Browsing by Subject "Comparison"
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Item A Comparative Study of Kalman Filter Implementations for Relative GPS Navigation(2011-02-22) Fritz, Matthew PeytonRelative global positioning system (GPS) navigation is currently used for autonomous rendezvous and docking of two spacecraft as well as formation flying applications. GPS receivers deliver measurements to flight software that use this information to determine estimates of the current states of the spacecraft. The success of autonomous proximity operations in the presence of an uncertain environment and noisy measurements depends primarily on the navigation accuracy. This thesis presents the implementation and calibration of a spaceborne GPS receiver model, a visibility analysis for multiple GPS antenna cone angles, the implementation of four different extended Kalman filter architectures and a comparison of the advantages and disadvantages of each filter used for relative GPS navigation. A spaceborne GPS model is developed to generate simulated GPS measurements for a spacecraft located on any orbit around the Earth below the GPS constellation. Position and velocity estimation algorithms for GPS receivers are developed and implemented. A visibility analysis is performed to determine the number of visible satellites throughout the duration of the rendezvous. Multiple constant fields of view are analyzed and results compared to develop an understanding of how the GPS constellation evolves during the proximity operations. The comparison is used to choose a field of view with adequate satellite coverage. The advantages and disadvantages of the relative navigation architectures are evaluated based on a trade study involving several parameters. It is determined in this thesis that a reduced pseudorange filter provides the best overall performance in both relative and absolute navigation with less computational cost than the slightly more accurate pseudorange lter. A relative pseudorange architecture experiences complications due to multipath rich environments and performs well in only relative navigation. A position velocity architecture performs well in absolute state estimation but the worst of the four filters studied in relative state estimation.Item Area, delay and power comparison of adder topologies(2015-12) Ganesan, Sarvesh; Swartzlander, Earl E., Jr., 1945-; Touba, NurAn adder is an indispensable component for a processing system and is ever-present on an integrated circuit. With scaling and the increasing levels of integration seen in the contemporary integrated circuits, power consumption has become an important factor in deciding the performance of any adder circuit in addition to the speed. Area has always been another factor which is taken into account based on the application. This work provides a comprehensive analysis of the standard cell based CMOS implementations of six adder topologies of different word sizes in 45nm technology. The analysis is done on leakage power, dynamic power, speed and area. The switching activities of the circuits were captured using dynamic gate level simulation to perform the time based peak power analysis. Static timing analysis was performed to estimate the delay of the critical path for each circuit. The complexity of the circuit is decided based on the number of gates used in the implementation and the area utilized by the standard cells in the circuit. The analysis and results presented in this report will be helpful in choosing a specific adder configuration for an integrated circuit based on the constraints related to its application.Item Comparison of Climate Action Plans among Three Major Cities: Vancouver, Chicago, and Mexico CityMiles, Holly Anne; Eoff, Shirley; Stewart, Kenneth; Lamberson, ChristineMunicipal climate action planning continues to grow as a section of climate action planning. Global climate action planning, conducted at a country level, will not suffice to stop climate change. Rather, cities need to step up and take responsibility for their emissions by creating climate action plans of their own. This paper analyzes three climate action plans of three diverse cities: Vancouver, British Columbia; Chicago, Illinois; and Mexico City, Mexico. The study analyzes for motivations behind plan creation, effectiveness of plan created, and effects each plan has had on city greenhouse gas emissions and urban heat island effects. Finally, highlights of each plan, recognized by international organizations, are discussed in order to determine applicability to other cities.Item Comparison of Two Diet and Exercise Approaches on Weight Loss and Health Outcomes in Women(2012-12-05) Mardock, Michelle 1967-The purpose of this study