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621.
Gerrit Coddens 《Foundations of Physics Letters》1995,8(3):261-277
We give a simple deductive derivation of the Dirac equation for a free particle. Our construction provides a clear distinction between what are the physical contents and what are purely mathematical expedients in the formalism of quantum mechanics (QM). 相似文献
622.
Information processing in nonlinear neural networks with a finite numberq of stored patterns is studied. Each network is characterized completely by its synaptic kernelQ. At low temperatures, the nonlinearity typically results in 2q–2–q metastable, pure states in addition to theq retrieval states that are associated with theq stored patterns. These spurious states start appearing at a temperature
, which depends onq. We give sufficient conditions to guarantee that the retrieval states bifurcate first at a critical temperatureT
c
and that
/T
c
0 asq. Hence, there is a large temperature range whereonly the retrieval states and certain symmetric mixtures thereof exist. The latter are unstable, as they appear atT
c
. For clipped synapses, the bifurcation and stability structure is analyzed in detail and shown to approach that of the (linear) Hopfield model asq. We also investigate memories that forget and indicate how forgetfulness can be explained in terms of the eigenvalue spectrum of the synaptic kernelQ. 相似文献
623.
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625.
部分控制集问题是对于给定的顶点赋权图G=(V,E;c)和正整数K,寻找图G一个顶点子集T,使得在其控制下的顶点个数不小于K且T中顶点权和达到最小。本文讨论了部分控制集问题的NP-困难性;给出了该问题的一种修正Greedy近似算法,并对其近似度H(K)给出了证明。 相似文献
626.
627.
Yunong Zhang W.E. Leithead D.J. Leith L. Walshe 《Journal of Computational and Applied Mathematics》2008,220(1-2):198-214
Maximum likelihood estimation (MLE) of hyperparameters in Gaussian process regression as well as other computational models usually and frequently requires the evaluation of the logarithm of the determinant of a positive-definite matrix (denoted by C hereafter). In general, the exact computation of is of O(N3) operations where N is the matrix dimension. The approximation of could be developed with O(N2) operations based on power-series expansion and randomized trace estimator. In this paper, the accuracy and effectiveness of using uniformly distributed seeds for approximation are investigated. The research shows that uniform-seed based approximation is an equally good alternative to Gaussian-seed based approximation, having slightly better approximation accuracy and smaller variance. Gaussian process regression examples also substantiate the effectiveness of such a uniform-seed based log-det approximation scheme. 相似文献
628.
空间光通信中基本振动对误码率的影响分析 总被引:1,自引:0,他引:1
在探讨卫星振动对空间光通信系统误码率所产生的影响时,有必要分析不同振动类型的影响问题。为了使讨论简单,本文主要侧重对正弦振动进行分析。分析结果表明,当振动持续时间为整周期时,误码率仅为振幅的函数,此时误码率随振幅的增加迅速上升,而与振动频率无关;当振动持续时间为非整周期时,误码率随时间的增加而波动,波动的起伏逐渐减小,误码率趋于仅与振幅有关的常数。该项工作为今后研究卫星复杂振动对空间光通信的影响打下了基础,同时也为研究对卫星振动影响的补偿分析提供了有意义的参考 相似文献
629.
考虑带有空竭服务多重休假的离散时间GI/G/1重试排队系统,其中重试空间中顾客的重试时间和服务台的休假时间均服从几何分布.通过矩阵几何方法,给出了该系统的一系列性能分析指标.最终利用逼近的方法得到了部分数值结果,并通过算例说明主要的参数变化对系统人数的影响. 相似文献
630.
Three related problems arising in retail facilities with front room and back room operations, and cross-trained workers, are considered. In the first problem, the goal is to determine an optimal policy for switching workers between the two rooms. In the second and third problems, the goal is to determine the minimum number of workers that should be hired by the facility such that a satisfactory switching policy exists. We analyze two questions arising from previous work on these problems. Firstly, we demonstrate that the previously proposed policy definition is sub-optimal and cannot represent a set of solutions that are reasonable in practice, and propose an alternative definition. Secondly, we examine the problem of finding the optimal combination of cross-trained and specialized workers under a complete set of assumptions regarding worker costs. This analysis shows that the structure of the optimal solution depends on the policy definition that is employed. Moreover, under some assumptions the cost of the ‘optimal’ solution with the original policy definition will be greater than the cost of the optimal solution with the new one. 相似文献