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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 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Improved Momentum Spread for Precision Physics Experiments Using Wedges

High precision experiments have become key in the search for physics beyond the Standard Model. Measurements that can be made in order to expand our knowledge of the Standard Model are the precise measurement of the magnetic dipole moment (MDM) of the muon and searches for a non-zero value of its electric dipole moment (EDM). In order to perform precise measurements of this type, the storage of particles with a precisely known momentum in a highly uniform magnetic field is required. This thesis is focused on how one may use a wedge of energy absorbing material and the optical parameters of an accelerator lattice to improve upon the amount of particles delivered into a storage ring. This thesis will rely on computer simulations to determine ideal optics parameters as well as to study how the beam parameters change as the beam traverses a lattice. As a case study, this thesis will look to the M4 and M5 lines in the Fermilab Muon g-2 experiment, where a wedge of energy absorbing material will be used to reduce the energy spread of a muon beam.

43 PARTICLE ACCELERATORS↗
NASA NTRS1991

Three-dimensional blade vortex interactions

A three-dimensional time dependent Navier-Stokes analysis was applied to the rotor blade vortex interaction problem. The numerical procedure is an iterative implicit procedure using three point central differences to represent spatial derivatives. A series of calculations were made to determine the time steps, pseudo-time steps, iterations, artificial dissipation level, etc. required to maintain a nondissipative vortex. Results show the chosen method to have excellent non-dissipative properties provided the correct parameters are chosen. This study was used to set parameters for both two- and three-dimensional blade vortex interaction studies. The case considered was the interaction between a vortex and a NACA0012 airfoil. The results showed the detailed physics during the interaction including the pressure pulse propagating from the blade. The simulated flow physics was qualitatively similar to that experimentally observed. The BVI phenomena is the result of the buildup and violent collapse of the shock waves and local supersonic pockets on the blade surfaces. The resulting pressure pulse build-up appears to be centered at the blade leading edge.

Davoudzadeh, Farhad↗
NASA NTRS1990

Two- and three-dimensional blade vortex interactions

A three-dimensional time dependent Navier-Stokes analysis was applied to the rotor blade vortex interaction (BVI) problem. The numerical procedure is an iterative implicit procedure using three point central differences to represent spatial derivatives. A series of calculations were made to determine the time steps, pseudo-time steps, iterations, artificial dissipation level, etc. required to maintain a nondissipative vortex. Results show the chosen method to have excellent non-dissipative properties provided the correct parameters are chosen. This study was used to set parameters for both two- and three-dimensional blade vortex interaction studies. The two-dimensional study considered the interaction between a vortex and a NACA0012 airfoil. The results showed the detailed physics during the interaction including the pressure pulse propagating from the blade. The simulated flow physics was qualitatively similar to that experimentally observed. The 2-D BVI phenomena is the result of the buildup and violent collapse of the shock waves and local supersonic pockets on the blade surfaces. The resulting pressure pulse build-up appears to be centered at the blade leading edge. The three-dimensional interaction study considered the case of a vortex at 20 deg incidence to the blade leading edge. Although the qualitative results were similar to that of the two-dimensional interaction, details clearly showed the three-dimensional nature of the interaction process.

Davoudzadeh, F.↗
DOE OSTI2024

Experimental and statistical study on the effect of process parameters on the quality of continuous fiber composites made via additive manufacturing

Ongoing research in additive manufacturing towards structural and industrial application has led to the use of commingled roving as a manufacturing feedstock for printing high fiber volume fraction composites. The prospects of using this technology for high performance applications necessitates the need for a comprehensive experimental investigation into the effects of processing parameters on the quality of an additively manufactured composite printed from commingled roving feedstock. Here, in this work, transverse flexure and void fraction matrix pyrolysis testing are both performed to evaluate composite quality. The transverse flexure test is a testing approach that evaluates the quality of the interfacial fiber-matrix bond while the void fraction test estimates the void content in the printed composite. A full observational study consisting of 27 different test combinations is done to investigate the effects of three different process parameters namely, temperature, pressure, and print speed across three different levels. Composite samples were made from commingled roving of E-glass and amorphous PET using an in-house built continuous fiber composite digital manufacturing system. Least squares regression analysis is performed to study the main, interaction and quadratic effects of process parameters. A statistical regression model having an R2 adjusted value of 80.1% is generated from the transverse flexure study, which is used to explain main and interaction effects and also predict performance. Response surface plots are also generated and are used to optimize process parameters which can subsequently be of help in scaling up composite manufacturing. Results show that all three process parameters are highly statistically significant at the 0.01 level of significance. Pressure * Temperature and Pressure * Printspeed are significant interaction terms. Pressure plays a weightier role when print speed is increased or temperature is decreased as it closes more voids that would ordinarily have been introduced because of drop in polymer melt viscosity. Micrographic analysis is also performed.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Tradeoffs among several synthetic aperture radar image quality parameters - Results of a user survey study

