• 한국소음진동공학회논문집
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• 제25권11호
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• pp.739-746
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• 2015

Several damage counting methods can be applied for the fatigue issues of a ground vehicle system using strain data and acceleration data is partially used for a high cyclic loading case. For a vibration test, acceleration data is, however, more useful than strain one owing to the good nature of signal-to-random ratio at acceleration response. The test severity can be judged by the fatigue damage and the pseudo-damage from the acceleration response stated in ISO-16750-3 is one of sound solutions for the vibration test. The comparison of fatigue damages, derived from both acceleration and strain, are analyzed in this study to determine the best choice of fatigue damage over multi-spectral input pattern. Uniaxial excitation test was conducted for a notched simple specimen and response data, both acceleration and strain, are used for the comparison of fatigue damages.

• The Journal of the Acoustical Society of Korea
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• 제23권2E호
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• pp.56-67
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• 2004

Despite abundant research outcomes of blind source separation (BSS) in many types of simulated environments, their performances are still not satisfactory to be applied to the real environments. The major obstacle may seem the finite filter length of the assumed mixing model and the nonlinear sensor noises. This paper presents a two-step speech enhancement method with multiple microphone inputs. The first step performs a frequency-domain BSS algorithm to produce multiple outputs without any prior knowledge of the mixed source signals. The second step further removes the remaining cross-channel interference by a spectral cancellation approach using a probabilistic source absence/presence detection technique. The desired primary source is detected every frame of the signal, and the secondary source is estimated in the power spectral domain using the other BSS output as a reference interfering source. Then the estimated secondary source is subtracted to reduce the cross-channel interference. Our experimental results show good separation enhancement performances on the real recordings of speech and music signals compared to the conventional BSS methods.

• 한국음향학회지
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• 제16권5호
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• pp.68-75
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• 1997

스펙트럼 차감법은 잡음이 더해진 환경에서의 음성인시기에 널리 사용되는 전처리 방법이지만, 이를 위해서는 잡음의 스펙트럼을 잘 추정할 필요가 있다. 본 논문에서는 잡음 스펙트럼의 추정방법으로 히스토그램 처리방법을 사용한다. 이 방법은 음성/비음성 구간의 구분을 할 필요가 없으며 서서히 변화하는 잡음의 스펙트럼도 추정할 수 있다는 점에서 여타의 잡음 추정방법에 비해 장점을 지닌다. 다양한 SNR 조건하에서 유색 가우시안 잡음 및 실제 자동차 소음을 부가시킨 음성에 대해 화자독립 고립단어 인식 실험을 수행한 결과, 히스토그램 처리방법에 기반을 둔 스펙트럼 차감법의 인식성능이 초기 비음성구간의 스펙트럼 평균을 이용한 기존의 잡음 스펙트럼 추정방법에 비해 우수한 성능을 나타내었다.

• Wind and Structures
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• 제29권6호
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• pp.389-403
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• 2019

In this study, two original spectral representations of stationary stochastic fields, say the continuous proper orthogonal decomposition (CPOD) and the frequency-wavenumber spectral representation (FWSR), are derived from the Fourier-Stieltjes integral at first. Meanwhile, the relations between the above two representations are discussed detailedly. However, the most widely used conventional Monte Carlo schemes associated with the two representations still leave two difficulties unsolved, say the high dimension of random variables and the incompleteness of probability with respect to the generated sample functions of the stochastic fields. In view of this, a dimension-reduction model involving merely one elementary random variable with the representative points set owing assigned probabilities is proposed, realizing the refined description of probability characteristics for the stochastic fields by generating just several hundred representative samples with assigned probabilities. In addition, for the purpose of overcoming the defects of simulation efficiency and accuracy in the FWSR, an improved scheme of non-uniform wavenumber intervals is suggested. Finally, the Fast Fourier Transform (FFT) algorithm is adopted to further enhance the simulation efficiency of the horizontal stochastic wind velocity fields. Numerical examplesfully reveal the validity and superiorityof the proposed methods.

• Journal of Biosystems Engineering
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• 제35권2호
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• pp.132-137
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• 2010

Site-specific N application for corn is one of the precision crop management. To implement the site-specific N application, various nitrogen stress sensing methods, including aerial image, tissue analysis, soil sampling analysis, and SPAD meter readings, have been used. Use of side-dressing, an efficient nitrogen application method than a uniform application in either late fall or early spring, relies mainly on the capability of nitrogen deficiency detection. This paper presents map-based variable rate nitrogen application based using a multi-spectral corn nitrogen deficiency(CND) sensor. This sensor assess the nitrogen stress by means of the estimated SPAD reading calculated from the corn leave reflectance. The estimated SPAD value from the CND sensor system and location information form DGPS of each field block was combined into the field map using a ArcView program. Then this map was converted into a raster file for a map-based variable rate application software. The relative SPAD (RSPAD = SPAD over reference SPAD) was investigated 2 weeks after the treatments. The results showed that the map-based variable rate application system was feasible.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 춘계학술발표회 논문집
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• pp.171-180
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• 2003

