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  • 1
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    Analysis of a transport fuselage section drop test (1984)
    In:  CASI
    Details
    Publikationsdatum: 2005-03-28
    Beschreibung: Transport fuselage section drop tests provided useful information about the crash behavior of metal aircraft in preparation for a full-scale Boeing 720 controlled impact demonstration (CID). The fuselage sections have also provided an operational test environment for the data acquisition system designed for the CID test, and data for analysis and correlation with the DYCAST nonlinear finite-element program. The correlation of the DYCAST section model predictions was quite good for the total fuselage crushing deflection (22 to 24 inches predicted versus 24 to 26 inches measured), floor deformation, and accelerations for the floor and fuselage. The DYCAST seat and occupant model was adequate to approximate dynamic loading to the floor, but a more sophisticated model would be required for good correlation with dummy accelerations. Although a full-section model using only finite elements for the subfloor was desirable, constraints of time and computer resources limited the finite-element subfloor model to a two-frame model. Results from the two-frame model indicate that DYCAST can provide excellent correlation with experimental crash behavior of fuselage structure with a minimum of empirical force-deflection data representing structure in the analytical model.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Res. in Struct. and Dyn., 1984; p 347-368
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  • 2
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    Crashworthiness of light aircraft fuselage structures: A numerical and experimental investigation (1984)
    In:  CASI
    Details
    Publikationsdatum: 2005-03-28
    Beschreibung: The dynamic behavior of aircraft fuselage structures subject to various impact conditions was investigated. An analytical model was developed based on a self-consistent finite element (CFE) formulation utilizing shell, curved beam, and stringer type elements. Equations of motion were formulated and linearized (i.e., for small displacements), although material nonlinearity was retained to treat local plastic deformation. The equations were solved using the implicit Newmark-Beta method with a frontal solver routine. Stiffened aluminum fuselage models were also tested in free flight using the UTIAS pendulum crash test facility. Data were obtained on dynamic strains, g-loads, and transient deformations (using high speed photography in the latter case) during the impact process. Correlations between tests and predicted results are presented, together with computer graphics, based on the CFE model. These results include level and oblique angle impacts as well as the free-flight crash test. Comparisons with a hybrid, lumped mass finite element computer model demonstrate that the CFE formulation provides the test overall agreement with impact test data for comparable computing costs.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Res. in Struct. and Dyn., 1984; p 325-346
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  • 3
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    Multiobjective optimization techniques for structural design (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The multiobjective programming techniques are important in the design of complex structural systems whose quality depends generally on a number of different and often conflicting objective functions which cannot be combined into a single design objective. The applicability of multiobjective optimization techniques is studied with reference to simple design problems. Specifically, the parameter optimization of a cantilever beam with a tip mass and a three-degree-of-freedom vabration isolation system and the trajectory optimization of a cantilever beam are considered. The solutions of these multicriteria design problems are attempted by using global criterion, utility function, game theory, goal programming, goal attainment, bounded objective function, and lexicographic methods. It has been observed that the game theory approach required the maximum computational effort, but it yielded better optimum solutions with proper balance of the various objective functions in all the cases.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 8 p
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  • 4
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    Overview: Applications of numerical optimization methods to helicopter design problems (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: There are a number of helicopter design problems that are well suited to applications of numerical design optimization techniques. Adequate implementation of this technology will provide high pay-offs. There are a number of numerical optimization programs available, and there are many excellent response/performance analysis programs developed or being developed. But integration of these programs in a form that is usable in the design phase should be recognized as important. It is also necessary to attract the attention of engineers engaged in the development of analysis capabilities and to make them aware that analysis capabilities are much more powerful if integrated into design oriented codes. Frequently, the shortcoming of analysis capabilities are revealed by coupling them with an optimization code. Most of the published work has addressed problems in preliminary system design, rotor system/blade design or airframe design. Very few published results were found in acoustics, aerodynamics and control system design. Currently major efforts are focused on vibration reduction, and aerodynamics/acoustics applications appear to be growing fast. The development of a computer program system to integrate the multiple disciplines required in helicopter design with numerical optimization technique is needed. Activities in Britain, Germany and Poland are identified, but no published results from France, Italy, the USSR or Japan were found.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 13 p
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  • 5
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    The structural optimization of a spreader bar for twin lift helicopter operations (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: An optimization study was performed to develop a minimum weight spreader bar to allow two helicopters to lift the same payload. With this arrangement, the maximum payload that can be lifted is almost doubled without the expense of designing and building a new helicopter. The concept has had some limited use by civil helicopter operators using small helicopters and has been demonstrated in large scale by two CH-54's which successfully lifted a total load of 20 ton. To this point, rather heavy available beams or tower structures have been used for the spreader bar. Since the weight of the bar not only detracts from payload but also adds to the logistics problem, there are more than the usual incentives to minimize weight. Since the design requirement is for classic beam column with uniform side loads resulting from bar weight and aerodynamic drag, the design problem is particularly amenable to optimization. A study has been performed at Sikorsky to establish the minimum weight for a spreader bar sized to carry a load equal to the capacity of two Army BLACK HAWK helicopters. Toward this end, a computer program was written to analyze the spreader bar deflections and stresses and coupled to the NASA developed CONMIN optimization routines.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 12 p
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  • 6
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    Optimization of helicopter rotor blade design for minimum vibration (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The optimization approach discussed is part of an ongoing effort to develop a general automated procedure for rotor blade design. This procedure can be used to determine the necessary geometric, structural, and material properties of a rotor system to achieve desired objectives relating to vibration, stress, and aerodynamic performance. The approach used for helicopter vibration is emphasized. Based on analytical studies performed at the United Technologies Research Center (UTRC), a simplified vibration analysis was developed to be used in conjunction with a forced response analysis in the optimization process. This simplified analysis improves the efficiency of the design process significantly. Results of applying this approach to the design of an existing rotor blade model are presented.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 17 p
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  • 7
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    Attack helicopter (AH-1T) cockpit systems integration (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: This discussion summarizes the effort conducted by the BHTI Human Factors and Cockpit Arrangement group for a study and design of the integration of a cockpit control system for the AH 1T (TOW). The resulting design is a culmination of studies that were conducted using the existing configuration as a baseline and complementing it with new equipment and subsystems that fulfill the attack helicopter requirements for the foreseeable future. Of primary concern was the requirement to add a missile control system, with secondary considerations for improved NOE and night operations. In addition, growth capabilities for improved target acquisition, weapons delivery, and precise navigation was considered. Along with the addition of new equipment, the aircraft was assumed to have a central multiplex data bus system for information transfer throughout the aircraft and its subsystems.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Ames Research Center Technical Workshop: Advanced Helicopter Cockpit Design Concepts; p 271-316
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  • 8
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    Operational requirements - system concepts (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Nine research areas that are most critical to the issue of cockpits for the single pilot are discussed. Helicopter are addressed in this report. They are as follows: (1) automation priority issues; (2) increased complexity of systems; (3) cockpit workload highest in navigation; (4) auto hover and flight trim controls; (5) voice technology in integrated form; (6) systems must have visual and auditory declutter modes; (7) cockpit should be designed to be NBC resistant; and (8) considerations for spillover to civilian public service.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Technical Workshop: Advanced Helicopter Cockpit Design Concepts; p 229-238