The imagery obtained with the aid of synthetic aperture radars (SAR) has been applied to several remote sensing disciplines such as geologic feature mapping, oceanic phenomena studies, and land use and urban morphology studies. The successful SAR experiment on Seasat and the Shuttle demonstrated the feasibility of global radar mapping at relatively high resolution from a spaceborn platform. The present investigation is concerned with the requirements of and the tradeoffs among several SAR image quality parameters. The results are presented from a survey study concerning the interpretability of a set of SAR images. The data used to generate these images were obtained by the Seasat SAR experiments. Attention is given to image scenes and the simulation experiment, image interpretation survey results, multiple-looks, the number of looks vs resolution, and number of bits vs resolution.

Li, F. K.↗
DOE OSTI2012

Neutron study and modeling of the lattice parameters in a NiAl-precipitate strengthened ferritic steel

The lattice misfit between the body-centered cubic {alpha}-Fe matrix and the B2-ordered NiAl-type {beta}{prime} precipitates is a parameter of significant importance in controlling the creep resistance of precipitate-strengthened ferritic steels. However, the measurement of the lattice misfit is complicated due to the fact that the fundamental reflections of {alpha} and {beta}{prime} phases almost completely overlap. In this study, neutron diffraction is used to determine the lattice parameters of these two phases in a Fe-18.9 Al-9.8 Cr-13 Ni-1.8 Mo (atomic percent, at.%) alloy as a function of temperature. The accuracy of the measurement at room temperature is verified by high-energy synchrotron X-ray diffraction. The comparison between these two techniques is discussed in terms of the difference in superlattice intensity. Furthermore, using the phase compositions determined by atom probe tomography, models are proposed to predict the lattice parameters of both phases at room temperature as a function of their compositions. The results are in very good agreement with those obtained experimentally.

36 MATERIALS SCIENCE↗
DOE OSTI2015

OPEN CLUSTERS AS PROBES OF THE GALACTIC MAGNETIC FIELD. I. CLUSTER PROPERTIES

Stars in open clusters are powerful probes of the intervening Galactic magnetic field via background starlight polarimetry because they provide constraints on the magnetic field distances. We use 2MASS photometric data for a sample of 31 clusters in the outer Galaxy for which near-IR polarimetric data were obtained to determine the cluster distances, ages, and reddenings via fitting theoretical isochrones to cluster color–magnitude diagrams. The fitting approach uses an objective χ{sup 2} minimization technique to derive the cluster properties and their uncertainties. We found the ages, distances, and reddenings for 24 of the clusters, and the distances and reddenings for 6 additional clusters that were either sparse or faint in the near-IR. The derived ranges of log(age), distance, and E(B−V) were 7.25–9.63, ∼670–6160 pc, and 0.02–1.46 mag, respectively. The distance uncertainties ranged from ∼8% to 20%. The derived parameters were compared to previous studies, and most cluster parameters agree within our uncertainties. To test the accuracy of the fitting technique, synthetic clusters with 50, 100, or 200 cluster members and a wide range of ages were fit. These tests recovered the input parameters within their uncertainties for more than 90% of the individual synthetic cluster parameters. These results indicate that the fitting technique likely provides reliable estimates of cluster properties. The distances derived will be used in an upcoming study of the Galactic magnetic field in the outer Galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

