• 한국정보처리학회논문지
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• 제4권4호
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• pp.1121-1131
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• 1997

높은 앞축율을 가지는 동영상 압축 방법에 있어, 공간영역에서의 프랙탈을 이용한 동영상 앞축 방법은 복원영상의 블록화 현상이 두드러지는 단점이 있고, 웨이브릿 / 변환 영역에서의 동영상 압축 방법은 에지의 열화가 생기는 단점이 있다. 그러므로 본 논문에서는 이러한 단점을 보완하기 위해 높은 압축률에서도 에지가 선명하고 블록화 현상이 없는 웨이브릿 변환 영역에서의 프랙탈을 이용한 동영상 압축 방법을 제안한다 제안한 방법에서는 서로 다른 부대역간의 상관성을 이용하여 가변 블록 크기의 움 직임을 추정하고, 움직임 추청에 의하여 효과적으로 부호화되지 않는 웨이브릿 계수들은 저해상도 부대역에서 고해상도 부대역을 계층적으로 추정하는 프레임간 프랙탈 부호화 한다. 실험을 통하여 제안한 방법이 기존의 프랙탈과 웨이브릿을 이용한 동영상 부호와 방법도 더 좋은 성능을 나타냄을 보였다.

• 한국통신학회논문지
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• 제34권11B호
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• pp.1296-1302
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• 2009

본 논문에서는 MCTF와 표준 비디오 압축 도구를 이용하여 디지털 홀로그램을 효율적으로 부호화하는 방법을 제안한다. 홀로그램은 객체 영상과 깊이 정보를 바탕으로 하여 컴퓨터 생성 알고리즘으로부터 생성되었다. 제안한 알고리즘은 홀로그램을 분리하는 국부화 과정, $64\times64$ 크기의 세그먼트를 나누는 과정, 상관성을 유도하기 위한 DCT 과정, MCTF 과정, 압축을 위해 비디오 시퀀스를 만드는 과정, 그리고 H.264/AVC를 이용하여 압축하는 과정으로 구성된다. 제안한 알고리즘은 이전의 연구와 비교할 때 복원된 객체에 대해서 10%만큼 압축 효율이 향상되었다.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.847-868
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• 2016

In this study, the free vibration analysis of axially moving beams is investigated according to Reddy-Bickford beam theory (RBT) by using dynamic stiffness method (DSM) and differential transform method (DTM). First of all, the governing differential equations of motion in free vibration are derived by using Hamilton's principle. The nondimensionalised multiplication factors for axial speed and axial tensile force are used to investigate their effects on natural frequencies. The natural frequencies are calculated by solving differential equations using analytical method (ANM). After the ANM solution, the governing equations of motion of axially moving Reddy-Bickford beams are solved by using DTM which is based on Finite Taylor Series. Besides DTM, DSM is used to obtain natural frequencies of moving Reddy-Bickford beams. DSM solution is performed via Wittrick-Williams algorithm. For different boundary conditions, the first three natural frequencies that calculated by using DTM and DSM are tabulated in tables and are compared with the results of ANM where a very good proximity is observed. The first three mode shapes and normalised bending moment diagrams are presented in figures.

• 한국인터넷방송통신학회논문지
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• 제17권2호
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• pp.179-190
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• 2017

Hand Accelerometer는 인간신체 운동 패턴을 실시간으로 파악하는데 널리 사용되고 있다. 그러므로 행동 유형을 정확하게 파악하는 것은 아주 중요하다. 이 과정에서 각 행동유형의 형태를 미리 정확하게 파악하는 것이 중요하다. 인간의 신체 행동은 센서를 통해 수집된 시계열 데이터로 표현된다. 이 데이터는 비안정적, 비선형적 성격을 가지고 있다. 그래서 이런 성격의 데이터의 유형을 효율적으로 추출하는 방법을 찾는 것은 매우 중요하다. 힐버트-황 변환은 비안정적 비선형적 요소를 시계열데이터에서 효율적으로 추출하는 방법이다. 이 방법을 위의 시계열 데이터에 적용한 결과 핵심패턴이 성공적으로 추출되었다.

• Earthquakes and Structures
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• 제20권4호
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• pp.457-471
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• 2021

This study aims at providing a simple and effective methodology to define a meaningful characteristic period for special class of earthquake records named "pulse-like ground motions". In the proposed method, continuous wavelet transform is employed to extract the large pulse of ground motions. Then, Fourier amplitude spectra obtained from the original ground motion and the residual motion is simply compared. This comparison permits to define a threshold pulse-period (Tp∗) as the threshold period above which the pulse component has negligible contributions to the Fourier amplitude spectrum. The effect of pulse on frequency content of motions was discussed on the light of this definition. The advantage and superior features of the new definition were related to the inelastic displacement ratio (IDR) for single-degree-of-freedom systems with period equal to one half of the threshold period. Analyses performed for the proposed period at three ductility levels u=2,4,6 were compared with the results obtained at half of pulse period derived from wavelet analysis, peak-point method and the peak of product of the velocity and the displacement response spectra (Sv x Sd). According to the results, pulse effects on inelastic displacement ratio seem to be more important when $\frac{T_p^*}{T}=2$ (T is the fundamental vibration period of system). The results showed that utilizing of the proposed definition could facilitate an enhanced understanding of pulse-like records features.

