• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1721-1725
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• 2007

본 연구에서는 안양천 유역의 물순환 건전화를 위한 계획수립의 첫 번째 단계로 HSPF 모형을 구축하고 중유역별 물순환 현황 및 BOD 부하량을 정량적으로 파악하였다. 모형을 구축하기 위해 HSPF 모형의 수량 및 BOD에 대한 민감도 분석을 수행하였으며 다양한 속성을 갖고 있는 안양천 유역을 토지이용, 경사도 및 사용한 기상자료 등의 특성에 따라 총 4개 지역으로 구분하여 검 보정을 실시하였다. 물순환 모의 결과 하류로 갈수록 도시화 비율이 높으며 이로 인해 기저유출량은 $11.1%{\sim}5.0%$로 줄어들고 직접유출량은 $42.5%\rightarrow56.9%$로, BOD 농도는 $3.3\;mg/L\rightarrow15.0mg/L$로, 단위면적당 원단위는 $55.4\;kg/ha/year\rightarrow354.5kg/ha/year$로 증가하였다.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.4-6
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• 2019

본 논문은 Modular Scalable Inverter System에서 큰 부피를 차지하는 인덕터를 저감하기 위한 방법을 제안한다. 최근 전력분야에서는 모듈형 전력변환 시스템을 사용함으로써 다양한 시스템에 필요한 전력을 공급하여 효율을 증가시키고 신뢰성을 높이는 방법들이 대두되고 있다. 하지만 모듈을 병렬로 사용하는 경우에는 모듈 간에 흐르는 순환 전류가 발생하게 된다. 이런 순환전류는 부하로 전력을 공급하지 않기 때문에 시스템 효율을 떨어트리고 전류제어 및 부하 분담을 방해한다. 따라서 병렬형 인버터에는 출력에 순환전류 저감을 위한 인덕터를 사용해야 한다는 단점이 있다. 모듈형 전력변환 장치에서 큰 크기의 출력 인덕터는 시스템 사이즈를 늘리고 비용을 증가시키고 전력밀도가 낮아지게 된다. 따라서 GaN HEMT (Gallium Nitride High Electron Mobility Transistor) 기반 인버터와 순환전류 저감 알고리즘을 사용하여 고속 스위칭을 함으로써 동일한 순환전류 저감 성능을 확보하지만 출력 인덕터의 크기를 줄이는 방안을 제시한다.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.527-533
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• 2004

One clinical technique recommended for improving marginal integrity is "rebonding" or application of unfilled resins to the surface of composite restoration. But continuously the restorations are affected with occlusal load. There is room for doubt that the rebonding agent has the positive effect on microleakage in spite of the stress generated by the occlusal load. This study determined the effect of rebonding on microleakage of Class V resin composite restorations under load cycling. Class V cavities were prepared on the buccal surface of 40 sound extracted premolars and restored with a hybrid light-cured resin composite according to manufacturers' directions. They were randomly divided into two groups consisting of 20 samples: a control(group I), without surface sealing, and the other group(group II) in which margins were etched and rebonded. After thermocycling, each of groups was divided into subgroups(group A, B), and load cycling(total 100,000 cycles with 4-100N load at a rate of 1 Hz) were applied on the group B. Assessment of microleakage utilized methylene blue dye penetration. The following results were obtained: 1. In the occlusal region, no significant difference was noted in the scores regardless of whether or not the rebonding agent was used(group TA-IIA, IB-IIB)(p>0.05). 2. In the cervical region, the control group with rebonding(group IIA) showed the better result than the group without rebonding(group IA)(p<0.05). 3. In the cervical region, the rebonded group with load cycling(group IIB) showed similar results to the group without rebonding(group IB) and no significant difference was noted(p>0.05).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.672-678
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• 2020

