Nonparametric estimation of the shape function in a Gamma process for degradation data

The author considers estimation under a Gamma process model for degradation data. The setting for degradation data is one in which n independent units, each with a Gamma process with a common shape function and scale parameter, are observed at several possibly different times. Covariates can be incorporated into the model by taking the scale parameter as a function of the covariates. The author proposes using the maximum pseudo‐likelihood method to estimate the unknown parameters. The method requires usage of the Pool Adjacent Violators Algorithm. Asymptotic properties, including consistency, convergence rate and asymptotic distribution, are established. Simulation studies are conducted to validate the method and its application is illustrated by using bridge beams data and carbon‐film resistors data. The Canadian Journal of Statistics 37: 102‐118; 2009 © 2009 Statistical Society of Canada     

超声波技术与方法在有机磷农药废水降解中的应用研究

农药水污染在中国是一个非常严重的问题,污染水的排放控制是遏制水污染扩大的关键。文章首先讨论了超声降解有机物质的基本物理机理,同时对超声技术在有机农药的降解研究现状进行了详细的综述,最后结合目前国内该技术的发展状况对超声技术在有机农药降解领域的发展前景进行了展望。     

堕落的天使——从精神分析学角度看葛薇龙的堕落

《沉香屑.第一炉香》是张爱玲一部较负盛名的小说,其主人公葛薇龙对于其堕落是具有着清醒意识的,但其堕落的原因又是复杂的,本文主要从弗洛伊德精神分析学中人格的内在结构的三个层次,即以色相为本钱的本我阶段,理想的闺秀之路的超我阶段,理想与诱惑博弈的自我阶段来具体分析其复杂的堕落过程。     

Designing a Degradation Test with a Two-Parameter Exponential Lifetime Distribution

Degradation testing (DT) is a useful approach to assessing the reliability of highly reliable products which are not likely to fail under the traditional life tests or accelerated life tests. There have been a great number of excellent studies investigating the estimation of the failure time distribution and the optimal design (e.g., the optimal setting of the inspection frequency, the number of measurement, and the termination time) for DTs. However, the lifetime distributions considered in the studies mentioned above are all those without failure-free life. Here, failure-free life is characterized by a threshold parameter below which no failure is possible. The main purpose of this article is to deal with the optimal design of a DT with a two-parameter exponential lifetime distribution. More specifically, with respect to a DT where a linearized degradation model is used to model the degradation process and the lifetime is assumed to follow a two-parameter exponential distribution, under the constraint that the total experimental cost does not exceed a predetermined budget, the optimal combination of the inspection frequency, the sample size, and the termination time are determined by minimizing the mean squared error of the estimated 100p-th percentile of the lifetime distribution of the product. An example is provided to illustrate the proposed method and the corresponding sensitivity analysis is also discussed.     

论郁达夫小说《沉沦》中的"他"

在郁达夫小说《沉沦》中,"他"展示了小说核心内涵,"他"最令人关注,也最让人争议。"他"性格诡异,忧郁和孤愤是"他"性格中的两个基本要素。"他"的性格生成严重的"自我拒绝"和"性格障碍"。"他"性格的稳定性和差异性、复杂性和主导性、表层性和深层性,呈现出"他"性格丰富多样性,展现了"他"性格的魅力。《沉沦》拓展了中国现代小说表现领域,首开"另类小说"之风,影响和意义深远。     

Mis-specification Analyses of Nonlinear Wiener Process-based Degradation Models

For some highly reliable products, degradation data have been studied quite extensively to evaluate their reliability characteristics. However, the accuracy of evaluation results depends strongly on the suitability of the proposed degradation model for capturing the degradation over time. If the degradation model is mis-specified, it may result in inaccurate results. In this work, we focus on the issue of model mis-specification between nonlinear Wiener process-based degradation models in which both the product-to-product variability and the temporal uncertainty of the degradation can be considered simultaneously with the nonlinearity in degradation paths. Specifically, a generalized Wiener process-based degradation model is wrongly fitted by its two limiting cases. The effects of model mis-specification in such situations on the MTTF (mean-time-to-failure) of the product are measured with the relative bias and the relative variability. Results from a numerical example concerning fatigue cracks show that the effect of mis-specification is serious under some parameter settings, i.e., the relative bias departs from 0, and the relative variability significantly departs from 1, if the generalized Wiener degradation process is wrongly assumed to be its limiting cases.     

论《沉沦》的创作源泉--兼论郁达夫对佐藤春夫文学思想的接受与修正

郁达夫<沉沦>的创作源泉是:(1)日本浪漫主义作家佐藤春夫对郁达夫早期文学观的形成产生了巨大影响;(2)佐藤春夫的<田园的忧郁>对郁达夫的<沉沦>在文学创作方法上产生了影响;(3)郁达夫的人生经历与留日生活为他的创作提供了素材;(4)郁达夫在精神与物质上的失衡使他产生了创作上的冲动.     

A Bayesian approach for non-homogeneous gamma degradation processes

A Bayesian approach based on the Markov Chain Monte Carlo technique is proposed for the non-homogeneous gamma process with power-law shape function. Vague and informative priors, formalized on some quantities having a “physical” meaning, are provided. Point and interval estimation of process parameters and some functions thereof are developed, as well as prediction on some observable quantities that are useful in defining the maintenance strategy is proposed. Some useful approximations are derived for the conditional and unconditional mean and median of the residual life to reduce computational time. Finally, the proposed approach is applied to a real dataset.     

Statistical Analysis of General Degradation Path Model and Failure Time Data with Multiple Failure Modes

ABSTRACT

This article considers degradation and failure time models with multiple failure modes which used to study the problem of longevity and aging in survival analysis and reliability. Degradation process is modeled using general nonparametric, nonlinear path models. Semi-parametric models for the intensities of the traumatic failures are used supposing that these intensities depend on degradation level. Semi-parametric estimators of various reliability characteristics are proposed and asymptotic properties of the estimators are obtained. The theoretical results are illustrated using simulated data.     

Degradation modeling based on gamma process models with random effects

The random effects in a gamma process are introduced in terms of its scale parameter. However, the scale parameter affects both its mean and variance. Hence, the variation of the degradation rates and the within degradation increments are expected to be large. For some products, the random effects affect just the rate or just the volatility of the process. Thus, two modifications of the parameters' structure of the gamma process are proposed. One implies that the random effects affect just the volatility and the second just the rate. A Bayesian estimation approach is provided and implemented in two case studies.