• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.32.1-32.1
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• 2011

39 K의 임계온도를 갖는 $MgB_2$ 초전도체를 이용한 전력에너지와 MRI 의료 기기로의 응용 가능성이 높아지고 있다. $MgB_2$ 초전도체 제조에 있어서 마그네슘과 반응성이 좋은 비정질의 붕소 원료 분말 가격이 비싼 반면 상대적으로 경제적인 결정질 분말의 기계적 밀링 공정을 이용하여 비정질화와 나노 입자로의 크기 감소 효과를 얻을 수 있다. 또한 탄소를 이용한 붕소 치환으로부터 고 자기장하에서 초전도 임계 성질을 향상시키고자 유, 무기물 형태의 여러 가지 탄소 소스를 개발하는 연구가 진행되어 왔다. 본 연구에서는 저가의 95~97% 순도, 약 1 ${\mu}m$ 이하 크기를 갖는 준결정상의 붕소 분말을 이용하여 기계적 밀링에 따른 붕소 분말의 비정질화 및 입자 나노화, $MgB_2$ 반응성 향상, $MgB_2$ 결정립 크기 감소 및 결정립계 피닝 증가에 의한 초전도 임계 물성 향상에 대하여 알아보았다. 또한 여러 시간 동안 밀링된 각 붕소 분말에 액체 글리세린을 이용한 탄소 도핑 전처리를 통하여 밀링 시간의 최적화를 알아보았고 이로부터 제조된 $MgB_2$ 초전도 벌크의 경우 적절한 임계온도 감소, 격자 왜곡 결함과 높은 결정립계 밀도 등에 의한 플럭스 피닝 향상으로 $MgB_2$ 초전도체의 임계전류밀도 및 비가역자기장이 증가함을 알 수 있었다. 즉, 경제성 있는 저급의 준결정상을 갖는 붕소 원료 분말의 입자 비정질 나노화 및 탄소 도핑 전처리를 통하여 $MgB_2$ 초전도 임계 물성을 향상시킬 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.160-160
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• 2011

In this work, magnesium (Mg) nanoparticles were plated onto the surfaces of multi-walled carbon nanotubes (MWNTs) in order to investigate the effects of their presence on the high pressure hydrogen storage behaviors of the resultant Mg/MWNTs. The structure of Mg/MWNTs was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The pore structure and total pore volumes of Mg/MWNTs were analyzed by $N_2$/77 K adsorption isotherms. The hydrogen storage behaviors of the Mg/MWNTs were investigated by BEL-HP at 298K and 100 bar. From the results, it was found that Mg particles were homogeneously distributed on the MWNT surfaces. The hydrogen storage capacity increased in proportion to the Mg content. It can be concluded that Mg paricles play an important role in hydrogen storage characteristics due to the hydrogen spillover effect.

• Applied Microscopy
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• v.35 no.4
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• pp.1-9
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• 2005

In this paper it is reported that a comprehensive study of the crystal structure of the fine size S-phase ($Al_2CuMg$) precipitate in Al-Cu-Mg alloy by electron diffraction experiments. The experiments involve taking the selected area diffraction pattern for a S-phase particle, simulations of the pattern based on the kinematical diffraction theory and quantitative data collection from the zone axis diffraction patterns for the comparison with calculated diffraction intensity using both the kinematical and the dynamical diffraction theory. As a result, a good fitting model of the S-phase structure turns out to be the model reported early by X-ray methods (Perlitz & Westgren, 1943), not the new model determined by HRTEM methods (Radmilovic et al., 1999).

