• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.267-270
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• 2000

This paper describes measurement of relative permittivity of illite found in young-dong area. A measurement of relative permittivity of illite used to cylindrical cavity resonators with moveable cap. A concentric dielectric-rod inserted cylindrical cavity resonator and an exact field representation of travelling wave mode are introduced for measurement of relative permittivity. The exact electromagnetic fields in cylindrical cavity with concentric dielectric rod is analysed. A relative permittivity of dielectric in cavity is calculated by analyzing the characteristic equation. The characteristic equation is solved by using the ContourPlot graph of Mathematica. We know that the field representation of travelling mode is exact. As a result, relative permittivity of dielectric materials were 7.820 at sample-1 and 7.894 at sample-2.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.320-325
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• 2004

The paper deals with the dynamic response of a cantilevered beam under a travelling mass with constant acceleration. Governing equations of motion taking into account all inertia effects of the travelling mass are derived by Galerkin's mode summation method, and Runge-Kutta integration method is applied to solve the differential equations. The effects of the speed, acceleration and the magnitude of the travelling mass on the response of the beam are fully investigated. A variety of numerical results allows us to draw important conclusions for structural design purposes.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.140-147
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• 2001

In this paper, the dynamic response of non-uniform beams subjected to a travelling mass is investigated. Dynamic behaviors of flexible beam structures under a moving mass have been a concern in the design of bridges, ceiling crain in industry, as well as gun barrel fields. Most of studies for moving mass problems have been related to the theoretical dynamic responses of a simple beam model with uniform cross-sections. In some experimental studies, only a few transverse inertia effects due to travelling mass have been studied so far. The intended aim of the present Paper is to investigate the dynamic response of non-uniform beams taking into account of inertia force. centrifugal force, Coriollis force and self weight due to travelling mass. Galerkin's mode summation method is applied for the discretized equations of motion. Numerical results for the dynamic response of non-uniform beams under a travelling mass are demonstrated for various magnitudes and velocities of the travelling mass. In order to verify propriety of numerical solutions, experiments were conducted. Experimental resu1ts have a good agreement wish theoretical Predictions.

• Journal of The Korean Astronomical Society
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• v.18 no.1
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• pp.15-31
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• 1985

Making use of the arbitrary shock theory developed by Ulmschneider (1967, 1971) and Ulmschneider and Kalkofen (1978), we have calculated the dissipation rates of upward-travelling slow-mode acoustic shock waves in umbral chromospheres for two umbral chromosphere models, a plateau model by Avrett (1981) and a gradient model by Yun and Beebe (1984). The computed shock dissipation rates are compared with the radiative cooling rate given by Avrett (1981). The results show that the slow-mode acoustic shock waves with a period of about 20 second can heat the low umbral chromospheres travelling with a mechanical energy flux of $2.6{\times}10^6\;erg/cm^2s$ at a height of $300{\sim}400km$ above the temperature minimum region.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.296-301
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• 1995

A single-mode erbium-doped fiber laser is constructed by using a intracore fiber Bragg grating and a unidirectional fiber loop mirror. The laser cavity is designed in such a way that the laser beam forms a travelling wave in the gain medium by placing the erbium-doped fiber inside the unidirectional loop and that the wavelength-selective feedback is made from the outside of the loop by a fiber grating with 0.2 nm reflection linewidth. An additional fiber ring resonator is constructed and used as an optical spectrum analyzer to observe the variation of the laser mode spectra. As the result, relatively stable single mode, single polarization output is observed for the most of the time except some mode hoppings in minute scale due to enviommental temperature variations. tions.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.256-259
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• 2005

Mixed-mode interlaminar fracture toughness of carbon fabric/epoxy composites, which are applicable to tilting train carbody, was evaluated through the MMB (Mixed-mode bending) test. Specimens were made of CF3327 plain woven fabric with epoxy and a starter delamination at one end was made by inserting Teflon film with the thickness of 12.5 μ m. Mixed-mode interlaminar fracture test was conducted for 6 types of specimens with the mode II ratio of 20 ,35, 50, 65, 80, 90%. Also crack propagating behaviors and fractured surfaces were examined through an optical travelling scope and a scanning electron microscope, respectively.

