Testing for the usefulness of forecasts

Ashley (Journal of Forecasting 1983; 2 (3): 211–223) proposes a criterion (known as Ashley's index) to judge whether the external macroeconomic variables are well forecast to serve as explanatory variables in forecasting models, which is crucial for policy makers. In this article, we try to extend Ashley's work by providing three testing procedures, including a ratio‐based test, a difference‐based test, and the Bayesian approach. The Bayesian approach has the advantage of allowing the flexibility of adapting all possible information content within a decision‐making environment such as the change of variable's definition due to the evolving system of national accounts. We demonstrate the proposed methods by applying six macroeconomic forecasts in the Survey of Professional Forecasters. Researchers or practitioners can thus formally test whether the external information is helpful. Copyright © 2010 John Wiley & Sons, Ltd.     

Evolution and ecological correlates of uniparental reproduction in freshwater snails

We review the spatial and temporal correlates of uniparental reproduction in freshwater snails as they pertain to the ecological hypotheses for the maintenance of biparental sex. The biogeographic evidence from two species (Potamopyrgus antipodarum andBulinus truncatus) presently supports the Red Queen hypothesis that biparental reproduction is selected as a way to reduce the risk to progeny of parasite attack. Uniparental reproduction in these species is associated with low levels of infection by parasites (castrating digenetic trematodes), suggesting that parthenogenesis or self-fertilization can replace cross-fertilization when the risk of infection is low. In addition, inB. truncatus, the opportunity for cross-fertilization coincides with the season in which parasite attack is highest. In a third species (Campeloma decisum), parthenogenetic reproduction is correlated with latitude and the presence of a non-castrating trematode that may prevent cross-fertilization; these patterns suggest that parthenogenesis has been selected as a mechanism to assure reproduction. Finally, we discuss the spotty taxonomic distribution of parthenogenetic species.     

Krashen的习得学说与外语教学

二十世纪八十年代初由美国语言学家克拉申(Krashen)教授提出的"语言输入说"(InputHypothesis)在语言学界引起一阵不小的反响。但对这种学说的研究大多局限于语言学本身。本文试图说明在外语教学实践中适度地引入该学说中可操作的理论部分将有利于扩充当前外语教学活动中的交际内容。     

基于飞行试验数据的仿真模型验证方法的研究

讨论了用飞行试验数据对仿真模型的静态和动态性能进行验证的定性和定量方法，并给了实际应用的例子，结果表明，尽管飞行试验的样本容量有限，只要方法恰当，仍能获得较好的验证结果。     

几种思维方法在物理学习中的应用

通过举例说明几种思维方法在物理学习中的应用。     

含氮小分子键级的计算与结构式的推断

提出了电子空位对假说，以新颖的观点指出了分子结构的规律．对含氮共价小分子进行了键级的简便计算，和结构式的简易推断．     

金属塑性损伤的电阻测试法及其本构模型

本文介绍了一种测量金属塑性损伤的新方法——电阻测试法。此方法的主要特点是设备简单,操作方便。运用此方法对工程实际中常用金属A3钢进行了测试,导出了用电阻率表示的金属塑性损伤D的数学模型。此模型是几何条件相依的。该法具有较广泛的应用价值。     

“疯牛病”与“疯人病”——蛋白粒与蛋白粒疾病

蛋白粒是一个不含核苷酸的蛋白性粒子,能够传染动物和人．引起大脑损伤及死亡．蛋白粒疾病包括羊瘙痒病、牛海绵体脑炎、人的克氏-约氏病、杰氏-斯氏-斯氏病以及致命性家族失眠症．本文从蛋白粒与人类和动物疾病的关系,回顾了蛋白粒疾病发生及传染的过程．具有不同氨基酸组成的蛋白粒,存在着可溶性的ＰｒＰC型及不溶性ＰｒＰＳＣ型．只有ＰｒＰＳＣ是传染性的．通过对蛋白粒结构与功能的剖析,讨论了蛋白粒的基因、蛋白粒的产生以及可能的致病机理（Ｘ蛋白被发现与细胞内蛋白粒增生有关）．最后,对蛋白质、ＤＮＡ和ＲＮＡ之间的遗传信息流提出了一个新的假说．     

具有部分缺失数据的两个幂分布总体参数的估计与检验

研究具有部分缺失数据的两个幂分布总体中的参数估计问题以及两总体参数相等的假设检验问题．证明了估计的强相合性以及渐近正态性,给出检验两总体参数相等的检验统计量以及检验统计量的极限分布．     

动物性别分离机制的研究进展

对动物的性别分离机制的研究进行了综述,认为性别分离指数测度公式的确立、数学模型的导入和粪便性别鉴定技术的使用对今后动物性别分离的研究具有巨大推动作用.提出,解释动物性别分离机制的假说除了包括动物自身的生态需求内因外,必须引入生境因子外因的作用.