• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.371-376
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• 2010

The GaAs epitaxial layers were grown on Si(100) substrates by molecular beam epitaxy (MBE) using the two-step method. The Si(100) substrates were cleaned with three different surface cleaning methods of vacuum heating, As-beam exposure, and Ga-beam deposition at the substrate temperature of $800^{\circ}C$ in the MBE growth chamber. Growth temperature and thickness of the GaAs epitaxial layer were $800^{\circ}C$ and $1{\mu}m$, respectively. The surface structure and properties were investigated by reflection high-energy electron diffraction (RHEED), AFM (Atomic force microscope), DXRD (Double crystal x-ray diffraction), PL (Photoluminescence), and PR (Photoreflectance). From RHEED, the surface structure of GaAs epitaxial layer grown on Si(100) substrate with Ga-beam deposition is ($2{\times}4$). The GaAs epitaxial layer grown on Si(100) substrate with Ga-beam deposition has a high quality.

• Journal of Food Hygiene and Safety
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• v.18 no.2
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• pp.87-93
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• 2003

This study was performed to investigate aflatoxin reduction resulting from the pre-treatment and the cooking and processing of corn. Aflatoxin was produced by Aspergillus parasiticus ATCC 15517 on a type of corn imported from the United States. The aflatoxin-produced com (AC) was pre-treated in three ways in order to reduce aflatoxin: exposure to sun light for 7 days (SC); ultraviolet irradiation for 56 hours (UC); and washing with water three times (WC). Four kinds of cooking and processing methods (boiling, steaming, baking, and popping) were used to reduce aflatoxin in the AC control, SC, UC, and WC. These treatments produced com gruel, com cakes, com bread and popcorn. The aflatoxin content in the samples was determined by high performance liquid chromatography. The total aflatoxin level of the AC was significantly decreased by sun light and UV (p<0.05), and decreased by washing. After cooking and processing the AC, SC, UC, and WC, and averaging the total aflatoxin levels in the final products, the greatest reduction was found in the com gruel, then the popcorn, then the corn cakes, and the least reduction in the com bread. These results indicate that sunlight and ultraviolet energy could be effective factors in aflatokin degradation in corn before cooking and processing. This study also indicates that boiling, steaming, baking and popping were helpful in reducing the aflatoxin level in the com and that the most helpful factors were exposure time to heat. More research is needed to reduce the aflatoxin level down to below the maximum tolerable level of aflatoxin in foods.

• The Korean Journal of Pesticide Science
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• v.7 no.3
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• pp.169-175
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• 2003

For safe and easy disposal of prochloraz wastewaters after used as rice seed disinfectant in Korean farms, this experiment was carried out. By addition of several agricultural materials commonly utilizing in farmers, removal effect of prochloraz from waste solution was also investigated. When rice seeds after soaking in diluted prochloraz solution were rinsed with water several times, prochloraz was removed $9.2\sim10.6%$ at the first rinse and less than 3 % at the fourth rinse. A half life of prochloraz was $4\sim5$ days in aqueous system. Hydrolysis of prochloraz was more rapidly in alkali solution than neutral and acidic one at $25^{\circ}C$ and $35^{\circ}C$. By the irradiation under $5530J/cm^2$ using xenone lamp, prochloraz was photo-degraded to 87.7% in aqueous system. The removal efficiency of prochloraz by addition of several agricultural materials were as follows: 93.6% by lime, 90.7% by composed pig manure, 89.4% by activated charcoal, 78.0% by straw ash, 70.3% by sandy loam soil, 47.0% by zeolite and 24.1 % by rice straw. When prochloraz solution was sprayed on the field soil, it was dissipated upto 90% within 35 days.

