• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.225-232
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• 1997

The performance characteristics of high rate discharge LiSOCl2 cells are highly affected by carbon cathode. During the cell discharge, SOCl2 reduction takes place at the porous carbon cathode, resulting in the precipitation of reaction products, mainly LiCl, within the pores of the substrate. This leads to eventual passivation of the cathode surface and resulting cell failure. To improve the cathode performance, we ex-amined discharge reactions of cathodes (half-cell, 50 mA/$\textrm{cm}^2$ constant current) with various surface density and thickness. The carbon cathode with the optimum capacity for our application is surface density 0.04 g/$\textrm{cm}^2$ and thickness 1.4mm carbon. The carbon cathode with surface density 0.04g/$\textrm{cm}^2$ and thickness 1.4 mm exhibits decreased polarization, increased discharge duration time and capacity (Ah/$\textrm{cm}^2$) as compared with that with surface density 0.04g/$\textrm{cm}^2$ and thickness 0.8mm. The porosities analyses on the two carbon cathodes show that total pore volume of the carbon cathode with thickness 1.4 mm is larger than that with thickness 0.8mm. The increased volume of mesopores (0.05$\mu$m~0.5$\mu$m) and macropores(>0.5$\mu$m) is ob-served with the carbon cathode with thickness 1.4mm as compared with that with thickness 0.8mm, which can be related with the observed capacity increase. We observed LiCl crystals, cubic crystallites and fused, plate-like aggregates, and some elemental S as discharge products by EDS and XRD.

• Membrane Journal
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• v.24 no.2
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• pp.113-122
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• 2014

Porous poly(L-lactic acid)(PLLA) scaffold membranes were prepared via. phase separation process. Chloroform, dichloromethane and 1,4-dioxane were used as solvent and, ethyl alcohol was used as non-solvent. Morphologies, mechanical properties and mass transfer characteristics of the scaffold membranes were investigated through SEM, stress-strain test and glucose diffusion test. The scaffold membranes obtained from the casting solutions with chloroform and with dichloromethane showed similar morphologies. They showed sponge-like porous structure with the pore size in the range of $3-10{\mu}m$ and, their porosities were in 50-80% range. Using 1,4-dioxane as solvent, nano-fibrous scaffold membranes with porosities over 80% were fabricated. When the polymer content in the solution with 1,4-dioxane was lowered to 4%, highly porous, macroporous and nano-fibrous scaffold membranes were obtained. The size of the macropore was tens of the microns and the porosity was around 90%. These results indicate that the solvent has significant effect on the scaffold membrane structure and, that scaffold membranes with various structures can be fabricated through phase separation method by choosing solvent and by controlling polymer concentration in the casting solution.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.204-210
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• 1997

Zeolite 4A-impregnated complex molecular sieve was prepared by hydrothermal reaction after aluminosilicate gel was penetrated into the pore of activated carbon granule. The crystals of zeolite 4A mainly were formed in the macropore of activated carbon, and their average diameter is $0.8{\mu}m$. The pore volume of activated carbon granule is $0.67m{\ell}/g$, and the pore volume of the sample including 21.6wt% of zeolite 4A crystal is $0.41m{\ell}/g$ decreasing the pore volume by 40% due to the crystallization of zeolite 4A crystals on the internal surface of activated carbon. The calcium ion exchange capacity of zeolite 4A-impregnated sample is 320mg $CaCO_3/g$ zeolite, and this value is almost the same as that of zeolite 4A powder. The crystal of zeolite 4A was not separated from the support of activated carbon granule in the course of ultrasonic dispersion. The adsorption isotherm of water on zeolite 4A-impregnated sample shows the intermediate shape between types, I and III. In addition, zeolite 4A-impregnated sample shows the hydrophilic and hydrophobic properties simultaneously.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.825-830
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• 2007

