• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.93-99
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• 2002

The Cartesian loop chip which is one of key devices in narrow-band Walky-Talky transmitter using RZ-SSB modulation method was designed and implemented with 0.35 Um CMOS technology. The reduced size and low cost of transmitter were available by the use of direct-conversion and Cartesian loop chip, which improved the power efficiency and linearity of transmitting path. In addition, low power operation was possible through CMOS technology. The performance test results of transmitter showed -23 dBc improvement of IMD level and -30 dEc below suppression of SSB characteristic in the operation of Cartesian loop chip (closed-loop). At that time, the transmitting power was about 37 dBm (5 W). The main parameters to improve the transmitting characteristic and to compensate the distortion in feed back loop such as DC-offset, loop gain and phase value are interfaced with notebook PC to be controlled with S/W.

• Proceedings of the KIEE Conference
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• 2001.07e
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• pp.95-99
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• 2001

In this paper, a drive system for multi-phase bipolar brushless DC (MPB BLDC) motor is presented. This drive system is used for an electric bicycle. In general, the maximum and minimum speed of electric bicycle are required by law. At first, the proposed controller is satisfied for the limited speed control. Secondly, the system has a technique of exited with modulation(EWM), bidirection control, and partial square wave control. Thirdly, the controller is designed for system stability Experimental results show the performance of the proposed controller of MPB BLDC motors for an electric bicycle.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2030-2032
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• 1998

It is always necessary to high performance power supplies for the magnet system in the accelerator, especially when the number of power supplies are large. When have developed the compact power supply using switching technology instead of SCR phase control. We adopt the pulse width modulation(PWM) method with a half bridge DC/DC converter. In this way, we can make a compact system with light weight and small volume. Actual system we developed is 1.2kW, 35V/35A bipolar DC power supply current precision of +/-0.02%. It is possible to mount 10 unit in a conventional 19 rack. The built in controller has an RS422 protocol to drive 10 unit by one serial port up to 1.2km distance. If we adopt RS485 protocol, one serial port can control 32 power supplies. In this paper, we will report the design and performance of the prototype power supply.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.635-636
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• 2006

A pulse with modulation(PWM) that keeps a constant angle of dwell and adjust duty ratio is a good method to control a speed of SRM. And a method of one pulse control is proper a operation on range of high speed in SRM for a good energy efficiency. Because PWM method is more safety than one pulse method, conversion of those is best choice according the speed range. So, some algorithm is need for smooth conversion of the mode of control. This paper presents a factor of conversion that proper the conversion of control mode between PWM and one pulse method This factor is from estimation of torque and proper at the variable range of conversion and show the better conversion characteristic than constant factor of conversion.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.1
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• pp.137-142
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• 1990

A theory for the synthesis of a SDF including the filter modulation is suggested. In the filter synthesis, the iteration equation was used to iterate trial solution vectors. A computer simulation of the fSDF method using threshold binary images of the flight objects over a range of aspect angles was performed for POF and BPOF. The constructed fSDF filters are capable of obtaining the specified peak correlation response within a 1.7%-4.0% error range, after several iterations. However, the conventional pSDF/POFs, BPOFs are not. The results indicate POFs and BPOs can be made to perform well for distortion invariant optical pattern recognition using the fSDF method.

• Proceedings of the KIPE Conference
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• 2004.11a
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• pp.64-69
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• 2004

This paper deals with an algorithm for controlling ac output voltage of Z-source inverter using Modified SVPWM (abbreviated as MSVPWM). Unlike the conventional space vector pulse width modulation, MSVPWM has one extra shoot-through zero time $T_{sh}$. During shoot-through zero time, both switches in a leg are conducted simultaneously in order to boost inverter output voltage to any desirable value regardless the line voltage. The algorithm to control linearly the capacitor voltage is suggested to improve the performance of Z-source inverter system. The performance of Z-source inverter using above algorithms is demonstrated in simulation results using PSIM. Index terms-Z-source inverter (ZSI), shoot-through time, three-phase carrier-based PWM, space vector PWM (SVPWM), modified space vector PWM (MSVPWM).

• Structural Engineering and Mechanics
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• v.55 no.2
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• pp.281-298
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• 2015

In this study, nonlinear transverse vibrations of tensioned Euler-Bernoulli nanobeams are studied. The nonlinear equations of motion including stretching of the neutral axis and axial tension are derived using nonlocal beam theory. Forcing and damping effects are included in the equations. Equation of motion is made dimensionless via dimensionless parameters. A perturbation technique, the multiple scale methods is employed for solving the nonlinear problem. Approximate solutions are applied for the equations of motion. Natural frequencies of the nanobeams for the linear problem are found from the first equation of the perturbation series. From nonlinear term of the perturbation series appear as corrections to the linear problem. The effects of the various axial tension parameters and different nonlocal parameters as well as effects of different boundary conditions on the vibrations are determined. Nonlinear frequencies are estimated; amplitude-phase modulation figures are presented for simple-simple and clamped-clamped cases.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.228-229
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• 2003

The quasi-phase matching (QPM) technique has dramatically changed the guidelines in developing nonlinear optical materials, which doesn't require birefringence and off-diagonal components for efficient wavelength conversion. Minimum requirement for QPM is the modulation of nonlinearity and ferroelectric materials with low coercive field has become fascinating in periodical poling. Stoichiometric lithium tantalate (SLT) has attractive advantages of low coercive field (∼l .5 KV/mm), high nonlinearity, high optical damage resistance and low thermo-optic coefficients, leading to a large aperture QPM devices for high power operation. (omitted)

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.154-155
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• 2003

반도체 소자에 있어서 굴절율의 변화는 중요한 역할을 한다. 굴절율을 변화시키는 다양한 요소들은, 전계에 의한 1차 전기광학(linear electro-optic： LEO) 효과와 2차 전기광학 (quadratic electro-optic： QEO) 효과, 자유 운반자에 의한 밴드천이(band-gap shift： BS) 효과와 플라즈마(plasma： PL) 효과 등으로 잘 알려져 있다. 본 논문에서는, 오로지 TE 모드에 대해서만 선택적으로 위상 변화를 주는 P-I-i-I-N GaAs／Al／sub0.35／Ga／sub 0.65／As 도파로 위상변조기를 보고한다. (중략)

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.284-285
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• 2018

최근 전력품질 향상을 위해 계통전류에 대한 THD 규제가 강화되고 있음에 따라 THD와 누설전류의 개선 문제가 대두되고 있다. 단상 계통연계형 ESS에서는 흔히 인버터와 DC-DC컨버터를 사용하여 배터리를 충 방전 하는데, 이때 단상 인버터의 대지누설전류 또한 개선이 필요하다. 단상 인버터의 누설전류는 모듈레이션 방식을 변경함에 따라 차이가 나타난다. 따라서 본 논문에서는 단상 풀-브릿지 인버터의 유니폴라(Unipolar) 모듈레이션과 바이폴라(Bipolar) 모듈레이션 방버에 따른 누설전류의 크기를 PSIM을 통한 시뮬레이션과 실험을 통하여 비교 분석하였다.