• 대한인간공학회지
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• 제16권1호
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• pp.1-13
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• 1997

In this research, and investigation of the eye movement was performend when the objects perceived by the eye are three-dimensional objects, two dimensional images, and trhee dimensional images. This investigation was done by observing the EQG(Electro- oculogram) waves which were obtained from experiments. The observed waves were categorized into several groups. Differences among the waves were analyzed for each object and image perceived by the eye. In order to obtain waves for analysis, two kinds of experiments were performen. In each experiment, the saccadic eye movement and the smooth pursuit eye movement were considered as an independent variables. Waves obtained from the experiments were categorized into 4 types (Wave-1, Wave-2, Wave-3, Wave-4) depending on their characteristics. Unlike the other images, three dimensional image was revealed as a key factor for the active movement of the eye. Futhermore, a unique eye movement was observed in the case of three dimensional images where the focus of the eye was achieved through three steps.

• Ocean Systems Engineering
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• 제9권3호
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• pp.219-240
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• 2019

This paper presents the comparison between SFT response with linear and nonlinear cables. The dynamic response analysis of submerged floating tunnel (SFT) is presented computationally with linear and nonlinear tension legs cables. The analysis is performed computationally for two wave directions one at 90 degrees (perpendicular) to tunnel and other at 45 degrees to the tunnel. The tension legs or cables are assumed as linear and non- linear and the analysis is also performed by assuming one tension leg or cable is failed. The Response Amplitude Operators (RAO's) are computed for first order waves, second order waves for both failure and non-failure case of cables. For first order waves- the SFT response is higher for sway and heave degree of freedom with nonlinear cables as compared with linear cables. For second order waves the SFT response in sway degree of freedom is bit higher response with linear cables as compared with nonlinear cables and the SFT in heave degree of freedom has higher response at low time periods with nonlinear cables as compared with linear cables. For irregular waves the power spectral densities (PSD's) has been computed for sway and heave degrees of freedom, at $45^0$ wave direction PSD's are higher with linear cables as compared with nonlinear cables and at $90^0$ wave direction the PSD's are higher with non-linear cables. The mooring force responses are also computed in y and z directions for linear and nonlinear cables.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.628-629
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• 2009

A variety of technologies have already been developed to capture energy from the ocean waves, this one is simple to construct. Rather then looking at the surface waves, the technique used lets the waters current beneath the waves directly drive the rotors. The novel ocean wave energy convertor consists of savonius rotor which is mounted in the ocillating water column (OWC) chamber. This study investigates the performance of a 3 blade and 5 bladed savonius rotor under same wave condition using commercial CFD code. Initially the performance analysis of savonius type turbine have been carried out with conventional three bladed curved rotors. From the experieneces of the simulations, 5 bladed savonius rotor have been developed and studied. Performace caracteristics of the 5 bladed savonius rotor has been evaluated and the results obgtained are comopared with the conventional three bladed curved rotors.

• Journal of Ship and Ocean Technology
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• 제4권1호
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• pp.28-36
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• 2000

Numerical simulation based on the superposition of ring waves generated by the linear periodic source distributions for the plunger type wave maker was accomplished. The characteristics of directional spreading function were investigated. Mirror images are also introduced to consider reflections of side-wall together with the reflection coefficient to account for the imperfect reflection from the real side wall in the long experimental towing tank. Unexpected spurious waves, resulting from the combined effect of finite breadth of segmented wave maker, wavelength and main wave maker, wavelength and main wave propagating direction, were observed in the line source method and also in the analysis of the directivity. The influence of spurious waves to the directional spreading function was also investigated.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.17-22
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• 2006

Shear modulus is directly linked to material's stiffness and is one of the most critical engineering parameters. Seismically, shear-wave velocity (Vs) is its best indicator. Although methods like refraction, down-hole, and cross-hole shear-wave surveys can be used, they are generally known to be tougher than any other seismic methods in field operation, data analysis, and overall cost. On the other hand, surface waves, commonly known as ground roll, are always generated in all seismic surveys with the strongest energy, and their propagation velocities are mainly determined by Vs of the medium. Furthermore, sampling depth of a particular frequency component of surface waves is in direct proportion to its wavelength and this property makes the surface wave velocity frequency dependent, i.e., dispersive. The multichannel analysis of surface waves (MASW) method tries to utilize this dispersion property of surface waves for the purpose of Vs profiling in 1-D (depth) or 2-D (depth and surface location) format. The active MASW method generates surface waves actively by using an impact source like sledgehammer, whereas the passive method utilizes those generated passively by cultural (e.g., traffic) or natural (e.g., thunder and tidal motion) activities. Investigation depth is usually shallower than 30 m with the active method, whereas it can reach a few hundred meters with the passive method. Overall procedures with both methods are briefly described.

