• 한국해양공학회지
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• 제21권6호
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• pp.26-33
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• 2007

Finite element simulation of elastic wave propagation in a concrete plate was carried out to investigate its modeling and damage detection procedures. For the numerical stability three criteria were introduced and tested. With a proper element size and time increment, two different kinds of damage scenarios (crack and deterioration) were applied to verify the feasibility of the finite element simulation. It is shown that the severities of those damages are sensitive to the received displacement signals.

• 비파괴검사학회지
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• 제20권2호
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• pp.91-101
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• 2000

초음파 탐촉자로부터 방사된 음장을 모델링하는 것은 초음파 측정 모델을 구성하는 첫 번째 단계이며, 그 정확도를 결정짓는 핵심 요소이기 때문에 지금까지 다양한 연구가 진행되었다. 본 논문에서는 지금까지 제안된 다양한 기법 중에서 현재 널리 사용되고 있는 Rayleigh-Sommerfeld 적분 모델, 경계회절파모델(boundary diffraction wave model), 가장자리요소모델(edge element model)에 대해 간략하게 논의하고, 이 세가지 모델을 적용하여 평면 원형 및 사각형 초음파 탐촉자의 방사 음장을 계산하고, 각 기법의 정확성과 계산 효율을 비교하였다.

• 한국전자통신학회논문지
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• 제14권5호
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• pp.825-836
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• 2019

군 병력의 효율적 운용을 위한 정보공유의 수단으로서 높은 망 유연성을 제공할 수 있는 드론형 기지국이 최적의 플랫폼이 될 것으로 예상된다. 또한 넓은 대역폭을 활용 가능한 밀리미터파 주파수대역은 대용량 데이터를 송수신하는데 적합하지만 shadowing에 취약한 특성을 가지게 되는데, 자유롭게 고도를 조절할 수 있는 드론형 기지국의 특성을 활용하면 LoS를 안정적으로 확보하여 취약점을 상쇄할 것으로 기대된다. 본 논문에서는 다양한 요소가 반영된 드론형 기지국의 성능분석을 위한 모델링을 수행함으로써, 차후 군 통신망으로써 활용가능성이 기대되는 드론형 기지국의 성능평가에 대한 틀을 제공하고자 한다.

• 한국항행학회논문지
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• 제13권6호
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• pp.943-949
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• 2009

본 논문에서는 고속의 무선 채널 환경에 적합한 Jakes 채널 모델을 적용하여 5.9GHz WAVE 무선 채널을 모델링하고, WAVE 통신시스템에 대한 표준화 작업이 진행 중인 IEEE 802.11p 스펙트럼 마스크, 도플러효과, 변조방식에 따른 페이딩 신호 성좌도 및 스펙트럼을 분석한다. 또한 차량속도 즉 도플러 효과에 따른 WAVE 통신시스템의 성능을 분석한다.

• Earthquakes and Structures
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• 제13권5호
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• pp.465-471
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• 2017

This work derives a generalized time fractional differential equation governing wave propagation in a radially vibrating non-classical cylindrical medium. The cylinder is made of a transversely isotropic hyperelastic John's material which obeys frequency-dependent power law attenuation. Employing the definition of the conformable fractional derivative, the solution of the obtained generalized time fractional wave equation is expressed in terms of product of Bessel functions in spatial and temporal variables; and the resulting wave is characterized by the presence of peakons, the appearance of which fade in density as the order of fractional derivative approaches 2. It is obtained that the transversely isotropic structure of the material of the cylinder increases the wave speed and introduces an additional term in the wave equation. Further, it is observed that the law relating the non-zero components of the Cauchy stress tensor in the cylinder under consideration generalizes the hypothesis of plane strain in classical elasticity theory. This study reinforces the view that fractional derivative is suitable for modeling anomalous wave propagation in media.

