• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• Journal of Korean Society of Environmental Engineers
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• v.33 no.3
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• pp.162-166
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• 2011

Phosphorous contaminated in the effluent from sewage treatment plants can cause the eutrophication in surface water bodies. In this study, a powder of titanium oxysulfate-sulfuric acid made of ion-exchange materials was immobilized in an alginate gel and this material was examined to evaluate its phosphorous removal efficiency. Equilibrium and kinetic studies were carried out to quantify the adsorption capacity and time dependent removal rate of phosphorous. Adsorption isotherms and kinetic parameters were obtained for the entrapped titanium beads with three different methods. Equilibrium data were analyzed using Langmuir adsorption isotherm model and found to be well fitted to the model. The maximum adsorption capacity for phosphorous by the titanium bead synthesized with the solution method was 92.26 mg/g. Kinetic data followed a pseudo-second-order kinetic model. Due to the low production cost and high adsorption capacity, the titanium bead synthesized by the solution method has a potential to be utilized for the cost-effective removal of phosphorous from wastewater.

• Journal of Conservation Science
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• v.32 no.3
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• pp.313-320
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• 2016

The aim of this study was to obtain information on the ancient material of cast bronze through an investigation of the microstructure and impurity characteristics of the casting. Three Koryo bronze coins were analyzed using an optical microscope, scanning electron microscope, and electron dispersive X-ray analyses were used to determine the composition of the specimens. The three coins had 4 phases: ${\alpha}phase$, ${\delta}phase$, Pb, and impurities ($Cu_2S$). $Cu_2S$ was found to exist near Pb or in ${\delta}phase$. $Cu_2S$ is the inter mediate product of copper ore refining. Therefore, the copper ore was not completely refined. To find out the characteristic of $Cu_2S$, we melt 1)Koryo bronze coin and 2)$Cu_2S$ and Pb powder at 1273 K. The reaction between $Cu_2S$ and Pb at 1273 K yielded fine Cu and black gas, which was identified to be PbS and is presented below: $Cu_2S+Pb{\rightarrow}PbS{\uparrow}+2Cu$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.129-135
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• 2017

This study examined the antioxidant activity of the water extract from graviola leaves to develop a harmless and highly stable natural antioxidant. The total polyphenol content, total flavonoid content, DPPH radical scavenging activity, and MTT assay activity were measured. As a result, 62.3 g of the water extract from graviola leaves was obtained at $98^{\circ}C$ using 300 g of graviola leaf powder. The total polyphenol content was $291.97+2.39{\mu}g/mL$ and the total flavnoid content was $161{\pm}7.85{\mu}g/mL$ in a 1 mg/mL water extract from graviola leaves. The DPPH radical scavenging activity showed 51.6%, 67.8%, 79%, 82.4% and 83.9% at concentrations of 1, 2.5, 5, 10 and 15 mg/mL. This shows concentration-dependent scavenging activity and significant antioxidant activity. As a result of measuring the toxicity about HDF cells, a HDF cell survival rate of 100% was observed at a 150 mg /mL concentration, which was the same as that of the control group and a higher cell survival rate at a lower concentration. In conclusion, the graviola leaf extract can be developed as a material of food or cosmetics containing natural antioxidants.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.1
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• pp.42-45
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• 2008

It has been reported that FRP (fiber reinforced plastic) can be recycled by separating into layers instead of crushing into powder. F-fiber obtained from roving layer separated from FRP, has bigger tensile strength than the bundle of glass fibers of which FRP was made (more than 90%). SEM image of F-fiber shows the presence of some resin. Under the proposition of usage of F-fiber in the concrete material, tensile strength is examined after soaking in a basic solution (NaOH+KOH). The reaction mechanism of strength loss may be considered as an attack of hydroxide ion ($OH^-$) on a chemical bond of Si-O-Si of glass fiber. The simulation graph of the strength loss data implies certain reaction mechanism. While in the early stage kinetically controlled reaction results in a fast drop of tensile strength, after 30 days dispersion rate of hydroxide ion plays a major role in strength loss. This result is similar to the one for the AR glass. An extrapolation of the graph would make an assumption about the lift time of F-fiber possible.

• Journal of Conservation Science
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• v.18 s.18
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• pp.63-74
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• 2006

All rock materials of the three storied stone pagoda in Seoakri were composed of light gray alkali granite with medium grained and developed with small mialolitic cavities. This stone pagoda is preserving almost archetype except the head part because there was repair work already. But, foundation, basement and roof rocks are serious state by microbial invasion such as lichens. Because there are tree and grass that cause direct effect to stone pagoda surrounding. Therefore, conservation treatment executed the primary dry cleaning and secondary wet cleaning treatment. Stone surface is partly not removed well such as lichens which part removed using cleansing device that use high temperature steam. Some treated part concrete and epoxy resin remove and retreatment with mixing talc and alkali granite powder to epoxy resin. Did color matching at mixing process of epoxy resin and fillers to properties with set the feel of a material. Also, drainage ditched to minimize inflow of rainwater fall from slope that is on the east of stone pagoda, tree and grass in stone pagoda surrounding wished to do remove and control occurrence of lichens hereafter minimizing moisture conteats.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.3
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• pp.334-341
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• 2020

