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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in p p collisions at s = 13 TeV using the ATLAS detector

We report results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum. The search uses proton-proton collision data corresponding to an integrated luminosity of 3.2 fb $-$1 at $\sqrt{s}$ = 13 TeV collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between E$miss\atop{T}$ > 250 GeV and E$miss\atop{T}$ > 700 GeV . Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Heat of Melting of Small Clusters in the Model of the Potential with the Effective Well Depth

Within the framework of the cluster model using the Mie pair power-law interaction potential with the effective depth of the potential well, whose depth is determined by the number of particles in the cluster, an equation for the calculation of the heat of melting of cluster systems is obtained. The resulting mathematical expression does not contain empirical constants and shows that the ratio of the heat of melting of a cluster to the heat of melting of a macroscopic sample is a universal function of the number of particles in the cluster and mathematically described by the square of the hyperbolic tangent.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb -1 of \(\sqrt{s{\mathrm{}}} = 8\) TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with p T >120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between E miss T >150 GeV and E miss T >700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. Results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Investigation of Aerodynamic Interference between Twin Deck Bridges

Construction of a twin bridge can be a cost effective and minimally disruptive way to increase capacity when an existing bridge is not near the end of its service life. With ever growing vehicular traffic, when demand approaches the capacity of many existing roads and bridges. Remodeling a structure with an insufficient number of lanes can be a good solution in case of smaller and less busy bridges. Closing down or reducing traffic on crossings of greater importance for the construction period, however, can result in major delays and revenue loss for commerce and transportation as well as increasing the traffic load on alternate route bridges. Multiple-deck bridges may be the answer to this issue. A parallel deck can be built next to the existing one, without reducing the flow. Additionally, a new bridge can be designed as a twin or multi-deck structure. Several such structures have been built throughout the United States, among them: - The New NY Bridge Project - the Tappan Zee Hudson River Crossing, - SR-182 Columbia River Bridge, - The Thaddeus Kosciusko Bridge (I-87), - The Allegheny River Bridge, Pennsylvania, which carries I76, - Fred Hartman Bridge, TX, see Figure 1.2. With a growing number of double deck bridges, additional, more detailed, studies on the interaction of such bridge pairs in windy conditions appears appropriate. Aerodynamic interference effects should be examined to assure the aerodynamic stability of both bridges. There are many studies on aerodynamic response of single deck bridges, but the literature on double-deck structures is not extensive. The experimental results from wind tunnels are still limited in number, as a parametric study is required, they can be very time consuming. Literature review shows that some investigation of the effects of gap-width and angle of wind incidence has been done. Most of the CFD computational studies that have been done were limited to 2D simulations. Therefore, it is desirable to investigate twin decks of various cross-sections, gap-to-width ratios, wind speed and direction using three-dimensional CFD simulations. After verification with wind tunnel test results, this type of analysis could become a powerful tool for future designs as well as for monitoring of existing bridges.

42 ENGINEERING↗
DOE OSTI2018

A dynamic model for social networks

Social network graph models are data structures representing entities (often people, corporations, or accounts) as "vertices" and their interactions as "edges" between pairs of vertices. These graphs are most often total-graph models — the overall structure of edges and vertices in a bidirectional or directional graph are described in global terms and the network is generated algorithmically. We are interested in "egocentrie or "agent-based" models of social networks where the behavior of the individual participants are described and the graph itself is an emergent phenomenon. Our hope is that such graph models will allow us to ultimately reason from observations back to estimated properties of the individuals and populations, and result in not only more accurate algorithms for link prediction and friend recommendation, but also a more intuitive understanding of human behavior in such systems than is revealed by previous approaches. This report documents our preliminary work in this area; we describe several past graph models, two egocentric models of our own design, and our thoughts about the future direction of this research.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2026

The Role of Cooperative Interactions Among Surfaces, Solvents, and Reactive Intermediates on Catalysis at Liquid–Solid Interfaces (Final Report DE-SC0020224)

