Materials, such as vehicle lightweighting, intelligent materials, and aviation damping material, are frequently subjected to prolonged loading conditions. During the service life of materials, micro-damage will inevitably occur. The ultrasonic wave-mixing method is an emerging technique in detecting subtle damage in materials. Investigating the interaction between two waves in nonlinear materials guides the non-destructive detection of defects. In the ultrasonic wave-mixing technique, the resonance condition is commonly employed for the selection of the two primary wave frequencies. However, resonance conditions are often not strictly satisfied in practical applications. The mixing wave still contains important information that requires attention in detection. The theoretical solution of the mixing wave interacted by two-way collinear waves with arbitrary frequencies is derived. The results advance us to understand the intrinsic properties of wave interaction.

Ultrasonic wave mixing is a powerful new nondestructive evaluation technique for accessing hidden subtle imperfections in materials. First, this paper derives the resonance conditions of one-way collinear mixing with cubic nonlinearity. The results show that the mixing of two collinear longitudinal waves can generate a resonant longitudinal wave, the mixing of two transverse waves can generate a resonant transverse wave, and the resonant longitudinal wave and transverse wave can be generated, respectively, when two primary longitudinal and transverse waves satisfy different resonance conditions. This is different from the case with quadratic nonlinearity. Furthermore, we obtain the analytical solutions of resonant waves generated by the mixing of harmonic longitudinal and transverse pulses. The waveforms are approximate hexagonal shapes according to the analysis of the envelopes. Finally, the numerical simulation results conducted on material aluminum prove the correctness of the analytical solution. Compared with quadratic nonlinearity, the resonant wave is more sensitive to material constants for some materials when considering one-way collinear mixing of primary longitudinal and transverse pulses based on cubic nonlinearity. The results provide new opportunities on mixing wave applications in nondestructive evaluation.

The resonance conditions of two-way collinear mixing are derived when a longitudinal wave and a transverse wave are propagating in the opposite directions based on cubic nonlinearity. The analytical solutions for mixing waves are obtained. An interesting result is that the resonant longitudinal wave and the resonant transverse wave can be generated, respectively, when considering different resonance conditions. This is different from the case with quadratic nonlinearity that only resonant transverse wave can be generated. For the convenience of applications, the wave mixing of a time-harmonic longitudinal pulse and a time-harmonic transverse pulse is also investigated. A clear mixing process is presented by discussing the parameters introduced in the derivation. Numerical calculation is conducted on material Al, the hexagonal waveforms of the resonant transverse waves are depicted when considering different cases. The results could provide new opportunities for mixing wave applications in nondestructive evaluation.

给出了基于CANoe软件的特种车控制系统测试环境的设计方法,通过数据库的建立、界面的编制等步骤可以快速建立起方便高效的测试环境,并且给出了在两个特种车中成功运用的实例.

从大尺度和小尺度两方面研究郯庐断裂带苏鲁段地壳介质非均匀性.使用地震波数据,研究了郯庐断裂带苏鲁段地壳速度结构的非均匀性,单位虚波Qmps的非均匀性,地壳介质泊松比的非均匀性,反映地壳介质小尺度非均匀性的分层κ值和y值.计算了1668年郯城81/2级地震震源区长度和沿断裂带的震源区边界,根据地震构造和地震活动性确定断裂的闭锁段,地震应力的积累单元和调整单元.对比1668年郯城81/2级地震的地壳介质状况,将各种非均匀性参数综合分析,结果表明,各种参数指向一致,未来大震的可能区域是33°—34.5°N,118°—118.8°E的北北东向区域,震级可达8级.

依据沂沭断裂带及其附近地区断裂特征和应力场分布的分段特性将其划分为4个子区域,利用改进后的尾波Qc值测定方法计算了2010-2017年各子区域内ML≥2.0地震的尾波Qc值,并对其空间分布特征进行了研究.结果 显示:①沂沭断裂带尾波Qc值(1 Hz时的Qc值)整体差异不大,但显示出较好的分段特性,即莱州湾和附近海域平均尾波Qc值(34.95)明显高于其它区段,潍坊—孟疃段(23.22)、新沂—宿迁段(21.12)平均尾波Qc值相对偏低;②尾波Qc值空间分布与区域介质的地壳构造特点及地质环境关系紧密,揭示了沂沭断裂带作为构造边界带的属性.

