• Korean Journal of Microbiology
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• v.51 no.1
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• pp.7-13
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• 2015

Hydrotrope-combined copper (HCC) is a copper ($Cu^{2+}$)-based algicide, which is combined with a hydrotrope that keeps copper ion in solution to improve performance. This study assessed the growth inhibition effect of HCC against Microcystis aeruginosa which is one of the most common toxic cyanobacterium in eutrophic freshwater environment. Various HCC doses, ranging from 5.5 to $550{\mu}g/L$ as $Cu^{2+}$, were applied to either BG-11 or 1/4 diluted medium with low- or high-inoculum density of M. aeruginosa. Growth inhibition was monitored based on a decrease in chlorophyll-a content in culture medium during the incubation. Results showed that HCC significantly inhibited the growth of M. aeruginosa in a dose-dependent manner. In case of 1/4 diluted BG-11 medium, HCC dose as low as $5.5{\mu}g$ $Cu^{2+}/L$ completely inhibited the production of chlorophyll-a by M. aeruginosa. It was found that HCC did not induce any significant release of microcystin-LR from M. aeruginosa. Acute toxicity of HCC was tested using Daphnia magna, and the 24-h $EC_{50}$ value was 0.30 mg/L as $Cu^{2+}$ which was much higher than the actual inhibition dose. Ames test was performed using Salmonella enterica serovar Typhimurium TA100, and HCC showed no increase in the number of revertant colonies. The result suggested that HCC does not have any mutagenic potential in the aquatic environment. In addition, no genotoxic effect of HCC was also confirmed based on the SOS ChromoTest using Escherichia coli PQ37. Therefore, HCC could be used as a relatively safe and effective pre- and post-treatment agent to control hazardous algal blooming in aquatic environments.

• Korean Journal of Environment and Ecology
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• v.29 no.5
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• pp.736-742
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• 2015

Cosmopolitan green macroalga, Ulva pertusa is a widely spread species in most coastal waters. This benthic alga is appearing on marine objectives causes significantly economical and social problems. To prevent fouling organisms, new antifouling (AF) agents, such as ziram, diruon, zinc pyrithione, copper pyrithione, DBNPA and triclosan are used. However, the evaluations of new antifouling system of those agents strongly need more information on algae species for considering environment effect. Therefore, the purpose of this study was to evaluate the activity of antifouling system using Ulva spores and Nitzschia pungens. In addition, new AFS were evaluated the toxicity of microalga, Nitzschia pungens. In the motility of Ulva spores, ziram and zinc pyrithione were shown 50% higher inhibition motility than diuron, copper pyritione, DBNPA and triclosan. Ziram was appered the highest AFS of Ulva sore attachment. Copper pyrithione at the concentration of $100{\mu}g/L$ was inhibited 80% growth rate comparison of control. In conclusion, each new AF agents showed their specific AF activities against marine organisms based on this work.

• Advances in nano research
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• v.3 no.3
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• pp.169-176
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• 2015

Iron nanoparticles were made by using the modified coprecipitation technique. Usually the characteristics of synthesised particles depend upon the process parameters such as the ratio of the iron ions, the pH of the solution, the molar concentration of base used, type of reactants and temperature. A modified coprecipitation method was adopted in this study. A magnetic stirrer was used for mixing and the morphology and nature of particles were observed after synthesis. Nanoparticles were characterised through XRD. Obtained nanoparticles showed the formation of magnetite and maghemite under citric acid and oxalic acid as stabilisers respectively. The size of nanoparticle was greatly affected by the use of different types of stabilisers. Results show that citric acid greatly reduced the obtained particle size. Particle size as small as 13 nm was obtained in this study. The effects of different kinds of nucleating agents were also observed and two different types of nucleating agents were used i.e. potassium hydroxide (KOH) and copper chloride ($CuCl_2$). Results show that the use of nucleating agent in general pushes the growth phase of nanoparticles towards the end of coprecipitation reaction. The particles obtained after addition of nucleating agent were greater in size than particles obtained by not utilising any nucleating agent. These particles have found widespread use in medical sciences, energy conservation and electronic sensing technology.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.609-614
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• 1999

The effect of the amount of $SiO_2$dopant on the behavior of $AlO_2$$O_3$-composite formation by melt oxdation of Al-alloy was examined in this paper. The $SiO_2$powder was spread on the top surface of the Al-1Mg-3-Si-5Zn-1Cu alloy in th alumina crucible. The selected amount of each powder was 0.03, 0.10, 0.16g/$\textrm{cm}^2$. The oxidation behavior was determined by observing the weight gain after the heat treatment for 10 hours at 1373K. The macroscopic structure of formed oxide layer was examined by an optical microscope. The top surface and the cross-section of the grown oxide layer were investigated by SEM and analysed by EDX. The $SiO_2$ powder was determined to enhance oxidation by thermit reaction with Al which reduced the growth incubation period of the oxidation layer. As the amount of the $SiO_2$dopant increased, the growth rate decreased due to the precipitated Si which blocked the Al-alloy channel in the composite materials. However, more uniform layer was obtained due to the occurrance of the enhanced oxidation reaction in the whole alloy surface compared to the case of addition of less amount of dopant.

