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  • Weitere Quellen  (679)
  • SOLAR PHYSICS  (279)
  • FLUID MECHANICS AND HEAT TRANSFER  (225)
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  • 1
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    Effect of shear stress on cell cultures and other reactor problems (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Anchorage dependent cell cultures in fluidized beds are tested. Feasibility calculations indicate the allowed parameters and estimate the shear stresses therein. In addition, the diffusion equation with first order reaction is solved for the spherical shell (double bubble) reactor with various constraints.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 19 p
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  • 2
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    Measurement of the solar constant (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-06-04
    Beschreibung: The absolute value of the solar constant and the long term variations that exist in the absolute value of the solar constant were measured. The solar constant is the total irradiance of the Sun at a distance of one astronomical unit. An absolute radiometer removed from the effects of the atmosphere with its calibration tested in situ was used to measure the solar constant. The importance of an accurate knowledge of the solar constant is emphasized.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 3
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    Solar spectrum from 170 to 3200 nanometers (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-06-04
    Beschreibung: The spectral irradiance of the Sun between 170 and 3200 nanometers was measured to determine accurately the solar constant, its possible variation with the solar cycle, and the wavelength range responsible for the observed variations. It is pointed out that measurements over very long time periods (10 years) involving flights of the same instrument on future Spacelab missions will be required. Few spectral solar irradiation measurements ranging from the near ultraviolet to the near infrared have been performed yet. The most extensive solar irradiation measurements were obtained by a spectrometer onboard an aircraft or from high altitude observatories. The full disk irradiation flux was measured, corrections for atmospheric absorption are applied in all of the measurements.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Marshall Space Flight Center Spacelab Mission 1 Expt. Descriptions; 3 p
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  • 4
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    Capillary priming characteristics of a dual passage heat pipe in zero-g (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Technical improvements of a long life heat rejection system, suitable for long duration high power missions, that can be constructed and deployed in orbit is discussed. A mathematical model is formulated and a computer program developed which describes the transient priming characteristics of a dual passage heat pipe. An experimental test package is described for flight in the KC-135 Zero-g Aircraft, to be used to verify the modeling predictions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 50 p
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  • 5
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    Two-phase flow and heat transfer under low gravity (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Spacelab experiment to investigate two-phase flow patterns under gravity uses a water-air mixture experiment. Air and water are circulated through the system. The quality or the mixture or air-water is controlled. Photographs of the test section are made and at the same time pressure drop across the test section is measured. The data establishes a flow regime map under reduced gravity conditions with corresponding pressure drop correlations. The test section is also equipped with an electrical resistance heater in order to allow a flow boiling experiment to be carried out using Freon II. High-speed photographs of the test section are used to determine flow patterns. The temperature gradient and pressure drop along the duct can be measured. Thus, quality change can be measured, and heat transfer calculated.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 43-57
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  • 6
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    Effects of spacecraft motions on fluids experiments (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The equations of motion governing an incompressible fluid contained in an orbiting laboratory were examined to isolate various fictitious forces and their relative influence on the fluid. The forces are divided into those arising from the orbital motions and those arising from small local motions of the spacecraft about its center of mass. The latter dominate the nonrotating experiments. Both are important for rotating experiments. A brief discussion of the onset of time-dependence and violent instability in earth-based rotating and processing systems is given.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 96-102
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  • 7
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    Convection in fluids at reduced gravity (1981)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: Natural convection is not always harmful and, therefore, to be avoided. In some situations it may be desirable to have fluid flows in space processes, e.g., to stir the fluid phase for mixing and cooling or to help maintain concentration gradients. In may event, it is important to know the extent and nature of convection in space and the factors on which it depends, in order either to minimize the effects to convection, or to utilize the convection to advantage. The information needed to assess both conventional and unstable convection includes: (1) the magnitude and direction of accelerations; (2) geometric configuration; (3) imposed boundary conditions; and (4) material properties.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Marshall Space Flight Center Spacecraft Dyn. as Related to Lab. Expt. in Space; p 69-95
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  • 8
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    Geophysical fluid dynamics (1981)
    In:  CASI
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    Publikationsdatum: 2006-02-14
    Beschreibung: Systematic scaling or dimensional analysis reveals that certain scales of geophysical fluid flows (such as stellar, ocean, and planetary atmosphere circulations) can be accurately modeled in the laboratory using a procedure which differs from conventional engineering modeling. Rather than building a model to obtain numbers for a specific design problem, the relative effects of the significant forces are systematically varied in an attempt to deepen understanding of the effects of these forces. Topics covered include: (1) modeling a large-scale planetary atmospheric flow in a rotating cylindrical annulus; (2) achieving a radial dielectric body force; (3) spherical geophysical fluid dynamics experiments for Spacelab flights; (4) measuring flow and temperature; and (5) the possible effect of rotational or precessional disturbances on the flow in the rotating spherical containers.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Spacecraft Dyn. as Related to Lab. Expt. in Space; p 25-31
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  • 9
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    Analysis of low-g heat transfer for a cryogenic oxygen pressurization heater (1981)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: After the external tank separates from the Orbiter about 2000 pounds of residual liquid oxygen remain in the main propulsion system lines. The pressurization of liquid oxygen from a subcritical to a supercritical state by the use of the heaters of the PRSA tanks while in a low-g environment is investigated. The performance of the heaters while bringing the state of the substance from the subcritical state to the supercritical one is studied, with particular emphasis on the time the pressurization process takes, and the temperature of the heater as the process proceeds.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Houston Univ. The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 2; 38 p
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  • 10
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    Vibration of a liquid with a free surface in a spinning spherical tank (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The problem of forced fluid vibrations in a partially filled spinning spherical tank is solved numerically by using the finite element method. The governing equations include Coriolis acceleration and spatially homogeneous vorticity. An exponential instability is detected in the present simulation for fill ratios below 0.5 and centrifugal acceleration to thrust ratios less than 1.7. This fictitious instability appears in the model as a result of the homogeneous vortex assumption since the free slosh equations are neutrally stable in the Liapunov sense.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Sound and Vibration; 76; May 8
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  • 11
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    Solar Maximum Mission Experiment - Ultraviolet Spectroscopy and Polarimetry on the Solar Maximum Mission (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacecraft is described. It is pointed out that the instrument, which operates in the wavelength range 1150-3600 A, has a spatial resolution of 2-3 arcsec and a spectral resolution of 0.02 A FWHM in second order. A Gregorian telescope, with a focal length of 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F2 waveplates can be inserted behind the spectrometer entrance slit; it permits all four Stokes parameters to be determined. Among the observing modes are rasters, spectral scans, velocity measurements, and polarimetry. Examples of initial observations made since launch are presented.
