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带法向约束的圆平均非线性细分曲线设计
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作者 刘艳 寿华好 季康松 《中国图象图形学报》 CSCD 北大核心 2023年第2期556-569,共14页
目的对采样设备获取的测量数据进行拟合,可实现原模型的重建及功能恢复。但有些情况下,获取的数据点不仅包含位置信息,还包含法向量信息。针对这一问题,本文提出了基于圆平均的双参数4点binary非线性细分法与单参数3点ternary插值非线... 目的对采样设备获取的测量数据进行拟合,可实现原模型的重建及功能恢复。但有些情况下,获取的数据点不仅包含位置信息,还包含法向量信息。针对这一问题,本文提出了基于圆平均的双参数4点binary非线性细分法与单参数3点ternary插值非线性细分法。方法首先将线性细分法改写为点的重复binary线性平均,然后用圆平均代替相应的线性平均,最后用加权测地线平均计算的法向量作为新插入顶点的法向量。基于圆平均的双参数4点binary细分法的每一次细分过程可分为偏移步与张力步。基于圆平均的单参数3点ternary细分法的每一次细分过程可分为左插步、插值步与右插步。结果对于本文方法的收敛性与C1连续性条件给出了理论证明;数值实验表明,与相应的线性细分相比,本文方法生成的曲线更光滑且具有圆的再生力,可以较好地实现3个封闭曲线重建。结论本文方法可以在带法向量的初始控制顶点较少的情况下,较好地实现带法向约束的离散点集的曲线重建问题。 展开更多
关键词 线性细分 圆平均 加权测地线平均 点—法向量对 法向约束
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基于法向量的非线性逼近型细分格式
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作者 赵欢喜 陈紫薇 许玲玲 《计算机工程》 CAS CSCD 北大核心 2011年第1期215-217,共3页
提出一种二进制的几何非线性逼近型细分格式。在该格式中,新点不全是旧点的线性组合,其中一个新点是通过在法向量方向偏移所产生,且法向量在每次细分中能自适应计算。引入一些参数来控制细分过程,且参数对曲线形状的影响是局部的。实例... 提出一种二进制的几何非线性逼近型细分格式。在该格式中,新点不全是旧点的线性组合,其中一个新点是通过在法向量方向偏移所产生,且法向量在每次细分中能自适应计算。引入一些参数来控制细分过程,且参数对曲线形状的影响是局部的。实例证明,通过选择适当的参数值,产生的细分曲线具有保凸性和G1连续性。 展开更多
关键词 线性细分 逼近型 法向量 保凸
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一种基于切向量的非线性ternary插值细分法
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作者 宋倩 《纺织高校基础科学学报》 CAS 2014年第1期125-129,共5页
针对光滑曲线的构造,提出了一种基于切向量的非线性ternary插值细分方法.该细分法通过沿相邻两点的切向量方向产生偏移量来计算新点,其中偏移量可由参数进行控制.文中对该细分格式的性质进行了分析.结果表明该细分格式生成的极限曲线具... 针对光滑曲线的构造,提出了一种基于切向量的非线性ternary插值细分方法.该细分法通过沿相邻两点的切向量方向产生偏移量来计算新点,其中偏移量可由参数进行控制.文中对该细分格式的性质进行了分析.结果表明该细分格式生成的极限曲线具有G1连续性和保凸性,且在参数合适的取值范围内,极限曲线可以避免自交. 展开更多
关键词 线性细分 切向量 保凸性
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内心细分法的一个变式 被引量:2
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作者 李亚娟 邓重阳 《计算机辅助设计与图形学学报》 EI CSCD 北大核心 2012年第12期1542-1548,共7页
内心细分法中,临时切向调整的方法比较复杂,且几何意义不明显,为此给出了内心细分法的一个变式.给定初始点列及其切向,内心细分法的每一个细分步骤分为2个阶段:首先根据老点和切向确定新点及其临时切向,然后调整临时切向用于下一步细分... 内心细分法中,临时切向调整的方法比较复杂,且几何意义不明显,为此给出了内心细分法的一个变式.给定初始点列及其切向,内心细分法的每一个细分步骤分为2个阶段:首先根据老点和切向确定新点及其临时切向,然后调整临时切向用于下一步细分.文中给出了调整切向的新方法,使切向计算更简单、几何意义更明显.最后通过大量的数值实例验证了极限曲线的G2连续性及光顺性与细分参数选择之间的关系. 展开更多
关键词 线性细分方法 曲线插值 保形 保圆
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基于改进Loop细分的二维图像矢量化方法 被引量:2
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作者 邓重阳 熊玉丹 +2 位作者 郑乐豪 曹晨妤 朱明超 《杭州电子科技大学学报(自然科学版)》 2020年第2期52-55,共4页
现有的矢量化方法得到的矢量图缩放不方便,为此,用改进的Loop细分方法实现二维图像矢量化。首先用Douglas-Peucker算法提取图像边界,然后用Delaunay三角剖分算法得到三角网格,最后用改进的Loop细分算法细分三角网格得到矢量图。细分时,... 现有的矢量化方法得到的矢量图缩放不方便,为此,用改进的Loop细分方法实现二维图像矢量化。首先用Douglas-Peucker算法提取图像边界,然后用Delaunay三角剖分算法得到三角网格,最后用改进的Loop细分算法细分三角网格得到矢量图。细分时,对三角网格顶点进行线性细分,对顶点的像素值进行Loop细分,同时,在原有Loop细分规则的基础上,修改网格边界上的三角形内部新点生成规则。实验结果表明:提出的矢量化方法得到的矢量图缩放较为方便。 展开更多
关键词 图像矢量化 DOUGLAS-PEUCKER算法 DELAUNAY三角剖分 线性细分 LOOP细分
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基于多级细分的彩色模型表面体素化算法
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作者 王莉 张祥云 周正友 《计算机集成制造系统》 EI CSCD 北大核心 2022年第11期3652-3663,共12页
为充分发挥增材制造技术的体素级成型优势,实现多材料/多色彩模型的快速成型,提出一种彩色模型高精度体素化算法。该算法均匀细分三角面片,生成足够密集的点云数据,确保较小体素阈值对应的体素模型的表面能够完全封闭。针对模型包围盒... 为充分发挥增材制造技术的体素级成型优势,实现多材料/多色彩模型的快速成型,提出一种彩色模型高精度体素化算法。该算法均匀细分三角面片,生成足够密集的点云数据,确保较小体素阈值对应的体素模型的表面能够完全封闭。针对模型包围盒形状对体素模型精度的影响,在八叉树体素化表示的基础上,提出了基于边长比值的体素线性细分方法,极大地提高了体素模型的表面精度。通过编程实例证明了该算法能够实现三维彩色模型的高分辨率体素化,体素化模型满足聚合物喷射工艺的精度需求。 展开更多
