• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1665-1666
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• 2008

There are three main devices such as boiler producing steam, turbine driving generator and generator producing electricity. An electrical generator in power plant is driven and maintained its speed at rated by steam turbine which is coupled into generator directly. Therefore after the steam turbine reaches its rated speed and the generator gets into parallel operation with power grid, the electrical power can be increased by turbine controller or governor. The first governor was invented by James Watts for the steam engine to be maintained at a constant speed. The first governor by him was mechanical type with fly balls. The electrical type governor was created due to the progress of electronic devices such as operational amplifiers or integrated circuits. and Today digital electronic type of governor is being widely used in most prime movers.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.298-303
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• 2004

The active magnetic bearing system for a TMP consists of four couples of magnets, five gap sensors with its amplifiers and a digital PID controller. For stabilizing and providing damping, digital PID controller is applied for each control axes and the inter-axis cross feedback controller is also applied to suppress low frequency vibration caused by gyroscopic moment of the rotor. Therefore in this paper, a digital controller of magnetic bearing for a TMP is design and examined.

• 한국멀티미디어학회논문지
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• 제20권9호
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• pp.1551-1558
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• 2017

Audio power amplifiers have been designed based on the premise that the impedance of loudspeakers is fixed at nominal 4 ohms or 8 ohms. However, it is known that the impedance varies with frequency and takes on the nominal value at some limited frequencies. The principle of the loudspeaker operation reveals that the sound pressure produced by the loudspeaker is proportional to the current flowing in the voice coil, not the voltage between the two terminals. We take the characteristics of the loudspeaker into account and compare the frequency responses of the loudspeaker in voltage-drive mode and current-drive mode via computer simulations, to conclude that the audio amplifier drive mode should be re-considered in an effort to improve the sound quality.

• 한국멀티미디어학회논문지
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• 제21권9호
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• pp.1110-1118
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• 2018

Personal sound amplifiers(PSAPs) provide accessible and affordable healthcare to individuals with hearing disability. Many studies are in progress for affordable PSAP development, but still people do not have a best fitting profile for the PSAP depending on their hearing test. As a result, they do not have a personalized and profiled music and sound, which are very helpful for those who has hearing problems. In this paper, we propose a device and mobile system to provide music with an equalizer value according to the hearing condition of an individual to prevent the hearing loss. In order to overcome the limit of frequency band of the equalizer in a smart phone, we developed bluetooth controlled equalizer based on the fitting profiles.

• 한국정보통신학회논문지
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• 제9권5호
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• pp.1089-1095
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• 2005

본 논문에서는 5GHz 저잡음 증폭기(LNA)의 성능 측정을 위한 새로운 형태의 저가 BIST(Built-In Self-Test) 회로를 제안한다 이러한 BIST 회로는 system-on-chip (SoC) 송수신 환경에 적용될 수 있도록 설계되어 있다. 본 논문에서 제안하는 BIST 회로는 입력 임피던스, 전압이득, 잡음지수, 입력반사손실(input return loss) 및 출력 신호 대 잡음전력비(signal-to-noise ratio)와 같은 저잡음 증폭기의 주요 성능 지수를 측정 할 수 있으며, 단일 칩 위에 제작되어 있다.

• 한국항해학회지
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• 제20권3호
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• pp.117-126
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• 1996

Generally, the distortion of the negative feedback amplifier is reduced by a factor equal to the return difference (1+${\beta}_1A_1$), but the proposed feedforward amplifier is reduced by a factor equal to the square of the return difference (1+${\beta}_1A_1$). In this paper, a feedforward amplifier with error correction is designed and implemented. So as to evaluate the characteristics of the harmonic distortion that the inverting feedforward amplifier is compared with that of the reference amplifier without feedforward error correction. It is confirmed that the proposed method should be able to reduce much greater than compared with a conventional negative feedback amplifier. Therefore it should be noted that the proposed feedforward amplifier network is also acceptable for wide-band amplifiers and the network which is demanded to improve the harmonic distortion.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.596-600
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• 2009

We are developing a simple low-cost wind velocity sensor based on small microphones. The sensor system consists of 4 microphones covered with specially shaped wind screens, 4 pre-amplifiers that respond to low frequency, and a commercial sound interface with multi channel inputs. In this paper, we first present the principle of the sensor, i.e., technique to successfully suppress the influence of external noise existing in the environment in order to determine the wind velocity and the wind direction from the output from a microphone. Then, we present an application for generating realistic motions of a virtual tree swaying in real wind. Although the current sensor outputs significant leaps in a measured sequence of directions, the interactive animations demonstrate that it is usable for such applications, if we could reduce the leaps to some degree.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.569-574
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• 1998

This paper presents a two-paralleled 4 quadrant DC chopper type PWM power conversion circuit in order to generate a gradient magnetic field in the Magnetic Resonance Imaging (MRI) system. This power amplifier is connected in parallel with the conventional 4-quadrant DC chopper using IGBTs at their inputs/outputs to realize further high-power density, high speed current tracking control, and to get a low switching ripple amplitude in a controlled current in the Gradient Coils (GCs). Moreover, the power conversion circuit has to realize quick rise/fall response characteristics in proportion to various target currents in GCs. It is proposed in this paper that a unique control scheme can achieve the above objective. DSP-based control systems realize a high control facility and accuracy. It is proved that the new control system will greatly enlarge the diagnostic target and improve the image quality of MRI.

• 한국통신학회논문지
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• 제12권6호
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• pp.554-562
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• 1987

본 논문에서는 발진주파수 대역을 확장하기 위하여 3개의 연산증폭기로 구성된 RC 형 Wien-Bridge 발진기를 제시하였으며, 이 발진기를 LSI화 할 수 있도록 Forward Z변환법에 의하여 새로운 SC형 발진기로 실현하였다. 실현된 SC형 발진기는 Reddy, Budak과 Nay 가 제시한 발진기보다 주파수대역이 확장되었음을 발진주파수 함수 f의 근궤적 해석 방법을 이용하여 확인하였으며, 또한 발진조건에 충분히 만족됨을 개방 루프 측정에 의하여 확인하였다.

• 한국산학기술학회논문지
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• 제13권1호
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• pp.311-316
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• 2012

본 논문에서는 공학적 응용을 위한 로렌츠 카오스 시스템을 연산증폭기, 곱셈기 등을 이용하여 전자회로로 설계하였다. 시간파형, 위상특성 등 여러 가지 카오스 동적특성 등을 PSPICE 모의실험을 통하여 파악하였다. 저항값의 변화를 통하여 카오스 특성을 얻기 위한 최적화 된 회로 파라미터를 구하였으며, 각 저항값의 변화에 따른 시간파형 특성 및 위상 특성을 구하였다.