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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A indústria marítima mundial: uma análise sob a perspectiva da dinâmica de sistemas. / The maritime industry: a system dynamics approach.

Santos, Joaquim Rocha dos 25 April 2007 (has links)
A indústria marítima mundial (IMM) tem um comportamento reconhecidamente cíclico, em alguns momentos os armadores fazem grandes fortunas, em outros amargam enormes prejuízos, o que também ocorre com os demais setores dessa indústria. O objetivo deste trabalho é investigar a natureza e as causas desse comportamento. A IMM é um sistema complexo que pode ser dividido em quatro subsistemas principais: o mercado de frete, o mercado de navios de segunda mão, a indústria de construção naval e a indústria de demolição. Nem sempre as influências que essas quatro partes do mercado exercem umas sobre as outras é bem compreendida. Embora a IMM seja influenciada pela economia internacional, observou-se que seu comportamento é fortemente influenciado por fatores endógenos, tais como: sua própria estrutura; as relações organizacionais; e as decisões gerenciais que ocorrem nas várias partes dessa indústria. Adicionalmente, pode ser observado que tais relações têm características essencialmente dinâmicas. A Dinâmica de Sistemas (DS) parece ser uma ferramenta adequada à análise deste tipo de mercado, e, por essa razão, foi o método adotado para estudá-lo. Nesse método um modelo matemático é construído a partir do conhecimento descritivo das relações causais e funcionais existentes no mundo real. Foi elaborado um modelo preliminar que inclui três setores principais da indústria: o financeiro, o mercado de frete e a indústria de construção naval. Tais setores cobrem a maioria das interações relevantes determinantes do comportamento. O modelo é uma simplificação do mundo real em vários aspectos e se baseia em certas assunções, previamente estabelecidas. Apesar das simplificações, assunções e omissões, o comportamento do modelo, como pode ser observado nos resultados obtidos, reproduz de maneira razoável as séries históricas escolhidas para comparação (os Modos de Referência). Foi observado que a decisão pela encomenda de novos navios é um importante gerador do comportamento cíclico. Neste estudo preliminar tal decisão é fundamentada somente na análise da previsão de demanda de transporte marítimo e na expectativa de lucro dos armadores, que é função das receitas obtidas pelos armadores, seus custos totais, e uma taxa de retorno sobre o investimento, que foi arbitrada em 15%. O modelo aqui apresentado pode servir de fundamento para um maior desenvolvimento dessa área de investigação, e como guia para outros trabalhos. Espera-se que futuros trabalhos sejam realizados, de maneira a que se obtenha uma forte compreensão da IMM. Os resultados obtidos permitem concluir que a Dinâmica de Sistemas é uma ferramenta válida para investigação, e a continuação desta linha de pesquisa pode trazer resultados compensadores. / It is recognized that the world maritime industry has a cyclical behavior. Shipowners face periods of fabulous profits and disastrous miscalculations. The object of this work is to investigate the nature and causes of such behavior. The maritime industry is a complex system that can be split in four main markets: freight; second-hand ship; new ships and ships for demolition. The influences of one part on the others are not always well understood. Although the world economy influences the maritime industry, it has been observed that its behavior is fundamentally endogenous, such as: its own structure; the relationships between its parts; and the process of decision making. Furthermore, this behavior has strong dynamic characteristics. System Dynamics has been proving to be a suitable tool for analyzing such systems and, therefore, has been chosen. In this method a mathematical model is developed from a functional and causal description of the real system. A preliminary model was formulated which include three main sectors of industry: financial, freight market and shipbuilding industry. These sectors cover most of the relevant interactions and determinants of the behavior. The model simplified from the real world in many instances, and is based on certain assumptions previously stated. In spite of the simplifications, assumptions and omissions, the behavior of the model, as shown in computer results, replicates the most fundamental characteristics of the real world, the historical trends chosen as reference modes. It has been observed that the new ships ordering decisions are extremely important in stimulating the cyclical behavior. In this preliminary work this decision is founded on demand forecast and expected profitability of shipowners. This profitability is assumed as a function of shipowners total costs and a rate of return of investment, assumed as 15%. The model developed herein can serve as foundation structure upon which to develop more fully this area of investigation, and as a guide in such developments. It is hoped that further work is carried out towards gaining a sounder understanding of the maritime economics market cycles. Considering the results presented so far, it is possible to conclude that System Dynamics is a valid tool for investigation and can yield rewarding results.
12

Utilização de algoritmo genético para apoiar a simulação de sistemas complexos / Using genetic algorithms to support complex systems simulation

