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Manufacturing industries make use of the most prominent statistical tools such as the acceptance sampling procedures or the sampling inspection plans to reach a decision regarding the disposition of the lot(s) of products. In life testing experiments, product's lifetime is tested by taking samples from the lot received to check the working condition of the products in the hands of the consumer. The sampling procedures involved in testing the item's lifetime are called the reliability sampling plans. Products are assumed to follow certain continuous lifetime distributions. Compound distributions are the result of a mixture of two or more distributions that aid in modeling complex phenomena. Exponential-geometric distribution is one such kind, having its unique characteristics. In this work, reliability acceptance sampling plans are designed assuming that the product follows the exponential-geometric distribution satisfying both the producer's and consumer's risks. Numerical illustrations are given for the constructed life test sampling plans. [ABSTRACT FROM AUTHOR]

This work considers the design of a Bayesian reliability acceptance sampling plan (RASP) under a hybrid censored life test for the products sold under an optional warranty. The consumer and manufacturer agree on a common lifetime distribution of the product. However, they differ in the assessment of the prior distributions because of the adversarial nature of the consumer and manufacturer. The consumer takes a decision based on his/her utility and prior belief without a warranty offer by the manufacturer. If the decision is rejection, the manufacturer provides warranty offer to the consumer. If the consumer rejects the lot with a warranty, the manufacturer conducts a life test under the hybrid censoring scheme (HCS) and provides lifetime information to the consumer. The consumer updates his/her belief based on lifetime information provided by the manufacturer. The consumer then takes a decision of acceptance or rejection of the lot based on updated beliefs. The task of the manufacturer is to determine the optimal life testing plan. [ABSTRACT FROM AUTHOR]

Lifetime data has two distinguishing features: they are usually censored and have non-normal distributions. Generally speaking, censoring schemes can be classified into (i) censoring schemes with replacement and (ii) censoring schemes without replacement. Replacement during a life testing means that once observing a failure item, it is replaced by a new one. While there is a relatively large body of literature regarding control charts under censoring schemes without replacement, i.e., the second type schemes, designing control charts for the first type schemes has not yet received considerable attention. In this paper, two types of control charts are developed to monitor the lifetime data of an exponentially distributed item. To obtain the information of the lifetime data, failure censoring is conducted: n items are randomly selected and put on the test simultaneously. The test continues until observing r (r≤n) failures. During the test, once observing a failure time, it is replaced by a new one. Development of Shewhart type and exponentially weighted moving average control charts under failure censoring with replacement is the main novelty of the current study. Comparative and simulation studies are conducted. ARL curves are also derived with respect to different parameters of the process. [ABSTRACT FROM AUTHOR]

The concept of pseudocapacitance is explored as a rapid and universal method for the state of health (SOH) determination of batteries and supercapacitors. In contrast to this, the state of the art considers the degradation of a series of full charge/discharge cycles. Lithium-ion batteries, sodium-ion batteries and supercapacitors of different cell chemistries are studied by impedance spectroscopy during lifetime testing. Faradaic and capacitive charge storage are distinguished by the relationship between the stored electric charge and capacitance. Batteries with a flat voltage–charge curve are best suited for impedance spectroscopy. There is a slight loss in the linear correlation between the pseudocapacitance and Ah capacity in regions of overcharge and deep discharge. The correct calculation of quantities related to complex impedance and differential capacitance is outlined, which may also be useful as an introductory text and tutorial for newcomers to the field. Novel diagram types are proposed for the purpose of the instant performance and failure diagnosis of batteries and supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract The voltage endurance coefficient n of cross‐linked polyethylene (XLPE) insulation is an important indicator for the analysis of insulation failure mechanism. Accurately obtaining the value of n can provide technical support for the reliability evaluation of cable operation. The constant stress method and the step stress method are used to obtain the values of n, but the test parameters can influence the accuracy of the obtained n values. Two methods for selecting test parameters are proposed. The equivalence between the two methods is established, providing theoretical support for the accurate evaluation of the n value of solid insulation materials by using the step stress method. The accuracy of the evaluation results is verified by analyzing the test data. The test results show that the nstep = 13.04 evaluated by the step stress test with the proposed parameter selection method is consistent with the test result of constant stress nconstant = 12.83.

