• Korean Journal of Ecology and Environment
• /
• v.36 no.1 s.102
• /
• pp.1-8
• /
• 2003

Growth, colony formation and microcystin production of 'low-toxic' Microcysits aeruginosa $K{\"{u}}tzing$ were examined in relation to the 'info-chemicals' released by zooplankton. Algae were cultured in a medium with or without filtered water taken from cultures of Daphnia magna Straus (300 ind./L) or Moina macrocopa Straus (500 ind./L), The growth of M. aeruginosa, based on cell number, was also significantly different from populations cultured in the media with and without filtered zooplankton water from the exponential growth phase. In the 6-day experiment, the growth pattern of M. aeruginosa cultured with ZCMF was clearly different to control with-out ZCMF. Mean number of cells/particle and particle bio-volume of M. aeruginosa increased significantly from the day 2 for the Daphnia-CMF or Moina-CMF treat-ments. Microcystin production was promoted showing from 18.7 to 55 ${\mu}g/g$-dry cell in the zooplankton treatments relative to the controls. At peaked level on day 4, the highest level of up to $70.5{\pm}16.8\;{\mu}g/g$-dry cell was observed in the D. magna treatment. This study suggested that 'info-chemicals' from zooplankton might induce the increase of algal growth rates, colony formation and microcystin production, these seem to be advantageous to the alga and thus as a grazing defense mechanism.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1996.04a
• /
• pp.46-47
• /
• 1996

막분리 공정의 공업적인 이용을 위해서는 막을 특정 용기에 적재한 모듈의 형태가 요구되는데 모듈의 형태에 따라 평판형(plate and frame), 나권형(spiral wound), 관형(tubular), 중공사형(hollow fiber)모듈 등이 있다. 이 중에서 관형 시스템은 내경이 12.5~25 mm, 길이 0.6~6.4 m에 이르는 비교적 큰 open channel로 되어 있으며 공급액 유로가 일반적으로 커서 전처리를 행하지 않고도 fouling이 적으며, 또한 막 표면의 세정이 약품에 의한 것 이외에 스폰지 볼 등에 의한 물리적 세정도 가능하므로 응용 범위가 넓다는 것이 특징이다. 한외여과 공정의 가장 큰 문제점은 농도분극 및 fouling 현상에 의한 플럭스 감소이다. 농도분극 현상은 경계층에서 용질의 대류,확산적인 전달에 기인하여 막 표면으로 갈수록 진해지는 용액층의 형성을 의미한다. 이 현상은 가역적인 과정으로서 감압함으로 원상태로 회복이 가능하며 조작 압력에서 정상상태가 되면 막투과 플럭스는 일정한 값을 유지한다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.11a
• /
• pp.206-206
• /
• 2015

자동차 외장 부품은 미려한 외관과 경량화를 통한 연비향상을 위해 ABS수지 위에 다층 도금 공법이 적용된다. 하지만, 필드에서 종종 도금층의 부식에 대한 문제가 야기 되고 있다. 부식문제의 한 인자로 도금 두께의 불균일성을 들 수 있다. 도금공정에서 용액의 유동성, 제품이 걸리는 위치, 도금액의 불순물 등등 여러 가지 현장요소로 인해 도금 두께 편차가 생겨난다. 이러한 현장 요소와 함께 피도금물의 외형 형상 또한 도금 불균일의 주요한 원인이 된다. 특히, 제품 모서리 부분에서는 문제가 되는 과도금 현상이 쉽게 발생한다. 따라서, 도금 두께 편차를 줄이기 위해서는 도금 현장 요인을 분석하는 것도 중요하지만, ABS 제품의 외형 형상 디자인에 있어서 체계적인 접근이 필요하다. 그러나, 디자인의 구조적인 접근을 위해 현장에서 검증하려면 많은 비용과 시간이 소요된다. 이에 본 연구에서는 모서리 부분에서의 과도금 현상을 시뮬레이션을 활용하여 형상관점에서 과도금 형태 및 원인을 분석하고자 하였다.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1992.10a
• /
• pp.57-58
• /
• 1992

