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Health evaluation method for degrading systems subject to dependent competing risks

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Journal of Systems Engineering and Electronics 2018年第2期29卷 436-444页

作者： ZHAO Shuai MAKIS Viliam CHEN Shaowei LI Yong School of Electronics and Information Northwestern Polytechnical University Department of Mechanical and Industrial Engineering University of Toronto

This paper proposes a health evaluation method for degrading systems subject to competing risks of dependent soft and hard failures. To characterize the time-varying degradation rate, the degradation process is determined by a non-stationary Gamma process and the soft failure is encountered when it exceeds a predefined critical level. For the hard failure, a Cox’s proportional hazard model is applied to describe the hazard rate of the time to system failure. The dependent relationship is modeled by incorporating the degradation process as a time-varying covariate into the Cox’s proportional hazard model. To facilitate the health characteristics evaluation, a discretization technique is applied both to the degradation process and the monitoring *** health characteristics can be obtained in the explicit form using the transition probability matrix, which is computationally attractive for practical applications. Finally, a numerical analysis is carried out to show the effectiveness and the performance of the proposed health evaluation method.

关键词： competing risk conditional mean residual life health evaluation non-stationary Gamma process proportional hazards model

Regression Analysis of Right-censored Failure Time Data with Missing Censoring Indicators

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Acta Mathematicae Applicatae Sinica 2009年第3期25卷 415-426页

作者： Ping Chen Ren He Jun-shan Shen Jian-guo Sun Department of Statistics University of Missouri 146 Middlebush Hall Columbia MO 65211 U.S.A. School of Mathematical Sciences Peking University Beijing 100871 China

This paper discusses regression analysis of right-censored failure time data when censoring indicators are missing for some subjects. Several methods have been developed for the analysis under different situations and especially, Goetghebeur and Ryan considered the situation where both the failure time and the censoring time follow the proportional hazards models marginally and developed an estimating equation approach. One limitation of their approach is that the two baseline hazard functions were assumed to be proportional to each other. We consider the same problem and present an efficient estimation procedure for regression parameters that does not require the proportionality assumption. An EM algorithm is developed and the method is evaluated by a simulation study, which indicates that the proposed methodology performs well for practical situations. An illustrative example is provided.

关键词： Efficient estimation em algorithm incomplete data missing at random proportional hazards model

Level of education and mortality after radical prostatectomy

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Asian Journal of Andrology 2017年第2期19卷 173-177页

作者： Michael Froehner Rainer Koch Stefan Propping Dorothea Liebeheim Matthias Hfibler Gustavo B Baretton Oliver W Hakenberg Manfred P Wirth Department of Urology University Hospital 'Carl Gustav Carus' Technische Universit~t Dresden Fetscherstrasse 74 D-01307 Dresden Germany Department of Medical Statistics and Biometry University Hospital 'Carl Gustav Carus' Technische Universitat Dresden Fetscherstrasse 74 D-01307 Dresden Germany Department of Anesthesiology University Hospital 'Carl Gustav Carus' Technische Universitat Dresden Fetscherstrasse 74 D-01307 Dresden Germany Department of Pathology University Hospital 'Carl Gustav Carus' Technische Universitat Dresden Fetscherstrasse 74 D-01307 Dresden Germany Department of Urology University of Rostock Ernst-Heydemann-Strasse 6 D-18055 Rostock Germany

Estimating the risk of competing mortality is of importance in men with early prostate cancer to choose the most appropriate way of management and to avoid over- or under-treatment. In this study, we investigated the impact of the level of education in this context. The study sample consisted of 2630 patients with complete data on level of education （college, university degree, master craftsmen, comparable profession, or others）, histopathological tumor stage （organ confined or extracapsular）, lymph node status （negative or positive）, and prostatectomy specimen Gleason score （〈7, 7, or 8-10） who underwent radical prostatectomy between 1992 and 2007. Overall, prostate cancer-specific, competing, and second cancer-related mortalities were study endpoints. Cox proportional hazard models for competing risks were used to study combined effects of the variables on these endpoints. A higher level of education was independently associated with decreased overall mortality after radical prostatectomy （hazard ratio [HR]： 0.75, 95% confidence interval [95% CI]： 0.62-0.91, P = 0.0037）. The mortality difference was attributable to decreased second cancer mortality （HR： 0.59, 95% Ch 0.40-0.85, P = 0.0052） and noncancer mortality （HR： 0.73, 95% Ch 0.55-0.98, P = 0.0345） but not to differences in prostate cancer-specific mortality （HR： 1.16, 95% Ch 0.79-1.69, P = 0.4536 in the full model）. In conclusion, the level of education might serve as an independent prognostic parameter supplementary to age, comorbidity, and smoking status to estimate the risk of competing mortality and to choose optimal treatment for men with early prostate cancer who are candidates for radical prostatectomy.

关键词： comorbidity competing risk analysis level of education life expectancy mortality proportional hazards model prostate cancer radical prostatectomy smoking socioeconomic status

ESTIMATING HAZARD RATIOS IN NESTED CASE-CONTROL STUDIES BY MANTEL-HAENSZEL METHOD

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Acta Mathematicae Applicatae Sinica 2001年第4期17卷 457-468页

作者：张忠占 Institute of Statistics Beijing Polytechnic University Beijing China

In this article, a class of Mantel-Haenszel type estimators of hazard ratios in proportional hazards model is presented for simple nested case-control study. The estimators have the form of the Mantel-Haenszel estimator of odds ratios, and it is shown that the estimators are dually cousistent, and asymptotically normal. Dually consistently estimated covariance matrices of the proposed estimators are also developed. An example is given to illustrate the estimators.

关键词： Dually consistent estimator estimating equation partial likelihood estimator proportional hazards model

Prediction Approach to Life on Wing for Civil Aeroengine

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Journal of Southwest Jiaotong University(English Edition) 2008年第2期16卷 170-175页

作者：戎翔左洪福张海军 College of Civil Aviation Nanjing University of Aeronautics and Astronautics

To reduce engine maintenance cost and support safe operation, a prediction method of engine life on wing was proposed. This method is a kind of regression model which is a function of the condition monitoring and failure data. Key causes of engine removals were analyzed, and the life limit due to performance deterioration was predicted by proportional hazards model. Then the scheduled removal causes were considered as constraints of engine life to predicte the finai life on wing. Application of the proposed prediction method to the case of CF6-80C2A5 engine fleet in an airline proved its effectiveness.

关键词： Civil aeroengine Condition based maintenance Life on wing Scheduled and unscheduled removal causes proportional hazards model