Les plasmas induits par laser (PIL) ont depuis leurs apparitions dans les années soixante suscité un très grand intérêt notamment comme source de données spectroscopiques. Ils ont également acquis des nombreuses applications, comme sources des rayons X pour la lithographie, l’allumage plasma, la déposition par laser pulsé, ou sont devenues la base d’une technique d’analyse très populaire – la LIBS (laser induced breakdown spectroscopy). Cette dernière peut s’appliquer in situe à tout type d’échantillon et sans préparation. Toutefois, les mesures faites par cette méthode sont latéralement intégrées nécessitant des techniques d’inversion, mais dépendent également des conditions d’équilibre thermodynamiques local (ETL) dans le plasma. Afin de valider les mesures effectuées par LIBS, la diffusion Thomson qui est une méthode spatialement résolue et indépendante des hypothèses d’équilibre thermodynamique a été appliquée pour caractériser les PIL. Des plasmas d’ablation et de claquage ont donc été caractérisés à la fois par spectroscopie d’émission et par diffusion Thomson. La comparaison des paramètres température et densité électronique obtenues par les deux méthodes d’une part, et le critère de McWhirter ainsi que les temps de relaxation et les longueurs de diffusions des espèces contenues dans le plasma d’autre part, ont permis de statuer sur l’ETL. / Laser induced plasma (LIP) which was first reported in the beginning of sixties, has achieved a great interest as a source of spectroscopic data. It has also many applications like X-ray sources for lithography, plasma igniters, pulsed laser deposition or it has become a basis of a very popular analytical technique – LIBS (laser induced breakdown spectroscopy). The latter is mainly due to its applicability to different kinds of samples, no sample preparation or in-situ and remote sensing capability. However, LIBS measurements are laterally integrated and Abel inversion must be performed. Also the method assumes the plasma to be in local thermodynamic equilibrium (LTE). In order to validate LIBS measurements, Thomson scattering (TS) method which is spatially resolved and free from equilibrium assumption was applied. Thus, ablation and breakdown plasmas were characterized by both two methods. Comparison between plasma parameters (temperature and electron density) obtained by the two methods and McWhirter criterion as well as relaxation times and diffusion lengths of species in the plasma allowed to estimate LTE.

This thesis portrays new information concerning the cloud-to-ground (CG) lightning flashes or ground flashes produced by thunderclouds. It emphasizes the importance of characterizing lightning studies as the relationship between lightning mechanisms, and of incorporating the influence of geographical location, latitude and storm type. Sweden, Malaysia and USA were chosen as the main locations for field experiments in 2009 to 2011 to gather a significant number of negative and positive CG flashes. This work provided data on a total of 1792 CG lightning flashes (1685 negative and 107 positive ones) from a total of 53 thunderstorms by monitoring both the slow and the fast electric field and the narrowband radiation field at 3 and 30 MHz signals simultaneously. This thesis is comprised of: (i) the relationship of the Low Positive Charge Region (LPCR) and Preliminary Breakdown Pulse (PBP) trains to the occurrence of negative CG, (ii) slow field changes generated by preliminary breakdown processes in positive and negative ground flashes, and (iii) the occurrence of positive and negative ground flashes. It was revealed that the PBP train appeared have a higher strength in the in Sweden. The strength of the PBP train was caused by the LPCR; in contrast,  weak PBP trains were characteristic in tropical countries constituting insignificant LPCR and needing little energy to break the “blocking” agent to allow the flash to propagate downward to the ground. The second contribution concerns the characteristics of the PBP train mentioned; this includes novel information for Malaysia. Further, it is stated that there are some different characteristics in the PBP trains in Johor, Malaysia and Florida, USA. The studies of slow field changes generated by preliminary breakdown processes clarifies unclear features concerning the starting position of slow field changes generated by preliminary breakdown processes in positive and negative ground flashes. It was found that the slow field changes did not occur before the initial process of the commencement of preliminary breakdown. Single-station electric field measurements incorporating narrowband radiation field measurement and high resolution transient recording (12 bits) with an accuracy of several nanoseconds, allows one to distinguish between the intracloud activities and the preceding processes of ground flashes. The results for the interstroke intervals, amplitude distribution of subsequent return-stroke (SRS) and the number of strokes per flash in the tropics, subtropics and northern regions were similar. Finally, a significant number of positive return-stroke (RS) electric fields provided statistically significant information on the characteristics of these strokes.

