Search NASA⌕ Search

SEARCH · Search NASA

Results for “Application characterization”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

A PARAMETERIZED GALAXY CATALOG SIMULATOR FOR TESTING CLUSTER FINDING, MASS ESTIMATION, AND PHOTOMETRIC REDSHIFT ESTIMATION IN OPTICAL AND NEAR-INFRARED SURVEYS

We present a galaxy catalog simulator that converts N-body simulations with halo and subhalo catalogs into mock, multiband photometric catalogs. The simulator assigns galaxy properties to each subhalo in a way that reproduces the observed cluster galaxy halo occupation distribution, the radial and mass-dependent variation in fractions of blue galaxies, the luminosity functions in the cluster and the field, and the color-magnitude relation in clusters. Moreover, the evolution of these parameters is tuned to match existing observational constraints. Parameterizing an ensemble of cluster galaxy properties enables us to create mock catalogs with variations in those properties, which in turn allows us to quantify the sensitivity of cluster finding to current observational uncertainties in these properties. Field galaxies are sampled from existing multiband photometric surveys of similar depth. We present an application of the catalog simulator to characterize the selection function and contamination of a galaxy cluster finder that utilizes the cluster red sequence together with galaxy clustering on the sky. We estimate systematic uncertainties in the selection to be at the {<=}15% level with current observational constraints on cluster galaxy populations and their evolution. We find the contamination in this cluster finder to be {approx}35% to redshift z {approx} 0.6. In addition, we use the mock galaxy catalogs to test the optical mass indicator B{sub gc} and a red-sequence redshift estimator. We measure the intrinsic scatter of the B{sub gc}-mass relation to be approximately log normal with {sigma}{sub log10M}{approx}0.25 and we demonstrate photometric redshift accuracies for massive clusters at the {approx}3% level out to z {approx} 0.7.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Perturbative second-order optical susceptibility of bulk materials: a symmetry-enforced return to non-orthogonal localized basis sets

The second-order optical susceptibility of semiconductors $\chi^{(2)}_{ijk}(-2\omega;\omega,\omega)$ finds application in metrology, spectroscopy, telecommunications, material characterization, and quantum information. Pioneering calculations of $\chi^{(2)}_{ijk}(-2\omega;\omega,\omega)$ utilized non-orthogonal Gaussian orbitals centered at atoms. That formulation transitioned into plane-wave-based algorithms as time went by. As of late, nevertheless, multiple tools for calculating optical susceptibilities have recast the problem using Wannier (i.e. localized) orbitals, making a comeback onto frameworks based on localized basis sets. Here, in this work, we present an approach for calculating $\chi^{(2)}_{ijk}(-2\omega;\omega,\omega)$ reliant on numerical pseudo-atomic orbitals (PAOs) within perturbation theory in the velocity gauge. Its salient feature is a calculation of ‘Slater–Koster-like’ two-center integrals of the momentum operator in between PAOs identified by symmetry. The approach was successfully tested on paradigmatic cubic silicon carbide (3C-SiC) and gallium arsenide, for which linear responses are contributed as well.

Huamán, Angiolo [Univ. of Arkansas, Fayetteville, ↗
DOE OSTI2021

Bayesian inference for plasmonic nanometrology

Here, we introduce a Bayesian method for the characterization of plasmonic nanoparticles, which is applicable to both near- and far-field problems. Designed to combine data generated from any photon-plasmon interaction experiment with physically motivated theoretical models, our approach leverages state-of-the-art Markov chain Monte Carlo sampling techniques and returns parameter estimates on nanometric scales. Simulated spectral data sets, describing resonant scattering of photons from ellipsoidal and toroidal nanoparticles, are explored as concrete examples of our approach, with the resulting Bayesian estimates showing excellent agreement with the ground truth, even under conditions of high statistical noise. By incorporating Bayes factors into the method as well, we reveal how model selection can determine which one of competing geometric shapes better explains the observed data. Our comprehensive nanometrology procedure can be tailored to a variety of light-particle interaction models, and its reliance on Bayesian inference furnishes automatic uncertainty quantification. In addition to applicability to a host of plasmonic configurations such as nanoparticle dimers, trimers, and array studies, it is proposed that the presented analysis can be extended to the quantum regime, where nonclassical photon statistics may provide additional insight for inference of scatterer properties.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Relation between absorption and emission directivities for dipoles coupled with optical antennas

