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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.
781

Connaissance inter-entreprises et optimisation combinatoire / Inter-companies knowledge and combinatorial optimization

Ould Mohamed Lemine, Mohamed 17 June 2014 (has links)
La connaissance inter-entreprises permet à chaque société de se renseigner sur ses clients, ses fournisseurs et de développer son activité tout en limitant le risque lié à la solvabilité ou retard de paiement de ses partenaires. Avec les tensions de trésorerie, la nécessité de la croissance et l'augmentation de la concurrence, ce domaine devient plus que jamais stratégique aussi bien pour les PME que pour les grands groupes. La quantité de données traitée dans ce domaine, les exigences de qualité et de fraîcheur, la nécessité de croiser ces données pour déduire des nouvelles informations et indicateurs, posent plusieurs problèmes pour lesquels l'optimisation en général et l'optimisation combinatoire en particulier peuvent apporter des solutions efficaces. Dans cette thèse, nous utilisons l'optimisation combinatoire, l'algorithmique du texte et la théorie des graphes pour résoudre efficacement des problèmes issus du domaine de la connaissance inter-entreprises et posés par Altares D&B. Dans un premier temps, nous nous intéressons à la qualité de la base de données des dirigeants. Ce problème combine la détection et suppression des doublons dans une base de données et la détection d'erreurs dans une chaîne de caractères. Nous proposons une méthode de résolution basée sur la normalisation des données et l'algorithmique de texte et de comparaison syntaxique entre deux chaînes de caractères. Les résultats expérimentaux montrent non seulement que cette méthode est pertinente dans la détection et la suppression des doublons mais aussi qu'elle est efficace de point du vue temps de traitement. Nous nous focalisons par la suite sur les données des liens capitalistiques et nous considérons le problème de calcul des liens indirects et l'identification des têtes des groupes. Nous présentons une méthode de résolution basée sur la théorie des graphes. Nous testons cette méthode sur plusieurs instances réelles. Nous prouvons l'efficacité de cette méthode par son temps de traitement et par l'espace de calcul qu'elle utilise. Enfin, nous remarquons que le temps de calcul de celui-ci augmente de façon logarithmique en fonction de la taille d'instance. Enfin, nous considérons le problème de l'identification des réseaux d'influence. Nous formalisons ce problème en termes de graphes et nous le ramenons à un problème de partitionnement de graphe qui est NP-difficile dans ce cas général. Nous proposons alors une formulation en programme linéaire en nombre entier pour ce problème. Nous étudions le polyèdre associé et décrivons plusieurs classes de contraintes valides. Nous donnons des conditions nécessaires pour que ces contraintes définissent des facettes et discutons des algorithmes de séparations de ces contraintes. En utilisant les résultats polyédraux obtenus, nous développons un algorithme de coupes et branchements. Enfin, nous donnons quelques résultats expérimentaux qui montrent l'efficacité de notre algorithme de coupes et branchements / The inter-companies knowledge allows to every partner to learn about its customers, its suppliers and to develop its activity. Also this permits to limit the risk related to the creditworthiness, or the late payment of its partners. With the cash flow pressures, the need for growth and increased competition, this area becomes more strategic than ever, for both small (PME) and large groups. The amount of data processed in this domain, the requirements of quality and freshness, the need to cross these data to obtain new information and indicators, yield several optimization problems for which the recent techniques and computational tools can bring effective solutions. In this thesis, we use combinatorial optimization, text algorithms as well as graph theory to solve efficiently problems arising in the field of inter-companies knowledge. In particular, such problems was encountered in Altares D&B. First, we focus on the quality of the managers database. This problem combines the detection and removal of duplicates in a database, as well as the error detection in a string. We propose a method for solving this problem, based on data normalization, text algorithms and syntactic comparison between two strings. Our experimental results show that this method is relevant for the detection and removal of duplicates, and it is also very efficient in terms of processing time. In a second part of the thesis, we address a problem related to the data of ownership links. We compute the indirect links, and identify the group heads. We propose a method for solving this problem using graph theory and combinatorial optimization. We then perform a set of experiments on several real-world instances. The computational results show the effectiveness of our method in terms of CPU-time and resource allocation. In fact, the CPU time for computation increases logarithmically with the size of the instances. Finally, we consider the problem of identifying influence networks. We give a description of this problem in terms of graphs, and show that it can reduce to a graph partitioning problem. The latter is NP-hard. We then propose an integer linear programming formulation to model the problem. We investigate the associated polyhedron and describe several classes of valid inequalities. We give some necessaryand sufficient conditions for these inequalities to define facets of the considered polyhedron, and we discuss the related separation problems. Based on the obtained polyhedral results, we devise a Branch-and-Cut algorithm to solve the problem. Some numerical results are presented to show the efficiency of our algorithm.
782