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  • 9
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    HH-60D night hawk helicopter (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Fundamental development issues, system requirements and improvements are reported for the HH-60D night hawk helicopter. The HH-60D mission requirements are for combat search and rescue (aerospace rescue and recovery service user based at Scott AFB) and special operations (special operations forces based at Hurlburt AFB). Cockpit design, computer architecture and software are described in detail.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Ames Research Center Technical Workshop: Advanced Helicopter Cockpit Design Concepts; p 145-164
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  • 10
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    Space debris impact experiment (S0001) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The specific objectives of this experiment are to establish the population and size distribution of meteoroids in the mass range from 10 to the minus 10 power to 10 to the minus 4 power G, to establish the current population of man-made debris in the same mass range, and to obtain data on the physical properties (composition and density) of meteoroids.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Long Duration Exposure Facility (LDEF); p 136-137
    Format: text
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  • 11
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    Interplanetary dust experiment (A0201) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objective of this experiment is to study interplanetary dust, variously referred to as cosmic dust, cometary dust, zodiacial dust, or meteoric dust particles. Specific objectives are to obtain information regarding particle mass and velocity, and to undertake correlative analyses with other experiments, both on LDEF or near the time of the LDEF flight.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Long Duration Exposure Facility (LDEF); p 134-135
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  • 12
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    Attempt at dust debris collection with stacked detectors (A0138-2) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The primary objective of this experiment is to investigate the feasibility of future missions of multilayer thin-film detectors acting as energy sorter to collect micrometeoroids, if not in their original shape, at least as fragments suitable for chemical analysis. It is expected that this kind of particle collector will help in solving one of the most puzzling topics in cosmic-dust studies: the mineralogical and chemical composition of the particles. This is a matter of great interest in the study of the origin and evolution of the solar system.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 124-126
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  • 13
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    Analysis of fuel system technology for broad property fuels (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-09
    Beschreibung: An analytical study was performed in order to assess relative performance and economic factors involved with alternative advanced fuel systems for future commercial aircraft operating with broad property fuels. Significant results, with emphasis on design practicality from the engine manufacturer' standpoint, are highlighted. Several advanced fuel systems were modeled to determine as accurately as possible the relative merits of each system from the standpoint of compatibility with broad property fuel. Freezing point, thermal stability, and lubricity were key property issues. A computer model was formulated to determine the investment incentive for each system. Results are given.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Lewis Research Center Assessment of Alternative Aircraft Fuels; p 141-158
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  • 14
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    Aeroelastic-aerodynamic optimization of high speed helicopter-compound rotor (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Several problems related to the aeroelastic/aerodynamic optimization of a high speed helicopter compound rotor are discussed. The helicopter fuselage vibration problem, the effects of fuselage vibrations, the source of external and periodic air loads, typical airfoil environments and configurations, rotor dynamics, vibration reduction, and requirements for the rotor design optimization analysis are among the topics covered.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 20 p
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  • 15
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    Helicopter rotor blade aerodynamic optimization by mathematical programming (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Formal mathematical programing was applied to the aerodynamic rotor blade design process. The approach is to couple hover and forward flight analysis programs with the general-purpose optimization program CONMIN to determine the blade taper ratio, percent taper, twist distribution, and solidity which minimize the horsepower required at hover while meeting constraints on forward flight performance. Designs obtained using this approach for the blade of a representative Army helicopter compare well with those obtained using a conventional approach involving personnel-intensive parametric studies. Results from the present method can be obtained in 2 days as compared to 5 weeks required by the conventional procedure. Also the systematic manipulation of the design variables by the optimization procedure minimizes the need for the researcher to have a vast body of past experience and data in determining the influence of a design change on the performance.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 12 p
    Format: text
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  • 16
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    Integrated cockpit design for the Army helicopter improvement program (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The main Army Helicopter Improvement Program (AHIP) mission is to navigate precisely, locate targets accurately, communicate their position to other battlefield elements, and to designate them for laser guided weapons. The onboard navigation and mast-mounted sight (MMS) avionics enable accurate tracking of current aircraft position and subsequent target location. The AHIP crewstation development was based on extensive mission/task analysis, function allocation, total system design, and test and verification. The avionics requirements to meet the mission was limited by the existing aircraft structural and performance characteristics and resultant space, weight, and power restrictions. These limitations and night operations requirement led to the use of night vision goggles. The combination of these requirements and limitations dictated an integrated control/display approach using multifunction displays and controls.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Ames Research Center Technical Workshop: Advanced Helicopter Cockpit Design Concepts; p 121-144
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  • 17
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    Fuel system research and technology: An overview of the NASA program (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-09
    Beschreibung: The interactions between the design and operation of aircraft fuel systems and the properties of alternative aircraft fuels are discussed. An overview of fuels system research and technology in terms of its rationale, its progress, and future plans is given. The measurement of ambient air temperatures for a wide range of seasonal and geographic variations, design studies on the use of fuels with increased as well as conventional freezing temperatures, the evaluation of fuel heating systems, and the low temperature behavior of fuels are among the topics discussed.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Assessment of Alternative Aircraft Fuels; p 111-120
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  • 18
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    Multidisciplinary approach to the design of high pressure oxygen systems (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Several examples of spacecraft systems fires are examined. Much of the design, manufacture, inspection, test, and operation of current high pressure oxygen components and systems has been driven by weight, cost, functional, and schedule requirements. As a result, little coordination has been expended on design for safe operation. While the number of oxygen related fires has not been large, their cost, including program losses and delays, has been very large. Most of these failures need not have occurred.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 13 p
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  • 19
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    Fuel system design concepts for broad property fuels (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-09
    Beschreibung: The results of a study assessing the impact of using jet fuel with relaxed specification properties on an aircraft fuel system are given. The study objectives were to identify credible values for specific fuel properties which might be relaxed, to evolve advanced fuel system designs for airframe and engines which would permit use of the specified relaxed properties fuels, and to evaluate performance of the candidate advanced fuel systems and the relaxed property fuels in a typical transport aircraft. The study used, as a baseline, the fuel system incorporated in the Lockheed Tristar. This aircraft is powered by three RB.211-524 Rolls-Royce engines and incorporates a Pratt and Whitney ST6C-421 auxiliary power unit for engine starting and inflight emergency electrical power. The fuel property limits examined are compared with commercial Jet A kerosene and the NASA RFP fuel properties. A screening of these properties established that a higher freezing point and a lower thermal stability would impact fuel system design more significantly than any of the other property changes. Three candidate fuel systems which combine the ability to operate with fuels having both a high freeze point and a low thermal stability are described. All candidates employ bleed air to melt fuel freeze-out prior to starting the APU or an inoperable engine. The effects of incorporating these systems on aircraft weight and engine specific fuel consumption are given.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Lewis Research Center Assessment of Alternative Aircraft Fuels; p 159-170
