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The sphere is a natural and seamless parametric domain for closed genus-0 surfaces. We introduce an efficient hierarchical optimization approach for the computation of spherical parametrization for closed genus-0 surfaces by minimizing a nonlinear energy balancing angle and area distortions. The mapping results are bijective and lowly distorted. Our algorithm converges efficiently and is suitable to manipulate large-scale geometric models. We demonstrate and analyze the effectiveness of our mapping in spherical harmonics decomposition. 相似文献
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As an alternative to classical LP-modes used as a signal carrier in the optical fiber, we propose a superposition of angular
harmonics that can be obtained as a special combination of LP-modes, which also shows modal properties in an optical fiber.
Results of a number of natural experiments on selective excitation of both individual angular harmonics and their superposition
are discussed.
The text was submitted by the authors in English. 相似文献
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目前在光照模型中常用球面谐波函数(SH)来表示不同的光特性,该函数可通过控制它的基函数因子数量得到不同的光照效果,而传统的方法存在过程复杂、抗干扰能力差的缺点,为此研究并提出了基于能量控制光照模型中球面谐波函数因子的理论,新方法考虑到图像压缩对SH的因子带来噪音,提出对量化过程进行建模,分析施加的能量约束条件,求解出最恰当的因子数.实验结果表明新方法在光照模型中能有效地控制球面谐波函数因子,其对应的图像效果也较好. 相似文献
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谭晓 《计算机工程与应用》2011,47(19):194-196
提取关于坐标旋转不变的特征描述符以及提高特征描述符对噪声的鲁棒性是基于内容三维模型检索技术中有待进一步研究解决的问题之一。将三维模型表面离散成三维点数据,然后使用球面调和方法对得到的点数据进行调和分析得到三维模型旋转不变的特征向量,并且能够增加算法对模型表面噪声的鲁棒性提高检索准确度。实验证明该算法在检索准确度和对噪声的鲁棒性上都有所提高。 相似文献
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通过球麦克风阵列采集高阶声场的声压信息,采用球谐函数分解声场并建立信号模型,应用MUSIC算法提取出声源的方位。由于MUSIC算法在信号源相干性比较高,特别是声源比较接近时,其分辨率会严重下降,提出了一种基于空间平滑的瓣分块方法来提高定位的效果。仿真实验采用了一个72元的球阵,实验结果表明:提出的方法能同时有效地确定声场中多个声源的位置,能比较好地对抗噪声的影响。 相似文献
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According to the classic harmonic approach, an orientation density function (odf)f is expanded into its corresponding Fourier orthogonal series with respect to generalized spherical harmonics, and a pole density function (pdf)
into its corresponding Fourier orthogonal series with respect to spherical harmonics. While pdfs are even (antipodally symmetric) functions, odfs are generally not. Therefore, the part
of the odf which cannot be determined from normal diffraction pdfs can be mathematically represented as the odd portion of its series expansion. If the odff is given, the even part
can be mathematically represented explicitly in terms off itself. Thus, it is possible to render maps ofharmonic orientation ghosts, and to evaluatevariants of mathematical standard odfs resulting in identical pdfs independent of pdf data. However, if only normal diffraction pdfs are known, the data-dependentvariation width of feasible odfs remained unaccessible, and within the harmonic approach a measure of confidence in a solution of the pdf-to-odf inversion problem does not exist.According to any discrete approach, an odff defined on some setG of orientations is expanded into its corresponding Fourier orthogonal series with respect to indicator functions of the elements of a partition ofG, and a pdf
defined on the upper (lower) unit hemisphereS
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3
3 into its corresponding Fourier orthogonal series with respect to indicator functions of the elements of a partition ofS
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3
