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A trebuchet () is a type of catapult that uses a rotating arm with a sling attached to the tip to launch a projectile. It was a common powerful siege engine until the advent of gunpowder. The design of a trebuchet allows it to launch projectiles of greater weights and further distances than that of a traditional catapu... | Trebuchet | Wikipedia | 499 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The earliest appearance of the term "trebuchet" in French dates to the late 12th century and the first attestations of trebuchet as a siege weapon are from around the year 1200. The 1174-77 edition of Roman de Renart, an epic about Renard the Fox, describes it as a "trap whose trigger mechanism consists of an assembly ... | Trebuchet | Wikipedia | 472 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The trebuchet is a compound machine that makes use of the mechanical advantage of a lever to throw a projectile. They are typically large constructions, with the length of the beam as much as , with some purported to be even larger.
A trebuchet consists primarily of a long beam attached by an axle suspended high above... | Trebuchet | Wikipedia | 424 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
When the trebuchet is operated, the force causes rotational acceleration of the beam around the axle (the fulcrum of the lever). These factors multiply the acceleration transmitted to the throwing portion of the beam and its attached sling. The sling starts rotating with the beam, but rotates farther (typically about 3... | Trebuchet | Wikipedia | 392 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The first recorded use of traction trebuchets was in ancient China. They were probably used by the Mohists as early as 4th century BC; descriptions can be found in the Mozi (compiled in the 4th century BC). According to the Mozi, the traction trebuchet was high with buried below ground, the fulcrum attached was const... | Trebuchet | Wikipedia | 480 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The traction trebuchet was adopted by various peoples west of China such as the Byzantines, Persians, Arabs, and Avars by the sixth to seventh centuries AD. Some scholars suggest that the Avars carried the traction trebuchet westward while others claim that the Byzantines already possessed knowledge of the traction tre... | Trebuchet | Wikipedia | 496 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The traction trebuchet was most efficient as an anti-personnel weapon, used in a supportive position alongside archers and slingers. Most accounts of traction trebuchets describe them as light artillery weapons while actual penetration of defenses was the result of mining or siege towers. At the Siege of Kamacha in 766... | Trebuchet | Wikipedia | 482 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
There is little to no consensus as to where and when the counterweight trebuchet, which has been described as the "most powerful weapon of the Middle Ages", was first developed. The earliest known description and illustration of a counterweight trebuchet comes from a commentary on the conquests of Saladin by Mardi ibn ... | Trebuchet | Wikipedia | 448 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
Chevedden argues that counterweight trebuchets appeared prior to 1187 in Europe based on what might have been counterweight trebuchets in earlier sources. The 12th-century Byzantine historian Niketas Choniates may have been referring to a counterweight trebuchet when he described one equipped with a windlass, which is ... | Trebuchet | Wikipedia | 323 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The earliest solid reference to a "trebuchet" in European sources dates to the siege of Castelnuovo Bocca d'Adda in 1199. However it is unclear if this referred to counterweight trebuchets since the author did not specify what engine was used and described the machine as fairly light. They may have been used in Germany... | Trebuchet | Wikipedia | 396 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
Counterweight trebuchets do not appear with certainty in Chinese historical records until about 1268. Prior to 1268, the counterweight trebuchet may have been used in 1232 by the Jurchen Jin commander Qiang Shen. Qiang invented a device called the "Arresting Trebuchet" which only needed a few men to work it, and could ... | Trebuchet | Wikipedia | 308 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
While some historians have described the counterweight trebuchet as a type of medieval super weapon, other historians have urged caution in overemphasizing its destructive capability. On the side of the counterweight engine as a medieval military revolution, historians such as Sydney Toy, Paul Chevedden, and Hugh Kenne... | Trebuchet | Wikipedia | 319 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
In spite of the evidence regarding increasingly powerful counterweight trebuchets during the 13th century, "it remains an important consideration that not one of these appears to have effected a breach that directly led to the fall of a stronghold." In 1220, Al-Mu'azzam Isa laid siege to Atlit with a trabuculus, three ... | Trebuchet | Wikipedia | 388 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The counterweight trebuchet did not completely replace the traction trebuchet. Despite its greater range, counterweight trebuchets had to be constructed close to the site of the siege unlike traction trebuchets, which were smaller, lighter, cheaper, and easier to take apart and put back together again where necessary. ... | Trebuchet | Wikipedia | 394 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
There is some evidence that the counterweight trebuchet could be transported. Armies employed a magister tormentorum ('master of trebuchets') for the reconstruction of trebuchets after they were deconstructed for transportation to their destination, whether on carts or by ship. They could also be equipped with their ow... | Trebuchet | Wikipedia | 401 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
Hand-trebuchet
