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  • 1
    Publikationsdatum: 2006-02-14
    Beschreibung: A nozzle beam facility utilizing microwave discharge on a helium carrier gas seeded with oxygen to produce atomic oxygen fluxes of the order of 10 to the 15th power atoms/cu cm/sec is described. In addition, limited test results obtained from exposing a graphite/epoxy composite and Kapton (H) film are presented in terms of mass loss measurements and changes in surface morphology.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Goddard Space Flight Center 13th Space Simulation Conf.; p 169-192
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  • 2
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this LDEF experiment are to verify the validity of space environment simulation performed in the laboratory in order to measure the stability of the thermo-optical properties of thermal control coatings, and to compare the behavior in space of some materials for which the available ultraviolet solar simulation is inadequate (especially in the far ultraviolet). The experimental approach is to passively expose samples of the thermal coatings of interest. These coatings include black paint, aluminum paint, white paint, a solar absorber, an optical surface reflector, second surface mirrors, metal coatings, and silica fabrics. Preflight and postflight measurements of thermo-optical properties will be compared to determine the effects of space environment exposure.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 52-53
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  • 3
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to determine if the impingement of atomic oxygen in near-Earth orbit is a major factor in producing optically damaging outgassed products. The expected results will be to obtain samples which have been exposed to atomic oxygen for long durations. Analysis of these samples will determine if the impingement of atomic oxygen on the thermal control surfaces stimulates a significant amount of outgassed products. This experiment will give a clearer picture of the contamination problem and will assist in assuring that future Shuttle payloads, such as the Space Telescope and High-Energy Astronomy Observatory, will not experience Skylab contamination levels. Selected thermal control surfaces will be exposed to the atomic oxygen in near-Earth orbit. Passive collecting samples will collect any induced outgassing resulting from oxygen impingement. The optical condition of the passive samples will be measured using a ground-based integrating sphere reflectometer and a directional reflectometer.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 11-13
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  • 4
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: Since the introduction of silver-filled epoxy adhesives and silver-filled nitrocellulose lacquer as RFI control materials, a number of new materials have been introduced. The resin carriers have been changed in an effort to make the materials more usable or more EPA acceptable and the fillers have been varied in an effort to make the materials less costly. The corrosion-related properties of second-generation materials were assessed, including adhesives, caulks, and greases. Aluminum 2024 was used as the only substrate material. Ten days of salt fog was used as the corrosive environment. If a noble material such as silver, nickel, or carbon is sandwiched with aluminum an increase in dc resistance results given enough time. If this is unsatisfactory electrically it should either not be used or have all corrosive environments excluded.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Intern. Aerospace and Ground Conf. on Lightning and Static Elec.; 7 p
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  • 5
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The importance of understanding and modeling the unsteady flow phenomena in turbomachinery is discussed. Historical events in the application and development of gas turbines for aircraft propulsion are traced. Technology advancements over the years are highlighted with focus on the compression system components. Trends in compressor research within the National Advisory Committee for Aeronautics (NACA)/National Aeronautics and Space Administration (NASA) are noted. The impact of technology advancements on the increased occurrences of unsteady flow related problems in advanced engine development programs is discussed. The impact of the new and more demanding requirements being imposed on the propulsion system to meet advanced aircraft mission needs are also noted. Brief discussions on the present day understanding and modeling capability of the unsteady flow phenomena are presented to include discussions on rotating stall, surge, flutter, forced response and noise generation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Von Karman Inst. for Fluid Dynamics Unsteady Flow in Turbomachines, Vol. 1; p 1-20
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  • 6
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The effects of solar radiation and space environment on glasses in space flight by exposing glass specimens to the space environment was determined. The occurrence of optical, mechanical, and chemical property changes was analyzed. The property changes of samples receiving differing cumulative solar radiation exposure are compared.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 170-172
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  • 7
    Publikationsdatum: 2006-02-14
    Beschreibung: In-flight calibration for the solr and Earth flux channels was examined. Earth Radiation on Budget (ERB) channel components were exposed to the space environment and then retrieved and resubmitted to radiometric calibration after exposure. It is suggested that corrections may be applied to ERB results and information will be obtained to aid in the selection of components for future operational solar and Earth radiation budget experiments. To assure that these high accuracy devices are measuring real variations and are not responding to changes induced by the space environment, it is desirable to test such devices radiometrically after exposure to the best approximation of the orbital environment.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 167-169
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  • 8
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective is to verify the capability of a cascade variable conductance heat pipe (CVCHP) system to provide precise temperature control of long life spacecraft without the need for a feedback heater or other power sources for temperature adjustment under conditions of widely varying power input and ambient environment. Solar energy is the heat source and space the heat sink for thermally loading two series connected variable conductance heat pipes. Electronics and power supply equipment requirements are minimal. A 7.5 V lithium battery supplies the power for thermistor type temperature sensors for monitoring system performance, and a 28 V lithium battery supplies power for valve actuation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 66-69
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  • 9
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this LDEF experiment is to measure the effects of exposure to the shuttle launch and near Earth space environments on the optical properties of ion beam textured high absorptance solar thermal control surfaces, the optical and electrical properties of ion beam sputtered conductive solar thermal control surfaces, and the weight loss of ion beam deposited oxide polymer films. The various types of surfaces to be tested include six major categories: (1) ion beam textured surfaces suitable for space solar thermal (solar concentration) application; (2) painted and/or state of the art solar thermal surfaces; (3) ion beam sputtered conductive coatings for thermal and space charge control (e.g., indium-oxide coated metalized FEP Teflon); (4) ion beam sputtered conductive coated solar sail materials for space charge control and cooling through emittance; (5) micrometeoroid sensitive samples whose optical properties change only as a result of micrometeoroid impact; and (6) Kapton coated with oxide polymer films to minimize oxygen degradation at near Earth orbit altitudes.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 62-65
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  • 10
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to evaluate the zero-g performance of a number of transverse flat plate heat pipe modules. Performance will include the transport capability of the pipes, the temperature drop, and the ability to maintain temperature over varying duty cycles and environments. Additionally, performance degradation, if any, will be monitored over the length of the Long Duration Exposure Facility (LDEF) mission. This information is necessary if heat pipes are to be considered for system designs where they offer benefits not available with other thermal control techniques.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 74-77
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  • 11
    Publikationsdatum: 2006-02-14
    Beschreibung: The principal objectives of the experiment are to determine zero-g start-up performance for conventional and diode low temperature heat pipes, to evaluate heat pipe performance in zero-g for an extended period of time, to determine zero-g transport capability of each heat pipe, and to determine diode operation, including forward conductance, turndown ratio, and transient behavior. Two heat pipes, a fixed conductance transporter heat pipe and a thermal diode heat pipe, are coupled with a radiant cooler system. Both pipes are charged with ethane. Also integrated with the radiator is a phase change material (PCM) canister which provides temperature stability during transport tests. N-heptane, which has a melting/freezing point of 182 K, is used as the PCM. The high heat capacity (28 W-hr of latent heat) provided by the canister permits high power heat pipe testing at constant temperature.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 70-73
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  • 12
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this LDEF experiment are to determine the effects of the near Earth orbital environment and the Shuttle induced environment in spacecraft thermal control surfaces. Spectral reflectance measurements will be obtained and used to differentiate between different solid state damage mechanisms of environmental damage to separate the effects of contamination from those of natural environment damage, and for comparison and correlation with laboratory test data.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 57-61
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  • 13
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this LDEF experiment are to determine the effects of both the Shuttle-induced environment and the space radiation environment on selected sets of spacecraft thermal control coatings. The experimental approach is to passively expose samples of thermal control coatings to Shuttle-induced and space radiation environments and to return the samples for postflight evaluation and comparison with preflight measurements to determine the effects of the environmental exposure. Optical measurements of the samples will include total normal emittance and spectral reflectance. The experiment will utilize a 6 in. deep peripheral tray and an experiment exposure control canister (EECC). The EECC will provide protection for some of the samples against exposure to the launch and reentry environments. The EECC will be programmed to open about 2 weeks after LDEF deployment and close pior to LDEF retrieval by the Shuttle and reentry. Some samples will not be housed in the EECC and will be exposed to the Shuttle-induced environment during launch and reentry. Comparison of the data from these samples with data from samples in the EECC will yield information about possible contamination induced degradation effects.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Long Duration Exposure Facility (LDEF); p 54-56
