• Title/Summary/Keyword: Random Noise

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Vertical Seismic Vibration of Suspension Bridges (지진을 받는 현수교의 수직진동)

  • Choi, Jee-Hoon;Lee, Jon-Ja;Kim, Su-Bo;Lee, Yong-Jae
    • Journal of Korean Society of Steel Construction
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    • v.12 no.5 s.48
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    • pp.581-593
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    • 2000
  • In this study, vertical dynamic analyses on the suspension bridges under seismic load are developed. Time domain analysis, random vibration analysis, and spectral analysis are formulated theoretically. The random nitration analysis is checked by numerical integration and the mathematical integration with correlation coefficient which include CQC and SRSS method in the conditions of white noise and filtered white noise. Beam, truss and frame elements are used in order to model the suspension bridge. Geometric stiffness due to dead load is considered for cable and tower.

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A New Space Vector Random PWM Scheme for Induction Motor Drives

  • Kim Hoe-Geun;Na Seok-Hwan;Lim Young-Cheol;Jung Young-Gook
    • Proceedings of the KIPE Conference
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    • 2001.10a
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    • pp.160-168
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    • 2001
  • The RPWM (Random· Pulse Width Modulation) is a switching technique to spread the voltage and current harmonics over a wide frequency area. By using randomly changing switching frequency of the inverter, the power spectrum of the electromagnetic acoustic noise can be spread to the wide-band area. The wide­band noise is much more comfortable and less annoying than the narrow-band one. So, the RPWM has been attracting interest as an excellent method for the reduction of acoustic noise on the inverter drive system. In this paper a new RPPWM (Random Position Space Vector PWM) is proposed and implemented. Each of three phase pulses is located randomly in each switching interval. Along with the randomization of PWM pulses, the space vector modulation is also executed in the C167 micro-controller. The experimental results show that the voltage and current harmonics are spread to a wide band area and that the audible switching noise is reduced by the proposed RPPWM method.

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Application of Adaptive Line Enhancer for Detection of Ball Bearing Defects (볼 베어링의 결함검출을 위한 Adaptive Line Enhancer의 적용)

  • Kim Young Tae;Choi Man Yong;Kim Ki Bok;Park Hae Won;Park Jeong Hak;Kim Jong Ock;Lyou Jun
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.2
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    • pp.96-103
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    • 2005
  • The early detection of the bearing defects in rotating machinery is very important since the critical failure of bearing causes a machinery shutdown. However it is not easy to detect the vibration signal caused by the initial defects of bearing because of the high level of random noise. A signal processing technique, called the adaptive line enhancer(ALE) as one of adaptive filter, is used in this study. This technique is to eliminate random noise with little a prior knowledge of the noise and signal characteristics. Also we propose the optimal methods fir selecting the three main ALE parameters such as correlation length filter order and adaptation constant. Vibration signals f3r three abnormal bearings, including inner and outer raceways and ball defects, were acquired by Anderon(angular derivative of radius on) meter. The experimental results showed that ALE is very useful f3r detecting the bearing defective signals masked by random noise.

Performance Optimization of LLAH for Tracking Random Dots under Gaussian Noise (가우시안 잡음을 가지는 랜덤 점 추적을 위한 LLAH의 성능 최적화)

  • Park, Hanhoon
    • Journal of Broadcast Engineering
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    • v.20 no.6
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    • pp.912-920
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    • 2015
  • Unlike general texture-based feature description algorithms, Locally Likely Arrangement Hashing (LLAH) algorithm describes a feature based on the geometric relationship between its neighbors. Thus, even in poor-textured scenes or large camera pose changes, it can successfully describe and track features and enables to implement augmented reality. This paper aims to optimize the performance of LLAH algorithm for tracking random dots (= features) with Gaussian noise. For this purpose, images with different number of features and magnitude of Gaussian noise are prepared. Then, the performance of LLAH algorithm according to the conditions: the number of neighbors, the type of geometric invariants, and the distance between features, is analyzed, and the optimal conditions are determined. With the optimal conditions, each feature could be matched and tracked in real-time with a matching rate of more than 80%.

Flutter Control of Flexible Structure under Random Atmospheric Disturbance (불규칙한 대기교란을 받는 유연한 구조물의 플러터 제어)

  • Oh, Soo-Young;Kim, Yong-Kwan;Cho, Kyoung-Lae;Heo, Hoon;Cho, Yun-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1210-1215
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    • 2000
  • Investigation is performed on the stability of general form of dynamic system under colored noise random disturbance whose damping and stiffness are varying in irregular manner along time, which is a preliminary result in the course of research on the characteristic and the control of the stochastic system. Adopted physical model is airfoil under random atmospheric disturbance, which becomes a "time-varying system" whose the governing equation is derived via F-P-K approach in stochastic sense. Control performance and effect of 'Heo-stochastic controller for colored noise' is studied. Also stochastic feature of flutter boundary is discussed as well.

