• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.541-545
• /
• 1997

This paper presents a modified geometric active contour model or edge detection and segmentation of computed tomography(CT) scan images. The method is based on the level setup approach developed by Osher and Sethian and the modeling of propagation fronts with curvature dependent speeds by Malladi. Based on above algorithms, the geometric active contour is obtained through a particular level set of hypersurface lowing along its gradient force and curvature force. This technique retains the attractive feature which is topological and geometric flexibility of the contour in recovering objects with complex shapes and unknown topologies. But there are limitations in this algorithm which are being not able to separate the object with weak difference from neighbor object. So we use speed limitation filter to overcome those problems. We apply a 2D model to various synthetic cases and the three cases of real CT scan images in order to segment objects with complicated shapes and topologies. From the results, the presented model confirms that it attracts very naturally and efficiently to the desired feature of CT scan images.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.247-254
• /
• 2008

The primary objective of this research is to develop an efficient design and optimization methodology for SRM Wagon Wheel Grain and to develop of software for practical designing and optimization of Wagon Wheel grains. This work will provide a design process reference guide for engineers in the field of Solid Rocket Propulsion. Using these proposed design methods, SRM Wagon Wheel grains can be designed for various geometries, their optimal solutions can be found and best possible configuration be attained thereby ensuring finest design in least possible iterations & time. The main focus is to improve computational efficiency at various levels of the design work. These have been achieved by the following way. a. Evaluation of system requirements and design objectives. b. Development of Geometric Model of Wagon Wheel grain configuration. c. Internal ballistic performance predictions. d. Preliminary designing of the Wagon Wheel grain configuration involving various independent geometric variables. e. Optimization of the grain configuration using Sequential Quadratic Programming f. In depth analysis of the optimal results considering affects of various geometric variables on ballistic parameters and analysis of performance prediction outputs have been performed g. Development of software for design and optimization of Wagon Wheel Grain. By using these proposed design methods, SRM Wagon Wheel grains can be designed by using geometric model, their optimal solutions can be found and best possible configuration be attained thereby ensuring finest design.

• 연구논문집
• /
• s.34
• /
• pp.59-68
• /
• 2004

The hot spot stress approach and the notch strain approach are discussed with some results of them. And a stress model that can be applicable to several types of weld joints with single S-N curve of the base material. The stress model uses the geometric characteristics of the stress distribution vicinity of weld joints. The model was applied to five different weld joins(the base material is SM490B). By the representative stress, the experimental fatigue data are plotted very closely to the S-N curve of the base material.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.7
• /
• pp.108-115
• /
• 1997

In this paper, an algorithm of computing interference-free tool approach directions(visibility cone) with consideration of tool volume at an arbitrary point of a sculptured surface is developed. The surface is first approximated into a polyhedron with smaller subpatches and the tool approach directions are evenly sampled so as to test accessibility. Then the visibility cone is computed by testing if each approach direction is interfered by other surface subpatches. The results are represented as the binary spherical map which transform geometric information on sphere into aogebraic one. The developed algorithm is implemented and tested by several sculptured surfaces, convincing it can be easily used as a tool for not only interference- free tool approach directions but also determining process planning of multi-axis NC machining of sculp- tured surfaces

• Korean Management Science Review
• /
• v.18 no.1
• /
• pp.41-54
• /
• 2001

In this paper, we proposed a method to determine optimal wave source for mobile telephone communication. The approach is based on wave propagation simulation. Given a wave source we can determine wave propagation effects on every surfaces of wave simulation environment. The effect is evaluated as a cost function while the source’s position x, y, z work as variables for a parameter optimization. Wave propagated 3 dimensional space generates reflected waves whenever it hits boundary surface, it receives multiple waves which are reflected from various boundary surfacers in space. Three algorithms being implemented in this paper are based on a raytracing theory. If we get 3 dimensional geometry input as well as wave sources, we can compute wave propagation effects all over the boundary surfaces. In this paper, we present a new approach to compute wave propagation. First approach is tracing wave from a source. Source is modeled as a sphere casting vectors into various directions. This approach has limit in computing necessary wave propagation effects on all terrain surfaces. The second approach proposed is tracing wave backwards : tracing from a wave receiver to a wave source. For this approach we need to allocate a wave receiver on every terrain surfaces modeled, which requires enormous amount of computing time. But the second approach is useful for indoor wave propagation simulation. The last approach proposed in this paper is tracing sound by geometric computation. We allow direct, 1-relfe tion, and 2-reflection propagation. This approach allow us to save in computation time while achieving reasonable results. but due to the reflection limitaion, this approach works best in outdoor environment.

• Journal of the Korean Mathematical Society
• /
• v.44 no.6
• /
• pp.1469-1477
• /
• 2007

A family of balanced groups is introduced. We describe some geometric approach to find these groups in terms of the (orientable) closed 3-manifolds and its fundamental groups.

• Bulletin of the Korean Mathematical Society
• /
• v.53 no.4
• /
• pp.1043-1049
• /
• 2016

In this paper we study questions about automorphism groups of domains in ${\mathbb{C}}^n$, formulating the ideas entirely in terms of metric geometry. We also provide some applications.

• Bulletin of the Korean Chemical Society
• /
• v.2 no.2
• /
• pp.48-55
• /
• 1981

A new approach in calculating the dipole moments for transition metal complexes has been proposed and the calculated results are tabulated with the experimental values. The calculated dipole moments are applied to the theoretical prediction or confirmation of the geometric structure for the transition metal complexes.

• Kyungpook Mathematical Journal
• /
• v.63 no.4
• /
• pp.647-707
• /
• 2023

In this article, we discuss and survey the recent progress towards the Schottky problem, and make some comments on the relations between the André-Oort conjecture, Okounkov convex bodies, Coleman's conjecture, stable modular forms, Siegel-Jacobi spaces, stable Jacobi forms and the Schottky problem.

• Structural Engineering and Mechanics
• /
• v.25 no.5
• /
• pp.501-518
• /
• 2007

In this work, a new approach is developed for dynamic analysis of a composite beam with an interply crack, based on finite element solution of partial differential equations with the use of the COMSOL Multiphysics package, allowing for fast and simple change of geometric characteristics of the delaminated area. The use of COMSOL Multiphysics package facilitates automatic mesh generation, which is needed if the problem has to be solved many times with different crack lengths. In the model, a physically impossible interpenetration of the crack faces is prevented by imposing a special constraint, leading to taking account of a force of contact interaction of the crack faces and to nonlinearity of the formulated boundary value problem. The model is based on the first order shear deformation theory, i.e., the longitudinal displacement is assumed to vary linearly through the beam's thickness. The shear deformation and rotary inertia terms are included into the formulation, to achieve better accuracy. Nonlinear partial differential equations of motion with boundary conditions are developed and written in the format acceptable by the COMSOL Multiphysics package. An example problem of a clamped-free beam with a piezoelectric actuator is considered, and its finite element solution is obtained. A noticeable difference of forced vibrations of the delaminated and undelaminated beams due to the contact interaction of the crack's faces is predicted by the developed model.