低真空管道磁浮列车交会激波流场特性分析

为了解决管道列车高速运行时产生的激波等气动效应问题,通过建立三维仿真模型,针对不同阻塞比、线间距和列车外形,基于DES湍流模型,开展非稳态数值模拟研究,分析列车在低真空管道内交会时的激波流场结构、管道壁面压力、列车表面压力。研究结果表明:随阻塞比的增大,列车前端壅塞长度增加,且正压区域压力增大,激波反射更加剧烈,尾流激波反射强度增大,激波串长度加长;阻塞比增大有助于增大激波和膨胀波的入射角,从而增大激波和膨胀波的反射次数。随线间距的增大,管道内压力波动幅度相对增大,但改变线间距对管道内激波流场结构、管道壁面压力、列车表面压力的影响不大。列车头部压力和尾部激波强度与流线型长度存在一定的关系,随着列车流线型长度的增加,列车前端壅塞长度缩短,车头前端高压区壅塞强度和车尾末端尾流区域激波反射强度均减小。

升力翼对高速列车通过隧道时气动效应的影响

在高速列车上安装升力翼可以为高速列车提供升力,降低列车对轨道的压力,从而有效减少轮轨磨损,但安装升力翼对列车在隧道内行驶时的气动性能产生较大影响,为此,基于三维非定常可压缩RNG k−ε两方程湍流模型,对升力翼列车通过隧道时的气动效应进行数值模拟研究。研究结果表明:在列车进入隧道过程中,升力翼尾流结构增大,对列车表面压力产生一定的影响;升力翼尾流使列车表面压力下降,同时升力翼增加车隧阻塞比,使列车表面的压力上升,两者共同影响列车表面压力,导致列车表面压力分布复杂;安装升力翼使列车表面与隧道壁面的压力幅值均增加,列车表面压力幅值最大增加5.4%,隧道壁面压力幅值最大增加14.1%;同时,对隧道出口的微气压波产生不利影响,在距离隧道出口20 m处的微气压波幅值上升4.1%。研究结果可为升力翼的参数优化设计提供指导。

SolidWorks运动分析在周转轮系传动比计算教学中的应用研究

周转轮系传动比计算是机械基础教学中的重点与难点内容,其计算原理较为抽象,过程也比较复杂,学生不易掌握.为更简捷高效地求解周转轮传动比,应用SolidWorks建立了周转轮系各零件模型,并完成了仿真模型装配.在SolidWorks运动分析组件下模拟了周转轮系的运动过程,并依据模拟结果计算出了具有复杂结构的周转轮系传动比.模拟结果与理论计算结果比较接近,证明使用此方法计算周转轮系传动比是可行的.

高速铁路无砟轨道斜拉桥刚度理论分析与设计参数研究

为研究高速铁路无砟轨道斜拉桥的刚度特征以及合理结构设计参数,采用理论公式推导、数值分析等手段,得到结构设计参数刚度影响解析公式及其影响规律,用于指导桥梁设计。首先引入索梁活载刚度比的概念,通过建立斜拉桥主梁多点支承连续梁的三弯矩方程得到主梁刚度,通过考虑主塔变形和拉索伸长量得到斜拉索等效刚度,进而给出斜拉桥整体刚度、索梁活载刚度比和主梁跨中挠度的理论公式,并基于理论公式得出主梁惯性矩、斜拉索倾角、塔高以及拉索面积对斜拉桥整体刚度的影响。以广湛铁路东平水道特大桥主桥(67.5+60+60+350+60+60+67.5)m钢箱混合组合梁无砟轨道斜拉桥为例,通过对比跨中活载位移理论解与数值解验证本文理论公式的准确性,进而采用理论公式分析结构设计参数对桥梁刚度的影响。研究结果表明:随拉索倾角增大或者塔高增加,主梁的跨中位移先减小后增大,索梁活载刚度比先增大再减小,拉索倾角为29.2°~73.9°时主梁跨中位移达到最小值36.4 cm,此时索梁活载刚度比为15.4。随着主梁的梁高增加,主梁跨中位移减小,索梁活载刚度比减小,但是减小幅度较为缓慢。拉索面积增大,主梁跨中活载位移减小,索梁活载刚度比增加。提出了桥梁合理梁高、塔高和斜拉索规格及拉索面积。桥梁结构静动力检算、桥上轨道静态高低不平顺验算以及无砟轨道受力与层间压缩量等检算结果均表明,该桥具有良好的安全性和行车平稳性。