• KCI Concrete Journal
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• v.14 no.4
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• pp.171-177
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• 2002

Antifungal agents are used to impart antibacterial or bactericidal properties to commodities and various articles used in industries and can be classified into two broad groups i.e organic and inorganic. Inorganic antifungal agents comprise of Ag, Zn, or Cu, etc. These elements tend to exhibit high level of antifungal activities, non-uniform dispersion in substrates, and have poor properties in expensive and cheap adhesiveness. In this study, the organic antifungal agent was used for the purpose of investigating the antifungal activity of antifungal agent activated-cement mortar (AACM) on the aspergilus niger of various fungus which can be easily discovered in the interiors and exteriors of buildings. In addition, an experiment on the basic physical properties of AACM such as compressive and flexural strength was carried out. The conclusion of this investigation revealed that a dosage increase of antifungal agent exhibits a high inhibitory effect on the aspergilus niger, and although there is a slight decrease in the strength of AACM, the strength of AACM was almost equal to that of inactivated cement mortar.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.56-64
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• 1996

The objective of this investigation is to establish the rejection characteristics of caesium and cobalt from radioactive liquid waste by chemical/ultrafiltration process. An extensive experimental investigation was conducted with inactive caesium and cobalt ions, utilizing ultrafiltration stirred cell. Caesium and cobalt could be effectively removed from waste solution using copper ferrocyanide and polyarcylic acid(PAA). The rejection dependence of the caesium was found to be a function of caesiun to potassium copper ferrocyanide feed molar ratio. The binding behavior of caesium on K$_2$Cu$_3$(Fe(CN)$\sub$6/)$_2$, particles was explained in terms of a Langmuir adsorption isotherm. When Cs/K$_2$Cu$_3$(Fe(CN)$\sub$6/)$_2$molar ratio was 1.5, the removal of caesium was the most efficient. The rejection efficiency of cobalt is dependent upon various parameters such as pH, cobalt concentration and PAA concentration. The rejection behavior of cobalt was explained in term of a equilibrium model taking into account the reaction between the ligand group, the proton and the cobalt ion. At the conditions of PAA/Co ratio of 2 and pH of 5.6, the removal of cobalt was over 90%. Also, the effect of chemical addition sequence for the simultaneously removal of caesiun and cobalt was discussed.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.333-339
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• 1995

The reduction and diffusion process(R-D process) is an economical way to produce the functional materials which contain rare-earth elements and has been applied to the production of rare-earth magnet meterials($SmCo_5$, $Nd_{15}Fe_{77}B_8$), magneto-optical(MO) target materials and hydrogen storage alloy, etc. However, because of difficult to control of the final composition, the R-D process has not been applied to production of the 2-17 type rare earth permanent magnet materials which contain several elements. Therefore, this work was as a basic study for the production of the 2-17 type rare earth permanent materials with composition $Sm(Co_{0.72}Fe_{0.21}Cu_{0.05}Zr_{0.03})_{7.9}$ by the R-D process, the following were mainy examined ; the amount of metallic calcium as a reductant, homogenization condition of the alloy after the R-D reaction, masuring of magnetic properties of the sample after step aging. The sample prepared by the R-D process contained a little more oxygen than that prepared by the melting method, however, showed almost the same magnetic properties.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.4
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• pp.204-212
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• 1993

The preparation of $TiO_2$ fine particles from $TiCl_4$ and oxygen by the vapor-phasereaction was investigated at $850^{\circ}C$ with an emphasis on the effect of its experimental conditions on the crystal type of the products. Anatase $TiO_2$ particles prepared by experiment were used to study anatase-rutile transition by calcination temperature, the additives and gas atmosphere. The results were as follows. The kinetics of anatase-rutile transition was well agreed with A vrami equation, and the activation energy of transition was 35kcal/mol. The addition of CuO in anatase $TiO_2$ particles accelerated the anatase-rutile transition, and its transition was retarded in vaccum.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.162-162
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• 2022

This study was carried out to investigate the effects of nitrogen, phosphorus, potassium (three main macro elements of fertilizer) on growth, yield and mineral contents of Platycodon grandiflorum for. duplux and to obtain the basic data of the proper fertilizer application for increasing the yield of P. grandiflorum for. duplux. Plant height showed significantly good results in all fertilization treatments compared to non fertilizer group (the control, T0), and in particular, the highest was 85.7 cm in the complete group (T4). Chlorophyll content showed a high amount in the range of 20.7 to 23.8 against all fertilization treatment groups, except for non fertilizer (T0) and non nitrogen (T1). The fresh weight of roots were higher quantity than other fertilization treatments in the complete group 55.8 g (T4). The mineral nutrient content ofNa, Mg, Cu and Al of the roots of P. grandiflorum for. duplux from T1 group showed the lowest amount compared to other groups. In addition, P from T2 group, Mn from T3 group and Ca, Fe, Zn from T4 group also exhibited the lowest mineral content compared to other groups respectively.

• Journal of Welding and Joining
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• v.23 no.1
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• pp.41-47
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• 2005

Arc pressure is one of important factors in understanding physical arc phenomena. Especially it affects on the penetration, size and shape of TIG welding. Some researches were reported on the effect of arc pressure in low and middle current region. But there are not any research in high current region. The purpose of this study is to investigate the arc pressure distribution with mixing ratio of shield gas such as Ar and He gases. A Cu block with water cooling was specifically designed and used as an anode electrode in order to measure the arc pressure in high current region. Then, the arc pressure distribution was measured with change in welding current and mixing ratio of shield gases. The arc force was obtained by numerically integrating the measured results. As the results, it was shown that the arc pressure was concentrated at the central part of the arc in middle and high current regions when a pure Ar gas was used. In case of Ar + He mixing gas, the arc pressure was much lower than that of pure Ar gas. In addition, it was widely distributed to radial direction.