Bounded risk estimation of a linear combination of location parameters in negative exponential distributions via three-stage sampling

The paper deals with the problem of bounded risk point estimation for a linear combination of location parameters of two negative exponential distributions. Isogai and Futschik considered the situation when the location and scale parameters are all unknown. They proposed purely sequential procedures and gave second order expansions of the average sample sizes and risks. In this paper we propose three-stage procedures and derive second order expansions of the average sample sizes and risks. Further, we compare the results with those from previous work.     

A general class of non parametric tests for comparing scale parameters

In this paper, a general class of non parametric tests is proposed for the two-sample scale problem. Testing of the scale parameter is very useful in real-life situations commonly faced in engineering, trade, cultivation, industries, medicine, etc. In all these fields, one will prefer the method that gives more consistent results. Thus, it is worthwhile to test the equality of scale parameters. The distribution of the proposed test is established. To assess the performance of the proposed test, the asymptotic efficacies are studied for some underlying distributions and the results are interpreted with useful information. To see the working of the proposed test, an illustrative example for the real-life data set is provided. The simulation study is also carried out to find the asymptotic power of the proposed test. An extension of the general class of tests to the multiple-sample problem is also discussed.     

Asymptotic distributions in affiliation networks with an increasing sequence

A central limit theorem for a linear combination of all the maximum likelihood estimators with an increasing dimension for affiliation networks has been established. Simulation studies are provided to illustrate the asymptotic results.     

Multivariate normal estimation: the case (n < p)

Estimation in the multivariate context when the number of observations available is less than the number of variables is a classical theoretical problem. In order to ensure estimability, one has to assume certain constraints on the parameters. A method for maximum likelihood estimation under constraints is proposed to solve this problem. Even in the extreme case where only a single multivariate observation is available, this may provide a feasible solution. It simultaneously provides a simple, straightforward methodology to allow for specific structures within and between covariance matrices of several populations. This methodology yields exact maximum likelihood estimates.     

Conditional design of the EWMA median chart with estimated parameters

The exponentially weighted moving average (EWMA) chart is often designed assuming the process parameters are known. In practice, the parameters are rarely known and need to be estimated from Phase I samples. Different Phase I samples are used when practitioners construct their own control chart's limits, which leads to the “Phase I between-practitioners” variability in the in-control average run length (ARL) of control charts. The standard deviation of the ARL (SDARL) is a good alternative to quantify this variability in control charts. Based on the SDARL metric, the performance of the EWMA median chart with estimated parameters is investigated in this paper. Some recommendations are given based on the SDARL metric. The results show that the EWMA median chart requires a much larger amount of Phase I data in order to reduce the variation in the in-control ARL up to a reasonable level. Due to the limitation of the amount of the Phase I data, the suggested EWMA median chart is designed with the bootstrap method which provides a good balance between the in-control and out-of-control ARL values.     

重载铁路圆柱形桥墩横向振动试验研究

随着我国既有铁路扩能运输的实施,运营列车的轴重以及载运量逐步增加给圆柱形桥墩带来了越来越严重影响,如墩顶横向振幅过大、冲击振动加剧等,严重影响了铁路桥梁的安全运营。以朔黄铁路圆柱形桥墩为研究对象,理论结合试验分析其加固前后在列车荷载增大的情况下桥墩的横向动力特性,研究不同运营列车作用下桥墩横向振动的规律,评价分析该圆柱形桥墩加固效果,为重载铁路圆柱形桥墩的加固研究和维护管理提供科学依据。     

参数自适应模糊控制的自动送钻技术研究

针对传统送钻方式的不足及钻井过程复杂、数学模型难建立等特点,在简要分析交流变频自动送钻系统的工作原理和影响送钻的各因素之间关系后,提出将参数自调整模糊控制与交流变频恒钻压自动送钻相结合。通过对钻压趋势的判断,采用参数自调整模糊PI 控制,实现对送钻电机转速的控制。该算法不需要精确的数学模型,可通过自学习实时修正控制参数。试验表明：控制效果良好,在保证恒钻压的基础上,可实现稳速送钻,提高了系统调节的快速性、自适应性和鲁棒性,精度高,现场应用证实此算法控制效果优越,可实现送钻稳态精度在±0.5 t 之内,而且送钻更加平稳,控制算法亦具有通用性。     

基于扭转振动的多步态移动装置的运动学建模

为了实现移动机器人多步态稳定运动,提出一种新型的利用自身的结构特性来设计移动装置的方法。通过对其 倒立的U型结构的设计,再分别对该移动装置滑、走、跑和跳4个步态进行运动学建模,最后利用ADAMS仿真实现了该 移动装置稳定的多步态的运动。然后根据仿真结果给出了各运动相在每个步态周期中的足地接触距离以及横梁质心位 移的变化情况,最后讨论了影响该移动装置多步态运动的因素,如机体与两腿的长度之比r、共振频率和电机转速等。 结果表明该移动装置实现了多步态的运动,对未来研究多步态移动机器人提供了理论基础。     

Estimating ordered quantiles of two exponential populations with a common minimum guarantee time

The problem of estimating ordered quantiles of two exponential populations is considered, assuming equality of location parameters (minimum guarantee times), using the quadratic loss function. Under order restrictions, we propose new estimators which are the isotonized version of the MLEs, call it, restricted MLE. A sufficient condition for improving equivariant estimators is derived under order restrictions on the quantiles. Consequently, estimators improving upon the old estimators have been derived. A detailed numerical study has been done to evaluate the performance of proposed estimators using the Monte-Carlo simulation method and recommendations have been made for the use of the estimators.     

Approximate jackknife empirical likelihood method for estimating equations

It is known that the profile empirical likelihood method based on estimating equations is computationally intensive when the number of nuisance parameters is large. Recently, Li, Peng, & Qi (2011) proposed a jackknife empirical likelihood method for constructing confidence regions for the parameters of interest by estimating the nuisance parameters separately. However, when the estimators for the nuisance parameters have no explicit formula, the computation of the jackknife empirical likelihood method is still intensive. In this paper, an approximate jackknife empirical likelihood method is proposed to reduce the computation in the jackknife empirical likelihood method when the nuisance parameters cannot be estimated explicitly. A simulation study confirms the advantage of the new method. The Canadian Journal of Statistics 40: 110–123; 2012 © 2012 Statistical Society of Canada