• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.315-316
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• 2012

전기도금법으로 제조한 $Ni-TiO_2$ 복합체에 교반 속도가 전류효율에 미치는 영향을 연구하였다. 교반은 공기를 불어넣은 공기교반과 자석막대를 회전시킨 자석교반으로 나누어 실시하였다. 교반 속도는 공기교반의 경우에는 0.5, 1.0, 1.5 L/min, 자석교반의 경우에는 100, 200, 300, 400, 500 rpm으로 변화시켜 $Ni-TiO_2$ 복합체의 전류효율과 순수 니켈의 전류효율 변화를 관찰하였다. 순수 니켈의 경우 전류효율이 두 종류의 교반 방식 모두, 속도가 높아질수록 다소 감소하였으나, 그 폭이 크지 않았다. 반면, $Ni-TiO_2$ 복합체의 경우에는 교반 속도가 높아지면, 전류효율이 급격히 감소하였다. 특히, 공기교반의 경우에는 1.0L/min에서 1.5L/min으로 교반속도가 증가하면 전류효율이 크게 감소하였다.

• Resources Recycling
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• v.27 no.1
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• pp.45-54
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• 2018

This study aimed to investigate the effects of mechanical factors such as agitation speed and air rate in fly ash flotation. Specifically, we used thermal power plant fly ash with unburned carbon content of 3.4 to 3.7%. The effect of pH, agitation speed, collector dosage, and frother dosage - the key factors of froth flotation - showed unburned carbon recovery and unburned carbon content of 63% and 34%, respectively, when the dosage of safflower oil used as collector was 800 g/ton, pH was 7, agitation speed was 1,200 rpm, and frother dosage was 400 g/ton. The SEM/EDS analysis of fly ash in that case indicated that the spherical fly ash particles lowered the unburned carbon content as they floated with the air bubbles without being dissolved in the unburned carbon or settled in the ore solution. The other experiment of changing the mechanical factors such as agitation speed and air rate resulted in unburned carbon recovery and unburned carbon content of 74% and 67%, respectively, at air rate of 8 L/min and agitation speed of 900 rpm. The recovery and unburned carbon content increased as the low agitation speed and additional air injection decreased the strength of the eddy current in the ore solution and consequently prevented the floating of fine fly ash particles with unburned carbon. In addition, the recovery rate and unburned carbon increased further to 80% and 70%, respectively, showing the best performance when the agitation speed and air rate were lowered to 800 rpm and 6 L/min, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.69-75
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• 2020

This study was conducted to improve the solid-liquid separation efficiency of clarifiers. To do so, the study did a bio-flocculation experiment simply by controlling the stirring speed (rpm) and baffle angle of a clarifier on a lab scale, but without using a coagulant. For the purpose of the experiment, the feed wall of a clarifier was so improved that a baffle could be installed on the clarifier. Then, it was ensured to change its stirring speed (to 0.0rpm, 0.6rpm, and 1.2rpm), with the angle fixed at 10°. As a result, it was found that concentration efficiency increased by 2.0%, and effluent removal efficiency (SS concentration) by 7.8%, at a stirring speed of 0.6ppm. This indicates the bio-coagulation efficiency of sludge increased with changing stirring speeds. Then, the baffle angle of the sedimentation unit was changed to analyze how the changed baffle angle would affect the sedimentation of sludge. As a result, it was found that the compression of sludge interface was very effective at a baffle angle of 20°. It is hoped that these experimental findings will be useful in improving the sedimentation efficiency of circular clarifiers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.3
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• pp.51-59
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• 2006

The physical characteristics of autonomic microcapsules manufactured with various agitation speeds in a stirred tank were observed experimentally by a particle size analyzer and an optical microscope. The flow characteristics in a stirred tank were also investigated through a 3-dimensional numerical simulation to understand the manufacturing process of autonomic microcapsules. According to the results, we found that the agitation speed was the important factor to determine the sizes of microcapsules. The impeller-induced flow allowed the jet and tip-vortex pair components in the mixed fluid of a stirred tank. The vorticity around the blades in the impeller was increased as increasing the agitation speed. In addition, the size of autonomic microcapsules was strongly affected on the small scale mixing pattern such as a tip-vortex pair.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.650-655
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• 2013

In this study, the synthesis of succinic acid from hydrogenation of maleic anhydride over Pd/C were performed in aqueous solution at various reaction conditions. We confirmed that the distribution of product was different according to process parameters. When increasing the reaction pressure and agitation speed, the by-product decreased and the purity of succinic acid increased. From the result, we may conclude that the reaction pressure and agitation speed are important factors for promoting the mass transfer rate of gas-liquid interface by increasing gas-liquid solubility in liquid hydrogenation. When the reaction pressure increased from 5 bar to 10 bar, the reaction rate increased 2.14 times. When the agitation speed increased from 300 rpm to 700 rpm, the reaction rate increased 2.75 times.

• Korean Chemical Engineering Research
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• v.44 no.3
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• pp.289-293
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• 2006

In the CMSMPR (continuous mixed suspension mixed product removal)system, the effect of temperature and RPM on the CSD (crystal size distribution) in the calcium carbonate process was investigated. In the steady state operation, the change of solution pH was small. At the low temperature and below 300 RPM, volume mean size change of calcium carbonate was stable and CSD was narrow. In the SEM view, calcite and aragonite was obtained.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.22 no.1
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• pp.5-26
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• 1996

O/W/O(oil in water in oil)형 유화액막에 의한 2성분 탄화수소 혼합물인 toluene-cyclo hexane의 분리에 있어서 투과율, 막의 안정성과 분리계수에 미치는 영향을 계면활성제 농도, emulsion과 용매와의 교반속도 등을 변수로 하여 실험하였다. 계면활성제의 농도가 증가함에 따라 투과율은 증가하는데 0.5wt% 이상에서는 증가율이 둔화 되었다. 막 파괴율은 0.1wt%에서 가장 낮게 나타났으며, 그 이상에서는 농도가 증가하면서 파괴율도 증가하였다. 또한 분리계수는 계면활성제의 농도가 0.5wt%에서 가장 높게 나타났다. 에멀젼 제조 시 교반속도 변화에서는 투과율이나 막 파괴율에 큰 영향을 미치지 않는 것으로 나타났다. 막 강화제의 농도가 증가함에 따라 투과율은 감소하였고, 에멀젼과 용매의 접촉 시 교반속도가 증가 할수록 막 파괴율도 증가하였다.

