• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 341
  • 133
  • 67
  • 62
  • 37
  • 22
  • 19
  • 14
  • 11
  • 8
  • 7
  • 7
  • 6
  • 5
  • 4
  • Tagged with
  • 872
  • 219
  • 99
  • 95
  • 79
  • 73
  • 68
  • 63
  • 55
  • 51
  • 49
  • 46
  • 44
  • 42
  • 41
  • 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.
691

Geometric and algebraic approaches to mixed-integer polynomial optimization using sos programming

Behrends, Sönke 23 October 2017 (has links)
No description available.
692

L'indépendant faiblement connexe : études algorithmiques et polyédrales / Weakly connected independent sets : algorithmic and polyhedral studies

Mameri, Djelloul 25 November 2014 (has links)
Dans ce travail, nous nous intéressons à une topologie pour les réseaux de capteurs sans fil. Un réseau de capteurs sans fil peut être modélisé comme un graphe non orienté G = (V,E). Chaque sommet de V représente un capteur et une arête e = {u, v} dans E indique une transmission directe possible entre deux capteurs u et v. Contrairement aux dispositifs filaires, les capteurs sans fil ne sont pas a priori agencé en réseau. Une topologie doit être créée en sélectionnant des noeuds "dominants" qui vont gérer les transmissions. Les architectures qui ont été examinées dans la littérature reposent essentiellement sur les ensembles dominants connexes et les ensembles dominants faiblement connexes. Cette étude est consacrée aux ensembles indépendants faiblement connexes. Un indépendant S ⊂ V est dit faiblement connexe si le graphe GS = (V, [S, V \S]) est connexe, où [S, V \S] est l’ensemble des arêtes e = {u, v} de E avec u ∈ S et v ∈ V \S. Une topologie basée sur les ensembles faiblement connexes permet de partitionner l’ensemble des capteurs en trois groupes, les esclaves, les maîtres et les intermédiaires. Les premiers effectuent les mesures, les seconds rassemblent les données collectées et les troisièmes assurent les communications inter-groupes. Nous donnons d’abord quelques propriétés de cette structure combinatoire lorsque le graphe non orienté G est connexe. Puis nous proposons des résultats de complexité pour le problème de la recherche de l’indépendant faiblement connexe de cardinalité minimale (MWCISP). Nous décrivons également un algorithme d’énumération exact de complexité O∗(1.4655|V |) pour le MWCISP. Des tests numériques de cette procédure exacte sont présentés. Nous formulons ensuite le MWCISP comme un programme linéaire en nombres entiers. Le polytope associé aux solutions de ce problème est complètement caractérisé lorsque G est un cycle impair. Nous étudions des opérations de composition de graphes et leurs conséquences polyédrales. Nous introduisons des inégalités valides notamment les contraintes dites de multibord. Par la suite, nous développons un algorithme de coupes et branchement sous CPLEX pour résoudre ce problème en utilisant des heuristiques pour la séparation de nos familles de contraintes. Des résultats expérimentaux de ce programme sont exposés. / In this work, we focus on a topology for Wireless Sensor Networks (WSN). A wireless sensor network can be modeled as an undirected graph G = (V,E). Each vertex of V represents a sensor and an edge e = {u, v} in E implies a direct transmission between the two sensors u and v. Unlike wired devices, wireless sensors are not a priori arranged in a network. Topology should be made by selecting some sensor as dominators nodes who manage transmissions. Architectures that have been studied in the literature are mainly based on connected dominating sets and weakly connected dominating sets.This study is devoted to weakly connected independent sets. An independent set S ⊂ V is said Weakly Connected if the graph GS = (V, [S, V \S]) is connected, where [S, V \S] is the set of edges with exactly one end in S. A sensor network topology based on weakly connected sets is partition into three groups, slaves, masters and bridges. The first performs the measurements, the second gathers the collected data and the later provides the inter-group communications. We first give some properties of this combinatorial structure when the undirected graph G is connected. Then we provide complexity results for the problem of finding the minimum weakly connected independent set problem (MWCISP). We also describe an exact enumeration algorithm of complexity O∗(1.4655|V |) (for the (MWCISP)). Numerical tests of this exact procedure are also presented. We then present an integer programming formulation for the minimum weakly connected independent set problem and discuss its associated polytope. Some classical graph operations are also used for defining new polyhedra from pieces. We give valid inequalities and describe heuristical separation algorithms for them. Finally, we develop a branch-and-cut algorithm and test it on two classes of graphs.
693

Planification des réapprovisionnements sous incertitudes pour les systèmes d’assemblage à plusieurs niveaux / Replenishment planning under uncertainty for multi-level assembly systems

