Effect of Spray Rails on Takeoff Performance of Amphibian Aircraft

Amphibian aircraft have seen a rise in popularity in the recreational and utility sectors due to their ability to take off and land on both land and water, thus serving a myriad of purposes, such as aerobatics, surveillance, and firefighting. Such seaplanes must be aerodynamically and hydrodynamically efficient, particularly during the takeoff phase. Naval architects have long employed innovative techniques to optimize the performance of marine vessels, including incorporating spray rails on hulls. This research paper is dedicated to a comprehensive investigation into the potential utilization of spray rails to enhance the takeoff performance of amphibian aircraft. Several spray rail configurations obtained from naval research were simulated on a bare Seamax M22 amphibian hull to observe an approximate 10% - 25% decrease in water resistance at high speeds alongside a 3% reduction in the takeoff time. This study serves as a motivation to improve the design of the reference airplane hull and a platform for detailed investigations in the future to improve modern amphibian design.

A review of high performance computing applications in high-speed rail systems

Further improving the railway innovation capacity and technological strength is the important goal of the 14th Five-Year Plan for railway scientific and technological innovation.It includes promoting the deep integration of cutting-edge technologies with the railway systems,strengthening the research and application of intelligent railway technologies,applying green computing technologies and advancing the collaborative sharing of transportation big data.The high-speed rail system tasks need to process huge amounts of data and heavy workload with the requirement of ultra-fast response.Therefore,it is of great necessity to promote computation efficiency by applying High Performance Computing(HPC)to high-speed rail systems.The HPC technique is a great solution for improving the performance,efficiency,and safety of high-speed rail systems.In this review,we introduce and analyze the application research of high performance computing technology in the field of highspeed railways.These HPC applications are cataloged into four broad categories,namely:fault diagnosis,network and communication,management system,and simulations.Moreover,challenges and issues to be addressed are discussed and further directions are suggested.

Analyzing the Flow Field in the Oil Chamber of a Hydrostatic Guide Rail Used for Ultra-Precision Machining: Numerical Simulation and Performance Optimization

In order to explore the impact of different structural design parameters and environmental factors on the performance of the hydrostatic guide rail,the flow field inside its oil chamber is simulated,which provides direction and guidance for the design and optimization of the guide rail system.Based on the theory of fluid lubrication and the Reynolds equation,numerical simulations are performed through a mathematical model.The results suggest that the bearing capacity of the oil film increases with the oil supply pressure.The film thickness and the film stiffness share a positive correlation.Different oil film thickness and different input pressure parameters can have a significant impact on bearing capacity and oil film stiffness.The correlations identified in the present analysis can be used as a basis to optimize the guide rail design.

A multidimensional examination of performances of HSR (High-Speed Rail) systems

This paper deals with a multidimensional examination of the infrastructural, technical/technological, operational, economic, social, and environmental performances of high-speed rail （HSR） systems, including their overview, analysis of some real-life cases, and limited （analytical） modeling. The infrastructural performances reflect design and geometrical characteristics of the HSR lines and stations. The technical/technological performances relate to the characteristics of rolling stock, i.e., high-speed trains, and supportive facilities and equipment, i.e., the power supply, signaling, and traffic control and management system（s）. The operational performances include the capacity and productivity of HSR lines and rolling stock, and quality of services. The economic per- formances refer to the HSR systems＇ costs, revenues, and their relationship. The social performances relate to the impacts of HSR systems on the society such as congestion, noise, and safety, and their externalities, and the effects in terms of contribution to the local and global/country social- economic development. Finally, the environmental performances of the HSR systems reflect their energy consumption and related emissions of green house gases, land use, and corresponding externalities.

