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At least 343 records · Page 19
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NASA NTRS1992

JTEC panel report on machine translation in Japan

The goal of this report is to provide an overview of the state of the art of machine translation (MT) in Japan and to provide a comparison between Japanese and Western technology in this area. The term 'machine translation' as used here, includes both the science and technology required for automating the translation of text from one human language to another. Machine translation is viewed in Japan as an important strategic technology that is expected to play a key role in Japan's increasing participation in the world economy. MT is seen in Japan as important both for assimilating information into Japanese as well as for disseminating Japanese information throughout the world. Most of the MT systems now available in Japan are transfer-based systems. The majority of them exploit a case-frame representation of the source text as the basis of the transfer process. There is a gradual movement toward the use of deeper semantic representations, and some groups are beginning to look at interlingua-based systems.

Carbonell, Jaime↗
NASA NTRS1994

Homogeneous turbulence subjected to mean flow with elliptic streamlines

Direct numerical simulations are performed for homogeneous turbulence with a mean flow having elliptic streamlines. This flow combines the effects of rotation and strain on the turbulence. Qualitative comparisons are made with linear theory for cases with high Rossby number. The nonlinear transfer process is monitored using a generalized skewness. In general, rotation turns off the nonlinear cascade; however, for moderate ellipticities and rotation rates the nonlinear cascade is turned off and then reestablished. Turbulence statistics of interest in turbulence modeling are calculated, including full Reynolds stress budgets.

Blaisdell, G. A.↗
NASA NTRS1994

D/H ratios and H2O contents of mantle-derived amphibole megacrysts from Dish Hill, California

D/H ratios are, in principle, useful in characterizing reservoirs of mantle hydrogen and as tracers of volatile transfer processes in Earth's interior. In practice, however, interpretation of isotopic measurements on mantle derived H is complicated by surface processes such as contamination and degassing which may alter the primary D/H ratio. Although there are indications that water associated with subduction zones and certain chemically enriched basalts is enriched in D relative to 'typical' upper mantle water, the extent of isotopic heterogeneity of mantle H remains uncertain. Kaersutitic amphibole megacrysts in alkaline basalts are one of the most widespread sources of mantle water and are therefore potentially useful for large-scale regional studies of D/H variation. However, D/H ratios of these amphiboles vary widely (from plus 8 to minus 113 percent), even in samples from the same locality, so that this potential has yet to be realized. In order to investigate the origin of this variability, and to explore the possibility that primary mantle D/H ratios may be deduced from these amphiboles, we analyzed the D/H ratios and chemical compositions of a suite of 17 kaersutitic amphiboles from Dish Hill, California. This work contrasts with previous studies in which sampling is widespread, but representatives from any given locality are few. Samples were collected from a restricted area on the southern flank of the volcanic center and are associated with the basal volcanic breccia. Fourteen of the samples were large single crystals or crystal fragments (megacrysts, 0.4 to 30 grams), believed to derive from pegmatitic veins crystallized from melts in the mantle. Two were coarse-grained intergrowths of amphibole with olivine and spinel, and one was a thin (2 mm) selvage on a peridotite xenolith.

Bell, David R.↗
NASA NTRS1995

Proton affinity determinations and proton-bound dimer structure indications in C2 to C15, (alpha),(omega)-alkyldiamines

The 'kinetic method' was used to determine the proton affinity (PA) of a,coalkyldiamines from collision induced dissociation (CID) studies of protonated heterodimers. These PA values were consistently lower than those reported in the proton affinity scale. The apparent discrepancy was rationalized in terms of differences in the conformation of the protonated diamine monomers. The minimum energy species, formed by equilibrium proton transfer processes, have a cyclic conformation and the ion charge is shared by both amino-groups which are bridged by the proton. On the other hand, the species formed through dissociation of protonated dimers have a linear structure and the charge is localized on one of the amino-groups. Thus, the difference in the PA values obtained by both methods is a measure of the additional stability acquired by the protonated diamines through cyclization and charge delocalization. The major collision dissociation pathway of the protonated diamine monomers involved elimination of an ammonia moiety. Other reactions observed included loss of the second amino-group and several other bond cleavages. CID of the protonated dimers involved primarily formation of a protonated monomer through cleavage of the weaker hydrogen bond and subsequently loss of ammonia at higher collision energies. As observed from the CID studies, doubly charged ions were also formed from the diamines under conditions of the electrospray ionization.

