• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 66
  • 53
  • 14
  • 12
  • 9
  • 8
  • 4
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 185
  • 39
  • 32
  • 30
  • 25
  • 25
  • 24
  • 24
  • 22
  • 19
  • 16
  • 16
  • 15
  • 15
  • 15
  • 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

Development, setup and testing of a dynamic hydraulic fracture conductivity apparatus

Pongthunya, Potcharaporn 02 June 2009 (has links)
One of the most critical parameters in the success of a hydraulic fracturing treatment is to have sufficiently high fracture conductivity. Unbroken polymers can cause permeability impairment in the proppant pack and/or in the matrix along the fracture face. The objectives of this research project were to design and set up an experimental apparatus for dynamic fracture conductivity testing and to create a fracture conductivity test workflow standard. This entirely new dynamic fracture conductivity measurement will be used to perform extensive experiments to study fracturing fluid cleanup characteristics and investigate damage resulting from unbroken polymer gel in the proppant pack. The dynamic fracture conductivity experiment comprises two parts: pumping fracturing fluid into the cell and measuring proppant pack conductivity. I carefully designed the hydraulic fracturing laboratory to provide appropriate scaling of the field conditions experimentally. The specifications for each apparatus were carefully considered with flexibility for further studies and the capability of each apparatus was defined. I generated comprehensive experimental procedures for each experiment stage. By following the procedure, the experiment can run smoothly. Most of dry runs and experiments performed with sandstone were successful.
12

Process improvement proposal for the reduction of machine setup time in a copper transformation company using lean manufacturing tools

Lora-Soto, Anthony, Morales-Silva, Cristhoffer, Llontop-Jesus, Jose, Mamani, Nestor 01 January 2021 (has links)
This study aimed to identify the causes of significant problems existing in the metallurgical sector, and a solution is proposed for the setup process. We detail the theoretical background of the processes in the lean manufacturing methodology, which will be applied to a rolling machine. Further, we provide a brief description of the company and the sector’s problems. We describe success stories of companies that implemented various lean manufacturing tools. We also present some of the results achieved across sectors to gain an in-depth understanding of the technique and a practical support of the implemented model. Our proposal is based on the lean manufacturing methodology; tools such as Single Minute Exchanges of Dies, Kaizen, 5S, and value stream mapping (VSM) will be used to reduce setup times and to impact machine layout and productivity positively. We also show the implementation results of a pilot plan conducted in the company over a period of more than 3 months. / Revisión por pares
13

Métodos heurísticos para a programação em flow shop permutacional com tempos de setup separados dos tempos de processamento e independentes da seqüência de tarefas / Heuristic methods for the permutation flow shop scheduling problem with separated, non-batch, and sequence-independent setup times

