检索结果-南通市图书馆

Applications of survival functions to continuous semi-Markov processes for measuring reliability of power transformers

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2017年第6期5卷 959-969页

作者： Yifei WANG Mohammad SHAHIDEHPOUR Chuangxin GUO School of Automation Guangdong University of TechnologyGuangzhou 510006China Galvin Center for Electricity Innovation Illinois Institute of TechnologyChicagoIL 60616USA College of Electrical Engineering Zhejiang UniversityHangzhou 310058China

The reliability of power transformers is subject to service age and health *** paper proposes a practical model for the evaluation of two reliability indices:survival function(SF)and mean residual life(MRL).In the proposed model,the periodical modeling of power transformers are considered for collecting the information on health *** corresponding health condition is assumed to follow a continuous semi-Markov process for representing a state *** proportional hazard model(PHM)is introduced to incorporate service age and health condition into hazard *** addition,the proposed model derives the analytical formulas for and offers the analytical evaluation of SF and *** and MRL are calculated for new components and old components,*** both cases,the proposed model offers rational results which are compared with those obtained from comparative *** results obtained by the contrast of the proposed analytical method and the Monte Carlo *** impact of differentmodel parameters and the coefficient of variation(CV)on reliability indices are discussed in the case studies.

关键词： Power system reliability Transformers Proportional hazard model survival function Mean residual life Semi-Markov process

基于双边删失数据生存函数的非参数Bayes估计

在线全文

学校读者我要写书评

暂无评论

东南大学学报(自然科学版) 1990年第3期20卷 114-119页

作者：陈平东南大学数学力学系

关于参数估计问题,Bayes方法已经得到了广泛的研究,而在非参数估计问题中Bayes方法仅仅从1973年才开始受到注意,Ferguson将Dirichlet过程先验应用于多种函数及统计量的非参数Bayes估计。在此基础上,针对右删失数据,Susarla和Van Ryzin,T... 详细信息

关于参数估计问题,Bayes方法已经得到了广泛的研究,而在非参数估计问题中Bayes方法仅仅从1973年才开始受到注意,Ferguson将Dirichlet过程先验应用于多种函数及统计量的非参数Bayes估计。在此基础上,针对右删失数据,Susarla和Van Ryzin,Tsai研究了生存函数的非参数Bayes估计问题。本文进一步讨论了在双边删失场合下生存函数的非参数Bayes估计及相应的大样本性质。

关键词： non-parametric statistics/doubly censored survival function nonparametric estimation strong consistency

Statistical inference for right-censored data with nonignorable missing censoring indicators

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China Mathematics 2013年第6期56卷 1263-1278页

作者： SUN ZhiHua XIE TianFa LIANG Hua School of Mathematical Sciences University of Chinese Academy of Sciences College of Applied Sciences Beijing University of Technology Department of Biostatistics and Computational Biology University of RochesterRochester NY 14642 USA

We consider the statistical inference for right-censored data when censoring indicators are missing but nonignorable, and propose an adjusted imputation product-limit estimator. The proposed estimator is shown to be consistent and converges to a Gaussian process. Furthermore, we develop an empirical processbased testing method to check the MAR (missing at random) mechanism, and establish asymptotic properties for the proposed test statistic. To determine the critical value of the test, a consistent model-based bootstrap method is suggested. We conduct simulation studies to evaluate the numerical performance of the proposed method and compare it with existing methods. We also analyze a real data set from a breast cancer study for an illustration.

关键词： MAR mechanism testing nonignorable missing censoring indicators survival function quasi-likelihood

STATISTICAL INFERENCE OF WEIBULL DISTRIBUTION FOR TAMPERED FAILURE RATE MODEL IN PROGRESSIVE STRESS ACCELERATED LIFE TESTING

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2004年第2期17卷 237-243页

作者： WANGRonghua FEIHeliang CollegeofMathematicalSciences ShanghaiNormalUniversityShanghai200234China

In this note,the tampered failure rate model is generalized from the step-stress accelerated life testing setting to the progressive stress accelerated life testing for the first *** the parametric setting where the scale parameter satisfying the equation of the inverse power law is Weibull,maximum likelihood estimation is investigated.

关键词： tampered failure rate model weibull distribution survival function progressive stress accelerated life test maximum likelihood estimation inverse power law

Log-Rank Test for Comparing survival Curves of Neonatal Mortality Characteristic Groups in River Nile State-Sudan

在线全文

学校读者我要写书评

暂无评论

Open Journal of Statistics 2022年第4期12卷 532-547页

作者： Abdellateef Khalifa Hamid Ali Amin Ibrahim Adam Mohammed Department of Statistics Faculty of Mathematical Science Al-Fashir University Al Fashir Sudan Department of Statistics Faculty of Economic and Social Studies Omdurman Islamic University Omdurman Sudan

This paper concerns the Log-rank test for comparing survival curves of neonatal mortality characteristic groups in River Nile State, Sudan. In this paper, log-rank test is used to compare two or more survival curves for the characteristics of newborn associated with newborn death after using Kaplan-Meier methods to estimate and graph survival curves for the variable of interest as (sex of newborn, weight of newborn, gestational age, mode of delivery and resident type), at the hospital of River Nile state—Sudan, with a sample size 700 of newborn in which the admission to the Neonatal Intensive Care Unit (NICU) of those hospitals during the period 2018-2020. In term of risk of death for newborn we found that 25% of sample study for newborns who were born in River Nile State-Sudan died. In addition, we conclude that after the log-rank statistics and Kaplan-Meier methods were applied, gender does not affect the newborn’s risk of survival, while the risk of survival increases when the birth weight is greater than 4.35 kg and the gestational age is greater than 42 weeks. There is no difference in the probability of survival for newborns whether the delivery is normal or cesarean. However, newborns are significantly more likely to survive in urban areas than in rural areas.

