This research presents the first use of side-polished Panda fiber in the fabrication of slab-coupled optical sensors (SCOS). It is determined that the Panda SCOS provides a sensor that is comparable to the D-fiber SCOS in cases of electric field sensing. It exhibits greater power transfer and higher bandwidth than a typical D-SCOS. The Panda SCOS is also less costly and easier to splice than the D-fiber alternative. This comes at a cost of slightly decreased sensitivity and a more fragile fabrication process. This research also demonstrates the use of the Panda-SCOS as means of voltage characterization across both the spark gap of an ignition coil circuit along with the spark gap of an automobile. This paper demonstrates the use of a Panda SCOS to measure the voltages and time delays across the spark gaps at different stages of a Marx generator setup .

Thesis (Ph.D. (Physics)) -- University of Limpopo, 2018 / Beyond conventional intercalation chemistry, reaction of lithium with sulphur and oxygen (so-called “Li-air” batteries) have the potential to provide 2 to 5 times the energy density of current Li-ion battery systems. However, both Li/S and Li/O2 systems suffer from cycling performance issues that impede their commercial applications: Li/O2 cycling is limited by electrolyte decomposition and large cell polarization; Li/S suffers from the low conductivity of S and the solubility of intermediary polysulfide species during cycling. It has been reported that Se and mixed SexSy represent an attractive new class of cathode materials with promising electrochemical performance in reactions with both Li and Na ions. Notably, unlike existing Li/S batteries that only operate at high temperature, these new Se and Li/SexSy electrodes are capable of room temperature cycling. Initially, stabilities of insoluble discharge products of oxygen and sulphur in the Li-S and Li-O2 batteries were investigated using density functional theory within the generalized gradient approximation, and these were deduced from their structural, electronic and mechanical properties. The structural properties are well reproduced and agree to within 3% with the available experimental data. Li2S, Li2O and Li2O2 and Li2S2 structures all have negative heats of formations indicating that they are stable, however, that of Li2S2 structure was relatively high compared to others. Calculated phonon dispersion and elastic properties revealed that Li2O, Li2S and Li2O2 structures are mechanically stable and great agreement with experimental work. The Li2S2 structure displayed soft modes associated mainly with sulphur atoms vibrations in the a-b plane, hence it is not mechanically stable in agreement with the negative C13. Stable Li2S2 polymorphs were extracted from soft modes of calculated phonon dispersions along the gamma direction in the Brillioun zone. Temperature is known to have a significant impact on the performance, safety, and cycle lifetime of lithium-ion batteries (LiB). In order to explore properties of discharge products associated with Li/S and Li/Se batteries at different temperatures, molecular dynamics and cluster expansion methods were employed. The former was achieved by firstly deriving empirical interatomic potentials of Li2S and Li2Se which were fitted to experimental and DFT calculated data. The potentials were validated against available experimental and calculated structure, elastic properties and phonon spectra. In addition, complex high temperature transformations and melting of Li2S and Li2Se were reproduced, as deduced from molecular dynamics simulations. Both Li2S and Li2Se were found to withstand high temperatures, up to 1250K each which is a desirable in future advanced battery technologies. Furthermore, cluster expansion and Monte-Carlo simulations were employed to determine phase changes and high temperature properties of mixed Li2S-Se. The former generated 42 new stable multi-component Li2S-Se structures and ranked metastable structures by enthalpy of formation. Monte Carlo simulations produced thermodynamic properties of Li2S-Se system for the entire range of Se concentrations obtained from cluster expansion and it demonstrated that Li2S-Se is a phase separating system at 0K but changes to mixed system at approximately 350K which was confirmed by constructed by phase diagram of Li2S-Se system. It was finally demonstrated that molecular dynamics and Monte Carlo simulations techniques yield consistent results on phase separation and high temperature behavior of Li2S-Se at 50% of sulphur and selenium.

