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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.
111

Empirical Essays on the Efficiency of Heterogeneous Good Auction

Martin, Thomas A., IV 14 January 2010 (has links)
A recent pursuit of the auction design literature has been the development of an auction mechanism which performs well in a multi-good setting, when the goods are not substitutes. This work began in earnest with the Federal Communications Commission spectrum license auctions in the early nineties and continues to this day. In a setting in which goods are not substitutes, the value of one good depends nonnegatively on the quantities of other goods that are won. This type of interdependent value structure has proven difficult to account for in auction design. However, the need for mechanisms that account for such a value structure hinges on the magnitude of the interdependence, whose computation is an empirical exercise. I identify a setting in which to perform this computation. I develop an empirical methodology that allows me to recover bidders' value functions in a multi-good auction setting. This methodology allows me to assess the magnitude of any interdependence in the goods? value structure. Since the auction setting that I analyze is a variation of the standard uniform price auction, which has been adapted for a multi-good setting, I am able to measure the benefit of having a direct revelation mechanism. This counterfactual study is performed by maximizing the value of the auction using the recovered bidder value functions. I find evidence that there is an interdependent value structure in the setting. The counterfactual auction finds that the standard uniform price auction, adapted to a multi-good setting, performs poorly in the presence of such a value structure. The setting for this analysis is an auction for financial transmission rights held in Texas in 2002. The auction involved twenty two firms and collected almost $70 million in revenue. This research is the first to empirically assess efficiency in this type of auction setting.
112

Computer-Aided Design of Multi-Speed Hub System for Bicycles

Chen, Hung-Hsuan 25 July 2005 (has links)
The multi-speed drive hub mainly makes for change speed with planetary gear trains. It has some advantages such as small, change the shelf steadily to move and difficult to receive external environmental impact. So the multi-speed drive hub has already become the focal point that every bicycle's factory researches and develops gradually. The purpose of this work is to develop a system methodology for the computer-aided design of multi-speed bicycle drive hubs. First, analyzing multi-speed drive hub patents to identify the basic characteristics and requirement of multi-speed drive hub, and using a systematized method synthesizes the feasible gear trains. Second, a method is proposed to determine the feasible multi-speed sequence tables for each planetary gear train. Third, a method is formulated to find the gear ratios and gear teeth according to the feasible multi-speed sequence tables. Fourth, a method is to design and dispose the governors of multi-speed drive hubs easily. Finally, using Visual Basic 6.0 procedure language develop a computer software easy to use by utilizing the above-mentioned procedures, and the results of this work will be benefit to the development and design of multi-speed bicycle drive hubs.
113

Cost minimization in multi−commodity multi−mode generalized networks with time windows

Chen, Ping-Shun 25 April 2007 (has links)
The purpose of this research is to develop a heuristic algorithm to minimize total costs in multi-commodity, multi-mode generalized networks with time windows problems. The proposed mathematical model incorporates features of the congestion of vehicle flows and time restriction of delivering commodities. The heuristic algorithm, HA, has two phases. Phase 1 provides lower and upper bounds based on Lagrangian relaxations with subgradient methods. Phase 2 applies two methods, early due date with overdue-date costs and total transportation costs, to search for an improved upper bound. Two application networks are used to test HA for small and medium-scale problems. A different number of commodities and various lengths of planning time periods are generated. Results show that HA can provide good feasible solutions within the reasonable range of optimal solutions. If optimal solutions are unknown, the average gap between lower and upper bounds is 0.0239. Minimal and maximal gaps are 0.0007 and 0.3330. If optimal solutions are known, the maximal gap between upper bounds and optimal solutions is less than 10% ranges of optimal solutions.
114

Study of MIMO, orthogonal codes and core operator architecture design for ML decoder

Sevelimedu Veeravalli, Vinodh January 2007 (has links)
<p>In the high-end research process of wireless systems and in the race for the development of the new technologies, MIMO (Multiple Input, Multiple Output) is getting more attention now days. It has a high potential usage in the 3G and 4G communications and beyond. The MIMO based system has got the ability to increase the data throughput in spectrum-limited conditions. With the increase and complexity of wireless applications, the spectrum efficiency improvement in the physical layer will be saturated. MIMO is predicted to be one of the major features for the next generation wireless networking. This thesis work is a part of an ongoing project of the Generic MIMO decoder design carried out at the research laboratory, LESTER at Lorient, France. I was involved in the study of MIMO concepts, orthogonal and Space-time codes and later involved in the design and optimization of the architecture for the core operator for the ML decoder used in the reception of the MIMO system,which is presented in this report work.</p>
115

