This thesis focuses on the characterization and optimization of microwave power transistors using a commercial on-wafer harmonic load pull system. Specific attention is paid to the output tuning of the second harmonic impedance presented to the device. The ability to quantify the level of accuracy in a load pull system is explored by using various calibration validation methods, including a method called Delta-Gt. In this work experiments and simulation comparisons are described for three different device technologies, namely GaAs pHEMT, GaAs HJFET and InGaP HBT. Externally supplied non-linear models were used for the simulations and these were exercised and compared against 2.45 GHz fundamental frequency measurements made as part of this work to first validate the models against IV, S-Parameter and fundamental load-pull data and finally to explore performance variations under 2nd harmonic impedance tuning. The measured harmonic load-pull data pointed to different guidance on how one would match the 2nd harmonic for best performance. With regard to the model validation/assessment work it was found that only in the case of the pHEMT did the available non-linear model provide a good fit to all the different types of measurement data, including 2nd harmonic tuning data. This model was then used to show that even though the 2nd harmonic tuning measurement had a limited maximum reflection coefficient of about 0.8. Simulated results showed that the worst case linearity condition occurred for the same reflection angle as that measured, but that the variation between worst-case and best case linearity under 2nd harmonic tuning grows considerably larger as the magnitude of the 2nd harmonic reflection coefficient approaches 1. A key aspect of the methodology presented in this work is that once a non-linear model is proved to be valid for harmonic tuning conditions it can be used to explore harmonic tuning-related design trade-offs under a much wider range of frequency and tuning conditions than can be practically explored with measurements alone.

Given rising work and family demands in our society for both men and women, the experience of work-family conflict is commonplace. Work-family conflict occurs when the demands of work or family make it difficult to meet the demands of the alternate domain. A sizeable body of research has established work-family conflict and its nomological network. Despite decades of research, we have yet to form a precise understanding of when work-family conflicts occur and what happens when a conflict arises. The current research addresses these questions using an experience sampling, episodic approach. Two primary research questions are addressed. First, I used border and boundary theory to identify when work-family conflict episodes are likely to occur. Second, I used stressor-strain and allostatic load theories to examine what happens with regard to psychological, physiological, and behavioral strain following an episodic work-family conflict over time. The results suggest work-family conflict occurs when individuals transition in between work and family domains. Further, family-to-work conflict tends to occur in the morning, while work-to-family conflict tends to occur in the afternoon. Fatigue showed significant reactivity at the time of a family-to-work conflict and recovered in the following time point. Unhealthy eating also showed a sleeper pattern, such that unhealthy eating increased at the end of the day, following a work-to-family conflict. Unexpectedly, fatigue decreased at the time of a family-to-work conflict, indicating family-to-work conflict may be a restorative, rather than taxing. Post-hoc analyses showed some evidence that work-to-family conflict accumulation is associated with increased strain over the course of three days. Again, results suggest family-to-work conflict accumulation may reduce, rather than increase, strain. Implications for the theoretical relationship between work-family conflict and strain, as well as border/boundary theory are discussed. In addition, practical implications for flexible work initiatives and episodic research design are considered.

Excessive sympathetic cardiovascular reactivity to stressful tasks is a risk factor for the development of cardiovascular disease (CVD). Many populations with a greater risk for CVD instead demonstrate blunted cardiovascular reactivity to stressful tasks. The motivational intensity theory identifies how motivation and effort influence sympathetic reactivity. Blunted reactivity may be a potential index of motivational dysregulation, which leads to poor behavioral decisions such as excess smoking or alcohol use, in turn increasing the risk for CVD. The current study sought to demonstrate how inhibited effort due to poor ability feedback with a low-contingency reward could directly increase the risk for CVD through perseverative cognition and impaired recovery. Participants (N = 89) were given either poor or good feedback on a working memory task that was purported to be related to another related working memory task. Participants were then informed that they could secure a low- or high-contingency reward opportunity by meeting a performance standard. EKG, impedance cardiography, blood pressure, and pupillometry were recorded throughout. Pre-ejection period reactivity and self-reported effort were greatest in participants given good feedback with a high-contingency reward and poor feedback with a low-contingency reward. Greater effort and sympathetic reactivity support previous findings linking these two measures. The results also suggest evaluating both internal and external rewards is important when examining motivation.