사면에서 발생되는 강우유출과정에 기여하는 대공극의 영향은 그 중요성에도 불구하고 잘 알려져 있지 않다. 특히 대공극의 공간적분포특상에 대한 현장측정은 이뤄지지 않았다. 본 연구의 실험지역은 경기도 포천시 광릉수목원에 있는 작은 소유역이다. 이 지역의 정밀한 측량을 하여 수치고도모형(DEM)을 얻었다. 이 수치고도모형을 바탕으로 수치지형분석을 통해 흐름선을 파악하여 총 20지점을 선정하였다. 각 지점에서의 대공극을 통한 수직적인 유동들은 장력침투계를 사용하여 지표면아래 깊이 10cm에서 측정하였다. 공간적 토양의 특성분포를 파악하기 위해 각 지점에서의 체적밀도와 점토함량을 조사하였다. 토양수분의 공간적 분포 특성은 TDR(Time Domain Reflectometry)방식인 TRASE를 이용하여 토양수분 값을 얻었다. 이러한 다양한 공간적 특성들은 대공극발달의 공간적 분포특성을 파악하는 중요자료가 된다. 소유역을 크게 기여사면 면적을 기준으로 상부, 중부, 하부로 나누어 대공극의 유효 공극율과 대공극흐름율을 계산하였다. 상부에서의 유효 대공극율의 평균값과 변동계수는 각각 4.3%, 42.1%이고, 대공극흐름율의 평균값과 변동계수는 각각 45.0%, 26.6%이다. 중부에서는 유효 대공극율의 평균값과 변동계수는 6.8%, 37.3%이고, 대공극흐름율의 평균값과 변동계수는 56.2%, 14.4% 이다. 그리고 하부에서의 유효공극율의 평균값과 변동계수는 12.5%, 58.3% 이고 대공극흐름율의 평균값과 변동계수는 64.5%, 24%이다. 이는 유효 대공극율과 대공극흐름율의 비율은 기여사면 면적이 증가할수록 증가하였다. 이는 대공극을 통한 물 이송 능력이 원두부로 갈수록 증가한다는 것을 보여주고 있다.e, taurine, methionine, phenylalanine은 함량(含量)이 적었다. 5. 일건(日乾)중 총유리아미노산의 변화(變化)는 생시료(生試料)의 경우 2,041.2 mg%였으나 1일(日) 건조(乾燥) 후는 1,784.0 mg%로 감소(減少)하다가 그 이후 계속 증가(增加)하여 20일(日) 건조(乾燥) 후는 5,277.0 mg%였다. 6. 일건(日乾)중 leucine, isoleucine, valine은 대체로 증가(增加)하는 경향(傾向)을 나타내었으나 aspartic acid, proline, taurine은 대체로 감소(減少)하는 경향(傾向)을 나타내었다. 436.59mg%로 가장 많았고 군유산(軍有山) 차엽(茶葉)이 146.94mg%로 가장 적었으며 일반차엽(一般茶葉)의 평균치(平均値)는 264.59mg%, 용장(龍欌) 차엽(茶葉)이 223.10mg%, Yabukita 차엽(茶葉)이 256.49mg%였다. 7) 이상(以上)의 결과(結果)를 종합(綜合)할 때 용장(龍欌) 차엽(茶葉)은 일반차엽(一般茶葉)과 형질(形質) 뿐만 아니라, 성분(成分)도 다르므로 품종(品種)이 다른 수종(樹種)으로 추정(推定)되며 와운(臥雲) 차엽(茶葉)은 일반차엽(一般茶葉)과 형질(形質)은 다르나 성분상(成分上)의 비슷한 점으로 보아 동일계통(同一系統)의 변이(變異)된 대엽종(大葉種)으로 추정(推定)된다.5(${\pm}0.77$0.77) % 의 오차로 크게 감소하였다. 결론: 방사선이 통과하는 경로에 불균질조직인 폐가 존재할 경우에도 불균질조직에 대하여 조직의 밀도를 이용하여 보정하는 방법을 사용하여 투과선량으로부터 종양선량을 계산할 수 있음을 알 수 있었다.X>로 평균$43.26{\m

