• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.3
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• pp.43-50
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• 1984

A body form, which experiences minimum vertical wave-exciting forces in the vicinity of a prescribed wave frequency in water of finite depth, is obtained by an approximate method. Its configuration has the symmetry with respect to the vertical axis, expressed in terms of exponential functions. By distributing three-dimensional pulsating sources and dipoles on the immersed surface of the body, a velocity potential is determined and subsequently hydrodynamic forces including the 2nd-order time-mean drift forces are calculated. The dynamic behavior of the body moored in irregular waves is investigated numerically by using central difference method. Hereby irregular wave trains are simulated with examining its repeatability by comparing the resulting spectrum with original one. Numerical results indicated that the body form obtained from the present analysis possesses in general a favorable hydrodynamic characteristics in comparison with a spherical buoy and that the maximum excursion of the body can be significantly reduced by setting pre-tension of an appropriate amount in the mooring cable.

• 한국기계연구소 소보
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• s.9
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• pp.193-208
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• 1982

Flap type wave-maker, wave absorber, motion measuring equipment and related instruments were newly installed at Ship Experimental Towing Tank, Ship Research Station, KIMM. The model tests in regular head and following waves were successfully carried out and the motion and wave loads in regular and long crested irregular waves were calculated for a container ship model which was adopted as the hull form for the comparative calculations of the ITTC Seakeeping Committee. The results of model tests show good agreement with calculated results and the latter are generally in good agreement with the results of the comparative calculations.

• Bulletin of the Korean Mathematical Society
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• v.50 no.3
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• pp.811-821
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• 2013

We study the initial value problem of the exponential wave equation in $\math{R}^{n+1}$ for small initial data. We shows, in the case of $n=1$, the global existence of solution by applying the formulation of first order quasilinear hyperbolic system which is weakly linearly degenerate. When $n{\geq}2$, a vector field method is applied to show the stability of a trivial solution ${\phi}=0$.

• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.69-78
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• 2004

This paper treats the conditions for the existence of rotating wave solutions of a system modelling the behavior of students in graduate programs at neighbouring universities near each other which is a modified form of the model proposed by Scheurle and Seydel. We assume that both types of individuals are continuously distributed throughout a bounded two-dimension spatial domain of two types (circle and annulus), across whose boundaries there is no migration, and which simultaneously undergo simple (Fickian) diffusion. We will show that at a critical value of a system-parameter bifurcation takes place: a rotating wave solution arises.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.119-126
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• 1997

The relationship between the applied stresses and the change of elastic wave velocity has been established based on the acoustoelasticity theory. The non-uniform stress field in a loaded specimen has been evaluated from the surface acoustic wave velocity measured by the line-focus acoustic microscopy with the acoustoelastic constants obtained form a calibration test. The evaluated stresses are in good agreement with the results calculated by finite element method.

• Journal of the Optical Society of Korea
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• v.5 no.3
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• pp.76-82
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• 2001

The optical response for traveling-wave Mach-Zehnder modulators without-with phased reversal is successfully derived in more concise and succinct form than any other equations before. The obtained equation is applied to a bandpass traveling-wave modulator with 3-section phase reversal and is confirmed to be in reasonable agreement with the experimental data.

• The Journal of the Acoustical Society of Korea
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• v.17 no.2E
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• pp.47-52
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• 1998

An analysis of dynamic responses is carried out on monoclinic anisotropic system due to a buried harmonic line source. The load is in the form of a normal stress acting along an arbitrary axis on the plane of symmetry within the orthotropic materials: In case that the line load is acting along the symmetry axis normal to the plane of symmetry, plane wave equation is coupled with verital shear wave and longitudinal wave. However, if the line load is acting along an arbitrary axis normal to the plane of symmetry, plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in a reference coordinate system, where the line load is coincident with a symmetry axis of the orthotropic material. Then the equation of motion is transformed into one with respect to general coordinate system with azimuthal angle by using transformation tensor. Plane wave solutions of monoclinic systems are derived for infinite media. Finally complete solutions for the plane harmonic wave are obtained by calculating the inverse of the integral transforms, in which bulk wave poles are avoided by deforming the contour of the integration to the complex plane. Numerical results for examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.6
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• pp.339-347
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• 2021

Piston type wave makers or flap type wave makers are usually adopted as a wave maker which disturbing the fluid domain with sinusoidal motion. Recently hybrid wave maker which could be operated as not only piston type and/or flap type but also swing type wave maker have been devised by utilizing the link mechanism. The wave board of hybrid wave maker has been devised to be independently controlled by the horizontal actuators on upper and lower end of the wave board. The wave board could operate as a flap type wave board when the lower hinge is in a stationary condition and the upper hinge is operated with sinusoidal motion. On the contrary, the swing type wave board could be obtained by the lower hinge is activated and the upper hinge is in a stationary condition. When both end of the wave board is activated in a synchronized condition, the wave board motion become piston motion. In addition the hybrid wave maker could enhance the piston motion with flap motion or swing motion by selecting control parameters. Various wave board motion of hybrid wave maker and relevant wave form have measured on the wave board and departed location. It is appeared that the novel hybrid wave maker could be utilized for the improvement of wave qualities in experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1638-1642
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• 2007

This paper investigated the destruction effect of the semiconductors by impact of high power electromagnetic wave. The experiments is employed as an open-ended waveguide to study the destruction effects on semiconductor using a 2.45 GHz 600 W Magnetron as a high power electromagnetic wave. The semiconductors are located at a distance of $31cm\sim40cm$ from the open-ended waveguide and are composed of a LED drive circuit for visual discernment. Also the chip condition of semiconductor is observed by SEM(Scanning Electron Microscope) analysis. The semiconductor are damaged by high power electromagnetic wave at about 860 V/m. The SEM analysis of the destructed devices showed onchipwire and bondwire destructions. Based on the result, semiconductor devices should have plan to protect the semiconductor devices form high power electromagnetic wave. And the database from this experiment provides the basis for future investigation.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.128-133
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• 1990

An equation is presented to calculate wave height due to shoaling, refraction and bottom friction. The equation in an integral form is evaluated by two different methods： A numerical method and an analytical method based on approximation. Both methods are used to calculate wave height and show very good agreement between their results. As shown in the figure of wave height variation vs. relative water depth, an increase of incident angle leads to a decrease in wave height. For the case of normal incident wave, the present equation can be reduced, under some assumptions, to the existing equation of Bretschneider and Reid (1954).