• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1691-1693
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• 2001

펄스형 Nd:YAG 레이저는 연속형에 비해 효율이 높고 높은 첨두 출력(peak power)이 가능하므로 가공에 있어서 여러 가지 장점이 있다. 더구나 레이저 펄스 모양을 가변시키는 기능은 펄스형 Nd:YAG 레이저로 가공하기 힘든 특수분야에까지 가공을 가능하게 하였다. 본 연구에서는 3개의 플래쉬램프를 순차 점등시키는 MD(multi-discharge)방식의 레이저 시스템을 설계 및 제작하여, 램프 점등 시간의 변화에 따른 레이저 빔의 펄스폭과 펄스 세기(펄스 크기)를 조사하였다. 즉, PIC One-Chip microprocessor를 이용하여 실시간으로 3개의 플래쉬램프를 순차적으로 점등시켜 보다 다양한 펄스 모양을 만드는 기술을 개발하였다. 위 방식의 장점은 램프의 점등 지연시간을 0 $\sim$ 10ms 까지 다양하게 변화시킬 수 있고, 외부의 키보드로 실시간 제어가 가능하므로 보다 편리하게 펄스 모양을 변화시킬 수 있다. 또한 긴 펄스를 만들 수 있어 산업용 가공이나 의료용으로 널리 사용될 수 있을 것이다.

• 한국항만학회지
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• 제14권3호
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• pp.361-371
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• 2000

A demand of marine outfall system has been much increased for the effective disposal of the wastewater due to population and industrial development at the coastal areas. The outfall system discharges primary or secondary treated effluent into the coastline, or at the deep water, or between these two. The discharge is carried out by constructing a pipeline on the sea bed with a diffuser or with a tunnel, risers and appropriate. The effluent, which has a density similar to that of fresh water, rises to the sea surface forming plume or jet, together with entraining the surrounding salt water and becomes very dilute. Thus there have been growing interests about plume behaviour around the outfall system. Plume or jet discharged from single-port or multi-port diffuser might cause certain impacts on coastal environment. Near field mixing characteristics of discharged water field using CORMIX model have been studied for effective outfall design various conditions on ambient current, depth, flow rate, effluent concentration, diffuser specification, port specification etc.. This kind of analysis is necessary to deal with water quality problems caused by the ocean discharge. The analyzed result was applied to the Pusan Jungang effluent outfall system plan.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 추계학술대회논문집
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• pp.85.2-93
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• 2000

A demand of marine outfall system have been much increased for the effective disposal of the wastewater due to population and industrial development at the coastal areas. The outfall system discharges primary or secondary treated effluent into coastline or at the deep water, or between these two. The discharge is carried out by constructing a pipeline on the sea bed with a diffuser or with a tunnel, risers and appropriate. The effluent, which has a density similar to that of fresh water, rises to the sea surface forming plume or jet, together with entraining the surrounding salt water and becomes very dilute. Thus there have been growing interests about plume behaviour around the outfall system. Plume or jet discharged from single-port or multi-port diffuser might cause certain impacts on coastal environment. Near field mixing characteristics of discharged water field using CORMIX model with has been studied for effective outfall design various conditions on ambient current, depth, flow rate, effluent concentration, diffuser specification, port specification etc.. This kind of analysis is necessary to deal with water quality problems caused by the ocean discharge. The analyzed vesult was applied to the Pusan Jungang dffluent outfall system plan.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1752-1758
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• 2015

This paper presents partial discharge localization in stator winding of generators using multi-conductor transmission line (MTL) and RLC ladder network models. The high-voltage (HV) winding of a 6kV/250kW generator has been modeled by MATLAB software. The simulation results of the MTL and the RLC ladder network models have been evaluated with the measurements results in the frequency domain by applying of the Pearson’s correlation coefficients. Two PD generated calibrator signals in kHz and MHz frequency range were injected into different points of generator winding and the signals simulated/measured at the both ends of the winding. For partial discharge localization in stator winding of generators is necessary to calculate the frequency spectrum of the PD current signals and then estimate the poles of the system from the calculated frequency spectrum. Finally, the location of PD can be estimated. This theory applied for the above generator and the simulation/measured results show the good correlation for PD Location for RLC ladder network and MTL models in the frequency range of kHz (10kHz<f<1MHz) and MHz (1MHz<f<5MHz) respectively.

