基于MFCC和SVM的震动识别方法

针对在复杂的野外环境中识别人员移动的产生的震动信号时高虚警率高误报率的问题,首先对野外环境下采集的震动信号进行小波降噪,降低环境噪声对目标识别的干扰;然后通过MFCC对震动目标信号进行特征提取,最后将提取到的特征合成特征向量并输入到设计的支持向量机中对信号进行分类识别,通过采集野外环境下的人车震动信号对方案进行实验验证。实验表明,方案有很好的鲁棒性。

An automatic seismic signal detection method based on fourth-order statistics and applications

Real-time, automatic, and accurate determination of seismic signals is critical for rapid earthquake reporting and early warning. In this study, we present a correction trigger function（CTF） for automatically detecting regional seismic events and a fourth-order statistics algorithm with the Akaike information criterion（AIC） for determining the direct wave phase, based on the differences, or changes, in energy, frequency, and amplitude of the direct P- or S-waves signal and noise. Simulations suggest for that the proposed fourth-order statistics result in high resolution even for weak signal and noise variations at different amplitude, frequency, and polarization characteristics. To improve the precision of establishing the S-waves onset, first a specific segment of P-wave seismograms is selected and the polarization characteristics of the data are obtained. Second, the S-wave seismograms that contained the specific segment of P-wave seismograms are analyzed by S-wave polarization filtering. Finally, the S-wave phase onset times are estimated. The proposed algorithm was used to analyze regional earthquake data from the Shandong Seismic Network. The results suggest that compared with conventional methods, the proposed algorithm greatly decreased false and missed earthquake triggers, and improved the detection precision of direct P- and S-wave phases.

支持向量机在舶航程智能终端节能降耗中的应用

三维传感器有激活阈值参数,达到该参数时,可触发采集加速度数据;船舶的运行状态与三维加速度有密切联系;支持向量机是一种监督分类方法,学习三维加速度对应的船舶状态,再通过支持向量机学习参数,识别船舶的运动状态以及修正三维传感器激活阈值,可以达到记录运动轨迹的目的,减少不必要的GPS、北斗定位,实现系统的节能降耗及航程记录。

dentification of blasting vibration and coal-roc fracturing microseismic signals

A new method based on variational mode decomposition （VMD） is proposed to distinguish between coal-rock fracturing and blasting vibration microseismic signals. First, the signals are decomposed to obtain the variational mode components, which are ranked by frequency in descending order. Second, each mode component is extracted to form the eigenvector of the energy of the original signal and calculate the center of gravity coefficient of the energy distribution plane. Finally, the coal-rock fracturing and blasting vibration signals are classified using a decision tree stump. Experimental results suggest that VMD can effectively separate the signal components into coal-rock fracturing and blasting vibration signals based on frequency. The contrast in the energy distribution center coefficient after the dimension reduction of the energy distribution eigenvector accurately identifies the two types of microseismic signals. The method is verified by comparing it to EMD and wavelet packet decomposition.

Analysis of Ship Refuge Action in Tsunami Using AIS Data： Case of the 2011 East Japan Earthquake and Tsunami

A massive earthquake occurred in the Tohoku and Kanto regions of Japan on the 1 lth of March 2011. In response, a tsunami alert, a tsunami warning and an advisory were issued for the entire Pacific coast region. This research investigates the evacuation behavior of ships by AIS （automatic identification system） data in Onahama port after the tsunami warning was issued. The unusual behavior observed was attributed to the emergency evacuation of ships. This research investigates the evacuation behaviors of the vessels using the data obtained from AIS, around the Onahama Port during alerting the major tsunami warning. The result shows that most vessels in the port started evacuating approximately 10 min after the major tsunami warning and completed offshore evacuation 40 min after this warning. This contributed in understanding the actual status of the vessel evacuation. In addition, the travel paths of each vessel revealed the influence of the tsunami on the vessels. Furthermore, the exceptional situation where several vessels moved in the same direction at the speed almost same for about 2 hours was confirmed. As a result, it can be estimated that the waves that affected both vessels were the drawback of the tsunamis.

