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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 253 records · Page 14

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NASA NTRS1973

High-quantum-efficiency infrared up-conversion.

Experimental study in which 100% conversion of infrared photons into visible photons was achieved through three wave interactions in a nonlinear medium. The first experimental evidence of overconversion is presented, and the classical theory of up-conversion in the high-conversion-efficiency region is confirmed. A laser pump light feedback technique is described that promises to make the process practical with modestly powerful pump lasers and less than perfect nonlinear crystals. The nonlinear medium used was a LiIO3 crystal that cannot be 90-deg phase-matched. The 'walk off' that resulted helped make possible the attainment of 100% conversion efficiency.

Gurski, T. R.↗

NASA NTRS1972

Unsteady viscous effects in the flow over an oscillating surface

A theoretical model for the interaction of a turbulent boundary layer with an oscillating wavy surface over which a fluid is flowing is developed, with an application to wind-driven water waves and to panel flutter in low supersonic flow. A systematic methodology is developed to obtain the surface pressure distribution by considering separately the effects on the perturbed flow of a mean shear velocity profile, viscous stresses, the turbulent Reynolds stresses, compressibility, and three-dimensionality. The inviscid theory is applied to the wind-water wave problem by specializing to traveling-wave disturbances, and the pressure magnitude and phase shift as a function of the wave phase speed are computed for a logarithmic mean velocity profile and compared with inviscid theory and experiment. The results agree with experimental evidence for the stabilization of the panel motion due to the influence of the unsteady boundary layer.

Lerner, J. I.↗

NASA NTRS1974

Recent theories of cavitation damage including non-symmetrical bubble collapse effects

Theories of cavitation damage mechanisms are discussed. Photographic evidence has shown that the actual collapse of bubbles near a symmetry-destroying feature such as a nearby wall results in a toroidal-like collapse, with the final generation of a liquid microjet oriented toward the wall. Numerical analyses indicate that the shock wave intensity emitted during collapse is not likely to be strong enough to be damaging to most materials. It has been determined that actual damage is usually a result of a combination of impact effect of the microjet and the shock wave pressures generated by bubble rebounds.

Hammitt, F. G.↗

NASA NTRS1982

Diffusive-convective physical vapor transport of PbTe from a Te-rich solid source

Crystal growth of PbTe by physical vapor transport (sublimation) in a closed ampoule is governed by the vapor species in thermal equilibrium with the solid compound. Deviations from stoichiometry in the source material cause diffusion limitation of the transport rate, which can be modified by natural (gravity-driven) convection. Mass-transport experiments have been performed using Te-rich material wherein sublimation rates have been measured in order to study the effects of natural convection in diffusion-limited vapor transport. Linear velocities for both crystal growth and evaporation (back sublimation) have been measured for transport in the direction of gravity, horizontally, and opposite to gravity. The experimental results are discussed in terms of both the one-dimensional diffusive-advective model and current, more sophisticated theory which includes natural convection. There is some evidence that convection effects from radial temperature gradients and solutal density gradients have been observed.

Zoutendyk, J.↗

NASA NTRS1984

Umbral oscillations in sunspots

Contrary to the claim by von Uexkuell et al. (1983), their observations of upward phase propagation of umbral oscillations in the chromosphere are in agreement with the photospheric resonance theory of Thomas and Scheuer (1982) and in contradiction to the chromospheric resonance theory of Zhugzhda et al. (1983). Other observational evidence also indicates that the fundamental 3-min umbral oscillation is due to a photospheric resonance, although the closely-spaced multiple peaks sometimes seen in the power spectrum of chromospheric oscillations may well be due to chromospheric resonances.