Interference Alignment with Distributed Antenna Systems

Starr, Jonathan Kenneth 17 February 2012 (has links)
This paper considers the combination of interference alignment and distributed antenna systems to improve the rate performance of cell-edge users in the cellular downlink. Because the power resources of each antenna in distributed antenna systems are geographically separated, practical implementations of distributed antenna systems require consideration of per-antenna power constraints on the transmit antennas. For this reason, we consider interference alignment with two types of power constraints: per-antenna power inequality constraints and per-antenna power equality constraints. On one hand, we show that interference alignment with per-antenna power inequality constraints is arbitrarily feasible using a technique of antenna power back-off but suffers from a loss of performance that we quantify in the case of Rayleigh-fading. On the other hand, we show that interference alignment with per-antenna power equality constraints does not suffer from a systematic loss of performance but yet requires more antennas to be feasible. We develop algorithms for implementing interference alignment with both types of constraints and numerically validate the results of our analysis. Finally, we demonstrate using the 3rd Generation Partnership Project spatial channel model in a cellular setting that interference alignment with distributed antenna systems has better rate performance than interference alignment with centralized antenna systems throughout the entire cell, especially near the cell boundary. / text
116

Study of MIMO, orthogonal codes and core operator architecture design for ML decoder

Sevelimedu Veeravalli, Vinodh January 2007 (has links)
In the high-end research process of wireless systems and in the race for the development of the new technologies, MIMO (Multiple Input, Multiple Output) is getting more attention now days. It has a high potential usage in the 3G and 4G communications and beyond. The MIMO based system has got the ability to increase the data throughput in spectrum-limited conditions. With the increase and complexity of wireless applications, the spectrum efficiency improvement in the physical layer will be saturated. MIMO is predicted to be one of the major features for the next generation wireless networking. This thesis work is a part of an ongoing project of the Generic MIMO decoder design carried out at the research laboratory, LESTER at Lorient, France. I was involved in the study of MIMO concepts, orthogonal and Space-time codes and later involved in the design and optimization of the architecture for the core operator for the ML decoder used in the reception of the MIMO system,which is presented in this report work.
117

Recalage multi-modal automatique : technique de multi-résolution parallèle appliquée à la TEP et l'IRM / Multi-modal automatic registration : A parallel multi-resolution approach applied to PET-MRI

Bernier, Michaël January 2012 (has links)
Résumé : Le recalage automatique des images issues de la tomographie par émission de positrons (TEP) et de l’imagerie par résonance magnétique (IRM) du petit animal pose un problème difficile à résoudre, tant sur l’aspect de la précision, du taux de réussite et de convergence que sur la rapidité d’exécution. En fait, la plupart des techniques de recalage actuelles sont développées et appliquées aux cerveaux humains, mais ne sont pas aussi efficaces lorsqu’appliquées sur des données animales. L’anisotropie impor¬tante des voxels (résolution fine dans le plan de l’acquisition, mais grande épaisseur de coupe) et la dégradation des images associée à ce type d’acquisition s’additionne au manque d’information d’intensité et de complexité anatomique de ce type de jeu de données. Ce mémoire met l’accent sur les techniques multimodales de recalage automatique et de leurs limites, appliquées particulièrement à la TEP et l’IRM du petit animal. Dans l’article principal présenté dans ce mémoire, nous proposons une mesure qui utilise un recalage multirésolution en parallèle (imbriqué dans la fonction d’énergie) au lieu d’une approche classique de multirésolution séquentielle, influen¬çant directement la procédure du recalage. En combinant les niveaux de basse et haute résolution des images, nous nous assurons une plus grande insensibilité par rapport au bruit, d’une ouverture accrue permettant une meilleure convergence et rapidité d’exécution. L’article démontre que notre nouvelle approche automatique est un algorithme de recalage robuste et efficace avec un taux de réussite élevé. Nous présentons également dans ce mémoire certains détails d’implantation de l’outil, qui a été créé par l’auteur de ce document, reposant sur le recalage classique et la nouvelle méthode décrite dans ce mémoire.||Abstract: Automatic registration of small animal Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) data represents a difficult problem in terms of convergence speed, accuracy and success rate. In fact, most existing registration methods are developed and applied to human brain volumes but these are not as effective for small animal data because of the lack of intensity information in the images and often the large anisotropy in voxel dimensions (very small in-plane resolution and large slice thickness). This master thesis focuses on multi-modal automatic registration techniques and their limitations, especially applied to PET-MRI registration. In the main article of this master thesis, we propose a new registration measure that combines multi-resolution in parallel (in the same energy function) instead of a classic sequential multi-resolution, which influence the procedure of the registration as well. By combining low and high resolution levels of images, we can gain from the low noise sensitivity and aperture at coarse levels and higher contrast and details at higher levels, which helps convergence accuracy and speed. The paper shows that our new approach is therefore an automatic, robust and efficient registration algorithm with a high success rate. We also present in this document some implementation details on the tool which was created by the author of this thesis based on the classic registration and the new approach described in this thesis.
118