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.
783

行政部門的資訊優勢對立法的影響力—以第八屆立法院為例 / The Informational Advantage of the Executive Branch in the Legislation: The Case of Legislative Yuan from 2012 to 2016

宋至晟, Sung, Chih Cheng Unknown Date (has links)
本研究以行政院在立法上的影響力為焦點。筆者認為立法委員有動機成就好的立法,在行政部門的資訊優勢下,立法委員會傾向接受行政部門陳述的觀點,並導致行政部門對於立法產生相當突出的影響力。本文先以深入訪談法瞭解與佐證行政部門的資訊優勢確實存在且影響卓越,再以內容分析法分析行政部門的態度對於立法結果的影響。 研究結果發現,行政部門對於立法院的優勢呈現在其對於資訊的壟斷、行政執行經驗及專業程度等優勢上。另外,經驗分析顯示,行政部門的意見確實對於重大法案的結果,具有相當重要的影響,筆者認為,行政部門的立法影響力,已近乎於否決者的角色。換句話說,若一個法案想要順利通過,行政部門的肯認,或至少不表達反對,已成為立法成功的必要條件之一。 最後,過去相關的文獻曾指出一個提案的提案者黨籍、是否為委員會成員及召集委員、有無經過黨團協商等因素,皆與該提案能否順利三讀通過有關。本文的經驗數據也呈現相似的結論。更進一步地,本研究發現,在考量上述因素後,行政部門對於立法的影響依然最為深遠。 / This thesis focuses on the legislative influence of the Executive Yuan. The author believes the legislators are motivated to achieve the high quality of law-making. Because of the informational advantage of the executive branch, the legislators tend to accept the perspective made by the executive branch, which leads to the significant influence in the Legislation. First, this paper uses intensive interviews to find out and justify the existence of the informational advantage of the executive branch and its profound influence on the legislation. Furthermore, by using content analysis, this paper intends to dissect what the attitude of the executive branch has an effect on the legislative outcomes. The result revealed the relative advantage of the executive branch over the Legislative Yuan lies on the informational monopoly, administrative executive experiences and the high-level of professionalization. Additionally, the empirical analysis shows the executive branch does have the significant impact on the outcomes of major bills. In the author’s opinion, the effect of the executive branch has come close to the role of veto players. In other words, the approval of the executive branch, or at least the attitude of non-objection, has become one of the necessary conditions for successful legislation. Finally, relevant literature reviews have pointed out several factors that are associated with whether a bill can pass or not. Those factors include the partisanship, committee member, committee chair and the process of party negotiation, etc. The empirical analysis of this thesis disclosed similar conclusions as other literature reviews. Further, this thesis discovers, by taking the above factors into consideration, the executive branch plays the most significant role in the legislation.
784

Mathematical programming approaches to pricing problems

Violin, Alessia 18 December 2014 (has links)
There are many real cases where a company needs to determine the price of its products so as to maximise its revenue or profit.<p>To do so, the company must consider customers' reactions to these prices, as they may refuse to buy a given product or service if its price is too high. This is commonly known in literature as a pricing problem.<p>This class of problems, which is typically bilevel, was first studied in the 1990s and is NP-hard, although polynomial algorithms do exist for some particular cases. Many questions are still open on this subject.<p><p>The aim of this thesis is to investigate mathematical properties of pricing problems, in order to find structural properties, formulations and solution methods that are as efficient as possible. In particular, we focus our attention on pricing problems over a network. In this framework, an authority owns a subset of arcs and imposes tolls on them, in an attempt to maximise his/her revenue, while users travel on the network, seeking for their minimum cost path.<p><p>First, we provide a detailed review of the state of the art on bilevel pricing problems. <p>Then, we consider a particular case where the authority is using an unit toll scheme on his/her subset of arcs, imposing either the same toll on all of them, or a toll proportional to a given parameter particular to each arc (for instance a per kilometre toll). We show that if tolls are all equal then the complexity of the problem is polynomial, whereas in case of proportional tolls it is pseudo-polynomial.<p>We then address a robust approach taking into account uncertainty on parameters. We solve some polynomial cases of the pricing problem where uncertainty is considered using an interval representation.<p><p>Finally, we focus on another particular case where toll arcs are connected such that they constitute a path, as occurs on highways. We develop a Dantzig-Wolfe reformulation and present a Branch-and-Cut-and-Price algorithm to solve it. Several improvements are proposed, both for the column generation algorithm used to solve the linear relaxation and for the branching part used to find integer solutions. Numerical results are also presented to highlight the efficiency of the proposed strategies. This problem is proved to be APX-hard and a theoretical comparison between our model and another one from the literature is carried out. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
785