No description available.

No description available.

La planification automatique est un domaine de recherche de l’Intelligence Artificielle qui vise à calculer automatiquement une séquence d’actions menant d’un état initial donné à un but souhaité. Cependant, résoudre des problèmes réalistes est généralement difficile car trouver un chemin solution peut demander d’explorer un nombre d’états croissant exponentiellement avec le nombre de variables. Pour faire face à cette explosion combinatoire, les algorithmes performants ont recours aux heuristiques ou à des solutions hiérarchiques, décomposant le problème en sous-problèmes plus petits et plus simples. Dans une grande majorité des cas, le planificateur doit prendre en compte un certain nombre de contraintes telles que des phases d’actions prédéfinies ou des protocoles. Ces contraintes aident à résoudre le problème en élaguant un grand nombre de branches de l’arbre de recherche. Nous proposons alors une nouvelle méthode pour modéliser et résoudre des problèmes de planification déterministe en se basant sur une approche hiérarchique et heuristique. Nous nous sommes inspirés des formalismes de programmation structurée afin de fournir à l’utilisateur un cadre de travail plus intuitif pour la modélisation des domaines de planification hiérarchique. D’autre part, nous avons proposé un algorithme de planification capable d’exploiter ce formalisme et composer des stratégies à différents niveaux de granularité, ce qui lui permet de planifier rapidement une stratégie globale, tout en étant en mesure de pallier aux difficultés rencontrées à plus bas niveau. Cet algorithme a fait ses preuves face au principal planificateur HTN, SHOP2, sur des problèmes de planification classique. / Automated planning is a field of Artificial Intelligence which aims at automatically computing a sequence of actions that lead to some goals from a given initial state. However, solving realistic problems is challenging because finding a solution path may require to explore an exponential number of states with regard to the number of state variables. To cope with this combinatorial explosion, efficient algorithms use heuristics, which guide the search towards optimistic or approximate solutions. Remarkably, hierarchical methods iteratively decompose the planning problem into smaller and much simpler ones. In a vast majority of problems, the planner must deal with constraints, such as multiple predefined phases or protocols. Such constraints generally help solving the planning problem, because they prune lots of search paths where these constraints do not hold. In this thesis, we assume that these constraints are known and given to the planner. We thus propose a new method to model and solve a deterministic planning problem, based on a hierarchical and heuristic approach and taking advantage of these constraints. We inspired ourselves from structured programming formalisms in order to offer a more intuitive modeling framework in the domain of hierarchical planning to the user. We also proposed a planning algorithm able to exploit this formalism and build strategies at various levels of granularity, thus allowing to plan quickly a global strategy, while still being able to overcome the difficulties at lower level. This algorithm showed its performances compared with the main HTN planner, SHOP2, on classical planning problems.

