Dissertations / Theses on the topic 'Initial boundary'
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Mugnolo, Delio. "Second order abstract initial-boundary value problems." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971647674.
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Zhao, Kun. "Initial-boundary value problems in fluid dynamics modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31778.
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Thesis (Ph.D)--Mathematics, Georgia Institute of Technology, 2010.Committee Chair: Pan, Ronghua; Committee Member: Chow, Shui-Nee; Committee Member: Dieci, Luca; Committee Member: Gangbo, Wilfrid; Committee Member: Yeung, Pui-Kuen. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Al-Kharafi, Abdulmohsen A. H. "Finite element solution of initial/boundary value problems." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/32335.
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In the last few decades, the Finite Element Method (F.E.M.) has become one of the best techniques used to solve a vast variety of the world's initial/boundary value problems. When such a powerful method is facilitated by a 'user friendly' computer program that possess both pre- and post-processors together with an automatic mesh generation and refinement processor, it becomes indeed a powerful tool to solve a wide range of problems in Applied Mathematics and Engineering. This thesis is an attempt to show the potential of the method which is implemented by a general purpose program used to solve problems governed by partial differential equations (P.D.E.s).
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Qin, Jingsheng. "Initial boundary value problems associated with a spinning string." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq23465.pdf.
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Forgoston, Eric T. "Initial-Value Problem for Perturbations in Compressible Boundary Layers." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195810.
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An initial-value problem is formulated for a three-dimensional perturbation in a compressible boundary layer flow. The problem is solved using a Laplace transform with respect to time and Fourier transforms with respect to the streamwise and spanwise coordinates. The solution can be presented as a sum of modes consisting of continuous and discrete spectra of temporal stability theory. Two discrete modes, known as Mode S and Mode F, are of interest in high-speed flows since they may be involved in a laminar-turbulent transition scenario. The continuous and discrete spectrum are analyzed numerically for a hypersonic flow. A comprehensive study of the spectrum is performed, including Reynolds number, Mach number and temperature factor effects. A specific disturbance consisting of an initial temperature spot is considered, and the receptivity to this initial temperature spot is computed for both the two-dimensional and three-dimensional cases. Using the analysis of the discrete and continuous spectrum, the inverse Fourier transform is computed numerically. The two-dimensional inverse Fourier transform is calculated for Mode F and Mode S. The Mode S result is compared with an asymptotic approximation of the Fourier integral, which is obtained using a Gaussian model as well as the method of steepest descent. Additionally, the three-dimensional inverse Fourier transform is found using an asymptotic approximation. Using the inverse Fourier transform computations, the development of the wave packet is studied, including effects due to Reynolds number, Mach number and temperature factor.
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Bozkaya, Canan. "Boundary Element Method Solution Of Initial And Boundary Value Problems In Fluid Dynamics And Magnetohydrodynamics." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609552/index.pdf.
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In this thesis, the two-dimensional initial and boundary value problems invol-ving convection and diffusion terms are solved using the boundary element method (BEM). The fundamental solution of steady magnetohydrodynamic (MHD) flow equations in the original coupled form which are convection-diffusion type is established in order to apply the BEM directly to these coupled equations with the most general form of wall conductivities. Thus, the solutions of MHD flow in rectangular ducts and in infinite regions with mixed boundary conditions are obtained for high values of Hartmann number, M.
For the solution of transient convection-diffusion type equations the dual reciprocity boundary element method (DRBEM) in space is combined with the differential quadrature method (DQM) in time. The DRBEM is applied with the fundamental solution of Laplace equation treating all the other terms in the equation as nonhomogeneity. The use of DQM eliminates the need of iteration and very small time increments since it is unconditionally stable. Applications include unsteady MHD duct flow and elastodynamic problems. The transient Navier-Stokes equations which are nonlinear in nature are also solved with the DRBEM in space - DQM in time procedure iteratively in terms of stream function and vorticity. The procedure is applied to the lid-driven cavity flow for moderate values of Reynolds number. The natural convection cavity flow problem is also solved for high values of Rayleigh number when the energy equation is added.
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Kalimeris, Konstantinos. "Initial and boundary value problems in two and three dimensions." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/225180.
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This thesis: (a) presents the solution of several boundary value problems (BVPs) for the Laplace and the modified Helmholtz equations in the interior of an equilateral triangle; (b) presents the solution of the heat equation in the interior of an equilateral triangle; (c) computes the eigenvalues and eigenfunctions of the Laplace operator in the interior of an equilateral triangle for a variety of boundary conditions; (d) discusses the solution of several BVPs for the non-linear Schrödinger equation on the half line. In 1967 the Inverse Scattering Transform method was introduced; this method can be used for the solution of the initial value problem of certain integrable equations including the celebrated Korteweg-de Vries and nonlinear Schrödinger equations. The extension of this method from initial value problems to BVPs was achieved by Fokas in 1997, when a unified method for solving BVPs for both integrable nonlinear PDEs, as well as linear PDEs was introduced. This thesis applies "the Fokas method" to obtain the results mentioned earlier. For linear PDEs, the new method yields a novel integral representation of the solution in the spectral (transform) space; this representation is not yet effective because it contains certain unknown boundary values. However, the new method also yields a relation, known as "the global relation", which couples the unknown boundary values and the given boundary conditions. By manipulating the global relation and the integral representation, it is possible to eliminate the unknown boundary values and hence to obtain an effective solution involving only the given boundary conditions. This approach is used to solve several BVPs for elliptic equations in two dimensions, as well as the heat equation in the interior of an equilateral triangle. The implementation of this approach: (a) provides an alternative way for obtaining classical solutions; (b) for problems that can be solved by classical methods, it yields novel alternative integral representations which have both analytical and computational advantages over the classical solutions; (c) yields solutions of BVPs that apparently cannot be solved by classical methods. In addition, a novel analysis of the global relation for the Helmholtz equation provides a method for computing the eigenvalues and the eigenfunctions of the Laplace operator in the interior of an equilateral triangle for a variety of boundary conditions. Finally, for the nonlinear Schrödinger on the half line, although the global relation is in general rather complicated, it is still possible to obtain explicit results for certain boundary conditions, known as "linearizable boundary conditions". Several such explicit results are obtained and their significance regarding the asymptotic behavior of the solution is discussed.
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Mantzavinos, Dionyssios. "Initial-boundary value problems for linear and integrable nonlinear evolution PDEs." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610568.
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Ran, Yu. "Nonhomogeneous Initial Boundary Value Problems for Two-Dimensional Nonlinear Schrodinger Equations." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/47930.
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The dissertation focuses on the initial boundary value problems (IBVPs) of a class of nonlinear Schrodinger equations posed on a half plane R x R+ and on a strip domain R x [0,L] with Dirichlet nonhomogeneous boundary data in a two-dimensional plane. Compared with pure initial value problems (IVPs), IBVPs over part of entire space with boundaries are more applicable to the reality and can provide more accurate data to physical experiments or practical problems. Although there is less research that has been made for IBVPs than that for IVPs, more attention has been paid for IBVPs recently. In particular, this thesis studies the local well-posedness of the equation for the appropriate initial and boundary data in Sobolev spaces H^s with non-negative s and investigates the global well-posedness in the H^1-space. The main strategy, especially for the local well-posedness, is to derive an equivalent integral equation (whose solution is called mild solution) from the original equation by semi-group theory and then perform the Banach fixed-point argument. However, along the process, it is essential to select proper auxiliary function spaces and prepare all the corresponding norm estimates to complete the argument. In fact, the IBVP posed on R x R+ and the one posed on R x [0,L] are two independent problems because the techniques adopted are different. The first problem is more related to the initial value problem (IVP) posed on the whole plane R^2 and the major ingredients are Strichartz's estimate and its generalized theory. On the other hand, the second problem can be studied as an IVP over a half-line and periodic domain, which is established on the analysis for series inspired by Bourgain's work. Moreover, the corresponding smoothing properties and regularity conditions of the solution are also considered.Ph. D.