关键词 增材制造 表面体素化 三角形加密 八叉树 线性细分
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一种新型实现高倍编码器细分的软件设计 被引量:4
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作者 贺传敏 杨健武 《电子测量技术》 2008年第8期143-146,共4页
在光栅编码器细分程序设计中的细分位移计算部分,通常使用的方法是通过把2个信号采样值相除变换为求反正切的形式,再求出角度值。介绍一种软件实现的求光栅编码器细分角度的方法,如果计算角度细分可根据直线关系算出来的话,细分计算会... 在光栅编码器细分程序设计中的细分位移计算部分,通常使用的方法是通过把2个信号采样值相除变换为求反正切的形式,再求出角度值。介绍一种软件实现的求光栅编码器细分角度的方法,如果计算角度细分可根据直线关系算出来的话,细分计算会更加简单直观。文中特别说明了编写软件时应当注意的问题。使用该方法,可以提高细分计算的效率和精确度。并且在TI的DSP控制器TMS320F2812上实现并验证了该方法。在文中也给出了Matlab仿真结果及实验测试结果,从实际使用情况看来,同理论的假设仿真结果基本相符,因此是可行的。 展开更多
关键词 线性关系实现细分计算 锯齿波信号的补偿 细分位置象限区间的划分与判定
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小视场环境下三维立体测量技术 被引量:3
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作者 刘笑 仲思东 +1 位作者 隋莉斌 刘勇 《工程图学学报》 CSCD 北大核心 2005年第2期132-136,共5页
介绍了传统的基于摄像机内外参数获得空间三维信息的方法;并通过建立空间三维点阵与像面空间映射关系,提出一种新的获得三维信息的方法,该方法不用求解摄像机的任何内外参数。在小视场范围内验证了两种方法的精度,分析了两种方法的优缺... 介绍了传统的基于摄像机内外参数获得空间三维信息的方法;并通过建立空间三维点阵与像面空间映射关系,提出一种新的获得三维信息的方法,该方法不用求解摄像机的任何内外参数。在小视场范围内验证了两种方法的精度,分析了两种方法的优缺点。试验表明后一种方法的精度比较高,说明了它的可行性和适用范围。 展开更多
关键词 计算机应用 立体测量技术 摄像机内外参数 空间三维网格场 线性细分
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Kernelized fourth quantification theory for mineral target prediction
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作者 CHEN Yongliang LI Xuebin LIN Nan 《Global Geology》 2011年第4期265-278,共14页
This paper presents a nonlinear multidimensional scaling model, called kernelized fourth quantifica- tion theory, which is an integration of kernel techniques and the fourth quantification theory. The model can deal w... This paper presents a nonlinear multidimensional scaling model, called kernelized fourth quantifica- tion theory, which is an integration of kernel techniques and the fourth quantification theory. The model can deal with the problem of mineral prediction without defining a training area. In mineral target prediction, the pre-defined statistical cells, such as grid cells, can be implicitly transformed using kernel techniques from input space to a high-dimensional feature space, where the nonlinearly separable clusters in the input space are ex- pected to be linearly separable. Then, the transformed cells in the feature space are mapped by the fourth quan- tifieation theory onto a low-dimensional scaling space, where the sealed cells can be visually clustered according to their spatial locations. At the same time, those cells, which are far away from the cluster center of the majority of the sealed cells, are recognized as anomaly cells. Finally, whether the anomaly cells can serve as mineral potential target cells can be tested by spatially superimposing the known mineral occurrences onto the anomaly ceils. A case study shows that nearly all the known mineral occurrences spatially coincide with the anomaly cells with nearly the smallest scaled coordinates in one-dimensional sealing space. In the case study, the mineral target cells delineated by the new model are similar to those predicted by the well-known WofE model. 展开更多
关键词 kernel function feature space fourth quantification theory nonlinear transformation mineral target prediction
