论经济发展中的金融效率

金融是现代市场经济的核心,金融运行的效率状况对经济社会的健康发展,具有十分重要的意义。当前,我国的金融效率还不十分理想。借鉴西方金融效率理论,通过深化金融体制改革,提高金融机构和金融市场的运行效率,高效合理地配置和使用有限的金融资源,以最大限度地发挥金融对经济的促进作用是我们在实践中迫切需要解决的问题。     

利用情感因素提高英语教学效果

在英语教学中,认知因素固然重要,但情感因素对学习者的影响和作用也不可忽视。积极的情感因素可以激发学生的学习兴趣,从而提高学习成绩。因此,调动学生积极的情感因素以激发其学习动机、促进学习进程是十分重要的。     

Real nonparametric regression using complex wavelets

Summary.  Wavelet shrinkage is an effective nonparametric regression technique, especially when the underlying curve has irregular features such as spikes or discontinuities. The basic idea is simple: take the discrete wavelet transform of data consisting of a signal corrupted by noise; shrink or remove the wavelet coefficients to remove the noise; then invert the discrete wavelet transform to form an estimate of the true underlying curve. Various researchers have proposed increasingly sophisticated methods of doing this by using real-valued wavelets. Complex-valued wavelets exist but are rarely used. We propose two new complex-valued wavelet shrinkage techniques: one based on multiwavelet style shrinkage and the other using Bayesian methods. Extensive simulations show that our methods almost always give significantly more accurate estimates than methods based on real-valued wavelets. Further, our multiwavelet style shrinkage method is both simpler and dramatically faster than its competitors. To understand the excellent performance of this method we present a new risk bound on its hard thresholded coefficients.     

大股东自利动机下的资本投资与配置效率研究

本文将终极控制人和直接控制人两类大股东的利益动机纳入统一的分析框架,实证考察了大股东自利动机下的资本投资选择与配置效率。研究发现:(1)终极控制人的现金流权比例越低,越有动机增加资本在固定资产、无形资产和长期股权上的自利性投入,导致总体投资规模扩张;(2)地方企业集团投资扩张受终极控制人自利动机的影响最强,央企投资所受影响最弱,民营企业居中;(3)随着控制层级的增加,终极控制人决策权的履行成本增大,企业资本配置行为因直接控制人持股比例高低而表现出"利益攫取"与"利益协同"两种效应;(4)在较高持股比例的收益分配激励下,直接控制人将减少自利性资本投入,抑制过度投资,提高资本配置效率。     

On the Effect of Probability Distributions of Input Variables in Public Health Risk Assessment

A central part of probabilistic public health risk assessment is the selection of probability distributions for the uncertain input variables. In this paper, we apply the first-order reliability method (FORM)^(1–3) as a probabilistic tool to assess the effect of probability distributions of the input random variables on the probability that risk exceeds a threshold level (termed the probability of failure) and on the relevant probabilistic sensitivities. The analysis was applied to a case study given by Thompson et al. ⁽⁴⁾ on cancer risk caused by the ingestion of benzene contaminated soil. Normal, lognormal, and uniform distributions were used in the analysis. The results show that the selection of a probability distribution function for the uncertain variables in this case study had a moderate impact on the probability that values would fall above a given threshold risk when the threshold risk is at the 50th percentile of the original distribution given by Thompson et al. ⁽⁴⁾ The impact was much greater when the threshold risk level was at the 95th percentile. The impact on uncertainty sensitivity, however, showed a reversed trend, where the impact was more appreciable for the 50th percentile of the original distribution of risk given by Thompson et al. ⁴ than for the 95th percentile. Nevertheless, the choice of distribution shape did not alter the order of probabilistic sensitivity of the basic uncertain variables.     

Ultrastructural elliptical models

Dolby's (1976) ultrastructural model with no replications is investigated within the class of the elliptical distributions. General asymptotic results are given for the sample covariance matrix S in the presence of incidental parameters. These results are used to study the asymptotic behaviour of some estimators of the slope parameter, unifying and extending existing results in the literature. In particular, under some regularity conditions they are shown to be consistent and asymptotically normal. For the special case of the structural model, some asymptotic relative efficiencies are also reported which show that generalized least squares and the method of moment estimators can be highly inefficient under nonnormality.     

Using the EM-algorithm for survival data with incomplete categorical covariates

Incomplete covariate data is a common occurrence in many studies in which the outcome is survival time. With generalized linear models, when the missing covariates are categorical, a useful technique for obtaining parameter estimates is the EM by the method of weights proposed in Ibrahim (1990). In this article, we extend the EM by the method of weights to survival outcomes whose distributions may not fall in the class of generalized linear models. This method requires the estimation of the parameters of the distribution of the covariates. We present a clinical trials example with five covariates, four of which have some missing values.     

低沸点工质水平蒸发换热强化管评述

本文分析总结了许多低沸点工质水平蒸发换热强化管的实验和理论研究成果,得到如下结论:在通常情况下,螺旋微翅片管的强化换热为最佳,其强化效果好、压力损失小;较优的翅片形状为锯齿形或翅顶为平形、翅槽为圆形;较佳的结构几何尺寸范围为:螺旋角β为10～25°、翅高h为0.15～0.20 mm、翅片数n为60～70.据此,作者提出了进一步深化研究的设想.