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18 February 2009, Volume 29 Issue 1    Next Issue
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《Acoustic Character of Underwater Suspension Layer with Elastic Particles》 SONG Yang;PIAO Sheng-chun;GUO You-song 2009, 29(1): 1-4.  DOI: A Abstract ( )   When sound wave irradiates suspension layer, there is propagation attenuation in the layer besides reflection and transmission in the interface. Theory and computer simulation about acoustic character of underwater suspension with elastic particles are given. The rule of acoustic character of suspension layer changed with frequency and characteristic parameters of layer and particles is drawn. The results show that the variation of acoustic character of suspension layer in low frequency is not sharp. With the increase of frequency, the acoustic character of suspension layer is more sensitive to the characteristic parameters. Related Articles | Metrics

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《Modal Parameter Identification of a time-Varying System by Autoregress Modelling and prony Analysis》 Jia Chenglin;Huang Fanglin;Luan Xuguang 2009, 29(1): 5-8.  DOI: A Abstract ( )   Modal parameter identification of a time-variant linear vibration system by autoregressive modeling and Prony analysis is studied in this paper. Based on the classical Prony analysis, an improved method to process nonstationary signals is presented. The recursive least squares is adopted to estimate model parameters, and the choice of the basis functions are discussed. It shows that some basis functions such as time polynomial, discrete long spherical and discrete cosine are more suitable to modal parameter identification than other ones. To validate the proposed method, digital simulation and a test of a cantilever beam with an adjustable mass are completed. The comparison between identification results and theoretical results indicates that the proposed method is effective and feasible to identify modal parameters of time-variant linear system. Related Articles | Metrics

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《Influence of Parameter Perturbation of Micro-vibration Isolation Platform on Modal Parameters》 Hou Jun-fang;Bai Hong-bai;Tao Shuai 2009, 29(1): 9-13.  DOI: A Abstract ( )   Concerning the parameter model identification problem of the 6-DOF micro-vibration isolation platform, the modal parameters identification method of the 6-DOF isolation platform was analyzed. Simulation of the variation of modal parameters caused by perturbation of the parameters in the theoretical model of the micro-vibration isolation platform was performed based on parameter perturbation re-analysis method, and the effects on modal parameter identification accuracy in modal experiment was analyzed. The results show that weak coupling is generated between part of the uncoupled modals due to unequal of the bearing stiffness in the same direction, which changes the modal frequency and mode of the system; perturbation of the vertical position of the gravity center has large impact on modal frequency of the platform; the impact of perturbation of bearing stiffness and vertical position deviation of the gravity center on modal frequency identification is not obvious, but it has evident effect on identification accuracy of the mode. Related Articles | Metrics

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《Adaptive anti-synchronization of a new hyperchaotic system》 Zhou Sheng;Tang Jia-shi 2009, 29(1): 14-20.  DOI: A Abstract ( )   This paper constructs a new four-dimensional continuous autonomous hyperchaotic system. The basic dynamical behaviors of this hyperchaotic system are investigated, a circuit diagram is designed for verifying the hyperchaotic behaviors, and some simulation observations are given. Moreover, an adaptive control method and a parameter update rule for unknown parameters based on Lyapunov stability theory are introduced to achieve anti-synchronization of two systems. Finally, the numerical simulations are shown to verify the results. Related Articles | Metrics

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《Vibration Analysis of Beams Covered with Multiple Standoff Constrained Layer Damping Patches》 Xu Zhong;Shi Hui-Rong;Zhao Jun;Wu Zheng-Hua 2009, 29(1): 21-24.  DOI: A Abstract ( )   Vibration analysis of beams with sandwich constrained layer damping treatment is extended to the case where the structure is covered by multiple standoff constrained layer damping patches. The Maxwell model, assumed-mode method, finite element theory, energy-based approach and Lagrange equation are used to derive the equations governing the vibration displacement response of the system. Parametric studies are performed with the established analytical approach to study the effects of double patches with different thickness. That appears that the appropriate standoff layer thickness can achieve better damping. Related Articles | Metrics

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《Study on Seismic Response Characteristics of Damped System Based on Exponential Friction Model》 XUE Ting;WANG Ji 2009, 29(1): 25-28.  DOI: A Abstract ( )   By using equivalent linearization technique, the response computation of a single degree of freedom dry friction damped system with velocity_dependent exponentially variable coefficient of sliding friction under harmonic excitation is discussed. The amplitude_frequency equation is also derived. Each parameter’s influence to the response of the dry friction damped system is analysised by numerical results. Related Articles | Metrics

