• 한국환경과학회지
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• 제11권10호
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• pp.1081-1087
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• 2002

This study was performed to research the characteristics of suspended particulate for Yellow Sand of January, 1999 in Busan. Yellow Sand frequency during 13 years(1988~2000) in Busan showed maximum in April(57%), next to March(21%), May(16%). According to result of 850hPa weather map and backward isentropic trajectory, this event originated from the Gobi Desert and the Loess Plateau of China. And three mode was found in time series of TSP and PM10 concentration, primary peak showed the maximum hourly concentration at ali station. Gamjeondong as industrial site showed the highest TSP concentration and also had the longest high concentration($geq700\mu\textrm{g}/m^3$). In PM10, concentration of primary peak showed maximum value at Yeonsandong, maximum concentration of secondary and third peak was Deokcheondong. Lasted time from primary peak to secondary peak was about 30 hours, between secondary peak and third peak was 18 hours in Busan, The traveling time between occurrence of Yellow Sand the finding of it was 8~9 hours in Busan and 4~5 hours in central area.

• 한국표면공학회지
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• 제49권2호
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• pp.119-124
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• 2016

Plasma electrolytic oxidation (PEO) is a promising coating process to produce ceramic oxide on valve metals such as Al, Mg and Ti. The PEO coating is carried out with a dilute alkaline electrolyte solution using a similar technique to conventional anodizing. The coating process involves multiple process parameters which can influence the surface properties of the resultant coating, including power mode, electrolyte solution, substrate, and process time. In this study, ceramic oxide coatings were prepared on commercial Al alloy in electrolytes with different KOH concentrations (0.5 ~ 4 g/L) by plasma electrolytic oxidation. Microstructural and electrochemical characterization were conducted to investigate the effects of electrolyte concentration on the microstructure and electrochemical characteristics of PEO coating. It was revealed that KOH concentration exert a great influence not only on voltage-time responses during PEO process but also on surface morphology of the coating. In the voltage-time response, the dielectric breakdown voltage tended to decrease with increasing KOH concentration, possibly due to difference in solution conductivity. The surface morphology was pancake-like with lower KOH concentration, while a mixed form of reticulate and pancake structures was observed for higher KOH concentration. The KOH concentration was found to have little effect on the electrochemical characteristics of coating, although PEO treatment improved the corrosion resistance of the substrate material significantly.

• Journal of the Korean Wood Science and Technology
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• 제48권4호
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• pp.417-430
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• 2020

4종의 판상형 목재제품의 방염제 도포량과 침지시간에 따른 방염성능을 분석하기 위하여 소방청의 방염성능기준에 따라 목재제품의 탄화길이와 탄화면적을 측정하였다. 잣나무 합판, 낙엽송 합판, 편백 판재, 타공처리된 자작나무 합판에 자체 개발된 방염제를 각각 300, 500 g/㎡씩 도포하고 방염처리되지 않은 시험편과 비교하였다. 일반적으로 방염제의 도포량이 증가함에 따라 탄화길이와 탄화면적이 감소하여 방염성능이 증가하는 경향을 나타냈으나, 낙엽송 합판을 제외하고 탄화길이와 탄화면적의 감소량이 크지 않았다. 타공처리된 자작나무 합판의 침지시간에 따른 방염성능은 60분의 침지시간까지 양의 상관관계를 나타냈으나, 그 이후 점차 완만해지는 경향을 보였다. 방염제의 도포량과 침지시간에 따른 목재제품의 방염성능은 추후 방염성능 기준에 맞는 불연·준불연 목재의 생산을 위한 기초자료로 이용될 것으로 기대된다.

• 한국포장학회지
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• 제17권2호
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• pp.33-37
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• 2011

변패성 식품의 하나로서 양념돼지불고기의 미생물적 저장수명을 실시간적으로 제어하는 방법으로서 포장 내 $CO_2$ 농도의 측정을 이용하는 방법을 고안하고 동적온도조건에서 그 적용가능성을 확인하였다. 식품으로부터의 $CO_2$ 생산 속도 혹은 포장 내 $CO_2$ 농도변화가 증가하기 시작하는 시점이 미생물적 한계품질에 해당되었고, 이를 저장수명의 결정의 지표로 사용할 수 있는 것으로 나타났다. 이는 또 특정 $CO_2$ 농도에 도달되는 시점, 즉 $CO_2$ 농도변화의 유도기와도 일치하였다. 제안된 logic은 $CO_2$ 농도를 실시간으로 측정하고 무선으로 데이터를 전송할 수 있는 sensor 시스템에 의하여 가능성이 확인되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.183-183
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• 2008

