• Resources Recycling
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• v.3 no.2
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• pp.17-23
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• 1994

The dissolution of gold and silver from concentrate was studied with acidic thiourea solution. The results showed that the gold and silver extraction was severely affected by concentration of thiourea and oxidant, pulp density, etc. Especially, oxidant such as ferric ions enhanced the leching rate of gold and silver. High concentration of ferric ions, however, dissolved the sulfide ore to form electrochemically passive layer on the surface of ore particles, which caused the precious metal not to be leached out from the ore. The use of $SO_2$could not effectively enhance the recovery of precious metal but reduce to some extent the consumption of thiourea. The leaching of gold and silver was achieved with recovery more than 90% and 80%, respectively, under the following conditions; Thiourea conc. :0.4M Oxidant : None $H_2SO_4$ conc. : 0.5M Pulp density : <10% Leaching time :4 Hrs Potential :250mV The Thiourea was consumed about 10% in comparison with its initial concentration.

• Journal of Sericultural and Entomological Science
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• v.52 no.1
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• pp.59-63
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• 2014

The effects of LED irradiation on growth and functional components of crops are actively being studied. We investigated the effects of red LED on the cordyceps cultivation because Cordyceps is very difficult to find in the wild and to cultivation. The synnemata formation rate of P. tenuipes was 100% under red LED. Also weight, length, and number of the synnemata were significantly increased. We expect that the red LED treatment will be of help to improve farm income.

• Analytical Science and Technology
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• v.14 no.3
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• pp.259-265
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• 2001

Photocatalytic degradation of Congo red was performed using various semiconductors as ZnO, CdS, rutile-$TiO_2$ or mixed rutile-$TiO_2$/ZnO. The change of degradation of the dye was investigated by UV-visible spectrophotometric method. The photocatalytic action of CdS was greater than ZnO and rutile-$TiO_2$ in account of low band gap energy of CdS. The rate of photocatalytic degradation reaction increased drastically in according to increasing ratio of ZnO on mixed rutile-$TiO_2$/ZnO. These photocatalytic effect of rutile-$TiO_2$ was suppressed by more stable rutile-$TiO_2$, doping the hydrolysis product with $Zn^{2+}$ prior to calcination onto the rutile-$TiO_2$ surface.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.5
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• pp.501-509
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• 2016

In this study, a flat-type photocatalytic reactor is applied under solar irradiation for simultaneous treatment of target pollutants: reduction of Cr(VI) to Cr(III) and oxidation of EDCs (BPA, EE2, E2). An immobilized type of photocatalyst was fabricated to have self-grown nanotubes on its surface in order to overcome limitations of powdery photocatalyst. Moreover, Ti mesh form was chosen as substrate and modified to have both larger surface area and photocatalyst content. Ti mesh was anodized at 50V and $25^{\circ}C$ for 30min in the mixed electrolytes ($NH_4F-H_2O-C_2H_6O_2$) and annealed at $450^{\circ}C$ for 2 hours in ambient oxygen to have anatase structure. Surface characterization was done with SEM and XRD methodologies. Fabricated NTT was applied to water treatment, and coexisting Cr(VI) and organics (EDCs) enhanced each other's reactions by scavenging holes and electrons and thus impeding recombination. Also, several experiments were conducted outdoor under direct sunlight and it was observed that both solar-tracking and applying modified photocatalyst were proven to enhance reaction efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.6
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• pp.476-481
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• 2014

In this paper, we design the pre-equalizer of transmitter circuit in order to enhancement modulation bandwidth of white LED which is light source of VLC (Visible Light Communication). Also, we eliminate yellow light component by optical filtering which mitigate frequency response of white LED. Power loss by optical filtering is overcome by using convex lens. By applying proposed system, 3 dB bandwidth deciding modulation bandwidth of white LED increases from 3 MHz to more than 25 MHz and the transmission distance increases by optical design which secure additional signal power. We optically modulate NRZ-OOK signal to LED and receive light signal using APD. We analyze received data using CSA and RFSA. As a result, we experimently demonstrate the possibility that transmits NRZ-OOK signal up to 30 Mbps in 4.5 m, 50 Mbps in 1.5 m through the pre-equalizer and optical design.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.76-76
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• 2019