The hand-trebuchet () was a staff sling mounted on a pole using a lever mechanism to propel projectiles. Basically a one-man traction trebuchet, it was used by troops of emperor Nikephoros II Phokas around 965 to disrupt enemy formations in the open field. It was also mentioned in the Taktika of general... | Trebuchet | Wikipedia | 505 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
The largest currently-functioning trebuchet in the world is the machine at Warwick Castle, England, constructed in 2005. Based on historical designs, it stands tall and throws missiles typically 36 kg (80 lbs) up to . The trebuchet gained significant interest from numerous news sources when in 2015 a burning missile ... | Trebuchet | Wikipedia | 439 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
Although rarely used as a weapon today, trebuchets maintain the interest of professional and hobbyist engineers. One modern technological development, especially for the competitive pumpkin-hurling events, is the "floating arms" design. Instead of using the traditional axle fixed to a frame, these devices are mounted o... | Trebuchet | Wikipedia | 365 | 43380 | https://en.wikipedia.org/wiki/Trebuchet | Technology | Artillery | null |
A simulation is an imitative representation of a process or system that could exist in the real world. In this broad sense, simulation can often be used interchangeably with model. Sometimes a clear distinction between the two terms is made, in which simulations require the use of models; the model represents the key c... | Simulation | Wikipedia | 506 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Discrete-event simulation studies systems whose states change their values only at discrete times. For example, a simulation of an epidemic could change the number of infected people at time instants when susceptible individuals get infected or when infected individuals recover.
Stochastic simulation is a simulation w... | Simulation | Wikipedia | 482 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Simulation in failure analysis refers to simulation in which we create environment/conditions to identify the cause of equipment failure. This can be the best and fastest method to identify the failure cause.
Computer simulation
A computer simulation (or "sim") is an attempt to model a real-life or hypothetical situa... | Simulation | Wikipedia | 468 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Less theoretically, an interesting application of computer simulation is to simulate computers using computers. In computer architecture, a type of simulator, typically called an emulator, is often used to execute a program that has to run on some inconvenient type of computer (for example, a newly designed computer th... | Simulation | Wikipedia | 490 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Social simulations may be used in social science classrooms to illustrate social and political processes in anthropology, economics, history, political science, or sociology courses, typically at the high school or university level. These may, for example, take the form of civics simulations, in which participants assu... | Simulation | Wikipedia | 432 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Body tracking: The motion capture method is often used to record the user's movements and translate the captured data into inputs for the virtual simulation. For example, if a user physically turns their head, the motion would be captured by the simulation hardware in some way and translated to a corresponding shift in... | Simulation | Wikipedia | 391 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Current research into user input systems
Research in future input systems holds a great deal of promise for virtual simulations. Systems such as brain–computer interfaces (BCIs) offer the ability to further increase the level of immersion for virtual simulation users. Lee, Keinrath, Scherer, Bischof, Pfurtscheller prov... | Simulation | Wikipedia | 162 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Visual display: Visual displays provide the visual stimulus to the user.
Stationary displays can vary from a conventional desktop display to 360-degree wrap-around screens to stereo three-dimensional screens. Conventional desktop displays can vary in size from . Wrap around screens is typically used in what is known a... | Simulation | Wikipedia | 490 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Vestibular display: These displays provide a sense of motion to the user (motion simulator). They often manifest as motion bases for virtual vehicle simulation such as driving simulators or flight simulators. Motion bases are fixed in place but use actuators to move the simulator in ways that can produce the sensations... | Simulation | Wikipedia | 106 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Clinical healthcare simulators
Clinical healthcare simulators are increasingly being developed and deployed to teach therapeutic and diagnostic procedures as well as medical concepts and decision making to personnel in the health professions. Simulators have been developed for training procedures ranging from the basi... | Simulation | Wikipedia | 466 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Simulation is being used to study patient safety, as well as train medical professionals. Studying patient safety and safety interventions in healthcare is challenging, because there is a lack of experimental control (i.e., patient complexity, system/process variances) to see if an intervention made a meaningful differ... | Simulation | Wikipedia | 454 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Since antiquity, these representations in clay and stone were used to demonstrate clinical features of disease states and their effects on humans. Models have been found in many cultures and continents. These models have been used in some cultures (e.g., Chinese culture) as a "diagnostic" instrument, allowing women to ... | Simulation | Wikipedia | 483 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Immersive disease state simulations allow a doctor or HCP to experience what a disease actually feels like. Using sensors and transducers symptomatic effects can be delivered to a participant allowing them to experience the patients disease state.
