Shape reconstruction of parallelogram flaw

To reconstruct the shape of the scatterer in elastic media, the authors deduce the Born approximation solution of the two-dimensional scattering problem, which includes the shape factor that embodies all information about the shape of the scatterer. Accordingly, the change in the shape of the scatterer only necessitates the number of the corresponding new shape factors. For a parallelogram void in a long Al rod, its shape factor can be obtained. In view of the definition of a characteristic function, the shape factor has a corresponding integral representation. Obviously, the shape factor can be considered as a Fourier transform of the characteristic function, which is reconstructed from the inverse Fourier transform. The integral equation is considered as the basic equation to reconstruct the shape of the scatterer. The identification of the geometrical character of a flaw is then given by the two dimensional inverse Born approximation in a low-frequency range. For the parallelogram void, a theoretical calculating identification is performed. At the same time, the numerical results are obtained by the finite element method.     

Shape reconstruction of mixed type void flaws using Born inversion method

We study an approximate technique for determining the shapes of mixed type void flaws in elastic media from knowledge of the ultrasonic scattering amplitudes. It is well known that the technique is highly effective under weak scattering conditions. In the paper, two cement paste cylindrical specimens with mixed type void flaws are prepared and ultrasonic measurements are carried out by experimental means. The measurement area is restricted in the plane perpendicular to the axis of cylindrical specimen. The measured wave data are fed into the approximate technique formula—the Born inversion method and cross-sectional image is obtained. We find that good results have been obtained for strong scattering void flaws such as mixed type void flaws in cement paste cylindrical specimens.     

Shape Reconstruction from Unorganized Points Using Voronoi Diagrams

Given only a set of points, without any geometric information such as the adjacency among the points, the scanning order or the scanning direction, it is a difficult problem to reconstruct a surface model corresponding to the original shape. For the reconstruction of open shapes, many effective approaches have been proposed. It is, however, hard to find a robust and effective method for the reconstruction of closed shapes. In this paper, an algorithm is proposed to reconstruct a three-dimensional closed shape from a set of good sample points using the properties of Delaunay triangulation and Voronoi diagrams. The proposed method consists of three steps; (1) constructing a convex hull consisting of mutually exclusive tetrahedra by 3D Delaunay triangulation of input points, (2) generating a Voronoi diagram of input points by utilising the properties of Delaunay triangulation, and (3) extracting the triangles on the shape boundary, defined by input points, after selecting the tetrahedra which are contained inside the shape using the properties of Voronoi diagrams. The proposed method in this paper has some advantages compared to the previous approaches. First, the distance parameter, such as α in the α-shape approach, is not required in the proposed approach. The determination of a proper parameter by trial and error is not appropriate, especially in the automation of shape reconstruction. Secondly, the time complexity of the proposed approach is O(n) since, in a single pass, this algorithm determines whether each tetrahedron is located inside or outside the shape boundary. ID="A1"Correspondance and offprint requests to: Dr K. S. Kim, Department of Industrial Engineering, Pohang University of Science and Technology, San 31, Hyojadong, Pohang, 790–784, Korea. E-mail: kskim@postech.ac.kr     

用二维逆Born近似法对杆中混合型缺陷的重构

为了重构弹性介质中缺陷的形状,本文在三维弹性波散射问题的Born近似解基础上,进一步分析了在纵波入射条件下二维散射问题的Born近似解,对铝质长杆中的混合型空穴缺陷的散射场情况进行了对比分析;最后,提出了在低频下识别缺陷几何特征的二维逆Born近似法,并用此法对铝质长杆中的混合型空穴缺陷作了计算机模拟.     

三维误差的分解与重建

在分析小波变换理论的基础上 ,提出采用小波变换方法对三维误差进行去噪处理和三维误差的重建 ,获得剔除随机误差和高频误差的周期性三维误差 ,实现有用信息的提取 ,从而为误差的分离和可补偿研究提供补偿依据。     

镗削内孔形状误差的诊断

在具备精密镗削的工艺条件下，工件仍出现精度超差现象，本文给出了这类问题探源方法和实例。     

逆向工程中扫描数据点的曲面重构

针对三维扫描数据点的曲面重构技术在实际系统中的应用,提出了一种以B样条曲面为基础的曲面构造算法。已知数据点按简明行方式排列,算法产生一个连续的B样条曲面,该曲面的参数化过程不受每行数据点分布的影响。根据所传递的候选节点矢量,采用柔性间距选择,有效地减少了控制顶点数,同时应用三维图形标准以及图形函数库,在VC 6．0平台上完成了该软件的编制。通过实际系统应用验证,该算法改进了传统曲面重构方法在处理非均匀扫描数据点时曲线曲面形状的失真和运算的不稳定现象,计算简单,易于编程实现。     

