Structural dynamic interaction with solar tracking control for evolutionary Space Station concepts

The sun tracking control system design of the Solar Alpha Rotary Joint (SARJ) and the interaction of the control system with the flexible structure of Space Station Freedom (SSF) evolutionary concepts are addressed. The significant components of the space station pertaining to the SARJ control are described and the tracking control system design is presented. Finite element models representing two evolutionary concepts, enhanced operations capability (EOC) and extended operations capability (XOC), are employed to evaluate the influence of low frequency flexible structure on the control system design and performance. The design variables of the control system are synthesized using a constrained optimization technique to meet design requirements, to provide a given level of control system stability margin, and to achieve the most responsive tracking performance. The resulting SARJ control system design and performance of the EOC and XOC configurations are presented and compared to those of the SSF configuration. Performance limitations caused by the low frequency of the dominant flexible mode are discussed

Regge phenomenology of pion photoproduction off the nucleon at forward angles

We present a Regge model for pion photoproduction which is basically free of parameters within the framework of the s-channel helicity amplitude. We use coupling constants of all exchanged mesons determined from empirical decay widths or from the SU(3) relations together with consistency check with existing estimates that are widely accepted in other reaction processes. Cross sections and spin polarization asymmetries at various photon energies are analyzed and results are obtained in better agreement with experimental data without referring to any fitting procedure.Comment: 19 pages, 20 figures, two column, revtex

Exactly Soluble Quantum Wormhole in Two Dimensions

We are presenting a quantum traversable wormhole in an exactly soluble two-dimensional model. This is different from previous works since the exotic negative energy that supports the wormhole is generated from the quantization of classical energy-momentum tensors. This explicit illustration shows the quantum-mechanical energy can be used as a candidate for the exotic source. As for the traversability, after a particle travels through the wormhole, the static initial wormhole geometry gets a back reaction which spoils the wormhole structure. However, it may still maintain the initial structure along with the appropriate boundary condition.Comment: v1. 13 pages, 1 figure, REVTeX3; v2. 1 Ref. added, REVTeX4, to appear in Phys. Rev.

Absorption cross section and Hawking radiation in two-dimensional AdS black hole

We calculate the absorption coefficient of scalar field on the background of the two-dimensional AdS black hole, which is of relevance to Hawking radiation. For the massless scalar field, we find that there does not exist any massless radiation.Comment: 6 pages, revtex, no figure

The Chemical and Ionization Conditions in Weak Mg II Absorbers

We present an analysis of the chemical and ionization conditions in a sample of 100 weak Mg II absorbers identified in the VLT/UVES archive of quasar spectra. Using a host of low ionization lines associated with each absorber in this sample, and on the basis of ionization models, we infer that the metallicity in a significant fraction of weak Mg II clouds is constrained to values of solar or higher, if they are sub-Lyman limit systems. Based on the observed constraints, we present a physical picture in which weak Mg II absorbers are predominantly tracing two different astrophysical processes/structures. A significant population of weak Mg II clouds, those in which N(Fe II) is much less than N(Mg II), identified at both low (z ~ 1) and high (z ~ 2) redshift, are potentially tracing gas in the extended halos of galaxies, analogous to the Galactic high velocity clouds. These absorbers might correspond to alpha-enhanced interstellar gas expelled from star-forming galaxies, in correlated supernova events. On the other hand, N(FeII) approximately equal to N(Mg II) clouds, which are prevalent only at lower redshifts (z < 1.5), must be tracing Type Ia enriched gas in small, high metallicity pockets in dwarf galaxies, tidal debris, or other intergalactic structures.Comment: 35 pages (including tables & figures). Accepted for publication in ApJ. A high resolution version of the paper is available at "http://www.astro.wisc.edu/~anand/weakMgII.pdf

Enhanced performance of sulfur-infiltrated bimodal mesoporous carbon foam by chemical solution deposition as cathode materials for lithium sulfur batteries

The porous carbon matrix is widely recognized to be a promising sulfur reservoir to improve the cycle life by suppressing the polysulfide dissolution in lithium sulfur batteries (LSB). Herein, we synthesized mesocellular carbon foam (MSUF-C) with bimodal mesopore (4 and 30 nm) and large pore volume (1.72 cm 2 /g) using MSUF silica as a template and employed it as both the sulfur reservoir and the conductive agent in the sulfur cathode. Sulfur was uniformly infiltrated into MSUF-C pores by a chemical solution deposition method (MSUF-C/S CSD) and the amount of sulfur loading was achieved as high as 73% thanks to the large pore volume with the CSD approach. MSUF-C/S CSD showed a high capacity (889 mAh/g after 100 cycles at 0.2 C), an improved rate capability (879 mAh/g at 1C and 420 mAh/g at 2C), and a good capacity retention with a fade rate of 0.16% per cycle over 100 cycles.118Ysciescopu

Duality of Quasilocal Black Hole Thermodynamics

We consider T-duality of the quasilocal black hole thermodynamics for the three-dimensional low energy effective string theory. Quasilocal thermodynamic variables in the first law are explicitly calculated on a general axisymmetric three-dimensional black hole solution and corresponding dual one. Physical meaning of the dual invariance of the black hole entropy is considered in terms of the Euclidean path integral formulation.Comment: 19 pages, Latex, no figures, to be published in Class. Quantum Grav. Some minor changes, references adde

Symplectic embedding and Hamilton-Jacobi analysis of Proca model

Following the symplectic approach we show how to embed the Abelian Proca model into a first-class system by extending the configuration space to include an additional pair of scalar fields, and compare it with the improved Dirac scheme. We obtain in this way the desired Wess-Zumino and gauge fixing terms of BRST invariant Lagrangian. Furthermore, the integrability properties of the second-class system described by the Abelian Proca model are investigated using the Hamilton-Jacobi formalism, where we construct the closed Lie algebra by introducing operators associated with the generalized Poisson brackets.Comment: 24 page

Electrical properties of Bi-implanted amorphous chalcogenide films

The impact of Bi implantation on the conductivity and the thermopower of amorphous chalcogenide films is investigated. Incorporation of Bi in Ge-Sb-Te and GeTe results in enhanced conductivity. The negative Seebeck coefficient confirms onset of the electron conductivity in GeTe implanted with Bi at a dose of 2x1016 cm-2. The enhanced conductivity is accompanied by defect accumulation in the films upon implantation as is inferred by using analysis of the space-charge limited current. The results indicate that native coordination defects in lone-pair semiconductors can be deactivated by means of ion implantation, and higher conductivity of the films stems from additional electrically active defects created by implantation of bismuth.Comment: This is an extended version of the results presented in Proc. SPIE 8982, 898213 (2014

Higher dimensional flat embeddings of black strings in (2+1) dimensions

We obtain (3+1) and (3+2) dimensional global flat embeddings of (2+1) uncharged and charged black strings, respectively. In particular, the charged black string, which is the dual solution of the Banados-Teitelboim-Zanelli black holes, is shown to be embedded in the same global embedding Minkowski space structure as that of the (2+1) charged de Sitter black hole solution.Comment: 11 pages, REVTEX, no figur