• 원예과학기술지
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• 제30권4호
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• pp.442-448
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• 2012

최근 상추와 같은 농산물에 의한 식중독사고가 발생하고 있으며 그 원인으로 병원성 미생물에 오염된 퇴비, 관개용수의 사용이라고 보고되고 있다. 따라서 본 연구는 육묘단계의 상토, 재배과정의 토양, 관개용수의 Escherichia coli와 Bacillus cereus 오염이 상추의 안전성에 미치는 영향을 구명하고자 수행하였다. 이를 위하여 상토는 두 균주로 7.5log CFU/g 수준으로 오염시킨 후 상추종자를 파종하고 28일간 생육시켰고, 오염되지 않은 토양과 6.0log CFU/g 수준으로 오염시킨 토양에 오염된 상토에서 21일간 자란 묘를 이식하고 49일간 인공기상동 ($25^{\circ}C$, 상대습도 70-80%)에서 생육시켰다. 또한 8.0log CFU/mL로 오염된 관개용수로 지표면관수법과 살수관수법으로 상추에 관수하고 40일간 병원성 미생물의 오염 및 생존을 조사하였다. 그 결과 육묘기의 상토와 상추 중 E. coli와 B. cereus는 시간이 경과함에 따라 점차 감소하였지만 육묘기 내내 생존 가능한 것으로 확인되었다. 토양에서는 42일간 E. coli와 B. cereus가 6.0log CFU/g 내외로 유의적인 감소 없이 유지되고 있었다. 오염된 토양에 이식된 상추는 21일째까지 E. coli와 B. cereus의 농도가 4.0log CFU/g 이상 유지되었고 이식 후 42일까지도 검출되었다. 또한 살수관수법으로 처리한 구에서 지표면관수법으로 처리한 구보다 상추의 오염수준이 5.0log CFU/g 정도 높았다. 따라서 본 연구의 결과는 병원성미생물에 오염된 상토, 토양, 관개용수는 농산물의 병원성미생물 오염에 직접적인 원인이 될 수 있음을 시사한다.

• 한국식품위생안전성학회지
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• 제22권4호
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• pp.365-369
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• 2007

본 연구는 현재 유통 판매되고 있는 쌀뜨물 발효액 라이젠의 살균소독력을 평가하기 위해 최적 조건 탐색 연구 및 오염된 행주에 대한 일반적인 세척 및 소독제들과의 살균력 비교 실험을 실시하였다. 라이젠은 2 또는 3배 희석 용액에서 2시간 처리하였을 때 $2.65\;log_{10}cfu/g$의 E. coli를 감소시켜 가장 우수한 효과를 나타내었다. 또한 라이젠 농축액의 경우 원액과 2배 희석한 용액에서 각각 2, 5시간 처리하였을 때 완전 살균효과를 나타내었다. 반면 $3{\sim}5$배 희석한 용액은 24시간 동안 처리해야만 완전 살균이 가능하였다. 행주에 오염된 E. coli에 대한 라이젠 및 농축액의 살균소독력을 비교 평가하기 위해 무처리, 물세척, 합성세제(15 ppm), 차아염소산나트륨(200 ppm)으로 처리한 결과 행주 내 잔여 균수가 각각 5.05, 4.32, 3.70, $3.02\;log_{10}cfu/g$로 나타난 반면 라이젠 2, 3배 희석액, 농축액 원액, 2배 희석액은 각각 2.30, 2.43, 0, $1.88\;log_{10}cfu/g$로 나타나 라이젠은 생균제로서 우수한 살균소독 효과를 보여주었다. 또한 행주에 오염된 S. Typhimurium을 대상으로 살균 실험을 실시한 결과 E. coli의 결과와 유사한 결과를 보여주었다. 행주 내 잔여 균수는 무처리에서 4.80, 물세척 처리에서 4.12, 합성세제 처리에서 3.58, 차아염소산나트륨 처리에서 $2.81\;log_{10}cfu/g$로 나타났다. 라이젠 2, 3배 희석액 및 농축액 2배 희석액은 2.03, 2.14, $1.59\;log_{10}cfu/g$로 나타났으며 농축액 원액은 완전 살균효과를 보여주었다. 본 연구 결과 쌀뜨물 발효액은 생균제로서 행주내 대장균, 살모넬라 등 식품위해미생물 제거를 위한 살균제로서 효과가 우수하였다.

• The Plant Pathology Journal
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• 제27권2호
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• pp.138-147
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• 2011

Xylogone ganodermophthora, an ascomycetous fungus, is known to cause yellow rot in the cultivated mushroom Ganoderma lucidum. In this study, we investigated the dissemination of this fungal pathogen in G. lucidum grown in cultivation houses. To determine the role of ascospores produced by X. ganodermophthora in disease development, we constructed a green fluorescent protein-labeled transgenic strain. This X. ganodermophthora strain produced a number of ascomata in the tissues of oak logs on which G. lucidum had been grown and on the mushroom fruit bodies. However, the ascospores released from the ascomata were not able to germinate on water agar or potato dextrose agar. Moreover, less than 0.1% of the ascospores showed green fluorescence, indicating that most ascospores of X. ganodermophthora were not viable. To determine the manner in which X. ganodermophthora disseminates, diseased oak logs were either buried in isolated soil beds as soil-borne inocula or placed around soil beds as air-borne inocula. In addition, culture bottles in which G. lucidum mycelia had been grown were placed on each floor of a five-floor shelf near X. ganodermophthora inocula. One year after cultivation, yellow rot occurred in almost all of the oak logs in the soil beds, including those in beds without soil-borne inocula. In contrast, none of the G. lucidum in the culture bottles was infected, suggesting that dissemination of X. ganodermophthora can occur via the cultivation soil.

