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61.
In this paper, a high resolution technique for estimating DOAs of spatially close source signals is presented. It is observed that the array manifold over a sector of interest is rank deficient and the dimension of the array manifold space, which is the range space of the array manifold, is less than the number of sensors in the array. The true signal subspace is a subspace in the array manifold space. A novel technique is provided that searches for the signal subspace in this array manifold space. The resulting estimated signal subspace has minimum principal angles with the data signal subspace generated by eigen-decomposing the covariance matrix of the array data vector. It is proved that the proposed estimator is asymptotically consistent and the estimated signal subspace is closer to the true signal subspace than the data signal subspace formed by MUSIC. The proposed novel technique has better performance than the MUSIC algorithm. Its performance is comparable to MLE and MD-MUSIC yet it requires only one-dimensional searches and is computationally much less intense. Simulation results are presented to show the effectiveness of the proposed technique, and comparisons with MUSIC, MLE, and MD-MUSIC algorithms are also included.This research was supported by TRIO and NSERC. 相似文献
62.
D.F. Zheng P.M. Hui K.F. Yip N.F. Johnson 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(2):213-218
We present generalized dynamical models describing the sharing of information, and the corresponding herd behavior, in a population
based on the recent model proposed by Eguıluz and Zimmermann (EZ) [Phys. Rev. Lett. 85, 5659 (2000)]. The EZ model, which is a dynamical version of the herd formation model of Cont and Bouchaud (CB), gives a
reasonable model for the formation of clusters of agents and for actions taken by clusters of agents. Both the EZ and CB models
give a cluster size distribution characterized by a power law with an exponent -5/2. By introducing a size-dependent probability
for dissociation of a cluster of agents, we show that the exponent characterizing the cluster size distribution becomes model-dependent
and non-universal, with an exponential cutoff for large cluster sizes. The actions taken by the clusters of agents generate
the price returns, the distribution of which is also characterized by a model-dependent exponent. When a size-dependent transaction
rate is introduced instead of a size-dependent dissociation rate, it is found that the distribution of price returns is characterized
by a model-dependent exponent while the exponent for the cluster-size distribution remains unchanged. The resulting systems
provide simplified models of a financial market and yield power law behaviour with an easily tunable exponent.
Received 31 December 2001 相似文献
63.
An optical TE-TM mode splitter and modulator with an improved design using a Y-junction waveguide by Ti-diffusion in a Y-cut LiNbO3 substrate has been fabricated and characterized. Improvements in fabrication and measurement techniques are discussed. Experimental results on the device characteristics are presented. 相似文献
64.
Numerical results for the density and current correlation functions in dense hard-sphere fluids are obtained from a kinetic equation which is the extension of the linearized Enskog equation to finite wavelengths in order to demonstrate the convergence of the method of solution. Comparison is made to a previously proposed approximate solution.This work was performed in part under the auspices of the U.S. Department of Energy by the Lawrence Livermore Laboratory under contract number W-7405-ENG-48 and in part supported by the National Science Foundation. 相似文献
65.
66.
The field distribution and polarization state of waveguide modes propagating around a curved dielectric optical fibre are investigated analytically by using a first-order perturbation theory. It is shown that the polarization direction of all modes except the HE1m modes changes due to bending. Field distributions are also deformed and the shift in the field maximum, which takes place in the plane of curvature, is clarified for the dominant HE11 mode. 相似文献
67.
Congruence of arbitrary square matrices over an arbitrary field is treated here by elementary classical methods, and likewise for conjunctivity of arbitrary square matrices over an arbitrary field with involution. Uniqueness results are emphasized, since they are largely neglected in the literature. In particular, it is shown that a matrix S is congruent [conjunctive] to S0⊕S1 with S1 nonsingular, and that if S1 here is of maximal size among all nonsingular matrices R1 for which R0⊕R1 is congruent [conjunctive] to S, then the congruence [conjunctivity] class of S determines that of S1. Partially canonical forms (most of them already known) are derived, to the extent that they do not depend on the field. Nearly canonical forms are derived for “neutral” matrices (those congruent or conjunctive with block matrices with the two zero blocks being square). For a neutral matrix S over a field F,the F-congruence [F-conjunctivity] class of S is determined by the F-equivalence class of the pencil S+tS' [S+tS1] and, if the pencil is nonsingular, by the F[t]-equivalence class of S+tS' [S+tS1]. 相似文献
68.
69.
We consider a question raised by Suhov and Voice from quantum information theory and quantum computing. An element of a partition
of {1, ..., n} is said to be block-stable for
if it is not moved to another block under the action of π. The problem concerns the determination of the generating series
for elements of
with respect to the number of block-stable elements of a canonical partition of a finite n-set, with block sizes k1, ..., kr, in terms of the moment (power) sums pq(k1, ..., kr). We also consider the limit
subject to the condition that
exists for q = 1, 2,....
Received January 31, 2006 相似文献
70.
X.?Y.?Chen C.?T.?Yip M.?K.?Fung A.?B.?Djuri?i? W.?K.?Chan 《Applied Physics A: Materials Science & Processing》2010,100(1):15-19
GaN nanowires typically exhibit high electron mobility and excellent chemical stability. However, stability of GaN is detrimental
for successful attachment of dye molecules and its application in dye-sensitized solar cells (DSSCs). Here we demonstrate
DSSCs based on GaN/gallium oxide and GaN/TiO
x
core–shell structures, and we show that coating of GaN nanowires with a TiO
x
shell significantly increases dye adsorption and consequently photovoltaic performance. The best cells exhibited short circuit
current density of 1.83 mA/cm2 and power conversion efficiency of 0.44% under AM 1.5 simulated solar illumination. 相似文献