Ben Ammar, Oussama 09 October 2014 (has links)
Dans le contexte actuel marqué par l’instabilité des marchés, les clients sont de plus en plus exigeants. un client qui n’est pas approvisionné à une date souhaitée peut soit remettre son achat à plus tard, soit aller chercher le produit chez un concurrent. de plus, l’entreprise doit faire face à de multiples imprévisibilités internes, de la concurrence ou d’événements extérieurs. ces aléas induisent de l'incertitude dans la planification de la production et génèrent des sources nombreuses de retard, de désynchronisation et de pertes de productivité. ce travail de thèse s’intègre dans la problématique de la planification de la production dans un environnement incertain. nous étudions des problèmes de la planification des réapprovisionnements pour un système d’assemblage à plusieurs niveaux, quand les délais d’approvisionnement sont incertains. nous avons choisi comme indicateur de performance l’espérance du coût total moyen qui est égal à la somme du coût de stockage des composants, le coût de rupture du produit fini et le coût de stockage du produit fini. des propriétés théoriques, des modèles analytiques ainsi que des méthodes d’optimisation ont été proposés. nous avons montré que la résolution du problème ne dépend pas seulement de la méthode de résolution et du nombre de niveaux, mais aussi du coût de rupture en produit fini et de la structure du système d’assemblage. / In the current industrial context, the offer is largely higher than the demand. Therefore, the customers are more and more exigent. To distance themselves, companies need to offer to their customers the best quality products, the best costs, and with controlled lead times as short as possible. Last years, the struggle for reducing costs was accentuated within companies. However, stocks represent an important financial asset, and therefore, it is essential to control them. In addition, a bad management of stocks led either to delays in delivery, which generate additional production costs, either to the unnecessary inventory. The latter one can occur at different levels (from components at the last level to finished product), it costs money and immobilize funds. That is why, planners have to look for efficient methods of production and supply planning, to know exactly for each component, and when to order and in which quantity.The aim of this doctoral thesis is to investigate the supply planning in an uncertain environment. We are interested in a replenishment planning for multi-level assembly systems under a fixed demand and uncertainty of components lead times.We consider that each component has a fixed unit inventory cost; the finished product has an inventory cost and a backlogging cost per unit of time. Then, a general mathematical model for replenishment planning of multi-level assembly systems, genetic algorithm and branch and bound method are presented to calculate and to optimize the expected value of the total cost which equals to the sum of the inventory holding costs for the components, the backlogging and the inventory holding costs for the finished product. We can state by the different results that the convergence of the GA doesn't depend only on the number of components in the last level but also on the number of levels, the type of the BOM and the backlogging cost for the finished product.
694

Strategická analýza podniku / Strategic Analysis of an Enterprise

Bláhová, Eliška January 2008 (has links)
The aim of this thesis is to implement strategic analysis of a particular company (Patria Direct, a.s.) using the internal and external analysis to determine the current position of the company on the market and propose recommendations for its possible future direction.
695

Účetní a daňové aspekty různých forem vstupu na zahraniční trhy / Accounting and tax aspects of different types of the foreign market entrance

Peciválová, Lenka January 2009 (has links)
The major topic of this thesis is tax and accounting aspects of different types of foreign market entrance. Basic types of foreign market entrance and their accounting and tax comprehension are defined in the first chapter. The second chapter is focused on legal point of view of the foreign entities business in Czech Republic and there are defined the main differences in foreign entities business by czech corporate entity and branch. The main differences of these subjects from the tax point of view are established in the third chapter, tax registration, tax duty origin, tax base, double taxation, mutual relations and transfer pricing. The fourth chapter is focused on the accounting duties both subjects, their differences and transactions accounting in practice of branch and its founder, foreign entity, in centralized and separated accounting system.
696

Techniques hybrides de recherche exacte et approchée : application à des problèmes de transport / Hybrid techniques of exact and approximate search : application in transport problems