• Korean journal of food and cookery science
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• v.25 no.3
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• pp.365-378
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• 2009

This study performed microbiological hazards analysis in raw food materials, cooking processes, kitchen staff, utensils, and the environment in order to obtain contamination levels of S. aureus in school foodservice operations. S. aureus was not detected in cooked foods offered by the foodservice operations; however, it was found in raw food materials prior to cooking. In the case of vegetables, S. aureus was detected in washed mung bean sprouts, parboiled mung bean sprouts, and bellflower roots both before and after disinfection, at levels of 2.2, 1.0, 1.0, and 1.0 log CFU/g, respectively. For processed foods, S. aureus was detected in one sample of packaged bean curd as well as in mung bean jelly cake at the level of 1.5 log CFU/g. For meat products, S. aureus was detected in beef brisket and chicken at levels of 2.3 and 1.3 log CFU/g, respectively. To determine microbiological hazard data for the hands and gloves of cooking personnel, the staff members were divided into two groups: a group presenting Enterobacteriaceae or coliforms, and another group presenting neither Enterobacteriaceae nor coliforms. The results showed that S. aureus was detected on the hands of staff in each group at levels of 2.0 and 2.1 log CFU/hand, respectively, and at 1.8 and 0.0 log CFU/hand on the gloves of staff in each group, respectively. Among kitchen utensils, as an environmental factor in school foodservice operations, S. aureus was detected on meat knives, mixing bowls, and dish cloths at levels exceeding 1.0 log CFU/hand.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.4
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• pp.299-310
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• 2006

The eye irritant test of lens washing agent, $SOLOCARE^{TM}$ was conducted using Draize methods according to KFDA Guidelines 1999-61. In addition, to test the potential toxicity of test articles the ratio of inflammatory cells and non-inflammatory epitheloid cells were also observed using smear cytology methods against ocular discharge. At sacrifice, the histopathological changes on Cornea, Iris, Retina and Sclera were also observed in all animals. Slight (1~2 degrees) irritancy of cornea and conjunctiva were observed at 1, 2 and 3 days after dropping in non-washing group. The MIOI of these points are detected as 4.33, 3.33 and 2.00, respectively. In washing group, slight irritancy of cornea and conjunctiva were restricted to 1 and 2 days after dropping with MIOI as 3.00 and 1.33, respectively. Therefore, $SOLOCARE^{TM}$ was also considered as non-irritating materials because the MIOI is detected below 5.00 throughout the whole experimental periods in both washing and non-washing groups and the IAOI is also detected as 4.33 (1 day after dropping). No meaningful changes on smear cytology of ocular discharges are observed in this study compared to that of non-treated intact eyes. In addition, no abnormal histopathological changes on the cornea, iris, retina and sclera were also detected in $SOLOCARE^{TM}$ dropping group compared to that of non-treated intact eyes.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2002.10a
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• pp.153-153
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• 2002

수돗물의 염소소독 과정에서 부식질의 초기 분해생성물인 MX(Mutagen X)는 수돗물의 전체 돌연변이유발성의 최고 60%까지 차지하는 것으로 알려져 있다. 그러나 존재하는 농도는 수 ng/L로 정량분석을 위해서는 resin을 사용하여 10 ~ 20L의 물을 농축하여야 한다. 이 연구에서 MX의 농축에 사용된 resin은 XAD-4와 XAD-7HP의 1:1 mixture이었으며, 사용 전에 Soxhlet extractor를 사용하여 ethyl acetate와 methanol로 각각 12시간씩 세척하였다. 15L의 물 시료는 37%의 염산으로 pH 2에 맞춘 후 직경 2cm의 유리관에 15cm의 높이로 채워진 resin을 40mL/min의 유속으로 통과시켰다. 유리관에 잔류하는 물은 질소가스로 대부분 불어 제거한 후 ethyl acetate 200mL를 가해 1mL/min의 유속으로 흘려주어 MX를 용출시킨 후 회전증발기로 5mL의 부피까지 농축시키고 10% H$_2$SO$_4$ in MeOH 0.1mL를 가하여 6$0^{\circ}C$에서 methyl ester화하였다. 과포화된 $Na_2$SO$_4$ 수용액 0.3ml를 가한 후 MTBE 0.3mL로 추출하고 GC/ECD로 분석하였다. MX의 회수율은 60% 이상이었으며 일부수돗물 시료에 대해 분석하였다.

