• 한국소음진동공학회논문집
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• 제20권4호
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• pp.414-421
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• 2010

The proper orthogonal decomposition(POD) is used to the vibration analysis of microcantilever in tapping mode atomic force microscopy(AFM). The proper orthogonal modes (POM) are extracted from vibrating signals of microcantilever when it resonates and taps the sample. We present recent ideas based on POD and detailed experiments that yield new perspectives into the microscale structures such as the tapping cantilever. The linearized modeling technique based on POD is very useful to show the principal characteristics of the complex dynamic responses of the AFM microcantilever.

• Wind and Structures
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• 제3권2호
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• pp.97-115
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• 2000

The technique of proper orthogonal decomposition is potentially useful in specifying the fluctuating surface pressure field around structures. However there has been a degree of controversy over whether or not the calculated modes have physical meanings. This paper addresses this issue through consideration of the results of full scale experiments, and through an analytical investigation. It is concluded that the lower, most energetic modes are likely to reflect different fluctuating flow mechanisms, although no mode is likely to be associated with just one flow mechanism or vice versa. The higher, less energetic modes are likely to represent interactions between different flow mechanisms, and to be significantly affected by the number of measurement points and measurement errors. The paper concludes with a brief description of the application of POD to the problem of building ventilation, and the calculation of cladding pressures.

• Asia-Pacific Journal of Atmospheric Sciences
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• 제54권4호
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• pp.611-622
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• 2018

Observed climate data are processed under the assumption that their time series are stationary, as in multi-step temperature and precipitation prediction, which usually leads to low prediction accuracy. If a climate system model is based on a single prediction model, the prediction results contain significant uncertainty. In order to overcome this drawback, this study uses a method that integrates ensemble prediction and a stepwise regression model based on a mean-valued generation function. In addition, it utilizes empirical mode decomposition (EMD), which is a new method of handling time series. First, a non-stationary time series is decomposed into a series of intrinsic mode functions (IMFs), which are stationary and multi-scale. Then, a different prediction model is constructed for each component of the IMF using numerical ensemble prediction combined with stepwise regression analysis. Finally, the results are fit to a linear regression model, and a short-term climate prediction system is established using the Visual Studio development platform. The model is validated using temperature data from February 1957 to 2005 from 88 weather stations in Guangxi, China. The results show that compared to single-model prediction methods, the EMD and ensemble prediction model is more effective for forecasting climate change and abrupt climate shifts when using historical data for multi-step prediction.

• 한국전자파학회논문지
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• 제25권6호
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• pp.690-699
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• 2014

제트엔진변조(Jet Engine Modulation: JEM) 식별기법은 제트엔진의 주기적인 회전에 의해 변조되는 레이더 반사 신호로부터 제트엔진의 종류를 식별하는 기법이다. 본 논문에서는 JEM의 새로운 접근법으로서, 제트엔진의 특성을 추출하기 위한 자동화 알고리즘을 제안한다. 먼저 복소 신호의 경험적인 모드 분리법(Complex Empirical Mode Decomposition: CEMD)을 거친 JEM 신호의 자기상관도로부터 제트엔진의 회전 주기를 산출한다. 그 후 DM(Divisor-Multiplier) 규칙 및 'Scoring' 개념을 JEM 스펙트럼 해석에 도입하여 최종적인 날개개수를 추정한다. 시뮬레이션 및 측정 JEM 신호로의 적용 결과를 통해 제안된 알고리즘이 정확하고 자동적인 제트엔진 정보 추출에 효과적임을 입증하였다.

• 한국산학기술학회논문지
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• 제9권6호
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• pp.1569-1573
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• 2008

본 논문은 핵발전소 증기발생기의 초음파 비파괴 검사용 프로그램 개발에 관한 것이다. 개발된 프로그램은 A, B, C, D-스캔과 같은 고전적인 해석방법뿐만 아니라 3차원 영상처리 기법을 이용하여 증기발생기 내부에 발생한 결함을 해석하고 검출할 수 있다. 결함의 3차원 영상은 핵발전소의 파이프라인으로부터 얻어진 1차원 초음파 데이터를 EMD(Empirical Mode Decomposition)로 분석해 결함의 위치를 구하고 voxel을 이용하여 구현하였다. 얻어진 3차원 영상은 2차원 해석방법을 사용하지 않더라도 결함의 위치, 형태, 크기 등과 같은 유용한 정보를 얻는데 용이하다. 개발된 프로그램은 이미 결함의 위치 및 모양, 크기 등을 알고 있는 시편의 측정에 사용하여 프로그램의 정확성을 검증하였고, 3차원 영상으로 결함의 입체적 모양을 구현하였다.