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  • 14
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    In:  CASI
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to assess the effects of long-term exposure of candidate balloon films, tapes, and lines to the hostile environment above the Earth's atmosphere. Degradation of mechanical and radiometric properties will be observed by a series of tests on exposed materials. The experiment is passive and will test candidate balloon films, tapes, and lines. The experiment will occupy one-third of a 3-in.-deep peripheral tray. Two additional identical sets of material will be prepared. The first set will be tested immediately and the second will be held in a controlled environment until the recovery of the samples placed on orbit. Tests will then be performed on this second set to determine any effects of aging. The specimens that are recovered from the Long Duration Exposure Facility will also be tested and the effects of long-duration exposure noted. In addition to these specimens, another set of specimens will be exposed at an accelerated exposure facility and the results will be compared with those of specimens exposed in situ.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 49-51
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  • 15
    Publikationsdatum: 2011-08-19
    Beschreibung: The crystallization of a number of glasses of the fluorozirconate family has been studied (using powder X-ray diffraction and DSC) as a function of time and temperature of heating. The main crystalline phases were beta BaZrF6 and beta BaZr2F10. Stable and metastble transformations to the low-temperature alpha phases were also investigated. The size of crystallites in fully devitrified glasses was calculated (from line broadening of the X-ray diffraction peaks) to be about 60 nm.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Materials Research Bulletin (ISSN 0025-5408); 19; 5, 19; 577-590
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  • 16
    Publikationsdatum: 2011-08-19
    Beschreibung: Numerical experiments are used to study thermally driven flows which occur during vertical Bridgman crystal growth of a single component fluid. The solid-liquid interface was specified as parabolic and flow patterns were calculated for various insulation thicknesses, Grashof, Prandtl, and Biot numbers. When the melt is on top and the gravity vector is axially downward it is shown that flow persists as long as a radial temperature gradient is present. If the interface is convex, as viewed from the liquid, a single cell is observed. A concave interface exhibits multiple counterrotating cells. The insulation thickness and Grashof, Prandtl, and Biot numbers influence the flow in a quantitative manner.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 68; 747-756
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  • 17
    Publikationsdatum: 2011-08-19
    Beschreibung: The stability of the parallel flow between a vertical crystal-melt interface and a vertical wall held at a temperature above the melting point of the crystal is analyzed for Prandtl numbers, P, ranging from 0.01 to 100. Three modes of instability occur: (1) a buoyant mode, (2) a shear mode, and (3) a coupled crystal-melt mode. The buoyant and shear modes are similar to those that occur for flow between two vertical rigid walls held at different temperatures. For Prandtl numbers greater than approximately two, the coupled crystal-melt mode occurs at a lower Grashof number than the other two modes. Specific results are given for succinonitrile (P = 22.8) and lead (P = 0.0225). These calculations and similar calculations for a cylindrical geometry were motivated by and are in general agreement with recent experiments on succinonitrile.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 66; 514-524
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  • 18
    Publikationsdatum: 2011-08-19
    Beschreibung: The solid-liquid interface position and the temperature gradients in both the solid and liquid at the interface have been studied in a modified Bridgman-Stockbarger crystal growth furnace. These crystal growth factors have been studied as a function of ampoule translation rate, materials properties, and the size and temperature of a small auxiliary heater placed at the edge of the furnace hot zone. It has been found that the interface position with respect to a furnace reference point is essentially constant during a run for a low thermal conductivity material whereas the interface position changes continuously during a run with high thermal conductivity material. However, the ampoule translation rate and auxiliary heater conditions produce interface position changes in both high and low thermal conductivity materials.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Crystal Growth (ISSN 0022-0248); 69; 509-514
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  • 19
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Addition polyimide oligomers have been synthesized from bis(gamma-aminopropyl) tetramethyldisiloxane and 3, 3', 4, 4'-benzophenonetetracarboxylic dianhydride using a variety of latent crosslinking groups as endcappers. The prepolymers were isolated and characterized for solubility (in amide, chlorinated and ether solvents), melt flow and cure properties. The most promising systems, maleimide and acetylene terminated prepolymers, were selected for detailed study. Graphite cloth reinforced composites were prepared and properties compared with those of graphite/Kerimid 601, a commercially available bismaleimide. Mixtures of the maleimide terminated system with Kerimid 601, in varying proportions, were also studied.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 15; 24-30
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  • 20
    Publikationsdatum: 2011-08-18
    Beschreibung: In order to improve solvent resistance of aromatic thermoplastic polymers, ethynyl-terminated aromatic sulfone polymers (ETS), sulfone/ester polymers (SEPE) containing pendent ethynyl groups, and phenoxy resin containing pendent ethynyl groups are synthesized. Cured polysulfones and phenoxy resins containing ethynyl groups on the ends or pendent on the molecules exhibited systematic behavior in solvent resistance, film flexibility, and toughness as a function of crosslink density. The film and composite properties of a cured solvent-resistant ETS were better than those of a commercially available solvent sensitive polysulfone. The study was part of a NASA program to better understand the trade-offs between solvent resistance, processability and mechanical properties which may be useful in designing composite structures for aerospace vehicles.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Journal (ISSN 0091-1062); 20; 18-23
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  • 21
    Publikationsdatum: 2011-08-18
    Beschreibung: The extent and thermal stratification of the region of convective overshoot underneath the convection zone of the sun are investigated. The phenomenon of convective overshoot in general is discussed, and some of the modal and model approaches to studying it are briefly reviewed. A detailed theoretical description of the motion of plumes in a stably stratified medium is given, leading to a 'derivation' of the plume equations from the hydrodynamic equations. Entrainment is discussed, and it is shown how the plume equations can be used to compute convective overshoot in the sun. The limitations of the plume model are addressed, arguing that a thin boundary layer must exist which separates convective and radiative regions. The results of numerical integrations of the plume equations, as applied to the region of convective overshoot underneath the solar convective zone, are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 282; 316-329
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  • 22
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: The motion of two and four rectilinear vortices inside a cylindrical pipe is studied under the restriction that the total circulation be zero. In the two-vortex case, it is shown that the motion is always periodic and an expression for the period is derived. In the four-vortex case, the motion is determined not to be periodic in general. However, a class of solutions where the motion is periodic is found. Several sample calculations of the vortex motion are included.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Physics of Fluids (ISSN 0031-9171); 27; 1583-158
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  • 23
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Some turbulent solutions of the unaveraged Navier-Stokes equations (equations of fluid motion) are reviewed. Those equations are solved numerically in order to study the nonlinear physics of incompressible turbulent flow. Initial three-dimensional cosine velocity fluctuations and periodic boundary conditions are used in most of the work considered. The three components of the mean-square velocity fluctuations are initially equal for the conditions chosen. The resulting solutions show characteristics of turbulence such as the linear and nonlinear excitation of small-scale fluctuations. For the stronger fluctuations, the initially nonrandom flow develops into an apparently random turbulence. Thus randomness or turbulence can arise as a consequence of the structure of the Navier-Stokes equations. The cases considered include turbulence which is statistically homogeneous or inhomogeneous and isotropic or anisotropic. A mean shear is present in some cases. A statistically steady-state turbulence is obtained by using a spatially periodic body force. Various turbulence processes, including the transfer of energy between eddy sizes and between directional components, and the production, dissipation, and spatial diffusion of turbulence, are considered. It is concluded that the physical processes occurring in turbulence can be profitably studied numerically.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Reviews of Modern Physics (ISSN 0034-6861); 56; 223-254
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  • 24
    Publikationsdatum: 2011-08-18
    Beschreibung: Preliminary pribological studies on polyimides formulated from the diamine 2,2-bis 4-(4-aminophenoxy)phenyl hexafluoropane (4-BDAF) indicate that polyimides formulated from this diamine have excellent potential for high temperature tribological applications. The dianhydrides used to make the polyimides were pyromellitic (PMDA) and benzophenonetetracarboxylic acid (BTDA). Friction and wear studies at 25 and 200 C indicate that polyimides formulated using 50 mole percent of the PMDA dianhydride and 50 mole percent of the BTDA dianhydride perform better than polyimides formulated solely with the BTDA dianhydride. Graphite fiber reinforced polyimide composites were formulated with the polyimide made from the BTDA dianhydride and both graphitic and non-graphitic fibers were evaluated. Graphitic fibers produced better tribological results, since thin, flowing, 'layer-like' transfer films were produced which did not build up with long sliding durations. Non-graphitic fibers did not produce this type of transfer. Previously announced in STAR as N83-22423
