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961.
John W. Nicklow Larry W. Mays 《Journal of the American Water Resources Association》2001,37(1):197-211
ABSTRACT: An optimal control methodology and computational model are developed to evaluate multi‐reservoir release schedules that minimize sediment scour and deposition in rivers and reservoirs. The sedimentation problem is formulated within a discrete‐time optimal control framework in which reservoir releases represent control variables and reservoir bed elevations, storage levels, and river bed elevations represent state variables. Constraints imposed on reservoir storage levels and releases are accommodated using a penalty function method. The optimal control model consists of two interfaced components: a one‐dimensional finite‐difference simulation module used to evaluate flow hydraulics and sediment transport dynamics, and a successive approximation linear quadratic regulator (SALQR) optimization algorithm used to update reservoir release policies and solve the augmented control problem. Hypothetical two‐reservoir and five‐reservoir networks are used to demonstrate the methodology and its capabilities, which is a vital phase towards the development of a more robust optimal control model and application to an existing multiple‐reservoir river network. 相似文献
962.
探究4种改良剂施用对酸性花椒园土壤有效Cd和花椒各部位Cd含量及土壤酶活性的影响,为紫色土酸化改良及重金属污染治理提供科学依据.采用田间试验,设置不施肥(CK)、单施化肥(F)、石灰+化肥(SF)、有机肥+化肥(OM)、生物炭+化肥(BF)和酒糟灰渣+化肥(JZ)这6个处理,研究不同处理土壤pH、有效态Cd(DTPA-Cd)、花椒枝条、叶片、椒壳、椒籽Cd含量及土壤过氧化氢酶(S-CAT)、酸性磷酸酶(S-ACP)和脲酶(S-UE)活性,阐明其相互关系.结果表明:①酒糟灰渣+化肥和石灰+化肥两处理均显著提高土壤pH(P < 0.05),分别比对照提高了3.39和2.25个单位;与对照处理相比,酒糟灰渣+化肥处理和石灰+化肥两处理土壤有效态Cd含量分别降低了28.91 %和20.90 %.②酒糟灰渣+化肥处理显著降低了花椒叶片、椒壳和椒籽的Cd含量,降幅分别为31.33 %、30.24 %和34.01 %;花椒各部位对Cd的富集能力不同,具体表现为:叶片 > 枝条 > 椒籽 > 椒壳,与对照相比,酒糟灰渣+化肥处理的花椒各部位富集系数降低最为显著(P < 0.05),降幅为27.54 %~40.0 %.③改良剂处理下土壤过氧化氢酶和脲酶活性的变化规律相似,相较对照,酒糟灰渣+化肥处理对以上两种酶活性提高最为显著,分别提高了191.26 %和199.50 %,而酸性磷酸酶活性则降低了16.45 %.相关性分析表明,土壤有效Cd含量与土壤pH值呈极显著负相关(P < 0.01),过氧化氢酶和脲酶活性与土壤pH呈极显著正相关(P < 0.01),与土壤有效Cd含量呈极显著负相关(P < 0.01),酸性磷酸酶则完全相反.酸性紫色土壤施用石灰、酒糟灰渣中和土壤酸度效果最显著,在降低土壤有效Cd含量、改善土壤环境的同时,抑制花椒各部位对Cd的吸收和转运,是改良酸性紫色土及防治重金属污染的有效措施. 相似文献
963.
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966.
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
967.
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
968.
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
969.
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
970.
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