救护车平顺性的研究概况与展望

综合分析救护车平顺性的研究概况 ,其中包括卧位人体受振舒适性的评价 ,振动对卧位乘员生理指标测量的影响 ,卧位人体的振动模型及救护车平顺性的改进等。同时提出了救护车平顺性领域需要进一步研究的项目。

NONLINEAR DYNAMIC ANALYSIS OF THE PLATFORM STRUCTURES SUBJECTED TO ICE EXCITATION(PART Ⅰ): EQUATION OF MOTION

In this paper,we established the equation of motion of a platform structure with four legs by way of Hamilton' s Principle and obtained the nonlinear dynamical model of platform structures. By using Laplace transformation we obtain the mode shapes of the system. The nonlinear model of the platform structure in this paper provded an accurate way of analysis for the engineering prediction of the dynamical characteristics of the platform and the understanding of its vibrational mechanism.

Ride quality evaluation of the soil compactor cab supplemented by auxiliary hydraulic mounts via simulation and experiment

In order to evaluate the ride quality of the soil compactor cab supplemented by the auxiliary hydraulic mounts (AHM), a nonlinear dynamic model of the soil compactor interacting with the off-road deformable terrain is established based on Matlab/Simulink sofware. The power spectral density (PSD) and the weighted root mean square (RMS) of acceleration responses of the vertical driver s seat, the cab s pitch and roll angle are chosen as objective functions in low-frequency range. Experimental investigation is also used to verify the accuracy of the model. The influence of the damping coefficients of the AHM on the cab s ride quality is analyzed, and damping coefficients are then optimized via a genetic algorithm program. The research results show that the cab s rubber mounts added by the AHM clearly improve the ride quality under various operating conditions. Particularly, with the optimal damping coefficients of the front-end mounts c a 1,2 = 1 500 N · s/m and of the rear-end mounts c a 3,4 =2 335 N · s/m, the weighted RMS values of the driver s seat, the cab s pitch and roll angle are reduced by 22.2%, 18.8%, 58.7%, respectively. Under the condition of the vehicle travelling, with the optimal damping coefficients of c a 1,2 = 1 500 N · s/m and c a 3,4 =1 882 N · s/m, the maximum PSD values of the driver s seat, the cab s pitch and roll angle are clearly decreased by 36.7%, 54.7% and 50.6% under the condition of the vehicle working.

The Outer Performance Degradation of Shock Absorber and Its Effect on Ride Comfort and Driving Safety

Based on the well-known quarter car representation of the automobile suspension,this paper deals with the effect of shock absorber outer performance degradation(OPD)on vehicle ride comfort and driving safety.Based on an elastici- ty model of a flat circular plate having a central hole,a program for the determina- tion of shock absorber outer performance(SOP)has been developed. Based on a hy- drodynamic theory,principles for the inter performance design of shock absorbers are presented to ensure expected SOP and the concept of critical velocity for the pre- vention of OPD is studied.By analysing the mechanism of degradation,a method for the elimination of shock absorber degradation is offered for practical structural design,i.e,the structural design of dual-tube gas charge shock absorbers.A good deal of experimental data,are presented to prove the theoreticaly studies.

Low-frequency ride comfort of vibratory rollers equipped with cab hydro-pneumatic mounts

Based on the advantages of hydraulic and pneumatic mounts,a new hydro-pneumatic mount(HPM)is proposed to improve the low-frequency ride comfort of vibration rollers.Through the experiment of the vibratory roller,a nonlinear vehicle dynamic model working on off-road soil grounds is then established to assess the HPM's ride comfort in the low-frequency region.Two indices,the power spectral density(PSD)acceleration and root mean square(RMS)acceleration of the operator vibration and cab shaking,are chosen as objective functions in both the frequency and time regions.The research results show that when the cab isolations are equipped with the HPM,the RMS values of the operator's seat,cab's pitch and roll angles are reduced by 35%,42%and 53%;and the maximum PSD of the operator's seat,cab's pitch and roll angles are decreased by 39%,59%and 65%,respectively.Consequently,the characteristics of the nonlinear damper and high-static stiffness of HPM can greatly reduce the operator vibration and cab shaking in the low-frequency region when compared to the vibratory roller's cab using the rubber mounts.

