Precise 3D image alignment in micro-axial tomography

Micro (µ‐) axial tomography is a challenging technique in microscopy which improves quantitative imaging especially in cytogenetic applications by means of defined sample rotation under the microscope objective. The advantage of µ‐axial tomography is an effective improvement of the precision of distance measurements between point‐like objects. Under certain circumstances, the effective (3D) resolution can be improved by optimized acquisition depending on subsequent, multi‐perspective image recording of the same objects followed by reconstruction methods. This requires, however, a very precise alignment of the tilted views. We present a novel feature‐based image alignment method with a precision better than the full width at half maximum of the point spread function. The features are the positions (centres of gravity) of all fluorescent objects observed in the images (e.g. cell nuclei, fluorescent signals inside cell nuclei, fluorescent beads, etc.). Thus, real alignment precision depends on the localization precision of these objects. The method automatically determines the corresponding objects in subsequently tilted perspectives using a weighted bipartite graph. The optimum transformation function is computed in a least squares manner based on the coordinates of the centres of gravity of the matched objects. The theoretically feasible precision of the method was calculated using computer‐generated data and confirmed by tests on real image series obtained from data sets of 200 nm fluorescent nano‐particles. The advantages of the proposed algorithm are its speed and accuracy, which means that if enough objects are included, the real alignment precision is better than the axial localization precision of a single object. The alignment precision can be assessed directly from the algorithm's output. Thus, the method can be applied not only for image alignment and object matching in tilted view series in order to reconstruct (3D) images, but also to validate the experimental performance (e.g. mechanical precision of the tilting). In practice, the key application of the method is an improvement of the effective spatial (3D) resolution, because the well‐known spatial anisotropy in light microscopy can be overcome. This allows more precise distance measurements between point‐like objects.     

Wheel alignment inspection by 3D point cloud monitoring

Today’s wheel alignment inspection systems adopt various computer vision technologies. They, however, require high-end cameras, precisely manufactured targets, and massive calculation loops because they rely on low-dimensional data (two-dimensional images) for measuring higher-dimensional information (three-dimensional orientation) of the wheel posture. To improve this, a simple and inexpensive method using a consumer-grade depth-sensing camera such as Kinect is presented. It directly utilizes point clouds generated from its range image stream. All points within the region of interest (ROI) contain geometrical information of the wheel and are used for the alignment inspection procedures. Its feasibility is evaluated by examining whether the orientation could be aligned to the desired orientation using only the point cloud data. For verification, a one-wheel-based prototype was implemented, and comparative experiments with an existing commercial system were conducted. The experimental results showed that the proposed method provides satisfactory performance. We believe that the proposed method is feasible for practical usage and has a great potential to be an effective alternative to existing wheel alignment inspection methods.     

Linear and nonlinear methods of 2D signal processing during automated ultrasonic testing

Problems of signal preprocessing as applied to automated ultrasonic testing are considered. Methods for signal processing in the spatial and frequency domains are presented.     

径向锻造三维成形锻透性的数值模拟

根据径向锻造的原理和GFM锻造机万能锤头锻打φ480 mm圆棒料至φ250 mm的工艺参数,采用DEFORM 3D软件对锻造过程进行了数值模拟;并从坯料心部的等效应变状态来研究锻件的锻透性.结果表明:用万能锤头锻打φ480 mm至φ250 mm坯料是可以锻透的,并得到锻透性随压下量的增加而增大的定量关系;同时在相同的压下量时,锻透性随拉打速度增大而减小.     

不锈钢三元叶轮加工效率提升的影响因素分析

三元叶轮是压缩机转子部件最难加工的零件,而加工效率问题一直是三元叶轮制造过程中的难题。本文从几个方面着重分析了影响制约三元叶轮加工效率的关键因素,指出了提高叶轮加工效率应从多方面入手综合考虑各个因素,为今后解决叶轮加工效率问题提供了可行的参考依据。     

The 2D measurement of soot diameter and number density in a diesel engine using laser induced methods

It is necessary to diagnose accurately the characteristics of soot formation and oxidation in a diesel engine. Whereas past measurement techniques for soot concentration give limited information for soot, laser-based two-dimensional imaging diagnostics have a potential to provide temporally and spatially superior resolved measurements of the soot distribution. The technique using laser sheet beam has been applied to an optically accessible diesel engine for the quantitative measurement of soot. The results provided the information for reduction of soot from the diesel engine. Both LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence) techniques were used simultaneously in this study. The images of LIS and LII showed the quantitative distribution of the soot concentration in the diesel engine. In this study, several results were obtained by the simultaneous measurements of LIS and LII technique. The diameter and number density of soot in combustion chamber of the test engine were obtained from ATDC 20 degree to 110 degree. The soot diameter increased about 37% between ATDC 20 degree and 110 degree. The number density of soot, however, decreased significantly between ATDC 40 degree and 70 degree.     

