Systems identification technology development for large space systems

A methodology for synthesizinng systems identification, both parameter and state, estimation and related control schemes for flexible aerospace structures is developed with emphasis on the Maypole hoop column antenna as a real world application. Modeling studies of the Maypole cable hoop membrane type antenna are conducted using a transfer matrix numerical analysis approach. This methodology was chosen as particularly well suited for handling a large number of antenna configurations of a generic type. A dedicated transfer matrix analysis, both by virtue of its specialization and the inherently easy compartmentalization of the formulation and numerical procedures, is significantly more efficient not only in computer time required but, more importantly, in the time needed to review and interpret the results

An analysis of reported accidents to patients in hospital X for the year 1954.

Thesis (M.S.)--Boston Universit

Test program to provide confidence in liquid oxygen cooling of hydrocarbon fueled rocket thrust chambers

An experimental program has been planned at the NASA Lewis Research Center to build confidence in the feasibility of liquid oxygen cooling for hydrocarbon fueled rocket engines. Although liquid oxygen cooling has previously been incorporated in test hardware, more runtime is necessary to gain confidence in this concept. In the previous tests, small oxygen leaks developed at the throat of the thrust chamber and film cooled the hot-gas side of the chamber wall without resulting in catastrophic failure. However, more testing is necessary to demonstrate that a catastrophic failure would not occur if cracks developed further upstream between the injector and the throat, where the boundary layer has not been established. Since under normal conditions cracks are expected to form in the throat region of the thrust chamber, cracks must be initiated artificially in order to control their location. Several methods of crack initiation are discussed in this report. Four thrust chambers, three with cracks and one without, should be tested. The axial location of the cracks should be varied parametrically. Each chamber should be instrumented to determine the effects of the cracks, as well as the overall performance and durability of the chambers

Is FIRST J102347.6+003841 Really a Cataclysmic Binary?

The radio source FIRST J102347.6+003841 was presented as the first radio-selected cataclysmic. In the discovery paper, Bond et al. (2002) show a spectrum consistent with a magnetic AM Her-type system and a light curve with rapid, irregular flickering. In contrast, Woudt, Warner, and Pretorius (2004) found a smoothly-varying light curve with a period near 4.75 h and one minimum per orbit, indicating a dramatic change. We present time-resolved spectra showing a superficially normal, mid-G type photosphere, with no detectable emission lines. The absorption-line radial velocity varies sinusoidally, with semi-amplitude 268 +- 4 km/s, on the orbital period, which is refined to 0.198094(2) d. At this orbital period the secondary's spectral type is atypically early, suggesting an unusual evolutionary history. We also obtained BVI photometry around the orbit. The light curve resembles that given by Woudt et al., and the color modulation is consistent with a heating effect. A simple illumination model matches the observations strikingly well with a Roche-lobe filling secondary near 5650 kelvin being illuminated by a primary giving out around 2 solar luminosities. The modest amplitude of the observed modulation constrains the orbital inclination to be less than about 55 deg, unless the gravity darkening is artificially reduced. The resulting primary star mass is above the Chandrasekhar limit (assuming conventional gravity darkening). We examine the possibility that the compact object in this system is not a white dwarf, in which case this is not actually a cataclysmic variable. On close examination, FIRST J102347.6+003841 defies easy classification.Comment: 24 pages, 5 postscript and two JPG figures; Astronomical Journal, accepte

Stochastic homogenization of Hamilton-Jacobi and degenerate Bellman equations in unbounded environments

We consider the homogenization of Hamilton-Jacobi equations and degenerate Bellman equations in stationary, ergodic, unbounded environments. We prove that, as the microscopic scale tends to zero, the equation averages to a deterministic Hamilton-Jacobi equation and study some properties of the effective Hamiltonian. We discover a connection between the effective Hamiltonian and an eikonal-type equation in exterior domains. In particular, we obtain a new formula for the effective Hamiltonian. To prove the results we introduce a new strategy to obtain almost sure homogenization, completing a program proposed by Lions and Souganidis that previously yielded homogenization in probability. The class of problems we study is strongly motivated by Sznitman's study of the quenched large deviations of Brownian motion interacting with a Poissonian potential, but applies to a general class of problems which are not amenable to probabilistic tools.Comment: 51 pages, 2 figures. We have added material and made some corrections to our previous versio

