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1
Luangpaiboon, Pongchanun. "A comparison of algorithms for automatic process optimisation." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324922.
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Guertler, Marion. "Modelling and solution methods for portfolio optimisation." Thesis, Brunel University, 2004. http://bura.brunel.ac.uk/handle/2438/4855.
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In this thesis modelling and solution methods for portfolio optimisation are presented. The investigations reported in this thesis extend the Markowitz mean-variance model to the domain of quadratic mixed integer programming (QMIP) models which are 'NP-hard' discrete optimisation problems. In addition to the modelling extensions a number of challenging aspects of solution algorithms are considered. The relative performances of sparse simplex (SSX) as well as the interior point method (IPM) are studied in detail. In particular, the roles of 'warmstart' and dual simplex are highlighted as applied to the construction of the efficient frontier which requires processing a family of problems; that is, the portfolio planning model stated in a parametric form. The method of solving QMIP models using the branch and bound algorithm is first developed; this is followed up by heuristics which improve the performance of the (discrete) solution algorithm. Some properties of the efficient frontier with discrete constraints are considered and a method of computing the discrete efficient frontier (DEF) efficiently is proposed. The computational investigation considers the efficiency and effectiveness in respect of the scale up properties of the proposed algorithm. The extensions of the real world models and the proposed solution algorithms make contribution as new knowledge.
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Hamilton, Daniel. "Decomposition and diet problems." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/3798.
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The purpose of this thesis is to efficiently solve real life problems. We study LPs. We study an NLP and an MINLP based on what is known as the generalised pooling problem (GPP), and we study an MIP that we call the cattle mating problem. These problems are often very large or otherwise difficult to solve by direct methods, and are best solved by decomposition methods. During the thesis we introduce algorithms that exploit the structure of the problems to decompose them. We are able to solve row-linked, column-linked and general LPs efficiently by modifying the tableau simplex method, and suggest how this work could be applied to the revised simplex method. We modify an existing sequential linear programming solver that is currently used by Format International to solve GPPs, and show the modified solver takes less time and is at least as likely to find the global minimum as the old solver. We solve multifactory versions of the GPP by augmented Lagrangian decomposition, and show this is more efficient than solving the problems directly. We introduce a decomposition algorithm to solve a MINLP version of the GPP by decomposing it into NLP and ILP subproblems. This is able to solve large problems that could not be solved directly. We introduce an efficient decomposition algorithm to solve the MIP cattle mating problem, which has been adopted for use by the Irish Cattle Breeding Federation. Most of the solve methods we introduce are designed only to find local minima. However, for the multifactory version of the GPP we introduce two methods that give a good chance of finding the global minimum, both of which succeed in finding the global minimum on test problems.
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Wang, Yang. "Robust and stable discrete adjoint solver development for shape optimisation of incompressible flows with industrial applications." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24870.
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This thesis investigates stabilisation of the SIMPLE-family discretisations for incompressible flow and their discrete adjoint counterparts. The SIMPLE method is presented from typical \prediction-correction" point of view, but also using a pressure Schur complement approach, which leads to a wider class of schemes. A novel semicoupled implicit solver with velocity coupling is proposed to improve stability. Skewness correction methods are applied to enhance solver accuracy on non-orthogonal grids. An algebraic multi grid linear solver from the HYPRE library is linked to flow and discrete adjoint solvers to further stabilise the computation and improve the convergence rate. With the improved implementation, both of flow and discrete adjoint solvers can be applied to a wide range of 2D and 3D test cases. Results show that the semi-coupled implicit solver is more robust compared to the standard SIMPLE solver. A shape optimisation of a S-bend air flow duct from a VW Golf vehicle is studied using a CAD-based parametrisation for two Reynolds numbers. The optimised shapes and their flows are analysed to con rm the physical nature of the improvement. A first application of the new stabilised discrete adjoint method to a reverse osmosis (RO) membrane channel flow is presented. A CFD model of the RO membrane process with a membrane boundary condition is added. Two objective functions, pressure drop and permeate flux, are evaluated for various spacer geometries such as open channel, cavity, submerged and zigzag spacer arrangements. The flow and the surface sensitivity of these two objective functions is computed and analysed for these geometries. An optimisation with a node-base parametrisation approach is carried out for the zigzag con guration channel flow in order to reduce the pressure drop. Results indicate that the pressure loss can be reduced by 24% with a slight reduction in permeate flux by 0.43%.
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Koulibaly, Issa. "Automatisation et optimisation de la synthèse du ((pyridyl-4)-2 ethyl)-3 indole, précurseur d'un antidépresseur." Paris 6, 1986. http://www.theses.fr/1986PA066413.
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Dans le cadre des recherches concernant l'application des techniques d'automatisation et des méthodes d'optimisation, sur les procédés de fabrications industrielles de produits pharmaceutiques, nous avons choisi l'automatisation et l'optimisation de la synthèse d'un précurseur de l'indalpine, qui est un produit pharmaceutique important par ses propriétés d'antidépresseur. Nous montrons, dans la première partie de ce travail, qu'il est possible d'automatiser, à l'échelle du laboratoire, et pour un cout réduit, une synthèse organique complexe à l'aide d'un automate de bas de gamme et de capteurs et actionneurs adéquats, que l'automatisation nécessite une bonne description du mode opératoire; pour cela, nous avons utilisé le langage grafcet afin de structurer le mode opératoire industriel. Dans la deuxième partie, nous prouvons qu'il est aussi possible d'améliorer le rendement d'une synthèse organique en établissant la fonction réponse et en l'optimisant pour obtenir les coordonnées de l'optimum. Pour la synthèse concernée dans ce travail, le gain de rendement a été de 22 points.
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Ao, Wai Kei. "Electromagnetic damping for control of vibration in civil structures." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/31145.
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This thesis investigates an alternative solution to deal with the civil structure vibration. Non-contact electromagnetic or Eddy current damping is selected as a score of vibration suppression. Electromagnetic damping relies on the interaction between a permanent magnet and conductor. An electromagnetic damper (EMD) is applied both to a laboratory footbridge structure and 6-storey model-scale aluminium moment resisting frame (AMRF). In this first study the EMD is connected in series with an electronic shunt circuit to construct an electromagnetic shunt damper (EMSD). A robust optimisation method is applied to develop the corresponding optimal design formula of the EMSD. The principle of an EMSD is to convert mechanical energy to electrical energy. Hence, the induced electromotive force (emf) is generated by electromagnetic induction. This emf induces an amount of shunt damping, which is fedback to the structure to achieve vibration suppression. It was found that when the impedance was applied, the shunt damping feature was of a similar nature to viscous dampers. In contrast, when an RLC (resistance-inductance-capacitance) circuit is connected, the shunt damping is analogous to a tuned mass damper. A second form of EMD is Eddy current damper (ECD), which relies on a geometrical arrangement of permanent magnets and conductors to produce damping forces. The vertical and horizontal orientation of the magnet, unidirectional and alternative pole projection and moving different direction of the conductor are investigated. A theoretical study involving the infinite boundary and finite boundary (the method of images current) is carried out to obtain an analytical calculation of the damping force. On the basis of this analysis, one type of ECD prototype was physically built. A performance test was carried out to determine the damping characteristics of the ECD, which agreed with the results of the numerical analysis. In addition, the ECD was applied to control the dynamics of the 6-storey AMRF. It was found that, the ECD can effectively increase system damping and have a satisfactory control effect.
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AIDO, LAETITIA. "Optimisation de la fabrication de l'indole-2 carboxylate d'ethyle : automatisation de la reaction de wislicenus et thoma et de la reaction d'hydrogenation de brehm, etude de differents systemes de commande : correlateur logique (...) microprocesseur." Paris 6, 1986. http://www.theses.fr/1986PA066370.
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Cette etude a ete faite pour demontrer l'efficacite des methodes d'optimisation et d'automatisation; elle a permis un gain de rendement de 36 points (de 41 a 77%) associe a une forte diminution de la duree globale de la reaction (76h a 2h30)
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Huangfu, Qi. "High performance simplex solver." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7952.