• 조명전기설비학회논문지
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• 제18권4호
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• pp.112-117
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• 2004

본 논문에서는 GIS내에 존재할 수 있는 부분방전원을 추정하기 위하여 모의 GIS를 제작하고 부분방전의 원천으로 모의된 코로나방전, 연면방전, 파티클의 자유운동, 보이드(void) 방전, 그리고 플로팅(floating) 전극으로부터 발생하는 UHF신호의 특성을 분석하였다. UHF 신호의 특성 분석의 결과로써 각 부분방전원에 대한 UHF 신호의 주파수 스팩트럼과 위상 특성을 도출하였다. 이 결과를 실제 GIS 내의 부분방전원을 분석하는데 체계적으로 적용하기 위하여 취득된 모든 UHF 신호의 특성을 정량화하고 다층구조를 갖는 역전파학습 신경회로망에 기초한 알고리즘의 데이터로 활용하였다. 구축된 알고리즘의 인식률은 학습과 테스트 데이터에서 각각 약 94(%)와 82(%) 정도로 양호하였다.

• 조명전기설비학회논문지
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• 제17권6호
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• pp.77-82
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• 2003

본 논문에서는 강한 불평등전계를 형성시킬 수 있는 다선형전극을 강전해수 발생장치내에 설치하여 전계집중효과에 의해 발생되는 기포내의 선행방전의 형태와 기포방전이 수소이온농도와 산화환원전위반응에 미치는 영향을 검토하고자 하였다. 실험결과, 강전해수 발생장치내의 양전극측을 다선형으로 함으로써 양전극측에서 발생되는 기포내에서 비유전율 차이에 의한 기포내의 선행방전을 관찰할 수 있었다. 그리고 기포방전에 의해 발생된 이온들이 강전해수 발생장치내에 용해됨으로써 전해수의 이온농도를 증가시켰다. 이때 발생된 고농도의 이온들을 분리집속 시키고 산화환원작용을 크게 증가시켜 고농도의 강전해수를 발생시킬 수 있었다.

• 한국환경과학회지
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• 제25권4호
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• pp.491-504
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• 2016

This study, examines the flow characteristics of upstream channel depending on water gate operation of Nakdan Multi-fuctional weir. The specific purpose of this study are to simulate the variation of flow velocity depending on the operation of the weir using 1-dimensional hydraulic model, HEC-RAS, and compare it with observed velocity. For discharge conditions from $50m^3/s$ to $3,500m^3/s$, it is observed that the velocity of upstream channel is almost constant, whereas for probability flood discharge, the velocity and froude number are increased as the discharge values are increased. The velocity values for downstream boundary condition EL, 40.0 m are more decreased than those for EL. 40.5m. From comparison on the variation of water stage depending on water gate operation, it is observed that the stage values are almost constant for discharges below $300m^3/s$, whereas 5 cm to 20 cm for discharges over $700m^3/s$. Flow velocity at streamflow gauging station. Nakdong, is decreased by more than 875% after installing the weir. The results obtained from this study indicate that the velocity of upstream channel is decreased and the discharge and velocity of downstream channel are significantly varied after installing the weir.

