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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A generic approach to behaviour-driven biochemical model construction

Wu, Zujian January 2012 (has links)
Modelling of biochemical systems has received considerable attention over the last decade from bioengineering, biochemistry, computer science, and mathematics. This thesis investigates the applications of computational techniques to computational systems biology, for the construction of biochemical models in terms of topology and kinetic rates. Due to the complexity of biochemical systems, it is natural to construct models representing the biochemical systems incrementally in a piecewise manner. Syntax and semantics of two patterns are defined for the instantiation of components which are extendable, reusable and fundamental building blocks for models composition. We propose and implement a set of genetic operators and composition rules to tackle issues of piecewise composing models from scratch. Quantitative Petri nets are evolved by the genetic operators, and evolutionary process of modelling are guided by the composition rules. Metaheuristic algorithms are widely applied in BioModel Engineering to support intelligent and heuristic analysis of biochemical systems in terms of structure and kinetic rates. We illustrate parameters of biochemical models based on Biochemical Systems Theory, and then the topology and kinetic rates of the models are manipulated by employing evolution strategy and simulated annealing respectively. A new hybrid modelling framework is proposed and implemented for the models construction. Two heuristic algorithms are performed on two embedded layers in the hybrid framework: an outer layer for topology mutation and an inner layer for rates optimization. Moreover, variants of the hybrid piecewise modelling framework are investigated. Regarding flexibility of these variants, various combinations of evolutionary operators, evaluation criteria and design principles can be taken into account. We examine performance of five sets of the variants on specific aspects of modelling. The comparison of variants is not to explicitly show that one variant clearly outperforms the others, but it provides an indication of considering important features for various aspects of the modelling. Because of the very heavy computational demands, the process of modelling is paralleled by employing a grid environment, GridGain. Application of the GridGain and heuristic algorithms to analyze biological processes can support modelling of biochemical systems in a computational manner, which can also benefit mathematical modelling in computer science and bioengineering. We apply our proposed modelling framework to model biochemical systems in a hybrid piecewise manner. Modelling variants of the framework are comparatively studied on specific aims of modelling. Simulation results show that our modelling framework can compose synthetic models exhibiting similar species behaviour, generate models with alternative topologies and obtain general knowledge about key modelling features.
2

Stray loss analysis of AC machines using time-stepped finite elements

Zhan, Yang 06 1900 (has links)
This thesis investigates stray losses in AC machines using the time-stepped finite element technique. Two aspects of this topic are involved in this thesis. The first aspect is to construct a finite element model for AC machine systems and develop an efficient numerical solution for the system equation; as the emphasis of this thesis, the second aspect is use the above model to analyze stray losses in AC machines under a variety of operation, design and manufacturing conditions. The thesis modifies the traditional 2-D finite element technique to account for the variations in electromagnetic field along the machines axis resulting from skewed structures, rotor interbar currents and ventilation ducts. Domain decomposition and parallel computation are incorporated to efficiently give a numerical solution to the system equation. The factors affecting harmonic stray losses in AC machines including pulse width modulation (PWM) supply, interbar resistance and slot shape are investigated using the above efficient analysis tool. Simulations and tests under different load conditions are carried out for an induction motor to investigate the additional harmonic stray loss caused by the PWM supply. For a large synchronous generator, simulations and tests are performed to study the effect of different amortisseur interbar resistances on the slot harmonic contents and the resulting harmonic stray loss in the amorisseur cage. As a factor influential to magnet stray loss in permanent magnet synchronous machines, various slot shape designs are assessed by simulations. An optimization based on an evolutionary strategy is implemented to find the best slot shape design with minimum machine loss. The conclusions in the thesis provide valued information to direct the future design and manufacture of efficient AC machines. / Power Engineering and Power Electronics
3

Stray loss analysis of AC machines using time-stepped finite elements

Zhan, Yang Unknown Date
No description available.
4

Metody optimalizace plánování nákladní přepravy / Optimizations Methods for Freight Transportation

Gabonay, Michal January 2020 (has links)
The following work concerns the study of the evolutionary algorithm, which optimizes freight transport planning. The demand for freight transport is constantly increasing nowadays and with creating, implementing and using proper route planning we are able to significantly reduce transportation costs. However, it is preferably to implement it in companies with large numbers of served customers and with a sufficiently large fleet of vehicles.   The study starts by defining what fright transport planning problem is and by characterizing its existing specifications and variants. My work proceeds to give a background of the possible solutions to the multifaceted aspects of the problem. The specific subproblem I choose to focus on is the Vehicle routing problem with Pickup and Delivery for which I apply the optimization solution. In the main body of my thesis, I will elaborate on the chosen optimization solution which encompasses the genetic algorithm and evolutionary strategy. The aim of the study is to measure the suitability of the algorithms and techniques used, for which reason the final part of my work will deal with the analysis and evaluation of the experiments.
5

