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Fast Boundary Element Method for Far Field Sound Radiation Analysis 2013, 33(2): 1-4.  DOI: 10.3969/j.issn.1006-1335.2013.02.001 Abstract ( )   PDF (1048KB) ( )   To overcome the inherent singular of traditional boundary element method for computing structure radiated field, an alternative approach was implemented. The indirect boundary element model was established by using the acoustic field from a series of monopole, dipole, or tripole dipole sources, which were collocated in the interior virtual surface to replace the actual acoustic field, and the boundary condition was determined by the volume velocity matching scheme. Then a numerical example with spherical cap radiator was used to demonstrate the computational effectiveness and accuracy of the current method for analysis of far field sound radiation characteristic, and the results showed that the presented method can provide a new analysis and design guideline for radiator with desired wide spatial directivity. Related Articles | Metrics

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Numerical Method for Aerodynamic Noise Prediction Using    Exact Green’s Function 2013, 33(2): 5-10.  DOI: 10.3969/j.issn.1006-1335.2013.02.002 Abstract ( )   PDF (1943KB) ( )   The exact Green’s function is used in the acoustic analogy during predicting the aero- dynamic noise generated by unsteady flows interacting with non-compact body. However, except for the very simple geometries, the exact Green’s function has to be found numerically. Thus, a numerical method based on the Boundary Element Method is presented to compute the exact Green’s function and its spatial derivatives in the frequency domain directly. For the case of two-dimensional cylinder, the analytical representations of the exact Green’s function and its spatial derivatives are deduced correctly. And all the numerical results are in good agreement with analytical ones, indicating that the proposed method is available for noise prediction. Related Articles | Metrics

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Dynamic Characteristic Analysis of Fluid-filled Pipe under the Action of Fluctuating Pressure 2013, 33(2): 11-14.  DOI: 10.3969/j.issn.1006-1335.2013.02.003 Abstract ( )   PDF (1936KB) ( )   The flow field simulation of fluid-filled pipe was first researched by Fluent in this paper and the features of pressure changes of fluid-filled pipe was analysed under the influence of periodic velocity. Then, the model of only-way fluid-structure coupling was based on ANSYSWorkbench, and the characteristics of vibration mode was analysed under the effect of pressure fluctuating pressures and with different support interval of fluid-filled pipe. The study can be used as a reference for the design of engineering. Related Articles | Metrics

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Optimization of Placements and Parameters of Dampers for Reducing Dynamic Response of Structures 2013, 33(2): 15-18.  DOI: 10.3969/j.issn.1006-1335.2013.02.004 Abstract ( )   PDF (983KB) ( )   Related Articles | Metrics

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Algorithm for Kernel Principal Component Analysis Based on Parallel Genetic Optimization 2013, 33(2): 19-22.  DOI: 10.3969/j.issn.1006-1335.2013.02.005 Abstract ( )   PDF (1009KB) ( )   Aiming to kernel parameters settings and principal components selection of kernel principal component analysis, an improved KPCA algorithm with parallel optimization of kernel function parameters and principal components number is put forward. Base on class separability criterion, the algorithm applys adaptive genetic algorithm to optimize the kernel parameters and principal components number synchronously, achieving parallel selection of kernel parameters and principal components number. The improved KPCA algorithm is applied to feature extraction of typical faults for diesel valve train. The results show that optimal KPCA can effectively reduce dimensions of fault feature vectors, improve samples clustering effect of various classes and lay a good foundation for classification precision improvement. Related Articles | Metrics

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Analysis of Spatial Parametric Resonance for Thin-walled Circular Arches with Closed Section 2013, 33(2): 23-26.  DOI: 10.3969/j.issn.1006-1335.2013.02.006 Abstract ( )   PDF (966KB) ( )   Spatial dynamic stability differential equation of thin-walled circular arch with closed section subject to under distributing radial periodic load was established through applying the energy method and Hamilton principle. Galerkin’s method was used to convert the partial differential equations into the ordinary differential Mathieu equations, so as to deduce the critical frequency equations of primary parameter resonance of deep arch, and then dynamic instability regions surrounded by periodic solutions were obtained. Spatial dynamic stability problems of parametric vibration was discussed about thin-walled circular arch with closed section，through analyzing the influences of dead load, radius of circle and central angle etc. on the dynamic stabilities, which provides reference basis for dynamic analysis and design in structure engineering. Related Articles | Metrics

