A Generalized Class of Ratio Type Exponential Estimators of Population Mean Under Linear Transformation of Auxiliary Variable

Recently, Shabbir and Gupta [Shabbir, J. and Gupta, S. (2011). On estimating finite population mean in simple and stratified random sampling. Communications in Statistics-Theory and Methods, 40(2), 199–212] defined a class of ratio type exponential estimators of population mean under a very specific linear transformation of auxiliary variable. In the present article, we propose a generalized class of ratio type exponential estimators of population mean in simple random sampling under a very general linear transformation of auxiliary variable. Shabbir and Gupta's [Shabbir, J. and Gupta, S. (2011). On estimating finite population mean in simple and stratified random sampling. Communications in Statistics-Theory and Methods, 40(2), 199–212] class of estimators is a particular member of our proposed class of estimators. It has been found that the optimal estimator of our proposed generalized class of estimators is always more efficient than almost all the existing estimators defined under the same situations. Moreover, in comparison to a few existing estimators, our proposed estimator becomes more efficient under some simple conditions. Theoretical results obtained in the article have been verified by taking a numerical illustration. Finally, a simulation study has been carried out to see the relative performance of our proposed estimator with respect to some existing estimators which are less efficient under certain conditions as compared to the proposed estimator.     

On the moment generating functions for integer valued random variables

Abstract

In this note, we give explicit expressions of moment generating functions for integer valued random variables in both univariate and multivariate cases, which extend the results obtained by Nadarajah and Mitov [Communications in Statistics–Theory and Methods, 32, 2003, 47–60] and more recently by Chakraborti, Jardim and Epprecht [The American Statistician, 2017], Kwong and Nadarajah [Communications in Statistics–Theory and Methods, 2017]. Some examples are also discussed.     

变截面压杆的临界荷载计算

变截面杆件的临界载荷问题，其平衡方程为变系数微分方程，只有少部分的情况可以得到其解析解，采用改进的WBK法,计算了若干变截面压杆的临界荷载，并与有限差分法进行了对比，证实了其可靠性。     

基于变量轮换法的支持向量机在隧道围岩变形预测中的应用

采用变量轮换法对支持向量机(SVM)参数进行优化处理，结合时间序列分析理论，建立起隧道围岩变形时间序列非线性模型，并以此对隧道围岩变形进行预测。结果表明：改进的支持向量机具有简单、方便、实时等特点，对围岩后续变形预报准确，可科学地指导现场监测和施工建设。     

Using quantile averages in matched observational studies

In two observational studies, one investigating the effects of minimum wage laws on employment and the other of the effects of exposures to lead, an estimated treatment effect's sensitivity to hidden bias is examined. The estimate uses the combined quantile averages that were introduced in 1981 by B. M. Brown as simple, efficient, robust estimates of location admitting both exact and approximate confidence intervals and significance tests. Closely related to Gastwirth's estimate and Tukey's trimean, the combined quantile average has asymptotic efficiency for normal data that is comparable with that of a 15% trimmed mean, and higher efficiency than the trimean, but it has resistance to extreme observations or breakdown comparable with that of the trimean and better than the 15% trimmed mean. Combined quantile averages provide consistent estimates of an additive treatment effect in a matched randomized experiment. Sensitivity analyses are discussed for combined quantile averages when used in a matched observational study in which treatments are not randomly assigned. In a sensitivity analysis in an observational study, subjects are assumed to differ with respect to an unobserved covariate that was not adequately controlled by the matching, so that treatments are assigned within pairs with probabilities that are unequal and unknown. The sensitivity analysis proposed here uses significance levels, point estimates and confidence intervals based on combined quantile averages and examines how these inferences change under a range of assumptions about biases due to an unobserved covariate. The procedures are applied in the studies of minimum wage laws and exposures to lead. The first example is also used to illustrate sensitivity analysis with an instrumental variable.     

MRP系统应用中的技术问题及改进方案

针对MRP系统的应用现状,指出MRP系统是结合企业实际,对生产中的各项资源进行计划与控制,并结合有关生产职能所形成的一个综合性的生产信息系统。从变型产品、安全库存、生产提前期、批量几个方面分析了企业在实施MRP系统中存在的主要问题,并提出了修正实施MRP的方案对策,以充分发挥MRP的全部功能和作用。     

一类可积的变系数线性微分方程

利用变换的方法,给出了二阶、三阶、四阶变系数线性微分方程可积的一个充分条件.     

机床主轴的无穷大刚度设计

本文探讨传动齿轮位置对机床主轴端部刚度的影响,导出了无穷大刚度设计点存在的条件给出了无穷大刚度设计的方法和程序,并给出了具体算例。     

碳纤维布提高钢筋混凝土梁刚度的试验研究与计算

通过试验研究了粘贴碳纤维布对钢筋混凝土梁刚度的提高作用,在此基础上提出了粘贴碳纤维布后混凝土梁刚度的实用计算模式,计算结果和试验结果吻合,可供设计参考.     

成本计算法比较研究

制造成本法是我国现行有关会计制度规定的企业计算成本的方法,但在实际中,企业为了加强内部管理或适应成本管理的需要,也采用完全成本法和变动成本法计算成本。制造成本法、完全成本法和变动成本法因其各自的特点、使用对象和范围的不同,可从不同的角度满足企业成本计算和成本管理的需要。