• Journal of Microbiology and Biotechnology
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• v.16 no.3
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• pp.399-407
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• 2006

In this study, an electrical conductive carbon fiber was used as a biofilter matrix to electrochemically improve the biofilter function. A bioreactor system was composed of carbon fiber (anode), titanium ring, porcelain ring, inorganic nutrient reservoir, and VOC reservoir. Electric DC power of 1.5 volt was charged to the carbon fiber anode (CFA) to induce the electrochemical oxidation potential on the biofilter matrix, but not to the carbon fiber (CF). We tested the effects of electrochemical oxidation potential charged to the CFA on the biofilm structure, the bacterial growth, and the activity for metabolic oxidation of VOCs to $CO_2$, According to the SEM image, the biofilm structure developed in the CFA appeared to be greatly different from that in the CF. The bacterial growth, VOCs degradation, and metabolic oxidation of VOCs to $CO_2$ in the CFA were more activated than those in the CF. On the basis of these results, we propose that the biofilm structure can be improved, and the bacterial growth and the bacterial oxidation activity of VOCs can be activated by the electrochemical oxidation potential charged to a biofilter matrix.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.1028-1033
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• 2009

In this study, the dynamics of living cells (LC) and dead cells (DC) in a laboratory-scale biofilm membrane bioreactor for waste gas treatment was examined. Toluene was used as a model pollutant. The bacterial cells were enumerated as fluoromicroscopic counts during a 140 operating day period using BacLight nucleic acid staining in combination with epifluorescence and confocal laser scanning microscopy (CSLM). Overall, five different phases could be distinguished during the biofilm development: (A) cell attachment, (B) pollutant limitation, (C) biofilm establishment and colonization, (D) colonized biofilm, and (E) biofilm erosion. The bioreactor was operated under different conditions by applying different pollutant concentrations. An optimum toluene removal of 89% was observed at a loading rate of 14.4 kg $m^{-3}d^{-1}$. A direct correlation between the biodegradation rate of the reactor and the dynamics of biofilm development could be demonstrated. This study shows the first description of biofilm development during gaseous toluene degradation in MBR.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.11
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• pp.619-623
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• 2004

We proposed the bridge type superconducting fault current limiter(SFCL) using switching operation of high-Tc superconducting(HTSC) thin film. The proposed bridge type SFCL consists of HTSC thin film, a diode bridge and a dc reactor. The controller for the operation of an interrupter is required in the conventional bridge type SFCL to prevent the continuous increase of fault current after a fault happens. On the other hand, the proposed bridge type SFCL can limit the fault current without the interrupter and the controller for its operation by the resistance generated when the gradually increased fault current exceeds HTSC thin film's critical current. We calculated the time when the gradually increased fault current started to be limited by the resistance generated in HTSC thin film after a fault happened and confirmed that it could be dependent on the amplitude of source voltage. The experimental results well agreed with the calculated ones from simulation.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.83-85
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• 2004

We proposed the bridge type fault current limiter(FCL) using switching operation of high-Tc superconducting(HTSC) thin film. The proposed bridge type FCL consists of HTSC thin film, a diode bridge and a dc reactor. The controller for the operation of an interrupter is required in the conventional bridge type FCL to prevent the continuous increase of fault current after a fault happens. On the other hand, the proposed bridge type FCL can limit the fault current without the interrupter and the controller for its operation by the resistance generated when the gradually increased fault current exceeds HTSC thin film's critical current. We calculated the time when the gradually increased fault current started to be limited by the resistance generated in HTSC thin film after a fault happened and confirmed that it could be dependent on the amplitude of source voltage. The experimental results well agreed with the calculated ones from simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.437-442
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• 2001

Recently, transformerless inverters have been studied to reduce sizes and costs of utility-connected PV systems. This paper presents a transformerless PV inverter using a two-phase boost converter of reduced ripples in input current and output voltage, low voltage stress of semiconductor device and reduced size of input reactor. And new PWM method is introduced, whose on-off time is calculated from simultaneous equation induced by fourier series. To verify a validity of the proposed transformerless inverter, computer simulation has been carried out.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.305-306
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• 2007

