• Smart Structures and Systems
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• 제17권2호
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• pp.327-345
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• 2016

The existence of SH-wave in a piezomagnetic layer overlying an initially stressed orthotropic half-space is investigated. The coupled of differential equations are solved for piezomagnetic layer overlying an orthotropic elastic half-space. The general dispersion equation has been derived for both magnetically open circuit and magnetically closed circuits under the four types of boundary conditions. In the absence of the piezomagnetic properties, initial stress and orthotropic properties of the medium, the dispersion equations reduce to classical Love equation. The SH-wave velocity has been calculated numerically for both magnetically open circuit and closed circuits. The effect of initial stress and magnetic permeability are illustrated by graphs in both the cases. The velocity of SH-wave decreases with the increment of wave number.

• 한국해양공학회지
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• 제15권1호
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• pp.31-35
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• 2001

By applying the Boundary Integral Equation Method (BIEM) to obliquely incident for Rubble Mound Breakwater (RMB), wave reflection and transmission the coefficients are studied numerically. The validity of and the present BIEM is confirmed by comparing it with 1)numerical results of the eigenfunction expansion method of Dalrymple et al.(1991), and 2)numerical results of the BIEM of Kojima et al.(1988). Therefore, the characteristics of RMB for obliquely incident waves are investigated according to the variations of the wave period, equivalent linear nondimensional friction coefficient and direction of incident waves. It is revealed that the wave transformations of obliquely incident waves are different from those of normally incident waves.

• 한국안전학회지
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• 제24권1호
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• pp.37-42
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• 2009

The present study is to estimate the effect of wave height affecting at the front face of breakwater systems, when a submarine trench is dredged in the distant offshore from outer breakwater. The wave diffraction field, which is important hydraulic factor in the ocean, is considered to be two dimensional(2D) plane and the configuration of the submarine trench on the sea bed designated by single horizontal long-rectangular system. The numerical simulation is performed by using Green function based on the boundary integral equation and meshed at moving boundary conditions. The results of present numerical simulations are illustrated by applying the normal incidence. It is shown that the ratios of wave height reduction at the front face of breakwater systems are approximately 20% by the effect of placing long trench on the sea bed. This study can effectively be utilized for safety assessment to various breakwater systems in the ocean field.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 Asia Navigation Conference
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• pp.217-225
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Ulsan Harbor and Ulsan New Port, etc. due to construction of New Port in Ulsan Bay. This type of trial might be a milestone for port development in macro scale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2006년도 공동학술대회 논문집
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• pp.181-186
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• 2006

본 논문에서는 지진파 역행 전파를 이용하여 지진원을 영상화 하는 방법에 대한 연구를 수행하였다. 시간 역행 전파는 파동 방정식의 시간 반전의 불변성과 상반정리로 설명할 수 있으며 파동의 시간 역행 전파는 의학적인 목적을 비롯한 비파괴 검사, 그리고 탄성파 파형 역산에 사용되어 매질을 영상화 하는데 활용되고 있다. 지진 관측소에서 관측된 지진파형은 지진원으로부터 방출된 에너지를 기록한 것이다. 이를 시간의 역순으로 매질로 전파시키면, 지진으로부터 전파되었던 에너지가 진원시각의 지진원 위치에 집중하게 되어 지진원을 영상화 시키는 원리이다. 본 연구에서는 3차원 지진파 전파의 수치 모의를 위해 엇갈린 격자 유한 차분법과 병렬 처리 기법을 이용하여 탄성 매질에서의 파동방정식의 해를 구하였다. 수치모의 결과로부터 지진파 역행 전파를 이용해 지진의 시공간적 발생양상을 살펴볼 수 있음을 확인하였다.

• 자원환경지질
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• 제23권3호
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• pp.353-358
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• 1990

This paper presents numerical experiments on migration of synthetic seismograms using by $45^{\circ}$ wave equation. The seismograms used are zero-offset seismogram (corresponding to stacked section) on point reflectors, dipping plane reflector, faulted and folded layers. The seismograms are constructed by upward continuation of seismic source wavelets, exploading on subsurface reflection interfaces, to the earth surface. The synthetic seismograms are migrated by downward continuation and imaging. The upward and downward continuations are implemented by solving the $45^{\circ}$ wave equation with the finite-difference method. Migration of the synthetic data used in this study results in relatively accurate reposition of subsurface structures while the synthetic sections are quite different from the structures.

• Structural Engineering and Mechanics
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• 제27권6호
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• pp.683-696
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• 2007

This article is concerned with the presentation of a time-domain BEM approach applied to the solution of the scalar wave equation for 2D problems. The basic idea is quite simple: the basic variables of the problem at time $t_n$ (potential and flux) are computed with the results related to the potential and to its time derivative at time $t_{n-1}$ playing the role of "initial conditions". This time-marching scheme needs the computation of the potential and its time derivative at all boundary nodes and internal points, as well as the entire discretization of the domain. The convolution integrals of the standard time-domain BEM formulation, however, are not computed; the matrices assembled, only at the initial time interval, are those related to the potential, flux and to the potential time derivative. Two examples are presented and discussed at the end of the article, in order to verify the accuracy and potentialities of the proposed formulation.

• 전기의세계
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• 제20권5호
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• pp.15-18
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• 1971

Up to now, there have been numerous investigations about the effect of diffusion on the wave propagation in gaseous plasmas, but not so much in semiconductor magnetoplasmas. However, currently, it becomes the centor of interest to work with the latter problem, and this paper deals with the dispersion equation including diffusion effect in the latter case to see how diffusion affects the equation in which diffusion term is neglected in the first place, and the analysis is based on the assumption that the plasma can be treated as a hydrodynamical fluid, since, from a macroscopic view point, the plasma interacting with a magnetic field can be considered as a magneto-hydrodynamical fluid, an electrically conducting fluid subjected to electromagnetic force, and the system is linear. The results of the relation and computation show that in the non-streaming case the diffusion terms appear in the equation as perturbation terms and the amplitude of the wave vector changes parabolically with the variation of the angular frequency and the longitudinal modes are observed.

• Selected Papers of The Society of Naval Architects of Korea
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• 제1권1호
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• pp.45-51
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• 1993

By using multiple-scale expansion techniques, the Mach reflection of sinusoidally- modulated nonlinear Stokes waves by a stationary thin wedge has been studied within the framework of potential theory. It is shown that the evolution of diffracted wave amplitude can be described by the Zakharov equation to the loading order and that It reduces to the cubic Schrodinger equation with an additional linear term in the case of stable modulations. Computations are made for the cubic Schrodinger equation for different values of nonlinear and dispersion parameters. Numerical results reflect the experimental findings in terms of the amplitude and width of generated stem waves. Based on the computations it is concluded that the nonlinearity dominates the wave field, while the dispersion does not significantly affect the wave evolution.

• 콘크리트학회논문집
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• 제11권4호
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.