Assessment of the curving performance of heavy haul trains under braking conditions

To study the curving performance of trains, 1D and 3D dynamic models of trains were built using nu- merical methods. The 1D model was composed of 210 simple wagons, each allowed only longitudinal motion; whereas the 3D model included three complicated wagons for which longitudinal, lateral, and vertical degrees of freedom were considered. Combined with the calculated results from the 1D model under braking conditions, the behavior of draft gears and brake shoes were added to the 3D model. The assessment of the curving performance of trains was focused on making comparisons between idling and braking conditions. The results indicated the following： when a train brakes on a curved track, the wheel-rail lateral force and derailment factor are greater than under idling conditions. Because the yawing movement of the wheelset is limited by brake shoes, the zone of wheel contact along the wheel tread is wider than under idling conditions. Furthermore, as the curvature becomes tighter, the traction ratio shows a nonlinear increasing trend, whether under idling or braking conditions. By increasing the brake shoe pressure, train steering becomes more difficult.

INVESTIGATION ON THE DYNAMIC RESPONSE PERFORMANCE OF A NOVEL THREE-WAY SOLENOID VALVE

Objective A novel high-speed three-way solenoid valve is developed, which is used for the common-rail injection system equipped on DME powered engine. In order to improve the dynamic response performance of the three-way solenoid. Methods Experimental studies have been conducted to investigate the effects of spool stroke, drive voltage, negative demagnetizing pulse and two drive schemes on the dynamic response performance of the three-way solenoid valve. Results The results show that the dynamic response performance of the three-way solenoid valve can be remarkably improved by shortening the spool stroke and increasing the drive voltage. Simultaneously, the difference between the response time of closing valve and that of opening valve decreases. At each different drive voltage, there exists an optimal negative demagnetizing pulse corresponding to the same positive exciting pulse. At this optimal pulse, the dynamic response performance of the three-way solenoid valve is the best. In addition, the high drive voltage can lead to the smaller optimal negative demagnetizing pulse. It is also indicated from the experiments that the dynamic response performance of the three-way solenoid valve is better when the NO.1 drive scheme is adopted. The lower drive voltage results in the larger difference between the dynamic response performances for the two drive schemes. Conclusion The dynamic response performance of a novel three-way solenoid valve is good.

两轴径向独立轮副轨道车辆动力学性能

针对独立车轮导向问题提出后倾角导向方法,使独立轮副轨道车辆获得自导向能力。阐述车辆的自导向原理,利用横向轮轨力和后倾角力臂形成摇头力矩,使独立车轮自动转向。关于中心对称的前后独立轮副分别向相反方向转向,使独立车轮处于径向位置。采用多体动力学方法分析独立轮副轨道车辆的自导向性能。结果表明:在直线轨道上,后倾角对车辆横向位移和摇头角的影响明显。带后倾角车辆出现类蛇行运动现象。具有后倾角的车辆在直线轨道上能够自动复位。在曲线轨道上,左前导向轮具有较大的冲角。后倾角能够使车辆动态对中,最终回到轨道中心线位置。带后倾角的独立轮副轨道车辆在曲线轨道上具有有限的导向能力。

轨底坡耦合轮径差对地铁车辆动力学性能及轮轨接触特性的影响

为了研究轨底坡耦合轮径差对于地铁车辆动力学性能及轮轨接触特性的影响规律,设置了3种轨底坡工况(1/20、1/30和1/40)和5种轮径差工况,通过建立地铁车辆动力学仿真模型和轮轨接触三维弹性有限元模型,分析轨底坡耦合轮径差对地铁车辆直线平稳性和曲线通过性能的影响。结果表明:直线路段车辆平稳性指标受到轮径差变化的影响大于轨底坡变化的影响,轮轨等效应力和接触应力会随着轮径差的增加而增大;曲线路段的各个动力学指标会随着轮径差的增加而增大;综合考虑动力学指标和轮轨接触特性,直线路段下尽量减少使用1/20轨底坡;曲线路段下,可以选择1/30轨底坡,减少轮径差对车辆的影响。