Intensification of ATRP polymer syntheses by microreaction technologies / Intensification de la synthèse de polymères par ATRP au moyen de technologies de microréaction

Parida, Dambarudhar 13 February 2014 (has links)
L'objectif de ce travail fut d'intensifier des procédés de polymérisation radicalaire par transfert d'atomes (ATRP) du méthacrylate de 2-(dimétylamino)éthyle (DMAEAMA) au moyen de technologies de microréaction (microréacteurs, micromélangeurs) et de paramètres de procédé (géométrie du réacteur, température, pression ... ).L'impact du prémélange sur les caractéristiques d'un copolymère statistique du DMAEMA et du méthacrylate de benzyle synthétisé dans des microréacteurs hélicoïdaux (CT) fut étudié en utilisant des principes différents de micromélange: bilamination, multilamination interdigitale (!MM) et jet d'impact. Des caractéristiques bien mieux contrôlées ont été obtenues avec !'IMM et l'intensification du procédé (Pl) a été clairement démontrée encomparaison d'un réacteur fermé ; en effet des masses molaires et conversions plus élevées ainsi que de plus faibles indices de polymolécularité (PDI) ont été obtenus pour des temps de passage inférieurs. Pour la production de PMADAME linéaire, le PI a également été réalisé par augmentation de la température et de la pression (jusqu'à 1 OO bars). Toutefois de trop hautes températures se sont avérées préjudiciables notamment pour de longs temps de passage. L'effet de l'augmentation du taux de cisaillement (via la longueur du réacteur) ne fut bénéfique qu'en régime dilué à un stade précoce de la réaction lorsque les masses molaires sont encore faibles. Comparés aux CT, un mélange interne favorisé par une technique d'inversion de flux s'est révélé être une stratégie très efficace pour réduire davantage le PDI et obtenir des masses molaires et conversions plus élevées. Des polymères branchés synthétisés en microréacteurs à inversion de flux (CFI) par ATRP en présence d'inimère présentèrent une structure plus ramifiée soulignant ainsi la supériorité des CFI sur les CT et réacteurs fermés en termes de PDI et d'efficacité de branchement. Considérant les caractéristiques des CFI, l'augmentation d'échelle des microréacteurs fut considérée par accroissement de leur diamètre. La productivité du procédé a été augmentée d'un facteur 4 tout en gardant un bon contrôle sur les caractéristiques macromoléculaires. Ainsi fut-il démontré que l'inversion de flux est un moyen très efficace pour contrebalancer l'effet négatif d'une augmentation du diamètre du microréacteur. / The aim of this work was to intensify Atom Transfer Radical polymerization (ATRP) processes for the production of DMAEMA-based (co)polymers by relying on microreaction technology tools (microreactor, micromixers) and process parameters (reactor geometry, temperature, pressure ... ). Impact of premixing on macromolecular characteristics of P(DMAEMA-co-BzMA) synthesized in coiled tube (CT) microreactors was studied using different micromixing principles: bilamination, interdigital multilamination (IMM) and impact jet.Better controlled characteristics were obtained with !MM and process intensification (PI) was clearly demonstrated in comparison with batch mode as higher molecular weights, increased monomer conversions and lower polydispersity indices (PDI) were obtained for lower residence times. For the production of linear PDAEMA, PI was also achieved by application of elevated temperature and pressure (up to 100 bars). However, high temperature was found to be detrimental for long residence times. Effect of increased shear rate (i.e. reactor length) was found only beneficial in dilute regime at the early stage of the polymerization reaction when molecular weights are low. ln comparison with CT reactors, internal mixing promoted by flow inversion technique was found to be quite an effective strategy to reduce further PDI and obtain higher molecular weights and monomer conversions. Branched polymers synthesized by self condensing vinyl copolymerization (SCVCP) adapted to ATRP in tubular coil flow inverter (CFI) microreactors exhibited higher branched structure highlighting the superiority of CFI microreactor over CT and batch reactors in terms of PD! and branching efficiency. Finally, considering such features of CFI, attempt was made to scale-up microreactors by increasing their diameter. lt was found that process throughput can be increased by more than a factor of 4 while keeping a good control over macromolecular characteristics. Thus itwas demonstrated that flow inversion is quite effective to counter balance the detrimental effect of an increase in microreactor diameter.
786

