Determination and application of path duration of seismic ground motions based on the K-NET data in Sagami Bay,Japan

Duration models are one of the important parameters in ground-motion simulations. This model varies in different study areas, and plays a critical role in nonlinear structural response analysis. Currently, available empirical models are being globally used in ground-motion simulations, with limited research focusing on path duration in specific regions. In this study, we collected 6,486 sets of three-component strong-motion records from 29 K-NET stations in the Sagami Bay, Japan, and its surrounding areas between January 2000 to October 2018. We extracted the effective duration of 386 pieces of ground-motion records by manually picking up the S-wave arrival time and calculating the significant duration. We then obtained the path duration model of the study area based on the empirical equation of dynamic corner frequency and source duration of [7]. Compared with the results of the available empirical models, the Fourier spectrum of the simulated ground motion from our effective duration model showed higher accuracy in the long-term range, with less fitting residuals. This path duration model was then applied to simulate two earthquakes of M_W5.4 and M_W6.2, respectively, in the region using the stochastic finite-fault method with a set of reliable source, path, and site parameters determined for the study area. The simulation results of most stations fit well with observation records in the 0–30 Hz frequency band. For the M_W5.4 earthquake, the simulated ground motions at KNG005/KNG010/SZO008 stations were relatively weak in the mid to high frequency band (1–30 Hz) because the quality factor and geometric diffusion model used in the simulation were the averages of the entire Sagami Bay region, causing a bias in the results of a few stations owing to local crustal velocity anomalies and topographic effects. For the M_W6.2 earthquake, the simulated ground motions were relatively weak at all SZO and TKY stations, mainly because of the close distance from these stations to the epicenter and the complex seismic-wave propagation paths. The analysis suggests that the differences between the simulation results of the two earthquakes were mainly related to complex geological conditions and seismic-wave propagation paths.     

冻融循环对青藏红黏土物理力学性质影响试验研究

以红黏土为研究对象,使土样在封闭系统下进行不同次数的冻融循环作用,对冻融循环后的冻结土样进行粒度成分和物理力学性质测试,研究不同次数冻融循环作用下冻结红黏土粒度成分和物理力学性质的变化规律。结果表明：粉粒组和黏粒组质量含量受冻融循环作用次数影响较大。红黏土中颗粒在前10次冻融循环过程中向粒径小于0.001 mm及粒径在0.01~0.05 mm范围富集;冻融循环10次之后,随冻融循环次数的增加,粒径范围在0.002~0.005 mm的土颗粒含量明显增加,粒径范围在0.01~0.05 mm的土颗粒含量明显减小,其他粒径范围的土颗粒含量基本不受冻融循环次数的影响。红黏土的液、塑限大体上随冻融循环次数的增加而增加。冻融循环作用对红黏土等效黏聚力强度影响较明显,冻融循环作用10次以内红黏土等效黏聚力强度变化较大,在红黏土地区新修路基应考虑冻融循环作用引起的附加沉降影响。建议采用维亚洛夫或吴紫汪长期强度预报方程预测红黏土长期等效黏聚力强度。     

基于等效地球半径和地形的电磁波覆盖范围分析

针对电磁波覆盖范围分析的研究现状,文章研究了计算和分析相对简便的等效地球半径法:介绍了等效地球半径的定义及确定方法,探讨了基于等效地球半径和地形的电磁波覆盖范围分析方法,并基于投影原理分析了等效地球与实际地球的投影,实现了电磁波覆盖范围的高效分析及结果的精确可视化。     

GNSS/里程计组合定位抗差估计法

利用Kalman滤波进行GNSS/里程计组合定位难以实现两种传感器的最优利用。针对轮轨相对运动时里程计数误差增大的情况,提出了对GNSS位置导出里程、速度导出里程和里程计输出里程使用抗差最小二乘求取最优里程;并使用中位数求取抗差迭代初值。增加GNSS测速里程观测值,提高了观测冗余,有利于计算抗差初值。抗差等价权能够平衡3种观测值的比重,增强鲁棒性。计算结果表明,引入速度信息的抗差解法优于单一传感器定位解;也优于传统滤波解法。     

