Application of autocorrelation method on ionospheric short-term forecasting in China

IONOSPHERIC MOTIONS AND VARIATIONS ARE AFFECTED BY THE SOLAR WIND AND THE MAGNETOSPHERE FROM THE UPPER AND THE MESOSPHERE FROM THE LOWER. APART FROM DIURNAL, SEASONAL AND SOLAR CYCLE VARIATIONS, THE IONOSPHERE EX- PERIENCES AN OBVIOUS DAY-TO-DAY VARIATION…     

一类具有较好自相关性质的密码函数

通过级联一类特殊的二次函数和线性函数，构造出具有较好自相关性质的平衡布尔函数，同时这类函数还具有较高的非线性度和较高的代数次数．     

基于短波段电离层探测数据分析地下核爆引起的电离层扰动

同GNSS（全球导航卫星系统,Global Navigation Satellite System）获取电离层TEC（总电子含量,Total Electron Content）数据相比,传统的电离层垂测、斜测等短波段数据具有特征参数丰富、高度分辨率高、历史数据多等优点。为利用电离层垂测和斜测数据,研究地下核爆引起的电离层扰动。本文利用2016年1月6日朝鲜地下核试验当天的斜测、垂测数据分析电离层扰动现象。结果表明,本次地下核爆造成的行波电离层扰动为小尺度电离层扰动,传播速度在150.3-158.7(m·s-1)之间。同时核爆发生后半小时在距离爆点421.4 km处,观测到foF2较月中值增加了0.7 MHz,较1月5日、1月7日在2:00 UTC（协调世界时,Coordinated Universal Time)的foF2（F2层临界频率,critical frequency of the F2 layer）增加了0.5 MHz,极有可能是地下核爆通过岩石圈-大气圈-电离层圈耦合机制造成电离层电子浓度增加。本文分析结果与其他文献资料非常吻合。由此可见,基于短波段电离层探测方式感知电离层扰动从而实现地下核爆炸事件的监测,是一种有效的核爆电离层效应监测手段,可与其他直接监测手段相印证,提高核爆事件监测能力。     

Adaptive Radio Frequency Interference Mitigation for HF Surface Wave Radar

The paper analyses the characteristics of radio frequency interference （RFI） in HF surface wave radar （HFSWR） which adopts the linear frequency modulated interrupted continuous wave （FMICW）. RFI will influence all the range cells including all the positive frequency and negative frequency, and the negative frequency range cells contain only the interference information. Based on the above characteristics, we introduce and analyze a new adaptive interference mitigation beamforming algorithm using the negative frequency range cells samples to estimate the interference covariance matrix. Experimental results confirm that this general and robust algorithm can achieve effective RFI suppression using the data recorded by the HFSWR, located near Zhoushan in Zhejiang China.     

昆嵛山腮扁叶蜂幼虫空间自相关研究

运用全局Moran’s Ⅰ和局部Moran’s Ⅰ方法对昆嵛山腮扁叶蜂幼虫空间分布的自相关性进行了研究。结果表明：昆嵛山腮扁叶蜂幼虫在样地的分布具有一定的空间自相关性,但未达到显著的程度,没有形成特定的空间分布格局;局部空间自相关分析结果显示也没有局部空间聚集现象。由于样地环境比较单一,因此只考虑昆嵛山腮扁叶蜂易感林木的空间自相关对昆嵛山腮扁叶蜂空间自相关的影响。用相关性分析昆嵛山腮扁叶蜂全局Moran’s Ⅰ值和易感林木全局Moran’s Ⅰ值的相关性可知,昆嵛山腮扁叶蜂全局空间自相关性受易感林木全局空间自相关性显著影响。     

便携式高频地波雷达双频接收天线的设计与实现

现有高频地波雷达大多采用单一工作频率,较易受外部干扰影响,且回波包含信息有限。设计与实现了一种便携式高频地波雷达双频接收天线,通过对原有单频接收天线电路进行修改,增加频率控制端和开关电路,实现了三元交叉环/单极子接收天线同时双频工作的功能。室内测试及现场实验结果均验证了该双频接收天线的有效性。     

基于分时双频的高频地波雷达海面目标探测

提出了一种分时双频方法用以提高其目标探测性能.分析了分时双频雷达波形,针对分时双频探测引起的目标相干积累时间减少以及多普勒谱点不对齐等问题,利用非均匀傅里叶变换将其转换为一不适定问题,并利用Cauchy-Gaussian模型正则化方法进行外推处理,从而获得目标多普勒谱图.仿真结果表明该方法能够有效地消除海面移动目标的检测盲区,提高检测性能.     

Estimation of the Direction of Arrival Using Virtual Matrix Method for HF Ground Wave Radar

According to the characteristic of the echo of highfrequency ground wave radar（HF GWR）, which is one-dimensional narrow band signal, a virtual direction of arrival（DOA） matrix is constructed at first, then the DOA of target evaluation is achieved by the method of resolving equations for two-dimensional DOA matrix. And this method bases on the redundancy information of a linear two-row array of antennae. Both the simulation process and the treatment results of measured data （in the case of low SNR echoes and short data series） are given at the end of this paper. By comparing with GPS data of the targets, the validity and practical applicability of the method in this paper is verified.     

