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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.
21

Procedimento para projeto de arranjo físico modular em manufatura através de algoritmo genético de agrupamento / Procedure to the design of modular facility layouts through clustering genetic algorithm

Ana Rita Tiradentes Terra Argoud 16 March 2007 (has links)
O objetivo desta tese foi desenvolver um procedimento para projeto de arranjo físico modular. O procedimento usa um algoritmo genético de agrupamento para gerar módulos de arranjo físico em manufatura. Um módulo é um grupo de máquinas com um fluxo característico. O algoritmo genético de agrupamento (AGA) permite ao usuário especificar a priori o número desejado de módulos (problema de K-agrupamentos), e também trabalhar de forma que o número e formação dos módulos seja uma otimização do problema (problema de agrupamento automático). Uma característica importante do AGA é sua flexibilidade, pois fornece possibilidade ao usuário de dirigir seu raciocínio através da escolha de diferentes codificações do cromossomo, de funções de aptidão para avaliar a qualidade da solução, de medidas de similaridade para comparação de seqüências de operações e de métodos de geração da nova população. Para tal foram desenvolvidos três operadores de cruzamento e quatro operadores de mutação. Os experimentos permitiram avaliar o comportamento do AGA com diferentes operadores e configurações de parâmetros, através do número de vezes em que a melhor solução foi encontrada. Os módulos de arranjo físico gerados pelo AGA e o arranjo físico final da fábrica foram comparados aqueles da principal referência encontrada na bibliografia em projeto de arranjo físico modular. No arranjo físico final da fábrica, elaborado a partir das soluções do AGA, houve importante redução da distância total percorrida pelo conjunto de peças, demonstrando a eficácia do algoritmo genético de agrupamento. Dessa forma, os resultados apontaram o algoritmo genético de agrupamento como uma alternativa à geração de módulos de arranjo físico em projeto de arranjo físico modular. / The objective of this thesis was the development of a procedure to the design of modular facility layouts. The procedure uses a clustering genetic algorithm to generate layout modules. A module is a group of machines with a specific patterned flow. The clustering genetic algorithm (CGA) allows the specification of the desired number of modules (K-grouping problem) and also the optimization of the number of modules (automatic clustering problem). The genetic algorithm is very flexible and the user can guide his reasoning. It supplies different options of chromosome encoding, generation of the initial population, fitness function to evaluate the solution quality, different similarity measures for comparison of operation sequences and methods for generation of the new population. Three crossover operators and four mutation operators have been developed. The experiments have allowed evaluating the behavior of the CGA with different operators and parameters configurations, through the number of times in which the best solution was found. The layout modules generated by the CGA and the block layout were compared with the main reference which was found in literature in the design of modular facility layouts. In the block layout elaborated from the solutions of the CGA there was an important reduction of the total distance traveled by the set of parts, demonstrating the effectiveness of the clustering genetic algorithm. The results indicated that the clustering genetic algorithm is an alternative for generation of layout modules in the design of modular facility layouts.
22

Material Flow Cost Versus Congestion In Dynamic Distributed Facility Layout Problem

Ozen, Aykut 01 July 2008 (has links) (PDF)
In this thesis, we study both dynamic and distributed facility layout problems, where the demand for product mix changes over time. We propose a new simulated annealing algorithm, SALAB, for the dynamic facility layout problem. Four variants of SALAB find the best known solution for 20 of the 48 benchmark problems from the literature, improving upon the best known solutions of 18 problems. We modify SALAB to obtain DSALAB, solving the dynamic distributed facility layout problem with the objective of minimizing relocation cost and total (full and empty) travel cost of the material handling system. We simulate DSALAB solutions of randomly generated problems to study the tradeoff between total cost and congestion in the system. Our experimental results indicate that distributing the department duplicates throughout the facility reduces the total cost with diminishing returns and causes increasing congestion. Therefore, distribution beyond a certain level is not justified.
23

Semidefinite Cuts and Partial Convexification Techniques with Applications to Continuous Nonconvex Optimization, Stochastic Integer Programming, and Facility Layout Problems

