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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Electronic Origin of T c in Bulk and Monolayer FeSe

FeSe is classed as a Hund’s metal, with a multiplicity of d bands near the Fermi level. Correlations in Hund’s metals mostly originate from the exchange parameter J, which can drive a strong orbital selectivity in the correlations. The Fe-chalcogens are the most strongly correlated of the Fe-based superconductors, with d xy the most correlated orbital. Yet little is understood whether and how such correlations directly affect the superconducting instability in Hund’s systems. By applying a recently developed ab initio theory, we show explicitly the connections between correlations in d xy and the superconducting critical temperature T c . Starting from the ab initio results as a reference, we consider various kinds of excursions in parameter space around the reference to determine what controls T c . We show small excursions in J can cause colossal changes in T c . Additionally we consider changes in hopping by varying the Fe-Se bond length in bulk, in the free standing monolayer M-FeSe, and M-FeSe on a SrTiO 3 substrate (M-FeSe/STO). The twin conditions of proximity of the dxy state to the Fermi energy, and the strength of J emerge as the primary criteria for incoherent spectral response and enhanced single- and two-particle scattering that in turn controls T c . Using c-RPA, we show further that FeSe in monolayer form (M-FeSe) provides a natural mechanism to enhance J. We explain why M-FeSe/STO has a high T c , whereas M-FeSe in isolation should not. Our study opens a paradigm for a unified understanding what controls Tc in bulk, layers, and interfaces of Hund’s metals by hole pocket and electron screening cloud engineering.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Hidden Rotation Symmetry of the Jordan–Wigner Transformation and Its Application to Measurement in Quantum Computation

Using a global rotation by 𝜃 about the z-axis in the spin sector of the Jordan–Wigner transformation rotates Pauli matrices 𝑋̂ and 𝑌̂ in the 𝑥−𝑦 -plane, while it adds a global complex phase to fermionic quantum states that have a fixed number of particles. With the right choice of angles, this relates expectation values of Pauli strings containing products of 𝑋̂ and 𝑌̂ to different products, which can be employed to reduce the number of measurements needed when simulating fermionic systems on a quantum computer. Here, we derive this symmetry and show how it can be applied to systems in Physics and Chemistry that involve Hamiltonians with only single-particle (hopping) and two-particle (interaction) terms. We also discuss the consequences of this for finding efficient measurement circuits in variational ground state preparation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Correlating Power Outage Spread with Infrastructure Interdependencies During Hurricanes

Power outages caused by extreme weather events, such as hurricanes, can significantly disrupt essential services and delay recovery efforts, underscoring the importance of enhancing our infrastructure's resilience. This study investigates the spread of power outages during hurricanes by analyzing the correlation between the network of critical infrastructure and outage propagation. We leveraged datasets from Hurricanemapping.com, the North American Energy Resilience Model Interdependency Analysis (NAERM-IA), and historical power outage data from the Oak Ridge National Laboratory (ORNL)'s EAGLE-I system. Our analysis reveals a consistent positive correlation between the extent of critical infrastructure components accessible within a certain number of steps (k-hop distance) from initial impact areas and the occurrence of power outages in broader regions. This insight suggests that understanding the interconnectedness among critical infrastructure elements is key to identifying areas indirectly affected by extreme weather events.

Bose, Avishek↗
NASA NTRS1971

Pulsation phenomena observed in long-duration vlf whistler-mode signals.

Whistler-mode signals from station NAA (14.7 and 17.8 kHz), Cutler, Maine, show periodic fluctuations (?pulsations') in amplitude and bandwidth. The data were recorded at Eights station, Antarctica, during unmodulated (?key-down') transmissions from NAA lasting up to 2 min. In three of four instances, the pulsations consist of a series of moderate enhancements of the amplitude and bandwidth of the signal, each pulsation lasting about 50 msec. The fourth instance, however, was unusual in that the key-down signal exhibited remarkably regular and intense amplitude variations. In all four occurrences, the period of the pulsation was in the range from 0.3 to 0.6 sec. In three occurrences, this period was roughly the same as the one-hop whistler-mode delay along the field-line path; however, no demonstrable mechanism to explain this association could be found. An explanation of pulsations in terms of multipath fading effects could not be supported by the data. More likely explanations include intrinsic oscillation in the emission generation mechanism, natural oscillation in the energetic-particle population, or modulation of the VLF growth rate by Pc 1 micropulsations in the region of wave growth.

Bell, T. F.↗
NASA NTRS1972

Adaptive multibeam experiment for aeronautical and maritime services /AMEAMS/.

An experiment using NASA's ATS-G satellite was designed to provide essential data and field experience for the application of adaptive multiple satellite beam techniques to small mobile terminal communications system designs. Two approaches to the system were considered: an adaptive simultaneous multibeam mode and a hopped-beam mode. In the former case, both interbeam and intrabeam adaptive power management are used, while in the latter, beam energy is controlled through the use of time division techniques. The objectives of the experiment, design and implementation approaches, and potential applications are discussed.

