• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1755-1757
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• 1998

Pulse transformers have been developed to apply for pulsed power technology as an alternative of a Marx generator. To obtain repetitive pulsed power generation, it is necessary to observe the rising time of output of pulse transformer. In this paper, using the equivalent circuit, The rising wave of output of pulse transformer is simulated for various input wave by using the Electromagnetic transient program(EMTP).

• Current Optics and Photonics
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• v.5 no.2
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• pp.191-197
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• 2021

The anomalous propagation characteristics of a single Airy beam in nonlocal nonlinear medium are investigated by utilizing the split-step Fourier-transform method. We show that besides the normal straight propagation trajectory, the breathing solitons formed by the interaction between Airy beam and nonlocal nonlinear medium can propagate along the sinusoidal trajectory, and the anomalous trajectory can be modulated arbitrarily by altering the initial amplitude and the nonlocal nonlinear coefficient. In addition, the initial amplitude and the nonlocal nonlinear coefficient can have inverse impacts on the formation and transformation of the equilibrium state of spatial solitons, when the two parameters are larger than certain values. Therefore, the reversible transformation of the evolution dynamics of two soliton states can be realized by adjusting those two parameters properly. Finally, it is shown that the propagation properties of the solitons formed by the interaction between Airy beam and nonlocal nonlinear medium can be controlled arbitrarily, by adjusting the distribution factor and nonlocal coefficient.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.3
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• pp.339-346
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• 2015

Aerodynamic flow control phenomena were investigated with a low-current DC surface discharge plasma actuator. The plasma actuator was found to operate in three different discharge modes with similar discharge currents of about 1 mA or less. Stable continuous DC discharge without audible noise was obtained at higher ballast resistances and lower discharge currents. However, even with continuous DC power input, a low-frequency self-pulsed discharge was obtained at lower ballast resistances, and a high-frequency self-pulsed discharge was obtained at higher set-point currents and higher ballast resistances, both with audible noise. The Schlieren image reveals that the low-frequency self-pulsed mode produces a synthetic jet-like flow implying that a gas heating effect plays a role, even though the discharge current is small. The high-frequency self-pulsed mode produces pulsed jets in a tangent direction, and the continuous DC mode produces a steady straight pressure wave. Particle image velocimetry (PIV) images reveal that the induced flow field by the low-frequency self-pulsed mode has flow propagating in the radial direction and centered between the electrodes. The high-frequency self-pulsed mode and continuous DC mode produce flow from the anode to the cathode. The perturbed region downstream of the cathode is larger in the high-frequency self-pulsed mode with similar maximum speeds.

• Journal of Welding and Joining
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• v.31 no.2
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• pp.57-62
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• 2013

Magnesium has good castability and limited workability, so its products have been manufactured by almost casting processes. In this study, a pulsed Nd:YAG laser was used to butt-weld the sand casting magnesium alloys. And the effect of welding conditions such as peak power, pulse width, welding speed was evaluated in detail. As a result of this study, large underfill and plenty of spatter taken place under the conditions with high peak power. Thus, it is recommended to use low peak power and long pulse width to obtain good welds with deep penetration. It is also confirmed that the welding speed and pps(pulse per second) are directly connected at weld defects such as underfill, porosity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.4
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• pp.484-491
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• 2008

In this paper, we design and fabricate the L-band high speed pulsed HPA using LDMOS FET. And we propose the high voltage and high speed switching circuit for LDMOS FET. The pulsed HPA using LDMOS FET is simpler than using GaAs FET because it has a high gain, high output power and sin81e voltage supply. LDMOS FET is suitable for pulsed HPA using switching method because it has $2{\sim}3$ times higher maximum drain-source voltage(65 V) than operating drain-source voltage($V_{ds}=26{\sim}28\;V$). As results of test, the output peak power is 100 W at 1.2 GHz, the rise/fall time of output RF pulse are 28.1 ns/26.6 ns at 2 us pulse width with 40 kHz PRF, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.88-99
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• 2007

