Three dimensional reconstruction of coronary arteries from two views

Geometric representation and measurements of localized lumen stenosis of coronary arteries are important considerations in the diagnosis of cardiovascular diseases. This discrete narrowing of the arteries typically impairs blood flow in regions of the heart, and can be present along the entire length of the artery. Three-dimensional (3-D) reconstruction of coronary arterial tree allows clinician to visualize vascular geometry. Three-dimensional representation of tree topology facilitates calculation of hemodynamic measurements to study myocardial infarction and stenosis. The 3-D arterial tree, computed from two views, can provide more information about the tree geometry than individual views. In this paper, a 3-step algorithm for 3-D reconstruction of arterial tree using two standard views is presented. The first step is a multi-resolution segmentation of the coronary vessels followed by medial-axis detection along the entire arterial tree for both views. In the second step, arterial trees from the two views are registered using medial-axis representation at the coarsest resolution level to obtain an initial 3-D reconstruction. This initial reconstruction at the coarsest level is then modified using 3-D geometrical a priori information. In the third step, the modified reconstruction is projected on the next higher-resolution segmented medial-axis representation and an updated reconstruction is obtained at the higher resolution. The process is iterated until the final 3-D reconstruction is obtained at the finest resolution level. Linear programming based constrained optimization method is used for registering two views at the coarse resolution. This is followed by a Tree-Search method for registering detailed branches at higher resolutions. The automated 3-D reconstruction method was evaluated on computer-simulated as well as human angiogram data. Results show that the automated 3-D reconstruction method provided good registration of computer-simulated data. On human angiogram data, the computed 3-D reconstruction matched well with manual registration.     

Three dimensional extension of Bresenham’s Algorithm with Voronoi diagram

Bresenham’s Algorithm for plotting a two-dimensional line segment is elegant and efficient in its deployment of mid-point comparison and integer arithmetic. It is natural to investigate its three-dimensional extensions. In so doing, this paper uncovers the reason for little prior work. The concept of the mid-point in a unit interval generalizes to that of nearest neighbours involving a Voronoi diagram. Algorithmically, there are challenges. While a unit interval in two-dimension becomes a unit square in three-dimension, “squaring” the number of choices in Bresenham’s Algorithm is shown to have difficulties. In this paper, the three-dimensional extension is based on the main idea of Bresenham’s Algorithm of minimum distance between the line and the grid points. The structure of the Voronoi diagram is presented for grid points to which the line may be approximated. The deployment of integer arithmetic and symmetry for the three-dimensional extension of the algorithm to raise the computation efficiency are also investigated.     

牙齿三维数据模型的建立

牙齿的解剖形态学研究是口腔医学的重要基础内容之一。了解和掌握人类牙齿外观形态和内部构造，对口腔医学的各个领域诸如：日腔修复、口腔内科、日脏外科和日腔正畸的教学、临床和科研都是非常必要的。本研究通过对离体恒牙以黑色树脂包埋，用数控磨床每隔２００Ｐｍ间距逐层磨除，拍摄照片并将图象输人计算机的方法，构成了每个牙齿的三维数据模型。该模型可逼真地显示在计算机屏幕上，可从任意选定的角度观察和从任意平面剖开，从而成为易于理解记忆的可视化教材，为日腔医学邻域中牙体解剖学的学习提供了方便的条件。这一系列的数据和相应的牙的图象、精度远高于美国著名的“数据亚当”的颅颌牙列部分，每个牙齿还能被单独地进行处理，能充分满足口腔医学专业的特点和需要。本研究建立的数据牙模型从标本制备到图象输人和三维重建各环节均有创新，为计算机图象图形技术、ＣＡＤ／ＣＡＭ技术、虚拟现实技术在口腔医学邻域中的应用推广奠定了重要基础。     

Graph learning in low dimensional space for graph convolutional networks

Multimedia Tools and Applications - Graph Convolutional Networks (GCNs) recently have been adopted in several feature representation studies for different classification tasks. While many of these...     

