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排序方式: 共有697条查询结果,搜索用时 15 毫秒
21.
嫩江水体溶解氧变化规律的混沌研究 总被引:1,自引:0,他引:1
针对目前溶解氧研究主要是从生物、化学等方面开展,而对溶解氧自身变化规律的研究很少的特点,以嫩江干流浏园水文站测得的溶解氧质量浓度序列为例,首先进行相空间重构,应用自相关函数法确定出延迟时间、伪邻近点法确定出嵌入维数;然后应用主分量分析(PCA)方法对序列进行分析,表明该序列不是噪声序列而可能是混沌序列,通过计算Kolmogorov熵得出溶解氧质量浓度序列具有混沌特性的结论;最后应用基于关联度的局域加权线性回归预测法对该序列进行了混沌预测研究,得到了比较理想的预测结果,这为应用混沌理论进行溶解氧变化规律的研究提供了依据. 相似文献
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液化天然气(LNG)瞬时泄漏扩散的模拟研究 总被引:1,自引:0,他引:1
对液化天然气泄漏扩散过程进行了分析,考虑其泄漏后发生闪蒸时的液滴夹带以及混合空气量,将闪蒸完的状态作为箱模型的初始状态,考虑空气的湿度影响建立了重气扩散过程的箱模型,并应用实例进行了验证,得出了泄漏后有火灾爆炸危险性的区域以及距离泄漏源的位置,为应急救援预案的制定提供参考,模拟结果显示了重气扩散过程中的重力沉降,空气夹带等一般特征,同时云团初始闪蒸时的液滴夹带对云团的扩散行为具有一定的影响,不能忽略.最后提出了今后的研究方向. 相似文献
24.
Information technologies and the sharing of disaster knowledge: the critical role of professional culture 总被引:3,自引:0,他引:3
Marincioni F 《Disasters》2007,31(4):459-476
A comparative survey of a diverse sample of 96 US and Italian emergency management agencies shows that the diffusion of new information technologies (IT) has transformed disaster communications. Although these technologies permit access to and the dissemination of massive amounts of disaster information with unprecedented speed and efficiency, barriers rooted in the various professional cultures still hinder the sharing of disaster knowledge. To be effective the available IT must be attuned to the unique settings and professional cultures of the local emergency management communities. Findings show that available technology, context, professional culture and interaction are key factors that affect the knowledge transfer process. Cultural filters appear to influence emergency managers' perceptions of their own professional roles, their vision of the applicability of technology to social issues, and their perspective on the transferability of disaster knowledge. Four cultural approaches to the application of IT to disaster communications are defined: technocentric; geographic,; anthropocentric; and ecocentric. 相似文献
25.
Berghahn R Mohr S Feibicke M Meinecke S Sperfeld E 《Environmental science and pollution research international》2007,14(3):190-193
Goal, Scope and Background One of the advantages of long-term mesocosm experiments as compared to short-term standard toxicity tests in the laboratory
is the potential for detecting secondary effects due to the interaction of species and recovery with biomass of macrophytes
being an important endpoint. However, generating biomass data by harvesting is often laborious, time-consuming, costly and
restricted to the end of the experiment. Moreover, valuable information may get lost, in particular in single application
studies, since maximal primary effects and secondary effects or recovery occur per se at different times. Potamogeton natans was used as an example in order to test whether number and area of floating leaves can be reliably measured and be used as
intermediate and final endpoints in mesocosm effect studies.
Methods Digital photos, which were taken of the water surface in the course of an indoor pond mesocosm study on herbicide effects,
were subjected to image analysis. The results were compared to wet weight and ash-free dry weight of Potamogeton at the end of the herbicide study.
Results and Discussion Both number and area of floating leaves indicated the same herbicide effects as wet weight and ash-free dry weight of Potamogeton. Error introduced by the different work steps is small and can be further minimised by a number of method improvements.
Recommendations and Perspectives In indoor mesocosm studies, errors due to the perspective adjustment may be circumvented by taking the photos perpendicular
to the water surface. Correction for lens aberration, identical light conditions and the use of fluorescence images are considered
promising. Field applications are proposed. 相似文献
26.
The main achievements of the debates on deliberative democracy and democratised science are investigated in order to analyse the reasons, meanings and prospects for a democratisation of global environmental policy. A deliberative systems approach, which emphasises the need to explore how processes in societal spheres interact to shape the deliberative qualities of the system as a whole, is adopted. Although science plays a key role in this, its potential to enhance deliberative capacity has hardly been addressed in deliberative theories. The democratisation of science has potential to contribute to the democratisation of global environmental policy, in that it also shapes the potential of deliberative arrangements in the policy sphere. Deliberative arrangements within the policy sphere may stimulate the democratisation of science to different degrees. 相似文献
27.
Reports of the damage from wolf attacks have increased considerably over the last decade in Georgia (in the Caucasus). We interviewed locals about this problem in two focal regions: the Lanchkhuti area (in western Georgia) and Kazbegi District (in eastern Georgia) where livestock numbers had increased by an order of magnitude owing to dramatic shifts in the local economies over the last decade. This coincided with expanding habitats for wolves (abandoned plantations, for example). We found that the perceived damage from wolves was positively correlated with a poor knowledge of wolf habits and inappropriate livestock husbandry practices. Our results suggest a loss of traditional knowledge contributes strongly to the wolf–human conflicts in Georgia. Restoring traditional, simple but good practices—such as protecting herds using shepherd dogs and introducing bulls into the herds—can help one solve this problem.
Electronic supplementary material
The online version of this article (doi:10.1007/s13280-014-0580-1) contains supplementary material, which is available to authorized users. 相似文献28.
面源模式的通用算法探讨 总被引:1,自引:0,他引:1
提出了矩形面源扩散模拟计算的数值积分法和中心虚点源法,以及二者结合的综合法,并用算例进行了计算精度、计算速度和结果连续性的对比.结果表明:与传统的后置虚点源法及其改进算法——谷清经验法相比,该算法与理论真值的相对误差可从20%以上降低到3%以下,并且可以准确地反映风向和面源的形状,但在计算量上要增大十几倍到上百倍.对于任意不规则面源,提出了正方形分割算法,并对分割正方形的取舍采用简便的重心判断法,以准确方便地模拟其形状.综合运用笔者提出的适于机算的通用面源算法,对不同的计算任务权衡速度和精度采用合适的算法,可以处理各种气象条件下任意形状面源的扩散计算,并可取得理想的计算精度. 相似文献
29.
30.