• 한국전기전자재료학회논문지
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• 제24권4호
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• pp.280-284
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• 2011

Silicon carbide (SiC)-based gas sensors can be operated at very high temperatures. So far, catalytic metal-schottky diodes respond fast to a change between a reducing and an oxidizing atmosphere. Therefore SiC diodes have been suggested for high temperature gas sensor applications. In this work, the effect of reactivity of the catalytic surface on the 4H-SiC sensor-structures in 375 K~775 K have been studied and some fundamental simulations have also been performed.

• 에너지공학
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• 제12권2호
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• pp.65-73
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• 2003

국내의 HAPs(Hazardous Air Pollutants)중 수은은 아직까지 관심의 대상이 아니지만 머지않아 문제가 될 것으로 예측된다. 본 논문에서는 현재 국내외의 배가스 수은 배출현황과 처리기술에 대해 요약하였다. 미국을 중심으로 구미 각국에서는 대기분야의 연구개발이 수은에 집중되고 있다. 수은 제어 프로그램은 크게 두 가지로 방향을 잡고 있다. 하나는 기존의 WFGD(Wet Flue Gas Desulfurization)를 이용하여 수은을 산화시켜 제거하는 방법이며 다른 하나는 수은 제거효율이 높은 활성탄 또는 다른 novel sorbent (low-cost sorbent)를 사용하는 방법이다. 선진국에서는 2007년에 발전소 수은 제거설비 설치가 의무화 될 것이다. 본 논문에서 제공하는 자료는 국내에서 발전소 수은 규제가 시작될 때 효과적으로 적용될 수 있을 것이다.

• 한국재료학회지
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• 제27권3호
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• pp.155-160
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• 2017

Doped-$LaCrO_3$ perovskites, because of their good electrical conductivity and thermal stability in oxidizing and/or reducing environments, are used in high temperature solid oxide fuel cells as a gas-tight and electrically conductive interconnection layer. In this study, perovskite $(La_{0.8}Ca_{0.2})(Cr_{0.9}Co_{0.1})O_3$ (LCCC) coatings manufactured by atmospheric plasma spraying followed by heat treatment at $1200^{\circ}C$ have been investigated in terms of microstructural defects, gas tightness and electrical conductivity. The plasma-sprayed LCCC coating formed an inhomogeneous layered structure after the successive deposition of fully-melted liquid droplets and/or partially-melted droplets. Micro-sized defects including unfilled pores, intersplat pores and micro-cracks in the plasma-sprayed LCCC coating were connected together and allowed substantial amounts gas to pass through the coating. Subsequent heat treatment at $1200^{\circ}C$ formed a homogeneous granule microstructure with a small number of isolated pores, providing a substantial improvement in the gas-tightness of the LCCC coating. The electrical conductivity of the LCCC coating was consequently enhanced due to the complete elimination of inter-splat pores and micro-cracks, and reached 53 S/cm at $900^{\circ}C$.

• 한국자동차공학회논문집
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• 제17권3호
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• pp.142-148
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• 2009

The direct injection(DI) diesel engine has become a prime candidate for future transportation needs because of its high thermal efficiency. However, nitrogen oxides(NOx) increase in the local high temperature regions and particulate matter (PM) increases in the diffusion flame region within diesel combustion. Therefore, the demand for developing a suitable after treatment device has been increased. NOx absorbing catalysts are based on the concept of NOx storage and release making it possible to reduce NOx emission in net oxidizing gas conditions. This De-NOx system, called the LNT(Lean NOx Trap) catalyst, absorbs NOx in lean exhaust gas conditions and release it in rich conditions. This technology can give high NOx conversion efficiency, but the right amount of reducing agent should be supplied into the catalytic converter at the right time. In this research, a performance characteristics of LNT with a hydrogen enriched gas as a reductant was examined and strategies of controlling the injection and rich exhaust gas condition were studied. The NOx reduction efficiency is closely connected to the injection timing and duration of reductant. LNT can reduce NOx efficiently with only 1 % fuel penalty.

