• Journal of the Korean Institute of Telematics and Electronics
• /
• v.21 no.4
• /
• pp.52-57
• /
• 1984

The electrical properties and their instability of InP tunnel MIS diodes fabricated by inserting the chemically grown oxide between metal and n-lnP (100) surface have been in-vestigated. The structure of the gown oxide was the mixture of In2O3 and P2O5, as was other low-temperature grown oxide, and its thickness was estimated to be the order of 200 $A^{\circ}$. The forward and reverse currents increased even with slight heat treatment of diodes in vacuum, and they were reduced when the diodes were exposed to humid ambient. It was discussed that the observed instability in I-V characteristics is due to a change of the physicochemical properties of the oxide film and of the interface states between oxide and InP according to the absorption of H2O.

• Korean Journal of Optics and Photonics
• /
• v.14 no.1
• /
• pp.1-7
• /
• 2003

We determined the optical constants of organic light emitting material of Alq$_3$ in a spectral range between 1.5 and 6 eV using the physical model introduced by Forouhi and Bloomer［Phys. Rev. B 34, pp. 7018-7026, 1986.］. The initial parameters of $A_i,\;B_i,\;C_i$ of Forouhi-Bloomer dispersion relations were determined from the absorption peaks and widths of absorption spectra of the Alq$_3$ film. The refractive index of substrate, a fused silica, is derived from the Sellmeier equation with the measured transmittance and reflectance spectra. Then, the complex refractive index and thickness of the Alq$_3$ film were calculated by use of a nonlinear least square fitting program with the Forouhi-Bloomer dispersion relation and the measured transmittance and reflectance spectra.

• Progress in Medical Physics
• /
• v.16 no.3
• /
• pp.138-147
• /
• 2005

The Monte Carlo method cannot have been used for routine treatment planning because of heavy time consumption for the acceptable accuracy. Since calculation time is proportional to particle histories, we can save time by decreasing the number of histories. However, a small number of histories can cause serious uncertainties. In this study, we proposed Monte Carlo dose computation time and uncertainty reduction method using specially designed filters and adaptive denoising process. Proposed algorithm was applied to 6 MV photon and 21 MeV electron dose calculations in homogeneous and heterogeneous phantoms. Filtering time was negligible comparing to Monte Carlo simulation time. The accuracy was improved dramatically in all situations and the simulation of 1 $\%$ to 10$\%$ number of histories of benchmark in photon and electron dose calculation showed the most beneficial result. The empirical reduction of necessary histories was about a factor of ten to fifty from the result.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.1
• /
• pp.146-151
• /
• 2013

This paper reveals the performance decrease and recovery of PEMFC when the contaminated fuel gas and air source with sulfur impurities such as hydrogen sulfide and sulfur dioxide were simultaneously introduced to anode and cathode, respectively. Three different GDLs were fabricated with different carbon black and activated carbon to prevent an introduction of sulfur compound impurities into MEA. components. The severity of $SO_2$ and $H_2S$ poisoning was depended on concentrations(3 ppm - 10 ppm) of sulfur impurities. Especially, cell performance degradation rate was rapid when MEA fabricated with CN-2 GDL because it had little porosity on GDL surface. Moreover, the cell performance can be recovered up to 90%-95% only with neat hydrogen and fresh air feeding.. Conclusively, MEA fabricated with porous CN-1 GDL showed the best cell performance and recovery efficiency during exposure to poisoning condition by simultaneous sulfur impurities.

• Journal of Advanced Navigation Technology
• /
• v.16 no.5
• /
• pp.731-737
• /
• 2012

In the present study, a feasibility study on an innovative satellite attitude control actuator is performed. The actuator is specially designed to generate the reaction torque in an arbitrary axis, so that a satellite attitude can be controlled by using itself. It consists of a spherical flywheel and electromagnets for levitation and rotation control of the ball. As the earlier study, a rotating performance test on the spherical actuator is conducted in a single rotating axis and vertical levitation condition. From the test results, it can be confirmed that the maximum speed and torque of the innovative device are 7,200rpm and 0.7Nm, respectively. Using a velocity-voltage characteristic curve of the spherical motor, an open-loop control (V/f constant control) is performed, and the test results show excellent control performance in acceleration and deceleration phases.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.19
• /
• pp.39-46
• /
• 1975

The optimum plot size and shape for soybean yield trials were estimated by using two different soybean varieties, Kumkang-daelip and Clark. Long narrow shape plot was generaIly showed lower C.V. value as compared to the plots consisted of more row number with short row length. The results obtained in this experiment provided the optimum size and shape of plots for Clark as 1. 4m x 6m, and for Kumkang-dailip as 1.4m $\times$ 9m, respectively.

• Journal of Korea Water Resources Association
• /
• v.38 no.3 s.152
• /
• pp.245-257
• /
• 2005

The purpose of the present study is examining the changes of runoff characteristics and extracting hydrologic parameters by applying ModClark model on grid divided watershed. Bocheong stream basin in Geum River system, one of the representative watersheds of IHP projects, is selected. Hydrology-based topographical informations are calculated using GIS data in the HEC-GeoHMS V1.1 extension in Arcview 3.2. The ModClark model requires precipitation data in a gridded format. The gridded data must be recorded in the HEC Data Storage System file format. Therefore, kriging method was used to interpolate the point values to create a grid that gives each cell over the entire watershed a precipitation value. Hec-DSSVue program was used to create DSS file for the rain gage data. The completed HEC-HMS model was calibrated for use in simulating three measured storm events and cell size of 10000m, 5000m, 2000m, 1000m was chosen for the application. As the result of applying distributed rainfall-runoff model to analyze relatively good agreement for peak discharge, runoff volume and peak time.

