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At least 1,405 records · Page 78
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Experimental thermal equation of state of B 2–KCl

The alkali halides are often used as optically-transparent pressure-transmitting media and thermal insulators in laser-heated diamond anvil cell experiments. High P-T equations of state for these materials would allow them to be used simultaneously as sensitive in situ pressure markers, making sample preparation and data analysis simpler. KCl is especially useful for this application because its high melting point, crystallographic simplicity, and low electron density are ideal for use in high-temperature X-ray diffraction experiments. However, the high-temperature static equation of state data for this material is limited in pressure to 8 GPa. As experiments routinely exceed 100 GPa in pressure and thousands of Kelvin, it is necessary for the equation of state of KCl to be determined experimentally at these conditions if it is to be used as an equation of state calibrant in the future. This work combines new high-pressure, high-temperature data of the B2 phase of KCl (up to 167 GPa and 2400 K) with the previously published room-temperature data of Dewaele et al. (2012) to produce a Mie-Gruneisen-Debye thermal equation of state for this material. The room temperature equation of state parameters are similar to those reported previously: V 0 = 32.0(3) cm 3 /mole, K 0 = 24(1) GPa and $K$$^{'}_{0}$ = 4.56(5). The thermal parameters, 0 and q, are 2.9(4) and 1.0(1), respectively. While a q of 1 is expected, the 0 is higher than expected from previous calculations, lower pressure experimental data, and the available shockwave data. Here, previously-reported equations of state underestimate the pressure of KCl at high temperatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Modeling of molecular nitrogen collisions and dissociation processes for direct simulation Monte Carlo

The Direct Simulation Monte Carlo (DSMC) method typically used for simulating hypersonic Earth re-entry flows requires accurate total collision cross sections and reaction probabilities. However, total cross sections are often determined from extrapolations of relatively low-temperature viscosity data, so their reliability is unknown for the high temperatures observed in hypersonic flows. Existing DSMC reaction models accurately reproduce experimental equilibrium reaction rates, but the applicability of these rates to the strong thermal nonequilibrium observed in hypersonic shocks is unknown. For hypersonic flows, these modeling issues are particularly relevant for nitrogen, the dominant species of air. To rectify this deficiency, the Molecular Dynamics/Quasi-Classical Trajectories (MD/QCT) method is used to accurately compute collision and reaction cross sections for the N{sub 2}({sup 1}Σ{sub g}{sup +})-N{sub 2}({sup 1}Σ{sub g}{sup +}) collision pair for conditions expected in hypersonic shocks using a new potential energy surface developed using a ReaxFF fit to recent advanced ab initio calculations. The MD/QCT-computed reaction probabilities were found to exhibit better physical behavior and predict less dissociation than the baseline total collision energy reaction model for strong nonequilibrium conditions expected in a shock. The MD/QCT reaction model compared well with computed equilibrium reaction rates and shock-tube data. In addition, the MD/QCT-computed total cross sections were found to agree well with established variable hard sphere total cross sections.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

An investigation of low temperature electronic phase arrest in Sm{sub 0.55}Sr{sub 0.45}MnO{sub 3} phase separated manganite

The temperature dependence of electronic-transport and magneto-transport of polycrystalline Sm{sub 0.55}Sr{sub 0.45}MnO{sub 3} manganite at low temperatures has been investigated in detail. The low temperature resistivity data show a distinct minimum in the resistivity versus temperature plots for all fields. The low temperature resistivity upturn below this minimum has been fitted to an expression, which includes three terms, namely, residual resistivity, inelastic scattering, and electron-electron (e-e) interaction or Kondo effects. It has been found that the dominating mechanism is e-e interaction. The resistivity of the sample shows strong dependence on the magnetic field–temperature history. The electronic-transport property clearly confirms that the electronic phase of the sample gets arrested to a low resistive state during field cooling and cannot return to its original state even after the magnetic field is removed. The magnetoresistance of the sample also shows a strong irreversibility with respect to the sweeping of the magnetic field between its highest positive and negative values. Moreover, the resistivity of the sample is found to be time dependent. All the observed phenomena have been explained through the phase separation scenario and kinetic arrest of electronic phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Computational modeling of latent-heat-storage in PCM modified interior plaster

