• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.668-673
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• 2008

The objective of this study is to optimize the leaching conditions of sequential leaching and extracting processes for selective Ni recovery from spent Ni-Mo-based catalyst. The selective Ni recovery process consists of two processes of leaching and extracting process. In this 2-step process, Ni component is dissolved from solid spent Ni-Mo-based catalyst into leaching agent in leaching process and sequentially extracted to Ni complex with an extracting agent in the extracting process. The solutions of nitric acid ($HNO_3$), ammonium carbonate ($(NH_4)_2CO_3$) and sodium carbonate ($Na_2CO_3$) were used as a leaching agent in leaching process and oxalic acid was used as an extracting agent in extracting process. $HNO_3$ solution is the most efficient leaching agent among the various leaching agent. Also, the optimized leaching conditions for the efficient and selective Ni recovery were the leaching temperature of $90^{\circ}C,\;HNO_3$ concentration of 6.25 vol% and elapsed time of 3 h. As a result, Nickel oxalate having the highest yield of 88.7% and purity of 100% was obtained after sequentially leaching and extracting processes under the optimized leaching conditions.

• Journal of environmental and Sanitary engineering
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• v.7 no.2
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• pp.1-10
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• 1992

Since 1960's along with industrialization and urbanization, economic growth has been . achieved, however, at the same time, environmental condition has been seriously deteriorated. . Currently, volume of wastewater has been increasing at annual rate of 7% in sewage and 20% in industrial wastewater. However, the nation's sewage treatment serves only 33% of the municipal wastewater as of 1991. Major portion of air pollutants comes from combustion of oil and coal which comprise 81% of total energy use and emission gases from motor vehicles increasing at an accelerated rate. It is known that Korea generates the highest amount of waste per capta. Nevertheless, it is not sufficient to reduce the volume of waste by means of resources recovery and recycling. Recognizing the importance of global environmental problems such as ozone layer depletion, global warming and acid rain, international society has been making various efforts since the 1972 Stockholm conference. In particular, it is expected that the Rio conference which has adopted the Rio declaration and Agenda 21 will form a crucial turning point of the emerging new world order after the Cold War confrontation. To cope with such issues as domestic pollution and global environmental problems, the fundamental national policy aims at harmonizing "environmental protection and sustainable development". The Ministry of Environment has recently set up a mid-term comprehensive plan which includes annual targets for environmental protection. According to the government plan, gradual improvement of various environmental conditions and specific measures to achieve them is planned in time frame. Additional sewage treatment plants will be constructed in urban areas with the target to treat 65% of the nation's municipal sewage by 1996. Supply of clean fuels such as LNG will also be expanded starting from large cities as a cleaner substitute energy for coal and oil. In parallel with expansion of LNG, emphasis will be placed on installation of stack monitoring system. Due to the relatively limited land, government's basic policy for solid waste treatment is to develop large scale landfill facilities rather than small sized ones. Thirty three regional areas have been designated for the purpose of waste management. For each of these regions, big scale landfill site is going to be developed. To increase the rate of waste recycling the government is planning to reinforce separate collection system and to provide industries with economic incentives. As a part of meeting the changing situation on global environmental problems after UNCED, and accommodation regulatory measures stipulated in the global environmental conventions and protocols, national policy will try to alter industrial and economic structure so as to mitigate the increasing trends of energy consumption, by encouraging energy conservation and efficiency. In this regard, more attention will be given to the policy on the development of the cleaner technology. Ultimately, these policies and programs will contribute greatly to improving the current state of national public health.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.876-880
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• 2015

In 2016, the IMO's new rules for an 80% reduction in NOx emissions in newly built ships will necessitate the use of LNG as a clean fuel. So far, the developed European countries have led the development of LNG bunkering ships and related facilities. An LNG bunkering system stores LNG in a horizontal or vertical IMO "C"-Type tank insulated with perlite powder, and a vacuum in the annular space between the double walls, like the cryogenic liquid nitrogen tank. Current storage tanks have high heat leakage, evaporating over 2.0% daily, and are difficult to build with the required vacuum. A more efficiently insulated storage tank could reduce the evaporation rate. This research carried out thermal analysis on a new effective insulation method that separates high vacuum in the annular space between two tanks with a solid insulation material, such as urethane foam, lining the outer vessel. This highly efficient insulation system obtained an evaporation rate of 0.03% per day under a $10^{-3}torr$ vacuum, and an evaporation rate of 0.11% at $10^{-45}torr$. Even if the space loses its vacuum, the new insulation system showed a lower evaporation rate of 4.12% than the present perlite system of 4.9%. This newly developed tank can increase the efficiency of LNG storage tank and may help keep LNG bunkering systems safe.

