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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.
411

Um novo método heurístico construtivo de alto desempenho para o problema noidle flow shop / A new constructive heuristic method for high performance in no-idle flow shop problem

Branco, Fábio José Ceron 01 August 2011 (has links)
Este trabalho é direcionado ao problema de Programação de Operações No-Idle Flow Shop Permutacional. Uma propriedade do problema, oriunda de estudo sobre a sua característica, é apresentada e utilizada para o desenvolvimento de um novo método heurístico construtivo, com o objetivo de minimizar a Duração Total da Programação (makespan). O novo método é comparado com os melhores heurísticos construtivos reportados na literatura, conhecidos por IG, KK e FRB3. Os resultados da experimentação computacional mostraram o melhor desempenho do método proposto, denominado BHBN, para os problemas testes de Ruiz et al. (2008) e Taillard (1993), quanto à qualidade da solução, apresentando também eficiência computacional. / This work is addressed to the No-Idle Flow Shop Sequencing problem. As a result of an investigation on the problem characteristics it is presented a property of this scheduling problem, which is used for the development of a new constructive heuristic with the objective of minimizing the Total Time to complete the schedule (makespan). The new method is compared with the best constructive heuristics reported in the literature, named IG, KK and FRB3. Results from computational experience showed the best performance of the proposed method, denoted by BHBN, for the instances of Ruiz et al. (2008) and Taillard (1993), as to the quality of the solution, and also computational efficiency.
412

Análise, proposição e solução de modelos para o problema integrado de dimensionamento de lotes e sequenciamento da produção / Analysis, proposition and solution of models for the simultaneous lot sizing and scheduling problem

Soler, Willy Alves de Oliveira 21 November 2017 (has links)
Esta tese aborda um problema de dimensionamento e sequenciamento de lotes de produção baseado em uma indústria alimentícia brasileira que opera por meio de diversas linhas de produção heterogêneas. Nesse ambiente produtivo, as linhas de produção compartilham recursos escassos, tais como, trabalhadores e máquinas e devem ser montadas (ativadas) em cada período produtivo, respeitando-se a capacidade disponível de cada recurso necessário para ativação das mesmas. Modelos de programação matemática inteira mista são propostos para representação do problema, bem como diversos métodos heurísticos de solução, compreendendo procedimentos construtivos e de melhoramento baseados na formulação matemática do problema e heurísticas lagrangianas. São propostas heurísticas do tipo relax-and-fix explorando diversas partições das variáveis binárias dos modelos e uma heurística baseada na decomposição do modelo para construção de soluções. Procedimentos do tipo fix-and-optimize e matheuristics do tipo iterative MIP-based neighbourhood search são propostas para o melhoramento das soluções iniciais obtidas pelos procedimentos construtivos. Testes computacionais são realizados com instâncias geradas aleatoriamente e mostram que os métodos propostos são capazes de oferecer melhores soluções do que o algoritmo Branch-and-Cut de um resolvedor comercial para instâncias de médio e grande porte. / This doctoral dissertation addresses the simultaneous lot sizing and scheduling problem in a real world production environment where production lines share scarce production resources. Due to the lack of resources, the production lines cannot operate all simultaneously and they need to be assembled in each period respecting the capacity constraints of the resources. This dissertation presents mixed integer programming models to deal with the problem as well as various heuristic approaches: constructive and improvement procedures based on the mathematical formulation of the problem and lagrangian heuristics. Relax-and-fix heuristics exploring some partitions of the set of binary variables of a model and a decomposition based heuristic are proposed to construct solutions. Fix-and-optimize heuristics and iterative MIP-based neighbourhood search matheuristics are proposed to improvement solutions obtained by constructive procedures. Computational tests are performed with randomly instances and show that the proposed methods can find better solutions than the Branch-and-Cut algorithm of a commercial solver for medium and large size instances.
413

