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  • Other Sources  (8)
  • 2020-2023
  • 2005-2009
  • 1990-1994  (8)
  • 1993  (8)
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  • 2020-2023
  • 2005-2009
  • 1990-1994  (8)
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  • 1
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    Anuradha and low-energy cosmic rays (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: After critically reviewing observational results obtained by astronomical spacecraft in the interplanetary medium for several aspects of galactic cosmic rays (GCRs) and anomalous cosmic rays (ACRs), attention is given to spacecraft data gathered in the magnetosphere and a detailed description is given of the Anuradha cosmic-ray experiment carried by Spacelab-3. The Anuradha results discussed concern the orbit average flux and ionization state of ACRs, the origins of partially ionized galactic cosmic-ray sub-Fe and Fe ions, and the significance of enhanced abundance ratios of sub-Fe and Fe ions in GCRs inside the magnetosphere.
    Keywords: SPACE RADIATION
    Type: Space Science Reviews (ISSN 0038-6308); 62; 1-2; p. 3-65.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Ionization states of low-energy cosmic rays - Results from Spacelab 3 cosmic-ray experiment (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Indian cosmic ray experiment Anuradha, conducted onboard Spacelab 3 during April 29-May 6, 1985 was designed to obtain information on the ionization states of low-energy cosmic rays, using the geomagnetic field as a rigidity filter to place an upper limit on the ionization state of individual cosmic ray particles. This paper presents data confirming the presence of three distinct groups of energetic particles in the near-earth space: (1) low-energy (15-25 MeV/nucleon) anomalous cosmic rays that are either singly ionized or consistent with their being in singly ionized state, (2) fully ionized galactic cosmic ray ions, and (3) partially ionized iron and sub-iron group ions (which account for about 20 percent of all the iron and sub-iron group ions detected at the Spacelab 3 orbit within the magnetosphere in the energy interval 25-125 MeV/nucleon). It is argued that these partially ionized heavy ions are indeed a part of the low-energy galactic cosmic rays present in the interplanetary space.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 411; 1; p. 418-430.
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    NASA TECHNICAL REPORTS
  • 3
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    Thermal processing of omicron-terphenyl - A Raman study (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Raman spectra from omicron-terphenyl sealed in glass capillary tubes were acquired over temperatures ranging from 233 to 343 K. Over this temperature range, omicron-terphenyl can exist in the solid-crystalline, molten, supercooled-liquid, and amorphous-glassy states. Representative structure-sensitive spectra are presented along with a qualitative description. The lattice spectral feature occurring at a Raman shift of 123/cm displays abrupt changes in profile and intensity as melting and glass transition occur. The intensity ratio of the C-C stretching 996/cm line and C-H stretching line at 1008/cm displays a change related to the transformation of the ordered-crystalline phase to the disordered-liquid or glassy state. At a Raman shift of 1162/cm the solid-crystalline state shows a splitting due to the effect of the crystal field. The possibility of using these structure-sensitive Raman characteristics for in situ diagnostics during materials processing is discussed.
    Keywords: MATERIALS PROCESSING
    Type: Applied Spectroscopy (ISSN 0003-7028); 47; 4; p. 458-462.
