• 대한기계학회논문집
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• 제15권6호
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• pp.2181-2188
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• 1991

본 연구에서는 주파수도메인에서의 측정방법중 진폭 스펙트럼 방법에 대한 이 론적 배경을 알아보고, 얇은 두께의 재료에 적용한 측정결과를 보이고자 하며, 비교적 두께가 두꺼운 재료에서의 측정결과를 위상 스펙트럼 방법으로의 측정 결과와 비교하 여 측정의 정확성을 서로 비교하였다.

• 수산해양기술연구
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• 제42권1호
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• pp.44-53
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• 2006

The expansion of near shore aquaculture is feasibility of moving aquaculture facilities into the open ocean. Numerical modeling technique using finite element method was used to enable the optimum design and evaluation of submersible aquaculture cage system. The characteristics of mooring loads response in mooring lines under waves and current and their response amplitude operators were calculated for single and three point mooring configuration at the surface condition and submerged one. The static mooring loads without wave and current loading were similar for both the surface and submerged configuration. It was calculated that three point mooring was more adequate than single point mooring for the mooring configuration of submersible aquaculture cage system. The wave induced response amplitude operators for the single point mooring configuration with the influence of currents were identical to those without the influence of currents.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.356-361
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• 1996

Nowadays, Electronic Speckle Pattern Interferometry is a well established measuring technique with a wide range of industrial applications, particularly in the fields of deformation measurement and vibration analysis. Comparing with holographic inteferometry, it has some attractive features, which are rapid recording and reconstruction, satisfiable automation etc. Time-average ESPI was used to provide vibration mode shape of an object whose vibration amplitude is given as a fringe pattern. However, it is not possible to determine the direction of motions of a point on the object at any given time, because time-average method does not give any information about the phase of vibration. A better technique is stroboscopic method which can measure the amplitude and phase of vibrating surface. In this paper, loudspeakers were tested by these two methods and the mode shape and amplitude of vibration were visualized. As measured results, we can assume that these techniques will be applied directly in the loudspeaker industry.

• 천문학회보
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• 제41권1호
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• pp.73.2-73.2
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• 2016

We present the results of KaVA SgrA* observation together with Takahagi(32m), Yamaguchi(32m) and Nobeyama(45m) telescopes at 22 and 43GHz, respectively. In early 2014, G2 cloud was expected to encounter with SgrA* and to make a significant flux variation, but it has not been measured yet. So it's worth to check our amplitude calibration method to confirm if we have a missing flux caused by uncertainty in measuring it. We have tested both a standard method using system noise temperature(Tsys) with antenna gain information, and a template method in order to calibrate antenna gain using nearby maser source. As a result, we found that the latter method is useful for antennas which have inaccurate gain information or poor Tsys measurements, and is especially effective for sources at low elevation like SgrA*. In addition, the comparison shows that the amplitude calibration by standard method can be improved up to 10% with a correction factor using a template method. This result implies we can get more accurate flux from a standard method when any maser source not exists around target.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.645-646
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• 2006

The oscillation amplitude of a probe tip is an important parameter to determine the resolution of atomic force microscopy (AFM) techniques. In this work, we introduce a new method for the measurement of the oscillation amplitude of a quartz tuning fork tip sub-nanometer resolution.

• 한국해양공학회지
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• 제20권6호
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• pp.67-74
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• 2006

A high-order spectral/boundary-element method is newly adapted as an efficient numerical tool. This method is one of the most efficient numerical methods by which the nonlinear gravity waves can be simulated and hydrodynamic forces also can be calculated in time-domain. In this method, the velocity potential is expressed as the sum of surface potential and body potential. Then, surface potential is solved by using the high-order spectral method and body potential is solved by using the high-order boundary element method. By the combination of these two methods, the wave-making problems by a submerged sphere oscillating with large amplitude under the free~surface are solved in time-domain. Through the example calculations, nonlinear effects on free-surface profiles and hydrodynamic forces are shown and discussed.

