考虑经验驾驶行为的入弯实时类人速度规划方法

为提高自动驾驶汽车的安全性、舒适性与通行效率,提出了一种考虑到滑行及安全速度的类人入弯速度规划策略。该策略基于混沌优化理论与实车弯道行驶速度数据,通过将车辆的入弯速度规划问题构建为多目标优化问题,建立了舒适模式与效率模式。通过定义奇点速度,简化了非线性高阶约束条件。结果表明:在该策略规划中,在不同弯道场景下,横向加速度和纵向加速度均在摩擦圆约束内,可保证车辆的行驶安全。相比于未考虑滑行的方法,在舒适模式下,该策略产生的纵向加速度减小9.76%,通行效率提高61.73%;在效率模式中,纵向加速度为加速度阈值,满足加速度约束,通行效率提高88%。因而,无论舒适模式还是效率模式,该方法均可兼顾舒适性和通行效率。

女子短道速滑运动员入弯与出弯躯干角度的运动学研究

运用影像测量法,对高水平运动员入弯与出弯蹬冰技术的动作结构规律进行研究,旨在为确立正确的入弯与出弯道蹬冰技术概念提供参考。

对吉林省青年男子速度轮滑运动员入弯与出弯技术的运动学分析

运用Simi motion生物力学分析系统对吉林省3名青年男子速度轮滑运动员入弯技术与出弯技术进行动作解析,通过运动生物力学理论参数进行分析,得出运动员入弯阶段与出弯阶段运动学特征,主要是身体倾斜角度和速度以及重心轨迹的变化。得出入弯时的速度没有出弯时的速度快但入弯阶段运动员身体起伏变化频率比出弯阶段快。

基于视觉的智能车转向控制策略

在第三届全国大学生"飞思卡尔"智能车大赛参赛过程中,对提前入弯理论的提出与实践的一个总结。该策略是在获取赛道实时图像的基础上,提取引导线信息,通过对舵机理想模型的分析,创新性地利用实时检测的速度动态地改变入弯点,实现提前入弯策略,控制转向舵机,使之达到较为完美的转弯特性。实验表明,该方法提高了舵机的动态性能,实现了智能车过弯路径的最优,最终平均车速达到2m/s,入弯最大速度达到2.4m/s,弯道平均速度达到1.5m/s,满足全程高速状态的要求。

Deterioration mechanism and rapid detection of performances of an existing subgrade in southern China

To relieve the increasing traffic load, many early built highways need to be widened or reconstructed. The rapid performance detection to existing subgrades is important to their reasonable evaluation and maximized utilization. Based on five kinds of soils taken from an existing highway in southern China, three commonly detecting methods were used to determine their moisture contents, compaction degrees and resilient moduli. The results showed that the measured moisture contents were greater than the design value, and the compaction degrees decreased sharply compared to the original ones. The moisture and heat exchange produced a decrease in the resilient modulus of plate loading test(PLT) from the standard 60 MPa down to 40 MPa. Afterwards, the portable falling weight deflectometer(PFWD) and dynamic cone penetrometer(DCP) were used to evaluate the subgrade performances. The measured PFWD moduli and the DCP penetration rates were correlated with the resilient moduli of PLT, deflections of the Beckman beam test, compaction degrees and moisture contents. The correlation analysis indicates that both of two methods are suitable in rapid detecting subgrade performances, but PFWD method is more recommended for it has higher accuracy and efficiency.

“Passive-bending colonoscope”significantly improves cecal intubation in difficult cases

Colonoscopy sometimes causes pain during insertion,especially in difficult cases.Over-insufflation of air causes elongation or acute angulations of the colon,making passage of the scope difficult and causing pain.We previously reported a sedative-risk-free colonoscopy insertion technique,namely,"Water Navigation Colonoscopy".Complete air suction after water infusion not only improves the vision,but also makes water flow down to the descending colon,while the sigmoid colon collapses and shortens.While non-sedative colonoscopy can be carried out without pain in most cases,some patients do complain of pain.Most of these patients have abnormal colon morphology,and the pain is caused while negotiating the "hairpin" bends of the colon.The "hairpin" bends of the colon should be negotiated by gently pushing the full-angled colonoscope.The proximal 10-20 cm from the angulated part of the conventional colonoscope is stiff,with a wide turning radius,therefore,a conventional colonoscope cannot be negotiated through the "hairpin" bends of the colon without stretching them and causing pain.The "passive-bending colonoscope" has a flexible tip with a narrow turning radius,so that the scope can be negotiated through the "hairpin" bends of the colon with a minimum turning radius and minimal discomfort.Therefore,the intubation and pain-reducing performance of the "passive-bending colonoscope" was assessed in difficult cases.

Influence factors on stress corrosion cracking of P 110 tubing steel under CO2 injection well annulus environment

Stress corrosion cracking （SCC） behavior of P 110 tubing steel in simulated C02 injection well annulus environments was investigated through three-point bent tests, potentiodynamic polarization and EIS measurements. The results demonstrate that SCC of P110 tubing steel could occur in acidulous simulated environment, and the sensitivity of SCC increases with the decrease ofpH, as well as increase of sulfide concentration and total environmental pressure. Both anodic dissolution and hydrogen embrittlement make contributions to the SCC. Adequate concentration of corrosion inhibitor can inhibit the occurrence of SCC on account of the inhibition of localized anodic dissolution and cathodic hydrogen evolution.

S弯进气道出口畸变对风扇性能影响研究

为了研究某半埋入式S弯进气道出口畸变对其后风扇级性能的影响,分别将其原型及优化后模型与风扇级对接进行进气道加风扇级全流道数值研究。结果表明:全周畸变条件下,风扇级效率及增压比相比均匀进气工况明显下降,堵塞流量下降约1.20%,最高效率下降约3.77%;优化后风扇稳定工作范围有较大幅度提升,堵塞流量增加约0.19%,效率最大值增加约0.23%;受动叶旋转影响,进气道出口截面底部显著低能流体区在发展至动叶前缘的过程中逐渐减小,畸变流体与非畸变流体出现相互掺杂趋势,且这一现象在进气道优化前后始终存在。

Extreme transmission of elastic metasurface for deep subwavelength focusing

In this paper,elastic metasurfaces composed of zigzag units are proposed to manipulate flexural waves at a deep subwavelength scale.Through the parameter optimization of the genetic algorithm,units with full transmission and full phase control can be found,while the width is only one-fifth of the wavelength.The outstanding capability of the units is explained by analyzing.their wave fields.The flat and the curved metasurfaces for focusing are designed and simulated,showing excellent performance.Experimental results of the flat metasurface show that the incident wave energy at the focal point is enhanced over 6 times,verifying the simulation results.The proposed metasurfaces could be useful in the design of.compact and efficient elastic devices.