应用秩和比法综合评价浙江省住院医师临床实践能力结业考核结果

目的综合评价浙江省住院医师规范化培训(简称住培)临床实践能力结业考核结果,提出对策建议,为完善培训和考核提供参考依据。方法从浙江省医学教育信息服务平台获取数据,应用秩和比法,对21个专业临床实践能力考核结果进行综合评价并排序。结果考核结果分优、良、中、差4个档,核医学科和神经外科属于优档;耳鼻咽喉科、放射肿瘤科、超声医学科、麻醉科、儿科、皮肤科、神经内科、小儿外科和骨科属于良档;急诊科、康复医学科、全科医学科、口腔科、内科、外科、眼科、妇产科和放射科属于中档;精神科属于差档。结论应用秩和比法综合评价浙江省各专业临床实践能力考核情况具有理论和实践优势,有利于发现培训和考核的问题并及时改进,从而促进住院医师质量的提升。

Aerodynamic simulation of evacuated tube maglev trains with different streamlined designs

Based on the Navier-Stokes （N-S） equations of incompressible viscous fluids and the standard k-ε turbu- lence model with assumptions of steady state and two dimensional conditions, a simulation of the aerodynamic drag on a maglev train in an evacuated tube was made with ANSYS/FLOTRAN software under different vacuum pressures, blockage ratios, and shapes of train head and tail. The pressure flow fields of the evacuated tube maglev train under different vacuum pressures were analyzed, and then compared under the same blockage ratio condition. The results show that the environmental pressure of 1 000 Pa in the tube is the best to achieve the effect of aerodynamic drag reduction, and there are no obvious differences in the aerodynamic drag reduction among different streamline head shapes. Overall, the blunt-shape tail and the blockage ratio of 0.25 are more efficient for drag reduction of the train at the tube pressure of 1 000 Pa.

新型小径向/轴向刚度比的橡胶节点设计

为满足高速动车组电机悬挂要求,文章设计了一种新型小径向/轴向刚度比(径向刚度与轴向刚度比值)的橡胶节点,并通过有限元仿真分析、静刚度试验、疲劳试验及装车试验进行了验证。结果表明,这种结构的橡胶节点符合技术要求,且其预压缩简单有效,刚度范围可调,抗疲劳性能良好,具有良好的高温耐受性,满足电机运行环境的要求。

Analysis of torque transmitting behavior and wheel slip prevention control during regenerative braking for high speed EMU trains

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.

奥美沙坦酯联合利拉鲁肽注射液治疗糖尿病肾病对氧化应激损伤和尿白蛋白肌酐比值的影响

目的分析奥美沙坦酯联合利拉鲁肽注射液治疗糖尿病肾病对氧化应激损伤以及尿白蛋白肌酐比值的影响。方法在2019年7月~2023年2月诊治的糖尿病肾病患者中选取80例作为研究对象,采用随机数字表法将其分为对照组和观察组,各40例。两组均进行基础治疗,对照组在基础治疗基础上使用奥美沙坦酯治疗,观察组在基础治疗的基础上使用奥美沙坦酯联合利拉鲁肽注射液治疗,比较两组治疗效果、氧化应激水平[丙二醛(MDA)、超氧化物歧化酶(SOD)、总抗氧化能力(T-AOC)]、肾功能指标[血肌酐(Scr)、尿素氮(BUN)、尿白蛋白排泄率(UAER)]和尿白蛋白肌酐比值(UACR)。结果观察组治疗有效率90.00%(36/40)高于对照组60.00%(24/40)(P<0.05);两组治疗后MDA水平均降低,且观察组水平较低,两组SOD、T-TOC水平均升高,且观察组水平均较高(P<0.05);两组治疗后Scr、BUN、UAER、UACR水平均降低,且观察组水平较低(P<0.05)。结论奥美沙坦酯联合利拉鲁肽注射液治疗糖尿病肾病具有较好的临床效果,能够减轻患者氧化应激损伤,降低尿白蛋白肌酐比值,改善肾功能。

Numerical simulation and analysis of aerodynamic drag on a subsonic train in evacuated tube transportation

The aerodynamic drag on a train running in an evacuated tube varies with tube air pressure, train speed and shape, as well as blockage ratio. This paper uses numerical simulations to study the effects of different factors on the aerodynamic drag of a train running at subsonic speed in an evacuated tube. Firstly, we present the assumption of a steady state, two dimensional, incompressible viscous flow with lubricity wall conditions. Subsequently, based on the Navier-Stokes equation and the k-c turbulent models, we calculate the aerodynamic drag imposed on the column train with a 3-meter diameter running under different pressure and blockage ratio conditions in an evacuated tube transporta- tion （ETT） system. The simulation is performed with FLUENT 6.3 software package. An analyses of the simulation re- sults suggest that the blockage ratio for ETT should be in the range of 0.25-0.7, and the tube internal diameter in the range of 2-4 m, with the feasible vacuum pressure in the range of 1-10 000 Pa for the future subsonic ETT trains.