Boiko, Thays Josyane Perassoli 11 June 2008 (has links)
Este trabalho dedica-se ao problema de programação em flow shop permutacional com tempos de setup separados dos tempos de processamento e independentes da seqüência de execução das tarefas com o objetivo de minimizar a duração total da programação (Makespan). Por intermédio de investigações realizadas sobre as características estruturais do problema de programação e sua solução, uma propriedade deste problema é apresentada. Esta propriedade, denominada \"Propriedade LBY\", considerando quaisquer duas tarefas adjacentes Ju e Jv (Ju imediatamente precede Jv) independentemente de suas posições na seqüência de tarefas, fornece, um limitante inferior do tempo de espera para a tarefa Jv entre o fim do seu processamento na máquina Mk e o início do seu processamento na máquina seguinte. Dois novos métodos heurísticos são desenvolvidos, com base na propriedade apresentada e no procedimento de inserção de tarefas dos conhecidos métodos N&M e NEH: um construtivo, denominado BMc; e, um melhorativo, denominado BMm. Os métodos heurísticos propostos são comparados com os métodos heurísticos melhorativos de Cao; Bedworth (1992) e Rajendran; Ziegler (1997), através de um grande número de problemas gerados aleatoriamente. Os tempos de processamento são distribuídos no intervalo [1, 99] e os tempos de setup nos intervalos de [1, 49], [1, 99], [51, 149] e [101, 199]. Os métodos são avaliados quanto à porcentagem de sucesso em obter a melhor solução, ao desvio relativo médio e o tempo médio de computação. Os resultados da experimentação computacional mostram a qualidade do método construtivo BMc e a melhor performance do método melhorativo BMm. Estes resultados são apresentados e discutidos. / This work addresses the permutation flow shop scheduling problem with separated, non-batch, and sequence-independent setup times with the objective of minimizing the total time to complete the schedule (Makespan). Following an investigation of problem structural characteristics and your solution a property of this scheduling problem is presented. This property, denoted by \"Property LBY\", given any two adjacent jobs Ju e Jv (Ju immediately precedes Jv), regardless of their position in the sequence of jobs, provides an lower bound of the waiting time for job Jv between the end of its operations on the machine Mk and the beginning on machine M(k+1). Two news heuristics methods are development, on the basis of the presented property and in the job insertion procedure of the known methods named N&M and NEH: one constructive, denote by BMc; and, one improvement, denote by BMm. The proposed heuristics methods are compared with the improvement heuristics methods of Cao; Bedworth (1992) and Rajendran; Ziegler (1997), by a large number of randomly generated problems. The processing time are sampled from a distribution ranging from [1, 99] and, the setup times are sampled from distributions ranging from [1, 49], [1, 99], [51, 149] and [101, 199]. The methods are evaluated by the percentage of success in find the best solution, the average relative deviation and the average computation time. The results of the computational investigation show the quality of the constructive heuristic method BMc and that the improvement heuristic method BMc outperforms all others. These results are presented and discussed.
14

Flexible flow line com tempos de setup: métodos heurísticos / Flexible flow line with setup times: heuristic methods

Fuchigami, Helio Yochihiro 03 May 2010 (has links)
Este trabalho aborda o problema de programação da produção em um flexible flow line com tempos de setup. De acordo com a literatura, este ambiente pode ser considerado como um caso especial do Flow Shop com múltiplas máquinas, onde as tarefas podem saltar estágios. Neste estudo, foram analisados dois problemas: o primeiro, com tempos de setup independentes da sequência, e o segundo, com setup dependente da sequência de tarefas. Além disso, o setup das máquinas para as tarefas pode ser antecipado ou não. No primeiro caso, as máquinas de um estágio podem ser preparadas para o processamento de uma tarefa antes do seu término no estágio anterior. Se o setup não pode ser antecipado, a tarefa deve esperar o seu término no estágio de produção anterior. Este ambiente produtivo pode ser encontrado em um vasto número de indústrias tais como química, eletrônica, automotiva e têxtil. A medida de desempenho dos problemas é a duração total da programação (makespan). Este é um critério apropriado para sistemas de produção com grandes cargas de trabalho e em que a utilização dos recursos produtivos em longo prazo deve ser otimizada. O exame da literatura mostrou que há poucos estudos abordando a programação em flexible flow line. Considerando este aspecto, este trabalho apresenta heurísticas construtivas originais para a obtenção de programações apropriadas ao problema mencionado. Uma extensiva experimentação computacional foi executada para avaliar o desempenho relativo das heurísticas. Os resultados experimentais foram analisados e discutidos. / This work addresses the job scheduling on a flexible flow line with separate setup times. According to the literature, this scheduling problem can be considered as a special case of the Flow Shop with multiple machines, where the jobs may skip stages. Two modeled problems have been studied. In the first scheduling problem the setup times are sequence independent, and in the second one these times are sequence dependent. Moreover, the machine setup task can be either anticipatory or non-anticipatory. In the first case, a k-stage machine may be prepared for a job processing before its completion on the k-1 production stage. Otherwise, the setup task must wait for the job completion on the former production stage. This production environment can be found in a number of industries such as chemicals, electronics, automotive, and textiles. The performance measure of the production schedules is the makespan, that is, the total time to complete the schedule. This is an appropriate performance criterion for production systems with large workloads, and where the utilization of productive resources in the long term should be optimized. The literature examination has shown that there is a small number of studies dealing with flexible flow line scheduling. Having this in mind, this work introduces original constructive heuristics in order to obtain suitable schedules for the aforementioned scheduling problem. An extensive computational experience has been carried out in order to evaluate the relative performance of the heuristics. Experimental results are discussed.
15

