未破碎变浅随机海浪的波高统计分布     

黄培基  陈雪英  刘新安 《海洋科学进展》1999,(1)

利用青岛海洋大学海洋实验室现代化的大型水槽,设计进行了多种海浪强度下,由深水传入近岸不同坡度水底上的变浅随机海浪的模型实验。依据实验资料统计分析结果表明：对近岸变浅随机海浪而言,其波高分布不再符合Ｒａｙｌｅｉｇｈ分布,与Глуховский的经验分布也有差异,它不仅与参量Ｈ＊＝Ｈ／ｄ有关,且与表征深水海浪的波形特征量Ｈ０／Ｔ２０有关,并获得其经验关系,为实验应用变浅随机海浪的波高统计分布提供了可能。  相似文献   

Modeling, synthetics and engineering applications of strong earthquake wave motion     

Masanobu Shinozuka  George Deodatis  Ruichong Zhang  Apostolos S. Papageorgiou 《Soil Dynamics and Earthquake Engineering》1999,18(3):182

State of the art in modeling, synthetics, statistical estimation, and engineering applications of strong ground motion is reported in this paper. In particular, models for earthquake wave motion are presented, in which uncertainties both in the earth medium and the seismic source are taken into consideration. These models can be used to synthesize realistic strong earthquake ground motion, specifically near-field ground motion which is quite often not well recorded in real earthquakes. Statistical estimation techniques are also presented so that the characteristics of spatially-correlated earthquake motion can be captured and consequently used in investigating the seismic response of such large scale structures as pipelines and long-span bridges. Finally, applications of synthesized strong ground motion in a variety of engineering fields are provided. Numerical examples are shown for illustration.  相似文献   

Stochastic significance of peaks in the least-squares spectrum   总被引：3，自引：1，他引：2  

S. D. Pagiatakis 《Journal of Geodesy》1999,73(2):67-78

The least-squares spectral analysis method is reviewed, with emphasis on its remarkable property to accept time series with an associated, fully populated covariance matrix. Two distinct cases for the input covariance matrix are examined: (a) it is known absolutely (a-priori variance factor known); and (b) it is known up to a scale factor (a-priori variance factor unknown), thus the estimated covariance matrix is used. For each case, the probability density function that underlines the least-squares spectrum is derived and criteria for the statistical significance of the least-squares spectral peaks are formulated. It is shown that for short series (up to about 150 values) with an estimated covariance matrix (case b), the spectral peaks must be stronger to be statistically significant than in the case of a known covariance matrix (case a): the shorter the series and the lower the significance level, the higher the difference becomes. For long series (more than about 150 values), case (b) converges to case (a) and the least-squares spectrum follows the beta distribution. The results of this investigation are formulated in two new theorems. Received: 27 May 1997/Accepted: 30 September 1998  相似文献   

基于R值和统计分布检验的年度地震危险区个数评估     

苑争一  姜祥华  刘琦 《中国地震》2023,39(1):88-97

针对年度地震危险区划定的个数问题开展了一些尝试性研究,旨在从统计学角度给出危险区个数的最佳估值,对年度地震预测实践给出一定参考意见。通过R值评分算法反推出年度地震危险区个数的估算公式,同时改进了传统聚类算法用于识别空间距离较近的地震“丛集区”,在此基础上分别统计中国大陆地区1950—2019年满足目标震级的年度地震发生个数、地震“丛集区”和“孤立发生地震”的个数之和,最后进行多种统计分布模型拟合与检验,结合置信区间确定危险区个数的合理上限。结果表明,由两种统计结果得出的年度危险区个数的参考值也略有差别,第一种基于中国大陆地区东部(107°E以东)M_S5.5、西部(107°E以西)M_S6.0以上地震年度发生率的危险区个数参考值为9个,适用于稍大震级的判定;第二种基于中国大陆地区年度M_S5.0以上地震“丛集区”识别结果的危险区个数参考值为13个,与目前中国地震台网中心使用的个数一致,对判定年度M_S5.0以上地震具有较好的应用实效。  相似文献   

基于JUNO卫星WAVES仪器波动数据的木星磁层哨声波分析研究   总被引：1，自引：0，他引：1       下载免费PDF全文

黄靖  倪彬彬  付松  顾旭东  曹兴  项正  王琦  罗琼  何颖  闫玲  王敬之 《地球物理学报》2019,62(3):817-824

等离子体波的空间分布在木星磁层高能电子动力学过程中起着重要的作用.现有大多数对木星磁层哨声波的观测仅限于|λ|≤15°的磁纬范围内,但是最新的JUNO卫星WAVES仪器提供的波动数据使得更高纬度、更广区域范围内的等离子体波动分布研究成为可能.本文通过对JUNO卫星WAVES仪器数据进行分析处理,详细研究了木星磁层哨声波的空间分布特性.观测表明,存在位于高LJ、高磁纬的木星磁层哨声波,它们广泛分布于距木星中心距离35～75个木星半径、磁纬为|λ|≤30°的空间区域.分析研究发现,WAVES仪器观测的木星磁层哨声波幅度一般为几个pT,远小于地球磁层哨声波的强度.木星磁层哨声波幅会随着LJ的增大缓慢增加,也会随着磁纬的减小趋向平缓变化.基于以上观测事实,本文利用指数幂函数分别拟合得到木星磁层哨声波幅随LJ和磁纬变化的经验模型.该模型将有助于精确理解哨声波对木星磁层高能电子动力学过程的重要影响.  相似文献   

