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Castro, Nicholas D. "Numerical Modeling of Synthetic Jets in Quiescent Air with Moving Boundary Conditions". VCU Scholars Compass, 2005. http://scholarscompass.vcu.edu/etd/1466.
Pełny tekst źródłaAblikim, Medina. "Boundary sinh-Gordon model and its supersymmetric extension". Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4853/.
Pełny tekst źródłaTrovant, Michael. "A boundary condition coupling strategy for the modeling of metal casting processes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/NQ35346.pdf.
Pełny tekst źródłaChenaghlou, Alireza. "Quantum corrections to the classical reflection factor of the sinh-Gordon model". Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4347/.
Pełny tekst źródłaJolley, Kenny. "Multiscale methods for nanoengineering". Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/7809.
Pełny tekst źródłaMoretti, Rocco. "Étude et amélioration des méthodologies de couplage aérothermique fluide-structure". Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM076.
Pełny tekst źródłaThis work deals with the solution of coupled aerothermal problems. The aim of the work is to improve the accuracy and robustness of the coupling techniques. The stability of the aerothermal coupling for steady state problems is first studied (weak coupling). A numerical Biot number is defined, which allows to evaluate the intensity of the fluid-structure thermal interaction. Several methods (Dirichlet-Robin, Neumann-Robin and Robin-Robin) are studied and their ranges of validity are defined. The Dirichlet-Robin method with a safety coefficient, which presents the easiest implementation, proves to be the most robust. Taking radiation into account implies a major destabilization of the aerothermal problem. Thus, the stabilization method is modified in order to be able to stabilize this type of calculation. In the second part, the solution of coupled aerothermal problems in the transient regime is studied using the quasidynamic partitioned algorithm. This is an iterative procedure (strong coupling) between the thermal problem in the solid solved in the transient regime and the flow field at the steady state, thus ensuring equal heat flux and temperature at each coupling time. The accuracy of this algorithm is analysed and improved. Finally, the quasi-dynamic algorithm is analysed on quasi-industrial aerothermal problems of aeronautical compressor and turbine discs
Mikhaylenko, Maxim A. "Development and Application of the Boundary Singularity Method to the Problems of Hydrodynamic and Viscous Interaction". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1442423671.
Pełny tekst źródłaMaati, Amel. "Mise en œuvre de formalismes pour la modélisation de grands réseaux périodiques d'antennes". Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0009/document.
Pełny tekst źródłaThis thesis is organized in the general context of modeling a large antenna arrays with the aim of achieving a high level of precision. This modeling allows a complete optimization of the performances and an enhancement of the energy efficiency. Given that the electromagnetic optimization of large arrays still represents a challenge if the mutual coupling is not efficiently modeled. This work offers the implementation of a method allowing the precise modeling of large antenna arrays while reducing the computation time and maintaining a high degree of precision. The aim is to demonstrate that the derived approach from the infinite periodic formalisms makes it possible to obtain a full [S] matrix of an array based on the study of a unit cell. After presenting a state of the art of antenna arrays and their methods of analysis, the proposed modeling approach is explained. Numerical and Experimental demonstrators are then made for the validation. Finally, this method is successfully used for two types of applications
Warman, Craig S. "Understanding the spatial and temporal variation in anthropogenically induced channel response in the Irwin River catchment". University of Western Australia. School of Earth and Geographical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0214.
Pełny tekst źródłaFajardo, Peña Pablo. "Methodology for the Numerical Characterization of a Radial Turbine under Steady and Pulsating Flow". Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/16878.
Pełny tekst źródłaFajardo Peña, P. (2012). Methodology for the Numerical Characterization of a Radial Turbine under Steady and Pulsating Flow [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16878
Palancia
Müller-Bierl, Bernd Michael. "Rayonnement et couplage entre les interconnexions dans les circuits hyperfréquences : étude au moyen de la méthode tlm". Grenoble INPG, 1997. http://www.theses.fr/1997INPG0026.