• Nuclear Engineering and Technology
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• 제35권3호
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• pp.226-233
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• 2003

The discharge characteristics of a prototype ion source was investigated, which was developed and upgraded for the NBI (Neutral Beam Injection) heating system of KSTAR (Korea Superconducting Tokamak Advanced Research). The ion source was designed for the arc discharge of magnetic bucket chamber with multi-pole cusp fields. The ion source was discharged by the emission-limited mode with the control of filament heating voltage. The maximum ion density was 4 times larger than the previous discharge controlled by a space-charge-limited mode with fully heated filament. The plasma (ion) density and arc current were proportional to the filament voltage, but the discharge efficiency was inversely proportional to the operating pressure of hydrogen gas. The maximum ion density and arc current were obtained with constant arc voltage ($80{\sim}100V$), as $8{\times}10^{11}cm^{-3}$ and 1200 A, respectively. The estimated maximum beam current was about 35 A, extracted by the accelerating voltage of 80kV.

• 한국환경과학회지
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• 제24권4호
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• pp.371-381
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• 2015

In the mountain streams in Jeju Island, strong turbulence and roughness usually made it nearly impossible to utilize most of intrusive instrumentation for streamflow discharge measurements. Instead, a non-intrusive fixed electro-magnetic wave surface velocimetry (fixed EWSV: Kalesto) became alternatively popular in many representative streams to measure stream discharge seamlessly. Currently, Kalesto has shown noteworthy performance with little loss in flood discharge measurements and also has successfully provided discharge for every minute. However, Kalesto has been operated to regard its measured one-point velocity as the representative mean velocity for the given cross-section. Therefore, it could be highly possible to potentially encompass discharge measurements errors. In this study, we analyzed the difference between such Kalesto discharge measurements and other alternative concurrent discharge measurements such as Acoustic Doppler Current Profiler (ADCP) and mobile EWSV which were able to measure velocity in multi-points in the cross-section. Consequently, Kalesto discharge deviated from ADCP discharge in amount of 48% for relatively low flow, and more than 20% difference for high flow compared with mobile EWSV discharge measurements. These results indicated that the one-point velocity measured by Kalesto should be used as a cross-sectional mean velocity, rather it should be accounted for as an index-velocity in conjunction with directly measured cross-sectional mean velocity by using more reliable instrumentations. After inducing Kalesto Discharge Correction Coefficient (KDCC) that actually means relationship between index velocity and cross-sectional mean velocity, the corrected discharge from Kalesto was significantly improved. Therefore, we found that index velocity method should be applied to obtain better accuracy of discharge measurement in case of Kalesto operation.

• 대한환경공학회지
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• 제37권10호
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• pp.563-572
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• 2015

본 연구는 영산강 수계 승촌보에서 시행되었던 조류배제를 위한 다기능보 운영 사례를 대상으로, 3차원 모델링을 통한 효과 분석을 목적으로 수행되었다. 2013년 5월 영산강 승촌보 구간에서 녹조류 Eudorina sp.가 대량 발생하였으며, 집적된 녹조의 배제를 위하여 서로 다른 방법으로 두 차례에 걸쳐 플러싱 방류를 시행하였다. 조류 발생의 공간적 분포에 대한 상세분석과 이해를 위해 고해상도의 3차원 모형 ELCOM-CAEDYM을 적용하여 1개월 동안의 수질과 chl-a 분포를 모의하였다. 모델링 결과 ELCOM-CAEDYM 모형은 실제 조류의 발생 패턴을 우수하게 모의하였으며, 저비용으로 조류 발생에 대한 고해상도의 공간적인 데이터를 재생산 하는데 적합할 것으로 판단되었다. 모델링 결과를 이용하여 두 가지 방법의 플러싱 방류 CASE를 분석한 결과, 가동보를 이용하여 플러싱 방류를 실시한 CASE1의 경우 서창교~황룡강 합류지점에 발생하였던 조류는 가동보 운영에 의하여 빠르게 하류로 이동되었으나, 이후 방류량이 감소하면서 보 내에 잔류하였던 것으로 분석되었다. 반면, 소수력발전을 중단하고 고정보를 통한 월류를 실시한 CASE2는 비교적 배제 효과가 크게 나타나 대부분의 조류가 플러싱되어 감소된 것을 관측 자료와 모델링 결과로서 확인할 수 있었다.