Trapped waves within the blocking frequency under compressed sea ice and two-dimensional current

The existence of trapped modes due to a horizontal submerged rigid cylinder placed below a compressed ice-covered surface is shown to exist within the frequency band of wave blocking by employing linearized water wave theory and with the inclusion of the effects of a two-dimensional current and the obliqueness of the propagating wave. A new modified multipole expansion method catering to the multiple propagating modes is proposed. The impact of different choices of propagating modes at a fixed frequency within the above-mentioned band on the trapped modes is detailed. Multiple trapped modes whose number depends on the direction and magnitude of the current exist within the frequency band. Out of the three choices of current types considered, while two of them result in the generation of trapped modes for all three possible choices of the propagating wave, the remaining one shows that only one propagating mode can generate a trapped wave. A break in the continuous spectrum of the trapped mode frequency due to the wave blocking and at the point of inflexion is presented. There exists a region of angle of propagation within which an abundance of the trapped mode is shown. The surface profiles for different angles of propagation and choices of propagating modes are illustrated graphically. The trapped modes associated with a higher angle of propagation decay at a faster rate.     

Experimental research on dynamic vibration absorber with negative stiffness for longitudinal vibration control of propulsion shafting system北大核心CSCD

［Objectives］In order to control the first longitudinal vibration mode of propulsion shafting systems, a dynamic vibration absorber with disc spring negative stiffness is proposed and its experimental verification carried out. ［Methods］A test bench is established for the propulsion shafting system containing a dynamic vibration absorber with negative stiffness. According to the first longitudinal vibration mode of the shafting, a dynamic vibration absorber with negative stiffness integrated into the thrust bearing is developed. Vibration transmission tests under different rotational speeds, static thrusts and negative stiffness are then carried out, and acceleration response data on the thrust bearing foundation and shafting is obtained. ［Results ］ The results show that the developed dynamic vibration absorber with negative stiffness can achieve vibration suppression of 7.8 dB for the thrust bearing foundation in the first longitudinal mode of the propulsion shafting with a mass ratio of 1.6%, and the vibration control effect of the negative stiffness dynamic vibration absorber is maintained at 3.3 dB when the natural frequency changes by 5% and the thrust changes by 40%. The vibration response on the thrust bearing foundation and shafting do not deteriorate even at non-optimal negative stiffness. ［Conclusions］This study shows that a dynamic vibration absorber with negative stiffness can effectively suppress vibration transmission at the first longitudinal mode of a shafting under different rotational speeds. © 2023 Authors. All rights reserved.     

城市轨道交通车辆段 综合利用操作模式创新

结合城市轨道交通建设中车辆段的发展状 况,对已实施完成的北京地铁 10 号线二期五路停车场 综合利用项目进行分析,通过适当的模式加以开发利 用。结合项目具体操作实践,归纳总结出车辆段综合 利用操作模式的创新成果,并在此基础上提出未来车 辆段综合利用的思考与建议。     

基于手机信令数据的旅客联程出行时空特征分析方法

为高效准确地识别旅客联程出行方式,基于旅客联程出行行为特征,引入不同运输方式场站地理位置、场站数据取样最佳半径、旅客行驶速度等关键参数,对旅客手机信令数据进行筛选、校核和计算,提出了基于手机信令数据的旅客联程出行方式识别方法,同时测算了不同运输方式场站数据取样最佳半径。以2018年国庆假期广东省内旅客出行为例进行分析,剔除了约98%的无关信令数据。分析结果显示,广东省内公铁联运出行比例最高,广州、深圳两大枢纽城市的客流集疏运效应突出,广佛城际出行联系较为密切,佛山机场的潜力较大。研究表明,识别方法大幅降低了信令数据分析量和运算成本,方法原理和技术路线清晰,分析结果准确、符合实际。     

基于高次最小二乘原理的连续刚构桥挠曲线拟合分析

为充分利用连续刚构桥桥梁健康监测系统中有限数量位移传感器,提出一种基于高次最小二乘原理的数值拟合方法,用有限测点信息有效拟合全桥的挠曲线方程。以某连续刚构桥为实际算例,全桥挠曲线拟合分析结果表明:该方法拟合连续刚构桥挠曲线方法简单、思路清晰,有利于工程实践;在边跨和中跨的拟合值与实测值的最大相对误差均小于5%,用高次最小二乘原理拟合连续刚构桥挠曲线具有足够精度。     