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The dual simplex method is frequently the most efficient technique for solving linear programming (LP) problems. This thesis describes an efficient implementation of the sequential dual simplex method and the design and development of two parallel dual simplex solvers. In serial, many advanced techniques for the (dual) simplex method are implemented, including sparse LU factorization, hyper-sparse linear system solution technique, efficient approaches to updating LU factors and sophisticated dual simplex pivoting rules. These techniques, some of which are novel, lead to serial performance which is comparable with the best public domain dual simplex solver, providing a solid foundation for the simplex parallelization. During the implementation of the sequential dual simplex solver, the study of classic LU factor update techniques leads to the development of three novel update variants. One of them is comparable to the most efficient established approach but is much simpler in terms of implementation, and the other two are specially useful for one of the parallel simplex solvers. In addition, the study of the dual simplex pivoting rules identifies and motivates further investigation of how hyper-sparsity maybe promoted. In parallel, two high performance simplex solvers are designed and developed. One approach, based on a less-known dual pivoting rule called suboptimization, exploits parallelism across multiple iterations (PAMI). The other, based on the regular dual pivoting rule, exploits purely single iteration parallelism (SIP). The performance of PAMI is comparable to a world-leading commercial simplex solver. SIP is frequently complementary to PAMI in achieving speedup when PAMI results in slowdown.
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Awad, Barre Mohamed 1955. "APPLICATION OF THE SIMPLEX METHOD TO SLOPE STABILITY ANALYSIS." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276340.
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Koberstein, Achim. "The dual simplex method, techniques for a fast and stable implementation." kostenfrei, 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978580478.
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Kibiikyo, Deogratias Sekabira. "Optimisation of thermodynamic systems using the energy method." Thesis, Queen Mary, University of London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261577.
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Hu, Jing. "Solving linear programs using primal-dual subproblem simplex method and quasi-explicit matrices." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/24863.
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Ouzký, Karel. "Zlomkový simplexový algoritmus ve VBA." Master's thesis, Vysoká škola ekonomická v Praze, 2009. http://www.nusl.cz/ntk/nusl-17368.
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Basic idea of fractal simplex algorithm is based in the theory of matrix counting and knowledge of matrix representation of simplex tabuleao from revised simplex method. My desire is to explain theoretical basics on which this algorithm works and provide solution in language Visual Basic for Applications in application MS Excel 2007. Main benefit I see in the fact, that algorithm can solved specific class of mathematical problems in a way of exactness counting whithout necessity of using decimal numbers.
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Cantane, Daniela Renata. "Contribuição da atualização da decomposição LU no metodo Simplex." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260212.
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Orientadores: Aurelio Ribeiro Leite de Oliveira, Christiano Lyra Filho<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação<br>Made available in DSpace on 2018-08-14T10:57:39Z (GMT). No. of bitstreams: 1
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Previous issue date: 2009<br>Resumo: A solução eficiente de sistemas lineares é fundamental em problemas de otimização linear e o primeiro método a obter êxito nesta classe de problemas foi o método Simplex. Com o objetivo de desenvolver alternativas eficientes para sua implementação, são apresentadas nesta tese técnicas de atualização da decomposição LU da base para aperfeiçoar a solução dos sistemas lineares oriundos do método Simplex, utilizando um reordenamento estático nas colunas da matriz. Uma simulação do método Simplex é implementada, realizando troca de bases obtidas pelo MINOS e verificando sua esparsidade. Somente os elementos afetados pela mudança de base são considerados para obter uma atualização da decomposição LU eficaz. As colunas da matriz são reordenadas de acordo com três estratégias: mínimo grau; forma bloco triangular e estratégia de Björck. Assim, obtém-se uma decomposição esparsa para qualquer base sem esforço computacional para obter a ordem das colunas, pois o reordenamento da matriz é estático e as colunas da base obedecem esta ordem. A forma bloco triangular obteve os melhores resultados, para os maiores problemas testados, em relação ao mínimo grau e a estratégia de Björck. Resultados computacionais para problemas da Netlib mostram a robustez e um bom desempenho computacional do método de atualização da decomposição LU proposto, pois não são necessárias refatorações periódicas da base como nos métodos de atualização tradicionais. O método proposto obteve uma redução do número de elementos não nulos da base em relação ao MINOS. Esta abordagem foi aplicada em problemas de corte de estoque e a atualização da decomposição LU proposta obteve uma redução do tempo computacional na solução destes problemas em relação ao GPLK.<br>Abstract: Finding efficient solution of linear systems is fundamental in the linear programming problems and the first method to obtain success for this class of problems was the Simplex method. With the objective to develop efficient alternatives to its implementation, techniques of the simplex basis LU factorization update are developed in this thesis to improve the solution of the Simplex method linear systems towards a matrix columns static reordering. A simulation of the Simplex method is implemented, carrying through the change of basis obtained from MINOS and verifying its sparsity. Only the factored columns actually modified by the change of the base are carried through to obtain an efficient LU factorization update. The matrix columns are reordered according to three strategies: minimum degree; block triangular form and the Björck strategy. Thus, sparse factorizations are obtained for any base without computational effort to obtain the order of columns, since the reordering of the matrix is static and base columns follow this ordering. The application of the block triangular form achieved the best results, for larger scale problems tested, in comparison to minimum degree method and the Björck strategy. Computational results for Netlib problems show the robustness of this approach and good computational performance, since there is no need of periodical factorizations as used in traditional updating methods. The proposed method obtained a reduction of the nonzero entries of the basis with respect to MINOS. This approach was applied in the cutting stock problems and the proposed method achieved a reduction of the computational time in the solution of such problems with respect to the GLPK.<br>Universidade Estadual de Campi<br>Automação<br>Doutor em Engenharia Elétrica
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Atanackov, NatasÌŒa. "Trend forecasting by constrained optimisation and method selection protocols." Thesis, Brunel University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400597.
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Sadhukan, Jhuma. "A novel value analysis method for process network optimisation." Thesis, University of Manchester, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503544.
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Salvador, Thaís Reigadas. "Um estudo do método simplex e sua aplicação na radioterapia." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8081.
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Previous issue date: 2016-06-15<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>This work presents an application of the Simplex Method for solving an optimal planning problem for cancer treatment by radiotherapy. The Simplex Method, proposed by George Dantzig, is a matrix procedure walks along extreme points of the feasible region in search of an optimal solution problem. The optimal planning for radiation therapy can be aided by Linear Programming, where the concern is to aplly a high enough radiation in the tumor while saving significantly healthy regions or critical organs.<br>Este trabalho visa apresentar uma aplicação do Método Simplex para resolução de um problema de planejamento ótimo para o tratamento de câncer por radioterapia. O Método Simplex, proposto por George Dantzig, é um procedimento matricial que percorre pontos extremos da região factível em busca de uma solução ótima do problema. O planejamento ótimo para radioterapia pode ser auxiliado pela Programação Linear, onde a preocupação é aplicar uma radiação suficientemente alta no órgão ou tumor e ao mesmo tempo, poupar significativamente regiões saudáveis ou órgãos de risco.
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Ek, Jonatan. "Optimisation of flat dielectric lenses using an interior point method." Thesis, Linköpings universitet, Tillämpad matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-176361.
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This thesis aims to study how flat dielectric lenses can be designed. The usage of flat lenses is steadily increasing as they are smaller and less bulky than traditional convex lenses. Instead of a lens with a curved surface the permittivity in the lens is varied to achieve the same effect. Two different computational methods were investigated when approaching this problem: physical and geometrical optics. In physical optics the incoming radio waves are treated as waves in contrast to geometrical optics where it is considered as rays. Both methods are used as approximations of Maxwell's equations. The variation of permittivity in the lens was formulated as an optimisation problem where the lens' focusing abilities were maximised. The optimisation was implemented with an interior point method. Both arbitrary permittivity distributions as well as predetermined distributions were examined in this work. All optimised lens models were then simulated in a full wave commercial simulation software to verify and compare the two. The simulations showed that both approaches gave promising results as they focused the electromagnetic wave in a satisfying way. However the physical optics approach was more prominent as the focused radio waves had a much higher magnitude than the approach based on geometrical optics. The conclusion was therefore that physical optics is the preferred approach.
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Vafaeyan, Shadi. "A new approach to the Rough Set multicriteria optimisation method." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/28031.
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In the recent years, enormous amount of attention has been given to multicriteria optimisation problems. These are problems with conflicting objectives, to which it is impossible to obtain an optimum solution that contains the best value for every criterion simultaneously, therefore the decision maker must decide on a reasonable compromise. There have been numerous developments of optimisation methods to aid the decision-maker in addressing such problems. These methods can be divided to two categories based on the use or not of the Pareto domain (PD). The Pareto domain is the set of all non-dominated solutions to the multicriteria problem, where no solution is better or worse than any other in the set when all the criteria are considered equal in importance.