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: ASLE Transactions; 27; 189-196
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  • 25
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Thermal barrier coatings (TBCs) have been developed as a means of protecting turbine blades and other engine hot section components whose surfaces are exposed to the most extreme operating conditions. By adding a thin, insulating ceramic oxide layer to an air-cooled turbine blade, the difference between the gas temperature and the metal temperature is further increased as a function of ceramic coating thickness, heat flux, and oxide thermal conductivity. An 0.04-cm thick ceramic layer can typically yield a 100-300 C temperature drop. Of the various techniques available for the deposition of thermal barrier coatings, the most common is that of plasma spraying. Significant improvements have been made in TBC durability through the use of bond coat compositions with increased oxidation resistance.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Research and Development (ISSN 0160-4074); 26; 122-125
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  • 26
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    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: It is demonstrated that the common assumption made in solar flare beam transport theory that the beam-accompanied return current is purely electrostatically driven is incorrect, and that the return current is both electrostatically and inductively driven, in accordance with Lenz's law, with the inductive effects dominating for times greater than a few plasma periods. In addition, it is shown that a beam can only exist in a solar plasma for a finite time which is much smaller than the inductive return current dissipation time. The importance of accounting for the role of the acceleration mechanism in forming the beam is discussed. In addition, the role of return current driven anomalous resistivity and its subsequent anomalous Joule heating during the flare process is elucidated.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 448-456
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  • 27
    Publikationsdatum: 2011-08-18
    Beschreibung: The way in which the initial development of solar filament radiative cooling and the magnetic reconnection of a solar flare can occur in the center of a field-shear layer is demonstrated. Since the present treatment unites these two mechanisms, it indicates the common as well as the disparate features they possess. Unstable radiation serves to increase the Coulomb resistivity at the X-point, so that the reconnection is not self-quenching. The surprising dominance of the magnetic component of the perturbation in the midwavelength range indicates the need to examine the nonlinear saturation of the energy transport of the radiative mode, taking the accompanying magnetic reconnection and potential-energy release into account, for comparison with observations of filaments as well as for clues to the character of the preflare state.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 391-398
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  • 28
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    Publikationsdatum: 2011-08-18
    Beschreibung: Using NASA's Tracking and Data Relay Satellite as a communications link, astronomers are able to receive scans from the Solar Maximum Mission (SMM) satellite immediately and regularly at the Goddard Space Flight Center. This major operational improvement permits the examination of SMM imagery and spectra as they arrive, as well as the formulation of future observational sequences on the basis of the solar activity in progress. Attention is given to aspects of the sun that change in the course of the 11-year sunspot cycle's movement from maximum to minimum. Proof has been obtained by means of SMM for the near-simultaneity of X-ray and UV bursts at flare onset.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Sky and Telescope (ISSN 0037-6604); 67; 498-500
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  • 29
    Publikationsdatum: 2011-08-18
    Beschreibung: An experiment was conducted to measure the heat transfer from a heated cylinder in crossflow in an array of circular cylinders. All cylinders had a length-to-diameter ratio of 3.0. Both in-line and staggered array patterns were studied. The cylinders were spaced 2.67 diameters apart center-to-center in both the axial and transverse directions to the flow. The row containing the heated cylinder remained in a fixed position in the channel and the relative location of this row within the array was changed by adding up to five upstream rows. The working fluid was nitrogen gas at pressures from 100 to 600 kPa. The Reynolds number range based on cylinder diameter and average unobstructed channel velocity was from 5,000 to 125,000. Turbulence intensity profiles were measured for each case at a point one half space upstream of the row containing the heated cylinder. The basis of comparison for all the heat transfer data was the single row with the heated cylinder. For the in-line cases the addition of a single row of cylinders upstream of the row containing the heated cylinder increased the heat transfer by an average of 50 percent above the base case. Adding up to five more rows caused no increase or decrease in heat transfer. Adding rows in the staggered array cases resulted in average increases in heat transfer of 21, 64, 58, 46, and 46 percent for one to five upstream rows, respectively. Previously announced in STAR as N82-19493
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 106; 42-48
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  • 30
    facet.materialart.
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    Publikationsdatum: 2011-08-18
    Beschreibung: Phosphorus-based flame retardants have been effectively used in a wide variety of polymeric materials. Such additives, however, may either influence the decomposition reaction in polymers or lack durability due to a tendency to be leached out by solvents. Attention is given to the synthesis, characterization, thermal stability and degradation mechanisms of bisimide resins, and an evaluation is conducted of the flammability and mechanical properties of graphite cloth-reinforced laminates fabricated from one of the six phosphorus-containing bisimide resins considered.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: IN: Contemporary topics in polymer science. Volume 4. New York; 115-139
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  • 31
    Publikationsdatum: 2011-08-18
    Beschreibung: Recent investigations using measurements at 1 AU have discovered three types of long term variation in the interplanetary magnetic field: solar minimum decreases, solar maximum enhancements, and small decreases around solar reversal. In this study the 1972-1982 Helios 1, 2, ISEE-3, and Pioneer 10, 11 observations between 0.3 and 12 AU are examined to further investigate these changes. It was found that all three IMF solar cycle effects are also present in the Helios and Pioneer measurements, confirming that these variations occur throughout the low latitude heliosphere. In addition, the comparison of measurements by identical magnetometers on ISEE-3, Pioneer 10 and Pioneer 11 has revealed a more rapid decrease in IMF intensity than predicted by classical Parker theory. Causes and ramifications of both the long term variations and steeper-than-expected radial gradients in the interplanetary magnetic field are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 11; 279-282
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  • 32
    Publikationsdatum: 2011-08-18
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: International Journal of Solar Energy (ISSN 0142-5919); 2; 171-187
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  • 33
    Publikationsdatum: 2011-08-18
    Beschreibung: A numerical investigation is conducted into the way in which a solar wind model initially satisfying both steady state and energy balance conditions is disturbed and deformed, under the assumption of heating that correspoonds to the energy release of solar flares of an importance value of approximately 1 which occur in radial open field regions. Flare-associated solar wind transient behavior is modeled for 1-8 solar radii. The coronal temperature around the heat source region rises, and a large thermal conductive flux flows inward to the chromosphere and outward to interplanetary space along field lines. The speed of the front of expanding chromospheric material generated by the impingement of the conduction front on the upper chromosphere exceeds the local sound velocity in a few minutes and eventually exceeds 100 million cm/sec.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 379-391
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  • 34
    Publikationsdatum: 2011-08-19
    Beschreibung: The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 470-478
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  • 35
    Publikationsdatum: 2011-08-19
    Beschreibung: Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 479-490
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  • 36
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    Publikationsdatum: 2011-08-19
    Beschreibung: The numbers and spectra of the accelerated protons and nuclei that produce the neutrons and gamma-rays observed in solar flares are derived, and the results are compared with interplanetary observations of flare protons. The two most widely studied flare acceleration mechanisms, stochastic and diffusive shock acceleration, are discussed, and the arguments favoring the thick-target interaction model for neutron and gamma-ray production at the sun are briefly reviewed. The pertinent results of the theory of neutron and gamma-ray production are presented. The number and spectrum of the accelerated particles are derived from observations of nuclear deexcitation lines and the 2.223 MeV line from several flares. The June 21, 1980 and June 3, 1982 flares, from which a wealth of neutron, gamma-ray and energetic-particle data has recently become available, are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 37
    Publikationsdatum: 2011-08-19
    Beschreibung: Time sequences of recurrent mass ejections have been observed during a coordinated SMY program (Sept. 1, 1980 - Sept. 23, 1980 - Oct. 2, 1980). Comparison of the temporal evolution of H-alpha and CIV brightnesses shows a weak phase lag between H-alpha and CIV maxima, in the case of homologous flares, with CIV brightness maxima preceding H-alpha maxima. The analysis of the variation of the ejection velocities is expected to lead to the determination of an energy balance. Such recurrent ejections could be due to periodic energy storage and periodic reorganization of magnetic field as envisaged to occur for flares, but at lower energy levels.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 38
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2011-08-19
    Beschreibung: Hydroxy-terminated polyarylates (HTPA) with number-average molecular weights of approximately 2500, 5000, 7500, and 10,000 were synthesized and converted to corresponding 4-ethynylbenzoyloxy-terminated polyarylates (ETPA) by reaction with 4-ethynylbenzoyl chloride. The terminal ethynyl groups were thermally reacted to provide chain extension and crosslinking. The cured ETPA exhibited higher glass transition temperatures (Tg) and better solvent resistance than a high molecular weight linear polyarylate. Solvent resistance was further improved by curing 2,2-bis(4-ethynylbenzoyloxy-4-prime-phenyl) propane, a coreactant, with ETPA at concentrations of approximately 10 percent (w/w).
