La nécessité de protéger les véhicules de rentrée atmosphérique a conduit à la sélection des matériaux carbonés pour les applications les plus extrêmes [1, 2]. Au vu du coût prohibitif des essais en conditions réelles [1], la simulation permet de prédire et comprendre le comportement du matériau lors de la rentrée atmosphérique. Les modèles de l’ablation du carbone n’ont cessé de se complexifier [1, 3, 4, 5, 6]. Cependant, ils ne donnent pas de descriptions fines de la surface du matériau. C’est pour remédier à cela que plusieurs études ont été lancées au Laboratoire des Composites Thermostructuraux (LCTS) [7, 8]. Le Plasmatron du VKI est le moyen à haut flux de chaleur et à haute vitesse utilisé pour cette thèse [9, 10]. Dans cette étude, des échantillons sont testés sous des flux de chaleur allant jusqu’à 2800 kW/m2. Ces essais sur le composite 3D carbone/carbone (Cf/C) ont mené à des résultats très intéressants sur la morphologie du composite lors de l’ablation. Le four à image d’arc est le moyen à très haut flux de chaleur et à convection nulle utilisé au cours de cette thèse. Des flux de chaleurs de 10 MW m-2 ont pu être appliqués à des échantillons de 3D Cf/C. Les observations MEB couplées à la reconstruction numérique du four ont permis de noter les différences entre l’oxydation et la sublimation du composite. Un code de diffusion/ablation est développé depuis plusieurs années au LCTS [7, 11, 12, 13, 14] : AMA. Il permet de simuler l’ablation d’un matériau en carbone. Ce code a été validé par J. Lachaud sans prise en compte de l’écoulement [7]. Un nouveau couplage avec le code Open-Foam [15] a été développé et validé. Le code AMA a été utilisé afin de déterminer les paramètres influençant la rugosité du 3D Cf/C sous un écoulement laminaire. / Carbonaceous materials have been selected to protect atmospheric re-entry vehicles under the most extremes conditions [1, 2]. Because real flight experiments are very expensive [1], simulation is an important means to predict and understand the material behaviour during atmospheric re-entry. The models of carbonaceous materials ablation have become more and more complex [1, 3, 4, 5, 6]. However, they are not accurate to describe finely the material surface. To find a solution to this problem, several studies have been conducted at the Laboratoire des Composites Thermostructuraux (LCTS) [7, 8]. The Plasmatron of the VKI is the experimental means which has been used in this doctoral thesis. It can reach moderately high heat flux under high speed flow [9, 10]. In this study, several samples have been tested under an heat flux up to 2800 kW/m2. These tests on the 3D carbon/carbon (Cf/C) composite have given very interesting results about the material morphology during ablation. An arc image furnace, which can reach very high heat flux but without important flow field, has been used during this doctoral study. 3D Cf/C samples have been ablated under heat flux up to 10 MW m-2. SEM observations with the help of a numerical simulation of the furnace, have put the differences between oxidation and sublimation forward. A diffusion/ablation code has been developed at LCTS for several years [7, 11, 12, 13, 14] : AMA. This piece of software is designed to simulate the ablation of a carbonaceous material. It has been validated without flow field by J. Lachaud [7]. A new coupling method between AMA and Open-Foam [15] has been developed and validated. Finally, AMA has been used to point out the parameters which drive the 3D Cf/C surface recession under laminar flow field.

Abstract Cognitive Radio (CR) improves the efficiency of spectrum utilization by allowing non- licensed users to utilize bands when not occupied by licensed users. In this thesis, we address several challenges currently limiting the wide use of cognitive radios. These challenges include identification of unoccupied bands, energy consumption and other technical challenges. Improved accuracy edge detection techniques are developed for CR to mitigate both noise and estimation error variance effects. Next, a reduced complexity Simplified DFT (SDFT) is proposed for use in CR. Then, a sub-Nyquist rate A to D converter is introduced to reduce energy consumption. Finally, a novel multi-resolution PSD estimation based on expectation-maximization algorithm is introduced that can obtain a more accurate PSD within a specified sensing time.