This thesis is a collection of two papers that focuses on a new approach to the Rough Set multicriteria optimisation technique. Rough Set method (RSM) requires the determination of the PD as the first step to the optimisation process. In the suggested new approach to RSM, a more systematic way in the selection of points from the PD, that is given to the expert for ranking and then the generation of rules by which the entire PD is ranked, is presented. The RSM that operates based on this new approach was applied to three case studies in paper 1 and to "Beer quality optimisation" in the second paper. The results were compared to the ones obtained by the traditional RSM, Net Flow method and the simple Least Squares method. In conclusion, the new RSM showed to be the most reliable and robust method of all.
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Duller, A. W. G. "Parallel computation applied to the finite element method." Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376605.
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Silva, Adriana Batista da. "O método simplex e o método gráfico na resolução de problemas de otimização." Universidade Federal de Goiás, 2016. http://repositorio.bc.ufg.br/tede/handle/tede/5905.
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Previous issue date: 2016-04-29<br>Financiadora de Estudos e Projetos- Finep<br>Linear Programming is an operational search tool applied to problem solving aimed
at the optimization of a study system. This study aims to show some applications of
linear programming and how it can be used as a motivating teaching skills of Mathematics
in High school. We will cover two methods of linear programming problems
resolution, Graphics resolution method and the algebraic solution way, which is the
Simple Method. We so decided to solve under the assistance of these two methods
quoted, optimization problems with two or three variables, since the problems with
multiple variables do not match the curriculum of mathematics for high school. We
suggest the use of two free applications for mobile phones, to solve optimization problems
with several variables, in order to contribute in a di erent approach, seeking to
boost in students, interest in the study of mathematics.<br>A Programação Linear é uma ferramenta da Pesquisa Operacional aplicada à solução de
problemas que objetivam a otimização de um sistema de estudo. O presente trabalho
busca mostrar algumas aplicações da Programação Linear e como ela pode ser utilizada
como elemento motivador no ensino da Matemática no Ensino Médio. Abordaremos
dois métodos de resolução de problemas de Programação Linear, o método de Resolução
Grá ca e a forma algébrica de solução que é o Método Simplex. Vamos solucionar
com auxílio desses dois métodos citados, problemas de otimização com duas e três
variáveis, já que problemas com várias variáveis não se adequam a matriz curricular de
Matemática para o Ensino Médio. Sugerimos a utilização de dois aplicativos gratuitos
para celulares, que solucionam problemas de otimização com várias variáveis como forma
de contribuir com uma abordagem diferente, visando despertar no aluno, o interesse
pelo estudo da Matemática.
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Fidkowski, Krzysztof J. 1981. "A simplex cut-cell adaptive method for high-order discretizations of the compressible Navier-Stokes equations." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39701.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007.<br>Includes bibliographical references (p. 169-175).<br>While an indispensable tool in analysis and design applications, Computational Fluid Dynamics (CFD) is still plagued by insufficient automation and robustness in the geometry-to-solution process. This thesis presents two ideas for improving automation and robustness in CFD: output-based mesh adaptation for high-order discretizations and simplex, cut-cell mesh generation. First, output-based mesh adaptation consists of generating a sequence of meshes in an automated fashion with the goal of minimizing an estimate of the error in an engineering output. This technique is proposed as an alternative to current CFD practices in which error estimation and mesh generation are largely performed by experienced practitioners. Second, cut-cell mesh generation is a potentially more automated and robust technique compared to boundary-conforming mesh generation for complex, curved geometries. Cut-cell meshes are obtained by cutting a given geometry of interest out of a background mesh that need not conform to the geometry boundary. Specifically, this thesis develops the idea of simplex cut cells, in which the background mesh consists of triangles or tetrahedra that can be stretched in arbitrary directions to efficiently resolve boundary-layer and wake features.<br>(cont.) The compressible Navier-Stokes equations in both two and three dimensions are discretized using the discontinuous Galerkin (DG) finite element method. An anisotropic h-adaptation technique is presented for high-order (p > 1) discretizations, driven by an output-error estimate obtained from the solution of an adjoint problem. In two and three dimensions, algorithms are presented for intersecting the geometry with the background mesh and for constructing the resulting cut cells. In addition, a quadrature technique is proposed for accurately integrating high-order functions on arbitrarily-shaped cut cells and cut faces. Accuracy on cut-cell meshes is demonstrated by comparing solutions to those on standard, boundary-conforming meshes. In two dimensions, robustness of the cut-cell, adaptive technique is successfully tested for highly-anisotropic boundary-layer meshes representative of practical high-Re simulations. In three dimensions, robustness of cut cells is demonstrated for various representative curved geometries. Adaptation results show that for all test cases considered, p = 2 and p = 3 discretizations meet desired error tolerances using fewer degrees of freedom than p = 1.<br>Krzysztof Jakub Fidkowski.<br>Ph.D.
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Tai, Kang. "Shape and topology design optimisation using the boundary integral equation method." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294748.
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Turnbull, A. "A preliminary sizing method for unmanned aircraft using multi-variate optimisation." Thesis, Cranfield University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305509.
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Melliani, Mohamed. "Analyse numérique d'algorithmes proximaux généralisés en optimisation convexe." Rouen, 1997. http://www.theses.fr/1997ROUES030.
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La thèse a pour objet l'étude d'une généralisation de l'algorithme du point proximal en optimisation convexe tant d'un point de vue théorique que numérique. L'équivalent de cette généralisation pour l'algorithme de Tikhonov est également proposé. S'inscrivant, dans un premier temps, dans le cadre de la convergence variationnelle, la méthode proximale généralisée est tout d'abord combinée avec les méthodes des pénalités. Puis, lorsqu'appliquée au problème dual, elle permet d'obtenir de nouvelles méthodes de multiplicateurs, différentes de celles introduites par Eckstein et Teboulle. Ces méthodes des multiplicateurs englobent, en particulier, la méthode de Hestenes et Powell, celle de Rockafellar et certaines des méthodes de Kort et Bertsekas.
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Brampton, Christopher. "Applications of level set topology optimisation." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675725.
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Level set method is a boundary tracking method that uses an implicit function to define the boundary location. By using the implicit function to define the structural boundary the level set method can be used for topology optimisation. The level set method has previously been used to solve a range of structural optimisation problems. The aim of this thesis is to extend the application of the level set method to additional applications of structural optimisation. A robust method of 3D level set topology optimisation is developed and tested. The use of a hole insertion method was found to be advantageous, but not vital, for 3D level set topology optimisation. The level set method is used to optimise the internal structure of a proximal femur. Similarities between the optimal structure and real internal trabecular bone architecture suggest that the internal bone structure may be mechanically optimal. Stress constrained level set topology optimisation is performed in 2D. Stress shape sensitivities are derived and interpolated to obtain smooth boundary sensitivity, resulting in feasible stress constrained solution in numerical examples. A new generic objective hole insertion method is used to reduce dependence on the initial solution. A level set method for optimising the design of fibre angles in composite structures is also introduced. Fibre paths are implicitly defined using the level set function. Sensitivity analysis is used to update the level set function values and optimise the fibre path. The method implicitly ensures continuous fibre paths in the optimum solution, that could be manufactured using advanced fibre placement.
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Sun, Huafei. "A robust simplex cut-cell method for adaptive high-order discretizations of aerodynamics and multi-physics problems." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85764.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 189-199).<br>Despite the wide use of partial differential equation (PDE) solvers, lack of automation still hinders realizing their full potential in assisting engineering analysis and design. In particular, the process of establishing a suitable mesh for a given problem often requires heavy person-in-the-loop involvement. This thesis presents work toward the development of a robust PDE solution framework that provides a reliable output prediction in a fully-automated manner. The framework consists of: a simplex cut-cell technique which allows the mesh generation process to be independent of the geometry of interest; a discontinuous Galerkin (DG) discretization which permits an easy extension to high-order accuracy; and an anisotropic output-based adaptation which improves the discretization mesh for an accurate output prediction in a fully-automated manner. Two issues are addressed that limit the automation and robustness of the existing simplex cut-cell technique in three dimensions. The first is the intersection ambiguity due to numerical precision. We introduce adaptive precision arithmetic that guarantees intersection correctness, and develop various techniques to improve the efficiency of using this arithmetic. The second is the poor quadrature quality for arbitrarily shaped elements. We propose a high-quality and efficient cut-cell quadrature rule that satisfies a quality measure we define, and demonstrate the improvement in nonlinear solver robustness using this quadrature rule. The robustness and automation of the solution framework is then demonstrated through a range of aerodynamics problems, including inviscid and laminar flows. We develop a high-order DG method with a dual-consistent output evaluation for elliptic interface problems, and extend the simplex cut-cell technique for these problems, together with a metric-optimization adaptation algorithm to handle cut elements. This solution strategy is further extended for multi-physics problems, governed by different PDEs across the interfaces. Through numerical examples, including elliptic interface problems and a conjugate heat transfer problem, high-order accuracy is demonstrated on non-interface-conforming meshes constructed by the cut-cell technique, and mesh element size and shape on each material are automatically adjusted for an accurate output prediction.<br>by Huafei Sun.<br>Ph. D.
