一种基于CLEAN的SAR图像旁瓣抑制方法

把通常用于图像处理的CLEAN算法引入到SAR成像处理中,提出一种基于CLEAN 的SAR图像旁瓣抑制方法.分析算法流程,比较点目标仿真结果和RADARSAT-1海洋稀疏目标场景成像结果,表明该方法在保证成像分辨率的同时,能够有效地抑制合成孔径雷达图像的旁瓣.     

Micro-Doppler-based target detection and feature extraction in indoor and outdoor environments

In many cases, a target or a structure on a target may have micro-motions, such as vibrations or rotations. Micro-motions of structures on a target may introduce frequency modulation on the returned radar signal and generate sidebands on the Doppler frequency shift of the target's body. The modulation due to micro-motion is called the micro-Doppler (m-D) phenomenon. In this paper, we present an effective quadratic time-frequency S-method-based approach in conjunction with the Viterbi algorithm to extract m-D features. For target recognition applications, mainly those in military surveillance and reconnaissance operations, m-D features have to be extracted quickly so that they can be used for real-time target identification. The S-method is computationally simple, requiring only slight modifications to the existing Fourier transform-based algorithm. The effectiveness of the S-method in extracting m-D features is demonstrated through the application to indoor and outdoor experimental data sets such as rotating fan and human gait. The Viterbi algorithm for the instantaneous frequency estimation is used to enhance the weak human m-D features in relatively high noise environments. As such, this paper contributes additional experimental m-D data and analysis, which should help in developing a better picture of the human gait m-D research and its applications to indoor and outdoor imaging and automatic gait recognition systems.     

Characterization of wall dispersive and attenuative effects on UWB radar signals

This paper addresses the potentials of ultra-wideband (UWB) through-wall imaging radars compared with conventional narrowband systems. The challenges that limit the utilization of high precision UWB systems are examined with the aim of mitigating them. These challenges include multi-path, pulse dispersion, and antenna effects on the pulse shape due to angles of transmission and arrival. The propagation of UWB signals through walls is a crucial factor in determining the success of UWB radar technology. UWB signals, when propagating through walls, not only suffer attenuation but also distortion due to dispersive properties of the walls. This paper examines time- and frequency-domain techniques for measuring the electromagnetic properties of construction materials in the UWB frequency range. The measured parameters provide valuable insights in appreciating the capabilities and limitations of the UWB technology. Special attention is paid to time gating as a mean to extract the direct-path signal from the multi-path components. Both single-pass and multi-pass models are discussed. Multi-pass models account for the multiple reflections within the wall while the single-pass model assumes the possibility of gating out a single transmission. The partition-dependent narrowband propagation model is modified to account for the ultra-wide bandwidth of the signal. The paper illustrates the application of the modified model in indoor environments. The modified model is helpful in estimating the link power budget. It is also useful in studying the performance of UWB systems for indoor communication and positioning applications.     

Vega环境中视点模型的改进

本文针对目前Vega环境中观察者视点定位方法进行了分析,对当前国内外有关Vega环境中自定义视点问题进行了总结。在分析Vega中观察者观察场景原理的基础上,提出了一种全角度视点模型,并对该模型算法进行了系统研究。最后,通过仿真实验,总结了该算法的优势所在。     

基于仿射变换的双波段红外图像配准算法研究

图像配准是图像融合技术中的首要环节,只有经过配准的图像才能够进行融合。虽然双波段红外探测器探测的是同一场景,但是由于光学系统的构造产生了两幅图像,而两幅图像之间却存在了几何位置上的差异,所以在本文中提出一种配准方法。通过点检测方法获取图像的特征点,然后再选取其中两组较为明显的特征点组,再根据仿射变换关系式,确定其中的模型参数,并且对图像进行配准。     

基于OSG的三维实时场景模拟系统的研究

以雷达目标信息的三维实时显示为背景,文章在OSG框架下研究了三维实时场景模拟的关键技术,包括三维场景的组织和管理、实时显示与更新、交互漫游以及三维地形的生成。结合MFC实现了三维实时场景模拟系统,应用于雷达目标信息的三维显示领域,效果良好,在未来信息战争环境下有着重要的应用价值。     

基于机器学习SAR图像噪声抑制技术研究

为提高含噪声SAR（合成孔径雷达）图像的目标识别能力,提出基于机器学习的图像噪声抑制技术的研究思路。该思路通过问题估计,为舍噪声图像获得清晰的输出景物,从而生成一个与含噪声图像相符合的增强的合成景物世界。该技术以马尔可夫网络为体系,根据图像与景物、景物与景物之间的联系来确定网络上的信息传递规则,从大量的训练事例中学习并获得网络参数,利用贝叶斯方法为原图像找到理想的后验概率,生成一个清晰的超分辨率结果图。     

