明线会车、隧道会车及过隧道时的高速列车动力响应

明线会车、隧道会车和过隧道工况下的气动压力波对高速列车的动力响应和运行安全产生很大影响,本文建立了三辆编组的高速列车动力学模型,通过数值仿真得到了列车在三种工况下的车体所受的气动力,基于数值积分分析了列车的动力响应和脱轨系数。研究发现:明线会车和隧道会车工况相比,车辆的侧向运动相反。明线会车和过隧道时,气动载荷对列车的脱轨系数影响较小,而隧道会车时,气动载荷作用对尾车的安全性影响较大

Hunting Stability of High-Speed Railway Vehicle Considering the Actions of Aerodynamic Loads

我国经济和社会的发展推动着我国高速列车的运营速度不断发展。2010年12月，中国“和谐号”动车组CRH380A在“京沪线”先导段以486.1km/h的速度创造了运营车的最高试验速度。与此同时，我国高速列车的持续运营速度也有明显提高，我国京津、武广、郑西高铁线路曾长时间以350km/h的速度进行商业运行。考虑到普通民航飞机在时速300km/h左右就可以在气动作用下离地起飞，显然有必要探讨气动载荷对高速列车性能的影响。其中一个重要问题就是：在高速度等级空气流作用下，列车的蛇行运动稳定性会如何发生改变？由于高速气流作用下气动载荷比低速时迅速增加，有必要对气动载荷作用下高速铁路车辆的运动稳定性进行定量分析。目前还缺乏相关的研究工作。因此，本文的目的是通过研究，建立一套完整的考虑气动载荷作用下的高速列车运动稳定性的分析理论和计算方法，为我国高速列车的研发、设计提供理论支持。 现有的分析方法只是把气动载荷作为强迫力，无法考虑气动载荷对列车振动系统参数的影响；常用的商业软件也难以处理这一问题。因此，本文在考虑气动效应对列车轴重、轮轨蠕滑系数、重力刚度和角刚度等参数影响的基础上，建立了气动载荷作用下高速列车的数学模型，提出了考虑气动载荷影响的高速列车蛇行运动稳定性分析方法，分别针对车辆和列车系统建立了计算模型，编写了相应的计算程序，并对程序的正确性进行了考核。其中，车辆模型主要用于分析车辆的特征值问题和分岔问题；列车系统由三节车组成的编组列车（包含了头车、中间车和尾车）主要用于分析特殊气动载荷（隧道压力波、会车压力波等）作用下列车系统的动力响应特性。 本文所做的主要工作有： （1） 针对考虑气动效应的高速列车运动稳定性问题，分析了气动载荷对高速列车振动系统参数的影响，建立了气动载荷作用下高速列车运动微分方程，提出了考虑气动载荷影响下的高速列车蛇行运动稳定性分析方法，并编写了四套具有不同功能的分析软件； （2） 考虑气动载荷作用的铁路车辆的特征值问题。分别针对明线运行（气动升力）和横风（考虑各个方向气动载荷）作用两种工况进行计算分析。对于明线运行时，分别求解了考虑气动载荷下头车（气动负升力）和尾车（气动正升力）的线性临界速度，以及悬挂参数与临界速度的关系；对于横风（考虑各个方向气动载荷）作用时，针对不同风速横风进行了线性临界速度的计算，并分析了气动载荷对车辆各个运动模态的影响； （3） 考虑定常气动载荷作用下，铁路车辆非线性分岔特性研究。针对明线运行（气动升力）和横风（考虑各个方向气动载荷）作用两种工况进行数值计算。研究中分析了不同气动载荷对列车分岔、极限环、失稳频率等的影响； （4） 考虑非定常气动载荷作用下，铁路车辆非线性分岔特性研究。针对不同外激频率的气动载荷，分析气动载荷对列车非线性稳定性的影响。研究中分析了非定常气动载荷作用下车辆的分岔、极限环和复杂运动。研究表明，非定常气动载荷会导致车辆发生复杂的拟周期运动； （5） 考虑气动载荷的高速列车随机振动响应研究。通过多编组列车系统模型，在考虑轨道不平顺激励的基础上，针对运营中常见的过隧道、明线会车、隧道会车和横风作用四种工况进行数值计算分析气动载荷和气体压力波对列车系统动力响应的影响

