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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Medium-range atomic correlation in simple liquids. I. Distinction from short-range order

Physical properties of liquids and glasses are controlled not only by the short-range order (SRO) in the nearest-neighbor atoms but also by the medium-range order (MRO) observed for atoms beyond the nearest neighbors. In this article the nature of the MRO as the descriptor of point-to-set atomic correlation is discussed focusing on simple liquids, such as metallic liquids. Through the results of x-ray diffraction and simulation with classical potentials we show that the third peak of the pair-distribution function, which describes the MRO, shows a distinct change in temperature dependence at the glass transition, whereas the first peak, which represents the SRO, changes smoothly through the glass transition. Finally, the result suggests that the glass transition is induced by the freezing of the MRO rather than that of the SRO, implying a major role of the MRO on the viscosity of supercooled liquid.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Climate Change Mitigation Potential of Wind Energy

Global wind resources greatly exceed current electricity demand and the levelized cost of energy from wind turbines has shown precipitous declines. Accordingly, the installed capacity of wind turbines grew at an annualized rate of about 14% during the last two decades and wind turbines now provide ~6–7% of the global electricity supply. This renewable electricity generation source is thus already playing a role in reducing greenhouse gas emissions from the energy sector. Here we document trends within the industry, examine projections of future installed capacity increases and compute the associated climate change mitigation potential at the global and regional levels. Key countries (the USA, UK and China) and regions (e.g., EU27) have developed ambitious plans to expand wind energy penetration as core aspects of their net-zero emissions strategies. The projected climate change mitigation from wind energy by 2100 ranges from 0.3–0.8 °C depending on the precise socio-economic pathway and wind energy expansion scenario followed. The rapid expansion of annual increments to wind energy installed capacity by approximately two times current rates can greatly delay the passing of the 2 °C warming threshold relative to pre-industrial levels. To achieve the required expansion of this cost-effective, low-carbon energy source, there is a need for electrification of the energy system and for expansion of manufacturing and installation capacity.

17 WIND ENERGY↗
NASA NTRS1971

Temperature compensated current source

A current source was designed which is substantially independent of variations of temperature. The current source may be made either to have a linear dependence upon changes of temperature or, by the simple addition of a resistor, may be made substantially independent of temperature variations. Since the current source consists only of transistors of one conductivity type and resistors, it is ideally suited for manufacture in the form of a monolithic integrated circuit.

Breuer, D. R.↗
NASA NTRS1980

Absorption coefficients of solid NH3 from 50 to 7000 per cm

Thin-film spectra of solid NH3 at a resolution of 1 per cm were used to determine its absorption coefficient over the range 50-7000 per cm. The thin films were formed inside a liquid N2 cooled dewar using a variety of substrates and dewar windows. The spectra were recorded with two Fourier spectrometers, one covering the range from 1 to 4 microns and the other from 2.6 to 200 microns. The thickness of the films was measured with a laser interference technique. The absorption coefficients were determined by application of Lambert's law and by a fitting procedure to the observed spectra using thin-film theory. Good agreement was found with the absorption coefficients recently determined by other investigators over a more restricted wavelength range. A metastable phase was observed near a temperature of 90 K and its absorption coefficient is reported. No other major spectral changes with temperature were noted for the range 88-120 K.

Sill, G.↗
NASA NTRS1981

The Dynamics Explorer Langmuir probe instrument

The Dynamics Explorer Langmuir probe instrument (DE-LANG), a spare unit from the Pioneer Venus mission that has been modified to work with the DE spacecraft, is described. Two independent sensors are connected to individual adaptive sweep voltage circuits that continuously track the changing electron temperature and spacecraft potential while autoranging electrometers adjust their gain in response to the changing plasma density. The control signals used in achieving this automatic tracking provide a continuous monitor of the ionospheric parameters without telemetering each volt-ampere curve. In addition, internal data storage circuits permit high-resolution, high-data-rate sampling of selected volt-ampere curves for transmission to the ground to verify or correct the inflight processed data.

