A rápida e crescente demanda por tecnologias que permitam a redução das dimensões dos transistores planares de porta única leva a uma nova era de dispositivos tensionados mecanicamente. Os transistores de múltiplas portas (MuGFET) com canal de silício e o MOSFET planar convencional com canal de germânio são alguns destes promissores dispositivos avançados a receberem o tensionamento mecânico para aumento da mobilidade dos portadores. O tensionamento mecânico uniaxial, biaxial e ambos combinados são analisados através de simulação numérica de processos e dispositivos e medidas experimentais em três técnicas de tensionamento diferentes, além da análise de medidas obtidas de dispositivos experimentais para análise do aumento da mobilidade dos portadores através da transcondutância máxima. A linha de corte 1D de cada componente do tensionamento simulado é estudado de acordo com a sua dependência com a largura, altura, comprimento do canal e materiais utilizados, assim como a influência que as componentes de tensionamento exercem sobre os parâmetros elétricos analógicos, como transcondutância, ganho intrínseco de tensão e frequência de ganho de tensão unitário. A operação dos dispositivos de silício sobre isolante (SOI Silicon On Insulator) MuGFETs de porta tripla com variações no formato da secção transversal do canal do transistor e variações no comprimento e largura da aleta é estudada em casos selecionados. Um completo estudo da distribuição do tensionamento mecânico gerado por tensionamento global e por tensionamento local é realizado em estruturas com aleta retangular e trapezoidal, juntamente com o impacto destas na mobilidade e nos parâmetros analógicos são realizados. Estruturas nMuGFET SOI com comprimento de canal mais curto alcançaram aumentos maiores de mobilidade utilizando-se o tensionamento uniaxial, enquanto que as estruturas com comprimento de canal mais longo retornaram maior mobilidade com o tensionamento biaxial, resultado da diferente efetividade de cada técnica de tensionamento em cada estrutura. Estruturas MOSFETs convencionais planares com tensionadores embutidos na fonte e dreno em canal de germânio para incremento da mobilidade também são analisadas. Simulações numéricas do processo de fabricação são realizadas e calibradas com dispositivos experimentais em transistores tipo n e tipo p, possibilitando o estudo futuro de estruturas MuGFET de germânio. / The fast and growing demand for technologies that enable the reduction of dimensions of planar single gate transistors leads to a new era of mechanically stressed devices. Multiple gate transistors (MuGFET) with silicon channel and planar bulk MOSFET with germanium channel are some of these promising advanced devices to receive the mechanical stress to increase carriers mobility. The uniaxial stress, biaxial stress and both of them combined are analyzed by process and device numerical simulations in three different strain techniques and also the analysis of experimental measurements for analysis of carriers mobility increase through maximum transconductance. The 1D cut line of each simulated stress component is studied according to their dependence on the width, height and length of the channel and the materials used, as well as the influence that stress components causes on analog electrical parameters, such as transconductance, intrinsic voltage gain and unity gain frequency. The operation of silicon-on-insulator (SOI) triple gate MuGFETs with variations in the shape of the cross section of the transistor channel and variations in the length and width of the fin is studied in selected cases. A complete study in the distribution of the mechanical stress generated by the local and global stress is performed in rectangular and trapezoidal fins and also the impact of these on mobility and analog parameters are studied. SOI nMuGFET structures with shorter channel length achieved higher mobility increases using the uniaxial stress, while structures with longer channel lengths returned higher mobility using the biaxial stress, result of the different effectiveness in each stress technique for each structure. Conventional MOSFET structures with embedded stressors in the source and drain regions with germanium channel are also analyzed. Numerical process simulations are realized and calibrated with experimental devices in both n and p type transistors, making possible the future study of MuGFET structures with germanium.

