Made available in DSpace on 2014-10-09T12:51:26Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:17Z (GMT). No. of bitstreams: 1 11307.pdf: 4388306 bytes, checksum: c125267132b30edad3f63953bc6e68a5 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

The electrical resistivities of typical AWG20-Class3 and AWG18-Class27 Ni-coated Cu wires were monitored at 400 ºC for times up to 5500 hours; the resistivities increased by 6.9% and 2.3%, respectively. Microstructural analysis of the thermally aged wires revealed evidence of Ni-Cu interdiffusion. Diffusion experiments were performed on Ni-Cu metal foils in the range 400 to 600 ºC; Ni-Cu compositional profiles across the Ni-Cu interface were collected by energy dispersive X-ray spectrometry. Ni-Cu interdiffusivities determined by the Boltzmann-Matano method were typically 2.5×10-17 m2s-1;calculated activation energies for Ni-Cu interdiffusion were between 79.4 and 89.8 kJ•mol-1. Analysis of the available Ni-Cu interdiffusion data suggested a dependence on grain size of the Cu foils used. A concentric-circle, diffusion-resistivity model was developed. Using the experimentally determined Ni-Cu interdiffusion data, it was possible to accurately predict the resistivity of a Ni-coated Cu wire at 400 ºC as a function of time. It is predicted that the resistivity of the AWG20-Class3 wire would increase by 10% after annealing for 48,000 hours at 400 ºC; in contrast, heating an AWG18-Class27 wire for a much longer time of 140,000 hours would incur the same increase in its resistivity. Low temperature co-fired ceramics (LTCC) with a formulation of 11ZnO-10MoO3 (NSZM) were prepared with additions of 0.5 to 2.0 wt% B2O3 via the mixed oxide route. The NSZM samples were sintered at 850-950ºC to over 96% of theoretical density with co-existence of both ZnMoO4 and Zn3Mo2O9 phases. With increasing the addition of B2O3 to NSZM the relative permittivity, dielectric strength and thermal conductivity increased. NSZM prepared with 1.0 wt% B2O3 exhibited a relative permittivity of 11.1, dielectric strength of 17.6 kV•mm-1, linear thermal expansion of 4.7 ppm•K-1and thermal conductivity of 1.3 W•m-1•K-1. The LTCC material is a possible candidate for insulating applications because of its low dielectric constant and adequate dielectric strength. LTCC insulation films were applied to Ni disc substrates by dip coating; the suspensions contained 5 to 20 vol% NSZM ceramic powders, 1.0 wt% B2O3, a polyvinyl butyral (PVB) based binder system, plus solvents and organic additives. A microstructural study of the LTCC films revealed that the insulation thickness varied from 4.3 to 47.3 µm with the ceramic content of starting suspension. The dielectric strength of these films was in the range 24.2 to 43.7 kV•mm-1. These results showed that dip coating is a promising method for applying the LTCC insulation to Ni-based metal substrates. LTCC-insulated wires were manufactured by withdrawing Ni-coated Cu conductors from the suspension, containing 15 vol% ceramic powders, followed by co-firing at 500 ºC. The LTCC-coated wire exhibited an insulation thickness of 40.3 µm and a breakdown voltage of 798 V. These results suggest that the LTCC-coated wire is a possible candidate for use in high temperature machine windings.

Research evaluating the surgical repair of femoral neck fractures in dogs is limited. This study evaluated the in vitro mechanical properties of canine femoral neck fractures stabilized with two medium Orthofix® Partially-threaded Kirschner Wires (Orthofix pins), a 2.7 mm cortical bone screw placed in lag fashion with anti-rotational Kirschner wire (K-wire), and three 1.1 mm divergent K-wires. This study compared the mean compressive pressure, compressive force and area of compression created by the insertion the Orthofix pins and a 2.7 mm cortical bone screw placed in lag fashion. Monotonic testing was used to quantify mechanical strength and pressure sensitive film was used to quantify compression. There was no significant difference in the stiffness or load to failure for the three repair methods evaluated. There was no significant difference in the compressive pressure, compressive force or area of compression in osteotomies stabilized with Orthofix pins and 2.7 mm bone screws.

