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排序方式: 共有173条查询结果,搜索用时 93 毫秒
31.
George H. Nieswand Robert M. Hordon Theodore B. Shelton Budd B. Chavooshian Steven Blarr 《Journal of the American Water Resources Association》1990,26(6):959-966
ABSTRACT: Buffer strips are undisturbed, naturally vegetated zones around water supply reservoirs and their tributaries that are a recognized and integral aspect of watershed management. These strips can be very effective in protecting the quality of public potable water supply reservoirs by removing sediment and associated pollutants, reducing bank erosion, and displacing activities from the water's edge that represent potential sources of nonpoint source pollutant generation. As part of a comprehensive watershed management protect for the State of New Jersey, a parameter-based buffer strip model was developed for application to all watersheds above water supply intakes or reservoirs. Input requirements for the model include a combination of slope, width, and time of travel. The application of the model to a watershed in New Jersey with a recommended buffer strip width that ranges from 50 to 300 feet, depending upon a number of assumptions, results in from 6 to 13 percent of the watershed above the reservoir being occupied by the buffer. 相似文献
32.
Using structured systems analysis to design an integrated system for transport planning and environmental analysis 总被引:1,自引:0,他引:1
S. P. LoseeA. L. Brown 《环境科学学报(英文版)》1996,8(2):129-144
Usingstructuredsystemsanalysistodesignanintegratedsystemfortransportplanningandenvironmentalanalysis¥S.P.Losee;A.L.Brown(Facu... 相似文献
33.
通过对满足选点标准的5个调查点和7个空气质量质控对照点,一年四个季度每季度抽样5d以上连续自动监测环境空气质量的科研性监测方式,共获取各类有效数据约20万个,从而以定量的方式确定了重庆市主要公共集会场所,交通道路和风景旅游区的环境空气质量水平。 相似文献
34.
基于碳排放系数法估算了1997~2015年中国城镇、农村和整体(包含城镇和农村)居民生活消费引起的直接碳排放量,进一步采用Dagum基尼系数和Kernel密度函数估计方法对中国城镇和农村居民生活消费碳排放的地区差距及分布动态进行实证研究.同时,采用乘积式对数平均迪式指数模型(M-LMDI)分析了直接能源消费强度、居民人均消费水平和单位能源碳排放强度3大因素对居民消费碳排放变化的影响,并重点考察了各省份相关变量对生活消费碳排放影响的城乡差异.结果表明:(1)中国城镇和农村居民人均生活消费碳排放量在研究期内呈现逐年递增的趋势,在空间上均存在显著非均衡特征.(2)中国居民人均生活消费碳排放的地区总差异呈现波动下降的趋势,从1997年的0.379下降到2015年的0.244.1997~1999年城镇和农村居民生活消费碳排放的组间差距是城乡差距的主要来源,其贡献率超过50%.2000年后组内差距成为城乡差距的主要来源,其贡献率均大于40%并超过了组间差距.(3)城镇和农村居民人均生活消费碳排放均在增加,地区差异均在扩大.(4)对全国居民生活消费碳排放变动贡献最大的省区是内蒙古,累计贡献值达0.1005.贡献最小的省区是云南,累计贡献值为0.0125.(5)农村的能源消费强度和人均消费水平的贡献程度在研究期内均大于城镇,单位能源碳排放强度在两个地区的贡献水平表现出了波动性. 相似文献
35.
基于Kikuji Togawa所提出的常用人员疏散行动时间经验公式,使用拉丁超立方抽样法,研究房间人员密度和出口宽度的不确定性对疏散行动时间的影响。得出二者服从均匀分布和正态分布条件下,疏散行动时间的概率密度直方图和累积概率曲线。结果表明,人员密度和出口宽度的不同分布形式对疏散行动时间都有显著影响,二者服从正态分布时,计算得到的疏散行动时间范围比服从均匀分布小,且较为集中。而服从均匀分布时,计算得到的疏散行动时间在其范围内则较为均匀、分散。在小概率0~0.1区间范围内,人员密度和出口宽度服从正态分布时,计算得到的疏散行动时间累计概率值明显较均匀分布小,说明二者服从正态分布得到的疏散行动时间值偏于保守。二者均为不确定参数时,假定人员密度服从均匀分布,出口宽度服从正态分布时计算得出的疏散行动时间值偏于保守。 相似文献
36.
为弥补安全社区现场评定指标体系中过多依靠人为主观因素的不足,客观反映并优化安全社区建设成效的评价结果,构建安全社区居民满意度(SCRSI)评估模型。运用AMOS17.0和SPSS17.0l软件分析从不同类型安全社区回收的280份调查问卷,验证该模型的合理性,得出SCRSI回归方程,并以此作为安全社区评估标准进行实例验证。结果表明,在安全社区建设过程中,应重视对居民期望的管理,确保宣传信息是准确和客观的,抓住影响居民满意度的关键因素,重点根据居民意见、建议和抱怨情况制定相应的预防和纠正措施。 相似文献
37.
Past on-site experience was linked to the crowding perceptions and use displacement of 383 on-site visitors to the peri-urban
Danube Floodplains National Park, Austria. Three visitor groups were determined according to their area experience: local
residents from Vienna and rural communities, having the highest level of experience; regional visitors from the city and eastern
Austria; and tourists from Austria and abroad with the lowest degree of experience. Crowding perceptions were significantly
different across the user groups. More than 50% of local residents perceived the national park as crowded, whereas only 27%
of regional visitors and 19% of tourists reported such an evaluation. Even among local residents and regional visitors, respondents
with more on-site experience expressed a greater impression of a crowded park. Differences in crowding evaluations between
local rural and urban residents and between regional rural and urban visitors were not found. For 27% of local residents and
15% of regional visitors, use levels were so unacceptable that they displaced temporally and spatially, whereas use displacement
was relatively irrelevant for tourists. The use displacement strategies involved differ among the three user groups. Management
implications were discussed, taking the specific situation of the small national park on the urban-rural fringe into consideration. 相似文献
38.
Anwar Battikhi Don Kirkham 《Journal of the American Water Resources Association》1979,15(4):1004-1015
ABSTRACT: A mathematical solution based on porous media flow is developed for solute travel time to a well as affected by a leak around the upper part of the casing. Consider a well of radius 0.2 meters (m) penetrating, fully, a semiconfined aquifer of thickness 6 m with impermeable casing length of 4.5 m, and screened casing length 1.5 m. Around the upper 1.5 m of the impermeable casing length, there is a highly permeable region (a leak). The radius of influence of the well is 10 m. The porous flow medium has a hydraulic conductivity of 10 m/day and a porosity of 0.25. Between the water table and the water level in the well, there is a steady state pumped down head difference of 0.3 m. Solute travel time from a point at the bottom of the leak to the well is 2.33 days. If the leak is sealed (grouted), the travel time is 6.24 days. Examples of six different geometries are given. Laboratory studies verify the theory. The computations should be useful in the design and protection of water wells from solutes, such as from agriculture, industry, strip mines, or sanitary landfills. 相似文献
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