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661.
东北红豆杉植物地理学研究 总被引:14,自引:0,他引:14
总结了东北红豆杉的地理分布概况和分布区特点,绘制了分布图,以在我国境内分布区域的主导气象因子构成指示指标组建立了东北红豆杉自然地理分布模型,并通过实例证明了该模型的有效性。 相似文献
662.
The fire simulation processes of the National Fire Management System's (NFMAS) Initial Attack Analysis (IAA) processor were
evaluated by conducting two types of sensitivity analysis: one based on a hypothetical set of data to assess IAA's outputs
under a wide range of fire input values, and the other using an actual Stanislaus National Forest database to test IAA's validity
with a real set of data. The results revealed that IAA's outputs (projected annual number of fires and area burned) were most
sensitive, in descending order, to the input values of the fire spread rate, the productivity rates of the suppression forces,
and the initial attack time, for all fuel models tested. In contrast, IAA's outputs were extremely insensitive to variations
in the fire size at discovery. Changes are necessary in the ways IAA incorporates the fire size at discovery to facilitate
the comparison among various fire detection options. The program's “escaped fire situation” analysis was found inadequate,
because the projected annual frequencies and final sizes of the simulated escaped fire events produced unacceptable results
with the Stanislaus National Forest database. Assigning final sizes to simulated escaped fires according to the fire intensity
level in which they are historically expected to occur provides a consistent way of calculation of the projected annual area
burned and the consequent cost plus net value change (C + NVC). 相似文献
663.
Non-parametric MLE for Poisson species abundance models allowing for heterogeneity between species 总被引:6,自引:0,他引:6
The proper management of an ecological population is greatly aided by solid information about its species' abundances. For the general heterogeneous Poisson species abundance setting, we develop the non-parametric mle for the entire probability model, namely for the total number N of species and the generating distribution F for the expected values of the species' abundances. Solid estimation of the entire probability model allows us to develop generator-based measures of ecological diversity and evenness which have inferences over similar regions. Also, our methods produce a solid goodness-of-fit test for our model as well as a likelihood ratio test to examine if there is heterogeneity in the expected values of the species' abundances. These estimates and tests are examined, in detail, in the paper. In particular, we apply our methods to important data from the National Breeding Bird Survey and discuss how our methods can also be easily applied to sweep net sampling data. To further examine our methods, we provide simulations for several illustrative situations. 相似文献
664.
Understanding Managers’ Views of Global Environmental Risk 总被引:1,自引:0,他引:1
This research investigated managers’ views of two global environmental risks: climate change and loss of biodiversity. The
intent was to understand why different managers place varying levels of attention and priority on these issues. The data came
from in-depth interviews with 28 senior corporate managers across Canada and a range of sectors, although most were employed
in the energy sector. Approximately half had direct environmental responsibilities and half had other management duties. Grounded
theory was used to collect and analyze the data. From the results, a theoretical framework was constructed to explain important
factors that can influence managers’ mental models of environmental risk. Four factors relevant to managers’ appraisal of
the threat of environmental risk include: (1) salience, (2) intrinsic value of nature, (3) knowledge, and (4) perceived resilience
of nature. In addition, four factors relevant to managers’ view of the appeal of a particular response strategy were: (1)
avoidability, (2) perceived costs and benefits, (3) fairness and equity, and (4) effectiveness. The time horizon for decision
making was seen as being important in both portions of the mental model. 相似文献
665.
Darcian preferential water flow and solute transport through bimodal porous systems: Experiments and modelling 总被引:1,自引:1,他引:0
Antonio Coppola Vincenzo Comegna Angelo Basile Nicola Lamaddalena Gerardo Severino 《Journal of contaminant hydrology》2009,104(1-4):74
Soils often exhibit a variety of small-scale heterogeneities such as inter-aggregate pores and voids which partition flow into separate regions. In this paper a methodological approach is discussed for characterizing the hydrological behaviour of a heterogeneous clayey–sandy soil in the presence of structural inter-aggregate pores. For the clay soil examined, it was demonstrated that, coupling the transfer function approach for analyzing BTCs and water retention data obtained with different methods from laboratory studies captures the bimodal geometry of the porous system along with the related existence of fast and slow flow paths. To be effectively and reliably applied this approach requires that the predominant effects of the soil hydrological behaviour near saturation be supported by accurate experimental data of both breakthrough curves (BTCs) and hydraulic functions for high water content values. This would allow the separation of flow phases and hence accurate identification of the processes and related parameters. 相似文献
666.