    Schlagwort(e): SOLAR PHYSICS
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  • 12
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    Practical implementation of the double linear damage rule and damage curve approach for treating cumulative fatigue damage (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Simple procedures are given for treating cumulative fatigue damage under complex loading history using either the damage curve concept or the double linear damage rule. A single equation is given for use with the damage curve approach; each loading event providing a fraction of damage until failure is presumed to occur when the damage sum becomes unity. For the double linear damage rule, analytical expressions are given for determining the two phases of life. The procedure comprises two steps, each similar to the conventional application of the commonly used linear damage rule. Once the sum of cycle ratios based on Phase I lives reaches unity, Phase I is presumed complete, and further loadings are summed as cycle ratios based on Phase II lives. When the Phase II sum attains unity, failure is presumed to occur. It is noted that no physical properties or material constants other than those normally used in a conventional linear damage rule analysis are required for application of either of the two cumulative damage methods described. Illustrations and comparisons are discussed for both methods.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Fracture; 17; Apr. 198
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  • 13
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    Surface phenomena in elasticity (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Problems of elasticity associated with the behavior of free surfaces of elastic bodies are reviewed with particular reference to the propagation of characteristic waves and the criteria of wrinkling of free surfaces. All transformations are given for the case when a free surface of an elastic body is streamlined by the flow of inviscid fluid. The wrinkling phenomenon is illustrated by example.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Elasticity; 11; Apr. 198
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  • 14
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    High resolution X-ray spectra of solar flares. V - Interpretation of inner-shell transitions in Fe XX-Fe XXIII (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper examines high-resolution solar flare iron line spectra recorded between 1.82 and 1.97 A by a spectrometer flown by the Naval Research Laboratory on an Air Force spacecraft launched on 1979 February 24. The emission line spectrum is due to inner-shell transitions in the ions Fe XX-Fe XXV. Using theoretical spectra and calculations of line intensities obtained by methods discussed by Merts, Cowan, and Magee (1976), electron temperatures as a function of time for two large class X flares are derived. These temperatures are deduced from intensities of lines of Fe XXII, Fe XXIII, and Fe XXIV. The determination of the differential emission measure between about 12-million and 20-million K using these temperatures is considered. The possibility of determining electron densities in flare and tokamak plasmas using the inner-shell spectra of Fe XXI and Fe XX is discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 245
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  • 15
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    Preliminary observations and results obtained with the ultraviolet spectrometer and polarimeter (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: New observation with the Ultraviolet Spectrometer and Polarimeter (UVSP) of a number of manifestations of solar activity obtained during the first three months of Solar Maximum Mission operations are presented. Attention is given to polarimetry in sunspots, oscillations above sunspots, density diagnostics of transition-zone plasmas in active regions, and the eruptive prominence - coronal transient link.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 244
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  • 16
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    The solar flare of 1980 March 29 at 0918 UT as observed with the hard X-ray burst spectrometer on the Solar Maximum Mission (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 244
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  • 17
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    On the polarization state of hydromagnetic fluctuations in the solar wind (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: From presently available observations one can infer that the Alfvenic turbulence measured in the solar wind, predominantly on trailing edges of high-speed streams, is a mixture of modes with two different polarizations, namely, Alfvenic modes and modes which are the incompressible limit of slow magnetosonic waves. Using Helios 2 magnetic data and a variance analysis, parallel (to the mean field) and perpendicular components of the fluctuations are separated, and the possible correlation between such components which would be predicted as a consequence of the incompressible character of the turbulence is studied. Correlations between eigenvalues of the variance matrix are also investigated and discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research; 86; Mar. 1
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  • 18
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    Time and energy dependence of heavy ion abundances in solar flare energetic particle events (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Examples are presented of the time and energy dependence of the abundances and spectra of the major heavy ions He, C, O and Fe during solar flare events, taken from a survey using the UMD/MPI ULET telescope on IMP-8 during 1973-1977. In some cases, time variations were found in the O/He, O/C and Fe/O ratios which appear to be inconsistent with models based solely on rigidity dependent propagation in the interplanetary medium.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Contrib. to the 17th Intern. Conf. on Cosmic Rays; p 5-8
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  • 19
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    High-sensitivity circular polarimetry of the Sun, 0.5 - 1.7 microns (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Using an isometric (symmetrical) photoelastic-modulator polarimeter and a Cassegrain telescope, broadband polarization measures of the Sun were obtained with unprecedented sensitivity. With an instrumental background of x 10 to the minus 6th power differential effects delta q = V/I of 1 x 10 to the minus 7th power were detectable. Some results: (1) the lambda dependence of broadband circular polarization in spots was observed out to 1.7 mu, extending the visible-light measurements of Illing, Landman, and Mickey. The q drops to of the order of 1 x 10 to the minus 5 power at 1.2 mu (in a strong spot), then rises at 1.6 mu. While molecules or other special mechanisms must play a role in the visible-light polarization, at lambda 1.5 mu the q values seem consistent with gray magneto-opacity. (2) By surveying inactive regions upper limits are set to broadband polarization due to global or deep-seated magnetic fields. For a double-toroidal pattern a differential measure is found, q sub b = (q sub ne + q sub sw - q sub nw - q sub - se) 14, at 1.7 mu, of (+1.2 + or = 0.7) x 10 to the minus 7th power a mean from three series in 1981. Based on a simple estimate by L. Biermann this would correspond to deep-down toroidal fields of or approx 2000 gauss. Extension of this work are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 191-197
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  • 20
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    Solar plages and the interpretation of stellar Ca 2 H and K line variations in late type dwarfs (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Approximately a dozen late type dwarf stars have been observed by Wilson (1978) to undergo cyclic variability in Ca II H and K line emission which seems analogous to the solar activity cycle. What might be learned about these stars from solar analogies? The Ca II K index is estimated variation of the Sun viewed as a star, and compared with the observed range of Wilson's stellar observations. Results indicate trends of increasing relative variation H-K(max)/H-K(min) with later spectral type, due to decreasing dilutional contribution of residual photospheric flux to a 1 A band at line center, and of increasing relative variation with decreasing relative time of rise to maximum tau rise/tau reminiscent of the observed solar correlation of a quick rise to sunspot maximum with a strong cycle.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 181-189
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  • 21
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    Modification of average coronal properties in the presence of periodic temperature and density variations near the base (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Conductive damping of the transient motion of the solar corona, and the consequences on the average flow field of conductively re-distributed energy are discussed. A particular example is treated. First, a steady solution for solar wind flow is found for a given set of steady boundary conditions, between 1.4 and 28 solar radii. These boundary conditions are that the density is 1.6xEO6 cm-3 and the temperature is 1.6xEO6 degrees. The flow profiles for this initial state are those shown at t=0 in the figures. Then, at t=0, periodic, in phase, sinusoidal variations in temperature and density are initiated and continued indefinitely. The amplitudes of the variations are 5 percent and 7.5 percent for the temperature and density respectively, imposed at 1.4 solar radii. The variations have a period of 1 hour shorter than a coronal transit time, but sufficiently long for the disturbances to propagate for small distances (2 to 3 solar radii). These oscillations are like those that might occur for acoustic oscillations, although no explanation is offered as to how an acoustic oscillation might extend to this radius in the first place.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 113-120
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  • 22
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    Dynamic phenomena in coronal flux tubes (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The study of stellar atmospheres and the determination of specific physical mechanisms, geometries, and magnetic structures by which coronae are maintained is examined. Ultraviolet and soft X-ray components observed in the radiative output of cool stars and the Sun require counterentropic temperature gradients for their explanation. The existence of a hot corona is recognized as a result of mechanical or fluid dynamic effects and the importance of the magnetic field in the heating is accepted. Magnetohydrodynamic energy release associated with the emergence of magnetic flux through the chromosphere and its dynamic readjustment in the corona are major counterentropic phenomena which are considered as primary candidates for corona heating. Systematic plows in coronal flux tubes result from asymmetric heating and systematic flows can exist without substantial chromospheric pressure differences.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Smithsonian Astrophysics Observatory 2nd Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Vol. 1; p 53-58
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  • 23
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    Eruptive solar magnetic fields (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes is considered, with particular attention given to the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates is extended to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated through the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and then solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move apart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasing heights.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 251
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  • 24
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    Reliability-based optimization under random vibration environment (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A methodology of formulating the optimum design problem for structural systems with random parameters and subjected to random vibration as a mathematical programming problem is presented. The proposed method is applied to the optimum design of a cantilever beam with a tip mass and a truss structure supporting a water tank. The excitations are assumed to be Gaussian processes and the geometric and material properties are taken to be normally distributed random variables. The probabilistic constraints are specified for individual failure modes since it is easier to specify the reliability level for each failure mode keeping in view the consequences of failure in that particular mode. The time parameter appearing in the random vibration based constraints is eliminated by replacing the probabilities of failure by suitable upper bounds. The numerical results demonstrate the feasibility and effectiveness of applying the reliability-based design concepts to structures with random parameters and operating in random vibration environment.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures; 14; 5-6,; 1981
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  • 25
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    Radio evidence for shock acceleration of electrons in the solar corona (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is pointed out that the new class of kilometer-wavelength solar radio bursts observed with the ISEE-3 Radio Astronomy Experiment occurs at the reported times of type II events, which are indicative of a shock wave. An examination of records from the Culgoora Radio Observatory reveals that the associated type II bursts have fast drift elements emanating from them; that is, a herringbone structure is formed. It is proposed that this new class of bursts is a long-wavelength continuation of the herringbone structure, and it is thought probable that the electrons producing the radio emission are accelerated by shocks. These new events are referred to as shock-accelerated events, and their characteristics are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Geophysical Research Letters; 8; Dec. 198
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  • 26
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    Solar wind motion within 30 R solar masses - Spacecraft radio scintillation observations (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: New remote-sensing observations are reported of the solar wind motion within about 30 earth radii. Use is made of the interplanetary scintillation (IPS) spaced receiver technique with the radio source being a spacecraft signal (rather than a natural radio source as in previous spaced receiver studies). The spacecraft used are Helios A and B and the Viking orbiters. The purposes of the study are (1) to augment the scarce estimates of solar wind bulk flow speed near the sun and in the ecliptic with measurements made using spacecraft signals, and (2) to estimate random velocity components and identify the region where the random velocity is a significant fraction of the mean velocity. In addition, the radial evolution of speed and random velocity is compared with that of the plasma density fluctuation spectrum. Also reported are the first accurately normalized IPS scintillation index measurements using a monochromatic point source.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astronomy and Astrophysics; 103; 2, No; Nov. 198
