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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Direct imaging of electron transfer and its influence on superconducting pairing at FeSe/SrTiO 3 interface

The exact mechanism responsible for the significant enhancement of the superconducting transition temperature (T c ) of monolayer iron selenide (FeSe) films on SrTiO 3 (STO) over that of bulk FeSe is an open issue. We present the results of a coordinated study of electrical transport, low temperature electron energy-loss spectroscopy (EELS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements on FeSe/STO films of different thicknesses. HAADF-STEM imaging together with EELS mapping across the FeSe/STO interface shows direct evidence of electrons transferred from STO to the FeSe layer. The transferred electrons were found to accumulate within the first two atomic layers of the FeSe films near the STO substrate. An additional Se layer is also resolved to reside between the FeSe film and the TiO x -terminated STO substrate. Our transport results found that a positive backgate applied from STO is particularly effective in enhancing T c of the films while minimally changing the carrier density. Furthermore, this increase in T c is due to the positive backgate that “pulls” the transferred electrons in FeSe films closer to the interface and thus enhances their coupling to interfacial phonons and also the electron-electron interaction within FeSe films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1970

Snowfield mapping with K-band radar

Snow field mapping with K band radar imagery determining signal return difference with surrounding terrain, noting role of volume scattering and old snow structure

Macdonald, H. C.↗
NASA NTRS1972

Mineral exploration from high altitude imagery

Types of remote sensing which can best be done from spacecraft and types which can best be done from aircraft are discussed. Five geologically distinctive areas in northwestern Saudi Arabia were selected for detailed study. The areas were mapped as thoroughly as possible on each of several different types of imagery. The final objective was to identify those classes of geologic problems that can best be resolved using satellite data and then to identify areas where orbital imagery might profitably be used to extend existing knowledge, with emphasis placed on mineral exploration.

Blodget, H. W.↗
NASA NTRS1974

Use of ERTS data for a multidisciplinary analysis of Michigan resources

The author has identified the following significant results. The results of this investigation of ratioing simulated ERTS spectral bands and several non-ERTS bands (all collected by an airborne multispectral scanner) indicate that significant terrain information is available from band-ratio images. Ratio images, which are based on the relative spectral changes which occur from one band to another, are useful for enhancing differences and aiding the image interpreter in identifying and mapping the distribution of such terrain elements as seedling crops, all bare soil, organic soil, mineral soil, forest and woodlots, and marsh areas. In addition, the ratio technique may be useful for computer processing to obtain recognition images of large areas at lower costs than with statistical decision rules. The results of this study of ratio processing of aircraft MSS data will be useful for future processing and evaluation of ERTS-1 data for soil and landform studies. Additionally, the results of ratioing spectral bands other than those currently collected by ERTS-1 suggests that some other bands (particularly a thermal band) would be useful in future satellites.

Andersen, A. L.↗
NASA NTRS1975

Snowcover mapping by machine processing of Skylab and LANDSAT MSS data

Skylab and LANDSAT MSS data were analyzed using computer-aided analysis techniques (CAAT). Results indicated that the middle infrared wavelength bands of the Skylab S-192 scanner would allow effective discrimination between snowcover and water-droplet clouds, whereas the limited spectral response of the LANDSAT-1 or 2 scanners do not allow such spectral discrimination. Five spectral classes of snowcover were defined and mapped. These classes were found to be related to differences in the proportion of snow and forest cover in the individual resolution elements.

Bartolucci, L. A.↗
NASA NTRS1981

Geological terrain models

The initial phase of a program to determine the best interpretation strategy and sensor configuration for a radar remote sensing system for geologic applications is discussed. In this phase, terrain modeling and radar image simulation were used to perform parametric sensitivity studies. A relatively simple computer-generated terrain model is presented, and the data base, backscatter file, and transfer function for digital image simulation are described. Sets of images are presented that simulate the results obtained with an X-band radar from an altitude of 800 km and at three different terrain-illumination angles. The simulations include power maps, slant-range images, ground-range images, and ground-range images with statistical noise incorporated. It is concluded that digital image simulation and computer modeling provide cost-effective methods for evaluating terrain variations and sensor parameter changes, for predicting results, and for defining optimum sensor parameters.

Kaupp, V. H.↗
NASA NTRS1983

Spectrophotometry of the broad absorption-line QSO PHL 5200

Spectrophotometric observations of PHL 5200 conducted from 1974 to 1979 are presented. The semiforbidden C III 1909 and Mg II 2799 emission lines give an emission redshift of 1.981 + or - 0.002 using the peak of the profile. The semiforbidden C III 1909/C IV 1549 emission line ratio, after correction for absorption, is more than the average for normal quasars. In addition, the spectrum shows more structure between C IV 1549 emission and semiforbidden C III 1909 emission than in the case of normal quasars. The absorption profiles are investigated by using symmetrical logarithmic profiles to model the emission lines. The residual intensities at different wavelengths in the absorption troughs are employed to map optical depth as a function of velocity, assuming that the absorption region covers a small part of the sky as seen from the central source. Spectra from five observing seasons are compared, and no apparent changes in the C IV and Si IV absorption troughs are found.