Etude des plages sableuses : Relations entre les vagues, le niveau d'eau, la nappe et la morphologie. / Study of sandy Beaches : relations between Waves, Water Level, Groundwater and Morphology

Petitjean, Lise 06 December 2016 (has links)
Ce travail de thèse s’inscrit dans le contexte général de l’étude de la dynamique de la frangelittorale. Le but de ce travail de thèse était l’étude des couplages entre les ondes de surface (vagues, ondeslongues dont les ondes infra-gravitaires), les variations du niveau marin et les courants ainsi que les variationsà haute-fréquence du niveau d’eau sur la plage et les déplacements de la nappe phréatique au sein de la plagesableuse. L’approche retenue est essentiellement expérimentale in-situ.La campagne de mesure ROUSTY201412 a permis de récolter un jeu de données hydro- morphodynamiquesconsidérable, qui viendra alimenter l’étude des plages sableuses dans de nombreux domaines. Elle permeten particulier de décrire l’ensemble d’une saison hivernale sur un même site soumis à une grande variété declimats de houles et de vents, ce qui en fait un jeu de données unique dans le contexte méditerranéen.Dans cette thèse nous nous intéressons à trois domaines d’étude : la dynamique de la surface libre avecl’analyse des relations existantes entre les différentes échelles (vagues, variations du niveau marin, ondeslongues, wave-setup, ...), la structure et l’évolution du courant ainsi que le lien avec la dynamique de surface,et la circulation souterraine dans la nappe de plage et en particulier sous la zone de swash. / This PhD work is part of the general context of littoral dynamic study. The purpose of this workwas to study couplings between surface waves (waves and long waves including infra-gravity waves), sea waterlevel variations and currents, as well as high-frequence water level variations on shoreline and groundwatermovements within sandy beaches. The approach is mostly experimental in-situ.The field campaign ROUSTY201412 allowed the collection of a substantial hydro- morphodynamic dataset,supplying sandy beaches studies in several fields. In particular, it will allow, on a same site, the descriptionof a full winter season under various waves and winds climates, making it a unique dataset in Mediterraneancontext.In this PhD, we are interested in three fields : free surface dynamics, including multi scale relations analysis(waves, water level variations, long waves, wave-setup, ...), currents structure and evolution linked withsurface dynamics, and groundwater circulation within the coastal aquifer and particularly under the swashzone.
16

Fix-and-Optimize Heuristic and MP-based Approaches for Capacitated Lot Sizing Problem with Setup Carryover, Setup Splitting and Backlogging

January 2015 (has links)
abstract: In this thesis, a single-level, multi-item capacitated lot sizing problem with setup carryover, setup splitting and backlogging is investigated. This problem is typically used in the tactical and operational planning stage, determining the optimal production quantities and sequencing for all the products in the planning horizon. Although the capacitated lot sizing problems have been investigated with many different features from researchers, the simultaneous consideration of setup carryover and setup splitting is relatively new. This consideration is beneficial to reduce costs and produce feasible production schedule. Setup carryover allows the production setup to be continued between two adjacent periods without incurring extra setup costs and setup times. Setup splitting permits the setup to be partially finished in one period and continued in the next period, utilizing the capacity more efficiently and remove infeasibility of production schedule. The main approaches are that first the simple plant location formulation is adopted to reformulate the original model. Furthermore, an extended formulation by redefining the idle period constraints is developed to make the formulation tighter. Then for the purpose of evaluating the solution quality from heuristic, three types of valid inequalities are added to the model. A fix-and-optimize heuristic with two-stage product decomposition and period decomposition strategies is proposed to solve the formulation. This generic heuristic solves a small portion of binary variables and all the continuous variables rapidly in each subproblem. In addition, the case with demand backlogging is also incorporated to demonstrate that making additional assumptions to the basic formulation does not require to completely altering the heuristic. The contribution of this thesis includes several aspects: the computational results show the capability, flexibility and effectiveness of the approaches. The average optimality gap is 6% for data without backlogging and 8% for data with backlogging, respectively. In addition, when backlogging is not allowed, the performance of fix-and-optimize heuristic is stable regardless of period length. This gives advantage of using such approach to plan longer production schedule. Furthermore, the performance of the proposed solution approaches is analyzed so that later research on similar topics could compare the result with different solution strategies. / Dissertation/Thesis / Masters Thesis Industrial Engineering 2015
17