A rápida e crescente demanda por tecnologias que permitam a redução das dimensões dos transistores planares de porta única leva a uma nova era de dispositivos tensionados mecanicamente. Os transistores de múltiplas portas (MuGFET) com canal de silício e o MOSFET planar convencional com canal de germânio são alguns destes promissores dispositivos avançados a receberem o tensionamento mecânico para aumento da mobilidade dos portadores. O tensionamento mecânico uniaxial, biaxial e ambos combinados são analisados através de simulação numérica de processos e dispositivos e medidas experimentais em três técnicas de tensionamento diferentes, além da análise de medidas obtidas de dispositivos experimentais para análise do aumento da mobilidade dos portadores através da transcondutância máxima. A linha de corte 1D de cada componente do tensionamento simulado é estudado de acordo com a sua dependência com a largura, altura, comprimento do canal e materiais utilizados, assim como a influência que as componentes de tensionamento exercem sobre os parâmetros elétricos analógicos, como transcondutância, ganho intrínseco de tensão e frequência de ganho de tensão unitário. A operação dos dispositivos de silício sobre isolante (SOI Silicon On Insulator) MuGFETs de porta tripla com variações no formato da secção transversal do canal do transistor e variações no comprimento e largura da aleta é estudada em casos selecionados. Um completo estudo da distribuição do tensionamento mecânico gerado por tensionamento global e por tensionamento local é realizado em estruturas com aleta retangular e trapezoidal, juntamente com o impacto destas na mobilidade e nos parâmetros analógicos são realizados. Estruturas nMuGFET SOI com comprimento de canal mais curto alcançaram aumentos maiores de mobilidade utilizando-se o tensionamento uniaxial, enquanto que as estruturas com comprimento de canal mais longo retornaram maior mobilidade com o tensionamento biaxial, resultado da diferente efetividade de cada técnica de tensionamento em cada estrutura. Estruturas MOSFETs convencionais planares com tensionadores embutidos na fonte e dreno em canal de germânio para incremento da mobilidade também são analisadas. Simulações numéricas do processo de fabricação são realizadas e calibradas com dispositivos experimentais em transistores tipo n e tipo p, possibilitando o estudo futuro de estruturas MuGFET de germânio. / The fast and growing demand for technologies that enable the reduction of dimensions of planar single gate transistors leads to a new era of mechanically stressed devices. Multiple gate transistors (MuGFET) with silicon channel and planar bulk MOSFET with germanium channel are some of these promising advanced devices to receive the mechanical stress to increase carriers mobility. The uniaxial stress, biaxial stress and both of them combined are analyzed by process and device numerical simulations in three different strain techniques and also the analysis of experimental measurements for analysis of carriers mobility increase through maximum transconductance. The 1D cut line of each simulated stress component is studied according to their dependence on the width, height and length of the channel and the materials used, as well as the influence that stress components causes on analog electrical parameters, such as transconductance, intrinsic voltage gain and unity gain frequency. The operation of silicon-on-insulator (SOI) triple gate MuGFETs with variations in the shape of the cross section of the transistor channel and variations in the length and width of the fin is studied in selected cases. A complete study in the distribution of the mechanical stress generated by the local and global stress is performed in rectangular and trapezoidal fins and also the impact of these on mobility and analog parameters are studied. SOI nMuGFET structures with shorter channel length achieved higher mobility increases using the uniaxial stress, while structures with longer channel lengths returned higher mobility using the biaxial stress, result of the different effectiveness in each stress technique for each structure. Conventional MOSFET structures with embedded stressors in the source and drain regions with germanium channel are also analyzed. Numerical process simulations are realized and calibrated with experimental devices in both n and p type transistors, making possible the future study of MuGFET structures with germanium.

All modern High Temperature Reactors (HTR) thermal cycles have one thing in common: the use of some form of heat exchanger. This heat exchanger is used to pre-heat or cool the primary loop gas, from where the secondary power generation cycle is driven. The Compact Heat Exchanger (CHE) type offers high heat loads in smaller volumes. Various studies have been done to improve the heat transfer in the flow channels of these CHEs but little focus has been placed on the thermal design of surrounding material in such a heat exchanger. The focus of this study is on the effective material usage in a CHE. Three test cases were investigated (trapezoidal, serpentine and zigzag layouts with semi-circular cross-sections) all under the same boundary conditions. Computational Fluid Dynamics (CFD) was used to simulate these test cases and the results were evaluated according to four factors, the volume ratio, heat spots, temperature difference and the combined enhancement factor. From the results it was concluded that the zigzag layout performs best when evaluated according to the volume ratio and the temperature difference and gave the best overall enhancement factor. The serpentine layout performed the worst when evaluated according to the enhancement factor. / Thesis (MIng (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013

All modern High Temperature Reactors (HTR) thermal cycles have one thing in common: the use of some form of heat exchanger. This heat exchanger is used to pre-heat or cool the primary loop gas, from where the secondary power generation cycle is driven. The Compact Heat Exchanger (CHE) type offers high heat loads in smaller volumes. Various studies have been done to improve the heat transfer in the flow channels of these CHEs but little focus has been placed on the thermal design of surrounding material in such a heat exchanger. The focus of this study is on the effective material usage in a CHE. Three test cases were investigated (trapezoidal, serpentine and zigzag layouts with semi-circular cross-sections) all under the same boundary conditions. Computational Fluid Dynamics (CFD) was used to simulate these test cases and the results were evaluated according to four factors, the volume ratio, heat spots, temperature difference and the combined enhancement factor. From the results it was concluded that the zigzag layout performs best when evaluated according to the volume ratio and the temperature difference and gave the best overall enhancement factor. The serpentine layout performed the worst when evaluated according to the enhancement factor. / Thesis (MIng (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2013