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Thornburg, Jonathan. "Coordinates and boundary conditions for the general relativistic initial data problem." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25060.
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Techniques for numerically constructing initial data in the 3+1 formalism of general relativity (GR) are studied, using the theoretical framework described in Bowen and York (1980), Physical Review D 21(8), 2047-2056. The two main assumptions made are maximal slicing and 3-conformal flatness of the generated spaces. For ease of numerical solution, axisymmetry is also assumed, but all the results should extend without difficulty to the non-axisymmetric case.
The numerical code described in this thesis may be used to construct vacuum spaces containing arbitrary numbers of black holes, each with freely specifyable (subject to the axisymmetry assumption) position, mass, linear momentum, and angular momentum. It should be emphasised that the time evolution of these spaces has not yet been attempted.
There are two significant innovations in this work: the use of a new boundary condition for the surfaces of the black holes, and the use of multiple coordinate patches in the numerical solution.
The new boundary condition studied herein requires the inner boundary of the numerical grid to be a marginally trapped surface. This is in contrast to the approach used in much previous work on this problem area, which requires the constructed spaces to be conformally isometric under a "reflection mapping" which interchanges the interior of a specified black hole with the remainder of the space. The new boundary condition is found to be easy to implement, even for multiple black holes. It may also prove useful in time evolution problems.
The coordinate choice scheme introduced in this thesis uses multiple coordinate patches in the numerical solution, each with a coordinate system suited to the local physical symmetries of the region of space it covers. Because each patch need only cover part of the space, the metrics on the individual patches can be kept simple, while the overall patch system still covers a complicated topology. The patches are linked together by interpolation across the interpatch boundaries. Bilinear interpolation suffices to give accuracy comparable with that of common second order difference schemes used in numerical GR.
This use of multiple coordinate patches is found to work very well in both one and two black hole models, and should generalise to a wide variety of other numerical GR problems. Patches are also found to be a useful (if somewhat over-general) way of introducing spatially varying grid sizes into the numerical code. However, problems may arise when trying to use multiple patches in time evolution problems, in that the interpatch boundaries must not become spurious generators or reflectors of gravitational radiation, due to the interpolation errors. These problems have not yet been studied.
The code described in this thesis is tested against Schwarzschild models and against previously published work using the Bowen and York formalism, reproducing the latter within the limits of error of the codes involved. A number of new spaces containing one and two black holes with linear or angular momentum are also constructed to demonstrate the code, although little analysis of these spaces has yet been done.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Fang, Chin-Lung. "Predictability of Japan/East Sea (JES) system to uncertain initial/lateral boundary conditions and surface winds." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03sep%5FFang.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, September 2003.Thesis advisor(s): Peter C. Chu, Steve Haeger. Includes bibliographical references (p. 73-77). Also available online.
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Carey, John Fernando. "Initial assessment in forensic psychiatry : the forensic assessment format as a boundary object." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/12134/.
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This research project offers initial assessment in forensic psychiatry a new assessment guideline, the Forensic Assessment Format, (Carey 2006) which is a development from Jane Ussher’s material-discursive-intrapsychic model of critical realism, (Ussher 2000a). It presents a review of the technical and theoretical literature looking at the development of assessment methods in forensic psychiatry and discusses current practice and how a critical realist perspective could inform the assessment process. It is a qualitative study using both an empirical and an analytic auto-ethnographic approaches, (Anderson 2006). The research project presents data from 19 semi-structured interviews and a focus group analysed using grounded theory, (Glaser and Strauss 1967) to aid both deductive and abductive approaches, (Timmermans and Tavory 2012). Service users were involved from the beginning of the project to inform the themes that developed into the interview questions. The outcomes of the study offer support for the potential of this critical method of initial assessment to be collaborative, holistic and inclusive and that it could act as a boundary object, (Star and Griesemer 1989), between different social worlds providing a bridge for information to flow. This encourages cooperation in completing the assessment and then formulating and meeting the identified needs. It explores and provides an insight into the initial assessment process in forensic psychiatry from the perspective of the service user, referrer and assessor. Further suggestions are offered in associated areas such as how plural realities can be understood and how the assessment process in forensic psychiatry could be further improved.
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Doroshenko, V. O., N. P. Klimova, N. P. Stognii, and Yu D. Kostyn. "Mathematical Modelling of Impulse Excitation of a Superwideband PEC Cone Antenna." Thesis, 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers, CAOL*2019, 2019. https://openarchive.nure.ua/handle/document/16284.
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The method for solving initial-boundary electromagnetic problems is proposed. It uses the Green’s function method and the Laplace and Meler-Fock integral transforms in a time domain. The model problem of special slotted cone antenna excitation is studied. Integral and series representation of electromagnetic field component are given.
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Thorning, Casper. "Grain boundary ridge formation during initial high temperature oxidation of Mn/Al TRIP steel /." Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4081.
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Negron, Luis G. "Initial-value technique for singularly perturbed two point boundary value problems via cubic spline." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4597.
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A recent method for solving singular perturbation problems is examined. It is designed for the applied mathematician or engineer who needs a convenient, useful tool that requires little preparation and can be readily implemented using little more than an industry-standard software package for spreadsheets. In this paper, we shall examine singularly perturbed two point boundary value problems with the boundary layer at one end point. An initial-value technique is used for its solution by replacing the problem with an asymptotically equivalent first order problem, which is, in turn, solved as an initial value problem by using cubic splines. Numerical examples are provided to show that the method presented provides a fine approximation of the exact solution. The first chapter provides some background material to the cubic spline and boundary value problems. The works of several authors and a comparison of different solution methods are also discussed. Finally, some background into the specific singularly perturbed boundary value problems is introduced. The second chapter contains calculations and derivations necessary for the cubic spline and the initial value technique which are used in the solutions to the boundary value problems. The third chapter contains some worked numerical examples and the numerical data obtained along with most of the tables and figures that describe the solutions. The thesis concludes with some reflections on the results obtained and some discussion of the error bounds on the calculated approximations to the exact solutions for the numeric examples discussed.ID: 029051011; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.)--University of Central Florida, 2010.; Includes bibliographical references (p. 48-50).
M.S.
Masters
Department of Mathematics
Sciences
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Nilsson, Jonas. "Initial-boundary-value problems for the Stokes and Navier-Stokes equations on staggered grids /." Uppsala : Acta universitatis Upsaliensis, 2000. http://catalogue.bnf.fr/ark:/12148/cb392870516.
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Jakab, Tunde. "Parabolic layer potentials and initial boundary value problems in Lipschitz cylinders with data in Besov spaces." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4438.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 27, 2007) Vita. Includes bibliographical references.
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Trumper, Miles Thomas. "A study of nozzle exit boundary layers in high-speed jet flows." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/31797.
