• Current Photovoltaic Research
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• 제6권4호
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• pp.91-93
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• 2018

Polythiophene-$TiO_2$ composite was synthesized with different molar ratios of thiophene and titaniumisopropoxide ($Ti(OPr)_4$) for flexible solar cell application as a flexible electrode or an active material. The $Ti(OPr)_4$ was stabilized by thiophene. The thiophene was polymerized by ferric chloride catalyst. The synthesized polythiophene exhibited strong UV-visible absorption in the range of the wavelength shorter than 500 nm. Field emission scanning electron microscope (FESEM) image of low concentration of $TiO_2$ film showed smooth surface. However, FESEM image of high concentration of $TiO_2$ film exhibited relatively rough surface. Polythiophene concentration dependent strong photoluminescence quenching of surfrhodamine-B was observed.

• 한국결정성장학회지
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• 제26권5호
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• pp.175-180
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• 2016

본 연구에서는 수용액 상에서 침전법과 수열합성법을 이용하여 나노크기의 ZnO 분말을 합성하였다. 두 합성방법 모두 출발원료로는 Zn-nitrate hexahydrate($Zn(NO_3)_2{\cdot}6H_2O$)와 NaOH 수용액을 사용하였고, 이들의 혼합용액에 합성조건 즉 반응 pH, 온도 및 Zn precursor의 몰 농도를 달리하여 ZnO 분말을 얻을 수 있었다. 두 합성법 모두에서 단일 상 ZnO는 낮은 Zn 농도 높은 pH 및 높은 온도 조건에서 합성되기 쉬웠다. 합성된 분말의 형상은 flake(plate), multipod 및 rod 형태로 합성 조건에 따라 그 형태의 조절이 가능하였다. 침전법에 비해 수열합성법은 $100^{\circ}C$ 이하인 비교적 낮은 합성온도에서도, 본 연구의 Zn 농도 전 구간(0.1~1 M)과 넓은 pH 범위에서 결정성이 우수한 ZnO 단일 상을 합성할 수 있는 장점을 보여주었다.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.235-238
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• 1997

Basic properties of new cement pastes based on the system $CaO-Al_2O_3-P_O_5-H_2O$were studied Phosphoric acid solutions and calcium dialuminate clinkers synthesized by the hydration-burning method were used for liquid and powder components of the paste, respectively Variation in the compositions of the paste was achieved by changing the liquid/powder ratio and the concentration of phosphoric acid solution. The hardening rate of the paste was so largely affected by the amount of phosphoric acid that hardening was inhibited with the low-concentrated solution but was explosively accelerated with the high-concentrated solution. The phosphoric acid solutions of concentration of 45~50% and the liquid/powder ratio of 0.5~1.5 were favoured for the high early-strength cement paste with the reasonable hardening rate and high strength. The binding phase of hardened paste was the dense amorphous gel of the system $CaO-Al_2O_3-P_O_5-H_2O$. in which the unreacted calcium dialuminate grains were embeded.

• 한국안전학회지
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• 제30권6호
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• pp.117-121
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• 2015

$O_2$-deficiency related accidents occur every year and the most effective way to prevent them is to measure $O_2$ concentration in air with a properly-calibrated $O_2$ monitoring device before entering low-$O_2$ areas. An electro-chemical sensor, Texas Instrument gas platform, and iPhone are used to construct a smartphone-based $O_2$ monitoring device. The smartphone based $O_2$ measuring approach offers advantages of small size, accessibility, internet-connectivity, and programmability in comparison to conventional $O_2$ measuring devices. Multiple gas sensors can be conveniently interfaced to single smartphone, allowing for creating a network of gas sensors distributed across workplaces and remote monitoring via existing mobile communication network. To check proper function of the $O_2$ monitoring device the sensor was exposed to shallow and deep human breaths. The readings decreased immediately after being exposed to exhalation and recovered during inhalation to a calibrated level of 20.9%. When readings decreased below a preset warning value of 19.5%, a low $O_2$ warning was successfully activated on the smartphone.

• 한국대기환경학회지
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• 제13권1호
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• pp.1-7
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• 1997

Anion concentrations and distributions of airborne fine particles less than 2 $\mu$m in urban atmosphere were determined from Feb. 5 to 16, 1996. The sampling was carried out using 8 stages Hering's low pressure impactor (LPI, aerodynamic cutoff diameters are 0.05, 0.075, 0.11, 0.26, 0.50, 1.0, 2.0, and 4.0$\mu$m) on the top of a five-story building located at Kon-Kuk university in Seoul. Average concentrations if C $l^{[-10]}$ , N $O_3$$^{[-10]}$ and S $O_4$$^{2-}$ were 9.4, 8.4, and 14.5 $\mu\textrm{g}$/㎥, respectively. The distributions of these anion concentrations were bimodal types which showed two peaks in the range of 0.075~0.12 ${\mu}{\textrm}{m}$ and 0.5~1 ${\mu}{\textrm}{m}$ in aerodynamic diameter. These results were 2.5~4.7 times higher than anion concentrations collected by Anderson low volume air sampler.

