Browsing by Subject "Design and construction"
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Item A methodology for the rapid design and implementation of digital systems(Texas Tech University, 2001-12) Ba, Samba AlassaneNot availableItem A switched-current CMOS-only parallel pipelined A/D converter(Texas Tech University, 2003-08) Huang, ZhaohuiA pipelined analog-to-digital converter is presented, which employs the switched-current technique to achieve CMOS-only implementation. Four time-interleaved component ADCs are paralleled to increase the throughput to 40Msamples/s, with each operating at the sampling rate of 10MHz. In consideration of linearity and performance, 1.5-bit/stage Digital Error Correction strategy is used and provides 8 effective number of bits for the overall system. For the 0.5pm CMOS implementation, the converter achieves the resolution of 52.1 dB with 500kHz input and its power consumption is 81mW under 3.0V voltage supply. The potential of the ADC is to be integrated in the System-on-Chip for complex applications.Item Analysis and design of a forward power converter(Texas Tech University, 2004-12) Nathadi, Raghotham RWith advances in microelectronic fabrication and semiconductor devices, the size of electronic equipment is ever decreasing. Virtually, every piece of electronic equipment is powered from a DC power source, be it a battery or a DC power supply. The power supply constitutes to a main portion of any electronic device. Therefore, the key requirements for a power supply are lighter weight, reduced size, and reduced heat dissipation. There have been two technologies in power supplies: Linear and Switched mode. Though linear supplies have many desirable characteristics such as simplicity, low output ripple, excellent line and load regulation, fast response time to line or load changes, and low EMI, they suffer from poor efficiency and occupy large volumes. Switching power supplies are becoming popular because they offer better solutions to these problems. Switching voltage regulation is the technique by which an unregulated source power is efficiently converted to regulated load power through the use of controlled power switching devices and energy transfer elements. DC to DC conversion is the heart of any switched mode power supply. There are many choices for DC to DC conversion but forward converter has dominated the market for the past 50 years for commercial power supplies in excess of 50W. At the beginning, this thesis describes the basic functional blocks of a switched mode power supply. Then the design of various elements that are generally used in any switched mode power supply is extensively covered. Later the theory and operating principles and limitations of a forward converter are discussed. Finally, the simulation results for a forward converter and test results on an engineering reference switched mode power supply are presented.Item Analysis of stress singularity of adhered contacts in MEMS(Texas Tech University, 2004-08) Chakkarapani, VenkatasubbaraoMEMS devices are usually multimaterial systems where interfaces are formed at the junction of two materials. Failure occurs at adhered contacts because of biomaterial stress singularities at interface comers. Magnitude of the stress field induced due to this singularity is given by the value of the notch stress intensity. Hence it becomes very important to design MEMS devices based on the stress intensity-fracture toughness failure criterion. Inherent uncertainty of design parameters (which includes singularity parameters) in MEMS devices necessitates probabilistic design rather than deterministic design. The probabilistic design of MEMS devices, with a microswitch as our device example, has been performed to find the probability of failure of the switch based on stress intensity-fracture toughness failure criterion. The two main objectives of this research are to determine the stress field around a bimaterial singularity for a given bimaterial specimen and evaluate the probability of failure based on stress intensity-fracture toughness failure criterion using probabilistic analysis. The scope of work is fourfold. First, the order of the singularity is determined using two different methods, namely, Complex potential method and Airy stress function method. The equivalence of these methods is verified. Second, the influence coefficients are determined using analytical methods. Third, the stress intensity factor is determined using finite element methods. Fourth, the probabilistic analysis of the microswitch is performed based on stress intensity-fracture toughness failure criterion. The order of singularity has been determined to be 0.512 and 0.696. The stress intensity factor has been determined to be 0.7708 MPa m0.488 from finite element analysis. The probability that the notch stress intensity exceeds the fracture toughness is found to be 0.612.Item Design and fabrication of an instrument to test the mechanical behavior of aluminum alloy sheets during high-temperature gas-pressure blow-forming(2008-05) Vanegas Moller, Ricardo; Taleff, Eric M.Hydraulic bulge forming has been used as a method to determine the properties of sheet metal alloys in biaxial stretching at room temperature. Gas-pressure bulge forming alleviates the issues of using hydraulic fluids when the tests are conducted at high temperatures (above 200°C). Testing a sheet metal alloy by gas-pressure blow-forming (GPBF) under controlled temperature and pressure conditions requires an accurate and reliable mechanism that delivers repeatable results. It was the purpose of this work to design and implement such an instrument. This instrument should deliver real-time data for material displacement during forming, which can then be used to better understand