针对激光捷联惯组系统级标定控制流程复杂、运算量大、可靠性要求高的问题,提出了一种用于激光捷联惯组的系统级标定软件设计及实现方法.软件基于VxWroks实时操作系统实现,通过运用多任务处理机制完成了对转台和激光捷联惯组的协同控制,通过设计控制流程文件实现对不同标定流程的灵活适用,通过消息队列、内存共享等任务间通信方法实现了数据的可靠传输和存储.最终得到了一种操作简单、运行可靠、灵活高效的系统级标定软件.

In this paper, a set of earthquake early-warning system is designed and implemented, and the key technologies such as earthquake location, magnitude estimation and information release are expounded. Finally, the system is tested by offline. The test results show that system has the characteristics of high precision of location, accurate estimation of magnitude and fast response speed. This has accumulated technical foundation for further implementation of online earthquake warning.

An improved Newton-type iteration method for regularizing the abstract nonlinear ill-posed operator equation is presented and also certain stopping criterion to determine the iteration is proposed in this paper by using the Newton-Landber iteration and the linear Tikhonov regularization. Under the condition that the Frechet-derivation operator is uniformly boundary and further assumptions on the closeness and smoothness of the exact solution, the local convergence of the approximate solution is obtained.

介绍了用向量方法求解平面反射光线方程的过程,推导后得到了简明的计算公式,使得结果具有清晰的几何意义.

This paper analyzes the seismic anisotropy parameters in the crust and obtains the characteristics of the stress field.The results show that the characteristics of the seismic anisotropy in Rushan region are influenced by both regional stress and local tectonics.Predominant polarization directions of fast shear-waves at DSDC are nearly NW.Combining the direction of epicenters of earthquake sequence and larger earthquake focal mechanism,it is concluded that the active fault in nearly NW direction is near the DSDC,and may be the possible generating fault of the RSH earthquake sequence.Polarization directions of fast shear-waves at BSTZ and CXZX are nearly EW;thus,there is probably possible active structure in nearly EW direction around the two stations.

采用山东地震台网记录的地震资料,基于Atkinson方法计算得出研究区非弹性衰减Q值与频率f的关系为Q(f)=457.1f0.4317.基于Moya方法得到山东台网中46个台站的场地响应,其中大部分台站效果比较理想,BSH、BZH、DOY、KEL、SHH、TZH、WEF台站存在较明显的放大效应,BZH、CHD、DOY、KEL、SHH、TCH、WEF台站的场地响应在6Hz以上出现显著的高频衰减.

利用山东数字地震台网记录到的2007-2014年的郯庐断裂带山东段ML≥1.0小震的震源机制解和视应力值,借助三角形图解法和平均力轴张量法,并结合b值等参数,综合分析了该区近年的应力状态.研究结果表明:郯庐断裂带山东段的主应力场方向为NEE-SWW向,是受西太平洋板块的俯冲作用和印度板块与欧亚板块挤压作用的共同影响的结果;震源错动类型以走滑型为主,逆冲型和正断型次之;通过视应力的时空演化图像看到郯庐断裂带山东段视应力值从2008年汶川地震之后呈现总体减弱的趋势,而空间上视应力分布很不均匀,高应力主要集中在安丘段和郯城—莒县段,尤其是安丘段出现了小震级高视应力的情况,同时安丘段的b值也显示同样的高应力,低b值反映高应力,低频度反映低应力释放,表明安丘段可能正在积累较高的应力,处于断层闭锁阶段.