• Membrane Journal
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• v.8 no.3
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• pp.157-169
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• 1998

The effects of solvents (DMAc, NMP, 1,4-dioxane) and nonsolvents ($H_2O$, Methanol, n-hexane) on the morphology of 6FDA-p-TeMPD polyimide membrane, prepared by the wet phase inversion method, were studied. In the polymer/solvent/nonsolvent ternary system, the binodal curve, the coagulation value and the relative light transmission were measured, and the solubility parameter difference was calculated. The onset state and rate of liquid-liquid alemixing were predicted and the morphology of membrane was analyzed. It is found that the finger-like pores are formed within discontinuous polymer nodules when the binoclal curve is close to the polymer-solvent (P-S) axis, the coagulation value is small, the reduction of light transmission is easy to occur and the order of solubility parameter difference ($\Delta \delta_{i-j}$) is $\Delta \delta_{S-NS} > \Delta \delta_{P-NS} > \Delta \delta_{P-S}$. The dense skin with small nodules and the sponge type sublayer with macrovoid are formed in the case that the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is long and the order of $\Delta \delta_{i-j}$ is $\Delta \delta_{P-NS} >(\Delta \delta_{S-NS} < > \Delta \delta_{P-S})$. The thick layer of fine nodule coagulation and loosely grown sublayer of nodules appear when the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is very long and the order of $\Delta \delta_{i-j}$가 $\Delta \delta_{S-NS} > (\Delta \delta_{P-NS}$\lessgtr$ > (\Delta \delta_{P-NS} < >)\Delta \delta_{P-S}$ ).

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.1
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• pp.67-71
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• 1998

This study was carried out to granulate artificial zeolite powder that remove ammonium nitrogen and phosphorous simultaneously in wastewater treatment. Optimum water content was required for 30 percent volume to granulate artificial zeolite with 1.7mm diameter and 1~2cm length using granulator. Portland cement could remove much $NH_4{^+}$ and $PO_4{^{3-}}$ from the wastewater than other binding materials. Mixed 33, 25. 20. 16 percent of portland cement to artificial zeolite powder(v/v), cation exchange capacity of the granulars were 66.5, 81.4, 126.8, $151.2cmol^+kg^{-1}$ and hardness of that were 176.1, 24.4, 4.1, $0.4kg\;cm^{-2}$, respectively. Content of portland cement in the granular were related with removal of $PO_4{^{3-}}$ positively and that of $NH_4{^+}$ negatively. Shaked 1g of the granulars that made of portland cement 33 percent with 40ml synthetic wastewater containing $NH_4{^+}$ $1545mgl^{-1}$ and $PO_4{^{3-}}$ $417mgl^{-1}$, 99.4 percent of $NH_4{^+}$ and 90.3 percent of $PO_4{^{3-}}$ were removed simultaneously after 48 hours shaking. The longer shaking, the more $NH_4{^+}$ and $PO_4{^{3-}}$were removed. The artificial zeolite granular had both micropore and macropore that could be useful in the wastewater purification.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.81-94
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• 1997

In many solute transport studies, either flux or resident concentration has been used. Choice of the concentration mode was dependent on the monitoring device in solute displacement experiments. It has been accepted that no priority exists in the selection of concentration mode in the study of solute transport. It would be questionable, however, to accept the equivalency in the solute transport parameters between flux and resident concentrations in structured soils exhibiting preferential movement of solute. In this study, we investigate how they differ in the monitored breakthrough curves (BTCs) and transport parameters for a given boundary and flow condition by performing solute displacement experiments on a number of undisturbed soil columns. Both flux and resident concentrations have been simultaneously obtained by monitoring the effluent and resistance of the horizontally-positioned TDR probes. Two different solute transport models namely, convection-dispersion equation (CDE) and convective lognormal transfer function (CLT) models, were fitted to the observed breakthrough data in order to quantify the difference between two concentration modes. The study reveals that soil columns having relatively high flux densities exhibited great differences in the degree of peak concentration and travel time of peak between flux and resident concentrations. The peak concentration in flux mode was several times higher than that in resident one. Accordingly, the estimated parameters of flux mode differed greatly from those of resident mode and the difference was more pronounced in CDE than CLT model. Especially in CDE model, the parameters of flux mode were much higher than those of resident mode. This was mainly due to the bypassing of solute through soil macropores and failure of the equilibrium CDE model to adequate description of solute transport in studied soils. In the domain of the relationship between the ratio of hydrodynamic dispersion to molecular diffusion and the peclet number, both concentrations fall on a zone of predominant mechanical dispersion. However, it appears that more molecular diffusion contributes to the solute spreading in the matrix region than the macropore region due to the nonliearity present in the pore water velocity and dispersion coefficient relationship.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.146-152
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• 2005