Bontoux, Boris 08 December 2008 (has links)
Nous nous intéressons dans cette thèse aux possibilités d’hybridation entre les méthodes exactes et les méthodes heuristiques afin de pouvoir tirer avantage de chacune des deux approches : optimalité de la résolution exacte, caractère moins déterministe et rapidité de la composante heuristique. Dans l’objectif de résoudre des problèmes NPdifficiles de taille relativement importante tels que les problèmes de transports, nous nous intéressons dans les deux dernières parties de ce mémoire à la conception de méthodes incomplètes basées sur ces hybridations. Dans la première partie, nous allons nous intéresser aux méthodes de résolution par recherche arborescente. Nous introduisons une nouvelle approche pour la gestion des décisions de branchement, que nous appelons Dynamic Learning Search (DLS). Cette méthode définit de manière dynamique des règles de priorité pour la sélection des variables à chaque noeud et l’ordre des valeurs sur lesquelles brancher. Ces règles sont conçues dans une optique de généricité, de manière à pouvoir utiliser la méthode indépendamment du problème traité. Le principe général est de tenir compte par une technique d’apprentissage de l’impact qu’ont eu les décisions de branchement dans les parties déjà explorées de l’arbre. Nous évaluons l’efficacité de la méthode proposée sur deux problèmes classiques : un problème d’optimisation combinatoire et un problème à satisfaction de contraintes. La deuxième partie de ce mémoire traite des recherches à grand voisinage. Nous présentons un nouvel opérateur de voisinage, qui détermine par un algorithme de programmation dynamique la sous-séquence optimale d’un chemin dans un graphe. Nous montrons que cet opérateur est tout particulièrement destiné à des problèmes de tournées pour lesquels tous les noeuds ne nécessitent pas d’être visités. Nous appelons cette classe de problème les Problèmes de Tournées avec Couverture Partielle et présentons quelques problèmes faisant partie de cette classe. Les chapitres 3 et 4 montrent, à travers des tests expérimentaux conséquents, l’efficacité de l’opérateur que nous proposons en appliquant cette recherche à voisinage large sur deux problèmes, respectivement le Problème de l’Acheteur Itinérant (TPP) et le Problème de Voyageur de Commerce Généralisé (GTSP). Nous montrons alors que cet opérateur peut être combiné de manière efficace avec des métaheuristiques classiques, telles que des algorithmes génétiques ou des algorithmes d’Optimisation par Colonies de Fourmis. Enfin, la troisième partie présente des méthodes heuristiques basées sur un algorithme de Génération de Colonnes. Ces méthodes sont appliquées sur un problème complexe : le problème de Tournées de Véhicules avec Contraintes de Chargement à Deux Dimensions (2L-VRP). Nous montrons une partie des possibilités qu’il existe afin de modifier une méthode a priori exacte en une méthode heuristique et nous évaluons ces possibilités à l’aide de tests expérimentaux / We are interested in this thesis in the possibilities of hybridization between the exact methods and the methods heuristics to be able to take advantage of each of both approaches: optimality of the exact resolution, the less determinist character and the speed of the constituent heuristics. In the objective to resolve problems NP-hard of relatively important size such as the transportation problems, we are interested in the last two parts of this report in the conception of incomplete methods based on these hybridizations. In the first part, we are going to be interested in the methods of resolution by tree search. We introduce a new approach for the management of the decisions of connection, which we call Dynamic Learning Search ( DLS). This method defines in a dynamic way rules of priority for the selection of variables in every knot and the order of the values on which to connect. These rules are conceived in an optics of genericity, so as to be able to use the method independently of the treated problem. The general principle is to take into account by a technique of learning of the impact which had the decisions of connection in the parts already investigated in the tree. We estimate the efficiency of the method proposed on two classic problems: a combinatorial optimization problem and a constraints satisfaction problem. The second part of this report handles large neighborhood search. We present a new operator of neighborhood, who determines by an algorithm of dynamic programming the optimal sub-sequence of a road in a graph. We show that this operator is quite particularly intended for problems of tours for which all the vertices do not require to be visited. We call this class of problem the Problems of Tours with Partial Cover and present some problems being a part of this class. Chapters 3 and 4 show, through consequent experimental tests, the efficiency of the operator which we propose by applying this search to wide neighborhood on two problems, respectively the Traveling Purchaser Problem (TPP) and Generalized Traveling Salesman Problem ( GTSP). We show while this operator can be combined in a effective way with classic metaheuristics, such as genetic algorithms or algorithms of Ant Colony Optimization
697

Max-résolution et apprentissage pour la résolution du problème de satisfiabilité maximum / Max-resolution and learning for solving the Max-SAT problem

