• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권2호
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• pp.116-122
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• 2004

A micromachined self-exited piezoelectric cantilever has been fabricated using PZT(52/48) thin film. For the application to biosensor using antigen-antibody interaction, electromechanical properties such as resonant frequency and quality factor of micromachined piezoelectric cantilever were important factors. Electromechanical properties and resonant behaviors of microfabricated cantilever were simulated by FEA (Finite Element Analysis) using Coventorware$^{TM}$2003. And these characterization of microcantilever were measured by using LDV(Laser Doppler Vibrometer) to compare with FEA data. We present the resonant frequency shift of micromachined piezoelectric cantilevers due to combination of mass loading and change of spring constant by gold deposition. Experimental mass sensitivities of microcantilever were characterized by Au deposition on the backside of microcantilever. Mass sensitivities with $100{\times}300$ ${\mu}{\textrm}{m}$ dimension cantilever from simulation and experimental were 5.56 Hz/ng and 16.8 Hz/ng respectively.y.

• 한국전기전자재료학회논문지
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• 제11권10호
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• pp.820-825
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• 1998

We deposited stearic acid LB films by using Langmuir-Blodgett (LB)method and investigated anisotropy electrical conduction characteristics by I-V measurement for horizontal direction and vertical direction. Also, we measured gad response between deposited LB films and organic gas for various temperature(0~8$0^{\circ}C$) by 9MHz At-cut quartz crystal microbalance. The LB films have electrical conduction characteristics such as semiconducting and insulating properties. The is, the conductivity of LB films for the horizontal and vertical direction is about 10\ulcornerS/cm and 10\ulcorners/cm, respectively. the frequency shift of stearic acid LB films for the organic gases depended on the mass change by the surface adsorption and the inner penetration to the sensing films. The resonant frequency shift of the quartz crystal microbalance for temperature properties of LB films is thought to the effect of the rearrangement or the damage pf LB films above the melting point and the mobility increasement of the organic gas by the temperature rising.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1134-1136
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• 2002

This paper proposes a FSK(Frequency Shift Keying) transmitter which has a inverter for power amplification instead of linear amplifier. As it can generate large signal using resonant circuit under the low voltage source even if the impedance of antenna is large as like a loop antenna of TWC(Train to Way-side Communication) system. In this paper, the proposed fully digital controlled transmitter including FSK modulation is presented and its control schemes are discussed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.27-30
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• 2003

This paper describes two novel current fed high frequency resonant inverter can be used as the power supp]y for wax-sealing. This two topology can be obtained higher output frequency than switching frequency by composing modified unit inverter based on conventional half-bridge serial resonant inverter in parallel with input power source. also, By using time-sharing gate control method, this proposed inverter can not only realize the output control of dependence irrespective of the switching frequency using phase-shift but also reduce switching loss because it has ZVS function. Simulation results through the Pspice have demonstrated the feasibility of the proposed inverter. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, DC-DC converter etc.

• Journal of Magnetics
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• 제20권4호
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• pp.347-352
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• 2015

The magnetoelectric (ME) characteristics for Terfenol-D/PZT laminate composite dependence on bias magnetic field is investigated. At low frequency, ME response is determined by the piezomagnetic coefficient $d_{33,m}$ and the elastic compliance $s_{33}^H$ of magnetostrictive material, $d_{33,m}$ and $s_{33}^H$ for Terfenol-D are inherently nonlinear and dependent on $H_{dc}$, leading to the influence of $H_{dc}$ on low-frequency ME voltage coefficient. At resonance, the mechanical quality factor $Q_m$ dependences on $H_{dc}$ results in the differences between the low-frequency and resonant ME voltage coefficient with $H_{dc}$. In terms of ${\Delta}E$ effect, the resonant frequency shift is derived with respect to the bias magnetic field. Considering the nonlinear effect of magnetostrictive material and $Q_m$ dependence on $H_{dc}$c, it predicts the low-frequency and resonant ME voltage coefficients as a function of the dc bias magnetic field. A good agreement between the theoretical results and experimental data is obtained and it is found that ME characteristics dependence on $H_{dc}$ are mainly influenced by the nonlinear effect of magnetostrictive material.

