GPU-accelerated three-dimensional reconstruction method of the Compton camera and its application in radionuclide imaging

A novel and fast three-dimensional reconstruction method for a Compton camera and its performance in radionuclide imaging is proposed and analyzed in this study. The conical surface sampling back-projection method with scattering angle correction(CSS-BP-SC) can quickly perform the back-projection process of the Compton cone and can be used to precompute the list-mode maximum likelihood expectation maximization(LM-MLEM). A dedicated parallel architecture was designed for the graphics processing unit acceleration of the back-projection and iteration stage of the CSS-BP-SC-based LM-MLEM. The imaging results of the two-point source Monte Carlo(MC) simulation demonstrate that by analyzing the full width at half maximum along the three coordinate axes, the CSS-BP-SC-based LM-MLEM can obtain imaging results comparable to those of the traditional reconstruction algorithm, that is, the simple back-projection-based LM-MLEM. The imaging results of the mouse phantom MC simulation and experiment demonstrate that the reconstruction results obtained by the proposed method sufficiently coincide with the set radioactivity distribution, and the speed increased by more than 664 times compared to the traditional reconstruction algorithm in the mouse phantom experiment. The proposed method will further advance the imaging applications of Compton cameras.

Boundary effect of toppling failure based on three-dimensional mechanical model

Previous researches on the mechanical model of toppling failure mainly concentrated on twodimensional mechanical model(TwDM) analysis. The TwDM analysis assumes the width of the slab beam is unit width without considering the lateral constraint force. The assumed conditions are obviously different from the site conditions, thus there is a certain difference between the calculated results and the field work. A three-dimensional mechanical model(ThDM)of toppling failure was established, considering that the slab beam was mainly subject to self-weight, the frictional resistance of interlayer and lateral constraint force. Due to the progressive characteristics of toppling failure, the concept and the formula of the first fracture depth(FFD) of toppling was raised and constructed. The case study indicates that the ThDM is more effective and can be accurately used to calculate the toppling fracture depth of the slab beam. The FFD decreases proportionally with the increase of slab beam width. FFD grows fast when the slab beam width is less than 2.0 m and it tends to be stable when the slab beam width is above 2.0 m. The FFD decreases with the increase of the lateral constraint coefficient, indicating that the boundary condition of the free space is positively correlated with the stability and depth of toppling. This is a good explanation of the free space effect. This study provides a reference for the stability evaluation and prevention-control design of toppling slope in the future.

Three-dimensional anthropometry in periorbital region

Anthropometry can analyze the size,weight,and proportion of the human body objectively and quantitatively to supplement the visual assessment.Various non-invasive three-dimensional(3D)anthropometric techniques have been applied to assess soft tissues’3D morphology in the clinical practice.Among them,non-invasive stereophotogrammetry and laser scanning techniques are becoming increasingly popular in craniofacial surgery and plastic surgery.They have been applied for craniofacial growth estimation and morphometric investigation,genetic and acquired malformation diagnosis,as well as orthodontic or surgical treatment arrangement and outcome evaluation.However,few studies have been published for assessing the 3D morphology of soft tissues in the periorbital region.This paper reviews the studies involving the application and evaluation of the increasingly popular 3D photogrammetry in the periorbital region.These studies proposed detailed and standardized protocols for three-dimensionally assessing linear,curvilinear,angular,as well as volumetric measurements,and verified its high reliability in the periorbital region(even higher than caliper-derived direct measurements).In the future,reliable and accurate 3D imaging techniques,as well as standardized analyzing protocols,may find applications in following up morphological growth,preoperatively diagnosing and assessing patient periorbital conditions,planning surgical procedures,postoperatively evaluating treatment outcomes of a specific procedure,and comparing the differences in surgical results between various procedures,studies,as well as populations.

