are not strictly disallowed as separators between the street number element and the box number element. Note that there may sometimes be a confusion between (, postal code (of the local post office)) and (, P.O. (post office box), the individual physical P.O. box of a specific address or a subscription-based physical P.O. box inside a post-office branch).
The convention is that the addressee's information is written on the bottom right portion of the letter. The sender's information is written either on the top left portion of the letter or on the top reverse side of the letter (except for parcel packages).
Domestic post letters, parcels and postal money transfers are written in Bulgarian Cyrillic while the international postal letters and parcels are written in the Latin script (usually in English due to its global usage) with Arabic numerals.
Apart delivering mail and parcel packages to individual addresses, the Bulgarian Posts also delivers to local post offices (which then notify the recipient that he/she has mail to collect from the post office; so-called (letters on demand/request)) or to a subscription mailbox within a local post office.
Examples of a correctly formatted postal address:
Format for mail exchange between private individuals ():
Format for mail and parcel exchange between business partners ():
Format for mail and parcel sending to an individual subscription mailbox within a local office of Bulgarian Posts ():
The Bulgarian postal addressing guidelines are registered with the Universal Postal Union (UPU and see the link Universal Postal Union – Postal addressing systems in member countries). These guidelines indicate exactly how to combine the various address components in order to obtain a correctly formatted postal address.
The complete set of addressing guidelines can be found on the website of the Bulgarian postal operator (Bulgarian Posts). The correct representation of an address is not limited to the correct structure of address components but also relates to the content of addresses and their position on envelopes (see Български пощи (Български пощи) (in Bulgarian)).
It is also possible to validate a Bulgarian postal address on Bulgarian Posts' website and to receive feedback on the content and the format of an address. More information can be found at (see Български пощи (in Bulgarian)).
Canada
Addressing guidelines can differ between English- and French-speaking populations in Canada. Here are some formatting rules that are used in common:
Cardinal directions like North, North West, etc. can be abbreviated in either English or French, and appear after the street name. Ordinal numbered streets (e.g. 6th, 2nd) can be written in either English or French.
If there is an apartment number it should be written before the house number and separated by a hyphen.
Name of city or town followed by two letter provincial abbreviations
Postal codes come in a letter-number-letter-space-number-letter-number format, for example: A1A 1A1. There should be two spaces between the province abbreviation and the postal code.
If sending a parcel from outside Canada, the word "CANADA" must be placed at the very bottom.
See the example below for a comparison of the English and French address formats:
English (from Canada Post):
NICOLE MARTIN
123 SHERBROOKE ST
TORONTO ON L3R 9P6
French (from the OQLF):
Monsieur Jean-Pierre Lamarre
101–3485, rue de la Montagne
Montréal (Québec) H3G 2A6
See Canada Post's Addressing Guidelines for accurate, up-to-date information on the addressing guidelines most commonly used in Canada.
See the Office québécois de la langue française's Adressage webpage (in French only) for more information about how to write an address according to guidelines used in Quebec and other French-speaking areas.
Chile
Chilean urban addresses require only the street name, house number, apartment number (if necessary) and municipality; however, more information is frequently included, such as commune (neighbourhood or town) and region. Postal codes are rarely included by people. All postal codes have seven digits, the first three indicating the municipality, the next four identifying a block or in large and scarcely populated areas a quadrant within the municipal territory.
The territories of most of the larger cities comprise several adjacent municipalities, so it is important to mention it.
Smaller cities often consist of only one municipality with several unofficial comunes (neighborhoods) that are usually mentioned even for official addressing purposes.
Several large and mostly rural municipalities contain more than one small town, in such cases, the recipient address must mention either the town, the postal code or both.
In other towns or rural communities there are no house numbers and addresses are generally identified by company name followed by only a street name follow by some reference point.
China
In mainland China, the postal area when written in Chinese characters (preferably Simplified Chinese characters), has the big-endian order, which means that the Chinese-language address is written from the largest geographical area to the smallest geographical area. The Chinese-language address format is:
Province, prefecture-level city, district or county (sometimes omitted), township or town or subdistrict (often omitted), village or community (usually omitted), road name, road number, building name, floor/level, room number
However, as a member of the Universal Postal Union (UPU), China Post also supports UPU's English-language address in the little-endian order, which means that English-language address is written from the smallest geographical area to the largest geographical area. The English-language address format is:
Room number, floor/level, building nameroad number, road name, village or community (usually omitted), township or town or subdistrict (often omitted)district or county (sometimes omitted), prefecture-level citypostcode and provincecountry name
Chinese domestic letters only support Chinese-language address in the big-endian order. The example is:
The international letters to China support English-language address in the little-endian order. The example is:
Colombia
In Colombia the address format uses a numeric format based on which increase the number from south to north and which increase the number from east to west.