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Polymer Science: Polymer Chemistry Edition (ISSN 0360-6376); 22; 3011-302
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  • 39
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2011-08-19
    Beschreibung: In NOAA Active Region 2372 (April 1980), 4 x 10 to the 20th maxwells of magnetic flux concentrated in an area 30 arcsec across disappeared overnight. Vector magnetograms show that all components of the magnetic field weakened together. If the field had weakened through diffusion or fluid flow, 90 percent of the original flux would still have been detected by the magnetograph within a suitably enlarged area. In fact there was a threefold decrease in detected flux. Evidently, magnetic field was removed from the photosphere. Since the disappearing flux was located in a region of low magnetic shear and low activity in H-alpha and Ly-alpha, it is unlikely that the field dissipated through reconnection. It is argued that the most likely possibility is that flux submerged. The observations suggest that even during the growth phase of active regions, submergence is a strong process comparable in magnitude to emergence.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 404-411
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  • 40
    Publikationsdatum: 2011-08-19
    Beschreibung: Coronal bullets are small ejecta of cool, dense plasma observed to accelerate through the solar atmosphere from 20 to 450 km/s. The NRL Dynamic Flux Tube Model has been used to simulate the evolving physical properties of these dynamic events. The present calculations utilize an adaptive-gridding technique to resolve the fine structure within and around the bullets. In this work, an identification was made of a component of shocked plasma which piles up ahead of the bullet and eventually dominates both the dynamics and heating of the original bullet mass. The observational consequences of this shocked component are discussed in terms of the available HRTS EUV data, and suggestions are made for optimizing future observations of this phenomenon. An investigation has also been conducted of the structure of the bullet material visible in EUV spectral lines and the observable characteristics of the EUV-emitting plasma. Finally, the most likely mechanisms for accelerating the bullets, as well as favorable sites of origin are evaluated.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 396-403
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  • 41
    facet.materialart.
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    Publikationsdatum: 2011-08-19
    Beschreibung: Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 42
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2011-08-19
    Beschreibung: Friction, wear, and wear mechanisms of several different polyimide films, solid bodies, composites, and bonded solid lubricant films are compared and discussed. In addition, the effect of such parameters as temperatures, type of atmosphere, contact stress, and specimen configuration are investigated. A friction and wear transition occurs in some polyimides at elevated temperatures and this transition is related to molecular relaxations that occur in polyimides. Friction and wear data from an accelerated test (pin-on-disk) are compared to similar data from an end use test device (plain spherical bearing), and to other polymers investigated in a similar geometry.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 43
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2011-08-19
    Beschreibung: The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 44
    Publikationsdatum: 2011-08-19
    Beschreibung: Although graphite-reinforced polyimide matrix composites offer outstanding specific strength and stiffness, together with high thermal oxidative stability, processing problems connected with their rheological behavior remain to be addressed. The present rheological studies on neat polyimide resin systems encountered outgassing during cure. A staging technique has been developed which can successfully handle polyimide samples, and novel methods were applied to generate rheological curves for graphite-reinforced prepregs. The commercial graphite/polyimide systems studied were PRM 15, LARC 160, and V378A.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 45
    facet.materialart.
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    Publikationsdatum: 2011-08-19
    Beschreibung: A polymer system has been prepared which has the excellent thermoplastic properties generally associated with polysulfones, and the solvent resistance and thermal stability of aromatic polyimides. This material, with improved processability over the base polyimide, can be processed in the 260-325 C range in such a manner as to yield high quality, tough unfilled moldings; strong, high-temperature-resistant adhesive bonds; and well consolidated, graphite-fiber-reinforced moldings (composites). The unfilled moldings have physical properties that are similar to aromatic polysulfones which demonstrates the potential as an engineering thermoplastic. The adhesive bonds exhibit excellent retention of initial strength levels even after thermal aging for 5000 hours at 232 C. The graphite-fiber-reinforced moldings have mechanical properties which makes this polymer attractive for the fabrication of structural composites.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 46
    Publikationsdatum: 2011-08-19
    Beschreibung: Low-noise (S/N greater than 100), high spectral resolution observations of two pure rotation transitions of OH from the solar photosphere are used to make inferences concerning the thermal structure and inhomogeneity of the upper photosphere. It is found that the v = O R22(24.5)e line strengthens at the solar limb, in contradiction to the predictions of current one-dimensional photospheric models. The results for this line support a two-dimensional model in which horizontal thermal fluctuations in the upper photosphere are of the order plus or minus 800 K. This thermal bifurcation may be maintained by the presence of magnetic flux tubes and may be related to the solar limb extensions observed in the 30-200-micron region.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics (ISSN 0038-0938); 94; 57-74
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  • 47
    Publikationsdatum: 2011-08-19
    Beschreibung: Light optical and scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight-polyethylene (UHMWPE). Erosion was caused by a jet of spherical micro-glass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibit incubation, acceleration and steady state periods. A continuously increasing erosion rate period was observed however for PMMA instead of a steady state period. At early stages of damage and at low impact pressure material removal mechanisms appear to be similar to those for metallic materials.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: ASLE Transactions; 27; 373-379
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  • 48
    Publikationsdatum: 2011-08-19
    Beschreibung: Thermogravimetric analysis data are presented on the unmeltable polycarbosilazane precursor of silicon carbide-silicon nitride fibers, over the room temperature-1000 C range in a nitrogen atmosphere, in order to establish the weight loss at various temperatures during the precursor's pyrolysis to the fiber material. The fibers obtained by this method are excellent candidates for use in applications where the oxidation of carbon fibers (above 400 C) renders them unsuitable.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science Letters (ISSN 0261-8028); 3; 802-804
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  • 49
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    Publikationsdatum: 2011-08-19
    Beschreibung: Solar irradiance measurements from the ACRIM experiment show a clear response to the rotation periods of g-mode oscillations (l = 1, 2, and 3) and their first harmonics. Peaks in the ACRIM spectrum at 16.6, 18.3, 20.7, 36.5, and about 71 days all lie within about 1 percent of periods arising from g-mode rotation. This means that the g-modes are a fundamental cause of irradiance fluctuations. On time scales of months and less they modulate the irradiance by means of transient flows of global scale which they stimulate in the sun's convective envelope. Dimensional arguments indicate that the flows carry up heat at an average rate of about 0.001 solar luminosities, which is not in conflict with observed changes in the irradiance. Five additional tests for g-modes and large-scale convection are given. An instability is described which undermines diffusion models of sunspot energy storage.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics (ISSN 0038-0938); 93; 1-13
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  • 50
    Publikationsdatum: 2011-08-18
    Beschreibung: The effects of mass injection and pressure gradients on the drag of surfaces were studied theoretically with the aid of boundary-layer and Navier-Stokes codes. The present investigation is concerned with the effects of spatially varying the injection in the case of flat-plate drag. Effects of suction and injection on wavy wall surfaces are also explored. Calculations were performed for 1.2 m long surfaces, one flat and the other sinusoidal with a wavelength of 30.5 cm. Attention is given to the study of the effect of various spatial blowing variations on flat-plate skin friction reduction, local skin friction coefficient calculated by finite difference boundary-layer code and Navier-Stokes code, and the effect of phase-shifting sinusoidal mass transfer on the drag of a sinusoidal surface.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 22; 143-145
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  • 51
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    Publikationsdatum: 2011-08-18
