• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.2
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• pp.142-149
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• 2009

This paper investigates operating characteristics of three-phase matrix converter with unity input power factor by direct duty-ratio pulse-width modulation in the case of balanced and unbalanced load. It can be found from the system analysis that (1) The control algorithm for unity power factor is not related to the variables of load sides but the input voltages, (2) With the balanced three-phase load except for the pure reactive load, the unity input power factor can be achieved, (3) In the case of the unbalanced linear load, the equivalent input characteristics of the matrix converter can be seen like the nonlinear resister, (4) When the input frequency and the output frequency have the specific relationship, each input phases have the same sharing of the average power. The feasibility and validity of the analysis were verified by simulation and experimental results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.7
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• pp.44-51
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• 2008

A stereo audio digital-to-analog converter (DAC) with a power amplifier using asymmetric pulse-width modulation (PWM) is presented. To adopt class-D amplifier mainly used in high-power audio appliances for head-phones application, this work analyzes the noise caused by the inter-channel interference during the integration and optimizes the design of the sigma-delta modulator to decrease the performance degradation caused by the noise. The asymmetric PWM is implemented to reduce switching noise and power loss generated from the power amplifier. This proposed architecture is fabricated in 0.13-mm CMOS technology. The proposed audio DAC including the power amplifier with single-ended output achieves a dynamic range (DR) of 95-dB dissipating 4.4-mW.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.3 s.303
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• pp.71-80
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• 2005

This paper proposes a new circuit topology of the half-bridge resonant inverter and presents its digital control scheme. As the proposed half-bridge inverter can be operated in the load-freewheeling modes, pulse width modulation (PWM) control method can be used for the output power control. The proposed half-bridge inverter can keep unity output displacement factor under the load-impedance varying conditions, if a new PWM control scheme based on the resonant frequency tracking algorithm is adopted. In this paper, the operation principle, electrical characteristics and detailed digital control scheme of the proposed half-bridge resonant inverter and loss analysis comparing with a conventional half bridge inverter is described. The experimental results of the proto-type experimental setup to verify the validity of the proposed half-bridge resonant inverter are presented and discussed.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.1-7
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• 2003

The crystallized stable cobalt silicide$(CoSi_2)$ films were prepared on $poly-Si/SiO_2/Si$substrates for the application of inkjet printing head as a heating element with omega shape. The structural images and temperature resistance coefficient were investigated. The value of temperature resistance coefficient of the heating element was found to be about $0.0014/^{\circ}C$. The maximum power of the heating element was 2 W at the applied voltage of 2 V, 10 kHz in frequency and $1{\mu}s$ in pulse width. From the investigation of fatigue property according to the repeated applied voltages, there was no drastic changes in the resistances of heating element under the condition of $10^8$ pulsed cycles at below 15 V biased voltage. In contrast, the resistance of heating element was greatly increased at $10^6$ pulsed cycles when the heating element was operated at 17 V.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.1
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• pp.79-89
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• 2013

PURPOSE: To identify the effects of single trial transcutaneous electrical nerve stimulation (TENS) application on chronic neuropathic pain and the repeated TENS application to development of neuropathic pain following peripheral nerve injury. METHODS: First, 20 rats were given the median nerve ligation to induce chronic neuropathic pain. After the ligation, neuropathic pain was assessed by measuring the forepaws withdrawal threshold to von Frey filaments for 3 weeks. Afterward, rats were randomly divided into TENS group and placebo-TENS group. TENS (frequency 100Hz, pulse width $200{\mu}s$) was applied to the forearm for 20 minutes. Second, 34 rats were randomly allocated into two group after median nerve ligation: TENS group and placebo-TENS group. Both interventions were applied to the forearm for 20 minutes from 1 day to 3 weeks after injury. Neuropathic pain to mechanical was measured on each rat for 3 weeks. RESULTS: Exeprimental rats showed a clear neuropathic pain-like behaviors, such as reduced forepaw withdrawal threshold to mechanical stimulation for 3 weeks, after median nerve ligation. And, TENS decreased effectively the chronic neuropathic pain originated from median nerve injury. TENS also diminished the development of neuropathic pain after nerve injury. CONCLUSION: Our animal model studying for neuropathic pain following median nerve injury may be useful to investigate peripheral neuropathic pain in human. Also, TENS may be used to mediate chronic neuropathic pain and to prevent the development of neuropathic pain following median nerve injury.

