• Title, Summary, Keyword: Korean Wave

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A Study on Stress Wave Propagation by Finite Element Analysis (유한요소법에 의한 2차원 응력파 전파 해석에 관한 연구)

  • 황갑운;조규종
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.12
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    • pp.3369-3376
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    • 1994
  • A finite element program for elastic stress wave propagation is developed in order to investigate the shape of stress field and analysis the magnitude of stress wave intensity at time increment. Accuracy and reliance of the finite element analysis are acquired when the element size is smaller than the product of the stress wave speed and the critical value of increasing time step. In the finite element analysis and theoretical solution, the longitudinal stress wave is propagated to the similar direction of impact load, and the stress wave intensity is expressed in terms of the ratio of propagated area. The direction of shear wave is declined at an angle of 45 degrees compared with longitudinal stress wave and the speed of shear wave is half of the longitudinal stress wave.

Optimal Wave Source Position Determination Based on Wave Propagation Simulation (전자파 영향 평가를 통한 최적의 전파 기지국 위치 결정 방법)

  • 박성헌;박지헌
    • Korean Management Science Review
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    • v.18 no.1
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    • pp.41-54
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    • 2001
  • In this paper, we proposed a method to determine optimal wave source for mobile telephone communication. The approach is based on wave propagation simulation. Given a wave source we can determine wave propagation effects on every surfaces of wave simulation environment. The effect is evaluated as a cost function while the source’s position x, y, z work as variables for a parameter optimization. Wave propagated 3 dimensional space generates reflected waves whenever it hits boundary surface, it receives multiple waves which are reflected from various boundary surfacers in space. Three algorithms being implemented in this paper are based on a raytracing theory. If we get 3 dimensional geometry input as well as wave sources, we can compute wave propagation effects all over the boundary surfaces. In this paper, we present a new approach to compute wave propagation. First approach is tracing wave from a source. Source is modeled as a sphere casting vectors into various directions. This approach has limit in computing necessary wave propagation effects on all terrain surfaces. The second approach proposed is tracing wave backwards : tracing from a wave receiver to a wave source. For this approach we need to allocate a wave receiver on every terrain surfaces modeled, which requires enormous amount of computing time. But the second approach is useful for indoor wave propagation simulation. The last approach proposed in this paper is tracing sound by geometric computation. We allow direct, 1-relfe tion, and 2-reflection propagation. This approach allow us to save in computation time while achieving reasonable results. but due to the reflection limitaion, this approach works best in outdoor environment.

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A Study on the Characteristics of the Impulse Wave Discharged from the Exit of a Pipe (관출구로부터 방출하는 펄스파 특성에 관한 연구)

  • 이동훈;김희동;이명호;박종호
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.1
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    • pp.48-56
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    • 2002
  • A computational work of the impulse wave which is discharged from the open end of a pipe is compared to the Lighthill\`s aeroacoustics theory. The second-order total variation diminishing(TVD) scheme is employed to solve the axisymmetric, compressible, unsteady Euler equations. The relationship between the initial compressure wave form and the resulting impulse wave is characterized in terms of the peak pressure. The overpressure, pressure gradient and wavelength of the initial compression wave are changed to investigate the influence of the initial compressure wave form on the peak pressure of impulse wave. The results obtained show that for the initial compression wave of a large wavelength and small pressure gradient the peak pressure of the impulse wave depends upon the wavelength and pressure gradient of compression wave, but for the initial compression wave of a short wavelength and large pressure gradient the peak pressure of the impulse wave is almost constant regardless of the wavelength and pressure gradient of compression wave. The peak pressure of the impulse wave is increased with an increase in the overpressure of the initial compression wave. The results from the numerical ana1ysis are well compared to the results from the aeroacoutics theory with a food agreement.

Computational Study of The Pulse Waves Discharged From The Open End of a Duct (관 출구로부터 방출되는 펄스파의 수치해석적 연구)

  • Kim, H.D.;Kim, H.S.;Kweon, Y.H.;Lee, D.H.
    • Proceedings of the KSME Conference
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    • pp.355-360
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    • 2001
  • This study addresses a computational work of the impulsive wave which is discharged from the open end of a pipe. An initial compression wave inside the pipe is assumed to propagate toward atmosphere. The over pressure and wave-length of the initial compression wave are changed to investigate the characteristic values of the impulsive wave. The second order total variation diminishing (TVD) scheme is employed to solve the axisymmetric, compressible, unsteady Euler equations. The relationship between the initial compression wave form and impulsive wave is characterized in terms of the peak pressure of the impulsive wave and its directivity. The results obtained show that for the initial compression wave of a large wave-length the peak pressure of the impulsive wave does not depend on the over pressure of the initial compression wave, but for the initial compression wave of a very short wave-length, like a shock wave, the peak pressure of the impulsive wave is increased with an increase in the over pressure of the initial compression wave. The directivity of the impulsive wave to the pipe axis becomes significant with a decrease in the wave-length of the initial compression wave.

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Investigation of Characteristics of Waves Generated in Two-Dimensional Wave Channel (2차원 조파수조에서의 파 생성 특성 조사)

  • Ahn, Jae-Youl;Choi, Jung-Kyu;Kim, Hyoung-Tae
    • Journal of Ocean Engineering and Technology
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    • v.27 no.4
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    • pp.68-75
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    • 2013
  • This paper investigates the characteristics of waves generated by a flap-type wave maker in a two-dimensional wave channel. Measurements are carried out for various water depths, wave heights, periods, and lengths capacitance-type wave height gages. The experimental results are shown to satisfy the dispersion relation of the linear wave theory. For waves with a small height and long period, the wave profiles agree well with those of the linear wave theory. However, as the wave height and period become higher and shorter, respectively, it is shown that the wave profiles measured in the present experiments are different from the linear wave profiles, and the measured wave heights are smaller than the target wave heights, which may be due to the non-linearity of the waves. As the wave progresses toward the channel end, the wave height gradually decreases. This reduction in the wave height along the wave channel is explained by the wave energy dissipation due to the friction of the side walls of the channel. The performance of the wave absorber in the channel is found to be acceptable from the results of the wave reflection tests.