Tesis para optar al grado de Magíster en Gestión y Dirección de Empresas / Actualmente existen importantes desafíos en minería, no solo por las cifras de inversión estimadas, sino también por necesidad de incorporar nuevas tecnologías, generadas en base a los desafíos planteados por el aumento de costos. Los principales nuevos desafíos son derivados de las características de la roca primaria, la baja en la ley de mineral, los requerimientos de sustentabilidad y la mayor preocupación por mejorar los estándares de seguridad y salud ocupacional de los operadores. Para el futuro se requieren procesos altamente automatizados, equipamientos autónomos y operaciones telecomandadas, gestionadas fuera de las minas en busca de la continuidad operacional. Tratar de mantener los costos bajos y mejorar la productividad es el gran desafío que presenta la Minería Subterránea. En esta tesis se analizará el estado del arte de la tecnología de equipos LHD semiautónomos, sus limitaciones, las lecciones aprendidas, así como los sistemas y metodologías de navegación existentes asociados con el automatizado subterráneo en la carga, transporte y descarga, además de los resultados obtenidos en la División el Teniente. La implementación de esta tecnología en División el Teniente nació como solución a los problemas de seguridad y calidad de vida de los trabajadores, así como también para contar con un equipo robusto capaz de enfrentar las exigencias que demanda el mineral primario a ser extraído, una de las ventajas que se espera obtener como resultado, es un mayor tiempo de operación en comparación con los equipos manuales. El análisis se basará en la utilización de equipos LHD (cargadores de bajo perfil para la tarea de extracción de mineral, que consiste en cargar, transportar y descargar la roca mineralizada), los cuales cuentan con la tecnología que les permite operar en una condición semi-automática, es decir sin operador a bordo, controlados a distancia por operadores ubicados al exterior de la mina en una la sala de control distante kilómetros del área productiva. La tecnología ha demostrado ser factible de aplicar, sin embargo, se han detectado brechas en el desempeño y funcionalidades respecto de los requerimientos planteados para la División El Teniente en su Proyecto Estructural Nuevo Nivel Mina, por lo cual se requiere incorporar nuevos desarrollos tecnológicos a través de un programa de innovaciones incrementales de la tecnología de automatización de LHD, bajo un Modelo de Negocio ad-hoc y efectuar un cambio significativo de las estrategias y tácticas operacionales, mantenimiento, planificación, control centralizado, diseños mineros, entre las más relevantes, para así optimizar y capturar el mayor valor del uso de los equipos LHD semi-autónomos. El gran desafío que hoy nos impone la minería, de expandir la capacidad de producción para satisfacer las futuras demandas de los minerales, está requiriendo con urgencia de un mayor desarrollo y apoyo de las tecnologías de automatización en la minería. La dimensión de los proyectos permite generar cambios tecnológicos en pos de encontrar herramientas y sistemas que garanticen en mayor medida la calidad, eficiencia y control de las operaciones mineras. Es ahí donde está el desafío: identificar, adaptar, prepararse e implementar estas tecnologías.

Abstract not available

Cognitive load theory uses the immense size of human long-term memory and the significantly limited capacity of working memory to design instructional methods. Five basic principles: information store principle, borrowing and reorganizing principle, randomness as genesis principle, narrow limits of change principle, and environmental linking and organizing principle explain the cognitive basics of this theory. The theory differentiates between three major types of cognitive load: extraneous load that is caused by instructional strategies, intrinsic cognitive load that results from a high element interactivity material and germane load that is concerned with activities leading to learning. Instructional methods designed in accordance with cognitive load theory rely heavily on the borrowing and reorganizing principle, rather than on the randomness as genesis principle to reduce the imposed cognitive load. As learning fractions incorporates high element interactivity, a high intrinsic cognitive load is imposed. Therefore, learning fractions was studied in the experiments of this thesis. Knowledge held in long-term memory can be used to reduce working memory load via the environmental linking and organizing principle. It can be suggested that if fractions are presented using familiar objects, many of the interacting elements that constitute a fraction might be embedded in stored knowledge and so can be treated as a single element by working memory. Thus, familiar context can be used to reduce cognitive load and so facilitate learning. In a series of randomized, controlled experiments, evidence was found to argue for a contextual effect. The first three experiments of this thesis were designed to test the main hypothesis that presenting students with worked examples concerning fractions would enhance learning if a real-life context was used rather than a geometric context. This hypothesis was tested using both a visual and a word-based format and was supported by the results. The last two experiments were intended to test the context effect using either worked examples or problem solving. The results supported the validity of the previous hypothesis using both instructional methods. Overall, the thesis sheds some light on the advantages of using familiar objects when mastering complex concepts in mathematics.

