Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coeffic...Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coefficients of super Gauss vibration stress and temperature stress. Then, by applying these coefficients, an accelerated reliability qualification testing curve was obtained from the standard tests. Finally,the actual experiment on a digital marine control device was carried out under the proposed testing method.The experiment result shows that the proposed method can reduce the total experiment time and improve the efficiency of the reliability qualification test.展开更多
By analyzing the shortage of reliability test design and thinking over the producer's risk and consumer's risk, the information fusion technology is used to set up a reliability test design model( RTDM). By an...By analyzing the shortage of reliability test design and thinking over the producer's risk and consumer's risk, the information fusion technology is used to set up a reliability test design model( RTDM). By analyzing the demands and constraint conditions of the RTDM and with applications of Bayesian approach and Monte Carlo method( MCM),this paper puts forward the exponential distributed subsystems and the information fusion technology among them. According to the posteriori risk criteria,formulas of producer's risk and consumer's risk were also inferred,and with the help of Matlab software,selection of the optimum test plan was solved. Finally,validity of the model had been proved by a test of series parallel system.展开更多
[Objective] The aim was to test the reliability and validity of questionnaire on the adaptation strategy of cryosphere changes in arid inland river basin. [Method] A questionnaire on "the adaptation strategy of c...[Objective] The aim was to test the reliability and validity of questionnaire on the adaptation strategy of cryosphere changes in arid inland river basin. [Method] A questionnaire on "the adaptation strategy of cryosphere changes in arid inland river basin" was carried out in Urumchi River basin and Aksu River basin, and its reliability and validity were tested by means of statistical method, so as to investigate the stability and accuracy of questionnaire. [Result] Reliability analysis of questionnaire showed that the split-half reliability coefficient of questionnaire in Urumchi River basin and Aksu River basin was 0.729 and 0.750, respectively, and Cronbach's α reliability coefficient was 0.613 and 0.616, respectively, which revealed that the questionnaire had good equivalence and internal consistency which reflected good reliability and stability. According to validity analysis on questionnaire, there was significant correlation between the score of most questions and questionnaire, and it indicated that questionnaire had high content validity. There were 8 common factors collected from 26 questions, which were summarized as agricultural planting, agricultural water conservation, life satisfaction, cultivated land variation, social integration sense, climate and cryosphere changes, capital input improved by environment and family economic condition, respectively. Meanwhile, the contribution rate of various questions in corresponding indexes was higher, and reflected structure was in full accord with questionnaire content, which revealed that questionnaire owned good construct validity. [Conclusion] With higher stability and accuracy, the questionnaire could determine the desired topic and content and was suitable for the study on the perception of common people and choices of adaptive strategy under cryosphere changes in arid inland river basin in northwestern China.展开更多
Parametric Accelerated Life Testing (ALT) was used to improve the reliability of ice-maker system with a fractured helix upper dispenser in field. By using bond graphs and state equations, a variety of mechanical load...Parametric Accelerated Life Testing (ALT) was used to improve the reliability of ice-maker system with a fractured helix upper dispenser in field. By using bond graphs and state equations, a variety of mechanical loads in the assembly were analyzed. The acceleration factor was derived from a generalized life-stress failure model with a new load concept. To reproduce the failure modes and mechanisms causing the fracture, new sample size equation was derived. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly reproduce early failure in field. Consequently, the failure modes and mechanisms found were identical with those of the failed sample. The design of this testing should help an engineer uncover the design parameters affecting the reliability of fractured helix upper dispenser in field. By eliminating the design flaws, gaps and weldline, the B1 life of the redesign of helix upper dispenser is now guaranteed to be over 10 years with a yearly failure rate of 0.1% that is the reliability quantitative test specifications (RQ).展开更多
Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits,but also the weak spots in reliability tests.Most of failures in power devices are caused ...Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits,but also the weak spots in reliability tests.Most of failures in power devices are caused by the malfunction of interconnections,including failure of bonding wire as well as cracks of solder layer.In fact,the interconnection failure of power devices is the result of a combination of factors such as electricity,temperature,and force.It is significant to investigate the failure mechanisms of various factors for the failure analysis of interconnections in power devices.This paper reviews the main failure modes of bonding wire and solder layer in the interconnection structure of power devices,and its failure mechanism.Then the reliability test method and failure analysis techniques of interconnection in power device are introduced.These methods are of great significance to the reliability analysis and life prediction of power devices.展开更多