生命线系统拓扑优化问题的Benchmark模型是评测新型算法正确性和适用性的重要手段。基于此,首先以生命线网络系统抗震拓扑优化分析模型为背景,建立了该优化问题的三个Benchmark模型,并在Visual Compaq Fortran开发环境下,通过穷举法统计出解空间的所有网络,进而甄选出不同节点可靠度约束下的最优网络和若干次优网络,最后利用上述Benchmark模型对生命线网络系统抗震拓扑优化中的蚁群算法进行测试。结果表明,当网络规模较小时,蚁群算法能精确地搜索到最优解;当网络规模增大后,蚁群算法也能以较大概率搜索到最优解或次优解。 相似文献
667.
Issues concerning dam safety and equitable sharing of catchment run-off are receiving more attention throughout the world. This paper assesses these matters in the context of Australia, and the need for policy responses. Landholders often overlook the common law obligation to review/design dams to current standards because of high costs, leaving them vulnerable to litigation if their dam fails. The paper reports on an innovative spillway design/review procedure, applicable to southeast Australia, but transferable to any region worldwide. Dam safety policy models and guidelines derived from international best practice are linked to the procedure and intended to aid government decision-making. The procedure minimises costs to landholders and provides an acceptable level of safety assurance to downstream communities. Also discussed are recent surveys testing community attitudes to the procedure and implemented dam safety and water allocation policies. These further guide any government wanting to implement this'integrated engineering and community partnerships'approach to preventing potential disasters due to private dam failure and achieving sustainable and safe water storage and use. 相似文献
668.
通过测算武汉城市圈土地利用空间关联的碳排放效率及其收敛性,为该城市群提供碳减排方案。通过运用结合Bootstrap技术的Malmquist指数方法测算了武汉城市圈土地利用空间关联的碳排放效率及其技术进步和技术效率,并对该效率做σ-收敛和β-收敛分析。研究发现该城市圈土地利用空间关联的碳排放效率在2010年前呈上升趋势,之后出现下降;究其原因,虽然技术进步是持续的,但是不足以弥补技术效率的不断降低;将武汉城市圈按照土地类型分为三类城市,收敛性分析发现它们均出现了不同程度的收敛,而且收敛于较高的碳排放水平。根据以上的分析结果,结合该城市圈的产业布局,提出了相应的减碳方案。 相似文献
669.
三种生产论:可持续发展的基本理论 总被引:29,自引:15,他引:29
本文通过研究人与环境的辩证关系,提出了物质生产、人的生产和环境生产是可持续发展系统的基本模型,分析了三种生产之间的和谐关系,并对深化环境影响评价、开展环境建设、建立新伙伴关系等问题进行了探讨。 相似文献
670.
基于空间面板模型的碳排放影响因素分析——以长江经济带为例 总被引:1,自引:0,他引:1
随着全球变暖问题的日益严峻,气候问题引起了国际社会的广泛关注。长江经济带作为中国区域发展"三大战略"之一,面临着严峻的碳减排压力。为此,以二氧化碳排放为测度指标,定量分析了1998~2012年长江经济带二氧化碳的时空格局特征,并构建碳排放影响因素的空间面板模型,分析了产业结构、人口总量、经济水平、技术水平与城市化水平对长江经济带碳排放的影响。研究结果表明:1碳排放的绝对差异呈增大趋势,相对差异呈波动变化趋势;碳排放与人均GDP(1997年不变价)的相关性较弱;2碳排放空间格局相对稳定,高碳排放区域以江苏为中心,逐渐向四周扩散;3空间面板模型结果表明:人口总量是影响长江经济带碳排放时空格局演化的决定性因素,其次依次为经济水平、技术水平和城市化水平。 相似文献