长江口及邻近海域表层水体溶解氧饱和度的季节变化和特征   总被引：3，自引：0，他引：3  

卢勇  李宏亮  陈建芳  金海燕  陈法锦  高生泉  王奎  王文亮  白有成 《海洋学研究》2011,(3):71-77

根据“908”ST04区块调查的夏、冬、春、秋季四个航次和“908”补充调查的8月航次资料对长江口及邻近海区表层水体溶解氧及其饱和度进行了探讨.研究表明东海北部表层水体在夏季和春季以浮游植物光合作用为主要控制过程,特别是7、8月份长江口外、杭州湾外及浙江近海存在大范围的强光合作用区;秋季以有机质氧化分解过程为主,表层溶...  相似文献   

隔离变压器在电源系统防雷中的应用     

周方君  周萌  张佳晖  万瀚仁  汪胜宝 《气象科技》2015,43(5):969-972

分析了危害弱电设备的主要电涌类型及特点,探讨了在实际防雷工程中低压配电系统中常用的氧化锌（ZnO）电涌保护器（SPD）存在启动电压偏高,对耐过电压能力较低的电气电子设备存在对电涌防护不到位的问题;将隔离变压器作为防电涌器件引入到弱电设备防雷工程中,利用初级绕组与次级绕组之间只有电磁耦合,无直接电气通道的特性隔离共模过电压;利用铁芯的磁饱和、磁滞现象抑制和削减雷击感应过电压的差模分量。将隔离变压器用于氧化锌电涌保护器之后作为精保护单元,弥补氧化锌电涌保护器的缺点,使弱电设备得到可靠保护,经实际运用验证了它的防雷效果。  相似文献   

大沽河地下咸淡水过渡带的水-岩作用模拟     

陈然  郑西来 《中国海洋大学学报(自然科学版)》2015,45(1):95-101

大沽河是青岛市最大的地下水源地,过量开采导致严重的地下咸水入侵,研究地下咸-淡水的地球化学作用对于地下咸水的治理具有重要的指导作用。本文选取大沽河地下咸淡水过渡带作为研究区,在地下水动态监测的基础上,通过地下水水质和含水介质矿物分析,借助当前成熟的水文地球化学模拟软件—PHREEQC 2.0,计算地下水中主要离子和络合离子的含量,定量确定矿物的饱和指数和地下水流向上矿物相与水之间的物质交换量。研究结果表明:(1)地下水中钠、钾、镁、钙主要以单一离子形态存在,硫、碳主要以络阴离子形态存在,而硅和铝主要以络合物形态存在;(2)在地下水流动路径上,方解石、白云石、伊利石、高岭土处于过饱和状态;而石膏、CO2、氯化钠、萤石、玉髓处于不饱和状态;(3)咸淡水过渡带地下水化学类型由HCO3-Ca·Na型水向Cl-Na型水转变的趋势。  相似文献   

Fluoride enrichment in aquifers of the Thar Desert: controlling factors and its geochemical modelling     

Chander Kumar Singh  Rina Kumari  Neha Singh  Javed Mallick  Saumitra Mukherjee 《水文研究》2013,27(17):2462-2474

The groundwater is the only source of drinking water in the Jaisalmer district of Rajasthan, India. The study area is a part of the Thar Desert. It has low and scattered population and no industries; hence, the possibility of anthropogenic input of fluoride is almost negligible. Thus, the enrichment of fluoride is only possible due to geochemical processes taking place in the groundwater of the region. A total of 100 groundwater samples, 34 samples from Jaisalmer and 66 samples from the Pokharan administrative blocks, were collected. It was observed that the concentration of fluoride ranged from 0.08 mg/l to 4.56 mg/l in the groundwater of Jaisalmer and from 0.56 mg/l to 6.60 mg/l in the samples of the Pokharan block. The alkaline condition (average pH, 7.7 ± 0.22 and 8.01 ± 0.25 in Jaisalmer and the Pokharan administrative block, respectively) in the region favours fluorite dissolution. Ion exchange, dissolution of calcite, semi‐arid climate, alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

高浓度气体共振光声光谱信号饱和特性研究     

袁长迎  炎正馨  蒙瑰  李智慧  尚丽平 《海洋学报》2010,32(10):6908-6913

采用恒流驱动耦合机械斩波技术在激光光声光谱装置上系统测量了5%—100%宽浓度范围甲烷气体的共振光声信号,发现在高浓度区共振光声信号呈现异常的饱和特征.基于气体吸收和光声光谱原理定量分析了光声信号饱和的主要原因及影响因素,研究表明,气体样本对入射光强吸收而导致的声源与本征共振模式的耦合系数改变是异常饱和的主要原因,并导出判定光声信号饱和深度的准则以用于判定高浓度气体饱和深度.  相似文献   

饱和冻土中弹性体波传播特性影响参数研究     

仇浩淼  夏唐代  郑晴晴  周飞 《岩土力学》2018,39(11):4053-4062

基于Leclaire对饱和双相孔隙弹性介质Biot模型的扩展,研究含有两种不同固相组分的三相多孔弹性介质中体波的传播特性。以饱和冻土为例,分析了各相体积分数、颗粒形状,接触参数等因素对波动方程中惯性参数、黏性参数、刚度参数的影响;对该三相介质模型进行了退化,分析了孔隙中只含液态水或固态冰时体波的特性;以饱和冻土为例,通过数值计算,探讨了饱和冻土中体波的相速度和衰减系数与胶结参数、接触参数、频率、饱和度、孔隙率等参数的关系。结果表明：与一般的饱和土不同,饱和冻土中存在5种体波,即3种纵波和2种横波;5种体波均具有弥散性和衰减性,且P1波、S1波弥散性和衰减性远小于P2、P3、S2波;胶结参数、饱和度、孔隙率对5种体波的传播特性影响显著,接触参数对传播特性影响较小。  相似文献   

