几何参数对空心楼板刚度的影响研究

本文采用ANSYS软件,以肋宽、肋高、底板和顶板厚度等构造参数为变量建立了系列有限元模型,分析研究了这些参数对现浇混凝土空心楼板刚度的影响大小和规律。为空心楼板的设计提供参考。     

兰尖铁矿无底柱分段崩落法结构参数研究与确定

本文对兰尖铁矿无底柱分段崩落法结构参数的选择进行了研究分析,指出了参数选择的依据,对其它类似矿山选择结构参数提供了参考。     

On Families of Distributions with Shape Parameters

Univariate continuous distributions are one of the fundamental components on which statistical modelling, ancient and modern, frequentist and Bayesian, multi‐dimensional and complex, is based. In this article, I review and compare some of the main general techniques for providing families of typically unimodal distributions on with one or two, or possibly even three, shape parameters, controlling skewness and/or tailweight, in addition to their all‐important location and scale parameters. One important and useful family is comprised of the ‘skew‐symmetric’ distributions brought to prominence by Azzalini. As these are covered in considerable detail elsewhere in the literature, I focus more on their complements and competitors. Principal among these are distributions formed by transforming random variables, by what I call ‘transformation of scale’—including two‐piece distributions—and by probability integral transformation of non‐uniform random variables. I also treat briefly the issues of multi‐variate extension, of distributions on subsets of and of distributions on the circle. The review and comparison is not comprehensive, necessarily being selective and therefore somewhat personal. © 2014 The Authors. International Statistical Review © 2014 International Statistical Institute     

Unconditional tests for association in 2 × 2 contingency tables in the total sum fixed design

The asymptotic approach and Fisher's exact approach have often been used for testing the association between two dichotomous variables. The asymptotic approach may be appropriate to use in large samples but is often criticized for being associated with unacceptable high actual type I error rates for small to medium sample sizes. Fisher's exact approach suffers from conservative type I error rates and low power. For these reasons, a number of exact unconditional approaches have been proposed, which have been seen to be generally more powerful than exact conditional counterparts. We consider the traditional unconditional approach based on maximization and compare it to our presented approach, which is based on estimation and maximization. We extend the unconditional approach based on estimation and maximization to designs with the total sum fixed. The procedures based on the Pearson chi‐square, Yates's corrected, and likelihood ratio test statistics are evaluated with regard to actual type I error rates and powers. A real example is used to illustrate the various testing procedures. The unconditional approach based on estimation and maximization performs well, having an actual level much closer to the nominal level. The Pearson chi‐square and likelihood ratio test statistics work well with this efficient unconditional approach. This approach is generally more powerful than the other p‐value calculation methods in the scenarios considered.     

用PKPM系列程序优化分析高层结构的几点体会

介绍了作者应用PKPM系列的程序,在高层建筑结构设计计算中的体会,其中对若干抗震设计的控制参数的含义、电算分析与调整操作作了介绍,包括:位移比、周期比、侧刚比、受剪承载力比、剪重比、刚重比、层间位移角以及各种参数的调整等方面。供结构设计工程师参考。     

Bayesian robustness modelling using the O‐regularly varying distributions

The theory of robustness modelling is essentially based on heavy‐tailed distributions, because longer tails are more prepared to deal with diverse information (such as outliers) because of the higher probabilities on the tails. There are many classes of distributions that can be regarded as heavy tails; some of them have interesting properties and are not explored in statistics. In the present work, we propose a robustness modelling approach based on the O‐regularly varying class (ORV), which is a generalization of the regular variation family; however, the ORV class allows more flexible tails behaviour, which can improve the way in which the outlying information is discarded by the model. We establish sufficient conditions in the location and in the scale parameter structures, which allow to resolve automatically the conflicts of information. We also provide a procedure for generating new distributions within the ORV class.     

Forecasting extreme financial risk: A score-driven approach

This paper develops a new class of dynamic models for forecasting extreme financial risk. This class of models is driven by the score of the conditional distribution with respect to both the duration between extreme events and the magnitude of these events. It is shown that the models are a feasible method for modeling the time-varying arrival intensity and magnitude of extreme events. It is also demonstrated how exogenous variables such as realized measures of volatility can easily be incorporated. An empirical analysis based on a set of major equity indices shows that both the arrival intensity and the size of extreme events vary greatly during times of market turmoil. The proposed framework performs well relative to competing approaches in forecasting extreme tail risk measures.     

截面形状对洞库内爆冲击波流场影响的数值模拟研究

运用LS-DYNA动力有限元软件,采用ALE及多物质流固耦合方法,对截面面积相等而形状不同的弹药洞库内部爆炸冲击波流场进行了数值模拟研究。结果表明,截面面积相同而形状不同的2个洞库在炸药轴线上对应点的冲击波压力基本相同。     

稻壳循环流化燃烧热风炉的研究与开发

本文介绍了稻壳热风炉的结构特点及普遍存在的问题.根据稻壳燃烧特性,采用循环流化床燃烧技术,开发了稻壳循环流化燃烧热风炉,分析了其燃烧原理及结构特点,能够较好的解决稻壳挥发分迅速析出、固定碳难以燃尽的特点,克服炉排式燃烧效率低的弊端.     

优化参数对CPM-PSWF信号性能的影响

基于椭圆球面波信号的连续相位调制（Continuous Phase Modulation Based on Prolate Spheroidal Wave Function,CPM-PSWF）方法是一种新颖的数字调制方式,调制参数的优化与其调制信号性能有着直接联系。分析不同调制参数对CPM-PSWF信号性能的影响,优化选择调制参数,对获得能量聚集性和功率效率都较高的CPM信号具有重要意义。首先,对基于椭圆球面波信号的CPM信号进行描述;其次,采用韦尔奇(Welch)谱密度估计法,对时间带宽积、调制指数、关联长度等不同参数对CPM-PSWF调制信号的功率谱密度和带宽特性的影响进行了仿真分析。实验结果表明,选用0阶椭圆球面波信号,小时间带宽积、调制指数和符号进制数越小,关联长度越大时,CPM-PSWF信号具有频谱带外高频滚降快、占用带宽小的特点。