基于图形处理器的X射线锥束成像模拟算法

针对X射线锥束成像模拟计算量大、速度慢的问题,提出了一种基于图形处理器（GPU）的快速成像模拟算法。该算法沿着每条射线累加所经过体素对投影值的贡献量,实现了对X射线成像的模拟。在计算射线与体素的交线长时,采用分类处理交线的方法,减少了增量Sid—don算法的动态分支计算。为了提高投影图像质量,该算法还用GPU硬件线性插值采样取代Sid—don算法的邻近插值采样。对三维Shepp—logan模型的测试结果表明,该算法的速度比基于GPU的增量Siddon算法平均提高了44％,而且图像质量明显提高。最后,用实测数据进一步验证了算法的有效性。     

一种基于时空MRF的工业CT图像序列分割方法

提出了一种基于时空马尔科夫随机场的工业CT图像序列分割算法。此算法根据工业CT图像序列信息连续性的特点,建立时空Markov随机场,并且构造相应的混合高斯统计模型能量函数,利用条件迭代算法（ICM）实现最大后验概率（MAP）估计。仿真试验表明,该方法能够较好地实现工业CT图像序列的分割。     

EM算法在X射线CT重建中的应用研究

计算机断层成像（CT）广泛地应用于医疗诊断和工业无损检测等领域。具有无损、无接触、高分辨率等优点。X射线CT是目前最为常用的计算机断层成像技术。在X射线CT成像系统中，重建算法是其核心部分。本文将最大似然估计理论推广到X射线CT，基于投影数据统计模型，实现了期望最大化（EM）算法在X射线CT中的应用。并进行了实际X射线扫描数据的实验，结果表明该算法有效可行，重建图像清晰准确。     

基于X射线胶片的固体火箭发动机断面图像重建

固体火箭发动机切向X射线实际检测结果是稀疏视角型和截断型数据,其检测胶片只能显示二维重叠影像信息,显示结果不直观.在滤波反投影算法的基础上,提出了根据X射线胶片信息进行固体火箭发动机断面局部感兴趣区域(ROI)图像重建方法.仿真计算表明,在有限角度切向照相情况下,该方法对固体火箭发动机切向缺陷,特别是脱粘缺陷的断面图像...     

多元平衡相图计算机辅助教学研究

在工作站大型工程有限元分析软件ANSYS上建立了二元及多元平衡相图辅助教学系统。该系统拥有典型相图教学模型库,能够直观地观察相图的构造。并且可以实现沿任意断面剖切,生成任意成分和任意温度的截面图,为课堂提供教学材料。     

焊接检验及其设备

提出了基于图像色彩信息的焊缝识别算法,旨在为用于自动化焊接及自动无损检测的焊缝跟踪技术探索可能的解决方案。从色彩理论和图像分割的基本原理出发,开展了对ROB（红、绿、蓝）彩色空间中图像色彩信息表达的研究,提出了彩色空间变换的方法,根据灰度直方图对图像进行阈值分割,     

焊接检验及其设备

提出了基于图像色彩信息的焊缝识别算法,旨在为用于自动化焊接及自动无损检测的焊缝跟踪技术探索可能的解决方案。从色彩理论和图像分割的基本原理出发,开展了对ROB（红、绿、蓝）彩色空间中图像色彩信息表达的研究,提出了彩色空间变换的方法,根据灰度直方图对图像进行阈值分割,     

粘接结构超声波C扫描检测的三维图像重构

基于虚拟仪器技术构建了超声波检测系统,该系统依据模块化的思想进行设计,可同时实现A、C扫描功能。利用该系统对固体火箭发动机粘接结构进行扫描检测,并对粘接结构的体数据进行采集、存储和阈值分割。在此基础上研究了基于体素的三维重构算法。重构后的三维图像比较直观,能够较真实地反映粘接结构内部的缺陷情况。     

一种数字化智能焊接质量无损检测系统研制

为了提高焊接构件质量检测的自动化和效率,研制了一种基于X射线探测器的焊接质量无损检测系统.给出了所设计的系统各主要组成部分并对其主要功能做了介绍,然后对探测器导致图像退化的各种嗓声,分别散了校正,最后介绍了所开发的图像检测软件的主要功能模块,提出了一种最优阈值的求取算法,该算法不受图像灰度线性平移变化的影响,具有极强的鲁棒性.试验表明,系统成像质量能达到工业检测最高级B级,能够实现常规焊接质量的自动或人工检测.     

