• Journal of Korean Vacuum Science & Technology
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• v.4 no.4
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• pp.112-121
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• 2000

The paper investigates electrical discharge properties in neon gas mixed with xenon. The breakdown temperature T$\sub$b/ and voltage V$\sub$b/ are obtained in terms of the gas mixture ratio X. It is shown that the breakdown voltage decreases, reaches the minimum value at X=0.02 and then increases again, as the mixture ratio X increases from zero to unity. Therefore, mixing the neon gas with a few percent of xenon is the most beneficial to reduce the breakdown voltage. Plasma density at breakdown in neon gas mixed with xenon is described in terms of the gas mixture ratio. The optimum value of mixture ratio for highest plasma density is found to be Xm=0.03. A preliminary experiment of AC-PDP is carried out for neon gas mixed with a few percent of xenon to verify some of the theoretical models. The experimental data agree qualitatively well with theoretical predictions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.336-342
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• 2003

In this paper, a new differential detector is introduced, in which a solar cell is used to reduce the low frequency interference from environmental optical noise. The solar cell also supplies electrical power to the detector circuit using the optical noise power. The DC voltage from the solar cell is used as a power supply to the detector, and the AC voltage is used to reduce the optical noise in a photodiode with the differential detection method. The signal to noise ratio was improved by about 20 dB.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.22-24
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• 1998

The Synchronous reluctance motor is a sinewave ac motor and it has cylindrical surfaces on both sides of the air gap. The stator is a conventional polyphase ac stator, while the rotor has internal flux barriers shaped to maximize the ratio of d-axis to g-axis reactance. This paper presents the finite element analysis and parameter measurement of the synchronous reluctance motor(SRM). The model motor is a 3-phase SRM with the segmental rotor and its rating is 0.175kw. The torque characteristic is analysed by finite element method and compared with that from measurement.

• Journal of Power Electronics
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• v.6 no.4
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• pp.290-297
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• 2006

Various methods have been discussed to reduce detent force in a tubular permanent magnet type linear single phase AC generator. In particular, the proposed methods depend on variations of the permanent magnet construction. These methods include two approaches in the form of sloped magnets, and conical magnets in addition to the conventional method of optimizing the magnet length. The undesired detent force ripples were calculated by a two dimensional Finite Element Method (FEM). Moreover, the generated electromotive force in the stator coils was calculated for each configuration of the permanent magnet. The experimental results agreed well with those obtained from the FEM-based simulations. Sufficient reduction in the detent force was achieved over the range of 40% while the root mean square of the output voltage was maintained. It was found that sloping the permanent magnet decreased the detent force and at the same time increased the generated rms voltage of the AC generator. The performance of the designed linear AC generator was evaluated in terms of its efficiency, total weight, losses, and power to weight ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1639-1644
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• 2016

In this paper, we consider the performance improvement that can be obtained with interference alignment (IA) technique applied to 802.11ac based multi-BSS WiFi service. To this end, we developed a system simulator consisting of a link-level PHY simulator, based on 802.11ac specification, and multi-BSS proportional-fair scheduler. Specifically, assuming perfect channel side information and synchronization of signals from multiple APs, we used a SLNR based interference alignment algorithm proposed in [13] and compared its performance with that of multiuser beamforming based time-sharing system. The performance was evaluated in terms of average throughput per BSS and 5% worst user throughput. The results show that 70 to 100% throughput gain can be obtained in this ideal scenario.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.34-38
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• 2014

In Display such as LCD, LED, and AMOLED or semiconductor related industries are required to have static ionizer in order to produce reliable goods since the ionizer can create balanced ion that is delivered to producing goods to minimize electrical damages when manufacturing. However, the most general type of ionization is called, "Corona Discharge" that has a slight chances to generate unequal and unstable amount of each +/- ion to the target object. Then, the ionization performance will drastically decrease and end up with quality deterioration problem. In this research, our objective to resolve the current issue via applying "Coupling Condenser" on each counter electrodes of Corona discharging type ionizer. The result is that the ion balance was maintained the satisfied range that is within +/-100V when we changed the duty ratio of the High Voltage of Pulse AC about 40 ~ 70%. In addition, when levelling the High Voltage of Pulse AC, the ion balance holds the range within +20 ~ 0V. Even though we have tested the same experiment for a year, we have seen the range changes roughly ${\pm}50V$.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.271-273
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• 2002

The ac loss in Bi-2223 tapes has been studied by a magnetic method. A brief overview of the theoretical background and the experimental set-up is presented. Measurements are made at 77 K in a magnetic fields. The magnitude of the ac loss indicates that filaments are fully coupled, which agrees with theory. As in other measurements, the loss in perpendicular field is larger than that in the parallel field by about a factor 10, which is close to the aspect ratio of the tape.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.377-382
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• 2008

For stator winding protection of AC generator, KCL(Kirchhoff's Current Law) is widely applied. Actually a CRDR(Current Ratio Differential Relay) based on DFT(Discrete Fourier Transform) has been used for protecting generator. It has been pointed out that defects can occur during the process of transforming a time domain signal into a frequency domain one which can lead to loss of time domain information. Wavelets techniques are proposed for the analysis of power system transients. This paper introduces an algorithm to choose a suitable Mother Wave1et for generator stator fault detection. For optimal selection, we analyzed db(Daubechies), sym(Symlets), and coif(Coiflects) of Mother Wavelet. And we compared with performance of the choice algorithm using detail coefficients energy and RMS(root mean square) error. It can be improved the reliability of the conventional DFT based CRDR. The feasibility and effectiveness of the proposed scheme is proved with simulation using collected data obtained from ATP (Alternative Transient Program) package.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.689-696
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• 2017

The practical applications of ordinary high-fluidity concrete have been limited due to several drawbacks, such as high hydration heat, high amount of shrinkage, and non-economic strength development. On the other hand, due to its advantages, such as improvement of construction quality, reduction of construction cost and period, the development of high-fluidity concrete is a pressing need. This study examined the properties of high-fluidity concrete, which can be manufactured on the low binders using a viscosity agent to prevent the segregation of materials. The optimal viscosity agent was selected by an evaluation of the mechanical properties of high-fluidity concrete among six viscosity agents. The acrylic type and urethane type viscosity agents showed the best performance within the range where no material separation occurred. The mechanical properties were evaluated to examine the optimal amount of AC and UT viscosity agent added by mixing two viscosity agents according to the adding ratio and blending them together with high performance water reducing agent. When the ratio of the AC : UT viscosity agents was 5:5, it was most suited for high-fluidity concrete with low binders by increasing the workability and effect of the reducing viscosity.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.11
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• pp.84-92
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• 2014

In this paper, we propose a three-phase isolated electrolytic capacitorless charger available for quick charger. In the proposed charger, electrolytic capacitor in DC link is eliminated by direct conversion from AC input to DC output. Conventional chargers are two stage structure including AC-DC and DC-DC converters, but the proposed charger can be simplified into single stage converter by using a matrix converter. And the waveform of input currents is improved by giving the weighting factor to the duty ratio of auxiliary switches. In order to verify the effectiveness of the proposed charger, simulations are carried out and a 1.2kW charger was constructed and experimented.