International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Recent years have seen a sharp rise in the size of satellite constellations. The monitoring and analysis tools in use today, however, were developed for smaller constellations and are ill-equipped to handle the increased volume of telemetry data. A new technology that can accommodate vast quantities of data is 3-D visualization. Data is abstracted to show the degree to which it deviates from normal, allowing an analyst to absorb the status of thousands of parameters in a single glance. Trend alarms notify the user of dangerous trends before data exceeds normal limits. Used appropriately, 3-D visualization can extend the life of a satellite by ten to twenty percent.

In the first part of this thesis we transfer a result of Guillopé et al. concerning the number of zeros of the Selberg zeta function for convex cocompact Schottky groups to the setting of certain types of graph directed Markov systems (GDMS). For these systems the zeta function will be a type of Ruelle zeta function. We show that for a finitely generated primitive conformal GDMS S, which satisfies the strong separation condition (SSC) and the nestedness condition (NC), we have for each c>0 that the following holds, for each w \in\$C$ with Re(w)>-c, |\Im(w)|>1 and for all k \in\$N$ sufficiently large: log | zeta(w) | <<e {delta(S).log(Im|w|)} and card{w \in\ Q(k) | zeta(w)=0} << k {delta(S)}. Here, Q(k)\subset\%C$ denotes a certain box of height k, and delta(S) refers to the Hausdorff dimension of the limit set of S. In the second part of this thesis we show that in any dimension m \in\$N$ there are GDMSs for which the Hausdorff dimension of the uniformly radial limit set is equal to a given arbitrary number d \in\(0,m) and the Hausdorff dimension of the Jørgensen limit set is equal to a given arbitrary number j \in\ [0,m). Furthermore, we derive various relations between the exponents of convergence and the Hausdorff dimensions of certain different types of limit sets for iterated function systems (IFS), GDMSs, pseudo GDMSs and normal subsystems of finitely generated GDMSs. Finally, we apply our results to Kleinian groups and generalise a result of Patterson by showing that in any dimension m \in\$N$ there are Kleinian groups for which the Hausdorff dimension of their uniformly radial limit set is less than a given arbitrary number d \in\ (0,m) and the Hausdorff dimension of their Jørgensen limit set is equal to a given arbitrary number j \in\ [0,m).

<p>This dissertation extends the empirical industrial organization literature with two essays on strategic decisions of firms in imperfectly competitive markets and one essay on how inertia in consumer choice can result in significant welfare losses. Using data from the airline industry I study a well-known puzzle in the literature whereby incumbent firms decrease fares when Southwest Airlines emerges as a potential entrant, but is not (yet) competing directly. In the first essay I describe this so-called Southwest Effect and use reduced-form analysis to offer possible explanations for why firms may choose to forgo profits today rather than wait until Southwest operates the route. The analysis suggests that incumbent firms are attempting to signal to Southwest that entry is unprofitable so as to deter its entry. The second essay develops this theme by extending a classic model from the IO literature, limit pricing, to a dynamic setting. Calibrations indicate the price cuts observed in the data can be captured by a dynamic limit pricing model. The third essay looks at another concentrated industry, mobile telecoms, and studies how inertia in choice (be it inattention or switching costs) can lead to consumers being on poorly matched cellphone plans and how a simple policy proposal can have a considerable effect on welfare.</p> / Dissertation

