Fluidization of a granular assembly of solid particles is a process where particles are suspended in a fluid by the upward flow of fluid through the bed. This process is important in industry as it has a wide range of applications due to the high mixing and mass transfer rates present as a result of the rapid movement of particles which occurs in the bed. The dynamics of fluidization is heavily dependent on the particle scale physics and the forces acting at a particle level. For particles with sizes and densities less than 100μm and 103 kg/m3, the importance of interparticle forces such as cohesion to the fluidization phenomena observed increases compared to larger particles where phenomena observed are more dependent on hydrodynamic forces. These smaller sized particles are increasingly in high demand in industrial processes due to the increasing surface area per unit volume obtained by decreasing the particle size. Decreasing particle however leads to an increase in the impact of cohesive interparticle forces present between particles thus altering fluidization phenomena. It is thus necessary to get a greater understanding of how these cohesive forces alter fluidization behaviour both at the particle and also at the bulk scale. This work begins with an experimental study of a fluidized bed using high speed imaging. The applicability of particle image velocimetry for a dense bed is examined with verification and validation studies showing that particle image velocimetry is able to accurately capture averaged velocity profiles for particles at the front wall. A digital image analysis algorithm which is capable of accurately extracting particle solid fraction data for a dense bed at non-optimum lighting conditions was also developed. Together both experimental techniques were used to extract averaged particle mass flux data capable of accurately capturing and probing fluidization phenomena for a dense fluidized bed. This simulation studies carried out for this work looks to examine the impact of cohesive forces introduced using a van der waal cohesion model on phenomena observed at different length scales using DEM-CFD simulations. Numerical simulations were run for Geldart A sized particles at different cohesion levels represented by the bond number and at different inlet gas velocities encompassing the different regimes fluidization regimes present. A stress analysis was used to examine the mechanical state of the expanded bed at different cohesion levels with the vertical component of the total stress showing negative tensile stresses observed at the center of the bed. Further analysis of the contact and cohesive components of the stress together with a kcore and microstructural analysis focusing on the solid fraction and coordination number profiles indicated that this negative total stress was caused by a decrease in the contact stress due to breakage of mechanical contacts as cohesive forces are introduced and increased. A pressure overshoot analysis was also conducted with the magnitude of the overshoot in pressure seen during the pressure drop analysis of a cohesive bed shown to be of equivalent magnitude to the gradient of the total negative stress profile. The in-homogeneous nature of the bed was probed with the focus on how introducing cohesion levels increase the degree of inhomogeneity present in the expanded bed and how local mesoscopic structures change with cohesion and gas velocity. It was shown that increasing cohesion increases the degree of inhomogeneity in the bed as well as increasing the degree of clustering between particles. A majority of particles were shown to be present in a single macroscopic cluster in the mechanical network with distinct local mesoscopic structures forming within the macroscopic cluster. The cohesive bed also expanded as distinct dense regions with low mechanical contact zones in between these regions. A macroscopic cluster analysis showed that the majority of particles are in strong enduring mechanical and cohesive contact. Increasing cohesive forces were also shown to not only create a cohesive support network around the mechanical network but also strengthen the mechanical contact network as well. The significance of the strong and weak mechanical and cohesive forces on fluidization phenomena was also examined with analysis showing that the weak mechanical forces act to support the weak mechanical forces. The cohesive force network however was non coherent with strong forces significantly greater than weak forces. Fluidization phenomena was shown to be driven by the magnitude of the strong cohesive forces set by the minimum particle cutoff distance. This also called into question the significance of the cohesive coordination number which is dependent on the maximum cohesive cutoff. The value of the maximum cutoff was shown to be less significant as no significant changes were observed in the stress and microstructure data as the maximum cutoff was altered. Simulations with different ratios of cohesive and non cohesive particles were also undertaken and showed that a disruption in the cohesive force network leads to changes in the stress state and microstructure of the bed thus changing the fluidization phenomena observed at all length scales. The nature of the strong cohesive force network thus drives fluidization phenomena seen in the bed.