Krehbiel, J. P.↗
NASA NTRS1980

Pioneer Venus Orbiter Electron Temperature Probe

The Orbiter Electron Temperature Probe (OETP) instrumentation and measurement technique has been designed to perform in-situ measurements of electron temperature and electron and ion density in the ionosphere of Venus. Adaptive sweep voltage circuitry continuously tracks the changing electron temperature and spacecraft potential while auto-ranging electrometers adjust their gain in response to the changing plasma density. Control signals used in the instrument to achieve this automatic tracking provide a continuous monitor of the ionospheric parameters without telemetering each volt-ampere curve. Internal data storage permits high data rate sampling of selected raw characteristic curves for low rate transmission to earth. These curves are used to verify or correct the inflight processed data. Sample in orbit measurements are presented to demonstrate instrument performance.

Krehbiel, J. P.↗
NASA NTRS2011

Sensitivity of Seawater Oxygen Isotopes to Climatic and Tectonic Boundary Conditions in an Early Paleogene Simulation with GISS ModelE-R

An isotope-enabled ocean-atmosphere general circulation model (GISS ModelE -R) is used to estimate the spatial gradients of the oxygen isotopic composition of seawater (delta O-18(sub sw), where delta is the deviation from a known reference material in per mil) during the early Paleogene (45.65 Ma). Understanding the response of delta O-18(sub sw) to changes in climatic and tectonic boundary conditions is important because records of carbonate delta O-18 document changes in hydrology, as well as changes in temperature and global ice -volume. We present results from an early Paleogene configuration of ModelE -R which indicate that spatial gradients of surface ocean delta O-18(sub sw) during this period could have been significantly different to those in the modern ocean. The differences inferred from ModelE -R are sufficient to change early Paleogene sea surface temperature estimates derived from primary carbonate delta O-18 signatures by more than +/-2 C in large areas of the ocean. In the North Atlantic, Indian, and Southern Oceans, the differences in d18Osw inferred from our simulation with ModelE -R are in direct contrast with those from another d18O ]tracing model study which used different, but equally plausible, early Paleogene boundary conditions. The large differences in delta O-18(sub sw) between preindustrial and early Paleogene simulations, and between models, emphasizes the sensitivity of d18Osw to climatic and tectonic boundary conditions. For this reason, absolute estimates of Eocene/ Paleocene temperature derived from carbonate delta O-18 alone are likely to have larger uncertainties than are usually assumed.

Roberts, Christopher D.↗
DOE OSTI2020

Human-induced changes to the global ocean water masses and their time of emergence

The World Ocean is rapidly changing, with global and regional modification of temperature and salinity, resulting in widespread and irreversible impacts. While the most pronounced observed temperature and salinity changes are located in the upper ocean, changes in water masses at depth have been identified and will probably strengthen in the future. In this study, using 11 climate models, we define when anthropogenic temperature and salinity changes are expected to emerge from natural variability in the ocean interior along density surfaces. The models predict that in 2020, 20–55% of the Atlantic, Pacific and Indian basins have an emergent anthropogenic signal; reaching 40–65% in 2050 and 55–80% in 2080. The well-ventilated Southern Ocean water masses emerge very rapidly, as early as the 1980–1990s, while the Northern Hemisphere water masses emerge in the 2010–2030s. Our results highlight the importance of maintaining and augmenting an ocean observing system capable of detecting and monitoring persistent anthropogenic changes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

The effect of relative humidity and temperature on the response of stomatal conductance to vapor pressure deficit in tropical trees

