Interaction of subway LIM vehicle with ballasted track in polygonal wheel wear development

This paper develops a coupled dynamics model for a linear induction motor (LIM) vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen- Hedrick-Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system (LMS), Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.     

Synthesis of a New Cerebroside Isolated from Typhonium giganteum Engl

The stereoselecfive synthesis of typhoniside, a new cerebroside isolated from Typhonium giganteum Engl. was accomplished.Cerebrosides are a kind of glycolipids highly enriched on the surface of myelin-producing cells and are composed by C18-4,8-sphingadienine, a-hydroxy acid and a saccharide head. It was the first time that cerebrosides were isolated from this traditional Chinese medicine (TCM) by us. In this paper, C18-4,8-sphingadienine was synthesized from D-xylose via a SN2 type reaction, α-Hydroxy acid was prepared from (R)-4-hydroxyte-trahydrofuran-2-one, which in turn could be obtained from Lascorbic acid.     

Synthesis,Crystal Structure,Theoretical Studies and Sensitive Response toward Fe~(3+) of a Novel Tripyrazole Derivative Ligand

A novel pyrazole derivative ligand, BTA(BTA = bis-(4-ethoxy-phenyl)-[4-(tripyrazol-1-yl-methyl)-phenyl]-amine), was synthesized and fully characterized by 1H-NMR, MALDI-TOF-MS spectra and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P1, with a = 11.827(1), b = 16.000(2), c = 16.527(2), α = 108.510(1), β = 91.116(5), γ = 101.734(1)°, V = 2894.5(6) 3, Z = 1, Dc = 1.262 g/m3, F(000) = 1162, Μr = 545.63, μ = 0.083 mm-1, the final R = 0.0728 and w R = 0.2213 for 7541 observed reflections with I 2(I). The structural analysis revealed that three pyrazole units are attached to the same carbon atom connected with bis-(4-ethoxy-phenyl)-phenyl-amine group. UV-vis spectral features of the ligand in various solutions were explained by time dependent density functional theory(TD-DFT). It was also found that the ligand(BTA) exhibits an exclusively selective and sensitive response toward Fe3+ using UV-vis spectroscopic method.     

On analytic formulas of Feynman propagators in position space

We correct an inaccurate result of previous work on the Feynman propagator in position space of a free Dirac field in(3+1)-dimensional spacetime; we derive the generalized analytic formulas of both the scalar Feynman propagator and the spinor Feynman propagator in position space in arbitrary(D+1)-dimensional spacetime; and we further find a recurrence relation among the spinor Feynman propagator in(D+l)-dimensional spacetime and the scalar Feynman propagators in(D+1)-,(D-1)-and(D+3)-dimensional spacetimes.     

The Near Surface Morphology of P3HT：PCBM Blend Films Studied by Near-Edge X-Ray Absorption Fine Structure

The microstructure of poly（3-hexylthiophene） （P3HT） and [6,6]-phenyl-C61 butyric acid methyl ester （PCBM） blends with various annealing temperatures are investigated in detail by the near-edge x-ray absorption fine structure. Under higher anneMing temperature （Tanneal ≥ 160℃）, P3HT shows an unusual fluidity and aggregation in the surface. After annealing, the enrichment polymer component recrystallizes and forms a single P3HT phase layer in the surface of blend films. Moreover, it gives direct evidence of the PCBM content diffusing to the near surface of blend films during annealing treatment. These findings are beneficial to improving the morphology of polymer/fullerene blend films.     

线性规划中一个避免人工变元的方法的改进

有许多文献讨论了线性规划问题中单纯形方法的改进(如文献[1～5]等)。我们在文献[1]的基础上,突破了传统方法中要求单纯形表中的基变量始终非负的想法,给出了求解线性规划问题中一个新的避免人工变量的方法,使其计算量得到减少。     

A new lignan from the leaves of <Emphasis Type="Italic">Loropetalum chinensis</Emphasis>

Investigation on the EtOH extract of the leaves of Loropetalum chinensis led to the isolation of seven compounds (1–7). Their structures were identified using spectroscopic methods. Among these compounds, compound 1 is a new lignan, and 2–7 were isolated from this plant for the first time.     

Development of a simulation model for dynamic derailment analysis of high-speed trains

The running safety of high-speed trains has become a major concern of the current railway research with the rapid development of high-speed railways around the world.The basic safety requirement is to prevent the derailment.The root causes of the dynamic derailment of highspeed trains operating in severe environments are not easy to identify using the field tests or laboratory experiments.Numerical simulation using an advanced train–track interaction model is a highly efficient and low-cost approach to investigate the dynamic derailment behavior and mechanism of high-speed trains.This paper presents a three-dimensional dynamic model of a high-speed train coupled with a ballast track for dynamic derailment analysis.The model considers a train composed of multiple vehicles and the nonlinear inter-vehicle connections.The ballast track model consists of rails,fastenings,sleepers,ballasts,and roadbed,which are modeled by Euler beams,nonlinear spring-damper elements,equivalent ballast bodies,and continuous viscoelastic elements,in which the modal superposition method was used to reduce the order of the partial differential equations of Euler beams.The commonly used derailment safety assessment criteria around the world are embedded in the simulation model.The train–track model was then used to investigate the dynamic derailment responses of a high-speed train passing over a buckled track,in which the derailmentmechanism and train running posture during the dynamic derailment process were analyzed in detail.The effects of train and track modelling on dynamic derailment analysis were also discussed.The numerical results indicate that the train and track modelling options have a significant effect on the dynamic derailment analysis.The inter-vehicle impacts and the track flexibility and nonlinearity should be considered in the dynamic derailment simulations.     

Investigating the temperature dependence of elastic constants by thermal fluctuation formula

The differences between the calculated values of elastic constants of materials and the experimental data are consistently restricting the application of thermal fluctuation formula to the mechanical properties of materials. In this work, the temperature dependence of elastic constants of many-body potentials is studied by thermal fluctuation formula. The differences between the calculated values and the experimental data are investigated in detail. Our studies show that the differences come from the thermal expansion of the materials: the calculated zero-stress states are bigger than the experimental zero-stress states of the materials, and this deviation makes Born terms of the thermal fluctuation formula decrease sharply as the temperature increases, while the fluctuation terms and the kinetic terms change little. As a result, the elastic constants, which are the sum of these three terms, decrease faster than the experimental data as the temperature increases. Our studies show that when the experimental zero-stress states are used as the reference states in constant volume and constant energy (NVE) simulations, the elastic constants calculated by thermal fluctuation formula are in good agreement with the experimental values.     

几个新组合恒等式及其应用

得到四个新的组合恒等式,由此给出文献[1]中的一个结论的初等证明.