Flexible flow line com tempos de setup: métodos heurísticos / Flexible flow line with setup times: heuristic methods

Helio Yochihiro Fuchigami 03 May 2010 (has links)
Este trabalho aborda o problema de programação da produção em um flexible flow line com tempos de setup. De acordo com a literatura, este ambiente pode ser considerado como um caso especial do Flow Shop com múltiplas máquinas, onde as tarefas podem saltar estágios. Neste estudo, foram analisados dois problemas: o primeiro, com tempos de setup independentes da sequência, e o segundo, com setup dependente da sequência de tarefas. Além disso, o setup das máquinas para as tarefas pode ser antecipado ou não. No primeiro caso, as máquinas de um estágio podem ser preparadas para o processamento de uma tarefa antes do seu término no estágio anterior. Se o setup não pode ser antecipado, a tarefa deve esperar o seu término no estágio de produção anterior. Este ambiente produtivo pode ser encontrado em um vasto número de indústrias tais como química, eletrônica, automotiva e têxtil. A medida de desempenho dos problemas é a duração total da programação (makespan). Este é um critério apropriado para sistemas de produção com grandes cargas de trabalho e em que a utilização dos recursos produtivos em longo prazo deve ser otimizada. O exame da literatura mostrou que há poucos estudos abordando a programação em flexible flow line. Considerando este aspecto, este trabalho apresenta heurísticas construtivas originais para a obtenção de programações apropriadas ao problema mencionado. Uma extensiva experimentação computacional foi executada para avaliar o desempenho relativo das heurísticas. Os resultados experimentais foram analisados e discutidos. / This work addresses the job scheduling on a flexible flow line with separate setup times. According to the literature, this scheduling problem can be considered as a special case of the Flow Shop with multiple machines, where the jobs may skip stages. Two modeled problems have been studied. In the first scheduling problem the setup times are sequence independent, and in the second one these times are sequence dependent. Moreover, the machine setup task can be either anticipatory or non-anticipatory. In the first case, a k-stage machine may be prepared for a job processing before its completion on the k-1 production stage. Otherwise, the setup task must wait for the job completion on the former production stage. This production environment can be found in a number of industries such as chemicals, electronics, automotive, and textiles. The performance measure of the production schedules is the makespan, that is, the total time to complete the schedule. This is an appropriate performance criterion for production systems with large workloads, and where the utilization of productive resources in the long term should be optimized. The literature examination has shown that there is a small number of studies dealing with flexible flow line scheduling. Having this in mind, this work introduces original constructive heuristics in order to obtain suitable schedules for the aforementioned scheduling problem. An extensive computational experience has been carried out in order to evaluate the relative performance of the heuristics. Experimental results are discussed.
18

Métodos heurísticos para a programação em flow shop permutacional com tempos de setup separados dos tempos de processamento e independentes da seqüência de tarefas / Heuristic methods for the permutation flow shop scheduling problem with separated, non-batch, and sequence-independent setup times