    Beschreibung: The result of a study on the application of an improved statistical prediction method for estimating the intermediate-term (months) and long-term (years) behavior of solar flux is discussed. The study indicates that better predictions, in a chi square sense, are possible by selecting sets of the solar flux data such that each set (cycle) starts and ends at the maxima (or minima) for the data base and initialization point of the procedure. Then one applies a Lagrangian least-squares statistical technique. Evidence is also presented to support the existence of an aperiodic variation in the periods as well as the amplitudes.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 11-16
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  • 52
    Publikationsdatum: 2011-08-18
    Beschreibung: This work relates to a series of collaborative investigations involving the application of a computational model for the determination of the detailed plasma and magnetic field properties associated with the global interaction of the solar wind with various planetary obstacles throughout the solar system. The theoretical method is based on an established single fluid, steady, dissipationless, magnetohydrodynamic continuum model, and is appropriate for the calculation of supersonic, super-Alfvenic solar wind flow past planetary obstacles. The investigations undertaken relate to studies of various solar wind interaction phenomena with Venus, Earth, Jupiter, and Saturn.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Appl. of a Global Solar Wind/Planetary Obstacle Interaction Computational Model 11p (SEE N84-26509 16-88)
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  • 53
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    Publikationsdatum: 2011-08-18
    Beschreibung: The numerical aspects of simulation unsteady flows which arise in turbomachinery are addressed. In particular the simulation of rotating stall and surge is discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Von Karman Inst. for Fluid Dynamics Unsteady Flow in Turbomachines, Vol. 2; 75 p
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  • 54
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    Publikationsdatum: 2011-08-19
    Beschreibung: The dynamic and static fatigue behavior of a machinable glass ceramic was investigated to assess its susceptibility to stress corrosion-induced delayed failure. Fracture mechanics techniques were used to analyze the results so that lifetime predictions for components of this material could be made. The resistance to subcritical crack growth of this material was concluded to be only moderate and was found to be dependent on the size of its microstructure.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 55
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    Publikationsdatum: 2011-08-19
    Beschreibung: The results of observations of solar flares, obtained by means of the UV Spectrophotometer and Polarimeter (UVSP) instrument on board the Solar Maximum Mission satellite are summarized and discussed. The results are grouped into three main topics: (1) plasma diagnostics in the flare transition zone plasmas, (2) spatial and temporal evolutions of the UV and hard X-ray bursts, and (3) energy release processes in the impulsive phase. The methods of spectral UV analysis, comparison with the hard X-ray burst results, and the interpretation of the results are summarized. It is concluded that the energy release processes in the flare phase can be best interpreted in terms of multiple large and small interloops interacting with each other either mechanically or inductively. Furthermore, the majority of impulsive UV and hard X-ray bursts occurs in small compact loops with high densities and transition-zone temperatures. The impulsive hard X-ray and UV bursts are emitted by nonthermal particles, accelerated by the loop interactions and impinging on the footpoints of these loops.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 55; 4, 19; 663-672
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  • 56
    Publikationsdatum: 2011-08-19
    Beschreibung: A brief review is given of non-flare investigations using data obtained by the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission. The major topics described are sunspot research including magnetic field measurements, oscillations, and models; mass motions in quiet and active regions including steady flows and acoustic waves; and prominence research including physical conditions, dynamics, and mass motions around prominences. Also discussed are studies of UV bursts, the formation of the Cl I line at 1351 A, ozone in the terrestrial atmosphere, and active regions using correlated observations from other instruments on the spacecraft or on the ground.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 55; 4, 19
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  • 57
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    Publikationsdatum: 2011-08-19
    Beschreibung: New results obtained with the Clark Lake multifrequency radioheliograph at meter-decameter wavelengths and from satellite multifrequency directive observations at hectometer and kilometer wavelengths are reviewed. Evidence is presented that type III electrons propagate in dense coronal streamers and that frequently observed microbursts (presumably type III) at meter-decameter wavelengths are due to plasma radiation. Observations of hectometer and kilometer type III radio storms which reveal information about active region structures, the interplanetary magnetic field configuration, and solar wind acceleration are discussed. Kilometer type II bursts and interactions between type III electrons and interplanetary shocks are examined, and some new results on shock-associated events are presented.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 58
    Publikationsdatum: 2011-08-19
    Beschreibung: An attempt is made to develop a self-consistent model which accounts for the line and continuum data generated by the three X-ray imaging instruments on the SMM satellite. The intensities measured covered the 4-500 kV energy range. The model is based on a differential emission measure and electron beam parameters and is used to predict absolute signals detected by the 15 channels of the SMM sensors. Consideration is given to the thermal contribution, instrumental characteristics, thin target excitation and thick target bremsstrahlung. In comparison with data from a flare event on June 29, 1980, model predictions provide a good fit, including the identification of hard electrons with a 5.3 index during the impulsive phase.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 59
    Publikationsdatum: 2011-08-19
    Beschreibung: Solar Maximum Mission observations have been used to study the origin and amount of energy, mechanism of storage and release, and conditions for the occurrence of solar flares, and some results of these studies as they pertain to homologous flares are briefly discussed. It was found that every set of flares produced 'rafales' of homologous flares, i.e., two, three, four, or more flares separated in time by an hour or less. No great changes in macroscopic photospheric patterns were observed during these flaring periods. A quantitative brightness parameter of the relation between homologous flares is defined. Scale changes detected in the dynamic spectrum of flare sites are in good agreement with a theoretical suggestion by Sturrock. Statistical results for different homologous flare active regions show the existence in homologous flaring areas of a 'pivot' of previous filaments interpreted as a signature of an anomaly in the solar rotation.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 60
    Publikationsdatum: 2011-08-19
    Beschreibung: The observational difficulties of obtaining the magnetic field distribution in the chromosphere and corona of the sun has led to methods of extending photospheric magnetic mesurements into the solar atmosphere by mathematical procedures. A new approach to this problem presented here is that a constant alpha force-free field can be uniquely determined from the tangential components of the measured photospheric flux alone. The vector magnetographs now provide measurements of both the solar photospheric tangential and the longitudinal magnetic field. This paper presents derivations for the computation of the solar magnetic field from these type of measurements. The fields considered are assumed to be a constant alpha force-free fields or equivalent, producing vanishing Lorentz forces. Consequently, magnetic field lines and currents are related by a constant and hence show an identical distribution. The magnetic field above simple solar regions are described from the solution of the field equations.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics (ISSN 0038-0938); 94; 219-234
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  • 61
    Publikationsdatum: 2011-08-19
    Beschreibung: A numerical algorithm that is second-order accurate in time has been developed for the conjugated problem of a separated, compressible flow field and a conductive solid body. The full two-dimensional time-dependent Navier-Stokes equations are coupled with the time-dependent energy equation for the solid body and are solved simultaneously. using implicit algorithms. The energy equation for the solid body may include arbitrarily distributed heat sources. The algorithm has been exmined for the case of two-dimensional supersonic compression-corner interaction, with a heat source embedded in the wall in the vicinity of the separation bubble and the attached boundary layer. The effect of the heat source on the flow field is studied for steady and transient cases.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Numerical Heat Transfer (ISSN 0149-5720); 7; 395-411
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  • 62
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    Publikationsdatum: 2011-08-19
    Beschreibung: A power-law relationship between the average erosion rate and cumulative erosion is presented. Data analyses from Venturi, magnetostriction, and liquid-impingement devices conform to this unified relation. A normalization technique is also suggested for prediction purposes.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal of Mechanical Sciences (ISSN 0020-7403); 26; 5, 19
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  • 63
    facet.materialart.
