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  • 1
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    Control of boundary layer transition location and plate vibration in the presence of an external acoustic field (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The experiment is aimed at controlling the boundary layer transition location and the plate vibration when excited by a flow and an upstream sound source. Sound has been found to affect the flow at the leading edge and the response of a flexible plate in a boundary layer. Because the sound induces early transition, the panel vibration is acoustically coupled to the turbulent boundary layer by the upstream radiation. Localized surface heating at the leading edge delays the transition location downstream of the flexible plate. The response of the plate excited by a turbulent boundary layer (without sound) shows that the plate is forced to vibrate at different frequencies and with different amplitudes as the flow velocity changes indicating that the plate is driven by the convective waves of the boundary layer. The acoustic disturbances induced by the upstream sound dominate the response of the plate when the boundary layer is either turbulent or laminar. Active vibration control was used to reduce the sound induced displacement amplitude of the plate.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Structural dynamics: Recent advances; Proceedings of the 4th International Conference, Univ. of Southampton, United Kingdom, July 15-18, 1991 (A93-45104 18-39); p. 702-711.
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  • 2
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    VICONOPT - Program for exact vibration and buckling analysis or design of prismatic plate assemblies (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1927
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  • 3
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    Structural dynamic and aeroelastic considerations for hypersonic vehicles (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Structural dynamic and aeroelastic considerations applicable to hypersonic vehicles are discussed. Emphasis is given to aerospace plane configurations. The definition of aerothermoelasticity and the operational flight environment are reviewed, and structural dynamic and aeroelastic areas of concern are individually discussed, including vibration, landing and taxiing, propellant dynamics, acoustics, lifting surface flutter, panel flutter, control surface buzz, buffeting, gust response, and static aeroelasticity. Recent research results from all-moveable delta-wing aerolastic studies, engine inlet lip aeroelastic analysis, and studies of thermal effects on vibration frequencies, aerodynamic heating effects on flutter, and active control of aeroelastic response are reviewed.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 91-1255
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  • 4
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    Geostationary earth climate sensor: Scientific utility and feasibility, phase A (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The possibility of accurate broad band radiation budget measurements from a GEO platform will provide a unique opportunity for viewing radiation processes in the atmosphere-ocean system. The CSU/TRW team has prepared a Phase 1 instrument design study demonstrating that measurements of radiation budget are practical from geosynchronous orbit with proven technology. This instrument concept is the Geostationary Earth Climate Sensor (GECS). A range of resolutions down to 20 km at the top of the atmosphere are possible, depending upon the scientific goals of the experiment. These tradeoffs of resolution and measurement repeat cycles are examined for scientific utility. The design of a flexible instrument is shown to be possible to meet the two goals: long-term, systematic monitoring of the diurnal cycles of radiation budget; and high time and space resolution studies of regional radiation features.
    Keywords: GEOPHYSICS
    Type: NASA-CR-191919 , NAS 1.26:191919
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  • 5
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    User manual for VICONOPT: An exact analysis and optimum design program covering the buckling and vibration of prismatic assemblies of flat in-plane loaded, anisotropic plates, with approximations for discrete supports, and transverse stiffeners (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A computer program which is designed for efficient, accurate buckling and vibration analysis and optimum design of composite panels is described. The capabilities of the program are given along with detailed user instructions. It is written in FORTRAN 77 and is operational on VAX, IBM, and CDC computers and should be readily adapted to others. Several illustrations of the various aspects of the input are given along the example problems illustrating the use and application of the program.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-181966 , NAS 1.26:181966
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  • 6
