基于ML-II方法的k/n-系统Bayes可靠性评估

n中取k系统(简称k/n-系统)是工程实践中应用最广泛的系统类型之一。为了在系统现场试验样本量很小的情况下进行可靠性评估,首先利用次序统计量推导了k/n-系统寿命分布的密度函数,并给出了模型参数的第二类极大似然估计(ML-Ⅱ估计);然后给出了k/n-系统Bayes可靠性评估的一般步骤;仿真实例表明了方法的可行性。     

大间隔分类学习研究现状

在机器学习领域中,间隔扮演着重要的角色。可以用来度量分类的置信度;其理论泛化界也可用于指导分类算法的设计。近年来,该理论已广泛应用于特征选择,分类器训练和集成学习。实际上,间隔思想表明如果在训练阶段模型能够产生大的间隔,那么分类任务将有好的置信度和高可靠性。文中介绍大间隔分类学习方法的研究现状,并给出了其存在的问题。     

Plastic encapsulated microcircuit reliability predicition: why?

Reliability prediction models for microcircuits have been a function of steady-state temperature. Failure rates generated from accelerated temperature tests were extrapolated to predict system reliability at system use temperatures. This is now known to be completely inaccurate. Attempts are now being made to predict the reliability of plastic encapsulated microcircuits (PEMs) based on accelerated temperature/humidity testing. Failure rates generated due to corrosion failure mechanisms at these high stress levels are then extrapolated and used to predict system reliability at used temperature/humidity conditions.This paper discusses the fallacy of this approach. A new concept for the assurance of PEM corrosion resistance is proposed. It will be shown that today's best commercial practice suppliers have already addressed the design, materials, and processing issues of molded packaged microcircuits, and corrosion is no longer a mechanism of concern to the user.     

最大间隔核优化的雷达目标高分辨距离像识别新方法

基于目标高分辨率距离像的雷达自动目标识别技术在军事和民用上都有巨大的应用价值。但是由于雷达目标高分辨距离像的姿态敏感性以及高特征维数,造成了其非线性可分性。针对此问题,本文提出了一种基于最大间隔核优化的雷达目标高分辨距离像识别方法。本方法首先采用了最大间隔准则算法来优化数据依赖核函数,然后利用支持向量机分类器实现了雷达目标高分辨距离像识别,最后进行了基于5种战斗机目标高分辨距离像的实验仿真。实验结果表明了基于最大间隔核优化的目标识别算法对于SVM分类器可以有效实现核函数优化,从而能够提高目标识别性能。      

Use of voltage stressing at wafer probe for reliability predictions

In two independent evaluations, good correlation has been found between I_DDQ degradation due to voltage stressing at wafer probe and the reliability of devices built from a given wafer or wafer lot. This provides a useful reliability predictor and screening tool at the wafer level. This technique also provides a useful vehicle for the manufacturing facility to better understand and modify those portions of their wafer fabrication process where reliability improvements are warranted. The usefulness of this method should be applicable to evolving integrated circuit (IC) manufacturing technologies that have reduced feature sizes and operating voltages, provided proper precautions are taken in the selection of voltage stress values     

To reject or not to reject: that is the question-an answer in caseof neural classifiers

A method defining a reject option that is applicable to a given 0-reject classifier is proposed. The reject option is based on an estimate of the classification reliability, measured by a reliability evaluator Ψ. Trivially, once a reject threshold σ has been fixed, a sample is rejected if the corresponding value of Ψ is below σ. Obviously, as σ represents the least tolerable classification reliability level, when its value varies the reject option becomes more or less severe. In order to adapt the behavior of the reject option to the requirements of the considered application domain, a function P characterizing the reject option's adequacy to the domain has been introduced. It is shown that P can be expressed as a function of σ and, consequently, the optimal value for σ is defined as the one which maximizes the function P. The method for determining the optimal threshold value is independent of the specific 0-reject classifier, while the definition of the reliability evaluators is related to the classifier's architecture. General criteria for defining appropriate reliability evaluators within a classification paradigm are illustrated in the paper and are based on the localization, in the feature space, of the samples that could be classified with a low reliability. The definition of the reliability evaluators for three popular architectures of neural networks (backpropagation, learning vector quantization and probabilistic network) is presented. Finally, the method has been tested with reference to a complex classification problem with data generated according to a distribution-of-distributions model     

Reliability and MTTF evaluation of a repairable complex system under waiting

This paper deals with the reliability and mean time to failure (MTTF) evaluation of a complex system under waiting incorporating the concept of hardware failure and human error. Failure rates of the complex system follow exponential time distributions, whereas repair follows a general repair time distribution. Laplace transforms of various state probabilities have been evaluated and then reliability is obtained by the inversion process. A formula for variance of time to failure has also been developed. A particular case is also given to highlight some important results. Moreover, various plots have been sketched at the end.     