HUNTING STABILITY OF HIGH-SPEED RAILWAY VEHICLE CONSIDERING THE ACTIONS OF STEADY AERODYNAMIC LOADS

随着高速列车运行速度的提高,气动载荷会对车辆蛇行运动稳定性带来不利影响,现有文献对此研究很少。为此,考虑沿列车反向运动高速气流以及侧风的作用,研究了定常气动载荷下高速铁路车辆横向运动的线性稳定性。分析中计入了气动载荷改变轴重、使各轮法向支反力各不相同;以及使重力刚度、重力角刚度、轮对蠕滑系数等发生变化的效应。给出了计及气动影响的17个自由度铁路车辆蛇行运动分析模型,编制了相应的计算程序并进行了算例验证。进而,计算了在不同风速条件下,各个方向定常气动力和气动力矩单独以及共同作用时车辆运动稳定性特征值,并求出临界速度。结果表明:气动载荷会降低车辆临界速度;临界速度随横风风速增加而单调降低;与其他方向气动载荷相比,点头力矩和升力对临界速度的影响更大

流固耦合力学专题序

流固耦合力学是流体力学与固体力学交叉而成的力学分支,以两相介质之间的相互作用为重要特征,研究可变形固体在流场作用下的行为及固体变形对流场影响的相互作用.流固耦合现象存在于海洋工程、航空航天、石油化工、核能工程、土木工程等几乎所有涉及国计民生的重大领域中,并会诱发结构静发散

基于卷积神经网络的SCMA-VLC接收机研究

发光二极管(LED)有限的带宽与其非线性电光转换引起的信号失真，是限制可见光通信(VLC)传输性能的重要因素。传统的消息传递算法(MPA)在稀疏码分多址(SCMA)-VLC系统中对抗信号非线性失真的能力有限。针对上述问题，文章提出了一种基于卷积神经网络(CNN)接收机，通过对接收信号进行特征提取、分类和判决，可有效提升SCMA-VLC系统抗非线性失真的能力。实验结果表明，在非线性失真较强的情况下，CNN接收机比MPA接收机表现出了更优的误码率(BER)性能，有效地扩大了偏置电压的动态范围，减少了系统对信噪比(SNR)的要求

Hunting Stability of High-Speed Railway Vehicles Under Steady Aerodynamic Loads

With the rising speed of high-speed trains, the aerodynamic loads become more significant and their influences on the hunting stability of railway vehicles deserve to be considered. Such an effect cannot be properly considered by the conventional model of hunting stability analysis. To this end, the linear hunting stability of high-speed railway vehicles running on tangent tracks is studied. A model considering the steady aerodynamic loads due to the joint action of the airflow facing the moving train and the crosswind, is proposed for the hunting stability analysis of a railway vehicle with 17 degrees of freedom (DOF). The key factors considered include: variations of the wheel-rail normal forces, creep coefficients, gravitational stiffness and angular stiffness due to the actions of the aerodynamic load, which affects the characteristics of hunting stability. Using the computer program developed, numerical calculations were carried out for studying the behavior of the linear hunting stability of vehicles under steady aerodynamic loads. The results show that the aerodynamic loads have an obvious effect on the linear critical speeds and instability modes. The linear critical speed decreases monotonously as the crosswind velocity increases, and the influences of pitch moment and lift force on the linear critical speed are larger than the other components of the aerodynamic loads

复发/转移宫颈癌患者应用PD-1抑制剂卡瑞利珠单抗联合阿帕替尼治疗的患者报告结局

目的本科室既往一项多中心、单臂Ⅱ期临床研究报道了复发/转移宫颈癌患者接受PD-1抑制剂卡瑞利珠单抗联合抗血管生成药物阿帕替尼治疗后的有效性和安全性。本研究旨在报告该宫颈癌队列的患者报告结局（PRO）的结果。方法对纳入本研究的患者以面对面的方式进行问卷宫颈癌量表（FACT-Cx）的填写，评估时间包括用药前（基线）及每两个用药周期1次，直至患者出现疾病进展，未出现疾病进展者问卷收集时间截止至2020年10月12日。结果本研究有41例患者至少完成1份FACT-Cx问卷。患者基线、用药后前6周期及治疗6个周期后（范围7-15周期）的生活质量评分分别为114.53±18.23、124.08±15.23和132.82±21.97。结果显示，用药后前6个周期、治疗6个周期后生活质量均显著高于患者的基线生活质量水平（P＜0.05）。FACT-Cx问卷的四个维度，包括生理状况维度（如精神状态、肢体疼痛等）、情感状况（如悲伤、紧张程度等）、功能状况（如日常活动能力等）及附加关注（如性功能等），在治疗6个周期后的各维度均分显著高于基线各维度的均分（P＜0.05）。但社会/家庭状况维度（如家庭关系等）变化不显著。用药后前6个周期，3～4级不良反应（AEs）发生率为71.11%。而治疗6个周期后，3～4级AEs发生率显著下降至25.0%，其中高血压、疲劳等AEs发生率明显下降。结论复发性宫颈癌患者接受卡瑞利珠单抗联合阿帕替尼治疗后，FACT-Cx调查量表在生理状况、情感状况、功能状况及附加关注等多个维度的评分均有升高，生活质量明显提高。并且，生活质量评分在治疗6个周期后较前6个治疗周期仍有升高，提示生活质量改善时间持久

