Thesis (Ph. D.)--Drexel University, 2005. / Includes abstract and vita. Includes bibliographical references (leaves 146-154).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 71-73). Also available via the Internet.

A técnica de análises PIXE (Particle Induced X-ray Emission) de alvos finos é rotineiramente usado no Instituto de Física da Universidade de São Paulo (USP) pelo Lamfi (Laboratório de Materiais e Feixes Iônicos) em análises quantitativas elementares. A calibração do arranjo experimental do Lamfi é realizada através da irradiação de filmes finos padrões evaporados, sendo o rendimento de produção de raios X ajustado a partir deprimeiros princípios. Em análises PIXE de alvos espessos (TTPIXE), a composição daparticular amostra introduz efeitos de perda de energia das partículas incidentes e autoabsorção dos raios X produzidos. Estes efeitos são inexistentes na análise PIXE de alvosfinos. Paradoxalmente há a necessidade de se conhecer a composição da amostra, paracomputar estes efeitos, numa análise elementar quantitativa de alvos espessos. Este trabalhopropõe a diluição de amostras sólidas numa matriz conhecida onde as características de perda de energia das partículas incidentes e auto absorção da radiação produzida estejam caracterizadas (exemplo: ácido bórico, grafite) e supostamente não sofram alterações devido à introdução da amostra (diluição). Para o cálculo do rendimento de produção de raios X em análises TTPIXE é proposto um fator de correção para alvos espessos, dependente exclusivamente da matriz diluidora, aplicado ao rendimento de produção de raios X de alvos finos. Este procedimento viabiliza a utilização da curva de resposta para análises de alvos finos, já calibrada, do arranjo. Utilizando os modelos mais aceitos para o poder de freamento para prótons incidentes, seções de choque de produção de raios X e coeficientes de absorção de radiação pela matéria, o software (Clara) foi desenvolvido para o cálculo do rendimento de produção de raios X em alvos espessos, bem como os fatores de correção para dado raio X e determinada matriz. Alvos espessos foram confeccionados a partir de amostra padrão de referência (SRM-IAEA356 Marine sediment) para verificar os valores calculados pelo Clara e da metodologia de análise proposta. Os valores experimentais encontram-se em concordância com os valores certificados para um coeficiente de intervalo de confiança de 95% considerando o novo limite de detecção imposto pela diluição. Um roteiro para preparação de alvos espessos a partir de amostras sólidas, bem como a descrição do arranjo experimental, estão inclusos. / Thin film PIXE (Particle Induced X-ray Emission) analysis is been routinely used in the Institute of Physics of the University of Sao Paulo (USP) for quantitative analysis of materials. The X-ray production yield of the PIXE-SP setup is calibrated with monoelementary evaporated thin film standards, and fitted with a first principles yield function. However, in thick target PIXE (TTPIXE) analysis, the particular sample composition needs to be known in advance to calculate the stopping power and the X-ray absorption coefficients. In this work, a matrix standardization is proposed, in which a powdered solid sample is diluted in a known light element matrix (like graphite, boric acid, etc.) whose energy loss and selfabsorption are known and supposed almost unchanged. Furthermore, a scheme is proposed where elementary TTPIXE yields are calculated applying a pre-determined thick target correction factor to the thin target PIXE yields. This procedure enables the use of the already calibrated thin film X-ray yields also for thick target analysis. Using the most accepted stopping power model, ionization cross-sections and X-ray attenuation coefficients, a software (Clara) was developed to calculate the elementary TTPIXE X-ray yields and the corresponding thick target correction factors, for a given and pre-determined matrix. The program also allows testing the addition of any contaminant to the primary matrix and to compute the corresponding change in the thick target PIXE X-ray yields. This option was used to calculate the effect of increasing sample mass in the light element matrix, on the calculated yields, the effect of small changes in target composition, and the quantitative limitations of the proposed scheme. Thick test targets were prepared with a standard reference material (SRM-IAEA356 Marine sediment) and used to verify the accuracy of Clara and of the proposed scheme. The experimental values of the sample composition agreed with the certified values for 95% confidence interval coefficient to the new detection limit imposed by dilution. A protocol for target preparation of solid samples using this technique as well as the description of the experimental setup, are included.

