The GSFC NASTRAN thermal analyzer new capabilities

An overview of four analysis capabilities, which developed and integrated into the NASTRAN Thermal Analyzer, is given. To broaden the scope of applications, these additions provide the NTA users with the following capabilities: (1) simulating a thermal louver as a means of the passive thermal control, (2) simulating a fluid loop for transporting energy as a means of the active thermal control, (3) condensing a large sized finite element model for an efficient transient thermal analysis, and (4) entering multiple boundary condition sets in a single submission for execution in steady state thermal analyses

NASTRAN cyclic symmetry capability

A development for NASTRAN which facilitates the analysis of structures made up of identical segments symmetrically arranged with respect to an axis is described. The key operation in the method is the transformation of the degrees of freedom for the structure into uncoupled symmetrical components, thereby greatly reducing the number of equations which are solved simultaneously. A further reduction occurs if each segment has a plane of reflective symmetry. The only required assumption is that the problem be linear. The capability, as developed, will be available in level 16 of NASTRAN for static stress analysis, steady state heat transfer analysis, and vibration analysis. The paper includes a discussion of the theory, a brief description of the data supplied by the user, and the results obtained for two example problems. The first problem concerns the acoustic modes of a long prismatic cavity imbedded in the propellant grain of a solid rocket motor. The second problem involves the deformations of a large space antenna. The latter example is the first application of the NASTRAN Cyclic Symmetry capability to a really large problem

A design study for the incorporation of aeroelastic capability into NASTRAN

Modifications and computational tasks required for aeroelastic capability in NASTRA

Transformation of 1,1,1-trichloroethane in an anaerobic packed-bed reactor at various concentrations of 1,1,1-trichloroethane, acetate and sulfate

Biotransformation of 1,1,1-trichloroethane (CH3CCl3) was observed in an anaerobic packed-bed reactor under conditions of both sulfate reduction and methanogenesis. Acetate (1 mM) served as an electron donor. CH3CCl3 was completely converted up to the highest investigated concentration of 10 µM. 1,1-Dichloroethane and chloroethane were found to be the main transformation products. A fraction of the CH3CCl3 was completely dechlorinated via an unknown pathway. The rate of transformation and the transformation products formed depended on the concentrations of CH3CCl3, acetate and sulfate. With an increase in sulfate and CH3CCl3 concentrations and a decrease in acetate concentration, the degree of CH3CCl3 dechlorination decreased. Both packed-bed reactor studies and batch experiments with bromoethanesulfonic acid, an inhibitor of methanogenesis, demonstrated the involvement of methanogens in CH3CCl3 transformation. Batch experiments with molybdate showed that sulfate-reducing bacteria in the packed-bed reactor were also able to transform CH3CCl3. However, packed-bed reactor experiments indicated that sulfate reducers only had a minor contribution to the overall transformation in the packed-bed reactor.

The Role Of Positive Regard In Self-Regulated Learning: An Analysis Of Student Evaluation Data

Learning outcomes in classroom settings are impacted by many components of the course structure and delivery.  One of these is positive regard from the instructor as perceived by students.   Similarly, perceived positive regard is an important aspect of learning outcomes in a distance education environment, although the ways in which regard are shown are much different.  The present study seeks to quantify the impact of perceived positive regard on learning outcomes in both classroom and distance modalities and compare the results for similarities and differences.  Data from the Student Instructional Report, both classroom and distance versions, from the authors’ institution is used to validate the relationships among positive regard, motivation, and learning outcomes shown in Eflides’s (2011) metacognitive and affective model of self-regulated learning (MASRL).  Analysis of data from one academic year of available data does support these relationships, with some differences found between distance and traditional classroom settings.  Support and suggested direction for future research on the role of positive regard in distance learning are offered. 

Effectiveness of Online Videos to Modify Students\u27 Knowledge and Perceived Barriers Regarding Study Abroad Opportunties

The need to increase the number of students participating in study abroad is a goal that higher education must recognize. For ten years, the level of participation among students enrolled in colleges of agricultural sciences has remained at constant level. In a society that is globally interconnected, it is imperative that future graduates comprehend various dimensions of culture, agricultural production, and economy to succeed. The purpose of this study was to determine the effectiveness of online videos to modify students’ knowledge and perceived barriers regarding study abroad opportunities. The objectives of this paper are: 1. Describe the amount of learning obtained through watching study abroad videos; 2. Determine changes to students’ perceived barriers regarding their possible participation in study abroad programs. In order to assess students’ perceptions, three online videos were developed. Videos were based on a semester-long study abroad program in Russia and two study tour programs in Puerto Rico and Brazil, respectively. A quasi-experimental research design was used in this study. One hundred fifty six students from nine sections of the first year seminar participated in the study. In this study, the use of online videos was effective in communicating information and diminishing the perceived barriers to study abroad. Other colleges and programs could use this strategy to promote their international programs. In addition, administrators could use the results of this study to develop online videos to teach content and dispel myths regarding study abroad programs

Simulation study of GaAsP/Si tandem solar cells

A model, adapted from the Shockley-Queisser detailed balance model to tandem solar cells with a monolithically grown GaAsxP1-x top junction on a Si bottom junction, has been developed. Updated data have been used for the absorption spectrums. Two surface geometries, flat and ideally textured, have been investigated. As an important improvement over existing models, the effects of threading-dislocations related Shockley-Read-Hall recombinations in the GaAsxP1-x cell, due to the lattice mismatch between the GaAsxP1-x epilayers and the Si substrate, have been taken into consideration. Auger recombinations in the Si bottom cell and luminescent coupling between the cells have also been considered. For a dislocation free 2-μm thick top cell, maximal theoretical efficiencies of 41.6% and 39.1% have been calculated for a textured and a flat surface, respectively. For threading dislocation (TD) densities below 10^4 cm^-2, the impact of TDs in the GaAsxP1-x layers on the solar cell performances is very limited. With TD densities over 10^5 cm^-2, the top cell open circuit voltage is reduced, hence the overall efficiency. For TD densities over 4×10^6 cm^-2, as the diffusion length of minority carriers in the base gets smaller than the base thickness, the short circuit current in the top GaAsxP1-x cell is also reduced, resulting in a decrease in the optimal top cell bandgap. Using non ideal EQEs and surface recombination rates from published experimental data, the long-term efficiency potential of the investigated technology has been estimated to be ~35.1% for an ideally textured GaAsxP1 x/Si tandem cell with a TD density of 10^5 cm^-2 (~33.0% with a flat surface)