Optical antennas have been widely used to control the absorption and emission properties of dipole emitters. Understanding the relationship between the absorption and emission processes of such dipole emitters in the presence of optical antennas is therefore of fundamental importance. Here we provide an in-depth analysis of the relationship between the absorption and emission directivities of dipoles coupling to optical antennas. Here, we show that, for reciprocal systems, the absorption and emission directivities are identical for a single dipole emitter, and also in the case of multiple dipole emitters when one considers incoherent emission from the emitters. On the other hand, in general, the coherent emission directivities of the dipoles are always different from the absorption directivities in the multiple-dipole case. But there are special situations in the multiple-dipole case where the coherent emission has directivities that are approximately the same as the absorption directivity. This study clarifies the relation between absorption and emission directivities for emitters coupled with optical antennas and may provide useful insights into the design and characterization of optical antennas for various applications.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

Itinerant Antiferromagnetism in FeMnP 0.8 Si 0.2

Compounds based on the Fe 2 P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a noncentrosymmetric crystal structure, and because of the recent developments of these materials for magnetocaloric applications. We report the growth and characterization of millimeter-sized single crystals of FeMnP 0.8 Si 0.2 with the Fe 2 P structure. Single-crystal x-ray diffraction, magnetization, resistivity, and Hall and heat capacity data are reported. The crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room-temperature resistivity is close to the Ioffe-Regel limit for a metal. Single-crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism were not changed after high-temperature anneals and a rapid quench to room temperature

36 MATERIALS SCIENCE↗
DOE OSTI2018

Fundamental Principles for Calculating Charged Defect Ionization Energies in Ultrathin Two-Dimensional Materials

Defects in two-dimensional (2D) materials are becoming prominent candidates for quantum emitters and scalable optoelectronic applications. However, several physical properties that characterize their behavior, such as charged defect ionization energies, are difficult to simulate with conventional first-principles methods, mainly because of the weak and anisotropic dielectric screening caused by the reduced dimensionality. We establish fundamental principles for accurate and efficient calculations of charged defect ionization energies and electronic structure in ultrathin 2D materials. We propose to use the vacuum level as the reference for defect charge transition levels (CTLs) because it gives robust results insensitive to the level of theory, unlike commonly used band-edge positions. Furthermore, we determine the fraction of Fock exchange in hybrid functionals for accurate band gaps and band-edge positions of 2D materials by enforcing the generalized Koopmans’ condition of localized defect states. We found that the obtained fractions of Fock exchange vary significantly from 0.2 for bulk hexagonal boron nitride (h-BN) to 0.4 for monolayer h-BN, whose band gaps are also in good agreement with experimental results and calculated GW results. The combination of these methods allows for the reliable and efficient prediction of defect ionization energies (the difference between CTLs and band-edge positions). We motivate and generalize these findings with several examples including different defects in monolayer to few-layer h-BN, monolayer MoS 2 , and graphane. Lastly, we show that increasing the number of layers of h-BN systematically lowers defectionization energies, mainly through CTLs shifting towards vacuum, with conduction band minima kept almost unchanged.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Wavefront sensing at X-ray free-electron lasers