Redisch, W. N.↗
NASA NTRS1972

Apollo 15 time and motion study

A time and motion study of Apollo 15 lunar surface activity led to examination of four distinct areas of crewmen activity. These areas are: an analysis of lunar mobility, a comparative analysis of tasks performed in 1-g training and lunar EVA, an analysis of the metabolic cost of two activities that are performed in several EVAs, and a fall/near-fall analysis. An analysis of mobility showed that the crewmen used three basic mobility patterns (modified walk, hop, side step) while on the lunar surface. These mobility patterns were utilized as adaptive modes to compensate for the uneven terrain and varied soil conditions that the crewmen encountered. A comparison of the time required to perform tasks at the final 1-g lunar EVA training sessions and the time required to perform the same task on the lunar surface indicates that, in almost all cases, it took significantly more time (on the order of 40%) to perform tasks on the moon. This increased time was observed even after extraneous factors (e.g., hardware difficulties) were factored out.

Kubis, J. F.↗
NASA NTRS1972

Apollo 16 time and motion study

A time and motion study is presented of astronaut lunar surface activity on Apollo 16 which consists of five distinct analyses: an evaluation of lunar mobility, a comparison of task performance in 1-g training and lunar EVA, a study of metabolic costs and adaptation, a discussion of falls, and retrieval of fallen objects. Two basic mobility patterns, the hop or canter and the traditional walking gait, were consistently utilized in longer traverses. The metabolic rates associated with these two mobility types, each used by a different astronaut, were relatively equivalent. The time to perform tasks on the lunar surface was significantly longer (on the order of 70%) than the time to perform the same tasks during the last 1-g training session. These results corroborated the findings on Apollo 15 and were not significantly different from them. There was general improvement in lunar EVA performance upon repetition of tasks. Metabolic rate (BTU/hr.) and metabolic cost (BTU) decreased over successive EVAs. Specifically, the metabolic rate associated with riding the lunar roving vehicle (LRV) decreased by approximately 18% from EVA 1 to EVA 2 and by 15% from EVA 2 to EVA 3.

Kubis, J. F.↗
NASA NTRS1972

Life cycle of brief CAT episodes determined by mesoscale analysis.

Using finely detailed data of the 1970 Haven Hop rawisonde network, it is shown that accurate delineation of clear air turbulence in space and short-term forecasting of CAT are possible with rawinsondes aviable at short time intervals and in a dense network. The present synoptic rawinsonde network of widely spaced stations with 12-hr observation intervals is insufficient to provide accurate depiction of meteorological functions accompanying CAT.

Boucher, R. J.↗
NASA NTRS1973

Competition between charge exchange and chemical reaction - The D2/+/ + H system

Study of the special features of molecular charge exchange and its competition with chemical reaction in the case of the D2(+) + H system. The trajectory surface hopping (TSH) model proposed by Tully and Preston (1971) is used to study this competition for a number of reactions involving the above system. The diatomics-in-molecules zero-overlap approximation is used to calculate the three adiabatic surfaces - one triplet and two singlet - which are needed to describe this system. One of the significant results of this study is that the chemical reaction and charge exchange are strongly coupled. It is also found that the number of trajectories passing into the chemical regions of the three surfaces depends very strongly on the surface crossings.-

Preston, R. K.↗
NASA NTRS1973

Cyclotron resonance wave amplification in the magnetosphere and energetic particle stability

Detailed electron distribution measurements in the outer magnetosphere now available indicate that the energetic electron anisotropy may be very energy dependent, there being positive anisotropies near the magnetic equator for low-energy particles and negative anisotropies in this region for high-energy particles. Previous wave growth calculations assuming the energetic particle anisotropy to be independent of energy are inaccurate at high energies. The net one-hop whistler mode wave amplification is calculated as a function of frequency for a measured electron distribution at L = 7 for a number of assumed equatorial plasma densities. It is found that an increase in cold plasma density results in a change from a net wave damping to significant wave amplification.

Lucas, C.↗
NASA NTRS1973

Satellite attitude control simulations

Work was conducted to develop an extremely low drift rate gyroscope and a very precise star tracker. A proposed relativity satellite will measure very accurately the theoretically predicted 'relativistic' precession of the gyroscope relative to an inertial reference frame provided by the star tracker. Aspects of precision spinning attitude control are discussed together with questions of gyro operation, and the hopping mode for lunar transportation. For the attitude control system of the lunar hopper, a number of control laws were investigated. The studies indicated that some suboptimal controls should be adequate for the system.

Debra, D. B.↗
NASA NTRS1974

Drift mobility of holes in phenanthrene single crystals

The temperature dependence of drift mobilities of holes in single crystals of phenanthrene was measured in the range from 203 to 353 K in three crystallographic directions. Below the anomaly temperature of 72 C, the mobility temperature dependences are consistent with the Munn and Siebrand slow-phonon hopping process in the b direction and the Munn and Siebrand slow-phonon coherent mode in the a and c prime directions. The drift mobility temperature dependences in crystals that have been cooled through the anomaly temperature in the presence of illumination and an electric field are consistent with the model of Spielberg et al. (1971), in which the hindered vibration of the 4,5 hydrogens introduces a new degree of freedom above 72 C.

