Browsing by Subject "Systems"
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Item The application of systems engineering to a Space-based Solar Power Technology Demonstration Mission(2012-05) Chemouni Bach, Julien; Fowler, Wallace T.; Guerra, Lisa A.This thesis presents an end-to-end example of systems engineering through the development of a Space-based Solar Power Satellite (SSPS) technology demonstration mission. As part of a higher education effort by NASA to promote systems engineering in the undergraduate classroom, the purpose of this thesis is to provide an educational resource for faculty and students. NASA systems engineering processes are tailored and applied to the development of a conceptual mission in order to demonstrate the role of systems engineering in the definition of an aerospace mission. The motivation for choosing the SSPS concept is two fold. First, as a renewable energy concept, space-based solar power is a relevant topic in today's world. Second, previous SSPS studies have been largely focused on developing full-scale concepts and lack a formalized systems engineering approach. The development of an SSPS technology demonstration mission allows for an emphasis on determining mission, and overall concept, feasibility in terms of technical needs and risks. These are assessed through a formalized systems engineering approach that is defined as an early concept or feasibility study, typical of Pre-Phase A activities. An architecture is developed from a mission scope, involving the following trade studies: power beam type, power beam frequency, transmitter type, solar array, and satellite orbit. Then, a system hierarchy, interfaces, and requirements are constructed, and cost and risk analysis are performed. The results indicate that the SSPS concept is still technologically immature and further concept studies and analyses are required before it can be implemented even at the technology demonstration level. This effort should be largely focused on raising the technological maturity of some key systems, including structure, deployment mechanisms, power management and distribution, and thermal systems. These results, and the process of reaching them, thus demonstrate the importance and value of systems engineering in determining mission feasibility early on in the project lifecycle.Item Case studies of low socioeconomic Mexican American graduates in the Austin Independent School District: why they didn't drop out(Texas A&M University, 2007-04-25) Duncan, Lucila DiazResearch data revealed that Mexican Americans have the highest dropout rate of any other Hispanic group. Since Hispanics are becoming the highest minority group in the U.S., the primary purpose of this qualitative study was to investigate what helped third generation low socioeconomic Mexican American A.I.S.D. students successfully graduate from high school. Three former students were selected from three different high schools. The researcher collected data through individual interviews with each participant and with key informants such as parents and school personnel. Issues examined included participant perceptions of factors that kept them in school, the support systems they believed were important, and the challenges they encountered. The overall findings revealed that the three participants had a strong sense of control, positive relationships with peers and school staff, parents who valued education, and strong school support through programs or personnel. Recommendations for educators based on the findings include 1) staff development on building relationships with students and communicating with parents, 2) creation of nurturing and academically rigorous school environments.Item Managing academic and personal life in graduate studies : an interactive qualitative analysis of graduate student persistence and transformation(2011-08) Winston, Rachel Anne; Roueche, John E.; Northcutt, Norvell; McClenney, Kay; McCombs, Maxwell; Butler, Jess; Reddick, Richard; McCoy, DannyThis study examines the impact of academic and personal life on graduate student persistence and transformation. Of particular interest are the relationships, emotions, and life management skills required throughout the graduate experience and how socialization, emotional intelligence, and advising aid students through their academic program. With an average of seven to eight years required to complete a doctoral program, life happens. Students enter and leave relationships, children are born, family members have emergencies, health issues arise, and emotional growth takes place. Therefore, students transform not only academically, but in many ways. These are intertwined as evidenced by the data-derived system representation. The importance of understanding the interconnected links in graduate experience spans academic, social, economic, and societal spheres. Each year hundreds of thousands of students enter graduate school. However, for doctoral students, there is an enormous gap between acceptance and completion. After seven years, approximately 50 percent complete their program and after ten years the rate climbs to only 57 percent (Council of Graduate Schools, 2010). This study offers a systemic representation and a four-stage model of graduate student development, incorporating student-identified factors: Faculty Impact, Life Management, Relationships, Playing the Game, Growth/Transformation, Emotions, and Reward/Purpose. Stage I: Orientation and Socialization Stage II: Adjustment and Transition Stage III: Navigation and Transformation Stage IV: Completion and Advancement The results, presented as a systems-based model, along with analysis, may be used to support faculty, advisors, and administrators in