There are various energy dissipation mechanisms that affect the dynamic response of microstructures used in MEMS devices. A cumulative effect of such losses is captured by an important characteristic of the structure called Quality factor or Q-factor. Estimating Q-factor at the design stage is crucial in all applications that use dynamics as their principle mode of operation. A high Q-factor indicates sharp resonance that, in turn, can indicate a broad flat response region of the structure. In addition, a high Q-factor typically indicates a high sensitivity. Microstructures used in MEMS are generally required to have much higher Q-factors than their macro counterparts. However some damping mechanisms present in microstructures can reduce the Q-factor of the structure significantly. In the present work, we investigate the dependence of Q-factor on the squeeze film damping an energy dissipation mechanism that dominates by a couple of orders of magnitude over other losses when a fluid (e.g., air) is squeezed through gaps due to vibrations of a microstructure. In particular, we show the effect of nonlinear terms in the analysis of squeeze film damping on the Q-factor of a structure. We also show the effect of rarefaction, surface roughness along with their coupled effect and with different boundary conditions such as open border effect, blocked boundary effect on the squeeze film damping. Finally, we develop similitude laws for calculating squeeze film damping force in up-scaled structures. We illustrate the effects by studying various type of microstructures including parallel plates, beams, plate and beam assemblies such as MEMS microphone, vibratory gyroscope etc. We view the contributions of this work as a significant in investigating and integrating all important effects altogether on the squeeze film damping, which is a significant factor in the design and analysis of MEMS devices.

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Published Article / A component, which has a perfect combination of different materials (probably including homogeneous materials and three different types of heterogeneous materials) in its different portions for a specific application, is considered as the component made of a multiphase perfect material. To fabricate such components, a hybrid layered manufacturing process has been developed. In order to accurately spray different materials with their required volume fractions for every pixel during fabrication, it is important to investigate its spraying operation. This paper establishes the behavior model of the spraying device and proves its validity using digital simulations.

The objective of this research is to achieve high-efficiency, low-cost, commercial-ready, screen-printed Silicon (Si) solar cells by reducing material costs and raising cell efficiencies. Two specific solutions to material cost reduction are implemented in this thesis. The first one is low to medium concentrator (2-20 suns) Si solar cells. By using some optics to concentrate sunlight, the same amount of output power can be achieved with cell area reduced by a factor equal to the concentration ratio. Since the cost of optics is less than the semiconductor material, electricity price from the concentrator photovoltaics (PV) system is therefore reduced. The second solution is the use of epitaxially grown Si (epi-Si) wafers. This epi-Si technology bypasses three costly process steps (the need for polycrystalline silicon feedstock, ingot growth, and wafer slicing) compared to the traditional Si wafer technology and therefore reduces the material cost by up to 50% in a finished PV module. In addition, high efficiency Si solar cells with reduced metal contact recombination are studied and modeled by implementation of passivated contacts composed of tunnel oxide, n+ polycrystalline Si and metal on top of n-type Si absorber to reduce the cost ($/Wp) of PV module.

Objective: To gather knowledge related to patient satisfaction and mobility with lower limb prosthetic and orthotic devices and to investigate satisfaction with services received. Another purpose of this study is to analyze potential differences between orthotic and prosthetic patients in relation to patient satisfaction and mobility. Design: Cross-sectional study Subjects: 21 participants with a mean age of 58 (SD 16) with an average duration of use of devices of 10 (SD 10) years. 12 out of the 21 participants were orthotic users and 9 were prosthetic users. Methods: Patients were asked to complete two questionnaires, one regarding satisfaction with assistive device and service (QUEST 2.0) and one regarding mobility. Results: Patients mean score regarding satisfaction with assistive device and service were 4.0 (SD 0.8) and 4.2 (SD 1.0) respectively. 91% reported that they had the ability to walk at least 100 meters with their assistive device. The areas where participants experienced most difficulties were walking on uneven ground (70%), walking up and down a hill (57%) and walking on stairs (57%). Conclusion: Overall this study demonstrates that participants were quite satisfied with their assistive device and the service received by the P&O clinic. No statistically significant differences regarding satisfaction with assistive device and service, or mobility, were found between prosthetic and orthotic participants.

