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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.
11

Konstruktionsoptimierung mittels parametrischer FE-Simulation am Beispiel eines Übertragungselements in Klauenkupplungen / Design optimization of a transmission element in a jaw coupling using parametric FE-simulation

Ballmann, Markus 01 July 2015 (has links) (PDF)
Im Vortrag wird das Vorgehen zur Konstruktionsoptimierung mittels parametrischer FE-Simulation beschrieben. Die einzelnen Schritte werden dargestellt und am Beispiel eines Übertragungselements für Klauenkupplungen erläutert. Zunächst wird der Optimierungsgegenstand vorgestellt und die Festlegung der Entwurfsvariablen und Zielfunktionen beschrieben. Im Anschluss werden die Erstellung des FE-Modells und die Durchführung der Optimierungsrechnung schrittweise erläutert. Abschließend folgen ein Vergleich verschiedener Optimierungsmethoden und die Zusammenfassung. Als Software wurden ANSYS und Autodesk Inventor verwendet.
12

[en] OPTIMIZATION OF MICROWAVE ROUTES BY THE DUAL DECOMPOSITION / [pt] OTIMIZAÇÃO DE ROTAS DE MICROONDAS POR DUALIZAÇÃO

NELSON HENRIQUE DHEIN 23 January 2007 (has links)
[pt] O assunto deste trabalho é o dimensionamento otimizado de rotas de microondas, utilizando-se técnicas de decomposição. O modelo matemático utilizado é baseado nos critérios de projetos de sistemas de microondas, adotado no Brasil, pela empresa Brasileira de Telecomunicações S.A., EMBRATEL, e é constituído por uma função objetivo não linear, várias restrições de desigualdades, sendo algumas não convexas. A solução do problema foi obtida usando-se o método de decomposição dual, e o algoritmo da aproximação da tangente. Alguns exemplos simulados e outros reais, foram resolvidos, com auxilio de um computador IBM 4341. / [en] The purpose of this work is to present a method for optimization of microwave routes in radio relay links, using decompositions techniques. The mathematical model is based on microwaves systems design criteria adopted in Brasil by the Empresa Brasileira de Telecomunicações S.A., EMBRATEL, and consists of a nonlinear objective function, several inequalities constraints, some of them nonconvex. The problem was solved by the dual decomposition techniques through the tangent approximation method. Some simulated exeamples and others real ones, were solved with the aid of an IBM 4341 computer.
13

A Performance Evaluation of RPL in Contiki / A Performance Evaluation of RPL in Contiki