The latent heat storage systems represent a promising way for decrease of buildings energy consumption with respect to the sustainable development principles of building industry. The presented paper is focused on the evaluation of the effect of PCM incorporation on thermal performance of cement-lime plasters. For basic characterization of the developed materials, matrix density, bulk density, and total open porosity are measured. Thermal conductivity is accessed by transient impulse method. DSC analysis is used for the identification of phase change temperature during the heating and cooling process. Using DSC data, the temperature dependent specific heat capacity is calculated. On the basis of the experiments performed, the supposed improvement of the energy efficiency of characteristic building envelope system where the designed plasters are likely to be used is evaluated by a computational analysis. Obtained experimental and computational results show a potential of PCM modified plasters for improvement of thermal stability of buildings and moderation of interior climate.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Use of a GPS-Derived Troposphere Model to Improve InSAR Deformation Estimates in the San Gabriel Valley, California

We evaluate the potential of troposphere models derived from ground meteorological data (pressure, temperature, and relative humidity) and Global Positioning System (GPS) data to improve InSAR measurements and models derived from them. We test this approach on an ERS-2/Envisat data set collected during a transient surface deformation episode that occurred from January to July 2005 in the San Gabriel Valley, southern California, USA. We find that the interferometric phase change observed over the corresponding period cannot be solely attributed to hydrological uplift associated with rising groundwater levels but also includes a significant contribution from differential tropospheric delay due to differing quantities of water vapor in the troposphere on the two SAR observation dates. We show that, if the tropospheric phase contribution is mistakenly interpreted as the range change associated with changes in groundwater storage, both the surface displacement and the groundwater storage coefficient may be overestimated by up to 30%. Finally, this method could be applied in real time where meteorological measurements are available near one or more GPS permanent site(s).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Analysis of soil moisture extraction algorithm using data from aircraft experiments

A soil moisture extraction algorithm is developed using a statistical parameter inversion method. Data sets from two aircraft experiments are utilized for the test. Multifrequency microwave radiometric data surface temperature, and soil moisture information are contained in the data sets. The surface and near surface ( or = 5 cm) soil moisture content can be extracted with accuracy of approximately 5% to 6% for bare fields and fields with grass cover by using L, C, and X band radiometer data. This technique is used for handling large amounts of remote sensing data from space.

Burke, H. H. K.↗
NASA NTRS1988

The atmospheric model in the region 90 to 2000 km

A comprehensive revision of the MSIS-83 earth atmosphere model was undertaken to extend predictions to the mesopause, on the basis of temperature, density, and composition data obtained by sounding rockets, satellites, and incoherent scatter radars. Attention is presently given to a semiempirical model similar to MSIS-83, which incorporates additional terms in order to represent seasonal differences in the morphology of composition variations under both quiet and disturbed polar region conditions. The data base is expanded to include both composition and temperature data from the Dynamics Explorer-2 satellite.

Hedin, A. E.↗
NASA NTRS1994

Global-scale modes of surface temperature variability on interannual to century timescales

Using 100 years of global temperature anomaly data, we have performed a singluar value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio-temporal modes of global climate variability. Statistical significance is determined from confidence limits obtained by Monte Carlo simulations. Secular variance is dominated by a globally coherent trend; with nearly all grid points warming in phase at varying amplitude. A smaller, but significant, share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude North Atlantic with a roughly centennial timescale. Spatial patterns associated with significant peaks in variance within a broad period range from 2.8 to 5.7 years exhibit characteristic El Nino-Southern Oscillation (ENSO) patterns. A recent transition to a regime of higher ENSO frequency is suggested by our analysis. An interdecadal mode in the 15-to-18 years period and a mode centered at 7-to-8 years period both exhibit predominantly a North Atlantic Oscillation (NAO) temperature pattern. A potentially significant decadal mode centered on 11-to-12 years period also exhibits an NAO temperature pattern and may be modulated by the century-scale North Atlantic variability.

