Using velocimeter signal to noise ratio as a surrogate measure of suspended mud concentration   总被引：1，自引：0，他引：1  

Mehrdad SalehiKyle Strom 《Continental Shelf Research》2011,31(9):1020-1032

This study examines the relationship between suspended sediment concentration (SSC) and the signal to noise ratio (SNR) recorded by a 6 MHz Nortek Vector velocimeter in a laboratory water tank using four different synthetic and natural mud mixtures and different combinations of the user-set Vector parameters transmit power level and velocity range. For concentrations less than 1500 mg/l (1.5 g/l), a region of linearity between the logarithm of concentration and time-average SNR was found for all sediment types and transmitter power level settings. Within this concentration range, the experimental data was used to develop calibrated equations of the form, log(SSC)=c₁SNR+c₂; R² values for all calibrated equations were greater than 0.98, suggesting that properly calibrated relations can yield accurate time-averaged SSC measurements using Vector measured SNR. An analysis of the general calibration equation indicated that the predicted SSC values are sensitive to changes in the coefficient values for c₁ and c₂. Even small (10%) deviations in coefficient values resulted in 20%-65% changes in the predicted SSC. Variation in c₁ and c₂ values among all four mud mixtures were significant enough that the calibrated equations could not be used interchangeably. This was true even among three samples that had similar particle-size distributions. Translation of raw 32 Hz SNR data to 32 Hz SSC time series produced excessively large variation in the SSC time series. Several smoothing and filtering schemes were examined to reduce the magnitude of these fluctuations to more reasonable levels. Of the methods tested, a two-sided moving average functioned best at removing fine-scale variation while retaining larger-scale trends. A 96-point (3 Hz) averaging window brought 98.6% of the Vector estimated SSC time series values to within ±10% of the time-average physical samples. Impacts of turbulent kinetic energy and sampling volume size on instrument recorded SNR were also empirically examined.  相似文献   

渤海海冰现场监测的数字图像技术及其应用     

季顺迎  王安良  王宇新  李海  岳前进 《海洋学报(英文版)》2011,30(4):79-87

在渤海冰区油气开发中,海冰给平台结构、油气运输和施工作业带来很大影响。油气作业区海冰参数精确、连续、实时的现场监测对分析油气开发的可靠性、检验海冰数值模式、校正海冰卫星遥感数据具有重要意义。针对渤海油气作业区的海冰运动和分布特性,通过数字图像技术对海冰的厚度、运动速度和密集度三个参数的提取进行了算法开发和软件研制。在2009-2010年采用该海冰数字图像监测软件对渤海辽东湾JZ20-2油气作业区的海冰参数进行了全冰期的连续监测,获得了翔实可靠的海冰厚度、密集度和冰速等海冰监测资料。现场监测应用表明,该海冰数字图像监测软件具有操作性强、精确度高、可靠性好的优点。该监测技术进一步完善后可广泛应用于渤海油气作业区的海冰现场监测,成为海冰业务化现场监测的重要组成部分。  相似文献   

Experimental study on suspended sediment concentration and its vertical distribution under spilling breaking wave actions in silty coast     

夏云峰  徐华  陈中  吴道文  张世钊 《中国海洋工程》2011,25(4):565-575

In this paper,flume experiments are focused on sediment transport inside and outside the surf zone.According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump,formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves.Assuming that the sediment diffusion coefficient,which is related with energy dissipation,is proportional to water depth,formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves,and the prediction shows a good agreement with the measurement.  相似文献   

Hypoxia by degrees: Establishing definitions for a changing ocean   总被引：1，自引：0，他引：1  

A.F. Hofmann  E.T. PeltzerP.M. Walz  P.G. Brewer 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(12):1212-1226

The marked increase in occurrences of low oxygen events on continental shelves coupled with observed expansion of low oxygen regions of the ocean has drawn significant scientific and public attention. With this has come the need for the establishment of better definitions for widely used terms such as “hypoxia” and “dead zones”. Ocean chemists and physicists use concentration units such as ??molO₂/kg for reporting since these units are independent of temperature, salinity and pressure and are required for mass balances and for numerical models of ocean transport. Much of the reporting of dead zone occurrences is in volumetric concentration units of mlO₂/l or mgO₂/l for historical reasons. And direct measurements of the physiological state of marine animals require reporting of the partial pressure of oxygen (pO₂) in matm or kPa since this provides the thermodynamic driving force for molecular transfer through tissue. This necessarily incorporates temperature and salinity terms and thus accommodates changes driven by climate warming and the influence of the very large temperature range around the world where oxygen limiting values are reported. Here we examine the various definitions used and boundaries set and place them within a common framework. We examine the large scale ocean pO₂ fields required for pairing with pCO₂ data for examination of the combined impacts of ocean acidification and global warming. The term “dead zones”, which recently has received considerable attention in both the scientific literature and the press, usually describes shallow, coastal regions of low oxygen caused either by coastal eutrophication and organic matter decomposition or by upwelling of low oxygen waters. While we make clear that bathyal low oxygen waters should not be confused with shallow-water “dead zones”, as deep water species are well adapted, we show that those waters represent a global vast reservoir of low oxygen water which can readily be entrained in upwelling waters and contribute to coastal hypoxia around the world and may be characterized identically. We examine the potential for expansion of those water masses onto continental shelves worldwide, thereby crossing limits set for many not adapted species.  相似文献   