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Moss, Aaron. "Basis Enumeration of Hyperplane Arrangements up to Symmetries." Thesis, Fredericton: University of New Brunswick, 2012. http://hdl.handle.net/1882/44593.
Full textAbstract:
This thesis details a method of enumerating bases of hyperplane arrangements up to symmetries. I consider here automorphisms, geometric symmetries which leave the set of all points contained in the arrangement setwise invariant. The algorithm for basis enumeration described in this thesis is a backtracking search over the adjacency graph implied on the bases by minimum-ratio simplex pivots, pruning at bases symmetric to those already seen. This work extends Bremner, Sikiri c, and Sch urmann's method for basis enumeration of polyhedra up to symmetries, including a new pivoting rule for nding adjacent bases in arrangements, a method of computing automorphisms of arrangements which extends the method of Bremner et al. for computing automorphisms of polyhedra, and some associated changes to optimizations used in the previous work. I include results of tests on ACEnet clusters showing an order of magnitude speedup from the use of C++ in my implementation, an up to 3x speedup with a 6-core parallel variant of the algorithm, and positive results from other optimizations.
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Lau, Mark C. "Small Signal Equivalent Circuit Extraction From A Gallium Arsenide MESFET Device." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36952.
Full textAbstract:
The development of microwave Gallium Arsenide Metal Semiconductor Field
Effect Transistor (MESFET) devices has enabled the miniaturization of pagers, cellular
phones, and other electronic devices. With these MESFET devices comes the need to
model them. This thesis extracts a small signal equivalent circuit model from a Gallium
Arsenide MESFET device. The approach taken in this thesis is to use measured S-
parameters to extract a small signal equivalent circuit model by optimization. Small signal
models and S-parameters are explained. The Simplex Method is used to optimize the
small signal equivalent circuit model. A thorough analysis of the strengths and
weaknesses of the Simplex method is performed.<br>Master of Science
30
Arca, Ahmet. "The design and optimisation of nanophotonic devices using the Finite Element Method." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11169/.
Full textAbstract:
The aim of this thesis is to develop a technique which can be used in the reliable modelling, design and optimisation of practical suboptical wavelength sized photonic/plasmonic devices, which may involve arbitrary geometries on various scales. The technique involves the application of numerical electromagnetic simulation led by theoretical knowledge and physical insight to determine, design and optimise the operating mechanism of such devices. The work in this thesis contains a variety of problems/devices which involve arbitrary structures of different scales. This poses difficulties in both the fabrication and the modelling aspects of the design. The problems range in difficulty from those which can be simply and perfectly described via an analytical solution, to those which would be impractical to design using any other technique. The nature of the problems considered, i.e. the complicated geometry and the range of scales, necessitates the use of a flexible modelling technique. Finite Element Method (FEM) was found to be a valuable tool in the design and optimisation of the devices throughout this thesis, owing its success mainly to its versatility and flexible meshing abilities which allowed its operation in different length scales in an efficient manner. Three nanophotonic/plasmonic devices are considered in an effort to demonstrate the implementation and the application of the developed technique. The devices considered in this thesis demonstrate different challenges in the modelling and design while being of considerable interest in their own right as nanostructures for sensing and measurement. These devices are: A self-calibrated plasmon sensor, a plasmon resonator and an ultrahigh frequency optical acoustic surface wave detector. Whilst the first two devices are important as an application of plasmonics, the third device links the mechanical and optical processes together.
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Thein, Chung Ket. "An effective optimisation method for multifactor and reliability-related structural design problems." Thesis, University of Hull, 2011. http://hydra.hull.ac.uk/resources/hull:5338.
Full textAbstract:
This thesis first presents a systematic design procedure which satisfies the required strength and stiffness, and structural mass for conceptual engineering structural designs. The procedure employs a multi-objective and multi-disciplinary (MO–MD) optimisation method (multifactor optimisation of structure techniques, MOST) which is coupled with finite element analysis (FEA) as an analysis tool for seeking the optimum design. The effectiveness of the MOST technique is demonstrated in two case studies. Next, a reliability-related multi-factor optimisation method is proposed and developed, representing a combination of MOST (as a method of multi-factor optimisation) and the reliability-loading case index (RLI) (as a method of calculating the reliability index). The RLI is developed based on a well-known reliability method: the first-order reliability method (FORM). The effectiveness and robustness of the proposed methodology are demonstrated in two case studies in which the method is used to simultaneously consider multi-objective, multi-disciplinary, and multi-loading-case problems. The optimised designs meet the targeted performance criteria under various loading conditions. The results show that the attributes of the proposed optimisation methods can be used to address engineering design problems which require simultaneous consideration of multi-disciplinary problems. An important contribution of this study is the development of a conceptual MO–MD design optimisation method, in which multi-factor structural and reliability design problems can be simultaneously considered.
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Petersson, Nina. "Optimisation of capillary gel electrophoresis method for enhanced separation of mRNA shortmers." Thesis, Uppsala universitet, Institutionen för kemi - BMC, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-351119.
Full textAbstract:
Advancements in the field of modified messenger RNA (mRNA) has led to new ventures in the pharmaceutical industry. However, new drug products demand new analytical methods to ensure the efficacy and purity of the drug. Capillary gel electrophoresis (CGE) with UV detection shows great potential for separation of mRNA samples due to the equal mass-to-charge ratio of mRNA and the flexible parameters of the CGE methods. This thesis investigates the optimal parameters of the capillary electrophoresis method, sample treatment procedure and sieving medium composition for enhanced shortmers separation of mRNA by CGE analysis. An RNA ladder with 100-1000 nucleotides and EPO mRNA with 900 nucleotides were used as model compounds. The effect of capillary dimensions and separation temperature on the resolution of the RNA peaks was established through comparative experiments. Sample treatment processes were evaluated to achieve an optimal conformation of the mRNA for CGE analysis. By heating the mRNA sample for 15 min at 80°C all multimers were seemingly eradicated. Moreover, it was found that addition of 4 M of urea to mRNA sample before heating resulted in improved peak shape. A sieving medium consisting of a mix of the two polymers polyvinylpyrrolidine (PVP) and hydroxyethyl cellulose (HEC) proved to have beneficial qualities for separation. The addition of sucrose as viscosity modifier in the sieving medium surprisingly further enhanced the resolution. Moreover, during the project a heavy wash was established which drastically improved repeatability of the analyses through more efficient regeneration of the capillary. ISSN:
33
Burger, Gert Cloete. "Optimisation of the pulse-echo method with an application to acoustic thermometry." Thesis, Cape Peninsula University of Technology, 2010. http://hdl.handle.net/20.500.11838/1105.
Full textAbstract:
Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009<br>In acoustics, pulse echo methods are well known as a means of measuring time of Hight. Traditional
techniques for generating acoustic waves in solid ferromagnetic waveguides include piezoelectric,
capacitive and magnetostriction. Piezoelectric and capacitive techniques are preferred
due to the inefficiency of magnetostriction caused by electro-mechanical coupling losses and the
fact that most ferromagnetic materials show low levels of magnetostriction. The aim of this
study was to optimise the magnetostrictive effects for sensing applications based on a ferromagnetic
waveguide using the pulse echo method. The results obtained were implemented in the
design of an acoustic thermometer.
Two configurations for signal generation and recovery were examined, the use of a single
wound copper coil acting as a transceiver coil, and the use of separate transmit and receive
coils. Results obtained using the latter configuration indicated better signal to noise ratio's and
provided the flexibility to manipulate the point of signal recovery. The pulse echo method was
implemented and optimised.
An acoustic thermometer based on an existing design was developed by inducing a partial
reflection from a set position in the waveguide, defining a sensing probe. Awareness of the elastic
properties of the waveguide material enabled the guaging of its temperature by measuring the
acoustic pulse velocity in the probe.
The accuracy of the instrument was increased through signal conditioning, examined together
with cross correlation and an increased sampling frequency. Systematic errors were resolved
through calibration, giving the instrument an overall accuracy of ±O.56"C for the range of
temperatures between 2O"C and 400"C.
