• 한국기계가공학회지
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• 제2권1호
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• pp.32-38
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• 2003

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study alumina($Al_2O_3$) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02mm, 27kHz frequency, three slurry ratios (abrasives water by weight) of 11, 13 and 15 with different tool shapes and applied pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 11 and static pressure of $25kg/cm^2$, maximum material removal rate of $18.97mm^3/mm$ was achieved with mesh number of 600 SiC abrasives and static pressure of $30kg/cm^2$, best surface roughness of $0.76{\mu}m$ Ra was obtained.

• 에너지공학
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• 제27권1호
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• pp.21-32
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• 2018

In this paper, we reported the current technologies of water scaling removal and also water recovery from the flue gases, which are funded by Department of Energy (DOE), USA. Globally, water resources are limited due to the climate change. The potential impacts of climate change is food and water shortages. In the $21^{st}$ century, water shortages and pollution are expected to become more acute as populations grow and concentrate in cities. At present, the water stress increases over 62.0 ~ 75.8% of total water basin area and decreases over 19.7 ~ 29.0%. Many renewable energy sources demand secure water resources. Water is critical for successful climate change mitigation, as many efforts to reduce greenhouse gas emissions depend on reliable access to water resources. Water hardness is one of the major challenge to coal power plants. Department of energy (DOE) funded and encouraged for the development of advanced technologies for the removal of hardness of water (scaling) and also water recovery from the flue gases from coal power plants.

• Journal of Mechanical Science and Technology
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• 제20권2호
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• pp.227-233
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• 2006

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study, alumina $(Al_2O_3)$ was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02mm, 27kHz frequency, three slurry ratios of 1:1, 1:3 and 1:5 with different tool shapes and applied static pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 1:1 and static pressure of $2.5kg/cm^2$, maximum material removal rate of $18.97mm^3/min$ was achieved. With mesh number of 600 SiC abrasives and static pressure of $3.0kg/cm^2$, best surface roughness of $0.76{\mu}m$ Ra was obtained.

• 한국의류산업학회지
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• 제3권5호
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• pp.455-465
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• 2001

Assessing soil removal is of interest to the washing machine industry because of government-mandated energy savings and changes in detergent formulation and consumer laundry practices. We designed this study to examine the laundry process from a holistic perspective by integrating factors perceived to be of importance. Our purpose was to assess the impact of selected variables (fabric and soil type, wash temperature and time. detergent amount, and degree of agitation) on soil removal using accelerated laundry conditions. We used the Taguchi method to develop the research design and ANOVA to analyze the data. Although soil removal was affected by fabric type, soil type, type and amount of detergent, degree of agitation, wash time and temperature, and water hardness and volume, wash temperature was the most significant variable.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2012년 춘계학술대회
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• pp.117-137
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• 2012

In the ALC(Autoclaved lightweight concrete) manufacturing process, if the pre-cured semi-cake is removed after proper time is passed, it will be hard to retain the moisture and be easily cracked. Therefore, in this research, we took the research by multiple regression analysis to find relationship between variables for the prediction the hardness that is the control standard of the removal time. We study the relationship between Independent variables such as the V/T(Vibration Time), V/T movement, expansion height, curing time, placing temperature, Rising and C/S ratio and the Dependent variables, the hardness by multiple regression analysis. In this study, first, we calculated regression equation by the regression analysis, then we tried phased regression analysis, best subset regression analysis and residual analysis. At last, we could verify curing time, placing temperature, Rising and C/S ratio influence to the hardness by the estimated regression equation.

• 한국식품저장유통학회지
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• 제6권4호
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• pp.392-397
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• 1999

본 연구는 떫은감의 삽미를 제거하기 위한 $CO_2$가스 탈삽에서 탈삽온도를 달리하여 품종별 품질변화를 비교함으로써, 품종별 탈삽양상에 따라 연화나 장해없이 탈삽되는 가장 적합한 방법을 개발하는 자료로 삼고자 한다. 공시재료로는 도근조생, 청도반시, 사곡시의 떫은감 3품종을 사용하였다 2$0^{\circ}C$, $CO_2$탈삽에서는 3품종 공히 탈삽처리 후 2일만에 식용가능한 탈삽지수 2이하가 되었으나, 2$^{\circ}C$에서는 도근조생과 사곡시는 6일, 청도반시는 10일만에 식용가능하게 됨으로서 품종별 차이를 나타내었다. 가용성 탄닌함량의 변화는 탈삽지수와 같은 경향으로 감소하여 2$^{\circ}C$에서는 식용가능한 6일, 10일째에 도근조생, 청도반시, 사곡시 각각 29mg%, 35mg%, 22mg%, 2$^{\circ}C$에서는 2일째 각각 32mg%, 23mg%, 35mg%를 나타내었다. 탈삽경과 중 당도의 변화는 품종에 따라 약간의 차이는 있었지만, 2$^{\circ}C$, 2$0^{\circ}C$탈삽 모두 시간이 지남에 따라 다소 감소하는 경향이었으며, 식용가능한 탈삽일에는 탈삽전보다 약 l~3%정도 감소하였다. 경도는 2$^{\circ}C$탈삽처리에서는 품종에 관계없이 식용가능 탈삽일수를 지난 후에까지 경도가 1.0kg/$\psi$5mm 이상으로 유지되었고, 특히 청도반시는 경도의 탈삽전과 차이가 없이 유지되었다 2$0^{\circ}C$에서는 청도반시와 사곡시는 식용가능 탈삽일수를 지난 후에도 경도가 1.0kg/$\psi$5mm 상으로 유지되었으나. 도근조생은 탈삽 3일째에는 0.3kg/$\psi$5mm로 저하해 상품성을 상실하였다. 탈삽과정 중 색상의 변화는 온도에 관계없이 3품종 모두 탈삽전과 거의 차이가 없었다. 장해과의 발생은 청도반시, 사곡시에서는 나타나지 않았으며, 도근조생은 2$^{\circ}C$탈삽처리 6일째부터 장해과가 발생해 10일째에는 과실의 78%가 장해현상을 보였다.

