• 제목/요약/키워드: nonlinear AR

검색결과 59건 처리시간 0.032초

AR 모델을 이용한 심음의 진단적 특성에 관한 연구 (Research on diagnostic property of heart sound using AR model)

  • 김형석;백승화
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1998년도 하계학술대회 논문집 G
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    • pp.2486-2488
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    • 1998
  • In this paper, Prameters esimated t using AR model in order to approach linearly the heart sound which include the nonlinear characteristic from the characteristics based on a statistical theory. The parameters which is figured out using AR model is a very important information which show the characteristic heart sound In this paper parameters estimated using autocorrelation method and order selected by proposed Akaike[6] method. Compared the similirities of the spectrums between estimated by using AR model and estimated by using FFT method.

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규칙화 역과정 방법을 이용한 Ar-Ar의 분자간 위치에너지 결정 (The Intermolecular Potential of Ar-Ar by Regularized Inverse Method)

  • 김화중;김영식
    • 대한화학회지
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    • 제40권1호
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    • pp.20-27
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    • 1996
  • 분광학적 실험 자료들로부터 안정하고 정확한 위치에너지를 역으로 얻어내는 방법에 대하여 연구하였다. 이러한 역과정 방법은 비선형 역과정 문제에서 야기되는 불안정성을 위치에너지가 유연하게 연속적이라는 제한 조건을 사용하여 최적의 해를 얻어내는 Tikhonov의 규칙화에 기초를 두고 있다. 이 방법의 장점은 특정한 형태의 위치에너지 변수를 맞추는 보통의 방법과는 달리 위치에너지를 분자간 거리의 연속함수로 다루었다. 이 방법을 실험적으로 얻은 Ar-Ar계의 분광학적 자료에 적용하여 전 구간에서 정확한 위치에너지를 찾아가는 것을 보여주었고, Morse나 RKR 방법으로 얻은 위치에너지의 부정확한 먼거리 인력 부분을 보정할 수 있음을 보여주었다.

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Recent Review of Nonlinear Conditional Mean and Variance Modeling in Time Series

  • Hwang, S.Y.;Lee, J.A.
    • Journal of the Korean Data and Information Science Society
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    • 제15권4호
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    • pp.783-791
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    • 2004
  • In this paper we review recent developments in nonlinear time series modeling on both conditional mean and conditional variance. Traditional linear model in conditional mean is referred to as ARMA(autoregressive moving average) process investigated by Box and Jenkins(1976). Nonlinear mean models such as threshold, exponential and random coefficient models are reviewed and their characteristics are explained. In terms of conditional variances, ARCH(autoregressive conditional heteroscedasticity) class is considered as typical linear models. As nonlinear variants of ARCH, diverse nonlinear models appearing in recent literature including threshold ARCH, beta-ARCH and Box-Cox ARCH models are remarked. Also, a class of unified nonlinear models are considered and parameter estimation for that class is briefly discussed.

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웨이브렛 평면 AR 모델을 이용한 초음파 비파괴 검사의 스펙클 잡음 감소 및 결함 검출 (Speckle Noise Reduction and Flaw Detection of Ultrasonic Non-destructive Testing Based on Wavelet Domain AR Model)

  • 이영석;임래묵;김덕영;신동환;김성환
    • Journal of Welding and Joining
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    • 제17권6호
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    • pp.100-107
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    • 1999
  • In this paper, we deal with the speckle noise reduction and parameter estimation of ultrasonic NDT(non-destructive test) signals obtained during weld inspection of piping. The overall approach consists of three major steps, namely, speckle noise analysis, proposition of wavelet domain AR(autoregressive) model and flaw detection by proposed model parameter. The data are first processed whereby signals obtained using vertical and angle beam transducer. Correlation properties of speckle noise are then analyzed using multiresolution analysis in wavelet domain. The parameter estimation curve obtained using the proposed model is classified a flaw in weld region where is contaminated by severe speckle noise and also clear flaw signal is obtained through CA-CFAR threshold estimator that is a nonlinear post-processing method for removing the noise from reconstructed ultrasonic signal.

