Many mechanical systems have the characteristics of multiple failure modes and complex failure mech- anisms. On the basis of stress-strength interference （SSI） model, this paper takes the mechanical system with comm...Many mechanical systems have the characteristics of multiple failure modes and complex failure mech- anisms. On the basis of stress-strength interference （SSI） model, this paper takes the mechanical system with common cause failure （CCF） as the research object. The relationship between the stress distribution and the strength distribution is studied, and the failures of components are independent of each other under the determin- istic stress. Then, the concept of conditional reliability is introduced to build the system reliability models under the action of one-stress and multi-stress for both series and parallel systems. Finally, the corresponding properties of the DrODosed methods are discussed to show their advantages.展开更多
The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, en...The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, energy and aviation industries. High availability of the CNC heavy-duty lathes is demanded to guarantee the efficiency and benefit of these manufacturing industries. As one of the key subsystems of the HDHLs, the feeding control system is studied in this paper on reliability modeling and reliability analysis. The fault tree analysis(FTA) method is used for reliability modelling of the feeding control system. Considering the multiple common cause failure groups(CCFGs) existing in the system, a modified beta factor parametric model is introduced to model the common cause failure(CCF) in system. The reliability of feeding control system is then obtained and the effect of CCF on the reliability of the whole system is studied as well.展开更多
In the process of continuously improving the level of urbanization construction, the level of urban economic development is increasing, which also provides more opportunities for the development of the construction in...In the process of continuously improving the level of urbanization construction, the level of urban economic development is increasing, which also provides more opportunities for the development of the construction industry. Facing the increasingly serious contradiction between people and land, the construction of construction projects needs to develop towards high-rise buildings. In high-rise buildings, elevators can provide many conveniences for peoples lives. The safety and stability of their operation will be closely related to the safety of peoples lives and properties. Therefore, it is necessary to do a good job in the research of elevator braking in order to comprehensively improve the stability of elevator operation. In the following paragraphs, the principle of elevator brake is firstly discussed, then the reasons of elevator brake failure are analyzed, then the main requirements of elevator brake work are studied, and finally the inspection measures of elevator brake failure are comprehensively analyzed for reference.展开更多
At present, China is accelerating its urbanization construction, and a large number of people are flooding into big cities. The scale of city residents' commercial buildings has been further expanded. Elevator has...At present, China is accelerating its urbanization construction, and a large number of people are flooding into big cities. The scale of city residents' commercial buildings has been further expanded. Elevator has become the main means of transportation and is playing an increasingly important role in people's daily life. As an essential means of transportation in urban buildings, the performance of elevator is directly related to the personal safety of users. In the elevator system, the brake system is the key to ensure the safety of the elevator operation. When the inspection and maintenance of the elevator system, special attention should be paid to the analysis and inspection of the fault reasons. Determine the cause of elevator failure and put forward specific control measures.展开更多
Diaphragm failure is a common failure of diaphragm compressors. This paper makes statistics on diaphragm failures in high purity hydrogen production units, and makes statics analysis on diaphragm. Through the calculat...Diaphragm failure is a common failure of diaphragm compressors. This paper makes statistics on diaphragm failures in high purity hydrogen production units, and makes statics analysis on diaphragm. Through the calculation results of statics analysis, the causes of diaphragm failures are analyzed, and measures to prolong the service life of diaphragm are put forward.展开更多
Objective To analyze the clinical and genetic features of four children with pediatric acute liver failure(PALF)caused by neuroblastoma-amplified sequence(NBAS)gene variant,as well as the correlation between clinical ...Objective To analyze the clinical and genetic features of four children with pediatric acute liver failure(PALF)caused by neuroblastoma-amplified sequence(NBAS)gene variant,as well as the correlation between clinical phenotype and genotype.Methods The clinical data and genetic test results of four children with NBAS gene variants admitted to the Department of Gastroenterology,Children's Hospital Affiliated to Zhejiang University School of Medicine from August 2015 to June 2023 mainly presenting with pediatric acuteliverfailure(PALF)were retrospectively analyzed.The relevant literature from January 2015 to May 2024 was retrieved using the Chinese and English keywords"NBAS,""neuroblastoma amplified sequence,""SOPH,""short stature with optic nerve atrophy and Pelger Huet anomaly,""liver failure,"and"neuroblastoma amplified sequence"indexed in the CNKI database,Wanfang Data Knowledge Service Platform,and PubMed database.The clinical features and gene mutation characteristics of domestic patients were summarized.Results The age at which the initial PALF attack occurred in the four children varied from eight months to three years and seven months.All patients developed PALF within 1-2 days after the onset of fever,with symptoms such as vomiting,convulsions,and mental depression or confusion,accompanied by a sharp increase in