地下爆炸炸点定位方法及布局精度分析

针对地下爆炸炸点定位中,缺乏具体指标完成不同算法及传感节点布局下定位精度的评估,难以定量分析各种方案及布局优劣程度以选出最佳方案。该文提出一种定位精度计算方法,利用到达时间差、到达角度及融合定位算法分别计算不同布局的定位精度,通过定位精度的准确度、稳定度等指标,完成经典布局在不同算法下的定位效果评估。仿真结果表明,所提出的精度计算方法评估体系可以有效反映出空间定位中垂直定位和水平定位精度分布对比,其中,融合算法能够有效改善其他算法在水平和垂直定位中的不足,在使用最优布局情况下,垂直定位精度可达1.5 m,水平定位精度可达0.2 m,在整体区域定位中稳定性最高。     

基于局部网络拓扑特征的鲁棒节点定位算法

针对无线传感器网络的较大测距误差严重影响定位算法精度和鲁棒性的问题,利用节点均匀部署网络的拓扑特征,提出了一种基于局部网络拓扑特征的鲁棒节点定位算法(LFLS算法).该算法通过构建节点测距高估粗差阈值参数和测距低估粗差阈值参数,在对未知节点1跳测距数据集进行粗差识别及剔除等预处理滤波的基础上,使用高斯加权最小二乘定位算法实现节点定位.仿真结果表明,基于局部网络拓扑特征的鲁棒节点定位算法的定位精度明显优于未采用局部网络拓扑特征进行粗差预处理的加权最小二乘定位算法,其中粗差测距直接相关节点的定位精度改进尤为明显.     

基于限定搜索高斯曲面拟合的星点质心提取算法

星点光斑图像目标识别技术对于空间监视装备和系统至关重要,由于星点图像中光斑成像的特点以及不同背景下图像噪声的干扰,目标光斑的自动识别和定位精度受限。高斯曲面拟合法与密度质心法是使用较为广泛的星点光斑目标定位算法,通过理论分析和实验表明传统方法对星点质心的定位存在一定误差。该文提出一种基于限定区域搜索的星点质心提取算法(LASACE),该算法首先通过中值滤波算法与最大熵阈值分割法对星点图像进行预处理,然后使用高斯曲面拟合算法获得星点光斑的像素分布。最后以星点中心建立目标搜索区域,采用距离强加权质心法提取出目标星点光斑的质心位置。实验结果表明,相较于密度质心法、高斯曲面拟合法和加权质心法,该文所提算法在降低星点光斑质心定位误差的同时提高了抗噪性,能够满足空间卫星的识别需求。     

基于Canny算子的椭圆拟合算法在数字相机标定中的应用

精确获取靶标在数字相机CCD靶面上成像中心的像点坐标是决定数字相机校准精度的主要因素之一。本文研究了靶标像中心定位精度对数字相机校准精度的影响,得出数字相机校准对靶标像中心定位精度的要求为优于0. 23像素。采用基于Canny算子的椭圆拟合定位算法,对不同尺寸的星点靶标板,在不同相机视场角分别进行了目标像定位,并对实验结果进行了分析,实验结果表明椭圆拟合算法定位精度达到了0. 05像素,满足数字相机校准的精度要求。     

调制度测量轮廓术高度信息获取新算法

理论分析表明,在正弦光栅成像面前后调制度分布是一种高斯分布,据此提出一种基于高斯曲线拟合的调制度测量轮廓术高度信息获取新算法：高斯曲线拟合法。该算法对调制度分布序列中极值位置附近的部分数据点利用高斯函数进行拟合,从获得的拟合曲线求出调制度极大值的真实位置,该位置对应的扫描距离即为对应点的高度信息。对同一测量数据利用三种高度算法分别计算高度,测量精度为：极值算法0．78mm、重心算法0．37mm和高斯曲线拟合算法0．22mm,表明高斯曲线拟合法可以获得更高的测量精度。     

基于矢量传感器的双基地声纳数据融合

提出了一种基于单矢量传感器的双基地声纳定位数据融合算法.阐述了矢量双基地声纳数据融合定位算法的基本原理与解决方案.与常规声压双基地T/R-R声纳系统相比,矢量双基地声纳系统拥有更为丰富的声场观测信息.较之传统声压型,基于时延定位的算法(TOL),此新算法可带来更高的定位精度.在近基线三角区域,定位精度提高约23%,而在基线定位盲区附近,定位精度提高近40%.此新算法同时还解决了TOL算法的定位二值模糊问题.     

