基于Davis-Smith方法计算卫星磁强计零位补偿的误差特征研究   总被引：1，自引：1，他引：0       下载免费PDF全文

孟立飞  潘宗浩  易忠  王国强  张铁龙 《地球物理学报》2018,61(9):3545-3551

卫星所携带的磁通门磁强计会随时间发生零位漂移,因此需要对其进行补偿.基于行星际磁场的剪切阿尔芬波动特性,利用Davis-Smith方法可计算磁强计的零位磁场.本文利用数值模拟,分析了总磁场幅度B_T及压缩波动对Davis-Smith方法所产生零位补偿的误差特征.我们发现,B_T越大,零位补偿误差越大;且当压缩波动频率和剪切波动频率不同时,磁场各分量的零位补偿之间的比值与对应背景磁场的比值近似相等;压缩波动的幅度越小,零位补偿的误差趋于更小;此外,压缩波动的频率和初始相位等也会影响零位补偿的误差.这些误差特征可为提高零位补偿的可靠性提供重要的理论依据.  相似文献   

Timing the time of concentration: shedding light on a paradox     

Eleni Maria Michailidi  Sylvia Antoniadi  Antonis Koukouvinos  Baldassare Bacchi  Andreas Efstratiadis 《水文科学杂志》2018,63(5):721-740

From the origins of hydrology, the time of concentration, t_c, has conventionally been tackled as a constant quantity. However, theoretical proof and empirical evidence imply that t_c exhibits significant variability against rainfall, making its definition and estimation a hydrological paradox. Adopting the assumptions of the Rational method and the kinematic approach, an effective procedure in a GIS environment for estimating the travel time across a catchment’s longest flow path is provided. By application in 30 Mediterranean basins, it is illustrated that t_c is a negative power function of excess rainfall intensity. Regional formulas are established to infer its multiplier (unit time of concentration) and exponent from abstract geomorphological information, which are validated against observed data and theoretical literature outcomes. Besides offering a fast and easy solution to the paradox, we highlight the necessity of implementing the varying t_c concept within hydrological modelling, signalling a major shift from current engineering practices.  相似文献   

宁夏地区近震震级短周期量规函数的研究与修正          下载免费PDF全文

李青梅  吕俊强  谢辉 《地震工程学报》2017,39(6):1076-1083

选取宁夏"十五"宽频带数字地震台网2009年1月—2016年12月的1 782个地震事件、7 345条地震记录资料,通过震级残差统计和多元回归分析计算各台站单台震级与台网平均震级的偏差、平均偏差和标准偏差,分析震级偏差的频次分布,修正M_L量规函数,得到宁夏地区的地方性均匀震级量规函数和台基改正量。且采用多元回归分析方法,得到最大地动位移的衰减关系及与之对应的量规函数。结果表明,修正后的震级均方差由原来的0.237 0降低为0.228 9,震级修正最大值为0.51。  相似文献   

Novel mass-aggregation-based calibration of an acoustic method of monitoring bedload flux by infrequent desert flash floods     

Eran Halfi  Dror Paz  Kyle Stark  Uri Yogev  Ian Reid  Michael Dorman  Jonathan B. Laronne 《地球表面变化过程与地形》2020,45(14):3510-3524

The monitoring of bedload flux under flash flood conditions has been successfully achieved since 1992 using slot samplers in the semiarid Nahal Eshtemoa. In the present study, a surrogate bedload monitoring technique - the Japanese plate microphone - has been deployed and calibrated against data from the slot samplers. Since a slot sampler has a sensitivity threshold that becomes especially important when transport rates are low, different averaging periods should be considered for high and low fluxes. In order to overcome the deficiencies of time-based aggregation used hitherto, we have developed a new method involving mass aggregation and commensurably variable intervals, thereby enabling a more accurate analysis and optimizing the bedload sampler's capabilities. The data derived with this new method has then been utilized to calibrate the Japanese plate microphone. The Eshtemoa is an ephemeral gravel bed channel with a high proportion of fine gravel (< 0.02 m); for these conditions, acoustic sensors have not been calibrated as yet. Two multiple linear regression models incorporating the effect of median bedload grain size on pulse rate have been established to predict bedload flux and cumulative transported bedload mass. The coefficients in these models are statistically significant. Good predictions are obtained for bedload flux (adj. r² = 0.83) and for cumulative bedload mass (adj. r² = 0.98) during flood recession. Overall, the multiple linear regression models, used in conjunction with the mass aggregation method of estimating bedload flux, suggest that field calibration of acoustic devices is feasible under these conditions for ca. 90% of the duration of bedload transport. © 2020 John Wiley & Sons, Ltd.  相似文献   

Production rate calculations for cosmic-ray-muon-produced 10Be and 26Al benchmarked against geological calibration data     

