步降应力加速寿命试验的可靠性仿真

研究武器装备寿命实验准确评估可靠性问题,为进一步完善步降试验的统计分析方法,建立依赖于加速模型的数据折算公式,再对步降试验下的三步分析法做出改进,改进后的方法在处理数据时更具灵活性,且计算复杂度有所降低.进而,为比较步进试验与步降试验下三步分析法的精确性与稳定性,首次利用Monte - Carlo仿真法对两试验下的三步分析法进行仿真.仿真结果显示,相比步进试验,步降试验能显著提高三步分析法的精度和稳定性,说明了步降应力试验具有优越性为可靠性评估提供了依据.     

双应力交叉步降加速寿命试验的数值模拟

双应力交叉步降加速寿命试验是可靠性工程中不同于传统增应力加速寿命试验的一种新思路,投入实践前,针对其是否能提高可靠性试验效率进行计算机模拟。仿真相似条件下双应力交叉步降加速寿命试验和原有双应力交叉步进加速寿命试验的步骤,应用于产品寿命服从Weibull分布的实际算例,统计得出二者的试验平均耗费时间和效率比。由效率比曲线,证实双应力交叉步降加速寿命试验在应用于高可靠性、长寿命产品可靠性分析时多数情况下能较大程度提高试验效率。     

恒定应力加速寿命试验及其数据统计分析软件

加速寿命试验是为了缩短试验时间,在不改变产品失效机理的条件下,用加大应力（如温度应力、电压应力等）的方法对产品进行的寿命试验。通过加大应力水平,加快产品失效,获得失效数据,运用加速寿命模型外推产品在正常应力水平下的可靠性特性。本文主要介绍恒定应力加速寿命试验的组织实施方法,以及其试验数据统计分析软件。     

电子产品可靠性寿命试验的分类与应用

介绍常用的电子产品可靠性寿命试验方法的分类及各方法的应用.     

加速寿命试验方法及评估

加速寿命试验是为缩短试验时间,在不改变故障模式和故障机理的条件下,用加大应力的方法进行的试验。随着元器件水平的迅速提高,高可靠、长寿命的产品越来越多,在正常应力水平下进行寿命试验来评定产品的可靠性已不能满足实际需要,代价很高,不现实,目前广泛采用了加速寿命试验。本文介绍了加速寿命试验方法及评估,并给出了案例。     

弹药步进应力寿命试验数据处理

弹药的步进应力加速寿命试验数据处理的关键是异常数据的处理和弹药长贮寿命分布参数的估计.针对这两个问题,人们提出了许多相关解决办法,但迄今为止,尚没有一种通用的、行之有效的方法.为此,尝试依据贝叶斯理论对试验中可能出现的数据异常进行预处理,并利用鲍维尔法先求取各级加速应力下的样品分布参数的似然估计,再结合加速方程得到常应力下弹药的贮存寿命分布参数.最后,通过实例说明了方法的可行性.     

恒定应力加速寿命试验算法探讨

恒定应力加速寿命试验具有试验方法简单、理论成熟、得到信息多、试验结果较为准确等优点。本文利用三种被广泛运用的统计推断方法对同一恒定应力加速寿命试验结果进行推断,分析比较算法的优劣：在样本量较小的情况下极大似然估计优于线性无偏估计,但是当各应力水平下的样品失效数较大时,极大似然估计与线性无偏估计几乎等效,而线性回归的方法计算较为简单,但是在应力水平较少的情况下误差较大。     

恒定应力加速寿命试验模型及应用——威布尔分布

加速寿命试验是可靠性试验技术的基本方法之一。检验加速寿命试验中的数据是否服从威布尔分布,进而得出加速系数和加速寿命方程,用在不同应力水平下试验得到的数据,运用威布尔分布模型,并对其中的待估参数进行点估计和区间估计,最终得出产品在正常应力水平下的各项可靠性特征量的估计。     

