基于恒定束宽波束输出的宽带相干源高分辨测向

本文给出了基于恒定束宽波束输出的宽带相干源分辨测向方法。计算机仿真表明本方法在降低运算量的同时,得到了优于相干信号子空间方法的方位估计性能。     

Correlated imaging with partially coherent light for remote sensing

Based on the extended Huygens–Fresnel integral and the theory of coherence of light field, we have investigated the correlated imaging by using the transverse normalized second-order intensity fluctuation correlation function with partially coherent light radiation. The imaging for a reflected object with relative long distance is determined by the feature of speckle-to-speckle correlation. By using the correlation function, we study the effects of imaging distance, the sizes of object lens and reference lens, the source’s transverse coherent width and its transverse size on the quality of correlated imaging. Numerical results show that the parameters of imaging system and the properties of partially coherent light source have significant influences on the imaging resolution and visibility. For an object lens with large enough diameter, the resolution is determined by the transverse coherent width of light source. On the contrary, it depends on the aperture of object lens. The magnification of the system depends only on the propagation distance. This speckle-to-speckle correlated imaging with unbalanced arms have potential applications in remote sensing due to its unique features.     

机载激光荧光雷达激光参数与飞行参数之关系

讨论了机载激光荧光遥感监测系统的空间分辨率及探测速度与搭载飞机扫描装置及束有关参数之间的关系,导出了相应的数学表达式。结果表明,增大激光脉冲重复率可以在不影响系统其他性能的情况下有效提高其空间辨率、而对多数参数的选取则位综合考虑它们对系统不同特性的影响。     

Spatial resolution implications of digitizing aerial photography for environmental applications

Abstract

Accuracy, flexibility and cost effectiveness are advantages of using digitized aerial photographs as a data source for remote sensing studies of the environment, such as forests. However, the relationship between the resolution of digital images and the aerial photographs from which they were derived must be addressed to ensure valid application using the environmental data. This communication considers issues that affect the information content of environmental data through the spatial resolution of photographs and digitized images, and suggests how users can optimize the spatial resolution of the latter by selecting an appropriate scanning aperture. An optimal scanning aperture can be chosen by considering the combination of the resolving power of the camera system, the scale of the original photograph and the desired pixel size of the digital image. Optimizing spatial resolution while scanning will maximize the spatial information obtained from the original photographs without generating unnecessarily large file sizes. The authors make several recommendations for the digitization of aerial photographs for environmental applications, such as analyses of forests.     

High resolution electron microscopy of long range ordered alloys

In this paper a survey is given of the application of high resolution electron microscopy and selected area electron diffraction to the study of long range ordered alloys. The characteristic features of the diffraction effects and of the imaging of ordered alloys are discussed. Group theoretical considerations allow prediction of microtexture of such alloys. A number of simple alloy structures are imaged and it is shown, by means of simulated images, that under suitable diffraction conditions the columns of minority atoms are represented as bright dots. The columns of majority atoms are only visible at very small thicknesses. Subsequently a number of one- and two-dimensional long period superstructures derived from these simple structures are analysed, using high resolution micrographs. Finally the observed microtexture of the same alloy superstructures is compared with the predictions of group theory. Strongly non-conservative antiphase boundaries are found to dissociate inapb’s which are as close to conservative as is compatible with thefcc lattice.     

基于统计特征的水下目标一维距离像识别方法研究

目标探测与识别是水下预警监视、信息对抗的重要组成部分。针对水下目标一维距离像识别问题,通过提取目标的长度、重心、高阶中心矩等特征,分析了所提取特征的统计分布特性,利用假设检验构建了目标识别特征的统计模型。结合Bayes统计分类器开展了5类水下目标的识别实验,并与基于距离像回波匹配相关的识别方法进行对比分析,对比结果显示所提出的方法在识别率和运算量方面均有明显改善。     

印刷版正确晒版范围的实验与研究

在测试获得印刷版分辨率的基础上,讨论了印刷版的正确晒版范围和曝光宽容度的分析过程与方法,并对3种类型的PS版进行了实测和分析,给出了它们的正确晒版范围和曝光宽容度.     

提高脉冲LD测距系统测距能力的一种方法

从激光测距机的噪声构成分析入手,寻求提高脉冲 LD 测距机测距能力的方法。脉冲 LD测距系统的噪声主要包括热噪声、散粒噪声、背景噪声、暗电流噪声及放大器噪声。在一定的光功率、暗电流情况下,LD 测距的测距能力更容易受背景噪声的影响。研究表明,LD 测距系统中探测器偏压的变化只补偿温度变化,由此提出,在背景光照射较强时让背景噪声参与偏压调整从而抑制背景噪声的方案。实验结果证实,强背景下的信噪比提高 1 倍以上,测距能力提高 1 倍。     

应用模糊逻辑理论提高B型超声图像分辨力方法的探讨

本文介绍了利用模糊逻辑控制理论提高Ｂ型超声图像横向分辨力的方法,文章中介绍了变孔径技术,电子聚焦时原理及动态实时聚焦。     

一种基于MSR的中等斜视多子阵合成孔径声呐距离多普勒算法

针对现有斜视多子阵合成孔径声呐成像算法忽略了"非停走停"假设的孔径依赖性和阵元依赖性,导致中等斜视时成像效果差的问题,提出了一种基于级数反演方法(Method of Series Reversion, MSR)的中等斜视多子阵合成孔径声呐距离多普勒算法(Range Doppler Algorithm, RDA)。首先,为了解决"非停走停"假设孔径依赖的问题,直接对精确距离史在波束中心处进行泰勒级数展开,得到近似距离史,并借用MSR求得近似距离史对应窄带回波信号的二维谱解析解。然后,为了解决阵元依赖的问题,使用基于MSR的RDA分别对每个子阵单独成像,再通过将每个子阵的成像结果进行相干叠加的方式消除单个子阵欠采样带来的混叠现象,得到完整的成像结果。最后,通过与现有算法的仿真对比实验,验证了该算法的有效性。     

