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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.
111

Origine des fractionnements isotopiques de l'azote et des gaz rares dans les météorites et les atmosphères planétaires / Origin of isotopic fractionations of nitrogen and noble gases in meteorites and planetary atmospheres

Kuga, Maïa 27 June 2014 (has links)
L’azote et les gaz rares présents dans les astéroïdes, les comètes et les atmosphères planétaires sont piégés dans de la matière organique et ont des compositions chimiques qui sont différentes de celle du Soleil, représentatif du gaz primordial à partir duquel les différents objets du système solaire se sont formés il y a 4,5 milliards d’années. Au cours de cette thèse, des synthèses de matière carbonée à partir d’un mélange de gaz ont été réalisées dans un plasma appelé le Nébulotron, afin de mieux comprendre les processus à l’origine des compositions de l’azote et des gaz rares présents dans les météorites. Les caractéristiques de la matière organique ainsi que la composition des gaz rares piégés dans les météorites sont relativement bien reproduites dans les expériences, mais pas celle de l’azote. Ces résultats expérimentaux permettent de proposer des mécanismes clé à l’origine des compositions des éléments volatils présents dans les objets du système solaire. / Nitrogen and noble gases present in asteroids, comets or planetary atmospheres are trapped in organic matter and bear a composition that is different from the composition of the Sun, which is representative of the primordial gas from which the different objects in the solar system were formed 4.5 billion years ago. During this thesis, experimental syntheses of organic matter from gas mixtures in a plasma setup called the Nebulotron were performed in order to better understand the processes responsible for this chemical difference between the meteorites and the Sun for nitrogen and noble gases. The characteristics of the organic matter and the signature of the noble gases trapped in meteorites are relatively well reproduced in the experiments, whereas the composition of nitrogen is not. These experimental results give hints about the key mechanisms that are responsible for the variations of the volatile elements composition in the solar system objects.
112

Mapeamentos Simpléticos em Dinâmica Asteroidal / Symplectic mappings in asteroidal dynamics

Fernando Virgilio Roig 08 August 1997 (has links)
Neste trabalho, desenvolvemos um mapeamento simplético que nos permite estudar o comportamento dinâmico de ressonâncias asteroidais no âmbito do problema dos três corpos restrito, elíptico, espacial. Para obter este mapeamento, combinamos um esquema simplético similar ao desenvolvido por Hadjidemetriou (1986) junto com o desenvolvimento assimétrico da função perturbadora (Ferraz-Mello, 1987), que leva em conta as inclinações do perturbado e do perturbador como sendo referidas a um plano invariante (Roig et al., 1997). Este mapeamento é aplicado aos casos das ressonâncias asteroidais 2/1 e 3/2. Estudam-se um grande número de condições iniciais no espaço de fase, de forma a conseguir tirar conclusões de tipo estatístico sobre os processos envolvidos na geração de mecanismos difusivos que podem agir nessas ressonâncias. / In this work, we developed a symplectic mapping which allow us to study the dynamical behaviour of asteroidal resonances in the frame of the non-planar elliptic restricted three-body problem. To obtain such a mapping we combine a symplectic scheme similar to that of Hadjidemetriou (1986) together with an asymmetric expansion of the disturbing funtion (Ferraz-Mello, 1987) which takes into account the inclinations of both the perturber and the disturbed bodies (Roig et al., 1997). This mapping is applied to the 2/1 and 3/2 mean motion resonances in the asteroidal belt. We explore a wide range of initial conditions in the phase space in order to get a large number of results which allow us to make some statistical conclusions about the generation of diffusion mechanisms acting in these resonances.
113

Stárnutí teplonosných kapalin v termických solárních systémech a propan-1,3-diol jako nová možnost / Degradation of Heat Transfer Fluids in Thermal Solar Systems and Propane-1,3-diol as a New Option

