Dissertations / Theses on the topic 'Finite differences Computer programs'
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Ampadu, Ebenezer. "Implementation of some finite difference methods for the pricing of derivatives using C++ programming." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/.
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Bodden, Eric. "Verifying finite-state properties of large-scale programs." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86909.
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Designers of software components can use finite-state properties to denote behavioral interface specifications which enforce client-side programming rules that state how the components ought to be used. This allows users of these components to check their client code for compliance with these rules, both statically and at runtime.In this dissertation we explain the design and implementation of Clara, a framework for specifying and verifying finite-state properties of large-scale programs. With Clara, programmers specify finite-state properties together with runtime monitors, using a syntactic extension to the aspect-oriented programming language AspectJ. Clara then uses a sequence of three increasingly detailed static analyses to determine if the program satisfies the finite-state properties, i.e., is free of property violations.
Clara produces a list of program points at which the program may violate the properties, ranked by a confidence value. If violations are possible, Clara also instruments the program with the supplied runtime monitor, which will capture property violations when the program executes. Due to its static analyses, Clara can omit the instrumentation at program locations which the analyses proved safe, and so optimize the instrumented program. When much instrumentation remains, Clara partitions the instrumentation into subsets, so that one can distribute multiple partially instrumented program versions that each run with a low overhead.
We validated the approach by applying Clara to finite-state properties denoted in multiple formalisms over several large-scale Java programs. Clara proved that most of the programs fulfill our example properties. For most other programs, Clara could remove the monitoring overhead to below 10%. We also found multiple property violations by manually inspecting the top entries in Clara's ranked result list.
Les concepteurs des différentes composantes logicielles peuvent utiliser les propriétés des automates finis pour fixer les spécifications de l'interface comportementale qui contrôleront les règles de programmations définissant l'utilisation des composantes. Ceci permet aux utilisateurs de ces composantes de vérifier le respect de ses règles par leurs codes sources, à la fois lors d'une analyse statique qu'à l'exécution.
Dans cette dissertation, nous montrerons la conception de Clara, une structure qui permet de spécifier et de vérifier les propriétés des automates finis dans des programmes étendus, puis expliquerons son implantation. Le programmeur, à l'aide de Clara, peut définir les propriétés des automates finis en complément aux processus de vérification à l'exécution, en utilisant une extension de la syntaxe d'AspectJ, un langage de programmation orienté aspect. Clara utilise alors, en séquence, trois analyses statiques de précision croissante pour déterminer si le programme respecte les propriétés des automates finis.
Clara produit une liste des positions dans le code source où il y a risque de violation de ces «propriétés», en ordre décroissant de certitude d'une violation. Quand cela est possible, Clara ajoute au programme des processus de vérification permettant d'étudier la violation de «propriétés» lors de son exécution. Grâce à son analyse statique, Clara n'ajoute pas au code ces processus dans les portions de code qui n'ont pas la possibilité de violer les propriétés des automates finis, ce qui limite les ralentissements dus aux processus de vérification. Lorsque ses ajouts restent considérables, Clara organise les processus de vérification à l'exécution en sous-groupe, de sorte qu'il soit possible de distribuer différentes versions du programme contenant seulement une partie de ceux-ci, limitant ainsi l'utilisation des ressources système à l'exécution.
Nous avons validé cette approche en soumettant à Clara les propriétés des automates finis sous différents modèles à appliquer sur différents programmes Java. Clara a permis de prouver que la plupart de ces programmes respectaient déjà les propriétés définies. Dans les autres cas, Clara a pu réduire le coût des processus de vérification à moins de 10%. De plus, nous avons pu localiser de nombreuses violations de propriété manuellement, en inspectant les entrées en importance dans la liste produite par Clara.
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DuVarney, Daniel C. "Abstraction-Based Generation of Finite State Models from C Programs." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-20020328-101420.
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byDaniel C. DuVarney
PhD Dissertation submitted to the Faculty of the North Carolina State University in partial fulfillment of the requirements for the degree of
PhD
in
Computer Science
Approved
S. Purushothaman Iyer, Chair
W. Rance Cleaveland
K.C. Tai
John W. Baugh
January 22, 2002
Raleigh, North Carolina
Abstract
Model checking is a major advancement in the quest forpractical automatic verification methods for computer systems, and has been effectively used to discoverflaws in real-world hardware systems. Unfortunately, applying model-checking techniques to software systems has proved to be more difficult, due to the large number of states and irregular transitions of such systems. One promising method for generating reasonably-sized models from programs is the use of data abstraction, in which the program data is mapped from a large set of possible values to a much smaller set of abstract values. This thesis develops a method which, given a program in the C language and an abstraction mapping, allows the automatic construction of an abstract labeled transition system (LTS), which is much smaller than the concrete LTS (the LTS which would be generated without the benefit of abstraction). The method is shown to be sound in the sense that if a program is well-behaved in its use of pointers, then any linear temporal logic formula which holds true for the corresponding abstract LTS will also hold true for the concrete LTS. Furthermore, if a design exists in the form of a transition system, then the abstract LTS can be checked against the design for bisimilarity. Bisimilarity ensures that the program is a faithful implementation ofthe design. A suite of software tools has been implemented based upon the theory. These tools interface with the Concurrency Workbench, a model checking system. A case study is presented which shows the practicality of this technique for verifying real-world C programs.
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Werpers, Jonatan. "Numerical simulation of solitons in the nerve axon using finite differences." Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-234383.
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A High-order accurate finite difference scheme is derived for a non-linear soliton model of nerve signal propagation in axons. Boundary conditions yielding well-posed problems are suggested and included in the scheme using a penalty technique. Stability is shown using the summation-by-parts framework for a frozen parameter version of the non-linear problem.
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Kelley, Helen Marie, and University of Lethbridge Faculty of Arts and Science. "The importance of individual differences in developing computer training programs for end users." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 1994, 1994. http://hdl.handle.net/10133/55.
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Research emphasises that effective and efficient end-user training is a vital component of the successful utilization of computer technology and that individual differences (e.g., learning styles, cognitive reasoning schemata) may effect the outcomes of end-user training. This study investigates the relationships between end users' Motivational Intent to use computer technology and individual differences. End users' Motivational Intent to use computer technology is significantly different for between-subjects grouped according to their level of anxiety (i.e., positive, neutral, negative). The empirical results indicate that end users' scholastic ability is an important predictor of the incremental change over time to end users' Motivational Intent to use computer technology. End users' learning styles impact the incremental change over time to end users' Motivational Intent to use computer technology. The results suggest that the tailoring of end-user training methods, techniques and materials to accomodate individual differences may be beneficial and worthwhile.x, 99 leaves : ill. ; 28 cm.
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Brown, Steven Andrew. "Development of a coupled finite element - boundary element program for a microcomputer." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45713.
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This thesis describes the development of a coupled finite element — boundary element program for a microcomputer. The steps outlined in the thesis include the adaptation of a mainframe—based boundary element code for use on a microcomputer, the Verification of this program with sample problems, the development of an algorithm for coupling the Finite Element Method to the Boundary Element Method, the implementation of the coupling
algorithm with finite element and boundary element codes, including the development of a Constant Strain Triangular finite element, and the Verification of the coupled program with sample problems. Conclusions are drawn from the results presented, and suggestions are made for future research in this area.Master of Science
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Kanellopoulos, Vassilios N. "Vectorial finite element analysis of E-plane waveguide junctions." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64027.
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Pester, Matthias. "Visualization Tools for 2D and 3D Finite Element Programs - User's Manual." Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600436.
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This paper deals with the visualization of
numerical results as a very convenient method to
understand and evaluate a solution which has been
calculated as a set of millions of numerical values.