Fraticelli, Barbara M. P. 26 April 2001 (has links)
This dissertation develops efficient solution techniques for general and problem-specific applications within nonconvex optimization, exploiting the constructs of the Reformulation-Linearization Technique (RLT). We begin by developing a technique to enhance general problems in nonconvex optimization through the use of a new class of RLT cuts, called semidefinite cuts. While these cuts are valid for any general problem for which RLT is applicable, we demonstrate their effectiveness in optimizing a nonconvex quadratic objective function over a simplex. Computational results indicate that on average, the semidefinite cuts have reduced the number of nodes in the branch-and-bound tree by a factor of 37.6, while decreasing solution time by a factor of 3.4. The semidefinite cuts have also led to a significant reduction in the optimality gap at termination, in some cases producing optimal solutions for problems that could not be solved using RLT alone. We then narrow our focus to the class of mixed-integer programming (MIP) problems, and develop a modification of Benders' decomposition method using concepts from RLT and lift-and-project cuts. This method is particularly motivated by the class of two-stage stochastic programs with integer recourse. The key idea is to design an RLT or lift-and-project cutting plane scheme for solving the subproblems where the cuts generated have right-hand sides that are functions of the first-stage variables. An illustrative example is provided to elucidate the proposed approach. The focus is on developing a first comprehensive finitely convergent extension of Benders' methodology for problems having 0-1 mixed-integer subproblems. We next address a specific challenging MIP application known as the facility layout problem, and we significantly improve its formulation through outer-linearization techniques and concepts from disjunctive programming. The enhancements produce a substantial increase in the accuracy of the layout produced, while at the same time, providing a dramatic reduction in computational effort. Overall, the maximum error in department size was reduced from about 6% to nearly zero, while solution time decreased by a factor of 110. Previously unsolved test problems from the literature that had defied even approximate solution methods have been solved to exact optimality using our proposed approach. / Ph. D.
24

Models and Algorithms for Some Combinatorial Optimization Problems: University Course Timetabling, Facility Layout and Integrated Production-Distribution Scheduling

Wang, Yuqiang 24 August 2007 (has links)
In this dissertation, we address three different combinatorial optimization problems (COPs), each of which has specific real-life applications. Owning to their specific nature, these problems are different from those discussed in the literature. For each of these problems, we present a mathematical programming formulation, analyze the problem to determine its useful, inherent structural properties, and develop an efficient methodology for its solution by exploiting these properties. The first problem that we address is the course timetabling problem encountered at Virginia Tech. The course timetabling problem for a university is a difficult problem and has been studied by many researchers over the years. As a result, a plethora of models and approaches have been reported in the literature. However, most of these studies have focused on applications pertaining to course scheduling for a single or at most few departments of a university. The sheer size of the university-wide timetabling problem that we address, involving thousands of courses to be scheduled in hundreds of classrooms in each semester, makes it a challenging problem. We employ an appropriate decomposition technique that relies on some inherent structural properties of the problem both during the modeling and algorithmic development phases. We show the superiority of the schedules generated by our methodology over those that are currently being used. Also, our methodology requires only a reasonable amount of computational time in solving this large-size problem. A facility layout problem involving arbitrary-shaped departments is the second problem that we investigate in this dissertation. We designate this problem as the arbitrary-shaped facility layout problem (ASFLP). The ASFLP deals with arranging a given set of departments (facilities, workstations, machines) within the confines of a given floor space, in order to optimize a desired metric, which invariably relates to the material handling cost. The topic of facility planning has been addressed rather extensively in the literature. However, a major limitation of most of the work reported in the literature is that they assume the shape of a department to be a rectangle (or even a square). The approach that relies on approximating an arbitrary-shaped department by a rectangle might result in an unattractive solution. The key research questions for the ASFLP are: (1) how to accurately model the arbitrary-shaped departments, and (2) how to effectively and efficiently determine the desired layout. We present a mixed-integer programming model that maintains the arbitrary shapes of the departments. We use a meta-heuristic to solve the large-size instances of the ASFLP in a reasonable amount of time. The third problem that we investigate is a supply chain scheduling problem. This problem involves two stages of a supply chain, specifically, a manufacturer and one or more customers. The key issue is to achieve an appropriate coordination between the production and distribution functions of the manufacturer so as to minimize the sum of the shipping and job tardiness costs. We, first, address a single customer problem, and then, extend our analysis to the case of multiple customers. For the single-customer problem, we present a polynomial-time algorithm to solve it to optimality. For the multiple-customer problem, we prove that this problem is NP-hard and solve it by appropriately decomposing it into subproblems, one of which is solvable in polynomial time. We propose a branch-and-bound-based methodology for this problem that exploits its structural properties. Results of an extensive computational experimentation are presented that show the following: (1) our algorithms are efficient to use and effective to implement; and (2) significant benefits accrue as a result of integrating the production and distribution functions. / Ph. D.
25

Um formalismo relacional para o desenvolvimento de arranjo físico industrial.

