纸张振动中的整数与分数振动

本文使用微扰论方法对纸张振动建立非线性动力学方程模型,通过该模型预测纸张产生的低音与高音现象以及它们之间的联系,并通过实验验证.该模型的非线性动力学方程中存在与低音解相关的分数倍频解,这与实验中存在的分数倍频振动现象相吻合.该模型解释了整数倍频高音产生的非线性本征性以及分数频低音与分数倍频高音产生的衍生性,实验结果中的整数振动与分数振动现象满足理论预测.

滚珠自动控制转子系统强迫振动研究(1/2次分数谐波振动)

应用两个滚珠在线自动平衡转子系统,并控制转子系统的强迫振动。目前相关研究主要集中在线性转子系统,然而实际的转子系统大多属于非线性系统,特别是在常见的滚动轴承等支承的转子系统中,由于装配误差等原因出现弱非线性弹性恢复力。对具有弱非线性弹性恢复力作用的转子系统,在已完成的对主振动控制研究的基础上,通过理论解析与数值模拟,研究了两滚珠平衡制振时转子系统的1/2次分数谐波振动的响应特性及滚珠质量对振动响应大小的影响规律等。研究表明平衡滚珠在高速区域能够完全平衡非线性转子系统,对系统的1/2次分数谐波振动具有良好的制振性能。

线性分数阶强迫振动的稳态响应

利用分数阶导数算子-∞βt研究线性分数阶振动系统在谐波激励下的稳态响应。采用复指数函数形式的谐波激励，利用待定函数法得到与激励同频率的稳态响应，以及幅频关系和相频关系。讨论了分数阶导数项对刚度和阻尼的影响。

2 + 1维Caputo型时间分数阶膜振动方程的各种精确解

本文利用变量分离法研究了一个2 + 1维Caputo型时间分数阶膜振动方程的精确求解问题。通过Laplace变换及其逆变换,在一定的初始条件下,借助于Bessel方程的解的相关性质,系统地对此方程的解进行了研究,获得了Caputo型时间分数阶膜振动方程的几种精确解的一般表达式。

VIBRATION NUMERICAL ANALYSIS OF COUNTER-ROTATING TURBINE WITH WAKE-FLOW USING FLUID-STRUCTURE INTERACTION METHOD

The design of counter-rotating turbine is one of new techniques to improve the thrust-weight ratio of jet propulsion engines.Numerical analysis of a low pressure（LP）counter-rotating turbine rotor blade is presented by using ANSYS/CFX software.Interaction of aerodynamics and solid mechanics coupling in the computation is applied.In some rating of turbine,stress distribution and vibration characteristics of low pressure turbine（LPT）blade are computed.The wake aerodynamic forces and LPT blade vibration are transformed in frequency domain using fast Fourier transform（FFT）method.The results show that under wake aerodynamic force excitation,the first order modal vibration is more easily aroused and the higher order response cannot be ignored.Moreover,with different temperature fields,the vibration responses of blade are also different.

An amplitude suppression method based on the decibel criterion

To suppress the strong noise in seismic data with wide range of amplitudes, commonly used methods often yield unsatisfactory denoising results owing to inappropriate thresholds and require parametric testing as well as iterations to achieve the anticipated results. To overcome these problems, a data-driven strong amplitude suppression method based on the decibel criterion in the wavelet domain （ISANA） is proposed. The method determines the denoising threshold based on the decibel criterion and statistically analyzes the amplitude index rather than the abnormally high amplitudes. The method distinguishes the frequency band distributions of the valid signals in the time-frequency domain based on the wavelet transformation and then calculates thresholds in selected time windows, eventually achieving frequency-divided noise attenuation for better denoising. Simulations based on theoretical and real-world data verify the adaptability and low dependence of the method on the size of the time window. The method suppresses noise without energy loss in the signals.

CALCULATING ACCURATE PERIODIC MOTIONS OF HARMONICALLY FORCED PIECEWISE LINEAR OSCILLATORS

This paper presents an efficient numerical scheme for calculating the periodic motion of a harmonically forced piecewise linear oscillator very accurately. The scheme is based on the shooting technique with the traditional numerical Poincare mapping and its Jacobian replaced by the piecewise analytic ones. Thus, the scheme gets rid of the requirement of the current schemes for an assumed order of the oscillator trajectory passing through different linear regions. The numerical examples in the paper demonstrate that the new scheme, compared with the current schemes, enables one to cope with more complicated dynamics of harmonically forced piecewise linear oscillators.

Oscillation of Neutral Differential_difference Equations with Positive and Negative Periodic Coefficients

Some sufficient conditions are obtained for the oscillation of first order neutral differential_difference equations with positive and negative periodic coefficients.

Simulation of Screening Process Based on MATLAB/Simulink

Screening is an important process in mineral industry. In this paper, a study has been made to simulate the screening process based on a high-performance MATLAB/Simulink software, with an example of simulating the sieving process of a vibrating screen. A simulation model of the sieving process with a vibrating screen （SMSPVS） was proposed, using correlative mathematical models and Simulink blocks. The results show that the simulation data was very close to the actual data, The minimum errors of size distribution of oversize and undersize are 0.65% and 0.20%, resoectivelv. The sieving orocess can be accurately simulated by the SMSPVS.

Ultrasonic dissolution of brazing of 55% SiC_p/A356 composites

The brazing of 55% SiCp/A356 (volume fraction) composites in air using Zn-Al alloy as a filler metal was investigated.During the brazing process,ultrasonic vibrations were applied to samples for bonding and a significant dissolution of the filler metal into the matrix alloy in the base materials occurred.As brazing temperatures were increased,the thickness of the partial melting layers in the base material increased.SiC particles in the partial melting layer of the base material were transferred into the liquid filler under ultrasonic action and a bond with homogeneously distributed reinforcements was obtained after solidification.The volume fraction of SiC particles in the bonds could be varied by changing the brazing temperature.The maximum SiC particle volume fraction of the bond material reached 37% at a brazing temperature of 500 ℃.The shear strength of the brazed bonds was improved at pressures up to 244 MPa (at 20 ℃) and increased by 133.8% (at 200 ℃) compared with the filler of the Zn-based alloy.

