• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 100
  • 27
  • 11
  • 7
  • 7
  • 5
  • 4
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 195
  • 93
  • 50
  • 37
  • 34
  • 30
  • 26
  • 22
  • 21
  • 21
  • 19
  • 17
  • 15
  • 13
  • 13
  • 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.
181

Operadores de recombinação baseados em permutação para representações de grafos / Permutation based recombination operators for graph representations

Lima , Roney Lopes 23 August 2017 (has links)
Submitted by JÚLIO HEBER SILVA (julioheber@yahoo.com.br) on 2017-09-13T18:01:57Z No. of bitstreams: 2 Dissertação - Roney Lopes Lima - 2017.pdf: 3471034 bytes, checksum: 2dd29fe3cd16f3d5ac0ddabf0ce316b4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-09-19T14:01:45Z (GMT) No. of bitstreams: 2 Dissertação - Roney Lopes Lima - 2017.pdf: 3471034 bytes, checksum: 2dd29fe3cd16f3d5ac0ddabf0ce316b4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-19T14:01:45Z (GMT). No. of bitstreams: 2 Dissertação - Roney Lopes Lima - 2017.pdf: 3471034 bytes, checksum: 2dd29fe3cd16f3d5ac0ddabf0ce316b4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-23 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The application of Evolutionary Algorithms in the solution of problems characterized by the unviability through deterministic methods, has made this technique a vast object investigated. Its application to Network Design Problems (NDPs), has been specially studied. NDPs are characterized by modeling real world problems related to network design applied to resource distribution, logistics, telecommunications, routing and even social networks. The solution to these problems involves searching for a graph such as trees that meets criteria for cost minimization, availability, scaling among other constraints that make them complex. The application of Evolutionary Agorithms to NDPs requires a Representation that codes solutions properly towards to these problems. The Node-Depth Encoding (NDE) has been studied and presented results that have aroused the attention of researchers in this topic. In this work, we propose the development of a new recombination operator for NDE called NCX, based on the permutation recombination operator CX. In addition, a method is proposed for correction of infeasible solutions due to an invalid depth for a position in the array. The correction method is applied to both NCX, NOX and NPBX. The operators with their methods of correction are validated for the bias and heritability properties and finally are applied to the Bounded Diameter Minimmum Spanning Tree (BDMSTP) through Evolutionary Algorithms developed for this NDP. The results show that the operators have bias towards to star like trees and good heritability of the edges and depths of the vertices. The developed operators also showed competitiveness when applied to the BDMSTP, even surpassing other representations in the quality of the solutions. / A aplicação de Algoritmos Evolutivos na resolução de problemas caracterizados pela inviabilidade de solução através de métodos determinísticos, fez dessa técnica um objeto vastamente investigado. Sua aplicação para Problemas de Projeto de Redes (PPRs), tem sido especialmente estudada. PPRs são caracterizados por modelar problemas reais relacionados a design de redes aplicados a distribuição de recursos, logística, telecomunicações, roteamento e até mesmo redes sociais. A solução desses problemas envolve a busca de um grafo como uma árvore por exemplo que atenda a critérios de minimização de custos, disponibilidade, escala entre outras restrições que os tornam complexos. A aplicação de Algoritmos Evolutivos a PPRs demanda a utilização de uma Representação que codifique adequadamente soluções para esses problemas. A Representação Nó-Profundidade (RNP) tem sido estudada e apresentado resultados que despertaram a atenção dos pesquisadores nesse tema. Neste trabalho, propõe-se o desenvolvimento de um novo operador de recombinação para a RNP chamado NCX, com base no operador CX de recombinação em permutações. Além disso, é proposto um método para correção de soluções infactíveis devido a profundidade inválida para a posição no \textit{array}. O método de correção é aplicado tanto para NCX, quanto para outros dois operadores de recombinação já desenvolvidos para a RNP, o NOX cujo funcioamento é inspirado no operador OX, e NPBX cujo funcionamento é inspirado no operador PBX. Os operadores com os seus devidos métodos de correção são validados para as propriedades tendência e hereditariedade e por fim são aplicados ao Problema da Árvore Geradora Mínima com Restrição de Diâmetro (BDMSTP) através de Algoritmos Evolutivos desenvolvidos para esse PPR. Os resultados mostram que os operadores possuem tendência para árvores estrela e boa hereditariedade das arestas e das profundidades dos vértices. Os operadores desenvolvidos também mostraram competitividade ao serem aplicados ao BDMSTP, chegando a superar outras representações em qualidade das soluções.
182