The activated carbon was produced from Sancheong bamboo by carbon dioxide gas activation methods. The carbonization of raw material was conducted at $900^{\circ}C$, and $CO_2$ activation reactions were conducted under various conditions: activation temperatures of $750-900^{\circ}C$, flow rates of carbon dioxide $5-30cm^3/g-char{\cdot}min$, and activation time of 2-5 h. The yield, adsorption capacity of iodine and methylene blue, specific surface area and pore size distribution of the prepared activated carbons were measured. The adsorption capacity of iodine (680.8-1450.1 mg/g) and methylene blue (23.5-220 mg/g) increased with increasing activation temperature and activation time. The adsorption capacity of iodine and methylene blue increased with the $CO_2$ gas quantity in the range of $5-18.9cm^3/g-char{\cdot}min$. But those decreased over those range due to the pore shrinkage. The specific volume of the mesopore and macropore of bamboo activated carbon were $0.65-0.91cm^3/g$. Because of this large specific volume, it can be used to the biological activated carbon process. Bamboo activated carbon phisically adsorbed the $CO_2$ of maximum 106 mg/g-A.C in the condition of 90% $CO_2$ and adsorption temperature of $20^{\circ}C$. The $CO_2$ adsorption ability of bamboo activated carbon was not changed in the 5 cyclic test of desorption and adsorption.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.2
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• pp.71-78
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• 2000

Preferential flow has recently been the subject of increasing interest because these phenomena contribute to solute transport in soils. Commonly, preferential flow paths are associated with macropores or highly structured soils. We presented an analysis of the measured breakthrough curves (BTCs) of $Cl^-$ and $Cu^{2+}$ ions to test the occurrence of preferential flow in soils using miscible displacement technique under steady flow conditions. We also analyzed soil water retention curves and from this curves induced cumulative pore size distribution of undisturbed soils, which sampled from Ap1, B1, and C horizons of Songjeong series soils (the fine loamy, mesic family of Typic Hapludults). In this study, miscible displacement experiment on C horizon was excluded, because it is structureless sandy loam with saturated hydraulic conductivity of $5.2cmhr^{-1}$. The saturated hydraulic conductivity of Ap1 horizon was $2.0cmhr^{-1}$, which was about 7 times higher than that of B1 horizon ($0.27cm hr^{-1}$). Cumulative pore size distribution predicted that Ap1 horizon had more macropores (pore diameter larger than $49{\mu}m$, equivalent to -6 kpa of soil matric potential) than B1 horizon. The hydrodynamic dispersion coefficient from chloride BTCs was estimated as $1.3cm^2hr^{-1}$ for B1 and $34cm^2hr^{-1}$ for Ap1 horizon. However the retardation factors of B1 and Ap1 horizon were significantly different, i.e. 1 and 0.6, respectively, which means that there was distinct partition between mobile water and immobile phase in Ap1 horizon. The copper retardation effect of Ap1 horizon was less than that of B1 horizon, even though cation exchange capacity of Ap1 horizon was higher than that of B1 horizon. Thus, breakthrough curves of $Cl^-$ and $Cu^{2+}$ obviously showed the probability that preferential flow would occur in Ap1 horizon.