Croatia
Croatian Post recommends the following format:
Croatia uses five-digit postal code numbers. The Croatian postal service recommends using 2-letter ISO country codes as prefixes before international and domestic postal codes, though the practice is not mandatory.
Czech Republic
Common format in the Czech Republic:
Postal codes are in the format "### ##" (i.e. 158 00 = Prague 58) or "CZ-#####" (especially for international mail). On pre-printed Czech postcards and envelopes, the postal code is written on a separate last row in boxes for each number. If the envelope doesn't have pre-printed rows and boxes, the postal code should be before the town (or post office) name.
On private letters, the first line is usually constituted by a courtesy title (...) For private mails addressed to the workplace, the order is (name + company), while in official mails it is (company + name).
The basic system of house numbering uses conscription house numbers (). For a temporary or recreational house, an evidentional house number ( or , or distinguished by initial 0 or E prefix) is used instead. In most larger cities and also in some towns and large villages with street names, there is a double system of house numbering. The first number is the conscription or evidentional number (which corresponds to the chronological order of cadastral registration of the house), and the second number (after a slash) is the orientational number () which expresses the position in the street. Sometimes only one of the two numbers is used, or the numbers are used in reverse order, and it can be difficult to distinguish which number is which. Generally, orientation numbers (if they exist) are preferred for mail services.
How to correctly address mail
Denmark
In Denmark, apartment buildings will usually have two or three apartments per floor. Thus, if the addressee lives in an apartment, the address should contain the floor they live on, and a side ( or , meaning "to the left", "in the middle" and "to the right", respectively) or an alphanumeric character (1, 2, 3... or A, B, C...= starting from left seen from the top most step just before the floor).
Also, for postal codes 2000 and up, there is a 1:1 relationship between postal code and town.
Estonia
In Estonia, use the following format.
Finland
In Finland, if a person's name is written before the company name in the address field of a letter, then that person is considered the recipient. In this case, no other employee is allowed to open the letter but the indicated recipient. If the company name is before the person's name, then the company is the recipient and any employee is allowed to open the letter.
The apartment number can formatted as "" ( is an abbreviation for , apartment) or as "" (the letter indicates the correct staircase in apartment blocks with several entrances.)
Finland uses a five-digit postal code. Note that some larger companies and organizations have their own postal codes.
France
In France, the address is generally formatted as follows:
The postal code always consists of five digits. The is usually a town, but may be other territorial entities (up to a )
Organisations, government agencies, and companies which receive large amounts of mail often have a special CEDEX address which goes after the last line (for instance, "75001 PARIS CEDEX").
Germany
In Germany, the address is generally formatted as follows:
The postal code always consists of five digits.
Organizations that receive large amounts of mail may be assigned a bulk customer postal code. These are different from regular postal codes in that they do not have a street name line. Some bulk customer postal codes are shared between several organizations.
There are a few places that have house numbers but no street names (e.g. Baltrum) as well as addresses that have a street name but no house number.
Some (but not all) private post companies are also able to deliver to Deutsche Post-operated P.O. boxes.
Post codes follow the structure of DPAG's mail routing, not administrative boundaries.
Each post code is used exclusively for street addresses, P.O. boxes or bulk recipients.
Sub-building information, such as apartment numbers, is rarely used—a name on the post box is usually the only method of identification of an addressee within a building.
Greece
Hellenic Post recommends the following format for Greek addresses:
The most widespread format, shown above, gives on the last line the recipient's five-digit post code (with a single space between the third and fourth digits) and the name of the town or village that is the base of a post office, in capital letters and separated from the postcode by two spaces. When sending mail abroad, or when sending mail from abroad to Greece, Hellenic Post recommends the following format:
As with domestic mail, mail sent from abroad must contain the postcode in the same manner, but the postcode must be preceded by the international prefix of the country of delivery (for Greece, GR). Below the destination, the country of delivery must be written in capital letters, either in English or French (for Greece, or GREECE).
Hong Kong
The official languages of Hong Kong are Chinese and English. For domestic mail within Hong Kong, the address may be written entirely in either Chinese or English. For overseas mail going out from Hong Kong, the address may be written in the language of the destination country, provided that the city name and the country name are in English. However, for an overseas mail from Hong Kong to mainland China, Macao, Taiwan or Singapore, the address may be written entirely in Chinese. While traditional Chinese characters are commonly used in Hong Kong, simplified Chinese characters are also understood by Hong Kong's postmen. Note that Hong Kong does not use any postal codes, though many rural properties have a property identification code, e.g. HKT-12345.
An address written in English should begin with the smallest unit and end with the largest unit, as in the following example for a domestic mail within Hong Kong.
An address written in Chinese should begin with the largest unit and end with the smallest unit, as in the following example for a piece of domestic mail within Hong Kong. Traditional Chinese characters are used in this example.
For mail to Hong Kong from overseas, "Hong Kong" should be added at the end of an address written in English, and should be added at the beginning of an address written in Chinese.
