中国地下经济研究与估计（1990～2004）

一、问题提出及背景对于我国经济增长率,国际组织、国内外专家学者纷纷提出GPD被“低估”或“高估”等种种说法。笔者认为,在我国处于这样的前所未有的社会转轨与经济转型的关键时期,中国的实际经济增长率明显地高于我国的预期,也高于世界其他机构的预测和估计。这部份由于官方统计之外存在的大量地下经济活动。随着我国社会转型的不断深化,大批农村剩余劳动力向城市迁移中产生了非正规部门就业。在城市化进程继续加快的过程中,我国的城乡劳动力流动变得更加自由,这都促使了农村剩余劳动力在这个过程中向非正规经济的扩展。地下经济在我国…     

Testing the Significance of Categorical Predictor Variables in Nonparametric Regression Models

In this paper we propose a test for the significance of categorical predictors in nonparametric regression models. The test is fully data-driven and employs cross-validated smoothing parameter selection while the null distribution of the test is obtained via bootstrapping. The proposed approach allows applied researchers to test hypotheses concerning categorical variables in a fully nonparametric and robust framework, thereby deflecting potential criticism that a particular finding is driven by an arbitrary parametric specification. Simulations reveal that the test performs well, having significantly better power than a conventional frequency-based nonparametric test. The test is applied to determine whether OECD and non-OECD countries follow the same growth rate model or not. Our test suggests that OECD and non-OECD countries follow different growth rate models, while the tests based on a popular parametric specification and the conventional frequency-based nonparametric estimation method fail to detect any significant difference.     

Effects of unmeasured heterogeneity in the linear transformation model for censored data

We investigate the effect of unobserved heterogeneity in the context of the linear transformation model for censored survival data in the clinical trials setting. The unobserved heterogeneity is represented by a frailty term, with unknown distribution, in the linear transformation model. The bias of the estimate under the assumption of no unobserved heterogeneity when it truly is present is obtained. We also derive the asymptotic relative efficiency of the estimate of treatment effect under the incorrect assumption of no unobserved heterogeneity. Additionally we investigate the loss of power for clinical trials that are designed assuming the model without frailty when, in fact, the model with frailty is true. Numerical studies under a proportional odds model show that the loss of efficiency and the loss of power can be substantial when the heterogeneity, as embodied by a frailty, is ignored. An erratum to this article can be found at     

Estimation of Distribution Functions Using Data from Different Environments

Suppose that when a unit operatesin a certain environment, its lifetime has distribution G,and when the unit operates in another environment, its lifetimehas a different distribution, say F. Moreover, supposethe unit is operated for a certain period of time in the firstenvironment and is then transferred to the second environment.Thus we observe a censored lifetime in the first environmentand a failure time of a ``used' unit in the second environment.We propose an EM algorithm approach for obtaining a self-consistentestimator of F. Moreover, suppose using observations from both environments.The case where failure times are subject to right censoring isconsidered as well. We also establish the maximum likelihoodestimator of F. Moreover, suppose when the unit is repairable. Applicationand simulation studies are presented to illustrate the methodsderived.     

Dependence Estimation Over a Finite Bivariate Failure Time Region

This articleconcerns nonparametric estimation of association between bivariatefailure times. In the presence of independent right censoring,the support for failure time variates may be restricted and measuresof dependence over a finite failure time region may be of particularinterest. To this end, the reciprocal cross ratio function, weightedby the bivariate failure time density, is proposed as a summarymeasure of dependence over a failure time region. This `relativerisk' estimator is shown to be consistent and asymptoticallynormally distributed, with consistent bootstrap variance estimator.A finite-region version of Kendall's tau, which is suitable forcensored failure time data, is also proposed, and correspondingasymptotic distribution theory is noted. The accuracy of theseasymptotic approximations is studied in simulations and an illustrationis provided.     

蔑视与改造精英——世纪末小说的一大景观

本文以世纪末小说为立足点,揭示了转型期中国社会文化冲突的一大特征———颠覆精英,及其潜在的现实背景。并指出：文化痞子、城市平民、都市白领对精英的蔑视与挑战固然有其不可替代的革命意义,但如果走向另一个极端,也可能导致灾难性社会危机,因而主张各阶层的文化交流与沟通     

用跳马步系列研究奇素数阶规则完美幻方的个数

本文先介绍跳马步系列的有关概念及性质,然后用跳马步系列研究奇素数阶规则完美幻 方的个数。     

初等树变换的算法改造

本文利用王氏代数对用初等树变换生成树的方法进行了改造,提出了一种新的初等树变换的算法。新算法较之原法简洁、直观、运算方便、概念清楚,并保留了原法的所有优点。     

单李代数不可约表示的标记

对于n秩单李代数g,当采用Dynkin关于素根的分类时,其不可约表示可以用n个非负整数Λ_(αi)标记,也可通过初等表示的权用数组li来标记。利用Cartan逆矩阵,我们给出了计算Λ_(α_i)与li之间关系的方法。对于B_n、C_n、D_n和F_4,利用Cartan逆矩阵证明了这些li是与采用Cartan关于素根的分类时的Λi是一致的。     

悬汞电极阴极溶出伏安法测定人发中的痕量硒

本工作用悬汞电极—示波极谱仪研究了Se(Ⅳ)在HClO_4—KI—EDTA底液中的阴极溶出测定的。在选定条件下,Se(Ⅳ)于—0.5V左右产生一灵敏的导数波,灵敏度为5×10~(-10)M(0.04ppb)。Se(Ⅳ)件浓度在1×10~(-7)M～5×10~(-9)M间与峰电流呈良好线性关系。本法用于人发中痕量硒的测定,结果满意。