单目标旋转摄影方法标定图像全站仪相机

为了实现图像全站仪望远镜相机和广角相机的高精度标定,采用单目标旋转摄影法推导了旋转摄影模式下图像全站仪的相机标定模型,并对模型参数展开相关性分析,针对其中存在的参数耦合问题,提出了双盘观测法进行参数解耦;对单目标旋转摄影方法的可行性进行了实验验证,取得了图像全站仪望远镜相机和广角相机的高精度标定结果。结果表明,标定得到的相机参数可用于不同摄影距离的图像测量,望远镜相机标定点重投影误差平均为1.0 pixel,对应图像角分辨率达2.0″;望远镜相机定焦摄影时标定点重投影误差平均为0.15 pixel,对应图像角分辨率达0.3″;广角相机标定点重投影误差平均为0.6 pixel,对应图像角分辨率达13.3″。该研究对提高图像全站仪的图像测量精度及拓展其相关应用有一定参考意义。

基于近红外成像的舱内摄像头补光技术

汽车舱内摄像头DMS和OMS是对车内人员的精神状态、生命特征、肢体表达等进行识别的,为了保证算法识别的成功率,对图像中人脸或肢体的亮度有一定要求。针对近红外成像需要主动光源补光的特点,提出了一种汽车舱内摄像头近红外补光的技术方案,依据红外辐射光源空间通量分布、人体表皮的近红外特征、几何光学的折反射规律、Sensor的光电转换能力等方面的理论,建立计算模型,推导出补光LED的功率与图像中人脸亮度DN值之间的关系公式。在数据模型中通过该公式推算应用5.2W近红外补光LED对人脸进行补光后,图像中所拍摄的人脸的亮度DN值进行模拟计算。同时搭建了舱内摄像头的验证系统,通过对试验车内人员实际补光后拍摄图像数据进行亮度DN值分析,并与理论推算结果进行比对,实验结果与计算结果误差小于±5%,满足算法要求,验证了舱内摄像头近红外补光的技术方案的可行性。

矿用摄像仪智能自清洁系统的研究与应用

针对综采工作面现有摄像仪球罩容易附着煤尘或煤泥,影响视频监控的效果、且需要人工擦拭的问题,提出了采用具有疏水涂层的聚碳酸酯光学球罩,通过在现有的摄像仪壳体上增加喷水自清洁装置,自清洁装置连接支架喷雾系统,由自清洁装置对摄像仪球罩进行除尘清洁,开发出可以通过地面监控中心进行远程控制的摄像仪自清洁系统,并在煤矿井下进行了工业性试验。经验证,摄像仪自清洁系统满足现场需求,极大地节省了人力,解决了综采工作面摄像仪“看得见”、“看得清”的问题,为实现智能化无人开采奠定了基础。

Design Theory of Full Face Rock Tunnel Boring Machine Transition Cutter Edge Angle and Its Application

At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.

SKEWED SYMMETRY DETECTION OF QUADRIC SURFACE SOLIDS UNDER ORTHOGRAPHIC PROJECTION

The skewed symmetry detection plays an improtant role in three-dimensional（3-D） reconstruction. The skewed symmetry depicts a real symmetry viewed from some unknown viewing directions. And the skewed symmetry detection can decrease the geometric constrains and the complexity of 3-D reconstruction. The detection technique for the quadric curve ellipse proposed by Sugimoto is improved to further cover quadric curves including hyperbola and parabola. With the parametric detection, the 3-D quadric curve projection matching is automatical- ly accomplished. Finally, the skewed symmetry surface of the quadric surface solid is obtained. Several examples are used to verify the feasibility of the algorithm and satisfying results can be obtained.

The three-dimension model for the rock-breaking mechanism of disc cutter andanalysis of rock-breaking forces

To study the rock deformation with three- dimensional model under rolling forces of disc cutter, by car- rying out the circular-grooving test with disc cutter rolling around on the rock, the rock mechanical behavior under rolling disc cutter is studied, the mechanical model of disc cutter rolling around the groove is established, and the the- ory of single-point and double-angle variables is proposed. Based on this theory, the physics equations and geometric equations of rock mechanical behavior under disc cutters of tunnel boring machine （TBM） are studied, and then the bal- ance equations of interactive forces between disc cutter and rock are established. Accordingly, formulas about normal force, rolling force and side force of a disc cutter are de- rived, and their validity is studied by tests. Therefore, a new method and theory is proposed to study rock- breaking mech- anism of disc cutters.