Here a direct comparison is made between various X-ray wavefront sensing methods with application to optics alignment and focus characterization at X-ray free-electron lasers (XFELs). Focus optimization at XFEL beamlines presents unique challenges due to high peak powers as well as beam pointing instability, meaning that techniques capable of single-shot measurement and that probe the wavefront at an out-of-focus location are desirable. The techniques chosen for the comparison include single-phase-grating Talbot interferometry (shearing interferometry), dual-grating Talbot interferometry (moiré deflectometry) and speckle tracking. All three methods were implemented during a single beam time at the Linac Coherent Light Source, at the X-ray Pump Probe beamline, in order to make a direct comparison. Each method was used to characterize the wavefront resulting from a stack of beryllium compound refractive lenses followed by a corrective phase plate. In addition, difference wavefront measurements with and without the phase plate agreed with its design to within λ/20, which enabled a direct quantitative comparison between methods. Finally, a path toward automated alignment at XFEL beamlines using a wavefront sensor to close the loop is presented.

42 ENGINEERING↗
DOE OSTI2019

Test-Based Modeling of Photovoltaic Inverter Impact on Distribution Systems

Distributed PV has important effects on overcurrent, overvoltage and islanding protection. These effects are more difficult to analyze because the faulted behavior of PV inverters is less well understood than for rotating machines. Full transient models of the inverter can be accurate, but that approach requires inverter design details and simulation software that doesn’t easily interoperate with utility protection system software. Further, anomalous model behaviors often emerge at different grid conditions, and these are difficult to fix in a proprietary model. Testing provides another approach to characterize inverters, validate models or answer questions of application. This earlier work found major impacts from the inverter design, firmware, operating point and balance-of-system components. Our objective is to characterize PV inverters from black-box testing, leading to standard test reports that could provide parameter sets for widely-implemented models in software tools. The tool vendors can then develop standard inverter models, as they did for rotating machines and exciters. Besides fully detailed transient models, inverters can be represented with steady-state current sources, dynamically controlled current sources or non-linear frequency-dependent black boxes. Type-test data could support the last three kinds of model. Short circuit and sag tests would encompass the basic fault types, reporting the maximum transient and rms currents over all power levels and points-on-wave within four time ranges : 1) 0 to 1 cycles, for close and latch consideration 2) 1 to 4 cycles, for equipment withstand 3) 4 to 30 cycles, for interrupt ratings 4) 30 cycles and beyond, for backup protection analysis Open circuit tests would vary output power and power factor, and report the maximum rms voltage from 1 to 10 cycles after the event. Without models, the type-test data could also provide upper limits on the expected overvoltages and overcurrents.

Wieserman, Laura M.↗
DOE OSTI2019

Master Curve Fracture Toughness Characterization of Eurofer97 Steel Variants Using Miniature Multi-Notch Bend Bar Specimens for Fusion Applications

In this study, we performed fracture toughness testing of ten Eurofer97 steel variants using precracked miniature multi-notch bend bar (M4CVN) specimens based on the Master Curve method in the ASTM E1921 standard. Additional Vickers microhardness and room temperature tensile testing complemented the fracture toughness testing. Compared with standard Eurofer97, the ten variants didn’t show a comprehensive improvement of mechanical properties. The Master Curve method was found to yield a reasonable prediction of fracture toughness results obtained from M4CVN specimens with most valid fracture toughness data within the 2% and 98% tolerance boundaries of the Master Curve. The three-parameter Weibull distribution with Weibull exponent b = 4 also yielded excellent prediction of the relationship between fracture toughness results KJc and the cumulative probability for failure pf for one steel variant.