• 생명과학회지
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• 제32권12호
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• pp.971-978
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• 2022

본 실험은 축산분뇨의 악취제거 활성이 우수한 세균을 분리하기 위하여 돈분뇨와 토양으로부터 황산화균 분리용 배지, 암모늄산화균 분리용 배지 그리고 질소산화균 선택배지를 사용하여 12종의 세균들을 분리하였다. SK2654 균주는 Paenibacillus amylolyticus로, SK2656, SK2658, SK2659 균주들은 각각 Rhodococcus jostii, Rhodococcus qingshengii, Rhodococcus opacus로, SK2657과 SK2672 균주들은 Alcaligenes faecalis로, SK2660과 SK2662 균주들은 Kastia adipata로, SK2665 균주는 Microbacterium oxydans로, SK2673 균주는 Halomonas campisalis로, SK2675 균주는 Acinetobacter oleivorans로, SK2676 균주는 Micrococcus luteus로 동정되었다. 돈분뇨 액상원액에 상기 균주 배양액을 1% 접종하였을 때 발효액의 pH는 전반적으로 8.0을 유지하였다. 총균수는 실험 15일차까지 7.3~7.9 log CFU/ml 수준을 유지하다가 15일차 이후로 5.1~5.5 log CFU/ml 수준으로 급격히 감소하였다. 암모니아태질소 농도는 시험 후반부인 30일차에는 Rhodococcus opacus SK2659 균주를 접종한 처리구가 대조구의 39% 수준을 나타내면서 비교적 높은 암모니아태질소 제거능을 보였다. 실험 100일 후 Rhodococcus opacus SK2659 균주를 접종한 처리구는 대조구와 비교하였을 때에 황화수소 농도는 3.23% 수준으로 악취제거에 가장 효과적이었다. 가스발생량은 대부분의 처리구가 대조구에 비해서 낮았으며 실험기간 중 가스량의 측정 누계량은 대조구의 1/4 수준으로 나타났으며, 그 중 Acinetobacter oleivorans SK2675 균주를 접종한 처리구가 대조구에 비해서 12.39% 수준으로 가장 낮게 나타났다. 돈분뇨의 생물학적 처리시 본 연구에서 분리한 Rhodococcus opacus SK2659와 Acinetobacter oleivorans SK2675 균주들을 혼합하여 사용하면 악취저감 효과가 증대할 것으로 판단된다.

• 한국물환경학회지
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• 제22권6호
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• pp.1014-1021
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• 2006

SMMIAR (Submerged Moving Media Intermittent Aeration Reactor) Process is a very efficient system which remove ammonia to nitrogen gas in one reactor. In this study, we determined the diversity of ammonia oxidizing bacteria and denitrifying bacteria using specific PCR amplification and the clone library construction. An ammonia monooxygenase gene(amoA) was analyzed to investigate the diversity of nitrifiers. Most of amoA gene fragments (27/29, 93%) were same types and they are very similar (>99%) to the sequences of Nitrosomonas europaea and other clones isolated from anoxic ammonia oxidizing reactors. ANAMMOX related bacteria have not determined by specific PCR amplification. A nitrite reductase gene(nirK) was analyzed to investigate the diversity of denitrifying bacteria. About half (9/20, 45%) of denitrifiers were clustered with Rhodobacter and most of others were clustered with Mesorhizobium (6/20, 30%) and Rhizobium (3/20, 15%). All of these nirK gene clones were clustered in alpha-Proteobacteria and this result is coincide with other system which also operate nitrification and denitrification in one reactor. The molecular monitoring of the population of nitrifiers and denitrifiers would be helpful for the system stabilization and scale-up.

• 한국환경농학회지
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• 제39권1호
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• pp.26-35
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• 2020

BACKGROUND: Microbes that govern a unique biochemical process of oxidizing ammonia into dinitrogen gas, such as anaerobic ammonium oxidation (anammox) have been reported to play a pivotal role in agricultural soils and in oceanic environments. However, limited information for anammox bacterial abundance and distribution in the terrestrial habitats has been known. METHODS AND RESULTS: Phylogenetic and next-generation sequencing analyses of bacterial 16S rRNA gene were performed to examine potential anammox bacteria in paddy soils. Through clone libraries constructed by using the anammox bacteria-specific primers, some clones showed sequence similarities with Planctomycetes (87% to 99%) and anammox bacteria (94% to 95%). Microbial community analysis for the paddy soils by using Illumina Miseq sequencing of 16S rRNA gene at phylum level was dominated by unclassified Bacteria at 33.2 ± 7.6%, followed by Chloroflexi at 20.4 ± 2.0% and Acidobacteria at 17.0 ± 6.5%. Planctomycetes that anammox bacteria are belonged to was 1.5% (± 0.3) on average from the two paddy soils. CONCLUSION: We suggest evidence of anammox bacteria in the paddy soil. In addition to the relatively well-known microbial processes for nitrogen-cycle, anammox can be a potential contributor on the cycle in terrestrial environments such as paddy soils.