The assumption of normality is usually tied to the design and analysis of an experimental study. However, when dealing with lifetime testing and censoring at fixed time intervals, we can no longer assume that the outcomes will be normally distributed. This generally requires the use of optimal design techniques to construct the test plan for specific distribution of interest. Optimal designs in this situation depend on the parameters of the distribution, which are generally unknown a priori. A Bayesian approach can be used by placing a prior distribution on the parameters, thereby leading to an appropriate selection of experimental design. This, along with the model and number of predictors, can be used to derive the D‐optimal design for an allowed number of experimental runs. This paper explores using this Bayesian approach on various lifetime regression models to select appropriate D‐optimal designs in regular and irregular design regions. [ABSTRACT FROM AUTHOR]

This paper presents a very simple circuit that is able to measure capacitors capacitance, based on the estimation of capacitors discharge time. The proposed prototype is able to compute the time required by a capacitor to discharge three fourths of the stored energy. For that, a simple RC circuit is used, composed of the capacitor under test and some resistors, two operational amplifiers, which are used to identify the starting and ending points of the discharge time, four 4-bit counters, four BCD to 7 segment drivers and four displays of 7 segments, which show the computed capacitor capacitance. Several experimental results are presented. [ABSTRACT FROM AUTHOR]

The voltage endurance coefficient n of cross‐linked polyethylene (XLPE) insulation is an important indicator for the analysis of insulation failure mechanism. Accurately obtaining the value of n can provide technical support for the reliability evaluation of cable operation. The constant stress method and the step stress method are used to obtain the values of n, but the test parameters can influence the accuracy of the obtained n values. Two methods for selecting test parameters are proposed. The equivalence between the two methods is established, providing theoretical support for the accurate evaluation of the n value of solid insulation materials by using the step stress method. The accuracy of the evaluation results is verified by analyzing the test data. The test results show that the nstep = 13.04 evaluated by the step stress test with the proposed parameter selection method is consistent with the test result of constant stress nconstant = 12.83. [ABSTRACT FROM AUTHOR]

Life tests for highly reliable products often take a long time even using accelerated life testing with censoring. When the production process is monitored by control charts with the product lifetime as the key quality characteristic, the time spent on life testing could incur significant delays for practitioners to make decisions after sampling. However, shortening the test duration, that results in excessive right-censored observations, inevitably degrades the test power for anomaly detection. This study pays close attention to the determination of censoring time in life tests when monitoring lifetime data with the likelihood-based control charts. To interpret the optimal censoring time, the performance metric—out-of-control average time to signal (OC ATS), is deconstructed into two parts: the original OC ATS and the delay caused by life testing. Finite-sample analytical and large-sample asymptotic expressions of ATS metrics are derived for Type-I censored exponential lifetimes. Similar analytical expressions are also derived for the Weibull case. For general distributions, a Monte Carlo simulation procedure is developed for obtaining approximate results. Our numerical investigation uncovers the 2-fold impact of censoring time on the actual performance of control charts under various scenarios and provides useful references for practitioners to set more sensible censoring times in life testing. [ABSTRACT FROM AUTHOR]

The majority of approaches proposed in the past few decades to solve life test problems have differed markedly from those used for closely related, yet broader, issues. Due to the complexity of data that are generated each day in many practical domains, as a result of the development of scales for rating the success or failure of reliability, a new domain of reliability has been created. This domain is referred to as life classes, where specific probability distributions are presented. In this study, it is shown that the use of the quality-of-fit technique to solve problems involving life testing makes sense, and produces simpler processes that are roughly equivalent or superior to those used in traditional procedures. They may also behave better in limited samples. This work investigates a novel quality-of-fit test statistic; it is based on an exponential transform and is compared to the best renewal used Laplace test in increasing convex ordering (NBRULC). Evidence for approach normality is provided. The calculated variables include powers, Pitman asymptotic effectiveness, and critical points. Methods on how to handle censored data were also studied. Our experiments have real-world applications in the fields of medicine and engineering. [ABSTRACT FROM AUTHOR]

