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Feature Selection for Improving the Usability of Classification Results of High-Dimensional Data
Source: University of Siegen
The semiconductor industry is one of the many fields of applications, where the usage of computational tools is inevitable in order to analyze huge amounts of data. As quality demands and production costs are rising, data mining methods move into the focus of interest. They should help maximizing the generation of information from the data being gathered during the production process and therewith supporting the human experts. In this paper the authors present a system being adopted in the evaluation of measurements from a semiconductor production process. | <urn:uuid:e1201888-2f11-4e75-b654-96a6f45702e1> | {
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Date of this Version
This project is in the area of nanomanufacturing of advanced nanostructured materials. Nanostructured materials (NSMs) with unusual and extreme properties will play a key role in many emerging technologies. However, manufacturing of NSMs with the desired properties is highly complex and currently is over-reliant on empirical data. In this project, a novel manufacturing process producing a new class of ceramic materials, i.e. continuous ceramic nanofibers, is addressed. The novel sol-gel electrospinning technique (patents pending), invented recently by two of the PI’s (Dzenis and Larsen), produces ceramic fibers of submicron diameters with potentially extreme thermomechanical properties. This technique is being analyzed and further optimized for the production of nanocrystalline ceramic nanofibers with superior mechanical properties, based on a comprehensive, multidisciplinary research effort. The research team develops an efficient and robust computational methodology for simulating realistic nanocrystalline nanofibers and their mechanical response at finite temperatures. A novel atomistic-continuum modeling approach based on a hybrid Monte-Carlo finite element technique is being developed and used. These models will be applied to design strong nanofibers by predicting the effects of the chemical composition and atomic structures of grain boundaries and defects on mechanical properties. The results will be used to develop chemistry and to direct manufacturing of strong nanocrystalline nanofibers. The achievement of the enhanced mechanical properties of the resulting nanofibers will be demonstrated experimentally utilizing novel mechanical characterization techniques based on scanning probe microscopy. | <urn:uuid:e9325b29-ab5d-4e38-8ad9-e449330439ff> | {
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Noh, Mohamad Zaky and Hussain, Luay Bakir and Ahmad, Zainal Arifin (2008) Alumina-mild steel friction welded at lower rotational speed. Journal of Materials Processing Technology , 204 . 279-283 . ISSN 0924-0136
Full text not available from this repository.
Official URL: http://dx.doi.org/10.1016/j.jmatprotec.2007.11.100
The joining of ceramic-metal can be done using different techniques such as brazing, diffusion bonding, and friction welding. However, the mechanism of ceramic-metal joining has still not been fully understood. In this study, an alumina rod was bonded to a mild steel rod via the friction welding technique by using an Al 1100 sheet as an interlayer. The diameters of the rods were both 10 mm, respectively. A friction pressure of 20 MPa and a forging pressure of 40 MPa were used. Rotational speed was maintained at 900 rpm and friction times from 2 to 20 s were applied. The joining strength was determined through a four point bending test. The maximum bending strength, 240 MPa was obtained when the friction time of 20 s was used. Under optical microscope and scanning electron microscope observation, the bonding aluminum interface was clearly obtained. Mechanical interlocking and close contact between the alumina-aluminum and aluminum-mild steel were observed at magnifications of 3000×. The strength of alumina-steel bonding is much dependent on the wettability of the alumina surface by the partially molten aluminum interlayer and the existence of mechanical interlocking between the interlayer and mild steel.
|Uncontrolled Keywords:||alumina-mild steel, friction welding, interlayer materials, rotational speed|
|Subjects:||Q Science > QD Chemistry|
|Deposited By:||Liza Porijo|
|Deposited On:||03 Jun 2011 05:20|
|Last Modified:||22 Jul 2011 09:31|
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Skip to Main Content
We consider the communication needs of cognitive radios, in order to ensure the unimpaired operation of licensed users and secondary users' communications isn 't intermitted. This paper proposes a STBC MC- CDMA cognitive radio systems and a hand-off technique for secondary users. We design a novel power control game algorithm named NCPG to efficiently use spectrum resources. Simulation results show that our algorithm can meet the different SIR requirements and yields significant improvement in throughput under the same power consumption.
Date of Conference: July 30 2007-Aug. 1 2007 | <urn:uuid:29cda711-0509-468b-b58c-910810ff778c> | {
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Stofel, Edwin Jule (1962) Plastic flow and fracture of zinc single crystals. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-07012004-154735
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.
Plastic flow and fracture of zinc single crystals subjected to tension parallel to the hexagonal crystallographic axis, torsion about that axis, and combinations of such tension and torsion have been investigated experimentally at 25[degrees]C and -77[degrees]C. The results show that under tension alone, cleavage fracture on the basal plane is preceded by plastic elongation in the direction of the hexagonal crystallographic axis. Some evidence is presented which indicates that this newly discovered mode of plastic deformation of zinc crystals probably occurs by slip on [...] planes in [...] directions. The temperature dependence of this mode of plastic deformation is anomalous. The tensile stress required to produce a given amount of plastic strain is greater at 25[degrees]C than at -77[degrees]C.
The critical resolved shear stress for basal slip, as determined from the results of torsional tests, is increased markedly by prior tensile plastic deformation. The tensile stress-strain relation is raised moderately by prior basal slip.
Fracture was always found to occur by cleavage on a basal plane. The observed combinations of tensile stress and shear stress on the basal plane at fracture are not consistent with predictions based upon current dislocation theories for the initiation of cleavage fracture in zinc. The present results indicate that dislocations having Burgers vectors that do not lie in the basal plane may be of crucial importance in the dislocation mechanism of cleavage fracture of zinc. Such dislocations have not been considered in previously proposed theories.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Mechanical Engineering|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||1 January 1962|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||01 Jul 2004|
|Last Modified:||26 Dec 2012 02:54|
- Final Version
See Usage Policy.
Repository Staff Only: item control page | <urn:uuid:c904a107-0016-46fd-b5e0-5aab2ece2708> | {
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Copyright © 2009 Wanyou Cheng and Zongguo Zhang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Recently, Zhang (2006) proposed a three-term modified HS (TTHS) method for unconstrained optimization problems. An attractive property of the TTHS method is that the
direction generated by the method is always descent. This property is independent of the
line search used. In order to obtain the global convergence of the TTHS method, Zhang
proposed a truncated TTHS method. A drawback is that the numerical performance of the
truncated TTHS method is not ideal. In this paper, we prove that the TTHS method with
standard Armijo line search is globally convergent for uniformly convex problems. Moreover,
we propose a new truncated TTHS method. Under suitable conditions, global convergence is
obtained for the proposed method. Extensive numerical experiment show that the proposed
method is very efficient for the test problems from the CUTE Library. | <urn:uuid:7c729029-6890-49c4-b998-5db449a5956d> | {
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US 7727210 B2
A method of making a tampon applicator having four separable components includes forming a barrel having a forward end and a rearward end opposite the forward end, forming a fingergrip having a barrel end and a plunger end, where the fingergrip has an axially extending channel between the barrel end and the plunger end and the plunger end has a cross-sectional area that is less than a cross-sectional area of the barrel end, forming an insertion tip having a first end and a second end, forming a plunger having a forward end, connecting the barrel end of the fingergrip with the rearward end of the barrel, where the barrel end of the fingergrip and the rearward end of the barrel create a continuous surface flush with the barrel when connected, connecting the second end of the insertion tip to the forward end of the barrel, and inserting the forward end of the plunger into the channel of the fingergrip.
1. A method of making an applicator having four separate components comprising the steps of
(a) forming separately in any order:
(1) a barrel having a tubular shape and having a forward end and a rearward end opposite said forward end, said forward end having an innermost surface and an outermost surface with an outermost diameter, said innermost surface and said outermost surface forming a forward end surface therebetween;
(2) a fingergrip having a barrel end and a plunger end, said plunger end having a cross-sectional area that is less than a cross-sectional area of said barrel end;
(3) an insertion tip having a first end and a second end, said insertion tip having a plurality of petals that taper toward said first end to form a conical shape, said plurality of petals being connected at said second end, said second end having an inner surface and an outer surface, and said inner surface and said outer surface forming an end surface therebetween;
(4) a plunger having a forward end; and
then (b) inserting a tampon pledget into said barrel;
(c) connecting said barrel end of said fingergrip to said rearward end of said barrel;
(d) connecting said end surface of said insertion tip to said forward end surface of said barrel; and
(e) inserting said forward end of said plunger into said plunger end.
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This application is a divisional of U.S. patent application Ser. No.: 11/137,809, filed on May 25, 2005 entitled “Multiple-Component Tampon Applicator,” now pending, which is a divisional of U.S. patent application Ser. No. 10/081,528, filed on Feb. 22, 2002, and issued on Aug. 8, 2005, as U.S. Pat. No. 6,923,789. The aforementioned applications are herein incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to an insertion device, such as a catamenial tampon applicator. More particularly, the present invention relates to a multiple-component tampon applicator formed from at least three distinct and separate components.
2. Description of Related Art
The majority of commercial tampon applicators are of approximately uniform cross-section and are formed from only two components, namely a barrel and a plunger. The fingergrip, if any, is formed as an integral part of the barrel component. Some applicators have a fingergrip and a plunger of a cross-sectional area reduced from that of the applicator barrel. This feature has been found not only to render the tampon applicator more grippable, but it is also more aesthetically preferred.
For current reduced cross-sectional area fingergrip tampon applicators, the tampon pledget must be loaded into the insertion end of the applicator due to the smaller opening at the fingergrip end. Thus, these tampons are restricted to top or insertion end loading. This requires the petals of the applicator, if any, to be post-formed to their final shape after the pledget has been loaded. Post-forming of petals requires the material to be plasticized. Typically, plastic petals are plasticized by heat and are easily shaped by the use of an external forming die.
On the other hand, cardboard petals are more difficult to plasticize and require the additional use of an internal mandrel. Usual methods involve heating the tip to volatize the water (either existing or supplemental moisture), and then forcing the petal into shape using an internal mandrel in conjunction with the external die. The internal mandrel has a cross-sectional area that is approximately the same as the barrel's interior, and consequently would not be able to enter through a reduced cross-sectional fingergrip area. Therefore, the necessity of the internal mandrel to shape the petal tip has thus far precluded the manufacture of a reduced cross-sectional fingergrip area on a cardboard applicator.
Therefore, there is a need for a tampon applicator, and more specifically a cardboard applicator, that can be manufactured such that petal tips can be pre-formed or integrated on the insertion end of the applicator barrel, prior to loading an absorbent pledget, using existing manufacturing processes and equipment.
It is an object of the present invention to provide a tampon applicator that is assembled from at least three distinct and separate components.
It is another object of the present invention to provide such a tampon applicator that has a barrel formed from cardboard.
It is still another object of the present invention to provide such a tampon applicator having a fingergrip with a reduced cross-sectional area compared to that of the applicator barrel.
It is a further object of the present invention to provide such a tampon applicator having petals at the insertion end of the cardboard barrel prior to loading the barrel with an absorbent pledget.
It is still a further object of the present invention to provide such a tampon applicator in which the petals are pre-formed using existing processes and equipment.
It is yet a further object of the present invention to provide such a tampon applicator in which the petals are formed on a separate and distinct insertion tip component that may be connected to a separate barrel component either before or after a pledget is loaded into the barrel component.
It is still yet a further object of the present invention to provide such a tampon applicator that prior to assembly of the applicator, and prior to loading the barrel component with an absorbent pledget, petals may be formed on the insertion end of the barrel using existing processes and equipment.
These and other objects of the present invention will be appreciated from a multiple-component tampon applicator formed from at least three separate and distinct components. A separate insertion tip component having petals may be formed. This separate component may then be connected to the barrel component either before or after an absorbent pledget is loaded into the barrel component. Also, a fingergrip may be formed as a separate component or it may be integrally formed with the barrel.
The multiple components may be formed from materials including, for example, plastic, cardboard, paper slurry, pulp slurry, pulp molded paper, heat shrink plastic, plastic tubing, biopolymers including carbohydrates and proteins, or any combinations thereof.
Referring to the drawings and in particular
The barrel 12 retains its approximately uniform cross-section, thus allowing petals 18 to be formed prior to pledget insertion. The petals 18 can be formed with the assistance of an internal mandrel, if desired.
Barrel 12 of the multiple-component applicator 10 of the present invention may be formed from any suitable material. Suitable materials for forming barrel 12 include, for example, biopolymer, cardboard, heat shrink plastic, paper slurry, plastic, plastic tubing, pulp slurry, pulp-molded paper, or any combinations thereof. Preferably, barrel 12 is formed from cardboard. Barrel 12 may be formed from spiral wound or convolutely wound cardboard.
Any individual component that forms the multiple-component applicator, and especially barrel 12, may be internally and/or externally coated with any suitable material to enhance its strength and/or reduce surface friction. Suitable coatings include, for example, cellophane, cellulose, epoxy, lacquer, nitrocellulose, nylon, plastic, polyester, polylactide, polyolefin, polyvinyl alcohol, polyvinyl chloride, silicone, wax, or any combinations thereof. It should also be understood that barrel 12, while depicted as a single component, may be formed from one or more components, such that when assembled, the one or more components form barrel 12.
Plunger 14 may be formed from any suitable material. Suitable materials for forming plunger 14 include, for example, biopolymer, cardboard, heat shrink plastic, paper slurry, plastic, plastic tubing, pulp slurry, pulp-molded paper, or any combinations thereof. Preferably, plunger 14 is formed from cardboard.
As shown in
By way of example,
It should be understood that the multiple-component tampon applicators depicted in
It should also be understood that each component of the tampon applicator set forth above may be formed from one or more individual parts or sections (i.e. barrel 12, plunger 14, fingergrip 16 and/or insertion tip 19 may be formed from one or more individual parts or sections that are connected to form the component). In addition, it should be understood that while each applicator component is shown above as being discrete and separate from each other, any two or more of the components may be integrally formed and then assembled with the one or more separate components. By way of example, the insertion tip 19, the barrel 12, the fingergrip 16, and/or the plunger 14 may be integrally formed, in any combination. In addition, any component that is made up from two or more parts or sections, as set forth above, may be connected to form that component, prior to connecting with any other individual component to form an assembled applicator 10. However, the overall applicator will, nonetheless, have at least three components.
Fingergrip 16 can be formed from any suitable moldable material. Suitable moldable materials include, for example, biopolymer, cardboard, heat shrink plastic, paper slurry, plastic, plastic tubing, pulp slurry, pulp-molded paper, or any combinations thereof. In a preferred embodiment of the present invention, fingergrip 16 is formed from pulp molded paper.
The fingergrip 16 may be formed with any number and/or configuration of gripping structures, to further enhance the applicator's grippability. Fingergrip 16 may be smooth or, more preferably, may include one or more patterned or textured structures extending above and/or below the surface of the fingergrip.
The gripping structures may include, for example, one or more abrasive materials, embossments, grooves, high wet coefficient of friction materials, lances, pressure sensitive adhesives, protuberances, slits, treads, or any combinations thereof. In addition, the gripping structures may be formed in any shape, including, for example, arc, circle, concave, cone, convex, diamond, line, oval, polygon, rectangle, rib, square, triangle, or any combinations thereof.
It should be understood that the gripping structures may be arranged circumferentially around fingergrip 16 in any pattern suitable for forming a gripping area. For example, the gripping structures can form a distinct pattern, such as, rows, columns or may be formed intermittently with breaks in structure or in any random order or pattern.
Any combinations of the features depicted in
It is also understood that the cross-section of barrel 12, plunger 14, fingergrip 16 and insertion tip 19 can be circular, oval, polygonal or elliptical. Also, insertion tip 19 can be tapered, elliptical, dome-shaped or flat. Barrel 12 can be straight, tapered, or curvilinear along its length.
The foregoing specification and drawings are merely illustrative of the present invention and are not intended to limit the invention to the disclosed embodiments. Variations and changes, which are obvious to one skilled in the art are intended to be within the scope and nature of the present invention, which is defined in the appended claims.
Citas de patentes | <urn:uuid:51de313b-10f8-4403-81cf-4b1119001b60> | {
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The general class of separation processes is one of the most attractive targets for improving energy efficiency in industry, as some separation processes have thermal efficiencies as low as 6 percent. Much of industrial separation now is done by distillation, especially in the petroleum and chemical industries, and technologies are available that could significantly reduce the energy required for this process. However, attention has recently begun to shift to the development of separation processes based on membranes and other porous materials, which could reduce industry’s energy intensity and total energy use.
The industrial sector needs advanced materials that resist corrosion, degradation, and deformation at high temperatures and pressures. Relatively low-energy-intensity materials with particular properties and potential uses, such as composites and nanomaterials for structural applications, could substitute for energy-intensive materials such as steel.
Numerous technologies and practices are available that could optimize and improve steam heating and process heating in industrial facilities. Some changes could take place immediately and could reduce natural gas consumption. Even further efficiency gains could result from R&D, particularly on ultrahigh-efficiency boilers. Such boilers, which employ a combination of advanced technologies, could offer considerable efficiency gains over today’s state-of-the-art boilers.
Electric motors make up the largest single category of electricity end-use in the U.S. economy. They also offer considerable opportunity for electricity savings, especially in the industrial sector. Based on an inventory of motor systems conducted in 1998 (Xenergy, Inc., 1998), it is estimated that industrial motor energy use could be reduced by 11–18 percent if facility managers undertook all cost-effective applications of proven energy efficiency technologies and practices. Specifically, implementation of all established motor-system energy efficiency technologies and practices that meet reasonable investment criteria could yield annual energy savings of 75–122 billion kWh. A next generation of motor and drive improvements is on the horizon, including motors with high-temperature superconducting materials that could extend savings much further.
New fabrication processes could improve yields per unit energy cost for multiple elements of the manufacturing supply chain, reduce waste, | <urn:uuid:ed4c7b9b-3c4f-4da8-a2a8-1faa728cf703> | {
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Proactive routing protocols are mainly used in mobile networks since they are capable to distribute recent information very quickly. However, even reactive and hybrid protocols can be modified to achieve high end-to-end reliability in mobile networks while not increasing the end-to-end delay in a significant way. In this paper the performance of ad-hoc on-demand distance vector (AODV), optimized link state routing (OLSR), and the statistic-based routing (SBR) is simulated in various mobile scenarios with different traffic patterns. The protocols are compared with respect to reliability and routing overhead. The results show that the hybrid SBR protocol is able to achieve a high end-to-end reliability without frequent end-to-end route calculations or a large amount of overhead.
Date of Conference: 7-9 May 2008 | <urn:uuid:1446d95f-d2de-4bca-adac-dca982f0e98b> | {
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Below are the courses of the undergraduate Materials Science and Engineering programme.
MATLS 1M03 Structure and Properties of Materials
An introduction to the structure of both crystalline and amorphous solids; the physical and chemical basis for properties exhibited by materials; an overview of material properties including mechanical, electrical, magnetic and thermal behaviour.
MATLS 2B03 Thermodynamics of Materials
Thermodynamics of gases and critical phenomena. The three laws of thermodynamics applied to materials processing. An introduction to statistical thermodynamics.
MATLS 2D03 Solutions Thermodynamics
Thermodynamicactivity in solid and liquid systems: Gibbs energy of solutions; binary phase diagrams; equilibrium constant; reaction equilibria in gases; Ellingham diagrams.
MATLS 2H04 Measurements and Communication All Students Must Attend the First Lecture.
Basic experimental, simulation and data collection skills relating to materials structure and propoerties. Written and presentation skills development through lab report writing, assignments and plant visits.
MATLS 2X03 Crystalline Structure of Materials
Crystal geometry, point groups, space groups, x-ray diffraction methods for the determination of crystalline structures and chemical compositions, electron and neutron diffraction methods, microanalysis, crystalline defects, physical properties of crystals, crystal growth, phase analysis, phase diagrams, phase transitions, protein crystallography.
MATLS 3B03 Materials Production
Surface science and technology related to the preparation of fine particles of minerals, metals and ceramics for industrial production. Application of electrochemistry for diverse materials processing, such as electrometallurgy, thin film production and anodizing.
MATLS 3C04 Thermodynamics of Multicomponent Systems
Reaction equilibria in solution; stability diagrams; ternary phase diagrams; aqueous and high temperature electrochemistry; use of computerized thermodynamic databases.
MATLS 3E04 Mass Transfer
Phenomenological and mechanistic approaches to diffusion; boundary conditions; diffusion in fluids and solids; point defects in solids.
MATLS 3F03 High-Temperature Materials Production
Fundamentals of processing, building on a knowledge of heat and mass transfer. High temperature processing of materials, focusing on heat sources, solid state processing of powders and liquid state processing, high temperature production routes for most important metals.
MATLS 3M03 Mechanical Behaviour of Materials
How materials are made strong, tough, ductile, formable. How to prevent failures. Materials selection using computer databases.
MATLS 3Q03 Materials for Electronic Applications
Fundamental properties of materials used in electronic applications, operation of devices and fabricaiton methods of electronic circuits and packaging. Includes description of dielectric, magnetic and optoelectronic properties.
MATLS 3T04 Phase Transformations
Review of thermodynamics, binary phase diagrams and solid state diffusion. Role of interfaces; solidification, diffusional and martensitic transformations; welding; oxidation. Materiallographic examination is featured in laboratory work.
MATLS 4AA3 Computational Thermodynamics
Thermodynamic modelling. Principels of computational thermodynamics and its applications. Thermo-Calc. Fortran programming. TQ interface and its incorportion into problem-oriented programs.
MATLS 4C03 Modern Iron and Steelmaking
Theory and practice of iron making. New processes for reduced energy consumption and pollution. Thermodynamics and kinetics of steel making. Steel refining. Casting, including new near net shape technologies. Specialty steelmaking.
MATLS 4D03 Materials and the Environment
The environments experienced by engineering materials in service, and economic methods of ensuring their survival. The basic science of high temperature oxidation and aqueous corrosion leads to an appreciation for methods of corrosion control.
MATLS 4FF3 Synthesis, Applications and Environmental Impact of Nanomaterials
Synthesis routes for nanomaterials, bottom-up and top-down approaches, green chemistry methods, properties of materials: carbon nanotubes, nanoparticles, quantum dots. Environmental and health impact of nanomaterials.
MATLS 4G03 Characterization of Nanomaterials
Interaction of electrons and photons with matter. Imaging methods with electron microscopy and x-ray photoelectron spectroscopy and x-ray absorption analysis with high spatial resolution.
MATLS 4H03 Thin Films Science and Engineering
Deposition and fabrication techniques, surfaces, growth mechanisms, epitaxy, kinetic effects in thin films, defects and properties of thin films. Materials for packaging.
MATLS 4I03 Sustainable Manufacturing Processes
Sustainable development, traditional economic growth, materials cycles, methods for measuring environmental impact, life cycle analysis, waste treatment technologies and recycling technologies. Assessment will consist of a combination of individual assignments and a group project.
MATLS 4K06 Senior Thesis
Individual experimental research problem with a selected supervisor. A preliminary written and oral report is required at the end of the first term. The thesis is defended orally. A minimum of six unscheduled hours each week, both terms. (Note: There are some restrictions on enrollment in this course.)
MATLS 4L04 Materials Manufacturing (Combination of 4L02 & 4A02 in 2008/2009)
A sequence of experiments based on processing methods used in industry. Plant visits with oral and written reports. Seminars and discussions by personnel from industry on manufacturing. Course sections.
MATLS 4N03 Hydrogen, Solar & Nuclear Materials
Fundamental physics of materials used in non-fossil energy technologies. Solar cells, irradiation damage and nuclear materials, modern battery materials, fuel cells.
MATLS 4NN3 Computational Modelling in Materials Engineering
Introduction to numerical modelling of heat and mass transfer processes, microstructure development in alloys, interface properties and simple atomic and molecular modelling.
MATLS 4P03 Properties of Polymeric Materials
Structure of amorphous and crystalline polymeric materials; mechanical, electrical and optical properties, and their modification through processing.
MATLS 4R03 Ceramic Science
The unique properties of structural and functional ceramics are explored, including ferro-electric, piezo-electric and magnetic ceramics, clays, porcelains and refractories. The importance of processing for achieving properties is emphasized.
MATLS 4T03 Properties and Processing of Composites
Intrinsic properties of matrix materials and fibres; mechanics and thermodynamics of interfaces; mechanical properties and fabrication of engineering composites.
MATLS 4Z06 Industrial Projects
Projects, in cooperation with industry, involving materials design in manufacturing, complemented by lectures in group problem solving and design methodology.
ENGINEER 2EO3 Structure and Properties of Engineering Materials -- for Electrical and Computer Engineering
Bonding, crystal structure, defects and diffusion; mechanical and electrical properties; semiconductor device fabrication; optical magnetic and superconductor properties.
Students registered in this course click here to access the course WebCT site
Structure of materials as the basis of mechanical, thermal, electrical, magnetic and chemical properties. Basic approaches to selection of materials in engineering design.
ENGINEER 4J03 Materials Fabrication
Offered jointly by the Departments of Mechanical Engineering and Materials Science and Engineering. Processing methods for a wide range of materials, including metals, ceramics and plastics. The analytical basis for understanding and optimizing materials processes. Exercises in mathematical modeling and the use of software packages to optimize processes.