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Influence of Parameters Variation of Metallic Cylindrical Shell on Its Buffering-absorption Effect 2013, 33(2): 27-31.  DOI: 10.3969/j.issn.1006-1335.2013.02.007 Abstract ( )   PDF (1455KB) ( )   According to energy conservation and increment of angle fold method, velocity-displacement curve of impact object mean load-displacement curve of cylinder shell instantaneous load-displacement curve of cylinder shell are obtained under different materials and different geometrical parameters. Calculation results show that reasonable mean load -displacement curve instantaneous load-displacement curve can be confirmed by changing cylindrical shell material and geometrical parameters ; vertical fold displacement in impact process can be reduced by increasing the number of cylindrical shells. Related Articles | Metrics

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Dynamic Analysis of Shock Response for Crank and Connecting Rod Mechanism in Diesel Engines 2013, 33(2): 32-35.  DOI: 10.3969/j.issn.1006-1335.2013.02.008 Abstract ( )   PDF (1582KB) ( )   Related Articles | Metrics

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Design of Cylindrical Shell for Dynamic Performance Optimization under Multi-excitations 2013, 33(2): 36-39.  DOI: 10.3969/j.issn.1006-1335.2013.02.009 Abstract ( )   PDF (1170KB) ( )   The paper realized Optimization design of cylindrical shells under multi-excitations based on discrete variables in ANSYS. In the premise of not changing structure parameter, adopted APDL language to program, location and phase of three simple harmonic excitations was designed variable, distance of excitations was restrict term, and shell radial of average square root velocity was objective function. Three layer optimized project was designed, then the most excellent design in location and phase of multi-excitations which minimized vibration of shell was achieved. The results showed optimized design was effective, which can provide new approach of controlling vibration in underwater great aircraft. Related Articles | Metrics

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Analysis and Test of Shock Response of an Anti-impact Chair 2013, 33(2): 40-43.  DOI: 10.3969/j.issn.1006-1335.2013.02.010 Abstract ( )   PDF (1047KB) ( )   Related Articles | Metrics

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Design of LQR Active Control System of Hypersonic Airfoil Flutter 2013, 33(2): 44-48.  DOI: 10.3969/j.issn.1006-1335.2013.02.011 Abstract ( )   PDF (1087KB) ( )   This paper presents an active control system design based on LQR (Linear Quadratic Regulator) method for hypersonic airfoil flutter. Firstly, based on hypersonic two-dimensional airfoil model with cubic physical nonlinearity and aerodynamic nonlinearity, eigenvalues at the zero equilibrium point are analyzed, and a Hopf-bifurcation point is obtained. Then, a quadratic performance index of system is given, and an active control system based on the LQR method for hypersonic airfoil flutter is designed. The control algorithm can effectively inhibit the continuous oscillation at the Hopf-bifurcation point, moreover, it is simple and easy to realize in engineering. Finally, the simulation results verify the effectivity of the control method. Related Articles | Metrics

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Numerical Study on Pressure Pulsation near the Propeller with Non-uniform Wake Field 2013, 33(2): 49-53.  DOI: 10.3969/j.issn.1006-1335.2013.02.012 Abstract ( )   PDF (1692KB) ( )   Related Articles | Metrics

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Analysis of Sound Radiation from Double-layer Cylindrical Shells Connected by a New Type of Joint-structure 2013, 33(2): 54-59.  DOI: 10.3969/j.issn.1006-1335.2013.02.013 Abstract ( )   PDF (1599KB) ( )   The vibro-acoustic design of the connection structure between double cylindrical shells was done from the view of attenuating vibration wave transmission. Applied the theory of vibration reduction and isolation, based on Snowdon isolator, a new-type connection between double cylindrical shells that composed of rubber-mass was proposed which approximated mass-spring–damping vibration reduction system with the characteristics of high elastic and damping. Then numerical simulation of vibro-acoustic characteristics of the double cylindrical shell was analyzed. Finally the effect of stiffness, damping and addition mass of elastic connection variation on the vibro-acoustic performance of double cylindrical shell is also discussed. The results shows that the new-type connection could depress vibration and acoustic radiation effectively; the variation of stiffness, damping and addition mass of elastic connection have a larger influence on the vibration attenuation and noise reduction efficiency. The research results could become a reference for submarine acoustic stealth designing. Related Articles | Metrics

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Analysis of Temporal and Spatial Factors of Traffic Noise 2013, 33(2): 60-63.  DOI: 10.3969/j.issn.1006-1335.2013.02.014 Abstract ( )   PDF (920KB) ( )   As a type of sound signal, noise should be a combination of the spatial and temporal factors. Temporal factors extracted from autocorrelation function (ACF) and spatial factors extracted from interaural cross-correlation function (IACF) were adopted to analyze the acoustical properties of noise segments in order to find out the suitable physical parameters that could represent road traffic noise and railway noise in this paper. Afterwards, those noise segments were replayed and subjects were asked to evaluate their annoyance caused by those noise stimuli. By doing that, the relationship between subjective annoyance and physical indicators extracted from ACF and IACF was tried to be found. As a result, it was shown that temporal and spatial factors extracted from ACF and IACF could represent the acoustical information of railway and road traffic noise. However, further study needs to be done to derive the relationship between subjective evaluation and the ACF and IACF factors in details. Related Articles | Metrics