All heat pump cycles have one common feature that connects them to one another; this feature is the presence of a heat exchanger. There are even some heat–driven cycles that are completely composed of heat exchangers, every heat exchanger fulfilling a different, though critical role. The need therefore exists to optimize heat exchangers, more specifically Compact Heat Exchangers (CHE). This study deals with the optimization of such a CHE by determining an optimal hydraulic diameter of the micro–channels in a CHE, for minimal hydraulic losses. Two Computational Fluid Dynamics (CFD) models were developed for a single micro–channel that is present in a CHE. The first model had a semi–circular cross–section, the second a triangular cross–section. The results were verified by comparing it with existing experimental data. Following the verification of the results, the micro–channel was optimized by implementing an optimum diameter for the lowest pressure drop over the micro–channel. This was done for both the semi–circular and triangular micro–channel cross–sections. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

All heat pump cycles have one common feature that connects them to one another; this feature is the presence of a heat exchanger. There are even some heat–driven cycles that are completely composed of heat exchangers, every heat exchanger fulfilling a different, though critical role. The need therefore exists to optimize heat exchangers, more specifically Compact Heat Exchangers (CHE). This study deals with the optimization of such a CHE by determining an optimal hydraulic diameter of the micro–channels in a CHE, for minimal hydraulic losses. Two Computational Fluid Dynamics (CFD) models were developed for a single micro–channel that is present in a CHE. The first model had a semi–circular cross–section, the second a triangular cross–section. The results were verified by comparing it with existing experimental data. Following the verification of the results, the micro–channel was optimized by implementing an optimum diameter for the lowest pressure drop over the micro–channel. This was done for both the semi–circular and triangular micro–channel cross–sections. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

This work deals with design of front trapezoidal suspension for racing car Škoda 130RS. The first part describes types of current suspensions and provides a review of important suspension parameters that have great influence to vehicle handling. The second part deals with kinematic analysis existing suspension, its modification and design of new type.

The aim of the diploma thesis is design construction and calculation of mechanism for parallel run of ram and adjusting position of ram in the face of table board of vertical hydraulic press. First part of thesis is about design calculation of vertical hydraulic press ram. Second part focuses on design calculation of ram and hydraulic cylinders. Third part solves design and construction of positioning hydraulic–electric system. Final fourth part analyses press construction from aspects of safeness, riskiness and economical factors.

Yes / Natural earth-bounded channel flows usually subject to various sidewall turbulences, i.e. in the form of secondary currents, due to non-constant channel shapes at different sections. This paper investigates an improved Shiono-Knight model (SKM) by combining it with a Multi-Zonal (MZ) method (proposed by Pu, 2019) to represent lateral flow turbulence and secondary currents in different shapes of open channel, i.e. rectangular and trapezoidal. By applying the proposed analytical model to both rectangular and trapezoidal channel flows, we have inspected different streamwise velocity characteristics across transverse direction generated by their sidewalls in order to provide crucial fundamental understanding to real-world natural flow system. The proposed model has also been validated via various experimental data conducted in national UK Flood Channel Facility (UK-FCF). It has been observed that the trapezoidal channel has created a larger sidewall zone where secondary current can affect flow velocity; however, the intensity of the secondary flow in trapezoidal channel has been found lesser than that of the rectangular channel. By improving the modelling of natural flow at sidewall, the studied approach could be adapted into different existing analytical models to improve their accuracy.

An experimental program was conducted at the Ferguson Structural Engineering Laboratory of The University of Texas at Austin, under the auspices of Texas Department of Transportation (TxDOT) Research Project 5831, to investigate the tensile stresses that develop in the end regions of pretensioned concrete U-beams at transfer of prestress. Understanding the effect of these “bursting” and “spalling” stresses is essential in order to design standard details that might lead to reliably-serviceable end regions. Two full-scale beam specimens, designed to be worst-case scenarios for bursting and spalling, were fabricated. Each beam had one square and one highly skewed end. Extensive instrumentation, including strain gages on transverse and lateral reinforcing bars, was employed in the end regions of these U-beams. Experimentally determined bursting and spalling stresses in these bars were compared to results of past projects (from the literature) investigating I-beams and inverted T-beams. Preliminary recommendations are made for changes in the standard reinforcing details for U-beam end regions. Such recommended details will be tested in the upcoming phase of Research Project 5831. / text