분리막을 이용한 물질의 분리는 최근 들어 많은 연구가 수행되어 일부 실용화 되고 있으나, 최근에 관심을 끌고 있는 Pervaporation 분리법에 의한 유기물의 분리는 여러가지 이유에서 아직 큰 성과를 올리지 못하고 있다고 생각된다. 그러나, 이 방법만이 갖는 잇점 때문에 국내.외에서 다방면으로 활발히 연구가 진행되고 있다. 한편 Pervaporation 분리법의 분리기구를 규명하는데는 많은 어려움이 있으므로 아직까지 명확히 밝혀지지 않고 있으나 언제인가는 밝혀져야 할 과제라고 생각된다. 따라서 본 연구에서는 투과현상을 좀 더 구체적으로 파악하므로써 분리기구를 해석하는 데 다소나마 기여하기 위하여 물 선택성 막은 Carboxy-methylcellulose(CMC) 막을 제작하여 알코올류, DMF, DMAc, Dioxane등의 유기 수용액의 분리실험을 하였으며, 투과 증기의 조성을 짧은 시간 간격으로 측정하므로써 분리특성과 아울러 투과현상을 파악하였다.

• Journal of the Korean Geotechnical Society
• /
• v.17 no.1
• /
• pp.15-24
• /
• 2001

흙필터는 일반적으로 침식이나 파이핑으로부터 지반 구조물을 보호하기 위하여 사용된다. 세립자들이 유동하여 필터에 퇴적하는 폐색현상이 발생하는 경우, 간극수압이 증가하고 이로 인해 지반구조물의 불안정을 유발시키게 된다. 미세입자의 유동에 의한 폐색현상은 옹벽의 뒤채움재에 설치한 필터, 흙댐의 저부에 설치된 필터, 그리고 터널의 라이닝 뒤에 설치한 필터 등에서 발생할 수 있다. 폐색현상은 필터의 투수능을 저하시켜 배수능력에 상당한 위험을 초래할 수 있다. 본 연구에서는 필터의 폐색으로 인한 투수능 저하 정도를 실험을 통해 관찰하고 이론적인 모델을 통해 정량화 시키고자 하였다. 일정한 농도의 현탁액이 필터로 유입되는 분리형 실험과 현장상태를 모사하는 흙-필터 시스템의 결합형 실험을 통해 투수능의 저하현상이 압력 제어조건과 유량 제어조건에서 관찰되었고, 서로 비교 분석되었다. 미세입자가 통과하는 필터의 간극을 모세관으로 가정한 후 모세관에서 유체의 흐름 원리를 이용하여 물리적인 폐색에 의해 발생하는 투수능 저하현상을 이론적인 모델로 구성하였다. 일반적으로 투수능은 1/10 수준으로 감소되었으며, 분리형 실험에 의한 결과와 이론적인 모델의 결과는 잘 일치하였다. 또한, 결합형 실험결과와 분리형 실험결과가 비교적 잘 일치하여 투수능 저하예측은 분리형 실험이나 이론적 모델에 의하여 가능하리라 판단되었다.

• Korean Journal of Environmental Agriculture
• /
• v.24 no.2
• /
• pp.132-138
• /
• 2005

Objective of this research was to evaluate the fate of nitrogen and phosphorous in hydroponic waste solution from the plastic film house cultivation applied to the upland soil by column leaching and field experiment. The pH and EC of leachate were decreased by the reaction with the upland soil in the column leaching experiment. The EC and concentrations of $H^+,\;K^+,\;and\;{NH_4}^+$ of leachate were decreased as the column length (soil depth) was increased. But these were increased as the amounts of the hydroponic waste solution were increased field experiment growing red pepper (Capsicum annum L.) to monitor the nutrients movement using ion exchange resin capsule demonstrated that the nutrient concentration of soil solution was increased in the orders of $PO_4-P. Nitrate concentration of resin capsule inserted into the soil was relatively higher than other nutrients $(NH_4-N\;and\;PO_4-P)$ at the 45 cm of soil depth. The overall results demonstrated that the hydroponic waste solution could be recycled as plant nutrients to enhance fertility of soils. But nitrate leaching was a major factor for safe use of the hydroponic waste solution in soil.