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  • 27
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    The structure and dynamics of the heliospheric current sheet (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It has been suggested that the sector structure observed in the interplanetary magnetic field may be interpreted in terms of a warped equatorial current sheet in the heliosphere. The reported study seeks to investigate this suggestion and to provide a clear picture of the topology of the current sheet. An analysis is presented of the magnetic field data obtained by the Pioneer 10 and 11 spacecraft during the time from 1972 to 1976, taking into account a range of heliocentric distances from 1 to 8.5 AU. The single most convincing observation in support of the warped current sheet hypothesis is the almost complete disappearance of the sector structure in the Pioneer 11 data when the spacecraft reaches a heliographic latitude of 16 deg in 1976. The observation suggests that the spacecraft was consistently above the current sheet for a period of several months.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research; 86; Dec. 1
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    Heat transfer in cooled porous region with curved boundary (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Heat transfer characteristics are analyzed for a cooled two-dimensional porous medium having a curved boundary. A general analytical procedure is given in combination with a numerical conformal mapping method used to transform the porous region into an upper half plane. To illustrate the method, results are evaluated for a cosine shaped boundary subjected to uniform external heating. The results show the effects of coolant starvation in the thick regions of the medium, and the extent that internal heat conduction causes the heated surface to have a more uniform temperature.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 29
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    The field and plasma configuration of a filament overlying a solar bipolar magnetic region (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: This paper presents an analytic model for a finite-size straight filament suspended horizontally in a steady state over a bipolar magnetic region. The equations of magnetostatic equilibrium are integrated exactly. The solution obtained illustrates the roles played by the electric current, magnetic field, pressure, and plasma weight in the balance of force everywhere in space. A specific example of a filament of diameter 50,000 km, with a density two orders of magnitude over the corona and supported by a magnetic field of about 4 gauss is included. The filament temperature can take values ranging from a small fraction to a few times the coronal temperature, depending on the internal electric current of the filament. To produce a cool filament, such as the quiescent prominence, the solution is required to have an internal field with a strong component along the filament, giving rise to helical structures. A hot filament such as the X-ray coronal loop can be produced as a twisted magnetic flux tube embedded in a strong background field aligned parallel to the filament and having lower density and temperature. The basic steps of construction can be used to develop models more realistic than the ones presented for their analytic simplicity.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 246
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  • 30
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    Interactive method for computation of viscous flow with recirculation (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An interactive method is proposed for the solution of two-dimensional, laminar flow fields with identifiable regions of recirculation, such as the shear-layer-driven cavity flow. The method treats the flow field as composed of two regions, with an appropriate mathematical model adopted for each region. The shear layer is computed by the compressible boundary layer equations, and the slowly recirculating flow by the incompressible Navier-Stokes equations. The flow field is solved iteratively by matching the local solutions in the two regions. For this purpose a new matching method utilizing an overlap between the two computational regions is developed, and shown to be most satisfactory. Matching of the two velocity components, as well as the change in velocity with respect to depth is amply accomplished using the present approach, and the stagnation points corresponding to separation and reattachment of the dividing streamline are computed as part of the interactive solution. The interactive method is applied to the test problem of a shear layer driven cavity. The computational results are used to show the validity and applicability of the present approach.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics; 40; Apr. 198
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    SPAR analysis of LDEF vibration characteristics (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: This paper presents a structural dynamic modeling of the Long Duration Exposure Facility (LDEF), which is a Space Shuttle payload of passive scientific experiments contained in trays mounted on a large cylindrically shaped structure. Special detailed finite element modeling, using the SPAR system of computer programs was required to obtain good agreement between analytical and test vibrations modes. Experimental trays contributed significantly to overall LDEF stiffnesses, and these contributions were realistically represented for each tray by the stiffness matrix of an equivalent orthotropic panel in the overall LDEF SPAR model. Orthotropic stiffnesses for this panel were obtained from finely detailed statically loaded tray SPAR models in which stiffness coupling was accounted for along with partial relative sliding allowed by the tray clamping attachments. Joint boundary conditions were also significant in the structural dynamic modeling of LDEF, and static data proved valuable in assessing modeling of local end fittings.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Computers and Structures; 13; Aug. 198
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    Bowen fluorescence on the sun (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An identification is made of a weak line in the high-resolution EUV solar spectrum, and the contribution of the Bowen fluorescence mechanism to line emission is considered. The line at 303.625 A is noted to coincide with the 2p 3d(3P2 0) - 2p2(3P1) transition of O III at 303.621 A, which could be excited by He II line excitation of the O III 2p2(3P2) - 2p 3d(3P2 0) transition at 303.799 A. Computations of the collisionally induced intensities of the 2p2(3P) - 2p3d(3P 0) multiplet are shown to result in values not observed in the solar spectrum, indicating that Bowen fluorescence, rather than collisional excitation, is the source of the line. The Bowen fluorescence mechanism is noted to have implications for the identification of other spectral lines, and for models of the solar corona.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 243
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    Large-eddy simulation of the shear-free turbulent boundary layer (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The shear-free turbulent boundary layer is calculated by the large-eddy simulation technique. The filtered Navier-Stokes equations are used; the method of integration employs Fourier expansions in the homogeneous directions and finite differences in the cross-stream direction. Results indicate that the simulation is capable of predicting the primary Reynolds-number effects.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics; 103; Feb. 198
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  • 34
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    Existence of axisymmetric modes of thin cylindrical shells with axial displacement restraint (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A necessary and sufficient condition is derived for the existence of the axisymmetric mode of cylindrical shells with a radial displacement having one half wave along the axis and axial displacement restrained at both ends. The condition is purely geometric and consists of an upper bound on the mean radius of thickness ratio for a given fixed value of the length to mean radius ratio, above which the mode with one half wave in radial displacement along the axis ceases to exist. The proof is based on enforcing two basic lemmas concerned with the simplicity of the eigenvalues of the shell and the uniform ordering of these eigenvalues with the number of nodes of their corresponding radial displacement eigenfunctions.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration; 74; Feb. 8
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  • 35
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    Latitude dependence of solar wind velocity observed at not less than 1 AU (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The large-scale solar wind velocity structure in the outer heliosphere has been systematically analyzed for Carrington rotations 1587-1541 (March 1972 to April 1976). Spacecraft data were taken from Imp 7/8 at earth, Pioneer 6, 8, and 9 near 1 AU, and Pioneer 10 and 11 between 1.6 and 5 AU. Using the constant radial velocity solar wind approximation to map all of the velocity data to its high coronal emission heliolongitude, the velocity structure observed at different spacecraft was examined for latitudinal dependence and compared with coronal structure in soft X-rays and H-alpha absorption features. The constant radial velocity approximation usually remains self-consistent in decreasing or constant velocity solar wind out to 5 AU, enabling us to separate radial from latitudinal propagation effects. Several examples of sharp nonmeridional stream boundaries in interplanetary space (about 5 deg latitude in width), often directly associated with features in coronal X-rays and H-alpha were found.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research; 86; Jan. 1
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  • 36
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    A molecular model for ice nucleation and growth, attachment 1 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The quantum mechanical technique is used to study ionic, configurational, and impurity defects in the ice surface. In addition to static calculations of the energetics of the water monomer-ice surface interactions, molecular dynamics studies were initiated. The calculations of the monomer-ice surface interaction, molecular dynamics studies were initiated. The calculations of monomer-ice surface interactions indicate that many adsorption sites exist on the ice surfaces and that the barriers between bonding sites are relatively low. Bonding on the prism face of ice is preferentially above lattice sites.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: A Mol. Model for Ice Nucleation and Growth; 27 p
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    A molecular model for ice nucleation and growth, attachment 2 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The central field empirical pair potential model is applied to studying the effects of kinks, ledges, and vacancies on the absorption of water molecules from the vapor. Molecular dynamics simulations indicate that cluster and/or surface modes play a primary role in the absorption process, the flexibility of the hydrogen bond serves to decrease the energy required for structural interconversion, and the rapid distribution of added energy in a hydrogen bonded system lead to aggregate stability which greatly exceeds that predicted by static energy calculations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: A Mol. Model for Ice Nucleation and Growth; 22 p
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  • 38
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    Report of the panel on fluid dynamics (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Areas of investigation in fluid dynamics, recommended experiments, and use of the facility for theory evaluation are discussed. Tunnel flow quality and calibration of the NTF are considered. Recent technological advances affecting tunnel design are surveyed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: High Reynolds Number Res. - 1980; p 169-195
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  • 39
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    Flux vector splitting of the inviscid gasdynamic equations with application to finite-difference methods (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The conservation-law form of the inviscid gasdynamic equations has the remarkable property that the nonlinear flux vectors are homogeneous functions of degree one. This property readily permits the splitting of flux vectors into subvectors by similarity transformations so that each subvector has associated with it a specified eigenvalue spectrum. As a consequence of flux vector splitting, new explicit and implicit dissipative finite-difference schemes are developed for first-order hyperbolic systems of equations. Appropriate one-sided spatial differences for each split flux vector are used throughout the computational field even if the flow is locally subsonic. The results of some preliminary numerical computations are included.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics; 40; Apr. 198
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  • 40
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    Dynamics of solar cosmic ray events - Processes at large heliocentric distances /much greater than 1 AU/ (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of solar cosmic ray events at heliocentric distances up to 6 AU and beyond obtained by the Pioneer 10 and 11 spacecraft are discussed in terms of the propagation of energetic charged particles in interplanetary space. Following a review of the diffusion propagation model used to explain cosmic ray transport, the statistical studies of McCarthy and O'Gallagher (1976) and Zwickl and Webber (1977) of the relations of event parameters with radial distance and the simultaneous observation studies of Hamilton (1977) are reviewed, and it is noted that the results imply a slowly increasing radial diffusion coefficient out to about 6 AU. More recent analyses of data obtained at heliocentric distances greater than 10 AU are then presented which indicate that the coefficient of radial diffusion may actually be decreasing with radial distance beyond 5 AU. Finally, theoretical predictions of the radial variation of the diffusion coefficient are presented which take into account the background interplanetary medium and are shown to be in agreement with observations.