Impact of train speed on the mechanical behaviours of track-bed materials

For the 30,000 km long French conventional railway lines(94% of the whole network),the train speed is currently limited to 220 km/h,whilst the speed is 320 km/h for the 1800 km long high-speed lines.Nowadays,there is a growing need to improve the services by increasing the speed limit for the conventional lines.This paper aims at studying the influence of train speed on the mechanical behaviours of track-bed materials based on field monitoring data.Emphasis is put on the behaviours of interlayer and subgrade soils.The selected experimental site is located in Vierzon,France.Several sensors including accelerometers and soil pressure gauges were installed at different depths.The vertical strains of different layers can be obtained by integrating the records of accelerometers installed at different trackbed depths.The experimentation was carried out using an intercity test train running at different speeds from 60 km/h to 200 km/h.This test train was composed of a locomotive(22.5 Mg/axle) and 7 'Corail'coaches(10.5 Mg/axle).It was observed that when the train speed was raised,the loadings transmitted to the track-bed increased.Moreover,the response of the track-bed materials was amplified by the speed rise at different depths:the vertical dynamic stress was increased by about 10% when the train speed was raised from 60 km/h to 200 km/h for the locomotive loading,and the vertical strains doubled their quasistatic values in the shallow layers.Moreover,the stressestrain paths were estimated using the vertical stress and strain for each train speed.These loading paths allowed the resilient modulus Mrto be determined.It was found that the resilient modulus(M_r) was decreased by about 10% when the train speed was increased from 100 km/h to 200 km/h.However,the damping ratio(D_r) kept stable in the range of speeds explored.

Diffusion tensor imaging of spinal microstructure in healthy adults： improved resolution with the readout segmentation of long variable echo-trains

Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal the fine structure of the spinal cord with precision. We used the readout segmentation of long variable echo-trains（RESOLVE） sequence in this cross-sectional study of 45 healthy volunteers aged 20 to 63 years. We found that the RESOLVE sequence significantly increased the resolution of the diffusion images and improved the median signal-to-noise ratio of the middle（C4–6） and lower（C7–T1） cervical segments to the level of the upper cervical segment. In addition, the values of fractional anisotropy and radial diffusivity were significantly higher in white matter than in gray matter. Our study verified that the RESOLVE sequence could improve resolution of diffusion tensor imaging in clinical applications and provide accurate baseline data for the diagnosis and treatment of cervical spinal cord diseases.

地下车站排热通风系统困境及其原因探讨

对列车空调冷凝器运行热环境的控制能力是衡量地铁车站轨区排热系统性能的重要指标,然而现有排热通风系统客观上存在排热效果不佳、能耗高、风道调试难和施工周期长,以及安全隐患等问题。本文通过对不同车站排热系统的运行状态实测和调研发现,排热系统控温效果不明显、风口风量分布不均,且不同地铁环境中设置排热系统的必要性有差异。进一步对排风口现状典型风量和目标风量下的热环境和排热效率进行了CFD计算和对比分析,结果显示:排热风口风量分布不均是影响排热系统性能的主要原因;当每台冷凝器对应排风量达到2.5 m^(3)/s时,排热效率超过55%、热风比达到16.7 J/m^(3),系统控制轨区热环境的能力显著提高。

A PTS Optimization Scheme with Superimposed Training for PAPR Reduction in OFDM System

Partial Transmit Sequences (PTS) is an efficient scheme for Peak-to-Average Power Ratio (PAPR) reduction in Orthogonal Frequency Division Multiplexing (OFDM) system. It does not bring any signal distortion. However, its remarkable drawback is the high computational complexity. In order to reduce the computational complexity, currently many PTS methods have been proposed but with the cost of the loss of PAPR performance of the system. In this paper, we introduce an improved PTS optimization method with superimposed training. Simulation results show that, compared with conventional PTS, improved PTS scheme can achieve better PAPR performance while be implemented with lower computation complexity of the system.

一种3K-H行星轮系自锁与效率最大化设计

行星轮系主要用于动力传递,研究其自锁及效率具有重大意义。针对一种3K-H型行星轮系进行了自锁分析与效率最大化设计。首先,运用传动比法对该轮系正反机构效率进行了计算;然后,对该行星轮系效率总结出了一个统一公式,并且通过Matlab软件绘制了效率曲线;接着,分析了该行星轮系效率变化的趋势以及能够实现自锁的条件;最后,研究了在保证自锁条件下如何实现其相反机构效率最大化的设计。