Thermal fatigue life estimation and delamination mechanics studies of multilayered MEMS structures

This paper is concerned with the application of a Physics of Failure (PoF) methodology to assessing the reliability of Micro-Electro-Mechanical-System (MEMS) switches. Numerical simulations, based on the finite element method (FEM) using a sub-domain approach, were performed to examine the damage onset (e.g. yielding) due to temperature variations and to simulated the crack propagation arising after thermal fatigue. In this work remeshing techniques were employed in order to develop a damage tolerance approach based on the assumption that initial flaws exist in the multi-layered structure due, for instance, to manufacturing processes and/or are originates after thermal fatigue, as preliminary experimental tests has shown.     

Approximated reliability of r-out-of-n(F) system with common cause failure and maintenance

In modern industries very high reliability system are needed. To improve the reliability of system, the component redundancy and maintenance of component or system play an impotant role and must be studied. This paper presents a reliability model of a r-out-of-n(F) redundant system with maintenance and Common Cause Failure. Failed component repair times are arbitrarily distributed. The system is in a failed state when r units failed because of the combination of single element failure or CCF(Common Cause Failure). Laplace transformation of reliability is derived by using analysis of Markov state transition graph. By using the analyzed MTBF, we compute MTBF of r-out-of-n(F) system. The MTBF with CCF is saturable even if repair rate is large.Approximated reliability of the r-out-of-n(F) system with maintenance and Common Cause Failure O.SummaryThe paper presents a reliability model of a r-out-of-n(F) redundant system with maintenance and Common Cause Failure. Failed component repair times are arbitrarily distributed. The system is in a failed state when r units failed because of the combination of single element failure or Common Cause Failure. Laplace transformation of reliability is derived by using analysis of Markov state transition graph. By analyzing this mean visiting time equations, we compute MTBF and shows computational example. The MTBF with CCF is saturable even if repair rate is large. In general the maintenance overcomes MTBF bounds, But the repair method not overcome the MTBF saturation when the system has Common Cause Failure.     

无线终端指纹仪可靠性试验探讨

可靠性试验是一种验证试验。验证试验就其方法而言是一种抽样检验程序,与其他抽样验收的区别在于,它考虑的是与时间有关的产品质量特性,如平均故障间隔时间(MTBF)。因此,产品可靠性指标的验证工作原理是建立在一定寿命分布假设的基础上。在实际工作中为了验证无线终端指纹仪的可靠性是否满足标准要求,制订了相应的检测大纲,对其可靠性试验进行了探讨。     

Drop impact reliability of edge-bonded lead-free chip scale packages

This paper presents the drop test reliability results for edge-bonded 0.5 mm pitch lead-free chip scale packages (CSPs) on a standard JEDEC drop reliability test board. The test boards were subjected to drop tests at several impact pulses, including a peak acceleration of 900 Gs with a pulse duration of 0.7 ms, a peak acceleration of 1500 Gs with a pulse duration of 0.5 ms, and a peak acceleration of 2900 Gs with a pulse duration of 0.3 ms. A high-speed dynamic resistance measurement system was used to monitor the failure of the solder joints. Two edge-bond materials used in this study were a UV-cured acrylic and a thermal-cured epoxy material. Tests were conducted on CSPs with edge-bond materials and CSPs without edge bonding. Statistics of the number of drops-to-failure for the 15 component locations on each test board are reported. The test results show that the drop test performance of edge-bonded CSPs is five to eight times better than the CSPs without edge bonding. Failure analysis was performed using dye-penetrant and scanning electron microscopy (SEM) methods. The most common failure mode observed is pad lift causing trace breakage. Solder crack and pad lift failure locations are characterized with the dye-penetrant method and optical microscopy.     

C波段功率GaAs MESFET的可靠性

本文通过功率GaAs MESFET的筛选与环境、寿命试验阐述了器件的早期失效模式模型,估计了可靠性水平,指出了主要失效因素,并用实验方法讨论了突变烧毁失效,分析了失效原因,探讨了提高可靠性的途径。     

Evaluation of MTTF and reliability of a power plant by BF technique

In this paper, investigations have been carried out for the evaluation of reliability and MTTF (mean time to failure) of a parallel redundant complex system; viz. a power plant. The object of the system is to supply power generated by generators from a power house to a very important consumer, connected by cables and switches. The reliability and MTTF have been evaluated by using Boolean Function (BF) technique. Failure times for the various components of the complex system follow arbitrary distribution. A numerical example has also been appended to highlight the important results. Two graphs on reliability and MTTF have also been given in the end to forecast the operable behaviour of the system at any time.     