Strul--a method for 3D alignment of single-particle projections based on common line correlation in Fourier space

A central problem of 3D reconstruction in single-particle electron microscopy is the determination of relative orientations of the individual projections contributing to the reconstruction. This article describes an implementation of the method of common lines correlation in Fourier space that allows generation of common lines between an arbitrary number of projections which might posses an arbitrary point group symmetry. Based on this method, it is possible to optimize rotational and translational alignment parameters for individual single-particle projections. The underlying philosophy and details of implementation are discussed, and as an illustration a 3D reconstruction in ice of peroxisomal alcohol oxidase from Pichia pastoris, an octameric assembly with 422-symmetry and a molecular weight of 592 kDa is presented.     

PROTOS2-2卷烟设备效率提升改进研究

针对PROTOS2-2高速卷烟设备生产高档品牌卷烟出现设备堵丝、效率低的问题,进行了研究,提出了解决方案,达到了预期目标.     

“高分二号”上相机和星敏感器相对安装姿态的测量

为了精确测量"高分二号"(GF-2)卫星上相机和星敏感器的相对安装姿态,建立了一套高精度自动化测量系统。针对该系统研究了基于多传感器数据融合的高精度测量算法、基于理论安装数据驱动的自动测量模型、以及基于图像识别的立方镜法线搜索算法。该测量系统主要由二维龙门导轨、精密转台和CCD成像辅助准直的自准直经纬仪构成,通过融合精密转台的转动角度、自准直经纬仪的俯仰角和偏航角等数据计算被测设备安装姿态角度。测量时需先对系统进行标定,制定自动测量规划,然后通过电机驱动使设备自动到达预定位置和角度进行测量。若星上设备安装偏差较大导致被测对象超出自准直经纬仪测量范围时,可启动CCD相机对被测对象局部区域进行搜索识别,并引导自准直经纬仪实现精确准直测量。对测量系统进行了实验验证,结果显示:该系统姿态测量精度可以达到5″,与标准值比对最大偏差为4.1″;该测量系统已用于GF-2卫星的相机和星敏器相对姿态测量中,重复标准差最大为3.5″,满足GF-2对机上设备安装姿态测量精度的需求。     

3D and 2D structural characterization of 1D Al/Al2O3 biphasic nanostructures

1D Al/Al₂O₃ nanostructures have been synthesized by chemical vapour deposition (CVD) of the molecular precursor [^tBuOAlH₂]₂. The deposited nanostructures grow chaotically on the substrate forming a layer with a high porosity (80%). Depending on the deposition time, diverse nanostructured surfaces with different distribution densities were achieved. A three‐dimensional (3D) reconstruction has been evaluated for every nanostructure density using the Focus Ion Beam (FIB) tomography technique and reconstruction software tools. Several structural parameters such as porosity, Euler number, geometrical tortuosity and aspect ratio have been quantified through the analysis with specified software of the reconstructions. Additionally roughness of the prepared surfaces has been characterized at micro‐ and nanoscale using profilometry and AFM techniques, respectively. While high aspects ratio around 20–30 indicates a strong anisotropy in the structure, high porosity values (around 80%) is observed as a consequence of highly tangled geometry of such 1D nanostructures.     

使用二维视觉测头实现三维测量的方法研究

提出了探针扫描和深度聚焦的两种方法,实现了使用二维视觉测头对Z向的测量。两种方法均基于自动聚焦原理。对采集到的图像去噪和聚焦曲线平滑后,使用峰值附近点进行高斯函数拟合,寻找准焦点。根据得到的XYZ向的数据实现三维重构。与接触式测量相比,本文方法Z向测量的最大偏差不到6μm。     

