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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 739 records · Page 41
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DOE OSTI2010

Scaling laws of resistive magnetohydrodynamic reconnection in the high-Lundquist-number, plasmoid-unstable regime

The Sweet-Parker layer in a system that exceeds a critical value of the Lundquist number (S) is unstable to the plasmoid instability. In this paper, a numerical scaling study has been done with an island coalescing system driven by a low level of random noise. In the early stage, a primary Sweet-Parker layer forms between the two coalescing islands. The primary Sweet-Parker layer breaks into multiple plasmoids and even thinner current sheets through multiple levels of cascading if the Lundquist number is greater than a critical value S{sub c}approx =4x10{sup 4}. As a result of the plasmoid instability, the system realizes a fast nonlinear reconnection rate that is nearly independent of S, and is only weakly dependent on the level of noise. The number of plasmoids in the linear regime is found to scales as S{sup 3/8}, as predicted by an earlier asymptotic analysis [N. F. Loureiro et al., Phys. Plasmas 14, 100703 (2007)]. In the nonlinear regime, the number of plasmoids follows a steeper scaling, and is proportional to S. The thickness and length of current sheets are found to scale as S{sup -1}, and the local current densities of current sheets scale as S{sup -1}. Heuristic arguments are given in support of theses scaling relations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

A Brief Discussion of Convergences in Interpretations of Quantum Mechanics

Bohr's approach to the measurement process implies a shifty split between the classical and quantum descriptions of the world. The current work presents arguments purporting to show that this split has not been satisfactorily removed from subsequent interpretations of the quantum theory. However, in their attempts to do so, rather obscure notions needed to be invoked, which were anticipated, explicitly or implicitly, and carefully circumvented by Bohr. We discuss von Neumann's description of the measurement process, the decoherence approach, the de Broglie-Bohm interpretation, and dynamical collapse models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Comment on 'Energy transfer in nanowire solar cells with photon-harvesting shells' [J. Appl. Phys. 105, 124509 (2009)]

In a recent article, Peters et al. [J. Appl. Phys. 105, 124509 (2009)] claim to have observed photosensitization of crystalline silicon by energy transfer from an optically absorbing thin polymer film. We show that this claim is not justified. Their experimental design is not adequate to establish enhanced photoexcitation of silicon; moreover, the theoretical arguments in their interpretation do not stand up to scrutiny.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2010

CO{sub 2} reduction by group 6 transition metal suboxide cluster anions

Reactions between small group 6 transition metal suboxide clusters, M{sub x}O{sub y}{sup -} (M={sup 98}Mo or {sup 186}W; x=1-4; y{<=}3x) and both CO{sub 2} and CO were studied in gas phase using mass spectrometric analysis of high-pressure, fast flow reaction products. Both Mo{sub 2}O{sub y}{sup -} and W{sub 2}O{sub y}{sup -} show evidence of sequential oxidation by CO{sub 2} of the form, M{sub 2}O{sub y}{sup -}+CO{sub 2}{yields}M{sub 2}O{sub y+1}{sup -}+CO for the more reduced species. Similar evidence is observed for the trimetallic clusters, although Mo{sub 3}O{sub 6}{sup -} appears uniquely unreactive. Lower mass resolution in the M{sub 4}O{sub y}{sup -} range precludes definitive product mass assignments, but intensity patterns suggest the continued trend of sequential oxidation of the more reduced end of the M{sub 4}O{sub y}{sup -} oxide series. Based on thermodynamic arguments, cluster oxidation by CO{sub 2} is possible if D{sub 0}(O-Mo{sub x}O{sub y}{sup -})>5.45 eV. Although simple bond energy analysis suggests that tungsten oxides may be more reactive toward CO{sub 2} compared to molybdenum oxides, this is not born out experimentally, suggesting that the activation barrier for the reduction of CO{sub 2} by tungsten suboxide clusters is very high compared to analogous molybdenum suboxide clusters. In reactions with CO, suboxides of both metal-based oxides show CO addition, with the product distribution being more diverse for Mo{sub x}O{sub y}{sup -} than for W{sub x}O{sub y}{sup -}. No evidence of cluster reduction by CO is observed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

On p-Adic Sector of Open Scalar Strings and Zeta Field Theory

We consider construction of Lagrangians which may be suitable for description of p-adic sector of an open scalar string. Such Lagrangians have their origin in Lagrangian for a single p-adic string and they contain the Riemann zeta function with the d'Alembertian in its argument. However, investigation of the field theory with Riemann zeta function is interesting in itself as well. We present a brief review and some new results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Guided ion beam and theoretical study of the reactions of Hf{sup +} with H{sub 2}, D{sub 2}, and HD

