Thesis (Ph. D.)--Louisiana State University and Agricultural and Mechanical College, 2004. / Includes bibliographical references.

Ο στόχος της παρούσας διπλωματικής εργασίας είναι η παρουσίαση της χρησιμότητας του ηλεκτρονικού υπολογιστή στην εκπαιδευτική διαδικασία, η ευρεία χρήση των βάσεων δεδομένων στον σύγχρονο κόσμο καθώς και η μελέτη των λειτουργικών περιοχών μίας βάσης δεδομένων. Επίσης, παρουσιάζεται ο τρόπος με τον οποίο οργανώνονται τα δεδομένα μιας βάσης δεδομένων στο σκληρό δίσκο και η χρησιμότητα των ευρετηρίων. Στο πρώτο κεφάλαιο, γίνεται μια εισαγωγή στην χρησιμότητα του ηλεκτρονικού υπολογιστή στην καθημερινότητα μας και κυρίως, στην εισβολή του στην εκπαιδευτική διαδικασία. Παρουσιάζονται κάποια κύρια στοιχεία που κάνουν τον Η/Υ απαραίτητο - πλέον - στην εκπαίδευση, οι τρόποι με τους οποίους μπορεί να χρησιμοποιηθεί στην εκπαίδευση και φυσικά η μεγάλη συμβολή της συνεργατικής μάθησης με την βοήθεια των ηλεκτρονικών υπολογιστών. Στο δεύτερο κεφάλαιο, αναφέρεται η γενική ιδέα των Βάσεων Δεδομένων, η εξέλιξή τους και κάποια ιστορικά στοιχεία. Στη συνέχεια παρουσιάζονται τα βασικά στοιχεία της δομής των βάσεων δεδομένων και οι λειτουργικές περιοχές τους (αρχιτεκτονική, μοντέλα, γλώσσες, ασφάλεια). Στο τρίτο κεφάλαιο, ασχολούμαστε με την αποθήκευση των βάσεων δεδομένων, κυρίως σε δευτερεύοντα αποθηκευτικά μέσα, όπως ο σκληρός δίσκος. Αναφέρονται τα επιμέρους στοιχεία ενός σκληρού δίσκου και τον τρόπο με τον οποίο αποθηκεύονται τα δεδομένα σε μορφή εγγραφών, τοντρόπο οργάνωσης και διάταξης των εγγραφών σε αρχεία καθώς και περιληπτικά η μέθοδος του κατακερματισμού. Στο τέταρτο κεφάλαιο, παρουσιάζεται η δομή των ευρετηρίων για την διάταξη των εγγραφών σε ένα αρχείο. Αναφέρονται οι βασικοί τύποι ευρετηρίων (πρωτέυον, δευτερεύον, συστάδων και πολυεπίπεδο) καθώς και τα δυναμικά πολυεπίπεδα ευρετήρια με την χρήση Β-δένδρων και Β+-δένδρων. Στο πέμπτο κεφάλαιο, παρουσιάζεται μία εφαρμογή των ευρετηρίων σε μία δειγματική βάση δεδομένων (Sakila), η οποία χρησιμοποιείται για εκπαιδευτικούς σκοπούς. Συντάσσονται ερωτήματα SQL με την βοήθεια εντολών δημιουργίας ευρετηρίων, ώστε να δειχθεί και πειραματικά ότι τα ευρετήρια είναι μία πολύ καλή μέθοδος μείωσης του χρόνου αναζήτησης, ειδικά σε μία βάση με πάνω από 1000-2000 εγγραφές. / The aim of the present thesis is to show the utility of computers in education, the widespread use of databases in the modern world and the study of the functional areas of a database. It is also presented the way the data are organized in a database on the hard disk and the structure of indexes. The first chapter includes an introduction to the usefulness of the personal computer to our everyday life and especially, in its invasion in the educational process. There are presented some key elements that make the PC necessary in education, the ways in which it can be used in education and of course the great contribution of collaborative learning with the help of computers. The second chapter refers to the concept of databases, their development and some historical data. Also, there are presented the basic elements of the structure of databases and their functional areas (architecture, models, languages, security). The third chapter deals with the storage of databases, particularly in a secondary storage media, such as the hard disk. There are indicated the components of a hard disk and how the data is stored in records, the organization and provision of records in files and briefly the method of hashing. The fourth chapter presents the structure of indexes for the order of the records in a file. The basic types of indexes are described (primary, secondary, clustering and multilevel), as well as, the dynamic multi-level indexes using B-trees and B+-trees. The fifth chapter presents an application of indexes in a sample database (Sakila), which is used for educational purposes. SQL queries are drafted with the help of create indexes command, in order to show – experimentally - that the indexes are a great way to reduce search time, especially, in a database which contains over 1000-2000 records.

