• 비파괴검사학회지
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• 제32권4호
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• pp.347-354
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• 2012

Using a single-line pulsed laser beam is well known as a useful noncontact method to generate a directional surface acoustic wave. In this method, different laser beam energy profiles produce different waveforms and frequency characteristics. In this paper, we considered two typical kinds of laser beam energy profiles, Gaussian and square-like, to find out a difference in the frequency characteristics. To achieve this, mathematical models were proposed first for Gaussian laser beam profile and square-like respectively, both of which depended on the laser beam width. To verify the theoretical models, experimental setups with a cylindrical lens and a line-slit mask were respectively designed to produce a line laser beam with Gaussian spatial energy profile and square-like. The frequency responses of the theoretical models showed good agreement with experimental results in terms of the existence of harmonic frequency components and the shift of the first peak frequencies to low.

• 한국태양에너지학회 논문집
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• 제23권2호
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• pp.99-105
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• 2003

This paper presents the effect of rotor geometry on the performance of a small-scale Wells turbine for wave energy conversion. In this study, four kinds the Wells turbine of blade profile were selected from previous studies. The types of blade profile included in the papers are as follows: NACA0020 ; NACA0015; CA9; and HSIM 15-262123-1576. The experimental investigations have been performed for two solidities by testing model under steady flow conditions. The effect of blade profile on the running and starting characteristics under sinusoidal flow conditions have also been investigated by a numerical simulation based on a quasi-steady analysis. In addition, the effect of sweep on the turbine characteristics has been studied for the cases of CA9 and HSIM 15-262123-1576. Based on the evaluation, a suitable choice of these design factors has been suggested. As a result, it seems that a suitable choice of the sweep ratio of 0.35 for the blade profile of the Wells turbine.

• 대한토목학회논문집
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• 제14권6호
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• pp.1445-1451
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• 1994

해안구조물에 작용하는 설계파압(設計波壓)을 수치적으로 계산하기 위해서는 먼저 쇄파한계(碎波限界)에 가까운 큰 중복파랑을 수치적으로 재현할 필요가 있다. 이를 위해서는 지배방정식(支配方程式)과 비선형항(非線形項)을 포함하는 경계조건을 효과적으로 반영해야 하며 특히, 자유표면(自由表面) 경계조건(境界條件)에서의 속도의 제곱항의 처리가 중요하다. 본 연구에서는 Newton 방법을 이용하여 제곱항을 충실히 반영하므로써 일반적인 셜계파 성향에 거의 상응하는 중복파랑을 재현하였으며 기존의 섭동법(攝動法) 또는 Fourier 전개 기법 및 수리실험 결과와 비교하여 그 정확도를 검토하였다.

• 한국세라믹학회지
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• 제32권3호
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• pp.341-348
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• 1995

An analysis of the use of temperature profiles in the determination of the kinetic parameters of combustion synthesis of Ti5Si3 were investigated. From profile analysis, an apparent activation energy of 12KJ/mol was calculated. The Maximum heating rate achieved during 10wt% Ti5Si3 reaction by the product dilution method was approximately $1.5\times$104 K/s. Coupling this value with the measured wave velocity of 7.02 cm/s yields a maximum thermal gradient of 2.14$\times$103 K/cm. The value of tr (=t*) was calculated to be 1.2$\times$10-1 s and the value of td (=tx) was calculated to be 32.89 s. Using the definition of t* and the measured wave velocity, the effective thermal diffusivity, $\alpha$, was calculated to be 0.59$\times$10 $\textrm{cm}^2$/s. From these analysis, the power function, G, was also calculated.

• 한국해안해양공학회지
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• 제4권4호
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• pp.219-224
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• 1992

이차원 비선형 정상파의 파낭포텐셜과 수면 파형곡선을 임의 계수를 갖는 Fourier 급수로 대치하고 그 계수를 지배방정식 및 경계조건으로부터 비롯되는 비선형 연립방정식의 Newton 해법에 의하여 결정하는 방법을 제시하였다. 해석결과의 유효성을 검증하기 위하여 본 교치분석을 재내의 4차 미소치 섭동기법과 비교하였으며, 또한 파형과 파염을 관측하기 위한 수리실험을 실시하여 그 결과를 수치해석결과와 비교ㆍ검토하였다. 검토 결과, 본 해석 기법은 수심조건에 관계없이 비교적 큰 파형 경사에서도 정확한 해를 주는 것으로 나타났으며 또한 비선형성이 강한 정상파에서 파염곡선의 파봉부분에 일반적으로 나타나는 이중 돌출부를 잘 예측함으로써 그 타당성을 입증하였다.

