Comparison of the several parameterized estimators for the positive extreme value index

In the paper we compare several parameterized estimators for the positive extreme value index, which is a very important parameter appearing in the estimation of the probability of rare events. Firstly, asymptotic comparison at optimal levels of the corresponding tail index estimators is performed. Secondly, the practical validation of asymptotic results for moderate finite samples is done by means of Monte-Carlo simulations. We demonstrate that theoretical domination of the positive extreme value index estimators, which are asymptotically normal with a null asymptotic bias, is not reflected in Monte-Carlo simulations. Moreover, the estimators of such type do not demonstrate stability in the sense of empirical mean-squared error.     

模切机传纸机构驱动凸轮参数化设计

运用MATLAB强大的可视化编程功能,针对模切机传纸机构中的关键零件—凸轮进行了参数化设计计算,得到了驱动递纸牙按照规定的轨迹运动的2个凸轮轮廓轨迹曲线,并检验了凸轮压力角,以验证传纸机构的合理性。当需要进行机构的某方面调整时,可以利用修改凸轮个别参数从而非常方便的进行更新,大大提高了机构设计的调整适应性,提高了快速设计产品的进程。     

A multi-city epidemic model

Some analytical results are given for a model that describes the propagation of a disease in a population of individuals who travel between n cities. The model is formulated as a system of 2n 2 ordinary differential equations, with terms accounting for disease transmission, recovery, birth, death, and travel between cities. The mobility component is represented as a directed graph with cities as vertices and arcs determined by outgoing (or return) travel. An explicit formula that can be used to compute the basic reproduction number, {\cal R}_0 , is obtained, and explicit bounds on {\cal R}_0 are determined in the case of homogeneous contacts between individuals within each city. Numerical simulations indicate that {\cal R}_0 is a sharp threshold, with the disease dying out if {\cal R}_0 1 .     

The generalized exponential family of distributions and its characteristics

In this paper we generalize the exponential family (EF) of distributions into a wider family which includes important distributions such as the normal, log-normal, Student-t, Cauchy, logistic and Birnbaum–Saunders distributions. Furthermore, we derive several characteristics of the proposed family. The importance of such family is also discussed.     

面向对象的参数化CAD二次开发方法研究

通用CAD系统采用开放式结构体系,提供相应的二次开发手段和方法。研究了面向对象的参数化二次开发技术及方法,以期为CAD的二次开发提供指导,并以Pro/Engineer为软件平台,利用其二次开发工具Pro/Toolkit,实现了面向对象技术在参数化设计二次开发中的应用。