• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.2
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• pp.78-85
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• 1998

The design method of a temperature stable bandpass filter using dielectric coaxial resonators of with two dielectric ceramics with opposite signs of temperature coefficient of dielectric constant (${\tau}_{\epsilon}$) to compensate for each other in this method. $MgTiO_3$(${\tau}_{\epsilon}$=+99 ppm/${\circ}C$) as a positive ${\tau}_{\epsilon}$ material and Ba($Zn_{1/3}Nb_{2/3}$)$O_3$(${\tau}_{\epsilon}$=-77ppm/${\circ}C$) as a negative material were selected. The length of a SIR for the temperature stability was calculated according to the design method and the susceptance slope parameter of the SIR was obtained. A temperature stable bandpass filter using dielectric SIR's was designed, simulated and fabricated. The center frequency of this filter was 915 MHz and the pass bandwidth was 20 MHz. Temperature properties of this bandpass filter by simulations were compared with the measured results of the bandpass filter fabricated.

• Journal of Periodontal and Implant Science
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• v.38 no.sup2
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• pp.273-298
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• 2008

Purpose: The aim of this review is to introduce a novel bone-graft material for hard-tissue regeneration based on the calcium phosphate glass(CPG). Materials and Methods: CPG was synthesized by melting and subsequent quenching process in the system of CaO-$CaF_2-P_2O_5$-MgO-ZnO having a much lower Ca/P ratio than that of conventional calcium phosphates such as HA or TCP. The biodegradability and bioactivity were performed. Effects on the proliferation, calcification and mineralization of osteoblast-like cells were examined in vitro. Influence in new bone and cementum formations was investigated in vivo using calvarial defects of Sprague-Dawley rats as well as 1-wall intrabony defect of beagle dogs. The application to the tissue-engineered macroporous scaffold and in vitro and in vivo tests was explored. Results: The extent of dissolution decreased with increasing Ca/P ratio. Exposure to either simulated body fluid or fetal bovine serum caused precipitation on the surface. The calcification and mineralization of osteoblast-like cells were enhanced by CPG. CPG promoted new bone and cementum formation in the calvarial defect of Sprague-Dawley rats after 8 weeks. The macroporous scaffolds can be fabricated with $500{\sim}800{\mu}m$ of pore size and a three-dimensionally interconnected open pore system. The stem cells were seeded continuously proliferated in CPG scaffold. Extracellular matrix and the osteocalcin were observed at the $2^{nd}$ days and $4^{th}$ week. A significant difference in new bone and cementum formations was observed in vivo (p<0.05). Conclusion: The novel calcium phosphate glass may play an integral role as potential biomaterial for regeneration of new bone and cementum.

• Journal of Plant Biotechnology
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• v.31 no.4
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• pp.313-317
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• 2004

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases produced by a variety of cell type, and have a fundamental role in the degradation and remodeling of extracellular matrix. In this study, we screened the secretion of MMPs in leaves of different developmental stages and in response to environmental stress using tobacco. Compare with fully maturing leaves and older leaves, the rate of MMPs activity was high in expanding and younger leaves. It is tempting to speculate that MMPs may be involved in tissue modeling, which must occur during leaf expansion. The MMPs activity in tobacco leaves grown in the presence of stressors showed a significantly increase at salinity treatment and pathogen infection. The MMPs activity in salinity and pathogen treatment increased respectively, by 1.2- and 1.5-fold with respect to the control. These results suggest that MMPs may be involved in plant defence against adverse environment and pathogenic infection.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.98-103
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• 2012

Recently, development of Al-based alloys for high mechanical performance has been an important issue in automotive industry. The present study focused on the design of a high strength Al-based alloy for rheo-diecasting. The research was based on thermodynamic calculation and experimentals to optimize the alloy compositions. Two important considerations were carried out: i) to obtain uniform slurry with fine and globular microstructures for rheo-diecasting, ii) to be strengthend by T6 heat treatment. In order to evaluate the effect of Si content on the slurry microstructure and castability, thermodynamic calculation and fluidity test were carried out. The effects of various alloying components, such as Mg, Cu and Zn, on age hardenability were also investigated. The mechanical properties of the rheo-diecasting products using the newly developed alloy are 324MPa in tensile strength, 289MPa in yield strength, and 11.2% in elongation after T6 heat treatment.

