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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Two-dimensional correlation analysis for x-ray photoelectron spectroscopy

Abstract X-ray photoelectron spectroscopy (XPS) measures the binding energy of core-level electrons, which are well-localised to specific atomic sites in a molecular system, providing valuable information on the local chemical environment. The technique relies on measuring the photoelectron spectrum upon x-ray photoionisation, and the resolution is often limited by the bandwidth of the ionising x-ray pulse. This is particularly problematic for time-resolved XPS, where the desired time resolution enforces a fundamental lower limit on the bandwidth of the x-ray source. In this work, we report a novel correlation analysis which exploits the correlation between the x-ray and photoelectron spectra to improve the resolution of XPS measurements. We show that with this correlation-based spectral-domain ghost imaging method we can achieve sub-bandwidth resolution in XPS measurements. This analysis method enables XPS for sources with large bandwidth or spectral jitter, previously considered unfeasible for XPS measurements.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Benchmarking embedded chain breaking in quantum annealing*

Quantum annealing solves combinatorial optimization problems by finding the energetic ground states of an embedded Hamiltonian. However, quantum annealing dynamics under the embedded Hamiltonian may violate the principles of adiabatic evolution and generate excitations that correspond to errors in the computed solution. Here we empirically benchmark the probability of chain breaks and identify sweet spots for solving a suite of embedded Hamiltonians. We further correlate the physical location of chain breaks in the quantum annealing hardware with the underlying embedding technique and use these localized rates in a tailored post-processing strategies. Our results demonstrate how to use characterization of the quantum annealing hardware to tune the embedded Hamiltonian and remove computational errors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

A supernodal all-pairs shortest path algorithm

We show how to exploit graph sparsity in the Floyd-Warshall algorithm for the all-pairs shortest path (Apsp) problem. Floyd-Warshall is an attractive choice for Apsp on high-performing systems due to its structural similarity to solving dense linear systems and matrix multiplication. However, if sparsity of the input graph is not properly exploited, Floyd-Warshall will perform unnecessary asymptotic work and thus may not be a suitable choice for many input graphs. To overcome this limitation, the key idea in our approach is to use the known algebraic relationship between Floyd-Warshall and Gaussian elimination, and import several algorithmic techniques from sparse Cholesky factorization, namely, fill-in reducing ordering, symbolic analysis, supernodal traversal, and elimination tree parallelism. When combined, these techniques reduce computation, improve locality and enhance parallelism. We implement these ideas in an efficient shared memory parallel prototype that is orders of magnitude faster than an efficient multi-threaded baseline Floyd-Warshall that does not exploit sparsity. Our experiments suggest that the Floyd-Warshall algorithm can compete with Dijkstra's algorithm (the algorithmic core of Johnson's algorithm) for several classes sparse graphs.

Sao, Piyush↗
DOE OSTI2021

Quantum Sensed Electron Spin Resonance Discovery Platform (Final Report)

The properties of materials can change dramatically at the nanoscale new and useful properties can emerge. An example is found in the paramagnetism in iron oxide magnetic nanoparticles. Using magnetically sensitive nitrogen-vacancy centers in diamond, we developed a platform to study electron spin resonance of nanoscale materials. To implement the platform, diamond substrates were prepared with nitrogen vacancy centers near the surface. Nanoparticles were placed on the surface using a drop casting technique. Using optical and microwave pulsing techniques, we demonstrated T1 relaxometry and double electron-electron resonance techniques for measuring the local electron spin resonance. The diamond NV platform developed in this project provides a combination of good magnetic field sensitivity and high spatial resolution and will be used for future investigations of nanomaterials and quantum materials.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Metallic positive expulsion diaphragms

High-cycle life ring-reinforced hemispherical type positive expulsion diaphragm performance was demonstrated by room temperature fluid expulsion tests of 13" diameter, 8 mil thick stainless steel configurations. A maximum of eleven (11) leak-free, fluid expulsions were achieved by a 25 deg cone angle diaphragm hoop-reinforced with .110-inch cross-sectional diameter wires. This represents a 70% improvement in diaphragm reversal cycle life compared to results previously obtained. The reversal tests confirmed analytic predictions for diaphragm cycle life increases due to increasing values of diaphragm cone angle, radius to thickness ratio and material strain to necking capacity. Practical fabrication techniques were demonstrated for forming close-tolerance, thin corrugated shells and for obtaining closely controlled reinforcing ring stiffness required to maximize diaphragm cycle life. A non-destructive inspection technique for monitoring large local shell bending strains was developed.

Gleich, D.↗
NASA NTRS1974

Earth Observatory Satellite system definition study. Report no. 7: EOS system definition report. Appendixes A through D

An analysis of the systems involved in the operation and support of the Earth Observatory Satellite (EOS) is presented. Among the systems considered are the following: (1) the data management system, (2) observatory to primary ground station communications links, (3) local user system, (4) techniques for recognizing ground control points, (5) the central data processing-implementation concept, and (6) program effectiveness analysis.