Mann, Michael E.↗
DOE OSTI2017

Discovery and analysis of a potential blind geothermal system in southern Gabbs Valley, western Nevada

The southern Gabbs Valley geothermal prospect is a blind thermal anomaly located 5 km north of the Gabbs Valley Range and ~15 km southeast of the Don A. Campbell geothermal power plant in west-central Nevada. The discovery of this blind thermal anomaly was initiated from the development of a detailed geothermal potential map covering 96,000 km2 of the Great Basin region. This map synthesized about 9 geologic and geophysical parameters and showed high geothermal potential in southern Gabbs Valley. Subsequent geologic reconnaissance identified areas of favorable structure for hosting a blind geothermal system. Areas displaying complex fault relationships were then targeted for further exploration utilizing a shallow 2-meter thermal survey. The first 2-meter survey incorporated 60 data points in the basin, with one anomalously high temperature point located in the southern portion of the basin. Water samples were taken from the Diamond A ranch 6 km northwest of the thermal anomaly. These samples yielded a geothermometer of 130-140°C. Additional shallow temperature survey work has been completed constraining the extent of the thermal anomaly and establishing a 7 km2 area with elevated 2-meter temperatures. Subsurface data generated from a new gravity survey show that the 2-meter thermal anomaly corresponds to a significant gravity gradient that probably reflects a subsurface fault and possible fault intersection. Exploration of the system is ongoing, and further detailed mapping of bedrock and Quaternary exposures in the area will aid in understanding the structural controls of this potential geothermal system. The integration of geochemical, geophysical, and geologic datasets in this area will elucidate the probability of a commercial-grade geothermal system and produce a conceptual model to be used in the selection of possible drill targets.

15 GEOTHERMAL ENERGY↗
NASA NTRS1991

Temperature trends in the lower mesosphere

The largest atmospheric temperature changes due to the increase of greenhouse gases are expected in the 40 to 60 km altitude region, where enhanced infrared cooling decreases the temperature. Ten-year (1980-1990) temperature trends at 55 km and 0.4 mb, derived using data from the ground-based lidar at Haute Provence, (France), and the SSU-instrument channel 47X on several satellites, are presented. These data show temperature decreases that are as large and in some cases exceed predictions based on current models. At 44 deg N, the ground-based lidar and satellite techniques give a negative trend of -0.10 + or - 0.04 percent per year and -0.14 + or - 0.02 percent per year, respectively. Agreement between these two data sets based on different measurement techniques gives confidence in the detected trends at this latitude. Further analysis of the SSU 47X satellite data between 45 deg S and 45 deg N indicates a maximum decline of 0.16 percent per year near 30 deg N. A minimum trend decrease of 0.07 percent per year is detected between 20 and 30 deg S. Based on NOAA satellite radiance observations, these long-term temperature changes are larger than changes at any of the other stratospheric levels below 55 km monitored during this period.

Aikin, A. C.↗
NASA NTRS1976

Vertical wind velocities from superpressure balloons - A case study using Eole data

A method for determining vertical wind velocities using the pressure- and temperature-change data from superpressure (constant-density) balloons was proposed in an earlier paper (1975). In this paper, we present a case study using actual balloon data to test the method. Data from the Eole balloon experiment were used to estimate the sign of vertical wind velocities, as well as the horizontal velocity field, near 200 mb over Australia. The resulting patterns of vertical velocity compare favorably with satellite pictures and with current models of flow near jet-stream maxima. Additionally, this study provides evidence that areas of vertical motion in the troposphere extend upward into the lower stratosphere without changing sign.

Banta, R. M.↗
NASA NTRS1981

The chemical composition, gravity, and temperature of Sirius

Observational data available for Sirius are of poorer quality than those for Vega, with both the angular diameter and absolute fluxes at different wavelengths being less accurately known. While these data yield an effective temperature of 10,000 + or - 250 K, the 13-color photometry of Johnson and Mitchell (1975) suggests that Sirius is about 450 K hotter than Vega's effective temperature of 9650 + or - 200 K. The c(1) color of the uvby system, the 33-52 and 35-52 colors of the 13-color photometry, and the H-alpha, H-beta and H-gamma line profiles all give log g values of about 4.3, which is in agreement with the value deduced from the mass and the radius, the latter being deduced from the angular diameter and the parallax.

