M.Com. (Business Management) / Please refer to full text to view abstract

Ph.D. (Economics) / Please refer to full text to view abstract

Este trabalho aplica metodologia de Wang (2003a, 2003b) para definir uma nova medida do produto de bancos brasileiros. Acredita-se que tal medida seja superior às comumente utilizadas na literatura por se tratar de uma variável de fluxo, incorporar os depósitos bancários de maneira teoricamente embasada e levar em consideração a exposição ao risco. Esta nova variável de produção é utilizada na estimação de fronteiras estocásticas de produção e custo para o setor bancário brasileiro, visando a mensurar sua eficiência técnica e econômica, assim como a magnitude de suas economias de escala. As fronteiras estimadas apresentam especificação dada pela forma funcional flexível de Fourier e incorporam variáveis determinantes da eficiência. Os resultados apontam para uma acentuada ineficiência do setor bancário, assim como para a ocorrência de retornos crescentes de escala. / This work applies the Wang (2003a, 2003b) methodology to define Brazilian banks\' output. It is believed that this new output measure is superior to the ones commonly used by the literature, since it treats output as a flow variable, provides a theoretical basis for defining the role of deposits and takes account of risk exposure in defining output. This new measure is applied to the estimation of stochastic production and cost frontiers for the Brazilian banking sector, aiming at measuring its technical and economic efficiency, and also the size of its scale economies. The frontiers follow a Fourier flexible functional form especification and incorporate efficiency determinants. The results point to the existence of high inneficiency in the banking industry, and also to the ocurrence of increasing returns to scale.

Membrane wings are used both in nature and small aircraft as lifting surfaces. For these low Reynolds number applications, separated flows are common and are the main sources of unsteadiness. Adaptability of the membrane wing is known to improve the vehicle performance; and membrane compliancy in animal wings such as bats contributes significantly to their astonishing flights. Yet, the aerodynamic characteristics of the membranes are still largely unknown. An experimental study of flexible membranes at low Reynolds numbers was undertaken. Two-dimensional membrane aerofoils were investigated, with particular focus on the unsteady aspects. Membrane deformation, flow fields and fluid-structure interaction were examined over a range of angles of attack and freestream velocities. A comprehensive study of the effect of membrane pre-strain and excess length was carried out. Low aspect ratio membrane wings were investigated for rectangular and nonslender delta wings. The amplitude and mode of membrane vibration are found to be dependent mainly on the location and the unsteadiness level of the shear layer. The results indicate a strong coupling of unsteady flow with the membrane oscillation. With increasing Reynolds number, the separated shear layer becomes more energetic and closer to the surface. The membrane not only has smaller size of the separation region compared to a rigid aerofoil, but also excites the roll-up of large vortices which might lead to delayed stall. The membrane aerofoils with excess length exhibit higher vibration modes, earlier roll-up and smaller separated region, compared to the ones with pre-strain. This smaller separated region delays the onset of membrane vibrations to a larger incidence. For the low aspect ratio membrane wings, the combination of tip vortices and leading-edge vortex shedding results in a mixture of streamwise and spanwise vibrational modes. The flexibility benefits the rectangular wing more than the delta wing by increasing the maximum normal force and the force slope by a larger amount. Similar to the two-dimensional membrane aerofoils, the Strouhal numbers of the oscillations are on the order of unity, and there is a coupling with the wake instabilities in the post-stall region. Stronger tip vortices on membrane wings contribute significantly to total lift enhancement.

With the prolonged lifespan of the average person, the number of hospital stays have increased. Currently, pressure ulcers are one of the most severe complications associated with prolonged hospital stay. The protocol in today€™s hospital is to rotate bedridden patients once every two hours to prevent pressure ulcers. This puts a strain on attending nurses as the risk of a pressure ulcer for a patient is not universal and therefore, a universal preventative protocol is not the most effective solution. This thesis describes the circuit design and physical implementation of a device to address the issue of pressure ulcers. The device has the form factor of a patch to be placed on specific, at risk areas of the human body. The device was designed and prototyped first on a rigid structure and then on a flexible printed circuit board substrate. A calibration procedure was developed to reduce part to part variability inherent to the pressure sensor. The resistance measurement was achieved through a novel approach including the use of a timer removing the need for an analog-to-digital converter. A seven hour experiment was conducted with live, animal subjects to measure the pressure and temperature of at risk areas of the body. The results of the experiment successfully prove the fundamental approach outlined in this thesis and justify continued research and refinement into the product design.

