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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.
311

Process modeling of very-high-gravity fermentation system under redox potential-controlled conditions

Yu, Fei 31 August 2011
The objective of this study is to evaluate and compare, both technically and economically, various glucose feeding concentrations and different redox potential settings on ethanol production under very-high-gravity (VHG) conditions. Laboratory data were collected for process modeling and two process models were created by two individual process simulators. The first one is a simplified model created and evaluated by Superpro Designer. The second one is an accurate model created by Aspen Plus and evaluated by Aspen Icarus Process Evaluator (Aspen IPE). The simulation results of the two models were also compared. Results showed that glucose feeding concentration at 250±3.95 g/L to the fermentor resulted in the lowest unit production cost (1.479 $/kg ethanol in the Superpro model, 0.764 $/kg ethanol in the Aspen Plus model), with redox potential control effects accounted. Controlling redox potential at -150 mV increased the ethanol yield under VHG fermentation conditions while no significant influences were observed when glucose feeding concentration was less than 250 g/L. Results of product sales analysis indicated that for an ethanol plant with a production rate of 85~130 million kg ethanol/year, only maintaining the glucose feeding concentration to the fermentor at around 250 g/L resulted in the shortest payout period of 5.33 years in average,, with or without redox potential control. If 300±6.42 g/L glucose feeding concentration to the fermentor is applied, it is essential to have the redox potential only controlled at -150 mV in the fermentor to limit the process payout period within 6 years. In addition, fermentation processes with glucose feeding concentration at around 200 g/L to the fermentor were estimated to be unprofitable under all studied conditions. For environmental concerns, two disposal alternatives were presented for CO2 produced during fermentation process rather than emission into atmosphere. One is to sell CO2 as byproduct, which brought 1.52 million $/year income for an ethanol plant with a capacity of 100 million kg ethanol/year. Another option is to capture and transport CO2 to deep injection sites for geological underground storage, which is already a safe and mature technology in North America, and also applicable to many other sites around the world. This would roughly add 4.78 million dollars processing cost annually in the studied scenario. Deep injection of captured CO2 from ethanol plants prevents emission of CO2 into the atmosphere, thus makes it environmental friendly.
312

Géo-localisation en environnement fermé des terminaux mobiles

Dakkak, Mustapha 29 November 2012 (has links) (PDF)
Récemment, la localisation statique et dynamique d'un objet ou d'une personne est devenue l'un des plus importantes fonctionnalités d'un système de communication, du fait de ses multiples applications. En effet, connaître la position d'un terminal mobile (MT), en milieu extérieur ou intérieur, est généralement d'une importance majeure pour des applications fournissant des services basés sur la localisation. Ce développement des systèmes de localisation est dû au faible coût des infrastructures de réseau sans fil en milieu intérieur (WLAN). Les techniques permettant de localiser des MTs diffèrent selon les paramètres extraits des signaux radiofréquences émis entre des stations de base (BSs) et des MTs. Les conditions idéales pour effectuer des mesures sont des environnements dépourvus de tout obstacle, permettant des émissions directes entre BS et MT. Ce n'est pas le cas en milieu intérieur, du fait de la présence continuelle d'obstacles dans l'espace, qui dispersent les rayonnements. Les mesures prises dans ces conditions (NLOS, pour Non Line of Sight) sont imprévisibles et diffèrent de celles prises en condition LOS. Afin de réduire les erreurs de mesure, différentes techniques peuvent être utilisées, comme la mitigation, l'approximation, la correction à priori, ou le filtrage. En effet, l'application de systèmes de suivi (TSs) constitue une base substantielle pour la navigation individuelle, les réseaux sociaux, la gestion du trafic, la gestion des ressources mobiles, etc. Différentes techniques sont appliquées pour construire des TSs en milieu intérieur, où le signal est bruité, faible voire inexistant. Bien que les systèmes de localisation globaux (GPS) et les travaux qui en découlent fonctionnent bien hors des bâtiments et dans des canyons urbains, le suivi d'utilisateurs en milieu intérieur est bien plus problématique. De ce fait, le problème de prédiction reste un obstacle essentiel à la construction de TSs fiable dans de tels environnements. Une étape de prédiction est inévitable, en particulier, dans le cas où l'on manque d'informations. De multiples approches ont été proposées dans la littérature, la plupart étant basées sur un filtre linéaire (LF), un filtre de Kalman (KF) et ses variantes, ou sur un filtre particulaire (PF). Les filtres de prédiction sont souvent utilisés dans des problèmes d'estimation et l'application de la dérivation non entière peut limiter l'impact de la perte de performances. Ce travail présente une nouvelle approche pour la localisation intérieure par WLAN utilisant un groupement des coordonnées. Ensuite, une étude comparative des techniques déterministes et des techniques d'apprentissage pour la localisation intérieure est présentée. Enfin, une nouvelle approche souple pour les systèmes de suivi en milieu intérieur, par application de la dérivation non entière, est présentée
313

Process modeling of very-high-gravity fermentation system under redox potential-controlled conditions