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The requirement for reduced jet noise in order to meet stringent noise legislation (civil aviation), and low infra-red observability and the use of unconventional exhaust nozzle configurations to improve aircraft survivability and performance (military aviation) is driving research to develop a better understanding of jet development and mixing mechanisms. One option open to the engineer is the use of small-scale model testing to investigate jets flows and provide valuable data for the validation of numerical models. Although more economical than large/full scale testing, additional factors that influence jet development may be present which would not be present at full scale and whose influence needs to be fully understood in order to allow small scale–large scale read-across. One such factor is the nozzle exit boundary layer. Although considerable data exist on the influence of nozzle exit boundary layers on low speed jet flows, current information on high speed jet flows is limited. It was, therefore, the aim of this thesis to extend the current understanding of nozzle exit boundary layers and their influence on the jet development for high speed jet flows through a combination of experimental and computational techniques. A combination of pneumatic probe measurements and Laser Doppler Anemometry (LDA) was used to investigate nozzle inlet and exit boundary layers of simple conical nozzles and the influence of adding a parallel extension piece. The measurements showed that the rapid acceleration of the boundary layer within the nozzle significantly reduced its momentum thickness Reynolds number and changed the state of the boundary layer from turbulent to laminar-like. The addition of a parallel extension to the nozzle exit returned the boundary layer to a fully turbulent state. A low Reynolds number RANS CFD approach was used to investigate the flow within the nozzle. Simulations using the Launder-Sharma low Reynolds number k–ε model revealed that the magnitude of the acceleration within the conical nozzles resulted in the boundary layer beginning to relaminarise. Full relaminarisation was not achieved due to the short axial distance over which the acceleration was sustained. The addition of a parallel extension provided a relaxation region in which the boundary layer could recover from the acceleration to become fully turbulent. Measurements of the jet plume originating from nozzles with laminar-like and turbulent boundary layers showed little influence of the boundary layer shape and thickness on shear layer spreading and jet centreline development.
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Kunik, Matthias [Verfasser], and Gerald [Gutachter] Warnecke. "Selected initial and boundary value problems for hyperbolic systems and kinetic equations / Matthias Kunik ; Gutachter: Gerald Warnecke." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2019. http://d-nb.info/1220035262/34.
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VARGAS, JOSE VIRIATO COELHO. "INITIAL VALUE METHOD FOR THE SOLUTION OF NON-SIMILAR BOUNDARY LAYERS APPLIED TO A WEDGE IN MEXED CONVECTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1992. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19598@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROO presente trabalho apresenta o método de varredura de valores iniciais para a solução de problemas não-similares de camada limite, aplicado a uma cunha em convecção mista. É feita uma análise dos efeitos da força de empuxo nas características de transferência de calor e atrito, na superfície da cunha submetida a um escoamento laminar em convecção forçada. Os casos analisados referem-se a temperatura uniforme na superfície e a fluxo de calor uniforme através da superfície. Apresentam-se resultados numéricos para a placa vertical e a cunha em 120 graus celsius (problema similar), os quais foram comparados com os disponíveis na literatura, apresentando-se excelente concordância. Ainda são apresentados resultados para a cunha em 90 graus celsius e em 180 graus Celsius. Os resultados foram obtidos para o número de Prandtl 0,7 em uma larga faixa do parâmetro de não-similaridade (0 a 100 para temperatura uniforme e 0 a 5 para fluxo de calor uniforme). Em geral, verifica-se que para ambos os casos estudados de condições da superfície, o coeficiente de atrito local e o número de Nusselt local aumentam com o aumento da força de empuxo para o escoamento ajudado e diminuem com o aumento da força de empuxo para o escoamento ajudado e diminuem com o aumento da força de empuxo para o escoamento oposto. Verifica-se também que os efeitos de convecção natural diminuem com o aumento do ângulo da cunha. Compara-se, por fim os resultados de transferência de calor entre os dois casos estudados. O método possibilita a obtenção de resultados com o uso de um microcomputador PC AT-286 com o co-processador matemático, sem o uso de dupla precisão. As tolerâncias utilizadas para a convergência são as mesmas dos resultados disponíveis na literatura. Adicionalmente, o tempo computacional necessário para a obtenção das soluções foi bastante reduzido. Para toda a faixa de variação do parâmetro de não-similaridade, o equacionamento utilizado foi o mesmo, baseado em parâmetros de correlação para convecção forçada em uma superfície plana com injeção de massa, com ótima concordância com resultados disponíveis na literatura.
The present work introduces a method for searching initial values, to solve non-similar Boundary Layer problems. The new method has been applied to the problem of mixed convection on a Wedge. An analysis is performed to study the effects of buoyancy force on the heat transfer and friction characteristics of laminar forced convection flow which is either maintained at a uniform temperature or subjected to a uniform temperature or subjected to a uniform heat flux. Numerical results are presented for Prandtl number of 7,0 over a wide range of values of the buoyancy force parameters (0 to 100 for uniform temperature and 0 to 5 for uniform heat flux). The results for the vertical plate and for the similar wedge (120 graus celsius) Have been compared with solutions availabein the literature, showing an excellent agreement. In addition, solutions for the 90 degree celsius wedge and for the flat wall (180 degree celsius are also obtained. In general, it is found that for both surface heating conditions, the local friction factor and the local Nusselt number increase with increasing bouyancy force for assisting flow and decrease with inscreasing bouyancy force for opposing flow. Further, the effects of the buoyancy force on these two quantities are found to diminish as the angle of the wedge increases. A comparison is also made of the results beteween the case of uniform wall temperature and the case of uniform surface heat flux. The method turns possible to obtain results with the use of a microcomputer PC AT-286 with a Math co-processor, discarding the use of double precision. The tolerances for convergence are the same as the results available in the literature. The necessary computacional time to get the solution was greatly reduced. For the entire range of the buoyancy force parameter, the governing equations are the same, based upon forced convection parameters. To illustrate the flexibility of the method, the surface mass trasnfer problem of uniform injection (blowing) in a flat plate under forced cnvection, has been solved and the results compared with the available ones in the literature.
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Tiwari, Shreevant. "Methods for atomistic input into the initial yield and plastic flow criteria for nanocrystalline materials." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53059.
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Nanocrystalline (NC) metals and alloys are known to possess superior mechanical properties, e.g., strength, hardness, and wear-resistance, as compared to conventional microcrystalline materials. NC metals are characterized by a mean grain size <100 nm; in this grain size regime, inelastic deformation can occur via a combination of interface-mediated mechanisms viz., grain boundary sliding/migration, and dislocation nucleation from grain boundary sources. Recent studies have suggested that these interface-mediated inelastic deformation mechanisms in fcc metals are influenced by non-glide stresses and interfacial free volume, unlike dislocation glide mechanisms that operate in microcrystalline fcc metals. Further, observations of tension-compression strength asymmetry in NC metals raise the possibility that yield and inelastic flow in these materials may not be adequately described by solely the deviatoric stress. Unfortunately, most literature concerning the mechanical testing of NC metals is limited to uniaxial deformation or nanoindentation techniques, and the multiaxial deformation behavior is often predicted assuming initially isotropic yield and subsequent flow normal to the yield surface.
The primary objective of this thesis is to obtain a better understanding of the nature of inelasticity in NC metals by simulating multiaxial deformation at the atomistic resolution, and developing methods to interpret the results in ways that would be useful from a continuum constitutive modeling viewpoint. First, we have presented a novel, statistical mechanics-based approach to unambiguously resolve the elastic-plastic transition as an avalanche in the proliferation of mobile defects. This approach is applied to nanocrystalline Cu to explore the influence of pressure and multiaxial stress states on the inelastic deformation behavior. The results suggest that initial yield in nanocrystalline Cu under biaxial loading is only weakly anisotropic in the 5 nm grain size regime, and that plastic flow evolves in a direction normal to the von Mises yield surface. However, triaxial deformation simulations reveal a significant effect of the superimposed hydrostatic stress on yielding under shear. These results are analyzed in detail in order to assess the influence of pre-existing internal stresses and interfacial excess volume on the inelastic deformation behavior.