• Journal of the Korean Applied Science and Technology
• /
• v.24 no.1
• /
• pp.54-60
• /
• 2007

이 논문에서는 게이트 절연막 위에 vapor deposition polymerization(VDP)방법을 사용하여 성막한 유기 점착층을 진공 열증착하여 유기 박막 트랜지스터(OTFTs)소자를 제작할 수 있음을 증명하였다. 우리가 제작한 Staggered-inverted top-contact 구조를 사용한 유기 박막 트랜지스터는 전기적 output 특성이 포화 영역안에서는 포화곡선을, triode 영역에서는 비선형적인 subthreshold를 확실히 볼 수 있음을 발견했다. $0.2{\mu}m$ 두께를 가진 게이트 절연막위에 유기 점착층을 사용한 OTFTs의 장 효과 정공의 이동도와 문턱전압, 그리고 절멸비는 각각, 약 0.4cm2/Vs, -0.8V, 106 이 측정되었다. 게이트 절연막의 점착층으로써 폴리이미드의 성막을 위해, 스핀코팅 방법 대신 VDP 방법을 도입하였다. 폴리이미드 고분자막은 2,2bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA)와 4,4'-oxydianiline(ODA)을 고진공에서 동시에 열 증착 시킨 후, 그리고 $150^{\circ}C$에서 1시간, 다시 $200^{\circ}C$에서 1시간 열처리하여 고분자화된 막을 형성하였다. 그리고 점착층이 OTFTs의 전기적 특성에 주는 영향을 설명하기 위해 비교 연구하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2002.11a
• /
• pp.784-787
• /
• 2002

We prepared the PLT(28) thin film by using sol-gel method and investigated the structure and electrical properties of the film. With the XRD and AFM analyses, it is found that PLT(28) thin film annealed at 6sot has a complete perovskite structure and its surface roughness is about 22$\AA$. We prepared PLT(28) thin film on the Pt/TiO$_{x}$SiO$_2$/Si substrate, in which the specimen has a planar capacitor structure, and analyzed the electrical properties of PLT(28) thin film. In result, PLT(28) thin film has a paraelectric phase and its dielectric constant and loss tangent at 10kHz are 761 and 0.024, respectively. Also, the storage charge density and leakage current density of PLT(28) thin film at W are 134fC/$\mu$m2 and 1.01 $\mu$A/cm2, respectively. As a result of this, we concluded that the PLT(28) thin film is a promising material to be used as a capacitor dielectrics for next generation DRAM.M.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.80.2-80.2
• /
• 2012

홀로 고립되어 존재하는 은하는 주변 은하와 상호작용을 하지 않은 채 진화하므로 은하의 진화를 연구하기에 아주 좋은 대상이다. 은하의 정량적 연구를 위해 꼭 알아야 하는 중요한 물리량으로 거리와 성간소광량이 있다. 우리는 허블 우주망원경(HST) Advanced Camera for Surveys(ACS)/High Resolution Channel(HRC)로 관측한 고립된 왜소불규칙은하 NGC 1156 ($RA_{2000}$=02:59:42.19, $DEC_{2000}$=+25:14:14.2) 중심부($26^{\prime\prime}{\times}29^{\prime\prime}$)의 archive 자료를 분석하여 이 은하의 거리와 성간소광량을 새로 구했다. 이 은하의 거리를 측정한 과거 자료는 Tully(1988, Nearby Galaxies Catalog) 목록과 Special Astrophysical Observatory 6m 망원경/VI(각 300s) 영상자료의 가장 밝은 별로 거리를 구한 Karachentsev et al. (1996) 자료 뿐이다. 우리는 HST/ACS/HRC+UBVI 자료 중 U자료를 이용하여 아주 신뢰할 만한 소광량 값($E(B-V)=0.35{\pm}0.05$)을 얻었고, 가장 밝은 빨간 별과 파란 별 자료를 이용하여 새로운 거리지수($(m-M)_0=29.39{\pm}0.20$, $d=7.6{\pm}0.7$ Mpc)를 결정했다. 이 거리 값은 과거의 값들(Tully $6.4{\pm}1.2$ Mpc; Karachentsev et al. $7.8{\pm}0.5$ Mpc)과 크게 다르지 않으며, 기존의 거리 자료들 역시 신뢰할만함을 보여준다. ACS/Wide Field Channel과 달리 ACS/HRC의 경우 등급 표준화 방정식이 완벽하지 않은데, 우리의 경우 F550M자료를 표준화할 수 없었다. 그러나 우리는 여러 파장, 많은 관측자료가 존재하는 47 Tucanae (NGC 104) 구상성단의 관측자료와 Padova 등연령곡선을 이용하여 성공적인 등급변환을 수행할 수 있었다.