• 한국진공학회지
• /
• 제7권s1호
• /
• pp.1-6
• /
• 1998

The influence of the order-disorder structural transition on the magnetic and mageto-optical, and transport properties of Fe-Al and Co-Al alloy films has been investigated. The disordered states in the alloy films were prepared by vapor quenching deposition on glass substrates cooled by liquid nitrogen. The experimental study of the magento-optical properties of the ordered and disordered Fe-Al and Co-Al alloy films has been carried out in 1.05-5.0 eV energy range at room temperature. The transport properties have been measured in 2-300K temperature range with and without magnetic field of 0.5T. The influence of the order-disorder structural transition on the magnetic and magneto-optical properties was discussed by using the effective medium approximation and the structural defect approach. That on the temperature dependence of the resistivity was analyzed in a framework of the partial localization of the electronic states and the variable range hopping conductivity.

• 한국환경과학회지
• /
• 제11권10호
• /
• pp.1133-1140
• /
• 2002

The growth and extent of the local pressure field at any point is of primary importance as it supplies the driving force for the local wind circulation which causes a medium-range transport of air pollutants. The local pressure field is produced by the variation of temperature in the lower layers of the atmosphere, and is called the thermal wave. The thermal wave is influenced by the difference in the diurnal variations between two regions with different surface condition, for example land and sea. This difference produces the land- and sea-breeze phenomenon, and brings corresponding variations in the form of the thermal wave. Daytime temperature over the inland area (Daegu) was higher than that of the coastal area (Busan). The temperature difference reached about 5~6$^{\circ}C$ in the late afternoon(30-31 May 1999). The low pressure system of Daegu was most fully developed at the time. In this study, we investigated the possibility of thermal low onset around Daegu in summer with an analytical model. The topography effect was neglected in the model. We could predict a thermal low-pressure of about 3.4hPa at Daegu with wide flat land surface, when the inland area is about 6K warmer than the coastal area temperature. The pressure decrease is somewhat less than the observed value(4~5 hPa).

• 한국ITS학회 논문지
• /
• 제7권4호
• /
• pp.107-117
• /
• 2008

본 논문에서는 국내 ETC(Electronic Toll Collection)인 한국도로공사의 하이패스 시스템의 보급에 힘입어 2008년 현재까지 약 125만대가 보급되어 있는 IR(Infrared)/RF(Radio Frequency)-DSRC(Dedicated Short Range Communication)를 BIS(Bus Information System) 혹은 UTIS(Urban Traffic Information System)와 같은 보다 향상되고, 많은 차량 단말(OBE; On Board Equipment)을 제어해야 하는 시스템에 사용하기 위한 척도로써 IR/RF-DSRC의 전송 효율에 관한 성능을 시뮬레이션을 통해 평가하고, 각 시스템의 장단점을 찾아보고자 한다. 특히 DSRC는 짝은 통신 영역에서 높은 이동도를 갖는 개체에게 고속의 데이터를 전송하여야 한다는 점에서 일반적인 통신 시스템에 비해 MAC(Media Access Control)의 속성이 가장 중하다고 할 수 있다. 따라서 본 논문에서는 이러한 매체 접근성의 관점에서 IR/RF-DSRC, 두 시스템의 성능을 분석하고자 한다.

• Journal of Electrical Engineering and Technology
• /
• 제10권4호
• /
• pp.1734-1737
• /
• 2015

Insulating characteristics of Cl₂-He mixture gases in gas discharges were analysed to evaluate ability of these gases for using in medium voltage and many industries. These are electron transport coefficients, which are the electron drift velocity, density-normalized longitudinal diffusion coefficient, and density-normalized effective ionization coefficient, in Cl₂-He mixtures. A two-term approximation of the Boltzmann equation was used to calculate the electron transport coefficients for the first time over a wide range of E/N (ratio of the electric field E to the neutral number density N). The limiting field strength values of E/N, (E/N)_lim, for these binary gas mixtures were also derived and compared with those of the pure SF₆ gas.

• 전기학회논문지P
• /
• 제53권2호
• /
• pp.65-69
• /
• 2004

This paper calculates and gives the analysis of electron swarm transport coefficients as described electric conductive characteristics of pure Ar, pure $SiH_4$, Ar-$SiH_4$ mixture gases($SiH_4$-0.5%, 2.5%, 5%) over the range of E/N = 0.01~300[Td], P = 0.1, 1, 5.0 [Torr] by Monte Carlo the backward prolongation method of the Boltzmann equation using computer simulation without using expensive equipment. The results have been obtained by using the electron collision cross sections by TOF, PT, SST sampling, compared with the experimental data determined by the other author. It also proved the reliability of the electron collision cross sections and shows the practical values of computer simulation. Electron swann parameters in argon were drastically changed by adding a small amount of mono-silane. The electron drift velocity in these mixtures showed unusual behaviour against E/N. It had negative slope in the medium range of E/N, yet the slope was not smooth but contained a small hump. The longitudinal diffusion coefficient also showed a corresponding feature in its dependence on E/N. A two-tenn approximation of the Boltzmann equation analysis and Monte Carlo simulation have been used to study electron transport coefficients.