[en] AUTOMATIC TRACING OF ENVELOPES IN PLANAR STRUCTURES USING A EVOLUTIONARY ALGORITHM / [pt] TRAÇADO AUTOMÁTICO DE ENVOLTÓRIAS DE ESFORÇOS EM ESTRUTURAS PLANAS UTILIZANDO UM ALGORITMO EVOLUCIONÁRIO

GISELE CRISTINA DA CUNHA HOLTZ 21 December 2005 (has links)
[pt] O objetivo deste trabalho é desenvolver dentro do programa FTOOL uma ferramenta para obtenção de envoltórias de esforços internos devido a cargas móveis. Envoltórias geralmente são obtidas através de interpolação de valores limites de seções pré-selecionadas ao longo da estrutura. Estes valores são obtidos com base no posicionamento da carga móvel em relação às linhas de influência dos esforços internos. A determinação de valores limites de um esforço em uma seção constitui um problema de otimização cujo objetivo é minimizar ou maximizar os valores dos esforços em relação à posição do tremtipo que percorre a estrutura. Porém, não existe uma expressão analítica que defina os valores limites de um esforço em uma seção para um dado trem-tipo, o que impossibilita o uso da maioria dos métodos clássicos de otimização para resolver o problema, porque esses métodos requerem, na maioria das vezes, o uso de pelo menos a primeira derivada da função objetivo em relação às variáveis de projeto. Portanto, este trabalho adotou algoritmos da Estratégia Evolutiva ( EE ) para determinar os valores limites devidos a cargas móveis. Foram feitas duas implementação distintas de Estratégia Evolutiva, conhecidas como EE − + ) 1 ( (lambda) e EE − + ) ( (lambda) (mi) . Além de utilizar algoritmos de EE para resolver o problema de envoltórias, foi desenvolvido um outro processo de solução denominado Força Bruta, que consiste em percorrer com o trem-tipo toda estrutura por passos pré-estabelecidos e calcular os valores dos esforços mínimos e máximos. Para a grande maioria dos casos, os resultados obtidos com a Estratégia Evolutiva foram corretos, porém, em alguns casos mais críticos, o valor exato da envoltória não é encontrado em algumas seções da estrutura, embora encontre um valor muito próximo a ele. Observou-se que os resultados da EE podem ser melhorados quando se enriquece a solução com uma estratégia econômica de posicionamento de cargas concentradas em cima de picos da linha de influência. / [en] The objective of this work is to develop a tool for obtaining envelopes of internal forces due to load-trains in the FTOOL software. Usually, envelopes are obtained through interpolation of limiting values on pre- selected sections along the structure. These values are obtained based on the positioning of the loadtrain in relation to influence lines of internal forces. The determination of limiting values of an effect at a section represents an optimization problem whose objective is to minimize or maximize the values of that effect in relation to the position of a load-train that passes along the structure. However, there is no analytical expression that defines a limiting value of an effect on a section for a specific load-train. Therefore, classical optimization methods cannot be used to solve this problem. Rather, the solution requires a method that does not require derivatives of the objective function. For this reason, this work adopts algorithms of the Evolution Strategy (ES) to achieve the limiting values due to load-trains. Two distinct algorithms of the ES, known as ES − + ) 1 ( (lambda) and ES − + ) ( (lambda) (mi) , were implemented. In addition to the ES algorithms to trace the envelopes, another process of solution called Force Brute was developed. It consists of moving the load-train in pre-determined steps along the structure and calculating minimum e maximum values. In general, the ES method converges to the correct solution. However, there are cases, depending on the complexity of the load-train, that the algorithms do not find the exact limiting value (although usually very close to it). It was observed that the ES results could be complemented and improved with results from an inexpensive solution in which concentrated loads are positioned on peak values of the influence lines.
6

Discriminac¸ ˜ao salarial e diferenc¸as na capacidade produtiva entre grupos no mercado de trabalho