用Origin 6.0绘制波函数立体图形

Origin6．0作为一个数学软件平台,具有数据管理与分析、二维及三维函数和离散数据绘图、程序开发等多种功能,广泛用于工程设计和科学研究。本文利用Origin6．0软件的三维函数绘图功能,绘制势箱波函数、氢原子轨道、及其电子云密度函数的立体图形、等值线图和等密度线图。详细给出了各类绘图函数的程序可读化形式、图形及操作过程。该绘图方法操作界面更友好,适用于一般化学化工过程中的三维解析函数可视化。     

基于块空间中低维流形恢复的图像去噪

针对基于块处理的图像去噪,最近出现一种新的假设:真实无噪的图像块在块空间中的分布有一定的规律,即会形成若干个低维流形,而在带噪图像中这些流形受到噪声污染而变形,若能恢复这些低维流形便可去噪.若干真实图像的二维块分布表明了该假设的正确性.接下来根据该假设给出了在块空间中通过复原受噪声污染流形来去噪的一个迭代算法.最后还考察了基于该假设图像去噪的最优化模型,即最小化这些流形所对应矩阵的秩.初步实验表明,该算法能取得良好的去噪效果,与当今最好的去噪算法有可比性.     

Affective rating ranking based on face images in arousal-valence dimensional space

In dimensional affect recognition, the machine learning methods, which are used to model and predict affect, are mostly classification and regression. However, the annotation in the dimensional affect space usually takes the form of a continuous real value which has an ordinal property. The aforementioned methods do not focus on taking advantage of this important information. Therefore, we propose an affective rating ranking framework for affect recognition based on face images in the valence and arousal dimensional space. Our approach can appropriately use the ordinal information among affective ratings which are generated by discretizing continuous annotations. Specifically, we first train a series of basic cost-sensitive binary classifiers, each of which uses all samples relabeled according to the comparison results between corresponding ratings and a given rank of a binary classifier. We obtain the final affective ratings by aggregating the outputs of binary classifiers. By comparing the experimental results with the baseline and deep learning based classification and regression methods on the benchmarking database of the AVEC 2015 Challenge and the selected subset of SEMAINE database, we find that our ordinal ranking method is effective in both arousal and valence dimensions.     

2-芳基苯并噁唑衍生物的三维定量构效关系研究

溶血磷脂酸酰基转移酶-β(LPAAT-β)是肿瘤治疗的新靶点,2-芳基苯并噁唑衍生物是最近发现的LPAAT-β抑制剂,可以选择性抑制LPAAT-β的活性,从而抑制肿瘤细胞的增殖。本文运用比较分子力场分析(CoMFA)建立了2-芳基苯并噁唑LPAAT-β抑制剂的三维定量构效关系(3D-QSAR)模型,考察了网格步长对模型的影响。优化后的模型交叉验证系数q~2=0.626,最佳主成分数为3,传统的相关系数r~2=0.933,统计方差比F=102.391。该模型对训练集和测试集化合物进行预测,预测值和实验值非常接近,表明模型具有很好的预测能力。该模型显示立体场和静电场对生物活性的贡献分别为59.5%和40.5%。CoMFA模型的三维等值图可为改造化合物结构提供理论依据。     

Three dimensional finite element analysis of damage accumulation in composite laminate

A three dimensional finite-element computer program has been developed to analyze layered fiber-reinforced composite laminate. This program is capable of: (1) calculating the detailed stress distribution, (2) identifying the damage zone and mode of failure, (3) analyzing the damage accumulation, and (4) determining the ultimate strength of the composite laminate.     

Three dimensional dynamic motor performance of the normal trunk

Traditionally, human strength has been described in terms of the maximum force one could exert under isometric conditions. However, in the past decade ergonomists have attempted to find strength measures that better represent the dynamic aspects of occupational tasks. Recent efforts have focussed upon dynamic motor performance capabilities of the human body that go beyond the traditional measures of isometric strength. The objective of this study was to document the three dimensional dynamic motor performance capabilities of the normal human trunk as subjects flexed and extended their trunks as fast as they could under 'sagittaly symmetric and asymmetric “back lifting” conditions. The results indicated that the range of motion, trunk angular velocity and trunk angular acceleration decreased in the sagittal plane as the trunk became more asymmetric. Dynamic motor performance characteristics increased in the frontal and transverse planes as the trunk became more asymmetric, however, these differences were also dependent upon the device used to measure trunk motor performance.     