Torres, Isaías 01 March 2007 (has links)
Made available in DSpace on 2016-06-02T19:49:59Z (GMT). No. of bitstreams: 1 TeseIT2007.pdf: 4427190 bytes, checksum: 8697d139441060709a94cd9b17e8ac87 (MD5) Previous issue date: 2007-03-01 / Financiadora de Estudos e Projetos / The facility layout planning is an important factor of production systems. It is an important step of the facility planning process where converge determinants from business strategy, economic and work factors, among others. The knowledge and techniques of this application area have evolved as the factory concept itself have changed and new aspects were considered as important ones. The traditional tools and techniques have considered just part of the aspects related to the layout, as proximity relationships and material flows. This work aimed to determine a formalism able to represent, in an integrated way, the aspects considered during the creation and evaluation of layout alternatives by multidisciplinary design teams. This formalism, based on objects and relationships, breaks with the prescriptive vision present in traditional facility layout software. The software that has been developed from the formalism presents an innovative way for layout designing, and points out to several other innovation opportunities. It is expected that this formalism may be used for developing software to support work activities of people involved with industrial facilities planning. / O arranjo físico é um fator importante dos sistemas de produção e constitui-se em uma etapa do projeto de instalações produtivas onde convergem determinantes da estratégia de negócios, fatores econômicos e de trabalho, entre outros. Os conhecimentos e técnicas dessa área de aplicação evoluíram na medida em que o próprio conceito de fábrica era alterado e novos aspectos passaram a ser considerados importantes. Tradicionalmente as ferramentas e técnicas desenvolvidas trataram geralmente de apenas um dos aspectos considerados no arranjo físico, como as relações de proximidade e de fluxo de materiais. O trabalho desenvolvido buscou determinar um formalismo capaz de representar de forma integrada os aspectos considerados durante a criação e avaliação de alternativas de arranjo físico por grupos multidisciplinares de projeto. Esse formalismo, baseado em objetos e relações, rompe com a visão prescritiva do uso de programas computacionais usados em projetos de arranjo físico. O programa computacional desenvolvido a partir do formalismo apresenta uma forma inovadora para projetar alternativas de layout, além de apontar várias outras oportunidades de inovação. Espera-se que o formalismo desenvolvido sirva de modelo para o desenvolvimento de outros programas computacionais desse tipo.
26

A new framework considering uncertainty for facility layout problem

Oheba, Jamal Bashir January 2012 (has links)
In today’s dynamic environment, where product demands are highly volatile and unstable, the ability to design and operate manufacturing facilities that are robust with respect to uncertainty and variability is becoming increasingly important to the success of any manufacturing firm in order to operate effectively in such an environment. Hence manufacturing facilities must be able to exhibit high levels of robustness and stability in order to deal with changing market demands. In general, Facility Layout Problem (FLP) is concerned with the allocation of the departments or machines in a facility with an objective to minimize the total material handling cost (MHC) of moving the required materials between pairs of departments. Most FLP approaches assume the flow between departments is deterministic, certain and constant over the entire time planning horizon. Changes in product demand and product mix in a dynamic environment invalidate these assumptions. Therefore there is a need for stochastic FLP approaches that aim to assess the impact of uncertainty and accommodate any possible changes in future product demands.This research focuses on stochastic FLP with an objective to present a methodology in the form of a framework that allows the layout designer to incorporate uncertainty in product demands into the design of a facility. In order to accomplish this objective, a measure of impact of this uncertainty is required. Two solution methods for single and multi period stochastic FLPs are presented to quantify the impact of product demand uncertainty to facility layout designs in terms of robustness (MHC) and variability (standard deviation). In the first method, a hybrid (simulation) approach which considers the development of a simulation model and integration of this model with the VIPPLANOPT 2006 algorithm is presented. In the second method, mathematical formulations of analytic robust and stable indices are developed along with the use of VIPPLANOPT for solution procedure. Several case studies are developed along with numerical examples and case studies from the literature are used to demonstrate the proposed methodology and the application of the two methods to address different aspects of stochastic FLP both analytically and via the simulation method. Through experimentation, the proposed framework with solution approaches has proven to be effective in evaluating the robustness and stability of facility layout designs with practical assumptions such as deletion and expansion of departments in a stochastic environment and in applying the analysis results of the analytic and simulation indices to reduce the impact of errors and make better decisions
27

Modélisation et résolution du problème d’implantation des ateliers de production : proposition d’une approche combinée Algorithme Génétique – Algorithme A* / Modeling and solving the problem of implementation of production workshops : proposition of a combined approach Algorithm genetic-algorithm A *