No description available.

Significant characteristic of any VLSI design circuit is its power, reliability, operating frequency and implementation cost. Dynamic CMOS designs provide high operating speeds compared to static CMOS designs combined with low silicon area requirement. This thesis describes the design and the optimization of high performance carry select adder. Previous researchers believed that existing CSA designs has reached theoretical speed bound. But, only a considerable portion of hardware resources of traditional adders are used in worst case scenario. Based on this observation our proposed design will improve on theoretical limit. The major scope of this proposed design is to increase the speed of carry generation between intermediate blocks of Carry select Adder (CSA) by introducing fast multiple clock Domino Manchester carry chain (MCC) that generates carry outputs. This design technique will have some advantages compared to pre-existing implementations in operating speed and power delay product. Simulation has been done using GPDK (Generic Process Design Kits) technology using cadence virtuoso. Thus the proposed technique provides advantages over pre-existing techniques in terms of operating speed.

Arithmetic units and logic circuits are critical components of any VLSI system. Thus realizing efficient arithmetic units and logic circuits is required for better performance of a data path unit and therefore microprocessor or digital signal processor (DSP). Adders are basic building blocks of any processor or data path application. For the design of high performance processing units, high-speed adders with low power consumption is a requirement. Carry Select Adder (CSA) is known to be one of the fastest adders used in many data processing applications. This first contribution of the dissertation is the design of a new CSA architecture using Manchester carry chain (MCC) in multioutput domino CMOS logic. It employs a novel MCC blocks in a hierarchical approach in the design of the CSA. The proposed MCC block is also extended in designing a power-delay and area efficient Vedic multiplier based on "Urdhva-Tiryakbhyam”. The simulation results shows that the proposed architecture achieves two fold advantages in terms of power-delay product (PDP) and hardware overhead. Apart from adders and multipliers, counters also play a major role in a data path unit. Counters are basic building blocks in many VLSI applications such as timers, memories, ADCs/DACs, frequency dividers etc. It is observed that design of counters has power overhead because of requirement of high power consumption for the clock signal distribution and undesired activity of flip-flops due to presence of clocks. The second contribution of the dissertation is the power efficient design of synchronous counters that reduces the power consumption due to clock distribution for different flip-flops and offers high reliability. The simulation results shows that the proposed counter design has lower power requirement and power-area product than existing counter architectures. Pipelines can be used for achieving high circuit operating speeds. However, as the operating frequency increases, the number of pipeline stages also increase linearly and so the memory elements. The third contribution of the dissertation is the dynamic memory-less pipeline design based on sinusoidal three-phase clocking scheme that reduces the power required by the clock and offers high circuit operating frequencies. Finally, the dissertation presents a novel tool for Boolean-function realization with minimum number of transistor in series. This tool is based on applying a new functional decomposition algorithms to decompose the initial Boolean-function into a network of smaller sub-functions and subsequently generating the final circuit. The effectiveness of proposed technique is estimated using circuit level simulations as well as using automated tool. The number of levels required using proposed technique is reduced by an average of 70% compared to existing techniques.

