19,986 research outputs found
SRB-3D Solid Rocket Booster performance prediction program. Volume 1: Engineering description/users information manual
The modified Solid Rocket Booster Performance Evaluation Model (SRB-3D) was developed as an extension to the internal ballistics module of the SRB-2 performance program. This manual contains the engineering description of SRB-3D which describes the approach used to develop the 3D concept and an explanation of the modifications which were necessary to implement these concepts
Anisotropic spin splitting and spin relaxation in asymmetric zinc-blende semiconductor quantum structures
Spin relaxation due to the D'yakonov-Perel' mechanism is intimately related
with the spin splitting of the electronic states. We determine the spin
relaxation rates from anisotropic spin splittings of electron subbands in
n-(001) zinc-blende semiconductor quantum structures calculated
self-consistently in the multi-band envelope function approach. The giant
anisotropy of spin relaxation rates found for different spin-components in the
(001) plane can be ascribed to the interplay between the bulk and quantum well
inversion asymmetry. One of the in-plane relaxation rates may exhibit a
striking nonmonotonous dependence on the carrier density.Comment: 6 pages, 7 figures; revised version with minor changes after
refereein
Statistical characterization of phenolic-novolak structures
Three statistical methods of general validity are valuable for characterizing any polymer which results from chain polymerization of multifunctional branching monomers linked through bifunctional monomers
Periodic orbit theory for the H\'enon-Heiles system in the continuum region
We investigate the resonance spectrum of the H\'enon-Heiles potential up to
twice the barrier energy. The quantum spectrum is obtained by the method of
complex coordinate rotation. We use periodic orbit theory to approximate the
oscillating part of the resonance spectrum semiclassically and Strutinsky
smoothing to obtain its smooth part. Although the system in this energy range
is almost chaotic, it still contains stable periodic orbits. Using Gutzwiller's
trace formula, complemented by a uniform approximation for a codimension-two
bifurcation scenario, we are able to reproduce the coarse-grained
quantum-mechanical density of states very accurately, including only a few
stable and unstable orbits.Comment: LaTeX (v3): 10 pages, 9 figures (new figure 6 added), 1 table; final
version for Phys. Rev. E (in print
Side-jumps in the spin-Hall effect: construction of the Boltzmann collision integral
We present a systematic derivation of the side-jump contribution to the
spin-Hall current in systems without band structure spin-orbit interactions,
focusing on the construction of the collision integral for the Boltzmann
equation. Starting from the quantum Liouville equation for the density operator
we derive an equation describing the dynamics of the density matrix in the
first Born approximation and to first order in the driving electric field.
Elastic scattering requires conservation of the total energy, including the
spin-orbit interaction energy with the electric field: this results in a first
correction to the customary collision integral found in the Born approximation.
A second correction is due to the change in the carrier position during
collisions. It stems from the part of the density matrix off-diagonal in wave
vector. The two corrections to the collision integral add up and are
responsible for the total side-jump contribution to the spin-Hall current. The
spin-orbit-induced correction to the velocity operator also contains terms
diagonal and off-diagonal in momentum space, which together involve the total
force acting on the system. This force is explicitly shown to vanish (on the
average) in the steady state: thus the total contribution to the spin-Hall
current due to the additional terms in the velocity operator is zero.Comment: Added references, expanded discussion, revised introductio
A program for calculating optimum dimensions of alpha radioisotope capsules exposed to varying stress and temperature
Method and computer program for calculating creep and optimizing dimensions of capsules filled with alpha-emitting radioisotopes and exposed to varying stress and temperatur
Cubic Dresselhaus Spin-Orbit Coupling in 2D Electron Quantum Dots
We study effects of the oft-neglected cubic Dresselhaus spin-orbit coupling
(i.e., ) in GaAs/AlGaAs quantum dots. Using a semiclassical
billiard model, we estimate the magnitude of the spin-orbit induced avoided
crossings in a closed quantum dot in a Zeeman field. Using these results,
together with previous analyses based on random matrix theory, we calculate
corresponding effects on the conductance through an open quantum dot. Combining
our results with an experiment on conductance through an 8 um^2 quantum dot [D
M Zumbuhl et al., Phys. Rev. B 72, 081305 (2005)] suggests that 1) the GaAs
Dresselhaus coupling constant, , is approximately 9 eVA^3,
significantly less than the commonly cited value of 27.5 eVA^3 and 2) the
majority of the spin-flip component of spin-orbit coupling can come from the
cubic Dresselhaus term.Comment: 4 pages plus supplementary tabl
Hydrogen Generation Catalyzed by Fluorinated Diglyoxime−Iron Complexes at Low Overpotentials
Fe^(II) complexes containing the fluorinated ligand 1,2-bis(perfluorophenyl)ethane-1,2-dionedioxime (dAr^FgH_2; H = dissociable proton) exhibit relatively positive Fe^(II/I) reduction potentials. The air-stable difluoroborated species [(dAr^FgBF_2)_2Fe(py)_2] (2) electrocatalyzes H_2 generation at −0.9 V vs SCE with i_(cat)/i_p ≈ 4, corresponding to a turnover frequency (TOF) of ~ 20 s^(–1) [Faradaic yield (FY) = 82 ± 13%]. The corresponding monofluoroborated, proton-bridged complex [(dArFg2H-BF2)Fe(py)2] (3) exhibits an improved TOF of ~ 200 s^(–1) (i_(cat)/i_p ≈ 8; FY = 68 ± 14%) at −0.8 V with an overpotential of 300 mV. Simulations of the electrocatalytic cyclic voltammograms of 2 suggest rate-limiting protonation of an Fe“0” intermediate (k_(RLS) ≈ 200 M^(–1) s^(–1)) that undergoes hydride protonation to form H_2. Complex 3 likely reacts via protonation of an Fe^I intermediate that subsequently forms H_2 via a bimetallic mechanism (k_(RLS) ≈ 2000 M^(–1) s^(–1)). 3 catalyzes production at relatively positive potentials compared with other iron complexes
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