基于3次样条插值的数控机床几何与热复合定位误差建模

通过分析机床整个温升直到热平衡的误差数据,总结误差分布的数学规律,将热误差和几何误差分离,运用基于压紧样条条件下的3次样条插值算法,以线性拟合后的余差为建模数据,建立了数控机床几何与热复合定位误差数学模型.实验结果表明,该数学模型能很好地拟合数控机床定位误差曲线,补偿后数控机床定位精度提高了80%以上.该方法可运用于不同时刻或不同机床温度下的机床定位误差补偿,建模原理明了、过程快速,模型适用性好.     

Privacy Quantification Model Based on the Bayes Conditional Risk in Location-Based Services

The widespread use of Location-Based Services(LBSs),which allows untrusted service providers to collect large quantities of information regarding users’locations,has raised serious privacy concerns.In response to these issues,a variety of LBS Privacy Protection Mechanisms(LPPMs)have been recently proposed.However,evaluating these LPPMs remains problematic because of the absence of a generic adversarial model for most existing privacy metrics.In particular,the relationships between these metrics have not been examined in depth under a common adversarial model,leading to a possible selection of the inappropriate metric,which runs the risk of wrongly evaluating LPPMs.In this paper,we address these issues by proposing a privacy quantification model,which is based on Bayes conditional privacy,to specify a general adversarial model.This model employs a general definition of conditional privacy regarding the adversary’s estimation error to compare the different LBS privacy metrics.Moreover,we present a theoretical analysis for specifying how to connect our metric with other popular LBS privacy metrics.We show that our privacy quantification model permits interpretation and comparison of various popular LBS privacy metrics under a common perspective.Our results contribute to a better understanding of how privacy properties can be measured,as well as to the better selection of the most appropriate metric for any given LBS application.     

WOD样本密度函数和失效率函数递归核估计的逐点强相合性

考虑同分布宽象限相依(WOD)随机样本未知密度函数的一类递归型密度核估计量.利用WOD序列的Rosenthal型不等式,在一定条件下证明了该估计量的逐点强相合性,并讨论了失效率函数估计的逐点强相合性.     

广义帕累托分布的应力-强度可靠性的贝叶斯估计

基于不同形状参数的广义帕累托分布,讨论应力-强度参数的贝叶斯估计.通过模拟得出在平方损失函数和0-1损失函数下的贝叶斯估计值比较相近;有先验信息条件下的贝叶斯估计的均方误差值低于无信息先验条件下的贝叶斯估计的均方误差值.     

估计量无偏性的证明

目前在点估计的理论和实用中 ,无偏性占据很重要的地位 ,对与同一参数的不同的点估计量 ,无偏性是对估计量最基本的要求 ,无偏估计量的证明 ,关键在于求出未知参数 θ的估计 θ的期望     

SGZ-764／400运输机减速器的改造与应用

针对SGZ-764／400运输机在井下生产运转过程中出现高速轴与闸盘经常性损坏的现象，将原减速机高速轴中的平键连接改为平键与花键连接配合使用，并针对漏油低速轴现象，采用骨架密封来封油解决漏油问题，提高了开机率和工作效率。     

Generalised Estimators for Seasonal Forecasting by Combining Grouping with Shrinkage Approaches

In this paper, generalised estimators are proposed to estimate seasonal indices for certain forms of additive and mixed seasonality. The estimators combine one of two group seasonal indices methods—Dalhart's group method and Withycombe's group method—with a shrinkage method in different ways. Optimal shrinkage parameters are derived to maximise the performance of the estimators. Then, the generalised estimators, with the optimal shrinkage parameters, are evaluated based on forecasting accuracy. Moreover, the effects of three factors are examined, namely, the length of data history, variance of random components and the number of series. Finally, a simulation experiment is conducted to support the evaluation. Copyright © 2011 John Wiley & Sons, Ltd.     

矩形花键轴的扭转强度计算和少齿数齿轮轴的扭转实验研究

首先,基于极惯性矩的概念和平面假设理论推导出了矩形花键轴横截面的极惯性矩和最大扭转切应力公式,并验证了此计算方法的准确性.其次,采用Ansys软件对矩形花键轴的扭转切应力分布规律进行了仿真研究.最后,对少齿数齿轮进行正反转扭转实验,得出了一些重要结论.     

一类两点边值问题的四次样条解法

利用四次样条函数求得一类两点边值问题的数值解。该方法将求解边值问题的数值解最终化为求解三对角线性方程组，计算较为简单。数值算例充分证明该方法比已有方法具有更高的精度。     

样条子域法在桥头搭板内力分析中的应用

对具有一边简支支承的部分悬空，部分支承在温克勒弹怀地基上的板作为整体式桥头搭板的力学计算模型，采用样条子域法建立了桥头搭板内力计算的基本公式，并编制了计算程序。