Thomas, J. H.↗

DOE OSTI2023

Prospect Theory and the Favorite Long-Shot Bias in Baseball

We provide new evidence of a favorite long-shot bias for bets placed on baseball games. Our analysis uses the difference of mean run differentials as an observable proxy for the probability of a team to win. When baseball is viewed through this proxy, we see that bettors believe favorites are less likely to win than they actually are and long-shots more likely. This result is consistent with prospect theory, which suggests that large and small probabilities are poorly estimated when making decisions with risk.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2021

Evidence of E × B staircase in HL-2A L-mode tokamak discharges

Theory and simulation suggest the existence of an E ×B staircase in the plasma core consisting of a series of nested m/n = 0/0 E×B shear layers that regulate turbulent transport across the layers together with mesoscale transport events occurring between them. Here, we show evidence for these phenomena in HL-2A L-mode discharges. Both high resolution electron cyclotron emission Te profiles and frequency modulated continuous wave reflectometer ne profiles show multiple gradient corrugations. The analysis of simultaneous poloidally and radially separated beam emission spectroscopy turbulent density fluctuation measurements over most of the minor radius of the plasma provides the evidence of eddy tilting and propagation direction reversals largely coincident with the profile corrugations, with long-range transport events occurring between these locations. The results provide significant additional evidence for the existence of an E × B staircase that influences particle and heat transport in L-mode discharges.

Liu, Wenbin (ORCID:0000000310424117)↗

DOE OSTI2020

Backpropagated frame transformation theory: A reformulation

In this work, the energy-dependent frame transformation theory of Gao and Greene [H. Gao and C. H. Greene, Phys. Rev. A 42, 6946 (1990)] is extended to yield a quantitatively accurate description of the dissociative recombination process. Evidence is presented to show that direct application of the original theory leads to inaccurate cross sections. A major revision, based on an interaction-free backpropagation of the Born-Oppenheimer solutions, markedly improves the frame transformation theory, reducing its average error by orders of magnitude. The original theory and its extension are tested on the previously explored two-dimensional (2D) model that is tailored to describe the singlet ungerade states of molecular hydrogen. The 2D model can be solved exactly (within the numerical accuracy) without implementing the Born-Oppenheimer approximation. These exact results then serve as a benchmark for the frame transformation theory developed in this paper.

74 ATOMIC AND MOLECULAR PHYSICS↗

NASA NTRS1986

Interaction between workload and training - Converging evidence from psychophysiology and performance measurement

Traditionally, the domains of mental workload and training have been studied in isolation even though they share many common characteristics. The present paper integrates findings from psychophysiological and performance-based studies which address both of these issues. By augmenting traditional indices of skill acquisition such as RMS error scores, reaction times, and accuracy measures with psychophysiological measures such as the event-related brain potential, it is shown that workload effects can be assessed throughout the training process. More specifically, it is argued that the development of skill and the effects of workload on the human operator can be modeled within the framework of resource theories of attentional allocation. Also described is how converging evidence from psychophysiological and behavioral studies can be used to examine subtle changes in operator strategies during training.

Kramer, Arthur F.↗

NASA NTRS1982

Theoretical and experimental power from large horizontal-axis wind turbines

A method for calculating the output power from large horizontal-axis wind turbines is presented. Modifications to the airfoil characteristics and the momentum portion of classical blade element-momentum theory are given that improve correlation with measured data. Improvement is particularly evident at low tip-speed ratios where aerodynamic stall can occur as the blade experiences high angles of attack. Output power calculated using the modified theory is compared with measured data for several large wind turbines. These wind turbines range in size from the DOE/NASA 100 kW Mod-0 (38 m rotor diameter) to the 2000 kW Mod-1 (61 m rotor diameter). The calculated results are in good agreement with measured data from these machines.

Viterna, L. A.↗

DOE OSTI2020

Subleading corrections to the free energy in a theory with N 5/3 scaling

We numerically investigate the sphere partition function of a Chern-Simons-matter theory with SU(N) gauge group at level k coupled to three adjoint chiral multiplets that is dual to massive IIA theory. Beyond the leading order N 5/3 behavior of the free energy, we find numerical evidence for a term of the form (2/9) log N. We conjecture that this term may be universal in theories with N 5/3 scaling in the large-N limit with the Chern-Simons level k held fixed.