Mikšík, František January 2018 (has links)
Stárnutí teplonosných kapalin na organické bázi je dlouhodobým problémem, který je znám od počátku jejich používání. První část této disertační práce je tak věnována případové studii funkčního experimentálního systému, který byl jako nový naplněn teplonosnou kapalinou na bázi propan-1,2-diol a pozorován po období 7 let. Pro analýzu stárnutí kapaliny v tomto systému byly sledovány základní provozní vlastnosti kapaliny jako jsou hustota, viskozita, teplota tuhnutí, pH a obsah kovů. Skrze tyto vlastnosti tak bylo sledováno stárnutí kapaliny nepřímo. Přímé sledování stárnutí bylo posléze provedeno analýzou degradačních produktů, jako jsou organické kyseliny a změny ve složení směsi pomocí izotachoforézy a hmotnostní spektrometrie. Pro srovnání byly taktéž analyzovány vybrané vzorky z několik dalších systémů plněných identickou kapalinou s prokazatelně pokročilou formou degradace. V druhé části práce jsou představeny základní fyzikálně-chemické vlastnosti směsí propan-1,3-diolu s vodou a jejich analytické hodnocení a matematické modelování pro universální použití jakožto nového základu pro nemrznoucí teplonosné kapaliny. Na základě dostupných informací je pak hodnocena použitelnost této směsi. Výhoda propan-1,3-diolu je spatřována především ve výrobě z obnovitelných zdrojů a v některých fyzikálních a chemických vlastnostech, které dle dosavadních poznatků předčívají doposud používané glykolové směsi.
114

Energetický audit / Energy audit

Peichl, Petr January 2020 (has links)
The diploma thesis deals with the energy audit of the kindergarten building Špálova in Ostrava, according to order No. 480/2012 Sb. as amended. It is divided into three parts. The first part deals with the project of photovoltaic power plants in the energy audit, the second part analyzes the calculation procedures in the design of energy-saving measures and the third part completes the energy audit according to the requirements of the above-mentioned decree.
115

Hybrid solar district heating: combinations of high and low temperature solar technologies : A case study of Swedish DH system

Giorgio, Lucrezia January 2021 (has links)
In Sweden, the residential and industrial energy demand is provided by a significant part of district heating. In a decarbonization plan to reduce the CO2 emissions, the integration of a large-scale solar system in the district heating can be a suitable option. The most used types of collectors are flat plate collectors (FPC), for which efficiency drops at high temperature levels. Parabolic through collectors (PTC) have seen increased interest in later years, due to their higher efficiency at higher temperature levels, which could improve system performance both energetically and economically. A hybrid concept using a combination of FPC and PTC for a solar thermal system has previously been studied for a solar district heating system in Denmark, with the aim to maximize the solar production by operating the solar collectors in the temperature ranges where they excel. The first aim of this thesis was to adapt the hybrid solar system in a district heating system for a Swedish case study and to evaluate if the hybrid optimization studied has similar positive effects in the overall thermal production of the system in Sweden, as it did in Denmark. The second aim of this thesis was to investigate the use of photovoltaic thermal collectors (PVT) instead of FPC for parts of the solar thermal system. With PVT, a single solar collector module allows for simultaneous production of heat and electricity and integration of photovoltaic thermal collectors in the solar assisted district heating could improve the overall performance of the system, both in terms of energy production and economical gain.The study was performed using the simulation tool TRNSYS based on a model developed in a danish case study. It was performed a parametric analysis on the percentage of share of the different types of solar collectors in the total area. The results given from the simulations have been used to carry out an economic evaluation based on the levelized cost of substituted energy, the annual operation and maintenance costs, and the marginal operational cost difference between a conventional district heating system supplied by a boiler only and a solar assisted district heating system. Based on the results found, it has been proved that a greater proportion of parabolic trough collectors in the solar field contribute to a greater production of thermal energy but also to higher expenses in the economy of the project. The best configuration which balanced these two factors was composed by 70 % of flat plate collectors and 30 % of parabolic trough collectors, based on the total area. The integration of photovoltaic thermal has been demonstrated to be not cost-effective for the studied location compared to the optimized ratio of FPC to PTC, mainly due to the high and uncertain price of the new technology. The use of photovoltaic thermal system is not yet widely developed in projects and there are only a few existing projects in operation today. In the future, the development of photovoltaic thermal in solar assisted district heating projects might have a higher realizable economic potential due to the industry learning curve, but more studies will need to be performed on this.
116

