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排序方式: 共有692条查询结果,搜索用时 31 毫秒
641.
多层递阶预测是近十几年提出并发展起来的动态系统新型统计预测理论。由于该方法把动态系统看成是一个时变参数系统,因而符合客观这际预测误差相对较小,用它对水资源进行预测具有一定的实用价值。 相似文献
642.
基于遗传算法的大气颗粒物的源解析 总被引:19,自引:0,他引:19
遗传算法是一种全局优化的随机搜索方法,适用于模型参数寻优。将遗传算法用于大气颗粒物源解析的CMB方程组中参数的优化,得到各污染源对大气颗粒物的优化贡献率。该方法应用于成都市大气颗粒物的源解析结果与用其他多种源解析法得出的结果基本一致。理论分析和应用实践表明了遗传算法用于大气颗粒物源解析研究具有简便、准确和实用性强等特点。 相似文献
643.
Evaluation of biological water purification functions of inland lakes using an aquatic ecosystem model 总被引:1,自引:0,他引:1
An effective measure to cope with eutrophication of lakes is to remove nutrients that can cause algal blooming by taking advantage of natural water purification processes. Here the term “purification” is defined, in a wide sense, as the potential role of a water body to contribute to the reduction of pollutants and thus controlling eutrophication. Also regarded as a kind of ecological regulating services, biological purification involves various processes concerning seasonal nutrient fixation, such as uptake by aquatic macrophytes, biofouling onto foliage substrates, feeding by organisms in higher trophic level, and eternal loss or removal of substance from the water. In order to evaluate the water purification ability, a numerical lake ecosystem model highlighting the role of macrophyte colonies in the shore zone was developed and applied to Lakes Suwa, Kasumi and Biwa, as well as five small lakes attached to Lake Biwa. 相似文献
644.
Th. Eikmann S. Michels V. Makropoulos Th. Krieger H. J. Einbrodt K. Tsomi 《毒物与环境化学》2013,95(1):461-466
An investigation was undertaken to study the exposure of children in areas with different air pollution and of adults working in three different plants (lead processing, battery plant, oil refinery) using arsenic in urine as a biological parameter. The arsenic excretion of the children are in agreement with the air pollution in the investigated areas. The workers in the lead processing plant are found to have the highest urine excretion values of the three worker collectives. The mean excretion values is nearly ten times higher than that found in the normal population. 相似文献
645.
以常用锚杆支护理论为依托,根据锚杆的受力特点,分析了大变形隧道长短锚杆各自的支护机理,提出了其参数的设计方法,并通过算例计算和数值模拟验证的方式对其合理性进行了验证.结果表明,大变形隧道长短锚杆组合支护中,短锚杆加固浅部围岩形成承载拱结构,长锚杆将浅部承载拱结构稳定到深部围岩,两者联合支护有效地控制了隧道的大变形,支护方式有救,参数设计方法合理,保证了隧道的支护效果,对隧道支护设计具有重要的工程参考意义. 相似文献
646.
在淹水和非淹水条件下,在河流湿地土壤中加入高浓度(10mg·kg-1)和极高浓度(200mg·kg-1)芘,研究了芘降解过程、芘生物有效性和土壤酶活性的长期动态变化.结果表明,培养91d后,高浓度芘处理的土壤中芘的残留率在淹水和非淹水条件下分别为79.0%和51.4%,而极高浓度处理的芘残留率在淹水和非淹水条件下分别为61.1%和33.9%.利用Tenax-ta树脂提取快速解吸态生物有效芘,结果发现,有效芘浓度在高浓度芘处理的两种土壤中的值比较接近,分别为1.01mg·kg-1和1.23mg·kg-1;而有效芘浓度在极高浓度处理的两种土壤的相应值差别较大,分别为20.31mg·kg-1和9.44mg·kg-1.采用四参数Logistic模型能够精确地拟合芘降解过程和生物有效性变化过程(p<0.0001).土壤蔗糖酶、脲酶和多酚氧化酶对芘污染敏感,而过氧化氢酶对芘污染不敏感.实验结果揭示了河流湿地土壤芘在淹水条件下降解活跃阶段持续时间短和芘生物有效性高的特征以及土壤蔗糖酶、脲酶和多酚氧化酶活性可以作为评估芘污染影响的候选指标. 相似文献
647.
Peter R. Jaffe 《Journal of the American Water Resources Association》1988,24(3):585-592
ABSTRACT: Water quality data collected between 1978 and 1981 in a highly lake in Northern Venezuela, Lake Valencia, were analyzed to detect spatial and temporal trends. Based on the results of the analyses, an appropriate nutrient-algae dynamics model was formulated. Because many parameters, such as the algae concentration were constant over time, and the model is time dependent, the model had to be calibrated with the use of a large and structured trial-and-error calibration process. Through the calibration process, the most sensitive parameters of the model were identified, and are in order of importance: the chlorophyll-to-nitrogen ratio for algae, the algae settling velocity, the phosphorus release rate from the sediments, the chlorophyll-to-phosphorus ratio for algae, and the exchange coefficient in the upper layer of the lake. Model simulations showed that a reduction in the nitrogen load to the lake as well as a reduction in the phosphorus load will decrease the algae population. These model simulations had a high degree of uncertainty associated with them, making additional sampling directed towards the measurement of the sensitive parameters desirable. 相似文献
648.
从武汉市取缔正三轮摩托车("麻木")的事件出发,简述了正三轮摩托车的污染危害,计算了取缔车辆1年排放的有害物质,通过监测数据说明了对大气环境的影响。 相似文献
649.
Terrance W. Cundy Kenneth N. Brooks 《Journal of the American Water Resources Association》1981,17(5):775-782
The Streamflow Synthesis and Reservoir Regulation (SSARR) model was calibrated and verified on the Madison and Gallatin watersheds in the upper Missouri River drainage. The study was performed to determine if the SSARR model could simulate snowmelt-runoff volumes to effect better operation of six multipurpose reservoirs on the Missouri River. Physical watershed characteristics and parameter sensitivity are incorporated into a procedure which expedites model calibration. Criteria are established to facilitate parameter development and to objectively evaluate calibration and verification results. A ratio of simulated to observed snowmelt-runoff volumes of the Madison River averaged 1.00 and 1.02 for calibration (N = 8 years) and verification (N = 6 years) with corresponding standard deviations of 0.08 and 0.13. Gallatin volume ratios averaged 0.99 and 0.95 for calibration (N = 7 years) and verification (N = 5 years) with respective standard deviations of 0.08 and 0.28. 相似文献
650.
ABSTRACT: This paper introduces the application of Computer Intensive Statistics (CIS) to the evaluation of parameter uncertainty with specific reference to the parameters in the ARMA models used in the synthesis of streamflows. The CIS provides an empirically derived joint distribution for all parameters. Random values from this distribution can be drawn for application in the model for the generation of a specific synthetic sample. The CIS originally proposed by Efron and discussed herein is of general applicability in the evaluation of uncertainty in any statistic derived from a set of data. Some comments and limitations of the CIS are discussed in the concluding remarks. 相似文献