Topological edge and corner states of valley photonic crystals with zipper-like boundary conditions

We present a stable valley photonic crystal(VPC)unit cell with C_(3v)symmetric quasi-ring-shaped dielectric columns and realize its topological phase transition by breaking mirror symmetry.Based on this unit cell structure,topological edge states(TESs)and topological corner states(TCSs)are realized.We obtain a new type of wave transmission mode based on photonic crystal zipper-like boundaries and apply it to a beam splitter assembled from rectangular photonic crystals(PCs).The constructed beam splitter structure is compact and possesses frequency separation functions.In addition,we construct a box-shaped triangular PC structures with zipper-like boundaries and discover phenomena of TCSs in the corners,comparing its corner states with those formed by other boundaries.Based on this,we explore the regularities of the electric field patterns of TESs and TCSs,explain the connection between the characteristic frequencies and locality of TCSs,which helps better control photons and ensures low power consumption of the system.

Actively Reconfigurable Valley Topological Edge and Corner States in Photonic Crystals Based on Phase Change Material Ge2Sb2Te5

The immunity of topological states against backscattering and structural defects provides them with a unique advantage in the exploration and design of high-precision low-loss optical devices.However,the operating bandwidth of the topological states in certain photonic structures is difficult to actively tune and flexibly reconfigure.In this study,we propose a valley topological photonic crystal(TPC)comprising two inverse honeycomb photonic crystals,consisting of hexagonal silicon and Ge2Sb2Te5(GST)rods.When GST transitions from the amorphous phase to the crystalline phase,the edge band of the TPC appears as a significant redshift and is inversed from a“∪”to an“∩”shape with topological phase transition,which enables active tuning of the operating bandwidth and propagation direction of topological edge states.Both the topological edge and corner states in a triangular structure constructed using TPCs can be simultaneously adjusted and reconfigured via GST phase transition,along with a change in the group number of corner states.Using the adjustability of topological edge states and electromagnetic coupling between two different topological bearded interfaces,we develop a multichannel optical router with a high tuning degree of freedom,where channels can be actively reconfigured and their on/off states can be freely switched.Our study provides a strategy for the active regulation of topological states and may be beneficial for the development of reconfigurable topological optical devices.

Visual positioning of rectangular lead components based on Harris corners and Zernike moments

With the increasing necessities for reliable printed circuit board(PCB) product, there has been a considerable demand for high speed and high precision vision positioning system. To locate a rectangular lead component with high accuracy and reliability, a new visual positioning method was introduced. Considering the limitations of Ghosal sub-pixel edge detection algorithm, an improved algorithm was proposed, in which Harris corner features were used to coarsely detect the edge points and Zernike moments were adopted to accurately detect the edge points. Besides, two formulas were developed to determine the edge intersections whose sub-pixel coordinates were calculated with bilinear interpolation and conjugate gradient method. The last experimental results show that the proposed method can detect the deflection and offset, and the detection errors are less than 0.04° and 0.02 pixels.

一种在尺度空间下基于边缘的角点目标检测方法

图像中的目标角点位置是实现很多计算机视觉任务的关键数据。为了克服传统检测算法产生的数据冗余问题,提出了一种在尺度空间下基于边缘的角点目标检测方法。首先,构建一个分组多层的尺度空间,将原图投影到其中后得到多个平滑图像。与此同时,采用定义的边缘算子检出平滑图像中所有边缘而得到多个按序存放的像素点集,当点集数量稳定时停止更大尺度的变换。然后,在当前尺度下,计算点集中各元素反映其角点强度的特征值。根据这些特征值变化规律检出角点的支撑集区间,并在此区间中采用高斯拟合函数确定最终的目标角点。实验表明,该方法能够检出特征显著的目标角点及其角度,其中合成图像精度在像素级,应用案例中的平均误差与图幅比约为1.5/100。

基于FPGA的图像处理硬件加速系统的设计

为解决图像处理算法越来越复杂,普通的计算平台已满足不了当前需求的问题,根据现场可编程门阵列(field programmable gate array, FPGA)的并行计算特点对FAST角点检测算法和Sobel边缘检测算法进行硬件加速,采用HLS(high-level synthesis, HLS)高层次综合技术对两种算法进行设计并进行相应的优化。为提升系统整体性能,在FPGA上实现全部视频输入输出接口和图像算法的完整通路,通过FPGA算法电路与OpenCV算法程序进行对比,前者的图像处理速度快于后者9~11倍,系统功耗也仅为1.9 W,图像检测可达56 fps,满足实时图像处理要求,为以后设计复杂的图像处理系统提供了参考。

