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RISS 인기검색어
- 검색키워드
- 저자 : Caiming Zhang (검색결과 9 건)
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Yunfeng Zhang,Fangxun Bao,Caiming Zhang,Qiang Guo,Qi Duan (사)한국CDE학회 2013 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
Spline surface is a very important part in Computer Aided Geometric Design. A bivariate rational interpolation spline surface based on function values has been constructed in[9]. It can achieve good approximation effect with parameters, but it would also make the surface control difficult. This paper deals with the constraint methods of partial derivative and directional derivative. the sufficient conditions to modified the partial derivative and directional derivative are derived. The partial derivative and directional derivative can be changed by selecting suitable parameters under the condition that the interpolating data are not changed. Numerical example are given to show how the parameters can be chosen and the shape of surface changed.
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Depth Enhancement Using Domain Transform-Based Multipoint Filter
Li Li,Caiming Zhang (사)한국CDE학회 2013 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
The paper presents a novel depth enhancement method to improve the spatial resolution and quality of initial depth estimates. Our solution is based on a domain transform-based multipoint filter framework. Compared to the pointwise filter, the estimates are calculated for all observation pixels in the multipoint filter model. We use the piecewise constant model to calculate the estimates in an adaptive support region which is computed based on the domain transformation of color image. Then a number of such estimates are aggregated together by weighted averaging to final depth estimate. By quantitative and qualitative experiments on publicly available test sequences, we demonstrate the capabilities of our domain transform-based multipoint filter on the depth enhancement task.
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Geometric Hermite Curves Based on Curvature Variation Minimization
Chi, Jing,Zhang, Caiming,Wu, Xiaoming Society for Computational Design and Engineering 2006 International Journal of CAD/CAM Vol.6 No.1
Based on the smoothness criterion of minimum curvature variation of the curve, tangent angle constraints guaranteeing an optimized geometric Hermite (OGH) curve both mathematically and geometrically smooth is given, and new methods for constructing composite optimized geometric Hermite (COH) curves are presented in this paper. The comparison of the new methods with Yong and Cheng's methods based on strain energy minimization is included.
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[ $C^1$ ] Continuous Piecewise Rational Re-parameterization
Liang, Xiuxia,Zhang, Caiming,Zhong, Li,Liu, Yi Society for Computational Design and Engineering 2006 International Journal of CAD/CAM Vol.6 No.1
A new method to obtain explicit re-parameterization that preserves the curve degree and parametric domain is presented in this paper. The re-parameterization brings a curve very close to the arc length parameterization under $L_2$ norm but with less segmentation. The re-parameterization functions we used are $C^1$ continuous piecewise rational linear functions, which provide more flexibility and can be easily identified by solving a quadratic equation. Based on the outstanding performance of Mobius transformation on modifying pieces with monotonic parametric speed, we first create a partition of the original curve, in which the parametric speed of each segment is of monotonic variation. The values of new parameters corresponding to the subdivision points are specified a priori as the ratio of its cumulative arc length and its total arc length. $C^1$ continuity conditions are imposed to each segment, thus, with respect to the new parameters, the objective function is linear and admits a closed-form optimization. Illustrative examples are also given to assess the performance of our new method.
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An adaptive nonlocal filtering for low-dose CT in both image and projection domains
Wang, Yingmei,Fu, Shujun,Li, Wanlong,Zhang, Caiming Society for Computational Design and Engineering 2015 Journal of computational design and engineering Vol.2 No.2
An important problem in low-dose CT is the image quality degradation caused by photon starvation. There are a lot of algorithms in sinogram domain or image domain to solve this problem. In view of strong self-similarity contained in the special sinusoid-like strip data in the sinogram space, we propose a novel non-local filtering, whose average weights are related to both the image FBP (filtered backprojection) reconstructed from restored sinogram data and the image directly FBP reconstructed from noisy sinogram data. In the process of sinogram restoration, we apply a non-local method with smoothness parameters adjusted adaptively to the variance of noisy sinogram data, which makes the method much effective for noise reduction in sinogram domain. Simulation experiments show that our proposed method by filtering in both image and projection domains has a better performance in noise reduction and details preservation in reconstructed images.
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