Strongly nonlinear long interfacial waves in uniform basic flows and their dispersion relationship

In this paper, long interfacial waves of finite amplitude in uniform basic flows are considered with the assumption that the aspect ratio between wavelength and water depth is small. A new model is derived using the velocities at arbitrary distances from the still water level as the velocity variables instead of the commonly used depth-averaged velocities. This significantly improves the dispersion properties and makes them applicable to a wider range of water depths. Since its derivation requires no assumption on wave amplitude, the model thus can be used to describe waves with arbitrary amplitude.

Oscillations for Second Order Nonlinear Differential Equations

This paper discusses a class of second order nonlinear differential euqations. By using the generalized Riccati technique and the averaging technique, some new oscillation criteria are obtained.

Amplitude-Squared Squeezing in a Kerr-Nonlinear Blackbody

We find that amplitude-squared squeezing of the photon field is present in a new blackbody, namely, a Kerr- nonlinear blackbody. The squeezing effect decreases as temperature T increases. The amount of the amplitude-squared squeezing in a Kerr-nonlinear blackbody is much larger than the corresponding squeezing in normal blackbody, and the degree of amplitude-squared squeezing is much larger than the amplitude squeezing for the same range of parameters in a Kerr-nonlinear blackbody.

△-Resonances in Ground State Properties of _(20)^(40)Ca Spherical Cold Finite Nucleus at Equilibrium and under Compression

The ground state properties of the spherical nucleus ^40Ca have been investigated by using constrained spherical Hartree Fock （CSHF） approximation at equilibrium and under high radial compression in a six major shells. The effective baryon-baryon interaction that includes the △（1236） resonance freedom degrees to calculate nuclear properties is used. The nucleon-nucleon （N-N） interaction is based on Reid soft core （RSC） potential. The results of calculations show that much of increase in the nuclear energy generated under compression is used to create the massive △ particles. The number of △ ＇s can be increased to about 2.1% of constituents of nucleus when nuclear density reaches about 1.34 times of normal density. The single particle energy levels are calculated and their behavior under compression is also examined. △ good agreement has been found between current calculations and phenomenological shell model for low lying single-particle spectra. The gap between shells is very clear and L-S coupling become stronger as increasing the static load on the nucleus. The results show a considerable reduction in compressibility when freedom degrees of △＇s are taken into account. It has been found that the total nuclear radial density becomes denser in the interior and less dense in the exterior region of nucleus. The surface of nucleus becomes more and more responsive to compression than outer region.

Analytic Solution to Nonlinear Dynamical System of Dragon Washbasin

Based on phase-plane orbit analysis, the mathematical model of piecewise-smooth systems of multi-degree-of-freedom under the mode coordinate is established. Approximate analytical solution under the physical coordinate of multi-degree-of-freedom self-excited vibration induced by dry friction of piecewise-smooth nonlinear systems is derived by means of average method, the results of which agree with those of the numerical solution. An effective and reliable analytical method investigating piecewise-smooth nonlinear systems of multi-degree-of-freedom has been given. Furthermore, this paper qualitatively analyses the curves about stationary amplitude versus rubbing velocity of hands and versus natural frequency of hands, and about angular frequency versus rubbing velocity of hands. The results provide a theoretical basis for identifying parameters of the system and the analysis of steady region.

Study of Nonpolaritons in a Kerr Nonlinear Optical Resonator

We find that in a Kerr nonlinear optical resonator, the photon system possesses a new kind of quasiparticle, the nonpolariton. The existence of nonpolaritons should be testified by observing the energy density dependence of the velocity and squeezing of nonpolaritons. As we have investigated, the transition energy density of a Kerr nonlinear optical resonator is larger than that of a normal state.