No description available.

This study was conducted to test the hypothesis that, during renal development, the Na-K-2Cl cotransporter type 2 (NKCC2) activates the tonicity-responsive enhancer binding protein (TonEBP) transcription factor by creating medullary hypertonicity. TonEBP, in turn, drives the expression of aldose reductase (AR) and urea transporter-A (UT-A). Kidneys from 13- to19-day-old fetuses (F13-F19), 1- to 21-day-old pups (P1-P21), and adult mice were examined by immunohistochemistry. NKCC2 was first detected on F14 in differentiating macula densa and thick ascending limb (TAL). TonEBP was first detected on F15 in the medullary collecting duct (MCD) and surrounding endothelial cells. AR was detected in the MCD cells of the renal medulla from F15. UT-A first appeared in the descending thin limb (DTL) on F16 and in the MCD on F18. After birth, NKCC2-positive TALs disappeared gradually from the tip of the renal papilla, becoming completely undetectable in the inner medulla on P21. TonEBP shifted from the cytoplasm to the nucleus in both vascular endothelial cells and MCD cells on P1, and its abundance increased gradually afterward. Immunoreactivity for AR and UT-A in the renal medulla increased markedly after birth. Treatment of neonatal animals with furosemide dramatically reduced expression of TonEBP, AR, and UT-A1. Furosemide also prevented the disappearance of NKCC2-expressing TALs in the papilla. The sequential expression of NKCC2, TonEBP, and its targets AR and UT-A and the reduced expression TonEBP and its targets in response to furosemide treatment support the hypothesis that local hypertonicity produced by the activity of NKCC2 activates TonEBP during development.

<p> Thick-film resistors are being used in the hybrid microelectronics industry. One characteristic that has been considered for the thick film resistor i s the reproduceability in resistor value associated with the production techniques employed in the reproduceability in resistor value associated with the production techniques employed in the resistor manufactured. </p> <p> One parameter that has been associated with reproduceability is the yield figure; another parameter is the width of the resistance distribution for a given resistor production. These parameters can be used to identify the degree of reproduceability for the resistor production. A high yield figure or a small spread figure indicates a high degree of reproduceability. </p> <p> The effect of aspect ratio and sheet resistivity on the reproduceability has been evaluated for paste system A. Aspect ratios of 10, 5, 2 and 0.7 for a range of sheet resistivities (100, 1K, 10K, 100K, and 1M ohms per square) were investigated. Results show that for a given aspect ratio the amount of variation in spread for the range of sheet resistivities is negligible within the limits of error in the experiment. For a given sheet resistivity, the variation in spread for the range of aspect ratios is considerable. The spread of an aspect ratio of 10 is 25 ± 4%. For an aspect ratio of 0.7 the spread is 59± 7%. </p> <p> The effect of resistor location on spread for a 2" x 2" substrate has been studied. Results indicate that a higher degree of reproduceability can be associated with resistors located near the central (1" x 1") region of the substrate than the resistors located near the perimeter. </p> <p> The effect of increasing the resistor width on the reproduceability has been evaluated for resistors having aspect ratios near unity. Results show that as the resistor width is increased the spread in resistance decreases. For a width of 30 mil the spread in resistance is 37%. When the width is increased to 100 mil, the spread decreases to 21%. </p> / Thesis / Master of Engineering (MEngr)

No description available.