Chen, Xiang↗
DOE OSTI2014

The use of strain tensor to estimate thoracic tumors deformation

Purpose: Respiration-induced kinematics of thoracic tumors suggests a simple analogy with elasticity, where a strain tensor is used to characterize the volume of interests. The application of the biomechanical framework allows for the objective determination of tumor characteristics. Methods: Four-dimensional computed tomography provides the snapshots of the patient's anatomy at the end of inspiration and expiration. Image registration was used to obtain the displacement vector fields and deformation fields, which allows one for the determination of the strain tensor. Its departure from the identity matrix gauges the departure of the medium from rigidity. The tensorial characteristic of each GTV voxel was determined and averaged. To this end, the standard Euclidean matrix norm as well as the Log-Euclidean norm were employed. Tensorial anisotropy was gauged with the fractional anisotropy measure which is based on the normalized variance of the tensors eigenvalues. Anisotropy was also evaluated with the geodesic distance in the Log-Euclidean framework of a given strain tensor to its closest isotropic counterpart. Results: The averaged strain tensor was determined for each of the 15 retrospectively analyzed thoracic GTVs. The amplitude of GTV motion varied from 0.64 to 4.21 with the average of 1.20 cm. The GTV size ranged from 5.16 to 149.99 cc with the average of 43.19 cc. The tensorial analysis shows that deformation is inconsiderable and that the tensorial anisotropy is small. The Log-Euclidean distance of averaged strain tensors from the identity matrix ranged from 0.06 to 0.31 with the average of 0.19. The Frobenius distance from the identity matrix is similar and ranged from 0.06 to 0.35 with the average of 0.21. Their fractional anisotropy ranged from 0.02 to 0.12 with the average of 0.07. Their geodesic anisotropy ranged from 0.03 to 0.16 with the average of 0.09. These values also indicate insignificant deformation. Conclusions: The tensorial framework allows for direct measurements of tissue deformation. It goes beyond the evaluation of deformation via comparison of shapes. It is an independent and objective determination of tissue properties. This methodology can be used to determine possible changes in lung properties due to radiation therapy and possible toxicities.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Preparation and Characterization of Sol–Gel Dip Coated Al: ZnO (AZO) Thin Film for Opto-Electronic Application

Aluminum doped zinc oxide (AZO) thin film was prepared by sol–gel dip coating method from methanol and monoethanolamine respectively, used as solvent and stabilizer agent. From the XRD study, it was confirmed that the aluminum was incorporated into the ZnO lattice. The prepared film have polycrystalline in nature and the film exhibit hexagonal wurtzite structure with (002) direction. SEM and AFM studies showed well defined smooth and uniformed wrinkle shaped grains distributed regularly on to the entire glass substrate without any pinholes and cracks. From the optical study, the observed highest transmittance was about 82% in the visible range and the band gap is 3.15 eV. Room temperature PL spectra exhibited a strong UV emission peak located at 390 nm for the deposited film. The electrical properties of the AZO thin film was studied by Hall-Effect measurement and found that it has n-type conductivity with low resistivity (ρ) of about 9.06 × 10{sup –3} Ω cm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

From Intermolecular Interaction Energies and Observable Shifts to Component Contributions and Back Again: A Tale of Variational Energy Decomposition Analysis

Quantum chemistry in the form of density functional theory (DFT) calculations is a powerful numerical experiment for predicting intermolecular interaction energies. However, no chemical insight is gained in this way beyond predictions of observables. Energy decomposition analysis (EDA) can quantitatively bridge this gap by providing values for the chemical drivers of the interactions, such as permanent electrostatics, Pauli repulsion, dispersion, and charge transfer. These energetic contributions are identified by performing DFT calculations with constraints that disable components of the interaction. This review describes the second-generation version of the absolutely localized molecular orbital EDA (ALMO-EDA-II). The effects of different physical contributions on changes in observables such as structure and vibrational frequencies upon complex formation are characterized via the adiabatic EDA. Example applications include red- versus blue-shifting hydrogen bonds; the bonding and frequency shifts of CO, N 2 , and BF bound to a [Ru(II)(NH 3 ) 5 ] 2 + moiety; and the nature of the strongly bound complexes between pyridine and the benzene and naphthalene radical cations. Additionally, the use of ALMO-EDA-II to benchmark and guide the development of advanced force fields for molecular simulation is illustrated with the recent, very promising, MB-UCB potential.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Seismic-velocity inversion using surface-wave tomography

