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261.
FANG Xiangzhong & CHEN Jiading School of Mathematical Science LMAM Peking University Beijing China 《中国科学A辑(英文版)》2005,48(8):1065-1074
In medicine and industry, small sample size often arises owing to the high test cost. Then exact confidence inference is important. Buehler confidence limit is a kind of exact confidence limit for the function of parameters in a model. It can be always defined if the order in sample space is given. But the computing problem is often difficult, especially for the cases with high dimension parameter or with incomplete data. This paper presents an algorithm to compute the Buehler confidence limits by EM algorithm. This is the first-time usage of EM algorithm on Buehler confidence limits, but the algorithm is often used for maximum likelihood estimate in literatures. Three computation examples are given to illustrate the method. 相似文献
262.
Based on the theories of electromagnetic (EM) field and generalized reflection coefficient, a simple method is put forward
to deal with the EM reflection coefficient of conductive plate coated with nonuniform plasma. The plasma slab is modeled by
a series of subslabs, in which the electron-number density is assumed to be constant. The overall number density profile across
the whole slab follows any practical distribution function. The reflection coefficient is then deduced and its functional
dependence on the number density, incident wave frequency, collision frequency, and background magnetic field is discussed. 相似文献
263.
Sampling from a truncated multivariate normal distribution (TMVND) constitutes the core computational module in fitting many statistical and econometric models. We propose two efficient
methods, an iterative data augmentation (DA) algorithm and a non-iterative inverse Bayes formulae (IBF) sampler, to simulate TMVND and generalize them to multivariate normal distributions with linear inequality constraints.
By creating a Bayesian incomplete-data structure, the posterior step of the DA algorithm directly generates random vector
draws as opposed to single element draws, resulting obvious computational advantage and easy coding with common statistical
software packages such as S-PLUS, MATLAB and GAUSS. Furthermore, the DA provides a ready structure for implementing a fast
EM algorithm to identify the mode of TMVND, which has many potential applications in statistical inference of constrained
parameter problems. In addition, utilizing this mode as an intermediate result, the IBF sampling provides a novel alternative
to Gibbs sampling and eliminates problems with convergence and possible slow convergence due to the high correlation between
components of a TMVND. The DA algorithm is applied to a linear regression model with constrained parameters and is illustrated
with a published data set. Numerical comparisons show that the proposed DA algorithm and IBF sampler are more efficient than
the Gibbs sampler and the accept-reject algorithm. 相似文献
264.
探地雷达是利用超高频脉冲电磁波探测地下介质分布的一种浅层地球物理勘探方法,探地雷达超高频、宽频带脉冲电磁波在地下有耗介质中的衰减特性是一个十分复杂的过程。本文从电磁波传播的麦克斯韦方程出发,较为系统地研究和分析了雷达脉冲电磁波在有耗介质中传播的衰减特性,对研究雷达脉冲电磁波在地下有耗介质中的传播机制有指导意义。 相似文献
265.
266.
文章采用共耦合谐振单元结构设计制作了一款高温超导五工器, 五工器五个信道的工作频率分别为807.5 MHz、810.5 MHz、813.5 MHz、816 .5 MHz、819 .5 MHz, 每信道通带宽度均为1 MHz. 滤波器电路用镝钡铜氧(DyBCO) 双面超导薄膜制作, 衬底为3 英寸0.5 mm 厚度的氧化镁( MgO) 基片. 文章给出了高温超导五工器的等效电路、 理论曲线、 耦合参数、Sonnet 软件全波电磁场模拟仿真和实际测试曲线, 取得较为理想的结果 相似文献