Earth rotation parameters from an on-site study of laser ranging data

A multi-faceted effort was maintained to achieve the following goals: (1) provide for state-of-the-art, on-site, near-real-time Earth orientation parameter determinations at levels of precision and accuracy commensurate with a 'quick-look' type of an analysis, using the lunar laser ranging (LLR) data type from the McDonald Laser Ranging Station (MLRS) and other LLR facilities around the world; (2) create a state-of-the-art, highly transportable, LLR-based Earth orientation solution package, which could be easily implemented at LLR facilities other than the MLRS; (3) accommodate, within the routine MLRS lunar range prediction and Earth orientation data analysis software packages, the standard set of Jet Propulsion Laboratory (JPL) Solar System ephemerides, lunar librations, and Solar System partial derivatives; and (4) examine, wherever possible, opportunities for the performance of state-of-the-art, on-site, joint, simultaneous, quick-look analysis for Earth orientation parameters, using both MLRS lunar and LAGEOS (and, perhaps, Etalon) ranging observations, as well as from multiple LLR station observations. Excellent results were obtained at all levels of effort and it can be said that all of these goals were attained. The reader is referred to the complete series of our semi-annual reports for a full description of our efforts.

Shelus, Peter J.↗
DOE OSTI2019

An Investigation of Process Parameter Modifications on Additively Manufactured Inconel 718 Parts

Additive manufacturing (AM) allows for the fabrication of complex parts via layer-by-layer melting of metal powder. Laser powder-bed AM processes use a variety of process parameters including beam power, beam velocity, and hatch spacing to control melting. Alterations to these parameters have often been attempted to reduce porosity, for example, but less work has been done to on comprehensive effects of process parameter modifications. This study looks at the effects of altering these parameters on microstructure, porosity, and mechanical performance of Inconel 718. The results showed that process parameter modifications that result in porosity formation can significantly reduce fatigue life, while microstructure changes were minimal and had little effect on tensile properties. The precipitate structure was not found to be changed significantly. These results can inform future process parameter modifications, as well as heat treatments to optimize mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2013

An Expectation-Maximization Method for Calibrating Synchronous Machine Models

The accuracy of a power system dynamic model is essential to its secure and efficient operation. Lower confidence in model accuracy usually leads to conservative operation and lowers asset usage. To improve model accuracy, this paper proposes an expectation-maximization (EM) method to calibrate the synchronous machine model using phasor measurement unit (PMU) data. First, an extended Kalman filter (EKF) is applied to estimate the dynamic states using measurement data. Then, the parameters are calculated based on the estimated states using maximum likelihood estimation (MLE) method. The EM method iterates over the preceding two steps to improve estimation accuracy. The proposed EM method’s performance is evaluated using a single-machine infinite bus system and compared with a method where both state and parameters are estimated using an EKF method. Sensitivity studies of the parameter calibration using EM method are also presented to show the robustness of the proposed method for different levels of measurement noise and initial parameter uncertainty.

EM Algorithms↗
NASA NTRS1989

Vortex/boundary layer interactions

Detailed and high quality measurements with hot-wires and pressure probes are presented for two different interactions between a vortex pair with common flow down and a turbulent boundary layer. The interactions studied have larger values of the vortex circulation parameter than those studied previously. The results indicate that the boundary layer under the vortex pair is thinned by lateral divergence and that boundary layer fluid is entrained into the vortex. The effect of the interaction on the vortex core (other than the inviscid effect of the image vortices behind the surface) is small.

Cutler, A. D.↗
NASA NTRS2002

Fissioning Plasma Core Reactor

Institute for Scientific Research, Inc. (ISR) research program consist of: 1.Study core physics by adapting existing codes: MCNP4C - Monte Carlo code; COMBINE/VENTURE - diffusion theory; SCALE4 - Monte Carlo, with many utility codes. 2. Determine feasibility and study major design parameters: fuel selection, temperature and reflector sizing. 3. Study reactor kinetics: develop QCALC1 to model point kinetics; study dynamic behavior of the power release.

Albright, Dennis↗
NASA NTRS2009

Precision Measurement of Complete Black Hole Binary Inspiral-Merger-Ringdown Signals with LISA

Until recently, only the inspiral and ringdown phases of black hole binary (131-113) coalescences had been modeled. The merger signals, which were expected to be the most luminous portion of the total signal, were unavailable due to the technical difficulty of calculating the behavior of a BHB in this highly dynamical and non-linear regime. Advancements in the field of numerical relativity make it possible to include the merger segment of 131113 coalescence in the search for and characterization of gravitational wave signals. The implications for LISA include an increase in the event rate due to the increase in achievable signal-to-noise ratio, as well as potentially improved accuracy regarding the extraction of the source parameters. We investigate the degree to which mergers improve parameter estimation, by studying the impact of including mergers on achievable parameter accuracy over a significant range of masses and mass ratios for nonspinning systems, and its impact on LISA science.

