4,686 research outputs found
Evaluation criteria for commercially oriented materials processing in space proposals
An approach and criteria for evaluating NASA funded experiments and demonstrations which have commercial potential were developed. Methods for insuring quick initial screening of commercial proposals are presented. Recommendations are given for modifying the current evaluation approach. New criteria for evaluating commercially orientated materials processing in space (MPS) proposals are introduced. The process for selection of qualified individuals to evaluate the phases of this approach and criteria is considered and guidelines are set for its implementation
Redetermination of parameters for semi-empirical model for spallogenic He and Ne in chondrites
A semi-empirical model described previously satisfactorily reproduced a number of shielding-dependent variations in the relative production rates of spallogenic He and Ne in chondrites. However, data for cores of the Keyes and St. Severin meteorites showed a subsurface build-up in He-3 which was not predicted with the original model parameters and the model was not pursued. Renewed interest in the preatmospheric size of meteorites, spurred in part by the desirability of understanding the exposure history of the SNC meteorites, justifies redetermination of model parameters
Publication - A Scotch-Irish Neighborhood
A booklet by F. B. McDowell on the Sotch-Irish neighborhood, published by the Mecklenburg Historical Society.
Notation on front by Fay Webb Gardner - :This booklet reminds me of the Scotch-Irish neighborhood surrounding old Brittain Church, Rutherford Co. where the Andrews, Watson, Long, and Robertson family lived.:https://digitalcommons.gardner-webb.edu/fay-webb-gardner-brittain-presbyterian-church/1018/thumbnail.jp
On the micro mechanics of one-dimensional normal compression
Discrete-element modelling has been used to investigate the micro mechanics of one-dimensional compression. One-dimensional compression is modelled in three dimensions using an oedometer and a large number of particles, and without the use of agglomerates. The fracture of a particle is governed by the octahedral shear stress within the particle due to the multiple contacts and a Weibull distribution of strengths. Different fracture mechanisms are considered, and the influence of the distribution of fragments produced for each fracture on the global particle size distribution and the slope of the normal compression line is investigated. Using the discrete-element method, compression is related to the evolution of a fractal distribution of particles. The compression index is found to be solely a function of the strengths of the particles as a function of size
Infrared Emission from the Radio Supernebula in NGC 5253: A Proto-Globular Cluster?
Hidden from optical view in the starburst region of the dwarf galaxy NGC 5253
lies an intense radio source with an unusual spectrum which could be
interpreted variously as nebular gas ionized by a young stellar cluster or
nonthermal emission from a radio supernova or an AGN. We have obtained 11.7 and
18.7 micron images of this region at the Keck Telescope and find that it is an
extremely strong mid-infrared emitter. The infrared to radio flux ratio rules
out a supernova and is consistent with an HII region excited by a dense cluster
of young stars. This "super nebula" provides at least 15% of the total
bolometric luminosity of the galaxy. Its excitation requires 10^5-10^6 stars,
giving it the total mass and size (1-2 pc diameter) of a globular cluster.
However, its high obscuration, small size, and high gas density all argue that
it is very young, no more than a few hundred thousand years old. This may be
the youngest globular cluster yet observed.Comment: 6 pages, 2 color figures, Submitted to the ApJL, Revised 4/6/01 based
on referee's comment
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