- 1 - Flexible forms of employment Abstract This diploma thesis deals with flexible forms of employment, as already mentioned in its title. The diploma thesis focuses mainly on the Czech legislation of these forms. However, the text also contains chapters dealing with flexible forms of employment that are used at the level of the European Union and the United States of America. The aim of this thesis is to map the current situation in the field of atypical forms of employment applied in the legislative framework of the Czech labor market, finding out whether and how these forms are used in practice, description limiting factors preventing their further development and proposing possible changes to the legislation for more effective application. The thesis itself consists of the following five basic sections: General issues of flexible forms of employment Definition of flexible forms of employment Types of flexible forms of employment Development and future of flexible forms of employment Flexible forms of employment in practice Of course, these sections are further developed. The main parts of the thesis are sections number 3 and 5. Section Three includes defining and describing individual flexible forms of employment. The forms that the Czech legal system knows are discussed in more detail. The...

Le grand intérêt des fréquences THz (0.1-10 THz) pour l’imagerie, la spectroscopie et les communications sans fils a conduit à un important développement de dispositifs pour la génération et la détection d’ondes THz. Les photodiodes à transport unipolaire font partie des principales sources grâce à leur comportement large bande (0-3 THz), leur fonctionnement à température ambiante, leur longueur d’opération à 1.55 µm et leur taille compacte. Le plus grand inconvénient est la leur faible puissance RF générée à haute fréquence (ordre du µW à 1 THz). Une technique pour l’augmenter consiste à utiliser des puissances optiques en entrée plus élevées. Par contre, cette solution peut conduire à leur destruction due à l’échauffement, surtout en cas d’absorption non voulue.Dans la première partie de la thèse un contact électrique basé sur un réseau sub-longueur d’onde a été développé pour réduire ce problème. Cette solution donne des bonnes propriétés électriques, optiques et thermiques avec un procédé plus simple en termes de fabrication et caractérisation par rapport aux travaux précédents.Un deuxième inconvénient est relié à leur caractère non-linéaire qui conduit à un bruit à basse fréquence à cause du large spectre des sources optiques. Ce problème est critique dans le cas de mesures à haute fréquence avec des détecteurs incohérentes car les puissances RF sont très faibles.Dans la deuxième partie de la thèse un filtre passe-haut avec une haute transparence et large bande a été développé sur un diélectrique avec faible pertes aux fréquences THz. Le procédé développé peut être utilisé pour des dispositifs en espace libre grâce aux propriétés optique du diélectrique. / The increasing interest in the THz region (0.1-10 THz) for applications like imaging, spectroscopy and wireless communications is leading to a strong development of devices for the generation and detection of THz waves. Uni-travelling carrier photodiodes (UTC-PDs) are one of the main sources due to their broadband behavior (0-3 THz), room temperature operation, driving wavelength of 1.55 µm and compactness. Their main drawback comes from the low output RF powers at high frequencies (order of µW at 1 THz). A technique to increase their RF powers consists in using higher optical driving powers. However, this solution may lead to their failure because of heating, especially in case of unwanted absorption.In the first part of the thesis an electrical contact based on sub-wavelength apertures has been developed to reduce this issue. This solution has been shown valuable under multiple aspects. It provides good electrical, optical and thermal properties, while leading to an easier process in terms of fabrication and characterization with respect to previous works.A second drawback of UTC-PDs is due to their non-linear behavior which leads to a noise at low frequency because of the broad spectrum of the driving optical signals. This issue is critical for measurements at high frequencies with incoherent detectors due to the low RF powers to be detected.In the second part of the thesis a high-transparency broadband high-pass mesh filter has been developed on a novel low-loss dielectric material to filter-out this noise. The developed process can be exploited in other free-space devices like metamaterials due to the remarkable properties of this dielectric at THz frequencies.