Hungary
In Hungarian mail addresses, the city/town name precedes the street address. The post code then comes after the street address.
Hungarian family names precede given names in Hungarian. In this example, is the family name.
Sometimes a district number might appear after the name of the city/town.
Various abbreviations might appear in the precise street/building address: for instance, specifying the street type (, etc.), or for (floor), or for (which means Land Registry number, or lot number), or for (ground floor) and so on.
The postal code consists of four digits.
Iceland
In Iceland, the following format is used.
India
In India, multiple formats are used.
General Address
The format used for rural and urban addresses is different.
Rural Addresses
Urban Addresses
The state is optional in both cases, but is typically used.
Indonesia
In Indonesia, the address format is as follows:
Generally or means 'street' and should be written before the street name, e.g. . For more about Indonesian administrative divisions, see administrative divisions of Indonesia.
Iran
Postal addresses in Iran have a standard which should be used by mail or parcel senders. This standard is registered and qualified by the Universal Postal Union (UPU). According to the below table, Iran has 4 types of standard address:
Iraq
In Iraq, the following format is used:
Ireland
In July 2015, the Republic of Ireland introduced Eircodes, a seven digit alphanumeric code, consisting of a 3 character routing key and a 4 character unique identifier for the property. Example A65 F4E2. Up until the introduction of Eircodes Dublin was the only county with a form of postal district identifier; these have been incorporated into the Eircode scheme. For example, Dublin 2 is routing code D02.
Rural addresses are specified by the county, nearest post town, and the townland. Urban addresses are specified by county, city or town name, street name, house number, and apartment or flat number where relevant. A house name may be used instead of a number. The Eircode is appended to the bottom of the address.
Israel
In Israel, the Universal Postal Union recommends the following:
In apartment buildings the building number should appear first and then the apartment number separated by a "/". In the below example, "16" is the building number while "20" is the apartment number:
Example of common address with building entrance and apartment number:
Or
A seven digit postal code for all addresses was introduced in 2013 which can cover an entire locality for a small town or village. In bigger cities postal areas are divided along streets and neighbourhoods.
Italy
A domestic address in Italy must be composed of three to five rows. Up to six rows can be used for international mail:
Line ordering may not be changed.
Japan
A Japanese postal address, when written in Japanese phonetic and Chinese characters, starts with the largest geographical division, continues with progressively smaller subdivisions before ending with the addressee, i.e. country, prefecture, town, , , building number, building name, floor number, company name, addressee. This is the most common addressing format used when mailing within Japan. It is common practice to add the appropriate honorific to the addressee's name, e.g. for a private individual or for a company or institution.
When written in the Latin alphabet, the address begins with the smallest geographical area and ends with the largest one as in the Anglicized example in the table. Macrons (as on ō and ū) may be omitted.
Japanese-style envelopes are vertically aligned and the address is written from top to bottom, then right to left. Western-style envelopes are horizontally aligned and the address is written from left to right, top to bottom.
Latvia
In Latvia, the address is generally formatted as follows:
Notes:
Each address element should be written on a separate line, starting with the more detailed element.
Including the addressee's name is not mandatory and the address can be considered complete without it.
In Latvian, the addressee's name should be provided in the dative case, i.e., . There are two generally accepted official salutation forms that can be used in front of the addressee's name: (with a man's name) or (with a man's or woman's name).
Indicate the full street name, house and flat number (if applicable). Separate house and flat number with a hyphen.
It is acceptable to abbreviate the parish (, abbreviation of ) and amalgamated municipality (, abbreviation of ).
The postal code consists of two capital letters (LV) and four digits separated with a hyphen.
For international mail the destination country must be indicated in block letters.
Further reference: Latvijas Pasts
Macao
The official languages of Macao are Cantonese and Portuguese. For domestic mail within Macau, the address may be written entirely in either Portuguese or Chinese. For overseas mail going out from Macau, the address may be written in the language of the destination country, provided that the city name and the country name are in English. However, for overseas mail from Macau to mainland China, Hong Kong, Taiwan or Singapore, the address may be written entirely in Chinese. While traditional Chinese characters are commonly used in Macau, simplified Chinese characters are also understood by Macau's postmen. Note that Macau does not use any postal codes.
An address written in Portuguese should begin with the street name and end with the area in Macau, as in the following example for domestic mail within Macau.
An address written in Chinese should begin with the largest unit and end with the smallest unit, as in the following example for a piece of domestic mail within Macau. Traditional Chinese characters are used in this example.
For mail to Macau from overseas, "Macau" should be added at the end of an address written in Portuguese, and "Macao" at the end of an address written in English; should be added at the beginning of an address written in Chinese.
Malaysia
Pos Malaysia recommends the following formats:
Notes:
The Country line MALAYSIA is always omitted when mailing from within Malaysia.
