Multi-point Contact of the High-speed Vehicle-turnout System Dynamics

The wheel-rail contact problems, such as the number, location and the track of contact patches, are very important for optimizing the spatial structure of the rails and lowering the vehicle-turnout system dynamics. However, the above problems are not well solved currently because of having the difficulties in how to determine the multi-contact, to preciously present the changeable profiles of the rails and to establish an accurate spatial turnout system dynamics model. Based on a high-speed vehicle-turnout coupled model in which the track is modeled as flexible with rails and sleepers represented by beams, the line tracing extreme point method is introduced to investigate the wheel-rail multiple contact conditions and the key sections of the blade rail, longer nose rail, shorter rail in the switch and nose rail area are discretized to represent the varying profiles of rails in the turnout. The dynamic interaction between the vehicle and turnout is simulated for cases of the vehicle divergently passing the turnout and the multi-point contact is obtained. The tracks of the contact patches on the top of the rails are presented and the wheel-rail impact forces are offered in comparison with the contact patches transference on the rails. The numerical simulation results indicate that the length of two-point contact occurrence of a worn wheel profile and rails is longer than that of the new wheel profile and rails; The two-point contact definitely occurs in the switch and crossing area. Generally, three-point contact doesn’t occur for the new rail profile, which is testified by the wheel-rails interpolation distance and the first order derivative function of the tracing line extreme points. The presented research is not only helpful to optimize the structure of the turnout, but also useful to lower the dynamics of the high speed vehicle-turnout system.

Necking Point in PET High-speed Fiber Spinning

Cross-over method is established to predict necking point for PET high- speed fiber spinning. Even slowly crystallizing polymers such as PET can crystallize on the spinline at sufficiently high spinning speed. The development of rtmning velocity, temperature, crystallinity and theological force is investigated for the take-up velocity over a range of 6 000 - 10 000 m/min. The position of necking point, temperature rise and abrupt increase of crystallinity move closer to the spinneret with the increase of take-up velocity,

Excel和Power Point在物理实验中的应用

物理实验离不开填表、计算和作图,我们利用Excel进行快速填充表格和快速计算;Power Point具有田字型虚线网格线,即坐标纸,且可根据需要调整网格的大小,使得作图快速准确,从而,提高物理实验的质量.

Frequency-Speed Control Model Identification of Ultrasonic Motor Using Step Response

Control model of ultrasonic motor is the foundation for high control performance.The frequency of driving voltage is commonly used as control variable in the speed control system of ultrasonic motor.Speed control model with the input frequency can significantly improve speed control performance.Step response of rotating speed is tested.Then,the transfer function model is identified through characteristic point method.Considering time-varying characteristics of the model parameters,the variables are fitted with frequency and speed as the independent variables,and the variable model of ultrasonic motor system is obtained,with consideration of the nonlinearity of ultrasonic motor system.The proposed model can be used in the design and analysis of the speed control system in ultrasonic motor.

Positioning performance analysis on combined GPS/BDS precise point positioning

Combining the observation data from five Multi-GNSS Experiment(MGEX)stations with the precise orbit and clock products from Global Positioning System(GPS)and BeiDou Navigation Satellite System(BDS),we studied the model of combined GPS/BDS precise point positioning,and then analyzed the convergence speed and short-time(6 h)positioning accuracy.The calculation results show that in static positioning,the average convergence time of GPS is about 50 min,and its horizontal accuracy is better than 2 cm while the vertical accuracy is better than 4 cm.The convergence speed of combined GPS/BDS is about 40 min,and its positioning accuracy is close to that of GPS.In kinematic positioning,the average convergence time of GPS is about 72 min,and its horizontal accuracy is better than 5 cm while the vertical accuracy is better than 12 cm.The average convergence time of GPS/BDS is about 57 min,and its horizontal accuracy is better than 3 cm while the vertical accuracy is better than 9 cm.Combined GPS/BDS has significantly improved the convergence speed,and its positioning accuracy is slightly than that of GPS.