Pełny tekst źródłaEhrhardt, Matthias. "Discrete artificial boundary conditions". [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=965232921.
Pełny tekst źródłale, coupanec erwan. "Boundary conditions for the lattice Boltzmann method : Mass conserving boundary conditions for moving walls". Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10154.
Pełny tekst źródłaBased on the no-slip boundary condition for walls at rest for the lattice Boltzmann Bathnagar-Gross-Krook method by J.C.G. Verschaeve [Phys. Rev. 80,036703 (2009)], a no-slip boundary condition for walls with a tangential movement is derived. Numerical tests verify that the present boundary condition is second order accurate and stable for relaxation frequencies close to two.
Boström, Erik. "Boundary Conditions for Spectral Simulations of Atmospheric Boundary Layers". Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-218054.
Pełny tekst źródłaEtt atmosfäriskt gränsskikt (ABL) är generellt sett ett gränsskikt med väldigt högt Reynolds-tal över en rand med ojämn yta och som är påverkad av yttre krafter. Numeriska simuleringar av ABLs är typiskt sett väldigt krävande, speciellt på grund av de höga Reynolds-talen. Large eddy simulation (LES) där de filtrerade Navier--Stokes ekvationerna är lösta tillsammans med en turbulensmodell för the oupplösta skalorna är den mest noggranna och mest använda tekniken för ABLs. Men, för höga Reynolds-tal, filtrerade ekvationer och ytojämnheter är inte ``no-slip'' randvillkor giltiga för en genomförbart hög nätupplösning. En viktig del för kvalitén hos en ABL LES simulering ligger därför i prestandan i approximativa randvillkor, så kallade väggmodeller. Majoriteten av alla LES koder som används för ABL simuleringar är baserade på en lågordnings finita-differens diskretisering för derivatorna i den inhomogena väggnormalriktningen. Dessutom så är vägg-randvillkoren typiskt valda nätberoende och icke-lokala och direkt beroende av finita-differens diskretiseringen. I den här avhandlingen så fokuserar vi i att lösa ABL LES ekvationerna med en fullt (pseudo) spektral Fourier--Chebyshev kod. Vi förklarar vidare hur väggrandvillkor kan formuleras genom Robin-randvillkor och hur man implementerar dessa i normalhastighet normalvorticitet formuleringen som vi löser. En ny idé i att specifiera randvillkor direkt i Fourier-rummet där statistiken för den turbulenta intensiteten kan kontrolleras är också presenterad och verifierad. Resultaten vi härmed presenterar visar att Robin-randvillkor formuleringen är effektiv åtminstone for gränsskikt i nära jämvikt. Den numeriska koden och randvillkoren var testade för kanalströmning (öppen och stängd) av både neutral och stabil stratifikation och för både låga och höga Reynolds-tal. Våra resultat visar på en god potential hos både den nya randvillkorsformuleringen och den nya kodimplementationen. Vidare analys i mer komplexa flödessituationer kommer att visa om Robin-randvillkor formuleringen ger lika goda resultat.
QC 20171122
Gamlin, Samuel. "Boundary conditions in Abelian sandpiles". Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687371.
Pełny tekst źródłaFouchet-Incaux, Justine. "Modélisation, analyse numérique et simulations autour de la respiration". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112043.