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Nonlinearities and Forecasting in the Economic Time Series

  • Lee, Woo-Rhee
    • Communications for Statistical Applications and Methods
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    • 제10권3호
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    • pp.931-954
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    • 2003
  • It is widely recognized that economic time series involved not only the linearities but also the non-linearities. In this paper, when the economic time series data have the nonlinear characteristics we propose the forecasts method using combinations of both forecasts from linear and nonlinear models. In empirical study, we compare the forecasting performance of 4 exchange rates models(AR, GARCH, AR+GARCH, Bilinear model) and combination of these forecasts for dairly Won/Dollar exchange rates returns. The combination method is selected by the estimated individual forecast errors using Monte Carlo simulations. And this study shows that the combined forecasts using unrestricted least squares method is performed substantially better than any other combined forecasts or individual forecasts.

요일 특성을 고려한 일별 최대 전력 수요예측 알고리즘 개발 (Development of Daily Peak Power Demand Forecasting Algorithm Considering of Characteristics of Day of Week)

  • 지평식;임재윤
    • 전기학회논문지P
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    • 제63권4호
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    • pp.307-311
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    • 2014
  • Due to the increasing of power consumption, it is difficult to construct accurate prediction model for daily peak power demand. It is very important work to know power demand in next day for manager and control power system. In this research, we develop a daily peak power demand prediction method considering of characteristics of day of week. The proposed method is composed of liner model based on AR model and nonlinear model based on ELM to resolve the limitation of a single model. Using data sets between 2006 and 2010 in Korea, the proposed method has been intensively tested. As the prediction results, we confirm that the proposed method makes it possible to effective estimate daily peak power demand than conventional methods.

Nonlinear damage detection using higher statistical moments of structural responses

  • Yu, Ling;Zhu, Jun-Hua
    • Structural Engineering and Mechanics
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    • 제54권2호
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    • pp.221-237
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    • 2015
  • An integrated method is proposed for structural nonlinear damage detection based on time series analysis and the higher statistical moments of structural responses in this study. It combines the time series analysis, the higher statistical moments of AR model residual errors and the fuzzy c-means (FCM) clustering techniques. A few comprehensive damage indexes are developed in the arithmetic and geometric mean of the higher statistical moments, and are classified by using the FCM clustering method to achieve nonlinear damage detection. A series of the measured response data, downloaded from the web site of the Los Alamos National Laboratory (LANL) USA, from a three-storey building structure considering the environmental variety as well as different nonlinear damage cases, are analyzed and used to assess the performance of the new nonlinear damage detection method. The effectiveness and robustness of the new proposed method are finally analyzed and concluded.

MODEL PREDICTIVE CONTROL OF NONLINEAR PROCESSES BY USE OF 2ND AND 3RD VOLTERRA KERNEL MODEL

  • Kashiwagi, H.;Rong, L.;Harada, H.;Yamaguchi, T.
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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    • pp.451-454
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    • 1998
  • This paper proposes a new method of Model Predictive Control (MPC) of nonlinear process by us-ing the measured Volterra kernels as the nonlinear model. A nonlinear dynamical process is usually de-scribed as Volterra kernel representation, In the authors' method, a pseudo-random M-sequence is ar plied to the nonlinear process, and its output is measured. Taking the crosscorrelation between the input and output, we obtain the Volterra kernels up to 3rd order which represent the nonlinear characteristics of the process. By using the measured Volterra kernels, we can construct the nonlinear model for MPC. In applying Model Predictive Control to a nonlinear process, the most important thing is, in general, what kind of nonlinear model should be used. The authors used the measured Volterra kernels of up to 3rd order as the process model. The authors have carried out computer simulations and compared the simulation results for the linear model, the nonlinear model up to 2nd Volterra kernel, and the nonlinear model up to 3rd order Vol-terra kernel. The results of computer simulation show that the use of Valterra kernels of up to 3rd order is most effective for Model Predictive Control of nonlinear dynamical processes.

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