creating better advising, orientation, evaluation, and support systems. Departmental policies may be improved to identify at-risk students, provide mentorship opportunities, or obtain continual feedback to understand the underlying factors that may stop students from progressing. This research might also help identify students during the application/admission process. The methodological framework used to create the system produced in this study is Interactive Qualitative Analysis (Northcutt & McCoy, 2004), a methodology that provides the quantitative rigor of algorithmically generated data analysis, combined with the qualitative descriptiveness of interviews, in order to provide insights into the drivers of graduate school persistence. This methodology uses a systematic, protocol-driven research procedure to construct a unified, descriptive diagram to illustrate the phenomenon.Item Switched systems as models of dynamic treatment scheduling(2009-05) Wang, Ning; Martin, Clyde F.; Surles, James; Trindade, A. AlexandreOne interesting problem in treating a disease with multiple drug therapies is the timing of the drug treatment. In this thesis, we study the switching time of the drug therapies by using the theories of switching system developed by Dayawansa and Martin [2]. The model we are interested in is developed in the following manner. We assume some 2 by 1 vector, x, to represent the state of the patient in the treatment, then the length of the vector is being measured and that is scaled so that the length 0 represent death and 1 represent remission. For each treatment we assume the model of the form xn+1 = Axn where A is 2 by 2 matrix with |A| 6= 0. Then for two treatments, we have the combined model xn+1 = (nA + (1 − n)B)xn where |A||B| 6= 0 and n 2 {0, 1}. We consider n to be a control variable which represents the treatment to be applied. Then for each sequence of n, the switched linear system can be written as the product of random matrices A and B. In this thesis we give conditions that a discrete time switched linear system must satisfy if it is stable. We do this by calculating the mean and covariance of the set of matrices obtained by using all possible switches. The theory of switched linear systems has received considerable attention in the systems theory literature in the last two decades. However, for discrete time switched systems the literature is much older going back to at least the early 1960��s with the publication of the paper of Furstenberg and Kesten in the area of products of random matrices, or if you like the random products of matrices. The way that we have approached this problem is to consider the switched linear system as evolving on a partially ordered network that is, in fact, a tree. This allows us to make use of the developments of 50 years of study on random products that exists in the statistics literature. A nice byproduct of this research is that we use K��onig��s theorem of finatary trees. This may be the first use of this theorem in systems and control. In this thesis, based on the proof of several theories, we apply a 2 by 2 matrices example, to the timing of drug treatment problem and we can find a particular switching treatments regime to drive the system away from the origin, which means the patients could be cured.Item Systems engineering processes for a student-based design laboratory(2009-12) Garner, Michael Dax; Bishop, Robert H., 1957-; Guerra, Lisa A.A student-based university environment for engineering design and development is much different from a product development environment within the aerospace industry. Therefore, a different approach to systems engineering should be considered. By its very nature, a university product development laboratory thrives on creativity and rejects bureaucracy. Experience shows that continuity and discipline within a project is crucial for success. The practice of systems engineering enables technical project discipline. Systems engineering is the art and science of developing an operable system that meets requirements within imposed constraints. The purpose of this thesis is to describe the systems engineering processes and techniques necessary for a student-based project, and explicitly show how to implement these processes. Although attempts have been made to utilize a few systems engineering techniques in past projects, many students did not properly and consistently apply those techniques to the technical design work. The goal of the thesis is to tailor the NASA systems engineering processes to a student-based design laboratory environment and to apply the methodologies to the mission design of Paradox. The Picosatellite for Autonomous Rendezvous and Docking on-Orbit eXperiment, or Paradox, is the second of four missions to demonstrate autonomous rendezvous and docking with a picosatellite-class satellite. A strong technical contribution highlighted within the thesis involves developing an open architecture rendezvous targeting algorithm for the Paradox mission in the face of large mission architecture uncertainties. The robust targeting algorithm builds from previous work utilizing an optimizer based on the Clohessey-Wiltshire equations and an iterative Lambert targeter. The contribution extends the rendezvous transfer times by including a multi-revolution Lambert targeter. The rendezvous algorithm will perform successfully given any launch vehicle and target spacecraft vehicle supporting the notion of an open architecture to satisfy the mission. The development of the algorithm is embedded within the context of the systems engineering processes to clearly showcase the intimate connection between systems engineering processes and the technical engineering design of a mission.