• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.352-355
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• 2013

In this paper, a high power tuneable resonator for a wireless power transfer system based on magnetic resonance is proposed. A spiral structure is used for a self-resonant coil and tuneable trimmer capacitors are added at the edges of resonant coils such that the frequency can be easily tuned. 3D simulation tools and equivalent circuit modeling method are used for predicting self-resonant frequency and scattering parameters according to the change of capacitor values. From the measurement of the prototype WPT system, the resonant frequency could be controlled from 3.0 MHz to 4.5 MHz and the transmission efficiency way over 50 % when the distance between transmitting coil and receiving coil was 160 mm.

• Progress in Superconductivity and Cryogenics
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• v.22 no.3
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• pp.13-19
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• 2020

This study presents the experiment and simulation results on the magnetic field response and electrical stability behaviors of no-insulation (NI) and metal insulation with stainless steel tape (MI-SS) which wound in form of racetrack type coils. First of all, the structural design of the racetrack type bobbin was shown along with its parameters. Then, the current-voltage tests were carried out to measure the critical current of both test coils. Also, the sudden discharging and charging tests were performed in the steady state to estimate the decay field time and magnetic field response, respectively. Finally, the overcurrent tests were conducted in the transient state to investigate the electrical stability of these test coils. Based on the experimental results, the contact surface resistances were calculated and applied to the field coils (FCs) of 10-MW-class second generation high temperature superconducting generator (2G HTSG) used in wind offshore environment. The charging delay time and electrical stability for NI and MI-SS HTS FCs of 10-MW-class 2G HTSG are analyzed by the equivalent circuit model and the key parameters which were obtained from the electromagnetic finite element analysis results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3608-3613
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• 2009

In this paper, we propose a mobile Radio Frequency Identification antenna for mobile hand set. The proposed antenna with directive radiation characteristics based on combination of electric-magnetic radiators can be installed in the mobile hand-set. The combination of PIFA antenna for electric radiator and loop antenna for magnetic radiator is presented and designed for료 m-RFID reader system. Target frequency band is 900-MHz band. and desired gain is 4dBi. The antenna is simulated using Ansoft HFSS software and shows expected results. The antenna is also manufactured using FR4-epoxy circuit board (h=1 mm, $\varepsilon_{\tau}=4.4$). There are good agreements between the simulated and measured VSWR curves and radiation characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1125-1131
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• 2013

Wireless power transmission technology has been studied variety. Recently, wireless power transmission technology used by resonance and magnetic induction field is applied to various fields. However, magnetic resonance and inductive coupling are have drawbacks - power transmission distance is short. Microwave transmission and accept techniques have been developed to overcome short distance. However, improvement in efficiency is required. This paper, propose a high-efficiency microwave energy acceptor IC(EAIC). Suggested EAIC is consists of RF-DC converter and DC-DC converter. Wide Input power range is -15 dBm ~ 20 dBm. And output voltage is boosted up to 5.5 V by voltage boost-up circuit. EAIC can keep the output voltage constant. Available efficiency of RF-DC converter is 95.5 % at 4 dBm input. And DC-DC efficiency is 94.79 % at 1.1 mA load current. Fully EAIC efficiency is 90.5 %.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1495-1502
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• 2017

The Theory of operation of switched reluctance motors (SRM) depends on the reluctance torque, where energy is transferred to stator winding only. Although its construction is simple, the electrical design is complex, due to the switching configuration needed to deliver power to stator coils. However, because of the nonlinearly of magnetic circuit, SRM has torque ripple. This paper proposes a new strategy to drive SRM from a single-phase AC supply. Each stator winding is connected to AC-DC or AC-AC converters, which is called branch. All branches are connected in parallel to a single-phase AC supply. A shaft encoder allows current production in stator winding during the positive torque production region and terminates it during the negative torque production region. A magnetic flux is produced between stator poles when current is supplied from AC supply to stator coil and repeats many cycles as long as the rate of change of stator inductance is positive. Different possibilities for the configurations of AC-AC or AC-DC converters are introduced to drive SRM from the single-phase AC supply. A case study is presented for a SRM fed from AC supply through semi-controlled AC-DC converter is presented. A simulation model is introduced and verified by experimental rig for two-phase SRM.

