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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.
171

Discrétisation spectrale du transfert de chaleur et de masse dans un milieu poreux / Spectral discretization of transfer of heat and mass in porous medium

Maarouf, Sarra 06 July 2015 (has links)
Cette thèse se donne comme ambition de montrer que la simulation numérique de transfert de chaleur et de masse dans un milieu poreux, peut être traitée de manière efficace par un programme de calcul basé sur une discrétisation spatiale de type spectral. La méthode spectrale s'avère optimale en ce sens que l'erreur obtenue n'est limitée que par la régularité de la solution. Le point de départ de cette étude est le système des équations de Darcy non linéaire et non stationnaire qui modélise l'écoulement instationnaire d'un fluide visqueux dans un milieu poreux quand la perméabilité du milieu dépend de la pression. Le deuxième problème proposé est le transfert de la chaleur dans un milieu poreux décrit par un couplage des équations de Darcy avec l'équation de la chaleur. Dans la dernière partie, la concentration de masse est prise en compte dans le milieu, nous décrivons un problème non linéaire instationnaire qui modélise le transfert de chaleur et de masse dans un milieu poreux.Dans les trois problèmes proposés, les résultats d'existence et unicité sont établis. Puis les problèmes discrets correspondants sont décrits. Nous avons prouvé des estimations d'erreur a priori et nous avons confirmé l'étude théorique par des résultats numériques. / This thesis aims to show that the numerical simulation of heat and mass transfer in porous media can be effectively treated by a numerical program which is based on a space discretization of spectral type. The spectral method is optimal in the sense that the error obtained is only limited by the regularity of the solution. The starting point of this study is the system of nonlinear unsteady Darcy equations that models the unsteady flow of a viscous fluid in a porous medium when the permeability of the medium depends on the pressure. The second problem which we study models transfer of heat in a porous medium which is described by Darcy equations coupling with the heat equation. In the last part, the concentration of mass is taken into account in the medium, we describe a nonlinear problem that models unsteady transfer of heat and mass in porous media. In the three proposed problems, the results of the existence and the uniqueness are established. Then the corresponding discrete problems are described. We prove the error a priori estimates and we confirm the theoretical study with numerical results.
172

Approximation et estimation de densité pour des équations d'évolution stochastique / No English title available

Aboura, Omar 19 December 2013 (has links)
Dans la première partie de cette thèse, nous obtenons l’existence d’une densité et des estimées gaussiennes pour la solution d’une équation différentielle stochastique rétrograde. C’est une application du calcul de Malliavin et plus particulièrement d’une formule d’I. Nourdin et de F. Viens. La deuxième partie de cette thèse est consacrée à la simulation d’une équation aux dérivées partielles stochastique par une méthode probabiliste qui repose sur la représentation de l’équation aux dérivées partielles stochastique en terme d’équation différentielle doublement stochastique rétrograde, introduite par E. Pardoux et S. Peng. On étend dans ce cadre les idées de F. Zhang et E. Gobet et al. sur la simulation d’une équation différentielle stochastique rétrograde. Dans la dernière partie, nous étudions l’erreur faible du schéma d’Euler implicite pour les processus de diffusion et l’équation de la chaleur stochastique. Dans le premier cas, nous étendons les résultats de D. Talay et L. Tubaro. Dans le second cas, nous étendons les travaux de A. Debussche. / No English summary available.
173

Transport optimal et équations des gaz sans pression avec contrainte de densité maximale / Optimal transportation and pressureless Euler equations with maximal density constraint

Preux, Anthony 21 November 2016 (has links)
Dans cette thèse, nous nous intéressons aux équations des gaz sans pression avec contrainte de congestion qui soulèvent encore de nombreuses questions. La stratégie que nous proposons repose sur des précédents travaux sur le mouvement de foule dans le cadre de l'espace de Wasserstein, et sur un modèle granulaire avec des collisions inélastiques.Elle consiste en l'étude d'un schéma discrétisé en temps dont les suites doivent approcher les solutions de ces équations.Le schéma se présente de la manière suivante : à chaque pas de temps, le champ des vitesses est projeté sur un ensemble lui permettant d'éviter les croisements entre particules, la densité est ensuite déplacée selon le nouveau champ des vitesses, puis est projetée sur l'ensemble des densités admissibles (inférieures à une valeur seuil donnée).Enfin, le champ des vitesses est mis à jour en tenant compte du parcours effectué par les particules. En dimension 1, les solutions calculées par le schéma coïncident avec les solutions connues pour ce système. En dimension 2, les solutions calculées respectent les propriétés connues des solutions des équations de gaz sans pression avec contrainte de congestion. De plus, on retrouve des similarités entres ces solutions et celles du modèle granulaire microscopique dans des cas où elles sont comparables. Par la suite, la discrétisation en espace pose des problèmes et a nécessité l'élaboration d'un nouveau schéma de discrétisation du coût Wasserstein quadratique. Cette méthode que nous avons baptisée méthode du balayage transverse consiste à calculer le coût en utilisant les flux de masses provenant d'une certaine cellule et traversant les hyperplans définis par les interfaces entre les cellules. / In this thesis, we consider the pressureless Euler equations with a congestion constraint.This system still raises many open questions and aside from its one-dimensional version,very little is known. The strategy that we propose relies on previous works of crowd motion models withcongestion in the framework of the Wasserstein space, and on a microscopic granularmodel with inelastic collisions. It consists of the study of a time-splitting scheme. The first step is about the projection of the current velocity field on a set, avoiding the factthat trajectories do not cross during the time step. Then the scheme moves the density with the new velocity field. This intermediate density may violate the congestion constraint. The third step projects it on the set of admissible densities. Finally, the velocity field is updated taking into account the positions of physical particles during the scheme. In the one-dimensional case, solutions computed by the algorithm matchwith the ones that we know for these equations. In the two-dimensional case, computed solutions respect some properties that can be expected to be verified by the solutions to these equations. In addition, we notice some similarities between solutions computed by the scheme and the ones of the granular model with inelastic collisions. Later, this scheme is discretized with respect to the space variable in the purpose of numerical computations of solutions. The resulting algorithm uses a new method to discretize the Wasserstein cost. This method, called Transverse Sweeping Method consists in expressing the cost using the mass flow from any cell and crossing hyperplanes defined by interfaces between cells.
174