transaminases,elevated bilirubin and blood ammonia,hyperlactatemia,and hepatomegaly.The PALF gradually improved,and three pediatric patients showed extrahepatic manifestations following antipyretic,fluid replacement,and other symptomatic supportive treatment.Long-term follow-up showed that active temperature control and symptomatic therapy reduced the recurrence of PALF.Genetic testing identified eight kinds of NBASgenevariantssites.Family testing validated compound heterozygous variants,which included four missense variants,one nonsense variants,and three frameshift mutations.A literature study revealed that out of 51 Chinese patients with NBAS gene variants,98.0%(50/51)had liver involvement,and 37 cases showed PALF.A total of 61 mutation sites were identified,with c.3596G>A(45.1%,23/51)as a hotspot variants.Conclusion PALF caused by NBAS gene variant has obvious clinical and genetic characteristics,and there is a correlation between genotype and clinical phenotype.The c.3596G>A variant site is a hotspot mutation in China and is strongly correlated with the liver failure phenotype.展开更多
Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requir...Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. This paper presents an overview of current researches on the typical characteristics and causes of bridge failures based on 10 former investigations. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than70% of the bridge failures. Causes of bridge failures are closely related to regional economy,structural type, type of use, material type, and service age. The failure rate is very high for steel bridges, which is inseparable from excessive emphasis on structure strength but lack of consideration on structure stability and fatigue in early years. Researchers need to strengthen their research on the stability and fatigue of steel bridges, as well as inspection and maintenance. Extreme loads such as flood, collision, and overload contribute to a large number of bridge failures because of the lack of extreme loads data and design theory defects. It is critical for such bridges to have sufficient redundancy and capacity protection measures to reduce the probability of bridge failure due to extreme loads. Previous statistical methods and classification methods for the characteristics and causes of bridge failures lack unified standards, and a more scientific method needs to be established. A comprehensive electronic database on bridge damage and failures needs to be developed to establish damage models and conduct forensic studies to improve the design theory and specifications.展开更多
Mission-critical IEC 61850 system architectures are designed to tolerate hardware failures to achieve the highest reliability performance.Hence,multi-channel systems are used in such systems within industrial faciliti...Mission-critical IEC 61850 system architectures are designed to tolerate hardware failures to achieve the highest reliability performance.Hence,multi-channel systems are used in such systems within industrial facilities to isolate machinery when there are process abnormalities.Inevitably,multi-channel systems introduce Common Cause Failure(CCF)since the subsystems can rarely be independent.This paper integrates CCF into the Markov reliability model to enhance the model flexibility to investigate synchronous generator intra-bay SCN architecture reliability performance considering the quality of repairs and CCF.The Markov process enables integration of the impact of CCF factors on system performance.The case study results indicate that CCF,coupled with imperfect repairs,significantly reduce system reliability performance.High sensitivity is observed at low levels of CCF,whereas the highest level of impact occurs when the system diagnostic coverage is 99%based on ISO 13849-1,and reduces as the diagnostic coverage level reduces.Therefore,it is concluded that the severity of CCF depends more on system diagnostic coverage level than the repair efficiency,although both factors impact the system overall performance.Hence,CCF should be con-sidered in determining the reliability performance of mission-critical communication networks in power distribution centres.展开更多
An enhanced ordered binary decision diagram （EOBDD） algorithm is proposed to evaluate the reliability of wireless sensor networks （WSNs）, based on the considerations of the common cause failure （CCF） and a large...An enhanced ordered binary decision diagram （EOBDD） algorithm is proposed to evaluate the reliability of wireless sensor networks （WSNs）, based on the considerations of the common cause failure （CCF） and a large number of nodes in WSNs. The EOBDD algorithm analyzes the common cause event （CCE） and the network structure when CCE takes place according to the stochastic graph and the CCF model of WSNs. After constructing the ordered binary decision diagram （OBDD） of the original network with node expansion, it uses a set of OBDD variables （SOV） to guide reliability computations along this OBDD. The two steps about OBDD can decrease the cost of OBDD constructions and storage. Furthermore, the efficient OBDD structure and Hash tables can greatly decrease redundant computations of isomorphs. The experiment results show that the EOBDD can be used to evaluate the reliability of WSN efficiently.展开更多
基金the National Natural Science Foundation of China(Nos.71771186 and 71471147)the 111 Project(No.B13044)the Basic Research Foundation of Northwestern Polytechnical University(No.3102014JCS05013)
文摘Many mechanical systems have the characteristics of multiple failure modes and complex failure mech- anisms. On the basis of stress-strength interference （SSI） model, this paper takes the mechanical system with common cause failure （CCF） as the research object. The relationship between the stress distribution and the strength distribution is studied, and the failures of components are independent of each other under the determin- istic stress. Then, the concept of conditional reliability is introduced to build the system reliability models under the action of one-stress and multi-stress for both series and parallel systems. Finally, the corresponding properties of the DrODosed methods are discussed to show their advantages.