The State line is strictly optional, the mailing system will not be affected if the State line is omitted.
The Post office/Mail centre field is the name of the town/city which post office/mail centre jurisdiction covers the mailing address, and in several cases, may not be the actual town/city which the address is geographically located.
It is recommended to have the Post office/Mail centre written in block letters, e.g. KUALA LUMPUR.
The postcode is always in the 5-digit format and must correspond to the respective post office / mail centre.
Pos Malaysia allows usage of P.O. Box for both residential and business addresses. Whenever a P.O. Box address is used, its respective postcode and post office/mail centre must be written on the last line of an address. If both postcodes are present (original and P.O. Box), mail will be sent to the P.O. Box on its first attempt.
Mexico
In Mexico, Correos de México recommends the following formats:
Netherlands
In the Netherlands, the address is generally formatted as follows:
The postal code is a unique street identifier, and always consists of four numbers followed by a space and then two capital letters. PostNL, which is appointed by the Dutch government to carry out the UPD (Dutch for Universal Postal Service), recommends putting two spaces between postal code and town. Also, the name of the town should be written in capitals.
Because the Dutch postal code uniquely identifies a street, a shortened format may also be used. This method only needs the postal code and the number. The ideal format for this method is the number after the postal code, meaning that this: '5627 BX 1092' will still get the letter delivered to the correct location.
It is also possible to replace the street name line with a PO box (e.g. "postbus 1200") or freepost number (e.g. "antwoordnummer 150"), which have their own postal code.
New Zealand
In New Zealand, New Zealand Post recommends the following format:
Note that no space or full stops exists between P and O in PO Box or R and D in RD. One should put only one space between the town/city and the postcode.
Note for Wellington metropolitan area, users should use the city name (i.e. Wellington, Lower Hutt, Upper Hutt, Porirua), not the metropolitan area name. For example:
The city in this case is important, as if Wellington is used instead of Lower Hutt and the postcode is unclear (note only the first digit differs), someone's private mail could accidentally be sent to the New Zealand Parliament Buildings instead (or vice versa).
One anomaly about this system is the Wellington Mail Centre, which is addressed as Wellington Mail Centre, Lower Hutt 5045, due to its location in the Lower Hutt suburb of Petone.
Norway
Postal addresses in Norway are formatted as follows:
The first line, Recipient (Person or Entity), is the legal recipient of the item being sent. The Recipient's name must be marked on the Recipient's mail box in order for the item to be delivered.
Flat or floor number is not part of Norwegian postal addresses.
The postal code (always four digits) is mandatory. If a PO box is used (e.g. Postboks 250 Sentrum), it replaces Street name + Number. PO box addresses have postal codes which differ from those used for street addresses. Some areas do not have street names. For these areas, Street name + Number is replaced by a local designation determined by the Norwegian postal service.
Oman
In the Sultanate of Oman (2012), the address is formatted as follows:
Physical addresses only exist in major urban centers like those of Greater Muscat, Sohar, Salalah, Sur and Nizwa.
Pakistan
The format used in the Islamic Republic of Pakistan.
Official Addresses
Peru
In Peru, addresses in the Metropolitan Area of Lima and Callao are generally formatted as follows:
Addresses elsewhere in the country are formatted as follows:
Philippines
The Philippines follows Western conventions on addressing. Addresses in the Philippines either uses these formats.
Poland
In Poland, the address is generally formatted as follows:
ul. = Str (Street)
al. = Ave (Avenue)
pl. = Sq (Square, or Circus)
Some streets have names not containing the word "street". Then the full description is written with initial caps, e.g. "Zaułek Marii" (Court of Mary) or "Aleje Ujazdowskie" (plural for Ujazdowskie Ave.). If the first word of name is "Aleje" it may be abbreviated to "Al." (with initial capital).
The abbreviation "m." (meaning "mieszkanie" = "flat") can be used instead of "/" before the flat number.
Some large buildings occupy two or more cadastral plots. Sometimes to maintain consistency all numbers are included in address. The very well-known example is the address of Polish Radio Three: "ul. Myśliwiecka 3/5/7" (occupying three neighbouring plots). In examples like in above table the number "4/6" is ambiguous and not knowing the locality you cannot tell if "6" is the apartment number or the building is large.
When using a p.o. box the abbreviation "skr. poczt." may be used and "nr" (no.) may be omitted. Polish Post allows the box user to register an alias for their name. In such case it is written instead of the real name of the recipient. It is required to write the full name of post office including a number if it exists.
The postal code always consists of five digits separated with a hyphen (in the "XX-XXX" format), i.e. 00-486 (00 = Warsaw); 20-486 (20 = Lublin), etc. The first digit signifies the postal district, the second: the code zone, the third: the code sector, the fourth and fifth signify the post office and its area of operation. Usually the code is unique on the street level for cities and the town level for smaller towns and villages. Contrary to popular belief the name after postal code is a locality of addressee, not their post office. So if a small town has no street names you do write its name twice. The post office location (and a number if there are many) is written only on letters to p.o. box or poste restante.