电磁轨道发射系统动力学理论与设计方法研究进展

电磁轨道发射作为电磁发射技术的重要分支,具有发射速度高、射速可调节等显著优势,被誉为改变未来战争样式的颠覆性技术之一。目前,电磁轨道发射技术仍然面临射击精度低及装置寿命短等关键瓶颈问题,这些都与电磁轨道发射装置所涉及的复杂电、磁、热和力等多领域耦合发射动力学行为密切相关,然而国内外对极端冲击条件下电磁轨道发射装置的系统动力学分析尚缺少成熟理论方法和技术手段。针对上述情况,从动力学建模、性能预测、优化设计等方面综合阐述近期电磁轨道发射系统动力学理论与设计方法的国内外研究进展,总结相应的研究方向和需求。随着电磁轨道发射装置的工程化发展,电磁轨道发射系统的建模与仿真应考虑发射环境的全系统因素,建立电磁轨道发射装置和发射环境耦合的发射动力学性能快速预测和优化设计系统,详细阐明电磁轨道发射装置和发射环境多领域耦合振动机理等基础科学问题,为电磁轨道发射装置系统动力学的深入研究和相关装备研制提供支撑。

城市轨道交通企业财务表现能力研究

[目的]为了系统性地把握企业财务状况,提升城市轨道交通企业的经营决策能力,需研究城市轨道交通企业的财务表现能力。[方法]从营业总成本、盈利能力、偿债能力、营运能力和成长能力五个方面,统计分析了我国10座城市的轨道交通企业的营业总成本及人工成本、偿债能力比率、盈利能力比率、营运能力比率和成长能力比率,并基于此研究了企业的财务表现能力。[结果及结论]天津地铁存量PPP(公私合营)项目盘活资金超150亿元,减轻了政府债务负担。其他城市的轨道交通企业的营业总成本和人工成本整体呈上升趋势,建议通过PPP模式来减轻政府财务压力,提高成本效率。北京、成都、武汉、青岛、南京的轨道交通企业的长期偿债能力较弱。针对2021年成都、武汉、南京的轨道交通企业的负债程度偏高问题,建议采取光伏发电、地源热泵、共享车辆基地、设备国产化等措施减少企业成本。对于企业盈利偏低问题,建议通过提供运营服务咨询、运营管理服务等方式增加收入。

不同曲线半径下轨底坡与轮径差最佳匹配研究

为了研究不同曲线半径下地铁车辆动力学性能最优的轨底坡与轮径差最佳匹配,运用SIMPACK软件建立了地铁车辆动力学仿真模型,设置9种轨底坡工况和5种轮径差工况,以轮轨横向力、轮对横移量、脱轨系数、轮重减载率和轮轨磨耗指数作为车辆动力学性能的评价指标,以4种不同C型曲线半径作为研究对象,分析45种轨底坡和轮径差耦合工况下各指标的变化规律。采用熵权法对各指标进行加权求和处理,得到不同工况下的车辆动力学性能综合得分,最终分析得出车辆在不同半径曲线下轨底坡和轮径差的最佳匹配。研究结果表明:在300,400,500,600 m这4种曲线半径下,外轨轨底坡、内轨轨底坡和轮径差最优匹配方案分别为(1/20,1/40,+1),(1/20,1/40,+1),(1/30,1/30,-1),(1/40,1/30,-1)。

TOD导向下的城市轨道交通站区用地绩效评价——以广州若干地铁站区为例

为推动TOD的本土化实践,聚焦于现有的地铁站区用地成果,应用用地绩效评价分析框架并结合TOD用地原则,构建TOD导向下的站区用地“强度—结构—价值”三维绩效评价体系,同时采用改进的TOPSIS法与障碍度模型对广州若干地铁站区进行实证研究,得出案例站区的TOD用地绩效水平,并从中总结TOD用地实践的积极经验。结果表明,部分案例站区已具有一定的TOD用地特征,尤其在用地结构、价值等维度上表现出良好水平,汲取相关成熟经验对于TOD的本土化实践具有较强的借鉴意义,但也需正视传统用地强度模式与TOD理念间的冲突、用地结构的优化与经济、社会等多元价值的协调等重点问题。