No presente trabalho foi investigada a nitretação a plasma do aço rápido ASTM M2 utilizando diferentes configurações, envolvendo as técnicas convencional e com tela ativa. Na técnica convencional, o material a ser nitretado atua como o cátodo do sistema, sendo coberto diretamente pela bainha da descarga luminescente. Nos tratamentos conduzidos com a técnica de tela ativa, uma estrutura de tela em formato cilíndrico atua como cátodo e o material a ser nitretado é posicionado no seu interior. Neste novo processo, como não há potencial elétrico externo aplicado aos substratos, a descarga luminescente se desenvolve apenas na estrutura da tela, evitando problemas intrínsecos do método convencional de nitretação a plasma. Todos os tratamentos investigados foram executados com os seguintes parâmetros: Temperatura de 500 °C, mistura gasosa composta 76% de volume de gás nitrogênio e 24% de volume de gás hidrogênio e pressão de 3 milibar. Para os tratamentos com tela ativa, os substratos foram mantidos eletricamente isolados. Os resultados foram comparados observando a diferença de método de nitretação (com e sem o uso de tela ativa) e a influência do tempo de tratamento (variando sua duração em 1, 4 e 8 horas) Todos os experimentos foram realizados utilizando uma fonte de potência de tensão retificada aplicada na tela ou nas amostras, dependendo da configuração. Adicionalmente, para o tempo de nitretação de 4 horas uma fonte de potência com tensão pulsada também foi aplicada. As amostras nitretadas foram caracterizadas por ensaios de rugosidade, ensaios de dureza e microdureza, microscopia ótica, microscopia eletrônica de varredura e difração de raios-X. Ensaios tribológicos para avaliação da resistência ao desgaste das diferentes condições de tratamento foram conduzidos. Dentre os principais resultados foi observada uma clara diferença na profundidade de camada nitretada, que foi sempre mais profunda nos tratamentos convencionais. Apesar de formadas camadas menos profundas, as amostras nitretadas oriundas dos tratamentos com tela ativa demonstraram melhor desempenho nos ensaios tribológicos, resultando em taxas de desgaste até sete vezes inferior do que as amostras do nitretadas convencionalmente, este resultado foi atribuído a não formação da zona de compostos nas amostras nitretadas com tela ativa. / In the present work an investigation on the plasma nitriding of ASTM M2 High-Speed Steel using different configurations was carried out, involving traditional and active screen techniques. In the traditional technique, the material to be nitrided act as the system cathode, being directly covered by the glow discharge sheath. In the active screen treatments, a cylindrical mesh structure (screen) plays the role of the cathode and the material to be nitrided is positioned in its interior. In this new process, as there is no external electric potential applied to the specimens, the glow discharge develops only in the screen structure, avoiding intrinsic problems from the conventional plasma nitriding method. All the studied treatments were carried out with the following parameters: temperature of 500 °C, gas mixture of 76 vol.-% N2 and 24 vol.-% H2 and pressure of 3 millibar. For the active screen treatments, the samples were kept electrically insulated. The results were compared observing the differences in the nitriding method (with and without the use of active screen) and the nitriding time influence (varying its duration in 1, 4 and 8 hours) All experiments were carried using a rectified voltage power supply applied to the screen or to the samples, depending on the configuration. Additionally, for the nitriding time of 4 hours a pulsed voltage power supply was also employed. The nitrided samples were characterized by roughness tests, hardness and microhardness tests, optical microscopy and scanning electron microscopy, X-ray diffraction. Tribological tests to evaluate the wear resistance of the different treatment conditions were also carried out. Among the main results a clear difference in the case layer depth was noticed, which was always deeper in the conventional treatments. Although forming shallower case depths, the active screen nitrided specimens presented better performance in the tribological tests, resulting in wear rates up to seven times lower than the wear rate for conventionally plasma nitrided samples, this result was assigned due to the non-formation of compound layer in the active screen plasma nitrided samples.

High-Speed Rail (HSR) as a fast, reliable and environmentally friendly mode of transportation has received a lot of attention in recent decades. The International Union of Railways reported that there are more than 18600 miles of HSR in operation and about 1.6 billion passengers per year are carried by them. Although there are plans for HSR in many states including Florida, the United States, however, is still hesitant to develop its own HSR network. One of the main barriers to developing high-speed rail is excessive vibration propagation to the media which may cause annoyance to people who live in the track neighborhood. Train induced vibration also contributes to track settlement, developing track flaws, and increasing life cycle cost of track and supporting structures. The aim of this research is to address this problem by conducting a comprehensive investigation into track dynamics. For this purpose, three-dimensional mass-spring-damper models of vehicle, track and supporting structures were developed and matrices of mass, stiffness, and damping of each subsystem were formed. The response of the whole system was, then, determined by coupling the subsystems using Hertz contact theory. The differential equations of the coupled system were solved by the Newmark integration method and the results including vertical and lateral displacements and forces were presented in the time domain. Since the purpose of this dissertation is to quantify the effect of track and vehicle condition on vibration level, rail defects were also taken into account and rail random irregularities for the vertical profile, Gauge, alignment and cross level (super elevation) were incorporated into a numerical solution. The results of the study show the effect of track and vehicle parameters on the response of the vehicle, track, and substructures. Since Florida and some other states in the United States are very prone to hurricanes, an investigation was conducted into the effect of wind speed on vehicle stability. For this purpose, a curved beam was modeled to consider the influence of track curvature, cant deficiency, wind speed and train speed simultaneously. The results from the study show the maximum allowable values of train speed and axle load for different wind speeds. The findings can be used to decide under what circumstances there is a risk of vehicle overturning and how to avoid it.