基于马蹄涡前缘吸气控制的压气机叶栅流动机理

为探究从源头抑制角区分离的流动控制方法,采用数值模拟方法,以NACA65叶栅为研究对象,利用叶栅前缘端壁吸气技术控制马蹄涡,结合拓扑分析对叶栅通道内的三维流动结构进行精确重构,以研究前缘端壁吸气控制马蹄涡进而改善叶栅通道流场结构的机理。结果表明:叶栅前缘端壁吸气技术可以有效推迟马蹄涡形成并削弱其强度,同时在吸气狭缝末端形成一对反旋流向涡对,在向下游发展过程中与通道涡相互作用;前缘端壁吸气通过控制马蹄涡,降低端壁边界层厚度,叶栅前缘通道涡发展受限,由回流组成的叶表分离被抑制;前缘及压力面侧吸气(EPS)直接作用于马蹄涡压力面分支,通道涡强度进一步被削弱,角区分离模式由闭式分离转为不完全闭式分离。最后,对比最优吸气系数下不同方案出口总压损失,发现当吸气量为进口质量流量的0.2%时,EPS方案出口截面总压损失降低5.8%;并且通过调整吸气系数,可以获得较好的变工况控制性能。

基于Android平台的虚拟试衣关键技术研究

为了突破时间与空间的限制,达到服装实体店试衣的逼真效果,提出一种基于实例驱动的虚拟试衣方法.首先根据角点检测方法自动获取人体关键尺寸;然后根据实例检索算法获取与客户体形最接近的模特试衣效果;再使用移植配准与肤色融合实现头像移植;最后在Android平台上实现初步的系统模型.为提高网上服装交易的成功率与扩展服装的款式奠定了良好的基础.

基于引导滤波的巡检无人机自主循迹自动控制

巡检无人机自主循迹控制过程一直是一个难点,该文提出了一种基于引导滤波的巡检无人机自主循迹自动控制方法。引导滤波通过色彩空间转换、滤波分层和加权融合得到高质量的无人机视觉图像。以所得的无人机视觉图像为基础,利用拉普拉斯算子与Harris算子检测航迹点。以航迹点为循迹目标,利用外环方位控制器和内环姿势控制器实现无人机自主循迹的自动控制。实验结果表明,巡检无人机的循迹方位偏差和姿态角度偏差较小,波动区间均稳定在允许的范围内,说明该方法能准确控制无人机实现自主循迹的目标,实际应用价值较高。

提高预焙阳极焙烧外观合格率的研究及实践

针对预焙阳极在焙烧过程中影响外观质量的问题,结合装炉技术操作和设备现状对影响合格率的原因进行了分析,提出了改进的相应措施。经过生产实践,预焙阳极不合格块占总炭块的百分比由0.58%下降至0.44%。

赫尔默特方差分量估计在边角网中的应用

在融合多源异构信息时,不同种类的观测值应具有不同的权阵。但是在数据处理前,往往不知道不同观测值之间的关系,进而无法对不同观测值进行定权。针对边角网布设时对角度和边长两类观测值进行测量平差时观测值种类不同的问题,本文在经典最小二乘基础上将赫尔默特(Helmert)方差分量估计应用到边角网平差过程中,并通过算例进行分析。结果表明,将Helmert方法应用于两类观测值的平差后,精度有所提高,可为多类观测值、平差网形较大、精度要求高的工程应用提供一定的参考。

Subpixel accuracy for extracting groove center based on corner detection

Subpixel accuracy for V-groove center in robot welding is researched and a software measure to increase the accuracy of seam tracking by laser is presented. LOG （ Laplacian of Gaussian ） operator is adopted to detect image edge. Vgroove center is extracted by corner detection of extremum curvature. Subpixel position is obtained by Lagarange polynomial interpolation algorithm. Experiment results show that the method is brief and applied, and is sufficient for the real time of robot welding by laser sensors.

Corner-Based Image Alignment using Pyramid Structure with Gradient Vector Similarity

This paper presents a corner-based image alignment algorithm based on the procedures of corner-based template matching and geometric parameter estimation. This algorithm consists of two stages: 1) training phase, and 2) matching phase. In the training phase, a corner detection algorithm is used to extract the corners. These corners are then used to build the pyramid images. In the matching phase, the corners are obtained using the same corner detection algorithm. The similarity measure is then determined by the differences of gradient vector between the corners obtained in the template image and the inspection image, respectively. A parabolic function is further applied to evaluate the geometric relationship between the template and the inspection images. Results show that the corner-based template matching outperforms the original edge-based template matching in efficiency, and both of them are robust against non-liner light changes. The accuracy and precision of the corner-based image alignment are competitive to that of edge-based image alignment under the same environment. In practice, the proposed algorithm demonstrates its precision, efficiency and robustness in image alignment for real world applications.