Pełny tekst źródłaIn this thesis, we study the modelling of the human mecanical ventilation and the numerical analysis of linked systems. Direct simulations of air flow in the whole airways are impossible (complex geometry, unavailable meshes). Then a reduced area of interest can be considered, working with reduced geometries and artificial boundaries. One can also use reduced models, simple but realistic. If one try to make 3D numerical simulations where the fluid flow is described by the Navier-Stokes equations, various issues are raised:- If we consider that ventilation is the result of pressure drops, the associated boundary conditions are Neumann conditions. It leads to theoretical questions in terms of existence and uniqueness of solution and numerical issues in terms of scheme choice and appropriate numerical methods.- When working in a truncated domain, it may be necessary to take into account non-described phenomena with appropriate models. Here we consider 0D models. These 3D/0D couplings imply numerical instabilities that we mathematically and numerically study in this thesis.Furthermore, when we focus on forced breathing, linear usual models are invalidated by experiments. In order to observe the differences between the experimental and numerical results, it is necessary to take into account several types of non-linearities, such as deformation of the domain or the Bernoulli phenomenon. A reduced model approach is adopted in this work. Finally, we sought to validate the obtained models by comparing numerical and experimental results in the context of interdisciplinary work.Achieving model and simulate these flows allow to better understand phenomena and parameters that come into play in diseases (asthma, emphysema ...). A medium-term objective is to study the influence of helium-oxygen mixture in the aerosol deposition. In the longer term, the application of these models to pathological situations could afford to build decision support tools in the medical field (understanding of pathology, therapy optimization ...)
Roman, Svetlana. "Green's functions for boundary-value problems with nonlocal boundary conditions". Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20111227_092148-01085.
Pełny tekst źródłaDisertacijoje tiriami antros ir aukštesnės eilės diferencialinis ir diskretusis uždaviniai su įvairiomis, tame tarpe ir nelokaliosiomis, sąlygomis, kurios yra aprašytos tiesiškai nepriklausomais tiesiniais funkcionalais. Pateikiamos šių uždavinių Gryno funkcijų išraiškos ir jų egzistavimo sąlygos, jei žinoma homogeninės lygties fundamentalioji sistema. Gautas dviejų Gryno funkcijų sąryšis uždaviniams su ta pačia lygtimi, bet su papildomomis sąlygomis. Rezultatai pritaikomi uždaviniams su nelokaliosiomis kraštinėmis sąlygomis. Įvadiniame skyriuje aprašyta tiriamoji problema ir temos objektas, išanalizuotas temos aktualumas, išdėstyti darbo tikslai, uždaviniai, naudojama tyrimų metodika, mokslinis darbo naujumas ir gautų rezultatų reikšmė, pateikti ginamieji teiginiai ir darbo rezultatų aprobavimas. m-tosios eilės diferencialinis uždavinys ir jo Gryno funkcija nagrinėjami pirmajame skyriuje. Surastas uždavinio sprendinys, išreikštas per Gryno funkciją. Pateikta Gryno funkcijos egzistavimo sąlyga. Antrajame skyriuje pateikti pirmojo skyriaus pagrindiniai apibrėžimai ir rezultatai antros eilės diferencialinei lygčiai. Pavyzdžiuose išsamiai išanalizuotas gautų rezultatų pritaikymas uždaviniams su nelokaliosiomis kraštinėmis sąlygomis. Trečiajame skyriuje nagrinėjama antros eilės diskrečioji lygtis su dviem sąlygomis. Surastos diskrečiosios Gryno funkcijos išraiška ir jos egzistavimo sąlyga. Taip pat pateiktas dviejų Gryno funkcijų sąryšis, kuris leidžia surasti diskrečiosios... [toliau žr. visą tekstą]
Onyango, Thomas Tonny Mboya. "Boundary element methods for solving inverse boundary conditions identification problems". Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/11283/.
Pełny tekst źródłaSchulze, Bert-Wolfgang, i Nikolai Tarkhanov. "Boundary value problems with Toeplitz conditions". Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2009/2983/.
Pełny tekst źródłaStephenson, P. W. "Glueball spectra with twisted boundary conditions". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276836.
Pełny tekst źródłaPark, Kyeong M. "Boundary conditions of font size effects". Thesis, The University of Alabama in Huntsville, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10130786.
