Depuis une vingtaine d'années, le GRAMS et le CIMS travaillent en collaboration dans le domaine de l'imagerie médicale, plus précisément sur la tomographie d'émission par positrons destinée à la recherche préclinique sur petits animaux. Après le scanner TEP Sherbrooke en 1994 et le LabPET I commercialisé par Advanced Molecular Imaging (AMI) Inc., Gamma Medica Ideas et GE Healthcare au cours des années 2000, l'aspiration vers de meilleures performances est le moteur de la réalisation d'une nouvelle version : le LabPET II. L'augmentation importante du nombre de détecteurs, nécessaire pour atteindre une meilleure résolution spatiale, amène de nouveaux défis autant sur le plan matériel que logiciel. Un des défis est de compenser les disparités en gain des détecteurs à base de photodiodes à avalanche (PDA) qui engendrent des différences intercanaux. Le but de ce projet de maîtrise est de développer et d'implémenter un algorithme capable de corriger ces différences de façon automatisée.

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L'objectif de ce travail est de comprendre l'influence des particules très fines sur le phénomène de ré-agglomération lors du broyage. Des billes de verre de taille 0 à 20 µm avec un pourcentage massique variant entre 0 à 1% sont ajoutées dans un tas granulaire de billes de verre de 200 à 300 µm dans un tambour tournant cylindrique de diamètre et longueur 10 cm. La présence des particules fines montre un effet ambivalent sur la stabilité du tas granulaire. Nous avons établi un diagramme de stabilité du milieu granulaire en fonction de la concentration de particules fines et cherché à quantifier l'effet des fines combiné avec d'autres paramètres (humidité relative et vitesse de rotation du tambour). La stabilité d'un tas granulaire dans un tambour tournant est déterminée par la mesure de son angle maximum de stabilité θm. Dans un premier temps, nous avons étudié l'évolution de cet angle à des vitesses de rotation différentes. Les expériences montrent qu'à faible concentration (< 0; 15%), le tas se déstabilise par avalanches lorsque le tambour tourne, θm diminue lorsqu'on augmente la quantité de fines. Quand la vitesse de rotation augmente, le mouvement du tas évolue du régime d'avalanche intermittent au régime d'écoulement continu. En revanche, lorsque la concentration des fines est supérieure à 0,15%, la déstabilisation du tas se traduit par un phénomène de stick-slip à la paroi du tambour, et la quantité de fines augmente la stabilité du tas. Ce comportement apparemment contradictoire est lié au fait que la localisation de la déstabilisation est modifiée. Dans le régime des faibles concentrations, les avalanches commencent à la surface du tas, et le remplissage de l'espace intermédiaire entre les grosses billes par les fines rend la surface de plus en plus lisse, ce qui déstabilise le tas. Par ailleurs, les fines induisent une augmentation de la cohésion du tas par la nucléation des ponts capillaires entre les grains. Ainsi, dans le régime des fortes concentrations, le tas granulaire se comporte comme un corps solide et la déstabilisation a lieu à l'interface tas-tambour. Nous avons également étudié l'influence de l'humidité relative sur la stabilité et montré que dans le régime de faible concentration de particules fines, la déstabilisation est indépendante de l'humidité. D'autre part dans le régime des hautes teneurs en fines, une humidité relative élevée induit une forte cohésion due à la condensation capillaire entre les grains et le tambour ce qui entraîne une augmentation de l'angle maximum de stabilité. / The aim of this work is to understand the effect of very fine particles on the phenomenon of re-agglomeration in the grinding process. Various amount of fine glass beads of 0 to 20 µm (0 to 1% mass concentration) are added to a granular pile of glass beads of 200 to 300 µm rotated in a drum with inner diameter and length of 10 cm. The presence of fine particles shows an ambivalent effect on the stability of the granular heap. We established a stability diagram of the granular medium as a function of fine concentration and quantified the effect of fines combined with other parameters (relative humidity and rotation velocity). The stability of a granular heap in a rotating drum is determined by the measurement of the maximum angle of stability θm. Firstly, we studied the evolution of this angle with different rotation velocities. The experiments indicate that at low fine concentration (< 0:15%), the heap destabilizes through avalanches when the drum rotates, and increasing the fine quantity tends to decrease θm. When the rotation velocity increases, the granular medium transits from intermittent avalanche to continuous flow. In contrast, once the concentration is more than 0:15%, the destabilization of the heap proceeds through a stick-slip phenomenon at the drum wall, and the increase of the fraction of fines tends to increase the stability of the heap. This apparent contradictory behavior is linked to the modification of the destabilization location. In the small concentration regime, the avalanches start at the surface of the heap, and the filling of the interstitial space by the fine particles makes this surface smoother and smoother, thus destabilizing the heap. Besides, the fines induce, through the nucleation of capillary bridges between grains, an increase of the bulk cohesion of the heap. So in the large concentration regime, the heap behaves as a solid body and the destabilization occurs at its bottom. We also studied the influence of relative humidity on the granular stability in our experiment. We found out in the low fine concentration regime, the destabilization is independent of humidity. On the other hand, in the regime of high content of fines, high relative humidity induces a large cohesion due to the capillary condensation between the grains and the wall which induce the increase of the maximum stability angle.