ENGINEER 4T04 Materials Selection in Design and Manufacturing
Importance of materials selection in design and manufacturing, overview of materials properties, materials selection charts, performance indices, case studies with simple and complex design constraints, fabrication process selection. | <urn:uuid:e4c6db44-4279-468e-b986-e825412211bc> | {
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We present a general machine learning framework for modelling the phenomenon of missing information in data. We propose a masking process model to capture the stochastic nature of information loss. Learning in this context is employed as a means to recover as much of the missing information as is recoverable. We extend the Probably Approximately Correct semantics to the case of learning from partial observations with arbitrarily hidden attributes. We establish that simply requiring learned hypotheses to be consistent with observed values suffices to guarantee that hidden values are recoverable to a certain accuracy; we also show that, in some sense, this is an optimal strategy for achieving accurate recovery. We then establish that a number of natural concept classes, including all the classes of monotone formulas that are PAC learnable by monotone formulas, and the classes of conjunctions, disjunctions, k-CNF, k-DNF, and linear thresholds, are consistently learnable from partial observations. We finally show that the concept classes of parities and monotone term 1-decision lists are not properly consistently learnable from partial observations, if RP ≠ NP. This implies a separation of what is consistently learnable from partial observations versus what is learnable in the complete or noisy setting.
Subjects: 12. Machine Learning and Discovery; 9.3 Mathematical Foundations
Submitted: Oct 16, 2006 | <urn:uuid:80321720-bfc9-4693-8746-b096f6947fa2> | {
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Strategic Analysis of Plastics in the Electric Vehicles Market in Europe and North America
Strategic analysis of plastics in the electric vehicles market provides an in-depth analysis of the major plastic materials used in components of electric vehicles. Segments of the research service include thermal management systems, wire and cables, powertrains, and battery casings. In thermal management systems, liquid piping, air ducts, fans and water pumps have been discussed. In battery casing, the external casing for the battery pack is discussed. In wire and cable, the insulation material has been covered. In powertrains, power electronics module casings, energy recovery devices and battery control module casings are discussed. Drivers, restraints, units and revenue forecast have been discussed.
1. Plastics used in Electric Vehicles | <urn:uuid:055c6a38-cee7-42ad-9e3c-8547d3b8544b> | {
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} |
Ahmed S. Hefny, Ayat Hatem, Mahmoud Shalaby, Amir Atiya
Applying machine learning techniques to real-time computer games is an active research field. In this paper we present Cerberus, a machine learning framework for team–based Capture The Flag (CTF) games. This framework utilizes reinforcement learning to select high-level actions that achieve best team behaviour and utilizes neural networks to control fighting behaviour of team individuals. Our proposed framework also combines waypoints and influence maps for effective path planning.
Subjects: 1.8 Game Playing; 12.1 Reinforcement Learning
Submitted: Aug 10, 2008 | <urn:uuid:f3b6acc2-bc9a-446e-8d01-03dc5e3f6afe> | {
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Random Testing (RT) is a fundamental software testing technique. Adaptive Random Testing (ART) improves the fault-detection capability of RT by employing the location information of previously executed test cases. Compared with RT, test cases generated in ART are more evenly spread across the input domain. ART has conventionally been applied to programs that have only numerical input types, because the distance between numerical inputs is readily measurable. The vast majority of computer programs, however, involve non-numerical inputs. To apply ART to these programs requires the development of effective new distance measures. Different from those measures that focus on the concrete values of program inputs, in this paper we propose a method to measure the distance using coverage information. The proposed method enables ART to be applied to all kinds of programs regardless of their input types. Empirical studies are further conducted for the branch coverage Manhattan distance measure using the replace and space programs. Experimental results show that, compared with RT, the proposed method significantly reduces the number of test cases required to detect the first failure. This method can be directly applied to prioritize regression test cases, and can also be incorporated into code-based and model-based test case generation tools. | <urn:uuid:84930072-72cb-41c0-bbf4-b7d1346c2ec9> | {
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US 5936164 A
An all-silicon monolithic capacitive absolute pressure-sensing device and method for making the same. The device employs a single-crystal silicon diaphragm that serves at a flexible capacitor plate of a variable capacitor. The diaphragm is bonded to a single-crystal silicon wafer to overlie a cavity etched into the wafer. A fixed capacitor plate of the variable capacitor is formed by a heavily-doped region at the bottom of the cavity. A thin dielectric layer is grown on the fixed capacitor plate to complete the capacitor. The cavity has a minimal depth such that the fixed capacitor plate provides overpressure protection for the diaphragm. At least a portion of the operating range of the pressure sensor occurs while the diaphragm is contacting the doped region. As a result, the capacitive output signal of the pressure sensor is produced by changes in contact area between the diaphragm and a thin dielectric situated on the doped region in response to pressure applied to the diaphragm.
1. A capacitive pressure sensor comprising:
a semiconductor wafer, at least a portion of the semiconductor wafer being characterized by a first electrical conductivity type;
a doped region of the first electrical conductivity type in a surface of the semiconductor wafer, the doped region being a fixed capacitor plate of the capacitive pressure sensor; and
a diaphragm bonded to the semiconductor wafer such that the diaphragm overlies the fixed capacitor plate and forms a hermetic seal around the fixed capacitor plate, the diaphragm being of the first electrical conductivity type and electrically insulated from the fixed capacitor plates, the diaphragm being a flexible capacitor plate of the capacitive pressure sensor;
wherein the flexible capacitor plate forms a gap with the fixed capacitor plate of up to about ten micrometers, and a capacitive output signal of the capacitive pressure sensor is produced by changes in contact area between the diaphragm and the semiconductor wafer in response to pressure applied to the diaphragm.
2. A capacitive pressure sensor as recited in claim 1 wherein the diaphragm overlies a limited portion of the semiconductor wafer to yield an exposed surface portion of the semiconductor wafer.
3. A capacitive pressure sensor as recited in claim 2 further comprising a contact to the fixed capacitor plate formed in the exposed surface portion of the semiconductor wafer.
4. A capacitive pressure sensor as recited in claim 1 wherein the diaphragm is formed of single-crystal silicon doped with boron and germanium.
5. A capacitive pressure sensor as recited in claim 1 wherein the capacitive pressure sensor is an all-silicon monolithic absolute pressure sensor.
6. A capacitive pressure sensor as recited in claim 1 further comprising a cavity in the surface of the semiconductor wafer, the doped region being in the cavity such that the gap between the flexible and fixed capacitor plates is about two to seven micrometers.
7. A capacitive pressure sensor as recited in claim 1 wherein:
the semiconductor wafer comprises a heavily-doped substrate and an overlying layer formed by a lightly-doped epitaxy or an oxide;
an opening is present in the overlying layer so as to expose a portion of the heavily-doped substrate, the portion exposed by the opening constituting the doped region; and
the diaphragm is bonded to the overlying layer and overlies the opening in the overlying layer, such that the opening establishes a cavity between the diaphragm and the doped region.
8. A capacitive pressure sensor as recited in claim 1 further comprising a dielectric layer between the doped region and the diaphragm so as to electrically insulate the flexible and fixed capacitor plates.
The present invention generally relates to semiconductor pressure sensing devices. More particularly, this invention relates to an all-silicon monolithic capacitive pressure sensor and a method for its manufacture, in which the output signal of the sensor is produced by changes in contact area between a diaphragm serving as a flexible capacitor plate and a thin dielectric situated on a fixed capacitor plate in response to pressure applied to the diaphragm.
There is a continuing emphasis for pressure sensors that are lower in cost and smaller in size, yet are characterized by high reliability, sensitivity and linearity. Sensors finding wide acceptance on the basis of furthering these characteristics include those that utilize semiconductor materials with a micromachined sensing diaphragm. There are generally two technologies for micromachined semiconductor pressure sensors--a bulk etching technique and a surface thin film technique. In bulk etching, a silicon wafer is selectively etched to produce a flexible diaphragm overlying a cavity. In surface micromachined sensors, thin films of an electrically conductive material, such as polysilicon or metal, are formed over sacrificial layers on a substrate. By selectively removing portions of the sacrificial layers, the films form a diaphragm that is free to move relative to the substrate in response to an applied pressure. With surface micromachining, sensing can be achieved through a capacitive electrode formed on the diaphragm and a second "fixed" capacitive electrode formed on the substrate underlying the diaphragm, such that a capacitive output is produced based on the distance between the capacitive electrodes.
Considerable prior art exists within the pressure sensing art, and numerous techniques and structures have been proposed for attaining pressure sensors that are lower in cost and smaller in size, while achieving high reliability and performance characteristics. However, as noted above, there is an intense and continuing effort to promote these characteristics, while further optimizing the design of pressure sensors to enhance design flexibility and reduce processing.
It is an object of this invention to provide an improved method for fabricating an all-silicon monolithic capacitive pressure sensor.
It is another object of this invention that such a method entails a minimal number of processing steps to form a micromachined capacitive sensing element for the pressure sensor.
It is still another object of this invention that such a method yields a pressure sensor that operates within a range in which the sensing element is sufficiently deflected to contact a thin dielectric situated on a fixed capacitor plate, thereby yielding a sensor characterized by enhanced linearity and overpressure protection.
It is still another object that such a method is conducive to optimizing the size and geometry of the sensing element in order to promote its reliability and performance characteristics.
In accordance with a preferred embodiment of this invention, these and other objects and advantages are accomplished as follows.
The present invention provides an all-silicon monolithic capacitive pressure sensor that includes a base wafer and a diaphragm bonded to the base wafer. The diaphragm overlies, but is electrically insulated from, a doped region in a cavity formed in the surface of the base wafer. Both the diaphragm and the doped region are of the first electrical conductivity type, such that the diaphragm forms a flexible capacitor plate and the doped region forms a fixed capacitor plate of the pressure sensor.
According to the invention, the diaphragm forms a hermetic seal around the fixed capacitor plate, such that a gap between the diaphragm and the doped region is isolated from the ambient atmosphere surrounding the pressure sensor. The gap has a depth of about two to seven micrometers, such that at least a portion of the operating range of the pressure sensor occurs while the diaphragm is contacting a thin dielectric situated on the doped region. As a result, the capacitive output signal of the pressure sensor is produced by changes in contact area between the diaphragm and the thin dielectric in response to pressure applied to the diaphragm.
The method for producing the pressure sensor of this invention generally entails forming a doped region within a cavity formed in the base wafer. The doped region can be formed in any portion or be substantially all of the base wafer. A thin dielectric is then formed over the doped region, and the diaphragm is bonded to the base wafer such that the diaphragm overlies the cavity, thin dielectric and doped region. Other than being capacitively coupled through the thin dielectric, the diaphragm and doped region are electrically insulated from each other. The bonding operation also yields a hermetic seal around the fixed capacitor plate, such that the gap between the diaphragm and the doped region is sealed from the ambient pressure conditions surrounding the pressure sensor. As noted above, the gap is specifically sized to enable the diaphragm to contact the thin dielectric on the doped region, such that the capacitive output signal of the pressure sensor is produced by changes in contact area between the flexible and fixed capacitor plates in response to pressure applied to the diaphragm.
From the above, it can be appreciated that the present invention provides a pressure sensor characterized by an uncomplicated fabrication process as well as built-in overpressure protection due to the minimal gap between the diaphragm and the doped region forming the flexible and fixed capacitor plates, respectively. A further advantage of this invention is that the pressure sensor exhibits a larger capacitive output signal as a result of the output being in response to changes in contact area between the diaphragm and the thin dielectric, as opposed to changes in distance between the diaphragm and the doped region. Furthermore, the method of this invention yields a relatively low cost pressure sensor capable of achieving high reliability and high performance within a relatively small sensor package.
Other objects and advantages of this invention will be better appreciated from the following detailed description.
The above and other advantages of this invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
FIGS. 1 through 4 show, in cross-section, processing steps for the manufacture of an all-silicon monolithic absolute pressure sensor in accordance with one embodiment of this invention;
FIG. 5 represents, in cross-section, the pressure sensor of FIGS. 1 through 4 following a final processing step; and
FIGS. 6 and 7 illustrate alternative processing steps in accordance with this invention.
FIG. 5 represents an all-silicon monolithic capacitive absolute pressure sensor 10 of a type in accordance with the present invention. As illustrated, the sensor 10 includes a base wafer, referred to as a handle wafer 12, in which a cavity 24 has been formed. The handle wafer 12 includes a doped region 14 within the cavity 24, and a single-crystal silicon diaphragm 16 bonded to the handle wafer 12 so as to hermetically enclose the cavity 24. The doped region 14 and the diaphragm 16 form a fixed capacitive plate and a flexible capacitive plate, respectively, of the capacitive sensor 10. Accordingly, the handle wafer 12, doped region 14 and diaphragm 16 are all suitably doped to be electrically conductive. Bond pads 18 and 20 formed on the handle wafer 12 and diaphragm 16, respectively, provide electrical contacts for the fixed and flexible capacitive plates, respectively. The bond pads 18 and 20 enable conditioning circuitry (not shown) to be electrically interconnected with the capacitive plates through the use of wire bonds, solder bumps, leadframes, or any other conventional technique.
According to this invention, a gap 22 between the diaphragm 16 and the doped region 14 is not more than about ten micrometers, and preferably about two to seven micrometers in depth. It will become apparent that the gap 22 and cavity 24 shown in FIG. 5 are greatly exaggerated for purposes of illustrating the invention. Furthermore, the relative physical relationships that appear in the Figures are primarily for illustrative purposes and should not be construed as a restriction to the teachings of the present invention. Essentially, the size of the sensor 10 can vary considerably, with the process encompassed by this invention being most efficient if multiple sensors 10 are simultaneously formed from a wafer stack that is subsequently sawed to separate the individual sensors 10.
The above structure yields an absolute pressure sensor 10 characterized by a built-in overpressure protection due to the minimal gap 22 between the flexible and fixed capacitor plates formed by the diaphragm 16 and doped region 14, respectively. In addition, the dominant portion of the operating range of the pressure sensor 10 occurs while the diaphragm 16 is contacting (though electrically insulated from) the doped region 14. As a result, the capacitive output signal of the pressure sensor 10 is produced by changes in contact area between the diaphragm 16 and the doped region 14 in response to ambient pressure applied to the diaphragm 16.
Processing steps for the fabrication and assembly of the sensor 10 of FIG. 5 are generally indicated in FIGS. 1 through 5. As shown in FIG. 1, the handle wafer 12 is a single-crystal silicon wafer. As will become apparent, the wafer 12 can be either lightly-doped or heavily-doped to be either p or n-type. In the embodiment of FIG. 5, the handle wafer 12 is lightly doped p-type to achieve a resistivity of about three to ten ohm-centimeters. A typical thickness for the wafer 12 is about 0.75 millimeters (about 30 mils), though the thickness could vary significantly.
FIG. 1 shows the result of an etch to produce the cavity 24. The depth of the cavity 24 is preferably about two to seven micrometers to yield the preferred gap 22 shown in FIG. 5, though it is foreseeable that a depth of up to about ten micrometers would be acceptable and yet maintain the operating characteristics desired for the pressure sensor 10. The cavity 24 can be formed by a timed etch into the lightly-doped handle wafer 12 through a mask oxide (not shown) in accordance with known practices. Alternatively, an electrochemically-stopped etch can be employed through a mask oxide if the surface of the wafer 12 is defined by a lightly-doped epitaxial layer while the remainder of the wafer 12 is more highly-doped, as will be discussed in reference to FIG. 6. The surface area of the cavity 24 can be tailored to achieve the desired capacitance range for the sensor 10. In accordance with this invention, the opening formed by the cavity 24 in the surface of the wafer 12 can have any desired shape (e.g., rectangular or circular) and/or the edge and corners between the cavity 24 and the surface of the wafer 12 can be beveled in order to tailor the output-versus-pressure performance of the sensor 10. In one embodiment, the opening and base of the cavity 24 are rectangular-shaped, and the width of the base is about 400 micrometers.
Finally, FIG. 1 shows a masking oxide layer 26 overlying the opposing surfaces of the wafer 12. The thickness of this oxide layer 26 may be about 8000 angstroms, though this thickness could vary. FIG. 2 shows the result of several subsequent processing steps, including the masking and implantation of the doped region 14. For this purpose, the oxide layer 26 on the upper surface of the handle wafer 12 is etched to expose base of the cavity 24, and a suitable P-type dopant for the doped region 14 is introduced either by chemical means or by ion implantation in accordance with known practices. Simultaneously, a portion of the oxide layer 26 at either surface of the wafer 12 can also be etched to enable a p-type contact 28 for the doped region 14 to be formed in the wafer 12. Thereafter, the oxide layer 26 is stripped and an oxide layer 30 grown to a thickness of about 500 to 2000 angstroms.
FIG. 3 illustrates the next step in the method of this invention, in which a layer of silicon nitride 34 has been deposited, lithographically defined and then removed everywhere but the bottom of the cavity 24 and the optional contact 28. A local thick oxide (LOCOS) 36 is then grown on the surface areas of the wafer 12 where the silicon nitride 34 has been removed. A suitable thickness for the nitride 34 is about 1000 to 2000 angstroms, while a suitable thickness for the thick oxide 36 is about 10,000 to 25,000 angstroms.
As shown in FIG. 4, the silicon nitride 34 and the remaining oxide layer 30 beneath the nitride 34 has been removed, and a capacitor-quality oxide has been regrown at the bottom of the cavity 24 and over the contact 28. The oxide overlying the bottom of the cavity 24 forms a pad oxide 38, while a resulting oxide layer overlying the contact 28 is identified by the reference number 40 in FIG. 4. As a "capacitor-quality oxide," the pad oxide 38 and the oxide layer 40 are characterized as oxides that have seen no prior processing, as understood by those skilled in the art. A suitable thickness for these oxide layers is about 500 to 2000 angstroms.
As an alternative to the processing steps shown in FIGS. 2 and 3, the thick oxide 36 can be grown immediately after stripping the oxide layer 26. The thick oxide 36 overlying areas corresponding to the desired placement of the pad oxide 38 and oxide layer 40 can then be lithographically defined and removed by etching, followed by growth of the oxide for the pad oxide 38 and oxide layer 40.
As shown in FIG. 5, the pad oxide 38 over the doped region 14 provides a dielectric layer that electrically insulates the doped region 14 (the fixed capacitor plate of the sensor 10) from the diaphragm 16 (the flexible capacitor plate of the sensor 10), the latter of which is also shown in FIG. 4. A preferred method for forming the diaphragm 16 is to provide a second silicon wafer (not shown) having a lightly-doped substrate with a heavily-doped epitaxial layer. Preferred dopants for the epitaxial layer are boron and germanium. Boron contributes to conductivity and provides for etch-stop control, for reasons that will become subsequently apparent, while germanium is desirable as a dopant to promote stress relief within the diaphragm 16. Optionally, an epitaxial layer lightly-doped with boron may be formed over the heavily-doped boron-germanium epitaxial layer for the purpose of increasing the thickness of the diaphragm 16. The heavily-doped boron-germanium epitaxial layer preferably has a thickness of at least about one micrometer. If the lightly-doped epitaxial layer is also present, the total thickness of the two epitaxial layers is preferably about three to seven micrometers.
Thereafter, the second wafer is inverted and the epitaxial layer at the surface of this wafer (the heavily-doped boron-germanium epitaxial layer or, if present, the lightly-doped epitaxial layer) is brought into contact with the surface of the handle wafer 12 in which the cavity 24 is formed. Conventional wafer-to-wafer bonding techniques can then be employed to bond the second wafer to the handle wafer 12 under a vacuum, such that the cavity 24 is evacuated and the resulting wafer-to-wafer bond forms a hermetic seal around the cavity 24 that enables the pressure sensor 10 to sense absolute pressures. The lightly-doped substrate of the second wafer is then etched back, stopping at the heavily-doped boron-germanium epitaxial layer, to leave an epitaxial plate 42 shown in FIG. 4. This plate 42 (consisting of the heavily-doped boron-germanium epitaxial layer and, if present, the lightly-doped epitaxial layer) is then lithographically defined and plasma etched to expose the oxide layer 40 overlying the contact 28, thereby yielding the diaphragm 16 shown in FIG. 5. As such, the diaphragm 16 is formed by the epitaxial plate 42, which consists of the heavily-doped boron-germanium epitaxial layer and optionally the lightly-doped boron epitaxial layer of the second wafer. Furthermore, the resulting thickness of the diaphragm 16 is the total thickness of the epitaxial plate 42, i.e., at least about one micrometer and preferably about four to seven micrometers. As shown in FIG. 5, the perimeter of the diaphragm 16 is bonded to the wafer 12 as a result of the above-noted wafer-to-wafer bonding process, such that a hermetic seal is maintained for the cavity 24.
The pressure sensor 10 formed by the above steps is then placed in a buffered hydrofluoric acid etch to remove the oxide layer 40 overlying the contact 28 (if present). Thereafter, conventional processing may continue, including the formation of the bond pads 18 and 20 by depositing aluminum, aluminum-silicon or aluminum-silicon-copper metallization over the entire wafer. As is conventional, the metallization is then lithographically defined and wet etched to yield the sensor 10 as it appears in FIG. 5. Notably, because the sensor 10 of this invention has an all-silicon construction, it can be integrated with integrated circuit devices, such as control and signal conditioning circuitry, to yield a "smart sensor." For example, appropriate transistor devices can be formed in the surface of the wafer 12 or the epitaxial layers 12b and 42.
According to this invention, the requirement to form the doped region 14 as a discrete region of the handle wafer 12 can be eliminated by heavily-doping the wafer 12, e.g., P+ type as shown in FIG. 6. In reference to the above-noted techniques for forming the cavity 24, the wafer 12 can be a heavily-doped substrate 12a with an overlying lightly-doped epitaxial layer 12b, as shown in FIG. 6. In so doing, the doped region 14 is formed by the portion of the highly-doped substrate 12a exposed at the bottom of the cavity 24. With this embodiment of the invention, the cavity 24 is formed using an electrochemically-stopped etch through a mask oxide 44, by which the lightly-doped epitaxial layer 12b is preferentially etched while the heavily-doped substrate 12a remains unaffected. Contact to the substrate 12a may be accomplished by removing a portion of the mask oxide 44 from the backside of the substrate 12a and employing standard backside contact techniques.
A second processing embodiment of this invention is represented in FIG. 7. As shown, a thick oxide layer 46 is present on the surface of a heavily-doped handle wafer 12c, and exposes a portion of the wafer 12c to form the cavity 24 and contact 28. The cavity 24 can be formed by selectively growing the oxide layer 46 on the surface of the wafer 12c. Alternatively, the cavity 24 can be formed by growing the oxide layer 46 on the entire surface of the wafer 12c, followed by etching to expose the wafer 12c. After growing the capacitor-quality oxide to form the pad oxide 38 and the oxide layer 40 (not shown) on the exposed surface regions of the wafer 12c, processing of the wafer 12c can proceed to the level shown in FIG. 4.
In view of the above alternative processing techniques, the term "doped region" as used herein is not to be construed as limited to a discrete region that has been selectively formed in the surface of the handle wafer 12, but may encompass a large region of the wafer 12 or a heavily-doped substrate 12a/12c underlying a lightly-doped epitaxial layer 12b or a thick oxide layer 46 at the surface of the wafer 12.
While conventional silicon processing materials can be employed to form the sensor 10 as noted above, other materials could be used, including elemental and compound semiconductor materials, or layers of conducting and insulating materials. As those skilled in the art will appreciate, the choice of materials will determine the appropriate processes for forming selective regions of conductivity in the handle wafer 12. In addition, while p-type and n-type regions in semiconductor devices are generally interchangeable, each conductivity type incurs tradeoffs that would be appreciated and accommodated by one skilled in the art. Consequently, it is foreseeable that the present invention can be utilized to encompass a multitude of applications through the addition or substitution of other processing or material. It is also foreseeable that the processing techniques described above could be used to make piezoresistive or piezoelectric pressure sensors.
Therefore, while our invention has been described in terms of a preferred embodiment, other forms could be adopted by one skilled in the art. Accordingly, the scope of our invention is to be limited only by the following claims.