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    Publikationsdatum: 2011-08-19
    Beschreibung: The adhesion, friction, wear and lubricated behaviors of both oxide and non-oxide ceramics are reviewed. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Grit size effects in two- and three-body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Wear (ISSN 0043-1648); 100; 333-353
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  • 64
    Publikationsdatum: 2011-08-19
    Beschreibung: The Solar Maximum Mission (SMM) spacecraft has provided high time resolution observational data regarding the soft X-ray emission from solar-flare plasma during 1980. The present investigation is concerned with the characteristics of a soft X-ray flare and the energetics of the impulsive phase on the basis of the data collected with the aid of two of the instruments on board the SMM, taking into account the Hard X-ray Burst Spectrometer (HXRBS) and the Bent Crystal Spectrometer (BCS). Attention is given to an analysis of soft X-ray flare spectra, the relative motion of the soft X-ray sources, the phenomenology of the soft X-ray flare, energy and mass transport during the impulsive phase, and energy deposition in the chromosphere during evaporation.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 917-925
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  • 65
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    Publikationsdatum: 2011-08-19
    Beschreibung: The coil planet centrifuge designed by Ito employs flow of a single liquid phase, through a rotating coiled tube in a centrifugal force field, to provide a separation of particles based on sedimentation rates. Mathematical solutions are derived for the linear differential equations governing particle behavior in the coil planet centrifuge device. These solutions are then applied as the basis of a model for optimizing particle separations.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Chromatography (ISSN 0021-9673); 295; 1-11
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  • 66
    facet.materialart.
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    Publikationsdatum: 2011-08-19
    Beschreibung: A melt processable polyimide which contains sulfur and oxygen bridges between the aromatic rings (BDSDA/APB) was synthesized and characterized. Its physical, mechanical, thermal and flow properties were determined as was its resistance to some of the more commonly used solvents. The melt flow properties were measured for the temperature range 250 C - 350 C and under the conditions (stress/strain) encountered in commercial processes.
    Schlagwort(e): NONMETALLIC MATERIALS
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  • 67
    Publikationsdatum: 2011-08-19
    Beschreibung: For the past 25 years, there has existed in the Thermosciences Laboratory of the Mechanical Engineering Department of Stanford University a research program, primarily experimental, concerned with heat transfer through turbulent boundary layers. In the early phases of the program, the topics considered were the simple zero-pressure-gradient turbulent boundary layer with constant and with varying surface temperature, and the accelerated boundary layer. Later equilibrium boundary layers were considered along with factors affecting the boundary layer, taking into account transpired flows, flows with axial pressure gradients, transpiration, acceleration, deceleration, roughness, full-coverage film cooling, surface curvature, free convection, and mixed convection. A description is provided of the apparatus and techniques used, giving attention to the smooth plate rig, the rough plate rig, the full-coverage film cooling rig, the curvature rig, the concave wall rig, the mixed convection tunnel, and aspects of data reduction and uncertainty analysis.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
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  • 68
    Publikationsdatum: 2011-08-19
    Beschreibung: The mass ejections of 1 September, 1980 are studied from observations obtained with the MSDP spectrograph and with the Ultraviolet Spectrometer and Polarimeter aboard the Solar Maximum Mission satellite. The analysis is focused on observations in the chromospheric H-alpha line and the transition region C IV 1548 A line. It is noted that cold and hot material had the same projection, although the upward C IV velocity structure was more extended than the H-alpha one. It is shown that the observed contrast of the H-alpha absorbing structure can be interpreted in terms of a dynamic cloud model overlying the chromosphere. Radial velocities of 25-30 km/s and -40 km/s are estimated for the first and second phases of ejection, respectively.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics (ISSN 0038-0938); 94; 133-150
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  • 69
    Publikationsdatum: 2011-08-19
    Beschreibung: An experiment, using 100-keV electrons and 10 to the 9th -rad doses, was conducted on Ultem polyetherimide film. Mechanical, electron paramagnetic resonance, and infrared spectroscopic data suggested that the radiation produced crosslinking and embrittlement of the material.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-31; 1293-129
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  • 70
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    Publikationsdatum: 2011-08-19
    Beschreibung: Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y2O3 specimens survived 3000 of the 0.5 sec cycles with falling. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 1 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-2O percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Thin Solid Films (ISSN 0040-6090); 119; 195-202
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  • 71
    Publikationsdatum: 2011-08-19
    Beschreibung: The current investigation has the objective to provide data which will make it possible to obtain a better estimate regarding the roughness drag for surface waviness. The data employed for this investigation were acquired in connection with a wavy wall study which was conducted as part of an overall program to reduce the skin friction of turbulent boundary layers in external flows. The results of the present investigation show that the low-speed roughness drag of small-amplitude sinusoidal wave trains having wavelengths of the order of the boundary-layer thickness is not only a function of h/lambda (h = total wave height, lambda = wavelength), but, in addition, is also a function of the roughness Reynolds number.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Aircraft (ISSN 0021-8669); 21; 978
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  • 72
    Publikationsdatum: 2011-08-19
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: AIAA Journal (ISSN 0001-1452); 22; 1810-181
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  • 73
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    Publikationsdatum: 2011-08-19
    Beschreibung: A solidified pendant drop technique is presently used in the measurement of surface tension of a 62 mol pct ZrF4, 33 mol pct BaF2, 5 mol pct LaF3 heavy metal-fluoride glass, in keeping with a requirement from a comparison experiment planned for microgravity conditions aboard the Space Shuttle. The surface tension at 550 C is 0.174 + or - 0.005 J/sq m.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society, Communications (ISSN 0002-7820); 67; C-197
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  • 74
    Publikationsdatum: 2011-08-19
    Beschreibung: Acetylene terminated polyimide oligomers having a range of molecular weights have been synthesized by reacting bis (gamma-aminopropyl) tetramethyldisiloxane, aminophenylacetylene and 3, 3', 4, 4' benzophenonetetracarboxylic dianhydride in different molar ratios. The prepolymers were isolated and characterized for melt flow and cure properties. They show promise as adhesives for bonding titanium to titanium and as matrix resins for graphite cloth reinforced composites. The most promising system has been blended in varying proportions with Thermid 600, a commercially available acetylene terminated polyimide oligomer, and the mixtures have been tested for application as composite matrix resins.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: SAMPE Quarterly (ISSN 0036-0821); 16; 6-12
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  • 75
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    Publikationsdatum: 2011-08-19
    Beschreibung: Based on the principal component analysis technique and evidence for a 22-yr double-sunspot cycle periodicity. The time series of sunspot numbers is represented as a sum of mutually orthogonal eigenvectors in the time domain. It is shown that the first two eigenvectors account for about 90 percent of the cumulative 'signal power,' and that this is sufficient for reconstruction of the raw data curve. It is also noted that the second eigenvector behaves as the time derivative of the first, and that a phase-plane plot of these eigenvectors (i.e. a plot of a variable vs. its rate of change) suggests that the sun's sunspot cycle is driven by an oscillator; the implication is that, embedded within the sun, a chronometer is at work (e.g. Dicke, 1979).
