• Journal of IKEEE
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• v.24 no.2
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• pp.392-402
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• 2020

This paper proposes a solar tracking system without photo-sensors. The system can be classified into four modules: Solar Tracking, MPPT, ESS, and Real-Time Monitoring. Nine solar panels, as a basic unit, are adopted with grid structures of different heights to reduce wind influence and to enable solar tracking without photo-sensors. The low-cost MCU implements MPPT method which generates PWM switching signal for boost converter. The unit of ESS consists of three-series and four-parallel lithium-ion batteries in order to enable monitoring for abnormalities in temperature and electrical characteristics of battery. Four MCUs used in the system consists of two AVR Atmega128, and two Raspberry PI, and they exchanges operation informations. Experimental results of the proposed system show the solar tracking performance, the possibility of on-site and remote monitoring and the convenience of maintenance based on IoT technology.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.5
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• pp.43-50
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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 high input power factor of 97[%] and an efficiency of 98[%] are also obtained. The harmonic guide lines of proposed rectifier is no interfered with inverter switching, resulting in a simple, reliable and low-cost ac-to dc converters in comparison with the boost-type current-improving circuits.It compared conventional pulse-widthmodulated(PWM)inverter with half pulse-widthmodulated (HPWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switchingloss and holding over-shooting.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.364-369
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• 2012

The development of solar thermal energy used adsorption desalination technology have been examined as a viable option for supplying clean energy. In this study, the modelling of the main devices for solar thermal energy used and adsorption desalination system was introduced. Silica gel type adsorption desalination system is considered to be a promising low-temperature heat utilization system. The design is divided into three parts. First, the evaporator for the vaporization of the tap water is designed, and then the reactor for the adsorption and release of the steam is designed, followed by the condenser for the condensation of the fresh water is designed. In addition, new features based on the energy balance are also included to design absorption desalination system. In this basic research, One-bed(reactor) adsorption desalination plant that employ a low-temperature solar thermal energy was proposed and experimentally studied. The specific water yield is measured experimentally with respect to the time controlling parameters such as heat source temperatures, coolant temperatures, system switching and half-cycle operational times. Desalination is processes that permeate our daily lives, but It requires substantial energy input, powered either from electricity or from thermal input. From the environmental and sustainability perspecives, innovative thermodynamic cycles are needed to produce the above-mentioned useful effects at a lower specific energy input. This article describes the development of adsorption cycles for the production of desalting effects. We want that this adsorption system can be driven by low temperature heat sources at 60 to $80^{\circ}C$, such as renewable, solar thermal energy.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.421-434
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• 2018

Water supply/intake pumps operation use 70~80% of power costs in water treatment plants. In the water treatment plant, seasonal and hourly differential electricity rates are applied, so proper pump scheduling can yield power cost savings. Accordingly, the purpose of this study was to develop an optimal water supply pump scheduling scheme. An optimal operation method of water supply pumps by using genetic algorithm was developed. Also, a method to minimize power cost for water supply pump operation based on pump performance derived from the thermodynamic pump efficiency measurement method was proposed. Water level constraints to provide sufficient disinfection performance in a clearwell and reservoirs were calibrated. In addition, continuous operation time constraints were calibrated to prevent frequent pump switching. As a result of optimization, savings ratios during 7 days in winter and summer were 4.5% and 5.1%, respectively. In this study, the method for optimal water pump operation was developed to secure disinfection performance in the clearwell and to save power cost. It is expected that it will be used as a more advanced optimal water pump operation method through further studies such as water demand forecasting and efficiency according to pump combination.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.23-27
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• 2011

Fabrication of porous silicon(PS) double layer by electrochemical etching is the first step in process of ultrathin solar cell using PS layer transfer process. The porosity of the porous silicon layer can be controlled by regulating the formation parameters such as current density and HF concentration. PS layer is fabricated by electrochemical etching in a chemical mixture of HF and ethanol. For electrochemical etching, highly boron doped (100) oriented monocrystalline Si substrates was used. Ths resistivity of silicon is $0.01-0.02\;{\Omega}{\cdot}cm$. The solution composition for electrochemical etching was HF (40%) : $C_2H_5OH$(99 %) : $H_2O$ = 1 : 1 : 2 (by volume). In order to fabricate porous silicon double layer, current density was switched. By switching current density from low to high level, a high-porosity layer was fabricated beneath a low-porosity layer. Etching time affects only the depth of porous silicon layer.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.19-27
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• 1999

This paper propose a contention resolution policy featuring dynamic change of the threshold for the occupancy of the input buffer for an input buffering ATM switching architecture and its hardware implementation strategy. The strategy is provided with the aim of the simple structure that achieves the reduction of the signal path and the power consumption. The threshold is changed dynamically every time slot based both the arrived of cells and the cell service resulting from the contention resolution. The performance on the cell loss of the proposed policy is performed and compared with the conventional policy under the diverse traffic conditions through both the analysis based ont the Markov chain and the simulation.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.2
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• pp.1-11
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• 2001

In this paper, a chattering alleviation VSS controller for the sinusoidal type BLDC motor is designed. Dead Zone function is proposed to change the chattering occurring in the transient state from high frequency to low frequency and time varying gains arc applied for the control input to eliminate the steady state excessive chattering in the conventional ISM. The proposed Dead Zone function represents the sliding layer composed of two switching surfaces and if a state vector exists in this layer, the chattering don't occur. Simulation and experimental results confirm the useful effects of the above algorithm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.5
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• pp.44-51
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• 2008

UV lamp systems have been used for cleaning of display panels of TFT LCD or Plasma Display Panel (PDP). However, the needs for high efficient cleaning and low cost made high voltage plasma cleaning techniques to be developed and to be improved. Dielectric-Barrier Discharges (DBDs), also referred to as barrier discharges or silent discharges have been exclusively related to ozone generation for a long time. In this paper, a 6kW high voltage plasma power supply system was developed for LCD cleaning. The 3-phase input voltage is rectified and then inverter system is used to make a high frequency pulse train, which is rectified after passing through a high-power transformer. Finally, hi-directional high voltage pulse switching circuits are used to generate the high voltage plasma. Some experimental results showed the usefulness of atmospheric plasma for LCD panel cleaning.

• Journal of IKEEE
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• v.14 no.1
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• pp.55-64
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• 2010

In this paper, we proposed the novel TIGBT with an additional p-type MOS structure to achieve the improved trade-off between turn-off and on-state voltage drop(Vce(sat)). These low on-resistance and the fast switching characteristics of the proposed TIGBT are caused by an enhanced electron current injection efficiency which is caused by additional p-type MOS structure. In the simulation result, the proposed TIGBT has the lower on state voltage of 1.67V and the shorter turn-off time of 3.1us than those of the conventional TIGBT(2.25V, 3.4us).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.47-55
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• 2012

This paper describes the developed HILS and test equipment in order to test the performances of MMW(Millimeter-Wave) seeker which can detect and track a high speed of short-range ballistic missile and aircraft. This system is used to 141 horn antenna array, array switching, and gain and phase control algorithm to simulate various kind of targets and trajectory of high speed and maneuver moving target. In addition, it simulates not only velocity and range for these targets but also clutter and jamming environments. System configuration and implementation and the measurement results of major subsystems such as target motion simulator, simulation signal generator, high speed data aquisition unit, and central control unit are presented. These systems could verify the detection and tracking performance of MMW seeker through dynamic real-time test based on simulation flight scenario.