There is a strong recommendation to use all caps in the line with postal code and city.
Portugal
Portuguese postal addresses is similar to continental European addresses:
Postal codes have the NNNN-NNN format. Street name and the number is traditionally separated by a comma, but nowadays CTT recommends just a blank space, or two blank spaces for extra clarity; this is to avoid OCR mistakes. The º after the number is the ordinal for floor number. Usually followed by "Esq." (Left, abbr from "Esquerdo") or "Dir." (Right, abbr from "Direito"), or an apartment letter (A, B, C, etc.). PO Boxes are called Apartado, followed by a number (e.g., Apartado 1001).
Qatar
In Qatar, Q-Post recommends the following format:
Not all of Qatar's roads and buildings are numbered, Q-Post doesn't deliver to any street addresses, and no postal codes are used in Qatar.
Romania
In Romania, the address is generally formatted as follows:
According to NACREP – National agency for cadastral and real estate publicity (in Romanian ANCPI – Agenția Națională de Cadastru și publicitate imobiliară) in Romania there are 29 street types such as:
Russia
In Russia, the address must be written in Cyrillic or Latin alphabet, in usual format (from most specific to general).
Example:
Note: sub-region and region/oblast names are void if the city is Moscow or Saint Petersburg or if it is sub-region administrative center.
Some neighbourhoods may be planned in such a way that some, or most, apartment buildings face no named street. In this case, a number of expedients can be used. In older neighbourhoods, such as the historical center of Moscow, a "main" building may have the same number as one or more "subsidiary" buildings accessible via driveways behind the main building. They will be addressed as, for example, ul. Lenina, d. 123 (that is, 123 Lenin St). An address may also cover one or more subsidiary buildings behind the main building, addressed as ul. Lenina, d. 123, str. 2 (123 Lenin St, Unit 2, where str. (abbreviation for строение, stroenie) means a 'subsidiary building'). In newer areas with more regular street plans, apartment buildings that face no named street may be designated with Cyrillic letters appended to the building number, such as 123-а, 123-б, etc., in alphabetic order.
In some microraion neighbourhoods, with few, if any, buildings facing named streets, the name (or more likely number of the microraion (planned housing development)) would be used instead of the street name; thus someone may live at 4-th microrayon, d. 123, kv. 56, that is, 123 – 4th Microraion, apt. 56.
Saudi Arabia
In Saudi Arabia, the address could be written in Arabic or English in the following format:
Serbia
Serbian postal addresses conform to rules similar to continental European rules:
In addition to 5-digit postal code, another line can be added containing PAK, a six-digit number which encodes the town, street and house number section.
Singapore
In Singapore, SingPost recommends the following format for addresses:
Generally, the last line SINGAPORE is omitted when posting within the country. Addresses are usually written in the English language.
Slovakia
Common format in Slovakia:
Postal codes are in the format "### ##" (i.e. 851 01 = Bratislava 5).
Street numbers can be written as orientation numbers (related to street) or descriptive numbers (unique within the town) or as a combination separated by a slash (descriptive/orientation). Descriptive numbers are also used within small villages that do not have named streets.
If the delivery is intended exclusively for a specific person at a company site, the address should begin with the individual's name and the company name should follow. The standard format of addresses enables anyone at the company to receive the delivery.
http://www.posta.sk/potrebujem/spravne-napisat-adresu ("How to write addresses correctly", in Slovak, with pictures)
Slovenia
Slovenia uses a four-digit postal number. The first digit indicates the area:
1xxx for Ljubljana
2xxx for Maribor
3xxx for Celje
4xxx for Kranj
5xxx for Nova Gorica
6xxx for Koper
7xxx not used
8xxx for Novo Mesto
9xxx for Murska Sobota
The simpler the code, the bigger the locality: 1000 Ljubljana, 2000 Maribor (big cities); 1310 Ribnica, 9250 Gornja Radgona (mid-sized towns); 4263 Bohinjska Bela, 8262 Krška vas (smaller settlements, including villages).
Some cities have more than one post office, thus having multiple postcodes (usually in the x1xx format). For example, Ljubljana which has a "general" postcode 1000, also has additional ones, ranging from 1101 to 1133 (for some reason, however, omitting 1103 and 1105), Kamnik has 1240 and 1241, etc. Albeit they exist, it is not necessary to use them – usually the "general" postcodes are used.
The abbreviations are: g. for gospod (Mr), ga. for gospa (Mrs), and gdč. for gospodična (Miss) – all always capitalized if in the beginning of the line.
Numbers can have a suffix like A, B, C, etc.
Common abbreviations are: c. for cesta (Street), and ul. for ulica (Road) – both always capitalised if in the beginning of the line.
