No description available.

A technique which employs a laser-excited optical resonator has been developed to measure the electron density distribution, both temporal and spatial, in the collapse stage of a fast Z-pinch discharge. The resonator device has an experimentally determined time resolution of better than 0.05 µsec and is suitable for measuring electron densities in excess of 5 • 10¹⁶ /Lʎ cm⁻³, where L is the length of the plasma in cm and ʎ is the wavelength of the laser in microns. A novel feature of this instrument is the use of an unstable optical resonator. The technique is applied to a discharge in argon at filling pressures of 100 and 1000 µHg. The temporal and radial electron density distributions obtained exhibit several interesting features which are discussed from the point of view of the collapse process. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

L'utilisation des matériaux polymères dans les applications de l'ingénierie augmente de plus en plus da part le monde. L'utilisation du polyéthylène (PE) dans la construction de canalisations est l'un des exemples les plus courant. Ceci exige de nouvelles méthodes afin d'évaluer la capacité du matériau à supporter des chargements mécaniques. Dans la présente thèse, le comportement contrainte-déformation en grandes déformations du PE haute densité (PEHD) a été examinée dans différentes configurations de triaxialité. Un large domaine de conditions de chargements (traction, compression et cisaillement simple) a été exploré. L'investigation a été réalisée à partir d'échantillons découpés dans des canalisations en PEHD. Les essais de traction ont été faits à partir d'échantillons sabliers présentant plusieurs rayons de courbure afin de fixer différents états de contrainte dans la section médiane. Une attention particulière a été portée à l'évolution de la déformation volumique résultant de l'endommagement par cavitation. L'effet de la triaxialité sur la déformation à rupture a pu également être dégagé. La méthode des éléments finis (EF) a été utilisée pour simuler le comportement en grandes déformations du PEHD. De plus, le phénomène d'endommagement par croissance de vide a été étudié à partir de cellules unitaires soumises à différentes conditions de triaxialité. Afin d'évaluer le comportement à la rupture du PEHD, une méthode expérimentale basée sur l'hypothèse de la séparation de la charge a été élaborée. En outre, une analyse numérique par EF a été réalisée pour le calcul des paramètres de rupture. L'investigation a été réalisée dans les directions longitudinale et radiale. / The use of thermoplastic materials in engineering applications is growing more and more all over the world. The use of polyethylene (PE) in pressure vessels and pipelines is one of the most common examples. This issue demands new methodologies in order to assess the material capability to withstand loads. In the present thesis, the stress-strain response under large plastic deformation of high density PE (HDPE) was investigated in different triaxiality frameworks. A wide range of loading conditions (tension, compression and simple shear) was explored. Investigation was performed using specimens cut from HDPE pipes. The tensile tests were achieved on hourglass-shaped specimens with different curvature radii in order to set different stress states in the median cross-section. The tests were achieved by means of an optical measuring system. A particular attention was given on the evolution of volumetric strain resulting from cavitation damage. The effect of stress triaxilality on the fracture strain was also examined. The finite element (FE) method was used to simulate the large deformation bahaviour of HDPE material when subjected to tensile loading. Moreover, the damage phenomenon by void growth was studied using an axisymmetric representative volume element with different triaxiality conditions. In order to evaluate the fracture behaviour of HDPE pipe, an experimental method based on load separation assumption was developed. Furthermore, a numerical analysis using FE method has been conducted for calculating the fracture parameters. The investigation of fracture parameters and bahaviour of HDPE was performed in longitudinal and radial directions.

A radio-frequency positive-ion source and a fifty-kilovolt linear accelerator were designed and constructed in order to produce sizable quantities of hydrogen, helium, nitrogen, neon, and argon. Plans were then made to equip this ion source with charge-exchange apparatus suitable for charge-exchange cross-sectional measurements. It is the purpose of this paper to present the design of the equipment and to present operational knowledge of the equipment and of ion beams which are producible.

No description available.

No description available.

