基于MC算法的医学建模方法与研究

针对现有医学图像特点,提出了一种医学三维建模的新方法.该方法基于传统MC算法,结合种子填充思想进行等值面扩展,并利用DMC方法进行插值位置取代,最后直接连接等值点生成多边形网,从而减少了面片数量,很好的解决了二义性问题.实验表明,该方法较传统方法在拓扑结构、存储空间和处理速度方面均有较大改善.     

MC 算法在 CT 医学图像三维重建中的应用*

MC 算法是三维重建面绘制的经典方法,采用等值面提取的方式把所需的数据分离出来进行重建。通过对 MC 算法的原理进行分析,结合 VTK 类库编程,研究基于 MC 算法提取CT 图像病灶的方法,并通过坐标平滑的方法对算法进行改进,提高三维重建的平滑显示效果和重建速度。     

基于图像分割的三维重构

三维重构方法是医学图像可视化系统、治疗计划系统的重要技术。基于图像分割的三维重构方法结合了图像分割、等值面抽取、网格简化三种技术,是不同于传统Marching Cubes算法的一种三维重构方法。它首先将医学图像分割为二值图,然后利用Marching Cubes方法进行等值面抽取,最后对得到的网格模型进行简化。实验结果表明,基于图像分割的三维重构方法加快了Marching Cubes的运算速度,改善了重构的效果,有利于实现对基于三维重构的大型几何模型的实时绘制和交互。     

基于气象雷达回波3D重建的Marching Cubes改进算法

根据气象雷达回波数据的三维极坐标分布特点,提出一种改进的Marching Cubes三维重建算法.该算法将Marching Cubes常规算法中的单位正立方体构建转换为直接对回波极坐标数据的拟柱体构建,生成相应的等值三角面,并对三角面的顶点数据进行地曲订正,供OpenGL显示.为进一步提高重建算法的效率,该算法避免了对高仰角远距离无回波区的重建.实验表明,该算法有效实现了雷达回波的三维重建.     

Synthesis and characterization of shaped ZnS nanocrystals in water in oil microemulsions

Shaped zinc sulfide nanocrystals were synthesized in W/O microemulsions by using cyclohexane/Triton X-100/n-pentanol/water system. Under different synthetic conditions appearance of two distinct morphologies of ZnS nanocrystals, either cubes or nanowires, was proven by transmission electron microscopy (TEM). The ZnS cubes have an average size of about 25 nm, while the ZnS nanowires have 25 Å diameter and length ranging from several hundred nanometers up to a few microns. The X-ray diffraction analysis (XRD) revealed formation of ZnS with cubic zinc blende crystal structure. Due to two dimensional confinement the exciton of ZnS nanowires is blue shifted compared to the bulk material. Four well-resolved photoluminescence bands in visible spectral region were observed upon excitation of cubic ZnS particles, while in the case of ZnS nanowires emission band was observed at 421 nm. The origin of photoluminescence bands was discussed in details.     

Electron beam induced synthesis of CdSe nanomaterials: Tuning of shapes from rods to cubes

Cadmium selenide (CdSe) nanomaterials of different shapes have been synthesized in the water pool of the water-in-oil microemulsions through 7 MeV electron beam irradiation. The rod shaped CdSe nanomaterials of lengths and breadths up to 1 μm and 200 nm, respectively with aspect ratios from 3 to 5 were grown in the case of microemulsions containing lower water content, water to surfactant concentrations ratio, w₀ = 10. In contrast, the cubic shaped CdSe nanomaterials of dimensions about 100 nm were formed in the microemulsions with higher water contents, w₀ values from 20 to 40. Such a transformation of shape from rod to cube was attributed to the change in the hydrophobicity and hydrophilicity of the micro-environment in the microemulsions. The as-grown CdSe nanomaterials were stable at ambient conditions and thus expected to be very useful in the device applications.     

Exact Isosurfaces for Marching Cubes

In this paper we study the exact contours of a piecewise trilinear scalar field. We show how to represent these contours exactly as trimmed surfaces of triangular rational cubic Bézier patches. As part of this, we introduce an extension of the marching cubes algorithm which gives a topologically exact triangular approximation of the contours for any case. Finally, we modify the exact contours to be globally  G¹  continuous without changing their topologies. We test the algorithm on both theoretical and practical data sets.     

Lossless binary image compression using logic functions and spectra

A lossless compression of images using coding schemes and patterns that include minterm, cube and coordinate data coding, Walsh, triangular and Reed-Muller weights based patterns, Reed-Muller spectra and reference row technique is proposed. The experimental results indicate that the technique is fairly efficient when compared with other methods based on representations of logic functions.     

MC算法与MT算法的比较

三维医学图像表面重建算法是近来的一个研究热点,目前已有多种算法,其中最具代表性的是Marching Cubes(MC)算法和Marching Tetrahedra(MT)算法.本文对这两种算法的实现原理进行了分析比较,给出了实现这两种算法的数据结构,分析了两者的实现过程,并针对具体的实验结果比较了两者的优劣.     

电容层析成像系统三维数据场可视化研究

以油水两相流系统为研究对象，在电容层析成像系统获得的两相流截面相分布数据基础上，对三维数据场可视化最常用的Marching Cubes算法加以改进，将两相流系统的流动、变化过程以可视化形式显示出来，为流动测量、控制提供可视化信息，使工业现场的“黑箱”系统变成透明系统。经仿真实验，可视化效果能形象反映油水两相流系统内部动态变化情况。