Sonnonstine, T. J.↗
NASA NTRS1974

Crossed beam study of the reaction O/+/ + N2 yields NO/+/ + N

The kinematics of the reaction O(+)(4 S) + N2 yields NO(+) + N were studied using crossed molecular beams. Product angular and energy distributions were measured for the initial relative translational energy range from 1.5 to 15.8 eV. The products are formed in their ground electronic states. The product distributions are described, with some deviations, by the spectator stripping model. No evidence was found for a persistent complex or for a second mechanism. A scattering chamber study of 0 deg lab was made of the related reactions 15N(+) + 14NO yields 15N14N(+), 15NO(+), 14NO(+). The results obtained are discussed in terms of possible surface hopping effects.

Smith, G. P. K.↗
NASA NTRS1974

Tri- and tetraterpenoid hydrocarbons in the Messel oil shale

The high-molecular-weight constituents of the branched and cyclic hydrocarbon fraction of the Messel oil shale (Eocene) have been examined by high-resolution gas chromatography and combined gas chromatography/mass spectrometry. The following compounds are present: perhydrolycopene, together with one or more unsaturated analogs with the same skeleton; a series of 4-methylsteranes in higher abundance than their 4-desmethyl analogs; two series of pentacyclic triterpanes, one series based on the hopane structure, and the other based on the 17 alpha-H hopane structure; and an intact triterpene hop-17(21)-ene. Only two additional triterpanes were detected in minor concentrations - namely, 30-normoretane and a C31 triterpane based on the hopane/lupane-type skeleton. The presence of these compounds suggests a significant microbial contribution to the forming sediment.

Kimble, B. J.↗
NASA NTRS1974

Orbit design concepts for Jupiter orbiter missions

Advanced mission and orbit planning efforts are currently in progress for a Mariner-class Jupiter orbiter. Baseline spacecraft and orbit design criteria are the goals of a NASA effort to define such a mission. Orbit design concepts that have been discovered during the early stages of mission planning are both challenging and exciting. A description is given of several such concepts that may greatly increase the flexibility and scientific return of orbiters designed for close study of the Galilean satellites and exploration of the Jovian system. Some new jargon is introduced in discussions to describe the exploitation of gravity-assist trajectories using the giant satellites for orbit control. Orbit 'pumping' and 'cranking' and 'resonance hopping' are defined and shown to be dynamically feasible means of controlling the orbit and, thus, the scientific return. A candidate encounter sequence is presented for an equatorial tour of the Galilean moons.

Uphoff, C.↗
NASA NTRS1974

Propulsion dynamics of lunar hoppers

A feasibility study was recently completed on a hopping transporter concept for locomotion on the moon. Termed a Lunar Pogo because it would operate similarly to a conventional pogo stick, this vehicle would accelerate up an inclined leg, pick up the leg, and then enter ballistic flight over the moon's surface. Upon recontacting the lunar surface, the Lunar Pogo would decelerate down the leg. Propulsion would be provided by expansion of gas against a piston. Operation would be partially conservative because much of the energy expended by the gas during takeoff would be recovered by compressing the gas during landing. Two models of the ballistics and propulsion have been set up to estimate performance. The simplified first-order model illuminates the thermodynamics of ideal operation. The second-order model, which includes realistic effects such as sliding, provides a better approximation to actual performance. In a one-man Lunar Pogo, an astronaut would typically make 15-m (50-ft) leaps at an average speed of 5-8 km (3-5 miles) per hour.

Meetin, R. J.↗
NASA NTRS1979

Electromagnetic noise and radio wave propagation below 100 kHz in the Jovian atmosphere. I - The equatorial region

The Galileo satellite program includes the delivery of an entry probe to the Jovian equatorial atmosphere in mid-1985. Optical and RF sensors for a lightning detection system are included as a part of the probe experimental payload. In this paper, calculations of the RF wave propagation and reflection characteristics of the equatorial Jovian atmosphere and ionosphere for frequencies less than 100 kHz are presented. It is shown that wave propagation is limited to line-of-sight and one-hop from the ionosphere. Results are also presented of a statistical treatment of the RF wave power densities for the case of a finite number of events and for the case of a uniformly distributed source. The results can be applied to specific RF experiment configurations concerned with establishing the statistical characteristics of Jovian lightning.

Rinnert, K.↗
NASA NTRS1980

Feasibility and cost study on VOIR SAR data transfer via a bent pipe link

An INTELSAT/DOMSAT double hop bent pipe link for the Venus orbiting imaging radar synthetic aperture radar imaging data transfer from deep space stations 43 and 63 to the Jet Propulsion Laboratory was investigated. The cost for the bent pipe transfer was estimated and compared to that for the planned tape record/airfreight-the-tape transfer method.

Park, Y. H.↗