Besbes, Mariem 20 November 2019 (has links)
Pour faire face à la concurrence, les entreprises cherchent à améliorer leurs performances industrielles. L’une des solutions à ce défi réside dans la détermination de la meilleure configuration des ateliers de production. Ce type de problème est connu en anglais par Facility Layout Problem « FLP». Dans ce contexte, notre travail propose une méthodologie pour la définition de la configuration d’atelier à travers une approche réaliste. Plus précisément, notre objectif est de prendre en compte les distances réelles parcourues par les pièces dans l’atelier et des contraintes liées au système qui n’ont pas encore été intégrées aux modèles proposés dans la littérature. Pour ce faire, notre première contribution scientifique consiste à développer une nouvelle méthodologie qui utilise l’algorithme A* pour identifier les distances les plus courtes entre les postes de travail de manière réaliste. La méthodologie proposée combine l’Algorithme Génétique (AG) et l’algorithme A* afin d’explorer des espaces de solutions. Pour se rapprocher de plus en plus des cas réels, notre deuxième contribution consiste à présenter une nouvelle formulation généralisée du FLP initialement étudié, en tenant compte de différentes formes et de dimensions des équipements ainsi que de l’atelier. Les résultats obtenus prouvent l’applicabilité et la faisabilité de cette approche dans diverses situations. Une étude comparative de l’approche proposée avec les essaims particulaires intégrés avec A* a prouvé la qualité de la première approche en terme de coût de transport. Finalement, notre troisième contribution consiste à traiter le FLP dans un espace 3D où des contraintes spatiales sont intégrées dans la phase de modélisation. La résolution est une extension de la méthodologie proposée pour le problème 2D, qui intègre donc l'algorithme A* et l’AG afin de générer diverses configurations dans l’espace 3D. Pour chacune de ces contributions, une analyse de sensibilité des différents paramètres d’AG utilisés a été faite à l’aide de simulations de Monte Carlo. / To face the competition, companies seek to improve their industrial performance. One of the solutions to this challenge lies in determining the best configuration of the production workshops. This type of problem is known in English by Facility Layout Problem "FLP". In this context, our work proposes a methodology for the definition of the workshop configuration through a realistic approach. More precisely, our goal is to take into account the actual distances traveled by the parts in the workshop and system-related constraints that have not yet been incorporated into the models proposed in the literature. To do this, our first scientific contribution is to develop a new methodology that uses the A* algorithm to identify the shortest distances between workstations in a realistic way. The proposed methodology combines the Genetic Algorithm (GA) and the algorithm A* to explore solution spaces. To get closer to real cases, our second contribution is to present a new generalized formulation of FLP initially studied, taking into account different shapes and dimensions of the equipment and the workshop. The results obtained prove the applicability and the feasibility of this approach in various situations. A comparative study of the proposed approach with particle swarms integrated with A * proved the quality of the first approach in terms of transport cost. Finally, our third contribution is to treat the FLP in a 3D space where spatial constraints are integrated into the modeling phase. The resolution is an extension of the proposed methodology for the 2D problem, which therefore integrates the A * algorithm and the AG to generate various configurations in the 3D space. For each of these contributions, a sensitivity analysis of the different AG parameters used was made using Monte Carlo simulations.
28

Effektivisering av material- och produktionsflöde : En fallstudie på SWEP International AB / Streamlining material- and production flow : A case study at SWEP International AB

Carlsson, Ebba, Tingström, Torsten January 2022 (has links)
Effektivisering av material- och produktionsstyrning skaparförutsättningar att åstadkomma mätningar och uppföljningar som senarekan påverka beteenden i företaget. Att uppnå en högproduktionseffektivitet där material hamnar på rätt plats, i rätt tid och irätt skick kan vara ett komplext problem om ett flertal produkter rör siginom samma område på ett okontrollerat sätt (Jonsson & Mattsson,2013; Bjurström, 2016). Därmed är fallstudiens syfte att öka förståelsekring hur effektiviteten av ett produktionsflöde i ett tillverkande företagkan öka. Målet med studien är att utveckla förbättringsförslag avfabrikslayout och materialstyrningsmetoder samt- system i produktionengenom kvalitativt arbete med intervjuer samt observationer. Teori ochempiri analyseras för att avslutningsvis presentera ett resultat i form avett förslag på en layoutförändring med optimerat flöde relaterat tillslöserier, tillsammans med ytterligare rekommendationer som innehållermaterialstyrningsmetoder samt- system i produktionen. Studien visar atteffektiviteten av ett produktionsflöde kan öka genom att kartläggamaterialflöden mellan arbetsstationer och därmed finna åtgärder somkrävs för att minimera slöserier. Föreslagna åtgärder är av teoretisknatur och har inte testats.
29

