• Proceedings of the KIEE Conference
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• 2004.11d
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• pp.83-88
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• 2004

As the electric system is getting larger to meet the increasing demand for electric power, the rating of power apparatus is becoming inevitably higher in its working voltage and larger in its capacity. According to KEPCO reports, power transformers in the KEPCO system have undergone troubles such as winding short insulation breakdowns every year since 1981. the cause of this troubles were high one line grounding fault currents in KEPCO systems that had direct grounding systems. KEPCO has installed the NGR(neutral grounding reactor) to lower this fault current and reduced winding short insulation breakdowns in power transformers. But when a circuit breaker opened a no load bus, some trips of circuit breakers for protecting transformer have occurred by mal-operation of 59GT(overvoltage ground relay) that detect disconnection of NGR. Therefore, in this paper, we analyzed the cause and examined the effect of time delav circuit to prevent wrong operation of 59GT.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.349-351
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• 1999

This paper presents a new control algorithm for series active power filters that are applied to 3-phase 3-wire and 3-phase 4-wire systems with capacitive loads. It is difficult to reduce harmonic currents in neutral lines of the 3-phase 4-wire systems using conventional series active power filter control methods. 3-phase 4-wire series active power filter systems using the proposed method in this study lower neutral line harmonics. Simulation was carried out to verify the algorithm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.445-450
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• 1995

This paper deals with conversion from STL file to Slice cross-sectional information for Stereolithography. The STL file consist of three vertices of triangle and normal vectors in order to represent three dimension shape, but It is very difficult to convert STL file intoSlice file directly, because of file size from one Mbyte to tens of Mbytes. So, The system is accomplished data flow such as neutral.dat, .SL1, .SL2, .SL3, and .SLC file. The data processing is as follows: 1. Create a neutral file including common information. 2. Modify STL file within effective scope of SLA. 3. Calculate a point of intersection between plane equation and line equation. 4. Sort z values by increasing order. 5. Search closed loop by method of singlylinked linear list. The system is developed by using Borland C++ 3.1 compiler in the environment of Pentium PC. We get a satisfactory prototype as a result of application about a lot of household electrical appliances.

• 전기의세계
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• v.20 no.4
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• pp.5-11
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• 1971

This is a study on the insulation methods of home appliances and wiring devices proper to the new electric distribution system, primary side is 22.9/13.2KV, 3 phase 4 wire multigrounding system and secondary side is 380/220V, 3 phase 4 wire common neutral system. 1800V is determined as the electrical insulation voltage of the functional insulation because the abnormal voltage rise of the neutral line is 1300V. In the case of the functional insulation faults, the following safety methods will be suggested to protect the accidental faults: (a) class I appliance (accessible metal part is earthed), (b) class II appliance (doublly insulated), (c) class III appliance (operates at low voltage source). The mechanisms of the wiring devices are not improved to guarantee for the harmful electric shock but also the electrical insulation voltage is rised to 2000V.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.270-272
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• 2018

This paper proposes an open-phase fault control system using 3-phase neutral voltage. The proposed control system is designed as a new topology which uses the potential difference between neutral point and ground(G) of three phase. And the open-phase detection system is configured to three resistance devices(Y-wiring) of the same capacity to each line of three phase power source R,S,T. This paper also designs a mobile phone application for remote alarm of open-phase fault.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.145-148
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• 2003

P-Cygni type Ly$\alpha$ from starburst galaxies, either nearby galaxies or Lyman Break galaxies, are believed to be formed by galactic outflows such as galactic supershells or galactic superwinds. We develope a Monte Carlo code to calculate the Ly$\alpha$ line transfer in a galactic supershell which is expanding and formed of uniform and dusty neutral hydrogen gas. The escape of Ly$\alpha$ photons from the system is achieved by a number of back-scatterings. A series of emission peaks are formed by back-scatterings. When we observe P-Cygni type Ly$\alpha$ emissions of starforming galaxies, we can usually see merely singly-peaked emission. Hence the secondary and the tertiary emission humps should be destroyed. In order to do this, dust should be spatially more extended into the inner cavity than neutral supershell. We find that the kinematic information of the expanding supershell is conserved even in dusty media. We discuss the astrophysical applications of our results.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1489-1491
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• 2005

This paper proposes a design method using PQR instantaneous power theory on the active power filter, unbalanced nonlinear load condition and unbalanced source voltage condition in three-phase four-wire systems. For reduction of current harmonics and neutral current, the control structure including repetitive controller is proposed and controller gain is designed. For fully-digital implementation, ramp comparison PWM method was adopted. Simulation results verify good performance of the proposed current control strategy on the shunt APFs.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.540-542
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• 2019

This paper proposes an open-phase fault control system using 3-phase neutral voltage. The proposed control system is designed as a new topology which uses the potential difference between neutral point and ground of three phase. The open-phase detection system is also configured to Y-wiring of three capacitance devices of the same capacity to each line of three phase power source R-S-T. This paper also designs a mobile phone application for remote alarm of open-phase fault.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.4-6
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• 2018

This paper proposes an open-phase fault control system using 3-phase neutral voltage. The proposed control system is designed as a new topology which uses the potential difference between neutral point and ground(G) of three phase. And the open-phase detection system is configured to Y-wiring of three capacitance devices of the same capacity to each line of three phase power source R-S-T. This paper also designs a mobile phone application for remote alarm of open-phase fault.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.41.1-41.1
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• 2021

Neutral (HI) gas clouds associated with galaxies are responsible for fuelling the star-formation in the universe. In literature, the extremely strong damped Lyman-alpha absorbers (or ESDLAs) have been known to be sensitive to the effects of HI-H2 transition and star-formation in galaxies. Yet, ESDLAs are rare to probe due to the smaller cross section they subtend on the sky (similar to galaxies). In my talk, I will focus primarily on my study of the nature of ESDLAs that are observed as absorption signature along the line-of-sight (LOS) of a quasar (QSO). I will further look at the HI-H2 transition and interesting results relevant to diffuse molecular gas and the multi-phase medium (gas in different ionization states) that are associated with ESDLAs. Furthermore, I will also discuss how the ESDLA environments differ from the high star-forming and molecular environments detected in blind optical and radio surveys consecutively.