• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.392-401
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• 2012

This paper gives a electromagnetic coupling mechanism of the high altitude electromagnetic pulse (HEMP) into large- scale underground multilayer structures using analytic and numerical methods. The modeling methods are firstly addressed to the HEMP source which can be generated by intentional nuclear explosion. The instantaneous and intense electromagnetic pulse of the HEMP source is concerned from DC to 100 MHz band, because the power spectrum of the HEMP is rapidly decreased under -30 dB over the 100 MHz band. Through this range, a penetrated electric field distribution is computed within the large-scale underground multilayer structures. As a result, the penetrated electric field intensities at 0.1 and 1 MHz are about 10 and 5 kV/m, respectively. Therefore, additional shielding techniques are introduced to protect buried structures within the large-scale underground structures such as high-lossy material and filtering structures (wire screen).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.463-468
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• 2017

For transdermal drug delivery, needless injection system is composed of laser and microjet injector. Main mechanism of microjet injector is the laser-induced bubble. Nd:YAG and Er:YAG laser are used as a power source. Laser parameters such as pulse duration and wavelength are considered, which are core parameters to control the bubble motion. The Nd:YAG laser, pulse duration is short than bubble life time making cavitation like bubble while in Er:YAG laser, long pulse duration and high absorption in water drive bubble as a boiling bubble. Detailed motion of bubble and microjet is captured by the high speed camera. So it is observed that microjet characteristics are determined by the bubble behavior. The performance of drug delivery system is evaluated by fluorescent staining of guinea pig skin.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.10
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• pp.581-586
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• 2002

To improve the current waveform of diode rectifiers, we propose a new operating principle for the voltage-doubler diode rectifiers. In the conventional voltage-doubler rectifier circuit, relatively large capacitors are used to boost the output voltage, while the proposed circuit uses smaller ones and a small reactor not to boost the output voltage but improve the input current waveform. A circuit design method is shown by experimentation and confirmed simulation. The experimental results of the proposed diode rectifier satisfies the harmonic guide lines. A high input power factor of 97(%) and an efficiency of 98[%] are also obtained. The new rectifier with no controlled switches meet the harmonic guide lines, resulting in a simple, reliable and low-cost at-to dc converters in comparison with the boost-type current-improving circuits. This paper proposes a nonlinear impedance circuit composed by diodes and inductors or capacitors. This circuit needs no control circuits and switches, and the impedance value is changed by the polarity of current or voltage. And this paper presents one of these applications to improve the input current of capacitor input diode rectifiers. The rectifier using the nonlinear impedance circuit is constructed with four diodes and four capacitors in addition to the conventional rectifiers, that is, it has eight diodes and five capacitors, including a DC link capacitor. It makes harmonic components of the input current reduction and the power factor improvement. Half pulse-width modulated (HPWM) inverter was explained compared with conventional pulse width modulated(PWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.55-60
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• 2017

Capacitor Charging Power Supply(CCPS) is one of the most important components of a pulsed power system. The CCPS is widely used in source of lasers, accelerators and plasma generators. This paper presents design of a dead time control circuit and operation characteristics for stable high repetition rate of high voltage CCPS. The CCPS consists of battery, high voltage transformer and controller with a dead time control circuit. A dead time control circuit was simulated by PSpice. The performance test of the CCPS was carried out with a 7[nF] load capacitor at output voltage of 50[kV] and a pulse repetition frequency of 100[Hz]. As a result, we can verify that charging and discharging waveform is stable at 100[Hz]. The experiment results indicate that 3[ms] dead time made it possible for stable high repetition rate of 100[Hz]. This paper paves the way for designing an advanced CCPS which is more applicable outside experiments.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.319-328
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• 2003

