• 수산해양기술연구
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• 제58권1호
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• pp.59-67
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• 2022

This study assessed the levels of water qualities and microbials contamination of inland olive flounder farms in Jeju in the summers from 2015 to 2017. Three farms (A-C) located in a concentrated area using mixing coastal seawater and underground seawater and one farm (D) located in an independent area using only coastal seawater were selected. Total ammonia nitrogen (TAN) reached a maximum of 0.898 ± 1.024 mg/L as N in the coastal seawater of A-C, which was close to the limit of the water quality management goal of the fish farm. TAN in the influent from A-C was up to three times higher than that of D, so that the discharged water did not spread to a wide range area along the coast and continued to affect the influent. TAN of the effluent in A-C increased by 2.7-4.6 times compared to the influent, resulting in serious self-pollution in the flounder farm. Heterotrophic marine bacteria in the influent of A-C was about 600 times higher than D, and the discharge of A-C was increased by about 30 times compared to the influent.

• 한국안전학회지
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• 제33권4호
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• pp.119-126
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• 2018

In recent years, as flood damage caused by heavy rains increased, the great-depth tunnel using urban underground space is emerging as a countermeasure of urban inundation. The great-depth tunnel is used to reduce urban inundation by using the underground space. The drainage efficiency of great-depth tunnel depends on the intake design, which leads to increase discharge into the underground space. The spiral intake and the tangential intake are commonly used for the inlet facility. The spiral intake creates a vortex flow along the drop shaft and reduces an energy of the flow by the wall friction. In the tangential intake, flow simply falls down into the drop shaft, and the design is simple to construct compared to the spiral intake. In the case of the spiral intake, the water level at the drop shaft entrance is risen due to the chocking induced by the flowrate increase. The drainage efficiency of the tangential intake decreases because the flow is not sufficiently accelerated under low flow conditions. Therefore, to compensate disadvantages of the previously suggested intake design, the multi-stage intake was developed which can stably withdraw water even under a low flow rate below the design flow rate. The hydraulic characteristics in the multi-stage intake were analyzed by changing the flow rate to compare the drainage performance according to the intake design. From the measurements, the drainage efficiency was improved in both the low and high flow rate conditions when the multi-stage inlet was employed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.500-502
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• 2002

Receltly, Underground transmission system is getting increased. Therefore the design of grounding system becomes very important to discharge overcurrent of lightning and fault through earth and reduce sheath induced voltage and sheath circulation current. This paper describes fault current distribution ratio for grounding line with grounding types of normal joint box and sheath grounding resistor at line-to-ground fault of cable.

• 한국터널지하공간학회 논문집
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• 제21권1호
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• pp.127-136
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• 2019

TBM 터널공사 시 스크류컨베이어의 배토 거동에 대한 이해는 굴진율 향상을 위한 중요한 요소이다. 본 연구에서는 지반에서 디스크 커터에 의해 생성되는 암반칩의 형상에 따라 스크류컨베이어 내부에서의 이동 및 배토 거동에 대한 연구를 수행하였다. 입자기반의 DEM 수치해석기법을 이용하여, 6가지의 대표적인 모양에 대한 암반칩을 클러스터로 형성하였다. 또한, 실제 스크류컨베이어의 3D 축소모델을 형성한 후, 다른 모양의 암반칩의 시간당 배토량을 측정 하였다. 시뮬레이션 결과, 스크류컨베이어의 경사각이 $0^{\circ}$일 때, 동일한 암반에서 암반칩의 형상과 부피와 상관없이 10 RPM 속도에서의 스크류컨베이어 배토량은 스크류컨베이어 최대 배토량의 약 20%로 나타났다(표준편차: 1.3%). 본 연구 결과는 암반용 TBM 설계 및 암반에서의 TBM 굴착 시 스크류컨베이어 운용에 참고할 수 있는 자료로 사용될 수 있을 것으로 예상된다.

