Based on the digital waveform data recorded by Xinjiang Digital Seismic Network for the Xinyuan-Hejing M_L6.8 earthquake sequences of June 30,2012,this paper analyzes the stress drops of earthquake sequences and the c...Based on the digital waveform data recorded by Xinjiang Digital Seismic Network for the Xinyuan-Hejing M_L6.8 earthquake sequences of June 30,2012,this paper analyzes the stress drops of earthquake sequences and the correlation coefficients of focal mechanisms significant for strong aftershocks.Firstly,the source parameters of the Xinyuan-Hejing M_L6.8 earthquake sequences are obtained by applying the spectrum analysis and the Brunes source model.Then,the correlation coefficients of spectral amplitudes are calculated using the low-frequency spectral amplitude recorded by the same station for the different events.Finally,based on the results of the correlation coefficients of spectral amplitudes,the events with similar focal mechanisms are grouped using the clustering method.The results show that:(1)The stress drop values show a steady trend in the aftershock sequence calm period and the stress drop values show a rise-fall in strong aftershocks.(2)The moving average correlation coefficient of amplitude spectrum begins to spread after the main shock.It shows that the correlation decreases between the main shock and the aftershocks in mechanisms.(3)The results of focal mechanism groups show that the earthquake sequences are mainly strike slips.The stress distribution of the main pressure axis is nearly NS,which is the same as the structural stress field.(4)The magnitude and mechanism show that there is an agreement before the strong aftershock,which shows that the regional stress field is enhanced.展开更多
The so-called quasi-period of an ML-sequence has been introduced. It is noted that an ML-sequence may degenerate in the sense that it has the quasi-period shorter than its period, and the problem of constructing the n...The so-called quasi-period of an ML-sequence has been introduced. It is noted that an ML-sequence may degenerate in the sense that it has the quasi-period shorter than its period, and the problem of constructing the nondegenerative ML-sequences has been solved by giving a criterion for nondegenerative primitive polynomials.展开更多
针对目前欺骗式干扰源定位场景中定位精度低、信息利用率不足等问题,本文提出了一种基于导航信号特征的直接定位方法(DeSpreading Direct Position Determination,DS-DPD).通过建立融合传输时延、多普勒频移、扩频序列的接收信号模型,...针对目前欺骗式干扰源定位场景中定位精度低、信息利用率不足等问题,本文提出了一种基于导航信号特征的直接定位方法(DeSpreading Direct Position Determination,DS-DPD).通过建立融合传输时延、多普勒频移、扩频序列的接收信号模型,利用最大似然准则构建直接定位的目标函数,并通过求解目标函数得到待定位欺骗式干扰源的位置信息.仿真结果表明,DS-DPD能够有效提升对欺骗式干扰源的定位精度.尤其在低干噪比环境下,与传统的基于时延和多普勒信息的直接定位方法相比,所提方法的定位精度可提高10倍以上.展开更多
This article discusses the developing process of the version sequencesof specifications and the formal expressions of various reconstructions including theexpansion and revision of the version at each stage. The autho...This article discusses the developing process of the version sequencesof specifications and the formal expressions of various reconstructions including theexpansion and revision of the version at each stage. The author suggests using ECC(Extended Calculus of Construction) to describe the specifications of formal systemand using functional language ML to implement this developing process.展开更多
Prior to hardware implementation, simulation is an important step in the study of systems such as Direct Sequence Code Division Multiple Access (DS-CDMA). A useful technique is presented, allowing to model and simulat...Prior to hardware implementation, simulation is an important step in the study of systems such as Direct Sequence Code Division Multiple Access (DS-CDMA). A useful technique is presented, allowing to model and simulate Linear Feedback Shift Register (LFSR) for CDMA. It uses the Scilab package and its modeling tool for dynamical systems Xcos. PN-Generators are designed for the quadrature-phase modulation and the Gold Code Generator for Global Positioning System (GPS). This study gives a great flexibility in the conception of LFSR and the analysis of Maximum Length Sequences (MLS) used by spread spectrum systems. Interesting results have been obtained, which allow the verification of generated sequences and their exploitation by signal processing tools.展开更多
基金sponsored by the Earthquake Situation Tracking Program of 2014 (2014020110)the Science and Technological Fund of Earthquake Administration of Xinjiang Uygur Autonomous Region,China (201402)
文摘Based on the digital waveform data recorded by Xinjiang Digital Seismic Network for the Xinyuan-Hejing M_L6.8 earthquake sequences of June 30,2012,this paper analyzes the stress drops of earthquake sequences and the correlation coefficients of focal mechanisms significant for strong aftershocks.Firstly,the source parameters of the Xinyuan-Hejing M_L6.8 earthquake sequences are obtained by applying the spectrum analysis and the Brunes source model.Then,the correlation coefficients of spectral amplitudes are calculated using the low-frequency spectral amplitude recorded by the same station for the different events.Finally,based on the results of the correlation coefficients of spectral amplitudes,the events with similar focal mechanisms are grouped using the clustering method.The results show that:(1)The stress drop values show a steady trend in the aftershock sequence calm period and the stress drop values show a rise-fall in strong aftershocks.(2)The moving average correlation coefficient of amplitude spectrum begins to spread after the main shock.It shows that the correlation decreases between the main shock and the aftershocks in mechanisms.(3)The results of focal mechanism groups show that the earthquake sequences are mainly strike slips.The stress distribution of the main pressure axis is nearly NS,which is the same as the structural stress field.(4)The magnitude and mechanism show that there is an agreement before the strong aftershock,which shows that the regional stress field is enhanced.
文摘The so-called quasi-period of an ML-sequence has been introduced. It is noted that an ML-sequence may degenerate in the sense that it has the quasi-period shorter than its period, and the problem of constructing the nondegenerative ML-sequences has been solved by giving a criterion for nondegenerative primitive polynomials.
文摘针对目前欺骗式干扰源定位场景中定位精度低、信息利用率不足等问题,本文提出了一种基于导航信号特征的直接定位方法(DeSpreading Direct Position Determination,DS-DPD).通过建立融合传输时延、多普勒频移、扩频序列的接收信号模型,利用最大似然准则构建直接定位的目标函数,并通过求解目标函数得到待定位欺骗式干扰源的位置信息.仿真结果表明,DS-DPD能够有效提升对欺骗式干扰源的定位精度.尤其在低干噪比环境下,与传统的基于时延和多普勒信息的直接定位方法相比,所提方法的定位精度可提高10倍以上.
文摘This article discusses the developing process of the version sequencesof specifications and the formal expressions of various reconstructions including theexpansion and revision of the version at each stage. The author suggests using ECC(Extended Calculus of Construction) to describe the specifications of formal systemand using functional language ML to implement this developing process.
文摘Prior to hardware implementation, simulation is an important step in the study of systems such as Direct Sequence Code Division Multiple Access (DS-CDMA). A useful technique is presented, allowing to model and simulate Linear Feedback Shift Register (LFSR) for CDMA. It uses the Scilab package and its modeling tool for dynamical systems Xcos. PN-Generators are designed for the quadrature-phase modulation and the Gold Code Generator for Global Positioning System (GPS). This study gives a great flexibility in the conception of LFSR and the analysis of Maximum Length Sequences (MLS) used by spread spectrum systems. Interesting results have been obtained, which allow the verification of generated sequences and their exploitation by signal processing tools.