The dynamic responses of high-speed trains passing tunnel, passing by each other on open track and inside tunnel

建立了头尾车为动车,中间车为拖车的三辆编组、51个自由度的高速列车动力学模型,通过多体动力学计算得到了列车在明线会车、过隧道及隧道会车工况下的动力学响应。并对列车在此三种工况下的动力学响应进行了分析讨论。研究发现:气动力对列车系统动力学行为的影响非常明显,使列车振动加剧,其中头车和尾车相对剧烈。其中,隧道会车对列车系统动力学行为的影响更为明显

Dynamic characteristics of tube bundles with crack subjected to cross-flow and loose support

Flow-induced vibration of the tube bundles subjected to cross-flow and loose support is an important issue in the security of a steam generator. In the operation of nuclear power station, the flow-induced vibration of the tube bundles may lead to crack initiation and propagation, which can affect the natural frequency and the dynamic response of the tube. However, there is seldom theoretical analysis to study the dynamic characteristics of cracked tube bundles subjected to cross-flow. Therefore, a mathematical model of a single cracked tube in a rotated triangular tube array subjected to cross-flow and loose support was presented in this paper. The model takes into account the variations of the tube natural frequency and mode of vibration owing to the crack damage. The effect of the crack damage on the dynamic characteristics of a flexible tube in tube bundles subject to cross-flow and loose support was investigated, and the dynamic responses of the cracked tube for three flow pitch velocity conditions were calculated. (c) 2021 Elsevier Ltd. All rights reserved

Wall shear stress and wall heat flux in a supersonic turbulent boundary layer

We report the characteristics of wall shear stress (WSS) and wall heat flux (WHF) from direct numerical simulation (DNS) of a spatially developing zero-pressure-gradient supersonic turbulent boundary layer at a free-stream Mach number M-& INFIN; = 2.25 and a Reynolds number Re-tau = 769 with a cold-wall thermal condition (a ratio of wall temperature to recovery temperature T-w/T-r = 0.75). A comparative analysis is performed on statistical data, including fluctuation intensity, probability density function, frequency spectra, and space-time correlation. The root mean square fluctuations of the WHF exhibit a logarithmic dependence on Re-tau similar to that for the WSS, the main difference being a larger constant. Unlike the WSS, the probability density function of the WHF does not follow a lognormal distribution. The results suggest that the WHF contains more energy in the higher frequencies and propagates downstream faster than the WSS. A detailed conditional analysis comparing the flow structures responsible for extreme positive and negative fluctuation events of the WSS and WHF is performed for the first time, to the best of our knowledge. The conditioned results for the WSS exhibit closer structural similarities with the incompressible DNS analysis documented by Pan and Kwon [ "Extremely high wall-shear stress events in a turbulent boundary layer, " J. Phys.: Conf. Ser. 1001, 012004 (2018)] and Guerrero et al. [ "Extreme wall shear stress events in turbulent pipe flows: Spatial characteristics of coherent motions, " J. Fluid Mech. 904, A18 (2020)]. Importantly, the conditionally averaged flow fields of the WHF exhibit a different mechanism, where the extreme positive and negative events are generated by a characteristic two-layer structure of temperature fluctuations under the action of a strong Q4 event or a pair of strong oblique vortices. Nevertheless, we use the bi-dimensional empirical decomposition method to split the fluctuating velocity and temperature structures into four different modes with specific spanwise length scales, and we quantify their influence on the mean WSS and WHF generation. It is shown that the mean WSS is mainly related to small-scale structures in the near-wall region, whereas the mean WHF is associated with the combined action of near-wall small-scale structures and large-scale structures in the logarithmic and outer regions