The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is consider...The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is considered. First, based on the assumption of cumulative shock, the probabilistic models for hard failure and soft failure are built respectively. On this basis, the dependent competing failure model involving degradation and shock processes is established. Furthermore, the situation of the shifting-threshold is also considered, in which the hard failure threshold value decreases to a lower level after the arrival of a certain number of shocks. A case study of fatigue crack growth is given to illustrate the proposed models. Numerical results show that shock has a significant effect on the failure process; meanwhile, the effect will be magnified when the value of the hard threshold shifts to a lower level.展开更多
Considering the dependence and competitive relation-ship between traumatic failure and degradation,the reliability assessment of products based on competing failure analysis is studied.The hazard rate of traumatic fai...Considering the dependence and competitive relation-ship between traumatic failure and degradation,the reliability assessment of products based on competing failure analysis is studied.The hazard rate of traumatic failure is regarded as a Weibull distribution of the degradation performance,and the Wiener process is used to describe the degradation process.The parameters are estimated with the maximum likelihood estimation（MLE）method.A reliability model based on competing failure analysis is proposed.A case study of the GaAs lasers is given to validate the effectiveness of the model and its solving method.The results indicate that if only the degradation failure is considered,the estimated result will be comparably optimistic.Meanwhile,the correlation between the degradation and traumatic failure has a great influence on the accuracy of reliability assessment.展开更多
Data obtained from accelerated life testing(ALT)when there are two or more failure modes,which is commonly referred to as competing failure modes,are often incomplete.The incompleteness is mainly due to censoring,as w...Data obtained from accelerated life testing(ALT)when there are two or more failure modes,which is commonly referred to as competing failure modes,are often incomplete.The incompleteness is mainly due to censoring,as well as masking which might be the case that the failure time is observed,but its corresponding failure mode is not identified.Because the identification of the failure mode may be expensive,or very difficult to investigate due to lack of appropriate diagnostics.A method is proposed for analyzing incomplete data of constant stress ALT with competing failure modes.It is assumed that failure modes have s-independent latent lifetimes and the log lifetime of each failure mode can be written as a linear function of stress.The parameters of the model are estimated by using the expectation maximum(EM)algorithm with incomplete data.Simulation studies are performed to check'model validity and investigate the properties of estimates.For further validation,the method is also illustrated by an example,which shows the process of analyze incomplete data from ALT of some insulation system.Because of considering the incompleteness of data in modeling and making use of the EM algorithm in estimating,the method becomes more flexible in ALT analysis.展开更多
A method for reliability analysis of the competing failure with the probabilistic failure threshold value not the fixed threshold value is presented, which involves the random shocks and the degradation is independent...A method for reliability analysis of the competing failure with the probabilistic failure threshold value not the fixed threshold value is presented, which involves the random shocks and the degradation is independent and dependent respectively. Specifically, for the dependent condition, the effect due to the random shocks on the degradation is considered with a damage factor. In addition, the dependent competing failure model is applied to the reliability analysis of the k-out-of-n systems. Finally, two studied cases are presented to illustrate the proposed method, and the results show the proposed method is reasonable.展开更多
In this article, we assume that the product in the burn-in procedure only experiences continuous smooth degradation process, while in the field operation period the product experiences both continuous smooth degradati...In this article, we assume that the product in the burn-in procedure only experiences continuous smooth degradation process, while in the field operation period the product experiences both continuous smooth degradation process and shock process. The shock process can cause the product not only traumatic failure,but also additional abrupt degradation damage. After the system reliability model and maintenance model have been proposed, the optimal burn-in setting and age replacement duration are obtained under the considering of minimizing the long run average cost rate. A numerical example with the real data is analyzed to illustrate the application of the model.展开更多
Reliability evaluation for aircraft engines is difficult because of the scarcity of failure data. But aircraft engine data are available from a variety of sources. Data fusion has the function of maximizing the amount...Reliability evaluation for aircraft engines is difficult because of the scarcity of failure data. But aircraft engine data are available from a variety of sources. Data fusion has the function of maximizing the amount of valu- able information extracted from disparate data sources to obtain the comprehensive reliability knowledge. Consid- ering the degradation failure and the catastrophic failure simultaneously, which are competing risks and can affect the reliability, a reliability evaluation model based on data fusion for aircraft engines is developed, Above the characteristics of the proposed model, reliability evaluation is more feasible than that by only utilizing failure data alone, and is also more accurate than that by only considering single failure mode. Example shows the effective- ness of the proposed model.展开更多
