对承担行业标准编制工作的认识与思考

根据近几年黄河勘测设计公司承担行业标准编制工作的情况、主要做法与体会，作者谈了几点个人认识和建议，强调行业标准主要是体现行业的意志和行为，在当前形势下，行业主管部门应进一步加大对标准编制工作的领导和管理力度，以促进行业标准化工作的顺利开展。     

现阶段网络食品安全存在的问题及对策

食物是人类社会不断发展、进化的动力源泉。食品安全问题关系着每个国人的切身利益。近年来,随着互联网逐渐走进千家万户,网购食品也就应运而生。人们在享受着这种便利的同时,也承担着一定的风险。特别是最近网络食品安全问题被接连曝光,使食品安全成为人们关心的热点问题。本文分析了现阶段网络食品存在的问题,如网络食品质量问题、卖家信用问题及消费者维权问题,并提出了相应的对策,以期能逐渐改善目前的网络食品安全问题,切实保障消费者的权益。     

A NOTE ON SEMIPARAMETRIC ESTIMATION OF FINITE MIXTURES OF DISCRETE CHOICE MODELS WITH APPLICATION TO GAME THEORETIC MODELS*

We view a game abstractly as a semiparametric mixture distribution and study the semiparametric efficiency bound of this model. Our results suggest that a key issue for inference is the number of equilibria compared to the number of outcomes. If the number of equilibria is sufficiently large compared to the number of outcomes, root‐n consistent estimation of the model will not be possible. We also provide a simple estimator in the case when the efficiency bound is strictly above zero.     

基于遗传算法的城际客运专线列车开行方案研究

分析城际客运专线列车开行方案的特点。以旅客时间消耗最小为目标，建立城际客运专线旅客列车开行方案的最小费用流模型。根据模型的特点，设计相应的遗传算法，并对遗传算法的适应值函数、算法步骤和算法复杂度进行分析。分析结果表明，该算法是一个收敛于全局最优解的近似有效算法。     

邻羟基苯乙醚的制备及其前景分析

文章简要阐述了几种邻羟基苯乙醚的合成方法,其中以邻氨基苯乙醚法为好。通过对国内外乙基香兰素市场情况的分析得知,邻羟基苯乙醚作为合成香料及其它精细化学品的重要中间体,其市场前景是很好的。     

经济增长方式的多指标判别方法

本文就经济增长方式的类型及相关指标以及如何对经济增长方式进行判别作了讨论，提出了多指标判别方法。     

The Hausman test and weak instruments

We consider the following problem. There is a structural equation of interest that contains an explanatory variable that theory predicts is endogenous. There are one or more instrumental variables that credibly are exogenous with regard to this structural equation, but which have limited explanatory power for the endogenous variable. Further, there is one or more potentially ‘strong’ instruments, which has much more explanatory power but which may not be exogenous. Hausman (1978) provided a test for the exogeneity of the second instrument when none of the instruments are weak. Here, we focus on how the standard Hausman test does in the presence of weak instruments using the Staiger–Stock asymptotics. It is natural to conjecture that the standard version of the Hausman test would be invalid in the weak instrument case, which we confirm. However, we provide a version of the Hausman test that is valid even in the presence of weak IV and illustrate how to implement the test in the presence of heteroskedasticity. We show that the situation we analyze occurs in several important economic examples. Our Monte Carlo experiments show that our procedure works relatively well in finite samples. We should note that our test is not consistent, although we believe that it is impossible to construct a consistent test with weak instruments.     

Test of random versus fixed effects with small within variation

Comparisons of within and between estimators using the conventional Hausman test may be subject to statistical problems if the within variation is not sufficiently large. Adopting an alternative asymptotic approximation, we propose a modification of Hausman test that is valid whether the within variation is small or large.