基于可见光与红外图像特征融合的目标跟踪

针对单一图像源下目标跟踪精度不高的问题,利用跟踪状态下的目标存在于可见光与红外图像中的特征对连续自适应均值移动跟踪算法做出改进。首先选取可见光图像的“颜色梯度背投影”作为改进的目标模型,选取红外图像的“灰度梯度背投影”作为改进的目标模型;然后根据可见光序列图像和红外序列图像各自进行连续自适应均值移动跟踪算法得到的对应的qi系数判定两种图像跟踪的效果,对两种图像的权重进行自适应调整,得到这两种图像的特征级融合图像和跟踪结果。实验结果表明,对于320像素×240像素的可见光和红外图像,基于可见光与红外图像特征融合的目标跟踪算法在复杂背景下能够较准确的跟踪目标,目标跟踪精度为0.5像素,跟踪速度为30~32 ms/帧。     

基于结构低秩编码的复杂环境红外弱小目标检测算法

针对复杂环境红外弱小目标检测难的问题,依据背景慢变特性,提出了一种将背景优化和低秩表达相结合的结构低秩编码小目标检测算法。首先,利用梯度0l范数约束提取背景中梯度较大的成分,保留灰度快变结构,同时平滑慢变结构,对背景进行优化;其次,使用核函数刻画背景图像块之间的低秩特性,用秩描述背景的主要结构并进行建模;最后,分解得到的误差矩阵具有稀疏性,主要包含快变的小目标结构,通过稀疏矩阵1,2l范数定位红外弱小目标。实验结果表明,结构低秩编码检测算法能够有效发掘复杂背景图像块之间的关系,抑制杂波干扰,在虚警为2时,最低检测率为92%。提高了复杂环境下红外弱小目标的检测性能,基本能满足实际应用要求。     

联合行稀疏与l_(1/2)-范数稀疏表示的红外小目标检测算法

针对红外图像的小目标检测问题,提出了一种联合行稀疏与l_(1/2)-范数稀疏表示的小目标检测算法。首先采用滑动窗口对原始红外图像进行分块,构建分块图像矩阵;然后,根据稀疏与低秩表示理论建立行稀疏与l_(1/2)-范数稀疏表示的模型,并利用交替方向乘子算法求解得到稀疏矩阵和低秩矩阵;最后,通过图像重构,得到小目标的图像,并采用阈值分割的方法确定小目标的真实位置。实验结果表明,算法可以实现对不同背景红外图像中的小目标准确检测,与红外块图像建模算法相比,检测后的图像信杂比接近的情况下,检测速度提升了约1倍。     

基于非线性光流方程的高阶时域DIC算法

针对极端测试环境中采集的低质量测试图像,提出一种解析高精度变形场的高阶时域DIC(Digital Image Correlation)算法.采用模拟散斑方法建立了含高斯白噪声的亚像素级位移图像,通过最小二乘迭代法求解高阶时域DIC算法的位移量,分析了算法的测试精度.研究结果表明,非线性光流方程能够描述变形前后像素点灰度...     

基于局部幅值统计的海杂波背景下小目标检测

针对传统舰载雷达和岸基雷达很难检测出海杂波背景下小目标的现状,提出一种基于局部回波幅值统计的方法来检测海杂波背景下小目标。该算法基于数学统计思想：计算不同距离单元海杂波的幅值的最大值和标准偏差,发现距离单元含有小目标回波的最大幅值明显小于其它距离单元只含有海杂波回波的最大幅值,距离单元含有小目标回波的幅值的标准偏差明显大于距离单元只含有海杂波回波的幅值的标准偏差,因此可以在对小目标没有任何先验知识条件较准确地检测出海杂波背景下的小目标。实验证明,该算法是有效的。     

基于Kalman预测器的改进的CAMShift目标跟踪

CAMShift目标跟踪算法遇到目标被遮挡时容易陷入局部最大值,对快速运动目标容易跟踪失败,且无法从失败中复原。针对该问题,利用Kalman预测器改进CAMShift算法。首先利用Kalman预测器预测下帧图像中目标的位置,以此位置为中心确定CAMShift算法进行目标跟踪的搜索区域;然后利用目标匹配时的Bhattacharyya系数及目标大小来判断目标是否被遮挡以及被遮挡的程度。如果没有被遮挡,则用CAMShift算法得到的目标位置更新Kalman预测器中参数;如果遮挡不严重,则用Kalman预测器的预测值作为目标的位置和大小,且用该组值更新Kalman预测器中参数;如果遮挡非常严重,则用Kalman预测器的预测值作为目标当前位置,目标大小为固定值,用该组值更新Kalman预测器中参数。实验结果表明,改进算法能够准确地跟踪被遮挡目标和快速运动目标。     