In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a de...In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a deterministic model, rather than a probabilistic one, can be established. Three steps comprise the developed method. First, physics-of-failure（PoF） models are utilized to model each failure mechanism. Then, interactions among failure mechanisms are modeled as a combination of three basic relations, competition, superposition and coupling. This is the reason why the method is referred to as ＂compositional method＂. Finally, the PoF models and the interaction model are combined to develop a deterministic model of the dependent failure behavior. As a demonstration, the method is applied on an actual spool and the developed failure behavior model is validated by a wear test. The result demonstrates that the compositional method is an effective way to model dependent failure behavior.展开更多
Degradation and overstress failures occur in many electronic systems in which the operation load and environmental conditions are complex.The dependency of them called dependent competing failure process(DCFP),has bee...Degradation and overstress failures occur in many electronic systems in which the operation load and environmental conditions are complex.The dependency of them called dependent competing failure process(DCFP),has been widely studied.Electronic system may experience mutual effects of degradation and shocks,they are considered to be interdependent.Both the degradation and the shock processes will decrease the limit of system and cause cumulative effect.Finally,the competition of hard and soft failure will cause the system failure.Based on the failure mechanism accumulation theory,this paper constructs the shock-degradation acceleration and the threshold descent model,and a system reliability model established by using these two models.The mutually DCFP effect of electronic system interaction has been decomposed into physical correlation of failure,including acceleration,accumulation and competition.As a case,a reliability of electronic system in aeronautical system has been analyzed with the proposed method.The method proposed is based on failure physical evaluation,and could provide important reference for quantitative evaluation and design improvement of the newly designed system in case of data deficiency.展开更多
Fostering students＇ pragmatic competence in ESL/EFL classrooms has been the subject of a large number of studies over the last several decades. This paper will examine the importance of pragmatic competence in L2 spo...Fostering students＇ pragmatic competence in ESL/EFL classrooms has been the subject of a large number of studies over the last several decades. This paper will examine the importance of pragmatic competence in L2 spoken communication and investigate factors leading to pragmatic failures. It will also discuss possible ways to help foster students＇ pragmatic competence in EFL speaking classes.展开更多
This paper probes how to foster Chinese English learners＇ pragmalinguistic competence through classroom instruction, thus reducing the occurrence of pragmalinguistic failure and improving learners＇ communicative com...This paper probes how to foster Chinese English learners＇ pragmalinguistic competence through classroom instruction, thus reducing the occurrence of pragmalinguistic failure and improving learners＇ communicative competence.展开更多
According to the principals of the Course Standard of English for Ordinary Senior Schools, published by China Education Ministry in 2001, the general goal of English curriculum on the basic education stage is to foste...According to the principals of the Course Standard of English for Ordinary Senior Schools, published by China Education Ministry in 2001, the general goal of English curriculum on the basic education stage is to foster the students＇ cross-cultural awareness, which is to develop their cross-cultural communicative competence. To achieve this goal, most of all, teachers of English at high school must have a good command of cross-cultural pragmatic competence. By looking through papers in various periodicals and the Internet, the writer finds that most of the studies have coped with pragmatic failures of ESL students but few of ESL teachers＇. Therefore, this thesis studies the present situation --- how much do schoolteachers of English know about pragmatics？ What about their cross-cultural communicative competence？ Can they communicate with the native speakers fluently and appropriately？ What are the most serious problems among them in pragmatics？ What can be done to solve the problems？ With all the questions, this research has collected considerable firsthand data and information. Only after the basic situations are known overall, can actions be taken to solve the problems existing in everyday ESL teaching. So this research is necessary and urgent for the present basic English pedagogy. However, since the present writer＇s ability and research conditions are limited, it is not possible to make a wider investigation in many places. Therefore, the district --- Bameng League, Inner Mongolia, China, is selected as the basic range of the survey, the situation of which is believed to be able to represent the basic educational ones in the poor and remote districts in the north and the west of China where education is more backward. The questionnaire consists of two parts： a table of individual information and a test paper. The former investigates informants＇ basic information, including the items of name, age, sex, teaching age, title of the technical post, degree, academic career, college or university that they graduated from, working unit, grades for teaching and the others. The latter is the test paper cited from He Ziran and Yan Zhuang （1986）, that is, Chinese Students＇Pragmatic Failure in English Communication --- Survey of the Pragmatic Difference between Chinese and English. And it contains 48 items, with items of pragmalinguistic and socio-pragmatic competence mixedly arranged. 