• Title, Summary, Keyword: Charge transport equation

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1-Dimensional Simulation of the Corona Discharge using Fluid Method (유체법을 이용한 코로나 방전의 1차원 수치해석)

  • 이용신;심재학;고광철;강형부
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.172-176
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    • 1997
  • It is likely that the corona discharge appears due to the motion and the multiplication of electron and ion under the nonuniform electric field. Because the motion and the multiplication of electron and ion are the function of electric field, for the simulation of the corona discharge, we have to calculate the electric field, before the calculation of the motion and the multiplication of electron and ion. In this paper, the electric field is calculated on the assumption that the gap between a hyperboloidal needle and a plane is 1-dimension, and the motion and the multiplication of electron and ion are determined by Flux-Corrected Transport method. For this purpose, we solve the electron and ion continuity equation together with Poisson equation. We calculated the current density and the electron and ion density distributions between electrodes as well as electric field distortion due to the space charge assuming that the discharge channel radius is 100${\mu}{\textrm}{m}$. In this simulation, it is found that the current density has one peak as observed by experiment, and electric field distortion is important to the formation and the stability of the corona discharge.

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Two-dimensional simulation of corona discharge characteristics in nitrogen (질소가스에 대한 2차원 코로나 방전특성 해석)

  • Choi, Jong-Dae;Shim, Jae-Hak;Ko, Kwang-Cheo;Kang, Hyung-Boo
    • Proceedings of the KIEE Conference
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    • pp.1834-1836
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    • 1997
  • In this study, we simulated the developing process of two-dimensional corona discharge using the fluid method in 760 torr. It was assumed that the transport coefficients of nitrogen gas were only the function of local electric field. Discharge mechanisms considered were a Townsend first ionization and a secondary electron emission. We obtained spatio-temporal distribution of electron and ion by calculating continuity equation using FCT algorithm and calculated an electric field distribution considering a space charge.

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Studies on Ion Selective Charged Membranes(II) -Permselectivity of Some Ions through Charged Carboxyethyl Cellulosic Membranes- (Ion 선택 투과성 하전막에 관한 연구(II) -하전 Carboxyethyl Cellulos 의 Ion 선택 투과성-)

  • 박수민
    • Textile Science and Engineering
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    • v.27 no.4
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    • pp.54-60
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    • 1990
  • The effect of diffusant size, shape and effective charge density, which govern various transport processes in a charged membrane was specially investigated at $25^{\circ}C$. The systems examined here were charged carboxyethyl cellulosic membranes with cesium chloride and tetraalkylammonium chlorides. Permeation coefficient was found to decrease with the increase of the hydrated radius of the ions in a sequence of cesium chloride>tetramethyl ammonium chloride>tetraethyl ammonium chloride> terrabutyl ammonium chloride. This sequence was interpreted by considering the partition sorption and the hydration of ions in hydrophilic membranes. The molar mobilities of ions in charged membranes were determined by use of the permeation measurement and the analysis by the Nernst-Planck-based equation in wide range of salt concentration. The molar mobility of counter-ions decreased with the increase of the stokes radius, while that of co-ions increased. The effective fixed changed density was found on the diffusant size and was explained by considering electrostatic binding by the negatively charged groups in the membranes.

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Accurate Prediction Method of Breakdown Voltage in Air at Atmospheric Pressure

  • Kim, Nam-Kyung;Lee, Se-Hee;Georghiou, G.E.;Kim, Dong-Wook;Kim, Dong-Hun
    • Journal of Electrical Engineering and Technology
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    • v.7 no.1
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    • pp.97-102
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    • 2012
  • To predict accurately the breakdown voltage in air at atmospheric pressure, a fully coupled finite element analysis combining the hydrodynamic diffusion-drift equations with Poisson's equation is proposed in the current paper. As three kinds of charged transport particles are nonlinearly coupled with spatial electric fields, the equations should be solved by an iterative numerical scheme, in which secondary effects, such as photoemission and photoionization, are considered. The proposed method has been successfully applied to evaluate the breakdown voltage in circular parallel-plane electrodes. Its validity has been proved through the comparison of the predicted and experimental results. The effects of numerical conditions of the initial charge, photoemission, and background ionization on the discharge phenomena are quantitatively assessed through Taguchi's design of experiment method.

