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Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter]

Directed reflectivity, long life AMTEC condenser (DRC). Final report of Phase II SBIR program[Alkali Metal ThermoElectric Converter]

Date: September 10, 2001
Creator: Hunt, Thomas K.
Description: The Alkali Metal Thermal to Electric Converter (AMTEC) is a static energy conversion device that operates at high thermal to electric conversion efficiencies that are essentially independent of size, have reached 19% and are expected to reach 25% to 30% in 1997. AMTEC systems have been chosen by NASA and DOE for spacecraft applications and have considerable promise for a wide variety of terrestrial applications. Reduction of parasitic heat losses in AMTEC systems related to radiative heat transfer from the hot side to the condenser can make a substantial contribution to system efficiency. Through design, analysis and the fabrication and testing of cells and systems, the proposed program to develop a Directed Reflectivity Condenser (DRC) has investigated the feasibility of an improved AMTEC condenser component. Phase 1 work showed the potential for adding from 4% to 7% to overall system efficiency for identical operating conditions using the concept. A detailed thermal analysis of several DRC capped cell designs was carried out and some of the conditions under which a DRC, used as the condenser at an end cap of a cylindrical converter, can reduce thermal radiation related losses were determined. A model experimental converter was built and tested to compare ...
Contributing Partner: UNT Libraries Government Documents Department
Directed Relation Graph with Expert Knowledge for Skeletal Mechanism Reduction

Directed Relation Graph with Expert Knowledge for Skeletal Mechanism Reduction

Date: February 7, 2011
Creator: Lu, T; Plomer, M; Luo, Z; Sarathy, S M; Pitz, W J; Som, S et al.
Description: Abstract not provided
Contributing Partner: UNT Libraries Government Documents Department
The Direction Cosine Method of Scatterer Location Extended to Spotlight-Mode IFSAR

The Direction Cosine Method of Scatterer Location Extended to Spotlight-Mode IFSAR

Date: October 26, 2000
Creator: EICHEL,PAUL H.
Description: In this paper we have shown how the direction cosine method of stripmap-mode IFSAR maybe modified for use in the spotlight-mode case. Spotlight-mode IFSAR geometry dictates a common aperture phase center, velocity vector, and baseline vector for every pixel in an image. Angle with respect to the velocity vector is the same for every pixel in a given column and can be computed from the column index, the Doppler of the motion compensation point and the Doppler column sample spacing used in image formation. With these modifications, the direction cosines and length of the line of sight vector to every scatterer in the scene may be computed directly from the raw radar measurements of range, Doppler, and interferometric phase.
Contributing Partner: UNT Libraries Government Documents Department
Direction-Preserving and Schur-Monotonic Semi-Separable Approximations of Symmetric Positive Definite Matrices}

Direction-Preserving and Schur-Monotonic Semi-Separable Approximations of Symmetric Positive Definite Matrices}

Date: March 16, 2010
Creator: Gu, M; Li, X S & Vassilevski, P S
Description: For a given symmetric positive definite matrix A {element_of} R{sup N x N}, we develop a fast and backward stable algorithm to approximate A by a symmetric positive-definite semi-separable matrix, accurate to a constant multiple of any prescribed tolerance. In addition, this algorithm preserves the product, AZ, for a given matrix Z {element_of} R{sup N x d}, where d << N. Our algorithm guarantees the positive-definiteness of the semi-separable matrix by embedding an approximation strategy inside a Cholesky factorization procedure to ensure that the Schur complements during the Cholesky factorization all remain positive definite after approximation. It uses a robust direction-preserving approximation scheme to ensure the preservation of AZ. We present numerical experiments and discuss potential implications of our work.
Contributing Partner: UNT Libraries Government Documents Department
Direction-Sensitive Hand-Held Gamma-Ray Spectrometer