An eco-solution for track & trace of goods and third party logistics

This paper presents a new economic cost-effective solution known as the Web and telephony based method for tracking and tracing of goods and small and medium sized third party logistic providers. Considering that these companies usually operate on very flat margins, a comparison is made of the available track and trace technologies like GPS, mobile phone approximated GPS and Java based cell tracking in terms of costs, operating risks, and other evaluation criteria

Error estimates and convergence rates for the stochastic homogenization of Hamilton-Jacobi equations

We present exponential error estimates and demonstrate an algebraic convergence rate for the homogenization of level-set convex Hamilton-Jacobi equations in i.i.d. random environments, the first quantitative homogenization results for these equations in the stochastic setting. By taking advantage of a connection between the metric approach to homogenization and the theory of first-passage percolation, we obtain estimates on the fluctuations of the solutions to the approximate cell problem in the ballistic regime (away from flat spot of the effective Hamiltonian). In the sub-ballistic regime (on the flat spot), we show that the fluctuations are governed by an entirely different mechanism and the homogenization may proceed, without further assumptions, at an arbitrarily slow rate. We identify a necessary and sufficient condition on the law of the Hamiltonian for an algebraic rate of convergence to hold in the sub-ballistic regime and show, under this hypothesis, that the two rates may be merged to yield comprehensive error estimates and an algebraic rate of convergence for homogenization. Our methods are novel and quite different from the techniques employed in the periodic setting, although we benefit from previous works in both first-passage percolation and homogenization. The link between the rate of homogenization and the flat spot of the effective Hamiltonian, which is related to the nonexistence of correctors, is a purely random phenomenon observed here for the first time.Comment: 57 pages. Revised version. To appear in J. Amer. Math. So

Exploring Students’ Perceptions of their Experiences in a Social Justice Living–Learning Community

