21,546 research outputs found
Concentration in local commercial banking markets: a study of the Eighth Federal Reserve District
Federal Reserve District, 8th ; Banks and banking
Evaluation of thermal sprayed metallic coatings for use on the structures at Launch Complex 39
The current status of the evaluation program is presented. The objective was to evaluate the applicability of Thermal Sprayed Coatings (TSC) to protect the structures in the high temperature acid environment produced by exhaust of the Solid Rocket Boosters during the launches of the Shuttle Transportation System. Only the relatively low cost aluminum TSC which provides some cathodic protection for steel appears to be a practical candidate for further investigation
An application of interactive computer graphics technology to the design of dispersal mechanisms
Interactive computer graphics technology is combined with a general purpose mechanisms computer code to study the operational behavior of three guided bomb dispersal mechanism designs. These studies illustrate the use of computer graphics techniques to discover operational anomalies, to assess the effectiveness of design improvements, to reduce the time and cost of the modeling effort, and to provide the mechanism designer with a visual understanding of the physical operation of such systems
An adaptive, hanging-node, discontinuous isogeometric analysis method for the first-order form of the neutron transport equation with discrete ordinate (SN) angular discretisation
In this paper a discontinuous, hanging-node, isogeometric analysis (IGA) method is developed and applied to the first-order form of the neutron transport equation with a discrete ordinate (SN) angular discretisation in two-dimensional space. The complexities involved in upwinding across curved element boundaries that contain hanging-nodes have been addressed to ensure that the scheme remains conservative. A robust algorithm for cycle-breaking has also been introduced in order to develop a unique sweep ordering of the elements for each discrete ordinates direction. The convergence rate of the scheme has been verified using the method of manufactured solutions (MMS) with a smooth solution. Heuristic error indicators have been used to drive an adaptive mesh refinement (AMR) algorithm to take advantage of the hanging-node discretisation. The effectiveness of this method is demonstrated for three test cases. The first is a homogeneous square in a vacuum with varying mean free path and a prescribed extraneous unit source. The second test case is a radiation shielding problem and the third is a 3×3 “supercell” featuring a burnable absorber. In the final test case, comparisons are made to the discontinuous Galerkin finite element method (DGFEM) using both straight-sided and curved quadratic finite elements
Evaluation of Composite Materials for Use on Launch Complexes
Commercially available composite structural shapes were evaluated for use. These composites, fiberglass-reinforced polyester and vinylester resin materials are being used extensively in the fabrication and construction of low maintenance, corrosion resistant structures. The evaluation found that in many applications these composite materials can be successfully used at the space center. These composite materials should not be used where they will be exposed to the hot exhaust plume/cloud of the launch vehicle during the liftoff, and caution should be taken in their use in areas where electrostatic discharge and hypergolic propellant compatibility are primary concerns
Application of the Trend Filtering Algorithm on the MACHO Database
Due to the strong effect of systematics/trends in variable star observations,
we employ the Trend Filtering Algorithm (TFA) on a subset of the MACHO database
and search for variable stars. TFA has been applied successfully in planetary
transit searches, where weak, short-lasting periodic dimmings are sought in the
presence of noise and various systematics (due to, e.g., imperfect flat
fielding, crowding, etc). These latter effects introduce colored noise in the
photometric time series that can lead to a complete miss of the signal. By
using a large number of available photometric time series of a given field, TFA
utilizes the fact that the same types of systematics appear in several/many
time series of the same field. As a result, we fit each target time series by a
(least-square-sense) optimum linear combination of templates and
frequency-analyze the residuals. Once a signal is found, we reconstruct the
signal by employing the full model, including the signal, systematics and
noise. We apply TFA on the brightest ~5300 objects from subsets of each of the
MACHO Large Magellanic Cloud fields #1 and #79. We find that the Fourier
frequency analysis performed on the original data detect some 60% of the
objects as trend-dominated. This figure decreases essentially to zero after
using TFA. Altogether, We detect 387 variables in the two fields, 183 of which
would have remained undetected without using TFA. Where possible, we give
preliminary classification of the variables found.Comment: 12 pages, 15 figures, 3 tables with online material; to appear in
Astronomy and Astrophysic
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