Karpas, Z.↗
NASA NTRS1994

Transport out of the lower stratospheric Arctic vortex by Rossby wave breaking

The fine-scale structure in lower stratospheric tracer transport during the period of the two Arctic Airborne Stratospheric Expeditions (January and February 1989; December 1991 to March 1992) is investigated using contour advection with surgery calculations. These calculations show that Rossby wave breaking is an ongoing occurrence during these periods and that air is ejected from the polar vortex in the form of long filamentary structures. There is good qualitative agreement between these filaments and measurements of chemical tracers taken aboard the NASA ER-2 aircraft. The ejected air generally remains filamentary and is stretched and mixed with midlatitude air as it is wrapped around the vortex. This process transfers vortex air into midlatitudes and also produces a narrow region of fine-scale filaments surrounding the polar vortex. Among other things, this makes it difficult to define a vortex edge. The calculations also show that strong stirring can occur inside as well as outside the vortex.

Waugh, D. W.↗
NASA NTRS1992

Thermally-included convection in confined air

This study includes the development and design of a space experiment for the investigation of the thermally-induced convection heat transfer process in an enclosure containing air. Various features of the design including the optical method used in the fluid temperature measurement are presented and discussed. A series of ground experiments were carried out in support of the in-space experiment design. Their results are discussed briefly and compared with numerical predictions.

Crocker, D. S.↗
NASA NTRS1995

Spectroscopy and excitation dynamics of the trivalent lanthanides Tm(3+) and Ho(3+) in LiYF4

A detailed study of the spectroscopy and excitation dynamics Tm3+ and Ho3+ in yttrium lithium fluoride, LiYF4 (YLF), has been done. Absorption spectroscopy is utilized in the Judd-Ofelt theory to determine radiative transition rates of spontaneous emission. Luminescence spectroscopy is studied under cw diode laser excitation at 785nm. The effect of dopant ion concentration and excitation power on the observed luminescence are considered in these measurements. An analysis of these measurements have been used to determine channels of energy transfer between Tm3+ and Ho3+ ions. The temporal response of Tm and Ho in singly and co-doped YLF to pulsed laser excitation with a Ti:Al2O3 laser and a CoMgF2 laser turned to various wavelengths have also been studied. The energy transfer mechanisms of cross relaxation, upconversion, and resonant energy transfer between Tm3+ and Ho3+ ions have been modeled, and the model parameters extracted by a fitting procedure to the measured temporal response curves. Rate equation approaches to modeling are presented that result in predictions of rate constants for energy transfer processes, as well as more conventional approaches to modeling such as the Forster-Dexter models, which give the interaction strengths in terms of microscopic interaction parameters.

Walsh, Brian M.↗
NASA NTRS1995

Analysis of solar spectral irradiance measurements from the SBUV/2-series and the SSBUV instruments

The principle purpose of this work is to use yearly flights of the Shuttle SBUV/w (SSBUV) instrument to maintain the long-term calibration of the NOAA-11 SBUV/2 instrument. During this period of performance we have begun updating the NOAA-11 SBUV/2 characterization and have further refined the SSBUV calibration, both steps which must be completed before the long-term calibration of the SBUV/2 can be completed. We have also performed a first attempt of the calibration transfer, demonstrating the viability of the transfer process.