    Schlagwort(e): SOLAR PHYSICS
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  • 41
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    Photospheric subrotations, differential rotation and zonal wind bands - A reverse pirouette (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is noted that on the sun the core is assumed to be rotating with a period of about 12 days while the overlying 'mantle' convection zone has a solid body component of about 27 days. It is proposed that this phenomenon could simply be understood as a 'reverse pirouette'. It is noted that while previously proposed models provide solutions of valid equations and computer analyses, they lack a simple physical picture to explain the phenomenon. In the model proposed here, the solar oblateness is conventionally providing added heat input at the poles. The result is the large scale transport of material toward the equator, causing subrotation. The model is thus seen as facilitating an understanding of the formation of a slowly rotating convection zone above the more rapidly rotating core. The latitudinal photospheric differential rotation is interpreted as a 'second order' effect associated with the horizontal transport of momentum.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics; 71; May 1981
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    Fast plasma heating by anomalous and inertial resistivity effects in the solar atmosphere (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A simple model is presented to describe fast plasma heating by anomalous and inertial resistivity effects. It is noted that a small fraction of the plasma contains strong currents that run parallel to the magnetic field and are driven by an exponentiating electric field. The anomalous character of the current dissipation derives from the excitation of electrostatic ion-cyclotron and/or ion-acoustic waves. The possible role of resistivity deriving from geometrical effects ('inertial resistivity') is also considered. Using a marginal stability analysis, equations for the average electron and ion temperatures are derived and numerically solved. No loss mechanisms are taken into account. The evolution of the plasma is described as a path in the drift velocity diagram, where the drift velocity is plotted as a function of the electron to ion temperature ratio.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 245
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  • 43
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    The corona associated with solar filaments (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Spectroheliograms in high temperature ions such as Fe XV show the existence of both filaments that are brighter than the ambient corona and filaments that are darker than the ambient corona. The relationship of the filaments to photospheric magnetograms is described, and a possible physical mechanism to explain the differences is discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics; 71; May 1981
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    Effect of elastic end rings on the eigenfrequencies of thin cylinders (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The effect of elastic end rings on the eigenfrequencies of thin cylindrical shells is studied by using an exact solution of the linear eigenvalue problem. The out-of-plane and torsional rigidities of the rings are responsible for the overall shell stiffness. Considerable mode interaction exists for modes with low circumferential wave numbers when the mass of the ring is comparable with that of the shell. The hypothetical simply supported and clamped boundary conditions are practically impossible to realize with a finite-mass ring for relatively short and thin shells.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration; 74; Jan. 8
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    Flares and dynamic aspects (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Theory of the dynamic nature of solar flares, eruptive prominences, and coronal transients is surveyed. Two types of flare are considered: compact eruptions (small flares) which are probably loops, and large eruptions of double filament flares. The physical sense of this classification is justified, using solar observations. Even leaving the question unanswered of whether a coronal transient is a loop of ejected matter or a shock wave, the important, perhaps fundamental, role of mass motion in flare physics is evidenced.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Obs. de Paris-Meudon Forum on Solar Activity; 13 p
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    The coronal and interplanetary current sheet in early 1976 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A comparison of Helios 1 and 2 observations of the interplanetary sector pattern in early 1976 with the maximum brightness curves in the K coronameter data at 1.5 solar radii shows that the latter may be identified with the footprints of the sector boundary surface to an accuracy of about 10 deg. The sector boundary surface probably extended to about 15 deg in the Northern Hemisphere and to about 30 deg in the Southern Hemisphere, with little change between 1.5 solar radii and 1 AU. The surface was warped appreciably from a single titled plane (a dipole configuration) suggesting a significant magnetic quadrupole contribution.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research; 86; Oct. 1
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    On the theory of coronal heating mechanisms (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The present state-of-the-art of two classes of theories of coronal heating is examined: (1) heating by acoustic processes in the 'nonmagnetic' parts of the atmosphere (the shock-wave theory is an example); and (2) heating by electrodynamic processes in the magnetic regions of the corona (beta much less than 1) either by MHD waves or current heating in regions with high electric current densities (flare-type heating). It is concluded that the mechanism of the heating of the solar chromosphere and corona remains an open question, especially in explaining detailed atmospheric structures. The acoustic theory might be correct with little modification for most of the chromosphere, but as soon as the atmosphere shows a high degree of structure as in the corona and transition layer the magnetic field must play a dominant role. It appears that the current heating theories have a small range of applicability, while the MHD-wave theories are the most promising.
    Schlagwort(e): SOLAR PHYSICS
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    Identification of new solar OH lines in the 10-12 micron region (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: High-resolution (0.02/cm) infrared solar spectra obtained with a balloon-borne interferometer reveal new solar absorption features, which appear as regularly spaced quartets, in the 825-960/cm region. The lines are interpreted as high N-double-prime (25-33) pure rotation lines of solar OH. An effective amount of approximately 8 x 10 to the 15th molecules/sq cm of OH is estimated from the spectra.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 248
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    On ionization equilibrium in solar flares as determined from X-ray emissionlines of Ca XVIII and Ca XIX (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A diagnostic capable of determining the state of ionization equilibrium in flare plasmas is important for the determination of the physical conditions in flares. An experiment on the Air Force satellite P78-1 has provided high-resolution X-ray spectra which make it possible to determine the state of the ionization equilibrium in coronal flare plasmas. The considered investigation has the objective to show that the interpretation of the calcium results is complicated by several possible blends to line q, and to point out a variation in the observed ratios which seems difficult to account for. Possible explanations for the observations are discussed, taking into account the possibility that the ionization equilibrium calculations have to be improved. Another possible explanation is related to a suggestion made by Urnov (1981) and Karev et al. (1980) concerning the effects produced by the presence of high-energy nonthermal electrons.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 251
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    Stress-intensity factors and crack-opening displacements for round compact specimens (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An improved method of boundary collocation based on the complex variable analysis of Muskhelishvili (1953) is applied to the two-dimensional stress analysis of round compact specimens with pin-loaded holes. Stress intensity factors and crack opening displacements are calculated for various round compact specimens as a function of crack-length-to-specimen-width ratios. A wide-range equation for the stress intensity factors and equations for crack-surface displacements and load-point displacements are developed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: International Journal of Fracture; 17; Dec. 198
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    Solar observations and atomic data for the 3s2 1s0-3s3p 3P1 transition in S v (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: High resolution solar observations of the S v intersystem line at 1199.18 A are available from Skylab. This line is potentially useful as a density diagnostic for high density plasmas expected in solar flares. S v lines are also prominent in solar spectra at wavelengths below 1000 A. Collision strengths and radiative decay rates are calculated for levels of the configurations 3 s2, 3s3p, 3p2, and 3s3d. Level populations for the five lowest energy levels have been calculated as a function of electron density. These calculations are carried out assuming the temperature at which S v is most abundant in solar plasmas. The calculated population of the 3s3p 3P1 level reaches a pseudo-Boltzmann equilibrium at a density which is about five times higher than is derived from solar spectra and previous density determinations. It is believed that the discrepancy is due to a significant contribution from resonances to the 3s2-3s3p 3P excitation rate coefficient. It is suggested that the contribution of the resonances to the S v excitation rate coefficient can be estimated from a comparison of the experimental results and the theoretical calculations.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 250
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    Multi-parameter yield zone model for predicting spectrum crack growth (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A phenomenological load interaction model referred to as the Multi-Parameter Yield Zone model is presented which accounts for crack growth retardation caused by previous overloads, acceleration due to current overloads, and underload effects. In the present model, load interaction effects are calculated utilizing a residual stress intensity concept. Crack growth retardation and acceleration are accounted for by decreasing or increasing, respectively, the effective stress ratio used in a modified Forman's (1967) crack growth equation. Results of spectrum crack growth predictions for 2219-T851 aluminum are presented.