L’électronique flexible est une thématique en plein essor, et impacte de nombreux secteurs applicatifs. L’objectif de cette thèse est de développer des composants sur substrats flexibles, pour des applications dans le domaine des radiofréquences. Elle est constituée de deux grandes parties : (i) la fabrication de composants passifs RF en utilisant la technologie d’impression par jet d’encre ; (ii) la fabrication de transistors graphène sur substrats flexibles. Ces travaux sont partiellement intégrés au projet Européen flagship GRAPHENE, et au projet ANR GRACY. La technique d’impression jet d’encre est particulièrement adaptée à la fabrication de composants sur substrats flexibles. L’un des challenges de cette approche technologique est de pouvoir atteindre une définition et une résolution adaptée au fonctionnement en régime radiofréquence. Le travail mené dans cette thèse a permis de réaliser des lignes homogènes de largeur minimale de 50 µm, et une résolution (distance entre 2 lignes de l’ordre de 15 µm. Différents composants passifs ont été fabriqués et caractérisés avec succès, et ce même en appliquant des contraintes en flexion aux dispositifs.Nous avons également développé et optimiser un procédé technologique, adapté à la fabrication de transistors à effet de champ à base de graphène (GFET), sur substrat flexible. Ce procédé présente un bilan thermique faible, et est basé sur l’utilisation d’une grille arrière à base d’aluminium dont l’oxyde naturel sert d’oxyde de grille. De nombreux transistors ont été fabriqués sur substrat kapton, et avec un bon rendement. Les meilleures performances en termes de fréquence de coupure du gain en courant (ft=39 GHz) et la fréquence maximale d’oscillation (fmax=13GHz) ont été mesurées sur un transistor de longueurs de grille Lg=100 nm et un développement de 12µm. Cette performance est à l’état de l’art de GFET flexibles. Ces performances sont conservées pour des contraintes atteignant 0,5%. / Flexible electronic has drawn growing attentions for past several years due to its largely potential applications. The objective of my PhD work is to develop devices based on flexible substrate, for RF applications. There are mainly two parts involved: (i) fabrication of passive devices (transmission lines, antenna, etc) using inkjet printing technology; (ii) fabrication of graphene field effect transistors on flexible substrate using graphene growth by CVD technique. This work is partially involved in the European Flagship program GRAPHENE, and the ANR program GRACY. Inkjet printing is a promising fabrication technology for flexible electronics. The challenge of this technology is the quality and reliability of printed patterns in terms of geometry. Based on optimized printing parameters, the structures of coplanar wave guide (CPW) transmission lines with nice printing quality were realized (definition of 50 µm, resolution down to 20 µm). The RF characterization of these transmission lines combining the considerations of geometric dimensions, sintering temperature, and substrate bending are presented. The outstanding electrical and mechanical properties make graphene suitable for flexible transistors. In this thesis, we have developed and optimized a new low temperature process based on back-gated structure either on rigid substrate than on flexible substrate (here kapton). From flexible transistors, we report as measured current gain cut-off frequency ( ft-DUT ,without any de-embedding) of 39 GHz and maximum oscillation frequency (fmax) of 13 GHz in devices with 100 nm gate length and 12 µm gate width. This result is at the level of the state of art for flexible GFETs.

Memoria para optar al título de Ingeniero Civil / Uno de los grandes problemas de las estructuras que se requieren en grandes espacios libres de elementos en su interior o que posean grandes luces, más específicamente en el ámbito minero, es que estos requieren una gran cantidad de acero al necesitar ser sistemas muy robustos. Esto es un problema principalmente económico debido al alto costo asociado a materiales. Es por esto que se han desarrollado estructuras más ligeras para resolver esta problemática. Muchas de estas soluciones, que están siendo aplicadas en el mundo, contemplan sistemas auto-sostenibles de cables y membranas tensadas flexibles. Se abordarán todos los aspectos de los cables y membranas, desde sus componentes básicos, materiales y normas que los controlan, ejemplos destacados y métodos de análisis para luego poder aplicar esta experiencia en un ejemplo práctico de un Stockpile minero, en el cual se comparará una solución convencional con elementos rígidos de acero y método constructivo actual con 2 soluciones aplicando los principios aprendidos de estructuras ligeras. Dentro de la experiencia se verán todas las dificultades que implica tratar con estructuras de cables o membranas a tener en consideración si se desea en un futuro trabajar con estos sistemas. La finalidad de esta memoria es poder extrapolar estas experiencias en la realidad de Chile y más específico para la gran minería. Aquí se entregan las bases y consideraciones que debe tener alguien para poder materializar un proyecto con estas características.

A new Direct Simulation fibre model was developed which allowed flexibility in the fibre during the simulation of fibre suspension flow.This new model was called the �Chain-of-Spheres �model.It was hypothesised that particle shape and deformation could signi ficantly a ffect partic e dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that flexible fibres in shear flow resulted in an order of 7 −10% bulk relative viscosity increase over the �rigid �fibre result.Results also es- tablished the existence of a relationship between bulk viscosity and particle sti ffness.In comparison with experimental results,other more conventional rigid fibre based methods appeared to underpredict relative viscosity.The flexible fibre method thus markedly improved the ability to estimate relative viscosity.The curved rigid fibre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid fibre suspension.With such sensitivity to fibre shape,this result has some important implications for the quality of fibre inclusions used.For consistent viscosity,the shape quality of the fibres was shown to be important. The �Chain of Spheres �simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian flow field.This new �3D Particle �simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex flow fields.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear flow. In later sections, the simulation demonstrated inertia-induced particle migration inthe non-linear shear gradient Couette cylinder flow,and was used to predict the fibre orientation within a diverging channel flow.The performance of the method was verified against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great fidelity. The broad aim of this research was to better understand the microstruc- tural dynamics within the fibre-filled suspension and from it,derive useful engineering information on the bulk flow of these fluids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may bene fit from the new approaches and algorithms developed here.