<p>Limit-periodic (LP) structures exhibit a type of nonperiodic order yet to be found in a natural material. A recent result in tiling theory, however, has shown that LP order can spontaneously emerge in a two-dimensional (2D) lattice model with nearest-and next-nearest-neighbor interactions. In this dissertation, we explore the question of what types of interactions can lead to a LP state and address the issue of whether the formation of a LP structure in experiments is possible. We study emergence of LP order in three-dimensional (3D) tiling models and bring the subject into the physical realm by investigating systems with realistic Hamiltonians and low energy LP states. Finally, we present studies of the vibrational modes of a simple LP ball and spring model whose results indicate that LP materials would exhibit novel physical properties.</p><p>A 2D lattice model defined on a triangular lattice with nearest- and next-nearest-neighbor interactions based on the Taylor-Socolar (TS) monotile is known to have a LP ground state. The system reaches that state during a slow quench through an infinite sequence of phase transitions. Surprisingly, even when the strength of the next-nearest-neighbor interactions is zero, in which case there is a large degenerate class of both crystalline and LP ground states, a slow quench yields the LP state. The first study in this dissertation introduces 3D models closely related to the 2D models that exhibit LP phases. The particular 3D models were designed such that next-nearest-neighbor interactions of the TS type are implemented using only nearest-neighbor interactions. For one of the 3D models, we show that the phase transitions are first order, with equilibrium structures that can be more complex than in the 2D case. </p><p>In the second study, we investigate systems with physical Hamiltonians based on one of the 2D tiling models with the goal of stimulating attempts to create a LP structure in experiments. We explore physically realizable particle designs while being mindful of particular features that may make the assembly of a LP structure in an experimental system difficult. Through Monte Carlo (MC) simulations, we have found that one particle design in particular is a promising template for a physical particle; a 2D system of identical disks with embedded dipoles is observed to undergo the series of phase transitions which leads to the LP state. </p><p>LP structures are well ordered but nonperiodic, and hence have nontrivial vibrational modes. In the third section of this dissertation, we study a ball and spring model with a LP pattern of spring stiffnesses and identify a set of extended modes with arbitrarily low participation ratios, a situation that appears to be unique to LP systems. The balls that oscillate with large amplitude in these modes live on periodic nets with arbitrarily large lattice constants. By studying periodic approximants to the LP structure, we present numerical evidence for the existence of such modes, and we give a heuristic explanation of their structure.</p> / Dissertation

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Commercial technologies for the objective assessment of balance exist in clinical settings. Training requires integration of sensory information to produce a coordinated motor response related to balance. These systems have had measurable phase delays of up to 250ms in the visual feedback provided to the patient. This provokes an unnatural response, requiring prediction from the subject. The proposed research investigates the impact of visual feedback phase delays on the performance of weight shift tracking tasks in a population of individuals with no known balance deficits.Visual feedback delays were investigated by simulating popular balance training software which utilizes force plates to measure center of pressure and display the results in a stimulus and response study. Ten healthy young-adult subjects with no known balance deficits were recruited to participate in this study. Subjects were asked to stand on a pair of force platforms that were linked to a computer. The system was designed to provide visual feedback corresponding to lateral weight shifts. A computer generated target provided a moving stimulus the subjects attempted to match. The stimulus files presented approximately 20 seconds of movement in a periodic (sinusoidal) or non-periodic pattern. Stimulus frequencies ranged between 0.2 and 1.0 Hz with amplitude sufficient to require the subject to move safely within 50% of his/her base of support. Stimulus presentation was randomized and included both normal (control) and phase delayed (experimental) trials. Results of the experiment point to a noticeable improvement of performance with repeated trials. Regardless of introduced phase delays, study participants improved their performances as they were exposed to more trials, suggesting learning and predictive behavior. Random stimuli produced no noticeable improvements in performance across days of testing, as expected. Visual biofeedback systems may skew performance assessments of balance training because they contain periodic stimuli that are predictable.