It is important in understanding the potential benefits of ultraviolet (UV-C) field applications for control of powdery mildew to know how long the lamps will last before replacement. We conducted a laboratory evaluation of a sample of low-pressure discharge germicidal UV-C lamps that have been used in field trials to control strawberry powdery mildew. None of the lamps tested failed to start after more than a year of operation. The degradation of UV-C output followed trends similar to those described by the manufacturer. Based on these measurement data and on the long history of this lamp technology, we predict that these lamps can continue to perform in the field after the manufacturer's rated life of approximately 10,000 hours of continuous operation, by reducing the speed of application to deliver the prescribed UV-C dose. With protective sleeves, these low pressure discharge UV-C lamps can be expected to last for many years of service. [ABSTRACT FROM AUTHOR]

It is commonly discussed by the quality/reliability engineers that acceptance sampling plans and life testing schemes designed using the concept of sequential probability ratio test (SPRT) can effectively decrease the cost and time of the experiment/inspection. Nevertheless, reaching a procedure to perform an SPRT-based life test usually involves some computations which are not simple and straightforward, even for simple forms of statistical distributions. Moreover, for each statistical distribution describing the model of the lifetime data, different specialized computations should be performed to propose a procedure for the life test. To address these shortcomings, we develop a novel life test according to the SPRT of the Bernoulli/binomial distribution, which can be simply, straightforwardly and effectively adapted for life testing of different continuous distributions. Our adaptable SPRT abbreviated to ASPRT is first designed considering the Weibull distribution and is then extended for gamma and other continuous distributions. In order to evaluate the performance, ASPRT is applied to different real-world and simulated data sets. To better prove the efficiency, it is also compared with a benchmark SPRT on different data sets. Both computational and comparative results demonstrate that ASPRT is able to effectively and efficiently conduct the life testing of different continuous distributions. [ABSTRACT FROM AUTHOR]

The lifetime of light-emitting diodes (LEDs) is highly dependent on usage conditions such as operating temperature and drive current. It is costly and impractical to test the LEDs on every usage condition. Previous studies used the Arrhenius equation and Black’s model to investigate the relationship of operating temperature, drive current and lumen maintenance life. However, they are found to be less accurate for certain conditions. The study aims to improve the prediction of lumen maintenance life under different thermal-electrical conditions. The Eyring model is proposed in this study. The model parameters are determined by regression approach, which provides the goodness of fit of the prediction model as well as the prediction interval. Furthermore, a method to predict lumen depreciation trend for different operating conditions based on the Eyring model and regression approach is established. As a result, the Eyring model produced higher prediction accuracy compared to Arrhenius equation and Black’s model. [ABSTRACT FROM AUTHOR]

In this paper, we describe how to analyze and propose the accelerated life test plans for the development of the excellence and reliability of the product. We focus on estimating the costs of maintenance service policy because it has a very significant position to assist any manufacturing organization for sale and available its equipment and maintenance cost-effective. The constant-stress partially accelerated life test is assumed when the lifetime of test units follows Generalized Inverted Exponential distribution under the progressive censoring scheme. The maximum likelihood estimates, Fisher Information matrix, and the asymptotic variance and covariance matrix are obtained. The confidence intervals of the estimators are also obtained. Furthermore, a simulation study is conducted to check the accuracy of the findings. [ABSTRACT FROM AUTHOR]