• 한국해양공학회지
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• 제22권5호
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• pp.44-51
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• 2008

The planning and design of coastal structures against wave attack is required to accurately predict wave transformation, wave run-up, and fluid. particlevelocities an a slope. On tire other hand, in tire swash and surf zones of a natural beach, where coastal erosion and accretion occur at tire land-sea boundary, hydrodynamic analysis is essential. In this study, a RBREAK2 numerical model was created based on the nonlinear shallow water equation and laboratory measurements were carried out in terms of tire free surface elevations and velocities for tire cases of regular and irregular waves on 1 : 10 and 1 : 5 impermeable slopes. The data were used to evaluate tire applicability and limitations of tire RBREAK2 numerical model. The numerical mode1 could predict tire cross-shore variation of the wave profile reasonably well, but showed more accurate results for slopes that were steeper than 1 : 10. Except near tire wave crest, tire computed depth averaged velocities could represent tire measured profile below tire trough level fairly well.

• 한국지반공학회논문집
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• 제20권6호
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• pp.51-59
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• 2004

공학적 물성치로서의 저변형율에서의 전단탄성계수의 결정은 다양한 토목분야에서 매우 중요하다. 본 논문에서는 저변형율에서의 전단탄성계수를 결정하기 위하여 개발된 HWAW(Harmonic Wavelet Analysis of Wave)방법을 이용한 지반조사기법의 실제 현장에서의 타당성을 검증하기 위하여 두 곳의 현장에 HWAW방법을 적용하였다. HWAW방법을 검증하기 위하여 동일한 현장에서 수행된 SASW시험과 PS-Suspension Logging 실험의 결과와 비교하였다. 이를 통하여 HWAW방법이 배경잡음과 지반의 횡방향 불균일성에 의한 오류를 기존 방법에 비하여 최소화 할 수 있으며, 국부적이며 정밀한 대상지반의 실제 전단파 속도 주상도를 매우 효과적으로 결정할 수 있음을 확인할 수 있었다.

• 구강회복응용과학지
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• 제30권2호
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• pp.121-130
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• 2014

목적: Reciprocating 파일인 WaveOne과 continuous rotary 파일인 ProTaper와 ProFile로 근관 형성시 상아질 벽의 표면성상과 상아질 삭편 크기와 도말층 제거 효과를 비교하였다. 연구 재료 및 방법: 60개 단근치를 ProFile, ProTaper, WaveOne으로 성형 후 근관이 보이도록 grinding 하였다. 근관 성형 동안 상아질 삭편을 모아 건조하였다. Scanning electron microscope으로 상아질 삭편 크기와 근관 표면의 불규칙성과 도말층을 관찰하였다. 결과: 표면 함요부의 범위는 ProFile, ProTaper 그리고 WaveOne에서 $150{\mu}m$, $70{\mu}m$, 그리고 $80{\mu}m$의 범위 내에서 관찰되었다. 상아질 삭편의 크기는 ProFile, ProTaper 그리고 WaveOne에서 $7{\mu}m$, $6.5{\mu}m$, 그리고$4{\mu}m$의 범위 내에서 관찰되었다. 도말층은 WaveOne의 중간 1/3과 근단 1/3에서 유의하게 더 많이 관찰되었다. 결론: WaveOne은 중간 1/3과 치근단 1/3의 도말층 제거 효과를 제외하고, ProFile과 ProTaper와 근관 표면 성상과 상아질 삭편에서 큰 차이가 없는 것으로 사료된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.872-879
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• 2010

High rock-fill embankment is relatively flexible, which makes crest of embankment subject to excessive amplification in displacement due to earthquake loading. To overcome problems related with site response in high embankment, it is essential to evaluate shear-wave velocity profile of the embankment with improved accuracy and reliability. In this aspect, an experimental research was performed to answer how to perform surface-wave tests and to analyze measurements at an embankment site with a sloping ground surface. Unlike flat ground surface, sloping ground may hamper and slow down propagation of surface waves due to multiple reflections and refractions in embankment. To figure out this reasoning for the effect of multiple reflections and refractions due to sloping surface, surface wave tests were performed at a reservoir embankment of Chung-Song in North KyeongSang Province. Parameters involved in surface wave tests at non-flat surface, including source directionality, geometry-related constraint and frequency components in source function, were investigated using field measurements.

• 비파괴검사학회지
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• 제31권6호
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• pp.656-664
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• 2011

In this work, a numerical model is proposed for the relation between the magnitudes and the depth residual stress with the velocity of Rayleigh wave. Three cases, stress-free, uniform stress and layered stress, are investigated for the change tendency of the Rayleigh wave speed. Using the simulated signal with variation of residual stress magnitude and depth, investigation of the parameters for fitting residual stress and velocity change are performed. The speed change of Rayleigh wave shows a linear relation with the magnitude and an exponential relation with the depth of residual stress. The combination of these two effects could be used for the depth profile evaluation of the residual stress.