• Proceedings of the Korean Vacuum Society Conference
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• 1999.02a
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• pp.21-21
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• 1999

• Proceedings of the Korea Crystallographic Association Conference
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• 2005.11a
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• pp.12-13
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• 2005

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1291-1296
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• 2017

Single-phase and three-phase load can be used together in 3-phase 4-wire system. Single-phase and three-phase loads can be classified as linear loads without harmonics and nonlinear with harmonics. Single-phase linear loads are linear loads such as lamps and heat, and single-phase nonlinear loads are power converters such as rectifiers. It is recommended that the distribution of loads in the 3-phase, 4-wire distribution lines be evenly distributed within a certain range. However, harmonic currents generated in a nonlinear load flow on the neutral line and affect the phase current magnitude. The difference in the magnitude of the individual phase current due to the influence of the harmonic current present in the neutral line can produce a difference in current and load unbalance. In this study, current unbalance ratio and load unbalance ratio which can occur when a combination of linear and nonlinear loads are applied to 3-phase 4-wire distribution line are calculated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3008-3020
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• 1994

Condensation heat transfer on a single horizontal tube with electric fields (Electro-Hydro-Dynamics, (EHD)) has been studied experimentally. Results are presented for EHD enhanced condensation of R-113 on a single horizontal tube using several electrode geometries. Especially, its attention was focused on the effects of electrode geometry, electric field strength and the gap of the electrode. In this study, single wire, helical, ring and mesh electrode were used. The range of the imposed voltage was 0~20 kV. As the voltage was increased the surface of liquid became an unstable wave, stream jet, liquid column and then liquid extraction in sequence. Among the various kinds of electrodes, the single wire electrode is suitable for practical application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.26-33
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• 2016

Recently, the use of transformer-less UPS has increased to improve the efficiency of UPS. However, transformer-less UPS is required in three-phase four-wire input IGBT PWM rectifier and the existing three-phase three-wire PFC algorithm cannot be applied in the three-phase four-wire system due to the neutral current problem of UPS input. To control the three-phase four-wire input IGBT PWM rectifier, there are two existing algorithms: 3D SVM and single phase control method. These two algorithms have advantages/disadvantages in controlling the rectifier. The single phase control method is unstable for controlling the rectifier and the 3D SVM method has a problem that must increase the L value of the input-side inductor considerably. Therefore, this paper proposes digital single phase control technology and another new algorithm considering the d-q control, to improve the characteristics of the existing control algorithm. In addition, this paper performed a simulation and experiment based on the proposed control algorithm. The simulation results showed that the proposed technology can control three-phase four-wire IGBT PWM rectifier in a stable manner and can also reduce the neutral current. The proposed algorithm is a useful tool for controlling the three-phase four-wire IGBT PWM rectifier.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.2
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• pp.161-169
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• 2000

The experiment was conducted to obtain correlation of the air side heat transfer coefficient of wire-on-tube type heat exchanger using the single layer heat exchanger. The correction factors to Zhukauskas correlation was driven from the experimental results. The numerical analysis and experiment with several wire-on-tube type condensers to validate the correction factors are also peformed. The maximum discrepancy between experimental results and the numerical results using the correction factors of this study and Zhukauskas correlation is 10.0%, while that of reference correlation is 47.5%.

• The korean journal of orthodontics
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• v.29 no.6 s.77
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• pp.673-688
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• 1999

This study was conducted in order to analyze the mechanical characteristics of multiloop edgewise archwire (MEAW). The purposes were 1) to compare load deflection rate (LDR) of MEAW with that of various other arch wires in the individual interbracket span, 2) to compare the wire stiffness in the interbracket span with that in the multi-L-loop region (the span from distal border of the bracket of the lateral incisor to the mesial border of the buccal tube of the second molar), and 3) to verify the experimental results with theoretically derived formula. The single L-loops of five different horizontal lengths and multi-L-loops for the upper and lower arches were made out of .$016\times.022$ permachrome stainless steel wire. Straight segment of plain stainless steel, TMA and NiTi wire of the same dimension were prepared. The LDR was measured using Instron model 4466 with the load cell of 50N capacity at cross head speed of 1.0mm/min, and maximum deflection of 1.0mm. Five specimens were tested under each experimental condition. The wire stiffness number for each interbracket region and multi-L-loop region was calculated from the LDR and the interbracket spans. By dividing the theoretical model of multi-L-loop into 35 linear segments, the energy stored in each segment was obtained. Then the LDR and wire stiffness of single L-loop and multi-L-loop were calculated and compared. The findings were as follows : 1) The average LDR of MEAW in the individual interbracket region was 1/1.53 of that of the NiTi,1/2.47 of TMA and 1/5.16 of the plain stainless steel wire. 2) The wire stiffness of MEAW in the multi-L-loop region was 1.53 times larger than that in the interbracket region, and the LDR was almost twice as large as that of NiTi in that region. 3) According to the theoretically derived equation, the wire stiffness of the single L-loop was lower than that of multi-L-loop. The results of this study suggest that MEAW has the unique mechanical Property which could allow individual tooth movement and transmit elastic force effectively through the entire arch wire.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.176-183
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• 2014

Three-phase four-wire distribution systems are used for both three-phase three-wire loads and single-phase two-wire consumer appliances in South Korea, Myanmar and other countries. Unbalanced load conditions frequently occur in these distribution systems. These unbalanced load conditions cause unbalanced voltages for three-phase and single-phase loads, and increase the loss in the distribution transformer. In this paper, we propose constant DC capacitor voltage control based strategy for the active load balancer (ALB) in the three-phase four-wire distribution systems. Constant DC capacitor voltage control is always used in active power line conditioners. The proposed control strategy does not require any computation blocks of the active and reactive currents on the distribution systems. Balanced source-side currents with a unity power factor are obtained without any calculation block of the unbalanced active and reactive components on the load side. The basic principle of the constant DC capacitor voltage control based strategy for the ALB is discussed in detail and then confirmed by both digital computer simulations using PSIM software and prototype experimental model. Simulation and experimental results demonstrate that the proposed control strategy for the ALB can balance the source currents with a unity power factor in the three-phase four-wire distribution systems.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.25.2-25.2
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• 2011

The tungsten oxide wire-like nanostructure is fabricated by deposition and thermal oxidation of tungsten metal on porous single wall carbon nanotubes (SWNTs). The morphology and crystalline quality of materials are investigated by SEM, TEM, XRD and Raman analysis. The results prove that $WO_3$ wire-like nanostructure fabricated on SWNTs show highly porous structures. Exposure of the sensors to NH3 gas in the temperature range of 150~300$^{\circ}C$ resulted in the highest sensitivity at $250^{\circ}C$ with quite rapid response and recovery time. Response time as a function of test concentrations and NH3 gas sensing mechanism is reported and discussed.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.141-145
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• 2017

This paper presents a method to improve Li-ion battery charging speed for portable electronic devices maintaining stable operating temperature. The proposed method uses multiple chargers which consist of a master module and slave modules designed with single wire communication signal for parallel current path in order to simplify the additional hardware needs. A single wire communication signal control between a master module and slave modules makes the number of pins of parts lowered and the required area small, furthermore leading to lower cost. Therefore the proposed charging method can be practically used for implementing battery charging modules requiring high speed Li-ion battery charging.