Cebula, Richard P.↗
NASA NTRS1995

Investigation of biomass burning and aerosol loading and transport in South America utilizing geostationary satellites

This study attempts to assess the extent of burning and associated aerosol transport regimes in South America and the South Atlantic using geostationary satellite observations, in order to explore the possible roles of biomass burning in climate change and more directly in atmospheric chemistry and radiative transfer processes. Modeling and analysis efforts have suggested that the direct and indirect radiative effects of aerosols from biomass burning may play a major role in the radiative balance of the earth and are an important factor in climate change calculations. One of the most active regions of biomass burning is located in South America, associated with deforestation in the selva (forest), grassland management, and other agricultural practices. As part of the NASA Aerosol Interdisciplinary Program, we are utilizing GOES-7 (1988) and GOES-8 (1995) visible and multispectral infrared data (4, 11, and 12 microns) to document daily biomass burning activity in South America and to distinguish smoke/aerosols from other multi-level clouds and low-level moisture. This study catalogues the areal extent and transport of smoke/aerosols throughout the region and over the Atlantic Ocean for the 1988 (July-September) and 1995 (June-October) biomass burning seasons. The smoke/haze cover estimates are compared to the locations of fires to determine the source and verify the haze is actually associated with biomass burning activities. The temporal resolution of the GOES data (half-hourly in South America) makes it possible to determine the prevailing circulation and transport of aerosols by considering a series of visible and infrared images and tracking the motion of smoke, haze and adjacent clouds. The study area extends from 40 to 70 deg W and 0 to 40 deg S with aerosol coverage extending over the Atlantic Ocean when necessary. Fire activity is estimated with the GOES Automated Biomass Burning Algorithm (ABBA). To date, our efforts have focused on GOES-7 and GOES-8 ABBA development, algorithm development for aerosol monitoring, data acquisition and archiving, and participation in the SCAR-C and SCAR-B field programs which have provided valuable information for algorithm testing and validation. Implementation of the initial version of the GEOS-8 ABBA on case studies in North, Central, and South America has demonstrated the improved capability for monitoring diurnal fire activity and smoke/aerosol transport with the GOES-8 throughout the Western Hemisphere.

Menzel, Paul↗
NASA NTRS1995

Troika partnership model for licensing NASA-LaRC technologies

The Technology Applications (TAG) Group at NASA Langley Research Center has currently more than 100 technologies that are ripe for commercialization. These technologies are categorized by various sectors including: Energy and the Environment; Materials and Structures; Manufacturing; Information and Communications; Transportation, and Medical/Sensor/ Instrumentation. A requirement that TAG has placed on all technologies ready for licensing is that there will be some university involvement in the technology transfer or knowledge transfer process. This model involves the troika of government (LaRC), industry and university. A number of variations on the Troika Partnership Model (TPM) were developed as a part of this ASEE Fellowship. Furthermore, five technologies were identified - three of which industrial interests have been matched: LaRC-SI, a thermoplastic that can be used as a coating; Variable Geometry Truss Manipulator Arm that can be used for nuclear waste clean -up and as scaffolding; and ADAPT (Approach to Data Management, Archive Protection, and Transmission) is a technology that could be used for a variety of multi-tasking operations over the Internet. The aim of this work was to initiate a Space Act Agreement (SAA) for at least one of these technologies using one of the options of the TPM. A preliminary partnership agreement using the SAA is currently being negotiated with NASA-LaRC, VPI and Virginia Power for the LaRC-SI thermoplastic that will be used as a coating.

Maclin, Arlene P.↗
NASA NTRS1996

Ocean observations with EOS/MODIS: Algorithm development and post launch studies

Several significant accomplishments were made during the present reporting period. We have completed our basic study of using the 1.38 micron MODIS band for removal of the effects of thin cirrus clouds and stratospheric aerosol. The results suggest that it should be possible to correct imagery for thin cirrus clouds with optical thicknesses as large as 0.5 to 1.0. We have also acquired reflectance data for oceanic whitecaps during a cruise on the RV Malcolm Baldrige in the Gulf of Mexico. The reflectance spectrum of whitecaps was found to be similar to that for breaking waves in the surf zone measured by Frouin, Schwindling and Deschamps. We installed a CIMEL sun photometer at Fort Jefferson on the Dry Tortugas off Key West in the Gulf of Mexico. The instrument has yielded a continuous stream of data since February. It shows that the aerosol optical thickness at 669 nm is often less than 0.1 in winter. This suggests that the Southern Gulf of Mexico will be an excellent winter site for vicarious calibration. In addition, we completed a study of the effect of vicarious calibration, i.e., the accuracy with which the radiance at the top of the atmosphere (TOA) can be predicted from measurement of the sky radiance at the bottom of the atmosphere (BOA). The results suggest that the neglect of polarization in the aerosol optical property inversion algorithm and in the prediction code for the TOA radiances is the largest error associated with the radiative transfer process. Overall, the study showed that the accuracy of the TOA radiance prediction is now limited by the racliometric calibration error in the sky radiometer. Finally, considerable coccolith light scattering data were obtained in the Gulf of Maine with a flow-through instrument, along with data relating to calcite concentration and the rate of calcite production.