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.307-312
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• 2009

Motukoreaite and quintinite-3T, Mg-Al layered double hydroxides, were found in the Sinyangri Formation of Jeju Island. They fill the pores of basaltic volcaniclastic sediments in globular and botryoidal aggregates of fine platy particles. Globular aggregates of quintinite-3T were crusted with the parallel overgrowth of motukoreaite plates. X-ray diffraction data and chemical composition are consistent with those reported in literature, while the Mg/Al ratio of motukoreaite is higher. Structural formula of motukoreaite and quintinite-3T derived from electron microprobe analysis are $Na_{1.6}Ca_{0.1}Mg_{40.7}Al_{20.7}Si_{0.9}(CO_3)_{13.6}(SO_4)_{7.4}(OH)_{108}56H_2O$, and $Mg_{3.7}Al_{1.9}Si_{0.2}(OH)_{12}(CO_3)_{0.8}(SO_4)_{0.2}3H_2O$, respectively. Motukoreaite and quintinite-3T were formed by reaction between seawater and basaltic glass, and contributed to the cementation and lithification of the volcaniclastic sediments.

• Analytical Science and Technology
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• v.31 no.6
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• pp.247-258
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• 2018

The purpose of the present study was to investigate whether the degree of air pollution can be evaluated via examination of local plants. Selected sites included two parks in an industrial area, as well as two parks in an urban area. Selected plant samples comprised one-year-old pine shoot leaves. Leaves growing over 2 m from the ground were collected from over 10 pine trees. Leaf surface was analyzed for deposition of 14 trace elements and 16 polycyclic aromatic hydrocarbons (PAHs), including particle size and mass, surface imaging, precipitation-mediated particle removal rate, and concentration. Particle size ranged from 0.4 to $200{\mu}m$, and the volume percentage of particles ${\leq}10$ was 20 %. Deposited particle mass ranged from 0.450-0.825 mg, and precipitation-mediated removal rate ranged from 10.0-27.6 %. Trace element concentration, as measured by ICP/MS after microwave acid digestion, was 18.8-26.3 mg/kg As, 0.08-0.13 mg/kg Be, 0.06-0.08 mg/kg Cd, 4.91-17.8 mg/kg Cr, 5.26-405 mg/kg Cu, 1,930-2,670 mg/kg Fe, 3.03-28.1 mg/kg Pb, 26.9-42.8 mg/kg Mn, 2.66-10.4 mg/kg Ni, 4,560-8,730 mg/kg Al, 2,500-6,120 mg/kg Ba, 5.27-17.8 mg/kg Rb, 40.9-95.3 mg/kg Sr, and 4,030-8,260 mg/kg Zn. Concentration of PAHs, as analyzed by GC/MS/MS after liquid-liquid extraction and purification of deposited particles, ranged from 1.17 to 12.378 mg/kg for ${\Sigma}PAH_{16}$ and from 1.17 to 12.378 mg/kg for ${\Sigma}PAH_7$.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.1
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• pp.41-50
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• 2012

The study was carried out to analyze the relationship between analysis of antioxidant activity and the level of functional components according to particle size of corn silk. Particle size was classified into 5 groups. By particle size distribution and color difference, the total phenol content and DPPH radical scavenging activity were observed. The particle sizes of corn silk were $199.17{\mu}m$, $178.27{\mu}m$, $85.48{\mu}m$, $27.4{\mu}m$ and $20.97{\mu}m$, respectively. The lightness of colored pigments was increased when the particle size was decreased. The contents of free sugar (fructose, glucose, galactose, sucrose, and maltose) of corn silk were analyzed using a HPLC. The total phenol contents by the particle sizes of corn silk were 2.01 mg/g, 2.02 mg/g, 2.06 mg/g, 2.26 mg/g and 2.26 mg/g, respectively. DPPH radical scavenging activities of samples were 21.00%, 21.75%, 22.90%, 24.35% and 23.67%, respectively. Antioxidative activities of Trolox and Fe(II) in corn silk were measured by ferric reducing antioxidant power (FRAP) assay and Trolox equivalent antioxidant capacity (TEAC) assay. TEAC values of samples were $2.36{\mu}mol$ TE / g dw, $2.81{\mu}mol$ TE / g dw, $3.20{\mu}mol$ TE / g dw, $3.36{\mu}mol$ TE / g dw, and $3.44{\mu}mol$ TE / g dw, respectively. FRAP values of samples were $11.67{\mu}mol$ Fe(II) / g dw, $12.80{\mu}mol$ Fe(II) / g dw, $13.43{\mu}mol$ Fe(II) / g dw, $13.85{\mu}mol$ Fe(II) / g dw and $15.95{\mu}mol$ Fe(II) / g dw, respectively. Total phenolic content and antioxidantive activities based on FRAP assay and TEAC assay were increased with decreasing particle size. In addition, DPPH radical scavenging activity was also increased. A significant correlation was also noted between DPPH radical scavenging activities and the content of phenolic compounds.