One of the central research fields of the Chemnitz
SFB 393 is the analysis of parallel numerical
algorithms for large systems of linear equations
arising from differential equations (e.g. in solid
and fluid mechanics). Solving large problems on
massively parallel computers makes it more and
more impossible to store numerical data from the
distributed memory of the parallel computer to
the disk for later postprocessing. However, the
developer of algorithms is interested in an
on-line response of his algorithms. Both visual
and numerical response of the running program may
be evaluated by the user for a decision how to
switch or adjust interactively certain parameters
that may influence the solution process.
The paper gives a survey of current programmer
and user interfaces that are used in our various
2D and 3D parallel finite element programs for
the visualization of the solution.
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Sharp, Richard Paul. "Computational approaches for diffusive light transport finite-elements, grid adaption, and error estimation /." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1154705561.
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McDavid, Charles Scott. "Weight optimum arch structures." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245954.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Salinas, David. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Arches, Stress Analysis, Weight, Finite Element Analysis, Computer Programs, Optimization, Theses, Degrees Of Freedom, FORTRAN, Stiffness, Case Studies. Author(s) subject terms: Finite Element Method, Arches, Weight Optimization. Includes bibliographical references (p. 107). Also available in print.
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Ostendorp, Markus. "Improved Methodology for Limit States Finite Element Analysis of Lattice Type Structures using Nonlinear Post-Buckling Member Performance." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/1179.
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In an attempt to achieve more efficient designs, the technological frontier is pushed further and further. Every year science probes for a better understanding of natural phenomena, discovering new and improved methods to perform the same task more efficiently and with better results. One of the new technologies is the nonlinear analysis of structural systems using inelastic post-buckling member performance. Inelastic post-buckling member performance is defined as the constitutive relationship between axial load and displacement after the ultimate member capacity has been exceeded. A nonlinear analysis is able to predict the failure behavior of a structural system under ultimate loads more accurately than the traditionally used linear elastic analysis. Consequently, designs can be improved and become more efficient, which reduces the realization cost of a project. An improved nonlinear analysis solution algorithm has been developed, that allows the analyst to perform a nonlinear analysis using post-buckling member performances faster than previously possible. Furthermore, the original post-buckling member performance database was expanded using results obtained from physical member compression tests. Based on the experimental results, new post-buckling member performance model curves were developed to be used together with the improved nonlinear solution algorithm. In addition, a program was developed that allows the analyst to perform a valid nonlinear analysis using a finite element program (LIMIT). The program combines a numerical pre-processor, and input and output data evaluation modules based on human expertise together with the LIMIT analysis package. Extensive on-line help facilities together with graphical pre- and post-processors were also integrated into the program. The resulting analysis package essentially combines all of the necessary components required to perform a nonlinear analysis using post-buckling member performances into one complete analysis package.
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Beirami, Ahmad. "Characterizing the redundancy of universal source coding for finite-length sequences." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45750.
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In this thesis, we first study what is the average redundancy resulting from the universal compression of a single finite-length sequence from an unknown source. In the universal compression of a source with d unknown parameters, Rissanen demonstrated that the expected redundancy for regular codes is asymptotically d/2 log n + o(log n) for almost all sources, where n is the sequence length. Clarke and Barron also derived the asymptotic average minimax redundancy for memoryless sources. The average minimax redundancy is concerned with the redundancy of the worst parameter vector for the best code. Thus, it does not provide much information about the effect of the different source parameter values. Our treatment in this thesis is probabilistic. In particular, we derive a lower bound on the probability measure of the event that a sequence of length n from an FSMX source chosen using Jeffreys' prior is compressed with a redundancy larger than a certain fraction of d/2 log n. Further, our results show that the average minimax redundancy provides good estimate for the average redundancy of most sources for large enough n and d. On the other hand, when the source parameter d is small the average minimax redundancy overestimates the average redundancy for small to moderate length sequences. Additionally, we precisely characterize the average minimax redundancy of universal coding when the coding scheme is restricted to be from the family of two--stage codes, where we show that the two--stage assumption incurs a negligible redundancy for small and moderate length n unless the number of source parameters is small.
%We show that redundancy is significant in the compression of small sequences. Our results, collectively, help to characterize the non-negligible redundancy resulting from the compression of small and moderate length sequences. Next, we apply these results to the compression of a small to moderate length sequence provided that the context present in a sequence of length M from the same source is memorized. We quantify the achievable performance improvement in the universal compression of the small to moderate length sequence using context memorization.
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Wadham-Gagnon, Matthew. "Hyperelastic modelling of rubber behaviour in finite element software." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99797.
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Experimental characterisation of rubber in uniaxial, equi-biaxial and planar tension under cyclic quasi-static loading shows strain-induced stress softening, hysteresis and unrecoverable strain. The objective of this work is to study the applications and limitations involved in predicting the behaviour of rubber with hyperelastic models. To assume a preconditioned perfectly elastic material, the data obtained from experiments must first be simplified. The data is then fitted to popular hyperelastic models in the finite element analysis (FEA) software ANSYS(TM). A single hyperelastic model (with given coefficients) is shown to only provide a good fit to a single characterisation test and level of preconditioning at the time. A two-iteration preconditioning method is developed using different hyperelastic models for a given material to approximate the softening effect of cyclic loading in a static FEA simulation. A biaxiality test is developed, providing information on the dominant mode of simple strain in the elements of a FE model. FEA simulations and experimental tests of a cantilevered rubber plate subjected to a bending load at its free end as well as a rubber guide lug subjected to a transverse deflection are presented and discussed. It is shown that using a single hyperelastic model is insufficient to predict the behaviour of these experiments in FEA simulations. The preconditioning iteration, when applied to these simulations, shows very good agreement with the experiments, both qualitatively and quantitatively. The biaxiality test provides insight on which characterisation test is the most appropriate for curve fitting hyperelastic models for a given analysis.
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Ritter, Baird S. "Solution strategies for second order, nonlinear, one dimensional, two point boundary value problems by FEM analysis." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA246063.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor: Salinas, D. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Boundary value problems, finite element analysis, differential equations, problem solving, theses, interpolation, iterations, one dimensional, computer programs, approximation/mathematics, linearity. Author(s) subject terms: Galerkin FEM, nonlinear, quasilinearization, linearization, interpolation, iteration, differential equation, convergence. Includes bibliographical references (p. 164). Also available in print.
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Schneider, Thomas. "An experimental investigation of the finite time efficiency of a Peltier refrigeration device." PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/4261.
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Since the need of energy conservation has become more and more urgent in the past decades, there has been an increased interest in the study and development of more efficient energy conversion systems. One of the fields that have arisen from that endeavor is a branch of physics called Finite Time Thermodynamics (FIT). It may be said that FIT was initiated through the famous paper by Curzon and Ahlborn (1975) that established new bounds on the efficiency of a finite time Carnot heat engine. Before, the traditional treatments gave a fundamental upper limit on the efficiency of any heat engine. However, this figure, the well-known Carnot efficiency, is far too optimistic in comparison to real heat engines. The reason lies in the fact that the traditional Carnot engine is operating infinitely slowly, thus having zero power output. Curzon and Ahlborn were able to improve upon this treatment and to set an upper limit on engines producing finite power.
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Price, Daniel Kenneth. "Development of an accelerated finite-difference time-domain solver using modern graphics processors." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 111 p, 2009. http://proquest.umi.com/pqdweb?did=1654487621&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Chan, Andrew Hin-Cheong. "A unified finite element solution to static and dynamic problems of geomechanics." Thesis, Swansea University, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624605.
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Cook, William Digby. "Studies of reinforced concrete regions near discontinuities." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75457.
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A non-linear finite element computer program capable of predicting the complete response of two-dimensional reinforced concrete members was developed. This tool which accounts for the stress strain characteristics of cracked concrete was used to predict the responses of a number of members containing discontinuities. These members included corbels, dapped end beams, beams with web holes, and deep beams. The results of tests performed by the author as well as tests performed by other researchers were compared with the non-linear predictions. In addition, simple strut and tie models suitable for designing regions near discontinuities were developed. The predictions obtained by these models were compared with the non-linear finite element predictions and with the test results.
