Space power technology 21: Photovoltaics

The Space Power needs for the 21st Century and the program in photovoltaics needed to achieve it are discussed. Workshops were conducted in eight different power disciplines involving industry and other government agencies. The Photovoltaics Workshop was conducted at Aerospace Corporation in June 1987. The major findings and recommended program from this workshop are discussed. The major finding is that a survivable solar power capability is needed in photovoltaics for critical Department of Defense missions including Air Force and Strategic Defense Initiative. The tasks needed to realize this capability are described in technical, not financial, terms. The second finding is the need for lightweight, moderately survivable planar solar arrays. High efficiency thin III-V solar cells can meet some of these requirements. Higher efficiency, longer life solar cells are needed for application to both future planar and concentrator arrays with usable life up to 10 years. Increasing threats are also anticipated and means for avoiding prolonged exposure, retraction, maneuvering and autonomous operation are discussed

Air Force and DOD solar power requirements

It is noted that future power requirements are increasing for some expanded and new missions within the Air Force and Department of Defense. New requirements are needed in terms of lifetime, survivability, power level and performance. The photovoltaic arrays have a demonstrated record of reliable performance, life, affordable cost, and utility. It is argued that there is a need to push for the research and development resources needed to develop the technology base for these future power system needs

Counting cycles in labeled graphs: The nonpositive immersion property for one-relator groups

We prove a rank 1 version of the Hanna Neumann Theorem. This shows that every one-relator 2-complex without torsion has the nonpositive immersion property. The proof generalizes to staggered and reducible 2-complexes.Comment: 12 pages, 2 figure

Does it Matter if Students Have the Same Instructor for Both Lecture and Lab Sections? An Analysis of Introductory Biology Students

With the goal of increasing the immediacy of the relationship between tenure-track professors and students, science departments in liberal arts colleges may try to arrange their curriculum so that students have the same professor in both the lecture and the lab section of introductory courses. While this goal seems laudable, empirical data are currently lacking to justify the logistical hurdles and professional sacrifices likely required to match professors to students in both lecture and lab sections of large courses. To address this data gap, I analyzed student evaluations and grades from three years of an introductory biology course that included separate lecture and lab sections. There was no evidence that matching a student’s lecture and lab instructor had any benefit on either the students’ perception of the effectiveness of the labs, or on the students’ performance in their lab or lecture sections. In addition, there was no consistent pattern in students’ perceptions of the relative effectiveness of tenure-track professors, visiting professors, and adjunct instructors. This study suggests that students may even benefit from having different instructors in their lecture and lab, whether they are tenured professors, visiting professors, or part-time adjuncts

Concert recording 2013-02-02

[Track 01]. Black music symposium. The history and development of the negro spiritual / Raymond Wise -- The history and development of gospel music / Clark Joseph -- Using folk melodies as a foundation for composition / Shawn Okpebholo

Progress on Gust Load Alleviation Wind Tunnel Experiment and Aeroservoelastic Model Validation for a Flexible Wing with Variable Camber Continuous Trailing Edge Flap System

This paper discusses a wind tunnel experiment of active gust load alleviation of a flexible wing which took place at University of Washington (UW) in 2019. The experiment performed under a NASA SBIR contract with Scientific Systems Company, Inc (SSCI). The objective of the experiment is to demonstrate active controls of the Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for gust load alleviation and real-time drag optimization. The wind tunnel model is a 8.2% sub-scale Common Research Model (CRM) wing. The wing structure is designed to provide a substantial degree of flexibility to represent that of a modern high-aspect ratio wing. Eight active control surfaces are employed in the VCCTEF. A new gust generator system was designed and installed by UW under a sub-contract with SSCI. The first test entry started in July 2019 and ended in September 2019. During this test entry, many significant issues were found with the hardware and software. The significant issues with the servos prevented the test objective from being completed. A follow-up second test entry in 2020 is being planned. The wing system is being repaired by SSCI. This paper reports on the progress of this experimental effort and the aeroservoelastic (ASE) model validation which was conducted during the test entry

Revisiting Brown Versus Board of Education: Differences in School Context and the influence of Racial Attitudes on Academic Attainment and Civic Engagement among Black Americans across the Lifespan

Since Brown versus the Board of Education 60 years ago, educators and social and behavioral scientists have tried to identify factors related to better achievement for Black Americans. Since the desegregation of schools in the U.S., Black American students have reported lower grade point averages, standardized test scores, and graduation rates (Allen, 1992). Previous research has investigated school context and climate as well as the influence of racial attitudes on academic achievement. Findings suggest that positive student perceptions of school climate and context (e.g., pride, social support, relationships with a teacher, access to resources) were related to better academic outcomes (Hurley & Lustbader, 1997). However, the research on the influence of racial attitudes have been inconclusive (Chavous et al., 2003; Fordham & Ogbu 1986). Thus, the purpose of this study is two-fold. First, to explore whether racial attitudes were related to academic attainment and civic engagement, and second, to examine whether there are differences in perceptions in school pride and school climate for students in historically black high schools and historically white high schools. To assess the aforementioned research questions, thirty-three Black American high school graduates from a historically white high school and eighty-two Black Americans from historically black high schools were sampled. Spearman Rho correlations and Independent sample T-tests were run to assess the relationship between the following. 1) Racial attitudes, educational attainment, and civic engagement. 2) Differences in perceptions of school climate for Blacks at historically White and Black high schools. Findings reveal statistically significant associations between racial attitudes and educational attainment as well as civic engagement. Moreover, differences were also found in perceptions of climate across school types. Given these results, further research is needed to explore the influence of students’ perception of their school experience and racial attitudes upon educational and life outcomes