O equilíbrio correlacionado de Aumann e as convenções sociais

Santos, Rodrigo Prates dos January 2008 (has links)
O principal objetivo deste trabalho é mostrar que uma convenção social está fortemente relacionada com o conceito de equilíbrio correlacionado. Através da interação de longo prazo e do aprendizado, os agentes podem chegar a um acordo, mesmo com suposições pouco restritivas e que possibilitem uma interpretação mais natural e realista do conceito de equilíbrio em Teoria dos Jogos. Inicialmente a suposição de conhecimento comum é apresentado de maneira formal e informal. O conceito de equilíbrio correlacionado é apresentado com exemplos. Finalmente, a relação entre o equilíbrio correlacionado e a convenção social é analisada. / The main purpose of this dissertation is to show that a convention can be related to a correlated equilibrium. Through the long run interaction and learning, the players can reach an agreement, even if we relax the traditional assumptions of Game Theory, and we can find a more natural and plausible interpretation of equilibrium. Initially the common knowledge assumption is presented in a formal and informal way. The correlated equilibrium is presented with examples. Finally, the relation between correlated equilibrium and convention is analyzed.
414

Inteligência governamental como política pública : fatores cognitivos e institucionais na explicação de falhas e dilemas de efetividade

Ambros, Christiano Cruz January 2011 (has links)
O objetivo do artigo apresentado é analisar dilemas de efetividade na atividade de Inteligência Governamental. Explorando a literatura sobre falhas de inteligência e surpresa estratégica, avançamos em um campo pouco explorado pelos Estudos de Inteligência no Brasil: os aspectos cognitivos dos analistas de inteligência e as relações entre a comunidade política e a comunidade de inteligência. Primeiramente discorremos sobre os desafios de se avaliar a Inteligência Governamental como política pública, em especial no que se refere à dimensão da efetividade. Na segunda sessão abordamos os principais vieses cognitivos e heurísticas possíveis de ocorrer durante a análise de inteligência. A terceira sessão trata das tensões relacionais características entre a esfera política e a comunidade de inteligência e como essa relação afeta no resultado final da atividade de inteligência. Nas considerações finais apontamos para os limites e possibilidades das reformas organizacionais e procedimentais no que se refere à efetividade dos sistemas de inteligência. / The objective of this paper is to analyze the effectiveness‟ dilemmas of government intelligence activities. Exploring the literature on intelligence failures and strategic surprise, we move towards a little explored field on Brazilian Intelligence Studies: the cognitive aspects of intelligence analysts and the relations between the political community and the intelligence community. First we balance the challenges of evaluating government intelligence as public policy, particularly regarding the effectiveness dimension. In the second session, we discuss the main cognitive biases and heuristics that can occur during intelligence analysis. The third section discusses the typical relational tensions between the political sphere and the intelligence community and how that relationship affects the final result of intelligence activity. In the concluding remarks, we point to the limits and possibilities of organizational and procedural reforms on the effectiveness of intelligence systems.
415

Résolution à base d'heuristiques du problème de routage dans les réseaux ad hoc de vehicules / Heuristic resolution of the routing problem within vehicular ad hoc network (VANET)

Hajlaoui, Rejab 18 December 2018 (has links)
Les réseaux ad hoc véhiculaires (VANETs) sont constitués par un ensemble de véhicules qui échangent des données de sécurité et de confort même s’ils ne sont pas toujours directement à portée radio.Les problèmes liés aux réseaux VANETs ne sont pas encore tous résolus. Dans ce contexte, et dans le but de maximiser la stabilité dans ce type de réseaux, nous proposons différentes contributions pour assurer le routage en combinant les métaheuristiques et la technique de clustérisation.Tout d’abord, nous présentons un modèle de routage utilisant l’algorithme de clustérisation le plus efficace k-medoids. Ensuite, nous proposons plusieurs améliorations en utilisant les métaheuristiques, plus précisément les algorithmes génétiques, la recherche tabou et la recherche par dispersion. Enfin, nous proposons une application réelle de communication entre trois robots mobiles dans les zones non couvertes par le réseau VANET.A l’aide de diverses métriques, des simulations extensives montrent que nos contributions donnent de bons résultats par rapport à d’autres modèles conçus dans le même but. / Vehicular ad hoc networks (VANETs) consist of a set of vehicles trying to exchange security and comfort data even if they are not directly within radio range of each other. The problems related to VANET networks are not yet solved. In this context, and in order to maximize the stability in the VANETs networks, we propose different contributions combining the metaheuristics and the clustering technique. First, we propose a routing model using the most efficient clustering algorithm K-medoids. Then, we propose several improvements using metaheuristics, more precisely the AGs, the RT and the Scatter Search. Finally, we propose a real application that uses the Arduino Uno platform to allow communication between three mobile robots in an areas not covered by the VANET network.Using various metrics, extensive simulations prove that our contributions show good results compared to other models designed for the same purpose.
416