본 논문은 차세대 원전 신고리 #3, 4호기 NSSS(Nuclear Steam Supply System) 제어계통의 검증시스템을 개발하기 위한 설계개념에 관한 것이다. 차세대 원전 신고리 #3, 4호기는 KHNP(Korea Hydro & Nuclear Power Co., Ltd.)가 개발한 APR1400(Advanced Power Reactor 1400 [MWe])을 적용하는 최초의 원자력 발전소이다. APR1400은 3세대 원자력발전소로 인정받고 있으며, APR1400 원자력발전소의 안전한 운영을 위하여 I&C(Instrumentation and Control)시스템이 디지털 표준 플랫폼으로 설계되었다[2]. 특히, 차세대 원전 신고리 #3, 4호기의 비안전계통(제어 감시 및 경보계통)은 WEC (Westinghouse Electric Company)의 DCS(Distributed Control System) 상용 단일 플랫폼으로 구성될 예정이다. 우리는 신고리 #3, 4호기의 제어계통 중에서 NSSS(Nuclear Steam Supply System) 제어계통의 검증시스템을 개발하기 위하여 Stimulated Simulator의 방법론을 적용하여 "Simulator"라는 설계 개념을 정립하였다. 현재 원자력발전소 NSSS 제어계통의 DCS Stimulator 개발을 위하여 차세대 원전 신고리 #3, 4호기에 시설될 WEC의 DCS와 Simulation 서버 그리고 I/O 설비를 구축 중에 있으며, 원자력발전소 현장 기기 모델링 소프트웨어와 I/O 설비간의 인터페이스를 위한 동신 소프트웨어도 개발하고 있다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.216-218
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• 2016

In this study, we used not chemical and physical synthesis method but the solution plasma sputtering method in the synthesis of silver nano-particles. Synthesis of all the silver nano-particles was conducted for 1hour in 360 ml of distilled water and characteristics of changing the input voltage and frequency of the synthesised silver nano-particles by using the solution plasma sputtering method were analyzed through FE-SEM(Field Emission-Scanning Electron Microscope). We changed the input voltage from 8 kV to 10 kV in steps of 1 kV, input frequency from 20 kHz to 30 kHz in steps of 5 kHz in the solution plasma reactor with the advanced device which can control the DC voltage and frequency. We confirmed that the size of silver nano-particles were larger according to the change of the input voltage and frequency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.413-420
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• 2004

In this paper, the control algorithm of DC source device for inverter starting is proposed and the control method for compensating unbalance system source on operating time in the voltage type PWM converter with driving and regenerative faculty is suggested. The maintaining method of balancing condition for converter of AC source is used the compensating unbalanced status by current control loop. In order to solve the problem which the unbalanced system control is used to leakage transformer not equaled reactance by each phase in rectifier system. The proposed H/W and control algorithm of rectifier system is contributed to minimize of device and rising efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.211-216
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• 2000

In this paper, experimental investigations were carried out to remove NOx, SOx simultaneously from a simulated combustion flue gas [$NO(0.02%)-SO_2(0.08%)-CO_2-Air-N_2$] by using a pulse corona induced plasma chemical processing. Discharge domain of wire-cylindrical plasma reactor was separated from a gas flow duct to avoid unstable discharge by aerosol particle deposited on discharge electrode and grounded electrode. The NOx, SOx removal was experimentally investigated by a reaction induced to ammonium nitrate, ammonium sulfate using a low price of aqueous NaOH solution and a small quantity of ammonia. Volume percentage of aqueous NaOH solution used was 20% and $N_2$ flow rate was $2.5{\ell}/min$ for bubbling aqueous NaOH solution. Ammonia gas(l4.82%) balanced by argon was diluted by air and was introduced to a main simulated flue gas duct through $NH_3$ injection system which was in downstream of reactor. The $NH_3$ molecular ratio(MR) was determined based on [$NH_3$] and [$NO+SO_2$]. MR is 1.5. The NOx removal rates increased in the order of DC, AC and pulse, but SOx removal rates was not significantly effected by source of electricity. The NOx removal rate slightly decreased with increasing initial concentration. but SOx removal rate was not significantly affected by initial concentration. The NOx, SOx removal rates decreased with increasing gas flow rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.979-984
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• 2011

Although sludge production has been increased due to the number of the wastewater treatment plants expanded, needs of the techniques for the sludge reduction and disposal has been issued importantly because the sludge dumping to ocean is prohibited from 2012 by the London Dumping Convention. Therefore, the sludge solubilization using electrolysis as an alternative techniques for the sludge disposal was carried out in this study. Iridium coated titanium based insoluble electrodes were used and 20 volt was applied to the electrolysis reactor using DC power supply. Supernatants of the treated sludge was monitored: The soluble COD, TN, TP of it was increased to 151%, 22% and 6% respectively. And the sludge floc size distribution was changed, that is, the flocs ranged from 0.1 to 1.0 ${\mu}m$ were increased. All of these results indicate that the cells were lysed and the internal matters bursted out of the cell after electrolysis. As well as the reduction of the sludge production, the soluble organic matters from the cells could be used as an external carbon sources in the advanced wastewater treatment plants.