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  • 20
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    Application of numerical optimization to rotor aerodynamic design (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: Based on initial results obtained from the performance optimization code, a number of observations can be made regarding the utility of optimization codes in supporting design of rotors for improved performance. (1) The primary objective of improving the productivity and responsiveness of current design methods can be met. (2) The use of optimization allows the designer to consider a wider range of design variables in a greatly compressed time period. (3) Optimization requires the user to carefully define his problem to avoid unproductive use of computer resources. (4) Optimization will increase the burden on the analyst to validate designs and to improve the accuracy of analysis methods. (5) Direct calculation of finite difference derivatives by the optimizer was not prohibitive for this application but was expensive. Approximate analysis in some form would be considered to improve program response time. (6) Program developement is not complete and will continue to evolve to integrate new analysis methods, design problems, and alternate optimizer options.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 2; 15 p
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  • 21
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    Passive exposure of Earth radiation budget experiment components (A0147) (1984)
    In:  CASI
    Details
    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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  • 22
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    Interstellar-gas experiment (A0038) (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: The objectives of this experiment are to collect and isotopically analyze interstellar gas atoms around the orbit of the Earth for the purpose of obtaining new data relevant to understanding nucleosynthesis, and to study the dynamics of the interstellar wind inside the heliosphere and the isotopic composition of the interstellar medium outside the heliosphere. The experiment hardware will act as a set of simple cameras with high-purity copper-beryllium collecting foils serving as the film. The experiment housing will mount and thermally control the foils, establish the viewing angles and viewing direction, provide baffling to reject ambient neutral particles, provide a voltage grid to reject ionospheric charged particles, sequence collecting foils, control exposure times, and protect the foils from contamination during the deployment and retrieval of the LDEF. After being returned to Earth, the entrapped atoms can be analyzed by mass spectroscopy to determine the relative abundance of the different isotopes of helium and neon. An attempt will also be made to detect argon.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Langley Research Center Long Duration Exposure Facility (LDEF); p 98-100
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  • 23
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    Computer control for automated flight test maneuvering (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The application of an experimental flight test maneuver autopilot test technique for collecting aerodynamic and structural flight research data on a highly maneuverable aircraft is described in this paper. This technique, which was developed to increase the quality and quantity of data obtained during flight test, was applied to the highly maneuverable aircraft technology (HiMAT) vehicle. A primary flight experiment was to verify the design techniques used to develop the HiMAT aerodynamics and structures. This required the performance of maneuvers for collection of large quantities of high-quality pressure distribution, loads, and wing and canard deflection data. Flight data obtained while executing these research maneuvers are presented to demonstrate the effectiveness of this new technique.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Aircraft (ISSN 0021-8669); 21; 776-782
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  • 24
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    Status review of a supersonically biased fighter wing design study (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Aircraft (ISSN 0021-8669); 21; 767-775
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  • 25
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    High spatial resolution IR observations of young stellar objects - A possible disk surrounding HL Tauri (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: High spatial resolution images of the T Tauri star HL Tau were obtained at 1.6 microns and 2.2 microns. The original images as well as maximum entropy image reconstructions reveal a circumstellar envelope structure, similar at both wavelenghts, and extended along P.A. = 112 deg; the 10 percent width of the structure is 1.9 sec (300 AU at 160 pc). The extended structure is interpreted as light scattered toward earth by dust in a disk surrounding this young stellar object. Polarization measurements made at 2.2 microns support this hypothesis. The total solid particle mass is, at minimum, 5 x 10 to the -7th solar mass.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 283; L57-L61
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  • 26
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    The overshoot region at the bottom of the solar convection zone (1984)
    In:  Other Sources
    Details
    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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  • 27
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    Very slow classical Cepheids - Theoretical models with periods longer than 50 days (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Systematics of the light curves of classical Cepheids with the longest known periods have been investigated with the help of full-amplitude models of pulsating stellar envelopes. For periods exceeding about 60 days, flat-topped light curves of the S Vul type are found to replace the smooth, asymmetric light curves characteristic of the slightly faster Cepheids. Predicted light and velocity amplitudes (although not the predicted radius amplitudes) agree well with observations. Variables with fluctuating light minima are observed to lie well off the mean period-luminosity relation, as are a few other (more stable?) variables with similarly long periods. The explanation for the long periods is probably low effective temperature rather than a low stellar mass. Because of the abnormal slowness of the classical Cepheids with periods longer than about 100 days, it is recommended that these variables not be used to calibrate the mean period-luminosity relation. Analogies between the slow classical Cepheids and the slow Population II Cepheids are drawn.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 811-814
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  • 28
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    On the '3 kiloparsec arm' - Resonance excitation of linear and nonlinear waves by an oval distortion in the central region (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The mechanism responsible for the massive rapidly expanding Galactic feature known as the 3-kpc arm (Rougoor and Oort, 1960) is investigated theoretically in the framework of a density-wave model of the Galaxy. The arm is attributed to outgoing waves excited at the outer Lindblad resonance (OLR) of a small rotating oval distortion near the Galactic center. Linear and nonlinear models are developed, and it is shown that a density crest at 3.5 kpc with expansion velocity 53 km/s can be generated by a distortion turning at 118 km/s kpc with a 10-percent perturbation of the main gravitational field at the OLR (located at 3 kpc). The wave character of the nonlinear solution is found to be the same as that of the linear solution and to give good agreement with the observations in terms of expansion velocity, size, shape, and mass; only the observed asymmetry of the arm is not reproduced.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 600-613
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  • 29
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    Superclustering and the large-scale structure of the Universe (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A complete redshift survey of nearby rich galactic clusters is analyzed in terms of a spatial correlation function, the growth of supercluster, the presence of superclusters around the Bootes void and the discovery of a 300 Mpc void. Abell's (1958) statistical sampling of rich clusters is used for the study. Attention is given to the dependence of the correlation function on the richness of the system, with finding that chances are greater of finding rich neighbors closer together than poor neighbors. Samples of redshifts of 4 or less correlate well with clusters of redshift 5 or more. The size of intergalactic voids is proportional to the surrounding galactic excesses. Finally, the superclusters exist on scales of about 100 Mpc/h, which is larger than expected.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 3; 10-12
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  • 30
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    Ultraviolet spectral morphology of the O stars - The remarkable luminosity dependence of the Si IV stellar wind effect (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: An extensive survey of ultraviolet O type spectra, by means of high-resolution data from the International Ultraviolet Explorer archives, shows a strong correlation between both the photospheric and stellar wind features, and the optical spectral types. In particular, the stellar wind effect in the Si IV resonance doublet displays a strong luminosity dependence which has not been completely described before: there is no effect anywhere on the main sequence, but it develops gradually through the intermediate luminosity classes into a full P Cygni profile in the supergiants. This behavior is in sharp contrast to that of the C IV and N V, which have strong P Cygni profiles throughout most of the O type domain, including the main sequence. The Si IV effect simultaneously provides a sensitive classification criterion and poses an outstanding problem for detailed astrophysical interpretation. In addition, a new emission feature at 1574 A, possibly due to N III or to N IV forbidden line, is reported.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 280; L27-L30