. The ambiguity of the pdf-to-odf inversion problem is discussed in terms of column-rank deficiency of the augmented projection matrix. The implication of the harmonic approach to split an odf into auniquely determined and anundetermined part does no longer seem to be reasonable. However, it is possible to numerically determine data-dependent confidence intervals for the Fourier coefficients with respect to the indicator functions which can be immediately interpreted as mean orientation densities within the elements of the partition ofG. Doing so for all Fourier coefficients in the finite series expansion, i.e. for all elements of the partition of the setG, eventually results in the data-dependent variation width of odfs feasible with respect to given pdf data, and to the partitions ofG andS
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3
.Thus it is confirmed that the appearance of orientation ghosts, in particular correlations oftrue andghost orientation components, depends on the representation of an odf. It may be questioned whether in practical applications the implicit assumption of the harmonic method that the even part
can be determined uniquely and free of error is generally a reasonable initial condition to develop ghost correction procedures. 相似文献
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为了减少电力系统中谐波的危害,本文将神经网络理论应用于谐波监测,使用界面设计方便美观的Labview编程语言制作了一种谐波监测仪。文中构造了一个目前应用最为广泛的BP网络,给出了网络算法,形成了训练样本。并用基于Labview工作平台的G语言,编写了训练程序,将所形成的样本对网络进行了训练,然后对训练好的网络进行仿真实验。结果表明:所设计的神经网络可很好的监测谐波,并对谐波参数的显示设计了很好的人机界面。 相似文献
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Robert A. Werner 《Computers & Geosciences》1997,23(10):212
Recurrent relationships for the definitions of fully normalized spherical harmonic coefficients C?n,m and S?n,m are derived and integrated analytically to yield the gravitational potential of a constant-density polyhedron. The algorithm is expressed in a C language computer program. 相似文献
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主要研究加性噪声中二维谐波频率的估计问题。针对现有算法估计精度不高和计算量较大的缺点,提出了一种基于矩阵旋转不变性的免配对谐波频率估计方法。利用矩阵旋转不变性,通过观测数据获得一组具有对角结构的矩阵组。将矩阵组相加并对此进行一次奇异值分解同时获得两个信号子空间。同时对角化信号子空间的构造矩阵,得到了二维频率的估计,并且所得的二维频率能自动配对。仿真实验结果表明,在数据维数和信噪比都比较低时,该算法明显优于现有算法。在数据矩阵维数[60×60],信噪比[5 dB]时,该算法估计精度高于现有算法近3倍。 相似文献
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用于3D模型检索的扩展距离球面调和表达 总被引:1,自引:0,他引:1
使用光线投射方法对3D模型定义了一个对应的球函数--扩展距离球函数,然后引入了球面调和分析方法,构造了一种对于平移、缩放和旋转变换具有不变性的特征向量,并用于基于形状的3D模型检索中.与基于向径方法结合,提高了检索的效果,扩大了应用范围. 相似文献
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以MATLAB为设计语言,开发了系列用于原子轨道球谐函数Y_(1m)(θ,φ)如s、p、d、f原子轨道及sp~3和d~2sp~3杂化轨道角度函数可视化的精确、快速、简便的m函数库。根据球坐标的自变量定义域:φ∈[0,2π]、θ∈[0,π],设定离散的自变量值T,P,对球谐函数Y_(1m)(θ,φ)及杂化轨道角度函数的解析式进行计算机程序化,根据解析式计算对应的R值,然后由MATLAB矩阵变换命令[X,Y,Z]=sph2cart(T,P,R)和绘图命令mesh(X,Y,Z)实现球谐函数Y_(1m)(θ,φ)及杂化轨道角度函数的可视化。详细介绍了程序设计思路、编写方法,给出了球谐函数Y_(1m)(θ,φ)及杂化轨道角度函数的解析式数组算法表达式、m-file绘图程序和运行结果。 相似文献
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以平板孔缝耦合为典型对象,选取圆形、正方形、长方形孔形,建立了无限大平板的小孔耦合模型,然后利用矩量法对孔缝耦合模型进行求解分析,得到了表征电磁耦合强弱的能量传输系数。为验证方法的有效性,搭建了实验系统对不同的孔缝类型进行了测试。结果表明,电磁波通过不同形状孔缝耦合过去的能量和孔缝的面积以及电磁波的入射角度有密切的关系。 相似文献
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Title of program: SU(3)VCC Catalogue number: AAWA Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland (see application form in this issue) Computer: IBM 360/40; Installation: Indiana University of Pa. Operating system: Disk operating system Programming language used: Fortran IV High speed storage required: 8,178 words. No. of bits in a word: 32 Is the program overlaid? No No. of magnetic tapes required: None Other peripherals used: Card reader, line printer No. of cards in combined program and test deck: 817 Card punching code: EBCDIC 相似文献
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针对2000系列DSP产生的正弦脉宽调制(Sinusoidal Pulse Width Modulation,SPWM)波,使用傅里叶级数模型,提出了将改进的粒子群优化(Improved Particle Swarm Optimization,IPSO)用于各次谐波的幅值和相位的参数估计方法,着重分析了在不同的调制波频率和电压下,载波比与谐波总畸变率(Total Harmonic Distortion,THD)之间的关系,通过大量的实验,得到在一定范围的调制波频率和电压下,均能保持高次谐波较小,从而得到高质量的正弦输出。这一结论不仅对SPWM的产生起指导作用,而且对要求正弦交流电的用电设备有着降低高频损耗与节能的重要实际意义。 相似文献