Contribution of ionospheric TEC anomalies to detecting the seismic precursors related to the 2008 Oran-Algeria event

The ionospheric anomalies observed before any notable earthquake have become the subject of predictive research in the field of seismo-ionospheric coupling and/or Solid Earth-Atmosphere. In this paper, the concept of ionospheric modeling has been applied using total electronic content (TEC); derived from dual-frequency GPS recordings from about sixty permanent geodetic stations. The study and the analysis of the anomalous TEC variations, quantifiable on a regional scale, allowed us to detect the principal precursors of the M_w 5.5 earthquake that hit Oran on June 06th, 2008. The envisaged analytical approach is based principally on the time delays estimation relating to the seismic responses from the triggering (lithospheric seismic source) until their recording in data Rinex (GPS_IGS stations) through the reflection system of the electromagnetic waves on the ionospheric level (F2-layer).Indeed, in term of location, the longitude-latitude coordinates of the Oran event epicenter (0.658°W, 35.883°N) affecting the coastal margin of Western Algeria without too much material damage. Although the magnitude of this earthquake is qualified moderate (M_w 5.5, seismic intensity scale V-VI), one can observe apparent disturbances in the terrestrial electromagnetic spectrum associated with ionospheric TEC variations. In the domain of geodetic data analysis, we have noted a significant increase in the ionospheric TEC, which announces the arrival of a seismic precursor several days before the main studied event. Against this background, we emphasize that any seismic event, of significant magnitude, often carries information associated with other variants involved in the package of earthquake studied. Among these variants we evoke the effect of the magnetic field and the effect of the surrounding environment, etc. As for the specific behavior of the GPS_TEC signal, obtained from the Rinex data, and its interaction with the associated seismic activity, we highlight the existence of a spectral conformity between the geomagnetic field and that of the TEC content (spontaneous polarization of the TEC).Finally, we have just confirmed the effectiveness of this forecasting approach which relates the seismo-ionospheric precursors that are embedded in the physical trace of the electromagnetic signal relative to significant and/or moderate earthquakes (M ≥ 5); such as the envisaged case of the 2008 Oran event.     

基于 PCIE 的高速密码卡 PCB 设计与研究

为了实现更可靠的高速印刷电路板（PCB）设计，解决电磁兼容（EMC）、信号完整性和电源完整性等问题对系统带来的不利影响，从叠层及布局、电源设计、过孔设计、高速信号布线四个方面详细讨论了具有高速加解密功能的基于PCIE总线的高速密码卡印刷电路板的设计技术，并结合实际应用给出了具体实现办法和有关实例。实践表明：这些技术在高速印刷电路板的实际设计中可行有效。     

脉冲信号快沿计测中的问题

对周期性脉冲信号的频谱进行了简要分析。论述了脉冲信号快沿计测中的问题，讨论了用通用示波器计测脉冲信号时，被测信号的最高频率fM、前沿tr与示波器频带宽度人的关系图和计算公式，讨论了正确选用示波器探头及输入耦合方式．提出了脉冲信号快沿计测中应注意的几个问题。     

一种用于 ACAS 的相位校准方法

校准是用于 ACAS 发射机的一项关键技术,本文给出了一种新的基于比相的实时校准方法,去除了发射通道幅度对通道相位差的影响,介绍了该方法的原理,并在 FPGA 硬件平台上完成了该方法的仿真和验证,通过实测数据的分析与处理,证明了这种方法的可行性     

A novel LAAS pseudo-range error over-bound method based on improved pseudo-range error distribution model

The high level of safety demand of civil aviation requests local area augmentation system (LAAS) extremely high navigation integrity performance. A new LAAS pseudo-range error overbound method is proposed in this paper to improve the integrity of LAAS. Firstly, a more practical pseudo-range error distribution model is established. Then, by calculating the relationship between the statistical uncertainty of the model parameter and the integrity risk, a new method is proposed to calculate the pseudo-range error over-bound model. This method can effectively reduce the inflation factor and the resulting conservativeness of the over-bound model. Comparative experiments show that the method proposed in this paper performs better and satisfies the requirements of real applications.     

BP网络在信号检测中的应用

本文对ＢＰ网络在信号的检测和处理方面的性能进行了分析，对该网络在信号检测中的应用进行了讨论并给出了计算机仿真结果。     

旋转导弹单通道控制方法研究

通过分析旋转导弹的控制原理 ,从弹体舵面产生的周期等效控制力与导引头输出的误差信号之间的方位误差和幅值线性度两个方面 ,提出了一个最优的线性化信号与主控信号的频率比。建立了刚体弹道仿真软件 ,以某型防空导弹为背景进行了一系列的仿真计算。仿真结果表明 ,这一最佳频率比大大提高了导弹的制导精度 ,减小了脱靶量。     

科研成果统计系统的设计与实现

本文从需求分析、系统设计、系统实现详细阐述了学院科研统计系统的设计与实现过程,为了保证系统的松耦合和可维护性,采用了n层架构,为了使系统开发稳定、高效除使用成熟的程序开发框架和集成开发环境外,还使用了代码生成工具辅助开发。该系统的设计与实现不仅满足了学院的科研统计工作,还对类似的系统开发有一定的参考价值。     

PCM系统中数字相敏检波器的设计与仿真

在PCM（埋地管道电流测绘）系统中，实际的信号采集需要解决在非常恶劣的环境中对ELF（甚低频）信号的精确测量的问题。传统的方法一般都采用APSD（模拟相敏检波器）来实现，然而在实际的电路中用模拟相敏检波器效果并不是很理想，结果存在严重的误差。针对目前模拟相敏检波器存在的问题，设计一种DPSD（数字相敏检波器）实现消除PCM系统中ELF信号中工频干扰的目的。该检波器能有效的克服模拟相敏检波器的缺点，更精确的进行微弱信号的检测，最后使用MATLAB仿真软件对模拟和数字相敏检波器进行了仿真比较。     

一种改进的雷达低空目标仰角估计算法

由于地(海)面反射的多径镜像信号的存在,使雷达低空目标的仰角估计成了难题。而三子孔径算法是针对该难题而提出的一种有效算法。此算法基于极大似然算法将等距线阵均分为三个子孔径,从而简化了估计函数,也使计算量大大减少。本文在三子孔径算法的基础上,利用目标信号与镜像信号在入射角度上的正弦约束条件,给出了一种改进算法。计算机仿真结果显示改进算法在性能上要优于三子孔径算法。