Features of the Electric Fields Generated by Lightning with Special Attention to Positive Ground Flashes

Johari, Dalina January 2017 (has links)
This thesis focuses on the main processes in positive ground flashes and the distant lightning environment for both positive and negative ground flashes. It presents the characteristics of the preliminary breakdown pulses (PBPs), the characteristics of the electric field pulses observed during leader propagation, and the characteristics of the electric fields produced by the first and the subsequent return strokes. It also features the observations of distant positive and negative ground flashes at distances up to 1000 km. The results were based on electric field measurements conducted remotely during summer thunderstorms in Sweden in 2014. We found that the majority of the positive ground flashes were preceded by PBPs. Some were preceded by more than one PBP train, and the parameter values for the subsequent PBP trains were found to be smaller than the values for the first PBP train. Three types of PBPs were also identified. The results suggest that the PBPs in positive ground flashes during summer thunderstorms in Sweden are weak, and the inverted dipole charge cloud configuration is consistent with our observation. A small percentage of these positive ground flashes were observed to be preceded by pronounced leader pulses. The presence of these pulses suggests that the leaders propagate in a stepped manner. We inferred that these pulses were due to the upward-connecting negative leader since their characteristics were similar to those of a negative stepped leader. On the basis of the leader pulses’ time of initiation and the average speed of the leader, we estimated the distance travelled by the leader. One case of positive return stroke preceded by negative leader pulses was also observed, and the occurrence of these pulses was the first in positive ground flashes to be reported. The majority of these positive ground flashes were found to be single-stroke. Comparison between the first and the subsequent return strokes showed that the average durations of the subsequent stroke parameters were smaller than that of the first strokes. The distances reported by the lightning location system suggest that the subsequent strokes probably created new terminations to ground. Two possible reasons were given to explain the reason for the shorter duration of the subsequent return strokes parameters compared to the first strokes. Finally, observations of distant positive and negative ground flashes showed that the electric field waveforms have a typical shape, like a distorted ‘W’ (or distorted ‘M’ for negative ground flashes) followed by small oscillations. These small oscillations were more pronounced in negative ground flashes, especially at a greater distance. The heights of the ionospheric reflections estimated for both ground flashes were found to likely correspond to a D-layer of the ionosphere. Two possible reasons were suggested for the small oscillations observed in the waveforms.
787

Interaction between Flow Induced Pulsations and Multiphase Flows in Gas Liquid Systems / Oscillations auto-induites en systèmes de conduites en présence d’écoulement diphasique air/eau