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Vibration Control for the Wounded-inside  Tracked Emergency-ambulance Xin-xi xinxiXu 2013, 33(2): 64-67.  DOI: 10.3969/j.issn.1006-1335.2013.02.015 Abstract ( )   PDF (1411KB) ( )   The vibration from tracked chassis to bottom of carriage and to supine body was controlled effectively for the wounded inside tracked emergency ambulance by using two-level damping device, and the ride comfort of the wounded was improved. The results show that the first level damping efficiency is 61%-79% and the second level damping efficiency is 43%-79% under various road and speed conditions, the weighted RMS of acceleration of supine body is between 0.322 m/s2 and 0.883 m/s2, and the evaluation grade of ride comfort is “Comfort” 、“Comparative Comfort” and “Basic Comfort” respectively. Related Articles | Metrics

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Analysis of Underwater Performance of Sound Insulation Structure with Air Cushion 2013, 33(2): 68-72.  DOI: 10.3969/j.issn.1006-1335.2013.02.016 Abstract ( )   PDF (1112KB) ( )   The sound insulation structure with air cushion is raised in this article. Compared with the isolating-sound and decoupled title based on rubber damp material, it is characterized by higher cavity rate, which can lead better performance on sound insulation and decoupling. The underwater sound insulation performance of infinite double-leaf panel is studied with analytical method. The STL dip due to the “mass-spring-mass” resonance disappears and there exists a better performance with in low frequencies, compared with those of in air condition. The effects on STL of panel thickness and specific impendence of middle layer are analyzed respectively; it shows that the STL almost all depends on the latter. Traveling wave acoustic measurement is carried to investigate finite-sized structure, demonstrating its high performance. The experimental data show that the STL dips appears at certain nature frequencies of the panels. Related Articles | Metrics

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Test and Analysis of Noise Inside?Light Rail Vehicles 2013, 33(2): 73-76.  DOI: 10.3969/j.issn.1006-1335.2013.01.017 Abstract ( )   PDF (1050KB) ( )   Through noise testing experiment of light rail vehicles interior, analyzing passengers stand and sit high station noise spectrum characteristics、light rail vehicles interior noise source, that gets acoustic field distribution rule of light rail vehicle interior and noise spectrum characteristics. the main noise sources in light rail vehicles is wheel/rail noise, frequency range mainly concentrated in 400-2000 Hz. Light rail vehicle meeting frequently at run time, so this paper studies interior noise spectrum change when they are meeting, concludes that meeting will enhance interior noise, and air power noise can’t be ignored to light rail vehicle department. The analysis above provides basis for noise reduction, and may be helpful for further improvement of light rail vehicle interior acoustic environmental quality. Related Articles | Metrics

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Identification of Vehicle’s Interior Noise Source with   Operational Transfer Path Analysis 2013, 33(2): 77-81.  DOI: 10.3969/j.issn.1006-1335.2013.02.018 Abstract ( )   PDF (1302KB) ( )   Transfer path analysis is an important tool to analyze the vehicle interior noise. Operational transfer path analysis is an improvement upon the traditional transfer analysis method. In the paper, the operational transfer path analysis model of vehicle interior noise was built and the algorithm was discussed. The method was applied to a passenger car. The contribution of each noise sources was analyzed, which was benefit for the interior noise control. Related Articles | Metrics

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Study on the Fracture of Guide-rod of Air-valve-bridge of a Type of Marine Medium-speed Diesel Engines 2013, 33(2): 82-86.  DOI: 10.3969/j.issn.1006-1335.2013.02.019 Abstract ( )   PDF (2541KB) ( )   There are often occurring fractures of the valve bridge guide rods for a certain type of marine medium speed diesel engine during the using process, mainly focused on the valve bridge guide rod of exhaust valve side, and a few in air inlet valve side. In order to find the fracture reasons, the fracture surface of valve bridge guide rod is scanned by electron microscope, and the guide rod fracture belonging to fatigue fracture is determined by analyzing the fracture form, and then by setting up the simplified physical model of entire valve train, several critical stresses based on NASTRON by finite element analysis is also carried out to determine the main reasons for the fracture of guide rod. Related Articles | Metrics

