场地土层模型参数的地震动记录反演方法   总被引：1，自引：0，他引：1       下载免费PDF全文

李小军  荣棉水  喻烟 《地球物理学报》2020,63(1):236-246

考虑场地土层不同物理参数的综合反演,改进了水平与竖向谱比(Horizontal-to-Vertical Spectral Ratio,简称HVSR)混合全局优化反演方法,进一步通过土层的S、P波波速、厚度、泊松比、密度和S、P波品质因子等土层参数反演的敏感性分析,形成了可同时反演场地土层厚度及剪切波速的混合全局优化反演方法.以美国GVDA和日本IWTH27竖向强震动观测台阵为例,分别以理论HVSR及加速度观测记录获得的HVSR曲线为目标,反演获得了场地浅层速度结构,并与观测台阵场地钻孔揭示的土层模型进行比较,验证了发展的反演方法的合理性和适用性.本文研究表明,基于地震加速度记录的HVSR全局优化反演方法是获取场地土层速度结构的一种有效的途径.  相似文献   

动态变化率与最大差值相结合的陆表生态变化检测     

李晓东  宋开山 《遥感学报》2021,25(6):1338-1350

为了实现更大尺度上的陆表生态变化检测,一种基于综合生态指数的动态变化检测方法用于不同时期卫星影像变化信息的提取。本文以东北地区的松嫩平原地表植被覆盖类型作为主要研究对象,2006年和2018年作为变化检测研究的标准年,陆地资源卫星影像数据作为实验数据源。动态变化的主要检测内容划分为年内变化和年际变化,最大差值算法计算影像数据的年内最大变化差异,同时动态比率算法计算年际动态变化。方法的实现过程如下,选择3个主要生态指数（水体指数、植被指数和土壤指数）用于计算年内最大差异和年际动态比率。然后,采用主成分分析法提取年内最大差异和年际动态比率的第一主成分,主要研究内容包括年内变化的显著性生态评价和年际变化方向、变换类型的分析与评价以及方法精度的验证。最终结果表明：（1）动态比率算法用于研究区年际变化检测,具有更高的变化检测精度,总体精度为93.80%,Kappa系数为0.876。（2）年内生态指数变化的最大差值用于定量衡量研究区年内变化检测。其中,第一主成分保留了83.04%的变化信息。同时,植被和水体对研究区的陆表生态变化有正方向的贡献。土壤裸露程度对陆表生态变化有负方向贡献。动态比率变化检测方法不需要设定适合的、动态的变化阈值,更便于大范围高效更新土地覆被类型。  相似文献   

北斗观测量时间相关随机模型构建及评估     

李慧  信泽宇  刘学  田迪迪  贾春 《测绘通报》2021,(4):60-63

传统多历元累积观测量随机模型通常忽略各历元间观测量的时间相关性,导致其对观测量整体随机特性刻画不准确。考虑北斗系统中GEO卫星观测量的时间相关性较强,本文提出一种适用于多历元下北斗观测量的时间相关随机模型构建方法。在传统多历元随机模型的基础上,将时间相关系数直接引入随机模型,通过观测量站间差分残差计算各历元间观测量的时间相关系数,生成多历元下北斗观测量时间相关随机模型,并利用实际试验数据对其在整周模糊度解算中的表现进行评估。试验结果表明,时间相关随机模型在一定程度上解决了传统随机模型存在的整周模糊度PCF下限估值虚高的问题,提高了整周模糊度Ratio值,有助于整周模糊度顺利通过检验。此外,相比于传统随机模型,时间相关随机模型有效减少了整周模糊度漏检及误警的情况出现,提高了整周模糊度解算的可靠性。  相似文献   