Contemporary higher education leaders continue to deem the development of civic-minded graduates as among the primary goals of postsecondary education (Astin, 1996Astin, H. S. (1996). Leadership for social change. About Campus, 1(3), 4–10. doi:10.1002/abc.v1.3[Crossref] , [Google Scholar]; Cress, Burack, Giles, Elkins, & Stevens, 2010Cress, C., Burack, C., Giles, D. E., Elkins, J. E., & Stevens, M. C. (2010). A promising connection: Increasing college access and success through civic engagement. Boston, MA: Campus Compact. [Google Scholar]; Hurtado, Ruiz, & Whang, 2012Hurtado, S., Ruiz, A., & Whang, H. (2012). Assessing student social responsibility and civic learning. Paper presented at the 2012 Annual Forum of the Association for Institutional Research, New Orleans, Louisiana. [Google Scholar]). Today’s undergraduates are poised to engage with their communities in numbers greater than their predecessors in previous generations, believing it is their responsibility to make society better (Kiesa et al., 2007Kiesa, A., Orlowski, A. P., Levine, P., Both, D., Kirby, E. H., Lopez, M. H., & Marcelo, K. B. (2007). Millennials talk politics: A study of college student political engagement. New York, NY: The Center for Information & Research on Civic Learning & Engagement. [Google Scholar]). In 2012, more than two-thirds of postsecondary students reported participation in community service over the past year, despite their overwhelming disillusionment with the United States government and social institutions (Levine & Dean, 2012Levine, A., & Dean, D. R. (2012). Generation on a tightrope: A portrait of today’s college student. San Francisco, CA: Wiley. [Google Scholar]) Civic engagement lacks a common definition in the literature (Jacoby, 2009Jacoby, B. (Ed.). (2009). Civic engagement in higher education: Concepts and practices. San Francisco, CA: Jossey-Bass. [Google Scholar]), however it typically includes involvement in the community with the purpose of “enhancing students’ understanding of civic life” (Cress et al., 2010Cress, C., Burack, C., Giles, D. E., Elkins, J. E., & Stevens, M. C. (2010). A promising connection: Increasing college access and success through civic engagement. Boston, MA: Campus Compact. [Google Scholar], p. 4). A growing body of research raised concerns with community service, service-learning, and other forms of civic engagement as reinforcing stereotypes (Dooley & Burant, 2015Dooley, J. C., & Burant, T. J. (2015). Lessons from pre-service teachers: Under the surface of service learning. In O. Delano-Oriaran, M. Penick-Parks, & S. Fondrie (Eds.), Service-learning and civic engagement: A sourcebook (pp. 325–332). Thousand Oaks, CA: SAGE Publications.[Crossref] , [Google Scholar]). These studies urged greater care when designing community involvement opportunities, including attention to students’ development and previous experience, meaningful curricular connections, and adequate contextualization and reflection (Dooley & Burant, 2015Dooley, J. C., & Burant, T. J. (2015). Lessons from pre-service teachers: Under the surface of service learning. In O. Delano-Oriaran, M. Penick-Parks, & S. Fondrie (Eds.), Service-learning and civic engagement: A sourcebook (pp. 325–332). Thousand Oaks, CA: SAGE Publications.[Crossref] , [Google Scholar]). Some campuses have linked social justice to civic engagement to advance students’ knowledge about inequity, thus moving them away from a savior orientation (Dooley & Burant, 2015Dooley, J. C., & Burant, T. J. (2015). Lessons from pre-service teachers: Under the surface of service learning. In O. Delano-Oriaran, M. Penick-Parks, & S. Fondrie (Eds.), Service-learning and civic engagement: A sourcebook (pp. 325–332). Thousand Oaks, CA: SAGE Publications.[Crossref] , [Google Scholar]) and deepening their understanding of the experience (Prentice, 2007Prentice, M. (2007). Service-learning and civic engagement. Academic Questions, 20(2), 135–145. doi:10.1007/s12129-007-9005-y[Crossref] , [Google Scholar]). Although conceptualized in varying ways, for this article social justice is defined as work toward ending the system of oppression giving certain social groups greater privilege and power over other groups (Broido, 2000Broido, E. M. (2000). The development of social justice allies during college: A phenomenological investigation. Journal of College Student Development, 41(1), 3–18.[Web of Science ®] , [Google Scholar]). When coupled, the terms civic engagement and social justice often indicate the educators’ desire to situate students in their broader communities and increase their awareness of social inequity, which may inspire them to work for social change at the individual, cultural, and institutional levels (Boyle-Baise & Langford, 2004Boyle-Baise, M., & Langford, J. (2004). There are children here: Service learning for social justice. Equity & Excellence in Education, 37(1), 55–66. doi:10.1080/10665680490422115[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). Living–learning communities (LLCs) are increasingly utilized to deepen and cohere students’ collegiate experiences (Matthews, Smith, & MacGregor, 2012Matthews, R. S., Smith, B. L., & MacGregor, J. (2012). The evolution of learning communities: A retrospective. In K. Buch & K. E. Barron (Eds.), New directions for teaching and learning: No. 132. Discipline centered learning communities (pp. 99–111). San Francisco, CA: Jossey-Bass.[Crossref] , [Google Scholar]). Although variation exists in thematic and organizational type, these communities typically group students together in a residence hall, offer a shared academic experience, and provide co-curricular activities related to a theme (Inkelas & Soldner, 2011Inkelas, K. K., & Soldner, M. (2011). Undergraduate living–learning programs and student outcomes. Higher Education: Handbook of Theory and Research, 26, 1–55.[Crossref] , [Google Scholar]). Social justice LLCs, which focus on increasing students’ awareness of social inequity and providing them with opportunities to work for social change, are often found on college campuses (Inkelas, 2007Associates; Inkelas, K. K. (2007). National study of living–learning programs: 2007 report of findings. College Park, MD: Authors. [Google Scholar]). Yet little formal research has been done that explores the impact of these communities on students. Thus, the purpose of this study was to explore students’ experiences throughout their time in a social justice-focused LLC (hereafter referred by the pseudonym SJLLC) and one year after participation, focusing on how students described their participation in SJLLC and what aspects of the LLC had a lasting impression on them

An application of multivariable design techniques to the control of the national transonic facility

The digital versions of optimal linear regulator theory and eigenvalue placement theory are applied to the Mach number control loop of the National Transonic Facility cryogenic wind tunnel. The control laws developed are evaluated on a nonlinear simulation of the tunnel process for a typical est condition and are found to significantly reduce the open loop time required to achieve a Mach number set point

Three dimensional thrust chamber life prediction

A study was performed to analytically determine the cyclic thermomechanical behavior and fatigue life of three configurations of a Plug Nozzle Thrust Chamber. This thrust chamber is a test model which represents the current trend in nozzle design calling for high performance coupled with weight and volume limitations as well as extended life for reusability. The study involved the use of different materials and material combinations to evaluate their application to the problem of low-cycle fatigue in the thrust chamber. The thermal and structural analyses were carried out on a three-dimensional basis. Results are presented which show plots of continuous temperature histories and temperature distributions at selected times during the operating cycle of the thrust chamber. Computed structural data show critical regions for low-cycle fatigue and the histories of strain within the regions for each operation cycle