Anacleto, Junia Coutinho 22 November 1996 (has links)
Este trabalho apresenta a técnica de Algoritmo Genético para apoiar o processo de modelagem e simulação de sistemas complexos. Tal técnica pode ser vista como uma opção as técnicas tradicionais de modelagem e análise dos dados de simulação, simplificando todo esse processo, por suas características de simplicidade e generalidade, não exigindo conhecimento especifico do domínio do problema. É apresentada uma ferramenta computacional - SimAG - baseada em Algoritmo Genético para modelagem e simulação de sistemas dessa natureza. Um exemplo de aplicação e estudado, onde pode ser constatada a viabilidade da utilização da técnica no processo de simulação / This work presents the Genetic Algorithm technique supporting the process of complex systems modeling and simulation. Such technique can be seen as an option to both the traditional modeling and the simulation data analysis techniques. Due to its inherent simplicity and generic application, it simplifies the whole process of simulation, demanding no specific knowledge over the problem domain. A genetic algorithm based computational tool - SimAG - for the modeling and simulation of such systems is here presented, and an example of its use is analyzed, thus demonstrating the feasibility of this new technique application in simulation processes
13

Simulation of a Cogeneration System in Developing the Concept of Smart Energy Networks

Chai, Dong Sig 16 August 2012 (has links)
In recent years, there has been significant pressure to reduce greenhouse gas emissions, to achieve higher efficiency and to integrate greater amounts of renewable energy resources in energy system. Governments at all levels have recognized the environmental impacts of the energy sector, as well as the ways in which this sector is closely-linked to a range of economic issues (e.g., industrial development, inflationary prices and local economic development). In general, every effort has been made to cope with the challenges in providing a sustainable energy solution for achieving the goals. Even though the concept of “Smart Grid” has recently been highlighted in the electricity sector to improve efficiency of energy use and to reduce greenhouse gases to achieve business goals, the driving initiatives for generating a Smart Grid are straightforward and its scope and functions differ from a Smart Energy Network (SEN) which has a broader boundary and more components. A comprehensive concept of SEN beyond Smart Grid is presented to effectively integrate energy systems which can not only cover available energy resources but also address sustainability issues. The availability of new technologies for utilizing the renewable energy such as solar, wind and biomass, and reducing the carbon footprint of fossil fuels by including natural gas within an integrated energy network provides a base for better conservation of energy usage and providing a cleaner environment. Moreover, the new energy carriers such as hydrogen and sustainable natural gas integrated into cogeneration systems should be taken into account when such a network is developed. A cogeneration system is a promising solution for effectively supplying energy to district consumers for high density urban environment. In this thesis, a new community-scale cogeneration system is modeled using TRNSYS (Transient System Simulation) software, which enables analysis of transient characteristics of cogeneration and to investigate critical factors which should be considered for successful integration into a SEN. This thesis focuses on defining what a Smart Energy Network is, its functions and the critical criteria of demonstrating and validating this concept, and developing a model for cogeneration system according to the concept of Smart Energy Network.
14

A Study of Embedding Collaborative Replenishment Mechanism within e-Procurement Platform by System Simulation Technique

Liu, Ling-Chun 23 August 2010 (has links)
Cost control and rapid response to market changes have become keys to survival of modern enterprises, especially during today¡¦s ever-increasing business competitions. Communication obstacles such as information inconsistency and delays still exist among members of supply chains, leading to problems like inventory turnover decline and lead time stretch, and eventually are resulting inefficient reactions to the demand of final customers. In recent years, a number of firms have begun to adopt various electronic supply chain management systems to enhance the quality and efficiency of business communication among their suppliers. These systems have helped businesses parties simplify their communication time and enhance business partnerships and alliances, thus enhanced their overall competitive advantages. In additional, the wide implementation of such information technology is promoting healthy integration among industries towards much more efficient supply chains. In a typical supply chain management scenario, businesses with ineffective operation management capability are often disturbed by rapid changes in market demands, short product life cycles, and lacks of integration from levels of suppliers, because the curial marketing information has not been efficiently delivered to proper functional departments, disabling the entire organization to reflect the changing demands and market conditions. This study is aimed to business and industrial models on examining firms¡¦ competitive advantages and their relationship with suppliers. Based on the result of the analysis, it would be the reference to build up the system of e-procurement. Moreover, in market-based systems, it always exits supply-demand relationship between suppliers and buyer powers, when facing high supplier power; companies should provide sufficient information to negotiate with the suppliers. The research is on the basis of Taiwan optoelectronic industry to investigate the companies of the TFT-LCD panel, and the supply chains of the industry. In analyzing the main TFT-LCD panel providers, the paper will probe into TFT-LCD firms to import e- procurement system by building the CPFR mechanism to improve the reaction capacity of businesses and to respond to the market rapid change. The study exerts simulation software, Arena, to conduct simulation and improvement of such models,then according to the simulation results to utilize them as a reference to purchasing cooperative enterprise into the future operation.
15

