• 전자공학회논문지SC
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• 제44권5호
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• pp.45-54
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• 2007

시/주파수 분석은 생체 신호 처리에서 널리 사용되어왔다. 전기 생리학적 신호로부터 중요한 특징들을 추출함으로써 이 방법들은 특정 질병의 임상 병리학적 기전 해석이 가능하다. 하지만 이 방법은 신호가 안정하다는 가정 아래 적용되었으며 불안정한 시스템에서의 적용은 제한이 되어 있다. 본 연구에서는 비선형적이고 비정상적인 심실세동 심전도 파형의 분석을 위해 Hilbert-Huang 변환을 사용한 새로운 신호처리 방법을 제안하였다. Hilbert-Huang 변환은 경험모드분리법(EMD)과 힐버트 변환으로 크게 두 가지로 구성된다. Hilbert-Huang 변환은 EMD를 사용하여 각각의 특성을 지니고 있는 독립적인 내부모드함수들로 나누어지며, 힐버트 변환에 의해 순간 주파수와 크기를 구할 수 있게 된다. 이런 특성으로 신호의 국부적인 작용에 대하여 정확하게 설명할 수 있게 된다. 본 연구에서는 Hilbert-Huang 변환을 기반으로 심실세동 심전도 파형으로부터 두 종류의 파라미터(EMD-IF, EMD-FFT)를 추출하고 서포트 벡터 머신(Support Vector Machine)을 이용하여 소생성공 및 실패 여부 예측에 관하여 연구하였다. 평균적으로 민감도와 특이도는 각각 87.57%와 76.92%로 나타났다. Hilbert-Huang 변환은 더욱 정확하게 심실세동에서의 소생성공 예측을 가능하게 하였다.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2011년도 후기공동학술대회 논문집
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• pp.106-106
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• 2011

• Journal of Advanced Marine Engineering and Technology
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• 제36권2호
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• pp.258-266
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• 2012

음향방출(Acoustic Emission, AE) 시스템은 최근 조기 결함 검출 시스템 개발을 위해 적용되고 있으며, 그에 따르는 신호처리 기법에 대한 문제를 해결하기 위해 많은 노력을 기울이고 있다. 신호처리 기법 중 포락처리(Envelope analysis)가 베어링 결함 분석에 사용되고, Wavelet Transform은 기어 등의 결함 분석에 용이한 것으로 알려져 있다. 하지만 여전히 AE 신호를 위한 신호처리 기법은 불확실하다. 따라서 본 논문에서는 AE 시스템을 적용한 조기 결함 검출 시스템 개발을 위한 사전 연구로, AE 신호를 분석하기 위한 신호처리 기법으로 Hilbert Transform(HT)과 Hilbert-Huang Transform(HHT)에 대해 비교 분석한다. AE 신호는 피로시험을 통해 취득되었으며, 취득된 AE 신호를 두 신호처리 기법을 적용하여 주파수 및 시간 신호에 대해 분석하였다. HT에 비해 HHT가 시간-주파수 영역에 대해 결과를 나타내기 때문에 좀 더 명확한 특징을 보이는 데에 반해 신호처리 시간 및 필터링에 대한 단점을 보이고 있음을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제20권11호
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• pp.1781-1789
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• 2006

Fourier methods are not generally an appropriate approach in the investigation of faults signals with transient components. This work presents the application of a new signal processing technique, the Hilbert-Huang transform and its marginal spectrum, in analysis of vibration signals and faults diagnosis of gear. The Empirical mode decomposition (EMD), Hilbert-Huang transform (HHT) and marginal spectrum are introduced. Firstly, the vibration signals are separated into several intrinsic mode functions (IMFs) using EMD. Then the marginal spectrum of each IMF can be obtained. According to the marginal spectrum, the wear fault of the gear can be detected and faults patterns can be identified. The results show that the proposed method may provide not only an increase in the spectral resolution but also reliability for the faults diagnosis of the gear.

