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991.
首先对济南城市防汛GIS系统进行了总体设计,给出了系统的数据库设计,并重点介绍积水模拟模型的输入输出设计,然后对组件技术、积水模拟模型等系统实现的关键技术进行了阐述,最后介绍了济南城市防汛GIS的特色功能模块。系统运行良好,为济南的城市防汛提供了科学决策的依据。 相似文献
992.
993.
Evolution of scouring process downstream of grade‐control structures under steady and unsteady flows
For many incised channels, one of the most common strategies is to install some hard structures, such as grade‐control structures (GCSs), in the riverbed to resist further incision. In this study, a series of experiments, including both steady and unsteady flow conditions, were conducted to investigate the scouring process downstream of a GCS. Three distinct phases, including the initial, developing and equilibrium phases, during the evolution of scour holes were identified. In addition, a semi‐empirical method was proposed to predict the equilibrium scour‐hole profile for the scour countermeasure design. In general, the comparisons between the experimental and simulated results are reasonably consistent. As the studies on temporal variation of the scour depth at GCSs caused by floods are limited, the effect of flood hydrograph shapes on the scour downstream of GCSs without upstream sediment supply was also investigated experimentally in this study. Based on the dimensional analysis and the concept of superposition, a methodology is proposed to simulate the time evolution of the maximum scour depth downstream of a GCS for steady flows. Moreover, the proposed scheme predicts reasonably well the temporal variations of the maximum scour depth for unsteady flows with both single and multiple peak. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
994.
995.
In many coastal regions, oil spills can be considered as one of the most important and certainly the most noticeable forms of marine pollution. Efficient contingency management responding to oil spills on waters, which aims at minimizing pollution effects on coastal resources, turns out to be critically important. Such a decision making highly depends on the importance attributed to different coastal economic and ecological resources. Economic uses can, in principal, be addressed by standard measures such as value added. However, there is a missing of market in the real world for natural goods. Coastal resources such as waters and beach cannot be directly measured in money terms, which increases the risk of being neglected in a decision making process. This paper evaluates these natural goods of coastal environment in a hypothetical market by employing stated choice experiments. Oil spill management practice in German North Sea is used as an example. Results from a pilot survey show that during a combat process, beach and eider ducks are of key concerns for households. An environmental friendly combat option has to be a minor cost for households. Moreover, households with less children, higher monthly income and a membership of environmental organization are more likely to state that they are willing to pay for combat option to prevent coastal resources from an oil pollution. Despite that choice experiments require knowledge of designing questionnaire and statistical skills to deal with discrete choices and conducting a survey is time consumed, the results have important implications for oil spill contingency management. Overall, such a stated preference method can offer useful information for decision makers to consider coastal resources into a decision making process and can further contribute to finding a cost-effective oil preventive measure, also has a wide application potential in the field of Integrated Coastal Zone Management (ICZM). 相似文献
996.
内陆碱化湿地土壤有机质和全磷的时空分布特征 总被引:1,自引:0,他引:1
以付老文泡湿地为研究对象,分析了内陆碱化湿地土壤有机质和全磷含量的时空分布特征。研究结果表明7月表层土壤有机质和全磷空间分布格局的异质性高于亚表层,而9月亚表层土壤则呈现出较高的异质性。2采样期内有机质和全磷含量均呈现由表层向下呈减少趋势,除9月土壤有机质外,上下土壤层内的有机质和全磷含量均存在显著性差异。湿地全磷随土壤有机质增加呈幂函数增长变化。湿地土壤有机质和全磷随土壤水分含量增加均呈对数衰减变化,但土壤有机质和全磷随pH值增加则分别呈现指数和幂函数衰减变化。 相似文献
997.
998.
根据2004年9月18日—10月2日南海北部航次所获得的表层浮游植物群数据, 对其组成及数量分布进行了探讨分析。该次调查鉴定浮游植物共53属152种(含变种和变型), 分别属于硅藻门35属88种、甲藻门15属60种、蓝藻门1属2种及金藻门1属1种等; 优势种中分布较广泛的有柔弱伪菱形藻Pseudo-nitzschia delicatissima、反曲原甲藻Prorocentrum sigmoides、微小原甲藻P. mininum、锥状施克里普藻Scrippsiella trochoidea和红海束毛藻Trichodesmium erythraeum等; 浮游植物细胞丰度的数量范围为(0.11—23.61)×106cells•m-3, 呈现近岸区域高于远岸区域的平面分布格局, 最大值和最小值分别出现在海南岛东北部海域的E506站和海南岛东南部海域的B3站; 浮游植物物种丰富度也是近岸的站点较高, 以靠近珠江口E708站的51种为最多。硅藻类细胞丰度范围为(0.02—8.13)×106cells•m-3, 主要分布在高盐的外海水域, 其中产二甲基磺酸丙酯(DMSP)的小环藻Cyclotella spp.在多个站点出现; 甲藻类以近岸水域居多, 细胞丰度最高达15.67×106cells•m-3(E506站), 其中数量较多的赤潮种类主要有锥状施克里普藻、反曲原甲藻、微小原甲藻、环沟藻Gyrodinium spp.等; 固氮的红海束毛藻在调查海域广泛分布, 但主要集中于东部, 以E206站最多, 高达1.8×107cells•m-3。结合水文资料和其他层次的浮游植物资料进行对比分析, 结果表明, 红海束毛藻的分布与黑潮水的入侵存在一定关系, 其分布受水团和海流的影响。 相似文献
999.
为了分析黄海区虾拖网网囊网目对副渔获物的选择性,运用套网法对30,33,40 mm 3种网目尺寸的网囊进行了选择性试验。用统计学方法求得几种优势副渔物的逃逸率,并用极大似然法对渔获数据进行处理求得相关的选择性参数。结果表明,大部分副渔获物的逃逸率随着网囊网目尺寸的增大而增大,在网目尺寸为30,33,40 mm时矛尾虎鱼(Chaeturichthys stigmatias)的逃逸率分别为48.3%,59.7%和62.6%;细巧仿对虾(Parapenaeopsis tenella)的逃逸率分别为67.0%,68.2%,68.7%。矛尾虎鱼的选择性参数也随着网目尺寸的增大而增大,在网目尺寸为30,33,40 mm时,矛尾虎鱼的50%选择体长L50分别为81.858,86.715和88.028 mm,选择范围SR分别为41.097,45.007和50.423 mm。研究表明,单靠放大网囊网目尺寸来释放虾拖网中副渔获物,效果不甚理想。 相似文献
1000.
着重对当前海洋测绘信息处理技术的几个研究热点进行了介绍,内容包括海陆基准的统一、海洋遥感图像的精校正、卫星测高和遥感测深技术,并对海洋测量信息处理与多元化表示作了简要的讨论。 相似文献