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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.
421

Influence de la liaison chimique sur la structure des surfaces d'alliages métalliques complexes / Influence of chemical bonding on surface structures of complex metallic alloys

Meier, Matthias 09 December 2015 (has links)
Un alliage métallique complexe est un intermétallique dont la maille est constituée d'un nombre important d'atomes et dont la structure peut être souvent décrite comme un empilement de motifs d'atomes reliés par des liaisons de type covalent. Al5Co2 est l'un de ces composés et est un catalyseur potentiel pour la semi-hydrogénation d'acétylène. L'influence de la structure tridimensionnelle sur les surfaces bidimensionnelles et donc la réactivité est étudiée. Pour se faire, le système massif est analysé en utilisant la DFT afin d'éclaircir ses propriétés thermodynamiques, électroniques et vibrationnelles. Les valeurs calculées, expérimentales et celles de la littérature sont en bon accord. La structure des surfaces de bas indice, (001), (100) et (2-10) est étudiée. Une combinaison de techniques d'analyse de surface sous ultra-vide - LEED, STM - et de DFT est utilisée pour les déterminations structurales. Les résultats indiquent que: (i) la structure des surfaces dépend des conditions de préparation, comme la température de recuit, (ii) la structure des surfaces peut être interprétée comme étant constituée de motifs tronqués où certaines liaisons de type covalent sont brisées. Les sites et les énergies d'adsorption des molécules impliquées dans la réaction de semi-hydrogénation sont calculés pour les trois surfaces. Pour les sites favorables, des distances spécifiques entre atomes d'hydrogène adsorbés et atomes de Co de surface et de sous-surface peuvent être observées. Les atomes de Co de sous-surface ont un caractère donneur d'électrons, stabilisant les atomes adsorbés en surface. En se basant sur des calculs NEB, de possibles chemins réactionnels sur la surface (2-10) sont proposés. L'activité calculée est similaire à celle obtenue pour la surface d'Al13Co4, qui est considérée comme un bon catalyseur. La sélectivité - la compétition entre la désorption d'éthylène et son hydrogénation en éthyle - est discutée. / A complex metallic alloy is an intermetallic with a large unit cell and whose structure can often be seen as a stacking of motifs of strongly covalent-like bonded atoms. Al5Co2 is such a compound and is a potential catalyst for the semi-hydrogenation of acetylene. The influence of the 3-dimensional structure on 2-dimensional surfaces is investigated. Therefore, the bulk system is analysed using DFT to gain insight in the thermodynamic, electronic and vibrational properties. Good agreements between calculated results, experimental ones and results found in the literature are obtained. The low index (001), (100) and (2-10) surfaces are investigated. A combination of surface analysis techniques under ultra high vacuum - LEED, STM - and DFT calculations is used for the structural investigations. The results show that: (i) the surface structure depends on the preparation conditions, such as the annealing temperature, (ii) the surface structure can be interpreted as truncated motif parts, where the covalent-like bonds are broken. Adsorption sites and energies of molecules involved in the semi-hydrogenation reaction are calculated for all three surfaces. For favourable adsorption sites, specific distances of adsorbed H atoms with Co surface and subsurface atoms are observed. These Co subsurface atoms have an electron donor character, stabilising the adsorbed atoms at the surface. Based on NEB calculations, possible reaction paths on the (2-10) surface are proposed. The calculated activity is similar to the one obtained for the Al13Co4 surface, which is considered a good catalyst. The selectivity - the competition between desorption of ethylene and its further hydrogenation - is discussed.
422

Étude par ARPES et STS des propriétés éléctroniques de réseaux métalliques et organiques nanostructurés / Electronic properties of nanostructured metallic and organic interfaces studied by ARPES and STS

