• E2M - 전기 전자와 첨단 소재
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• 제7권6호
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• pp.490-495
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• 1994

We investigated photoreflectance of semi-insulating GaAs with respect to modulation sources, that is, modulation beam intensity, modulation frequency, temperature, and thickness of sample. PR spectra by each modulation source turned out to be signals of low electric field third differential, and band gap values of sample were fitted by least square root method for Aspnes' theoretical equation.

• 한국음향학회지
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• 제25권8호
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• pp.370-374
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• 2006

음성인식의 특징벡터로서 멜-주파수 켑스트럴 계수 (MFCC, mel-frequency cepstral coefficients)가 가장 널리 사용되고 있다. FMCC 추출과정은 입력되는 음성신호를 푸리에 변환한 후, 주파수 대역별로 필터를 취하여 에너지 값을 구하고 이산 코사인 변환을 하여 그 계수 값을 구한다. 본 논문에서는 멜-스케일 된 주파수 대역필터를 취할 때 가중함수에 의해서 구해진 각 대역필터별 가중치를 적용하여 필터의 출력 에너지를 계산한다. 여기서 가중치를 구하기 위해 사용된 가중함수는 포만트가 존재하는 대역을 중심으로 인접한 대역들이 가우시안 분포를 가지는 함수이다. 제안한 방법으로 실험한 결과, 잡음이 거의 없는 음성신호에 대해서는 기존의 MFCC를 사용했을 때와 비슷한 인식률을 보이고 잡음성분이 많을수록 가중치가 적용된 방법이 인식률에서 보다 높은 성능 향상을 가져온다.

• 대한전기학회논문지
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• 제43권2호
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• pp.339-345
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• 1994

A new filter-bank is proposed in order to track center frequency of narrow band signal. The two banks are connected in series-parallel. The master filter bank which is made of traditional filter bank detects the center frequency roughly. And the performance for tracking center frequency is greatly improved by the slave filter bank which is based on energy-difference estimator. Computer simulations show that it achieves a good tracking accuracy.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.463-469
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• 2016

In this paper, the use of a dual composite right/left-handed coplanar waveguide (CPW) transmission line is proposed for the design of a band rejection filter. The notch property of the filter is achieved by combining the convex signal line with the shorted concave meander line, and the equivalent circuit model is extracted from the geometry of the unit cell for organizing the band rejection property. Then the equivalent parameters of the unit cell are analyzed to identify those behaviors. And the dispersion characteristics and energy distributions are simulated. In the end, the band rejection filter is manufactured by cascading two proposed unit cells. We show that the measurement result for the resonant frequency demonstrates good agreement with the simulation result and the band rejection filter provides a rejection performance of 17.5 dB at the stopband frequency ranging from 869 MHz to 894 MHz.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3122-3125
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• 2021

Electromagnetic vortex flowmeter is a new type of instrument for detecting leakage of steam generator, and the signal processing method based on the envelope to calculate energy ratio can effectively detect bubbles in sodium flow. The signal processing method is not affected by changes in the amplitude of the sensor output signal, which is caused by changes in magnetic field strength and other factors. However, the detection sensitivity of the electromagnetic vortex flowmeter is reduced. To this end, a signal processing method based on inverse Fourier transform to calculate energy ratio is proposed. According to the difference between the frequency band of the bubble noise signal and the flow signal, only the amplitude in the frequency band of the flow signal is retained in the frequency domain, and then the flow signal is obtained by the inverse Fourier transform method, thereby calculating the energy ratio. Using this method to process the experimental data, the results show that it can detect 0.1 g/s leak rate of water in the steam generator, and its performance is significantly better than that of the signal processing method based on the envelope to calculate energy ratio.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.939-951
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• 2019

A novel empirical mode decomposition strategy based on Fourier transform and band-pass filter techniques, contributing to efficient instantaneous vibration analyses, is developed in this study. Two key improvements are proposed. The first is associated with the adoption of a band-pass filter technique for intrinsic mode function sifting. The primary characteristic of decomposed components is that their bandwidths do not overlap in the frequency domain. The second improvement concerns an attempt to design narrowband constraints as the essential requirements for intrinsic mode function to make it physically meaningful. Because all decomposed components are generated with respect to their intrinsic narrow bandwidth and strict sifting from high to low frequencies successively, they are orthogonal to each other and are thus suitable for an instantaneous frequency analysis. The direct Hilbert spectrum is employed to illustrate the instantaneous time-frequency-energy distribution. Commendable agreement between the illustrations of the proposed direct Hilbert spectrum and the traditional Fourier spectrum was observed. This method provides robust identifications of vibration modes embedded in vibration processes, deemed to be an efficient means to obtain valuable instantaneous information.

• 한국전자통신학회논문지
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• 제14권5호
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• pp.877-886
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• 2019

본 연구에서는 band anticrossing 모델을 사용하여 온도와 조성비 변화에 따른 4원계 질화물계 화합물 반도체 $In_yGa_{1-y}As_{1-x}N_x$의 에너지 밴드갭과 광학상수를 계산하였다. 300K의 조성비 구간($0{\leq}x{\leq}0.05$, $0{\leq}y{\leq}1.0$)에서 에너지 밴드갭들이 연속적으로 감소하며, 계산된 휨 매개변수는 0.522eV가 사용되었다. 에너지 밴드갭 계산 결과는 다른 연구 결과와 대체로 잘 일치하였다. 또한 에너지 밴드갭 결과를 새롭게 제안한 모델식에 적용하여 굴절률 n과 고주파 유전상수 ${\varepsilon}$를 계산하였다.

• 전자공학회논문지
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• 제54권1호
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• pp.157-163
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• 2017

본 논문은 주파수대역검출센서(FBDS)를 이용하여 전력 케이블에서 부분방전(PD)가 발생했을 때 이것을 검출하고 진단하는 시스템 개발에 관한 논문이다. 주파수대역검출센서는 각 주파수대역에서 발생하는 부분방전을 음향학적으로 변환하여 검출한다. 부분방전은 그 음향학적 신호 형태로 잡음과 유사하다. 따라서 본 논문에서 상대적 레벨교차율(RLCR)과 주파수에너지 스펙트럼을 이용하여 정상과 비정상을 구별하여 부분방전을 검출하였다.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.55-64
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• 2007

In the built-up structure consisting of a stiff beam and a flexible plate, Grice showed that the plate behaves as an energy absorber in narrow frequency bands(called plate blocking effect). This paper deals with such beam-plate coupled structures, where the plate is an energy absorber and the excited beam is an energy path. It is found that such energy dissipation can occur in the relatively broad bands, if different stiffnesses are used in the rectangular plate. It was experimentally verified by Heckl that the energies in terms of one-third octave band averages transferred to the plate(or dissipated in the plate) increase for increased plate damping. This Paper, however, shows that the energy absorption suddenly reduces at the certain narrow frequency bands where the plate damping effect upon the coupled beam is maximum. Also, in order to minimize energy transfer through the beam in terms of one-third octave band averages, it is advantageous to increase the plate damping closer to the excitation point All these results are based on the wane method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1857-1861
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• 2003

This paper proposes a method for controlling energy distribution to 1 phase induction heating coil by using the Binary Rate Modulation (BRM) Technique. Such method provides proper frequency to the heating coil's requirement by control the frequency at the resonance point, that is, 64-kHZ frequency band. System design are classified to 2 parts. The first part determines main frequency , and the second part generates the frequency from the 8-bit BRM derived from IC no. PAL22V10 in order to control the frequency for Full-bridge connected inverter when supplying the energy required by the 1 phase induction heating coil. Therefore, efficiency of the energy supply can be increate.