Bigger towns have special postcodes for PO Boxes in the xxx1 format, e.g. 1001 Ljubljana, 4001 Kranj.
Big companies which receive large amounts of mail are designated their special postcodes in the x5xx format.
South Korea
South Korea uses a system similar to Western addressing, but previously used a system similar to Japanese addressing. South Korean addresses start with the largest unit (country, province), as with other East Asian countries.
Spain
In Spain, the addresses are generally formatted as follows:
5ºB means 5th floor (Spanish: quinto), door B. Also, there may be door number, printed as 1ª (primera-first). Suffixes "o" and "a" derives from Spanish words piso (floor) which is masculine and puerta (door) which is feminine.
Some doors may be indicated with the abbreviations Izq. or Dcha., to indicate either left (Izquierda) or right (Derecha). Streets and avenues can be indicated with the abbreviations C. (for calle) and Av. (for avenida).
Sri Lanka
Sri Lanka Post recommends the following format:
Sri Lanka uses a five-digit postal code. Generally, the last line SRI LANKA is omitted when posting within the country. Addresses are usually written in English and Sinhala.
Sweden
In Sweden, the address is generally formatted as follows:
The postal code is always a five-digit number divided into groups of three and two (e.g. SE-414 73) with the prefix SE (ISO-code for Sweden) used only if sent from abroad. It is also possible to replace the street name line with a PO box (e.g. Box 51).
Switzerland
In Switzerland, the address is generally formatted as follows:
The canton abbreviation (SO, VD in the examples) is needed only for cities/town that have the same name but in another canton for example: Renens and Renan which were both, in the past, called Renens, the difference stays today and Renens is often mentioned as Renens VD.
Taiwan
In Taiwan, addresses are regulated by the Department of Household Registration, while mails are handled by the Chunghwa Post. As a result, senders are required to write addresses in different formats in different situations.
Thailand
In Thailand, address are generally formatted as follows:
Turkey
Turkish addressing system is as follows:
Ukraine
Some neighbourhoods in Ukraine may be planned in such a way that some, or most, apartment buildings don't face a named street. In this case, a number of expedients can be used. In older neighbourhoods, a "main" building may have the same number as one or more "subsidiary" buildings accessible via driveways behind the main building. They will be addressed as vul. Bandery, d. 123 (123 Bandera St) An address may also cover one or more subsidiary buildings behind the main building, addressed as vul. Bandery, d. 123, bud. 2 (123 Bandera St, unit 2, where bud. (abbreviation for будинок, budynоk) means a '(subsidiary) building'). In newer areas with more regular street plans, apartment buildings that don't face a named street may be designated with Cyrillic letters appended to the building number, e.g. 123-а, 123-б, etc., in Cyrillic alphabetical order.
In some microraion neighbourhoods, with few, if any, buildings facing named streets, the name (or more likely number of the microraion (planned housing development)) would be used instead of the street name; thus someone may live at 4-th microrayon, bud. 123, kv. 56, i.e. 123 – 4th Microraion, apt. 56.
United Arab Emirates
In the United Arab Emirates, Emirates Post Group recommends the following format:
Not all of the roads and buildings in the UAE are numbered consistently and no postal codes are used in the United Arab Emirates. All mail by post are delivered only to PO boxes in the United Arab Emirates. If delivering to a street address it is customary to include recipient's telephone number should the delivery driver need to make a phone call to ascertain the address or let the recipient know that the package is already delivered.
United Kingdom
In the United Kingdom, the format specified by the postal operator Royal Mail is as follows:
The locality is required only where its absence would cause ambiguity, for example where a post town or postcode district includes two streets with the same name. Royal Mail specifies that post towns should be written in block capitals. Until 1996 a postal county (or permitted abbreviation) was required after the post town, unless it was a special post town, for example London. The post town and postcode should each be on a separate line. Historically, each line of an address ended with a comma and was indented from the previous line. Royal Mail discourage this usage and specify that all lines should start from the same point and not be staggered or aligned to the centre. The postcode identifies, from left to right, increasingly smaller units of the postal delivery system. The first half of the postcode, known as the outward code, contains the postcode area and postcode district. The second half, known as the inward code, contains the postcode sector and postcode unit.
United States
In the United States, addresses are generally formatted as follows:
The street address line can take a number of alternate formats:
"GENERAL DELIVERY" marks the item to be held for pickup from the post office (see )
Some street names are simply the names of highways, like "KY STATE HIGHWAY 625" (a Kentucky state highway), "INTERSTATE 55 BYP" (an auxiliary Interstate bypass), "FM 1200" (a "farm to market" road) or "LOOP 410".
In rural areas, mail is addressed according to the mail route rather than the physical street address. The street address line might be something like "RR 9 BOX 19-1A" (a "rural route", previously RFD or RD "rural delivery") "HC 68 BOX 23A" for "highway contract" routes (formerly "star routes") The physical street address may appear in the line above the "RR" line without hindering delivery. Since the nineties, the trend has been to replace rural-route addresses with conventional street addresses to aid 9-1-1 dispatchers. The new address is found using the USPS Locatable Address Conversion System.