城市空间扩展非协调性识别的基础理论与实证分析     

孙平军  修春亮  吕飞 《地球科学进展》2015,30(2):247-258

针对当前国内外现有城市空间扩展研究因数据和方法的制约而相对缺乏合理性评价以及伴随快速城镇化进程推进的我国城市空间扩展引发了一系列区域可持续发展问题的现实背景,试图基于逆向思维和问题诊断视角构建一座由非协调病理诊断通向协调发展道路的桥梁,从非协调性视角构建城市空间扩展合理性评价指标体系;内涵上具体表征为城市建设用地总量控制非协调性、城市建设用地与农用地、生态用地配比结构非协调性以及城市建设用地空间配置非协调性3个层面。并在此基础上,以2008年中国246个地级市为样本单元展开实证分析。期间从分区(经济区划)、分类(行政等级、道路交通、城市规模、城市属性、气候条件、地形条件等)的思维对其内在规律性进行了揭示、归纳与汇总。结果表明该识别体系较为合理,揭示结果与现实情况相吻合,可以作为认知城市空间扩展,缓解人多地少的基本国情和人地矛盾冲突,促进土地资源的集约高效、合理利用和区际公平可持续发展的理论依据。  相似文献   

CSAMT单分量数据解释方法   总被引：3，自引：1，他引：2       下载免费PDF全文

闫述  薛国强  邱卫忠  周楠楠 《地球物理学报》2017,60(1):349-359

可控源音频大地电磁法(CSAMT)一直沿用大地电磁法(MT)的办法,通过计算电场分量与磁场分量的比值,求取卡尼亚视电阻率.而CSAMT场源已知,电场分量和磁场分量都与地下电阻率存在一定的关系,可以单独采用CSAMT电场分量或者磁场分量提取地下介质的视电阻率.本文通过分析电场分量与磁场分量的数据特性,提出利用CSAMT电场单分量数据进行视电阻率的计算,用改进的广义逆矩阵反演方法,使初始模型中的地电层数等于频道个数,克服了以往反演计算中层数较少的问题;实现全场区电场分量视电阻率曲线的拟合反演.同时对单分量视相位计算方法进行分析,结合山西大同地区积水采空区探测及数据解释结果,论证本文提出的单分量解释方法的有效性.  相似文献   

Effect of reciprocating and unidirectional airflow on primary conversion of a pentagonal Backward Bent Duct Buoy     

《Applied Ocean Research》2019

An Oscillating Water Column (OWC) device can output energy through reciprocating or unidirectional airflow. The unidirectional airflow is helpful to utilize a simple and high-efficiency unidirectional air turbine. The pentagonal BBDB proposed by us based on OWC principle can be regarded as a floating Oscillating Body and its Power Take-Off (PTO) consists of a chamber, a water column, a turbine and a generator. The Capture Width Ratio (CWR) of the pentagonal BBDB model with the reciprocating and unidirectional airflow was studied in this paper. The wave flume test results indicate the mean CWR of the pentagonal BBDB model with reciprocating airflow can reach up to 121.91% and the mean CWR of the model with unidirectional airflow could reach 100.94% during the whole wave cycle in regular waves. For irregular waves, the mean CWR of the model with the unidirectional airflow is as high as 62.83% during the whole wave cycle. Hopefully, the combination of the pentagonal BBDB with the check valve to output power during the air exhalation and conventional high-efficiency unidirectional turbine will improve the total efficiency of the BBDB.  相似文献   

Shear wave attenuation characteristics over the Central India Tectonic Zone and its surroundings     