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Bahlis, Jihad. "An experimental-analytical investigation of hypoelastic models for plain and reinforced concrete /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73996.
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Sannes, Kevin Markle 1964. "Finite element analysis of aerosol particle deposition on surfaces inside a clean room." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277120.
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Aerosol particle deposition rates on surfaces inside a clean room are predicted by a model developed to account for particle convection, diffusion and sedimentation. External forces acting on the particle also influence the rate of deposition. Both electrical charge build up on product surfaces and temperature gradients in the air near the product surface are known to effect the rate of deposition. A description of an electrostatic and thermophoretic force on the particle is thus included in the model. The equations governing the particle deposition process and the approach used in obtaining a solution to these equations are both described. A finite element numerical solution is detailed, followed by a description of the electrostatic force models. Finally, predictions of the model are presented with a comparison to data experimentally obtained by other researchers.
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Stein, S. C. "Modelling of the filament-winding fabrication process." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41585.
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A stress model of the filament-winding fabrication process, previously implemented in a finite element program, was improved. Pre- and post-processing codes were developed to make the program easier and more efficient to use. A program which is used to design filament wound composite rocket motor cases was modified to write a model file for the fabrication stress code in the pre-processing stage. The same code was altered to provide post-processing output in the form of graphic displays. Also, a new code was written to provide additional post-processing capability for the fabrication stress model.
Verification of the model of the filament-winding process was performed by comparing experimental pressure and strain data, for the fabrication of a filament wound bottle, with results of an analytical model. The final analytical results using consecutive models of the filament wound bottle show reasonable agreement with experimental pressure and hoop strain data. The maximum difference in the analytical and experimental values in the pressure data was about 25% for the final winding stage. The difference was smaller during the winding progression. These results also show that the accuracy of the model depends heavily on the assumptions made for input parameters during modelling. The stiffness of the segmented steel mandrel, simulated by an effective modulus (degraded by segmentation), and the instantaneous laydown tension loss parameters significantly affected the results of the model. Including the effective modulus for the segmented mandrel in the model reduced the difference in the experimental and analytical pressure results by about 150%. The inclusion of instantaneous laydown tension loss in the model reduced the analytical-experimental difference by roughly 225%. These two parameters reduced the largest difference in the predicted pressure values from about 400% for the first model to around 25% for the final model.
The fabrication stress model was coupled with the thermo-kinetic cure model to provide more accurate fiber motion tension loss analysis capability. The stress model was modified to use the thermo-kinetic model as a subroutine to calculate fiber motion tension loss using a two-dimensional analysis. The results of the qualitative verification show that fiber motion tension loss is more important in the later stages of winding than in the beginning stages which indicates that it may provide the needed accuracy in the final winding stages.Master of Science
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Lee, Richard Todd. "A novel method for incorporating periodic boundaries into the FDTD method and the application to the study of structural color of insects." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29772.
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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Smith, Glenn; Committee Member: Buck, John; Committee Member: Goldsztein, Guillermo; Committee Member: Peterson, Andrew; Committee Member: Scott, Waymond. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Holifield, Steven Lee. "Mathematics, technology, and gender: Closing gender differences with a high school web site." CSUSB ScholarWorks, 2001. https://scholarworks.lib.csusb.edu/etd-project/1871.
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This project focuses on using technology to help motivate young females to make use of a high school web site to lesson anxieties and increase interest in mathematics and the use of technology. Additionally, it acts as a model to create an educational web site that brings about better communication within a community.
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Woods, Juliette Aimi. "Numerical accuracy of variable-density groundwater flow and solute transport simulations." Title page, contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phw8941.pdf.
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Guney, Murat Efe. "High-performance direct solution of finite element problems on multi-core processors." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34662.
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A direct solution procedure is proposed and developed which exploits the parallelism that exists in current symmetric multiprocessing (SMP) multi-core processors. Several algorithms are proposed and developed to improve the performance of the direct solution of FE problems. A high-performance sparse direct solver is developed which allows experimentation with the newly developed and existing algorithms. The performance of the algorithms is investigated using a large set of FE problems. Furthermore, operation count estimations are developed to further assess various algorithms. An out-of-core version of the solver is developed to reduce the memory requirements for the solution. I/O is performed asynchronously without blocking the thread that makes the I/O request. Asynchronous I/O allows overlapping factorization and triangular solution computations with I/O. The performance of the developed solver is demonstrated on a large number of test problems. A problem with nearly 10 million degree of freedoms is solved on a low price desktop computer using the out-of-core version of the direct solver. Furthermore, the developed solver usually outperforms a commonly used shared memory solver.
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Abrahamsson, Andreas, and Rasmus Pettersson. "Smoothing of initial conditions for high order approximations in option pricing." Thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302322.
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In this article the Finite Difference method is used to solve the Black Scholes equation. A second order and fourth order accurate scheme is implemented in space and evaluated. The scheme is then tried for different initial conditions. First the discontinuous pay off function of a European Call option is used. Due to the nonsmooth charac- teristics of the chosen initial conditions both schemes show an order of two. Next, the analytical solution to the Black Scholes is used when t=T/2. In this case, with a smooth initial condition, the fourth order scheme shows an order of four. Finally, the initial nonsmooth pay off function is modified by smoothing. Also in this case, the fourth order method shows an order of convergence of four.
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Quan, Liang. "Using FDM and FEM to simulate the decarburization in AISI 1074 during heat processing and its impact." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44769.
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The metallurgical processes and the products developed from these processes have been the cornerstone on which our civilizations have developed and flourished. Many of the new materials that have been developed over centuries were often the result of serendipitous occurrences. Because of the importance of new materials to the improvement of society, it is necessary to accelerate the way in which new alloys and processes are designed, developed and implemented.
Over the last two decades the computational side of materials science has thrived as a result of bigger and faster computers. However, the application of new computational methods to the development of new materials and structures is still in the early stages primarily because of the complexity of most metallurgical processes. One such process is the decarburization of steel. Because of the importance of the microstructure on the mechanical properties, changes in the near surface properties are affected by the loss of carbon in the alloy. The topics investigated in this thesis include a variety of alloys and microstructures that are considered to be important in the development of a unique structure necessary for a more efficient method of recovering natural gas and oil from underground reserves as well as structures for energy absorbing systems. Since both the material application and the structure are new, this research represents an ideal opportunity to combine processing, properties, microstructure and computations to accelerate the development of these new structures.
Compared to other commercially available proppants which tend to fail in demanding environments, the thin-walled hollow metal proppants are regarded more promising due to the low density and high mechanical strength. The energy-absorbing composite material manufactured by embedding said spheres in the Mg/Al matrix material is optimized by improving sphere and matrix properties at each step in the process. Ultimately the mechanical strength, fracture toughness, and energy absorption are expected to achieve a factor of 2-5 higher than previously reported.
Modeling makes it economically practical to assess the targeted materials' overall properties, behaviors and the mechanical responses in conjunction with stress environment, material properties, material dimensions among other variables, before a structure is built. Additionally, more advanced modeling can enable the quantitative descriptions of more complex metallurgical phenomena such as the effects of impurity elements and deformation under complex loading conditions.
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Sharpe, Alton Russell. "Functional validation of a novel technique for assembling high density polyimide cochlear implants." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45741.
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It has been hypothesized that increasing the number of active sites on a cochlear implant electrode array will enable the recipient to distinguish a higher number of pitch precepts, thus creating a more natural sound. While DSP processing strategies for cochlear implants have evolved significantly to address this, technology for the actual electrode array has remained relatively constant and limits the number of physical electrodes possible. Previous work introduced the concept of using Thin-Film Array (TFA) technology to allow for much higher site densities, although the original devices proved unreliable during surgical insertion tests. This work presents a new method of combining polyimide-based TFA's with supporting silicone insertion platforms to create assembled electrode arrays that are a more viable option for surgical insertion. The electrical and mechanical properties of these assemblies are investigated with physical deformation tests and finite element analysis in COMSOL to quantify how they will perform upon insertion into the cochlea, and the preliminary results of a surgical insertion study into human cadaveric temporal bones will be discussed.
