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991.
992.
993.
一维平流输送问题的欧拉-泰勒-伽辽金算法及数值试验 总被引:1,自引:1,他引:0
介绍了一维常系数平流输送问题的Euler-Taylor-Galerkin(ETG)算法?为获得精确的时间导数,该算法采用了包括二阶和三阶时间导数的前向泰勒级数展开,这些导数值可从空间控制微分方程求出?由此产生一般的时间分离方程?该方程采用标准的Bubnov-Galerkin有限元方法在空间离散化?在使用线性元(帽子函数)和Euler时间差分格式时,可获得精确的Taylor-Galerkin算法?当采用2步显示步骤时,算法为计算效率很高的显式?数值实验结果显示,ETG算法的误差很小,而相误差更可忽略不计,结果令人满意 相似文献
994.
Haochu Ku Yihe Miao Yaozu Wang Xi Chen Xuancan Zhu Hailong Lu Jia Li Lijun Yu 《Frontiers of Environmental Science & Engineering》2023,17(7):80
995.
Heavy Metal Transport in the Hindon River Basin, India 总被引:1,自引:0,他引:1
Total mass transfers of heavy metal in dissolved and particulate form has been determined in the downstream section of river
Hindon, an important tributary of river Yamuna (India). The contribution of different point sources to the river Hindon has
also been assessed. The river Kali has the largest contribution to the river Hindon. The highest metal loads were related
to the highest flow of the river and thereby increased both by surface runoff and sediment resuspension. The contribution
of monsoon months to the total transported load was also calculated and it was observed that monsoon months contributes more
than 40% of total loading annually for all the metals. The metal fluxes from the river Hindon were compared with other rivers
of Indian sub-continent. 相似文献
996.
Ravindra K Wauters E Tyagi SK Mor S Van Grieken R 《Environmental monitoring and assessment》2006,115(1-3):405-417
Public transport in Delhi was amended by the Supreme Court of India to use Compressed Natural Gas (CNG) instead of diesel or petrol. After the implementation of CNG since April 2001, Delhi has the highest fraction of CNG-run public vehicles in the world and most of them were introduced within 20 months. In the present study, the concentrations of various criteria air pollutants (SPM, PM10, CO, SO2 and NOx) and organic pollutants such as benzene, toluene, xylene (BTX) and polycyclic aromatic hydrocarbons (PAHs) were assessed before and after the implementation of CNG. A decreasing trend was found for PAHs, SO2 and CO concentrations, while the NOx level was increased in comparison to those before the implementation of CNG. Further, SPM, PM10, and BTX concentrations showed no significant change after the implementation of CNG. However, the BTX concentration demonstrated a clear relation with the benzene content of gasoline. In addition to the impact of the introduction of CNG the daily variation in PAHs levels was also studied and the PAHs concentrations were observed to be relatively high between 10 pm to 6 am, which gives a proof of a relation with the limited day entry and movement of heavy vehicles in Delhi. 相似文献
997.
Strobl RO Robillard PD Shannon RD Day RL McDonnell AJ 《Environmental monitoring and assessment》2006,112(1-3):137-158
The principal instrument to temporally and spatially manage water resources is a water quality monitoring network. However,
to date in most cases, there is a clear absence of a concise strategy or methodology for designing monitoring networks, especially
when deciding upon the placement of sampling stations. Since water quality monitoring networks can be quite costly, it is
very important to properly design the monitoring network so that maximum information extraction can be accomplished, which
in turn is vital when informing decision-makers. This paper presents the development of a methodology for identifying the
critical sampling locations within a watershed. Hence, it embodies the spatial component in the design of a water quality
monitoring network by designating the critical stream locations that should ideally be sampled. For illustration purposes,
the methodology focuses on a single contaminant, namely total phosphorus, and is applicable to small, upland, predominantly
agricultural-forested watersheds. It takes a number of hydrologic, topographic, soils, vegetative, and land use factors into
account. In addition, it includes an economic as well as logistical component in order to approximate the number of sampling
points required for a given budget and to only consider the logistically accessible stream reaches in the analysis, respectively.
The methodology utilizes a geographic information system (GIS), hydrologic simulation model, and fuzzy logic. 相似文献
998.
1980—2009年三峡库区空中水资源变化特征 总被引:6,自引:5,他引:1
利用1980—2009年三峡库区及周边15个气象探空站的高空资料,分析了三峡库区空中水资源的变化特征,结果表明:三峡库区上空整层水汽含量分布从东北到西南逐渐增加。三峡库区的水汽主要来自西南水汽输送,夏季西南风水汽输送强度最大。三峡库区上空水汽多以辐合为主,尤其在库区西北部和东南部的辐合特征更为明显。三峡库区的水汽主要从南边界流入,而主要从东边界流出。三峡库区各月的净水汽通量都为正值,呈单峰型变化,在7月达到最大值。近30 a,三峡库区净水汽通量经历了明显的先上升后下降的抛物线型年代际变化,春季和冬季的平均净水汽通量整体呈减少趋势,而夏季、 秋季和年平均的净水汽通量呈增加趋势。 相似文献
999.
运用TaPL3.0模型对7种PBDEs同系物在广州地区的长距离迁移潜力(LRTP)和总持久性(Pov)进行了模拟研究,并通过灵敏度分析得到了模型的关键参数.研究结果显示,PBDEs排放至大气中,特征迁移距离(CTD)为296~811km,均值为557km;Pov为19~279d,均值为184d;PBDEs平均约有73.8%分布在土壤中,16.9%分布在沉积物中,9.3%分布在其他三相中.PBDEs排放到水体时,CTD为3090~4291km,均值为3731km;Pov范围为228~854d,均值为731d;平均约92.1%分布在沉积物中,6.8%分布在水相中,1.1%在大气、土壤和植被相中.BDE47迁移潜力最大,BDE209易残留于源区形成点源性污染.PBDEs各同系物主要分布在沉积物和土壤中.随着溴代程度升高,CTD逐渐降低,Pov逐渐升高,与国外研究趋势一致. 相似文献
1000.