Further, we have studied the effects of imposed hydrostatic pressure on the shear deformation behavior of Cu bicrystals containing symmetric tilt interfaces, as well as Cu nanocrystals of different grain sizes. Most interfaces exhibit an increase in shear strength with imposed compressive hydrostatic pressure. However, for some interfaces, this trend is reversed. Neither the sign nor the magnitude of the pressure-induced elevation in shear strength appears to correlate with interface structure or particular deformation mechanism(s). In Cu nanocrystals, we observe that imposed compressive pressure leads to strengthening under shear deformation, and the effect of imposed pressure on the shear strength becomes stronger with increase in grain size or temperature. Activation parameters for shear deformation have been computed for these nanocrystals, and computed values seem to agree with existing experimental and theoretical estimates. Finally, we have proposed some modifications to conventional isothermal molecular dynamics algorithms, in order to isolate dislocation nucleation events from interfacial sources, and thereby permit explicit computation of the activation parameters for such events.
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Mudavanhu, Blessing. "A new renormalization method for the asymptotic solution of multiple scale singular perturbation problems /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/6794.
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Schmitt, Johann Michael [Verfasser]. "Optimal Control of Initial-Boundary Value Problems for Hyperbolic Balance Laws with Switching Controls and State Constraints / Johann Michael Schmitt." München : Verlag Dr. Hut, 2019. http://d-nb.info/1188516450/34.
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Göransson, Albin. "Stability and accuracy for difference methods using asynchronous processors." Thesis, Linköpings universitet, Matematiska institutionen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-146045.
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We solve initial boundary value problems with information unavailable at random time-steps. The randomly unavailable information represents asynchrony between processing elements. To approximate the initial boundary value problem, finite difference operators with summation-by-parts proper-ties and weak boundary procedures are used. Utilizing the energy method, we derive energy estimates for synchronous and asynchronous problems. The simulations show that the solutions may remain accurate and stable, even in the asynchronous case.
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Schultz, Richard. "Vodní ráz v oblasti nízkých tlaků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230123.
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The subject of the submitted thesis „Low pressure water hammer“ is handling the problems of dynamic conduct of water in low pressures. In this work are developed problems of the effect of changing pressure on the speed of sound in liquid. The problem is solved in the time domain using the Lax - Wendroff method in the theoretical analysis. At the end the mathematical model solved using Lax - Wendroff method is confront with the experiment.
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Rivas, Ivonne. "Analysis and Control of the Boussinesq and Korteweg-de Vries Equations." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321371582.
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Sharma, Sushank. "Transition laminaire turbulent dans les couches limites supersoniques : différents scénarios et contrôle possible Control of oblique-type breakdown in a supersonic boundary layer employing streaks Turbulent flow topology in supersonic boundary layer with wall heat transfer Laminar-to-turbulent transition in supersonic boundary layer : : Effects of initial perturbation and wall heat transfer Effect of thermo-mechanical non-equilibrium on the onset of transition in supersonic boundary layers." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR16.
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Les simulations numériques directes (DNS) des couches limites supersoniques adiabatiques et isothermes (chauffées et refroidies) sont effectuées. Deux différents scénarios de transition, à savoir la décomposition de type oblique et la transition de type 'by-pass', sont présentés en détail. Pour le scénario de transition de type oblique, les résultats montrent que les modes contrôles avec un nombre d'onde quatre à cinq fois supérieur au nombre fondamental se révèlent être bénéfiques pour contrôler la transition. Dans la première région après le forçage du mode de contrôle, la distorsion de flux moyenne (MFD) bénéfique générée en induisant le mode de contrôle est uniquement responsable de l'entrave à la croissance du mode fondamental. Globalement, le MFD et la partie tridimensionnelle du contrôle contribuent également à contrôler la rupture oblique. Les effets de paramètres physiques tels que la température de paroi, l'intensité de la perturbation et le 'baseflow' sont étudiés pour la transition de 'By-pass'. Les résultats concernant le scénario de by-pass révèlent que l'augmentation de l'intensité de la perturbation déplace le début de la transition en amont et augmente également la longueur de la région de transition. De plus, en dessous de 1 % des niveaux de perturbation, le refroidissement de la paroi stabilise le flux, tandis que l'inverse se produit à des valeurs plus élevées. L'existence d'un non-équilibre thermomécanique avance le début de la transition pour les cas chauffés alors que la paroi refroidie se comporte dans le sens opposé. Les analyses de la couche limite turbulente montrent que les facteurs thermiques influencent la topologie et l'inclinaison des structures tourbillonnaires. De plus, en ce qui concerne le flux de chaleur, un processus de transfert différent est dominant dans la région proche paroi pour la paroi refroidieDirect numerical simulations (DNS) of both adiabatic and isothermal (heated and cooled) supersonic boundary layers are performed. Two different transition scenarios, namely the Oblique-type breakdown and the By-pass transition are presented in detail. For the oblique-type transition scenario, the results show that the control modes with four to five times the fundamental wavenumber are beneficial for controlling the transition. In the first region, after the control-mode forcing, the beneficial mean-flow distortion (MFD) generated by inducing the control mode is solely responsible for hampering the growth of the fundamental-mode. Globally, the MFD and the three-dimensional part of the control contribute equally towards controlling the oblique breakdown. Effects of physical parameters like wall-temperature, perturbation intensity and baseflow are investigated for the By-pass transition. The results regarding the by-pass scenario reveal that increasing the perturbation intensity moves the transition onset upstream and also increases the length of the transition region. Additionally, below 1% perturbation levels, wall-cooling stabilizes the flow while inverse happens at higher values. The existence of the thermo-mechanical non-equilibrium advances the onset of transition for the heated cases while the cooled wall behaves in the opposite sense. The analyses of the turbulent boundary layer show that the thermal factors influence the topology and inclination of the vortical structures. Moreover, regarding the heat flux, different transfer process is dominant in the near-wall region for the cooled wall
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Exare, Christelle. "Les aspirations intrusives dans l’anglais des apprenants francophones." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCA008.