• 환경위생공학
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• 제16권3호
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• pp.96-103
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• 2001

This study was carried out to investigate the major factors for the removal of NOMs (Natural Organic Matters) by alum ferric chloride and blended coagulants that consisted of alum and ferric chloride. Investigated factors were pH, the dosage of coagulant, alkalinity, hardness and bloc strength. The particle size contained in the test water came from the Han River was also measured. DOC(Dissolved Organic Carbon) removal at pH 6 was two to three times higher than at pH 8.5. The blended coagulant showed 9 to 10 percent higher DOC removal efficiency and 2 to 4 percent higher turbidity under the same condition. Alkalinity consumption of alum, ferric chloride and blended coagulant was 81%, 90% and 86% of theoretical value, respectively. The limit concentration of alkalinity to avoid pin floe was 10 mg $CaCO_3/L$ when alum was used. Hardness had no apparent effect on coagulation. The residual turbidity and $UV_{254}$ showed a tendency of increasing with floc strength($sec^{-1}$) increase. The order of floe strength was the following; alum >blended coagulant > ferric chloride. The particle counter test showed 89 percent of the small particle size(SPS, $1~5{\;}{\mu}textrm{m}$) and 11 percent of the medium to large particle size(M.LPS, $5~125{\;}{\mu}textrm{m}$). At PH7.85, the particle removal efficiencies of SPS($1~5{\;}{\mu}textrm{m}$) and M.LPS($5~125{\;}{\mu}textrm{m}$) in the coagulation process were 81% and 95%, respectively.

• 상하수도학회지
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• 제31권4호
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• pp.329-338
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• 2017

The problem of disposal of brine due to increased MD/RO desalination plant has recently become a big social issue. The chlor-alkali process through electrolysis of brine has been studied as a method to overcome this problem. In order to increase the electrolysis efficiency, a pretreatment process for removal of hard substances must be preceded. In this study, we investigated the mechanism of removal of hardness through chemical precipitation. As a result, Ca was greatly influenced by addition of $Na_2CO_3$, and Mg was strongly influenced by pH. Also, the addition of NaOH and $Na_2CO_3$ enabled simultaneous removal of Ca and Mg, and showed a removal efficiency of 99.9% or more. Finally, the residual concentrations of Ca and Mg in the brine after the reaction were 0.14 and 0.13 mg/L, respectively. Saturation index was calculated using Visual MINTEQ 3.1, and solid phase analysis of the precipitate was performed by FE-SEM and PXRD analysis. It was confirmed that precipitate formed by the formation of calcite and brucite.

• 한국물환경학회지
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• 제29권4호
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• pp.559-567
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• 2013

In recent years, NF (nanofiltration) membrane has been receiving great attention for hardness removal and has begun to replace traditional lime soda ash softening process, particularly in Florida, USA, mainly due to less sludge production and easy operation. This study aimed to provide detailed surface characteristics of various commercial NF membranes by performing sophisticated surface analysis, which would help more fundamentally understand the performance of NF membranes. More specifically, a total of 7 NF membranes from top NF/RO manufacturers in the world were examined for basic performance tests, surface analysis, and fouling potential assessment. The results demonstrated that NF membranes are classified into two groups in terms of surface zeta potential; they are highly negatively charged ones, and neutral and/or less negatively charged ones. Their hydrophobicities, measured by contact angle, varied from hydrophilic to slightly hydrophobic ones. The AFM measurements showed various surface roughness, ranging from 23 nm (smooth) to 162 nm (rough) of average peak height. Lab-scale fouling experiments were performed using feedwater obtained from conventional water treatment plants in the province of Korea, and their results attempted to correlate to surface characteristics of NF membranes. However, unlike typical RO membranes, no clear correlation was found in this study, indicating that fouling mechanisms of NF membrane may be different from those of typical RO membranes, and both cake deposition and pore blocking mechanisms should be considered simultaneously.

• 한국식품영양과학회지
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• 제27권4호
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• pp.648-652
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• 1998

Astringency in persimmons was removed by immersing in 0.5% acetic acid or various concentrations(0.1%, 0.5%, and 1.0%) of chitosan solutions for 4 days at 18$^{\circ}C$. During 5-days immersion, soluble tannin contents in persimmons decreased more rapidly while pH, 。Brix, and hardness decreased more slowly with increasing chitosan concentration. No noticeable color changes and decay were observed during this period. Sensory analyses 4 days after immersion indicated that persimmons immersed in 1.0% chitosan solution showed the best results for firmness and overall acceptability.