McWilliams, Sean T.↗
DOE OSTI2012

Sensitivity Analysis of FEAST-Metal Fuel Performance Code: Initial Results

This memo documents the completion of the LANL milestone, M3FT-12LA0202041, describing methodologies and initial results using FEAST-Metal. The FEAST-Metal code calculations for this work are being conducted at LANL in support of on-going activities related to sensitivity analysis of fuel performance codes. The objective is to identify important macroscopic parameters of interest to modeling and simulation of metallic fuel performance. This report summarizes our preliminary results for the sensitivity analysis using 6 calibration datasets for metallic fuel developed at ANL for EBR-II experiments. Sensitivity ranking methodology was deployed to narrow down the selected parameters for the current study. There are approximately 84 calibration parameters in the FEAST-Metal code, of which 32 were ultimately used in Phase II of this study. Preliminary results of this sensitivity analysis led to the following ranking of FEAST models for future calibration and improvements: fuel conductivity, fission gas transport/release, fuel creep, and precipitation kinetics. More validation data is needed to validate calibrated parameter distributions for future uncertainty quantification studies with FEAST-Metal. Results of this study also served to point out some code deficiencies and possible errors, and these are being investigated in order to determine root causes and to improve upon the existing code models.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2016

The systematic study of N/Z dependence on surface diffuseness parameter in the fusion of heavy neutron-rich colliding nuclei

Surface diffuseness parameter used in Woods-Saxon form of potential have been extracted from a large number of experimentally studied neutron-rich fusion cross sections at near barrier energies. The results of our systematic study reveals that the extracted diffuseness parameter depend linearly on the N/Z ratio of the fusing nuclei. Further, we demonstrated that the extracted values of surface diffuseness parameter lies within the range a = 0.40 to 0.77 fm as compared to commonly accepted value form scattering i.e. 0.63 fm.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1991

Validating a large geophysical data set - Experiences with satellite-derived cloud parameters

The goal of this study is to validate the global cloud parameters derived from the satellite-borne HIRS2 and MSU atmospheric sounding instrument measurements, and to use the analysis of these data as one prototype for studying large geophysical data sets in general. The HIRS2/MSU data set contains a total of 40 physical parameters, filling 25 MB/day; raw HIRS2/MSU data are available for a period exceeding 10 years. Validation involves developing a quantitative sense for the physical meaning of the derived parameters over the range of environmental conditions sampled. This is accomplished by comparing the spatial and temporal distributions of the derived quantities with similar measurements made using other techniques, and with model results. The need to work with Level 2 (point) data, rather than Level 3 (gridded) data for validation purposes is discussed, and some techniques developed for charting the assumptions made in deriving an algorithm and generating a code to produce geophysical quantities from measured radiances are presented.

Kahn, Ralph↗
NASA NTRS1978

Studies of vorticity imbalance and stability, moisture budget, atmospheric energetics, and gradients of meteorological parameters during AVE 3

Four diagnostic studies of AVE 3. are presented. AVE 3 represents a high wind speed wintertime situation, while most AVE's analyzed previously represented springtime conditions with rather low wind speeds. The general areas of analysis include the examination of budgets of vorticity, moisture, kinetic energy, and potential energy and a synoptic and statistical study of the horizontal gradients of meteorological parameters. Conclusions are integrated with and compared to those obtained in previously analyzed experiments (mostly springtime weather situations) so as to establish a more definitive understanding of the structure and dynamics of the atmosphere under a wide range of synoptic conditions.

Scoggins, J. R.↗
DOE OSTI2012

A study on the effect of various design parameters on the natural circulation flow rate of the ex-vessel core catcher cooling system of EU-APR1400

In this paper, a study on the effect of various design parameters such as the channel gap width, heat flux distribution, down-comer pipe size and two-phase flow slip ratio on the natural circulation flow rate is performed based on a physical model for a natural circulation flow along the flow path of the ex-vessel core catcher cooling system of an EU-APR1400, and these effects on the natural circulation flow rate are analyzed and compared with the minimum flow rate required for the safe operation of the system. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