基于ARIMA模型的补远江含沙量预测     

钟荣华  傅开道  何大明  邢煜民  苏斌 《水文》2011,31(6):48-52

流域输沙的估算是水资源管理中广泛面临的问题。基于时间序列自回归滑动平均(ARIMA)预测模型,分别对补远江曼安水文站1993～2008年雨季、旱季月平均含沙量资料进行建模拟合。综合AIC值、相对误差,确定模型的阶数,运用Marquardt非线性最小二乘法估计模型参数,建立ARIMA预测模型。经检验,雨季AIC=-61.046,旱季AIC=-131.785,相对误差低于20%的合格率分别为92.1%、76.9%,残差序列均为白噪声序列,表明旱季ARIMA(1,1,1)、雨季ARIMA(1,1,2)模型较为合理。应用模型对2009～2011年曼安水文站的雨季、旱季平均含沙量进行了预测,实现了河流输沙状况的短期预报。  相似文献   

基于ADCP反向散射强度估算悬沙浓度在洋山港的应用研究     

张志林  邓乾焕  朱巧云  钱峰 《水文》2011,31(2):62-68

洋山深水港地形差异大,流态复杂,在宽阔的西口门和窄深东口门,以传统方法同步开展悬沙输移监测十分困难。详述了在颗珠山汊道应用ADCP走航测沙的实现方法,结论显示,与传统代表垂线法成果相比,通过ADCP声反向散射信号计算的垂线平均含沙量,其对比标准差约为6%,随机不确定度在12%(置信水平为95%)左右,误差分布基本成正态,两种方法之间的断面输沙率相关系数达到0.96,可见,利用ADCP的声反向散射信号,只要标定得当,在洋山港区得到的垂线平均含沙量和断面输沙率是可信的,该技术将为洋山港区关键控制断面悬沙监测提供新思路。  相似文献   

卵砾石地层钻探用大直径加强型金刚石钻头的研制          下载免费PDF全文

朱英  周原  赵宪富 《探矿工程》2011,38(8):68-71

采用不同于常规金刚石钻头的设计理念,选用高强度金刚石及耐磨金刚石聚晶体,对普通金刚石钻头胎体配方进行了改进,对常规金刚石钻头的烧结工艺参数作了适当的调整,试制出大直径加强型金刚石钻头。该钻头在耐磨性、抗冲击韧性及保径等方面较常规金刚石钻头显现出较大优势。在不改变常规钻进参数的情况下,较好地解决了卵砾石、破碎地层钻头寿命短、钻进速度慢、钻头易过早损坏等问题,可供类似的地层钻探施工选用。  相似文献   

皖南庐江-枞阳多金属矿集区反射地震剖面的速度结构     

卢占武  高锐  匡朝阳  刘金凯  酆少英  王海燕  侯贺晟 《中国区域地质》2011,(9):1412-1417

利用反射地震剖面处理过程中获取的叠加速度得到庐枞（庐江-枞阳）矿集区地壳浅部的速度结构剖面,为研究庐枞矿集区近地表-上地壳的结构提供了新依据。地震剖面综合研究表明：郯庐断裂、罗河-缺口断裂、长江断裂是庐枞地区的3条重要的断裂,断裂深部均表现为低速异常。罗河-缺口断裂、长江断裂的发育深度和规模均不及郯庐断裂。火山岩出露地区表现为地震波速高和反射波组凌乱的特征;新生代沉积地层则表现为波速低和反射波组连续的地球物理特征。罗河矿区位于强、弱反射转换区,同时也是低、高速体的转换区。  相似文献   

“区域异常集中度”的概念、计算方法及其与成矿的关系     

严己宽 《中国区域地质》2011,(11):1802-1808

为了解释普遍存在的成矿规模与区域化探异常面积大小不成比例的问题,提出了＂区域异常集中度＂的概念,给出了概念的定义、相关要素和计算方法。探讨了区域异常集中度的主要特点,数值大小、计算尺度与成矿规模的关系,适用条件等。认为区域异常集中度反映了成矿物质的集中程度,应用它找大矿是在区域成矿要素范围内众多异常中＂同中求异＂的过程。初步提出了区域成矿要素集中度的概念,并讨论了它与区域异常集中度的关系。区域异常集中度的提出为区域化探异常解释评价提供了一个全新的地质地球化学指标和视角,将成矿相关元素异常与区域成矿要素联系起来的综合方法对于深化异常与成矿关系的认识有重要意义,对于寻找大中型矿床或矿田有重要的指导作用。  相似文献   

浓度梯度引起的固相速度测量误差          下载免费PDF全文

石健  郭波  弓扶元  何小刚  李丹勋 《水科学进展》2011,22(1):67-74

用粒子示踪技术测量明渠挟沙水流中固相颗粒的速度时,流速梯度和浓度梯度的存在会引起测量误差.选用典型的垂线流速与浓度分布公式对时均速度测量误差进行分析,得出了误差的解析表达式.对该解析式的理论分析表明,测量误差恒小于零,即速度测量值比实际值偏小.误差的大小与采样窗口的相对位置、尺寸及颗粒的悬浮指数有关.对误差大小随自变量...  相似文献