• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.206-210
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• 1997

In the fields of the optics, precise machine, semiconductors, the micro-positioning actuators are required for the control of position in the submicron range. PNN-P2N-PZT ceramics were fabricated with various mole ratio of the PZT[Pb(Zr$_{1}$2//Ti$_{1}$2)O$_3$]. PNN (Pb(Ni$_{1}$3/Nb$_{2}$3/)O$_3$]and PZN[Pb(Zn$_{1}$3//Nb/sbu 2/3/)O$_3$] powders prepared by double calcination and PZT powders prepared by molten- salt synthesis method. The relative permittivity of specimen with PZT 0.3 mole ratio was shown 5,320 and appeared the relaxor ferroelectric feature. The maximum Piezoelectric coefficient d$_{31}$ to be used for evaluation the displacement of piezoceramics in PNN-PZN-PZT ceramics was 324$\times$10$^{-12}$ (C/V) at the vicinity of morphotropic phase boundary and was larger than that of solid PZT ceramics(120$\times$10$^{-12}$ C/V).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.651-653
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• 2000

In this study, a distance-measurement system was proposed by using principle of the Michelson Interferometer and a fundamental research was carried out. In case of the rnichelson interferometer, relativity distance was measured by relativity-difference of two course of light. But wavelength of light source were changed in this system in order to use interference phenomenon of michelson interferometer in measuring absolutely distance. Wavelength of input signal were changed periodically and were interfered electrically. So absolute distance can be calculated by using $\Delta\lambda$ and measuring $\eta\Delta$ in electric interference. Nose by a external factor was small in this system because a absolutely distance was measured by phase difference. And a dispersion of noise was small in pulse-echo response because a error was occurred in range of phase difference of signal. Also very wide range can be measured by only single system because informations of distance were acquisited in wavelength level.

• Progress in Superconductivity
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• v.14 no.1
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• pp.52-59
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• 2012

In this paper, the robust superconductor flywheel energy storage system(SFESS) controller using $H_{\infty}$ control theory was designed to damp low frequency oscillation of power system. The main advantage of the $H_{\infty}$ controller is that uncertainties of power system can be included at the stage of controller design. Both disturbance attenuation and robust stability for the power system were treated simultaneously by using mixed sensitivity $H_{\infty}$ problem. The robust stability and the performance for uncertainties of power system were represented by frequency weighted transfer function. To verify control performance of proposed SFESS controller using $H_{\infty}$ control, the closed loop eigenvalue and the damping ratio in dominant oscillation mode of power system were analyzed and nonlinear simulation for one-machine infinite bus system was performed under disturbance for various operating conditions. The results showed that the proposed $H_{\infty}$ SFESS controller was more robust than conventional power system stabilizer (PSS).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.445-446
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• 2022

In this paper, in order to improve port work preparation and berth scheduling efficiency in an artificial intelligence-based berthing monitoring system that can monitor the ship's berthing process, we develop a mooring line recognition model to check an exact berthing time. By improving the pre-designed AI model, it is possible to segment the mooring line from the input image, and to recognize when the mooring line arrives or falls on the berth, thereby providing the correct ship's berthing time. The proposed AI model confirmed by the results that mooring line recognition is possible with evaluation data about the actual berthing situation.

• The Journal of Korea Robotics Society
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• v.8 no.1
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• pp.51-57
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• 2013

Recently, the number of jellyfish has been rapidly grown because of the global warming, the increase of marine structures, pollution, and etc. The increased jellyfish is a threat to the marine ecosystem and induces a huge damage to fishery industries, seaside power plants, and beach industries. To overcome this problem, a manual jellyfish dissecting device and pump system for jellyfish removal have been developed by researchers. However, the systems need too many human operators and their benefit to cost is not so good. Thus, in this paper, the design, implementation, and experiments of autonomous jellyfish removal robot system, named JEROS, have been presented. The JEROS consists of an unmanned surface vehicle (USV), a device for jellyfish removal, an electrical control system, an autonomous navigation system, and a vision-based jellyfish detection system. The USV was designed as a twin hull-type ship, and a jellyfish removal device consists of a net for gathering jellyfish and a blades-equipped propeller for dissecting jellyfish. The autonomous navigation system starts by generating an efficient path for jellyfish removal when the location of jellyfish is received from a remote server or recognized by a vision system. The location of JEROS is estimated by IMU (Inertial Measurement Unit) and GPS, and jellyfish is eliminated while tracking the path. The performance of the vision-based jellyfish recognition, navigation, and jellyfish removal was demonstrated through field tests in the Masan and Jindong harbors in the southern coast of Korea.

• Microbiology and Biotechnology Letters
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• v.42 no.4
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• pp.413-416
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• 2014

The antibacterial activity of chitosan against Escherichia coli and Staphylococcus aureus was investigated in the presence of NaCl, acetic acid, lactic acid, and citric acid to assess its potential use as a food preservative. The inhibitory activity of chitosan decreased slightly upon adding NaCl to culture broth containing 100 ppm of chitosan (MW 3,000), while adding acetic acid, lactic acid, or citric acid enhanced the inhibitory activity of chitosan on growing cells. Our results indicate that food components, such as NaCl, acetic acid, lactic acid, and citric acid, can significantly affect the bactericidal activity of chitosan.

• Korean Journal of Pharmacognosy
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• v.51 no.4
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• pp.291-296
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• 2020

Filipendula glaberrima (FG) is a plant endemic to South Korea. It is economically important as a food source and used as a medicine in treating ailments. Filipendula flowers are characterized by the presence of several polyphenolic constituents. The aim of this study is to determine the content of (+)-catechin in Filipendula glaberrima collected from different regions at different flowering stages. High-performance liquid chromatography with a gradient elution system (0.5% acetic acid in water : acetonitrile = 95 : 5 to 0 : 100 for 35 min) was used. A reverse-phase INNO column with UV detection at 278 nm was employed. The results revealed that F. glaberrima from Mt. Odae has the highest (+)-catechin content (10.600 mg/g). Furthermore, its content was the lowest in samples collected during the pre-flowering period and the highest at the early-flowering stage. This study provides a basis in establishing the optimal period and the best region for collecting F. glaberrima with maximized (+)-catechin yield.