Citations de brevets | <urn:uuid:96c8a001-af8a-4378-835b-a86c07236d6a> | {
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Transport properties of porous membranes based on electrospun nanofibers
Electrospinning is a process by which high voltages are used to produce an interconnected membrane-like web of small fibers (10-500 nm in diameter). This novel fiber spinning technique provides the capacity to lace together a variety of types of polymers, fibers, and particles to produce ultrathin layers. Of particular interest are electrospun membranes composed of elastomeric fibers, which are under development for several protective clothing applications. The various factors influencing electrospun nonwoven fibrous membrane structure and transport properties are discussed. Performance measurements on experimental electrospun fiber mats compare favorably with transport properties of textiles and membranes currently used in protective clothing systems. Electrospun layers present minimal impedance to moisture vapor diffusion required for evaporative cooling. There may be special considerations in the application of elastomeric membranes for protective clothing. Effects of membrane distortion upon transport behavior of the structure might be significant. Preliminary measurements have found that changes in elastomeric membrane structure under different states of biaxial strain were reflected in measurements of air flow through the membrane. Changes in membrane structure are also evident in environmental scanning electron microscope (SEM) images of the pore/fiber rearrangement as the membrane is stretched. Experimental measurements and theoretical calculations show electrospun fiber mats to be extremely efficient at trapping airborne particles. The high filtration efficiency is a direct result of the submicron-size fibers generated by the electrospinning process. Electrospun nanofiber coatings were applied directly to an open cell polyurethane foam. The air flow resistance and aerosol filtration properties correlate with the electrospun coating add-on weight. Particle penetration through the foam layer, which is normally very high, was eliminated by extremely thin layers of electrospun nanofibers sprayed on to the surface of the foam. Electrospun fiber coatings produce an exceptionally lightweight multifunctional membrane for protective clothing applications, which exhibits high breathability, elasticity, and filtration efficiency. | <urn:uuid:ff685d03-497e-47ca-be68-164c6f38f674> | {
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"Spicy world of NanoScience"
Department of Nanoscience, School of Basic Science, Vels University,
Chennai – 600 117, India
CNT application is regarded as extremely promising for the development of novel energy storage techniques, sensors and sorbent materials for myriad uses including waste management. The progress in science and advanced engineering at nanometer scale provides a range of unprecedented opportunities to develop more efficiently (in terms of costs) and ecologically the processes of water purification. However, water purification technology is often complicated, requires sophisticated equipment and is expensive to run and maintain. Moreover, it usually requires a final costly disinfection stage. They explain that toxic trace elements such as arsenic, cadmium, lead, copper, nickel, zinc, chromium and viscous liquid impurities such as oil can be removed using nanotechnology. Vertically-aligned carbon nanotubes possess many advantages for a wide range of multifunctional applications. While many innovative synthetic methods have been developed for controlled growth of vertically-aligned single-walled carbon nanotubes, various interesting physical and chemical approaches have recently been devised for functionalization of the constituent carbon nanotubes in vertically-aligned carbon nanotube arrays with their alignment being largely retained. In this present study we have grown highly dense vertical aligned carbon nanotubes by CVD technique at very low temperature (550 °C). The synthesised materials were used for the removal of heavy toxic metals from nuclear plants. | <urn:uuid:726f3584-1ad7-429f-af30-e4c66690802b> | {
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The integrated circuit (IC) technology makes use of many diverse fields of science and engineering.
- The physics and operation of semiconductor devices involve understanding of band theory of solids, statistical distribution of electrons and holes in semiconductors, and fundamentals of electrostatics fields.
- The design of microelectronic circuits requires a sound knowledge of electronics and circuit analysis.
- The optical lithography tools, which print microscopic patterns on wafers, represent one of the most advanced applications of the principles of Fourier optics.
- Plasma etching and chemical mechanical planarization involve some of the most complex chemistries used in manufacturing today. Ion implantation draws upon understanding from research in high-energy physics.
- Thin films on semiconductor surface exhibit complex mechanical and electrical behavior that stretches our understanding of basic materials properties.
- Computing skills are necessary to design, model, simulate and predict processes and device behavior, extremely vital to manufacturing.
- A thorough knowledge of statistics is required to manipulate data and process control.
As the devices are shrinking in size approaching nanoscale regime where molecular and atomic scale phenomena come into play, elements of quantum mechanics become important.
One of the great challenges in integrated circuit manufacturing is the need to draw on scientific principles and engineering developments from such an extraordinary wide range of disciplines. Scientists and engineers, who work in this field need broad understanding and the ability to seek out, integrate and use ideas from many fields. | <urn:uuid:f7eb16ae-5b7d-4a70-880a-5047bfd4c35c> | {
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Guruvenket, S and Komath, Manoj and Vijayalakshmi, SP and Raichur, AM and Rao, Mohan G (2003) Wettability enhancement of polystyrene with electron cyclotron resonance plasma with argon. In: Journal of Applied Polymer Science, 90 (6). pp. 1618-1623.
Polystyrene cell-culture substrates were treated with argon glow discharge to make their surfaces hydrophilic. The process was novel in that it used a microwave electron cyclotron resonance (ECR) source for polymer surface modification. The substrates were processed at different microwave powers and time periods, and the surface modification was assessed with by measurement of the water contact angle. A decrease in contact angle was observed with increasing microwave power and processing time. Beyond a certain limit of power and duration of exposure, however, surface deterioration occurred. The optimum conditions for making the surfaces hydrophilic without deterioration of the samples were identified. The plasma parameters were assessed by Langmuir probe measurement. Fourier transform infrared spectroscopy with attenuated total reflectance showed evidence for the induction of hydrophilicity on the surface. The surface micromorphology was examined with scanning electron microscopy. The results prove that the ECR glow discharge was an efficient method for enhancing the wettability of the polymer surfaces.
|Item Type:||Journal Article|
|Additional Information:||The copyright of this article belongs to Wiley Periodicals, Inc.|
|Keywords:||biocompatibility;cold plasma;crosslinking;hydrophilic polymers;polystyrene|
|Department/Centre:||Division of Physical & Mathematical Sciences > Instrumentation and Applied Physics (Formally ISU)
Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
|Date Deposited:||15 Jun 2004|
|Last Modified:||19 Sep 2010 04:12|
Actions (login required) | <urn:uuid:f32d4fa1-f63f-4b90-bbbb-9d0a24c943e7> | {
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"url": "http://eprints.iisc.ernet.in/397/"
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Skip to Main Content
This work presents an information retrieval model based on a kind of probabilistic network. The dependence relationships between terms and documents are represented by the topology of the network. The network contains two parts: the term layer and the document layer. The term relationships are represented as an undirected probabilistic network, with the directed arcs toward the nodes indexed in the document layer. Using a learning algorithm, the topology and the probabilities encoding the strength of the relationships can be learned from the document collection automatically. We also provide a two-part inference process to obtain the relevance of the documents to a given query.
Date of Conference: 15-18 Sept. 2004 | <urn:uuid:31b6c55d-5ecb-48d2-993f-7dfab1420f39> | {
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"url": "http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=1358034&contentType=Conference+Publications"
} |
Skip to Main Content
In this paper, an error resilience scheme based on H.264/AVC progressive image transmission over wireless fading channels is proposed. The source coding approach is based on data partitioning (DP) defined in H.264 standard. DP units with unequal important data are applied optimal channel code allocation in terms of their importance, thus yielding a certain degree of error resilience. To overcome frequency selective fading of wireless channels and improve capacity of the system, OFDM system using space-time block coding (STBC) is considered. Simulation results show that the scheme can obviously improve the error resilience compared to the scheme without DP, especially when the channel is in bad condition; the performance of the scheme with higher spatial diversity gains is better than the scheme with lower spatial diversity gains.
Date of Conference: 20-22 Dec. 2008 | <urn:uuid:b1ea2033-eebd-4344-ae7a-c1008efa90ba> | {
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"url": "http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=4736949&contentType=Conference+Publications"
} |
Residual stresses and stored elastic energy of composites and polycrystals
Residual Stresses in heterogeneous materials may arise because of differential or anisotropic thermal expansion of constituents. The paper is concerned with thermoelastic solids whose material properties fluctuate on the microscopic scale. Rigorous general relations between stored elastic energy and statistical averages (mean values and fluctuations) of residual stresses are derived. These results are applied to two-phase composites and to materials where the fluctuations of elastic constants can be neglected. One obtains exactly the stored energy, certain conditional mean values and the covariance matrix of the residual stresses. Under the assumptions of statistical homogeneity and isotropy, the results hold for any type of heterogeneous microstructure. | <urn:uuid:4c8c2980-9d79-447d-bf02-97a9c99708ec> | {
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US 6902650 B2
The present invention provides a method making stratified paper by redistributing the pulp suspension inside the headbox nozzle using acoustic radiation waves. Acoustic radiation forces fractionate fibers based on fiber radius. The acoustic radiation waves separate the fibers by pushing the coarse and longer fibers to the inner area while fines and smaller fibers remain in the outer area. This has a similar effect of multi-layer stratification headbox, and provides paper with a smoother surface.
1. A method of making a stratified paper comprising the steps of:
(a) introducing a pulp fiber suspension into a headbox of a paper making machine, said which-headbox comprising a single layer zone and having at least one ultrasonic means in proximity to said single layer zone;
(b) subjecting said pulp suspension inside the single layer zone of the headbox to acoustic radiation forces produced by said ultrasonic means;
(c) causing the pulp suspension in the single layer zone to separate into two or more fractions according to the relative sizes of the fibers;
(d) depositing said pulp suspension onto a wire; (e) draining said pulp suspension; and (f) drying said pulp suspension.
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13. A method of making a stratified paper comprising the steps of:
(a) introducing a pulp fiber suspension into a single layer headbox of a paper making machine, which headbox has at least one ultrasonic means;
(b) subjecting said pulp suspension inside the headhox to acoustic radiation forces produced by said ultrasonic means;
(c) causing the pulp suspension to separate into two or more fractions according to the relative sizes of the fibers;
(d) depositing said pulp suspension onto a wire;
(e) draining said pulp suspension; and
(f) drying said pulp suspension.
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This application benefits of Provisional application 60/423,266 filed on Nov. 1, 2002.
The present invention relates to improvements in paper making machines. More particularly the invention provides a novel method of making a stratified paper by separating wood pulp fibers located inside a headbox nozzle into various fractions based on fiber radius by means of acoustic radiation forces.
In the papermaking process, a papermaking machine is used for making a fiber web, such as a paper web, from a fiber suspension. The fiber suspension is typically in the form of fibers that are suspended in water. The fiber suspension is introduced into a headbox, at the wet end of the machine. Headbox apparatuses of such type are disclosed in, for example, from U.S. Pat. No. 4,087,321.
The quality of paper and the board forming depends significantly upon the uniformity of the rectangular jet generated by the headbox. High quality typically means good formation, uniform basis weight profiles, uniform sheet structure and high sheet strength properties. These parameters are affected to various degrees by paper fiber distributions, fiber orientations, fiber density and the distributions of fines and fillers. Thus, separation or fractionation of fibers into two or more fractions that are relatively enriched in longer or shorter fibers is an important step of the papermaking process, because it allows for the efficient use of fiber properties. Fiber fractionation allows an optimized use of raw materials, increases production versatility, and contributes to waste and energy consumption reduction.
Various technologies have been devised during the past forty years to fractionate wood pulp fibers. Pressure screen systems, which fractionate fibers based on fiber length, are generally perceived as the most successful technology on a commercial standpoint. It is also known to place a vertical partition within a headbox for the purpose of deflocculating the fiber suspension. For example, a stratifying headbox or multi-layer headbox having a single headbox converging nozzle with a separate cross machine distribution channel for each layer is disclosed in U.S. Pat. No. 4,141,788 Each suspension package (layers) is separated throughout the headbox nozzle by means of sheets or plates. In multiple headbox forming, a number of headboxes are arranged so as to form a sheet that contains multiple layers.
Attempts to establish uniform paper stock flow in the headbox component, particularly the nozzle chamber, and to improve paper fiber orientation at the slice output of the headbox also include using a diffuser installed between the headbox distributor (inlet) and the headbox nozzle chamber (outlet). The diffuser block enhances the supply of a uniform flow of paper stock across the width of the headbox in the machine direction (MD). Such a diffuser box typically includes multiple conduits or tubular elements between the distributor and the nozzle chamber which may include step widening or abrupt opening changes to create turbulent flows for deflocculation or disintegration of the paper fiber stock to ensure better consistency of the stock. See for example, U.S. Pat. Nos. 5,792,321, 5,876,564, 6,153,057, 6,303,004, 6,406,595, 6,368,460, 6,425,984, 6,475,344, and published application no. US2002/0117285.
Further, it is known to place a mechanical device within the headbox for the purpose of agitating the fiber suspension and thereby deflocculating the fiber suspension. For example, a method for generating fine scale turbulence of the fibers within the stock as it passes through the headbox is disclosed in U.S. Pat. No. 3,853,694. The method consists of welding or soldering plate(s) on the inside wall of a flow channel or headbox, wherein the plate(s) is of such material and thickness that will vibrate due to the flow of stock past the plate, with the vibration being of a higher acoustic and super-acoustic range. Such vibration aids in the dispersion of fiber networks as it passes through the headbox. See also U.S. Pat. No. 6,136,152, which discloses a headbox that includes a turbulence insert.
The feasibility of using acoustic fractionation as a means of separating fibers is disclosed in U.S. Pat. Nos. 5,803,270 and 5,979,664. These patents disclose the use of a plane ultrasonic wave field to induce lateral deflections of moving fiber suspensions in a channel flow and thereby separate fibers into two separated streams.
However, none of the above patents teach or suggest a method that comprises a method for producing stratified paper by placing at least one ultrasound transducer in the headbox, so that sound waves pass transversely through the pulp discharge and thereby separate fibers in one stratified fiber suspension stream.
The present invention provides a method for making a stratified paper which method comprises continuously separating fibers inside the headbox into two or more fractions in one stratified fiber suspension stream. The described embodiments are based upon the use of acoustic wave fields (acoustic radiation forces) to induce deflections of the fibers causing agglomeration and reorientation of the fibers suspensions to separate the fibers inside the headbox nozzle chamber so that the fiber will be separated into two or more fractions according to the relative sizes of the fibers. Since the acoustic radiation force acting on the fibers is primarily a function of the fiber diameter or radius (i.e., fiber width), large radius fibers are more deflected than small radius fibers.
Thus, it is an object of the present invention to provide a method of making a three-ply stratified paper wherein the finer fibers are on the outside of the paper and the coarse fibers are sandwiched inside the paper.
It is a further object of the present invention to provide a method of making a two-ply stratified paper wherein the finer fibers are on one side of the paper and the coarse fibers are on the other side of the paper.
A feature of the present invention is to provide a method and mechanism for separating the fibers within the stock as it passes through the headbox.
Another feature of the present invention is to provide a method of redistributing pulp suspension inside the headbox nozzle by means of acoustic radiation forces.
A further feature of the present invention is to provide a method of separating dilute suspensions of fibers into plural fractions according to the relative fiber sizes of differing fibers.
A feature of the present invention is to generate radiation waves inside the headbox by means of placing at least one ultrasound transducer on the top wall of a headbox and at least one additional ultrasound transducer on the bottom wall of a headbox, so as to pushing the larger fibers of the paper pulp towards the middle, and leaving the smaller fibers on the outer surfaces of the discharge.
A feature of the present invention is to generate radiation waves inside the headbox by means of placing at least one ultrasound transducer on the top wall or the bottom wall of a headbox, so as to separate the fibers into large and smaller fibers.
A further feature of the present invention is to generate radiation waves inside the headbox by means of retrofitting a headbox with at least one ultrasound transducer.
Other advantages and features, as well as equivalent structures and methods which are intended to be covered hereby, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings.
The particulars shown herein are by way of example and for purposes of illustrative discussion of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
The present invention provides a method of making a stratified paper comprising redistributing pulp suspension, inside the headbox nozzle, using acoustic radiation forces. More specifically, the method comprises placing at least one ultrasound transducer on the top and/or the bottom of the inside of a headbox or alternative replacing part of the wall of the headbox with an ultrasound transducer. The pulp suspension in said headbox is then subjected to acoustic radiation forces, causing the sound waves to pass transversely through the pulp discharge, and inducing deflections of the fibers in said fiber suspension thereby causing said fibers in said pulp suspension to separate into two or more fractions according to the relative sizes of the fibers in one stratified fiber suspension stream.
A plane progressive acoustic wave propagating through a fluid medium will generate an acoustic radiation pressure on a particle suspended in the fluid. The force exerted on the particle will be a function of the acoustic frequency, acoustic amplitude, speed of sound in the fluid, density of the fluid, density of the particle and shape of the particle. When two different particles, each with their own density and shape, are suspended in the fluid, there exists the possibility that the acoustic force exerted on each may be significantly different. These forces can generate sufficient difference in particle velocity and deflection angle such that one type of particle is separated from the other. The present invention uses this concept of acoustic stratification, to separate fibers based on the lengths and the diameters of fibers so as to improve sheet properties such as smoothness and bulk.
In the present invention the acoustic radiation force is used to stratify fibers into two or more fractions inside the headbox in one stratified fiber suspension stream. Ultimately, a multi-layer paper is attained using a single layer headbox. This results in more utilization of southern pine fibers; bulk preservation with good sheet smoothness; and optimization of filler and fine distribution. Thus, the end product is an acoustic stratifying headbox that provide similar effect of multi-layer stratification headbox.
Thus, the present invention provides a method for acoustic fiber fractionation using an ultrasonic wave field interacting with suspended fibers circulating in a headbox using acoustic radiation forces to separate fibers into two or more fractions based on fiber radius and length, with applications of the separation concept in the pulp and paper industry. The continuous process relies on the use of at least one transducer placed along the surface of the headbox, wherein the transducer selectively deflects flowing fibers as they penetrate the ultrasonic field.
A typical paper making machine normally comprises a “wet end” including a headbox, a wire (a “wire” is a fast-moving foraminous conveyor belt or screen) and a press section, a drying section, a size press, calender section and parent reel.
The fiber suspension of the present invention is typically in the form of wood fibers, preferably softwood such as southern pine fibers or hardwood, which are suspended in water. Softwood and hardwood fibers available from International Paper's Texarkana, Hwy 59 South, FM 3129, Texarkana, Tex. 75504 and Courtland mills, 16504 Country Road 150, Courtland, Ala. 35618, respectively. The fiber suspension may be treated before it is introduced into the headbox. For example, the fiber suspension may be cleaned and bleached prior to introduction into the headbox.
In an embodiment of the present invention, the acoustic radiation force is used to stratify coarse and larger fibers, such as southern pine fibers into the inner layer of sheet forming zone while fines, filler and smaller fibers, such as hardwood fibers, stay the outer layer, thereby forming a sandwich in which the smaller fibers are on the outside. In another embodiment of the present invention the fibers are separate into two layers of large and small fibers thereby producing a two-layer paper web such that one side is rough and the other is smooth.
The headbox may be any width depending on the paper machine. There are different types of headboxes used in the industry. However, there are some features that are common among all of these devices. The fiber suspension is introduced into the headbox at the wet end of a papermaking machine. A furnish is then discharged by the headbox (a “furnish” is predominantly water and stock) onto a wire which serves as a table to form the paper. As the furnish moves along, gravity and suction boxes under the wire draw the water out. The volume and density of the material and the speed at which it flow onto the wire determine the paper's final weight. Adjusting the pressure inside the headbox controls the speed of the jet leaving the headbox (or the flow rate inside the headbox). The forming jet velocity has a quite large effect on the fiber separation efficiency or separation depth.
Typically, after the paper leaves the “wet end” of the papermaking machine, it still contains a predominant amount of water. Therefore, the paper enters a press section, which can be a series of heavy rotating cylinders, which press the water from the paper, further compacting it and reducing its water content. Subsequent to pressing the paper enters a drying section. Typically hot air or steam-heated cylinders contact both sides of the paper, evaporating the water. The paper optionally passes through a sizing liquid to make it less porous and to help printing inks remain on the surface instead of penetrating the paper. The paper can go through additional dryers that evaporate the liquid in the sizing and costing. Calenders or polished steel rolls make the paper even smoother and more compact. The paper is then wound onto a parent reel and taken off the papermaking machine.
Describing now the drawings, it is to be understood that to simplify the showing thereof, only enough of the structure of the headbox apparatus for a papermaking machine has been illustrated therein as is needed to enable one skilled in the art to readily understand the underlying principles and concepts of this invention.
The transducers are preferably installed all the way across the machine direction. Thus, depending on the size of the machine, several hundred or thousand such transducers may be required. Preferably the transducers are installed in series in the stream-wise direction. Preferably, the acoustic transducers have the dimension of 5 cm by 5 cm. However, it is to be understood that the acoustic transducers can have different dimensions. The same signal generator and signal amplifier can drive each sonic transducer and receiver. The power intensity is preferably in the range of 5 W/cm2 to 100 W/cm2 and most preferably it is 10 W/cm2 or less. The acoustic transducers preferably have a frequency in the range of 20 kHz to 150 MHz and most preferably of 150 kHz or less.
According to the present invention, depending on the machine width, at least one acoustic transducer is mounted on the walls 11 and 12 of the headbox 10. A receiver may also be optionally mounted on the walls 11 and 12. The acoustic transducer is connected to and controlled by commercial available signal generator and ultrasound amplifier. The acoustic transducers are available from Sonic Concepts, Inc., 20018 163rd Avenue NE, Woodinville, Wash. 98072.
Of importance are at least four variables: acoustic intensity, pulp flow velocity, pulp consistency and frequency of the transducer. Preferably, the acoustic intensity is in the range of 0 W/cm2 to 150 W/cm2, the pulp flow rate is 0 m/s to 25 m/s, the pulp consistency is 0% to 2.0%, and the frequency of the transducer is 20 kHz to 150 MHz. All of the above variables will affect the stratified depth of the jet issued from the headbox slice, which will then further affect the percentage of paper or board covered with fine and short fibers in the thickness direction. The stratified depth of the jet issued from the headbox increases with acoustic intensity, and decreases with pulp suspension flow rate and pulp consistency. With the increase of frequency, the acoustic forces will increase and thus increase the stratified depth. However, with the increase of the frequency, there is also an increase in the attenuate rate of the acoustic power. This has the effect of reducing the travel distance of ultrasound in the pulp suspension and thus reducing the stratified depth.
The acoustic transducers provide sonic energy to the fiber suspension within the headbox so that sound waves pass transversely through the pulp discharge thereby pushing the larger fibers of the paper pulp towards the middle, and leaving the smaller fibers on the outer surfaces of the discharge. Where in this application the term “sonic” is used, it is to be understood that the term may include the meaning of the term “ultrasonic.” That is, “sonic” may or may not include frequencies above 20 kHz. Sonic transducer 10 is preferably an ultrasonic transducer, emitting ultrasonic energy with a frequency above 20 kHz, so that a higher energy lever is transmitted into the fiber suspension.
A vertical straight channel was used and exposed to the acoustic radiation pressure. The flow loop system including the flow channel, pump, drive controller and reservoirs were installed at the Institute of Paper Science and Technology. The channel width was reduced to increase the mean velocity and a small bleeding valve was installed to sample the fiber suspension under the acoustic radiation pressure. The flow channel was made out of Plexiglas for the visual investigation.
A Kodak High Motion Analyzer that records the dynamic events up to 1000 frames per second at 50 μsec shutter opening was used for visualization. All the images were recorded and saved into an optical disk in a Kodak bay file format. Then the bay file images were converted to a common image file format. Front light systems with 1000 W tungsten light were used. Due to short shutter opening time and high frame grabbing rate, it is necessary to use a strong and direct front lighting system.
As summarized in Table 1, the experiments were conducted at three different velocities, 0.5 m/sec, 1 m/sec and 2 m/sec, and used four different types of furnish at 0.25% and 0.5% consistencies.
Comparison of High Frequency and Low Frequency Transducers
Both high frequency (150 kHz) and low frequency (1.5 MHz) acoustic transducers were evaluated. Both high and low frequency transducers were systematically compared to determine the most effective frequency range of the acoustic transducer. As the result of the evaluation, the lower frequency (150 kHz) transducer showed significant stratification based on fiber length and diameter, while the higher frequency (1.5 MHz) transducer didn't show major stratification. Presently, only 150 kHz transducers were used. The result is summarized in
Visualization Study of Acoustic Stratification
The following conditions were used in this experiment: (1) Rectangular channel flow (5 cm×3 m); (2) High Speed Digital Imaging Device (records the dynamic events at 1000 frames per second); (3) Front lighting method (the light stands in front of camera but behind the visualized object). Flow velocity: 0.5 m/sec (about 100 feet/min); Consistency: 0.25-0.28%; Acoustic Power: 10 W/cm2.
As predicted, the acoustic radiation force acts selectively on certain types of fibers. As shown on
The stratification depth should be large enough to cover the surface with layers of hardwood fibers to improve the smoothness. Data in
As shown in
Weight averaged fiber length were used as a parameter to evaluate the effectiveness of the stratification. Because the amount of long softwood fibers reduces under the acoustic radiation pressure, the overall average fiber length should decrease. In
It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the invention has been described with reference to a preferred embodiment, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. | <urn:uuid:18a89032-03ad-4075-a1d2-b6fca98a8c8a> | {
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Call Us: +44 20 7594 3575
Plaxica’s Optipure technology is a novel and low cost route to the building blocks for conventional and stereocomplex polylactic acid (PLA). PLA made using our process has mechanical and thermal properties which can compete with traditional oil-based polymers such as PET.
Plaxica is a process technology licensing business. We develop, demonstrate and design process plant for the production of the key intermediates for conventional and stereocomplex PLA and work with global partners to deploy the technology.
