• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.2
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• pp.223-232
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• 1997

The accuracy and precision of a modified method of NIOSH Method 7600 and EPA method 218.6 was determined for analyzing hexavalent chromium, Cr(VI), collected on PVC filter from workplace air. The method was designed to extract from Cr(VI) on PVC filter with a alkali solution, 2% NaOH/3% $Na_2CO_3$, and to analyze it using ion chromatography/visible absorbance detection(IC/VAD). The results and conclusion are as the following. 1. The peak of Cr(VI) was separated sharply on chromatogram and was linearly related with Cr(VI) concentration in sloution. The correlation coefficient was 0.9999 in a calibration curve. The limit of detection was 0.25 $0.25{\mu}g/sample$. 2. The accuracy(% recovery) was 93.3% in a set of sample($9-50{\mu}g$) stored for a day, and 100.1%($10-60{\mu}g$) in another set of samples stored for 2 hours. It is assumed that the difference in recovery by storage time was due to reduction of Cr(VI) to Cr(III). 3. The precision(coefficient of variation, CV) of the method was 0.015 in spiked samples with Cr(VI) standard solution, and 0.010 in spiked samples with plating solution from a chrome electroplating factory. The overall CV in all types of samples was 0.0013. 4. The Cr(VI) was stable in 2% NaOH/3% $Na_2CO_3$ at least for 10 hours. In conclusion, the IC/VAD method is appropriate for determining low-level Cr(VI) in workplace air containing various interferences.

• KIEAE Journal
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• v.13 no.5
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• pp.43-50
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• 2013

Recent researches on plant factory system deal with the convergence of lighting technology, agricultural technology inclusive to the high-tech industries worldwide in order to respond to the decreasing crop harvest due to global warming and abnormal weather phenomena. However, the fundamental performance standard is not currently being introduced in the case of plants factory and its commercialization is not activated because of high initial investment and operating cost. Large portion of the initial investment and operating cost of a plant factory is ascribed to artificial light sources and thermal control facilities, therefore, innovation should be provided in order to improve the economics of the plant factory. As an alternative, new plant factory could harness solar thermal and geothermal systems for heating, cooling and ventilation. In this study, a natural light dependent multi-layer plant factory's thermal environment was analyzed with two-dimensional numerical methods to elicit efficient operation conditions for optimized internal physical environment. Depending on the supply air temperature and airflow rate introduced in the facility, the temperature changes around the crops was interpreted. Since the air supplied into the plant factory does not stay long enough, the ambient temperature predicted around the plating trays was not significantly different from that of the supplied air. However, the changes of airflow rate and air flow pattern could cause difference to the temperature around the planting trays. Increasing the amount of time of air staying around the planting trays could improve energy performance in case the thermal environment of a natural light based multi-layer plant factory is considered.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.196-197
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• 2005

Cathodic protection is one of the successful ways to prevent corrosion of steel structures in marine environments. The unique feature of cathodic protection in seawater is the formation of calcareous deposits on cathodic metal surface. The formation principles of calcareous deposit seawater had been known for a long time. That is, cathodic reduction reactions associated with cathodic protection in seawater generate $OH^-$ at the metal surface in accordance with the formular ; 1/2 $O_2$ + $H_2O$ + $2e^-$ $2OH^-$ and $2H_2O$ + $2e^-$ ${\rightarrow}$ $H_2$ + $2OH^-$. These reactions increase the pH at the metal / seawater interface. The high pH causes precipitation of $Mg(OH)_2$ and $CaCO_3$ in accordance with the formular ; $Mg^{2+}$ + $2(OH)^-$ ${\rightarrow}$ $Mg(OH)_2$ and $Ca^{2+}$ + $HCO_3^-$ + $OH^-$ ${\rightarrow}$ $H_2O$ + $CaCO_3$. These are typically the main compounds in calcareous deposits. It obviously has several advantages compared to the conventional coatings, since the environment-friendly calcareous deposit coating is formed by the elements($Mg^{2+}$, $Ca^{2+}$) naturally present in seawater. In this study, environmental friendly calcareous deposit films were prepared on steel plates by electro plating technic in natural seawater. The influence of current density on composition ratio, structure and morphology of the coated films were investigated by scanning electron microscopy formation process of calcareous deposits films in natural seawater. And we confirmed the properties of all the films can be improved greatly by controlling the material structure and morphology with effective use of the electroplating method in natural seawater.