    Schlagwort(e): STRUCTURAL MECHANICS
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    A crack-closure model for predicting fatigue crack growth under aircraft spectrum loading (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The present paper is concerned with the development and application of an analytical model of cyclic crack growth that includes the effects of crack closure. The model was based on a concept like the Dugdale model, but was modified to leave plastically deformed material in the wake of the advancing crack tip. The model was used to correlate crack growth rates under constant-amplitude loading and to predict crack growth under aircraft spectrum loading on 2219-T851 aluminum alloy plate material. The predicted crack growth lives agreed well with experimental data. The ratio of predicted-to-experimental lives ranged from 0.66 to 1.48.
    Schlagwort(e): STRUCTURAL MECHANICS
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    A root-mean-square approach for predicting fatigue crack growth under random loading (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A method for predicting fatigue crack growth under random loading which employs the concept of Barsom (1976) is presented. In accordance with this method, the loading history for each specimen is analyzed to determine the root-mean-square maximum and minimum stresses, and the predictions are made by assuming the tests have been conducted under constant-amplitude loading at the root-mean-square maximum and minimum levels. The procedure requires a simple computer program and a desk-top computer. For the eleven predictions made, the ratios of the predicted lives to the test lives ranged from 2.13 to 0.82, which is a good result, considering that the normal scatter in the fatigue-crack-growth rates may range from a factor of two to four under identical loading conditions.
    Schlagwort(e): STRUCTURAL MECHANICS
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    Spectral energy transfer for inhomogeneous turbulence (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is noted that several terms in the two-point spectral equation for homogeneous turbulence can be interpreted as spectral-transfer terms; that is, they represent the net rate of energy transfer into a wavenumber region from all other wavenumbers. This holds for terms associated with both turbulence and self-interaction and interaction between turbulence and mean gradients. It is not seen as obvious, however, that similar interpretations apply when the turbulence is not homogeneous. In particular, one might question the interpretation for the terms associated with turbulence self-interaction because the condition of homegeneity is generally used in making the interpretation. It is the purpose here to consider whether terms interpretable as transfer terms exist in the equations for inhomogeneous turbulence. It is found that certain terms in the two-point spectral equation can be interpreted as transfer terms.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids; 24; Oct. 198
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    Distorted turbulence in axisymmetric flow (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A solution to the rapid-distortion theory for small-scale turbulence in flow round an axisymmetric obstacle is derived. General formulae for velocity covariances and Eulerian time scales are obtained and are evaluated for the particular case of flow round a sphere. The large-scale limit for this flow is also discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Quarterly Journal of Mechanics and Applied Mathematics; 34; Nov. 198
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  • 57
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    Solar variability (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Reference is made to direct measurements carried out by space-borne detectors which have shown variations of the solar constant at the 0.2 percent level, with times scales ranging from days to tens of days. It is contended that these changes do not necessarily reflect variations in the solar luminosity and that, in general, direct measurements have not yet been able to establish (or exclude) solar luminosity changes with longer time scales. Indirect techniques, however, especially radius measurements,suggest that solar luminosity variations of up to approximately 0.7 percent have occurred within a period of tens to hundreds of years.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: (ISSN 0185-1101)
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  • 58
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    Some approximations in the linear dynamic equations of thin cylinders (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Theoretical analysis is performed on the linear dynamic equations of thin cylindrical shells to find the error committed by making the Donnell assumption and the neglect of in-plane inertia. At first, the effect of these approximations is studied on a shell with classical simply supported boundary condition. The same approximations are then investigated for other boundary conditions from a consistent approximate solution of the eigenvalue problem. The Donnell assumption is valid at frequencies high compared with the ring frequencies, for finite length thin shells. The error in the eigenfrequencies from omitting tangential inertia is appreciable for modes with large circumferential and axial wavelengths, independent of shell thickness and boundary conditions.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration; 76; June 22
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  • 59
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    Multivalued velocity field model of turbulence (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The considered study is based on new theoretical concepts regarding a post-instability model of a fluid discussed by Zak (1980). The model permits the completion of the governing equations of turbulence by introducing multivalued fields of velocities. Attention is given to the mechanism of energy dissipation, the characteristic wave propagation, a simplified model, the formation of turbulence around stagnation points, the formulation of boundary conditions, and the mechanism of turbulence formation. The mechanism of turbulence formation can be understood as propagation of initial discontinuities from the boundaries into a flow with the characteristic velocity which is defined by the normal (to the boundary) velocity components. These components emerge at the boundary as a result of jumps in the tangential components due to the continuity equation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Mechanics Research Communications; 8; 2, 19; 1981
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  • 60
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    Magnetic loop behind an interplanetary shock - Voyager, Helios, and IMP 8 observations (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The flow behind an interplanetary shock was analyzed through the use of magnetic field and plasma data from five spacecraft, with emphasis on the magnetic cloud identified by a characteristic variation of the latitude angle of the magnetic field. The size of the cloud was found to be about 0.5 AU in radial extent and greater than 30 deg in azimuthal extent, with its front boundary almost normal to the radial direction. Because the field direction of the magnetic cloud as it moved past the spacecraft was observed to rotate nearly parallel to a plane, it is thought that the field configuration of the cloud was essentially two-dimensional. These results further suggest that the lines of force in the magnetic cloud formed loops, but it could not be determined whether these loops were open or closed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research; 86; Aug. 1
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  • 61
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    On the mixing of a rectangular jet (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Hot-wire measurements in an incompressible rectangular jet, issuing into a quiet environment at ambient conditions, are presented. A blow-down-type air supply system was used to provide the airflow to a cylindrical settling chamber 1.75 m in length and 0.6 m in diameter. The measurements were made with constant-temperature anemometers in conjunction with linearizers. The two signals from the linearizers were sent through a sum and difference unit which was calibrated from dc to 100 kHz. The distributions of mean velocity and the turbulence shear stresses were measured in the two central planes of the jet stations up to 115 widths downstream of the nozzle exit. Three distinct regions characterized the jet flow field: a potential core origin, a two-dimensional-type region, and an axisymmetric type region. The onset of the second region appeared to be at a location where the shear layers separated by the short dimension of the nozzle meet; and the third region occurred at a downstream location where the two shear layers from the short edges of the nozzle meet. In the central plane, similarity was found both in the mean velocity and shear stress profiles beyond 30 widths downstream of the nozzle exit; profiles of rms velocity showed similarity in the second, but not the third region.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics; 107; June 198
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  • 62
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    Coronal activity below 2 solar radii - 1980 February 15-17 (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Coronal observations concerning the area between the solar surface and 2.0 solar radii can now be conducted by making use of a new ground-based K-coronameter and a prominence monitor on Mauna Loa in Hawaii. Observations made by the K-coronameter on three consecutive days surrounding the eclipse of 1980 February 16 show that the solar corona was very active during this time. Definite changes occurred between each day's observations. During one period of K-coronameter observations (1980 February 15) a coronal transient was observed to move through the coronameter's field of view. A description is presented of the general changes which occurred in the corona during this period, taking into account the coronal transient observed by the prominence monitor and K-coronameter. The most important aspects of these new observations pertain to the relationship between the H alpha prominence and the surrounding coronal material.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 246
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  • 63
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    Cyclic plasticity models and application in fatigue analysis (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An analytical procedure for prediction of the cyclic plasticity effects on both the structural fatigue life to crack initiation and the rate of crack growth is presented. The crack initiation criterion is based on the Coffin-Manson formulae extended for multiaxial stress state and for inclusion of the mean stress effect. This criterion is also applied for the accumulated damage ahead of the existing crack tip which is assumed to be related to the crack growth rate. Three cyclic plasticity models, based on the concept of combination of several yield surfaces, are employed for computing the crack growth rate of a crack plane stress panel under several cyclic loading conditions.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 64
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    Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The latitudinal variation of the solar proton flux and energy causes a density increase at high solar latitudes of the neutral gas penetrating the heliosphere. Measurements of the neutral density by UV resonance radiation observations from interplanetary spacecraft thus permit deductions on the dependence of the solar proton flux on heliographic latitude. Using both the results of Mariner 10 measurements and of other off-ecliptic solar wind observations, the values of the solar proton fluxes and energies at polar heliographic latitudes are determined for several cases of interest. The Mariner 10 analysis, together with IPS results, indicate a significant decrease of the solar proton flux at polar latitudes.