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  • 31
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    Beam-return current systems in solar flares (1984)
    In:  Other Sources
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    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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  • 32
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    Radiative and reconnection instabilities - Filaments and flares (1984)
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    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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  • 33
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    A second chance for Solar Max (1984)
    In:  Other Sources
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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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  • 34
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    Do bipolar magnetic regions exist on the surfaces of early-type stars? (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The observations of relatively narrow absorption components of the UV resonance lines in the spectra of early-type stars are reviewed, and some new observational data are presented for Rho Leo (B1 Ib). It is shown that the discrete components which are seen in the UV resonance lines of early-type stars are a result of ejection from local spots above the photospheres of hot stars. It is suggested that localized ejection is caused by magnetic flux lines associated with a bipolar magnetic region on the surface of the star.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 712-728
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  • 35
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    Models of the hard X-ray spectrum of AM Herculis and implications for the accretion rate (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Phenomenological fits to the hard X-ray spectrum of AM Hercules have failed to explain the high equivalent width (0.8 + or - 0.1 keV) of Fe K-alpha emission. The scattering and fluorescent line production in a cold or partially ionized accretion column of hard X-rays emitted at the base are investigated using the Monte Carlo method. It is shown that the Fe emission equivalent width observed in the spectrum of AM Her can be explained without resorting to an overabundance of Fe in the accreting material. For sufficient optical depth across the accretion column, equivalent widths of K-alpha emission even larger than the observed values can be obtained. The accretion rate and gravitational power can be deduced from the optical depth across the column, if the column size is known, and, together with the observed hard X-ray and polarized light luminosities, imply a lower limit for the luminosity in the UV to soft X-ray range, for which the observations give model-dependent values.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 280; 734-743
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  • 36
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    Disappearance and disintegration of comets (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Icarus (ISSN 0019-1035); 58; 81-100
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  • 37
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    X-ray spectral signatures of accreting black holes (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The X-ray properties of the binary black hole candidates include distinctive bimodal spectral behavior where the X-ray spectra switch between being very soft (alpha greater than 3) and hard (alpha about 0.7). It is pointed out that this spectral transition occurs at about 1 percent L(edd) (for accretion onto a 10 solar masses black hole), and that this corresponds to the luminosity where an optically thick electron-positron pair plasma will form. Active galactic nuclei (AGN) are often considered to be accreting black holes. An X-ray spectral similarity between the above binary sources and both the Seyfert I and BL Lac classes of AGN is demonstrated. As many of these objects radiate most of their luminosity as X-rays, such a similarity may be expected if the underlying mechanisms are similar.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 133; 2, Ap
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  • 38
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    Spectral analysis of magnetohydrodynamic fluctuations near interplanetary shocks (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Preliminary results of an investigation of magnetic fluctuations seen upstream of two interplanetary shocks are presented. The spectral analysis includes calculation of the normalized reduced magnetic helicity spectrum, the normalized reduced cross-helicity spectrum, and the Alfven ratio as discussed by Matthaeus and Goldstein (1982). Minimum variance methods are used to compute wave polarization as a function of frequency. The Taylor 'frozen in flow' hypothesis is assumed to convert frequencies to wave vectors. Some of the basic properties of the waves, including the probable mode of propagation in association with both quasi-parallel forward and reverse shocks, are described. A comparison with previous results on the generation of waves at interplanetary and planetary shocks is presented.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 3762-377
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  • 39
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    HEAO 3 observations of the Crab pulsar (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Crab pulsar (PSR 0531+21) is the only pulsar which has been observed throughout almost the entire electromagnetic spectrum from 0.5 keV to over 2000 GeV. In general, the emission from the Crab nebula and its pulsar has been remarkably constant in time (except for the pulsations). However, several recent observations, especially of gamma-ray line emission, indicate possible time variations. The present investigation is concerned with the data obtained with the HEAO C-1 experiment. The data have been studied with the hope of finding information regarding a number of questions, taking into account the existence of line emission from the pulsar, the variation of the shape of the light curve with time, and the spectral variations as a function of pulsar phase. The spectrum of the total phase-averaged pulsed emission is found to be consistent with a single power-law spectrum from 50 keV to 10 MeV.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 784-790
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  • 40
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    X-ray observations of X Persei (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The HEAO 2 Einstein Observatory was used to confirm the identification of 4U 0352 + 30 with X Per. The HEAO 2 data were analyzed in order to determine an additional point in the pulse period history of the X-ray source and to search for short binary periods. In addition, a majority of the historical X-ray observations was reanalyzed and more refined values for the pulse period as a function of time were obtained. The period history possess significant scatter, but no evidence for a measurable long-term spin-up trend is found, and hence a lower limit to the spin-up time scale is set. This lower limit is consistent with the presence of a neutron star, but it does not rule out a degenerate dwarf. The period history was also searched for evidence of binary motion, and upper limits to a(x) sin i were obtained.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 711-715
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  • 41
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    Creating competitive rotorcraft noise technology (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Rotorcraft noise includes turbofan engine noise components, as well as noise from the main and tail rotors that is conditioned by the aircraft's various operational modes. Both of the rotors generate loading noise and broadband noise. Another noise contributor is blade/vortex interaction noise, which results when shed vortices are encountered by a following blade, releasing impulsive acoustic energy. Attention is presently given to the experimental and developmental initiatives to be made by a NASA/industry five-year program that began in 1983. Aeroacoustic data acquired from experiments conducted in NASA facilities can be used in the development of empirical noise prediction methods, in the improvement of existing noise prediction methodology, in the evaluation of proposed reduced noise designs, and in the establishment of useful scaling relationships for selected noise-generating mechanisms.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Aerospace America (ISSN 0740-722X); 22; 60-63
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  • 42
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    Variable ultraviolet emission in SY Muscae (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The results of continued IUE monitoring of the symbiotic variable SY Muscae, following an earlier report of a radical enhancement in UV emission from the star, are reported. Over the course of one year, the prominent emission lines of N V, O V, C IV, and He II appear to be gradually decreasing in absolute intensity. This appears to coincide with a steady decline in electron density in the emission line forming region. The data are consistent with a sudden ejection event in which material expelled from the surface of a hot subdwarf has exposed the underlying UV continuum of the star. A number of strong emission lines that are photoexcited by the intense radiation field of the secondary also exhibit broad pedestal emission that suggests turbulent velocities of about 150-300 km/s in an expanding shell or possibly in an accretion disk.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 207; 575-583
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  • 43
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    Large scale temporal and radial gradients in the IMF - Helios 1, 2, ISEE-3, and Pioneer 10, 11 (1984)
    In:  Other Sources
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    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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  • 44
