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501.
John H. Carson 《Environmental and Ecological Statistics》2001,8(3):201-211
A new tool is presented based on the principle of maximum entropy for enhanced hot spot detection based on composite sampling with no (or minimal) requirement for composite breakdown. The methodology presented here is easy to implement and facilitates the use of multiple criteria for evaluating attainment of site remediation objectives. The new methodology provides very simple decision rules that can easily be used by non-statisticians and complements the use of composites for control of residual mean concentrations. 相似文献
502.
Jonathan G. Kennen 《Journal of the American Water Resources Association》1999,35(4):939-955
ABSTRACT: The level of macroinvertebrate community impairment was statistically related to selected basin and water-quality characteristics in New Jersey streams. More than 700 ambient biomonitoring stations were chosen to evaluate potential and known anthropogenic effects. Macroinvertebrate communities were assessed with a modified rapid-bioassessment approach using three impairment ratings (nonimpaired, moderately impaired, and severely impaired). Maximum-likelihood multiple logistic-regression analysis was used to develop equations defining the probability of community impairment above predetermined impairment levels. Seven of the original 140 explanatory variables were highly related to the level of community impairment. Explanatory variables found to be most useful for predicting severe macroinvertebrate community impairment were the amount of urban land and total flow of municipal effluent. Area underlain by the Reading Prong physiographic region and amount of forested land were inversely related to severe impairment. Nonparametric analysis of variance on rank-transformed bioassessment scores was used to evaluate differences in level of impairment among physiographic regions and major drainage areas simultaneously. Rejection of the null hypothesis indicated that the levels of impairment among all six physiographic regions and five major drainage areas were not equal. Physiographic regions located in the less urbanized northwest portion of New Jersey were not significantly different from each other and had the lowest occurrence of severely impaired macroinvertebrate communities. Physiographic regions containing urban centers had a higher probability of exhibiting a severely impaired macroinvertebrate community. Analysis of major drainage areas indicates that levels of impairment in the Atlantic Coastal Rivers drainage area differed significantly from those in the Lower Delaware River drainage area. 相似文献
503.
Annie J. Morris Joseph J. Donovan Michael Strager 《Environmental Modeling and Assessment》2009,14(1):73-84
Streamflow values are commonly synthesized for locations where flow measurement stations are lacking or where only intermittent
measurements are available. In an Appalachian Mountains dataset comprised of 29 watersheds, the most appropriate among geomorphic,
geologic, and hydrogeologic datasets were selected for use in prediction of streamflow at watershed scale. A statistical model
was developed using principal components analysis (PCA) and cluster analysis (CA) for. Using CA on variables derived from
the PCA, an optimum set of variables was derived for predicting streamflow. Results indicate there are two categories of watersheds
in the study area. The first is strongly correlated with climatic variables (precipitation, temperature, elevation, and groundwater
recharge). The second is strongly correlated with two geomorphic variables (watershed slope and percentage of forested area).
The spatial distribution of cluster classifications shows that watersheds dominated by the climatic component are located
along the Allegheny Front while watersheds dominated by the geomorphic component are located in the Allegheny Plateau and
Valley and Ridge physiographic provinces. These variations between the Allegheny Plateau and Valley and Ridge physiographic
provinces suggest that, to accurately model streamflow, modeling needs be done based on natural physiographic boundaries rather
than political boundaries. In this physiographic setting, elevation seems to be a major control. 相似文献
504.
505.
为加强分接开关故障的事前预防与隐患排查,保障电力系统的安全稳定运行,根据故障类型、产品类型和应用环境等维度,对国家电网公司在运分接开关进行故障统计分析.研究结果表明:分接开关发生"分接头不同步"的概率相对最高,二次回路的继电器故障频次最高;真空灭弧分接开关的故障概率略低于绝缘油灭弧分接开关;气候湿润地区、昼夜温差大地区... 相似文献
506.
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508.
Bruce D. Lindsey William J. Gburek Gordon J. Folmar 《Journal of the American Water Resources Association》2001,37(5):1103-1117
ABSTRACT: A study of stream base flow and NO3‐N concentration was conducted simultaneously in 51 subwatersheds within the 116‐square‐kilometer watershed of East Mahantango Creek near Klingerstown, Pennsylvania. The study was designed to test whether measurable results of processes and observations within the smaller watersheds were similar to or transferable to a larger scale. Ancillary data on land use were available for the small and large watersheds. Although the source of land‐use data was different for the small and large watersheds, comparisons showed that the differences in the two land‐use data sources were minimal. A land use‐based water‐quality model developed for the small‐scale 7.3‐square‐kilometer watershed for a previous study accurately predicted NO3‐N concentrations from sampling in the same watershed. The water‐quality model was modified and, using the imagery‐based land use, was found to accurately predict NO3‐N concentrations in the subwatersheds of the large‐scale 116‐square‐kilometer watershed as well. Because the model accurately predicts NO3‐N concentrations at small and large scales, it is likely that in second‐order streams and higher, discharge of water and NO3‐N is dominated by flow from smaller first‐order streams, and the contribution of ground‐water discharge to higher order streams is minimal at the large scale. 相似文献
509.
针对黑龙江龙凤山区域本底站2009年1月~2011年12月大气CO2在线观测数据,研究基于地面风、日变化等大气本底/非本底数据筛分方法(SWDV)和稳健局部近似回归大气本底/非本底数据筛分方法(REBS)在龙凤山区域本底站的适用性.研究表明:2种筛分方法在春、秋和冬季都能很好反映龙凤山大气CO2浓度的趋势变化及局地源汇对观测CO2浓度的影响,对于高浓度的非本底数据都能够较好的识别,但在夏季使用REBS方法会影响筛分的准确性,不建议在龙凤山区域本底站使用REBS筛分方法.SWDV和REBS法筛分出的本底数据分别占总数据量的30.7%和 58.9%.2种方法均筛分为本底浓度和非本底浓度的数据分别占总数据量的21.5%和32.0%.二者筛分的本底季平均浓度在春季相差最小为(0.1±0.3)×10-6(摩尔比,下同),冬季和秋季次之,在夏季相差最大为(4.2±1.0)×10-6.典型个例分析表明,SWDV法会将白天一些受西南污染气流影响的CO2浓度误筛分为本底浓度,REBS法会将个别在静稳天气条件下受局地影响大的CO2观测值误筛分为本底浓度.夏季局地污染状况可能被植被强烈的光合作用抵消,CO2浓度变化不大,使得REBS误筛分为本底浓度,以及对于一些较低的CO2浓度值,REBS误筛分为非本底浓度,这些因素导致2种筛分方法在夏季本底浓度差别较大. 相似文献
510.
对我国城市固体废物(MSW)清运量、无害化处理量、卫生填埋量和场所、焚烧量和堆肥量的变化进行了趋势分析、相关性分析以及时空分布分析;并且对联合国气候变化框架公约(UNFCCC)官方网站公布的《京都议定书》中附件1国家温室气体的排放数据进行了统计分析. 结果表明:我国城市固体废物清运量和卫生填埋量很大并逐年增加;城市固体废物卫生填埋处理厌氧消化产生的温室气体随着填埋量以及标准卫生填埋场所的变化而变化;从发达国家各领域的温室气体排放情况来看,废物领域的减排潜力很大,尤其是城市固体废物卫生填埋处理,这对我国开展城市固体废物卫生填埋处理温室气体减排有一定启示. 相似文献