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    NASA TECHNICAL REPORTS
  • 4
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    Dynamic mesh adaption for triangular and tetrahedral grids (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The following topics are discussed: requirements for dynamic mesh adaption; linked-list data structure; edge-based data structure; adaptive-grid data structure; three types of element subdivision; mesh refinement; mesh coarsening; additional constraints for coarsening; anisotropic error indicator for edges; unstructured-grid Euler solver; inviscid 3-D wing; and mesh quality for solution-adaptive grids. The discussion is presented in viewgraph form.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA. Langley Research Center, Unstructured Grid Generation Techniques and Software; p 181-192
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  • 5
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    Calibration of the receiver channel for the GOPEX precursor experiments (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Calibration measurements for the cooled (253 K) photomultiplier tube (PMT) detector, used on the receiver channel of the transmit/receive (T/R) switch for GOPEX, were conducted in the laboratory. A pulsed frequency-doubled neodymium:yttrium-aluminum-garnet (Nd:YAG) laser was used to direct 532-mn light on the PMT. By monitoring the energy per pulse of the light incident on the PMT, the minimum number of photons detected could be determined. These results agreed with the photon flux back-calculated from the PMT output waveform. Approximately 700 incident photons arriving during a temporal pulse width of approximately 65 nsec were detected with a signal-to-noise ratio (SNR) of approximately 1. Other receiver channel characteristics, such as PMT dark currents, optical transmission, and interference filter sensitivity to angle of light incidence, were also measured.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Report; p 205-212
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  • 6
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    An adaptive mesh-moving and refinement procedure for one-dimensional conservation laws (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We examine the performance of an adaptive mesh-moving and /or local mesh refinement procedure for the finite difference solution of one-dimensional hyperbolic systems of conservation laws. Adaptive motion of a base mesh is designed to isolate spatially distinct phenomena, and recursive local refinement of the time step and cells of the stationary or moving base mesh is performed in regions where a refinement indicator exceeds a prescribed tolerance. These adaptive procedures are incorporated into a computer code that includes a MacCormack finite difference scheme wih Davis' artificial viscosity model and a discretization error estimate based on Richardson's extrapolation. Experiments are conducted on three problems in order to qualify the advantages of adaptive techniques relative to uniform mesh computations and the relative benefits of mesh moving and refinement. Key results indicate that local mesh refinement, with and without mesh moving, can provide reliable solutions at much lower computational cost than possible on uniform meshes; that mesh motion can be used to improve the results of uniform mesh solutions for a modest computational effort; that the cost of managing the tree data structure associated with refinement is small; and that a combination of mesh motion and refinement reliably produces solutions for the least cost per unit accuracy.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: Applied Numerical Mathematics (ISSN 0168-9274); p. 259-282
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    NASA TECHNICAL REPORTS
  • 7
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    Unstructured adaptive mesh computations of rotorcraft high-speed impulsive noise (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new method is developed for modeling helicopter high-speed impulsive (HSI) noise. The aerodynamics and acoustics near the rotor blade tip are computed by solving the Euler equations on an unstructured grid. A stationary Kirchhoff surface integral is then used to propagate these acoustic signals to the far field. The near-field Euler solver uses a solution-adaptive grid scheme to improve the resolution of the acoustic signal. Grid points are locally added and/or deleted from the mesh at each adaptive step. An important part of this procedure is the choice of an appropriate error indicator. The error indicator is computed from the flow field solution and determines the regions for mesh coarsening and refinement. Computed results for HSI noise compare favorably with experimental data for three different hovering rotor cases.
    Keywords: ACOUSTICS
    Type: NASA-CR-195090 , NAS 1.26:195090 , RIACS-TR-93-10 , AIAA PAPER 93-4359 , AIAA Aeroacoustics Conference; Oct 25, 1993 - Oct 27, 1993; Long Beach, CA; United States
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  • 8
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    A new procedure for dynamic adaption of three-dimensional unstructured grids (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new procedure is presented for the simultaneous coarsening and refinement of three-dimensional unstructured tetrahedral meshes. This algorithm allows for localized grid adaption that is used to capture aerodynamic flow features such as vortices and shock waves in helicopter flowfield simulations. The mesh-adaption algorithm is implemented in the C programming language and uses a data structure consisting of a series of dynamically-allocated linked lists. These lists allow the mesh connectivity to be rapidly reconstructed when individual mesh points are added and/or deleted. The algorithm allows the mesh to change in an anisotropic manner in order to efficiently resolve directional flow features. The procedure has been successfully implemented on a single processor of a Cray Y-MP computer. Two sample cases are presented involving three-dimensional transonic flow. Computed results show good agreement with conventional structured-grid solutions for the Euler equations.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: AIAA PAPER 93-0672 , RIACS-TR-93-01 , AD-A268651 , AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States|; 13 p.
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