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[en] Energy storage is a challenge, notably for spacecraft, submarines and non-polluting automotive vehicles. After a comparison of mass energies of different principles of energy accumulation (magnetic, electrostatic, solid elasticity, kinetic energy, gaseous elasticity, electro-chemistry, sensitive heat, freezing heat, fuels, radioactivity, nuclear fission or fusion, mass energy), the author discusses the choice of thermal storage, presents the main bodies used for thermal energy accumulation (molten salts such as lithium hydride or lithium salt eutectics, or other compounds such as alumina, paraffins), and gives an overview of the main theoretical problems
[fr]Le stockage d'energie thermique utilisant la chaleur latente de fusion de certains corps (sels de lithium, alumine) permet d'atteindre, en association avec des machines thermiques de haut rendement, des performances energetiques dix fois superieures a celles des accumulateurs classiques. De nombreux problemes se posent neanmoins pour l'utilisation pratique de tels systemes, tels que les differences de densite et de conductibilite entre phase liquide et phase solide, la corrosion des parois du recipient de stockage, le danger de manipulation. De tels systemes sont deja etudies en technique medicale, dans les engins spatiaux et les sous-marins de moyenne profondeur. Un projet de sous-marin de grande profondeur utilisant l'eutectique (LiOH, LiF) est a l'etude au Naval Undersea Center (California). De nombreuses autres utilisations sont envisagees. Outre les projets de voitures automobiles a moteur thermique Stirling (General Motor, Phillips) promettant d'etre tres peu polluantes, de nombreux projets utilisant l'accumulation d'energie thermique sont etudies: citons le chauffage individuel de plongeurs autonomes de grande profondeur, ou de cosmonautes. Nous rappelons enfin l'utilisation de l'accumulation thermique en puits de chaleur, permettant a certaines pieces associees a un micro-accumulateur de ne pas souffrir des contraintes thermiques dues a des pics de chaleur. Ce principe est deja utilise dans les techniques spatiales, et peut s'averer tres interessant en siderurgie. (author)
[en] This thesis focuses on the use of alternative renewable energy sources as a full replacement for traditional non-renewable resources. We focus on ways to increase the heating value of the raw materials by drying and pyrolysis. Pyrolysis, as we consider, is the most universal process. It generates heat and products which may be used directly as fuel or after modification as additives to fuels. If we store the solid pyrolysis residue, pyrolysis can be considered as a suitable method of capturing CO2 from the atmosphere. Pyrolysis is a process contributing to sustainable energy recovery and disposal of municipal, biological and contaminated wastes. Moreover, the production in local conditions from local resources increases land use, employment in the regions and energy self-sufficiency of the state. Furthermore, we deal with possibility of affecting low heating value of fuels by using pyrolysis products. With combined production of fuels (pellets, briquettes) from biomass, wastes and pyrolysis products we expect an increase in heating value of well over 20 MJ·kg-1. (author)
[en] The topic of exploitation of nuclear energy is becoming increasingly actual in the present time in connection with frequently discussed question of 'renaissance of nuclear energetics'. The work is aimed at research of geographical aspects of exploitation of nuclear energy for military and civil purposes on the territory of Europe. The base of work represents the analysis of theoretical aspects of research of energy, mainly of nuclear energy. The work examines the historical development of exploitation of nuclear energy since its discovery, through development of military nuclear industry in Europe, big attention is paid to spreading of nuclear energetics on the territory of Europe from its beginnings up to the present time. The main part of the work represents the analysis of the present situation of exploitation of nuclear energy for civil purposes in Europe. The attention is paid to so-called nuclear fuel cycle as complex chain of several reciprocally interconnected operations of nuclear fuel treatment. The monitoring of spatial relations among individual countries within their nuclear fuel cycles is emphasised. The analysis of historical development and of the present state of nuclear energetics finished up in the outline of the perspectives of its further development in Europe. The analysis of the tendencies of evolution of world energetic economy mentions on the trend of growth of energy consumption in the world and Europe, as well as on the important position of nuclear energy in the structure of energy sources. Summary in English language is included. (author)
[en] The first part of this work contains a general survey of the use of Lie groups and algebras in quantum mechanics, followed by an extensive description of tbe invariance algebra and invariance group of the non-relativistic hydrogen atom; the realization of this group discovered by FOCK is specially examined. The second part is a two-hundred items bibliography on invariance groups and algebras of classical and quantum-mechanical simple systems. (author)
[fr]Ce travail comporte deux parties: la premiere fait suivre un expose general sur les groupes et algebres de Lie en mecanique quantique par la description de l'algebre et du groupe d'invariance de l'atome d'hydrogene non relativiste; la realisation du groupe decouverte par V.A. FOCK est examinee particulierement. La seconde partie contient une mise au point bibliographique sur les groupes et algebres d'invariance des systemes classiques et quantiques simples. (auteur)
[en] As anaerobic digestion is a way to valorise organic wastes under the form of energy, the management and control of this process requires a detailed study of biochemical and microbiological mechanisms. This research study more particularly focuses on the role of volatile fat acids which play a crucial role in methanization, in order to better understand their production and degradation mechanisms. The author first reports a bibliographical study on metabolisms and micro-organisms involved in each stage. Then, he reports an experimental study which first addressed the mechanism of production of volatile fat acids from two substrates comprising 3 carbons (lactate and glycerol), and focused on kinetic, metabolic and microbiological aspects, and secondly addressed mechanisms of degradation of volatile fat acids (kinetic and metabolic aspects of acetogenic/methanogenic reactions).
