Estimators for type-II censored (log)normal samples

Three common estimators for the parameters of the log-normal distribution are evaluated for censored samples. Correction factors which eliminate essentially all the bias, and formulas for the standard deviations of the estimators, are presented. It is reported that the Persson-Rootzen estimators are about as good as the maximum-likelihood estimators, without the penalty of requiring iterative (computer) optimization. Also, the estimators resulting from (least squares) fitting a line to the plot of log lifetimes on normal (Gaussian) probability paper are reasonably good. Formulas are given for obtaining these latter estimators without actually plotting the points. The author simulated 5 k to 30 k samples (more samples for smaller N for each case) and calculated the following: the means, standard deviations, and third moments of each estimator; correlations between the two members of each pair; comparisons between the estimators; and simple corrections to improve the performance of the estimators     

Parameter estimation for a modified Weibull distribution, for progressively type-II censored samples

In this paper, the estimation of parameters based on a progressively Type-II censored sample from a modified Weibull distribution is studied. The likelihood equations, and the maximum likelihood estimators are derived. The estimators based on a least-squares fit of a multiple linear regression on a Weibull probability paper plot are compared with the MLE via Monte Carlo simulations. The observed Fisher information matrix, as well as the asymptotic variance-covariance matrix of the MLE are derived. Approximate confidence intervals for the parameters are constructed based on the s-normal approximation to the asymptotic distribution of MLE, and log-transformed MLE. The coverage probabilities of the individual s-normal-approximation confidence intervals for the parameters are examined numerically. Some recommendations are made from the results of a Monte Carlo simulation study, and a numerical example is presented to illustrate all of the methods of inference developed here.     

Goodness-of-fit tests based on spacings for progressively type-II censored data from a general location-scale distribution

There has been extensive research on goodness-of-fit procedures for testing whether or not a sample comes from a specified distribution. These goodness-of-fit tests range from graphical techniques, to tests which exploit characterization results for the specified underlying model. In this article, we propose a goodness-of-fit test for the location-scale family based on progressively Type-II censored data. The test statistic is based on sample spacings, and generalizes a test procedure proposed by Tiku . The distribution of the test statistic is shown to be approximated closely by a s-normal distribution. However, in certain situations it would be better to use simulated critical values instead of the s-normal approximation. We examine the performance of this test for the s-normal and extreme-value (Gumbel) models against different alternatives through Monte Carlo simulations. We also discuss two methods of power approximation based on s-normality, and compare the results with those obtained by simulation. Results of the simulation study for a wide range of sample sizes, censoring schemes, and different alternatives reveal that the proposed test has good power properties in detecting departures from the s-normal and Gumbel distributions. Finally, we illustrate the method proposed here using real data from a life-testing experiment. It is important to mention here that this test can be extended to multi-sample situations in a manner similar to that of Balakrishnan et al.     

Admissibility of a conditionally specified test procedure for time censored life data

A test procedure may have a sufficiently large power and size under control, but its use is not advisable unless it is admissible. In other words, the admissibility of a test procedure is a desirable property in addition to having size and power. In this paper, the necessary and sufficient conditions for the admissibility of a conditionally-specified test procedure, for testing the scale parameter called ‘average life’ in a two-parameter exponential distribution under time censoring, have been derived.     

A study of a time dependent queueing system with two parallel channels

A time dependent queueing system is studied by obtaining the probabilities of the exact number of arrivals and departures by a given time. The service is accomplished through two parallel channels, each channel having a different service rate. The marginal probability of exactly i arrivals and the mean number of i arrivals are obtained.     

多控制器并行处理的安全和起爆电路测试装置

针对现有测试技术一次上电只能完成对单发引信测试且测试过程繁琐的缺点,提出基于多控制器并行处理的安全和起爆电路测试装置.该测试装置通过一台计算机、两个单片机和温度控制器构成了多机通讯控制系统,两个单片机通过相应的电源模块、触发模块和采集模块与多发被测安全和起爆电路相连,多机间通过串口通讯方式进行信息交换,获得多发被测安全和起爆电路的各种测试数据.分析和试验表明该测试装置能够很好的完成对多发被测安全和起爆电路的测试任务,具有测试效率高、实时性强、操作方便快捷、人为误差小等特点.     