Ali, Hazrat January 2012 (has links)
A Wireless Sensor Network is formed of several small devices encompassing the capability of sensing a physical characteristic and sending it hop by hop to a central node via low power and short range transceivers. The Sensor network lifetime strongly depends on the routing protocol in use. Routing protocol is responsible for forwarding the traffic and making routing decisions. If the routing decisions made are not intelligent, more re-transmissions will occur across the network which consumes limited resources of the wireless sensor network like energy, bandwidth and processing. Therefore a careful and extensive performance analysis is needed for the routing protocols in use by any wireless sensor network. In this study we investigate Objective Functions and the most influential parameters on Routing Protocol for Low power and Lossy Network (RPL) performance in Contiki (WSN OS) and then evaluate RPL performance in terms of Energy, Latency, Packet Delivery Ratio, Control overhead, and Convergence Time for the network. We have carried out extensive simulations yielding a detailed analysis of different RPL parameters with respect to the five performance metrics. The study provides an insight into the different RPL settings suitable for different application areas. Experimental results show ETX is a better objective, and that ContikiRPL provides very efficient network Convergence (14s), Control traffic overhead (1300 packets), Energy consumption (1.5% radio on time), Latency (0.5s), and Packet Delivery Ratio (98%) in our sample RPL simulation of one hour with 80 nodes, after careful configuration of DIO interval minimum/doublings, Radio duty cycling, and Frequency of application messages. / En Wireless Sensor Network består av flera små enheter som omfattar de förmåga avkänning en fysisk egenskap och skicka den hoppa med hopp till en centrala noden via låg effekt och kort sändtagare räckvidd. Det sensornätverk livslängd är starkt beroende av routingprotokoll som används. Routingprotokoll är ansvarar för att vidarebefordra trafik och göra routing beslut. Om dirigeringen beslut som fattas inte är intelligenta, kommer fler återsändningar förekomma på nätverk som förbrukar begränsade resurser trådlösa sensornätverk som energi, bandbredd och bearbetning. Därför är en noggrann och omfattande prestanda analys behövs för routingprotokoll används av alla trådlösa sensornätverk. I denna studie undersöker vi mål Funktioner och den mest inflytelserika parametrar Routing Protokoll för låg effekt och Förstörande nätverk (RPL) prestanda i Contiki (WSN OS) och sedan utvärdera RPL prestanda vad gäller av energi, fördröjning, Packet Delivery Ratio, kontroll overhead och konvergens Dags för nätverket. Vi har genomfört omfattande simuleringar som ger en detaljerad analys av olika RPL parametrar med avseende på de fem resultatstatistik. Studien ger en inblick i de olika RPL inställningar som är lämpliga för olika användningsområden. Experimentella resultat visar ETX är en bättre målsättning och att ContikiRPL ger mycket effektivt nätverk Konvergens (14s), Control trafik overhead (1300 paket), Energiförbrukning (1,5% radio i tid), Latens (0,5 s), och paket Leverans Ratio (98%) i vårt urval RPL simulering av en timme med 80 noder, efter noggrann konfiguration av DIO intervall minimum / dubbleringar, Radio plikt cykling, och frekvensen av ansökan meddelanden. / tocomputerscientist@gmail.com Mob: 0046760721720
14

Utilisation de méta-modèles multi-fidélité pour l'optimisation de la production des réservoirs / Use of multi-fidelity meta-models for optimizing reservoir production

Thenon, Arthur 20 March 2017 (has links)
Les simulations d'écoulement sur des modèles représentatifs d'un gisement pétrolier sont généralement coûteuses en temps de calcul. Une pratique courante en ingénierie de réservoir consiste à remplacer ces simulations par une approximation mathématique, un méta-modèle. La méta-modélisation peut fortement réduire le nombre de simulations nécessaires à l'analyse de sensibilité, le calibrage du modèle, l'estimation de la production, puis son optimisation. Cette thèse porte sur l'étude de méta-modèles utilisant des simulations réalisées à différents niveaux de précision, par exemple pour des modèles de réservoir avec des maillages de résolutions différentes. L'objectif est d'accélérer la construction d'un méta-modèle prédictif en combinant des simulations coûteuses avec des simulations rapides mais moins précises. Ces méta-modèles multi-fidélité, basés sur le co-krigeage, sont comparés au krigeage pour l'approximation de sorties de la simulation d'écoulement. Une analyse en composantes principales peut être considérée afin de réduire le nombre de modèles de krigeage pour la méta-modélisation de réponses dynamiques et de cartes de propriétés. Cette méthode peut aussi être utilisée pour améliorer la méta-modélisation de la fonction objectif dans le cadre du calage d'historique. Des algorithmes de planification séquentielle d'expériences sont finalement proposés pour accélérer la méta-modélisation et tirer profit d'une approche multi-fidélité. Les différentes méthodes introduites sont testées sur deux cas synthétiques inspirés des benchmarks PUNQ-S3 et Brugge. / Performing flow simulations on numerical models representative of oil deposits is usually a time consuming task in reservoir engineering. The substitution of a meta-model, a mathematical approximation, for the flow simulator is thus a common practice to reduce the number of calls to the flow simulator. It permits to consider applications such as sensitivity analysis, history-matching, production estimation and optimization. This thesis is about the study of meta-models able to integrate simulations performed at different levels of accuracy, for instance on reservoir models with various grid resolutions. The goal is to speed up the building of a predictive meta-model by balancing few expensive but accurate simulations, with numerous cheap but approximated ones. Multi-fidelity meta-models, based on co-kriging, are thus compared to kriging meta-models for approximating different flow simulation outputs. To deal with vectorial outputs without building a meta-model for each component of the vector, the outputs can be split on a reduced basis using principal component analysis. Only a few meta-models are then needed to approximate the main coefficients in the new basis. An extension of this approach to the multi-fidelity context is proposed. In addition, it can provide an efficient meta-modelling of the objective function when used to approximate each production response involved in the objective function definition. The proposed methods are tested on two synthetic cases derived from the PUNQ-S3 and Brugge benchmark cases. Finally, sequential design algorithms are introduced to speed-up the meta-modeling process and exploit the multi-fidelity approach.
15

