• 센서학회지
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• 제18권4호
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• pp.269-273
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• 2009

In this paper, a study on a portable hydrogen alarm system based on the palladium coated single mode fiber sensor has been reported. The fabricated hydrogen sensor exhibited 0.14 dB, 0.41 dB and 0.54 dB optical intensity variation when it was exposed by the nitrogen and hydrogen mixed gas containing 0.5 %, 1 % and 4 % of the hydrogen concentration, respectively. The fabricated sensor exhibited 20 second of response time and 120 second of recovery time for 4 % hydrogen containing gas. The fiber optics layout and software algorithm for detection of hydrogen leakage have been presented. The implanted portable hydrogen alarm system successfully generated an alarm signal when a 4 % hydrogen containing gas was leaked out.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.66-69
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• 2001

Effect of $N_2$ flow rate on properties of GaN thin films grown by plasma-enhanced molecular beam epitaxy(PEMBE) was discussed to optimize the quality of thin films. It was found that at low $N_2$ flow rate indicating high III/V flux ratio, the growth rate of GaN thin films was controlled by $N_2$ flux, and at high $N_2$ flow rate the growth rate was not controlled by $N_2$ flux any longer. It was also found that III/V flux ratio affected film quality. The film grown at higher $N_2$ flow rate showed low background carrier concentration, higher carrier mobility, and narrow FWHM in band-edge emission of low temperature PL. It is thought that the film in more Ga flux region was grown by 2-dimensional layer-by-layer growth mode, and the film in more nitrogen region was grown by 3-D island growth mode. All samples exhibited a good crystallinity.

• International Journal of Advanced Culture Technology
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• 제4권1호
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• pp.10-18
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• 2016

In the present study, a single cylinder four stroke dual fuel diesel engine was tested to investigate the performance and emission characteristics of various test fuels. The engine was tested in dual fuel mode using diesel and Karanja biodiesel blends as pilot fuel along with Natural gas as primary fuel with a constant gas flow rate under different loading conditions. From the experimentation it was found that smoke opacity and oxides of nitrogen (NOx) are at low level for all the prepared test fuels in dual fuel mode but the emissions of carbon monoxide (CO), carbon dioxide ($CO_2$) and hydrocarbon (HC) were found higher. In comparison to diesel fuel, by increasing the blend percentage different emission parameters are found to be reduced. At different loading conditions all the test fuels show poor performance in dual fuel mode of operation when compared with single mode of operation with diesel and biodiesel. With increase in gas flow rates, except (NOx) and smoke emissions, the other emission parameters like CO, HC and $CO_2$ values increased for all test fuels. Again, all blended fuels showed lower performance compared to diesel. The maximum pilot fuel savings for diesel was found decreasing with the increase in karanja biodiesel. From the present work it may be concluded that Karanja biodiesel with Natural gas in dual mode can be can used as promising alternative for diesel with some required engine modifications and further research must be carried out to minimize the emissions of CO, HC and $CO_2$.

• 한국물환경학회지
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• 제24권5호
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• pp.618-625
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• 2008

Advanced Phase Isolation Ditch (APID) process was studied to develop economic retrofitting technology, for the plants where retrofitting of common activated sludge process is required. In this study, to evaluate the effluent BOD, SS, T-N, and T-P concentrations as process capable and stable parameters for treating municipal wastewater, a demonstration plant was installed and operated in the existing sewage treatment plant of P city. During this study, the average effluent BOD, SS, T-N, and T-P concentrations were 4.56, 5.20, 9.30, and 1.75 mg/L at the conventional mode and 3.95, 3.17, 7.65, and 1.18 mg/L at the modified mode. The modified mode (BOD: 3.69, SS: 3.19, T-N: 1.27, and T-P: 0.69) increased the process capability more than the conventional mode (BOD: 1.80, SS: 1.05, T-N: 2.17, and T-P: 0.15) in this study. If process capability over 1.0, this process is capable and stable to treat wastewater. Therefore, newly developed APID process with modified intermittent aeration mode can be one of the useful processes for stable organic matter and nutrients removal.

• 한국환경농학회지
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• 제33권4호
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• pp.314-320
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• 2014

BACKGROUND: Run off from agricultural sites contaminates water bodies with nitrogen which is toxic and causes eutrophication when excessively accumulated. Hence, the interest in monitoring nitrogen toxicity in aquatic environment has been continuously increasing. METHODS AND RESULTS: To detect a real time toxicity of various nitrogen compounds, we applied biomonitoring method (biosensor) based on sulfur-oxidizing bacteria (SOB). The toxicity biomonitoring test was conducted in semi-continuous mode in a reactor filled with sulfur particles (2~4 mm diameter) under aerobic condition. Relative toxicity was simply determined by measuring the change in electrical conductivity (EC). Various nitrogenous compounds at different concentrations were evaluated as a potential toxic substance. Nitrite was found to be very toxic to SOB with a 90% inhibition even when the concentration as low as 3 mg/L. However, nitrate and ammonia have any inhibitory effect on SOB's activity. CONCLUSION: The biosensor based on SOB responded sensitively to nitrite even at substantially low concentrations. Therefore, it can be used as a reliable biological alarm system for rapid detection of contaminants due to its simplicity and sensitive nature.

