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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.
81

Application de l'inf-convolution spline au traitement des chromatogrammes de gasoils

Valera Garcia, Daniel 30 October 1984 (has links) (PDF)
On expose deux logiciels de traitement de chromatogrammes de gas oils qui permettent l'évaluation des richesses de composants particuliers: les n-paraffines. Le premier permet par des recalages par «moindres carrés» d'estimer ces richesses à partir de deux chromatogrammes: celui du gas oil, mais aussi celui de ce même gas oil, sans les n-paraffines. Le deuxième ne nécessite plus que le seul chromatogramme du gas oil: on remplace l'information manquante par la connaissance théorique acquise sur la forme des n-paraffines. On procède en deux étapes: 1) application de la théorie de l'inf-convolution spline, en vue de séparer au mieux, par un profil de n-paraffine normalisé celle-ci du reste du gas oil; 2) application des méthodes de minimisation à plusieurs variables pour choisir, parmi les formes possibles pour une n-paraffines la forme optimale
82

Filtrage non linéaire par convolution de particule. Application à un procédé de dépollution biologique

Rossi, Vivien 04 December 2004 (has links) (PDF)
Cette thèse considère le problème du filtrage non linéaire, c'est à dire l'estimation au cours du temps de l'état, indirectement observé, d'un système dynamique non linéaire. Ce type de problématique concerne une large gamme de modèles relatifs à divers domaines scientifiques.<br />Une approche originale utilisant les noyaux de convolution et des simulations d'un grand nombre de variables aléatoires est développée. Le cas des modèles contenant des paramètres inconnus à estimer est aussi traité. Des propriétés théoriques de convergence sont établies pour ces nouvelles approches.<br />Afin de compléter l'étude de nos techniques, des comparaisons avec les méthodes traditionnelles, notamment avec les différents filtres particulaires, sont réalisées en simulation.<br />Puis nos nouvelles approches sont appliquées sur un problème réel, un bioréacteur de retraitement d'eaux usées. Les performances obtenues, sur données réelles, permettent d'apprécier la robustesse de la méthode par rapport aux erreurs de modèles et aux données de mauvaises qualités.
83

Une approche par formalisme de green réduit pour le calcul des structures en contact dynamique : application au contact pneumatique/chaussée

Meftah, Rabie 15 November 2011 (has links) (PDF)
Le travail de cette thèse s'inscrit dans le cadre de la réduction du bruit du traffic routier. Le contact pneumatique/chaussée représente la principale source de ce phénomène dès la vitesse de 50 km/h. Dans ce contexte, une nouvelle démarche de modélisation du comportement dynamique d'un pneumatique roulant sur une chaussée rigide est développée. Au niveau du pneumatique, un modèle périodique est adopté pour calculer les fonctions de Green du pneumatique dans la zone de contact. Ce modèle permet de réduire considérablement le temps de calcul et de modéliser le pneumatique dans une large bande de fréquence. Le modèle est validé en le comparant avec un modèle d'éléments finis classique réalisé sous le logiciel Abaqus. Habituellement, la réponse temporelle du pneumatique peut être calculée par une convolution des fonctions de Green et des forces de contact. Cette technique est très coûteuse en terme de temps de calcul. Nous avons adopté une nouvelle démarche. L'idée consiste à décomposer les fonctions de Green dans une base modale. Les paramètres modaux sont ensuite utilisés pour construire une convolution plus rapide. La convolution modale est adaptée au problème de contact par l'addition d'une condition de contact cinématique. Le modèle de contact est comparé à la méthode de pénalité dans le cas d'un exemple académique. Il présente l'avantage de sa stabilité et de sa facilité de mise en oeuvre. Dans la dernière partie de ce travail, le modèle de contact est appliqué au cas d'un pneumatique roulant sur différents types de chaussée. Le contenu spectral des forces de contact est étudié en fonction de la vitesse de déplacement et la rugosité des chaussées. Afin de construire le modèle de contact d'un pneumatique réel sur une chaussée réelle, plusieurs exemples à complexité croissante sont traités. Le modèle d'anneau circulaire sous fondation élastique est largement étudié dans cette thèse. Une étude détaillée du modèle est réalisée dans les cas analytique et numérique
84

Modeling full-scale fire test behaviour of polyurethane foams using cone calorimeter data

