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排序方式: 共有849条查询结果,搜索用时 9 毫秒
91.
在借鉴国内外河流生态需水量研究的基础上,对汉江中下游河流生态需水量计算进行了分析,重点分析了维护汉江中下游河流生态所需要的最小水量,探讨了河流自净需水量和防止水华发生的生态需水量,并初步探讨了三峡工程和南水北调中线工程建成后对汉江中下游生态需水量的影响。 相似文献
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A matching algorithm is proposed for aligning microscope images obtained using different modalities, making use of cross-correlations of outputs from Prewitt's edge filter. Brightfield, phase contrast and differential interference contrast microscope images of algal and bacterial cells from an experimental, high-rate algal pond are used for illustration. The information content of multimodal images is explored using principal components analysis and colour displays, and an image which represents optical thickness is constructed digitally. 相似文献
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重轨钢的炉外精炼与连铸 总被引:6,自引:1,他引:5
论述了重轨钢真空处理的必要性及国外重轨厂家采用真空处理的现状。对用连铸坯轧制重轨的优点及重轨钢连铸工艺特点作了说明,介绍了国外改善连铸方坯质量的措施和用连铸坯轧制重轨的主要厂家。 相似文献
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This study investigates the toxicity and post-exposure effects of dissolved microcystin (MC-LR) on the dominant copepods of the upper San Francisco Estuary (SFE), where blooms of the toxic cyanobacteria Microcystis aeruginosa coincide with record low levels in the abundance of pelagic organisms including phytoplankton, zooplankton, and fish. The potential negative impact of Microcystis on the copepods Eurytemora affinis and Pseudodiaptomus forbesi has raised concern for further depletion of high quality fish food. Response of copepods to MC-LR (MC) was determined using a 48-h standard static renewal method for acute toxicity testing. Following exposure, a life table test was performed to quantify any post-exposure impacts on survival and reproduction. The 48-h LC-50 and LC-10 values for MC were 1.55 and 0.14 mg/L for E. affinis; and 0.52 and 0.21 mg/L for P. forbesi. Copepod populations recovered once dissolved MC was removed and cultures returned to optimal conditions, suggesting no post-exposure effects of MC on copepod populations. Dissolved microcystin above 0.14 mg/L proved likely to have chronic effects on the survival of copepods in the SFE. Since such high concentrations are unlikely, toxicity from dissolved microcystin is not a direct threat to zooplankton of the SFE, and other mechanisms such as dietary exposure to Microcystis constitute a more severe risk. 相似文献
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This paper proposes fuzzy models for forecasting the complex behavior of algal blooms. The models are developed through the integration of autoregressive models, the Takagi-Sugeno fuzzy model, and discrete wavelet transform algorithms. The premise parts of the proposed models are determined using the subtractive clustering technique and the consequent parts are optimized using weighted least squares. To train and validate the proposed fuzzy models, a large number of data sets were collected from Daecheong reservoir in Geum River in the Republic of Korea. The data include both water quality and hydrological variables. Total nitrogen, total phosphorous, dissolved oxygen, chemical oxygen demand, biochemical oxygen demand, pH, air temperature, water temperature and outflow water were evaluated as input signals while chlorophyll-a was used as an output. It is demonstrated from the simulation that the proposed fuzzy models are effective in forecasting algal blooms. 相似文献