• Fire Science and Engineering
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• v.28 no.6
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• pp.108-113
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• 2014

The combined process of Sliding Arc Plasma and corona dielectric barrier discharge process (CDBD) was used to efficiently improve harmful substance, which convert into OH radicals which have strong oxidation potential, and so have deodorization and sterilizing effects, by generating specific radicals and anion and then reacting with the moisture contained in harmful substance. As a result of experiment, even if the size of SAP reactor is reduced from 80 A to 50 A, there is no much change and therefore it is judged the size of reactor may be minimized. And it was confirmed that after the anion and ozone generated from CDBD rector react with harmful substance, a anion was reduced from 510,000 ppb to 470 ppb and ozone from 98 ppb to 22 ppb. It was also judged the stability and durability of plasma producer are excellent. Accordingly, it is considered the harmful substances which exist in indoor air quality will be efficiently improved and removed by using further plasma combined process through this study.

• Membrane Journal
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• v.21 no.2
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• pp.118-126
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• 2011

A method of light pre-irradiation, one of methods modifying hydrophobic surface to hydrophilic surface in a membrane, was proposed to overcome the drawback of previous methods such as blending, chemical treatment and post-irradiation, Process of membrane preparation in the study was comprised of 4 parts as follows: firstly process of precursor preparation to introduce hydrophilic nature under atmosphere and aqueous vapor by irradiating electron beam (EB), secondly process of dope solution preparation to cast on non-woven fabrics, thirdly process of casting to prepare membrane and finally process of coagulation in non-solvent to form porous structure. The merit of this method might show simple process as well as homogenous modification compared to previous methods. To carry it out, precursor was prepared by irradiating EB to powder PVDF at 75~125 K Gray dose. Precursor prepared was analyzed by FTIR, EDS and DSC to confirm the introduction of hydrophilic function and its mechanism. From their results, it was inferred I conformed that hydrophilic function was hydroxy1 and it was introduced by dehydrozenation. Hydrophilicity of membranes prepared was evaluated by contact angle (pristine PVDF : $62^{\circ}$, 125 K Gray-PVDF$13^{\circ}$). Porosity was evaluated by mercury intrusion method, simultaneously morpholoy and surface pore size were observed by SEM phothographs. The result showed the trend that more dose of EB led to smaller pore size and to lower porosity (pristine PVDF : 82%, 125 K Gray-PVDF : 63%). Trend of water permeability was similar to result above (pristine PVDF : 892 LMH, 125 K Gray-PVDF : 355 LMH).

• Korean Chemical Engineering Research
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• v.44 no.2
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• pp.216-226
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• 2006

Total trihalomethanes (THMs), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) that are the major disinfection byproducts (DBPs) are monitored continuously in drinking water in Seoul. Study on characteristics of DBPs is crucial to judge the safety of drinking water in Seoul. Analysis of THMs, haloacetonitriles (HANs), chloral hydrate (CH), and haloacetic acids (HAAs) was carried out in several distribution systems from January 2002 to December 2004. The concentration of THMs was 0.015 mg/L in purified water, 0.019 mg/L in tapwater by direct service, and 0.023 mg/L in tapwater through watertank, respectively. It might be due to the increased contact time with chlorine by a process of the distribution system. And the other DBPs show a tendency to increase in its concentration by a process of the distribution system. Also, in summer, the concentration of DBPs was higher than in spring and winter. It might be due to the higher temperature of water in summer. In all cases, the quantities of detected DBPs were 4-6 times lower than those of regulation limits of drinking water in Seoul. In view of these results, the tapwater in Seoul is good to drink it all the times.

• Korean Journal of Food Science and Technology
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• v.46 no.4
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• pp.432-437
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• 2014

This study was carried out to examine the quality properties of honey in Korean commercial markets. The moisture content, stable carbon isotope ratio, invert sugar, cane sugar, and hydroxy-methylfurfural (HMF) contents of honey were measured according to the Korea Food Code and AOAC's (Association of Official Analytical Chemists) official methods. The stable carbon isotope ratio ranged from -25.18‰ to -12.60‰, which clearly differed between honey of $C_3$ origin (flower) and $C_4$ origin (artificial). Results of quality measurements revealed a moisture content of 18.12 to 19.70%, fructose content of 36.10 to 43.94%, glucose content of 22.61 to 31.91%, sucrose content of 1.56 to 4.75%, invert sugar content of 64.89 to 72.79%, and HMF content of 4.10 to 78.66 mg/kg. These values demonstrate that the quality of the tested honey meets the standard criteria of the Korean Food Code and Codex. However, it is necessary to reconsider the appropriate criteria for imported honey because it is circulated in the market through a long distribution process.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.2
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• pp.194-199
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• 2024

Accidents due to aircraft fuel defects rank in the top 13 of the 34 accident types described by CAST-ICAO Common Taxonomy Team(CICTT). Aircraft accidents occur because of the inflow of moisture or pollutants depending on the distribution process and storage environment. To confirm the change in physical properties of the aircraft oil stored for a long time, we stored JET A-1 aircraft oil in a metal can to observe the change after six months. We confirmed that the aircraft oil stored for a long time satisfied the quality standards, and the stability of the fuel oil was high. However, in scenarios in which aircraft oil is stored separately on ships, onshore storage facilities, oil fields, etc., owing to the nature of missions, such as in marine police aircraft, the inflow of moisture or pollutants may likely occur due to changes in the internal and external environment. In addition, pollutants can be analyzed using existing tests and distillation properties, but for moisture, domestic and international standards and domestic laws determine the moisture separation ability of aircraft oil through the water separation index, but the moisture content is not analyzed. Therefore, aviation safety must be secured by adding quality control standards for moisture content and performing revisions to uniformize domestic and international standards and laws.

