潮汐河网区水污染总量控制及其分配方法

本文介绍了潮汐河网地区水污染总量控制的两种方法和水污染负荷总量分配的六种方法。对各种方法都建立了相应的数学模型,介绍了求解方法,并给出了各种方法的应用实例。      

感潮河网水域(广州河段)纵向离散系数的研究

感潮河网地区的污染物质混合输移的机制十分复杂,本文结合广州河段1987年枯水期的水文水质同步实测资料,利用理论分析,室内实验及计算机模拟识别等方法,对感潮河网地带的纵向离散系数进行了全面的研究。对天然河流的振荡剪切离散提出了一个实用的解析分析方法;通过实验研究分析了等效离散系数D*与振荡剪切离散系数D-的关系;利用实测数据分析了典型断面的D*/D-的基本特征,并通过计算机模拟,为广州河段提供了D*的预测公式。      

泉州白濑水利枢纽工程升鱼机进鱼口位置选择研究

水库大坝建设会对鱼类洄游造成阻隔影响,为减少大坝阻隔对鱼类遗传交流的影响,大坝应建设过鱼设施。福建省泉州白濑水利枢纽工程采用升鱼机过鱼设施,而进鱼口位置选择是影响过鱼设施设计成败的关键因素。根据白濑水利枢纽布置特点,从坝下流场、工程条件、过鱼效果等方面进行进鱼口位置比选研究,为类似水库工程过鱼设施进鱼口位置选择提供参考和借鉴。     

电除尘器改造场地局促时进气烟箱的设计

在原地将1套300 MW机组配备的双列双室3电场侧部挠臂锤振打式电除尘器(ESP),改造为双列双室4电场顶部电磁锤振打式ESP时,先将其竖井式进气烟箱的前半部改为结构紧凑的下部进气烟箱,以便在各室增加1个电场。受场地制约,第1、第2层气流均布板设置在壳体之内,导致两板的间距、第2层板与第1电场的间距均小于800 mm。加之取消壳体的进口下端板,因而显著地影响第1电场内的气流分布均匀性。在模型上适当调整导流板和气流均布板的结构之后,第1电场内的气流分布均匀性、粉尘浓度分布均匀性都获得了改善,且ESP内的气体流动形式已成为有利于收尘的上斜式流动。     

C/SiC复合材料波纹点阵结构进气道前缘设计与制备

目的 C/SiC复合材料进气道前缘轻量化设计与制备。方法基于进气道气动外形和结构要求,建立波纹点阵夹芯结构的进气道前缘有限元模型,然后按照德国航空中心H2K超声速风洞试验室试验的数据进行反演,得到进气道前缘的热流密度分布,据此进行边界条件加载,在模型中考虑固体导热、表面辐射以及空腔辐射三种传热方式。采用瞬态传热算法,求解100 s下进气道前缘的温度场,为了进一步降低C/SiC复合材料波纹点阵结构进气道前缘的最高温度,设计不同的进气道前缘尖端半径,并进行优化。最后根据优化得到的波纹点阵进气道几何参数,采用PIP法制备出C/SiC复合材料点阵结构进气道前缘。结果进气道尖端半径小于0.5mm时,最高温度高于1800℃,超过C/SiC复合材料极限温度;进气道尖端半径大于1.0 mm时,最高温度为1520℃,低于C/SiC复合材料极限温度;进气道尖端半径大于2.0 mm时,增大半径对降低进气道前缘最高温度没有明显的作用。不同进气道前缘尖端半径下,最高温度达到稳态的时间不一样,半径等于0.5 mm时,进气道前缘达到稳态的时间约为30 s左右。随着前缘尖端半径增大,最高温度达到稳态的时间增加,半径为1.0 mm时,达到稳态时间约为60 s。结论进气道前缘最高温度随着尖端半径增大明显降低,当半径大于2.0 mm时,增大半径对降低进气道前缘最高温度没有明显的作用。     

Quantitative assessment of tidal wetlands using remote sensing

Effective management of tidal wetlands requires periodic data on the boundaries, extent, and condition of the wetlands. In many states, wetlands are defined wholly, or in combination with other criteria, by the presence of particular emergent halophytic plants. Many important characteristics of the wetlands ecosystem are related directly to the production of emergent plant material or may be inferred from knowledge of the distribution of emergent plant species. Remote-sensing techniques have been applied to mapping of the distribution of wetland vegetation but not to quantitative evaluation of the condition of that vegetation.Recent research in the tidal wetlands of Delaware and elsewhere has shown that spectral canopy reflectance properties can be quantitatively related to the emergent green biomass ofSpartina alterniflora (salt marsh cord grass) throughout the peak growing season (April through September, in Delaware). Periodic measurements of this parameter could be applied to calculations of net aerial primary productivity for large areas ofS. alterniflora marsh in which conventional harvest techniques may be prohibitively time consuming. The method is species specific and, therefore, requires accurate discrimination ofS. alterniflora from other vegetation types. Observed seasonal changes in species spectral signatures are shown to have potential for improving multispectral categorization of tidal wetland vegetation types.     