基金the National Science and Technology Major Project of China(No.2014ZX04014-011)
文摘The lathes are basic machine tools for manufacturing cylindrical parts. In recent years, the DLseries computer numerical control(CNC) heavy-duty horizontal lathes(HDHLs) have been widely used in the transportation, energy and aviation industries. High availability of the CNC heavy-duty lathes is demanded to guarantee the efficiency and benefit of these manufacturing industries. As one of the key subsystems of the HDHLs, the feeding control system is studied in this paper on reliability modeling and reliability analysis. The fault tree analysis(FTA) method is used for reliability modelling of the feeding control system. Considering the multiple common cause failure groups(CCFGs) existing in the system, a modified beta factor parametric model is introduced to model the common cause failure(CCF) in system. The reliability of feeding control system is then obtained and the effect of CCF on the reliability of the whole system is studied as well.
文摘In the process of continuously improving the level of urbanization construction, the level of urban economic development is increasing, which also provides more opportunities for the development of the construction industry. Facing the increasingly serious contradiction between people and land, the construction of construction projects needs to develop towards high-rise buildings. In high-rise buildings, elevators can provide many conveniences for peoples lives. The safety and stability of their operation will be closely related to the safety of peoples lives and properties. Therefore, it is necessary to do a good job in the research of elevator braking in order to comprehensively improve the stability of elevator operation. In the following paragraphs, the principle of elevator brake is firstly discussed, then the reasons of elevator brake failure are analyzed, then the main requirements of elevator brake work are studied, and finally the inspection measures of elevator brake failure are comprehensively analyzed for reference.
文摘At present, China is accelerating its urbanization construction, and a large number of people are flooding into big cities. The scale of city residents' commercial buildings has been further expanded. Elevator has become the main means of transportation and is playing an increasingly important role in people's daily life. As an essential means of transportation in urban buildings, the performance of elevator is directly related to the personal safety of users. In the elevator system, the brake system is the key to ensure the safety of the elevator operation. When the inspection and maintenance of the elevator system, special attention should be paid to the analysis and inspection of the fault reasons. Determine the cause of elevator failure and put forward specific control measures.
文摘Diaphragm failure is a common failure of diaphragm compressors. This paper makes statistics on diaphragm failures in high purity hydrogen production units, and makes statics analysis on diaphragm. Through the calculation results of statics analysis, the causes of diaphragm failures are analyzed, and measures to prolong the service life of diaphragm are put forward.
文摘Objective To analyze the clinical and genetic features of four children with pediatric acute liver failure(PALF)caused by neuroblastoma-amplified sequence(NBAS)gene variant,as well as the correlation between clinical phenotype and genotype.Methods The clinical data and genetic test results of four children with NBAS gene variants admitted to the Department of Gastroenterology,Children's Hospital Affiliated to Zhejiang University School of Medicine from August 2015 to June 2023 mainly presenting with pediatric acuteliverfailure(PALF)were retrospectively analyzed.The relevant literature from January 2015 to May 2024 was retrieved using the Chinese and English keywords"NBAS,""neuroblastoma amplified sequence,""SOPH,""short stature with optic nerve atrophy and Pelger Huet anomaly,""liver failure,"and"neuroblastoma amplified sequence"indexed in the CNKI database,Wanfang Data Knowledge Service Platform,and PubMed database.The clinical features and gene mutation characteristics of domestic patients were summarized.Results The age at which the initial PALF attack occurred in the four children varied from eight months to three years and seven months.All patients developed PALF within 1-2 days after the onset of fever,with symptoms such as vomiting,convulsions,and mental depression or confusion,accompanied by a sharp increase in transaminases,elevated bilirubin and blood ammonia,hyperlactatemia,and hepatomegaly.The PALF gradually improved,and three pediatric patients showed extrahepatic manifestations following antipyretic,fluid replacement,and other symptomatic supportive treatment.Long-term follow-up showed that active temperature control and symptomatic therapy reduced the recurrence of PALF.Genetic testing identified eight kinds of NBASgenevariantssites.Family testing validated compound heterozygous variants,which included four missense variants,one nonsense variants,and three frameshift mutations.A literature study revealed that out of 51 Chinese patients with NBAS gene variants,98.0%(50/51)had liver involvement,and 37 cases showed PALF.A total of 61 mutation sites were identified,with c.3596G>A(45.1%,23/51)as a hotspot variants.Conclusion PALF caused by NBAS gene variant has obvious clinical and genetic characteristics,and there is a correlation between genotype and clinical phenotype.The c.3596G>A variant site is a hotspot mutation in China and is strongly correlated with the liver failure phenotype.
