Distribution-based degradation models （or graphical approach in some literature） occur in a wide range of applications. However, few of existing methods have taken the validation of the built model into consideratio...Distribution-based degradation models （or graphical approach in some literature） occur in a wide range of applications. However, few of existing methods have taken the validation of the built model into consideration. A validation methodology for distribution-based models is proposed in this paper. Since the model can be expressed as consisting of assumptions of model structures and embedded model parameters, the proposed methodology carries out the validation from these two aspects. By using appropriate statistical techniques, the rationality of degradation distributions, suitability of fitted models and validity of degradation models are validated respectively. A new statistical technique based on control limits is also proposed, which can be implemented in the validation of degradation models＇ validity. The case study on degradation modeling of an actual accelerometer shows that the proposed methodology is an effective solution to the validation problem of distribution-based de qradation models.展开更多
A lifetime prediction method for high-reliability tantalum （Ta） capacitors was proposed, based on multiple degradation measures and grey model （GM）. For analyzing performance degradation data, a two-parameter mode...A lifetime prediction method for high-reliability tantalum （Ta） capacitors was proposed, based on multiple degradation measures and grey model （GM）. For analyzing performance degradation data, a two-parameter model based on GM was developed. In order to improve the prediction accuracy of the two-parameter model, parameter selection based on particle swarm optimization （PSO） was used. Then, the new PSO-GM（1, 2, co） optimization model was constructed, which was validated experimentally by conducting an accelerated testing on the Ta capacitors. The experiments were conducted at three different stress levels of 85, 120, and 145℃. The results of two experiments were used in estimating the parameters. And the reliability of the Ta capacitors was estimated at the same stress conditions of the third experiment. The results indicate that the proposed method is valid and accurate.展开更多
Reliability enhancement testing(RET) is an accelerated testing which hastens the performance degradation process to surface its inherent defects of design and manufacture. It is an important hypothesis that the degrad...Reliability enhancement testing(RET) is an accelerated testing which hastens the performance degradation process to surface its inherent defects of design and manufacture. It is an important hypothesis that the degradation mechanism of the RET is the same as the one of the normal stress condition. In order to check the consistency of two mechanisms, we conduct two enhancement tests with a missile servo system as an object of the study, and preprocess two sets of test data to establish the accelerated degradation models regarding the temperature change rate that is assumed to be the main applied stress of the servo system during the natural storage. Based on the accelerated degradation models and natural storage profile of the servo system, we provide and demonstrate a procedure to check the consistency of two mechanisms by checking the correlation and difference of two sets of degradation data. The results indicate that the two degradation mechanisms are significantly consistent with each other.展开更多
For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency ...For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency of the parameters estimation are not high, and the current degradation state of the target device is not accurately estimated. In this paper, a nonlinear Wiener degradation model with random effect is proposed and the corresponding probability density function(PDF) of the first hitting time(FHT)is deduced. A parameter estimation method based on modified expectation maximum(EM) algorithm is proposed to obtain the estimated value of fixed coefficient and the priori value of random coefficient in the model. The posterior value of the random coefficient and the current degradation state of target device are updated synchronously by the state space model(SSM) and the Kalman filter algorithm. The PDF of RL with random effect is deduced. A simulation example is analyzed to verify that the proposed method has the obvious advantage over the existing methods in parameter estimation error and RL prediction accuracy.展开更多
Advanced traveler information systems （ATIS） can not only improve drivers＇ accessibility to the more accurate route travel time information, but also can improve drivers＇ adaptability to the stochastic network cap...Advanced traveler information systems （ATIS） can not only improve drivers＇ accessibility to the more accurate route travel time information, but also can improve drivers＇ adaptability to the stochastic network capacity degradations. In this paper, a mixed stochastic user equilibrium model was proposed to describe the interactive route choice behaviors between ATIS equipped and unequipped drivers on a degradable transport network. In the proposed model the information accessibility of equipped drivers was reflected by lower degree of uncertainty in their stochastic equilibrium flow distributions, and their behavioral adaptability was captured by multiple equilibrium behaviors over the stochastic network state set. The mixed equilibrium model was formulated as a fixed point problem defined in the mixed route flows, and its solution was achieved by executing an iterative algorithm. Numerical experiments were provided to verify the properties of the mixed network equilibrium model and the efficiency of the iterative algorithm.展开更多
