Papers by Keyword: Level Set

Abstract: A transverse isotropic viscous model accounting for the anisotropy exhibited in fiber-reinforced composite is integrated in the numerical platform of the software Rem3D®. Simulations under various mechanical loading are tested for volume fiber concentrations of 3.5% and 14.7%. Equivalent stresses and equivalent strain rate deformations given by the software were compared to the ones predicted by the model, finding very good agreements. As a second point developed on this paper, we comment on the slip condition between Die/Punch tool with the composite under compression. We noticed that the variation of the viscosity value on a small layer between the Die/Punch tooland the composite affects the nature of the contact. A viscous friction is then formulated as a technique to set slip/no-slip contact condition. We found that the slip condition is recovered at lower values of the viscosity in the interface Die/Punch with the reinforced composite, whereas the no slip condition stated for higher viscosity values.

Abstract: Synthetic Aperture Radar (SAR) has become one of the important means for the ocean remote sensing detection of oil spills. The existing SAR image segmentation method has the issues of edge blur, poor contrast, non-uniform intensity image, so the segmentation effect is not ideal. This paper presents a variational level set SAR image of oil spill detection method based on fuzzy clustering. First of all, apply the threshold method on initial segmentation of the original SAR image to transform the initial segmented image as fuzzy clustering. Secondly, introduce the clustering results into the initial level set function to achieve the initial contour. Finally, add fuzzy clustering model in the level set energy function to complete the level set evolution process and get the final segmented image. This paper uses the threshold segmentation results to achieve the initialization of the variational level set function profile. In theory, it could improve the level set method for efficiency, and reduce the wrong segmentation phenomenon. The experimental results show that the SAR image segmentation method of oil spill has good segmentation qualities and is suitable for the edge complex image segmentation.

Abstract: Image segmentation is one of the most fundamental and important areas in the field of image processing and computer vision. The traditional level set methods need initialize the level set function as a distance function. If the initial contour is selected inappropriate, we may not get the desired ideal segmentation result. In order to solve the problem of level set automation initial, we proposed a new image segmentation algorithm based on level set and marker extraction. First, we extract the internal mark as level set initial curve by using Extended-minima transform. And then, through using the local binary fitting active contour model, we evolve the labeled image to get the final segmentation result. The simulation results show that this method has low computing complexity than the traditional level set method requirements, and can effectively solve the initialization problem of level set.

Abstract: To solve the problem that many image segmentation methods cannot be applied to forward looking sonar image accurately, an improved level set segmentation method was proposed in this paper. Firstly, the level set evolution without re-initialization was introduced. Secondly the different characteristics of forward looking sonar image from the optical image were analyzed, and we got the factors affecting segmentation. Then, to overcome these negative effects, this paper did preprocessing by morphological top-hat and bottom-hat transformation, and carried on level set method without re-initialization to construct an improved level set sonar image segmentation system. Finally, our method was compared with the traditional level set method in computer experiments. Simulation results show that it is more adapted to forward looking sonar image segmentation.

Abstract: This paper presents a wavelet energy map based on an active contour model for medical image segmentation and bias correction in a variational level set framework. In our model the wavelet transform amplifies the faint dissimilarities between regions, and we model the distribution of intensity belonging to each tissue as a Gaussian distribution with spatially varying mean and variance. In addition, we modify the intensity mean as the product of the bias field and true image. Tissue segmentation and bias correction are simultaneously achieved via a level set evolution process. Experiments on images of various modalities demonstrated the superior performance of the proposed approach.

Abstract: Locating object regions is particularly important for image segmentation. Incorporating knowledge of human anatomy, such as numerical anatomical models, into image segmentation to produce more effective results. This paper presents a method of automatic gallbladder location and segmentation based on anatomical knowledge. Firstly, located liver according to the anatomic knowledge that the liver is the largest internal organ using distance transformation and then segmented liver with located outline as initial function using level set method. Secondly, located gallbladder according to the anatomic knowledge that the gallbladder is wrapped in liver using the circumscribed sphere of the liver surface and the sphere of maximum similarity with gallbladder is the location of gallbladder. Finally, segmented gallbladder with the sphere as initial function using level set method.

Abstract: Resin Infusion (RI) process is one of the common techniques used in the industry for large composite parts production. This technique uses vacuum pressure to drive the resin into a laminate. Preform is laid dry into the mold and the vacuum is applied before the resin is introduced. Once a complete vacuum is achieved, resin is sucked into the laminate via placed tubing. Fig.1 shows a diagram of this process.An appropriate modeling of flow front’s shapes constrained by LRI process during filling can be based on the continuous deformation of the vent oriented flow pattern due to the driving pressure from the inlet. One of the main objectives is that the flow achieves the contour vent uniformly to avoid pressure drop and ensuring complete filling. In LRI, the flow front shape progression is mainly conditioned by the initial arrangement of the injection line allocation and the permeability of the preform that can evolve along the mold

Abstract: While smooth isosurface and the subsequent body mesh construction is a well-developed modeling technique and widely used in medical imaging and engineering modeling, it is rarely performed in transient analysis and other iterative procedures due to relatively high computational cost. Voxelized modeling is often used as an alternative for simplicity at a cost of numerical accuracy. To overcome this problem, an isosurface modeling technique is developed in this paper to enable its seamless integration into iterative processes. This approach involves a rapid construction of closed isosurfaces using the Marching Cubes methods and a selective clean-up operation to smooth the surface mesh. This technique generates high quality isosurface meshes with clearly defined 3D domains and boundaries, which in turn provide a suitable foundation for the finite element analysis of two-phase problems. Its robustness, flexibility and suitability for applications in medical imaging and topology optimization are also demonstrated in this paper.

Abstract: Mass balance between metal and electrolytic solution, separated by a moving interface, in stable pit growth results in a set of governing equations which are solved for concentration field and interface position (pit boundary evolution), which requires only three inputs, namely the solid metal concentration, saturation concentration of the dissolved metal ions and diffusion coefficient. A combined eXtended Finite Element Model (XFEM) and level set method is developed in this paper. The extended finite element model handles the jump discontinuity in the metal concentrations at the interface, by using discontinuous-derivative enrichment formulation for concentration discontinuity at the interface. This eliminates the requirement of using front conforming mesh and re-meshing after each time step as in conventional finite element method. A numerical technique known as level set method tracks the position of the moving interface and updates it over time. Numerical analysis for pitting corrosion of stainless steel 304 is presented. The above proposed method is validated by comparing the numerical results with experimental results, exact solutions and some other approximate solutions.

Abstract: The techniques and the processes to divide the image into several parts which have different features and to pick up foreground are called image segmentation. In this work, we propose a new approach for gray scale image segmentation based on level set method. At first, every pixel on the image is divided into either similar-property class or dissimilar-property class based on the variance of a small area centered at the pixel. Then, the velocity of curve evolution for these two classes is defined respectively. It is determined by a value called the dissimilarity of the area. Experimental results show that this approach can obtain good segmentation results of artificial images and real medical images fast and accurately.