Development of a second order approximation for the Navier-Stokes equations

The purpose of this paper is the development of a 2nd order finite difference approximation to the steady state Navier-Stokes equations governing flow of an incompressible fluid in a closed cavity. The approximation leads to a system of equations that has proved to be very stable. In fact, numerical convergence was obtained for Reynolds numbers up to 20,000. However, it is shown that extremely small mesh sizes are needed for excellent accuracy with a Reynolds number of this magnitude. The method uses a nine point finite difference approximation to the convection term of the vorticity equation. At the same time it is capable of avoiding values at corner nodes where discontinuities in the boundary conditions occur. Figures include level curves of the stream and vorticity functions for an assortment of grid sizes and Reynolds numbers.     

The preparation of CdSnP2/InP heterojunctions by liquid phase epitaxy from Sn-solution

Heterojunctions of n-type CdSnP₂ on p-type InP substrates are prepared by LPE from Sn-solutions. The significance of the tipping arrangement, of the initial solution composition and of the temperature program for preparing LPE layers of high quality is discussed. Heterodiodes cleaved from such LPE wafers electroluminesce under forward bias between 1 μm and 1.8 %m with internal quantum efficiencies approaching 1.8% at room temperature. When used as photovoltaic detectors, the quantum efficiency of these diodes surpasses that of Si for λ > 1.09 μ, and exceeds 1% for all wave-lengths between 0.96 and 1.3 μ.     

Carburization and gas reactions of hydrocarbon-nitrogen mixtures at 850 °C and 925 °C

Rates of carburization of low-carbon steel by CH₄, C₂H₂, C₂H₄, C₂H₆, and C₃H₈ in N₂ have been measured gravimetrically at 850 °C and 925 °C. Methane appears to be the slowest and acetylene the fastest carburizing agent among the hydrocarbons tested. Hydrogen enhances the rates of carburizing of all hydrocarbons, probably by removing adsorbed oxygen from the steel surface. At high H₂/CH₄ ratios, H₂ will decarburize steel at 925 °C. All hydrocarbons, including CH₂, are also involved in gas phase reactions. These reactions may lead to the formation of soot at carburizing temperatures. Sooting is inhibited by the addition of H₂ to hydrocarbon-nitrogen gas mixtures. Acetylene appears to be a key intermediate for the formation of soot as the final product of hydrocarbon reactions in the gas phase.     

The great debate over unclassified information: national securityversus scientific freedom

The author examines the fundamental conflict between controlling the dissemination of scientific and technical data and promoting openness and peer review of the data. She focuses on the control of unclassified scientific and technical data for national security purposes. She explains the reasons for such controls, the federal government's policies, and how some foreign governments deal with this problem. She summarizes and evaluates the arguments for and against controls and presents some recommendations for the current administration     

Experimental diagnostics of an avalanche discharge excited HgBr/HgBr2dissociation laser

We have investigated the effects of discharge power and nitrogen partial pressure on small signal gain, fluorescence, and discharge driver efficiency for an avalanche discharge Ne/N2/HgBr2laser. This work helps clarify the role of nitrogen in these lasers, as well as presenting the first experimental evidence for bottlenecking in the HgBr laser. An optimum intrinsic laser efficiency of 2.0 percent is also reported.     

A Benchmark Characterization of the EEMBC Benchmark Suite

Benchmark consumers expect benchmark suites to be complete, accurate, and consistent, and benchmark scores serve as relative measures of performance. However, it is important to understand how benchmarks stress the processors that they aim to test. This study explores the stress points of the EEMBC embedded benchmark suite using the benchmark characterization technique.     

Fast Garbling of Circuits Under Standard Assumptions

Protocols for secure computation enable mutually distrustful parties to jointly compute on their private inputs without revealing anything, but the result. Over recent years, secure computation has become practical and considerable effort has been made to make it more and more efficient. A highly important tool in the design of two-party protocols is Yao’s garbled circuit construction (Yao 1986), and multiple optimizations on this primitive have led to performance improvements in orders of magnitude over the last years. However, many of these improvements come at the price of making very strong assumptions on the underlying cryptographic primitives being used (e.g., that AES is secure for related keys, that it is circular-secure, and even that it behaves like a random permutation when keyed with a public fixed key). The justification behind making these strong assumptions has been that otherwise it is not possible to achieve fast garbling and thus fast secure computation. In this paper, we take a step back and examine whether it is really the case that such strong assumptions are needed. We provide new methods for garbling that are secure solely under the assumption that the primitive used (e.g., AES) is a pseudorandom function. Our results show that in many cases, the penalty incurred is not significant, and so a more conservative approach to the assumptions being used can be adopted.     

Life events, fitness, hardiness, and health: A simultaneous analysis of proposed stress-resistance effects.

The effects of exercise participation, self-perceived fitness level, and dispositional hardiness for promoting stress resistance were examined in a sample of 373 college students. Self-report measures of stressful life experience and recent physical illness were positively correlated, and fitness and hardiness were negatively correlated with illness as expected. Multiple regression analyses indicated that neither fitness nor hardiness provided a stress-moderator effect because neither was found to significantly interact with stress in the prediction of illness scores. Structural equation analyses suggested that hardiness may affect health indirectly by first influencing either the occurrence or subjective interpretation of stressful life events. No direct effect on health was found for exercise participation, although exercise may reduce illness indirectly by improving fitness. Implications for the multivariate modeling of proposed stress-resistance-enhancing effects are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extension of life-span by introduction of telomerase into normal human cells

Normal human cells undergo a finite number of cell divisions and ultimately enter a nondividing state called replicative senescence. It has been proposed that telomere shortening is the molecular clock that triggers senescence. To test this hypothesis, two telomerase-negative normal human cell types, retinal pigment epithelial cells and foreskin fibroblasts, were transfected with vectors encoding the human telomerase catalytic subunit. In contrast to telomerase-negative control clones, which exhibited telomere shortening and senescence, telomerase-expressing clones had elongated telomeres, divided vigorously, and showed reduced straining for beta-galactosidase, a biomarker for senescence. Notably, the telomerase-expressing clones have a normal karyotype and have already exceeded their normal life-span by at least 20 doublings, thus establishing a causal relationship between telomere shortening and in vitro cellular senescence. The ability to maintain normal human cells in a phenotypically youthful state could have important applications in research and medicine.