• Journal of Astronomy and Space Sciences
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• v.7 no.2
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• pp.125-139
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• 1990

Luminosity profiles and dynamical parameters of 12 globular clusters in the Large Magellanic Cloud(SB(s)m) are obtained from the concentric aperture photoelectric photometry of 3 different aged clusters and the collected photometric data of 9 clusters. The total masses of the globular clusters are calculated using the equation $M_\bigoplus$= ${Mr_t}^j(4\Omega^2-k^2)$, which is derived from the theroetical rotation curve for the exponential disk(Chun 1978). These masses lie between $0.3\times10^4$ and $15.8\times10^4M_\bigoplus$. From the determined total mass and luminosity, the mass-to-luminosity ratios are also derived. The M/L ratio of a cluster increases with the cluster age ; about 0.03 for the youngest clusters(SWB I) and about 0.24 for the oldest clusters (SWB VII). There is a difference in M/L by a factor of 10 between the galactic globular clusters and the old globular clusters in the LMC.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.9 no.1
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• pp.17-29
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• 2005

In this paper we consider finite element methods for nonlinear hyperbolic integro-differential problems defined in ${\Omega}\;{\subset}\;R^d(d\;{\leq}\;4)$. A new initial approximation of $u_t(0)$ is taken. Optimal order error estimates in $L_p$ for $2\;{\leq}\;p\;{\leq}\;{\infty}$ are established for arbitrary order finite element. One order superconvergence in $W^{1,p}$ for $2\;{\leq}\;p\;{\leq}\;{\infty}$ are demonstrated as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.29-32
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• 1996

AlGaAs/GaAs 에피 구조와 제조 공정에 사용될 마스크를 설계 및 제작하여, 이를 이용하여 다양한 크기의 HBT를 제작하였다. 제작될 소자의 특성에 영향 을 미치는 공정에 대해서는 단위 공정을 수행하여 발생될 수 있는 문제점들을 사전에 제거하고, 안정된 공정 조건을 확립하도록 하였다. 금속의 저항성 접촉특성 향상을 위한 단위 실험 결과, n형 및 p형 금속에 대하여 각각 3.5$\times$$10^{-6}$-$ extrm{cm}^2$와 1.0$\times$$10^{-5}$$\Omega$-$\textrm{cm}^2$의 접촉 비저항 특성을 얻었다. 또한, 제작된 HBT는 HP4145B 와 HP8510C의 장비를 이용하여 DC 및 AC 특성을 측정하였는데, 에미터 크기가 3$\times$10um$^2$인 소자의 경우, $\beta$=51, f$_{T}$= 42GHZ 및 f$_{max}$=19GHz의 특성을 얻었다.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1688-1691
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• 1997

In this work, we have developed the off-line diagnostic system for power cable insulation using DC voltage decay method to diagnose the insulation degradation of underground power cables. Measurement errors of diagnostic system are less than 1% for $1T{\Omega}$ internal resistor. We have also developed measurement and diagnostic programs for win95 which is suitable for the database construction and the management of data. We could conclude that it is possible to apply this system to the multi-grounded underground cable systems.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.730-732
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• 2007

We fabricated a coplanar type organic thin-film transistors using ink-jet printed silver source/drain electrodes and ${\alpha},{\omega}-dihexylquaterthiophene$ (DH4T) which is an active layer. Use of ink-jet printed silver nanoparticle-based metal electrode assists the energetic mismatch with p-type organic semiconductor via modification of their interfacial properties to enable ohmic contact formation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.191-194
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• 1998

This Paper present a new structure for a piezoelectric transformer, operating in thickness extensional vibration mode. Modified PbTiO$_3$ family ceramics were used for the Piezoelectric transformer, because it is a material with large anisotropy between electromechanical coupling facters k$\sub$t/ and k$\sub$p/. Piezoelectric transformer was fabricated that is 20mm long, 20mm wide and 3.1mm thick. Resonant frequencies of sencond thickness extensional vibration mode is 1.72MHz at loading resistance 100{$\Omega$]. And Voltage gain of piezoelectric ceramics is showed 0.53 at resonant frequency of sencond thickness extensional vibration mode.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.855-860
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• 1998

This paper presents a new structure for a piezoelectric transformer, operating in thickness extensional vibration mode. Modified $PbTiO_3$ family ceramics were used for the piezoelectric transformer, because it was a material with large anisotropy between elecromechanical coupling factors $K_t$ and $K_p$ . The size of piezoelectric transformer was 20mn long, 20mm wide and 3.1mm thick. The second harmonic resonant frequency of thickness extensional vibration mode was 0.72MHz at loading resistance 100[$\omega$], And Voltage gin of piezoelectric ceramics showed 0.53 at resonant frequency of sencond thickness extensional vibration mode.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.250-253
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• 1998

This paper has proposed a method to analyze a 30 KVA superconducting generator using 3-dimensional FEM program. 3 kinds of 3D formulation methods are employed such as scalar potential in core region, reduced scalar potential in air region and T-${\omega}$ formulation in stator coil region. As results of the simulation, various parameters of the generator have been analyzed like air gap flux density, induced voltage, inductance, etc.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.69-71
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• 2003

The magnetic field sensor was fabricated with superconducting ceramics of YBaCuO system. The sensor at liquid nitrogen temperature showed the increase of electrical resistance by applying magnetic field. Actually the voltage drop across the sensor was changed from zero to a value more than 100 $mutextrm{V}$ by the applied magnetic field. The change in electrical resistance depended on magnetic field. The sensitivity of this sensor was 2.9 $\Omega$/T. The sensing limit was about $1.5\times$10$^{-5}$. The increase of electrical resistance by the magnetic field was ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material. Considering the observed properties of the superconductor with trapped magnetic flux, a magnetic sensor was fabricated to detect simultaneously both the intensity and the direction of the magnetic field.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.485-487
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• 2003

본 논문은 기설 WSI제 CVT에 대해 전자 과도해석 프로그램((EMTP : Electromagnetic Transient Program)을 통한 모의실험으로 철공진현상 제동저항 크기($0.5{\Omega}$)를 선정하고, 기설 154kV 및 345kV CVT의 철공진방지회로를 제동저항 단독취부 형태에서 과포화리액터와 제동저항을 직렬회로로 구성하여 취부하는 방식으로 개선한 후 실증시험 및 현장적용 시험을 통해 CVT 쳔공진현상 제동여부 확인 및 외함온도 변화추이 비교하여 개선효과를 제시함으로써 WSI제 CVT 고장예방에 기어코자 한다.