拟周期激励下非线性半车模型的混沌振动研究

为了克服单一频率路面激励下车辆悬架模型不能真实反映实际车辆的非线性动力学特性问题,建立了双频拟周期动态路面激励函数,并构建了4自由度非线性1/2车辆悬架模型.运用庞加莱图、相位图,功率谱密度分析了车辆4自由度非线性半主动悬架模型通过凹凸不平路面时的动力学特性,得到了系统发生混沌振动时的激励振幅和振动特性,即车辆通过凹凸不平路面时的振动特性为:拟周期→过渡态→混沌态.同时通过调整弹簧刚度系数,有效抑制了混沌振动的发生.研究结果表明:双频拟周期激励下的4自由度非线性半主动悬架模型模拟更能接近实际情况,这有助于汽车悬架的设计和路面铺装设计.

Dynamic behavior of reinforced concrete frame structure during construction

The effects of concrete's time-variant elastic modulus,casting structural components,assembling temporary shoring framework system,and shock by operating construction equipment on dynamic behavior of the reinforced concrete frame structure during construction were investigated. The dynamic tests of an eight-storey reinforced concrete frame structure during full-scaled stages of the sixth storey construction cycle were carried out by ambient vibration. Natural frequencies,corresponding mode shapes and damping ratio were determined by power spectrum processing the tested signal data in frequency domain. The changes of frequencies,mode shapes and damping ratios at different construction stages were given. The results show that natural frequencies and modal damping ratios reach the maximum at stage of casting fresh concrete,especially for higher modes. Modal damping ratios at each construction stage are less than 5% of those during usage.

Torsional vibration active control of hybrid construction machinery complex shafting

Due to the coaxial connection of engine, motor and pump, the dynamic characteristics of hybrid construction machinery are changed, which generates a new torsional vibration problem of multi-power sources. To reduce the torsional vibration of the hybrid construction machinery complex shafting, torsional vibration active control was proposed. The three-mass model of coaxial shafting of hybrid construction machinery was established. The PID control and the fuzzy sliding mode control were chosen to weaken torsional vibration by controlling the motor speed and torque. The simulation results show that the fuzzy sliding mode control has 12% overshoot of the PID control when the engine torque changes. The active control is effective and can realize smooth power switch.

Peculiarities of the C2 Swan Band System Intensities in Gas Discharges through CO-Contained Mixtures

The paper discusses the experimental results pointing to the efficient channel of the CO vibrational to the C2 electronic energy-transfer. The radiation spectra of the d3Hg electronic state of C2 molecule are investigated and the relation of their kinetics to a vibrational excitation of CO molecules in the He-CO-O2 plasma is discussed. The changes of CO VED （vibrational energy distribution） were imposed by an application of a laser resonator to the discharge tube under investigation. Strong correlation has been found in experiments between concentrations of vibrationally excited CO molecules and the electronically excited state d31qg of C2 molecule. Modulation of the intensity of lasing oscillation cased marked modulation of the intensity of the emission from d3Hg （Swan bands）. It was found that the vibrational levels 12 〈 w 〈 20 of the CO molecules most effect on the concentration of the C2 （d3flg）. The facts discussed above most probably point to the existence of efficient channel for the VE energy transfer： CO （w） ＋ C2 →CO ＋ C2 （d3II）. The efficiency of this channel increases with the growth of populations of high vibrational levels of CO （X1∑, w）.

Seismic Retrofit of Masonry Buildings with Polymer Grid

The performance of masonry walls reinforced using innovative polymer grids embedded into thin plaster layers as a tool for the seismic enhancement of brick masonry buildings has been investigated by experimental tests. A number of diagonal compression, shear compression and out-of-plane tests were executed on sample panels; experimental activities included pseudo-dynamic and shaking table tests on infills and reduced scaled building mock-ups, respectively. The results of the experimental activities are presented and discussed. Experimental campaigns have been supported by theoretical and numerical investigations; based on the experimental data and on the results of detailed numerical simulations, simplified models for the design of the retrofitting intervention are hereinafter proposed. The models：, calibrated on the experimental evidence, properly consider the collapse mechanisms as well as the grid effect in the evolution of the above mentioned mechanisms.

Densities and viscosities of binary mixtures of n-decane + 1-pentanol,+1-hexanol,+1-heptanol at temperatures from 293.15 to 363.15 K and atmospheric pressure

Densities(ρ) and dynamic viscosities(η) for three binary mixtures of n-decane with 1-pentanol,1-hexanol and1-heptanol are presented at temperatures from 293.15 to 363.15 K and atmospheric pressure over the entire composition range.The density and viscosity are measured using a vibrating tube densimeter and a cylindrical Couette type rotating viscometer,respectively.Excess molar volumes(V^E),viscosity deviations(△η) and excess Gibbs energy of activation of viscous flow(△G^(*E)) are calculated from the experimental measurements.Intermolecular and structural interactions are indicated by the sign and magnitude of these properties.Partial molar volumes and infinity dilution molar partial volumes are also calculated for each binary system.These results are correlated using Redlich-Kister type equations.