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Load Transferring Technique of Excitation Sources for Ship’s Equipment and Its Application 2013, 33(2): 87-90.  DOI: 10.3969/j.issn.1006-1335.2013.02.020 Abstract ( )   PDF (1271KB) ( )   It is necessary and valuable to build the transferring relationship between test bed datum and ship datum for satisfying the boundary requirements of exciting forces in ship’s vibration-acoustic analysis. Principle of the force transferring technique is introduced first, and then the measurement method for free velocities of machineries is given. An engineering method for transferring test bed datum to ship datum of machinery force characteristics is discussed and applied to deal with a practical problem, in which the numerical simulation is used for predicting admittance of ship mounting seat absenting reality. Vibration velocity predictions and its experimental results of a machine agree well with each other, which shows that the proposed method can be applied for engineering problems. Related Articles | Metrics

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Dynamic Optimization for Puncturing and Stirring Mechanisms of Sewing Machines 2013, 33(2): 91-94.  DOI: 10.3969/j.issn.1006-1335.2013.02.021 Abstract ( )   PDF (1385KB) ( )   Industrial sewing machine is one of the equipments, which is most widely used in sewing industry. The puncturing and stirring mechanism is found to play an important role in the vibration and shock of the sewing machine. The analysis and optimization for the mechanism can help to reduce vibration and noise. The virtual prototype model of the puncturing and stirring mechanism of sewing machine is made to carry out dynamic analysis. Based on partial equilibrium theory, the optimal objective function considering of making the maximum inertia force in the vicinity of the needle bar crank become minimum is built in order to achieve the best balance. It is carried out by the means of changing the parameters such as mass and the placement of mass centroid of the mechanism. The experimental results indicate that the optimization method has the certain credibility. Partial equilibrium method applied to solve vibration and noise of complex mechanical systems such as high-speed industrial sewing machine is of the reference value. Related Articles | Metrics

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Response and vibration control method of steel box-girder bridge for vehicle induced vibration at expansion joint 2013, 33(2): 95-100.  DOI: 10.3969/j.issn.1006-1335.2013.02.022 Abstract ( )   PDF (1545KB) ( )   As the vehicle bumping at bridge expansion joint has become a serious problem affecting bridge structure, in this paper a simply supported bridge with steel box girders was presented for case study. Based on vehicle-bridge coupling vibration theory the vibration characteristics of bridge considering the effect of expansion joint was investigated through numerical calculation. In order to simulate the influence of expansion joint the roughness of road surface at expansion joint was adjusted. Wavelet transformation (WT) is adopted to obtain the dynamic characteristics in time- and frequency- domain. The effectiveness of vibration control method for this kind of vibration was studied. The results show that: the acceleration re-sponse is amplified due to the existing of expansion joint; the response is dominated by high frequency; this kind of vibration can be effectively reduced by filling the girder end with concrete. Related Articles | Metrics

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Influence of Damping Layer’s Thickness on Vibration Damping Performance of Structures 2013, 33(2): 101-104.  DOI: 10.3969/j.issn.1006-1335.2013.02.023 Abstract ( )   PDF (780KB) ( )   There are few studies on the design of damping layer thickness which is the main subject of damping optimization, the finite element methods based on modal strain energy method (MSE) was selected in this paper. Firstly, the accuracy of MSE was verified accurate, and the errors of first five natural frequency and modal loss factor were 0.038 and 0.155, respectively. Then, using damping layer thickness as variable, analyzed the dynamic mechanical property of the typical passive structural style--free damping structure and constrained damping structure. The results showed that: under the same work conditions, the vibration damping characteristic of constrained damping structure was obviously superior to free damping structure; With damping layer thickness increased from 0.5mm to 5mm，the first five natural frequency of two kinds of structures were all reduced, the loss factor were all improved, the loss factor of free damping structure and constrained damping structure could be 0.1 and 0.4 respectively; Simultaneously, the natural frequency and modal loss factor of constrained damping structure gradually tend to be stable. Related Articles | Metrics

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Experimental Analysis of Vibration Excitation Effect of Airflow Velocity on Ventilation Pipeline Li ZhiYin 2013, 33(2): 105-108.  DOI: 10.3969/j.issn.1006-1335.2013.02.024 Abstract ( )   PDF (1395KB) ( )   Through the experimentation research on ventilation piping vibration in representative environment, to test the airflow velocity effect on vibration excitation of ventilation piping system. The results show that airflow velocity in ventilation pipe has obviously affected the vibration excitation. Its effects focus on the frequency range from 200Hz to 630Hz, and get the top affects around 400Hz. The experimentation also gets the different vibration excitation results between different airflow velocities; it will be a important guidance for the design of vibration reducing and vibration isolation. Finally this paper put forward a flexible vibration isolation measure with double suspension clamp, and the experimentation result shows that this vibration isolation measure has obvious effect. Related Articles | Metrics