최근 기후변화로 인해 퇴적 및 세굴이 심화되었고, 4대강 사업으로 인해 급격한 하천 지형 변화가 발생하였다. 특히, 4대강 사업 이후 하상변동 모니터링에 대한 지속적인 수요가 증가하고 있다. 이에 따라 개정된 하천법에 따르면 하상변동조사를 기본 10년 주기로 정기적으로 실시하되, 퇴적 및 세굴 발생 구간에 대해서는 기본 2년을 기준으로 하상변동이 큰 곳에 대해서는 1년 주기로, 하상변동이 작은 곳에 대해서는 5년 주기로 실시해야 한다. 하지만 기술 및 예산의 한계로 인해 하상변동조사의 경우 현장 유사량 및 하상토 입도 측정과 유량-총유사량 관계식을 활용하여 모델링을 통해 하상변동을 예측하고 있는 실정이다. 하상변동은 기본적으로 하천 수심을 기본으로 하고 있으며, 사람이 직접 투입하여 임의의 지점에 대한 수심 계측을 실시하고 있다. 하지만 직접 수심 계측의 경우 낮은 자료의 밀도로 인해 많은 인력과 예산, 시간이 소요되며 무엇보다도 관측 대상인 물이라는 작업환경에서는 인명피해가 발생할 수 있는 문제점을 가지고 있다. 최근에는 이러한 한계를 극복하기 위해 초음파 센서가 탑재된 이동식 보트를 활용하여 경로형 수심 계측을 실시하고 있으나, 초음파 센서가 가지는 기기적 한계로 인해 약 50cm 이하에 대한 수심은 측정이 어려운 실정이다. 특히, 국내 하천의 경우는 홍수기를 제외하면 수심이 얕기 때문에 얕은 수심에 대한 자료 확보가 어려워 공간적 정밀도 확보가 어려운 실정이다. 따라서 기존의 하천계측의 패러다임을 지점, 선형 계측이 아닌 면 측량을 실시를 통해 높은 밀도의 자료를 확보해야 한다. 이러한 측량이 가능한 기술로 하천원격탐사가 대안으로 제시되고 있다. 하천원격탐사는 직접 접촉하지 않고, 대상체의 광학적 특성을 통해 물리적 특성을 파악하는 기술로서 적은 시간에 높은 밀도의 자료의 확보와 저예산의 고효율 방법으로 알려져 있다. 본 연구에서는 기존의 하천원격탐사에서 활용한 고비용, 저해상도의 시공간 스케일에 해당하는 위성 및 유인항공기가 아닌 하천의 흐름방향으로 비행이 가능하고 상대적으로 저비용, 고해상도의 시공간 스케일의 측정이 가능한 드론을 활용하여 하천원격탐사를 수행하는 방법에 대해 논하고자 한다. 특히, 기술적 한계가 존재하는 청색, 녹색, 적색에 해당하는 RGB 영상을 활용한 하천원격탐사를 극복하기 위한 대안으로 초분광 영상을 수집하고 활용하는 방법을 제시하고자 한다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.4 s.48
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• pp.439-444
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• 2004

UV irradiation produces free radicals and related reactive oxygen species (ROS), and these are injury to all most of organisms of skin cells and extracellular matrix (ECM). In addition, free radicals and ROS stimulate the overexpression of matrix metalloproteinases (MMPs) that can degrade most components of ECM such as collagen. Since collagen constitutes almost of skin connective tissue, their disarrangement causes wrinkle formation and droop of skin. Therefore, scavenging activity on free radicals, ROS and suppression of MMP-1 is expected to prevent skin photoaging. In this study, to investigate the relationship between photoaging and Draconis sanguis, we examined the effects of antioxidant, in vitro MMP inhibition and expression of UVA-induced MMP-1 in human dermal fibroblasts. Draconis sanguis was found to show scavenging activities of radicals and ROS with the $IC_{50}$ values of $183{\;}{\mu}g/mL$ against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and $30{\;}{\mu}g/mL$ against superoxide radicals in the xanthine/xanthine oxidase system, respectively. Draconis sunguis inhibited the activities of MMP-1 in a does-dependent manner and the $IC_{50}$ value calculated from semi-log plots was $200{\;}{\mu}g/mL$. Also, UVA induced MMP expression was reduced $74\%$ by treatment with Draconis sanguis, and MMP-1 mRNA expression was reduced in a dose-dependent manner. Therefore Draconis sanguis was able to significantly inhibit MMP expression in protein and mRNA level. All these results suggested that Draconis sanguis may act as an anti-photoaging agent by antioxidation and reducing UVA-induced MMP-1 production.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.4
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• pp.275-286
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• 2008

