苹果树根系吸水研究方法的讨论

介绍了根系吸水模型研究现状;对建立苹果树根系吸水模型所需要的植株蒸腾量、棵间蒸发量、根系密度、土壤含水量等的测定方法进行了探讨．分析了苹果树与作物根系吸水的不同之处．介绍了热脉冲技术测定苹果树蒸腾量、微型蒸渗仪(microlysimeter)测定棵间蒸发量、剖面法测定根系密度、TDR测土壤含水率的技术;最后,探讨了建立苹果树根系吸水模型应注意的具体问题,并进一步提出了利用空间随机场理论研究整个苹果园中苹果树的根系吸水模型的观点,即：将苹果园中的各个苹果树看作小扰动的空间随机变量,然后利用空间随机场理论研究整个苹果园中苹果树的根系吸水情况。     

南水北调东线工程水期权交易及其定价模型

提出将美式看跌水期权模式应用于南水北调东线工程水权交易市场,农业用水户运用二叉树定价模型对美式看跌期权各个阶段水价的波动以及期权价值进行分析,以做出对自身有益的决策。结果表明,南水北调东线工程水期权交易及其定价模型有利于激励节水灌溉技术的推广。     

基于事故树分析的水泵断轴事故的危险评价

基于事故致因理论建立水泵断轴事故模型,将水泵断轴事故危险源分为工作应力超负荷、工作强度超负荷、泵轴维护正确三类,提出基于事故树分析法的水泵断轴危险性专项评价方法。通过对最小割集和最小径集的分析可知,对水泵断轴影响最大的是作用时间过长、次数过多、承受应力过大、对中不符合要求、装配过紧或过松、形位公差过大。对水泵断轴事故的预防提出建议,对水泵运行时间进行合理分配,正确合理地装配水泵并且时刻关注水泵的运行状态。     

Democracy and Growth: Alternative Approaches

This article focuses on two previously unexamined aspects of the relationship between economic growth and democracy. First, the growth experiences of countries that experience significant changes in democracy are examined directly. Countries that democratize are found to grow faster than a priori similar countries, while countries that become less democratic grow more slowly than comparable countries. These differences do not seem to be due to differences in education or investment levels. Second, regression tree analysis suggests that democracy, along with initial income and literacy, contributes to the identification of regimes of countries facing similar aggregate production functions.     

Hydrologic thresholds for riparian forest conservation in a regulated large Mediterranean river

Most riparian trees are phreatophytic, water table‐dependent plants which broadly differ in their tolerance to drought and permanent flooding. In semi‐arid settings, as water is limiting, inundations may be regarded as inputs rather than stresses for the survival of phreatophytes. In this study, the mortality rates and abundances of Populus alba, P. nigra, Salix alba and local Tamarix spp. were examined in 43 plots with different hydrologic conditions distributed across the floodplain of a large semi‐arid and Mediterranean river, the Ebro River (Spain). The objectives were to determine hydrologic thresholds for the maintenance of declining populations of those species, while providing novel information on their phreatophytic nature, and to examine shifts in the species composition along hydrologic gradients. All species exhibited significant relationships between mortality rates and hydrologic variables (deepest water table—WT, flood duration—FD and flood frequency—FF). S. alba was found to be the species with lowest tolerance to drier conditions (hydrologic thresholds for maintaining a mortality rate <50%: WT > ?1.22 m; FD: out of observation range; FF > 5.4 events y^?1), followed by P. nigra (WT > ?2.18 m; FD > 11.1%; FF > 3.8 events y^?1), Tamarix spp. (WT > ?2.96 m; FD > 3.7%; FF > 2.5 events y^?1) and P. alba (WT > ?3.45 m; FD > 1.7%; FF > 2.0 events y^?1). Only a significant reduction in S. alba relative abundance was observed as conditions got drier. The results provided quantitative information useful to guide management plans for the protection of Mediterranean phreatophytic tree species from further degradation and suggested that eventual natural or regulation‐induced droughts and groundwater declines would accelerate the loss of all phreatophytic species, especially S. alba. Copyright © 2010 John Wiley & Sons, Ltd.     

FTA分析法在建筑工程施工风险分析中的应用研究

概率预测是评估建筑工程事故风险的基本手段,基于对建筑工程风险因素的综合分析,确定了建筑工程风险源因素FTA(Fault Tree Analysis)分析方法,目的在于为建筑工程概率预测方法的研究提供一种新的尝试,故为采取合理的防治技术措施在理论上、方法上提供有益的指导,并最终减少和控制建筑工程事故的发生.     

LDPC码的树图法构造

LDPC码译码采用的是BP算法,但由于回路的存在,使译码重复迭代,特别是短长度的回路使LDPC码的性能下降.为此,用树图法分析了LDPC码的回路及其特性,给出了求解回路长度和所经过节点的方法,非常适合于计算机进行求解.同时也用树图的方法来构造LDPC码,可以在树生成的过程中了解其中的回路数目及长度.     

论企业内部人力资源管理的有效性

企业中的“人”将决定企业能否最终取得市场或战略上的成功。在诸多的论著中经常会看到“员工是上帝”这种说法,那么企业的员工又处于什么样的位置呢?从一个较新的视角——“顾问咨询与市场交流”这个角度来探讨企业内部人力资源管理中“员工”问题,并尝试着如何从战略的高度解决或者说提升企业内部人力资源管理方面的有效性问题。     

一个与供应链协同的虚拟价值网集成增值矩阵

运用集成原理及系统方法论探讨了虚拟价值网集成的结构机理,从集成意义上构造了一个与供应链协同的增值矩阵,即基于信息共享、知识共享、价值共享的三个平台,虚拟实现与工作流、知识流、价值流协同的供应链上的信息流、财务流和物流增值。同时作出虚拟价值网集成管理的优化树图,为现行供应链管理模式的优化升级提供模拟支持和方法选择。