Source record↗
NASA NTRS1975

The influence of crack closure and elasto-plastic flow on the bending of a cracked plate

The influence of crack closure and elastoplastic flow on the bending behavior of thin cracked plates is investigated using an incremental elastoplastic plate bending finite element computer program. The finite element program was developed using assumptions consistent with Kirchhoff fourth-order plate theory while the material property treatment permits general isotropic work hardening with local elastic unloading. This technique is applied to the problem of a large centrally through cracked plate subject to remote circular bending. Comparison is drawn between two cases of the bending problem. The first neglects the possibility of crack face interference with bending, and the second includes a kinematic prohibition against the crack face from passing through the symmetry plane. Results are reported which isolate the effects of elastoplastic flow and crack closure.

Jones, D. P.↗
NASA NTRS1980

Planetary observations with the Tidbinbilla interferometer

Radio observations at a wavelength of 13.1 cm of Saturn and Uranus made with the Tidbinbilla interferometer during 1978 and 1979 are summarized. The observations were made with 64-m and 26-m antennas on a 200-m north-south baseline at a bandwidth of 12 MHz with RCP polarization and a primary beamwidth of about 12 arcmin. A flux density of 198 + or - 15 mJy was measured for Saturn, which indicates a surface temperature, corrected for the occulting effect of the rings, of 191 + or - 15 K, in excellent agreement with previous determinations. With the use of a background subtraction technique to remove the local background confusion, Uranus was found to have a flux density of 11.7 + or - 0.8 mJy, indicating a disk-averaged brightness temperature of 255 + or - 18 K. The increase in Uranus brightness temperature over that measured 15 years previously is attributed to variations in temperature or opacity below the cloud tops, or to a reduction in relative ammonia abundance most likely reflecting a change in the aspect of the planet as viewed from earth.

Batty, M. J.↗
NASA NTRS1980

Physical and dynamical conditions in interstellar clouds

Techniques for measuring the local and global parameters that describe molecular clouds are presented and illustrated by selected results. The local parameters which characterize a given location in a cloud are gas kinetic temperature, dust temperature, total density, magnetic field strength, abundance of species i, volume cooling and heating rates for gas and dust, and the thermal and turbulent velocities. Global properties which characterize the cloud as a whole include the size expressed as a length or area, the orientation and shape, the mass, and the integrated heating and cooling rates. If the cloud as a whole is collapsing or rotating, then the collapse velocity and the rotational velocity or angular momentum are global properties. An intermediate class of parameters which shares features of local and global properties includes the column density of species i, the total column density, and the average density.

Evans, N. J., II↗
NASA NTRS1982

The effect of grooves in amorphous substrates on the orientation of metal deposits. I - Carbon substrates

The graphoepitaxial alignment of vapor-deposited discrete metal crystallites is investigated in the nucleation and growth stages and during annealing by in situ UHV/TEM techniques. Various stages of nucleation, growth and coalescence of vapor deposits of Au, Ag, Pb, Sn, and Bi on amorphous, topographically structured C substrates are analyzed by advanced dark-field techniques to detect preferred local orientations. It is found that the topography-induced orientation of metal crystallites depends strongly on their mobility and their respective tendency to develop pronounced crystallographic shapes. Lowering of the average surface free energies and increasing the crystallographic surface energy anisotropies cause generally improved graphoepitaxial alignments.

Anton, R.↗
NASA NTRS1983

Use of the VAS for analysis of a prethunderstorm environment

The information content of the VAS radiances can be converted to meteorological parameters useful for analyzing a severe weather environment. The method by which the VAS variances are converted to vertical profiles of temperature, dewpoints, and equivalent potential temperature involves a basic regression technique using the most local radiosonde data available for establishing a correlation matrix. The results indicate that mesoscale features apparent within images of the radiances can be converted to usable temperature and moisture fields using regression when surface temperature and dewpoint observations are included within the total data base. In addition, results indicate that surface data are very important for better defining lower tropospheric structure that the VAS radiances alone cannot properly resolve. Analyses of these retrievals distinctly show mesoscale structure in the temperature and moisture fields derived with VAS radiances collected every 3 hours, and 0000 GMT. The retrievals capture the moisture structure. More important, convective instability is clearly detected immediately before the onset of convection. The results indicate that the VAS is capable of providing valuable mesoscale information suitable for analyzing a preconvective environment that is generally clear.

Uccellini, L. W.↗
NASA NTRS1991

Sensitivity analysis of a wing aeroelastic response

A variation of Sobieski's Global Sensitivity Equations (GSE) approach is implemented to obtain the sensitivity of the static aeroelastic response of a three-dimensional wing model. The formulation is quite general and accepts any aerodynamics and structural analysis capability. An interface code is written to convert one analysis's output to the other's input, and visa versa. Local sensitivity derivatives are calculated by either analytic methods or finite difference techniques. A program to combine the local sensitivities, such as the sensitivity of the stiffness matrix or the aerodynamic kernel matrix, into global sensitivity derivatives is developed. The aerodynamic analysis package FAST, using a lifting surface theory, and a structural package, ELAPS, implementing Giles' equivalent plate model are used.