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    The remarkable ultraviolet spectrum of the planetary nebula Abell 30 (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Abell 30 has been identified as a planetary nebula in which the nucleus has experienced a final helium shell flash after ejection of the original, outer envelope. Around the central star of the nebula, four knots of material are observed. In view of the importance of the chemical composition of the ejected material for studies of advanced stages of stellar evolution, clarification of the physical conditions in the knots is vital. Data obtained of Abell 30 with the aid of the International Ultraviolet Explorer (IUE) satellite are discussed along with aspects of extinction, the He II flux, ionic abundances, the C II lambda 4267 line, questions regarding the existence of a carbon-rich core in the knot, the heating of the nebular gas, the central star, and heating by suprathermal particles from the stellar wind. The UV spectrum of the inner nebulosity of Abell 30 indicates that an extraordinary amount of energy is being deposited in the gas.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 716-724
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  • 45
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    Transient behavior of a flare-associated solar wind. I - Gas dynamics in a radial open field region (1984)
    In:  Other Sources
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    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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  • 46
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    A study of extreme carbon stars. I - Silicon carbide emission features (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 10-micron spectra of many extreme carbon stars reveal a prominent emission feature near 11 microns. This is compared with laboratory spectra of SiC grains. Two distinct types of features are found, perhaps indicative of different mechanisms of grain formation in different stars. Estimates are made of probable column densities and total masses of SiC in the circumstellar shells.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 206; 137-147
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  • 47
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    MHD processes in the outer heliosphere (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The magnetic field measurements from Voyager and the magnetohydrodynamic (MHD) processes in the outer heliosphere are reviewed. A bibliography of the experimental and theoretical work concerning magnetic fields and plasmas observed in the outer heliosphere is given. Emphasis in this review is on basic concepts and dynamical processes involving the magnetic field. The theory that serves to explain and unify the interplanetary magnetic field and plasma observations is magnetohydrodynamics. Basic physical processes and observations that relate directly to solutions of the MHD equations are emphasized, but obtaining solutions of this complex system of equations involves various assumptions and approximations. The spatial and temporal complexity of the outer heliosphere and some approaches for dealing with this complexity are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Space Science Reviews (ISSN 0038-6308); 39; 255-316
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  • 48
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    Cosmogony as an extrapolation of magnetospheric research (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A theory of the origin and evolution of the Solar System which considered electromagnetic forces and plasma effects is revised in light of information supplied by space research. In situ measurements in the magnetospheres and solar wind can be extrapolated outwards in space, to interstellar clouds, and backwards in time, to the formation of the solar system. The first extrapolation leads to a revision of cloud properties essential for the early phases in the formation of stars and solar nebulae. The latter extrapolation facilitates analysis of the cosmogonic processes by extrapolation of magnetospheric phenomena. Pioneer-Voyager observations of the Saturnian rings indicate that essential parts of their structure are fossils from cosmogonic times. By using detailed information from these space missions, it is possible to reconstruct events 4 to 5 billion years ago with an accuracy of a few percent.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Space Science Reviews (ISSN 0038-6308); 39; 65-90
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  • 49
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    Solar-flare neutrons and gamma-rays (1984)
    In:  Other Sources
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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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  • 50
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    Recurrent mass ejections observed in H-alpha and CIV (1984)
    In:  Other Sources
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    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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  • 51
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    A case for submergence of magnetic flux in a solar active region (1984)
    In:  Other Sources
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    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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  • 52
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    Detailed studies of the dynamics and energetics of coronal bullets (1984)
    In:  Other Sources
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    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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  • 53
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    Thermal bifurcation in the upper photosphere inferred from heterodyne spectroscopy of OH rotational lines (1984)
    In:  Other Sources
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    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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  • 54
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    Abundances in galactic H II regions. III - G25.4-0.2, G45.5+0.06, M8, S159, and DR 22 (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Measurements of the ARII (6.99 microns), ArIII (8.99 microns), NeI (12.81 microns), SIII (18.71 microns), and SIV (10.51 microns) lines are presented for five compact HII regions along with continuum spectroscopy. From these data and radio data, lower limits to the elemental abundances of Ar, S, and Ne were deduced. The complex G25.4-0.2 is only 5.5 kpc from the galactic center, and is considerably overabundant in all these elements. Complex G45.5+0.06 is at seven kpc from the galactic center, and appears to be approximately consistent with solar abundance. The complex S159 in the Perseus Arm, at 12 kpc from the galactic center, has solar abundance, while M8 in the solar neighborhood may be somewhat overabundant in Ar and Ne. Complex DR 22, at 10 kpc from the galactic center in the Cygnus Arm, is overabundant in Ar. A summary of results from a series of papers on abundances is given.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 174-180
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  • 55
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    Intense X-ray flares from active stellar systems - EV Lacertae and HD 8357 (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The HEAO A-1 Sky Survey Experiment included X-ray data used to define light curves for the flare star EV Lac and for X-ray flares observed in the binary system HD 8357. The data were taken during flare events and were detailed enough to calculate the flare rates and flaring luminosities. The peak luminosities during flares were several times the luminosities in normal X-ray flares emitted by the objects. Peak luminosities reached 30-50 times the normal variations and were associated with an order of magnitude increase in energy output. EV Lac was sufficiently active to be recommended for inclusion in future X-ray monitoring programs.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 270-277
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  • 56
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    Regularized Monte-Carlo calculations of the optical polarization induced by scattering in X-ray binaries (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The results of regularized Monte Carlo calculations of the optical polarization Stokes parameters expected as a result of scattering from gas streams or accretion wakes in close binary systems whose properties resemble those of X-ray binaries are presented. The physical processes occurring in the system are represented by a model which follows a selected sample of individual photon paths from each emitting element on the surface of the primary to the photon's detection at earth. The result represents the variations in the intensity from each individual emitting element caused by the effects of limb darkening, gravity darkening, and variation in the projected area of the emitting element as seen from the scattering element.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 138; 1, Se
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  • 57
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    Precession model for the nucleus of periodic Comet Kopff (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The existing data base on certain characteristics of the periodic Comet Kopff, a candidate for a NASA rendezvous mission in the 1990s, is summarized. The comet was discovered in 1906. The data are used to calculate limits to the nuclear mass (0.7-1.5 x 10 to the 16th g), equatorial radius (1.26-1.64 km), and a geometric albedo of 0.08. An equatorial rotation velocity of 8.1-10.7 hr is projected. The estimates are highly dependent on the present photometric data, which in turn depend on the insolation rate, which if different than assumed could mean that all parameters would be revised upward significantly.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Journal (ISSN 0004-6256); 89; 1573-158
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  • 58
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    The H flux peak and the hydrogen abundance in N type carbon stars (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: For galactic N and late R type irregularly variable carbon stars, a comparison is made of airborne infrared spectrophotometry to spectral flux distributions derived from model atmospheres. Although the agreement is good in several respects, the H(-) emission peak at 1.6 microns, so prominent in the models, is significantly weakened in the stellar spectrophotometry. It seems unlikely that molecular bands in the stars can completely obliterate this peak. A plausible explanation is that hydrogen is deficient in these stars, most probably from an episode of mass loss. The resultant cold shells surrounding these stars should be amenable to observation by IRAS, or other far-infrared observatories.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 284; L39-L42
