• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1529-1534
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• 2008

Recently, mixers are being widely used in the display and semiconductor company in order to mix the chemical materials. The mixer normally consists of shaft, hub, reduction gear, and driving motor. It is one of the key design factors to evaluate the dynamic characteristics caused by the rotation. In this study, the dynamic characteristics of the high speed mixer, such as vibration, noise and thermal radiation, are verified by the experiment. Through the experiment, it is shown that the structural unbalance mass of high speed mixer is the important source of the severe vibrations and maximum temperature is mixer bowl.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.434-441
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• 2016

Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.585-592
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• 2014

Mixing effect on anaerobic digestion of livestock wastewater was different results depending on the researchers have been reported. The purpose of this study was to understand application of Korea livestock waste it was necessary to determine the effect of mixing. 4 anaerobic reactors were operated mesophilic and thermophilic temperature with continuous mixing or non mixing condition, respectively. Experimental result showed If temperature was same, TCOD removal efficiency of continuous mixing reactor was 0.11-0.58% higher than non mixing reactor. Different mesophilic and thermophilic temperature, there was no significant difference of TCOD removal efficiency. Continuously mixed digester gas production was 1.7-4.6% higher than non mixed digester. In addition, mesophilic digester gas production was 29.1-32.1% higher than the thermophilic digester. It was due to the thermophilic digester believe the inhibition of ammonia. This study suggest that the optimized operation condition of anaerobic digestion for livestock wastewater treatment was mesophilic continuous mixing state.

• Korean Journal of Food Science and Technology
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• v.24 no.4
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• pp.353-360
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• 1992

This study was carried out to investigate the changes of quality in yogurt during delivery and storage. To do this, microbiological, physico-chemical and sensory properties in stirred yogurt were studied at different temperatures $(10^{\circ}C$ & $20^{\circ}C)$ and shakings (100 rpm & 200 rpm for 30 min). Titratable acidity and TCA soluble nitrogen in yogurt were increased in accordance with increase of temperature and time, while pH, lactose and lactic acid bacteria tended to be decreased. Interestingly enough, shaking conditions almost did not influence these studies. In sensory evaluation it showed that acidity was strong and sweetness was weak as increasing the storage temperature and time, but there were no significant differences until 10 days at $10^{\circ}C$ and 3 days at $20^{\circ}C$. Off-flavor was developed after 12 days at $10^{\circ}C$ with only 200 rpm shaking and after 6 days at $20^{\circ}C$ in both shaking conditions. These yogurts were not suitable for consumer. Viscosity in the yogurt became high as the temperature and time were increased. Viscosity was lower in yogurt shaked at 200 rpm than in non-shaked yogurt. Finally, this study indicates that temperature and shaking during delivery of yogurt may be critical in keeping quality of yogurt.

• Composites Research
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• v.13 no.4
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• pp.19-32
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• 2000

The fabrication process of particulate metal matrix composites(PMMCs) with homogeneous distribution of reinforcement and reheating for thixoforming has been studied. Both of eletro-magnetic stirring and mechanical stirring were used to fabricate particulate metal matrix composites(PMMCs) for variation of particle size. The electrical and mechanical processing conditions for fabricating PMMCs are also suggested. For thixoforming of PMMCs, fabricated bi1lets are reheated by using the designed optimal coil with as function of length between PMMC billet and coil surface, and coil diameter and billet. The effect of reinforcement distribution according to variation of billet temperature were investigated with solid fraction theory with a function of matrix alloy and volume fraction of reinforcement.

• 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.

• 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.

• Journal of Mushroom
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• v.16 no.1
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• pp.45-50
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• 2018

This study was performed to compare medium characteristics during the composting stage for medium turning performed using an excavator agitator and a prototype medium turner in button mushroom cultivation. The changes in temperature in the medium did not significantly differ between the treatments until the 3rd turn performed using the excavator agitator. However, during the 4th and 5th turns, the temperature increased during turning with the prototype medium turner. During outdoor composting, various types of microorganisms such as thermophilic bacteria (Bacillus spp.), Actinomycetes, fluorescent Pseudomonas spp., and filamentous fungi were found to be distributed in the medium. The counts of aerobic bacteria and fluorescent Pseudomonas spp. did not significantly differ between treatments, and the counts of thermophilic bacteria and thermophilic actinomycetes were slightly higher during turning with the prototype medium turner. The rice straw was slightly shorter and water content lower for the prototype medium turner. There was no significant difference between pH and EC treatments. The L, a, and b values tended to increase on turning with the prototype medium turner.

• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.45-54
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• 2006

The Construction policy of government ever since 1970s have brought the economical growth, but has been causing environmental problems. Most roads were paved either asphalt concrete or portland cement concrete. These types of pavements has caused to rise temperature by making local heat islands in urban during summer time. Recently the wet-mixing solidified soil pavement, a kind of soil-cement, has developed and has been applied to the environment-oriented pavement. The solidified soil wet-mixed is placed on the subgrade along with asphalt concrete and portland cement concrete. Thermistors are laid in these field test pavements. The temperature gradients of these pavements are automatically measured with time. As the results of this test, the equation estimating surface temperature of pavement is proposed by analyzing measured temperature data. It is shown that the temperature change within the surface layer due to the change of air temperature is the greatest in the asphalt mixture and the least in the solidified soil mixture. Since it is proven that this wet-mixing solidified soil pavement emit less radiant heat than other existed pavements. Therefore this type of pavement can be successfully applied to the roads, such as walks, parkways, and bikeways, which are required to be human-friendly and environment-oriented.

• 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.