Markowitz投资组合模型改进的三帧差分法运动目标检测

移动机器人的目标检测要求其对特定的静止或运动物体进行运动分析及检测。以Voyager-III移动机器人系统为研究对象,实现非理想光照下,对橘红色目标足球的运动检测。提出在传统三帧差分法基础上,先利用Markowitz投资组合模型进行足球目标的特征提取,将场地非感兴趣的目标中,出现全部像素值发生变化的目标去除,再进行图像帧间差分。利用CCD摄像机对比赛环境中足球的运动轨迹进行录制,选取具有代表性的各帧视频图像、Markowitz算法优化后的差分图像和跟踪图像,结果表明跟踪图像不含非目标物的干扰,克服了差分图像存在空洞的问题,为移动机器人提供了一种实用的运动目标检测方法。     

一种改进的高浓度风沙图像的动态灰度阈值分割算法

风沙跃移是塑造干旱区地貌的最主要的动力,其伴生的粉尘的释放、输送和沉降不但严重地影响了大气环境质量,也引起了全球气候 系统和海洋系统的变化. 单个沙粒轨迹形成是理解粒--床碰撞过程和风沙两相流耦合过程的重要纽带. 高浓度风沙图像处理算法是深入理解沙粒轨迹形成机制的关键技术. 为了实现对高浓度风沙图像精细处理, 本文提出了不依赖于经验参数的动态灰度阈值分割算法,它包括背景模板去噪、绿光通道灰度化处理、图像微分、灰度方差阈值目标检测和 最大类间方差灰度阈值分割等,其中背景模板去噪和灰度方差阈值目标检测等是新算法的主要亮点. 高浓度风沙图像分割实验显示, 扣减背景模板去除了条纹状和斑点状的稳定噪声;图像微分和灰度方差阈值目标检测显著地提高了暗沙粒识别的数量并有效地去除了随机噪声; 改进算法的沙粒有效识别个数(人 机判读坐标一致的沙粒数目)、查全率(计算机提取沙粒数目与人工判读的实际沙粒数比值)和查准率(有效沙粒数目与实际沙粒数目的比值) 分别为461, 71%和86%,显著地高于传统算法对应的85, 13%和82%,这表明新算法对高浓度风沙图像的分割效果良好. 避免单粒子分割和表观重叠问题是进一步完善高浓度风沙图像的分割算法的可能途径.      

一种改进的高浓度风沙图像的动态灰度阈值分割算法

风沙跃移是塑造干旱区地貌的最主要的动力,其伴生的粉尘的释放、输送和沉降不但严重地影响了大气环境质量,也引起了全球气候系统和海洋系统的变化.单个沙粒轨迹形成是理解粒-床碰撞过程和风沙两相流耦合过程的重要纽带.高浓度风沙图像处理算法是深入理解沙粒轨迹形成机制的关键技术.为了实现对高浓度风沙图像精细处理,本文提出了不依赖于经验参数的动态灰度阈值分割算法,它包括背景模板去噪、绿光通道灰度化处理、图像微分、灰度方差阈值目标检测和最大类间方差灰度阈值分割等,其中背景模板去噪和灰度方差阈值目标检测等是新算法的主要亮点.高浓度风沙图像分割实验显示,扣减背景模板去除了条纹状和斑点状的稳定噪声;图像微分和灰度方差阈值目标检测显著地提高了暗沙粒识别的数量并有效地去除了随机噪声;改进算法的沙粒有效识别个数(人机判读坐标一致的沙粒数目)、查全率(计算机提取沙粒数目与人工判读的实际沙粒数比值)和查准率(有效沙粒数目与实际沙粒数目的比值)分别为461,71%和86%,显著地高于传统算法对应的85,13%和82%,这表明新算法对高浓度风沙图像的分割效果良好.避免单粒子分割和表观重叠问题是进一步完善高浓度风沙图像的分割算法的可能途径.     

基于深度卷积神经网络的SAR图像舰船小目标检测

针对合成孔径雷达(SAR)图像舰船目标背景复杂的特点,提出一种基于改进YOLOv3的SAR图像舰船小目标检测算法。首先,通过分析残差网络的设计原理,针对不同场景下舰船目标的特点,重新设计底层残差单元;其次,改进特征金字塔的网络结构,解决感受野与定位之间的矛盾问题,提高了小尺度舰船的检测效果;最后,通过引入平衡因子,优化损失函数中的小目标权重。实验结果显示,相比原始YOLOv3方法,所提方法在舰船目标公开数据集上F1值提高6.3%,同时,较快的检测速度使得所提算法可用于实时目标检测。     

The 7th International Conference on Fluid Mechanics May 24-27,2015,Qingdao,China

正http://www.icfm7.org First Announcement and Call for PapersThe objective of International Conference on Fluid Mechanics(ICFM)is to provide a forum for researchers to exchange new ideas and recent advances in the fields of theoretical,experimental,computational Fluid Mechanics as well as interdisciplinary subjects.It was successfully convened by the Chinese Society of Theoretical and Applied Mechanics(CSTAM)in Beijing(1987,     

INFORMATION FOR CONTRIBUTORS

Contributions： The Journal, Acta Mechanica Solida Sinica, is pleased to receive papers from engineers and scientists working in various aspects of solid mechanics. All contributions are subject to critical review prior to acceptance and publication.     