Markerless Respiratory Motion Tracking Using Single Depth Camera

The aim of this study is to propose a novel system that has an ability to detect intra-fractional motion during radiotherapy treatment in real-time using three-dimensional surface taken by a depth camera, Microsoft Kinect v1. Our approach introduces three new aspects for three-dimensional surface tracking in radiotherapy treatment. The first aspect is a new algorithm for noise reduction of depth values. Ueda’s algorithm was implemented and enabling a fast least square regression of depth values. The second aspect is an application for detection of patient’s motion at multiple points in thracoabdominal regions. The third aspect is an estimation of three-dimensional surface from multiple depth values. For evaluation of noise reduction by Ueda’s algorithm, two respiratory patterns are measured by the Kinect as well as a laser range meter. The resulting cross correlation coefficients between the laser range meter and the Kinect were 0.982 for abdominal respiration and 0.995 for breath holding. Moreover, the mean cross correlation coefficients between the signals of our system and the signals of Anzai with respect to participant’s respiratory motion were 0.90 for thoracic respiration and 0.93 for abdominal respiration, respectively. These results proved that the performance of the developed system was comparable to existing motion monitoring devices. Reconstruction of three-dimensional surface also enabled us to detect the irregular motion and breathing arrest by comparing the averaged depth with predefined threshold values.

Spatial correlation between groundwater seepage faces and fault zone in high bedrock channel: method and application

The groundwater may recharge the surface water bodies through seepage faces and springs.The spatial correlation between the fault zones and the groundwater seepage faces results in deep understanding of the hydrogeologic regime,especially where there is no monitoring boreholes.Locating these recharging zones by conventional methods is a challenging task;particularly in areas where(1)there is no hydrogeologic monitoring boreholes or reliable data,(2)private pumps withdraw the stream,and(3)intense canopy limits the use of drones and satellite images.This paper aims to study the relationship between the fault zones and occurrence of the groundwater seepage faces by using the high resolution handheld thermal imaging cameras as a tool to locate the seepage faces along a small river in the Damavand County,north of Iran.The correlation between the structural geology features and occurrence of the groundwater seepage faces revealed that the stream in the study area is being recharged by the groundwater at extensive fault zones.Additionally,this study suggests that the handheld thermal imaging cameras are a useful robust tools to evaluate the surface-groundwater interaction.However,it is essential to use the field structural geologic and hydrogeologic observations to interpret the thermal images.

Low Resolution Face Recognition in Surveillance Systems

In surveillance systems, the captured facial images are often very small and different from the low-resolution images down-sampled from high-resolution facial images. They generally lead to low performance in face recognition. In this paper, we study specific scenarios of face recognition with surveillance cameras. Three important factors that influence face recognition performance are investigated: type of cameras, distance between the object and camera, and the resolution of the captured face images. Each factor is numerically investigated and analyzed in this paper. Based on these observations, a new approach is proposed for face recognition in real surveillance environment. For a raw video sequence captured by a surveillance camera, image pre-processing techniques are employed to remove the illumination variations for the enhancement of image quality. The face images are further improved through a novel face image super-resolution method. The proposed approach is proven to significantly improve the performance of face recognition as demonstrated by experiments.

基于深度相机的虚拟眼镜试戴

当前,网上购物极大便利人们的生活,但是在网上购买眼镜时,消费者无法像在实体店中一样试戴眼镜,不能直观地看到眼镜佩戴效果,因而难以做出购买决策。针对这一问题,提出一种基于深度相机的虚拟眼镜试戴方法。该方法由2个阶段组成:第一阶段是重建人脸三维模型,利用深度相机采集得到的多角度人脸点云进行点云配准。点云配准时,首先得到特征点云完成一次粗配准,然后提取点云的重叠部分完成一次精细配准,由配准后的点云得到三维人脸模型;第二阶段是眼镜试戴,首先自动对齐人脸模型和眼镜模型并根据视频流实时估计的人脸姿态参数变换模型,并渲染模型,然后将经过消隐处理后的眼镜模型融合进视频流中,最终实现虚拟眼镜试戴效果。实验结果表明,该算法实时性好,试戴效果逼真,给用户带来良好的试戴体验。