《Quaternary Geochronology》2017

First, I benchmark existing methods of calculating subsurface ²⁶Al, ¹⁰Be, and ¹⁴C production rates due to cosmic-ray muons against published calibration data from bedrock cores and mine excavations. This shows that methods based on downward propagation of the surface muon energy spectrum fit calibration data adequately. Of these methods, one that uses a simpler geographic scaling method based on energy-dependent attenuation of muons in the atmosphere appears to fit calibration data better than a more complicated one that uses the results of a global particle transport model to estimate geographic variation in the surface muon energy spectrum. Second, I show that although highly simplified and computationally much cheaper exponential function approximations for subsurface production rates are not globally adequate for accurate production rate estimates at arbitrary location and depth, they can be used with acceptable accuracy for many exposure-dating and erosion-rate-estimation applications.  相似文献   

四川四分量钻孔应变观测数据精度评价     

周朝晖  张晓明  袁燕妮  伍永秀  林丽萍 《地震地磁观测与研究》2019,40(6):118-124

利用邱泽华等给出的观测数据和回归分析方法,计算钻孔应变仪四分量元件的相对标定系数,并根据偏差计算自检内精度等指标,对观测数据进行质量评价。选取2017年四川四分量钻孔应变观测台网记录资料,结合四分量钻孔应变仪观测特点,计算并分析应变观测仪相对标定自检内精度,客观评价观测数据精度,结果发现,2017年仁和台四分量钻孔应变数据各月及全年相对标定系数K_i最大,偏差s最小,自检内精度数值最小,表明该台钻孔应变观测数据精度最高。分析认为,相对标定自检内精度可如实反映台站记录资料的可信度,可以更好、更客观地评价台站四分量钻孔应变观测资料质量。  相似文献   

基于AlphaGUARD P2000F测氡仪利用水中溶解氡对DDL-1型气氡仪校准的实验研究          下载免费PDF全文

起卫罗  曹舸斌  方伟 《地震工程学报》2019,41(6):1560-1567

对测氡仪器进行定期校准是保证测量结果准确性和可靠性的关键。基于用国际公认的计量传递仪器AlphaGUARD P2000F作为氡气溯源仪器及其自带水氡测量组件对三套DDL-1型电离法测氡仪使用水中溶解氡进行校准实验。实验结果和用固体氡源校准三套仪器的结果与仪器出厂校准结果进行对比,两种校准方法的K值相对误差均小于5%,达到目前地震监测氡观测技术要求。实验结果表明,水中溶解氡代替固体氡气源校准,可以解决目前固体氡源校准中存在的运输困难、维修技术要求高、国家环保部门监管严格等问题,为地震氡观测仪器校准技术找到了一种新的途径。  相似文献   

海水浊度测量传感器研究   总被引：6，自引：1，他引：5  

任永琴  王世忠 《海洋技术学报》2004,23(4):29-31

利用光学散射原理,设计并研制了一种浊度传感器,发射器与接收器成90°,中心波长880 nm,使用Formazine标准液进行标定。通过试验表明,使用此种方法设计的浊度传感器,要准确快速地测量海水浊度。  相似文献   

基于双目成像云底高度测量方法   总被引：4，自引：0，他引：4       下载免费PDF全文

陶法  马舒庆  秦勇  胡树贞  雷勇  郭伟  温显罡  张春波 《应用气象学报》2013,24(3):323-331

采用基线长为60 m的一对数字摄像机,构成双目成像云底高度测量系统,随着数字摄像技术和立体视觉传感器的发展,尤其是双目成像视觉传感器以结构简单、使用方便、测量精度高等诸多优点而被广泛应用。通过直方图均衡化方法对图像进行增强,利用亚像素角点检测器检测角点提高测量精度,并采用归一化互相关方法进行区域相关检测寻找同名点,将外极线约束引入图像匹配过程中进行同名点粗差去除,提高测量准确度;再根据匹配特征点得到相对视差,利用摄影测量原理计算云底高度;建立三维实验室标校场对相机进行内外方位元素标校,利用星星相对位置与相机姿态角的关系对相机进行现场标校,简化标校系统提高测量精度。利用2011年5月1日—6月30日采集的样本,在北京市观象台与维萨拉生产的CL31激光云高仪进行对比试验,并对产生云底高度测量系统误差的可能原因做出具体分析。  相似文献   

Improved parameter estimation for hydrological models using weighted object functions     

A. Stein  W. J. Zaadnoordijk 《水文研究》1999,13(9):1315-1328

This paper discusses the sensitivity of calibration of hydrological model parameters to different objective functions. Several functions are defined with weights depending upon the hydrological background. These are compared with an objective function based upon kriging. Calibration is applied to piezometric readings from the Isle of Goeree in the Netherlands. For a study on the permeability of the first aquifer, the kriging predictor yields weights that differ from using prior knowledge, and emphasizes more strongly spatially isolated points than commonly applied objective functions. It reduces the range of differences between measurements and model simulations, but the mean absolute error increases. For a study on the resistance of the top layer and of the aquitard, use of prior information in the objective functions leads to a reduction in standard deviations of the differences between measured and calculated values by 40–80%. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献