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Cette thèse décrit les aspirations intrusives, saillantes mais labiles, souvent représentées par /h/ ou [h], dans l’anglais L2 des francophones (par exemple : I hate pasta au lieu de I ate pasta). Le phonème /h/ est débile dans les langues indo-européennes. Historiquement, la consonne subit une lénition progressive, avec une forte variation linguistique et extralinguistique (diatopique, diastratique et diachronique). La fricative glottale /h/ à l’attaque de mot en anglais L1 est caractérisée par i) l’ouverture de la glotte et ii) la configuration supraglottale de la voyelle suivante. Dans cette étude, les réalisations des attaques de mot en anglais sont étudiées à partir de trois sortes de données : i) un texte lu par 8 anglophones et 10 francophones, ii) la parole spontanée de 25 francophones et iii) un test de perception passé par 30 francophones. La fréquence d’apparition des aspirations intrusives montre une forte variabilité inter- et intra-locuteurs. Elles sont retrouvées exclusivement i) en position initiale absolue ou ii) après un phone vocalique. Une pause, une glottalisation ou une aspiration sont trois procédés qui conduisent à augmenter l’écart temporel entre deux voyelles en hiatus. Une glottalisation ou une aspiration ont en commun de correspondre à une tension glottale. Les aspirations illicites semblent être des traces d’hypercorrection qui pourraient être dues i) à une assimilation incomplète du contraste phonétique [ʔ] ~ [h] de l’anglais, ii) à la réparation phonologique facultative de *#V, iii) à un geste de constriction glottale n’atteignant pas sa cible (glottalisation inchoative) et à un geste intrusif d’ouverture glottale. La correction phonétique proposée par le professeur recherche la prise de conscience par l’apprenant i) du contrôle de la glotte pour l’aspiration, la glottalisation et le maintien d’un voisement modal en frontière morphologique, et ii) des particularités syllabiques du français et de l’anglais qui font des frontières de mot des points d’achoppement potentiels en anglais L2This dissertation describes some salient, yet variable, intrusive tokens of aspiration, often represented by /h/ or [h], in French learners’ L2 English productions (e.g. : I hate pasta instead of I ate pasta). The phoneme /h/ is weak in Indo-European languages. Historically, the consonant has undergone progressive lenition and exhibits strong intralinguistic and extralinguistic --diachronic, dialectal and stylistic-- variation. The glottal fricative /h/ at English word onsets is characterised by i) an open glottis and ii) the supraglottal configuration of the following vowel. In the present study, the onsets of English words are analysed in three types of data: i) a text read by 8 native English speakers and 10 French learners of English, ii) spontaneous speech elicited from 25 French learners and iii) a perception test taken by 30 French-speaking students. The frequency of intrusive tokens of aspiration at L2 English word onsets shows high inter- and intra-speaker variability. Importantly, however, they only surface i) in strict initial position or ii) after a vocalic sound. A pause, some glottalisation or some aspiration are three processes that contribute to increasing the time span between two vowels in a hiatus context. Glottalisation and aspiration both correspond to glottal tension. Illicit tokens of aspiration can be considered as occurrences of hypercorrection, which may result from : i) incomplete assimilation of the English [ʔ] ~ [h] contrast, ii) optional phonological repair of *#V, iii) a glottal constriction gesture that fails to reach its target (i.e. inchoative glottalisation) and an intrusive gesture of glottal opening. Phonetic corrective feedback in L2 learning is proposed. It aims at raising the learner’s awareness of i) glottal control for aspiration, glottalisation, and continuous modal voicing across word boundaries and ii) some syllabic specificities of French and English that make word boundaries potential stumbling blocks in French learners’ L2 English
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El, Ouaraini Rachida. "Sensibilité des assimilations d'ensemble globales et régionales aux conditions initialites et aux conditions limites latérales." Phd thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/15999/1/ElOuaraini.pdf.
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La mise en œuvre de méthodes d'assimilation d'ensemble est une technique assez récente visant à simuler les erreurs d'analyse et de prévision d'un système d'assimilation de données. Cela permet d'une part d'estimer des covariances spatiales des erreurs de prévision, qui sont un ingrédient essentiel des systèmes d'assimilation de données, dans la mesure où elles permettent de filtrer et de propager spatialement l'information observée. La dépendance de ces covariances d'erreur à la situation météorologique devient ainsi accessible avec ces techniques d'ensemble. D'autre part, l'assimilation d'ensemble est également une méthode de plus en plus utilisée pour fournir des perturbations initiales aux systèmes de prévision d'ensemble. Une telle approche peut être mise en place non seulement dans un système modélisant l'atmosphère sur l'ensemble du globe, mais aussi dans un système régional à aire limitée, en utilisant dans ce cas des conditions limites latérales appropriées. Le sujet de thèse proposé consiste à examiner certaines propriétés de sensibilité de ces techniques d'assimilation d'ensemble dans ces deux types de contextes (à savoir global et régional, respectivement). Il s'agit premièrement d'étudier la sensibilité d'un système global d'assimilation d'ensemble à son initialisation. Cela sera mené en comparant une technique d'initialisation "à froid" (basée sur des perturbations initiales nulles) avec une méthode basée sur des perturbations initiales tirées d'un modèle de covariance. Dans une deuxième partie, la sensibilité d'une assimilation d'ensemble régionale aux conditions limites latérales sera examinée. Dans cette perspective, une comparaison entre différentes techniques de production des perturbations latérales sera réalisée. Il s'agit notamment de comparer les approches basées sur des perturbations latérales qui sont soit nulles, soit tirées d'un ensemble global, ou encore produites à l'aide d'un modèle de covariance. Ces études de sensibilité seront menées d'une part en utilisant des expérimentations avec les systèmes global Arpege et régional Aladin. Ce travail s'appuiera d'autre part sur une formalisation des équations qui gouvernent l'évolution des perturbations au sein d'une assimilation d'ensemble. Ces études devraient permettre de documenter les propriétés de ces assimilations d'ensemble, et de définir des stratégies de mise en œuvre en grandeur réelle pour l'assimilation de données ainsi qu'éventuellement pour la prévision d'ensemble.
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Tiwari, Ganesh. "Numerical Analysis of Non-Fickian Diffusion with a General Source." ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/honors_theses/49.
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The inadequacy of Fick’s law to incorporate causality can be overcome by replacing it with the Green–Naghdi type II (GNII) flux relation. Combining the GNII assumption and conservation of mass leads to [see document for equation] where r (x, t) is the density function, S(p) is a source term and c¥ is a positive constant which carries (SI) units of m/sec. A general source term given by [see document for equation] is proposed. Here, the constants y and ps are the rate coefficient and saturation density respectively. The travelling wave solutions and numerical analysis of four special cases of equation (2), namely: Pearl-Verhulst Growth law, Zel’dovich Law, Newmann Law and Stefan- Boltzmann Law are investigated. For both analysis, results are compared with the available literature and extended for other cases. The numerical analysis is carried out by imposing well-studied Initial Boundary Value Problem and implementing a built-in method in the software package Mathematica 9. For Pearl-Verhulst source type, the results are compared to those found in literature [1]. Confirming the validity of built-in method for Pearl-Verhulst law, the generic built-in method is extended to study the transient signal response for similar initial boundary value problems when the source terms are Zel’dovich law, Newmann law and Stefan-Boltzmann law.
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Velissariou, Panagiotis. "Development of a Coastal Prediction System That Incorporates Full 3D Wave-Current Interactions on the Mean Flow and the Scalar Transport With Initial Application to the Lake Michigan Turbidity Plume." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1229959016.
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Grenier, Muriel. "Attraction d'ondes pour des systèmes à résonance d'ondes contra-propagatives." Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00696097.
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L'attraction d'ondes dans des systèmes contra-propagatifs est un phénomène général, établi initialement en Physique dans le contexte de l'attraction de polarisation entre deux ondes contra-propagatives se propageant dans des fibres optiques. Ce phénomène a été observé expérimentalement, et ses propriétés étudiées via des simulations numériques. Les modèles qui s'y rattachent sont des systèmes hyperboliques d'équations aux dérivées partielles, avec des conditions aux bords dépendant du temps sur un intervalle fini. Le mécanisme sous-jacent peut être expliqué par l'existence de tores singuliers dans les équations stationnaires correspondantes. Le but de cette thèse est d'analyser en détail l'exemple le plus simple dans cette famille de modèles. Nous montrons que la plupart des phénomènes de processus d'attraction d'ondes sont en fait existants dans un modèle linéaire avec intéraction résonnante. Nous établissons l'existence et la régularité des solutions et analysons la relaxation vers la solution stationnaire qui caractérise les propriétés de l'attraction d'ondes.