• 응용통계연구
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• 제22권3호
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• pp.499-513
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• 2009

An economic signal in the real world usually reflects complex phenomena. One may have difficulty both extracting and interpreting information embedded in such a signal. A natural way to reduce complexity is to decompose the original signal into several simple components, and then analyze each component. Spectral analysis (Priestley, 1981) provides a tool to analyze such signals under the assumption that the time series is stationary. However when the signal is subject to non-stationary and nonlinear characteristics such as amplitude and frequency modulation along time scale, spectral analysis is not suitable. Huang et al. (1998b, 1999) proposed a data-adaptive decomposition method called empirical mode decomposition and then applied Hilbert spectral analysis to decomposed signals called intrinsic mode function. Huang et al. (1998b, 1999) named this two step procedure the Hilbert-Huang transform(HHT). Because of its robustness in the presence of nonlinearity and non-stationarity, HHT has been used in various fields. In this paper, we discuss the applications of the HHT and demonstrate its promising potential for non-stationary financial time series data provided through a Korean stock price index.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.484-490
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• 2008

For CSLDV, the Chebyshev demodulation (or polynomial) technique and Hilbert transform approach have been used for mode shape reconstruction with harmonic excitation. In this paper, the Hilbert-Huang transform approach was applied as an alternative to impact excitation cases in terms of a numerical approach. The vibration of the tested structure is modeled using impulse response functions. In order to verify this technique, a simply supported beam was chosen as the test rig. With additional innovative steps which are the ideal-band pass filter and the nodal point determination, Hilbert-Huang transformation can be used for a good mode shape reconstruction even in the impact excitation case.

• 대한기계학회논문집A
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• 제33권12호
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• pp.1442-1448
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• 2009

Transient characteristics of a signal can be effectively exhibited in time-frequency domain. Hilbert-Huang Transform (HHT) is one of the time-frequency domain analysis methods. HHT is known for its several advantages over other signal analysis methods. The capability of analyzing non-stationary or nonlinear characteristics of a signal is the primary advantage of HHT. Moreover, it is known that HHT can provide fine resolution in high frequency region and handle large size data efficiently. In this study, the effectiveness of Hilbert-Huang transform is illustrated by employing structural systems undergoing impact. A simple discrete system and an axially oscillating cantilever beam undertaking periodic impulsive force are chosen to show the effectiveness of HHT.

• 응용통계연구
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• 제24권6호
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• pp.995-1006
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• 2011

A time series can be decomposed into simple components with a multiscale method. Empirical mode decomposition(EMD) is a recently invented multiscale method in Huang et al. (1998). It is natural to apply a classical prediction method such a vector autoregressive(AR) model to the obtained simple components instead of the original time series; in addition, a prediction procedure combining a classical prediction model to EMD and Hilbert spectrum is proposed in Kim et al. (2008). In this paper, we suggest to adopt principal component analysis(PCA) to the prediction procedure that enables the efficient selection of input variables among obtained components by EMD. We discuss the utility of adopting PCA in the prediction procedure based on EMD and Hilbert spectrum and analyze the daily worm account data by the proposed PCA adopted prediction method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.453-458
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• 2002

A recently developed Hilbert-Huang transform (HHT) technique is applied to the detection of the damage locations of bridge structures. The HHT may be used to identify the locations of damages which exhibit nonlinear and non-stationary behavior, since the instantaneous frequency characteristics of the measured signal can be analyzed by the HHT. Numerical simulations were conducted on two bridge systems with damages using controlled excitations with sweeping frequency. Nonlinear plastic model using a gap element is employed to model the behavior of the cracked elements in the numerical simulations. The results indicate that the HHT method can reasonably identify the damage locations based on a limited number of acceleration sensors. Experimental study has been 실so carried out on a steel frame to confirm the applicability of the HHT to detect a structural connection with loosened bolts.

• 산업경영시스템학회지
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• 제37권4호
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• pp.35-41
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• 2014

Real-life time series characteristic data has significant amount of non-stationary components, especially periodic components in nature. Extracting such components has required many ad-hoc techniques with external parameters set by users in a case-by-case manner. In this study, we used Empirical Mode Decomposition Method from Hilbert-Huang Transform to extract them in a systematic manner with least number of ad-hoc parameters set by users. After the periodic components are removed, the remaining time-series data can be analyzed with traditional methods such as ARIMA model. Then we suggest a different way of setting control chart limits for characteristic data with periodic components in addition to ARIMA components.