The parallel-feeding operation of an AC traction power supply system has the advantages of extending the power supply section and increasing the power supply capacity by reducing the voltage drop and peak demand caused by a train operation load. On the other hand, the parallel-feeding operation is restricted because of the circulating power flow induced from the phase difference between substations. Moreover, the power supply capacity is limited because of the unbalanced substation load depending on the trainload distribution, which can be changed by the train operation along the railway track. This paper suggests a Thyristor-controlled Phase Angle Regulator (TCPAR) to reduce the circulating power flow and the unbalanced substation load, which depends on the phase difference and the trainload distribution and provides a feasibility study. A dedicated control model of TCPAR is also provided, which uses substation power supplies as the input to control the circulating power flow and an unbalanced substation load depending on the phase difference and the trainload distribution. Simulation studies using PSCAD/EMTDC shows that the proposed TCPAR control model can reduce the circulating power flow and the unbalanced substation load depending on the phase difference and the trainload distribution. The proposed TCPAR can extend the parallel-feeding operation of an AC traction power system and increase the power supply capacity.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.5
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• pp.379-386
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• 2009

This paper investigates the operation of ITER(International Thermonuclear Experimental Reactor) Vertical Stabilization(VS) converter with circulating current. The VS converter has two subunits in parallel. The subunit is composed two back-to-back 12 pulse thyristor converter in series. The circulating current free technique can not always maintain the closed path for the load current because of a dead time zone of the converter operation at the region of the load current inversion. The complex circulation current technique for the load current inversion with VS converter can achieve the fast response and always maintain the closed path for the load curret. The paper proposes the new circulating current algorithm for the load current inversion of ITER VS converter and proves the performance of the circulating current technique with PSIM simulation study.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.356-357
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• 2013

ITER(국제 열핵융합 실험로) 핵융합 토카막 장치의 초전도 코일 부하에는 대용량 AC-DC 4상한 컨버터가 필요하다. 4상한 컨버터는 대용량 부하에 전력을 공급하기 위해서 12펄스 위상 제어 정류기의 양방향성 병렬 구조로 이루어져 있다. 컨버터의 안정된 정역 변환 동작을 위한 방법으로 순환 전류를 이용한 알고리즘이 필요하며, 본 논문에서는 4상한 컨버터의 안정된 동작을 위한 순환전류의 알고리즘을 해석 및 연구하였다. 또한 RTDS(Real Time Digital Simulator)의 RSCAD 시뮬레이션을 통해 동작 모드에 따른 컨버터의 스위칭 동작을 확인하였으며, 실제 4상한 컨버터를 RTDS와 연계하여 순환전류를 이용한 정역 운전 변환에 대한 실험 결과를 입증하였다.

• Journal of Animal Environmental Science
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• v.18 no.3
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• pp.235-246
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• 2012

Reusing livestock manure have various advantages in securing soil organic resources. In this study, the N-loading and recycling capacity assessment of animal manure was analyzed by comparing between the cultivated areas of crops and the amount of manure units that are generated from livestock manure. From this assessment, the possibility of recycling resources of livestock manure was evaluated. The amount generated of livestock manure in Gyeonggi-do were evaluated by applying the manure units to the number of livestock manure. The analysis of manure unit per ha shows that the N loading by MU is quite different by region. When it comes to nitrogen loading, the MU per ha of cultivated land in excess of the N-amount was the highest in the Gyeonggi-do province with 2.70 MU/ha, which is higher than the appropriate level. The Chungcheongnam-do province came next with 2.31 MU. So the recycling capacity assessment was carried out mainly based on areas of forage crops, rice that can be provided by recycling livestock manure. The recycling capacity ware highest in Jeollanam-do and Jeollabuk-do. In order to properly apply the livestock manure into organic resources, the seasonal situation that effects the nitrogen demands of crops along with the regional effects crop cultivation should be seriously analyzed. In addition, a system that can effectively produce and manage fertilizer should be established.

• Magazine of RCR
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• v.14 no.1
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• pp.22-28
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• 2019

• 보일러설비
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• s.76
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• pp.100-106
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• 2000

• 보일러설비
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• s.75
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• pp.104-111
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• 2000