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 139; 2, Oc
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  • 76
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    Publikationsdatum: 2011-08-19
    Beschreibung: Silane-endcapped polyimide high temperature adhesive formulations were prepared by reacting anhydride-terminated poly(amic acid), obtained from benzophenonetetracarboxylic dianhydride and a diamine (3,3'-, 3,4'- or 4,4'-diaminodiphenylmethane and 3,3', 3,4'- or 4,4'-diaminobenzophenone) with varying amounts of gama-aminopropyltriethoxysilane in dimethylacetamide. Resin properties were evaluated by torsional braid analysis and thermogravimetric analysis. Lap shear strengths of some of the adhesive bonds were determined at room temperature and at 177 C before and after ageing at 200 C for 2500 h and after boiling in water for 72 h.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: International Journal of Adhesion and Adhesives (ISSN 0143-7496); 4; 129-132
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  • 77
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    Publikationsdatum: 2011-08-19
    Beschreibung: Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 359-367
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  • 78
    Publikationsdatum: 2011-08-19
    Beschreibung: Selected plasma parameters observed by Pioneer 10 and Pioneer 11 between launch (1972 and 1973) and the end of 1979 are used to find the large-scale radial structure of the solar wind. Comparison of data from the two spacecraft is used to separate temporal from spatial variations. The average bulk speed is found to remain constant at about 430 km/s, with stream structure still evident, though of diminished amplitude, at 20.5 AU (Pioneer 10's distance by the end of 1979). Proton density, flux, pressure, and kinetic energy flux are found to have radial profiles consistent with 1/R-squared. Proton temperatures decrease as R to the -0.6 power, too slowly for an adiabatic expansion.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 339-346
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  • 79
    Publikationsdatum: 2011-08-19
    Beschreibung: To avoid metallic impurities normally introduced by milling ceramic powders in conventional steel hardware, an attrition mill (high-energy stirred ball mill) was constructed with the wearing parts (mill body, stirring arms, and media) made from silicon nitride. Commercial silicon and Si3N4 powders were milled to fine uniform particles with only minimal contamination - primarily from wear of the sintered Si3N4 media.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: American Ceramic Society Bulletin (ISSN 0002-7812); 63; 1176-117
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  • 80
    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of oscillations in filaments, which are cold magnetic structures suspended in the corona, are used to test theories of coronal heating by acoustic waves high in the atmosphere. Long lived stationary motions observed in filaments suggest exchanges of material between them and the surrounding corona. A coupling between upflows in filaments and subphotospheric convective motions, dragging the field lines of the prominence magnetic support, is possible.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 55; 1-2,
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  • 81
    Publikationsdatum: 2011-08-18
    Beschreibung: Using the 'dynamo theory' method to predict solar activity, a value for the smoothed sunspot number of 109 + or - 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 + or - 1 year. Concommitantly, F(10.7) radio flux is expected to reach a smoothed value of 158 + or - 18 flux units. Global mean exospheric temperature is expected to reach 1060 + or - 50 K and global total average total thermospheric density at 400 km is expected to reach 4.3 x 10 to the -15th gm/cu cm + or - 25 percent.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 11; 873-876
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  • 82
    Publikationsdatum: 2011-08-18
    Beschreibung: Considering the solar atmosphere in its entirety, that large-scale nonadiabatic processes (MHD waves, and so on) effectively tend to yield an 'equalization of temperature', such that the atmospheric temperature is limited to the base temperature associated with its heat source. This conjecture suggests that (1) the chromospheric temperature is limited by the granulation base temperature (10,000 K), (2) the spicule temperatures are limited by the base temperature (100,000 K) where the supergranular cells form, and (3) the quiet coronal temperature is less than or equal to the convection zone base temperature (2,000,000 K). Thermodynamical arguments are provided which may serve to augment the detailed heating models wherein large-scale mechanical energy is transported into the solar atmosphere involving MHD waves, current dissipation, and other nonthermal processes.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 283; 853-858
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  • 83
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    Publikationsdatum: 2011-08-18
    Beschreibung: The two-dimensional, linear hydrodynamics of quiet solar and umbral model atmospheres in a plane-parallel, adiabatic approximation are investigated. The 5.5-8.5 mHz oscillations observed in umbral chromospheres and transition regions are interpreted as acoustic waves propagating parallel, or nearly parallel, to the temperature gradient. These waves are not totally internally reflected by the steep temperature gradient and, thus, are not trapped. Partial reflections, however, are effective in modulating the transmission as a function of frequency. The resonant transmission mechanism of Zugzda, Locans, and Staude (1983) is found to produce a spectrum of resonances in the transmission of acoustic waves in any atmosphere with a temperature minimum. Since the observed umbral oscillations display power in only a narrow range of frequencies, characteristics of the umbral models, wave propagation, and observations that would tend to suppress the higher frequency resonances are examined.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 283; 859-869
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  • 84
    Publikationsdatum: 2011-08-18
    Beschreibung: The possibility of the existence in soft X-ray flare plasmas of conditions that result in a steady state departure of ion abundances from ionization equilibrium values is considered. The observed flare plasma is assumed to be a result of many small 'elementary bursts' that occur on time scales comparable to the ionization and recombination times of highly ionized atoms of iron and calcium. Specific models are adopted, the time-dependent equations for ion abundances are solved numerically, and X-ray line intensities and line ratios are computed and averaged over the effective time of a single burst. The computed results are compared to observed variations for a number of different line ratios. Although the behavior of certain line ratios can be explained in the context of the burst models considered in this paper, the behavior of the set of all the available line ratios cannot be explained in this manner. The observed departures of line ratios from equilibrium values that can be explained in terms of a burst scenario can also be accounted for by uncertainties in the atomic physics.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 283; 404-412
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  • 85
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    Publikationsdatum: 2011-08-18
    Beschreibung: A cylindrical axisymmetric tearing mode model for solar flares is investigated numerically. Large magnetic energy release only occurs when there are at least two mode rational surfaces in the current-carrying plasma.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Physics of Fluids (ISSN 0031-9171); 27; 2063-206
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  • 86
    Publikationsdatum: 2011-08-18
    Beschreibung: Galerkin finite-element approximations are combined with computer-implemented perturbation methods for tracking families of solutions to calculate the steady axisymmetric flows in a differentially rotated cylindrical drop as a function of Reynolds number Re, drop aspect ratio and the rotation ratio between the two end disks. The flows for Reynolds numbers below 100 are primarily viscous and reasonably described by an asymptotic analysis. When the disks are exactly counter-rotated, multiple steady flows are calculated that bifurcate to higher values of Re from the expected solution with two identical secondary cells stacked symmetrically about the axial midplane. The new flows have two cells of different size and are stable beyond the critical value Re sub c. The slope of the locus of Re sub c for drops with aspect ratio up to 3 disagrees with the result for two disks of infinite radius computed assuming the similarity form of the velocity field. Changing the rotation ratio for exact counter-rotation ruptures the junction of the multiple flow fields into two separated flow families.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 144; 403-418
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  • 87
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    Publikationsdatum: 2011-08-18
    Beschreibung: A new system of approximation equations is derived for three-dimensional steady viscous compressible flows in which a primary-flow direction is present, but in which both transverse velocity components can be large. Previous approaches which address simplification of the steady Navier-Stokes equations are discussed, and a new approach is proposed. The transverse velocity vector which corrects a given potential flow has been decomposed into potential and rotational components. It is found that the potential-velocity vector may be assumed small, whereas the rotational-velocity vector may be assumed small, whereas the rotational velocity vector and hence the composite secondary flow can be of order unity. This assumption leads to a system of governing equations whose characteristic polynomial has a non-elliptic form for arbitrary Mach numbers. The resulting non-elliptic approximation equations can be solved as an initial/boundary-value problem. Computed results confirm the small scalar-potential approximation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Fluid Mechanics (ISSN 0022-1120); 144; 47-77
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  • 88
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    Publikationsdatum: 2011-08-18
    Beschreibung: Prograde and retrograde sectoral oscillations of the sun have been observed so as to determine frequency differences produced by rotation. Oscillations in the frequency range 2.1-3.7 mHz and with spherical harmonic degrees from 1 to 100 have been identified. Average frequency shifts due to rotation in a sidereal reference frame are found to range from a high of about 660 nHz at degree 1 to a low of about 423 nHz at degree 6, rising to about 471 nHz at degree 100. These results indicate that most of the sun's volume rotates at a rate close to that of the surface, but also that the energy-generating core may rotate more rapidly than the surface.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Nature (ISSN 0028-0836); 310; 19-22
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  • 89
    Publikationsdatum: 2011-08-18
