• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 12
  • 9
  • 6
  • 6
  • 5
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 38
  • 38
  • 8
  • 8
  • 6
  • 6
  • 6
  • 6
  • 6
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 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

Fuzzy C-Means Clustering Approach to Design a Warehouse Layout

Naik, Vaibhav C 08 July 2004 (has links)
Allocation of products in a warehouse is done by various storage policies. These are broadly classified into three main categories: dedicated storage, randomized storage, and class-based storage. In dedicated storage policy a product is assigned a designated slot while in random storage policy incoming product is randomly assigned a storage location close to the input/output point. Finally, the class-based storage is a mixed policy where products are randomly assigned within their fixed class. Dedicated storage policy is most commonly used in practice. While designing large warehouse layout, the product information in terms of throughput and storage level is either uncertain or is not available to the warehouse designer. Hence it is not possible to locate products on the basis of the throughput to storage ratio method used in the above mentioned storage location policies. To take care of this uncertainty in product data we propose a fuzzy C-means clustering (FCM) approach. This research is mainly directed to improve the efficiency (distance or time traveled) by designing a fuzzy logic based warehouse with large number of products. The proposed approach looks for similarity in the product data to form clusters. The obtained clusters can be directly utilized to develop the warehouse layout. Further, it is investigated if the FCM approach can take into account other factors such as product size, similarity and/or characteristics to generate layouts which are not only efficient in terms of reducing distance traveled to store/retrieve products but are effective in terms of retrieval time, space utilization and/or better material control.
22

Fuzzy Vulnerability Assessment Model Of Coastal Areas To Sea Level Rise

Ozyurt, Gulizar 01 October 2010 (has links) (PDF)
Climate change and anticipated impacts of sea level rise such as increased coastal erosion, inundation, flooding due to storm surges and salt water intrusion to freshwater resources will affect all the countries but mostly small island countries of oceans and low-lying lands along coastlines. Turkey having 8333 km of coastline including physically, ecologically and socio-economically important low-lying deltas should also prepare for the impacts of sea level rise as well as other impacts of climate change while participating in adaptation and mitigation efforts. Thus, a coastal vulnerability assessment of Turkey to sea level rise is needed both as a part of coastal zone management policies for sustainable development and as a guideline for resource allocation for preparation of adaptation options for upcoming problems due to sea level rise. In this study, a fuzzy coastal vulnerability assessment model (FCVI) of a region to sea level rise using physical and human activity indicators of impacts of sea level rise which use commonly available data are developed. The results enable decision makers to compare and rank different regions according to their vulnerabilities to sea level rise, to prioritize impacts of sea level rise on the region according to the vulnerability of the region to each impact and to determine the most vulnerable parameters for planning of adaptation measures to sea level rise. The sensitivity and uncertainty analysis performed for the results of the model (FCVI) is the first time application of a fuzzy uncertainty analysis model to coastal vulnerability assessments. These analysis ensure that the decision makers could be able to interpret the results of such vulnerability assessments based primarily on expert perceptions accurately enough. This in turn, would increase the confidence levels of adaptation measures and as well as accelerate implementation of adaptation of coastal areas to climate change. The developed coastal vulnerability assessment model is applied successfully to determine the vulnerability of G&ouml / ksu, G&ouml / cek and Amasra regions of Turkey that have different geological, ecological and socio-economical properties. The results of the site studies show that G&ouml / ksu has high vulnerability, G&ouml / cek has moderate vulnerability and Amasra shows low vulnerability to sea level rise. These results are in accordance with the general literature on impacts of sea level rise at different geomorphological coastal areas thus the applicability of fuzzy vulnerability assessment model (FCVI) to coastal areas is validated.
23

Enquadramento tarifário de energia elétrica em agroindústria utilizando teoria Fuzzy