1/N Expansion↗

DOE OSTI2024

Evidence for Topological Protection Derived from Six-Flux Composite Fermions

The composite fermion theory opened a new chapter in understanding many-body correlations through the formation of emergent particles. The formation of two-flux and four-flux composite fermions is well established. While there are limited data linked to the formation of six-flux composite fermions, topological protection associated with them is conspicuously lacking. Here we report evidence for the formation of a quantized and gapped fractional quantum Hall state at the filling factor ν = 9/11, which we associate with the formation of six-flux composite fermions. Our result provides evidence for the most intricate composite fermion with six fluxes and expands the already diverse family of highly correlated topological phases with a new member that cannot be characterized by correlations present in other known members. Our observations pave the way towards the study of higher order correlations in the fractional quantum Hall regime.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1980

Organic compounds in meteorites

Recent studies of carbonaceous chondrites provide evidence that certain organic compounds are indigenous and the result of an abiotic, chemical synthesis. The results of several investigators have established the presence of amino acids and precursors, mono- and dicarboxylic acids, N-heterocycles, and hydrocarbons as well as other compounds. For example, studies of the Murchison and Murray meteorites have revealed the presence of at least 40 amino acids with nearly equal abundances of D and L isomers. The population consists of both protein and nonprotein amino acids including a wide variety of linear, cyclic, and polyfunctional types. Results show a trend of decreasing concentration with increasing carbon number, with the most abundant being glycine (41 n Moles/g). These and other results to be reviewed provide persuasive support for the theory of chemical evolution and provide the only natural evidence for the protobiological subset of molecules from which life on earth may have arisen.

Lawless, J. G.↗

NASA NTRS1966

Short Period Fluctuations in Intelligence Final Report

The problem of isolating fluctuations in intellectual function is one that has long intrigued both psychologists and non-psychologists, We are all aware of our own short-period physiological, mood and motivational changes and many believe that their intelligence must undergo similar change. 1965 for a recent review) does not provide support for this kind of argu- ment. It indicates that measures of intelligence - -at least those intended for use with people other than infants --are usually highly stable over both short and rather extended periods of time: the changes which are indicated have almost always been regarded as errors of measurement. Thus in scientific developments (as opposed, perhaps, to common- sense discussions) ;intelligence usually has been regarded as a highly stable attribute of man. But existing scientific evidence (see Tyler, A notable exception to the scientific theory arguing (albeit im- plicitly) that human intellect does not fluctuate over short period of time is that of Moran (1961) and his co-workers (Moran, Kimble & Mefferd, 1960; 1964; Moran & Mefferd, 1959). The work of these in- vestigators has been directed at designing alternate -form tests to measure some of what are now regarded as the major, replicated-by- research dimensions of human intelligence, viz., what are known as the primary mental abilities (French, 1951: French, Ekstrom & Price, 1963; Guilford, 1966; Guilford & Merrifield, 1960). The Repetitive Psychological Measures (RPM) resulting from this work are intended to assess "change in performance with time" (Moran & Mefferd, 1959: p. 269). little has been done to determine whether or not the performances actually assessed do, in fact, change in a reliable manner. Indeed, evidence somewhat contrary to an hypothesis of short-period change is provided by the high (relative to test length) test-retest correlations ob- tained over a period of 3 hours with the RPM tests (Moran & Mefferd, 1959; Table 2). Hence, while a basic hypothesis underlying this work certainly does imply that abilities change over short periods, evidence for this hypothesis either has not been developed or, where it has (as in test-retest correlations), does not provide convincing support for the hypothesis

Intelligence↗

NASA NTRS2012

Impact of Aerosols on Convective Clouds and Precipitation

Aerosols are a critical factor in the atmospheric hydrological cycle and radiation budget. As a major agent for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosol effects on clouds could further extend to precipitation, both through the formation of cloud particles and by exerting persistent radiative forcing on the climate system that disturbs dynamics. However, the various mechanisms behind these effects, in particular the ones connected to precipitation, are not yet well understood. The atmospheric and climate communities have long been working to gain a better grasp of these critical effects and hence to reduce the significant uncertainties in climate prediction resulting from such a lack of adequate knowledge. Here we review past efforts and summarize our current understanding of the effect of aerosols on convective precipitation processes from theoretical analysis of microphysics, observational evidence, and a range of numerical model simulations. In addition, the discrepancy between results simulated by models, as well as that between simulations and observations, are presented. Specifically, this paper addresses the following topics: (1) fundamental theories of aerosol effects on microphysics and precipitation processes, (2) observational evidence of the effect of aerosols on precipitation processes, (3) signatures of the aerosol impact on precipitation from largescale analyses, (4) results from cloud-resolving model simulations, and (5) results from large-scale numerical model simulations. Finally, several future research directions for gaining a better understanding of aerosol--cloud-precipitation interactions are suggested.