Study on dynamic response of embedded long span corrugated steel culverts using scaled model shaking table tests and numerical analyses

A series of scaled-model shaking table tests and its simulation analyses using dynamic finite element method were performed to clarify the dynamic behaviors and the seismic stability of embedded corrugated steel culverts due to strong earth-quakes like the 1995 Hyogoken-nanbu earthquake. The dynamic strains of the embedded culvert models and the seismic soil pressure acting on the models due to sinusoidal and random strong motions were investigated. This study verified that the cor-rugated culvert model was subjected to dynamic horizontal forces (lateral seismic soil pressure) from the surrounding ground, which caused the large bending strains on the structure; and that the structures do not exceed the allowable plastic deformation and do not collapse completely during strong earthquake like Hyogoken-nanbu earthquake. The results obtained are useful for design and construction of embedded long span corrugated steel culverts in seismic regions.

Interference of Two-Component Bose-Einstein Condensates with a Coupling Drive in Presence of Dissipation

The interference of the two-component Bose-Einstein condensates with a coupling drive in the presence of the dissipation is studied. We find that when the two-component Bose-Einstein condensates are initially in the coherent states, for the smaller dissipation parameters compared with that of the rf frequency ωrf, the interference intensity exhibits damply oscillation behavior, whereas when the dissipation parameters are larger than that of the ωry, the interference intensity exhibits a fast attenuation behavior. As a comparison, the interference intensity in the absence of the dissipation is also studied. We conclude that the dissipation of the system can be evaluated by selecting the ωrf experimentally.

Chaotic Roll Motions of Ships in Regular Longitudinal Waves

Parametric resonance can lead to dangerously large rolling motions, endangering the ship, cargo and crew. The QR-faetorization method for calculating （LCEs） Lyapunov Characteristic Exponents was introduced; parametric resonance stability of ships in longitudinal waves was then analyzed using LCEs. Then the safe and unsafe regions of target ships were then identified. The results showed that this method can be used to analyze ship stability and to accurately identify safe and unsafe operating conditions for a ship in longitudinal waves.

Detection of cylinder pressure in diesel engines using cylinder head vibration and time series methods

This paper investigates the vibration characteristics of diesel engine cylinder heads by means of the time series method. With the concept of "Assumed System",the vibration transfer function of real cylinder head structures is established using the autoregressive-moving average models(ARMA models) of cylinder head surface vibration signals. Then this transfer function is successfully used to reconstruct the gas pressure trace inside the cylinder from measured cylinder head vibration signals. This offers an effective means for diesel engine cylinder pressure detection and condition monitoring.

Viscoelastic Rod Vibration Problem when Constitutive Relationship Contains a Fractional Derivative and its Limiting Case

The equation of motion of a viscoelastic rod of density rod p is considered when the Constitutive Relationships contains fractional derivatives （in the Riemann-Liouville sense） of order β, 0 ≤ β ≤ 1. The solution of this equation is given in a general case. It is shown that for the limit values of the derivative index ,β, i.e. when β = 0 or β = 1, the general solution gives rise to classical solutions of hyperbolic and parabolic equations.

Vibration measurement and modal analysis for tunneller

In this paper, the method of vibration measurement and modal analysis for AM50 Tunneller machine is presented. When the machine was used for cutting man made coal bed and real coal bed, the vibration of the machine was measured and the results of signal analysis show that the vibration characteristics under the two kinds of working situations are similar. The modal model of the machine is established, and then, the intrinsic vibration characteristics of AM50 tunneller are investigated by means of the method of experimental modal analysis. The vibration response simulation under a set of loading spectra measured is carried out by force response simulation software.

Oscillation of Neutral Differential Equations with Integrally Small Coefficients

Some new sufficient conditions for the oscillation of the neutral equationddt[y（t）-R（t）y（t-r）]+P（t）y（t-τ）- Q（t）y（t-σ）=0, where P,Q,R∈C（[t0,∞）,R+) and r,τ,σ∈（0,∞）,are obtained for the case where former results can not be applied in this paper.

Double Symplectic Eigenfunction Expansion Method of Free Vibration of Rectangular Thin Plates

The free vibration problem of rectangular thin plates is rewritten as a new upper triangular matrix differential system. For the associated operator matrix, we find that the two diagonal block operators are Hamiltonian. Moreover, the existence and completeness of normed symplectic orthogonal eigenfunction systems of these two block operators are demonstrated. Based on the completeness, the general solution of the free vibration of rectangular thin plates is given by double symplectie eigenfunction expansion method.

Application of Power Series on Vibration Analyses

Power series is extensively used for engineering studies. To raise the synthesis efficiency and computation accuracy of vibration mode synthesis (MS), the choosing of power series as the component mode-function is studied in this paper, and emphasis is laid on its effect upon the system computation accuracy when using the mode synthesis method for a high speed compound rotating elastic system.

Path Integral Liouville Dynamics Simulations of Vibrational Spectra of Formaldehyde and Hydrogen Peroxide

Formaldehyde and hydrogen peroxide are two important realistic molecules in atmospheric chemistry.We implement path integral Liouville dynamics(PILD)to calculate the dipolederivative autocorrelation function for obtaining the infrared spectrum.In comparison to exact vibrational frequencies,PILD faithfully captures most nuclear quantum effects in vibrational dynamics as temperature changes and as the isotopic substitution occurs.