[fr]Actuellement, l'interdependance des interets economiques et des problemes ecologiques fait entrevoir ce processus anaerobie comme un moyen de revaloriser les dechets organiques sous forme d'energie. Une des applications les plus rationnelles est rencontree dans le secteur Agro-Alimentaire dont les dechets solubles a forte charge polluante excluent une trop onereuse epuration aerobie. Si la mise en oeuvre d'un tel processus peut paraitre, a premiere vue, rudimentaire, il s'avere que sa maitrise passe par une etude detaillee des mecanismes biochimiques et microbiologiques dont la diversite n'a pas permis jusqu'ici d'en comprendre tous les rouages. En effet, la digestion anaerobie implique un ecosysteme microbien des plus complexes, comparable a celui du rumen, et dont la comprehension du fonctionnement a fait l'objet de bien des recherches: de nombreuses etudes ont porte sur l'hydrolyse des polymeres, etape premiere et limitante de la digestion de la matiere vegetale. D'autres travaux se sont interesses a l'etape finale, egalement lente et qui aboutit au methane. Dans tout processus fermentaire, ce sont les acides gras volatils (AGV) qui jouent le role de plaque tournante, et c'est a ces intermediaires majeurs de la methanisation que l'on s'interessera ici, afin de mieux cerner les mecanismes de leur production et de leur degradation. Cette etude s'articulera donc selon les points suivants: - mise au point bibliographique concernant les metabolismes et les microorganismes impliques dans chaque etape. - experimentation menee en deux temps: Mecanisme de production d'AGV a partir de deux substrats a 3 carbones, peu etudies jusqu'ici le lactate et le glycerol. Aspects cinetique, metabolique et microbiologique. - Mecanismes de degradation des AGV. Aspects cinetique et metabolique des reactions acetogenes - methanogenes.
[en] The main results and new knowledge of the presented Thesis can be summarized as follows: - The daily mean discharge time series of the river Danube at Bratislava has been supplemented with data from years 1876-1890. So it has been extended into the full-uninterrupted daily data series for the length of 130 years. Such series of the daily mean discharges is suitable for statistical analyses of the hydrological characteristics changes, and also for identification of the multi-annual (up to 30- years) cycles. - Using the combined periodogram method and the series filtration, in the discharge time series, the variegation cycles of dry and wet time periods were searched. For such objective, the time series were used, of more than 100 rivers of the world. From the longer cycles in the series the approximately 28-30 and 20-22 yrs. cycles of the dry and wet periods occurrence were identified. However, the cycle lengths is not exactly 28 and 21 years, but in the long term average, they come close to these values. From the shorter cycles, those with 7.8-, 6.5-, 5.2-; 4.14-, 3.65, and 2.4- years were identified. - These periods were documented for the discharge series of the analyzed rivers in various physiographic latitudes of the world. It is then possible to consider this piece of knowledge as generally valid for the whole Earth. These periods are connected with the Solar activity and with the thermohaline circulation (ocean conveyor belt). Their parts are also the El Nino, AO, NAO, and QBO phenomena. - Through the cross-correlations (two variables), time shift of the dry and wet periods was identified depending upon the geographical longitude and latitude of the river basins location. From these results it follows, that the dry and wet periods do not occur at the same time on various locations. This time shift depends upon the basins location, and it follows upon the shift in the precipitations occurrence. - The trend analysis did not indicate any significant trends in runoff series on the territory of Europe as a whole (neither of the Danube basin), for the last 150 years. - There were analyzed also time series of the extreme flood discharges of Danube at Bratislava, as well as those of flood volumes of these floods. Here also the statistical tests did not confirm any statistically significant trends. - A scenario was elaborated of the catastrophic 1000-year flood of Danube for the Bratislava gauging profile. Using a simple (one-dimensional) hydrological model, this catastrophic flood wave was routed down the Danube from Bratislava to Sturovo through the almost whole Danube section on the territory of Slovakia. Of course, the whole hydrological system of the Earth is subject to random geophysical and also (anthropogenic) shocks. Therefore, it is necessary always to take into account also random behavior of the hydrological time series.