Thays Josyane Perassoli Boiko 11 June 2008 (has links)
Este trabalho dedica-se ao problema de programação em flow shop permutacional com tempos de setup separados dos tempos de processamento e independentes da seqüência de execução das tarefas com o objetivo de minimizar a duração total da programação (Makespan). Por intermédio de investigações realizadas sobre as características estruturais do problema de programação e sua solução, uma propriedade deste problema é apresentada. Esta propriedade, denominada \"Propriedade LBY\", considerando quaisquer duas tarefas adjacentes Ju e Jv (Ju imediatamente precede Jv) independentemente de suas posições na seqüência de tarefas, fornece, um limitante inferior do tempo de espera para a tarefa Jv entre o fim do seu processamento na máquina Mk e o início do seu processamento na máquina seguinte. Dois novos métodos heurísticos são desenvolvidos, com base na propriedade apresentada e no procedimento de inserção de tarefas dos conhecidos métodos N&M e NEH: um construtivo, denominado BMc; e, um melhorativo, denominado BMm. Os métodos heurísticos propostos são comparados com os métodos heurísticos melhorativos de Cao; Bedworth (1992) e Rajendran; Ziegler (1997), através de um grande número de problemas gerados aleatoriamente. Os tempos de processamento são distribuídos no intervalo [1, 99] e os tempos de setup nos intervalos de [1, 49], [1, 99], [51, 149] e [101, 199]. Os métodos são avaliados quanto à porcentagem de sucesso em obter a melhor solução, ao desvio relativo médio e o tempo médio de computação. Os resultados da experimentação computacional mostram a qualidade do método construtivo BMc e a melhor performance do método melhorativo BMm. Estes resultados são apresentados e discutidos. / This work addresses the permutation flow shop scheduling problem with separated, non-batch, and sequence-independent setup times with the objective of minimizing the total time to complete the schedule (Makespan). Following an investigation of problem structural characteristics and your solution a property of this scheduling problem is presented. This property, denoted by \"Property LBY\", given any two adjacent jobs Ju e Jv (Ju immediately precedes Jv), regardless of their position in the sequence of jobs, provides an lower bound of the waiting time for job Jv between the end of its operations on the machine Mk and the beginning on machine M(k+1). Two news heuristics methods are development, on the basis of the presented property and in the job insertion procedure of the known methods named N&M and NEH: one constructive, denote by BMc; and, one improvement, denote by BMm. The proposed heuristics methods are compared with the improvement heuristics methods of Cao; Bedworth (1992) and Rajendran; Ziegler (1997), by a large number of randomly generated problems. The processing time are sampled from a distribution ranging from [1, 99] and, the setup times are sampled from distributions ranging from [1, 49], [1, 99], [51, 149] and [101, 199]. The methods are evaluated by the percentage of success in find the best solution, the average relative deviation and the average computation time. The results of the computational investigation show the quality of the constructive heuristic method BMc and that the improvement heuristic method BMc outperforms all others. These results are presented and discussed.
19

Avaliação do uso de troca rápida de ferramentas em fornecedores de usinagem do Estado de São Paulo / Evaluation of the use of quick tool exchange by machining suppliers in companies of São Paulo State

