基于分数阶Fourier变换的声波测井全波列特征时频分析     

王祝文  向旻  刘菁华  王晓丽  张雪昂  杨闯 《吉林大学学报(地球科学版)》2012,(5):1553-1559,1570

目前,阵列声波测井信号处理大多在时间域或频率域中进行。但是,单纯的时间域或频率域方法有很大的局限性。为了打破这些局限性,笔者将分数阶Fourier变换方法用于阵列声波测井信号的分析之中,研究了不同性质储集层中信号幅度随分数阶Fourier变换阶数变化的规律。实验结果表明:在干层,幅度呈"1"型分布;在水层,幅度呈"Y"型分布,"Y"的两支开口较小,在阶数大于0.3的区域中,幅度较大;在油层,幅度呈"Y"型分布,"Y"的两支开口较大,在阶数大于0.6的区域中,幅度较大。因此,分数阶Fourier变换在提取阵列声波测井蕴含的储集层流体性质信息方面具有很好的前景。  相似文献   

加速度记录测定近震震级在江苏地区的计算研究     

詹小艳  徐顺强  章东  王凯 《大地测量与地球动力学》2021,41(5):539-543

基于江苏强震台网和江苏测震台网的地震记录,采用时间域内实时仿真WA记录方法,对2007~2018年记录到的M2.3以上地震进行近震震级测定。为了定量分析基于加速度测定近震震级的可靠性,首先采用国标规定的新震级测定方法和量规函数测定了基于加速度记录的震级,并将结果与江苏测震台网基于速度记录测定的结果进行对比分析,得到线性拟合关系式：ML(ACC)=0.987ML＋1.371;另外计算了15 324组基于加速度测定的震级与人工编目震级之间的绝对偏差,结果显示,偏差在±0.5级以内的结果占87%;通过4阶多项式拟合后发现,在小于200 km范围内测定的震级略低于人工编目的结果,震中距超过200 km后无系统偏差。总体而言,两者结果的一致性较好,表明利用加速度记录仿真WA位移记录来计算近震震级是可行的,得到的结果也是可靠的。  相似文献   

大亚湾西部海域沉积物中生物硅的含量及其分布特征          下载免费PDF全文

周鹏  李冬梅  李海涛  赵力  赵峰  郑远来  吴梅桂  余汉生 《应用海洋学学报》2019,38(1):109-117

采用2. 0 mol/dm~3Na_2CO_3溶液5h单点化学提取-硅钼蓝连续分光光度分析法分别测定了大亚湾西部海域13个表层沉积物和1个沉积物岩芯中生物硅的含量.表层沉积物和沉积物岩芯中生物硅含量占比分别为0. 69%～2. 02%和1. 24%～2. 05%,平均值分别为1. 42%和1. 60%.结果证实西大亚湾沉积物中生物硅含量水平与我国南海近岸海域基本一致.在210Pbex测年的基础上,通过分析沉积物岩芯中生物硅、有机物、无机碳等多指标,揭示近百年来大亚湾周边环境变化对海洋环境的影响,证实了上世纪80年代以来西大亚湾周边农业、海水养殖业和工业发展等人类活动加剧了该海域生态环境变化,尤其90年代核电站运行对海洋生态变化造成一定的影响.  相似文献   

分布式社区口腔医疗信息管理系统设计   总被引：3，自引：1，他引：2  

谢明元  刘福祥  郭在华  刘维成 《成都信息工程学院学报》2004,19(1):7-11

利用SQL Server和VB设计分布式社区口腔医疗信息管理系统,建立牙科电子病历,实现远程医疗信息共享和IC卡一卡通服务,改善口腔医疗服务水平.  相似文献   

A multiproxy climate record from a raised bog in County Fermanagh,Northern Ireland: a critical examination of the link between bog surface wetness and solar variability     

Graeme T. Swindles  Gill Plunkett  Helen M. Roe 《第四纪科学杂志》2007,22(7):667-679

A proxy climate record from a raised bog in County Fermanagh, Northern Ireland, is presented. The record spans the interval between 2850 cal. yr BC and cal. yr AD 1000 and chronological control is achieved through the use of tephrochronology and ¹⁴C dating, including a wiggle‐match on one section of the record. Palaeoclimatic inferences are based on a combination of a testate amoebae‐derived water table reconstruction, peat humification and plant macrofossil analyses. This multiproxy approach enables proxy‐specific effects to be identified. Major wet shifts are registered in the proxies at ca. 1510 cal. yr BC, 750 cal. yr BC and cal. yr AD 470. Smaller magnitude shifts to wetter conditions are also recorded at ca. 380 cal. yr BC, 150 cal. yr BC, cal. yr AD 180, and cal. yr AD 690. It is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest Europe. Harmonic analysis of the proxies illustrates statistically significant periodicities of 580, 423–373, 307 and 265 years that may be related to wider Holocene climate cycles. This paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing. Relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Elevated biomass of mesozooplankton and enhanced fecal pellet flux in cyclonic and mode-water eddies in the Sargasso Sea   总被引：2，自引：0，他引：2  

Sarah A. Goldthwait  Deborah K. Steinberg 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1360