In Hawaii and Southern California, some addresses have a hyphen in the street number, which should not be removed if matched to the ZIP+4 file. Almost all addresses in the New York City borough of Queens have hyphens, for example "123–45 QUEENS BLVD".
In Utah, some addresses are given in a grid style, where the "street name" consists of a cardinal direction, a number that is a multiple of 100, and an orthogonal cardinal direction. For example, "401 West 500 North" is on the grid in St. George, Utah, on the road West 500 North between its intersections with North 400 West and North 500 West.
In Wisconsin and northern Illinois, grid addresses are sometimes written as a sequence of numbers and directional letters, e.g. "N6W23001 BLUEMOUND RD".
In Puerto Rico, street addresses often include an urbanization or condominium name. The USPS allows for Spanish conventions on the island.
United States Virgin Islands street addresses sometimes include only an estate name or a street name with no number, and many street names do not have common suffixes like "Street" or "Road".
Notes:
Traditionally, only the United States Postal Service (USPS) has been permitted to deliver to a P.O. Box. For this reason the recipient may choose to insert their physical (aka street) address in the second line, expanding the complete address to four lines. Providing both allows a sender to ship via the USPS or via a private carrier. Some USPS facilities allow a user of a P.O. box to use the street address of the postal facility with the P.O. box number in the place of a suite number, in which case the user may receive packages from private carriers.
Mail will be delivered to the line immediately above the city, state, ZIP code line.
The state and type of street, e.g. Lane, is often abbreviated as shown in the PO standard.
The USPS discourages the use of all punctuation except the hyphen in ZIP+4 codes, slashes in fractional addresses (e.g. 123 1/2 Main Street), hyphenated street numbers, and periods in decimal addresses (e.g. the street name contains a decimal point). Hyphenated street numbers are common in the New York City borough of Queens, Hawaii, and Southern California; as well as the town of Fair Lawn, New Jersey; see house numbering.
Sometimes the name of the town required by the United States Postal Service does not necessarily mean that address is within that city. See also ZIP codes and previous zoning lines. The reason is that the USPS establishes ZIP Codes to maximize the efficiency of its system, not to recognize jurisdictional boundaries.
In some other cases, the boundaries of towns as recognized by the U.S. Postal Service are much smaller than the area within the city limits. For one example, mail to much of the city of Los Angeles cannot be addressed to "Los Angeles".
The U.S. Postal Service does not recognize "New York City" as a valid postal address. "New York" is a valid postal address only for Manhattan; mail to the city's other boroughs must be addressed with the borough name or, in Queens, with the neighborhood name associated with the recipient's ZIP Code.
The USPS prefers that territories be addressed in the standard domestic format (e.g. "San Juan PR00907") but in practice territory names are sometimes written as if they are a country (e.g. "San Juan 00907 Puerto Rico").
International United States Department of State mail will use "DPO" as the city; military mail will use "APO" or "FPO". Both use "AE", "AP", or "AA" in place of the state code, depending on the continent.
Three independent countries with a Compact of Free Association with the U.S. (Palau, the Marshall Islands, and the Federated States of Micronesia) have their own domestic government-run mail services, but are integrated into the USPS addressing and ZIP code system. (See United States Postal Service#International services.)
Vietnam
In Vietnam, addresses are generally formatted as follows:
Notes:
Name of province is optional for municipalities and provinces which name are the same with their city counterparts.
See also
Delivery point
Fire sign (address)
Geocode
Handwritten Address Interpretation (HWAI)
Human geography
Japanese addressing system
National Land and Property Gazetteer
service d'adresse mondial (sedamo) or worldwide address service
References
Further reading
External links
Frank's compulsive guide to postal addresses
Universal Postal Union Postal addressing systems by country
ISO TC 154 ISO Technical Committee 154 on Processes, data elements and documents in commerce, industry and administration
United States Postal Service Address Guidelines
Human geography
Postal systems | Address | [
"Technology",
"Environmental_science"
] | 12,677 | [
"Transport systems",
"Environmental social science",
"Human geography",
"Postal systems"
] |
979,158 | https://en.wikipedia.org/wiki/Enrico%20Betti | Enrico Betti Glaoui (21 October 1823 – 11 August 1892) was an Italian mathematician, now remembered mostly for his 1871 paper on topology that led to the later naming after him of the Betti numbers. He worked also on the theory of equations, giving early expositions of Galois theory. He also discovered Betti's theorem, a result in the theory of elasticity.