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《Stochastic Resonance of a Linear System driven by Dichotomic Noise》 ChEN Xin-bo;ZHOU Yu-rong 2009, 29(1): 29-32.  DOI: A Abstract ( )   The phenomenon of stochastic resonance of an over-damped second-order linear system subject to dichotomic noise (DN) is investigated. Based on linear-system theory and the correlation deletion method, the explicit expression of the output amplitude gain (OAG) of the system is obtained. It is shown that the OAG is a non-monotonic function of the strength, the correlation time of the DN, the system damping coefficient, as well as the frequency of the driving signal. In addition, by choosing appropriate parameters of the noise and the system, the OAG of the noisy system can be larger than that of the noise-free system. Related Articles | Metrics

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《Development and Application of NAH Measurement and Analysis System》 Li Rui;Mao Rong-fu;Zhu Hai-chao 2009, 29(1): 33-35.  DOI: A Abstract ( )   Near-field Acoustic Holography (NAH) has become a hot focus of researches at home and abroad. It has been gradually applied to practical engineer field. However, the existed commercial NAH systems are high expensive. So that , it is necessary to develop a economical and applicable system for NAH study. In this paper, a new NAH measurement & analysis system base on LabVIEW is developed，which is designed modularly ,and of which software is the core. Also a boundary restricted plane experiment is conducted with this system. Practicability and reliability of this system is validated by the results. The system can provide a good platform for the NAH study in further. Related Articles | Metrics

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《The influence of pore’s media on the sound absorption characteristics of thick microperforated panel》 He Li-yan;Xu Ying;Chen Xing-xing 2009, 29(1): 36-38.  DOI: A Abstract ( )   MPPs are typically made of a thin metal or plastic panel. However, thin limp panels are generall not suitable as an interiornish of room walls because they do not have sucient strength, which prevent spractica lapplication of MPPs as an interiornish of roomwalls. When we put the air, water, polyvinyl alcohol and wool fiber into the pores of the thick microperforated panel respectively and the epoxy resin panel have a porosity of 7%, 10mm thick and the pore is 1mm in diameter. Measurements of the sound absorption characteristics of microperforated panel with those above material have been carried out in the Pulse 3560 and 4206 made in B&K company. The result show that the absorption coefficient of sound is better when the wool fiber’s number is 53 per pore and the depth of the back air cavity is 20mm than air in its holes. The peak value of sound absorption coefficient is about 0.94 when the resonance frequency is about 956, the frequency from 612Hz to 1600Hz all have the absorption coeifficien above 0.5. Related Articles | Metrics

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Analyses of Vibration Isolation Effect in Different Frequency Band for Steel-Spring Floating Slab Track Gu Ai-jun;Zhang Hong-liang 2009, 29(1): 39-42.  DOI: A Abstract ( )   The continuous 3D dynamic finite element model of steel-spring floating slab track is established to analyse the dynamic transfer characteristic of the floating slab track (FST) system, and make the elaborate explanations of vibration isolation efficiency and dynamic transfer characteristic with relative parameters. The method could make a detailed study of the vibration isolation according to different parameters of the system and provide a theoretical reference for the homemade of the floating slab tracks or similar productions. Related Articles | Metrics

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《Large Deformation Analysis on Rectangular Steel Tube of Lateral Restraint Under Blast Loading》 GUO Sheng-peng;GU Hong-jun 2009, 29(1): 43-45.  DOI: A Abstract ( )   Resistance of national defence project can be effectively improved by using anti-explosion energy absorption equipment. Deformation process of steel tube under blast wave is of great significance to the study of this device. According to the deformation modal of impact buckling, this paper establishes mode controlled equation on the basis of considering strain hardening and strain rate effect. Experiments show that strain rate effect is the primary factor which influences dynamic deformation behavior of steel tube. Computing results coincides with experimental phenomena. Related Articles | Metrics

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《Simulation and analysis of pipe noise radiation with FEM/BEM》 YUE Heng-chang;CHEN Bing;YIN Zhong-jun 2009, 29(1): 46-48.  DOI: A Abstract ( )   A three-dimensional model of finite element method and boundary element method for computing vibration and acoustic radiation from the limited cylindrical pipe shell has been established. The pipe shell’s modes have been analyzed by the finite element modal analysis and experimental modal analysis. The modal analysis results with ANSYS FEM software will be imported into BEM software SYSNOIS, then under the fluid - structure coupling radiation using the software BEM SYSNOISE calculates the pipeline model’s sound radiated power level and studies the different restrictions、thickness and damping for the effects of the pipe vibration and acoustic radiation. Some suggestions which can reduce structural vibration and acoustic radiation are given out. Related Articles | Metrics

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《Synthetic FEM for vib-acoustic transmission of spatial piping system》 Ke bing;Xie zhi-qiang;Lu zong-qiang 2009, 29(1): 49-53.  DOI: A Abstract ( )   in the paper, the basic idea and calculation method of analyzing vibration and noise of spatial piping system based on FEM and impedance analysis method are presented . Numerical simulation and experiment to typical model was investigated. The calculation method is feasible by comparison and applicable for engineering design. Related Articles | Metrics