等速离心训练对肩关节内外旋肌的肌力平衡及神经肌肉控制能力的影响

背景肩关节内外旋肌肌力失衡会增加肩部运动损伤的风险,研究等速离心训练(IET)能否提高肌力平衡并改善神经肌肉控制能力具有重要的损伤预防意义。目的探讨IET对健康青年人肩关节内外旋肌的肌力平衡及神经肌肉控制能力的影响。方法2020年12月至2021年11月在复旦大学附属中山医院招募32例健康青年志愿者为研究对象,随机将其分为试验组(n=16)和对照组(n=16)。试验组接受4周IET,对照组接受4周连续被动运动训练(2次/周)。采用Biodex System 4 Pro多关节等速肌力测试与训练系统(美国Biodex公司)对两组研究对象的优势侧肩关节内、外旋肌群进行训练干预,分别在60(°)/s、120(°)/s速度下进行,干预前1周、干预结束后1周对两组肩关节内外旋肌的功能性比率(FR)、加速时间(AT)和达峰力矩时间(TPT)进行评估并比较。结果试验组全部完成了4周的训练干预和评估,对照组2例中途退出。最终共30例研究对象数据纳入统计学分析。在60(°)/s和120(°)/s速度下,试验组干预后FR高于对照组(P<0.001),试验组干预后FR高于干预前(配对t检验:t_(60(°)/s)=-7.881,P<0.001;t_(120(°)/s)=-6.563,P<0.001);试验组外旋肌、内旋肌干预后AT低于对照组(P<0.05),试验组外旋肌干预后AT低于干预前(配对t检验:t_(60(°)/s)=2.383,P<0.05;t_(120(°)/s)=2.849,P<0.05),试验组内旋肌干预后AT低于干预前(配对t检验:t_(60(°)/s)=3.138,P<0.05;t_(120(°)/s)=2.839,P<0.05);试验组外旋肌、内旋肌干预后TPT低于对照组(P<0.05)。结论IET能够提高肩关节内外旋肌的肌力平衡,保持肩关节的动态稳定,并能改善神经肌肉控制能力,以此可能会降低运动损伤的风险。

一种基于最优频带的走行部故障检测方法

基于振动信号的走行部故障诊断是目前列车健康监测的重要途径之一,选择准确的解调频带是故障识别的先决条件。由于列车走行部结构复杂、运行环境恶劣,早期故障信号容易被各种干扰信号遮蔽。针对走行部复杂的振动环境,结合故障识别(fault diagnosis,FD)算法在三分法的基础上引入了循环分量占比(ratio of cyclic content, RCC),提出了RCCFD算法。通过对仿真信号、滚动台振动信号、列车轴箱振动信号的对比分析,结果表明:RCC-FD算法能够在强循环脉冲干扰、随机脉冲干扰的工况下提取出以目标故障特征信息为主导的最优频带,同时具有更高的计算效率,更加适用于列车走行部实时故障诊断。

考虑客流空间分配的城轨市郊线快慢车开行比例优化

为实现城轨市郊线运能与客流最大限度的匹配,提升轨道交通服务水平,首先构建了路段广义费用函数,基于Beckmann交通平衡模型分配方法,建立乘客换乘方式选择的客流分配模型;其次,以单位时间路段客流分配矩阵为样本点,采用有序聚类分割算法,根据乘客空间分布特征,将快慢车选择相近时段划分为同一运营时段,建立快慢车开行比例及停站优化模型,实现线路上所提供的运能与客流需求最大限度的匹配;最后,通过算例分析比较优化前后快慢车开行数量和比例及停站次数,验证该优化模型的有效性。研究结果表明,综合考虑乘客时间和空间分布规律的快慢车开行方案优化模型,不仅能够减少线路全日停车次数,而且在满足乘客出行需求提升服务水平的同时降低企业运营成本。

永磁悬浮列车磁路设计与仿真研究

国家“碳达峰、碳中和”战略对城市轨道交通载运工具的能耗提出更高的要求。永磁悬浮列车可实现“零功率”悬浮,具有无噪声、造价低且载重能力强等诸多优势,契合未来交通制式的发展趋势。文章针对永磁悬浮列车的磁路设计,在有限元仿真软件中对所设计的悬浮模式进行建模,并在阵列的原始计算参数约束下对永磁体的磁体间距、宽度、高度进行尺寸优化,得到初始永磁悬浮模型下的最优磁路设计。对比2种直线型4模块Halbach永磁阵列与初始永磁悬浮模型的悬浮效率,并利用一个极距内磁场最大化的浮重比优化函数,辅助Halbach阵列的磁体尺寸优化,最后成功构建“1m长永磁导轨悬浮3t、3.5t、4t、4.5t重车载”4种可行性方案,并确定最优浮重比。

纯电动汽车传动系参数的区间优化方法

在分析纯电动汽车传动系减速比传统优化模型的基础上,提出了区间优化方法。优化的目的是在满足电动汽车基本动力性能的前提下,求优化变量的最大可行区间,而不是一个确定的最优值。区间优化方法便于产品的系列化,可以解决传动系齿轮配齿问题。以XL2000型纯电动汽车传动系参数的优化设计为例,对所建模型进行了验证。