Vliv malých domácích spotřebičů na ekonomiku solárních systémů / Influence of small home appliances on economy of solar systems

Kučerová, Simona January 2012 (has links)
This Master´s thesis deals with the influence of small household appliances to the economy of solar systems. The theoretical part is focused to solar systems and describes the possibilities of linking these systems with small household appliances. It adds an effective, ecological and economic aspect of washing and small home appliances suitable for economic household. The practical part evaluates the economic utilization of solar systems with small household appliances.
117

Regulátor pro nabíjení olověných akumulátorů z fotovoltaického panelu / Charge controller for solar panel based charging of lead-acid batteries

Korenčiak, Peter January 2011 (has links)
Tato diplomová práce se zabývá návrhem a realizací regulátoru pro použití v solárním systému s větším počtem olověných akumulátorů. Takový regulátor umožňuje nezávislé připojení a řízení nabíjení většího počtu akumulátorů různého stáří a parametrů. To je v kontrastu s řešeními obsahujícími jedno připojení pro více baterií připojených paralelně, kde se míchání baterií různého druhu a stáří nedoporučuje. Tento regulátor nabízí vysokou škálovatelnost skladování energie v solárním systému. Umožňuje také používat starší baterie s novými, místo nutnosti staré baterie nahradit, když jejich kapacita klesne pod požadovanou úroveň. V této práci jsou podrobně popsány požadavky, návrh hardwaru a softwaru a implementace regulátoru s nominálním výstupním proudem 20A pro pět 12V olověných baterií. Práce popisuje také další funkce, stejně jako alternativní návrhy a algoritmy. Důležitá část práce se zabývá designem spínačů pro velké proudy, ochrany proti zkratu a obvodů pro měření stejnosměrného proudu. Správná funkčnost regulátoru byla ověřena měřením.
118

Kvantifikace energetických ztrát fototermického systému ohřevu TUV při napájení fotovoltaikou / Quantification of energy loss in photothermic system of hot water supply in photovoltaics

Havlíček, Lukáš January 2014 (has links)
This masters’s thesis is about quantify of energy losses in the solar system for heating of hot water by energy from photovoltaics. During the April in year 2014 will be realized a practical data collection on the real system. Then, based on these measurements, calculations will be performed.
119

Aplikace obnovitelných zdrojů energie pro vytápění rodinného domu v Bosně a Hercegovině / Application of Renewable Energy Sources for the Family House Heating in Bosnia and Herzegovina

Štefková, Daniela January 2013 (has links)
Diploma thesis is focused on renewable energy sources and its applications for heating of family house in Bosnia and Herzegovina. The project contains two design variants which are described in part B in detail. Alternatives are compared in conclusion and the most suitable one is chosen for given building. The part of experimental solution deals with measurement of solar intensity and air temperature in Bosnia and Herzegovina and in the Czech Republic. Obtained data are processed, compared and graphically represented. Experimental part also includes stationary state simulation of floor heating carried out in CalA software. Simulations were made in different variants.
120

Vytápění historického objektu alternativními palivy / Heating historic building alternative fuels

Lampa, Jan January 2014 (has links)
The introduction of theoretical part deals with issue of fuel. There are basic kinds of fuels, their properties and calorific values. In next part a summary of types of boilers depending on the kind of fuel is described. A process of burning in each type is discussed. Then the basic issue of heat transmission, heat losses and design of individual elements of central heating system is described. In the second part there are two studies compared to each other. In the first one an automatic pellet boiler is used as a source of energy and in the second one it’s a heat pump, type air-water. At the end both of the variants are reviewed and the better option is chosen. In the last part the better option is designed, into detailed design documentation. Important design values for using the heating system and hot water service are calculated.

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