Métodos heurísticos aplicados ao problema de programação da frota de navios PLVs. / Heuristics methods applied in a PLV fleet scheduling problem.

Queiroz, Maciel Manoel de 03 October 2011 (has links)
O presente trabalho abordou um problema de programação de embarcações que realizam o lançamento de dutos ou linhas de produção e a interligação destes à infra-estrutura submarina, em uma operação de exploração de petróleo offshore. As tarefas são realizadas por embarcações PLVs (pipe layer vessels), e possuem como atributos: duração, em dias; lista de embarcações compatíveis; instante de liberação; penalidade relacionada ao atraso na execução da tarefa. Este problema é uma variação da classe de problemas de programação de máquinas paralelas não-relacionadas, em que o objetivo é minimizar o atraso ponderado total. Este trabalho empregou como métodos de solução a meta-heurística GRASP com path relinking. Esta técnica foi implementada utilizando os recursos de processamento multi-threading, de forma a explorar múltiplas trajetórias simultaneamente. Testes foram feitos para comprovar o desempenho das heurísticas propostas, comparando-as com limitantes fornecidos pelo método geração de colunas. / This work addressed a fleet scheduling problem present in the offshore oil industry. Among the special purpose services one will find the pipe layer activities and its connection to the subsea infrastructure, accomplished by the Pipe Layer Vessels (PLV). The jobs are characterized by a release date, which reflects the expected arrival date of the necessary material at the port. There are compatibility constraints between job and vessel, so that some vessels may not be able to perform a certain job; the duration of the jobs can be differentiated by vessel and if a job is finished after its due date, a penalty is incurred. This is a variation of the unrelated parallel machine problem with total weighted tardiness objective function. This research employed a metaheuristic GRASP with Path Relinking, which have proved to be competitive and an effective solution strategy. This method was implemented in a multi-threading scheme allowing multiple paths to be explored simultaneously. Computational experiments were conducted, comparing solutions with bounds provided by linear column generation.
417

Why buy green? : An exploration of drivers and barriers related to sustainable purchasing in the Swedish food sector

Adolfsson, Henrik, Wickström, Freddy January 2019 (has links)
Sustainability has become a subject of much interest in recent years, due to the deterioration of the natural environment. In response there has been increasing public pressure on businesses to provide environmentally friendly product alternatives for consumers. However, the demand for said products is surprisingly low, which constitutes a challenge for marketers; how can the demand for sustainable products be increased? In order to answer this question, a deeper understanding of the green consumer profile is needed. As such, the purpose of this study is to: Increase the understanding of the green consumer profile by exploring drivers of, and barriers to, green purchasing behaviour. In order to fulfil this purpose within the chosen context of sustainable foods, the subsequent main research questions were formulated: <ol type="1">What do consumers perceive to be drivers motivating them to purchase sustainable foods? What do consumers perceive to be barriers preventing them from purchasing sustainable foods? The study adopts a qualitative and exploratory approach and utilizes semi-structured focus groups to accumulate empirical material. The questions for these focus groups stem from an integrative model created through synthesis of existing theory related to marketing of sustainable products, while adopting a consumer perspective. Three focus groups were subsequently held, with a total of 12 participants. Data display and analysis was used to produce insights related to the purpose and research questions of the study. Among these, the most important insights include the lack of specific knowledge relating to the benefits of sustainable food products, and the social factors that influence consumers’ purchasing behaviour of sustainable foods. Moreover, the findings suggest that the confusion regarding the definition of sustainable foods has implications that call into question contemporary theory on the matter.
418