Att täcka en obekant yta med Spanning Tree Covering, Topologisk Täckande Algoritm, Trilobite / Covering an unknown area with Spanning Tree Covering, Topologisk Täckande Algoritm, Trilobite

Carlsson, Josefin, Johansson, Madeleine January 2005 (has links)
Det har blivit mer och mer vanligt med ny, datoriserad teknik i hemmen. Fler människor har ett allt stressigare liv och inte längre samma tid att ta hand om det egna hemmet. Behovet av en hjälpande hand med hushållsarbete har blivit allt större. Tänk själv att komma hem från jobbet eller skolan och så har golvet blivit skinande rent utan att Ni knappt har behövt göra någonting! Det finns idag flera olika robotar på marknaden för detta ändamål. En av dessa är den autonoma dammsugaren, som är det vi inriktat vår uppsats på. I huvudsak är uppsatsen inriktad på mjukvaran, som kan användas i en autonom dammsugare. Vi har valt att titta närmare på två stycken sökalgoritmer, som kan användas av autonoma mobila robotar, exempelvis en autonom dammsugare, som har i uppdrag att täcka en hel obekant yta. Dessa algoritmer är Spanning Tree Covering (STC) och ”A Topological Coverage Algorithm”, också kallad ”Landmark-based World Model” (fritt översatt till Topologisk Täckande Algoritm, TTA). Vi har också undersökt hur ett av Sveriges största märken på marknaden för autonoma dammsugare, nämligen Electrolux Trilobite ZA1, klarar sig i test. Vi har även analyserat testet med Trilobiten och jämfört detta med antaget beteende hos Trilobiten ifall den hade varit implementerad med sökalgoritmerna STC eller TTA. Hur fungerar sökalgoritmerna? Hur kan en autonom dammsugare hitta på en hel obekant yta? Hur beter sig Electrolux Trilobite ZA1? Täcker de alla en obekant yta? Är de effektiva?
183

Approches de résolution exacte et approchée en optimisation combinatoire multi-objectif, application au problème de l'arbre couvrant de poids minimal / Exact and approximate solving approaches in multi-objective combinatorial optimization, application to the minimum weight spanning tree problem

Lacour, Renaud 02 July 2014 (has links)
On s'attache dans cette thèse à plusieurs aspects liés à la résolution de problèmes multi-objectifs, sans se limiter au cas biobjectif. Nous considérons la résolution exacte, dans le sens de la détermination de l'ensemble des points non dominés, ainsi que la résolution approchée dans laquelle on cherche une approximation de cet ensemble dont la qualité est garantie a priori.Nous nous intéressons d'abord au problème de la détermination d'une représentation explicite de la région de recherche. La région de recherche, étant donné un ensemble de points réalisables connus, exclut la partie de l'espace des objectifs que dominent ces points et constitue donc la partie de l'espace des objectifs où les efforts futurs doivent être concentrés dans la perspective de déterminer tous les points non dominés.Puis nous considérons le recours aux algorithmes de séparation et évaluation ainsi qu'aux algorithmes de ranking afin de proposer une nouvelle méthode hybride de détermination de l'ensemble des points non dominés. Nous montrons que celle-ci peut également servir à obtenir une approximation de l'ensemble des points non dominés. Cette méthode est implantée pour le problème de l'arbre couvrant de poids minimal. Les quelques propriétés de ce problème que nous passons en revue nous permettent de spécialiser certaines procédures et d'intégrer des prétraitements spécifiques. L'intérêt de cette approche est alors soutenu à l'aide de résultats expérimentaux. / This thesis deals with several aspects related to solving multi-objective problems, without restriction to the bi-objective case. We consider exact solving, which generates the nondominated set, and approximate solving, which computes an approximation of the nondominated set with a priori guarantee on the quality.We first consider the determination of an explicit representation of the search region. The search region, defined with respect to a set of known feasible points, excludes from the objective space the part which is dominated by these points. Future efforts to find all nondominated points should therefore be concentrated on the search region.Then we review branch and bound and ranking algorithms and we propose a new hybrid approach for the determination of the nondominated set. We show how the proposed method can be adapted to generate an approximation of the nondominated set. This approach is instantiated on the minimum spanning tree problem. We review several properties of this problem which enable us to specialize some procedures of the proposed approach and integrate specific preprocessing rules. This approach is finally supported through experimental results.
184