L'étude de la fiabilité représente un enjeu majeur de la qualification des technologies de l'industrie de la microélectronique. Elle est traditionnellement étudiée en suivant la dégradation des paramètres des transistors au cours du temps, qui sert ensuite à construire des modèles physiques expliquant le vieillissement des transistors. Nous avons fait le choix dans ces travaux d'étudier la fiabilité des transistors à l'échelle microscopique, en nous intéressant aux mécanismes de ruptures de liaisons atomiques à l'origine de la création des défauts de l'oxyde de grille. Nous avons tout d'abord identifié la nature des défauts et modéliser leurs dynamiques de capture de charges afin de pouvoir reproduire leur impact sur des mesures électriques complexes. Cela nous a permis de développer une nouvelle méthodologie de localisation des défauts, le long de l'interface Si-SiO2, ainsi que dans le volume de l'oxyde. La mesure des dynamiques de créations de défauts pour des stress de type porteurs chauds et menant au claquage de l'oxyde de grille nous a permis de développer des modèles de dégradation de l'oxyde, prédisant les profils de défauts créés à l'interface et dans le volume de l'oxyde. Nous avons enfin établi un lien précis entre l'impact de la dégradation d'un transistor sur la perte de fonctionnalité d'un circuit représentatif du fonctionnement d'un produit digital.L'étude et la modélisation de la fiabilité à l'échelle microscopique permet d'avoir des modèles plus physiques, offrant ainsi une plus grande confiance dans les extrapolations de durées de vie des transistors et des produits. / Reliability study is a milestone of microelectronic industry technology qualification. It is usually studied by following the degradation of transistors parameters with time, used to build physical models explaining transistors aging. We decided in this work to study transistors reliability at a microscopic scale, by focusing on atomic-bond-breaking mechanisms, responsible of defects creation into the gate-oxide. First, we identified defects nature and modeled their charge capture dynamics in order to reproduce their impact on complex electrical measurements degradation. This has allowed us developing a new methodology of defects localization, along the Si/SiO2 interface, and in the volume of the gate-oxide. Defects creation dynamics measurement, for Hot Carrier stress and stress conditions leading to the gate-oxide breakdown, has allowed us developing gate-oxide degradation models, predicting generated defect profiles at the interface and into the volume of the gate-oxide. Finally, we established an accurate link between a transistor degradation impact on circuit functionality loss.Reliability study and modeling at a microscopic scale allows having more physical models, granting a better confidence in transistors and products lifetime extrapolation.

A thesis submitted in ful lment of the requirements for the degree Doctor of Philosophy in Electrical Engineering May 2016 / Modern electrical networks provide an opportunity for inevitable interaction between metal oxide arresters and power system harmonics. Therefore, these arrester devices are continuously exposed to the combined e ect of distorted system voltage and envi- ronmental thermal stresses. Recent studies supported by eld experiments have shown signi cant rise in the leakage current through these surge arrester devices when exposed to ac voltage with harmonics. However, the major shortcoming in the current knowledge and applications of varistor arresters resides on the reliability and the electrical stabil- ity of these overvoltage protection units, when subjected to long-term and continuous distorted ac voltage and thermal stresses from the environment. Commercially-sourced ZnO arresters of similar size and electrical properties are tested using standard ac accelerated degradation procedure or electro-thermal ageing test. The times to degradation, the coe cient of non-linearity, the reference voltages, as well as the clamping voltage measured are used to analyse the reliability and the electrical stability of the metal oxide-based arrester samples. The resistive component of the leakage current is extracted from the measured total leakage current. The three-parameter Weibull probability model is invoked in order to analyze the degradation phenomenon. / MT2016