Manzine, Luiz Gonzaga [UNESP] 05 November 2004 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:31:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-11-05Bitstream added on 2014-06-13T19:20:49Z : No. of bitstreams: 1 manzine_lg_dr_botfca.pdf: 570411 bytes, checksum: 7ffe63fb122d825827f76347ba38c828 (MD5) / Universidade Estadual Paulista (UNESP) / O presente trabalho tem como objetivo utilizar a Teoria Fuzzy para obtenção de uma metodologia alternativa na escolha da estrutura tarifária de energia elétrica mais conveniente para a agroindústria e, em conseqüência, colaborar, reduzindo também os custos da oferta de energia elétrica para o país. A metodologia citada utiliza como variáveis principais o índice de utilização de energia elétrica e o fator de carga do horário de ponta. Estes dois parâmetros elétricos, juntamente com o fator de carga do horário fora de ponta, fornecem o enquadramento tarifário que mais se ajusta a uma determinada UC. Uma aplicação da metodologia estudada é apresentada num estudo de caso, envolvendo resultados obtidos com a migração tarifária de uma UC e ainda uma abordagem comparando os preços médios da energia elétrica para um consumidor em pleno funcionamento e para um projeto de planta elétrica. O Modelo Fuzzy alternativo construído teve desempenho comparável ao modelo, usando as fórmulas de preço médio de energia elétrica para o enquadramento tarifário de uma UC, fato confirmado no estudo de caso levado a efeito neste trabalho. Relativamente ao estudo de caso, chegou-se à conclusão afirmativa para a migração tarifária da ETC para a MTHSV, com diminuição no valor da demanda contratada. As análises feitas com o GMG, instalado na UC, mostraram ganho financeiro ao se gerar energia elétrica na atual estrutura e organização da linha de produção da UC, sendo desaconselhável sob o ponto de vista financeiro, se o GMG tiver de ser adquirido. Quanto ao controle das demandas de potências solicitadas, estudos mostraram que é necessário, não sendo, porém viável levando-se em conta o aspecto estritamente financeiro com um controlador de demanda nos moldes propostos por uma empresa especializada, consultada com esta finalidade. / The present work aims to use Fuzzy Theory to obtain an alternative methodology in choosing the most convenient tariff structure of electric energy for agroindustry and as consequence to cooperate for its rational use and also reduce the costs in offering electric energy for the country. The methodology uses as main variables the index of electric energy usage and the load factor at peak hours. These two electric parameters along with the load factor out of peak hours make up the tariff adjustment which best applies to a determined consuming unit. One usage of the studied methodology is shown in a case study involving obtained results from tariff migration of one consuming unit. It is also presented an approach comparing average tariff of electric energy for consumers at full work as well as for an electric plant project. The built alternative Fuzzy Model had a performance comparable to the main model using formulas of electric energy average tariff for tariff adjustment of one consuming unit. Such procedure was confirmed in the case study carried out in this work. Concerning the case study there was a positive conclusion for tariff migration of CCT to GSTTM with a decrease on the value of the contracted demand. Analysis carried out with GMG, which was installed at consuming unit, showed a financial profit when generating electric energy on the current structure and organization of production line at consuming unit thus being unadvisable under financial aspects if GMC is to be purchased. Researches show that it is necessary the control of required energy demand. However it is not viable considering only the financial aspects with a demand controller under the proposed models for a specialized company which was consulted for such aim.
24

Desenvolvimento de um modelo fuzzy para otimização da energia gerada por um sistema híbrido (solar-fotovoltaico e eólico)