Such a simulator meets the goals of an objective and standardized exami... | Simulation | Wikipedia | 451 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Pre-virtual cinematography era (early 1980s to 1990s)
Advances in technology in the 1980s made the computer more affordable and more capable than they were in previous decades, which facilitated the rise of computer such as the Xbox gaming. The first video game consoles released in the 1970s and early 1980s fell prey t... | Simulation | Wikipedia | 501 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Simulation games
Simulation games, as opposed to other genres of video and computer games, represent or simulate an environment accurately. Moreover, they represent the interactions between the playable characters and the environment realistically. These kinds of games are usually more complex in terms of gameplay. Sim... | Simulation | Wikipedia | 466 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
An automobile simulator provides an opportunity to reproduce the characteristics of real vehicles in a virtual environment. It replicates the external factors and conditions with which a vehicle interacts enabling a driver to feel as if they are sitting in the cab of their own vehicle. Scenarios and events are replicat... | Simulation | Wikipedia | 459 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Several Christmas-themed simulations exist, many of which are centred around Santa Claus. An example of these simulations are websites which claim to allow the user to track Santa Claus. Due to the fact that Santa is a legendary character and not a real, living person, it is impossible to provide actual information on ... | Simulation | Wikipedia | 358 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Modern satellite communications systems (SATCOM) are often large and complex with many interacting parts and elements. In addition, the need for broadband connectivity on a moving vehicle has increased dramatically in the past few years for both commercial and military applications. To accurately predict and deliver hi... | Simulation | Wikipedia | 496 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
One organization that has used simulation training for disaster preparedness is CADE (Center for Advancement of Distance Education). CADE has used a video game to prepare emergency workers for multiple types of attacks. As reported by News-Medical.Net, "The video game is the first in a series of simulations to address ... | Simulation | Wikipedia | 443 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
In a live-emergency situation, emergency responders do not have time to waste. Simulation-training in this environment provides an opportunity for learners to gather as much information as they can and practice their knowledge in a safe environment. They can make mistakes without risk of endangering lives and be given ... | Simulation | Wikipedia | 491 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Ergonomics
Ergonomic simulation involves the analysis of virtual products or manual tasks within a virtual environment. In the engineering process, the aim of ergonomics is to develop and to improve the design of products and work environments. Ergonomic simulation utilizes an anthropometric virtual representation of t... | Simulation | Wikipedia | 429 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
In finance, computer simulations are often used for scenario planning. Risk-adjusted net present value, for example, is computed from well-defined but not always known (or fixed) inputs. By imitating the performance of the project under evaluation, simulation can provide a distribution of NPV over a range of discount r... | Simulation | Wikipedia | 446 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
There also exist "engineering flight simulators" which are a key element of the aircraft design process. Many benefits that come from a lower number of test flights like cost and safety improvements are described above, but there are some unique advantages. Having a simulator available allows for faster design iteratio... | Simulation | Wikipedia | 504 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Another application is to evaluate risks related to events such as communication network breakdowns or the inability of participants to send payments (e.g. in case of possible bank failure). This kind of analysis falls under the concepts of stress testing or scenario analysis.
