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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Generalized Spatio-Temporal Model of Backsheet Degradation From Field Surveys of Photovoltaic Modules

Photovoltaic (PV) module backsheets degrade at different rates because of the specific polymeric materials and the local exposure environments of the installations. Studies of real-world backsheet degradation provide valuable information to understand backsheet degradation and failure. Field surveys of PV module backsheets were conducted on 1310 modules in four commercial PV power plant sites with different exposure times. The backsheet's local exposure environment is determined by its location along the rack length and depth, the modules' elevation above the ground, and the ground cover albedo. Backsheets that are installed at the ends of the module rack length exhibit larger degradation rates (with yellowness index difference of 1.14 $\pm$ 0.45 and 7.80 $\pm$ 1.3 for backsheets of poly (ethylene terephthalate) and poly (ethylene naphthalate) as the air-side layer, respectively) than backsheets in the center section of the rack. A generalized spatio-temporal model was developed to predict the large-scale backsheet degradation of different backsheet polymers across time/age and location in the PV power plant rack. The model utilizes a cubic-spline relationship between backsheet degradation and rack length, and a quadratic relationship between backsheet discoloration and rack depth. This generalized spatio-temporal model predicts the outdoor backsheet degradation with an adjusted- $R^2$ range between 0.31 to 0.89. The similarity between this model and the spatial variation of the rear-side irradiance, indicates that the irradiance plays a significant role in outdoor backsheet degradation. The generalized spatio-temporal model can be used to evaluate large scale PV backsheet performance, as well as a guidance for PV site designers and operations and maintenance crews.

14 SOLAR ENERGY↗
DOE OSTI2018

Nonresonant pump/probe electronic Raman scattering within nonequilibrium dynamical mean-field theory

We develop the theory for nonresonant Raman scattering of strongly correlated electrons in time-resolved pump-probe experiments. The electrons are initially pumped with an intense pulse of light and then a probe pulse measures the Raman response function after an adjustable time delay. Here, we describe how the width of the probe pulse and the strength of the electron correlations affect the Raman cross section. The theory is developed for the case of B 1g symmetry, where incident and scattered light are polarized perpendicular to each other. We illustrate the exact solution with the Falicov-Kimball model, which is solved via nonequilibrium dynamical mean-field theory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Investigations of CuFeS{sub 2} semiconductor mineral from ocean rift hydrothermal vent fields by Cu NMR in a local field

The results of investigating natural samples of chalcopyrite mineral CuFeS{sub 2} from massive oceanic sulfide ores of the Mid-Atlantic ridge by the {sup 63}Cu nuclear magnetic resonance (NMR {sup 63}Cu) in a local field at room temperature are presented. The significant width of the resonance lines found in the {sup 63}Cu NMR spectrum directly testifies to a wide distribution of local magnetic and electric fields in the investigated chalcopyrite samples. This distribution can be the consequence of an appreciable deviation of the structure of the investigated chalcopyrite samples from the stoichiometric one. The obtained results show that the pulsed {sup 63}Cu NMR can be an efficient method for studying the physical properties of deep-water polymetallic sulfides of the World Ocean.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Magnetic-field-dependent microwave absorption in HgSe in weak magnetic fields

The low-temperature magnetoresistive effect in the semiconductor HgSe:Fe in weak magnetic fields at microwave frequencies is examined. The negative and positive components of magnetoabsorption based on the magnetoresistive effect in the degenerate conduction band are analyzed. The special features of experiments carried out in the investigated frequency range are noted. The momentum and electron-energy relaxation times are determined from the experimental field and temperature dependences.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Algorithms for Computing the Magnetic Field, Vector Potential, and Field Derivatives for Circular Current Loops in Cylindrical Coordinates

A numerical algorithm for computing the field components B r and B z and their r and z derivatives with open boundaries in cylindrical coordinates for circular current loops is described. An algorithm for computing the vector potential is also described. For the convenience of the reader, derivations of the final expressions from their defining integrals are given in detail, since their derivations (especially for the field derivatives) are not all easily found in textbooks. Numerical calculations are based on evaluation of complete elliptic integrals using the Bulirsch algorithm cel. Since cel can evaluate complete elliptic integrals of a fairly general type, in some cases the elliptic integrals can be evaluated without first reducing them to forms containing standard Legendre forms. The algorithms avoid the numerical difficulties that many of the textbook solutions have for points near the axis because of explicit factors of 1=r or 1=r 2 in the some of the expressions.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

National High Magnetic Field Laboratory: Pulsed Field Facility Capability Overview [Slides]

High magnetic fields are a fundamental thermodynamic probe of quantum matter. Magnetic fields couple to both electons' spin and charge degrees of freedom. They can be used to manipulate the phase of the electron wavefunction and importantly provide a measure of coherence through orbital quantization. They can both probe and influence the state of a material.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Toward Autonomous Field Inspection of CSP Collectors With a Polarimetric Imaging Drone

We developed a polarimetric imaging drone to perform field inspections of heliostats and carried out field tests at Sandia’s National Solar Thermal Test Facility (NSTTF). The preliminary results show that Degree of Linear Polarization (DOLP) and Angle of Polarization (AOP) images greatly enhanced the edge detection results compared with the conventional visible images, supporting fast and accurate detection of heliostat mirror edges and cracks. The system holds the promise to enable future automated detection of heliostats optical errors and mirror defects.

14 SOLAR ENERGY↗
DOE OSTI2011

Symmetries and strings in field theory and gravity

We discuss aspects of global and gauged symmetries in quantum field theory and quantum gravity, focusing on discrete gauge symmetries. An effective Lagrangian description of Z{sub p} gauge theories shows that they are associated with an emergent Z{sub p} 1-form (Kalb-Ramond) gauge symmetry. This understanding leads us to uncover new observables and new phenomena in nonlinear {sigma} models. It also allows us to expand on Polchinski's classification of cosmic strings. We argue that in models of quantum gravity, there are no global symmetries, all continuous gauge symmetries are compact, and all charges allowed by Dirac quantization are present in the spectrum. These conjectures are not new, but we present them from a streamlined and unified perspective. Finally, our discussion about string charges and symmetries leads to a more physical and more complete understanding of recently found consistency conditions of supergravity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Strong longitudinal color-field effects in pp collisions at energies available at the CERN Large Hadron Collider

We study the effect of strong longitudinal color fields (SCF) in p + p reactions up to Large Hadron Collider (LHC) energies in the framework of the hijing/BB (v2.0) model that combines (collinear factorized) perturbative quantum chromodynamics multiple minijet production with soft longitudinal string excitation and hadronization. The default vacuum string tension, {kappa}{sub 0} = 1 GeV/fm, is replaced by an effective energy-dependent string tension, {kappa}(s)={kappa}{sub 0}(s/s{sub 0}){sup 0.06} that increases monotonically with center-of-mass energy. The exponent {lambda}=0.06 is found sufficient to reproduce well the energy dependence of multiparticle observables in the Relativistic Heavy Ion Collider, Tevatron, as well as recent LHC data. This exponent is half of that predicted by the color glass saturation (CGC) model, {lambda}{sub CGC}=0.115, where gluon fusion multiparticle production mechanisms are assumed. In hijing/BB (v2.0), the rapid growth of dN{sub ch}/d{eta} with energy is due to the interplay of copious minijet production with increasing SCF contributions. The large (strange) baryon-to-meson ratios measured at Tevatron energies are well described. A significant enhancement of these ratios is predicted up to the highest LHC energy (14 TeV). The effect of JJ loops and SCF on baryon-antibaryon asymmetry, and its relation to baryon number transport, is also discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