Study of the Judder Characteristics of Friction Material for an Automobile Clutch and Test Verification

The friction judder characteristics during clutch engagement have a significant influence on the NVH of a driveline.In this research,the judder characteristics of automobile clutch friction materials and experimental verification are studied.First,considering the stick-slip phenomenon in the clutch engagement process,a detailed 9-degrees-of-freedom(DOF)model including the body,each cylinder of the engine,clutch and friction lining,torsional damper,transmission and other driveline parts is established,and the calculation formula of friction torque in the clutch engagement process is determined.Second,the influence of the friction gradient characteristics on the amplification or attenuation of the automobile friction judder is analyzed,and the corresponding stability analysis and the numerical simulation of different friction gradient values are carried out with MATLAB/Simulink software.Finally,judder bench test equipment and a corresponding damping test program are developed,and the relationship between the friction coefficient gradient characteristics and the system damping is analyzed.After a large number of tests,the evaluation basis of the test is determined.The research results show that the friction lining with negative gradient characteristics of the friction coefficient will have a judder signal.When the friction gradient value is less than-0.005 s/m,the judder signal of the measured clutch cannot be completely attenuated,and the judder phenomenon occurs.When the friction gradient is greater than-0.005 s/m,the judder signal can be significantly suppressed and the system connection tends to be stable.

Econometric Investigation of DSE＇s Portfolios through Selective Micro and Macro Economic Indicators

This paper examines the impact of the portfolios of Dhaka Stock Exchange （DSE） with corresponding to the selective macro and micro economic indicators of Bangladesh. The microeconomic indicators are Invested Market Capital （1MC） （US$） and the number of Total Enlisted Company （TEC） which have direct and immediate impact on the Stock Turnover Ratio （STR） of DSE and the macroeconomic indicators are Gross Domestic Product （GDP）, Gross National Income （GNI）, Gross Saving （GS）, Gross Inflation （GI）, Deposit Interest Rate （DIR）, and Gross Foreign Investment （GFI） which have indirect and long run impact on DSE portfolios. To investigate the direct impact on DSE＇s turnover ratio, the Cobb-Douglas production function is applied and to investigate the indirect and long run impact, multiple linear regression models are also applied. The estimated results are diagnosed using magnitudes of derivatives, gradient and Wald＇s coefficient restriction with respect to the macro and micro economic indicators.

In situ NMR diffusion coefficients assessment of lithium ion conductor using electrochemical priors and Arrhenius constraint——A computational study

In situ NMR measurements of the diffusion coefficients,including an estimate of signal strength,of lithium ion conductor using diffusion-weighting pulse sequence are performed in this study.A cascade bilinear model is proposed to estimate the diffusion sensitivity factors of pulsed-field gradient using prior information of the electrochemical performance and Arrhenius constraint.The model postulates that the active lithium nuclei participating electrochemical reaction are relevant to the NMR signal intensity,when discharge rate or temperature condition is varying.The electrochemical data and the NMR signal strength show a highly fit with the proposed model according our simulation and experiments.Furthermore,the diffusion time is constrained by temperature based on Arrhenius equation of reaction rates dependence.An experimental calculation of Li_4Ti_5O_（12）（LTO）/carbon nanotubes（CNTs） with the electrolyte evaluating at 20 ℃ is presented,which the b factor is estimated by the discharge rate.