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Influence and Local Influence for Explained Variation in Survival Analysis
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作者 Refah Alotaibi 《Journal of Mathematics and System Science》 2014年第8期523-545,共23页
The amount of explained variation R2 is an overall measure used to quantify the information in a model and especially how useful the model might be when predicting future observations, explained variation is useful in... The amount of explained variation R2 is an overall measure used to quantify the information in a model and especially how useful the model might be when predicting future observations, explained variation is useful in guiding model choice for all types of predictive regression models, including linear and generalized linear models and survival analysis. In this work we consider how individual observations in a data set can influence the value of various R2 measures proposed for survival analysis including local influence to assess mathematically the effect of small changes. We discuss methodologies for assessing influence on Graf et al.'s R2G measure, Harrell's C-index and Nagelkerke's R2N. The ideas are illustrated on data on 1391 patients diagnosed with Diffuse Large B-cell Lymphoma (DLBCL), a major subtype ofNon-Hodgkin's Lymphoma (NHL). 展开更多
关键词 INFLUENCE local influence C-index explained variation.
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A reliable analysis of oxygen diffusion in a spherical cell with nonlinear oxygen uptake kinetics 被引量:2
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作者 Randolph Rach Abdul-Majid Wazwaz Jun-Sheng Duan 《International Journal of Biomathematics》 2014年第2期165-176,共12页
In this paper, we investigate the diffusion of oxygen in a spherical cell including nonlin- ear uptake kinetics. The Lane-Emden boundary value problem with Michaelis-Menten kinetics is used to model the dimensionless ... In this paper, we investigate the diffusion of oxygen in a spherical cell including nonlin- ear uptake kinetics. The Lane-Emden boundary value problem with Michaelis-Menten kinetics is used to model the dimensionless oxygen concentration in our analysis. We first convert the Lane-Emden equation to the equivalent Volterra integral form that incorporates the boundary condition at the cell's center, but which still leaves one unknown constant of integration, as an intermediate step. Next we evaluate the Volterra integral form of the concentration and its flux at the cell membrane and substitute them into the remaining boundary condition to determine the unknown constant of integration by appropriate algebraic manipulations. Upon substitution we have converted the equivalent Volterra integral form to the equivalent Fredholm Volterra integral form, and use the Duan Rach modified recursion scheme to effectively decompose the unknown constant of integration by formula. The Adomian decomposition method is then applied to solve the equivalent nonlinear Fredholm-Volterra integral representation of the LaneEmden model for the concentration of oxygen within the spherical cell. Our approach shows enhancements over existing techniques. 展开更多
关键词 Oxygen diffusion Volterra integral form Michaelis-Menten kinetics Adomian decomposition method Adomian polynomials.
