鄱阳湖二桥结构动力特性分析

桥梁结构动力特性分析是进行车桥耦合分析、地震反应分析及风振分析的理论基础,系统而深入地认识桥梁结构动力特性十分重要。该文针对鄱阳湖二桥工程设计实例,采用Ansys和Midas Civil两种大型有限元分析程序,在考虑模型精细程度的影响下,建立了3种有限元模型。结合这3种模型的动力特性计算结果,对全桥动力特性进行了对比分析。结果表明:依据规范估算的竖向弯曲基频值较实际计算值偏小;采用Ansys建立的杆系斜拉桥模型计算速度快、模型简单且有效。     

Investigation of the impact of locomotive creep control on wear under changing contact conditions

This paper presents the locomotive traction controller performance with respect to the track wear under different operation conditions. In particular, an investigation into the dynamic response of a locomotive under changing wheel–rail friction conditions is performed with an aim to determine the effect of controller setting on track wear. Simulation using a full-scale longitudinal–vertical locomotive dynamic model shows that the appropriately designed creep threshold, controller, settings can effectively maintain a high tractive effort while avoiding excessive rail damage due to wear, especially during acceleration under low speed.     

高铁外流场对站台建筑物的影响

采用LS-DYNA数值模拟计算的方法,对高铁某站台列车进站时造成的空气扰动对雨棚的受力进行分析。主要分别模拟了两列车同时同向进站,两列车不同方向进站,单独一辆车进站4种不同情况下造成的空气扰动对雨棚的影响,给出其在不同时刻的等效应力云图,同时给出其不同情况下的最大应力值。     

Research on High Power Inter-Channel Crosstalk Attack in Optical Networks

While all-optical networks become more and more popular as the basis of the next generation Internet(NGI)infrastructure,such networks raise many critical security issues.High power inter-channel crosstalk attack is one of the security issues which have negative effect on information security in optical networks.Optical fiber in optical networks has some nonlinear characteristics,such as self phase modulation(SPM),cross phase modulation(XPM),four-wave mixing(FWM)and stimulated Raman scattering(SRS).They can be used to implement high power inter-channel crosstalk attack by malicious attackers.The mechanism of high power inter-channel crosstalk attack is analyzed.When an attack occurs,attack signal power and fiber nonlinear refractive index are the main factors which affect quality of legitimate signals.The effect of high power inter-channel crosstalk attack on quality of legitimate signals is investigated by building simulation system in VPI software.The results show that interchannel crosstalk caused by high power attack signal leads to quality deterioration of legitimate signals propagated in the same fiber.The higher the power of attack signal is,the greater the fiber nonlinear refractive index is.The closer the channel spacing away from the attack signal is,the more seriously the legitimate signals are affected by attack.We also find that when attack position and power of attack signal are constant,attack signal cannot infinitely spread,while its attack ability shows a fading trend with the extension of propagation distance.     

基于自航流场数值模拟的舵球节能流场分析

本文采用快速性数值模拟方法对加装舵球的36000吨散货船进行了节能评估。结果显示,加装舵球能起到一定的节能效果。之后本文对有、无舵球的两种方案的自航数值模拟流场进行了对比,分析获得了舵球节能的原理。本文模拟结果不仅可作为模型试验的有力补充,也可为舵球的优化设计提供重要参考。     

基于Atkinson循环的混合动力汽车用发动机探讨

Atkinson循环发动机在低速小负荷时性能较差,但混合动力汽车在低速小负荷时采用电动机驱动避开其性能不好的工况范围,使其在中间负荷区域充分发挥优势。Atkinson循环利用进气门晚关控制负荷,减少了泵气损失和压缩功,可以更大程度地将热能转换为机械能,提高发动机热效率,从而降低燃油消耗;实际压缩比的降低使缸内燃烧温度降低,有利于改善NOX排放。采用Atkinson循环能提高整车的燃油经济性和排放性能。     

框架式地道桥考虑纠偏内力影响的结构优化设计

利用ANSYS有限元软件计算某大型斜交框架式地道桥顶进纠偏施工时桥体产生的剪应力和主拉应力,并依此应力作为施工顶进纠偏的控制参数之一,对该地道桥体结构尺寸进行了优化设计。     

一种CSPRs起飞尾流安全间隔动态缩减方法

国内近距错列平行跑道的主流运行模式是隔离平行运行,由于该模式采用了较为保守的尾流安全间隔,在航空器离场相对集中时段会出现一定程度的放行拥堵问题.对此,文章选取了双起双落相关运行模式,以近距错列平行跑道为研究对象,结合起飞尾流的演化特征,提出一种基于气象条件的航空器起飞尾流动态缩减方法,并以黄花国际机场的跑道主要参数为仿...     

回汽控制对舰用蒸汽动力系统的影响

[目的]船用蒸汽动力系统在紧急减速或换向操作过程中,回汽控制技术是缓解锅炉内锅筒超压问题的有效手段,需对其带来的影响进行研究。[方法]建立增压锅炉、主汽轮机和螺旋桨等设备的蒸汽动力系统仿真模型,针对大型舰船紧急减速过程和换向操作过程中快关阀无回汽、快关阀有回汽、慢关阀无回汽这3种工况,开展回汽控制特性的仿真对比分析。[结果]仿真结果表明：回汽控制可以有效避免紧急减速过程和换向过程中的锅筒超压问题,且系统稳定耗时分别缩短了3 min和1 min左右。[结论]研究成果可为舰船机动性设计和安全性设计提供参考。     

民用载货汽车发展对军用汽车编配的启示

为促进我军汽车部队发展,充分利用民用载货汽车发展优势,有效弥补当前部队运力不足的问题,提高部队运输力,详细分析了我国民用载货汽车规模类型与运营现状,结合民用运力专业化服务水平高、运营成本低、越野性能差的特点,根据军用汽车编配现状及发展需求,提出了适当减少普通运输车编配以降低运营成本、针对性发展专用运输车以提高专业化服务水平以及合理编配越野运输车等几项措施。为促进汽车部队的发展,提升运输保障能力提供有益参考。