The volumetric rendering of 3 D medical image data is very effective method for communication about radiological studies to clinicians. Algorithms that produce images with artifacts and inaccuracies are not clinically...The volumetric rendering of 3 D medical image data is very effective method for communication about radiological studies to clinicians. Algorithms that produce images with artifacts and inaccuracies are not clinically useful. This paper proposed a direct voxel projection algorithm to implement volumetric data rendering. Using this algorithm, arbitrary volume rotation, transparent and cutaway views are generated satisfactorily. Compared with the existing raytracing methods, it improves the projection image quality greatly. Some experimental results about real medical CT image data demonstrate the advantages and fidelity of the proposed algorithm.展开更多
Objective image quality measure, which is a fundamental and challenging job in image processing, evaluates the image quality consistently with human perception automatically. On the assumption that any image distortio...Objective image quality measure, which is a fundamental and challenging job in image processing, evaluates the image quality consistently with human perception automatically. On the assumption that any image distortion could be modeled as the difference between the directional projection-based maps of reference and distortion images, we propose a new objective quality assessment method based on directional projection for full reference model. Experimental results show that the proposed metrics are well consistent with the subjective quality score.展开更多
This paper addresses the problem of testing goodness-of-fit for several important multivariate distributions: (I) Uniform distribution on p-dimensional unit sphere; (II) multivariate standard normal distribution; and ...This paper addresses the problem of testing goodness-of-fit for several important multivariate distributions: (I) Uniform distribution on p-dimensional unit sphere; (II) multivariate standard normal distribution; and (III) multivariate normal distribution with unknown mean vector and covariance matrix. The average projection type weighted Cramér-von Mises test statistic as well as estimated and weighted Cramér-von Mises statistics for testing distributions (I), (II) and (III) are constructed via integrating projection direction on the unit sphere, and the asymptotic distributions and the expansions of those test statistics under the null hypothesis are also obtained. Furthermore, the approach of this paper can be applied to testing goodness-of-fit for elliptically contoured distributions.展开更多
This paper presents a new three-dimensional(3D) volume measurement approach of bubble in gas-liquid two-phase flow. According to the dual perspective imaging principle,bubble feature images can be captured from two di...This paper presents a new three-dimensional(3D) volume measurement approach of bubble in gas-liquid two-phase flow. According to the dual perspective imaging principle,bubble feature images can be captured from two different view angles. The least square ellipse fitting algorithm is used to figure out the feature parameters from the captured images. Then the 3D volume of bubble can be quantitatively measured. Compaerd with the traditional volume estimation methods based on single perspective imaging,it can effectively reduce the loss of bubble feature information. In the experiment,the 3D volume reconstruction of bubbles from dual perspective images is conducted,and the variation of bubble volume in the bubble rising process is studied. The results show that the measurement accuracy based on the proposed 3D method is higher than those based on traditional methods. The volume of rising bubble is periodically changed,which indicates that bubble achieves periodic rotation and deformation in the rising process.展开更多
A numerical study is given on the spectral methods and the high order WENO finite difference scheme for the solution of linear and nonlinear hyperbolic partial differential equations with stationary and non-stationary...A numerical study is given on the spectral methods and the high order WENO finite difference scheme for the solution of linear and nonlinear hyperbolic partial differential equations with stationary and non-stationary singular sources.The singular source term is represented by theδ-function.For the approximation of theδ-function,the direct projection method is used that was proposed in[6].Theδ-function is constructed in a consistent way to the derivative operator.Nonlinear sine-Gordon equation with a stationary singular source was solved with the Chebyshev collocation method.Theδ-function with the spectral method is highly oscillatory but yields good results with small number of collocation points.The results are compared with those computed by the second order finite difference method.In modeling general hyperbolic equations with a non-stationary singular source,however,the solution of the linear scalar wave equation with the nonstationary singular source using the direct projection method yields non-physical oscillations for both the spectral method and the WENO scheme.The numerical artifacts arising when the non-stationary singular source term is considered on the discrete grids are explained.展开更多
基金Shanghai Science and Technology Devel-opment Fund(9944 190 2 7)
文摘The volumetric rendering of 3 D medical image data is very effective method for communication about radiological studies to clinicians. Algorithms that produce images with artifacts and inaccuracies are not clinically useful. This paper proposed a direct voxel projection algorithm to implement volumetric data rendering. Using this algorithm, arbitrary volume rotation, transparent and cutaway views are generated satisfactorily. Compared with the existing raytracing methods, it improves the projection image quality greatly. Some experimental results about real medical CT image data demonstrate the advantages and fidelity of the proposed algorithm.
文摘Objective image quality measure, which is a fundamental and challenging job in image processing, evaluates the image quality consistently with human perception automatically. On the assumption that any image distortion could be modeled as the difference between the directional projection-based maps of reference and distortion images, we propose a new objective quality assessment method based on directional projection for full reference model. Experimental results show that the proposed metrics are well consistent with the subjective quality score.
基金This workwas supported by the National Natural Science Foundation of China (Grant Nos. 19771011 and 10071009) by the Excellent Young Teacher Program of the Ministry of Education.
文摘This paper addresses the problem of testing goodness-of-fit for several important multivariate distributions: (I) Uniform distribution on p-dimensional unit sphere; (II) multivariate standard normal distribution; and (III) multivariate normal distribution with unknown mean vector and covariance matrix. The average projection type weighted Cramér-von Mises test statistic as well as estimated and weighted Cramér-von Mises statistics for testing distributions (I), (II) and (III) are constructed via integrating projection direction on the unit sphere, and the asymptotic distributions and the expansions of those test statistics under the null hypothesis are also obtained. Furthermore, the approach of this paper can be applied to testing goodness-of-fit for elliptically contoured distributions.
基金supported by the National Natural Science Foundation of China(Nos.61372143 and 61671321)
文摘This paper presents a new three-dimensional(3D) volume measurement approach of bubble in gas-liquid two-phase flow. According to the dual perspective imaging principle,bubble feature images can be captured from two different view angles. The least square ellipse fitting algorithm is used to figure out the feature parameters from the captured images. Then the 3D volume of bubble can be quantitatively measured. Compaerd with the traditional volume estimation methods based on single perspective imaging,it can effectively reduce the loss of bubble feature information. In the experiment,the 3D volume reconstruction of bubbles from dual perspective images is conducted,and the variation of bubble volume in the bubble rising process is studied. The results show that the measurement accuracy based on the proposed 3D method is higher than those based on traditional methods. The volume of rising bubble is periodically changed,which indicates that bubble achieves periodic rotation and deformation in the rising process.
基金support of this work from the National Science Foundation under Grant No.DMS-0608844.
文摘A numerical study is given on the spectral methods and the high order WENO finite difference scheme for the solution of linear and nonlinear hyperbolic partial differential equations with stationary and non-stationary singular sources.The singular source term is represented by theδ-function.For the approximation of theδ-function,the direct projection method is used that was proposed in[6].Theδ-function is constructed in a consistent way to the derivative operator.Nonlinear sine-Gordon equation with a stationary singular source was solved with the Chebyshev collocation method.Theδ-function with the spectral method is highly oscillatory but yields good results with small number of collocation points.The results are compared with those computed by the second order finite difference method.In modeling general hyperbolic equations with a non-stationary singular source,however,the solution of the linear scalar wave equation with the nonstationary singular source using the direct projection method yields non-physical oscillations for both the spectral method and the WENO scheme.The numerical artifacts arising when the non-stationary singular source term is considered on the discrete grids are explained.