Urban Wind Speed Analysis in Global Climate Change Perspective: <i>Karachi as a Case Study</i>

It is now well known that coastal urban local climate has been showing changing pattern due to global climate change. This communication attempts to explore fluctuating pattern of urban average monthly wind speed during past 50 years (1961-2010). It shows peculiar results taking Karachi (24?53'N, 67?00'E), a coastal mega-city of Pakistan, as a case study. Mann-Kendall trend test shows that March, April and October and both summer and winter seasons show positive trends for the average monthly wind speed during the whole study period (1961-2010). For the earlier 25 years data, it has been found that January, March, May, August, November and December and annual wind speed data have shown the negative trends. Only summer season has shown the positive trend for the wind speed. Similarly, for the most recent 25 years data it has been found that January, February, March, April, May, June, October, November and December and annual and both summer and winter wind speed data have shown the positive trends showing some degree of change in wind speed pattern. Probabilistic analysis reveals that average monthly wind speed data sets follow lognormal, logistic, largest extreme value, and Weibull (two-and three-parameters) probability distributions. Change point analysis has also confirmed the change in the pattern of observed average monthly wind speed data near 1992. The analysis performed reveals the effect of global warming on the local urban wind speed which appears to be temporal non-stationary.

煤巷掘进过程中煤岩破裂微震事件研究

目的为了监测和预警煤矿掘进巷道前方可能发生的危险,方法利用微震监测技术实时监测,利用监测系统捕获到的数据信息研究掘进影响下微震事件的空间分布规律、发生时间、频次和能量关键点,然后利用短时傅里叶变换和S变换方法分析典型煤岩破裂微震信号的时频特征。结果结果表明:(1)微震事件主要分布在沿掘进巷道前方50~100 m区域,大多为中低能量微震事件,仅在掘进工作面前方出现少量强度较大的煤岩破裂事件,且震级多为-2~0;(2)掘进速度和发生微震事件的数量及能量大小成正相关,同时掘进速度也影响着煤岩动力灾害的发生;(3)巷道掘进会造成煤岩体失稳,其中岩体破裂信号频率高,为0~2000 Hz,比重值大,主频约700 Hz;煤岩破裂微震事件信号频率为90~1000 Hz,主频约250 Hz;岩体破裂后,支撑力下降,压力转移给煤体,导致煤体破裂,煤体破裂微震事件信号频率为90~1000 Hz,主频约350 Hz。结论微震事件能够综合反映煤岩体受力破坏程度,判别掘进过程中煤岩破裂类型,为矿井生产中煤岩动力灾害的预警提供理论基础。

不同跑步速度对大鼠股骨皮质骨组织失效应变的影响

目的 预测皮质骨组织失效应变,探究不同跑步速度对大鼠股骨皮质骨力学性能的影响。方法 设定皮质骨材料失效应变阈值,针对大鼠股骨有限元模型进行三点弯曲下的断裂模拟,将每次预测所得载荷-位移曲线与同一样本实验曲线进行比较拟合,以此反演预测组织失效应变。结果 皮质骨组织失效应变在不同跑步速度下存在显著差异,说明不同跑步速度对皮质骨结构微观力学性能产生一定影响。其中组织失效应变在以12 m/min速度跑步中最大,在以20 m/min速度跑步中最小。结论 通过观测组织失效应变变化趋势,并结合皮质骨结构的宏观断裂载荷与纳观组织弹性模量变化趋势,探讨不同跑步速度对皮质骨结构力学性能的综合影响,并找到有利于提升皮质骨力学性能的跑步速度,为通过跑步锻炼提高骨强度提供理论依据。

关于高铁地震波场虚拟道集生成的理论分析

中国约80%的高铁运行于高架桥上,高铁振动通过桥墩传入地面.本文对运行于等间隔桥墩的高架桥上高铁振动产生的地下地震波场形态进行了理论分析,根据其在特定方向形成相干相位稳相点区域的特征,设计了一种基于多个不同速度高铁列车振动记录叠加,分离单桥墩激发虚拟地震波场的方法,并对单层与多层介质的情形进行了理论验证.

