• 대한기계학회논문집B
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• 제29권11호
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• pp.1277-1284
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• 2005

The combustion characteristics of methane oxygen diffusion flames have been investigated to give basic information for designing industrial oxyfuel combustors. NOx reduction has become one of the most determining factors in the combustor design since the small amount of nitrogen is included from the current low cost oxygen production process. Flame lengths decreased with increasing fuel or oxygen velocity because of the enhancement of mixing effect. Correlation equation between flame length and turbulent kinetic energy was proposed. NOx concentration was reduced with increasing fuel or oxygen velocity because of the enhanced entrainment of the product gas into flame zone as well as the reduction of residence time in combustion zone.

• 한국수소및신에너지학회논문집
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• 제28권5호
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• pp.554-560
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• 2017

Reduction reactivity of new oxygen carriers for chemical looping combustion system were investigated using $CH_4$ as a reduction gas in a bubbling fluidized bed reactor and compared with that of former SDN70 oxygen carrier. New oxygen carriers showed good reduction reactivity at different $CH_4$ concentration. N018-R2 particle represented better reactivity than SDN70 at high $CH_4$ concentration. N018-R2 particle showed higher fuel conversion and $CO_2$ selectivity than those of SDN70 particle within the temperature range of $750-900^{\circ}C$. Moreover, attrition loss of N018-R2 particle was almost same with that of SDN70 particle. Consequently, we could select N018-R2 particle as the best oxygen carrier.

• 전기학회논문지
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• 제67권12호
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• pp.1641-1647
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• 2018

In this paper, we describe a portable potentiostat which is capable of cyclic voltammetry(CV) and amperometry for electrochemical dissolved oxygen sensor. In addition, this portable potentiostat can also transmit the measured data wirelessly to android devices such as smart phone, tablet, etc. through Bluetooth. The potentiostat system consists of three parts; a voltage generator circuit which is controlled by Arduino nano and 12-bit DAC(digital to analog converter) to generate necessary electric potential for operating the electrochemical sensor, an oxidation/reduction current measurement circuit, and a Bluetooth module to transmit data wirelessly to an android device. Once measurements are carried out with the android application, the measured data is transmitted to the android device via Bluetooth and displayed using the android app. in real time. In this paper, we report the measured reduction current with a fabricated dissolved oxygen sensor in both saturated-oxygen state and zero-oxygen states. The results of the developed portable potentiostat system are in good agreement with those of the commercial portable potentiostat (${\mu}stat200$, Dropsens inc.). The measured peak reduction currents using the developed potentiostat and the commercial ${\mu}stat200$ potentiostat were $-0.755{\mu}A$ and $-0.724{\mu}A$, respectively. The reduction currents measured at zero-oxygen state were $-0.005{\mu}A$ and $-0.004{\mu}A$. The discrepancy between those two systems seems very small, which implies successful development of a portable and wireless potentionstat.

• 공업화학
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• 제30권1호
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• pp.43-48
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• 2019

본 연구는 매체순환연소공정용 산소전달입자로서 $CaSnO_3$ 입자의 타당성을 조사하기 위해 수행하였다. $CaSnO_3$은 페롭스카이트 구조를 가지고, 반복되는 환원-산화 반응 후에도 구조적안정성을 보였다. 산소전달량은 환원 반응 시 결정구조 변화를 통해 계산된 이론 수치와 거의 동일한 15.4 wt%를 가졌다. 10번의 환원과 산화 반응 후에, 산소전달량과 산소전달속도는 작동 온도에서 일정하게 유지되었다. 결론적으로, $CaSnO_3$ 입자는 CLC의 산소 운반체로서 좋은 대체 물질이 될 수 있다고 판단하였다.

• 한국해양공학회지
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• 제22권5호
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• pp.75-82
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• 2008

As a basic study for establishing a countermeasure for an oxygen deficient water mass (ODW), we investigated the variation of ODW volume according to the enforced total pollution load management in Jinhae Bay. This study estimated the inflowing pollutant loads into Jinhae Bay and predicted the reduction in ODW by using a sediment-water ecological model (SWEM). The result obtained in this study are summarized as follows: 1) The daily average pollutant loads of COD, SS, TN, TP, DIN, and DIP inflowing into Jinhae bay in 2005 were estimated to be about 12,218 kg-COD/day, 91,884 kg-SS/day, 5,292 kg-TN/day, 182 kg-TP/day, 4,236 kg-DIN/day, and 130 kg-DIP/day. 2) The calculated results of the tidal current by the hydrodynamic model showed good agreement with the observed currents. Also, an ecological model well reproduced the spatial distribution of the water quality in the bay. 3) This study defined the ODWDI (ODW decreasing index) in order to estimate the ODW decreasing volume caused by a reduction in the inflowing pollutant loads. As a result, the ODWDI was predicted to be about 0.91 (COD 30% reduction), 0.87 (COD 50% reduction), 0.79 (COD 70% reduction), 0.85 (ALL 30% reduction), 0.66 (ALL 50% reduction), and 0.45 (ALL 70% reduction). The ODW volume was decreased 1.5 $\sim$ 2.6 times with a reduction in the COD, TN, and TP inflowing pollutant loads compared to a reduction in just the COD inflowing pollutant load. Therefore, it is necessary to enforce total pollution load management, not only for COD, but also fm TN and TP.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.288-288
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• 2012

