• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.3
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• pp.325-331
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• 2018

This paper deals with the dynamical analysis of a vessel that leads to capsize in regular beam seas. The complete investigation of nonlinear behaviors includes sub-harmonic motion, bifurcation, and chaos under variations of control parameters. The vessel rolling motions can exhibit various undesirable nonlinear phenomena. We have employed a linear-plus-cubic type damping term (LPCD) in a nonlinear rolling equation. Using the fourth order Runge-Kutta algorithm with the phase portraits, various dynamical behaviors (limit cycles, bifurcations, and chaos) are presented in beam seas. On increasing the value of control parameter ${\Omega}$, chaotic behavior interspersed with intermittent periodic windows are clearly observed in the numerical simulations. The chaotic region is widely spread according to system parameter ${\Omega}$ in the range of 0.1 to 0.9. When the value of the control parameter is increased beyond the chaotic region, periodic solutions are dominant in the range of frequency ratio ${\Omega}=1.01{\sim}1.6$. In addition, one more important feature is that different types of stable harmonic motions such as periodicity of 2T, 3T, 4T and 5T exist in the range of ${\Omega}=0.34{\sim}0.83$.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.361-366
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• 2016

This paper presents an arbitrary impedance transformer with unequal split, based on S- to admittance parameter conversion. When compared even/ odd- mode analysis, the parameter conversion design method constitutes a simple design method to include phase delay information and arbitrary port impedances and asymmetrical configurations. To validate this design method, we designed a 50 to $12.5{\Omega}$ impedance transformer with a 3:1 unequal power split, at an operating frequency of 1 GHz. To implement the proposed impedance transformer, the low impedance transmission lines of calculated result are fabricated by the transmission line connected shunt open stub. Good experimental performances were obtained, in full agreement with simulated results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1802-1811
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• 1994

In this paper, the corrugated horn antenna used in the reflector feed horn of satellite is analyzed using the modal expansion method. The modal expansion method is represented by the summations of modals at each point so the exact prediction of field and phase patterns can be obtained. The least number of iterations to compute field patterns is proposed. By using this number. calculation of accurate near and far field patterns without comsuming a lot of computational effort is available. Three kinds of corrugated horn antenna is designed to verify the method and experimented. The VSWR of designed frequency is from 1.04 to 1.1. The input impedance is nearly matched to $50\Omega$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.67-68
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• 2009

In this study, we studied the nature of thin films formed by photodoping chalcogenide materials with for use in programmable metallization cell devices, a type of ReRAM. We investigated the resistance of Ag-doped chalcogenide thin films varied in the applied voltage bias direction from about $1\;M{\Omega}$ to several hundreds of $\Omega$. As a result of these resistance change effects, it was found that these effects agreed with PMC-RAM. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from the chalcogenide materials.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.123-124
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• 2008

In this study, we studied the nature of thin films formed by photodoping chalcogenide materials with for use in programmable metallization cell devices, a type of ReRAM. We investigated the resistance of Ag-doped chalcogenide thin films varied in the applied voltage bias direction from about $1M{\Omega}$ to several hundreds of ${\Omega}$. As a result of these resistance change effects, it was found that these effects agreed with PMC-RAM. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from the chalcogenide materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.354-354
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• 2010

In this study, we studied the nature of thin films formed by photodoping chalcogenide materials with for use in programmable metallization cell devices, a type of ReRAM. We investigated the resistance of Ag-doped chalcogenide thin films varied in the applied voltage bias direction from about $1\;M{\Omega}$ to several hundreds of $\Omega$. As a result of these resistance change effects, it was found that these effects agreed with PMC-RAM. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from the chalcogenide materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.86-87
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• 2008

In this study, we studied the nature of thin films formed by photodoping chalcogenide materials with for use in programmable metallization cell devices, a type of ReRAM. We investigated the resistance of Ag-doped chalcogenide thin films varied in the applied voltage bias direction from about 1 M$\Omega$ to several hundreds of $\Omega$. As a result of these resistance change effects, it was found that these effects agreed with PMC-RAM. The results imply that a Ag-rich phase separates owing to the reaction of Ag with free atoms from the chalcogenide materials.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.45-45
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• 1991

We describe a simple method for obtaining a narrow dip with subnatural linewidth in Doppler-free laser spectroscopy. The method is based on detecting the absolute magnitude, ｜Re[$\chi$NL($\omega$-$\omega$o)]｜, of the dispersive component (real part) of the nonlinear susceptibility induced by the pump beam, and the line shape recorded therefore exhibits a fully resolved technique and a dual phase lock-in amplifier, we have demonstrated the dip as narrow as 3 MHz in the laser-induced birefringence spectrum of the Na D1 line (natural linewidth 10 MHz). Possible spectroscopic applications are considered.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1842-1846
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• 2008

This work reports development of novel liquid-level sensors based on the $3{\omega}$ method. The sensors determine the liquid level by measuring the thermal response as in the conventional hot-wire technique. However the sensors employ an AC heating method to enhance the sensitivity, noise resistance and time response. Also, the microfabricated thin-film structure of the sensor provides mass-producibility as well as improved sensor performance owing to the increase in the surface-volume ratio of the sensor. Two different types of the sensor are developed: one for point detection of the fluid phase and the other for monitoring continuous variation of liquid level. Notable is that the performance of the sensor is not considerably affected by the liquid flow.

• Journal of Astronomy and Space Sciences
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• v.10 no.1
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• pp.17-27
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• 1993

The orbit characteristics and perturbation effects of an artificial satellite with critical inclination have been studied. The critical inclination problem in artificial satellite theory is treated as Ideal Resonance Problem(IRP). The KITSAT-1 satellite launched by Arian 42P at Guiana in August 11, 1992 has orbital inclination close to the critical value cos-1(1/√5). In that case, there is a singularity in some perturbation terms and perigee of the orbit is fixed because d$\omega$/dt is theoretically equal to zero. But actually the long periodic behaviour in argument of perigee, $\omega$ shows a small oscillation. The causes of the oscillation and the relativistic effect in IRP have been studied and applied to the KITSAT-1. The geo-potential perturbation terms which are seperated inclination terms have been obtained using Algebraic manipulation. Also luni-solar disturbing funtion based on the relative position of the sun, moon, and satellite has been obtained. Phase portraits are used to depict the change of eccentricity and grgument of perigee. The variations of each orbital elements have been obtained in case of the KITSAT-1.