A Heuristic Method for Routing Snowplows After Snowfall

Sochor, Jana, Yu, Cecilia January 2004 (has links)
<p>Sweden experiences heavy snowfall during the winter season and cost effective road maintenance is significantly affected by the routing of snowplows. The routing problem becomes more complex as the SwedishNational Road Administration (Vägverket) sets operational requirements such as satisfying a time window for each road segment. </p><p>This thesis focuses on route optimization for snowplows after snowfall; to develop and implement an algorithm for finding combinations of generated routes which minimize the total cost. The results are compared to those stated in the licentiate thesis by Doctoral student Nima Golbaharan (2001). </p><p>The algorithm calculates a lower bound to the problem using a Lagrangian master problem. A common subgradient approach is used to find near-optimal dual variables to be sent to a column-generation program which returns routes for the snowplows. A greedy heuristic chooses a feasible solution, which gives an upper bound to the problem. This entire process is repeated as needed. </p><p>This method for routing snowplows produces favorable results with a relatively small number of routes and are comparable to Golbaharan's results. An interesting observation involves the allocation of vehicles in which certain depots were regularly over- or under-utilized. This suggests that the quantity and/or distribution of available vehicles may not be optimal.</p>
419

Birnbaum Importance Patterns and Their Applications in the Component Assignment Problem

Yao, Qingzhu 01 May 2011 (has links)
The Birnbaum importance (BI) is a well-known measure that evaluates the relative contribution of components to system reliability. It has been successfully applied to tackling some reliability problems. This dissertation investigates two topics related to the BI in the reliability field: the patterns of component BIs and the BI-based heuristics and meta-heuristics for solving the component assignment problem (CAP).There exist certain patterns of component BIs (i.e., the relative order of the BI values to the individual components) for linear consecutive-k-out-of-n (Lin/Con/k/n) systems when all components have the same reliability p. This study summarizes and annotates the existing BI patterns for Lin/Con/k/n systems, proves new BI patterns conditioned on the value of p, disproves some patterns that were conjectured or claimed in the literature, and makes new conjectures based on comprehensive computational tests and analysis. More importantly, this study defines a concept of segment in Lin/Con/k/n systems for analyzing the BI patterns, and investigates the relationship between the BI and the common component reliability p and the relationship between the BI and the system size n. One can then use these relationships to further understand the proved, disproved, and conjectured BI patterns.The CAP is to find the optimal assignment of n available components to n positions in a system such that the system reliability is maximized. The ordering of component BIs has been successfully used to design heuristics for the CAP. This study proposes five new BI-based heuristics and discusses their corresponding properties. Based on comprehensive numerical experiments, a BI-based two-stage approach (BITA) is proposed for solving the CAP with each stage using different BI-based heuristics. The two-stage approach is much more efficient and capable to generate solutions of higher quality than the GAMS/CoinBonmin solver and a randomization method.This dissertation then presents a meta-heuristic, i.e., a BI-based genetic local search (BIGLS) algorithm, for the CAP in which a BI-based local search is embedded into the genetic algorithm. Comprehensive numerical experiments show the robustness and effectiveness of the BIGLS algorithm and especially its advantages over the BITA in terms of solution quality.
420

Soziale Informationsverarbeitung in der juristischen Urteilsfindung : experimentelle Untersuchungen zur Ankerheuristik / Social information processing and legal decision making : experimental studies on anchoring and adjustment