Traditionally, fermentation methods are used for the production of lactic acid in PLA manufacture. Plaxica’s Optipure process uses a low cost and flexible chemical process for the conversion of a wide variety of sugars, including those derived from cellulosic materials, which are byproducts of agriculture and forestry operations, into L and D lactic acid and lactide. | <urn:uuid:801c6031-15f7-4b1b-991d-6080fd0ab9f3> | {
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Adaptive Electricity Scheduling With Quality of Usage Guarantees in Microgrids
Source: Auburn University
MicroGrid (MG) is a key component for future Smart Grid (SG) deployment with high potentials. Balancing the supply and demand of energy is one of the most important goals of MG management. In this paper, the authors explore effective schemes for Quality-of-Usage (QoU) guarantees for local residents in an MG, under randomness in both electricity supply and demand. The MicroGrid Control Center (MGCC) aims to maintain the QoU blocking probability around a target value by serving or blocking QoU requests. The problem is formulated as a queue stability problem by introducing the concept of a QoU blocking virtual queue. | <urn:uuid:5bdc5840-218b-4040-94f6-e709109a82d3> | {
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"url": "http://www.techrepublic.com/whitepapers/adaptive-electricity-scheduling-with-quality-of-usage-guarantees-in-microgrids/32870589"
} |
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We study the distributed and decentralized load balancing problem on arbitrary connected graphs, representing an homogeneous network. The network contains several tasks, represented by possibly different integer numbers, to be processed at nodes. We propose a randomized algorithm based on gossip that achieves consensus on the load distribution within fixed bounds of the optimal one; we also show by simulations that in most cases the achieved consensus is optimal. We finally present a computationally convenient heuristic and show that it ensures the same bounds: simulation results, however, show that the heuristic performs worse.
Decision and Control, 2007 46th IEEE Conference on
Date of Conference: 12-14 Dec. 2007 | <urn:uuid:1908f5ea-ed0a-4459-b488-be37623933bc> | {
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The electrical load demand in automobiles has been increasing steadily due to the usage of several subsystems to improve engine performance, passenger comfort, and safety. The current production Lundell alternator is not able to meet the future growing power demand due to its inherent design limitations. Therefore, an efficient, high-power generation system is needed to meet the growing electric power demand in automobiles. The trend to adopt the 42-V power system in automobiles allows one to add more subsystems in an efficient way. In this paper, a three-phase 42-V 4-kW induction-machine-based automotive power generation scheme is proposed to meet the future electrical power demand in automobiles. This scheme uses a low-cost diode bridge rectifier directly connected to the induction machine to transfer active power to the battery and the load. The excitation to the machine is supplied by means of a low-power pulsewidth-modulation (PWM) inverter to control the output voltage of the generator connected to the diode bridge rectifier. This paper presents a new control methodology to regulate the output voltage of an induction generator directly connected to a diode bridge rectifier by controlling the auxiliary PWM inverter. The simulated performance results of a 4-kW 42-V induction generator scheme at various speeds and loads are presented.
Date of Publication: Sept.-Oct. 2003 | <urn:uuid:5af373ed-155a-40b4-98b4-79e9da0f5951> | {
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} |
Pipeline wear is a very complex problem and at present there is limited understanding of the wear mechanisms responsible for the reduction of wall thickness in severe wear regions of alumina conveying pipelines. The ability to determine the wear mechanisms in these areas holds the key in determining the service life of pneumatic conveying pipelines in these industries. In a previous paper it was revealed that delamination and subsequent cracking and spalling of a thin layer plays a major role in material removal in the severe wear regions in the pipeline. The thin surface layer is believed to be the transfer film of alumina generated in the internal pipe surface. In this paper, the transfer film developed in these areas of the pipeline have been analysed to determine its mechanical properties and to correlate the properties with the wear mechanisms observed earlier. In this work, the transfer film formed on mild steel pipes during pneumatic conveying is investigated by using a UMIS nanoindenter. The benefit of using the nanoindenter lies in the very small force that can be applied so that only the properties of the transfer film are measured. The mechanical properties of the film such as the hardness and Young's modulus at different loads are measured. Attempts are also made to measure the fracture behaviour of the film. The elemental analysis of the surface as well as the through depth was conducted using the SEM microanalytical technique EDS (energy dispersive X-ray spectroscopy) and XPS (X-ray photoelectron spectroscopy). The study found that the top layer of the surface is primarily aluminium with hardness value similar to that of sintered alumina. | <urn:uuid:0e60d027-a31f-4d17-ac81-6dd7849e82e8> | {
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} |
Fluctuations of a stochastic approximation procedure with diffusion perturbation
A stochastic approximation procedure with a singularly perturbed regression function is considered. The form of the limit process is obtained that corresponds to the fluctuation of the stochastic approximation procedure in the neighborhood of an equilibrium point. A generator for the limit process is also constructed. The solution of the singular perturbation problem is given for the asymptotic representation of the generator of a Markov renewal process. The results obtained allow one to extend the possibilities of investigation of the asymptotic behavior of the procedure itself. | <urn:uuid:bcdf0f23-4962-493c-b381-c153afe22e9e> | {
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Changes in Interfacial Bonding Energies in the Chemical Activation of GaAs Surfaces
Authors: Liu, Ning; Kuech, Thomas F.
Source: Journal of Electronic Materials, Volume 34, Number 7, July 2005 , pp. 1010-1015(6)
Abstract:The bonding chemistry and the role of the additional HCl-based prebonding treatment when combined with ozone and oxygen plasma treatments on the GaAs/GaAs direct bonding were investigated using multiple internal transmission Fourier transform infrared spectroscopy (MIT-FTIR) and atomic force microscopy (AFM). The results showed that the additional HCl-based pretreatment led to an increased bonding strength and a qualitative reduction in the void density. The removal of the initial native oxide facilitates the diffusion of water to the GaAs wafer surface where it can react to form primarily Ga-based oxides, leading to a substantially increased bond strength compared to those without the removal of interfacial native oxide.
Document Type: Regular paper
Publication date: 2005-07-01 | <urn:uuid:40a67e8f-3ed3-43e1-af1b-48c412cf5980> | {
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Today, R&D continues in many missions on various concepts for deployable structures in space. One unique concept was tested on the SFU. It is a coil-extension mast that uses no hinges to support scientific instruments and/or deployable structures such as the flexible 2-dimensional deployable structure solar array (2-D array). The highly rigid, jointed mast used in the 2-D array was modified for HALCA’s deployable antennas. Research is also carried out on smart and adaptive structures and inflatable structures for future space systems, thus creating many pioneer structures.
2D deployable structure experiment and indirect-type highly rigid extension mast
Deployable flexible solar array and coil-extension mast | <urn:uuid:790088b4-455e-442d-9446-d5b962b1991e> | {
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"url": "http://www.isas.jaxa.jp/e/enterp/tech/st/07.shtml"
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It has been recently suggested that the dynamics of a quantum spin system may provide a natural mechanism for transporting quantum information. I'll show that one dimensional rings of qubits with fixed (time-independent) interactions, constant around the ring, allows high fidelity communication of quantum states. I'll then show that the problem of maximising the fidelity, in a restricted subspace of a single up spin, of the quantum communication is related to a classical problem in fourier wave analysis. By making use of this observation I'll argue that if both communicating parties have access to limited numbers of qubits in the ring (a fraction that vanishes in the limit of large rings) it is possible to make the communication arbitrarily good. I'll then show how to extend our results beyond the restricted 1-spin subspace. These results provide a novel interpretation of a spin systems as a second-quantised optical fibre or waveguide. | <urn:uuid:fc314316-c89c-406a-8cd0-2920a0ca5e52> | {
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The theory of a large class of optical resonators has been developed in a compact form by the means of raising and lowering differential operators (commonly used in quantum mechanics). The theory is applicable to any cavity for which paraxial ray theory may be applied successfully and where losses, aperturing, and aberrations can be ignored. The resonator need not be planar (so that image rotation may occur), the optical elements may be astigmatic and the optic axis incompletely defined (such as when dispersive prisms are used). A discussion of existence and uniqueness of paraxial (pencillike) modes is provided, including the modification of the theory when degeneracies are present. It is proved that unstable cavities do not possess paraxial modes.
Ernest E. Bergmann, "Optical Resonators with Paraxial Modes," Appl. Opt. 11, 113-119 (1972) | <urn:uuid:507be5f7-bc29-49cd-a6e8-585934b8eaac> | {
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"url": "http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-11-1-113"
} |
Design and Analysis of Virtual Bus Transport Using Synchronous Digital Hierarchy/Synchronous Optical Networking
Source: University of Strathclyde
This paper presents a new data link layer design for the virtual bus architecture. The virtual bus is a hierarchical access network offered a broadcast capability for data and signaling. The proposed of the study is to support Quality of Service (QoS) in network. During study, the most promising technology capable of delivering full service access at high data rates is Synchronous Digital Hierarchy (SDH)/Synchronous Optical Networking (SONET). For that reason, the authors develop SDH/SONET as a physical layer for the virtual bus network. The main goal of this investigation was to study the performance of transmission medium and the overall performance of the network. | <urn:uuid:2b8db99c-3d45-4433-acad-762ec4491975> | {
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"url": "http://www.techrepublic.com/whitepapers/design-and-analysis-of-virtual-bus-transport-using-synchronous-digital-hierarchysynchronous-optical-networking/3237347"
} |
Masano Nakayama, Satoko Abiko, Xin Jiang, Atsushi Konno, and Masaru Uchiyama
Soft-tissue fracture simulation is a key to surgery simulation virtually reproducing cutting, dissection, and removal. Soft-tissue fracture is modeled by finite element fracture in which elements are removed if their stress exceeds a specified fracture stress. Removing elements without considering connection to adjacent elements may produce structurally unstable elements, that cause computational instability. We propose geometric limitation and element fracture method to avoid this instability. We confirmed the feasibility of our proposals by comparing blunt dissection simulation results to blunt dissection experiment results using agar.
Keywords: fracture, surgery simulation, FEM, soft tissue | <urn:uuid:26127715-d03b-4556-933e-07e016dfa019> | {
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} |
Adaptive Cooperative Spectrum Sensing Based on a Novel Robust Detection Algorithm
The optimal data fusion rule for multiple sensor detection systems based on the Bayesian criterion has been derived by Chair and Varshney in 1986. However, most of the following works are focused on how to implement such a fusion rule, since the probability of false alarm and the probability of miss detection are hard to evaluate in practice. Till now, although more and more satisfactory data-fusion implementation schemes are available, most of the cooperative spectrum sensing techniques are based on the simple energy-detection algorithm, which only relies on the energy of the received signal. However, when noise is relatively large or the time-varying characteristics of the signal are conspicuous, the energy-detection spectrum sensing algorithm is more prone to fail. | <urn:uuid:c3a49d14-5878-414a-961f-3e237ded297e> | {
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Dr. Mo’s research interest includes vehicular and structural vibration control, energy harvesting: self-powered medical implants and self-powered structural health monitoring, micro actuators and sensors, adaptive structure technology, and smart structures for sustainable buildings.
Currently he is working on:
- Surface reconfigurable device using thermally-activated shape memory polymer
- Energy harvesting devices for smart buildings and agriculture application
- Piezoelectric ultrasound power transmitting devices for medical implants
- Investigating optimal current properties for electric stimulating to enhance bone cell proliferation.
Dr. Mazher’s research interest includes modeling and computer simulation, CFD, dynamic modeling of turbulence, dice dynamics, boundary layer control, small satellite design, social modeling, engineering education and curriculum development.
Dr. Mazher’s current research topics include Dynamic Modeling of Turbulence and Assessing the Role of Homework in Learning. | <urn:uuid:f73491f8-ff31-4e48-9770-535f2a70cfea> | {
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PolyU Institutional Repository >
Industrial and Systems Engineering >
ISE Theses >
Please use this identifier to cite or link to this item:
|Title: ||The design and development of an intelligent planning and scheduling holarchy system for flexible manufacturing systems|
|Authors: ||Keung, Kwok-wai William|
|Subjects: ||Flexible manufacturing systems|
Hong Kong Polytechnic University -- Dissertations
|Issue Date: ||2002 |
|Publisher: ||The Hong Kong Polytechnic University|
|Abstract: ||This research study is concerned with the design and development of an intelligent planning and scheduling holarchy (IPSH) system for a holonic flexible manufacturing workstation (HFMW) which is a type of a flexible manufacturing system (FMS) built on holonic manufacturing concepts. The disadvantages and limitations of conventional manufacturing control architectures result in the evolution of a holonic architecture which is a hybrid type of hierarchical and heterarchical architecture. The Holonic Manufacturing Systems (HMS) exhibits the attributes of an autonomous and a cooperative system which has recently attracted many research interests; for example, the Product-Resources-Order-Staff Architecture (PROSA) developed at PMA/K.U. Leuven in 1998. The basic building blocks of PROSA are called the "basic holons". The main part of this research is the design and development of an intelligent planning and scheduling holarchy (IPSH) which is a decision supporting holon to the "basic holons" of the HFMW. The IPSH is constructed into three problem domains where they are mapped into three sub-holons, namely: the Process Selection Sub-holon; the Master Scheduling Sub-holon; and the Job Sequencing Sub-holon. These sub-holons are designed, developed and experimented in a hierarchical form while they can also function independently.|
In the analysis and modeling of the IPSH, it is made up of a functional model, a structural model, and a mathematical model. The functional model identifies the functions of sub-holons being performed in the IPSH. The structural model delineates the interactions of the sub-holons to the "basic holons". The mathematical model presents the programming formulation of the functions of the IPSH. Moreover, the IPSH is implemented using a genetic-based coordinator. After comparison and evaluation of different heuristic techniques, Genetic Algorithms (GA) was proposed and implemented within the IPSH architecture. A prototype IPSH system had been developed to test the proposed concepts. The experimental results confirmed that the genetic-based coordinator, which consists of three GA solution methodologies, is powerful and robust to solve the three problem domains in the IPSH architecture. The completion of this research has contributed to bridge the gap between the planning and scheduling of manufacturing to the holonic shop floor control.
|Degree: ||Ph.D., Dept. of Industrial and Systems Engineering, Hong Kong Polytechnic University, 2002.|
|Description: ||xvi, 255 leaves : ill. ; 30 cm.|
PolyU Library Call No.: [THS] LG51 .H577P ISE 2002 Keung
|Rights: ||All rights reserved.|
|Appears in Collections:||ISE Theses|
PolyU Electronic Theses
All items in the PolyU Institutional Repository are protected by copyright, with all rights reserved, unless otherwise indicated.
No item in the PolyU IR may be reproduced for commercial or resale purposes. | <urn:uuid:f2004652-0b6e-46a7-8f88-c27866ee7200> | {
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Ahmad, H. Y.; Fitzpatrick, M. E.; Wallhead, I. R. and Edwards, L.
Measurements of stress intensity factors of an interface crack under mixed mode loading.
Journal of Adhesion, 56(1-4),
The optical method of caustics has been utilised to measure both the stress intensity factor for a crack lying along the interface of an aluminium/epoxy bimaterial specimen, and the mode mixity arising from the difference in the elastic properties across the interface. Measurements were carried out by using a novel modification to the method whereby caustics are produced and measured from both sides of the specimen, so compensating automatically for the distortion induced in the specimen due to misaligned loading fixtures. A flat reflective surface across the interface was obtained by adhering a reflective coating to the specimen. Verification that this coating does not affect measurement accuracy was obtained by comparing stress intensity factors measured from coated and uncoated monolithic aluminium specimens where good agreement was found to exist between both measurements.
Actions (login may be required) | <urn:uuid:7b40615b-3791-4919-99e8-d576ef5750b9> | {
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The issue of formalizing skepticism relations between argumentation semantics has been considered only recently in the literature. In this paper we provide a twofold contribution to this kind of analysis. First, starting from the traditional concepts of skeptical and credulous acceptance, we introduce a comprehensive set of seven skepticism relations, which provide a formal counterpart to several alternative notions of skepticism at an intuitive level. Then we carry out a systematic comparison of a significant set of literature semantics (namely grounded, complete, preferred, stable, semi-stable, ideal, prudent and CF2 semantics) on the basis of the proposed skepticism relations.
Publisher's on-line resources
Return to publication list | <urn:uuid:b539f99a-fdbf-459b-bf50-72e183a72121> | {
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Two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched and P25-coated TiO2 nanotube arrays and their photocurrent performances
Citation and License
Nanoscale Research Letters 2011, 6:91 doi:10.1186/1556-276X-6-91Published: 18 January 2011
We report here for the first time the synthesis of two novel hierarchical homogeneous nanoarchitectures of TiO2 nanorods branched TiO2 nanotube arrays (BTs) and P25-coated TiO2 nanotube arrays (PCTs) using two-step method including electrochemical anodization and hydrothermal modification process. Then the photocurrent densities versus applied potentials of BTs, PCTs, and pure TiO2 nanotube arrays (TNTAs) were investigated as well. Interestingly, at -0.11 V and under the same illumination condition, the photocurrent densities of BTs and PCTs show more than 1.5 and 1 times higher than that of pure TNTAs, respectively, which can be mainly attributed to significant improvement of the light-absorbing and charge-harvesting efficiency resulting from both larger and rougher surface areas of BTs and PCTs. Furthermore, these dramatic improvements suggest that BTs and PCTs will achieve better photoelectric conversion efficiency and become the promising candidates for applications in DSSCs, sensors, and photocatalysis. | <urn:uuid:11955b41-4f3f-49af-a9b2-66df22fa70b3> | {
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Date of this Version
This study used two different approaches to model changes in biomass composition during microwave-based pretreatment of switchgrass: kinetic modeling using a time-dependent rate coefficient, and a Mamdani-type fuzzy inference system. In both modeling approaches, the dielectric loss tangent of the alkali reagent and pretreatment time were used as predictors for changes in amounts of lignin, cellulose, and xylan during the pretreatment. Training and testing data sets for development and validation of the models were obtained from pretreatment experiments conducted using 1–3% w/v NaOH (sodium hydroxide) and pretreatment times ranging from 5 to 20 min. The kinetic modeling approach for lignin and xylan gave comparable results for training and testing data sets, and the differences between the predictions and experimental values were within 2%. The kinetic modeling approach for cellulose was not as effective, and the differences were within 5– 7%. The time-dependent rate coefficients of the kinetic models estimated from experimental data were consistent with the heterogeneity of individual biomass components. The Mamdani-type fuzzy inference was shown to be an effective approach to model the pretreatment process and yielded predictions with less than 2% deviation from the experimental values for lignin and with less than 3% deviation from the experimental values for cellulose and xylan. The entropies of the fuzzy outputs from the Mamdani-type fuzzy inference system were calculated to quantify the uncertainty associated with the predictions. Results indicate that there is no significant difference between the entropies associated with the predictions for lignin, cellulose, and xylan. It is anticipated that these models could be used in process simulations of bioethanol production from lignocellulosic materials. | <urn:uuid:f8b62cb2-d640-43c3-a2f2-13d1c5c5a300> | {
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A problem commonly encountered in computer vision is the recovery of the transformation parameters between two affinely distorted images. In this paper, we propose a novel feature-based approach that casts the matching problem to the search of a maximum clique over an auxiliary hypergraph. We also introduce a continuous-based characterization of cliques in hypergraphs that allows us to handle the hard combinatorial problem using tools from the continuous domain. Finally, we present experimental result and comparisons with a state-of-the-art algorithm.
Date of Conference: 8-11 Dec. 2008 | <urn:uuid:c913f51e-2640-40d2-bd2e-f4048a0af9b6> | {
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Energy storage is a natural option toward adding the much-needed flexibility for integrating higher amounts of wind generation into the existing power system. This paper presents field results and analyses quantifying the ability and the value of Sodium Sulfur (NAS) battery energy storage toward shifting wind generation from off-peak to on-peak, limiting the ramp rate of wind farm output, and a strategy to integrate the aforementioned goals. The battery can also be considered on a system level independent of wind. It is argued that even in its capacity as a system resource independent of wind, the battery can aid integration of wind generation. Analyses quantifying the value of the battery in the energy and operating reserve markets are presented. Financially optimal locations to site the battery have also been identified. The presented research is a part of the “Wind to Battery” project led by Xcel Energy, a major U.S. utility.
Date of Publication: Feb. 2013 | <urn:uuid:c6646e07-cfb2-4e53-b7e5-9fa5ffe25e04> | {
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The paper describes a method of minimising the material cost of starting windings for split-phase induction motors. The quantities considered as variables are the number of turns and the wire diameter. The method is considered in the context of a typical starting specification for this type of motor, and the effect of various constraints is discussed.
Electrical Engineers, Proceedings of the Institution of (Volume:125 , Issue: 11 )
Date of Publication: November 1978 | <urn:uuid:cec86c8b-8861-445a-aa2a-a495517e67e0> | {
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A new efficient method for TiO2 fucntionalization with different molecules is presented in this paper. The method is based on TiO2 functionalization with lysine, followed by reaction between amino group from lysine and a functional group from another molecule. In this case the reaction was performed with crown ether using cyanuric chloride as spacer. An infra red spectroscopy study was performed in order to characterize the synthesized molecules.
Semiconductor Conference (CAS), 2010 International (Volume:02 )
Date of Conference: 11-13 Oct. 2010 | <urn:uuid:28a4f02d-ab76-4c5d-bc54-2fede09790aa> | {
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Physical load test is required to determine the serviceability of the structure. Load arrangements, load intensity, loading criteria, instrumentation are explained.
STRUCTURAL EVALUATION PROCESS This procedure is applicable for conventionally reinforced cast-in-place concrete, precast-prestressed concrete and post-tensioned cast-in-place concrete. The evaluation of an existing concrete building is usually performed for stability, strength, safety and future expected life. Evaluation of a structure may be required in the following situations: Structures are subjected to excess or improper loading,(…) | <urn:uuid:ea062068-88fc-4306-9d67-b21237d83e95> | {
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Discovering and visualizing temporal-based Web access behavior
Discovering and understanding Web users' surfing behavior are essential for the development of successful Web monitoring and recommendation systems. In this paper, we propose a Web usage mining approach for the automatic discovery and visualization of temporal-based Web access behavior of individual users by mining client-side logs. The proposed approach is based on a Web usage lattice model which represents a hierarchy of Web access activities. To describe such Web access activities, we incorporate fuzzy logic to represent real life temporal concepts such as morning, afternoon and evening, and meaningful Web categories such as news, sports and chat. Based on the lattice, temporal and association behavior patterns can be extracted and visualized. | <urn:uuid:4c2a9fe4-fb0d-4fc5-84f7-cd29421125cc> | {
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Date: November 1991
Creator: United States. Congress. Office of Technology Assessment.
Description: This paper presents the status of national efforts to cleanup dioxin-contaminated sites and the technologies that have been used, proposed, and researched. It covers thermal and nonthermal treatment techniques as well as approaches such as stabilization and storage. It discusses the development of these technologies as well as advantages and disadvantages of their use.
Contributing Partner: UNT Libraries Government Documents Department | <urn:uuid:c157ae99-2259-4404-8f99-d52692e1d5bc> | {
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High sensitivity and selectivity of C-doped WO3 gas sensors are reported in this paper. C-doped WO3 is synthesized by a facile infiltration and calcination process using the cotton fibers as templates. The response of C-doped WO3 sensor toward toluene (50 ppm) and xylene (50 ppm) reach 91 and 199, respectively. By comparing the response of C-doped WO3 sensor toward various indoor noxious gases (toluene, formaldehyde, ethanol, methane, benzene, and xylene), distinctive selectivity toward toluene and xylene is found. In addition, C-doped WO3 exhibits relative hygro-stability, differing from traditional gas sensor material. The results indicate that C-doped WO3 has good potential in practical applications, due to its remarkable performance and facile synthesized methods.