（1）研究区三维速度结构的非均匀性。用6268个地震，123022个Sg-Pg,Sm-Pm,Sn-Pn到时差资料，使用多震相地震走时成像法获得了郯庐断裂带鲁苏段及附近地壳（30°～37°N，113°～122° E）三维速度结构，发现在20～25 km层部分地区存在低速异常区,主要是郯庐断裂带临沭到定远及以东的地区，1668年郯城地震区位于其内,1668年郯城地震发生在莫霍面埋深变化的区域，而郯庐带宿迁到泗洪及以东地区是莫霍面变化较大的地方。

As an effective means of reducing casualties and economic losses,earthquake early warning systems have received considerable attention and many have been implemented around the world.A complete earthquake early warn-ing system includes the identification of the earthquake location,estimation of its magnitude,estimation of its intensity at a target zone,and the dissemination of relevant information.The rapid determination of the earthquake magnitude is the most important part of such a system,after determining the location of the earthquake,because its accuracy affects predictions of ground motion of a target area and has influence on the issuance of warnings.An earthquake early warn-ing system should provide the longest emergency response time possible.Full use must be made of the limited infor-mation from seismic stations nearest to the epicenter when calculating the earthquake magnitude,using special algo-rithms to extract the parameters that can better reflect the characteristics of earthquake magnitude from few data. Therefore,it is necessary to develop some method to calculate earthquake magnitude that is non-traditional,stable, and reliable.In this study,we used a simple function of the form Bt ·exp (-At )and determined A and B in terms of the least-squares method by fitting this function with a 2-s time window of the first-arrival P waveform envelope.We proposed three methods for drawing waveform envelopes,which we then compared and analyzed using actual seismic records.An optimal method of drawing the envelopes was achieved,improving the method using the waveform enve-lope to obtain the magnitude.Based on 225 vertical recordings from the sensors of the Shandong Seismic Network, whose distances of separation are <100 km and that have an SNR ≥ 3 after processing and statistics,we obtained a statistical relationship with magnitude,envelope parameter B ,and the maximum speed for the 2-s time window of the first-arrival P waveform.An inspection of the results shows that the difference between this and the actual magnitude is small (0.36).According to a computational analysis of the Shandong Seismic Network data,we found a good linear relationship between lgB and epicentral distance Δ,regardless of the magnitude.Therefore,we can quickly estimate the magnitude of an earthquake using empirical formulas with the maximum amplitude of the 2-s P waveform and pa-rameter B ,effectively increasing the warning time and greatly reducing the warning blind spot.The fitting formula used to estimate the magnitude in this study has lower error and higher accuracy compared with the existing empirical formula when estimating earthquake magnitude in the Shandong region.However,because of the lack of seismic data for earthquakes >M 5,the inversion formula has some limitations,and in addition,parameter B has strong regional characteristics.This study is based on the Rushan earthquake in the Shandong region,for which the statistical relation-ship between magnitude,envelope parameter B ,and the maximum speed for the 2-s time window of the first-arrival P waveform was based.Therefore,the empirical relationship could be applied to the Jiaodong Peninsula that has similar geological structural characteristics.When an earthquake next occurs in the Jiaodong Peninsula,we will be able to ob-tain parameter B quickly using the data for the 2-s time window of the first-arrival P waveform at the station nearest to the epicenter.From this,it will be possible to estimate the earthquake magnitude simply and quickly,and effectively increase the warning time,which will greatly reduce the warning blind spot.