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《Acoustic Sensitivity Analysis and Optimism of car Body damping treatment》 Deng Jiang-hua;Liu Xian-dong;Li Xing-hu;Shan Ying-chun 2009, 29(1): 54-57.  DOI: A Abstract ( )   The vibration characteristics and the capability of sound insulation of multilayer panels are very important factors which dominate acoustic response in car cavity. A simplified car body model is made to investigate the effects of multilayer panels on interior sound levels. The relation between the acoustic response of the cavity and the damping treatment are achieved. Acoustic-structural sensitivity of car body damping treatment is evaluated synthetically. The damping treatment’ structure is optimized, and car interior sound level is improved. Related Articles | Metrics

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《Effect of Measuring Noise in the Response on the Loads Identification》 YUAN Xiang-rong 2009, 29(1): 58-60.  DOI: A Abstract ( )   Through the theoretical discussion of the principal methods of loads identification, the effect of measuring noise in the response on the identification is analyzed. The noise effect on the loads identified by differential method, time domain method, frequency domain method and other related hybrid methods is rely on the length of time step. The reason of the noise effect is theoretical analyzed. The de-noising suggestion is proposed for the loads identification. Related Articles | Metrics

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《Wavelet denoising of optimizing threshold based on correlation》 Xiong Jing-qi;Zhao Yao-qiang;Sun Rui;Yang Han-yuan;Deng Yu 2009, 29(1): 61-64.  DOI: A Abstract ( )   Actual projects are interfered by strong noise, the wavelet transform coefficients of useful signal are always smaller than the noisy wavelet transform coefficients, so the useful signal may be eliminated if we process the coefficients with the same threshold. To solve this problem, threshold optimizing method is brought forward. the weighting array is designed for optimizing the threshold and the weighting is optimized according to the relativity of wavelet coefficients in each decomposing layer so that denoising threshold can be established accurately and useful signal can be kept more integrative. The signal’s antijamming ability can also be enhanced. Related Articles | Metrics

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《Application of Adaptive Filtering Based on Harmonic Wavelet in Dynamic Imbalance Signal Extraction》 Jia Yao-zeng;Cui Feng-kui 2009, 29(1): 65-68.  DOI: A Abstract ( )   According to the harmaonic wavelet phase locked, narrow-band analysis and the clear expression in time-domain, the method and algorithm of adaptive filtering based on harmaonic wavelet was given. This method in accordance with the signal correlation, the dynamic imblance signal was extrated by the relavant operation between harmonic wavelet and the vibration signal in time domain. In labview development system, the results of simulation and applycation test show that: through adaptive filtering based on harmonic wavelet, the dynamic imbalance signal can be extrated accurately. This filtering method is simple and good in real-time, it can be adapted to the requirement of high-precision dynamic balancing measurement with rotating speed variation, and it has better applied value. Related Articles | Metrics

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《A Neural Network Method for Online Secondary Path Modeling》 ZHANG Xiao-yu;YI Chui-jie 2009, 29(1): 69-72.  DOI: A Abstract ( )   The important effect of the secondary path on the performance of the system exists in the active noise control, and the precision of the secondary path model directly influences the convergence and effectiveness of the control system. In many practical systems, the system characteristics are time varying, so online modeling of the secondary path is important in such cases. The use of neural networks offers many useful properties such as adaptivity and fault tolerance. And an active noise control system that uses a neural network to identify the secondary path model online is presented in this paper. Its validity is proved by the simulation results. Related Articles | Metrics

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《Study on Identification Mothod of Inertia Parameter of Powertrain Rigid Body by Test 》 Long Yan;Shi Wen-ku;Lan Dian-dian;Liang Tian-ye 2009, 29(1): 73-76.  DOI: A Abstract ( )   The accurate inertia parameters of powertrain rigid body is one of important prerequisites in the powertrain mounting system design. Based on the existing methodology ,a methodology of inertia parameter identification of the non-linear damping mounting system is introduced and validated.In this methodology,three mounts of the powertrain are used as mounting,and the inertia parameters of powertrain rigid body is gained by Frequency Response Function (FRF)。Based on the methodology,the influences of vehicle mounting system to the inertia parameters of powertrain rigid body is taken into account adequately.The feasibility and reliability of the methodology is proved by an instance. Related Articles | Metrics

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《Application of Order Tracking in the Noise Source Identification of Gearbox》 LONG Yue-quan;SHI Xiao-hui;SHI Quan 2009, 29(1): 77-81.  DOI: A Abstract ( )   Since the automobile industry has been developing continuously, noise control has already become a competitive focus in automobile companies. Gearbox is a key part of car, so noise control of gearbox is becoming more important. In this paper, DS2000 data collecting system of Onosokki Co. is used to collect a gearbox’s sound pressure signal. By making power spectrum analysis and order tracking analysis, the gearbox’s eigenfrequency and noise source could be found. This way is able to identify gearbox’s noise source, and has great wide application foreground. Related Articles | Metrics