中亚地震目录震级转换及其完整性分析   总被引：1，自引：0，他引：1  

吴果  周庆  冉洪流 《震灾防御技术》2014,9(3):368-383

为编制能够应用于地震危险性分析的中亚地区统一震级标度为矩震级的地震目录,从国际地震中心（ISC）下载得到该地区1907-2012年的地震数据,该数据包含众多机构不同震级标度的地震记录.以MW,GCMT为参考机构震级标度,并用最小二乘法拟合了其他机构震级标度与MW,GCMT之间的转换关系.在挑选某次地震事件的唯一震级记录时,以对应转换关系的相关系数大且剩余标准差小为准则进行筛选.对于少量没有震级转换关系或者拟合优度过差的地震记录,使用间接转换关系或者全球转换关系予以补充转换.震级转换后,用时空窗法删除前余震,并考虑构造环境和地震活动水平的空间差异性将研究区划分成5个子区域.采用地震记录时间累积曲线法、最大曲率法（MAXC）和拟合优度检验法（GFT）综合分析各个分区的最小完整震级（MC）,并在此基础上用极大似然法拟合相应的地震活动性参数.结果表明,每种完整性分析方法各具一定的优缺点,但采用综合分析的方法能够得出最佳的MC.地震记录时间累积曲线法能分析出高质量地震目录的起始时间,以作为后两种方法的基础,但容易受到地震活动水平随时间波动的影响.由于研究区目录质量较差,最大曲率法误差过大以至于只能作为其他方法的补充,拟合优度检验法的GFT参数也普遍只能达到80％左右.GFT最大值点可能并不对应MC,但是MC通常都在GFT极大值点取得.5个分区1964-2012年的MC普遍在Mw4.8左右,b值在1.136-1.514之间波动.  相似文献   

Investigating the optically stimulated luminescence dose saturation behavior for quartz grains from dune sands in China     

《Quaternary Geochronology》2014

The optically stimulated luminescence (OSL) signals from quartz have been widely used to estimate the equivalent dose (D_e) of environment radiation after the deposition of mineral grains. However, the usage of quartz is often limited due to the lower saturation behavior compared with feldspar. Saturation limits among quartz (defining the upper dating range) vary significantly. It is important to better understand the reason for various dose saturation behaviors of the quartz OSL signals. In this study, coarse quartz grains were extracted from the Taklimakan Desert and the Hunshandake sandy land in north China and the dose saturation behavior of quartz OSL signals were studied. Our results suggest that the quartz grains produce very different aliquot-specific dose response curves, showing the significant variability in dose saturation characteristics for OSL signals. Laboratory dosing, optical bleaching and heating experiments were designed to simulate their effects on the dose saturation behavior for the quartz OSL. The results demonstrate that cycles of dosing and optical bleaching have insignificant impact on the OSL dose growth curves, while the heating to high temperature (above 400 °C) can significantly change the dose saturation characteristics for the quartz OSL. Such results suggest that the different heating history of quartz might be an important factor for the variability in dose saturation characteristics for OSL signals. Additionally, the quartz grains from the Hunshandake sandy land exhibit lower dose saturation level for OSL signals, compared with that from the Taklimakan Desert. This can be explained that the quartz grains from Hunshandake sandy land are mainly of igneous origin, while the quartz grains from Taklimakan Desert are mainly of metamorphic origin.  相似文献   

A novel dynamic stretching solution to eliminate saturation effect in NDVI and its application in drought monitoring     

Fang Liu  Qiming Qin  Zhiming Zhan 《中国地理科学(英文版)》2012,22(6):683-694

The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a challenge.This paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is proposed.Dynamic range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to 1.00.Moreover,the saturation effect in NDVI is effectively removed by using the S-NDVI.Further analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,respectively.In the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are used.In this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture content.Thus,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.  相似文献   

表面活性剂强化空气扰动修复氯苯污染含水层     

秦传玉  赵勇胜  郑苇 《地球科学》2011,36(4):761-764

通过一维砂柱实验研究了阴离子表面活性剂十二烷基苯磺酸钠(SDBS)对空气扰动技术(air sparging,AS)修复氯苯污染地下水的强化效果.结果表明,SDBS的加入降低了地下水的表面张力,减小了水气两相毛细压力,从而提高了地下水中的空气饱和度.当曝气量为100 mL/min,地下水的表面张力由72.2 mN/m降至49.5 mN/m时,地下水中空气饱和度由13.2%提高至50.1%,而后随着表面张力的进一步降低,空气饱和度不再提高,反而有小幅下降.通过污染物的去除实验发现,SDBS的加入大大提高了氯苯的去除率,且去除率的变化与空气饱和度的变化趋势基本相符.因此,表面活性剂的加入可以作为空气扰动技术一种十分有效的强化手段.   相似文献