• Journal of IKEEE
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• v.19 no.1
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• pp.118-123
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• 2015

According to the recent report, solar street lamp connected to a non Maximum Power Point Tracking(MPPT) charger, can lead to a system-wide decline in power output with as much as 30%. This paper proposes the charge controller with direct duty ration control for 250W solar street lamp in order to improve the efficiency of photovoltaic from these output power reduction. This paper covers the Pulse Width Modulation(PWM) controller and power conversion topology and analyze the MPPT method for charge controller. The power conversion part consists of push pull converter based on PWM controller using 8bit MCU in order to have lower manufacturing cost. The PWM controller with direct duty ratio control algorithm is constantly tracking the maximum power point of photovoltaic module and increases energy output power. The test results shows 97.1~97.4% MPPT efficiency and the experimental hardware is implemented based on the solar simulator condition for 241W. Thus, the implemented charge controller shows its feasibility for the real application, especially under solar street lamp.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.11
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• pp.1186-1193
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• 2009

In this paper, we propose DDS(Direct Digital Synthesizer) as a new implementation method of chirp LO(Local Oscillator) for compressive receiver applied for RFID signal detection in UHF band. We designed a receiver whose input frequency range is 908.5~914 MHz, DDL(Dispersive Delay Line) bandwidth is 6 MHz, and dispersion delay time is $13\;{\mu}s$. Chirp LO based on DDS is designed to meet $26\;{\mu}s$ sweep time and 12 MHz bandwidth for complete compressive mechanism. The measured 3 dB pulse width of the compressed signal of the fabricated receiver is 260 ns and the frequency resolution for simultaneous input signals is below 200 kHz. These performances indicate that the proposed chirp LO based on DDS and the compressive receiver is suitable for RFID signal detection in UHF band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.9
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• pp.685-697
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• 2017

In this paper, it is presented the result of design and fabrication for C-band solid state high power amplifier unit and components using in search radar. The solid state power amplifier(SSPA) assembly was fabricated using GaN(Gallium Nitride), which is semiconductor device, and the transmit signal output power of the solid state high power amplifier unit is generated by combining the transmit signal power of the solid state power amplifier configured in parallel through a design and fabricated waveguide type transmit signal combine assembler. Designed solid state high power amplifier unit demonstrated C-band 500 MHz bandwidth, maximum 10.5% duty cycle, transmit pulse width from $0.0{\mu}s{\sim}000{\mu}s$, and transmit signal power is 44.98 kW(76.53 dBm).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.250-254
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• 2016

Currently, power conversion system which converts AC to DC Power is applied in domestic urban railway. The diode rectifier is used in most of them. However the diode rectifier can not control the output voltage and can not regenerate power as well. On the other hand, PWM (pulse width modulation) converter using IGBT (isolated gate bipolar transistor) can control output voltage, allowing it to reduce the output voltage drop. Moreover the Bi-directional conduction regenerates power which does not require additional device for power regeneration control. This paper compared the simulation results for the DC power supply system on both the diode rectifier and the PWM converter. Under the same load condition, simulation circuit for each power supply system was constructed with the PSIM (performance simulation and modeling tool) software. The load condition was set according to the resistance value of the currently operating impedance of light rail line, and the line impedance was set according to the distance of each substations. The train was set using a passive resistor. PI (proportional integral) controller was applied to regulate the output voltage. PSIM simulation was conducted to verify that the PWM Converter was more efficient than the diode rectifier in DC Traction power supply system.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.85-101
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• 1991

The purpose of this study was to determine the optimum range of laser energy density to the enamel surface of permanent incisors when they are irradiated with the pulsed Nd : YAG laser, Laser impacts on each experimental group were made at energy density of $20\sim50J/cm^2$ by 20 pulses of the pulse width 1.2 msec. The author investigated the enamel surface with the sunning electron microscope(SEM) and the surface roughness tester, and measured the shear bond strength between electrolytically etched Ni-Cr-Be alloy casting and composite resin. The obtained results were as follows: 1. The surface roughness of enamel after laser irradiation showed the significant difference level from the energy density $40J/cm^2(P<0.05)$. 2. The mean shear bond strength of etched-metal resin-bonded specimens were $154.23{\pm}33.30kg/cm^2$ at unlased enamel surface and $195.72{\pm}29.56kg/cm^2$ at lased energy density $30J/cm^2$, and showed a significant difference(P<0.05). 8. SEM photographs showed the irregular microcracks and the structural changes of lased enamel surface. 4. SEM photographs of the fracture surface after testing the shear bond strength showed the aspect of interfacial fracture between bonding agent and composite resin at the metal sides.