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All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Modal model reduction or model reduction of large space structures in frequency domain

Large space structures are characterized by a large number of modes, grouped frequencies, and small inherent damping. Model reduction techniques in time domain may not be effective due to small damping. The model truncation method is generally used. This method can not solve the problem of grouped frequencies, and will lose all the information about the higher order modes. A new method developed in this paper, which tries to minimize the error of interested transfer functions, makes use of all the information of the original system, and achieves improvement not only from a smaller error of transfer functions but also from better frequency distribution.

Mifang, Ruan↗
NASA NTRS1972

Phase transformations and exsolution in lunar and terrestrial calcic plagioclases.

A coarse domain structure had been discovered in plagioclase in an electron microscopic study of lunar rocks reported by Christie et al. (1971). The domain structures are described in more detail, and their significance in the light of current knowledge concerning the crystal structures of the plagioclases is discussed. An exsolution texture is also described. On the basis of the scale of exsolution it appears that the Apollo 11 and 12 basalts examined cooled more rapidly than the Apollo 14 basalt, which in turn cooled more rapidly than the Stillwater rock.

Heuer, A. H.↗
NASA NTRS1985

Geometry of miocene extensional deformation, lower Colorado River Region, Southeastern California and Southwestern Arizona: Evidence for the presence of a regional low-angle normal fault

The geometry of Miocene extensional deformation, which changes along a 120 km-long, northeast-trending transect from the southestern Chocolate Mountains, southeastern California, to the Trigo and southern Dome Rock Mountains, southwestern Arizona is discussed. Based upon regional differences in the structural response to extension and estimated extensional strain, the transet can be divided into three northwesterly-trending structural domains. From southwest to northeast, these domains are: (1) southestern Chocolate-southernmost Trigo Mountains; (2) central to northern Trigo Mountains; and (3) Trigo Peaks-southern Dome Rock Mountains. All structures formed during the deformation are brittle in style; fault rocks are composed of gouge, cohesive gouge, and local microbreccia. In each structural domain, exposed lithologic units are composed of Mesozoic crystalline rocks unconformably overlain by Oligocene to Early Miocene volcanic and minor interbedded sedimentary rocks. Breccia, conglomerate, and sandstone deposited synchronously with regional extension locally overlie the volcanic rocks. Extensional deformation largely postdated the main phase of volcanic activity, but rare rhyolitic tuff and flows interbedded with the syndeformational clastic rocks suggest that deformation began during the waning stages of valcanism. K-Ar isotopic ages indicate that deformation occurred in Miocene time, between about 22 and m.y. ago.

Tosdal, R. M.↗
NASA NTRS1993

Magnetic Force Microscopy Images of Magnetic Garnet With Thin-Film Magnetic Tip

We present magnetic force microscopy images of YGdTmGa/YSmTmGa magnetic garnet, usinga thin Fe film deposited on Si_3N_5 tips. We have found correlations between the topography andthe magnetic domain structure. We have observed the domain wall contrast with a iron thin-film tip. We report on domain wall imaging of garnet with magnetic force microscopy.

Wadas, A.↗
NASA NTRS2003

Physical and Structural Studies on the Cryo-cooling of Insulin Crystals

Reflection profiles were analyzed from microgravity-(mg) and earth-grown insulin crystals to measure mosaicity (h) and to reveal mosaic domain structure and composition. The effects of cryocooling on single and multi-domain crystals were compared. The effects of cryocooling on insulin structure were also re-examined. Microgravity crystals were larger, more homogeneous, and more perfect than earth crystals. Several mg crystals contained primarily a single mosaic domain with havg of 0.005deg. The earth crystals varied in quality and all contained multiple domains with havg of 0.031deg. Cryocooling caused a 43-fold increase in h for mg crystals (havg=0.217deg) and an %fold increase for earth crystals (havg=0.246deg). These results indicate that very well-ordered crystals are not completely protected from the stresses associated with cryocooling, especially when structural perturbations occur. However, there were differences in the reflection profiles. For multi-mosaic domain crystals, each domain individually broadened and separated from the other domains upon cryo-cooling. Cryo-cooling did not cause an increase in the number of domains. A crystal composed of a single domain retained this domain structure and the reflection profiles simply broadened. Therefore, an improved signal-to-noise ratio for each reflection was measured from cryo-cooled single domain crystals relative to cryo-cooled multi-domain crystals. This improved signal, along with the increase in crystal size, facilitated the measurement of the weaker high- resolution reflections. The observed broadening of reflection profiles indicates increased variation in unit cell dimensions which may be linked to cryo-cooling-associated structural changes and disorder.

