• International Journal of Naval Architecture and Ocean Engineering
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• 제6권1호
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• pp.60-73
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• 2014

The seaward reverse wave, occurring on the submerged dual porous horizontal plate, can contribute to the reduction of the transmitted wave as it reflects the propagating wave. However, the collision between the propagating and seaward reverse waves increases the water level and acts as a weight on the horizontal plate. This study investigated the characteristics of the wave pressure created by the seaward reverse wave through the analysis of experimental data. The analysis confirmed the following results: 1) the time series of the wave pressure showed reverse phase phenomena due to the collision, and the wave pressures acted simultaneously on both upper and lower surfaces of the horizontal plate; 2) the horizontal plate became repeatedly compressed and tensile before and after the occurrence of the seaward reverse wave; and 3) the seaward reverse wave created the total wave pressure to the maximum towards the direction of gravity, primarily on the upper plate. It was also confirmed that the wave distributions showed a similar trend to the wave steepness. Such outcome of the analysis will provide basic information to the structural analysis of the horizontal plate as a wave dissipater of the steel-type breakwater (STB).

• The Journal of Asian Finance, Economics and Business
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• 제2권4호
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• pp.13-20
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• 2015

The purpose of this research is to identify the relation between the Korean wave and Korean cosmetics export. Instead of using UN COMTRADE data as with other researches on the similar studies, this paper adopts Google Trends query index with keyword 'Korean drama'as a proxy variable for cultural trade. With controlling export determining factors such as GDPs of import and export countries, distance, R&D, and FTA, this paper examines whether the Korean wave represented by Google Trends contributes to the explosive increase of Korean cosmetics export in the recent years. Moreover, this study also investigates the possible effects of the Korean wave on export that could vary according to the different trade groups by classifying import countries into two groups: 74 countries worldwide and 9 ASEAN member countries. The results reveal that the Korean wave indeed leads to cosmetics export to ASEAN countries but show weak relation with cosmetics export to worldwide.

• 한국해안해양공학회지
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• 제13권3호
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• pp.209-229
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• 2001

옥계항 내외의 5개 정점에서 부이형 파향·파고계와 수압식 파고계를 사용하여 연속관측한 장·단주기파의 장기간 자료를 분석하여 옥계항 주변 해역에서의 장주기파 에너지의 공간적, 시간적 분포를 검토하였다. 장주기파 자료 분석에 일정평활화법, 점증평활화법 및 이동평균평활화법을 적용하여 각각의 장·단점을 검토한 결과 해당 항만의 제1 공진 모드의 주기와 사용하는 자료의 길이에 따라 적절한 에너지 평활화 방법을 사용해야 함을 보였다. 장기간 자료와 2일 길이의 자료들의 분석 결과를 비교하여 평상시와 폭풍시를 구분하여 해석하는 것이 타당함을 보였다. 한편, 관측 자료의 종합적인 분석 결과 옥계항의 Helmholtz 공진 주기는 약 9.6분(상대진폭비 9∼10)으로 제시되었으며 저중력파 주기대의 주기 1.2∼1.3분과 0.7분의 국부 부진동이 매우 뚜렷하게 나타났다. 그리고, 평상시 자료에서는 항입구와 항내 정점에서 주기 9분 이상에서의 에너지가 저중력파 주기대의 에너지에 비해 100배 이상으로 매우 크게 나타났지만, 폭풍시에는 주파수 대폭에 무관하게 에너지가 크게 나타났으며, 특히 항내에서는 국부 부진동의 에너지가 평상시에 비해 최소 100배 이상으로 제시되었다. 마지막으로 항내에서는 Helmholtz 공진 모드와 주기 1∼2분의 저중력파 에너지가 폭풍파고의 크기에 비례하는 것으로 나타났다.

• 암석학회지
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• 제20권3호
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• pp.141-149
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• 2011

암석의 물리적 특성 변화에 대해 온도의 영향을 연구하기 위해 2종의 화강암류와 대리암, 사암을 전기로에서 $400^{\circ}C$와 $600^{\circ}C$로 가열하였다. 모든 시료에서 가열 후 물리적 특성(비중, 공극률, 흡수율, 초음파속도)과 색상 변화는 보이나, 편광현미경을 이용한 광물학적 변화는 뚜렷하지 않다. 특히 물리적 특성 변화에서 공극률과 흡수율은 증가하고, 비중과 초음파 속도는 감소하는 경향을 보이며, 온도가 증가할수록 변화폭은 크게 나타난다. 여기서 측정한 공극률은 암석의 전체 공극률을 반영하지 못하고 있으나 온도에 의한 암석의 표면 상태 변화를 반영한다 반면 초음파 속도는 암석의 전체적인 손상 정도를 파악하는데 유용하다. 그러므로 온도에 의한 암석의 물리적 특성 변화를 설명하기 위해 공극률과 초음파 속도는 상호 비교해야 한다.

