GaAs solar cells

The major thrusts proposed for GaAs were increased efficiency and improved radiation damage data. Current laboratory production cells consistently achieve 16 percent AMO one-Sun efficiency. The user community wants 18-percent efficient cells as soon as possible, and such a goal is though to be achievable in 2 years with sufficient research funds. A 20-percent research cell is considered the efficiency limit with current technology, and such a cell seems realizable in approximately 4 years. Future efficiency improvements await improved substrates and materials. For still higher efficiencies, concentrator cells and multijunction cells are proposed as near-term directions

Space Laser Power Transmission System Studies

Power transmission by laser technique is addressed. Space to Earth and space to space configurations are considered

The Youngest Lobe-Dominated Radio Sources

We present an analysis of multi-epoch global VLBI observations of the Compact Symmetric Objects: 2352+495 and 0710+439 at 5 GHz. Analysis of data spread over almost two decades shows strong evidence for an increase in separation of the outer components of both sources at a rate of ~0.2 h^{-1} c (for q_{0}=0.5 and H_{0}=100 h kms^{-1} Mpc^{-1}). Dividing the overall sizes of the sources by their separation rates implies that these Compact Symmetric Objects have a kinematic age < 10^{4} years. These results (and those for other CSOs) strongly argue that CSOs are indeed very young sources and that they are probably evolve into the much larger classical doubles.Comment: 6 pages, 4 figures, the preprint from the 4th EVN/JIVE Symposium, submited and accepted by the refereed journal New Astromomy Reviews. It is also available at: http://www.nfra.nl/jive/evn/symp/preprints.htm

Principles of Antifragile Software

The goal of this paper is to study and define the concept of "antifragile software". For this, I start from Taleb's statement that antifragile systems love errors, and discuss whether traditional software dependability fits into this class. The answer is somewhat negative, although adaptive fault tolerance is antifragile: the system learns something when an error happens, and always imrpoves. Automatic runtime bug fixing is changing the code in response to errors, fault injection in production means injecting errors in business critical software. I claim that both correspond to antifragility. Finally, I hypothesize that antifragile development processes are better at producing antifragile software systems.Comment: see https://refuses.github.io

Langley program of GaAs solar cells

A brief overview of the development of GaAs solar cell technology is provided. An 18 to 20 percent AMO efficiency, stability under radiation and elevated-temperature operation, and high power-to-weight ratio are among the factors studied. Cell cost and availability are also examined

Observation and mechanism of direct-current quenching of alternating-current electro- luminescence in typical zinc sulfide phosphors

Direct current quenching of alternating current electroluminescence in zinc sulfide phosphor

Estimating the size of the cosmic-ray halo using particle distribution moments

Context: Particle transport in many astrophysical problems can be described either by the Fokker–Planck equation or by an equivalent system of stochastic differential equations. Aims: It is shown that the latter method can be applied to the problem of defining the size of the cosmic-ray galactic halo. Methods: Analytical expressions for the leading moments of the pitch-angle distribution of relativistic particles are determined. Particle scattering and escape are analyzed in terms of the moments. Results: In the case of an anisotropic distribution, the first moment leads to an expression for the halo size, identified with the particle escape from the region of strong scattering. Previous studies are generalized by analyzing the case of a strictly isotropic initial distribution. A new expression for the variance of the distribution is derived, which illustrates the anisotropization of the distribution. Conclusions: Stochastic calculus tools allow one to analyze physically motivated forms for the scattering rate, so that a detailed realistic model can be developed