• Korean journal of applied entomology
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• v.10 no.1
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• pp.7-12
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• 1971

1. The number of Rhizoctonia solani, Pythium debaryanum, Fusarium and Trichoderma was detected by the modification of Boosails special plating method when ginseng seed bed was drenched with Captan, Difolatan, Zineb, Maneb and PCNB at weekly intervals. Pythium debaryanum Hesse was described for the first time on Panax ginseng in Korea. 2. The number of Rhizoctonia solani and Pythium debaryanum was decreased gradually as the geason Progressed, whereas that of Fusarium and rrichcderma was increased. 3, The number of Rhixoctonia solani was greatly reduced by PCNB, and soils treated with other fungicides generally showed less Rhizoctonie solani than in the control. The number of Pythium debaryanum was significantly reduced by Zineb, Maneb, followed by Captan and Difolatan. None of the fungicids reduced the number of Fusarium colonies in the fourth week. Effects of the chemicals on Trichoderma were not statistically significant. 4. More fresh weight of the seedling roots was obtained using Difolatan, Maneb and PCNB. Phytotoxicity was noted with Maneb, Zineb and Captan after the third treatment.

• Food Science of Animal Resources
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• v.35 no.1
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• pp.108-113
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• 2015

The purpose of this study was to develop predictive models for the growth of Listeria monocytogenes in pork Bulgogi at various storage temperatures. A two-strain mixture of L. monocytogenes (ATCC 15313 and isolated from pork Bulgogi) was inoculated on pork Bulgogi at 3 Log CFU/g. L. monocytogenes strains were enumerated using general plating method on Listeria selective medium. The inoculated samples were stored at 5, 15, and $25^{\circ}C$ for primary models. Primary models were developed using the Baranyi model equations, and the maximum specific growth rate was shown to be dependent on storage temperature. A secondary model of growth rate as a function of storage temperature was also developed. As the storage temperature increased, the lag time (LT) values decreased dramatically and the specific growth rate of L. monocytogenes increased. The mathematically predicted growth parameters were evaluated based on the modified bias factor ($B_f$), accuracy factor ($A_f$), root mean square error (RMSE), coefficient of determination ($R^2$), and relative errors (RE). These values indicated that the developed models were reliably able to predict the growth of L. monocytogenes in pork Bulgogi. Hence, the predictive models may be used to assess microbiological hygiene in the meat supply chain as a function of storage temperature.

• Food Science of Animal Resources
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• v.34 no.2
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• pp.257-261
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• 2014

The objective of this study was to evaluate the effects of NaCl on the biofilm formations of the isolate from Staphylococcus aureus outbreaks linked to ham. The S. aureus ATCC13565 isolated from ham was exposed to NaCl concentrations of 0%, 2%, 4%, and 6% supplemented in tryptic soy broth (TSB) for 24 h at $35^{\circ}C$, followed by plating 0.1 mL of the culture on tryptic soy agar containing 0%, 2%, 4%, and 6% NaCl, respectively. After incubating at $35^{\circ}C$ for 24 h, the colonies on the plates were collected and diluted to $OD_{600}$ = 0.1. The diluents of S. aureus were incubated on a 96-well flat bottom plate containing TSB plus the appropriate NaCl concentrations, and the biofilm formation was quantified by crystal violet staining after being incubated at $35^{\circ}C$ for 9 h. Confocal laser scanning microscope (CLSM) was also used for visualizing the biofilm formation of S. aureus at NaCl concentrations of 0%, 2%, 4%, and 6%. The transcriptional analysis of biofilm-related genes, such as icaA, atl, clfA, fnbA, sarA, and rbf, was conducted by quantitative real-time PCR. Crystal violet staining and CLSM showed that the biofilm formations of S. aureus increased (p<0.05) along with the NaCl concentrations. Moreover, the expression of the icaA genes was higher at the NaCl concentrations of 4% and 6% as compared with 0% of NaCl by approximately 9-folds and 20-folds, respectively. These results indicated that the NaCl formulated in processed food may increase the biofilm formations of S. aureus by increasing the icaA gene expressions.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.27-32
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• 2011

