• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.6
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• pp.237-246
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• 2022

Based on the random-vibration-theory methodology, dynamic responses of nuclear facilities subjected to obliquely incidental and incoherent earthquake ground motions are calculated. The spectral power density functions of the 6-degree-of-freedom motions of a rigid foundation due to the incoherent ground motions are obtained with the local wave scattering and wave passage effects taken into consideration. The spectral power density function for the pseudo-acceleration of equipment installed on a structural floor is derived. The spectral acceleration of the equipment or the in-structure response spectrum is then estimated using the peak factors of random vibration. The approach is applied to nuclear power plant structures installed on half-spaces, and the reduction of high-frequency earthquake responses due to obliquely incident incoherent earthquake ground motions is examined. The influences of local wave scattering and wave passage effects are investigated for three half-spaces with different shear-wave velocities. When the shear-wave velocity is sufficiently large like hard rock, the local wave scattering significantly affects the reduction of the earthquake responses. In the cases of rock or soft rock, the earthquake responses of structures are further affected by the incident angles of seismic waves or the wave passage effects.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.268-273
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• 2004

A study on experimental method of the model test for the impulse turbine is carried out. the wave simulator is used to reproduce the real wave condition. It controls two parameter correspond to wave height and wave frequency. The optimum design which is reported by T. Setoguchi is manufactured and tested for the validation of our test facilities. The comparison of model test show that our facilities produce little bit higher efficiency at maximum efficiency point. To increase the efficiency of turbine, the new rotor with negative tip clearance is designed and being tested.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.175-185
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• 2001

A numerical model is represented to calculate the reflected waves, the runup of waves and the wave induced velocities on impermeable slopes for the normally incident wave trains of nonlinear monochromatic wave and solitary wave. The finite amplitude shallow water equations with the effects of bottom friction are solved numerically in time domain using an explicit dissipative Lax-Wendroff finite difference method. The numerical model is verified by comparisons with the other numerical results, the measured data and asymptotic results. It is found that the uprushing and downrushing of incident waves may be accurately predicted by the present numerical model. Therefore, the present numerical model can be applicable to swells as well as long waves.

• Journal of Industrial Technology
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• v.17
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• pp.261-275
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• 1997

The objective of this paper is to develop two numerical model for predicting the wave height with set-up/down near the surfzone on a arbitrary beach profile. Two wave models, regular wave model and random wave model, are based on the energy flux equation with the energy dissipation effects. The developed numerical models are verified by comparison of numerical results with analytical solutions that are derived under the simple conditions. The characteristics of parameters included in each model are then investigated and decided to the range of behaviour by the sensitivity analysis. For sensitivity analysis, we carried out total 46 laboratory tests. Finally, the developed numerical models are applied to the field where the wave height near the surfzone has been measured. From the applications of numerical models, it is concluded that the developed numerical models may accurately predict the wave height with the set-up/down near the surfzone on a arbitrary beach profile.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.655-658
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• 1995

Recently years, these has been considerable interst in analysis of stress under shock wave. Stress wave is important problem for mechanical device and structural design. This paper was studied to develope the finite element program to analysis single materials and composite materials. This paper is studied for the stress wave propagation of single materials and predicted reflection of stress wave in materials. the developed program was able to analysis of stress wave propagation of composite materials and descride reflection of stress wave at contact surface.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1155-1163
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• 2006

Calculation was carried out for phase velocity and deformation wave decay in a layer of viscoelastic material fixed tightly on the solid substrate. Analysis has been performed regarding the inner structure of the wave, i.e., the proportions between the vertical and horizontal displacements and their profiles. The wave characteristics depend strongly on media compressibility factor. The effect of viscous losses on parameters of the main oscillation mode was studied in detail. Results were compared with the model of coating with local deformation. A new experimental approach was made in order to measure such wave properties of a compliant coating as the dependency of deformation wave velocity on frequency and decay factor was made. The method for estimation of coating parameters enabling the drag reduction in turbulent flow was then refined.

• Electronics and Telecommunications Trends
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• v.35 no.5
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• pp.69-82
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• 2020

In many technologies, artificial intelligence (AI) is becoming an important topic for areas based on the field of big data. However, applied AI cases and the research status of radio wave technology are not widely known to the public. The spread of AI to other areas is being followed by radio wave technologies, and much effort is being taken to evolve it into intelligent radio wave technologies in the future. This paper presents the recent areas of interest in radio wave technology, such as spectral sharing, illegal spectrum monitoring, radar detection, radio wave medical imaging, and channel modeling; examines the requirements for applying AI; and describes the applied cases, research trends, and standardization efforts that apply AI technology to them. On this basis, we will discuss the prospects of AI application to the expected radio wave technology of the future.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.35-37
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• 2005

In this study, a P- and T-wave detection algorithm in ECG, obtained by minimized filtering to prevent waveform distortion, has been realized. The algorithm uses two slope tracing waves, the descending slope tracing wave and the ascending slope tracing wave, developed for efficient determination of slope inverting points and sudden slope changing points. The algorithm generates the slope tracing waves which trace the original ECG wave, and subtracts one tracing wave from the other to detect P- and T-waves. The algorithm has been applied to MIT/BIH database in order to verify its efficacy and validity in practical applications.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2061-2067
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• 2005

In this study, we focus on the submerged plate built into the Very Large Floating Structure with the partial openings of Sm long, which enables the reverse flow of incident wave to generate the wave breaking. The purpose of this study is to investigate the characteristics of wave exciting forces acting on the submerged plate and the fore part of VLFS. Firstly, we have carried out the extensive experiments to understand the characteristics of the wave exciting forces. Then we have performed the numerical simulations by applying the Marker and Cell method (MAC method) and compared with the experimental results. We discuss the validity of MAC method and the effects of the submerged plate on the motion of VLFS. As a result, we get the conclusion that the submerged plate is useful for reducing the wave exciting forces acting on the structure behind the submerged plate.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.605-617
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• 2005

A sudden discharge of mass flow from the exit of a duct can generate an impulsive wave, generally leading to undesirable noise and vibration problems. The present study develops an understanding of unsteady flow physics with regard to the impulsive wave discharged from a duct, using a numerical method. A second order total variation diminishing scheme is employed to solve three-dimensional, unsteady, compressible Euler equations. Computations are performed for several exit conditions with and without ground and wall effects under a change in the Mach number of an initial shock wave from 1.1 to 1.5. The results obtained show that the directivity and magnitude of the impulsive wave discharged from the duct are significantly influenced by the initial shock Mach number and by the presence of the ground and walls.