Significant maldistribution negatively influences performance of equipment containing dense tube bundles and, moreover, it can cause a wide range of operating issues. This thesis therefore focuses on analysis of fluid flow in complete distribution systems via computational fluid dynamics (CFD). Data obtained from simulations carried out using the software ANSYS Fluent were also statistically analysed. Influence of system arrangement, tube bundle parameters and operating parameters on flow distribution non-uniformity and pressure drop was investigated. According to the results, system arrangement is the crucial differentiating parameter in terms of flow distribution as well as pressure drop. Additionally, data obtained via the classical CFD approach were compared with those yielded by a simplified CFD model for three selected distribution systems. Simplified CFD approach can - given its low computational demand - be utilised in optimization algorithms as well as in the course of the initial stage of equipment design process. Furthermore, this thesis discusses a simulation tool which is based on the simplified CFD approach. Although this tool is still being developed, the results it yields are very promising.

The master thesis devotes to value of external works by cost method and simplified manner in Nový Jičín. The theoretical part describes a terminology of real estates, value and worth of affair. The main purpose is to value of external works and describe relevant methods. The practical part includes both methods which conduce to value external works and compare both methods in time and figures of external works for purpose how to assess the official price.

Flow distribution has big importance in equipment with limited tube rows because it provides correct operation and sometimes specific flow distribution for technology purposes is needed. This thesis is focusing on flow analysis in these units using computational fluid dynamics (CFD). For analysis of such systems models with varying tube rows and varying perforated segment lengths were created. Analysis showed significant impact of flow manifold layout along with tube layout and number of tubes. Simplified 1D model using static pressure regain coefficient was created which provides much shorter computational times. Comparison of 1D and CFD models was made to determine field of their usage.

Tato diplomová práce se zaměřuje na modelování proudění tekutiny v paralelních distribučních systémech, kde hraje důležitou roli rovnoměrnost distribuce tekutin. Pro tento účel je vytvořen vlastní CFD kód. Kód je napsán v programovacím jazyce Java a používá ke zlepšení výkonu knihovny třetích stran, které se vyznačují přímým přístupem ke hardwarovým a systémovým prostředkům. Kód se také vyznačuje určitými zjednodušeními, u nichž se očekává, že sníží výpočetní časy. Vliv použitých zjednodušujících opatření je vyhodnocen porovnáním výsledků simulací proudění na několika geometriích s údaji získanými z podrobných modelů CFD. Geometrie použitých svazků trubek se odlišují různými uspořádáními toku a trubek a také různým počtem trubek.

Diploma thesis ‚The project of a small water reservoir in the Níhov cadastral area’ has goal to introduce to reader the small water reservoir as the important landscape element. Small water reservoir is cornerstone of local ecological stability, which has important income for microclima in the closes surrounding. Furthermore, the function of constant improvement water quality in the basis or contribute to increasing of ground water level. Thesis is divided into two parts. In the first theoretical part thesis describes the topic of small water reservoirs briefly. The first part shortly describes the details of designing process or inner process within the reservoir. In the second practical part is created basic project documentation based on the data collected and measured in the affected area. The project was created in cooperation and upon request of investor the representation of the village Níhov.

This thesis concerns with construction design of manipulator. The purpose of the manipulator is to transport beech logs. It is a part of the production line for heating and steaming veneering of the logs before their subsequent processing. This thesis presents a new design solution. It offers detailed descriptions of the purpose of the construction and of individual functional assemblies. It also describes the means for operating the machine and the types of sensors used. Calculation of forces and reactions in the mechanism, based on a simplified load calculation model, constitutes an important part of the work. Design of key components of the machine is then based on the results of the analysis of the forces involved. The supplements of the thesis include photographs of the manipulator realization and selected technical design.

This thesis is focused on measurement and analysis of dynamic effects on railway turnouts. Two same-type turnouts with different fastening elasticity were chosen. My attention was focused mainly on the crossing part of the turnout, where the highest dynamic impacts occur. The point of the thesis is comparison of the crossing part of turnouts in term of dynamic behaviour and assessment of influence of soft rail pads on spread of dynamic energy through the construction. A part of the thesis is choice of methodology of the measurement and proposal of convenient mathematical apparatus for analysing of the dynamic effects on crossings.

This diploma thesis deals with the comparing prices of external work on an estate in detached house as a whole functional complex set by cost method to prices of simplified method situated in a village with no more than 1000 inhabitants. The theoretical part is concerned with explanation of basic terms commonly used in evaluation real estate such as a detached house or external work. This part also describes methods and technique used during the valuation. The practical part of my diploma thesis is focused on the valuation of the external work what make accessories of a detached house, by the cost and simplified method and their subsequent comparison.