鞋的三维设计与二维展开

该文论述了用计算机辅助设计鞋楦、帮面及其展开的宏观过程。对3D鞋楦及其展开作了详细的描述。对展帮及展帮展楦混合法亦作了介绍。     

Efficiency of grid representation and its algorithms for areal 3D scan data

This paper describes the efficiency of a grid representation for an areal 3D scan data and the algorithms for managing measurement data captured by areal 3D scanners. Due to the measurement principles of areal 3D scanners, a measurement point is generated for each pixel of the imaging sensor inside the 3D scanner. Therefore, when the measurement points are perspectively projected on the image plane of the imaging sensor, each point has one-to-one correspondence to the imaging elements of the sensor that has a regular grid structure. By using this property, measurement points are represented by their depth values in a grid representation model. Compared to the conventional representation model, such as triangular mesh and cloud of points, the grid representation uses less memory and allows efficient algorithms for processing the measurement data captured by areal 3D scanners. This paper was recommended for publication in revised form by Associate Editor Soon Hung Han Minho Chang is a Professor at the department of mechanical engineering at Korea University in Seoul Korea. He received a PhD degree in Mechanical Engineering from MIT in 1996. He worked for Korea Institute of Science and Technology. His research interests include mechanical design, three-dimensional measurement, and CAD. Yun Chan Chung is a Professor in the department of die and mold engineering at Seoul National University of Technology, Korea. He worked for Cubictek and DaimlerChrysler, developing CAD/CAM systems mainly in die and mold making. He received PhD in Industrial Engineering from KAIST in 1996. His research interests include digital manufacturing, tool-path generation and verification, and software engineering.     

产品原型技术反求理论在三元叶轮中的应用

通过对压缩机机组中关键零部件三元叶轮的结构特点进行分析，合理的数据采集、矩阵转换、曲面建模、加工图样数据生成、快速成型等技术的应用，总结出一套典型三元叶轮反求的方法。     

Reconstructing complex 3D objects by a Structured illumination methods

The problem of creating exact 3D models of complex real objects for virtual reality applications is considered. One of the systems reconstructing 3D coordinates of a scene from its 2D image by means of structured illumination is presented. Problems related with system operation and leading to reconstruction errors are described. A new method is proposed for improving performance of the system due to considering optical distortions and using several images for reconstructing the same scene area.     

3D digital image correlation methods for full-field vibration measurement

In the area of modal test/analysis/correlation, significant effort has been expended over the past twenty years in order to make reduced models and to expand test data for correlation and eventual updating of the finite element models. This has been restricted by vibration measurements which are traditionally limited to the location of relatively few applied sensors. Advances in computers and digital imaging technology have allowed 3D digital image correlation (DIC) methods to measure the shape and deformation of a vibrating structure. This technique allows for full-field measurement of structural response, thus providing a wealth of simultaneous test data. This paper presents some preliminary results for the test/analysis/correlation of data measured using the DIC approach along with traditional accelerometers and a scanning laser vibrometer for comparison to a finite element model. The results indicate that all three approaches correlated well with the finite element model and provide validation for the DIC approach for full-field vibration measurement. Some of the advantages and limitations of the technique are presented and discussed.     

利用二维图形进行三维建模的应用研究

在计算机辅助设计(CAD)应用工程中,利用已有的二维工程图进行三雏模型的设计,是一个十分重要的研究内容。文章对此进行了探讨。以叉车的连接支座为例,利用CAXA电子图板把工程图转换成Inventor三维设计软件可以直接输入的文件类型。在Inventor中对其进行处理,提取出特征造型用的轮廓线和几何图元,添加尺寸和约束,在此基础上利用特征造型工具。创建三维零件模型,并进一步以叉车的整车模型为例分析了三维建模中零件装配和仿真分析的有关问题。     

PIC单片机A/D转换数据存储及串口效率

PIC单片机A/D转换后的数据通常需要占用两个8位宽的RAM单元,而PIC单片机的存储单元有限,因此造成了单片机的存储单元不能被有效利用,同时通过串口向上位机传送数据时也需要花费较多的时间.为此提出一种数据打包的方法,使得相同的数据量占用较少的存储空间,并可提高传输效率.     

开式三元叶轮高效率数控粗加工策略

论述了五轴数控粗加工的高效铣削策略和关键技术,对于影响数控粗加工效率的主要因素进行了分析,对于高速钢铣刀和硬质合金铣刀采用侧铣和插铣数控加工方法以及刀具选择进行了简要叙述,并且通过大量三元叶轮实际加工总结了一种面向三元叶轮加工特征、考虑刀具寿命的粗加工策略的原则,使三元叶轮的加工效率大大提高。