[en] The development of mankind has depended on availability of water resources. Already the first agricultural civilizations noticed the temporal variability of water resources and oscillation of the multi-annual dry and wet periods. The presented thesis summarizes results of more than fifteen years research activities of the author in the field of long-term runoff prediction. Statistical analysis of the runoff oscillations depends on availability of long time series of data. Systematic measurements of discharge in modern era started relatively late. The longest time series are available in Europe, but they do not exceed 200 years. Such long series are exceptional and in most parts of the world only much shorter series exist. Since studies dealing with the natural runoff oscillation and NAO phenomenon recently absent in Slovakia, there is the one aim of the thesis to fill in the gap in the long-term runoff fluctuation analysis and long-term discharge prediction methods development. The thesis focuses on the natural runoff cyclicity identification. In stochastic models, the climate changes scenarios caused by atmosphere warming are not involved however the runoff tele-connection around the Earth is studied. Scientific objectives of the thesis: 1. To reconstruct the Danube daily discharge series at Bratislava (1876-1890) based upon the Bratislava gauge daily water level observations; 2. to analyze variability and long term trends of the selected discharge Danube series characteristics for its Bratislava gauge; 3. to propose and develop the combined periodogram method for more exact spectral density identification in discharge time series; to analyze trends and periodicity in discharge long term series; to identify occurrence of the wet and dry periods over the world, to identify the influence of the NAO/AO/ENSO/QBO phenomena and the Sun activity on the runoff variability. 4. to present some long term stochastic prediction methods; to use two of them, the classical analysis and the Box-Jenkins methodology in order to provide a long term prediction for Danube discharge time series for the next decade. 5. to analyze the historical Danube floods at Bratislava, in order to determine the N/ year floods at that gauge; 6. to analyze for the Danube at Bratislava the respective flood volumes; 7. in sense of the European Parliament Directive 2007/60/EC, to elaborate for the Bratislava Danube gauge the catastrophic flood wave scenario; 8. to develop a mathematical model, and to simulate by it, the catastrophic flood wave routing through the Slovak Danube reach (Devin-Sturovo. The thesis consists of eight chapters according to the eight scientific objectives mentioned above. It provides a wide survey of the obtained results from the methodological approach to the time series analysis, through stating new hypotheses on the discharge oscillations over the world, up to the application of theoretical results to the practice. The thesis is based primarily on 10 selected papers of the author. The papers were published in monographs, and CC journals. The long annual discharge data series of all the continents were obtained from the following data sources: (i) Global Runoff Data Center in Koblenz, Germany; (ii) CD ROM of the Hydro-Climatic Data Network (HCDN), U.S. Geological Survey Streamflow Data Set for the United States; (iii) CD-ROM World Freshwater Resources prepared by I. A. Shiklomanov in the framework of the International Hydrological Programme (IHP) of UNESCO; (iv) URL http://waterdata.usgs.gov.