• Microbiology and Biotechnology Letters
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• v.33 no.1
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• pp.51-55
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• 2005

The effect of rotation speed and culture temperature on the growth of T. aureum and also the biosynthesis of lipid and DHA was investigated. The optimal temperature for the growth was $32^{\circ}C$, but the best temperature for the maximum production of lipid and DHA was $18^{\circ}C$ in the range of $4^{\circ}C\;to\;39^{\circ}C$. In the case that the temperature was higher than $39^{\circ}C$ and lower than $11^{\circ}C$, the growth was very slow and the production of DHA was also very low. However, the lipid content in the biomass became higher with decrease in the culture temperature. The rotation speed for the maximum growth was 100rpm. But the growth and the production of DHA were not affected by the change of rotation speed in the range of 100 to 250 rpm. When the rotation speed was 50 rpm, the growth as well as the production of DHA and lipid was greatly reduced.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.3-27
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• 1996

분체의 입자 배열이 불규칙한 경우뿐만 아니라 입자 크기가 극미세하여 X선회절분석이 불가능한 경우에도 비정질물질이라 한다. 수용액 속에서 이런 비정질 물질을 합성하기 위해서는 합성용액의 과포화도를 높여 계속 유지시킴에 따라 극미세 1차핵 생성의 지속적인 유도에 따른 입자 성장을 최대한 억제시켜야만 한다. 본 연구에서는 흡습제, 칼슘제 및 식품 첨가제 등으로 이용되는 비정질 탄산칼슘을 계에서 합성하고, 이때 생성된 비정질 상태의 겔을 수용액 환경을 변화시켜가면서 따라 결정화를 유도하고 탄산칼슘의 동질이상을 관찰하였다. CO2의 유속을 11/min, 교반속도를 600rpm으로 고정시키고, Ca(OH)2의 양을 10g에서 50g까지 변화시켜가면서 겔 상태의 비정질 탄산칼슘을 합성하였다. 이때 전기전도도는 CO2의 용해와 더불어 Ca(OH)2의 용해도가 증가함에 따라 변화하였으며, 반응종반부에는 겔화가 시작될 때까지 거의 일정하였다. 따라서, 이러한 사실들로부터 현탁액 내에서의 전기전도도의 변화는 Ca이온의 영향을 받는 것으로 사료된다. 비정질 탄산칼슘은 수용액에서 불안정하여 CO2 가스를 방출하면서 급격히 결정화되는데, 본 연구에서는 Ca(OH)2의 양을 20g으로 하여 위의 방법에 의해 얻어진 겔을 수용액의 종류와 농도 및 결정화 온도, 교반속도를 달리하면서 결정화시켰다. 교반속도를 100rpm으로 하여 물의 온도변화에 다라 결정화시킨 경우 전 온도범위에서 칼사이트상이었으며, 물의 온도가 5$^{\circ}C$일 경우에는 미세한 입자들이 응집된 형태였으나, 그 외의 온도변화조건에서는 모두 평균입경 0.4$\mu\textrm{m}$정도의 비교적 균일하 능면체 형태였다. 또한 교반속도를 500rpm으로 증가시켰을 경우에는 8$0^{\circ}C$에서 침상의 아라코나이트가 소량생성되었음을 SEM사진으로 관찰할 수 있었으며, 소량의 바테라이트도 혼재되어 결정화되었음을 XRD결과로 알 수 있었다. 교반속도를 100rpm으로 한 NH4Cl 0.5mol/l 수용액에서는 입자의 형태와 크기가 불규칙한 칼사이트로 결정화되었으며, MgCl2 0.05mol/l 수용액의 경우에는 순수한 H2O의 경우에서와는 달리 2$0^{\circ}C$에서는 모서리가 무딘 매우 균일한 크기의 칼사이트 입자가 관찰되었으며, 6$0^{\circ}C$부터는 아라고나이트가 생성됨을 관찰할 수 있었다. 따라서, 고온(8$0^{\circ}C$)의 농도 MgCl2 수용액(0.1, 0.2 mol/l)에서 교반속도를 높여(800rpm) 겔을 결정화시킨 결과 아라고나이트의 생성수율이 증가되는 것을 확인할 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.191-196
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• 1999

Effects of agitation and heating rate on crystallinity, size distribution and mean size of $\alpha$-$SiO_2$powder prepared hydrothermally were investigated. $\alpha$-$SiO_2$crystalline powder, in mean particle size of 1~3.2 $\mu\textrm{m}$, was obtained at $350^{\circ}C$ using KOH as a mineralized for a 3 h reaction. Experimental results showed that particle size became smaller as the rate of agitation increased if it was introduced from the beginning of reaction, however, crystallinity was reduced at the low rate of agitation and it was became enhanced at above 150 r/min. Particle size became larger if agitation was introduced at any time during the reaction rather than introduced from the beginning of reaction. It was also found that particle size became smaller if heating rate was reduced, while the rate of agitation kept constant.