Caneppele, Fernando de Lima [UNESP] 30 November 2007 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:24:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-11-30Bitstream added on 2014-06-13T18:21:07Z : No. of bitstreams: 1 caneppele_fl_me_botfca.pdf: 1429117 bytes, checksum: c8c896af07e13fd2373df60b74a0e4c2 (MD5) / O uso de energias alternativas e renováveis tem sido cada vez mais discutido em todos os setores da sociedade. O interesse nessas fontes de energias, alternativas e renováveis, é de fundamental importância, tanto no que se refere à escassez, quanto ao preço do petróleo, além das questões ambientais envolvidas no uso dessas energias. Sistemas de geração eólica e fotovoltaica com armazenamento de energia em baterias tem-se apresentado como uma forma de geração alternativa de energia. A variabilidade na intensidade da energia eólica e solar pode ser contornada pela complementação entre uma fonte e outra, ou pela maior estabilidade configurada à geração do sistema. O objetivo desta dissertação é criar uma metodologia fuzzy e simular seu uso no controle inteligente de um sistema híbrido de geração de energia elétrica, utilizando as energias solar-fotovoltaica e eólica. Quando utilizamos um sistema de controle baseado na lógica fuzzy, é atingido o ponto de máxima geração de energia, desta forma transferindo toda a energia gerada à partir das fontes alternativas, solar-fotovoltaica e eólica, à carga e/ou as baterias quando seu uso não imediato. O modelo utilizado adota três variáveis de entrada, que são: velocidade do vento, radiação solar e carga do banco de baterias.Serão utilizados para as simulações alguns softwares como o MATLAB e outros, que serão citados ao longo do trabalho. Nestes ambientes serão analisadas e simuladas todas as modelagens matemáticas, regras e demais variáveis descritas no sistema fuzzy. Este modelo foi utilizado para a implementação de um sistema de controle de sistemas híbridos de geração de energia, proporcionando o melhor aproveitamento das fontes de energia, sol e vento, de modo que possamos extrair o máximo de energia possível dessas fontes alternativas sem nenhum prejuízo ao meio ambiente... / The use of alternative and renewable energy has been increasingly discussed in all sectors of society. The interest in these sources of energy, alternative and renewable, it is of fundamental importance, both in terms of shortage, as the price of oil, in addition to the environmental issues involved in the use of these energies. Systems with photovoltaic and wind generation storage of energy in batteries has been presented as a form of alternative energy generation. The variability in the intensity of solar and wind energy can be circumvented by complementation between a source and another, or the more stable set to the generation of the system. The objective of this dissertation is to create a methodology fuzzy and simulate their use in intelligent control of a hybrid system of generating power, using the energy solar-photovoltaic and wind.When you use a system of control based on fuzzy logic, is reached the point of maximum generation of energy, thus transferring all the energy generated on the basis of alternative sources, solar, photovoltaic and wind, to the load and / or batteries when its use not immediately. The model takes three variables of entry, which are: wind speed, solar radiation and loading the bank of batteries. The simulations will be used for some software such as MATLAB and others, that will be cited during the work. In these environments will be analyzed and simulated all mathematical modeling, rules and other variables in the system described fuzzy. This model could be used in the implementation of a system of control of hybrid systems to generate energy, providing the best use of energy sources, sun and wind, so we can extract the maximum energy possible these alternative sources without any prejudice to the environment. The work was developed in the Laboratory of Energização Rural, of the Department of Rural Engineering of UNESP - FCA...(Complete abstract, click electronic access below)
25

Enquadramento tarifário de energia elétrica em agroindústria utilizando teoria Fuzzy /

Manzine, Luiz Gonzaga, 1951- January 2004 (has links)
Orientador: Nelson Miguel Teixeira / Banca: Carlos Roberto Padovani / Banca: Isidoro Casal Caminha Junior / Banca: Luiz Francisco da Cruz / Banca: Odival Faccenda / Resumo: O presente trabalho tem como objetivo utilizar a Teoria Fuzzy para obtenção de uma metodologia alternativa na escolha da estrutura tarifária de energia elétrica mais conveniente para a agroindústria e, em conseqüência, colaborar, reduzindo também os custos da oferta de energia elétrica para o país. A metodologia citada utiliza como variáveis principais o índice de utilização de energia elétrica e o fator de carga do horário de ponta. Estes dois parâmetros elétricos, juntamente com o fator de carga do horário fora de ponta, fornecem o enquadramento tarifário que mais se ajusta a uma determinada UC. Uma aplicação da metodologia estudada é apresentada num estudo de caso, envolvendo resultados obtidos com a migração tarifária de uma UC e ainda uma abordagem comparando os preços médios da energia elétrica para um consumidor em pleno funcionamento e para um projeto de planta elétrica. O Modelo Fuzzy alternativo construído teve desempenho comparável ao modelo, usando as fórmulas de preço médio de energia elétrica para o enquadramento tarifário de uma UC, fato confirmado no estudo de caso levado a efeito neste trabalho. Relativamente ao estudo de caso, chegou-se à conclusão afirmativa para a migração tarifária da ETC para a MTHSV, com diminuição no valor da demanda contratada. As análises feitas com o GMG, instalado na UC, mostraram ganho financeiro ao se gerar energia elétrica na atual estrutura e organização da linha de produção da UC, sendo desaconselhável sob o ponto de vista financeiro, se o GMG tiver de ser adquirido. Quanto ao controle das demandas de potências solicitadas, estudos mostraram que é necessário, não sendo, porém viável levando-se em conta o aspecto estritamente financeiro com um controlador de demanda nos moldes propostos por uma empresa especializada, consultada com esta finalidade. / Abstract: The present work aims to use Fuzzy Theory to obtain an alternative methodology in choosing the most convenient tariff structure of electric energy for agroindustry and as consequence to cooperate for its rational use and also reduce the costs in offering electric energy for the country. The methodology uses as main variables the index of electric energy usage and the load factor at peak hours. These two electric parameters along with the load factor out of peak hours make up the tariff adjustment which best applies to a determined consuming unit. One usage of the studied methodology is shown in a case study involving obtained results from tariff migration of one consuming unit. It is also presented an approach comparing average tariff of electric energy for consumers at full work as well as for an electric plant project. The built alternative Fuzzy Model had a performance comparable to the main model using formulas of electric energy average tariff for tariff adjustment of one consuming unit. Such procedure was confirmed in the case study carried out in this work. Concerning the case study there was a positive conclusion for tariff migration of CCT to GSTTM with a decrease on the value of the contracted demand. Analysis carried out with GMG, which was installed at consuming unit, showed a financial profit when generating electric energy on the current structure and organization of production line at consuming unit thus being unadvisable under financial aspects if GMC is to be purchased. Researches show that it is necessary the control of required energy demand. However it is not viable considering only the financial aspects with a demand controller under the proposed models for a specialized company which was consulted for such aim. / Doutor
26

