Hydrological management strategies for the control of algal blooms in regulated lowland rivers     

Jian Li  Wei Yin  Haiyan Jia  Xiaokang Xin 《水文研究》2021,35(6):e14171

Reservoirs of lowland floodplain rivers with eutrophic backgrounds cause variations in the hydrological and hydraulic conditions of estuaries and low-dam reservoir areas, which can promote planktonic algae to proliferate and algal bloom outbreaks. Understanding the ecological effects of variations in hydrological and hydraulic processes in lowland rivers is important for algal bloom control. In this study, the middle and lower reaches of the Han River, China, a typical regulated lowland river with a eutrophic background, are selected. Based on the effect of hydrological and hydraulic variability on algal blooms, a hydrological management strategy for river algal bloom control is proposed. The results showed that (a) differences in river morphology and background nutrient levels cause significant differences in the critical threshold flow velocities for algal bloom outbreaks between natural river and low-dam reservoir sections; there is no uniform threshold flow velocity for algal bloom control. (b) There are significant differences in the river hydrological/hydraulic conditions between years with and without algal blooms. The average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms. (c) For different river sections where algal blooms occur and to meet the threshold flow velocities, the joint operation of cascade reservoirs and diversion projects is an effective method to prevent and control algal blooms in regulated lowland rivers. This study is expected to deepen our understanding of the ecological significance of special hydrological processes and guide algal bloom management in regulated lowland rivers.  相似文献   

试论新世纪地理信息科学的发展   总被引：1，自引：0，他引：1  

黄雪樵  陈昱 《地球信息科学学报》2002,4(2):32-37

本文重点分析了当前国内外地理信息科学的形成与发展趋势和地理信息科学不断发展的历程 ,提出近期发展的前沿 ,以及当前地理信息产业化面临的一些重要问题。最后提出对地理信息科学发展的意见。  相似文献   

广西海洋资源概况及开发刍议     

傅中平  黄巧 《南方国土资源》2002,15(2):61-64

广西海洋资源丰富 ,品种繁多 ,为了更好开发 ,建议从法制、宣传教育、普及海洋资源有关知识 ,提高人们整体素质做起 ,进一步抓住机遇 ,合理开发 ,才能取得良好效益 ,达到预定目标  相似文献   

双酶法制备低黏度辛烯基琥珀酸淀粉钠的工艺条件   总被引：4，自引：0，他引：4  

阳元娥  罗发兴  黄强  谭伟 《广东海洋大学学报》2004,24(4):49-53

对双酶法制备用作微胶囊壁材的低黏度辛烯基琥珀酸淀粉钠的工艺路线与工艺条件进行了研究。正交实验结果表明 ,在酯化淀粉乳质量浓度 2 0 %、每 g淀粉α 淀粉酶的用量为 6SKBU的条件下 ,影响产品性能的各因素中 ,糖化酶的用量对产品的DE值和流度的影响最大 ,各因素的重要性依次是 :糖化酶的用量、糖化酶作用时间、α 淀粉酶保温作用时间。最佳工艺条件是 :α 淀粉酶保温作用时间 4min ,每 g淀粉糖化酶用量 0 .2GAU ,糖化酶作用时间 2 .5h ,此时产品的DE值为 30 ,流度为 80左右  相似文献   

小波分析理论在GPS技术中的应用     

ZHENG Zuoya HUANG Cheng LU Xiushan 《中国科学院上海天文台年刊》2003,(1)

在GPS数据处理中 ,存在着误差影响、影响波的干扰、周跳和数据量大等问题。误差影响和影响波的干扰实质是在接收卫星信号时受到其它因素的影响 ;周跳是由于卫星信号的失锁而造成信号的不连续 ;数据量大是因为GPS观测需要采样间隔小又连续观测所致。由于小波理论具有时频分析、波形分解、特征提取和快速小波变换等特性 ,应用小波变换和波形分解可以解决误差影响和影响波的干扰的问题 ;应用特征提取可以解决周跳检测问题 ;应用快速小波变换可进行数据压缩  相似文献   