Indiana University-Purdue University Indianapolis (IUPUI) / Ideal orthodontic springs are able to provide a controlled moment-to-force (M/F) ratio and a low load deflection rate. A great deal of research has gone into describing force systems generated by orthodontic springs. Most studies investigating the force system generated by T-loops have used rigid fixation for the spring ends. This is practical for laboratory studies, but it does not truly represent clinical situations in which orthodontic brackets are used to anchor spring ends. Results from laboratory studies have been applied to clinical situations without regard to what effect, if any, the method of end fixation may have. It is the goal of this study to determine the effects of spring fixation on generated force systems. The springs were held by rigid fixation and bracket ligation with either elastomeric or steel ligature ties. Comparison of these fixation methods was made by testing T-loops of different dimensions, with and without heat treatment at various activation distances. In theory, the wire is ligated rigidly against the bracket, so that the combination acts as a single unit by rigid fixation. Thus, there should be no difference between the generated force systems when spring ends are held by rigid fixation, or when they are held in place with orthodontic brackets and ligated by either elastomeric or steel ligature ties. However, the results indicate that are significant differences among the methods of fixation for each spring variation and heat treatment. The rigid fixation method consistently produced smaller moments and M/F ratios for all springs with every activation and heat treatment combination.

An 8 blade, 7 passage linear compressor cascade with tip leakage was built. The flowfield downstream of the cascade was measured using four sensor hot-wire anemometers, from which the mean velocity field , the turbulence stress field and velocity spectra were obtained. Oil flow visualizations were done on the endwall underneath the blade row. Also studied were the effects of tip gap height, and blade boundary layer trip variations. The results revealed the presence of two distinct vortical structures in the flow. The tip leakage vortex is formed due to the roll up the tip flow as it exits the tip gap region. A second vortex, counter-rotating when compared to the tip leakage vortex, is formed due to the separation of the flow leaving the tip gap from the endwall. Increasing the tip gap height increases the strength of the tip leakage vortex, and vice versa. Changing the boundary layer trip had no effect on the flowfield due the fact that boundary layers on the blade surface had separated. As the vortices develop downstream, the tip leakage vortex convects into the passage "pushing" the counter rotating vortex with it. As it does so, the tip leakage vortex dominates the endwall flow region, and is responsible for most of the turbulence present in the downstream flow field. This turbulence production is primarily due to axial velocity gradients in the flow, and not due to the circulatory motion of the vortex. Velocity spectra taken in the core of the vortex show the broadband characteristics typical of such turbulent flows. The results also revealed that the wakes of the blades exhibit characteristics of two-dimensional plane wakes. The wake decays much faster than the vortex. Velocity spectra taken in the wake region show the broadband characteristics of such turbulent flows, and also suggest that there might be some coherent motion in the wake as a result of vortex shedding from the trailing edge of the blades. The present study reveals the complex nature of such flows, and should provide valuable information in helping to understand them. This study was made possible with support from NASA Langley through grant number NAG-1-1801 under the supervision of Dr. Joe Posey / Master of Science

O objetivo da presente pesquisa foi avaliar o comportamento da força em função da deflexão na ativação e desativação de fios ortodônticos de níquel-titânio, de secção circular (.016"). Ensaiaram-se três marcas de fio (Forestadent, GAC e Morelli). As temperaturas de ensaio foram três (32, 37 e 42ºC). As ativações máximas foram até 1, 2, 3 e 4mm. O espécime de ensaio consistiu de uma placa de resina acrílica, sobre a qual eram fixados cilindros metálicos por meio de parafusos, simulando dentes, com distribuição semelhante aos dentes naturais. Sobre os cilindros foram cimentados os bráquetes (distância de 8mm entre eles). Sobre os bráquetes era fixado, conforme clinicamente, o arco do fio em ensaio. O “dente" correspondente ao incisivo central era liberado (desparafusado) para poder se deslocar livremente no sentido vestíbulo-lingual durante os ensaios e o fio poder sofrer a deflexão. O conjunto era levado à máquina de ensaio (Instron), com câmara de temperatura