The adaptive long-distance HF broadcasting system based on backscatter technique

We put forth a project, that is: using the backscatter technique to realize adaptive long-distance HF broadcasting system in order to improve the quality of HF broadcasting. Then, we analyze errors of the system due to the deviation of the ionospheric parameters' prediction. From the analysis, we draw the conclusion that our project is feasible. In addition, we point out that we can use frequency-spreading and information-coding technique to acquire more clear ionograms. We also offer a judgment on how to choose the control propagation mode on condition of multihop and the existence of more than one propagation mode on the signals' path. Supported by the National Natural Science Foundation of China (No. 6927008) Guang Rongsheng: born 1938, Professor     

Application of ESPRIT in Broad Beam HF Ground Wave Radar Sea Surface Current Mapping

HF surface wave radar system OSMAR2000 is a broad-beam sea-state detecting radar.ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique) algorithm is proposed to apply in DOA (direction of arrival) determination of sea echoes.The algorithm of ESPRIT is briefly introduced first.Then discussions are made on the technique for application in the OSMAR2000 framework.Numerical simulation results are presented to demonstrate the feasibility of radial current mapping based on this method.The algorithm manifests significant performance and computational advantages compared with that of MUSIC.Data acquired by OSMAR2000 are processed to give radial current map and the synthesized vector currents are compared with the in-situ measurement with traditional means.The results show the validity of ESPRIT application in DOA determination for broad-beam radar.     

基于空间自相关的江苏省县域新型城镇化水平分析

从经济质量、基础设施、人民生活、公共服务、景观环境5个方面选取30个指标,构建出新型城镇化综合评价指标体系,运用熵值法定量评价2010年江苏省县域新型城镇化发展的综合水平,并结合GeoDA软件,运用空间自相关分析江苏省县域新型城镇化发展的总体相关性和各县市之间的空间相关性．结果表明,江苏省县域新型城镇化发展水平：1）整体上存在明显的南北差异,即苏南高于苏中,苏中高于苏北,其中苏南在5个方面均处于领先地位,而苏中在公共服务、景观环境方面相对较弱,苏北则在经济质量、基础设施、人民生活方面相对较弱;2）在空间分布上存在着相似区域之间的空间集聚特征,但仍有少部分县市的新型城镇化发展存在异质性．     

基于自相关函数相位的频率估计方法方差分析

为了分析基于自相关函数相位频率估计方法的性能,推导了加性高斯白噪声背景中正弦信号观测数据的相关函数相位噪声的表示式,得到了相位噪声方差的计算公式和基于自相关函数相位的频率估计方差的计算公式,给出了此类频率估计方法的估计方差与信噪比、观测数据长度以及对相关函数相位差进行平滑时利用的相关函数的点数关系.仿真结果与该文给出的公式计算结果吻合很好.     

三值自相关二进序列偶的构造方法研究

利用2阶分圆以及直积方法构造出几类几乎差集偶,通过几乎差集偶与三值自相关二进序列偶的等价关系,进而构造出几类新的三值自相关二进序列偶,为三值自相关二进序列偶的直接构造提供了新的数学方法.     

一种基于自相关估计的水声直扩信号检测方法

利用直接序列扩频信号的自相关特性,提出了一种直扩信号相关峰累积检测方法.理论上分析了直扩信号的自相关特性,可知在伪码周期整数倍处可能会出现峰值,利用这些相关峰及其倍数关系可以对直扩信号进行判别.但由于信元信号与噪声的影响,这一系列相关峰并非连续稳定出现.在低载噪比时,一些自相关峰淹没在噪声中,直接对其检测比较困难.利用相关峰出现的周期关系,设计了相关峰累积检测器.该检测器不仅可以实现自动检验,而且可适用于低载噪比情况,具有实际应用价值.计算机仿真结果和海试数据都验证了该方法的可行性与实用性.     

高频地波雷达电离层距离方程建模及仿真

针对电离层的空间分布特征,构建了体目标和面目标的雷达距离方程.根据不规则体对高频电波的相干散射原理,估算了电离层RCS的散射系数,进而给出基于电离层物理机制的广义高频地波雷达方程,从而量化了电离层特征参数对高频雷达系统的影响.通过仿真发现,对于面散射情形,斜向散射电离层杂波符合波束限制模型,垂直向的电离层杂波符合脉冲限...     

基于空气质量指数AQI的空间自相关特征分析——以福建省为例

以福建省9个地级市为研究对象，运用时间序列模型、全局空间自相关分析、K-medoids聚类及相关分析等研究方法，探索福建省各地级市空气质量指数的空间自相关特征。研究结果显示，相比秋冬两季，各地级市春夏两季的空气质量相关性较低，具体表现为，春夏两季各地级市莫兰指数（Moran's I）显著较低 。以空气质量指数AQI的6个空气质量分指标作为聚类标准进行研究，发现福建省地级市的空气相关性区分为两大类。进一步对AQI进行相关性分析，发现AQI与PM10、PM2.5、NO2分指标高度相关，由此说明，空气微粒与NO2是福建空气污染的主要来源。空气质量季节上的分布差异，可以为政府准确地制定治理方案提供有力证据。     

A study on ionospheric HF channel with bitemporal response and scattering function

At first the bitemporal response method is introduced to solve the scattering function of the ionospeeric channel. We can get the scattering function, as a function, of the group path time delay and Doppler frequency. Thus Doppler effect resulting from the continuous movement of the ionosphere is analyzed to study the characteristics of the various ionospheric irregularities and diturbance. many possible problems and correction are researched lastly. Foundation item: Supported by the National Natural Science Foundation of China (69571020) and the Research Fund for the Doctoral Program of Higher Education (RFDP1999048602) Biography: Chong Yan-wen(1972-), male, Ph. D. candidate, research direction: ionospheric modeling and inversion.