Gordan, Howard R.↗
NASA NTRS1996

Analysis of Subgrid Eddy Diffusivity in Turbulence Using Direct Numerical Simulation Databases

Direct numerical simulation data in isotropic turbulence at Taylor-scale Reynolds number 90 are used to compute subgrid transfer and spectral eddy diffusivities for passive scalars at Schmidt numbers 1 and 1/8. The results are consistent with spectral transfer processes dominated by a local forward cascade in wavenumber space which is a consequence of moderately nonlocal interactions in the scalar fields. Data decompositions show that resolvable-subgrid interactions make (in general) substantially stronger contributions than fully-subgrid interactions to the eddy diffusivity, which has a non-negligible inverse cascade, or backscatter, component. The eddy diffusivity has a strong cusp at wavenumbers close to the cutoff value separating resolvable and subgrid ranges. At low wavenumbers the eddy diffusivity is generally small, but there the details depend on Schmidt number. The behavior of the subgrid turbulent Schmidt number (the ratio of effective eddy viscosity to eddy diffusivity) is observed to depend strongly on Schmidt number. In interpreting the results at a given spectral cutoff it is important to note that the spectrum of less diffusive scalars (of higher Schmidt number) has more high-wavenumber content.

Yeung, P. K.↗
NASA NTRS1995

Marketing NASA Langley Polymeric Materials

A marketing tool was created to expand the knowledge of LaRC developed polymeric materials, in order to facilitate the technology transfer process and increase technology commercialization awareness among a non-technical audience. The created brochure features four materials, LaRC-CP, LaRC-RP46, LaRC-SI, and LaRC-IA, and highlights their competitive strengths in potential commercial applications. Excellent opportunities exist in the $40 million per year microelectronics market and the $6 billion adhesives market. It is hoped that the created brochure will generate inquiries regarding the use of the above materials in markets such as these.

Flynn, Diane M.↗
NASA NTRS1997

Effects of Convection During the Photodeposition of Polydiacetylene Thin Films

In this work, we describe a preliminary investigation of buoyancy-driven heat transfer during the growth of thin films from solution following exposure to ultraviolet (UV) light. Irradiation of the growth cell occurs at various directions relative to gravitational acceleration. Through numerical computations, the steady-state flow and temperature profiles are simulated during the course of light exposure. Light-induced polymerization accompanies a heat transfer process through a fairly complicated recirculating flow pattern. A scaling analysis shows that buoyancy-driven velocities only reduce by a factor of 10 for gravity levels as low as 10(exp -2)g(sub 0). Paley et al. observe what appears to be gravitationally sensitive particle development and inclusion in thin films using a photodeposition process. From this study it is clear that production of homogeneous thin films would have to occur in the environment of a complicated flow pattern of recirculation with a nonuniform temperature distribution. Indeed, even when irradiation occurs from the top of the cell, the most stable stratified cell orientation, defects remain in our films due to the persistence of buoyancy-driven convection. To achieve homogeneity, minimal scattering centers, and possible molecular order, photodeposition of polymer films by UV light exposure must proceed in a reduced-convection environment. Fluid mechanics simulations are useful for establishing gravitational sensitivity to this recently discovered process (patent # 5,451,433) for preparing thin films having quite promising nonlinear optical characteristics.