Lovelace, J.↗
NASA NTRS1981

A new view of Baryon symmetric cosmology based on grand unified theories

Within the framework of grand unified theories, it is shown how spontaneous CP violation leads to a domain structure in the universe with the domains evolving into separate regions of matter and antimatter excesses. Subsequent to exponential horizon growth, this can result in a universe of matter galaxies and antimatter galaxies. Various astrophysical data appear to favor this form of big bang cosmology. Future direct tests for cosmologically significant antimatter are discussed.

Stecker, F. W.↗
NASA NTRS2018

Direct Observation of Electron Distributions Inside Millisecond Duration Electron Holes

Despite the importance of millisecond duration spatial structures [chorus wave nonlinearity or time domain structures (TDS)] to plasma dynamics, there have been no direct observations of the generation and interaction of these waves and TDS with electrons at the millisecond timescale required for their understanding. Through superposition of 0.195 ms Magnetospheric Multiscale Satellite electron measurements inside 37 superposed, millisecond duration electron holes, the first observations of electron spectra and pitch angle distributions on a submillisecond timescale have been obtained. They show that keV electrons inside the superposed electron hole are accelerated by several hundred volts and that the spectrum of electrons inside the electron hole contain several maxima and minima that are explained by a model of electron energy changes on entering the holes. We report the first observation of trapped electrons inside the TDS, in accordance with the theoretical requirement that such electrons must be present in order to form the phase space holes. Mechanisms of electron acceleration by electron holes (through perpendicular energy gain as the TDS moves into a converging magnetic field) and scattering (due to the perpendicular electric field) are discussed.

Mozer, F. S.↗
NASA NTRS1979

Globally baryon symmetric cosmology, GUT spontaneous symmetry breaking, and the structure of the universe

Grand unified theories (GUT) such as SU(5), with spontaneous symmetry breaking, can lead more naturally to a globally baryon symmetric big bang cosmology with a domain structure than to a totally asymmetric cosmology. The symmetry is broken at random in causally independent domains, favoring neither a baryon nor an antibaryon excess on a universal scale. Because of the additional freedom in the high-energy physics allowed by such GUT gauge theories, new observational tests may be possible. Arguments in favor of this cosmology and various observational tests are discussed.

Stecker, F. W.↗
NASA NTRS1994

Wing-Body Aeroelasticity Using Finite-Difference Fluid/Finite-Element Structural Equations on Parallel Computers

In recent years significant advances have been made for parallel computers in both hardware and software. Now parallel computers have become viable tools in computational mechanics. Many application codes developed on conventional computers have been modified to benefit from parallel computers. Significant speedups in some areas have been achieved by parallel computations. For single-discipline use of both fluid dynamics and structural dynamics, computations have been made on wing-body configurations using parallel computers. However, only a limited amount of work has been completed in combining these two disciplines for multidisciplinary applications. The prime reason is the increased level of complication associated with a multidisciplinary approach. In this work, procedures to compute aeroelasticity on parallel computers using direct coupling of fluid and structural equations will be investigated for wing-body configurations. The parallel computer selected for computations is an Intel iPSC/860 computer which is a distributed-memory, multiple-instruction, multiple data (MIMD) computer with 128 processors. In this study, the computational efficiency issues of parallel integration of both fluid and structural equations will be investigated in detail. The fluid and structural domains will be modeled using finite-difference and finite-element approaches, respectively. Results from the parallel computer will be compared with those from the conventional computers using a single processor. This study will provide an efficient computational tool for the aeroelastic analysis of wing-body structures on MIMD type parallel computers.

Byun, Chansup↗
NASA NTRS1993

Evolution of EF-hand calcium-modulated proteins. IV. Exon shuffling did not determine the domain compositions of EF-hand proteins

In the previous three reports in this series we demonstrated that the EF-hand family of proteins evolved by a complex pattern of gene duplication, transposition, and splicing. The dendrograms based on exon sequences are nearly identical to those based on protein sequences for troponin C, the essential light chain myosin, the regulatory light chain, and calpain. This validates both the computational methods and the dendrograms for these subfamilies. The proposal of congruence for calmodulin, troponin C, essential light chain, and regulatory light chain was confirmed. There are, however, significant differences in the calmodulin dendrograms computed from DNA and from protein sequences. In this study we find that introns are distributed throughout the EF-hand domain and the interdomain regions. Further, dendrograms based on intron type and distribution bear little resemblance to those based on protein or on DNA sequences. We conclude that introns are inserted, and probably deleted, with relatively high frequency. Further, in the EF-hand family exons do not correspond to structural domains and exon shuffling played little if any role in the evolution of this widely distributed homolog family. Calmodulin has had a turbulent evolution. Its dendrograms based on protein sequence, exon sequence, 3'-tail sequence, intron sequences, and intron positions all show significant differences.