Fundamentals of Particle Fouling in Membrane Processes

  • Bhattacharjee Subir;Hong Seungkwan
    • Korean Membrane Journal
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    • v.7 no.1
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    • pp.1-18
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    • 2005
  • The permeate flux decline due to membrane fouling can be addressed using a variety of theoretical stand-points. Judicious selection of an appropriate theory is a key toward successful prediction of the permeate flux. The essential criterion f3r such a decision appears to be a detailed characterization of the feed solution and membrane properties. Modem theories are capable of accurately predicting several properties of colloidal systems that are important in membrane separation processes from fundamental information pertaining to the particle size, charge, and solution ionic strength. Based on such information, it is relatively straight-forward to determine the properties of the concentrated colloidal dispersion in a polarized layer or the cake layer properties. Incorporation of such information in the framework of the standard theories of membrane filtration, namely, the convective diffusion equation coupled with an appropriate permeate transport model, can lead to reasonably accurate prediction of the permeate flux due to colloidal fouling. The schematic of the essential approach has been delineated in Figure 5. The modern approaches based on appropriate cell models appear to predict the permeate flux behavior in crossflow membrane filtration processes quite accurately without invoking novel theoretical descriptions of particle back transport mechanisms or depending on adjust-able parameters. Such agreements have been observed for a wide range of particle size ranging from small proteins like BSA (diameter ${\~}$6 nm) to latex suspensions (diameter ${\~}1\;{\mu}m$). There we, however, several areas that need further exploration. Some of these include: 1) A clear mechanistic description of the cake formation mechanisms that clearly identifies the disorder to order transition point in different colloidal systems. 2) Determining the structure of a cake layer based on the interparticle and hydrodynamic interactions instead of assuming a fixed geometrical structure on the basis of cell models. 3) Performing well controlled experiments where the cake deposition mechanism can be observed for small colloidal particles (< $1\;{\mu}m$). 4) A clear mechanistic description of the critical operating conditions (for instance, critical pressure) which can minimize the propensity of colloidal membrane fluting. 5) Developing theoretical approaches to account for polydisperse systems that can render the models capable of handing realistic feed solutions typically encountered in diverse applications of membrane filtration.

Influence of Delay Time on the Ground Vibration (발파공간 지연시차가 지반진동에 미치는 영향)

  • Kim, Ji-Soo;Choi, Tae-Hong;Lee, Chang-Won
    • Explosives and Blasting
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    • v.32 no.2
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    • pp.1-8
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    • 2014
  • In this study, 16 test blastings had been carried out with different spacings, burdens, drilling lengths, and charges per delay for investigating the characteristics of ground vibration propagation, which depends on the delay time. From the tests, it was possible to derive a ground vibration equation. Using the equation, the characteristics of ground vibration could be investigated by analyzing the nomogram and predicting the Peak Particle Velocity (PPV), which are influenced by the delay time and the priming location. The trend of ground vibration change depending on the delay time was analyzed for the standards charges of 0.5, 1.6, 5, and 15 kg, which were suggested in "Blasting design and construction guidelines to road construction" by the Ministry of Land, Infrastructure and Transport. From the study, it would be possible to suggest a favorable vibration control method, which depends on the charge.

An Analysis of Decision Making Process in Voluntary Reducing Private Car Use (자발적 자가용 이용 저감의 의사결정과정 분석 연구)

  • Lee, Backjin;Kim, Joon-Ki;Yi, Choonyong
    • Journal of The Korean Society of Civil Engineers
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    • v.33 no.2
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    • pp.679-689
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    • 2013
  • To relieve Green-house Gas Emission is the key issue in urban area. Urban transport policies have focused on the reduction of private car use. The most common of these is Travel Demand Management(e.g., congestion charge, environmental tax, etc.) that forces individuals to reduce their private car use. An alternative way is Mobility Management(MM) that induces individuals to voluntarily change their car use through communications. MM is founded on social psychology theory and focuses on individuals' decision making processes to change their perception and attitude on private car use. Although some researchers have reported the relevance of MM approach, still few researches have explicitly studied on individuals' decision making processes. Therefore, the aims of the paper are to analyze the decision making process of individuals and to provide the basis of introducing MM approach in Korea. Structural equation model(SEM) is applied for the analysis of individuals' decision making process. A empirical study shows that psychological factors such as perception/attitude on global environment or individual norms impact significantly to reduce private car use and accordingly the relevance of introducing MM approach instead of imposing regulations or expanding transport facilities.

Dependence of Extinction Ratio on the Carrier Transport in $1.55{\mu}m$ InGaAsP/InGaAsP Multiple-Quantum-Well Electroabsorption Modulators ($1.55{\mu}m$ InGaAsP/InGaAsP 다중양자우물구조 전계흡수형 광변조기에서 캐리어 수송현상이 소광특성에 미치는 영향)

  • Shim, Jong-In;Eo, Yung-Seon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.37 no.9
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    • pp.15-22
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    • 2000
  • The effects of carrier transport and input power on the extinction ratio was theoretically analyzed in a 1.55${\mu}m$ InGaAsP/InGaAsP multiple-quantum-well(MQW) electroabsorption(EA) modulator. Poisson's equation, current continuity equations for electrons and holes, and optical field distribution were self-consistently solved by considering electric field dependent absorption coefficients. The field screening effect due to the carrier accumulation in heterointerface and the space-charge region occurred more seriously at the input side of modulator as input optical intensity increased. It was revealed that extinction ratio could be steeply degraded for modulator with the length of 200${\mu}m$ when an input power exceeds 10mW. A degradation of extinction ratio due to the field screening effect would be more significantly at high-performance devices such as a 1.55${\mu}m$DFB-LD/EA-modulator integrated source where optical coupling efficiency is almost complete or a very high-speed modulator with its length as short as a few tens ${\mu}m$.

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