Date of Publication: June 2012 | <urn:uuid:36dd7690-6abe-4fcc-9089-3fc1374a3d15> | {
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Jun Xu, Hang Li, and Chaoliang Zhong
29 June 2009
This paper is concerned with relevance ranking in search, particularly that using term dependency information. It proposes a novel and unified approach to relevance ranking using the kernel technique in statistical learning. In the approach, the general ranking model is defined as a kernel function of query and document representations. A number of kernel functions are proposed as specific ranking models in the paper, including BM25 Kernel, LMIR Kernel, and KL Divergence Kernel. The approach has the following advantages. (1) The (general) model can effectively represent different types of term dependency information and thus can achieve high performance. (2) The model has strong connections with existing models such as BM25 and LMIR. (3) It has solid theoretical background. (4) The model can be efficiently computed. Experimental results on web search dataset and TREC datasets show that the proposed kernel approach outperforms MRF and other baseline methods for relevance ranking. | <urn:uuid:e33d4334-901d-48e6-a458-a39d9353d5c2> | {
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A 3D-CTM with detailed online PSC-microphysics: analysis of the Antarctic winter 2003 by comparison with satellite observations
1Belgian Institute for Space Aeronomy BIRA-IASB, Brussels, Belgium
2Danish Meteorological Institute, Copenhagen, Denmark
3Belgian Federal Science Policy, Brussels, Belgium
4Naval Research Laboratory, Washington D.C., USA
Abstract. We present the first detailed microphysical simulations which are performed online within the framework of a global 3-D chemical transport model (CTM) with full chemistry. The model describes the formation and evolution of four types of polar stratospheric cloud (PSC) particles. Aerosol freezing and other relevant microphysical processes are treated in a full explicit way. Each particle type is described by a binned size distribution for the number density and chemical composition. This set-up allows for an accurate treatment of sedimentation and for detailed calculation of surface area densities and optical properties. Simulations are presented for the Antarctic winter of 2003 and comparisons are made to a diverse set of satellite observations (optical and chemical measurements of POAM III and MIPAS) to illustrate the capabilities of the model. This study shows that a combined resolution approach where microphysical processes are simulated in coarse-grained conditions gives good results for PSC formation and its large-scale effect on the chemical environment through processes such as denitrification, dehydration and ozone loss. | <urn:uuid:606da0c1-e40e-470b-944c-2136458e350a> | {
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Nano Gripper using Carbon Nanotube
J-S Lee, S-K Kwon, J-S Choi, G-S Kang, Y-K Kwak, S-H Kim
Keywords: carbon nanotube, nano probe, tungsten tip, electrochemical etching
In this paper, we proposed a nano gripper that was made from two nano probes. And, those nano probes were made from the tungsten tip and multi-wall carbon nanotube with acrylic adhesive under optical microscope. We used the electrochemical etching method to make tungsten tip used in nano gripper. With the electrochemical etching, the diameter at the end of tungsten tip was reduced from 500_ to a few _. In Figure 1, the tip manufactured in this process is shown with normal and fine images. The multi-wall carbon nanotube grown by the chemical vapor deposition method was used. It is possible to make nano probe with the mechanical contact and acrylic adhesive such as carbon tape. We used two tungsten tips to make nano probe. The procedure was monitored with the optical microscope and the detail images were captured with the scanning electron microscope. The overall process to make nano probe is shown in Figure 2. The image in Figure 2(d) is the nano probe made through this process. The length of the carbon nanotube in nano probe made by the previous method was various depending on the growth condition of carbon nanotube. So, in this paper, we proposed a new method to cut the carbon nanotube with electrochemical etching. The potassium hydroxide solution was used as the electrolyte. The cutting accuracy is about a few hundreds _ due to the surface tension of electrolyte. The immersed length of the carbon nanotube in electrolyte can be controlled by the nano stage such as piezo actuator. In Figure 3, there are images of nano probe that the length of carbon nanotube was shortened by the method proposed in this paper. All process was monitored with the optical microscope. We made a nano gripper using two nano probes. Two nano probes were approached to each other by nano stages under optical microscope. The gap size at the end of carbon nanotube in nano probe was reduced to about 1 or 2 _, and the nano probes were fixed at that position. The nano gripper can be applied for the handling of nano object depending on the applied voltage. In this paper, we proposed a new method to make nano gripper using two nano probes. We also proposed to cut the carbon nanotube in the nano probe with a few hundreds _ resolution. With this method, it is convenient to make nano gripper with carbon nanotube.
Nanotech 2004 Conference Technical Program Abstract | <urn:uuid:28552d61-9057-45ae-bb11-54911219039a> | {
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We propose a novel image-recovery method using the covariance matrix of the red–green–blue (R–G–B) color histogram and tensor theories. The image-recovery method is called the color histogram normalization algorithm. It is known that the color histograms of an image taken under varied illuminations are related by a general affine transformation of the R–G–B coordinates when the illumination is changed. We propose a simplified affine model for application with illumination variation. This simplified affine model considers the effects of only three basic forms of distortion: translation, scaling, and rotation. According to this principle, we can estimate the affine transformation matrix necessary to recover images whose color distributions are varied as a result of illumination changes. We compare the normalized color histogram of the standard image with that of the tested image. By performing some operations of simple linear algebra, we can estimate the matrix of the affine transformation between two images under different illuminations. To demonstrate the performance of the proposed algorithm, we divide the experiments into two parts: computer-simulated images and real images corresponding to illumination changes. Simulation results show that the proposed algorithm is effective for both types of images. We also explain the noise-sensitive skew-rotation estimation that exists in the general affine model and demonstrate that the proposed simplified affine model without the use of skew rotation is better than the general affine model for such applications.
© 2001 Optical Society of America
[Optical Society of America ]
Soo-Chang Pei, Ching-Long Tseng, and Chai-Che Wu, "Using color histogram normalization for recovering chromatic illumination-changed images," J. Opt. Soc. Am. A 18, 2641-2658 (2001) | <urn:uuid:c990a414-d632-4da8-bd95-485fdac5feb8> | {
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Towards Automated Determination of USERMAT for the Nonlinear Constitutive Behavior of Composites
Over the last 30 years NRL's Composite Materials and Structures (CMS) group has been developing a data driven system identification inverse approach for characterizing the constitutive behavior of polymer matrix composites (PMCs). The core concept in this approach has been the experimental identification of a dissipated energy density (DED) function. This is achieved through establishing a non-linear optimization scheme for determining the free coefficients of the sum of the basis functions that are used to construct the DED function and is based on the energy balance of the specimen under test. The method used was based on using massive amounts of experimental data that would be produced by exposing PMC specimens to multidimensional loading paths with the help of custom made multi-axial computer-controlled testing machines. The analytical and numerical implementation that has been followed up to now has been developed within various custom environments and this has been one of the main stumbling blocks in transferring this technology to end users in the design and material communities. Recent advances in finite element techniques and design optimization integration technologies along with the parallel hardware and software evolution have directed the CMS group to turn its attention to utilizing "of the shelf" technology of achieving the same goals. Thus, the “Z-mat” and "Z-Optim" packages from Northwest Numerics, Inc., have been utilized to extract the non-linear constitutive response from the available experimental data in an integrated and automated manner and in conjunction with the ANSYS/Mechanical infrastructure. The automation lies on the fact that the process automatically generates the code of a "USERMAT" subroutine that it can be subsequently used with any geometry and loading specification definable within the limits of ANSYS' non-linear element library. The geometry of the single notched specimen of NRL's In Plane has been used for developing and verifying the process. | <urn:uuid:04566b44-ea25-4b15-af4f-05c206bffd7b> | {
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} |
8750 Delaware Avenue
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TrueGage is a provider of software solutions for micro and nano-surface metrology
for use in research laboratory, industrial and production environments.
Our TrueMap and TrueSurf software is used in the measurement and analysis of
3D surface texture, in non-contact measurement and analysis, and in the analysis
of measurements made by scanning probe microscopes which are commonly used in
nanoscience and nanotechnology. | <urn:uuid:9288d809-d507-4030-bc51-c1da7143f71a> | {
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Topological defects in the buckling of elastic membranes
We investigate the effects of topological defects on the low-energy shapes of single-component two-dimensional elastic membranes with spherical topology. The membrane is described as a closed, triangulated two-dimensional manifold embedded in three-dimensional space using a dynamic triangulation model, thus allowing the creation of topological defects. Low-energy structures and connectivities are explored using a Monte Carlo simulated annealing method while also constraining the internal volume of the membrane to simulate incompressible contents within the membrane, such as in colloidosomes and viruses. We find that since the volume constraint partially suppresses the buckling transition such that the buckled icosahedral shape has a reduced asphericity, defect scars are favorable over a larger range of elastic parameters of the membrane compared with systems having no constraint on volume. | <urn:uuid:09eeef5f-fb71-475b-8b13-ef2de19b074a> | {
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Sn-doped In2O3 nanowires: enhancement of electrical field emission by a selective area growth
Department of Materials Science and Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013, Taiwan
Nanoscale Research Letters 2012, 7:684 doi:10.1186/1556-276X-7-684Published: 21 December 2012
Selective area growth of single crystalline Sn-doped In2O3 (ITO) nanowires synthesized via vapor–liquid–solid (VLS) method at 600°C was applied to improve the field emission behavior owing to the reduction of screen effect. The enhanced field emission performance reveals the reduction of turn-on fields from 9.3 to 6.6 V μm−1 with increase of field enhancement factors (β) from 1,621 to 1,857 after the selective area growth at 3 h. Moreover, we find that the screen effect also highly depends on the length of nanowires on the field emission performance. Consequently, the turn-on fields increase from 6.6 to 13.6 V μm−1 with decreasing β values from 1,857 to 699 after the 10-h growth. The detailed screen effect in terms of electrical potential and NW density are investigated in details. The findings provide an effective way of improving the field emission properties for nanodevice application. | <urn:uuid:f7ae4422-c653-431f-b91b-9bcc165c0dcd> | {
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A finite element method involving Johnson-Cook material model and fracture criterion was used to simulate the cutting temperature distribution on tool rake face during high speed machining AISI 1045 hardened steel using commercial finite element software ABAQUS which can preferably handle such strongly non-linear problems and allow the definition of complex contact conditions. The simulation shows that the highest temperature region is not at the tool tip but is located at certain distance from tool tip, and the comparison between simulation and experiment shows good consistency. Therefore, this finite element simulation method presented in this paper can be use to predict the temperature field distribution accurately during high speed machining hardened steel.
Intelligent Computation Technology and Automation, 2009. ICICTA '09. Second International Conference on (Volume:3 )
Date of Conference: 10-11 Oct. 2009 | <urn:uuid:c8a438f9-72d9-4a54-aa1b-4866df7514ea> | {
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In this paper we present the design concept and experimental evaluation results of a newly developed DWDM Radio on Free Space Optics (RoFSO) system capable of transmitting simultaneously multiple RF service signals. The system performance is evaluated under effects of atmospheric turbulence over 1-km free-space transmission. Effectiveness of a proposed tracking scheme used to mitigate beam angle-of-arrival (AOA) effect and the viability of the communication system using a specially designed optical antenna are illustrated. An initial attempt to estimate an additional link margin to compensate for tracking error loss is also presented. Finally, we evaluate the performance of heterogeneous wireless signals after being transmitted over the system. We verify that the system can provide a stable connection for heterogeneous wireless services especially in the absence of strong atmospheric turbulence.
Date of Conference: Nov. 30 2009-Dec. 4 2009 | <urn:uuid:826f8e1e-0710-4fa8-81c0-e3b44038b6a2> | {
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3M™ Glass Bubbles HGS6000 have a density of 0.46 g/cc and an isostatic crush strength of 6,000 psi. The HGS series glass bubbles are designed for low-density drilling fluids and cements used in the oil and gas industry.
Reduce rig time required compared to multiple stage cementing
Reduce the possibility of formation break-down
Reduce the possibility of lost circulation
Increase efficiency of mud removal by allowing pipe rotation or reciprocation | <urn:uuid:4b49363b-e072-4afd-9e39-10422edca686> | {
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} |
Professor of Physics
Ph.D. 2002, Stanford University
Prof. Hasan is interested in the fundamental physics of quantum condensed-matter systems. Scattering based spectroscopic methods are used in the investigations of novel quantum phases realized via topological ordering, strong-interaction or geometrical frustration and their combinations. Quantum Hall phases, correlated superconductors and frustrated magnets have profoundly changed our microscopic understanding of interacting quantum matter. My research is focused on the frontier aspects of these areas of fundamental physics such as the quantum Hall-like effect without external magnetic field, non-BCS superconductivity in correlated materials and fractionalized phases in higher dimensions as well as the development of novel instrumentation capability necessary to address these issues. High-energy probes (Synchrotron photons, electrons, neutrons) are used as spectroscopic tools. Experiments are performed at Brookhaven, Argonne, LBL/Berkeley, SLAC/Stanford as well as in Joseph Henry Labs at Princeton. | <urn:uuid:3a08629d-3593-4487-9988-ad83fa0e0b5d> | {
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Comp 511 Project: A Staged Interpreter for Featherweight Java
Source: Rice University
The staged interpreter presented in this paper is very specific: it breaks execution into several stages with respect to the values that must be supplied to the methods that are invoked in a Featherweight Java program. Yet, such an interpreter allows building specific pieces of code that can accept different values for the invocation of the same method multiple times over. Such pieces of code provide valuable abstraction capabilities, similar to the use of macros in imperative languages. This paper presents the design, implementation, and testing of a staged interpreter for Featherweight Java. | <urn:uuid:7457282b-f679-4cc6-a5d0-121bb6baf0bc> | {
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Date of Completion
The efficiency of sampling remains as one of the major challenges for uncertainty analysis in structural dynamics. In the context of numerical experiments, this difficulty primarily lies in the fact that every single run of a numerical model, which usually is of large scale in modern engineering practice, would be expensive in terms of CPU times and memories. Nonetheless, understanding and predicting dynamic characteristics of structural systems with uncertainties is important for structural design, assessment and control. In order to develop fast and economical sampling techniques for characterizing structural dynamics, we explored two categories of methods from two opposite direction: the first is first-principle-based order reduced simulation and the second is data based statistical emulation. This thesis particularly focuses on component mode synthesis (CMS) and Gaussian processes regression (GPR).The former is a family of finite-element-based techniques that have drawn significant attention in computational structural dynamics, and the latter is a recently developed statistical approach which has proved to be potentially useful in engineering applications. A general free interface CMS formulation, which has been developed by the author, a concise self-sustained description of GPR and two-level GPR, and a series of application examples will be presented in this thesis.
XIA, ZEPING, "Efficient Characterization of Structural Dynamic Responses under Uncertainties: from Order-Reduced Simulation to Data-Driven Emulation" (2012). Master's Theses. Paper 325. | <urn:uuid:9c940dda-9a85-4417-ad78-aaf75db6bd57> | {
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Venkatesha, KS and Ramamurthy, TS and Dattaguru, B (1996) Generalized Modified Crack Closure Integral (GMCCI) and its Application to Interface Crack Problems. In: Computers and Structures, 60 (4). pp. 665-676.
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It is well known that at an interface crack tip, mode mixity exists even under single mode loading situations. The modified crack closure integral (MCCI) technique together with finite element analysis has been extensively used in the past to estimate the mixed mode strain energy release rate (SERR) components at these crack tips. One of the aspects which attracted considerable attention in these problems is the convergence of SERR components as the virtual crack extension size is progressively decreased to zero. Such studies have proved to be computationally expensive as the problem has to be solved each time for various sizes of virtual crack extension. Also it was not possible to estimate the effect of preventing the crack face interpenetration on SERR estimates for large sizes of virtual crack extension greater than the contact zone size. To overcome these in this paper, a generalized modified crack closure integral (GMCCI) algorithm is proposed for four and eight-noded isoparametric quadrilateral elements, which can estimate the SERR components for several sizes of virtual crack extension through a single finite element analysis. This is achieved through a numerical integration of the crack closure integral (CCI) and for various sizes of virtual crack extension covering a large number of equal or unequal size elements ahead and behind the crack tip. The procedure developed is demonstrated with application to typical interface crack problems under remote tension and shear.
|Item Type:||Journal Article|
|Additional Information:||Copyright of this article belongs to Elsevier.|
|Department/Centre:||Division of Mechanical Sciences > Aerospace Engineering (Formerly, Aeronautical Engineering)|
|Date Deposited:||27 Dec 2006|
|Last Modified:||19 Sep 2010 04:33|
Actions (login required) | <urn:uuid:7f5978a4-fa14-43ae-a6e9-bd71148d0f89> | {
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Due to recent trends in society, enhanced car safety is strongly required. To prevent traffic accidents, it is important to estimate the direction of approaching vehicles at intersections. Conventional research employs the cross correlation of a 4-microphone array to detect a single approaching vehicles, the detection of multiple vehicles has not yet been attempted. This paper describes a technique that uses a linear microphone array with four microphones to detect two approaching vehicles simultaneously. Field trials show that the proposed scheme offers accurate direction estimation of two approaching vehicles.
Date of Conference: 26-29 Oct. 2010 | <urn:uuid:21f46b10-464d-425e-8c6a-7f04ccb78350> | {
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The effect of 1.75-D array element height on time-shift compensation is analyzed using a two-dimensional array system and a distributed aberration phantom. The analysis uses hydrophone measurements of transmit beams. The results indicate that, for imaging at 3 MHz through aberration representative of the abdominal wall, similar focus compensation performance can be expected from arrays with element pitches less than or equal to 3.0 mm.
Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on (Volume:49 , Issue: 9 )
Date of Publication: Sept. 2002 | <urn:uuid:fe4e3731-5395-4365-a923-30f3c22e9544> | {
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a1 Department of Chemical Engineering, Indian Institute of Science, Bangalore 560012, India
A fluctuating-force model is developed for representing the effect of the turbulent fluid velocity fluctuations on the particle phase in a turbulent gas–solid suspension in the limit of high Stokes number, where the particle relaxation time is large compared with the correlation time for the fluid velocity fluctuations. In the model, a fluctuating force is incorporated in the equation of motion for the particles, and the force distribution is assumed to be an anisotropic Gaussian white noise. It is shown that this is equivalent to incorporating a diffusion term in the Boltzmann equation for the particle velocity distribution functions. The variance of the force distribution, or equivalently the diffusion coefficient in the Boltzmann equation, is related to the time correlation functions for the fluid velocity fluctuations. The fluctuating-force model is applied to the specific case of a Couette flow of a turbulent particle–gas suspension, for which both the fluid and particle velocity distributions were evaluated using direct numerical simulations by Goswami & Kumaran (2010). It is found that the fluctuating-force simulation is able to quantitatively predict the concentration, mean velocity profiles and the mean square velocities, both at relatively low volume fractions, where the viscous relaxation time is small compared with the time between collisions, and at higher volume fractions, where the time between collisions is small compared with the viscous relaxation time. The simulations are also able to predict the velocity distributions in the centre of the Couette, even in cases in which the velocity distribution is very different from a Gaussian distribution.
(Received December 20 2008)
(Revised October 14 2009)
(Accepted October 14 2009) | <urn:uuid:f67c32ba-ea72-443b-8b8a-ae6a8fc41be0> | {
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Finite element aided tracking of signal intensity changes in deforming intervertebral disc tissue
Tracking of signal intensity changes in soft tissue over time is often hampered by deformation of the tissue. In this study a method is described that uses finite element modeling to compensate for tissue deformation. The method is applied to the quantification of fluid redistribution in an intervertebral disc that deforms under mechanical load. The clinical importance of this application emerges from the increased susceptibility of the intervertebral disc to damage after a period of mechanical loading. The study shows that the use of the finite element aided approach results in a detailed map of tissue MRI signal changes, where the distorting effects of tissue deformation are eliminated.
- *Magnetic Resonance Imaging
- Stress, Mechanical
- *Models, Theoretical
- Intervertebral Disk/*anatomy & histology | <urn:uuid:3afe3fdd-6409-4745-a010-a28def8afa57> | {
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US 4808266 A
Continuous elimination of at least part of the liquid contained in a layer formed by depositing a liquid compound having a low solid matter content on a mobile, continuous, liquid-porous support, is effected by dripping, pressing and evaporation while the layer is maintained on the formation support without transfer. Evaporation means include means for passing a heated, gaseous flux through the layers.
1. A process for the continuous removal according to a paper production process of at least a portion of the liquid in a layer formed by pouring from a headbox, on a moving, continuous, liquid-porous formation support, of a liquid suspension comprising highly absorbent cellulose fibers having a polymerized olefinic monomer grafted thereon and having hydrolyzable functional groups, and said liquid to be removed comprising an alcohol selected from the group consisting of ethyl alcohol, methyl alcohol, isopropyl alcohol and mixtures thereof, said suspension having a solid matter content of less than about 10% by weight, said liquid being removed by gravitational dripping and/or by suction, by pressing, and evaporation, to form a paper layer of said grafted cellulose fibers, the improvement comprising that all of these liquid removal operations bring the layer to a solid matter concentration greater than about 30% and are performed on a single porous substantially horizontal formation support, and wherein the evaporation of a part of the liquid in the layer deposited on said formation support is achieved by passing a nitrogen flux through the layer and further wherein the layer is sandwiched between the formation support and a continuous porous upper support during the entire liquid removal treatment.
2. Process according to claim 1, wherein all of the operations are performed in a closed chamber.
3. Process according to claim 2, wherein the chamber is provided with a nitrogen atmosphere.
4. The process according to claim 3 wherein the dry matter concentration of the liquid in the headbox is less than 1%.
5. In a process for the continuous removal according to a paper production process of at least a portion of the water in a layer formed by pouring from a headbox, on a moving, continuous, liquid-porous formation support, of a liquid composition composed of an aqueous suspension of cellulose fibers having a solid matter content of less than about 10% by weight, said water being removed by gravitational dripping and/or by suction, by pressing, and by evaporation, to form a cellulose-fiber based paper layer with a basis weight under 30 g/m.sup.2, the improvement comprising that all of these water removal operations bring the layer to a solid matter concentration greater than about 30% and are performed on a single porous substantially horizontal support, which is the porous formation support for the layer, and wherein the evaporation of a part of the water in the layer deposited on said formation support is achieved by passing hot air through the layer and further wherein the layer is sandwiched between the formation support and a continuous porous upper support during the entire water removal treatment.
6. The process according to claim 1 wherein the dry matter concentration of the liquid in the headbox is less than 1%.
This application is a continuation of application Ser. No. 809,047 filed on Dec. 16, 1985 now abandoned.
1. Field of the Invention
This invention pertains to the elimination of at least a portion of the liquid in a layer formed by the depositing, especially through the use of paper producing process, of a liquid compound with a low dry material (solid) content, on a mobile, continuous, liquid-porous support. The invention pertains specifically to the continuous production of a layer, by the depositing, on a mobile, continuous, porous support, of a liquid compound with a low dry material content, especially a liquid compound containing cellulose fibers, with the deposited layer having insufficient mechanical properties, during the liquid extraction phase, to allow the transfer from one support to another at a high speed.
2. Background of the Prior Art
The removal of the liquid portion of a layer with a low solid matter content is a problem which is encountered in various industries. This occurs in the removal of water from sediments, for example, sediments obtained in purification stations or those which one seeks to refine, especially as fertilizers.
This can also be useful in the paper industry, in which a liquid compound with a low paper fiber content is deposited on a mobile, porous cloth, to form a layer from which the liquid portion is subsequently extracted.
Although the invention pertains to various industries, the following description will be especially directed towards the application of the invention to the paper industry. In accordance with the invention, "paper" is defned as any cellulose fiberbased material, in the form of layers or sheets.
In the industrial production of paper, a liquid compound with a low paper fiber content, i.e., a low dry content, is poured on a continuously moving porous cloth. To pass from the liquid layer deposited on the formation cloth to the fibrous solid layer, the liquid is eliminated first by a gravitational dripping step, and/or by a suction through the porous cloth, by pressing between cloths and/or rollers; this operation can take place on the initial cloth, i.e., the layer formation cloth, or on one or several other subsequent cloths. After this, the fibrous layer is removed from the last cloth on which it was deposited so that it can be heated, for example, through contact with hot cylinders, so that more of its liquid content can be removed by evaporation. The elimination of liquid by dripping, then by pressing, then by heating and evaporation, is performed while the fibrous layer or bed is placed on different supports, the passage from the formation support to the subsequent support generally being done while the dry matter content is under 30%. Patent publication GB-A No. 1 389 992 describes such a liquid removal process with passage from one support to another.
In the specific case of low basis-weight papers, i.e., basis weights under about 30 g/m.sup.2, the removal of water by evaporation is effected on a single drying cylinder and the transfer of the sheet of paper from the porous formation cloth to the drying cylinder is performed while the dry matter concentration is about 20% to 30% by weight. This implies that the production capacity of a line for low basis weights is limited by the diameter of the drying cylinder.
Other processes or devices for the removal of a portion of the water from a liquid compound with a low dry matter content, or those which are more concentrated, such as a slurry, are known. Thus, patent publication No. GB-A-2 047 396 describes a drying device for a slurry, by dripping, with suction, followed by evaporation of the water. Water extraction is not done in a continuous and effective manner in this case.
Accordingly, a need continues to exist for an effective method of removing liquid from a liquid compound layer with low solid content.
The invention proposes a new process for the continuous extraction of at least a portion of the liquid in a layer formed by continuous depositing on a mobile, porous support, of a liquid compound with a low dry matter (solid) content. According to the invention, the liquid is at least partially eliminated from the layer by gravitational dripping and/or, if need be, by suction, by pressing, and by evaporation, with all of these operations being effected while the layer is deposited on a same liquid-porous cloth, which is the formation support for the layer, thus, without any transfer from one support to another.
The process in accordance with the invention allows the continuous and rapid elimination of a quantity of liquid which can bring the layer to solid matter content level between about 30 and 100%, without said layer leaving the formation support, beginning with a liquid compound with a dry content under about 10% and preferably under 1%.
According to one advantageous characteristic of this procedure, the liquid is evaporated from the layer deposited on the formation support by the passage of a flow of gas through the layer. This can be a flux of air, nitrogen or another gas, depending especially on the nature of the liquid to be eliminated, as described in further detail below.
According to another advantageous characteristic of the invention, a second cloth or band is used, which sandwiches the layer to be processed between itself and the cloth utilized for the entire treatment. In one form of the process, the layer to be processed is sandwiched between the two cloths for only a part of the liquid extraction process. In one variation, the second cloth is utilized during essentially the entire liquid elimination treatment. The utilization (or not) of a second porous cloth in one or several areas, or in essentially the entire treatment, is dictated by the nature of the layer to be treated, i.e., especially its composition, its mechanical resistance in the forward direction, and also the liquid to be eliminated.