A 1 log N parallel algorithm for detecting convex hulls on imageboards

By finding the maximum and minimum of {y(i)-mx(i)|1=/相似文献   

BLUEs of location and scale parameters of laplace distribution based on type-II censored samples and associated inference

In this paper, we first present the Best Linear Unbiased Estimators (BLUEs) of the location and scale parameters, μ and σ, of the Laplace distribution based on Type-II censored samples. We next present some simulated percentage points for three pivotal quantities which will enable one to construct confidence intervals or carry out tests of hypotheses for the parameters μ and σ. Finally, we present an example to illustrate the methods of inference developed in this paper.     

基于差分压缩的大规模日志压缩系统

大型信息系统的日志数据规模呈现快速增长趋势,导致线速压缩与存储大规模日志数据成为当今数据管理的一大挑战。对大量的网络系统日志进行了研究,发现日志数据存在冗余的结构模式,在内容上存在时间局部相似性。提出了基于模板的细粒度日志差分压缩架构,针对具体日志数据,可配置与其相适应的细粒度差分策略。实验结果表明,与gzip工具相比,所提日志压缩系统在压缩速度上提高了2~10倍,压缩率比gzip更低,可达到10%。     

基于AOP技术的邮件日志系统研究

大多数软件都采用日志记录系统的关键操作,而且把日志代码与业务代码交织在一起,并散布到关键操作的业务逻辑中。本人在研发邮件服务系统的过程中,采用面向方面编程（Aspect Oriented Programming,AOP）技术将邮件日志与邮件服务的业务逻辑分离,并把日志单独作为一个模块来实现,然后使用代理的方法将日志功能与业务联接在一起,组合成一个完整的软件系统。这种设计方法增强了日志模块的独立性和可重用性,提高了系统的灵活性与可维护性。     

A novel hardware/software embedded system based on automatic censored target detection for radar systems

This paper presents a practical design exploration for a new application related to real-time, high-resolution target detection for radar systems. In this paper, an embedded architecture that combines the hardware and software components in a single platform is experienced using a field programmable gate array FPGA-based PC-board. The detection process utilises three techniques: namely, automatic censored ordered statistics detection (ACOSD), cell averaging (CA) and ordered statistics (OS) CFAR techniques, all of which operate in parallel to increase the accuracy of the detection and to reduce the false-alarm rate for both homogeneous and non-homogeneous environments. A prototype of the embedded system detector has been implemented for homogeneous and non-homogeneous environments on Stratix IV FPGA Board. The prototype operates at 200 MHz and performs real-time target detection with an execution delay of 0.27 μs, which is less than the critical time (0.5 μs) for high-resolution detection.     

基于时域特性的并行系统的采样误差估计算法

为了降低并行时间交替采样系统中通道失配误差的 硬性,利用两个标准斜波 信号的时域特性,对斜波信号多次采样,采样点减去偏置误差得到的无偏置采样值,从而求 解采样点的时间误差和增益误差联立方程,计算时间和增益误差。本文算法的采样点数和推导计算量较少,是一种快速而 精确的工程实用算法;并使用Matlab对本文算法进行模拟仿真证明其可行性,并通过Farrow 结构的滤波器对估计所得的通道失配误差进行校正验证,校正后的无杂散动态范围(SFDR,spurious free dynamic range)至少达到50dB。     

基于LabVIEW的Xe核自旋横向弛豫时间自动测试系统

核磁共振陀螺仪是基于量子调控技术的前沿研究,具有高精度、小体积、低功耗等显著优点,是未来高精度微小型陀螺的主要发展方向之一。原子气室内Xe核自旋的横向弛豫时间是衡量原子气室性能的一个重要参数,直接影响陀螺的角随机游走,准确快速地测量横向弛豫时间有利于研制性能更优的原子气室。根据推导的核自旋横向弛豫时间测量原理,基于LabVIEW软件平台设计了一种气室核自旋横向弛豫时间的自动化测试系统,实现了温度控制、氙共振频率找寻、磁场控制及数据处理存储功能。实际应用表明,采用自动化测试系统工作稳定可靠、测量效率高、测试精度高、人机交互性好,为检验核磁共振陀螺仪原子气室的性能提供了有效测试手段。     

