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101.
Consider K ≥ 2 independent copies of the random walk on the symmetric group SN starting from the identity and generated by the products of either independent uniform transpositions or independent uniform neighbor transpositions. At any time $n\in \mathbb{N}$, let Gn be the subgroup of SN generated by the K positions of the chains. In the uniform transposition model, we prove that there is a cut‐off phenomenon at time N ln(N)/(2K) for the non‐existence of fixed point of Gn and for the transitivity of Gn, thus showing that these properties occur before the chains have reached equilibrium. In the uniform neighbor transposition model, a transition for the non‐existence of a fixed point of Gn appears at time of order $N^{1+\frac{2}{K}}$ (at least for K ≥ 3), but there is no cut‐off phenomenon. In the latter model, we recover a cut‐off phenomenon for the non‐existence of a fixed point at a time proportional to N by allowing the number K to be proportional to ln(N). The main tools of the proofs are spectral analysis and coupling techniques. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2012 相似文献
102.
Kuei-Yi Chu Shiou-Ying Cheng Meng-Hsueh Chiang Yi-Jung Liu Chien-Chang Huang Tai-You Chen Chi-Shiang Hsu Wen-Chau Liu Wen-Yu Cheng Bin-Cian Lin 《Superlattices and Microstructures》2011,50(4):289-295
The characteristics of InGaP/InGaAs/GaAs dual channel pseudomorphic high electron mobility transistors (DCPHEMTs) with different graded triple delta-doped sheets are investigated and experimentally demonstrated. Based on a two-dimensional simulator of ATLAS, the band diagrams, electron densities and DC characteristics of studied devices are comprehensively analyzed. Due to the use of properly graded triple delta-doped sheets, good pinch-off and saturation characteristics, improved transport properties and wide current swing are obtained. For comparison, a practical DCPHEMT with good device performances is fabricated as well. It is found that the simulated data are in good agreement with experimental results. 相似文献
103.
Let M
n =X1+...+Xn be a martingale with bounded differences Xm=Mm-Mm-1 such that {|Xm| m}=1 with some nonnegative m. Write 2=
1
2
+ ... +
n
2
. We prove the inequalities {M
nx}c(1-(x/)), {M
n x} 1- c(1- (-x/)) with a constant
. The result yields sharp inequalities in some models related to the measure concentration phenomena. 相似文献
104.
Consider a closed Jackson type network in which each queue has a single exponential server. Assume that N customers are moving among k queues. We establish simple closed form bounds on the network throughput (both lower and upper), which are sharper than those that are currently available. Numerical evaluation indicates that the improvements are significant. 相似文献
105.
A simple technique is given in this paper for the construction and analysis of a class of finite element discretizations for convection-diffusion problems in any spatial dimension by properly averaging the PDE coefficients on element edges. The resulting finite element stiffness matrix is an -matrix under some mild assumption for the underlying (generally unstructured) finite element grids. As a consequence the proposed edge-averaged finite element scheme is particularly interesting for the discretization of convection dominated problems. This scheme admits a simple variational formulation, it is easy to analyze, and it is also suitable for problems with a relatively smooth flux variable. Some simple numerical examples are given to demonstrate its effectiveness for convection dominated problems.
106.
Dimitri P. Bertsekas 《Computational Optimization and Applications》1999,12(1-3):41-51
Given a single feasible solution
and a single infeasible solution
of a mathematical program, we provide an upper bound to the optimal dual value. We assume that
satisfies a weakened form of the Slater condition. We apply the bound to convex programs and we discuss its relation to Hoffman-like bounds. As a special case, we recover a bound due to Mangasarian [11] on the distance of a point to a convex set specified by inequalities. 相似文献
107.
用三次B样条函数配点法,求得在矩形波冲击下具有立方非线性产品包装的冲击谱。讨论了软、硬非线性及外界激励幅值对产品损坏边界的影响。提出用损坏边界曲面来描述非线性产品包装的安全区域,并作出了相应的损坏边界曲面. 相似文献
108.
A new quasi-phase-matching technique for efficient second-harmonic generation is reported. It is based on the spatial periodic modulation of the light intensity along the propagation direction, rather than the conventional spatial periodic modulation of the nonlinear optical coefficients. It can be realized by using a novel dual-channel waveguide frequency doubler structure for the desired light intensity distribution. This dual-channel waveguide device has major advantages including very small beam size, high light intensity within long nonlinear-waveguide interaction length, highly efficient second-harmonic generation, ease in fabrication of the nonlinear channel waveguides without any spatially periodic poling, and low waveguide propagation losses. The new quasi-phase-matching technique can also be applied to third-harmonic generation and other nonlinear optics processes. 相似文献
109.
Roberto D. Galvão 《European Journal of Operational Research》1981,6(2):162-165
The p-median problem is a minisium network location problem that seeks to find the optimal location of p centres in a network. In the present paper a graph-theoretical bound is developed for the problem. This bound is based on shortest spanning trees and arborescences and other graphical properties of the problem. It is shown that the graph-theoretical bound dominates a bound based on shortest distances. 相似文献
110.
According to the universal entropy bound, the entropy (and hence information capacity) of a complete weakly self-gravitating
physical system can be bounded exclusively in terms of its circumscribing radius and total gravitating energy. The bound’s
correctness is supported by explicit statistical calculations of entropy, gedanken experiments involving the generalized second
law, and Bousso’s covariant holographic bound. On the other hand, it is not always obvious in a particular example how the
system avoids having too many states for given energy, and hence violating the bound. We analyze in detail several purported
counterexamples of this type, and exhibit in each case the mechanism behind the bound’s efficacy.
In memoriam Asher Peres. 相似文献