• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.93-98
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• 2016

This study analyzed the inflow characteristics of debris flow according to shape of defensive structure and computed risk index. In order to simulate debris flow, two shapes of defensive structure were considered. Initial mass distribution was set with a rectangular shape and defensive structures were set semi-circular shape and rectangular shape, respectively. It was found that a defensive structure with semicircular shape was more vulnerable to debris impact compared with rectangular shape because the flow mass became concentrated in quadrant part of the inner circle. If the velocity of the debris flow was less than 1 m/s, the risk assessment by FII (Flood Intensity Index) was much appropriate. However, when the movement of debris runout was faster than 1 m/s, the risk index of FHR (Flood Hazard Rating) provided improved classification due to its subdivided hazardous range.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.1
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• pp.11-16
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• 2007

The fatigue properties of Ti-Ni shape memory alloy wires were investigated. In Ni-rich Ti-Ni shape memory alloys, $Ti_3Ni_4$ precipitates formed by aging treatments are believed to vary the shape memory and mechanical properties. In this study, the effect of aging temperature and aging time on shape memory properties and fatigue life were investigated using Ti-50.9 at% Ni alloy wires. The specimens were solution-treated at 1073 K for 3.6 ks followed by aging at 573 K, 673 K and 773 K for periods between 3.6 ks and 3600 ks. It was found that the fatigue life under a constant stress decreased with increasing aging temperature. When the specimens were aged at 573 K for periods between 36 ks and 360 ks, superior shape memory and fatigue properties were obtained. The fatigue life also decreased when the test temperature and strain amplitude increased. It was concluded that the fatigue life exhibited a linear relationship with the critical stress for slip.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.5
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• pp.356-361
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• 2014

Accurate block shape assessment is critical for ship manufacturing and a careful assessment of the shape of a fabricated block against the design shape is a core issue. However, in current fabrication practice, the shape of each block is evaluated manually using rigid body transformation. This manual evaluation process entirely depends on workers' experiences and knowledge and makes automation of block shape assessment difficult. In this paper we propose a computation method on the registration for shape assessment of a block during the fabrication process and for evaluation of its completion against the design shape. A conversion on matching method by adding DOF(degree of freedom) restriction is required to reach the goals. We test our method using a real block quality assessment data to demonstrate its applicability to real ship manufacturing process.

• Journal of Biosystems Engineering
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• v.30 no.5 s.112
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• pp.268-273
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• 2005

This study was conducted to investigate the specificities of four fulcrum types for geo-statistical analysis of elevation within rice paddy field. In Korea, the spaces between inter-rows and between hills for rice transplanting are 30cm and 11cm to 14cm, respectively. So, the size and shape of fulcrum for field elevation measurement should be considered according to the inter-row and the hill spaces. Four kinds of fulcrum were chosen such as round-shape with 2.5cm diameter, circular-shape with 10cm diameter, 10cm (one third of inter-row space) by 24cm (double of hill space) rectangular-shape, and 20cm (two-thirds of inter-row space) by 24cm rectangular-shape. The resulting descriptive statistics couldn't determine the best fulcrum type to measure the rice paddy field elevation. But the results of geo-statistical analysis could determine the best fulcrum type. In the case of 10cm by 24cm rectangular-shape fulcrum, Nugget and range, meaning measurement error and/or noise, and limit of spatial connection, respectively, were minimum; Q value meaning weight of spatial structure and $r^2$ value were minimum, and residual sum of squares was minimum. It means that 10cm by 24 cm rectangular-shape fulcrum could best describe the rice paddy field elevation.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.3
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• pp.161-166
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• 2017

Inconel 718, a typical ultraheat-resistant alloy, is recognized as a useful component in aircraft parts owing to its high-temperature strength and good chemical stability. Although many studies have been conducted to determine the proper drill shape to overcome the poor machinability when drilling into Inconel 718, most have involved a cutting process program known as AdvantEdge, as an experimental approach requires much time and money. In this study, our purpose is to optimize the drill shape for efficient drilling by conducting a trust force and temperature analysis using AdvantEdge. In order to achieve this purpose, the reliability of the results of the analysis was verified and by applying design of experiment an analysis of the geometric parameters of the drill shape considering the thrust force and temperature was conducted.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.130-138
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• 2007

A coupled variational equation for fluid-structure interaction (FSI) problems is derived from a steady state Navier-Stokes equation for incompressible Newtonian fluid and an equilibrium equation for geometrically nonlinear structures. For a fully coupled FSI formulation, between fluid and structures, a traction continuity condition is considered at interfaces where a no-slip condition is imposed. Under total Lagrange formulation in the structural domain, finite rotations are well described by using the second Piola-Kirchhoff stress and Green-Lagrange strain tensors. An adjoint shape design sensitivity analysis (DSA) method based on material derivative approach is applied to the FSI problem to develop a shape design optimization method. Demonstrating some numerical examples, the accuracy and efficiency of the developed DSA method is verified in comparison with finite difference sensitivity. Also, for the FSI problems, a shape design optimization is performed to obtain a maximal stiffness structure satisfying an allowable volume constraint.