• 한국ITS학회 논문지
• /
• 제2권1호
• /
• pp.93-100
• /
• 2003

본 논문에서는 한국전자 통신 연구원에서 연구 개발한 차세대 DSRC 패킷 통신 기술을 소개하였다. 차세대 DSRC 패킷 통신 시스템의 요구 사항, 목표 시스템 규격, 차세대 DSRC 패킷 통신시스템의 구조에 대하여 설명하였다. 차세대 DSRC 시스템은 최대 24 Mbps 데이터를 5.8GHz 대역으로 전송하는 고속 패킷 통신 시스템으로 기존의 ITS 서비스뿐 아니라 모바일 오피스 서비스를 지원한다. 현재 차세대 DSRC 시스템은 각 모듈 별 기능 시험을 실시하였으며 차세대 DSRC RE 모듈의 front end부분에 대한 MMIC(microwave monolithic integrated circuit) 개발하였다. 본 차세대 DSRC 패켓 통신 시스템은 Mobile PC 제조산업, 차량 탑재 무선 인터넷 산업, 차세대 이동통신으로 차량에 탑재되는 고속 무선 인터넷 단말기로서 모바일 인터넷, 게임 등 모바일 오피스 응용 및 텔레매틱스 서비스 차세대 이동통신 산업 발전에 기여할 것으로 기대된다

• 산업경영시스템학회지
• /
• 제46권4호
• /
• pp.160-172
• /
• 2023

In contemporary global warfare, the significance and imperative of air transportation have been steadily growing. The Republic of Korea Air Force currently operates only light and medium-sized military cargo planes, but does not have a heavy one. The current air transportation capability is limited to meet various present and future air transport needs due to lack of performance such as payload, range, cruise speed and altitude. The problem of population cliffs and lack of airplane parking space must also be addressed. These problems can be solved through the introduction of heavy cargo planes. Until now, most studies on the need of heavy cargo plane and increasing air transport capability have focused on the necessity. Some of them suggested specific quantity and model but have not provided scientific evidence. In this study, the appropriate ratio of heavy cargo plane suitable for the Korea's national power was calculated using principal component analysis and cluster analysis. In addition, an optimization model was established to maximize air transport capability considering realistic constraints. Finally we analyze the results of optimization model and compare two alternatives for force structure.

• 한국태양에너지학회 논문집
• /
• 제28권5호
• /
• pp.78-84
• /
• 2008

Heat pipes are considered to be promising candidates to enhance the heat transport capability of evacuated solar collectors in a wide temperature range. The working fluid must be selected properly considering various operating conditions of heat pipes for medium-high temperature range to avoid dry-out, local overheating, and frozen failure. The advantage of using binary mixture as heat pipe working fluid is that it can extend operating temperature range of the system as it can overcome operating temperature limit of a single fluid. Various operating temperature ranges were imposed in the experiments to simulate the actual operation of solar collectors using water-ethanol binary mixture. Tests were conducted for the coolant temperature range of -10$^{\circ}C$ to 120$^{\circ}C$, and mixing ratio range was from 0 to 1 based on mass fraction.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.387-390
• /
• 1999

Electron swarm parameterdthe drift velocity and longitudinal diffusion coefficienthn $SiH_4-Ar$ mixtures containing 0.5% and 5% monosilane were measured using over the range of E/N from 0.01 to 300 Td at room temperature. Electron swarm parameters in argon were drastically changed by adding a small amount of monosilane. The electron drift velocity in both mixtures showed unusual behaviour against E/N. It had negative slope in the medium range of E/N, yet the slope was not smooth but contained a small hump. The longitudinal diffusion coefficient also showed a corresponding feature in its dependence on E/N. A two-tern approximation of the Boltzmann equation analysis and Monte Carlo simulation have been used to study electron transport coefficients.

• 대기
• /
• 제26권4호
• /
• pp.649-663
• /
• 2016

This study investigates eddy transports in terms of space and time for momentum, heat, and moisture, emphasizing comparison of the results in three reanalysis data sets including ERA-Interim from the European Center for Medium-range Weather Forecasts (ECMWF), NCEP2 from the National Center for Environmental Prediction and the Department of Energy (NCEP-DOE), and JRA-55 from the Japan Meteorological Agency (JMA) during boreal winter. The magnitudes for eddy transports of momentum in ERA-Interim are represented as the strongest value in comparison of three data sets, which may be mainly come from that both zonal averaged meridional and zonal wind tend to follow the hierarchy of ERA-Interim, NCEP2, and JRA-55. Whereas in relation to heat and moisture eddy transports, those of NCEP2 are the strongest, implying that zonal averaged air temperature (specific humidity) tend to follow the raking of NCEP2, ERA-Interim, and JRA-55 (NCEP2, JRA-55, and ERA-Interim), except that transient eddy transports for heat in ERA-Interim are the strongest involving both meridional wind and air temperature. The stationary and transient eddy transports in the context of space and time correlation, and intensity of standard deviation demonstrate that the correlation (intensity of standard deviation) influence the structure (magnitude) of eddy transports. The similarity between ERA-Interim and NCEP2 (ERA-Interim and JRA-55) of space correlation (time correlation) closely resembles among three data sets. A resemblance among reanalysis data sets of space correlation is larger than that of time correlation.