Par la mise en œuvre de simulations numériques d'un modèle bidimensionnel de verre de Lennard-Jones, nous étudions l'effet de la température sur les mécanismes élémentaires de la déformation dans les matériaux amorphes. Nous présentons un ensemble très complet de données couvrant plusieurs décades de taux de cisaillement à différentes températures en dessous et jusqu'à la transition vitreuse. Les mesures, qui portent sur la diffusion transverse, la contrainte macroscopique ainsi que sur des champs mésoscopiques (déformation, contrainte) et leurs corrélations spatiales, conduisent à proposer que la dynamique des avalanches identifiée précédemment dans les simulations athermiques continue d'être à l'œuvre - en restant presque inchangée - jusqu'à la transition vitreuse. Nous arguons que dans la gamme de paramètres utilisée l'effet des fluctuations thermiques revient à déplacer les seuils auxquels les événements dissipatifs se produisent, ce qui se traduit par une forte baisse du niveau de contrainte macroscopique aux températures les plus basses / Using numerical simulations of a model two-dimensional Lennard-Jones glass, we study the effect of small temperatures on the elementary mechanisms of deformation in amorphous materials. A very extensive data set covering several decades of shear rate at various temperatures below and up to the glass transition was compiled. Measurements, which include transverse diffusion, macroscopic stress, and coarse-grained fields (strain, stress) and their spatial correlations, lead us to propose that the avalanche dynamics previously identified in athermal simulations continues to be at work -- and nearly unchanged -- up to the glass transition. It is then argued that in this range, thermal fluctuation essentially shift the strains at which dissipative events take place, which results in a sharp drop of the macroscopic stress level at the lowest temperatures

The microplasma discharges in the PN junction local defect micro-regions are as a rule, accompanied by the emission of light. This radiation from solar cell PN junctions was measured by means of a optical fibre connected to the optical input of a photomultiplier. By inching the fibre by means of computercontrolled X-Y plotter above the cell surface a 2-D image of the irradiation local regions has been created. It is seen that a cell of a superficial area of 100 square cm contains a large number of defects, which depends on applied reverse voltage. This method can be a convenient tool for study and diagnostics of optoelectronic devices.

This diploma thesis is focused on several ways of communication among people involved in alavanche accident. Different ways of communication are compared. Diploma is focused on verification of features and parameters of avalanche transceivers. Basic introduction in the field of usage of these devices is included. Practical measurement in high-altitude winter mountain terrain and measurement in laboratory verify parameters provided by producers of avalanche transceivers. Different models of avalanche transceivers will be compared. Behaviour of devices will be modeled on computer. Based on simulation results and other findings wiring of receiving and transmitting par of avalanche transceiver will be designed.

