Constructing and evaluating core inflation measures from component‐level inflation data

This paper undertakes a comprehensive examination of 10 measures of core inflation and evaluates which measure produces the best forecast of headline inflation out‐of‐sample. We use the Personal Consumption Expenditure Price Index as our measure of inflation. We use two sets of components (17 and 50) of the Personal Consumption Expenditure Price Index to construct these core inflation measures and evaluate these measures at the three time horizons (6, 12 and 24 months) most relevant for monetary policy decisions. The best measure of core inflation for both sets of components and over all time horizons uses weights based on the first principal component of the disaggregated (component‐level) prices. Interestingly, the results vary by the number of components used; when more components are used the weights based on the persistence of each component is statistically equivalent to the weights generated by the first principal component. However, those forecasts using the persistence of 50 components are statistically worse than those generated using the first principal component of 17 components. The statistical superiority of the principal component method is due to the fact that it extracts (in the first principal component) the common source of variation in the component level prices that accurately describes trend inflation over the next 6–24 months.     

建筑物地基处理的设计与施工探讨

以具体工程为例，介绍了建筑物地基处理的设计、施工中遵循的原则，施工中遇到特殊情况时采取的处理方法和必要的检测方法，对几种桩基的设计要求、施工工艺及过程、质量控制等情况进行了简单阐述。     

《科学》杂志主编唐纳德·肯尼丹论述2001年度的重大科技进展

每一年 ,《Ｓｃｉｅｎｃｅ》杂志的编辑们都要聚在一起讨论该年度重大科技进展的提名问题。面对众多的新发现 ,往往是很具有挑战性的。今年我们遇到了一个尤为困难的任务 :找到一个能够和果蝇以及其他生命体的基因组测序相当的科技成就。果蝇以及其他生命体的基因组测序这项成果不仅仅席卷了去年的重大科技进展奖 ,而且它还导致了众多的后续项目 ,这决不亚于人类基因组草图的发表。这些后续的成功成了本年度科学中无人认领的珍宝中的一部分 ,而且就像去年一样完好的保存着。本年度重大科技进展的提名像去年的一样使人难忘 ,它涉及了从纳米技…     

范德华力：生物学家、化学家、工程师和物理学家手册

分子间的范德华力是十分微弱的，但可以说普遍的存在着，在很多体系中起着巨大的作用，在物理学、化学、生物学等学科中得到了广泛的研究。但怎样计算范德华力？如何考虑各种条件对范德华力的影响？     

Overcompensation and population cycles in an ungulate.

Although theoretical studies show that overcompensatory density-dependent mechanisms can potentially generate regular or chaotic fluctuations in animal numbers, the majority of realistic single-species models of invertebrate populations are not overcompensatory enough to cause sustained population cycles. The possibility that overcompensation may generate cycles or chaos in vertebrate populations has seldom been considered. Here we show that highly overcompensatng density-dependent mortality can generate recurrent population crashes consistent with those observed in a naturally limited population of Soay sheep. The observed interval of three or more years between crashes points to sharp 'focusing' of mortality over a narrow range of population density.