This thesis investigates the effects of elastic restraint at the supports on the behaviour of shallow concrete arches, and the time-dependent effects of shrinkage and creep of concrete on the nonlinear behaviour of shallow arches. The nonlinear behaviour of shallow circular arches with elastic rotational restraints at each support and subjected to a uniformly distributed radial load is firstly investigated. A virtual work formulation is used to establish both the nonlinear equilibrium equations and the buckling equilibrium equation for shallow arches. The analytical results show that the effects of the stiffness of the rotational restraints on the prebuckling and buckling response are significant. An analytical model is developed for the in-plane elastic stability analysis of shallow parabolic arches with horizontal spring supports subjected to a uniformly distributed vertical load. A parametric study is undertaken using the proposed analytical model. It is found that the effects of the stiffness of the horizontal springs on the prebuckling response, buckling load and buckling behaviour of arches are significant. An analytical model is developed to simulate the time-dependent behaviour of shallow concrete parabolic arches with horizontal spring supports subjected to a sustained loading, and in particular to investigate creep buckling. The time-dependent buckling load and the critical time (or age) of the arches are calculated by using an iterative process based on the proposed model. A systematic parametric study is undertaken, and the results show that the various parameters have a profound effect on the time-dependent buckling load and the prebuckling life of arches. Both short-term and long-term experimental investigations of shallow parabolic tied concrete arches are described and used to validate the analytical models. For the short-term tests, three concrete arches were subjected to a uniformly distributed vertical load and were loaded to failure. For the long-term tests, seven concrete arches were subjected to sustained service loads. The instantaneous and time-dependent deflections were recorded throughout the period of loading, together with the distribution of the horizontal thrust at the supports. Comparisons between the experimental results and the analytical predictions using the analytical models are made to verify the accuracy of the theoretical models.

This thesis explores the design of flexible pipes, buried in shallow trenches with dry sand backfill. The thesis reports the comprehensive analysis of twenty-two full-scale load tests conducted between 1989 and 1991 on pipe installations, mainly within a laboratory facility, at the University of South Australia. The pipes were highly flexible, spirally-wound, uPVC pipes, ranging in diameter from 300 to 450 mm. Guidelines were required by industry for safe cover heights for these pipes when subjected to construction traffic. The tests were designed by, and conducted under the supervision of, the author, prior to the author undertaking this thesis. As current design approaches for pipes could not anticipate the large loading settlements and hence, soil plasticity, experienced in these tests, finite element analyses were attempted. Extensive investigations of the materials in the installations were undertaken to permit finite element modelling of the buried pipe installations. In particular, a series of large strain triaxial tests were conducted on the sand backfill in the buried pipe installations, to provide an understanding of the sand behaviour in terms of critical state theory. Subsequently a constitutive model for the soil was developed. The soil model was validated before implementation in an element of finite element program, AFENA (Carter and Balaam, 1995). Single element modelling of the triaxial tests proved invaluable in obtaining material constants for the soil model. The new element was applied successfully to the analysis of a side-constrained, plate loading test on the sand. The simulation of the buried pipe tests was shown to require three-dimensional finite element analysis to approach the observed pipe-soil behaviour. Non-compliant side boundary conditions were ultimately adjudged chiefly responsible for the difficulty in matching the experimental data. The value of numerical analyses performed in tandem with physical testing was apparent, albeit in hindsight. The research has identified the prediction of vertical soil pressure above the pipe due to external loading as being the major difficulty for designers. Based on the finite element analyses of the field tests, a preliminary simple expression was developed for estimation of these pressures, which could be used with currently available design approaches to reasonably predict pipe deflections.