Os métodos de primeiros princípios dentro da Teoria do Funcional Densidade têm se desenvolvido bastante, devido aos avanços computacionais ocorridos nas últimas décadas. Por outro lado, a Termodinâmica e a Mecânica Estatística têm representado um papel importante na compreenssão da Física de Materiais, em especial no estudo dos materiais intermetálicos ordenados. A aliança entre estas duas abordagens têm se tornado cada vez mais factível, uma vez que os cálculos de estrutura eletrônica de primeiros princípios são hoje capazes de proporcionar resultados extremamente precisos para energias de formação de compostos estequiométricos. É dentro deste contexto que neste trabalho investigamos o diagrama de fases composição-temperatura do sistema Fe-Al-Mo, na estrutura cúbica de corpo centrado utilizando o método Full-Potential Linear Augmented Plane Wave (FP-LAPW) aliado ao Método Variacional de Clusters (CVM) na aproximação do tetraedro irregular. Através do método FP-LAPW determinamos a energia total de configurações cristalinas do sistema Fe-Mo-Al cúbico de corpo centrado. Estes valores são utilizados como parâmetros de entrada do CVM para determinação do potencial termodinâmico do sistema em suas diferentes fases e os correspondentes equilíbrio entre estas fases em função da composição e da temperatura, ou seja, o diagrama de fases do sistema. Embora o Fe-Al tenha grande interesse tecnológico, o seu comportamento magnético é bastante complicado e normalmente mal descrito pelos métodos de cálculos usuais. Este trabalho procura enfrentar este problema com ferramentas \"estados de arte\" e apontam para as limitações inerentes ao procedimento geral aqui utilizado. / First-principles methods within the framework of Density Functional Theory, have been developed sufficiently, due to the computational advances occurrences in the last decades. On the other hand, the Thermodynamics and the Statistical Mechanics have represented an important role in the understanding of the Physics of Materials, in special in the study to ordered intermetallic compounds. The alliance between these two approaches has become each more feasible with the time due to the fact that electronic structure calculations of first principles are today to provide almost exact results for the formations energies of stoichiometric compounds. It is inside of this context that in this work we investigate the composition-temperature phases diagram of the Fe-Al-Mo system, in the body centered cubic structure (BCC), using the Full-Potential Liner Augmented Plane Wave (FP-LAPW) method allied to the Cluster Variation Method (CVM) in the irregular tetrahedron approximation. Through the FP-LAPW method we determined the total energy of crystalline configurations of BCC Fe-Mo-Al system. These values are used as input parameters of the CVM for the determination of the thermodynamic potential of the system in its different phases and corresponding to the equilibria between these phases as a function of the composition and the temperature, that is the phase diagram of the system. Although the Fe-Al has great technological interest, its magnetic behavior is complicated and badly described by the methods used in the actual ab-initio calculations. This work faces this problem with state-of-art tools and points to the inherent limitations of the general procedure used here.

Nos últimos anos, a Espectrometria de Emissão Atômica com Plasma induzido por Laser (LIBS) vem despertando grande interesse e pesquisas voltadas às aplicações analíticas dessa técnica tem aumentado significativamente. No entanto, sua aplicação na análise de amostras líquidas não é trivial, podendo haver comprometimento na sensibilidade e na precisão do método. Além disso, a análise quantitativa é considerada o \"calcanhar de Aquiles\" da técnica, especialmente devido à falta de materiais de referência certificados e à forte interferência de matriz. Nesse contexto, com a intenção de viabilizar a análise de matrizes líquidas por LIBS, esse trabalho propõe o uso de cerâmica como fase sólida para extração, pré-concentração e especiação de Cr em amostras de água. Foi realizado também um estudo de otimização dos parâmetros instrumentais do LIBS para o desenvolvimento de um método de medição de Cr na fase sólida, empregando cerâmica enriquecida com concentrações crescentes desse analito como material calibrante sintético. Os resultados obtidos mostraram que a cerâmica adsorve seletivamente a espécie Cr(III) em pH 7, sendo este um processo rápido, de baixo custo, cuja eficiência é pouco afetada pela presença de outros eletrólitos. Os estudos relacionados à otimização dos parâmetros instrumentais do LIBS indicaram que um diâmetro de focalização de 65 µm, um tempo de atraso de 0,75 µs, a energia por pulso de 20 mJ, uma taxa de repetição de 10 Hz e um número de pulsos igual a 403 podem ser recomendados para a quantificação de Cr no material cerâmico. Nessas condições, obteve-se uma curva de calibração analítica que possibilitou a medição Cr adsorvido em cerâmica. Uma amostra de água de torneira foi então enriquecida com 0,9 mg L-1 de Cr(III) e 0,9 mg L-1 de Cr(VI) para que um teste de recuperação fosse realizado com a finalidade de se verificar a aplicabilidade do método proposto, foi possível constatar a adsorção seletiva da espécie Cr(III), com recuperação de 105±2%. A quantificação da espécie Cr(VI) por LIBS também é possível após a redução dessa espécie a Cr(III) utilizando Fe(II) como agente redutor. Os limites de detecção (LOD) e quantificação (LOQ) estimados para o método foram respectivamente 21 mg kg-1 e 70 mg kg-1, equivalentes a 0,1 mg L-1 e 0,35 mg L-1, considerando-se o coeficiente de pré-concentração igual a 200 (m/m). / In recent years, Laser Induced Breakdown Spectroscopy (LIBS) has deserved attention of scientific community and researches using this technique have increased significantly. However, its application in the analysis of liquid samples is not trivial, because the sensitivity and accuracy of the method can be affected. In addition the quantitative analysis is considered the \"Achilles\' heel\" of the technique, especially due to the lack of certified reference materials and to the strong interference matrix. To enable the analysis of liquid matrices by LIBS, this work proposes the use of ceramic as solid phase in the extraction, preconcentration and speciation of Cr in water samples. LIBS instrumental parameters were also optimized to allow the measurement of Cr in this solid phase, for the development of a method for measuring the analyte in the solid phase, which was also used as synthetic calibrating material by the addition of increasing concentrations of the analyte. Results showed the ceramic selectively adsorbs Cr(III) species at pH 7, which is a low cost and rapid process, whose efficiency is not significantly affected by the presence of other electrolytes. Studies related to the optimization of LIBS instrumental parameters indicated that spot size of 65 µm, delay time of 0,75 µs , energy per pulse of 20 mJ, repetition rate of 10 Hz and a number of pulses equal to 403 can be recommended for the quantification of Cr the ceramic material. Under these conditions, it was obtained an analytical calibration curve which allowed a Cr measurement in ceramics. A tap water sample was enriched with 0.9 mg L-1 of Cr(III) and 0.9 mg L-1 of Cr (VI) and a recovery test was done in order to verify the applicability of the proposed method. It was observed the selective adsorption of the Cr(III) species, with recovery of 105 ± 2 %. The quantification of Cr(VI) species by LIBS was also possible, after reduction of this species to Cr(III) using Fe(II) as reducing agent. The limit of detection (LOD) and the limit of quantification (LOQ) obtained by the proposed method were respectively, 21 mg kg-1 and 70 mg kg-1, equivalent to 0.1 mg L-1 and 0.35 mg L-1, considering the preconcentration coefficient of 200 (on a w/w basis).