This paper presents the time responses of calcium ($Ca^{2+}$) ion concentration of MG-63 cells induced by a constant shear stress in micro channel were observed in the real time. Most of cells have similar rising time. There were some time delays because of the initial position of the cell in the micro channel along the pressure-driven fluid flow. The concentration of $Ca^{2+}$ exponentially decreased while time constant of each profile did not have any relation to the peak value of concentration.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1972-1979
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• 2003

Transport of a scalar quantity, such as chemical concentration or temperature, is important in many engineering applications and environmental flows. Here we report on results obtained from the large eddy simulations of flow and concentration fields inside the tank performed using a spectral multi-domain technique. The computations were driven by specifying the impeller-induced flow at the blade tip radius (Yoon et al. $^{(1)}$). This study focused on the concentration development at different molecular diffusivities in a stirred tank operated under turbulent conditions. The main objective of the work presented here is to study the large-scale mixing structure at different molecular diffusivities in a stirred tank by using the large eddy simulation. The time sequence of concentration and flow fields shows the flow dependency of the concentration development. The presence of spatial inhomogenieties is detailed by observing the time variation of local concentration at different positions.

• 한국수자원학회논문집
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• 제33권2호
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• pp.195-205
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• 2000

도달시간 산정에 있어 고려되어야 할 요소에는 유역형상과 흐름상태, 유출특성 등이 있다. 한편 Singh(1976)은 지표면흐름을 Kinematic Wave 이론으로 해석하였으며 유역형상을 평면형상과 수렴형상, 발산형상으로 분류하여 유역형상에 따른 도달시간 산정식을 제시하였다. 본 논문에서는 Singh이 제시한 평면형상에서의 도달시간 산정식에 기초하여 불투수 지표면 유출에서의 도달시간 산정을 다루었다. 이를 위한 이론식 유도는 흐름을 개수로 흐름(층류, 완난류, 전난류)으로 파악하여 수행하였고 각 개수로 흐름상태에 대한 이론식을 제시하였다. 또한 강우강도를 주요 인자로 고려하여 재현기간별 강우강도를 포함한 근사식 즉 복합형 도달시간 산정식을 개발하였다.

• 대한치과보철학회지
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• 제38권2호
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• pp.178-190
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• 2000

The purpose of this study was to evaluate the surface roughness of Ni-Cr-Be alloy($Verabond^{(R)}$, Aalba Dent Inc., USA) according to electrolyte concentration and etching time. Total of 150 metal specimens ($12{\times}10{\times}1.5mm$) composed of 5 polisded specimens, 5 sandblasted specimens, 140 etched specimens were prepared. Etched groups were divided into 28 groups by the $HClO_4$ concentrations(10, 30, 50, 70%) and etching times(15, 30, 60, 120, 180, 240, 300 seconds). The mean surface roughness(Ra) and the etching depth were measured with Optical 3-dimensional surface roughness measuring machine(Accura 1500M, Intek Engineering Co., Korea) and observed under SEM. The results obtaind were as follows: 1. Surface roughness(Ra) and etching depth were affected by the order of etching time, electrolyte concentration, and their interaction(P<0.05). 2. Surface roughness(Ra) and etching depth were increased with etching time in 10%, 30% electrolyte concentrations, but they had no significant difference with etching time in 70% (P<0.05). 3. Surface roughness(Ra) and etching depth decreased in the order of 30, 10, 50, 70% electrolyte concentrations from 120 seconds etching time(P<0.05). 4. The remarkable morphologic changes in etched surface were observed along the grain boundaries in 15, 30 seconds of 10%, 30% concentrations and the morphologic changes could be denoted in the grains themselves as well as along the boundaries with the lapse of time. Even though the noticeable morphologic changes also took place in etched surface with 50% concentration, the degree of changes were less than that of changes with 10%, 30%. However, there were little morphologic changes with 70% concentration regardless of etching time. 5. Surface roughness(Ra) of sandblasting group with $50{\mu}m\;Al_2O_3$ had no significant difference with 30%-30 seconds etched group(P<0.05).