Bell, R. A.↗
NASA NTRS1991

A new method for analyzing IRAS data to determine the dust temperature distribution

In attempting to analyze the four-band IRAS images of interstellar dust emission, it is found that an inversion theorem recently developed by Chen (1990) enables distribution of the dust to be determined as a function of temperature and thus the total dust column density, for each line of sight. The method and its application to a hypothetical IRAS data set created by assuming a power-law dust temperature distribution, which is characteristic of the actual IRAS data for the Monoceros R2 cloud, are reported. To use the method, the wavelength dependence of the dust emissivity is assumed and a simple function is fitted to the four intensity-wavelength data points. The method is shown to be very successful at retrieving the dust temperature distribution in this case and is expected to have wide applicability to astronomical problems of this type.

Xie, Taoling↗
NASA NTRS1992

Results of thermal vacuum tests for the PASP Plus flight panels

The PASP+ experiment is collection of 16 individual cell strings on 12 different photovoltaic modules, representing a wide variety of cell and array technologies, which will be launched from a Pegasus in early 1993. The main objectives of the experiment are to obtain environmental interaction data between the modules and the space plasma; and to obtain radiation damage data on the newer types of cells. The orbit will be about 1050 nautical miles by 190 nautical miles with an inclination of 70 degrees. During late June and early July of this year, we took the PASP+ panels with all 12 modules and the flight controller to Boeing for a series of thermal vacuum tests. The main objectives of these tests were to verify the thermal balance model of the space experiment; to obtain good data for temperature coefficients of the various modules; and to have an 'end-to-end' test of the modules and controller. We will present data on the module temperatures and the measured temperature coefficients. We shall discuss the limitations of the test setup and some of the assumptions that were made. We shall also present some module performance as a function of temperature.

Guidice, Don↗
DOE OSTI2015

Building the Next Generation of Regional Geothermal Potential Maps: Examples from the Great Basin Region, Western USA

Over the past decade research has greatly advanced our understanding of structurally controlled geothermal systems and the potential for “deep stratigraphic reservoirs” in the Great Basin region, western USA. For example, studies have shown that structurally controlled geothermal systems are associated with specific structural settings, such as terminations of major normal faults, accommodation zones, pull-aparts in strike-slip faults, displacement transfer zones, or step-overs in range-front faults. However, we know that not every structure (e.g., termination of a major normal fault or step-over in a range-front fault) hosts an active geothermal system. Recent research has also shown that regional strain rate model as determined from GPS geodesy, the composition of that strain (extensional versus shear or compressive strain), recency of Quaternary faulting, and slip and dilation tendency of faults correlate positively with the distribution of both high and low-temperature, structurally controlled geothermal systems within the Great Basin. Combining these strain data and fault slip history data sets with existing temperature gradient data, heat flow data, spring temperatures, fluid geothermometry, and geophysical data provides an effective platform for evaluating the geothermal potential of respective structural plays. Recent studies focused on deep stratigraphic reservoirs indicate the best conditions for economically viable development are associated with thick sedimentary basins with low-thermal-conductivity sedimentary cap rocks overlying permeable host rocks (e.g. carbonates) and co-located with areas of high heat flow. Some of the factors that contribute to the potential for deep stratigraphic reservoirs and conventional structurally controlled geothermal systems apply to both types of resources, and in some places the potential for these two types of resources overlap in space, suggesting the potential for hybrid reservoirs (structurally controlled deep stratigraphic reservoirs). Effective and complete evaluation of geothermal potential in the Great Basin should include parameters that cover both types of resources. In this study, two areas with a combined area of 26,000 km 2 were evaluated for geothermal resource potential, equating to <4% of the total 680,000 km 2 size of the Great Basin region. Within these two study areas, 73 potential structural targets and 8 potential deep sedimentary target areas were identified. Four of the 73 potential structural target areas are associated with known thermal anomalies. All 73 structural target areas were ranked according to multiple data sets.

15 GEOTHERMAL ENERGY↗
NASA NTRS1983

Planetary atmospheres

During the period from 1979 to 1982, Pioneer and Voyager missions to Venus, Jupiter, and Saturn combined with ongoing analysis and data collection from the Viking-Mars mission have contributed greatly to an understanding of planetary atmospheres. Research concerning the atmosphere of Venus is discussed, taking into account the atmospheric composition, the isotopic ratios of noble gases, data concerning temperature and pressure, information regarding various atmospheric layers, atmospheric density data, and models regarding the dynamical properties of Venus' atmosphere. Information concerning the atmosphere of Mars is also examined. Isotopic ratios of carbon and oxygen are considered along with altitude profiles, diurnal heating and cooling, and thermal tides and their relationship to dust storms. Attention is given to the temperature structure of the Jovian atmosphere, the morphology of Jovian cloud features, features in the Saturnian atmosphere, information with respect to the atmosphere of Titan, the rotation rates of Uranus, masses and densities of Uranus and Neptune, and the identification of Pluto as a small icy body.