• Journal of the Korean Society for Railway
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• v.8 no.2
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• pp.195-201
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• 2005

Mode II interlaminar fracture behaviors of carbon fabric/epoxy composites, which are applicable to tilting train carbodies, was investigated by the ENF (End notched flexure) test. The specimens were made of CF3327 plain woven fabric with epoxy and a starter delamination at one end was made by inserting Teflon film with the thickness of 12.5$mu$m or 25.0$mu$m. The equation for mode II interlaminar fracture toughness was suggested based on the effective crack length from the compliance of load-displacement curve. Mode II interlaminar fracture toughness was evaluated for several types of the specimens. Also crack propagating behaviors and fracture surfaces were examined through an optical travelling scope and a scanning electron microscope.

• Wind and Structures
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• v.26 no.5
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• pp.267-277
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• 2018

Numerical simulations are performed of a long flexible cylinder undergoing vortex-induced vibration at a Reynolds number of 500. The cylinder is pinned at both ends, having an aspect ratio of 100 (cylinder length to cylinder diameter) and a mass ratio of 4.2 (structural mass to displaced fluid mass). Temporal and spatial information on the cross-flow (CF) and in-line (IL) vibrations is extracted. High modal vibrations up to the $6^{th}$ in the CF direction and the $11^{th}$ in the IL direction are observed. Both the CF and IL vibrations feature a multi-mode mixed pattern. Mode competition is observed. The $2^{nd}$ mode with a low frequency dominates the IL vibration and its existence is attributed to a wave group propagating back and forth along the span. Distributions of fluid force coefficients are correlated to those of the CF and IL vibrations along the span. Histograms of the x'-y motion phase difference are evaluated from the total simulation time and a complete vibration cycle representing the standing or travelling wave pattern. Correlations between the phase difference and the vibrations are discussed. Vortex structures behind the cylinder show an interwoven near-wake pattern when the standing wave pattern dominates, but an oblique near-wake pattern when the travelling wave pattern prevails.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.33-36
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• 1998

This paper is a study on a linear ultrasonic motor with a first longitudinal$(L_1)$ and fourth bending $(B_4)$ double-mode rectangular plate. The stator vibrator is composed of an elastic material plate and of a piezo-ceramic element having a motion by electrical excitation. Each strain vector differs by $90^{\circ}$ generate travelling wave with the elliptical displacement motion of a point on the surface. To magnify displacement of longitudinal direction in elliptical displacement motion, the motor has a mechanism of the.displacement enlargement. In this paper, the vibration shape of the stator is simulated using the finite element method. A detailed model considered of the piezoelectric effect and of the exact geometry of the stator is used to calculate the displacement. The position of displacement mechanism is decided by the maximum displacement.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.125-129
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• 2000

In this paper, We designed and fabricated C-band bandpass filter using dielectric resonators. From waveguide cutoff frequency which applied the region between adjacent dielectric resonators, the height of cavity is determined. The cavity's diameter is determined to the twice of dielectric resonator's diameter considering the conductor loss. The resonant frequency of the DR-cavity is calculated with travelling wave mode analysis. Conventionally, circular cylindrical dielectric resonator is analysed by Cohn's model which use the evanescent mode in the region between dielectric resonator wall and circular cavity wall, which is an approximated method. The external quality factor, Q$_{ex}$ has found with simulation result using Ansoft's Maxwell simulation tool. The designed filter using dielectric resonators with dielectric constant of 45 has the passband center at 5.065GHz. The bandpass filter using dielectric resonators have about 1dB insertion loss. 20MHz bandwidth and more than 30dB attenuation at f$_{0}$$\pm$15MHz.z.z.