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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 Study on Multi-objective Section Steel Cutting Plan Using Meta-Heuristic Approaches

Su, Ming-Jian 27 July 2009 (has links)
Section Steel usually is a order-oriented production and not easy to resell. The material cost is large percentages of overall production cost. Hence, the key to boost efficient management is to increase the material output rate. In other words, we need to publish a efficient and reasonable cutting plan before production. And the cutting plan can cope with change to meet the market demand. The cutting plan designing is a one-dimensional cutting stock problem, and also is a typical bin packing problem. In this study we examine a combined heuristic approach for this problem. The proposed approach combines two themes of solving method¡Ga neighborhood search algorithm with threshold accepting techniques, and a Branch and Bound method. The performance of the combined heuristic approach was verified by running several benchmarking problems and the results were reported. Experimental results indicate that the proposed solving process can effectively search the feasible region and avoid being trapped in local optimal.
2

Maintenance policies optimization in the Industry 4.0 paradigm

Urbani, Michele 10 December 2021 (has links)
Maintenance management is a relevant issue in modern technical systems due to its financial, safety, and environmental implications. The need to rely on physical assets makes maintenance a necessary evil, which, on the other hand, allows achieving a high quality of end products, or services, and a safety level that is adequate for the regulatory requirements. The advent of the fourth industrial revolution offers meaningful opportunities to improve maintenance management; technologies such as Cyber-Physical Systems, the Internet of Things, and cloud computing enable realizing modern infrastructure to support decisions with advanced analytics. In this thesis, the optimization of maintenance policies is tackled in this renewed technological context. The research methods employed in this thesis include interviewing of subject experts, literature research, and numerical experiments. Mathematical modelling is used to model network effects in complex technical systems, and simulations are used to validate the proposed models and methodologies. The problem of maintenance policies comparison is addressed in one of the publications; using the proposed bi-objective analysis, an effective maintenance policy was identified. Maintenance of complex systems organized in a networked fashion is studied in another project, where maintenance costs and system performances are considered. The proposed model allowed to identify a set of non-dominated (in the Pareto sense) maintenance policies, and an efficient resolution procedure was developed. The possibility to use a digital twin to replicate a Cyber-Physical System for maintenance policies optimization is addressed in another publication. The main hurdles in realizing such a complex infrastructure are analyzed, and managerial implications are presented. Finally, following a qualitative research approach, the opportunities offered by additive manufacturing are identified and presented in a book chapter. The opportunities for both maintenance efficiency gains and new business models are identified and discussed.
3

Heuristické a metaheuristické metody řešení úlohy obchodního cestujícího / Heuristic and metaheuristic methods for travelling salesman problem

Burdová, Jana January 2010 (has links)
Minimal length of a travelling salesman's problem had been studied in this diploma these. Travelling salesman must come trough each place just once and then go back to the starting place. This problem can be illustrated as a problem of graph theory, such that places are the vertices, roads are the edges, distances of roads are the lengths of edges. The optimal travelling salesman's problem tour is the shortest Hamiltionian cycle in the graph. It is a classical NP-complete problem. There is no algorithm that solves this problem in polynomial time. This problem can be solved by using various approximation algorithms, they offer less time consumption and lowest quality than optimization. This diploma these had been dedicated to approximation algorithms, for example: nearest neighbor method, minimal spanning tree method, Christofide's method, 2-opt., genetic algorithm, etc.
4

Metoda tvorby tras přepravní úlohy / Method of generation transport routes

Bartásková, Petra January 2010 (has links)
This thesis is focused on optimizing the routes which are implemented in our country at night. Goods are transporting between designated central cities. It deals with creating cyclic routs, along which the goods should be effectively transported, with the respect of the cost. The instruction how to create these paths represents a heuristic method for generating cyclic paths. The algorithm uses the results provided by model that is based on a search for multiple product chart. The chart contains the minimum number of vehicles that provide transport and individual amount of transported goods. The principle of this heuristic method is to create cyclic paths in such a way to be able to serve all transportation requirements with the lowest number of reloads. This approach leads to the fact that the direct paths are preferred.
5

Optimalizácia investičných rozhodnutí v medzinárodnom prostredí / Optimization of investment decisions in international trade