This project established quantitative links between inner‑sphere chemistry (active metal identity, coordination, and zeolite topology) and outer‑sphere organization (solvent identity, hydrogen‑bond networks, and pore condensation) that govern rates, activation barriers, and selectivities for alkene epoxidation and epoxide ring‑opening at solid–liquid and quasi‑liquid–solid interfaces. We deconvoluted contributions from covalent interactions at active sites and noncovalent, solvent‑mediated interactions within pores by pairing well‑defined metal substituted zeolites with controlled solvent environments. We then mapped those contributions onto measurable kinetics (ΔH‡, ΔS‡), adsorption thermodynamics (ITC), and in situ spectroscopy. The transferrable outcomes include a set of design rules that include the following understandings. First, tune silanol ((SiOH)x) density and pore topology to organize solvent networks that selectively stabilize transition states. Second, exploit activity‑coefficient‑normalized rates and adsorption– barrier correlations to diagnose when solvent reorganization rather than surface chemistry limits performance. Third, use partial pore condensation (e.g., acetonitrile, water but also generalizable to other solvents) to elicit liquid‑like stabilization effects even in nominally vapor‑phase reactors. Collectively, these results provide strategies to increase epoxidation rates, improve oxidant utilization (i.e., selectivities), and steer regioselectivity in zeolite‑based catalytic processes relevant to sustainable oxidation chemistry. These outcomes should be transferable to other classes of reactions that proceed in microporous materials and under confinement provided by organized solvents (e.g., electrochemical double layers).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1969

Second-order dispersion-energy series for axially symmetric molecules.

With the aid of a model representing each molecule as a set of semi‐isotropic dipole oscillators, the London‐van der Waals interaction energy of a pair of unexcited axially symmetric molecules is calculated, in the second order of perturbation theory, as an infinite series in negative powers of the intermolecular separation.

Johannes H van der Merwe↗
NASA NTRS1976

Three dimensional aspects of interplanetary shock waves

Most of the interplanetary shock waves observed with 1 AU of the sun originate from some short lived solar event, such as a solar flare, and then propagate out as a more-or-less spherical shock wave until they leave the solar system. Beyond 1 AU another class of interplanetary shock wave becomes common--the corotating shock pair formed by the interaction of long lived solar wind streams. The three dimensional geometry of these two classes of interplanetary shocks is discussed. Also discussed are how these geometries can be statistically studied with an out-of-the-ecliptic mission. Diagrams of shock wave propagation are shown. Also given are numerical examples of shock wave propagation.

Siscoe, G. L.↗
NASA NTRS1976

Three-dimensional aspects of interplanetary shock waves

The three-dimensional geometries of two classes of interplanetary shock waves are analyzed: (1) the more or less spherical shock wave originating from some short-lived solar event, such as a solar flare, and (2) the corotating shock pair formed by the interaction of long-lived solar wind streams. The systematic distortion of a spherical wave due to persistent latitudinal solar wind structure should amount to 25 deg for an equator-to-pole solar wind speed differential of 200 km/sec. A geometrical argument is given for determining the heliocentric distance of the onset of corotating shocks formed by contiguous long-lived solar streams. Estimates are obtained for the heliocentric distance to the inner edges of shock waves as a function of speed difference between the streams and as a function of heliographic latitude. Means by which the three-dimensional structures studied can be observed by out-of-the-ecliptic space missions are discussed.

Siscoe, G. L.↗
NASA NTRS1980

Modeling of radiation damage in silicon solar cells

One MeV electron irradiation produces preponderantly isolated vacancy interstitial pairs. If neither of these defects is mobile, the concentration of each grows linearly with fluence. Annealing of damage depends on the nature of the damage. Vacancy interstitial pairs which are bound by an interaction such that they mutually annihilate rather than dissociate are termed close pairs; close pair recovery usually occurs at a lower temperature than the temperature at which long distance defect migration occurs. Annealing of the remaining frozen in damage occurs when a temperature is reached where the vacancy or interstitial is mobile; usually the interstitial is more mobile than the vacancy. The recovery occurs in two regimes which may be resoluable.