âAplicaÃÃo da Teoria Fuzzy em um Modelo Bidimensional de Transporte de Massa, para Estudar o Risco Fuzzy em Rios Urbanos, Sujeitos a LanÃamentos de Agentes Poluentesâ. / Application of Fuzzy Theory in Two-Dimensional Mass Transport Model to study the Fuzzy Risk in Urban Rivers, Subject to Release of pollutants

Vanessa Ueta Gomes 28 July 2011 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A modelagem matemÃtica tem se tornado uma importante ferramenta para quantificar a qualidade de Ãgua nos mais diversos sistemas hÃdricos. Estas formulaÃÃes se tornaram mais frequentes a partir dos anos 60 com os avanÃos dos mÃtodos numÃricos e dos computadores digitais. Atualmente, como os problemas de qualidade de Ãgua se tornaram mais crÃticos, a busca por modelos mais consistentes que consigam levar em conta e quantificar as incertezas inerentes aos processos de transporte de poluentes e suas relaÃÃes com os mecanismos da hidrÃulica e da hidrologia, tem se tornado mais intensa. Neste contexto, a Teoria Fuzzy desponta como uma alternativa viÃvel para estudar o risco de falha de sistemas hÃdricos sujeitos a lanÃamentos de efluentes. Esta teoria, combinada com o Principio de Transporte de Massa, tem permitido que campos de risco possam ser determinados e, com isso, que um melhor controle nos lanÃamentos possam ser estabelecidos. Este trabalho propÃe uma metodologia, baseado em uma modelagem matemÃtica dos processos de transporte de poluentes, em rios naturais, onde os seus parÃmetros principais sÃo FunÃÃes de PertinÃncias, definidas segundo a Teoria Fuzzy. A pesquisa usa esses conceitos na soluÃÃo da EquaÃÃo da DifusÃo Advectiva Bidimensional âfuzzificadaâ, para determinar o comportamento do risco de falha e a garantia de sustentabilidade dos rios sujeitos, por exemplo, a variados tipos de lanÃamentos. Desta forma, campos de concentraÃÃo, campos de risco e campos de confiabilidade sÃo determinados, tanto do ponto de vista espacial, como do ponto de vista temporal. Os resultados mostraram que esta formulaÃÃo pode se tornar uma alternativa consistente na avaliaÃÃo dos impactos causados por derramamento de substÃncias poluidoras e provir aos gestores dos recursos hÃdricos subsÃdios para uma melhor tomada de decisÃo. / Mathematical modeling has become an important tool to quantify the water quality in various water systems. These formulations have become more frequent in the last 50 years with the advances in numerical methods and digital computers. Currently, as the water quality problems have become more critical, the research for more robust models, able to consider and quantify the uncertainties, inherent in the processes of pollutant transport and their relationship with the mechanisms of hydraulics and hydrology, has become more intense. In this context, the fuzzy theory emerges as a viable alternative to study the risk of failure of water systems subject to effluent discharges. This theory, combined with the Principle of Mass Transport, has allowed that risk fields could be determined and, thus, a better control over releases can be established. This research proposes a methodology, based on mathematical modeling of transport of pollutants, in natural rivers, where their main parameters are membership functions, defined according to the Fuzzy Theory. The research uses these concepts in solving the advection bi-dimensional Diffusion Equation, in its fuzzy way, to determine the behavior of the risk of failure and the reliability of rivers subject, for example, all kinds of releases. Thus, field of concentration, field of risk are determined, both from the spatial point of view, as the temporal point of view. The results showed that this formulation is becoming a consistent alternative in the assessment of impacts caused by the spreading of pollutants, giving to the managers of water resources subsidies to better decision making.
27

Metodologia para a monitoração eficiente de variações de tensão de curta duração em sistemas elétricos de potência. / Methodology for monitoring voltage SAGs and SWELLs in power systems.