In this paper, seven LED lamps are selected to investigate how the junction temperature (Tj) of LED varies during the step-stress temperature accelerated aging test. The ambient temperatures are 80 °C and 70 °C for the first and second step of the aging test, respectively, and the total aging time is 2180 h. A non-contact method for monitoring junction temperatures of samples, by the ratio of white light energy to blue light energy (W/B), is applied. Experimental measurements show that the W/B ratio and Tj satisfy good linear relationship during the aging for all samples. Then, the junction temperatures are acquired at eight typical points of aging time which are used to eliminate the impact of Tj variation on the estimation of the decay rate and accelerated lifetime. It is shown that the estimated lifetime is longer than that acquired by the traditional method. The estimation errors of the accelerated lifetimes by the traditional method are in a range from 12.8% to 18.6% under the aging temperature of 80 °C and from 12.5% to 20.3% under the aging temperature of 70 °C for the seven samples. The estimation accuracy of the decay rates and accelerated lifetimes of LED lamps in the step-stress accelerated aging test is improved by the proposed methodology to a certain extent.

It is known that marine cable is responsible for the transmission of electric energy and electrical signals of the ship. In order to predict the residual life of cable under discontinuous operation, a non-destructive online life prediction model is established based on retention rate of hardness (RRH). This study takes the marine ethylene propylene rubber (EPR) cable as the research object. Using time temperature superposition principle, the optimal time temperature shift factor is calculated using particle swarm optimisation and steepest descent method. After that the main curve was fitted exponentially to acquire the relationship between RRH and ageing time. Compared with the existing model, the results indicate that the proposed model has higher prediction accuracy. On this basis, the residual life prediction model based on RRH of marine EPR under discontinuous operation is presented by adding time parameters. The effectiveness of the method is verified by simulation. Thus, it provides theoretical guidance for solving the problem of marine cable replacement time. [ABSTRACT FROM AUTHOR]

Though perovskite solar cells have outstanding commercialisation potential, perovskite materials are very vulnerable to moisture and oxygen. So the main issue for perovskite solar cell is very fast degradation. In order to elaborate on this concern, the stability of perovskite solar cells were investigated in this study. The effect of oxygen and moisture on perovskite solar cells decreased with encapsulation of the cells. Encapsulation has been carried out with ultraviolet cured epoxy resin. Stability tests were taken place in laboratory conditions under solar simulator and also shelf‐life tests. Perovskite solar cells showed the highest power conversion efficiency (PCE) of 9.77% with a short circuit current density of 22.5 mA/cm2, the open‐circuit voltage of 0.94 V and fill factor of 0.46. After 2800 h, perovskite solar cells were still 85% stable in atmospheric conditions. Perovskite solar cells exhibited distinctive durability for shelf‐life test in laboratory conditions. The PCE of perovskite solar cells were decreased only 15% of its initial value after 2800 h. In order to elaborate the degradation of perovskite solar cells, the cells are exposed to solar irradiation AM1.5G. Perovskite solar cells degraded gradually with time under solar irradiation; however, this stability test indicated that the solar cells were durable 20% after 500 h exposure to solar irradiation. [ABSTRACT FROM AUTHOR]

The condition assessment of oil–paper insulation is a vital issue in transformer management. To investigate the effect of moisture content on the accuracy of the prediction model, accelerated ageing experiments were performed with different initial moisture content (IMC) in laboratory condition. Two types of multi-parameter lifetime prediction models, e.g. with and without consideration of IMC, were presented for comparison purpose. The authors found that a better accuracy for its prediction results could be achieved by establishing the prediction models with the consideration of IMC. Besides, models considering IMC have better economic feasibility than that without considering IMC(non-IMC) as its total cost is cheaper according to life cycle cost (LCC) calculations. In addition, failure probability based on the proposed prediction models was also calculated as a direct indicator for evaluating the oil–paper insulation status. [ABSTRACT FROM AUTHOR]