Tao, Wei-Kuo↗

NASA NTRS2011

Impact of Aerosols on Convective Clouds and Precipitation

Aerosols are a critical factor in the atmospheric hydrological cycle and radiation budget. As a major reason for clouds to form and a significant attenuator of solar radiation, aerosols affect climate in several ways. Current research suggests that aerosol effects on clouds could further extend to precipitation, both through the formation of cloud particles and by exerting persistent radiative forcing on the climate system that disturbs dynamics. However, the various mechanisms behind these effects, in particular the ones connected to precipitation, are not yet well understood. The atmospheric and climate communities have long been working to gain a better grasp of these critical effects and hence to reduce the significant uncertainties in climate prediction resulting from such a lack of adequate knowledge. The central theme of this paper is to review past efforts and summarize our current understanding of the effect of aerosols on precipitation processes from theoretical analysis of microphysics, observational evidence, and a range of numerical model simulations. In addition, the discrepancy between results simulated by models, as well as that between simulations and observations will be presented. Specifically, this paper will address the following topics: (1) fundamental theories of aerosol effects on microphysics and precipitation processes, (2) observational evidence of the effect of aerosols on precipitation processes, (3) signatures of the aerosol impact on precipitation from large-scale analyses, (4) results from cloud-resolving model simulations, and (5) results from large-scale numerical model simulations. Finally, several future research directions on aerosol - precipitation interactions are suggested.

Tao, Wei-Kuo↗

NASA NTRS1971

Nucleosynthesis in the Magellanic Clouds and the Galaxy.

Available evidence on the chemical composition of the Magellanic Clouds (when compared to the Galaxy) is not sufficient for a detailed theory of the chemical evolution of the Clouds to be developed at present. However, this evidence is thus far compatible with the view that much of the material of the Clouds went through a considerable amount of nucleosynthesis early in its history. The Clouds could once have been part of the Galaxy, or they could have formed as satellites when the protogalaxy condensed. The general problem of the chemical evolution is tied closely to the problem of galaxy formation which remains unsolved.

Burbidge, G.↗

DOE OSTI2024

Strategically Modified Ligand Incorporating Mixed Phosphonate and Carboxylate Groups to Enhance Performance in All-Iron Redox Flow Batteries

Iron redox flow batteries (Fe-RFBs) hold significant promise for achieving cost-effectiveness and utilizing abundant materials for stationary energy storage applications. Here, a design of a novel Fe complex utilizing a nitrogenous phosphonate/carboxylate mixed ligand, N,N-Bis(phosphonomethyl)glycine (BMPG), is presented to achieve high performance Fe anolyte. Compared to its all-phosphonate form, nitrilotri(methylphosphonic acid) (NTMPA), the new complex Fe(BPMG) 2 demonstrates a negatively shifted redox potential, resulting in ≈0.07 V (≈10%) increase in battery output voltage. Full battery testing paired with ferrocyanide catholyte demonstrates stable cycling (capacity degradation <0.0001%/cycle) over 730 consecutive charge/discharge cycles with Coulombic Efficiency of 100% at a current density of 20 mA cm -2 under near neutral pH (≈8). Of particular interest, density functional theory (DFT) studies and operando Raman measurements provide strong evidence supporting a molecular structure in BPMG, which reveals the mixed phosphonate/carboxylate groups in BPMG maintain the octahedral coordination of the Fe ion center with phosphonates exclusively, while leaving the carboxylate unbound for both Fe(II) and Fe(III) complexes. This structural similarity between BPMG-based Fe(II) and Fe(III) complexes effectively mitigates the slow redox reaction kinetics observed in Fe(NTMPA) 2 anolyte, where significant ligand reorientation occurs between Fe(II) and Fe(III) complexes.

25 ENERGY STORAGE↗