controlada. Durante o ensaio a velocidade de deslocamento para a deflexão foi de 0,5mm/min. Durante a ativação e desativação as forças foram registradas de 0,10 em 0,10mm de deflexão. Por meio de software esses valores eram impressos numericamente e em gráficos da força em função da ativação/desativação. Com 4 ativações máximas, 3 marcas de fios e 3 temperaturas obtiveram-se 36 condições experimentais e com 5 repetições (n=5) foram feitos 180 ensaios. Os gráficos obtidos mostraram uma não linearidade entre força e deflexão e com ativação de 1 e 2mm não foi detectado platô de superelasticidade, mas que foi observado na desativação, das ativações máximas de 3 e 4mm. Dos gráficos e tabelas foram extraídos valores específicos para serem analisados e comparados: 1) força máxima de ativação; 2/3) diminuição da força na desativação de 0,20mm e 0,70mm (esta só na ativação de 3 e 4mm); 4/5) extensão e forças no platô (apenas nas ativações máximas de 3 e 4mm); 6/7/8) desativação até alcançar 50g de força, a partir de 0,80 e 1,80mm (ativações de 1 e 2mm), ou no final dos platôs (ativações de 3 e 4mm), a força ao iniciar-se a desativação, afastamento da origem ao registrar 50g de força; 9) deformação permanente ao atingir a força zero. As principais conclusões foram: a força de ativação máxima aumentou com o aumento desta e da temperatura, o material Morelli apresentou a menor e o GAC a maior; a diminuição da força máxima foi tanto maior quanto maior a ativação; apenas as ativações até 3 e 4mm apresentaram platôs de superelasticidade e que foram bem mais extensos na ativação de 4mm, que por sua vez apresentaram menor força; em todos os ensaios for observada deformação permanente / The purpose of this study was to evaluate the behaviour of force as function of loading and unloading orthodontic nickel-titanium wires. Three defferent brands (Forestadent, GAC and Morelli) were tested. Testing temperature were 32, 37 and 42 o C. Loading were up to 1, 2, 3 and 4mm deflection. Specimens consisted of a acrylic base where were fixed metallic cylinders simulating teeth. Over the teeth were fixed brackets to maintain arch wire in position. Tooth corresponding to central incisor was loosened and at the correspondig bráquete was applied the force in an Instron equipment, with temperature control. Head speed was 0.5mm/min. During loading and unloading forces were read every 0.10mm deflection and registered. The pair values of forces and deflections were also plotted as graphs. With 4mm maximum loading, 3 brands and 3 temperatures were obtained 36 experimental conditions and with 5 repetitions (n=5) were performed 180 tests. Graphs showed that there is no linearity between forces and deflection and with loading up to 1 and 2mm was not obtained the formation of superelasticity plateaus. But they were observed with 3 and 4mm deflections. From the graphs and registered numerical values for each specimen were selected special values to be analysed: 1) maximum loading force; 2/3) force decrease during unloading 0.20 and 0.70mm (the last only at 3 and 4mm activation); 4/5) exte nsions and forces at plateaus (only for 3 and 4mm activations); 6/7/8) extension until 50g force, since 0.80 and 1.80mm (respectively activation up to 1 and 2mm), or ends of plateau (3 and 4mm activation). In these conditions, the force at beginning unloading. Distance of origin at register 50g force; 9) permanent deformation at zero force. The main conclusions were: maximum loading forces increase with deflection and temperature increases, and brand Morelli presented the smallest force and GAC the greatest; the decrease of forces with unloading was as larger as activation force; only the activation until 3 and 4mm presented superelasticity plateaus, and was longer with 4mm activation, but it presented lower force at plateaus; in all tests was noted permanent deformation

O objetivo da presente pesquisa foi avaliar o comportamento da força em função da deflexão na ativação e desativação de fios ortodônticos de níquel-titânio, de secção circular (.016”). Ensaiaram-se três marcas de fio (Forestadent, GAC e Morelli). As temperaturas de ensaio foram três (32, 37 e 42ºC). As ativações máximas foram até 1, 2, 3 e 4mm. O espécime de ensaio consistiu de uma placa de resina acrílica, sobre a qual eram fixados cilindros metálicos por meio de parafusos, simulando dentes, com distribuição semelhante aos dentes naturais. Sobre os cilindros foram cimentados os bráquetes (distância de 8mm entre eles). Sobre os bráquetes era fixado, conforme clinicamente, o arco do fio em ensaio. O “dente” correspondente ao incisivo central era liberado (desparafusado) para poder se deslocar livremente no sentido vestíbulo-lingual durante os ensaios e o fio poder sofrer a deflexão. O conjunto era levado à máquina de ensaio (Instron), com câmara de temperatura controlada. Durante o ensaio a velocidade