Robustness and preferences in combinatorial optimization

Hites, Romina 15 December 2005 (has links)
In this thesis, we study robust combinatorial problems with interval data. We introduce several new measures of robustness in response to the drawbacks of existing measures of robustness. The idea of these new measures is to ensure that the solutions are satisfactory for the decision maker in all scenarios, including the worst case scenario. Therefore, we have introduced a threshold over the worst case costs, in which above this threshold, solutions are no longer satisfactory for the decision maker. It is, however, important to consider other criteria than just the worst case.<p>Therefore, in each of these new measures, a second criteria is used to evaluate the performance of the solution in other scenarios such as the best case one. <p><p>We also study the robust deviation p-elements problem. In fact, we study when this solution is equal to the optimal solution in the scenario where the cost of each element is the midpoint of its corresponding interval. <p><p>Then, we finally formulate the robust combinatorial problem with interval data as a bicriteria problem. We also integrate the decision maker's preferences over certain types of solutions into the model. We propose a method that uses these preferences to find the set of solutions that are never preferred by any other solution. We call this set the final set. <p><p>We study the properties of the final sets from a coherence point of view and from a robust point of view. From a coherence point of view, we study necessary and sufficient conditions for the final set to be monotonic, for the corresponding preferences to be without cycles, and for the set to be stable.<p>Those that do not satisfy these properties are eliminated since we believe these properties to be essential. We also study other properties such as the transitivity of the preference and indifference relations and more. We note that many of our final sets are included in one another and some are even intersections of other final sets. From a robust point of view, we compare our final sets with different measures of robustness and with the first- and second-degree stochastic dominance. We show which sets contain all of these solutions and which only contain these types of solutions. Therefore, when the decision maker chooses his preferences to find the final set, he knows what types of solutions may or may not be in the set.<p><p>Lastly, we implement this method and apply it to the Robust Shortest Path Problem. We look at how this method performs using different types of randomly generated instances. <p> / Doctorat en sciences, Orientation recherche opérationnelle / info:eu-repo/semantics/nonPublished
185

Performance Optimization of Network Protocols for IEEE 802.11s-based Smart Grid Communications

Saputro, Nico 16 June 2016 (has links)
The transformation of the legacy electric grid to Smart Grid (SG) poses numerous challenges in the design and development of an efficient SG communications network. While there has been an increasing interest in identifying the SG communications network and possible SG applications, specific research challenges at the network protocol have not been elaborated yet. This dissertation revisited each layer of a TCP/IP protocol stack which basically was designed for a wired network and optimized their performance in IEEE 802.11s-based Advanced Metering Infrastructure (AMI) communications network against the following challenges: security and privacy, AMI data explosion, periodic simultaneous data reporting scheduling, poor Transport Control Protocol (TCP) performance, Address Resolution Protocol (ARP) broadcast, and network interoperability. To address these challenges, layered and/or cross-layered protocol improvements were proposed for each layer of TCP/IP protocol stack. At the application layer, a tree-based periodic time schedule and a time division multiple access-based scheduling were proposed to reduce high contention when smart meters simultaneously send their reading. Homomorphic encryption performance was investigated to handle AMI data explosion while providing security and privacy. At the transport layer, a tree-based fixed Retransmission Timeout (RTO) setting and a path-error aware RTO that exploits rich information of IEEE 802.11s data-link layer path selection were proposed to address higher delay due to TCP mechanisms. At the network layer, ARP requests create broadcast storm problems in IEEE 802.11s due to the use of MAC addresses for routing. A secure piggybacking-based ARP was proposed to eliminate this issue. The tunneling mechanisms in the LTE network cause a downlink traffic problem to IEEE 802.11s. For the network interoperability, at the network layer of EPC network, a novel UE access list was proposed to address this issue. At the data-link layer, to handle QoS mismatch between IEEE 802.11s and LTE network, Dual Queues approach was proposed for the Enhanced Distributed Channel Access. The effectiveness of all proposed approaches was validated through extensive simulation experiments using a network simulator. The simulation results showed that the proposed approaches outperformed the traditional TCP/IP protocols in terms of end to end delay, packet delivery ratio, throughput, and collection time.
186