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Vibration Analysis and Control for Combined Air-preheater of Coking Furnace 2013, 33(2): 109-111.  DOI: 10.3969/j.issn.1006-1335.2013.02.025 Abstract ( )   PDF (795KB) ( )   Combined air preheater produces strong vibration when coke device test run , by analysing reason of the combined air preheater to vibrate, pointed out that Carmen vortex is the main reason of preheater to produce vibration, and then put forward the reasonable damping scheme,through the transformation , the vibration is eliminated, the preheater to resume normal operation. Related Articles | Metrics

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Robust H∞ Control of Building Structure Vibration Based on     LMI Approach 2013, 33(2): 112-116.  DOI: 10.3969/j.issn.1006-1335.2013.02.026 Abstract ( )   PDF (1148KB) ( )   In this paper, we present a new robust H∞ control approach that can provide a convenient design procedure for active controllers to facilitate practical implementations of control systems through the use of a quadratic performance index and the use of an efficient solution procedure based on linear matrix inequalities (LMI). A MDOF (Multiple-Degree-of-Freedom) frame structure model containing active brace systems is analyzed. In the simulation, the active control forces of the active brace systems are designed by the robust H∞ control algorithm and the structural system uncertainties are assumed in the model errors and seismic disturbance. The simulation results obtained from the proposed control method are compared with those obtained from traditional H∞ control method, which shows preliminarily that the robust H∞ controller can acquire considerably better performance of robust than traditional H∞ controller under the optimal response quantities. Therefore, the robust H∞ control method is quite promising for practical implementations of active control systems on seismically excited linear structures. Related Articles | Metrics

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Filtering Analysis Based on Improved Wavelet Threshold Function 2013, 33(2): 117-122.  DOI: 10.3969/j.issn.1006-1335.2013.02.027 Abstract ( )   PDF (1278KB) ( )   Wavelet analysis, as one of the best time-frequency analysis methods, has been widely used in signal, figure processing, damage detection and other fields. In this paper, based on binary wavelet transformation and sigmoid function, a new threshold function is build between soft and hard threshold functions. By changing different parameters of this function, it can approximate the soft and hard threshold function in different degrees. According to the filtering results of six different signals by different threshold, the new threshold function can not only improve the signal-noise ratio, but also make the filtered signal more approaching the true signal. Related Articles | Metrics

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Fault Feature Extraction Methods of Ball Bearings Based on EMD SU Tao 2013, 33(2): 123-127.  DOI: 10.3969/j.issn.1006-1335.2013.02.028 Abstract ( )   PDF (760KB) ( )   Ball bearing fault feature extraction is the key link in its fault diagnosis．In this paper, First introduced the Empirical Mode Decomposition method; then introduced several methods based on the Empirical Mode Decomposition such as the Hilbert-Huang Transform ,the Local Mean Decomposition and the method of Ensemble Empirical Mode Decomposition. The basic principles and characteristics of these methods were analyzed. The integration use of the multi-sensor data and a variety of feature extraction methods is the focus of future research directions. Related Articles | Metrics

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Review of Signal Processing Methods in Fault Diagnosis  for Machinery 2013, 33(2): 128-132.  DOI: 10.3969/j.issn.1006-1335.2013.02.029 Abstract ( )   PDF (1088KB) ( )   Related Articles | Metrics

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Time-frequency Analysis of Vibration Signal from Cylinder Head of a Diesel Engine Based on EMD and STFT 2013, 33(2): 133-137.  DOI: 10.3969/j.issn.1006-1335.2013.02.030 Abstract ( )   PDF (1186KB) ( )   A Time-Frequency analysis method based on empirical mode decomposition (EMD) and Short Time Fourier Transform (STFT) was put forward to research the vibration signal from cylinder head of diesel. The vibration signal was self adapting decomposed by EMD, and series of IMF were get. Gauss window and Hamming window were chosen to STFT according to different IMF, the Time-Frequency aggregation index was used as an object function so as to calculate the best Time-Frequency distribution of each IMF, then add them to get the best Time-Frequency distribution of origin signal. From comparison, this method settled the selection problem of window, effectively increased the Time-Frequency resolution of STFT, and described Time-Frequency distribution of vibration signal from cylinder head exactly Related Articles | Metrics

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Active Control of Impulsive Noise Based on On-line Parameter Identification 2013, 33(2): 138-143.  DOI: 10.3969/j.issn.1006-1335.2013.02.031 Abstract ( )   PDF (1317KB) ( )   Active noise control is a kind of active control method and has been widely used to obtain the attenuation of Gaussian noise signals. But for most of non-Gaussian impulsive noises, the traditional adaptive algorithms are not appropriate for controlling impulsive noise; the main reason is that there are no finite second-order moments for impulsive noise. In this paper, two kinds of on-line parameter identification algorithms based on the classical Filter-x LMS algorithm are presented, these algorithms are appropriate for the non-Gaussian impulsive noise. One is FxLMPest and FxLMADadapt algorithm based on on-line parameters identification to estimate characteristics exponent of impulsive noise with an SαS distribution; and the other is BDP algorithm based on a simple on-line recursive procedure to estimate amplitude thresholds of Sun’s method. Both methods do not need prior information of characteristics exponent and amplitude thresholds of impulsive noise, and the simulation results also show that the two methods can effectively suppress the impulsive noise, and its robust performance is significantly better than Filter-x LMS algorithm. Related Articles | Metrics