Gondeková, Tatiana January 2009 (has links)
In this thesis, a portfolio optimization with integer variables which influence optimal assets allocation in domestic as well as in international environment, is studied. At the beginning with basic terms, assets and portfolio background, incentives of portfolio creation, fields of portfolio application and portfolio management is dealt. Following the characteristics of assets and portfolios (expected return, risk, liquidity), which are used by investors to value their properties, are introduced. Next the mean-risk models are derived for the measures of risk - variance, Value at Risk, Conditional Value at Risk and prepared for a practical application. Heuristics implemented in Matlab and standard algorithms of software GAMS are used for solving problems of the portfolio optimization. At the end optimization methods are applied on real financial data and an outputs are compared.
6

O projeto da produção e a programação multi-projetos integrados a um sistema de administração de produção para a construção civil / The production design and the multi-project scheduling integrated with a production management system for civil construction

Santos, Myrian Tizuko Sassaki 14 December 2001 (has links)
O processo de produção, no ambiente da Construção Civil, é abordado segundo certos princípios gerenciais que absorvem conceitos vindo da Engenharia de Produção. Para obter a qualidade na produção, pelo critério competitivo que envolve prazos e confiabilidade de entrega, é fundamental a integração entre o projeto do produto e a produção através do projeto da produção. O processo de planejamento, no contexto do projeto da produção, requer o uso de ferramentas de suporte à tomada de decisão, fazendo da programação uma etapa essencial para o ganho de consistência deste processo decisório. A pesquisa trata da programação de projetos com limitação de recursos, a fim de encontrar uma boa solução para o problema de programação de forma simples e satisfatória. O método utiliza como ferramenta de apoio o software Microsoft Project para manipular os projetos com mais agilidade e flexibilidade, considerando as regras de prioridades que são usadas a depender dos critérios gerenciais adotados pelas empresas. O método é baseado na classe de procedimentos heurísticos: Job Oriented Heuristic Scheduling, já que o grau de prioridade dos projetos orienta o desenvolvimento da programação conjunta, denominada Programação multi-projetos. / The production process in the Civil Construction environment is approached according to some management principles that reinforce concepts from Production Engineering. To obtain Quality in production through the competitive criterion, which comprehends fast delivery time and on-time delivery, it is fundamental the integration between Product Design and production through Production Design. The planning process requires the use of procedures to support the decision-making process concerning global production systems in construction companies. Thus scheduling would be an essential stage for the acquisition of decision consistence. This dissertation deals with the resource-constrained Project Scheduling Problem using a heuristic method based on priority rules. Heuristic procedures are used to obtain a good solution to the problem in a practical and satisfactory way. The method uses Microsoft Project as a supporting tool to deal with the projects with more agility and flexibility. The priority rules are based on management criteria adopted by the companies. The method is based on the category of heuristic procedures known as Job Oriented Heuristic Scheduling, since the project priority degrees orient the steps of the multi-project scheduling.
7

Heuristic methods applied on Weibull curve fitting in wind energy / MÃtodos heurÃsticos aplicados no ajuste de curvas de Weibull em energia eÃlica

