新型车载油气回收装置设计

针对某液封式车载油气回收装置(ORVR)存在的缺陷进行了分析,提出了新型ORVR的技术方案,并设计了新型ORVR.试验结果表明,新型OVER加油枪可自动关闭而不受油气压力变化的影响,在加满油前不会出现提前停喷的现象,且油气压力的升高比较平缓,加油管内的燃油不会反溅向加油者;采用新型ORVR后汽车的加油排放量相对减少,加油排放的控制更加安全可靠.     

Climate change mitigation and co-benefits of feasible transport demand policies in Beijing

Urban car transportation is a cause of climate change but is also associated with additional burdens such as traffic congestion and air pollution. Studies of external costs and potential impacts of travel demand management help to define policy instruments that mitigate the damaging impact of transportation. Here, we analyze different externalities of car transportation in Beijing and show that social costs induced by motorized transportation are equivalent to about 7.5–15.0% of Beijing’s GDP. Congestion and air pollution contribute the most with climate change costs being the most uncertain. We show that a road charge could not only address congestion but also has environmental benefits. The paper investigates the role of demand elasticities and demonstrates that joint demand and supply-side policies provide considerable synergies.     

Influence of slip boundary on flow separation and drag of flow past bluff body at high Reynolds numbers北大核心CSCD

［Objectives］Flow separation increases the drag and noise of underwater vehicles, and influences the controllability of their control surfaces. Therefore, the influence of slip caused by superhydrophobic surfaces on drag reduction and flow separation is studied. ［Methods］A partial slip boundary condition is developed, and the flow around a circular cylinder and foil with a slip boundary at high Reynolds numbers are numerically simulated. ［Results］The results show that the when the slip length increases, the flow around the cylinder goes through three stages: the turbulent Kármán vortex street, laminar Kármán vortex street and non-separation Stokes flow. The drag coefficient increases first and then decreases, and the vortex shedding frequency increases. For flow around a foil, the separation position moves downstream until the separation region disappears when the slip length increases, and the drag coefficient decreases while the lift coefficient increases. ［Conclusions］The results of this study show that for flow past bluff body at high Reynolds number, the slip boundary can control flow separation and reduce drag effectively, providing technical support for the application of superhydrophobic surfaces for the flow control of underwater vehicle appendages. © 2022 Journal of Clinical Hepatology. All rights reserved.     

锌铝镁镀层钢板化学转化膜耐蚀性能研究

采用扫描电子显微镜(SEM)、能谱分析仪(EDS)研究了锌铝镁镀层钢板合金的化学转化膜形貌和元素组成。以热镀锌钢板和冷轧钢板作为比较对象,通过电化学工作站、中性盐雾试验箱对3种合金的腐蚀行为进行对比研究。结果表明,锌铝镁镀层钢板化学转化膜结晶整体呈现为长条针状,结晶排布致密,平均晶粒尺寸约为4μm,膜重达到了3.1 g/m²。锌铝镁镀层钢板的化学转化膜中Al、Mg元素含量高于热镀锌钢板和冷轧钢板。相比而言,锌铝镁镀层钢板化学转化膜的自腐蚀电位最高,为-0.889 V,腐蚀电流和腐蚀速率均最低,分别为26.94μA和2.338×10^-3μA/cm²。在经中性盐雾腐蚀200 h后,锌铝镁镀层钢板基材腐蚀程度最小,说明锌铝镁镀层钢板的耐蚀性能优于热镀锌钢板和冷轧钢板。     

城市轨道交通车辆制动系统的零速信号和非零速信号方案选用及安全性分析

详细阐述了制动系统提供零速信号或非零速信号的串联及并联使用特点,根据信号真值表,深入讨论了不同组合方式的安全性及弊端,以及给列车运行带来的安全隐患.综合分析了各组合方案的安全性.根据分析结果,并联使用非零速信号方案是安全性最高的制动控制单元信号方案,建议城市轨道交通车辆在电气原理设计时应选用制动系统提供的非零速信号作为车辆的控制信号.     

碰撞单元阻尼对桥梁碰撞效应的影响

城市桥梁的抗震防灾问题日益受到学术界和工程界的高度重视。近几十年的几次大地震表明,地震时桥梁大多因发生碰撞而引发破坏、落梁甚至坍塌等严重灾害。本文以南山路T605主线南段第二联的(20+20+20)三跨简支梁桥为工程背景,借鉴相关规范和桥梁建设过程中的相关经验,采用Kelvin接触单元模型,建立三跨简支梁桥的全桥有限元模型,分析了纵梁间的碰撞单元阻尼对全桥地震响应的影响。     

上海地区道路空洞排查和综合修复方法探讨

结合上海地区的实践经验,对道路下空洞病害的主要成因进行了分析和梳理,总结提出了病害排查的一些主要检测方法,并研究提出了空洞病害综合修复整治的若干对策,为今后的工作提供参考。     

连拱隧道衬砌厚度不足对结构安全性的影响研究

为解决因衬砌厚度不足而诱发的连拱隧道结构裂损及安全问题，针对整体式曲中墙连拱隧道，通过相似模型试验，重点研究衬砌厚度不足条件下连拱隧道围岩压力特征、衬砌内力分布以及裂损演化规律。研究结果表明： 1)连拱隧道中墙墙角部位的弯矩最大，中墙墙角外表面产生裂缝,内表面结构压溃，裂损程度最为严重，为最不利位置。 2)衬砌厚度不足部位的边缘是衬砌薄弱截面，左线左拱肩存在衬砌厚度不足时，厚度不足位置右边缘的衬砌内侧开裂；左线左边墙存在衬砌厚度不足时，厚度不足位置上边缘的衬砌外侧开裂。 3)连拱隧道中墙顶部与拱腰接触部位出现较大的拉应力，衬砌厚度不足位置的改变对中墙顶部衬砌受力造成一定的影响，厚度不足位置对侧隧道中墙右上角部位的裂缝出现晚于拱顶裂缝，是连拱隧道结构破坏的重点区域。     

Coordinated collision avoidance for connected vehicles using relative kinetic energy density

Vehicular collision often leads to serious casualties and traffic congestion, and the consequences are worse for multiple-vehicle collision. Many previous works on collision avoidance have only focused on the case for two consecutive vehicles using on-board sensors, which ignored the influence on upstream traffic flow. This paper proposes a novel coordinated collision avoidance (CCA) strategy for connected vehicles, which has potential to avoid collision and smooth the braking behaviors of multiple vehicles, leading to an improvement of traffic smoothness. Specifically, model predictive control (MPC) framework is used to formulate the CCA into an optimization problem, where the objective is to minimize the total relative kinetic energy density (RKED) among connected vehicles. Monte Carlo simulations are used to demonstrate the effectiveness of proposed CCA strategy by comparison with other two strategies. Among all the three control strategies, the RKED based control strategy shows the best performance of collision avoidance, including the best crash prevention rates (99.2 % on dry asphalt road and 90.5 % on wet asphalt road) and the best control of distance headways between vehicles.