• Journal of the Society of Naval Architects of Korea
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• v.36 no.3
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• pp.50-59
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• 1999

This paper is concerned on the generation of an optimal section of wing in ground effect by a SQP method which is one of nonlinear optimization techniques. A potential panel method is used for the flow analysis and the ground effect is taken into account by an image method. The numerical method is first verified by an inverse problem where a shape of wing section is sought for the prescribed pressure distribution. The purpose of the present paper is to generate a wing section which can give a maximum lift subjected to the design constraints including the height stability which is important in the WIG design. The effect of the tail wing is also included.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.2
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• pp.96-108
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• 2022

In this paper, we propose a systematic hull form variation technique which automatically satisfies the displacement constraint and guarantees a high level of fairness. This method is possible through multiple parameter correction curves. The present method is to improve the hull form variation method based on parametric modification function and consists of two sub-categories: SAC variation and section lines modification. For SAC variation, the utilization of two B-Spline curves satisfying GC¹ condition led to the satisfaction of displacement constraint and high level of fairness at the same time. Section lines modification methods involves in using two fuctions: the first is the waterplane modification function combining two cubic splines. the other function is the sectional area modification function consisting of 2nd order polynomial over the DLWL(Design Load Waterline) and 3rd order polynomial below the DLWL, This function enables not only the fundamental U-V section shape variation but also systematically modified section lines. The present method is expected to be more useful in the hull form optimization process using CFD compared to the existing method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.4
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• pp.487-497
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• 2015

Using existing tunnel for section enlargement and remodeling is being considered as an optimal alternative in order to solve traffic jam in tunnel. The existing method has been performed while blocking the traffic flow. Recently, New enlargement method was developed which can maintain traffic flow during the construction by using protector. It can minimize social loss due to keeping traffic flow. On the other hand, installing and operating protector can cause economic disadvantages. So, social cost estimation considering traffic flow should be considered for relevant economic evaluation of tunnel section enlargement methods. This paper presents the social cost estimation method of tunnel section enlargement methods considering traffic flow. In addition, to compare economic efficiency existing method with new method, suggested method was applied to Maebong Tunnel.

• Proceedings of the IEEK Conference
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• 2003.07e
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• pp.2379-2382
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• 2003

This paper describes the design, implementation and results of a unified non-rigid image registration method for the purposes of 3D shape reconstruction from serial section images. The proposed method uses active contour-based segmentation and compensation of radial distortion. Experimental results show that multiple images can be segmented and reconstructed by active single contour as well as intra- and inter-section registration.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.4
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• pp.189-195
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• 2017

In the seismic design of building structural members, due to the complexity of the placement of PC steels in prestressed concrete members, it is necessary to review and define the definition of member damage in comparison with reinforced concrete members. In this study, the results of past experiments compared with the calculation results by 'section Analysis Method', with the aim of reviewing the precision of calculation results when member damage evaluation is performed using the section analysis method. Furthermore, it is also compared with the calculation results by the 'split Element Method'. In addition, parametric studies were carried out, and the influence of the difference between the amount of PC steels and reinforced bar on the residual strain was examined.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.5
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• pp.380-386
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• 2015

Panel methods are useful tools for analyzing fluid-flow around a wing section. It has the advantage of fast and accurate calculation, compared to other CFD Methods such as RANS solvers. This paper suggests a piecewise linear panel method in order to improve accuracy of existing panel methods by changing the piecewise constant singularity strength to linear singularity strength(for dipole strength). The piecewise linear panel method adopts the linear distribution of singularity strength, while control point is located at the node of each panel. Formulation of the piecewise linear panel method is given, and some calculation results are shown for typical wing sections.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.68-71
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• 2006

Traditional section-based method develops blank along section planes and find trimming line by generating loop of end points. This method suffers from inaccurate results for regions with out-of-section motion. In this study, new fast method to find feasible trimming line is proposed. One step FEM is used to analyze the flanging and incremental development method is proposed to handle bad-shaped mesh and undercut part. Also in order to remedy mesh distortion during development, energy minimization technique is utilized. The proposed method is verified by shrink/stretch flange forming and successfully applied to the complex industrial applications such as door outer flanging process.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.629-638
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• 2009

In this paper, the existing formulas of the step-by-step method were generalized for effective estimation of responses of complicated composite sections due to long-term deformation of concrete. The initial transformed section properties of the composite section were derived from material and section properties of concrete section and sections which confine the longterm deformation of concrete. The transformed section properties at each step were derived from the effective modulus of elasticity considered the creep coefficient variation. Improved formulas of the step-by-step method for generalized responses were derived by introducing 5 generalized parameters. The formulas can be more simplified by applying constant increment of creep coefficient at each step. The constant increment of creep coefficient at each step can also reduce computing time and make equal computing error of each step. The generalized responses for axial elastic strain of concrete section were most sensitive to the area rate of concrete section, and the ratio of the second moment of the confining section area was more sensitive than that of the concrete section. Those for elastic curvature of concrete section were most sensitive to the ratio of the second moment of concrete section area.

• Proceedings of the KSR Conference
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• 1998.11a
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• pp.54-60
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• 1998

PSC box bridges by MSS construction method in high-speed railway may not be cast in place at one step. Web and bottom flange(U member) in the cross section are cast in place at first, then top flange will be cast in place later with some time lag. In this section, stress distributions of U member and top flange are different with those in generally complete cast in place cross section. In the composite section composed of two different aged members, the redistribution of stresses takes place. This results from time-dependent strain characteristics of concrete and the effects of forces applied at the various stages. For comparison in the present paper, two models, one with the composite cross section and the other with generally complete cast in place cross section, are analyzed. The longitudinal stress differences of two models on considering construction stages are compared. As the analysis results show the considerable differences in the stresses of cross section between two models, the composition of cross section is considered for rational design of PSC box girder bridge.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.4
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• pp.95-112
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• 2009

The river cross section in the input/output data which are needed in the area of river flow analysis is very important factor. The bottom elevation of actual river cross section has to be correctly reflected to obtain correct results when two dimensional flow analysis is conducted for natural river. But to reflect virtually the bottom elevation of river cross section is impossible. The objective of this study is to suggest a method for creating equi-distance river cross section by using both HEC section and ArcView and constructing the finite element mesh. The main channels of Han and Nakdong river were selected and equi-distance river cross sections constructed in this study have shown good agreement with the observed river cross sections. In addition, high quality finite element meshes can be applied to many areas of study such as finite element analysis for water quality and two dimensional flow analysis using the suggested method for equi-distance river cross sections in this study.