• Composites Research
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• v.32 no.5
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• pp.296-300
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• 2019

Two dimensional transition metal carbides and/or nitrides, known as MXenes, are a promising electrode material in energy storage due to their excellent electrical conductivity, outstanding electrochemical performance, and abundant functional groups on the surface. Use of $Ti_3C_2$ as electrode material has significantly enhanced electrochemical performance by providing more chemically active interfaces, short ion-diffusion lengths, and improved charge transport kinetics. Here, we reports the efficient method to synthesize $Ti_3C_2$ from MAX phase, and opens new avenues for developing MXene based electrode materials for Lithium-Ion batteries.

• Water for future
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• v.28 no.6
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• pp.107-118
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• 1995

Mathematical models have been developed in which storage-relaease processes of pollutants are modeled to explain storage effect of variations of flow and channel geometry on mixing and transport of polluted releases in natural channels including low flow conditions. The models were tested by using the laboratory dispersion data. Comparisons between concentration-time curves predicted by using the proposed model incorporating two different submodels show that Storage-Diffusion Model seems to be superior in explaining physical processes inside the storage zone to the Storage-Exchange Model even though accuracies of simulation results by two models are about the same. The proposed model shows significant improvement over the conventional one-dimensional dispersion model in predicting natural mixing processes in open channels.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.520-525
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• 2000

Glucose oxidase was immobilized in polypyrrole by electrosynthesis. The enzyme had an influence on the redox properties of a complex enzyme electrode. In the cyclic voltammograms of the enazyme electrode new peaks were appeared at the potential around 0.7V vs. Ag/AgCl in additional to the typical peaks for polypyrrole. The more immobilized the stronger the peaks became. During the cycling the pH of electrolyte solution was decreased to about 4.4 The reason for that is to be the proton released from the carboxyl in the glucose oxidase in order to keep on a charge neutrality of the oxidized enzyme. This fact suggests that the new peaks in the voltammograms are caused by the redox of glucose oxidase. In the AC impedance spectrum analysis of the electrode the diffusion of electrolyte anion was limited because of chained structure of the enzyme. The faradic impedance was large since the glucose oxidase is an insulator. Therefore when glucose oxidase is entrapped the enzyme should be limited in amount. Because the growth of the polypyrrole is accompanied both charge transfer and mass transport. For the traditional electrosynthesis that means amount of enzyme present in the electrode is limited to as much as film growable.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.445-449
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• 1999

Hydrophilic polyphosphazenes were synthesized from hydrophobic polyphosphazenes by adding methoxyethylenoxy side chains and cast by dip-coating method into membranes supported on porous polypropylene mesh filter sheet for metal separation testing. A solution of $Cr^{3+},\;Co^{2+},\;Mn^{2+}$ nitrates was used in diffusion experiments which were conducted from $25^{\circ}C$ to $60^{\circ}C$. lt was found that the ion transport properties were increased as the repeating number of ethylenoxy side chain increased. Membrane from trifluoroethoxy methoxyethoxyethoxyethoxy co-substituted polyphosphazenes was found to separate $Cr^{3+}$ ion from $Mn^{2-}$ and $Co^{2+}$ ions with separation factor of 4.5 at $60^{\circ}C$.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2540-2543
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• 2008

Liquid crystal displays (LCD's) are continuously coated with some chemicals in the clean room of a factory. Spreading of these chemicals is causing serious problems both in controlling clean room quality as well as to the workers inside the factory. It is required to alleviate or properly control the offensive odor which is mainly composed of propylene glycol mono ethyl acetate, novolak resin and photo active compound. The control strategy employed is to bleed the offensive odor gas out the clean room. A full scale 3D CFD model was created with anisotropic porous media, chemical species transport with no volumetric reaction, and thermal diffusion with propane gas (tracer gas) to simulate the odor spreading. A segregated implicit solver with standard k-$\varepsilon$ model is employed. The detailed CFD analysis made it possible to develop an effective method of ventilating the coater room and optimizing their capacities.