Management of gas safety is becoming important with increasing use of gas facilities. U-safety system is being promoted as part of national management of gas, and thus real-time and in-situ gas sensor should be developed. Detection method for When the gas sensor is installed in gas conduit, explosion may be likely, because hydrocarbon gases is usually used the difference of thermal resistance between reference and working electrode. Therefore, it is required to detect the hydrocarbons, such as $CH_4$ and CO, at room temperature via electrochemically catalytic reaction. In this study, Pt nanoparticle was doped on the porous gold powder by electrolytic plating method, and then it was used as catalytic electrode for CO oxidation. For Pt/PAu electrode, approximately 21% of CO conversion was obtained. It is noted that Pt/PAu electrode could be used to react the oxidation of hydrocarbon gases at room temperature via applying of external voltage.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1892-1897
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• 2003

A new thermal inkjet printer head on SOI wafer with virtual valve was proposed. It was composed of two rectangular heaters with same size. So we could call it T-jet(Twin jet). T-jet has a lot of merits. It has the advantage of being fabricated with one wafer and is easy to change the size of chamber, nozzle, restrictor and so on. However, above all, It is the best point that T-jet has a virtual valve. And it was manufactured on SOI wafer. The chamber was formed in its upper silicon whose thickness was 40um. The chamber's bottom layer was silicon dioxide of SOI wafer and two heaters were located underneath the chamber's ceiling. And the restirctor was made beside the chamber. Nozzle was molded by process of Ni plating. Ni was 30um thick. Nozzle ejection test was performed by printer head having 56 nozzles in 2 columns with 600NPI(nozzle per inch) and black ink. It measured a drop velocity of 12m/s, a drop volume of 30pl, and a maximum firing frequency of 12KHz for single nozzle ejection. Throwing out the ink drop in whole nozzles at the same time, it was observed that the uniformity of the drop velocity and volume was less than 4%.

• Journal of Plant Biotechnology
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• v.30 no.4
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• pp.359-363
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• 2003

Mass propagation of tulip tree (Liriodendron tulipifera L) via somatic embryogenesis was successfully achieved with immature samaras collected from adult trees. Embryogenic tissues were induced by culturing them samaras on 1/2 LM medium (Litvay's) containing 2,4-D and BA. Somatic embryos developed from the embryogenic tissues and germinated to normal plants (emblings) upon transfer onto the same medium containing either AgNO$_3$ or activated charcoal. So far, several factors appeared to influence both the induction of embryogenic tissues and germination of the embryos into plants. These include the collection time of samaras for the induction of embryogenic tissue, sucrose level in the culture medium, the level of both AgNO$_3$ and activated charcoal, and plating density of somatic embryos on germination medium for maturation and germination of somatic embryos into plantlets.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.960-965
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• 1995

Hard Ti(C, N) layers of various compositions were coated on ASP30 tool steel employing a reactive HCD ion plating technique. The effect of film composition on the wear characteristics were investigated in lights of hardness, adhesion and wear mechanism. With an increase in the amount of nonmetallic component(N, C), the hardness of films increased, but the increase in carbon content resulted in poor adhesion. Within the concentration range of ([C+N]/Ti<1), these trends became mute clear than in the concentration below stoichiometry. Therefore, the wear resistance could be maximized when the film is deposited with the concentration of ([C+N]/Ti<1) for high microhardness and, at the same time, with the low carbon contents not to wear out in adhesive mode.