• 전기의세계
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• v.24 no.1
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• pp.75-85
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• 1975

In order to develop the commercial frequency (60Hz) plasma torch of small capacity for material cutting, welding and other industrial heating, the A.C plasma jet generator of non-transfered type is made domestically and the electrode configurations of plasma torch are composed of two kinds of electrodes W-C and W-Cu, combined by thermal emission and field emission electrode materials. In this paper, the characteristics of input power, thermal efficiency, electrode consumption, the flame and forms of arc voltage and arc current for A.C plasma torch are investigated in relation to such variables as arc current, argon flow and magnetic field intensity to obtain the basic design data necessary to A.C plasma jet generator. The result are as follows; (1)The input power, thermal efficiency and electrode consumption are influenced greatly by argon flow, magnetic field intensity and nozzle materials. (2)A.C arc voltage and current are non-symmetrial, involving D.C Component. Due to this current of D.C Component, transformer core is saturated and a large abnormal current flows into the primary winding coil. In order to prevent this abnormal current flow, a condenser must be connected in series to the main discharge circuit. (3)The stability and sharpness of jet flame are improved more in the torch of W-C electrode configuration than in the torch of W-Cu electrode configuration.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.5
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• pp.19-26
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• 2000

In this paper, to improve the mechanical response of the Moving Magnet Type LDM, the design of the LDM was optimized to achieve a large force to volume ratio without reduction the force. The model of the LDM and its optimization procedure were developed on the initial assumption that the magnetic circuit is linear. To analyze the magnetic flux distribution throughout the volume of the LDM and the slider back iron, a 2D finite element analysis of the LDM was performed.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2535-2542
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• 2020

To understand the fundamental parameters of Alvand tokamak, A Rogowski coil with an active integrator was designed and constructed. Considering the characteristics of the Alvand tokamak, the structural and electrical parameters affecting the sensor function, were designed. Calibration was performed directly in the presence of plasma. The sensor has a high resistance against interference of external magnetic fields. Plasma current was measured in various experiments. Based on the plasma current profile and loop voltage signal, the time evolution of plasma discharge was investigated and plasma behavior was analyzed. Alvand tokamak discharge was divided into several regions that represents different physical phenomena in the plasma. During the plasma discharge time, plasma had significant changes and its characteristic was not uniform. To understand the plasma behavior in each of the phases, the Rogowski sensor should have sufficient time resolution. The Rogowski sensor with a frequency up to 15 kHz was appropriate for this purpose.

• Korean Journal of Biological Psychiatry
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• v.28 no.2
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• pp.36-49
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• 2021

Suicide is a leading cause of death worldwide, especially among adolescents and young adults. Considering this fact, it is imperative that we understand the neural mechanisms underlying suicidal thoughts and behaviors in youth from a neurodevelopmental perspective. In this review, we focused on the magnetic resonance imaging studies that examined the neural correlates of suicidal ideations (SI) or attempts (SA) in youth. We reviewed twenty-three cross-sectional studies reporting the structural and functional alterations in association with SI or SA among adolescents and young adults with various mental disorders. The previous literature suggests that the dorsolateral prefrontal cortex, anterior cingulate cortex, and ventral frontolimbic circuit, may play an important role in the pathophysiology of suicidal behavior in youth through altered top-down control over emotion and impulsivity. Future studies with a longitudinal design and using multimodal imaging techniques may be of help to identify novel therapeutic targets specific for youth with suicidal thoughts and behaviors.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.40-45
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• 2009

Many superconductor applications such as MRI and SMES must be operated in persistent current mode to eliminate the electrical ohmic loss. This paper presents the characteristic analysis of the high temperature superconducting (HTS) power supply made of YBCO coated conductor (CC). In this research, we have manufactured the HTS power supply to charge the 0.73 mH HTS double-pancake magnet made of YBCO CC. Among the all design parameters, the heater triggerring time and magnet applying time were the most important factors for the best performance of the HTS power supply. In this paper, three-dimensional simulation through finite element method (FEM) was used to study the heat transfer in YBCO CC and the magnetic field of the magnetic circuit. Based upon these results, the final operational sequence could be determined to generate the pumping current. In the experiment, the maximum pumping current reached about 16 A.