烘焙技术在X3D虚拟场景的应用研究

针对X3D虚拟场景的真实程度,从显示效果和文件大小角度研究烘焙技术在X3D虚拟场景中的应用,提出了在X3D虚拟场景中应用烘焙技术的操作方法,结合室内模型的地板烘焙实例阐述在建模、烘焙和导出X3D虚拟场景阶段的操作要点,验证了方法的可行性和有效性。     

基于BBU＋RRU的西江航道典型场景无线覆盖解决方案

针对西江航道典型覆盖场景进行了分析和研究,提出了基于BBU＋RRU（室内基带单元＋远端射频单元）的航道应用场景组网方式,并重点分析了航道场景的站址选择、设备和天线选型及相关的配套解决方案。     

基于专利视角的区域知识结构测度方法研究

技术知识的积累与构成对区域创新和产业发展有着重要影响,掌握区域知识结构,有利于进一步挖掘区域知识能力,寻求不同知识基础间的桥梁,激发形成新产业。本文提出在ISI-OST-INPI技术分类基础上结合ALP-DM和DG方法生成适合中国专利数据库的IPC-产业技术对照表,对区域专利数据进行分类处理,利用自然对数雷达图和百分占比雷达图,从量能和势能两个角度可视化展示一个区域知识结构的测度方法。基于此方法采集我国33个省市近五年的发明申请类专利数据,分析结果表明两种雷达图能有效展示区域知识结构,且基于产业技术的知识结构划分能有效地将技术知识构成与区域产业经济政策相关联。     

浅谈王维诗歌中的禅意表达

王维作为现代广泛认可的“诗佛”,他的诗作所蕴含的禅意和禅趣历来为评论家们所称道。这种禅意在王维诗歌中的整体表达是一种“空寂”的意境,也契合了禅宗对于“空”的追求。而这种物我两忘、心灵与自然无间的意境在诗歌中的具体表达,则是通过多个特定意象的选取展现出来,并且情景相互融合,使得诗歌的表达更加浑然天成,给人发自内心的美的享受。     

超宽带穿墙雷达非相关成像方法

超宽带穿墙成像雷达作为一种能够隔墙探测和定位的新型雷达系统，在很多领域得到应用。穿墙成像雷达有非相干方法和相干方法两种成像方法。本文采用一发二收的天线组合形式，用非相关成像方法，研究了在无墙体和有墙体两种情况下目标的定位，分析了雷达的方位向分辨率,并通过二维FDTD仿真验证了目标定位方法。     

一种车载雷达的结构总体设计

本文介绍了一种车载雷达的结构总体设计。该雷达采用了转台翻转机构和方舱一体化设计,减少了车辆的改装要求,降低了雷达的制造成本和使用成本。同时还具有多种工作方式,增强了该雷达的阵地适应性。利用液压作为翻转机构的动力来源,结构简单,工作可靠且易维护;同时该雷达还具有良好的人机工程设计和可维性设计。     

Semisupervised SAR image change detection based on a siamese variational autoencoder

In synthetic aperture radar (SAR) image change detection, the deep learning has attracted increasingly more attention because the difference images (DIs) of traditional unsupervised technology are vulnerable to speckle noise. However, most of the existing deep networks do not constrain the distributional characteristics of the hidden space, which may affect the feature representation performance. This paper proposes a variational autoencoder (VAE) network with the siamese structure to detect changes in SAR images. The VAE encodes the input as a probability distribution in the hidden space to obtain regular hidden layer features with a good representation ability. Furthermore, subnetworks with the same parameters and structure can extract the spatial consistency features of the original image, which is conducive to the subsequent classification. The proposed method includes three main steps. First, the training samples are selected based on the false labels generated by a clustering algorithm. Then, we train the proposed model with the semisupervised learning strategy, including unsupervised feature learning and supervised network fine-tuning. Finally, input the original data instead of the DIs in the trained network to obtain the change detection results. The experimental results on four real SAR datasets show the effectiveness and robustness of the proposed method.     

