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1.
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
2.
利用内蒙古西部12个台站的地脉动噪声数据,采用噪声谱比法研究台站的场地响应情况。分析表明,台站场地响应按曲线形态可分为3类,且可能受地形地貌、局部构造和台基状况等条件影响。对比分析噪声谱比法与Moya方法的场地响应结果发现,场地响应曲线形态基本一致,只有极少数台站存在明显差异。结果表明,内蒙古西部区域大部分台站的台基状况总体较好,场地响应曲线较为平坦,无明显频率放大点。 相似文献
3.
重庆地面最高气温与最大风速年极值的渐近分布 总被引:3,自引:0,他引:3
利用重庆1951-1990年间地面最高气温和1956-1990年间地面最大风速年极值的记录,采用韦伯分布和耿贝尔分布分别对其渐近分布进行拟合.通过统计推断,找出重庆地面最高气温和地面最大风速年极值遵循的最佳渐近分布--韦伯分布. 相似文献
4.
CHUDongsheng LIANGMeng SHIXin ZHANGLing 《中国海洋大学学报(英文版)》2004,3(1):106-110
1 Introduction Inrecentyearstherehasbeengrowingresearchin terestinthetwo dimensional (2 D )systemtheory .The 2 Dsystemsmayfindapplicationsinareassuchasmarineseismicdataprocessingandimageprocessing .Althoughmoreandmorevaluableresultshavebeengained ,mos… 相似文献
5.
Yu Xin 《Astrophysics and Space Science》1992,194(1):159-163
A critical re-examination of the self-consistency of Einstein's gravitational radiation theory is given in the present paper with special reference to its claimed prediction of the observed data on PSR 1913+16.The author is Alfred Yu 相似文献
6.
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
7.
8.
Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn. 相似文献
9.
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
10.
A new compilation of N‐isotope and abundance data for metasedimentary rocks, and hyrdothermal micas that proxy for bulk crust, show systematic patterns. (1) δ15N values of kerogen in Precambrian cherts are more negative relative to siliciclastic counterparts, probably due to a mantle hydrothermal component. (2) There is a secular trend from average δ15N 15.3 ± 1.8‰ in Archean shales, through intermediate values in the Proterozoic, to Phanerozoic counterparts where δ15N averages +3.5‰. (3) Hydrothermal micas in metamorphic hydrothermal systems of Palaeozoic and Mesozoic age that proxy for crust have δ15N within the range of contemporaneous sedimentary rocks. (4) Hydrothermal micas track the secular trend of δ15N for kerogen from 2.7 Ga to the Phanerozoic. (5) Within Precambrian datasets δ15N does not increase with decreasing N content; accordingly, high δ15N values cannot stem either from metamorphism or form Rayleigh fractionation. (6) Previous studies show isotopic shifts during metamorphism are only +1 to +3‰ up to amphibolite facies. Values of 10–24‰ are attributed to a high δ15N Archean atmosphere, a residual signature of CI carbonaceous chondrites where δ15N is +30‰ to + 42‰. 相似文献