30,533 research outputs found
Process for utilizing low-cost graphite substrates for polycrystalline solar cells
Low cost polycrystalline silicon solar cells supported on substrates were prepared by depositing successive layers of polycrystalline silicon containing appropriate dopants over supporting substrates of a member selected from the group consisting of metallurgical grade polycrystalline silicon, graphite and steel coated with a diffusion barrier of silica, borosilicate, phosphosilicate, or mixtures thereof such that p-n junction devices were formed which effectively convert solar energy to electrical energy. To improve the conversion efficiency of the polycrystalline silicon solar cells, the crystallite size in the silicon was substantially increased by melting and solidifying a base layer of polycrystalline silicon before depositing the layers which form the p-n junction
Low-Cost thin-layer silicon solar cells
Two methods have been found to lower cost of polycrystalline silicon solar cells. Successive layers of polycrystalline silicon are deposited over supporting substrates of relatively inexpensive metallurgical-grade polycrystalline silicon, graphite, or steel
SAM 2 data user's guide
This document is intended to serve as a guide to the use of the data products from the Stratospheric Aerosol Measurement (SAM) 2 experiment for scientific investigations of polar stratospheric aerosols. Included is a detailed description of the Beta and Aerosol Number Density Archive Tape (BANAT), which is the SAM 2 data product containing the aerosol extinction data available for these investigations. Also included are brief descriptions of the instrument operation, data collection, processing and validation, and some of the scientific analyses conducted to date
Physical phenomena related to crystal growth in the space environment
The mechanism of crystal growth which may be affected by the space environment was studied. Conclusions as to the relative technical and scientific advantages of crystal growth in space over earth bound growth, without regard to economic advantage, were deduced. It was concluded that the crucibleless technique will most directly demonstrate the unique effects of the greatly reduced gravity in the space environment. Several experiments, including crucibleless crystal growth using solar energy and determination of diffusion coefficients of common dopants in liquid silicon were recommended
Boron Arsenide and Boron Phosphide for High Temperature and Luminescent Devices
The crystal growth of boron arsenide and boron phosphide in the form of bulk crystals and epitaxial layers on suitable substrates is discussed. The physical, chemical, and electrical properties of the crystals and epitaxial layers are examined. Bulk crystals of boron arsenide were prepared by the chemical transport technique, and their carrier concentration and Hall mobility were measured. The growth of boron arsenide crystals from high temperature solutions was attempted without success. Bulk crystals of boron phosphide were also prepared by chemical transport and solution growth techniques. Techniques required for the fabrication of boron phosphide devices such as junction shaping, diffusion, and contact formation were investigated. Alloying techniques were developed for the formation of low-resistance ohmic contacts to boron phosphide. Four types of boron phosphide devices were fabricated: (1) metal-insulator-boron phosphide structures, (2) Schottky barriers; (3) boron phosphide-silicon carbide heterojunctions; and (4) p-n homojunctions. Easily visible red electroluminescence was observed from both epitaxial and solution grown p-n junctions
Development of low cost thin film polycrystalline silicon solar cells for terrestrial applications
The AMO efficiencies (no anti-reflection coating) obtained to date are 2.5% for solar cells deposited on graphite substrates, 3.5% for solar cells deposited on metallurgical silicon substrates, and 4.5% for solar cells fabricated from purified metallurgical silicon
Probing the Region of Massless Quarks in Quenched Lattice QCD using Wilson Fermions
We study the spectrum of with being the
Wilson-Dirac operator on the lattice with bare mass equal to . The
background gauge fields are generated using the SU(3) Wilson action at
on an lattice. We find evidence that the spectrum of
is gapless for , implying that the physical quark is
massless in this whole region.Comment: 22 pages, LaTeX file, uses elsart.sty, includes 11 figures A
typographical error in one reference has been fixe
The n-body problem in General Relativity up to the second post-Newtonian order from perturbative field theory
Motivated by experimental probes of general relativity, we adopt methods from
perturbative (quantum) field theory to compute, up to certain integrals, the
effective lagrangian for its n-body problem. Perturbation theory is performed
about a background Minkowski spacetime to O[(v/c)^4] beyond Newtonian gravity,
where v is the typical speed of these n particles in their center of energy
frame. For the specific case of the 2 body problem, the major efforts underway
to measure gravitational waves produced by in-spiraling compact astrophysical
binaries require their gravitational interactions to be computed beyond the
currently known O[(v/c)^7]. We argue that such higher order post-Newtonian
calculations must be automated for these field theoretic methods to be applied
successfully to achieve this goal. In view of this, we outline an algorithm
that would in principle generate the relevant Feynman diagrams to an arbitrary
order in v/c and take steps to develop the necessary software. The Feynman
diagrams contributing to the n-body effective action at O[(v/c)^6] beyond
Newton are derived.Comment: 39 pages. The Mathematica code used in this paper can be found at
http://www.stargazing.net/yizen/PN.html Version 2: Slight re-wording of
section on removal of accelerations in 2 PN lagrangian; comments added in
conclusion; and typographical errors fixed. Article is similar to that
published in PR
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