• Title/Summary/Keyword: non-stationary input

Search Result 53, Processing Time 0.028 seconds

Comparison of Fatigue Damage of Linear Elastic System with Respect to Vibration Input Conditions (입력가진 조건에 따른 선형 시스템의 피로손상도 비교 평가)

  • Heo, Yun Seok;Kim, Chan-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.24 no.6
    • /
    • pp.437-443
    • /
    • 2014
  • Vibration testing is conducted for evaluate the fatigue resistance of responsible system over excitation situations and two kinds of vibration profiles, harmonic or random, are widely used in engineering fields. Harmonic excitation profile is adequate for the rotating machinery that is primarily exposed to the orderly excited force subjected for a rotating speed; Random profile is suitable for the non-stationary vibration input, that is a ground excitation for example. Recently, the sine on random(SOR) testing method was sometimes considered to represent the real excitation conditions since the measured response signals of a target system, expecially for moving mobility, shows usually a mixture of them. So, it is important to understand the accumulated fatigue damage over different excitation patterns, harmonic and/or random, to determine the efficient vibration profile of a target system. A uniaxial vibration testing with a notched simple beam was introduced to evaluate the fatigue damage for different excitation profiles and the best choice of vibration profile was concluded from those comparison of calculated fatigue damages.

Comparison of fatigue damage of linear elastic system with respect to vibration input conditions (입력가진 조건에 따른 선형 시스템의 피로손상도 비교 평가)

  • Kim, Chan-Jung;Heo, Yun Seok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2014.04a
    • /
    • pp.340-345
    • /
    • 2014
  • Vibration testing is conducted for evaluate the fatigue resistance of responsible system over excitation situations and two kinds of vibration profiles, harmonic or random, are widely used in engineering fields. Harmonic excitation profile is adequate for the rotating machinery that is primarily exposed to the orderly excited force subjected for a rotating speed; Random profile is suitable for the non-stationary vibration input, that is a ground excitation for example. Recently, the sine on random (SOR) testing method was sometimes considered to represent the real excitation conditions since the measured response signals of a target system, expecially for moving mobility, shows usually a mixture of them. So, it is important to understand the accumulated fatigue damage over different excitation patterns, harmonic and/or random, to determine the efficient vibration profile of a target system. A uniaxial vibration testing with a notched simple beam was introduced to evaluate the fatigue damage for different excitation profiles and the best choice of vibration profile was concluded from those comparison of calculated fatigue damages.

  • PDF

Generation of synthetic accelerograms using a probabilistic critical excitation method based on energy constraint

  • Bazrafshan, Arsalan;Khaji, Naser
    • Earthquakes and Structures
    • /
    • v.18 no.1
    • /
    • pp.45-56
    • /
    • 2020
  • The application of critical excitation method with displacement-based objective function for multi degree of freedom (MDOF) systems is investigated. To this end, a new critical excitation method is developed to find the critical input motion of a MDOF system as a synthetic accelerogram. The upper bound of earthquake input energy per unit mass is considered as a new constraint for the problem, and its advantages are discussed. Considering this constraint, the critical excitation method is then used to generate synthetic accelerograms for MDOF models corresponding to three shear buildings of 10, 16, and 22 stories. In order to demonstrate the reliability of generated accelerograms to estimate dynamic response of the structures, three target ground motions with considerable level of energy contents are selected to represent "real critical excitation" of each model, and the method is used to re-generate these ground motions. Afterwards, linear dynamic analyses are conducted using these accelerograms along with the generated critical excitations, to investigate the key parameters of response including maximum displacement, maximum interstory drift, and maximum absolute acceleration of stories. The results show that the generated critical excitations can make an acceptable estimate of the structural behavior compared to the target ground motions. Therefore, the method can be reliably implemented to generate critical excitation of the structure when real one is not available.

Speech Signal Processing using Adaptative Filter (적응필터를 이용한 음성신호처리)

  • Kim, Soo-Yong;Jee, Suk-Kun;Park, Dong-Jin
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2007.06a
    • /
    • pp.743-749
    • /
    • 2007
  • Today, we can use radio communication device anywhere-anytime. Sometimes, we use the device in acoustic noise environment. The acoustic noise makes many problems in communication system. In acoustic noise environment, speaker cannot send clear information to receiver, because the received signal includes both speech signal and noise signal. A digital filter is useful to remove noise to get desired signal. One of methods is the adaptive digital filter using the adaptive noise canceller that automatically adjust filter parameters. This thesis addresses articulation algorithms against actual acoustic noises by means of two adaptive filtering methods. One is the adaptive noise canceller with two input channels and another is the spectral subtraction filter with one input channel. The experimental result from the proposed filter shows that the adaptive noise canceller is useful to reduce the non-stationary noises, while the spectral amplitude filter is effective for stationary noises.

  • PDF

Enhanced Pseudo Affine Projection Algorithm with Variable Step-size (가변 스텝 사이즈를 이용한 개선된 의사 인접 투사 알고리즘)

  • Chung, Ik-Joo
    • The Journal of the Acoustical Society of Korea
    • /
    • v.31 no.2
    • /
    • pp.79-86
    • /
    • 2012
  • In this paper, we propose an enhanced algorithm for affine projection algorithms which have been proposed to speed up the convergence of the conventional NLMS algorithm. Since affine projection (AP) or pseudo AP algorithms are based on the delayed input vector and error vector, they are complicated and not suitable for applying methods developed for the LMS-type algorithms which are based on the scalar error signal. We devised a variable step size algorithm for pseudo AP using the fact that pseudo AP algorithms are updated using the scalar error and that the error signal is getting orthogonal to the input signal. We carried out a performance comparison of the proposed algorithm with other pseudo AP algorithms using a system identification model. It is shown that the proposed algorithm presents good convergence characteristics under both stationary and non-stationary environments despites its low complexity.