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  • 59
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    An X-ray survey of variable radio bright quasars (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A sample consisting primarily of radio bright quasars was observed in X-rays with the Einstein Observatory for times ranging from 1500 to 5000 seconds. Detected sources had luminosities ranging from 0.2 to 41.0 x 10 to the 45th power ergs/sec in the 0.5 to 4.5 keV band. Three of the fourteen objects which were reobserved showed flux increases greater than a factor of two on a time scale greater than six months. No variability was detected during the individual observations. The optical and X-ray luminosities are correlated, which suggests a common origin. However, the relationship (L sub x is approximately L sub op to the (.89 + or - .15) found for historic radio variables may be significantly different than that reported for other radio bright sources. Some of the observed X-ray fluxes were substantially below the predicted self-Compton flux, assuming incoherent synchrotron emission and using VLBI results to constrain the size of the emission region, which suggests relativistic expansion in these sources. Normal CIV emission in two of the sources with an overpredicted Compton component suggests that although they, like BL Lac objects, have highly relativistic material apparently moving at small angle to the line of sight, they have a smaller fraction of the continuum component in the beam.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 491-496
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  • 60
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    Some properties of the filamentary nebula at 1723 - 46 (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: High resolution spectra of the interstellar NaI D2 absorption line have been obtained for seven B-type stars aligned with an extensive filamentary nebula. Very fine filaments have now been found on a high contrast print of a deep H-alpha and forbidden N II plate, making identification as a fossilized remnant probable but uncertain. The inferred age is about 20,000 yr, the distance less than 200 pc, the diameter less than 17.5 pec, but the initial energy is only about 2 x 10 to the 47th erg.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 693-699
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  • 61
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    Solar irradiance changes caused by g-modes and large scale convection (1984)
    In:  Other Sources
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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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  • 62
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    Lagrangian least-squares prediction of solar flux (F-bar 10.7) (1984)
    In:  Other Sources
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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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  • 63
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    Grain destruction in interstellar shocks (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The destruction of interstellar grains by nonthermal sputtering, thermal sputtering, and grain-grain collisions is discussed. It is concluded that large grains are easily destroyed by shocks in the interstellar medium, but that small grains are much more persistent. Since the MRN model has many more small grains than large ones, this means that the total number of grains is not significantly reduced even when half or more of the grain material is returned to the gas phase. Thus, the small grains are always available as condensation cores for mantle formation or redepletion of refractory grain materials.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Royal Observatory Lab. and Observational Infrared Spectra of Interstellar Dust; p 26-32
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  • 64
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    Application of a global solar wind/planetary obstacle interaction computational model: Earth, Venus, Mars, Jupiter and Saturn studies (1984)
    In:  Other Sources
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    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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  • 65
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    Analysis of potential helicopter vibration reduction concepts (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Several recent helicopter vibration reduction research programs are described. Results of studies of blade design parameters in rotor vibratory response and of an advanced blade design for reduced vibration are examined. An optimization approach to develop a general automated procedure for rotor blade design is described, and analytical results for an articulated rotor operating at a steady 160 kt flight condition are reported. The use of a self-adaptive controller to implement higher harmonic control in closed-loop fashion is addressed, and a computer simulation used to evaluate and compare the performance of alternative algorithms included in the generic active controller is discussed. Results are presented for steady level flight conditions, short-duration maneuvers, blade stresses and rotor performance, blade-appended aeroelastic devices, vibratory airloads, wake-induced blade airloads, and airloads from blade motions, the interaction of rotor and fuselage, and the interaction of rotor and empennage.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
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  • 66
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    Ultraviolet observations of solar flares from the Solar Maximum Mission (1984)
    In:  Other Sources
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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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  • 67
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    Results from the Ultraviolet Spectrometer and Polarimeter Non-flare investigations (1984)
    In:  Other Sources
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    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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  • 68
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    Thermal modeling of Halley's Comet (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The comet thermal model of Weissman and Kieffer is used to calculate gas production rates and other parameters for the 1986 perihelion passages of Halley's Comet. Gas production estimates are very close to revised pre-perihelion estimates by Newburn based on 1910 observations of Halley; the increase in observed gas production post-perihelion may be explained by a variety of factors. The energy contribution from multiply scattered sunlight and thermal emission by coma dust increases the total energy reaching the Halley nucleus at perihelion by a factor of 2.4. The high obliquity of the Halley nucleus found by Sekanina and Larson may help to explain the asymmetry in Halley's gas production rates around perihelion.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 221-224
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    IRAS observations of cometary dust (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is pointed out that solid material present in the coma and tail of a comet is revealed by the scattering of sunlight and thermal emission of absorbed solar radiation. The large beam size and low background of the cold Infrared Astronomy Satellite (IRAS) telescope make it extremely well suited to the measurement of faint diffuse thermal emission from solid grains associated with comets. The IRAS project was conducted jointly by the Netherlands, the United Kingdom, and the U.S. Its basic objective involved a survey of the sky in four wavelength regions centered on 12, 25, 60, and 100 microns. The present paper is mainly concerned with IRAS observations of the coma-nucleus regions as defined by the maximum in the intensity distribution. Attention is given to circumstances of comet observations, dust production rates, and a discussion of the results.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19
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  • 70
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    A comparison of the dust properties in recent periodic comets (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Measurements of the thermal emission from the cometary dust coma can be used to derive the rate of dust production from the nucleus as well as the size distribution of absorbing grains. More than ten short-period comets have now been observed in the infrared over a wide range in heliocentric distance. Dust production rates are derived for these comets based on theoretical models of the thermal emission from small absorbing grains and calculations of dust grain velocities. The mean size and albedo of the dust grains is similar in these comets, with the exception of Comet Crommelin, which seems to have had larger, darker grains.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 189-196
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    A new calibration of the semi-empirical photometric theory for Halley and other comets (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The semiempirical photometric theory of gas and dust production in comets (Newburn, 1979, 1981, and 1982) is recalibrated on the basis of the 17-comet compilation of spectrophotometric data of Newburn and Spinrad (1984). The results are presented in graphs and tables, and it is shown that no corrections are required for the constant R and the function delta, but that the mixing ratios (obtained as functions of heliocentric distance) can be improved, with implications for the visual-photometric comet model. Recently calculated light curves for comet Halley are compared, and the use of the nearly identical curves of Bortle and Morris (1984) and Marcus (1983) is recommended.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Advances in Space Research (ISSN 0273-1177); 4; 9, 19; 185-188
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    Observations of solar radio bursts from meter to kilometer wavelengths (1984)
    In:  Other Sources
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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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  • 73
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    Combined analysis of soft and hard X-ray spectra from flares (1984)