Direction-Sensitive Hand-Held Gamma-Ray Spectrometer

Date: October 4, 2012
Creator: Mukhopadhyay, S.
Description: A novel, light-weight, hand-held gamma-ray detector with directional sensitivity is being designed. The detector uses a set of multiple rings around two cylindrical surfaces, which provides precise location of two interaction points on two concentric cylindrical planes, wherefrom the source location can be traced back by back projection and/or Compton imaging technique. The detectors are 2.0 × 2.0 mm europium-doped strontium iodide (SrI2:Eu2+) crystals, whose light output has been measured to exceed 120,000 photons/MeV, making it one of the brightest scintillators in existence. The crystal’s energy resolution, less than 3% at 662 keV, is also excellent, and the response is highly linear over a wide range of gamma-ray energies. The emission of SrI2:Eu2+ is well matched to both photo-multiplier tubes and blue-enhanced silicon photodiodes. The solid-state photomultipliers used in this design (each 2.0 × 2.0 mm) are arrays of active pixel sensors (avalanche photodiodes driven beyond their breakdown voltage in reverse bias); each pixel acts as a binary photon detector, and their summed output is an analog representation of the total photon energy, while the individual pixel accurately defines the point of interaction. A simple back-projection algorithm involving cone-surface mapping is being modeled. The back projection for an event cone ...
Contributing Partner: UNT Libraries Government Documents Department
Directional dependency of air sampling; Research and development grant {number_sign}4

Directional dependency of air sampling; Research and development grant {number_sign}4

Date: January 15, 1994
Creator: unknown
Description: A field study was performed by Idaho State University-Environmental Monitoring Laboratory (EML) to examine the directional dependency of low-volume air samplers. A typical continuous low volume air sampler contains a sample head that is mounted on the sampler housing either horizontally through one of four walls or vertically on an exterior wall `looking down or up.` In 1992, a field study was undertaken to estimate sampling error and to detect the directional effect of sampler head orientation. Approximately 1/2 mile downwind from a phosphate plant (continuous source of alpha activity), four samplers were positioned in identical orientation alongside one sampler configured with the sample head `looking down`. At least five consecutive weekly samples were collected. The alpha activity, beta activity, and the Be-7 activity collected on the particulate filter were analyzed to determine sampling error. Four sample heads were than oriented to the four different horizontal directions. Samples were collected for at least five weeks. Analysis of the alpha data can show the effect of sampler orientation to a know near source term. Analysis of the beta and Be-7 activity shows the effect of sampler orientation to a ubiquitous source term.
Contributing Partner: UNT Libraries Government Documents Department
Directional Extreme Wind Speed Data for the Design of Buildings and Other Structures

Directional Extreme Wind Speed Data for the Design of Buildings and Other Structures

Date: March 1984
Creator: Changery, Michael J.; Dumitriu-Valcea, Eugene J. & Simiu, Emil
Description: Report issued by the National Bureau of Standards over wind speed data collected for the design of buildings. The wind speed data is discussed. This report includes tables.
Contributing Partner: UNT Libraries Government Documents Department
Directional muon jet chamber for a muon collider (Groovy Chamber)

Directional muon jet chamber for a muon collider (Groovy Chamber)

Date: October 1, 1996
Creator: Atac, M.
Description: A directional jet drift chamber with PAD readout is proposed here which can select vertex originated muons within a given time window and eliminate those muons which primarily originate upstream, using only a PAD readout. Drift time provides the Z-coordinate, and the center of gravity of charge distribution provides the r-{psi} coordinates. Directionality at the trigger level is obtained by the timing measurement from the PAD hits within a given time window. Because of the long drift time between the bunch crossings, a muon collider enables one to choose a drift distance in the drift chamber as long as 50 cm. This is an important factor in reducing cost of drift chambers which have to cover relatively large areas.
Contributing Partner: UNT Libraries Government Documents Department
Directional Ordering and Dynamics in Dusty Plasmas

Directional Ordering and Dynamics in Dusty Plasmas

Date: May 24, 1999
Creator: Hammerberg, J. E.; Holian, B. L.; Murillo, M. S. & Winske, D.
Description: We use molecular dynamics (MD) simulation methods to investigate dusty plasma crystal structure, with the grains subject to a spherically symmetric Debye-Hueckel potential, a uni-directional external potential and an asymmetric wake potential. The structure is studied as a function of Mach number and magnitude of the wake as well as the strength of the rf input power, using parameters from a self-consistent dust-sheath model.
Contributing Partner: UNT Libraries Government Documents Department
Directional Shear Force Microscopy

Directional Shear Force Microscopy

Date: October 3, 2000
Creator: Burns, A. R. & Carpick, R. W.
Description: No abstract prepared.
Contributing Partner: UNT Libraries Government Documents Department