De manière classique, une caractérisation large signal des amplificateurs de puissance s'effectue en présence d'un signal sinusoïdal CW dans le but de fournir aux concepteurs les informations nécessaires permettant un compromis entre puissance de sortie et rendement en puissance ajoutée. Cependant, Dans les systèmes de communications modernes, les amplificateurs de puissance sont soumis à des signaux de plus en plus complexes (modulations numériques) pour lesquels la linéarité est un critère capital supplémentaire pour les performances globales de ces systèmes. Il est donc indispensable de disposer d'outils de caractérisation fonctionnelle permettant de mesurer l'ensemble de ces critères en présence de ces signaux complexes afin de rendre compte au mieux du comportement du dispositif sous test en le plaçant dans ses conditions réelles de fonctionnement. Ce mémoire présente l'étude et la mise en oeuvre d'un banc de caractérisation fonctionnelle de type "load-pull" pour la mesure de l'ensemble des critères de puissance, rendement et linéarité en présence de tous types de signaux (CW, CW-pulsés, GMSK, QPSK, QAM, etc.). L'ENST dispose d'un banc de mesure "source-pull" et "load-pull" multi-harmonique capable d'optimiser la puissance de sortie et le rendement en puissance ajoutée en mode CW. Ce banc est constitué de réflectomètres six-portes, pour la mesure des impédances et des puissances. Afin de permettre l'utilisation de signaux modulés nous avons implémenté des détecteurs de puissance rapides bas coût à base de diodes Schottky non polarisées pour la détection de puissance au niveau des jonctions six-portes. Pour l'optimisation de la linéarité en plus, nous avons ajouté des modules de contrôle des impédances basses fréquences en entrée et en sortie du composant à tester. Un transistor de puissance MESFET a été testé à la fréquence 1.575 GHz en présence d'un signal modulé QPSK de largeur 1.25 MHz et d'un signal bi-porteuses séparées de 800 kHz pour une polarisation de type A et AB. L'ensemble des mesures effectuées permet d'aboutir aux trois principales conclusions montionnées ci-dessous. Premièrement, les contours "load-pull" d'iso-puissances, d'iso-rendement, d'iso-ACPR et d'iso-produits d'intermodulation d'ordre 3 et 5 montrent que les conditions optimales de puissance, de rendement et de linéarité sont différentes d'où la nécessité de trouver des compromis entre les différents critères. D'autre part, ces résultats montrent qu'il existe une forte corrélation entre l'ACPR et le produit d'intermodulation d'ordre 3 en classe A mais pas en classe AB. De toute façon, quel que soit le degré de corrélation, il apparaît difficile de prédire l'ACPR à partir de la connaissance des produits d'intermodulation. Deuxièmement, l'effet des impédances de source BF n'est notable qu'en classe AB dans la zone de saturation. Cet effet se fait sentir uniquement sur la linéarité (variation de 5 dB pour l'ACPR). Finalement, l'effet des impédances de charge BF apparaît quelle que soit la classe de fonctionnement avec évidemment un effet très prononcé pour les classes fortement non-linéaire comme la classe AB pour laquelle on a observé des variations de 5 à 20 dB pour l'ACPR sur toute la dynamique de mesure. Notons que l'impédance optimale n'est pas obligatoirement un court-circuit, et que cette impédance optimale n'est pas toujours l'impédance minimisant la dissymétrie. Par ailleurs, ces impédances ont également une grande influence sur le rendement (variation observée de 10 points) et sur la puissance de sortie (variation de 1 dB).

<p>Autoliv has developed the Night Vision system, which is a safety system for use incars to improve the driver’s situational awareness during night conditions. It is areal-time system that is able to detect pedestrians in the traffic environment andissue warnings when there is a risk of collision. The timing behaviour of programsrunning on real-time systems is vital information when developing and optimisingboth hardware and software. As a part of further developing their Night Visionsystem, Autoliv wanted to examine detailed timing behaviour of a specific part ofthe Night Vision algorithm, namely the Tracking module, which tracks detectedpedestrians. Parallel to this, they also wanted a reliable method to obtain timingdata that would work for other parts of that system as well, or even other applications.</p><p>A preliminary study was conducted in order to determine the most suitable methodof obtaining the timing data desired. This resulted in a measurement-based approachusing software profiling, in which the Tracking module was measured usingvarious input data. The measurements were performed on simulated hardwareusing both a cycle accurate simulator and measurement tools from the systemCPU manufacturer, as well as tools implemented specifically to handle input andoutput data.</p><p>The measurements resulted in large amounts of data used to compile performancestatistics. Using different scenarios in the input data, we were able to obtain timingcharacteristics for several typical situations the system may encounter duringoperation. By manipulating the input data we were also able to observe generalbehaviour and achieve artificially high execution times, which serves as indicationson how the system responds to irregular and unexpected input data.</p><p>The method used for collecting timing information was well suited for this particularproject. It provided the possibility to analyse behavior in a better waythan other, more theoretical, approaches would have. The method is also easilyadaptable to other parts of the Night Vision system, or other systems, with onlyminor adjustments to measurement environment and tools.</p>