Constant stress accelerated life tests(ALTs) can be applied to obtain a high estimation accuracy of reliability measure?ments, but these are time?consuming tests. Progressive stress ALTs can yield failures more quickl...Constant stress accelerated life tests(ALTs) can be applied to obtain a high estimation accuracy of reliability measure?ments, but these are time?consuming tests. Progressive stress ALTs can yield failures more quickly but cannot guaran tee the estimation accuracy of reliability measurements. In this paper, a progressive?constant combination stress ALT is proposed to combine the merits of both tests. The optimal plan, in which the design variables are the initial pro?gressive stress level, the progressive stress ramp rate, the sample allocation proportion of the progressive stress and the constant stress level, is determined using the principle of minimizing the asymptotic variance of the maximum likelihood estimator of the natural log reliable life for the connectors. A comparison between the optimal PCCSALT plan and the CSALT plan with the same sample size and estimation accuracy shows that the test time is reduced by 13.59% by applying the PCCSALT.展开更多
Ramming system is the key device to guarantee the firing speed of self-propelled gun. Based on traditional reliability enhancement testing method, a new kind of reliability enhancement testing simulation method of ram...Ramming system is the key device to guarantee the firing speed of self-propelled gun. Based on traditional reliability enhancement testing method, a new kind of reliability enhancement testing simulation method of ramming system is put forward firstly. In CAD software Pro/E and dynamic simulation software ADAMS, the virtual prototype of ramming system is established. In EASY5 software, the corresponding hydraulic system and control system models are built. The reliability enhancement testing virtual environment of ramming system is developed using the mechanical-electrical-hydraulic co-simulation technology. Based on the load spectra provided by virtual prototype, and the stress distribution provided by finite element analysis and material's S-N curve(S is fatigue strength, N is fatigue life), a model of fatigue enhancement coefficient is established through the failure mechanism analysis. The simulation processes and simulation results show the feasibility of reliability enhancement testing based on virtual prototype, and provide sufficient theory reference for structure improvement and optimization of ramming system.展开更多
The CET 4 writing test is widely used in China,but whether it is a more reliable and valid test ofwriting for CET 4 than other methods of evaluation is still not clear.The purpose of this study was to examine the reli...The CET 4 writing test is widely used in China,but whether it is a more reliable and valid test ofwriting for CET 4 than other methods of evaluation is still not clear.The purpose of this study was to examine the reliability and the validity of a modification of this test.In carrying out the study,a total of 60 Band 4 students in Zhejiang University took the modified test,aCET 4 test and a First Certificate Practice Test.The results of this study demonstrate that themodified version is a significantly more reliable and valid writing test than the present CET 4 writingtest.These results suggest that the CET 4 writing test needs modification.展开更多
文摘Based on the theoretical inference and experiment verification,a method was proposed to carry out the accelerated reliability qualification testing. First,theoretical inference was used to get the acceleration coefficients of super Gauss vibration stress and temperature stress. Then, by applying these coefficients, an accelerated reliability qualification testing curve was obtained from the standard tests. Finally,the actual experiment on a digital marine control device was carried out under the proposed testing method.The experiment result shows that the proposed method can reduce the total experiment time and improve the efficiency of the reliability qualification test.
基金National Natural Science Foundation of China(No.70971133)
文摘By analyzing the shortage of reliability test design and thinking over the producer's risk and consumer's risk, the information fusion technology is used to set up a reliability test design model( RTDM). By analyzing the demands and constraint conditions of the RTDM and with applications of Bayesian approach and Monte Carlo method( MCM),this paper puts forward the exponential distributed subsystems and the information fusion technology among them. According to the posteriori risk criteria,formulas of producer's risk and consumer's risk were also inferred,and with the help of Matlab software,selection of the optimum test plan was solved. Finally,validity of the model had been proved by a test of series parallel system.
基金Supported by Major State Basic Research Development Program of China(2007CB411507)Open Foundation Project of State Key Laboratory of Cryospheric Sciences,Chinese Academy of Sciences(SKLCS08-04)
文摘[Objective] The aim was to test the reliability and validity of questionnaire on the adaptation strategy of cryosphere changes in arid inland river basin. [Method] A questionnaire on "the adaptation strategy of cryosphere changes in arid inland river basin" was carried out in Urumchi River basin and Aksu River basin, and its reliability and validity were tested by means of statistical method, so as to investigate the stability and accuracy of questionnaire. [Result] Reliability analysis of questionnaire showed that the split-half reliability coefficient of questionnaire in Urumchi River basin and Aksu River basin was 0.729 and 0.750, respectively, and Cronbach's α reliability coefficient was 0.613 and 0.616, respectively, which revealed that the questionnaire had good equivalence and internal consistency which reflected good reliability and stability. According to validity analysis on questionnaire, there was significant correlation between the score of most questions and questionnaire, and it indicated that questionnaire had high content validity. There were 8 common factors collected from 26 questions, which were summarized as agricultural planting, agricultural water conservation, life satisfaction, cultivated land variation, social integration sense, climate and cryosphere changes, capital input improved by environment and family economic condition, respectively. Meanwhile, the contribution rate of various questions in corresponding indexes was higher, and reflected structure was in full accord with questionnaire content, which revealed that questionnaire owned good construct validity. [Conclusion] With higher stability and accuracy, the questionnaire could determine the desired topic and content and was suitable for the study on the perception of common people and choices of adaptive strategy under cryosphere changes in arid inland river basin in northwestern China.
