• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.940-949
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• 2013

In this paper, wrinkle reduction design was studied for triangular sail. Wrinkles in the solar sail membrane can change the load path and surface topology which may have an adverse effect on propulsion performance and controllability. In this study, wrinkle reduction strategies of adjusting cable angle, catenary and catenary-wire schemes were considered and the design parameters for wrinkle reduction were systematically investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.851-858
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• 2008

In this paper, the wrinkling behavior of vertically creased corner-loaded square membranes was studied using geometrically nonlinear post-buckling analysis. The membranes were modeled using shell elements, and the meshes were seeded with semi-random geometrical imperfection to instigate the buckling deformation. A pristine and creased membranes with various initial deployment angles were considered in the analyses and the results were compared. Results showed that local wrinkles initiated near the corner where the higher load was applied, which grew to form a single diagonal global wrinkle as the load ratio increased. It was also found that the local wrinkle initiation and the global wrinkle formation were significantly dependent on the initial deployment angles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.423-430
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• 2012

In this paper, the effect of wrinkling on the cut propagation direction of thin membrane was studied using geometrically nonlinear shell element post-buckling analysis. In the analysis, rectangular tensile membrane configuration with a slanted center cut was considered. The cut propagation direction was predicted by maximum energy release rate method, $K_{II}$-zero method, and maximum tangential stress method. The cut propagation angle and the $J$-integral values were calculated for the wrinkled and unwrinkled cases and the results were compared. Various initial cut orientation angles were considered and the effect on the propagation direction was studied. The cut propagation paths were also predicted by virtual cut extension approach.

• 전자공학회논문지 IE
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• v.44 no.2
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• pp.32-40
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• 2007

In this paper, the crease extraction method is proposed to improve the accuracy of feature extraction within the fingerprint image. First of all, for each pixel in fingerprint image, it calculates the average grey level and variance to determine if the current pixel composes the crease, and estimates the direction of crease. Secondly, once the direction of every pixel in crease candidate area is estimated, it is decomposed into 8 different images, depending on their direction. The properties of crease consists of the length of the crease candidate area, the correspondence between the crease direction and the pixel distribution direction, the difference between the ridge direction and the pixel distribution direction, and finally the grey level of the candidate pixels. The proposed method finally extracts the crease from the crease clusters estimated from directional images. In conclusion, applying the proposed method improved the accuracy of overall feature extraction by 91.4% by accurately and precisely extracting the crease from fingerprint image.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.90-97
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• 2007

For a highly reliable fingerprint recognition system, the precise and accurate feature extraction is indispensable. In this paper, We propose a highly efficient crease extraction method, which can improve the accuracy of feature extraction within the fingerprint image. The proposed method applies the 1-dimensional directional slit for each pixel in fingerprint image. And then it calculates the average grey level and variance to determine whether the current pixel composes the crease, and estimates the direction of crease. Once the direction of every pixel in crease candidate area is estimated, it is decomposed into 8 different images depending on their direction. From the 8 directional images, the crease clusters are estimated by utilizing the property of crease area. The proposed method finally extracts the crease from the crease clusters estimated from directional images. In conclusion, the proposed method highly improved the accuracy of overall feature extraction by accurate and precise extraction of the crease from fingerprint image.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.39-43
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• 2011

In this study, the stress and deformation behavior characteristics of a flexible joint for a gas pipe have been analyzed by a finite element method. These characteristic results may investigate the strength safety analysis of a flexible joint, which is composed by a spiral corrugation pipe or a rectangular corrugation model and a plane pipe. The FEM computed results show that an optimized spiral corrugation pipe model is a inclined angle of $4.7^{\circ}$ and a corrugation height of 1.5mm. And also, a rectangular corrugation pipe model of $90^{\circ}$ is recommended in strength safety rather than a spiral corrugation pipe with an inclined angle. Thus, a corrugated pipe for an increased strength safety is to recommend a reduced pitch and curvature radius of an inclined corrugation.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.697-700
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• 2010

피부 이미지의 여러 가지 특징들 중 주름은 피부의 상태를 판단하는 중요한 요소이다. 따라서 주름을 추적하기 위해 확대경으로 촬영된 원본 이미지에서 질감 대비 증가, 노이즈 제거 등의 전처리 과정을 수행한 후 Watershed 알고리즘을 이용하여 주름을 선분으로 표현하였다. 이렇게 생성된 주름의 깊이, 너비, 길이 등은 피부 분석 시 특징 정보로 이용할 수 있다. 또한 주름과 주름이 연결되어 이루는 다각형을 논문에서는 셀(Cell)이라고 정의하는데 그것의 크기나 개수 같은 정보도 추출할 수 있게 된다. 그러나 주름으로 만들어진 셀들은 실제와 다르게 과분할 되는 경향을 보인다. 과분할 된 셀들은 잘못된 정보를 제공하기 때문에 피부 상태를 판단하는 결과의 정확도를 떨어뜨린다. 본 논문에서는 이러한 문제점을 인지하고 차후 정확한 셀 정보를 획득하기 위한 확장성 측면에서 각 셀들을 개체화시키고 과분할 된 셀을 검출하는 방법을 제안한다.

• The Journal of the Acoustical Society of Korea
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• v.23 no.3
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• pp.192-196
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• 2004

A decision of the modulus of elasticity is made by using the degree of bending strength of materials for loudspeaker damper and the radius of corrugation lines and the radius of curvature of each corrugation as a geometrical element. And it is compared with experimental measurements. As a result. the elasticity of damper is proportional to the degree of bending strength and inversely proportional to the radius of corrugation lines and inversely proportional to the square of the radius of curvature. We made a small loudspeaker using a modified damper which take the form of inner small curvature and outer large curvature of each corrugation. This loudspeaker have the increased sensitivity in high frequency and also in low frequency region.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.154-159
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• 2012

For numerical analysis of the plate heat exchanger, a lot of time are required in modeling work and calculation. Whereas, this paper was purposed to identify characteristic of the plate heat exchanger through simplification of modeling by interpreting the numerical analysis proximity with the actual model. This study was also examined temperature difference between inlet side and outlet side, inner pressure drop, heat transfer area of plate and change of heat transfer coefficient on the plate depending on the inner corrugation angle and corrugation pitch of a herring bon pattern of the plate heat exchanger among chevron types of the plate exchanger.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.195-203
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• 2015

In this paper, the dynamic behavior of wrinkled triangular solar sail was studied by finite element analysis. The analysis was proceeded first by performing static wrinkle analysis under tensile corner load on sail membrane, and then performing modal analysis. The membrane element method with wrinkle algorithm and the shell element post-buckling analysis method were used to account for the wrinkle deformation and the results were compared for analysis methods throughly. The comparison was also made to that without wrinkle consideration to investigate the effect of wrinkle deformation on the results. Cases with various loading cable angles were analyzed and the results were systematically examined.