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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Global operators for delta functions - Extension to scattering states and the inclusion of spin

The paper presents an extension of the identities of Hiller, Sucher, and Feinberg for the evaluation of bound-state matrix elements of delta function operators, to scattering states. Attention is given to the technical difficulties encountered in the application of the scattering-state identities and how they can be overcome, including infrared singularities which arise if Coulomb forces are present and the velocity of the incident particle is small. In addition, both the scattering and bound-state identities are generalized to include spin-dependent contact interactions and spin-dependent Hamiltonians. Finally, it is stressed that the identities can be used to improve the accuracy of calculations of interest for diverse physical phenomena, ranging from positron annihilation to hyperfine structure.

Sucher, J.↗
NASA NTRS1979

Inclusion of unsteady aerodynamics in longitudinal parameter estimation from flight data

A simple vortex system, used to model unsteady aerodynamic effects into the rigid body longitudinal equations of motion of an aircraft, is described. The equations are used in the development of a parameter extraction algorithm. Use of the two parameter-estimation modes, one including and the other omitting unsteady aerodynamic modeling, is discussed as a means of estimating some acceleration derivatives. Computer generated data and flight data, used to demonstrate the use of the parameter-extraction algorithm are studied.

Queijo, M. J.↗
NASA NTRS1983

Computed tomographic analysis of meteorite inclusions

The feasibility of obtaining nondestructively a cross-sectional display of very dense heterogeneous rocky specimens, whether lunar, terrestrial or meteoritic, by using a fourth generation computed tomographic (CT) scanner, with modifications to the software only, is discussed. A description of the scanner, and of the experimental and analytical procedures is given. Using this technique, the interior of heterogeneous materials such as Allende can be probed nondestructively. The regions of material with high and low atomic numbers are displayed quickly; the object can then be cut to obtain for analysis just the areas of interest. A comparison of this technique with conventional industrial and medical techniques is made in terms of image resolution and density distribution display precision.

Arnold, J. R.↗
NASA NTRS1983

Inclusion of discrete-to-continuum coupling in multiphoton excitation and dissociation calculations

A nonperturbative approach to multiphoton excitation and dissociation of molecules is presented in which coupling to the continuum is treated explicitly. Transitions among continuum levels are not modeled directly, but something of their effect is represented by assuming that the continuum population density is so low as to be effectively zero at all times. Two trial applications are briefly discussed.

Zimmerman, I. H.↗
NASA NTRS1983

Ca-Al-rich chondrules and inclusions in ordinary chondrites

Ca-Al-rich objects, hitherto mostly found in carbonaceous chondrites, are shown to be widespread, albeit rare, constituents of type 3 ordinary chondrites. Widespread occurrence and textural similarities of Ca-Al-rich chondrules to common, Mg-Fe-rich chondrules suggest that they formed by related processes. It is suggested in this article that Ca-Al-rich chondrules were formed by total melting and crystallization of heterogeneous, submillimeter- to submillimeter-sized dustballs made up of mixtures of high-temperature, Ca-Al-rich and lower-temperature, Na-K-rich components.

Bischoff, A.↗
NASA NTRS1984

Influence of soft inclusions on the strength of wrought materials

The three dimensional soft particles (such as sulfides, silicates and voids) present in most materials are modelled by circular voids in sheet metal. Relationships are sought between the shape and orientation of a hole after rolling and testing in tension. Then, the effect of hole shape and size on mechanical properties is considered experimentally. The presence of voids has a negligible influence on the ultimate tensile stress of ductile materials based on the unperforated area because plastic flow neutralizes the stress intensification present in the elastic region. However, the shape and orientation of the defects are found to play an important role relative to strain at fracture. In certain engineering applications the strain at fracture is more important than the stress at fracture and in this sense the presence of voids are considered to influence the strength of a ductile material.

Pai, D. M.↗
NASA NTRS1985

Scaling violation in the fragmentation region of inclusive nucleon spektrum

Spectra of cosmic ray showers associated with hadrons of various energies from 5 to 80 TeV were investigated. Results could be interpreted as scaling violation in the fragmentation region of secondary particles generated in inelastic interactions of primary protons at the energy above 30 TeV.

Machavariani, S. K.↗
NASA NTRS1984

Phosphoran pyroxene and olivine in silicate inclusions in natural iron-carbon alloy, Disko Island, Greenland

A survey of literature data on the P contents of olivine, pyroxene, and garnet in mantle xenoliths and the bulk P contents of mantle xenoliths shows that available data is ambiguous as to whether mantle P is primarily contained in silicates or in phosphates, even though phosphates are rarely observed in mantle xenoliths. Garnet probably contains more of the mantle's P than olivine or pyroxene. Bulk P contents of mantle xenoliths vary significantly. Estimation of the primitive mantle P content from xenoliths requires interpretation of the partial melting and contamination histories of the xenoliths.

Goodrich, C. A.↗
NASA NTRS1985

Bocaiuva - A silicate-inclusion bearing iron meteorite related to the Eagle-Station pallasites

On the basis of its metal composition, the unique Bocaiuva meteorite, which consists of major metal having a high Ge/Ga ratio and minor silicates, appears distantly related to certain iron meteorites with similar Ge contents and similar Ge/Ga ratios. Detailed comparisons with six such irons shows, however, that none of these is closely related to Bocaiuva. The composition and texture of the Bocaiuva metal-silicate assembly indicate mixing in an impact event. It is suggested that the Eagle-Station pallasites were also formed by impact heating rather than by a long-lived internal heat source.

Malvin, D. J.↗