• 한국환경과학회지
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• 제16권7호
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• pp.813-821
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• 2007

Laboratory scale experiments were conducted to investigate the removal characteristics of nitrogen and phosphorus in two sequencing batch biofilm reactors (SBBRs). SBBR1 had a short first non-aeration period and SBBR2 had a long first non-aeration period. The removal characteristics of nitrogen and phosphorus in each SBBR were precisely observed according to the variation of influent TOC concentration, and the operation control parameters (pH, DO concentration, ORP) in each reactor were measured. In biological nitrogen removal, there was little difference between SBBR1 and SBBR2 and the nitrogen removal efficiencies were very low. The nitrogen and phosphorus removal characteristics in high influent TOC concentration were different from those in low TOC. Nitrogen removals by simultaneous nitrification/denitrification (SND) were occurred in both SBBR1 and SBBR2. The P removal in SBBR1 was superior to that in SBBR2. The second P release was observed in SBBR1 which had long second non-aeration period.

• 한국안전학회지
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• 제19권4호
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• pp.74-79
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• 2004

[ $CO_3O_4/{\gamma}-Al_2O_3$ ] catalysts were reported high activity on the low temperature CO oxidation. The effects of the calcination temperature, the loaded amount of cobalt and the oxygen concentration on the characteristics of CO oxidation have been investigated for a emergency escape mask cartridge. $Co(NO_3)_2\cdot6H_2O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. TGA shows that enough calcination is accomplished at $450^{\circ}C$ and cobalt phase is $Co_3O_4$ after calcination in the temperature range of $300\ ~500^{\circ}C$. The specific surface area and pore volume of catalysts are decreased with increasing of loaded amount of cobalt. And with the increase of loaded amount of cobalt and the oxygen concentration, the catalytic activity is increased.

• Advances in environmental research
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• 제5권1호
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• pp.61-77
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• 2016

$NanoTiO_2$ was synthesized by ultrasonication assisted sol-gel process and subjected to iron doping and carbon-iron codoping. The synthesized catalysts were characterized by XRD, HR-SEM, EDX, UV-Vis absorption spectroscopy and BET specific surface area analysis. The average crystallite size of pure $TiO_2$ was in the range of 30 - 33 nm, and that of Fe-$TiO_2$ and C-Fe $TiO_2$ was in the range of 7 - 13 nm respectively. The specific surface area of the iron doped and carbon-iron codoped nanoparticles was around $105m^2/g$ and $91m^2/g$ respectively. The coupled semiconductor photo-Fenton's activity of the synthesized catalysts was evaluated by the degradation of a cationic dye (C.I. Basic blue 9) and an anionic dye (C.I. Acid orange 52) with concurrent investigation on the operating variables such as pH, catalyst dosage, oxidant concentration and initial pollutant concentration. The most efficient C-Fe codoped catalyst was found to effectively destruct synthetic dyes and potentially treat real textile effluent achieving 93.4% of COD removal under minimal solar intensity (35-40 kiloLUX). This reveals the practical applicability of the process for the treatment of real wastewater in both high and low insolation regimes.

• 한국초지조사료학회지
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• 제13권2호
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• pp.93-98
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• 1993

To determine the effects of potassium($K_2O$) fertilization level(0, 100, 200 and 300 kg/ha/year) on the growth, dry matter(DM) yield, nutritive value and nitrate nitrogen($NO_3$-N) concentration of grasses grown under shading condition, this experiment was carried out in Grassland Div., LES, 1989. The plants were sampled on different growing seasons (spring, summer and autumn) and growth stages (grazing and soiling), respectively. Shade was controlled artificially ca. 45-50%, and the level of nitrogen fertilization was 200 kg/ha/year in all treatments. Higher DM was produced in spring 1, 453 kg at grazing and 2, 364 kg/ha at soiling stage, and DM production was increased with increasing level of $K_2O$. In this experiment, the optimum amount of $K_2O$ fertilizer was 200 kg/ha. The neutral detergent fiber, acid detergent fiber, DM digestibility, and relative feed value of grasses were not affected by $K_2O$ fertilization, regardless of growing season and growth stage. The $NO_3$-N concentration of grasses grown in spring was very low (ca. 1.0%), regardless of growth stage and $K_2O$ level. However, $NO_3$-N concentration was very high in summer and autumn season, also $NO_3$-N was decreased significantly with increasing level of $K_2O$ fertilization (P<0.05). Application of $K_2O$ fertilizer, therefore, is thoughs to be desirable for reducing $NO_3$-N concentration of grasses, especially in summer and autumn season. So annual split fertilization of $K_2O$ could be recommended on woodland pasture.

• 대한의용생체공학회:의공학회지
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• 제23권4호
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• pp.295-300
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• 2002

국부적 저산소증(localized hypoxia)은 산소공급의 저하로 인하여 조직세포를 파괴하고 관강압력에 대한 동맥류 벽의 저항을 현저하게 감소시킨다고 보고되고 있다. 본 연구에서는 동맥류 파열의 원인이 되는 저산소증의 기전을 이해하기 위하여 혈전의 두께에 따라 세 가지의 축대칭 동맥류 모델을 구성하여 동맥류 내 혈전을 통한 정상 층류유동 (steady laminar flow)에서의 산소전달현상(O$_2$transport phenomenon)을 유체-고체 열전달 현상과의 유사성을 이용하고 Fick의 법칙을 적용하여 해석하였다. 전산해석을 통해서 혈전이 형성된 혈관에서 산소농도는 혈관 벽에서 가장 낮게 나타났으며 혈전의 크기가 증가할수록 저산소농도(low $O_2$concentration) 영역이 혈관 벽 가까이 넓게 분포되어 저산소증의 가능성이 증가됨을 알 수 있었다 본 연구를 통해서 동맥류 내의 혈전은 구조와 크기에 따라 산소의 흐름에 주요한 영향을 미침을 확인할 수 있었다.