《Journal of Asian Earth Sciences》2013

The study area lies between latitude 18–26°N and longitude 73–83°E, and mainly covers the Central India Tectonic Zone (CITZ). The frequency-dependent shear wave quality factor (Q_s) has been estimated over the CITZ and its surroundings using Double Spectral Ratio (DSR) method. We have considered 25 local earthquakes with magnitude (M_L) varies from 3.0 to 4.7 recorded at 11 stations running under national seismic network. The Fast Fourier Transformed (FFT) spectra were computed from the recorded waveform having time-window from onset of S-phase to 1.0 s and for a frequency-band of 0.1–10 Hz. Three different shear wave velocities (i.e., 3.87, 3.39 and 3.96 km/s) were obtained over the study area based on a pair of earthquakes recorded at a pair of stations. The low Q_s values of 51–96 at 1 Hz (i.e., Q_s = 51f^0.49; Q_s = 90f^0.488 and Q_s = 96f^0.53) were found in the area covering the Son–Narmada–Tapti (SONATA) lineament, CITZ, eastern part of the Satpura fold belt, Vindhyan and Gondwana basins, Godavari and Mahanadi grabens, and southern part of Gangetic plain. Intermediate Q_s values of the order of 204–277 (i.e., Q_s = 204f^0.56 and Q_s = 277f^0.55) were noted in the cartonic areas, namely, Bundelkhand, Dharwar-Bhandara and Bastar. While the higher Q_s values of 391–628 at 1 Hz (i.e., Q_s = 391f^0.49, Q_s = 409f^0.48, Q_s = 417f^0.48, Q_s = 500f^0.66, Q_s = 585f^0.65 and Q_s = 628f^0.69) were found in the eastern part of the SONATA, CITZ, and the northeastern part of the Satpura fold belt. The low Q_s values might be attributing to the more heterogeneous SONATA rift system. Low Q_s values further may presumably be associated with lower-level of seismicity and apparently account for higher tectonic stress accumulation over long duration. The long-term accumulated stress is generally released through occasional triggering of moderate magnitude earthquakes in the SONATA zone. Surrounding the SONATA region, the higher Q_s values possibly accounts for a more homogeneous subsurface structure along the SONATA zone.  相似文献   

It goes both ways: measurements of simultaneous evapotranspiration and fog droplet deposition at a montane cloud forest     

E. Beiderwieden  V. Wolff  Y.‐J. Hsia  O. Klemm 《水文研究》2008,22(21):4181-4189

Fluxes of latent heat, sensible heat, and water vapor, including turbulent deposition of fog droplets, were measured for two months in autumn 2005 within a subtropical montane cypress forest in Taiwan. The goal of the study was to determine whether significant evapotranspiration can occur during foggy conditions. Water vapor fluxes, Q_W, as determined with the Bowen Ratio method, were compared to those simultaneously measured with the eddy covariance method. The median Bowen Ratio was 1.06, and the median Q_W flux was 5 · 2 × 10^?5 kg m^?2 s^?1. The vertical gradients of temperature and specific humidity over the forest, ΔT and Δq, peaked around noon during days without fog, and were reduced during foggy conditions. For 66% of the data points, ΔT and Δq were negative, corresponding to positive (upward) fluxes of sensible heat Q_H and latent heat Q_E. A Monte Carlo simulation proved that statistically significant evapotranspiration rates, i.e., upward water vapor fluxes, occurred during fog. At the same time, deposition fluxes of fog droplets occurred. Our results show that even during fog events, significant evapotranspiration may occur. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

海流剖面仪信号处理系统中最小二乘改进算法的应用研究     

朱昊  刘文耀  梁捷  郝永杰 《海洋技术学报》2004,23(3):41-45

ADCP技术是海洋测流领域的热门技术，而频谱估计方法的研究是该技术的核心。文章介绍一种最小二乘的改进算法(ELMS)，利用该算法可以很好的提取出淹没在白噪声下的正弦频谱。和传统的快速傅立叶变换方法(FFT)相比，该算法极大的压缩了数据量的要求，而且在信噪比为0DB的时候，仍能够较准确的估计出信号的谱峰位置。实验结果辩明该算法具有良好的鲁棒性。  相似文献   

海河流域沉降区地下水资源承载力评价指标体系   总被引：2，自引：0，他引：2  

董克刚  王威  于强  易长荣  周俊 《地下水》2008,30(4):12-15

海河流域大部分地区资源性缺水,历史上过度开采地下水导致了一系列的地质环境灾害,尤其是流域东部天津地区的地面沉降问题,是经济社会发展和地下水资源承载力不相协调调的具体表现。在有效进行地下水资源管理来防治地面沉降的过程中,面临的首要问题之一就是地下水资源承载力的评估。探讨了此前天津地区地下水环境容量指标在地下水资源承载力评价中的局限性,并提出“土水比”评价指标,构建“土水比”指标体系。  相似文献