A common way to conduct these simulations... | Simulation | Wikipedia | 504 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Simulations are useful in modeling the flow of transactions through business processes, such as in the field of sales process engineering, to study and improve the flow of customer orders through various stages of completion (say, from an initial proposal for providing goods/services through order acceptance and instal... | Simulation | Wikipedia | 456 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Simulation was used at Kennedy Space Center (KSC) to train and certify Space Shuttle engineers during simulated launch countdown operations. The Space Shuttle engineering community would participate in a launch countdown integrated simulation before each Shuttle flight. This simulation is a virtual simulation where rea... | Simulation | Wikipedia | 499 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
The only true way to test GNSS receivers (commonly known as Sat-Nav's in the commercial world) is by using an RF Constellation Simulator. A receiver that may, for example, be used on an aircraft, can be tested under dynamic conditions without the need to take it on a real flight. The test conditions can be repeated exa... | Simulation | Wikipedia | 340 | 43444 | https://en.wikipedia.org/wiki/Simulation | Technology | General | null |
Operations research () (U.S. Air Force Specialty Code: Operations Analysis), often shortened to the initialism OR, is a branch of applied mathematics that deals with the development and application of analytical methods to improve decision-making. Although the term management science is sometimes used similarly, the tw... | Operations research | Wikipedia | 494 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
History
In the decades after the two world wars, the tools of operations research were more widely applied to problems in business, industry, and society. Since that time, operational research has expanded into a field widely used in industries ranging from petrochemicals to airlines, finance, logistics, and government... | Operations research | Wikipedia | 427 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
Scientists in the United Kingdom (including Patrick Blackett (later Lord Blackett OM PRS), Cecil Gordon, Solly Zuckerman, (later Baron Zuckerman OM, KCB, FRS), C. H. Waddington, Owen Wansbrough-Jones, Frank Yates, Jacob Bronowski and Freeman Dyson), and in the United States (George Dantzig) looked for ways to make bett... | Operations research | Wikipedia | 503 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
While performing an analysis of the methods used by RAF Coastal Command to hunt and destroy submarines, one of the analysts asked what colour the aircraft were. As most of them were from Bomber Command they were painted black for night-time operations. At the suggestion of CC-ORS a test was run to see if that was the b... | Operations research | Wikipedia | 404 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
Bomber Command's Operational Research Section (BC-ORS), analyzed a report of a survey carried out by RAF Bomber Command. For the survey, Bomber Command inspected all bombers returning from bombing raids over Germany over a particular period. All damage inflicted by German air defenses was noted and the recommendation w... | Operations research | Wikipedia | 441 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
Operational research doubled the on-target bomb rate of B-29s bombing Japan from the Marianas Islands by increasing the training ratio from 4 to 10 percent of flying hours; revealed that wolf-packs of three United States submarines were the most effective number to enable all members of the pack to engage targets disco... | Operations research | Wikipedia | 482 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
In the 1950s and 1960s, chairs of operations research were established in the U.S. and United Kingdom (from 1964 in Lancaster) in the management faculties of universities. Further influences from the U.S. on the development of operations research in Western Europe can be traced here. The authoritative OR textbooks from... | Operations research | Wikipedia | 510 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
Problems addressed
Critical path analysis or project planning: identifying those processes in a multiple-dependency project which affect the overall duration of the project
Floorplanning: designing the layout of equipment in a factory or components on a computer chip to reduce manufacturing time (therefore reducing c... | Operations research | Wikipedia | 509 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
The management scientist's mandate is to use rational, systematic, science-based techniques to inform and improve decisions of all kinds. Of course, the techniques of management science are not restricted to business applications but may be applied to military, medical, public administration, charitable groups, politic... | Operations research | Wikipedia | 452 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
Societies
The International Federation of Operational Research Societies (IFORS) is an umbrella organization for operational research societies worldwide, representing approximately 50 national societies including those in the US, UK, France, Germany, Italy, Canada, Australia, New Zealand, Philippines, India, Japan and... | Operations research | Wikipedia | 315 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
Other journals
These are listed in alphabetical order of their titles.
4OR-A Quarterly Journal of Operations Research: jointly published the Belgian, French and Italian Operations Research Societies (Springer);
Decision Sciences published by Wiley-Blackwell on behalf of the Decision Sciences Institute
European Journ... | Operations research | Wikipedia | 306 | 43476 | https://en.wikipedia.org/wiki/Operations%20research | Mathematics | Other | null |
In probability theory, a probability density function (PDF), density function, or density of an absolutely continuous random variable, is a function whose value at any given sample (or point) in the sample space (the set of possible values taken by the random variable) can be interpreted as providing a relative likelih... | Probability density function | Wikipedia | 419 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
Suppose bacteria of a certain species typically live 20 to 30 hours. The probability that a bacterium lives 5 hours is equal to zero. A lot of bacteria live for approximately 5 hours, but there is no chance that any given bacterium dies at exactly 5.00... hours. However, the probability that the bacterium dies between... | Probability density function | Wikipedia | 500 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
Formal definition
(This definition may be extended to any probability distribution using the measure-theoretic definition of probability.)
