Timber price dynamics after a natural disaster: Hurricane Hugo revisited

Timber prices in the area struck by a natural disaster such as a hurricane or pest infestation are known to drop sharply immediately following the disaster, only to recover after about a year or so. Previous research attributes the rapid recovery to shifts in supply and demand curves. Our analysis suggests the more probable explanation is rotation in the curves. Supply and demand shifts come into play in the second and third years as rebuilding from the hurricane begins in earnest, and as timber inventory is rebuilt in response to elevated price expectations. But for the period in which price recovery occurs, model simulations based on data for Hurricane Hugo indicate the major causal factors of the observed price dynamics are curve rotation and trade with the surrounding undamaged region. Inventory-based supply shifts, the previously-identified causal factor, play a minor role in the observed price dynamics. Getting the causal factors right is important for predicting the price effects of forest inventory shocks, and for proper measurement of their welfare effects.     

矢跨比对大跨度格构式拱屋盖结构性能的影响

以大跨度格构式拱屋盖结构为研究对象,运用3D3S软件设计建模,对矢跨比为0.15、0.2、0.25、0.3、0.35的模型进行受力分析,取其第六榀结构数据进行结果分析,得到内力位移图。通过分析,指出了该结构的薄弱部位,并提出了在结构设计时选用矢跨比为0.2-0.3之间最佳,为格构式拱结构稳定性设计提供参考价值。     

Nonparametric Analysis of Longitudinal Binary Data: An Application to the Intergroup Prisoner's Dilemma Game

The intergroup prisoner's dilemma game was suggested by Bornstein (1992, Journal of Personality and Social Psychology. 7, 597–606) for modelling intergroup conflicts over continuous public goods. We analyse data of an experiment in which the game was played for 150 rounds, under three matching conditions. The objective is to study differences in the investment patterns of players in the different groups. A repeated measures analysis was conducted by Goren and Bornstein (1999, Games and Human Behaviour: Essays in Honor of Amnon Rapoport, pp. 299–314), involving data aggregation and strong distributional assumptions. Here we introduce a nonparametric approach based on permutation tests. Two new measures, the cumulative investment and the normalised cumulative investment, provide additional insight into the differences between groups. The proposed tests are based on the area under the investment curves. They identify an overall difference between the groups as well as pairwise differences. A simultaneous confidence band for the mean difference curve is used to detect the games which account for any pairwise difference.     

基坑支护技术在某深基坑支护中的综合应用

一个优秀的基坑支护体系,必定要综合考虑到地质条件及周边地上、地下建筑体的存在,基坑开挖后对其会造成哪些影响,如何防止因基坑垂直开挖导致地面下沉、崩塌或断裂等情况,确保基坑开挖后周边的建筑物及地形地貌能保持原状,然后综合已经成熟的基坑支护技术,逐项细分,既能应对可能会发生的状况,又能合理地节约基坑支护成本.     

提高油田固井质量的施工措施探析

固井工程是一项应用工程,是建井过程中的重要环节,它直接影响钻井周期和建井成本,以及油田开发方案的实施。深井、超深井的井下地质条件非常复杂,对固井质量有许多不利的因素,在井下条件确定的情况下,决定性的因素是环空流动的壁面剪应力,它是影响顶替效率的主要因素。     

The pecuniary and non-pecuniary costs of job displacement—The risky job of being back to work

This paper investigates the effect of displacement on workplace injury risk and earnings using Italian administrative data on work histories merged with data on individual job-related accidents. Compared to a control group of non-displaced workers selected with propensity score matching techniques, re-employed displaced workers are exposed to moderate earnings losses and experience approximately a 79% increase in workplace injuries. This sizeable reduction in the quality of non-pecuniary working conditions is driven by the transition to new occupations and the risk imposed by new work environments.     

水晶塘电站大坝静力分析的有限元无限元方法

文章运用有限元及无限元模型对水晶塘电站进行静力分析,并将2种模型的计算结果进行了比较,结果表明无限元模型应用于坝体与地基共同作用时的静力分析具有使用单元少、节省计算工作量、精确度较高的特点。同时也表明,对于大坝的计算分析,地基与基础的弹性作用时坝踵、坝趾的应力影响是非常大的。     

围岩位移特性曲线预测的自适应神经模糊推理方法在软岩巷道中的应用

本文采用自适应神经模糊推理方法对水口山矿务局康家湾铅锌矿巷道围岩位移特征曲线进行了预测,并据以对巷道施工过程中的支护时间,支护刚度进行了分析。分析结果表明,该方法具有良好的工程适用性,可在工程实践中推广应用。