A Study of The Service Quality Improvement of The Network Deployment Process for The Telecommunications Industry by Simulation Technique

Chang, Jung-Wen 24 August 2011 (has links)
With the liberalization of the telecommunications industry, Taiwan has become a broadband networked society. People hope greatly that the current three private fixed network companies will break the telecommunications monopoly and bring new technology. Nevertheless, due to the fact that the existing service provider, Chunghwa Telecom, keeps raising difficulties over the connection of their lines and the regional governments also have many restrictions of the excavation and pipe laying, the service is unavailable in the place where there is no network deployment. Thus the fixed network companies build networks strategically in high-income metropolitan area and industrial park. The related quality management of network building is much significant. A service blueprinting will identify possible fail points and weak links in the service delivery process and then improve service quality. This study of the analysis of the telecommunications network deployment is to explore possible fail points in the process and provide improvement plans through service blueprints. In order to know the results of process improvement, system simulation which can build the original and improved process modes and ARENA process simulation software for simulation and analysis in a variety of conditions will be used. When the related industries establish the perfect service model, this is for their reference.
16

Theory of Constraints applied to multi-project management in resource allocation and monitoring mechanisms

Huang, Ching-ju 17 February 2012 (has links)
As the world¡¦s high degree of urbanization, greenhouse gas emission by vehicles, home appliances and industrial production is increasing year by year and according to the UNEP (United Nations Environment Programme) report urban carbon-dioxide emissions accounted for 80% of total global emissions. In order to encourage the alternative energy development, Taiwan government actively promotes the subsidy for alternative energy implementation, thus making the solar energy industry booming in recent years. Based on the government procurement competition mechanism, the procurement competition needs to be transparent and fair. Faced with competition in the industry, companies must reduce costs and improve quality while also required to enhance the customer satisfaction. Therefore, a good engineering project control becomes the most important factor to enhance a company's competitive ability. Particularly, when professional management is getting more and more important nowadays, solar energy system¡¦s building construction is not only limited to technology and equipment level, but also the enterprise configuration of internal human resources and outsourcing. Moreover, how to minimize cost and how to use efficient way to make the project work on schedule are the important issues for policy makers. This study is based on a domestic solar systems engineering project, and focuses on the distribution and configuration of the limited internal and external resources of multiple projects in progress. It uses the Critical Chain Project Management in the Theory of Constraints to break through limitations. VBA programming is used to find the minimum cost of human resource conflict in the project scheduling, furthermore Arena simulation system is utilized to establish the best configuration of human resources deployment to provide decision-making mechanism. The simulation result is verified that it can really help to provide a decision-making reference to project managers to obtain the ideal scheduling and resource allocation.
17

Simulation of a Cogeneration System in Developing the Concept of Smart Energy Networks

Chai, Dong Sig 16 August 2012 (has links)
In recent years, there has been significant pressure to reduce greenhouse gas emissions, to achieve higher efficiency and to integrate greater amounts of renewable energy resources in energy system. Governments at all levels have recognized the environmental impacts of the energy sector, as well as the ways in which this sector is closely-linked to a range of economic issues (e.g., industrial development, inflationary prices and local economic development). In general, every effort has been made to cope with the challenges in providing a sustainable energy solution for achieving the goals. Even though the concept of “Smart Grid” has recently been highlighted in the electricity sector to improve efficiency of energy use and to reduce greenhouse gases to achieve business goals, the driving initiatives for generating a Smart Grid are straightforward and its scope and functions differ from a Smart Energy Network (SEN) which has a broader boundary and more components. A comprehensive concept of SEN beyond Smart Grid is presented to effectively integrate energy systems which can not only cover available energy resources but also address sustainability issues. The availability of new technologies for utilizing the renewable energy such as solar, wind and biomass, and reducing the carbon footprint of fossil fuels by including natural gas within an integrated energy network provides a base for better conservation of energy usage and providing a cleaner environment. Moreover, the new energy carriers such as hydrogen and sustainable natural gas integrated into cogeneration systems should be taken into account when such a network is developed. A cogeneration system is a promising solution for effectively supplying energy to district consumers for high density urban environment. In this thesis, a new community-scale cogeneration system is modeled using TRNSYS (Transient System Simulation) software, which enables analysis of transient characteristics of cogeneration and to investigate critical factors which should be considered for successful integration into a SEN. This thesis focuses on defining what a Smart Energy Network is, its functions and the critical criteria of demonstrating and validating this concept, and developing a model for cogeneration system according to the concept of Smart Energy Network.
18

PPS-Systeme auf Basis von Simulation /

Steude, Volker. Werners, Brigitte. January 2003 (has links) (PDF)
Univ., Diss.--Bochum, 2000.
19

Impacts of energy storage on power systems with stochastic generation

Klöckl, Bernd January 2007 (has links)
Zugl.: Zürich, Techn. Hochsch., Diss., 2007
20

A indústria marítima mundial: uma análise sob a perspectiva da dinâmica de sistemas. / The maritime industry: a system dynamics approach.

