Estimation of Distribution Functions Using Data from Different Environments

Suppose that when a unit operatesin a certain environment, its lifetime has distribution G,and when the unit operates in another environment, its lifetimehas a different distribution, say F. Moreover, supposethe unit is operated for a certain period of time in the firstenvironment and is then transferred to the second environment.Thus we observe a censored lifetime in the first environmentand a failure time of a ``used' unit in the second environment.We propose an EM algorithm approach for obtaining a self-consistentestimator of F. Moreover, suppose using observations from both environments.The case where failure times are subject to right censoring isconsidered as well. We also establish the maximum likelihoodestimator of F. Moreover, suppose when the unit is repairable. Applicationand simulation studies are presented to illustrate the methodsderived.     

On cramér-von mises tests of goodness of fit with censored data

The paper considers the goodness of fit tests with right censored data or doubly censored data. The Fredholm Integral Equation (FIE) method proposed by Ren (1993) is implemented in the simulation studies to estimate the null distribution of the Cramér-von Mises test statistics and the asymptotic covariance function of the self-consistent estimator for the lifetime distribution with right censored data or doubly censored data. We show that for fixed alternatives, the bootstrap method does not estimate the null distribution consistently for doubly censored data. For the right censored case, a comparison between the performance of FIE and the η out of η bootstrap shows that FIE gives better estimation for the null distribution. The application of FIE to a set of right censored Channing House data and to a set of doubly censored breast cancer data is presented.     

The random partition masking model for interval-censored and masked competing risks data

We study the nonparametric maximum likelihood estimate (NPMLE) of the cdf or sub-distribution functions of the failure time for the failure causes in a series system. The study is motivated by a cancer research data (from the Memorial Sloan-Kettering Cancer Center) with interval-censored time and masked failure cause. The NPMLE based on this data set suggests that the existing masking models are not appropriate. We propose a new model called the random partition masking model, which does not rely on the commonly used symmetry assumption (namely, given the failure cause, the probability of observing the masked failure causes is independent of the failure time; see Flehinger et al. Inference about defects in the presence of masking, Technometrics 38 (1996), pp. 247–255). The RPM model is easier to implement in simulation studies than the existing models. We discuss the algorithms for computing the NPMLE and study its asymptotic properties. Our simulation and data analysis indicate that the NPMLE is feasible for a moderate sample size.     

内开槽结构高次谐波回旋管自洽非线性研究

采用自洽非线性理论对内开糟结构高次谐波回旋管进行数值模拟，发现内开槽结构有利于实现高次谐波互作用，其效率高达３０％以上。     

锥形场发射体尖端温度的分析

从热传导方程出发,考虑Nottingham效应和焦耳热情况下,采用自洽求解了圆锥形场发射体的尖端表面温度;定量讨论了温度与给定的圆锥形场发射体的结构参量与物理参量的关系。结果表明Nottingham效应、热导率和锥体横截面积的大小对尖端表面温度起决定作用,由Nottingham效应和焦耳热产生的温度在通常发射电流情况下,并不会达到钼的熔点温度而引起微尖锥发射体的失效。     

矩形波导FEL的三维非线性理论

研究了带有双绕螺旋 Wiggler 场和轴向导引磁场的矩形波导中,轴对称电子注自由电子激光放大器的三维非线性理论。波、电子注和 Wiggler 场在三维空间中的变化均考虑在内,忽略了电子注的自身场和空间电荷效应;导出了一组完全自洽的互作用非线性微分方程。数值计算表明:采用空心电子注与TE_(11)波作用可以得到比圆波导结构高的增益和电子能量转换效率。     

Non-parametric Hypothesis Testing and Confidence Intervals with Doubly Censored Data

The non-parametric maximum likelihood estimator (NPMLE) of the distribution function with doubly censored data can be computed using the self-consistent algorithm (Turnbull, 1974). We extend the self-consistent algorithm to include a constraint on the NPMLE. We then show how to construct confidence intervals and test hypotheses based on the NPMLE via the empirical likelihood ratio. Finally, we present some numerical comparisons of the performance of the above method with another method that makes use of the influence functions.     

On Consistency of the Self-Consistent Estimator of Survival Functions with Interval-Censored Data

The self-consistent estimator is commonly used for estimating a survival function with interval-censored data. Recent studies on interval censoring have focused on case 2 interval censoring, which does not involve exact observations, and double censoring, which involves only exact, right-censored or left-censored observations. In this paper, we consider an interval censoring scheme that involves exact, left-censored, right-censored and strictly interval-censored observations. Under this censoring scheme, we prove that the self-consistent estimator is strongly consistent under certain regularity conditions.     

介质切伦可夫脉塞的线性理论

利用自洽线性场理论，在有无纵向引导磁场的情况下，分别分析了电子的三维扰动速度和三维扰动电流密度对介质切伦可夫脉塞注波互作用的影响，导出了其色散方程和注波工作用的同步条件，所得方程清楚地表明，其互作用不稳定性是由介质简慢波波导中的ＴＭ模与电子注模通过电子注耦合所致，并求得了电子注引起的频偏和波的增长率。