The effect of increasing train lengths on the fatigue lifespan of a bridge.

Monballiu, Franck, Schils, Wouter January 2016 (has links)
More and more pressure is exerted on railway infrastructure due to an increasing transportation demand and population density. Instead of expanding the net, a possible solution could lie in the enlargement of the capacity by operating longer trains rather than more short ones. However, close attention has to be paid to the behaviour and the lifetime of the infrastructure under these changed loads. In special bridges are delicate aspects in this matter. In the current thesis the simply supported Banafjäl bridge located on the Bothnia Line in the North of Sweden is studied more in detail with regards to this aspect. It is a high-speed composite railway bridge with a span of 42 m. A detailed 3D finite element (FE) model is made available. However in order to make reliable predictions about the behaviour under increasing train length loads, it had to be further improved. Different methods of calibrating measured response data to an existing FE model, finite element model updating (FEMU), are available and a detailed overview is given at the beginning of this thesis. Next a sensitivity analysis was performed to select the material parameters which are most influential for the result and will be updated. In the following, FEMU is carried out by means of two iterative updating methods, genetic and gradient-based optimization, after which also a combination of these two is implemented. Two objective functions are chosen and it is shown that all methods converge to a global optimal solution. After adjusting the initial model with the updated parameter values, a fatigue analysis on this updated model is carried out for high-speed trains of multiple lengthsby means of the Palmgren-Miner rule. The fatigue is found to increase with increasing train length and in particular when the speed approaches resonance speed. By extension an operating chart is created to indicate the maximum amount of train passages per day in function of speed and train length for a type 4 fatigue train. Furthermore, damping has been shown to have a positive effect on the fatigue, the larger this effect for shorter trains. The static behaviour has been proven not to be a problem and so will solely the weight of trains induce little to no fatigue problems in this particular bridge.
16

Optimisation topologique des transferts thermiques et massiques dans un canal asymétriquement chauffé / Topology optimization of heat and mass transfer in an asymmetrically-heated vertical channel