The oxidation characteristics of tungsten line pattern during the carbon-based mask layer removal process using oxygen plasmas and the reduction characteristics of the WOx layer formed on the tungsten line surface using hydrogen plasmas have been investigated for sub-50 nm patterning processes. The surface oxidation of tungsten line during the mask layer removal process could be minimized by using a low temperature ($300^{\circ}K$) plasma processing instead of a high temperature plasma processing for the removal of the carbon-based material. Using this technique, the thickness of WOx on the tungsten line could be decreased to 25% of WOx formed by the high temperature processing. The WOx layer could be also completely removed at the low temperature of $300^{\circ}K$ using a hydrogen plasma by supplying bias power to the tungsten substrate to provide an activation energy for the reduction. When this oxidation and reduction technique was applied to actual 40 nm-CD device processing, the complete removal of WOx formed on the sidewall of tungsten line could be observed.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.97.2-97.2
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• 2011

Pt-Ru and Pt-Ni bimetallic catalysts were prepared and tested for heavy hydrocarbon reforming. Metals were supported on CGO($Ce_{0.8}Gd_{0.2}O_{2.0-x}$) by incipient wetness method. The prepared catalysts were characterized by Temperature programmed reduction(TPR). Oxidative steam reforming of n-dodecane was conducted to compare the activity of the catalysts. The reforming temperature was varied from $500^{\circ}C$ to $800^{\circ}C$ at fixed $O_2$/C of 0.3, $H_2O$/C of 3.0 and GHSV of 5,000/h.Reduction peaks of metal oxide, surface CGO and bulk CGO were detected. Reduction temperature of metal oxide decreased over the bi-metallic catalysts. It is considered that interaction between metals leads to decrease interaction between metal and oxygen. On the other hands, reduction temperatures of surface CGO were dectected in the order of Pt-Ru > Pt-Ni > Pt. low reduction temperatures of surface CGO indicates the low activation energy for oxygen ion conduction to metal. Oxygen ion conduction is known as de-coking mechanism of ionic conducting supports such as CGO. In activity test, fuel conversion was in the same order of Pt-Ru > Pt-Ni > Pt. Especially, 100% of fuel conversion was obtained over Pt-Ru catalysts at $500^{\circ}C$.

• Nuclear Engineering and Technology
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• 제53권6호
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• pp.1931-1938
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• 2021

Uranium ingot is produced by metallothermic reduction of uranium tetrafluoride using magnesium or calcium as reductant. Presence of oxygen containing compounds viz. uranyl fluoride and uranium oxide in the starting uranium fluoride has a significant effect on the firing time, final temperature of the charge, slag-metal separation and hence the metal recovery. As reported in the literature, the maximum tolerable limit for uranyl fluoride in the UF₄ is 2.5 wt% and limit for uranium oxide content is in the range 2-3 wt%. No theoretical or experimental basis is available till date for these limits. Analyses have been carried out in this study to understand the effect of UO₂F₂ concentration in the starting fluoride on the final temperature of the products and thus the reduction characteristics. UF₄ having uranyl fluoride concentration, less than as well as more than 2.5 wt%, have been investigated. Thermodynamic calculations have been carried out to arrive at a general expression for the final temperature attained by the products during calciothermic reduction of UF₄. Finally, an upper limit for the oxygen containing impurities has been estimated using the CaO-CaF₂ phase diagram.

• 자원리싸이클링
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• 제18권5호
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• pp.12-18
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• 2009

고분자전해질 연료전지용 캐소드 촉매로서 화학환원법을 이용하여 20% Pt/C 제조하고 다양한 온도($300-600^{\circ}C$)열처리하여 산소환원반응을 평가하였다 $300-400^{\circ}C$에서 열처리한 20% Pt/C가 높은 산소환원반응 활성을 나타냈으며, 특히 $300^{\circ}C$에서 열처리한 촉매를 0.6V에서의 정전위를 측정한결과, 열처리하지 않은 촉매에 비해서 산소환원 반응 활성정도가 2배 높게 나타났다. TEM 및 XRD 분석을 이용하여 조사한 결과, 열처리 온도가 높아짐에 따라서 백금 입자 크기가 커지고 결정화도가 증가하는 것을 확인하였다. 이러한 결과에서 산소환원반응 활성을 위한 백금의 입자 크기와 결정화도가 $300^{\circ}C$에서 최적화되는 것으로 판단된다.

• 한국자동차공학회논문집
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• 제12권5호
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• pp.66-72
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• 2004

In this study, the effects of oxygen component in fuel and exhaust gas recirculation(EGR) method on the exhaust emissions has been investigated for a D.I. diesel engine. It was tested to estimate change of exhaust emission characteristics for the commercial diesel fuel and oxygenate blended fuel which has five kinds of blending ratio. Dimethoxy methane(DMM) contains oxygen component 42.5% in itself, and it is a kind of effective oxygenated fuel for reduction of smoke emission. It was affirmed that smoke emission was decreased with increasing of DMM blending ratio. But, NOx emission was increased compared with commercial diesel fuel. It was needed a NOx reduction counterplan that EGR method was used as a countermeasure for NOx reduction. It was found that simultaneous reduction of smoke and NOx emission was achieved with DMM blended fuel and cooled EGR method(1015%).