• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.3
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• pp.268-274
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• 2004

Patch type piezo-polymer sensors for smart structures were experimented to detect elastic wave. The pencil lead braking test was performed to analyze the characteristics of patch-type piezo-polymer sensors such as polyvinyliden fluoride (PVDF) and polyvinylidene fluoride trifluorethylene (P(VDF-TrFE)) for several test specimens with various elastic wave velocities and acoustical impedances. The characteristics of the patch-type piezo-polymer sensor were compared with the commercial PZT acoustic emission (AE) sensor. The vacuum grease and epoxy resin were used as a couplant for the acoustic impedance matching between the sensor and specimen. The peak amplitude of elastic wave increased as the diameter of piezo-film and acoustical impedance of the specimen increased. The frequency detection range of the piezo-film sensors decreased with increasing diameter of the piezo-film sensor. The P(VDF-TrFE) sensor was more sensitive than the PVDF sensor.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1988.10a
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• pp.114-117
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• 1988

In mobile radio communication system involving geostationary satellites the field intensity of electromagnetic wave varies with frequency shape and location of an obstacle between a tramamitter and a receiver. In this paper a ring type obstacle between the propagation paths is presented. On the basis of Fresnel diffraction theory, the field intensity varying with ring-type obstacle’s radius is obtained by computer simulation.]

• East Asian mathematical journal
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• v.32 no.3
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• pp.355-364
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• 2016

In this paper, we study exponential stabilization of the vibrations of the Kelvin-Voigt type wave equation with Balakrishnan-Taylor damping and acoustic boundary in a bounded domain in $R^n$. To stabilize the systems, we incorporate separately, the internal material damping in the model as like Kang [3]. Energy decay rate are obtained by the exponential stability of solutions by using multiplier technique.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.270-271
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• 2000

Among many optical modulators, we are interested in traveling-wave(TW) multiple quantum well(MQW) electro-absorption modulator which can be used for wide-band applications, covering DC to 30GHz or higher frequencies. In this study, we simulate a 1.3mm InGaAs/lnGaAsP TW MQW EAM using the 3D Finite Difference-Time Domain (FDTD) method. We identify that several geometric factors affect Microwave charateristics. Our calculated data provide useful information to optimize and fabricate ridge-type TW CPW EAM.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.16 no.2
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• pp.85-91
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• 2012

In this paper, we study uniform exponential stabilization of the vibrations of the Kelvin-Voigt type wave equation with acoustic boundary in a bounded domain in $R^n$. To stabilize the systems, we incorporate separately, the internal material damping in the model as like Gannesh C. Gorain [1]. Energy decay rates are obtained by the exponential stability of solutions by using multiplier technique.

• East Asian mathematical journal
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• v.28 no.3
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• pp.339-345
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• 2012

In this paper, we study uniform exponential stabilization of the vibrations of the Kirchho type wave equation with acoustic boundary in a bounded domain in $R^n$. To stabilize the system, we incorporate separately, the passive viscous damping in the model as like Gannesh C. Gorain [1]. Energy decay rate is obtained by the exponential stability of solutions by using multiplier technique.

• East Asian mathematical journal
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• v.30 no.3
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• pp.249-258
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• 2014

In this paper, we study uniform exponential stabilization of the vibrations of the Kirchhoff type wave equation with Balakrishnan-Taylor damping and acoustic boundary in a bounded domain in $R^n$. To stabilize the systems, we incorporate separately, the passive viscous damping in the model as like Kang[14]. Energy decay rates are obtained by the uniform exponential stability of solutions by using multiplier technique.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.264-269
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• 2002

The wave profiles of directional breaking waves are investigated experimentally in a directional wave basin. The directional breaking waves are generated by component wave focusing both in direction and frequency based on constant wave steepness and constant wave amplitude spectrum models. the profile parameters of wave crest steepness and asymmetry are adapted to analyze the evolution of breaking ware characteristics in a view of focusing efficiency. The generated breaking waves are classified into the incipient, single and multi breaking waves.

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.223-228
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• 2007

This paper deals with the secondary excited induction generator applied to random wave input generation system. As it is preferred to stabilize the output voltage and frequency in the constant level, microcomputer controlled CSI connected to the secondary windings supplies the secondary current with slip frequency. For testing this method, the input torque simulator is constructed, according to the power flow analysis. The experimental and numerical results show the advantage of secondary excited induction generator system for the random input wave generation system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.661-666
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• 2000

Traveling wave on the structure can be generated by superposing two standing waves. Precise matching of the amplitudes and phase shift between two standing waves in time and space is the key to the success of generating a traveling wave. The principle of generating a traveling wave on the structure is utilized in the construction of linear and rotary type ultrasonic motors. This paper demonstrates experimentally generating a traveling wave on the simply supported beam.