基于偏移补偿模型的大曲率复杂芯模编织牵引轨迹优化控制方法

针对大曲率复杂芯模编织过程中机器人示教困难、织物编织角不稳定等问题,提出一种基于偏移补偿模型的编织牵引轨迹优化控制方法。首先基于不稳定编织阶段收敛距离的变换,建立预成型编织点预测模型;其次对芯模进行离散化处理,调整每一段离散芯模的轴线垂直通过动态编织点平面,修正每段芯模编织进给长度,利用芯模变截面过程的不稳定编织阶段进行芯模姿态调整,同时调整不稳定阶段牵引速度以更快达到稳定编织状态。试验结果表明,该轨迹优化方法能有效避免大曲率复杂芯模预成型体的纱线堆积和编织角波动范围大的问题,能够提高预成型体编织质量。

改进差分进化的光伏最大功率点跟踪

针对现有差分进化算法在局部遮阴情况下跟踪速度慢的问题,提出一种新的改进差分进化算法的光伏发电系统最大功率点跟踪控制策略。首先,引入三角突变策略,并将其嵌入传统差分进化算法的交叉公式当中,避免因迭代前后输出相同的占空比造成重复采样功率的情况。其次,引入自适应比例因子策略,以加强个体的收敛性。最后,通过奖励惩罚机制平衡所提算法的全局开发和局部探索能力。仿真结果表明,与对比文献的差分进化算法相比,改进算法在跟踪速度、稳定性方面具有显著的优势。

基于分类配准与全景像素坐标系的显微图像快速拼接算法

目的提出一种基于分类配准与全景像素坐标系的显微图像实时拼接算法,以解决现有图像拼接算法精度低、计算复杂度高等问题。方法依据单视野图像的质量特征,利用评价函数对图像进行分类配准,适应不同的配准模型;构建全景像素坐标系,依据配准结果在此坐标系下进行整体拼接与缝隙融合;基于自主搭建的尿液样本显微扫描系统进行实验,以验证算法的有效性。结果实验结果表明,相比现有的图像拼接方法,本文基于分类配准与全景像素坐标系的显微图像快速拼接算法更有利于拼接缝隙的融合,且更稳定,拼接效果显著优于加速鲁棒特征和快速傅里叶变换单独拼接;在拼接时间方面,基于分类配准与全景像素坐标系的显微图像实时拼接算法的拼接时间大大缩短,拼接速度提升了1倍,且对于矩形扫描区域拼接的大视野图像,无明显拼接缝隙痕迹,可完成高质量的实时拼接。结论基于分类配准与全景像素坐标系的显微图像快速拼接算法能够满足快速高分辨率的大视野图像拼接需求,为显微图像拼接提供了一种更优的方法,便于相关人员进一步分析和应用。

基于IB-SURF算法的无人机图像拼接技术研究

针对传统SURF算法(speeded up robust features)在拼接高分辨率无人机航拍图像时运行速度慢、特征匹配率低的特点,提出了一种基于IB-SURF(image block-SURF)技术的无人机图像拼接算法。结合无人机定位定姿系统(position and orientation system,POS)求取图像重叠区域;构造掩模在无人机图像重叠区域检测特征点,减少特征提取时间;借助图像分块(image block,IB)的思想对图像划分网格,精简筛选特征点;引入Neighborhood-KNN(neighborhood-K nearest neighbors)进行特征点匹配,提高图像匹配效率。实验结果表明,IB-SURF算法有较快的运行速度和较高的特征匹配率,平均特征匹配率达到84.3%,特征匹配正确率超过95.1%,为图像高质量拼接提供了技术基础。

C型料场刮板机取料速度控制方法与系统开发

在C型料场刮板机自动化作业过程中,取料过快经常导致刮板机跳闸故障,取料过慢会导致供料不足、效率低等问题。对此,本文提出一种基于点云模型的C型料场刮板机取料速度控制方法,并在某C型料场现场试验验证,该控制方法步骤:(1)获取料堆点云数据和形状,将其转换为高度灰阶图,并采用一种新型点云过滤算法降低其噪声、提高平滑度;(2)基于刮板机链板恒定条件建立物料流量模型,结合能量转换构建刮板机电流-速度模型,将模型结果实时写入刮板机PLC中,进而实时控制刮板机取料速度。结果表明:使用该模型,料堆点云模型的内存资源降低98.64%,点与点之间形成有效的拓扑关系,计算的复杂度降低,料堆点云模型的平滑度显著提高;刮板机作业时料流的流量波动在8.29%内,刮板机的设备故障率减少5.24%,生产效率提高9.68%。本文提出的取料速度控制方法可用于替代人工调节刮板机的取料速度,减少刮板机的作业故障,提高生产效率,有效提高设备的无人化、智能化水平,并可为各种刮板机取料速度控制与作业稳定性控制提供参考。