Vasseur, Guillaume 13 November 2014 (has links)
Dans ce travail nous démontrons, au travers de deux études, l'intérêt fondamental du couplage des techniques de photoémission résolue en angle (ARPES) et de spectroscopie tunnel (STS) dans l'analyse des propriétés électroniques d'interfaces nanostructurées. Dans la première partie, nous présentons une méthodologie permettant de déduire le potentiel de surface induit par la reconstruction triangulaire d'une monocouche d'Ag/Cu(111). Cette méthode est basée sur la mesure des gaps caractérisant la structure de bande de l'état de Shockley du système aux points de haute symétrie de la zone de Brillouin. L'évaporation d'adatomes de potassium permet d'augmenter le nombre de gaps accessibles en photoémission en décalant les bandes vers les états occupés. Dans un modèle d'électrons presque libres, leur amplitude nous donne accès aux premières composantes de Fourier du potentiel. La reconstruction de ce dernier dans l'espace direct nous permet ensuite de calculer la densité d'états locale que nous comparons aux mesures de conductance STS. La seconde partie est consacrée à l'étude de la croissance et des propriétés électroniques des molécules de 1,4-dibromobenzène (DBB) et 1,4-diiodobenzène (DIB) évaporées sur Cu(110). Leur dépôt à température ambiante sur la surface entraîne la déshalogénation des molécules et la formation de phases organométalliques. A 200°C, le système polymérise pour former des chaînes unidimensionnelles de poly(p-phénylène) parfaitement alignées. Les mesures ARPES révèlent l'existence d'une bande pi unidimensionnelle d'états HOMOs dispersant sous le niveau de Fermi. En STS, nous observons également, pour des petites chaînes, le confinement des états LUMOs dans la partie inoccupée du spectre. Le déconfinement de ces états pour les grandes chaînes conduit à la formation d'une bande continue croisant le niveau de Fermi, conférant au polymère un caractère métallique 1D. Le gap HOMO-LUMO est alors mesuré à 1.15 eV / In this work, through two different studies, we demonstrate the fundamental interest in the coupling of angle resolved photoemission (ARPES) and scanning tunneling spectroscopy (STS) to investigate the electronic properties of nanostructured interfaces. In the first part we present a methodology to determine the surface potential of the triangular reconstructed one monolayer of Ag/Cu(111) interface from ARPES. This method is based on the measurement of the Shockley state band structure’s gaps at the high symmetry points of the Brillouin zone. Deposition of potassium adatoms allows us to shift the surface state towards higher binding energies in order to increase the number of accessible gaps in photoemission. From the magnitude of these gaps we deduce the two first Fourier components of the potential felt by electrons using the nearly free electron model. Then we reconstruct it and calculate the local density of states in order to compare it with the conductance maps probed by STS. In the second part we report the study of the growth and the electronic properties of the two molecules 1,4-dibromobenzene (DBB) and 1,4-diiodobenzene (DIB) evaporated on Cu(110). For room temperature deposition, we first observe their deshalogenation and the formation of an intermediate organometallic phase. Then, above 200°C, the system polymerizes into a long-range ordered array of one dimensional poly(p-phenylene) polymer. ARPES intensity maps allowed us to identify a one dimensional graphene-like strongly dispersive pi-band below the Fermi energy. By STS we also observed LUMOs confined states for small chains over the Fermi level. The loss of confinement for long chains induces the formation of a continuous dispersive band which crosses the Fermi energy, conferring a 1D metallic character to the polymer. The HOMO-LUMO gap is found to be 1.15 eV
423

Výpočtové hodnocení konstrukčních staviv na energetickou náročnost budovy / Computational assessment of structural building materials in terms of energy performance of the building

Křenek, Daniel January 2018 (has links)
Theme of the diploma thesis is computational assessment of structural building materials in terms of energy performance of the building. The history and types of the objects with low energy performance are described. There are listed elements of constructionally energetic concept with low energy performance and overview of building materials used for their construction. In the practical part a selected building was tested for energy performance by legislation. Then two structural material solutions on selected detached house are compared by using a simulation program.
424

Studium užitných vlastností termoreflexních izolací pro stavebnictví / Study of utility properties thermal-reflective insulations in the buildings

Holeček, Dominik January 2019 (has links)
The diploma thesis is partly dedicated to energetic efficiency of buildings and describes possibilities how to evaluate energetic efficiency of buildings in the Czech Republic. We also get to know with distribution of thermal insulators by material base and use in construction. There are also mentioned methods how to determine thermal insulations characteristics of heat insulations, so called heat conductivity coefficient. The last and the crucial chapter of theoretic part is dedicated to thermal-reflective insulations. There are mentioned some of the basic characteristics of insulations, material composition and heat transfer mechanism in their structure as well. Practical part describes measurement of thermal resistance of chosen samples of thermal-reflective insulations per measuring device on the principal of Hot Box method. In the next step was determined emissivity of aluminium foils which forms the surface of chosen samples of thermal-reflective insulations. In the end of thesis are defined possibilities of use thermal-reflective insulations in building structures especially in passive and low-energy buildings in climatic conditions of the Czech Republic.
425

Sídlo firmy Dlabaja a.s. / Corporate headquarters Dlabaja a.s.