三维有限元网格图形的剖切及场变量可视化

为了更好地分析三维有限元模拟过程中工件内部场变量的变化分布规律, 本文着重介绍了在屏幕工件上用鼠标任意点取3个点构造一平面, 然后应用该平面将基于八节点三维六面体单元的工件进行剖切的方法, 给出了剖切后网格图形上场量值所对应的等值线、彩色云图及速度矢端图等的生成算法。文中算例表明, 该算法灵活、可靠, 具有很好的可行性。     

铝合金MIG焊丝伸出长度视觉提取算法及动态过程辨识

建立了一种基于视觉传感的铝合金MIG焊丝伸出长度检测系统,并提出了相应的图像处理算法,通过使用CCD摄像机,实时获取焊接区图像,根据焊丝特征定位其在图像中的纵坐标,然后对图像进行剪切,移位并叠加,使焊丝特征与背景之间的差别得到强化并提取焊丝伸出长度信息,结果表明,该算法快速有效.在以上工作的基础上,设计了阶跃响应试验,对焊丝伸出长度受送丝速度的影响规律进行了辩识,得到了数学模型,为铝合金MIG焊接过程中焊丝伸出长度传感与控制奠定了基础.     

Improvement of image characteristics in high-voltage computed tomography (CT) by applying a compressed-sensing (CS)-based image deblurring scheme

We have established a high-voltage computed tomography (CT) system with a 1–3 MV LINAC x-ray generator for industrial nondestructive testing. However, reconstructed CT images are typically blurred, limiting its image performance, mainly due to the finite focal spot size of the x-ray source, aspects inherent to detector such as the detector pixel size and the detector resolution, and the reconstruction procedure as well. Thus the recovery of the reconstructed CT images from their degraded version is essential for improving the image characteristics. In this work, we investigated the compressed-sensing (CS)-based deconvolution scheme for more accurate image deblurring in CT. We implemented the proposed image deblurring algorithm for CT and performed a systematic simulation and experiment to demonstrate its viability. Our results indicate that the proposed deblurring scheme appears to be effective for the blurring problems in CT and is applicable to improve its present image characteristics.     

基于K-SVD算法的带钢表面缺陷图像去噪

目的有效滤除带钢表面缺陷图像高斯噪声。方法高斯噪声是影响带钢图像质量的主要噪声类型之一,针对带钢表面缺陷图像高斯噪声去噪,首先对传统K-SVD(K-means and singular value decomposition)算法中的字典进行升级改造,然后采用正交匹配追踪(OMP,Orthogonal Matching Pursuit)算法对图像进行重构,滤除噪声,最后运用此算法对缺陷图像进行高斯滤波处理。为验证该算法去噪效果,选取几种常见的典型缺陷图像(划伤、气泡、氧化色、粘结纹)进行测试仿真,并选用中值滤波、均值滤波、小波变换、维纳滤波、3维块匹配(BM3D)等多种传统滤波方法进行比较。结果该算法对四种典型缺陷去噪的PSNR(Peak Signal to Noise Ratio)值平均可达33.976 d B,MSE(Mean Square Error)平均值为27.607,SSIM(Structural Similarity)平均值为0.912。结论该算法对带钢表面缺陷重构图像的边缘细节清晰,PSNR、MSE、SSIM三个性能指标明显优于其他传统滤波算法,去噪效果良好。     

3D image reconstruction using cone beam tomography

3D X-ray cone beam tomography for possible NDT application is illustrated via the Feldkamp convolution backprojection reconstruction algorithm. Gauss and Ham filter functions are implemented in order to alleviate artifacts (streaks and ringing). In addition, the effect of cone vertex position error on image reconstruction is investigated. Finally, film based X-ray projection radiographs were scanned into the computer to reconstruct the 3D images and verify the performance of the software program.     

