车辆视频检测感兴趣区域确定算法

利用最大方差阈值方法对灰度图像二值化后,对车辆底部阴影突变行检测,对感兴趣区域确定方法进行改进,实现了感兴趣区域的精确确定.通过计算精确确定后的感兴趣区域的灰度对称性和熵值归一化对称性测度,实现了车辆的精确检测,找到车辆的对称轴,并在车辆区域上边界一定范围内,进行灰度突变检测,实现了车辆上边界的准确定位.通过实验验证算法较好地实现了复杂环境下的车辆检测和上边界定位.     

一种新的SIFT匹配定位技术研究

在基于局部特征点匹配的目标定位系统中,匹配点和误匹配点数量的多少直接影响定位准确度。传统SIFT方法为保证匹配过程中有足够的匹配点数,通常选取较小的统计区域,特征点缺失了对周边区域的关联性,造成误匹配。为提高定位准确度,提出一种改进的SIFT特征描述子。在传统的SIFT局部特征描述子中引入PCA统计特征,在获得更高的正确匹配率的同时降低了错误匹配率。针对常用的SIFT误匹配滤除算法（NN法）滤除误匹配时需牺牲大量正确匹配,提出在NN法基础上,利用匹配特征点的坐标信息对误匹配进行二次滤除,进一步减少了误匹配。实验结果表明,定位算法的准确度优于传统方法。     

无线传感器网络三维自身定位方法

针对部署在三维空间的无线传感器网络,提出了一种传感器节点自身定位方法APIT-3D(Approximate Point-In-Tetrahedron),通过判断传感器节点是否位于由锚节点组成的四面体的内部,筛选出可能的位置区域,并最终计算这些区域交集部分的重心,作为待定位节点的位置.仿真实验表明,作为一种不基于测量设备的定位方法,APIT-3D可以达到节点通信半径的40%以下的较高精度的三维定位,而且通信开销相比于二维定位方法增幅不明显.APIT-3D定位方法无需复杂的测距设备和昂贵的外部设施,且通信协议相对简单,因此是一种低成本、低功耗的无线传感器网络三维自身定位方法.      

伪卫星增强的北斗双星定位系统及其算法的研究

提出了使用伪卫星来增强北斗系统的方案,并研究了此系统的定位原理和几何布局。仿真结果表明,此方案是可行的,能够独立实现实时、高精度的无源定位,为发展区域定位系统提供了一种成本相对较低的新思路。     

基于小波的非线性模型的孔探图像压缩

针对涡轮发动机内部图像细节丰富的特点,为了实现在高压缩比下对细节信息的保留,以不影响发动机内部故障检测,采用小波域的非线性表示和建模方法,利用多尺度边缘检测对边缘进行定位,通过轮廓加剖面模型在定位的边缘进行边缘影响区域划分;之后通过阈值将边缘影响区域进一步划分为较重影响系数区域与较轻影响系数区域,在不同区域应用不同的编码质量控制,从而实现了一种基于小波着重于边缘的图像编码系统.实验结果表明,与一般的小波图像压缩方法相比较,在不同的压缩率下,峰值信噪比均得到小幅度的提高,并且从视觉感官上也得到较好的效果.      

基于边缘与颜色信息的车牌精确定位算法

针对现有车牌定位算法定位率不高和速度慢等问题,结合数学形态学,提出了一种基于车牌边缘检测与颜色信息的精确定位算法.首先对图像进行灰度化、平滑去噪及灰度拉伸等预处理,然后对图像进行垂直边缘检测和二值化处理;再采用线过滤算法滤去干扰边缘线信息,并利用车牌区域灰度变化次数多的特性定位出车牌上下边缘;对经过上下边缘定位后的车牌采用点密度过滤算法滤去零散点,接着采用数学形态学方法寻找连通域粗定位出车牌区域;最后对粗定位车牌在HSV空间进行颜色分割和倾斜矫正,从而精确定位出车牌.实验结果表明,该算法能够实现车牌的快速精确定位.      

空舰导弹纯方位攻击目标指示优化方法

纯方位攻击是中远程空舰导弹适应复杂电磁环境下作战的有效途径,但由于目标距离信息缺失,其目标指示和火控解算问题难以解决.在分析机载传感器方位角量化误差的基础上,提出了基于机载传感器方位角速度测量的目标参数优化估计方法,对优化前后的误差进行了分析和对比;从机载无源雷达和全向告警器两个途径分析了所提出优化方法的定位精度分布情况.仿真结果表明:该方法的定位误差受目标方位与机载传感器量化误差的共同影响,存在误差发散区域.在此基础上,提出纯方位攻击条件下载机机动优化的策略是对目标定位误差发散区域进行规避,并尽可能远离该区域.     