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Ilgner, Robert Georg. "A comparative analysis of the performance and deployment overhead of parallelized Finite Difference Time Domain (FDTD) algorithms on a selection of high performance multiprocessor computing systems." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85572.
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Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: The parallel FDTD method as used in computational electromagnetics is implemented on a variety of different high performance computing platforms. These parallel FDTD implementations have regularly been compared in terms of performance or purchase cost, but very little systematic consideration has been given to how much effort has been used to create the parallel FDTD for a specific computing architecture. The deployment effort for these platforms has changed dramatically with time, the deployment time span used to create FDTD implementations in 1980 ranging from months, to the contemporary scenario where parallel FDTD methods can be implemented on a supercomputer in a matter of hours. This thesis compares the effort required to deploy the parallel FDTD on selected computing platforms from the constituents that make up the deployment effort, such as coding complexity and time of coding. It uses the deployment and performance of the serial FDTD method on a single personal computer as a benchmark and examines the deployments of the parallel FDTD using different parallelisation techniques. These FDTD deployments are then analysed and compared against one another in order to determine the common characteristics between the FDTD implementations on various computing platforms with differing parallelisation techniques. Although subjective in some instances, these characteristics are quantified and compared in tabular form, by using the research information created by the parallel FDTD implementations. The deployment effort is of interest to scientists and engineers considering the creation or purchase of an FDTD-like solution on a high performance computing platform. Although the FDTD method has been considered to be a brute force approach to solving computational electromagnetic problems in the past, this was very probably a factor of the relatively weak computing platforms which took very long periods to process small model sizes. This thesis will describe the current implementations of the parallel FDTD method, made up of a combination of several techniques. These techniques can be easily deployed in a relatively quick time frame on computing architectures ranging from IBM’s Bluegene/P to the amalgamation of multicore processor and graphics processing unit, known as an accelerated processing unit.
AFRIKAANSE OPSOMMING: Die parallel Eindige Verskil Tyd Domein (Eng: FDTD) metode word gebruik in numeriese elektromagnetika en kan op verskeie hoë werkverrigting rekenaars geïmplementeer word. Hierdie parallele FDTD implementasies word gereeld in terme van werkverrigting of aankoop koste vergelyk, maar word bitter min sistematies oorweeg in terme van die hoeveelheid moeite wat dit geverg het om die parallele FDTD vir 'n spesifieke rekenaar argitektuur te skep. Mettertyd het die moeite om die platforms te ontplooi dramaties verander, in the 1980's het die ontplooings tyd tipies maande beloop waarteenoor dit vandag binne 'n kwessie van ure gedoen kan word. Hierdie tesis vergelyk die inspanning wat nodig is om die parallelle FDTD op geselekteerde rekenaar platforms te ontplooi deur te kyk na faktore soos die kompleksiteit van kodering en die tyd wat dit vat om 'n kode te implementeer. Die werkverrigting van die serie FDTD metode, geïmplementeer op 'n enkele persoonlike rekenaar word gebruik as 'n maatstaf om die ontplooing van die parallel FDTD met verskeie parallelisasie tegnieke te evalueer. Deur hierdie FDTD ontplooiings met verskillende parallelisasie tegnieke te ontleed en te vergelyk word die gemeenskaplike eienskappe bepaal vir verskeie rekenaar platforms. Alhoewel sommige gevalle subjektief is, is hierdie eienskappe gekwantifiseer en vergelyk in tabelvorm deur gebruik te maak van die navorsings inligting geskep deur die parallel FDTD implementasies. Die ontplooiings moeite is belangrik vir wetenskaplikes en ingenieurs wat moet besluit tussen die ontwikkeling of aankoop van 'n FDTD tipe oplossing op 'n höe werkverrigting rekenaar. Hoewel die FDTD metode in die verlede beskou was as 'n brute krag benadering tot die oplossing van elektromagnetiese probleme was dit waarskynlik weens die relatiewe swak rekenaar platforms wat lank gevat het om klein modelle te verwerk. Hierdie tesis beskryf die moderne implementering van die parallele FDTD metode, bestaande uit 'n kombinasie van verskeie tegnieke. Hierdie tegnieke kan maklik in 'n relatiewe kort tydsbestek ontplooi word op rekenaar argitekture wat wissel van IBM se BlueGene / P tot die samesmelting van multikern verwerkers en grafiese verwerkings eenhede, beter bekend as 'n versnelde verwerkings eenheid.
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Almeida, José Ricardo Ferreira de. "Modelagem matemática e simulação computacional para análise de dispersão de poluentes em um trecho do Rio Paraíba do Sul." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/307275.
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Orientador: João Frederico da Costa Azevedo MeyerDissertação (mestrado profissional) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
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Resumo: Este trabalho usa o modelo clássico de Difusão-Advccção-Reação para simular o comportamento evolutivo bidimensional de manchas de poluentes em um domínio aquático. Em função da ausência de possibilidade de solução analítica (primordialmente pelo tipo de domínio em que sit estuda o referido problema), recorre-se a um método de aproximação baseado em diferenças finitas centradas tanto para as variáveis espaciais quanto para a variável temporal (esta, via uso adequadamente explicitado do método de Crank-Nicolson). As condições de contorno são definidas com foco na situação real, considerando a absorção de poluentes nas margens em trechos determinados em função de seu comportamento. O trecho de rio considerado é o do rio Paraíba do Sul na região de Volta Redonda. RJ, que se caracteriza por ser um trecho reto do referido corpo aquático. Adota-se, como perfil de velocidades, a parábola devida a Poiseuille [11], o que afeta a montagem do sistema de diferenças finitas. Especial atenção é dedicada à precisão numérica resultante da estratégia de aproximação, bem como à possibilidade de visualizar qualitativamente os resultados, criando, assim, um recurso de software que podo ser usado em muitas outras situações minimamente semelhantes de contaminação hídrica sistemática ou emergência
Abstract: His work use the classical model of diffusiou-advection-reaction to simulate the evolutionary two-dimensional behavior of patch.es of pollutants in an aquatic domain. Because of the lack of possibility of analytical solution (primarily by the type of domain where you study the problem), it resorts to an approximation method based on finite differences centered for both spatial variables and for the time variable (this, via the use adequately explained of the Crank-Nicolson method). The boundary conditions are set to focus on the real situation, considering the absorption of pollutants into the bank in determined sections depending on their behavior. The considered stretch of river is this Paraíba do Sul river in region of Volta Redonda, RJ, which is characterized by a straight stretch of that body of water. It is adopted, such a velocity profile, the parabola due to Poiseuillc, which affects the mounting of the system of finite differences. Special attention is devoted to numerical accuracy resulting from the approximation strategy, and the ability to qualitatively visualize the results, thus creating a software feature that can be used in many other similar minimally situations of systematic water contamination or emergency
Mestrado
Matematica Aplicada
Mestre em Matemática Aplicada
31
Ferreira, Adriano da Silva 1984. "Desenvolvimento de um ambiente computacional para um simulador eletromagnético baseado no método FDTD." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259185.