• Korean Journal of Environmental Agriculture
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• v.24 no.4
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• pp.370-378
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• 2005

The characteristics of heavy metal biosorption on the seaweeds were investigated to develop a biological treatment technology for wastewater polluted with heavy metals. The heavy metal biosorption on seaweeds ranked in the tallowing order: U. pinnatifida$\geq$E. stolonifera$\geq$Laminaria sp.>G. amansii. The Pb was biosorbed in the range of $93{\sim}99%$, and the Cu and Cd were biosorbed in the range of $70{\sim}80%$ at the concentration of the heavy metal of $100mg/{\ell}$ respectively. The seaweed which was pretreated with $CaCl_2$ solution improved the biosorption of the heavy metals. The temperature and pH didn't affect the biosorption of heavy metals. The Langmuir isotherm reasonably fit the data of heavy metal biosorption compared to the Freundlich isotherm. The affinity of metals on the biosorption ranked in the following order: Pb>Zn>Cu>Cd. The biosorption efficiency of the heavy metals on the U. pinnatifida decreased in the multi-component rather than the single component. The heavy metals adsorbed on the U. pinnatifida were recovered using 0.3%-NTA. U. pinnatifida among the seaweed used in this work showed the best performance for the biosorption of the heavy metals.

• Asian Journal of Turfgrass Science
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• v.16 no.1
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• pp.1-10
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• 2002

The influence of calcium on the growth of creeping bentgrass 'Penn-Al', perennial ryegrass 'Palmer II', Kentuckuy bluegrass 'Nassou' and tall fescue 'Boonsai 2000' in greenhouse was investigated. Creeping bentgrass 'Penn-A1', Kentucky bluegrass 'Nassou' and tall fescue 'Boonsai 2000' at Ca 4.0 me/L, and perennial ryegrass 'Palmer II' at Ca 2.0 me/L showed the best shoot growth. Creeping bentgrass 'Penn-A1', perennial ryegrass 'Palmer II' and Kentucky bluegrass 'Nassou' at Ca 1.0 me/L, and tall fescue 'Boonsai 2000' at Ca 4.0 me/L showed the best root growth, and there was little or no difference between different Ca concentrations. Creeping bentgrass 'Penn-Al' and Kentucky bluegrass 'Nassou' at Ca 4.0 mea, and perennial ryegrass 'Palmer II' at Ca 1.0 me/L had the highest number of tillers, and tall fescue 'Boonsai 2000' at Ca 4.0 me/L had the highest, but there was no difference between different Ca concentrations. As application rate of Ca concentration became higher, the concent of Ca in plant tissue increased, while the content of Mg in plant tissue decreased, and the content of Fe in plant tissue increased to Ca 4.0 me/L. The Ca treatment had not effect on N, p, K, and Zn of tissue content. The wick pot applied will be to research of plant nutrition in future because utilization of wick pot has an excellent precision and convenience.

• Economic and Environmental Geology
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• v.30 no.1
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• pp.61-65
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• 1997

Cadmium occurs as a minor element in sphalerite ((Zn, Fe)S) from the Boseong-Jangheung gold-silver mine district. We analyzed the abundance of cadmium in sphalerite using an electron probe micro analyzer (EPMA) and discussed the natural sources of cadmium in terms of bedrock geochemistry, in order to preliminarily reconnoiter the potential cadmium contamination in mine districts. Cadmium contents of sphalerites from the Au-Ag mines (Bodeok, Mundeok, Jeonbo, Boknae, Keumsan) in the Boseong-Jangheung district are considerably high, compared with cadmium contents of sphalerites (average = 0.5 wt.% Cd, maximum = 4.4 wt.% Cd) in the world. Sphalerites from the Keumsan mine (average = 9.49 wt.% Cd, maximum=11.22 wt. Cd) are highly enriched in cadmium. Our data suggest that the Boseong-Jangheung area is an important potential site of cadmium contamination in Korea. Based on bedrock geochemistry, natural causes of cadmium enrichment in sphalerite from the mine district are thought to be the mixing of cadmium leached from organic-rich, metasedimentary rocks (including coal) and/or black shales. From this study, we propose that the pinpointing of potential sites of pollution by toxic heavy metals can be done effectively through detailed reconnaisance study on mineralogical compositions of ore minerals such as sphalerite from the mine area.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.505-517
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• 1997