随着锂电池在动力和储能等领域得到广泛应用,锂电池的寿命问题成为限制其发展的重要桎梏。电池处于存储状态时也会发生性能衰退而影响寿命,因此,研究电池自放电过程中的阻抗变化以表征内部电化学反应与结构相变过程,对于电池寿命模型完...随着锂电池在动力和储能等领域得到广泛应用,锂电池的寿命问题成为限制其发展的重要桎梏。电池处于存储状态时也会发生性能衰退而影响寿命,因此,研究电池自放电过程中的阻抗变化以表征内部电化学反应与结构相变过程,对于电池寿命模型完善有十分重要的意义。基于此,该文通过容量增量曲线对电池容量衰减的内因展开分析;在不同影响因素下自放电过程中电池阻抗谱变化规律的基础上,利用弛豫时间分布法进行理论原理分析;最后,在电池自放电老化过程的原理推导的基础上总结电池容量衰减量随时间的变化规律,并结合实验数据建立不同影响因素下电池容量衰减模型。结果表明,在存储过程中,电池的固体电解质界面(solid electrolyte interface,SEI)膜内阻增大,且存储温度越高、初始充电状态(state of charge,SOC)越大,相应的阻抗增加幅度越大。自放电过程电池老化主要原因是可循环活性锂离子的消耗和SEI膜的生长。同时该文推导出电池容量损失与时间近似呈0.5次方关系,并利用实验数据拟合得到电池在不同初始SOC和不同存储温度影响下的容量变化模型,为锂电池寿命模型预测提供更进一步的参考。展开更多
文摘Distribution-based degradation models （or graphical approach in some literature） occur in a wide range of applications. However, few of existing methods have taken the validation of the built model into consideration. A validation methodology for distribution-based models is proposed in this paper. Since the model can be expressed as consisting of assumptions of model structures and embedded model parameters, the proposed methodology carries out the validation from these two aspects. By using appropriate statistical techniques, the rationality of degradation distributions, suitability of fitted models and validity of degradation models are validated respectively. A new statistical technique based on control limits is also proposed, which can be implemented in the validation of degradation models＇ validity. The case study on degradation modeling of an actual accelerometer shows that the proposed methodology is an effective solution to the validation problem of distribution-based de qradation models.
基金Project(Z132012) supported by the Second Five Technology-based Fund in Science and Industry Bureau of ChinaProject(1004GK0032) supported by General Armament Department for the Common Issues of Military Electronic Components,China
文摘A lifetime prediction method for high-reliability tantalum （Ta） capacitors was proposed, based on multiple degradation measures and grey model （GM）. For analyzing performance degradation data, a two-parameter model based on GM was developed. In order to improve the prediction accuracy of the two-parameter model, parameter selection based on particle swarm optimization （PSO） was used. Then, the new PSO-GM（1, 2, co） optimization model was constructed, which was validated experimentally by conducting an accelerated testing on the Ta capacitors. The experiments were conducted at three different stress levels of 85, 120, and 145℃. The results of two experiments were used in estimating the parameters. And the reliability of the Ta capacitors was estimated at the same stress conditions of the third experiment. The results indicate that the proposed method is valid and accurate.
基金supported by the Natural Science Foundation of Hunan Province(2018JJ2282)
文摘Reliability enhancement testing(RET) is an accelerated testing which hastens the performance degradation process to surface its inherent defects of design and manufacture. It is an important hypothesis that the degradation mechanism of the RET is the same as the one of the normal stress condition. In order to check the consistency of two mechanisms, we conduct two enhancement tests with a missile servo system as an object of the study, and preprocess two sets of test data to establish the accelerated degradation models regarding the temperature change rate that is assumed to be the main applied stress of the servo system during the natural storage. Based on the accelerated degradation models and natural storage profile of the servo system, we provide and demonstrate a procedure to check the consistency of two mechanisms by checking the correlation and difference of two sets of degradation data. The results indicate that the two degradation mechanisms are significantly consistent with each other.
基金supported by the National Defense Foundation of China(71601183)the China Postdoctoral Science Foundation(2017M623415)
文摘For the large number of nonlinear degradation devices existing in a project, the existing methods have not systematically studied the effects of random effect on the remaining lifetime(RL),the accuracy and efficiency of the parameters estimation are not high, and the current degradation state of the target device is not accurately estimated. In this paper, a nonlinear Wiener degradation model with random effect is proposed and the corresponding probability density function(PDF) of the first hitting time(FHT)is deduced. A parameter estimation method based on modified expectation maximum(EM) algorithm is proposed to obtain the estimated value of fixed coefficient and the priori value of random coefficient in the model. The posterior value of the random coefficient and the current degradation state of target device are updated synchronously by the state space model(SSM) and the Kalman filter algorithm. The PDF of RL with random effect is deduced. A simulation example is analyzed to verify that the proposed method has the obvious advantage over the existing methods in parameter estimation error and RL prediction accuracy.