"Pressing", according to the invention, is defined as all operations tending to exert a pressure on the layer to extract the liquid from it.
Pressing can also vary according to the composition of the layer to be treated. It can vary in intensity and/or in the means implemented to accomplish it. It can vary according to its location, as well as according to the mechanical properties of the layer to be treated, at a precise location. It can also be of progressive intensity.
The process in accordance with the invention applies to the removal of a liquid, which can be water or any other diluting agent, allowing the formation of the layer on a porous formation support, for example, an alcohol, or a mixture of alcohols, chosen notably from the methyl, ethyl, or isopropyl alcohols.
Layers which can be treated according to the invention are any layers which are formed by the continuous depositing of a highly dilute liquid compound, on a continuously moving liquidporous support. These are, for example, layers containing sediments which must be dried, either to remove them without expending large amounts of energy, or to refine them. Included also are fiber-based layers, and, specifically, modified or unmodified cellulose fiber-based layers.
Thus, an advantageous application of the process consists of utilizing it for the production of beds or layers of fibers, especially for paper production, i.e. for the elimination of water or other diluting agents from liquid layers containing cellulose fibers, deposited on a porous formation cloth.
In addition, because the layer is maintained, according to the invention, on one support during the entire liquid removal treatment, the invention applies especially and advantageously to layers which are very fragile or which have very low mechanical resistance in the forward direction, and especially those which are not self-supporting.
Thus, the invention applies especially to the production of very low basis weight papers, which cannot be produced without the risk of tearing on a conventional paper production line, which requires a high-speed transfer of the fibrous layer from the formation cloth to cylinders for pressing. By using a continuous and single support for the entire treatment to remove the liquid contained in the layer, there is no risk of tearing this layer during treatment.
The invention thus applies advantageously to the production of paper with basis weights under about 30 g.
The invention also advantageously applies to the removal of liquid from a layer containing grafted cellulose fibers and especially to the production of dry, highly absorbant cellulose materials, i.e., those with a high capacity to retain water and physiological liquids. Thus, the invention applies in particular to the elimination of water from a fibrous layer of a material formed, for example, as the result of the following operations:
the cellulose contained in cellulose paste is activated,
a polymerizable monomer is grafted at olefinic nonsaturation, having functional groups which can be hydrolyzed on the cellulose,
the grafted cellulose paste is hydrolyzed with an alkali, the product is washed with water until it reaches a maximum state of expansion,
the product is acidified to a pH such that, after the water is eliminated, it is at a minimum state of expansion, the product is transformed into its salt form, in the presence of a water-miscible liquid,
and the liquid is eliminated after the formation of a layer conforming to the invention.
The water-miscible liquid is generally an alcohol such as methyl, ethyl or isopropyl alcohol, such that the liquid removal according to the invention consists of eliminating this alcohol.
The evaporation of the liquid in the layer supported by the porous cloth is advantageously improved through the use of a flow of gas passing through the layer. This gas flux can consist of a flow of hot air. In one variation, it can be a flow of nitrogen.
The evaporation treatment post is advantageously placed in a closed chamber in cases in which the liquid to be removed from the layer is an organic liquid, especially to avoid harmful fumes. Moreover, all of the liquid elimination operations can be conducted in a nitrogen atmosphere, if needed.
The invention also applies to the removal of liquid contained in superimposed layers by simultaneous or successive jets.
The invention also pertains to a device to eliminate the liquid part of a layer formed continuously by depositing a highly dilute compound on a moving support.
The device in accordance with the invention comprises a moving support cloth, which is continuous, porous to the liquid to be eliminated, extending over the entire area of the device, means to deposit the liquid compound on the porous cloth, with these means being placed in the upsteam part of the device, means to eliminate a part of the liquid by pressing, means to eliminate another part of the liquid by evaporation, with all of these means being placed above and/or below the porous cloth supporting the poured layer, with the porous cloth having characteristics such that it permits drippng, pressing, heating, etc...
In addition, to accentuate the pressing, the device can include a wide variety of pressing means, which are known especially in the paper producing industry, for example, one or several pair of cylinders between which the layer to be treated is pressed, one or several toggles, etc...
One embodiment of the device also comprises an upper band or cloth which, combined with the lower depositing cloth, sandwiches the layer to be treated in at least one of the liquid removal areas. When the device is utilized to treat particularly fragile layers, this second band maintains the layer to be treated in a sandwich, preferably from the time it is formed or immediately thereafter, until the end of the treatment.
When the device is utilized to remove an organic liquid, such as alcohol, the complex can be placed in an enclosed chamber under an atmosphere which is inert with respect to the liquid to be removed from the layer.
The means to remove the liquid by evaporation are advantageously means which create a flow of gas passing through the layer. These means can comprise suction vessels and their associated blowing vessels, which are placed opposite the suction vessels on both sides of the porous support cloth.
Other characteristics and advantages of the invention will emerge in the examples for the embodiment of the device according to the invention.
FIG. 1 shows a device utilized for the production of a very low basis weight paper.
FIG. 2 shows a device utilized for the production of a highly absorbant layer made of grafted cellulose fibers.
The device shown in FIG. 1 comprises a continuous support cloth 1, which is kept stretched between the rollers 101 and especially its upper part, between an upstream roller 2 and a downstream roller 3. In the upstream part of the device, a headbox 4 extends transversally above the cloth 1. Located further downstream, the device is endowed with a press, which is comprised of two rollers 5 and 6, placed on both sides of the transporting cloth. A vat 7 is placed under the upper part of the transporting cloth, to collect the liquid removed by and pressing.
Downstream from the press, the device has means 8 to remove water by evaporation. Here, these means are comprised of a succession of gaseous flux blowing vessels 9 and suction vessels 10, arranged above and below the transporting cloth. Each blowing vessel faces a suction vessel on the opposite side of the cloth. These vessels are fed with hot air 11.
The operation of the device is described in relation to the production of paper with a basis weight of 10 g/m2. Aqueous paper compound 102, with a dry matter concentration of about 0.2% is brought to the headbox, from which it is poured to form a layer of liquid with a homogeneous thickness, on the support cloth 1.
While it is transported, a part of the water 12 is eliminatetd by dripping, passing through the porous cloth 1 by force of gravity. More of the water is removed by pressing, in which it is pressed between the two rollers 5 and 6. The water which passes through the porous cloth 1 is collected in the vat 7. In passage between the blowing vessels 9 and suction vessels 10, an additional quantity of water is removed in the form of steam 13 by the hot air flow. At the end of the device, the sheet of paper 14 is removed from the cloth, to be rolled on a reel 15 and stored.
The device shown in FIG. 2 is utilized in the production of a highly absorbant grafted cellulose fiber-based layer. This device comprises a continuous support cloth 21, whose upper part is kept stretched between rollers, notably an upstream roller 22 and a downstream roller 23. Rollers 24, 25, some of which 25 have adjustable positions, act on the lower part of the cloth and allow it to be properly stretched. A second porous cloth 26 is placed above the first cloth, parallel to it, streteched between rollers, notably an upstream roller 27 and a downstream roller 28. Rollers 29, 30, some of which 30 have adjustable positions, stretch the cloth 21 appropriately. A headbox 31 extends transversally above the lower support cloth, upstream from the roller 27. The device is also endowed with a press 32, comprised of two rollers 33 and 34, placed on both sides of the two cloths. Between the roller 27 and the press 32, three rollers 35, 36, 37, constitute a toggle for the two cloths. There is a vat 38 located under the upper part of the lower transporting cloth 26, to collect the liquid removed by dripping and pressing. Downstream from the press 32, the device is equipped with means 39 to eliminate liquid by evaporation. These means are gaseous flux blowing vessels 40 and suction vessels 41, placed above and below the two cloths. Each blowing vessel faces a suction vessel on the opposite side of the two cloths. These vessels are fed with nitrogen 42.
The whole complex is described in relation with the production of a sheet of highly absorbant cellulose material.
A liquid compound 103 containing modified cellulose fibers on which a polymer is chemically bonded in the form of an alkaline metal salt coming from a monomer which can be polymerized at olefinic non-saturation, in a mixture of ethyl alcohol and ammonia solution, having a dry matter concentration of about 0.3%, is brought to the headbox, from which it is made into sheets on the transporting cloth 21. The liquid layer is carried by said cloth and it is sandwiched between this cloth 21 and the upper cloth 26. A part of the liquid 44 is eliminated by dripping and pressing through the lower cloth 21 and is collected in the vat 38, under the cloth 21 to be subsequently recycled. The pressing is accentuated at the passage of the toggle. The layer, still sandwiched between the two cloths, next passes between the two press rolls, which further supplements the pressing. The layer next passes between the blowing and suction vessels. At this time a flow of nitrogen 42 passing through the upper cloth eliminates an additional part of the liquid through evaporation by contact with the flux 42. The gaseous nitrogen current laden with the gaseous alcohol--ammonia solution mixture 45 passes through the lower cloth, passes into the suction vessels and is sent to an additional steam collection device (not shown). When it issues from the vessel zone, the layer, which is still between the two clothes, is dry. After the upper cloth is removed from the fibrous layer, it separates from the lower cloth, and the layer is rolled on a reel 46 through the use of a rolling device 45.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
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US 4842924 A
A process for fabricating a composite in the form of a network of microfibrils which includes interpenetrating the microfibrils with a matrix material to form a composite which includes two continuous interpenetrating phases, a matrix-material phase and a microfibrillar-reinforcing-network phase. There is disclosed composites in the form of a fiber and in the form of a film.
1. A composite that comprises a network of interconnected microfibrils of rigid polymer chains that are oriented along the long axis of the microfibrils and constitute one continuous microfibrillar-network-reinforcing phase of the composite, and a solid-matrix material interpenetrated within the three dimensional network and adhered to the microfibrils of the three dimensional microfibrillar chains to constitute a second continuous phase, in which the matrix phase serves to transmit at least one of enhanced shear forces, compression forces and tension forces between the microfibrils.
2. A composite according to claim 1 in which the matrix material is taken from the group consisting of cross-linkable organic materials.
3. A composite according to claim 1 in which the matrix material is an inorganic.
4. A composite according to claim 1 in which the matrix material is a glass.
5. A composite according to claim 1 in which the matrix material is sodium silicate.
6. A composite according to claim 1 in which the composite is a fiber and in which the microfibrils are oriented along the long axis of the fiber and constitute one continuous microfibrillar-reinforcing phase of the fiber.
7. A composite according to claim 1 in which the composite is formed in the form of a mat.
8. A multilayered composite that comprises a plurality of layer of the mat in claim 7 formed one upon the other and cured, whereby the solid-matrix material serves, upon curing, as a binder between layers.
9. A composite according to claim 8 in which individual microfibrils have cross-dimensions between about 50 Å and 100 Å, in which adhesion between the microfibrils is about as strong as cohesion within the microfibrils and in which the microfibrils are oriented along the long axis of the composite and constitute one continuous microfibrillar-network-reinforcing phase of the composite.
10. A composite according to claim 1 in which the polymers that form the microfibrils are taken from the groups consisting of aromatic polyamides; polyhydrazides and polyamide-hydrazides; aromatic-heterocyclic polymers; poly isocyanates; cellulose and its derivatives; polyamino acids and copolymers thereof.
11. A composite according to claim 10 in which the aromatic polamides are taken from the groups consisting of poly(p-benzamide) (PBA) and poly(p-phenyleneterephthalamide) (PPTA); the aromatic-heterocyclic polymers are taken from the groups consisting of poly(p-phenylene benzobisthiazole) (PBT), poly(p-phenylene benzobisoxazole) (PBO), poly(p-phenylene benzobisimidazole) (PDIAB), poly(2,5(6)benzothiazole) (AB-PBT), and poly(2,5(6)benzimidazole) (AB-PBI); the cellulose and its derivatives is taken from the group consisting of cellulose, cellulose acetate, and hydroxypropyl cellulose; and the polyamino acids are taken from the group consisting of poly(γ-benzyl-L-glutamate), poly(ε-carbobenzoxy-L-Lysine), and poly(L-alanine).
12. A composite according to claim 1 is which the matrix materials are taken from the group consisting of: organic materials; monomers which can polymerize to a linear polymer; polymers which can infiltrate after coagulation or can be spun together in solution with rigid-chain polymer in a common solvent; and an inorganic material.
13. A composite according to claim 1 in which adhesion between fibrils of the microfibrils by virtue of the solid-matrix material is about as strong as cohesion between said microfibrils.
14. A composite according to claim 1 in which the composite is one that effectively utilizes the strength and stiffness characteristics of the microfibrils and in which the solid-matrix material enhances those characteristics.
15. A composite according to claim 1 in which the individual microfibrils have cross-dimensions no greater than about 100 Å and the composite is a fiber about ten micrometers in diameter.
16. A composite according to claim 15 in which the individual microfibrils have cross-dimensions between 50 and 100 Å, in which adhesion between the microfibrils is about as strong as cohesion within the microfibrils and in which the microfibrils are oriented along the long axis of the composite and constitute one continuous three-dimensional microfibrillar-network-reinforcing phase of the composite.
17. A composite according to claim 1 in which the microfibrils of rigid polymer chains denote a polymer which has the ability to form a liquid crystalline phase, either in solution or melt, the reinforcing phase in the composite material being an interconnected network and having a typical width three orders of magnitude smaller than other composites.
18. A composite that comprises a three-dimensional network of many interconnected microfibrils, that is, the microfibrils are directly connected to other like microfibrils, of rigid polymer chains that are oriented along the long axis of the microfibrils and of the composite and constitute one continuous three-dimensional microfibrillar-network-reinforcing phase of the composite, and a solid-matrix material interpenetrated within the three-dimensional network and adhered to the microfibrils of the microfibrillar chains to constitute a second continuous phase, in which the matrix phase serves to transmit at least one of enhanced shear forced, compression forces and tension forces between the microfibrils of the composite.
19. A composite according to claim 18 in which said composite is a composite fiber.
20. A composite according to claim 19 in which said fiber is of the order of ten micrometers in diameter.
21. A composite according to claim 18 in which said composite is a composite film.
22. A composite according to claim 21 in which the composite film is the order of ten micrometers thick.
The fiber labeled 1 in FIG. 2 is a composite fabricated in accordance with the present teachings. It includes a network of interconnected microfibrils (see the network labeled 2 in FIG. 1B) in which the microfibrils labeled 3 in FIG. 1B are oriented generally along the long axis of the fiber and constitute one continuous microfibrillar-network-reinforcing phase of the composite 1 in FIG. 2. The other phase of the composite, as explained in some detail later herein, is a matrix material which, in the composite fiber, is a material that serves to transmit shear forces, compression forces and tension forces between the microfibrils 3. In the final product, the matrix material fills the gaps (i.e., the spaces between the microfibrils 3) labeled 4 in FIG. 1B, but, as later noted, at the state of the network in FIGS. 1A and 1B the gaps 4 are filled with a coagulant (e.g., water). The dark parts in FIG. 2 (which is an electron micrograph) are the microfibrils 3 and the light parts consist of the matrix material. For example, the microfibrillar network 2 can be formed in apparatus like the system in FIG. 4 during the dry-jet-wet spinning of solutions of poly(p-phenylene benzobisthiazole) which is called PBT. The coagulation (i.e., phase separation) of lyotropic liquid crystalline polymers from solution under certain conditions yields 50-100 Å diameter microfibrils of the rigid-chain polymer which forms a three-dimensional network of the microfibrils with surprisingly high mechanical integrity. The present invention utilizes the microfibrillar network formed by rigid-chain polymers in a composite that effectively utilizes the strength and stiffness of the microfibrils and enhances those characteristics.
The phase separation of rigid-chain polymers from solution into microfibrils is discussed, for example, in: W. G. Miller et al., in J. Polym. Sci., Polym. Symp., 65, 91 (1978); K. Tohyama et al., Nature, 289, 813 (1981), and elsewhere.
One system for producing a network of microfibrils is the dry-jet/wet-spinning system labeled 20 in FIG. 4 for PBT or other materials. The polymer chain axis in the fiber or film thus formed is oriented parallel to the long axis of the microfibrils, as shown in FIG. 1B.
The polymer from which the network is formed is first in the form of a polymer solution, as above indicated, within an extrusion chamber 6 from which it is emitted through a spinnerette 7 as a highly viscous ribbon (or film) or fiber 5 which is formed between the spinnerette and a coagulation (e.g., water) bath 8. Essentially what occurs in the system 20 is that the viscous polymer solution at 5 is stretched before it enters the coagulation bath 8 where it takes the form shown in FIGS. 1A and 1B. In that form the microfibrils are from 50-100 Å in diameter with a coagulant (e.g., water) between them. These water-filled microfibrillar networks exhibit significant tensile force at break as indicated by the lower curve labeled WC in FIG. 5. The upper curve, labeled AS, is that of the dried material, and the relative strengths are not significantly different from one another. (It should be noted at this juncture that the resulting product can be a fiber typically about ten micrometers in diameter or it can be a film about ten micrometers thick but much wider, depending upon the geometry of the die through which the viscous ribbon or fiber 5 is emitted.)
The swollen fiber/film in the bath 8 passes around take-up rolls 9 and 11 and is wound around a roll 12, but can pass around the roll 12 to a further wrapping roll (not shown). According to the present teaching, the fiber/film within the bath (which is numbered 13 for present purposes) is that which is used; that is, the microfibrillar mesh is not dried (as shown in FIG. 1C) but is, rather, treated while in the wet state, as depicted by the diagrammatic representation of FIG. 1B.
The object of this stage of the process is to introduce the matrix-forming material into the microfibrillar network formed as described before. This can be achieved by collecting the microfibrillar mesh 13 on the roll 11 which can take up the fiber or film for further treatment. Irrespective of how the mesh 13 is collected, it is subjected to a process whereby a matrix-forming material is introduced by a diffusion process of the matrix material or its precursor. If the matrix-forming molecules are soluble in the coagulant (e.g., water), they can be added in increasing concentration into the coagulant in which the microfibrillar mesh is immersed, or the collected mesh can be placed in solutions of increasing concentration of matrix-forming material, without allowing it to dry. Alternatively, the coagulant can be gradually replaced by solvent in which the matrix-forming material is soluble, and which is miscible with the coagulant. This solvent is then gradually exchanged by the matrix-forming material as explained above.
After the matrix-forming material is infiltrated into the microfibrillar mesh, whether in the form of fiber or film, excess coagulant or solvent (if any) is dried. If the matrix-forming material is a reactive mixture of organic material, it can be cured to form a solid matrix within the individual fiber or film, thus forming a microfibrillar-network-composite fiber or film.
Alternatively, the fibers and films impregnated with the matrix-forming material may be laid out as desired, such as depicted in FIG. 3, and subsequently solidified so that the matrix material also serves to bond the individual microfibrillar-network-composite fibers or films together.
By way of illustration, if the microfibrillar network used is made of PBT, and the coagulant is water, the microfibrillar mesh is placed in alcohol-water mixtures of increasing alcohol content, without drying, until water is totally replaced by alcohol. It is then introduced into solutions of an epoxy resin in alcohol with increasing epoxy resin content. This resin includes all the components (epoxide, hardener and catalyst) needed to form a suitable epoxy-matrix material upon curing. Then the microfibrillar network with the epoxy resin within it is suitably treated to solidify the matrix material.
As is noted above, in conventional composite fibers, the reinforcing fibers are typically about ten micrometers in diameter. In the present material, the composite fiber 1 in FIG. 2 is also about ten micrometers in diameter, but it is made up of microfibrils 3 (FIG. 1B) that are about 50 to 100 Å in diameter, and these microfibrils are interconnected to one another by microfibrillar interconnection; then they are connected, as well, by the solid-matrix material which, as before noted, transmits forces among the microfibrils 3. The adhesion between fibrils by virtue of the solidified-matrix material is about as strong as cohesion within the microfibrils. In addition to PBT, a number of polymers can be employed to produce the microfibrillar networks 3 as illustrated in the Table I below.
1. Aromatic polyamides:
2. Polyhdrazides and polyamide-hydrazides
3. Aromatic-heterocyclic polymers
poly(p-phenylene benzobisthiazole) (PBT)
poly(p-phenylene benzobisoxazole) (PBO)
poly(p-phenylene benzobisimidazole) (PDIAB)
4. Poly isocyanates
5. Cellulose and its derivatives
6. Polyamino acids
and copolymers of the above
The coagulated PBT (or other fibers) 2 (i.e., formed of interconnected microfibrils 3) can consist of as much as 95 percent coagulant. That coagulant, as noted, can be first replaced by a compatible solution which is replaced by the matrix material; or a compatible solution such as water-soluble sodium silicate can be used when the coagulant is water. Later, excess solvent or coagulant is dried off, and the composite is treated to render the matrix material solid.
The only requirement for impregnation of coagulated fibers (or films) with a matrix material is that the matrix material or matrix precursor readily diffuse into the fibrillar network and replace the coagulant. Consequently, there are numerous organic and inorganic materials that may be selected as candidates for matrices to tailor the properties of microfibrillar-network composites. Examples of potential matrix materials include: (1) thermosetting polymers that may be extended to other systems such as urethane and other low-viscosity reactants which diffuse into microfibrillar networks and replace coagulant, the composite being formed by polymerization and cross-linking after impregnation; (2) thermoplastic polymers wherein a thermoplastic matrix if formed by monomer impregnation, followed by polymerization (for example, caprolactam may be substituted for coagulant and subsequently polymerized in situ to nylon-6) and (3) low-molecular weight materials, crystalline and amorphous organic and inorganic materials that are selected to form composites with unique compositions. Organic matrixes can be heat treated in situ to form a carbon matrix; ceramics and glasses can be introduced into the microfibrillar network from solution. For example, soluble silicates can be deposited in a microfibrillar network to form a continuous glass-matrix phase; and low-melting soluble glass formulations can be used to allow fusion of the glass matrix after deposition from solution.
As indicated above, substances that form the basis for the matrix material must be such that in solution such substances are able to diffuse into the microfibrillar network. These substances can be compatible with the coagulant so that a very concentrated solution thereof will result in the matrix-forming substance diffusing into the replacing most or all of the coagulant; or an intermediate step using a compatible solvent can be employed to remove the coagulant, the compatible solvent then being replaced by a substance which forms the matrix material.
Example of matrix-forming materials are given below.
I. Organic materials which can be polymerized to form a cross-linked network.
A. Epoxy resins
The infiltration mixture should include all the reaction components, i.e., epoxide, cross-linking agent and catalyst.
The epoxide can be of the following class: aromatic, aliphatic, cycloaliphatic.
The cross-linking agent can be either of the anhydride or amine type.
__________________________________________________________________________Examples:Epoxide Cross-linking Agent Catalyst Comments__________________________________________________________________________*Epon Boron triflouride- -- aromatic mono-ethyl-amine epoxide complex (BF.sub.3 MEA)*ERL nonenyl succinic dimethyla- eycloaliphatic(Vinyl cyclo- mino-ethanol epoxide ("Spurr Resin")hexene dioxide)diglycidyl ether dodecenyl succinic 2,4,6 tris- aliphaticof polypropylene annhydride (diamethyl- epoxideglycol DER amino-ethanol)__________________________________________________________________________ *These formulations have been tested. .sup.(1) Shell Chemical Corporation. .sup.(2) Union Carbide Corporation. .sup.(3) Dow Chemical Corporation.
B. Phenolic resins
E.g., a novolac with hexamethylene tetramine.
C. Silicone resins
1. Polyamic-acid precursor (e.g., Skybond 703
2. Imide oligomers or bisimide monomers containing unsaturated aliphatic end groups.
E. Polyurethanes and polyureas
II. Monomers which can polymerize to a linear polymer.
A. Heterocyclic monomers
(1) ε-caprolactam (forming nylon 6)
(2) ε-caprolactone (forming polyester)
B. Vinyl monomers with suitable initiator
E.g., styrene, methyl methacrylate, acrylonitrile.
III. Polymers infiltrated after coagulation, or spun together in solution with the rigid-chain polymer in a common solvent.
polyamides (Nylon 6, Nylon 6,6)
poly ether ketone (PEEK)
cellulose nitrate (lacquer)
IV. Inorganic materials.
A. Silicates sodium silicate, potassium silicate, and water soluble formulations of the above.
(1) Na.sub.2 O: 3.3 SiO.sub.2 (40
(2) Mixtures of (1) with metal oxides (such as zinc oxide, magnesium oxide) which render the glass fusible at moderate temperature so that a homogeneous interconnected glass matrix if formed
B. Silicon alkoxides
E.g., tetraethyl orthosilicate
The batch process referred to above can be employed, but a step-saving variation of the fabrication of microfibrillar-network composites is to spin polymer fibers into a coagulation bath containing a matrix precursor. This would eliminate the need for a diffusion controlled exchange of matrix for coagulant. Also, multiple loops of the fiber at 13 can be employed with multiple chambers of concentrated-matrix material.
