• 한국자동차공학회논문집
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• 제7권9호
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• pp.97-104
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• 1999

Brake squeal noise has been a problem since the early days of motoring . It is important to obtain vibration mode shape for reduction of brake noise . Stroboscopic Electronic Speckle Pattern Interferometry is a very powerful measuring method for study of vibrating objects in static state compared with conventional methods because this method can give both resonance frequency and quantitative visualization of vibration mode shape at the same time. In this paper, we performed qualitative visualization and quantitative analysis of vibration mode shpae of disk brake by using stroboscopic ESPI and phase shifting method. The stroboscopic wavefronts are obtained by chopping continuous wave laser beam using acousto-optic modulator .Experiments were performed at the same constraint conditions as disk brake of the practical vehicle as far as possible. The experimental results of this paper show quantitative measurement of vibration mode shape and quantiative visualization of vibration amplitude of disk brake with 3D plotting.

• 대한음성학회지:말소리
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• 제45호
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• pp.63-77
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• 2003

The purpose of voice color conversion is to change the speaker identity perceived from the speech signal. In this paper, we propose a new voice color conversion algorithm through the formant shifting and the spectrum-tilt modification in the frequency domain. The basic idea of this technique is to convert the positions of source formants into those of target speaker's formants through interpolation and decimation and to modify the spectrum-tilt by utilizing the information of both speakers' spectrum envelops. The LPC spectrum is adopted to evaluate the position of formant and the information of spectrum-tilt. Our algorithm enables us to convert the speaker identity rather successfully while maintaining good speech quality, since it modifies speech waveforms directly in the frequency domain.

• 한국작물학회:학술대회논문집
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• 한국작물학회 1997년도 춘계 학술대회지
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• pp.106-107
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• 1997

• 전자공학회논문지
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• 제54권5호
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• pp.74-84
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• 2017

휴대용 지뢰 탐지기의 특성상 병사가 직접 손에 들고 운용하기 때문에 빠르고 정확하게 표적 탐지를 수행하는 시스템을 개발해야한다. 그러나 우리나라의 군에서 사용하고 있는 휴대용 지뢰 탐지기는 금속 성분의 지뢰만 탐지가 가능하다는 문제점이 있다. 이러한 문제를 해결하고, 우리나라 환경에 알맞은 휴대용 지뢰 탐지 시스템을 개발하는 것이 중요하다. 본 논문에서는 지면 투과 레이더를 이용하여 지뢰를 탐지 하고, 우리나라 환경에 알맞은 휴대용 지뢰 탐지 시스템을 제안한다. 제안하는 시스템은 전처리 단계로 깊이 보상, 정합 필터링, 주파수 이동 필터링을 이용하고, 탐지 단계에서 에지 비율을 통해 최종적으로 표적을 탐지한다. 제안하는 시스템의 성능을 검증하기 위하여 우리나라 토양의 대부분을 차지하는 사양토를 이용하였고, 탐지해야하는 지뢰를 매설한 후 휴대용 지뢰 탐지기를 이용하여 데이터를 획득하였다. 획득한 데이터를 기반으로 패치의 크기 및 위치와 이동 주파수에 대한 실험을 진행하여 최적의 성능을 나타내는 값을 찾아내고, 해당 값을 이용하여 탐지 성능을 확인하였다. 실험 결과, 제안하는 전처리 알고리즘이 낮은 오경보율에서 모든 지뢰를 탐지하는 우수한 성능을 나타내는 것을 확인하였고, 기존 연구와의 비교를 통해 제안하는 시스템의 성능이 우수함을 확인하였다.

• 한국자동차공학회논문집
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• 제4권6호
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• pp.223-228
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• 1996

The frequency of the brake squeal noise can be changed during braking, and this frequency shifting is due to variation of braking deceleration rate. The natural frequency of the brake system also shifted according to deceleration rate. It makes difficult to treat this problem. This paper shows an experimental study on the brake squeal noise having main frequencies of about 450~500Hz. And it shows how to improve the brake squeal noise problem.

• 산업기술연구
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• 제14권
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• pp.3-17
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• 1994

This paper develops a design technique for approximating nonseparable frequency characteristics by sums and products of separable transfer functions. Therefore nonseparable frequency characteristics includes the four-quadrant symmetry filters. The desired filter with half plan symmetry is obtained by shifting a low pass characteristic in the frequency domain, and by combining these shifted characteristics. Also the paper develops the technique for designing recursive and nonrecursive two dimensional digital filters by the application of a complex transformation to one dimensional low pass filter.

• 한국해양공학회지
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• 제24권1호
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• pp.166-171
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• 2010

In this paper, the front-end of a digital receiver with a 25 kHz carrier frequency, 5 kHz symbol rate, and any excess-bandwidth is designed using two basic facts. The first is known as the uniform sampling theorem, which states that the sampled sequence might not suffer from aliasing even if its sampling rate is lower than the Nyquist sampling rate if the analog signal is a bandpass one. The other fact is that if the sampling rate is 4 times the center frequency of the sampled sequence, the front-end processing complexity can be dramatically reduced due to the half of the sampled sequence to be multiplied by zero in the demixing process. Furthermore, the designed front-end is simplified by introducing sub-filters and sub-sampling sequences. The designed front-end is composed of an A/D converter, which takes samples of a bandpass filtered signal at a 20 kHz rate; a serial-to-parallel converter, which converts a sampled bandpass sequence to 4 parallel sub-sample sequences; 4 sub-filter blocks, which act as a frequency shifter and lowpass filter for a complex sequence; 4 synchronized switches; and 2 adders. The designed front-end dramatically reduces the computational complexity by more than 50% for frequency shifting and lowpass filtering operations since a conventional front-end requires a frequency shifting and two lowpass filtering operations to get one lowpass complex sample, while the proposed front-end requires only four filtering operation to get four lowpass complex samples, which is equivalent to one filtering operation for one sample.

• 한국정밀공학회지
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• 제24권11호
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• pp.15-21
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• 2007

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.313-314
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• 2008

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.34-36
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• 1990

The flow direction in a glass tube is measured by using a forward scatering dual beam laser Doppler velocimeter with an acousto-optic modulator. We can determine the flow direction by measuring the shifted Doppler frequency which is dependent on the order of modulation of the laser frequency shifting moves only the Doppler signal, enabling complete separation of the Pedestal and Doppler singal.