• Journal of Food Hygiene and Safety
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• v.28 no.1
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• pp.31-35
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• 2013

In this study, the pesticide residues of polished rice and brown rice were measured after washing and cooking process. The initial concentrations of isoprothiolane and fthalide were $7.134{\pm}0.03mg/kg$ and $2.024{\pm}0.04mg/kg$ for polished rice, and $17.941{\pm}1.41mg/kg$ and $6.413{\pm}0.19mg/kg$ for brown rice, respectively. After first washing process, the removal rates of isoprothiolane were 23.0% (polished rice) and 18.5% (brown rice). Also, the case of fthalide, the removal rates were 14.0% and 9.7%, respectively. The removal dose was increased, but the removal rate was decreased in proportion to the number of washing process, After the cooking process, the removal rates of isoprothiolane and fthalide were 66.0% and 79.0% (polished rice), and 88.7% and 92.9% (brown rice), respectively. The removal rate of isoprothiolane was higher in the washing process, and the case of fthalide was higher in the cooking process. The optimum washing process for the pesticides removal was five times and the cooking process was the most effective to use the new water after soaking the rice in water during 30 minutes.

• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.169-175
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• 2015

Recently, a stone is preferred as a cladding materials because of its outstanding durability and luxurious character. However, because of running out of natural resources and restriction of production, it is expected that difficulty of stable supply, and thus alternative cladding materials for concrete wall is needed. Therefore, in this research, as an alternative cladding materials, exposed-aggregate concrete is studied using saccharin based retarder. For evaluating factors, changing water-to-cement ratio, dosages of saccharin-based retarder, and timing of water jet washing were tested on the surface properties of exposed-aggregate concrete. As a result, the most favorable surface performance was obtained at 0.75 day after the placing in 25% of water-to-cement ratio, and at one day after the placing in 35 and 55% of water-to-cement ratio, 1.5 day after the placing in 65% of water-to-cement ratio with $24m{\ell}/m^2$ of retarder application.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.285-290
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• 2001

To utilize canned oyster processing waste water effectively, this study was carried out to prepare instant powdered soup using the waste water (IPSW), Instant powdered souu from oyster hot-water extracts (IPSE) was prepared by mixing hot-water extracts powder (15 g) with table salt (5 g), cream powder (19 g), milk replacer (12 g), wheat flour (20 g), corn flour (15 g), starch (5 g), glucose (7.5 g) and onion powder (1.5 g). In preparing IPSW, mixed powder from wash water and boiling liquid waste, instead of powder from hot-water extracts and table salt, was added (powder from boiling liquid waste: powder from wash water= 12: 8) and other additives were added in proportion to those in the IPSE, The IPSW consists mainly of carbohydrates (about $72\%$). It was not different from the IPSE. The volatile basic nitrogen, viable cell counts, coliform group of the IPSW contains 33.4 mg/100g, $2.2\times10^4CFU/g$, <180 MPN/100g, respectively, and its water activity has 0.257. So it was a hygienically safe and conservable instant food. The main fatty acids of IPSW were 16: 0 and 18: 1n-9. Its chemical score of protein was $61.4\%$ and its main inorganic matter was iron. According to a sensual evaluation, in contrast to the IPSE, the IPSW had a bit lower aroma but better taste, It was concluded from the above chemical and sensory evaluation that even the boiling liquid waste which had been mostly abandoned because of its high table salt content can be used as a good material for instant powdered soup if it's powdered and mixed adequately with powder from wash water, and its table salt content is properly adjusted.

• Journal of Conservation Science
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• v.27 no.4
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• pp.345-356
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• 2011

To remove metal stains of the ceramics, chemical cleaning is essential case by case. This study investigated the removal characteristics of iron stains by oxalic acid and citric acid including their application methods of soaking and poultice. The soaking method in cleaning agents showed removal process by color difference and released iron contents from iron stains on ceramics. Iron stains were removed successfully from ceramics, which soaked in oxalic acid for 60 hours. However, it is recommendable to soak in 0.25M oxalic acid for one to three hours because most iron stains were disappeared in 3 hours soaking. Citric acid is less effective than oxalic acid in removing iron stains because of heavy molecular weight and low acidity. Poultices (bentonite, sepiolite, activated carbon fiber and celite) with oxalic acid were applied on contaminated ceramics. After ten hours, iron stains on ceramics were removed successfully by poultice. Among them, bentonite and sepiolite have better application. Therefore, sepiolite with 0.25M oxalic acid was applied on the iron stains of whiteware and celadon from Ma Island, and then stains were removed. However, it is judged that the application methods can be varied according to the form and depth of contaminant. In addition, the residues of poultice on the ceramics will be considered for preventing contamination.