Pełny tekst źródłaPrior research has shown that people perceive items in a larger font size as being more memorable than items in a smaller font size. This perception leads to higher judgments of learning (JOLs; i.e., confidence ratings regarding the likelihood of recalling an item) for larger font size items than smaller font size items. Yet other research has shown that people recalled more when the information was presented in a smaller font than when it was presented in a larger font size. The present study examined if there are boundary conditions of font sizes affecting JOLs and actual recall performance. As we expected, the results show that JOLs increased as a function of the size category. The results also show that font size impacted recall performance such that items in the Smallest size category were recalled at a higher rate than items in the other three font size categories.
Deadman, Edvin. "Outer boundary conditions in numerical relativity". Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608394.
Pełny tekst źródłaSchulze, Bert-Wolfgang, i Y. Wei. "Edge-boundary problems with singular trace conditions". Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2009/3031/.
Pełny tekst źródłaCousins, William Bryan. "Boundary Conditions and Uncertainty Quantification for Hemodynamics". Thesis, North Carolina State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3575896.
Pełny tekst źródłaWe address outflow boundary conditions for blood flow modeling. In particular, we consider a variety of fundamental issues in the structured tree boundary condition. We provide a theoretical analysis of the numerical implementation of the structured tree, showing that it is sensible but must be performed with great care. We also perform analytical and numerical studies on the sensitivity of model output on the structured tree's defining geometrical parameters. The most important component of this dissertation is the derivation of the new, generalized structured tree boundary condition. Unlike the original structured tree condition, the generalized structured tree does not contain a temporal periodicity assumption and is thus applicable to a much broader class of blood flow simulations. We describe a numerical implementation of this new boundary condition and show that the original structured tree is in fact a rough approximation of the new, generalized condition.
We also investigate parameter selection for outflow boundary conditions, and attempt to determine a set of structured tree parameters that gives reasonable simulation results without requiring any calibration. We are successful in doing so for a simulation of the systemic arterial tree, but the same parameter set yields physiologically unreasonable results in simulations of the Circle of Willis. Finally, we investigate the extension of recently introduced PDF methods to smooth solutions of systems of hyperbolic balance laws subject to uncertain inputs. These methods, currently available only for scalar equations, would provide a powerful tool for quantifying uncertainty in predictions of blood flow and other phenomena governed by first order hyperbolic systems.
Zacher, Rico. "Quasilinear parabolic problems with nonlinear boundary conditions". [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969321899.
Pełny tekst źródłaStigner, Carl. "A classifying algebra for CFT boundary conditions". Licentiate thesis, Karlstad University, Faculty of Technology and Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4890.
Pełny tekst źródłaConformal field theories (CFT) constitute an interesting class of twodimensionalquantum field theories, with applications in string theoryas well as condensed matter physics. The symmetries of a CFT can beencoded in the mathematical structure of a conformal vertex algebra.The rational CFT’s are distinguished by the property that the categoryof representations of the vertex algebra is a modular tensor category.The solution of a rational CFT can be split off into two separate tasks, apurely complex analytic and a purely algebraic part.
The TFT-construction gives a solution to the second part of the problem.This construction gets its name from one of the crucial ingredients,a three-dimensional topological field theory (TFT). The correlators obtainedby the TFT-construction satisfy all consistency conditions of thetheory. Among them are the factorization constraints, whose implicationsfor boundary conditions are the main topic of this thesis.
The main result reviewed in this thesis is that the factorization constraintsgive rise to a semisimple commutative associative complex algebrawhose irreducible representations are the so-called reflection coefficients.The reflection coefficients capture essential information aboutboundary conditions, such as ground-state degeneracies and Ramond-Ramond charges of string compactifications. We also show that the annuluspartition function can be derived fromthis classifying algebra andits representation theory.
Olsen, Robert. "Time-dependent boundary conditions for multiphase flow". Doctoral thesis, [Trondheim : Norges teknisk-naturvitenskapelige universitet, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-237.
Pełny tekst źródłaMoore, Stuart Alex. "Lateral boundary conditions in numerical ocean models". Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402199.