Diese Arbeit beschäftigt sich mit zwei miteinander verbundenen Themen: einer einzigartigen Laser-Testanlage für die Erforschung von gasgefüllten Detektoren sowie der Untersuchungen von Widerstandsplatten-Zählern (RPC) und der Messung von Gasparametern unter realistischen Bedingungen der Timing-RPC. Eine gepulste UV-Laser-Testanlage wurde im HZDR aufgebaut. Der Fokus des Pikosekunden-Lasers wird in einem mit Zählergas gefüllten Detektor an einer bestimmten Stelle platziert, um ein Laser-Plasma zu erzeugen, wobei eine definierte Anzahl freier Elektronen durch Gas-Ionisation in einem Gas-Volumen mit einer Genauigkeit im Mikrometerbereich erzeugt wird. Es ist eine von Beschleunigern unabhängige Methode, um Untersuchungen an gasgefüllten Detektoren im Labor durchzuführen. Proben von RPC-Detektoren wurden für Experimente mit der Laser-Testanlage entworfen und gefertigt. Es wurden Verfahren entwickelt, um die Wellenformen von Elektronenlawinen für verschiedene Elektronen-Driftlängen zu erfassen und die wichtigsten Gasparameter zu bestimmen: den effektiven Townsend-Koeffizienten und die Elektronendriftgeschwindigkeit. Erstmalig wurden die Gasparameter direkt für die hohe Feldstärke des Timings-RPC bei Atmosphärendruck unter Experimentbedingungen gemessen. Es wurde gezeigt, dass sich die Laser-Testanlage für präzise Messungen der Gasparameter eignet und das Potenzial besitzt, um zur Öko-Gas-Forschung für zukünftige RPCs beizutragen. Der Messbereich des elektrischen Feldes der Gasparameter bei Atmosphärendruck wurde verdoppelt, vom Bereich des Trigger-RPC bis zu dem des Timing-RPC. Die Experimente haben einige grundlegende Mechanismen offenbart, die das Verständnis für die Eigenschaften von RPC und den Prozess der Elektronenlawine erweitern werden.:1 Introduction 2 Background 3 The Resistive Plate Chambers 4 The laser test facility 5 Experimental study on laser ionization 6 Experimental study on gas parameters with RPC 7 Analysis study of timing RPC waveforms 8 Conclusions and discussions 106

In computer graphics, when simulating fractured or cracked objects, most commonly physically based methods or hybrid solutions using physical and procedural methods are used to achieve the result. If only a static representation of a cracked surface, and not a simulation of an object cracking, is desired, these approaches of crack generation are not suitable. Non-physically based methods to generate the cracks or fractured objects has also been used where a fracture pattern is projected onto an object. In this thesis a novel method of generating 3D avalanche slabs directly from a 2D Voronoi pattern, in real-time, without using physically based methods or 3D procedural crack generation is presented. After the slabs are generated, they are placed on the surface of a terrain. To add a more realistic look, snow is added on the mountain around the avalanche slabs. Using this novel method of generating 3D avalanche slabs, separate 3D mesh objects are created directly from the Voronoi pattern, and no 3D model is needed initially to generate them from. The results show that this method can be used in real-time with limitations. With improvements suggested in this thesis, the presented method could be used to generate a large amount of slabs in a fairly large region, and software developers can benefit from using this method in their graphics renderer.