The Effect of the Korean Wave on Malaysian University Students' Perception

  • Lee, Sang-Hyeop;Lee, Kai-Sean;Kwak, Gong-Ho;Kim, Hak-Seon
    • Culinary science and hospitality research
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    • v.23 no.1
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    • pp.79-83
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    • 2017
  • This paper attempted to understand the university students' perception on the Korean Wave in Malaysia. Six Malaysian students were involved in this study and three research questions guided the entire study. The first question explored Malaysian university students' perception about the Korean Wave in general; the second involved how the media influences the perception of the Korean Wave; and third question looked into the economic effects that would influence students' perception of the Korean Wave. Among the six students, all of them had positive perception of the Korean Wave and were heavily influenced through the media. Thus, it can be said that it brought positive feedback to the Korean Wave. The awareness of the Korean Wave was found to be increasingly popular due to media development. This study helped understand the Korean Wave from Malaysian students' perception.

Correction Factor for Assessment of Nearshore Wave Energy (근해 파력에너지 산정을 위한 보정 기법에 관한 연구)

  • Kim, Gunwoo;Jeong, Weon Mu;Jun, Kicheon;Lee, Myung Eun
    • 한국신재생에너지학회:학술대회논문집
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    • pp.164.1-164.1
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    • 2011
  • Previously, many researchers assessed nearshore wave energy in two ways. The first is a simulation with respect to the offshore wave time series to validate the wave buoy data and the wave model results, and the other is to simulate the representative waves of typical seasonal wave conditions. The former requires enormous computational time and effort. The latter yields inspection on the patterns for the spatial and temporal distribution of nearshore wave energy but tends to underestimates the amount of wave energy in the nearshore region owing to the correlation between the significant wave height and wave period. $\ddot{O}$zger et al. (2004) derived the stochastic wave energy formulation by introducing a correction factor explicitly in terms of the covariance of the wave energy and significant wave height. In this study, a correction factor was applied for the assessment of nearshore wave energy obtained by numerical simulation of wave transformation with respect to representative waves.

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Electroencephalogram Variation by Electromagnetic Wave on Human Light Sensing (인체 광인식에 있어서 전자파에 의한 뇌파 변화)

  • Park Hyung-Jun;Yoon Jae-Hyun
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.55 no.2
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    • pp.82-89
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    • 2006
  • The electroencephalogram generated by light stimulation in human body of dark adaption state was measured and analyzed in the cases that electromagnetic wave was put in and not put in, respectively. Shieldroom being able to interrupt the light and the electromagnetic wave of outer was constructed, and the experimental system being able to apply any light and any electromagnetic wave was designed. When the electromagnetic wave was applied to body or not, the variation characteristics of each component in the electroencephalogram were i3s follows. The 6 wave was increased and the $\alpha$ wave and the $\beta$ wave were decreased in the case that the electromagnetic wave was applied, and the variation range of the $\Theta$ wave was small. And the influence of electromagnetic wave on human body was that the appearance time of the $\beta$ wave was late, and it moaned that the time of visual recognition was delayed.

Analytical Study for dispersed Phase Velocity Information of Love Waves (러브파의 위상속도 분산정보에 관한 해석적 연구)

  • 이일화
    • Journal of the Korean Society for Railway
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    • v.7 no.4
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    • pp.391-399
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    • 2004
  • This paper investigated the dispersion characteristics of horizontal surface waves as means to apply conversional SASW techniques. To verify this proposal, 3D finite element analysis and Transfer matrix solution were performed. SH wave(Love waves) has the some advantages in comparison with Rayleigh wave. Representatively, Love wave has a characteristics not affected by compression wave. These characteristics have the robust applicability for the surface wave investigation techniques. In this study, for the purpose of employing Love wave in the SASW method, the dispersion characteristics of the Love wave was extensively investigated by the theoretical and numerical approaches. The 3-D finite element and transfer matrix analyses for the half space and two-layer systems were performed to determine the phase velocities from Love wave as well as from both the vertical and the horizontal components of Rayleigh wave. Preliminary, numerical simulations and theoretical solutions indicated that the dispersion characteristics of horizontal surface wave(Love waves) can be sufficiently sensitive and appliable to SASW techniques.

Energy Dissipation and Transfer among Wave Components during Directional Breaking Processes (다방향 쇄파 발생 전후의 파랑 성분간 에너지 전이 및 소산)

  • 홍기용;에스똘히오메자
    • Journal of Ocean Engineering and Technology
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    • v.17 no.6
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    • pp.1-6
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    • 2003
  • Wave energy dissipation and energy transfer between wave components, during the directional wave breakings, are investigated. Directional incipient and plunging breakers were generated by focusing the multi-frequency and multi-directional wave components at a designed location, based on a constant wave amplitude and a constant wave steepness frequency spectrum. The time series of surface wave elevation was measured at 9 different locations around the wave focusing point, using a wave gauge array. In order to examine the variation of the directional spreading function, the horizontal velocity of fluid motion was also measured. By comparing energy spectrums, before and after the breaking, the characteristics of energy dissipation and energy transfer, caused by wave breaking, are investigated. Their dependencies on directionality, as well as frequency, are analyzed. The breakings significantly dissipate wave energy, through energy transfer, in the upper region of the peak-frequency band, while enhancing wave energy in the low-frequency band.