Almeida, Carlos Frederico Meschini 14 February 2007 (has links)
Esta dissertação apresenta uma metodologia baseada em Algoritmos Genéticos e Teoria dos Conjuntos Fuzzy que determina o número ótimo de medidores de Qualidade de Energia, bem como os pontos onde os mesmos devem ser instalados para monitorar Afundamentos e Elevações de Tensão em redes de transmissão de energia elétrica. A metodologia desenvolvida representa uma ferramenta para diversas áreas de uma empresa de energia elétrica, porque ela indica a melhor maneira para se alocar medidores de Qualidade de Energia, considerando as restrições econômicas a que as empresas estão sujeitas. Além disto, a metodologia também determina a melhor configuração para um sistema de medição para um sistema de potência, quando há barras que devem ser monitoradas e/ou o número de medidores disponíveis é menor que o mínimo necessário para atingir a completa Observabilidade. O trabalho desenvolvido também representa uma importante aplicação dos Algoritmos Genéticos em conjunto com a Teoria dos Conjuntos Fuzzy. Ele define aspectos a serem considerados no problema de monitoração de Qualidade de Energia Elétrica e sugere rapidamente a melhor forma de atender diferentes objetivos e restrições operacionais. A fim de validar o modelo proposto, nesta dissertação, três redes elétricas são avaliadas para determinar o número mínimo de medidores de Qualidade de Energia, bem como a localização onde esses equipamentos deveriam ser instalados. Os níveis de Redundância e de Observabilidade são apresentados, bem como as formulações usadas para atingir os resultados apresentados. / This dissertation presents a methodology based on Genetic Algorithms and Fuzzy Mathematical Programming to determine the optimum number of power quality monitors and the locations they should be installed to measure Voltage Sags and Swells in transmission power networks. The methodology developed represents a tool for planning power networks, because it indicates the best way to allocate the power quality monitors, considering economical constraints. Similar to this, the methodology also determines the best configuration for a monitoring system when there are important busses to monitor and the number of monitors available is lower than the minimal needed to accomplish completely Observability. The work presented here also represents an important Genetic Algorithms application. With fuzzy mathematical programming it easily allows the definition of aspects to be considered in the monitoring problem and quickly suggests the best way to attend different objectives and operational restrictions. In order to validate the developed model proposed in this dissertation three electric power networks are assessed to determine the minimum number of power quality monitors as well as the locations where these devices should be installed. The levels of Redundancy and Observability are presented as well as the formulations used to achieve the results.
28

上市建設公司營運績效評等之研究 / The performance grading of construction firm in Taiwan stock exchange market

施旻孝, Shin, Min-Hsiao Unknown Date (has links)
在房地產生命週期中,建設公司扮演了土地取得、資金籌措、個案企畫、規劃興建、銷售與管理維護等角色,可說是房地產相關行業中最主要之關鍵;因此包括購屋者、股票購買者、公司管理階層、金融機構、證券管理機構等,皆必須以不同的角度來關切個別建設公司的經營績效,以供其行為決策的參考。 基於此,本研究第一部份先運用模糊理論衍生之模糊綜合評估法對上市建設公司的財務績效等相關指標進行各種綜合評估,並以劃分為「劣」、「普」、「良」、「優」四個級距的方式對公司進行評等。第二部份則搭配定性描述的產品績效予以交叉探討,以進一步了解不同類型建設公司的經營特質,共獲致以下結論。 在公司財務績效評等方面,相較於傳統簡單加權法,模糊綜合評估法因搭配權重的不同而在測試考驗上有較大落差;不過就評估結果而言,幾種評估權重的一致程度皆相當高,其中以同時考量到建築投資業產業特質(如高負債比率、低周轉率、經營規模成長快等)與員工生產力的評等模式穫得了最佳的測試成績。在該評估模式下,八十三年第四季至八十六年第三季各公司的評等結果分別為:「劣」等級包括宏福、宏總等兩家;「普」等級包括潤建、龍邦、長谷、緯城、仁翔等五家;「良」等級包括國揚、太設、太子、長億、寶祥、宏璟、皇普、昱成、春池等九家;「優」等級包括國建、寶建、冠德、華建、三采、尖美、宏盛、宏普、基泰等九家。 而在上市建設公司財務績效與產品績效交叉探討的部份:本研究從公司上市時間、成立時間、資本額,存貨內涵、政府認證等幾個角度做為產品績效的測試基準,有以下三點重要發現: 1.財務表現優良的上市建設公司亦有不錯的股價表現,至於財務表現不良的公司股價表現相對較差。 2.財務表現優良的公司平均上市時問較短,財務表現不良的公司平均上市時間則較長。 3.財務表現優良的公司帳面上的養地比率較高,財務表現不良的公司帳面上養地比率則較低。
29

