• 한국정보통신학회논문지
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• 제19권4호
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• pp.895-902
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• 2015

본 논문은 대형 터치스크린을 위한 고속 터치감지 및 노이즈 제거를 위한 FDCS (Frequency division concurrent sensing) 기법을 제안한다. 기존의 터치스크린 감지방식은 대부분 구동신호를 순차적으로 인가하고 순차적으로 센싱신호를 분석하기 때문에 감지속도가 터치스크린 크기에 따라 급격히 감소하여 대형터치스크린에 적용하기 어려운 문제점이 있다. 제안된 기법은 모든 드라이브라인에 서로 다른 주파수의 신호를 동시에 인가하고 각 센스 라인의 신호를 주파수 영역에서 분석하는 기법으로 대형스크린에서도 고속의 감지속도를 제공한다. 또한 주파수영역에서 노이즈 필터링기법을 제안하여 터치감지신호는 누적하고 노이즈는 상쇄하며, 터치스크린의 주파수전달함수의 역의 특성을 가지는 pre-distortion equalizer를 적용하여 터치감도 SNR을 더욱 개선한다. 23" 대형 터치스크린 모델에 실제의 환경 노이즈를 적용하여 실험한 결과 본 제안기술이 기존 기법 대비 frame scan rate을 274%, SNR을 43dB 증가시킴을 보인다.

• 한국해안해양공학회지
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• 제13권3호
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• pp.195-201
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• 2001

본 논문은 파랑중에 다전 계류된 원유저장선에 대한 저주파수 운동을 수치 모사하였다. 시간영역에서의 운동방정식은 충격응답함수를 포함하여 수평면상의 운동 즉 전후, 좌우 및 선수 운동을 고려하였다. 시간영역의 운동방정식에 나타난 부가질량, 파랑감쇠계수, 1차항 파랑 강제력 그리고 2차항 파랑 강제력을 주파수 영역의 특이점 분포법을 사용하여 계산하였고, 다점 계류된 계류삭은 체인이 해저면에 닿은 운동 효과를 포함하여 준 정적 현수선 이론으로 산정되었다. 계산 예로서 장파정 불규칙 파랑 중에 놓인 바아지식 원유저장선에 대한 시간 영역 해석을 수행하였다.

• 대한기계학회논문집B
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• 제24권7호
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• pp.895-906
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• 2000

A three dimensional linear frequency-domain lifting surface panel method was used for the aerodynamic analysis of axial flow type micro-fans. As proven by the duct modeling, the tip clearance of the micro-fans tested is large enough to ignore the calculated effect of the duct system. As the numerical results and experimental data agreed well in the operating point region, the method was applicable in the parametric studies to determine the design parameters of axial flow fans. Experiments on micro-fans were carried out based on KS B 6311. The newly designed micro-fan showed improvements in both static pressure rise and volumetric flow rate compared to the existing fans at a given operating condition. No detection of surging and the smooth characteristic curve proved the improvement in performance. To reduce the fan noise in the fan design, it was necessary to make use of the frequency spectrum analysis data. Measurement of sound pressure level for micro-fans was conducted based on KS B 6361 and KS A 0705. The peak - which occurs at blade passage frequency and its higher harmonics due to the fan noise - was not detected. This justifies the design methodology of the blade.

• Advances in aircraft and spacecraft science
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• 제8권4호
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• pp.345-372
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• 2021

The analysis of nonlinear vibrations, buckling, post-buckling, flutter boundary determination and post-flutter behavior of a homogeneous curved plate assuming cylindrical bending is conducted in this article. Other assumptions include simply-supported boundary conditions, supersonic aerodynamic flow at the top of the plate, constant pressure conditions below the plate, non-viscous flow model (using first- and third-order piston theory), nonlinear structural model with large deformations, and application of mechanical and thermal loads on the curved plate. The analysis is performed with constant environmental indicators (flow density, heat, Reynolds number and Mach number). The material properties (i.e., coefficient of thermal expansion and modulus of elasticity) are temperature-dependent. The equations are derived using the principle of virtual displacement. Furthermore, based on the definitions of virtual work, the potential and kinetic energy of the final relations in the integral form, and the governing nonlinear differential equations are obtained after fractional integration. This problem is solved using two approaches. The frequency analysis and flutter are studied in the first approach by transferring the handle of ordinary differential equations to the state space, calculating the system Jacobin matrix and analyzing the eigenvalue to determine the instability conditions. The second approach discusses the nonlinear frequency analysis and nonlinear flutter using the semi-analytical solution of governing differential equations based on the weighted residual method. The partial differential equations are converted to ordinary differential equations, after which they are solved based on the Runge-Kutta fourth- and fifth-order methods. The comparison between the results of frequency and flutter analysis of curved plate is linearly and nonlinearly performed for the first time. The results show that the plate curvature has a profound impact on the instability boundary of the plate under supersonic aerodynamic loading. The flutter boundary decreases with growing thermal load and increases with growing curvature.

• 대한조선학회논문집
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• 제38권2호
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• pp.10-18
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• 2001

초대형 해상 공항은 길이나 폭이 수 킬로미터인 거대 구조물이며, 해상에 계류된 해상공항의 설계에 있어 파도에 의한 1차항 파강제력과 2차항 파강제력은 반드시 고려하여야 한다. 본 논문에서 파중에서 돌핀계류된 해상공항에 대한 운동응답의 시간영역해석이 제시된다. 운동방정식에서 동유체력 계수와 파도에 의한 힘은 주파수 영역의 3차원 패널 방법으로부터 계산되며, 동시에 돌핀계류계에 대한 계류력과 수평방향의 표류력이 본 계산에서 얻어진다. 본 논문의 계산 예로 일본에서 실증실험을 수행한 phase I 해상공항에 대해 불규칙파 중에서 시간영역 해석이 제시된다.

• 대한조선학회논문집
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• 제49권4호
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• pp.312-326
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• 2012

This paper considers a fully coupled 3D BEM-FEM analysis for the ship structural hydroelasticity problem in waves. Fluid flows and structural responses are analyzed by using a 3D Rankine panel method and a 3D finite element method, respectively. The two methods are fully coupled in the time domain using a fixed-point iteration scheme, and a relaxation scheme is applied for improve convergence. In order to validate the developed method, numerical tests are carried out for a barge model. The computed natural frequency, motion responses, and time histories of stress are compared with the results of the beam-based hydroelasticity program, WISH-FLEX, which was thoroughly validated in previous studies. This study extends to a real-ship application, particularly the springing analysis for a 6500 TEU containership. Based on this study, it is found that the present method provides reliable solutions to the ship hydroelasticity problems.

• 한국해양공학회지
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• 제33권6호
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• pp.504-509
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• 2019

The wave-generation performance of a piston-type wave maker was analyzed using the numerical wave tank technique, and the numerical results were compared with theoretical solutions. A two-dimensional frequency domain analysis was conducted based on the Rankine panel method. Various parameters were used to examine the wave-generation performance, such as the width and gap of the wave board. The effects of the thickness of the wave board and of the gap from the bottom of the tank were evaluated. The difference in the amplitude of the generated wave between the analytical solution and the numerical result was examined, and its causes were addressed due to the gap flow between the bottom of the tank and the wave board. This parametric analysis can be utilized to design an optimum wave make parametric analysis to design an optimum wave maker that can generate waves with amplitudes that can be predicted accurately.