• Environmental and Resource Economics Review
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• v.18 no.2
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• pp.217-239
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• 2009

As gas hydrate is recently emerging as a new energy source to solve environmental and exhaustion problems caused by fossil energy, Korea is working on a gas hydrate development project under a 10-year plan from 2005 to 2014. Gas hydrate is expected to have a big effect on the economy and society of Korea, which is largely depending on energy imports besides water energy and atomic energy. However, it is uncertain whether the project will produce successful results. Thus, it is very important to improve its validity and to propose effective execution strategies by evaluating the value of the project in advance. Thus, this study intended to include new information, which had not been evaluated in existing methods, and to reduce biases or errors in value evaluation results by applying a fuzzy risk analysis to the real option model in order to evaluate the value of a gas hydrate development project. It is advantageous that the real option model based on the fuzzy risk analysis modelizes the vagueness and inexactness of intangible element judgment into an appropriate language scale so as to evaluate these elements clearly and integrate them with estimated financial performance results. The application of the fuzzy risk analysis makes it possible to conduct an analysis by dissolving a decision-making issue with complicated and various attributes into several simplified problems. With the continuing high oil prices and today's demand of clean energy, the necessity of energy resources and technology development projects keeps growing. Amid this situation, it is expected that these study results will contribute to proposing a guideline not only for gas hydrate projects but also for policy decision-making related to future energy industries.

• Journal of Conservation Science
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• v.30 no.1
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• pp.95-101
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• 2014

Silver objects tarnish with black from reaction with sulfurous acid or hydrogen sulfide of atmospheric. Blackening of silver objects results from formation of silver sulfide($Ag_2O$) on the surface. Silver sulfide usually is usually removed by conservation treatment. There are several cleaning methods such as chemical, electrochemical and micro-abrasion cleaning, but all of them consume silver. This study investigated the safe and effective parameter of laser cleaning by test on silver coupons. Laser cleaning is a selective process for the removal of specific substances. At first, laser cleaning applied to plain silver coupons, which were not corroded, to find out the safe range of laser energy density. From results, plain silver coupons were not changed at 1064nm below $4.00J/cm^2$ and at 532nm below $2.39J/cm^2$. The corrosion layer(silver sulfide) of artifical corroded silver coupons was removed at 1064nm with $2.39J/cm^2$ by 5~10 pulses and at 532nm with $1.19J/cm^2$ by 5~10 pulses. The removal thickness of corrosion layer was about 13-25nm per a laser pulse using AES analysis. In addition, laser cleaning tested the tarnish silver rings based on the results of silver coupons. As a result of test, the black surface were clean successfully and gave luster of silver, which showed the application possibility of laser cleaning for silver objects.

• Analytical Science and Technology
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• v.23 no.5
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• pp.437-445
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• 2010

The aim of this study was to develop an analytical method for sulfonamide antibiotics (sulfadiazine, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfathiazole) and their metabolites ($N^4$-acetylsulfadiazine, $N^4$-acetylsulfamerazine, $N^4$-acetylsulfamethazine, $N^4$-acetylsulfamethoxazole, sulfamethoxazole-$N^1$-glucuronide) in environmental samples. The solid phase extraction (SPE) with LC/ESI-MS/MS have been used for the analysis of target compounds, and the recoveries of SPE clean-up were at the range of 12-94% for C18 cartridge, 60-95% for HLB cartridge, 25-123% for MCX cartridge, and 70-90% for tandem HLB/MCX. By established method, detection limit, recovery, and relative standard deviation were 0.001~0.187 ng/mL, 66~115%, and 5~17%, respectively. This method was effective and sensitive to use for the simultaneous determination of sulfonamide antibiotics and their metabolites in environmental samples. Four sulfonamide antibiotics were detected at the range of 0.008~2.153 ng/mL. For metabolites, only $N^4$-acetylsulfamethoxazole was detected, but the concentration was under the MDL level.

• Journal of Life Science
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• v.29 no.12
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• pp.1408-1414
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• 2019

Enzymes are widely used in industrial applications such as detergents, food, feed production, pharmaceuticals and medical applications and major contributors to clean industrial products and processes. To screen, identify, and characterize the enzymes the zymography techniques are routinely used. The zymography technique is a simple, sensitive, and quantifiable technique that is widely used to detect functional enzymes following electrophoretic separation in sodium dodecyl sulfate (SDS)-polyacrylamide gels. The method is a versatile two-stage technique involving protein separation by electrophoresis followed by the detection of enzyme activity in polyacrylamide gels under non-reducing conditions. It is based on SDS-polyacrylamide gel (PAG) copolymerization with substrates, which are degraded by the hydrolytic enzymes restored in enzyme reaction buffer after the electrophoretic separation. Any kind of biological sample can be applied and analyzed on zymography, including culture supernatants of microbes, plants extracts, blood, tissue culture fluids, enzymes in foods extracts and metaproteome. The advantage of zymography is that it is possible to directly detect the protein with activity on the electrophoretic gel as well as confirm the activity at the nanogram level. Thus, this zymography technology can be applied in various fields. However, these advantages are rather disadvantageous and can often lead to experimental errors. In this review, the advantages, disadvantages, and problem solving of zymography technique are described.