    Beschreibung: The frequency difference between prograde and retrograde sectoral solar oscillations is analyzed to determine the rotation rate of the solar interior, assuming no latitudinal dependence. Much of the solar interior rotates slightly less rapidly than the surface, while the innermost part apparently rotates more rapidly. The resulting solar gravitational quadrupole moment is J2 = (1.7 + or - 0.4) x 10 to the -7th and provides a negligible contribution to current planetary tests of Einstein's theory of general relativity.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Nature (ISSN 0028-0836); 310; 22-25
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  • 90
    Publikationsdatum: 2011-08-18
    Beschreibung: A statistical analysis of intensities and radial velocities of several solar plage filaments (i.e. prominences seen on the solar disk) observed at disk center is presented. Intensity and radial (= vertical) velocity maps were derived from simultaneous 2D measurements of the H-alpha chromospheric line with the Multichannel Subtractive Double Pass spectrograph operating on the Meudon solar tower, and also obtained from 2D recordings of the C IV transition-zone line (1548 A) with the UV Spectrometer and Polarimeter aboard the Solar Maximum Mission satellite. A good correlation (around 0.5) is found between intensities in both lines, as well as between velocities. Persistent upflows are measured in both lines at the filament location. The mean vertical velocities are respectively 0.5 km/s in H-alpha and 5.6 km/s in C IV. The analysis of mass fluxes suggests that C IV upflows occur in the transition region around prominences rather than below, in the chromosphere-corona transition zone.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 136; 1, Ju
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  • 91
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Active Cavity Radiometer Irradiance Monitor (ACRIM) of the Solar Maximum Mission satellite measures the radiant power emitted by the sun in the direction of the earth and has worked flawlessly since 1980. The main motivation for ACRIM's use to measure the solar constant is the determination of the extent to which this quantity's variations affect earth weather and climate. Data from the solar minimum of 1986-1987 is eagerly anticipated, with a view to the possible presence of a solar cycle variation in addition to that caused directly by sunspots.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Sky and Telescope (ISSN 0037-6604); 67; 501-503
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  • 92
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    Publikationsdatum: 2011-08-18
    Beschreibung: The heating of minor ions in solar flares by wave-wave-particle interaction with Langmuir waves, or ion acoustic waves, can be described by a diffusion equation in velocity-space for the particle distribution function. The dependence of the heating on the ion charge and mass, and on the composition of the plasma, is examined in detail. It is found that the heat mechanisms proposed by Ibragimov and Kocharov cannot account for the enhanced abundances of heavy elements in the solar cosmic rays.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 468-472
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  • 93
    Publikationsdatum: 2011-08-18
    Beschreibung: The paper presents a broad range of complementary observations (SMM and ground-based) of the onset and impulsive phase of the fairly large (1B, M1.2) but simple two-ribbon flare which occurred at 19:15 UT on November 1, 1980 in the northern part of the active region Boulder No. AR2776. It is found that the overall magnetic field configuration in which the flare occurred was a fairly simple, closed arch containing nonpotential substructure; the flare occurred spontaneously within the arch (it was not triggered by emerging magnetic flux). The two major spikes of the impulsive energy release are examined, and the three immediate products of this energy release are discussed.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Solar Physics (ISSN 0038-0938); 90; 41-62
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 94
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: An investigation is made of pressureless sintering of commercially available alpha-SiC powders at temperatures between 1900 and 2150 C for periods of 10 to 240 min under one atmosphere of argon pressure. It is found that alpha-SiC powder containing boron and carbon sintering aids is sinterable at 2150 C for a period of 30 min to a high final density (greater than 96 percent of theoretical). In alpha-SiC powder containing aluminum and carbon sintering aids, the final density achieved is only about 80 percent of theoretical. Determinations are made of room temperature and high temperature (1370 C) flexure strength and oxidation resistance on sintered high density (more than 96 percent of theoretical) alpha-SiC (boron, carbon) material. It is found that both the strength and the resistance to oxidation are equivalent and comparable to those of the sintered alpha-SiC which represents the state of the art.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Journal of Materials Science (ISSN 0022-2461); 19; 1307-131
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 95
    Publikationsdatum: 2011-08-18
    Beschreibung: Transient behavior of flare-associated solar wind in the nonradial open field region is numerically investigated, taking into account the thermal and dynamical coupling between the chromosphere and the corona. A realistic steady solar wind is constructed which passes through the inner X-type critical point in the rapidly diverging region. The wind speed shows a local maximum at the middle, O-type, critical point. The wind's density and pressure distributions decrease abruptly in the rapidly diverging region of the flow tube. The transient behavior of the wind following flare energy deposition includes ascending and descending conduction fronts. Thermal instability occurs in the lower corona, and ascending material flows out through the throat after the flare energy input ceases. A local density distribution peak is generated at the shock front due to the pressure deficit just behind the shock front.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 841-852
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: A cooled porous insert in a curved wall has a specified spatially varying heat flux applied to one side. It is desired to control the distribution of coolant flow out through this curved surface so that the surface will be kept at a desired uniform temperature. The flow regulation is accomplished by shaping the surface through which the coolant enters the region to obtain the required variation of flow resistance within the region. The proper surface shape is found by solving a Cauchy boundary value problem. Analytical solutions are given in two dimensions for various shapes of the heated boundary subjected to different heating distributions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: International Journal of Heat and Mass Transfer (ISSN 0017-9310); 27; 243-252
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    Publikationsdatum: 2011-08-18
    Beschreibung: Galerkin finite-element approximations and Newton's method for solving free boundary problems are combined with computer-implemented techniques from nonlinear perturbation analysis to study solidification problems with natural convection in the melt. The Newton method gives rapid convergence to steady state velocity, temperature and pressure fields and melt-solid interface shapes, and forms the basis for algebraic methods for detecting multiple steady flows and assessing their stability. The power of this combination is demonstrated for a two-phase Rayleigh-Benard problem composed of melt and solid in a veritical cylinder with the thermal boundary conditions arranged so that a static melt with a flat melt-solid interface is always a solution. Multiple cellular flows bifurcating from the static state are detected and followed as Rayleigh number is varied. Changing the boundary conditions to approach those appropriate for the vertical Bridgman solidification system causes imperfections that eliminate the static state. The flow structure in the Bridgman system is related to those for the Rayleigh-Benard system by a continuous evolution of the boundary conditions.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: Journal of Computational Physics (ISSN 0021-9991); 53; 1-27
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2011-08-18
    Beschreibung: Computational models of turbulence in incompressible Newtonian fluids governed by the Navier-Stokes equations are reviewed. The governing equations are presented, and both direct and large-eddy-simulations are examined. Resolution requirements and numerical techniques of spatial representation, definition of initial and boundary conditions, and time advancement are considered. Results of simulations of homogeneous turbulence in uniform shear, the evolution of a turbulent mixing layer, and turbulent channel flow are presented graphically and discussed.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: Thermal barrier coatings may be applied to air-cooled turbine section airfoils to insulate such components from hot gases in the engine. The coatings, which typically consist of about 0.01 to 0.04 cm of zirconia-yttria ceramic over about 0.01 cm of NiCrAlY or NiCrAlZr alloy bond coat, allow increased gas temperatures or reduced cooling air flows. This, in turn, leads to marked improvements in engine efficiency and performance. However, certain risks are associated with designing for maximum benefits, and eventually a point is reached where coating loss would immediately jeopardize the underlying component. Therefore, designers must be able to accurately predict the life of a given bill-of-material coating in any particular design. The results of an in-house aeronautics, base research and technology program which is designed to provide the first steps towards developing mission-capable life-prediction models are outlined.
    Schlagwort(e): NONMETALLIC MATERIALS
    Materialart: Turbine Engine Hot Section Technology, 1984; 6 p
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2016-06-07
    Beschreibung: About 1% of all sudden ionospheric disturbances (SIDs) observed at the Panska Ves Observatory (Czechoslovakia), were found to be not of solar-XUV origin. Among them, the very rare SWF events (observed at L = 2.4) of corpuscular origin are the most interesting. The IMF sector structure effects in the midlatitude lower ionosphere are minor in comparison with effects of solar flares, geomagnetic storms, etc. There are two basic types of effects. The first type is a disturbance, best developed in geomagnetic activity, and observed in the night-time ionosphere. It can be interpreted as a response to sector structure related changes of geomagnetic (= magnetospheric) activity. The other type is best developed in the tropospheric vorticity area index and is also observed in the day-time ionosphere in winter. This effect is quietening in the ionosphere as well as troposphere. While the occurrence of the former type is persistent in time, the latter is severely diminished in some periods. All the stratosphere, the 10-mb level temperature and height above Berlin-Tempelhof do not display any observable IMF section structure effect.
    Schlagwort(e): SOLAR PHYSICS
    Materialart: International Council of Scientific Unions Middle Atmosphere Program. Handbook for MAP, Vol. 10; p 193-199
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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