Lead and zinc mineralization of the Kwangsin mine was formed in quartz and carbonate veins that filled fault-related fractures in the limestone-rich Samtaesan Formation of the Chosun Supergroup and the phyllite-rich Suchangni Formation of unknown age. A K-Ar date of alteration sericite indicates that the Pb-Zn mineralization took place during Late Cretaceous (83.5 Ma), genetically in relation to the cooling of the nearby Muamsa Granite (83~87 Ma). Mineral paragenesis can be divided into three stages (I, II, III): (I) the deposition of barren massive white quartz, (II) the main Pb-Zn mineralization with deposition of white crystalline quartz and/or carbonates (rhodochrosite and dolomite), and (III) the deposition of post-ore barren calcite. Mineralogic and fluid inclusion data indicate that lead-zinc minerals in middle stage II (IIb) were deposited at temperatures between $182^{\circ}$ and $276^{\circ}C$ from fluids with salinities of 2.7 to 5.4 wt. % equiv. NaCl and with log $fs_2$ values of -15.5 to -11.8 atm. The relationship between homogenization temperature and salinity data indicates that lead-zinc deposition was a result of fluid boiling and later meteoric water mixing. Ore mineralization occurred at depths of about 600 to 700 m. Sulfur isotope compositions of sulfide minerals (${\delta}^{34}S_{CDT}=9.0{\sim}14.5$ ‰) indicate a relatively high ${\delta}^{34}S_{{\Sigma}S}$ value of ore fluids (up to 14 ‰), likely indicating an igneous source of sulfur largely mixed with an isotopically heavier sulfur source (possibly sulfates in surrounding sedimentary rocks). There is a remarkable decrease of calculated ${\delta}^{18}O$ value of water in hydrothermal fluids with increasing paragenetic time: stage I, 14.6~10.1 ‰; stage IIa, 5.8~2.2 ‰; stage IIb, 0.8~2.0 ‰; stage IIc, -6.1~-6.8 ‰, This indicates a progressive increase of meteoric water influx in the hydrothermal system at Kwangsin. Measured and calculated hydrogen and oxygen isotope values indicate that the Kwangsin hydrothermal fluids was formed from a circulating (due to intrusion of the Muamsa Granite) meteoric waters which evolved through interaction mainly with the Samtaesan Formation (${\delta}^{18}O=20.1$ to 24.9 ‰) under low water/rock ratios.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.9
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• pp.755-764
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• 2009

To estimate the pollutant removal efficiency by surface sediment, matter content within surface sediment and its release from the sediment were investigated at 12 sites in the Sihwa constructed wetland. The content of COD, TOC, IL, TN, and TP within sediment varied temporally and spacially, showing ranges of 4.1~7.7 mg/g, 0.29~2.81%, 1.88~8.15%, 0.03~0.35%, 362~1,150 ${\mu}g$/g, respectively. The contents of organic matter and TN were significantly highest in March and decreased towards fall (March${\geq}$May${\geq}$July${\geq}$September, p=0.003 for COD, p=0.001 for TOC, p=0.017 for IL, p=0.015 for TN), whereas TP content was not significant statistically in difference between sampling times. The contents of heavy metals also varied largely with sampling sites and times (As:3.5~3.9 ${\mu}g$/g, Cd:0.08~0.38 ${\mu}g$/g, Cr:51.8~107.0 ${\mu}g$/g, Cu:16.4~81.8 ${\mu}g$/g, Pb:26.~81.8 ${\mu}g$/g, Zn:85~559 ${\mu}g$/g). As compared with sediment quality guideline, the content of organic matter within surface sediment of the Sihwa constructed wetland was classified as unpolluted level. In contrast, the contents of TN, TP and heavy metals were classified as medium or severe pollution state, except some heavy metals (Cu and Pb). From the results of release experiment, TN, Pb, and Zn tend to be removed by surface sediment, but TP, Cd, and Cu have a tendency to released from sediment. Therefore, a relevant plan to improve the removal efficiency of pollutant (especially phosphorus) by surface sediment in the Sihwa constructed wetland is needed.

• Applied Biological Chemistry
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• v.44 no.4
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• pp.240-245
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• 2001

Suppression of nitrate accumulation in vegetables through foliar application of micronutrients was investigated. Spinach and lettuce were grown in pots under greenhouse condition. Micronutrient solutions containing Cu, Mn, Mo, and Zn were used; chitosan was added into one and the other contained chitosan oligomers. The micronutrient solutions were sprayed on the leaves at 3 and 4 weeks after transplanting of 20-day-old seedlings. Plants were harvested at 5-weeks after transplanting. Yield, contents of chlorophyll, Brix value, micronutrient, and nitrate, and nitrate reductase activity were measured. Fresh weights of lettuce and spinach were significantly increased by the foliar application of micronutrients. Contents of chlorophyll and micronutrients were higher in micronutrient-treated plants, while those of nitrate were reduced by about 10 and 14-23% in lettuce and spinach, respectively. Compared to the control plants, nitrate reductase activity was higher in plants treated with micronutrients. Results of this study indicate the effect of micronutrients on the suppression of nitrate accumulation was relatively small in comparison to the contents of nitrate in leaves of spinach and lettuce. To maximize the effect, nutrient composition in solution, application time, and frequency should be further examined, taking into consideration nitrogen level in soil and other environmental factors including light condition.