基金funded by the Communication Research Project of Department of Transport of Shaanxi Province(19-07K)the Special Fund for Basic Scientific Research of Central College of Chang’an University(300102219310)。
文摘Bridge failure, which is generally associated with serious economic and life losses, is defined as the incapacity of a constructed bridge or its components to perform as specified in the design and construction requirements. This paper presents an overview of current researches on the typical characteristics and causes of bridge failures based on 10 former investigations. Principal causes can be divided into internal causes and external causes or natural factors and human factors. Design error, construction mistakes, hydraulic, collision, and overload are the top 5 leading causes of bridge failures, resulting in more than70% of the bridge failures. Causes of bridge failures are closely related to regional economy,structural type, type of use, material type, and service age. The failure rate is very high for steel bridges, which is inseparable from excessive emphasis on structure strength but lack of consideration on structure stability and fatigue in early years. Researchers need to strengthen their research on the stability and fatigue of steel bridges, as well as inspection and maintenance. Extreme loads such as flood, collision, and overload contribute to a large number of bridge failures because of the lack of extreme loads data and design theory defects. It is critical for such bridges to have sufficient redundancy and capacity protection measures to reduce the probability of bridge failure due to extreme loads. Previous statistical methods and classification methods for the characteristics and causes of bridge failures lack unified standards, and a more scientific method needs to be established. A comprehensive electronic database on bridge damage and failures needs to be developed to establish damage models and conduct forensic studies to improve the design theory and specifications.
文摘Mission-critical IEC 61850 system architectures are designed to tolerate hardware failures to achieve the highest reliability performance.Hence,multi-channel systems are used in such systems within industrial facilities to isolate machinery when there are process abnormalities.Inevitably,multi-channel systems introduce Common Cause Failure(CCF)since the subsystems can rarely be independent.This paper integrates CCF into the Markov reliability model to enhance the model flexibility to investigate synchronous generator intra-bay SCN architecture reliability performance considering the quality of repairs and CCF.The Markov process enables integration of the impact of CCF factors on system performance.The case study results indicate that CCF,coupled with imperfect repairs,significantly reduce system reliability performance.High sensitivity is observed at low levels of CCF,whereas the highest level of impact occurs when the system diagnostic coverage is 99%based on ISO 13849-1,and reduces as the diagnostic coverage level reduces.Therefore,it is concluded that the severity of CCF depends more on system diagnostic coverage level than the repair efficiency,although both factors impact the system overall performance.Hence,CCF should be con-sidered in determining the reliability performance of mission-critical communication networks in power distribution centres.
基金supported by the National Natural Science Foundation of China (60672086)the Hi-Tech Research and Development Program of China (2007AA01Z2A1, 2008AA01A316)the EUFPT Project EFIPSANS (215547), and the Foundation for Western Returned Chinese Scholars of the Ministry of Education
文摘An enhanced ordered binary decision diagram （EOBDD） algorithm is proposed to evaluate the reliability of wireless sensor networks （WSNs）, based on the considerations of the common cause failure （CCF） and a large number of nodes in WSNs. The EOBDD algorithm analyzes the common cause event （CCE） and the network structure when CCE takes place according to the stochastic graph and the CCF model of WSNs. After constructing the ordered binary decision diagram （OBDD） of the original network with node expansion, it uses a set of OBDD variables （SOV） to guide reliability computations along this OBDD. The two steps about OBDD can decrease the cost of OBDD constructions and storage. Furthermore, the efficient OBDD structure and Hash tables can greatly decrease redundant computations of isomorphs. The experiment results show that the EOBDD can be used to evaluate the reliability of WSN efficiently.