试论企业组织结构--电子商务企业与传统企业的比较     

何兴贵  黄宗捷 《成都信息工程学院学报》2002,17(3):196-199

网络时代的到来，对传统企业的组织结构、运作模式、管理方法均提出了严峻的挑战。传统的企业组织结构是适应大工业生产而形成的等级组织结构形式，它有很大的局限性；电子商务企业的组织结构是适应网络社会而形成扁平化、双向多对多、以信息为基础的新型组织结构形式。电子商务企业以其组织结构扁平化和中空化，决策分散化，运作虚拟化，灵活高效为特点，它将成为传统企业在电子商务发展阶段变革的方向和目标。  相似文献   

差分法周跳探测与修复方法改进     

郑作亚  程宗颐  黄珹 《中国科学院上海天文台年刊》2004,(1)

在目前常用的周跳探测与修复方法基础上 ,提出了首先将观测资料按照观测历元不连续分成若干小弧段 ,然后利用差分法进行周跳探测 ,根据差分后周跳放大的特性判断周跳和野值 ,并确定其位置利用宽带组合和电离层组合的方法解算周跳大小。通过实例验证了其有效性。  相似文献   

彗星等离子体某些特征的讨论     

李中元  李嘉巍  段素平  陈耀  石志东 《紫金山天文台台刊》2003,(1)

本文讨论了彗星中尘埃粒子的充电机制 ,带电特性和平衡电势的变化规律 ,分析了彗星尘埃的破碎特性和临界半径 ,得出了很有意义的结果  相似文献   

Quantifying hydrogen‐deuterium exchange of meteoritic dicarboxylic acids during aqueous extraction     

Megan FULLER  Yongsong HUANG 《Meteoritics & planetary science》2003,38(3):357-363

Abstract— Hydrogen isotope ratios of organic compounds in carbonaceous chondrites provide critical information about their origins and evolutionary history. However, because many of these compounds are obtained by aqueous extraction, the degree of hydrogen‐deuterium (H/D) exchange that occurs during the process needs to be quantitatively evaluated. This study uses compound‐specific hydrogen isotopic analysis to quantify the H/D exchange during aqueous extraction. Three common meteoritic dicarboxylic acids (succinic, glutaric, and 2‐methyl glutaric acids) were refluxed under conditions simulating the extraction process. Changes in δD values of the dicarboxylic acids were measured following the reflux experiments. A pseudo‐first order rate law was used to model the H/D exchange rates which were then used to calculate the isotope exchange resulting from aqueous extraction. The degree of H/D exchange varies as a result of differences in molecular structure, the alkalinity of the extraction solution and presence/absence of meteorite powder. However, our model indicates that succinic, glutaric, and 2‐methyl glutaric acids with a δD of 1800%***_o would experience isotope changes of 38_o, 10_o, and 6_o, respectively during the extraction process. Therefore, the overall change in δD values of the dicarboxylic acids during the aqueous extraction process is negligible. We also demonstrate that H/D exchange occurs on the chiral α‐carbon in 2‐methyl glutaric acid. The results suggest that the racemic mixture of 2‐methyl glutaric acid in the Tagish Lake meteorite could result from post‐synthesis aqueous alteration. The approach employed in this study can also be used to quantify H/D exchange for other important meteoritic compounds such as amino acids.  相似文献   

滇西动态重力网的分形特征及空间分辨力   总被引：1，自引：1，他引：0  

贾民育 《大地测量与地球动力学》1996,(4)

介绍了用分形学描述地球物理观测网非均匀分布和联合应用分形特征与Ｓｈａｎｎｏｎ定理确定最佳网格距的方法。研究了滇西动态重力网的分形特征，它的分形维Ｄｆ＝１．２７，最佳网格距ｒ０＝２８ｋｍ。讨论了１９８６年至１９９４年间网区发生的８次Ｍｓ＞５．０级地震前重力场变化的可信性，指出这些变化的波长均大于１００ｋｍ，至少２倍于网的最小空间分辨力，因而是可信的  相似文献