Variation in hydraulic geometry for stable versus incised streams in the Yazoo River basin-USA     

Nidal Hadadin 《国际泥沙研究》2017,32(1)

The effects of basin hydrology on hydraulic geometry of channels variability for incised streams were investigated using available field data sets and models of watershed hydrology and channel hydraulics for the Yazoo River basin,USA.The study presents the hydraulic geometry relations of bankfull discharge,channel width,mean depth,cross-sectional area,longitudinal slope,unit stream power,and mean velocity at bankfull discharge as a function of drainage area using simple linear regression.The hydraulic geometry relations were developed for 61 streams,20 of them are classified as channel evolution model(CEM) Types Ⅳ and Ⅴ and 41 of them are CEM streams Types Ⅱ and Ⅲ.These relationships are invaluable to hydraulic and water resources engineers,hydrologists,and geomorphologists involved in stream restoration and protection.These relations can be used to assist in field identification of bankfull stage and stream dimension in un-gauged watersheds as well as estimation of the comparative stability of a stream channel.A set of hydraulic geometry relations are presented in this study,these empirical relations describe physical correlations for stable and incised channels.Cross-sectional area,which combines the effects of channel width and mean channel depth,was found to be highly responsive to changes in drainage area and bankfull discharge.Analyses of cross-sectional area,channel width,mean channel depth,and mean velocity in conjunction with changes in drainage area and bankfull discharge indicated that the channel width is much more responsive to changes in both drainage area and bankfull discharge than are mean channel depth or mean velocity.  相似文献   

利用早期余震预测的Omi-R-J方法对2017年四川九寨沟M_S7.0地震的应用研究          下载免费PDF全文

蒋长胜  毕金孟  王福昌  隗永刚  龙锋 《地球物理学报》2018,61(5):2099-2110

在地震序列的早期阶段获得科学可靠的余震预测结果,始终是地震预测研究的前沿课题.针对新近发展的Omi-R-J方法的适用性问题,以及相比于传统的Reseanberg-Jones （R-J）模型在地震序列参数拟合、余震预测效能上的差异等问题,本文以2017年四川九寨沟M_S7.0地震序列为例,利用多时间窗的连续滑动拟合、预测和检验,以及通过构建重采样随机地震序列目录的系统检验等方式,开展了应用研究和比较研究.结果表明：相比于R-J模型,Omi-R-J方法可在余震记录较不完整的地震序列早期阶段获得稳定、可靠的序列参数,p值、c值和b值的标准差相比于R-J模型参数明显减小.N-test方法检验结果表明,在R-J模型等传统方法无法获得预测结果的地震序列早期阶段,Omi-R-J方法预测结果可以较高的比例通过N-test检验,在后续时段的预测效果也明显优于R-J模型.利用随机地震序列目录的测试结果表明,余震记录完整性下降对Omi-R-J方法预测结果的影响相对较小,在全部时段的完整性下降的影响高于在部分时段的完整性下降.上述结果对进一步地将Omi-R-J方法应用在震后早期余震预测中具有一定科学借鉴意义.  相似文献   

仿射坐标系下的因子分析—仿射因子分析     

毕葵森 《江苏地质》1996,20(1):32-40

传统的因子分析以正交坐标系为其基础坐标系,因而存在某种固有缺陷。文中提出以仿射坐标系为因子分析的基础坐标系,并进而给出了仿射因子分析的方法。新方法不仅消除了原方法所存在的缺陷,同时还实现了样品和变量空间的统一。  相似文献   

察尔汗盐湖S3盐层晶间卤水分异特征及成因的统计研究          下载免费PDF全文

徐少康 《盐湖研究》1993,1(4):9-20

1962年,苏联学者М.Г.Баляшко提出了干盐湖晶间卤水分异的成因理论一“重力垂直分异”说,后来,此理论被我国盐矿地质学家引用到察尔汗盐湖。本文首次在“系统论”思想指导下,及数理统计方法深入细致地研究了该湖S_3盐层晶间卤水分异特征,提出了新的晶间卤水分异成因理论—“阶段性淡化”说,具有重要的经济和理论意义。  相似文献   

天山巴音布鲁克盆地汛期水资源变化趋势及其影响因素分析          下载免费PDF全文

刁鹏  李刚  张玮煊 《沙漠与绿洲气象(新疆气象)》2022,16(6):51-58

利用1982—2018年巴音布鲁克气象站逐日气象资料和开都河流上游大山口水文站逐月径流量资料，采用Morlet小波分析、气候敏感与水量平衡法，时间序列分析等方法，分析了汛期（5—9月）巴音布鲁克盆地地表径流量变化趋势及气候变化与人工增水作业对径流量的影响。结果表明：近37 a巴音布鲁克盆地汛期地表径流量呈增加趋势，突变年份为1989年，存在主周期依次为14 a、22 a、4 a 、7 a的周期变化，具有17~27 a、11~16 a年代际尺度和4~8 a年际尺度的丰枯位相交替变化特征。降水量是影响径流量变化的主导气候因素，对径流量变化的平均影响率为73.1%。因人工增水因素影响，盆地的降水可分为自然降水和人工催化降水，其中自然降水在历史期（1982—1993年）为69.5%，作业前期（1994—2006年）为59.28%，作业后期（2007—20018年）为74.56%，而人工催化降水在人工增水期（1994—2018年）对径流量变化的平均影响率为7.93%，表明径流量对降水的依赖程度正大幅增加，同时人工增水作业对径流量也有一定增加作用。  相似文献