A novel method for FDTD numerical GPR imaging of arbitrary shapes based on Fourier transform

Ground penetrating radar (GPR) systems are very powerful tools with a wide range of advantages in non-destructive testing. Target detection is one of the serious results of GPR application. The landmine detection in the soil and reinforcement bars and holes in the concrete is some of the GPR object detection examples. In this research, the targets are modeled in different cases, an air hole or a conductive material. A cracked surface is also modeled for both conductive and dielectric media. For modeling, the three-dimensional (3D) finite difference time-domain (FDTD) method is applied. Perfectly matched layer (PML) absorbing boundary condition is used for simulating the physical absorbers and free space. The results were shown in time domain. The difference between results helps to distinguish the target depth and electrical properties. For better specification of the target shape, a transform in frequency domain is used. This transform contains a Fourier transform in a selected frequency. The results show a sudden change in the frequency response over the hole or target scanning. By this idea, the shape of any arbitrary hole or crack can be extracted.     

模具零件的最小包围盒生成算法

提出一种实用的最小包围盒算法,将任意位置的复杂三维模型投影在3个主平面上,通过分析投影外轮廓的最小包围矩形来最终确定三维模型的最小包围盒。算法不再采用传统算法中旋转模型的方法,而根据旋转投影的外轮廓来确定最小包围盒,提高了算法的效率。同时算法通过分析识别模型的基本形状,将其分为箱体类、回转类和异形类,以快速确定一个主投影方向,将三维问题转化为求二维平面上的最小包围矩形,进一步提高了计算效率。算法可以嵌入NX等商用CAD系统,经过大量测试对比,相对传统算法更高效,并且稳定可靠,可广泛应用于任意位置的复杂模具零件的生成和干涉检查等。     

GPU based numerical simulation of core shooting process

Core shooting process is the most widely used technique to make sand cores and it plays an important role in the quality of sand cores. Although numerical simulation can hopefully optimize the core shooting process, research on numerical simulation of the core shooting process is very limited. Based on a two-fluid model (TFM) and a kinetic-friction constitutive correlation, a program for 3D numerical simulation of the core shooting process has been developed and achieved good agreements with in-situ experiments. To match the needs of engineering applications, a graphics processing unit (GPU) has also been used to improve the calculation efficiency. The parallel algorithm based on the Compute Unified Device Architecture (CUDA) platform can significantly decrease computing time by multi-threaded GPU. In this work, the program accelerated by CUDA parallelization method was developed and the accuracy of the calculations was ensured by comparing with in-situ experimental results photographed by a high-speed camera. The design and optimization of the parallel algorithm were discussed. The simulation result of a sand core test-piece indicated the improvement of the calculation efficiency by GPU. The developed program has also been validated by in-situ experiments with a transparent core-box, a high-speed camera, and a pressure measuring system. The computing time of the parallel program was reduced by nearly 95% while the simulation result was still quite consistent with experimental data. The GPU parallelization method can successfully solve the problem of low computational efficiency of the 3D sand shooting simulation program, and thus the developed GPU program is appropriate for engineering applications.     

红外热波序列图像的图像分割与三维显示

研究了针对红外热波序列图像的图像分割和三维显示方法。红外热波无损检测只能得到被测工件表面温度变化的时间序列图像,无法直观到检测缺陷,利用三维显示技术可以产生深度三维立体图,方便技术人员更直观、精确地进行无损检测。三维显示效果的好坏直接取决于图像分割的效果。为此提出了基于局部极小值的区域生长分割算法,成功地提取出红外热波图像中缺陷成分的目标图像,并进行了三维显示,取得了较好的效果。     

基于双目视觉系统的三维目标识别研究

双目视觉系统一般是由一个或两个摄相机从不同角度获取周围景物两幅数字图像,基于人类视觉的视差原理重建周围景物的三维几何信息。通过开源计算机视觉库(OpenCV)重建周围景物的三维几何信息,并提取三维目标的特征信息。采用支持向量机(Support Vector Machine)的软件包LIBSVM进行小样本的学习,从而达到对特定目标的识别。     

任意模具形状的金属三维体积成形过程刚塑性无网格RKPM分析方法

将无网格方法引入三维金属体积成形分析,在给出基于刚塑性流动理论的三维无网格再生核质点方法及其基本理论方程的基础上,为了提高分析系统的通用化和自动化,采用网格法来描述任意形状的三维模具型腔曲面,给出了三维无网格法数值模拟系统中动态接触边界自动处理的非线性接触算法,实现了任意模具形状的三维体积成形过程的无网格法数值模拟。对上模为半球形的三维立方体塑性变形过程进行了数值模拟,并与三维刚塑性有限元体积成形商品软件Deform3D的计算结果作了比较,验证了本文方法的正确性。