Trots att det finns många tekniska hjälpmedel ombord, vilka har i uppgift att hjälpa navigatören att framföra fartyget på ett säkert sätt, så fortsätter grundstötningar att inträffa. Denna litteraturstudie sammanställer och granskar grundstötningsolyckor som inträffat på svenska fartyg och på utländska fartyg som befunnit sig på svenskt territorialvatten under åren 2011-2016. Studien behandlar frågeställningar om vilka huvudsakliga faktorer som ligger till grund för att grundstötningar inträffar. Studien omfattar såväl inre som yttre faktorer. De inre faktorerna som behandlas är styrmetod, bryggbemanning och vilken typ av sjökort som använts. Våghöjd, vindstyrka, typ av farvatten, sikt- och ljusförhållande ingår i de yttre faktorerna. Både de inre- och yttre faktorerna sammanställs och presenteras för att kunna ge en bild av vad som kan ha föranlett grundstötningarna. Studiens resultatet visar att passagerar- och bulkfartyg av det mindre tonnaget står för majoriteten av olyckorna. I likhet med tidigare studier är antalet olyckor som beror på den mänskliga faktorn hög. / Even though there are plenty of technological aids onboard modern-day merchant vessels, intended to help the Officer on watch to drive his vessel safely, groundings continue to happen. This literature study summarises and reviews data from several groundings that involved Swedish-registered ships and ships within Swedish territory during the period 2011-2016. This study covers questions about the main factors that have caused the groundings. It covers both internal and external factors. Method of steering, bridge manning and type of chart belong to the internal factors. Factors such as wave height, wind force, type of waters, visibility and light conditons are part of the external factors. This data is then discussed and analysed to give a picture of what may have caused the groundings. The results show that the smaller tonnage passenger and bulk carriers account for the majority of the accidents. Like previous studies the number of accidents due to human factors are high.