120 of the questionnaire copies were handed out and 86 are collected, but only 64 are collected. The survey covers over 10 high schools in all the 7 banners of Bameng League, including two autonomous region-class key schools and five other league-class key schools. After the investigation, the present writer carefully corrects, marks, arranges, summarizes and analyzes the questionnaire, and obtains plenty of firsthand data and information. Then some conclusions have been drawn based on the data analysis. The result of the survey shows that linguistic competence is not equal to pragmatic competence, that ESL high school English teachers may use English rather fluently, without many mistakes in vocabulary and grammar,but it does not necessarily mean that they can use the target language appropriately to communicate with native speakers without pragmatic failures, and that the informants＇ knowledge of pragmatics and their pragmatic competence are rather poor. As a result, improving their knowledge and competence in pragmatics becomes a very necessary and urgent task to develop the quality of ELT in basic educational stages. In order to solve the above problems, the writer makes some suggestions as follows： （1） Pragmatics should be required as an essential course for the English majors in colleges and universities, especially in normal colleges and universities; （2） In-service high school English teachers must study courses of pragmatics and cross-cultural communication; （3） In some poor and remote districts, if educational conditions don＇t permit, textbooks of pragmatics and cross-cultural communication must be handed out to the high school English teachers who can study by themselves, then tests are regularly held for them and certificates will be given to those who have passed the tests; （4） In some developed districts, if conditions permit, English teachers can be sent abroad to English-speaking countries for further education in order to have a good command of the English language in the authentic contexts; （5） Modern multiple medias, such as VCD or DVD videos, TV or radio programs, the Internet, should be widely and frequently applied to training teachers; （6） More native language teachers and experts from English-speaking countries must be invited to high schools to train teachers of English.展开更多
基金The National Natural Science Foundation of China(No.50405021)Graduate Training Innovative Projects Foundation of Jiangsu Province(No.CXLX12_0081)
文摘The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is considered. First, based on the assumption of cumulative shock, the probabilistic models for hard failure and soft failure are built respectively. On this basis, the dependent competing failure model involving degradation and shock processes is established. Furthermore, the situation of the shifting-threshold is also considered, in which the hard failure threshold value decreases to a lower level after the arrival of a certain number of shocks. A case study of fatigue crack growth is given to illustrate the proposed models. Numerical results show that shock has a significant effect on the failure process; meanwhile, the effect will be magnified when the value of the hard threshold shifts to a lower level.
基金The National Natural Science Foundation of China(No.50405021)
文摘Considering the dependence and competitive relation-ship between traumatic failure and degradation,the reliability assessment of products based on competing failure analysis is studied.The hazard rate of traumatic failure is regarded as a Weibull distribution of the degradation performance,and the Wiener process is used to describe the degradation process.The parameters are estimated with the maximum likelihood estimation（MLE）method.A reliability model based on competing failure analysis is proposed.A case study of the GaAs lasers is given to validate the effectiveness of the model and its solving method.The results indicate that if only the degradation failure is considered,the estimated result will be comparably optimistic.Meanwhile,the correlation between the degradation and traumatic failure has a great influence on the accuracy of reliability assessment.
基金supported by Sustentation Program of National Ministries and Commissions of China(Grant No.203020102)
文摘Data obtained from accelerated life testing(ALT)when there are two or more failure modes,which is commonly referred to as competing failure modes,are often incomplete.The incompleteness is mainly due to censoring,as well as masking which might be the case that the failure time is observed,but its corresponding failure mode is not identified.Because the identification of the failure mode may be expensive,or very difficult to investigate due to lack of appropriate diagnostics.A method is proposed for analyzing incomplete data of constant stress ALT with competing failure modes.It is assumed that failure modes have s-independent latent lifetimes and the log lifetime of each failure mode can be written as a linear function of stress.The parameters of the model are estimated by using the expectation maximum(EM)algorithm with incomplete data.Simulation studies are performed to check'model validity and investigate the properties of estimates.For further validation,the method is also illustrated by an example,which shows the process of analyze incomplete data from ALT of some insulation system.Because of considering the incompleteness of data in modeling and making use of the EM algorithm in estimating,the method becomes more flexible in ALT analysis.