Kapania, Rakesh K.↗
NASA NTRS1991

On magnetothermal instability in cluster cooling flows

Lagrangian techniques appropriate to a local calculation are used to show that a weak ordered magnetic field can result in a generic condensational mode in cluster cooling flows. However, thermal instability appears possible only if the conductivity is well below its Spitzer value, for all nonradial wavenumbers. Wavenumbers not subject to conductive damping are subject to buoyant oscillations. It is shown that when instability is present, lateral magnetic confinement of high thermal pressure regions in the plasma by radial magnetic field lines is responsible in at least equal measure with radially directed magnetic tension for the suppression of oscillations and the reappearance of local condensational modes. The general importance of even very modest magnetic fields for destabilizing thermal time scale perturbations is emphasized.

Balbus, Steven A.↗
NASA NTRS1991

Development of an Accelerated Test Method for the Determination of Susceptibility to Atmospheric Corrosion

The theoretical rationale is presented for use of a repetitive cyclic current reversal voltammetric technique for characterization of localized corrosion processes, including atmospheric corrosion. Applicability of this proposed experimental protocol is applied to characterization of susceptibility to crevice and pitting corrosion, atmospheric corrosion and stress corrosion cracking. Criteria upon which relative susceptibility is based were determined and tested using two iron based alloys commonly in use at NASA-Kennedy; A36 (a low carbon steel) and 4130 (a low alloy steel). Practicality of the procedure was demonstrated by measuring changes in anodic polarization behavior during high frequency current reversal cycles of 25 cycles per second with 1 mA/sq cm current density amplitude in solutions containing Cl anions. The results demonstrated that, due to excessive polarization which affects conductivity of barrier corrosion product layers, A36 was less resistant to atmospheric corrosion than its 4130 counterpart; behavior which was also demonstrated during exposure tests.

Ambrose, John R.↗
NASA NTRS1993

Advanced adaptive computational methods for Navier-Stokes simulations in rotorcraft aerodynamics

A phase 2 research and development effort was conducted in area transonic, compressible, inviscid flows with an ultimate goal of numerically modeling complex flows inherent in advanced helicopter blade designs. The algorithms and methodologies therefore are classified as adaptive methods, which are error estimation techniques for approximating the local numerical error, and automatically refine or unrefine the mesh so as to deliver a given level of accuracy. The result is a scheme which attempts to produce the best possible results with the least number of grid points, degrees of freedom, and operations. These types of schemes automatically locate and resolve shocks, shear layers, and other flow details to an accuracy level specified by the user of the code. The phase 1 work involved a feasibility study of h-adaptive methods for steady viscous flows, with emphasis on accurate simulation of vortex initiation, migration, and interaction. Phase 2 effort focused on extending these algorithms and methodologies to a three-dimensional topology.

Stowers, S. T.↗
NASA NTRS1991

Long discontinuous fiber composite structure: Forming and structural mechanics

Cost effective composite structure has motivated the investigation of several new approaches to develop composite structure from innovative material forms. Among the promising new approaches is the conversion of planar sheet to components of complex curvature through sheet forming or stretch forming. In both cases, the potential for material stretch in the fiber direction appears to offer a clear advantage in formability over continuous fiber systems. In the present study, the authors have established a framework which allows the simulation of the anisotropic mechanisms of deformation of long discontinuous fiber laminates wherein the matrix phase is a viscous fluid. The initial study focuses upon the establishment of micromechanics models for prediction of the effective anisotropic viscosities of the oriented fiber assembly in a viscous matrix. Next, the developed constitutive relation is employed through an analogy with incompressible elasticity to exercise the finite element technique for determination of local fiber orientation and laminate thickness after forming. Results are presented for the stretch bending of a curved beam from an arbitrary composite laminate and the bulging of a clamped sheet. Structural analyses are conducted to determine the effect of microstructure on the performance of curved beams manufactured from long discontinuous fiber composites. For the purposes of this study, several curved beams with ideal and non-ideal microstructures are compared for response under pure bending. Material parameters are determined from a separate microstructural analysis.

Pipes, R. B.↗
NASA NTRS1992

Linear and nonlinear stability of the Blasius boundary layer

Two new techniques for the study of the linear and nonlinear instability in growing boundary layers are presented. The first technique employs partial differential equations of parabolic type exploiting the slow change of the mean flow, disturbance velocity profiles, wavelengths, and growth rates in the streamwise direction. The second technique solves the Navier-Stokes equation for spatially evolving disturbances using buffer zones adjacent to the inflow and outflow boundaries. Results of both techniques are in excellent agreement. The linear and nonlinear development of Tollmien-Schlichting (TS) waves in the Blasius boundary layer is investigated with both techniques and with a local procedure based on a system of ordinary differential equations. The results are compared with previous work and the effects of non-parallelism and nonlinearity are clarified. The effect of nonparallelism is confirmed to be weak and, consequently, not responsible for the discrepancies between measurements and theoretical results for parallel flow.

Bertolotti, F. P.↗
NASA NTRS1994

C style guide

This document discusses recommended practices and style for programmers using the C language in the Flight Dynamics Division environment. Guidelines are based on generally recommended software engineering techniques, industry resources, and local convention. The Guide offers preferred solutions to common C programming issues and illustrates through examples of C Code.

Doland, Jerry↗