• 한국해안·해양공학회논문집
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• 제32권6호
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• pp.531-552
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• 2020

선행연구에서는 3차원규칙파에 대해 olaFlow 수치모델을 적용하여 혼성방파제의 선단 주변에서 파랑특성 및 케이슨에 작용하는 파압특성을 검토하였다. 본 연구에서는 동일한 수치모델과 혼성방파제의 배치 및 형상을 적용하여 일방향불규칙파의 작용 하에 고천단의 마운드 상에 놓인 케이슨의 선단 주변에서 회절파의 발생과 배후역으로의 영향 및 케이슨에 작용하는 충격쇄파압을 포함한 파압의 공간적인 변동 등을 2차원 및 3차원적으로 검토한다. 또한, 수치해석으로부터 혼성방파제 주변에서 주파수스펙트럼, 평균유의파고, 평균수평유속 및 평균난류운동에너지의 변동특성도 면밀히 분석·검토한다. 이로부터 2차원수치해석에서는 발생되지 않았던 충격쇄파압이 3차원수치해석에서는 발생되는 경우가 나타나고, 충격쇄파압의 발생 시 경우에 따라 기존의 설계조건보다 매우 큰 파압이 정수면 근방의 케이슨의 전면 벽체에 작용되는 등의 중요한 결과를 얻을 수 있었다. 또한, 동일한 입사유의파랑에 대해 케이슨에 작용하는 파압분포가 방파제의 길이에 따라 변동하는 것을 확인할 수 있었으며, 이러한 변동은 크기에서 차이를 나타내지만, 3차원규칙파에 대한 선행연구의 경우와 유사한 특성을 갖는다.

• 한국수산과학회지
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• 제20권5호
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• pp.457-462
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• 1987

Stochastic stability criterias for ocean wave analysis add simulation are studied using the data simulated by the linear superposition method. To clarify the criterias, the effects of the simulation parameters on the variance of stochastic properties of ocean waves are investigated, and the stable conditions of the parameters are estimated through the comparative study on the stochastic properties of simulated waves and well-known ocean waves. The simulation parameters considered are high frequency cut-off, data length, and number and phase angle of component waves. Statistical characteristics analysed are wave height, period and steepness, and the formation of groups of higher waves, resonance periods, steeper higher waves and extreme run-length of the run.

• Structural Monitoring and Maintenance
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• 제2권3호
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• pp.213-236
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• 2015

The paper presents an investigation into the mode conversion and scattering characteristics of guided waves at delaminations in laminated composite beams. A three-dimensional (3D) finite element (FE) model, which is experimentally verified using data measured by 3D scanning laser vibrometer, is used in the investigation. The study consists of two parts. The first part investigates the excitability of the fundamental anti-symmetric mode ($A_0$) of guided wave in laminated composite beams. It is found that there are some unique phenomena, which do not exist for guided waves in plate structures, make the analysis become more complicated. The phenomena are observed in numerical study using 3D FE simulations. In the second part, several delaminated composite beams are studied numerically to investigate the mode conversion and scattering characteristics of the $A_0$ guided wave at delaminations. Different sizes, locations and through-thickness locations of the delaminations are investigated in detail. The mode conversion and scattering phenomena of guided waves at the delaminations are studied by calculating reflection and transmission coefficients. The results show that the sizes, locations and through-thickness locations of the delaminations have significant effects on the scattering characteristics of guided waves at the delaminations. The results of this research would provide better understanding of guided waves propagation and scattering at the delaminations in the laminated composite beams, and improve the performance of guided wave damage detection methods.

• 한국소음진동공학회논문집
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• 제24권12호
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• pp.999-1006
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• 2014

Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

• Journal of Astronomy and Space Sciences
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• 제33권3호
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• pp.197-205
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• 2016

We investigated two flares in the solar atmosphere that occurred on June 3, 2012 and July 6, 2012 and caused propagation of Moreton and EIT waves. In the June 3 event, we noticed a filament winking which presumably was caused by the wave propagation from the flare. An interesting feature of this event is that there was a reflection of this wave by a coronal hole located alongside the wave propagation, but not all of this wave was transmitted by the coronal hole. Using the running difference method, we calculated the speed of Moreton and EIT waves and we found values of 926 km/s before the reflection and 276 km/s after the reflection (Moreton wave) and 1,127 km/s before the reflection and 46 km/s after the reflection (EIT wave). In the July 6 event, this phenomenon was accompanied by type II and type III solar radio bursts, and we also performed a running difference analysis to find the speed of the Moreton wave, obtaining a value of 988 km/s. The speed derived from the analysis of the solar radio burst was 1,200 km/s, and we assume that this difference was caused by the different nature of the motions in these phenomena, where the solar radio burst was caused by the propagating particles, not waves.