Abramé, André 25 September 2015 (has links)
Cette thèse porte sur la résolution du problème d'optimisation Maximum Satisfiability (Max-SAT). Nous y étudions en particulier les mécanismes liés à la détection et à la transformation des sous-ensembles inconsistants par la règle de la max-résolution. Dans le contexte des solveurs de type séparation et évaluation, nous présentons plusieurs contributions liées au calcul de la borne inférieure. Cela va du schéma d'application de la propagation unitaire utilisé pour détecter les sous-ensembles inconsistants à l'extension des critères d'apprentissage et à l'évaluation de l'impact des transformations par max-résolution sur l'efficacité des solveurs. Nos contributions ont permis l'élaboration d'un nouvel outil de résolution compétitif avec les meilleurs solveurs de l'état de l'art. Elles permettent également de mieux comprendre le fonctionnement des méthodes de type séparation et évaluation et apportent des éléments théoriques pouvant expliquer l'efficacité et les limites des solveurs existants. Cela ouvre de nouvelles perspectives d'amélioration, en particulier sur l'augmentation de l'apprentissage et la prise en compte de la structure interne des instances. Nous présentons également un exemple d'utilisation de la règle de la max-résolution dans un algorithme de recherche local. / This PhD thesis is about solving the Maximum Satisfiability (Max-SAT) problem. We study the mechanisms related to the detection and transformations of the inconsistent subsets by the max-resolution rule. In the context of the branch and bound (BnB) algorithms, we present several contributions related to the lower bound computation. They range from the study of the unit propagation scheme used to detect inconsistent subsets to the extension of the learning criteria and to the evaluation of the impact of the max-resolution transformations on the BnB solvers efficiency. Thanks to our contributions, we have implemented a new solver which is competitive with the state of art ones. We give insights allowing a better understanding of the behavior of BnB solvers as well as theoretical elements which contribute to explain the efficiency of these solvers and their limits. It opens new development perspectives on the learning mechanisms used by BnB solvers which may lead to a better consideration of the instances structural properties. We also present an example of integration of the max-resolution inference rule in a local search algorithm.
698

Efeitos da terapia de ressincronização cardíaca (TRC) sobre a perfusão miocárdica: correlações clínico-funcionais / Effects of cardiac resynchronization therapy (CRT) on myocardial perfusion: clinical and functional correlations