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    A mechanism to produce a dawn-dusk component of plasma flow during magnetic reconnection in the magnetotail (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Magnetic reconnection between antiparallel field lines in the magnetotail is generally thought to produce plasma acceleration in the earthward-tailward direction. However, measurements of the plasma velocity in the magnetotail during substorm activity sometimes reveal a dawn-dusk component of plasma flow. In this paper, we show that a dawn-dusk component of plasma acceleration may be produced during reconnection if the neutral line is not perpendicular to the magnetic field. In this case, Magnetohydrodynamic (MHD) simulations show that reconnection between antiparallel field lines will initially produce plasma acceleration that is nearly parallel to the neutral line because the magnetic tension force is not opposed by a pressure gradient force in this direction. As the magnetic field topology evolves to a steady state, the plasma flow direction rotates until it is nearly parallel to the plane that initially contained the antiparallel magnetic field lines before reconnection (hereafter referred to as the initial field plane). However, the time required to reach a steady state (typically several hundred seconds in the magnetotail region) may be greater than the time during which the reconnection process is active. Consequently, bursts of plasma flow with a dawn-dusk component may occur in the magnetotail. The initial acceleration along the neutral line depends on the angle theta (sub B) between the neutral line and the initial field plane, with the largest burst of plasma flow along the neutral line occuring when theta (s ub B) = 45 degs.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 5869-5875
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  • 7
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    Optimum design using VICONOPT, a buckling and strength constraint program for prismatic assemblies of anisotropic plates (1992)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: A computer program for obtaining the optimum (least mass) dimensions of the kind of prismatic assemblies of laminated, composite plates which occur in advanced aerospace construction is described. Rigorous buckling analysis (derived from exact member theory) and a tailored design procedure are used to produce designs which satisfy buckling and material strength constraints and configurational requirements. Analysis is two to three orders of magnitude quicker than FEM, keeps track of all the governing modes of failure and is efficiently adapted to give sensitivities and to maintain feasibility. Tailoring encourages convergence in fewer sizing cycles than competing programs and permits start designs which are a long way from feasible and/or optimum. Comparisons with its predecessor, PASCO, show that the program is more likely to produce an optimum, will do so more quickly in some cases, and remains accurate for a wider range of problems.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers & Structures (ISSN 0045-7949); 43; 4, Ma; 699-708
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  • 8
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    Electric field measurements during supercharging events on the MAIMIK rocket experiment (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Data are presented on the evolution of electric field structures near the MAIMIK mother-daughter tethered rocket during active electron emissions from the rocket, which consisted of two separately instrumented payload sections which were detached in-flight. The results of the E field data analysis show that the temporal behavior of the fields was consistent with ion responses to the rapid charging of the active payload. A qualitative model of the interaction between the active payload and the ambient plasma background is developed to explain the electric field data, including the apparent causal relationship between the radial and tangential impulse components.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 3601-361
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  • 9
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    The ground-based measurement of ozone in the 9.6 micron band (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Stratospheric ozone has been measured using infrared emission spectroscopy of the 9.6 micron band. Thermal emission spectra of the zenith sky were measured from the ground. The spectra show the presence of the 1020 cm(exp -1) spectral feature of ozone on clear days. The spectra were measured with a BOMEM model 100 emission interferometer with a resolution of 4 cm(exp -1). The feature corresponds to a mixing ratio of 5 ppmv if the ozone is assumed to be uniformly distributed in the stratosphere from 25 to 35 km. The development of an inversion algorithm to derive the altitude distribution of the ozone in 3 layers is described. These measurements have been conducted from Peterborough, Ontario since June 1991; further investigations are planned to study the comparisons with Dobson and LIDAR ozone measurements.
    Keywords: GEOPHYSICS
    Type: NASA. Goddard Space Flight Center, Ozone in the Troposphere and Stratosphere, Part 2; p 778-781
    Format: application/pdf
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  • 10
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    Location and characteristics of the reconnection X-line deduced from low-altitude satellite and radar observations (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: We present an analysis of a cusp ion step observed between two poleward-moving events of enhanced ionospheric electron temperature. From the computed variation of the reconnection rate and the onset times of the associated ionospheric events, the distance between the satellite and the X-line can be estimated, but with a large uncertainty due to that in the determination of the low-energy cut-off of the ion velocity distribution function, f(E). Nevertheless, analysis of the time series f(t) shows the reconnection site to be on the dayside magnetopause, consistent with the pulsating cusp model, and the best estimate of the X-line location is 13 R(E) from the satellite. The ion precipitation is used to reconstruct the field-parallel part of the Cowley-D ion distribution function injected into the open low latitude boundary layer (LLBL) in the vicinity of the X-line. From this the Alfven speed, plasma density, magnetic field, parallel ion temperature, and flow velocity of the magnetosheath near the X-line can be derived.
    Keywords: GEOPHYSICS
    Type: NASA-TM-110114 , NAS 1.15:110114 , PB95-129805 , RAL-94-081
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