Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of th...Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of the probabilistic damage tolerance assessment is provided.Five core parts of the probabilistic damage tolerance method are introduced separately,including the anomaly distribution,stress processing and zone definition,fatigue and fracture calculation method,probability of failure(POF)calculation method,and the combination with residual stress induced by the manufacturing process.The above currently-available risk assessment methods provide practical tools for failure risk predictions and are applied by the airworthiness regulations.However,new problems are exposed with the development of the aeroengines.The time-consuming anomaly distribution derivation process restricts the development of the anomaly distribution,especially for the developing aviation industries with little empirical data.Additionally,the strong transient characteristic is prominent because of the significant temperature differences during the take-off and climbing periods.The complex loads then challenge the fatigue and fracture calculation model.Besides,high computational efficiency is required because various variables are considered to calculate the POF.Therefore,new technologies for the probabilistic damage tolerance assessment are provided,including the efficient anomaly distribution acquisition method based on small samples,the zone definition method considering transient process,and stress intensity factor(SIF)solutions under arbitrary stress distributions combined with the machine learning method.Then,an efficient numerical integration method for calculating failure risk based on the probability density evolution theory is proposed.Meanwhile,the influence of the manufacturing process on residual stress and the failure risk of the rotors is explored.The development of the probabilistic damage tolerance method can meet the requ展开更多
The opportunistic replacement of multiple Life-Limited Parts （LLPs） is a problem widely existing in industry. The replacement strategy of LLPs has a great impact on the total maintenance cost to a lot of equipment. ...The opportunistic replacement of multiple Life-Limited Parts （LLPs） is a problem widely existing in industry. The replacement strategy of LLPs has a great impact on the total maintenance cost to a lot of equipment. This article focuses on finding a quick and effective algorithm for this problem. To improve the algorithm efficiency, six reduction rules are suggested from the perspectives of solution feasibility, determination of the replacement of LLPs, determination of the maintenance occasion and solution optimality. Based on these six reduction rules, a search algorithm is proposed. This search algorithm can identify one or several optimal solutions. A numerical experiment shows that these six reduction rules are effective, and the time consumed by the algorithm is less than 38 s if the total life of equipment is shorter than 55000 and the number of LLPs is less than 11. A specific case shows that the algorithm can obtain optimal solutions which are much better than the result of the traditional method in 10 s, and it can provide support for determining tobe-replaced LLPs when determining the maintenance workscope of an aircraft engine. Therefore, the algorithm is applicable to engineering applications concerning opportunistic replacement of multiple LLPs in aircraft engines.展开更多
Background: Large numbers of Forcibly Displaced Myanmar Nationals (FDMN), also called the Rohingya community, in Bangladesh face chronic life-threatening illnesses. Symptoms concerning for a cancer diagnosis are not e...Background: Large numbers of Forcibly Displaced Myanmar Nationals (FDMN), also called the Rohingya community, in Bangladesh face chronic life-threatening illnesses. Symptoms concerning for a cancer diagnosis are not easily evaluated and treated by healthcare systems available to this population. We conducted a rapid needs assessment of cancer screening and pain and palliative care with the goal of identifying the prevalence of cancer risk factors among the Rohingya who attended local health facilities. Methods: A cross-sectional study was conducted in the Kutupalong camp of Ukhiya, Cox’s Bazar among the Rohingya community. Data were?collected through purposive sampling. Face-to-face interviews were done using a structured questionnaire. Statistics were analyzed by using IBM SPSS 23.?Results: Out of 85 participants, 75 were female and 10 were male. 70 (82.4%) were uneducated (defined as lacking any formal institutional education), 10 (11.8%) people completed the primary level education and only 5 (5.9%) people received secondary level education. There were many participants with pulmonary disease with 35 (41.2%) people endorsing a history of asthma, bronchitis, and/or tuberculosis. There was a lack of female menstrual sanitation and hygiene with only 25 (29.4%) patients using sanitary napkins, that were donated by Non Government Organizations. Only 5.9% of the women had received any form of cervical cancer screening.?Conclusion: This study identifies risk factors associated with cancers and life-limiting diseases among the FDMN Rohingya refugees in Bangladesh. It is necessary to develop targeted education, cancer screening and cancer awareness programs for this population.展开更多
基金the National Natural Science Foundation of China,grant number U2233213.