Pełny tekst źródłaGunson, James Reginald. "Estimating open-ocean boundary conditions : sensitivity studies". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/53024.
Pełny tekst źródłaIncludes bibliographical references (leaves 145-149).
by James Reginald Gunson.
Ph.D.
Savi, L. L. [UNESP]. "A geometric approach to cosmological boundary conditions". Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132136.
Pełny tekst źródłaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A assimetria temporal observada na física macroscópica se deve à configuração de entropia extremamente baixa do universo primordial. Apesar de a matéria estar muito quente e com uma temperatura uniforme naquele estágio, os graus de liberdade gravitacionais estavam em grande medida suprimidos, fato este que contribui para o baixo valor da entropia e está codificado no alto grau de simetria espacial (caráter aproximadamente Friedman-Lemaître-Robertson-Walker) da superfície de último espalhamento. Analisamos diferentes tentativas de explicar a origem de tal configuração especial. O paradigma inflacionário é testado com respeito a esse problema, e é concluído que a baixa entropia inicial não pode ser explicada dentro dele. Conclusões similares são obtidas com respeito a formulações estatísticas (i.e. antrópicas). Por outro lado, o paradigma conhecido como cosmologia cíclica conforme (CCC) se apresenta como uma nova alternativa que ultrapassa muitas das dificuldades enfrentadas pelos seus rivais, apesar de levantar suas próprias questões em aberto. Introduzimos o modelo juntamente com a estrutura matemática das geometrias de Cartan como um meio possível de atingir um melhor entendimento das condições de contorno cosmológicas. Um elemento que é crucial nessa análise é a modelagem de uma estrutura geométrica de Cartan sobre o espaço de de Sitter SOe(4,1)/SOe(3,1) com um parâmetro de comprimento variável. A introdução de um parâmetro de comprimento na cinemática é favorecida pela observação de uma constante cosmológica positiva e também desejável por motivos oriundos da gravitação quântica, devido à escala natural determinada pelo comprimento de Planck
The observed T-asymmetry of macroscopic physics is traced back to the extremely low entropy configuration of the early universe. Although matter was very hot and with a uniform temperature at that stage, the gravitational degrees of freedom were largely suppressed, which fact contributes to the lowness of the entropy and is encoded in the high level of spatial symmetry (nearly Friedman-Lemître-Robertson-Walker character) of the last scattering surface. I analyze different attempts to explain the origin of such special configuration. The inflation paradigm is probed with respect to this problem, and it is concluded that the initial low entropy cannot be accounted for within it. Similar conclusions are reached with respect to statistical (i.e. anthropic) reasonings. On the other hand, the paradigm known as conformal cyclic cosmology (CCC) presents itself as a new alternative which surpasses many of the difficulties faced by its rivals, although raising its own open questions. I introduce the model together with the mathematical structure of Cartan geometries as a possible means of achieving a better understanding of cosmological boundary conditions. One element which is crucial in this analysis is the modeling of the Cartan geometric structure over a de Sitter space SOe(4,1)/SOe(3,1) with varying length parameter. The introduction of a length parameter in the kinematics is favored by the observation of a positive cosmological constant and also desirable for quantum gravity reasons, due to the natural scale set by Planck's constant
Savi, L. L. (Lucas Lolli). "A geometric approach to cosmological boundary conditions /". São Paulo, 2015. http://hdl.handle.net/11449/132136.
