• Journal of the Korean Vacuum Society
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• v.4 no.2
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• pp.164-171
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• 1995

열처리에 따른 Cu 박막의 미세구조 및 전기 비저항의 변화를 조사하였다. Cu(hfac)(TMVS)를 원료로 하는 저압화학증착법에 의해 증착온도를 $160^{\circ}C$에서 $330^{\circ}C$까지 변화시키면서 TiN기판 위에 Cuqkr막을 제조하였고 $450^{\circ}C$에서 30분간 열처리하였다. 증착온도에 따라 표면이 평평한 Cu 박막을 형성하는 표면반응 제한지역과 표면이 거친 Cu 박막을 형성하는 물질전달제한지역이 관찰되었다. 열처리 후 Cu 박막은 전체적으로 표면이 평탄해졌고 결정립의 크기는 모든 증착온도에서 증가하였는데 그 편차 역시 증가하여 EM 저항성 측면에서는 큰 효과를 보이지 못할 것으로 판단된다. 비저항은 증착온도 $200^{\circ}C$에서 급격히 증가하였고 열처리 후에는 모든 증착온도에서 비저항이 감소하였는데 표면반응제한지역에서는 결정립 성장에 의한 약간의 비저항 감소를 보였으나 물질전달제한지역에서는 응집에 의해 Cu 결정립간의 전기적 연결상태가 향상되어 급격한 비저항 감소를 보였다.

• Microbiology and Biotechnology Letters
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• v.16 no.6
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• pp.510-516
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• 1988

The effects of input substrate concentration and dilution rate on mass transfer resistance in the operation of immobilized cell reactors were investigated using Rhodospirillum rubrum KS-301 immobilized by Ca alginate as reactor element and glucose as growth-limiting substrate. The kinetic parameters were obtained to estimate effectiveness factors. In the packed-bed reactor, internal mass transfer resistance was predominating although external resistance could not be neglected. The overall effectiveness factor was decreased with increase of dilution rate. In the continuous stirred-tank reactor, external resistance was nearly neglected and the overall effectiveness factor was not affected by dilution rate. In this experiment the overall effectiveness factors in PBR and CSTR were estimated to be 0.70 and 0.71 at D$_{i}$ = 0.2/h, R = 0.15 cm, and S$_{i}$ : 1.0g/L, respectively.

• Nuclear Engineering and Technology
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• v.16 no.2
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• pp.80-88
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• 1984

The removal mechanism of air borne methyl iodide by triethylenediamine (TEDA) impregnated charcoal bed was investigated. The analysis of experimental data indicates that pore diffusion is the rate controlling step when the air velocity is over 20cm/sec, and both fore diffusion resistance and external mass transfer resistance are contributed to the overall resistance when the air velocity is 10cm/sec. The adsorption model to describe the performance of impregnated charcoal bed under dry condition where water vapors do not exist in air, is proposed. The calculated values and experimental results are well matched.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.310-318
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• 1999

The concentration breakthrough curves were examined to predict mass transfer coefficients of nitrogen and oxygen in adsorption column for design data of PSA process. Experimental breakthrough curves for bulk gas flow were compared with theoretical simulation results. For quantitative analysis of the adsorption, coupled Langmuir isotherm was considered and LDF model was used to describe the mass transfer effect. In the experimental and theoretical results, it was found that mass transfer coefficient was not affected by flow rate but strongly affected by pressure. As a result of this tendency, mass transfer resistance in this system was proved to belong to the macropore diffusion controlling region and the mass transfer coefficients could be expressed by exponential functions of pressure change. The mass transfer coefficients for one component, nitrogen or oxygen, were successfully applied to breakthrough curves for bulk mixed gases. The experimental curves were reasonably in consistent with the theoretical curves and the error time was less than 5 percent.

• Polymer(Korea)
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• v.28 no.2
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• pp.121-127
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• 2004

The instantaneous removal of ethylene glycol is very important fur obtaining high molecular weight polymer because of the reversibility of the polycondensation reaction of poly(ethylene naphthalate)(PEN). In this study, we investigated the mass transfer phenomena in the thin film of PEN oligomer where the polycondensation reaction took place at 280$^{\circ}C$ and under 0.1mmHg. In case of less than 0.025cm film thickness the mass transfer resistance through the thin film of the polymer melt was not so high that the overall reaction rate was governed only by the polycondenstion reaction. Both the mass transfer model and the diffusion model predicted the experimenatal data well but the diffusion model showed faster reaction rate in the low molecular weight range than the mass transfer model . It was estimated from the two models that the diffusivity was 4.7${\times}$10$\^$-6/$\textrm{cm}^2$/sec and the mass transfer coefficient was 1.4 ${\times}$10$\^$-4/cm/sec both of which were smaller than In case of poly(ethylene terephthalate).