Dlabaja, Adam January 2019 (has links)
The project documentation, processed in the framework of the diploma thesis, solves the new building of the administrative building of the building company in the village Lukov u Moravských Budějovic. The building is made of traditional brick technology therm tl. 50 cm, without insulation, ceilings are reinforced concrete, flat roof, vegetation. Vegetation is also part of the facade of the building, which at the same time serves as a root cleaner. The philosophy of the whole design is to create a high-quality working environment for building company employees, a pleasant environment for customers and to best solve the environmental footprint of the building. The building is designed as a modern office building, with space for leisure activities of staff and their visits, taking into account the responsible approach to the development industrial site and the surrounding nature. The building efficiently manages potable, rain and wastewater, the envelope of the building, and the individual structures are designed to make the entire building as energy-consuming as possible, and do not pump irreparably by nature its natural resources in a larger quantity than necessary.
426

Firemní mateřská škola ve Zlíně / Corporate kindergarten in Zlín

Knotek, Michal Unknown Date (has links)
The aim of this diploma thesis is to design a low-energy corporate kindergarten with extended opening hours for the Thomas Bata Regional Hospital in Zlín. The building has one wheelchair accessible floor. It includes two separate classes for children with necessary facilities for children and staff. Envelope walls are designed from prefabricated wooden wall panels with PUR foam filing and ETICS. Internal walls are designed from ceramic blocks with clay plasters to provide heat accumulation and stable indoor environment. The superstructure is supported by strip foundations. The building has flat extensive green roof supported by timber I-beams. Energy for floor heating and domestic hot water is provided by a cascade of two air-water heat pumps and solar thermal collectors. Ventilation in the building is provided by air conditioning unit with heat recovery. Its operation is divided in two zones, kitchen and other spaces. The adjacent plot includes a garden with play elements, a stormwater storage basin with an overflow into an infiltration tank. The infiltration tank also serves for threated water from a wastewater treatment plant. Separate part of the thesis includes assessment of 2D thermal field with change proposal and evaluation of selected building structures, . The thesis is elaborated in Revit 2020, DEKSOFT and other software.
427

"Fit Body" Sporting Centre / Sportovní centrum "Fit Body"

Janíček, Vít January 2014 (has links)
Master thesis processes documentation for the realization of the new building of the multi-functional sporting centre. Object is designed as the two storey building with the external thermal insulation system ETICS. Object is designed according to the appropriate legislation. Object fulfills demands for the low-energy standard. Building is without cellar with the flat warm roof. Load bearing constructions of the floor ceilings are made out of prestressed concrete panels SPIROL. Load bearing construction of the hall roof is made of the glulam timber beams and purlins with the bracing.
428

Návrh teplovzdušného vytápění a větrání nízkoenergetického domku / Design of warm air heating system for low-energy house

Koutník, Martin January 2008 (has links)
The diploma thesis deals with design of warm air heating and ventilating system for low energy house. Introduction of this thesis is focused on dividing residential buildings by their heat requirement. Then problems of residential building ventilation and possibilities of warm air heating systems including heat recovery are presented. In the next chapter summary of ventilating units with heat recovery and warm air heating units for residential low energy buildings and pasive family houses is presented. Calculation of low energy house heat losses, which is solved, is based on CSN 06 0210, CSN 73 0540 and CSN EN 12831 standards. Design and calculation of warm air heating and ventilation system and ground heat exchangers is also described. Floor heating system, fireplace insert and solar heating system are designed as supplementary systems. At the end of this thesis the control system is presented. Project documentation is enclosed in appendix.
429

Teplovzdušný vytápěcí a větrací systém pro nízkoenergetický rodinný dům / Warm-air heating and ventilating system for low-energy family house

Musil, Zdeněk January 2012 (has links)
The diploma thesis deals with warm-air heating and ventilation system of energyefficient family house. The part of thesis is theoretical introduction to low-energy and passive houses, ventilation and heating. The proposal itself is based on the applicable standards and includes all progressive steps, including the calculation of the thermal performance and sizing individual parts of the system. The drawing project documentation is listed in appendixes.
430

Polyfunkční dům / Multifunctional house

Kmenta, Tomáš January 2016 (has links)
Developing  a part of project documentation for a multifunctional house is the main subject of my thesis.This particular object is planned for a constructional lot in a district of Hodonín. Building has  four levels,  is separately standing, made of brick and does not have any cellar.  First floor is intended for  business and service use. Second, third and fourth floor are designed for living. There are one-room, two-room and four-room flats. Multifunctional house is made of  calcium silicate blocks and will be covered with flat roof.

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