This study presents firstly, experimental results through an innovative reliability bench of pulsed RF life test in a radar application for device lifetime under pulse conditions, then the physical clarifications of the failure phenomenon. The results of accelerated aging stress relative to various temperatures (3000 h at 150 and 10°C) are presented. Based on the radio‐frequency (RF) behaviour parameters shifts (gain, Pout, drain efficiency: DE, and Psat), the reliability of different tests have been compared. To explain and confirm these effects according to the degradation data, the dominant physical phonemes involved have been studied and the failure modes of the metal‐oxide‐semiconductor field‐effect transistors have been examined and proved with the SILVACO‐ATLAS simulator. What supports finding a relationship between the shifts of RF electrical parameters to failure physical phenomena caused by impact ionisation. The behaviour degradation of N‐LDMOS is related to interface states generated by hot carriers (traps) and by the electrons that are trapped, which leads to an accumulation of negative charge at the Si/SiO2 interface. At low temperature, the interface states are created more, due to a maximum impact ionisation rate targeted in the gate edge area. Finally, RF behaviour reliability analysis has been discussed. [ABSTRACT FROM AUTHOR]

In this paper, a new reliability testing control chart has been developed using the hybrid censoring scheme for the Weibull distribution. The in-control and out-of-control probabilities are estimated for the desired quality characteristic using the reliability acceptance sampling plan. The performance of the proposed chart has been evaluated by estimating the average run lengths for the shifted process under the simulation. A numerical example has been given for the practical implementation of the proposed chart. It has been observed that the proposed chart is a valuable addition in the process monitoring for the life testing of the products.

Design of variables sampling plans based on the lifetime-performance index for the exponentially distributed hybrid censored data is described in this article. The exact distribution of the maximum likelihood estimator of the exponential lifetime parameter is used to construct the sampling plans. A simulation based algorithm is applied to compute the sampling plans. A comparative study with the existing methods in the literature is also carried out to validate the proposed method. Finally, one real-life data set is analyzed to demonstrate the applicability of the method in practice. [ABSTRACT FROM AUTHOR]

The accelerated failure time (AFT) model is most commonly used model in accelerated life testing (ALT). This model is restrictive as failure time distributions under different constant stresses differ only in terms of scale. If it is not the case, most papers on ALT use a generalization of the AFT model supposing that under different stresses not only scale but also shape parameters are different. This model has an undesirable property for accelerated experiments—the survival functions corresponding to usual and accelerated stresses intersect. In this paper, we propose flexible generalizations of the AFT model. Estimation procedures and properties of estimators are discussed. Goodness-of-fit (GOF) tests for the given models are proposed. Examples of data analysis are provided. Generalization of the results in case of step stresses is presented. [ABSTRACT FROM AUTHOR]

In this paper, a comparison between the life distribution of a new unit with that of a used unit in the increasing convex order is made leading to a new class of life distributions which we call "new better than used in convex ordering of second order". This class includes as subclasses the NBU and the NBUC and is a subclass of the NBUCA class. Preservation properties under convolution, random maxima, mixing and formation of coherent structures are established. Stochastic comparisons of the excess lifetime when the inter-arrival times belong to the NBUC(2) class are developed. Some applications of Poisson shock models and a test of exponentiality against NBUC(2) alternative are presented. [ABSTRACT FROM AUTHOR]

The service life of a transformer depends on the ageing degree of the internal oil–paper insulation. In order to reliably predict the remaining service life of oil–paper insulation for a single transformer, this study proposes a method based on monitoring the performance degradation data of oil–paper insulation. In this study, the remaining life prediction model of oil–paper insulation is established according to the Wiener stochastic process. The parameters of the model are iteratively updated by using the Bayesian rule and maximum expectation algorithm. The objective of remaining service life prediction of transformer oil–paper insulation is achieved. In the laboratory, multiple groups of oil–paper insulation samples undergo an ageing test at 130°C. Certain amount of performance degradation data is obtained by continuously monitoring the oil–paper insulation. Along with the prediction method of remaining life, the accuracy of the remaining life prediction of transformer oil–impregnated paper is verified when the model parameters are updated. This is a significant guiding factor for predicting the remaining life through the performance degradation data of the continuously operating transformer. [ABSTRACT FROM AUTHOR]