was to determine the effects of following either the Curves? Fitness and Weight Management Plan or the Weight Watchers? Momentum? Plan on body composition and markers of health and fitness in previously sedentary obese women. Fifty-one women (age 35?8 yrs; height 163?7 cm; weight 90?1 kg; BMI 34?5 kg/m2; 47?7% body fat) were randomized to participate in the Curves? (C) or Weight Watchers? (W) weight loss programs for 16-wks. Participants in the C group (n=24) followed a 1,200 kcal/d diet for 1-wk; 1,500 kcal/d diet for 3 wks (~30%:45% CHO:PRO); and 2,000 kcals/d for 2-wks (45:30) and repeated this diet while participating in a supervised Curves? with Zumba program 3-d-wk. Remaining subjects (n=27) followed the W point-based diet program, received weekly group counseling, and were encouraged to exercise. Body composition, anthropometrics, resting energy expenditure (REE), lipid biomarkers, and hormone concentrations were assessed at 0, 4, 10, and 16 weeks. Maximal cardiopulmonary exercise capacity and upper and lower body isotonic strength and endurance were assessed at 0 and 16 weeks. Data were analyzed using multivariate analysis of variance for repeated measures. MANOVA analysis of body composition data revealed overall time (Wilks? Lamda p=0.001) and time by diet effects (Wilks? Lamda p=0.003). Subjects in both groups lost a similar amount of total mass (C -2.4?2.0, -4.1?3.4, -5.1?3.9; W -2.3?2.3, -4.5?3.0, -5.5?4.6 kg, p=0.78). However, subjects in the C group tended to have a greater reduction in percent body fat (C -3.3?5.2, -3.2?4.6, -4.7?5.4; W 0.6?6.7, -0.6?8.3, -1.4?8.1%, p=0.10) and body fat mass (C -3.9?5.5, -4.6?5.3, -6.4?5.9; W -0.4?5.7, -2.1?6.7, -2.9?7.8 kg, p=0.09), while maintaining FFM (C 1.5?4.3, 0.52?3.7, 1.3?4.0; W -1.8?5.4, -2.4?5.8, -2.5?5.1, p=0.01). While both groups had increases cardiovascular fitness, the C group experienced improvements in upper body muscular endurance (C 1.4?3.9; W -1.2?2.4 repetitions, p=0.006). Both groups experienced improvements in lipid biomarkers; however, only the C group experienced a moderate increase in HDL-c. Results indicate that participants following the C program experienced more favorable changes in body composition and markers of fitness and health than participants in the W program.Item Design and comparison of single crystal and ceramic Tonpilz transducers(2010-08) Nguyen, Kenneth Khai; Haberman, Michael R.; Wilson, Preston S.; Hall, Neal A.Transducers utilizing single crystal piezoelectrics as the active elements have been shown to exhibit broader operating bands, higher response levels, and higher power efficiency than transducers using piezoceramics while also reducing the size and mass of the transducer (Moffett et al., J. Acoust. Soc. Am., 2007). The key to these high performance characteristics is the piezocrystal's inherent high electromechanical coupling coefficient. One potential application is to replace multiple narrowband piezoceramic transducers with a single broadband piezocrystal transducer which reduces the system's weight and size. This is very important for the new generation of smaller and power efficient unmanned underwater vehicles (UUVs). A third application is for use in very broadband communication networks. The work presented here focuses specifically on the design, modeling, and construction of Tonpilz transducers using piezoelectrics as the active material. The modeling includes lumped element and finite element analysis to approximate the performance of these transducers. These models serve as the main structure of an overall iterative design process. The objective of this research is to compare the performance characteristics of a piezocrystal and a piezoceramic Tonpilz transducer and to validate the models by comparing the model predictions with experimental results.Item Distances and proximities : Havana and San Juan from the point of view of literature and oral histories(2015-05) Mercado Diaz, Mario Edgardo; Salgado, César Augusto; Merabet, Sofian, 1972-Cuba y Puerto Rico have for long been considered sister islands, fighting together against the influences of the Spanish Empire and the United States. The decade of the 1950s, however, proved to be the splitting point for both islands, sending them into very different trajectories of development. In their shared experience of Spanish colonization and USA interventions, how do San Juan and Havana residents perceive and use space today in their particular socio-political contexts and how does this affect the resident's sense of citizenship? I closely engage with the different urban spaces using ethnographic data and photographs taken during my recent fieldwork, creative texts describing said spaces and case studies examining the