Simone Cristina Soares Brandão 17 September 2008 (has links)
Introdução: a cintilografia cardíaca com MIBI-99mTc sincronizada ao eletrocardiograma (gated SPECT) avalia integridade celular, perfusão miocárdica e função global e regional do ventrículo esquerdo (VE). A terapia de ressincronização cardíaca (TRC) pode melhorar os sintomas de insuficiência cardíaca (IC), mas seus benefícios sobre a função do VE são menos pronunciados. Objetivos: avaliar se as mudanças na captação miocárdica do MIBI-99mTc após a TRC estão associadas à melhora clínica, à redução do QRS ao eletrocardiograma e ao desempenho do VE e se a gated SPECT adiciona informação na seleção e acompanhamento de pacientes para a TRC. Método: trinta pacientes (idade media 59 ± 11 anos, 47% masculinos) com miocardiopatia dilatada não isquêmica, IC classe funcional III ou IV da New York Heart Association com tratamento medicamentoso otimizado, bloqueio de ramo esquerdo e fração de ejeção do ventrículo esquerdo (FEVE) inferior a 35% participaram deste estudo. Foram avaliados pré e três meses após TRC as seguintes variáveis: classe funcional de IC, duração do QRS, FEVE pela ecocardiografia, captação miocárdica do MIBI-99mTc (%) ao repouso e após estresse com adenosina, volumes diastólico (VDF) e sistólico finais (VSF) do VE, motilidade e espessamento regionais nas paredes do VE pela Gated SPECT. Após TRC, os pacientes foram divididos em dois grupos de acordo com a melhora na FEVE: grupo 1 (G1=12 pacientes) com aumento 5 pontos absolutos; e grupo 2 (G2=18 pacientes) sem aumento significante. Resultados: após TRC, ambos os grupos melhoraram significantemente a classe funcional de IC, reduziram QRS e aumentaram a captação miocárdica do MIBI-99mTc nas paredes ântero-septal e ínfero-septal. Apenas G1 apresentou mudanças favoráveis no VDF, VSF, motilidade e espessamento regionais do VE. Pré TRC, pela análise univariada, o VDF e ESV foram estatisticamente maiores no G2 em relação ao G1 (VDF: 477 ± 168 mL vs. 276 ± 94 mL, p<0,001; VSF: 401 ± 154 mL vs. 220 ± 85 mL, p<0,001, G2 e G1, respectivamente). A captação miocárdica do MIBI-99mTc foi menor no G2 em relação ao G1 nas paredes anterior (60 ± 10% vs. 67 ± 7%, p=0,049, repouso) e inferior (48 ± 10% vs. 59 ± 11%, repouso, e 47 ± 10% vs. 58 ± 9%, p=0,003, após estresse). A soma dos escores de hipocaptação após estresse foi significantemente maior no G2 em relação ao G1 (14 ± 9 e 9 ± 4, G2 e G1, respectivamente, p=0,039). Pela análise multivariada, o VDF foi o único preditor independente de aumento na FEVE após terapia, p=0,01. O ótimo ponto de corte do VDF pela curva ROC para predizer melhora na FEVE após terapia foi 315 mL com sensibilidade de 89% e especificidade de 94%. Conclusões: A TRC aumentou a captação miocárdica regional de MIBI-99mTc, melhorou a classe funcional de IC e reduziu QRS independentemente da melhora do desempenho cardíaco. Após TRC, o aumento da FEVE ocorreu em corações menos dilatados e com uma maior captação miocárdica regional do MIBI-99mTc, principalmente na parede inferior / Background: gated myocardial scintigraphy with 99mTc-MIBI (gated SPECT) evaluates myocyte integrity, myocardial perfusion and global and regional left ventricular (LV) function. Cardiac resynchronization therapy (CRT) may improve heart failure (HF) clinical symptoms, but its benefits for LV function are less pronounced. Objectives: we assessed whether changes on myocardial 99mTc-MIBI uptake post-CRT are related to improvement in clinical HF symptoms, reduction in QRS duration and improvement in LV performance, and whether gated SPECT with 99mTc-MIBI adds information to selection and follow-up of patients undergoing CRT. Methods: thirty patients (mean age 59 ± 11, 47% male) with nonischemic dilated cardiomyopathy, chronic HF in New York Heart Association functional class III or IV with optimized clinical treatment, left bundle-branch block, and LV ejection fraction (LVEF) inferior to 35% participated to this study. Pre- and 3 months post-CRT, the variables analyzed were: HF functional class, QRS duration, LVEF by echocardiography, myocardial 99mTc-MIBI uptake (%) at rest and after adenosine stress, LV end-diastolic (EDV) and end-systolic volumes (ESV), regional LV motion and thickness by gated SPECT. Post-CRT, patients were divided into 2 groups according to LVEF improvement: group 1 (G1=12 patients) with increase in LVEF5points and group 2 (G2=18 patients) without significant increase. Results: post-CRT, both groups improved significantly in HF functional class, reduced QRS width and increased antero-septal and infero-septal wall 99mTc-MIBI uptake. Only G1 had favorable changes in EDV, ESV, and LV regional motion and thickness. Pre- CRT, by univariate analysis, EDV and ESV were statistically higher in G2 compared with G1 (EDV: 477 ± 168 mL vs. 276 ± 94 mL, p<0.001; ESV: 401 ± 154 mL vs. 220 ± 85 mL, p<0.001, G2 and G1, respectively). Myocardial 99mTc-MIBI uptake was lower in G2 compared with G1 in the anterior wall (60 ± 10% vs. 67 ± 7%, p=0.049, at rest) and inferior wall (48 ± 10% vs. 59 ± 11%, at rest, and 47 ± 10% vs. 58 ± 9%, p=0.003, after adenosine stress). Summed stress score was significantly higher in G2 compared to G1 (14 ± 9 vs. 9 ± 4, G2 and G1, respectively, p=0.039). By multivariate analysis, EDV was the only independent predictor of LVEF increase posttherapy, p=0.01. By ROC curve, optimal EDV cutoff point was 315mL with 89% of sensitivity and 94% of specificity. Conclusions: CRT increased myocardial 99mTc- MIBI uptake, improved HF functional class, and reduced QRS width independently of LV performance improvement. Post-CRT, LVEF increase occurred in hearts less dilated showing higher regional myocardial 99mTc-MIBI uptake, mainly in the inferior wall
699

A customer satisfaction evaluation of the AFISC Data Analysis Branch

Asmus, Lawrence J. 01 January 1981 (has links)
No description available.
700

Tlumení tlakových pulzací a snižování hluku v potrubních systémech / Damping of pressure pulsations and noise reduction in pipeline systems

Čepl, Ondřej January 2021 (has links)
The diploma thesis deals with pressure pulsations in pipeline system with dynamic muffler. There is presented original geometry of side-branch resonator. Pressure pulsations are solved by a created mathematical model, numerical simulations and verified by an experimental approach. The influence of dynamic and bulk viscosity is involved in derived governing equations. A system of nonlinear equations is solved by genetic algorithm and frequency dependent relationship of bulk viscosity of air is determined afterwards. The correct function of used pressure sensors is tested. The processing of experimental data is performed by the fast Fourier transform with coherent sampling. Finally, a comparison of analytical, numerical and experimental approaches is introduced for different geometric variants of presented muffler.

Page generated in 0.0495 seconds