Yu, Fei 31 August 2011 (has links)
The objective of this study is to evaluate and compare, both technically and economically, various glucose feeding concentrations and different redox potential settings on ethanol production under very-high-gravity (VHG) conditions. Laboratory data were collected for process modeling and two process models were created by two individual process simulators. The first one is a simplified model created and evaluated by Superpro Designer. The second one is an accurate model created by Aspen Plus and evaluated by Aspen Icarus Process Evaluator (Aspen IPE). The simulation results of the two models were also compared. Results showed that glucose feeding concentration at 250±3.95 g/L to the fermentor resulted in the lowest unit production cost (1.479 $/kg ethanol in the Superpro model, 0.764 $/kg ethanol in the Aspen Plus model), with redox potential control effects accounted. Controlling redox potential at -150 mV increased the ethanol yield under VHG fermentation conditions while no significant influences were observed when glucose feeding concentration was less than 250 g/L. Results of product sales analysis indicated that for an ethanol plant with a production rate of 85~130 million kg ethanol/year, only maintaining the glucose feeding concentration to the fermentor at around 250 g/L resulted in the shortest payout period of 5.33 years in average,, with or without redox potential control. If 300±6.42 g/L glucose feeding concentration to the fermentor is applied, it is essential to have the redox potential only controlled at -150 mV in the fermentor to limit the process payout period within 6 years. In addition, fermentation processes with glucose feeding concentration at around 200 g/L to the fermentor were estimated to be unprofitable under all studied conditions. For environmental concerns, two disposal alternatives were presented for CO2 produced during fermentation process rather than emission into atmosphere. One is to sell CO2 as byproduct, which brought 1.52 million $/year income for an ethanol plant with a capacity of 100 million kg ethanol/year. Another option is to capture and transport CO2 to deep injection sites for geological underground storage, which is already a safe and mature technology in North America, and also applicable to many other sites around the world. This would roughly add 4.78 million dollars processing cost annually in the studied scenario. Deep injection of captured CO2 from ethanol plants prevents emission of CO2 into the atmosphere, thus makes it environmental friendly.
314

Flying friendlier skies : the effect of the 2002 ECJ "open skies" ruling on EU-US air transportation negotiations - a study in policy convergence

Smith, Edwin Keith 05 1900 (has links)
The international air transportation industry has historically been a paradox. While the industry enables globalization, historically, the international air transportation regulatory regime has been largely mired in protectionism. This restrictive regime was developed by national actors, who either owned or heavily subsidized their domestic carriers, and guarded their interests very closely, thus insulating the industry from large levels of foreign competition. This paradox of international air transportation continued until the development of convergence in regulatory policy through the 2007 ‘open skies-plus’ air transportation agreement between the United States (US) and the European Union (EU). This thesis examines the developmental process of this agreement as an examination of policy convergence theory, in order identify the explanatory powers leading to the formation of the ‘open skies-plus’ agreement. To identify the explanatory powers, a comparative analysis is established, using two historical reference points, t(0) and t(1), as case studies. This thesis uses two mechanisms for the development of policy convergence, international harmonization and regulatory competition, to identify why the convergence took place at this specific time and why it was set at this specific level of regulation. Using these mechanisms, the 2002 European Court of Justice (ECJ) ‘open skies’ ruling is identified as the explanatory power for the convergence of policy in this field, and the precedent set by the previous bilateral agreement between the US and the Netherlands is identified as establishing the standards of regulation in the 2007 ‘open skies-plus’ agreement. The thesis concludes with an examination of the prospects for further liberalization of transatlantic air transportation, as well as recommendations for the continued development of the field.
315

Design Of Glass Structures: Effects Of Interlayer Types On Heat-treated Laminated Glass

Akdeniz, Verda 01 September 2007 (has links) (PDF)
Glass is an inherrently strong and elastic building material that allows the enclosure of spaces to provide both comfort and &aelig / sthetic appeal. It is evidently due recognition of these properties that has resulted in the current propensity to use it in ever larger sizes / and then with minimum&ndash / if not total absence&ndash / of visible supporting structure. It is, however, its lack of plastic behavior under stress&ndash / leading to catastrophic failure without warning&ndash / that has been the main drawback preventing its use as a structural material on its own. Ergo, the development of composite configurations with plastic interlayers, commonly known as structural glass. Contemporary working methods for glass have also been able to provide better structural characteristics&ndash / particularly after heat treatments, which reduce its vulnerability to cracking and brittle failure. In com-bination, these methods offer designers the possibility of using glass panels capable of acting as load-carrying structural elements. The aim of this study was to investigate the performance of glass-adhesive-glass composite, or laminated, elements and the use of glass as a structural material in light of their inherent strength properties. Here, an attempt was made to define the be-havior of interlayers in structural glass and to then prepare a selection guide. To this end, it was necessary to first gather information about the materials and design methods used to create glass structures. As the literature notes that such stresses are particularly important to structural glass design due to the inability of the material to flow plastically and to thus relieve high stresses, pertinent simulation techniques (e.g., finite element analysis) were then used to investigate shear transfer between glass panes and interlayers. These simulations allowed determination of stiffness with different types of interlayer for panes of different dimensions and orien-tation in respect to loading conditions. It was the results of these analyses that were finally compiled into the selection guide already noted. It is expected that these results will make a worthwhile contribution to developing glass structure design and its application in practice.
316

