• 한국입자에어로졸학회지
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• 제5권3호
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• pp.123-131
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• 2009

This paper presents simulation results of particle transport in low-pressure, low-temperature plasma environment. The size dependent transport of particles in the plasma is investigated with a two-dimensional simulation tool developed in-house for plasma chamber analysis and design. The plasma model consists of the first two and three moments of the Boltzmann equation for ion and electron fluids respectively, coupled to Poisson's equation for the self-consistent electric field. The particle transport model takes into account all important factors, such as gravitational, electrostatic, ion drag, neutral drag and Brownian forces, affecting the motion of particles in the plasma environment. The particle transport model coupled with both neutral fluid and plasma models is simulated through a Lagrangian approach tracking the individual trajectory of each particle by taking a force balance on the particle. The size dependant trap locations of particles ranging from a few nm to a few ${\mu}m$ are identified in both electropositive and electronegative plasmas. The simulation results show that particles are trapped at locations where the forces acting on them balance. While fine particles tend to be trapped in the bulk, large particles accumulate near bottom sheath boundaries and around material interfaces, such as wafer and electrode edges where a sudden change in electric field occurs. Overall, small particles form a "dome" shape around the center of the plasma reactor and are also trapped in a "ring" near the radial sheath boundaries, while larger particles accumulate only in the "ring". These simulation results are qualitatively in good agreement with experimental observation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.96-100
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• 2001

Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport current and exposed to an external magnetic field generated by neighboring tape's AC currents simultaneously. AC loss taking into account such real applications is a crucial issue for power applications of the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1.5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tape's AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tape's critical current is a minor effect. The measured transport losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tape's AC currents. The transport losses do not depend on the frequency of the neighboring tape's AC currents but its arrangements in the range of small current especially.

• The Korean Journal of Ceramics
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• 제4권2호
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• pp.103-113
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• 1998

By using a gas-tight electrochemical cell, we can perform high-temperature coulometric titration and measure electronic transport properties to determine the elecronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilitized zirconia(YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressure ($pO_2=10^{-35}$ to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria $(Ca-CeO_2 \;and\; CeO_2)$, copper oxides and copper-oxide-based ceramic superconductors, transition metal oxides, $SrFeCo_{0.5}O_x,\; and \;BaTiO_2$.

• 한국결정성장학회지
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• 제24권2호
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• pp.54-58
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• 2014

PVT(물리 기상 이동법, Physical Vapor Transport) 법을 적용하여 질화알루미늄(AlN, Aluminum Nitride) 단결정을 성장하였으며, 성장된 결정의 결정성과 성장 온도에 따른 상에 대하여 고찰하였다. 성장된 단결정은 광학현미경을 이용하여 결정의 상을 관찰하였고, 관찰된 결과를 비교 분석하여 본 실험에 적용된 성장 장치에서의 최적의 성장 온도 조건을 설정할 수 있었다. 본 연구에서는 AlN 단결정 성장 결과를 비교 고찰하여 보고하고자 한다.

• 한국진공학회지
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• 제7권s1호
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• pp.1-6
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• 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.

• ETRI Journal
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• 제22권3호
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• pp.19-26
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• 2000

We describe a detailed numerical scheme to calculate electron transport in quantum wires using the Green function formalism combined with tight-binding orbital basis. As an example of the application, we study the electron transport in a Si nanowire containing a finite potential barrier. The effects of nonzero bias, temperature, and disorder on the barrier-induced oscillatory conductance are investigated within the context of coherent transport model. The oscillatory behavior of the conductance as a function of the Fermi energy is found to be highly sensitive to sample disorder and limited to a very low temperature and a small bias range.