Oehrlein, G.↗
NASA NTRS1986

Theoretical study of the X 2Pi and A 2Sigma(+) states of CuO and CuS

Theoretical spectroscopic constants and dipole moments are determined for the X 2Pi and A 2Sigma(+) states of CuO and CuS, using extended Gaussian basis sets and incorporating correlation using both configuration interaction (CI) and coupled pair (CPF) methods. Relativistic corrections (Darwin plus mass velocity), included using first-order perturbation theory, are found to be relatively small. At the CPF level, significant configuration mixing with the 3d(9)4s(1) occupation occurs for both states, resulting in some bond shortening and a significant increase in the dissociation energy. The best spectroscopic parameters are in excellent agreement with experiment for both CuO and CuS. In analogy with CuO, CuS is predicted to have a yet unobserved 2Sigma(+) state near 10,000 per cm.

Langhoff, S. R.↗
NASA NTRS1987

Positive ions of the first- and second-row transition metal hydrides

Theoretical dissociation energies for the first- and second-row transition metal hydride positive ions are critically compared against recent experimental values obtained from ion beam reactive scattering methods. Theoretical spectroscopic parameters and dipole moments are presented for the ground and several low-lying excited states. The calculations employ large Gaussian basis sets and account for electron correlation using the single-reference single- and double-excitation configuration interaction and coupled-pair-functional methods. The Darwin and mass-velocity contributions to the relativistic energy are included in the all-electron calculations on the first-row systems using first-order perturbation theory, and in the second-row systems using the Hay and Wadt relativistic effective core potentials. The theoretical D(0) values for the second-row transition metal hydride positive ions should provide a critical measure of the experimental values, which are not as refined as many of those in the first transition row.

Pettersson, Lars G. M.↗
NASA NTRS1988

The role of high energy photons and particles in accretion flows in active nuclei

The creation of high energy pairs and photons in the conversion of gravitational to thermal energy is a process common to most accretion models for active galactic nuclei. These are two observational methods designed to explore this process: direct observations of the hot photons, through hard X-ray and gamma-ray data, and indirect observations of the energetic pairs, through their polarized, nonthermal low frequency radiation. However, interpretation of these observations in terms of the conditions in the inner accretion flow requires understanding of the various processes which modify the pair and photon distributions within the hot, dense core. These processes include opacity effects within the pair/photon plasma, Compton losses on external photons, further acceleration of the pairs and further radiation by the pairs, and the dynamic interaction of the pair/photon plasma with the surrounding gas. Current observational and theoretical work is reviewed and new directions are considered in a search for constraints on or tests of accretion models of active nuclei.

Eilek, Jean A.↗
NASA NTRS1993

Stretch-induced quenching in flame-vortex interactions

The flame-vortex interaction problem is a natural configuration in which several issues relevant to turbulent combustion can be addressed: effect of strain-rate and curvature, effect of the Lewis number, effect of heat losses, effect of complex chemistry, and flame-generated turbulence. In such an approach, the interaction of an isolated vortex with a laminar premixed flame is viewed as a unit process of a turbulent premixed flame in which the reaction zone keeps a laminar like structure locally; this is precisely the case of the wrinkled flame or flamelet regime in turbulent combustion. The present work complements previous studies and involves the study of the interaction of a vortex pair and a laminar premixed flame in a planar two-dimensional geometry, together with numerical simulations. This geometry is quite unique since most studies have considered axisymmetric vortex rings. Such a geometry offers several advantages over previous studies.