非洲内罗毕城市变化的遥感监测与驱动因子分析

作为肯尼亚的首都,内罗毕是非洲发展最快的城市之一.本文研究了内罗毕市1988年-2010年城市建成区空间扩展情况.利用1988年Landsat TM、2000年Landsat ETM+以及2010年Landsat TM数据,采用主成分分析与混合分类的方法,提取了1988年-2000年、2000年-2010年、1988年-2010年内罗毕土地覆盖空间变化数据,并分析了城市用地面积扩展的驱动因素.分析结果表明,内罗毕从1988年到2010年总共扩展了141.24km2,扩展面积为1988年城市建成区面积的1.27倍,其中1988年到2000年扩展了60.03km2,2000年到2010年扩展了81.21km2.城市建成区所侵占的地类主要是荒草地和林地,城市建成区的扩展方向是以东西方向为主,并沿着主要交通路线的方向扩展.人口和经济快速增长、便利的交通、地质地形、政府政策是内罗毕城市扩展的驱动因素.     

Using surface plasmon resonance imaging to study bacterial biofilms

This paper describes the use of Surface Plasmon Resonance imaging (SPRi) as an emerging technique to study bacterial physiology in real-time without labels. The overwhelming majority of bacteria on earth exist in large multicellular communities known as biofilms. Biofilms are especially problematic because they facilitate the survival of pathogens, leading to chronic and recurring infections as well as costly industrial complications. Monitoring biofilm accumulation and removal is therefore critical in these and other applications. SPRi uniquely provides label-free, high-resolution images of biomass coverage on large channel surfaces up to 1 cm² in real time, which allow quantitative assessment of biofilm dynamics. The rapid imaging capabilities of this technique are particularly relevant for multicellular bacterial studies, as these cells can swim several body lengths per second and divide multiple times per hour. We present here the first application of SPRi to image Escherichia coli and Pseudomonas aeruginosa cells moving, attaching, and forming biofilms across a large surface. This is also the first time that biofilm removal has been visualized with SPRi, which has important implications for monitoring the biofouling and regeneration of fluidic systems. Initial images of the removal process show that the biofilm releases from the surface as a wave along the direction of the fluid flow.     

敦煌莫高窟室内外空气质量的初步研究

选择2006年4月30日至5月10日，结合“五一”长假前后参观游客数量的变化，对莫高窟室内外总悬浮颗粒物（TSP）和污染气体进行了为期两周的加强连续观测，获得了莫高窟室内外大气环境污染的初步数据。在观测期内，室外、非开放窟[320窟]和开放洞窟[257窟]大气TSP的日平均质量浓度分别为1138.4 μg m-3、228.5 μg m-3和286.4 μg m-3。TSP中水溶性离子分析表明，Ca2+、SO42-、Na+和Cl-是水溶性无机离子的主要组分，且室外水溶性离子浓度高于窟内水平，长假前后水溶性组分浓度有明显变化。碳气溶胶分析显示，开放洞窟相对于室外和非开放窟具有较高的碳气溶胶的浓度水平。获得了研究区NH3和气态HNO3的浓度水平。游客数量对TSP质量浓度，水溶性离子浓度，碳气溶胶浓度和污染气体均有显著影响，旅游高峰期污染物质浓度显著增高。     

基于光场渲染的动态3D目标重构技术

提出了一种基于光场渲染的动态3D目标重构的方法.目前基于图像建模的方法对于复杂场景难以建模,而基于图像渲染的方法因数据量大不利于动态场景的实时渲染.因此采用了模型和图像相结合的方法,从多视点视频图像中重建动态3D模型,采用光场映射算法对重建的3D模型进行光场采样,然后对样本分解压缩.实验结果表明,在保证真实感的同时,减少了数据量,并可实现动态3D目标的重构.     

基于GSM的远程室内移动监控系统设计

本系统基于GSM（Global System for Mobile Communication）移动通信网络,采用STM32作为现场监测和控制核心的一种远程监控系统。图像采集端搭载在一辆智能小车上,通过控制小车移动,就可以完成室内全方位的图像采集,并通过彩信（MMS, Multimedia Message Service）的方式将图片发送给用户,起到了监控防盗的作用。     

Through-wall radar imaging using UWB noise waveforms

This paper examines the results of our research on the use of ultrawideband noise waveforms for imaging objects behind walls. The advantages of using thermally generated noise as a probing signal are introduced. The technique of heterodyne correlation used to inject coherence in the random noise probing signal and to collapse the wideband reflected signal into a single frequency are presented. Central to successful imaging through building walls is the characterization of the wideband propagation properties of wall materials and these are discussed. The basic concepts of synthetic aperture radar image formation using noise waveforms and the unique problems associated with the random nature of the transmit waveform are analyzed. We also address issues related to locating, detection, and tracking humans behind walls, using new tools for human activity characterization, namely the Hilbert-Huang Transform approach. The results indicate that noise radar technology combined with modern signal processing approaches is indeed a viable technique for covert high-resolution imaging of obscured stationary and moving targets.