荷载分散型锚索差异补偿荷载的广义确定

研究目的:本文研究荷载分散型锚索张拉过程中差异补偿荷载的确定理论和方法.研究结论:本文提出的荷载分散型锚索张拉时差异补偿荷载的广义确定计算方法,适用于各种荷载分散型锚索,具有较强的实用性;锚索在进行整体张拉之前,从底部较长的锚索单元开始对各单元锚筋依次进行补偿张拉后再一起张拉至设计张拉荷载,可以使各单元锚筋的受力均匀;在考虑各单元锚筋计算变形段摩阻的情况下,锚索张拉后作用于锚固段的锚固力更接近于设计锚固力.     

考虑时间效应下新旧桥基础差异沉降研究

在桥梁拓宽改造工程中,必然涉及新建桥梁和原有桥梁基础差异沉降及桥面板的开裂等问题。考虑沉降与时间的关系下,对桥梁基础沉降量计算方法进行了研究,计算出了旧桥的总沉降量及工后沉降结果,结合新建桥的实际情况提出相应处理办法。     

Modeling Human Vehicle Driving by Model Predictive Online Optimization

A driver model is designed which relates the driver's action to his perception, driving experience, and preferences over a wide range of possible traffic situations. The basic idea behind the work is that the human uses his sensory perception and his expert knowledge to predict the vehicle's future behavior for the next few seconds (prediction model). At a certain sampling rate the vehicle's future motion is optimized using this prediction model, in order to meet certain objectives. The human tries to follow this optimal behavior using a compensatory controller. Based on this hypothesis, human vehicle driving is modeled by a hierarchical controller. A repetitive nonlinear optimization is employed to plan the vehicle's future motion (trajectory planning task), using an SQP algorithm. This is combined with a PID tracking control to minimize its deviations. The trajectory planning scheme is experimentally verified for undisturbed driving situations employing various objectives, namely ride comfort, lane keeping, and minimized speed variation. The driver model is then applied to study path planning during curve negotiation under various preferences. A highly dynamic avoidance maneuver (standardized ISO double lane change) is then simulated to investigate the overall stability of the closed loop vehicle/driver system.     

240火花塞式燃气机预燃燃烧技术研究

针对目前国内外气缸直径200 mm,单缸排量10 L以上火花塞式4冲程燃气机热效率低、热负荷高、可靠性低等问题,以南车资阳机车有限公司240系列火花塞式燃气机(燃气主要成分为CH4)为例,简要介绍对解决这些问题进行的预燃燃烧技术研究.     

A comparison of various algorithms to extract Magic Formula tyre model coefficients for vehicle dynamics simulations

Tyre models are a prerequisite for any vehicle dynamics simulation. Tyre models range from the simplest mathematical models that consider only the cornering stiffness to a complex set of formulae. Among all the steady-state tyre models that are in use today, the Magic Formula tyre model is unique and most popular. Though the Magic Formula tyre model is widely used, obtaining the model coefficients from either the experimental or the simulation data is not straightforward due to its nonlinear nature and the presence of a large number of coefficients. A common procedure used for this extraction is the least-squares minimisation that requires considerable experience for initial guesses. Various researchers have tried different algorithms, namely, gradient and Newton-based methods, differential evolution, artificial neural networks, etc. The issues involved in all these algorithms are setting bounds or constraints, sensitivity of the parameters, the features of the input data such as the number of points, noisy data, experimental procedure used such as slip angle sweep or tyre measurement (TIME) procedure, etc. The extracted Magic Formula coefficients are affected by these variants. This paper highlights the issues that are commonly encountered in obtaining these coefficients with different algorithms, namely, least-squares minimisation using trust region algorithms, Nelder–Mead simplex, pattern search, differential evolution, particle swarm optimisation, cuckoo search, etc. A key observation is that not all the algorithms give the same Magic Formula coefficients for a given data. The nature of the input data and the type of the algorithm decide the set of the Magic Formula tyre model coefficients.     

高速公路扩建工程中新路填筑对老路影响的参数分析

道路扩建中加宽路堤的填筑将会改变原有路堤及地基的应力场和应变场,引起老路的附加差异变形。采用弹塑性有限元参数分析方法探讨了不同加宽路堤宽度、不同软土层厚度、不同的新老路堤刚度比时加宽路堤的填筑对老路变形规律的影响。计算结果表明:拓宽路堤的填筑将会引起老路不同位置的过大附加差异沉降,导致路面横坡比改变值超过路面结构的容许值,从而引起路面结构性破坏和路面服务性能的降低。因此,必须采用合适的软基处理方案对加宽部分软基进行处理。     

带差速机构的跨坐式单轨车辆性能研究

借鉴轨道交通车辆差速控制技术,在跨坐式单轨车辆走行系统上增设差速机构,可使左、右走行轮以不同转速通过曲线,从而达到改善车辆动力学性能、降低走行轮磨损的目的。建立了带差速机构的跨坐式单轨车辆耦合动力学模型。与常规单轨车辆相比,带差速机构跨坐式单轨车辆在曲线工况下走行轮的纵向力、回正力矩降幅明显,车辆动力学性能更优,车辆走行轮磨损也得到有效控制。     

连续时间的均值-方差组合选择及其有效前沿

对于有限时间区间的(d+1)种资产市场模型,在模型系数为随机过程的条件下,根据均值-方差准则讨论了风险资产市场中的投资组合问题.利用K.It公式和倒向随机微分方程理论,建立了投资组合过程与财富过程之间的随机控制的倒向随机微分方程模型,得到了初始财富及最终财富之间的关系式,证明了投资组合的存在惟一性,在均值-方差准则下给出了有效投资组合的解析表达式,并得到了有效投资组合下的双曲线型有效前沿.     

基于GPS的实时机车运行信息传输系统

利用铁路既有的列车无线调度通信系统和铁路分组交换网络, 结合GPS技术, 提出了一种实现机车运行信息实时传输的方案。采用话音压缩/扩展和数据同传, 使无线列调在原来只传输话音的基础上增加了数据传送, 数据仓库又使得这些信息能在铁路相关部门实现共享, 可实现机车中低速率的数据传输。