Ces dernières années sont apparues de nouvelles techniques permettant le contrôle de la charge de nano-objets individuels (atome, molécule, agrégat métallique ou semi-conducteur, ...) déposés sur substrats isolants. Cet aboutissement a été rendu possible par le perfectionnement des méthodes de microscopie à effet tunnel (STM) et à force atomique (AFM). En combinant ces outils, les précurseurs ont réussi à maîtriser l'état de charge d'un atome d'or déposé sur une bicouche de NaCl(001) sur substrat Cu(111). Par la suite, ce type de manipulation a été étendu à des systèmes moléculaires notamment au CEMES avec Cu(dbm)2. Ce sujet s'inscrit dans la continuité de ces études. L'objectif était d'analyser l'impact de l'augmentation de l'épaisseur du film isolant sur les mécanismes de charge. Cette problématique requière une quantification de l'état de charge du système ainsi qu'une mesure de l'épaisseur d'isolant. Dans ce travail, nous avons pu étudier des films de KBr et NaCl déposés sur des surfaces de Cu(111) et Ag(111). Pour ces études, que ce soit en courant tunnel (STM) ou en gradient de force (NC-AFM), le contrôle de l'état de pointe est essentiel. Lorsque l'on travaille sur substrat isolant, la pointe a tendance à collecter des contaminants qui en changent les propriétés électroniques. Or, pour charger un système de manière reproductible, il nous faut impérativement contrôler la métallicité de l'apex. Cette maîtrise passe par une re-préparation fréquente de la pointe sur une surface métallique, difficile à trouver dans le cas d'un film épais. Pour pallier à cette rareté, nous avons mis en place un masque de dépôt permettant un contrôle du gradient de l'épaisseur du film isolant tout en préservant des zones de métal libre. Cela nous a permis de réaliser nos mesures avec un état de pointe mieux contrôlé. L'instabilité de l'état de pointe nous a également conduit à effectuer des spectroscopies à courant régulé de type Z(V). En contrôlant ce courant, il est alors possible de minimiser l'interaction entre la pointe et le film isolant, préservant ainsi plus longtemps la pointe. Ces spectroscopies Z(V) permettent également d'augmenter la tension de mesure jusqu'à atteindre le régime d'émission de champ. Nous avons observé par cette méthode une variation de la modulation de l'amplitude des résonances d'émission de champ (FER) en fonction de l'épaisseur du film isolant. Une modélisation numérique par différences finies a été développée afin de comprendre ce phénomène. [..] / In recent years, new techniques have emerged to control the charge of individual nano-objects (atom, molecule, metal aggregate or semiconductor, etc.) deposited on insulating substrates. This achievement has been made possible by the refinement of Tunneling Microscopy (STM) and Atomic Force (AFM) methods. By combining these tools, the precursors succeeded in controlling the state of charge of a gold atom deposited on a NaCl (001) bilayer on a Cu (111) substrate. Subsequently, this type of manipulation has been extended to molecular systems, in particular at the CEMES with Cu(dbm)2. This subject is part of the continuity of these studies. The objective was to analyze the impact of the increase of the thickness of the insulating film on the charge mechanisms. This problem requires a quantification of the state of the system charge as well as a measurement of the insulation thickness. In this work, we have been able to study KBr and NaCl films deposited on Cu(111) and Ag(111) surfaces. For these studies, whether in tunnel current (STM) or force gradient (NC-AFM), the control of the tip state is essential. When working on an insulating substrate, the tip tends to collect contaminants that change their electronic properties. However, to charge a system in a reproducible way, we must imperatively control the metallicity of the apex. This control requires a frequent re-preparation of the tip on a metal surface, difficult to find in the case of a thick film. To overcome this scarcity, we have implemented a deposition mask allowing a control of the gradient of the thickness of the insulating film while preserving clean metal zones. This allowed us to carry out our measurements with a better controlled state of the tip. The instability of the tip state has also led us to perform Z (V) regulated current spectroscopies. By controlling this current, it is then possible to minimize the interaction between the tip and the insulating film, thus making the tip last longer. These Z (V) spectroscopies also make it possible to increase the measurement voltage until reaching the field emission regime. We have observed a variation of the modulation of the field emission resonances (FER) amplitude as a function of the thickness of the insulating film. [...]

