• Journal of Surface Science and Engineering
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• v.54 no.1
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• pp.12-17
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• 2021

Among the various precious metals, silver is used in various fields because of its low price than other precious metals. However, the surface of silver remains after rain in the atmosphere containing sulfur ions and chlorine ions, causing silver corrosion and discoloration. Existing documents have developed a anode to prevent corrosion but that are concentrated on secondary batteries. This study tried to prevent corrosion and discoloration of silver by using an Al sacrificial anode. Sulfuric acid decreased the potential of silver and increased the current density at active polarization and OCP. The amount of corrosion of silver with the Al sacrificial anode was reduced from 0.5 % to 6.5%. When silver is used for decoration outside, corrosion and discoloration of silver can be suppressed by installing an Al anode.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.412-425
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• 2021

Because austenitic stainless steel causes localized corrosion such as pitting and crevice corrosion in environments containing chlorine, corrosion resistance is improved by surface treatment or changes of the alloy element content. Accordingly, research using cyclic potentiodynamic polarization experiment to evaluate the properties of the passivation film of super austenitic stainless steel that improved corrosion resistance is being actively conducted. In this investigation, the electrochemical properties of austenitic stainless steel and super austenitic stainless steel were compared and analyzed through cyclic potentiodynamic polarization experiment with varying temperatures. Repassivation properties were not observed in austenitic stainless steels at all temperature conditions, but super austenitic stainless steels exhibited repassivation behaviors at all temperatures. This is expressed as α values using a relational formula comparing the localized corrosion rate and general corrosion rate. As the α values of UNS S31603 decreased with temperature, the tendency of general corrosion was expected to be higher, and the α value of UNS N08367 increased with increasing temperatures, so it is considered that the tendency of localized corrosion was dominant.

• Journal of Environmental Science International
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• v.30 no.7
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• pp.537-545
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• 2021

This study aimed to investigate the improvement effect of 5% (w/w) mung bean (Phaseolus aureus L.) on lipid composition and protein concentration in hyperlipidemic rats. Seven-week-old male (Sprague-Dawley) rats were divided into four groups (n=6, each), and fed experimental diets containing mung bean meal [basal diet+5% (w/w) mung bean (BM), basal-hyperlipidemic diet+5% (w/w) mung bean (BHM)], basal-hyperlipidemic diet (BH), and control (basal diet, BD). Lipid composition in the mung bean diet groups (BM and BHM) evidenced significant reductions in serum total cholesterol, low-density lipoprotein cholesterol, atherosclerotic index, cardiac risk factor, triglyceride, phospholipid, free cholesterol, cholesteryl ester, blood glucose, nonesterified fatty acid, and an elevation in high-density lipoprotein cholesterol. The serum albumin/globulin ratio was increased in mung bean diet-supplemented rats compared to that in hyperlipidemic rats (p < 0.05). Total calcium, phosphorus and potassium concentrations in sera were higher in the BM, BHM and BD groups than in the BH group. Concentrations of sodium and chlorine in sera were lower in the mung bean diet-supplemented groups than in the hyperlipidemic group. The in vivo experiments showed that ingestion of mung bean was effective in improving lipid composition, protein concentration, and blood glucose.

• Journal of Korean Society of Water and Wastewater
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• v.36 no.5
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• pp.249-260
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• 2022

The effect of permanganate oxidation was investigated as water treatment strategy with a focus on comparing the reaction characteristics of NaOCl and sodium permanganate (NaMnO₄) in algae (Monoraphidium sp., Micractinium inermum, Microcystis aeruginosa)-contained water. Flow cytometry explained that chlorine exposure easily damaged algae cells. Damaged algae cells release intracellular organic matter, which increases the concentration of organic matter in the water, which is higher than by NaMnO₄. The oxidation reaction resulted in the release of toxin (microcystin-LR, MC-LR) in water, and the reaction of algal organic matter with NaOCl resulted in trihalomethanes (THMs) concentration increase. The oxidation results by NaMnO₄ significantly improved the concentration reduction of THMs and MC-LR. Therefore, this study suggests that NaMnO₄ is effective as a pre-oxidant for reducing algae damage and byproducts in water treatment process.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.61-69
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• 2022

The function of coolant in machining is to reduce the frictional force in the contact area in between the tool and the material, and to increase the precision by cooling the work-piece and the tool, to make the machining surface uniform, and to extend the tool life. However, cutting oil is harmful to the human body because it uses chlorine-based extreme pressure additives to cause environmental pollutants. In this study, the effect of cutting temperature and surface roughness of titanium alloy for medical purpose (Ti-6Al-7Nb) in eco-friendly ADL slot shape machining was investigated using the response surface analysis method. As the design of the experiment, three levels of cutting speed, feed rate, and depth of cut were designed and the experiment was conducted using the central composite planning method. The regression expressions of cutting temperature and surface roughness were respectively obtained as quadratic functions to obtain the minimum value and optimal cutting conditions. The values from this formula and the experimental values were compared. As a result, this study makes and establishes the basis to prevent environmental pollution caused by the use of coolant and to replace it with ADL (Aerosol Dry Lubricant) machining that uses a very small amount of vegetable oil with high pressure.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.6
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• pp.912-917
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• 2011

