轨道动力学层状梁模型与算法中的几个问题

研究目的:轨道结构层状梁模型由于模型简单,被广泛应用于轨道动力学及车辆-轨道耦合系统动力学分析中。简化的轨道结构层状梁模型能否反映半无限空间上实际轨道结构的变形规律和动态特性,运用轨道结构层状梁模型得到的车辆和轨道结构动力响应精度如何,这些问题还未见系统研究。本文通过建立车辆-轨道结构层状梁非线性耦合系统动力学模型,构建运用交叉迭代法分别独立求解车辆和轨道结构动力学方程的显示算法,对比分析轨道结构层状梁模型与轨道结构三维块体单元模型的计算结果,以及轨道结构层状梁模型与轨道结构半无限空间模型计算结果的差异,分析轨道结构层状梁模型在车辆-轨道耦合系统动力学分析中的适应性。同时,还对比分析交叉迭代法与传统的耦合方程算法在求解车辆-轨道耦合系统动力响应时的计算效率、计算精度和算法特点。研究结论:(1)采用层状梁轨道模型模拟轨道结构是可行的,计算结果具有良好的精度,能够满足工程问题的分析要求;(2)交叉迭代法相对于传统的耦合方程算法计算效率更高,精度更好,用时更省,程序设计更容易,不仅适用轮轨线性接触分析,而且适用轮轨非线性接触分析;(3)通过引入松弛因子对轮轨接触力进行修正,可加快交叉迭代算法的收敛速度;(4)验证了轨道结构层状梁模型的可行性和交叉迭代算法求解的优越性,可为高速铁路轨道动力学高效建模和精确分析提供参考。

动态社会网络中的社区挖掘算法研究

为解决社区挖掘问题,针对社会网络的动态特性,给出了新的社区定义,并结合连通性和频繁性概念提出一种新的算法DCSMA(Dynamic Community Structure Mining Algorithm)。挖掘时刻连通的个体集合作为社区,采用层状结构模型,根据重要性权重区分社区内个体,使社区结构更加清晰。在标准测试数据集上的实验结果表明了该算法的可行性和有效性。

CAI软件的开发和质量的度量

根据CAI软件开发状况,提出了组合式模糊评价CAI软件的三层次模型和度量的方法及过程。操作方便,结果客观公正。

Phase-field simulation of lamellar growth for a binary eutectic alloy

Using general multi-phase-field model,detailed microstructures corresponding to different initial lamellar sets were simulated in a binary eutectic alloy with an asymmetric phase diagram.The simulation results show that regular or unstable oscillating lamellar structures depend on the initial lamellar widths of two solid phases.A lamellar morphology map associating with the initial widths has been derived,which is capable of showing the condition of forming various lamella structures.For instance,a regular lamella was formed with fast solidification while large lamella resulted from disorder growth with low interfacial velocity. The investigated interface velocities indicate that with fast solidification to form regular lamella,a disorder growth manner or a large lamellar spacing causes a low interface velocity.These results are in good agreement with those proposed by Jackson-Hunt model.

Variation Characteristics of Focal Mechanisms of Small Earthquakes before Four Strong Earthquakes in Xinjiang

With the point source dislocation model and the velocity structure of a layered medium,focal mechanisms of small earthquakes are calculated using the maximum amplitude of the direct P- and S-waves in the vertical component. By system clustering,and using the vector synthesis method,the average focal mechanism solution is obtained. Using the above method,this paper analyzes the variation characteristics of the source ruptures and the P-axis azimuths of small earthquakes around the seismic zones before four strong earthquakes occurring since 2003 in the western part of north Tianshan and the middle part of Tianshan. The result shows that 2 ~ 3 years before the strong earthquakes,the focal mechanism types of small earthquakes are distributed randomly, and obvious dominant distributions are observed one year before the strong earthquakes. There are obvious changes in the P-axis azimuth.

Features of rainfall and latent heating structure simulated by two convective parameterization schemes

Using the latest version of SAMIL (Spectral Atmosphere Model of IAP LASG) developed by LASG/IAP,we evaluate the model performance by analyzing rainfall,latent heating structure and other basic fields with two different convective parameterization schemes:Manabe Scheme and Tiedtke Scheme.Results show that convective precipitation is excessively overestimated while stratiform precipitation is underestimated by Tiedtke scheme,thus causing less stratiform rainfall proportion compared with TRMM observation.In contrast,for Manabe scheme stratiform rainfall belt is well simulated,although precipitation center near Bay of Bengal (BOB) spreads eastward and northward associated with unrealistic strong rainfall downstream of the Tibet Plateau.The simulated latent heating structure indicates that Tiedtke scheme has an advantage over Manabe scheme,as the maximum convective latent heating near middle of troposphere is well reproduced.Moreover,the stratiform latent heating structure is also well simulated by Tiedtke scheme with warming above freezing level and cooling beneath freezing level.As for Manabe scheme,the simulated maximum convective latent heating lies near 700 hPa,lower than the observation.Additionally,the warming due to stratiform latent heating extends to the whole vertical levels,which is unreasonable compared with observation.Taylor diagram further indicates that Tiedtke scheme is superior to Manabe scheme as higher correlation between model output and observation data is achieved when Tiedtke scheme is employed,especially for the temperature near 200 hPa.Finally,a possible explanation is addressed for the unrealistic stratiform rainfall by Tiedtke scheme,which is due to the neglect of detrained cloud water and cloud ice during convective process.The speculation is verified through an established sensitivity experiment.