Multi-objective optimization scheme for static and dynamic multicast flows

Donoso Meisel, Yezid 21 June 2005 (has links)
Muchas de las nuevas aplicaciones emergentes de Internet tales como TV sobre Internet, Radio sobre Internet,Video Streamming multi-punto, entre otras, necesitan los siguientes requerimientos de recursos: ancho de banda consumido, retardo extremo-a-extremo, tasa de paquetes perdidos, etc. Por lo anterior, es necesario formular una propuesta que especifique y provea para este tipo de aplicaciones los recursos necesarios para su buen funcionamiento.En esta tesis, proponemos un esquema de ingeniería de tráfico multi-objetivo a través del uso de diferentes árboles de distribución para muchos flujos multicast. En este caso, estamos usando la aproximación de múltiples caminos para cada nodo egreso y de esta forma obtener la aproximación de múltiples árboles y a través de esta forma crear diferentes árboles multicast. Sin embargo, nuestra propuesta resuelve la fracción de la división del tráfico a través de múltiples árboles. La propuesta puede ser aplicada en redes MPLS estableciendo rutas explícitas en eventos multicast.En primera instancia, el objetivo es combinar los siguientes objetivos ponderados dentro de una métrica agregada: máxima utilización de los enlaces, cantidad de saltos, el ancho de banda total consumido y el retardo total extremo-a-extremo. Nosotros hemos formulado esta función multi-objetivo (modelo MHDB-S) y los resultados obtenidos muestran que varios objetivos ponderados son reducidos y la máxima utilización de los enlaces es minimizada.El problema es NP-duro, por lo tanto, un algoritmo es propuesto para optimizar los diferentes objetivos. El comportamiento que obtuvimos usando este algoritmo es similar al que obtuvimos con el modelo.Normalmente, durante la transmisión multicast los nodos egresos pueden salir o entrar del árbol y por esta razón en esta tesis proponemos un esquema de ingeniería de tráfico multi-objetivo usando diferentes árboles para grupos multicast dinámicos. (en el cual los nodos egresos pueden cambiar durante el tiempo de vida de la conexión). Si un árbol multicast es recomputado desde el principio, esto podría consumir un tiempo considerable de CPU y además todas las comuicaciones que están usando el árbol multicast serán temporalmente interrumpida. Para aliviar estos inconvenientes, proponemos un modelo de optimización (modelo dinámico MHDB-D) que utilice los árboles multicast previamente computados (modelo estático MHDB-S) adicionando nuevos nodos egreso.Usando el método de la suma ponderada para resolver el modelo analítico, no necesariamente es correcto, porque es posible tener un espacio de solución no convexo y por esta razón algunas soluciones pueden no ser encontradas. Adicionalmente, otros tipos de objetivos fueron encontrados en diferentes trabajos de investigación. Por las razones mencionadas anteriormente, un nuevo modelo llamado GMM es propuesto y para dar solución a este problema un nuevo algoritmo usando Algoritmos Evolutivos Multi-Objetivos es propuesto. Este algoritmo esta inspirado por el algoritmo Strength Pareto Evolutionary Algorithm (SPEA).Para dar una solución al caso dinámico con este modelo generalizado, nosotros hemos propuesto un nuevo modelo dinámico y una solución computacional usando Breadth First Search (BFS) probabilístico.Finalmente, para evaluar nuestro esquema de optimización propuesto, ejecutamos diferentes pruebas y simulaciones.Las principales contribuciones de esta tesis son la taxonomía, los modelos de optimización multi-objetivo para los casos estático y dinámico en transmisiones multicast (MHDB-S y MHDB-D), los algoritmos para dar solución computacional a los modelos. Finalmente, los modelos generalizados también para los casos estático y dinámico (GMM y GMM Dinámico) y las propuestas computacionales para dar slución usando MOEA y BFS probabilístico. / Many new multicast applications emerging from the Internet, such as TV over the Internet, Radio over the Internet, Video Streaming multi-point, etc., need the following resource requirements: bandwidth consumption, end-to-end delay, packet loss ratio, etc. It is therefore necessary to formulate a proposal to specify and provide for these kinds of applications the resources necessary for them to function well. In this thesis, we propose a multi-objective traffic engineering scheme using different distribution trees to multicast several flows. In this case, we are using the multipath approach to every egress node to obtain the multitree approach and of this way to create several multicast tree. Moreover, our proposal solves the traffic split ratio for multiple trees. The proposed approach can be applied in Multiprotocol Label Switching (MPLS) networks by allowing explicit routes in multicast events to be established.In the first instance, the aim is to combine the following weighting objectives into a single aggregated metric: the maximum link utilization, the hop count, the total bandwidth consumption, and the total end-to-end delay. We have formulated this multi-objective function (MHDB-S model) and the results obtained using a solver show that several weighting objectives are decreased and the maximum link utilization is minimized. The problem is NP-hard, therefore, an algorithm is proposed for optimizing the different objectives. The behavior we get using this algorithm is similar to what we get with the solver. Normally, during multicast transmission the egress node can leave and enter of the tree and for this reason in this thesis we propose a multi-objective traffic engineering scheme using different distribution trees for dynamic multicast groups (i.e. in which egress nodes can change during the connection's lifetime). If a multicast tree is recomputed from scratch, it may consume a considerable amount of CPU time and all communication using the multicast tree will be temporarily interrupted. To alleviate these drawbacks we propose an optimization model (dynamic model MHDB-D) that uses a previously computed multicast tree (static model MHDB-S) adding new egress nodes.Using the weighted sum method to solve the analytical model is not necessarily correct, because is possible to have a non-convex space solution and some solutions cannot be found. In addition, other kinds of objectives were found in different research works. For the above reasons, a new model called GMM is proposed and to find a solution to this problem a new algorithm using a Multi-Objective Evolutionary Algorithm (MOEA) is proposed too. This algorithm is inspired by the Strength Pareto Evolutionary Algorithm (SPEA). To give a solution to the dynamic case with this generalized model a dynamic GMM model is proposed and a computational solution using Breadth First Search (BFS) probabilistic is also proposed to give a solution to the dynamic case in multicast.Finally, in order to evaluate our proposed optimization scheme, we performed the necessary simulations and tests. The main contributions of this thesis are the taxonomy, the optimization model and the formulation of the multi-objective function in static and dynamic multicast transmission (MHDB-S and MHDB-D), as well as the different algorithms proposed to give computational solutions to this problem. Finally, the generalized model with several functions found in different research works in static and dynamic multicast transmission (GMM and Dynamic GMM), as well as the different algorithms proposed to give computational solutions using MOEA and BFS probabilistic.
119

