This paper presents a method for segmenting a 3D point cloud into planar surfaces using recently obtained discretegeometry results. In discrete geometry, a discrete plane is defined as a set of grid points lying betwe...This paper presents a method for segmenting a 3D point cloud into planar surfaces using recently obtained discretegeometry results. In discrete geometry, a discrete plane is defined as a set of grid points lying between two parallel planes with a small distance, called thickness. In contrast to the continuous case, there exist a finite number of local geometric patterns （LGPs） appearing on discrete planes. Moreover, such an LGP does not possess the unique normal vector but a set of normal vectors. By using those LGP properties, we first reject non-linear points from a point cloud, and then classify non-rejected points whose LGPs have common normal vectors into a planar-surface-point set. From each segmented point set, we also estimate the values of parameters of a discrete plane by minimizing its thickness.展开更多
Strip-like Fe Co films were patterned by a traditional lithograph process from intrinsically isotropic continuous Fe Co films. The strip-patterned Fe Co film shows a strong in-plane uniaxial magnetic anisotropy with e...Strip-like Fe Co films were patterned by a traditional lithograph process from intrinsically isotropic continuous Fe Co films. The strip-patterned Fe Co film shows a strong in-plane uniaxial magnetic anisotropy with easy axis along the length direction of the strip. The angular dependences of remanence ratio, switching field, and coercivity indicate that the magnetization reversal mechanism of the strip-patterned Fe Co film is coherent rotation and domain wall depinning when the applied field is near the hard axis and easy axis, respectively. The consistency of the experimental hysteresis loops of the strip-patterned Fe Co film and calculated hysteresis loops with a simple in-plane uniaxial anisotropy model indicates that the strip-patterned Fe Co film behaves as a single domain. The absence of the domain wall and the strong in-plane anisotropy field make the strip-patterned Fe Co films have much potential for high-frequency application.展开更多
The plane wave spectrum surface integration (PWS SI) is a practical and efficient method for antenna radome system analysis, especially for determining the boresight error (BSE) in the system. But it is only used f...The plane wave spectrum surface integration (PWS SI) is a practical and efficient method for antenna radome system analysis, especially for determining the boresight error (BSE) in the system. But it is only used for sum pattern calculation till now, and BSE is calculated by the beam maximum searching method. In this paper, the aperture distribution for difference pattern is formulated as the product of that for sum pattern and a two dimensional periodic window function. A series representation for the spectrum of difference pattern is then obtained according to the convolution theorem. The truncation error of the series has been analyzed by introducing the coverage radius of the spectrum of sum pattern. Based on this representation, the PWS SI technique is extended to difference pattern calculation of radome enclosed antennas. The BSE of a three dimensional multilayered radome, with thickness tapers in all layers, is calculated through the difference pattern null searching. Owing to the steep slope of difference pattern near the nulls, this method for BSE calculation is more stable and reliable than the original beam maximum searching method in PWS SI analysis. The results are compared with those from aperture integration surface integration (AI SI) analysis and the measured ones.展开更多
文摘This paper presents a method for segmenting a 3D point cloud into planar surfaces using recently obtained discretegeometry results. In discrete geometry, a discrete plane is defined as a set of grid points lying between two parallel planes with a small distance, called thickness. In contrast to the continuous case, there exist a finite number of local geometric patterns （LGPs） appearing on discrete planes. Moreover, such an LGP does not possess the unique normal vector but a set of normal vectors. By using those LGP properties, we first reject non-linear points from a point cloud, and then classify non-rejected points whose LGPs have common normal vectors into a planar-surface-point set. From each segmented point set, we also estimate the values of parameters of a discrete plane by minimizing its thickness.
基金financially supported by the National Natural Science Foundation of China (Nos. 51171076 and 51101079)the Fundamental Research Funds for Central Universities (Nos. lzujbky-2010-172 and Lzujbky-2012-27)
文摘Strip-like Fe Co films were patterned by a traditional lithograph process from intrinsically isotropic continuous Fe Co films. The strip-patterned Fe Co film shows a strong in-plane uniaxial magnetic anisotropy with easy axis along the length direction of the strip. The angular dependences of remanence ratio, switching field, and coercivity indicate that the magnetization reversal mechanism of the strip-patterned Fe Co film is coherent rotation and domain wall depinning when the applied field is near the hard axis and easy axis, respectively. The consistency of the experimental hysteresis loops of the strip-patterned Fe Co film and calculated hysteresis loops with a simple in-plane uniaxial anisotropy model indicates that the strip-patterned Fe Co film behaves as a single domain. The absence of the domain wall and the strong in-plane anisotropy field make the strip-patterned Fe Co films have much potential for high-frequency application.
文摘The plane wave spectrum surface integration (PWS SI) is a practical and efficient method for antenna radome system analysis, especially for determining the boresight error (BSE) in the system. But it is only used for sum pattern calculation till now, and BSE is calculated by the beam maximum searching method. In this paper, the aperture distribution for difference pattern is formulated as the product of that for sum pattern and a two dimensional periodic window function. A series representation for the spectrum of difference pattern is then obtained according to the convolution theorem. The truncation error of the series has been analyzed by introducing the coverage radius of the spectrum of sum pattern. Based on this representation, the PWS SI technique is extended to difference pattern calculation of radome enclosed antennas. The BSE of a three dimensional multilayered radome, with thickness tapers in all layers, is calculated through the difference pattern null searching. Owing to the steep slope of difference pattern near the nulls, this method for BSE calculation is more stable and reliable than the original beam maximum searching method in PWS SI analysis. The results are compared with those from aperture integration surface integration (AI SI) analysis and the measured ones.