Variation and evaluation of coastal salt marshes

Ten intertidal salt marshes along the Rhode Island coast were sampled and compared in terms of the relative standing crop and height of tallSpartina alterniflora, density of shoots, seed production and size, fish populations, and the abundance of grass shrimp, fiddler crabs, insects, and birds. The marshes ranged from 0.49 to 52.61 hectares (1.2 to 130 acres) and included fringe marsh in dense urban developments as well as unspoiled waterfowl preserves in rural isolation. Large variation in most parameters made it impossible to separate the sites with statistical significance using either univariate or multivariate techniques. Moreover, there was little meaningful intercorrelation among the parameters. Although more intensive sampling might make it possible to separate individual marshes with statistical rigor, these results suggest that the necessary effort may be too great to allow comparative field sampling to play a practical part in wetlands evaluation programs. The results also indicate that there is little, if any, correlation between visual esthetic perceptions of a marsh and its ecological characteristics. This work suggests that the development of ecological rating systems will not provide a reliable tool for the management of coastal wetlands.     

干法烟气脱硫电除尘器进口喇叭的设计与应用

电除尘器进口喇叭的设计直接影响其气流均布。针对CFB—FGD干法烟气脱硫后的烟气特点，分析了处理脱硫后烟气的电除尘器进口喇叭设计，进行了气流分布试验，为高烟尘电除尘器进口喇叭的设计提供参考。     

Towards carrying capacity assessment for aquaculture in the Bolinao Bay, Philippines: A numerical study of tidal circulation

The increase in intensive aquaculture production in the Bolinao Bay, Philippines reached the point of harmful influence to production stock. Up to the present, there has been no estimation of aquaculture carrying capacity which is based on quantification of processes responsible for (a) water quality inside the units, (b) impact to the seabed and (c) water quality in the whole Bolinao Bay. The numerical estimation of tidal circulation, which is the most dominant part of the hydrodynamical regime in the Bolinao Bay, represents an unavoidable step in the carrying capacity determination considering points (a), (b) and (c). The hydrodynamical model we apply is a free surface, 3D finite element tidal model, forced with sea elevation dynamics at three open boundaries. It incorporates an increase in bottom stress drag coefficients in the coral areas and advanced transport corrected advection scheme. The model simulations of water flow show good agreement with measured currents in the central part of the Bolinao Bay, southern and northeastern channel, while agreement in the areas in vicinity of northern channel is not as tight. In order to provide an insight into the water exchange in aquaculture units, to support local water quality models and seabed deposition models (points (a) and (b)), the area is mapped with neap tide mean, spring tide mean and 14-day mean current velocity contours. The highest 14-day mean velocities are attained in the southern channel (>17 cm s⁻¹), while the mean velocities characteristic for northern part (<6 cm s⁻¹) and shallow areas of coral reefs (<2 cm s⁻¹) are much lower. Area-mean difference between spring tide and 14-day mean velocities is estimated to be 18.32% (std=7.31%), while difference between neap tide and 14-day mean velocities is 17.62 % (std=11.19%). To support global basin-wide water quality models (point (c)), retention of water in the bay is estimated by Lagrangian and Eulerian calculation procedure of mean residence time field. Both calculations estimate the highest (no-wind) residence times (Lan: 25.4 days, Eul: 21.03 days) in the central northern part, but most of the area (Lan: 73.11%, Eul: 79.31%) is characterized by residence time values significantly lower than 15 days. The results are readily applicable for upcoming implementation in the models of local (aquaculture units, seabed) and basin-wide (Bolinao Bay) nutrient dynamics, primary and secondary production, organic matter decomposition and oxygen dynamics.     

Macroinvertebrate and fish populations in a restored impounded salt marsh 21 years after the reestablishment of tidal flooding

During the last two decades, the State of Connecticut has restored tidal flow to many impounded salt marshes. One of the first of these and the one most extensively studied is Impoundment One in the Barn Island Wildlife Management Area in Stonington, Connecticut. In 1990, twelve years after the re-establishment of tidal flooding, the density of the marsh snail Melampus bidentatus, the numerically dominant macroinvertebrate of the high marsh, in Impoundment One was about half that in reference marshes below the breached impoundment dike. By 1999 the densities of Melampus above and below the dike were not significantly different, but the shell-free biomass was greater above the dike as a result of the somewhat larger number and size of the snails there. Twenty-one years after the renewal of tidal flooding, three marsh macroinvertebrates (the amphipods Orchestia grillus and Uhlorchestia spartinophila and the mussel Geukensia demissa) were significantly less abundant in the previously impounded marsh than in the reference marshes, whereas another amphipod (Gammarus palustris) was more abundant above the breached dike where conditions appeared to be somewhat wetter. In 1991 the fish assemblage in a mosquito-control ditch in Impoundment One was similar to that in a ditch below the breached dike; however, the common mummichog Fundulus heteroclitus appeared to be less abundant in the restoring marsh. By 1999 the number of mummichogs caught in ditches was significantly greater in Impoundment One than in the reference marsh, but the numbers of mummichogs trapped along the tidal creek were comparable above and below the dike. The results obtained in this study and those of other restoring marshes at Barn Island indicate the full recovery of certain animal populations following the reintroduction of tidal flow to impounded marshes may require up to two or more decades. Furthermore, not only do different species recover at different rates on a single marsh, but the time required for the recovery of a particular species may vary widely from marsh to marsh, often independently of other species.