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Vašek, Lubomír. "Trhání vodního sloupce pod OK vodní turbíny při nestacionárních stavech." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230024.
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In this diploma thesis called Water column separation under the hydraulic turbine runner during unsteady operating regimes are solved the pressure pulsations of the reverse water hamer. In the thesis is deduced a mathematical relationship of elaboration the numerice model which is based on equations of continuity and equations of forces equilibrium. Numerical model is created in MS Excel uses for computation the numerical method Lax-Wendrof that allows consideration of variable sound speed as function of static pressure and allows variable lenght step in computation domain. Reverse water hammer is in the thesis solved with consideration of rotating flow behind shut-off valve, where we expect forming of vortex rope. This situation can be applied on the closing water turbine which has vertex rope under turbine runner. Specifically for this thesis was carried out the experiment of the reverse water hammer. Constants going into numerical solution are optimalized with using experiment and pressure pulsation are compared between numerical solution and experiment.
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Nguyen, Phuoc Tai. "Trace au bord de solutions d'équations de Hamilton-Jacobi elliptiques et trace initiale de solutions d'équations de la chaleur avec absorption sur-linéaire." Phd thesis, Université François Rabelais - Tours, 2012. http://tel.archives-ouvertes.fr/tel-00710410.
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Cette thèse est constituée de trois parties. Dans la première partie, on s'intéresse au problème de trace au bord d'une solution positive de l'équation de Hamilton-Jacobi (E1) $-\Delta u+g(|\nabla u|)=0$ dans un domaine borné $\Omega$ de ${\mathbb R}^N$, satisfaisant (E2) $u = \mu$ sur $\partial \Omega$. Si $g(r) \geq r^q$ avec $q > 1$, on prouve que toute solution positive de (E1) admet une trace au bord considérée comme une mesure de Borel régulière, pas nécessairement localement bornée. Si $g(r) = r^q$ avec $1 < q < q_c = \frac{N+1}{N}$ , on montre l'existence d'une solution positive dont la trace au bord est une mesure de Borel régulière $\nu \not \equiv \infty$ et on caractérise les singularités frontières isolées de solutions positives. Si $g(r) = r^q$ avec $q_c \leq q < 2$, on établit une condition nécessaire de résolution en terme de capacité de Bessel $C_{\frac{2-q}{q},q'} . On étudie aussi des ensembles éliminables au bord pour des solutions modérées. La deuxième partie est consacrée à étudier la limite, lorsque $k \to \infty$, de solutions d'équation $\partial_t u - \Delta u + f(u) =0$ dans ${\mathbb R}^N \times (0;\infty)$ avec donnée initiale $k\delta_0$ où $0$ est la masse de Dirac concentrée à l'origine et f est une fonction positive, continue, croissante et satisfaisant $f(0) = f^{-1}(0) = 0$. On prouve, sous certaines hypothèses portant sur f, qu'il existe essentiellement trois types de comportement possible en fonction des valeurs finies ou infinies des intégrales $\int_1^\infty f^{-1}(s)ds$ et $\int_1^\infty F^{-1/2}(s)ds$, où $F(s)=\int_0^s f(r)dr$. Grâce à ces résultats, on donne une nouvelle construction de la trace initiale et quelques résultats d'unicité et de non-unicité de solutions dont la donnée initiale n'est pas bornée. Dans la troisième partie, on élargit le cadre de nos investigations et généralise les résultats obtenus dans la deuxième partie au cas où l'opérateur est non-linéaire. En particulier, on s'intéresse à des propriétés qualitatives de solutions positives de l'équation $ \partial_t u-\Delta_p u+f(u)=0$ où $p > 1, \Delta_p u = div(\abs{\nabla u}^{p-2}\nabla u)$ et $f$ est une fonction continue, croissante, positive et satisfaisant $f(0) = 0 = f^{-1}(0)$. Si $p > \frac{2N}{N+1}$, on fournit une condition suffisante portant sur f pour l'existence et l'unicité des solutions fondamentales de données initiales $k\delta_0$ et on étudie la limite, lorsque $k \to \infty$, qui dépend du fait que $f^{-1}$ et $F^{-1/p}$ soient intégrables à l'infini ou pas, où $F(s) =\int_0^s f(r)dr. On donne aussi de nouveaux résultats de non-unicité de solutions avec donnée initiale non bornée. Si $p \geq 2$, on prouve que toute solution positive admet une trace initiale dans la classe de mesures de Borel régulières positives. Finalement on applique les résultats ci-dessus au cas modèle $f(u)=u^\alpha \ln^\beta(u+1)$ avec $\alpha>0$ et $\beta>0$.
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Pham, Thanh Tung. "Multiscale modelling and simulation of slip boundary conditions at fluid-solid interfaces." Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00980155.
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In most applications concerning a fluid flowing over a solid surface, the no-slip velocity condition was widely used because it is simple and produces the results in agreement with experiments. However, this dynamical boundary condition is not appropriate when the flow under consideration is at a micro or nano length scale.In order to model this effect at the macroscopic scale, the Navier boundary conditions have been introduced, with the slip length as a parameter. When the fluid is a gas, this length is related to the tangential momentum accommodation coefficient (TMAC) and the mean free path, according to the Maxwell model. The aim of this work is to systematically address this model using a multi-scale approach and to extend it by incorporating both the morphology and the anisotropy of a surface. The thesis consists of five chapters. In Chapter 1, the basics of the kinetic theory of gases, the Boltzmann equation and related solutions (Navier-Stokes-Fourier, Burnett, Grad, Direct Simulation Monte Carlo ...) are briefly presented. The models of gas-wall interaction and slip models introduced in the fluid mechanics are also recalled. The chapter ends with a description of the computational method used for the molecular dynamics simulations performed in this work. Chapter 2 is dedicated to the development of a simple technique to simulate the pressure driven flows. The principle is to rely on the atomistic formulas of the stress tensor (Irving Kirkwood, Method of Plane, Virial Stress) and to modify the periodic conditions by maintaining the difference between the kinetic energy of the ingoing and outgoing particles of the simulation domain. Several types of channels are studied with this technique. The results (temperature, velocity ...) are discussed and compared. Chapter 3 deals with the study of the gas-wall interaction potential by the ab-initio method. The code CRYSTAL 09 is used to obtain the potential between an atom of argon (Ar) and a surface of platinum (Pt) <111> as a function of distance. Then the gas-wall potential is decomposed into binary potential and approached by an analytic function. This function is then implemented in a MD code to simulate the gas-wall collisions and determine the TMAC coefficient. In Chapter 4, the effect of morphology is studied. The multi-body Quantum Sutton Chen (QSC) potential is used for Pt <100> solid and the binary potential proposed in the previous chapter for the Ar-Pt couple is employed. The QSC potential is needed to reproduce the surface effects that affect the final results. Different surfaces are treated : smooth, nanostructured surface and, random surface obtained by Chemical vapor deposition (CVD). The TMAC is determined using a generalized approach, i.e. depending on the angle of incident flux of gas atoms on the surface. The surface anisotropy and the scattering kernel are also examined. In Chapter 5, we propose a model of anisotropic slip for fluids based on accommodation tensor. The model is obtained by the analytical approximate calculations developed in the framework of the kinetic theory. We thus generalize Maxwell's equation by showing that the slip length tensor is directly related to the accommodation tensor. The model is in good agreement with the MD results. Thanks to our MD simulations, we develop a suitable technique for reproducing the anisotropy of the accommodation tensor. The thesis ends with a conclusion section in which we suggest some perspectives for a continuation of this work
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Ozfidan, Asli Isil. "Ab Initio Modeling of Thermal Barrier Coatings: Effects of Dopants and Impurities on Interface Adhesion, Diffusion and Grain Boundary Strength." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19974.