• Food Science and Biotechnology
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• 제16권4호
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• pp.565-571
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• 2007

This study was carried out to investigate an optimum condition for the high angiotensin-l converting enzyme (ACE) inhibitory activity and the yield on enzyme concentration, casein concentration, and hydrolysis time. The optimum condition was performed by response surface methodology for acquirement of casein hydrolysate of milk which shows high ACE inhibitory activity, Among 8 tested enzymes, Protamex showed the highest activation degree with 77.03 unit/g from casein. Their hydrolysis degrees of flovourzyme 500MG, protamex, mixture from 1% casein were 85.5, 88.5, and 93.5%, respectively. The ranges of enzyme concentration (0.25-1.25%), casein concentration (2.5-12.5%), and hydrolysis time (20-100 min) as 3 independent variables through preliminary experiments of the yield of casein hydrolysate and ACE inhibitory activity, and it shows optimum response surface at a saddle point. It shows enzyme concentration (0.64%), casein concentration (8.38%), and hydrolysis time (55.81 min) in the yield aspect and showed the highest activity at enzyme concentration (0.86%), casein concentration (5.97%), and hydrolysis time (63.86 min) in ACE inhibitory aspect. The $R^2$ value of a fitted optimum formula on the hydrolysis yield was 0.9751 as the significant level of 1%. The $R^2$ value of a fitted optimum formula on ACE inhibitory activity is 0.8398, and the significance is recognized in the range of 5%.

• 펄프종이기술
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• 제33권3호
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• pp.84-99
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• 2001

This study was carried out to acquire basic data necessary for the use of rice-straw chemical pulp. It investigated the proper bleaching conditions when rice-straw chemical pulp(alkaline sulfite-${Na_2}{S_2}{O_4}$) was bleached using the various kinds of bleaching agents by the two-stages bleaching methods. And, physical properties of pulps bleached with eight kinds of two-stages bleaching methods were tested. The results of this study were as follow; 1. The first-stage bleaching was conducted under the proper conditions with chlorine(C). And then, the proper conditions related to the calcium chlorite(H), hydrogen peroxide(P) and sodium hydrosulfite(Y) bleaching as the second-stage bleaching were investigated. The proper conditions of CH stage were determined to be 0.3% concentration of calcium chlorite, $30^{\circ}C$ of reaction temperature and 20min. of reaction time. For CP stage, the proper conditions of concentration of hydrogen peroxide, reaction temperature and reaction time were 1.5%, $60^{\circ}C$ and 90min., respectively. And for CY stage, the proper conditions were 0.5% concentration of sodium hydrosulfite, $40^{\circ}C$ of reaction temperature and 90min. of reaction time. 2. The first-stage bleaching was conducted under the proper conditions with chlorine dioxide(D). And then, the proper conditions related to the calcium chlorite(H), hydrogen peroxide(P) and sodium hydrosulfite(Y) bleaching as the second-stage bleaching were investigated. The proper conditions of DH stage were determined to be 0.5% concentration of calcium chlorite, $25^{\circ}C$ of reaction temperature and 5min. of reaction time. For DP stage, the proper conditions of concentration of hydrogen peroxide, reaction temperature and reaction time were 1.0%, $70^{\circ}C$ and 90min., respectively. And for DY stage, the proper conditions were 0.3% concentration of sodium hydrosulfite, $50^{\circ}C$ of reaction temperature and 20min. of reaction time. 3. The first-stage bleaching was conducted under the proper conditions with calcium chlorite(H). kAnd then, the proper conditions related to the hydrogen peroxide(P) and sodium hydrosulfite(Y) bleaching as the second-stage bleaching were investigated. The proper conditions of HP stage were determined to be 0.3% concentration of hydrogen peroxide, $30^{\circ}C$ of reaction temperature and 60min. of reaction time. For HY stage, the proper conditions of concentration of sodium hydrosulfite, reaction temperature and reaction time were 2.5%, $60^{\circ}C$ and 30min., respectively. 4. When the rice-straw chemical pulps were bleached with eight kinds of two-stages bleaching methods in the proper conditions mentioned above, respectively, the final brightnesses after CH, CP, CY, DH, DP, DY, HP, and HY bleachings were 62.0, 74.3, 61.4, 58.9, 66.9, 62.9, 50.4 and 60.1, respectively. And strengthes of pulps bleached with DP and DH methods were comparatively higher than those of pulps bleached with other bleaching methods.