Modeling the atmospheric entry of spacecraft is challenging because of the large number of physical phenomena that occur during the process. In order to study thermal protection systems, engineers rely on high fidelity solvers to provide accurate predictions of both the thermochemical environment surrounding the heat shield, and its material response. Therefore, it is necessary to guarantee that the numerical models are correctly implemented and thoroughly validated. In recent years, a high-fidelity modeling tool has been developed at the University of Kentucky for the purpose of studying atmospheric entry. The objective of this work is to verify and validate this code. The verification consists of the development of an automated regression testing utility. It is intended to both aid code developers in the debugging process, as well as verify the correct implementation of the numerical models as these are developed. The validation process will be performed through comparison to relevant ablation experiments, namely arc-jet tests. Two modules of the code are used: fluid dynamics, and material response. First the fluid dynamics module is verified against both computational and experimental data on two distinct arc-jet tests. The material response module is then validated against arc-jet test data using PICA.

This thesis centers around an electric arc furnace (EAF) at a steel mini-mill in Wilton, IA. First, the thesis replicates previous optimization attempts. Next, the modeling is greatly altered to produce a much improved steel-melting model. Then, a new optimal control system is created and used to reduce energy and fuel costs over the melting process. Finally, results are presented. This thesis shows that when the new optimal control is simulated, the system shows significant energy and fuel savings.

Abstract not available

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24175号 / 理博第4866号 / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)准教授 成瀬 元, 准教授 河上 哲生, 教授 田上 高広 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Thin film coatings are used to improve the properties of components and products in such diverse areas as tool coatings, wear resistant biological coatings, miniature integrated electronics, micro-mechanical systems and coatings for optical devices. This thesis focuses on understanding the development of intrinsic stress and microstructure in coatings of the technologically important materials of aluminium nitride (AlN) and titanium vanadium nitride (TiVN) deposited by filtered cathodic arc deposition. Thin films of AlN are fabricated under a variety of substrate bias regimes and at different deposition rates. Constant substrate bias was found to have a significant effect on the stress and microstructure of AlN thin films. At low bias voltages, films form with low stress and no preferred orientation. At a bias voltage of -200 V, the films exhibited the highest compressive stress and contained crystals preferentially oriented with their c axis in the plane of the film. At the highest bias of -350 V, the film forms with low stress yet continue to contain crystallites with their c axis constrained to lie in the plane of the film. These microstructure changes with bias are explained in terms of an energy minimisation model. The application of a pulsed high voltage bias to a substrate was found to have a strong effect on the reduction of intrinsic stress within AlN thin films. A model has been formulated that predicts the stress in terms of the applied voltage and pulsing rate, in terms of treated volumes known as thermal spikes. The greater the bias voltage and the higher the pulse rate, the greater the reduction in intrinsic stress. At high pulsing and bias rates, a strong preference for the c axis to align perpendicular to the substrate is seen. This observation is explained by dynamical effects of the incident ions on the growing film, encouraging channelling and preferential sputtering. For the first time, the effect of the rate of growth on AlN films deposited with high voltage pulsed bias was investigated and found to significantly change the stress and microstructure. The formation of films with highly tensile stress, highly compressive stress and nano-composites of AlN films containing Al clusters were seen. These observations are explained in terms of four distinct growth regions. At low rates, surface diffusion and shadowing causes highly porous structures with tensile stress; increased rates produced Al rich films of low stress; increasing the growth rate further led to a dense AlN film under compressive stress and the highest rates produce dense, low stress, AlN due to increased levels of thermal annealing. Finally this thesis analyses the feasibility of forming ternary alloys of high quality TiVN thin films using a dual cathode filtered cathodic arc. The synthesised films show exceptional hardness (greater than either titanium nitride or vanadium nitride), excellent mixing of the three elements and interesting optical properties. An optimum concentration of 23% V content was found to give the highest stress and hardness.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

