磁场效应的火车道报警信息采集系统设计

本文设计了一种基于磁场效应的火车道报警信息采集系统,对该系统的硬件结构和软件设计分别进行了介绍。最后给出了实验结果。实验结果表明,该系统工作稳定,可有效的判断火车的到来,从而给出相关的报警信息。

一杯咖啡背后的拓扑

日常喝咖啡,可以使我们感悟到奇妙的拓扑学原理。我们均匀搅拌咖啡,咖啡静止后会有一个分子回到初始位置,这是经典的布劳威尔不动点定理,我们用代数拓扑的方法加以证明;咖啡拉花经过搅拌后变得愈发复杂,但是咖啡拉花的抽象模式保持不变,这反映了曲面同胚映射的动力学特性,可以用泰希米勒空间和布劳威尔不动点定理加以证明。

Effect of two-channel gastric electrical stimulation with trains of pulses on gastric motility

AIM： To investigate the effect of two-channel gastric electrical stimulation （GES） with trains of pulses on gastric emptying and slow waves.METHODS： Seven dogs implanted with four pairs of electrodes and equipped with a duodenal cannula were involved in this study. Two experiments were performed.The first experiment included a series of sessions in the fasting state with trains of short or long pulses, each lasted 10 min. A 5-min recording without pacing was made between two sessions. The second experiment was performed in three sessions （control, single-channel GES, and two-channel GES）. The stimulus was applied via the 1st pair of electrodes for single-channel GES （GES via one pair of electrodes located at 14 cm above the pylorus）, and simultaneously via the 1st and 3rd channels for two-channel GES （GES via two pairs of electrodes located at 6 and 14 cm above the pylorus）, Gastric liquid emptying was collected every 15 min via the cannula for 90 min.RESULTS： GES with trains of pulses at a pulse width of 4 ms or higher was able to entrain gastric slow waves. Two-channel GES was about 50% more efficient than single-channel GES in entraining gastric slow waves. Two-channel but not single-channel GES with trains of pulses was capable of accelerating gastric emptying in healthy dogs. Compared with the control session, two-channel GES significantly increased gastric emptying of liquids at 15 rain （79.0% ± 6.4% vs 61.3% ± 6.1%, P 〈 0.01）, 30 min （83.2% ± 6.3 % vs 68.2% ± 6.9%, P 〈 0.01）, 60 min （86.9% ± 5.5 % vs 74.1% ± 5.9%, P 〈 0.01）, and 90 rain （91.0% ± 3.4% vs 76.5% ± 5.9%, P 〈 0.01）.CONCLUSION： Two-channel GES with trains of pulses accelerates gastric emptying in healthy dogs and may have a therapeutic potential for the treatment of gastric motility disorders.

A Control Simulation Method of High-Speed Trains on Railway Network with Irregular Influence

Based on the discrete time method, an effective movement control model is designed for a group of high- speed trains on a rail network. The purpose of the model is to investigate the specific traffic characteristics of high-speed trains under the interruption of stochastic irregular events. In the model, the high-speed rail traffic system is supposed to be equipped with the moving-block signalling system to guarantee maximum traversing capacity of the railway. To keep the safety of trains＇ movements, some operational strategies are proposed to control the movements of trains in the model, including traction operation, braking operation, and entering-station operation. The numerical simulations show that the designed model can well describe the movements of high-speed trains on the rail network. The research results can provide the useful information not only for investigating the propagation features of relevant delays under the irregular disturbance but also for rerouting and reseheduling trains on the rail network.

Estimation of Knock Wheel Noise of Rail Transport with an Acoustic Intensity Method

The application of railway wheel noise compensation method is considered. The effect can be obtained by shift a pair of usual parallel rail joints on a pair of offset rail joints, for example, the right rail joint is shifted concerning the left rail joint on the certain distance. The distance is depend on the speed of train and promotes the correlation interconnection between excited acoustical pulses. The intensity wheel knock spectrograms corresponding of different distance between rail joints registered by the microphone are estimated. The spectrograms considerably differed from each other in low frequency band are analyzed. The result of practical using the acoustic noise compensation method is proved.

Unsteady simulation for a high-speed train entering a tunnel

In order to study the unsteady aerodynamics effects in railway tunnels,the 3D Reynolds average Navier-Stokes equations of a viscous compressible fluid are solved,and the two-equation k-ε model is used in the simulation of turbulence,while the dynamic grid technique is employed for moving bodies.We focus on obtaining the changing tendencies of the aerodynamic force of the train and the aerodynamic pressures on the tunnel wall and train surface,and discovering the relationship between the velocity of the train and the intensity of the micro pressure wave at the tunnel exit.It is shown that the amplitudes of the pressure changes in the tunnel and on the train surface are both approximately proportional to the square of the train speed,so are the microwave and the drag of the train.

Seismic stability of loess tunnels under the effects of rain seepage and a train load

Loess tunnels are widely used in transportation engineering and are irreplaceable parts of transportation infrastructure. In this paper, a dynamic finite element method is used to analyze the coupled effects of a train vibration load and rainfall seepage. By calculating the variation in the safety factor of a loess tunnel because of the effects of various factors, such as different rainfall intensities and soil thicknesses, the dynamic stability of the loess tunnel is studied under the condition of a near-field pulse-like earthquake. The results show that the security and stability of the tunnel decrease gradually with decreasing burial depth. In addition, the plastic strain of the tunnel is mainly distributed on both sides of the vault and the feet, and the maximum value of the critical strain occurs on both sides of the arch feet. Because of the effects of the train vibration load and rainfall seepage, the safety factor of the loess tunnel structure decreases to a certain degree. Moreover, the range and maximum value of the plastic strain increase to various degrees.