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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Community reactions to aircraft noise in the vicinity of airport: A comparative study of the social surveys using interview method

A comparative study was performed on the reports of community reactions to aircraft noise. The direct and immediate reactions to aircraft noise such as perceived noisiness, interference with conversations, etc. and various emotional influences were most remarkable; indirect and long term influences such as disturbance of mental work and physical symptoms were less remarkable.

Osada, Y.↗
DOE OSTI2015

A comparative study of hyperon equations of state in supernova simulations

A comparative study of the Λ hyperon equations of state of Banik, Hempel and Banyopadhyay (BHB), Banik et al., and Shen et al. (denoted as HShen Λ) for core-collapse supernova (CCSN) simulations is carried out in this work. The dynamical evolution of a protoneutron star (PNS) into a black hole is investigated in CCSN simulations in the general relativistic one-dimensional code using the BHBΛϕ and HShen Λ equation of state (EOS) tables and different progenitor models from Woosley and Heger. Radial profiles of the mass fractions of baryons, the density, as well as the temperature in the PNS at different moments in time, are compared for both EOS tables. The behavior of the central density of the PNS with time is demonstrated for these two Λ hyperon EOS tables and compared with their corresponding nuclear EOS tables. It is observed that the black hole formation time is higher in the BHBΛϕ case than in the HShen Λ EOS case for the entire set of progenitor models adopted here, because the repulsive Λ–Λ interaction makes the BHBΛϕ EOS stiffer. Neutrino emission with the Λ hyperon EOS ceases earlier than that of its nuclear counterpart. The long-duration evolution of the shock radius and the gravitational mass of the PNS after a successful supernova explosion with enhanced neutrino heating are studied with the BHBΛϕ EOS and s20WH07 progenitor model. The PNS is found to remain stable for 4 s and might evolve into a cold neutron star.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Comparative studies of 2HDMs under the Higgs boson precision measurements

We perform comparative studies for four types of the two Higgs Doublet Models (2HDMs) under the precision measurements of the Standard Model (SM) Higgs observables at the proposed Higgs factories. We explore the discovery potential based on the hypothetical deviations in the precision data for the 2HDMs up to one-loop level. We find 5σ observability from the χ2 fitting in a significant theory parameter space at future Higgs factories. For the Type-I 2HDM, regions with cos(β - α) ≲ -0.1 or cos(β - α) ≳ 0.08 are discoverable at more than 5σ level. For the other three types of 2HDMs, the 5σ region is even bigger: | cos(β - α)| ≳ 0.02 for tan β ~ 1. At small and large values of tan β, the region in cos(β - α) is further tightened. We examine the extent to which the different 2HDM theories may be distinguishable from one to the other at the 95% Confidence Level with four benchmark points as case studies. We show that a large part of the parameter space of the other types of 2HDMs can be distinguished from the benchmark points of the target model. The impacts of loop corrections are found to be significant in certain parameter regions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2013

A Comparative Study of Four Impedance Eduction Methodologies Using Several Test Liners

A comparative study of four commonly used impedance eduction methods is presented for a range of liner structures and test conditions. Two of the methods are restricted to uniform flow while the other two accommodate both uniform and boundary layer flows. Measurements on five liner structures (a rigid-wall insert, a ceramic tubular liner, a wire mesh liner, a low porosity conventional liner, and a high porosity conventional liner) are obtained using the NASA Langley Grazing Flow Impedance Tube. The educed impedance of each liner is presented for forty-two test conditions (three Mach numbers and fourteen frequencies). In addition, the effects of moving the acoustic source from upstream to downstream and the refractive effects of the mean boundary layer on the wire mesh liner are investigated. The primary conclusions of the study are that: (1) more accurate results are obtained for the upstream source, (2) the uniform flow methods produce nearly identical impedance spectra at and below Mach 0.3 but significant scatter in the educed impedance occurs at the higher Mach number, (3) there is better agreement in educed impedance among the methods for the conventional liners than for the rigid-wall insert, ceramic, or wire mesh liner, and (4) the refractive effects of the mean boundary layer on the educed impedance of the wire mesh liner are generally small except at Mach 0.5.

