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结合密度阈值和三角形组逼近的点云压缩方法
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作者 钟文彬 孙思 +1 位作者 李旭瑞 刘光帅 《计算机应用》 CSCD 北大核心 2020年第7期2059-2068,共10页
针对非均匀采集点云数据压缩中压缩精度和压缩时间较难权衡的问题,提出一种结合密度阈值和三角形组逼近的压缩方法,并且用八叉树划分得到的非空体素来设置密度阈值以构造三角形组,实现点云表面模拟。首先,根据体素内点的分布确定三角形... 针对非均匀采集点云数据压缩中压缩精度和压缩时间较难权衡的问题,提出一种结合密度阈值和三角形组逼近的压缩方法,并且用八叉树划分得到的非空体素来设置密度阈值以构造三角形组,实现点云表面模拟。首先,根据体素内点的分布确定三角形组的顶点;接着,排序顶点以生成每个三角形;最后,引入密度阈值来构造平行于坐标轴的射线,根据射线与三角形的交点来生成不同密度区域上的细分点。采用dragon、horse、skull、radome、dog和PCB点云数据,对改进区域重心法、曲率压缩法、改进曲率分级法、K近邻长方体法和所提方法进行对比实验。实验结果表明,在相同体素尺寸下,所提方法的特征表达效果优于改进区域重心法;在压缩率接近的情况下,所提方法在时间效率上优于曲率压缩法、改进曲率分级法、K近邻长方体法;在压缩精度上,所提方法所建模型最大偏差、标准偏差和表面积变化率皆低于改进区域重心法、曲率压缩法、改进曲率分级法和K近邻长方体法所建模型。实验结果表明,所提方法在较好地保留特征信息的同时,可在较短的耗时下对点云实现有效压缩。 展开更多
关键词 体素密度 三角形组 点云压缩 非均匀采集点云 八叉树
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一类具有二次自然增长条件的三角形椭圆组弱解的正则性
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作者 麦治本 陈宝耀 《数学物理学报(A辑)》 CSCD 北大核心 1991年第2期154-163,共10页
考虑非线性椭圆组 是有界域 (0.1) 其系数满足下列条件: 当<j时;(三角形条件) (0.2) (0.3) (对角形椭圆性条件)。 (0.4) (二次自然增长条件) (0.5) (0.6) 本文证明当A_(kj)^(αβ)和α_k~αHlder连续时(0.1)
关键词 正则性 三角形椭圆 自然增长条件
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三角形退缩椭园组弱解的全局正侧性
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《Chinese Quarterly Journal of Mathematics》 CSCD 1994年第3期53-68,共16页
In this paper,using direct method,we prove the golbal Hoelder continuiy of teak solutions to degenerate eliptic systems in triangular form.
关键词 三角形退缩椭园 弱解 全局正侧性
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Research on Optimization wharf Structure Type of Triangle frame pier
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作者 ZHOU Yang 《International English Education Research》 2016年第4期97-98,共2页
Based on optimization wharf structure type of triangle flame pier proposed, namely" Spatial triangular flame pier + Big span bent which taking Slant supports" Simulating three-dimensional pier model of a variety of... Based on optimization wharf structure type of triangle flame pier proposed, namely" Spatial triangular flame pier + Big span bent which taking Slant supports" Simulating three-dimensional pier model of a variety of conditions in the actual loading by structural finite element software. Under the guidance of the three-dimensional structure of the most unfavorable load combination algorithm, three-dimensional combination algorithm is applied to the new structure by the MATLAB software programming. Search and calculate the most unfavorable combination of action effects and the corresponding intemal force of the main member, checking the feasibility of the three-dimensional algorithms, Calculating the new wharf structure structural features and stability, Providing numerical reference for the design of this sort of wharf. 展开更多
关键词 The triangle flame pier Slant supports Three-dimensional model Three-dimensional Algorithm
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Triangular Halogen Bond and Hydrogen Bond Supramolecular Complex Consisting of Carbon Tetrabromide, Halide, and Solvent Molecule: A Theoretical and Spectroscopic Study
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作者 Yu-jie Wu Xiao-ran Zhao +1 位作者 Hai-yue Gao Wei-jun Jin 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2014年第3期265-273,共9页
The theoretical calculation and spectroscopic experiments indicate a kind of triangular three bonding supramolecular complexes CBr4…X^-…-H-C, which consist of carbon tetrabromide, halide, and protic solvent molecule... The theoretical calculation and spectroscopic experiments indicate a kind of triangular three bonding supramolecular complexes CBr4…X^-…-H-C, which consist of carbon tetrabromide, halide, and protic solvent molecule (referring to dichloromethane, chloroform and acetonitrile), can be formed in solution. The strength of halogen and hydrogen bonds in the triangular complexes using halide as common acceptor obeys the order of iodide〉bromide〉chloride. The halogen and hydrogen bonds work weak-cooperatively. Charge transfer bands of halogen bonding complexes between CBra and halide are observed in UV-Vis absorption spectroscopy in three solvents, and then the stoichiometry of 1:1, formation constants K and molar extinction coefficients ε of the halogen bonding complexes are obtained by Benesi-Hildebrand method. The K and ε show a dependence on the solvent dielectric constant and, on the whole, obey an order of iodide〉bromide〉chloride in the same solvents. Furthermore, the C-H vibrational frequencies of solvent molecules vary obviously with the addition of halide, which indicates the C-H…X- interaction. The experimental data indicate that the halogen bond and hydrogen bond coexist by sharing a common halide acceptor as predicted by calculation. 展开更多
关键词 Halogen bond Hydrogen bond HALIDE Carbon tetrabromide Charge transfer
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Lie Triple Derivations of the Lie Algebra of Dominant Block Upper Triangular Matrices
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作者 Prakash Ghimire Huajun Huang 《Algebra Colloquium》 SCIE CSCD 2018年第3期475-492,共18页
Let N be the Lie algebra of all n x n dominant block upper triangular matrices over a field F. In this paper, we explicitly describe all Lie triple derivations of N when char(F) ≠ 2. As an application, we character... Let N be the Lie algebra of all n x n dominant block upper triangular matrices over a field F. In this paper, we explicitly describe all Lie triple derivations of N when char(F) ≠ 2. As an application, we characterize Lie derivations of N when char(F) ≠ 2. 展开更多
关键词 Lie triple derivation block upper triangular matrix Lie algebra
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