A reliability physics model for parallel system

Reliability analysis of a nonrepairable 2-unit parallel system is carried out using the stress-strength model of failure physics. The analysis is carried out for correlated strengths and altered stress distribution depending upon the number of components surviving. The analysis includes both the cases of deterministic and random cycle times. In the case of random cycle times, Poisson distributed stress cycle occurrences have been considered. Various system characteristics, such as failure time distribution, reliability and moments of time to failure of the system, have been evaluated for both deterministic and random cycle times. Two particular cases, namely (i) bivariate exponential distribution for strength variables and univariate exponential distributions for stress variables and (ii) bivariate normal distribution for strength variables and univariate normal distributions for stress variables, have also been considered.     

A system-based component test plan for a series system, withtype-II censoring

Acceptance testing is analyzed for a series system of n components, each having an unknown, different, constant failure rate. Components are tested individually, and tests are terminated when a preassigned number of failures is observed for each component. The total time-on-test for each component is noted, and a statistic is constructed using observed test times and the number of failures of the components; the statistic is based on the maximum likelihood estimation of system reliability. This statistic is then used in specifying a decision rule for accepting or rejecting the entire system. The design of the test plan is stated as an optimization problem which minimizes test costs while ensuring that specified consumer and producer risks on system reliability are not exceeded. Numerical examples are provided, and implications of the test plan are discussed     

Estimation of average survival time of a process having an exponential lifetime model for time censored data

Censoring is almost mandatory, especially in dealing with costly sophisticated items in a life testing experiment. Assuming the survival times to be distributed exponentially with two parameters we have proposed an estimator using a preliminary test of significance for the estimation of average survival time of the time censored life data. The bias and mean square error of the proposed estimator have been studied. Based on some mathematical results and an empirical study, recommendations have been made regarding the use of proposed estimator.     

基于交友网站的日志挖掘和分析系统

针对女之海交友广场网站日志挖掘的具体需求,设计和开发了一个用于会员宣传的Web日志挖掘系统。结合自动获取的网站拓扑结构,对站点日志数据进行关联规则挖掘,以便更好地确定宣传的时间、地区、所针对的用户群年龄特征以及相应的会员信息内容等,系统实现了预期的挖掘任务和目的。     

Optimal replacement policy (N, n) for a parallel system with common cause failure and geometric repair time

The purpose of this article is to present an improved replacement model for a parallel system of N identical units, by bringing in common cause failure (CCF), maintenance cost and repair cost per unit time additionally, and to develop a procedure to obtain the optimal redundant units N^* and optimal number of repairs n^* with the conditions that the system is allowed to undergo at most a prefixed number of repairs before to be replaced and the successive reapir times after failures constitute a non-decreasing Geometric process. Several conditions for the existence of the optimal N^* and n^* is stated and the results are illustrated by a numerical example.     

基于并行计算的实时数字全息显微镜

为了实现实时数字全息显微观测,采用数字全息并行算法达到实时再现要求。首先根据设计的数字全息显微镜光路结构,充分利用图像传感器空间带宽积,通过实时记录方案采集全息图、物光强及参考光强以消除0级;然后通过设计的并行再现软件,将采集到的图像均匀分割为4个区域,交由4个进程分别同时计算,每个进程实现对应区域的全息图再现后,将每个再现结果再均分成4个区域,并将对应区域重新组合成4组数据交由4个进程分别同时进行叠加,计算相位及强度;最后将4个进程计算得到的相位、强度重新拼接成完整的再现强度及相位图。结果表明,系统的数据采集和图像再现速度达到了18frame/s。该设计系统实现了实时全息显微观测。