Pełny tekst źródłaBanca: Bruto Max Pimentel Escobar
Banca: Roldão da Rocha Junior
Banca: Davi Cabral Rodrigues
Banca: José abdalla Helayel-Neto
Resumo: A assimetria temporal observada na física macroscópica se deve à configuração de entropia extremamente baixa do universo primordial. Apesar de a matéria estar muito quente e com uma temperatura uniforme naquele estágio, os graus de liberdade gravitacionais estavam em grande medida suprimidos, fato este que contribui para o baixo valor da entropia e está codificado no alto grau de simetria espacial (caráter aproximadamente Friedman-Lemaître-Robertson-Walker) da superfície de último espalhamento. Analisamos diferentes tentativas de explicar a origem de tal configuração especial. O paradigma inflacionário é testado com respeito a esse problema, e é concluído que a baixa entropia inicial não pode ser explicada dentro dele. Conclusões similares são obtidas com respeito a formulações estatísticas (i.e. antrópicas). Por outro lado, o paradigma conhecido como cosmologia cíclica conforme (CCC) se apresenta como uma nova alternativa que ultrapassa muitas das dificuldades enfrentadas pelos seus rivais, apesar de levantar suas próprias questões em aberto. Introduzimos o modelo juntamente com a estrutura matemática das geometrias de Cartan como um meio possível de atingir um melhor entendimento das condições de contorno cosmológicas. Um elemento que é crucial nessa análise é a modelagem de uma estrutura geométrica de Cartan sobre o espaço de de Sitter SOe(4,1)/SOe(3,1) com um parâmetro de comprimento variável. A introdução de um parâmetro de comprimento na cinemática é favorecida pela observação de uma constante cosmológica positiva e também desejável por motivos oriundos da gravitação quântica, devido à escala natural determinada pelo comprimento de Planck
Abstract:The observed T-asymmetry of macroscopic physics is traced back to the extremely low entropy configuration of the early universe. Although matter was very hot and with a uniform temperature at that stage, the gravitational degrees of freedom were largely suppressed, which fact contributes to the lowness of the entropy and is encoded in the high level of spatial symmetry (nearly Friedman-Lemître-Robertson-Walker character) of the last scattering surface. I analyze different attempts to explain the origin of such special configuration. The inflation paradigm is probed with respect to this problem, and it is concluded that the initial low entropy cannot be accounted for within it. Similar conclusions are reached with respect to statistical (i.e. anthropic) reasonings. On the other hand, the paradigm known as conformal cyclic cosmology (CCC) presents itself as a new alternative which surpasses many of the difficulties faced by its rivals, although raising its own open questions. I introduce the model together with the mathematical structure of Cartan geometries as a possible means of achieving a better understanding of cosmological boundary conditions. One element which is crucial in this analysis is the modeling of the Cartan geometric structure over a de Sitter space SOe(4,1)/SOe(3,1) with varying length parameter. The introduction of a length parameter in the kinematics is favored by the observation of a positive cosmological constant and also desirable for quantum gravity reasons, due to the natural scale set by Planck's constant
Doutor
Li, Hongwei. "Local absorbing boundary conditions for wave propagations". HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1434.
Pełny tekst źródłaWintz, Nick. "Eigenvalue comparisons for an impulsive boundary value problem with Sturm-Liouville boundary conditions". Huntington, WV : [Marshall University Libraries], 2004. http://www.marshall.edu/etd/descript.asp?ref=414.
Pełny tekst źródłaBertolaccini, Jonathan. "Modélisation et simulation des écoulements de contre-courant de l'hélium superfluide par la méthode Boltzmann sur réseau". Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1063/document.
Pełny tekst źródłaThe exceptional thermal properties of superfluid helium, or He-II, are exploited to the cryogenic refrigeration of high power installations, although the underlying physical mechanisms remain poorly understood. The He-II can be described macroscopically as the superposition of two fluids in interaction: a normal fluid behaves as an ordinary liquid, and a superfluid without viscosity. In the presence of a heat source, a counterflow established between these two components. The heat dissipation by this counterflow is limited by the occurrence of instabilities in misunderstood condition; the wide dispersion of experimental data does not allow to discriminate between the different theoretical models. This thesis examines using numerical simulations the role of boundary conditions and the mutual coupling between the two components of the He-II in triggering instabilities in counterflow.An innovative lattice Boltzmann type approach was developed to model the mesoscopic scale interaction between the two components of the He-II. A code reproducing counterflow in 2D and 3D conducts has been developed and validated. The results obtained indicate amplified entrance effects for superfluid component, which generate abnormally high pressure drops. The head of these entrance effects mechanism has been studied and it is shown that it can distort the detection of the transition threshold in too short pipes; This may partly explain the dispersion of experimental data.To illustrate the power of the approach in a complex geometry, the wake of an obstacle in a counterflow was simulated. The presence of recirculation areas on both sides of the obstacle, already observed experimentally, is found and explained by a new mechanism using "virtual walls"
Schulze, Bert-Wolfgang, i Jörg Seiler. "Pseudodifferential boundary value problems with global projection conditions". Universität Potsdam, 2002. http://opus.kobv.de/ubp/volltexte/2008/2623/.