Watson, Willie R.↗
NASA NTRS1989

A comparative study of Navier-Stokes codes for high-speed flows

A comparative study was made with four different codes for solving the compressible Navier-Stokes equations using three different test problems. The first of these cases was hypersonic flow through the P8 inlet, which represents inlet configurations typical of a hypersonic airbreathing vehicle. The free-stream Mach number in this case was 7.4. This 2-D inlet was designed to provide an internal compression ratio of 8. Initial calculations were made using two state-of-the-art finite-volume upwind codes, CFL3D and USA-PG2, as well as NASCRIN, a code which uses the unsplit finite-difference technique of MacCormack. All of these codes used the same algebraic eddy-viscosity turbulence model. In the experiment, the cowl lip was slightly blunted; however, for the computations, a sharp cowl leading edge was used to simplify the construction of the grid. The second test problem was the supersonic (Mach 3.0) flow in a three-dimensional corner formed by the intersection of two wedges with equal wedge angles of 9.48 degrees. The flow in such a corner is representative of the flow in the corners of a scramjet inlet. Calculations were made for both laminar and turbulent flow and compared with experimental data. The three-dimensional versions of the three codes used for the inlet study (CFL3D, USA-PG3, and SCRAMIN, respectively) were used for this case. For the laminar corner flow, a fourth code, LAURA, which also uses recently-developed upwind technology, was also utilized. The final test case is the two-dimensional hypersonic flow over a compression ramp. The flow is laminar with a free-stream Mach number of 14.1. In the experiment, the ramp angle was varied to change the strength of the ramp shock and the extent of the viscous-inviscid interaction. Calculations were made for the 24-degree ramp configuration which produces a large separated-flow region that extends upstream of the corner.

Rudy, David H.↗
DOE OSTI2014

Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

Comparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoïd thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable β-W phase.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A comparative study for Hydrogen storage in metal decorated graphyne nanotubes and graphyne monolayers

A comparative study for hydrogen storage in metal decorated graphyne nanotubes and graphyne monolayers has been investigated within the framework of first-principle calculations. Our results show that the binding energies of Li, Ca, Sc, Ti on graphyne nanotubes are stronger than that on graphyne monolayers. Such strong binding would prevent the formation of metal clusters on graphyne nanotubes. From the charge transfer and partial density of states, it is found that the curvature effect of nanotubes plays an important role for the strong binding strength of metal on graphyne nanotubes. And the hydrogen storage capacity is 4.82 wt%, 5.08 wt%, 4.88 wt%, 4.76 wt% for Li, Ca, Sc, Ti decorated graphyne nanotubes that promise a potential material for storing hydrogen. - Graphical abstract: Metal atoms (Li, Ca, Sc and Ti) can strongly bind to graphyne nanotubes to avoid the formation of metal clusters, and a capacity of Ca@graphyne nanotube is 5.08 wt% which is close to the requirement of DOE in 2015. Twenty-four hydrogen molecules absorb to Ti-decorated graphyne nanotube. - Highlights: • The binding strength for metal on graphyne nanotubes is much stronger than that on γ-graphyne monolayer. • Metal atoms can strongly bind to the curving triangle acetylenes rings to avoid the formation of metal clusters. • A capacity of Ca@graphyne nanotube is 5.08 wt% which is close to the requirement of DOE in 2015.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

A comparative study of computational solutions to flow over a backward-facing step

A comparative study was conducted for computational fluid dynamic solutions to flow over a backward-facing step. This flow is a benchmark problem, with a simple geometry, but involves complicated flow physics such as free shear layers, reattaching flow, recirculation, and high turbulence intensities. Three Reynolds-averaged Navier-Stokes flow solvers with k-epsilon turbulence models were used, each using a different solution algorithm: finite difference, finite element, and hybrid finite element - finite difference. Comparisons were made with existing experimental data. Results showed that velocity profiles and reattachment lengths were predicted reasonably well by all three methods, while the skin friction coefficients were more difficult to predict accurately. It was noted that, in general, selecting an appropriate solver for each problem to be considered is important.

Mizukami, M.↗
DOE OSTI2016

TRANSIENT GALACTIC COSMIC-RAY MODULATION DURING SOLAR CYCLE 24: A COMPARATIVE STUDY OF TWO PROMINENT FORBUSH DECREASE EVENTS

Forbush decrease (FD) events are of great interest for transient galactic cosmic-ray (GCR) modulation study. In this study, we perform comparative analysis of two prominent Forbush events during cycle 24, occurring on 2012 March 8 (Event 1) and 2015 June 22 (Event 2), utilizing the measurements from the worldwide neutron monitor (NM) network. Despite their comparable magnitudes, the two Forbush events are distinctly different in terms of evolving GCR energy spectrum and energy dependence of the recovery time. The recovery time of Event 1 is strongly dependent on the median energy, compared to the nearly constant recovery time of Event 2 over the studied energy range. Additionally, while the evolutions of the energy spectra during the two FD events exhibit similar variation patterns, the spectrum of Event 2 is significantly harder, especially at the time of deepest depression. These difference are essentially related to their associated solar wind disturbances. Event 1 is associated with a complicated shock-associated interplanetary coronal mass ejection (ICME) disturbance with large radial extent, probably formed by the merging of multiple shocks and transient flows, and which delivered a glancing blow to Earth. Conversely, Event 2 is accompanied by a relatively simple halo ICME with small radial extent that hit Earth more head-on.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Comparative studies of actinide and sub-actinide fission cross section calculation from MCNP6 and TALYS