Frazier, D. O.↗
NASA NTRS1997

Effects of Convection during the Photodeposition of Polydiacetylene Thin Films

In this work, we describe a preliminary investigation of buoyancy-driven heat transfer during the growth of thin films from solution following exposure to ultraviolet (UV) light. Irradiation of the growth cell occurs at various directions relative to gravitational acceleration. Through numerical computations, the steady-state flow and temperature profiles are simulated during the course of light exposure. Light-induced polymerization accompanies a heat transfer process through a fairly complicated recirculating flow pattern. A scaling analysis shows that buoyancy-driven velocities only reduce by a factor of 10 for gravity levels as low as 10(exp -2) g(sub 0). Paley et al. observe what appears to be gravitationally sensitive particle development and inclusion in thin films using a photodeposition process. From this study, it is clear that production of homogeneous thin films would have to occur in the environment of a complicated flow pattern of recirculation with a nonuniform temperature distribution. Indeed, even when irradiation occurs from the top of the cell, the most stable stratified cell orientation, defects remain in our films due to the persistence of buoyancy-driven convection. To achieve homogeneity, minimal scattering centers, and possible molecular order, photodeposition of polymer films by UV light exposure must proceed in a reduced-convection environment. Fluid mechanics simulations are useful for establishing gravitational sensitivity to this recently discovered process (patent # 5,451,433) for preparing thin films having quite promising nonlinear optical characteristics.

Frazier, D. O.↗
NASA NTRS1996

Ion Viscosity Mediated by Tangled Magnetic Fields: An Application to Black Hole Accretion Disks

We examine the viscosity associated with the shear stress exerted by ions in the presence of a tangled magnetic field. As an application, we consider the effect of this mechanism on the structure of black hole accretion disks. We do not attempt to include a self-consistent description of the magnetic field. Instead, we assume the existence of a tangled field with coherence length lambda(sub coh), which is the average distance between the magnetic 'kinks' that scatter the particles. For simplicity, we assume that the field is self-similar, and take lambda(sub coh) to be a fixed fraction zeta of the local disk height H. Ion viscosity in the presence of magnetic fields is generally taken to be the cross-field viscosity, wherein the effective mean free path is the ion Larmor radius lambda(sub L), which is much less than the ion-ion Coulomb mean free path A(sub ii) in hot accretion disks. However, we arrive at a formulation for a 'hybrid' viscosity in which the tangled magnetic field acts as an intermediary in the transfer of momentum between different layers in the shear flow. The hybrid viscosity greatly exceeds the standard cross-field viscosity when (lambda/lambda(sub L)) much greater than (lambda(sub L)/lambda(sub ii)), where lambda = ((lambda(sub ii)(sup -1) + lambda(sub (coh)(sup -1))(sup -1) is the effective mean free path for the ions. This inequality is well satisfied in hot accretion disks, which suggests that the ions may play a much larger role in the momentum transfer process in the presence of magnetic fields than was previously thought. The effect of the hybrid viscosity on the structure of a steady-state, two-temperature, quasi-Keplerian accretion disk is analyzed. The hybrid viscosity is influenced by the degree to which the magnetic field is tangled (represented by zeta = lambda(sub coh)), and also by the relative accretion rate M/M(sub E), where M(sub E) = L(sub E)/c(sup 2) and L(sub E) is the Eddington luminosity. We find that ion viscosity in the presence of magnetic fields (hybrid viscosity) can dominate over conventional magnetic viscosity for fields that are tangled on sufficiently small scales.

Subramanian, Prasad↗
NASA NTRS1998

From the Chemistry Lab to Licensing

This is a story of technology maturation and transfer, and licensing. It traces the history of the recently patented ion- exchange material (IEM) from the accidental discovery that this polymer, a battery separator of marginal performance, picked up copper from distilled water passing through corroded copper tubing in the laboratory, to a point where five organizations and one individual have applied for licenses to manufacture and market it or to use it in a wide variety of applications. This story discusses in detail the problems of converting an immature technology into a mature and eventually commercialized technology, without dedicated resources. Readers will develop an appreciation for how the obstacles to maturation and licensing of the technology were faced and overcome. The lessons learned will be discussed, with the hope of enhancing the technology transfer process.

Savino, Joseph M.↗
NASA NTRS1998

Droplet Combustion Experiment (DCE)

The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

Haggard, John B., Jr.↗