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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Technology for the product and process data base

The computerized product and process data base is increasingly recognized to be the cornerstone component of an overall system aimed at the integrated automation of the industrial processes of a given company or enterprise. The technology needed to support these more effective computer integrated design and manufacturing methods, especially the concept of 3-D computer-sensible product definitions rather than engineering drawings, is not fully available and rationalized. Progress is being made, however, in bridging this technology gap with concentration on the modeling of sophisticated information and data structures, high-performance interactive user interfaces and comprehensive tools for managing the resulting computerized product definition and process data base.

Barnes, R. D.↗
NASA NTRS1984

Evaporative coating of a sphere from a point source

To optimize the procedure for evaporating a metal film onto a sphere, calculations of the film thickness distribution for various motions of the sphere have been carried out. These calculations, including shadowing effects of sphere support rods, are presented in this paper. Also, an apparatus and procedure for the evaporative coating of a sphere are described. A comparison of measured thickness with the calculated values is made for one example of sphere motion. The implications of the calculated results for coating techniques are discussed.

Strayer, D. M.↗
NASA NTRS1985

Galactic antiprotons from photinos

Stable photinos, the photino being the supersymmetry partner of the photon, can explain both the 'missing mass' in galactic halos and the cosmic-ray antiproton spectrum up to the highest energies observed so far. This requires a photino mass around 15 GeV; significantly higher masses are cosmologically disfavored. As a consequence, the observed cosmic-ray antiproton-to-proton ratio is predicted to decrease abruptly just above the measured energy range, at E = m(x). If observed, this striking effect would strongly support the hypothesis that photinos make up the missing matter in the galaxy and also lead to a measurement of the photino mass from cosmic-ray data.

Stecker, F. W.↗
NASA NTRS1988

Abundance effects on the Cepheid distance scale

A new investigation of the dependence of the period-luminosity (PL) and period-luminosity-color (PLC) relations on the helium and metal abundances in classical Cepheids is presented. Composition dependences are assigned to all quantitites under study, so that the results represent a true theoretical prediction. It is found that the PLC relation in B,V magnitudes is at least five times more sensitive to chemical composition than is the PL relation. If the PL relation is adopted and the helium abundance is held fixed, a Cepheid with Z = 0.005 should be fainter than one with Z = 0.02 by about 0.04 mag. Since the slope of the predicted PL relation is independent of chemical composition, the PL relation can be considered to be effectively universal. Additional supporting observational evidence is described, and theoretical results are also presented for the bolometric PL relation, whose slope and dependence on metal abundance should be roughly applicable to infrared observations of Cepheids.

Stothers, Richard B.↗
NASA NTRS1988

Space Experiments with Particle Accelerators (SEPAC)

The purpose of Space Experiments with Particle Accelerators (SEPAC) on the Atmospheric Laboratory for Applications and Science (ATLAS 1) mission, is to carry out active and interactive experiments on and in the earth's ionosphere, atmosphere, and magnetosphere. The instruments to be used are an electron beam accelerator (EBA), plasma contactor, and associated instruments the purpose of which is to perform diagnostic, monitoring, and general data taking functions. Four major classes of investigations are to be performed by SEPAC. They are: beam plasma physics, beam-atmosphere interactions, the use of modulated electron beams as transmitting antennas, and the use of electron beams for remote sensing of electric and magnetic fields. The first class consists mainly of onboard plasma physics experiments to measure the effects of phenomena in the vicinity of the shuttle. The last three are concerned with remote effects and are supported by other ATLAS 1 investigations as well as by ground-based observations.

Obayashi, Tatsuzo↗
NASA NTRS1990

USSR Space Life Sciences Digest, issue 31

This is the thirty first issue of NASA's Space Life Sciences Digest. It contains abstracts of 55 journal papers or book chapters published in Russian and of 5 Soviet monographs. Selected abstracts are illustrated with figures and tables from the original. The abstracts in this issue have been identified as relevant to 18 areas of space biology and medicine. These areas include: adaptation, biological rhythms, cardiovascular and respiratory systems, endocrinology, enzymology, genetics, group dynamics, habitability and environmental effects, hematology, life support systems, metabolism, microbiology, musculoskeletal system, neurophysiology, nutrition, operational medicine, psychology, radiobiology, and space biology and medicine.

Hooke, Lydia Razran↗
NASA NTRS1991

Finite element analysis of nonlinear flutter of composite panels

A finite element formulation is developed to analyze large-amplitude panel flutter of arbitrary laminated plates. The plates considered are anisotropic composite, thin rectangular panels. The equations of motion for an oscillating plate are determined and solved by linearizing the nonlinear stiffness matrices. The solution procedure is presented to determine the limit-cycle motions which are caused by the large deflections and vibrations induced by the areodynamic load. The aerodynamic load is defined by the first-order piston theory. Examples studied include cross-ply laminates with various numbers of layers and three-layer angle-ply laminates with different lamination angles. The effects of simply supported and clamped boundary conditions of a cross-ply laminate are also examined.