文摘Probabilistic damage tolerance is a critical method to understand and communicate risk and safety.This paper reviews recent research on the probabilistic damage tolerance design for life-limited parts.The vision of the probabilistic damage tolerance assessment is provided.Five core parts of the probabilistic damage tolerance method are introduced separately,including the anomaly distribution,stress processing and zone definition,fatigue and fracture calculation method,probability of failure(POF)calculation method,and the combination with residual stress induced by the manufacturing process.The above currently-available risk assessment methods provide practical tools for failure risk predictions and are applied by the airworthiness regulations.However,new problems are exposed with the development of the aeroengines.The time-consuming anomaly distribution derivation process restricts the development of the anomaly distribution,especially for the developing aviation industries with little empirical data.Additionally,the strong transient characteristic is prominent because of the significant temperature differences during the take-off and climbing periods.The complex loads then challenge the fatigue and fracture calculation model.Besides,high computational efficiency is required because various variables are considered to calculate the POF.Therefore,new technologies for the probabilistic damage tolerance assessment are provided,including the efficient anomaly distribution acquisition method based on small samples,the zone definition method considering transient process,and stress intensity factor(SIF)solutions under arbitrary stress distributions combined with the machine learning method.Then,an efficient numerical integration method for calculating failure risk based on the probability density evolution theory is proposed.Meanwhile,the influence of the manufacturing process on residual stress and the failure risk of the rotors is explored.The development of the probabilistic damage tolerance method can meet the requ
基金co-supported by the Key National Natural Science Foundation of China (No. U1533202)the Civil Aviation Administration of China (No. MHRD20150104)the Fundamental Research Funds for the Central Universities (No. HIT.NSRIF.201704)
文摘The opportunistic replacement of multiple Life-Limited Parts （LLPs） is a problem widely existing in industry. The replacement strategy of LLPs has a great impact on the total maintenance cost to a lot of equipment. This article focuses on finding a quick and effective algorithm for this problem. To improve the algorithm efficiency, six reduction rules are suggested from the perspectives of solution feasibility, determination of the replacement of LLPs, determination of the maintenance occasion and solution optimality. Based on these six reduction rules, a search algorithm is proposed. This search algorithm can identify one or several optimal solutions. A numerical experiment shows that these six reduction rules are effective, and the time consumed by the algorithm is less than 38 s if the total life of equipment is shorter than 55000 and the number of LLPs is less than 11. A specific case shows that the algorithm can obtain optimal solutions which are much better than the result of the traditional method in 10 s, and it can provide support for determining tobe-replaced LLPs when determining the maintenance workscope of an aircraft engine. Therefore, the algorithm is applicable to engineering applications concerning opportunistic replacement of multiple LLPs in aircraft engines.
文摘Background: Large numbers of Forcibly Displaced Myanmar Nationals (FDMN), also called the Rohingya community, in Bangladesh face chronic life-threatening illnesses. Symptoms concerning for a cancer diagnosis are not easily evaluated and treated by healthcare systems available to this population. We conducted a rapid needs assessment of cancer screening and pain and palliative care with the goal of identifying the prevalence of cancer risk factors among the Rohingya who attended local health facilities. Methods: A cross-sectional study was conducted in the Kutupalong camp of Ukhiya, Cox’s Bazar among the Rohingya community. Data were?collected through purposive sampling. Face-to-face interviews were done using a structured questionnaire. Statistics were analyzed by using IBM SPSS 23.?Results: Out of 85 participants, 75 were female and 10 were male. 70 (82.4%) were uneducated (defined as lacking any formal institutional education), 10 (11.8%) people completed the primary level education and only 5 (5.9%) people received secondary level education. There were many participants with pulmonary disease with 35 (41.2%) people endorsing a history of asthma, bronchitis, and/or tuberculosis. There was a lack of female menstrual sanitation and hygiene with only 25 (29.4%) patients using sanitary napkins, that were donated by Non Government Organizations. Only 5.9% of the women had received any form of cervical cancer screening.?Conclusion: This study identifies risk factors associated with cancers and life-limiting diseases among the FDMN Rohingya refugees in Bangladesh. It is necessary to develop targeted education, cancer screening and cancer awareness programs for this population.