Danilo CÃsar Rodrigues Azevedo 08 July 2015 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / The application of heuristics optimization has proven quite effective when compared to traditional optimization methods by differentiation. It is known that in some cases, directly minimizing the functions involved in the process can be complicated or even impossible. This work aims to develop a Weibull curve fitting methodology, using Ant Colony Optimization method and the Particle Swarm Optimization method as far as the hybridization of these. The tipical stochastic characteristic should provide good results for any wind distribution, concentrated or dispersed, which would make it valid to use in coastal conditions, flat or complex terrain or even urban. The result obtained by the heuristic approach of two SONDA wind samples, referring to Petrolina, Pernambuco, Brazil and Sao Martinho da Serra, Rio Grande do Sul, Brazil was compared with eight other known methods and commercially applied: the least squares method, the moment method, empirical method, the maximum likelihood method, the modified maximum likelihood method, energy pattern method, equivalent energy method and the chi-squared method and the goodness of fit will be evaluated by RMSE tests, MAPE, R2, and the deviation in the forecast power density. Heuristic methods have proven competitive, with power forecast error values around 10−14%. / A aplicaÃÃo de mÃtodos heurÃsticos em otimizaÃÃo tem se mostrado bastante eficaz quando comparado aos tradicionais mÃtodos de otimizaÃÃo por diferenciaÃÃo. à sabido que, em alguns casos, minimizar de forma direta as funÃÃes envolvidas no processo pode ser complicado ou mesmo impossÃvel. Buscou-se com esse trabalho desenvolver uma metodologia para ajuste de curvas de Weibull para a caracterizaÃÃo do regime de ventos, utilizando a otimizaÃÃo pelo mÃtodo do Formigueiro e pelo mÃtodo do Enxame de PartÃculas (do inglÃs Ant Colony Optimization (ACO) e Particle Swarm Optimization (PSO), respectivamente) bem como a hibridizaÃÃo destes dois mÃtodos. Acredita-se que a caracterÃstica estocÃstica dos mÃtodos pode proporcionar resultados refinados para qualquer tipo de distribuiÃÃo de vento, seja concentrada ou dispersa, o que tornaria vÃlido utilizar o mÃtodo nas condiÃÃes de litoral, relevo plano, acidentado ou mesmo urbano, com obstÃculos na direÃÃo dos aerogeradores. O resultado obtido pela aproximaÃÃo heurÃstica de duas amostras de vento do projeto SONDA, referentes a Petrolina-PE e SÃo Martinho da Serra-RS foi comparado com outros oito mÃtodos jà conhecidos e comercialmente aplicados: mÃtodo dos mÃnimos quadrados, mÃtodo do momento, mÃtodo empÃrico, mÃtodo da mÃxima verossimilhanÃa, mÃtodo da mÃxima semelhanÃa, mÃtodo da energia padrÃo, mÃtodo da energia equivalente e mÃtodo do chi-quadrado e a qualidade do ajuste serà avaliada pelos testes de RMSE, MAPE, R2 e pelo desvio na previsÃo de densidade de potÃncia. Os mÃtodos heurÃsticos se mostraram competitivos, com valores de erro em previsÃo de potÃncia da ordem de 10−14%.
8

Localização de faltas em linhas de transmissão baseada em métodos heurísticos utilizando dados de um terminal. / Transmission line fault location with one-terminal data using heuristic methods.

Ronald Adrian Poma Fuentes 16 October 2015 (has links)
Este trabalho apresenta o desenvolvimento e a implementação computacional de um algoritmo para a localização de faltas em linhas de transmissão. O algoritmo proposto é baseado em métodos heurísticos, isto é, Algoritmos Genéticos (AG) e Pattern Search (PS), sendo capaz de identificar o ponto de ocorrência da falta utilizando fasores de tensão e corrente de pré e pós-falta, estimados a partir de medições disponíveis apenas no terminal local da linha de tranmsissão. Nesta abordagem, ambas as ferramentas de otimização possuem natureza heurísticas sendo menos propensas a cair em valores mínimos locais, o que implica uma maior eficiência e precisão na determinação da localização da falta. Além disso, o método utiliza potências de curto-circuito monofásicas e trifásicas de ambos os terminais da linha (local e remoto), a fim de obter seus equivalentes de Thévenin, e os parâmetros elétricos da linha de transmissão. Com o objetivo de avaliar o desempenho do algoritmo proposto, consideram-se nas simulações quatro sistemas de transmissão diferentes, que representam sistemas reais de transmissão brasileiros. O primeiro está constituído por uma típica linha de transmissão de 138 [kV] com circuito duplo, e os outros três sistemas são constituídos por linhas de transmissão típicas de 230, 500 e 765 [kV] com circuito simples. A partir dos quatro sistemas de transmissão simulados no software Alterative Transients Program (ATP/EMTP), foram gerados um total de 928 situações de falta. A versão do algoritmo desenvolvido para localização de faltas foram descritas e implementadas, através do software científico MATrix LABoratory (MATLAB), apresentando resultados com altos níveis de precisão. / This paper presents the development and implementation of a computational algorithm for location faults in transmission line. The proposed algorithm is based on heuristic methods, namely AG and PS, being able to identify the occurrence of the fault point using phasor voltage and current pre and post-fault, estimated from measurements available only on the local terminal of the transmission line. In this approach, both optimization tools have heuristic nature being less prone to falling into local minimum values, which implies grater efficiency and accuracy in the determination of fault location. Moreover, the method use singles-phase and three-phase short-circuit powers of both the line terminals (Local and remote), to obtain the Thévenin equivalent and the electrical parameters of the transmission line. In order to evaluate the performance of the proposed algorithm were considered four different transmission systems; these systems represent real systems of Brazilian transmission. The first this made up of a transmission line typical of 138 [kV] with double circuit, the other three systems are made up of transmission line typical of 230, 500 and 765 [kV] of single circuit. Whereas the four simulated transmission systems in the softwareATP/ EMTP, generated a total of 928 situations fault. The version of the algorithm designed to locate faults, have been described and implemented through scientific software MATLAB, presenting results high levels of accuracy.
9

Localização de faltas em linhas de transmissão baseada em métodos heurísticos utilizando dados de um terminal. / Transmission line fault location with one-terminal data using heuristic methods.