Florida, the fourth largest and sunshine state, is growing at the rate of 800 new residents daily.!! By the year 2000 the population is estimated to be 16 Million, and the annual tourists at 80 Million, generating 40 Million trips. The proposed High Speed Rail will connect Miami and West Palm Beach to Orlando and Tampa. This 325-mile corridor represents 70 % of all the "Socio-Economic Resources" of the whole of Florida and the trend will continue well into the next century. The Miami-Orlando ride will reduce to 2 hours speeding at up to 150 mph. It will be operational by 1995 and the system is estimated to cost 4.6 Billion Dollars. One of the major problems encountered by the new High Speed Rail (HSR) is the "RIDERSHIP FORECASTING," In the United States there is a lack of current information about the Total Volume of Intercity Trips and the Specific Characteristics of the Trips that determines a willingness to use HSR. The Quality, Comprehensiveness, and Acceptability, by the forecasts must be sufficient to generate Public Support, Confidence, and Response for the Implementation of HSR. The THESIS discusses the various Ridership Forecasting Techniques and chooses the “Most Suitable Model” applicable to conditions in South and Central Florida. A “Model Choice Based Model” is selected called, “THE LOGIT FUNCTION”, which takes into account, the Floridian Choice of available Travel Modes, and the Factors Affecting the Manner of the “Decision making Process”, in Favour of a Particular Mode. Evaluating Business and Non-Business Travel for the Internal Trips, (including the Induced Demand and the Short Trips) and the External Trips. The External and Short Trips were Not considered by Previous Studies. The standard guidelines for “Revenue and Ridership Forecasting,” by High Speed Rail Association are closely followed in this Study. Due consideration is also given to Socio-Economic data involving population, wealth, average per capita income, number of families, size of labor force, number of hotel / motel rooms and college enrollment. A Survey was carried out, to collect the data and to test the Sensitivity, under given set of conditions and scenarios. The studies conclude that HSR is a Feasible Project and by the year 2000, the Ridership will be 3.8 Million Annual Trips. The future studies will continue to improve the results, as an individual’s attitude and response towards HSR Travel becomes better known and recorded in Florida

abstract: The increase in computing power has simultaneously increased the demand for input/output (I/O) bandwidth. Unfortunately, the speed of I/O and memory interconnects have not kept pace. Thus, processor-based systems are I/O and interconnect limited. The memory aggregated bandwidth is not scaling fast enough to keep up with increasing bandwidth demands. The term "memory wall" has been coined to describe this phenomenon. A new memory bus concept that has the potential to push double data rate (DDR) memory speed to 30 Gbit/s is presented. We propose to map the conventional DDR bus to a microwave link using a multicarrier frequency division multiplexing scheme. The memory bus is formed using a microwave signal carried within a waveguide. We call this approach multicarrier memory channel architecture (MCMCA). In MCMCA, each memory signal is modulated onto an RF carrier using 64-QAM format or higher. The carriers are then routed using substrate integrated waveguide (SIW) interconnects. At the receiver, the memory signals are demodulated and then delivered to SDRAM devices. We pioneered the usage of SIW as memory channel interconnects and demonstrated that it alleviates the memory bandwidth bottleneck. We demonstrated SIW performance superiority over conventional transmission line in immunity to cross-talk and electromagnetic interference. We developed a methodology based on design of experiment (DOE) and response surface method techniques that optimizes the design of SIW interconnects and minimizes its performance fluctuations under material and manufacturing variations. Along with using SIW, we implemented a multicarrier architecture which enabled the aggregated DDR bandwidth to reach 30 Gbit/s. We developed an end-to-end system model in Simulink and demonstrated the MCMCA performance for ultra-high throughput memory channel. Experimental characterization of the new channel shows that by using judicious frequency division multiplexing, as few as one SIW interconnect is sufficient to transmit the 64 DDR bits. Overall aggregated bus data rate achieves 240 GBytes/s data transfer with EVM not exceeding 2.26% and phase error of 1.07 degree or less. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

