• Title, Summary, Keyword: time-domain methods

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A study on nonlinear seismic response analysis of building considering frequency dependent soil impedance in time domain

  • Nakamura, Naohiro
    • Interaction and multiscale mechanics
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    • v.2 no.1
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    • pp.91-107
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    • 2009
  • In order to accurately estimate the seismic behavior of buildings, it is important to consider both nonlinear characteristics of the buildings and the frequency dependency of the soil impedance. Therefore, transform methods of the soil impedance in the frequency domain to the impulse response in the time domain are needed because the nonlinear analysis can not be carried out in the frequency domain. The author has proposed practical transform methods. In this paper, seismic response analyses considering frequency dependent soil impedance in the time domain are shown. First, the formulation of the proposed transform methods is described. Then, the linear and nonlinear earthquake response analyses of a building on 2-layered soil were carried out using the transformed impulse responses. Through these analyses, the validity and efficiency of the methods were confirmed.

Two-dimensional energy transmitting boundary in the time domain

  • Nakamura, Naohiro
    • Earthquakes and Structures
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    • v.3 no.2
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    • pp.97-115
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    • 2012
  • The energy-transmitting boundary, which is used in the well-known finite element method (FEM) program FLUSH, is quite efficient for the earthquake response analysis of buildings considering soil-structure interaction. However, it is applicable only in the frequency domain. The author proposed methods for transforming frequency dependent impedance into the time domain, and studied the time domain transform of the boundary. In this paper, first, the estimation methods for both the halfspace condition under the bottom of the soil model and the pseudo three-dimensional effect were studied with the time domain transmitting boundary. Next, response behavior when using the boundary was studied in detail using a practical soil and building model. The response accuracy was compared with those using viscous boundary, and the boundary that considers the excavation force. Through these studies, the accuracy and efficiency of the proposed time domain transmitting boundary were confirmed.

Bootstrap methods for long-memory processes: a review

  • Kim, Young Min;Kim, Yongku
    • Communications for Statistical Applications and Methods
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    • v.24 no.1
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    • pp.1-13
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    • 2017
  • This manuscript summarized advances in bootstrap methods for long-range dependent time series data. The stationary linear long-memory process is briefly described, which is a target process for bootstrap methodologies on time-domain and frequency-domain in this review. We illustrate time-domain bootstrap under long-range dependence, moving or non-overlapping block bootstraps, and the autoregressive-sieve bootstrap. In particular, block bootstrap methodologies need an adjustment factor for the distribution estimation of the sample mean in contrast to applications to weak dependent time processes. However, the autoregressive-sieve bootstrap does not need any other modification for application to long-memory. The frequency domain bootstrap for Whittle estimation is provided using parametric spectral density estimates because there is no current nonparametric spectral density estimation method using a kernel function for the linear long-range dependent time process.

A Study on Road Noise Extraction Methods for Listening (청음용 자동차 로드노이즈 추출 방법 연구)

  • Kook, Hyung-Seok;Kim, Hyoung-Gun;Cho, Munhwan;Ih, Kang-Duck
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.7
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    • pp.844-850
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    • 2016
  • This study pertains to the extraction of the road noise component of signals from a vehicle's interior noise via the traditional frequency domain and time domain system identification methods. For road noise extraction based on the frequency domain system identification method, the appropriate matrix inversion strategy is investigated and causal and non-causal impulse response filters are compared. Furthermore, appropriate data lengths for the frequency domain system identification method are investigated. In addition to the traditional road noise extraction methods based on frequency domain system identification, a new approach to extract road noise via the time domain system identification method based on a parametric input-output model is proposed and investigated in the present study. In this approach, instead of constructing a higher order model for the full-band road noise, input and output signals are processed in the subband domain and lower order parametric models optimal to each subband are determined. These parametric models are used to extract road noises in each subband; the full band road noise is then reconstructed from the subband road noises. This study shows that both the methods in the frequency domain and the time domain successfully extract the road noise from the vehicle's interior noise.

Earthquake stresses and effective damping in concrete gravity dams

  • Akpinar, Ugur;Binici, Baris;Arici, Yalin
    • Earthquakes and Structures
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    • v.6 no.3
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    • pp.251-266
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    • 2014
  • Dynamic analyses for a suite of ground of motions were conducted on concrete gravity dam sections to examine the earthquake induced stresses and effective damping. For this purpose, frequency domain methods that rigorously incorporate dam-reservoir-foundation interaction and time domain methods with approximate hydrodynamic foundation interaction effects were employed. The maximum principal tensile stresses and their distribution at the dam base, which are important parameters for concrete dam design, were obtained using the frequency domain approach. Prediction equations were proposed for these stresses and their distribution at the dam base. Comparisons of the stress results obtained using frequency and time domain methods revealed that the dam height and ratio of modulus of elasticity of foundation rock to concrete are significant parameters that may influence earthquake induced stresses. A new effective damping prediction equation was proposed in order to estimate earthquake stresses accurately with the approximate time domain approach.