High‐speed backplane connectors are extensively used in digital baseband communication circuits. Connector degradation may lead to deterioration of the integrity of digital signals and is one of the major causes of low communication quality. In this study, an accelerated test was used to produce degraded connector samples. Based on the degradation characteristics of the connector electrical contact surface, the differential transmission method was applied to enhance signal integrity in such degraded electrical contact circuits. Referring to the Gigabit Ethernet standard, the differential signal waveforms and eye diagrams of high‐speed channels with un‐degraded and degraded connectors were studied. Improvement of the circuit reliability by differential transmission was demonstrated from the perspectives of both experimental investigations and analysis using probability calculations. [ABSTRACT FROM AUTHOR]

There are no reliable measures for identifying self-healing failures in capacitors. Therefore, the high-voltage self-healing capacitor have not been widely adopted in power systems yet. It is urgent to study new scheme to protect the self-healing failure of high-voltage capacitors. Simulations tests and experiments were conducted to further assess self-healing of capacitors. The broken-down capacitor samples were connected into the test circuit with a vacuum contactor, and recorded the experimental phenomena and current wave-forms. The impedance changes were measured before and after the test, and calculated the active power dissipated by the sample. The test results showed that the insulation of self-healing failure sample temporarily restores or deteriorates rapidly. No visual defects are observed in the case of temporarily restored insulation, and the capacitor can continue to operate. However, if the insulation was deteriorated, unwanted gas generation, consisting of 85% H2, potentially lead to smoke and fire. Our study showed no obvious correlation between impedance change and occurring self-healing phenomena. It is found that the process consumes a lot of active power in case of deterioration. Therefore, a method of capacitor self-healing failure protection based on active power variation was proposed. [ABSTRACT FROM AUTHOR]

The subjects of reliability acceptance sampling plans and failure-censored life tests have usually been investigated from the viewpoint of statistical properties; indeed, few researchers have shed light on the economic aspects of these issues. In this research, a constrained mathematical model is developed to optimally design a reliability sampling plan under failure censoring life testing. Minimizing the expected total cost (ETC) involved in the sampling and life testing is considered as the objective function of the model. Ensuring the producer’s and the consumer’s risks is taken into consideration as the constraint of the model. To minimize the ETC, the model optimally determines three decision variables including the total number of the items put to the life test, the number of the failed items to terminate the test, and a criterion to make decisions about the acceptance or rejection of the lot. Examples are provided and analyses are conducted to gain some insight regarding the model performance.

The advantages of light emitting diodes (LEDs) over previous light sources and their continuous spread in lighting applications is now indisputable. Still, proper modelling of their lifespan offers additional design possibilities, enhanced reliability, and additional energy-saving opportunities. Accurate and rapid multi-physics system level simulations could be performed in Spice compatible environments, revealing the optical, electrical and even the thermal operating parameters, provided, that the compact thermal model of the prevailing luminaire and the appropriate elapsed lifetime dependent multi-domain models of the applied LEDs are available. The work described in this article takes steps in this direction in by extending an existing multi-domain LED model in order to simulate the major effect of the elapsed operating time of LEDs used. Our approach is based on the LM-80-08 testing method, supplemented by additional specific thermal measurements. A detailed description of the TM-21-11 type extrapolation method is provided in this paper along with an extensive overview of the possible aging models that could be used for practice-oriented LED lifetime estimations.

There are no reliable measures for identifying self-healing failures in capacitors. Therefore, the high-voltage self-healing capacitor have not been widely adopted in power systems yet. It is urgent to study new scheme to protect the self-healing failure of high-voltage capacitors. Simulations tests and experiments were conducted to further assess self-healing of capacitors. The broken-down capacitor samples were connected into the test circuit with a vacuum contactor, and recorded the experimental phenomena and current wave-forms. The impedance changes were measured before and after the test, and calculated the active power dissipated by the sample. The test results showed that the insulation of self-healing failure sample temporarily restores or deteriorates rapidly. No visual defects are observed in the case of temporarily restored insulation, and the capacitor can continue to operate. However, if the insulation was deteriorated, unwanted gas generation, consisting of 85% H(2), potentially lead to smoke and fire. Our study showed no obvious correlation between impedance change and occurring self-healing phenomena. It is found that the process consumes a lot of active power in case of deterioration. Therefore, a method of capacitor self-healing failure protection based on active power variation was proposed.