• 한국환경과학회지
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• 제10권2호
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• pp.143-151
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• 2001

The atmospheric conditions and the transport mechanism of long-range transport of air pollutants from coastal area to inland area were investigated using regular meteorological data and air pollution data obtatined from the southeastern area of Korea. Daytime temperature over the inland area(Taegu) was higher than that over the coastal area(Pusan) and the temperature difference of about 5~6$^{\circ}C$ when the thermal low most fully developed and the sea level pressure over Taegu was lower than that over Pusan by about 4~5hPa at that time. Therefore this low pressure appeared to the thermally induced low. Air mass polluted from the coastal area during the morning period was transported inland area, at first by the sea breeze and by the large scale wind system toward the thermal low generated in the mountainous inland region. This was explained by the fact that the concentration of air pollutants over Taegu increased throughtout the late afternoon.

• 한국결정성장학회지
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• 제17권6호
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• pp.231-237
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• 2007

For an aspect ratio (transport length-to-width) of 5, Pr=3.34, Le=0.078, Pe=4.16, Cv=1.01, $P_B=50$ Torr, only thermally buoyancy-driven convection ($Gr=4.83{\times}10^5$) is considered in this study in spite of the disparity in the molecular weights of the component A ($Hg_2Cl_2$) and B which would cause thermally and/or solutally buoyancy-driven convection. The crystal growth rate and the maximum velocity vector magnitude are decreased exponentially for $3{\le}Ar{\le}5$, for (1) adiabatic walls and (2) the linear temperature profile, with a fixed source temperature. This is related to the finding that the effects of side walls tend to stabilize convection in the growth reactor. The rate for the linear temperature profiles walls is slightly greater than for the adiabatic walls far varied temperature differences and aspect ratios. With the imposed thermal profile, a fixed source region, both the rate and the maximum velocity vector magnitude increase linearly with increasing the temperature difference for $10{\le}{\Delta}T{\le}50K$.

• 한국의류산업학회지
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• 제2권3호
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• pp.220-226
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• 2000

This study was to determine the characteristics of vapor-permeable waterproof finished fabric by the coating method. 4 different kinds of coating fabrics (A : wet, porous, polyurethane, B : dry, no porous, polyurethane, C : shape memory polyurethane and D : dry, porous polyurethane) were used, which were developed recently With this sample, moisture transport rate ($40^{\circ}C$, 45%RH & $40^{\circ}C$, 95%RH), changes of coating side's shape by washing times, water repellency rate, contracted length, qmax, heat conductivity, heat keeping rate, heat keeping rate with cotton, heat keeping rate on humidity temperature and humidity within clothing etc. were checked. And it was done in a climate chamber under $20{\pm}2^{\circ}C$, $65{\pm}5%RH$. The results of this study were as follow; In the moisture vapor transmission of sample B and C increased on high temperature and high humidity while sample A and D decreased, on this condition. Qmax rate had high relation with ground fabric's surface properties and the order was A>C>D>B. Heat conductivity had high relation with thickness and surface properties. Heat keeping rates on sweat condition showed around half percents of heat keeping rates on normal condition, but had no relation with moisture vapor transport rate. Changes of the fabric's properties by washing times were different in accordance with the construction of fabrics and the coating resin. Sample C had tow heat keeping rate on the high temperature and humidity and high heat keeping rate on the low temperature and humidity Moisture transport rate of vapor-permeable waterproof finished fabrics had high relation with the properties of ground fabrics on low humidity condition, but on the high humidity condition, it was highly related with the properties of coating resin.

• Journal of Magnetics
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• 제19권2호
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• pp.140-145
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• 2014

The electrical transport properties of YBCO single layers thin film have been investigated using different physical techniques. For the purpose, the physical properties are probed numerically with help of simulation modelling. The physical transport properties were also estimated with temperature and magnetic fields limits using thermally-activated flux flow model with some modifications. The result of present simulation modelling indicated that the magnitude of activation energy depends on temperature and magnetic field. The simulations revealed thickness dependent physical transport properties including electrical and magnetic properties of deposited YBCO single layers thin films. Furthermore, it shows the temperature dependence of the pinning energy. In the nutshell, the result can be used to improve the Superconducting Properties ($T_c$) of the YBCO single layers thin films.