藉由小世界股票網路探索不同景氣區間的差異性 / Exploring economy-realated differences by small-world stock networks

邱建堯, Chiu, Chien Yao Unknown Date (has links)
股票市場對投資者而言是以極大化自有資產為目的,因此如何辨別不同景氣區間對股市的影響為投資者感興趣的議題。傳統上,使用統計資料來幫助我們比較不同景氣區間之差異,然而股票市場之複雜、非線性及不可預測性也經常成為各統計資料失準的關鍵,因此,本篇論文以複雜網路作為分析股票市場之模型,並將各個股票表示成節點、股價變化之關聯性作為連結下,建立出複雜網路,藉此探討股市中的景氣差異。   在本研究中,先利用國發會制定的景氣對策信號,來幫助我們選取四段景氣區間,接著將台積電作為網路核心建構個股的相關網路。並以最小生成樹(Minimum Spanning Tree) 將複雜的股票網路簡單化。同時我們計算出各股相關網路之全域網路參數(Global Network Parameters)及區域網路參數(Regional Network Parameters),以利我們討論兩段景氣好區間與兩段景氣差區間之差異。最後,我們將股市相關網路以分層樹(Hierarchical Tree)來表示,以了解網路分群的結果。   結果顯示,我們建構的個股相關網路符合小世界網路特性,在全域網路參數中,景氣好相關網路之常規化平均特徵路徑(Normalization Average Characteristic Path Length)及景氣差相關網路中之平均群聚係數(Average Clustering Coefficient)、平均特徵路徑(Average Characteristic Path Length)、常規化平均特徵路徑(Normalization Average Characteristic Path Length)有顯著差異。 在區域網路參數中,在景氣好相關網路中,被選為網路樞紐並有顯著差異之個股有台達化、宜進與華通,景氣差相關網路則有瑞利、日月光、矽品及萬企。在景氣好相關網路比較時,台積電的連結度與點效率皆具有顯著差異。
187

A Structure based Methodology for Retrieving Similar Rasters and Images

Jayaraman, Sambhavi 22 June 2015 (has links)
No description available.
188

行政組際協調之嵌套賽局分析 / A nested game analysis of interorganizational coordination in public administration