Poma Fuentes, Ronald Adrian 16 October 2015 (has links)
Este trabalho apresenta o desenvolvimento e a implementação computacional de um algoritmo para a localização de faltas em linhas de transmissão. O algoritmo proposto é baseado em métodos heurísticos, isto é, Algoritmos Genéticos (AG) e Pattern Search (PS), sendo capaz de identificar o ponto de ocorrência da falta utilizando fasores de tensão e corrente de pré e pós-falta, estimados a partir de medições disponíveis apenas no terminal local da linha de tranmsissão. Nesta abordagem, ambas as ferramentas de otimização possuem natureza heurísticas sendo menos propensas a cair em valores mínimos locais, o que implica uma maior eficiência e precisão na determinação da localização da falta. Além disso, o método utiliza potências de curto-circuito monofásicas e trifásicas de ambos os terminais da linha (local e remoto), a fim de obter seus equivalentes de Thévenin, e os parâmetros elétricos da linha de transmissão. Com o objetivo de avaliar o desempenho do algoritmo proposto, consideram-se nas simulações quatro sistemas de transmissão diferentes, que representam sistemas reais de transmissão brasileiros. O primeiro está constituído por uma típica linha de transmissão de 138 [kV] com circuito duplo, e os outros três sistemas são constituídos por linhas de transmissão típicas de 230, 500 e 765 [kV] com circuito simples. A partir dos quatro sistemas de transmissão simulados no software Alterative Transients Program (ATP/EMTP), foram gerados um total de 928 situações de falta. A versão do algoritmo desenvolvido para localização de faltas foram descritas e implementadas, através do software científico MATrix LABoratory (MATLAB), apresentando resultados com altos níveis de precisão. / This paper presents the development and implementation of a computational algorithm for location faults in transmission line. The proposed algorithm is based on heuristic methods, namely AG and PS, being able to identify the occurrence of the fault point using phasor voltage and current pre and post-fault, estimated from measurements available only on the local terminal of the transmission line. In this approach, both optimization tools have heuristic nature being less prone to falling into local minimum values, which implies grater efficiency and accuracy in the determination of fault location. Moreover, the method use singles-phase and three-phase short-circuit powers of both the line terminals (Local and remote), to obtain the Thévenin equivalent and the electrical parameters of the transmission line. In order to evaluate the performance of the proposed algorithm were considered four different transmission systems; these systems represent real systems of Brazilian transmission. The first this made up of a transmission line typical of 138 [kV] with double circuit, the other three systems are made up of transmission line typical of 230, 500 and 765 [kV] of single circuit. Whereas the four simulated transmission systems in the softwareATP/ EMTP, generated a total of 928 situations fault. The version of the algorithm designed to locate faults, have been described and implemented through scientific software MATLAB, presenting results high levels of accuracy.
10

User-centred design: the investigation, design and evaluation of an information handbook for coeliac patients

Walkinshaw, Rosemary January 2008 (has links)
Coeliac disease is an intestinal disorder, requiring patients to maintain a life-long gluten-free diet to ensure better health and reduce the risks of osteoporosis, intestinal lymphoma and other associated diseases. Patients must have access to clear information about the disease and about what foods are safe to eat, detect foods that contain gluten and make adjustments that need to be made to their diet. There is very little well designed information currently available for Coeliac patients. Eating out and shopping in supermarkets can become a nightmare. A User-centred design approach was used to generate information and insights on the Coeliac disease and patients' needs to conceptualise, design and evaluate an information handbook that is both functional and pleasurable to use. Questionnaires, interviews and focus groups were used to generate empirical data that guided a participative design process before the evaluation of the handbook. This project consists of a handbook as practical work that represents the main body of applied research. The practical work and the exegesis constitute 50% each of the thesis value.

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