This study was conducted to optimize the processing conditions of seasoned broughton's ribbed ark Scapharca broughtonii products (S-BRA-P) using response surface methodology (RSM). The concentrated oyster extract content (X₁, w/w), amino-based seasoning powder content (X₂, w/w), and enzyme-treated stevia content (X₃, w/w) were selected as independent variables, and amino nitrogen (Y₁) and overall acceptance in a sensory evaluation (Y₂) were selected as dependent variables. The optimal conditions of X₁, X₂, and X₃ were 97.5%, 20.0%, and 0.9%, respectively, and the predicted values of the multiple response optimal conditions were Y₁ (1,030 mg/100 g) and Y₂ (8.3). Under the optimum conditions, the experimental values of Y₁ and Y₂ were 1,034 ± 6.0 mg/100 g and 8.5 ± 0.4, respectively, which was no significant difference from the predicted values (P<0.05). In conclusion, the optimized models of X₁, X₂, and X₃ for the preparation of soy sauce-based sauce were suitably fitted. The optimum amount of seasoning sauce was 13% for the preparation of S-BRA-P. The S-BRA-P, which was prepared by adding the seasoning sauce and the other subsidiary material [finely chopped spring onion (3.8%) and cheongyang hot pepper (4.6%)], had a superior taste, color, and odor.

• Resources Recycling
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• v.24 no.3
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• pp.59-65
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• 2015

Recycling of vulcanized rubber products is a serious problem in the world. A quantity of generated waste tires becomes much more and more because of increasing demands on automobiles, resulted in the cause of serious secondary pollution by sulfur component that is crosslinked to incineration or landfill. In addition, crosslinked surfur is used to interfere with the binding of the raw material rubber. In this study, we analyzed the degree of devulcanization by the chemical devulcanization. Devulcanization ratio of the samples were systematically analysed by variables such as time and temperature. In addition, the effect of swelling method as a pre-treatment process was also measured. A rubber specimen was deepened in a organic 2-buthanol solutions during various times of 1 ~ 5 hrs at 100, 150, $200^{\circ}C$ respectively, then to calculate the crosslink density and the number average molecular weight by using a parallel expansion process, which showed devulcanization degree of analyzed samples quantitatively. Also, the mechanical properties were measured with the samples prepared by using a hot press.

• 보존과학연구
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• s.21
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• pp.5-55
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• 2000

The cultural properties are damaged by various causes according to the characteristics of material, the condition of preservation, and the period of time. Especially, biodeterioration makes lots of damages in organic properties than inorganic ones. The damages of wooden cultural properties by insects usually are caused by the three orders; Isoptera, Coleoptera, and Hymenoptera. As the result of investigation on the state of 141 buildings of wooden cultural properties in 1999, some of them were damaged by many kinds off actors; wasp, powder post beetle, cigarette beetle, termite, decay, and physical cracking. And it was found that the patterns of damages were related to species-specific habits of insects. There are several methods of pest control for the prevention of wooden cultural properties from damages caused by insects. Those are as follows; physical control, chemical control, biological control, and integrated pest management. When insects and fungi were detected at the wooden buildings, the fumigation is best treatment to stop biodeterioration. And then, wood materials also need to be treated with insecticidal and antiseptic chemicals to avoid a reinfestation, because the fumigant is volatile. The six commercial chemicals which are applied to the insecticidal and antiseptic treatment of wooden cultural properties were purchased to test their abilities. According to the comparative results of efficacy of them in laboratory, chemical D showed excellent efficacy in all items, including antiseptic and termiticidal items. The goal of these pest controls is to protect wooden buildings from insects and microorganisms. The most effective method used currently is chemical control(fumigation, insecticidal and anticeptic chemical treatment), but it has to be treated periodically to control pest effectively. Recently environmentally-friendly control methods such as bait system or biological treatments are replacing traditional barrier treatments using large amounts of chemicals. Especially, termite is a social insect which makes a colony. Although a building with fumigation treatment is safe for a while, once attacked building has a risk of damage by reinfestation of termite. Therefore, to control termites from damaged building, the entire colony including reproductives(queen and king) and larvae around buildings must beeliminated. Bait system can be used as a preventive measure in early detection of them through termites colony monitoring and baiting. It would be the most effective for termite control if bait system would be used together with the chemical controls.

• Food Science and Preservation
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• v.23 no.2
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• pp.246-251
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• 2016

This study was performed to determine the effects of drying methods (HD, hot air drying; FD, freeze-drying) on the antioxidant and physiological abilities of Haw (Crataegus pinnatifida Bunge). Powder color values of dried Haw, L and b, were higher for HD, while the chroma values were higher for FD. The total polyphenol, and flavonoid contents of HD Haw and FD Haw were found to be $9.29{\pm}0.50mg\;GAE/mL$ and $15.48{\pm}0.38mg\;GAE/mL$, and $9.41{\pm}0.26mg\;RHE/mL$ and $26.46{\pm}0.34mg\;RHE/mL$, respectively. DPPH radical scavenging abilities at 100 mg/mL concentration were higher for FD (64.90%) than HD (28.66%), as were the reducing power, ABTS radical scavenging ability, and nitrite scavenging ability. However, the HMG-COA reductase of HD (74.67%) was higher than that of FD (72.10%). The ${\alpha}-glucosidase$ inhibitory abilities of HD and FD at a concentration of 0.1 mg/mL were 24.69% and 97.38%, respectively. These results indicate that Haw is a potential functional material and that freeze-drying Haw is better than hot air drying.