    Schlagwort(e): SOLAR PHYSICS
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  • 65
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    What produces the high densities observed in solar flare plasmas (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Attention is drawn to the implications of the high densities observed in flare plasmas in the wide temperature range from 10 to the 4th K to more than 10 to the 7th K. The chromospheric evaporation theory for the decay phase is discussed, and it is found that it is not consistent with the observations. It is pointed out that all the flare mechanisms proposed so far, e.g., magnetic field reconnection in various geometries, have entirely ignored the fundamental problem of how the high densities arise in the first place, and, in fact, they are unable to answer this question. It is suggested that compressional heatings of a flaring loop might be responsible for the density and emission measure (EM) increases observed in flare plasmas. Chromospheric evaporation associated with local heating in the initial rising phase of the flare, in distinction to the existing evaporation theory which assumes a coronal heating source, is also discussed. Possible observational tests, utilizing the newly launched Solar Maximum Mission (SMM) satellite, are presented.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astronomy and Astrophysics; 97; 1, Ap; Apr. 198
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  • 66
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    Observations of solar flares on 1980 April 30 and June 7 with the hard X-ray burst spectrometer (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Descriptions of hard X-ray observations for solar flares occurring on 1980 April 30 and June 7 are presented. The hard X-ray light curve for the June 7 event shows complex intensity variations on time scales of 100 ms and spectral variations on time scales of seconds. The results for the 1980 April 30 flare are compared with simultaneous observations from other SMM instruments and from ground-based observatories. These comparisons have enhanced the interpretation of the hard X-ray data for this event and have permitted the tentative identification of the origin of the hard X-ray emission with a small loop structure within the flare region.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 244
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  • 67
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    Observations of the 1980 April 30 limb flare by the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of the M2 limb flare of 1980 April 30 by the ultraviolet spectrometer and polarimeter in the C IV 1548 A line are described and compared with observations from other SMM instruments and with ground-based H-alpha data. Events observed during the 18 minutes leading up to the flare impulsive phase include the filling of a small loop with material moving at about 20 km/s, followed by a rapid brightening in C IV, H-alpha, and hard X-rays, with a subsequent brightening of a higher set of loops. The rapid brightening appears to be at the junction of the small loop with the overlying magnetic structures, which suggests the flare may be caused by their interaction.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 244
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  • 68
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    Analysis of capacitive heat exchangers, part 1 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Governing equations are developed for a simple capacitive heat exchanger. This type of heat exchanger consists of hot spherical particles falling through an ascending cold gas stream. The assumptions made in deriving the continuity, momentum and energy equations are clearly stated. The analysis yields a system of first order, ordinary, nonlinear equations which form a complex boundary value problem. The method of solution is presented together with a comparison between the performance of capacitive heat exchangers and conventional counter flow ones.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 207-221
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  • 69
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    Some 20.7- and 31.4-GHz solar disk temperature measurements (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The performance of a 20.7/31.4 GHz water vapor radiometer was evaluated with respect to its use in measuring atmospheric noise temperature. Results are in good agreement with the results previously reported at the same frequency.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Telecommun. and Data Acquisition Progr. Rept. 42-64; p 140-159
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  • 70
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    Evolution of the energetic particle composition during solar flare events as observed by Voyager 1 and 2 (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Measurements of the composition and energy spectra of the energetic ions from two solar flare particle events are presented. Their evolution with time during each event is discussed. The data are from the Low Energy Particle Telescope (LEPT) on Voyager 2, which can identify the major ion species (Z = 1-26) over an energy range of approximately 0.5-50 MeV/nucleon.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Contrib. to the 17th Intern. Conf. on Cosmic Rays; p 14
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  • 71
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    Observations of interplanetary energetic charged particles from gamma-ray line solar flares (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of interplanetary energetic ions from the 7 June, 21 June and 1 July 1980 gamma ray line solar flares are presented. The observations are from the Max-Planck-Institut/University of Maryland Ultra Low Energy Wide Angle Telescope aboard the ISEE-3 spacecraft. Both June flares produced relatively low intensity proton events at earth with peak intensities at 10-20 MeV approximately 5 x .01 protons square cm sec sr MeV)-1. Neither flare showed evidence of being enriched in either 3He or Fe at approximately 1 MeV/nucleon. The 1 July flare produced no observable ion or electron enhancements.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Contrib. to the 17th Intern. Conf. on Cosmic Rays; p 1-4
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  • 72
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    A satellite investigation of energy flux and inferred potential drop in auroral electron energy spectra (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Because predicted relationship (epsilon directly varies with V squared) between auroral electron energy flux (epsilon) and the inferred acceleration potential drop (V) for accelerated Maxwellian distributions was favorably tested by other using sounding rocket data for the limiting case of eVE 1 (where Ec is the characteristic energy of the accelerated Maxwellian distribution) and for a single inverted-V observed by the Injun 5 satellite, data from Atmosphere D were used to extend these studies over the range .2 eV/Ec 5 and for a wide range of latitudes and local times on both the nightside and the dayside. Results show good agreement with the full accelerated Maxwellian model. An analytical approximation to the electron energy flux was derived which better describes the data over the range .2 eV/Ec approximated 3. Analyses of individual energy spectra at small and large pitch angles through well-defined inverted-V structures suggest that the altitude of the inferred potential drop maximizes near the center of the inverted-V's.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Texas Univ. at San Antonio Res. on Solar-Wind Magnetospheric Elec. Fields and Plasmas; 16 p
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  • 73
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    On the anticorrelation between the He-3/He-4 ratio and proton intensity in He-3 rich flares (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A model is presented which can explain the observed anticorrelation between the size of the 3He/4He abundance ratio at greater than or approximately 10 MeV/nuc and the peak intensity of approximately 10 MeV protons in 3He rich events. If 3He is preaccelerated with respect to 4He prior to the main ion acceleration phase, and if the main ion acceleration phase has an effective injection cutoff which varies from flare to flare, the observed anticorrelation follows naturally.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Contrib. to the 17th Inter. Conf. on Cosmic Rays; p 15-18
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  • 74
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    Wind loads for bar-truss structures (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: An analysis method developed to calculate the wind loads on the nodes or joints of the truss type support structure of the 64 meter antenna is described. The method uses the CBAR element and GRID coordinate cards of the NASTRAN or IDEAS structural analysis programs as inputs to the computer model of the structure. Cross flow principles and vector analysis are also used in the analysis. The algorithms used are described and probable accuracy of the solution is discussed.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: The Telecommun. and Data Acquisition; p 149-153
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  • 75
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    Temperature-dependent creep buckling of plates (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Time-dependent lateral deflection of flat rectangular plates is predicted by the Norton-Bailey (Norton 1929, Bailey 1935) power law for material creep. The plates have a through-thickness steady-state temperature distribution, and the effects are considered by using Maxwell's law to modify the power creep law. Equations are derived for creep exponents of 3 and 5, using the sandwich plate element to predict creep buckling of plates. Predictions of creep buckling with a temperature variation between the inner and outer plate surfaces are found to be somewhat dependent on the creep buckling relationship assumed. When significant scatter justifies a variation in the creep constants up to an order of magnitude, discrepancies in predictions using the two exponents are reasonable, and for one engineering material, the predictions have the same degree of agreement with experimental data as have the respective creep laws.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Thermal Stresses; 4; Apr. 198
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  • 76
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    The Schwarzschild criterion for convection in the presence of a magnetic field (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Schwarzschild criterion governing the onset of convective instability has been modified to include magnetic field. This may be of importance for solar variability. The revised condition suggests that the underside of field layers are stabilizing and the upper side destabilizing. Absolute instability can be reached to achieve conventional magnetic buoyancy. This may explain the inverse correlation between the time intervals between sunspot minima and sunspot maxima with the maximum values of sunspot number, which is found to be significant at the 5.5 sigma level.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Letters; 21; 3-4,; 1981
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  • 77
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    Spatial and temporal structures of impulsive bursts from solar flares observed in UV and hard X-rays (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: New observations are presented of impulsive UV and hard X-rays bursts in two solar flares obtained with instruments on Solar Maximum Mission. The UV bursts were observed in the Si IV and O IV emission lines, whose intensity ratio is density-sensitive. By comparing the spatially resolved Si IV/O IV observations with the corresponding hard X-ray observations, it is possible to study their spatial and temporal relationships. For one flare, the individual component spikes in the multiply peaked hard X-ray burst can be identified with different discrete Si IV/O IV flaring kernels of size 4 arcsec x 4 arcsec or smaller, which brighten up sequentially in time. For the other, many Si IV/O kernels, widely distributed over a large area, show impulsive bursts at the same time, which correlate with the main peak of the impulsive hard X-ray burst. The density of the flaring Si IV/O IV kernels is in the range from 5 x 10 to the 12th-13th/cu cm.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 248
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  • 78
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    Simple-loop flares - Magnetic instabilities (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The era of rocket and spacecraft observations of the sun has provided an entirely new view of the structure and evolution of the solar atmosphere. It is now clear, particularly since the extended series of Skylab flights, that the lower corona is quite nonuniform. In active regions, the strong ambient magnetic fields collimate and confine the emissive plasma into a myriad of loops and arcades. These features are observed to evolve slowly, with a time-scale much longer than the relevant hydromagnetic of Alfven period and, therefore, must be considered generally to be stable. A conspicuous exception is the sporadic flare activity of these loops, which is believed to be due to localized departures from infinite-conductivity behavior.