    In:  Other Sources
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    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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  • 74
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    Flare build-up study - Homologous flares group. I (1984)
    In:  Other Sources
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    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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    Computation of solar magnetic fields from photospheric observations (1984)
    In:  Other Sources
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    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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    On Bowen enhancement of the N III spectrum under solar and nebular conditions (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Expected enhancement of the N III emission-line spectrum by the Bowen He II to O III to N III resonant photoexcitation process is computed using a six-configuration model. Preliminary comparisons with available solar and nebular observations indicate that the process may play only a small role, although photoexcitation quenching of the N III and O III far-infrared fine-structure lines is noted as a possibly important mechanism. Some features are discussed in connection with the nebular emission at 1750 A, which is suggested as an indicator of excitation class for planetary nebulae.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 945-951
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  • 77
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    The energetics of chromospheric evaporation in solar flares (1984)
    In:  Other Sources
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    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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  • 78
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    The 41.5 day binary X-ray pulsar 4U 1223 - 62 (GX 301 - 2) (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Ariel 5 and SAS 3 X-ray pulse timing data for the 700 s X-ray pulsar 4U 1223 - 62 (GX 301 - 2) are reexamined in order to deduce the orbital elements of this system. The Ariel 5/SAS 3 arrival times are first reanalyzed to obtain the best solution for an orbital period close to 41.5 days and to estimate the uncertainties in it caused by unknown variations in the underlying pulse period. Spectral measurements by OSO 8 and HEAO 1 at a variety of orbital phases are presented and the origin of an unabsorbed, unpulsed soft component is discussed. OSO 8 observations of occasions when the amplitude and shape of the pulse profile changed dramatically are discussed. The global X-ray properties of the system are explained in terms of a simple stellar wind accretion model, and the interaction of the inflowing material with the neutron star magnetosphere is considered.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 856-867
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  • 79
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    Similar photospheres, different mantles - A study of four O stars (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The present investigation is concerned with a comparison of the spectra of four O stars (10 Lac, S Mon, HD 46223, and Zeta Pup) which have similar effective temperatures, taking into account an attempt to find the reason for differences regarding the spectral type of the stars. The photospheres of the stars are examined, taking into account the effective temperatures, radii, speed of rotation, and masses. Information is presented about the equivalent widths and profiles of strong lines in the visible and ultraviolet spectra of each star. It is found that the four stars have similar photospheres but different mantles. The stars are assigned different spectral types because the empirically selected lines used for determining spectral type in class O are sensitive primarily to conditions in the mantle of the star and not to conditions in the photosphere. Questions concerning the reasons for the differences regarding the mantles are also explored.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 874-891
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  • 80
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    Absorption features in the 5-8 micron spectra of protostars (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: High signal-to-noise ratio spectra in the range of 5-8 microns of four sources embedded in molecular clouds are examined using low-temperature laboratory measurements of the 5-8-micron spectra of simple molecules and their mixtures. The absorption, apparent in all four sources, is characterized by highly distinct features ranging from two relatively narrow bands at 6.0 and 6.8 microns in W33A to a broad, shallow, and partially structured feature extending from 5.2 to 7.8 microns in Mon R2-IRS2, BN, and NGC2264. The first feature (W33A) is explained by the OH bending mode in H2O and the CH deformation modes in saturated hydrocarbons; while the second feature (Mon R2-IRS2-type) is explained by the presence of a mixture of saturated and unsaturated hydrocarbons possibly containing strongly electronegative groups.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 697-706
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  • 81
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    Self-absorption of high-energy Gamma-rays in Cygnus X-3 (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Absorption of high-energy gamma-rays from Cyg X-3 in its own photon field by the reaction gamma + gamma yields e(+) + e(-) is considered. It is found that gamma rays with an energy around 10 to the 12th eV are attenuated, and the observed flux has to be corrected. Gamma rays with energy greater than 10 to the 15th eV which are observed are not affected by the photon field.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 338-340
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  • 82
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    Monte Carlo shock-like solutions to the Boltzmann equation with collective scattering (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The results of Monte Carlo simulations of steady state shocks generated by a collision operator that isotropizes the particles by means of elastic scattering in some locally defined frame of reference are presented. The simulations include both the back reaction of accelerated particles on the inflowing plasma and the free escape of high-energy particles from finite shocks. Energetic particles are found to be naturally extracted out of the background plasma by the shock process with an efficiency in good quantitative agreement with an earlier analytic approximation (Eichler, 1983 and 1984) and observations (Gosling et al., 1981) of the entire particle spectrum at a quasi-parallel interplanetary shock. The analytic approximation, which allows a self-consistent determination of the effective adiabatic index of the shocked gas, is used to calculate the overall acceleration efficiency and particle spectrum for cases where ultrarelativistic energies are obtained. It is found that shocks of the strength necessary to produce galactic cosmic rays put approximately 15 percent of the shock energy into relativistic particles.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 691-701
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  • 83
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    The collapse of the cores of slowly rotating isothermal clouds (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A generalized model which accounts for the effects of initially uniform and slow rotation is defined for the spherical collapse of a singular isothermal sphere such as protosolar and binary nebulae. An initial unstable equilibrium state is described for a sound speed of 0.35 km/sec and a rotation rate of 10 to the -14th/sec for the molecular cloud surrounding the accreting core. The total angular momentum and mass of the inner cloud is set equal to solar system values. The evolution of the collapse is traced by applying a perturbation analysis to the similarity solution for a nonrotating condition, and matched asymptotic expansions solve the hydrodynamic equations. The model is concluded a valid tool for studying star and nebular disk formation.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 286; 529-551
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  • 84
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    Evidence for a supersonic turbulent velocity gradient in the outer photosphere of the supergiant alpha Cygni (A2Ia) (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The balloon-borne UV Stellar Spectrometer's high resolution, near-UV spectra of the supergiant Alpha Cyg are subjected to analysis in order to determine the average microturbulent line-of-sight velocity component. A value of 15.0 + or - 0.5 km/sec is obtained, which is close to the 13.7 km/sec local sound velocity, and is consistent with the view that shock waves are the dominant structure in the outer photosphere of Deneb, so that shock wave dissipation determines the thermal structure of the photosphere.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 141; 2, De
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  • 85
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    Dynamic evolution of recurrent mass ejections observed in H-alpha and C IV lines (1984)
    In:  Other Sources
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    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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  • 86
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    Vibrational and rotational excitation of CO in comets Nonequilibrium calculations (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Ultraviolet observations of atomic carbon in cometary comae show that carbon-bearing compounds must comprise a significant fraction (approximately equal to or greater than 10 percent) of the volatiles. One likely source is CO. This compound is an important constituent of at least some cometary nuclei, even though it may not be the ultimate source of atomic carbon in all comets. Feldman (1983) has suggested that the relative abundance of CO may be one of the few fundamental characteristics which distinguish one comet from another. The present investigation is, therefore, concerned with the vibrational and rotational excitation of the CO molecule in cometary comae. Two previously neglected factors are taken into account in the study. The fractional populations of CO as solutions to time-dependent differential equations are derived, and a nonisothermal and cold kinetic temperature profile for the inner coma is considered.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 858-869