A suitable matrix-forming material may also be dissolved together with a rigid, microfibril-forming polymer, in a common solvent prior to the formation of a fiber or film such as in the spinning apparatus shown in FIG. 4. For example, a solution of PBT and nylon can be formed in methane sulfonic acid at room temperature. The solution thus prepared can be extruded to form fibers or films using an apparatus such as shown in FIG. 4. Upon coagulation, such as in a water bath (8 in FIG. 4), the rigid polymer will form an interconnected microfibrillar network, interpenetrated with the matrix material if the ratio of the rigid polymer to the matrix-forming material is high enough (e.g., above 1:3 weight). The spaces between the interconnected microfibrils are filled with both matrix material and coagulant. Removal of coagulant, as by drying, retains an interconnected rigid microfibrillar network, interpenetrated with the matrix material.
Advantages that may be realized from use of microfibrillar networks as reinforcement for composite materials include among others: (1) tremendous increase in interfacial surface area (improvements in utilization of reinforcement properties, toughness and mechanical energy absorption characteristics; furthermore, the network provides a tortuous path for crack propagation to reduce the tendency to fail catastrophically); (2) reduction of residual stresses and voids in the reinforcement phase (collapse of the coagulated fiber or film with drying is prevented by impregnation with a matrix); (3) because the microfibrillar-network composite is composed of two interpenetrating phases, transfer of external loads to each phase does not require a strong interfacial bond (therefore, microfibrillar-network composites may be designed to allow each phase to contribute to different material properties such as, for example, the polymer network can provide tensile strength while a ceramic or glassy matrix can provide compressive strength to the composite); and (4) microscopic fibers of rigid-rod polymers are composed of microfibrils which have been brought into contact after coagulation via drying and, therefore, the properties of such fibers can never equal those of the microfibrils. Unless the adhesion between microfibrils can be made as strong as the cohesion within microfibrils, the microfibrils will be the superior form of the polymer for reinforcement.
Modifications of the invention herein disclosed will occur to persons skilled in the art and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.
The invention is hereinafter described with reference to the accompanying drawing in which:
FIG. 1A is greatly enlarged a longitudinal view of a diagrammatic representation of a fiber in the form of an oriented network or mesh of microfibrils with a coagulant (e.g., water) within the network of microfibrils;
FIG. 1B shows a greatly enlarged view of the region designated 10 in FIG. 1A;
FIG. 1C shows the fiber of FIG. 1A after drying to remove the coagulant within the mesh;
FIG. 2 is an electron micrograph of a longitudinal view of a fiber like the fiber in FIG. 1A except with the coagulant within the mesh replaced by a matrix material in accordance with the present teaching;
FIG. 3 is an isometric view of a multilayered composite formed of fibers, like the fiber in FIG. 2, into a film and then formed in multilayers of the film;
FIG. 4 is a schematic of dry-jet/wet-spinning apparatus operable to form the oriented network of microfibrils shown in FIG. 1A;
FIG. 5 shows the tensile force-strain behavior of coagulated fibers of the type shown in FIG. 1A (curve WC) and the type in FIG. 1C (curve AS); and
FIG. 6 is a stress-strain curve for a composite fiber as shown in FIG. 2.
The present invention relates to processes for fabricating composites and to composites formed in accordance with the processes.
Prior art, fiber-reinforced composites are fabricated by impregnation of a yarn of fibers, which are typically on the order of ten micrometers in diameter, with a liquid matrix that is subsequently solidified to form a solid composite. The fiber-reinforced composite so formed is essentially a two-phase material composed of a continuous matrix (e.g., epoxy) that binds the more rigid-fiber phase (e.g., glass or carbon). The reinforcing-fiber phase may be either continuous or discontinuous.
An object of the present invention is to provide a new composite material in which the reinforcing phase is an interconnected network of microfibrils of a rigid-chain polymer. As used, the term rigid polymer denotes a polymer which has the ability to form a liquid crystalline phase, either in a solution or melt. The width of these microfibrils is on the order of 100 Å. Thus, the reinforcing phase in the composite material of the present invention differs from that of prior composites by being an interconnected network and by having a typical width three orders of magnitude smaller.
Another object is to utilize the rigid, oriented microfibrillar network for formation of composite fibers and films of enhanced strength characteristics in shear, compression and tension, by judicious combination of microfibril-forming material and matrix material.
A further object is to use the microfibrillar-network composite fibers or films to produce bulk structures of enhanced properties by bonding together the composite fibers or films; the microporous nature of the microfibrillar-network-reinforcing phase allows the precursor of the matrix material, imbibing the microfibrillar network, to be used for bonding between adjacent fibers or films.
Further objects are addressed hereinafter.
The foregoing objects are achieved, generally, in a process for fabricating a composite that includes forming a network of microfibrils of a rigid polymer; and interpenetrating the microfibrils with a matrix material to form a composite that includes two continuous and interpenetrating phases, a matrix-material phase and a microfibrillar-network-reinforcing phase. The objects are achieved also in a film formed in accordance with the foregoing process, a mat formed by weaving or otherwise combining many composites, and a multilayer composite that includes a plurality of the composites, films or mats stacked in layers, one on the other and then solidified so that the matrix material bonds together the films to form a multilayered composite structure.
Citas de patentes | <urn:uuid:c7d4b590-2601-49e3-8298-9acf4545a480> | {
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Toughening of cyanate ester resin by N-phenylmaleimideN-(p-hydroxy)phenyl-maleimidestyrene terpolymers and their hybrid modifiers
Source: Polymer International, Volume 50, Number 3, March 2001 , pp. 290-302(13)
Publisher: John Wiley & Sons, Ltd.
N-PhenylmaleimideN-(p-hydroxy)phenylmaleimidestyrene terpolymer (HPMS), carrying reactive p-hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N-phenylmaleimidestyrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co-continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (Mw 136 000 g mol-1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, Mw 15 500 g mol-1) led to 135% increase in the fracture toughness (KIC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system.
© 2001 Society of Chemical Industry
Document Type: Research article
Publication date: 2001-03-01 | <urn:uuid:732a3d07-1ab2-4ac2-a5d8-7fa5506c815d> | {
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Inertial instability in rotating and stratified flow
Seminar Room 1, Newton Institute
The unfolding of inertial instability in vortices in a uniformly rotating and stratified fluid is studied through numerical simulations. The vortex dynamics during the instability is examined in detail. We demonstrate that the instability is stabilized via redistribution of angular momentum in a way that produces a new equilibrated vortex with a stable velocity profile. Based on extrapolations from the results of a series of simulations in which the Reynolds number and strength of stratification are varied, we arrive at a construction based on angular momentum mixing that predicts the infinite-Reynolds-number form of the equilibrated vortex toward which inertial instability acting alone would drive an unstable vortex. The essential constraint is conservation of total absolute angular momentum. The construction can be used to predict the total energy loss during the equilibration process. | <urn:uuid:8af08f29-f755-4e86-92b0-90bd93b18675> | {
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A series of Pb(Zr,Ti)O3 (PZT) films with tetragonal/rhombohedral multilayered structures has been grown on Pt/TiO2/SiO2/Si substrates by rf magnetron sputtering at a relative low temperature. All the films comprise 12 periodicities of Pb(Zr20Ti80)O3/Pb(Zr80Ti20)O3 in constant thickness of 40 nm, but the layer thicknesses of tetragonal phase (dT) and rhombohedral phase (dR) in one periodicity are varied. The electric properties of the films are investigated as a function of dT/dR from 10/30 to 35/5. An enhanced dielectric property is observed in the multilayered films. Especially, a optimal value of dT/dR = 30/10 is obtained, where the dielectric constant reaches maximum value of 469 at 100 kHz with a loss tangent of 0.037, and the dielectric constant is about five times that of the single tetragonal phase PZT film formed under the identical condition. Moreover, the polarization also increases in the multilayered films, and remarkably, the film of 30/10 exhibits larger remanent polarization, lower coercive voltage, and more symmetric hysteresis than the other films. The enhancement of dielectric properties is attributed to the presence of interfaces between the tetragonal and the rhombohedral phase layer. This study suggests that the design of the multilayered PZT film capacitor with tetragonal and rhombohedral phase should be an effective way to enhance the dielectric and ferroelectric performance in devices. © 2003 American Institute of Physics. | <urn:uuid:3bc6e626-4fe5-4087-bcd0-d1ec8a54856f> | {
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Givelberg, Edward and Bunn, Julian (2003) A comprehensive three-dimensional model of the cochlea. Elsevier . http://resolver.caltech.edu/
See Usage Policy.
Use this Persistent URL to link to this item: http://resolver.caltech.edu/
The human cochlea is a remarkable device, able to discern extremely small amplitude sound pressure waves, and discriminate between very close frequencies. Simulation of the cochlea is computationally challenging due to its complex geometry, intricate construction and small physical size.We have developed,and are continuing to refine,a detailed three-dimensional computational model based on an accurate cochlear geometry obtained from physical measurements. In the model,the immersed boundary method is used to calculate the structure interactions produced in response to incoming sound waves. The model includes a detailed and realistic description of the various elastic structures present. In this paper, we describe the computational model and its performance on the latest generation of shared memory servers from Hewlett Packard. Using compiler generated threads and OpenMP directives,we have achieved a high degree of parallelism in the executable, which has made possible several large scale numerical simulation experiments that study the interesting features of the cochlear system. We show several results from these simulations, reproducing some of the basic known characteristics of cochlear mechanics.
|Item Type:||Report or Paper (Technical Report)|
|Group:||Center for Advanced Computing Research|
|Subject Keywords:||cochlea, immersed boundary method, navier-stokes equasions, parallel computation, shared memory|
|Usage Policy:||You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.|
|Deposited By:||Imported from CaltechCACR|
|Deposited On:||05 Apr 2004|
|Last Modified:||26 Dec 2012 14:31|
Repository Staff Only: item control page | <urn:uuid:72075861-8a6a-4751-84f1-ab6ac23af2cd> | {
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Identification of the through-thickness rigidities of a thick laminated composite tube
Moulart, Raphaël, Avril, Stéphane and Pierron, Fabrice (2006) Identification of the through-thickness rigidities of a thick laminated composite tube. Composites Part A: Applied Science and Manufacturing, 37, (2), 326-336. (doi:10.1016/j.compositesa.2005.05.050).
Full text not available from this repository.
In this paper, a novel experimental procedure is carried out for providing all the through-thickness rigidities of a thick glass-epoxy laminated ring cut from a tube, using only one diametral compression test. The procedure requires first to measure the strain field over a predefined area of the lateral surface of the ring coupon, and then to process it with the Virtual Fields Method. The region of interest where noise effects are minimized is first determined with simulated data. Then, the practical feasibility of the procedure is demonstrated with experimental data. The displacement fields are measured using the grid method. In order to filter the measurement noise at best, the strain fields are derived by polynomial fitting of the displacement fields. The validity of this approach is checked on simulated data. However, the experimentally identified stiffness values appear very scattered from one test to another. This is due to the non-uniform distribution of the load through the thickness, which is a well-known problem when testing thick composites. It has been shown that an optical system providing directly the images of both sides of the specimen can address this issue. Finally, such a system is set-up and successfully applied for identifying all the through-thickness rigidities of the ring.
|Keywords:||optical techniques, anisoropy, mechanical testing, virtual fields method|
|Subjects:||T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TJ Mechanical engineering and machinery
|Divisions:||Faculty of Engineering and the Environment > Engineering Sciences > Engineering Materials Surface Engineering
|Date Deposited:||09 Mar 2012 16:32|
|Last Modified:||09 Mar 2012 16:32|
|Contributors:||Moulart, Raphaël (Author)
Avril, Stéphane (Author)
Pierron, Fabrice (Author)
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
Actions (login required) | <urn:uuid:5ae2e83d-867e-4303-b43e-29431fa91fd5> | {
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KNTU CDRPM is a cable driven redundant parallel manipulator, which is under investigation for possible implementation of large workspace applications. This newly developed manipulators have several advantages compared to the conventional parable mechanisms. In this paper, the governing dynamic equation of motion of such structure is derived using the Newton-Euler formulation. Next, the dynamic equations of the system are used in simulations. It is shown that on the contrary to serial manipulators, dynamic equations of motion of cable-driven parallel manipulators can be only represented implicitly, and only special integration routines can be used for their simulations. In order to verify the accuracy and integrity of the derived dynamic equations, open- and closed-loop simulations for the system is performed and analyzed. Also, the effects of mechanical assembly tolerances on the closed-loop control performance of a cable driven parallel robot are studied in detail, and the sensitivity analysis of the precision in the construction and assembly of the system on the closed-loop behavior of the KNTU CDRPM is performed.
Date of Conference: 12-15 Oct. 2008 | <urn:uuid:6920ef67-0454-4aa6-bd0b-a832e080830e> | {
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This paper proposes a method which consists of a phase shift converter with a current doubler rectifier on the output side, the operating frequency of the phase shift converter being as high as 20-25 kHz (depending on the requirement of the application), ferrite core transformer is used instead of conventional one, which being bulky leads to very large amount of core loss. Unlike the conventional method, number of turns of the transformer is reduced and the overall power density is increased. The current doubler rectifier doubles the input current as needed for few vital applications. The circuit for phase shift converter with the current doubler was simulated using PSPICE SOFTWARE and the following results were obtained. For an input current of 4Amps, an output of 10.2Amps was obtained, that eventually settles at nearly 8.5 Amps. A hardware model of the proposed method validates the results verified with the simulation results.
Date of Conference: 3-5 Jan. 2011 | <urn:uuid:612d6455-3c59-4650-ac41-77e1adef27bb> | {
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Auf dem Publikationsserver der Universität unter:
For interactive construction of CSG models understanding the layout of a model is essential for its efficient manipulation. To understand position and orientation of aggregated components of a CSG model, we need to realize its visible and occluded parts as a whole. Hence, transparency and enhanced outlines are key techniques to assist comprehension. We present a novel real-time rendering technique for visualizing design and spatial assembly of CSG models. As enabling technology we combine an image-space CSG rendering algorithm with blueprint rendering. Blueprint rendering applies depth peeling for extracting layers of ordered depth from polygonal models and then composes them in sorted order facilitating a clear insight of the models. We develop a solution for implementing depth peeling for CSG models considering their depth complexity. Capturing surface colors of each layer and later combining the results allows for generating order-independent transparency as one major rendering technique for CSG models. We further define visually important edges for CSG models and integrate an image-space edgeenhancement technique for detecting them in each layer. In this way, we extract visually important edges that are directly and not directly visible to outline a model’s layout. Combining edges with transparency rendering, finally, generates edge-enhanced depictions of image-based CSG models and allows us to realize their complex, spatial assembly. | <urn:uuid:fd842b5f-2051-4069-95a2-b868c32da1a1> | {
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Design and Simulation of MEMS based Thermally Actuated Positioning Systems
D. Mallick1 P. K. Podder1 A. Bhattacharyya1
1Institute of Radio Physics & Electronics, University of Calcutta, Kolkata, India
With continuous advancement in nanotechnology, requirement is rising for high precision motion controlled positioning system. Such system plays crucial role in the fabrication of micro and nano-sized objects and assemblies. They can be used for automated mask aligner, as biological sensors, in optical technology as deformable mirrors. Most significant requirements for the actuators in a positioner include accuracy, range of motion, degrees-of-freedom, and bandwidth. While most conventional positioning systems are large in size, a major disadvantage of such macro scale positioners is errors like backlash and hysteresis. However using MEMS technology, such systems can be fabricated in wafers. These micro systems have a number of advantages. Firstly, micro-fabrication permits arrays of MEMS positioning stages to be constructed on a common substrate – Thus allowing highly efficient parallel manipulation. Also, Manipulation capability with multiple degrees-of-freedom (DOF) engaged simultaneously. In this paper, we have addressed the issues related to the design and behavioral simulation of MEMS based thermally actuated positioning system [Figure 1] with motion capabilities in all directions. The central positioning stage is a 250X250 micron square plate made of poly-silicon. The design is done in accordance with the design rules of PolyMUMPs, which is a commercially available multi user three layer poly-silicon MEMS fabrication process. A detailed dimension of the device is shown on Figure 2. The coupled multi physics simulation and study of the electrical, thermal and most importantly, the mechanical behavior of the mirror is done using thermal-electric-structural interaction mode of COMSOL Multiphysics MEMS module. Two types of thermal actuation mechanism are used in the designed device. For in-plane movement poly-silicon made hot arm, cold arm actuator [Figure 3] is used. Here, a hot arm is attached on both sides of a common cold arm. Electric current only passes through one hot arm and the cold arm; this causes that the temperature of the ‘thinner’ hot arm to become much higher than the ‘wider’ cold arm. This difference in temperature causes the hot arm to expand more than the cold arm, which results in the rotation of the actuator. For out-of-plane movement, advantage of difference in the resistivity of two different layers of poly-silicons has been taken [Figure 4]. When current passes through one layer, it warms up more compared to the other and thus bends. In the complete positioning structure, four in-plane and four out-of-plane actuators are attached to the central positioning stage to obtain displacements in all possible directions independently. The simulated structure is capable of producing comparable range of displacements in all possible directions using IC compatible voltages. The range of motion is in the micron order, while the resolution lies in the nanometer scale. The ability of precise control of movement of the positioner in space is likely to lead to potential applications in diverse fields. The use of thermal actuation process limits the bandwidth of the device within the KHz range, which is a typical drawback of such actuation mechanism. This is however offset by the simpler fabrication processes required for these devices. | <urn:uuid:2cc3751c-9394-4722-a025-7d091fb99017> | {
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US 5240886 A
A green tinted, ultraviolet absorbing glass is disclosed having a standard soda-lime-silica base glass composition and a colorant portion consisting essentially of:
CeO.sub.2 Less than 0.5 weight %Total iron Greater than 0.85 weight %(as Fe.sub.2 O.sub.3)FeO/total iron Less than 0.275.______________________________________
The glass reduces the amount of costly cerium required to yield low ultraviolet transmittance, viz., no greater than 31 percent (300 to 390 nanometers) at a reference thickness of 3.9 millimeters.
1. A green tinted, ultraviolet absorbing glass having a base glass composition consisting essentially of:
______________________________________SiO.sub.2 68-75 weight %Na.sub.2 O 10-20CaO 5-15MgO 0-5Al.sub.2 O.sub.3 0-5K.sub.2 O 0-5______________________________________
and a colorant portion consisting essentially of:
______________________________________CeO.sub.2 Less than 0.5 weight %Total Iron Greater than 0.85 weight %(as Fe.sub.2 O.sub.3)FeO/total iron Less than 0.275______________________________________
exhibiting ultraviolet transmittance no greater than 31 percent (300 to 390 nanometers) and luminous transmittance (illuminant A) of at least 70 percent, both at a reference thickness of 3.9 millimeters.
2. The glass of claim 1 wherein the glass contains less than 0.4 percent by weight CeO.sub.2.
3. The glass of claim 1 wherein the glass exhibits a dominant wavelength from 495 to 535 nanometers.
4. The glass of claim 1 wherein the glass exhibits a total solar energy transmittance less than 45 percent at a reference thickness of 3.9 millimeters.
5. The glass of claim 1 wherein the glass contains 0.20-0.40 percent by weight CeO.sub.2 and 0.85-1.132 percent by weight total iron (as Fe.sub.2 O.sub.3), and a value of FeO/total iron of equal to or greater than 0.161 and equal to or less tan 0.275.
This invention relates to soda-lime-silica glass particularly suitable for controlling transmittance of solar radiation in window glazing applications. The glass may be generally described as being green tinted, and is designed to have low heat transmittance and particularly enhanced absorption in the ultraviolet wavelength range. This is desirable for the sake of reducing the rate at which the sun's rays deteriorate plastics and fabrics in applications such as automobiles. A particular objective of the invention is to permit glass of this type to be made at a lower cost by reducing the amount of costly ingredients required.
Soda-lime-silica flat glass may be essentially characterized by the following composition on a weight percentage basis of the total glass:
______________________________________ SiO.sub.2 68-75% Na.sub.2 O 10-20 CaO 5-15 MgO 0-5 Al.sub.2 O.sub.3 0-5 K.sub.2 O 0-5______________________________________
Other minor ingredients, including melting and refining aids such as SO.sub.3, may also appear in the glass composition. Small amounts of K.sub.2 O, BaO or B.sub.2 O.sub.3 and other minor constituents have also sometimes been included in flat glass and may be considered optional. To this base glass are added the coloring constituents that produce the transmittance properties of the glass. The primary colorant in the category of glasses relevant to the present invention is iron, which is usually present in both the Fe.sub.2 O.sub.3 and FeO forms. As is conventional, the total amount of iron present in a glass is expressed herein as Fe.sub.2 O.sub.3, regardless of the form actually present. A typical green tinted automotive glass has about 0.5 percent by weight total iron, with the ratio of FeO to total iron being about 0.25.
Larger amounts of iron have been used in some specialty glasses intended to lower the total solar energy transmittance. However, merely increasing the amount of total iron does not reduce the ultraviolet transmittance to the extent desired even when the amount of iron present is sufficient to lower the luminous (visible light) transmittance to the minimum acceptable for automotive applications under conventional commercial melting conditions. The colorant composition and transmittance properties for examples of two commercial products of this high iron, dark green tinted type along with an example of the conventional, light green tinted glass described above are set forth below:
______________________________________ Light Green Dark Green Dark Green Example A Example B Example C______________________________________Total Iron (wt. %) 0.550 0.805 0.720FeO/Tot. Iron 0.251 0.293 0.270LT.sub.A (%) 79.5 70.9 71.6TSUV (%) 48.1 36.9 36.5TSIR (%) 36.7 22.9 29.2TSET (%) 56.8 44.6 48.8______________________________________
The transmittance data in the table above and throughout are based on a glass thickness of 3.9 millimeters (0.154 inch). Luminous transmittance (LT.sub.A) is measured using C.I.E. standard illuminant "A" over the wavelength range 380 to 770 nanometers. Total solar ultraviolet transmittance (TSUV) is measured over the wavelength range 300 to 390 nanometers. Total solar infrared transmittance (TSIR) is measured over the wavelength range 800 to 2100 nanometers. Total solar energy transmittance (TSET) represents a computed value based on measured transmittances from 300 to 2100 nanometers at 50 nanometer intervals.
Recently, a goal has been established to limit ultraviolet transmittance to no more than 31 percent in some automotive glass. At the same time, it is a requirement that glass in vision areas of automobiles have an LT.sub.A of at least 70 percent. Simply increasing the amount of iron to lower the ultraviolet transmittance would impermissibly lower the luminous transmittance as well, so an alternative approach is needed. The use of cerium oxide in glass to reduce ultraviolet transmittance is disclosed in U.S. Pat. No. 2,860,059, and the following two examples are of commercial products that take this approach:
______________________________________ Example D Example E______________________________________CeO.sub.2 (wt. %) 1.06 0.70Total Iron (wt. %) 0.780 0.858FeO/Tot. Iron 0.290 0.282LT.sub.A (%) 71.4 70.4TSUV (%) 27.8 28.3TSIR (%) 22.8 20.6TSET (%) 44.6 42.9______________________________________
These glasses exhibit the desired combination of low ultraviolet transmittance and high luminous transmittance, but the high cost of cerium sources substantially increases the cost of making these glasses. It would be desirable if these objectives could be met without incurring such high raw material costs. High cerium content also produces an undesirable solarization effect, that is, the glass tends to darken upon exposure to ultraviolet radiation. For these reasons, it would be desirable to lower the amount of cerium required in this type of glass.
An objective of the present invention is to provide green tinted glass that has luminous transmittance of at least 70 percent and ultraviolet transmittance of no more than 31 percent (both transmittances at a reference thickness of 3.9 millimeters), without requiring the use of as much costly cerium oxide as in prior compositions of this type. These properties may be achieved by the present invention with less than 0.5 percent by weight CeO.sub.2 in the glass, preferably less than 0.4 percent by weight CeO.sub.2. The optimized embodiments of the present invention contain less than 0.35 percent by weight CeO.sub.2. Compared to competing glasses, the glasses of the present invention are characterized by larger amounts of total iron and smaller proportions of the iron in the ferrous state. The total iron (expressed as Fe.sub.2 O.sub.3) is greater than 0.85 percent by weight of the total glass composition, and the ratio of FeO/total iron (ferrous iron expressed as FeO divided by the total iron expressed as Fe.sub.2 O.sub.3) is less than 0.275.
The base glass composition is not critical to the present invention and may consist of any conventional soda-lime-silica flat glass composition, which may be characterized by the ranges set forth above. Preferably, the base glass is one known by those of skill in the art to be producible in a continuous melting furnace and formed into a flat sheet by the float process. A specific example of a glass of the present invention can be seen in Example 1.