Optimisation de dispositifs FDSOI pour la gestion de la consommation et de la vitesse : application aux mémoires et fonctions logiques / FDSOI devices optimization to power and speed management : application to memory and logic function

Noël, Jean-Philippe 14 December 2011 (has links)
Avec la percée des téléphones portables et des tablettes numériques intégrant des fonctions avancées de traitement de l'information, une croissance exponentielle du marché des systèmes sur puce (SoC pour System On Chip en anglais) est attendue jusqu'en 2016. Ces systèmes, conçus dans les dernières technologies nanométriques, nécessitent des vitesses de fonctionnement très élevées pour offrir des performances incroyables, tout en consommant remarquablement peu. Cependant, concevoir de tels systèmes à l'échelle nanométrique présente de nombreux enjeux en raison de l'accentuation d'effets parasites avec la miniaturisation des transistors MOS sur silicium massif, rendant les circuits plus sensibles aux phénomènes de fluctuations des procédés de fabrication et moins efficaces énergétiquement. La technologie planaire complètement désertée (FD pour Fully depleted en anglais) SOI, offrant un meilleur contrôle du canal du transistor et une faible variabilité de sa tension de seuil grâce à un film de silicium mince et non dopé, apparaît comme une solution technologique très bien adaptée pour répondre aux besoins de ces dispositifs nomades alliant hautes performances et basse consommation. Cependant pour que cette technologie soit viable, il est impératif qu'elle réponde aux besoins des plateformes de conception basse consommation. Un des défis majeurs de l'état de l'art de la technologie planaire FDSOI est de fournir les différentes tensions de seuils (VT) requises pour la gestion de la consommation et de la vitesse. Le travail de recherche de thèse présenté dans ce mémoire a contribué à la mise en place d'une plateforme de conception multi-VT en technologie planaire FDSOI sur oxyde enterré mince (UTB pour Ultra Thin Buried oxide en anglais) pour les nœuds technologiques sub-32 nm. Pour cela, les éléments clefs des plateformes de conception basse consommation en technologie planaire sur silicium massif ont été identifiés. A la suite de cette analyse, différentes architectures de transistors MOS multi-VT FDSOI ont été développées. L'analyse au niveau des circuits numériques et mémoires élémentaires a permis de mettre en avant deux solutions fiables, efficaces et de faible complexité technologique. Les performances des solutions apportées ont été évaluées sur un chemin critique extrait du cœur de processeur ARM Cortex A9 et sur une cellule SRAM 6T haute densité (0,120 µm²). Egalement, une cellule SRAM à quatre transistors est proposée, démontrant la flexibilité au niveau conception des solutions proposées. Ce travail de recherche a donné lieu à de nombreuses publications, communications et brevets. Aujourd'hui, la majorité des résultats obtenus ont été transférés chez STMicroelectronics, où l'étude de leur industrialisation est en cours. / Driven by the strong growth of smartphone and tablet devices, an exponential growth for the mobile SoC market is forecasted up to 2016. These systems, designed in the latest nanometre technology, require very high speeds to deliver tremendous performances, while consuming remarkably little. However, designing such systems at the nanometre scale introduces many challenges due to the emphasis of parasitic phenomenon effects driven by the scaling of bulk MOSFETs, making circuits more sensitive to the manufacturing process fluctuations and less energy efficient. Undoped thin-film planar fully depleted silicon-on-insulator (FDSOI) devices are being investigated as an alternative to bulk devices in 28nm node and beyond, thanks to its excellent short-channel electrostatic control, low leakage currents and immunity to random dopant fluctuation. This compelling technology appears to meet the needs of nomadic