    Schlagwort(e): SOLAR PHYSICS
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  • 79
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    Sunspot dynamics - Gravitational draining - A cooling mechanism (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The inward and downward flow of cooled material below sunspots is considered as a possible explanation of the stability, temperature and heat flow characteristics of sunspots. It is suggested that the flow of material inwards towards the center of the sunspot and then downwards towards the center of the sun through magnetic field conduits plays a role in the cooling of sunspots as it does in pores and magnetic knots, although due to the larger size of a sunspot the downflow takes place below the photosphere. In this view, the inflow and cooling of sunspots are sustained by the release of energy by the convecting gas, which then becomes cooler and denser as it returns to the heat source. The lack of a bright ring around sunspots is explained by the entrainment of upward moving heat flux by the downward moving gases. The temperature and density distributions predicted by the present model are shown to be satisfactory agreement with the empirical model of Van't Veer (Tandberg-Hansen, 1966).
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal; vol. 247
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  • 80
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    A mechanism for solar ultraviolet flux variability (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Following an examination of solar UV emission observed by a filter photometer on Nimbus IV from 1969 to 1973 in an attempt to understand the 27-day and secular variability, two models are proposed to account for the variations: (1) a calcium plage model and (2) a chromospheric network faculae and spicule structure model. An association between UV brightenings and the large scale magnetic field has been found to be consistent with the network model. An increase in the UV emittance can be achieved by raising the effective chromospheric temperature closer to a photospheric level. If the sun's luminosity is constant on these time intervals, the enhanced UV radiation could be partially offset by an overall decrease in photospheric temperature such as that measured by Livingston (1978) in visible photospheric profiles.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics; 73; Sept
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    On the presence of electric currents in the solar atmosphere. I - A theoretical framework (1981)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The general magnetic field above the solar photosphere is divided by an elementary analysis based on Ampere's law into two parts: a potential field due to electric currents below the photosphere and a field produced by electric currents above the photosphere combined with the induced mirror currents. The latter, by symmetry, has a set of field lines lying in the plane taken to be the photosphere which may be constructed from given vector magnetograph measurements. These field lines also represent all the information on the electric currents above the photosphere that a magnetograph can provide. Theoretical illustrations are given, and implications for data analysis are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics; 73; Oct. 198
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    Vibrations of three-dimensional pipe systems with acoustic coupling (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A general algorithm is developed to calculate the beam-type dynamic response of three dimensional multiplane finite length pipe systems, consisting of elbow and straight ducts with continuous interfaces. Emphasis is on secondary acoustic wave effects giving rise to coupling mechanisms; and the simulation accounts for one-dimensional elastoacoustic coupling from a plane acoustic wave and secondary loads resulting from wave asymmetries. The transfer matrix approach is adopted in modeling the elastodynamics of each duct, with allowance for distribution loads. Secondary loads from plane wave distortion are considered with a solution of the Helmholtz equation in an equivalent rigid waveguide, and effects of path imperfection are introduced as a perturbation from the hypothetical perfectly straight pipe. Computations indicate that the one-dimensional acoustic assumption is valid for frequencies below one-half the first cut-off frequency, and the three-dimensional acoustic effects produce an increase in response levels near and above cut-off.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Journal of Sound and Vibration; 78; Sept. 8
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    Temperature anisotropy instabilities driven by Whang's ion model (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The behavior of four temperature anisotropy instabilities in a single-component space plasma is investigated theoretically using the solar wind model (i.e., heat flux modified non-Maxwellian velocity distribution functions) proposed by Whang (1972). The linear dispersion properties are studied in an infinite Vlasov plasma where the proton distribution is assumed to consist of one warm slow-speed component and where the electron background is isotropic. It is shown that the fire hose, mirror, and Harris instability do not occur under these conditions, and that only the ion cyclotron instability is of importance in Whang's ion model. Growth rates are shown to have values between 0.021 and 0.00011. Increasing temperature anisotropy causes the range frequencies where wave particle interaction occurs to be shifted toward the ion gyrofrequency.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research; 86; Sept. 1
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  • 84
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    Structural synthesis - Its genesis and development (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: An historical account is given of the development, from its conception in 1960, of the structural synthesis method. While synthesis techniques lag behind analytical ones in both sophistication and application, the structural design procedures created by combining finite element analysis and mathematical programming algorithms have progressed to the point of maturity. As in the case of finite element analysis, use and acceptance of structural synthesis methodology depends on the development and distribution of easily used and well-documented, production-quality computer programs. Attention is given such elementary applications of synthesis methods as the three-bar truss, an integrally stiffened waffle plate, a stiffened cylindrical shell, aircraft fuselage window panels, the structural efficiency of graphite-epoxy hat-stiffened panels, and an idealized delta wing.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: AIAA Journal; 19; Oct. 198
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  • 85
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    Role of coherent structures in turbulent shear flows (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A definition for the large-scale coherent structure is presented, and the nature and role of coherent structures in turbulent shear flows are examined. The equations governing the coherent motions and the experimental considerations as well as constraints in the investigations of coherent structures in wall-bounded and free turbulent shear flows are discussed. Results from a few of our recent and on-going studies of coherent structures in excited and unexcited free turbulent shear flows are reviewed. These results show that coherent structures are dominant in transport in the early stages of their formation, but not in the self-preserving regions of turbulent shear flows.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: vol. 4; Aug. 198
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  • 86
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    Green's function for cracks of equal length from a circular hole in an infinite sheet (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Stress-intensity factors are obtained for twin collinear cracks emanating from a hole in an infinite plate. Point forces that tend to make the crack surfaces separate and slide are applied to one of the cracks. A conformal mapping and the Muskelishvili formulation involving series representation of the Kolosov stress functions are used to derive the solutions. The variation of stress-intensity factor with crack length and with point of application of the loads is presented for both crack tips.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Res Mechanica Letters; 1; Dec. 198
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  • 87
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    Laminar free convection boundary layer heat transfer over non-isothermal surface (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Accurate heat transfer results are provided for the case of nonisothermal objects. A steady, laminar, free convection boundary layer flow over two-dimensional or rotationally symmetrical bodies of nonuniform surface temperature situated in an ambient fluid of undisturbed temperature is considered analytically. The surface heat flux is given in terms of the Nusselt number and wall derivatives of universal functions for Prandtl numbers of 0.72 and 100 are provided. The method is shown to be valid up to a temperature/radius ratio of 130 deg.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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    An empirical stress-intensity factor equation for the surface crack (1981)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: This paper presents an empirical stress-intensity factor equation for a surface crack as a function of parametric angle, crack depth, crack length, plate thickness and plate width for tension and bending loads. The stress-intensity factors used to develop the equation were obtained from a previous three-dimensional, finite-element analysis of semielliptical surface cracks in finite elastic plates subjected to tension or bending loads. A wide range of configuration parameters was included in the equation. The ratios of crack length to plate thickness and the ratios of crack depth to crack length ranged from 0 to 1.0. The effects of plate width on stress-intensity variations along the crack front were also included. The equation was used to predict patterns of surface-crack growth under tension or bending fatigue loads. The equation was also used to correlate surface-crack fracture data for a brittle epoxy material within + or - 10 percent for a wide range of crack shapes and crack sizes.
