Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomne...Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomness of failure threshold.Firstly,a random-coefficient regression(RCR)model is used to model the degradation process of aeroengines.Then,the RUL distribution based on fixed failure threshold is derived.The prior parameters of the degradation model are calculated by a two-step maximum likelihood estimation(MLE)method and the random coefficient is updated in real time under the Bayesian framework.The failure threshold in this paper is defined by the actual degradation process of aeroengines.After that,a expectation maximization(EM)algorithm is proposed to estimate the underlying failure threshold of aeroengines.In addition,the conditional probability is used to satisfy the limitation of failure threshold.Then,based on above results,an analytical expression of RUL distribution of aero-engines based on the RCR model considering random failure threshold(RFT)is derived in a closed-form.Finally,a case study of turbofan engine is used to demonstrate the effectiveness and superiority of the RUL prediction method and the parameters estimation method of failure threshold proposed.展开更多
目的探讨核黄素转运蛋白（RFT2）和Ki-67在食管鳞状细胞癌（ESCC）中的表达及临床意义。方法采用免疫组化SP法检测87例ESCC组织和48例食管正常黏膜组织中RFT2和Ki-67的表达,分析RFT2的表达与临床病理参数之间的关系以及与Ki-67表达的相...目的探讨核黄素转运蛋白（RFT2）和Ki-67在食管鳞状细胞癌（ESCC）中的表达及临床意义。方法采用免疫组化SP法检测87例ESCC组织和48例食管正常黏膜组织中RFT2和Ki-67的表达,分析RFT2的表达与临床病理参数之间的关系以及与Ki-67表达的相关性。结果 （1）RFT2在ESCC组织及食管正常黏膜组织中的阳性表达率分别为74.7%（65/87）及16.7%（8/48）,两者差异有统计学意义（P〈0.05）;（2）临床病理参数分析发现,RFT2的表达与临床分期、淋巴结转移和肿瘤最长径密切相关,T_3~T_4期的ESCC组织中RFT2阳性表达率96.4%（54/56）显著高于T_1~T_2期的35.5%（11/31）,差异有统计学意义（P〈0.05）;有淋巴结转移的ESCC组织中RFT2阳性表达率96.1%（49/51）显著高于无淋巴结转移的44.4%（16/36）,差异有统计学意义（P〈0.05）;肿瘤最长径≥3 cm ESCC组织中RFT2阳性表达率90.0%（45/50）显著高于最长径〈3 cm的54.1%（20/37）,差异有统计学意义（P〈0.05）;（3）ESCC组织中RFT2与Ki-67的表达呈显著正相关（r=0.336,P〈0.05）。结论食管鳞癌组织中RFT2的高表达与临床分期、淋巴结转移、肿瘤最长径及肿瘤细胞增殖密切相关,提示RFT2可能成为食管鳞癌早期诊断和判断预后的辅助指标。展开更多
基金supported by the National Natural Science Foundation of China(61703410,61873175,62073336,61873273,61773386,61922-089)the Basic Research Plan of Shaanxi Natural Science Foundation of China(2022JM-376).
文摘Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomness of failure threshold.Firstly,a random-coefficient regression(RCR)model is used to model the degradation process of aeroengines.Then,the RUL distribution based on fixed failure threshold is derived.The prior parameters of the degradation model are calculated by a two-step maximum likelihood estimation(MLE)method and the random coefficient is updated in real time under the Bayesian framework.The failure threshold in this paper is defined by the actual degradation process of aeroengines.After that,a expectation maximization(EM)algorithm is proposed to estimate the underlying failure threshold of aeroengines.In addition,the conditional probability is used to satisfy the limitation of failure threshold.Then,based on above results,an analytical expression of RUL distribution of aero-engines based on the RCR model considering random failure threshold(RFT)is derived in a closed-form.Finally,a case study of turbofan engine is used to demonstrate the effectiveness and superiority of the RUL prediction method and the parameters estimation method of failure threshold proposed.
文摘目的探讨核黄素转运蛋白（RFT2）和Ki-67在食管鳞状细胞癌（ESCC）中的表达及临床意义。方法采用免疫组化SP法检测87例ESCC组织和48例食管正常黏膜组织中RFT2和Ki-67的表达,分析RFT2的表达与临床病理参数之间的关系以及与Ki-67表达的相关性。结果 （1）RFT2在ESCC组织及食管正常黏膜组织中的阳性表达率分别为74.7%（65/87）及16.7%（8/48）,两者差异有统计学意义（P〈0.05）;（2）临床病理参数分析发现,RFT2的表达与临床分期、淋巴结转移和肿瘤最长径密切相关,T_3~T_4期的ESCC组织中RFT2阳性表达率96.4%（54/56）显著高于T_1~T_2期的35.5%（11/31）,差异有统计学意义（P〈0.05）;有淋巴结转移的ESCC组织中RFT2阳性表达率96.1%（49/51）显著高于无淋巴结转移的44.4%（16/36）,差异有统计学意义（P〈0.05）;肿瘤最长径≥3 cm ESCC组织中RFT2阳性表达率90.0%（45/50）显著高于最长径〈3 cm的54.1%（20/37）,差异有统计学意义（P〈0.05）;（3）ESCC组织中RFT2与Ki-67的表达呈显著正相关（r=0.336,P〈0.05）。结论食管鳞癌组织中RFT2的高表达与临床分期、淋巴结转移、肿瘤最长径及肿瘤细胞增殖密切相关,提示RFT2可能成为食管鳞癌早期诊断和判断预后的辅助指标。
