• 한국광학회:학술대회논문집
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• 한국광학회 1989년도 제4회 파동 및 레이저 학술발표회 4th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.169-171
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• 1989

The curved active layer inner stripe(CALIS) laser diode has been developed. The tight confinements of current and carrier result in low thershold current(20-30mA) with stable fundamental transverse mode operation up to the output power of 30mW CW.

• 한국물환경학회지
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• 제20권2호
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• pp.132-144
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• 2004

The purpose of this study was to evaluate alternatives for stable operation of WWTP(Wastewater Treatment Plant) with a higher rate of inflows and a higher concentration of pollutants during wet weather to minimize the pollution loads being discharged into receiving waters. 3Q(Q: dry weather flow) of a base flow is normally intercepted and flows into WWTP as it was current practice. It is revealed by simulation that the bypassing alternative of 1Q through secondary treatment and 2Q into the stream after primary treatment was as good as it is expected. The bypass pollution loads were in the range of 23.9 ~ 38.5 % of the total loads flowing into the WWTP indicating that the bypassed flows need an extra treatment such as stormwater detention reservoir, high-rate coagulation with sedimentation, and step-feed. The high-rate coagulation with sedimentation was the most effective with respect to removal of the pollution loads.

• 전력전자학회논문지
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• 제25권4호
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• pp.329-332
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• 2020

A back-electromotive force (back-EMF) estimator for a permanent magnet synchronous motor (PMSM) uses the three-phase voltage references of a current controller to estimate rotor position. However, owing to voltage drops caused by the nonlinear characteristics of switches and passive components, the actual voltage in the motor and the three-phase voltage reference may not match. This study proposes a sensorless control method using a sine-wave output filter applied between the motor drive system and PMSM. The precise voltage in the motor can be measured with the sine-wave output filter and applied to the input of the estimator. Moreover, given that the voltage in the motor can be measured precisely at extremely low speeds, the stable operation range of the back-EMF estimator can be secured. Experimental results show that the proposed sensorless control method has stable operation at extremely low speeds compared with conventional sensorless control.

• 한국유체기계학회 논문집
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• 제20권2호
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• pp.69-74
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• 2017

Sodium hypochlorite, used as water disinfectant, is generated by electrolysis of salt. Compared to chlorine gas disinfection, it is free from high-pressure gas regulation and does not generate toxic gas, so it is increasingly used as a safe disinfectant. Despite these advantages, the concentration of sodium hypochlorite decreases with temperature during long-term storage, and the amount of chlorate increases when a large amount is added, it has mainly been applied to small-scale waterworks. To solve this problem, high sodium hypochlorite generation was developed. In this study, the changes of concentration and chlorate of sodium hypochlorite with time has been studied. As a result of the test, it was found that the usable period of sodium hypochlorite produced at a certain temperature or less was increased from 1.5 days to 13 days. Overall, sodium hypochlorite can be applied even in large-scale waterworks, which makes operation more stable and also reduces the disinfection byproducts, thus it contributed greatly to securing water quality.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권5호
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• pp.338-344
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• 2000

This paper proposes a field-oriented control strategy without speed sensor in overall speed range. At low speed region including zero speed, the electrical saliency which is due to the main flux saturation is used in order to estimate an instantaneous flux position. This electrical saliency can be obtained from the difference of high frequency impedance by the high frequency signal injection. This method enables the stable operation at zero speed or stator frequency even under heavily loaded condition. However, because of the high frequency signal injection the loss and noise in motor increase and the voltage margin is reduced as the motor speed increases. Therefore, this algorithm must be supplemented with the algorithm based on the electrical model of motor, which is conventionally used in the region except the low speed. This paper proposes the combination algorithm between the high frequency signal infection method and the adaptive observer, in which the rotor flux and motor speed can be simultaneously estimated by the adaptive control theory. This combination algorithm enables the stable operation of field-oriented speed control without speed sensor in overall speed range. This is verified by experimental results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.265-268
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• 2005

This paper discusses a strategy and status for development and operation of durability mock-up test facilities for offshore structures. The strategy is examplified and facilitated using an offshore transmission tower crossing the West sea and the Shihwha lake, which was designed and constructed 345kV T/L lines transmitting power from Yeong-Heung fossil power plant to Seoul metropolitan area. Various data for corrosion protection, aging, life-prediction of concrete and steel offshore structures can be obtained using the proposed mock-up test facility. Acquired data will be used for further research on durability, life-prediction, and retrofit of structures. It is important to maintain the safety of 345 kV Yeong-Heung transmission line crossing the Shihwha lake because the offshore structure is one of the critical electric facilities transmitting large power to the metropolitan area. Operation of the offshore transmission tower mock-up is expected to make a significant contribution to stable power supply.