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Oscillatory blood flow through a capillary in presence of thermal radiation 被引量:1
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作者 A. Sinha G. C. Shit 《International Journal of Biomathematics》 2015年第1期181-199,共19页
This paper deals with the theoretical investigation of a fundamental problem of magne- tohydrodynamic (MHD) flow of blood in a capillary in the presence of thermal radiation and chemical reaction. The unsteadiness i... This paper deals with the theoretical investigation of a fundamental problem of magne- tohydrodynamic (MHD) flow of blood in a capillary in the presence of thermal radiation and chemical reaction. The unsteadiness in the flow and temperature fields is caused by the time-dependence of the stretching velocity and the surface temperature. The fluid is considered to be non-Newtonian, whose flow is governed by the equation of a third-order fluid. The problem is first reduced to solving a system of coupled nonlinear differential equations involving several parameters. Considering blood as an electrically conducting fluid and using the present analysis, an attempt is made to compute some parameters of the blood flow by developing a suitable numerical method and by devising an appropri- ate finite difference scheme. The computational results are presented in graphical form, and thereby some theoretical predictions are made with respect to the hemodynamical flow of the blood in a hyperthermal state under the action of a magnetic field. Com- putational results for the variation in velocity, temperature, concentration, skin-friction coefi^icient, Nusselt number and Sherwood number are presented in graphical/tabular form. Since the study takes care of thermal radiation in blood flow, the results reported here are likely to have an important bearing on the therapeutic procedure of hyperthermia, particularly in understanding blood flow and heat transfer in capillaries. 展开更多
关键词 Third-order fluid stretching wall thermal radiation oscillatory motion
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On a non-autonomous reaction-convection diffusion model to study the bacteria distribution in a river 被引量:1
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作者 Imene Meriem Mostefaoui Ali Moussaoui 《International Journal of Biomathematics》 2017年第6期25-49,共25页
In this paper, we propose a non-autonomous convection-reaction diffusion system (CDI) with a nonlinear reaction source function. This model refers to the quantification and the distribution of antibiotic resistant b... In this paper, we propose a non-autonomous convection-reaction diffusion system (CDI) with a nonlinear reaction source function. This model refers to the quantification and the distribution of antibiotic resistant bacteria (ARB) in a river. The main contributions of this paper are: (i) the determination of the limit set of the system by applying the semigroups theory, it is shown that it is reduced to the solutions of the associated elliptic system (CDI)e, (ii) sufficient conditions for the existence of a positive solution of (CDI)e based on the Leray-Schauder's degree theory. Numerical simulations which support our theoretical analysis are also given. 展开更多
关键词 Reaction-diffusion systems steady states problems degree theory semi-groups.
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STABILITY ANALYSIS OF A DISCRETE NONLINEAR DELAY SURVIVAL RED BLOOD CELLS MODEL
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作者 SHUFANG MA YUANGANG ZU 《International Journal of Biomathematics》 2012年第4期147-155,共9页
In this article we consider the kth-order discrete delay survival red blood cells model. The general form of the discrete dynamical system is rewritten as Xn+l = f(Pn,δn,xn,... ,xn+1) where Pn,δn converge to the... In this article we consider the kth-order discrete delay survival red blood cells model. The general form of the discrete dynamical system is rewritten as Xn+l = f(Pn,δn,xn,... ,xn+1) where Pn,δn converge to the parametric values P and 6. We show that when the parameters are replaced by sequences, the stability results of the original system still hold. 展开更多
关键词 Discrete delay survival red blood cells model stability.
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