Resumo: O plantio direto consiste em um sistema de manejo conservacionista da produção agrícola, que promove a melhoria das condições físicas, químicas e biológicas do solo. Desta forma, o objetivo do presente trabalho foi a avaliação de sistemas de acabamento de semeadura existentes no mercado nacional, utilizados em semeadoras de precisão para plantio direto, assim como novas propostas, levando em conta fatores que afetam a germinação das sementes e a emergência das plântulas no campo. O experimento foi conduzido na Fazenda Experimental do Instituto Agronômico do Paraná - IAPAR, em Londrina, utilizando-se o delineamento experimental em blocos ao acaso, com oito tratamentos e quatro repetições para a cultura do feijão e três repetições para a cultura da soja. Os tratamentos foram constituídos de oito sistemas de acabamento de semeadura, dotados de componentes com e sem aterramento, sistemas de controle de profundidade de sementes e rodas compactadoras. Foram avaliadas variáveis do solo, das sementes e parâmetros de desempenho das unidades semeadoras. Conclui-se que os discos aterradores melhoram os resultados das unidades de semeadura, beneficiando a operação em diferentes aspectos e aumentando a emergência. As rodas controladoras de profundidade paralelas melhoram os resultados dos discos aterradores, inclusive os de emergência. As rodas compactadoras lisas não são indicadas, pois promovem problemas de selamento superficial. As rodas compactadoras em "V" apresentaram bons resultados, mas as rodas compactadoras com garras e sulcos internos tendem a ser melhores / Abstract: No-till is a system of conservation management of agricultural production, which promotes the improvement of the physical, chemical and biological soil conditions. Thus, the purpose of this study was to evaluate the systems finish seeding on the market in Brazil, used in precision seeders for no-till planters, as well as new proposals, considering factors that affect seed germination and emergence seedlings in the field. The experiment was conducted at the Experimental Farm of the Agronomic Institute of Paraná - IAPAR, in Londrina, using the randomized block planning with eight treatments and four repetitions for the cultivation of beans and three repetitions for soybean. Treatments consist of eight systems of finish seeding that having components with and without ground finish systems, depth of seed and compactor wheels. Was evaluated soil variables, seeds variables and performance parameters of seeding units. It was concluded that soil cover disks improve the seeding units performance, benefit the operation in different aspects and increasing the emergency. Parallel depth controller wheels improve results of soil cover discs, including the emergency. The flat compactor wheels are not recommended, because they promote soil surface sealing problems. The wheels in "V" had good results, but the wheels with grip and internal ridges tend to be better / Orientador: Carlos Eduardo Angeli Furlani / Coorientador: Ruy Casão Júnior / Banca: Rouverson Pereira da Silva / Banca: Antonio Sérgio Ferraudo / Banca: Luiz Malcolm Mano de Mello / Banca: Wilson José Oliveira de Souza / Doutor