• 상하수도학회지
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• 제26권6호
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• pp.915-925
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• 2012

On-off control performance of target pumping station was experimented by changing measurement methods for storage level or inflow and operating logic for control system setting. Four scenarios with different measurement methods and operational logic were examined in the Matlab/Simulink environment. Controller's on-off control repetition that was frequent before has been reduced and more effective and stable system operation was found to be possible with the scenarios. Moreover, defensive operation enforced prevention of floods by changing measurement methods enabled economic operation that made an utmost use of storage volumes.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.99-100
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• 2002

Radial, tilting-pad proceeding bearings are applied in high speed rotating machines operating at stable small and mean loads and the peripheral speeds of proceeding reaching 150 m/s. The operation of bearing can be determined by static characteristics including the oil film pressure, temperature and viscosity distributions, minimum oil film thickness, load capacity, power loss, oil flow. The operation of 5-lobe tilted-pad proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions habe received by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss. oil flow, maximum oil film pressure, maximum temperature were computed for different sets of bearing geometric parameters as: bearing length to diameter ratio, pad angular length and width as well as pad relative clearance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.30-34
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• 2005

Due to old Toshiba EMS's database size limit and hardware old aging, KPX(Korea Power Exchange) had introduced New EMS from AREVA(old ALSTOM) in July 2002. After then KPX had committed many man power and time to normalize EMS NA(Network Analysis) functions for using real power system. At initial stage, to normalize State Estimator which is the backbone of all other NA functions and DTS(Dispatcher Training Simulator}, KPX had corrected numerous topology errors, network model errors, non-scanned and wrongly scanned SCADA measured errors. After SE function study, running test and tuning, State Estimator could finally have been run properly and stably from June 2003. Based on SE running, KPX had normalized real time Contingency Analysis, and study mode Power Flow, STNET and DTS. From early 2004, dispatchers have been trained to use NA and DTS for the purpose of stable SE running, NA operation & results reading and urgent equipment outage reviewing. EMS NA have been greatly contributed to operate real time power system stably. Above NA normal operation by KPX own efforts under the no experience of NA running, KPX made a good precedent. This paper is intended to introduce EMS NA normalization process, operation status, and etc in Korea power system operation.

• 미생물학회지
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• 제46권2호
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• pp.169-176
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• 2010

회전접촉장치와 점감포기 생물반응조를 이용한 실험용 규모의 폐수처리 공정을 식품산업폐수를 유입수로 사용하여 5개월 동안 운전하였으며, 16S rRNA 유전자의 말단단편길이다형성(T-RFLP) 분석과 계통분류학적 분석방법으로 폐수처리 공정의 세균군집을 조사하였다. 유기물 외에 고농도의 질소와 인이 함유된 식품산업폐수를 적용하였음에도 불구하고, 안정화 기간 동안 화학적산소요구량, 총질소, 총인의 제거효율은 각각 98%, 93%, 95% 이상이었다. 가동 초기의 세균 군집과 안정화 이후의 세균군집은 뚜렷하게 구분되었으며, 안정화 기간 동안 가장 우점한 세균군집은 Bacteroidetes였다. 운전 기간중의 주요 세균 군집은 사상균으로 분류되는 Haliscomenobacter, Sphaerotilus, Candidate division TM7이었으나, 이들 사상균에 의한 슬러지 팽화 현상은 관찰할 수 없었다. Haliscomenobacter와 유연관계가 가까운 세균군집이 안정화 시기에 증가하여 최대 우점 군집이 되었다. 본 연구결과는 회전접촉장치와 점감포기 생물반응조를 이용한 폐수처리공정의 영양물질 제거에 사상균이 중요함을 제시한다.