Understanding how leaf gas exchange responds to changes in vapor pressure deficit (VPD) is key to predicting tropical forest resilience to climate change. Stomata regulate leaf water and CO2 diffusion, and respond to changes in temperature and relative humidity (RH), two drivers of VPD. At high temperatures, the cuticular pathway may also become significant and participate in the overall leaf conductance. Here, we measured gas exchange under light and dark conditions to investigate the stomatal and cuticular responses to temperature and RH on detached branches in five tropical tree species. Leaf conductance in the dark, when stomata are essentially closed, was not markedly impacted by temperature and RH, suggesting a minimal response of the cuticular pathway to these conditions. We compared six steady-state conductance models incorporating different effects of photosynthesis and evaporative demand on stomatal control. All models performed well (residual standard deviation, σ, < 0.025 mol m-2 s-1), but the best-fitting model (σ = 0.017 mol m-2 s-1) used a nonlinear relationship between photosynthesis and stomatal conductance and incorporated RH rather than vapor pressure difference. All models overestimated the steady-state conductance at high RH. Furthermore, leaf conductance immediately increased after a decrease in RH (wrong-way response), but not after an increase in leaf temperature. This suggests that the mechanisms underlying stomatal response to VPD need further investigation. The non-linear coupling between photosynthetic rate and stomatal conductance indicates a sharper physiological response than previously acknowledged.

Lamour, Julien↗
NASA NTRS2011

Temperature Effects on Adhesive Bond Strengths and Modulus for Commonly Used Spacecraft Structural Adhesives

A study was performed to observe how changes in temperature and substrate material affected the strength and modulus of an adhesive bondline. Seven different adhesives commonly used in aerospace bonded structures were tested. Aluminum, titanium and Invar adherends were cleaned and primed, then bonded using the manufacturer's recommendations. Following surface preparation, the coupons were bonded with the adhesives. The single lap shear coupons were then pull tested per ASTM D 1002 Standard Test Method for Apparent Shear Strength of Single- Lap-Joint over a temperature range from -150 deg C up to +150 deg C. The ultimate strength was calculated and the resulting data were converted into B-basis design allowables. Average and Bbasis results were compared. Results obtained using aluminum adherends are reported. The effects of using different adherend materials and temperature were also studied and will be reported in a subsequent paper. Dynamic Mechanical Analysis (DMA) was used to study variations in adhesive modulus with temperature. This work resulted in a highly useful database for comparing adhesive performance over a wide range of temperatures, and has facilitated selection of the appropriate adhesive for spacecraft structure applications.

structural adhesives testing↗
NASA NTRS1991

Carbonate stability in the earth's mantle - A vibrational spectroscopic study of aragonite and dolomite at high pressures and temperatures

The structural changes of aragonite and dolomite taking place at high pressures and temperatures were investigated by measuring the Raman spectra of these materials to pressures of 23 and 28 GPa (generated in a diamond anvil cell), respectively; in addition, the IR spectra of aragonite were measured to 40 GPa. The spectroscopic data demonstrated that, at 300 K, dolomite and aragonite samples were stable to pressures of 28 and 41 GPa, respectively. No phase transitions were observed following heating of aragonite and dolomite to temperatures of 2000 K and 800 K, respectively. The mode Grueneisen parameters indicate that the carbonate group in these two minerals is relatively insensitive to pressure, with the dominant compaction mechanism being the compression of the Ca and Mg polyhedra.

Kraft, Susan↗
DOE OSTI2022

Thermal Modulation of Gigahertz Surface Acoustic Waves on Lithium Niobate

Surface-acoustic-wave (SAW) devices have a wide range of applications in microwave signal processing. Microwave SAW components benefit from higher quality factors and much smaller crosstalk when compared to their electromagnetic counterparts. Efficient routing and modulation of SAWs are essential for building large-scale and versatile acoustic wave circuits. Here, we demonstrate integrated thermoacoustic modulators using two SAW platforms: bulk lithium niobate and thin-film lithium niobate on sapphire. In both approaches, the gigahertz-frequency SAWs are routed by integrated acoustic waveguides, while on-chip microheaters are used to locally change the temperature, and thus, control the phase of the SAW. Using this approach, we achieve phase changes of over 720° with the responsibility of 2.6°/mW for bulk lithium niobate and 0.52°/mW for lithium niobate on sapphire. Furthermore, we demonstrate amplitude modulation of SAWs using acoustic Mach-Zehnder interferometers. Our thermoacoustic modulators can enable reconfigurable acoustic signal processing for next-generation wireless communications and microwave systems.