To study effects of pressure, humidity and aging time on the corona aging process, aging characteristics of silicone rubber composite insulators were researched by orthogonal tests. The test platform of adjustable pressure and humidity was constructed. TSC, SEM and FTIR tests were selected for aged samples. By the range analysis, it showed that the effect of pressure on trapped charges was related to humidity and aging time. There were more trapped charges when the humidity was higher, and the influence of humidity was more obvious along with the longer aging time at a low pressure. As the pressure increased, however, the effect of humidity on trapped charges was gradually reduced. But the influence of aging time was more significant, while aged degree of silicone rubber was deepened with increasing aging time. Furthermore, the aging state of materials was the collaboration effect of charged particles and nitric acid. Moreover, it could be seen from TSC, SEM and FTIR tests, sorting results of aging states were inconsistent. Results showed that the TSC test was comprehensively embodied the corona aging characteristics caused by physical and chemical defects. Therefore, results of TSC tests could be selected as an effective criterion for aging evaluations. [ABSTRACT FROM AUTHOR]

Due to the continuous demands for highly reliable and cost-effective power conversion, quantified reliability performances of the power electronics converter are becoming emerging needs. The existing reliability predictions for the power electronics converter mainly focus on the metrics of lifetime, accumulated damage, constant failure rate, or mean time to failure. Nevertheless, the time-varying and probability-distributed characteristics of the reliability are rarely involved. Moreover, in the public literatures, there are few evidences showing that the accuracy of the predicted reliability was experimentally validated. In this paper, a more advanced metric “cumulative distribution function (CDF)” is introduced to predict the reliability performance of the power electronics system based on mission profiles in motor drive application. Furthermore, the accuracy of the predicted reliability metrics is verified through a series of wear-out tests in a converter testing system. It is concluded that the CDF is a very suitable metric to predict the reliability performance of the converter, and it has shown good accuracy with much more reliability information compared to the existing approaches. In this method, the correct stress translation and dedicated strength tests based on mission profiles are two key factors to ensure the efficiency and accuracy of reliability prediction. [ABSTRACT FROM AUTHOR]

Consider a series system with n different components. Assume that the lifetime of i-th component follows exponential distribution with parameter λi(x),x∈Rk is a covariate vector, 1≤i≤n. For example, x may be (temperature, pressure, humidity), so that x∈R3 represents a three dimensional covariate vector. Assume that each λi(x),1≤i≤n, is distinct and depends upon x through linear relationship. Prior information available in the form of upper bounds on λi(x) are also incorporated in the design. We propose to obtain optimal reliability test plan based on maximum likelihood estimator of system reliability. A non-linear integer optimization problem is formulated for minimizing the maximum of total expected cost involved in testing satisfying usual probability requirements (Type-I and Type-II error constraints). In addition, it is also established through simulation that the derived sampling plan meets the specified producer’s and consumer’s risks as well. A sensitivity analysis is carried out to study the effect of various input parameters on maximum total expected testing cost. Finally, a qualitative analysis is presented at the end to discuss the nature of sampling plan derived. Several numerical examples are discussed to illustrate our test plan, and it is observed that the proposed plan has significant potential to reduce the total number of components to be tested for failure. It is noted that the number of components to be tested for failure is reduced by about 96% as compared to the existing test plans in the literature. [ABSTRACT FROM AUTHOR]

In this article, a dynamic reliability measure based on ranked set sampling is introduced, and its properties are investigated in theory and simulation. The results support the preference of the suggested index over the analogous one in simple random sampling. A data set from an agricultural experiment is analyzed for illustration. [ABSTRACT FROM AUTHOR]

