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排序方式: 共有275条查询结果,搜索用时 234 毫秒
271.
视觉影响评价技术研究与应用 总被引:7,自引:0,他引:7
文章首先对于国内外出现的视觉影响评价与景观影响评价的概念进行了对比分析,提出“视觉影响评价”在功能表述上更为确切,并给出了视觉影响评价的基本概念,然后针对视觉影响评价的特点,介绍了视觉模拟用以预测影响的手段以及评价方法和减缓措施,并通过一具体实例进行了说明,最后针对我国视觉影响评价的现状提出了一些加强和改善的建议。 相似文献
272.
易燃易爆危险物质泄漏扩散仿真及其应用的研究 总被引:14,自引:0,他引:14
以某轻烃厂泄漏事故为研究对象,研制并开发了一个事故后果仿真软件(PCIMS).针对仿真过程中存在的问题,如模型的复杂性、参数的不确定性等提出了处理方法.通过具体生产装置的泄漏扩散后果分析,演示了PCIMS的仿真结果 相似文献
273.
A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in
the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter
(Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will
decrease by nearly 20% ifBythotrephes successfully establishes itself in the lake. The model suggests that this decrease will result from lowered transfer efficiencies
within the food web and increased flux of contaminants to the hypolimnion. The model also indicates that phosphorus management
will have little effect on contaminant concentrations in salmonines. The modeling exercise helped identify weaknesses in the
data base (e.g., incomplete information on contaminant loadings and on the biomass, production, and ecological efficiencies
of dominant organisms) that should be corrected in order to make reliable management decisions. 相似文献
274.
Nonpoint Source Pollution Responses Simulation for Conversion Cropland to Forest in Mountains by SWAT in China 总被引:1,自引:0,他引:1
Several environmental protection policies have been implemented to prevent soil erosion and nonpoint source (NPS) pollutions
in China. After severe Yangtze River floods, the “conversion cropland to forest policy” (CCFP) was carried out throughout
China, especially in the middle and upper reaches of Yangtze River. The research area of the current study is located in Bazhong
City, Sichuan Province in Yangtze River watershed, where soil erosion and NPS pollution are serious concerns. Major NPS pollutants
include nitrogen (N) and phosphorus (P). The objective of this study is to evaluate the long-term impact of implementation
of the CCFP on stream flow, sediment yields, and the main NPS pollutant loading at watershed level. The Soil and Water Assessment
Tool (SWAT) is a watershed environmental model and is applied here to simulate and quantify the impacts. Four scenarios are
constructed representing different patterns of conversion from cropland to forest under various conditions set by the CCFP.
Scenario A represented the baseline, i.e., the cropland and forest area conditions before the implementation of CCFP. Scenario
B represents the condition under which all hillside cropland with slope larger than 25° was converted into forest. In scenario
C and D, hillside cropland with slope larger than 15° and 7.5° was substituted by forest, respectively. Under the various
scenarios, the NPS pollution reduction due to CCFP implementation from 1996–2005 is estimated by SWAT. The results are presented
as percentage change of water flow, sediment, organic N, and organic P at watershed level. Furthermore, a regression analysis
is conducted between forest area ratio and ten years’ average NPS load estimations, which confirmed the benefits of implementing
CCFP in reducing nonpoint source pollution by increasing forest area in mountainous areas. The reduction of organic N and
organic P is significant (decrease 42.1% and 62.7%, respectively) at watershed level. In addition, this study also proves
that SWAT modeling approach can be used to estimate NPS pollutants’ impacts of land use conversions in large watershed. 相似文献
275.
基于HSPF模型的大阁河流域径流量模拟 总被引:6,自引:0,他引:6
文章应用HSPF模型对潮河支流大阁河流域进行径流量模拟,采用大阁水文站1972~1975年逐日流量观测数据,通过参数灵敏度分析和校正,使模拟的流量和实测的数据拟合,对模型进行校正。在此基础上采用1982~1985年逐日流量观测数据对模型进行验证。采用相对误差(RE)以及Nash-Suttcliffe效率系数(Ens)作为模型适用性的评价系数,模拟结果得出流量多年相对误差为0.17、Ens为0.87,表明HSPF模型对研究区流域长期的连续径流量模拟具有较好的适用性。 相似文献