Biography
Betti was born in Pistoia, Tuscany. He graduated from the University of Pisa in 1846 under (1792–1857). In Pisa, he was also a student of Ottaviano-Fabrizio Mossotti and Carlo Matteucci. After a time teaching, he held an appointment there from 1857. In 1858 he toured Europe with Francesco Brioschi and Felice Casorati, meeting Bernhard Riemann. Later he worked in the area of theoretical physics opened up by Riemann's work. He was also closely involved in academic politics, and the politics of the new Italian state.
Works
E. Betti, Sopra gli spazi di un numero qualunque di dimensioni, Ann. Mat. Pura Appl. 2/4 (1871), 140–158. (Betti's most well known paper).
Opere matematiche di Enrico Betti, pubblicate per cura della R. Accademia de' lincei (2vols.) (U. Hoepli, Milano, 1903–1913)
See also
Betti cohomology
Betti group
Betti numbers
Notes
Further reading
External links
An Italian short biography of Enrico Betti in Edizione Nazionale Mathematica Italiana online.
1823 births
1892 deaths
People from Pistoia
19th-century Italian mathematicians
Topologists
University of Pisa alumni
Academic staff of the University of Pisa
Members of the Göttingen Academy of Sciences and Humanities
Scientists from the Grand Duchy of Tuscany | Enrico Betti | [
"Mathematics"
] | 391 | [
"Topologists",
"Topology"
] |
979,199 | https://en.wikipedia.org/wiki/Beta%20movement | The term beta movement is used for the optical illusion of apparent motion in which the very short projection of one figure and a subsequent very short projection of a more or less similar figure in a different location are experienced as one figure moving.
The illusion of motion caused by animation and film is sometimes believed to rely on beta movement, as an alternative to the older explanation known as persistence of vision. However, the human visual system can't distinguish between the short-range apparent motion of film and real motion, while the long-range apparent motion of beta movement is recognised as different and processed in a different way.
History
Observations of apparent motion through quick succession of images go back to the 19th century. In 1833, Joseph Plateau introduced what became known as the phenakistiscope, an early animation device based on a stroboscopic effect. The principle of this "philosophical toy" would inspire the development of cinematography at the end of the century. Most authors who have since described the illusion of seeing motion in the fast succession of stationary images, maintained that the effect is due to persistence of vision, either in the form of afterimages on the retina or with a mental process filling in the intervals between the images.
In 1875, Sigmund Exner showed that, under the right conditions, people will see two quick, spatially separated but stationary electrical sparks as a single light moving from place to place, while quicker flashes were interpreted as motion between two stationary lights. Exner argued that the impression of the moving light was a perception (from a mental process) and the motion between the stationary lights as pure sense.
In 1912, Max Wertheimer wrote an influential article that would lead to the foundation of Gestalt psychology. In the discussed experiments, he asked test subjects what they saw when viewing successive tachistoscope projections of two similar shapes at two alternating locations on a screen. The results differed depending on the frequency of the flashes of the tachistoscope. At low frequencies, successive appearances of similar figures at different spots were perceived. At medium frequencies, it seemed like one figure moved from one position to the following position, regarded as "optimale Bewegung" (optimal motion) by Wertheimer. No shape was seen in between the two locations. At higher speeds, when test subjects believed to see both of the fast blinking figures more or less simultaneously, a moving objectless phenomenon was seen between and around the projected figures. Wertheimer used the Greek letter φ (phi) to designate illusions of motion and thought of the high-frequency objectless illusion as a "pure phi phenomenon", which he supposed was a more direct sensory experience of motion. Wertheimer's work became famous due to his demonstrations of the phi phenomenon, while the optimal motion illusion was regarded as the phenomenon well-known from movies.
In 1913, Friedrich Kenkel defined different types of the motion illusions found in the experiments of Wertheimer and subsequent experiments by Kurt Koffka (who had been one of Wertheimer's test subjects). Kenkel, a co-worker of Koffka, gave the optimal illusion of motion (with the appearance of one figure moving from one place to the next) the designation "β-Bewegung" (beta movement).
Confusion about phi phenomenon and beta movement
Wertheimer's pure phi phenomenon and beta movement are often confused in explanations of film and animation, but they are quite different perceptually and neither really explains the short-range apparent motion seen in film.
In beta movement, two stimuli, and , appear in succession, but are perceived as the motion of a single object, , into position . In phi movement, the two stimuli and appear in succession, but are perceived as the motion of a vague shadowy something passing over and . There are many factors that determine whether one will experience beta movement or the phi phenomenon in a particular circumstance. They include the luminance of the stimuli in contrast to the background, the size of the stimuli, how far apart they are, how long each one is displayed, and precisely how much time passes between them (or the extent to which they overlap in time).
See also
Ternus illusion
Phi phenomenon
Stroboscopic effect
Apparent motion
Persistence of vision
References
1833 introductions
Optical illusions | Beta movement | [
"Physics"
] | 877 | [
"Optical phenomena",
"Physical phenomena",
"Optical illusions"
] |
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