• Korean Journal of Veterinary Research
• /
• v.44 no.4
• /
• pp.593-605
• /
• 2004

An egg has been considered as one of the most important food sources because of it's nutritional superiority and reasonable price. With the complexity of egg flow system from production to consumption in Korea, preventive measures for egg safety have been required. Therefore, our study was carried out to analyze hazards for the egg under farm level and develope preventive measures with a purpose of obtaining egg safety. To analyze biological hazards, microbial contamination of egg(normal, dirty and cracked), water, feed, manure and equipments associated with laying were investigated. One isolate of Salmonella enteritidis and S. bardo were detected from the manure and dirty egg shell respectively. The sanitary conditions in the farm were surveyed by questionaries. Confirmation of vaccination for purchasing chicks and establishment of sanitary guidances for water and type of water suppliers ought to be preceded. Feed supplier systems including feed tanks, feed pipes and hoppers were known that their contamination might give it a chance to infect individuals and egg content and shell. The safe and rapid disposal of dead chickens and rodent were reported as more crucial factors to prevent infectious disease and manage good sanitation. Egg selector and collecting belt should be kept properly not to be contaminated from egg fluids and feces. It should be also considered that regular gathering of eggs, removal of dirty or cracked ones, storage under refrigeration and the use of disposable egg tray were continuously fulfilled. Conclusively, Our results suggested that HACCP-based system for providing fresh and safe eggs to consumers should be applied to the farm.

• Korean Journal of Materials Research
• /
• v.9 no.12
• /
• pp.1188-1195
• /
• 1999

The effect of aluminosilicate sol on the formation of mullite layer in zircon shell mold was investigated. Aluminosilicate sol was prepared by mixing of colloidal silica(NALCO(R) 1130) and an aqueous solution of aluminium nitrate at room temperature. The sol gelled at 50$^{\circ}C$ for 48 hrs. It was identified that the gel consists of aluminosilicate complexes and gibbsite. The coordination number of all aluminium ion bonded with silicon ion was four. Mullite phase formed by sintering above 1300$^{\circ}C$. XRD peak of mullite sharpened with increasing sintering temperature and the content of aluminium nitrate. Mullite phase displayed whisker-like 0.5~5${\mu}m $ particles. Separation between 1st and 3rd layers during sintering and the difference in thermal expansion coefficient between residual silica and mullite.

• Korean Journal of Materials Research
• /
• v.18 no.10
• /
• pp.535-541
• /
• 2008

Growth behavior of InGaN/GaN self-assembled quantum dots (QDs) was investigated with respect to different growth parameters in low pressure metalorganic chemical vapor deposition. Locally formed examples of three dimensional InGaN islands were confirmed from the surface observation image with increasing indium source ratio and growth time. The InGaN/GaN QDs were formed in Stranski-Krastanow (SK) growth mode by the continuous supply of metalorganic (MO) sources, whereas they were formed in the Volmer-Weber (V-W) growth mode by the periodic interruption of the MO sources. High density InGaN QDs with $1{\sim}2nm$ height and $40{\sim}50nm$ diameter were formed by the S-K growth mode. Dome shape InGaN dots with $200{\sim}400nm$ diameter were formed by the V-W growth mode. InN content in InGaN QDs was estimated to be reduced with the increase of growth temperature. A strong peak between 420-460 nm (2.96-2.70 eV) was observed for the InGaN QDs grown by S-K growth mode in photoluminescence spectrum together with the GaN buffer layer peak at 362.2 nm (3.41 eV).

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.110-112
• /
• 2006

Membrane electrode assembly (MEA) for polymer electrolyte fuel cell (PEFC) are commonly prepared in the research laboratory by spraying, screen-printing and brushing catalyst slurry onto membrane or other support material like carbon paper or polyimide film in a batch style. These hand applications of the catalyst slurry are painstaking process with respect to precision of catalyst loading and reproducibility. It has been generally mentioned that the adoption of continuous process is very helpful to develop the reliable product. In the present work, we report the results of using continuous type coater with doctor-blade to coat catalyst slurry for preparing the MEA catalyst layers In a faster and highly reproducible fashion. We show that while expectedly faster than batch style, the machine coater requires the use of slurry of appropriate composition and a properly selected transfer decal material in order to achieve superior MEA plat lnw loading reproducibility. To make highly viscous catalyst slurry that is imperative for using coater, we use 40wt.% Nafion solution and minimize the content of organic solvent. And the choice of proper high surface area catalyst is important in the viewpoint of making well-dispersed slurry. After catalyst coating onto the support material, we transferred the catalyst layer to both sides of Nafion membrane by hot-pressing In this case, the degree of transfer was Influenced by hot-pressing condition including temperature, pressure, and time. To compare the transferring ability, we compared so many films and detaching papers. And among the support, polyethylene terephthalate(PET) film shows the prominent result.

• Korean Journal of Food Science and Technology
• /
• v.9 no.1
• /
• pp.24-30
• /
• 1977

The patterns of ginseng saponins in the commercial ginseng tea samples and each parts of ginseng plant were investigated by quantitative thin-layer chromatography. The quality of those sample teas were also evaluated. (1) White ginseng contained about $2.6{\sim}6.6$ times of Ra(o) than did other parts of ginseng. (2) Lateral roots, peelings and buds of ginseng were rich in $Rb_1$, $b_2$, c, which constituted about 50% of total saponin. (3) The ratio of Rb.c to Rg(f) in the leaves and stems of ginseng plant was 0.64 : 1. (White ginseng, 2 : 1 ; buds, 3 : 1 ; flower, 3.2 : 1 ; peelings, 5.8 : 1 ; lateral ginseng, 7 : 1) The relative content of Rg(f) in the white ginseng was about 3 times as much as the lateral ginseng. (4) The ratios of panaxadiol to panaxatriol in 13 kinds of commercial ginseng teas were in the range of $0.8{\sim}8\;:\;1$.