42 ENGINEERING↗
NASA NTRS1987

Elevated temperature strain gages

The objective is to study the electrical resistance of materials that are potentially useful as resistance strain gages at 1000 C. A set of criteria were set and used to select strain gage candidate materials that are electrically stable and reproducible at all temperatures up to 1000 C. For the experimental phase of this research, the electrical resistance change with temperature of three groups of materials (solid solution alloys, transition metal carbides, and semiconductors) were studied with the intention of identifying materials with low temperature coefficient of resistance and low resistance drift rate at 1000 C. A preliminary study of the gage factor on one of the best candidate materials, B sub 4 C, was also undertaken. The results of these investigations are presented.

Lei, J. F.↗
NASA NTRSDate not supplied

Advances in X-ray Instruments to Support Mars Sample Return

The Mars 2020 Perseverance rover is currently collecting drill cores of ancient igneous and sedimentary rock in and around Jezero crater for potential transport to Earth. These samples from the martian surface will enable detailed mineralogical, geochemical, and petrological measurements to characterize ancient depositional and diagenetic environments, quantitatively age-date the samples, and identify the building blocks for life or evidence for life itself. Furthermore, these drill cores are especially precious because they may represent the most pristine samples from the martian surface and our best chance at identifying martian life, as future sample return missions may be conducted by humans that can introduce biological contaminants to the samples. Because of the importance of these samples, we must take great care in their handling, curation, and preliminary analyses so that they are preserved for scientific measurements for decades to come. In-situ measurements by Perseverance have identified minerals that further warrant special treatment of the returned samples. Hydrated sulfate carbonate, swelling clay minerals, and oxychlorine salts are extremely sensitive to changes in temperature and relative humidity. The structures of hydrated sulfates and oxychlorine minerals, in particular, readily change when exposed to different conditions, meaning the mineral assemblage of the as-returned samples may be lost if the samples aren’t handled properly. Characterizing the as-returned mineral assemblage, particularly of the salts, is essential for reconstructing past aqueous conditions and habitability. To characterize the as-returned mineral assemblage, the samples must be analyzed rapidly before phase changes occur and/or under controlled conditions (e.g., within a glove box). Significant recent advances in X-ray instrumentation for robotic exploration of the solar system have resulted in high-resolution miniaturized instruments that would provide mineralogical, geochemical, and petrological information on the returned martian samples without degradation of the mineral assemblage. Here, we describe a combined X-ray diffractometer/X-ray fluorescence spectrometer (XRD/XRF), an X-ray computed tomographic (XCT) instrument, and a scanned beam XRF mapping instrument that could be used in a glove box so that the martian samples remain under controlled conditions.

E. B. Rampe↗
NASA NTRS1975

Monitoring physical and chemical parameters of Delaware Bay waters with an ERTS-1 data collection platform

The author has identified the following significant results. Results of the analysis of data collected during the summer of 1974 demonstrate that the ERTS Data Collection Platform (DCP) is quite responsive to changing water parameters and that this information can be successfully transmitted under all weather conditions. The monitoring of on-site probe outputs reveals a rapid response to changing water temperature, salinity, and turbidity conditions on incoming tides as the tidal salt wedge passes the probe location. The changes in water properties were corroborated by simultaneously sampling the water for subsequent laboratory analysis. Fluctuations observed in the values of salinity, conductivity, temperature and water depth over short time intervals were extremely small. Due to the nature of the probe, 10% to 20% fluctuations were observed in the turbidity values. The use of the average of the values observed during an overpass provided acceptable results. Good quality data was obtained from the satellite on each overpass regardless of weather conditions. Continued use of the DCP will help provide an indication of the accuracy of the probes and transmission system during long term use.