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Speed Measurement of Rotating Machine Using Multi-layer Autocorrelation and Chirp-Z Transform 2013, 33(2): 144-147.  DOI: 10.3969/j.issn.1006-1335.2013.02.032 Abstract ( )   PDF (1503KB) ( )   In the actual vibration tachometer process, effective signal is often submerged in the noise. And fast FFT algorithm can not accurately identify the vibration frequency of the signal. The anti-noise performance and measurement accuracy of FFT algorithm could not meet the practical need. This paper proposed an algorithm which combined the multi-layer autocorrelation and Chirp Z Transform. And this new algorithm can extract the effective signal in strong noise, and measurement of the speed of rotating machinery is accurate. Analysis of experimental data and simulation has been made to verify the robustness and effectiveness of this method. The results showed that this method could be used in a lot of engineering applications. Related Articles | Metrics

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Analysis and Suppression of Peak Noise Induced by Time Delay of Anti-noise Sources 2013, 33(2): 148-151.  DOI: 10.3969/j.issn.1006-1335.2013.02.033 Abstract ( )   PDF (1244KB) ( )   Time delay of anti-noise source may cause peak noise,it may affect the effect of active noise control.To analyse the effect of noise reduction,using spectrum analysis method to analyse superposed signal of random noise under different delay and analyse changes between frequency spectrum of superposed signal and primary signal.Relation between amplitude of superposed signal and primary signal had been deduced combining with least square method,and verifying correctness of the relation using simulation. Related Articles | Metrics

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EMD Based Threshold-optimizing De-noising Method 2013, 33(2): 152-156.  DOI: 10.3969/j.issn.1006-1335.2013.02.034 Abstract ( )   PDF (1160KB) ( )   To improve the de-noising effect based on EMD, aiming to the problems of the trip point determination in energy-based direct extraction method and the process of the singular IMFs, a threshold optimizing de-noising method based on EMD was put forward. Firstly, the standard of trip point in the energy viewpoint was offered, and the IMFs upping to the standard were selected. Secondly, through comparing the average energy of all eliminated IMFs with the energy of each selected IMF, the singular IMFs were confirmed and de-noised by threshold method. At last, the de-noised signal was derived by computing the sum of the selected IMFs. The current method combined the soft threshold de-noising method with the selection of the trip point together, compared with other de-noising methods, the effectiveness and superiority of the method was validated. The result provides support for improving the de-noising effect in engineering. Related Articles | Metrics

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Application of the Improved EMD Method Combined with Repeated Noise Reduction in Fault Diagnosis 2013, 33(2): 157-160.  DOI: 10.3969/j.issn.1006-1335.2013.02.035 Abstract ( )   PDF (1119KB) ( )   In fact, the roller bearing vibration signal collected often contained a lot of noise.Through to the signal wavelet packet noise reduction,by use of empirical mode decomposition to get a group of intrinsic mode functions.Calculated the correlation coefficient of the IMF and the denoised signal so as to determine which IMFs were effective set of signals to be analyzed,according to the mutations degree of the IMFs to choose Daubechies wavelet of different vanishing moments for wavelet denoising.Finally,through to analysing the marginal spectrum of IMF to determine which part of rolling bearing had been fault.This method removed the noise mixed with the fault signal well,improved the signal to noise ratio,determined the site of the rolling bearing failure accurately. Related Articles | Metrics

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Fault Diagnosis Method for Diesel Engines Based on Sound Signal Analysis 2013, 33(2): 161-165.  DOI: 10.3969/j.issn.1006-1335.2013.02.036 Abstract ( )   PDF (1340KB) ( )   Sound signal of diesel engine contains much abnormal state information and fault information. Such as components wearing and fracture damage, parts loosing, fit clearance increasing and improper assembly will be accompanied by a variety of abnormal sound. The experienced repair personnel using ear and combining with personal experience can judge the fault position and its reason. This paper uses a new method to detect and collect the real-time sound signal of the diesel engine. Digital filtering, wavelet transform and power spectrum analysis have been applied to extract and separate the different sound signal. At the same time, abnormal sound signal has been done the quantitative analysis in order to attain its characteristic parameters and then identify the fault. Related Articles | Metrics