COIMBRA, Leandro Willer Pereira 30 November 2015 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-12T12:19:01Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_LEANDRO WILLER P COIMBRA.pdf: 1061880 bytes, checksum: 11f8b239ae17788ee3e063586ea2e919 (MD5) / Made available in DSpace on 2016-08-12T12:19:01Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_LEANDRO WILLER P COIMBRA.pdf: 1061880 bytes, checksum: 11f8b239ae17788ee3e063586ea2e919 (MD5) Previous issue date: 2015-11-30 / FACEPE / Este trabalho foi dividido em trˆes ensaios que se complementam na mesma tem´atica: a discriminac¸ ˜ao salarial. O objetivo ´e a constatac¸ ˜ao do comportamento discriminat´orio no mercado de trabalho brasileiro e a compreens˜ao das motivac¸ ˜oes e efeitos deste comportamento a partir de uma perspectiva econˆomica. Primeiramente, ´e utilizado o m´etodo de Propensity Score Matching para comparar trabalhadores com mesmos n´ıveis de esforc¸os, ocupac¸ ˜ao social, background familiar e outras vari´aveis de circunstˆancias, de forma a evidenciar a discriminac¸ ˜ao salarial baseada na cor da pele. A an´alise aponta para uma remunerac¸ ˜ao por hora trabalhada cerca de 14% menor para os trabalhadores “n˜ao brancos”. Al´em disso, ´e observado uma tendˆencia “elitista”da discriminac¸ ˜ao. Na segunda parte, ´e proposta a modelagem do mercado de trabalho baseada no Modelo de Search de Dale Mortensen, caracterizado por uma distribuic¸ ˜ao de ofertas de sal´ario cont´ınua. Este modelo ´e modificado de forma a introduzir trabalhadores heterogˆeneos quanto a habilidade produtiva e um grau de assimetria informacional entre os agentes. Observou-se que o n´ıvel de assimetria de informac¸ ˜ao de um mercado n˜ao ´e apenas precursor da discriminac¸ ˜ao mas definidor da magnitude desta. Por fim, foca-se na evoluc¸ ˜ao e sobrevivˆencia do comportamento discriminat´orio. Para isto, utilizou-se de um modelo com equil´ıbrio dinˆamico evolutivo, dividido em dois casos diferentes, de forma a endogeneizar o n´ıvel de assimetria de informac¸ ˜ao e da capacidade produtiva dos trabalhadores. Observou-se que o mercado possui possibilidades diferentes de equil´ıbrio, enquanto no primeiro caso, o percentual de trabalhadores de alta habilidade est´a ligado ao maior interesse das firmas selecionarem, no outro, o elevado percentual de trabalhadores de alta habilidade no mercado indica menor necessidade de selec¸ ˜ao. Na realidade, a diferenc¸a entre os dois casos se resume aos prˆemios e punic¸ ˜oes relativos a detenc¸ ˜ao de informac¸ ˜ao por parte dos trabalhadores de baixa habilidade. / This thesis was divided into three works that complement each other with the same theme: wage discrimination. The objective of this study is investigate the discriminatory behavior in the Brazilian labor market and understand the motivations and effects from an economic perspective. First, it is used the method of Propensity Score Matching to compare workers with the same level of effort, social occupation, family background and others variables of circumstances, it highlights wage discrimination based on skin color. The analysis found a wage per hour worked about 14% lower for workers “non-white”. Moreover, a tendency “elite”discrimination is observed. Next, it is proposed to model the labor market based on the Search Model of Dale Mortensen, characterized by a continuous distribution of wage offers. This model is modified to introduce heterogeneous productive ability and a degree of information asymmetry between agents. It was observed that the asymmetric information level of a market is not only the precursor of discrimination but defining the magnitude. Finally, focuses on the evolution and survival of discriminatory behavior. For this, we used a model with evolutionary dynamic equilibrium, divided into two different cases, in order to endogenize the level of asymmetric information and the productive capacity of workers. It was observed that the market has different possibilities to balance, in the first case, the percentage of high-skill labor is linked to higher interest selecting firms, on the other, the high percentage of high-skill labor market indicates less need for selection. In fact, the difference between the two cases comes down to rewards and punishments for the possession of information on the part of low-skill workers.
7

Optimal High-Speed Design and Rotor Shape Modification of Multiphase Permanent Magnet Assisted Synchronous Reluctance Machines for Stress Reduction.

