Lognormal Approximations of Fault Tree Uncertainty Distributions

Fault trees are used in reliability modeling to create logical models of fault combinations that can lead to undesirable events. The output of a fault tree analysis (the top event probability) is expressed in terms of the failure probabilities of basic events that are input to the model. Typically, the basic event probabilities are not known exactly, but are modeled as probability distributions: therefore, the top event probability is also represented as an uncertainty distribution. Monte Carlo methods are generally used for evaluating the uncertainty distribution, but such calculations are computationally intensive and do not readily reveal the dominant contributors to the uncertainty. In this article, a closed‐form approximation for the fault tree top event uncertainty distribution is developed, which is applicable when the uncertainties in the basic events of the model are lognormally distributed. The results of the approximate method are compared with results from two sampling‐based methods: namely, the Monte Carlo method and the Wilks method based on order statistics. It is shown that the closed‐form expression can provide a reasonable approximation to results obtained by Monte Carlo sampling, without incurring the computational expense. The Wilks method is found to be a useful means of providing an upper bound for the percentiles of the uncertainty distribution while being computationally inexpensive compared with full Monte Carlo sampling. The lognormal approximation method and Wilks’s method appear attractive, practical alternatives for the evaluation of uncertainty in the output of fault trees and similar multilinear models.     

Moderate Deviations for Bayes Posteriors

Let ( X_k ) k be a sequence of i.i.d. random variables taking values in a set , and consider the problem of estimating the law of X₁ in a Bayesian framework. We prove, under mild conditions on the prior, that the sequence of posterior distributions satisfies a moderate deviation principle.     

英汉广告常用辞格及其功能

广告修辞新奇巧妙 ,独出心裁 ,凝聚了广告作者的丰富而非凡的想像力 ;广告语篇中恰当而巧妙地运用修辞格不但使广告语言生动活泼 ,言简意赅 ,或节奏感强 ,很有力量 ,而且深刻地描绘或强调广告商品或服务的特征、特性与功能 ,有助于创造其美好形象 ,促进广告走向成功。     

Statistical and Combinatorial Aspects of Comparative Genomics*

Abstract. This document presents a survey of the statistical and combinatorial aspects of four areas of comparative genomics: gene order based measures of evolutionary distances between species, construction of phylogenetic trees, detection of horizontal transfer of genes, and detection of ancient whole genome duplications.     

自我形象的映照——《镜花缘》中的"他者"形象透视

比较文学形象学意义上的形象指的是文学中所塑造的异国异族形象。这种异国异族形象是通过他本人所属社会或群体的想象描绘出来的。从比较文学形象学的视角对《镜花缘》中乌托邦类型的异国形象加以剖析,认为作者对海外诸国的认识只是当时社会集体想象的产物,在本质上是当时中国自我形象的映照。     

论张承志小说的意象建构与审美品格

张承志的小说具有强烈的倾诉性,小说文体的诗化色彩十分突出,小说作品的意象较为丰富。张承志常常以丰富的意象建构使作品充盈着浓郁的诗意和抒情性,同时也体现了其小说独特的审美品格。     

运用信息技术培养学生形象思维能力

从把握时机,掌握力度等方面提出遵循以学生为主体原则,符合学生认知过程的需要,同时保证语文教学按自身学科性质完成教学目标,在有利于学生形象思维发展的前提下,把握运用信息技术的最佳时机达到教学最佳效果.     

融贯中西与古今文化诗学的意象体系——鲁迅诗歌意象的类型分析

意象是诗歌的生命。鲁迅诗歌使用了大量的审美意象,融贯中西与古今文化诗学,形成了自己独立的体系。鲁迅诗歌意象为六种类型,以三组对立的形态出现,即:历史性意象/现实性意象;东方意象/西方意象;社会性意象/人化自然的意象。这些意象的使用,昭示了鲁迅忧国忧民的伟大人格,并形成鲁迅自己独特的诗风。同时,他的诗歌与我国传统诗歌相比较,具有鲜明的现代性,与后起的新诗相比,又具有深厚的传统文化诗学的底蕴。     

中国文学中叛逆女性形象的演进

以古代文学的典型判逆女性形象为依据,以社会发展、文化演进和妇女解放为历史背景,分析和论述了中国文学中女性形象之女性角色、女性精神追求的变化及文化意义,女性自我意识的逐渐觉醒和妇女解放的发展趋势的演进过程.