• 융합신호처리학회논문지
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• 제5권1호
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• pp.60-65
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• 2004

고주파 유도 가열 시스템에서 철과 같은 물체를 가열하게 되면, 가열된 금속이 큐리점 부근에서 전기적인 임피던스가 급격하게 변화하는 특징을 가지는 시변 시스템이 된다. 또한 부하 임피던스가 변화함에 따라 시스템의 부하 공진 주파수가 달라지므로 해서 시스템의 효율이 감소하는 문제점이 있었다. 그리고, 피가열 물체의 용융이나 삽입 상태에 따른 시스템의 단락 현상으로 인해 시스템이 파괴되는 문제점이 있었다. 본 논문에서는 이런 문제점을 해결하기 위한 방법으로 PLL에 의한 부하 공진 주파수를 추종하면서 스위칭 손실을 줄이고, 시변 부하에 대한 유도 가열시 큐리점 부근의 급격한 부하 임피던스 변화에도 안정된 정전력 제어가 가능할 뿐 아니라 대전력용에 적합하고, 단락현상으로부터 시스템을 보호하는 병렬 공진형 인버터 시스템에 적용되는 퍼지논리 제어기를 설계하였다.

• 조명전기설비학회논문지
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• 제17권1호
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• pp.94-102
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• 2003

본 논문은 고주파 전원에 사용되는 풀 브릿지 부하 병렬형 고주파 공진 인버터 회로를 연구대상으로 하고 출력제어기법으로는 펄스 주파수 변조(PFM, 펄스 폭 변조(PWM) 그리고 펄스 위상 변화(Phase-Shift)잎 경우를 비교 검토하였다. 회로의 해석은 정규화 파라메타를 도입하여 범용성 있게 기술하였고, 인버터 특성은 3가지 구동신호패턴에 의한 스위칭 주파수($\mu$), 펄스폭($\theta$d), Phase-Shift의 위상차각($\phi$)의 변화와 제 파라메타에 따라 특성 평가를 행하였다. 실험을 통해 이론해석의 타당성을 검증하였다. 향후, 3가지의 구동신호제어기법에 의한 특성들은 유도가열 응용, DC-DC 컨버터 등의 전원 시스템의 출력제어 시에 유용한 자료로 제공될 것으로 사료된다.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.145-152
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• 2004

Effects of various baffle designs on acoustic characteristics in combustion chamber are numerically investigated by adopting linear acoustic analysis. A hub-blade configuration with five blades is selected as a candidate baffle and five variants of baffles with various specifications are designed depending on baffle height and hub position. As damping parameters, natural-frequency shift and damping factor are considered and the damping capacity of various baffle designs is evaluated. Increase in baffle height results in more damping capacity and the hub position affects appreciably the damping of the first radial resonant mode. Depending on baffle height, two close resonant modes could be overlapped and thereby the damping factor for one resonant mode is increased exceedingly. The present procedure based on acoustic analysis is expected to be a useful tool to predict acoustic field in combustion chamber and to design the passive control devices such as baffle and acoustic resonator.

• ETRI Journal
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• 제46권4호
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• pp.727-736
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• 2024

Telecommunications through an electrically conductive medium require the use of carrier bands with very-low and ultralow frequencies to establish radiofrequency links in harsh environments. Recent advances in atomic magnetometers operating at very-low frequencies have facilitated the reception of digitally modulated signals. We demonstrate the transmission and reception of quadrature phase-shift keying (QPSK) signals using a multi-resonant loop antenna and atomic magnetometer, respectively. We report the measured error vector magnitude according to the symbol rate for QPSK modulation and analyze the bandwidth of a receiver based on the atomic magnetometer. The multi-resonant loop antenna noticeably enhances the bandwidth by over 70% compared with a single-loop antenna. QPSK modulation for a carrier frequency of 20 kHz and symbol rate of 150 symbols per second verifies the feasibility of demodulation, and the measured error vector magnitude and signal-to-noise ratio are 7.29% and 30.9 dB, respectively.

• 한국정보통신학회논문지
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• 제2권2호
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• pp.223-230
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• 1998

본 논문은 뉴랄퍼지를 이용한 디지탈식 제어기를 고주파 유도 가열기의 전력 조절을 위해 IGBT를 사용한 위상 전이(Phase-Shift) 펄스폭 변조(PWM)와 펄스 주파수 변조(PFM)가 조절되는 공진 고주파 인버터를 응용한 유도가열기를 설명한다. 이는 실제로 산업 현장에서 20KHz~500KHz 유도 가열 및 유도 용해 전원 장치용으로 쓰인다. 위상 전이(Phase-Shift) PWM 정전력 조절 기술을 바탕으로 한 적응 주파수 추종 기법은 스위칭 손실을 최소화하고 전력조절을 용이하게 하기 위해 소개되어졌다. IGBT를 사용하여 실험적으로 만들어진 실험장치는 성공적으로 논증과 토의가 되어졌다.