Junkkarinen, V. T.↗
NASA NTRS1985

Study of the physical properties of crystalline rocks in the southeast Voronezh anteclise

The physical properties of rocks, in the crystalline mass of the Voronezh anteclise, were studied. The study of the physical properties of rocks is important for the improvement of geophysical methods for mapping crystalline rocks in the foundation and exploration of different geological objects which are associated with the crystalline foundation, covered by the sedimentary mantle. It is found that: (1) rocks in the crystalline foundation are very different in physical properties; (2) the physical properties are closely related to their substance composition and genesis; (3) petrographic properties give clues of rock afficiation to certain complexes; and (4) physical and magnetic properties should be examined by petrography, chemical and X-ray analysis.

Dmitriyevskiy, V. S.↗
NASA NTRS1988

Magnetohydrodynamic boundary conditions for global models

Boundary conditions in the ionosphere and the upstream solar wind are important in determining the dynamics of global magnetohydrodynamic models of the magnetosphere. It is generally recognized that the orientation of the magnetic field in the upstream solar wind strongly modulates the rate of energy input into the magnetosphere by magnetic reconnection. However, other aspects of the upstream boundary conditions may determine whether the reconnection occurs in a patchy manner, as in flux transfer events, or in a global manner, as in the Paschmann et al. (1979) events. Ionospheric boundary conditions should also affect the reconnection process. For example, ionospheric line-tying can cause x-line motion in the outer magnetosphere. If it is assumed that auroras occur on field lines mapping to x-lines, then auroral motions are different than the local convective motion of the plasma in which they occur. Global magnetohydrodynamic models which incorporate both magnetospheric reconnection and ionospheric convection could be used to investigate the effect of reconnection and convection upon dayside and nightside auroral motions during the course of a magnetic substorm.

Forbes, T. G.↗
NASA NTRS1989

Integration of active and passive sensors for obstacle avoidance

The automatic obstacle-avoidance guidance problem is studied under the operational constraints imposed by the rotorcraft nap-of-the-earth (NOE) environment. The problem is discussed for two different circumstances. The first assumes that a full range map is available, irrespective of the type of sensor being used. Two approaches are proposed to extend a two-dimensional obstacle-avoidance concept presented by Cheng (1988). The situation where only a sparse range map is available from a passive sensor is also treated. An integrated approach that augments the passive sensor with an active one is discussed, along with the problem of data fusion and how it is affected by the characteristics of NOE flight.

Cheng, Victor H. L.↗
NASA NTRS1989

Seasat over-land scatterometer data. I - Global overview of the Ku-band backscatter coefficients

Statistics on the backscatter coefficient sigma(0) from the Ku-band Seasat-A Satellite Scatterometer (SASS) collected over the world's land surfaces are presented. This spaceborne scatterometer provided data on sigma(0) between latitudes 80 deg S and 80 deg N at incidence angles up to 70 deg. The global statistics of vertical (V) and horizontal (H) polarization backscatter coefficients for 10 deg bands in latitude are presented for incidence angles between 20 deg and 70 deg and compared with the Skylab and ground spectrometer results. Global images of the time-averaged V polarization sigma(0) at a 45 deg incidence angle and its dependence on the incidence angle are presented and compared to a generalized map of the terrain type. Global images of the differences between the V and H polarization backscatter coefficients are presented and discussed. The most inhomogeneous region, which contains the deserts of North Africa and the Arabian Peninsula, is studied in greater detail and compared with the terrain type.

Kennett, Rosemary G.↗
NASA NTRS1991

The diffuse soft X-ray background as seen with the Einstein Observatory

A systematic survey of the diffuse soft X-ray background as seen directly with the Einstein Observatory is presented. With the aid of 1633 selected 1 x 1 deg fields of view obtained by the IPC to provide about 5-percent sky coverage, with some bias toward the Galactic plane, the background in the 0.16-3.5 keV spectral region was spatially resolved on this angular scale. Maps of the background are characterized and produced at different energies within the Einstein passband. It is confirmed that the Galactic ridge is not present at energies below 0.33 keV and it is demonstrated that the appearance of the ridge above this energy is not due to hard Galactic sources with a flux above 10 exp -13 ergs/sq cm/s. A southern Galactic region is identified, with l between 80 and 180 deg and b less than -5 deg, where the mean background intensity has the lowest value and is homogeneous within better than 9 percent. The implications of these results for the Galactic structure and for the nature of the extragalactic X-ray background are discussed.

Micela, G.↗
NASA NTRS1992

Galactic structure from the Spacelab infrared telescope. I - 2.4 micron map

The Infrared Telescope, flown aboard the Space Shuttle as part of the Spacelab-2 mission, scanned a large fraction of the sky at 2.4 microns with a resolution of approximately 1 deg. A calibrated map of the Galactic plane in the region -20-120 deg l and -30-30 deg b. The photometry is accurate to a surface brightness of mu K = 20.0 mag/arcsec. Aside from uncertainties in the magnitude zero-point, the data agree quite well with previous maps derived from balloon experiments, except that some systematic differences at high Galactic longitudes are evident. These data will permit more extensive modeling of the 2.4-micron emissivity in the Milky Way than has been possible previously.