文摘Parametric Accelerated Life Testing (ALT) was used to improve the reliability of ice-maker system with a fractured helix upper dispenser in field. By using bond graphs and state equations, a variety of mechanical loads in the assembly were analyzed. The acceleration factor was derived from a generalized life-stress failure model with a new load concept. To reproduce the failure modes and mechanisms causing the fracture, new sample size equation was derived. The sample size equation with the acceleration factor also enabled the parametric accelerated life testing to quickly reproduce early failure in field. Consequently, the failure modes and mechanisms found were identical with those of the failed sample. The design of this testing should help an engineer uncover the design parameters affecting the reliability of fractured helix upper dispenser in field. By eliminating the design flaws, gaps and weldline, the B1 life of the redesign of helix upper dispenser is now guaranteed to be over 10 years with a yearly failure rate of 0.1% that is the reliability quantitative test specifications (RQ).
基金supported by the National Natural Science Foundation of China(Grant No.61904127 and 62004144)Guangdong Basic and Applied Basic Research Foundation(Grant No.2021A1515010651)+2 种基金Fundamental Research Funds for the Central Universities(Grant No.202401002,203134004,20212VA100 and 2021VB006)Hubei Provincial Natural Science Foundation of China(Grant No.2020CFA032)National Key R&D Program of China(Grant No.2019YFB1704600)。
文摘Interconnections in microelectronic packaging are not only the physical carrier to realize the function of electronic circuits,but also the weak spots in reliability tests.Most of failures in power devices are caused by the malfunction of interconnections,including failure of bonding wire as well as cracks of solder layer.In fact,the interconnection failure of power devices is the result of a combination of factors such as electricity,temperature,and force.It is significant to investigate the failure mechanisms of various factors for the failure analysis of interconnections in power devices.This paper reviews the main failure modes of bonding wire and solder layer in the interconnection structure of power devices,and its failure mechanism.Then the reliability test method and failure analysis techniques of interconnection in power device are introduced.These methods are of great significance to the reliability analysis and life prediction of power devices.
基金Supported by National Natural Science Foundation of China(Grant No.51405447)International Science&Technology Cooperation Program of China(Grant No.2015DFA71400)
文摘Constant stress accelerated life tests(ALTs) can be applied to obtain a high estimation accuracy of reliability measure?ments, but these are time?consuming tests. Progressive stress ALTs can yield failures more quickly but cannot guaran tee the estimation accuracy of reliability measurements. In this paper, a progressive?constant combination stress ALT is proposed to combine the merits of both tests. The optimal plan, in which the design variables are the initial pro?gressive stress level, the progressive stress ramp rate, the sample allocation proportion of the progressive stress and the constant stress level, is determined using the principle of minimizing the asymptotic variance of the maximum likelihood estimator of the natural log reliable life for the connectors. A comparison between the optimal PCCSALT plan and the CSALT plan with the same sample size and estimation accuracy shows that the test time is reduced by 13.59% by applying the PCCSALT.
基金the National Natural Science Foundation of China(No.51175508)
文摘Ramming system is the key device to guarantee the firing speed of self-propelled gun. Based on traditional reliability enhancement testing method, a new kind of reliability enhancement testing simulation method of ramming system is put forward firstly. In CAD software Pro/E and dynamic simulation software ADAMS, the virtual prototype of ramming system is established. In EASY5 software, the corresponding hydraulic system and control system models are built. The reliability enhancement testing virtual environment of ramming system is developed using the mechanical-electrical-hydraulic co-simulation technology. Based on the load spectra provided by virtual prototype, and the stress distribution provided by finite element analysis and material's S-N curve(S is fatigue strength, N is fatigue life), a model of fatigue enhancement coefficient is established through the failure mechanism analysis. The simulation processes and simulation results show the feasibility of reliability enhancement testing based on virtual prototype, and provide sufficient theory reference for structure improvement and optimization of ramming system.
文摘The CET 4 writing test is widely used in China,but whether it is a more reliable and valid test ofwriting for CET 4 than other methods of evaluation is still not clear.The purpose of this study was to examine the reliability and the validity of a modification of this test.In carrying out the study,a total of 60 Band 4 students in Zhejiang University took the modified test,aCET 4 test and a First Certificate Practice Test.The results of this study demonstrate that themodified version is a significantly more reliable and valid writing test than the present CET 4 writingtest.These results suggest that the CET 4 writing test needs modification.