devices, combining high performance and low power consumption. However, to be useful, it is essential that this technology is compatible with low operating power design platforms. A major challenge for this technology is to provide various device threshold voltages (VT), trading off power consumption and speed. The research work presented in this thesis has contributed to the development of a multi-VT design platform in FDSOI planar technology on thin buried oxide (UTB) for the 28nm and below technology nodes. In this framework, the key elements of the low power design platform in bulk planar technology have been studied. Based on this analysis, different architectures of FDSOI multi-VT MOSFETs have been developed. The analysis on the layout of elementary circuits, such as standard cells and SRAM cells, has put forward two reliable, efficient and low technological complexity multi- strategies. Finally, the performances of these solutions have been evaluated on a critical path extracted from the ARM Cortex A9 processor and a high-density 6T SRAM cell (0.120µm²). Also, an SRAM cell with four transistors has been proposed, highlighting the design flexibility brought by these solutions. This thesis has resulted in many publications, communications and patents. Today, the majority of the results obtained have been transferred to STMicroelectronics, where the industrialization is in progress.
120

Modelagem de redes de transporte para terminais multialocados e capacitados de carga parcelada. / Modeling of transport networks for multi allocated and capacitated terminals of parcel cargo.

Paulo Kenji Matsuo 06 October 2014 (has links)
O presente trabalho aborda a temática da modelagem de redes de transporte para terminais multialocados e capacitados de carga parcelada através de métodos quantitativos aplicados em Pesquisa Operacional, onde o objetivo principal é minimizar o custo total, além de determinar a configuração ótima da rede, levandos e em consideração os custos de transporte ponto a ponto, a capacidade de processamento de carga dos hubs e os custos de alocação dos mesmos. Uma rede Hub and Spoke é configurada de forma que as estações geradoras de cargas (spoke) se comunicam única e exclusivamente com os terminais consolidadores (hubs) que, por sua vez, direcionam as cargas para as estações destino. Esta operação de consolidação gera economia de escala e é o princípio utilizado em muitos modelos de localização de redes de transporte de carga. Os modelos matemáticos utilizados para a resolução pertencem à família dos problemas de localização com custos fixos e particularmente será utilizado o método CMAHLP (Capacitated Multiple Allocation Hub Location Problem), onde para a sua resolução será utilizado o software AIMMS (Advanced Integrated Multidimensional Modeling Software) como ferramenta de apoio. / This paper addresses the issue of modeling transportation networks for multi allocated and capacitated terminals for parcel cargos through quantitative methods applied in Operational Research, where the main objective is to minimize the total cost and to determine the optimal configuration of the network, taking into account the transportation costs, the loading capacity of the hubs and the cost of allocation thereof. A Hub and Spoke network is configured in a way that the generating stations (spokes) communicate solely with consolidators terminals (hubs) which dispatch the cargo to the destination stations. This consolidation operation generates economies of scale and it is the principle used in many models of location problems. The mathematical models used for the settlement belongs to the family of location problems with fixed costs and particularly the CMAHLP (Capacitated Multiple Allocation Hub Location Problem) method is used with the AIMMS (Advanced Integrated Multidimensional Modeling Software) software, which will be used will be used as a support tool.

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