de deslocamento para a deflexão foi de 0,5mm/min. Durante a ativação e desativação as forças foram registradas de 0,10 em 0,10mm de deflexão. Por meio de software esses valores eram impressos numericamente e em gráficos da força em função da ativação/desativação. Com 4 ativações máximas, 3 marcas de fios e 3 temperaturas obtiveram-se 36 condições experimentais e com 5 repetições (n=5) foram feitos 180 ensaios. Os gráficos obtidos mostraram uma não linearidade entre força e deflexão e com ativação de 1 e 2mm não foi detectado platô de superelasticidade, mas que foi observado na desativação, das ativações máximas de 3 e 4mm. Dos gráficos e tabelas foram extraídos valores específicos para serem analisados e comparados: 1) força máxima de ativação; 2/3) diminuição da força na desativação de 0,20mm e 0,70mm (esta só na ativação de 3 e 4mm); 4/5) extensão e forças no platô (apenas nas ativações máximas de 3 e 4mm); 6/7/8) desativação até alcançar 50g de força, a partir de 0,80 e 1,80mm (ativações de 1 e 2mm), ou no final dos platôs (ativações de 3 e 4mm), a força ao iniciar-se a desativação, afastamento da origem ao registrar 50g de força; 9) deformação permanente ao atingir a força zero. As principais conclusões foram: a força de ativação máxima aumentou com o aumento desta e da temperatura, o material Morelli apresentou a menor e o GAC a maior; a diminuição da força máxima foi tanto maior quanto maior a ativação; apenas as ativações até 3 e 4mm apresentaram platôs de superelasticidade e que foram bem mais extensos na ativação de 4mm, que por sua vez apresentaram menor força; em todos os ensaios for observada deformação permanente / The purpose of this study was to evaluate the behaviour of force as function of loading and unloading orthodontic nickel-titanium wires. Three defferent brands (Forestadent, GAC and Morelli) were tested. Testing temperature were 32, 37 and 42 o C. Loading were up to 1, 2, 3 and 4mm deflection. Specimens consisted of a acrylic base where were fixed metallic cylinders simulating teeth. Over the teeth were fixed brackets to maintain arch wire in position. Tooth corresponding to central incisor was loosened and at the correspondig bráquete was applied the force in an Instron equipment, with temperature control. Head speed was 0.5mm/min. During loading and unloading forces were read every 0.10mm deflection and registered. The pair values of forces and deflections were also plotted as graphs. With 4mm maximum loading, 3 brands and 3 temperatures were obtained 36 experimental conditions and with 5 repetitions (n=5) were performed 180 tests. Graphs showed that there is no linearity between forces and deflection and with loading up to 1 and 2mm was not obtained the formation of superelasticity plateaus. But they were observed with 3 and 4mm deflections. From the graphs and registered numerical values for each specimen were selected special values to be analysed: 1) maximum loading force; 2/3) force decrease during unloading 0.20 and 0.70mm (the last only at 3 and 4mm activation); 4/5) exte nsions and forces at plateaus (only for 3 and 4mm activations); 6/7/8) extension until 50g force, since 0.80 and 1.80mm (respectively activation up to 1 and 2mm), or ends of plateau (3 and 4mm activation). In these conditions, the force at beginning unloading. Distance of origin at register 50g force; 9) permanent deformation at zero force. The main conclusions were: maximum loading forces increase with deflection and temperature increases, and brand Morelli presented the smallest force and GAC the greatest; the decrease of forces with unloading was as larger as activation force; only the activation until 3 and 4mm presented superelasticity plateaus, and was longer with 4mm activation, but it presented lower force at plateaus; in all tests was noted permanent deformation

This thesis reports our work on transport related problems in mesoscopic physics using analytical as well as numerical techniques. Some of the problems we studied are: effect of interactions and static impurities on the conductance of a ballistic quantum wire[1], aspects of quantum charge pumping [2, 3, 4], DC and AC conductivity of a (dissipative) quantum Hall (edge) line junctions[5, 6], and junctions of three or more Luttinger liquid (LL)quantum wires[7]. This thesis begins with an introductory chapter which gives a brief glimpse of the underlying physical systems and the ideas and techniques used in our studies. In most of the problems we will look at the physical effects caused by e-e interactions and static scattering processes. In the second chapter we study the effects of a static impurity and interactions on the conductance of a 1D-quantum wire numerically. We use the non-equilibrium Green’s function (NEGF) formalism along with a self-consistent Hartree-Fock approximation to numerically study the effects of a single impurity and