In this paper, a novel new pulse power generator based on IGBT stacks is proposed for pulse power application. Because it can generate up to 60kV pulse output voltage without any step- up transformer or pulse forming network, it has advantages of fast rising time, easiness of pulse width variation and rectangular pulse shape. Proposed scheme consists of series connected 9 power stages to generate maximum 60kV output pulse and one series resonant power inverter to charge DC capacitor voltage. Each power stages are configured as 8 series connected power cells and each power cell generates up to 850VDC pulse. Finally pulse output voltage is applied using total 72 series connected IGBTs. To reduce component for gate power supply, a simple and robust gate drive circuit is proposed. For gating signal synchronization, full bridge invertor and pulse transformer generates on-off signals of IGBT gating with gate power simultaneously and it has very good characteristics of short circuit protection.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1421-1424
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• 2013

The electronic equipment which is exposed to high level pulsed radiation is damaged by Upset, Latchup, and Burnout. Those damages come from the instantaneous photocurrent from electron-hole pairs generated in itself. Such damages appear as losses of a power in military weapon system or as a blackout in aerospace equipment and eventually caused in gross loss of national power. In this paper, we have implemented a RDC(Radiation detection and control module) as a part of the radiation protection technology of the electronic equipment or devices from the pulsed gamma radiation. The RDC, which is composed of pulsed gamma-ray detection sensor, signal processors, and pulse generator, is designed to protect the an important electronic circuits from the a pulse radiation. To verify the functionality of the RDC, LM118s, which had damaged by the pulse radiation, were tested. The test results showed that the test sample applied with the RDC was worked well in spite of the irradiation of a pulse radiation. Through the experiments we could confirm that the radiation protection technology implemented with the RDC had the functionality of radiation protection for the electronic devices.

• Journal of the Korean institute of surface engineering
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• v.52 no.4
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• pp.211-226
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• 2019

Optical thin films were deposited by using a reactive pulsed DC magnetron sputtering method with a high density plasma(HDP). In this study, the effect of sputtering process conditions on the microstructure and optical properties of $SiO_2$, $TiO_2$, $Nb_2O_5$ thin films was clarified. These thin films had flat and dense microstructure, stable stoichiometric composition at the optimal conditions of low working pressure, high pulsed DC power and RF power(HDP). Also, the refractive index of the $SiO_2$ thin films was almost constant, but the refractive indices of $TiO_2$ and $Nb_2O_5$ thin films were changed depending on the microstructure of these films. Antireflection films of $Air/SiO_2/Nb_2O_5/SiO_2/Nb_2O_5/SiO_2/Nb_2O_5/Glass$ structure designed by Macleod program were manufactured by our developed sputtering system. Transmittance and reflectance of the manufactured multilayer films showed outstanding value with the level of 95% and 0.3%, respectively, and also had excellent durability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1289-1295
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• 2012

An active resonance damper for a DC Distributed Power System(DPS) with parallel loads is presented. Each pulse power load in a DC DPS comprises both a resistive power load and a step-up converter. The step-up converter behave as constant power load(CPL) when tightly regulated and usually cause a negative impedance instability problem. Furthermore, when an input filter is connected to a large constant power load, the instability of DC bus voltage. In this paper, a bidirectional DC/DC converter with a reduced storage capacitor quantitatively are proposed as a active resonance damper, to mitigate the voltage instability on the bus. The validity of the proposed method was confirmed by simulation and experimental works.

• KIEE International Transactions on Electrophysics and Applications
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• v.2C no.6
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• pp.304-308
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• 2002

We demonstrate a simple pulsed $CO_2$ laser with millisecond long pulse duration in a tube at a low pressure of less than 30 Torr. The novel power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply doesn't need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. To control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of SCR(Silicon Controlled Rectifier) gate is varied from 30。 to 150。. A ZCS (Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control precisely the gate signal of the SCR. The maximum laser output of 35 W is obtained at a total pressure of 18 Torr, a pulse repetition rate of 60 Hz, and a SCR gate firing angle of 90。 . In addition, the resulting laser pulse width is approximately 3㎳(FWHM). This is a relatively long pulse width, compared with other repetitively pulsed $CO_2$ lasers.