Pełny tekst źródłaMossige, Endre Joachim. "Curved Boundary Conditions for the Lattice Boltzmann Method". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14667.
Pełny tekst źródłaJung, Florian [Verfasser]. "Canonical group quantization and boundary conditions / Florian Jung". Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1025490088/34.
Pełny tekst źródłaAppelö, Daniel. "Non-reflecting Boundary Conditions for Wave Propagation Problems". Licentiate thesis, KTH, Numerical Analysis and Computer Science, NADA, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1664.
Pełny tekst źródłaWe consider two aspects of non-reflecting boundaryconditions for wave propagation problems. First we evaluate aproposed Perfectly Matched Layer (PML) method for thesimulation of advective acoustics. It is shown that theproposed PML becomes unstable for a certain combination ofparameters. A stabilizing procedure is proposed andimplemented. By numerical experiments the performance of thePML for a problem with nonuniform flow is investigated. Furtherthe performance for different types of waves, vorticity andsound waves, are investigated.
The second aspect concerns spurious waves, which areintroduced by any discretization procedure. We constructdiscrete boundary conditions, that are nonreflecting for bothphysical and spurious waves, when combined with a fourth orderaccurate explicit discretization of one-way wave equations. Theboundary condition is shown to be GKS-stable. The boundaryconditions are extended to hyperbolic systems in two spacedimensions, by combining exact continuous non-reflectingboundary conditions and the one dimensional discretelynon-reflecting boundary condition. The resulting boundarycondition is localized by the standard Pad´eapproximation.
Numerical experiments reveal that the resulting methodsuffers from boundary instabilities. Analysis of a relatedcontinuous problem suggests that the discrete boundarycondition can be stabilized by adding tangential viscosity atthe boundary. For the lowest order Pad´e approximation weare able to stabilize the discrete boundary condition.
Burgess, N. A. "Stable boundary conditions for the shallow water equations". Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380000.
Pełny tekst źródłaIlie, Alexandra. "Unethical Pro-Organizational Behaviors: Antecedents and Boundary Conditions". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4085.
Pełny tekst źródłaArbegard, Fredrik, i Håkan Jakobsson. "Evaluation of Boundary Conditions in Chassis Test Rig". Thesis, KTH, Hållfasthetslära (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176497.