气体传感器加速寿命试验方法研究

本文以ＣＯ传感器为例,提供了一种气体传感器加速寿命试验方法,根据该方法得到的实验结果,我们可以对采用了气体传感器的装置在某技术指标范围内估计气体传感器的可靠性。     

可靠性加速试验技术研究

为了更好地理解和运用可靠性加速试验技术,通过文献调研的方式,对加速寿命试验(ALT)、加速退化试验(ADT)、加速可靠性增长试验(ARGT)、高加速寿命试验(HALT)以及高加速应力筛选(HASS)等可靠性加速试验技术进行了研究。阐述了不同类型的可靠性加速试验技术在产品全生命周期内的适用阶段及其应用特点,并将可靠性加速试验与传统可靠性模拟试验技术进行了对比。对比结果表明,可靠性加速试验技术已经发展为产品寿命与可靠性评估的新途径,为高可靠性、小子样、长寿命、零失效产品的可靠性评估提供了有效方法,解决了传统可靠性模拟试验技术难以暴露产品设计缺陷和薄弱环节的问题。指出可靠性加速试验技术的应用前景以及未来方向。该研究有利于加强对可靠性加速试验技术的深入理解,以及推进该技术的长久发展。     

开关电源加速贮存寿命方法研究

开关电源具有体积小、重量轻、效率高等诸多优点,凭借其自身的诸多优势,开关电源已经广泛应用于航空航天、通信、以及电子类。由于应用领域的广泛性,开关电源的可靠性引起了人们的重视。论文以阿伦尼斯(Arrhenius)模型为基础,设计了一整套针对开关电源的可靠性评价和寿命预计的试验方案。该方案对试验器件施加温度应力,加速器件的失效过程,并通过一定的加速模型和统计分析方法,外推出正常工作条件下产品的寿命特征。     

Relative Loss Bounds for On-Line Density Estimation with the Exponential Family of Distributions

We consider on-line density estimation with a parameterized density from the exponential family. The on-line algorithm receives one example at a time and maintains a parameter that is essentially an average of the past examples. After receiving an example the algorithm incurs a loss, which is the negative log-likelihood of the example with respect to the current parameter of the algorithm. An off-line algorithm can choose the best parameter based on all the examples. We prove bounds on the additional total loss of the on-line algorithm over the total loss of the best off-line parameter. These relative loss bounds hold for an arbitrary sequence of examples. The goal is to design algorithms with the best possible relative loss bounds. We use a Bregman divergence to derive and analyze each algorithm. These divergences are relative entropies between two exponential distributions. We also use our methods to prove relative loss bounds for linear regression.     

生活方式发展趋势导向下的设计探讨

设计的最终目标是为了人本身。每一个人都用他们特定的和群体性的方式在社会中生活,因此从人们生活方式的角度来看待设计,通过分析生活方式的未来发展趋势来指导具体设计无疑将有十分重要的意义。在当前信息化时代,人与人、人与物或环境间的联系需要高效准确地实现信息的交流互换,所以以信息为出发点进行设计,就不仅仅是设计发展的一种可能,而是现实的必要要求。     

混合驱动精压机的优化设计和运动仿真

提出了用于精压的混合驱动精压机的机构构型 ,并对其进行正运动学分析 ;建立了混合驱动精压机优化设计的数学模型和方法 首先优化综合机构的几何参数 ,再用B啨ｚｉｅｒ曲线优化伺服电机的运动规律 ,从而可使滑块的输出运动为一组较理想的轨迹 ,并通过仿真结果分析了混合驱动精压机的优点     

多效蒸发系统优化设计目标函数的建立与求解

建立了带有冷凝水闪蒸的并流多效蒸发系统优化设计新模型。该模型以整个蒸发系统的年总费用（包括加热蒸汽年费用、真空系统年费用以及蒸发器和各辅助设备的年折旧维修费用等）最小为优化目标,以生蒸汽压力、冷凝器真空度及各效有效传热温度痉为决策变量,提出一种新算法——复合形法嵌套拉格朗日乘子法和矩阵法求最优解。算例表明,生蒸汽压力、冷凝器真空度、价格参数和冷凝水闪蒸对优化结果影响显著,按新模型优化设计比常规设计可节省年费用16％左右。新算法对初值要求不高、收敛稳定性好、收敛速度快。     

含离散和分布时变时延神经网络系统的指数稳定性

针对一类含有离散和分布时延神经网络,在神经激活函数较弱的约束条件下,通过定义一个更具一般性的Lyapunov泛函,使用凸组合技术,得到了新的基于线性矩阵不等式表示的指数稳定性判据.与现有结果相比,这些判据具有较小的保守性.仿真算例表明,得到的结果是有效的且保守性小.     