Le champ magnétique vertical joue un rôle prépondérant dans la dynamique des disques d'accrétion. L'émission de jet par un disque ainsi que la turbulence qu'on suppose y exister sont tous deux fortement contraints par l'intensité de ce champ vertical. Ce champ évolue lui même suivant les mécanismes d'advection par la matière et de diffusion par la turbulence. Depuis plus de vingt ans, la question de l'évolution d'un tel champ dans un disque fait l'objet de nombreuses études, mais une modélisation globale de disque prenant en compte tous ces ingrédients n'avait encore jamais été réalisée. Je propose ici un modèle, considérant le transport d'un champ magnétique vertical par le disque, mais également la rétroaction de ce champ sur la dynamique du disque. Une résolution analytique de configurations homogènes est réalisée. Elle confirme les résultats des études précédentes, à savoir qu'en l'état actuel des connaissances des processus de transport, un disque turbulent ne peut advecter significativement le champ vertical pour permettre l'émission d'un jet. Elle met cependant en avant une configuration nouvelle de disque, mixte, dans laquelle les conditions d'éjection sont réunies non pas à l'intérieur du disque mais dans ses régions externes. La stabilité des configurations homogènes calculée a été réalisée, et de nouvelles instabilités sont mises en avant. L'effectivité de ces instabilités dépend des dépendances fonctionnelles employées pour quantifier la dynamique du disque. Une caractérisation, via des simulation locales, des ces dépendances fonctionnelles, permettrait de savoir si ces instabilités peuvent être effectives dans un disque d'accrétion. Enfin, les outils numériques développé permettent d'étudier les configurations envisagées. Les configurations homogènes stationnaires sont récupérées, et une étude dynamique de la configuration mixte permet de caractériser les conditions d'advection de la limite disque éjectant/disque standard. / The vertical magnetic field plays a fundamental role in the dynamics of accretion discs. The jet launching, so as the turbulence that is supposed to exist in these discs are strongly constrained by the intensity of this field. This field evolves following the mechanisms of advection by the mater and diffusion by turbulence. The question of the evolution of such a field has been studied since more than 20 years, but a global modelisation, involving all these méchanisms wasn't done yet. I propose a model, taking into account the transport of a vertical magnetic field by the disc, and also the feedback of this field on the dynamics of the disc. Analytical solutions for standard configurations a calculated. It confirms previous studies in the sense that considering the state of the art, a turbulent disc can not advect a vertical field in order to allow a jet launching. However, a new configuration is rised, in wich the ejection conditions are realised in the outer radius of the disc. The stability of the standard configurations is calculated, and new instabilities are rised. The effectivity of such instabilities depends on the functionnal dependancies used to quantify the disc dynamics. A determination of such dependancies, via local simulations, would clarify if such instabilities could be effective in accretion discs. At last, the numerical tools developped allows to study the configurations. Standard one are found, and a dynamical study of the new configuration is done to determine the advection conditions for the limit ejecting disc/ standard disc.