Ezinwa, John Uzodinma 04 June 2009
Flexible polyurethane foam (PUF) is a very versatile material ever created. The material is used for various applications and consumer end-use products such as upholstered furniture and mattresses. The increased use of these polymeric materials causes fire safety concerns. This has led to the development of various regulations and flammability test standards aimed at addressing the hazards associated with polyurethane foam fires. Several fire protection engineering correlations and thermal models have also been developed for the simulation of fire growth behaviour of polyurethane foams. Thus, the overall objective of this research project is to investigate the laboratory test behaviour of this material and then use finer modeling techniques to predict the heat release rate of the specimens, based on information obtained from cone calorimeter tests.<p> Full-scale fire tests of 10 cm thick polyurethane foams of different sizes were conducted using center and edge-ignition locations. Flame spread and heat release rates were compared. For specimens of the same size, center-ignition tests produced flame areas and peak heat release rates which were respectively 10 and 20% larger compared to edge-ignition tests. Average flame spread rates for horizontal and vertical spread were determined, and results showed excellent agreement with literature. Cone calorimeter tests of the specimens were performed using steel edge frame and open durarock board. Results indicate that different test arrangements and heat sources have significant effects on the fire behaviour of the specimens.<p> Predictions using the integral convolution model and other fire protection engineering correlations were compared with the full-scale tests results. Results show that the model was more efficient in predicting the heat release rates for edge-ignition tests than the center-ignition tests. The model also was more successful in predicting the heat release rates during the early part of the growth phase than during the later stages of the fire. The predicted and measured peak heat release rates and total heat release were within 10-15% of one another. Flame spread and t-squared fire models also gave satisfactory predictions of the full-scale fire behaviour of the specimens.
85

On the simulation of overhead transmission lines

Silverman, Shawn F. 13 October 2005 (has links)
This thesis explores and implements techniques for frequency domain modelling and time domain simulation of overhead transmission lines. The popular Vector Fitting algorithm is employed to approximate the frequency domain model using rational functions, and the recursive convolution technique is applied to the rational approximation to generate a time domain form. The frequency domain model is translated into the time domain using delay extraction, modal decomposition, passivity enforcement, and rational approximation. Several approaches to each of these procedures are investigated. The thesis also discusses several choices for the integration method used within the recursive convolution procedure. In order to make the transmission line modeller and simulator easy to use, a Java-based library and partial graphical interface were developed. Specifically, the goal was to develop a platform-independent program that can run either stand-alone or as an applet inside a web page. / October 2005
86

Modeling full-scale fire test behaviour of polyurethane foams using cone calorimeter data

Ezinwa, John Uzodinma 04 June 2009 (has links)
Flexible polyurethane foam (PUF) is a very versatile material ever created. The material is used for various applications and consumer end-use products such as upholstered furniture and mattresses. The increased use of these polymeric materials causes fire safety concerns. This has led to the development of various regulations and flammability test standards aimed at addressing the hazards associated with polyurethane foam fires. Several fire protection engineering correlations and thermal models have also been developed for the simulation of fire growth behaviour of polyurethane foams. Thus, the overall objective of this research project is to investigate the laboratory test behaviour of this material and then use finer modeling techniques to predict the heat release rate of the specimens, based on information obtained from cone calorimeter tests.<p> Full-scale fire tests of 10 cm thick polyurethane foams of different sizes were conducted using center and edge-ignition locations. Flame spread and heat release rates were compared. For specimens of the same size, center-ignition tests produced flame areas and peak heat release rates which were respectively 10 and 20% larger compared to edge-ignition tests. Average flame spread rates for horizontal and vertical spread were determined, and results showed excellent agreement with literature. Cone calorimeter tests of the specimens were performed using steel edge frame and open durarock board. Results indicate that different test arrangements and heat sources have significant effects on the fire behaviour of the specimens.<p> Predictions using the integral convolution model and other fire protection engineering correlations were compared with the full-scale tests results. Results show that the model was more efficient in predicting the heat release rates for edge-ignition tests than the center-ignition tests. The model also was more successful in predicting the heat release rates during the early part of the growth phase than during the later stages of the fire. The predicted and measured peak heat release rates and total heat release were within 10-15% of one another. Flame spread and t-squared fire models also gave satisfactory predictions of the full-scale fire behaviour of the specimens.
87

