13,776 research outputs found
Metal matrix composite analyzer (METCAN) user's manual, version 4.0
The Metal Matrix Composite Analyzer (METCAN) is a computer code developed at Lewis Research Center to simulate the high temperature nonlinear behavior of metal matrix composites. An updated version of the METCAN User's Manual is presented. The manual provides the user with a step by step outline of the procedure necessary to run METCAN. The preparation of the input file is demonstrated, and the output files are explained. The sample problems are presented to highlight various features of METCAN. An overview of the geometric conventions, micromechanical unit cell, and the nonlinear constitutive relationships is also provided
Silicon materials task of the low cost solar array project, part 2
Purity requirements for solar cell grade silicon material was developed and defined by evaluating the effects of specific impurities and impurity levels on the performance of silicon solar cells. Also, data was generated forming the basis for cost-tradeoff analyses of silicon solar cell material. Growth, evaluation, solar cell fabrication and testing was completed for the baseline boron-doped Czochralski material. Measurements indicate Cn and Mn seriously degrade cell performance, while neither Ni nor Cu produce any serious reduction in cell efficiency
Advanced dendritic web growth development and development of single-crystal silicon dendritic ribbon and high-efficiency solar cell program
Efforts to demonstrate that the dendritic web technology is ready for commercial use by the end of 1986 continues. A commercial readiness goal involves improvements to crystal growth furnace throughput to demonstrate an area growth rate of greater than 15 sq cm/min while simultaneously growing 10 meters or more of ribbon under conditions of continuous melt replenishment. Continuous means that the silicon melt is being replenished at the same rate that it is being consumed by ribbon growth so that the melt level remains constant. Efforts continue on computer thermal modeling required to define high speed, low stress, continuous growth configurations; the study of convective effects in the molten silicon and growth furnace cover gas; on furnace component modifications; on web quality assessments; and on experimental growth activities
Silicon materials task of the low cost solar array project. Phase 3: Effect of impurities and processing on silicon solar cells
The 13th quarterly report of a study entitled an Investigation of the Effects of Impurities and Processing on Silicon Solar Cells is given. The objective of the program is to define the effects of impurities, various thermochemical processes and any impurity-process interactions on the performance of terrestrial silicon solar cells. The Phase 3 program effort falls in five areas: (1) cell processing studies; (2) completion of the data base and impurity-performance modeling for n-base cells; (3) extension of p-base studies to include contaminants likely to be introduced during silicon production, refining or crystal growth; (4) anisotropy effects; and (5) a preliminary study of the permanence of impurity effects in silicon solar cells. The quarterly activities for this report focus on tasks (1), (3) and (4)
Measurement of teicoplanin by liquid chromatography-tandem mass spectrometry:development of a novel method
Teicoplanin is an antibiotic used for the treatment of endocarditis, osteomyelitis, septic arthritis and methicillin-resistant Staphylococcus aureus. Teicoplanin is emerging as a suitable alternative antibiotic to vancomycin, where their trough serum levels are monitored by immunoassay routinely. This is the first report detailing the development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for measuring teicoplanin in patients' serum
Predictions of Quasar Clustering: Redshift, Luminosity and Selection Dependence
We show that current clustering observations of quasars and luminous AGN can
be explained by a merger model augmented by feedback from outflows. Using
numerical simulations large enough to study clustering out to 25 comoving
h^{-1} Mpc, we calculate correlation functions, biases, and correlation lengths
as a function of AGN redshift and optical and X-ray luminosity. At optical
wavelengths, our results match a wide range of current observations and
generate predictions for future data sets. We reproduce the weak luminosity
dependence of clustering over the currently well-measured range, and predict a
much stronger dependence at higher luminosities. The increase in the amplitude
of binary quasar clustering observed in the Sloan Digital Sky Survey (SDSS) is
also reproduced and is predicted to occur at higher redshift, an effect that is
due to the one halo term in the correlation function. On the other hand, our
results do not match the rapid evolution of the correlation length observed in
the SDSS at z\simeq 3, a discrepancy that is at least partially due to
differences in the scales probed by our simulation versus this survey. In fact,
we show that changing the distances sampled from our simulations can produce
changes as large as 40% in the fitted correlation lengths. Finally, in the
X-ray, our simulations produce correlation lengths similar to that observed in
the Chandra Deep Field (CDF) North, but not the significantly larger
correlation length observed in the CDF South.Comment: 13 page, 7 figures. Accepted for publication in Ap
Large-area sheet task advanced dendritic web growth development
The computer code for calculating web temperature distribution was expanded to provide a graphics output in addition to numerical and punch card output. The new code was used to examine various modifications of the J419 configuration and, on the basis of the results, a new growth geometry was designed. Additionally, several mathematically defined temperature profiles were evaluated for the effects of the free boundary (growth front) on the thermal stress generation. Experimental growth runs were made with modified J419 configurations to complement the modeling work. A modified J435 configuration was evaluated
Galaxy disks do not need to survive in the L-CDM paradigm: the galaxy merger rate out to z~1.5 from morpho-kinematic data
About two-thirds of present-day, large galaxies are spirals such as the Milky
Way or Andromeda, but the way their thin rotating disks formed remains
uncertain. Observations have revealed that half of their progenitors, six
billion years ago, had peculiar morphologies and/or kinematics, which exclude
them from the Hubble sequence. Major mergers, i.e., fusions between galaxies of
similar mass, are found to be the likeliest driver for such strong
peculiarities. However, thin disks are fragile and easily destroyed by such
violent collisions, which creates a critical tension between the observed
fraction of thin disks and their survival within the L-CDM paradigm. Here we
show that the observed high occurrence of mergers amongst their progenitors is
only apparent and is resolved when using morpho-kinematic observations which
are sensitive to all the phases of the merging process. This provides an
original way of narrowing down observational estimates of the galaxy merger
rate and leads to a perfect match with predictions by state-of-the-art L-CDM
semi-empirical models with no particular fine-tuning needed. These results
imply that half of local thin disks do not survive but are actually rebuilt
after a gas-rich major merger occurring in the past nine billion years, i.e.,
two-thirds of the lifetime of the Universe. This emphasizes the need to study
how thin disks can form in halos with a more active merger history than
previously considered, and to investigate what is the origin of the gas
reservoir from which local disks would reform.Comment: 19 pages, 7 figures, 2 tables. Accepted in ApJ. V2 to match proof
corrections and added reference
Inelastic Collapse of Three Particles
A system of three particles undergoing inelastic collisions in arbitrary
spatial dimensions is studied with the aim of establishing the domain of
``inelastic collapse''---an infinite number of collisions which take place in a
finite time. Analytic and simulation results show that for a sufficiently small
restitution coefficient, , collapse can
occur. In one dimension, such a collapse is stable against small perturbations
within this entire range. In higher dimensions, the collapse can be stable
against small variations of initial conditions, within a smaller range,
.Comment: 6 pages, figures on request, accepted by PR
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