Dixon, Iain R.↗
NASA NTRS1992

Progress of magnetic suspension and balance systems for wind tunnels in the USSR

Magnetic Suspension and Balance Systems (MSBS) for wind tunnels are being developed in order to solve the principal problems of aerodynamics which cannot be solved by conventional means: (1) measurements of aerodynamic loads acting on the aircraft models without the effects of mechanical supporting devices; and (2) the study of base pressure. This paper traces the progress of MSBS for wind tunnels in the Commonwealth of Independent States (CIS). The paper describes electromagnetic configuration, position sensing, and control and calibration systems of two wind tunnel MSBS existing in the CIS. The features of high-angle-of-attack control and roll control are discussed. The results of preliminary experiments on high-angle-of-attack and roll controls, digital control, and aerodynamic testing are also presented.

Kuzin, A. V.↗
NASA NTRS1991

On dipolarization and its relation to the substorm current wedge

The near-earth properties of magnetospheric substorms are investigated using the Hesse and Birn (1991) self-consistent 3D MHD model of magnetotail activity. The simulation shows that an increase of Bz, a decrease of the cross-tail current, and an increase of region-1 field-aligned currents occurs roughly simultaneously, consistent with the empirical picture described by McPherron et al. (1973). It was also found that the region where the cross-tail current is reduced and diverted is located tailward from the dipolarization region. The results indicate that the apparent tailward propagation of the dipolarization effects does not support an earlier suggestion that the underlying process is initiated further earthward.

Hesse, Michael↗
NASA NTRS1992

Domain-specific functional software testing: A progress report

Software Engineering is a knowledge intensive activity that involves defining, designing, developing, and maintaining software systems. In order to build effective systems to support Software Engineering activities, Artificial Intelligence techniques are needed. The application of Artificial Intelligence technology to Software Engineering is called Knowledge-based Software Engineering (KBSE). The goal of KBSE is to change the software life cycle such that software maintenance and evolution occur by modifying the specifications and then rederiving the implementation rather than by directly modifying the implementation. The use of domain knowledge in developing KBSE systems is crucial. Our work is mainly related to one area of KBSE that is called automatic specification acquisition. One example is the WATSON prototype on which our current work is based. WATSON is an automatic programming system for formalizing specifications for telephone switching software mainly restricted to POTS, i.e., plain old telephone service. Our current approach differentiates itself from other approaches in two antagonistic ways. On the one hand, we address a large and complex real-world problem instead of a 'toy domain' as in many research prototypes. On the other hand, to allow such scaling, we had to relax the ambitious goal of complete automatic programming, to the easier task of automatic testing.

Nonnenmann, Uwe↗
NASA NTRS1993

In search of ice-stream sticky spots

The form drag of large bedrock bumps sticking into the base of an ice stream can produce effective 'sticky spots' supporting large basal shear stress. Bedrock regions surrounded by lubricating till at the same topographic level can cause sticky spots, but tend to collect lubricating water and thus are unlikely to support a shear stress of more than a few tenths of a bar unless they contain abundant large bumps. Raised regions on the ice-air surface also can cause moderate increases in the shear stress supported on the bed beneath. Surveys of large-scale bedrock roughness, strain grids across the margins of ice-surface highs, and possibly, water-pressure measurements in regions of thin or zero till would help identify and characterize sticky spots.

Alley, Richard B.↗
NASA NTRS1993

Well-resolved observations by ISEE 2 of ion dispersion in the magnetospheric cusp

During a prolonged period of southward IMF on October 30, 1978, the ISEE 2 spacecraft observed an unusually prolonged and distinct region of ion energy-time dispersion in the dayside dawn magnetosphere. Observed plasma features included the (1) presence of magnetosheath electrons and initial absence of magnetosheath ions and (2) subsequent arrival and energy-time dispersion of magnetosheath ions as the spacecraft transited outbound from 6.03 to 7.66 Earth radii. We use ISEE 2 ion measurements to illustrate these dispersive time-of-flight effects and to support our interpretation of a location in the north magnetospheric cusp. Ion energy dispersion persists for about 35 min and includes well-resolved sequences of magnetosheath and magnetospheric ion distributions. We focus primarily on observations and time-of-flight analysis of ions from the magnetosheath, which are observed simultaneously entering and exiting the cusp at different energies. We discuss the observational support and shortcomings of various ion injection locations and durations and conclude that quasi-steady merging at the dayside magnetopause, with ion dispersion caused by spacecraft motion away from the last closed field line, is the most likely scenario.