The kinetic energy dependences of reactions of the third-row transition metal cation Hf{sup +} with H{sub 2}, D{sub 2}, and HD were determined using a guided ion beam tandem mass spectrometer. A flow tube ion source produces Hf{sup +} in its {sup 2}D (6s{sup 2}5d{sup 1}) electronic ground state level. Corresponding state-specific reaction cross sections are obtained. The kinetic energy dependences of the cross sections for the endothermic formation of HfH{sup +} and HfD{sup +} are analyzed to give a 0 K bond dissociation energy of D{sub 0}(Hf{sup +}-H)=2.11{+-}0.08 eV. Quantum chemical calculations at several levels of theory performed here generally overestimate the experimental bond energy but results obtained using the Becke-half-and-half-LYP functional show good agreement. Theory also provides the electronic structures of these species and the reactive potential energy surfaces. Results from the reactions with HD provide insight into the reaction mechanisms and indicates that Hf{sup +} reacts via a statistical mechanism. We also compare this third-row transition metal system with the first-row and second-row congeners, Ti{sup +} and Zr{sup +}, and find that Hf{sup +} has a weaker M{sup +}-H bond. As most third-row transition metal hydride cation bonds exceed their lighter congeners, this trend is unusual but can be understood using promotion energy arguments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2010

Study of a Narrow {pi}{sup +{pi}-} Peak at about 755 MeV/c{sup 2} in p-barn{yields}2{pi}{sup +}3{pi}{sup -} Annihilation at Rest

A narrow peak in the {pi}{sup +{pi}-} mass distribution was seen by the Rome-Syracuse Collaboration in p-barn{yields}2{pi}{sup +}3{pi}{sup -} annihilation at rest in 1970. It was ignored for 40 years. The reanalysis of this peak finds that it has the mass 757.4{+-}2.8{sub stat{+-}}1.2{sub sys} MeV/c{sup 2} and a width consistent with the experimental resolution. The evidence of the peak is 5.2 standard deviations. The peak is generated in (1.03{+-}0.21{sub stat{+-}}0.21{sub sys})% of the p-barn annihilations at rest. No spin analysis is possible with the statistics of the experiment but there are arguments suggesting that it has J{sup p} = 0{sup +}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Strangeness Nuclear Physics And Strange Matter In Universe

We introduce physics interests of hypernuclei related to astrophysics. Particularly, some remarkable information from precision spectroscopic studies of hypernuclei has been provided, which should be taken into consideration on arguments on hyperon constituent in a neutron star core. Further precision spectroscopic studies of hypernuclei have to be carried out at J-PARC.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Communication: Conditions for one-photon coherent phase control in isolated and open quantum systems

Coherent control of observables using the phase properties of weak light that induces one-photon transitions is considered. Measurable properties are shown to be categorizable as either class A, where control is not possible, or class B, where control is possible. Using formal arguments, we show that phase control in open systems can be environmentally assisted.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2010

Trigonometric Sutherland systems and their Ruijsenaars duals from symplectic reduction

Beside its usual interpretation as a system of n indistinguishable particles moving on the circle, the trigonometric Sutherland system can be viewed alternatively as a system of distinguishable particles on the circle or on the line, and these three physically distinct systems are in duality with corresponding variants of the rational Ruijsenaars-Schneider system. We explain that the three duality relations, first obtained by Ruijsenaars in 1995, arise naturally from the Kazhdan-Kostant-Sternberg symplectic reductions of the cotangent bundles of the group U(n) and its covering groups U(1)xSU(n) and RxSU(n), respectively. This geometric interpretation enhances our understanding of the duality relations and simplifies Ruijsenaars' original direct arguments that led to their discovery.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Benefits and concerns of a closed nuclear fuel cycle

Nuclear power can play an important role in our energy future, contributing to increasing electricity demand while at the same time decreasing carbon dioxide emissions. However, the nuclear fuel cycle in the United States today is unsustainable. As stated in the 1982 Nuclear Waste Policy Act, the U.S. Department of Energy is responsible for disposing of spent nuclear fuel generated by commercial nuclear power plants operating in a “once-through” fuel cycle in the deep geologic repository located at Yucca Mountain. However, unyielding political opposition to the site has hindered the commissioning process to the extant that the current administration has recently declared the unsuitability of the Yucca Mountain site. In light of this the DOE is exploring other options, including closing the fuel cycle through recycling and reprocessing of spent nuclear fuel. The possibility of closing the fuel cycle is receiving special attention because of its ability to minimize the final high level waste (HLW) package as well as recover additional energy value from the original fuel. The technology is, however, still very controversial because of the increased cost and proliferation risk it can present. To lend perspective on the closed fuel cycle alternative, this presents the arguments for and against closing the fuel cycle with respect to sustainability, proliferation risk, commercial viability, waste management, and energy security.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2010

On Production Mechanisms For Balmer Line Radiation From 'Cold' Atomic Hydrogen and Deuterium In Fusion Edge Plasmas

