采空区地层变形产生的隧道附加荷载及变形容许值计算与分析

文章分别计算了采空区上方地层弯曲时对隧道产生的附加荷载q1、q2及地层水平应变时对隧道产生的附加荷载qH,并推导出了采空区地层容许弯曲变形和水平应变数值.结果表明,现行交通部《采空区公路设计与施工技术细则》规定的采空区地基容许变形值较为笼统且偏大,结构偏于不安全.最后,文章根据计算结果对比,对不同围岩级别提出了更严格、更安全、更有针对性和可操作性的隧道对采空区地层变形限制要求,以供广大隧道工作者参考使用.     

汽车低速碰撞模拟中的关键因素识别

为了在车辆开发过程中快速准确地识别各种边界条件变化对车辆低速碰撞性能的影响,选取3种不同结构特征的防撞梁结构,就模型简化、模型剪切、整备质量、重叠量、Y向撞击位置、角碰角度偏差和碰撞速度偏差7大因素进行分析研究,并识别出关键影响因素,为后续指导防撞梁开发奠定基础。     

基于磁流变悬置的整车建模与振动控制的研究

以磁流变悬置动态性能试验结果为数据样本,利用广义回归神经网络(GRNN)辨识方法建立了磁流变悬置的正、逆模型,并将辨识模型用于悬置系统的控制;建立了基于磁流变悬置的整车10自由度动力学模型,以发动机转速和悬置点处的加速度信号为输入,设计了模糊控制器,对磁流变悬置进行半主动控制的仿真。结果表明:该模糊控制器具有较好的宽频隔振效果,悬置点处的振动加速度峰值明显减小,验证了GRNN模型和模糊控制器算法的正确性和有效性。     

西成客运专线车站布局方法研究

合理安排高速铁路客运站布局可以提高铁路通过能力,提高运营管理水平。文中阐述铁路客运专线客运站布局的一般方法;为估算高速铁路客运站数量引入了合理站间距的概念,介绍车站数量计算方法及站间距对车站布局研究的影响。为了评估客运车站布局方案,分层建立了客运站布局方案的评价指标体系,运用层次分析法确定各评价指标的权重。利用该模型对西安-成都客运专线车站布局的方案进行优选,得出最优方案,优选结果与实际是一致的。     

Realization of pmp-based control for hybrid electric vehicles in a backward-looking simulation

Optimal control is generally not possible without information about the future coming up, and it is not easy to obtain an optimal solution even though the information is given a priori. In this paper, a control concept based on Pontryagin’s Minimum Principle (PMP) is introduced as an efficient solution to generate an optimal control trajectory for Hybrid Electric Vehicles (HVEs) when the performance of the vehicles is evaluated on scheduled driving cycles at a simulation level. The main idea of the control concept is to minimize Hamiltonian, which is interpreted as equivalent fuel consumption, and the Hamiltonian is characterized by a co-state, which is interpreted as a weighting factor for the electrical usage. A key aspect of the control problem is that an appropriate initial condition of the co-state is required to satisfy the boundary condition of the problem. In this study, techniques to calculate the Hamiltonian in different hybrid configurations are introduced, and a methodology to look for the initial condition of the co-state is studied, so that the controller is able to realize a desired State Of Charge (SOC) trajectory. To address the issue, we utilize a shooting method with multiple initial conditions based on the concept of the Newton-Raphson method, and all these techniques are realized in a backward looking simulator. The simulation results show that the PMP-based control is a very efficient approach to produce the optimal control trajectory, and the performance is compared to the optimal solution solved by Dynamic Programming (DP).     

汽车整体式转向梯形机构优化设计

以MATLAB软件为优化工具,通过对汽车整体式转向梯形进行合理设计,尽可能地保证汽车在转向过程中全部车轮均绕同一个瞬时转向中心行驶,使在不同圆周上运动的车轮,作无滑动的纯滚动运动。     

汽车正面碰撞事故车速预测模型仿真研究

为了能有效准确地根据事故现场情况预测出碰撞前车辆的运行车速情况,文章利用反推算法,遵循相关物理定律,构建正面碰撞事故中车辆相关参数及道路条件与车速的函数关系,并基于Visual Basic平台搭建车速预测模型并进行实测验证。结果表明,所构建模型的误差率较低,所构建模型、系统是正确高效的,可用于正面碰撞事故的车速预测研究工作。     

基于功能原理的汽车ABS制动距离计算及分析

对装有ABS汽车的制动过程进行分析;依据根据功能原理,建立了制动距离的计算数学模型,用该模型推导了ABS汽车在平路和坡道上制动距离的计算公式,该公式表明汽车制动距离的相关影响因素。同时该公式可以应用于汽车制动性能的分析。     

F550Z海洋平台用钢SAW焊接接头低温韧性研究

为研究大热输入条件下埋弧自动焊（ submerged arc welding ,SAW）对海洋平台用550 MPa钢焊接接头组织与低温韧性的影响,采用50 kJ＆#183; cm-1的焊接热输入,测定接头各区域冲击吸收功,并观测各区断口形貌及显微组织．结果表明：焊接接头韧性从焊缝到母材,呈现先降低后升高的趋势,最低处在熔合线及熔合线2 mm处．焊缝处组织为针状铁素体加细小弥散的碳化物,断口形貌为韧窝和解理台阶,-60℃冲击吸收功为110 J．熔合线及熔合线2 mm处断口形貌基本相同,只由放射区组成,无纤维区,微观特征为大面积的解理面,没有韧窝;微观组织为粗大粒状贝氏体,冲击吸收功非常低只有25 J．熔合线5 mm处断口纤维区面积较大,微观形貌含有大量的韧窝,微观组织为细小的铁素体、碳化物及粒状贝氏体,该区为焊接接头的正火区,具有优异的低温韧性,-60℃冲击吸收功为202 J．     

Intrusion detection model with twin support vector machines

Intrusion detection system （IDS） is becoming a critical component of network security. However, the performance of many proposed intelligent intrusion detection models is still not competent to be applied to real network security. This paper aims to explore a novel and effective approach to significantly improve the performance of IDS. An intrusion detection model with twin support vector machines （TWSVMs） is proposed. In this model, an etficient algorithm is also proposed to determine the parameter of TWSVMs. The performance of the proposed intrusion detection model is evaluated with KDD＇99 dataset and is compared with those of some recent intrusion detection models. The results demonstrate that the proposed intrusion detection model achieves remarkable improvement in intrusion detection rate and more balanced performance on each type of attacks. Moreover, TWSVMs consume much less training time than standard support vector machines （SVMs）.