Real-time Arbitrary View Rendering From Stereo Video And Time-of-flight Camera

Ates, Tugrul Kagan 01 January 2011 (has links) (PDF)
Generating in-between images from multiple views of a scene is a crucial task for both computer vision and computer graphics fields. Photorealistic rendering, 3DTV and robot navigation are some of many applications which benefit from arbitrary view synthesis, if it is achieved in real-time. Most modern commodity computer architectures include programmable processing chips, called Graphics Processing Units (GPU), which are specialized in rendering computer generated images. These devices excel in achieving high computation power by processing arrays of data in parallel, which make them ideal for real-time computer vision applications. This thesis focuses on an arbitrary view rendering algorithm by using two high resolution color cameras along with a single low resolution time-of-flight depth camera and matching the programming paradigms of the GPUs to achieve real-time processing rates. Proposed method is divided into two stages. Depth estimation through fusion of stereo vision and time-of-flight measurements forms the data acquisition stage and second stage is intermediate view rendering from 3D representations of scenes. Ideas presented are examined in a common experimental framework and practical results attained are put forward. Based on the experimental results, it could be concluded that it is possible to realize content production and display stages of a free-viewpoint system in real-time by using only low cost commodity computing devices.
317

Error Concealment In 3d Video

Aydogmus, Sercan 01 December 2011 (has links) (PDF)
The advances in multimedia technologies increased the interest in utilizing three dimensional (3D) video applications in mobile devices. However, wireless transmission is significantly prone to errors. Typically, packets may be corrupted or lost due to transmission errors, causing blocking artifacts. Furthermore, because of compression and coding, the error propagates through the sequence and salient features of the video cannot be recovered until a key-frame or synchronization-frame is correctly received. Without the use of concealment and enhancement techniques, visible artifacts would inevitably and regularly appear in the decoded stream. In this thesis, error concealment techniques for full frame losses in depth plus video and stereo video structures are implemented and compared. Temporal and interview correlations are utilized to predict the lost frames while considering the memory usage and computational complexity.The concealment methods are implemented on jm17.2 decoder which is based on H.264/AVC specifications [1]. The simulation results are compared with the simple frame copy (FC) method for different sequences having different characteristics.
318

Performance of Asynchronous Band-Limited DS/SSMA Systems

Shibata, Takafumi, Katayama, Masaaki, Ogawa, Akira 08 1900 (has links)
No description available.
319

Stratégies d'Ordonnancement Conditionnelles Utilisant des Automates Temporisés

Kerbaa, Abdelkarim Aziz 02 October 2006 (has links) (PDF)
Cette thèse développe une méthodologie pour résoudre les problèmes d'ordonnancement de programmes conditionnels où savoir si une tâche doit être exécutée n'est pas connue à l'avance mais dynamiquement. Le modèle utilisé est à base d'automates temporisés représentant l'espace d'états à explorer. Le problème est donc formulé comme le calcul d'une stratégie gagnante (pire cas optimale) dans un jeu contre l'environnement. Dans un premier temps nous étudions le problème d'ordonnancement sur graphes de tâches déterministe puis nous étendons l'étude au problème d'ordonnancement avec incertitude conditionnelle. Pour les deux problèmes nous étudions différentes classes d'ordonnancements et de stratégies pour réduire l'espace d'états, des décompositions en chaînes pour réduire sa taille, puis nous investiguons plusieurs classes d'algorithmes exactes pour en évaluer l'efficacité et à partir desquels nous dérivons de bonnes heuristiques. Des résultats expérimentaux sur plusieurs exemples de benchmarks sont présentés afin de montrer l'efficacité de chaque algorithme et la précision des heuristiques proposées, puis des bornes théoriques sont déduites pour prouver la garantie de performance pire cas de chaque heuristique.
320

Processus empiriques, estimation non paramétrique et données censurées.

Viallon, Vivian 01 December 2006 (has links) (PDF)
La théorie des processus empiriques joue un rôle central en statistique, puisqu'elle concerne l'ensemble des résultats limites généraux se rapportant aux échantillons aléatoires. En particulier, des lois uniformes du logarithme ont permis d'aborder de manière systématique la convergence en norme sup des estimateurs à noyau. Dans cette thèse, nous obtenons premièrement des lois fonctionnelles uniformes du logarithme pour les incréments du processus des quantiles normé, qui permettent d'établir des propriétés nouvelles des estimateurs basés sur les k-plus proches voisins. Le même type de résultat est ensuite obtenu pour les incréments du processus empirique de Kaplan-Meier, conduisant naturellement à des lois du logarithme uniformes pour des estimateurs de la densité et du taux de mortalité en présence de censure à droite. Dans le cas de la régression multivariée, des lois analogues sont obtenues pour des estimateurs à noyau, notamment dans le cas censuré. Enfin, nous développons un estimateur non paramétrique de la régression sous l'hypothèse du modèle additif dans le cas de censure à droite, permettant de se défaire du fléau de la dimension. Cet estimateur repose essentiellement sur la méthode d'intégration marginale.

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