• Structural Engineering and Mechanics
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• 제85권2호
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• pp.247-263
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• 2023

The paper deals with the study of the mechanical time-harmonic forced vibration of the hydro-piezoelectric system consisting of the piezoelectric plate and compressible viscous fluid with finite depth. The exact equations of motion of the theory of linear electro-elasticity for piezoelectric materials are employed for describing the plate motion, however, the fluid flow is described by employing the linearized Navier-Stokes equations for a compressible (barotropic) viscous fluid. The plane-strain state in the plate and the plane flow of the fluid are considered and the corresponding mathematical problems are solved by employing the Fourier transform with respect to the space coordinate which is on the coordinate axis directed along the platelying direction. The expressions of the corresponding Fourier transform are determined analytically, however, the inverse transforms are found numerically. Numerical results on the interface pressure and the electrical potential are obtained for various PZT materials and these results are discussed. According to these results, in particular, it is established that the electromechanical coupling effect can significantly decrease the interface pressure.

• 한국통신학회논문지
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• 제28권4C호
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• pp.397-405
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• 2003

본 논문에서는 MRME(multiresolution motion estimation)의 처리속도를 개선하고자, 웨이블릿 계수의 각 대역별 특성을 이용하여 영상의 화질을 유지하면서 계산량을 줄일 수 있는 효율적인 움직임 추정 기법을 제안하였다. 일반적으로 동영상의 연속한 프레임간에는 유사성이 높기 때문에, 기저대역에서 블록간 MAD(mean absolute difference) 값을 임계치와 비교하여 먼저 움직임 벡터의 존재 여부를 파악한다. 움직임이 없는 영역으로 판단되어지면, 웨이블릿 변환의 특성에 따라 고주파 부대역에 대해서도 움직임이 없는 것으로 판단한다. 반대로 움직임이 있는 영역으로 판단되어질 경우는 고주파 부대역의 에너지 성분을 비교하여 선별적으로 움직임을 추정함으로써 계산량을 줄일 수 있다. 모의 실험 결과 제안된 기법에서 MRME와 비교하여 거의 대등한 PSNR을 유지하면서 30~50%의 처리속도 향상을 보였다.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.513-521
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• 2018

In this paper, the resonance response of spar-type floating platform in coupled heave and pitch motion is investigated using a CPU time-effective numerical method. A coupled nonlinear 2-DOF equation of motion is derived based on the potential wave theory and the rigid-body hydrodynamics. The transient responses are solved by the fourth-order Runge-Kutta (RK4) method and transformed to the frequency responses by the digital Fourier transform (DFT), and the first-order approximation of heave response is analytically derived. Through the numerical experiments, the theoretical derivation and the numerical formulation are verified from the comparison with the commercial software AQWA. And, the frequencies of resonance arising from the nonlinear coupling between heave and pitch motions are investigated and justified from the comparison with the analytically derived first-order approximation of heave response.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2393-2396
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• 2005

We present a method to detect on-road vehicle using geometric invariant of feature points on side planes of the vehicle. The vehicles are assumed into a set of planes and the invariant from motion information of features on the plane segments the plane from the theory that a geometric invariant value defined by five points on a plane is preserved under a projective transform. Harris corners as a salient image point are used to give motion information with the normalized correlation centered at these points. We define a probabilistic criterion to test the similarity of invariant values between sequential frames. Experimental results using images of real road scenes are presented.

• 대한인간공학회지
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• 제17권1호
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• pp.11-22
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• 1998

When grasping a movable object or making an object move, humans feel kinesthetic sense. The kinesthetic sense is the human sense that the human feels in response to the motion acted on him. The objective of the paper is to transform the kinesthetic sense associated with the human arm into the quantified data that are useful from the engineering viewpoint. A 2-dimensional motion generator composed of two linear motors was developed to provide various motion patterns. It can change its stiffness and damping values on the real-time basis by properly regulating the force generated by the linear motors. Based on Taguchi method, the most dominant factors to affect the kinesthetic sense were investigated. Also, a reference function adequate to quantify the kinesthetic sense was found. Based on this function, the effects of changes in stiffness and damping on the kinesthetic sense were investigated. Various tests show that the damping is a more dominant factor than the stiffness in forming the kinesthetic sense.