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Study on Dynamics of Anti-shock Ground Tiles for Warship’s Personnel 张磊 2013, 33(2): 166-168.  DOI: 10.3969/j.issn.1006-1335.2013.02.037 Abstract ( )   PDF (1134KB) ( )   Based on the analysis of the hyperelastic honeycomb structure characteristics of ground tile for shock protection of warship personnel, the single cell of the periodic cellular structure was modeled, and deformation behavior in condition of dynamic compression and shock was studied. Simulation results showed the anti-shock ground tile had enough supporting rigidity for warship personnel’s routine work, and could bulk rapidly under shock load to absorb shock energy as it had a preferable plateau phase. Related Articles | Metrics

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Design of Ship’s Vibration Isolator with Magnetorheological Elastomer and Its Property Analysis 2013, 33(2): 169-172.  DOI: 10.3969/j.issn.1006-1335.2013.02.038 Abstract ( )   PDF (901KB) ( )   Related Articles | Metrics

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Numerical Prediction Method for Stern Vibration of Refitting Naval Ships 2013, 33(2): 173-177.  DOI: 10.3969/j.issn.1006-1335.2013.02.039 Abstract ( )   PDF (1030KB) ( )   Numerical predictions of hull vibration including the stern and the superstructures, and then evaluation vibration levels based on naval ship specifications are main problems needed to solve for refitting of the imported warships. False prediction can lead to the decline in performance and the warships scrap. General vibration numerical prediction technologies are needed to establish. In this paper, take an imported destroyer as example, procedures and general numerical prediction methods of hull vibration for naval ships are proposed. The selection of finite element model types of hull structures, the determination of voyage conditions, the velocity tuning technology for vibration loads, the demands on parameters of vibration measurements on the original ships, the modifications on structural dynamic models of hull structure, and the evaluation of vibration levels according to the specifications are discussed. The verification of the proposed procedure is presented using experimental and numerical methods. Related Articles | Metrics

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Analysis and Comparison of Airport Noise Metrics 2013, 33(2): 178-182.  DOI: 10.3969/j.issn.1006-1335.2013.02.040 Abstract ( )   PDF (2094KB) ( )   This paper systematically analyzes the basic principle,calculation methods and control standards of the noise metrics of the world’s major countries and regions.A series of experiments were taken on based on the noise monitoring data of a large busy airport.Through the experimental analysis demonstrated the similarities and differences of the airport noise metrics,pointing out that the existing airport noise metrics are not complete and need improvement. Related Articles | Metrics

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Testing and Analysis of Noise from the Elevated Bridges of Cheng-Guan Rapid Railway 2013, 33(2): 183-187.  DOI: 10.3969/j.issn.1006-1335.2013.02.041 Abstract ( )   PDF (1650KB) ( )   Based on noise experiment of the elevated bridge of Chengdu-Dujiangyan high-speed railway, structural noise and the wheel-rail noise are researched in this paper. The test results indicate that, low-frequency noise plays an important part in the noise of the elevated structure; linear weighted method is suggested to use due to the quality of structural noise. In addition, there are two distinct band of noise peaks, one at the lower frequency band (under 100 Hz), and the other one at the higher frequency band in the center frequency of 800 Hz. The low frequency noise is mainly from structural noise. Furthermore, the structural noise is concentrated at the bridge’s ramp below and decays slower compared to the wheel-rail noise.Prediction data result from the noise prediction model which applies acoustic principles were compared with experimental results and error is successfully controlled in less than 4%. Related Articles | Metrics

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Noise Test and Objective Sound-quality Evaluation of a Heavy Commercial Vehicle 2013, 33(2): 188-192.  DOI: 10.3969/j.issn.1006-1335.2013.02.042 Abstract ( )   PDF (1155KB) ( )   With the commercial vehicle users to continuously improve vehicle comfort requirements,manufacturers more and more attention to the design of noise and vibration reduction.sound quality has become an important indicator of comfort evaluation. In this paper, based on the theory by Zwicker who presented objective quantificational methods for subjective evaluation of the noise,the experimental data of accelerating condition internal noise of a domestic and heavy commercial vehicles is analyzed through the calculation of six objective evaluation parameters of noise:loudness,sharpness,roughness,fluctuation strength,tonality and articulation index,the status and distribution regulations of various psychoacoustics parameters are obtained in the vehichle co-pilot position at accelerating condition,this work provides some reference basis for sound quality research of the commercial vehicles and parameter basis to establish objective and quantitative model of the accelerating conditions of commercial vehicle sound quality annoyance. Related Articles | Metrics