NASA Discipline Exobiology↗
NASA NTRS1972

Ordering Effects in NbC and TaC

By means of transmission electron microscopy and electron diffraction, evidence has been obtained for the existence of long range carbon atom ordering in single-crystal niobium carbide that has a carbon-to-metal ratio close to the integral composition Nb6C5. The ordering, which gives rise to superlattice and domain structures similar to those observed in V6C5, appears, however, only in samples that have been cooled slowly through the order-disorder temperature of 1025 C. In TaC of similar composition, the ordering, although present, remains very imperfect even after the crystals are subjected to the same thermal treatment. The results are interpreted in terms of the electronic structure of the transition metal carbides as it is currently understood, and their relevance to the mechanical properties of NbC and TaC are discussed.

Venables, J. D.↗
NASA NTRS1976

Study report on laser storage and retrieval of image data

The theoretical foundation is presented for a system of real-time nonphotographic and nonmagnetic digital laser storage and retrieval of image data. The system utilizes diffraction-limited laser focusing upon thin metal films, melting elementary holes in the metal films in laser focus. The metal films are encapsulated in rotating flexible mylar discs which act as the permanent storage carries. Equal sized holes encompass two dimensional digital ensembles of information bits which are time-sequentially (bit by bit) stored and retrieved. The bits possess the smallest possible size, defined by the Rayleigh criterion of coherent physical optics. Space and time invariant reflective read-out of laser discs with a small laser, provides access to the stored digital information. By eliminating photographic and magnetic data processing, which characterize the previous state of the art, photographic grain, diffusion, and gamma-distortion do not exist. Similarly, magnetic domain structures, magnetic gaps, and magnetic read-out are absent with a digital laser disc system.

Becker, C. H.↗
NASA NTRS1980

Soft CP violation and the global matter-antimatter symmetry of the universe

Scenarios for baryon production are considered within the context of SU(5) and SO(10) grand unified theories where CP violation arises spontaneously. The spontaneous CP symmetry breaking then results in a matter-antimatter domain structure in the universe. Two possible, distinct types of theories of soft CP violation are defined. In the first type the CP nonconservation originates only from the breaking of SU(2) sub L X U(1) symmetry, and in the second type, even at the unification temperature scale, CP violation can emerge as a result of symmetry breaking by the vacuum expectation values of the superheavy Higgs sector scalars.

Senjanovic, G.↗
NASA NTRS1979

Synthesis of regional crust and upper-mantle structure from seismic and gravity data

Available seismic and ground based gravity data are combined to infer the three dimensional crust and upper mantle structure in selected regions. This synthesis and interpretation proceeds from large-scale average models suitable for early comparison with high-altitude satellite potential field data to more detailed delineation of structural boundaries and other variations that may be significant in natural resource assessment. Seismic and ground based gravity data are the primary focal point, but other relevant information (e.g. magnetic field, heat flow, Landsat imagery, geodetic leveling, and natural resources maps) is used to constrain the structure inferred and to assist in defining structural domains and boundaries. The seismic data consists of regional refraction lines, limited reflection coverage, surface wave dispersion, teleseismic P and S wave delay times, anelastic absorption, and regional seismicity patterns. The gravity data base consists of available point gravity determinations for the areas considered.

Alexander, S. S.↗
NASA NTRS1981

Texas Symposium on Relativistic Astrophysics, 10th, Baltimore, MD, December 15-19, 1980, Proceedings

The present conference on relativistic astrophysics begins with consideration of such topics in the cosmology of the early universe as the implications of the neutrino rest mass, relic neutrino clustering, and the possibility of a matter-antimatter domain structure in the universe, and proceeds to the broader cosmological questions of the distances of extragalactic objects, the mass of the universe, and the dynamics of superclusters. Also considered are the cosmic microwave background, relativistic jet production and propagation in active galaxies, gravitational lenses, positron annihilation radiation from the galactic center region, supernova models, and the acceleration of cosmic rays by shock waves. Summaries are presented in closing, on workshops concerning such topics as gravitational radiation detectors, the UV cosmic ray background, pulsars, supernovae, active galaxies, and quasars.

Ramaty, R.↗
NASA NTRS1984

On the nature of the baryon asymmetry

Whether the baryon asymmetry in the universe is a locally varying or universally fixed number is examined with focus on the existence of a possible matter antimatter domain structure in the universe arising from a GUT with spontaneous CP symmetry breaking. Theoretical considerations and observational data and astrophysical tests relating to this fundamental question are reviewed.

Stecker, F. W.↗