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Araújo, Pedro Felippe da Silva. "Programação linear e suas aplicações: definição e métodos de soluções." Universidade Federal de Goiás, 2013. http://repositorio.bc.ufg.br/tede/handle/tede/3126.
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Previous issue date: 2013-03-18<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES<br>Problems involving the idea of optimization are found in various elds of study,
such as, in Economy is in search of cost minimization and pro t maximization in a rm
or country, from the available budget; in Nutrition is seeking to redress the essential
nutrients daily with the lowest possible cost, considering the nancial capacity of the
individual; in Chemistry studies the pressure and temperature minimum necessary to
accomplish a speci c chemical reaction in the shortest possible time; in Engineering seeks
the lowest cost for the construction of an aluminium alloy mixing various raw materials
and restrictions obeying minimum and maximum of the respective elements in the alloy.
All examples cited, plus a multitude of other situations, seek their Remedy by
Linear Programming. They are problems of minimizing or maximizing a linear function
subject to linear inequalities or Equalities, in order to nd the best solution to this
problem.
For this show in this paper methods of problem solving Linear Programming.
There is an emphasis on geometric solutions and Simplex Method, to form algebraic
solution. Wanted to show various situations which may t some of these problems, some
general cases more speci c cases.
Before arriving eventually in solving linear programming problems, builds up the
eld work of this type of optimization, Convex Sets. There are presentations of de nitions
and theorems essential to the understanding and development of these problems, besides
discussions on the e ciency of the methods applied.
During the work, it is shown that there are cases which do not apply the solutions presented, but mostly t e ciently, even as a good approximation.<br>Problemas que envolvem a ideia de otimiza c~ao est~ao presentes em v arios campos
de estudo como, por exemplo, na Economia se busca a minimiza c~ao de custos e
a maximiza c~ao do lucro em uma rma ou pa s, a partir do or camento dispon vel; na
Nutri c~ao se procura suprir os nutrientes essenciais di arios com o menor custo poss vel,
considerando a capacidade nanceira do indiv duo; na Qu mica se estuda a press~ao e a
temperatura m nimas necess arias para realizar uma rea c~ao qu mica espec ca no menor
tempo poss vel; na Engenharia se busca o menor custo para a confec c~ao de uma liga
de alum nio misturando v arias mat erias-primas e obedencendo as restri c~oes m nimas e
m aximas dos respectivos elementos presentes na liga.
Todos os exemplos citados, al em de uma in nidade de outras situa c~oes, buscam
sua solu c~ao atrav es da Programa c~ao Linear. S~ao problemas de minimizar ou maximizar
uma fun c~ao linear sujeito a Desigualdades ou Igualdades Lineares, com o intuito de
encontrar a melhor solu c~ao deste problema.
Para isso, mostram-se neste trabalho os m etodos de solu c~ao de problemas de
Programa c~ao Linear. H a ^enfase nas solu c~oes geom etricas e no M etodo Simplex, a forma
alg ebrica de solu c~ao. Procuram-se mostrar v arias situa c~oes as quais podem se encaixar
alguns desses problemas, dos casos gerais a alguns casos mais espec cos.
Antes de chegar, eventualmente, em como solucionar problemas de Programa c~ao
Linear, constr oi-se o campo de trabalho deste tipo de otimiza c~ao, os Conjuntos Convexos.
H a apresenta c~oes das de ni c~oes e teoremas essenciais para a compreens~ao e o desenvolvimento
destes problemas; al em de discuss~oes sobre a e ci^encia dos m etodos aplicados.
Durante o trabalho, mostra-se que h a casos os quais n~ao se aplicam as solu c~oes
apresentadas, por em, em sua maioria, se enquadram de maneira e ciente, mesmo como
uma boa aproxima c~ao.
35
Deng, Xiaoling. "Optimisation de structures sous contraintes technologiques de fonderie." Cachan, Ecole normale supérieure, 1993. http://www.theses.fr/1993DENS0004.
Full textAbstract:
L'optimisation de forme d'une pièce de fonderie nécessite la prise en compte de trois types de critères. Les critères géométriques assurent la cohérence topologique de la pièce ainsi que le respect des dimensions de la partie fonctionnelle. Les critères mécaniques garantissent la tenue en service de l'objet. Enfin les critères thermiques permettent l'obtention d'une pièce sans défaut lors du processus de fabrication. Les critères géométriques, souvent exprimes sous forme analytique, doivent être strictement respectes. Les critères mécaniques sont évalués à l'aide de calculs par la méthode des éléments finis. Enfin les critères thermiques sont obtenus en utilisant les résultats d'un calcul de solidification par la méthode des différences finies. Le travail de thèse a consiste dans un premier temps à trouver une méthode mathématique d'optimisation sous-contraintes adaptée aux problèmes traités. Ensuite cet algorithme a été interface avec les différents codes de calcul et de maillage afin d'obtenir une procédure automatique d'optimisation. Le processus itératif de minimisation peut induire des coûts de calculs élevés. Afin de réduire le temps de calcul, une technique d'approximation des fonctions couteuses a été développée. Le processus d'optimisation réalisé a été appliqué sur deux pièces de fonderie différentes. Cette étude montre l'intérêt et la faisabilité d'application d'une procédure d'optimisation des pièces de fonderie en tenant compte des critères de fabrication
36
Ahmat, Norhayati. "Geometric modelling and shape optimisation of pharmaceutical tablets. Geometric modelling and shape optimisation of pharmaceutical tablets using partial differential equations." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5702.
Full textAbstract:
Pharmaceutical tablets have been the most dominant form for drug delivery and they need to be strong enough to withstand external stresses due to packaging and loading conditions before use. The strength of the produced tablets, which is characterised by their compressibility and compactibility, is usually deter-mined through a physical prototype. This process is sometimes quite expensive and time consuming. Therefore, simulating this process before hand can over-come this problem. A technique for shape modelling of pharmaceutical tablets based on the use of Partial Differential Equations is presented in this thesis. The volume and the sur-face area of the generated parametric tablet in various shapes have been es-timated numerically. This work also presents an extended formulation of the PDE method to a higher dimensional space by increasing the number of pa-rameters responsible for describing the surface in order to generate a solid tab-let. The shape and size of the generated solid tablets can be changed by ex-ploiting the analytic expressions relating the coefficients associated with the PDE method.
The solution of the axisymmetric boundary value problem for a finite cylinder subject to a uniform axial load has been utilised in order to model a displace-ment component of a compressed PDE-based representation of a flat-faced round tablet. The simulation results, which are analysed using the Heckel model, show that the developed model is capable of predicting the compressibility of pharmaceutical powders since it fits the experimental data accurately. The opti-mal design of pharmaceutical tablets with particular volume and maximum strength has been obtained using an automatic design optimisation which is performed by combining the PDE method and a standard method for numerical optimisation.
37
Monokrousos, Antonios. "Optimisation and control of boundary layer flows." Licentiate thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10652.
Full text
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Mohamodhosen, Bibi Safoorah Bilquis. "Optimisation topologique de dispositifs électromagnétiques." Thesis, Ecole centrale de Lille, 2017. http://www.theses.fr/2017ECLI0028/document.
