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In this paper,we consider 3 D tomographic reconstruction for axially symmetric objects from a single radiograph formed by cone-beam X-rays.All contemporary density reconstruction methods in high-energy X-ray radiography are based on the assumption that the cone beam can be treated as fan beams located at parallel planes perpendicular to the symmetric axis,so that the density of the whole object can be recovered layer by layer.Considering the relationship between different layers,we undertake the cone-beam global reconstruction to solve the ambiguity effect at the material interfaces of the reconstruction results.In view of the anisotropy of classical discrete total variations,a new discretization of total variation which yields sharp edges and has better isotropy is introduced in our reconstruction model.Furthermore,considering that the object density consists of continually changing parts and jumps,a high-order regularization term is introduced.The final hybrid regularization model is solved using the alternating proximal gradient method,which was recently applied in image processing.Density reconstruction results are presented for simulated radiographs,which shows that the proposed method has led to an improvement in terms of the preservation of edge location. 相似文献
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高能X光照相中密度重建的共轭梯度算法 总被引:1,自引:0,他引:1
通过对高能X光照相过程的物理分析,得到了辐射照相的点扩展函数,给出了估价函数的表达式.并以典型的法国试验客体模型为例,将共轭梯度算法应用到高能X光照相的密度重建中,得到了较满意的结果.这种方法从模拟辐射照相过程出发,将辐射照相的模拟结果与实际测量结果做比较并找出最大可能解.可在一定程度上克服其它密度重建算法通过反卷积过程消除模糊效应所引起的不确定性. 相似文献
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In this paper,we consider 3 D tomographic reconstruction for axially symmetric objects from a single radiograph formed by cone-beam X-rays.All contemporary density reconstruction methods in high-energy X-ray radiography are based on the assumption that the cone beam can be treated as fan beams located at parallel planes perpendicular to the symmetric axis,so that the density of the whole object can be recovered layer by layer.Considering the relationship between different layers,we undertake the cone-beam global reconstruction to solve the ambiguity effect at the material interfaces of the reconstruction results.In view of the anisotropy of classical discrete total variations,a new discretization of total variation which yields sharp edges and has better isotropy is introduced in our reconstruction model.Furthermore,considering that the object density consists of continually changing parts and jumps,a high-order regularization term is introduced.The final hybrid regularization model is solved using the alternating proximal gradient method,which was recently applied in image processing.Density reconstruction results are presented for simulated radiographs,which shows that the proposed method has led to an improvement in terms of the preservation of edge location. 相似文献
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声波方程吸收边界条件的稳定性分析 总被引:3,自引:0,他引:3
引言对于无界区域中波动现象的数值模拟,必需引进人工边界将计算限制在一个有界区域上.为了确定解,需要在人工边界上加适当的边界条件.对于声波和弹性波方程,这样的一组人工边界条件,也叫吸收边界条件,在[1,2]中被系统地构造出来.对于声波方程,这些吸收边界条件恰好是单程波方程的近似.如山中所指出,减少边界反射,便于在计算中应用和稳定性是构造吸收边界条件的三点关键.Ellgqllist和Maid。用模态分析方法15]证明,带有[IJ中构造的吸收边界条件的波动方程初边值问题是适定的,并且估计了人工边界所产生的误差.对于更广… 相似文献
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