空舰导弹纯方位攻击目标指示优化方法

纯方位攻击是中远程空舰导弹适应复杂电磁环境下作战的有效途径,但由于目标距离信息缺失,其目标指示和火控解算问题难以解决.在分析机载传感器方位角量化误差的基础上,提出了基于机载传感器方位角速度测量的目标参数优化估计方法,对优化前后的误差进行了分析和对比；从机载无源雷达和全向告警器两个途径分析了所提出优化方法的定位精度分布情况.仿真结果表明:该方法的定位误差受目标方位与机载传感器量化误差的共同影响,存在误差发散区域.在此基础上,提出纯方位攻击条件下载机机动优化的策略是对目标定位误差发散区域进行规避,并尽可能远离该区域.     

基于顶点与主体区域同步检测的精准车牌定位

为应对非约束环境下的车牌精定位问题,提出一种基于顶点局部区域与主体区域同步检测策略的非约束性车牌定位算法。通过删减YOLOv5网络的输出结构,训练得到可同步检测车牌及顶点区域的车牌检测网络,在兼顾精度与计算速度的前提下,实现车牌顶点和主体区域的同步定位。针对一幅图中存在多个车牌区域及顶点区域存在少量漏检和误检的情况,分别设计了车牌顶点归类和单一缺失顶点预测后处理算法,借助顶点间的空间位置关系进行漏检目标预测和误检目标排查,有效改善了因场景复杂导致的个别顶点目标检测效果差的问题。所提算法在中国城市停车场数据集(CCPD)上的测试结果显示,平均精准率达99.25%,平均召回率达98.70%。所提算法不仅能够准确预测出车牌的4个顶点坐标,而且在中端GPU硬件平台上处理速度可达121帧/s,具有较好的应用价值。     

基于CNN的多尺寸航拍图像定位方法的研究与实现

图像定位常用于无人机视觉导航,传统的无人机视觉导航广泛采用景象匹配导航方式,随着计算机技术的不断发展,深度学习技术为视觉导航的实现提供了新途径。以无人机的垂直侦查为背景,将飞行区域的航拍图像划分成大小相同的若干网格,每个网格代表一类区域,用网格图像制作数据集训练卷积神经网络（CNN）。基于AlexNet设计了一种融合显著性特征的全卷积网络模型,有效实现了一个基于CNN的多尺寸输入的滑动窗口分类器,并提出了一种邻域显著性参照定位策略来筛选分类结果,从而实现多尺寸航拍图像的定位。      

Controlling factors of Region 2 field-aligned current and its relationship to the ring current: Model results

One essential component of magnetosphere and ionosphere coupling is the closure of the ring current through Region 2 field-aligned current (FAC). Using the Comprehensive Ring Current Model (CRCM), which includes magnetosphere and ionosphere coupling by solving the kinetic equation of ring current particles and the closure of the electric currents between the two regions, we have investigated the effects of high latitude potential, ionospheric conductivity, plasma sheet density and different magnetic field models on the development of Region 2 field-aligned currents, and the relationship between R2 FACs and the ring current. It is shown that an increase in high latitude potential, ionospheric conductivity or plasma sheet density generally results in an increase in Region 2 FACs’ intensity, but R2 FACs display different local time and latitudinal distributions for changes in each parameter due to the different mechanisms involved. Our simulation results show that the magnetic field configuration of the inner magnetosphere is also an important factor in the development of Region 2 field-aligned current. More numerical experiments and observational results are needed in further our understanding of the complex relationship of the two current systems.     

Winter cross polar cap current estimation

Digital ionosonde and magnetometer observations from a polar cap station are used to estimate the fraction of Region 1 current that flows across the polar cap. For a winter case study using data for 2001 Feb 18 the cross-cap current was 3.9 × 10⁴ A Pedersen current and 6 × 10⁴ A Hall current. This total current is only a small percentage, ∼5%, of the Region 1 current.     

Current carriers for the field-aligned current system

Recently the Dynamics Explorer satellites have returned a large body of data containing high resolution magnetometer measurements and distributions of charged particles of all but thermal electrons. From these data a systematic study has begun of the relations of the field-aligned currents to particle precipitation structures and the identification of the charge carriers. The data have been separated into three levels of magnetic activity and three local time sectors. Results of this study include the following:1. During very quiet periods, field-aligned currents exist primarily as fine structure.2. During onset of substorms, Region 1 and Region 2 become clearly evident but contain significant structure.3. As magnetic activity subsides, current regions become less distinct, and structure becomes more dominant.4. The distribution of the upward currents derived from magnetometer data and calculated from suprathermal electron data agree remarkably well in shape but not necessarily in magnitude.5. At all local times, >5 eV electrons seldom carry most of the upward current.6. Except for the accelerated Inverted-V electrons, the dominant upward current carriers which are measured are below 500 eV and are distributed in energy.7. Dusk upward currents (Region 1) are associated with the Boundary Plasma Sheet (BPS).8. Suprathermal electron bursts are important current carrying structures.     