A random variable with values in a measurable space (usually with the Borel sets as measurable subsets) has as probability distribution the pushforward measure X∗P on : the dens... | Probability density function | Wikipedia | 501 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
It is possible to represent certain discrete random variables as well as random variables involving both a continuous and a discrete part with a generalized probability density function using the Dirac delta function. (This is not possible with a probability density function in the sense defined above, it may be done w... | Probability density function | Wikipedia | 464 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
For continuous random variables , it is also possible to define a probability density function associated to the set as a whole, often called joint probability density function. This density function is defined as a function of the variables, such that, for any domain in the -dimensional space of the values of the va... | Probability density function | Wikipedia | 511 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
For functions that are not monotonic, the probability density function for is
where is the number of solutions in for the equation , and are these solutions.
Vector to vector
Suppose is an -dimensional random variable with joint density . If , where is a bijective, differentiable function, then has density :
... | Probability density function | Wikipedia | 512 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
This method crucially requires that the transformation from U,V to Y,Z be bijective. The above transformation meets this because can be mapped directly back to , and for a given the quotient is monotonic. This is similarly the case for the sum , difference and product .
Exactly the same method can be used to com... | Probability density function | Wikipedia | 138 | 43487 | https://en.wikipedia.org/wiki/Probability%20density%20function | Mathematics | Statistics and probability | null |
A windmill is a structure that converts wind power into rotational energy using vanes called sails or blades, by tradition specifically to mill grain (gristmills), but in some parts of the English-speaking world, the term has also been extended to encompass windpumps, wind turbines, and other applications. The term win... | Windmill | Wikipedia | 368 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
The first practical windmills were panemone windmills, using sails that rotated in a horizontal plane, around a vertical axis. Made of six to 12 sails covered in reed matting or cloth material, these windmills were used to grind grain or draw up water. A medieval account reports that windmill technology was used in Per... | Windmill | Wikipedia | 430 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
The earliest certain reference to a windmill in Northern Europe (assumed to have been of the vertical type) dates from 1185, in the former village of Weedley in Yorkshire which was located at the southern tip of the Wold overlooking the Humber Estuary. Several earlier, but less certainly dated, 12th-century European so... | Windmill | Wikipedia | 340 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
By the end of the 13th century, the masonry tower mill, on which only the cap is rotated rather than the whole body of the mill, had been introduced. The spread of tower mills came with a growing economy that called for larger and more stable sources of power, though they were more expensive to build. In contrast to th... | Windmill | Wikipedia | 435 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
Common sails consist of a lattice framework on which the sailcloth is spread. The miller can adjust the amount of cloth spread according to the wind and the power needed. In medieval mills, the sailcloth was wound in and out of a ladder-type arrangement of sails. Later mill sails had a lattice framework over which the ... | Windmill | Wikipedia | 367 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
In the Netherlands, the stationary position of the sails, i.e. when the mill is not working, has long been used to give signals. If the blades are stopped in a "+" sign (3-6-9-12 o'clock), the windmill is open for business. When the blades are stopped in an "X" configuration, the windmill is closed or not functional. A... | Windmill | Wikipedia | 463 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
In the 14th century, windmills became popular in Europe; the total number of wind-powered mills is estimated to have been around 200,000 at the peak in 1850, which is close to half of the some 500,000 water wheels. Windmills were applied in regions where there was too little water, where rivers freeze in winter and in ... | Windmill | Wikipedia | 425 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
A wind turbine is a windmill-like structure specifically developed to generate electricity. They can be seen as the next step in the development of the windmill. The first wind turbines were built by the end of the nineteenth century by James Blyth in Scotland (1887), Charles F. Brush in Cleveland, Ohio (1887–1888) and... | Windmill | Wikipedia | 483 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
In an attempt to make wind turbines more efficient and increase their energy output, they are being built bigger, with taller towers and longer blades, and being increasingly deployed in offshore locations. While such changes increase their power output, they subject the components of the windmills to stronger forces a... | Windmill | Wikipedia | 391 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