Depuis la découverte de la première planète orbitant une étoile de la séquence principale autre que le Soleil en 1995, ce champ de recherche a connu une croissance vertigineuse, tant au niveau des observations, que des modèles théoriques développés en parallèle. Même si la formation et l’évolution des systèmes planétaires restent encore mal comprises dans leur globalité, Il est à peu près certain que les planètes se forment dans des disques protoplanétaires et interagissent avec ces derniers durant la phase primordiale de leur évolution. Cette thèse s’attache à décrire certains aspects de ces interactions. Parmi les problèmes soulevés par les nombreuses observations d’exoplanètes, on peut citer l’existence des Jupiter chaudes, géantes gazeuses dont la révolution autour de leur étoile s’effectue en quelques jours à peine. Il est communément admis qu’elles se sont formées dans les parties externes du disque, pour ensuite migrer vers l’intérieur. Cependant , les processus de migration restent encore débattus. On pourra aussi noter qu’un nombre important de planètes détectées, notamment par la méthode des vitesses radiales, présentent de fortes excentricités. Cette observation contraste avec celle de notre propre Système Solaire, où les planètes géantes ont des orbites quasi-circulaires. Cette distribution d’excentricités témoigne probablement d’une certaine richesse dans les interactions dynamiques entre les planètes d’un même système. Un autre résultat majeur des quelques dernières années est l’observation de planètes à faible période orbitale dont l’orbite n’est pas alignée avec l’axe de rotation de leur étoile. Cette observation pourrait potentiellement remettre en question l’idée selon laquelle ces planètes acquièrent leur faible période par le biais de la migration au sein du disque. Par conséquent, il est important de pouvoir différencier quelles sont les caractéristiques observationelles des exoplanètes qui sont le fruit de leurs interactions mutuelles, et celles qui peuvent être expliquées lors de la phase d’interaction avec le disque protoplanétaire. D’une part, cela permet d’imposer des contraintes sur la physique des disques protoplanétaires. D’autre part, il est intéressant de savoir à quoi ressemble le système de planètes une fois que le disque se dissipe, et à quelles conditions intiales peut-on s’attendre lorsque les planètes commencent à interagir entre elles sans la présence du disque. Par exemple, est-il possible pour une ou des planètes d’acquérir de l’excentricité et de l’inclinaison au sein du disque, et de les maintenir par la suite. De plus, il est certain que le disque domine l’évolution des planètes au stage primordial de leur vie, mais jusqu’à quel point cela limite-t-il les interactions entre les planètes ? / Since the discovery of the first planet orbiting a main-sequence star outside the solar system in 1995, the field of exoplanet studies has grown rapidly, both from the observational and theoretical sides. Despite the fact that we are still lacking a global picture for the formation and evolution of planetary systems, it is now commonly accepted that planets form in protoplanetary discs and interact with them in the early stages of their evolution. This thesis aims at studying some of these interactions. The observations of extrasolar planets have brought several puzzling results to the attention of the community. One of them is the existence of hot Jupiters, giant gaseous planets which orbit their parent star with a period of a few days only. The commonly accepted scenario is that they formed in the outer parts of the disc and migrated inward. Furthermore, a significant number of planets detected so far, especially by the method of radial velocities, have high eccentricities. This is in contrast with our own solar system where giant planets have quasi-circular orbits. Such a distribution of eccentricities may be the signature of strong dynamical interactions between the different components of a same planetary system. Finally, there are short-period planets whose orbits is misaligned with the axis of rotation of their host star, which could possibly argue against the smooth migration of planets in their disc. Therefore, it is important to disentangle between the orbital characteristics that planets acquired through mutual dynamical interactions, and the ones they acquired when they interacted with the disc. Firstly, it gives constraints on the physical parameters of protoplanetary discs. Secondly, it is interesting to know the properties of the system of planets after the disc has dissipated, and what sort of initial conditions one can expect when planets start to interact freely one with each other. For instance, one can ask if it is possible for planets to reach large eccentricities and inclinations when the disc was still present, and whether they could maintain them or not.

Tidal stream energy is a predictable source of renewable energy. Tidal stream turbines have been proposed as a way to extract useful energy from the tide. Many arrays of such devices will need to be installed to extract significant amounts of energy. The presence of an array of turbines within a tidal flow will impact the flowfield, as complex fluid interactions occur across multiple scales. This thesis is concerned with the behaviour of tidal turbines arrayed across channels. Experimental and analytical work is carried out to investigate array behaviour and to create new modelling tools to replicate this behaviour. Linear Momentum Actuator Disc Theory (LMADT) is employed to develop a new analytical model for a long row array of tidal turbines split into multiple smaller, co- linear row arrays. An argument of separation of scales is used to facilitate this model. It is found that increases in power extraction beyond that of a single continuous row array are possible. Experimental work is carried out on a row array of eight porous discs, simulating a short row array of tidal turbines. Disc porosity and spacing are varied to investigate thrust on the array, flow behaviour behind the array and an 'inferred' power removed from the flow. The results are compared to previously developed theoretical models. Good agreement is found with the trends of the analytical model, for example that there is a peak power coefficient which can be reached through appropriate selection of spacing and disc resistance. Differences from theory are found in the total thrust and power measurements, as well as in some aspects of the flow behaviour in the array wake. Reductions in thrust and power towards the ends of the array are also identified as 'end effects' which are not included in the analytical model. Based on these results a new semi-empirical model is proposed, using LMADT with experimental data closure. This model allows variation of the disc resistance across a row array. Values from the experimental work are used as inputs to the model, and the results compared to experimental measurements of flowspeed, thrust and power. Although agreement with experimental results is found in some areas, there are still some discrepancies between the analytical model and the experimental results. This indicates that there are additional factors that contribute to end effects on a short row array.

