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41.
Irwin Guttman Ulrich Menzefricke 《Annals of the Institute of Statistical Mathematics》1982,34(1):319-326
Summary We consider a sequence of independent random variables whose densities depend on a parameter which is subject to a change
at an unknown time point. A Bayesian decision-theoretic approach is used to obtain an optimal choice of changepoint. The exponential
and multivariate normal models are analyzed, and some numerical examples are given. 相似文献
42.
Xian Zhou Xiaoqian Sun Jinglong Wang 《Annals of the Institute of Statistical Mathematics》2001,53(4):760-768
Let X
1, , X
n
(n > p) be a random sample from multivariate normal distribution N
p
(, ), where R
p
and is a positive definite matrix, both and being unknown. We consider the problem of estimating the precision matrix –1. In this paper it is shown that for the entropy loss, the best lower-triangular affine equivariant minimax estimator of –1 is inadmissible and an improved estimator is explicitly constructed. Note that our improved estimator is obtained from the class of lower-triangular scale equivariant estimators. 相似文献
43.
《Photonics and Nanostructures》2014,12(2):184-188
We propose a design of a low loss terahertz polarization splitter based on a dual-core terahertz fiber with crossed dielectric strips in the fiber cross section. Low transmission loss is realized by extending the mode field to the air holes adjacent to the solid material. An 11.4-cm-long terahertz polarization splitter is obtained with the extinction ratio better than −15 dB and a bandwidth of 16 μm. 相似文献
44.
二次损失下增长曲线模型参数阵的线性Minimax可容许估计 总被引:3,自引:0,他引:3
本文在二次损失函数下,给出了增长曲线模型参数阵的线性估计在给定的线性估计类中是Minimax可容许估计的充要条件. 相似文献
45.
A novel architecture for an optical time-division switch is investigated and demonstrated at a bit rate of 625 Mbit/s. The self-clocked configuration eliminates some of the limitations found in previous optical implementations of time-division switches: the switch operation is asynchronous, no read gate is required, and an optimal number of delay lines is used. Furthermore, this paper reports the first experimental demonstration of optical space-sorting demultiplexing. 相似文献
46.
Dieter Fiems Stijn De Vuyst Sabine Wittevrongel Herwig Bruneel 《Annals of Operations Research》2009,170(1):113-131
In this contribution we investigate higher-order loss characteristics for M/G/1/N queueing systems. We focus on the lengths of the loss and non-loss periods as well as on the number of arrivals during these
periods. For the analysis, we extend the Markovian state of the queueing system with the time and number of admitted arrivals
since the instant where the last loss occurred. By combining transform and matrix techniques, expressions for the various
moments of these loss characteristics are found. The approach also yields expressions for the loss probability and the conditional
loss probability. Some numerical examples then illustrate our results. 相似文献
47.
Falk M. Hante Günter Leugering Thomas I. Seidman 《Applied Mathematics and Optimization》2009,59(2):275-292
We consider networked transport systems defined on directed graphs: the dynamics on the edges correspond to solutions of transport
equations with space dimension one. In addition to the graph setting, a major consideration is the introduction and propagation
of discontinuities in the solutions when the system may discontinuously switch modes, naturally or as a hybrid control. This
kind of switching has been extensively studied for ordinary differential equations, but not much so far for systems governed
by partial differential equations. In particular, we give well-posedness results for switching as a control, both in finite
horizon open loop operation and as feedback based on sensor measurements in the system. 相似文献
48.
We consider a single server loss system in which arrivals occur according to a doubly stochastic Poisson process with a stationary
ergodic intensity functionλ
t
. The service times are independent, exponentially distributed r.v.'s with meanμ
−1, and are independent of arrivals. We obtain monotonicity results for loss probabilities under time scaling as well as under
amplitude scaling ofλ
t
. Moreover, using these results we obtain both lower and upper bounds for the loss probability. 相似文献
49.
Hui-Zhong Xu Xiao Chen Jing Hua Jun-Ming Liu 《Journal of magnetism and magnetic materials》2009,321(22):3698-3701
Micromagnetic simulations based on the Landau–Lifshitz–Gilbert equation are presented to study spin-polarized current induced magnetization switching in asymmetric nanoring-shaped magnetic tunnel junctions. The results show that in a nanoring with an intermediate eccentric distance S, the critical switching voltage VC reaches the minimum whose magnitude is less than half of the voltage for a symmetric nanoring. In addition to the spin-transfer torque, the current induced Ampère field is found to play a crucial part in the switching process. Analysis is given to explain the existence of such an energy valley that leads to the minimal voltage. 相似文献
50.
The multi-scale analysis of fracture toughness of ferroelectric ceramics under complicate mechanical–electrical coupling effect is carried out in this paper. The generalized stress intensity factor (SIF) arising from spontaneous strains and polarization transformation in switching domain zones is accurately obtained by using an extended Eshelby theory. Taking BaTiO3 ferroelectric ceramic for example, it is discovered that the crack propagation can be induced by domain switching arising from negative electrical field when the crack surface is parallel to the isotropic plane, and the obtained critical electric displacement intensity factor (EDIF) approximates closely to that obtained by the Green’s function method. Additionally, as pinning dislocations and slip dislocations can strongly influence properties of ferroelectric devices and induce the property degradation, it is necessary to investigate the dislocation toughening effects on fatigue and fracture mechanisms. The results show that the dislocation shielding and anti-shielding effects on mode II SIF, mode I SIF and EDIF are obviously different when a dislocation locates at a position near the crack tip. Through the calculation of the critical applied EDIF for crack propagation by using mechanical energy release rate (MERR) theory, it is discovered that the slip angles obviously influence fracture toughness, and the mode II SIF arising from dislocation has little influence on fracture toughness, however, the mode I SIF and EDIF arising from dislocation have great influences on fracture toughness. 相似文献