身管外壳对电磁轨道发射装置发射性能影响分析

电枢在发射过程中,瞬时变化的导轨电流会在金属身管外壳上感应出巨大的涡流,身管涡流会产生额外的损耗,同时外壳涡流的去磁效应会改变电枢、导轨等器部件的应力分布从而影响装置发射性能。该文建立了电磁轨道发射装置的数学模型,并针对整体式、上下分断式以及叠压式三种外壳结构有限元模型进行了电磁场-结构场联合仿真,获得了发射装置电磁参数和各部件应力分布。有限元电磁仿真结果表明,叠压式外壳结构外壳涡流最小、电感梯度最大、器部件应力最大,整体式外壳结构外壳涡流最大、电感梯度最小、器部件应力最小。全系统电气仿真和对比试验证明,在满足外壳支持强度和装置各部件应力条件下,选用高磁导率、低电导率的材料并设计抑制涡流的身管外壳结构,有利于提高发射装置电枢出口速度和系统效率,从而获得优良的发射性能。

横向静载作用下轨道交通预应力混凝土U型梁裂缝开展研究

为探究轨道交通预应力混凝土U型梁结构在腹板横向受力情况下的裂缝开展状况,通过回顾总结其裂缝开展成因,并以实际工程中的某标准梁段为例,进行了横向静载破坏试验,分析了U型梁结构在横向受力下的应变、挠度变化规律以及裂缝发育和损伤状况。研究结果表明,在横向对称荷载作用下,随着加载级的增大,U型梁展现出良好的整体性能和横向抗裂性能;该梁的裂缝损伤首先出现在腹板和底板处,随后逐步扩展到底板与腹板的连接部位;在破坏加载级下,腹板与翼缘发生破坏性裂缝损伤和明显的外扩变形;在高于规范撞击力建议值2倍的横向静载作用范围内,试验梁能够保持弹性工作状态,验证了采用美国ACI规范中对于列车脱轨撞击力的建议值进行U型梁横向抗撞设计的合理性。该研究成果可为轨道交通预应力混凝土U型梁的力学性能研究和结构优化设计提供更多参考。

石粉对轨道交通工程用机制砂混凝土性能的影响研究

研究了石粉含量对轨道工程用C20、C35、C50机制砂混凝土性能的影响及石粉含量的合理范围。结果表明:对于工作性和抗压强度,机制砂混凝土的强度等级越高,石粉的最佳含量越小,C20机制砂混凝土的石粉含量宜为10%~20%,C35宜为5%~10%,C50宜为5%以内;对于早期抗裂性能,C35机制砂混凝土的石粉含量宜控制在3%~7%,C50宜控制在5%以内;对于抗氯离子渗透性能,C35机制砂混凝土的石粉含量宜控制在5%~15%,C50机制砂混凝土的性能受石粉含量的影响较小;对于抗冻性能,当石粉含量在5%以内时,C35机制砂混凝土的抗冻性能变化不明显,超过5%后,抗冻性能下降,石粉含量对C50机制砂混凝土抗冻性能的影响不明显。

带波形钢板的UHPC免模板湿接缝抗弯模型试验研究

针对预制装配式桥梁中桥面板湿接缝处的受力特点和现有接缝构造形式,提出一种以预埋波形钢板为底模的超高性能混凝土(Ultra-High Performance Concrete,UHPC)免模板湿接缝构造形式,解决接缝现场支模问题。为研究新型接缝的力学性能,设计了5片试验梁,以钢纤维含量为试验参数,开展四点弯曲全过程抗弯性能试验。结果表明:各试验梁主裂缝均位于预制段,发生弯曲破坏,接缝段未产生较大破坏;提高钢纤维含量可以增强UHPC-NC(Normal Concrete)界面黏结,提升接缝的抗裂性能,但对结构的抗弯承载力影响较小;钢纤维含量为1.0%的免模板接缝梁抗裂性能仅次于UHPC整体梁,同时具有结构简单、施工简化、造价经济等优点,说明该接缝构造形式运用于实际工程中是可行和可靠的;UHPC钢纤维含量建议取1.0%。