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Sound Radiation Analysis for Structural Vibration Noise Control of Tire Under the Action of Random Moving Line Forces (불규칙 이동분포하중을 받는 타이어의 구조 진동 소음 제어를 위한 음향방사 해석)

  • 김병삼;이성철
    • Journal of KSNVE
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    • v.5 no.2
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    • pp.169-181
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    • 1995
  • A theoretical model has been studied to describe the sound radiation analysis for structural vibration noise control of tire under the action of random moving line forces. When a tire is analyzed, it has been modeled as a curved beam with distributed springs and dash-pots which represent the radial, tangential stiffness and damping of tire, respectively. The reaction due to fluid loading on the vibratory response of the curved beam is taken into account. The curved beam is assumed to occupy the plane y = 0 and to be axially infinite. The material of curved beam and elastic foundation are assumed to be lossless, and governed by the law of Bernoulli-Euler beam theory. The expression for sound power is integrated numerically and its results examined as a function of Mach number(M), wavenumber ratio(.gamma.) and stiffness factor(.PSI.). The experimental investigation for structural vibration noise of tire under the action of random moving line forces has been made. Based on the STSF(Spatial Transformation of Sound Field) techniques, the sound power and sound radiation are measured. The experimental results show that operating condition, material properties and design factors of the tire have a great effect on the sound power and sound radiation characteristics.

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MRF-based Adaptive Noise Detection Algorithm for Image Restoration (영상 복원을 위한 MRF 기반 적응적 노이즈 탐지 알고리즘)

  • Nguyen, Tuan-Anh;Hong, Min-Cheol
    • Journal of Korea Multimedia Society
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    • v.16 no.12
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    • pp.1368-1375
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    • 2013
  • In this paper, we presents a spatially adaptive noise detection and removal algorithm. Under the assumption that an observed image and the additive noise have Gaussian distribution, the noise parameters are estimated with local statistics, and the parameters are used to define the constraints on the noise detection process, where the first order Markov Random Field (MRF) is used. In addition, an adaptive low-pass filter having a variable window sizes defined by the constraints on noise detection is used to control the degree of smoothness of the reconstructed image. Experimental results demonstrate the capability of the proposed algorithm.

DYNAMICAL MODEL OF A SINGLE-SPECIES SYSTEM IN A POLLUTED ENVIRONMENT

  • Samanta, G.P.;Maiti, Alakes
    • Journal of applied mathematics & informatics
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    • v.16 no.1_2
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    • pp.231-242
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    • 2004
  • The effect of toxicants on ecological systems is an important issue from mathematical and experimental points of view. Here we have studied dynamical model of a single-species population-toxicant system. Two cases are studied: constant exogeneous input of toxicant and rapidly fluctuating random exogeneous input of toxicant into the environment. The dynamical behaviour of the system is analyzed by using deterministic linearized technique, Lyapunov method and stochastic linearization on the assumption that exogeneous input of toxicant into the environment behaves like ‘Coloured noise’.

Hamming Group ECC based on DCW(Dual Constant Weights) Modulation Code (DCW부호를 이용한 Hamming Group ECC)

  • 강병복;노재우;김근율;정흥상
    • Proceedings of the Optical Society of Korea Conference
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    • 2001.02a
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    • pp.64-65
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    • 2001
  • HDDS(Holographic Digital Data Storage) 시스템에서 저장밀도가 증가함에 따라서 기록/재생된 데이터는 중첩된 페이지 사이의 간섭과 인접 픽셀간의 간섭에서 기인하는 ISI (Intersymbol Interference) 및 Speckle 잡음을 포함하는 Random Noise와 광학 수차, 광학정렬 오차 및 Laser 광원의 비균일 광강도 분포 등에서 기인하는 Non- random Noise 등 다양한 시스템 잡음에 의해서 BER 이 급격히 저하되는 문제가 발생된다. 113 이러한 문제점을 해소하고 시스템의 기록/재생 데이터 신뢰도를 확보하기 위해서는 적절한 광신호처리 기법과 coding 기법이 도입되어야만 한다. (중략)

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Prediction of Acoustic Performance of Sound Barrier Using Multiple Random- Point Impact (임의의 다중 점가진을 이용한 흡차음재의 성능 예측)

  • 신재성;강연준
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.877-881
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    • 2001
  • In this paper, a model is developed that can predict insulation performance of sound barrier systems under the action of multiple random point impact. The predicted results are compared with the measured results obtained by using APAMAT II. The results show the error due to the difference between experimental environment and theoretical assumptions. The model is needed to be improved to obtain better agreement between predicted and measured results.

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