• Korean Chemical Engineering Research
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• v.54 no.5
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• pp.648-652
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• 2016

The study of $CO_2$ absorption in a packed column by 1,1,3,3-tetramethylguanidine (TMG) dissolved in ethylene glycol is presented. Absorption column of inner diameter 1 in and 0.6 m length was filled with Protruded-packing $0.16in{\times}0.16in$. We investigated the effect of operating conditions on overall mass transfer coefficients as well as on $CO_2$ removal efficiency. The loading values reached at about $1.0mol_{CO2}/mol_{TMG}$. In case of absorbent with lean $CO_2$ loading, the overall mass transfer coefficient was proportional to the concentration of TMG. However, in the range of more than ${\alpha}=0.5molCO_2/molTMG$, the overall mass transfer coefficients decreased with the concentration of TMG. It is due to the increasing of mass transfer resistance in liquid phase as increasing of viscosity at higher loading values.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.05a
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• pp.325-325
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• 1999

• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.50-55
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• 2011

To enhance the performance of a MEA (membrane electrode assembly) in a polymer electrolyte membrane fuel cell (PEMFC), optimum contents of Nafion ionomer as electrolyte in the 20 and 40 wt% Pt/C used in electrodes were examined. Variety characterization techniques were applied to examine optimum Nafion contents: cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). According to Pt wt% supported on carbon support, it has been observed that polarization, ohmic, and mass transfer resistances were changed so that the cell performance was significantly dependent on the content of Nafion ionomer. Optimum Nafion ionomer contents in the 20 wt% Pt/C and 40 wt% Pt/C were showed 35 wt% and 20 wt%, respectively. This is due to different surface area of the Pt/C catalyst, and formation of triple phase boundary seems to be affected by the Nafion contents.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.15 no.1
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• pp.67-81
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• 1986

냉각탑, 밀폐식냉각탑, 증발식응축기는 증발식냉각기의 분류에 속한다. 열은 증발에 의해 제거되어, 중력에 따라 유하하는 수 film으로 부터 충전물, 또는 밀폐식냉각탑, 증발식응축기의 관군상을 흐르는 공기에 전달된다. 따라서 공기측에서의 열과 물질의 이동프로세스는 기본적으로는 동일하다. 각 형식에서의 차이는 냉각되는 유체측에서의 열저항의 형태가 다르다는 점이다. 이 무저항은 냉각탑에서는 아주 작으나 다른 두 경우에 있어서는 계산상 고려하지 않으면 안된다. 이 논문은 이들 세 형식에 대해 통일된 이론을 적용할 수 있다는 것을 보여주기 위한 것이다. 그러므로 열 및 물질이동저항의 계산을 위한 식에 대해 논의하고 있다. 또한 복잡성을 피하기 위해, Merkel의 근사식을 공기측의 열 및 물질이동계산에 이용하였다.

• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1036-1042
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• 1998

It was investigated that the extraction of Cr(VI) from aqueous solution into the organic TDA and the stripping(back extraction) of Cr(VI) from the Cr(VI)-TDA complex into NaOH aqueous solution by hydrophobic hollow fiber membrane. It was found that the mass transfer rates of stripping process were smaller than those of the extraction process. This result was expected that membrane resistance, neglected in the extraction process, acts on the stripping process when organic phase flow in the tube side of the hydrophobic membrane. Hollow fiber modules were made by potting the desired number(60, 100, 150, 300fibers). We also examined the effect of flow rates of aqueous and organic phase on the mass transfer rate in the membrane modules. From these experiments, we identified for the extraction process by using hydrophobic membrane, the effect of flow rate of aqueous phase on the mass transfer rate was significant, but that of organic phase was negligible one. In the stripping process, however, mass transfer rate depend neither flow rate of aqueous(stripping solution) phase nor that of organic(Cr-TDA complex) phase.