Full textAbstract:
L’Optimisation Topologique (OT) est un sujet en plein essor qui suscite l’intérêt de nombreux chercheurs depuis ces deux dernières décennies dans le domaine de l’électromagnétisme. L’OT représente une méthode très attrayante et originale car elle permet de trouver des structures innovantes sans aucun a priori. Ce travail de thèse est orienté vers l’OT des dispositifs électromagnétiques en approfondissant plusieurs aspects du sujet. Tout d’abord, un outil d’OT est développé et testé, à partir des outils existant au L2EP. En effet, l’OT requiert un outil d’éléments finis et un outil d’optimisation devant être couplés. Une méthodologie originale d’OT fondée sur les principes de la Méthode de Densité est développée et testée. Un cas test académique est utilisé afin de tester et valider le couplage des outils et la méthodologie. Une approche visant à prendre en compte le comportement non-linéaire des matériaux ferromagnétiques avec nos outils OT est également mise en place. Ensuite, la méthode est appliquée afin d’optimiser un électroaimant en 3 dimensions, représentant un cas test proche de la réalité. Ce cas test permet de comparer les résultats avec un comportement linéaire et non-linéaire des matériaux. Diverses topologies sont présentées, par rapport aux différentes formulations du problème. Par la suite, la méthodologie est appliquée à un dispositif électromagnétique plus complexe : une Génératrice Synchrone à Pôles Saillants. Cet exemple nous permet de voir comment la définition du problème d’optimisation peut grandement affecter les résultats d’OT. Quelques topologies sont présentées, et leur faisabilité est analysée<br>Topology Optimisation (TO) is a fast growing topic that has been sparking the interest of many researchers for the past two decades in the electromagnetic community. Its attractiveness lies in the originality of finding innovative structures without any layout a priori. This thesis work is oriented towards the TO of electromagnetic devices by elaborating on various aspects of the subject. First of all, a tool for TO is developed and tested, based on the ‘home-made’ tools available at the L2EP. As TO requires a FE and an optimisation tool working together, a coupling is done using both. Furthermore, a TO methodology is developed and tested, based on the Density Method. An academic cubic test case is used to carry out all the tests, and validate the tools and methodology. An approach is also developed to consider the nonlinear behaviour of the ferromagnetic materials with our TO tools. Afterwards, the methodology is applied to a 3D electromagnet, which represents a more real test case. This test case also serves to compare the results with linear and nonlinear behaviour of the materials used. Various topologies are presented, for different problem formulations. Subsequently, the methodology is applied to a more complex electromagnetic device: a Salient Pole Synchronous Generator. This example allows us to see how the problem definition can largely affect TO results. Some topologies are presented and their viability is discussed
39
Alotaibi, Lafi. "Commande et optimisation d'une installation multi-sources." Thesis, Reims, 2012. http://www.theses.fr/2012REIMS039.
Full textAbstract:
Cette thèse traite la commande et l'optimisation d'une installation photovoltaïquepour un site isolé. Ainsi, nous avons proposé un algorithme par logique flouepermettant la poursuite du point de puissance maximal afin de remédier auxinconvénients des méthodes classiques. Ensuite, nous nous sommes intéressés àl'optimisation de la structure de l'installation. En effet, dans les installationsclassiques, dans le cas de défaillance d'un panneaux, tout le bloc série devientinutilisable, ce qui réduit considérablement les capacités de production del'installation. Pour résoudre ce problème, nous avons proposé un superviseur permettant la reconfiguration automatique de l'installation de telle sorte que seul lepanneaux défaillant est mis hors connexion. Par ailleurs, pour gérer le flux depuissance et pour répondre à la demande de l'utilisateur, nous avons développé un superviseur par logique floue. Ainsi, le surplus de production est stocké systématiquement dans la batterie pour l'utiliser ensuite en cas où la demandedépasse la production. De plus, la structure proposée permet de ne solliciter la batterie en cas de besoin de ce qui permet de prolonger considérablement sa duréede vie<br>This thesis addresses the control and optimization of a stand-alone photovoltaicsystem. Thus, we proposed a fuzzy logic algorithm for tracking the maximum powerpoint to overcome the disadvantages of classical methods. Then we focused onoptimizing the structure of the installation. Indeed, in conventional systems, in thecase of failure of a panel, the whole serie block becomes unusable, greatly reducingthe production capacity. To resolve this problem, we proposed a supervisor for theautomatic reconfiguration of the installation so that only the failed panels is takenoffline. Furthermore, to manage the power flow and to meet user demand, wedeveloped a fuzzy supervisor. Thus, the surplus production is systematically storedin the battery for later use in cases where demand exceeds production. In addition,the proposed structure can not draining the battery in case of need thereby greatlyextend its lifetime
40
Ahmat, Norhayati Binti. "Geometric modelling and shape optimisation of pharmaceutical tablets : geometric modelling and shape optimisation of pharmaceutical tablets using partial differential equations." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5702.
Full textAbstract:
Pharmaceutical tablets have been the most dominant form for drug delivery and they need to be strong enough to withstand external stresses due to packaging and loading conditions before use. The strength of the produced tablets, which is characterised by their compressibility and compactibility, is usually deter-mined through a physical prototype. This process is sometimes quite expensive and time consuming. Therefore, simulating this process before hand can over-come this problem. A technique for shape modelling of pharmaceutical tablets based on the use of Partial Differential Equations is presented in this thesis. The volume and the sur-face area of the generated parametric tablet in various shapes have been es-timated numerically. This work also presents an extended formulation of the PDE method to a higher dimensional space by increasing the number of pa-rameters responsible for describing the surface in order to generate a solid tab-let. The shape and size of the generated solid tablets can be changed by ex-ploiting the analytic expressions relating the coefficients associated with the PDE method. The solution of the axisymmetric boundary value problem for a finite cylinder subject to a uniform axial load has been utilised in order to model a displace-ment component of a compressed PDE-based representation of a flat-faced round tablet. The simulation results, which are analysed using the Heckel model, show that the developed model is capable of predicting the compressibility of pharmaceutical powders since it fits the experimental data accurately. The opti-mal design of pharmaceutical tablets with particular volume and maximum strength has been obtained using an automatic design optimisation which is performed by combining the PDE method and a standard method for numerical optimisation.
41
Amigo, Ricardo Cesare Roman. "Design of adsorption systems by topology optimisation." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-05112018-140813/.
Full textAbstract:
Adsorption is a retention mechanism of fluid molecules on solid surfaces and presents a wide range of applications, such as refrigeration, separation processes and fuel storage. This work describes the modelling of gas adsorption on porous media and presents an optimisation approach for the design of adsorption systems based on topology optimisation. A comprehensive formulation for the adsorption and desorption phenomena is presented, detailing the derivation of their weak forms and assembling the matrices for the implementation of the Finite Element Method (FEM). The sensitivities of objective functions to topology optimisation design variables are obtained by the adjoint method, which is presented in detail. The numerical implementation is aided by FEniCS and Dolfin Adjoint packages, resulting in a generic software for the optimisation of adsorption systems. The method is applied for the design of Adsorbed Natural Gas (ANG) tanks for on-demand consumption. Optimised tank layouts are proposed and compared with standard tanks, presenting improvement of the design objectives.<br>Adsorção é um mecanismo de retenção de moléculas de um fluido em superfícies sólidas e apresenta um vasto campo de aplicações, como em refrigeração, processos de separação e armazenamento de combustível. Este trabalho descreve o modelo de adsorção de gás em meios porosos e define uma abordagem de otimização de sistemas de adsorção baseada no Método de Otimização Topológica (MOT). Uma formulação abrangente para os fenômenos de adsorção e dessorção é apresentada, detalhando a dedução de seus formas fracas e montagem das matrizes para a implementação do Método dos Elementos Finitos (MEF). As sensibilidades das funções-objetivo em relação às variáveis de projeto são obtidas pelo método adjunto, que também é apresentado em detalhe. A implementação numérica é auxiliada pelos pacotes FEniCS e Dolfin Adjoint, originando uma ferramenta genérica para a otimização de sistemas de adsorção. Este método é aplicado ao projeto de tanques de Gás Natural Adsorvido (GNA) visando transporte, armazenamento e consumo. Tanques otimizados são propostos e comparados com tanques tradicionais, apresentando melhora dos objetivos de projeto.
42
Genest, Laurent. "Optimisation de forme par gradient en dynamique rapide." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC022/document.