• Wind and Structures
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• v.30 no.1
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• pp.15-27
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• 2020

This paper reports the study on development and verification of numerical models and analyzes of flow at high speed around structural elements in the shape of a curved pipe (e.g., a fragment of a water slide). Possibility of engineering estimation of wind forces acting on an object in the shape of a helix is presented, using relationships concerning toroidal and cylindrical elements. Determination of useful engineering parameters (such as aerodynamic forces, pressure distribution, and air velocity field) is presented, impossible to obtain from the existing standard EN 1991-1-4 (the so-called wind standard). For this purpose, flow at high speed around a torus and helix, arranged both near planar surface and high above it, was analyzed. Analyzes begin with the flow around a cylinder. This is the simplest object with a circular cross-section and at the same time the most studied in the literature. Based on this model, more complex models are analyzed: first in the shape of half of a torus, next in the shape of a helix.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.279-286
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• 2000

The objective of this research is to detect the papaya fruits on tree in an orchard. The detection of papaya on natural background is difficult because colors of fruits and background such as leaves are similarly green. We cannot separate it from leaves by color information. Therefore, this research will use shape information instead. First, we detect an interested object by detecting its boundary using edge detection technique. However, the edge detection will detect every objects boundary in the image. Therefore, shape description technique will be used to describe which one is the interested object boundary. The good shape description should be invariant in scaling, rotating, and translating. The successful concept is to use Fourier series, which is called "Fourier Descriptors". Elliptic Fourier Descriptors can completely represent any shape, which is selected to describe the shape of papaya. From the edge detection image, it takes a long time to match every boundary directly. The pre-processing task will reduce non-papaya edge to speed up matching time. The deformable template is used to optimize the matching. Then, clustering the similar shapes by the distance between each centroid, papaya can be completely detected from the background.

• Structural Engineering and Mechanics
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• v.72 no.2
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• pp.217-227
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• 2019

The methodology known as "shape sensing" allows the reconstruction of the displacement field of a structure starting from strain measurements, with considerable implications for structural monitoring, as well as for the control and implementation of smart structures. An approach to shape sensing is based on the inverse Finite Element Method (iFEM) that uses a variational principle enforcing a least-squares compatibility between measured and analytical strain measures. The structural response is reconstructed without the knowledge of the mechanical properties and load conditions but based only on the relationship between displacements and strains. In order to efficiently apply iFEM to the most common structural typologies of civil engineering, its formulation according to the kinematical assumptions of the Bernoulli-Euler theory is presented. Two beam inverse finite elements are formulated for different loading conditions. Depending on the type of element, the relationship between the minimum number of required measurement stations and the interpolation order is defined. Several examples representing common applications of civil engineering and involving beams and frames are presented. To simulate the experimental strain data at the station points and to verify the accuracy of the displacements obtained with the iFEM shape sensing procedure, a direct FEM analysis of the considered structures is performed using the LUSAS software.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1433_1434
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• 2009

AC PDP는 다른 디스플레이들에 비해 높은 소비전력과 낮은 발광효율에 대한 문제를 가지고 있다. 이러한 문제를 해결하기 위해 본 연구에서는 기존의 Stripe shape ITO(Indium Tin Oxide)전극구조에서 Lock shape ITO전극구조를 제안하였다. 이 구조는 long gap을 가진 Square형태의 전극구조에 'ㄱ'형태의 점화전극을 추가한 구조로, 소비전력을 줄이기 위해 전극면적을 줄이고, discharge current를 제어 하였다. 또한 점화전극 구조에 의해 늘어난 gap으로 인한 방전개시전압 상승을 줄 일수 있었다. 실험은 Stripe shape ITO구조와 Lock shape ITO의 전극구조들로 구성되어 있는 Test Panel을 직접 제작하여 방전개시전압, 휘도, 소비전력, 발광효율을 측정하여 그 특성들을 비교하였다. 그 결과 제안된 전극구조에서의 소비전력은 reference 구조에 비해 최대 18% 감소하였고, 발광효율은 최대 13% 상승을 함을 보였다.