Development of control models for the planning of sustainable transportation systems

Planning of sustainable transportation systems requires integration of multiple systems while considering a holistic approach. A limited amount of research has been conducted that simultaneously considers all the transportation, economic activity, environmental and social effects. The proposed research envisages incorporating considerations related to sustainability and providing solutions to stakeholders in policy making. In this paper, a dynamic model for planning and development of sustainable transportation systems is presented. This is given by a system of three nonlinear differential equations representing the dynamics of the three independent states, namely, transportation, activity, and environmental systems. A policy scenario considering investment in energy efficient technologies and its effects on the states is discussed to assist making investment decisions. Optimal control techniques are used to design the controls. The results show that it is possible to formulate an optimal control to achieve the desired target. Numerical results, based on actual parameters, are presented to illustrate the long-term trends of the states. The methodology discussed in this paper will be helpful to decision makers in making optimal decisions. The contribution of this research work is the introduction of a systems and controls methodology to develop optimal policies for the design of sustainable systems.     

Hybrid analytic-FEM approach for dynamic response analysis of air-cushion vehicle skirts

Focused on the assessment method for dynamic behavior of the skirts of an air cushion vehicle (ACV), this paper proposes a hybrid analytic-FEM approach, within which the self-developed subroutine considers the transient skirt-water contacting force through suggested semi-analytical formula based on the empirical results from CFD simulations of the equivalent flat-plate model. The dynamic explicit algorithm of FEM is adopted to solve the large deformation problem of flexible skirts. The validity of the approach has been confirmed by comparing with previous numerical results as well as published experimental results of steady seal deformation tests at University of Michigan. Afterward, more simulations for demonstration cases are carried out to study the complex dynamic response of the skirts under different skirt-water contacting conditions. The proposed method can obtain more reliable results than traditional analytical method and be more efficient than fluid-structure interaction simulations, thus providing a practical balanced approach aiming at the dynamic response analysis for whole skirts and contributing to the skirts dynamics performance assessment of an ACV.     

Learning marginal-cost pricing via a trial-and-error procedure with day-to-day flow dynamics

This paper investigates the convergence of the trial-and-error procedure to achieve the system optimum by incorporating the day-to-day evolution of traffic flows. The path flows are assumed to follow an ‘excess travel cost dynamics’ and evolve from disequilibrium states to the equilibrium day by day. This implies that the observed link flow pattern during the trial-and-error procedure is in disequilibrium. By making certain assumptions on the flow evolution dynamics, we prove that the trial-and-error procedure is capable of learning the system optimum link tolls without requiring explicit knowledge of the demand functions and flow evolution mechanism. A methodology is developed for updating the toll charges and choosing the inter-trial periods to ensure convergence of the iterative approach towards the system optimum. Numerical examples are given in support of the theoretical findings.     

磁流变阻尼器用于结构减振的控制策略研究

基于Bingham恢复力模型，对磁流变阻尼器用于结构减振的控制策略进行了探讨．根据磁流变液体阻尼器连续可调的特性，建立了一种改进控制策略的数学模型，并给出了它的简化求解方法．为了验证所建议控制策略的有效性，编制计算程序对一工程实例进行了仿真．结果表明，所建议的控制策略有更好的控制效果，具有较好的稳定性．     

龈沟液中MMP-2,9的量与牙周炎的关系

目的观察慢性牙周炎患者在牙周基础治疗前后龈沟液(GCF)中基质金属蛋白酶2,9(MMP2,9)水平的变化。方法采用滤纸条的袋内取样法取40例患者40个牙位治疗前(BT组)、治疗后(AT组)的GCF样本,同时取40例健康人的40个牙位的GCF样本,用酶联免疫法(ELISA)检测其中的MMP2,9的水平。结果牙周基础治疗后GCF中MMP2,9的总量均较治疗前显著下降(P<0.01),治疗前后MMP2,9的总量均与对照组有显著差别(P<0.01),治疗前后GCF中MMP2与MMP9的含量呈显著正相关(P<0.01)。结论GCF中MMP2,9的总量在牙周基础治疗后降低,其水平反映牙周组织的破坏和炎症程度,可作为评价疗效的客观指标。     

一系纵向定位间隙对磁流变耦合轮对车辆横向动力学性能的影响

为了合理控制车辆轮对定位间隙,提高磁流变耦合轮对车辆在高速时的横向动力学性能,建立该车辆的空间动力学模型,分析了轮对纵向定位间隙对车辆临界速度和曲线通过性能的影响。得出了纵向定位间隙的增大能使磁流变耦合轮对车辆的临界速度急剧下降,轮对横移量和冲角、轮轨横向力和车体横移加速度快速增大;只有在小间隙的条件下,车辆在高速铁路上才具有较高的临界速度和较好的曲线通过性能。     

关于带闭链工业机器人的动力学建模研究

本文在以影响系数矩阵为基础进行带闭链机器人的动力学方程推导时，采用了符号一数值方法。在计算机上获得一，二阶影响系数矩阵和动力学方程中各矩阵元素的最简解近表达式，解决了当分支的广义坐标数不等于６时出现的长方形（奇异）矩阵求逆的解析表达问题。在ＶＡＸ机上偏制调试出了该方法应的软件，并应用于一个带单闭链地的的孤焊机械手的动力学建模。     

机车—桁架桥梁耦合振动研究

建立了轮对和钢轨之间弹性联接３３个自由度的机车车辆动力学模型，采用有限元法分析计算了列车荷载作用下某铁路双线钢桁桥的动力响应。采用空间梁单元建立了桁架桥的振动方程。根据随机振动理论计算了当列车过桥时，车－桥耦合振动系统的空间动力响应，并与实测结果进行了比较，比较表明，采用弹性联接横型比密贴模型的计算结果更接近于实测值。     

船用空心电抗器温度场研究

建立了空心电抗器磁场-电路-流场-温度场的耦合计算模型。通过该模型可以计算得到磁场、电感和电流以及空心电抗器的气流场和温度场分布。以一种空心电抗器为例,将温度计算值与实测值作了比较。结果表明,该方法具有较高的计算准确度,能够满足工程设计的要求。     

道路交通事故模拟再现的车辆动力学三维模型

应用动力学理论，提出了用于道路交通事故模拟再现分析的车辆动力学三维模型，并引用日本汽车研究所的16例车对车实车碰撞实验数据对该三维模拟模型的计算误差进行界定，并与二维四轮模拟模型的计算精度进行了定量比较，针对实际道路交通事故案例进行了模拟再现。实例证明车辆三维模型在计算车辆碰撞动力学问题时的总体平均相对误差值为6．65％，虽然相对于车辆二维四轮模型其速度计算精度在总体水平上降低了1．43％，但若考虑到其对道路交通事故形态的包容性和形象化方面的优势，计算精度的适度降低是可以接受的。