International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A digital device for rapid acquisition of the initial phase of PN code has been implemented. The principles and results of the experiment are introduced in this paper. The m PN code is modulated on IF with BPSK type. The cycle of PN code P=255 chips. The rate of PN code R=5.1 × 10 chips /s. The IF is not acquired. The shift in Doppler 6 frequency f is within l-4KHz. In these conditions, the phase of PN code can be acquired d within 3 ms and the error of sychronization is less than 0.5 chip.

Why is it that we humans have a tendency to construct transcendental entities? That is one of the big questions the scientific discipline Cognitive Science of Religion is trying to answer. In order to gain validation for the concepts used by this discipline neural correlates are needed. The aim of the present work is to investigate the concepts Hypersensitive Agency Detection Device ((H)ADD) and Theory of Mind (ToM) both in psychological, cognitive and neural aspects to see if those concepts are enough to explain the human tendencies to construct transcendental entities. This work is developed as philosophical a literature study and uses literature from the scientific disciplines of cognitive neuroscience, cognitive science of religion, cognitive science, neurotheology, psychology of religion and philosophy of religion. This means that the present work is interdisciplinary and stands on a bridge between the theoretical and empirical sciences. A word of caution: Regardless the findings this work presents, the explanatory value is limited as it is a theoretical study in an empirical scientific field. It is when the findings in this work are tested empirically that the findings sustainability are decided.              What this work shows is that neural correlates for ToM already exist in the form of the Mirror Neuron-Theory (MNT), but it is problematic because it can not show how higher orders of representations are possible. No scientific data about neural correlates to (H)ADD has been found for this study, but here the amygdala may play a prominent role. Furthermore this work shows that (H)ADD and ToM is not enough to explain why humans have a tendency to construct transcendental entities. We are in need of peripheral cognitive mechanisms such as intuitive knowledge modules, ontological categories, teleological thinking, our drive to seek causal connections and our ability for pattern recognition.

Les sources d'énergie renouvelable connaissent un essor grandissant. Parmi celles-ci se trouvent les cellules photovoltaïques. Elles ont pour objet la transformation de la lumière en électricité. Les dispositifs actuels, basés sur le silicium, nécessitent des matériaux de très grande pureté et de hautes températures de mise en œuvre, les empêchant de concurrencer les principales sources d’énergie actuelles (fossile, nucléaire). Une alternative pourrait provenir des matériaux semi-conducteurs organiques. En effet, l’utilisation de méthodes de mise en œuvre à partir de solutions pourrait permettre la fabrication de dispositifs flexibles et bon marché. Des résultats encourageants ont été obtenus avec des polymères conjugués et de petites molécules organiques. Les cristaux liquides discotiques CLDs forment une catégorie particulièrement intéressante de matériaux. Ils ont en effet la capacité de s’organiser spontanément en colonnes de molécules, formant des semi-conducteurs à une dimension. Leurs propriétés intéressantes en tant que semi-conducteurs, combinées à une mise en œuvre facile, en font de bons candidats pour de futures applications. Dans ce travail, deux familles complémentaires de matériaux discotiques ont été développées, formant une paire de semi-conducteurs de type n et p. Leurs structures chimiques ont été étudiées en vue d'obtenir des matériaux possédant un ensemble de propriétés choisies afin d’optimiser les paramètres clefs du processus de photo-génération de charges. Ces propriétés sont les suivantes: forte absorption de la lumière dans le visible, fort caractère semi-conducteur de type n ou p, pas de phase cristalline à température ambiante, présence d'une phase cristal liquide colonne, phase isotrope en dessous de 200°C. De plus, les matériaux doivent être accessibles en un nombre minimum d’étapes d’une synthèse efficace, et ce avec un haut niveau de pureté. Ils doivent également être fortement solubles dans les solvants organiques usuels. Cette étude comporte, pour chacune des deux familles de matériaux, le design de leur structure chimique, leur synthèse et la caractérisation de leurs propriétés physiques (thermotropes, optoélectroniques, électrochimiques). Comme possible semi-conducteur de type p, cinq dérivés tétrasubstitués de la phthalocyanine non-métallée ont été synthétisés, donnant un matériau possédant l’ensemble des propriétés recherchées. Comme possible semi-conducteur de type n, six dérivés hexasubstitués de l’hexaazatrinaphthylène ont été étudiés. L’un d’eux possède les propriétés requises. Finalement, les propriétés optoélectroniques et photovoltaïques de mélanges des deux matériaux les plus prometteurs, ensemble ou avec d’autres matériaux, ont été étudiées. Des cellules solaires de rendement maximum de 1 % ont été obtenues pour deux dispositifs de compositions différentes. Ces rendements, bien qu’inférieurs à ceux obtenus précédemment par d’autres groupes (jusqu’à 34 % à ce jour), sont néanmoins révélateurs des potentialités des matériaux organiques, et plus particulièrement des cristaux liquides discotiques, pour de futures applications dans le domaine des dispositifs électroniques.