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Orientadores: Hugo Enrique Hernandez Figueroa, Marli de Freitas Gomes HernandezDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Este trabalho tem por objetivo desenvolver um ambiente computacional livre para o software MEEP (MIT Electromagnetic Equation Propagation), um simulador eletromagnético de código aberto baseado no método das Diferenças Finitas no Domínio do Tempo (Finite-Difference Time-Domain - FDTD). Este ambiente computacional foi implementado sob o paradigma de Programação Orientada à Objetos, através da linguagem de programação Java, e estruturado em Préprocessamento (configuração do cenário da simulação eletromagnética), Processamento (aplicação do FDTD no cenário configurado) e Pós-processamento (análise e visualização dos resultados da simulação), com o propósito de prover novas funcionalidades para o Préprocessamento e o Pós-processamento do MEEP. Através do VTK (Visualization Toolkit), um software de Visualização e Computação Gráfica Tridimensional, buscou-se implementar requisitos geométricos e gráficos ausentes no Pré-processamento do MEEP com o desenvolvimento de funcionalidades para leitura de arquivos gráficos e construção de modelos geométricos de cristais fotônicos pré-definidos, e com o desenvolvimento de mecanismos eficientes de geração, interação e visualização de objetos gráficos. Utilizou-se, do VTK, funcionalidades para leituras de arquivos STL (Standard Tessellation Language) e Wavefront OBJ, ambos fornecedores de geometrias, e implementou-se um importador de arquivos CAD (Computer-Aided Design), de formato DXF (Drawing Exchange Format), que fornece dados de geometrias e de materiais. O objetivo é prover uma interface gráfica de usuário para possibilitar e facilitar, através da inserção automática e visualização de objetos gráficos, a configuração de cenários mais elaborados nas simulações eletromagnéticas, em oposição ao mecanismo de scripting em linguagens de programação específicas disponíveis nas versões atuais do MEEP. Após executar o estágio de Processamento, o MEEP gera dois arquivos de saída, ambos em formato HDF5, que representam a geometria discretizada e o resultado dos cálculos da simulação. Softwares como MATLAB®, HDFView ou H5utils (ferramenta livre desenvolvida pelo próprio grupo do MEEP) podem manipular arquivos HDF5. Entretanto, essas ferramentas carecem de funcionalidades que permitem análises mais elaboradas e detalhadas em Pós-processamento, oferecendo mecanismos muito simples e limitados para a realização de cortes em geometrias e animação de simulações. Neste sentido, objetiva-se, com este ambiente computacional, contribuir com um Pós-processamento capaz de realizar cortes através de planos posicionados, arbitrariamente, em geometrias tridimensionais simuladas e gerar animações bidimensionais de propagação de ondas eletromagnéticas em simulações bidimensionais e tridimensionais, tomando, como base, os softwares H5utils e VTK
Abstract: This work aims the development of a free computational environment for the software MEEP (MIT Electromagnetic Equation Propagation), an open-source electromagnetic simulator based on Finite-Difference Time-Domain (FDTD) method. This computational environment has been implemented under the Object Oriented Programming paradigm using Java programming language, and it is structured in Preprocessing (configuration of electromagnetic simulation scenario), Processing (execution of the FDTD on defined scenario) and Post-processing (analysis and visualization of simulation results), with the purpose of providing new functionalities of Pre-processing and Postprocessing for the MEEP. Through the VTK (Visualization Toolkit), a 3D Visualization and Computer Graphics software system, we have implemented geometrical and graphical requirements missing in MEEP's Pre-processing with the development of features for reading graphics files and for building of geometrical pre-defined photonic crystals models, and with the development of efficient mechanisms for generation, interaction and displaying of graphics objects. We used VTK features for reading STL (Standard Tessellation Language) and Wavefront OBJ files, both suppliers of geometries, and we implemented a CAD file importer (Computer-Aided Design), based on DXF format (Drawing Exchange Format), which provides geometrical and material data. The goal is to provide a graphical user interface to enable and facilitate, through automatic insertion and visualization of graphical objects, the configuration of more elaborate scenarios in electromagnetic simulations, as opposed to the scripting engine in specific programming languages available in the current versions of MEEP. After executing the Processing stage, MEEP generates two output files, both in HDF5 format, which represent the discretized geometry and the calculation result of the simulation. Softwares such as MATLAB®, HDFView or H5utils (free tool developed by the MEEP's group) can manipulate HDF5 files. However, these tools lack features that allow more elaborate and detailed analysis in Post-processing, offering very simple and x limited mechanisms for making cuts in geometries and animation simulations. In this sense, the objective is, with this computing environment, to contribute with a Post-processing system able to perform cuts through arbitrary plans in three-dimensional simulated geometries and to generate two-dimensional animations of propagation of electromagnetic waves in two and three-dimensional simulations, based on H5utils and VTK softwares
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
32
Cajas, Guaca Denis 1983. "Impacto ambiental em meios aquáticos : modelagem, aproximação e simulação de um estudo na Baía de Buenaventura-Colômbia." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/307268.
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Orientador: João Frederico da Costa Azevedo MeyerDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
Made available in DSpace on 2018-08-26T22:20:05Z (GMT). No. of bitstreams: 1 CajasGuaca_Denis_M.pdf: 6132685 bytes, checksum: 5e3780d261cb1b925daf089e42c326af (MD5) Previous issue date: 2015
Resumo: Esta pesquisa visa descrever e ilustrar mediante a modelagem matemática e simulação computacional a poluição por esgoto que ocorre na Baía de Buenaventura no sudoeste do Pacífico Colombiano, e a influência do poluente no convívio de duas espécies de peixes. Para a dispersão de poluente usaremos o modelo que envolve a equação de Difusão-Advecção, a qual descreve as principais caraterísticas a considerar para o estudo do nosso problema, com suas respectivas condições de fronteira do entorno natural, considerando absorção de poluente nas margens da baía. Para a dinâmica populacional entre as espécies de peixes será usado um sistema não linear clássico do tipo Lotka-Volterra para modelar este problema, com condições de contorno de Neumann. A solução aproximada do modelo é obtida numericamente usando um método de segunda ordem no espaço e no tempo. Para a discretização da variável espacial usamos um método de diferenças finitas de segunda ordem e o método de Crank Nicolson para a discretização da variável temporal. Os resultados mostrados nas simulações computacionais para a concentração de poluente, e para a dinâmica populacional nos permitem julgar melhor o que está acontecendo ou o que pode acontecer, refletindo a necessidade de que os orgãos governamentais implementem mecanismos de mitigação ao problema ambiental para tentar diminuir os efeitos adversos do despejo direto no mar de águas residuais sem tratamento
Abstract: The propose of this research is to describe and illustrate the water pollution by sewage which occurs in Buenaventura Bay, in the southwest of the Colombian Pacific, and the influence of the pollutant in the interaction of two fish species, using mathematical modeling and computer simulation. Pollutant dispersion will be obtain using the model that involves the Diffusion - Advection equation, which describes the main features to be considered for the study of our problem with its respective boundary conditions of the natural environment, considering pollutant absorption in bayside. In order to describe the population dynamics between the fish species the classic Lotka -Volterra nonlinear system with Neumann boundary conditions will be used. The approximate solution of the model is obtained numerically using a second order method on the space and time. In order to discretize the spatial variable we use a second order finite difference method and the Crank Nicolson method for the time discretization. The results obtained in the computer simulations for the pollutant concentration, and the population dynamics allow us to judge what happening or what might happen. Reflecting in this way the necessity for the government agencies to implement mitigation mechanisms of the environmental problem in order to try reduce the adverse effects of dumping untreated sewage water directly into the sea
Mestrado
Matematica Aplicada
Mestra em Matemática Aplicada
33
Minchillo, Daniela Grintaci Vasconcellos. "Estudo de ligações pinadas com chapa de topo para aplicações em estruturas metálicas treliçadas tubulares planas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257814.