formation of racial, gender and class identities. Focusing on a specific place on the Malecón, Havana's iconic esplanade, I examine how practices of leisure, intimacy (e.g. erotic homosexual and heterosexual encounters), and self-expression challenge the revolutionary rhetoric of "sameness" (i.e. absence of race, class, crime or gender violence). As for San Juan, I dissect the layers of significance in public visual representation, as exemplified in the artwork painted over an abandoned house in Santurce, the site for queer, artistic and marginal expression. The scene, two black women drinking on the porch, rescues a sense of citizenship lost to the class and racial polarization, fragmentation, and the "ruination" of San Juan. Finally, I argue that an archipelagic city, composed of the descriptions of specific places in different cities, has been created in the sea, a space of crossing, endurance and death, within these inter-capillary exchanges of people, cultures and habits. This archipelagic city, not spoken about directly but referenced semantically, aids in the construction of trans-national identities and perspectives, specific perceptions on time and space, and the production of media and cultural forms of expression. My goal is to tie together these narrative strands linking trans-oceanic places into an urban map surpassing its own geographical context.Item Endogenous variables and weak instruments in cross-sectional nutrient demand and health information analysis: a comparison of solutions(Texas A&M University, 2004-09-30) Bakhtavoryan, Rafael GagikIn recent years, increasing attention has turned toward the effect of health information or health knowledge on nutrient intake. In determining the effect of health information on nutrient demand, researchers face the estimation problem of dealing with the endogeneity of health information knowledge. The standard approach for dealing with this problem is an instrumental variables (IV) procedure. Unfortunately, recent research has demonstrated that the IV procedure may not be reliable in the types of data sets that contain health information and nutrient intakes because the instruments are not sufficiently correlated with the endogenous variables (i.e., instruments are weak). This thesis compares the reliability of the IV procedure (and the Hausman test) with a relatively new procedure, directed graphs, given weak instruments. The goal is to determine if the method of directed graphs performs better in identifying an endogenous variable and also relevant instruments. The performance of the Hausman test and directed graphs are first assessed through conducting a Monte-Carlo sampling experiment containing weak instruments. Because the structure of the model is known in the Monte-Carlo experiment, these results are used as a guideline to determine which procedure would be more reliable in a real world setting. The procedures are then applied to a real-world cross-sectional dataset on nutrient intake. This thesis provides empirical evidence that neither the IV estimator (and Hausman test) or the directed graphs are reliable when instruments are weak, as in a cross-sectional dataset.Item Structural equation modeling compared with ordinary least squares in simulations and life insurers’ data(2013-05) Xiao, Xuan, active 2013; Sager, Thomas W.Structural equation model (SEM) is a general approach to analyze multivariate data. It is a relatively comprehensive model and combines useful characteristics from many statistical approaches, thus enjoys a variety of advantages when dealing complex relationships. This report gives a brief introduction to SEM, focusing especially the comparison of SEM and OLS regression. A simple tutorial of how to apply SEM is also included with the introduction and comparison. SEM can be roughly seen as OLS regression added with features such as simultaneous estimation, latent factors and autocorrelation. Therefore, SEM enjoys a variety of advantages over OLS regression. However, it is not always the case that SEM will be the optimal choice. The biggest concern is the complexity of SEM, for simpler model will be preferable for researchers when the fitness is similar. Two simulation cases, one requires special features of SEM and one satisfies assumptions of OLS regression, are applied to illustrate the choice between SEM and OLS regression. A study using data from US life insurers in the year 1994 serves as a further illustration. The conclusion is when special features of SEM is required, SEM fits better and will be the better choice, while when OLS regression assumptions are satisfied, SEM and OLS regression will fit equally well, considering the complexity of SEM, OLS regression will be the better choice.