Morphology of high latitude auroral electron precipitations obtained by the Aureol-3 satellite

Latitudinal distribution of auroral electron precipitations was studied using the Aureol-3 satellite data. Analysis of 148 events in the morning, night, and evening sectors showed that structures of all types have a wide MLT distribution. However, during low geomagnetic activity the distribution of latitudinally asymmetric events is close to Iijima and Potemra's Region 1 and 2 current picture: the equatorward events prevail in the morning and postmidnight sectors, and the polarward ones — in the evening and premidnight. An increase in geomagnetic activity makes the MLT distribution of different types of events more uniform. This fact may indicate existence of the multi-layer structure of currents and consequently medium scale electric fields, in which the maximum currents considerably exceed the average values observed in the Region 1 and 2.     

Remote sensing of the ring current using energetic neutral atoms

Energetic neutral atom (ENA) images of the storm-time ring current obtained from the ISEE-1 spacecraft provide information for a “zero-order” global model of the energetic ion distribution. With the assumption of isotropic pressure and magnetostatic, non-convective pressure balance, the global system of electrical currents driven by the ion pressure can be calculated using Euler potentials for the divergenceless current density. Radial pressure gradients drive azimuthal currents, and azimuthal pressure gradients drive radial currents. The radial currents cause current lines in the inner magnetosphere to close in the ionosphere, forming a “partial” ring current. The intensities and locations of these field-aligned currents driven into and out of the ionosphere resemble those of the observed Region 2 current system, but not all observed properties of the Region 2 system are reproduced by the “zero-order” model.     

基于定性模型的故障诊断方法

基于定性模型的故障诊断方法，利用定性模型描述系统结构和定性地预测系统行为，并通过与实际行为进行比较，可推理得到系统的故障诊断结果。详细介绍了基于定性模型故障诊断方法的诊断机理、建模方式及优缺点。此外，还概述了该方法的研究与应用现状及发展趋势。     

基于SDO/HMI全日面实时磁图的活动区自动识别

太阳活动区是太阳活动的主要发生源区,活动区的形态、结构、特征是预报太阳爆发的主要依据.因此,活动区的识别是实现太阳爆发预报的前提.SDO/HMI能够提供连续、高时空精度的全日面光球观测图像.参照文献[1]SOHO/MDI综合磁图中活动区的自动识别方法,利用实时可得的HMI全日面磁图,通过阈值法、数学形态法和区域增长法相...     

基于Cluster观测的磁尾场向电流在南北半球投影位置的分布

利用Cluster四颗卫星的磁场探测数据计算磁尾场向电流并投影到极区电离层,研究其投影位置在南北半球的分布规律,统计过程中去除了强磁暴（磁暴主相Dst<–100 nT）期间的场向电流事件。结果显示:磁尾场向电流事件在极区投影位置的纬度分布具有明显的南北半球不对称性,北半球为单峰结构,南半球为双峰结构。在北半球投影到较低纬度（<64°）的场向电流事件数目明显多于南半球,并且所能达到的最低纬度更低;在南半球投影到较高纬度（>74°）的场向电流事件数目明显多于北半球,并且所能达到的最高纬度更高。地磁平静条件下（|AL|<100 nT）,磁尾场向电流密度随磁地方时（MLT）呈递增趋势,这一结果与低高度卫星在极区对I区场向电流的探测结果符合很好。研究结果表明,磁尾场向电流投影位置的纬度分布呈现出明显的南北不对称性,这与南北半球磁尾场向电流的空间分布以及磁层中磁场结构具有密切关系。      

亚大地区F2电离层预测方法和CCIR方法的比较

本文将“国际参考电离层”所采用的CCIR频率预测方法和亚大地区F_2电离层预测方法预测的f_0F_2和M(3000)F_2,分别与第21太阳活动周的我国实测数据进行了比较。结果表明,从总体上看,在中国区域内亚大地区F_2电离层预测方法优于CCIR方法。文章建议,在没有更好方法的情况下,未来的“中国参考电离层”可以采用亚大地区F_2电离层预测方法。     

The solar wind control of the equatorial ionosphere dynamics during geomagnetic storms

The interplanetary magnetic field, geomagnetic variations, virtual ionosphere height h′F, and the critical frequency foF2 data during the geomagnetic storms are studied to demonstrate relationships between these phenomena. We study 5-min ionospheric variations using the first Western Pacific Ionosphere Campaign (1998–1999) observations, 5-min interplanetary magnetic field (IMF) and 5-min auroral electrojets data during a moderate geomagnetic storm. These data allowed us to demonstrate that the auroral and the equatorial ionospheric phenomena are developed practically simultaneously. Hourly average of the ionospheric foF2 and h′F variations at near equatorial stations during a similar storm show the same behavior. We suppose this is due to interaction between electric fields of the auroral and the equatorial ionosphere during geomagnetic storms. It is shown that the low-latitude ionosphere dynamics during these moderate storms was defined by the southward direction of the B_z-component of the interplanetary magnetic field. A southward IMF produces the Region I and Region II field-aligned currents (FAC) and polar electrojet current systems. We assume that the short-term ionospheric variations during geomagnetic storms can be explained mainly by the electric field of the FAC. The electric fields of the field-aligned currents can penetrate throughout the mid-latitude ionosphere to the equator and may serve as a coupling agent between the auroral and the equatorial ionosphere.