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Orientador: João Alberto Venegas RequenaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-19T15:03:35Z (GMT). No. of bitstreams: 1 Minchillo_DanielaGrintaciVasconcellos_D.pdf: 6597615 bytes, checksum: 5e256a912f052806cb5166fe84151bf7 (MD5) Previous issue date: 2011
Resumo: Este trabalho apresenta o desenvolvimento de uma concepção estrutural para ligações de treliças metálicas tubulares de seção circular com chapa de topo através de um estudo teórico-experimental. Nesta concepção as extremidades das diagonais são superpostas e unidas por um único parafuso fazendo com que a ligação seja pinada. A colocação da chapa faz com que apareça uma excentricidade na ligação originando esforços adicionais na estrutura que são aqui avaliados. Como vantagem desta ligação, destaca-se o baixo custo de fabricação, a rapidez de montagem das treliças, facilidade de transporte e versatilidade no detalhamento das ponteiras das diagonais. Pode ser utilizada em ligações de treliças planas ou multiplanares. Foi realizado um levantamento bibliográfico nas prescrições de cálculo e demais publicações, nacionais e internacionais, para ligações de estruturas tubulares, e um programa experimental foi desenvolvido com objetivo de certificar a ligação e obter um procedimento adequado para o cálculo da sua resistência. A análise experimental possibilitou a avaliação dos efeitos localizados na ligação, a interação entre a chapa e o perfil tubular e a identificação dos mecanismos de colapso. Os resultados experimentais são comparados com os resultados numéricos, que consideram como parâmetros, a influência do comprimento e da espessura da chapa de topo na resistência, no modo de colapso e na distribuição de tensões na ligação. Um modelo numérico, calibrado pelos resultados da análise experimental, foi utilizado para uma análise paramétrica. Com os resultados desta análise foi proposta uma formulação para obtenção da resistência da ligação
Abstract: This work presents a theoretical and experimental study of a gusset plate connection for application in trusses with circular hollow sections. In this connection the diagonals edges are superimposed and joined together at the plate by a single bolt causing the connection to be pinned. The placement of the plate leads to an eccentricity, resulting in additional efforts in the connection that are evaluated. Some of the advantages of this connection are the low manufacturing costs, the quickly assembly of trusses, versatility in the detailing of the braces ends and can be used properly on uniplanar or multiplanar trusses. A literature review is performed on codes, prescriptions and other publications, national and international for tubular connections, and an experimental program is developed in order to certify and obtain an appropriate procedure to determine the connection resistance. The experimental analysis allowed the evaluation of the local effects, the interaction between the gusset plate and tubular section and the identification of the failure modes. The experimental results are compared with numerical results considering parameters such as the influence of the length and thickness of the gusset plate in the connection resistance, failure mode and stress distribution. A numerical model, validated by the results of experimental analysis, was used for parametric analysis. With the parametric results, an analytical expression is proposed to predict the connection resistance
Doutorado
Estruturas
Doutor em Engenharia Civil
34
Coelho, da Silva Catherine Souto Costa 1986. "Estudo de ligações pinadas com chapa de topo para aplicações em estruturas metálicas treliçadas tubulares multiplanares." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258128.
Full textAbstract:
Orientador: João Alberto Venegas RequenaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-24T13:46:37Z (GMT). No. of bitstreams: 1 CoelhodaSilva_CatherineSoutoCosta_M.pdf: 3557954 bytes, checksum: afb90fa08dbf9c58642449f92217d07a (MD5) Previous issue date: 2014
Resumo: O objetivo deste trabalho é apresentar um tipo de ligação em treliças metálicas tubulares multiplanares de seção circular com chapa de topo. Nestas ligações as extremidades das diagonais são superpostas e unidas por um único parafuso fazendo com que a ligação seja pinada. A colocação da chapa de topo implica no aparecimento de uma excentricidade na ligação originando esforços adicionais na estrutura. Esse tipo de ligação tem como vantagem o baixo custo de fabricação, a rapidez de montagem das treliças, a facilidade de transporte e a versatilidade no detalhamento das ponteiras das diagonais. Foi realizado um levantamento bibliográfico nas prescrições de cálculo e demais publicações, nacionais e internacionais, para ligações de estruturas tubulares e encontrou-se um estudo para esse tipo de ligação, mas apenas analisando treliças planas. Para verificar o comportamento da ligação, serão analisados modelos numéricos desenvolvidos com o programa de elementos finitos ANSYS 14.0. Os resultados encontrados com esses modelos serão analisados e comparados com os resultados numéricos encontrados na pesquisa de ligação pinada com chapa em treliças tubulares planares para elaboração de um fator de correção entre os dois tipos de ligação
Abstract: This paper objective is to propose a connection type for tubular steel trusses with circular section, multiplanar and with gusset plate. In these connections the ends of the diagonals are overlapped and joined by a single pin resulting a pinned connection. The position of the gusset plate in the connections implies an eccentricity which results in additional efforts in the structure. The advantage of this connection type is the low manufacturing cost, the fast erection of trusses, the easier transportation and the versatility in the detailing constructive of the diagonals end. Survey in technical books, standards, manuals and scientific articles was made for tubular steel structures connection. In this survey was found a research for a similar type of connection, but in this there were only analysis of planar trusses. Numerical models using the commercial finite element software ANSYS 14.0 will be analyzed to check the connection. The results from these models will be analyzed and compared with numerical results in the bibliographic review about planar truss for preparation of a correction factor between the two types of connection. OBSERVAÇÃOA palavra gusset nas palavras chaves, título em inglês e no abstract devem ser grifadas em itálico
Mestrado
Estruturas e Geotécnica
Mestra em Engenharia Civil
35
Forti, Nadia Cazarim da Silva. "Estudo parametrico de estruturas tubulares com ligações multiplanares." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257812.
Full textAbstract:
Orientador: João Alberto Venegas RequenaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-15T22:06:00Z (GMT). No. of bitstreams: 1 Forti_NadiaCazarimdaSilva_D.pdf: 4434332 bytes, checksum: 7a022dba8cf147d4f048eb4863373d71 (MD5) Previous issue date: 2010
Resumo: Este trabalho apresenta um estudo paramétrico comparativo de ligações do tipo K e KK utilizando perfis tubulares circulares com afastamento entre diagonais e carregadas simetricamente. Para se comparar as ligações, foi desenvolvido um modelo numérico através do programa comercial de elementos finitos Ansys. Também foram desenvolvidos dois programas auxiliares para facilitar o estudo paramétrico. Foram analisadas 55 ligações do tipo KK e suas correspondentes K, comparando-se suas resistências. O objetivo deste trabalho é propor um critério objetivo para definir os modos de falha (1 e 2) da ligação tipo KK baseado na deformação diametral do banzo. O modo de falha 1 ocorre quando um par de diagonais vizinhas, carregadas no mesmo sentido, empurra ou puxa, a parede do banzo e no segundo, chamado modo 2 acontece uma deformação diametral da parede do banzo na região entre as diagonais vizinhas, criando quinas e dobras entre essas diagonais. Outro objetivo é estabelece uma demarcação do limite entre os dois modos de falha como uma função do afastamento transversal entre as diagonais. Os resultados permitiram o desenvolvimento de equações que preveem as resistências das ligações tipo KK, para os modos de falha 1 e 2 (plastificação da parede do banzo), a partir da resistência da ligação tipo K correspondente
Abstract: This work presents a parametric study of K and KK tubular steel connection. Gap connections with symmetric loading are analyzed. A numerical model using the commercial finite element software Ansys is proposed to compare K and KK connection resistances. Two auxiliary softwares are developed for setting the numerical model and to post-process results. A set of 55 KK connections and their correspondent K connections are analyzed and their resistances are compared. The objective of this work is purpose define the failure mode (1 or 2) of KK connections. This criteria is based on the chord diametric deformation. The results allowed the definition of limit values in function of the transversal gap for determining the connection failure mode. The connection resistance obtained in the parametric study allowed the development of an analytical expression which predict the KK connections resistance from the resistance of its correspondent K connection
Doutorado
Estruturas
Doutor em Engenharia Civil
36
Ben, Moussa Rim. "Contribution to thermal radiation to dust flame propagation : application to aluminium dust explosions." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2401/document.