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The aim of this thesis is to investigate the effects of additives, reactive elements and impurities, on the lifetime of thermal barrier coatings. The thesis consists of a number of studies on interface adhesion, impurity diffusion, grain boundary sliding and cleavage processes and their impact on the mechanical behaviour of grain boundaries.
The effects of additives and impurity on interface adhesion were elaborated by using total energy calculations, electron localization and density of states, and by looking into the atomic separations. The results of these calculations allow the assessment of atomic level contributions to changes in the adhesive trend. Formation of new bonds across the interface is determined to improve the adhesion in reactive element(RE)-doped structures. Breaking of the cross interface bonds and sulfur(S)-oxygen(O) repulsion is found responsible for the decreased adhesion after S segregation.
Interstitial and vacancy mediated S diffusion and the effects of Hf and Pt on the diffusion rate of S in bulk NiAl are studied. Hf is shown to reduce the diffusion rate, and the preferred diffusion mechanism of S and the influence of Pt are revealed to be temperature dependent.
Finally, the effects of reactive elements on alumina grain boundary strength are studied. Reactive elements are shown to improve both the sliding and cleavage resistance, and the analysis of atomic separations suggest an increased ductility after the addition of quadrivalent Hf and Zr to the alumina grain boundaries.
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Kitchen, Ryan L. "Improving Steering Module Efficiency for Incremental Loading Finite Element Numeric Models." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1248.pdf.
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Abitbol, Leïa. "Initier des coopérations inter-organisationnelles dans les démarches d’écologie industrielle et territoriale : une relecture en termes de sociologie de la traduction et de la théorie des objets-frontière." Thesis, Lyon 3, 2012. http://www.theses.fr/2012LYO30020/document.
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Les démarches d’écologie industrielle et territoriale (EIT) sont encore rares alors que d’une part, le développement durable dont elles se revendiquent est de plus en plus présent dans la vie des organisations et que d’autre part, elles relèvent de ce que certains appellent la « science de la durabilité ». On s’aperçoit par ailleurs que les travaux de recherche qui leur sont consacrés portent principalement sur la dimension physique des flux de matières et d’énergies échangés. Peu de choses sont dites sur les acteurs qui utilisent ces flux et sur les organisations qui les produisent ou les consomment. Pourtant, dire avec l’EIT qu’il faut sortir d’un fonctionnement optimisé aux bornes de l’organisation pour s’inspirer du fonctionnement performant des écosystèmes naturels, c’est dire qu’il faut parvenir à construire des coopérations inter-organisationnelles. La problématique des coopérations inter-organisationnelles n’est pas nouvelle pour les sciences de gestion. Les travaux disponibles traitent toutefois rarement de la phase amont d’initialisation des coopérations, en particulier lorsque l’intérêt de la coopération n’est pas évident a priori. L’objectif de cette thèse est alors de comprendre comment donner envie aux acteurs (organisation et individus) de coopérer quand, il n’y a ni contrainte règlementaire ni incitations économique évidente à le faire, comme c’est le cas pour l’instant dans les démarches d’EIT. En s’appuyant d’une part sur les travaux de la sociologie de la traduction et de la théorie émergente des objets-frontières et d’autre part, sur l’analyse de quatre démarches françaises d’EIT, notre travail propose des éléments de réponse sur ce qui permet d’ « enrôler » les acteurs dans ces démarches et partant, sur la façon dont il est possible d’initier les coopérations inter-organisationnelles qu’elles requièrent. Les résultats de ce travail suggèrent une grande souplesse dans la conduite de ces démarches : plutôt que d’essayer de convaincre d’un intérêt peu évident à formuler a priori, les promoteurs de projets peuvent avoir intérêt à laisser parler les besoins, envies et attentes des acteurs sollicités. A eux de mobiliser des objets-frontières qui puissent aider à construire un contexte partagé, et à identifier les intérêts de participer ensemble, à la dynamique d’une démarche d’EIT. La thèse montre en définitive comment la traduction doit être envisagée dans le contexte spécifique de l’EIT. Elle a cependant des implications concrètes et théoriques pour tous ceux qui s’intéressent à la dynamique des coopérations inter-organisationnelles, à la sociologie de la traduction et à la théorie des objets-frontièresIndustrial and territorial ecology (ITE) is still a very recent and rare approach. However, the method of sustainable development, to which ITE belongs, is more and more present in today's organizations and ITE is increasingly considered to be the 'science of sustainability'.Research on ITE is mainly focused on the physical dimension of energy exchanges and material flows. Today, little has been found on the actors who use these flows and the organizations who produce or consume them. However, stating that the implementation of ITE requires change from a mechanism optimized at the organizational boundaries to a performing natural ecosystems mechanism, means thinking outside organizational boundaries. While inter-organizational cooperation is not new to management studies, the research carried out on this topic rarely addresses the initiation phase of cooperation, especially when the interest of cooperation is not clear at first insight. The objective of the present thesis is to understand how to prompt actors (organizations and individuals) to cooperate when there are no regulatory constraints or obvious economic incentives to do so, as it is currently the case in ITE approaches. This thesis is based on first the work of the sociology of translation and the emerging theory of boundary objects, and second on the analysis of four French ITE approaches. This thesis provides a better understanding of the mechanisms that allow to "enrol" players in the ITE processes and how it is possible to initialize the inter-organizational cooperation they require. The results of this study suggest a high degree of flexibility in the conduct of the ITE approach: rather than trying to convince actors of a benefit that is difficult to formulate, project leaders may have more success letting the needs, desires and expectations emerge. If they see it as their responsibility to mobilize boundary objects that can help in building a shared context and identify the common interests to participate all together, the dynamics of a successful ITE process can emerge.Ultimately, this thesis shows how translation must be considered as an important element in the specific context of ITE. We show both practical and theoretical implications for those who are interested in the dynamics of inter-organizational cooperation, in the sociology of translation and in the theory of boundary objects
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Li, Siqian. "The atomic struture of inversion domains and grain boundaries in wurtzite semonconductors : an investigation by atomistic modelling and high resolution transmission electron microscopy." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC252/document.