In addition to meeting the stiffness, strength, and toughness requirements determined by the loading, the blade needs to be lightweight, and the weight of the blade scales with the cube of its radius. To determine which materials fit the criteria described above, a parameter known as the beam merit index is defined: Mb... | Windmill | Wikipedia | 465 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
Since 1996, according to an estimate made by Lykke Margot Ricard (SDU) in 2020, at least 8,810 tonnes of the wing scrap have been disposed of in Denmark, and the waste problem will grow significantly in the coming years when more and more wind turbines have reached their end of life. According to the SDU lecturer's cal... | Windmill | Wikipedia | 284 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
The "American windmill", or "wind engine", was invented by Daniel Halladay in 1854 and was used mostly for lifting water from wells. Larger versions were also used for tasks such as sawing wood, chopping hay, and shelling and grinding grain. In early California and some other states, the windmill was part of a self-con... | Windmill | Wikipedia | 352 | 43490 | https://en.wikipedia.org/wiki/Windmill | Technology | Energy and fuel | null |
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity (named for the rock). This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of pla... | Schist | Wikipedia | 351 | 43530 | https://en.wikipedia.org/wiki/Schist | Physical sciences | Petrology | null |
Definition
Before the mid-19th century, the terms slate, shale and schist were not sharply differentiated by those involved with mining. Geologists define schist as medium-grained metamorphic rock that shows well-developed schistosity. Schistosity is a thin layering of the rock produced by metamorphism (a foliation) t... | Schist | Wikipedia | 346 | 43530 | https://en.wikipedia.org/wiki/Schist | Physical sciences | Petrology | null |
Because schists are a very large class of metamorphic rock, geologists will formally describe a rock as a schist only when the original type of the rock prior to metamorphism (the protolith) is unknown and its mineral content is not yet determined. Otherwise, the modifier schistose will be applied to a more precise typ... | Schist | Wikipedia | 429 | 43530 | https://en.wikipedia.org/wiki/Schist | Physical sciences | Petrology | null |
The composition of the rock must permit formation of abundant platy minerals. For example, the clay minerals in mudstone are metamorphosed to mica, producing a mica schist. Early stages of metamorphism convert mudstone to a very fine-grained metamorphic rock called slate, which with further metamorphism becomes fine-gr... | Schist | Wikipedia | 415 | 43530 | https://en.wikipedia.org/wiki/Schist | Physical sciences | Petrology | null |
Uraninite, also known as pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes the mineral to contain oxides of lead and trace amounts of helium. It may... | Uraninite | Wikipedia | 488 | 43532 | https://en.wikipedia.org/wiki/Uraninite | Physical sciences | Minerals | Earth science |
Uraninite is a major ore of uranium. Some of the highest-grade uranium ores in the world were found in the Shinkolobwe mine in the Democratic Republic of the Congo (the initial source for the Manhattan Project) and in the Athabasca Basin in northern Saskatchewan, Canada. Another important source of pitchblende is at Gr... | Uraninite | Wikipedia | 271 | 43532 | https://en.wikipedia.org/wiki/Uraninite | Physical sciences | Minerals | Earth science |
Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rocks.
The general formula is .
Physical properties
Hornblende has a hardne... | Hornblende | Wikipedia | 491 | 43533 | https://en.wikipedia.org/wiki/Hornblende | Physical sciences | Silicate minerals | Earth science |
Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss, and schist. It crystallizes in preference to pyroxene minerals from cooler magma that is richer in silica and water.
It is the principal mineral of amphibolites, which form duri... | Hornblende | Wikipedia | 322 | 43533 | https://en.wikipedia.org/wiki/Hornblende | Physical sciences | Silicate minerals | Earth science |
Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemic... | Basalt | Wikipedia | 464 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
It is often not practical to determine the mineral composition of volcanic rocks, due to their very small grain size, in which case geologists instead classify the rocks chemically, with particular emphasis on the total content of alkali metal oxides and silica (TAS); in that context, basalt is defined as volcanic rock... | Basalt | Wikipedia | 501 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
The term basalt is at times applied to shallow intrusive rocks with a composition typical of basalt, but rocks of this composition with a phaneritic (coarser) groundmass are more properly referred to either as diabase (also called dolerite) or—when they are more coarse-grained (having crystals over 2 mm across)—as gabb... | Basalt | Wikipedia | 441 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Decompression melting can occur in a variety of tectonic settings, including in continental rift zones, at mid-ocean ridges, above geological hotspots, and in back-arc basins. Basalt also forms in subduction zones, where mantle rock rises into a mantle wedge above the descending slab. The slab releases water vapor and ... | Basalt | Wikipedia | 106 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Tholeiitic basalt, which is relatively rich in iron and poor in alkali metals and aluminium, include most basalts of the ocean floor, most large oceanic islands, and continental flood basalts such as the Columbia River Plateau.