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Ces travaux de thèse sont consacrés à l’examen du rôle du rayonnement thermique dans le processus de propagation des flammes issues de la combustion des particules d’aluminium dans l’air. Le sujet étant complexe et d’un intérêt industriel, il nécessite de prendre en compte le couplage de nombreux phénomènes physico-chimiques afin de prédire finement les conséquences des explosions de poussières. Une analyse bibliographique approfondie est proposée, concernant les mécanismes d’inflammation et de combustion des particules d’aluminium et aussi concernant les connaissances relatives à la propagation des flammes de poussières. La question spécifique de la nature des échanges thermiques et de l’influence du rayonnement thermique est étudiée. La revue bibliographique souligne les approximations et les hypothèses simplificatrices utilisées dans la littérature permettant donc de définir les pistes d’améliorations. Compte tenu des limitations importantes concernant la physique de ces flammes, un outil de simulation de physique numérique nommé « RADIAN », proche de la simulation numérique directe, a été développé proposant un couplage fin entre les différents modes d’échanges thermiques et la combustion pour modéliser la propagation de la flamme dans un nuage de poussières. La méthode des éléments discrets (MED) est utilisée pour modéliser numériquement les échanges radiatifs entre les particules et les échanges conductifs entre gaz et particules. La méthode des différences finies est utilisée pour modéliser numériquement la conduction thermique dans la phase gazeuse et la combustion. Un modèle radiatif est proposé se basant sur la théorie de Mie sur les interactions rayonnement-particules. Les résultats des simulations sont comparés avec des solutions analytiques et des données expérimentales de la littérature. Mais en plus, une étude expérimentale est aussi conduite afin de mesurer la distribution du flux radiatif devant la flamme et la vitesse de combustion laminaire pour des flammes Méthane-Sic, Méthane-Alumine et Al-air. Un bon accord entre les simulations et les expériences est démontré. La loi de Beer-Lambert relative au transfert radiatif devant le front de flamme s’avère inapplicable et une nouvelle solution analytique est proposée. La présence de particules absorbantes du rayonnement promeut la propagation de la flamme. En particulier, il a été montré expérimentalement et confirmé numériquement que les mélanges riches d’AL-air sont susceptibles d’accélérer rapidementIn this thesis, the role of thermal radiation in aluminum-air flames propagation is studied. The subject being complex and of industrial interest, it requires the coupling of many physiochemical phenomena to accurately predict the consequences of dust explosions. A thorough literature review is proposed about the ignition and the combustion of aluminum particles and about the available theoretical models of dust flames propagation. The specific question of the nature of thermal exchanges and the influence of thermal radiation is studied. The bibliographic review underlines the simplifying assumptions and hypotheses used in the literature making possible the definition of improvement areas. Because of the limited amount of knowledge available to address these questions, a numerical tool “RADIAN” is developed enabling an accurate coupling between the different modes of heat exchange and combustion. The Discrete Element Method (DEM) is used to numerically model the radiative exchanges between particles and the gas-particle thermal conduction. The Finite Difference method is used to numerically model the thermal conduction through the gas phase and combustion. A radiative model based on Mie theory for radiation-particles interactions is incorporated. The results of the simulations are compared with available analytical solutions and experimental data. An original experimental study is also conducted to measure the distribution of irradiance ahead of the flame front and the laminar burning velocity for methane-air-Sic, methane-air-alumina and Al-air flames. A good agreement between numerical simulations and experiments is demonstrated. The Beer-Lambert’s law for radiative transfer in front of the flame front is found to be inapplicable and a new analytical solution is proposed. The presence of absorbing particles may promote the flame propagation. In particular, it is shown experimentally and confirmed theoretically/numerically that Al-air rich mixtures are likely to rapidly accelerate
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Kahlon, Vineet Emerson E. Allen. "Model checking beyond the finite /." 2004. http://wwwlib.umi.com/cr/utexas/fullcit?p3143279.
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Kahlon, Vineet. "Model checking: beyond the finite." Thesis, 2004. http://hdl.handle.net/2152/1158.
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Wang, Yongxiang. "Extended Finite Element Methods for Brittle and Cohesive Fracture." Thesis, 2017. https://doi.org/10.7916/D8833XQ8.
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The safety of engineering structures depends heavily on the presence of cracks, which may propagate and lead eventually to structural failure. This dissertation aims to advance the computational modeling of fracture, within the context of linear elastic fracture mechanics (LEFM) and cohesive zone models (CZMs). The extended finite element method (XFEM) is employed as the discretization method and cracks in both homogeneous and bimaterial solids are considered in this work.
First, a novel set of enrichment functions within the framework of XFEM is proposed for the LEFM analysis of interface cracks in bimaterials. The motivation for the new enrichment set stems from the revelation that the accuracy of the widely accepted 12-fold bimaterial enrichment functions significantly deteriorates with the increase in material mismatch. To this end, we propose an 8-fold material-dependent enrichment set, derived from the analytical asymptotic displacement field, that well captures the near-tip oscillating singular fields of interface cracks, including the transition to weak discontinuities of bimaterials. The new enrichment set is tested on various examples and found to outperform the 12-fold set in terms of accuracy, conditioning, and total number of degrees of freedom (DOFs).
The formulation is then extended to include high-order enrichment functions and accurate stress and displacement fields are obtained. The complex stress intensity factors (SIFs) of interface cracks are evaluated by employing Irwin's crack closure integral. To this end, a closed-form SIF formulation in terms of the enriched DOFs is derived by matching the leading term in the XFEM with an analytical expression of Irwin's integral. Hence, the SIFs of interface cracks can be directly obtained upon the solution of the XFEM discrete system without cumbersome post-processing requirements. The proposed method is shown to work well on several benchmark examples involving straight and curved interface cracks, giving accurate SIF results.
Another contribution of the work is the application of Irwin's integral to the estimation of SIFs for curved homogeneous cracks. At the core, the proposed approach employs high-order enrichment functions to accurately capture the near-tip fields and evaluates the original definition of Irwin's integral through closed-form formulations in terms of enriched DOFs. An improved quadrature scheme using high-order isoparametric mapping together with a generalized Duffy transformation is proposed to integrate singular fields in tip elements with curved cracks. The proposed extraction approach is shown to yield decomposed SIFs with excellent accuracy and avoid the need for auxiliary fields as in J-integral method.
Second, with respect to cohesive fracture, a discrete damage zone model (DDZM) is proposed following a rigorous thermodynamic framework similar to that of continuum damage mechanics (CDM). For the modeling of mixed-mode delamination, a novel damage evolution law is proposed to account for the coupled interaction between opening and sliding modes of interface deformations. A comprehensive comparison made with several popular CZMs in the literature demonstrates the thermodynamic consistency of the DDZM. The proposed interface model is integrated with the XFEM and the effectiveness of this framework has been validated on various benchmark problems.
Finally, a novel continuous/discontinuous method is proposed to simulate the entire failure process of quasi-brittle materials: from the nucleation of diffuse damage to the development of discrete cracks . An integral-type nonlocal continuum damage model is coupled in this framework with DDZM with a new numerical energetic coupling scheme. The transition from the continuous (CDM) to the discontinuous approach (DDZM) can be triggered at any damage level with a weak energetic equivalence preserved. A few benchmark problems involving straight and curved cracks are investigated to demonstrate the applicability and robustness of the coupled XFEM cohesive-damage approach.
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Kirk, Benjamin Shelton. "Adaptive finite element simulation of flow and transport applications on parallel computers." Thesis, 2007. http://hdl.handle.net/2152/3115.
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Kirk, Benjamin Shelton 1978. "Adaptive finite element simulation of flow and transport applications on parallel computers." 2007. http://hdl.handle.net/2152/13302.
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"Computer simulation of IC packaging effects by FDTD method." 1998. http://library.cuhk.edu.hk/record=b5889580.