• Korean Journal of Plant Resources
• /
• v.20 no.4
• /
• pp.342-347
• /
• 2007

The present study was conducted to examine the effect of prunus mume extract on the Kimchi fermentation. The physicochemical and microbiological properties of Kimchi with the addition of various levels(0, 0.1, 0.3 or 0.5%)of prunus mume extract was measured up to 30 days at $4^{\circ}C$. pH was decreased sharply in control after 2 days . A typical decreasing pattern in pH values was noted in all treatments during the initial 18 days of fermentation followed by a gradual decrease afterwards. Total acidity was decreased by the addition of prunus mume extract. Reducing sugar content was reduced to approximately 70% by day 10-12 in prunus mume extract treatments. Total vitamin C content was reached to maximum on 6 days of fermentation and then decreased in all treatments. Reducing sugar and total vitamin C contents were slightly increased by the addition of prunus mume. Total viable cell number increased to reach peak on day 8 and then slowly decreased during the fermentation. Lactobacillus cell number in control treatment continued to increase to reach peak on day 12, while the numbers in prunus mume treatments reached peak on day 8-12 and then gradually decreased throughout the fermentation. The results of this study indicate that prunus mume extract causes to delay the Kimchi fermentation by slowing down pH drop and inhibiting the Lactobacillus cell growth.

• The Korean Journal of Food And Nutrition
• /
• v.16 no.1
• /
• pp.29-34
• /
• 2003

Prunus mume has been used for the folk medicine by many old civilizations to treat food-borne diseases or enteric disorders. This study was carried out to examine the antimicrobial effect of juice from Prunus mume against pathogens such as Escherichia coli, Salmonella enteritidis, Staphylococcus aureus, Listeria monocytogenes and Bacillus cereus. The juice of Prunus mume had the strongest antimicrobial activity to Sal. enteritidis. The concentrations of Prunus mume juice for the formation of clear zone were 1% for Sai. enteritidis(15.0mm), 3% for Lis. monocytogenes(14.7mm), and 5% for Bac. cereus(14.75mm), Esc. coli(13.45mm) and Sta. aureux(11.9mm). The growth of all tested microorganisms was inhibited apparently in tryptic soy broth containing 3% and 4% Prunus mume juice. And it was found that the Prunus mume juice showed the highest antimicrobial properties, followed by Sal. enteritidis, Bac. cereus, Sta. aureus, Lis. monocytogenes, Esc. coli.

• Journal of Convergence for Information Technology
• /
• v.10 no.5
• /
• pp.92-100
• /
• 2020

The purpose of this study is to analyze the relationship between export weight, import weight, export amount, import amount, and trade balance of ICT industry. The data used were gathered from the Korea Customs Service trade statistics. The analysis period used annual data for 19 years from 2000 to 2018. The change rate analysis was shown in order of trade balance, export amount, import amount, import weight and export weight. The increase rate analysis showed that the trade balance was the highest at 919%.. In the correlation analysis, the trade balance and export amount were 0.95, showing the highest correlation coefficient. As a result of the regression analysis, the export amount for the trade balance, the dependent variable, was Coefficient 2.37, which was positive(+). Each variable is changing independently of one another. Since 2000, the trade balance of the Korean ICT industry has led 84% of Korea's total trade balance. In the future, Korea's ICT industry should be further developed for Korea's economic development, and exports should be further increased to increase the trade balance. In the next paper, we will try to find a field that can be specifically developed by subdividing the ICT industry.

• Applied Chemistry for Engineering
• /
• v.18 no.1
• /
• pp.29-35
• /
• 2007

Recently, due to narrow margin on design factor of flue gas desulfurization (FGD) systems or aging of systems, some problems such as decrease of $SO_2$ removal efficiency and difficulty on coping with unstable state are arising on FGD systems. On this study, to cope with these problems several methods such as adjustment of reagent pH, inlet $SO_2$ concentration, variation of units of operation pump, installation of liquid distribution ring (LDR) were attempted to increase the $SO_2$ removal using spray type simulated FGD system. Also, sulfite and Al/Fx ion effects on limestone blinding were experimented. When three absorber recirculation pumps were operated, $SO_2$ removal was increased by 12% in comparison with that of two pumps operation. $SO_2$ removal was increased by 2~7% after installation of LDR. Dissolved oxygen increased up to 0.5 ppm and limestone binding effect was alleviated after injection of dibasic acid (DBA) with the concentration of 500 and 1,000 ppm. When $Al^{3+}$ and $F^-$ ions were coexisting, the dissolution rate of limestone was decreased by 20%.