Tarek, Md Tawhid Bin January 2017 (has links)
No description available.
8

Optimization of Aircraft Tracker Parameters / Optimization of Aircraft Tracker Parameters

Samek, Michal January 2015 (has links)
Diplomová práce se zabývá optimalizací systému pro sledování letadel, využívaného pro řízení letového provozu. Je popsána metodika vyhodnocování přesnosti sledovacího systému a přehled relevantních algoritmů pro sledování objektů. Dále jsou navrženy tři přístupy k řešení problému. První se pokouší identifikovat parametry filtrovacích algoritmů pomocí algoritmu Expectation-Maximisation, implementací metody maximální věrohodnosti. Druhý přístup je založen na prostých odhadech parametrů normálního rozložení z naměřených a referenčních dat. Nakonec je zkoumána možnost řešení pomocí optimalizačního algoritmu Evoluční strategie. Závěrečné vyhodnocení ukazuje, že třetí přístup je pro daný problém nejvhodnější.
9

Kriging-assisted evolution strategy for optimization and application in material parameters identification / Contribution à l’optimisation évolutionnaire assistée par modèle de Krigeage : application à l’identification des paramètres en mécanique

Huang, Changwu 06 April 2017 (has links)
Afin de réduire le coût de calcul pour des problèmes d'optimisation coûteuse, cette thèse a été consacrée à la Stratégie d'Evolution avec Adaptation de Matrice de Covariance assistée par modèle de Krigeage (KA-CMA-ES). Plusieurs algorithmes de KA-CMA-ES ont été développés et étudiés. Une application de ces algorithmes KA-CMA-ES développés est réalisée par l'identification des paramètres matériels avec un modèle constitutif d'endommagement élastoplastique. Les résultats expérimentaux démontrent que les algorithmes KA-CMA-ES développés sont plus efficaces que le CMA-ES standard. Ils justifient autant que le KA-CMA-ES couplé avec ARP-EI est le plus performant par rapport aux autres algorithmes étudiés dans ce travail. Les résultats obtenus par l'algorithme ARP-EI dans l'identification des paramètres matériels montrent que le modèle d'endommagement élastoplastique utilisé est suffisant pour décrire le comportement d'endommage plastique et ductile. Ils prouvent également que la KA-CMA-ES proposée améliore l'efficace de la CMA-ES. Par conséquent, le KA-CMA-ES est plus puissant et efficace que CMA-ES pour des problèmes d'optimisation coûteuse. / In order to reduce the cost of solving expensive optimization problems, this thesis devoted to Kriging-Assisted Covariance Matrix Adaptation Evolution Strategy (KA-CMA-ES). Several algorithms of KA-CMA-ES were developed and a comprehensive investigation on KA-CMA-ES was performed. Then applications of the developed KA-CMA-ES algorithm were carried out in material parameter identification of an elastic-plastic damage constitutive model. The results of experimental studies demonstrated that the developed KA-CMA-ES algorithms generally are more efficient than the standard CMA-ES and that the KA-CMA-ES using ARP-EI has the best performance among all the investigated KA-CMA-ES algorithms in this work. The results of engineering applications of the algorithm ARP-EI in material parameter identification show that the presented elastic-plastic damage model is adequate to describe the plastic and ductile damage behavior and also prove that the proposed KA-CMA-ES algorithm apparently improve the efficiency of the standard CMA-ES. Therefore, the KA-CMA-ES is more powerful and efficient than CMA-ES for expensive optimization problems.
10

以模擬最佳化評量銀行的資產配置

鄭嘉峰 Unknown Date (has links)
過去的文獻中,資產配置的方法不外乎效率前緣、動態資產配置等方式,但是,單獨針對銀行探討的文章並不多見,所以本文的貢獻在於單獨針對銀行的資產配置行為進行研究,希望能利用『演化策略演算法』,進行『模擬最佳化』來解決銀行資產配置的問題。基本上這個方法是由兩個動作結合而成,先是模擬,再來尋求最佳解。所以,資產面我們選擇了現金、債券、股票、不動產四項標的,而負債面則模擬了定存、活存與借入款這三項業務,然後透過重複執行模型的方式來求出最適解。並與單期資產配置方法下的結果作一比較,發現運用演化策略演算法有較佳的結果,此外,在不同的亂數下,仍具有良好的穩健性,可作為一般銀行經理人參考之用。 / We focus on the bank’s asset allocation problem in this thesis. We use simulation optimization to solve the problem by evolution strategy, which is relatively new in the financial field. Simulation optimization consists of two steps: simulate numerous situations and search for the optimal asset portfolios. In the simulation, we set up four assets, including cash, bond, stock, and real estate and three business lines, including demand deposits, time deposits, and borrowings. Then we search for the optimal solution by running the ES algorithm. The results show that simulation optimization generates better results than one-period asset allocation. Furthermore, the evolution strategy method generates similar results using different random numbers.

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