Level Set方法在自由面流动数值模拟中的应用

采用建立在固定的交错网格上隐式追踪界面的LevelSet方法来计算有自由面的流动问题.在计算中求解了两种互不相溶流体的N S方程.所参考的算例是瞬时溃坝问题,计算结果和实验观测基本符合,表明Lev elSet方法在液体自由面数值模拟中具有一定的适用性.     

经理层持股与上市公司经营绩效相互作用机制研究

不同于以往研究单纯强调经理人员持股对企业绩效的影响,以沪深两市3 70家上市公司为对象,对经理持股与企业绩效的相互作用机制进行了研究。研究表明:我国上市公司不存在持股与企业绩效相互作用的现象,经理持股水平不会对企业绩效产生影响,企业绩效也不是确定经理持股水平的依据;企业规模越大、负债水平越高以及董事长兼任总经理都会带来企业价值的降低,成长能力越强、上市时间越长有利于企业价值的提高;经理持股水平受公司所处行业的影响,而对企业规模、资产结构、自由现金流以及控股股东所有权属性等企业特征变量关注不够。     

全微分求偏导法和比较系数方法的同一性

给出了全微分求偏导法的证明,指出了比较系数法和全微分求偏导方法的同一性,并且给出了具体的例子.     

一类微分差分方程解的有界性和指数稳定性

通过构造函数和利用推广的Halanay一维时滞微分不等式,研究一类中立型微分差分方程解的有界性和零解的全局指数稳定性,给出其判定的充分性条件.     

抛物线扩散模型的实证研究

资产收益分布具有高峰厚尾、有偏性以及波动集聚性．为了反映这些经验特征，Bibby和Sorensen于1997年提出了抛物线扩散过程来描述资产收益的分布．作者运用抛物线扩散模型来研究中国股市的股指收益分布．     

正负系数中立型时滞微分方程有界正解的存在性

考虑正负系数中立型时滞微分方程（x（t）-P（t）x（t-τ））'＋Q（t）x（t-σ）－R（t）x（t-γ）＝0（*）本文获得了方程（*）存在有界正解的充分必要条件，本文结果回答了文献[1]中的公开问题3。     

双机TDOA/DD无源定位方法

利用辐射源信号到达两架飞机的时差(TDOA)与微分多普勒(DD)的组合TDOA/DD对该辐射源进行无源定位,给出了定位算法,推导了定位误差解析表达式。按等时差与等微分多普勒曲线表达式绘制了双机TDOA/DD定位的双曲线与微分多普勒曲线。用定位误差解析表达式,对TDOA/DD定位与测向定位的误差进行了分析和对比,显示了TDOA/DD定位方法的优良性能。     

The formation and outcomes of cohabiting and marital partnerships in early adulthood: the role of previous partnership experience

Summary.  We estimate a joint model of the formation and dissolution of cohabiting and marital unions among British women who were born in 1970. The focus of the analysis is the effect of previous cohabitation and marriage on subsequent partnership transitions. We use a multilevel simultaneous equations event history model to allow for residual correlation between the hazards of moving from an unpartnered state into cohabitation or marriage, converting a cohabiting union into marriage and dissolution of either form of union. A simultaneous modelling approach allows for the joint determination of these transitions, which may otherwise bias estimates of the effects of previous partnership outcomes on later transitions.     

Estimation in multitype epidemics

A multitype epidemic model is analysed assuming proportionate mixing between types. Estimation procedures for the susceptibilities and infectivities are derived for three sets of data: complete data, meaning that the whole epidemic process is observed continuously; the removal processes are observed continuously; only the final state is observed. Under the assumption of a major outbreak in a population of size n it is shown that, for all three data sets, the susceptibility estimators are always efficient, i.e. consistent with a √ n rate of convergence. The infectivity estimators are 'in most cases' respectively efficient, efficient and unidentifiable. However, if some susceptibilities are equal then the corresponding infectivity estimators are respectively barely consistent (√log( n ) rate of convergence), not consistent and unidentifiable. The estimators are applied to simulated data.     

一类一阶非线性微分方程的可积判据

提出一类更一般的一阶非线性常微分方程，论证它的可积性，给出其通解的参数形式，推广了相应文献的结论。