• The Plant Pathology Journal
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• 제21권4호
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• pp.328-333
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• 2005

Paenibacillus elgii SD17 (KCTC $10016BP^T$=NBRC $100335^T$) was recently reported as a new species. Based on its inhibitory activity to Thanatephorus cucumeris AG1-1, strain SD17 was further evaluated for its potential as a biocontrol agent against soil-borne diseases of turf grasses in Korea. P. elgii SD17 showed a broad spectrum of antimicrobial activity in vitro test and suppressed development of turf grass diseases; Pythium blight caused by Pythium aphanidermatum and brown patch caused by T. cucumeris AG1-1 on creeping bentgrass (Agrostis palustris) in the growth chamber tests. Under a condition for massive culture in a 5,000 L fermenter, P. elgii SD17 reached $6.4{\times}10^8$ spores/ml that resulted in approximately $1.0{\times}10^7$ cfu/g when formulated into a granule formulation (GR) using the whole culture broth instead of water. Using the GR formulation, biocontrol activity of P. elgii SD17 was confirmed. In the growth chamber tests, the GR formulation was effective against brown patch and Pythium blight with similar level of disease severity compared to each of the standard fungicides at the application rates of 10 g/$m^2$ or above. In the field tests, compared to each untreated control, the GR formulation also effectively controlled Pythium blight, brown patch and large patch at all the application rates of 5, 10 and 20 g/$m^2$, respectively, without significant response by the application rates. However its performance was inferior to each of the standard chemical fungicides. Based on these results, we consider this GR formulation of P. elgii SD17 as an effective biocontol agent to suppress Pythium blight, brown patch and large patch of turf grasses in Korea.

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 2008년도 International Meeting of the Microbiological Society of Korea
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• pp.93-95
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• 2008

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.483-486
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• 2002

Injection of microbubbles and/or polymer solution has been known to be a promising method for the reduction of frictional drag of water-borne vehicles. Naval Architects have been interested in friction drag reduction technology, since the friction drag of a commercial ship can be over $70{\%}$ of total resistance. The reduction of friction drag is also important for autonomous underwater vehicles and naval submarines to improve their durability and survivability In this study two sets of experiments were carried out for the friction drag reduction of 2-D channel wall and flat plate in the circulating water channels in Chungnam National University. Preliminary results from the experiments are presented and discussed.

• Journal of Ship and Ocean Technology
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• 제9권1호
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• pp.27-37
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• 2005

An experimental study has been carried out as a basic research for the development of the friction drag reduction technology for water-borne vehicles by injecting microbubbles or polymer solution. Experimental apparatus and procedures have been devised and prepared to measure the changes of the wall friction with the injection of additives and the basic experimental data on friction drag reduction are obtained for fully developed channel flows. The effects of key controlling parameters were investigated for higher drag reduction with varying the concentration and the injection rate of additives. The frictional drag has been reduced up to $25\%$ with the microbubble injection and $50\%$ with the polymer solution injection.

• Corrosion Science and Technology
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• 제15권6호
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• pp.297-302
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• 2016

Water-based systems are dominating the coating market because of worldwide VOCs regulations. Research is focusing especially on waterborne polyurethane (WPU) because of its unique mechanical and chemical properties. However, commercial WPU consists of linear thermoplastic polymers with polar groups on the main chain, which do not perform as well as solvent-borne PU in a two-pack system. In this study, APTES were used as a chain crosslink agent to overcome commercial WPU's limited performance. WPUs synthesized by using a sol-gel process were evaluated with FT-IR, particle analysis, TGA, tensile tests, pull-off tests, SEM, and EIS. The results showed that WPUs with added APTES had better thermal stability, mechanical properties, and water resistance than did WPUs without added APTES. Consequently, the sol-gel process increased the crosslink density of WPUs and modified the WPU's own properties.

• 대한조선학회논문집
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• 제45권6호
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• pp.688-694
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• 2008

The reduction of the structure-borne noise is very important in order to reduce the noise of a ship. The noise at the high frequency range usually comes from the fluid flowing. The noise from the sea-water conveying pipe is one of the main source on these high frequency range. Therefore, the transmissibility variations are evaluated according to the shape of the rubber mount. The evaluations are performed with the frequency response function numerically and experimentally.

• 한국응용과학기술학회지
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• 제39권6호
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• pp.924-931
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• 2022

Undenatured castor oil and trimethylolpropane (TMP) were used to obtain bio-based water-based polyurethane. Isophorone diisocyanate (IPDI) was incorporated into the formulation to obtain a transparent film, and ethylenediamine (EDA) was used for chain extension. In order to measure the change in physical properties according to the contents of castor oil and TMP, each tensile strength, elongation, and abrasion resistance test was conducted. As the contents of castor oil and TMP increased, the tensile strength increased, the elongation decreased, and the surface hardened strongly as the respective contents increased.