模糊時間序列與區間預測方法探討-以台灣加權股價指數為例 / A study on the Fuzzy time series and interval forecasting methods -with case study on the Taiwan Capitalization Weighted Stock Index

李栢昌, Li, Pai Chang Unknown Date (has links)
台灣加權股價指數(TAIEX),可以說是台灣最重要的經濟指數之一。在預測的方法中,時間序列分析一直都是熱門的課題,也是最常被使用來研究股價預測的方法。近年來,模糊理論在生醫、財務、社會、電機等各領域都有不錯的應用與發展 。本研究欲透過模糊區間的預測,主要是以時間序列預測台灣加權股價指數,來作為模糊區間精確度的探討,並針對區間時間序列進行模式的建構診斷和預測。最後我們將以2012年第一季(Q1),每日交易股價指數的最高價與最低價作為實際研究的例子,同時也比較不同預測方法所得的結果。結果顯示模糊區間預測提供不同於傳統預測方法所得的資訊,希望能提供投資者另一種投資的參考。 關鍵字 : 台灣加權股價指數(TAIEX) 、模糊理論、模糊區間、區間預測 / Taiwan Weighted Stock Index (TAIEX) is one of Taiwan's most important economic indicators. Among the forecasting methods of time series analysis is always a hot issue on the forecasting methods and is also the most commonly used to make the stock price predictions. In recent years , fuzzy theory makes a great of application and development in various fields , such as , biomedical , financial and social …etc.. For this study, through the fuzzy interval forecasting is mainly based on time series forecasting TAIEX as fuzzy interval accuracy of the construction of diagnosis and prediction of the mode and interval time series. Finally, we will take the daily highest / lowest stock index prices data in the first quarter of 2012 (Q1) for actual research example , and will compare different forecasting methods of the results. The results show that the fuzzy interval forecasting differented from the traditional one on the basis of these information. We hope to offer investors an alternative investment advice. Keyword : Taiwan Capitalization Weighted Stock Index (TAIEX) 、 Fuzzy theory 、 Fuzzy interval、Interval forecasting.
30

異質性無線網路下垂直換手機制之研究 / A vertical handoff mechanism in heterogeneous wireless network

莊森駒, Chuang, Sen Chu Unknown Date (has links)
隨著各種無線網路技術興起至今,各類無線網路技術及產品日益成熟與普及且無線網路的使用者也逐漸變多。而今在各種無線網路的廣泛使用下、時而可見的是當一個行動使用者手持行動裝置身處在一地理環境中,手持行動裝置一經掃描後,常會發現有許多無線網路其覆蓋範圍共同覆蓋在同一個地理區域中,此時多個無線存取點(Access Point)就會發生訊號覆蓋的重疊現象。行動使用者的行動裝置常需判斷是否應該切換到另一個無線網路,此種情形也就是所謂的遞換(Handoff)情形。遞換之產生,代表行動使用者從原本的無線網路區域範圍移動到另一個無線網路範圍,此時若因外界無線電訊號有所變化或是相關網路協定運作出現狀況時、就很容易產生通訊中斷的情形。 在本論文中我們將探討在異質性網路的情況下,根據多種不同的參數、來 設計一個垂直交握(Vertical handoff)的機制。以克服在異質性網路中,時常發生連線中斷之問題。本篇論文主要引使用模糊理論概念來推論其遞換(Handoff)執行的時間點,並且明確的告知終端設備要進入何種網路。 / In this paper, we propose a terminal –control scheme to avoid unnecessary vertical handovers between 3G cellular and WLAN hotspots. The proposed algorithm is a fuzzy logic based algorithm that can adapt itself to the dynamic conditions of the hybrid networks. The scheme can reduce the access delay, unnecessary handoff probability and aid the handoff decision for better connectivity. This handoff algorithm has much better performance than conventional algorithms and can be extended to other heterogeneous networks.

Page generated in 0.0358 seconds