高职高专Rhino建模软件教学方式探究

当前各类高职院校Rhino建模软件课程普遍专注于“教、学、做”一体化教学模式,但是本教学模式在实施过程中,由于“教、学、做”一体化、Rhino建模软件、高职院校学生三者都有其个性化特征,因此“一体化”这种优越的教学模式,不能不加分析的拿来就用。本文提出了多种方法相结合的立体化模式,与实际应用学科的教学实践相结合来辅助和完善一体化教学模式。此思路对于高职院校计算机辅助设计类课程教学方法的改革,是一种积极的探索。     

Who you are is how you travel: A framework for transportation mode detection using individual and environmental characteristics

With the increasing prevalence of geo-enabled mobile phone applications, researchers can collect mobility data at a relatively high spatial and temporal resolution. Such data, however, lack semantic information such as the interaction of individuals with the transportation modes available. On the other hand, traditional mobility surveys provide detailed snapshots of the relation between socio-demographic characteristics and choice of transportation modes. Transportation mode detection is currently approached using features such as speed, acceleration and direction either on their own or in combination with GIS data. Combining such information with socio-demographic characteristics of travellers has the potential of offering a richer modelling framework that could facilitate better transportation mode detection using variables such as age and disability. In this paper, we explore the possibility to include both elements of the environment and individual characteristics of travellers in the task of transportation mode detection. Using dynamic Bayesian Networks, we model the transition matrix to account for such auxiliary data by using an informative Dirichlet prior constructed using data from traditional mobility surveys. Results have shown that it is possible to achieve comparable accuracy with the most widely used classification algorithms while having a rich modelling framework, even in the case of sparse mobility data.     

乘务计划编制系统研究

乘务计划是其运输组织的基本计划之一,合理的乘务计划是乘务工作顺利、优质开展的保证.针对乘务工作中的值乘方式展开讨论,提出一种综合包乘制与轮乘制优点的相对固定的轮乘制;其次,以相对固定的轮乘制为基础设计算法智能编制乘务交路;最后,人工调整编制结果,制定乘务月计划.     

滚装甩挂运输牵引车调度优化及作业模式类比分析

针对滚装甩挂运输新船型可“直进直出”条件下的“边装边卸”作业模式,与传统船型“船艉进出”条件下的“先卸后装”作业模式对比,建立滚装甩挂码头牵引车调度的混合整数规划模型,并设计遗传算法求解模型。通过对比不同规模算例下CPLEX与所设计遗传算法的实验结果,验证模型的正确性和算法的有效性。结果表明：相较于传统船型“先卸后装”作业模式,新船型“边装边卸”作业模式在运营成本方面可降低约15%;当装卸任务分布密集时,卸船任务靠近船艏运营成本越高,装卸任务分布稀疏时,卸船任务远离船艏运营成本越高;总体而言,“边装边卸”作业模式的运营成本低于“先卸后装”作业模式。研究结论可为“边装边卸”作业模式下的港口滚装甩挂作业调度提供决策支持。     

需求变动下高铁快运货流分配与组织模式优化

基于高铁快运一地集货和多点发运的开行特点,综合考虑我国未来快递市场的需求变动,提出高铁快运常态化和规模化成网运营后的货流分配与组织模式优化方法,以客运动车组捎带运输货物、预留车厢和高铁快运专列模式下,各OD对间的高铁快运运量为主要决策变量,以总运输成本极小化为目标,构建货流分配混合整数规划模型,计算货流量在高铁快运网络中的分布,得到货流OD运输路线与各高铁快运通道运营组织模式的组合优化方案。通过高铁快运货流OD“三阶段”预测方法,预测城市间的高铁快运需求量作为货流输入,以9个国内快递业务中心城市组成的网络为案例,由Python语言调用Gurobi优化软件求解案例,验证所建模型的有效性。案例结果表明：在运量低谷期使用捎带和预留模式可满足90.7%的运输需求;在运量高峰期部分线路需开行高铁快运专列;运营组织模式可根据OD对间货流量与网络容量的适应性关系进行调整,以充分利用高铁闲置运力,提升运营效益。