Published arguments, which assign dominant roles to atomic metastability and molecular ion dissociation in the production of 'narrow' Zeeman component Balmer line radiation from the tokamak edge plasma, have been examined critically in relation to: l-redistribution by proton collisions, molecular ion-proton equipartition, and ion acceleration by the plasma sheath (scrape-off layer) potential. These processes are found to constrain the contributions from metastable atoms and from dissociative excitation of molecular ions to 'narrow' Balmer spectra emitted from the plasma edge, in relation to the corresponding contributions from electron impact-induced dissociative excitation of neutral molecules.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Plasma dispersion function for a Fermi-Dirac distribution

A plasma dispersion function (PDF) is defined for a nonrelativistic Fermi-Dirac distribution and its properties are explored. The degree of degeneracy is described by a parameter {xi}=e{sup {mu}}{sub e}{sup /T}{sub e}, for electrons, with {mu}{sub e}/T{sub e} large and negative in the nondegenerate limit, and large and positive in the completely degenerate limit. The PDF is denoted Z(y,{xi}), where the variable y={omega}/{radical}(2)kV{sub e}, is the argument of the conventional PDF, Z(y)=Z(y,0), for a Maxwellian distribution. In the completely degenerate limit, Z(y,{xi}) approaches a logarithmic function that depends on the Fermi temperature and is independent of T{sub e}. Analytic approximations to Z(y,{xi}) are derived in terms of polylogarithmic functions for y{sup 2}>>1 and for y{sup 2}<<1.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Dark-energy thermodynamic models

We study cosmological consequences of dark-energy thermodynamic models. The assumption that dark energy is conformed of quanta, and an extensivity argument generalize its equation of state. This implies that dark energy and another key component exchange energy. The energy densities of dark energy and the other component then tend asymptotically to a constant, thus explaining the coincidence of dark matter and dark energy today. On the other hand, a model of non-relativistic particles in a Bose-Einstein condensate, with a short-range attractive interaction, produces acceleration. It is shown that the phantom-acceleration regime, at the beginning of the universe, solves the horizon problem.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Comment on ''Terrestrial gamma-ray flashes caused by neutron bursts above thunderclouds''[J. Appl. Phys. 105, 083301 (2009)]

Paiva presented in these pages an argument that terrestrial gamma-ray flashes (TGFs) are created by the interaction of lightning-generated neutrons with nitrogen nuclei in air. I show that this model cannot produce the observed energy spectrum of TGFs, while the generally accepted model of bremsstrahlung from relativistic electrons fits the data well.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2010

Compositeness of bound states in chiral unitary approach

We study the structure of dynamically generated bound states in the chiral unitary approach. The compositeness of a bound state is defined through the wavefunction renormalization constant in the nonrelativistic field theory. We apply this argument to the chiral unitary approach and derive the relation between compositeness of the bound state and the subtraction constant of the loop integral. The compositeness condition is fairly compatible with the natural renormalization scheme, previously introduced in a different context.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Secondary Island Formation in Collisional and Collisionless Kinetic Simulations of Magnetic Reconnection

The evolution of magnetic reconnection in large-scale systems often gives rise to extended current layers that are unstable to the formation of secondary magnetic islands. The role of these islands in the reconnection process and the conditions under which they form remains a subject of debate. In this work, we benchmark two different kinetic particle-in-cell codes to address the formation of secondary islands for several types of global boundary conditions. The influence on reconnection is examined for a range of conditions and collisionality limits. Although secondary islands are observed in all cases, their influence on reconnection may be different depending on the regime. In the collisional limit, the secondary islands play a key role in breaking away from the slow Sweet-Parker scaling and pushing the evolution towards small scales where kinetic effects can dominate. In the collisionless limit, fast reconnection can proceed in small systems (30x ion inertial scale) without producing any secondary islands. However, in large-scale systems the diffusion region forms extended current layers that are unstable to the formation of secondary islands, giving rise to a time-dependent reconnection process. These instabilities provide one possible mechanism for controlling the average length of the diffusion region in large systems. New results from Fokker-Planck kinetic simulations are used to examine the role of secondary islands in electron-positron plasmas for both collisional and kinetic parameter regimes. Simple physics arguments suggest the transition should occur when the resistive layers approach the inertial scale. These expectations are confirmed by simulations, which demonstrate the average rate remains fast in large systems and is accompanied by the continuous formation of secondary islands.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Revisit to Grad's Closure and Development of Physically Motivated Closure for Phenomenological High-Order Moment Model

The Grad's closure for the high-order moment equation is revisited and, by extending his theory, a physically motivated closure is developed for the one-dimensional velocity shear gas flow. The closure is based on the physical argument of the relative importance of various terms appearing in the moment equation. Also, the closure is derived such that the resulting theory may be inclusive of the well established linear theory (Navier-Stokes-Fourier) as limiting case near local thermal equilibrium.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