Full textAbstract:
Afin de faire face aux nouveaux challenges de l’industrie automobile, les ingénieurs souhaitent appliquer des méthodes d’optimisation à chaque étape du processus de conception. En élargissant l’espace de conception aux paramètres de forme, en augmentant leur nombre et en étendant les plages de variation, de nouveaux verrous sont apparus. C’est le cas de la résistance aux chocs. Avec les temps de calcul long, la non-linéarité, l’instabilité et la dispersion numérique de ce problème de dynamique rapide, la méthode usuellement employée, l’optimisation par plan d’expériences et surfaces de réponse, devient trop coûteuse pour être utilisée industriellement. Se pose alors la problématique suivante : Comment faire de l’optimisation de forme en dynamique rapide avec un nombre élevé de paramètres ?. Pour y répondre, les méthodes d’optimisation par gradient s’avèrent être les plus judicieuses. Le nombre de paramètres a une influence réduite sur le coût de l’optimisation. Elles permettent donc l’optimisation de problèmes ayant de nombreux paramètres. Cependant, les méthodes classiques de calcul du gradient sont peu pertinentes en dynamique rapide : le coût en nombre de simulations et le bruit empêchent l’utilisation des différences finies et le calcul du gradient en dérivant les équations de dynamique rapide n’est pas encore disponible et serait très intrusif vis-à-vis des logiciels. Au lieu de déterminer le gradient, au sens classique du terme, des problèmes de crash, nous avons cherché à l’estimer. L’Equivalent Static Loads Method est une méthode permettant l’optimisation à moindre coût basée sur la construction d’un problème statique linéaire équivalent au problème de dynamique rapide. En utilisant la dérivée du problème équivalent comme estimation du gradient, il nous a été possible d’optimiser des problèmes de dynamique rapide ayant des épaisseurs comme variables d’optimisation. De plus, si l’on construit les équations du problème équivalent avec la matrice de rigidité sécante, l’approximation du gradient n’en est que meilleure. De cette manière, il est aussi possible d’estimer le gradient par rapport à la position des nœuds du modèle de calcul. Comme il est plus courant de travailler avec des paramètres CAO, il faut déterminer la dérivée de la position des nœuds par rapport à ces paramètres. Nous pouvons le faire de manière analytique si nous utilisons une surface paramétrique pour définir la forme et ses points de contrôle comme variables d’optimisation. Grâce à l’estimation du gradient et à ce lien entre nœuds et paramètres de forme, l’optimisation de forme avec un nombre important de paramètres est désormais possible à moindre coût. La méthode a été développée pour deux familles de critères issues du crash automobile. La première est liée au déplacement d’un nœud, objectif important lorsqu’il faut préserver l’intégrité de l’habitacle du véhicule. La seconde est liée à l’énergie de déformation. Elle permet d’assurer un bon comportement de la structure lors du choc<br>In order to face their new industrial challenges, automotive constructors wish to apply optimization methods in every step of the design process. By including shape parameters in the design space, increasing their number and their variation range, new problematics appeared. It is the case of crashworthiness. With the high computational time, the nonlinearity, the instability and the numerical dispersion of this rapid dynamics problem, metamodeling techniques become to heavy for the standardization of those optimization methods. We face this problematic: ”How can we carry out shape optimization in rapid dynamics with a high number of parameters ?”. Gradient methods are the most likely to solve this problematic. Because the number of parameters has a reduced effect on the optimization cost, they allow optimization with a high number of parameters. However, conventional methods used to calculate gradients are ineffective: the computation cost and the numerical noise prevent the use of finite differences and the calculation of a gradient by deriving the rapid dynamics equations is not currently available and would be really intrusive towards the software. Instead of determining the real gradient, we decided to estimate it. The Equivalent Static Loads Method is an optimization method based on the construction of a linear static problem equivalent to the rapid dynamic problem. By using the sensitivity of the equivalent problem as the estimated gradient, we have optimized rapid dynamic problems with thickness parameters. It is also possible to approximate the derivative with respect to the position of the nodes of the CAE model. But it is more common to use CAD parameters in shape optimization studies. So it is needed to have the sensitivity of the nodes position with these CAD parameters. It is possible to obtain it analytically by using parametric surface for the shape and its poles as parameters. With this link between nodes and CAD parameters, we can do shape optimization studies with a large number of parameters and this with a low optimization cost. The method has been developed for two kinds of crashworthiness objective functions. The first family of criterions is linked to a nodal displacement. This category contains objectives like the minimization of the intrusion inside the passenger compartment. The second one is linked to the absorbed energy. It is used to ensure a good behavior of the structure during the crash
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Nilsson, Angelica. "Optimisation of a method for isolation of Clostridium difficile from faeces." Thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-126892.
Full textAbstract:
Clostridium difficile is a pathogen for both humans and animals and is often associated with antibiotic-associated diarrhea. Recently, several human cases of C. difficile-infection with increased mortality and morbidity have been reported. In studies performed in different countries C. difficile has been found in meat. Therefore the question whether C. difficile can be a zoonotic agent has been raised. The aim of this study was to optimize a method for isolation of C. difficile from faeces. When C. difficile is isolated from animals that do not have diarrhea the sample must be cultivated in an enrichment broth. Parameters influencing the enrichment were tested such as enrichment before and after spore selection, enrichment time, alcohol and heat chock for spore selection and if the samples had to be centrifuged or not before cultivation on agar plates. Enrichment in broth before spore selection was better than after. Heat and alcohol chock showed similar results, therefore you can chose which method you want. Cultivation from the pellet after centrifugation of the sample was better than cultivating directly from the inoculated broth. When the sample had low concentration of bacteria long enrichment time, 7 days or more, was best. The next step will be isolation of C. difficile from food-producing animals and humans and the strains will then be compared to se if the same strain is found in humans and in animals, to se if C. difficile-infection can be a zoonoz.
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Le, Moigne Alan. "A discrete Navier-Stokes adjoint method for aerodynamic optimisation of BlendedWing-Body configurations." Thesis, Cranfield University, 2002. http://hdl.handle.net/1826/826.
Full textAbstract:
An aerodynamic shape optimisation capability based on a discrete adjoint solver for Navier-
Stokes flows is developed and applied to a Blended Wing-Body future transport aircraft.
The optimisation is gradient-based and employs either directly a Sequential Quadratic Programming
optimiser or a variable-fidelity optimisation method that combines low- and
high-fidelity models. The shape deformations are parameterised using a B´ezier-Bernstein
formulation and the structured grid is automatically deformed to represent the design changes.
The flow solver at the heart of this optimisation chain is a Reynolds averaged Navier-
Stokes code for multiblock structured grids. It uses Osher’s approximate Riemann solver
for accurate shock and boundary layer capturing, an implicit temporal discretisation and
the algebraic turbulence model of Baldwin-Lomax. The discrete Navier-Stokes adjoint
solver based on this CFD code shares the same implicit formulation but has to calculate
accurately the flow Jacobian. This implies a linearisation of the Baldwin-Lomax model.
The accuracy of the resulting adjoint solver is verified through comparison with finitedifference.
The aerodynamic shape optimisation chain is applied to an aerofoil drag minimisation problem.
This serves as a test case to try and reduce computing time by simplifying the fidelity
of the model. The simplifications investigated include changing the convergence level of
the adjoint solver, reducing the grid size and modifying the physical model of the adjoint
solver independently or in the entire optimisation process. A feasible optimiser and the use
of a penalty function are also tested. The variable-fidelity method proves to be the most ef-
ficient formulation so it is employed for the three-dimensional optimisations in addition to
parallelisation of the flow and adjoint solvers with OpenMP. A three-dimensional Navier-
Stokes optimisation of the ONERA M6 wing is presented. After describing the concept
of Blended Wing-Body and the studies carried out on this aircraft, several aerodynamic
optimisations are performed on this geometry with the capability developed in this thesis.
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Xie, Shuiwei Engineering & Information Technology Australian Defence Force Academy UNSW. "Dynamic Contribution-based Decomposition Method and Hybrid Genetic Algorithm for Multidisciplinary Engineering Optimisation." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/43899.
Full textAbstract:
A novel decomposition method that is referred to as Contribution-based Decomposition is presented in this thesis. The influence of variables on the values of objective functions and/ or constraints is interpreted as their contributions. Based on contributions of variables, a design problem is decomposed into a number of sub-problems so that variables have similar relative contributions within each sub-problem. The similarity in contributions among variables will lead to an even pressure on the variables when they are driven to better solutions during an optimisation process and, as a result, better solutions can be obtained. Due to nonlinearity of objectives and/ or constrains, variables??? contributions may vary significantly during the solution process. To cope with such variations, a Dynamic Contribution-based Decomposition (DCD) is proposed. By employing DCD, decomposition of system problems is carried out not only at the beginning, but also during the optimisation process, and as a result, the decomposition will always be consistent with the contributions of the current solutions. Further more, a random decomposition is also developed and presented to work in conjunction with the Dynamic Contribution-based Decomposition to introduce re-decompositions when it is required, aiming to increase the global exploring ability. To solve multidisciplinary engineering optimisation problems more efficiently, new solvers are also developed. These include a mixed discrete variable Pattern Search (MDVPS) algorithm and a mixed discrete variable Genetic Algorithm (MDVGA). Inside the MDVGA, new techniques including a flexible floating-point encoding method, a non-dominance ranking strategy and heuristic crossover and mutation operators are also developed to avoid premature convergence and enhance the GA???s search ability. Both MDVPS and MDVGA are able to handle optimisation problems having mixed discrete variables. The former algorithm is more capable of local searching and the latter has better global search ability. A hybrid solver is proposed, which incorporates the MDVPS and the MDVGA and takes advantage of both their strengths. Lastly, a Dynamic Sub-space Optimisation (DSO) method is developed by employing the proposed Dynamic Contribution-based Decomposition methods and the hybrid solver. By employing DSO, decomposed sub-problems can be solved without explicit coordination. To demonstrate the capability of the proposed methods and algorithms, a range of test problems have been exercised and the results are documented. Collectively the results show significant improvements over other published popular approaches.