Les procédés de mise en forme de tôles minces sont très largement répandus dans l’industrie. Néanmoins, l’utilisation de ces procédés est limitée par le niveau de formabilité du matériau formé, notamment dans le cas des alliages d’aluminium. Afin d’améliorer ces limites de formabilité, des procédés de mise en forme à chaud peuvent être envisagés. L’objectif de cette thèse est d’étudier à l’aide d’approches expérimentale et numérique l’effet de la température et de la vitesse de déformation sur la formabilité des tôles en alliage d’aluminium AA5086 et de proposer une modélisation capable de prédire ces effets. Une campagne d’essais a été réalisée sur ce matériau à partir d’un essai d’emboutissage de type Marciniak. Des courbes limites de formage (CLF) ont été établies sur une plage de température allant de l’ambiant jusqu’à 200°C et pour des vitesses de déformation allant du quasi-statique à 2s-1. Des effets, positif de la température et négatif de la vitesse de déformation sur la formabilité ont été mis en évidence. La prise en compte des effets de la température et de la vitesse de déformation dans les modèles prédictifs des CLF, qu’ils soient analytiques ou numériques, est à ce jour très limitée. Dans ce travail, un modèle numérique prédictif basé sur la simulation par éléments finis du modèle géométrique de Marciniak et Kuczynski (M-K) est proposé. Les déformations limites obtenues avec de ce modèle sont très sensibles à la description du comportement thermo-viscoplastique du matériau et à la calibration du défaut géométrique pilotant l’apparition de la striction dans le modèle M-K. Des essais de traction uniaxiale réalisés dans les mêmes conditions opératoires que les essais de mise en forme de Marciniak ont permis d’identifier des lois d’écrouissage de nature très différentes (rigidifiante, saturante ou mixte). Ces lois conduisent à des prédictions très différentes de la formabilité du matériau pour une valeur donnée du défaut géométrique du modèle EF M-K. Différentes stratégies de calibration de la taille de ce défaut initial ont été envisagées. L’utilisation du point expérimental de la CLF correspondant à des conditions de déformation plane permet de calibrer de manière satisfaisante la valeur de ce défaut. Cette procédure de calibration a été appliquée pour l’ensemble des lois identifiées. Les lois de nature rigidifiante de type Ludwick se sont montrées les plus effficaces alors que les lois saturante de type Voce se sont avérées incapables de prédire la formabilité du matériau pour certaines conditions opératoires. Finalement, il est démontré qu’une valeur constante du défaut géométrique ne peut être retenue pour l’ensemble des conditions opératoires étudiées même si le modèle M-K s’est avéré assez efficace pour représenter l’effet de la température plutôt que celui de la vitesse de déformation. / Sheet metal forming processes are widely used in industry. Nevertheless, the use of these processes is limited by the formability of the considered material, in particular in the case of the aluminium alloys. To improve the formability, warm forming processes can be considered. The objective of this work is to study by means of both experimental and numerical approaches, the effects of temperature and strain rate on the formability of AA5086 aluminium alloy sheets and to propose a modeling suitable to predict these effects. Experimental tests have been carried out on this material by means of the Marciniak stamping experimental device. Forming limit curves (FLCs) have been established on a temperature range going from ambient temperature to 200°C and on a strain rate range going from quasi-static up to 2s-1. A positive effect of the temperature and a negative effect of the strain rate on the formability limits were highlighted. To date, very few predictive models of the FLCs taking into account temperature and strain rate effects are proposed in the literature. In this work, in order to predict the experimental temperature and strain rate sensitivities, a predictive model based on the finite element simulation of the Marciniak and Kuczynski (M-K) geometrical model is proposed. The limit strains obtained with this model are very sensitive to the description of the thermo-viscoplastic behaviour modeling and to the calibration of the initial geometrical imperfection controlling the onset of the necking. Thanks to tensile tests carried out for the same operating conditions that those of Marciniak forming tests, several types (power law, saturation and mixed) of hardening laws have been identified. These hardening laws have been implemented in theFE M-K model to obtain numerical limit strains. Very different formability limits have been observed for a given value of the geometrical defect. Several strategies for the calibration of this initial imperfection size have been tested. The use of the experimental point of the FLC0 corresponding to plane strain condition allows a good calibration of the initial imperfection value. This calibration procedure was carried out for all hardening laws. It is shown that the power law type models such as Ludwick law are more efficient while saturation laws such as Voce law are unable to predict the material formability for some conditions. Finally, it is shown that a constant value of the geometrical defect cannot be used to the whole operating conditions studied even if FE M-K model is shown to be efficient to represent the temperature effect rather than strain rate one.

No description available.

>Magister Scientiae - MSc / The motivation to determine H2O2 lies in the fact that this chemical species plays a crucial role in diverse fields of practise such as cosmetic, food, diagnostic, pharmaceutical, clinical and environmental protection industries. Several methods such as chromatography, colorimetry, titrimetry and spectrophotometry have been developed for its detection. However, these methods are known to manifest underlying disadvantages such as high cost, time consuming, instability and complicated immobilization procedures. In this present study an enzyme-less electrochemical sensor based on Ag-Fe2O3/POM/RGO nanocomposite (POM stands for polyoxometalate and RGO stands for reduced graphene oxide) was successfully synthesised via a hydrothermal method and a photochemical reduction method for the detection of hydrogen peroxide (H2O2).

This thesis is focused around Edgeworths expansion for aproximation of distribution for parameter estimation. Aim of the thesis is to introduce term Edgeworths expansion, its assumptions and terminology associeted with it. Afterwords demonstrate process of deducting first term of Edgeworths expansion. In the end demonstrate this deduction on examples and compare it with different approximations (mainly central limit theorem), and show strong and weak points of Edgeworths expansion.