• Journal of Korean Society of Forest Science
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• v.100 no.1
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• pp.14-24
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• 2011

Anticancer activity of Acer mono aqueous extracts was enhanced by nano-encapsulation process of gelatin. The cytotoxicity on human normal lung cell (HEL299) of the extracts from WE (water extract at 100) showed 23.51%, lower than that from NE (nano-encapsulatioin of water extract of Acer mono) in adding the maximum concentration of 1.0 mg/mL. NE showed more potent scavenging effect as 73.15% than the WE. On SOD-like test, the NE showed highest activity as 32.33% at 1.0 mg/mL concentration. Human stomach adenocarcinoma, liver adenocarcinoma, breast adenocarcinoma and lung adenocarcinoma cell growth were inhibited up to about 59-73%, in adding 1.0 mg/mL of NE. NE was 15% higher than conventional water extraction. Among several cancer cell lines (stomach adenocarcinoma, liver adenocarcinoma), the growth of digestive related cancer cells were most effectively inhibited as about 71-73%. The size of nano particles was in the ranges of 100-200 nm, which can effectively the penetrate into the cells, it was observed by real time confocal microscope. It tells that the aqueous extracts of Acer mono bark could be definitely enhanced by nano-encapsulation process.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.157.2-157.2
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• 2011

In this work, we prepared Mg nanoparticles loaded graphite oxide (Mg-G) as a function of Mg content in order to investigate hydrogen storage behaviors. The structure and morphology of the Mg-G samples were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The textural properties of the samples were evaluated using $N_2$/77 K adsorption isotherms. The hydrogen adsorption capacities were investigated at 298 K/10 MPa. As a result, the hydrogen adsorption capacities of the Mg-G were enhanced with increasing the Mg content. Therefore, it was found that the presence of Mg on graphite surfaces created hydrogen-favorable sites, resulting in enhancing the hydrogen adsorption capacity.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.366-369
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• 2008

To evaluate the performance of a bipolar packed bed cell (BPBC) filled with granular aluminium, the experiments were carried out in two groups as batch and continuous processes. In a batch process, removal efficiency of total phosphate (T-P) was 88% in case of electrolytic treatment of phosphate solution, T-P 10 mg/L at 6 V during 3 h by BPBC filled with granular aluminium. In a continuous process, residual T-P concentration was about 2 mg/L in case of electrolytic treatment of phosphate solution, 10 mg/L at 6 V, HRT 3 h by BPBC filled with granular aluminium. Break-through point was observed after running for 120 h at hydraulic retention time (HRT) of 3 h.

• KSBB Journal
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• v.14 no.1
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• pp.124-130
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• 1999

To evaluate the technical of microbial coal desulfurization during the storage in coal dumps, microbial pyrite oxidation in a packed column reactor with Thiobacillus ferrooxidans has been investigated. For microbial desulfurization in a packed reactor system, coal particle size over 1.0 mm with uniform size distribution seems to be most suitable as fas as drainage behavior and accessability of pyrite are concerned. When coal samples of 1∼2 and 2∼4 mm particle size were size were used, about 32∼42% of pyritic sulfur was removed within 70 days. The rate of pyritic sulfur oxidation was in the range of 348∼803 mg S/kg coal ·d, and the sulfur removal rates in packed columns were about 15∼25% of those in suspension cultures. Without any circulation of liquid medium, microbial coal desulfurization could be possible by the inoculation of T. ferrooxidans along on the coal dump. It was concluded that a microbial percolation process is one of possible processes for the desulfurization of high sulfur coal during a long-term storage.