• Journal of Astronomy and Space Sciences
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• 제18권1호
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• pp.21-26
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• 2001

As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH(3-1) bands were derived from spectrometric observations of airglow emissions over King Sejong station($62.22^{circ}S,\;301.25^{circ}E$). These measurements were made with a Michelson interferometer to cover wavelength regions between 1000nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1) airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky’s parameter and compared with published values.

• Structural Engineering and Mechanics
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• 제35권3호
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• pp.365-377
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• 2010

In the present article, effect of non-uniform excitation due to spatially variation of seismic input on nonlinear response of concrete gravity dams is considered. The reservoir is assumed compressible. Isotropic damage mechanics approach is used to model static and dynamic nonlinear behavior of mass concrete in 2D space. The validity of utilized nonlinear model is considered using available theoretical results under static and dynamic conditions. The tallest monolith of Pine Flat dam is selected as a case study. Two cases are analyzed for considering the effect of limited wave propagation velocity on seismic behavior of the dam-reservoir system in which travelling velocities are chosen as 2000 m/s and infinity. It is found that tensile damage in neck and toe regions and also, in the vicinity of the base increase when the system is excited non-uniformly.

• Structural Engineering and Mechanics
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• 제87권5호
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• pp.475-485
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• 2023

The present study deals with wave propagation in a modified couple-stress generalized thermoelastic solid under the effect of gravity and magnetic field. The problem is solved by a refined microtemperatures multi-phase-lags thermoelastic theory. The Fourier series and Laplace transforms will be used to obtain the general solution for any set of boundary conditions. Some comparisons have been shown in figures to estimate the effects of the gravity field, the magnetic field, and different theories of thermoelasticity in the presence of the hall current effect on all the physical quantities. Some particular cases of special interest have been deduced from the present investigation.

• Journal of the korean society of oceanography
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• 제35권2호
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• pp.78-88
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• 2000

A weakly viscous wave and an approximate variational principle in viscous fluids are introduced, with which we can interpret the fundamentals such as how viscosity dissipation occurs with time elapse, and how the free surface boundary layer exists at the wavy surface in weakly viscous fluids. As an application, responses of a spherical buoy on the weakly viscous capillary gravity wave are investigated to show the viscosity effects. At the end, surfactant problems are briefly reviewed with the view of short viscous waves as expected future applications.

• 천문학회보
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• 제39권1호
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• pp.77.2-77.2
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• 2014

Numerical relativity is one of the crucial tools to theoretically probe systems of strong gravity such as compact binary coalescences and gravitational collapses. Understandings of such systems and gravitational wave forms extracted have been used for implementing data analysis pipelines on ground based gravitational wave observation experiments such as LIGO, Virgo and KGRA currently undergoing. In this talk, brief reviews and perspectives will be given for numerical studies on binary black holes.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(2)
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• pp.842-845
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• 2005

A method for the numerical simulation of two-dimensional free-surface flow resulting from the propagation of regular gravity waves over topography with arbitrary bottom shape is presented. The method is based on the numerical solution of the Euler equations subject to the fully nonlinear free-surface boundary conditions and the appropriate bottom, inflow and outflow conditions using a hybrid finite-differences and spectral-method scheme. The formulation includes a boundary-fitted transformation, and is suitable for extension to incorporate large-eddy simulation (LES) and large-wave simulation (LWS) terms for turbulence and breaking wave modeling, respectively. Results are presented for the simulation of the free-surface flow over two different bottom topographies, with constant slope values of 1:10 and 1:20, two different inflow wave lengths and two different inflow wave heights. An absorption outflow zone is utilized and the results indicate minimum wave reflection from the outflow boundary. Over the bottom slope, lengths of waves in the linear regime are modified according to linear theory dispersion, while wave heights remain more or less unchanged. For waves in the nonlinear regime, wave lengths are becoming shorter, while the free surface elevation deviates from its initial sinusoidal shape.