基金the Special Research Fund for the National Natural Science Foundation of China(No.11272082)the Fundamental Research Funds for the Central Universities(No.E022050205)the Open Research Fund of Key Laboratory of Fluid and Power Machinery of Xihua University(No.szjj2013-03)
文摘A method for reliability analysis of the competing failure with the probabilistic failure threshold value not the fixed threshold value is presented, which involves the random shocks and the degradation is independent and dependent respectively. Specifically, for the dependent condition, the effect due to the random shocks on the degradation is considered with a damage factor. In addition, the dependent competing failure model is applied to the reliability analysis of the k-out-of-n systems. Finally, two studied cases are presented to illustrate the proposed method, and the results show the proposed method is reasonable.
基金the National Natural Science Foundation of China(No.11171119)the Science and Technology Projects of Jiangxi Province Department of Education in 2012(No.GJJ12206)
文摘In this article, we assume that the product in the burn-in procedure only experiences continuous smooth degradation process, while in the field operation period the product experiences both continuous smooth degradation process and shock process. The shock process can cause the product not only traumatic failure,but also additional abrupt degradation damage. After the system reliability model and maintenance model have been proposed, the optimal burn-in setting and age replacement duration are obtained under the considering of minimizing the long run average cost rate. A numerical example with the real data is analyzed to illustrate the application of the model.
基金Supported by the National Natural Science Foundation of China and Aviation Fund(60879001)the Natural Science Foundation of Jiangsu Province(BK2009378)+1 种基金the Fundamental Research Fund of Nanjing University of Aeronautics and Astronautics(NS2010179)the Qinglan Project of Jiangsu Province~~
文摘Reliability evaluation for aircraft engines is difficult because of the scarcity of failure data. But aircraft engine data are available from a variety of sources. Data fusion has the function of maximizing the amount of valu- able information extracted from disparate data sources to obtain the comprehensive reliability knowledge. Consid- ering the degradation failure and the catastrophic failure simultaneously, which are competing risks and can affect the reliability, a reliability evaluation model based on data fusion for aircraft engines is developed, Above the characteristics of the proposed model, reliability evaluation is more feasible than that by only utilizing failure data alone, and is also more accurate than that by only considering single failure mode. Example shows the effective- ness of the proposed model.
基金supported by the National Natural Science Foundation of China (No. 71671009)supported by the National Natural Science Foundation of China (No. 61573043)supported by the National Natural Science Foundation of China (No. 51675025)
文摘In this paper, a new method is developed to model dependent failure behavior among failure mechanisms. Unlike the existing methods, the developed method models the root cause of the dependency explicitly, so that a deterministic model, rather than a probabilistic one, can be established. Three steps comprise the developed method. First, physics-of-failure（PoF） models are utilized to model each failure mechanism. Then, interactions among failure mechanisms are modeled as a combination of three basic relations, competition, superposition and coupling. This is the reason why the method is referred to as ＂compositional method＂. Finally, the PoF models and the interaction model are combined to develop a deterministic model of the dependent failure behavior. As a demonstration, the method is applied on an actual spool and the developed failure behavior model is validated by a wear test. The result demonstrates that the compositional method is an effective way to model dependent failure behavior.
基金supported by the National Natural Science Foundation of China(61503014,62073009)。
文摘Degradation and overstress failures occur in many electronic systems in which the operation load and environmental conditions are complex.The dependency of them called dependent competing failure process(DCFP),has been widely studied.Electronic system may experience mutual effects of degradation and shocks,they are considered to be interdependent.Both the degradation and the shock processes will decrease the limit of system and cause cumulative effect.Finally,the competition of hard and soft failure will cause the system failure.Based on the failure mechanism accumulation theory,this paper constructs the shock-degradation acceleration and the threshold descent model,and a system reliability model established by using these two models.The mutually DCFP effect of electronic system interaction has been decomposed into physical correlation of failure,including acceleration,accumulation and competition.As a case,a reliability of electronic system in aeronautical system has been analyzed with the proposed method.The method proposed is based on failure physical evaluation,and could provide important reference for quantitative evaluation and design improvement of the newly designed system in case of data deficiency.