• 한국통신학회논문지
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• 제34권3C호
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• pp.251-256
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• 2009

본 논문에서는 음성신호의 정현파 합성방법 중 하나인 선형위상을 사용한 중첩합산방법에 대하여 감쇄(Damping) 하모닉 크기 파라미터를 사용하여 합성음성의 연속성을 개선시킨 새로운 방법을 제안한다. 기존의 중첩합산 정현파 합성방법은 프레임의 중간 지점에 대한 정현파 파라미터를 얻기 위해서 가중치로 사용된 정현파 크기값을 과거 프레임과 현재 프레임의 평균값을 사용하였으나 제안하는 방법은 정현파 크기값을 단순히 과거와 현재 프레임에서 평균값이 아닌 원 신호와 합성신호 사이의 상관성을 이용하여 감쇄(Damping)요소를 정의하고 보다 정확한 정현파 크기의 파라미터 값을 추출한 후 합성한다. 이렇게 제안한 합성 방법의 성능을 관찰하기 위해 합성방법의 연속성 평가를 통해 기존의 방법과 비교 평가한다. 제안한 방법의 평균 MSE값이 N/2 중첩길이에서 0.251dB, N/4 중첩길이에서 0.298dB 낮아짐을 볼 수 있다.

• 대한조선학회논문집
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• 제49권6호
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• pp.461-468
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• 2012

In this study, a Cartesian-grid method based on finite volume approach is applied to simulate the ship motions in large amplitude waves. Fractional step method is applied for pressure-velocity coupling and TVD limiter is used to interpolate the cell face value for the discretization of convective term. Water, air, and solid phases are identified by using the concept of volume-fraction function for each phase. In order to capture the interface between air and water, the tangent of hyperbola for interface capturing (THINC) scheme is used with weighed line interface calculation (WLIC) method which considers multidimensional information. The volume fraction of solid body embedded in the Cartesian grid system is calculated using a level-set based algorithm, and the body boundary condition is imposed by a volume weighted formula. Numerical simulations for the two-dimensional barge type model and Wigley hull in linear waves have been carried out to validate the newly developed code. To demonstrate the applicability for highly nonlinear wave-body interactions such as green water on the deck, numerical analysis on the large-amplitude motion of S175 containership is conducted and all computational results are compared with experimental data.

• Corrosion Science and Technology
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• 제18권5호
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• pp.196-205
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• 2019

Surface modification techniques are known to improve SCC by adding large compressive residual stresses to metal surfaces. This surface modification technology is attracting attention because it is an economical and practical technology compared to the maintenance method of existing nuclear power plants. Surface modification techniques include laser, water jet and ultrasonic peening, pinning and ultrasonic Nano-crystal surface modification (UNSM). The focus of this study was on the effect of ultrasonic amplitude in UNSM treatment on the corrosion properties of Alloy 600. A microstructure analysis was conducted using an optical microscope (OM), scanning electron microscope (SEM) and electron backscattering diffraction (EBSD). A cyclic polarization test and AC-impedance measurement were both used to analyze the corrosion properties. UNSM treatment influences the corrosion resistance of Alloy 600 depending on its amplitude. Below the critical amplitude value, the pitting corrosion properties are improved by grain refinement and compressive residual stress, but above the critical amplitude value, crevices are formed by the formation of overlapped waves. These crevices act as corrosion initiators, reducing pitting corrosion resistance.

• 대한전자공학회논문지SP
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• 제38권2호
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• pp.191-198
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• 2001

HD ProjectionTV에서 CRT의 전자총 및 투영되는 스크린 상에서의 빔 프로파일에 의한 화질의 열화를 개선시키기 위한 방법으로는 영상신호의 진폭 변화량에 따라 수평 편향 속도를 선형적으로 변조시키는 SVM(Scan Velocity Modulation)방식이 있다. 그런데, 선형 SVM방식에서의 화질 개선은 입력 영상신호의 진폭변화에 대해 균일하지 않다. 본 논문에서는 HD Projection TV에서의 빔 프로파일의 특성을 분석하여 모델링하고, 고역의 HD 신호가 입력될 때 SVM효과를 모의실험을 통해 해석하였다. 그리고, 이를 근거로 영상신호에 따라 SVM량을 비선형적으로 조절하는 비선형 SVM방식이 HD Projection TV에서도 필요함을 이론적으로 제시하였다. 이를 바탕으로 SVM 회로를 직접 하드웨어로 제작하여 실제 TV에 장착하여 실험하였다. 실험 결과 영상 신호의 진폭이 작은 영역과 큰 영역의 경계부분에서 발생하는 화질의 열화를 거의 일정하게 개선시킬 수 있음을 확인 하였다.