Porucha tělesného schématu u pacientek hospitalizovaných s mentální anorexií / Execise Therapy in Female Adolescents Hospitalised with Anorexia Nervosa

Ulrichová, Michaela January 2021 (has links)
Objective: Body image disturbance is one of the main characteristics of anorexia nervosa (AN). It is present in different stages of the disease, often persisting even after the end of the treatment, and is one of the predictors of a relaps. Body image is composed of two main components - the perceptual component, and the attitudinal component. Anorexia nervosa patients show a disturbed attitudinal component of the body image. The perceptual component disruption hasn't been completely proven yet. Many authors do, however, warn about the overestimation of bodily proportions of patients with AN and it's possible relation with characteristics such as BMI. Goals: The main goal of the dissertation thesis was the objectivization of the body image disturbance of the patients hospitalized with anorexia nervosa, the comparison of their results with a group of healthy girls of the same age, and the search for factors connected to the defect of the body image. A side goal of the dissertation thesis was the measurement of the effect of kinesiotherapy on the anxiety level of AN patients. Methods: As a part of the practical section, the measurements of 27 hospitalized patients and 20 healthy girls were completed. Probands underwent body size estimation of 4 bodily segments. They estimated the length of their arm,...
175

Systém ucpávkové páry pro parní turbínu / Gland steam system for a steam turbine

Skala, Šimon January 2017 (has links)
The diploma thesis deals with preliminary design of condensing steam turbine with three unregulated steam outputs and its gland steam system particularly its description and design. The steam parameters in key outputs were determined in heat balance. The gland steam system parameters were calculated for different operating conditions. It also describes influence of pressure on performance of turbine in gland steam system. Finally, the inquiry sheet for gland steam system device was created based on calculated values.
176

Univerzální stroj pro odstraňování volných nečistot na montážních linkách světlometů / Universal machine for removing loose dirt on headlamp assembly lines

Chylík, Michal January 2019 (has links)
This diploma thesis deals with the construction design of a non-autonomous universal machine used for suction of free dirt on assembly lines for headlights according to customer requirements. This diploma thesis also focuses on safety analyses, a draft of development diagram for a control logic machine, and on a scheme of pneumatic mechanism. The thesis contains an illustration of design documentation.
177

Parní turbína / Steam turbine

Ondrůj, Jakub January 2019 (has links)
The aim of this diploma thesis is a design and thermodynamical calculation of a steam condensing turbine with one controlled steam extraction and assigned technical specifications. Technical specifications are turbine inlet temperature 440,0 °C, pressure of inlet steam 38,0 bar(a), pressure in controlled steam extraction 13,0 bar(a), mass flow rate of steam in controlled steam exraction 0,0-40 t/h, temperature in deaerator 105,0 °C and temperature of cooling water in condenser 25,0 °C. Designed steam turbine works in a Rankine-Clausius cycle with a water-cooled condenser, system of low-pressure feed water heater, feed water tank with deaerator and steam boiler. Turbine was designed with regular turbine stages with reaction type of blading and with two regulation stages with impulse blading. An extraction turbine map of the steam turbine is shown in the last chapter of this work. Final parameters of steam turbine are power of 21,7 kW, internal efficiency of turbine 85,1 % and reheat factor 1,048.
178

Návrh typu a zapojení parní turbíny pro konkrétní lokalitu / Type design and flowchart of a steam turbine for a specific location

Kalina, Leoš January 2019 (has links)
This master's thesis is deals with type designing and implementing the steam turbine to the machine part of heat plant in reconstruction. The thesis consists of two parts. First part is theoretical explanation of the heating industry, steam turbines, thermal cycles and components of thermal power plants. Second part of the thesis describes the design and calculation of thermal diagrams based on turbine parameters, which were provided from Tenza, a.s. tender. There is a simplified calculation of technical-economic study in the conclusion of the thesis. The thesis output is recommendation of single final implementation solution for customer.
179

Vliv vinutí na vlastnosti asynchronního motoru / Impact of winding on induction machine characteristics

Mikmek, Vladislav January 2020 (has links)
This thesis deals with the analysis of a three-phase winding of an induction engine. After the theoretical introduction concerning different types of windings, two types of their analysis and the importance of the winding factor, two methods of analysis and design tools are explained: Görges diagram and Tingley scheme. This scheme is then used for the design of all possible variants of winding for a certain number of stator slots and the theoretical shape of magnetic field is analysed. The next step is a deeper software analysis of the engines with variants of windings with different coil pitches and number of conductors per slot. Especially the finite element method is used in this part. The obtained values and their characteristics of the simulated engines are compared numerically and graphically. Then the changes of important values for different windings are described. The optimal winding according to chosen requirements is chosen.
180

Chladící jednotka pro projekt Barman / Refrigerating unit for the Barman project

Kupka, Ondřej January 2020 (has links)
The aim of this master’s thesis was to create cooling unit which will became part of project Barman. Thesis describe process from definition of requirements, proposal, selection of components, PI and D diagram and in the last chapter the construction work. In the second part describe design of cooling unit’s model and simulation of cooling process. The last part of the thesis is describing software of the cooling unit and tis results.

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