The merging of different scales or multi-sensor image data is becoming a widely used procedure of the complementary nature of various data sets. Ideally, the merging method should not distort the characteristics of the high-spatial and high-spectral resolution data used. To present an effective merging method for survey of reclaimed land, this paper compares the results of Intensity Hue Saturation (IHS), Principal Component Analysis (PCA), Color Normalized(CN) and High Pass Filter(HPF) methods used to merge the information contents of the high-resolution (6.6 m) Electro-Optical Camera (EOC) panchromatic image of the first Korea Multi-Purpose Satellite 1 (KOMPSAT-1) and the multi-spectral Moderate Resolution Imaging Spectroradiometer (MODIS) image data. The comparison is made by visual evaluation of three-color combination images of IHS, PCA, CN and HPF results based on spatial and spectral characteristics. The use of a contrasted EOC panchromatic image as a substitute for intensity in merged images with MODIS bands 1, 2 and 3 was found to be particularly effective in this study.

• 한국측량학회지
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• 제29권6호
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• pp.577-582
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• 2011

원격탐사에서 분광 및 공간정보가 왜곡되는 현상들은 영상융합 알고리즘의 가장 큰 문제점으로 알려져 있다. 특히, Worldview-2 위성영상은 멀티스펙트럴 밴드 간 공간정보의 지역적인 비유사성이 존재하기 때문에, 기존의 융합 기법에 의한 융합영상들은 건물이나 차량 등의 개체 등의 공간정보가 왜곡되는 문제를 지닌다. 본 연구에서는 Worldview-2 위성영상의 융합과정에서 발생하는 공간정보의 지역적 변위를 최소화하기 위한 융합 기법을 제안하였다. Worldview-2 위성영상에 제안된 기법을 적용한 결과, 기존의 영상 융합기법에 비하여 분광 정보 및 공간정보의 품질이 향상된 융합영상을 생성할 수 있음을 확인하였다.

• 한국정보통신학회논문지
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• 제14권4호
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• pp.959-966
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• 2010

정량적 초음파 분석(Quantitative Ultrasound Analysis)은 반향된 초음파 신호의 짧은 시간 간격의 주파수 성분을 추출하여 개별 초음파 지수의 값을 예측한다. 따라서 반향 신호의 정확한 주파수 특성 추출은 분석의 정확도와 정밀도 향상에 기본이 된다. 본 논문에서는 초음파 지수의 정량적인 예측 및 분석에 이용할 수 있는, 짧은 시간 간격의 반향 신호의 주파수 특성 추출 방법을 제안한다. 제안된 알고리듬은 인접한 반향 초음파 신호간의 위상 차이를 보상하고, 동일 반향 깊이를 가지는 작은 영역의 신호를 가중치 평균함으로써 보다 정확한 주파수 특성을 추출한다. 컴퓨터 모의 실험을 통한 수치 분석 결과, 제안된 알고리듬은 일반적인 주파수 추출 알고리듬보다 정확한 예측 결과를 보였으며, 예측 결과의 정밀도도 10% 이상 향상되었다.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.288-294
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• 2013

The diagnosis of motor failures using an on-line method has been the aim of many researchers and studies. Several spectral analysis techniques have been developed and are used to facilitate on-line diagnosis methods in industry. This paper discusses the first application of a motor flux spectral analysis to the identification of broken rotor bar (BRB) faults in induction motors using a multiple signal classification (MUSIC) technique as an on-line diagnosis method. The proposed method measures the leakage flux in the radial direction using a radial flux sensor which is designed as a search coil and is installed between stator slots. The MUSIC technique, which requires fewer number of data samples and has a higher detection accuracy than the traditional fast Fourier transform (FFT) method, then calculates the motor load condition and extracts any abnormal signals related to motor failures in order to identify BRB faults. Experimental results clearly demonstrate that the proposed method is a promising candidate for an on-line diagnosis method to detect motor failures.

• 전자공학회논문지S
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• 제36S권7호
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• pp.134-135
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• 1999

본 논문에서는 최근에 널리 연구되고 잇는 다해상도 신호해석 방법인 웨이브렛 변환, 웨이브렛 패킷, 그리고 코사인 패킷 알고리듬을 잡음음성의 음질개선에 이용하여 각각의 성능을 비교하였으며, 또한 이를 기존의 스펙트럼 차감법의 성능과 비교 분석하였다. 성능비교의 척도로는 SNR과 켑스트럼 거리를 이용하였다. 실험결과 SNR면에서는 코사인 패킷이 가장 좋은 결과를 보였고 켑스트럼 거리의 경우 코사인 패킷과 웨이브렛 패킷이 훨씬 나은 결과를 보였다. 주관적인 청취결과 역시 코사인 패킷이 가장 좋은 결과를 보였으며, 기존의 스펙트럼 차감법은 musical noise의 영향으로 인해 상대적으로 다른 방식에 비해 합성음의 음질이 많이 떨어짐을 확인할 수 있었다.