PreviousNext No AccessNear-Surface Asia Pacific Conference, Waikoloa, Hawaii, 7-10 July 2015Extraction of Weak Geophysical Information in the Strong Disturbing BackgroundAuthors: Shen PingZhou JianglinLiu XiqiangYang XuanhuiShen PingInstitute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaSearch for more papers by this author, Zhou JianglinInstitute of Geophysics, China Earthquake Administration, Beijing 100081, ChinaSearch for more papers by this author, Liu XiqiangCenter for analysis and Prediction, Seismological Bureau of Shandong Province, Jinan 250014, ChinaSearch for more papers by this author, and Yang XuanhuiInstitute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, ChinaSearch for more papers by this authorhttps://doi.org/10.1190/nsapc2015-125 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail AbstractThe research on geophysics is closely related to the solid observation data, but the observation data is interfered by underground medium, recording environment and some random factors. Such kind interference noise is sometime stronger than the real geophysical information in the near surface geophysics observations based on the records. For example, in the gravity data non-tidal variation contains zero drift which generated by recording instrument and other factors. Zero drift (noise) deduction is needed before identifying the relationship between variation of gravity and earthquake. Another example is the diurnal variation of the geomagnetic field, the noise can reach 10-20 γ from the geomagnetic observation, but the magnetic field change caused by earthquake is much smaller, to just a few γ. Therefore how to extract weak but real magnetic field variation data caused by the seismologic process from the background noise of strong interference (daily variation) is the first priority during the study on the relationship between magnetic field variation and seismogenic process. Certain progresses are made on recent study. In this paper, we explain some effective methods to eliminate many strong interference noise and obtain weak geophysical signal in the near surface geophysical observation recorded by the non-stationary and nonlinear signal processing theory.Keywords: random, noise, earthquakePermalink: https://doi.org/10.1190/nsapc2015-125FiguresReferencesRelatedDetails Near-Surface Asia Pacific Conference, Waikoloa, Hawaii, 7-10 July 2015ISSN (online):2159-6832Copyright: 2015 Pages: 501 publication data© 2015 Published in electronic format with permission by the Society of Exploration Geophysicists, Australian Society of Exploration Geophysicists, Chinese Geophysical Society, Korean Society of Earth and Exploration Geophysicists, and Society of Exploration Geophysicists of JapanPublisher:Society of Exploration Geophysicists HistoryPublished Online: 10 Jul 2015 CITATION INFORMATION Shen Ping, Zhou Jianglin, Liu Xiqiang, and Yang Xuanhui, (2015), "Extraction of Weak Geophysical Information in the Strong Disturbing Background," SEG Global Meeting Abstracts : 468-471. https://doi.org/10.1190/nsapc2015-125 Plain-Language Summary KeywordsrandomnoiseearthquakePDF DownloadLoading ...

Site effect on seismic peak ground acceleration is widely considered in such fields as seismic ground motion parameter zonation,earthquake early warning and quick assessment of seismic damage losses. Documents on seismic safety evaluation of engineering sites,including site type,overburden thickness,shear wave velocity,calculated seismic peak ground accelerations on both rock and soil surface for 2 630 engineering sites in Shandong Province have been collected in this paper. On the basis of these data,site amplification factor and site index for each site have been calculated. The site index is an integrated index to characterize the site condition and is computed from the shear wave velocity,density and thickness of the cover layers. Its values may change from 0 to 1. With the method of regression analysis,the relations among the site amplification factor,peak acceleration of bedrock and the site index are studied. A quantitative statistical relation between site amplification factor and other parameters is achieved. The site amplification factor in this paper is expressed as functions of peak acceleration of bedrock and site index,thus,its value may change continuously with the changing of the other parameters. The statistical relation for the site amplification factor in this paper is acquired on the basis of numerous,widely distributed data in Shandong Province,especially,site conditions can be represented in detail with site index. Therefore,the acquired statistical relation could characterize the changing scenarios of the site amplification factor with both the peak acceleration of the rock surface and the site condition details. The results show that the site amplification factor is negatively linearly related with the rock surface seismic peak ground acceleration and nonlinearly related with the site index.

提出了一种用于地震早期预警的S波震相实时自动识别方法.该方法不对原始信号进行任何滤波处理,直接对三分向记录进行计算分析.首先根据P波前0.5s数据的卓越频率计算适用于该三分向记录的窗长,采用由偏斜角和水平能量与总能量比值的平方积作为确定S波识别区间的特征函数,将特征函数已有数据的5倍均值和5倍方差之和作为识别区间的触发阈值;然后采用VAR AIC方法对两个水平分向识别区间的数据分别计算分析,对两个识别结果进行判断,最终确定S波初动时刻.经过对118个三分向记录的实际应用验证,通过自动识别结果与人机交互震相识别结果相比,本文方法对于S波相对P波尾波信噪比大于5 dB的地震记录,其识别误差小于0.1s的概率高达89.39％.

Based on the diagonal rule of two order determinant and three order determinant,the expansion law is summarized.Then the expansion method of four order determinant is provided by use of the graphical method.The computation of common four order determinant will be more practical.