This Dissertation is a study of Switched Mode Power Supply (SMPS) miniaturization and how to effectively use the available technologies to achieve the ultimate goal of a reduced size without loss of functionality while maintaining a cost effective design. This research investigates several methods used to obtain low loss, highly compact power supplies. Within these constraints, the Dissertation investigates the issues of design, materials, and cost in order to design and achieve these miniaturized power supplies. This research addresses high performance ceramic, passive component integration. Three key issues; electrical characterization, thermal analysis and simulation, and material characterization, are examined in this work. Thick film passive components (capacitors and resistors) on AlN have been developed. Also, guidelines for the design implementation and steps necessary to integrate these passive components on prefired alumina (Al2O3) and aluminum nitride (AlN) ceramic surfaces, for power electronic applications, have been generated. The use of aluminum nitride, as a high performance ceramic substrate and the resulting issues concerning compatible inks, have been investigated. Since a sizable amount of heat is generated by power electronic circuits, the integrated components are analyzed with respect to tolerance and degeneration over a range of temperatures and frequencies. Thick film capacitors on the order of 120pF/mm2 with breakdown voltage ratings of 250V have been developed on prefired AlN. Resistors were developed with impedances ranging from 10W to 10MegW. Thermal measurements, of these resistors, show that the thermal conductivity of the aluminum nitride with passivation layer is two to three times that of alumina. Several versions of a typical SMPS boost circuit have been generated using Direct Bond Copper (DBC) on ceramic, Insulated Metal Substrate (IMS), Printed Circuit Boards (PCB), and prefired ceramic thick film technology. The integrated passive components developed are applied on prefired ceramic versions and compared to the DBC, IMS and PCB versions. A small daughter board consisting of the boost circuit control is introduced to further supplement miniaturization and reduce cost. The daughter board uses thick film technology with integrated thick film resistors. The design of the mother board, which houses the power boost section,can be designedand implemented on virtually any type of substrate (PCB, DBC, IMS, or conventional thick film). The fabrication and testing of each version is reported in this work. / Ph. D.

The Eshelby-Stroh formalism is used to analyze the generalized plane strain quasistatic deformations of an anisotropic, linear elastic laminated plate.The formulation admits any set of boundary conditions on the edges and long faces of the laminate. Each lamina may be generally anisotropic with as many as 21 independent elastic constants. The three dimensional governing differential equations are satisfied at every point of the body.The boundary conditions and interface continuity conditions are satisfied in the sense of a Fourier series. Results are presented for three sample problems to illustrate the versatility of the method. The solution methodology is generalized to study the deformation of finite rectangular plates subjected to arbitrary boundary conditions. The effect of truncation of the series on the accuracy of the solution is carefully examined. Results are presented for thick plates with two opposite edges simply supported and the other two subjected to eight different boundary conditions. The results are compared with three different plate theories.The solution exhibits boundary layers at the edges except when they are simply supported. Results are presented in tabular form for different sets of edge boundary conditions to facilitate comparisons with predictions from various plate theories and finite element formulations. The Eshelby-Stroh formalism is also extended to study the generalized plane deformations of piezothermoelastic laminated plates. The method is capable of analyzing laminated plates with embedded piezothermoelastic patches. Results are presented for a thermoelastic problem and laminated elastic plates with piezothermoelastic lamina attached to its top surface. When a PZT actuator patch is attached to an elastic cantilever substrate, it is observed that the transverse shear stress and transverse normal stress are very large at the corners of the PZT-substrate interface. This dissertation is organized in the form of three self-contained chapters each of which will be submitted for possible publication in a journal. / Ph. D.

In this paper we explore Fibonacci heaps and their variants. The alternative versions of the Fibonacci heap, the thin and thick heaps, were introduced by H. Kaplan and R. E. Tarjan in 2008. We compare these heaps from both experimental and theoretical point of view and we also include some classic types of heaps, namely regular and pairing heap. In our experiments we will be most interested in the total time required to run an algorithm that works with heap. The results show that thin and thick heaps are usually faster than the Fibonacci heap and slower than the regular heap. In conclusion, we summarize the knowledge gained from experiments.