Layout Design of A Third Party-Logistics Centre: A Case Study

Eren, Nurdan, Sat, Yusuf Hasim January 2010 (has links)
<p>The purpose of this thesis is to develop an integrated model which involves creative and analytical features for designing a cost effective logistics centre layout on operational level, with respect to time and space utilization. Engineering methods, creative skills, simulation and multi-criteria decision making methods were integreted in the  developed model. The model has been implemented and validated in Oskarshamn Intralog, which is a sister company of Scania. After applying the model in the case company, three different layout concepts were generated based on engineering and simulation techniques. These concepts were evaluated from utilization of space, time and flexibility aspects. Furthermore, multi criteria decision making method was used to select the most cost effective layout concept among these concepts. Different aspects helped to see various effects of warehouse operations on layout design. Simulation was used as a powerful tool to test cycle time within designed concepts. Clearly it was concluded that a combination of two concepts led to reach the expected results as an optimum point among space, time utilization and flexibility which fullfilled the answer to both academical and practical problem</p> / <p><strong> </strong></p><p>Syftet med den här uppsatsen är att utveckla en integrerad modell som inbegriper kreativa och analytiska egenskaper. Modellen ska användas till att designa en kostnadseffektiv planering av anläggningen för ett logistikcentrum på en operationell nivå, med avseende på tid- och lagerplatsutnyttjande. Tekniska metoder, kreativitet, simulering, samt “multi-criteria decision making” är integrerade i modellen. Validering och implementering av modellen skedde på Oskarshamn Intralog, ett systerföretag till Scania. Efter tillämpning av modellen på fallföretaget, genererades tre olika koncept för planering av anläggningen. Koncepten utvärderades utifrån utnyttjande av plats, tid, samt flexibilitet. Dessutom har metoden “multi-criteria decision making” använts för att selektera det mest kostnadseffektiva av de tre koncepten. Olika aspekter på tid- och lagerplatsutnyttjande, samt flexibilitet bidrog till att se olika effekter på lagerhantering. Simuleringar genomfördes för att testa cykeltiden i de utvecklade koncepten. Slutsatsen är att en kombination av två koncept ledde till det förväntade resultatet; en optimal punkt för tid- och lagerplatsutnyttjande, samt flexibilitet, vilket uppfyller svar till de akademiska och praktiska problemen</p>
30

Improving facility layout &amp; logistics to increase the material flow efficiency / Förbättring av interna flöden &amp; anläggningsplanering för att uppnå en effektiv materialhantering

Besic, Dino January 2013 (has links)
When the internal logistics of a company is in a well working condition, the manufacturing process is more efficient and a more efficient material handling process can be developed. A company with the interest of decreasing internal material handling is Scapa Bedding AB, a middle size bed manufacturer situated in Rydaholm, Sweden. Today, Scapa Bedding AB is facing a problem since there is no documentation regarding the material handling, no maps have been developed that displays the internal transports. This thesis attends the question of how to decrease the material handling within the production areas. To construct a solution for the material handling problem tools such as PDCA and DMAIC were used as a foundation in the development of a model that would be applicable on a company of this size. The purpose of the work is to locate and identify the wasteful activities regarding the material handling, and to streamline the activities to reach a minimum of material handling. By extracting data from observations, discussions and interviews the thesis will provide the reader with a problem background and a constructed model the tackle the problem. The model will provide support to locate inefficiencies within the company and in a later stage to develop improvement alternatives relevant to the case. The chosen improvement alternative will in a cost effective way be a solution to the problem. / När den interna logistiken på ett företag är i ett välfungerande tillstånd kan en mer effektiv produktion och materialhanteringsprocess utvecklas. Ett företag som arbetar för att minska på den interna materialhanteringen är Scapa Bedding AB, en medelstor sängtillverkare belägen i Rydaholm, Sverige. Idag står Scapa Bedding inför ett problem då det saknas dokumentation och rutiner på dess befintliga materialhantering. Detta arbete kommer att hantera frågan om hur materialhanteringen inom produktionsarean kan reduceras. För att utveckla en lösning på materialhanteringsproblemen har verktyg som PDCA och DMAIC använts som en grund i utvecklandet av en modell som kan tillämpas på ett medelstort producerande företag. Syftet med detta arbete är att lokalisera och identifiera aktiviteter som bidrar med slöseri inom materialhanteringen samt att effektivisera dessa aktiviteter för att reducera den totala materialhanteringen. Genom att hämta data från observationer, diskussioner och intervjuer kommer detta arbete att erbjuda läsaren en bakgrund på ett problem och en lösning i form av en modell för att lösa det aktuella problemet. Modellen kommer att erbjuda stöd i sökandet efter ineffektiviteter inom företaget för att i ett senare skede utveckla ett kostnadseffektivt förbättringsalternativ.

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