This thesis presents the development and experimental testing of a lower-limb exoskeleton system. The device supplies assistive torque at the knee joint to alleviate the loading at the knee, and thus reduce the muscular effort required to perform activities of daily living. The hypothesis is that the added torque would facilitate the execution of these movements by people who previously had limited mobility. Only four specific movements were studied: level-waking, gradient-walking, sit-to-stand-to-sit and ascending stairs. All three major components of the exoskeleton system, i.e. the exoskeleton actuators and actuator control system, the user intention estimation algorithm, and the mechanical construction of the exoskeleton, were investigated in this work. A leg brace was fabricated in accordance with the biomechanics of the human lower-limb. A single rotational degree of freedom at the knee and ankle joints was placed to ensure that the exoskeleton had a high kinematic compliance with the human leg. The position of the pneumatic actuators and sensors were also determined after significant deliberation. The construction of the device allowed the real-world testing of the actuator control algorithm and the user intention estimation algorithms. Pneumatic artificial muscle actuators, that have high power to weight ratio, were utilized on the exoskeleton. An adaptive fuzzy control algorithm was developed to compensate for the inherent nonlinearities in the pneumatic actuators. Experimental results confirmed the effectiveness of the adaptive controller. The user intention estimation algorithm is responsible for interpreting the user's intended movements by estimating the magnitude of the torque exerted at the knee joint. To accomplish this, the algorithm utilizes biological signals that emanate from the knee extensor and flexor muscles when they are activated. These signals combined with the knee angle data are used as inputs to the estimation algorithm. The output is the magnitude and direction of the estimated torque. This value is then scaled by an assistance ratio, which determines the intensity of the assistive torque provided to the user. The experiments conducted verify the robustness and predictability of the proposed algorithms. Finally, experimental results from the four activities of daily living, affirm that the desired movements could be performed successfully in cooperation with the exoskeleton. Furthermore, muscle activity recorded during the movements show a reduction in effort when assisted by the exoskeleton.

Abdominal aortic aneurysm (AAA) occurs in developed nations. The current treatment, endovascular aneurysm repair (EVAR), while successful, has shortcomings. A solution to the concerns with EVAR is a polymeric endo-aortic paving (PEAP). Our goal is to further develop this treatment for AAA. We hypothesize that PEAP will overcome the current limitations associated with current AAA repair, while maintaining the desirable qualities of these materials are biocompatibility, thermoformability, and material compliance with aortic tissue. The purpose of this work was to evaluate potential PEAP material candidates, which include acrylate-based shape memory polymers (SMPs), polycaprolactone (PCL) and polyurethane (PU) blends, and finally a PCL-based bioresorbable copolymer poly (ester-urethane-urea) (PEUU). Materials were assessed by characterization of their chemical, thermomechanical and degradation properties. It was determined that acrylate- SMPs were too stiff to be candidates for use in PEAP. The control of the PEUU copolymer composition yielded a material that had increased degradability while maintaining valuable characteristics of the PCL/PU blend prior to, during, and following degradation. The difference between the PU hydrophobicity dictated MTM sensitivity to water immersion and degradation characteristics. Conventional statistics were used to develop three models for predicting key properties of PEUU. Important variables, such as PCL M(n), temperature, and crystallinity were found to impact both copolymer microstructure and mechanical properties.