This paper treats the s‐parameter performance degradation by hot electron induced for N‐MOSFET devices used in radar applications. This study is relevant for devices operating in the RF frequency regime. The power LD‐MOSFET device (0.8 µm channel length, Gate oxide thickness 0.065 µm and 2.2 GHz) are designed and fabricated. Subsequently, life tests in pulsed RF cause, after ageing, the electrical behaviour and its relation with charge trapping at the interface are presented and discussed. Unlike all other current methods, a complete evaluation of S parameters is carried out to obtain key information concerning the defects location. The s‐parameter performance degradation can be explained by the transconductance and the miller capacitance move, and by the leakage current augmentation IG, which is shown by hot‐carrier event from the Si/SiO2 interface state generation and/or in a build up of negative charge. Also, the degradation can be predicted by the experimental correlation of RF and dc performance shifts, favour by the measurement of dc performance or initial leakage current. The analysis accompanied proves that the s‐parameters shift by hot electron induced and should be taken into consideration in the design. Through physical processes of ATLAS‐SILVACO simulations these degradation phenomena are located and confirmed [ABSTRACT FROM AUTHOR]

The results of this paper are the continuation of the research presented by Bieniek [Optimal bounds for the mean of the total time on test for distributions with decreasing generalized failure rate. Statistics. 2016;50:1206-1220]. We consider the remaining total time on test after a given failure in a life test experiment. We derive sharp upper bounds on the mean of the total time on test optimal in the class of distributions with increasing generalized failure rate with respect to generalized Pareto distributions. Specific results are obtained for distributions with increasing density and increasing failure rate. We also provide exemplary numerical values of the obtained bounds and we compare them with the corresponding bounds for distributions with decreasing generalized failure rate. [ABSTRACT FROM AUTHOR]

The existing research on furfural analysis mainly focuses on the relationship between the furfural content in oil and the degree of polymerization (DP) of the paper, which are always obtained by accelerated thermal aging at high temperatures. However, the operating temperature of a winding is relatively low, approximately 60°C to 90°C. Thus, the relationship established at high temperature may be not suitable for the operating temperatures. In this research, aging tests of oil‐paper systems at different temperatures (from 100°C to 130°C) were carried out, with the DP, furfural content in oil and furfural content in paper being measured regularly to analyze the effect of temperature variation on the production and diffusion behavior of furfural in oil–paper insulation. The results show that temperature influences the production of furfural, i.e., there is no obvious difference in the amount of furfural produced by paper in the initial aging periods; however, a higher temperature results in more furfural being produced when the DP decreases to values below 600. An obvious diffusion process occurs after furfural is produced in paper in accelerated aging experiments, resulting in most of the furfural content remaining in the cellulose paper in the initial aging period. [ABSTRACT FROM AUTHOR]

In reliability engineering, the Weibull distribution and censoring are widely employed. The multiple Type-I censoring is the general form of Type-I censoring and represents that all the test units are terminated at different times. In this paper, the exact inference on Weibull parameters under multiple Type-I censoring is discussed, as the existing studies are limited. The least-square estimates (LSE) and maximum likelihood estimates (MLE) of Weibull parameters are presented. For the problem that the MLE does not always exist and has no closed-form, the approximate maximum likelihood estimate (AMLE) is proposed. Concerning the confidence interval (CI) for Weibull parameters, the pivotal quantity based on the LSE is developed to construct it. Another CI is obtained using the asymptotic normality of MLE. By the missing information principle, the observed Fisher information matrix is derived to replace the commonly approximate one through evaluating the second order derivatives of log-likelihood function with the MLE. As a comparison, the CI via the bootstrap method is provided. Monte Carlo simulation demonstrates that the proposed AMLE is convenient and superior to the MLE. And the proposed CI based on pivotal quantity outperforms others. Besides, the derived observed Fisher information matrix is also better. Finally, a real example is analyzed to illustrate the application of proposed methods. [ABSTRACT FROM AUTHOR]