Over 90% of traffic accidents are caused by human error. Therefore, the realization of autonomous driving could save countless lives and drastically reduce the associated financial expenses. Moreover, the collective behavior of self-driving cars would avoid traffic jams and thus reduce fuel consumption and greenhouse gas emissions. The majority of concepts is based on Light Detection And Ranging (LiDAR), which is the most precise method to measure distances. Matched to the 95% of commercial LiDAR systems based on laser wavelengths of mostly 905nm, siliconbased photo sensors are used. Avalanche photo diodes (APD) are the only sensor solution in mass production [6]. Due to an internal multiplication mechanism based on impact ionization, high signal-noise-ratios (SNR) are achieved and provide the required resolution of low signals from more than 100m distant targets. Currently none of the LiDAR technologies meet the reliability requirements of the automotive industry concerning the aging of installed components. Consequently, autonomous driving cannot yet be realized for public use. Very little is known about the aging of APDs in general and nothing at all in the field of automotive LiDAR. In order to provide novel insights into APD aging that help designers to achieve more robust sensors and thus to enable a step closer to the realization of autonomous driving, it was the aim of this thesis prepared in the industrial environment to reveal the underlying physical aging mechanisms and their effects on the function of APDs in automotive LiDAR application. At first, a novel APD degradation model was developed encompassing a wide range of processes, treating numerous fundamental aspects of negative oxide charge generation and Si:SiO2 interface trap generation. So far, no model is known covering the kinetics of APD degradation comprehensively in such deep detail. Due to the feedback between degradation phenomena and sensor internal fields and currents, a coupled problem arose. It was tackled by a sophisticated numerical iteration approach which was tailor-made and solved this problem self-consistently in a tandem procedure combining the simulation of sensor degradation and the Silvaco Atlas device simulator. This led to novel insights into the APD degradation behavior. The generation of negative oxide charges was identified to cause a drift of the impact ionization rate in the sensor edge. The generation of interface traps promotes the accumulation of negative oxide charges by their supply of thermally generated dark current. In this way, degradation is about 14% faster. In order to reflect not only the causal relations of APD degradation, the model was calibrated on experimental degradation data. With the calibrated degradation model and its self-consistent simulation approach an elaborated powerful tool was available. Stress experiments have been performed on test sensors under a variation of operation conditions and on APDs. APDs of the studied design are currently tested and installed in automotive LiDAR modules. The entire set of experimental results found its complete physical interpretation in conjunction with the degradation model which achieved an excellent agreement. Thereby, numerous novel insights were revealed: The extent of degradation is induced by the properties of the sensors oxide layer. The degradation pace increases with temperature, voltage and intensity of illumination whereas the impact of temperature is particularly strong due to the significant participation of the dark current during degradation. The oxygen vacancy was proven to be the dominant trap in the oxide layer of the studied sensors. An empirical distribution of individual sensor properties was achieved. In some cases, the impact ionization rate in the sensor edge increased which indicates a major problem, as noise increases when the generation- recombination processes in the sensor become more pronounced during degradation. In order to estimate the impact of the degradation induced increase of noise on the LiDAR application, the empirical distribution of individual sensor properties was extrapolated to the tail where sensors are very prone to degradation. Furthermore, the available noise models were extended to cover the effect of degradation. Application of the calibrated APD degradation model revealed, that the APD noise is highly effected and even triples during aging. The origin was exclusively assigned to the edge contribution. There, the avalanche breakdown of the edge dark current caused by degradation is the main initiator. Consequently, for the first time ever, the signal-noise-ratio (SNR) degradation mode of APDs in LiDAR application was identified. During degradation, the SNR of small signals from 100m distant objects degrades to a value below 1, where even theoretically a resolution is impossible. Finally, the picture of APD degradation was completed by the estimation of lifetime. In the case of the most severe conditions in LiDAR operation, it amounts to only 1000 h, which falls much below the requirements of the automotive industry of several decades.

The coast is a domain characterized by great complexity based on its dynamic and challenging nature, which can create both opportunities and challenges for attackers and defenders. The purpose of this study is to investigate Geoffrey Till's theory of defence against amphibious operations and to increase an understanding of how military resources can be used to achieve success in defence in the event of a military attack from the sea. Research and theory development in this area have long been under-prioritized and Till has created a relatively unique theory, based on the prevailing research situation. These are arguments that strengthen the reason for examining the theory and field further. Through a theory-testing case study, the Battle of Wake Island and Operation Avalanche are analyzed to ascertain to what extent empirical evidence is given to the chosen theory. In this way, the explanatory capacity of the theory is determined and whether its credence is strengthened or weakened. The study discloses that Till's theory successfully explains the outcome of the first case however not the second. The analysis shows that a defence that acts on and adjacent to land contributes to success, which Till's theory does not emphasize. The study indicates that the theory is underspecified as it does not give any indication of how to prioritize between the different areas of the theory, which indicates that wone should be vigilant against the explanatory value of the theory.