Barbary, Delphine 13 December 2017 (has links)
Les présents travaux de thèse envisagent une nouvelle technique d'optimisation au sens topologique dans des géométries de type canal vertical où se réalisent des transferts de chaleur conducto-convectifs en régime laminaire. Les équations qui décrivent l'écoulement du fluide et le transfert d'énergie sont discrétisées par la méthode des volumes finis. La première partie du mémoire présente une nouvelle technique d'optimisation et sa validation sur des cas d'études de la littérature (single pipe, bend pipe). Cette technique consiste à définir des fonctions d'interpolation de type sigmoïde et permet d'obtenir une amélioration de l'interface fluide-solide au cours du processus d'optimisation. La seconde partie met en évidence les phénomènes physiques dans le canal asymétriquement chauffé, notamment l'influence de la stratification thermique extérieure et du rayonnement de surface sur les quantités aérauliques et thermiques. Enfin, une nouvelle expression de la puissance mécanique pour contrôler les pertes de charge (malgré l'ajout de matière) dans le canal vertical combinée avec une nouvelle expression de la puissance thermique sont étudiées. Le problème ainsi posé est résolu pour un écoulement en convection naturelle. Pour les cas considérés, chacune des fonctions coût est optimisée sans détériorer l'autre. Nous comparons aussi les valeurs des puissances obtenues par notre algorithme avec celles couramment utilisées dans la littérature et montrons que ces nouvelles fonctionnelles sont performantes. / This thesis deals with topology optimization of mass and heat transfer in the framework of the vertical asymetrically-heated channel. The incompressible Navier-Stokes equations coupled to the convection-diffusion equation through the Boussinesq approximation are employed and are solved with the finite volume method. We first propose a new interpolation technique for heat transfer optimization and validate it on referenced cases such as the "single pipe" and the "bend pipe". This new technique consists in the introduction of sigmoid interpolation functions to obain a better definition of the interface between fluid and solid domains, during the optimization process. We study then physical phenomenon in the asymmetrically heated channel , in particular the influence of thermal stratification outside the channel and surface radiation on thermal and dynamic quantities. We thus highlight the size variation of reversed flow at the exit of the channel and the plug-effect linked on external thermal stratification. Finally, we propose a new expression of mechanical power in order to control charges losses (despite addition of material) in the vertical channel combined with the expression of thermal power. In all considered cases, our algorithm succeeds to enhance one of the phenomenon modelled by our new cost functions without deteriorating the other one. We also compare the values of standard cost functions from the litterature over iteration of our optimization algorithm and show that our new cost functions are effective.
17

Operativ transportplanering hos Gerdas Bröd / Operational transport planning at Gerdas Bröd

Carlén, Jesper, Lundberg, Hans January 2018 (has links)
Med fokus på distribution behandlar denna rapport planerandet och utförandet av ruttplaneringen hos fallföretaget Gerdas Bröd i Grästorp AB. Utifrån antagandet att resurserna är begränsade hos Gerdas så presenteras ruttförslag utifrån målfunktionerna fyllnadsgrad och minsta möjliga körsträcka. Syftet har aldrig varit att presentera några optimala rutter utan snarare visa hur man på ett rimligt, logiskt och metodiskt sätt kan arbeta med dessa frågor utan att ta särskilt stora resurser i anspråk. Genom datainsamling bestående av intervjuer, observationer och samtal med flera rollinnehavare inom verksamheten har denna fallstudie tagit form. Företagets nuläge och önskan om åtgärder kunde tack vare denna datainsamling identifieras och lägga grunden för vidare analys och rekommendationer. De begränsade resurserna kan i vissa avseenden förklara avsaknaden av planering och styrning inom verksamheten. Det har lett till att chaufförerna i stor omfattning får sköta sig själva i utförandet av inlastning och leverans. Som ett ansikte utåt för verksamheten sköter förarna i praktiken all distribution samtidigt som de hanterar en stor andel av den kontinuerliga kundkontakten. Utförandet av ruttförslag är därför i stor utsträckning till för att stötta dem i deras dagliga arbete. Efter analys och jämförelse mellan teori och empiri mynnar detta ut i en rad olika rekommenderade åtgärder för fallföretaget. Med den kraftigt varierande efterfrågan behöver man vara flexibla internt för att kunna parera mot eventuell över- och underbemanning. Tillgång till fler bilar och förare är därför en av flera åtgärder som rekommenderas. / With focus on distribution, this rapport touches the planning and excecution of routes at the business case Gerdas Bröd in Grästorp AB. From the assumption that the resources are limited at Gerdas this rapport will present route suggestions from the objective functions load factor and minimum mileage. The purpose has never been to present any optimized routes but rather show how to work with these things in a reasonable, logical and methodically way without claiming any remarkable amount of resources. Trough data collection of interviews, observations and dialogs with several employees with different roles within Gerdas, this rapport has developed into this final version. The present of the company and their desire of actions could, thanks to the data collection, be identified and be the foundation of further analysis and recommendation. The limited resources can in some ways explain the lack of planning and management within the distribution of the company. This has led to the drivers being on their own when it comes to the execution of the loading and transporting. As the public face of the company the drivers handles almost everything when it comes to distribution while they manage to handle a big majority of the continuous customer contact. The makings of the route suggestions are primarily to support them in their daily work. After analysing and comparing theory with the company empiricism this will end in a line of recommended actions for the business case. With the greatly varying demand you must be internal flexible to be able to respond to any under- or over staffing. The access to more trucks and drivers is one of several recommended actions.
18