Accumulating evidence points to the importance of mesoscale eddies in supplying nutrients to surface waters in oligotrophic gyres. However, the nature of the biological response and its evolution over time has yet to be elucidated. Changes in mesozooplankton community composition due to eddy perturbation also could affect biogeochemical cycling. Over the course of two summers we sampled seven eddies in the Sargasso Sea. We focused on and followed a post-phytoplankton bloom cyclonic eddy (C1) in 2004 and a blooming mode-water anticyclonic eddy (A4) in 2005. We collected zooplankton in all eddies using a Multiple Opening and Closing Net Environmental Sampling System (MOCNESS) and quantified biomass (>0.15 mm, in five size fractions) from 0 to 700 m over nine discrete depth intervals. Zooplankton biomass (>0.5 mm) in the upper 150 m was similarly enhanced at night for the periphery of C1 and the center of A4 at 0.514 g m⁻² and 0.533 g m⁻², respectively, compared to outside (0.183 g m⁻² outside C1 and 0.197 g m⁻² outside A4). Despite minimal chlorophyll a enhancement and dominance by picoplankton in C1, zooplankton biomass increased most for the largest size class (>5 mm). Gut fluorescence for euphausiids and large copepods was also elevated on the C1 periphery. In A4, peak biomass occurred at eddy center coincident with peak primary production, but was highly variable (changing by >3-fold) over time, perhaps resulting from the dense, but patchy distribution of diatom chains in this region. Shifts in zooplankton community composition and abundance were reflected in enhancement of fecal pellet production and active transport by diel vertical migration in eddies. Inside C1 the flux of zooplankton fecal pellets at 150 m in June 2004 was 1.5-fold higher than outside the eddy, accounting for 9% of total particulate organic carbon (POC) flux. The flux of fecal pellets (mostly from copepods) increased through the summer in eddy A4, matching concurrent increases in zooplankton <2 mm in length, and accounting for up to 12% of total POC flux. Active carbon transport by vertically migrating zooplankton was 37% higher on the periphery of C1 and 74% higher at the center of A4 compared to the summer mean at the Bermuda Atlantic Time-series Study (BATS) station. Despite contrasting responses by the phytoplankton community to cyclonic and mode-water eddies, mesozooplankton biomass was similarly enhanced, possibly due to differential physical and biological aggregation mechanisms, and resulted in important zooplankton-mediated changes in mesoscale biogeochemistry.  相似文献   

Numerical simulation research on multi-electrodes resistivity imaging survey array     

Jianjun NIU  Xiaopei ZHANG  Lizhi DU College of Construction Engineering  Jilin University  Changchun  China 《东北亚地学研究》2008,11(4):232-236

Multi-electrodes Resistivity Imaging Survey （MRIS） is an array method of electrical survey. In practice how to choose a reasonable array is the key to get reliable survey results. Based on four methods of MRIS such as Wenner, Schlumberger, Pole-pole and Dipole-dipole the authors established the model, by studying the result of the forward numerical simulation modeling and inverse modeling, and analyzed the differences among the different forms of detection devices.  相似文献   

Numerical simulation research on multi-electrodes resistivity imaging survey array     

《世界地质(英文版)》2008,11(4)

Multi-electrodes Resistivity Imaging Survey (MRIS) is an array method of electrical survey. In practice how to choose a reasonable array is the key to get reliable survey results. Based on four methods of MRIS such as Wenner, Schlumberger, Pole-pole and Dipole-dipole the authors established the model, by studying the result of the forward numerical simulation modeling and inverse modeling, and analyzed the differences among the different forms of detection devices.  相似文献   

On the use of iterative re-weighting least-squares and outlier detection for empirically modelling rates of vertical displacement     

E. Rangelova  G. Fotopoulos  M. G. Sideris 《Journal of Geodesy》2009,83(6):523-535

The proper identification and removal of outliers in the combination of rates of vertical displacements derived from GPS, tide gauges/satellite altimetry, and GRACE observations is presented. Outlier detection is a necessary pre-screening procedure in order to ensure reliable estimates of stochastic properties of the observations in the combined least-squares adjustment (via rescaling of covariance matrices) and to ensure that the final vertical motion model is not corrupted and/or distorted by erroneous data. Results from this study indicate that typical data snooping methods are inadequate in dealing with these heterogeneous data sets and their stochastic properties. Using simulated vertical displacement rates, it is demonstrated that a large variety of outliers (random scattered and adjacent, as well as jointly influential) can be dealt with if an iterative re-weighting least-squares adjustment is combined with a robust median estimator. Moreover, robust estimators are efficient in areas weakly constrained by the data, where even high quality observations may appear to be erroneous if their estimates are largely influenced by outliers. Four combined models for the vertical motion in the region of the Great Lakes are presented. The computed vertical displacements vary between  − 2 mm/year (subsidence) along the southern shores and 3 mm/year (uplift) along the northern shores. The derived models provide reliable empirical constraints and error bounds for postglacial rebound models in the region.  相似文献   

国际Argo计划执行现状剖析   总被引：1，自引：0，他引：1  

朱伯康  许建平 《海洋技术学报》2008,27(4)

国际Argo计划自2000年实施以来,世界上25个国家和团体已经在全球海洋中布放了5000余个Argo浮标,其中在海上正常工作的浮标已经超过3000个。这标志着全球Argo实时海洋观测网已经全面建成。文中将系统介绍国际Argo计划主要成员国在浮标布放、回收和Argo资料管理等方面所作出的贡献,以帮助读者对这21世纪的重大国际海洋观测计划有一较全面、深入的了解。  相似文献