形状记忆合金的应用

形状记忆合金是一种新型的功能材料，目前在许多领域都得到了应用。本文首先讨论了SMA材料的形状记忆原理，针对现行损伤模拟方法无法模拟结构损伤形成积累过程的不足之处，提出了将形状记忆合金SMA材料应用于损伤可控构件制作的方法，并介绍了形状记忆合金在机械、工程、电子以及医学领域的应用，并对前景作了分析。     

Morphometrical study of plant vacuolar dynamics in single cells using three-dimensional reconstruction from optical sections

In higher plants, vacuoles increase their volumes in accordance with cell enlargement and occupy most of the cell volume. However, quantitative analyses of vacuolar contributions during changes in cell morphology have been hampered by the inadequacies and frequent artifacts associated with current three-dimensional (3-D) reconstruction methods of images derived from light microscopy. To overcome the limitations of quantifying 3-D structures, we have introduced 3-D morphometrics into light microscopy, adopting a contour-based approach for which we have developed an interpolation method. Using this software, named REANT, the morphological and morphometrical changes in protoplasts and vacuoles during plasmolysis could be investigated. We employed the tobacco (Nicotiana tabacum) BY-2 cell line No.7, expressing a GFP-AtVam3p fusion protein, BY-GV7, using GFP as a marker of vacuolar membranes (VMs). By vital staining of the plasma membrane (PM) of cells, we simultaneously obtained optical sections of both the PM and VM. We, therefore, reconstructed the 3-D structures of protoplasts and vacuoles before and after plasmolysis. We were able to identify the appearance of elliptical structures of VMs in the vacuolar lumen, and to determine that they were derived from cytoplasmic strands. From the 3-D structures, the volumes and surface areas were measured at the single cell level. The shrinkage of vacuoles accounted for most of the decrease in protoplast volume, while the surface area of the vacuoles remained mostly unchanged. These morphometrical analyses suggest that the elliptical structures are reservoirs for excess VMs that result from the response to rapid decreases in vacuolar and protoplast volumes.     

Computer reconstruction of nucleolar architecture by interactive three-dimensional color display

The first complete three dimensional ultrastructural reconstruction of pancreatic cell nucleoli, was done using EM and computer 3D-assisted reconstruction of serial sections with interactive 3D back-to-front and color display methods based on voxel representation. The purpose of the study was to depict the architecture of the nucleolar components. We obtained information about the location of the nucleolus within the nuclear volume and about the shape and polarity of the 3 main nucleolar territories.     

基于明暗恢复形状的目标物体深度信息提取算法设计

明暗恢复形状的方法（shape from shading简称SFS）分为全局最小化法、全局演化法、局部分析法、局部线性化法,但这4种方法都有一定的局限性,故在参考局部分析法的基础上,提出了基于明暗恢复形状的目标物体深度信息提取的简单算法。’     

徒手设计效果图的三维重建技术研究

将徒手设计效果图,根据透视图的基本原理、应用数据融合算法进行透视反求,分析计算确定透视条件,实现二维信息到三维信息的转化,从而进行三维重建.     

Cryo-electron microscopy and three-dimensional reconstruction of actin filaments

Actin filaments have been examined by electron microscopy whilst in a frozen-hydrated state. Filaments embedded in a vitreous water layer are basically similar to those prepared by negative staining and show characteristic helical substructure, where the pitches of the helices are about 70 nm and 6 nm. Variability in spacing between long pitch helix cross-over points has been observed, which is consistent with intrinsic angular disorder between successive filament subunits. Fourier transforms of the most ordered filaments show four strong layer lines that index as the first, fifth, sixth and seventh orders of a 35 nm repeat. A three-dimensional helical reconstruction, calculated to a resolution of about 4 nm, shows the individual subunits to be orientated with their long axes roughly perpendicular to the filament axis. Each subunit is somewhat curved and is resolved into two domains. Most connections between successive subunits appear to be made close to the filament axis. We also report on the performance of the specimen holder (Philips PW 5699) used in this work.     