In this study, we investigated the anti-oxidative, anti-wrinkle and whitening effects of Platycarya strobilacea bark extracts. The free radical (1,1-diphenyl-2-picrylhydrazyl, DPPH) scavenging activity ($FSC_{50}$) of extract / fractions of Platycarya strobilacea was in the order: 50% ethanol extract ($6.75{\mu}g/mL$) < deglycosylated aglycone fraction ($6.62{\mu}g/mL$) < ethyl acetate fraction ($4.15{\mu}g/mL$). Reactive oxygen species (ROS) scavenging activities ($OSC_{50}$) of some Platycarya strobilacea extracts on ROS generated in $Fe^{3+}$-EDTA/$H_2O_2$ system were investigated using the luminol-dependent chemiluminescence assay. The order of ROS scavenging activity was ethyl acetate fraction (OSC50, $0.56{\mu}g/mL$) < 50% ethanol extract ($0.02{\mu}g/mL$) < deglycosylated aglycone fraction ($0.01{\mu}g/mL$). The deglycosylated aglycone fraction showed the most prominent scavenging activity. The protective effects of extract / fractions of Platycarya strobilacea on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The ethanol extract (50%) suppressed photohemolysis in a concentration dependent manner, particularly ethyl acetate fraction exhibited the most prominent cellular protective effect (${\tau}_{50}$, 717.27 min at $10{\mu}g/mL$). The inhibitory effect of Platycarya strobilacea extracts on tyrosinase were investigated to assess their whitening efficacy. Finally, their anti-elastase activities were measured to predict the anti-wrinkle efficacy in the human skin. The inhibitory effect ($IC_{50}$) on tyrosinase of some Platycarya strobilacea extracts was 50% ethanol extract ($243.98{\mu}g/mL$) < ethyl acetate fraction ($153.87{\mu}g/mL$) < deglycosylated aglycone fraction ($137.53{\mu}g/mL$). Also, The inhibitory effect of elastase ($IC_{50}$) of some Platycarya strobilacea extracts was 50% ethanol extract ($31.01{\mu}g/mL$) < ethyl acetate fraction ($14.42{\mu}g/mL$) < deglycosylated aglycone fraction ($1.48{\mu}g/mL$). The cream containing the ethyl acetate fraction of Platycarya strobilacea extracts was formulated. The skin hydration, transepidermal water loss, and the whitening effects were investigated after topical application of the cream. The skin hydration of cream containing extract was increased by $2{\sim}8%$ than the placebo cream, transepidermal water loss was decreased. The cream containing extract suppressed the melanogenesis of skin by 9.55% than the placebo cream. These results indicate that extract / fractions of Platycarya strobilacea can function as antioxidants in biological systems, particularly skin exposed to UV radiation by anti-oxidative activity and protect cellular membranes against ROS. The inhibitory effect on elastase and tyrosinase, and the increase of skin hydration and the whitening effect of the cream containing extract could be applicable to new functional cosmetics for antiaging.

• Journal of Mushroom
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• v.11 no.2
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• pp.99-106
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• 2013

This study was initiated to investigate the skin whitening activities of methanol extracts from fruiting bodies of I. obliquus. The total polyphenols and flavonoids contents of I. obliquus methanol extracts were 31.85 mg/g and 28.33 mg/g, respectively. The methanol extract of the mushroom treated on B16/F10 melanoma and NIH3T3 cell lines did not show cytotoxic activity. 2,2-diphenyl-1-picrylhydrazyl(DPPH) free radical scavenging activity and chelating activity on ferrous ions of I. obliquus methanol extract were lower than those of positive control, tocopherol and BHT. The tyrosinase and L-DOPA inhibitory activities of the extract were lower than those of positive control, kojic acid and ascorbic acid. The tyrosinase and melanin synthesis inhibitory activities of the melanoma cells treated with the extract were comparable with positive control, arbutin. The experimental results suggested that methanol extract of I. obliquus contained inhibitory activities of tyrosinase and melanin synthesis in the B16/F10 melanoma cells by dose dependent manner. High ultra-violet absorption spectra in the range of 280-350 nm showed that I. obliquus extract could protect skin from UV radiation damage. Therefore, fruiting bodies of I. obliquus can be used for developing skin whitening, anti-UV and skin care agents.

• Journal of Applied Biological Chemistry
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• v.55 no.4
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• pp.207-215
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• 2012

Phenolic compounds of $17.9{\pm}1.0mg/g$ were extracted from Ulmus pumila with 70% ethanol. The elastase inhibitory activity related with forming wrinkle was shown an excellent wrinkle improvement effect in 70% ethanol extracts as 55.5-69.5% at phenolic concentration of $50-200{\mu}g/mL$. The tyrosinase inhibitory activity related with skin-whitening was 24% in 70% ethanol extracts at phenolic concentration of $200{\mu}g/mL$. The astringent activity of 70% ethanol extracts was shown activity of 71% at phenolic concentration of $200{\mu}g/mL$ therefore it is judged that there is a high effect on pores reduction of the skin. The hyaluronidase inhibitory activity of U. pumila extracts was confirmed anti-inflammation effect of 80% at phenolic concentration of $50{\mu}g/mL$. Antimicrobial activity of U. pumila water extracts was shown each 8.7, 10.0, 11.1 and 11.8 mm clear zones on Propionebacterium acnes at phenolic concentration of $50-200{\mu}g/mL$. The stability of the multi-functional cosmetic (lotion) added U. pumila extracts was very stable for 28 days without changing of pH and viscosity also it's stable on temperature and sun lights. As the concentration of extracts was increased, the color of lotion was getting dark, but the sensory evaluation was high at score of 8.5.