廖洲棚, Liao, Zhou Peng Unknown Date (has links)
在當前的治理環境下,公共任務比以往更需要整合政府及各部門組織的行動方能克盡其功。因此,多數的公共管理者應會同意,行政組際協調已成為「治理時代」重要且迫切的議題之一,公共管理者需要擁有全新的能力,從解決民眾問題的角度來回應民眾需求。本文將行政組際協調定義為「藉由兩個或兩個以上行政組織的一致行動,使特定政策或計畫的執行,能達成最少的冗餘、不一致與空隙的執行結果」。在此定義下,本文討論的行政組際協調涉及三個層面:第一個層面為跨行政組織如何產生一致行動的問題;第二個層面為行政組織間的互動關係;第三個層面為跨行政組織執行成果的問題。 本文建構的「行政組際協調嵌套賽局模型」假定官僚制度中的專業分工與獲利轉換機制的制度設計,是造成行政組織分工但不合作的主因。在此前提下,筆者引入「效用損失」的概念,做為發展行政組織行為效用函數的基礎。在行政自主性「效用損失」的概念下,筆者僅保留與行政組織政策或計畫執行最相關的自變項,分別是相依關係、溝通、管轄領域、民意監督、外部課責與內部課責等六種,來解釋行政組織的合作行為以及協調的結果等兩種依變項。由於本文將制度視為對參賽者的限制與機會,在制度陳述概念的輔助下,筆者得以清楚地設定行政組際協調的賽局情境,並將行政責任的思考轉化為外部課責與內部課責等兩種課責參數型態。在此課責制度框架下,筆者建立行政組際協調的空間結構,透過行政組織自主性效用之簡單損失函數以及制度空間模型的運用,成功建立起一個階層管理者、兩個行政組織的行政組際協調嵌套賽局模型。這個模型依據外部課責是否一致,以及內部課責是否存有共識等兩個面向,將行政組際協調賽局情境區分為四種類型,並在分別推演參賽者的行為變化後,提出十項理論命題。為詮釋這些命題在現實環境中的意義,筆者在臺北市政府研考會的同意下,引用該會於2010年10月辦理之1999跨機關陳情案件問卷調查資料,進行次級資料分析。 綜合而言,本文建構的「行政組際協調嵌套賽局模型」,是建立在一個嚴格的假定條件之上的,因此其理論的解釋力與預測能力都僅能限縮在一定的範圍內,特別是一階層管理者、兩行政組織的三人完全訊息賽局。換言之,超出這個範圍之外的行政組際協調現象,就不適合使用本模型進行解釋。本文雖然只使用極精簡的相關研究變項,卻也足以展現一個理論模型應具備的解釋與預測能力。當然,本文的研究僅是一個開端,不論在模型的廣博性以及適用性都還有極大的待改善空間。筆者也鼓勵後繼的學者,能持續地擴展與修改本文提出之理論模型,讓行政組際協調研究領域能朝向更正面的發展。 / Under the present governance environment, the government would need more efforts to coordinate different organizations’ actions than before to make sure the public services would be provided successfully. Thus, most public managers would not only agree that the interorganizational coordination has become one of the important and urgent issues in the governance era, but also they need to learn new abilities to response the citizens’ needs. The author defined the concept of interorganizational coordination as “The end-state of a public policy or program which is implemented by two or more organizations in a consistent way is characterized by minimal redundancy, incoherence and lacunae.” Under this definition, the author discussed three different questions of interorganization coordination in public administration. The first question is How can we formulate a set of consistent actions for implementing a public policy or program? The second question is “How can we explain the interactive relationship between the organizations in public administration?” The third question is “What kind of results would be produced by multi-organizational implementation?” The nested game model of this dissertation has been assumed that the specification and unique side payment system of bureaucracy are the fundamental institution of interorganizational coordination. Under this assumption, the author introduced the concept of simple loss function and structure-induced equilibrium to create an utility function of public organizations and a spatial model for deducing propositions of interorganizational coordination in public administration. In order to verify the propositions of the nested game model of this dissertation, the author did a case study which was including 52 appealed cases of 1999 Citizen Hotline of Taipei City Government and tested the hypothesis derived from the propositions. Finally, the author concluded that there are six independent variables, including interdependency, communication, territory, supervision, outside accountability and inside accountability which can be used to explain two dependent variables, including cooperative behaviors and the result of interorganizational coordination. The author admitted that the interorganizational coordination is a contingent process and should be carefully defined its game rules before discussing what happened in this process. This dissertation has provided a simplicity model for explaining interorganizational coordination with one hierarchical organization and two horizontal organizations within four different situations. The author hoped that other researchers can modify this simple model to explain more complex situations of interorganizational coordination. Thus, this field could be continually developed in a positive way.
189

離散條件機率分配之相容性研究 / On compatibility of discrete conditional distributions

陳世傑, Chen, Shih Chieh Unknown Date (has links)
設二個隨機變數X1 和X2,所可能的發生值分別為{1,…,I}和{1,…,J}。條件機率分配模型為二個I × J 的矩陣A 和B,分別代表在X2 給定的條件下X1的條件機率分配和在X1 給定的條件下X2的條件機率分配。若存在一個聯合機率分配,而且它的二個條件機率分配剛好就是A 和B,則稱A和B相容。我們透過圖形表示法,提出新的二個離散條件機率分配會相容的充分必要條件。另外,我們證明,二個相容的條件機率分配會有唯一的聯合機率分配的充分必要條件為:所對應的圖形是相連的。我們也討論馬可夫鏈與相容性的關係。 / For two discrete random variables X1 and X2 taking values in {1,…,I} and {1,…,J}, respectively, a putative conditional model for the joint distribution of X1 and X2 consists of two I × J matrices representing the conditional distributions of X1 given X2 and of X2 given X1. We say that two conditional distributions (matrices) A and B are compatible if there exists a joint distribution of X1 and X2 whose two conditional distributions are exactly A and B. We present new versions of necessary and sufficient conditions for compatibility of discrete conditional distributions via a graphical representation. Moreover, we show that there is a unique joint distribution for two given compatible conditional distributions if and only if the corresponding graph is connected. Markov chain characterizations are also presented.
190

Untersuchung einzelner SNARE-vermittelter Membranfusionsereignisse auf planaren porenüberspannenden Membranen / Investigation of Single SNARE-mediated Membrane Fusion Events on Planar Pore-spanning Membranes

Schwenen, Lando Lantbert Gregor 04 June 2015 (has links)
No description available.

Page generated in 0.1137 seconds