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Agyei, Eugene Osei. "Groundwater modeling and management using the finite element method and evolutionary optimisation techniques /." Title page, synopsis and contents only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09pha284.pdf.
Full text
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Gibson, Myles. "The Heat Treatment of Nickel Titanium - An investigation Using Taguchi's Method of Optimisation." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-28769.
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Bekker, James. "Applying the cross-entropy method in multi-objective optimisation of dynamic stochastic systems." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71717.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: A difficult subclass of engineering optimisation problems is the class
of optimisation problems which are dynamic and stochastic. These
problems are often of a non-closed form and thus studied by means of
computer simulation. Simulation production runs of these problems
can be time-consuming due to the computational burden implied by
statistical inference principles. In multi-objective optimisation of engineering
problems, large decision spaces and large objective spaces
prevail, since two or more objectives are simultaneously optimised and
many problems are also of a combinatorial nature. The computational
burden associated with solving such problems is even larger than for
most single-objective optimisation problems, and hence an e cient
algorithm that searches the vast decision space is required. Many
such algorithms are currently available, with researchers constantly
improving these or developing more e cient algorithms. In this context,
the term \e cient" means to provide near-optimised results with
minimal evaluations of objective function values. Thus far research has
often focused on solving speci c benchmark problems, or on adapting
algorithms to solve speci c engineering problems.
In this research, a multi-objective optimisation algorithm, based on the
cross-entropy method for single-objective optimisation, is developed
and assessed. The aim with this algorithm is to reduce the number
of objective function evaluations, particularly when time-dependent
(dynamic), stochastic processes, as found in Industrial Engineering,
are studied. A brief overview of scholarly work in the eld of multiobjective
optimisation is presented, followed by a theoretical discussion
of the cross-entropy method. The new algorithm is developed, based
on this information, and assessed considering continuous, deterministic
problems, as well as discrete, stochastic problems. The latter include a
classical single-commodity inventory problem, the well-known buffer allocation problem, and a newly designed, laboratory-sized recon gurable
manufacturing system. Near multi-objective optimisation of two
practical problems were also performed using the proposed algorithm.
In the rst case, some design parameters of a polymer extrusion unit are
estimated using the algorithm. The management of carbon monoxide
gas utilisation at an ilmenite smelter is complex with many decision
variables, and the application of the algorithm in that environment is
presented as a second case.
Quality indicator values are estimated for thirty-four test problem
instances of multi-objective optimisation problems in order to quantify
the quality performance of the algorithm, and it is also compared to a
commercial algorithm.
The algorithm is intended to interface with dynamic, stochastic simulation
models of real-world problems. It is typically implemented in a
programming language while the simulation model is developed in a
dedicated, commercial software package.
The proposed algorithm is simple to implement and proved to be
efficient on test problems.<br>AFRIKAANSE OPSOMMING: 'n Moeilike deelklas van optimeringsprobleme in die ingenieurswese
is optimeringsprobleme van 'n dinamiese en stogastiese aard. Sulke
probleme is dikwels nie-geslote en word gevolglik met behulp van rekenaarsimulasie
bestudeer. Die beginsels van statistiese steekproefneming
veroorsaak dat produksielopies van hierdie probleme tydrowend is weens
die rekenlas wat genoodsaak word. Groot besluitnemingruimtes en
doelwitruimtes bestaan in meerdoelige optimering van ingenieursprobleme,
waar twee of meer doelwitte gelyktydig geoptimeer word, terwyl
baie probleme ook 'n kombinatoriese aard het. Die rekenlas wat met
die oplos van sulke probleme gepaard gaan, is selfs groter as vir die
meeste enkeldoelwit optimeringsprobleme, en 'n doeltre ende algoritme
wat die meesal uitgebreide besluitnemingsruimte verken, is gevolglik
nodig. Daar bestaan tans verskeie sulke algoritmes, terwyl navorsers
steeds poog om hierdie algoritmes te verbeter of meer doeltre ende
algoritmes te ontwikkel. In hierdie konteks beteken \doeltre end" dat
naby-optimale oplossings verskaf word deur die minimum evaluering
van doelwitfunksiewaardes. Navorsing fokus dikwels op oplossing van
standaard toetsprobleme, of aanpassing van algoritmes om 'n spesi eke
ingenieursprobleem op te los.
In hierdie navorsing word 'n meerdoelige optimeringsalgoritme gebaseer
op die kruis-entropie-metode vir enkeldoelwit optimering ontwikkel
en geassesseer. Die mikpunt met hierdie algoritme is om die aantal
evaluerings van doelwitfunksiewaardes te verminder, spesi ek wanneer
tydafhanklike (dinamiese), stogastiese prosesse soos wat dikwels in die
Bedryfsingenieurswese te egekom word, bestudeer word. 'n Bondige
oorsig van navorsing in die veld van meerdoelige optimering word gegee,
gevolg deur 'n teoretiese bespreking van die kruis-entropiemetode. Die
nuwe algoritme se ontwikkeling is hierop gebaseer, en dit word geassesseer
deur kontinue, deterministiese probleme sowel as diskrete, stogastiese probleme benaderd daarmee op te los. Laasgenoemde sluit
in 'n klassieke enkelitem voorraadprobleem, die bekende buffer-toedelingsprobleem,
en 'n nuut-ontwerpte, laboratorium-skaal herkon gureerbare
vervaardigingstelsel. Meerdoelige optimering van twee praktiese
probleme is met die algoritme uitgevoer. In die eerste geval word sekere
ontwerpparameters van 'n polimeer-uittrekeenheid met behulp van die
algoritme beraam. Die bestuur van koolstofmonoksiedbenutting in 'n
ilmeniet-smelter is kompleks met verskeie besluitnemingveranderlikes,
en die toepassing van die algoritme in daardie omgewing word as 'n
tweede geval aangebied.
Verskeie gehalte-aanwyserwaardes word beraam vir vier-en-dertig toetsgevalle
van meerdoelige optimeringsprobleme om die gehalte-prestasie
van die algoritme te kwanti seer, en dit word ook vergelyk met 'n
kommersi ele algoritme.
Die algoritme is veronderstel om te skakel met dinamiese, stogastiese
simulasiemodelle van regtew^ereldprobleme. Die algoritme sal tipies in
'n programmeertaal ge mplementeer word terwyl die simulasiemodel
in doelmatige, kommersi ele programmatuur ontwikkel sal word. Die
voorgestelde algoritme is maklik om te implementeer en dit het doeltre
end gewerk op toetsprobleme.
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Ghurbal, Ehsan. "Un-weighted multi-criteria mesh and structural optimisation method with finite element analysis." Thesis, University of Huddersfield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273718.
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Bouhaya, Lina. "Optimisation structurelle des gridshells." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00583409.
Full textAbstract:
Le terme gridshell désigne une coque discrète qui est obtenue par déformation élastique d'une grille bidirectionnelle continue plane sans rigidité en cisaillement puis rigidifiée par une troisième direction de barres. Ainsi défini, un gridshell a un potentiel structural intéressant et peut répondre à des exigences architecturales complexes. La recherche de forme de ces structures a été menée à travers l'histoire principalement par deux méthodes, la méthode du filet inversé et la relaxation dynamique. Ces deux méthodes permettent d'obtenir une forme approchée de celle proposée par l'architecte, dérivant d'une grille à plat et de conditions aux limites partiellement ou complètement imposées. Dans le cadre de cette thèse, nous nous sommes intéressés à générer un gridshell sur une surface à forme et contours imposés. Un outil numérique se basant sur la méthode du compas a été développé. Il permet de mailler un réseau de Tchebychev sur une surface connaissant son équation cartésienne. Un autre outil permettant le maillage se basant sur un calcul en éléments finis explicite a été mis en œuvre. La particularité de cette technique est de pouvoir tenir en compte des propriétés mécaniques de la structure et de simuler le comportement du gridshell. Des applications des deux méthodes sur des formes architecturalement intéressantes ont permis de voir les limitations de la possibilité de mailler une forme avec un réseau de Tchebychev. La méthode du compas a ensuite été couplée à des algorithmes métaheuristiques types génétiques. L'algorithme résultant permet d'optimiser un gridshell en minimisant la courbure dans les barres et donc les contraintes dans la structure introduites lors de la mise en forme. Il a été mis en œuvre et testé pour plusieurs surfaces