基于高斯积分曲线拟合的亚像素边缘提取算法

针对传统边缘提取算法定位精度低、对噪声敏感等缺点,提出一种基于高斯积分曲线拟合的亚像素边缘提取算法。通过曲面插值求取像素级边缘法截线上各离散点的灰度值,再进行高斯积分曲线拟合,寻找高斯积分曲线的均值点坐标,实现亚像素边缘的精定位。用量块直线边缘进行实验,并与现有亚像素边缘提取算法比较,实验证明基于高斯积分曲线拟合的亚像素边缘提取算法定位精度较高,可以达到1 μm,且算法可靠性高、计算速度快,能够用于高精度测量。     

人工复眼成像三维定位系统设计

本文提出了一种简单、实用,基于人工复眼成像的三维定位系统,给出了人工复眼系统高精度定位机理,建立了人工复眼成像三维定位系统设计方法。系统采用平面阵列相机作为系统成像主体结构,每个子相机作为复眼的子眼,子眼以正四边形阵稀疏方式排布,采用平行光轴设计,构造出稳定可靠的光学结构,使计算结果更为精确。通过多重方向视差关系得出几何约束条件,采用多方向性、选择性立体匹配算法,建立计算模型,实现高精度定位。制备了1套子相机数目为9的原理样机,完成了三维定位测试实验,实验获得定位精度为2.53?10-4 rad。     

一种低计算复杂度的无线传感器网络分簇定位算法

针对已有的集中式定位算法定位精度低,而分布式定位算法计算复杂度高、通信量大的问题,提出了一种适用于无线传感器网络的计算复杂度低的节点分簇定位算法.首先,提出满足最大连通度的多边界节点分簇算法,采用此算法把网络划分为若干个簇,各簇分别进行簇内节点定位;其次,各簇进行融合,最终实现全网节点的定位.仿真结果表明,这种分簇定位算法比分布式定位算法计算复杂度低、通信量小、定位精度相当或略差,比集中式定位算法计算复杂度低、通信量小、定位精度高.采用该算法可以降低传感器网络节点定位过程中的能耗,提高计算效率,延长网络寿命.     

Catheter localization using C-arm with flat-panel

比较了影像增强器型C臂和平板C臂这两种C臂系统在空间定位上的优劣势,在此基础上设计了一种针对平板C臂的定位方法,该方法借助相机的针孔模型标定C臂系统成像模型,应用三角测量原理进行空间点的定位.利用自行设计的标定模板进行了单、双平板C臂的标定及立体定位试验.试验结果表明,双平板C臂的定位精度高于单平板C臂,两者定位的最大误差均小于1.25mm,平均误差小于0.62mm,均能满足临床应用需要.该方法具有原理简单、易实现的优点,由于成像原理的一致性,对不同厂家生产的平板C臂具有通用性.     

A high efficiency single molecule localisation algorithm with sub-pixel resolution based on fluorescence images

We introduce a technique of fast single molecule localisation including image de-noising and Gaussian mask sub-pixel refinement (IDGM) with the characteristics of simplicity, great computational efficiency as well as high accuracy and precision. The image de-noising corrects images suffering from background and shot noise, and the Gaussian mask is used to derive the centres of single molecules with sub-pixel resolution. We quantitatively evaluate the performance of IDGM compared to two-dimensional direct Gaussian fitting (2DDGF) on 1000 simulated images at variable signal-to-noise ratios (SNRs), where the single molecule diffraction spot is simulated as a point spread function distribution. It is shown that IDGM performs better than 2DDGF in terms of accuracy and precision for all tested SNRs. In addition, the execution time is shorted by one order of magnitude, making the IDGM algorithm suitable for localising single molecules especially for on-line or time-critical applications.     

Three-dimensional localization precision of the double-helix point spread function versus astigmatism and biplane

Wide-field microscopy with a double-helix point spread function (DH-PSF) provides three-dimensional (3D) position information beyond the optical diffraction limit. We compare the theoretical localization precision for an unbiased estimator of the DH-PSF to that for 3D localization by astigmatic and biplane imaging using Fisher information analysis including pixelation and varying levels of background. The DH-PSF results in almost constant localization precision in all three dimensions for a 2 μm thick depth of field while astigmatism and biplane improve the axial localization precision over smaller axial ranges. For high signal-to-background ratio, the DH-PSF on average achieves better localization precision.     

Multicolor far-field fluorescence nanoscopy through isolated detection of distinct molecular species

By combining the photoswitching and localization of individual fluorophores with spectroscopy on the single molecule level, we demonstrate simultaneous multicolor imaging with low crosstalk and down to 15 nm spatial resolution using only two detection color channels. The applicability of the method to biological specimens is demonstrated on mammalian cells. The combination of far-field fluorescence nanoscopy with the recording of a single switchable molecular species at a time opens up a new class of functional imaging techniques.     

Molecular orientation affects localization accuracy in superresolution far-field fluorescence microscopy

We investigate the cooperative effect of molecular tilt and defocus on fluorophore localization by centroid calculation in far-field superresolution microscopy based on stochastic single molecule switching. If tilt angle and defocus are unknown, the localization contains systematic errors up to about ±125 nm. When imaging rotation-impaired fluorophores of unknown random orientation, the average localization accuracy in three-dimensional samples is typically limited to about ±32 nm, restricting the attainable resolution accordingly.     