Design of the Tail-biting Convolution Code Decoder with Error Detection Ability

Tseng, I-Ping 25 July 2012 (has links)
In wireless communication system, convolution code has been one of the most popular error-correcting code. To prevent from the interference of noise during transmission, the transmitter usually applies convolution encode to code the processed information, and the receiver will use Viterbi decoder to decode and correct the error bit to decrease the bit error rate. In 3G mobile communication, such decoder is often applied between the base station and the communication device as a decoding mechanism. Since traditional decoders of communication devices consume more than one third power of the whole receiver, the present study focuses on the way effectively reducing the power consumption of Viterbi decoder. Traditional convolution coders use zero-tail, which make decoder be able to resist the interference of noise; however, this method would increase extra tail bits, which would decrease the code rate and affect the efficiency of transmission, especially for those information with short length, such as the header of packet. Tail-biting convolution code is another error-correcting code, which maintains the code rate, and it has been used in the control channel of LTE. Tail-biting convolution code is more complex than traditional decoder. Therefore, this thesis modifies the Wrap-Around Viterbi Algorithm (WAVA) to enormously decrease the power consuming while maintaining the bit error rate and the correctness of decoding. The aim of the present study is achieved by decreasing iteration number of WAVA algorithm to reduce one fourth of the whole power consumption. On the other hand, if the received information is not interfered by noise, it¡¦s unnecessary to turn on Tail-biting Convolution Decoder. As a result, the present study introduces the error detection circuit so that the received information can be simply decode and detected with the error detection circuit. If there is no noise interference, it can directly be outputted; if there is noise interference, however, it should be decoded by Tail-biting Convolution Decoder. The experimental results show that the survivor memory unit saves more than 60% power than traditional decoders, moreover, it will save 55%~88% power consumption when it goes with the error detection circuit. Consequently, the proposed method is indeed able to reduce the power consumption of Tail-biting Convolution Decoder. Keyword¡Gwireless communication, tail-biting convolution code, code rate, Viterbi decoder, power consumption
88

Application of convolution and average pressure approximation for solving non-linear flow problems. constant pressure inner boundary condition for gas flow

Zhakupov, Mansur 16 August 2006 (has links)
The accurate description of fluid flow through porous media allows an engineer to properly analyze past behavior and predict future reservoir performance. In particular, appropriate mathematical models which describe fluid flow through porous media can be applied to well test and production data analysis. Such applications result in estimating important reservoir properties such as formation permeability, skin-factor, reservoir size, etc. "Real gas" flow problems (i.e., problems where the gas properties are specifically taken as implicit functions of pressure, temperature, and composition) are particularly challenging because the diffusivity equation for the "real gas" flow case is strongly non-linear. Whereas different methods exist which allow us to approximate the solution of the real gas diffusivity equation, all of these approximate methods have limitations. Whether in terms of limited applicability (say a specific pressure range), or due to the relative complexity (e.g., iterative character of the solution), each of the existing approximate solutions does have disadvantages. The purpose of this work is to provide a solution mechanism for the case of timedependent real gas flow which contains as few "limitations" as possible. In this work, we provide an approach which combines the so-called average pressure approximation, a convolution for the right-hand-side non-linearity, and the Laplace transformation (original concept was put forth by Mireles and Blasingame). Mireles and Blasingame used a similar scheme to solve the real gas flow problem conditioned by the constant rate inner boundary condition. In this work we provide solution schemes to solve the constant pressure inner boundary condition problem. Our new semi-analytical solution was developed and implemented in the form of a direct (non-iterative) numerical procedure and successfully verified against numerical simulation. Our work shows that while the validity of this approach does have its own assumptions (in particular, referencing the right-hand-side non-linearity to average reservoir pressure (similar to Mireles and Blasingame)), these assumptions are proved to be much less restrictive than those required by existing methods of solution for this problem. We believe that the accuracy of the proposed solution makes ituniversally applicable for gas reservoir engineering. This suggestion is based on the fact that no pseudotime formulation is used. We note that there are pseudotime implementations for this problem, but we also note that pseudotime requires a priori knowledge of the pressure distribution in the reservoir or iteration on gas-in-place. Our new approach has no such restrictions. In order to determine limits of validity of the proposed approach (i.e., the limitations imposed by the underlining assumptions), we discuss the nature of the average pressure approximation (which is the basis for this work). And, in order to prove the universal applicability of this approach, we have also applied this methodology to resolve the time-dependent inner boundary condition for real gas flow in reservoirs.
89

Convolution type operators on cones and asymptotic spectral theory

Mascarenhas, Helena 28 January 2004 (has links) (PDF)
Die Arbeit beschäftigt sich mit Faltungsoperatoren auf Kegeln, die in Lebesgueräumen L^p(R^2) (1<p<\infty) von Funktionen auf der Ebene wirken. Es werden asymptotische Spektraleigenschaften der zugehörigen Finite Sections studiert. Im Falle p=2 (Hilbertraum) wird das Invertierbarkeitsproblem von Operatoren vom Faltungstyp auf Kegeln mit Hilfe der Methode der Standard-Modell-Algebren untersucht.
90

Informacinės posistemės, aprašančios individualizuotą žmogaus fiziologinį modelį fizinio krūvio metu, kūrimas / The development of information subsystem for individual human physiologic model during load

Berškienė, Kristina 08 June 2005 (has links)
The statistics claim, that people who are not physically active live shorter and they are ill more often. Only an individual physical activity is useful. For choosing the right activity the doctors have to investigate the patient, analyse and store his data for the future.The aim of this work was to describe mathematically the integral estimation model, using the model of physical load effect. We created the information subsystem of human functional state model for individual person using the convolution of Meally and Moore automata. The result is the applied program for the consumer – physiologist. This subsystem can be used in e – health for modeling the virtual doctor.

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