• 대한환경공학회지
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• 제27권11호
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• pp.1141-1145
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• 2005

접촉부와 간헐포기부로 구성된 접촉조 결합형 연속회분식반응조를 질소제거를 위해 제안하고 실험적으로 연구하였다. 짧은 체류시간의 접촉반응을 통해 활성슬러지 플록에 유기물질이 생물흡착되지만 불완전 대사가 진행된다는데 근거를 두고 있다. 결과적으로 실하수의 경우 유입 유기물질의 61.2%가 접촉반응 30분 만에 흡착되었다. 유기물질의 비흡착량은 22.3 mg SCOD/g MLVSS였으며, 이는 후속되는 공정에서 탈질효율의 향상에 기여하였다. 연속운전을 통한 전체적인 처리효율은 TCOD/TKN 비가 6이하의 낮은 조건에서도 SCOD 및 T-N 제거율이 각 86%와 60%를 유지하였다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.443-452
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• 1993

Direct freezing tests of soybean seed by liquid nitrogen were carried out at various moisture contents and the following important conclusions were drawn from the results of temperature measurements of soybean seed and photographs of bubbles generated on its surface : 1) Assuming that the temperature gradient in a soybean seed is negligible because of its small seed size and the freezing ratio is followed the Heiss's formula, and a differential equation based on the heat energy balance was introduced . The equation was easily solved by the Runge-Kutta-Gill method and the predicted values of the temperature were in good agreement with the observed data. 2) The photographs of bubble generation during freezing showed the boiling mode was nucleate, and then the most suitable formula on the nucleate boiling heat transfer was introduced from many formulate proposed up to now by fitting the calculated values based on the formula to the observed data. The formula used for the predict on of the seed temperature was as follows: $\frac{{\partial}T_s}{\partial\theta}\;=\;-\frac{{\alpha}(T_s\;-\;T_L)^{3.3}}{W(C_s\;-\;\frac{{\delta}m(CT_s\;+\;{\sigma})}{T_s^2})}$ where C = difference of the specific heat between pure ice and water m=moisture content of soybean seed $T_s$ = seed temperature $T_L$ = Temperature of liquid nitrogen W = mass of soybean seed $\alpha$ = proportional constant $\delta$ = constant depends on variety or the type of seed $\theta$ = time $\sigma$ = latent heat of melting of pure ice This study will give important information in the hydro-freezing technique by liquid nitrogen, available as a new technique of processing agricultural products in the near future.

• 한국추진공학회지
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• 제21권5호
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• pp.1-9
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• 2017

초임계 환경에서 와류형 분사기의 극저온 질소 분무 동적 특성 분석을 위하여 3차원 LES 난류 모델을 적용하였다. 초임계 상태에서 질소의 상태량들을 정확하게 예측하기 위해 SRK 실기체 상태방정식을 사용하였고, 점성계수와 열전도도는 Chung의 고압 상태 혼합물에 대한 방정식, 그리고 확산 계수는 Fuller의 이론에 Takahashi의 보정식을 적용하였다. 질소 분무 결과, 분사기 내, 외부에서 유동장과 음향장 사이의 상호작용으로 복잡한 유동구조가 형성된다. 복잡한 유동 현상을 분석하기 위해 FFT, POD 그리고 DMD 기법을 적용하여 해석을 수행하였다. FFT 해석을 수행하여 분사기 내, 외부에서 나타나는 특정 주파수를 파악하였으며, POD와 DMD를 통해 각 주파수가 어떠한 유동 구조를 갖는지에 대한 연구를 수행하였다. 또한, DMD를 통해 각 주파수의 감쇠 계수를 파악하여 이를 실험 결과와 비교하였다.

• 한국연초학회지
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• 제29권2호
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• pp.140-145
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• 2007

Acrylamide has been found in many foods. Acrylamide in foodstuffs were analyzed by a GC/MS after bromination of acrylamide or by a LC/MS for underivatized acylamide. Time consuming and laborious clean up procedures is applied for the purification of the extract, in these methods. In this study, a simple and fast method without clean up step for the analysis of acrylamide in mainstream cigarette smoke was developed by using liquid chromatography-tandem mass spectrometry (LC/MS/MS) and the effects of tobacco leaf constituents on acrylamide content was observed. The analysis of acrylamide in mainstream cigarette smoke started to collect TPM (total particulate matter) from smoking and to extract by 0.1 % acetic acid solution and then to detect by liquid chromatography tandem mass spectrometry using electrospray in the positive mode. The recovery of acrylamide in 2R4F reference cigarette was 98 % and the reproducibility was 2.5 % and the limit of detection was 1.6 ng/mL. Reducing sugars and amino acids are considered to be main precursors of acrylamide in foodstuffs. Cut tobacco contain substantial amounts of reducing sugars and amino acid which may be explained the occurrence of acrylamide in mainstream cigarette smoke. The effects of reducing sugars and total nitrogen studied in an experiment with a various tobacco types. This result indicated that reducing sugars are not limiting factor for acrylamide formation, but the level of acrylamide in cigarette smoke was significantly correlated with the total nitrogen contents.

• 멤브레인
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• 제9권1호
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• pp.25-35
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• 1999

산소농축공기 제조용 폴리설폰 실관막에 대한 산소.질소의 수착 및 투과실험을 수행하였다. 폴리설폰 실관막에 대한 산소의 수착량이 질소의 수착량보다. 1.5배 ~2 배 높았다. 저압영역(약 3 kgf/$cm^2$이하) 에서는 Henry-type 수착량 ($C_D$)이 전체수착량의 약 15% 이었으며, Langmuir 수착이 약 85%이었다. 고압영역(약 3 kgF/$cm^2$이상)에서는 Langmuir 수착은 거의 포화되어 일정한 값에 도달하였으며, Henry 용해에 의한 수착($C_D$ = $k_D$.p) 의 증가에 의하여 전체 수착량이 증가하였다. 산소와 질소의 수착은 dual-mode sorption 모델을 만족시켰다. 산소의 투과 활성화에너지(Ep)가 질소보다 컸고, 이상분리인자 (${O_2}/{N_2}$)는 2~4를 나타내었으나 , 혼합물의 실제 분리인자는 1.7 ~2.2로 낮아졌다.