Orientador: Alessandro Roger Rodrigues / Banca: Hidekasu Matsumoto / Banca: Otávio Villar da Silva Neto / Resumo: Este trabalho apresenta um estudo sobre a influência das condições de fresamento na formação de cavaco, microestrutura, dureza e rugosidade da peça. Foi ensaiado um aço baixo carbono 0,15%C com dois tamanhos de grão distintos. Para ambos os materiais da peça, empregou-se 8 condições de usinagem variando a velocidade de corte, o avanço da ferramenta e a profundidade de usinagem visando à aplicação da Análise de Variância (ANOVA), dando-se destaque à usinagem considerada como alta velocidade de corte e convencional. Os ensaios de fresamento de topo concordante a seco foram conduzidos em um centro de usinagem CNC de 11 kW de potência e rotação do eixo-árvore de 7.500 rpm. Utilizou-se ferramenta de diâmetro 25 mm com dois insertos de metal duro revestidos com Al2O3. Os resultados apontam para uma influência dos parâmetros de corte sobre todas as variáveis de resposta, exceto a macrodureza. Velocidades de corte e profundidades de usinagem maiores causaram deformação da microestrutura do material "como recebido" próxima à superfície fresada. Os mesmos parâmetros governaram o aumento da microdureza superficial e da profundidade da camada endurecida. O material com grãos ultrafinos não apresentou deformação da microestrutura próxima à superfície fresada nem aumento de microdureza superficial. A velocidade de corte influiu apenas na profundidade da camada endurecida. A rugosidade foi inversa e diretamente influenciada pela velocidade de corte e avanço da ferramenta, respectivamente, sendo dependente também do tamanho de grão do material da peça. Os mesmos parâmetros de corte influíram de forma significativa no ângulo de deformação da microestrutura dos cavacos, cuja classificação foi dependente do material e das condições de usinagem. / Abstract: This work deals with the influence of milling conditions on chip formation, microstructure, hardness and roughness of workpiece. A 0.15%C low carbon steel with two different grain sizes was milled. For both workpiece materials eight milling conditions were employed where cutting speed, tool feed and depth of cut varied and combined aiming at Analysis of Variance application. The machining conditions considered as High-Speed Cutting (HSC) and Conventional were focused. The milling tests considering down-milling and dry conditions were carried out in a CNC machining center with 11 kW power and 7,500 rpm spindle rotation. A 25 mm diameter endmill with two inserts coated of Al2O3 was used. The results indicated the cutting parameters influenced on all output variables except the macrohardness. Greater cutting speed and depth of cut caused deformation of workpiece microstructure with 10.8 um grain size near milled surface. The same parameters governed the increase of surface microhardness and hardened layer depth. Refined grain material did neither present deformation of microstructure near milled surface nor increase of microhardness. The cutting speed influenced only on depth of hardened layer. Roughness was inverse and directly influenced by cutting speed and tool feed, respectively, and dependent on grain size of workpiece material. These parameters also influenced on deformation angle of chip microstructure which were classified as continuous for 10.8 um grain size and segmented for the ultrafine grain, in this case just for some milling conditions. / Mestre