• Journal of the Korean Institute of Gas
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• v.21 no.4
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• pp.84-91
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• 2017

Recent years have witnessed the increased usage of flammable metals, such as aluminum or magnesium, in wide range of high-tech industries. These metals are indispensable for the improvement of physical properties of materials as well as the design capability of the final product. During the process, unwanted metal dusts could be released to the environment. This can lead to an occupational health and safety issues. Due to their flammable nature, more serious problem of an explosion can happen in extreme cases. The explosion is the combustion of tiny solid particles and vapor mixture, caused by pyrolysis. This complex composition makes engineering analysis more difficult, compared to simple gas explosions or vapor cloud combustions. The study was conducted to assess this light metal dust explosion in an effort to provide the bases for a risk assessment. Dust explosion characteristics of each material was carefully evaluated and an appropriate analysis tool was developed. A comprehensive database was also constructed and utilized for the calibration of the developed response model and the verification for its accuracy. Subsequently, guidelines were provided to prevent dust explosions that could occur in top-notch industrial processes.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.38-41
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• 2008

In this research, we propose a new method for tracking the release rate using the concentration data obtained from the sensor. We used a sensor network that has already been set surrounding the area where hazardous gas releases can occur. From the real-time sensor data, we detected and analyzed releases of harmful materials and their concentrations. Based on the results, the release rate is estimated using the neural network. This model consists of 14 input variables (sensor data, material properties, process information, meteorological conditions) and one output (release rate). The dispersion model then performs the simulation of the expected dispersion consequence by combining the sensor data, GIS data and the diagnostic result of the source term. The result of this study will improve the safety-concerns of residents living next to storage facilities containing hazardous materials by providing the enhanced emergency response plan and monitoring system for toxic gas releases.

• Fire Science and Engineering
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• v.32 no.6
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• pp.108-116
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• 2018

A melted bead microstructure can be divided into a deformed and undeformed layer. Measurement errors occur in the presence of a deformed layer, which should be removed through grinding/polishing whilst preserving the original structure. This paper proposes a grinding/polishing process to analyze the microstructure of copper melted beads. For the removal of the deformed layer, the correlation between the abrasive type/size, the polishing time and polishing rate was analyzed and the thickness of the deformed layer was less than $1{\mu}m$. The results suggest a new grinding/polishing procedure: silicon carbide abrasive $15{\mu}m$ (SiC P1200) 2 min, and $10{\mu}m$ (SiC P2400) 1 min; and diamond abrasive $6{\mu}m$ 8 min, $3{\mu}m$ 6 min, $1{\mu}m$ 10 min, and $0.25{\mu}m$ 8 min. In addition, a method of increasing the sharpness of the microstructure by chemical polishing with $0.04{\mu}m$ colloidal silica for 3 min at the final stage is also proposed. The overall grinding/polishing time is 38 min, which is shorter than that of the conventional procedure.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.5
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• pp.612-617
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• 2009

Fresh vegetable juice is a non-heat treated product and the only step to reduce microbial growth is washing. Therefore, the materials for fresh vegetable juice including Angelica keiskei, Brassica loeracea var. acephala, and Daucus carota L. were treated by ozone after the first washing process and investigated for microbial and chemical changes. The number of the total aerobic bacteria in materials after selection step were $8.2{\times}10^5{\sim}5.0{\times}10^6\;CFU/g$, which was a higher contamination level than the limit of Korea food code ($10^5\;CFU/g$). However, after the 1st washing process and ozone treatment, the total aerobic bacterial number was reduced to $4.7{\times}10^4{\sim}6.7{\times}10^4\;CFU/g$, which showed 2 log microbial reduction. After the 2nd washing step followed by ozone treatment, there was no difference in microbial number. The number of colifroms in the materials of fresh vegetable juice were $8.0{\times}10^3{\sim}3.5{\times}10^3\;CFU/g$ initially but showed $1.5{\times}10^2{\sim}3.0{\times}10^2\;CFU/g$ after the ozone treatment (1 log reduction). On the other hand, there was no changes in the contents of ascorbic acid, flavonoids, polyphenols, minerals (cadmium and lead) during all processes. In addition, no color changes were observed during washing process. Therefore, ozone treatment in the materials of fresh vegetable juice decreased the microbial numbers. Also, chemical characteristics of ozone treated sample were not different when compared with control.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.126-132
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• 2016

This study numerically investigates the characteristics of chemical reactions and thermal deformation in a steam reformer. These phenomena are significantly affected by the high-temperature burner gas and the process gas conditions. Because the high temperature of the burner gas ranges from 800 to 1000 K, the reformer tubes undergo substantial thermal deformation, eventually resulting in structural failure. Thus, it is necessary to understand the characteristics of the reaction and thermal deformation under the operating conditions to evaluate the reformer tubes for sustainable, stable operation. Extensive numerical simulations were carried out using commercial CFD code (ANSYS FLUENT/MECHANICA Ver. 13.0) while considering three-dimensional turbulent flows and combined heat transfer including conduction, convection, and radiation. Structural analysis considering conjugated heat transfer between solid tubes and fluid flows was conducted using the Fluid-Solid Interaction (FSI) method. The results show that when the injection temperature of the process gas and burner gas decreased, the hydrogen production rate decreased significantly, and thermal deformation decreased by at least 15 to 20%.