文摘Fostering students＇ pragmatic competence in ESL/EFL classrooms has been the subject of a large number of studies over the last several decades. This paper will examine the importance of pragmatic competence in L2 spoken communication and investigate factors leading to pragmatic failures. It will also discuss possible ways to help foster students＇ pragmatic competence in EFL speaking classes.
文摘This paper probes how to foster Chinese English learners＇ pragmalinguistic competence through classroom instruction, thus reducing the occurrence of pragmalinguistic failure and improving learners＇ communicative competence.
文摘According to the principals of the Course Standard of English for Ordinary Senior Schools, published by China Education Ministry in 2001, the general goal of English curriculum on the basic education stage is to foster the students＇ cross-cultural awareness, which is to develop their cross-cultural communicative competence. To achieve this goal, most of all, teachers of English at high school must have a good command of cross-cultural pragmatic competence. By looking through papers in various periodicals and the Internet, the writer finds that most of the studies have coped with pragmatic failures of ESL students but few of ESL teachers＇. Therefore, this thesis studies the present situation --- how much do schoolteachers of English know about pragmatics？ What about their cross-cultural communicative competence？ Can they communicate with the native speakers fluently and appropriately？ What are the most serious problems among them in pragmatics？ What can be done to solve the problems？ With all the questions, this research has collected considerable firsthand data and information. Only after the basic situations are known overall, can actions be taken to solve the problems existing in everyday ESL teaching. So this research is necessary and urgent for the present basic English pedagogy. However, since the present writer＇s ability and research conditions are limited, it is not possible to make a wider investigation in many places. Therefore, the district --- Bameng League, Inner Mongolia, China, is selected as the basic range of the survey, the situation of which is believed to be able to represent the basic educational ones in the poor and remote districts in the north and the west of China where education is more backward. The questionnaire consists of two parts： a table of individual information and a test paper. The former investigates informants＇ basic information, including the items of name, age, sex, teaching age, title of the technical post, degree, academic career, college or university that they graduated from, working unit, grades for teaching and the others. The latter is the test paper cited from He Ziran and Yan Zhuang （1986）, that is, Chinese Students＇Pragmatic Failure in English Communication --- Survey of the Pragmatic Difference between Chinese and English. And it contains 48 items, with items of pragmalinguistic and socio-pragmatic competence mixedly arranged. 120 of the questionnaire copies were handed out and 86 are collected, but only 64 are collected. The survey covers over 10 high schools in all the 7 banners of Bameng League, including two autonomous region-class key schools and five other league-class key schools. After the investigation, the present writer carefully corrects, marks, arranges, summarizes and analyzes the questionnaire, and obtains plenty of firsthand data and information. Then some conclusions have been drawn based on the data analysis. The result of the survey shows that linguistic competence is not equal to pragmatic competence, that ESL high school English teachers may use English rather fluently, without many mistakes in vocabulary and grammar,but it does not necessarily mean that they can use the target language appropriately to communicate with native speakers without pragmatic failures, and that the informants＇ knowledge of pragmatics and their pragmatic competence are rather poor. As a result, improving their knowledge and competence in pragmatics becomes a very necessary and urgent task to develop the quality of ELT in basic educational stages. In order to solve the above problems, the writer makes some suggestions as follows： （1） Pragmatics should be required as an essential course for the English majors in colleges and universities, especially in normal colleges and universities; （2） In-service high school English teachers must study courses of pragmatics and cross-cultural communication; （3） In some poor and remote districts, if educational conditions don＇t permit, textbooks of pragmatics and cross-cultural communication must be handed out to the high school English teachers who can study by themselves, then tests are regularly held for them and certificates will be given to those who have passed the tests; （4） In some developed districts, if conditions permit, English teachers can be sent abroad to English-speaking countries for further education in order to have a good command of the English language in the authentic contexts; （5） Modern multiple medias, such as VCD or DVD videos, TV or radio programs, the Internet, should be widely and frequently applied to training teachers; （6） More native language teachers and experts from English-speaking countries must be invited to high schools to train teachers of English.
