背景、问题与思考——全球化时代面对英语扩散的我国的语言规划

目前,我国语言规划中面临着汉、英语言之间的不公平问题。在全球化时代和英语扩散的背景下,如何看待汉语和英语的关系、我国语言规划的模式、我国语言规划的目标以及如何实现这一目标等问题,是关涉民族语言生存发展的大问题。本文尝试性地提出了“语言友好型社会”、“语言战略管理”的概念。     

Estimation in Discretely Observed Diffusions Killed at a Threshold

Abstract. Parameter estimation in diffusion processes from discrete observations up to a first‐passage time is clearly of practical relevance, but does not seem to have been studied so far. In neuroscience, many models for the membrane potential evolution involve the presence of an upper threshold. Data are modelled as discretely observed diffusions which are killed when the threshold is reached. Statistical inference is often based on a misspecified likelihood ignoring the presence of the threshold causing severe bias, e.g. the bias incurred in the drift parameters of the Ornstein–Uhlenbeck model for biological relevant parameters can be up to 25–100 per cent. We compute or approximate the likelihood function of the killed process. When estimating from a single trajectory, considerable bias may still be present, and the distribution of the estimates can be heavily skewed and with a huge variance. Parametric bootstrap is effective in correcting the bias. Standard asymptotic results do not apply, but consistency and asymptotic normality may be recovered when multiple trajectories are observed, if the mean first‐passage time through the threshold is finite. Numerical examples illustrate the results and an experimental data set of intracellular recordings of the membrane potential of a motoneuron is analysed.     

Moderate Deviation for Parameter Estimation in the Rayleigh Diffusion Process

In this article, we study moderate deviation for parameter estimation in the Rayleigh diffusion process and obtain the moderate deviation principle of the maximum likelihood estimator with explicit rate function.     

Efficiency of a Class of Unbiased Estimators for the Invariant Distribution Function of a Diffusion Process

We consider the problem of the estimation of the invariant distribution function of an ergodic diffusion process when the drift coefficient is unknown. The empirical distribution function is a natural estimator which is unbiased, uniformly consistent and efficient in different metrics. Here we study the properties of optimality for another kind of estimator recently proposed. We consider a class of unbiased estimators and we show that they are also efficient in the sense that their asymptotic risk, defined as the integrated mean square error, attains the same asymptotic minimax lower bound of the empirical distribution function.     

Computational Aspects Related to Martingale Estimating Functions for a Discretely Observed Diffusion

Martingale estimating functions for a discretely observed diffusion have turned out to provide estimators with nice asymptotic properties. However, their expression usually involves some conditional expectation that has to be evaluated through Monte Carlo simulations giving rise to an approximated estimator. In this work we study, for ergodic models, the asymptotic properties of the approximated estimator and describe the influence of the number of independent simulated trajectories involved in the Monte Carlo method as well as of the approximation scheme used. Our results are of practical relevance to assess the implementation of martingale estimating functions for discretely observed diffusions.     

长江上游特旱特涝年夏季风特征的分析

本文采用700百帕、500百帕上的假相当位温θse和温度露点差(t—td)的候平均演变曲线,反映出长江上游地区夏季风的变化,并对比分析了长江上游特旱的1972年和特涝的1974年的夏季风活动规律,表明干旱年受夏季风影响的时间短于洪涝年。通过500百帕上的候平均θse值,构造了一个表征当年夏季风特征的夏季风的综合指数Icsm,分析结果表明,该指数能反映出夏季风到达迟早、持续时间及强度等特征,为长江上游的旱涝预报提供了一个依据。     

The effect of individual variability on the life table

A general formulation of the life table in the presence of individual jeterogeneity is presented. The possible effects of heterogeneity on the various life table functions are outlined. For the case of ordinary life tables, a method is presented for the evaluation of these effects. The proposed method id illustrated by a numerical example.     

Estimation of Diffusion Processes by Simulated Moment Methods

We consider the parameter estimation of a diffusion process and we suppose that the trend and the diffusion coefficient depend on the parameter θ. The process is observed at time ( t_i ) _{i =0,..., n} with Δ = t_{i +1}− t_i fixed and we propose here to estimate θ from simulated moment methods.     

文明的汇聚与传播——古代世界文明之交流

人类的交往的过程也是不同的文化汇聚、升华的过程。西部亚洲、中部亚洲在东方与西方文化交流事业中一直扮演着"桥梁"的角色。这些"桥梁"不仅传送东方文明到西方,而且也传送西方文明到东方;同时,"桥梁"自身独特的文化对东西方文明也产生了很大的影响。就是属于"桥梁"本身的各文明之间也是互动的,从而产生了独特而灿烂的各种文化——苏美尔文化、巴比伦文化、波斯文化、希腊化文化、阿拉伯文化,等等。这说明,任何一种文明都不能封闭自守,一种文明要想永葆青春,必须积极吸收各种外来文明。如果一定要讲究文化的"纯正性",那么反而会因世世代代近亲交配而有退化淘汰之虞。今日世界在急剧地缩小,人类各文明之间的不断交往,已势必将汇合为一个共同的人类文明。