• Korean Journal of Food Science and Technology
• /
• v.9 no.1
• /
• pp.73-80
• /
• 1977

In order to detect the occurrence of aflatoxins in some suspecious Korean foodstuffs, 54 samples of Meju (a naturally inoculated soybean substrate for soy sauce and paste fermentation), 125 samples of Doenjang (a Korean-style fermented soybean paste), both produced at household level, and 31 samples of peanut were collected from 8 major cities of South Korea and subjected to assay by the official method of AOAC. The results were as follows: 1) Frequencies for the occurrence of aflatoxins in Meju, Doenjang and peanut were 7.4%(4/54), 8.8%(11/125) and none (0/31), respectively, in which Meju and Doenjang samples from Daegu and Busan showed the high ratio of the presence. 2) A Doenjang sample from Busan was found to contain the highest content of aflatoxins, of which $B_1,\;B_2,\;G_1\;and\;G_2$ were 66 ppb, 13 ppb, non-detectable and 5 ppb, respectively, while other samples detected were for $G_2$ only. 3) The identity of aflatoxin $B_1$ isolated from the Doenjang sample from Busan was confirmed by thin-layer chromatographic behavior, derivative formation and chicken embryo bioassay.

• Journal of Surface Science and Engineering
• /
• v.44 no.3
• /
• pp.117-123
• /
• 2011

We investigated the spectroscopic and electrochemical properties of the citrate-based CuNi solution at different solution pH and analyzed various surface properties of CuNi codeposition layer. By combining UV-Visible spectroscopic data with potentiodynamic polarization curves, it could be found that the complexation of $Ni^{2+}$-citrate pair was completed at lower solution pH than $Cu^{2+}$-citrate pair and was affected by the coexistent $Cu^{2+}$ ions, while the complexation between $Cu^{2+}$ ions and citrate was not sensitive to the presence of $Ni^{2+}$ ions. Also, the electron transfer from cathode to $Cu^{2+}$-citrate and$Ni^{2+}$-citrate was hindered by strong complexation between $Cu^{2+}/Ni^{2+}$ ions and citrate and so apparent codeposition current densities were reduced as the solution pH increases. CuNi codeposited layers had a higher Cu content when they were prepared at high pH solution due to the suppression of Ni deposition, and when codeposition was executed in an agitated condition due to the acceleration of mass transfer of $Cu^{2+}$ ions in the solution. Actually, solution pH had little effect on the surface morphology and deposits orientation, but greatly influenced the corrosion resistance in 3.5% NaCl solution by modifying the chemical composition of CuNi layers and so pH 3 was expected as the most suitable solution pH in the viewpoint of corrosion coatings.

• Korean Journal of Microbiology
• /
• v.53 no.4
• /
• pp.320-322
• /
• 2017

A betaproteobacterium strain GR16-43 was isolated from a surface layer of the Geomnyong Pond in Republic of Korea by a dilution-to-extinction culturing method. We report the whole genome sequence of the strain GR16-43, which contains 4,806,848 bp with a G + C content 67.12%, and to include 4,424 protein-coding genes and 47 transfer RNA genes. The genome was determined to contain the genes encoding carbon monoxide dehydrogenase, nitrate reductase, nitrite reductase, nitric oxide reductase, and the sulfur oxidation (sox) gene cluster, highlighting the potential importance of the bacterial group represented by the strain in the cycling of inorganic elements. These results indicate that strain GR16-43 genome showed several traits indicating adaptation of the bacteria to living in freshwater environments.

• Journal of Powder Materials
• /
• v.26 no.5
• /
• pp.421-431
• /
• 2019

In this study, the formation, microstructure, and wear properties of Colmonoy 88 (Ni-17W-15Cr-3B-4Si wt.%) + Stellite 1 (Co-32Cr-17W wt.%) coating layers fabricated by high-velocity oxygen fuel (HVOF) spraying are investigated. Colmonoy 88 and Stellite 1 powders were mixed at a ratio of 1:0 and 5:5 vol.%. HVOF sprayed self-fluxing composite coating layers were fabricated using the mixed powder feedstocks. The microstructures and wear properties of the composite coating layers are controlled via a high-frequency heat treatment. The two coating layers are composed of ${\gamma}-Ni$, $Ni_3B$, $W_2B$, and $Cr_{23}C_6$ phases. Co peaks are detected after the addition of Stellite 1 powder. Moreover, the WCrB2 hard phase is detected in all coating layers after the high-frequency heat treatment. Porosities were changed from 0.44% (Colmonoy 88) to 3.89% (Colmonoy 88 + ST#1) as the content of Stellite 1 powder increased. And porosity is denoted as 0.3% or less by inducing high-frequency heat treatment. The wear results confirm that the wear property significantly improves after the high-frequency heat treatment, because of the presence of well-controlled defects in the coating layers. The wear surfaces of the coated layers are observed and a wear mechanism for the Ni-based self-fluxing composite coating layers is proposed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.459-462
• /
• 2008

In manufacture of slurry fuel, the effects of process parameters on the carbon dispersion stability have been investigated. The particle size and contents of the carbon slurry taken from 3 (top, medium, bottom) positions in fuel reservoir were analyzed to estimate the dispersion of the carbon in Jet A-1. Through the application of various additives, it was found that NB463S84 additive showed the best dispersion and stability of carbon at accelerated gravity condition. The mixer performance was compared by the observation of height change of carbon-containing layer and measurement of particle sizes at the same conditions. Application of the mixing conditions obtained from the lab-scale to bench scale manufacture confirmed the practical feasibility of our research.