A study on adaptive noise cancellation for enhancement of digital speech articulation (디지털음성명료도 향상을 위한 적응형 잡음제거 기법에 관한 연구)

  • Kim, Soo-Yong;Jee, Suk-Kun
    • Journal of the Korea Institute of Information and Communication Engineering
    • /
    • v.11 no.5
    • /
    • pp.961-968
    • /
    • 2007
  • Today, we can use radio communication device anywhere-anytime. Sometimes, we use the device in acoustic noise environment. The acoustic noise makes many problems in communication system. In acoustic noise environment, speaker cannot send clear information to receiver, because the received signal includes both speech signal and noise signal. A digital filter is useful to remove noise to get desired signal. One of methods is the adaptive digital filter using the adaptive noise canceller that automatically adjust filter parameters. This thesis addresses articulation algorithms against actual acoustic noises by means of two adaptive filtering methods. One is the adaptive noise canceller with two input channels and another is the spectral subtraction filter with one input channel. The experimental result from the proposed filter shows that the adaptive noise canceller is useful to reduce the non-stationary noises, while the spectral amplitude filter is effective for stationary noises.

A Study on Embedded DSP Implementation of Keyword-Spotting System using Call-Command (호출 명령어 방식 핵심어 검출 시스템의 임베디드 DSP 구현에 관한 연구)

  • Song, Ki-Chang;Kang, Chul-Ho
    • Journal of Korea Multimedia Society
    • /
    • v.13 no.9
    • /
    • pp.1322-1328
    • /
    • 2010
  • Recently, keyword spotting system is greatly in the limelight as UI(User Interface) technology of ubiquitous home network system. Keyword spotting system is vulnerable to non-stationary noises such as TV, radio, dialogue. Especially, speech recognition rate goes down drastically under the embedded DSP(Digital Signal Processor) environments because it is relatively low in the computational capability to process input speech in real-time. In this paper, we propose a new keyword spotting system using the call-command method, which is consisted of small number of recognition networks. We select the call-command such as 'narae', 'home manager' and compose the small network as a token which is consisted of silence with the noise and call commands to carry the real-time recognition continuously for input speeches.

An Adaptive Transform Code for Images (적응 변환코드를 이용한 영상신호 압축)

  • Kim, Dong-Youn;Lee, Kyung-Joung;Yoon, Hyung-Ro
    • Proceedings of the KOSOMBE Conference
    • /
    • v.1991 no.11
    • /
    • pp.44-47
    • /
    • 1991
  • There exists a transform trellis code that is optimal for stationary Gaussian sources and the squared-error distortion measure at all rates. In this paper, we train an asymptotically optimal version of such a code to obtain one which is matched better to the statistics of real world data. The training algorithm uses the M-algorithm to search the trellis codebook and the LBG-algorithm to update the trellis codebook. To adapt the codebook for the varying input data. we use two gain-adaptive methods. The gain-adaptive scheme 1, which normalizes input block data by its gain factor, is applied to images at rate 0.5 bits/pixel. When each block is encoded at the same rate, the nonstationarity among the block variances leads to a variation in the resulting distortion from one block to another. To alleviate the non-uniformity among the encoded image, we design four clusters from the block power, in which each cluster has its own trellis codebook and different rates. The rate of each cluster is assigned through requiring a constant distortion per-letter. This gain-adaptive scheme 2 produces good visual and measurable quality at low rates.

  • PDF

Behavior Analysis of a Seismically Isolated NPP Structure by Varying Seismic Input Generation Method and Strong Ground Motion Duration (입력운동 생성방법과 강진지속시간에 따른 면진원전의 거동 분석)

  • Kim, Hyun-Uk;Joo, Kwang-Ho;Noh, Sang-Hoon;Jung, Chang-Gyun
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.17 no.4
    • /
    • pp.187-195
    • /
    • 2013
  • In this paper, firstly, acceleration-time histories were generated by varying strong motion duration in the frequency domain for application to a seismically isolated nuclear power structure, so as to examine the effects of strong motion duration on the behavior of the structure. Secondly, real recorded earthquakes were modified to match the target response spectrum based on the revised SRP 3.7.1(2007) and the modified time histories were applied to the analysis of a seismically isolated nuclear power structure. The obtained values of acceleration and displacement responses of the structure were, finally, compared with the values obtained in case of applying acceleration-time histories generated in the frequency domain to the structure.

Instantaneous Following Control of Half-Bridge DC-DC Converter (하프브리지 DC-DC 컨버터의 순시추종제어)

  • Ra B.H.;Lee H.W.;Kim S.D.;Kim K.T.
    • Proceedings of the KIPE Conference
    • /
    • 2003.07a
    • /
    • pp.54-57
    • /
    • 2003
  • A new non linear, mean value, instantaneous following control technique to design half bridge converter is proposed in witch control principle uses characteristic that reset time of analog integrator is inverse proportion In input voltage. It is Important characteristic that compensation and follow-up control time are same with switching frequency. Is completed in one cycle that base control frequency. Have excellence characteristic that follow in order instruction value exactly stationary state as well as transient state. Half bridge converter that apply this control principle can know that have stabilize and excellence characteristic. This technique is verified through an experiment, and know that experiment result and theory agree well.

  • PDF