La convergence des thèmes de recherche abordés au Laboratoire d'Analyse Spectroscopique et d'Energétique des Plasmas (LASEP) de Bourges et dans l'équipe PHOTONIC de l'Université Jagellonne de Cracovie (Pologne) a favorisé le rapprochement de nos activités sur l'étude et le diagnostic des plasmas d'arcs. Les activités présentées dans le cadre de cette habilitation à diriger des recherches, sont orientées vers l'études des interactions arc-électrode, avec une ouverture vers les décharges à pression atmosphérique. Elles couvrent • Les sources de plasma de type arc électrique, avec l'étude de la zone cathodique d'un plasma d'arc éclatant dans l'argon à pression atmosphérique, des phénomènes liés aux effets anodiques (et cathodiques) en soudage MIG-MAG et des processus mis en jeu dans les plasmas d'électro-érosion ; • L'étude de décharges froides hors d'équilibre à pression atmophérique, qu'elles soient - glissantes, avec leurs éventuelles applications à la destruction des composés organiques volatils ou à la génération de radicaux hydrogène; - fixes entre deux pointes, pour l'étude des ondes d'ionisation. • La mise en oeuvre et l'élaboration de nouvelles méthodes de diagnostic de ces sources, par spectroscopies atomique et moléculaire, en émission ou laser, et leur application à la métrologie fine. Elles se situent à l'interface de la recherche fondamentale (développement de méthode de diagnostic laser de milieux plasmagènes et application à la détermination des constantes spectroscopiques fondamentales nécessaires à l'étude des milieux plasmagènes complexes) et de la recherche appliquée (contrôle en ligne des milieux hors d'équilibre utilisés en dépollution, et des plasmas thermiques pour la soudure ou la découpe). Les différents thèmes de recherche développés à ce jour ont été réalisés au GREMI, puis au LASEP (Université d'Orléans), en collaboration avec l'équipe de Cracovie. La spectroscopie constitue certainement le trait d'union principal de ces travaux, tant il est vrai que le diagnostic spectroscopique se révèle essentiel pour l'étude des différents milieux plasmagènes développés au laboratoire.

Les ontologies sont diversement employées notamment dans les domaines du Web sémantique, de l'ingénierie des connaissances,... En effet, elles permettent de partager, de diffuser et d'actualiser les connaissances d'un domaine. Afin de construire ces ontologies, notre méthodologie utilise tout d'abord des méthodes de Traitement Automatique de la Langue Naturelle (TALN) et d'Extraction d'Information (EI) pour extraire des données préparées à partir de chaque ressource du domaine (corpus de textes, bases de données, thesaurus). Puis, ces données sont fouillées avec les méthodes de fouilles : l'Analyse Formelle de concepts (AFC) et l'Analyse Relationnelle de Concepts (ARC). L'AFC regroupe des objets partageant les mêmes attributs dans des concepts d'un treillis. L'ARC, une extension de l'AFC, permet de regrouper des objets partageant les mêmes attributs, mais aussi les mêmes attributs relationnels. L'apposition de contextes (une propriété de l'AFC) permet d'associer ces attributs et relations à un ensemble de classes prédéfinies et hiérarchisées par les experts du domaine. De cette façon, des définitions étendues sont proposées aux experts du domaine pour ces classes prédéfinies ainsi que de nouvelles classes inexistantes dans la hiérarchie initiale. Ces nouvelles classes peuvent être considérées pertinentes et ajoutées par les experts en tant que nouvelles "unités de connaissances". Les treillis résultant des méthodes de fouille constituent ce que nous appelons schéma d'ontologie. Ce schéma d'ontologie est ensuite représenté par le langage FLE de la famille des logiques de descriptions afin d'avoir une ontologie. Cette ontologie, implémentée en OWL, a permis à notre système de répondre automatiquement à différentes questions proposées par les experts du domaine.<br>Des expériences pratiques ont été menées dans deux domaines d'application : l'astronomie et la microbiologie.