Beebe, R.↗
NASA NTRS2000

A Method for Assessing the Quality of Model-Based Estimates of Ground Temperature and Atmospheric Moisture Using Satellite Data

A method is developed for validating model-based estimates of atmospheric moisture and ground temperature using satellite data. The approach relates errors in estimates of clear-sky longwave fluxes at the top of the Earth-atmosphere system to errors in geophysical parameters. The fluxes include clear-sky outgoing longwave radiation (CLR) and radiative flux in the window region between 8 and 12 microns (RadWn). The approach capitalizes on the availability of satellite estimates of CLR and RadWn and other auxiliary satellite data, and multiple global four-dimensional data assimilation (4-DDA) products. The basic methodology employs off-line forward radiative transfer calculations to generate synthetic clear-sky longwave fluxes from two different 4-DDA data sets. Simple linear regression is used to relate the clear-sky longwave flux discrepancies to discrepancies in ground temperature ((delta)T(sub g)) and broad-layer integrated atmospheric precipitable water ((delta)pw). The slopes of the regression lines define sensitivity parameters which can be exploited to help interpret mismatches between satellite observations and model-based estimates of clear-sky longwave fluxes. For illustration we analyze the discrepancies in the clear-sky longwave fluxes between an early implementation of the Goddard Earth Observing System Data Assimilation System (GEOS2) and a recent operational version of the European Centre for Medium-Range Weather Forecasts data assimilation system. The analysis of the synthetic clear-sky flux data shows that simple linear regression employing (delta)T(sub g)) and broad layer (delta)pw provides a good approximation to the full radiative transfer calculations, typically explaining more thin 90% of the 6 hourly variance in the flux differences. These simple regression relations can be inverted to "retrieve" the errors in the geophysical parameters, Uncertainties (normalized by standard deviation) in the monthly mean retrieved parameters range from 7% for (delta)T(sub g) to approx. 20% for the lower tropospheric moisture between 500 hPa and surface. The regression relationships developed from the synthetic flux data, together with CLR and RadWn observed with the Clouds and Earth Radiant Energy System instrument, ire used to assess the quality of the GEOS2 T(sub g) and pw. Results showed that the GEOS2 T(sub g) is too cold over land, and pw in upper layers is too high over the tropical oceans and too low in the lower atmosphere.

Wu, Man Li C.↗
NASA NTRS1990

Acquisition and correlation of cryogenic nitrogen mass flow data through a multiple orifice Joule-Thomson device

Liquid nitrogen mass flow rate, pressure drop, and temperature drop data were obtained for a series of multiple orifice Joule-Thomson devices, known as Visco Jets, over a wide range of flow resistance. The test rig used to acquire the data was designed to minimize heat transfer so that fluid expansion through the Visco Jets would be isenthalpic. The data include a range of fluid inlet pressures from 30 to 60 psia, fluid inlet temperatures from 118 to 164 R, outlet pressures from 2.8 to 55.8 psia, outlet temperatures from 117 to 162 R and flow rate from 0.04 to 4.0 lbm/hr of nitrogen. A flow rate equation supplied by the manufacturer was found to accurately predict single-phase (noncavitating) liquid nitrogen flow through the Visco Jets. For cavitating flow, the manufacturer's equation was found to be inaccurate. Greatly improved results were achieved with a modified version of the single-phase equation. The modification consists of a multiplication factor to the manufacturer's equation equal to one minus the downstream quality on an isenthalpic expansion of the fluid across the Visco Jet. For a range of flow resistances represented by Visco Jet Lohm ratings between 17,600 and 80,000, 100 percent of the single-phase data and 85 percent of the two-phase data fall within + or - 10 percent of predicted values.

Papell, S. Stephen↗