中薄板坯角部纵向边裂的原因与措施

分析了中薄板坯角部纵向边裂的影响因素,采取优化结晶器振动台控制系统和同步精度,优化结晶器锥度,提高结晶器整备精度,适当减小结晶器冷却水量,提高扇形段辊缝和接弧精度标准等措施后,中薄板坯角部纵向边裂发生率由3.5%降至1.0%,保证了中薄板坯产品的质量。

双臂拉伸铺展皮革的方法设计与算法实现

为推动皮革工业的智能化发展,解决皮革加工过程中自动拉伸铺展的难题,提出了一种皮革拉伸铺展的方法,并设计出了检测抓取点的算法。该算法利用视觉识别技术获取皮革的图像信息,通过Harris角点检测算法确定抓取拉伸点后,使用双机械臂协同作业进行皮革的拉伸和铺展。视觉传感器获得皮革的图像信息后,首先利用边缘识别和角点检测算法获取皮革的两个角点,通过双机械臂抓取两个角点将皮革初步铺展在绷板上,然后根据皮革的颜色差异展开重叠的皮革,从而实现皮革的完全铺展。最后,通过实验验证所提出方法的有效性。

图像边缘检测技术对偏滤器X点的识别研究

利用计算机视觉技术,对HL-2A偏滤器放电X点进行了识别研究。首先根据HL-2A偏滤器放电图的分析需求,基于直观的等离子体标准下单零放电位形下的边缘可见光辐射模型建立了Canny边缘检测的处理模型,主要对图像中等离子体边缘进行了预处理。结合Harris角点检测的算法,在提取出图像特征点后,利用多边形逼近的方式确定了特征点在图像中的坐标值。分别拟合出强、弱场侧的等离子体边界曲线及其渐近线,渐近线交点近似为X点,边界曲线向中心逼近所包围的区域可近似为X点存在区域。通过实际的HL-2A装置第37638次放电偏滤器放电图验证,经过简化条件后,拟合出的X点与EFIT反演对比误差范围在3cm以内。

基于靶标内点与边缘角点双重约束的激光雷达与相机联合标定

针对激光雷达与相机联合使用过程中存在的空间位姿不一致问题,提出一种基于靶标内点与边缘角点双重约束的激光雷达与相机联合标定方法。该方法以刚体变换作为二者之间的变换模型,以任意矩形作为靶标,通过RANSAC直线拟合获取交点以进一步获取靶标在图像中的角点,通过对原始点云进行分割与滤波操作后获得对应的靶标点云。获取靶标点云后,将其分为内点与边缘角点,并分别建立基于内点与边缘角点的损失函数模型,最后进行模型优化求解出最优配准参数。实验表明,在15 m~28 m范围内,三维点云的重投影准确率为94.67%,考虑到激光雷达本身的测量误差以及数据采集过程中靶标距离两传感器过远,该联合标定方法具有较高的准确性。

基于增强模板的鞋体涂胶特征点快速匹配提取

拖鞋自动化生产装配中,胶水喷涂是最重要的环节,由于拖鞋鞋体为特定局部区域侧面喷涂,以及颜色不一、挤压形变和环境光变等因素,涂胶区域的图像特征提取变得尤为困难。应用3D激光相机进行鞋体图像采集,避免环境光变对图像的影响,通过调整相机曝光以及相机安装方式等解决像素跳动或缺失的问题,采取基于边缘特征的增强模板匹配的方法,对涂胶特征区域进行匹配定位,结合曲率尺度空间的角点提取方式,精准快速地实现涂胶特征点提取。实验结果表明,该方法针对不同鞋码不同颜色鞋体都具有良好的适用性与稳定性,实现快速检测,满足实际生产需求。

焊接机器人视觉系统对焊缝的标记方法研究

依托机器视觉技术,焊接机器人技术现已发展到了第三代。为了实现机器人的智能焊接,在前期工作中,机器人的焊接系统需要对焊缝进行标记和智能提取。课题组选用了Sobel算子、Canny算子、Forstner算子、Harris算子对模拟焊接件进行了焊缝标记,通过实验对比发现,对于课题组所选取的研究对象,Forstner算子效果优异。

复杂地质条件下的边角煤工作面优化布置

针对济宁二号煤矿四采区边角煤块段受断层构造及水患等复杂地质条件影响的实际情况,提出2个边角煤工作面布置优化方案。综合考虑矿井实际技术装备水平、两方案施工难度、经济性对比,最终选定方案二,可提高煤炭回采量,解决矿井采掘接续紧张局面。

不同制造工艺对高性能铜合金微细扁线尺寸、组织及性能的影响

通过对滑动拉丝机用微细扁线模具的设计及制造,采用拉制工艺成功制备出厚度(a)小于0.09 mm、宽厚比(b/a)接近8的高性能铜合金扁线导体,导体的抗拉强度、导电率和延伸率分别可达412.8 MPa、97.8%IACS、6.2%。通过尺寸测量、光学显微镜、电子背散射衍射分析(EBSD)、拉力和电阻等试验,研究了拉制法与精轧法两种制备工艺对铜合金微细扁线组织及性能的变化规律。试验结果表明,拉制工艺尺寸控制更精准,且可通过模具设计灵活控制扁线R角类型(圆角型、圆边型),更有利于提升扁线电机的能效,其加工硬化效果较精轧工艺更为缓慢,退火时两种工艺的软化特性有一定差异。