Design of testbed and emulation tools

The research summarized was concerned with the design of testbed and emulation tools suitable to assist in projecting, with reasonable accuracy, the expected performance of highly concurrent computing systems on large, complete applications. Such testbed and emulation tools are intended for the eventual use of those exploring new concurrent system architectures and organizations, either as users or as designers of such systems. While a range of alternatives was considered, a software based set of hierarchical tools was chosen to provide maximum flexibility, to ease in moving to new computers as technology improves and to take advantage of the inherent reliability and availability of commercially available computing systems

Current status of one- and two-dimensional numerical models: Successes and limitations

The capabilities of one and two-dimensional numerical solar cell modeling programs (SCAP1D and SCAP2D) are described. The occasions when a two-dimensional model is required are discussed. The application of the models to design, analysis, and prediction are presented along with a discussion of problem areas for solar cell modeling

A Simple Boltzmann Transport Equation for Ballistic to Diffusive Transient Heat Transport

Developing simplified, but accurate, theoretical approaches to treat heat transport on all length and time scales is needed to further enable scientific insight and technology innovation. Using a simplified form of the Boltzmann transport equation (BTE), originally developed for electron transport, we demonstrate how ballistic phonon effects and finite-velocity propagation are easily and naturally captured. We show how this approach compares well to the phonon BTE, and readily handles a full phonon dispersion and energy-dependent mean-free-path. This study of transient heat transport shows i) how fundamental temperature jumps at the contacts depend simply on the ballistic thermal resistance, ii) that phonon transport at early times approach the ballistic limit in samples of any length, and iii) perceived reductions in heat conduction, when ballistic effects are present, originate from reductions in temperature gradient. Importantly, this framework can be recast exactly as the Cattaneo and hyperbolic heat equations, and we discuss how the key to capturing ballistic heat effects is to use the correct physical boundary conditions.Comment: 9 pages, 5 figure

Flight tests of Viking parachute system in three Mach number regimes. 2: Parachute test results

Tests of the Viking 16.15-meter nominal-diameter disk-gap-band parachute were conducted at Mach number and dynamic pressure conditions which bracketed the range postulated for the Viking '75 mission to Mars. Parachutes were deployed at supersonic, transonic, and subsonic speeds behind a simulated Viking entry capsule. All parachutes successfully deployed, inflated, and exhibited sufficient drag and stability for mission requirements. Basic parachute data including loads, drag coefficients, pull-off angles, and canopy area ratios are presented. Trajectory reconstruction and onboard camera data methods were combined to yield continuous histories of both parachute and test-vehicle angular motions which are presented for the period from parachute deployment through steady inflation

Effect of Ankle Taping on Dynamic Balance and Perception of Stability

Purpose: The purpose of this study was to examine the actual and perceived effect of taping on dynamic stability. Methods: 21 physically active subjects [12 females (age = 20.33 ± 1.44 years, height = 165 ± 0.05 cm, mass = 68.76 ± 12.69 kg), and 9 males (age = 21.33 ± 1.66 years, height = 180 ± 0.10 cm, mass = 86.54 ± 9.46 kg)] participated in this study. Dynamic stability and perception of stability were assessed barefoot and with the ankle taped. The taped ankle condition used a standard preventive tape application including two anchors, three stirrups, close downs, horseshoes, two heel locks per side and two figures of eight. The Biodex Balance System SD was used to measure medial-lateral and anterior-posterior stability. Dynamic balance was assessed in a single leg stance during three 20-second trials at stability level 4. A 30-second rest period was provided between trials. Perception of stability was assessed using a 4-point Likert scale (1 = very unstable, 2 = unstable, 3 = stable, 4 = very stable) after each test session. Independent variables were counter-balanced to minimize the effects of fatigue associated with the testing procedures. A Repeated measures ANOVA was used to analyze the difference between barefoot and ankle tape for medial-lateral and anterior-posterior dynamic stability indices and perception of stability. All tests of significance were carried out at an alpha level = 0.05. The Bonferroni post hoc test was used for all paired comparisons. Results: Significant differences were not found for medial-lateral stability (Barefoot = 1.24 ± 0.63, Taped = 1.21 ± 0.72) nor anterior-posterior stability (Barefoot = 1.70 ± 1.07, Taped = 1.50 ± 0.89). Significant differences were found for perception of stability (Barefoot = 2.57 ± 0.60, Taped = 3.32 ± 0.67, p = 0.000). Conclusions: The use of ankle taping had no influence on dynamic stability measures in this study. Ankle taping did cause an increased perception of stability suggesting that ankle taping may have more of a placebo effect in uninjured ankles

Ballisticity of nanotube FETs: Role of phonon energy and gate bias

We investigate the role of electron-phonon scattering and gate bias in degrading the drive current of nanotube MOSFETs. Our central results are: (i) Optical phonon scattering significantly decreases the drive current only when gate voltage is higher than a well-defined threshold. It means that elastic scattering mechanisms are most detrimental to nanotube MOSFETs. (ii) For comparable mean free paths, a lower phonon energy leads to a larger degradation of drive current. Thus for semiconducting nanowire FETs, the drive current will be more sensitive than carbon nanotube FETs because of the smaller phonon energies in semiconductors. (iii) Radial breathing mode phonons cause an appreciable reduction in drive current.Comment: 16 pages, 1 table, 4 figure

Report on High Intensity Solar Cells. Period Covered: June 1, 1983 to November 4, 1984

The purpose of this program is to provide general analytic support to Sandia National Laboratory’s effort to develop high efficiency, high concentration solar cells. This support has taken the following forms: 1) Implementation of the two-dimensional silicon code on Purdue’s Cyber 205. 2) The release of both the one- and two-dimensional silicon codes to Sandia National Laboratory. 3) Continued enhancement of the codes and updating of the physical models used by the codes. 4) Use of the two-dimensional code to investigate the performance and design of high concentration solar cells.speed over conventional sequential multi-mode systems. The multi-mode system which uses Golay codes is shown to provide the best overall performanc