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Fast Measurement Method of Noise Emitted by Accelerating Motor Vehicles 2013, 33(2): 193-197.  DOI: 10.3969/j.issn.1006-1335.2013.02.043 Abstract ( )   PDF (867KB) ( )   According to the requirements of ISO 362-1:2007 standard, ECE R51-03 series, and the newest draft of GB 1495 regulation, this paper introduces a kind of fast measuring method for noise emitted by accelerating motor vehicles. This fast measuring method uses an appropriate test process, and integrates and synchronously acquires the vehicle speed, engine speed, vehicle longitudinal acceleration, state of accelerator pedal, vehicle relative position and other test data, with the existing test equipments. Related Articles | Metrics

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Pure Modal Test Technique and Its Application in Composite Panels 2013, 33(2): 198-200.  DOI: 10.3969/j.issn.1006-1335.2013.02.044 Abstract ( )   PDF (1013KB) ( )   The dynamic design are usually required for modern large complicated structure. The present paper aims to give an pure model test for the composite plate panel. The test results are compared with that from the modal parameter identification method, and it is shown that the former would give a more accurate results. Related Articles | Metrics

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Noise and Vibration Experiment of a Swashplate-rod Bilge Pump Set 2013, 33(2): 201-204.  DOI: 10.3969/j.issn.1006-1335.2013.02.045 Abstract ( )   PDF (1115KB) ( )   In order to understand the characteristics of the vibration and noise of the swashplate-rod bilge pump, AMESIM model of the bilge pump was used to analyze the pressure fluctuation characteristics of the valve ports. According to the structure and working principle of the pump, the frequencies of main vibration source were analyzed, also the experiment of the bilge pump’s vibration and noise were received. The experiment indicates that the noise source mainly consists of the vibration of the motor, gearbox and inlet pipe, and the impact of distributing valve has little influence on the vibration and noise of the pump. The results provide the theory and experiment basis for noise and vibration reduction of the pump groups. Related Articles | Metrics

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Modeling and Analysis of Rub-impact Vibration of a Centrifugal Compressor and Improvement Measures 2013, 33(2): 205-210.  DOI: 10.3969/j.issn.1006-1335.2013.02.046 Abstract ( )   PDF (963KB) ( )   The paper started from the practical fault of rub-impact vibration of the Centrifugal Compressor in one factory of Longyan. From the analysis of the mechanism, it was considered to be a special fault of the friction between the rotor and the static component. Local rub-impact vibration was generally asymmetric and nonlinear, the frequency of rub-impact vibration was 1/2 of the harmonic frequency vibration of Rotor speed in most cases, amplitude of twice and three times the harmonic was increased significantly because of additional nonlinear function in large scale rub-impact. By using nonlinear dynamics theory, we established the rub-impact vibration model. Experimental results show it is feasible, which can provide a basis for diagnosing and controlling rub-impact fault of centrifugal compressor. By analyzing the influential factors of rub-impact, radius clearance, eccentric quantity, rotational speed and radial stiffness of static component were thought to effect largely rub-impact vibration. By detecting the sign of rub-impact vibration with HHT detection methods, we can discover the fault in the early stage. In actual work, we put forward some concrete improvement measures, which is of guiding significance to reduce the occurrence of rub-impact fault. Related Articles | Metrics

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Noise Control of High-speed Closed Punch 2013, 33(2): 211-213.  DOI: 10.3969/j.issn.1006-1335.2013.02.047 Abstract ( )   PDF (998KB) ( )   High-speed closed punch, as the key equipment, has been widely used in modern production lines of various manufacturers, but also to some extent on the operation of the device caused by excessive noise emissions of the production workshop, must be govern. This paper introduces the process of modular noise control of acoustic enclosures in Hangzhou Hangyang Packings Co., Ltd. to illustrate the principle of high-speed closed punch noise control and design process. Related Articles | Metrics

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Structure Borne Noise Control of Goods Elevator Traction Machine 2013, 33(2): 214-219.  DOI: 10.3969/j.issn.1006-1335.2013.02.048 Abstract ( )   PDF (1181KB) ( )   Goods elevator traction machine of a large supermarket in a high-rise building having commercial and residential functions had an influence of noise propagated by building structure on residents. To eliminate the noise influence, based on the measurement and analysis of the noise and vibration signals in the machine room and residential bedroom, the noise source recognition was carried out and the vibration isolation measure on the goods elevator traction machine was designed. The actual engineering effect shows that, after taking the control measure, the difference of vibration acceleration level of 1/3-octave band at 5~1000Hz (except for the resonance frequency) between on and under the isolator reaches 15.0~32.4dB, and the efficiency of vibration isolation comes to 82.2~97.6%, while the sound pressure level of octave band at 63~2000Hz in the bedroom of the apartment decreases by 8.9~21.4dB, with a maximal drop at 250Hz. Eventually, the complaints from residents about noise was settled. Related Articles | Metrics