• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.380-384
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• 1993

In precision wire electrode discharge machining by CAD/CAM, it is the most important problem on machining method to determine the wire electrode offset amout from the accurate calculation of discharge gap in order to increase the machining accuracy, after fixing the main machining conditions such as machining speed, wire tension, coolant conductivity, gap vlotage. The present study shows the relationships between discharge gap and main machining conditions by means of a series of experiment concerned with the gap using the workpiece of STD 11, and suggests the experimental eguation to calculate the accurate wire electrode offset amount under the given machining conditions for spot workers.

• Smart Structures and Systems
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• v.10 no.3
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• pp.193-207
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• 2012

New insights into our previously proposed hybrid-type method for vibration control are highlighted in terms of energy analysis, such as the assessment of energy efficiency and system stability. The hybrid method improves the bang-bang active method by combining it with an energy-recycling approach. Its simple configuration and low energy-consumption property are quite suitable especially for isolated structures whose energy sources are strictly limited. The harmful influence of the external voltage is assessed, as well as its beneficial performance. We show a new chattering prevention approach that both harvests electrical energy from piezoelectric actuators and eliminates the displacement-offset of the equilibrium point of structures. The amount of energy consumption of the hybrid system is assessed qualitatively and is compared with other control systems. Experiments and numerical simulations conducted on a 10-bay truss can provide a thorough energy-efficiency evaluation of the hybrid suppression system having our energy-harvesting system.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.235-238
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• 2001

단일 단말기로부터 멀티 통신이 가능하게 됨에 따라 광대역 또는 듀얼대역에서 사용되는 RF 소자 개발이 중요시되고 있다. 그러므로 소형, 저 비용의 멀티대역 VCO(Voltage Controlled Oscillator)개발이 요구된다. 본 논문에서 GSM/DCN 대역에서 사용 가능한 듀얼밴드 VCO을 설계하였다. 하나의 발진부, 듀얼 공진부, 완충증폭기, 스위치회로로 구성되었으며, 위상 보정 기법을 이용하여 각 밴드에 대한 발진 조건을 만족시키므로 사용 부품의 수를 줄일 수 있어 저 비용, 소형화, 낮은 위상잡음(phase noise)을 얻을 수 있다. 설계된 듀얼 VCO는 GSM 대역에서 -110dBc/Hz(100kHz offset) 이하의 위상 잡음과 DCN 대역에서 -108dBc/Hz(100kHz offset)의 위상 특성을 보인다. 출력전력은 0$\pm$3dBm이며 소비전력 7mA로 만족할만한 성능을 보인다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.1
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• pp.27-32
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• 2017

This paper presents a Daubechies wavelet-based fault detection method for fault identification in transmission lines. After the Daubechies wavelet coefficients are calculated, the proposed algorithm has been implemented difference equation using C language. We have modeled a 154kV transmission line using the ATPDraw software and have acquired test data. In order to evaluate effects of DC offset, simulations carried out while varying an inception angle of the voltage $0^{\circ}$, $45^{\circ}$, $90^{\circ}$. For performance evaluation, fault distance was varied. As we can see from the off-line simulation, the proposed algorithm shows rapid and accurate fault detection. Also we can see the proposed algorithm is not affected by the fault inception angle change.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.492-492
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• 2014

On account of the good conductivity and optical properties, TCO is generally used in silicon heterojunction solar cell since the emitter material, hydrogenated amorphous silicon (a-Si:H), of the solar cell has low conductivity compare to the emitter of crystalline silicon solar cell. However, the work function mismatch between TCO layer and emitter leads to band-offset and interfere the injection of photo-generated carriers. In this study, work function engineering of TCO by oxygen reactive sputtering method was carried out to identify the trend of band-offset change. The open circuit voltage and short circuit current are noticeably changed by work function that effected from variation of oxygen ratio.

• Journal of information and communication convergence engineering
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• v.3 no.4
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• pp.184-186
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• 2005

The effect of power supply noise on the phase noise of a ring oscillator is studied. The power supply noise source in series with DC power supply voltage is applied to a 3 stage CMOS ring oscillator. The phase noise due to the power supply noise is modeled by the narrow band phase modulation. The model is verified by the fact that the spectrum of output of ring oscillator has two side bands at the frequencies offset from the frequency of the ring oscillator by the frequency of the power supply noise source. Simulations at several different frequency of the power supply noise reveals that the ring oscillator acts as a low pass filter to the power supply noise. This study, as a result, shows that the phase noise generated by the power supply noise is inversely proportional to the frequency offset from the carrier frequency.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.183-189
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• 2005

In precision instrumentation system, an A/D conversion of signal conditioning has some problems.; offset and drift errors with environmental situation. This paper suggested a development of the Multi-Channel A/D Data Acquisition System and a method of the evaluation and the temperature compensation for the A/D converters with the specific analog and digital circuit including the software. Also, we have designed a hardware and a software filters with smart algorithm for better signal processing of the proposed system. Software approach was adopted to obtain the stable data from A/D converter. As shown in our experimental works, the proposed system is expected to be used in the industrial field where a high precision measurement is required.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.35-38
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• 2010

A fully integrated parallel-coupled 6-GHz quadrature voltage-controlled oscillator (QVCO) has been designed. The symmetrical parallel-coupled quadrature VCO is implemented using 0.13-${\mu}m$ CMOS process. The measured phase noise is -101.05 dBc/Hz at an offset frequency of 1 MHz. The tuning range of 710 MHz is achieved with a control voltage ranging from 0.3 to 1.4 V. The average output phase error is about $1.26^{\circ}$ including cables and connectors. The QVCO dissipates 10 mA including buffer from the 1.5 V supply voltage. The output characteristic of the differential injection-locked frequency divider (DILFD), which has similar topology to the QVCO, is presented.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.685-692
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• 2011

DC/DC switching power converters produce DC output voltages from different DC input sources. The converters can be used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The current mode DC/DC converter is composed of a PWM (pulse width modulation) controller, a MOSFET, and inductor, etc. Pulse width modulation is applied to control and regulate the total output voltage. It is shown that the variation of threshold voltage at MOSFET and the offset voltage increase caused by radiation effects make the PWM pulse unstable. In the PWM operation, the missing pulses, the changes in pulse width, and a change in the period of the output waveform are studied by simulation program with integrated circuit emphasis (SPICE) and experiments.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.59-66
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• 2001

In this paper, a novel overmodulation strategy for PWM inverters to extend linearity region is presented. The proposed strategy uses the concept of space-vector PWM(SVPWM) based on the zero sequence signal(offset voltage) injection principle. So, by modifying the pole voltage simply, the linear control of inverter output voltage over the whole overmodulation range can be achieved easily. The proposed strategy is so simple that its practical implementation is easy. The validity of the proposed strategy is confirmed by the experimental results.