炼山对杉木人工幼林养分流失影响的定量研究

根据５ａ长期定位观察结果,本文应用两模型参数ｔ检验、弹性分析及边际分析法,探讨年时间序列对炼山与对照的杉木人工幼林养分流失的效应。ｔ检验表明,不同处理在年时间序列上的铵态氮、亚硝态氮、硝态氮、磷酸盐、钾、有机质流失模型的Ｂ、Ａ参数存在显著差异。弹性分析和边际分析表明,年时间对不同处理的上述养分效应呈负效应,在炼山条件下,上述养分流失的弹性系数分别为－１．２１５％、－１．２１４％、－１．２１５％、－１．２１５％、－１．２４１％、－１．２１４％,上述养分流失的边际量分别为－０．３９４ｋｇ、－０．０３３ｋｇ、－０．３６５ｋｇ、－０．０２３ｋｇ、－３０．０１０ｋｇ、－５９．４２１ｋｇ。在不炼山处理下,上述养分流失的弹性系数分别为－０．８４２％、－０．８５１％、－０．８４４％、－０．８５４％、－０．８４５％、－０．８４１％,上述养分流失边际量分别为－０．１５９ｋｇ、－０．０１０ｋｇ、－０．０８５ｋｇ、－０．００６ｋｇ、－１２．０２４ｋｇ、－１７．７６７ｋｇ。     

弹性填料表面亲水性对厌氧生化过程的影响研究

通过在普通塑料中添加水溶性高分子物进行亲水性改进，制得表面亲水的弹性塑料填料，并通过实验验证了新型填料的亲水性。填料表面的亲水性改进了微生物在其表面的吸附能力，新型填料与普通填料实验室的应用对比研究结果表明：亲水性改进的弹性填料在污水的厌氧处理中可提高污水的厌氧处理效率15％～30％，且亲水性改进大大提高了弹性填料的抗冲击负荷能力，此填料的工业应用结果也表明亲水性提高了填料的应用性能。     

基于零膨胀负二项回归模型的内河水上交通人命安全分析

运用零膨胀负二项回归模型,分析水上交通事故中人员死亡失踪数量的各影响因素的影响程度。通过Pearson相关分析得到与水上交通事故中人员死亡失踪人数密切相关的因素,建立ZINB回归模型得到各因素的参数估计值。运用弹性分析方法对不同影响因素的影响程度进行评估,根据影响程度对各影响因素进行排序。将该方法应用于长江海事局辖区范围内的水上交通事故人员死亡失踪分析,取得了理想效果。     

生态安全弹性与生态安全"倒U"曲线

文章从生态安全的研究现状入手,根据生态系统和人类社会系统之间的主要关系,论述了生态安全弹性和安全"倒U"曲线理论.生态安全弹性能够反映安全系数、安全阈值、干扰程度三者的关系,由它来判断人类向生态系统索取自然资源的活动更具有预测性、可操作性,并能保证生态系统自身也处于可持续发展的良性状态.     

437个火电厂项目环境影响宏观分析及对策研究

对2004-2005年上报国家环境保护总局环境工程评估中心的437个火电项目环境影响和宏观对策分4种方案进行了分析和探讨.结果表明:方案Ⅰ和方案Ⅱ的能源弹性系数分别为3.6和2.2,对环境、资源影响较大,不利于可持续发展;方案Ⅲ能源弹性系数为0.5,对环境、资源影响小,符合可持续发展,但目前难以实现;方案Ⅳ能源弹性系数为0.8,对环境、资源影响较小,按方案Ⅳ模式发展也有一定难度,但经过艰苦努力可以实现.分析了火电发展对煤炭资源和环境等方面的影响,并提出应尽快将我国能源弹性系数恢复到正常值,统筹火电厂规划,坚持经济发展模式的转变、节能降耗、调整产业结构等建议.      

Price perceptions in water demand

Economists advocate for using the price mechanism to manage water scarcity, but complex nonlinear rate structures prevalent in markets for municipal water obscure price signals. We conduct a randomized field experiment that jointly elicits knowledge about the cost of water and examines the impact of improved information on demand by linking a survey to water billing records. Half of our sample of 30,000 single family homeowners are randomly sent an invitation to a survey that asks questions about the water bill and the costs of water-use activities (e.g. the cost of taking a shower), and subsequently provides personalized accurate information. Results show that consumers have poor information about the marginal price of water and overestimate the costs of using water. Respondents are relatively better informed about their total bill and water consumption. In aggregate, respondents increase water use in response to the survey, potentially due to learning that water is cheaper than they previously thought. Increased consumption is concentrated among low users who are more likely to over-estimate the costs of using water.     

我国事故指标与经济社会发展指标多元回归分析

以安全生产相对指标工矿商贸十万就业人员生产安全事故死亡率为研究对象,通过文献调研分析,最终从经济发展、经济发展结构、经济活动水平和社会活动水平角度筛选出14个指标为观察对象,采用逐步多元回归分析法筛选出影响我国安全生产的主要经济社会发展指标为：第三产业增加值产值占GDP比重、第三产业就业人数占总就业人数的比重和固定资产投资增长速度,并建立了回归模型。应用弹性系数法对主要影响因素进行重要性排序,并推测工矿商贸就业人员十万人事故死亡率将保持持续下降的趋势。     

Is there a common metals demand curve?

Previous studies have identified a single, stable and strong correlation between the price of metals and their consumption, such that low priced metals are always used in large amounts and visa versa. Some have interpreted this as evidence that metals share a common demand curve so that a single price elasticity of demand exists. This paper reviews and tests this hypothesis against a number of other possible explanations, including the idea that the relationship is an empirical curiosity. Modifications to the demand curve were tested by allowing metals to have different intercepts and price elasticities. The results from this analysis suggest that metals do not share a common demand curve and that the correlation identified between the price of metals and their level of consumption is an empirical curiosity. As such, the singular price elasticities published in past papers should not be used for assessing future rates of metals substitution.     

公路改扩建导致新老路基差异沉降的因素分析

基于有限差分原理建立了三维有限元数值计算模型,对公路改扩建中导致新老路基差异沉降的因素进行探讨。结果表明,公路拓宽部分的沉降明显高于老路的沉降,且在新老路结合部位沉降发展最显著。路面的竖向沉降随公路拓宽宽度增加而增加,随新路基弹性模量增加而减小,随新地基土压缩模量增加而减小。其中拓宽宽度和新地基土压缩模量对路基表面沉降影响较大,新路基土弹性模量对路基表面沉降影响较小。这表明新地基土受到的压应力和新地基土压缩模量是影响路面差异沉降的主要因素。工程上可以着重从降低对新地基土的压应力和提高新地基的压缩模量两个角度来降低路面的差异沉降。