支持自主创建考试科目的考试系统设计与实现

支持自主创建考试科目的考试系统是工作于Internet或Intranet环境下,实现不同科目的教师共同拥有与应用的考试系统.将从组成系统的多个功能模块:自主创建考试科目、动态随机出题、考试时间锁定、系统自动判卷、计算机"死机"问题应对、考试信息管理对该考试系统进行设计并最终实现.     

汽车转向传动轴扭转疲劳寿命试验台设计

针对汽车转向传动轴扭转疲劳寿命的测试,设计了基于PIC16F877单片机的试验台,给出了具体的试验方法,在传动轴与方向盘联接的一端,利用步进电机驱动传动轴,模拟方向盘正反方向的转动,传动轴另外一端,由程控电源控制磁粉制动器,产生扭转负载,与磁粉制动器串联安装有扭矩传感器,能对试验负载进行检测反馈,单片机与程控电源通过串口通信,能自动调节程控电源输出的电流大小,从而使磁粉制动器输出的扭矩负载恒定;该系统测试数据准确,具有试验次数记忆和故障报警功能,成本低,具有实用价值。     

On SAT instance classes and a method for reliable performance experiments with SAT solvers

A recent series of experiments with a group of state-of-the-art SAT solvers and several well-defined classes of problem instances reports statistically significant performance variability for the solvers. A systematic analysis of the observed performance data, all openly archived on the Web, reveals distributions which we classify into three broad categories: (1) readily characterized with a simple ²-test, (2) requiring more in-depth analysis by a statistician, (3) incomplete, due to time-out limit reached by specific solvers. The first category includes two well-known distributions: normal and exponential; we use simple first-order criteria to decide the second category and label the distributions as near-normal, near-exponential and heavy-tail. We expect that good models for some if not most of these may be found with parameters that fit either generalized gamma, Weibull, or Pareto distributions. Our experiments show that most SAT solvers exhibit either normal or exponential distribution of execution time (runtime) on many equivalence classes of problem instances. This finding suggests that the basic mathematical framework for these experiments may well be the same as the one used to test the reliability or lifetime of hardware components such as lightbulbs, A/C units, etc. A batch of N replicated hardware components represents an equivalence class of N problem instances in SAT, a controlled operating environment A represents a SAT solver A, and the survival function (where x represents the lifetime) is the complement of the solvability function where x may represent runtime, implications, backtracks, etc. As demonstrated in the paper, a set of unrelated benchmarks or randomly generated SAT instances available today cannot measure the performance of SAT solvers reliably — there is no control on their hardness. However, equivalence class instances as defined in this paper are, in effect, replicated instances of a specific reference instance. The proposed method not only provides a common platform for a systematic study and a reliable improvement of deterministic and stochastic SAT solvers alike but also supports the introduction and validation of new problem instance classes.     

On SAT instance classes and a method for reliable performance experiments with SAT solvers

A recent series of experiments with a group of state-of-the-art SAT solvers and several well-defined classes of problem instances reports statistically significant performance variability for the solvers. A systematic analysis of the observed performance data, all openly archived on the Web, reveals distributions which we classify into three broad categories: (1) readily characterized with a simple ²-test, (2) requiring more in-depth analysis by a statistician, (3) incomplete, due to time-out limit reached by specific solvers. The first category includes two well-known distributions: normal and exponential; we use simple first-order criteria to decide the second category and label the distributions as near-normal, near-exponential and heavy-tail. We expect that good models for some if not most of these may be found with parameters that fit either generalized gamma, Weibull, or Pareto distributions. Our experiments show that most SAT solvers exhibit either normal or exponential distribution of execution time (runtime) on many equivalence classes of problem instances. This finding suggests that the basic mathematical framework for these experiments may well be the same as the one used to test the reliability or lifetime of hardware components such as lightbulbs, A/C units, etc. A batch of N replicated hardware components represents an equivalence class of N problem instances in SAT, a controlled operating environment A represents a SAT solver A, and the survival function R ^A (x) (where x represents the lifetime) is the complement of the solvability function S ^A (x)=1–R ^A (x) where x may represent runtime, implications, backtracks, etc. As demonstrated in the paper, a set of unrelated benchmarks or randomly generated SAT instances available today cannot measure the performance of SAT solvers reliably – there is no control on their 'hardness'. However, equivalence class instances as defined in this paper are, in effect, replicated instances of a specific reference instance. The proposed method not only provides a common platform for a systematic study and a reliable improvement of deterministic and stochastic SAT solvers alike but also supports the introduction and validation of new problem instance classes.