interactions between the electrons (with and without spin) on the conductance of a quantum wire [1]. We study the variation of the conductance with the wire length, temperature and the strength of the impurity and electron-electron interactions. We find our numerical results to be in agreement with the results obtained from the weak interaction RG analysis. We also discover that bound states produce large density deviations at short distances and have an appreciable effect on the conductance which is not captured by the renormalization group analysis. In the third chapter we use the equations of motion (EOM) for the density matrix and Floquet scattering theory to study different aspects of charge pumping of non-interacting electrons in a one-dimensional system. We study the effects of the pumping frequency, amplitude, band filling and finite bias on the charge pumped per cycle, and the spectra of the charge and energy currents in the leads[2]. The EOM method works for all values of parameters, and gives the complete time-dependences of the current and charge at any site of the system. In particular we study a system with oscillating impurities at several sites and our results agree with Floquet and adiabatic theory where these are applicable, and provides support for a mechanism proposed elsewhere for charge pumping by a traveling potential wave in such systems. For non-adiabatic and strong pumping, the charge and energy currents are found to have a marked asymmetry between the two leads, and pumping can work even against a substantial bias. We also study one-parameter charge pumping in a system where an oscillating potential is applied at one site while a static potential is applied in a different region [3]. Using Floquet scattering theory, we calculate the current up to second order in the oscillation amplitude and exactly in the oscillation frequency. For low frequency, the charge pumped per cycle is proportional to the frequency and therefore vanishes in the adiabatic limit. If the static potential has a bound state, we find that such a state has a significant effect on the pumped charge if the oscillating potential can excite the bound state into the continuum states or vice versa. In the fourth chapter we study the current produced in a Tomonaga-Luttinger liquid (TLL) by an applied bias and by weak, point-like impurity potentials which are oscillating in time[4]. We use bosonization to perturbatively calculate the current up to second order in the impurity potentials. In the regime of small bias and low pumping frequency, both the DC and AC components of the current have power law dependences on the bias and pumping frequencies with an exponent 2K−1 for spinless electrons, where Kis the interaction parameter. For K<1/2, the current grows large for special values of the bias. For non-interacting electrons with K= 1, our results agree with those obtained using Floquet scattering theory for Dirac fermions. We also discuss the cases of extended impurities and of spin-1/2 electrons. In chapter five, we present a microscopic model for a line junction formed by counter or co-propagating single mode quantum Halledges corresponding to different filling factors and calculate the DC [5] and AC[6] conductivity of the system in the diffusive transport regime. The ends of the line junction can be described by two possible current splitting matrices which are dictated by the conditions of both lack of dissipation and the existence of chiral commutation relations between the outgoing bosonic fields. Tunneling between the two edges of the line junction then leads to a microscopic understanding of a phenomenological description of line junctions introduced by Wen. The effect of density-density interactions between the two edges is considered exactly, and renormalization group (RG) ideas are used to study how the tunneling parameter changes with the length scale. The RG analysis leads to a power law variation of the conductance of the line junction with the temperature (or other energy scales) and the line junction may exhibit metallic or insulating phase depending on the strength of the interactions. Our results can be tested in bent quantum Hall systems fabricated recently. In chapter six, we study a junction of several Luttinger Liquid (LL) wires. We use bosonization with delayed evaluation of boundary conditions for our study. We first study the fixed points of the system and discuss RG flow of various fixed points under switching of different ‘tunneling’ operators at the junction. Then We study the DC conductivity, AC conductivity and noise due to tunneling operators at the junction (perturbative).We also study the tunneling density of states of a junction of three Tomonaga-Luttinger liquid quantum wires[7]. and find an anomalous enhancement in the TDOS for certain fixed points even with repulsive e-e interactions.