Bieneck, Steffen January 2006 (has links)
Heuristiken der Urteilsbildung umfassen bottom-up bzw. schemagesteuerte Strategien innerhalb der sozialen Informationsverarbeitung, mit deren Hilfe trotz unsicherer Datenlage hinreichend genaue Urteile gefällt werden können. Die Anker- und Anpassungsheuristik als eine Form solcher Faustregeln beschreibt im Wesentlichen die Wirkung von vorgegebenen Zahlen (den so genannten Ankerwerten) auf numerische Schätzungen. Urteile unter Unsicherheit sind zum Beispiel im Bereich der Rechtsprechung zu beobachten, wobei die Entscheidungsprozesse hier eher normativ auf der Basis der vorliegenden Informationen, d.h. einer datengesteuerten Verarbeitung, erfolgen sollten. <br><br> In einer Serie von drei Experimenten wurde die Ankerheuristik auf den Bereich der Rechtsprechung übertragen. Mit Hilfe der Vignettentechnik wurden <i>N</i> = 229 Rechtsreferendare sowie <i>N</i> = 600 Studierende der Rechtswissenschaften zu ihrem Strafverhalten befragt. Im Mittelpunkt standen drei Zielsetzungen: (1) die Replikation und Erweiterung der Ankereffekts in Bezug auf eine größere Gruppe von Deliktarten; (2) die Analyse individueller Unterschiede in der Ankernutzung unter Berücksichtigung verschiedener Persönlichkeitsvariablen (Need for Cognition und Need for Cognitive Closure) sowie (3) die Anregung zu verstärkter systematischer Informationsverarbeitung durch die Indizierung einer Genauigkeitsmotivation. <br><br> Der Ankereffekt in der juristischen Urteilsfindung konnte für die verschiedenen Deliktgruppen repliziert werden. Die Ergebnisse zeigen, dass die wahrgenommene Schwere der geschilderten Taten mit dem Strafmaß korrelierte. Dieser Zusammenhang wurde durch die Einführung von Ankerwerten deutlich reduziert. Entgegen den bisherigen Untersuchungen war zwar auch bei den Rechtsreferendaren ein Ankereffekt zu beobachten, der jedoch geringer ausfiel als bei den Studierenden der Rechtswissenschaften. Im Hinblick auf die Persönlichkeitsmerkmale konnte die Erwartung bestätigt werden, dass ein geringes Kognitionsbedürfnis sowie ein hohes Geschlossenheitsbedürfnis mit höherer Anfälligkeit für die Ankerheuristik einhergehen. Die Erzeugung eines Rechtfertigungsdrucks dagegen veranlasste die Probanden, sich intensiver mit den Materialien zu beschäftigen und eher datengeleitet vorzugehen. Implikationen für die juristische Praxis werden diskutiert. / Decisions are usually based on beliefs about the likelihood that an uncertain event will occur (i.e., the results of an election or the liability of the accused). In estimating the likelihood of those events people often revert to heuristics as a theory-driven processing strategy in order to reduce the effort of the decision-making process. On the one hand heuristics might be quite helpful in controlling information processing; on the other hand they can lead to systematic biases in judgments. Anchoring and adjustment describe a judgmental heuristic, where individuals gauge numerical size by starting from an initial arbitrary or irrelevant value (an anchor) and adjusting it during the subsequent course of judgment to arrive at their final judgment. However, the adjustment of the judgment typically remains insufficient, thus leading to judgments that are biased in the direction of the starting value. <br><br> The concept of judgmental heuristics can be applied to legal decision making. Legal decision-making is normatively defined as data-driven, which means that judgements about the culpability of a defendant need to be corroborated by evidence specific to the case at hand. Individuals involved in this process are required to assess the evidence without being affected by personal feelings and beliefs or by extraneous evidence. <br><br> A series of three experiments tested the impact of anchoring and adjustment on legal decision making. Using the vignette technique, <i>N</i> = 229 junior barristers and <i>N</i> = 600 law students evaluated scenarios describing criminal offences. Apart from replicating the anchoring effect in different samples, the studies explored the impact of individual differences in personality variables (need for cognition and cognitive closure) on the anchoring effect. Further, a strategy to promote data-driven processing by inducing an accuracy motivation was evaluated. <br><br> The results clearly indicate an anchoring effect in legal decision-making. The results showed a strong correlation between the perceived severity of the cases and the recommended sentence. This correlation was significantly reduced when an anchor was introduced. In contrast to previous studies, junior barristers showed a less extreme bias in their judgments compared to law students. In terms of individual differences regarding the readiness to engage in elaborate information processing the results showed a higher susceptibility for the anchoring information when need for cognition was low and need for cognitive closure was high. Introducing an accuracy motivation prompted the participants to engage in more data-driven processing, thus reducing the anchoring effect. The implications for social cognition research and legal practice are discussed.

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