Mitigação de incertezas atraves da integração com ajuste de historico de produção / Uncertainty mitigation through the integration with production history matching

Becerra, Gustavo Gabriel 12 July 2007 (has links)
Orientadores: Denis Jose Schiozer, Celio Maschio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias / Made available in DSpace on 2018-08-12T07:35:35Z (GMT). No. of bitstreams: 1 Becerra_GustavoGabriel_M.pdf: 16760750 bytes, checksum: 0609c24d13d46b9121f71356ce9d42a1 (MD5) Previous issue date: 2007 / Resumo: A escassez de informações de qualidade introduz risco ao processo de previsão da produção de petróleo tornando imprescindível o ajuste de histórico de produção, que é a calibração do modelo a partir da resposta produtiva registrada. O ajuste é um problema inverso, em que diferentes combinações dos valores dos parâmetros do reservatório podem conduzir a respostas aceitáveis, especialmente quando o grau de incerteza desses parâmetros é elevado. A integração do ajuste de histórico com a análise probabilística dos cenários representativos conduz à obtenção de uma metodologia para detecção dos modelos calibrados dentro de uma faixa de aceitaçãodefinida. O tratamento de atributos interdependentes de influência global e local e o avanço por etapas são necessários. Desta forma, o objetivo deste trabalho é apresentar uma metodologia que integra a análise de incertezas com o ajuste de histórico em modelos de reservatórios complexos. Este procedimento auxilia a detectar os atributos incertos críticos e sua possível variação com o intuito de estimar a faixa representativa das reservas a desenvolver. Não é alvo obter o melhor ajuste determinístico, mas refletir como o histórico possibilita uma mitigação das incertezas. Assim, a meta é usar modelos mais complexos e aprimorar a metodologia iniciada por Moura Filho (2006), desenvolvida para um modelo teórico simples. São utilizados dois casos de estudo de complexidade similar. Um deles referente ao reservatório do Campo de Namorado, utilizado para verificar e validar, em nível global, a aplicação da metodologia. Na etapa de aplicação, é usado um modelo sintético construído a partir de dados de afloramentos reais no Brasil e compreendendo informações de campos análogos com sistemas turbidíticos depositados em águas profundas. Os métodos aplicados, mediante a redefinição das probabilidades associadas e níveis dos atributos incertos, permitem: (1) reduzir a faixa de ajustes possíveis e obter modelos mais confiáveis; (2) identificar e condicionar à incerteza presente em função dos dados registrados; (3) diminuir os intervalos de incerteza dos parâmetros críticos identificados; (4) demarcar os limites seguros do desempenho futuro do reservatório. A conseqüência é um aumento da confiança no uso da simulação como ferramenta auxiliar do processo decisório. Além disso, procura-se fornecer à equipe multidisciplinar uma metodologia para reduzir o tempo empregado no gerenciamento de múltiplos atributos incertos na etapa de ajuste do modelo. / Abstract: The lack of reliable data or with high degree of uncertainty yields risk to the process of production prediction making the history matching, the model calibration from the registered field production indispensable. History matching is an inverse problem and, in general, different combinations of reservoir attributes can lead acceptable solutions, especially whit high degree of uncertainty of these attributes. The integration of history matching with a probabilistic analysis of representative models yields a way to detect matched models inside an acceptance interval, providing more efficient framework for predictions. It is necessary to consider dependences between global and local attributes. The scope of this work is to present a methodology that integrates the uncertainty analysis with the history matching process in complex models. This procedure helps to detect critical subsurface attributes and their possible variation, in order to estimate a representative range of the additional reserves to be developed. . It is not an objective to obtain the best deterministic model, but to mitigate uncertainties by using observed data. The objective is to improve the methodology initiated by Moura Filho (2006), applied to a simple model. The methodology presented in this work is applied in two study cases with similar complexity. Firstly, the methodology is verified and validated, on global scale, in Namorado Field. Then, at the application stage, it is chosen a synthetic reservoir model made from real outcrop data of Brazil and involving information from analog fields with turbiditic systems deposited in deep waters. The methodology allows the redefinition of the probability and levels of the dynamic and static attributes in order: (1) to reduce the group of possible history matching obtaining more realistic models; (2) to identify the existent uncertainty as a function of observed data; (3) to decrease the uncertainty range of critical reservoir parameters; (4) to increase the confidence in production forecast. One contribution of this work is to present a quantitative approach to increase the reliability on the use of reservoir simulation as an auxiliary tool in decision processes. Another purpose of this work is to provide a procedure to reduce the consumed time to handle multiples uncertainty attributes during the history matching. / Mestrado / Reservatórios e Gestão / Mestre em Ciências e Engenharia de Petróleo
19

