A new analytical model of mesh stiffness of helical gears is proposed using a combination of contact line analysis with slice method, which can well predict the dimensionless time-varying mesh stiffness. Based on the derived formula, the influence of gear basic parameters on mesh stiffness fluctuation coefficient is studied. The simulation shows that the influence of the overlap ratio on the mesh stiffness fluctuation coefficient is greater than that of the transverse contact ratio. By designing reasonable helix angle and tooth width, the overlap ratio is close to an integer, and then the mesh stiffness fluctuation coefficient can obtain a local minimum value, which is an effective way to reduce the vibration and noise of gear system.

The copolymerization reaction of m-toluidine and aniline has been induced by D-camphorsulfonic acid. When the total concentrations of the acid, the oxidant and the monomer were maintained, the ratio of two types of monomers was varied to realize the structure and property control of m-toluidine-aniline copolymers. FTIR, UV-Vis, CD and SEM were utilized to characterize the products. The results showed that the synthesized copolymers were of fiber and tube structure with the diameter of approximately 70 nm. The introduction of methyl moiety in the molecular chain of benzene weakened the conjugation and blue shifts were observed in both FTIR and UV-Vis spectra. Besides, CD spectra verified the chirality of the copolymers. Negative cotton effect could be discerned at 400 nm and the chirality inversed when [m-An]/[An]=1:5.