© 2018 SEG. In this paper, we present the workflow of the application of surface wave tomography to characterize the near surface. A near surface model is simulated with a shallow unconsolidated layer that has a variable thickness and a deep consolidated zone. Data is filtered by bandpass filters and surface wave phase arrival times are picked, and surface wave velocities are inverted using a ray theoretical tomographic approach. A good agreement is found between the inverted results and the original model. In another model, a thin fault zone is detected. Agreement between the tomographic results and the model suggests that surface wave tomography is well suited for characterizing shallow geology with the capability of identifying low velocity anomalies and general lateral variations.

Wu, Zheshu↗
DOE OSTI2015

Development of a Radial Deconsolidation Method

A series of experiments have been initiated to determine the retention or mobility of fission products* in AGR fuel compacts [Petti, et al. 2010]. This information is needed to refine fission product transport models. The AGR-3/4 irradiation test involved half-inch-long compacts that each contained twenty designed-to-fail (DTF) particles, with 20-μm thick carbon-coated kernels whose coatings were deliberately fabricated such that they would crack under irradiation, providing a known source of post-irradiation isotopes. The DTF particles in these compacts were axially distributed along the compact centerline so that the diffusion of fission products released from the DTF kernels would be radially symmetric [Hunn, et al. 2012; Hunn et al. 2011; Kercher, et al. 2011; Hunn, et al. 2007]. Compacts containing DTF particles were irradiated at Idaho National Laboratory (INL) at the Advanced Test Reactor (ATR) [Collin, 2015]. Analysis of the diffusion of these various post-irradiation isotopes through the compact requires a method to radially deconsolidate the compacts so that nested-annular volumes may be analyzed for post-irradiation isotope inventory in the compact matrix, TRISO outer pyrolytic carbon (OPyC), and DTF kernels. An effective radial deconsolidation method and apparatus appropriate to this application has been developed and parametrically characterized.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Nanoindentation of Electropolished FeCrAl Alloy Welds

The present report summarizes Berkovich nanoindentation modulus and hardness measurements on two candidate FeCrAl alloys (C35M and C37M) on as-received (AR) and welded samples. In addition, spherical nanoindentation stress-strain measurements were performed on individual grains to provide further information and demonstrate the applicability of these protocols to mechanically characterizing welds in FeCrAl alloys. The indentation results are compared against the reported tensile properties for these alloys to provide relationships between nanoindentation and tensile tests and insight into weldsoftening for these FeCrAl alloys. Hardness measurements revealed weld-softening for both alloys in good agreement with tensile test results. C35M showed a larger reduction in hardness at the weld center from the AR material compared to C37M; this is also consistent with tensile tests. In general, nanohardness was shown to be a good predictor of tensile yield strength and ultimate tensile stress for FeCrAl alloys. Spherical nanoindentation measurements revealed that the fusion zone (FZ) + heat affected zone (HAZ) has a very low defect density typical of well-annealed metals as indicated by the frequent pop-in events. Spherical nanoindentation yield strength, Berkovich hardness, and tensile yield strength measurements on the welded material all show that the C37M welded material has a higher strength than C35M welded material. From the comparison of nanoindentation and tensile tests, EBSD microstructure analysis, and information on the processing history, it can be deduced that the primary driver for weld-softening is a change in the defect structure at the grain-scale between the AR and welded material. These measurements serve as baseline data for utilizing nanoindentation for studying the effects of radiation damage on these alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Final Report on Small Particle Speciation for Forensics Analysis by Soft X-ray Scanning Transmission X-ray Microscopy