关键词： Neonatal Mortality Log-Rank Test survival function Kaplan-Meier Method

The NBEE and NWEE classes of lifetime distributions and their properties

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2012年第2期28卷 251-255页

作者：王冠军东南大学数学系南京211189

A class of lifetime distributions, new better than equilibrium in expectation （NBEE）, and its dual, new worse than equilibrium in expectation （NWEE）, are studied based on the comparison of the expectations of lifetime X and its equilibrium Xo. The relationships of the NBEE （NWEE） and other lifetime distribution classes are discussed. It is proved that the NBEE is very large, and increasing failure rate （IFR）, new better than used （NBU） and the L class are its subclasses. The closure properties under two kinds of reliability operations, namely, convolution and mixture, are investigated. Furthermore, a Poisson shock model and a special cumulative model are also studied, in which the necessary and sufficient conditions for the NBEE （NWEE） lifetime distribution of the systems are established. In the homogenous Poisson shock model, the system lifetime belongs to NBEE（NWEE） if and only if the corresponding discrete failure distribution belongs to the discrete NBEE（NWEE）. While in the cumulative model, the system has an NBEE lifetime if and only if the stochastic threshold of accumulated damage is NBEE.

关键词： lifetime distribution survival function closure property new better than equilibrium in expectation (NBEE) equilibrium distribution shock model cumulative damage model

The Cox Proportional Hazard Regression Model Vis-à-Vis ITN-Factor Impact on Mortality Due to Malaria

在线全文

学校读者我要写书评

暂无评论

Open Journal of Statistics 2021年第6期11卷 931-962页

作者： Anthony Joe Turkson John Awuah Addor Francis Ayiah-Mensah Department of Mathematics Statistics and Actuarial Science Takoradi Technical University Takoradi Ghana

This study has provided a starting point for defining and working with Cox models in respect of multivariate modeling. In medical researches, there may be situations, where several risk factors potentially affect patient prognosis, howbeit, only one or two might predict patient’s predicament. In seeking to find out which of the risk factors contribute the most to the survival times of patients, there was the need for researchers to adjust the covariates to realize their impact on survival times of patients. Aside the multivariate nature of the covariates, some covariates might be categorical while others might be quantitative. Again, there might be cases where researchers need a model that has the capability of extending survival analysis methods to assessing simultaneously the effect of several risk factors on survival times. This study unveiled the Cox model as a robust technique which could accomplish the aforementioned cases. An investigation meant to evaluate the ITN-factor vis-à-vis its contribution towards death due to Malaria was exemplified with the Cox model. Data were taken from hospitals in Ghana. In doing so, we assessed hospital in-patients who reported cases of malaria (origin state) to time until death or censoring (destination stage) as a result of predictive factors (exposure to the malaria parasites) and some socioeconomic variables. We purposefully used Cox models to quantify the effect of the ITN-factor in the presence of other risk factors to obtain some measures of effect that could describe the relationship between the exposure variable and time until death adjusting for other variables. PH assumption holds for all three covariate

关键词： Baseline Hazard Cox Model Hazard function Hazard Ratio survival function

Cox Proportional Hazard Model for survival Time of Neonatal Mortality in Neonatal Intensive Care Unit of Hospitals in River Nile State-Sudan

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Statistics 2022年第5期12卷 634-657页

作者： Abdellateef Khalifa Hamid Ali Amin Ibrahim Adam Mohammed Faculty of Mathematical Science El-Fashir University El-Fashir Sudan Faculty of Economics & Political Sciences Omdurman Islamic University Omdurman Sudan

Cox Proportional Hazard model is a popular statistical technique for exploring the relationship between the survival time of neonates and several explanatory variables. It provides an estimate of the study variables’ effect on survival after adjustment for other explanatory variables, and allows us to estimate the hazard (or risk) of death of newborn in NICU of hospitals in River Nile State-Sudan for the period (2018-2020). Study Data represented (neonate gender, mode of delivery, birth type, neonate weight, resident type, gestational age, and survival time). Kaplan-Meier method is used to estimate survival and hazard function for survival times of newborns that have not completed their first month. Of 700 neonates in the study area, 25% of them died during 2018-2020. Variables of interest that had a significant effect on neonatal death by Cox Proportional Hazard Model analysis were neonate weight, resident type, and gestational age. In Cox Proportional Hazard Model analysis all the variables of interest had an effect on neonatal death, but the variables with a significant effect included, weight of neonate, resident type and gestational age.

关键词： Neonatal Mortality Cox Proportional Hazard Model survival function Haz-ard function Kaplan-Meier Method

Asymptotic Normality of the Empirical Distribution under Negatively Associated Sequences and its Applications

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Mathematical Research and Exposition 2006年第3期26卷 457-464页

作者：李永明杨善朝上饶师范学院数学系江西上饶334001 广西师范大学数学系广西桂林541004

By the well-known large and small blocks parting method for dependent situations, we establish the asymptotic normality of the Empirical Distribution function under Negatively Associated Sequences. As its application in reliablity problems, a natural estimate Fn（x） for the survival function F（x） = P（X 〉 x） is proposed, and the asymptotic normality of n^1/2 [Fn（x） - F（x）] is established.

关键词： NA sequences empirical distribution survival function asymptotic normality.