Klemas, V.↗
DOE OSTI2024

From ionic clusters dynamics to network constraints in ionic polymer solutions

Physical networks formed by ionizable polymers with ionic clusters as crosslinks are controlled by coupled dynamics that transcend from ionic clusters through chain motion to macroscopic response. Here, the coupled dynamics, across length scales, from the ionic clusters to the networks in toluene swollen polystyrene sulfonate networks, were directly correlated, as the electrostatic environment of the physical crosslinks was altered. The multiscale insight is attained by coupling neutron spin echo measurements with molecular dynamics simulations, carried out to times typical of relaxation of polymers in solutions. The experimental dynamic structure factor is in outstanding agreement with the one calculated from computer simulations, as the networks are perturbed by elevating the temperature and changing the electrostatic environment. In toluene, the long-lived clusters remain stable over hundreds of ns across a broad temperature range, while the polymer network remains dynamic. In conclusion, though the size of the clusters changes as the dielectric constant of the solvent is modified through the addition of ethanol, they remain stable but morph, enhancing the polymer chain dynamics.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Cloud Top Scanning radiometer (CTS): User's guide

The CTS maps the Earth's surface with a resolution of 0.1 km from an altitude of 18km with 60km side-to-side coverage of the field. It has three spectral channels. The 0.625 micrometer centered visual channel detects reflectance to within 1 percent. The 6.75 micrometer centered water vapor channel detects changes in temperature of less than one degree Kelvin at 175 K. The 11.5 micrometer centered infrared window channel detects changes of less one half degree Kelvin at 175 K. The data can be converted graphically into three display images of the scene. Values for scene temperature and albedo are calculated from calibration equations. The equations were derived from in-situ and laboratory measurements. Intercomparisons of the flight data temperatures with ground based and other remote sensor results established the certainty of the derived temperature values to within 3 K over a wide temperature range (180 to 320 K). The system performance, calibration, and operation is successful and the engineering information describing this system should prove useful to scientists and potential users of the data.

Brown, K. S.↗
DOE OSTI2019

Combined effects of temperature and precipitation on soil organic carbon changes in the uplands of eastern China

Temperature and precipitation simultaneously influence soil organic carbon (SOC) in agroecosystems. While their individual impacts have been extensively studied, their combined effects remain poorly understood at a regional scale. This study quantified the combined influence of temperature and precipitation on SOC in upland-crop fields of northern Jiangsu Province in eastern China. We used the DeNitrification-DeComposition (DNDC, version 9.5) model with the currently most detailed upland soil database in China. This 1:50,000 soil database contains 17,024 upland soil polygons that were generated using 983 upland soil profiles. Model simulations indicated that under a combined scenario of rising air temperature (T) of 2 °C and a simultaneous decrease (or increase) in precipitation (P) by 20%, the 3.93 Mha of upland soils in the study region sequestered 39.10 (or 37.39) Tg C from 2010-2039. The C sequestration from the combined effects of T and P on SOC was 2.40 (or 2.12) Tg C less, relative to the sum of the amount produced from the individual effect. Moreover, if the increase in T changed from 2 °C to 4 °C, with P still decreasing (or increasing) by 20%, the C sequestration further decreased by 1.2 (or 1.68) Tg C. Our analysis of the combined effects of T and P on SOC changes suggests that future warming and P change in this region may have a negative influence on SOC sequestration, despite the upland agroecosystems serve as a long-term sink for atmospheric CO2. Furthermore, SOC changes in different upland soil groups and administrative areas varied widely due to the heterogeneity in soil properties and fertilizer applications. This emphasizes the importance of detailed soil datasets and the need to adopt on-farm management practices to different soil groups and administrative areas under future climate change.

Zhang, Liming↗