Principles of Shape from Specular Reflection

The reconstruction of (partially) specular object by means of deflectometric methods is a challenging task. It has a long and fairly branched history within the metrology and machine vision communities. We are not aware of any scientific publication surveying the state of the art in a unifying manner and thus stimulating further research. This contribution is intended to close this gap, bringing together prominent ideas from both fields. In avoidance of unnecessary technicality, we lay out the basic theory, including all known forward models of the reflection process. The corresponding inverse problem is ill-posed, so that special emphasis is put on the question of regularization. We embed some novel results on the uniqueness problem and the effectiveness of regularization approaches. Also an overview of numerical methods related to Shape from Specular Reflection is given. For the sake of completeness, we share some thoughts on the construction of an actual measurement system and discuss a practical example.     

The interpolation of fourier transform data in tilted-view three-dimensional reconstruction

A method is described for interpolating the unevenly sampled Fourier transform data on lattice lines, collected during a tilted-view three-dimensional reconstruction of a plane lattice specimen, onto equally spaced sample points. The method performs local averaging of noisy data and inserts values into gaps in the data which are consistent with the spatial boundedness of the specimen. The method can be implemented computationally using a simple algorithm.     

曲面反求中测量数据人机交互合成及优化

提出了一种简单而直观的测量数据合成算法———人机交互法。通过人机交互的方法对三维图形进行平移和旋转变换而与另一个图形进行拼合,从而实现测量数据的合成,并能对合成后的数据进行优化处理。实例证明,该方法具有操作简单、精度较高等特点,该方法已成功地应用于三维快速测量系统。     

Study of the direct Fourier method for the three-dimensional reconstruction of objects in the case of a missing angular data range

Some practical and theoretical considerations on the three-dimensional reconstruction of an object from its two-dimensional projections by the direct Fourier method have been obtained using computer generated images. The procedure applied has been designed to study the specific problems derived from the collection of images in transmission electron microscopes (TEM), making special emphasis on images of biological objects. The study of the calculated point spread function (PSF) of the experimental system and the mean and variance profiles of the reconstructions have provided useful criteria to assess the quality and the interpretability of three-dimensional reconstructions of real data.     

Automatic 3D model reconstruction of the diamond object

This paper addresses the problems presented by automatic 3D modeling and measurement in evaluating the diamond-cutting grade of the round brilliant cut diamond. (In this paper, we refer to the round brilliant cut diamond, the most common diamond, unless otherwise specified.) Diamond features such as small size (most are less than 1 cm), lack of texture, highlights, and light transmission intensify these problems, and commonly used methods in computer vision such as laser triangulation, structured light, stereo matching, and shape from shading fail to generate the diamond’s 3D model. Based on the image features of the diamond and the polishing process of the rough diamond, this paper proposes a “shape from multi-view closed contours” (SFMCC) method. First, the diamond is placed on a turntable, and a single CCD camera with one telecentric lens captures silhouette images from multiple views as the turntable rotates. Next, accurate closed contours are extracted from the silhouette images sequence, and a 3D model of the diamond can be retrieved through the space-carving process of the bounding box with multi-view closed contours. To implement the SFMCC method, a complete system including hardware and software is designed and constructed. Many different experiments have been designed to test this method, and results have proven its high efficiency and accuracy.     

Computer-assisted three-dimensional reconstruction technology in plant cell image analysis: applications of interactive computer graphics

Sequences of more than 100 serial thin sections were cut of entire generative cells of pollen of Brassica campestris. Using transmission electron micrographs, outlines of the cell nucleus, vacuoles and mitochondria were digitized and stored on disc using the Carl Zeiss-Kontron Videoplan Image Analysis System. The data collected concerned the geometry of cuts and logical collection of cuts into structures, both internal and external. A data translation and surface generation system was established to transfer these data to a VAX-751 computer to establish an interface to the Intergraph's Interactive Graphics Design System (IGDS). Definition of the surfaces is based on the translated boundaries and structural configuration, enabling three-dimensional visualization of: (a) the wireframe model; (b) the overall model with removed hidden lines, including colour or monochrome shading; and (c) the shaded image of the internal structures with superimposed wireframe representation of the external structures.     

LIP-model-based three-dimensional reconstruction and visualization of HIV-infected entire cells

This paper presents a global solution from acquisition to visualization for the three-dimensional reconstruction of cell sections. Original techniques are proposed for the correct handling of the geometrical section distortions, and a new interpretation based on the logarithmic image processing (LIP) model is applied in order to create normalized grey-level sections where these are missing. Finally, a new method for generating a mesh of triangles to describe the envelope of the reconstructed cell is proposed, as well as a visualization mixing image synthesis and grey-level information. The product allows the user to explore the reconstructed cellular block in any desired direction, by showing user-defined grey-level sections inside the block mixed to a synthetic view of the cell envelope.