• Journal of Powder Materials
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• v.31 no.2
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• pp.146-151
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• 2024

Pure SnO₂ has proven very difficult to densify. This poor densification can be useful for the fabrication of SnO₂ with a porous microstructure, which is used in electronic devices such as gas sensors. Most electronic devices based on SnO₂ have a porous microstructure, with a porosity of > 40%. In pure SnO₂, a high sintering temperature of approximately 1300℃ is required to obtain > 40% porosity. In an attempt to reduce the required sintering temperature, the present study investigated the low-temperature sinterability of a current system. With the addition of TiO₂, the compositions of the samples were Sn_1-xTi_xO₂-CoO(0.3wt%)-CuO(2wt%) in the range of x ≤ 0.04. Compared to the samples without added TiO₂, densification was shown to be improved when the samples were sintered at 950℃. The dominant mass transport mechanism appears to be grain-boundary diffusion during heat treatment at 950℃.

• Journal of Environmental Science International
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• v.13 no.7
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• pp.655-660
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• 2004

This paper demonstrates the numerical simulation of three dimensional flow pattern for vehicular exhaust dispersion in the street canyons. The wind flow around buildings in urban is computed by the SIMPLEST method. The convection-diffusion equation was used to compute the $NO_X$ concentration level near buildings. Details are given of important boundary conditions and turbulence quantities variations. The simple turbulence model was used for unisotropic viscous effect. A control-volume based finite-difference method with the upwind scheme is employed for discretization equation. The simple turbulence model applied in this study has been verified through comparison between predicted and measured data near buildings. By the predictive results, the updraft induced by the presence of high-rise buildings is important in the transport of street level pollutant out from the street canyons. Our suggestion for reducing ground level pollution is to have high-rise buildings constructed or to reduce the channelling effect of street canyons.

• Journal of Radiation Protection and Research
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• v.31 no.1
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• pp.9-15
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• 2006

A long-range atmospheric dispersion model named LADAS has been developed to understand the characteristics of the transport and diffusion of radioactive materials released into atmosphere. The developed numerical model for validation was compared with the results of the ETEX which is the long-range field tracer experiment. As a comparative study, the calculated concentration distributions agreed well in the case of the usage of the mixing heights calculated by the Richardson number than the usage of the constant mixing heights in LADAS model. Also, the calculated concentrations agreed with the time series of the measured ones at some sampling points.

• Journal of the Korean Electrochemical Society
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• v.16 no.4
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• pp.217-224
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• 2013

In this paper, we have investigated the characteristics of cyclic voltammetry of a self-assembled mono-layer(SAM) electrode which was modified by 3-Mercaptopropionic acid (3-MPA) on gold nanoparticle(AuNP)-deposited electrode. Also, the transport phenomena of electrons and ions around the electrode have been analyzed. The governing equation and its boundary conditions by adopting the semi-infinite diffusion model were formulated for the mass-transfer dominant system. In order to obtain the numerical solutions of cyclic voltammetry(CV) on SAM electrodes, MATLAB program was implemented by applying the explicit finite difference method. Resulting CV program for the SAM-modified electrode was verified in good agreements with the experimental CV results for the 3-MPA on AuNP electrode.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1407-1411
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• 2007

현재까지 우리나라에서 주로 사용되고 있는 2차원 흐름 해석모형은 미연방 도로국(U.S. Federal Highway Administration)과 연계하여 Brigham Young University에서 개발된 SMS(Surface-Water Modeling System) 모형이다. SMS모형 중 이송 확산 모형으로는 RMA-4가 포함되나 이 모형은 최신 수치기법을 반영하지 못하는 등의 문제점들로 인해 실제 물리적 현상 모의에 있어서 한계를 가지고 있다. 따라서 물리적 현상에 대한 적절한 모의를 위한 개선과정을 통하여 RAM4가 개발되었다. 본 연구에서는 현장실측 자료를 바탕으로 RMA-4와의 모의결과 비교를 통하여 오염 확산 해석모형인 RAM4의 적용성을 검증하고자 하였다. RAM4와 RMA-4 모의에 있어서 격자구성과 경계조건은 동일하게 설정하였으며, 유량조건은 평수량과 갈수량으로 선정하였다. 각각의 유량시 수위조건이 틀려지므로 각 유량조건에 대한 격자구성을 달리하였다. 모의구간은 낙동강 본류의 수산대교에서 삼랑진 철교까지의 약 13km 구간을 대상으로 하였다. 모의 구간내에는 밀양-하남 하수처리장이 상류 좌안측에 위치하고 있고, 만곡, 단면의 축소 및 확대, 하중도, 합류 등의 지형학적 특징들이 비교적 짧은 구간에 나타나고 있어 모형의 검증에 적합하다고 판단된다.