An Equitable Framework for Antiretroviral Therapy and COVID-19 Vaccine Allocation Strategies in Botswana

Park, Yhesaem 12 August 2021 (has links)
The HIV/AIDS epidemic and the COVID-19 pandemic have ruined many people's lives. Antiretroviral therapy (ART) has controlled the HIV/AIDS epidemic and COVID-19 vaccine is expected to ease confusion caused by the pandemic. However, the supply of health-resource falls far short of the demand in resource-constrained countries; thus, decision-making about resource allocation should be discussed. Botswana, as a resource-constrained country with a high prevalence of HIV, needs to construct its own framework for ART allocation. We propose an equitable framework for ART and COVID-19 vaccine allocation in Botswana based upon the egalitarian principle, which provides each individual has an equal chance of receiving them. We use a spatial mathematical model of treatment accessibility with an equity objective function, and sequential quadratic programming is used to address the nonlinear programming model. Considering Botswana's current health infrastructure, our strategy brings the most equal health outcomes. However, the disparity of accessibility still exists between rural and urban areas even from our equitable strategy. We present proposals that can increase the accessibility of rural areas using sensitivity analysis. Our work can be applied to different contexts, especially in sub-Saharan Africa.
20

Využití optimalizačních algoritmů při návrhování konstrukcí / Using Optimization's Algorithms by Designing of Structures

Fedorik, Filip Unknown Date (has links)
The application of optimization algorithms in the design of many economical and industrial problems currently represents a significant assignment. The development of high-powered computers allows an application of difficult mathematical techniques and physical phenomena to simulate real problems with sufficient accuracy. The optimization techniques used in engineering designs are mostly represented by modified mathematical programming methods with extension of their usability. The aim of the presented thesis "Using Optimization´s Algorithms by Designing of Structures" is to analyze the applicability of optimization procedures which are available in the widely used computing system ANSYS in civil and mechanical engineering practice. The numerical analyses were performed within the frame of multi-extreme, one to three dimensional optimization problems, multi-dimensional problems expressed by minimizing the weight of a truss beam and efficient design of air gap location in wooden studs from the point of view of thermal features of the structure. The analyzed optimization processes are in plurality verified with accurate manual computing and graphical solutions and the accent is put on optimization methods´ possibilities to improve robustness, efficiency and accuracy of the optimization algorithms in civil engineering problems´ designs. The optimization methods represent a suitable approach to improve the efficient design of a wide range of civil and mechanical engineering structures and elements. By combination of their advantages and FEM/FEA method it is possible to achieve very good results, although robustness of the solutions is not guaranteed. The robustness and accuracy of the procedure could be increased by competent exploration of design space and suitable selections of optimization methods´ features.

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