Phillips, J. L.↗
NASA NTRS1930

Strength in Shear of the Thin Curved Sheets of Alclad

This note is on an investigation made to obtain information on the strength of thin curved sheets of Alclad in shear. Designers may utilize this material as a strength member as well as for a covering for the wings and fuselages. A reduction may then be made in the size of the internal strength members. These experiments were undertaken with the object of securing the maximum value from the metal in this respect. The point at which buckling occurs is of primary importance. The buckling shear of a curved thin plate was determined mathematically and also experimentally. The following formula was obtained mathematically: s=K E t/r in which s is the unit shear, K is a constant, E is the modulus of elasticity, t is the thickness of the material, and r is the radius of curvature. The value of K as determined by the experiments was found to be .075. This formula applies only when s is within the elastic limit of the material. The breaking point of the material was obtained in most of the tests as a matter of information and the results are included in this report. The effect of the supporting ribs was determined by varying the number used.

Smith, George Michael↗
NASA NTRS1993

Stochastic dynamics of baroclinic waves

The maintenance of variance and attendant heat flux in linear, forced dissipative baroclinic shear flows subject to stochastic excitation is examined. The baroclinic problem, is intrinsically nonnormal and its stochastic dynamics is found to differ significantly from the more familiar stochastic dynamics of normal systems. When the shear is sufficiently great in comparison to dissipative effects, stochastic excitation supports highly enhanced variance levels in these nonnormal systems compared to variance levels supproted by the same forcing and dissipation in related normal systems. The eddy variance and associated heat flux are found to arise in response to transient amplification of a subset of forcing functions that obtain energy from the mean flow and project this energy on a distinct subset of response functions (EOFs) that are in turn distinct from the set of normal modes of the system. A method for obtaining the dominant forcing and response functions as well as the distribution of heat flux for a given flow is described.

Farrell, Brian F.↗
NASA NTRS1995

Alternate physical formats for storing data in HDF

Since its inception HDF has evolved to meet new demands by the scientific community to support new kinds of data and data structures, larger data sets, and larger numbers of data sets. The first generation of HDF supported simple objects and simple storage schemes. These objects were used to build more complex objects such as raster images and scientific data sets. The second generation of HDF provided alternate methods of storing data elements, making it possible to do such things as store extendible objects with in HDF, to store data externally from HDF files, and support data compression effectively. As we look to the next generation of HDF, we are considering fundamental changes to HDF, including a redefinition of the basic HDF object from a simple object to a more general, higher-level scientific data object that has certain characteristics, such as dimensionality, a more general atomic number type, and attributes. These changes suggest corresponding changes to the HDF file format itself.

Folk, Mike↗
NASA NTRS1993

The Stimulus Movement Effect: Allocation of Attention or Artifact?

In previous reports, including one by the author, learning has been shown to benefit by having discriminanda move rather than remain stationary. This stimulus movement effect might be attributed to several theoretical mechanisms, including attention, topological memory, and exposure duration. The series of experiments reported in this article was designed to Contrast these potential explanatory factors. Ten rhesus monkeys (Macaca mulatta) were tested on a variety of computerized tasks in which the stimuli remained stationary, flashed, or moved at systematically varied speeds. Performance was significantly best when the sample stimulus moved quickly and was poorest when the stimulus remained stationary. Further analysis of these data and other previously published data revealed that the distribution of the stimulus movement effect across trials supported an attention allocation interpretation.

Washburn, David A.↗
NASA NTRS1998

Buckling and Damage Resistance of Transversely-Loaded Composite Shells

Experimental and numerical work was conducted to better understand composite shell response to transverse loadings which simulate damage-causing impact events. The quasi-static, centered, transverse loading response of laminated graphite/epoxy shells in a [+/-45(sub n)/O(sub n)](sub s) layup having geometric characteristics of a commercial fuselage are studied. The singly-curved composite shell structures are hinged along the straight circumferential edges and are either free or simply supported along the curved axial edges. Key components of the shell response are response instabilities due to limit-point and/or bifurcation buckling. Experimentally, deflection-controlled shell response is characterized via load-deflection data, deformation-shape evolutions, and the resulting damage state. Finite element models are used to study the kinematically nonlinear shell response, including bifurcation, limit-points, and postbuckling. A novel technique is developed for evaluating bifurcation from nonlinear prebuckling states utilizing asymmetric spatial discretization to introduce numerical perturbations. Advantages of the asymmetric meshing technique (AMT) over traditional techniques include efficiency, robustness, ease of application, and solution of the actual (not modified) problems. The AMT is validated by comparison to traditional numerical analysis of a benchmark problem and verified by comparison to experimental data. Applying the technique, bifurcation in a benchmark shell-buckling problem is correctly identified. Excellent agreement between the numerical and experimental results are obtained for a number of composite shells although predictive capability decreases for stiffer (thicker) specimens which is attributed to compliance of the test fixture. Restraining the axial edge (simple support) has the effect of creating a more complex response which involves unstable bifurcation, limit-point buckling, and dynamic collapse. Such shells were noted to bifurcate into asymmetric deformation modes but were undamaged during testing. Shells in this study which were damaged were not observed to bifurcate. Thus, a direct link between bifurcation and atypical damage could not be established although the mechanism (bifurcation) was identified. Recommendations for further work in these related areas are provided and include extensions of the AMT to other shell geometries and structural problems.

Wardle, Brian L.↗