基于运动补偿的机械扫描式高频超声成像技术

由于高频相控阵超声成像系统和多阵元高频超声探头工艺复杂,成本较高、实现难度大,单阵元的机械扫描式高频超声成像探头因其结构简单、实现方便、成本低的特点仍具有较高的理论研究和实际应用价值。但目前机械扫描式成像系统的机械扫描的非均匀性是阻碍其性能进一步提升的主要问题,因此文章设计了一种高精度运动补偿的机械扫描式高频超声成像探头和系统,通过理论计算分析、运动系统结构设计加工、扫描成像系统搭建实现了高精度的扫描成像。最后,线靶和仿体的成像实验结果显示,经运动补偿后,系统能够有效克服传统机械扫描成像的伪影和失真,实现的横向几何位置精度误差为1.34%,纵向几何位置精度误差为1.33%,面积测量精度误差为3.15%,为高精度、高频超声成像算法和系统研究提供了一种有效的手段。     

Advancing Spectrally-Resolved Single Molecule Localization Microscopy with Deep Learning

Spectrally-resolved single molecule localization microscopy (srSMLM) is a recent technique enriching single molecule localization microscopy with the simultaneous recording of spectra of the single emitters. srSMLM resolution is limited by the number of photons collected per emitters. Sharing a photon budget to record the localization and the spectroscopic information results in a loss of spatial and spectral resolution—or forces the sacrifice of one at the expense of the other. Here, srUnet—a deep-learning Unet-based image processing routine trained to increase the spectral and spatial signals to compensate for the resolution loss inherent in additionally recording the spectral component is reported. Both localization and spectral precision are improved by srUnet—particularly for the low-emitting species. srUnet increases the fraction of localization whose signal can be both spatially and spectrally characterized. It preserves spectral shifts and the linearity of the dispersion of light. It strongly facilitates wavelength assignment in multicolor experiments. srUnet is a simple post-processing add-on boosting srSMLM performance close to conventional SMLM with the potential to turn srSMLM into the new standard for multicolor single molecule imaging.     

Fluorescence Anisotropy Reloaded—Emerging Polarization Microscopy Methods for Assessing Chromophores' Organization and Excitation Energy Transfer in Single Molecules,Particles, Films,and Beyond

Fluorescence polarization is widely used to assess the orientation/rotation of molecules, and the excitation energy transfer between closely located chromophores. Emerging since the 1990s, single molecule fluorescence spectroscopy and imaging stimulate the application of light polarization for studying molecular organization and energy transfer beyond ensemble averaging. Here, traditional fluorescence polarization and linear dichroism methods used for bulk samples are compared with techniques specially developed for, or inspired by, single molecule fluorescence spectroscopy. Techniques for assessing energy transfer in anisotropic samples, where the traditional fluorescence anisotropy framework is not readily applicable, are discussed in depth. It is shown that the concept of a polarization portrait and the single funnel approximation can lay the foundation for alternative energy transfer metrics. Examples ranging from fundamental studies of photoactive materials (conjugated polymers, light‐harvesting aggregates, and perovskite semiconductors) to Förster resonant energy transfer (FRET)‐based biomedical imaging are presented. Furthermore, novel uses of light polarization for super‐resolution optical imaging are mentioned as well as strategies for avoiding artifacts in polarization microscopy.     

3种亚像素位移测量算法的比较研究

梯度法、曲面拟合法和N-R法是数字散斑相关方法中提高位移测量精度的3种主要亚像素位移算法。研究了3种算法的原理并进行了数值模拟仿真。首先使用计算机模拟生成一系列位移为0.01 pixel的散斑图,并在生成的图像中添加方差不同的高斯噪声,对3种算法在噪声条件下的精度进行比较,结果显示在精度要求为0.01 pixel时,梯度法的噪声方差上限为0.006,N-R法的噪声方差上限为0.000 5,而曲面拟合法的计算精度具有较大不确定性,无法保证精度,梯度法更适用于工程应用。     

The double-helix microscope super-resolves extended biological structures by localizing single blinking molecules in three dimensions with nanoscale precision

The double-helix point spread function microscope encodes the axial (z) position information of single emitters in wide-field (x,y) images, thus enabling localization in three dimensions (3D) inside extended volumes. We experimentally determine the statistical localization precision σ of this approach using single emitters in a cell under typical background conditions, demonstrating σ?相似文献   

Single‐Molecule Manipulation in Zero‐Mode Waveguides

The mechanobiology of receptor–ligand interactions and force‐induced enzymatic turnover can be revealed by simultaneous measurements of force response and fluorescence. Investigations at physiologically relevant high labeled substrate concentrations require total internal reflection fluorescence microscopy or zero mode waveguides (ZMWs), which are difficult to combine with atomic force microscopy (AFM). A fully automatized workflow is established to manipulate single molecules inside ZMWs autonomously with noninvasive cantilever tip localization. A protein model system comprising a receptor–ligand pair of streptavidin blocked with a biotin‐tagged ligand is introduced. The ligand is pulled out of streptavidin by an AFM cantilever leaving the receptor vacant for reoccupation by freely diffusing fluorescently labeled biotin, which can be detected in single‐molecule fluorescence concurrently to study rebinding rates. This work illustrates the potential of the seamless fusion of these two powerful single‐molecule techniques.