北斗系统差分码偏差解算中一种新的定权方法

差分码偏差(DCB)参数是影响用户定位、导航、授时和电离层求解的重要误差源之一。分析了北斗卫星导航系统不同轨道卫星高度角与不同频点信噪比(SNR)差值间的关系。实验分析表明:不同轨道卫星间信噪比差值具有较大差距,IGSO卫星信噪比差值(DSNR)较小且较为稳定,明显优于其他卫星;GEO卫星信噪比差值变化较小但绝对值较大;MEO卫星变化频繁且幅度较大。针对北斗系统具有多种轨道卫星的特点,结合卫地距与不同频点信噪比差值,提出了一种新的定权公式,并系统分析了不同定权方式下卫星DCB解算结果。实测数据分析表明:新的定权公式可以提高DCB解算精度,增强解算结果的稳定性。其中对于B1,B2和B1与B3差分码偏差,GEO卫星分别提高1%~15%和9%~16%;IGSO卫星提高4.5%~16%和8%~9%;MEO卫星提高20%~22%和27%~28%。     

架空线路年平均雷电闪击频数计算方法探析

分析了规范推荐的架空线路年平均雷击次数计算方法,提出方法中存在截收面积与雷击大地密度对应的雷电流幅值不匹配的问题。为解决该问题,文章以某一具体架空线路为例,介绍了针对全部雷电流幅值,应用积分法计算年平均雷击次数的方法,计算结果与规范推荐方法计算结果的比较说明了积分方法的精密性及结果的合理性。具体的分析、计算方法为：基于电气〖CD*2〗几何模型推导出与雷电流幅值有关的架空线路截收闪电宽度的计算公式,并通过对雷电流幅值频率分布规律的多项式拟合确定任意雷电流幅值的雷击大地密度,任一雷电流幅值对应的截收面积及对应的雷击大地密度的乘积即为该雷电流对应的年平均雷击次数,在该区域雷电流幅值的分布范围内对得到的雷击次数进行积分,即可得到考虑雷电流幅值分布特征的架空线路年平均雷击次数计算结果。     

考虑桩土相互作用的高桩码头体系等效阻尼比及Pushover分析

为考虑桩土相互作用的高桩码头体系等效阻尼比,将地震作用下高桩码头的滞回耗能定义为各桩塑性铰耗能和桩-土相互作用耗能之和,桩-土相互作用耗能根据p-y曲线和Masing准则定义的滞回环确定,码头结构的塑性铰总耗能为各桩塑性铰耗能的总和,按照正弦激励下一个振动循环内高桩码头体系与相应单自由度体系粘滞耗能相等的原则,推导得到了高桩码头体系等效阻尼比计算公式,并对两个高桩码头进行了Pushover分析。分析表明,土体耗能对高桩码头体系阻尼贡献较大,根据码头各桩塑性铰出现顺序和转动情况计算码头的等效阻尼比更符合实际情况。     

基于单位四元数描述的单像空间后方交会

在3维空间里,四元数可以非常方便地表示空间方位、空间向量间的旋转、平移和缩放等关系.将四元数理论引入到摄影测量领域,用单位四元数对坐标旋转矩阵进行描述,提出了一种采用单位四元数描述航摄像片位置与姿态的单张像片空间后方交会新方法.该方法与传统方法相比,在平差时避免了频繁的三角函数运算,不仅收敛速度快,而且精度高.     

ON THE DESIGN OF A NEW HUMAN COMFORT INDEX

1 INTRODUCTION Researches on human comfort index have been carried out over 75 years. In 1923, Houghten and Yaglou[1] first published their effective temperature (ET) scale, using dry and wet bulb temperatures along with wind speed in their model. Later o…     

Generalized Sequential Gaussian Simulation on Group Size ν and Screen-Effect Approximations for Large Field Simulations

The modelling of spatial uncertainty in attributes of geological phenomena is frequently based on the stochastic simulation of Gaussian random fields. This paper presents a generalization of the sequential Gaussian simulation method founded upon the group decomposition of the posterior probability density function of a stationary and ergodic Gaussian random field into posterior probability densities of a set of groups of nodes of size . The method, which is termed generalized sequential Gaussian simulation on group size , relies computationally on sharing the neighborhood of adjacent nodes and simulates groups of nodes at a time, instead of the traditional node-by-node simulation. The new method is computationally efficient and suitable for simulation on large grids of nodes. Results suggest that, in terms of computing cost (time), an optimal size of a group is about 80% of the optimal neighborhood used for sequential Gaussian simulation and that computation can be up to 50 times faster than the regular sequential Gaussian method, with little loss in accuracy. The effectiveness of the method is assessed by using a general measure of accuracy, screen-effect approximation loss (SEA loss), defined herein as the mean-square difference between the simulated value posterior to the information in the neighborhood and the simulated value posterior to all information, and shown to be determined by the corresponding posterior variances. The results presented show that both the exponential and the spherical models perform well and can meet the less-than 5% relative SEA loss requirement for any grid setup using a relatively small neighborhood. The Gaussian covariance model was found to have a relatively high relative SEA loss in most cases.