No presente trabalho foi investigada a nitretação a plasma do aço rápido ASTM M2 utilizando diferentes configurações, envolvendo as técnicas convencional e com tela ativa. Na técnica convencional, o material a ser nitretado atua como o cátodo do sistema, sendo coberto diretamente pela bainha da descarga luminescente. Nos tratamentos conduzidos com a técnica de tela ativa, uma estrutura de tela em formato cilíndrico atua como cátodo e o material a ser nitretado é posicionado no seu interior. Neste novo processo, como não há potencial elétrico externo aplicado aos substratos, a descarga luminescente se desenvolve apenas na estrutura da tela, evitando problemas intrínsecos do método convencional de nitretação a plasma. Todos os tratamentos investigados foram executados com os seguintes parâmetros: Temperatura de 500 °C, mistura gasosa composta 76% de volume de gás nitrogênio e 24% de volume de gás hidrogênio e pressão de 3 milibar. Para os tratamentos com tela ativa, os substratos foram mantidos eletricamente isolados. Os resultados foram comparados observando a diferença de método de nitretação (com e sem o uso de tela ativa) e a influência do tempo de tratamento (variando sua duração em 1, 4 e 8 horas) Todos os experimentos foram realizados utilizando uma fonte de potência de tensão retificada aplicada na tela ou nas amostras, dependendo da configuração. Adicionalmente, para o tempo de nitretação de 4 horas uma fonte de potência com tensão pulsada também foi aplicada. As amostras nitretadas foram caracterizadas por ensaios de rugosidade, ensaios de dureza e microdureza, microscopia ótica, microscopia eletrônica de varredura e difração de raios-X. Ensaios tribológicos para avaliação da resistência ao desgaste das diferentes condições de tratamento foram conduzidos. Dentre os principais resultados foi observada uma clara diferença na profundidade de camada nitretada, que foi sempre mais profunda nos tratamentos convencionais. Apesar de formadas camadas menos profundas, as amostras nitretadas oriundas dos tratamentos com tela ativa demonstraram melhor desempenho nos ensaios tribológicos, resultando em taxas de desgaste até sete vezes inferior do que as amostras do nitretadas convencionalmente, este resultado foi atribuído a não formação da zona de compostos nas amostras nitretadas com tela ativa. / In the present work an investigation on the plasma nitriding of ASTM M2 High-Speed Steel using different configurations was carried out, involving traditional and active screen techniques. In the traditional technique, the material to be nitrided act as the system cathode, being directly covered by the glow discharge sheath. In the active screen treatments, a cylindrical mesh structure (screen) plays the role of the cathode and the material to be nitrided is positioned in its interior. In this new process, as there is no external electric potential applied to the specimens, the glow discharge develops only in the screen structure, avoiding intrinsic problems from the conventional plasma nitriding method. All the studied treatments were carried out with the following parameters: temperature of 500 °C, gas mixture of 76 vol.-% N2 and 24 vol.-% H2 and pressure of 3 millibar. For the active screen treatments, the samples were kept electrically insulated. The results were compared observing the differences in the nitriding method (with and without the use of active screen) and the nitriding time influence (varying its duration in 1, 4 and 8 hours) All experiments were carried using a rectified voltage power supply applied to the screen or to the samples, depending on the configuration. Additionally, for the nitriding time of 4 hours a pulsed voltage power supply was also employed. The nitrided samples were characterized by roughness tests, hardness and microhardness tests, optical microscopy and scanning electron microscopy, X-ray diffraction. Tribological tests to evaluate the wear resistance of the different treatment conditions were also carried out. Among the main results a clear difference in the case layer depth was noticed, which was always deeper in the conventional treatments. Although forming shallower case depths, the active screen nitrided specimens presented better performance in the tribological tests, resulting in wear rates up to seven times lower than the wear rate for conventionally plasma nitrided samples, this result was assigned due to the non-formation of compound layer in the active screen plasma nitrided samples.