• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.403-408
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• 2012

In this paper, we propose useful load flow algorithms called FEDL (fast enhanced decoupled load flow). The proposed load flow method can improve the convergence characteristics particularly when the P-Q coupling becomes significant and the power system operating states deviate from the conditions required for stable convergence of the FDL by reflecting in part the effects of the off-diagonal terms in the Jacobian. In our test with IEEE AEP-30 bus system and RTS-96 73-bus system, it converge even when the fast decoupled load flow (FDL) and its variations keeping load flow matrices constant experience convergence problems. Test results show promising performances of the proposed algorithms in their convergence characteristics both in number of iterations and overall convergence speeds.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.4
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• pp.148-155
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• 1986

This paper presents a new decoupled power system state estimation method. The decoupling is achieved via simple linear transformation on power measurements in contrast with the modified fast decoupled state estimation method which assumes decoupling by direct negligence of the off-diagonal blocks of the observation functions. The new estimation method is compared with the modified decoupled state estimation method against IEEE-14 bus model power system and 25 bus model power system in several system conditions. It is observed that the proposed method shows better convergence performance and filtering performance than a modified fast decoupled state estimation.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1170-1172
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• 1998

The electrical power of nuclear power plant consists of Safety related power systems and Non-Safety related power systems. The safety related power systems are designed to have sufficient capacity to safely shut down the unit and to mitigate the effects of an accident assuming loss of off-site power. This paper presents the operation scheme of the safety related power system for several plant conditions in Korean Next Generation Reactor and reviews the diversity of power supply to the safety related bus.

• Journal of Internet Computing and Services
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• v.21 no.2
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• pp.9-18
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• 2020

In the field of image processing, a method of detecting and counting passengers as moving objects when getting on and off the bus has been studied. Among these technologies, one of the artificial intelligence techniques, the deep learning technique is used. As another method, a method of detecting an object using a stereo vision camera is also used. However, these techniques require expensive hardware equipment because of the computational complexity of used to detect objects. However, most video equipments have a significant decrease in computational processing power, and thus, in order to detect passengers on the bus, there is a need for an image processing technology suitable for various equipment using a relatively low computational technique. Therefore, in this paper, we propose a technique that can efficiently obtain the number of passengers on the bus by detecting the contour of the object through the background subtraction suitable for low-cost equipment. Experiments have shown that passengers were counted with approximately 70% accuracy on lower-end machines than those equipped with stereo vision camera.

• Fire Science and Engineering
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• v.32 no.3
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• pp.95-107
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• 2018

This study analyzed the working conditions of the fire protection system in the Goyang Bus Terminal fire based on the fire investigation results. The results were as follows. First, extinguishing using an indoor fire hydrant was not attempted immediately after the fire burned the ceiling urethane foam. Second, a sprinkler alarm valve was turn off and did not work in the repair work space of the 1st basement. On the other hand, the sprinklers in the $2^{nd}$ basement, $1^{st}$ floor, $2^{nd}$ floor, and $3^{rd}$ floor worked and prevented the fire from moving to stories other than the $1^{st}$ basement. Third, although an exit light worked normally, it was not installed in the exit from the waiting room in the $2^{nd}$ floor to the bus stop. This resulted in many casualties. Fourth, although a fire receiver sent an electrical signal to the fan controller of the smoke control system, it was treated manually in the fan controller and the fan in the $2^{nd}$ floor did not work.

• 전기의세계
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• v.26 no.3
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• pp.84-91
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• 1977

A modified version of algorithm and computer program is proposed to improve the currently available contingency analysis methode for the security control of power system. The underlying principle is based upon the reasonable modification of the current methods suggested by Stagg, Tinny, Alsac, and Stott in consideration of speed, aceuracy, reliability and convergency characteristics. The algorithm and program are desirgned especially for On-Line operation, although Off-Line applications are readily available. Several case studies on the Koren Power Company's 48-bus, 91-line system have shown that the method proposed is efficiently powerful in a sense of practical applicability.

• Journal of Power Electronics
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• v.12 no.5
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• pp.708-714
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• 2012

This paper presents a new interleaved pulse-width modulation (PWM) boost-flyback converter to achieve power factor correction (PFC) and regulate DC bus voltage. The adopted boost-flyback converter has a high voltage conversion ratio to overcome the limit of conventional boost or buck-boost converter with narrow turn-off period. The proposed converter has wide turn-off period compared with a conventional boost converter. Thus, the higher output voltage can be achieved in the proposed converter. The interleaved PWM can further reduce the input and output ripple currents such that the sizes of inductor and capacitor are reduced. Since boundary conduction mode (BCM) is adopted to achieve power factor correction, power switches are turned on at zero current switching (ZCS) and switching losses are reduced. The circuit configuration, principle operation, system analysis, and design consideration of the proposed converter are presented in detail. Finally, experiments conducted on a laboratory prototype rated at 500W were presented to verify the effectiveness of the converter.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.1
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• pp.92-99
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• 2013

The ratio of mobility handicapped was 12,110,000 in late 2009 about 24.4% of total population. The number of handicapped population is increasing continuously due to traffic accidents and industrial disasters. Therefore, the purpose of this research is to suggest a design for passengers on wheelchairs to get into and off to raise handicapped or elderly people's right of mobility. The scope of this research is mobility handicapped especially wheelchair passengers who use vans, small buses, and trains. The ramp design of vans is module form. The ramp is moved with screw jack and guides are installed on each side to increase stability. Moreover, a bridge was installed for smooth getting in and off of the van. The ramp design for small bus is lowed by 200m in order not to have obstacle such as speed bump when getting in or off. In order to reduce vulnerable environment and administration, air slide cylinder was chosen. Lastly, for the ramp design of train, the principle of link was used that the simpler structure made the weight lighter and installation in the train became easier. If we look at the conjugation condition of heterogeneous materials to produce a ramp, proper welding condition for cold steel plate and stainless plate is 3kW output and 3-5m/min of welding speed using laser beam seems proper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.462-467
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• 2013

In this paper, we analyzed the effects of doctoring process on the patterns of Ag ink in gravure off-set printing. The parameters of doctoring process were the angle and the pressure, which was represented by the depth of blade movement to the gravure roll, of doctor blade to the surface of gravure roll, and the angle of patterns engraved on the gravure roll to the doctor blade moving direction. The proper parameters were extracted for the fine patterns and they were 15 mm for the pressure, $60^{\circ}$ for the blade angle. And the angle of patterns with respect to the blade movement should be less than $40^{\circ}$ for the best results. The gravure off-set printing with the above parameters was carried out to print gate electrodes and scan bus lines of OTFT-backplane for e-paper. The line width of $50{\mu}m$ was successfully obtained. The thickness of electrodes was $2.5{\mu}m$ and the surface roughness was $0.65{\mu}m$ and the sheet resistance was $15.8{\Omega}/{\Box}$.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.319-328
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• 2020

The recent use of distributed power generation systems constructed with DC-DC converters has become extremely popular owing to the rising need for environment friendly energy generation power systems. In this study, a new single-phase five-level inverter for off-grid applications constructed with a multilevel DC-DC step-up converter is proposed to boost a low-level DC voltage (36 V-64 V) to a high-level DC bus (380 V) and invert and connect them with a single-phase 230 V rms AC load. Compared with other traditional multilevel inverters, the proposed five-level inverter has a reduced number of switching devices, can generate high-quality power with lower THD values, and has balanced voltage stress for DC capacitors. Moreover, the proposed topology does not require multiple DC sources. Finally, the performance of the proposed topology is presented through the simulation and experimental results of a 400 W hardware prototype.