Samaniego, J.-M.↗
NASA NTRS1996

High-Resolution X-Ray Imaging of Colliding Radio-Jet Galaxies

We received ROSAT data for four program objects:3C31,3C278,3C449,and NGC1044. The first three sources were observed with the ROSAT HRI instrument. Our plan was to use the HRI to image the hot gas distribution in a few pairs of strongly disturbed interacting elliptical galaxies which are also strong radio sources having a bent-jet source morphology. The PSPC was used for NGC1044 in order to obtain a flux measurement to use in planning future High Resolution Imager (HRI) observations of that source. Though we never requested such HRI observations of NGC1044, others have used those archival PSPC data from our project for other research projects and analyses. The goal of the program was to elucidate the detailed distribution of hot gas into which the jets flow. The X-ray data were consequently analyzed in conjunction with existing VLA radio maps, optical broad-band and H-alpha Charge Couple device (CCD) images, and optical kinematic data to constrain models for the propagation of ballistic jets in interacting galaxies. We were able to test and validate the claimed causal connection between tidal interaction, the presence of gas, and the onset of activity in galaxies. The full multi-wavelength multi-observatory analyses described here are still on-going and will be published in the future. Because of the relevance of this research to on-going work in the field of active galaxies, the grant was used to support travel to several scientific meetings where our x-ray analysis, numerical modeling, and related radio results were presented and discussed.

Born, Kirk D.↗
NASA NTRS1998

Shear-Layer Effects on Trailing Vortices

Crosswind shear can influence the trailing vortex trajectories significantly, according to both field measurement and numerical simulations. Point vortex models are used in this paper to study the fluid dynamic mechanism in the interactions between trailing vortex pair and shear layers. It has been shown that the shear-layer deformation causes the vortex descent history difference in the two vortices of the vortex pair. When a shear layer is below the vortex pair with the same sign as the left vortex, the right vortex descends less than the left vortex. When the same shear layer is above the vortex pair, the right vortex descends more. The descent altitudes of the two vortices are the same when they go through a constant, non-deformed shear layer. Those trends are in agreement with Navier-Stokes simulations.

Zheng, Z. C.↗
NASA NTRS2009

Highly Efficient Design-of-Experiments Methods for Combining CFD Analysis and Experimental Data

It is the purpose of this study to examine the impact of "highly efficient" Design-of-Experiments (DOE) methods for combining sets of CFD generated analysis data with smaller sets of Experimental test data in order to accurately predict performance results where experimental test data were not obtained. The study examines the impact of micro-ramp flow control on the shock wave boundary layer (SWBL) interaction where a complete paired set of data exist from both CFD analysis and Experimental measurements By combining the complete set of CFD analysis data composed of fifteen (15) cases with a smaller subset of experimental test data containing four/five (4/5) cases, compound data sets (CFD/EXP) were generated which allows the prediction of the complete set of Experimental results No statistical difference were found to exist between the combined (CFD/EXP) generated data sets and the complete Experimental data set composed of fifteen (15) cases. The same optimal micro-ramp configuration was obtained using the (CFD/EXP) generated data as obtained with the complete set of Experimental data, and the DOE response surfaces generated by the two data sets were also not statistically different.

Anderson, Bernhard H.↗
NASA NTRS2013

Simple Sensitivity Analysis for Orion Guidance Navigation and Control

The performance of Orion flight software, especially its GNC software, is being analyzed by running Monte Carlo simulations of Orion spacecraft flights. The simulated performance is analyzed for conformance with flight requirements, expressed as performance constraints. Flight requirements include guidance (e.g. touchdown distance from target) and control (e.g., control saturation) as well as performance (e.g., heat load constraints). The Monte Carlo simulations disperse hundreds of simulation input variables, for everything from mass properties to date of launch. We describe in this paper a sensitivity analysis tool ("Critical Factors Tool" or CFT) developed to find the input variables or pairs of variables which by themselves significantly influence satisfaction of requirements or significantly affect key performance metrics (e.g., touchdown distance from target). Knowing these factors can inform robustness analysis, can inform where engineering resources are most needed, and could even affect operations. The contributions of this paper include the introduction of novel sensitivity measures, such as estimating success probability, and a technique for determining whether pairs of factors are interacting dependently or independently. The tool found that input variables such as moments, mass, thrust dispersions, and date of launch were found to be significant factors for success of various requirements. Examples are shown in this paper as well as a summary and physics discussion of EFT-1 driving factors that the tool found.

Pressburger, Tom↗