[en] This work presents an application of fuzzy control on dynamical system models. It has been observed that fuzzy controllers maybe used as a good alternative to the classical PI controller, once it incorporates human line behavior. Three implication relationships were used for the fussy controllers, namely, Mamdani Min, Larsen and Takagi-Sugeno. Performance comparisons were made aiming at achieving the best performance for each model used. The PI controller was used as a minimum standard, once it has been present in the industry for many years, giving acceptable performances and some degree of reliability . Two kinds of perturbations were introduced in the models to test the controllers: a ramp and chaotic perturbations. The first one is a monotonic, standard increase of an input parameter. The second one presents non-periodicity and irregularity in such a way to be quite rough to the controllers. The chaotic signal, as an analysis tool to dynamical systems, is an interesting contribution of this work. As a general conclusion it can be said the best performance, in this work, was achieved by the Takagi-Sugeno fuzzy controller. (author)
[en] This dissertation thesis is focused on the atmospheric pressure plasma and low-pressure plasma treatment of aluminium surface. The so-called Diffuse Coplanar Surface Barrier Discharge (DCSBD) and Radio-Frequency (RF) discharge were used as sources of non-equilibrium low-temperature plasma. The properties of the discharges were investigated by means of electrical measurements. Plasma treatment of the aluminium samples was conducted in a variety of working gases, i.e. air, nitrogen, oxygen and mixtures of these with water vapor. The optimal plasma treatment conditions (discharge power, treatment time, distance) were studied as well. The results of plasma treated aluminium samples were investigated by means of contact angle measurements, surface free energy measurements, Atomic Force Microscopy (AFM), Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM/EDX), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR FTIR), X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS) measurements. Various aging effects, depending on the plasma treatment conditions were observed and discussed. The ability of DCSBD plasma to clean and activate the treated aluminium surface is shown. Moreover the plasma pretreatment was used to activate the aluminium surface before the deposition of different organosilane films. Anticorrosion properties of the plasma polymerized film deposited in the aluminium surface using Hexamethyldisiloxane (HMDSO) as a primer were tested. The effect of plasma treatment of aluminium surface on its adhesion bond was verified by the lap shear test and charging of the aluminium surface after the interaction with plasma particles was also studied. The presented results indicate that the plasma generated using DCSBD discharge is suitable for cleaning, activation and deposition of organosilane coatings on aluminium surface. Comparing to RF discharge, DSCBD plasma source has a significant commercial potential for high-speed in-line processing. (author)
[en] This study is concerned with vertical ascending flows, in which the gravitational force plays a dominant role, and more particularly the case of an intermittent flow, which presents itself as a spatio-temporal succession of gas pockets in ascending motion in a flow of gas bubbles. This is a configuration frequently encountered in oil exploitation conditions, which has been studied previously with regard to 2-fluid flows. As such, this study is in line with Line's thesis, which it takes up most of the modeling while having a stronger experimental component, justified by the lack of databases for 3-fluid flows. the general equations of intermittent flows are first recalled. In view of the many studies concerning upward vertical flows, a great deal of work has been done to make a bibliographical study as exhaustive as possible. Then the test set-up that has been designed and realized for the study of 2-F and 3-F flows is presented. Results obtained in the 2-F and 3-F cases are discussed and the results concerning the gas fractions, the parietal friction and the pocket presence rate are compared with the existing models. Finally, an attempt is made to model from the solving of the Navier-Stokes equations on an imposed profiled gas pocket; this part is intended primarily to initiate a longer-term modeling work, which aims to better understand the major problem of ascension and interaction of gas pockets
[fr]On s'est attache dans cette etude au cas des ecoulements verticaux ascendants, dans lesquels la force de gravite joue un role dominant. On a choisi d'etudier plus particulierement le cas de l'ecoulement intermittent qui se presente comme une succession spatio-temporelle de poches de gaz, en mouvement ascendant dans un ecoulement a bulles de gaz. C'est une configuration frequemment rencontree en conditions d'exploitations petrolieres, qui a ete etudiee precedemment en ce qui concerne les ecoulements 2F. A ce titre, cette etude se situe dans le prolongement de la these de Line, dont elle reprend l'essentiel de la modelisation. Elle presente cependant une plus forte composante experimentale, justifiee par le manque de bases de donnees pour les ecoulements 3F. La synthese du travail de recherche est presentee dans six chapitres. On rappelle tout d'abord les equations generales des ecoulements intermittents, a partir de la methode developpee sur une idee de Masbernat, et reprise par Ferschneider et Line. Compte tenu des nombreux travaux concernant les ecoulements verticaux ascendants, on s'est attache a faire une etude bibliographique aussi exhaustive que possible. Sont ensuite presentes les moyens d'essai que nous avons concus et realises pour l'etude des ecoulements 2F et 3F. On discute ensuite des resultats obtenus dans le cas 2F d'une part, 3F d'autre part et l'on compare aux modeles existants les resultats concernant les fractions de gaz, le frottement parietal et le taux de presence de poche. Enfin, on a inclus une tentative de modelisation a partir de la resolution des equations de Navier-Stokes sur une poche de gaz a profil impose: cette partie se veut avant tout l'initiation d'un travail de modelisation a plus long terme, qui vise a mieux comprendre le probleme majeur de l'ascension et de l'interaction des poches de gaz