具有值机功能的轨道交通机场线车站布局方案

近年来,随着国内机场客流量的高速增长及城市轨道交通建设步伐的加快,各大、中城市也开启了轨道交通机场线的建设。结合国内外机场提前值机的概念,以西安北客站至咸阳国际机场的轨道交通机场线为例,分析了值机客流的特征,研究了具备提前值机功能的轨道交通机场线车站布局的3个可行性方案,并指出了实现机场功能外移所存在的问题。     

Prediction of the interaction between a simple moving vehicle and an infinite periodically supported rail – Green's functions approach

This paper herein describes the interaction between a simple moving vehicle and an infinite periodically supported rail, in order to signalise the basic features of the vehicle/track vibration behaviour in general, and wheel/rail vibration, in particular. The rail is modelled as an infinite Timoshenko beam resting on semi-sleepers via three-directional rail pads and ballast. The time-domain analysis was performed applying Green's matrix of the track method. This method allows taking into account the nonlinearities of the wheel/rail contact and the Doppler effect. The numerical analysis is dedicated to the wheel/rail response due to two types of excitation: the steady-state interaction and rail irregularities. The study points out to certain aspects regarding the parametric resonance, the amplitude-modulated vibration due to corrugation and the Doppler effect.     

On the security of multivariate hash functions

Multivariate hash functions are a type of hash functions whose compression function is explicitly defined as a sequence of multivariate equations. Billet et al designed the hash function MQ-HASH and Ding et al proposed a similar construction. In this paper, we analyze the security of multivariate hash functions and conclude that low degree multivariate functions such as MQ-HASH are neither pseudo-random nor unpredictable. There may be trivial collisions and fixed point attacks if the parameters of the compression ftmction have been chosen. And they are also not computation-resistance, which makes MAC forgery easily.     

美国交通运输机构及职能简介

从4个层次分别介绍美国联邦政府运输机构、美国联邦独立运输管理机构、美国地方交通运输机构及美国道路交通管理机构的职能分工，侧重于其在道路交通管理方面的职能。     

英语比喻修辞方法的巧用初探

在英语语言中,英语比喻修辞方法应用范围极为广泛。我们在深入学习英美文学和西方文化时,应特别注意对此加以研究,以便提高对英语语言背景的理解能力,指导英美文学赏析。本文从妙用英语比喻修辞方法的语言技巧入手,结合实例,探讨比喻方法的多元功能。     

Design of robust-stable and quadratic finite-horizon optimal controllers with low trajectory sensitivity for uncertain active suspension systems

This paper presents a design method for designing the robust-stable and quadratic-finite-horizon-optimal controllers of uncertain active suspension systems. The method integrates a robust stabilisability condition, the orthogonal functions approach (OFA) and the hybrid Taguchi-genetic algorithm (HTGA). Using the integrative computational method, a robust-stable and quadratic-finite-horizon-optimal controller with low-trajectory sensitivity can be obtained such that (i) the active suspension system with elemental parametric uncertainties is stabilised and (ii) a quadratic-finite-horizon-integral performance index including a quadratic trajectory sensitivity term for the nominal active suspension system is minimised. The robust stabilisability condition is proposed in terms of linear matrix inequalities (LMIs). Based on the OFA, an algebraic algorithm only involving the algebraic computation is derived for solving the nominal active suspension feedback dynamic equations. By using the OFA and the LMI-based robust stabilisability condition, the dynamic optimisation problem for the robust-stable and quadratic-finite-horizon-optimal controller design of the linear uncertain active suspension system is transformed into a static-constrained-optimisation problem represented by the algebraic equations with constraint of LMI-based robust stabilisability condition; thus greatly simplifies the design problem. Then, for the static-constrained-optimisation problem, the HTGA is employed to find the robust-stable and quadratic-finite-horizon-optimal controllers of the linear uncertain active suspension systems. A design example is given to demonstrate the applicability of the proposed integrative computational approach.     

某发动机冷却风扇噪声传递路径贡献量测试分析

某发动机冷却风扇存在明显的阶次噪声,冷却风扇噪声传递到车内主要有空气传递和结构传递两条路径。分析结果表明冷却风扇噪声随着转速的增加而增大,且在不同转速区间内,结构传递和空气传递贡献量不同。文章的研究对冷却风扇的阶次噪声控制具有重要意义。     

Economies of density and factor substitution in Dublin city bus services — a translog approach

The primary aim of the paper is to determine a short‐run cost function for Dublin City Bus Services (DCS), using a translog approach. The results show that there are significant economies of density in the transit operation. The results also indicate that the structure of DCS is characterised by a homothetic production function and that partial elasticities of substitution are non‐unitary.     

水下加肋双层圆柱壳体的振—声传递路径分析

简要介绍了有限元声振耦合和结构振-声传递路径分析(TPA)的基本理论。基于CAE技术建立了TPA模型,通过ANSYS声振耦合的谐响应分析,获得水下双层圆柱壳体振动响应和声场中的声压响应,利用矩阵条件数曲线优选测点位置,并结合奇异值修正的方法改善频响函数矩阵病态问题,求得振源的耦合激励力和振—声频响函数。由自编TPA程序计算得到两个振源作用下目标点的合成噪声响应与ANSYS实际计算吻合很好。利用频谱贡献云图、矢量叠加图及数据对比的方式分析了传递路径对壳外目标点噪声的贡献,从传递路径的角度找出了对壳外噪声起主导作用的环节。可见,基于CAE方法的水下双层圆柱壳体结构振-声TPA方法具有精度高、易操作、成本低等优点,对潜艇的优化设计、运行管理、针对性的维修均具有十分重要的意义。     

基于传递路径分析的乘用车车内噪声数值模拟

本文利用传递路释分析(TPA)方法对某一新型轿车进行轮胎引起的车内噪声分析,首先运用TPA方法拟合测试数据以求出路面对轮胎的轮心激励值,再将该值加载到CAE模型内进行数值模拟,计算车内噪声。数值模拟计算中发现乘用车后轴对整车噪声的贡献大于前轴,说明需要对乘用车的后轴进行改进;比较数值模拟结果与路面噪声的实际测试数据,发现分析误差可接受,完全可以反映出车辆车内噪声特性,验证了传递路径分析方法在车内噪声分析中的适用性和准确性。