40,919 research outputs found
Computer-aided modeling and prediction of performance of the modified Lundell class of alternators in space station solar dynamic power systems
The main purpose of this project is the development of computer-aided models for purposes of studying the effects of various design changes on the parameters and performance characteristics of the modified Lundell class of alternators (MLA) as components of a solar dynamic power system supplying electric energy needs in the forthcoming space station. Key to this modeling effort is the computation of magnetic field distribution in MLAs. Since the nature of the magnetic field is three-dimensional, the first step in the investigation was to apply the finite element method to discretize volume, using the tetrahedron as the basic 3-D element. Details of the stator 3-D finite element grid are given. A preliminary look at the early stage of a 3-D rotor grid is presented
Spectroscopic Evidence for the Specific Na+ and K+ Interactions with the Hydrogen-bonded Water Molecules at the Electrolyte Aqueous Solution Surfaces
Sum frequency generation vibrational spectra of the water molecules at the
NaF and KF aqueous solution surfaces showed significantly different spectral
features and different concentration dependence. This result is the first
direct observation of the cation effects of the simple alkali cations, which
have been believed to be depleted from the aqueous surface, on the hydrogen
bonding structure of the water molecules at the electrolyte solution surfaces.
These observations may provide important clue to understand the fundamental
phenomenon of ions at the air/water interface.Comment: 15 pages, 2 figure
Detecting and diagnosing faults in dynamic stochastic distributions using a rational b-splines approximation to output PDFs
Describes the process of detecting and diagnosing faults in dynamic stochastic distributions using a rational b-splines approximation to output PDFs
Interference Mitigation for Cognitive Radio MIMO Systems Based on Practical Precoding
In this paper, we propose two subspace-projection-based precoding schemes,
namely, full-projection (FP)- and partial-projection (PP)-based precoding, for
a cognitive radio multiple-input multiple-output (CR-MIMO) network to mitigate
its interference to a primary time-division-duplexing (TDD) system. The
proposed precoding schemes are capable of estimating interference channels
between CR and primary networks, and incorporating the interference from the
primary to the CR system into CR precoding via a novel sensing approach. Then,
the CR performance and resulting interference of the proposed precoding schemes
are analyzed and evaluated. By fully projecting the CR transmission onto a null
space of the interference channels, the FP-based precoding scheme can
effectively avoid interfering the primary system with boosted CR throughput.
While, the PP-based scheme is able to further improve the CR throughput by
partially projecting its transmission onto the null space.Comment: 12 pages, 4 figures, submitted to the IEEE Trans. Wireless
Communications in April 201
Electron correlation and Fermi surface topology of NaCoO
The electronic structure of NaCoO revealed by recent photoemission
experiments shows important deviations from band theory predictions. The six
small Fermi surface pockets predicted by LDA calculations have not been
observed as the associated band fails to cross the Fermi level for
a wide range of sodium doping concentration . In addition, significant
bandwidth renormalizations of the complex have been observed. We show
that these discrepancies are due to strong electronic correlations by studying
the multi-orbital Hubbard model in the Hartree-Fock and strong-coupling
Gutzwiller approximation. The quasiparticle dispersion and the Fermi surface
topology obtained in the presence of strong local Coulomb repulsion are in good
agreement with experiments.Comment: 5 pages, 4 figures, revtex4; minor changes, to be published in Phys.
Rev. Let
Quakes in Solid Quark Stars
A starquake mechanism for pulsar glitches is developed in the solid quark
star model. It is found that the general glitch natures (i.e., the glitch
amplitudes and the time intervals) could be reproduced if solid quark matter,
with high baryon density but low temperature, has properties of shear modulus
\mu = 10^{30~34} erg/cm^3 and critical stress \sigma_c = 10^{18~24} erg/cm^3.
The post-glitch behavior may represent a kind of damped oscillations.Comment: 11 pages, 4 figures (but Fig.3 is lost), a complete version can be
obtained by http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.htm, a new
version to be published on Astroparticle Physic
A LTE MIMO OTA Test System Using Vector Signal Transceivers
A 2 × 2 multiple-input-multiple-output over-the-air (MIMO OTA) test system based on four field-programmable Vector-Signal-Transceiver (VST) modules is presented. The system enables 2 x 2 MIMO OTA testing by assembling of a twochannel Evolved Node B (eNodeB) LTE base station emulator, a 2x2 channel emulator, and a two-channel user equipment (UE) simulator. A two-stage MIMO OTA test method has been demonstrated with downlink Long-Term Evolution Time-Division Duplex (LTE-TDD) mode using different modulation and coding schemes (MCSs). Test results and analysis are shown. This system will allow a systematic study of MIMO OTA metrology needs
Enhance synchronizability via age-based coupling
In this brief report, we study the synchronization of growing scale-free
networks. An asymmetrical age-based coupling method is proposed with only one
free parameter . Although the coupling matrix is asymmetric, our
coupling method could guarantee that all the eigenvalues are non-negative
reals. The eigneratio R will approach to 1 in the large limit of .Comment: 3 pages, 1 figur
Production of squeezed state of single mode cavity field by the coupling of squeezed vacuum field reservoir in nonautonomous case
The dissipative and decoherence properties as well as the asymptotic behavior
of the single mode electromagnetic field interacting with the time-dependent
squeezed vacuum field reservoir are investigated in detail by using the
algebraic dynamical method. With the help of the left and right representations
of the relevant algebra, the dynamical symmetry of the nonautonomous
master equation of the system is found to be . The unique equilibrium
steady solution is found to be the squeezed state and any initial state of the
system is proved to approach the unique squeezed state asymptotically. Thus the
squeezed vacuum field reservoir is found to play the role of a squeezing mold
of the cavity field.Comment: 5 pages, no figure, Revtex
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