Transformation from availability expression to failure frequency expression

The problem of computing the system's Failure Frequency is reduced to the problem of computing its Availability. This is performed by a transformation operator. However, the existing transformation operator is not practical because its transformation time increases exponentially with system size. To overcome this difficulty, this paper proposes a new method of transforming the Availability expression of a system into the corresponding Failure Frequency expression of the system. This method is based on a matrix approach using a 2 /spl times/ 2 matrix consisting of 0, Availability, and Failure Frequency in an appropriate manner. This transformation also enables algorithms for computing the Availability of a system to be transformed into algorithms for computing its Failure Frequency by replacing parameters and operations with matrix parameters and operations. The computation time after transformation is linear with respect to the original Availability algorithm. This implies that the problems of computing other well-known reliability measures including, Availability, Unavailability, MTBF, MTTR, MCT, Failure Rate, Failure Rate, and Failure Frequency, are reduced to only the Availability computation problem.     

Scene categorization based on local–global feature fusion and multi-scale multi-spatial resolution encoding

With the bag-of-contextual-visual-word (BOCVW) models, we propose a scene categorization method based on local–global feature fusion and multi-scale multi-spatial resolution encoding. First, the performances of the BOCVW models belonging to different features are mutually reinforced by fusing other types of features within local regions. Then, the spatial configuration information is explored using a multi-scale multi-spatial resolution encoding approach. Furthermore, these encoded BOCVW models are globally fused using an improved maximum-margin optimization strategy, which considers the margin between input vectors of different categories and the diameter of the smallest ball containing feature vectors simultaneously. The proposed method has been evaluated on three scene categorization datasets consisting of scene categories 8, 15, and 67, respectively. And its effectiveness has been verified by these experimental results.     

1+1保护式系统设计及在交通信息通信节点中的应用

介绍了1 1保护式系统的设计思想及其实现方法,给出了1 1保护式交通信息通信节点的系统的构成原理及主要程序中通信协议的设计方法。采用1 1保护式的方法,使得整个系统在硬件成本增加不多的情况下,提高了系统的可靠性和安全性。这种设计思想和方法同样适用于可靠性要求较高的其他系统中,具有一定的实用价值。     

基于多特征融合的弱小运动目标识别

利用单个特征识别强噪声中的弱小运动目标,常因所提取的目标特征与噪声特征易混淆而导致高的虚警率.提出一种新的基于多特征融合的弱小运动目标识别方法.分析了弱小运动目标的连续相关性、面积及质心位置偏移这三个特征的可靠性及提取方法,对获取的特征值进行归一化后采用多特征融合的方法构造更具有鲁棒性的联合特征,确定了以具有最大多特征融合值为真实目标的决策方法.通过与采用单一特征的目标识别方法进行比较,证明了提出的多特征融合方法能更准确地识别弱小运动目标.     

Hybrid redundancy approach to increase the reliability of FPGA based speed controller core for high speed train

With the progress of the railway technology, the railway transportation is becoming more efficient, intelligent and faster. High speed trains, as a major part of the railway transportation, are engaged with passenger＇s safety, and therefore the reliability issue is very important in such vital systems. In this paper, a dependable speed controller core based on FPGA has been developed for high speed trains. To improve the reliability and mitigate single upset faults on basic speed controller, this paper proposes a new effective method which is based on hardware redundancy. In the proposed Hybrid Dual Duplex Redundancy （HDDR） method, the original controller is quadruplicated and correct values are voted through the comparator and error detection unit. We have analyzed the proposed system with Reliability, Availability, Mean time to failure and Security （RAMS） theory in order to evaluate the effectiveness of proposed scheme. Theoretical analysis shows that the Mean Time To Failure （MTTF） of the proposed system is 2.5 times better than the traditional Triple Modular Redundancy （TMR）. Furthermore, the fault injection experimental results reveal that the capability of tolerating Single Event Upsets （SEUs） in the proposed method increases up to 7.5 times with respect to a regular speed controller.     

Effects of Glue on the Bend Performance of Flip Chip Packages

To combat reliability margin loss in ball grid array (BGA) packages specifically in mechanical shock and vibration testing, companies are exploring the possibility of using glue and complete underfill to mitigate risk to second-level interconnects (SLI). Though glue has been demonstrated to have a positive influence on SLI reliability margin, it can have adverse affects on the rest of the package such as substrate or first-level interconnects (FLI). This paper explains details on how glue modulates the overall reliability of the package. Finite-element modeling (FEM) along with low strain rate bend tests was done to prove the effect of glue on solder joint reliability. Further, shock testing was done to demonstrate how the glue modulates the shock performance. The improvement in SLI reliability was highly dependent on the choice of glue.