Full textAbstract:
by Ng Chi-Keung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1998.
Includes bibliographical references (leaves 127-134).
Abstract also in Chinese.
Abstract --- p.2
摘要 --- p.3
Acknowledgements --- p.4
Chapter Chapter 1 --- Introduction --- p.7
Chapter Chapter 2 --- Packaging Effects of Integrated Circuits --- p.9
Chapter 2.1 --- The Structure of the IC Package --- p.9
Chapter 2.2 --- Microstrip Discontinuities --- p.11
Chapter Chapter 3 --- The Finite-Difference Time-Domain Method --- p.19
Chapter 3.1 --- Basic Theory --- p.19
Chapter 3.2 --- Stability Criterion --- p.25
Chapter 3.3 --- Formulation of Source --- p.30
Chapter A. --- Source Function --- p.30
Chapter (i) --- Sinusoidal --- p.30
Chapter (ii) --- Gaussian Pulse --- p.31
Chapter B. --- Source Realization --- p.36
Chapter (i) --- Electric Field Source --- p.36
Chapter (ii) --- Lumped Source --- p.38
Chapter (iii) --- Current Source --- p.40
Chapter C. --- Source Placement --- p.41
Chapter 3.4 --- Parameter Extraction --- p.42
Chapter A. --- Voltage and Current --- p.42
Chapter B. --- Characteristic Impedance --- p.44
Chapter C. --- Effective Dielectric Constant --- p.45
Chapter D. --- Scattering Parameters --- p.46
Chapter 3.5 --- Termination and Boundary Treatment --- p.48
Chapter A. --- Perfect Electric Conductor (PEC) --- p.48
Chapter B. --- Perfect Magnetic Conductor (PMC) --- p.49
Chapter C. --- Interface between Two Materials --- p.50
Chapter 3.6 --- Perfectly Matched Layer (PML) --- p.54
Chapter A. --- Theory of PML in Three Dimensions --- p.56
Chapter B. --- Incorporation of PML as Absorbing Boundary Condition (ABC) --- p.65
Chapter C. --- Discretization of Maxwell's Equations in PML --- p.73
Chapter 3.7 --- Flowcharts --- p.75
Chapter A. --- Free Space Radiation by a Dipole Antenna --- p.77
Chapter B. --- Parameters of a Microstrip Line --- p.79
Chapter C. --- Scattering Parameters of Planar Network --- p.85
Chapter 3.8 --- Summary --- p.87
Chapter Chapter 4 --- Effects of Ground Via Allocation --- p.88
Chapter 4.1 --- Introduction --- p.88
Chapter 4.2 --- Simulation and Experimental Results --- p.91
Chapter 4.3 --- Equivalent Circuit Modelling --- p.108
Chapter 4.4 --- Summary --- p.124
Chapter Chapter 5 --- Conclusions --- p.125
Chapter Chapter 6 --- Recommendation for Future Work --- p.126
References --- p.127
Publication --- p.134
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Lee, Ki-Jang. "On the development of computer programs for the stress analysis of shear walls using Hermitian interpolation." 1986. http://hdl.handle.net/2097/22106.
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Thompson, Brenda E. "Three-dimensional finite element design procedure for the brushless doubly fed machine." Thesis, 1995. http://hdl.handle.net/1957/35570.
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Brushless Doubly Fed Machines (BDFM) have potential advantages in variable
speed generation and adjustable speed drive applications. The most significant of these
advantages is a reduction in the power electronic converter rating, and therefore a
reduction in overall system cost. Presently, efforts are being directed at optimizing the
design of the BDFM and investigating areas of commercial feasibility. One possible aid
in the investigation of design alternatives is finite element analysis.
Finite element analysis is a numerical method for determining the field
distribution in a dimensional model. Finite element techniques have been successfully
used for some time in the design of induction, reluctance and permanent magnet
machines. However, the characteristics of the BDFM require adjustment of the finite
element design procedure used for conventional singly-fed induction machines. In this
thesis, a three-dimensional finite element design procedure for modeling the BDFM has
been developed. This design procedure avoids the difficulties previously associated with finite element modeling of the BDFM.
The three-dimensional finite element design procedure developed in this thesis was used to model the 6/2 pole 5 horsepower BDFM laboratory machine. From the simulation results, the induced currents in the BDFM rotor bars were calculated.
In the course of investigating three-dimensional finite element analysis for the BDFM, two different commercially available finite element analysis software packages were examined and tested. The first was Maxwell 3D Field Simulator produced by Ansoft Corporation, and the second was MSC/EMAS (Electromagnetic Analysis System) and MSC/XL by MacNeal-Schwendler Corporation. These two software packages are compared and their advantages and disadvantages/limitations are discussed.
A tutorial for setting up and solving a three-dimensional BDFM model using MSC/XL and MSC/EMAS is presented. This goal of this tutorial is to guide a new user of MSC/XL and MSC/EMAS through the creation, setup, simulation, and analysis of a BDFM model. This tutorial contains condensed information included in the MSC/XL and MSC/EMAS program documentation provided by MacNeal-Schwendler. In addition, modeling techniques particular to the BDFM, which are not included in the program documentation, are described. This tutorial is applicable only to those individuals interested in learning how to use MSC/XL and MSC/EMAS in order to simulate a BDFM model.Graduation date: 1995
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Cloete, Renier. "A simplified finite element model for time-dependent deflections of flat slabs." Diss., 2004. http://hdl.handle.net/2263/25116.
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Grosshans, Nathan. "The limits of Nečiporuk’s method and the power of programs over monoids taken from small varieties of finite monoids." Thèse, 2018. http://hdl.handle.net/1866/21738.
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Woods, Juliette. "Numerical Accuracy of Variable-Density Groundwater Flow and Solute Transport Simulations." 2004. http://hdl.handle.net/2440/37924.
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The movement of a fluid and solute through a porous medium is of great practical interest because this describes the spread of contaminants through an aquifer. Many contaminants occur at concentrations sufficient to alter the density of the fluid, in which case the physics is typically modelled mathematically by a pair of coupled, nonlinear partial differential equations. There is disagreement as to the exact form of these governing equations. Codes aiming to solve some version of the governing equations are typically tested against the Henry and Elder benchmark problems. Neither benchmark has an analytic solution, so in practice they are treated as exercises in inter code comparison. Different code developers define the boundary conditions of the Henry problem differently, and the Elder problems results are poorly understood. The Henry, Elder and some other problems are simulated on several different codes, which produce widely-varying results. The existing benchmarks are unable to distinguish which code, if any, simulates the problems correctly, illustrating the benchmarks' limitations. To determine whether these discrepancies might be due to numerical error, one popular code, SUTRA, is considered in detail. A numerical analysis of a special case reveals that SUTRA is numerically dispersive. This is confirmed using the Gauss pulse test, a benchmark that does have an analytic solution. To further explain inter code discrepancies, a testcode is developed which allows a choice of numerical methods. Some of the methods are based on SUTRA's while others are finite difference methods of varying levels of accuracy. Simulations of the Elder problem reveal that the benchmark is extremely sensitive to the choice of solution method: qualitative differences are seen in the flow patterns. Finally, the impact of numerical error on a real-world application, the simulation of saline disposals, is considered. Saline disposal basins are used to store saline water away from rivers and agricultural land in parts of Australia. Existing models of disposal basins are assessed in terms of their resemblance to real fieldsite conditions, and in terms of numerical error. This leads to the development of a new model which aims to combine verisimilitude with numerical accuracy.Thesis (Ph.D.)--School of Mathematical Sciences (Applied Mathematics), 2004.
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Narasimhan, S. "Three Dimensional Viscoplastic And Geomertrically Non-Linear Finite Element Analysis Of Adhesively Bonded Joints." Thesis, 1998. http://etd.iisc.ernet.in/handle/2005/2166.
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