高速铁路无缝道岔天窗点内应力放散施工技术

无缝道岔铺设应当保证施工锁定轨温在设计规定的允许范围内,如超出设计锁定轨温上限或下限则应进行应力放散。道岔与线路不一致情况为道岔辙叉位置固定,原则上不进行拉伸放散。在夏季道岔铺设时可利用夜间在合适轨温下进行自然放散,在冬季铺设时受环境温度影响最高轨温无法达到设计轨温,而部分车站受联调及开通等因素影响,需在开通后进行天窗点内自然放散。结合北京丰台站京港高速场受征拆影响,高架平台于2022年1月才完成混凝土浇筑,道岔铺设是在低温季节铺设,无法达到设计锁定轨温,采取临时轨温锁定,在联调期内随环境温度、轨温上升至设计锁定轨温后,利用联调联锁期间天窗点对道岔进行自然放散,最终达到设计锁定轨温。

基于SURF-OKG特征匹配的三维重建技术

为了解决结构光三维重建中传统立体匹配存在的特征点匹配错误、匹配缺失和匹配重复等问题,本文将SURF算法中高斯滤波改进为自适应中值滤波结合小波变换,并提出了一种基于OKG算法的二次特征匹配方法。该算法首先使用自适应中值滤波结合小波变换算法对图像进行平滑和降噪处理,再进行初步特征点提取和匹配,然后将构建的尺度空间划分成多个网格,在每个网格内使用FAST算法提取尺度空间特征点,使用ORB算子提取左右图像的特征点,用BRIEF描述子对其进行描述,采用K-D树最近邻搜索法限制特征点选取,通过GMS算法剔除误匹配点。最后,将本文SURF-OKG算法与传统特征匹配算法进行对比分析,并对阶梯块进行三维重建来验证本文算法的有效性。实验结果表明:SURF-OKG算法的正确匹配率为92.47%;对阶梯宽度为40 mm,精度为0.02 mm的阶梯块进行三维重建,实验测得阶梯宽度的误差均值为1.312 mm,最大误差值不超过1.72 mm,基本满足结构光三维重建系统的实验要求。

高速摄像在某强冲击试验中的试验弹测速应用研究

为了提高强冲击试验的试验弹测速有效性与精度,本文设计了高速摄像试验弹测速方案测量试验弹冲击前的速度。依据试验条件进行了关键设备选型并搭建了高速摄像测速系统,利用有限脉冲响应(Finite impulse response,FIR)滤波器并选取不同滤波器半长进行速度分析计算,通过“四点矫正法”解决了图像倾斜畸变。将测速结果与传统的激光测速结果进行比对,二者测试结果高度吻合(相对误差在0.5%以内)。最后由测速系统分析的3组连续出口速度证明了该强冲击试验系统具备提供稳定速度的能力。

基于改进麻雀搜索算法分数阶PI的PMSM调速策略

永磁同步电机调速系统采用传统比例积分双闭环控制结构存在抗扰性能差与响应速度慢的问题。为此,文中在建立PMSM数学模型和分析传统PI参数设计方法的基础上,提出一种基于改进麻雀搜索算法分数阶比例积分的PMSM调速优化策略,通过在常规SSA中引入佳点集初始化策略和黄金正弦更新策略,解决了SSA易陷入局部最优的问题,提高了收敛速度和精度,以进一步改善PMSM调速系统的响应性能。最后通过MATLAB仿真对比结果可知,所述ISSA-FOPI调速改进策略在4种工况下具有最短的调节时间分别为1.2、0.9、9.9与12.1 ms,和最小的超调量分别为0.16%、0.16%、0.05%与0.6%,这充分体现了所述策略的有效性与优越性。

汽轮机组TSI系统转速监控点调试和故障处理对策

针对现有汽轮机组TSI系统在转速监测与故障处理方面中存在的问题,如人工操作繁琐、转速信号丢失、转速测量不准确及缺乏自动化故障检测与报警等,阐述了TSI系统在汽轮机组中的作用与重要性,深入探讨TSI系统转速监控点调试,包括转速监控点的选择与布置、传感器选择与安装及自动化调试方法,在此基础上给出一些有效的转速监控点故障处理对策,以期提高汽轮机组的可靠性与运行效率。