撞击流反应器内气固两相流动的数值模拟

采用标准k-ε湍流模型和颗粒轨道模型模拟了水平撞击流反应器内的气相流场和颗粒运动,实验采用压力计和PV4A光纤速度测量仪测量了整体压力损失和颗粒沿喷嘴轴线的速度变化,模拟得到的规律和实验结果基本吻合。通过模拟还得到了单侧颗粒进料时的颗粒运动特征、颗粒的最大渗透深度和平均飞行时间等信息。结果表明,撞击区域集中在2～3倍喷嘴直径范围之内,气流场的速度和压力呈对称分布,颗粒进入反向气流后速度急剧衰减,最大渗透深度约为喷嘴直径的2倍,颗粒的平均飞行时间在0.7 s～1.8 s之间。随着喷嘴气流速度的增加,颗粒物料更容易被气流带走。     

Finite dimensional approximation and Newton-based algorithm for stochastic approximation in Hilbert space

This paper presents a finite dimensional approach to stochastic approximation in infinite dimensional Hilbert space. The problem was motivated by applications in the field of stochastic programming wherein we minimize a convex function defined on a Hilbert space. We define a finite dimensional approximation to the Hilbert space minimizer. A justification is provided for this finite dimensional approximation. Estimates of the dimensionality needed are also provided. The algorithm presented is a two time-scale Newton-based stochastic approximation scheme that lives in this finite dimensional space. Since the finite dimensional problem can be prohibitively large dimensional, we operate our Newton scheme in a projected, randomly chosen smaller dimensional subspace.     

On computing the diameter of a point set in high dimensional Euclidean space

We consider the problem of computing the diameter of a set of n points in d-dimensional Euclidean space under Euclidean distance function. We describe an algorithm that in time O(dnlogn+n²) finds with high probability an arbitrarily close approximation of the diameter. For large values of d the complexity bound of our algorithm is a substantial improvement over the complexity bounds of previously known exact algorithms. Computing and approximating the diameter are fundamental primitives in high dimensional computational geometry and find practical application, for example, in clustering operations for image databases.     

Error estimation in reconstruction of quadratic curves in 3D space

Many natural and man-made objects have planar and curvilinear surfaces. The images of such curves do not usually have sufficient distinctive features to apply conventional feature-based reconstruction algorithms. In this paper, we describe a method for the reconstruction of various kinds of quadratic curves in 3D space as an intersection of two cones containing the respective projected digitized curve images in the presence of Gaussian noise. The advantage of this method is that it overcomes the correspondence problem that occurs in pairs of projections of the curve. Using nonlinear least-squares curve fitting, the parameters of a curve in 2D digitized image planes are determined. From this we reconstruct the 3D quadratic curve. Relevant mathematical formulations and analytical solutions for obtaining the equation of the reconstructed curve are given. Simulation studies have been conducted to observe the effect of noise on errors in the process of reconstruction. Results for various types of quadratic curves are presented using simulation studies. These are the main contributions of this work. The angle between the reconstructed and the original quadratic curves in 3D space has been used as the criterion for the measurement of the error. The results of this study are useful for the design of a stereo-based imaging system (such as the LBW decision in cricket, the path of a missile, robotic vision, path planning, etc.) and for the best reconstruction with minimum error.     

Three dimensional finite element analysis of layered fiber-reinforced composite materials

A three-dimensional finite element analysis was performed for a biaxially loaded composite laminate (with a centered hole) consisting of several fiber-reinforced composite layers each with a specified fiber orientation. The detailed stress distribution around the hole was determined. Also, the locations of initial damage zones due to different failure mechanisms were indicated.     

Two parallel algorithms for the convex hull problem in a two dimensional space

Two parallel algorithms for determining the convex hull of a set of data points in two dimensional space are presented. Both are suitable for MIMD parallel systems. The first is based on the strategy of divide-and-conquer, in which some simplest convex-hulls are generated first and then the final convex hull of all points is achieved by the processes of merging 2 sub-convex hulls. The second algorithm is by the process of picking up the points that are necessarily in the convex hull and discarding the points that are definitely not in the convex hull. Experimental results on a MIMD parallel system of 4 processors are analysed and presented.