______________________________________SiO.sub.2 71.88 percent by weightNa.sub.2 O 13.47CaO 8.91MgO 3.66Al.sub.2 O.sub.3 0.27K.sub.2 O 0.08SO.sub.3 0.15Fe.sub.2 O.sub.3 (total) 0.898CeO.sub.2 0.28______________________________________
Additionally, traces of impurities may be present without significant effect on the glass. Melting and fining aids such as SO.sub.3 are useful during production of the glass, but their residual amounts in the glass can vary and have no significant effect on the properties of the glass product. K.sub.2 O is present in this example as an impurity, and its presence is not required, although it serves a function in the glass essentially equivalent to that of Na.sub.2 O. the ratio of ferrous iron (expressed as FeO) to total iron (expressed as Fe.sub.2 O.sub.3) for Example 1 was 0.245. The batch mixture of raw materials from which the glass of Example 1 was melted was as follows:
______________________________________Sand 1000 parts by weightSoda ash 324Limestone 84Dolomite 242Salt cake 5Rouge 12.32Cerium carbonate 5.75(hydrate)Coal 1.55______________________________________
The glass of Example 1 exhibited the following transmittance properties at a thickness of 3.9 millimeters:
______________________________________ LT.sub.A 70.8% TSUV 29.6% TSIR 22.1% TSET 43.7%______________________________________
One of the ways to control the ratio of ferrous to total iron is by selecting the amount of coal or other reducing agent included in the batch mixture. Instead of coal, various other sources of carbon are known to serve as reducing agents during melting of glass. Another means of control is by way of the ratio of air to fuel in the melting furnace. A higher air to fuel ratio produces conditions in the melting furnace that are more oxidizing, which, in turn, leads to a lower ferrous to total iron ratio. Specifying the oxidizing control measures depends upon the particular operating characteristics of a particular melting furnace. In Example 1, oxidizing conditions during melting were exceptionally high, so the amount of coal included in the batch was larger than would b desired under other conditions. In some cases it may be desirable to include no coal or other reducing agent in order to attain the oxidizing conditions required for the present invention.
High melting temperatures also tend to have a reducing effect on the glass, as can be seen in the relatively high ferrous to total iron ratios of Examples D and E of the prior art, which indicates that those glasses probably required exceptionally high temperature melting conditions. Because of the low infrared transmittance of the category of dark green tinted, high iron containing glasses to which the present invention pertains, relatively high melting temperatures are to be expected. As a result, making the conditions more oxidizing in accordance with the present invention may yield ferrous to total iron ratios that are relatively low for dark green glass, but not substantially different from those for lightly tinted or clear glass. Therefore, the requirement of a ferrous to total iron ratio less than 0.26 in the present invention is relatively low for this type of glass.
Examples 2 through 7 are additional embodiments of the present invention. Only the colorant portion of the compositions are set forth because the base glass portions vary only slightly.
______________________________________ Exam- Exam- Exam- Exam- Exam- Exam- ple 2 ple 3 ple 4 ple 5 ple 6 ple 7______________________________________LT.sub.A 70.5 70.3 70.4 70.9 70.2 71.0TSUV 28.4 26.6 26.4 31.0 29.9 30.2TSIR 23.9 23.3 25.1 20.9 20.1 21.5TSET 44.3 43.9 44.9 43.4 42.6 43.7Fe.sub.2 O.sub.3 (total) 0.957 0.973 1.132 0.882 0.907 0.896FeO/Fe.sub.2 O.sub.3 0.222 0.222 0.161 0.261 0.254 0.243CeO.sub.2 0.27 0.28 <0.01 0.29 0.31 0.31______________________________________
Minimizing the amount of cerium oxide used is best for meeting the objectives of reducing the cost of the glass and avoiding solarization, and Example 4 is an embodiment within the scope of the invention in which no cerium was used. However, the very low ferrous to total iron ratio required when no cerium is used may be difficult to attain in some melting furnaces. Therefore, it is preferred that a small amount of cerium be used to yield the desired reduction in ultraviolet transmittance without requiring an unduly low ferrous to total iron ratio. Additionally, cerium oxide is itself an oxidizing agent whose presence assists in attaining the required ferrous to total iron ratio. Accordingly, the preferred embodiments disclosed above include 0.20 to 0.35 percent by weight CeO.sub.2 although some commercially operating furnaces may require up to 0.4 percent or more.
The ultraviolet transmittance herein has been reported with reference to the wavelength range 300 to 390 nanometers. Others may use the range 300 to 400 nanometers for measuring ultraviolet. The goal of a maximum ultraviolet transmittance of 31 percent for the present invention would be approximately equivalent to 38 percent if the range 300 to 400 nanometers is used.
Cerium is sometimes included in glass to "decolorize" the glass. But the glass of the present invention has a distinctly green color. The color may be a matter of taste, and the specific color characteristics need not be considered critical to the present invention, but the glasses that have been made in accordance with the invention have been characterized by excitation purity greater than 1 percent, usually from 2 to 4 percent, and dominant wavelength from 495 to 535 nanometers.
The total solar energy transmittance (TSET) of the glass of the present invention is relatively low, thereby significantly reducing the amount of thermal energy that passes through a window glazed with the glass. Although not critical to the invention, the TSET of the glasses of the present invention are generally lower than 45 percent.
The invention has been described with reference to specific embodiments, but it should be understood that variations and modifications that are known to those of skill in the art may be resorted to within the scope of the invention as defined by the claims that follow.
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Hänvisningar finns i följande patent | <urn:uuid:eb13f1f8-8428-4d0f-8982-07872f4ddc0c> | {
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The behavior of adaptive bone-remodeling simulation models
Weinans, H. and Huiskes, R. and Grootenboer, H.J. (1992) The behavior of adaptive bone-remodeling simulation models. Journal of Biomechanics, 25 (12). pp. 1425-1442. ISSN 0021-9290
|Abstract:||The process of adaptive bone remodeling can be described mathematically and simulated in a computer model, integrated with the finite element method. In the model discussed here, cortical and trabecular bone are described as continuous materials with variable density. The remodeling rule applied to simulate the remodeling process in each element individually is, in fact, an objective function for an optimization process, relative to the external load. Its purpose is to obtain a constant, preset value for the strain energy per unit bone mass, by adapting the density. If an element in the structure cannot achieve that, it either turns to its maximal density (cortical bone) or resorbs completely.
It is found that the solution obtained in generally a discontinuous patchwork. For a two-dimensional proximal femur model this patchwork shows a good resemblance with the density distribution of a real proximal femur.
It is shown that the discontinuous end configuration is dictated by the nature of the differential equations describing the remodeling process. This process can be considered as a nonlinear dynamical system with many degrees of freedom, which behaves divergent relative to the objective, leading to many possible solutions. The precise solution is dependent on the parameters in the remodeling rule, the load and the initial conditions. The feedback mechanism in the process is self-enhancing; denser bone attracts more strain energy, whereby the bone becomes even more dense. It is suggested that this positive feedback of the attractor state (the strain energy field) creates order in the end configuration. In addition, the process ensures that the discontinuous end configuration is a structure with a relatively low mass, perhaps a minimal-mass structure, although this is no explicit objective in the optimization process.
It is hypothesized that trabecular bone is a chaotically ordered structure which can be considered as a fractal with characteristics of optimal mechanical resistance and minimal mass, of which the actual morphology depends on the local (internal) loading characteristics, the sensor-cell density and the degree of mineralization.
|Copyright:||© 1992 Pergamon Press|
|Link to this item:||http://purl.utwente.nl/publications/32099|
|Export this item as:||BibTeX|
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Metis ID: 144340 | <urn:uuid:8af19d59-5bfd-42a2-acec-feaefb802e5f> | {
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The garment manufacturing is a traditional and fashion industry, that is globally competitive and customer centric. The most critical operation process is sewing, as it generally involves a great number of operations. The aim of assembly line balancing planning in sewing lines is to assign task to the workstation in order that the machines of the workstation can perform the assigned tasks with a balanced loading. Assembly line balancing problem (ALBP) is known as an NP-hard problem. Thus, the heuristic methodology could be a better way to plan the sewing lines in a reasonable time. This paper presents a grouping genetic algorithm (GGA) for assembly line balancing problem of sewing lines in garment industry. GGA was first developed by Falkenauer in 1992 as a type of GA which exploits the special structure of grouping problem, and overcomes the drawbacks of GA. GGA allocates workload among machines as evenly as possible, so the minimum mean absolute deviations (MAD) can be minimized. The performance is verified through solving two real problems in garment industry. The computational results reveal that GGA outperforms GA in both simple and complex problems by 13.81% and 8.81%, respectively. This shows GGA's effectiveness in solving ALBP.
Machine Learning and Cybernetics, 2009 International Conference on (Volume:5 )
Date of Conference: 12-15 July 2009 | <urn:uuid:45dc6c65-57ed-4b96-bc93-3aeac0641ebe> | {
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Activity instance oriented handling is a new means for vertical optimization of process cases. Unlike our previous batch processing mechanism in workflows, it focuses on the data characteristics of activity instances and utilizes explicit knowledge for planning. This paper introduces its concept and proposes activity instance pattern to model and represent the knowledge for execution optimization. A flexible and intelligent workflow enactment framework for activity instance oriented handling is also proposed and investigated.
Date of Conference: 24-26 Oct. 2011 | <urn:uuid:9fd91806-1b64-4e70-bc44-37fce727c2ac> | {
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In this paper, we develop a module that combines a heart rate and movement sensor with embedded algorithm software for in-situ monitoring of human body energy cost. In previous studies, we have simulated the monitoring of energy expenditure in a lab environment; however, lab conditions are different from the free-living environment. The sensor algorithm was proposed to realize the real-time monitoring of energy cost in a free-living environment. Thirty college students (twenty males, ten females) were recruited to participate in this study. The participants walked and ran at a school playground without any speed limitations. The estimated values were compared with those of the portable metabolic system. The experiment results show the combined sensor module is able to estimate calories cost under free-living conditions. | <urn:uuid:6f378504-ded7-4574-a3ed-8c7aa56ec9e9> | {
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The problem of coherent reflection of an acoustic plane wave from a rough seabed with a randomly inhomogeneous sediment layer overlying a uniform elastic basement is considered in this analysis. The randomness of the sound field is attributable to the roughness of the seabed and the sound-speed perturbation in the sediment layer, resulting in a joint rough surface and volume scattering problem. An approach based upon perturbation theory, combined with a derived Green's function for a slab bounded above and below by a fluid and an elastic half-space, respectively, is employed to obtain an analytic solution for the coherent field in the sediment layer. Furthermore, a boundary perturbation theory developed by Kuperman and Schmidt (1989) is applied to treat the problem of rough surface scattering. A linear system is then established to facilitate the computation of the coherent reflection field. The coherent reflection coefficients for various surface roughness, sediment randomness, frequency, sediment thickness, and basement elasticity have been generated numerically and analyzed. It was found that the higher/larger size of surface and/or medium randomness, frequency, thickness, and shear-wave speed, the lower the coherent reflection. Physical interpretations of the various results are provided.
Date of Publication: Oct 2002 | <urn:uuid:72bb640d-1536-4c77-8480-0d2b6658ddcd> | {
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KTH, Division of Neuronic Engineering, have a finite element model of the head. However, this model does not contain detailed modeling of the brain. This project consists of finding a method to extract brain tissues from T1-weighted MR images of the head. The method should be automatic to be suitable for patient individual modeling.
A summary of the most common segmentation methods is presented and one of the methods is implemented. The implemented method is based on the assumption that the probability density function (pdf) of an MR image can be described by parametric models. The intensity distribution of each tissue class is modeled as a Gaussian distribution. Thus, the total pdf is a sum of Gaussians.
However, the voxel values are also influenced by intensity inhomogeneities, which affect the pdf. The implemented method is based on the expectation-maximization algorithm and it corrects for intensity inhomogeneities. The result from the algorithm is a classification of the voxels. The brain is extracted from the classified voxels using morphological operations.
Source: Linköping University
Author: Caesar, Jenny | <urn:uuid:7c342f63-785e-4479-a2ed-9f0cdd744a3a> | {
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Wireless Num: Rate And Reliability Tradeoffs In Random Environments
Source: Stanford University
The author describe Wireless Network Utility Maximization, WNUM, and compare its performance to NUM for wireless networks of interfering links under random time varying channel conditions. WNUM is shown to simultaneously offer greater rate and reliability performance in simulations operating under Rayleigh fading. A general method for finding adaptive network control policies is presented that is sample-based and converges to the optimal control policies for the network. | <urn:uuid:6e5185cd-d292-4901-8e9c-c467c31506d2> | {
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This item is available under a Creative Commons License for non-commercial use only
In this paper the operation and performance of a high temperature solid oxide fuel cell (SOFC) stack on biomass syn-gas from a demonstration biomass gasification combined heat and power (CHP) plant is investigated. The objective of this work is to develop a computer simulation model of a biomass-SOFC CHP system, flexible enough for use in industry, capable of predicting system performance under various operating conditions and using diverse fuels. The biomass gasifier is of the dual fluidised bed (DFB) type with steam as the gasifying agent and is operated at atmospheric pressure. The tubular SOFC configuration, developed by Siemens Power Generation Inc (SPGI), is selected. It is considered to be the most advanced design and is approaching commercialisation. The SOFC stack model, developed using the chemical process flowsheet simulator Aspen Plus, is of equilibrium type and is based on Gibbs free energy minimisation. The SOFC model performs heat and mass balances and considers the ohmic, activation and concentration losses for the voltage calculation. Data available in the literature on the SPGI SOFC operating on natural gas is used to validate the model. The system model predicts thermodynamic condition and composition of all internal flow streams, the heat generated by the SOFC stack, voltage (V), current (I) and efficiency. Operating parameters are varied over a wide range, parameters such as fuel utilisation factor (Uf), current density (j) and steam to carbon ratio (STCR) have significant influence. The results indicate that there must be a trade-off between voltage, efficiency and power with respect to j and the SOFC stack should be operated at low STCR and high Uf, within certain limits. SOFC stack operation on biomass syn-gas is compared to operation on natural gas and as expected there is a drop in performance, which is attributed to increased input fuel and air flow due to the lower quality of the fuel gas. The optimum realistic operating conditions with regard to SOFC stack performance are identified. High electrical efficiencies are predicted making these systems very attractive for CHP applications.
Doherty, W., Reynolds, A., Kennedy, D.: Modelling and Simulation of a Biomass Gasification-Solid Oxide Fuel Cell Combined Heat and Power Plant Using Aspen Plus. Proc. 22nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, Foz Do Iguaçu, Brazil, 2009. | <urn:uuid:eb75d40d-acd6-45f7-9f82-f470bbcb51f7> | {
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The efficiency of a gas turbine has an inverse relationship to the clearance between the rotor blades and the casing. Recent efforts in miniaturization of micro gas turbine engines have created a new challenge in blade tip clearance measurement. This paper describes the development of a capacitive tip clearance measurement system, based on a synchronous detection of a phase-modulated signal, for a palm-sized gas turbine engine with an integral ceramic rotor piece. A surface modification of the ceramic compressor and rotor with conductive coating is utilized to create a novel configuration of a tip clearance probe. The probe capacitance varies by approximately 120 fF for a 100-μm blade displacement. Periodic autocalibration is used to reduce the effects of temperature drift on the sensor output. The remaining measurement error drift of 1.5 fF/°C was caused by the temperature drift of the probe parasitic capacitor. The random uncertainty was between 1.9 and 6.9 μm depending on the tip clearance gap.
Instrumentation and Measurement, IEEE Transactions on (Volume:54 , Issue: 3 )
Date of Publication: June 2005 | <urn:uuid:0e839ae1-83a5-4e5e-84ee-1df3472e3367> | {
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The personal network (PN) concept extends the personal area network (PAN) by including remote personal nodes, such as nodes at home or in the office. This extension is achieved through dynamic tunnels established between the remote PN entities. Scalability presents a major challenge for tunnel management in PNs due to their dynamic nature and the increasing number of simultaneously supported PNs. To reduce the PN management complexity, this paper proposes to use a peer-to-peer-based publish/subscribe naming (PPNS) system. The PPNS system enables an automated provisioning of the location information in the tunnel endpoints. A centralised management approach is proposed for the on-demand PN establishment and a distributed management approach is proposed for the always-on PN establishment.
Date of Conference: 13-15 Feb. 2008 | <urn:uuid:dd38dcb0-6c19-4026-b601-9ad2ea6e03f9> | {
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This letter introduces a novel in vivo method for determining the dielectric properties of deep human tissues, including lungs. A surgery-free method is proposed for an on-body monitoring system to evaluate the electrical properties of internal body organs and to detect irregularities in real time. The method uses a set of electrodes (16 or 40 MHz in operational frequency) to obtain data that relates the electrical properties of the underlying biological tissue(s) to the measured port scattering parameters. By using multiple electrodes, effects from outer layers (skin, fat, and muscle) can be suppressed, allowing for an accurate characterization of deeper layers. Specifically, the dielectric constant is expressed as a weighted sum of the scattering parameters from each probe. The weights of the scattering coefficients are then determined through a training process to ensure that various changes in the outer layers do not contaminate the extraction of the dielectric constant(s) associated with deeper tissues.
Antennas and Wireless Propagation Letters, IEEE (Volume:11 )
Date of Publication: 2012 | <urn:uuid:e9e46f5e-a909-4157-9959-ba0c3598f944> | {
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In this paper, we present a geometric discretization scheme for incompressible linearized elasticity. We use ideas from discrete exterior calculus (DEC) to write the action for a discretized elastic body modeled by a simplicial complex. After characterizing the configuration manifold of volume-preserving discrete deformations, we use Hamilton's principle on this configuration manifold. The discrete Euler-Lagrange equations are obtained without using Lagrange multipliers. The main difference between our approach and the mixed finite element formulations is that we simultaneously use three different discrete spaces for the displacement field.
In this paper we formulate a geometric theory of thermal stresses.
Given a temperature distribution, we associate a Riemannian
material manifold to the body, with a metric that explicitly
depends on the temperature distribution. A change of temperature
corresponds to a change of the material metric. In this sense, a
temperature change is a concrete example of the so-called
referential evolutions. We also make a concrete connection between
our geometric point of view and the multiplicative decomposition
of deformation gradient into thermal and elastic parts. We study
the stress-free temperature distributions of the
finite-deformation theory using curvature tensor of the material | <urn:uuid:2c3b249b-1bce-45ae-a5dc-720fa8fb1ba8> | {
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This letter presents a novel application of iterated function system (IFS) based three-dimensional (3D) fractal interpolation to compression elevation data. The parameters of contractive transformations are simplified by a concise fractal iteration form with geometric meaning. A local iteration algorithm is proposed, which can solve the non-separation problem when Collage Theorem is applied to find the appropriate fractal parameters. The elevation data compression is proved experimentally to be effective in reconstruction quality and time-saving.
© 2005 Chinese Optics Letters
(100.3020) Image processing : Image reconstruction-restoration
(100.6890) Image processing : Three-dimensional image processing
(280.0280) Remote sensing and sensors : Remote sensing and sensors
Siyuan Wu and Yuanhua Zhou, "Elevation data compression using IFS-based three-dimensional fractal interpolation," Chin. Opt. Lett. 2, 582-585 (2004) | <urn:uuid:c677fe8a-1997-4e8b-81ec-714e28f47a98> | {
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Dispersion Compensation Using Raised Cosine Filter in Optical Fibers
All Pass Filters (APFs) are used in dispersion compensation which is the foremost requirement in an optical fiber link. All pass filters can correct any order of dispersion by the careful design of multistage all pass filters starting from very simple components with the use of N port devices. Multiple channels, as in Wavelength Division Multiplexed (WDM) system, can be compensated with a single device since these filters are periodic in phase response. The design technique and implementation of these filters has been discussed in this paper. The simulation results obtained with Raised Cosine Filters (RCFs) are presented in this paper. The results obtained using RCF to compensate dispersion show improvement in terms of eye diagram. | <urn:uuid:fa6a6eb5-41b2-42a9-96c9-8079db4d77a6> | {
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"url": "http://www.techrepublic.com/whitepapers/dispersion-compensation-using-raised-cosine-filter-in-optical-fibers/32493222"
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Guidelines for Choosing Molecular "Alligator Clip" Binding Motifs in Electron Transport Devices
We employ a one-electron, tight-binding model of an electrode-molecule-electrode junction to explore the fundamental relationship between adsorption geometry and electron transport, producing exact results (within this model). By varying the chemisorption location (e.g., atop a surface atom or in a hollow site between surface atoms) and the molecule-electrode coupling, we find that the largest currents are realized when the molecule (i) is highly coordinated by the surface and (ii) has favorable overlap with electrode states near the Fermi level. We also show the importance of electrode-induced molecular level shifting for certain adsorption geometries, which can cause molecular levels far from the Fermi level to conduct better than those near the Fermi level. Since all of these factors are greatly influenced by the chemical moiety used to link the molecule to an electrode, these results present a set of guidelines to help choose "alligator clips" for molecular electronic devices. | <urn:uuid:0cd38ac9-4d9f-40d5-b08a-52fd0f1bf975> | {
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"url": "http://chemgroups.northwestern.edu/seideman/Publications/Abstracts/Guidelines%20for%20Choosing%20Molecular%20Alligator%20Clip%20Binding%20Motifs%20in%20Electron%20Transport%20Devices.html"
} |
Liu, Y., Arenas, M.A., Garcia-Vergara, S.J., Hashimoto, T., Skeldon, P., Thompson, G.E., Habazaki, H., Bailey, Paul and Noakes, T.C.Q. (2008) Behaviour of copper during alkaline corrosion of Al–Cu alloys. Corrosion Science, 50 (5). pp. 1475-1480. ISSN 0010-938XMetadata only available from this repository.
Enrichment of copper beneath amorphous anodic films on relatively dilute, solid-solution Al–Cu alloys is necessary before copper can be oxidized and incorporated into the oxide layer. A similar enrichment arises during electropolishing, which also develops an amorphous oxide. In these cases, external polarization is applied, usually generating a relatively high oxidation rate. In contrast, enrichment behaviour at the corrosion potential has received less attention. The present study examines the corrosion of Al–Cu alloys, containing up to 6.7 at.% Cu, in 0.1 M sodium hydroxide solution at 293 K. Copper is again found to enrich in the alloy, similarly to behaviour with anodic polarization. However, following enrichment, discrete copper-rich particles appear to be generated in the corrosion product. These are suggested to be nanoparticles of copper, since the corrosion potentials of the alloys are low relative to that required for oxidation of copper. The corrosion rate increases with increase of both time and copper content of the alloy, probably associated with a greater cathodic activity due to an increasing number of nanoparticles. The corrosion proceeds with loss of aluminium species to the sodium hydroxide solution, but with retention of copper in the layer of hydrated alumina corrosion product.
|Subjects:||Q Science > Q Science (General)|
Q Science > QD Chemistry
|Schools:||School of Applied Sciences|
|Depositing User:||Sharon Beastall|
|Date Deposited:||10 Jan 2012 10:33|
|Last Modified:||04 Sep 2012 09:49|
Item control for Repository Staff only: | <urn:uuid:b2ab273a-1614-4ccf-8f05-1c8ba7fd273b> | {
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"url": "http://eprints.hud.ac.uk/12444/"
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Skip to Main Content
Time domain synthesis of linear networks requires approximation of functions with a finite sum of weighted exponentials. In this paper an error function, obtained by orthonormal filtering, suitable to numeric optimization, is evaluated. The error function is the integrated squared difference between the obtained function and the desired one. The procedure can be used to form an optimum set of basis exponentials to an ensemble of functions. Finally, the procedure is illustrated with some simple examples. | <urn:uuid:034381e0-5d90-4123-9140-06cd385f8326> | {
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"url": "http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=1083644&contentType=Journals+%26+Magazines"
} |
Ellen Van Paesschen, Wolfgang De Meuter, Maja D’Hondt
In object-oriented software engineering roles are considered both classifications and instances. To reduce the gap between the conceptual modelling of roles and a corresponding implementation, we propose a new role modelling concept based on warped inheritance hierarchies. We integrated this new modelling concept in our prototype-based object-oriented round-trip engineering environment SelfSync. In this way it is possible to model roles in an Extended Entity-Relationship diagram while the corresponding implementation objects are automatically created and synchronized with the conceptual model. We apply constraint enforcement during the lifetime of role objects, based on dependency and role combinations. | <urn:uuid:a00b99cc-13c5-4103-b117-63fa4a0d107e> | {
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"url": "http://www.aaai.org/Library/Symposia/Fall/2005/fs05-08-023.php"
} |
Traditional silicon integration concepts are based on a few materials like silicon, silicon oxide and silicon nitride. Using only these materials limits the integration options. Resists - also used in conventional semiconductor processes - could be a fourth alternative, but are limited since processing at higher temperatures is not possible.
Infineon co-developed a new thermally stable organic polymer combining the advantages of both worlds and demonstrated the feasibility of this organic material for a DRAM trench integration scheme. In this approach, a modified version of an organic spin-on-polymer is used with ideal gap fill properties, good planarization and temperature stability beyond 450°C. Test samples of 256M DDR DRAM chips fabricated on 140 nm ground rules show high yields. This concept demonstrates the feasibility of FEOL (Front-End Of Line) integration schemes utilizing the newly developed material. Furthermore the demonstrated integration scheme is capable of extending DRAM trenches to generations below 70nm. | <urn:uuid:76963ce8-54ea-4177-a022-f95e85f6a085> | {
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"url": "http://www.azonano.com/article.aspx?ArticleID=351"
} |
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