基于改进侧扫声呐法的水下抛石精准识别研究

侧扫声呐法是水下抛石探测中较为常用的方法之一,具有横向分辨率高、工作效率高等特点.但通常只根据声波散射强度值的相对大小进行水底介质判断会存在较大误差.为了提高识别准确性,以保定圩水下抛石为研究对象,首先对侧扫声呐数据进行小波去噪处理;然后根据Lambert定律消除掠射角的影响,使散射强度与水下介质的类型直接相关;最后利...     

关于浅水湖泊沉水植物覆盖度设计依据的探讨

沉水植物是维持浅水湖泊清水态的关键因子,其覆盖度是水生态修复工程中植物措施的重要参数。从沉水植物作用机理出发,通过收集天然浅水湖泊沉水植物变迁情况,分析国内外相关学者和工程的研究成果,得出在浅水湖泊沉水植物覆盖度设计时可在50%~70%范围内取值;对于污染负荷小的湖泊,可以取相对较低的值;对于水塘,其取值可按约30%考虑;当营养盐浓度超过阈值时,覆盖度应处于较高的水平。根据工程经验,在污染源恒定的情况下,覆盖度越高,对水质可起到越好的维持效果。同时,针对影响沉水植物覆盖度的有关因素,例如底泥污染、水体透明度以及季节变化等作了思考并给出了相关建议。研究结果为今后浅水湖泊沉水植物恢复的相关工作提供一定的经验和借鉴。     

A Ten—Year Study of Phytoplankton Biomass and Composition in the Nanticoke Region of Long Point Bay,Lake Erie

Changes in abundance, taxonomic composition, and the seasonal succession of phytoplankton have been evaluated at seven stations in the vicinity of Nanticoke, east of Long Point Bay, Lake Erie from 1969 to 1978. Quantitative measurements of phytoplankton were recorded as Areal Standard Units per millilitre (A.S. U. per mL). The 10-year mean value was 374 A.S. U. per mL. Annual means over the 10-year period varied from a low of 224 A.S. U. per mL in 1969 to a high of 606 A.S.U. per mL in 1978.Seasonal succession patterns and biomass levels showed fluctuation expressing unimodal, bimodal, and even trimodal peaks from station to station and year to year. 1969 and 1974 had abnormally low levels of phytoplankton biomass while 1970 and 1978 showed mean biomass values that were exceptionally higher than the 10-year mean. A total of 240 taxa were recorded during the 10 years of study, 35 of which were present during all years.Temperature data collected at the same stations suggested that 1970 and 1973 were years in which the water was slightly warmer but followed very closely a normal seasonal curve ranging from 5°C in April to a maximum of 22°C in August. A comparison of seasonal succession of phytoplankton to temperature did not show any direct or inverse relationship to years in which one or the other parameter deviated from the normal pattern.Due to the similarity of the algal community in its year-to-year seasonal development and taxonomic composition, the ten years of data presented in this study should provide a sound data base for future comparisons of nearshore phytoplankton in Lake Erie.     

安徽省淮北地区除涝水文计算办法初探

在分析以往除涝水文计算办法及存在问题的基础上,研究了淮北地区水文计算主要影响因素的变化趋势,探讨了现行水文计算办法的不足并对其进行复核。     

基于熵权法的流域水资源脆弱性评价——以淮河流域为例

流域水资源脆弱性评价可以量化表现出水资源的脆弱性程度,客观地反映研究区的水安全状况。根据水资源脆弱性的表现形式及成因,设置了水量、水质、洪涝灾害、旱灾4个一级指标,自然因素、人为因素、承载因素3个二级指标,分级构建了水资源脆弱性评价指标体系,在线性加权法的基础上采用熵权法构建了水资源脆弱性评价模型。以淮河流域为例进行实证分析,从时间、空间2个维度上对2003—2012年淮河流域整体及流域内的4个省份进行水资源脆弱性评价。结果表明时间上,10 a间淮河流域整体水资源脆弱度数值逐年减小,水资源脆弱性呈现好转趋势,流域内河南、安徽、江苏、山东4省的水资源脆弱性在10 a间均有所缓解;空间上,淮河流域水资源自西向东越来越脆弱。研究结果表明目前淮河流域水资源脆弱性状况呈现好转趋势,但仍然存在一些问题,有待进一步管理和调控。