• Research in Plant Disease
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• v.16 no.2
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• pp.109-114
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• 2010

The occurrence factors of Rice stripe virus (RSV) in Chungcheongbukdo were analyzed by investigating the viruliferous insect rate (VIR) of overwintered small brown plant hopper (SBPH), the population density of SBPH, the infection rate of natural host plants, and the occurrence rate of RSV on rice paddy fields at the 3 areas of Cheongwon, Jincheon, and Boeun in 2008 and 2009. The average VIR of overwintered SBPH was 0.0% in 2008 and 1.1% in 2009. From SBPH collected on early June in 2009, VIR was higher as 1.4% at Jincheon and 4.2% at Boeun than those of overwintered SBPH, and this higher VIR might relate stronlgy with the adult population of SBPH immigrated from China. The populations of SBPH at Cheongwon, Jincheon and Boeun in 2008 were 3.8, 7.5 and 20.8 Head/$m^2$, respectively. However, those of Cheongwon and Jincheon increased up to about two folds as 8.4 and 13.1 in 2009. No RSV was detected on the natural host plants including barley. The factors involved in RSV occurrence were affected negatively by the low VIR of overwintered SBPH, the low population of overwintered SBPH, the low infection rate of RSV on the natural host plants, and the clean cultivation environment in Chungcheongbukdo.

• Journal of Food Hygiene and Safety
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• v.35 no.5
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• pp.411-418
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• 2020

In this study, we reviewed a group of marine biotoxins, namely yessotoxins (YTXs), focusing on their causative organisms, contaminated shellfish, domestic and foreign management status, and analytical methods. Although YTXs have not yet been reported in any cases of seafood contamination in South Korea, it is necessary to implement preemptive measures through continuous monitoring because there is a potential risk, due to the introduction of toxic microalgae associated with climate changes and the introduction of contaminated seafood from various countries. YTXs are produced by dinoflagellates, such as Protecratium reticulatum, Gonyaulax polygramma, Gonyaulax spinifera, and Lingulodinium polyedrum, all of which are species found along Korea's coastal areas. Analysis of YTXs in shellfish samples is mainly performed by use of LC-MS/MS after methanol extraction and SPE cartridge clean-up (HLB or strata-X). In the case of lipophilic marine biotoxins, including YTXs, pectenotoxins, and azaspiracids, the extraction and purification procedures are similar. Thus, it seems that the simultaneous analysis of several lipophilic marine biotoxins in shellfish samples is possible, and optimization is necessary. In addition, continuous monitoring studies on causative marine microalgae for YTXs in Korean coastal waters and contaminations in domestic and imported seafood are needed.

• Analytical Science and Technology
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• v.23 no.2
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• pp.196-204
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• 2010

In this study, the following concentrations of some PAHs (Polycyclic Aromatic Hydrocarbons) were investigated; [benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, indeno(1,2,3-c,d)pyrene] in processed foods (n=165) and cooked meats (n=45) and established the analytical method by characteristics of processed foods. The methodology involved extraction (alkali digestion, liquid-liquid extraction, microwave extraction), clean-up on Sep-Pak Florisil Cartridges and determination by HPLC/FLD (High Performance Liquid Chromatography/Fluorescence Detector). The recovery of overall method for 8 PAHs spiked into these products ranged from 92 to 103%. The mean level of detected foods was found to be benzo(b)fluoranthene $0.9\;{\mu}g/kg$ in smoked salmon, benzo(b)fluoranthene $1.0\;{\mu}g/kg$, benzo(k)fluoranthene $0.3\;{\mu}g/kg$, benzo(a)pyrene $0.9\;{\mu}g/kg$ in dried banana, benzo(b)fluoranthene $0.2\;{\mu}g/kg$, benzo(k)fluoranthene $0.1\;{\mu}g/kg$, benzo(a)pyrene $0.2\;{\mu}g/kg$ in smoked chicken, benzo(b)fluoranthene $1.3\;{\mu}g/kg$, benzo(k)fluoranthene $0.3\;{\mu}g/kg$, benzo(a)pyrene $0.9\;{\mu}g/kg$ in charcoal grilled pork, respectively.