material plastic response and formability. Four different subsystems within this mechanism must interact, but also have enough independence for analysis and for assembly purposes. The combined sub-systems produced a GPBF apparatus capable of forming a sheet aluminum alloy AA5182 with a thickness of 1.5 mm into a dome with a height nearly equal to its radius under a constant gas pressure as low as 40 psi at 450°C. This GPBF apparatus produced, for the first time, in-situ data for dome peak displacement during gas-pressure bulge forming of AA5182 sheet at 450°C.Item Low power/low voltage LVDS (low voltage differential signal) receiver design(Texas Tech University, 2001-08) McCormick, Michael DThe focus of this thesis is to investigate the application of low-voltage/low-power design to an LVDS (Low Power Differential Signal) receiver. The power consumption and necessary source voltage levels in current CMOS circuits is dependent on the size of the transistors used and the design topology utilized to realize the circuit. A CMOS process design solution is desired to reduce the power consumption and source voltage of an LVDS receiver while maintaining full speed operation to improve overall receiver efficiency and lower receiver operating voltage from 3.3V to 1.8V. Testing and optimizing of the design of the low-power/low-voltage LVDS receiver is done through simulation and measurement of various parameters on Pspice. Tradeoffs in low-power/low-voltage circuit design are presented and investigated to determine a solution for real world application.Item Simulation of communication time for a space-time adaptive processing algorithm on a parallel embedded system(Texas Tech University, 1998-08) West, Jack M.This thesis involves the investigation of parallelization and performance improvement for a class of radar signal processing techniques known as space-time adaptive processing (STAP). The assumed platform, which consists of multiple DSPs, is the commercially available Mercury RACE System. The main contribution of the thesis is the design and implementation of a network simulator for the RACE system. This simulator allows for the performance of various parallel STAP algorithm implementations to be predicted for existing or future RACE system configurations. A major challenge of implementing parallel STAP algorithms on multiprocessor systems is determining the best method for distributing the 3-D data cube across CEs of the multiprocessor system (i.e., the mapping strategy) and the scheduling of communication within each phase of computation. It is important to understand how mapping and scheduling strategies affect overall performance. The network simulator developed in this thesis is used to evaluate the performance of various mapping and scheduling strategies.Item Stabilizing techniques for curved steel I-girders during construction(2010-05) Petruzzi, Brian James; Helwig, Todd Aaron, 1965-; Engelhardt, Michael D.There are many issues and challenges to deal with when designing a curved I-girder bridge. These challenges primarily deal with the many performance stages that curved I-girder bridges have such as the erection, construction, and in-service stages. When design engineers assess the stability of a bridge system, they typically evaluate the system in its final configuration with all cross frames attached and the hardened concrete deck placed. The evaluation of girder stability during erection and early stages of construction stages is difficult because of the limited presence of bracing in the system. Due to a lack of readily available analytical tools, many contractors do not conduct detailed analytical evaluations of the bridge behavior during early stages of the construction when stability is often critical. Instead, many contractors use rules of thumb and experience to ensure stability during erection. Erection and construction practices typically vary among contractors and consistent erection methods are a rarity. Although some rules of thumb may be quite conservative, others are much less so. Therefore, coming up with design guidelines based on parametric studies rather than rules of thumb are desirable to help allow the contractor and the designer to work together to prevent issues that may occur due to the lack of communication between the two professions. Lastly, many challenges arise due to the complex geometry of curved I-girders. To prevent excessive rotation in erected girders, three points of vertical support are often provided. Two of these points usually consist of permanent supports in the form of bridge piers or abutments. The third point of support may consist of a temporary support in the form of a shore tower or holding crane. Cases where a holding crane may be satisfactory over a shore tower are also not well understood. To improve the understanding of lifting practices and temporary support requirements, parametric studies were conducted using the finite element program ANSYS. Field data consisting of displacement, stress, and girder rotations gathered from two tests were used to validate both the linear and geometric non-linear three-dimensional FEA models. Upon validation, the finite element model was used to conduct linear and geometric non-linear analyses to determine critical factors in curved I-girder bridges during construction. Specifically, serviceability limit states were studied for the lifting of curved girders. For partially constructed states, parametric studies were conducted to determine optimal locations to place temporary supports as well as to investigate stability differences between using a shore tower and a holding crane. Recommendations are presented to provide guidance for the lifting of curved I-girders as well as to maximize stability of partially constructed bridges.