Comparative studies of actinide and sub-actinide fission cross section calculation from MCNP6 and TALYS have been conducted. In this work, fission cross section resulted from MCNP6 prediction will be compared with result from TALYS calculation. MCNP6 with its event generator CEM03.03 and LAQGSM03.03 have been validated and verified for several intermediate and heavy nuclides fission reaction data and also has a good agreement with experimental data for fission reaction that induced by photons, pions, and nucleons at energy from several ten of MeV to about 1 TeV. The calculation that induced within TALYS will be focused mainly to several hundred MeV for actinide and sub-actinide nuclides and will be compared with MCNP6 code and several experimental data from other evaluator.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

SU-F-T-526: A Comparative Study On Gating Efficiency of Varian RPM Device and Calypso System

Purpose: In general, the linear accelerator is gated using respiratory signal obtained by way of external sensors to account for the breathing motion during radiotherapy. One of the commonly used gating devices is the Varian RPM device. Calypso system that uses electromagnetic tracking of implanted or surface transponders could also be used for gating. The aim of this study is to compare the gating efficiency of RPM device and the calypso system by phantom studies. Methods: An ArcCheck insert was used as the phantom with a Gafchromic film placed in its holder. The ArcCheck insert was placed on a Motion Sim platform and moved in the longitudinal direction simulating a respiratory motion with a period of 5 seconds and amplitude of ±6mm. The Gafchromic film was exposed to a 2 × 2cm{sup 2} field, i) with the phantom static, ii) phantom moving but ungated iii) gated with gating window of 2mm and 3mm. This was repeated with Calypso system using surface transponders with the same gating window. The Gafchromic films were read with an EPSON 11000 flatbed scanner and analysed with ‘Medphysto’ software. Results: The full width at half maximum (FWHM) as measured with film at the level of the film holder was 1.65cm when the phantom was static. FWHM measured with phantom moving and without gating was 1.16 cm and penumbra was 7 mm (80–20%) on both sides. When the beam was gated with 2 mm gating window the FWHM was 1.8 cm with RPM device and 1.9 cm with Calypso. Similarly, when the beam was gated with 3 mm window, the FWHM was 1.9cm with RPM device and 2cm with Calypso. Conclusion: This work suggests that the gating efficiency of RPM device is better than that of the Calypso with surface transponder, with reference to the latency in gating.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1984

Comparative study of the loss cone-driven instabilities in the low solar corona

A comparative study of the loss cone-driven instabilities in the low solar corona is undertaken. The instabilities considered are the electron cyclotron maser, the whistler, and the electrostatic upper hybrid. It is shown that the first-harmonic extraordinary mode of the electron cyclotron maser instability is the fastest growing mode for strong magnetized plasma (the ratio of plasma frequency to cyclotron frequency being less than 0.35). For values of the ratio between 0.35 and 1.0, the first-harmonic ordinary mode of the electron cyclotron maser instability dominates the emission. For ratio values greater than 1.0, no direct electromagnetic radiation is expected since other instabilities, which do not escape directly, saturate the electron cyclotron maser (the whistler or the electrostatic upper hybrid waves). It is also shown that the second-harmonic electron cyclotron maser emission never grows to an appreciable level. Thus, it is suggested that the electron cyclotron maser instability can be the explanation for the escape of the first harmonic from a flaring loop.

Sharma, R. R.↗
NASA NTRS1993

A comparative study of turbulence decay using Navier-Stokes and a discrete particle simulation

A comparative study of the two dimensional temporal decay of an initial turbulent state of flow is presented using a direct Navier-Stokes simulation and a particle method, ranging from the near continuum to more rarefied regimes. Various topics related to matching the initial conditions between the two simulations are considered. The determination of the initial velocity distribution function in the particle method was found to play an important role in the comparison. This distribution was first developed by matching the initial Navier-Stokes state of stress, but was found to be inadequate beyond the near continuum regime. An alternative approach of using the Lees two-sided Maxwellian to match the initial strain-rate is discussed. Results of the comparison of the temporal decay of mean kinetic energy are presented for a range of Knudsen numbers. As expected, good agreement was observed for the near continuum regime, but the differences found for the more rarefied conditions were unexpectedly small.