Barduzzi, Jaqueline 29 February 2016 (has links)
Submitted by Nadir Basilio (nadirsb@uninove.br) on 2016-12-01T13:36:09Z No. of bitstreams: 1 Jaqueline Barduzzi.pdf: 2154670 bytes, checksum: 2087badf8d9c70f0aaa0a763869b38a7 (MD5) / Made available in DSpace on 2016-12-01T13:36:09Z (GMT). No. of bitstreams: 1 Jaqueline Barduzzi.pdf: 2154670 bytes, checksum: 2087badf8d9c70f0aaa0a763869b38a7 (MD5) Previous issue date: 2016-02-29 / This essay presents a study on the exchange of tools in suppliers of machining service from São Paulo State. We pursued to identify if companies apply the principles of Quick-Change Tools – TRF - and discern the benefits provided by this application. After a survey conducted with representatives of 24,1% of the companies machining industry throughout the State, this study observes the individual and collective contributions of the companies concerning the exchange of industry tools. The analyses were conducted by the ROC algorithm (Rank Order Clustering) aimed at the formation of groups of companies in order to identify those whom know the benefits from the TRF and apply, those who claim knowing the benefits but don´t apply TRF effectively, and those who claim to ignore the benefits and end up not applying TRF effectively. The results revealed that the vast majority of companies know the methodology of SMED and realize its benefits; however, analysis of concerns relating to the changeover activities and their respective times also showed that more than half of companies surveyed do not effectively apply this methodology. / Esta dissertação apresenta um estudo sobre a troca de ferramentas nas empresas fornecedoras de serviços de usinagem do Estado de São Paulo. Procurou-se identificar se as empresas aplicam os princípios da Troca Rápida de Ferramentas - TRF e se conhecem os benefícios de sua aplicação. A partir de uma survey exploratória realizada com responsáveis do setor de usinagem de 24,1% das empresas em todo o Estado, este estudo analisa as percepções das empresas em relação à troca rápida de ferramentas. As análises foram conduzidas com uma adaptação do algoritmo ROC (Rank Order Clustering) visando a formação de grupos de empresas a fim de identificar aquelas que conhecem os benefícios advindos da TRF e a aplicam, aquelas que afirmam conhecer os benefícios mas não aplicam de forma efetiva a TRF, e aquelas que afirmam desconhecer os benefícios e acabam não aplicando a TRF efetivamente. Os resultados demonstraram que a grande maioria das empresas conhecem a metodologia de TRF e percebem seus benefícios; no entanto, as análises de questões relativas às atividades de troca de ferramentas e aos seus respetivos tempos também permitiram concluir que mais da metade das empresas pesquisadas não aplicam efetivamente essa metodologia.
20

Troca rápida de ferramenta com auxilio de simulação computacional aplicada em processo de extrusão de compostos

Janamilton Medeiros Oliveira 29 January 2013 (has links)
The competitively has transformed manufacturing environments, where the companys processes with increasingly complex seeking to reduce waste generated in manufacturing environment that not add value to the product and thus the setup machine downtime includes wasting time. The methodology for rapid exchange tool is used to reduce the time setup increasing productivity line where is implanted. This work must a main goal is implement as a technique for quick change tool in a line of extrusion of polymeric compounds with aid of computer simulation. Company producing polymeric compounds have as goal to be world in reference time setup with respect to other plants and accordingly justified the implementation of rapid exchange tool in your production line. This work have a approach quantitative diagnosis with the current situation, by means of documents and methods used, and trial with intervention of variables with computer simulation of the current situation and changes suggested by simulation. The results obtained after the implementation of expressive and improvements have been following the steps for proposal literature, got to get up, in certain cases of setup, the `one touch exchange of die and thus using the rapid exchange tool methodology as a tool for continuous improvement, attained the goal in reducing setup. / A competitividade vem transformando os ambientes de manufatura, onde as empresas com processos cada vez mais complexos procuram reduzir os desperdícios gerados no ambiente fabril que não agregam valor ao produto e desse modo o setup de máquina engloba tempo ocioso. A metodologia de troca rápida de ferramenta é utilizada para reduzir os tempos de setup aumentando a produtividade da linha onde é implantado. Esta dissertação tem como objetivo principal implantar a técnica de troca rápida de ferramenta em uma linha de extrusão de compostos poliméricos com auxilio de simulação computacional. A empresa produtora de compostos poliméricos tem como meta ser referência mundial em tempo de setup com relação a outras plantas e dessa forma justifica-se a implantação da troca rápida de ferramenta em sua linha de produção. Esta dissertação utiliza uma abordagem quantitativa com diagnóstico da situação atual, por meio de documentos e métodos utilizados, e experimentação com intervenção das variáveis com simulação computacional e modificação da situação atual sugerida pela simulação. Os resultados obtidos após a implantação das melhorias foram expressivos e, seguindo as etapas proposta pela literatura, conseguiu-se chegar, em determinados casos de setup, à troca de ferramenta em um toque e dessa forma, utilizando a metodologia de troca rápida de ferramenta como ferramenta de melhoria contínua, foi possível atingir a meta na redução do tempo de setup.

Page generated in 0.0204 seconds