• Wind and Structures
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• 제16권2호
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• pp.193-211
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• 2013

This paper presents results from a wind tunnel study that examined the drag coefficient and wind flow over an asymmetric wave train immersed in turbulent boundary layer flow. The modeled wavy surface consisted of eight replicas of a statistically-valid hurricane-generated wave, located near the coast in the shoaling wave region. For an aerodynamically rough model surface, the air flow remained attached and a pronounced speed-up region was evident over the wave crest. A wavelength-averaged drag coefficient was determined using the wind profile method, common to both field and laboratory settings. It was found that the drag coefficient was approximately 50% higher than values obtained in deep water hurricane conditions. This study suggests that nearshore wave drag is markedly higher than over deep water waves of similar size, and provides the groundwork for assessing the impact of nearshore wave conditions on storm surge modeling and coastal wind engineering.

• 한국해양공학회지
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• 제24권6호
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• pp.51-60
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• 2010

In this study, the performance evaluation of a conventional wave resonator at the entrance of a port or a pier against secondary undulation has been performed using 2D hydrodynamic modeling within port. A wave resonator has been designed for the attenuation of the secondary undulation induced by the long-periodic waves. The controlled performance of the wave resonator has been numerically investigated for CGWAVE MODULE of finite-element model of SMS (Surface water Modeling System) based on the elliptic mild-slope wave equation. SMS was verified though the comparisons with analytical solution performed by Ippen and Goda (1963). Also, It was confirmed that a wave resonator of a rectangular model harbor is effective enough to control the secondary undulation when it compares variation of water level with the case of no resonance system. From the above results, amplification phenomenon induced by long-period waves transferred from 1900 sec to 2100 sec when it applied a wave resonator in Busan Gamcheon Port which is a deep-sea. And it was confirmed that a wave resonator of Pohang New Port attenuates largely long-period waves which are within the range of 300 sec induced by long-period motion of the moored ship.

• 지구물리와물리탐사
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• 제21권4호
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• pp.213-219
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• 2018

본 연구에서는 제온 파이 x200 프로세서를 이용하여 3차원 파동 전파 모델링을 수행하고 기존의 제온 CPU를 사용한 경우와 병렬 연산 성능을 비교하였다. 제온 파이 1세대 프로세서인 제온 파이 나이츠 코너 보조프로세서와 달리 제온 파이 2세대 프로세서인 x200 프로세서는 직접 운영체제 실행이 가능하므로 내장 메모리와 주메모리 사이의 추가적인 통신이 필요 없다. 또한 제온 파이 x200 프로세서는 대용량 주메모리와 고대역폭 메모리를 이용하여 대규모 컴퓨팅을 독립적으로 실행할 수 있다. 병렬 연산 성능 비교를 위해 MPI (Message Passing Interface)와 OpenMP (Open Multi-Processing)를 이용해 모델링을 수행하였다. SEG/EAGE 암염돔 모델을 이용한 수치 실험 결과 제온 파이에서 다량의 연산 코어와 고대역폭 메모리를 이용해 12 코어 CPU 대비 2.69 ~ 3.24배 우수한 모델링 성능을 얻을 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.303-308
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• 2003

In this paper, wave numerical modeling was experimented for the analysis of impact factors for the wave transmission as the incident wave and topographic conditions in the narrow channel sea. Recently, Although the results of many researcher for the wave modelling, numerical equations have limited to simulation of wave transformation effects. Despite of thispresent problems, the models was used to design the coastal structures in barrow channel sites. Finally, this paper estimated the wave model(mild slope eq. model) as the analysis of the wave energy transmission according to changing of impact factors(width of channel, bottom slope in channel, incident wave angle, wave period). As the results of numerical experiment, the major impact factors which influence to wave energy transmission were the width of channel and incident wave direction. But in the case that the width of channel is larger than 3L(L=Length of wave), the reduction of wave energy was small.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.355-358
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• 2008

This study deals with a substantial problems with SEA modeling methods in shipboard noise predictions. As a first problems with respect to modeling, fineness of model that represents a real structure is numerically investigated by comparison among 3 models, Fine, Coarse and Simplified models. Comparison reveals that Fine model shows the lowest noise level among them since this model involve more energy transfer paths than the other models. Influence of in-plane wave is also examined by numerical comparison. It is clear that inclusion of in-plane wave affects the high frequency and the cabin far from a source.