Materials of interest for nuclear forensic science are often highly heterogeneous, containing complex mixtures of actinide compounds in a wide variety of matrices. Scanning transmission X-ray microscopy (STXM) is ideally suited to study such materials, as it can be used to chemically image specimens by acquiring X-ray absorption near-edge spectroscopy (XANES) data with 25 nm spatial resolution. In particular, STXM in the soft X-ray synchrotron radiation regime (approximately 120 – 2000 eV) can collect spectroscopic information from the actinides and light elements in a single experiment. Thus, STXM combines the chemical sensitivity of X-ray absorption spectroscopy with high spatial resolution in a single non-destructive characterization method. This report describes the application of STXM to a broad range of nuclear materials. Where possible, the spectroscopic images obtained by STXM are compared with information derived from other analytical methods, and used to make inferences about the process history of each material. STXM measurements can yield information including the morphology of a sample, “elemental maps” showing the spatial distribution of major chemical constituents, and XANES spectra from localized regions of a sample, which may show spatial variations in chemical composition.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

SECARB Commercial Scale CO 2 Injection and Optimization of Storage Capacity in the Southeastern United States

The Commercial Scale Project is a US DOE/NETL funded initiative aimed at enhancing the knowledge-base and industry’s ability to geologically store vast quantities of anthropogenic carbon. In support of this goal, a large-scale, stacked reservoir geologic model was developed for Gulf Coast sediments centered on the Citronelle Dome in southwest Alabama, the site of the SECARB Phase III Anthropogenic Test. Characterization of regional geology to construct the model consists of an assessment of the entire stratigraphic continuum at Citronelle Dome, from surface to the depth of the Donovan oil-bearing formation. This project utilizes all available geologic data available, which includes: modern geophysical well logs from three new wells drilled for SECARB’s Anthropogenic Test; vintage logs from the Citronelle oilfield wells; porosity and permeability data from whole core and sidewall cores obtained from the injection and observation wells drilled for the Anthropogenic Test; core data obtained from the SECARB Phase II saline aquifer injection test; regional core data for relevant formations from the Geological Survey of Alabama archives. Cross sections, isopach maps, and structure maps were developed to validate the geometry and architecture of the Citronelle Dome for building the model, and assuring that no major structural defects exist in the area. A synthetic neural network approach was used to predict porosity using the available SP and resistivity log data for the storage reservoir formations. These data are validated and applied to extrapolate porosity data over the study area wells, and to interpolate permeability amongst these data points. Geostatistical assessments were conducted over the study area. In addition to geologic characterization of the region, a suite of core analyses was conducted to construct a depositional model and constrain caprock integrity. Petrographic assessment of core was conducted by OSU and analyzed to build a depositional framework for the region and provide modern day analogues. Stability of the caprock over several test parameters was conducted by UAB to yield comprehensive measurements on long term stability of caprocks. The detailed geologic model of the full earth volume from surface thru the Donovan oil reservoir is incorporated into a state-of-the-art reservoir simulation conducted by the University of Alabama at Birmingham (UAB) to explore optimization of CO 2 injection and storage under different characterizations of reservoir flow properties. The application of a scaled up geologic modeling and reservoir simulation provides a proof of concept for the large scale volumetric modeling of CO 2 injection and storage the subsurface.

58 GEOSCIENCES↗
DOE OSTI2019

Multipaper Spectral Estimation: An Alternative to the Welch Periodogram Approach

Dynamic structural systems either operational or under test require complex spectral analysis in order to characterize their modal responses. In some applications constant vigilance in terms of analysis or potential failures demand an accurate methodology to estimate both modal frequencies as well as mode shapes. Typically, classical periodogram spectra are windowed and averaged applying the well-known Welch periodogram methodology (WPM) for spectral estimation [1]. In this report we discuss an alternative technique—the Multitaper Method (MTM) that can be applied to solve this challenging problem especially in the case of noisy, uncertain accelerometer measurements [2]. This approach is based on the development of a set of orthogonal tapers or windows enabling a superior statistical performance alleviating the need to section/overlap the measured data. Therefore, the MTM is capable of producing reliable and accurate spectral estimates enabling the extraction of the structural modal vibration frequencies.

42 ENGINEERING↗