Joaquim Rocha dos Santos 25 April 2007 (has links)
A indústria marítima mundial (IMM) tem um comportamento reconhecidamente cíclico, em alguns momentos os armadores fazem grandes fortunas, em outros amargam enormes prejuízos, o que também ocorre com os demais setores dessa indústria. O objetivo deste trabalho é investigar a natureza e as causas desse comportamento. A IMM é um sistema complexo que pode ser dividido em quatro subsistemas principais: o mercado de frete, o mercado de navios de segunda mão, a indústria de construção naval e a indústria de demolição. Nem sempre as influências que essas quatro partes do mercado exercem umas sobre as outras é bem compreendida. Embora a IMM seja influenciada pela economia internacional, observou-se que seu comportamento é fortemente influenciado por fatores endógenos, tais como: sua própria estrutura; as relações organizacionais; e as decisões gerenciais que ocorrem nas várias partes dessa indústria. Adicionalmente, pode ser observado que tais relações têm características essencialmente dinâmicas. A Dinâmica de Sistemas (DS) parece ser uma ferramenta adequada à análise deste tipo de mercado, e, por essa razão, foi o método adotado para estudá-lo. Nesse método um modelo matemático é construído a partir do conhecimento descritivo das relações causais e funcionais existentes no mundo real. Foi elaborado um modelo preliminar que inclui três setores principais da indústria: o financeiro, o mercado de frete e a indústria de construção naval. Tais setores cobrem a maioria das interações relevantes determinantes do comportamento. O modelo é uma simplificação do mundo real em vários aspectos e se baseia em certas assunções, previamente estabelecidas. Apesar das simplificações, assunções e omissões, o comportamento do modelo, como pode ser observado nos resultados obtidos, reproduz de maneira razoável as séries históricas escolhidas para comparação (os Modos de Referência). Foi observado que a decisão pela encomenda de novos navios é um importante gerador do comportamento cíclico. Neste estudo preliminar tal decisão é fundamentada somente na análise da previsão de demanda de transporte marítimo e na expectativa de lucro dos armadores, que é função das receitas obtidas pelos armadores, seus custos totais, e uma taxa de retorno sobre o investimento, que foi arbitrada em 15%. O modelo aqui apresentado pode servir de fundamento para um maior desenvolvimento dessa área de investigação, e como guia para outros trabalhos. Espera-se que futuros trabalhos sejam realizados, de maneira a que se obtenha uma forte compreensão da IMM. Os resultados obtidos permitem concluir que a Dinâmica de Sistemas é uma ferramenta válida para investigação, e a continuação desta linha de pesquisa pode trazer resultados compensadores. / It is recognized that the world maritime industry has a cyclical behavior. Shipowners face periods of fabulous profits and disastrous miscalculations. The object of this work is to investigate the nature and causes of such behavior. The maritime industry is a complex system that can be split in four main markets: freight; second-hand ship; new ships and ships for demolition. The influences of one part on the others are not always well understood. Although the world economy influences the maritime industry, it has been observed that its behavior is fundamentally endogenous, such as: its own structure; the relationships between its parts; and the process of decision making. Furthermore, this behavior has strong dynamic characteristics. System Dynamics has been proving to be a suitable tool for analyzing such systems and, therefore, has been chosen. In this method a mathematical model is developed from a functional and causal description of the real system. A preliminary model was formulated which include three main sectors of industry: financial, freight market and shipbuilding industry. These sectors cover most of the relevant interactions and determinants of the behavior. The model simplified from the real world in many instances, and is based on certain assumptions previously stated. In spite of the simplifications, assumptions and omissions, the behavior of the model, as shown in computer results, replicates the most fundamental characteristics of the real world, the historical trends chosen as reference modes. It has been observed that the new ships ordering decisions are extremely important in stimulating the cyclical behavior. In this preliminary work this decision is founded on demand forecast and expected profitability of shipowners. This profitability is assumed as a function of shipowners total costs and a rate of return of investment, assumed as 15%. The model developed herein can serve as foundation structure upon which to develop more fully this area of investigation, and as a guide in such developments. It is hoped that further work is carried out towards gaining a sounder understanding of the maritime economics market cycles. Considering the results presented so far, it is possible to conclude that System Dynamics is a valid tool for investigation and can yield rewarding results.

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