• 한국대기환경학회지
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• 제13권6호
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• pp.487-495
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• 1997

The most desirable diesel oxidation catalyst (DOC) should have the properties of oxidizing CO, HC and SOF effectively at low exhaust gas temperature while minimizing the formation of sulfate at high exhaust gas temperature. Precious metals such as platinum and palladium have been known to be sufficiently active for oxidizing SOF and also to have high activity for the oxidation of sulfur dioxide $(SO_2)$ to sulfur trioxide $(SO_3)$. There is a need to develop a highly selective catalyst which can promote the oxidation SOF efficiently, on the other hand, suppress the oxidation of $SO_2$. In this study, a Pt-V catalyst was prepared by impregnating platinum and vanadium onto a Ti-Si wash coated ceramic monolith substrate. A prepared Pt-V catalytic converter was installed on a heavy duty diesel engine and the effect of fuel sulfur on particulate matter (PM) of heavy duty diesel engine was measured. The effect of fuel sulfur on PM of Pt-V was also compared with that of a commercialized Pt catalyst currently being used in some of the heavy duty diesel engines in advanced countries. Only 1 $\sim$ 3% of sulfur in the diesel fuel was converted to sulfate in PM for the engine without catalyst, but almost 100% of sulfur conversion was achieved for the engine with Pt catalyst at maximum loading condition. In the case of Pt-V catalyst, there was no big difference in conversion with the base engine even at maximum loading condition. The reason of SOF increase according to the increase of suflate emission was identified as the washing off effect of bound water in sulfate.

• 조명전기설비학회논문지
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• 제29권12호
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• pp.77-82
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• 2015

Ozone is a powerful disinfectant and oxidizing agent, and it is used in a wide range of applications, such as waste water treatment, food processing, etc.. There is also a great potential of using ozone in new emerging medical applications, such as ozone dentistry and ozone oxygen therapy. For these purposes, simple, small, compact and efficient sources of ozone are needed. In this study, in order to increase the current-voltage range of the discharge and to avoid the overheating of the gas in the ozonizer we suggested ozonizer of injection needle and plate electrode type(INP Type) with the gas through the needle. A ozonizer of INP type have been investigated by focusing on ozone concentration and yield according to flow rates and Gap of two electrodes. The results of studies of ozone production for DC corona discharge in oxygen at atmospheric pressure about the ozonizer of INP type. The ozone concentration and the generation yield increased as the gap of two electrodes and gas flow were decreased. Also, when the gap of two electrodes and gas flow with no change, the ozone concentration and generation yield each have variation of direct proportion and inverse proportion with discharge voltage.

• 제어로봇시스템학회논문지
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• 제12권6호
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• pp.539-546
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• 2006

The Air Quality Sensor(AQS), located near the fresh air inlet, serves to reduce the amount of pollution entering the vehicle cabin through the HVAC(heating, ventilating, and air conditioning) system by sending a signal to close the fresh air inlet door/ventilation flap when the vehicle enters a high pollution area. The sensor module which includes two independent sensing elements for responding to diesel and gasoline exhaust gases, and temperature sensor and humidity sensor was designed for intelligent AQS in automobile. With this sensor module, AVR microcontroller was designed with back propagation neural network to a powerful gas/vapor pattern recognition when the motor vehicles pass a pollution area. Momentum back propagation algorithm was used in this study instead of normal backpropagation to reduce the teaming time of neural network. The signal from neural network was modified to control the inlet of automobile and display the result or alarm the situation in this study. One chip microcontroller, ATmega 128L(ATmega Ltd., USA) was used for the control and display. And our developed system can intelligently reduce the malfunction of AQS from the dampness of air or dense fog with the backpropagation neural network and the input sensor module with four sensing elements such as reducing gas sensing element, oxidizing gas sensing element, temperature sensing element and humidity sensing element.