The purpose of this paper is to develop a medical laser system using the semiconductor diode laser in order to photodynamic cancel therapy as a light source. The ideal light source for photodynamic therapy would be a homogeneous nondiverging light with variable spot size and specific wavelength with stability. After due consideration in this point, in this paper, we used a diode laser resonator of 635nm wavelength. The development laser system have a statistical laser out beam with accuracy control using the constant current control of method and clinic-friendly with compact. In order to protect the diode resonator from the over-current, the rush-current and electrical fault, we specially designed. The most importance therapeutic factor are the radiation mode for cancer therapy. So we developed the radiation mode of CW(Continuous Wave), long pulse, short pulse, and burst pulse and can adjust the exposure time from several milli-second to several minute. The experimental result shows that laser beam power was increased linear from 10mW to 300mW according to the increasing input current and the increasing exposure time. The developed new compact diode laser system have a stability of output power and specific wavelength with easy control and transportable for many applications of PDT.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1597-1604
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• 2016

The speed at which the SRM (Switched Reluctance Motor) makes a transition from chopping control to single pulse operation. (i.e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on energy efficient C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• Journal of Welding and Joining
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• v.8 no.3
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• pp.60-69
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• 1990

Plasma arc cutting is a fusion cutting process in which a gas-constricted arc is employed to produce a high-temperature, high-velocity plasma jet on the workpiece. This process provides some advantages such as increased cutting velocity, excellent working accuracy and the ability to cut special materials (widely used stainless steels and Al-alloys, for example), when compared with iconventional oxyfuel gas cutting. From the view point of price and reliability of the power source, plasma arc cutting has also some distinct advantages over laser beam cutting. High-speed machines with NC or CNC systems are needed for the plasma arc or laser beam cutting process, while for oxyfuel gas cutting, low-speed machines with copying templates or optical-shape tracking sensors can be applied. The low price and high flexibility of the microprocessor arc contributing more and more the application of CNC system in the plasma arc cutting process, as in other manufacturing fields. From these points of view, a microprocessor-based plasma arc cutting system was developed by using a reference-pulse system, and its performance was tested. The interpolating routines were programmed in the assembly language for saving the memory volume and improving the compouting speed, which has an intimate relationship with the available cutting velocity.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.72-78
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• 2008

The speed variation of SRM is fulfilled throughout a transition from chopping control to single pulse operation. (i,e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on conventional C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1730-1736
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• 2015

This paper presents a 16-channel transimpedance amplifier (TIA) array implemented in a standard $0.18-{\mu}m$ CMOS technology for the applications of panoramic scan LADAR (PSL) systems. Since this array is the front-end circuits of the PSL systems to recover three dimensional image for unmanned vehicles, low-noise and high-gain characteristics are necessary. Thus, we propose a voltage-mode inverter TIA (I-TIA) array in this paper, of which measured results demonstrate that each channel of the array achieves $82-dB{\Omega}$ transimpedance gain, 565-MHz bandwidth for 0.5-pF photodiode capacitance, 6.7-pA/sqrt(Hz) noise current spectral density, and 33.8-mW power dissipation from a single 1.8-V supply. The measured eye-diagrams of the array confirm wide and clear eye-openings up to 1.3-Gb/s operations. Also, the optical pulse measurements estimate that the proposed 16-channel TIA array chip can detect signals within 20 meters away from the laser source. The whole chip occupies the area of $5.0{\times}1.1mm^2$ including I/O pads. For comparison, a current-mode 16-channel TIA array is also realized in the same $0.18-{\mu}m$ CMOS technology, which exploits regulated-cascode (RGC) input configuration. Measurements reveal that the I-TIA array achieves superior performance in optical pulse measurements.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.859-863
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• 2005

This paper describes the improvement of power control characteristics of ship's emergency lighting power supply(SELPS), by which electric power is controlled extensively, and power ON-OFF is controlled and system parameter monitored in remote distance by PC serial communication. Proposed system is composed of step-down converter(SDC), emergency power supply circuit(EPSC), half bridge(HB) inverter, fluorescent lamp(FL) starting circuit, microprocessor control and multi communication circuit. Experimental works confirm that relative system stops when over current is detected and speedy and stable emergency power is supplied when main power source cut-off, and controls input power up to 35[$\%$] by adjusting pulse frequency of the HB inverter, and ON-OFF control of multiple SELS, real time transmission and monitor of parameters as to voltage, current, and power values are performed appropriately by PC communication.