• Korean Journal of Food Science and Technology
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• v.41 no.2
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• pp.225-229
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• 2009

The efficacy of ozone water in reducing food-borne pathogenic bacteria on High Density Polyethylene (HDPE) and wooden chopping boards in food industry was investigated in this study. 1-5 log reductions of E. coli O157:H7, S. aureus, S. Typhimurium, and B. cereus were observed with increasing concentrations of ozone water. The immersion treatment evidenced superior capability to inactivate food-borne pathogens than washing treatment. The Gram-negative bacteria, such as E. coli O157:H7 and S. Typhimurium, evidenced lower resistance against ozone water than was seen with the gram-positive bacteria, which included S. aureus and B. cereus. The sterilizing effects of ozone water on HDPE chopping boards was superior to that on wooden boards. This result might be utilized to remove food-borne pathogens from food contact surfaces in the food industry.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.221-223
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• 2008

This paper presents a maximum power point tracking(MPPT) of Photovoltaic system with chopping ratio of DC-DC converter considered load. A variation of solar irradiation is most important factor in the MPPT of PV system. That is nonlinear, aperiodic and complicated. The paper consists of solar radiation source, DC-DC converter, DC motor and load(cf, pump). NN algorithm apply to DC-DC converter through an adaptive control of neural network, calculates converter-chopping ratio using an adaptive control of NN. The results of an adaptive control of NN compared with the results of converter-chopping ratio which are calculated mathematical modeling and evaluate the proposed algorithm. The experimental data show that an adequacy of the algorithm was established through the compared data.

• 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 Power Electronics
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• v.15 no.6
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• pp.1533-1546
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• 2015

This study presents a novel method for reducing the switching losses of an asymmetric half-bridge converter for a three-phase, 12/8 switched reluctance motor operated in low speed. In particular, this study aims to reduce the switching-off losses of chopping switches in the converter when operated in the current regulated mode (chopping mode). The proposed method uses the mixed parallel operation of IGBT (chopping switch) and MOSFET (auxiliary switch). MOSFET is precisely controlled to momentarily conduct prior to the turn-off interval of the IGBT. Consequently, the voltage across the switches is clamped to approximately zero, substantially decreasing the turn-off switching losses. The analytical expressions of power losses are extensively elaborated. Compared with the conventional asymmetric half-bridge converter, the modified converter can effectively minimize the switching losses. Therefore, the efficiency of the converter is eventually improved. Computer simulation and experimental results confirm the effectiveness of the proposed technique.

• 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.67 no.9
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• pp.1159-1164
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• 2018

Vacuum circuit breakers(VCB) are widely used for current interruption of high-voltage inductive loads such as induction motors. This VCB can be chopped off before the current zero due to its high arc-extinguishing capability. One of the outstanding features of VCB is that it can cut off high frequency re-ignition current more than other circuit breakers. If the transient recovery voltage generated in the arc extinguishing is higher than the dielectric strength of the circuit breaker, a re-ignition phenomenon occurs. The surge voltage of the re-ignition is very high in magnitude and the steepness of the waveform is so severe that it can act as a high electrical stress on the winding. If the high frequency current of one phase affects the other two phases when the re-ignition occurs, it may cause a high surge voltage due to the virtual current chopping. If the magnitude of the voltage allowed in the motor winding is high or the waveform level is too severe, it may lead to insulation breakdown. Therefore, it is necessary to reduce the voltage to within a certain range. In this study, we briefly explain the various phenomena at the time of interruption, analyzed the magnitude of the dielectric strength and the transient recovery voltage at the simultaneous three-phase interruption that can give the greatest influence to the inductive load, proposed a method to reduce the impact.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.176-181
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• 2003

Damages by vibration and noise due to the construction performance are increasing. The rise of construction demand and enlargement of equipments are major reasons of this damage. As a result, the enmity of the people is provoked and this appears to be an obstacle of construction work. Especially, in case of ground improvement construction. Casing pipe is inserted into the Sand Drain, Sand Compaction Pile and Vibrated Crushed-stone Pile by vibration power when carrying out. Hence, a pillar is formed and it creates vibration and noise. This causes a lot of restrictions to construction condition. The low Vibration and low noise construction equipments uses earth auger and hydrulic cylinder for insertion and chopping operation instead of vibro hammer, which is the source of vibration and noise. This minimize ground disturbanceand decrease vibration and noise successfully, but increase chopping effect greatly. Thus, this new equipment is not only suitable for environment but also excellent engineering method of construction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.203-206
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• 2001

The reduction of chopping noise generated from inverter compressor and the piping design reducing vibration are the most important items in the quality of air conditioner. The chopping noise is identified by the study of the relationship between carrier frequency and natural frequency of the compressor shell. The high carrier frequency is the key factor in reduction of carrier noise. To keep the natural frequencies of the system as far as away from the operating frequencies appears to be the most important factor in the design of piping system.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.257-260
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• 2002

In this paper, the circuit of AC Choppers for $CO_2$laser Power Supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transfomer used with the proposed system. This improved circuit employs a 3 electrode-type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirment, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$: $N_2$: He = 1 : 9 : 15, total pressure of 15torr.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.230-237
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• 2013

This paper presents a novel nonlinear model of Switched Reluctance Generator (SRG) based on wind Energy Conversion system. Closed loop control with based Proportional Integrator current Chopping Control machine model is used. A Power converter in SRG can be controlled by using PI-CCC proposed model, and can be produced maximum power efficiency and minimize the ripple contents in the output of SRG. A second power converter namely PI based controlled PWM Inverter is used to interface the machine to the Grid. An effective control technique for the inverter, based on the pulse width modulation (PWM) scheme, has been developed to make the line voltage needs less power switching devices and each pair of turbine the generated active power starts increasing smoothly. This proposed control scheme feasibility and validity are simulated on SIMULINK/SIM POWER SYSTEMS only.