寻找非线性演化方程精确解的新的双曲函数法

基于齐次平衡法的思想,利用双曲函数建立了一种求解非线性偏微分方程的新的双曲函数法,其基本原理为,通过作一些特殊的变换,将非线性偏微分方程的求解问题转化为非线性超定代数方程组的求解问题,借助数学软件Mathematica,利用吴消元法等,求解此非线性超定代数方程组,最终获得非线性偏微分方程的精确孤波解.     

对双自由边界Stefan问题的进一步讨论

本文讨论了双自由边界 Stefan 问题的解对于初始条件的单调相依性,以及该解和一个Volterra 型的非线性积分方程组的等价关系。本文所得结果,是对 R.Canno,D.Hill 及 A.Friedman 相应结果的推广。     

MULTIPERIOD FORECASTING ANALYSIS OF A DYNAMIC MODEL FOR A SMALL SAMPLE

In this paper we derive the formulae for the bias and mean squared forecast error (MSFE) of the least squares forecast several periods ahead in the context of a dynamic model. Since the expressions are in terms of integrals, we have also obtained the numerical value of the bias and MSFE for different values of parameters and different disturbance structures. The results confirm some earlier studies (based on the AR(1) model), for example Lahiri (1975) and Hoque et al. (1988).     

一类半线性偏差分方程解的振动性

本文讨论了一类半线性偏差分方程解的振动性，得到了这类方程解的振动性的一些充分条件。     

Nonparametric testing for no covariate effects in conditional copulas

In dependence modelling using conditional copulas, one often imposes the working assumption that the covariate influences the conditional copula solely through the marginal distributions. This so-called (pairwise) simplifying assumption is almost standardly made in vine copula constructions. However, in recent literature evidence was provided that such an assumption might not be justified. Among the first issues is thus to test for its appropriateness. In this paper nonparametric tests for the null hypothesis of the simplifying assumption are proposed, and their asymptotic behaviours, under the null hypothesis and under some local alternatives, are established. The tests are fully nonparametric in nature: not requiring choices of copula families nor knowledge of the marginals. In a simulation study, the finite-sample size and power performances of the tests are investigated, and compared with these of the few available tests. A real data application illustrates the use of the tests.     

Vague值向Fuzzy值转化的系列方法

提出Vague值向Fuzzy值转化的系列均值法和偏值法．证明了这些方法均满足Vague值向Fuzzy值的转化准     

破解绘画色彩选择的两个障碍

在色彩写生中，能够引起人们审美愉悦、满足人们生理、心理需求的真实绘画色彩的道路上存在着许多障碍，其中“固有色观念”和“局部观察习惯”是经常碰到的易犯病。     

Incorporating heterogeneous intercourse records into time to pregnancy models

Information on the timing of intercourse relative to ovulation can be incorporated into time to pregnancy models to improve the power to detect covariate effects, to estimate the day-specific conception probabilities, and to distinguish between biological and behavioral effects on fecundability, and therefore the probability of conception in a menstrual cycle. In this paper, Bayesian methods are proposed for joint modeling of intercourse behavior and biologic fecundability. The model accommodates a sterile subpopulation of couples, general covariate effects, and heterogeneity among fecund couples in menstrual cycle viability and in frequency of unprotected intercourse. Methods are described for incorporating cycles with varying amounts of intercourse information into a single analysis. A Markov chain Monte Carlo algorithm is outlined for estimation of the posterior distributions of the unknowns. Themethods are applied to data from a North Carolina study of couples attempting pregnancy.     

中国养老制度变迁对城镇居民储蓄的影响

现收现付制和基金积累制是养老保险筹资的两种基本模式．我国目前正在推行的养老保险制度是统账结合制，在本质上是部分基金积累制。现收现付制可以实现养老金的代际转移，在支付规模小、人口负担较轻的情况下这种养老制度具有可行性，而在人口老龄化的压力下，此制度受到严重挑战，于是各国养老金制度纷纷向基金积累制过渡。本文通过实证的方法分析现收现付制与统账结合制对中国城镇居民储蓄的影响，结果显示统账结合制会使储蓄减少25％，其主要原因在于我国养老金制度变迁过程中转轨成本的消化会对城镇居民储蓄产生负作用。