    Schlagwort(e): STRUCTURAL MECHANICS
    Materialart: Engineering Fracture Mechanics; 15; 1-2,; 1981
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  • 89
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    A viscous-inviscid interaction model of jet entrainment (1981)
    In:  CASI
    Details
    Publikationsdatum: 2017-10-02
    Beschreibung: A viscous-inviscid interaction model for predicting jet entrainment effects on axisymmetric, nozzle afterbodies at subsonic speeds is presented. The model is based on a displacement thickness correction to the inviscid jet boundary that accounts for mixing-induced streamline deflections in the inviscid region. The displacement correction is shown to be related to the local mass entrainment rate and, for thin mixing layers, the model is shown to be analogous to displacement models used in conventional boundary-layer interaction theory. A method is presented for computing the entrainment rate by an overlaid mixing layer model that accounts for the nonsimilar behavior and pressure gradients occurring in the near field region. An iterative scheme for coupling the model to analyses for the external inviscid flow, the external boundary layer, and the inviscid jet exhaust is also given. Results are presented that illustrate the qualitative behavior of the entrainment interaction under various flow conditions and that demonstrate the validity of the model by comparisons with experiment.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AGARD Computation of Viscous-Inviscid Interactions; 15 p
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  • 90
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    Computational methods in nonlinear structural and solid mechanics; Proceedings of the Symposium, Washington, D.C., October 6-8, 1980. Symposium sponsored by the George Washington University and NASA (1981)
    In:  Other Sources
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    Publikationsdatum: 2016-03-09
    Beschreibung: Topics discussed include computational strategies for nonlinear problems in structural mechanics, time integration techniques and the numerical solution of nonlinear algebraic equations, material characterization and nonlinear fracture mechanics, nonlinear interaction problems, and seismic response and the nonlinear analysis of concrete structures. Also considered are nonlinear problems for nuclear reactors, crash dynamics and impact problems, nonlinear problems of fibrous composites and advanced nonlinear applications, and computerized symbolic manipulation and nonlinear analysis software systems.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 91
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    Effects of changes in convective efficiency on the solar radius and luminosity (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: A sequence of solar models has been constructed in order to investigate the sensitivity of the solar radius and luminosity to small changes in the ratio alpha of the mixing length lambda to the pressure-scale height Hp throughout the solar convective envelope. The basic procedure for determining this sensitivity was to impose a perturbation in alpha within the convective envelope and then to follow the resulting changes in the solar radius delta R and luminosity delta L for the next 10 to the 6th power yrs. These calculations gave the following results. (1) A perturbation in alpha produces immediate changes in the solar radius and luminosity. Initially delta L and delta alpha are related by delta L/L = 0.30 delta alpha/alpha. (2) The value of the ratio w = delta log R/delta log L is strongly time dependent. Its value just after the perturbation in alpha is 6.5 x 10 to the minus 4th power. (3) The ratio H = (delta log L) d delta log R/dt is much less time dependent and is a more suitable means for relating the changes in the solar radius and luminosity. (4) Both of these ratios imply that for any reasonable change in the solar luminosity the corresponding change in the solar radius is negligible.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Variations of the Solar Constant; p 143-164
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  • 92
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    Variation of the Solar He I 10830 A Line: 1977 - 1980 (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: Daily measurements of the equivalent width of the 10830 A He I line integrated over the visible disk show: (1) an increase from about 32 to about 74 mA in the monthly mean values from the minimum to the maximum of the current solar cycle; (2) the monthly mean values are more smoothly varying than most other indices of solar activity; (3) rotation modulates the daily values in a highly variable manner with amplitudes as large as plus or minus 20%; (4) the apparent synodic rotation period is 29 days rather than the expected 27 days associated with active regions; (5) despite great differences in the appearance of the sun in 3933 A Ca I and 10830 A He I, the central intensity of the former correlates with the equivalent width of the latter with a value r = 0.97.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 265-272
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  • 93
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    Methods and models for predicting fatigue crack growth under random loading (1981)
    In:  Other Sources
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    Publikationsdatum: 2016-03-09
    Beschreibung: Papers are presented in the volume summarizing the baseline data, methodology, procedures, and results of a round-robin analysis which was conducted to predict the fatigue crack growth in 2219-T851 aluminum center-cracked specimens subjected to flight loading in random cycle-by-cycle format. The objective of the analysis was to assess whether data from constant-amplitude fatigue crack growth tests on center-cracked specimens can be used to predict fatigue crack growth lives under random loading. The following approaches are discussed in detail: a root-mean-square approach, a crack-closure model, a multi-parameter yield zone model, and a load-interaction model.
    Schlagwort(e): STRUCTURAL MECHANICS
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  • 94
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    Sclera solar diameter observations (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: Focus is given to possible variations in solar luminosity and accurate methods of monitoring it. Aside from direct bolometry, one methodology for this type of research makes use of measurements of the solar diameter and limb darkening function as indirect indicators of the solar luminosity. This approach was reviewed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 123-128
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    The combined solar and tidal influence in climate (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: To provide an early warning indication of the CO2 warning signal, we are searching for periodic or projectable trends in climate. The strong 20.5 year oscillation in Eastern North American January temperature found by Mock and Hibler shows evidence of a beat between waves with periods of 22.36 (22.21 to 22.55) years and 18.64 (18.45 to 18.79) years with an opposition at about 1880. These are interpreted to be the 22.279 year solar Hale magnetic cycle and the 18.61 year lunar nodal tidal cycle. The lunar nodal cycle is known to produce changes in the sea surface temperature through increased mixing of the mixed layer of the ocean. This beat note is shown to be evident in the Western High Plains drought record of Mitchell, Stockton and Meko and to provide a better bit to the drought series, especially at the beat oppositions in 1880 and 1770.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 241-255
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    On the seat of the solar cycle (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: A discussion of some of the issues raised in connection with the seat of the solar cycle are presented. Is the cycle controlled by a strictly periodic oscillator that operates in the core, or is it a turbulent dynamo confined to the convection zone and possibly a thin boundary layer beneath it? Sunspot statistics are discussed, with a view to ascertaining the length of the memory of the cycle, without drawing a definitive conclusion. Also discussed are some of the processes that might bring about variations delta L and delta R in the luminosity and the radius of the photosphere. It appears that the ratio W = delta lnR/delta lnL increases with the depth of the disturbance that produces the variations, so that imminent observations might determine whether or not the principal dynamical processes are confined to only the outer layers of the Sun.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 185-206
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    Solar radius measurements (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: Preliminary results of measurements made during 1979-1980 are discussed. Variability in the radius measurements of 0.4 pi is found, of unknown origin.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Variations of the Solar Constant; p 129-130
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    A general method for computing the total solar radiation force on complex spacecraft structures (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: The method circumvents many of the existing difficulties in computational logic presently encountered in the direct analytical or numerical evaluation of the appropriate surface integral. It may be applied to complex spacecraft structures for computing the total force arising from either specular or diffuse reflection or even from non-Lambertian reflection and re-radiation.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Sixth Ann. Flight Mech.(Estimation Theory Symp.; 12 p
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    Predominant periods in the time series of drought area index for the Western High Plains AD 1700 to 1962 (1981)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The detection of the combined presence of the Hale magnetic sunspot cycle (22.28 years) and the lunar nodal tidal cycle (18.61 years) in both the Eastern North American January air temperatures and the Western U.S. High Plains drought series led to an extended analysis of the Drought Area Index time series. This analysis indicated that the mean dominant period of the drought series should be 20.0 to 20.5 years and that the principal period should be resolvable into two components of about 22.28 and 18.61 years. This note details the successful accomplishment of this task.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 257-264
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    Solar pulsations and long-term solar variability (1981)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: The seismology of the solar atmosphere is important in relating changes in luminosity to variations in other observables. This approach has already led to the identification of properties which were not previously observed or recognized. Equally important results from solar seismology are expected in the future.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Goddard Space Flight Center Variations of the Solar Constant; p 229-233
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