基于ScSPM-Reranking的高分辨率遥感影像的检索

为了从高分辨率遥感影像中获取详细的地表地物信息,为城市规划、环境监测以及灾情分析提供可靠的数据,进行了高分辨率遥感影像的检索研究,包括对图像的特征提取和图像之间相似度的描述。为了提高图像检索精度,运用了采用稀疏编码(Sc)的空间塔式匹配(Sc SPM)技术和重排序(Reranking)技术,提出了基于Sc SPM结合Reranking(ScSPM-Reranking)的遥感高分辨率影像的检索方法。该方法首先使用Sc SPM提取空间场景的特征,然后结合这些特征使用cityblock距离进行初步检索,最后对初步检索的结果进行Reranking排序,获得高精度的检索结果。同其他检索方法进行了对比实验,实验结果证明,该方法具有较高的检索精度。     

静止轨道高分辨率光学遥感探索

为了实现地球静止轨道高分辨率光学遥感,研究了在运载的动力学环境上与低轨的差异。分析了主动飞行段时间长、力学环境差、在成像方法上采用面阵成像、轨道高等原因使相机体积增大的问题。对静止轨道21.5m分辨率模拟相机进行了研究,开展了动力学模拟试验,得到了相机关键部位的测试参数,证明了地球静止轨道高分辨率光学遥感的核心环节即有效载荷研制的可行性。     

基于ART网络的无指导中文共指消解方法

提出了一种基于自适应谐振理论(ART)网络的无指导中文名词短语共指消解方法.该方法充分利用名词短语自身特征,通过改变网络参数动态调节聚类数量,有效地解决了目前聚类共指消解中输出类别数目难以确定的难题.另外采用了一种基于信息增益率的特征选择方法,减少了区分度较弱特征给聚类所带来的干扰.该方法在保证了识别正确率的前提下,不依赖人工标注语料,可直接应用于跨领域的真实文本.最后在ACE中文语料上进行了相关实验,并取得了较好的结果.     

大尺度二维直线度测量仪的研制

研制出一种新的基于离轴成像技术的远距离、大范围二维直线度测量仪。仪器的直线基准为整形的十字线激光光束,光电二维位置敏感元件采用互相正交的线阵CCD,所设计的带有狭缝的离轴光学系统,避开激光十字线光束的能量中心,以使线阵CCD输出信号不会出现饱和现像,从而扩大了测量距离,保证了测量精度。该仪器能在0-20m测量范围连续测量二维直线度,其直线度可达0-70mm,精度优于0.1mm。实际的多次室外环境测量表明,该仪器可适应不同天气环境下的野外作业。     

DFQM - an approach for improving the quality of assembled products

In this paper we introduce first the concept of quality manufacturability (QM), and second a new methodology that focuses exclusively on evaluating a design from a quality perspective. We label this new approach as Design for Quality Manufacturability (or DFQM). The QM of a design is defined as the likelihood that defects will occur during its manufacture. Some designs are more likely than others to have a lower production yield rate. The reason for this is that in any production facility there is an inherent defect occurrence process. This relationship between the defect occurrence process and the design is the basis for QM. DFQM enables product designers to evaluate and improve the QM of a design before prototype production. The key elements of DFQM are classes of defects, specific defects, influencing factors, factor variables, and error catalyst. A standard nomenclature for describing the specific defects and measuring the associated influencing factors is presented. The output of the DFQM method is the QM-Index matrix, which indicates the quality manufacturability of each part in the assembly, in terms of each class of defects. The concept of error catalysts and the derivation of the QM-Index matrix are presented. An illustrative example is included. The DFQM method is presently limited to assembly processes.     

航空遥感器定位误差分析

首先简要介绍了航空遥感器的重要用途。然后依次介绍了成像坐标变换过程、定位原理,从而得到目标位置的计算公式,接着归纳了定位误差的影响因素,并完成了定位误差的推导,最后根据公式分析了各因素的影响程度。     

A device to measure the effects of strong magnetic fields on the image resolution of PET scanners

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. As these systems approach sub-millimeter resolutions, the range of the positron is becoming the dominant contribution to image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as and , which are gaining importance in small animal studies, the width of the annihilation point distribution dominates the spatial resolution. This positron range effect can be reduced by embedding the field of view of the PET scanner in a strong magnetic field. In order to confirm this effect experimentally, we developed a high resolution PET instrument based on silicon pad detectors that can operate in a 7 T magnetic field. In this paper, we describe the instrument and present initial results of a study of the effects of magnetic fields up to 7 T on PET image resolution for and point sources.     

激光多普勒测速仪标定系统不确定度研究的自动测量设计

文章讨论激光多普勒测速仪标定系统不确定度研究中的自动测量原理与实现方法 ,给出了实现自动测量的设计思想和程序框图 .实验表明该程序设计是有效的 ,它可极大地提高系统不确定度研究的效率     

一种采用两个相干累加器提高自适应谱线增强器性能的方法

水声信道通常是一种时变的强噪声信道，频带狭窄且各种信号的频谱相互重叠，采用传统的滤波器或自适应谱线增强器（ALE）检测CW信号的效果不佳。本文提出了一种采用两个相干累加器进行ⅡR跟踪滤波的ALE，具有较好的窄带滤波性能，提高了在低信噪比的水声环境下对CW信号的检测能力；该算法还具有运算简单，易于用硬件实现的优点，文中给出了计算机模拟结果。