Sanna, Francesco 15 April 2016 (has links)
Le couplage entre un écoulement instable et des résonances acoustiques dans des systèmes de conduites peut conduire à des phénomènes d’oscillations auto-induites. Ce type de phénomènes trouve principalement place dans des conduites latérales fermées, par exemple dans des systèmes de transport ou de compression de gaz. L’objectif de ce travail est d’étudier les oscillations auto-induites dans le cas où le fluide transporté ne se limite pas à un gaz, mais est un mélange de gaz et de liquide. Les pulsations sont mesurées dans des conduites latérales fermées, pour deux types de configurations (en tandem et en croix), avec écoulement d’un mélange variable d’air et d’eau. La position de l’injection d’eau est variable afin d’obtenir plusieurs régimes d’écoulement diphasique. Les résultats indiquent que la présence d’eau a un effet important sur les niveaux de pulsations dans les conduites. Cet effet a pu être attribué à deux mécanismes dus à la présence d’eau : les instabilités de couches de mélange sont modifiées et l’amortissement des ondes acoustiques est amplifié.Le deuxième mécanisme a été quantifié à l’aide de mesures sur un montage expérimental dédié conçu pour avoir un écoulement stratifié. On a observé que, dans tous les cas, la présence d’eau augmente l’amortissement. Cette augmentation a pu être attribuée à la réduction de la section effective de la conduite (due au remplissage partiel par l’eau) et à l’augmentation de la friction turbulente à l’interface entre les phases liquide et gazeuse. / Coupling between flow instabilities and acoustic resonances in ducts with closed side branches leads to Flow Induced Pulsations (FIPs). This is a typical phenomenon in engineering applications (gas transport systems, compressor installations, and chemical plants). The objective of this work is to extend the knowledge about FIPs when the transported medium is not uniquely gas but a combination of gas and (a small quantity of) liquid. For two configurations of double side branches (in tandem and in quasi-cross), the amplitude of pressure pulsations in the side branches was measured for different liquid injection rates. This was repeated with the liquid injection point located at different places to allow different flow regimes at the pipe connections. The results show a strong effect of the water content on the pulsations. On basis of these results and additional measurements, the following hypotheses for the effect of liquid were made: (1) interaction of the liquid with the flow instability and (2) increase of the acoustical damping in the ducts in presence of liquid.The effect of liquid on damping was measured with a dedicated test setup designed to have a stratified flow. It was found that the liquid always increases the acoustical damping, mainly due to the reduction of the effective cross section by the liquid, and because of the increased turbulent friction at the interface between gas and liquid.
788

Analýza prístupu krajín strednej a východnej Európy k členstvu v bankovej únii / Analysis of the approaches of Central and Eastern European countries towards their membership in the Banking union

Samuelis, Tomáš January 2014 (has links)
The goal of this thesis is to analyze the approaches of countries in Central and Eastern European region towards their membership in the Banking Union. The selected topic has been investigated based on structural characteristics of the banking sectors of the impacted countries. The comparison of these characteristics resulted in identification of inconsistencies between the 2 standpoints (Opt-in and Opt-out). The thesis monitors the motivation of banks in choosing or changing the legal form of 'their' banks in host markets. The work identifies areas in which the host government can act to prevent banks from converting into branches, thus retaining the regulatory powers in local authorities. The thesis in the first 2 chapters maps the first and the second pillar of the Banking Union, Single Supervisory Mechanism and the Single Resolution Mechanism respectively. Furthermore, it summarizes the results of the European Central Bank in carrying out the Comprehensive Assessment exercise.
789

Účetní výkazy a finanční analýza / Financial statements and financial analysis

Skučková, Hana January 2008 (has links)
Financial analysis is very important in making decisions and also has some dificulties. The first part is about sources of information for financial analysis (balance sheet, income statement, cash flow, annual reports etc.). The second part describes elementary methods of financial analysis. Mainly methods of calculation, interpretation and usage of ratios for the purpose of firm's financial health evaluation (profitability, liquidity, financial stability etc.). The third part is about history of brewing indurstry, history and present of Pivovar Holba, a. s. There are calculated indicators and are compared with branch average and median.
790

Nové směry v přístupu ke strategii v německých slévárnách litiny / New Trends of Strategy Conceptions in Germany Iron Foundries

Kupec, Olga January 2009 (has links)
Doctoral dissertation work that results from the new management theory has explored in both theory and practice new directions in approach to the strategy in German iron-foundries. It has explained the reasons that lead to structural changes, made the foundation for decision process, described the problems that occur when put in practice and suggested their resolution. Further on, it was explored and critically evaluated which competitive advantages these strategy directions contributed to and consequently discussed the superior aim of strategy. It has resulted from the empirical research that the German iron-foundries have been strongly influenced especially by new information technologies and car industry and its strategies. The most significant trend of iron-foundries is the focus on the key branch of activity. Cooperation and innovative strategy represent the complementary strategy to the primary strategy and enable to merge the comprehensive requirements of customers with the needed specialization and hereby retain their competitiveness. The research respecting the global economic crisis in the car industry shows that German iron-foundries have to re-evaluate their actual strategies and convert the growth to stability and long lasting development.

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