A New Endpoint Detection Method Based on Chaotic System Features for Digital Isolated Word Recognition System

  • Zang, Xian;Chong, Kil-To
    • Proceedings of the IEEK Conference
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    • pp.37-39
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    • 2009
  • In the research of speech recognition, locating the beginning and end of a speech utterance in a background of noise is of great importance. Since the background noise presenting to record will introduce disturbance while we just want to get the stationary parameters to represent the corresponding speech section, in particular, a major source of error in automatic recognition system of isolated words is the inaccurate detection of beginning and ending boundaries of test and reference templates, thus we must find potent method to remove the unnecessary regions of a speech signal. The conventional methods for speech endpoint detection are based on two simple time-domain measurements - short-time energy, and short-time zero-crossing rate, which couldn't guarantee the precise results if in the low signal-to-noise ratio environments. This paper proposes a novel approach that finds the Lyapunov exponent of time-domain waveform. This proposed method has no use for obtaining the frequency-domain parameters for endpoint detection process, e.g. Mel-Scale Features, which have been introduced in other paper. Comparing with the conventional methods based on short-time energy and short-time zero-crossing rate, the novel approach based on time-domain Lyapunov Exponents(LEs) is low complexity and suitable for Digital Isolated Word Recognition System.

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Assessing Methods of Heart Rate Variability (심박변이에 대한 평가방법)

  • Park, Ki-Jong;Jeong, Heejeong
    • Annals of Clinical Neurophysiology
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    • v.16 no.2
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    • pp.49-54
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    • 2014
  • Heart rate variability is significantly associated with cardiovascular complications in various neurological disorders with cardiac impairment. Measures of spontaneous heart rate variability might be different from provocating tests of heart rate variability such as deep breathing and Valsava maneuver. Methods for analysis are divided into time domain methods and frequency domain methods. There are standard deviation of NN interval, standard deviation of average NN interval, root mean square of the successive differences, NN50, and pNN50 in time domain methods. Frequency domain bands can be divided into very low, low, and high frequency. Each variables are influenced by sympathetic and/or parasympathetic activity.

Finite Difference Time Domain Analysis for Film Bulk Acoustic Wave Resonator used in Microwave Region (시간 영역 유한 차분법(FDTD)을 이용한 마이크로파 대역의 압전 박막 공진기 해석)

  • 송영민;정재호;이용현;이정희;최현철
    • Proceedings of the IEEK Conference
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    • pp.489-492
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    • 2000
  • Film Bulk Acoustic Wave Resonator(FBAR) used in microwave region was analyzed with Finite Difference Time-Domain Methods(FDTD) in this paper. FBAR have been analyzed with one dimensional Mason model analysis or Finite Element methods(FEM), but the first couldn't analyze effect of area variation and spurious characteristics, the second had difficulty in element separation because of thin electrode. So in this paper FBAR was analyzed by Finite Difference Time-Domain Methods and it's results were transformed to frequency domain using Discrete Fourier Transform.

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Detection and Estimation of Multiple Faults on a Coaxial Cable Based on TFDR Algorithm (TFDR 기법을 이용한 Coaxial Cable상에 존재하는 다양한 결함 감지 및 추정)

  • 송은석;신용준;육종관;박진배
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.10
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    • pp.1079-1088
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    • 2003
  • In this paper, we propose a high-resolution time-frequency domain reflectometry technique as a methodology of detection and estimation of faults on a wire. This method adopts the time-frequency cross correlation characteristics of the observed signal in both time and frequency domains simultaneously. The accuracy of the proposed method is verified with experiments using a RG type coaxial cable and comparing it with traditional time domain as well as frequency domain reflectometry methods. It is clearly shown here that the proposed algorithm produces excellent results compared to the conventional methods for single as well as multiple fault cables.

ERROR ESTIMATIES FOR A FREQUENCY-DOMAIN FINITE ELEMENT METHOD FOR PARABOLIC PROBLEMS WITH A NEUMANN BOUNDARY CONDITION

  • Lee, Jong-Woo
    • Bulletin of the Korean Mathematical Society
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    • v.35 no.2
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    • pp.345-362
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    • 1998
  • We introduce and anlyze a naturally parallelizable frequency-domain method for parabolic problems with a Neumann boundary condition. After taking the Fourier transformation of given equations in the space-time domain into the space-frequency domain, we solve an indefinite, complex elliptic problem for each frequency. Fourier inversion will then recover the solution of the original problem in the space-time domain. Existence and uniqueness of a solution of the transformed problem corresponding to each frequency is established. Fourier invertibility of the solution in the frequency-domain is also examined. Error estimates for a finite element approximation to solutions fo transformed problems and full error estimates for solving the given problem using a discrete Fourier inverse transform are given.

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