Pełny tekst źródłaLastbilar utvecklas ständigt för att uppnå nya krav och regelverk. När lastbilschassin optimeras för hållfasthet måste olika prover utföras bland annat livslängdsprov. Livslängdsprov på ramar och hjulupphängningar utförs på Scania i en speciell kvasistatisk rigg, Ramriggen. Riggen utsätter ramarna för en lasthistorik skapad utifrån provbanemätningar. Dagens rigg för provning av ramar har randvillkor som snedfördelar lasterna inom chassiet, speciellt för dragbilar med pålagd ramvridning. Dragbilens framaxeltyck tags enbart upp utav motorn och vridningen av ramen införs i basfästena via en krängningsvagga. Vid större axeltryck blir felet ifrån vertikallasten allt större och vid ramvridning så har oförutsedda utfall skett i framvagnen. För att förbättra Ramriggens förmåga att efterlikna en verklig lastbil behöver randvillkoren utvecklas. Syftet med undersökningen är att jämföra olika randvillkor i dragbilens framvagn. En undersökning om nya randvillkor för dragbilens framvagn i riggen kan omfördela lasterna har genomförts. I undersökningen användes FEM. För att jämföra olika randvillkor har två lastfall syntetiserats utifrån olika mätningar inmätta på dragbil. Ett lastfall för hög vertikallast och två lastfall med ramvridning. Genom undersökningen har nya randvillkorskoncept för riggen tagits fram. De nya randvillkoren innefattar en hyttattrapp som kan bidra med mothåll för vertikallaster samt inducera ramvridning. Resultatet av undersökningen av de två lastfallen visar att motorbalken överlastas med som mest 40% och basfästet 150% med de nuvarande randvillkoren jämfört med det föreslagna konceptet.
Shepherd, Roger. "Coupled non-linear diffusion under periodic boundary conditions". Thesis, University of South Wales, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239985.
Pełny tekst źródłaPadbidri, Jagan. "Minimal boundary conditions for simulations of disordered materials". WSU all campuses online access, 2003. http://www.dissertations.wsu.edu/Thesis/Fall2003/j%5Fpadbidri%5F121503.pdf.
Pełny tekst źródłaDade, William Brian. "Studies on boundary conditions for fine-sediment transport /". Thesis, Connect to this title online; UW restricted, 1992. http://hdl.handle.net/1773/11052.
Pełny tekst źródłaBélanger-Rioux, Rosalie. "Compressed absorbing boundary conditions for the Helmholtz equation". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90179.
Pełny tekst źródła56
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 101-105).
Absorbing layers are sometimes required to be impractically thick in order to offer an accurate approximation of an absorbing boundary condition for the Helmholtz equation in a heterogeneous medium. It is always possible to reduce an absorbing layer to an operator at the boundary by layer-stripping elimination of the exterior unknowns, but the linear algebra involved is costly. We propose to bypass the elimination procedure, and directly fit the surface-to-surface operator in compressed form from a few exterior Helmholtz solves with random Dirichlet data. We obtain a concise description of the absorbing boundary condition, with a complexity that grows slowly (often, logarithmically) in the frequency parameter. We then obtain a fast (nearly linear in the dimension of the matrix) algorithm for the application of the absorbing boundary condition using partitioned low rank matrices. The result, modulo a precomputation, is a fast and memory-efficient compression scheme of an absorbing boundary condition for the Helmholtz equation.
by Rosalie Bélanger-Rioux.
Ph. D.
LaGrone, John. "Application and optimization of complete radiation boundary conditions". Thesis, Southern Methodist University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10144064.
Pełny tekst źródłaWe describe the implementation of optimal local radiation boundary condition sequences for second order finite difference approximations to Maxwell's equations and the scalar wave equation using the double absorbing boundary formulation. Numerical experiments are presented which demonstrate that the design accuracy of the boundary conditions is achieved and exceeds that of perfectly matched layers for comparable effort.
We also describe the application of CRBC type boundary conditions for elastic waves in (an)isotropic media. The results show that we can optimize the CRBC problems for a subset of elastic media. Additionally, we propose a generalized CRBC type boundary conditions that may be more applicable to elastic wave equations and present some preliminary results.
Mezzadri, Francesco. "Boundary conditions for torus maps and spectral statistics". Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/dcba3276-00be-4bae-a89f-f864750e77ff.
Pełny tekst źródłaMassa, Kenneth L. "Control of Burgers' Equation With Mixed Boundary Conditions". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36681.
Pełny tekst źródłaMaster of Science
Berrabah, Nassif. "On High Order On-Surface Radiation Boundary Conditions". University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1415620836.
Pełny tekst źródłaAhmed, Ashfaq. "Investigation of boundary conditions for hydrological design analysis". Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396238.
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