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Au cours de ce travail, nous avons étudié deux types de défauts interfaciaux: domaines d’inversion (DI) et joints de grains (JG) dans des semiconducteurs de structure wurtzite (nitrures- d’éléments III, ZnO et l’hétérostructure ZnO/GaN) en utilisant le MET haute résolution et la modélisation ab initio. Dans le cas des DI, nos analyses théoriques montrent qu'une configuration tête-à-tête avec une séquence d'empilement à l’interface AaBbAa-AcCaA (H4) est la structure la plus stable dans les composés binaires (nitrures et ZnO wurtzites). De plus, un gaz d’électrons (2DEG) ou de trous (2DHG) à 2 dimensions est formé pour les configurations « tête-à-tête » ou queue-à-queue. A l’interface ZnO/GaN, l'observation de MET très haute résolution a confirmé la configuration H4 avec une interface -Zn-O-Ga-N. Notre modélisation théorique a mis en évidence la formation d’un gas de trous à 2 dimensions à cette hétérointerface. Nous avons aussi réalisé l’étude topologique, théorique et par MET des joints de grains de rotation autour de l’axe [0001] dans ces matériaux. Dans le GaN, nous avons trouvé que les plans du joint sont simplement formés par des dislocations de type a déjà connues pour le matériau en couche mince. Par contre, dans ZnO, la théorie topologique est complétement démontrée, et la dislocation [101 ̅0] est une brique de base dans la constitution des joints de grains avec des cycles d’atomes 6-8-4-In this work, we investigated two kinds of interfacial defects: inversion domain boundaries (IDBs) and grain boundaries (GB) in wurtzite semiconductors (III-nitrides, ZnO and ZnO/GaN heterostructure) using high-resolution TEM and first-principle calculations. For IDBs, theoretical calculation indicated that a head-to-head IDB with an interfacial stacking sequence of AaBbAa-AcCaA (H4) is the most stable structure in wurtzite compounds. Moreover, 2-dimensional electron gas (2DEG) and 2-dimensional hole gas (2DHG) build up in head-to-head and tail-to-tail IDBs, respectively. Considering the IDB at the ZnO/GaN heterointerface, TEM observations unveiled the H4 configuration with a -Zn-O-Ga-N interface. Moreover the theoretical investigation also confirmed stability of this interface along with the corresponding formation of a 2DHG. A detailed topological, TEM and theoretical investigation of [0001] tilt Grain Boundaries (GBs) in wurtzite symmetry has also been carried out. In GaN, it is shown that the GBs are only made of separated a edge dislocations with 4, 5/7 and 8 atoms rings. For ZnO, a new structural unit: the [101 ̅0] edge dislocation made of connected 6-8-4-atom rings is reported for the first time, in agreement with an early theoretical report on dislocations and jogs in the wurtzite symmetry
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Tao, Liang. "Atomic-scale calculations of interfacial structures and their properties in electronic materials." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1127163029.
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Johansen, Jonathan Frederick. "Mathematical modelling of primary alkaline batteries." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16412/.
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Three mathematical models, two of primary alkaline battery cathode discharge, and one of primary alkaline battery discharge, are developed, presented, solved and investigated in this thesis. The primary aim of this work is to improve our understanding of the complex, interrelated and nonlinear processes that occur within primary alkaline batteries during discharge. We use perturbation techniques and Laplace transforms to analyse and simplify an existing model of primary alkaline battery cathode under galvanostatic discharge. The process highlights key phenomena, and removes those phenomena that have very little effect on discharge from the model. We find that electrolyte variation within Electrolytic Manganese Dioxide (EMD) particles is negligible, but proton diffusion within EMD crystals is important. The simplification process results in a significant reduction in the number of model equations, and greatly decreases the computational overhead of the numerical simulation software. In addition, the model results based on this simplified framework compare well with available experimental data. The second model of the primary alkaline battery cathode discharge simulates step potential electrochemical spectroscopy discharges, and is used to improve our understanding of the multi-reaction nature of the reduction of EMD. We find that a single-reaction framework is able to simulate multi-reaction behaviour through the use of a nonlinear ion-ion interaction term. The third model simulates the full primary alkaline battery system, and accounts for the precipitation of zinc oxide within the separator (and other regions), and subsequent internal short circuit through this phase. It was found that an internal short circuit is created at the beginning of discharge, and this self-discharge may be exacerbated by discharging the cell intermittently. We find that using a thicker separator paper is a very effective way of minimising self-discharge behaviour. The equations describing the three models are solved numerically in MATLABR, using three pieces of numerical simulation software. They provide a flexible and powerful set of primary alkaline battery discharge prediction tools, that leverage the simplified model framework, allowing them to be easily run on a desktop PC.
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"Boundary control of quasi-linear hyperbolic initial boundary-value problems." Université catholique de Louvain, 2004. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-09242004-170922/.
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O'Regan, Daniel J. "Initial and boundary value problems via topological methods /." 1985. http://hdl.handle.net/1957/16823.
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Chiang, Wen Shin, and 蔣文心. "Parameter Identification for Parabolic Initial-boundary Value Problem." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/53836384016955784570.
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Corbett, Norman Christopher. "Initial moving-boundary value problems associated with the wave equation." 1991. http://hdl.handle.net/1993/17356.
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Kang, Cheng-Hui, and 康政惠. "Solutions of the initial boundary value problem to the MBBM." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/25310176925994854478.
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碩士國立高雄師範大學
數學教育研究所
85
In this paper we study the existence and uniqueness of the initial-boundaryvalue problem for the modifiedBenjamin-Bona- Mahony (MBBM for short) equation \begin{displaymath} u_t+u_x+ u^2u_x-u_{xxt}=0\,, \end{displaymath} \begin{displaymath} u( x,0)=g(x)\,,\;\;x\in{\br}\,, \end{displaymath} \begin{displaymath} u(0,t)=h(x)\,,\;\;t\geq 0\,. \end{displaymath} under the conditionson the initial value $g(x) \in H^1(\br) \cap C_b^2( \br)$ andthe boundary value $h(t) \in C^1([0,T])$. We also study the property of continuous dependence on the specified data ofthe solutions for the MBBM equation.
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Mugnolo, Delio [Verfasser]. "Second order abstract initial-boundary value problems / vorgelegt von Delio Mugnolo." 2004. http://d-nb.info/971647674/34.
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Huang, I.-Ju, and 黃漪茹. "The Influences of Initial and Boundary Conditions on the Free Surface." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/35705448810947666339.
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碩士國立成功大學
機械工程學系碩博士班
91
This research investigates the transient characteristics of free surface vortex in a tank which has a vertical discharge pipe built on its bottom. The variations of flowrate, distributions of pressure, generations of dimple and critical submergence have been analyzed as initial submergence depth, size of the discharge pipe, distance between discharge pipe and wall and settling time are changed. From the experiments, we found that the change of flowrate bears relation to the size, length and outlet design of the discharge pipe and distance between discharge pipe and wall rather than initial submergence depth. Furthermore, the cross-sectional area of discharging is the primary factor influencing the flowrate. As the water-draining process goes on, a dimple forms on the free surface of liquid which is originally flat after the water level drops to a specific height. The dimple develops downward continually and an air column is thus generated. The water level corresponding to when the dimple and the air column are formed rises with initial submergence depth. As settling time gets longer, the water level corresponding to dimple and air column formation decreases. After several hours, it reaches a steady value. As to wall effects, they can be divided into two types: single wall effect, and corner effect. For a shorter distance between discharge pipe and wall, the formation of dimple and air column is slower, because the wall restrains the formation of dimple and air column. For water draining out of two discharge pipes, the formation of dimple and air column is also slower due to the mutual inhibition between the two vortices. If the distance between two discharge pipes is less than two times the pipe diameter, the air column is unstable.
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Olafson, Stephanie K. "An initial moving-boundary value problem associated with the spinning wave equation." 2001. http://hdl.handle.net/1993/19561.
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Ching, Guai-Ing, and 秦桂英. "The Existence Theory of the Initial-Boundary Value Problem for the GBBM Equation." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/16579633148662043664.
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碩士國立高雄師範大學
數學研究所
86
In this paper we study the existence and uniqueness of the initial- boundary value problem for the generalized Benjamin-Bona-Mahony (GBBM for short) equation ut + ux + upux-uxxt=0, for p≧1, u(x,0)=g(x),xεR+, u(0,t) = h(t),t≧0. where the initial value g(x) εH1(R+)∩C2b(R+) and the boundary value h(t) εC1 (〔0,T〕) are specified, with g(0) = h(0) for consistency. We also study the property of continuous dependence on the specific data, from initial and boundary conditions for example, of the solutions for the GBBM equation.