• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.299-306
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• 2006

Using a level set method and topological derivatives, a topological shape optimization method that is independent of an initial design is developed for linearly elastic structures. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. The 'Hamilton-Jacobi (H-J)' equation and computationally robust numerical technique of 'up-wind scheme' lead the initial implicit boundary to an optimal one according to the normal velocity field while minimizing the objective function of compliance and satisfying the constraint of allowable volume. Based on the asymptotic regularization concept, the topological derivative is considered as the limit of shape derivative as the radius of hole approaches to zero. The required velocity field to update the H -J equation is determined from the descent direction of Lagrangian derived from optimality conditions. It turns out that the initial holes is not required to get the optimal result since the developed method can create holes whenever and wherever necessary using indicators obtained from the topological derivatives. It is demonstrated that the proper choice of control parameters for nucleation is crucial for efficient optimization process.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.259-260
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• 2011

Using modern techniques from scientific computing and numerical analysis, natural phenomena or scientific experiment can be simulated effectively with a computer and used for computer graphics, for example as special effects for the film industry, manufacturing the thin film, multi-phase simulation and image processing. The Level Set method can make those things happen without a lot of difficulties. This method was devised by Osher and Sethian(1988) to represent dynamically moving interfaces as the zero level set of a scalar function that evolves in time. Since then, many researchers have worked on many applications using a Level Set Method. I will give a talk about the applications of the Level Set Method.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.565-567
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• 2008

In the present study, a least square/level set based two-phase flow code has been developed using finite element discretization, which can be utilized for the analysis of a free surface flow problem in a complex geometry. Since the finite element method is employed for the spatial discretization of governing equations, an unstructured mesh can be naturally adopted for the level set simulation of a bubble-in-liquid flow without an additional load for the code development except that solution methods of the hyperbolic type redistancing and advection equations of the level set function should be devised in order to give a bounded solution on the unstructured mesh. For the discretization of hyperbolic type redistancing and advection equations, least square method is adopted. From the numerical experiments of the present study, it is shown that the proposed method is both robust and accurate.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2401-2405
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• 2008

In the present study, a three-dimensional least square/level set based two-phase flow code was developed for the simulation of three-dimensional sloshing problems using finite element discretization. The present method can be utilized for the analysis of a free surface flow problem in a complex geometry due to the feature of FEM. Since the finite element method is employed for the spatial discretization of governing equations, an unstructured mesh can be naturally adopted for the level set simulation of a free surface flow without an additional load for the code development except that solution methods of the hyperbolic type redistancing and advection equations of the level set function should be devised in order to give a bounded solution on the unstructured mesh. From the numerical experiments of the present study, it is shown that the proposed method is both robust and accurate for the simulation of three-dimensional sloshing problems.

• Journal of Information Processing Systems
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• v.15 no.1
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• pp.7-21
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• 2019

In order to improve the edge segmentation effect of the level set image segmentation and avoid the influence of the initial contour on the level set method, a saliency level set image segmentation model based on local Renyi entropy is proposed. Firstly, the saliency map of the original image is extracted by using saliency detection algorithm. And the outline of the saliency map can be used to initialize the level set. Secondly, the local energy and edge energy of the image are obtained by using local Renyi entropy and Canny operator respectively. At the same time, new adaptive weight coefficient and boundary indication function are constructed. Finally, the local binary fitting energy model (LBF) as an external energy term is introduced. In this paper, the contrast experiments are implemented in different image database. The robustness of the proposed model for segmentation of images with intensity inhomogeneity and complicated edges is verified.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.161-164
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• 2000

The architecture of microprocessor for a embedded system should be one that can perform more tasks with fewer instruction codes. The machine codes that high-level language compiler produces are mainly composed of specific ones, and codes that have small size are more frequently used. Extended Instruction Set Architecture (EISC) was proposed for that reason. We have designed pipe-line system for 64 bit EISC microprocessor. function level simulator was made for verification of design and instruction set architecture was also verified by that simulator. The behavioral function of synthesized logic was verified by comparison with the results of cycle-based simulator.

• The Korean Journal of Applied Statistics
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• v.24 no.2
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• pp.335-345
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• 2011

In this paper, we propose a new hybrid speed function for image segmentation using level set. A new proposed speed function uses the region and boundary information of image object for the exact result of segmentation. The region information is defined by the probability information of pixel intensity in a ROI(region-of-interest), and the boundary information is defined by the gradient vector flow obtained from the gradient of image. We show the results of experiment for an various artificial image and real medical image to verify the accuracy of segmentation using proposed method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.744-752
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• 2003

A level set method is combined with the volume-of-fluid method so that the coupled method can not only calculate an interfacial curvature accurately but also can achieve mass conservation well. The coupled level set and volume-of-fluid(CLSVOF) method is efficiently implemented by employing an interface reconstruction algorithm which is based on the explicit relationship between the interface configuration and the fluid volume function. The CLSVOF method is applied for numerical simulation of droplet impact on solid surfaces with variable contact angles. The numerical results are found to preserve mass conservation and to be in good agreement with the data reported in the literature. Also, the present method proved to be applicable to the complex phenomena such as breakup and rebound of a droplet.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.340-346
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• 2008

A level-set method is developed for computation of drop motions in various engineering applications. Compared with the volume-of-fluid method based on a non-smooth volume-fraction function, the LS method can calculate an interface curvature more accurately by using a smooth distance function. Also, it is straightforward to implement for two-phase flows in complex geometries unlike the VOF method requiring much more complicated geometric calculations. The LS method is applied to simulation of inkjet process, thin film pattering and droplet collisions.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.340-346
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• 2008

A level-set method is developed for computation of drop motions in various engineering applications. Compared with the volume-of-fluid method based on a non-smooth volume-fraction function, the LS method can calculate an interface curvature more accurately by using a smooth distance function. Also, it is straightforward to implement for two-phase flows in complex geometries unlike the VOF method requiring much more complicated geometric calculations. The LS method is applied to simulation of inkjet process, thin film pattering and droplet collisions.