锥面联接的压入受力分析及其仿真

基于某设备搅拌轴上的锥面过盈联接,结合锥面角度因素和实际受力情况,建立关于压入过程中压入力和传递扭矩所需锥面间结合压力间的关系。在此基础上,使用ANSYS Workbench进行仿真,通过对锥轴施加相应的压入力,得到锥面接触面上的压力分布情况。仿真得到的结合压力与理论计算值基本吻合,也验证了锥面间结合压力与压入力之间的关系,为其实际应用提供了理论指导。     

空气锤钎头齿孔过盈配合数值模拟研究

传统方法在研究空气锤钎头齿孔过盈量问题时大都是针对单个齿孔进行的,而且对模型进行了过度简化,没有考虑钎头本体的复杂几何外形和相邻孔间应力的相互影响,无法得出整个钎头体上的应力分布。为此,分别用弹塑性力学方法和有限元方法对齿孔在不同过盈量下的应力分布情况进行了计算。结果表明,弹塑性分析与有限元分析结果一致,钎头中心齿齿孔过盈量取0.05～0.06mm、边齿齿孔过盈量取0.06～0.07mm时较合理,弹塑性力学方法的计算值比较保守,但仍有重要的参考价值。利用ANSYS软件对钎头齿孔过盈配合进行有限元计算,是改进齿孔设计的有效方法,此方法也可用来分析PDC钻头和牙轮钻头齿孔过盈配合问题。     

抛物线形断面正常水深简化解析式简

由于三次抛物线形断面正常水深求解涉及不可积分函数和超越方程计算问题,无法采用解析法完成。但通过引入二次抛物线近似积分法及优化拟合法,经逐次逼近拟合,获得了表达形式简单、计算过程简捷,实用范围广、便于工程设计人员实际应用的近似计算通式。误差分析及算例计算表明,在工程实用范围内,该算式的最大计算相对误差为0．941％,完全满足工程的设计精度要求,具有推广应用价值。     

On multiple portmanteau tests*

Abstract. The portmanteau statistic based on the first m residual autocorrelations is used for diagnostic checks on the adequacy of fitting a model with varying m. In this article, we propose an approximation of the joint probability of multiple portmanteau tests with different degrees of freedom (DF). This distribution is easy to compute when all DF are even integers; its empirical behaviour is clarified in terms of asymptotic theory.     

Akaike’s information criterion correction for the least‐squares autoregressive spectral estimator

In this article we propose a new correction for the penalty term of the Akaike’s information criterion (AIC), when it is used in the context of order selection for an autoregressive fit of the spectral density of a stationary time series. The classical AIC penalty term may be viewed as an approximation of an appropriate target quantity. Simulations show that the quality of this approximation strongly depends on the type of autoregressive estimator used, as well as on the discrepancy used. Therefore here we consider the least squares autoregressive estimator and the Whittle discrepancy only. In this context we propose a closed formula correction of the AIC penalty term. We also develop asymptotic theory which justifies this proposal: an asymptotically valid second‐order expansion of a stochastic approximation of the target quantity. This expansion assumes a non‐parametric framework: it does not assume gaussianity of the process and only requires its spectral density to be smooth enough. Simulations show that, as compared to previously introduced corrections, this new correction performs similarly to finite sample information criterion, while they both outperform AIC corrected and AIC.     

谈谈我国500kV输变电设备的技术进步与发展

述评了我国500kV输变电设备研究、制造、运行经验的水平及发展趋势，介绍了在实现引进技术国产化的基础上500kV输变电设备在电力生产和建设中发挥的作用。     

应用微机选择过盈配合

本文主要介绍程序设计中的数学模型和程序的组成；通过实例分析选择最佳配合的条件。     

PC—1500袖珍计算机拟合油脂实验数据和自动绘制拟合曲线图形的研究

运用数学方法将实验数据处理成某种数学模型,这是一切技术科学、自然科学实验的基本目标之一.本文利用PC—1500袖珍计算机对油脂实验数据进行了拟合处理和绘图输出.并分如下四个问题进行了讨论.一、拟合实验数据的最小二乘法;二、按最小二乘法拟合实验数据的BASIC语言程序;三、自动绘制拟合曲线图形的程序设计;四、拟合油脂实验数据和绘制图形的应用举例.