The sterilization efficacies of various washing solutions on the surfaces of vegetables such as sesame leaves, lettuce, and mini-cabbage were investigated. The washing solutions were tap water (TW), microbubble water (MB), electrolyzed water (EW), and microbubble electrolyzed water (MB＋EW). After Escherichia coli and Bacillus cereus were artificially inoculated onto the surfaces of vegetables, each vegetable was washed for 1, 3, and 5 min with TW, MB, EW 100 (100 mg/L of available chlorine), EW 200 (200 mg/L of available chlorine), MB+EW 100, and MB＋EW 200. The washing efficacy of MB was slightly higher than that of TW, and EW was more effective than MB (p<0.05). In all instances, the sterilization efficacies of MB+EW 100 and MB+EW 200 were higher than those of EW 100 and EW 200 (p<0.05). Thus, MB+EW offers an effective means of reducing the studied microorganisms in a short time period. The MB＋EW washing method provides microbial reduction on the surfaces of various vegetables and enhances the microbiological safety of the vegetables.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.9
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• pp.1265-1270
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• 2009

Pathogens contaminated on the surface of utensils could contribute to the occurrence of outbreaks due to cross-contamination to foods during the food preparation process. Therefore, the efficacy of chemical sanitizers (chlorine-based and alcohol-based commercial sanitizers) and dry-heat ($71^{\circ}C$) on inhibiting biofilms of five foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus) on the surface of stainless steel and polypropylene were investigated in this study. Initial populations of pathogens were 8.8$\sim$9.3 and 9.4$\sim$10.3 log CFU/coupon on the surface of stainless steel and polypropylene coupon, respectively, and these populations were not significantly reduced when they were treated with water for 5 min at room temperature. Treatments with chlorine sanitizer and dry-heat were not effective on inactivating pathogens on the surfaces of stainless steel and polypropylene. In contrast, treatments with alcohol sanitizer were very effective on inactivating pathogens on the surfaced of stainless steel and polypropylene. Reduction levels ranged from 3.4 to 6.4 log and from 5.5 to 7.4 log CFU/coupon in stainless steel and plastic coupons, respectively. From these results, alcohol-based sanitizer could be used as a potential way for controlling microbial contamination on the surface of utensils, cooking equipment, and other related environments.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.216-221
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• 2017

Diesel engines have the highest brake thermal efficiency among internal combustion engines. Therefore, they are utilized in medium and large transportation vehicles requiring large amounts of power such as heavy trucks, ships, power generation systems, etc. However, diesel engines have a disadvantage of generating large quantities of nitrogen oxides during the combustion process. Therefore, the authors tried to reduce the amount of nitrogen oxides in marine diesel engines using a wet-type exhaust gas cleaning system utilizing the undivided electrolyzed seawater method. In this method, electrolyzed seawater in injected into the harmful gas discharge from the diesel engine using real seawater. The authors investigated the reduction of NO and NOx from the pH value, available chlorine concentration, and the temperature of electrolyzed seawater. The results of this experiment indicated that when the electrolyzed seawater is acidic, the NO oxidation rate in the oxidation tower is higher than that when the electrolyzed seawater has a neutral pH. Likewise, the NO oxidation rate increased with the increase in concentration of chlorine. Further, it was confirmed that the electrolyzed seawater temperature had no effect on the NO oxidation rate. Thus, the NOx exhaust emission value produced by the diesel engine was reduced by means of electrolyzed seawater treatment.

• Clean Technology
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• v.24 no.4
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• pp.339-347
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• 2018

In order to cope with environmental problems and climate change caused by fossil fuels, renewable energy supply is increasing year by year. Currently, waste energy accounts for 60% of renewable energy production. However, waste has a lower calorific value than fossil fuels and contains various harmful substances, which causes serious problems when applied to power generation boilers. In particular, the chlorine in the waste fuel increases slagging and fouling of boiler heat exchangers, leading to a reduction in thermal efficiency and the main cause of high temperature corrosion, lowering facility operation rate and increasing operating cost. In this study, the high temperature corrosion experiments of superheater materials (ASME SA213/ASTM A213 T2, T12 and T22 alloy steel) by alkali chlorides were conducted, and their corrosion characteristics were analyzed by the weight loss method and SEM-EDS. Experiments show that the higher the temperature and chloride content, the more corrosion occurs, and KCl further corrodes the materials compared to NaCl under the same condition. In addition, the higher the chromium content of the material, the better the corrosion resistance to the alkali chlorides.

• Journal of the Society of Disaster Information
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• v.18 no.2
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• pp.306-313
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• 2022

Purpose: The purpose of this study is suggested to improve upon current existing methods of ammonia chemical accident prevention and damage reduction. Method: Ammonia is one of the most common toxic substances that causes frequent chemical accidents. And it was selected as leakage materials according to statistics on chemical accident. Based on actual cases of chemical accidents, CARIS modeling was used to compare the damage impact range of Ammonia and HCl and Cl. Also, find out problems with the current systems. Result: As a result of find out the range of accident influence that spreads to the surroundings when an ammonia chemical accident, it was longer than the range of influence of hydrochloric acid and shorter than that of chlorine. In addition, it was found that when chemical accident by ammonia, hydrochloric acid, or chlorine, there are apartments and schools, which can have an effect. Conclusion: It is decided that it is necessary to determine whether or not chemical accident prevention management plans and statistical investigations are submitted for workplaces dealing with ammonia, and detailed guidelines and reviews are necessary. In addition, it is judged that it is necessary to establish a DB for ammonia handling plants, and it is considered that information sharing and joint inspection among related organizations should be pursued.