In this thesis we explored the use of nuclear stellar discs as tracers of the merging history of early-type galaxies. These small structures, just a few tens to a few hundreds of parsecs across, are a common but poorly studied feature of early-type galaxies. They are formed during or shortly after merging events due to the infall of gas, which settles in a disc and leads to the formation of new stars. Initial simulations showed that they should not survive a following major merger and could, therefore, be used to trace the epoch when their host galaxies experienced their last major merger event. We produced the first census of nuclear discs and established that their incidence is 20%, fairly independent of the host-galaxy mass or galactic environment. Furthermore, we have more than doubled the sample of nuclear discs with known photometric properties, finding that they give a hint of possessing different characteristics from those of large, galactic discs. Using these nuclear discs as clocks for the assembly history of galaxies requires dating their stellar populations. By combining the use of integral-field spectroscopy with the a priori knowledge of the relative bulge- and disc-light contribution to the observed spectra, as determined by a photometric disc-bulge decomposition, we have shown that it is possible to reduce the degeneracies that affect the study of two superimposed populations and thus that the age of stellar discs can be measured more precisely. To illustrate our method, we present VLT-VIMOS data for NGC 4458, a low-mass slowly rotating early-type galaxy with a disc that we found to be at least 5-6 Gyr old. The presence of such an old central disc in such a small, slowly-rotating and, mostly likely, round galaxy is particularly puzzling and presents a challenge to existing models. Disc fragility is central to our studies and we have expanded the limited initial simulations to study it in more detail. By means of N-body simulations, we have reproduced the final stages of a galaxy encounter by exposing a nuclear disc rotating in the gravitational potential of its host bulge and central supermassive black hole to the impact of a secondary massive black hole. We explored not only major mergers (1:1 mass ratio), but also large minor mergers (1:5 and 1:10), across a variety of collision angles, and assessed the survival of the disc, as perceived by current observational limits, both for photometry and spectroscopy. As expected, the discs do not survive a major merger whereas it is in general possible to detect their presence after a 1:5 or 1:10 encounter, in particular when looking at kinematic signatures with spectroscopy. This thesis has demonstrated that nuclear discs constitute both a common and accurate tool for constraining the assembling history of nearby early-type galaxies. The advent of more sensitive integral-field spectrographs, such as MUSE, will make measuring the stellar age of nuclear discs not only more precise, but also more economical in terms of telescope time. This will allow embarking on a more systematic age dating campaign for nuclear stellar discs across a wider range of type, mass and galactic environments for their host galaxies. Combining such a census with a larger set of numerical simulations aimed at calibrating better the range of merger event that would erase any photometric or kinematic signature of a nuclear disc, should finally allow us to put firm constraints on the merging history of early-type galaxies.