矿用本安型双光谱融合摄像仪设计

为了解决煤矿综采工作面热成像监控设备分辨率较低的问题,提出了一种双光谱融合摄像仪的设计,实现热成像图像与可见光高清图像的优势互补。首先,由于井下环境对设备的安全性要求较高,对Hi3519V101的硬件电路进行本安化设计;其次,根据双光谱图像的特点,采用SURF算法进行特征点的提取,使用最近邻与次近邻算法实现特征点的匹配,由于匹配过程中存在部分错配点,设计采用RANSAC算法进行错配点的消除,利用提升小波算法实现双光谱图像融合,输出近似热成像图像的伪彩化图像;最后,对矿用本安型双光谱融合摄像仪样机进行测试。试验结果表明:该摄像仪可以有效增强井下图像的细节,满足对井下设备进行监测的要求。

基于散斑结构光编码的三维人脸重建方法研究

三维人脸信息获取通过三维相机和三维人脸重建算法进行三维人脸建模。真实环境中三维重建方法往往存在匹配误差较高、表面粗糙等问题。针对三维人脸重建中的问题设计一套三维人脸重建算法用以提高三维重建效果,通过向人脸投射散斑图案增强人脸纹理,改进ZNCC算法生成平滑的三维人脸模型。通过仿真实验验证了该算法可以得到较高精度的平滑三维人脸模型。

智能化矿用摄像仪测试方法中约束条件的研究

矿用摄像仪智能化发展迅速,普通的智能化摄像仪的测试方案中缺少与井下特殊环境相关的关键条件。针对这个问题,进行智能化矿用摄像仪测试方法中约束条件的研究。首先,介绍智能化矿用摄像仪的软件、硬件功能,对其分别进行矿井约束条件下的测试及分析研究。软件功能测试结果表明:环境照度及距离(约束条件)对纵撕检测功能的测试结果均存在较大影响,距离(约束条件)对井下人脸识别功能的测试结果存在较大影响。硬件功能方面,分析其与约束条件的相关性,结合产品防爆性能进行综合评价后得到测试关注点。最后,通过加入矿井约束条件及关注点,优化智能化矿用摄像仪的测试方法。根据实例结果表明:可提高检验有效性与可靠性。该研究对建立矿用摄像仪智能化评测标准和矿用摄像仪设计等提供有效的参考。

基于全景摄像机的人脸识别方法及应用

当前,人脸识别技术得到极速发展的同时也得到了非常广泛的应用,这是一种众所周知的脸部数据库基础。介绍了全景摄像机的特征和人脸识别的概念,分析了全景摄像机与人脸识别技术的应用,以供同行业人员进行参考。

一种基于PLC的码垛机安全防护系统的方案设计

人工在操作自动化设备时,因操作不当或误操作等原因造成的人身安全事故时有发生,工业安全备受政府和人们的关注,因此,提高自动化设备的安全防护等级尤为重要。本文采用“人脸识别+PLC+电子锁+上位机软件+工业摄像头”多种技术,设计了一种安全、可靠的防护系统。

与全方位全景图象有关的几个问题的研究

本文首先介绍了基于图象的绘制方法和全景图象 ,然后深入研究了三个与全方位全景图象有关的问题。 1、本文利用立方体表面来映射全方位全景图象 ,通过定向投影 ,推导了立方体表面与观察平面之间相互变换的公式 ,并实现了这些变换 ,这有利于在研究全方位全景图象时对立方体表面的图象进行观察。 2、准确的照相机标定是生成完整的全方位全景图象的必要条件 ,本文以常用的标准件标定法为基础 ,分析了其中产生误差的各项因素 ,认为与全方位全景图象有关的主要误差因素为物象距离 ,对此提出了一套修正方法 ,从而得到了一个简单有效的照相机标定方法。 3、本文提出了一个利用全方位全景图象来实现虚拟场景漫游的机制 ,实现了基于全方位全景图象的漫游 ,得到了一个简单的虚拟现实系统 ,用户在其中漫游的自由度远大于基于柱面全景图象的漫游系统。

基于三维模型的人脸姿态估计方法

提出一种三维人脸姿态估计方法。该方法通过估计三维平面人脸模型到图像平面的单应矩阵来获得人脸相对于摄像机坐标系的旋转矩阵,并利用M-估计优化方法迭代求精。其主要特点是:实施简单,不需要对透视摄像机参数预先进行标定,能够在较大范围内较精确地估计人脸姿态。对模拟数据及真实人脸图像的实验均验证了该方法的有效性。