A Review on Research of Foreshocks

This paper briefly introduces the current research progress in the field of foreshocks,both in China and abroad,and contrasts the common characteristics and the mechanisms of foreshocks of the sequence under the definition of different conditions of foreshocks. The main recognition methods of foreshocks are briefly reviewed,and their characteristics and existing problems are reviewed and discussed. Foreshocks are small earthquakes that occur before the mainshock and adjacent to the main source location. A foreshock sequence is constituted of a series of foreshock activities that occur before the mainshock. The proportion of earthquake cases includes direct foreshocks ranging from 10% - 40% at different defined conditions of foreshocks. Theoretically,cascade model or pre-slid model can explain foreshocks. Foreshocks are mainly concentrated in the range of 10km -75 km of the mainshock,but their time distribution form is very complicated,mostly prior to the mainshock from 1 or 2 days,the seismicity rate of part of foreshock sequences shows significant acceleration features,but many foreshock sequences often show the attenuation characteristics of mainshock-aftershock sequences. The most prominent feature of foreshocks is a focal consistent mechanism and low b-value of earthquakes of the earthquake sequence. Foreshocks seems to have a certain relationship with tectonic environment and the rupture form of the mainshock,in limited foreshocks earthquake cases,the dip-thrusting earthquakes seem to have relatively more foreshocks. The results of some of the earthquake cases show that the focal depth of foreshocks gradually moved downward with the mainshock approaching. So far,it is difficult to determine whether an earthquake or an earthquake sequence is a foreshock or foreshock sequence before the mainshock. The identification methods of foreshocks mainly include a statistical method of analogy,focal consistent mechanism and related derivative method,the fine detection of the earthquake nucleation process. From a few existing studies of earthquake cases,in spite of earthquake temporal clusters and focal consistent mechanism being the most significant features of foreshock sequence,there were not sufficient conditions for judging a foreshock sequence. Because the rupture rate of expansion and sliding displacement have a tendency to increase faster with time,the method of fine detection of the earthquake nucleation process is expected to play a more important role in the identification of foreshocks,but it needs more earthquake examples to be verified.

An Application of Damage Detection Methods to A Real World Structure Subjected to Ground Motion Excitation

This paper aims at investigating the efficacy of different state-of-art damage detection methods when applied to real worm structures subjected to ground motion excitations, for which the literature contributions are, at present, still not fully comprehensive. To this purpose the paper analyses two test structures： （1） a four-story scaled steel frame tested on a shake table in a controlled laboratory conditions, and （2） a seven-story reinforced concrete building monitored during the seismic excitations of the 1999 Chi-Chi （Taiwan） Earthquake main shock and numerous fore and afiershocks. Some model based damage approaches and statistics based damage indexes are reviewed. The different methodologies and indexes are, then, applied to the two test structures with the final aim of analysing their performance and validity within the case of a laboratory scaled model and a real world structure subjected to input ground motion.

Identification of flexible buildings with bending deformation and the unmeasured earthquake ground motion

It is important to explore efficient algorithms for the identification of both structural parameters and unmeasured earthquake ground motion.Recently,the authors proposed an algorithm for the identification of shear-type buildings and unknown earthquake excitation.In this paper,it is extended to the investigation of the identification of flexible buildings with bending deformation and the unmeasured earthquake ground motion.In the absolute co-ordinate system,the unmeasured ground motion can be treated as an unknown translational force and a bending moment at the 1st floor level of a flexible building.Structural unknown parameters above the 1st story of the building can be identified by the extended Kalman estimator and the 1st story stiffness and the unmeasured ground motion are subsequently estimated based on the least-squares estimation.The proposed algorithm is further extended to the identification of tall bending-type buildings based on substructure approach.Inter-connection effect between sub-buildings is treated as‘additional unknown inputs’to sub-buildings,which are estimated by the extended Kalman estimator without the measurements of rotational responses.Numerical examples demonstrate the identification of a multi-story,tall bending-type building and its unmeasured earthquake ground motions using only partial measurements of structural absolute responses.