基金Projects(51378119,51578150)supported by the National Natural Science Foundation of China
文摘Advanced traveler information systems （ATIS） can not only improve drivers＇ accessibility to the more accurate route travel time information, but also can improve drivers＇ adaptability to the stochastic network capacity degradations. In this paper, a mixed stochastic user equilibrium model was proposed to describe the interactive route choice behaviors between ATIS equipped and unequipped drivers on a degradable transport network. In the proposed model the information accessibility of equipped drivers was reflected by lower degree of uncertainty in their stochastic equilibrium flow distributions, and their behavioral adaptability was captured by multiple equilibrium behaviors over the stochastic network state set. The mixed equilibrium model was formulated as a fixed point problem defined in the mixed route flows, and its solution was achieved by executing an iterative algorithm. Numerical experiments were provided to verify the properties of the mixed network equilibrium model and the efficiency of the iterative algorithm.
文摘随着锂电池在动力和储能等领域得到广泛应用,锂电池的寿命问题成为限制其发展的重要桎梏。电池处于存储状态时也会发生性能衰退而影响寿命,因此,研究电池自放电过程中的阻抗变化以表征内部电化学反应与结构相变过程,对于电池寿命模型完善有十分重要的意义。基于此,该文通过容量增量曲线对电池容量衰减的内因展开分析;在不同影响因素下自放电过程中电池阻抗谱变化规律的基础上,利用弛豫时间分布法进行理论原理分析;最后,在电池自放电老化过程的原理推导的基础上总结电池容量衰减量随时间的变化规律,并结合实验数据建立不同影响因素下电池容量衰减模型。结果表明,在存储过程中,电池的固体电解质界面(solid electrolyte interface,SEI)膜内阻增大,且存储温度越高、初始充电状态(state of charge,SOC)越大,相应的阻抗增加幅度越大。自放电过程电池老化主要原因是可循环活性锂离子的消耗和SEI膜的生长。同时该文推导出电池容量损失与时间近似呈0.5次方关系,并利用实验数据拟合得到电池在不同初始SOC和不同存储温度影响下的容量变化模型,为锂电池寿命模型预测提供更进一步的参考。
文摘为探究碳含量、稳定碳同位素比值(δ^(13)C)与塑料薄膜降解性的关系,在各平台收集了89个市售塑料薄膜制品,按种类将其分为纯PE薄膜(Polyethylene Films,PEF)、降解助剂添加型薄膜(Degradation Aid-added Films,DAF)、生物基薄膜(Bio-based Films,BF)、混合基薄膜(Mixed Films,MF)。用热水、稀盐酸、过氧化氢对其逐级处理后,测定原样和逐级处理后残余物的碳含量和δ^(13)C值。结果表明,薄膜原样的碳含量均值表现为PEF(84.22%±1.00%)>DAF(72.93%±2.28%)>BF(59.52%±2.18%)>MF(53.00%±1.67%),δ^(13)C值均值表现为PEF(-29.04‰±0.26‰)<DAF(-29.02‰±0.40‰)<MF(-25.09‰±0.46‰)<BF(-23.79‰±0.92‰)。不同类型的塑料薄膜经热水处理后的碳含量和δ^(13)C值与原样相比均无明显差异;但稀盐酸处理后DAF和BF的碳含量分别升高了9.34个百分点和11.32个百分点,而PEF和MF碳含量几乎不变。对于δ^(13)C值来说,PEF仅偏负0.19个千分点,DAF、BF、MF的偏负值分别是PEF的5.4倍、11.6倍和6.8倍;过氧化氢处理对BF影响最大,碳含量同原样相比升高了10.25个百分点,δ^(13)C值偏负3.14个千分点。经化学逐级处理后四种类型塑料薄膜碳含量最终都呈升高趋势,δ^(13)C值呈偏负趋势。在建立的Logistic回归模型中,ROC曲线下面积(Area Under the Curve,AUC)为0.95,预测准确率达到86.5%,因此可通过样品碳含量和热水处理后δ^(13)C值对塑料薄膜的降解类型进行鉴别。