Goswami, A.↗
DOE OSTI2016

A comparative study of three-terminal Hanle signals in CoFe/SiO{sub 2}/n{sup +}-Si and Cu/SiO{sub 2}/n{sup +}-Si tunnel junctions

We performed three-terminal (3T) Hanle measurement for two types of sample series, CoFe/SiO{sub 2}/n{sup +}-Si and Cu/SiO{sub 2}/n{sup +}-Si, with various tunnel resistances. Clear Hanle signal and anomalous scaling between spin resistance-area product and tunnel resistance-area product were observed in CoFe/SiO{sub 2}/n{sup +}-Si devices. In order to explore the origin of the Hanle signal and the impurity-assisted tunneling effect on the Hanle signal in our devices, Hanle measurement in Cu/SiO{sub 2}/n{sup +}-Si devices was performed as well. However, no detectable Hanle signal was observed in Cu/SiO{sub 2}/n{sup +}-Si, even though a lot of samples with various tunnel resistances were studied in wide temperature and bias voltage ranges. Through a comparative study, it is found that the impurity-assisted tunneling magnetoresistance mechanism would not play a dominant role in the 3T Hanle signal in CoFe/SiO{sub 2}/n{sup +}-Si tunnel junctions, where the SiO{sub 2} was formed by plasma oxidation to minimize impurities.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Comparative study of electrical breakdown properties of deionized water and heavy water under pulsed power conditions

A comparative study of electrical breakdown properties of deionized water (H{sub 2}O) and heavy water (D{sub 2}O) is presented with two different electrode materials (stainless steel (SS) and brass) and polarity (positive and negative) combinations. The pulsed (∼a few tens of nanoseconds) discharges are conducted by applying high voltage (∼a few hundred kV) pulse between two hemisphere electrodes of the same material, spaced 3 mm apart, at room temperature (∼26-28 °C) with the help of Tesla based pulse generator. It is observed that breakdown occurred in heavy water at lesser voltage and in short duration compared to deionized water irrespective of the electrode material and applied voltage polarity chosen. SS electrodes are seen to perform better in terms of the voltage withstanding capacity of the liquid dielectric as compared to brass electrodes. Further, discharges with negative polarity are found to give slightly enhanced discharge breakdown voltage when compared with those with positive polarity. The observations corroborate well with conductivity measurements carried out on original and post-treated liquid samples. An interpretation of the observations is attempted using Fourier transform infrared measurements on original and post-treated liquids as well as in situ emission spectra studies. A yet another important observation from the emission spectra has been that even short (nanosecond) duration discharges result in the formation of a considerable amount of ions injected into the liquid from the electrodes in a similar manner as reported for long (microseconds) discharges. The experimental observations show that deionised water is better suited for high voltage applications and also offer a comparison of the discharge behaviour with different electrodes and polarities.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

A comparative study of satellite estimation for solar insolation in Albania with ground measurements

The main objective of this study is to compare data provided by Database of NASA with available ground data for regions covered by national meteorological net NASA estimates that their measurements of average daily solar radiation have a root-mean-square deviation RMSD error of 35 W/m{sup 2} (roughly 20% inaccuracy). Unfortunately valid data from meteorological stations for regions of interest are quite rare in Albania. In these cases, use of Solar Radiation Database of NASA would be a satisfactory solution for different case studies. Using a statistical method allows to determine most probable margins between to sources of data. Comparison of mean insulation data provided by NASA with ground data of mean insulation provided by meteorological stations show that ground data for mean insolation results, in all cases, to be underestimated compared with data provided by Database of NASA. Converting factor is 1.149.

14 SOLAR ENERGY↗
DOE OSTI2016

SU-F-T-391: Comparative Study of Treatment Planning Between IMRT and IMAT for Malignant Pleural Mesothelioma

Purpose: The purpose of this study was to compare the dosimetric differences between intensitymodulated radiation therapy (IMRT) and intensity modulated arc therapy (IMAT) for malignant pleural mesothelioma (MPM) patients with regard to the sparing effect on organs at risk (OARs), plan quality, and delivery efficiency. Methods: Ten MPM patients were recruited in this study. To avoid the inter-operator variability, IMRT and IMAT plans for each patient were performed by one experienced dosimetrist. The treatment planning optimization process was carried out using the Eclipse 13.0 software. For a fair comparison, the planning target volume (PTV) coverage of the two plans was normalized to the same level. The treatment plans were evaluated on the following dosimetric variables: conformity index (CI) and homogeneity index (HI) for PTV, OARs dose, and the delivery efficiency for each plan. Results: All plans satisfied clinical requirements. The IMAT plans gained better CI and HI. The IMRT plans performed better sparing for heart and lung. Less MUs and control points were found in the IMAT plans. IMAT shortened delivery time compared with IMRT. Conclusion: For MPM, IMAT gains better conformity and homogeneity for PTV with IMRT, but increases the irradiation dose for OARs. IMAT shows an advantage in delivery efficiency.

60 APPLIED LIFE SCIENCES↗