基于鲁棒滤波的捷联导引头视线角速度估计方法

针对捷联导引头无法直接获取视线角速度等信息的问题,研究了鲁棒滤波在大气层外飞行器捷联导引头视线角速度估计中的应用。为了建立非线性滤波估计模型,考虑目标视线角速度的慢变特性,采用一阶马尔科夫模型建立了状态方程;推导了视线角速度的解耦模型,并建立了量测方程;考虑到实际应用中存在系统噪声统计特性失准的问题,基于Huber-Based鲁棒滤波方法,设计了视线角速度滤波器,并完成了基于Huber-Based滤波方法和扩展卡尔曼滤波方法的数学仿真。仿真结果表明Huber-Based滤波方法的视线角、视线角速度及视线角加速度估计精度分别达到0.1140'、0.1423'/s、0.0203'/s2,而扩展卡尔曼滤波方法的视线角、视线角速度及视线角加速度估计精度仅分别为0.6577'、0.6415'/s、0.0979'/s~2。仿真结果证明了该方法可以有效地估计出相对视线角速度等信息,并且在非高斯噪声的条件下,依然可获得较高的估计精度,具有一定的鲁棒性。     

Guide for authors

正Each of the sections below provides essential information for authors.We recommend that you take the time to read them before submitting a contribution to Acta Mechanica Sinica.We hope our guide to authors may help you navigate to the appropriate section.How to prepare a submission This document provides an outline of the editorial process involved in publishing a scientific paper in Acta Mechanica     

Use specification of multiscale materials for life spanned over macro-, micro-, nano-, and pico-scale

Multiscale material intends to enhance the strength and life of mechanical systems by matching the transmitted spatiotemporal energy distribution to the constituents at the different scale, say—macro, micro, nano, and pico,—, depending on the needs. Lower scale entities are, particularly, critical to small size systems. Large structures are less sensitive to microscopic effects. Scale shifting laws will be developed for relating test data from nano-, micro-, and macro-specimens. The benefit of reinforcement at the lower scale constituents needs to be justified at the macroscopic scale. Filling the void and space in regions of high energy density is considered.Material inhomogeneity interacts with specimen size. Their combined effect is non-equilibrium. Energy exchange between the environment and specimen becomes increasingly more significant as the specimen size is reduced. Perturbation of the operational conditions can further aggravate the situation. Scale transitional functions and/or f_j/j+1 are introduced to quantify these characteristics. They are represented, respectively, by , and (f_mi/ma,f_na/mi,f_pi/na). The abbreviations pi, na, mi, and ma refer to pico, nano, micro and macro.Local damage is assumed to initiate at a small scale, grows to a larger scale, and terminate at an even larger scale. The mechanism of energy absorption and dissipation will be introduced to develop a consistent book keeping system. Compaction of mass density for constituents of size 10⁻¹², 10⁻⁹, 10⁻⁶, 10⁻³ m, will be considered. Energy dissipation at all scales must be accounted for. Dissipations at the smaller scale must not only be included but they must abide by the same physical and mathematical interpretation, in order to avoid inconsistencies when making connections with those at the larger scale where dissipations are eminent.Three fundamental Problems I, II, and III are stated. They correspond to the commonly used service conditions. Reference is made to a Representative Tip (RT), the location where energy absorption and dissipation takes place. The RT can be a crack tip or a particle. At the larger size scales, RT can refer to a region. Scale shifting of results from the very small to the very large is needed to identify the benefit of using multiscale materials.     

Impact non-pénétrant sur le thorax : influence de la courbure sur la propagation des ondesNonpenetrating impact on the thorax: influence of curvature on wave propagation

Theoretical studies of the propagation of impact waves through the thorax are needed to improve the design of bulletproof jackets and blast protections (Fung in ‘Biomechanics Motions, Flow, Stress, and Growth’, Springer-Verlag, 1990; Cooper et al., J. Trauma 40 (1996) S38–S41). The influence of the weak acoustic coupling at the interface between the thoracic wall and the lung were described in (Grimal et al., C. R. Acad. Sci. IIB 329 (2001) 655–662); in this work, we study, within the frame of elastodynamics and with an approximate analytical method, the effects of the curvature of this interface. Results are given in terms of strain energy for the pressure wave, transmitted or converted. Focalisation of energy in the medium representing the lung is important for curvatures measured in humans. To cite this article: Q. Grimal et al., C. R. Mecanique 330 (2002) 569–574.     

Vérification expérimentale de la relation de réciprocité d'Onsager pour l'électro-osmose et l'électro-filtration dans une argile naturelleExperimental verification of the Onsager's reciprocal relations for electro-osmosis and electro-filtration phenomena on a saturated clay

This Note is devoted to the experimental verification of the Onsager's reciprocal relations in the particular case of electro-osmosis and electro-filtration. A special set up has been designed to carry out the measurements of both the electro-osmotic permeability and the streaming potential. This has been performed by using a natural material i.e., saturated kaolinite. To cite this article: K. Beddiar et al., C. R. Mecanique 330 (2002) 893–898.