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  • 87
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    The ultraviolet variability of early-type supergiants (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Four early-type supergiants - HD 79186 (B5 Ia), HD 96919 (B9 Ia), HD 105056 (ON9.7 Iae), and HD 148379 (B2 Iae) - have been observed with the low-resolution spectrographs of IUE in the large aperture on 14 days. The behavior of the ultraviolet fluxes with time is studied. The light from all four stars seems to vary. Typically the dispersion about the mean magnitude at any wavelength corresponds to + or - 0.085, + or - 0.080, + or - 0.101, and + or - 0.106 mag, respectively. These amplitudes exceed the typical uncertainty in an IUE measurement of flux by about a factor of 3; they are somewhat larger than the variations known in the visible wavelength range. There are insufficient data to investigate periodicity in the observed light changes. The effective temperatures and angular diameters of the stars have been estimated using the present ultraviolet photometry, published UBV and uvby photometry, and the model-atmosphere fluxes reported by Kurucz in 1979. The program stars have dimensions typical for their spectral types. A brief discussion is given of possible causes of the variability of hot supergiants.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 668-673
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  • 88
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    Modification to shock fitting program (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A modified form of the Lepping-Argentiero single spacecraft, shock normal determination procedure is presented. The modified method incorporates a simple predictor-corrector algorithm which allows a faster convergence rate and the use of average values of the parameters for the starting vector.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 11004-11
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  • 89
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    Large-scale interplanetary magnetic fields - Voyager 1 and 2 observations between 1 AU and 9.5 AU (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The large-scale radial and temporal variations of the interplanetary magnetic field strength B observed by Voyagers 1 and 2 are discussed. Two components of the magnetic field strength were considered: (1) an average component, B sub zero, based on solar rotation averages, and (2) a fluctuation component, delta B, expressed by 10- or 24-hour averages of B normalized by the best-fit average field for the corresponding time and distance. Observations of the sector structure, interfaces, and shocks are presented to further describe magnetic field strength.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 89; 10659-10
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  • 90
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    Microwave-powered, unmanned, high-altitude airplanes (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: Journal of Aircraft (ISSN 0021-8669); 21; 966-970
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  • 91
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    Description of sunspot cycles by orthogonal functions (1984)
    In:  Other Sources
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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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  • 92
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    Cyclotron emission near stellar mass black holes (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Cyclotron emission in the inner regions of an accretion disk around a matter accreting black hole can be appreciable. In the case of the X-ray source Cyg X-1, cyclotron emission may provide the soft photons needed for 'Comptonization' to produce high energy X-rays. The inverse correlation between the fluxes of high energy and low energy X-rays during the 'high' and 'low' states of Cyg X-1, may be understood as a result of the variation of the rate of accretion and the Compton scattering of the cyclotron photons. In the case of the X-ray source GX 339-4, the observed optical flux during the high states does not seem to be due to cyclotron emission, but probably due to reprocessing of high energy X-rays by the outer regions of the disk.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 139; 2, Oc
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  • 93
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    The X-29 flight-research program (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The X-29 experimental aircraft, which is a technology integration and evaluation platform for such features as static longitudinal instability, sweptforward wings and three-surface longitudinal control, offers an opportunity to validate the entire aircrft design process through careful correlation and comparison of flight test results with wind tunnel results and design predictions. Attention is presently given to the design features of the aircraft, which encompass supercritical airfoils, digital flight control, and aeroelastically tailored composite wings, as well as to the flight test program that was formulated to investigate the interactions and relative merits of these design features, in light of data gathered by carefully positioned sensors.
    Schlagwort(e): AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Materialart: AIAA Student Journal (ISSN 0001-1452); 22; 2-12
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  • 94
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    Heating the sun's lower transition region with fine-scale electric currents (1984)
    In:  Other Sources
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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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  • 95
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    The far reaches of the solar wind - Pioneer 10 and Pioneer 11 plasma results (1984)
    In:  Other Sources
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    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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  • 96
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    Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg - Structure and energetics of the inner disk (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Observational results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 150, 250, and 300 microns, with a 10 x 10 arcmin beam. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz or CO emission, or both, and from an underlying diffuse background with a typical angular width of about 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources are identified and characterized, of which about half have not previously been reported at far-infrared wavelengths. The total infrared luminosity within the solar circle is about 1 to 2 x 10 to the 10th solar luminosity, and is probably emitted by dust that resides in molecular clouds.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 74-88
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  • 97
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    The variable component of the NGC 4151 IUE spectrum - Evidence for an expanding spherical emission shell (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The profile of the forbidden line of C III (1909) is the same in two pseudo-trailed, low-resolution SWP spectra of the nucleus of the Seyfert galaxy NGC 4151 obtained with the IUE in November 1980 and December 1982, respectively. In the 1980 spectrum, the C III forbidden line profile is also very nearly the same as that of the resonance line C IV (1550). In the 1982 spectrum, the continuum is 5 times higher and C IV is both much broader and much brighter. In the difference spectrum, which is interpreted to be the spectrum of a time-variable component, C IV (1550) is the only strong emission feature. The profile of this line closely resembles that of a spherical shell surrounding a less dense gas uniformly expanding from a central opaque object. From values of the profile parameters and from the observed time variability of the object, it is inferred that the shell has a radius of about 10 to the 15th cm, a mass of 0.25 solar mass, an expansion velocity of 13,000 km/s, and an electron density of 10 to the 11th per cu cm. From the line profile and the continuum, it is inferred that the opaque central source has approximate radius of 10 to the 14th cm and temperature 23,000 K.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 69-73
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  • 98
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    Gamma rays from atomic and molecular gas in the large complex of clouds in Orion and Monoceros (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A comparison of COS-B gamma-ray observations of the large complex of interstellar clouds in Orion and Monoceros with the Columbia CO and Berkeley H I surveys of this region reveals a good correlation between gamma-ray emission and total gas distribution. The observed gamma-ray emission is explainable in terms of interactions of cosmic rays that are uniformly distributed in this region with the interstellar gas. The correlation is used as the basis of a calibration of the ratio between H2 column density and the integrated CO line intensity; the value of (2.6 + or - 1.2) X 10 to the 20th mol/sq cm K km s thereby obtained is consistent with the value derived from a similar analysis for the inner galaxy.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 139; 1, Oc
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  • 99
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    On the orbit improvement results obtained by referring old cometary observations to the SAO Star Catalog (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An algorithm is presented for the automatic reduction to the SAO Star Catalog of old micrometer cometary observations of the type comet minus star. Results of a numerical test are presented showing the distinct influence of such a reduction on orbit determination results.
    Schlagwort(e): ASTROPHYSICS
    Materialart: JPL Cometary Astrometry; p 203-206
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  • 100
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    Oscillations and stationary motions in filaments (1984)
    In:  Other Sources
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    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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