The reflection of the X-rays emitted from a corona of energetic particles surrounding an accreting black hole from the accretion disc is investigated in the context of probing the structure of the central regions as well as the physical processes that power some of the brightest objects seen in the Universe. A method is devised to measure the emissivity profile of the accretion disc, that is the reflected flux as a function of radius in the disc. This method exploits the variation in the Doppler and gravitational redshift of emission from different radii in the disc to fit the observed reflection spectrum as the sum of contributions from successive radii and is applied to X-ray spectra of the narrow line Seyfert 1 galaxies 1H 0707-495, IRAS 13224-3809 and MCG-6-30-15 as well as the Galactic X-ray binary, Cygnus X-1. This illumination pattern of the accretion disc is a sensitive probe of the geometry of the corona that is illuminating the disc. A formalism is developed in which systematic ray tracing simulations can be run between X-ray emitting coronae and the accretion disc for a range of source geometries and other physical parameters, allowing observable data products to be simulated that can be directly compared to data from astrophysical black holes, in order to determine how these parameters affect the observed data, allowing them to be constrained observationally. The measured emissivity profiles are found to be in agreement with those expected theoretically and it is also discovered that the measured emissivity profile can be used to determine the radial extent of the X-ray emitting corona above the accretion disc. The X-ray emitting coronae are located and their radial extents constrained in 1H 0707-495, IRAS 13224-3809 and MCG-6-30-15, while the insight gained into accretion disc emissivity profiles from ray tracing simulations allows the low flux state that 1H 0707-495 was seen to drop in to in January 2011 to be explained in terms of a collapse of the X-ray emitting corona to a confined region around the central black hole. The rapid variability of the X-ray emission from accreting black holes is exploited in the use of reverberation time lags, where variability in the continuum is seen to lead that in its reflection from the accretion disc, to measure the distances between the X-ray emitting corona and the reflector. Ray tracing calculations are developed to simulate lag spectra that can be measured in X-ray observations to provide a means of constraining the extent and geometry of the corona, complimentary to the use of the emissivity profiles. Combining these methods, the X-ray emitting coronae are constrained to extend radially outward a few tens of gravitational radii over the accretion disc, while extending vertically a few gravitational radii above the plane of the disc. Furthermore, it is demonstrated how measured lag spectra can be used to understand the propagation of luminosity fluctuations through the extent of the corona and techniques are developed for analysing energy-resolved variability analysis that will be possible with future generations of X-ray telescopes. Finally, these methods, along with theoretical insight gained form ray tracing simulations, are applied to X-ray spectra extracted from 1H 0707-495 during periods of low and high flux during the observations. Evidence is found for the expansion of the corona along with a drop in the average energy density as the X-ray luminosity increases followed by its contraction as the luminosity decreases on timescales of hours.

Objective of this thesis is design of brake system of new car Formula Student class – Dragon 3. This car was built by students of faculty of mechanical engineering on Brno university of technology. Brake parts selection is described as well as designing hydraulic brake line circuits optimized for stable braking behavior on tracks of Formula Student competitions. One of main parts of this thesis is design of front and rear custom brake discs with related parts. These parts are FEM analyzed. In the end the whole brake system fitted on Dragon 3 car is tested on track and its performance is analyzed too.

The consequences of two key approximations of accretion-disc physics near black holes are studied in this thesis. First, the question of effective ``pseudo-Newtonian" potentials mimicking a black hole is investigated both through numerical simulations and analytical means, and second, the neglect of additional gravitating matter near accreted-upon black holes and its consequences are put to test. After some broader discussion of integrability, resonance and chaos, a general "pseudo-Newtonian" limit for geodesic motion is derived, and applied for the case of null geodesics near a glowing toroid and for time-like geodesics in the Kerr metric. Afterwards, a new Newtonian gravitational potential for non- singular toroids is proposed and its usefulness for the so-called Weyl space-times is discussed. Finally, a new pseudo-Newtonian potential is introduced and applied alongside already known potentials in models of free test particle motion in the field of a black hole with a disc or ring, in complete analogy with previous exact-relativistic studies, and the previous conclusion of chaos in disc/ring-hole models is confirmed. Overall, the pseudo-Newtonian framework is able to reproduce a number of key features of the original systems with notable differences arising only as a consequence of extremely strong or...