Kent, S. M.↗
NASA NTRS1992

Range image segmentation using Zernike moment-based generalized edge detector

The authors proposed a novel Zernike moment-based generalized step edge detection method which can be used for segmenting range and intensity images. A generalized step edge detector is developed to identify different kinds of edges in range images. These edge maps are thinned and linked to provide final segmentation. A generalized edge is modeled in terms of five parameters: orientation, two slopes, one step jump at the location of the edge, and the background gray level. Two complex and two real Zernike moment-based masks are required to determine all these parameters of the edge model. Theoretical noise analysis is performed to show that these operators are quite noise tolerant. Experimental results are included to demonstrate edge-based segmentation technique.

Ghosal, S.↗
NASA NTRS1991

Mechanisms of microgravity flame spread over a thin solid fuel - Oxygen and opposed flow effects

Microgravity tests varying oxygen concentration and forced flow velocity have examined the importance of transport processes on flame spread over very thin solid fuels. Flame spread rates, solid phase temperature profiles and flame appearance for these tests are measured. A flame spread map is presented which indicates three distinct regions where different mechanisms control the flame spread process. In the near-quenching region (very low characteristic relative velocities) a new controlling mechanism for flame spread - oxidizer transport-limited chemical reaction - is proposed. In the near-limit, blowoff region, high opposed flow velocities impose residence time limitations on the flame spread process. A critical characteristic relative velocity line between the two near-limit regions defines conditions which result in maximum flammability both in terms of a peak flame spread rate and minimum oxygen concentration for steady burning. In the third region, away from both near-limit regions, the flame spread behavior, which can accurately be described by a thermal theory, is controlled by gas-phase conduction.

Olson, S. L.↗
NASA NTRS2000

Quantitative Estimation of Some Possible Errors Associated With TRMM GV Monthly Rain Maps and a Scheme for Spatial Averaging of Radar Accumulations

The Tropical Rainfall Measuring Mission (TRMM) Ground Validation (GV) rain products are generated from ground-based radar observations using a bulk adjusted FACE radar reflectivity (Ze) - rain rate (R) relationship. Monthly Ze-R relationships are obtained by extracting the Ze data with a horizontal resolution of 2 km from an altitude of 1.5 km (from Constant Altitude PPIS, CAPPIS) over the locations of the gauges. The gauge and radar data are merged, and a quality control procedure is applied that eliminates poorly correlated gauge-radar data. Bulk adjusted Ze-R relations are then derived from this quality-controlled merged data base. These Z-R relations are applied to the base scan reflectivity to produce rain maps. The present study examines the effect of these different planes on the total accumulations from the radar and the associated effect on the bulk adjustment coefficient. In order to evaluate the credibility of these GV products, the effect of the different planes involved in the bulk adjustment method will be discussed, The gauge data will also be used to assess the impact of missing radar data (i.e., data gaps) upon the monthly radar-derived rainfall estimates. Experiments were also performed varying both the area of the radar data extracted over the gauges and the use of different weighting coefficients. Preliminary results from these sensitivity tests indicate improved agreement and consistency between the gauge and radar data.

Datta, Saswati↗
NASA NTRS2002

Combining Radar and Optical Data for Forest Disturbance Studies

Disturbance is an important factor in determining the carbon balance and succession of forests. Until the early 1990's researchers have focused on using optical or thermal sensors to detect and map forest disturbances from wild fires, logging or insect outbreaks. As part of a NASA Siberian mapping project, a study evaluated the capability of three different radar sensors (ERS, JERS and Radarsat) and an optical sensor (Landsat 7) to detect fire scars, logging and insect damage in the boreal forest. This paper describes the data sets and techniques used to evaluate the use of remote sensing to detect disturbance in central Siberian forests. Using images from each sensor individually and combined an assessment of the utility of using these sensors was developed. Transformed Divergence analysis and maximum likelihood classification revealed that Landsat data was the single best data type for this purpose. However, the combined use of the three radar and optical sensors did improve the results of discriminating these disturbances.

Ranson, K. Jon↗
NASA NTRS2002

Combining Radar and Optical Data for Forest Disturbance Studies

Disturbance is an important factor in determining the carbon balance and succession of forests. Until the early 1990's researchers have focused on using optical or thermal sensors to detect and map forest disturbances from wild fires, logging or insect outbreaks. As part of a NASA Siberian mapping project, a study evaluated the capability of three different radar sensors (ERS, JERS and Radarsat) and an optical sensor (Landsat 7) to detect fire scars, logging and insect damage in the boreal forest. This paper describes the data sets and techniques used to evaluate the use of remote sensing to detect disturbance in central Siberian forests. Using images from each sensor individually and combined an assessment of the utility of using these sensors was developed. Transformed Divergence analysis and maximum likelihood classification revealed that Landsat data was the single best data type for this purpose. However, the combined use of the three radar and optical sensors did improve the results of discriminating these disturbances.

Ranson, K. Jon↗