Neste trabalho investigamos a estrutura eletrônica de fios quânticos formados por distribuição de carga espacial, obtidos a partir da incorporação de dopantes nos degraus que delimitam planos vicinais em semicondutores. Estudos experimentais recentes, que combinam o crescimento epitaxial em planos vicinais (terraços) sobre o GaAs com as técnica de dopagem planar abrupta, sugerem que a incorporação do dopante (Silício) ocorre preferencialmente ao longo das linhas que delimitam os planos vicinais deste semicondutor. Baseados em resultados teóricos recentes, que sugerem que a aproximação semiclássica de Thomas-Fermi é capaz de reproduzir o potencial auto-consciente de sistemas eletrônicos criados a partir de distribuições de carga de origem puramente espacial, vários efeitos tais como: difusão de dopantes, temperatura finita e densidade residual de aceitadores puderam ser investigados neste nível de aproximação. As equações de Kohn-Sham na aproximação de densidade local (T=0K) foram também empregadas com o propósito de avaliar-se a possível influência de efeitos de não localidade do funcional energia cinética e efeitos de muitos corpos (troca e correlação) que foram ignorados pela abordagem semiclássica. / In this work we investigate the electronic structure of space-charge quantum wires obtained via attachment of donors in misorientation steps of semiconductor vicinal surfaces. Recent experimental studies, combining epitaxial growth on GaAs (100) vicinal surfaces (terraces) with the ?-doping technique, suggests that the incorporation of Silicon donors is preferential along the lines that delimit the vicinal terraces in this semiconductor. Based on recent theoretical results suggesting that the Thomas-Fermi is a reliable approximation for the self-consistent potential fo space-charge layers, we have employed this approximation to study the possible influence of various factors such as diffusion of dopants, finite temperature and residual density of acceptors on the electronic structure of these wires. The Kohn-Sham equations, within the local density approximation (T=0K), were also solved as the propose of evaluating the influence of effects due to the non-locality of the kinectic energy densities functional and many body effects (exchange and correlation) that were ignored in the semiclassical approximation.

Investigamos os efeitos de tamanho e do potencial de confinamento finito V0 nas taxas de espalhamento de absorção e de emissão de elétrons interagindo com os fônons longitudinais ópticos (fônons LO) de um fio quântico cilíndrico de GaAs à temperatura ambiente. Calculamos as taxas de espalhamento inter e intra-sub-banda e a taxa de espalhamento total para uma temperatura de 300 K, pois nesta temperatura o mecanismo de espalhamento dominante em semicondutores do tipo III-V é aquele devido aos fônons LO. Qualitativamente a taxa de emissão intra-sub-banda neste sistema tem o mesmo comportamento da sua correspondente em estruturas 2D. Para a absorção encontramos uma mudança suave de comportamento da taxa de absorção intra-sub-banda quando o raio do fio é da ordem do diâmetro do polaron (ou seja, da ordem de 80 ANGSTROM). Para raios pequenos ela tem um comportamento similar ao do bulk, mas para raios maiores ela cresce até atingir um máximo e depois cai monotonicamente à medida que aumentamos a energia do portador. Vimos que, o tamanho do fio e o potencial de confinamento têm grande influência na taxa de espalhamento total. / We investigated the size effects and the effects of the finite confining potential V0 on the absorption and emission scattering rates of electron interacting with longitudinal optical (LO) phonons for a cylindrical GaAs quantum wire. We calculated the inter and intrasubband total scattering rate for a temperature of 300K, because in this temperature the dominant mechanism of scattering in semiconductors III-V is that due LO phonons. Qualitatively the intrasubband emission scattering rate in this system has the same behavior of the correspondent in 2D structures. For absorption we found a smooth change in the intrasubband absorption scattering rate behavior when the radius the wire is near the polaron diameter (ie, about 80 ANGSTROM). For small radius the scattering rate has a similar behavior as that of the bulk, but for large radius it increases until reach a maximum and after ir drops monotonicaly with increase of carrier energy. We found that the size effect and the confining potential have a large influence in the total scattering rate