SOM拓扑保序机理的模拟弹性力分析

针对SOM内在原理和基本特性中一些未解决的重要问题 ,定义了输出阵列上神经元i承受的、正比于模式向量及权向量之间距离的 2种模拟弹性力 :输入模式向量对胜者i的拉力 ,以及阵列中胜者j对邻近i的牵动力 ;分析了弹性力的 9个性质 ,对SOM学习过程中神经元权向量的演变过程及拓扑映射保序的机理给出了易于理解的、形象的解释。

Molecular dynamics simulations on the relationship between the elastic parameters and the molecular structures of nano-hybrid POSS materials

To research the relationship between the elastic parameters and the molecular structures of nano hybrid polyhedral oligomeric silsesquioxanes （POSS） materials, the mechanical properties at different temperatures for three POSS polymers with different molecular architectures, polymerlized norbornene POSS homopolymer （PNPOSS, pedant architecture）, γ- （2, 3 glycidoxy） propyl diaminoethane POSS polymer （GPDP, catena architecture） and trimethoxysilylcyelopentyl POSS polymer （ TSCP, cage - cage network architecture） were obtained by molecular dynamics simulations based on the Compass force-field. Results indicate that the moleculax architectures of the POSS polymers have great influence on the reinforced effects. The effect of the cage-cage network architecture is best, while that of the catena architecture takes second place and the pedant architecture has the least influence comparatively. The reinforced effects of the POSS monomers were examined. The influences of the temperatures on these effects were analyzed also. It may provide some basis for the reasonable applications of the excellent mechanical properties of the organic-inorganic nano-hybrid materials. It may also provide references for exploitation and design of the POSS materials.

Numerical Simulation of New Friction Welded Joints

In developing the new friction welding technology, the thermal elastic-plastic stress analysis by the finite element method was carried out to seek the suitable welding conditions such as the friction pressure, the friction speed and the upset pressure. The results obtained are as follows： Heat transfer to the specimens and the intermediate material during friction process was made clear; The operational conditions such as the rotation number of the intermediate material and the friction pressure to reach the liquidus in the interface could be estimated; Further, as the overhang length near the interface is well related to the joint efficiency, we tried to obtain the operational conditions by numerical analysis to acquire a certain length of the overhang length near the interface.

Numerical study on the correlation of transonic single-degree-of-freedom flutter and buffet

Transonic single-degree-of-freedom(SDOF) flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are investigated using Unsteady Reynolds-Averaged Navier-Stokes(URANS) equations. The airfoil is free to vibrate in SDOF of pitching. It is found that, the coupling system may be unstable and SDOF self-excited pitching oscillations occur in pre-buffet flow condition, where the free-stream angle of attack(AOA) is lower than the buffet onset of a stationary airfoil. In the theory of classical aeroelasticity, this unstable phenomenon is defined as flutter. However, this transonic SDOF flutter is closely related to transonic buffet(unstable aerodynamic models) due to the following reasons. Firstly, the SDOF flutter occurs only when the free-stream AOA of the spring suspended airfoil is slightly lower than that of buffet onset, and the ratio of the structural characteristic frequency to the buffet frequency is within a limited range. Secondly, the response characteristics show a high correlation between the SDOF flutter and buffet. A similar "lock-in" phenomenon exists, when the coupling frequency follows the structural characteristic frequency. Finally, there is no sudden change of the response characteristics in the vicinity of buffet onset, that is, the curve of response amplitude with the free-stream AOA is nearly smooth. Therefore, transonic SDOF flutter is often interwoven with transonic buffet and shows some complex characteristics of response, which is different from the traditional flutter.

Molecular Dynamics Simulations of the Elastic Anisotropy of Pd at Extreme Conditions

It is very interesting to discover the elastic properties of engineering material palladium, especially its elastic anisotropy along Hugoniot states. We here investigate the evolution of its high pressure and temperature(PT) elastic ansotropy along Hugoniot using molecular dynamics simulations based on accurate classical interatomic potential. In order to testify the validity of the interatomic potential of Pd in describing the high PT elastic properties, we calculate its isothermal and adiabatic elastic moduli using molecular dynamics method. The obtained data are in good agreement with experimental data. From the isothermal elastic constants, we deduce the Hugoniot acoustic velocities and find that the resulting data are in good agreement with experimental acoustic velocity data. Based on the reliable elastic constants, we further investigate the spacial elastic ansotropy along Hugoniot PT states. It is found that the spacial elastic anisotropy of Pd increases along Hugoniot states.