N. Shishido, T. Ikeda, N. Miyazaki

CMES-Computer Modeling in Engineering & Sciences, Vol.35, No.1, pp. 1-20, 2008, DOI:10.3970/cmes.2008.035.001

Abstract We propose an image correction method that will accurately measure full-field displacement in a microstructure using the digital image correlation method (DICM); the proposed method is suitable for use with laser-scanned images. Laser scanning microscopes have higher spatial resolution and deeper depth of field than optical microscopes, but errors in laser scanning position (time-dependent distortion) affect the accuracy of the DICM. The proposed image correction method involves the removal of both time-dependant and time-independent distortions. Experimental results using images of prescribed rigid-body motions demonstrate that the proposed correction method is capable of identifying and removing both types of distortion. Specifically,… More >

C.B. Du^1,2, S.Y Jiang², W. Qin³, Y.M. Zhang²

CMES-Computer Modeling in Engineering & Sciences, Vol.81, No.3&4, pp. 229-248, 2011, DOI:10.3970/cmes.2011.081.229

Abstract A numerical analysis of concrete composites at the mesoscale based on three-dimensional (3D) reconstruction technology of X-ray computed tomography (CT) images is presented in this paper. For X-ray CT images of concrete, morphology processing was used to recover complete image information, including borders, and the median filtering method was applied to eliminate potential impurities in the images. The final X-ray CT images obtained after processing for a concrete section were composed of three-value pixels that indicated aggregate particles, mortar matrix and air voids, and the 3D structure of the concrete specimen was reconstructed using the volume data method. The mapping… More >

B.Y. Lee¹, Y. Lee², J.K.Kim³, Y.Y.Kim⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.2, pp. 111-132, 2010, DOI:10.3970/cmes.2010.061.111

Abstract In the present work, a micromechanics-based fiber-bridging constitutive model that quantitatively takes into consideration the distribution of fiber orientation and the number of fibers, is derived and a fiber-bridging analysis program is developed. An image processing technique is applied to evaluate the fiber distribution characteristics of four different types of strain-hardening cementitious composites. Then, the fiber-bridging curves obtained from image analysis are compared with those obtained from the assumption of two- and three-dimensional fiber distributions. The calculated ultimate tensile strains are also compared with experimental results. Test results showed that the tensile behavior of strain-hardening cementitious composites can be more… More >

Bohou Xu¹, Yibing Yang¹, Zhong-Ping Jiang², Daniel W. Repperger³

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.2, pp. 159-174, 2010, DOI:10.3970/cmes.2010.057.159

Abstract A modified two-dimensional parameter-induced stochastic resonance (2D-PSR) system is proposed. Both theoretical and simulation results indicate that the 2D-PSR system performs a resonant-like behavior when system parameters are properly adjusted. When applied to degraded image processing, 2D-PSR technique is proved to be able to attain higher SNR gain than traditional linear filters. Due to its strong robustness to environmental changes, adaptability, and complementarities with other methods, the proposed 2D-PSR technique turns out to be promising in the field of image processing. More >

Raquel R. Pinho¹, João Manuel R. S. Tavares¹

CMES-Computer Modeling in Engineering & Sciences, Vol.46, No.1, pp. 51-76, 2009, DOI:10.3970/cmes.2009.046.051

Abstract This work addresses the problem of tracking feature points along image sequences. In order to analyze the undergoing movement, an approach based on the Kalman filtering technique has been used, which basically carries out the estimation and correction of the features' movement in every image frame. So as to integrate the measurements obtained from each image into the Kalman filter, a data optimization process has been adopted to achieve the best global correspondence set. The proposed criterion minimizes the cost of global matching, which is based on the Mahalanobis distance. A management model is employed to manage the features being… More >

Francisco P. M. Oliveira¹, João Manuel R. S. Tavares¹

CMES-Computer Modeling in Engineering & Sciences, Vol.43, No.1, pp. 91-110, 2009, DOI:10.3970/cmes.2009.043.091

Abstract This paper presents a new methodology to establish the best global match of objects' contours in images. The first step is the extraction of the sets of ordered points that define the objects' contours. Then, by using the curvature value and its distance to the corresponded centroid for each point, an affinity matrix is built. This matrix contains information of the cost for all possible matches between the two sets of ordered points. Then, to determine the desired one-to-one global matching, an assignment algorithm based on dynamic programming is used. This algorithm establishes the global matching of the minimum global… More >

Patrícia C.T. Gonçalves^1,2, João Manuel R.S. Tavares^1,2, R.M. Natal Jorge^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 45-56, 2008, DOI:10.3970/cmes.2008.032.045

Abstract The main goals of the present work are to automatically extract the contour of an object and to simulate its deformation using a physical approach. In this work, to segment an object represented in an image, an initial contour is manually defined for it that will then automatically evolve until it reaches the border of the desired object. In this approach, the contour is modelled by a physical formulation using the finite element method, and its temporal evolution to the desired final contour is driven by internal and external forces. The internal forces are defined by the intrinsic characteristics of… More >

Francisco. P. M. Oliveira¹, João Manuel R. S. Tavares¹

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.1, pp. 1-12, 2008, DOI:10.3970/cmes.2008.031.001

Abstract This paper presents a new assignment algorithm with order restriction. Our optimization algorithm was developed using dynamic programming. It was implemented and tested to determine the best global matching that preserves the order of the points that define two contours to be matched. In the experimental tests done, we used the affinity matrix obtained via the method proposed by Shapiro, based on geometric modeling and modal matching. \newline The proposed algorithm revealed an optimum performance, when compared with classic assignment algorithms: Hungarian Method, Simplex for Flow Problems and LAPm. Indeed, the quality of the matching improved when compared with these… More >

Yongjie Zhang¹, Boyle C. Cheng², Changho Oh¹, Jessica L. Spehar², James Burgess³

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.2, pp. 55-62, 2008, DOI:10.3970/cmes.2008.029.055

Abstract The spinal column plays a vital biomechanical role in the human body by providing structural support and facilitating motion. As degenerative changes occur in the spine, surgical treatment may be necessary in certain instances. Such treatments seek to address pain, frequently through the restriction of spinal motion. Traditional spinal implant devices are designed to restrict the motion of a functional spinal unit (FSU) but newer device designs allow for semi-constrained motion such as spinal arthroplasty devices. In this study, a sequence of fluoroscopic imaging data was recorded during the flexibility protocol with an interspinous process spacer device placed at L2-L3.… More >

Jun Zhang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.2, pp. 91-96, 2007, DOI:10.3970/cmes.2007.022.091

Abstract The most commonly used wavelets for image processing are the tensor-product of univariate wavelets, which have a disadvantage of giving a particular importance to the horizontal and vertical directions. In this paper, a new class of wavelet, non-separable wavelet, is investigated for image compression applications. The comparative results of image compression preprocessed with two different kinds of wavelet transform are presented: (1) non-separable wavelet transform; (2) tensor-product wavelet transform. The results of our experiments show that in the same vanishing moment, the non-separable wavelets perform better than the tensor-product wavelets in dealing with still images. More >