Ce travail porte sur l'obtention et la caractérisation de composites polymères à charges organiques et inorganiques obtenus par polymérisation radicalaire in situ de monomères dans une matrice organique de type cellulose ou inorganique de type silicate. Avec la cellulose, les monomères retenus sont d'abord des dérivés vinyliques de type acide (méth)acrylique et de comonomères tels que l'anhydride maléique, le styrène et le chlorométhylstyrène. Les produits sont caractérisés notamment par ATG et XRD. La conductivité électrique de ces composites en fonction de leur gonflement a été étudiée. La copolymérisation de l'anhydride maléique avec le dicyclopentadiène est ensuite étudiée dans le toluène et le dioxane. Ce type de copolymère n'avait pas été étudié jusqu'à présent. L'influence du type de solvant sur la conduite de la réaction est étudiée. La caractérisation des composites est effectuée par IR, XRD et microscopie SEM. L'interaction entre les composants est mise en évidence par XRD. Les composites à base de silicate sont obtenus par polymérisation radicalaire contrôlée après greffage de l'amorceur sur le support inorganique. Le greffage est caractérisé par IR. Les analyses XRD et IR mettent en évidence la prédominance du greffage du polymère à la surface du silicate. L'étude de la copolymérisation chlorométhylstyrène - méthacrylate d'hydroxyéthyle a été effectuée qui montre in fine l'influence du support sur la structure des copolymères. De même, les analyses XRD et IR révèlent la modification de la structure du silicate. La microscopie SEM met en évidence des structures homogènes. Une étude complète de dégradation thermique a été menée par ATG qui montre l'influence des différents polymères / The synthesis of organic-polymer or inorganic-polymer composites was a real challenge within the last decades due to the difficulty of optimally dispersing the reinforcing agent into the polymeric matrix. A method to solve this problem is the "in situ "polymerization. The first part of the experimental study deals with the synthesis of the polymer-cellulose composites. Cellulose-containing composites based on copolymers of acrylic acid with styrene, 4-chloro-methyl-styrene and maleic anhydride or based on copolymers of methacrylic acid with styrene and 4-chloro-methyl-styrene were prepared for proton conducting membranes. Next, cellulose composites with maleic anhydride – dicyclopentadiene copolymer matrix were obtained by “in situ” free-radical polymerization. The syntheses were carried out in two different solvents: toluene and dioxane, aiming to determine their influence upon both the polymerization process and properties of the resulting materials. To the best of our knowledge, studies concerning the preparation of this composite have not been published in the literature until now. The second part of the original contributions section is dedicated to the investigation of some polymer-layered silicates composites, using a commercial layered silicate (Cloisite 30B), modified with OH-containing quaternary ammonium salts. First, a new ATRP-based procedure to synthesize polymer-layered silicate composites involving a simpler method than those published in the literature up to now, was studied. The novelty of the methods consists in the one-step preparation of the ATRP initiating sites anchored onto the layered silicate by reacting the OH groups of the quaternary ammonium salt with chloroacetic anhydride, followed by the "in situ” ATRP of the monomer. This way several intermediate stages are eliminated. The last experimental study concerns the synthesis and characterization of a composite with an inorganic support (Cloisite 30B) and a polymeric matrix synthesized by the copolymerization of two different monomers with high reactivity: 2-hydroxyethyl methacrylate and 4-chloro-methyl-styrene. To our knowledge, there are no studies published in the literature describing the preparation of this composite until now. The obtained composite materials were characterized both structurally by FT-IR, NMR, XRD and SEM, and from the thermal behavior point of view by TGA-DSC-MS

Indiana University-Purdue University Indianapolis (IUPUI) / With the growing popularity and use of devices under the great umbrella that is the Internet of Things (IoT), the need for devices that are smaller, faster, cheaper and require less power is at an all time high with no intentions of slowing down. This is why many current research efforts are very focused on energy harvesting. Energy harvesting is the process of storing energy from external and ambient sources and delivering a small amount of power to low power IoT devices such as wireless sensors or wearable electronics. A charge pumps is a circuit used to convert a power supply to a higher or lower voltage depending on the specific application. Charge pumps are generally seen in memory design as a verity of power supplies are required for the newer memory technologies. Charge pumps can be also be designed for low voltage operation and can convert a smaller energy harvesting voltage level output to one that may be needed for the IoT device to operate. In this work, an integrated FinFET (Field Effect Transistor) charge pump for low power energy harvesting applications is proposed. The design and analysis of this system was conducted using Cadence Virtuoso Schematic L-Editing, Analog Design Environment and Spectre Circuit Simulator tools using the 7nm FinFETs from the ASAP7 7nm PDK. The research conducted here takes advantage of some inherent characteristics that are present in FinFET technologies, including low body effects, and faster switching speeds, lower threshold voltage and lower power consumption. The lower threshold voltage of the FinFET is key to get great performance at lower supply voltages. The charge pump in this work is designed to pump a 150mV power supply, generated from an energy harvester, to a regulated 650mV, while supplying 1uA of load current, with a 20mV voltage ripple in steady state (SS) operation. At these conditions, the systems power consumption is 4.85uW and is 31.76% efficient. Under no loading conditions, the charge pump reaches SS operation in 50us, giving it the fastest rise time of the compared state of the art efforts mentioned in this work. The minimum power supply voltage for the system to function is 93mV where it gives a regulated output voltage of $25mV. FinFET technology continues to be a very popular design choice and even though it has been in production since Intel's Ivy-Bridge processor in 2012, it seems that very few efforts have been made to use the advantages of FinFETs for charge pump design. This work shows though simulation that FinFET charge pumps can match the performance of charge pumps implemented in other technologies and should be considered for low power designs such as energy harvesting.

No description available.