不同级别横风下虚拟轨道车辆动力学性能研究

为了研究虚拟轨道车辆在不同级别横风下的动力学性能,基于非线性胎地耦合关系建立了3编组虚拟轨道车辆多体动力学模型,研究虚拟轨道车辆在AW0和AW3状态下,不同级别横风对其胎地垂向力、抗倾覆稳定性、抗侧滚性能等主要动力学指标的影响。结果表明:AW0状态且低速工况下,不同风级的风载和运行速度对各编组车辆影响较小,车辆动力学性能等指标基本一致;AW3状态下,各个指标值均随着运行速度和风级的提高而增大,且AW0状态下车辆的抗倾覆稳定性总体上优于AW3状态;针对各编组车辆而言,中间车的抗侧滚性能优于头车和尾车,其中尾车的抗侧滚性能最差,但各编组之间的抗倾覆稳定性相差不大。

城市轨道交通建设、劳动力流动与企业绩效——基于中国上市公司财务绩效数据

采用SD分析方法和多期DID模型,并基于2006-2021年我国上市公司财务绩效数据,分析城市轨道交通建设与劳动力流动、企业绩效之间的关系。研究发现:城市轨道交通建设有助于加快劳动力流动,从而促进企业总体绩效的提升,但短期和中长期影响存在显著差异;轨道交通建设在提升企业绩效的同时,在一定程度上一定时期内也迫使企业追加人力资本投入,且这种影响存在一定的区位“极化效应”。因此,企业应根据劳动力加速流动趋势,加强人力资本投入、保持企业员工队伍的稳定,以促进企业绩效的提升。

弹性支承块式无砟轨道钢轨抗倾翻性能全参数化计算方法

列车通过弹性支承块式无砟轨道时,扣件和弹性支承块的弹性叠加容易使钢轨倾翻角和轨头横移量显著增大,导致动态轨距扩大,进而影响列车运行的安全性和平稳性。综合考虑轮轨激励形式及其载荷作用关系(包括轮轨垂向力的准静态成分、动态成分及其作用位置、轮轨水平力及其作用位置以及钢轨廓形等)、扣件系统力学特性及其几何参数(包括扣件系统的垂向及横向刚度和阻尼以及外形尺寸等)、弹性支承块力学特性及其几何参数(包括弹性支承块的各向刚度、模量、泊松比以及外形尺寸等),建立准确的力学分析模型和几何关系模型,全面清晰地表征了弹性支承块式无砟轨道结构受力特点。基于力矩平衡计算原理,提出弹性支承块式无砟轨道钢轨抗倾翻性能全参数化计算方法,根据单节点实尺模型残余变形试验对理论计算结果进行修正,若考虑消除初始装配间隙影响,支承块间距扩大理论计算值增加0.04 mm加以修正,轨距扩大量应增加0.2 mm加以修正,通过对比分析计算结果、单节点实尺模型试验结果与传统实体有限元模型仿真结果,证明数据吻合度极高。分析与计算结果表明,本文提出的全参数计算方法与单节点实尺模型试验结果、实体有限元模型仿真结果吻合程度良好;利用本文所提出的弹性支承块式无砟轨道钢轨抗倾翻性能全参数化计算方法,可以高效准确地开展多参数敏感性分析;能够为不同运营条件下弹性支承块式无砟轨道结构及其部件优化提供设计依据,并奠定充分的理论基础。

城市轨道交通网络系统效率评价指标改进

为提高城市轨道交通网络系统效率评价指标的可比性和完备性,引入有效行程速度和有效客流密度的概念,改进了网络系统效率评价指标,并以重庆市中心城区2017年和2019年运营的城市轨道交通线网为例验证了改进后评价指标的科学性和可操作性。研究表明:既有评价指标由于显著受到线网服务范围的影响,且未体现网络的投入产出效率,无法直接作为网络结构优化的目标函数;改进后的系统效率评价指标能够综合反映剔除线网服务范围影响后的网络结构性能和投入产出效率,且存在理论上的最优值;平衡网络中节点换乘时间和路段行程时间,并适度加密城市核心区域的轨道交通线路和站点,是持续提升网络系统效率的2个重要手段。