基于时间自动机模型的安全计算机平台的形式化验证

众多工业控制领域要求计算机控制系统具有高可靠、高可用和高安全的运行基础,2乘2取2冗余结构的安全计算机平台是提高系统安全性、可靠性的一种重要解决方式。CBTC列控系统的安全计算机平台采用2乘2取2冗余结构,它是一个实时系统,控制过程需要考虑时间因素。本文分析CBTC系统安全计算机平台系统的组成结构,提取出系统的功能约束,采用基于时间自动机理论的建模验证工具UPPAAL建立系统的自动机网络模型,进行仿真分析,验证系统的功能性、实时性、安全性要求。     

6240/275ZC型系列船用柴油机增压器的研制

介绍了6240/275ZC型船用柴油机增压器ZN270的研制情况.大连机车研究所公司针对该型柴油机的运用特点在性能、结构和维护等方面进行了增压器的设计,通过与不同柴油机制造厂家生产的此类型柴油机进行了配套试验,取得了良好效果,现已在国内使用,对于拓展该型柴油机的应用提供了有力地支持.     

考虑防撞墙影响的高速铁路桥梁声屏障及翼缘板上脉动力数值分析

以可压缩黏性流体的N-S方程和k-ε双方程湍流模型为基础,考虑防撞墙对空压的影响,采用计算流体力学软件PHOENICS,对高速列车行驶时作用在有防撞墙铁路桥梁声屏障和箱梁翼缘板上的脉动力分布进行数值分析.结果表明,列车车头驶入声屏障、经过声屏障中部区域和驶出声屏障时,声屏障各处脉动力时程曲线形式不同,脉动力沿声屏障高度的分布为先增大后减小,约在1/2声屏障高度处达到最大值;桥梁翼缘板上的脉动力峰值沿横桥向基本呈线性增大至防撞墙处;声屏障和桥梁翼缘板上的脉动力峰值与列车速度的平方呈线性关系.根据分析结果给出了脉动力峰值计算公式以及考虑脉动力的结构设计组合荷载.     

SD大鼠肝脏及附属管道的应用解剖

通过对150只成年SD大鼠肝脏及其附属管道的解剖学研究，明确了大鼠肝脏的位置、分叶、形态、韧带、管道系统及与周围脏器的毗邻关系，同时测量了肝脏各叶径线、重量百分比及肝脏附属管道的长度和直径。结果表明：大鼠肝脏分为6叶，即左外叶、左内叶、中叶、右叶、尾状叶、乳头叶，各叶县有相对独立的Glisson系统和肝静脉回流系统；各肝叶形态、比例较为恒定。本文还对以大鼠作肝胆疾病医学研究模型，如肝叶切除、肝脏再生、肝移植等的应用解剖问题进行了讨论。     

LEISHMANIA PROMASTIGOTES EVADE INTERLEUKIN 12 INDUCTION BY MACROPHAGES AND STIMULATE A BROAD RANGE OF CYTOKINES FROM CD_（4）~（＋

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用动物模型定位、克隆复杂性疾病的易感基因:以类风湿关节炎动物模型为范例(续前)

3在大鼠关节炎模型上定位克隆易感基因在大鼠关节炎模型定位克隆易感基因,如图1所示:是将经典的纯系育种分离技术,结合congenic和重组系的建立,窄化易感区域,定位克隆基因,最终确定基因变异、功能变化和关节炎表型的关系[34-35]。具体步骤见图1。图1在大鼠关节炎模型上,定位克隆关节炎易感基因流程图Fig.1 Identification of susceptible genes to arthritis in rat models3.1选择亲代近交系,建立关节炎模型在数种关节炎模型中,用于进行基因定位克隆的模型有:胶原诱导性关节炎、油诱导性关节炎和Pristane诱导的关节炎。我们的研究工作主要…     

Numerical analysis of the dynamic interaction between wheel set and turnout crossing using the explicit finite element method

A three-dimensional (3-D) explicit dynamic finite element (FE) model is developed to simulate the impact of the wheel on the crossing nose. The model consists of a wheel set moving over the turnout crossing. Realistic wheel, wing rail and crossing geometries have been used in the model. Using this model the dynamic responses of the system such as the contact forces between the wheel and the crossing, crossing nose displacements and accelerations, stresses in rail material as well as in sleepers and ballast can be obtained. Detailed analysis of the wheel set and crossing interaction using the local contact stress state in the rail is possible as well, which provides a good basis for prediction of the long-term behaviour of the crossing (fatigue analysis). In order to tune and validate the FE model field measurements conducted on several turnouts in the railway network in the Netherlands are used here. The parametric study including variations of the crossing nose geometries performed here demonstrates the capabilities of the developed model. The results of the validation and parametric study are presented and discussed.     

One-dimensional model on fuel penetration in diesel sprays with gas flow

In diesel engine, spray penetration is usually changed by in-cylinder gas flow. Accurate prediction on diesel spray with gas flow is important to the optimal design of diesel fuel injection system. This paper presents a theory investigation focusing on the penetration of diesel spray with gas flow. In order to understand the effect of gas flow on the penetration of diesel spray, a one-dimensional spray model is developed from an idealized diesel spray, which is able to predict the spray behavior under different gas flow conditions. The ambient gas flow is simplified as ideal flow that has only constant flow velocity along x-axial and y-axial directions of spray. The x-axial and y-axial directions are respectively defined as along and vertical spray directions. The main assumption is that the y-axial direction gas flow has no effect on the penetration of spray along x-axial direction. The principles of conservation of mass and momentum are used in the derivation. Momentum of in-cylinder air flow is also taken into consideration. Validation of the model at stable condition is achieved by comparing model predictions with experimental measurements of diesel spray without gas flow from Naber's experiments. Furthermore, CFD simulations on penetration of diesel spray with gas flow were performed with the commercial code AVL-fire. The onedimensional model is validated by the penetration results with gas flow from CFD calculation. Results show that a reasonable estimation of the spray evolution can be obtained for both with and without ambient gas flow conditions.     

Estimation of maximum road friction coefficient based on Lyapunov method

With the real time and accurate information of motor torque and rotation speed of the four-in-wheel-motordrive electric vehicles, a slip based algorithm for estimating maximum road friction coefficient is designed using Lyapunov stability theory. Modified Burckhardt tire model is used to describe longitudinal slip property of the tire. By introducing a new state variable, a nonlinear estimator is proposed to estimate the longitudinal tire force and the maximum road friction coefficient simultaneously. With the appropriate selection of estimation gain, the convergence of the estimation error of the tire longitudinal force and maximum road friction coefficient is proved through Lyapunov stability analysis. In addition, the error is exponentially stable near the origin. Finally the method is validated with Carsim-Simulink co-simulation and real vehicle tests under multi working conditions in acceleration situation which demonstrate high computational efficiency and accuracy of this method.