High- and low-titanium basalt rocks, which are sometimes classified based on their titanium ... | Basalt | Wikipedia | 506 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Ocean island basalts include both tholeiites and alkali basalts; the tholeiites predominate early in the eruptive history of the island. These basalts are characterized by elevated concentrations of incompatible elements, which suggests that their source mantle rock has produced little magma in the past (it is undeplet... | Basalt | Wikipedia | 68 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Petrology
The mineralogy of basalt is characterized by a preponderance of calcic plagioclase feldspar and pyroxene. Olivine can also be a significant constituent. Accessory minerals present in relatively minor amounts include iron oxides and iron-titanium oxides, such as magnetite, ulvöspinel, and ilmenite. Because o... | Basalt | Wikipedia | 467 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Geochemistry
Relative to most common igneous rocks, basalt compositions are rich in MgO and CaO and low in SiO2 and the alkali oxides, i.e., Na2O + K2O, consistent with their TAS classification. Basalt contains more silica than picrobasalt and most basanites and tephrites but less than basaltic andesite. Basalt has a ... | Basalt | Wikipedia | 379 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Mid-ocean ridge basalts (MORB) and their intrusive equivalents, gabbros, are the characteristic igneous rocks formed at mid-ocean ridges. They are tholeiitic basalts particularly low in total alkalis and in incompatible trace elements, and they have relatively flat REE patterns normalized to mantle or chondrite values.... | Basalt | Wikipedia | 512 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Aā types of blocky cinder and breccia flows of thick, viscous basaltic lava are common in Hawaii. Pāhoehoe is a highly fluid, hot form of basalt which tends to form thin aprons of molten lava which fill up hollows and sometimes forms lava lakes. Lava tubes are common features of pāhoehoe eruptions.
Basaltic tuff or py... | Basalt | Wikipedia | 491 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
When basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms a distinctive pillow shape, through which the hot lava breaks to form another pillow. This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environm... | Basalt | Wikipedia | 506 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Ancient Precambrian basalts are usually only found in fold and thrust belts, and are often heavily metamorphosed. These are known as greenstone belts, because low-grade metamorphism of basalt produces chlorite, actinolite, epidote and other green minerals.
Other bodies in the Solar System
As well as forming large part... | Basalt | Wikipedia | 407 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Venus
From 1972 to 1985, five Venera and two VEGA landers successfully reached the surface of Venus and carried out geochemical measurements using X-ray fluorescence and gamma-ray analysis. These returned results consistent with the rock at the landing sites being basalts, including both tholeiitic and highly alkaline ... | Basalt | Wikipedia | 390 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Compared to granitic rocks exposed at the Earth's surface, basalt outcrops weather relatively rapidly. This reflects their content of minerals that crystallized at higher temperatures and in an environment poorer in water vapor than granite. These minerals are less stable in the colder, wetter environment at the Earth'... | Basalt | Wikipedia | 374 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Life on basaltic rocks
The common corrosion features of underwater volcanic basalt suggest that microbial activity may play a significant role in the chemical exchange between basaltic rocks and seawater. The significant amounts of reduced iron, Fe(II), and manganese, Mn(II), present in basaltic rocks provide potentia... | Basalt | Wikipedia | 301 | 43534 | https://en.wikipedia.org/wiki/Basalt | Physical sciences | Petrology | null |
Ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional cardinal gems, alongside amethyst, sapphire... | Ruby | Wikipedia | 474 | 43551 | https://en.wikipedia.org/wiki/Ruby | Physical sciences | Mineral gemstones | null |
When a chromium atom replaces an occasional aluminium atom, it too loses 3 electrons to become a chromium ion to maintain the charge balance of the AlO crystal. However, the Cr ions are larger and have electron orbitals in different directions than aluminium. The octahedral arrangement of the O ions is distorted, and ... | Ruby | Wikipedia | 446 | 43551 | https://en.wikipedia.org/wiki/Ruby | Physical sciences | Mineral gemstones | null |
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