Shaking Table Test on Out-of-Plane Stability of Infill Masonry Wall

The behaviors of infill wall in earthquakes show that infill masonry walls,which are used as nonstructural elements of concrete frames,are vulnerable when they are subjected to earthquake.In order to achieve an optimal antiseismic behavior,or even stability,two methods of connection are investigated.The shaking table tests,with 1:3 scale walls of two-storey model subjected to horizontal earthquake loads,were carried out to investigate the out-of-plane behaviors with different connections between walls and beams.The test results show that the connection methods employed between walls and beams have a significant effect on the out-of-plane stability of infill walls.The walls bound by bars with the beams perform better than those with inclined bricks without gaps.

Controlling Nonlinear Dynamics in Continuous Crystallizers

Crystallization is used to produce vast quantities of materials. For several applications, continuous crystallization is often the best operation mode because it is able to reproduce better crystal size distributions than other operation modes. Nonlinear oscillation in continuous industrial crystallization processes is a well-known phenomenon leading to practical difficulties such that control actions are necessary. Nonlinear oscillation is a consequence of the highly nonlinear kinetics, different feedbacks between the variables and elementary processes taking place in crystallizers units, and the non-equilibrium thermodynamic operation. In this paper the control of a continuous crystallizer model that displays oscillatory behavior is addressed via two practical robust control approaches： （i） modeling error compensation, and （ii） integral high order sliding mode control. The controller designs are based on the reduced-order model representation of the population balance equations resulting after the application of the method of moments. Numerical simulations show good closed-loop performance and robustness properties

Passive vibration control of truss-cored sandwich plate with planar Kagome truss as one face plane

Kagome based high authority shape morphing structure is a kind of truss-cored sandwich metal plate with a planar Kagome truss as one of its face plane. The planar Kagome truss can achieve arbitrary in-plane nodal displacements with minimal internal resistance when its rods are deformed. Moreover, the in-plane deflection of the planar Kagome truss may induce the lateral deflection of the whole sandwich plate. In this paper, the feasibility to enhance the damping of the truss-cored sandwich plate through the replacement of a very small portion of rods in the planar Kagome truss by cylindrical viscoelastic dampers is exploited. The Biot model is chosen to simulate the behavior of the viscoelastic material in the dampers, and the fraction of axial modal strain energy of the rods in the planar Kagome truss is adopted as the index to decide the positions of the dampers. Through complex modal analysis and time-domain simulation, it is shown that the passive vibration control approach is very effective for the vibration reduction of this kind of truss-cored sandwich plates.

Nonstationary probability densities of a class of nonlinear system excited by external colored noise

This paper deals with the approximate nonstationary probability density of a class of nonlinear vibrating system excited by colored noise. First, the stochastic averaging method is adopted to obtain the averaged It6 equation for the amplitude of the system. The corresponding Fokker-Planck-Kolmogorov equation governing the evolutionary probability density function is deduced. Then, the approximate solution of the Fokker-Planck-Kolmogorov equation is derived by applying the Galerkin method. The solution is expressed as a sum of a series of expansion in terms of a set of proper basis functions with time- depended coefficients. Finally, an example is given to illustrate the proposed procedure. The validity of the proposed method is confirmed by Monte Carlo Simulation.

Solution of nonlinear cubic-quintic Duffing oscillators using He’s Energy Balance Method

In this study, He＇s Energy Balance Method （EBM） was applied to solve strong nonlinear Duffing oscillators with cubic-quintic nonlinear restoring force. The complete EBM solution procedure of the cubic-quintic Duffing oscillator equation is presented. For illustration of effectiveness and convenience of the EBM, different cases of cubic-quintic Duffing oscillator with different parameters of α,β and y were compared with the exact solution. We found that the solutions were valid for small as well as large amplitudes of oscillation. The results show that the EBM is very convenient and precise, so it can be widely appli- cable in engineering and other sciences.