• 한국추진공학회지
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• 제11권1호
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• pp.1-10
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• 2007

반응 진행 변수 보존 방정식 및 1단계 비가역 반응과 연계된 고해상도 전산유체 코드를 이용하여 관 내부를 전파하는 데토네이션 파의 삼차원 구조를 관찰하였다. 코드는 영역 분할에 기초하여 MPI 라이브러리를 이용하여 병렬화하였으며, AMD 프로세서로 구성된 Windows 클러스터를 이용하여 실행하였다. 삼차원 비정상 해석으로부터 데토네이션 파의 불안정성으로 유발된 그을음 막 기록(smoked-foil record)을 얻을 수 있었으며, 이로부터 초기 교란 조건에 따라 직사각 모드나 대각 모드의 셀 구조와 함께 작은 반응 상수 조건에서는 회전 데토네이션 파를 관찰할 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2166-2176
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• 2017

Electricity price prediction plays a crucial part in making the schedule and managing the risk to the competitive electricity market participants. However, it is a difficult and challenging task owing to the characteristics of the nonlinearity, non-stationarity and uncertainty of the price series. This study proposes a hybrid improved strategy which incorporates data preprocessor components and a forecasting engine component to enhance the forecasting accuracy of the electricity price. In the developed forecasting procedure, the Seasonal Adjustment (SA) method and the Ensemble Empirical Mode Decomposition (EEMD) technique are synthesized as the data preprocessing component; the Coupled Simulated Annealing (CSA) optimization method and the Least Square Support Vector Regression (LSSVR) algorithm construct the prediction engine. The proposed hybrid approach is verified with electricity price data sampled from the power market of New South Wales in Australia. The simulation outcome manifests that the proposed hybrid approach obtains the observable improvement in the forecasting accuracy compared with other approaches, which suggests that the proposed combinational approach occupies preferable predication ability and enough precision.

• Ocean Systems Engineering
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• 제6권3호
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• pp.217-231
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• 2016

This paper presents a new approach for underwater image analysis using the bi-dimensional empirical mode decomposition (BEMD) technique and the phase congruency information. The BEMD algorithm, fully unsupervised, it is mainly applied to texture extraction and image filtering, which are widely recognized as a difficult and challenging machine vision problem. The phase information is the very stability feature of image. Recent developments in analysis methods on the phase congruency information have received large attention by the image researchers. In this paper, the proposed method is called the EP model that inherits the advantages of the first two algorithms, so this model is suitable for processing underwater image. Moreover, the receiver operating characteristic (ROC) curve is presented in this paper to solve the problem that the threshold is greatly affected by personal experience when underwater image edge detection is performed using the EP model. The EP images are computed using combinations of the Canny detector parameters, and the binaryzation image results are generated accordingly. The ideal EP edge feature extractive maps are estimated using correspondence threshold which is optimized by ROC analysis. The experimental results show that the proposed algorithm is able to avoid the operation error caused by manual setting of the detection threshold, and to adaptively set the image feature detection threshold. The proposed method has been proved to be accuracy and effectiveness by the underwater image processing examples.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.475-476
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• 2007

Electroglottography (EGG) is a technique used to register laryngeal behavior indirectly by a measuring the change in electrical impedance across the throat during speaking. However, EGG waveform is affected by laryngeal muscles which fluctuate the vocal cords, and which result in baseline wander. It is required to reduce baseline wander in EGG waveform, because EGG waveform is used for input signal of nonlinear speech synthesizer in next chapter. In vocal cords, the abduction-adduction of glottis is mainly controlled by the posterior cricoarytenoid (abductor) and interarytenoid (adductor) muscles respectively. Empirical Mode Decomposition method was adopted in cancellation of EGG waveform baseline wandering, and showd better performance than that of high pass filter with 500 order.

• 한국연소학회지
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• 제6권2호
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• pp.29-35
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• 2001

Unsteady numerical study has been conducted on combustion dynamics of a lean-premixed swirl-stabilized gas turbine swirl injector. A three-dimensional computation method utilizing the message passing interface (MPI) parallel architecture, large eddy simulation(LES), and proper orthogonal decomposition (POD) technique was applied. The unsteady turbulent flame dynamics are simulated so that the turbulent flame structure can be characterized in detail. It was observed that some fuel lumps escape from the primary combustion zone, and move downstream and consequently produce hot spots. Those flame dynamics coincides with experimental data. In addition, basis modes of the unsteady turbulent flame are characterized using proper orthogonal decomposition (POD) analysis. The flame structure based on odd basis modes is apparently larger than that of even ones. The flame structure can be extracted from the summation of the basis modes and eigenvectors at any moment.