• 한국터널지하공간학회 논문집
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• 제26권3호
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• pp.243-254
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• 2024

현재 국내 지역의 산업 발달로 인해 주요 도심은 물론 주변 도시 지역에도 건축물이 포화 상태이다. 이에 따라 사람들의 관심은 지하공간으로 쏠리게 되었고, 특히 도시개발에 있어서 터널은 광범위하게 활용되고 있다. 이에 따라 터널 및 터널굴착공법에 대한 연구가 활발히 진행되고 있다. 그러나 이수식 쉴드 TBM 사용 시 슬러지 배출관의 마모 및 파손 문제에 대한 연구는 부족한 실정이다. 따라서 본 논문에서는 기존 슬러지 배출관에 사용된 L자형 곡관을 T자형 곡관으로 변형하여 슬러지를 이동시켰다. 그 결과, L자형 곡관에 비하여 T자형 곡관이 슬러지 배출 시 곡관에 미치는 영향이 감소하는 것을 확인할 수 있었다. 이러한 결과를 바탕으로 이수식 쉴드 TBM 장비 사용 시 T자형 곡관을 사용하면 슬러지 배출관의 마모를 최소화할 수 있을 것으로 기대된다. 이는 결국 터널 공사 시 곡관 교체나 추가 용접에 따른 비용을 절감하는 등 경제적 이익으로 이어질 것으로 기대된다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.161-165
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• 2006

In this paper, we developed HPF (high pass filter) consists of lumped LC components to decrease the noises that are detected in PD (partial discharge) measuring test, and adapted it to field test. We tested it under laboratory circumstances like the fields, and measured the phase change properties of detected signal in UHF sensor with Lemke Probe and oscilloscope (TDS-3054, Tektronix). As a result, we obtained available data showing the decrease of noises in the experiments with the developed HPF from the joint box of 22.9kV distribution line. The result can be adapted to prevent the degeneration of the XLPE power cable, and to observe and diagnosis the underground power transmission cable at the ultra-high voltage.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.166-171
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• 2006

In this paper, we have studied for analysis of the partial discharge(PD) signal in underground transmission line. The PD signal has estimated as detected signal accumulation of a PRPDA method by using Labview, and analyzed with fuzzy algorithm. In our algorithm, we developed system configuration that detected accumulating PD signal using by Labview and programmed fuzzy algorithm can be analyzed the PD signal using with Matlab. With practical PD logic implementation of theoretical detected system and hardware implementation, the device for Hipotronics Company's 50kV setup has generated and then has applied with $15k{\sim}17kV$ with 1:1 time probe. It's also used the LDPE 0.27mmt (scratch error 0.05mmt) to sample for making PD. In conclusion, Our new class of PD detected algorithm has also compared with previous PRPDA or Fuzzy algorithm. which has diagnose more conveniently by adding numerical values.

• 한국전기전자재료학회논문지
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• 제16권10호
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• pp.946-951
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• 2003

A high-Tc superconducting cable(HTS cable) is expected as an underground power line supplying the electrical power the densely populated city in future. The electrical insulation is very important for develop HTS cable system because it is operated a high voltage and in cryogenic temperature. We manufactured a mini-model cable and measured a tan$\delta$ of cable using schering bridge. The tan$\delta$ of PPLP was lower than that of Tyvek and Kraft at a given temperature, the tan$\delta$ of PPLP was 1.16${\times}$10-3. According to the increase of electric stress the tan$\delta$ increased because partial discharge occurred inside butt gap of mini-model cable. However, the tan$\delta$ decreased by increase of liquid nitrogen pressure. This reason is thought by decrease of part discharge between butt gap by increase of liquid nitrogen pressure.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.324-327
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• 2009

This paper presents the transient impedance in a discharge region when high voltage lightning impulse is applied to small-sized ground electrodes in frozen soil. For a realistic analysis of ionization characteristics near the ground electrode in the soil, ground rod installed outdoors and high voltage impulse voltage generator were used. From the analysis of response voltage and current flowing ground electrode to earth, it was verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively under high impulse voltage.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.215-216
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• 2005

To decrease and remove of much noises that is detected in PD (partial discharge) measuring test. we forced on detection of those. We made W-LC filter for measuring PD. which adapted that to field test. We tested after design laboratory circumstances like field line. and then the phase change properties of detected signal in UHF sensor were measured by Lemke Probe and oscilloscope (TDS-3054. Tektronix). Eventually we checked decrement of noises from experimental result. Also from experimental result at the joint box of 22.9[kV] distribution line. we obtained reasonable data which enable noises to decrease. Hereafter those results will be adapted at ultra-high voltage for trouble prevention and on-line cable watch. diagnosis of those.