京秦线提速路涵过渡段动力仿真与试验对比

结合京秦线提速改造工程进行了列车 路基动力仿真计算。在不同速度条件下,通过对路涵过渡段加固前后状态下机车车辆运行安全舒适性指标、轨道及路基主要动力性能指标的分析计算,对京秦既有线路涵过渡段提速到200km/h的适应性及加固方案的可行性提出了相应评价意见与建议,并与随后的实车试验进行了对比。试验测试结果验证了仿真分析的可靠性。     

Experimental ivnestigation on flow fields of viscous fluid around two-dimensional wings and comparison with computational results

To examine the flow field of a viscous fluid around the trailing edge of a wing with respect to the Kutta condition or the Joukowski hypothesis, an experimental investigation into the velocity fields around two-dimensional (2D) wings NACA0012 and NACA4412 was carried out using an X-type hot-wire anemometer in a wind tunnel and the method of colored milk injection in a circulating water channel. The results of these investigations revealed that the flow of a viscous fluid at the trailing edge of a 2D wing is tangential to the face on the pressure side, and that the flow is very slow or reversed on the suction side due to separation when the angle of attack is greater than 7.5°. By flow visualization, a Kármán vortex street was found in the wake of both wings (NACA0012 and NACA4412) when the angle of attack was 5°. These results show that the ordinary Kutta condition with respect to the direction of outflow at the trailing edge is not necessarily satisfied in a viscous fluid, but the Kutta condition with respect to the pressure at the trailing edge is satisfied as usual. Numerical results, which have been obtained as the solution of Reynolds-averaged Navier-Stokes equations, show good agreement with above-mentioned experimental results. Therefore, CFD (Computational Fluid Dynamics) simulation has proved to be very effective for studying steady viscous flow around the trailing edge of a 2D wing.     

房室隔疏松组织间隙及其有关的组织结构

利用４例人心房室隔水平连续组织切片，观察了房室隔内的疏松组织间隙和与其有关的组织结构：包括心房肌至房室结的过渡性心肌纤维，冠状窦末段的形态结构以及冠状窦口后方的右房后窝等。并结合临床进行了讨论。     

略论施工机械的选型

施工机械的选型,是施工机械前期管理中的一个重要问题.本文就施工机械选型前的准备工作,选型的基本原则,选型的经济性评价等方面进行了阐述论证,提出了施工机械选型的十条基本原则和定量评估的方法.     

多值非线性系统的自适应控制

提出了带有多值非线性环节的线性离散系统的自适应控制算法，仿真实验的结果表明：该算法简单易行具有明显的优点，跟踪误差比采用一般的自适应控制算法时要小得多，且能保证闭环系统大范围近收敛。     

Dynamic Simulation of a Smart Crank and Slider Mechanism

In this paper, a smart crank and slider mechanism is analyzed mostly from a dynamic view. By means of dynamic explicit finite element method, 3D nonlinear structure is simulated. It is proved that the mechanism can effectively accomplish smart movement prescribed. And in order to ensure reciprocal movement with higher frequency, measures should be taken to avoid over heating of parts. Compared with internal energy, kinetic energy of total rigid body is dominating, and Y direction equivalent rigid velocity is much higher than X direction velocity. Equivalent rigid velocity of all parts is consistent with respective movement condition. For both energy and velocity, slider effect is dominating. Three direction equivalent inertia force oscillates. Force amplitude in Y -direction is comparitively the greatest.     

提高铁路站场环形配电网络安全性的措施

鉴于目前铁路站场广为采用的环形配电网络存在着安全隐患,本文结合运营实践情况对此提出了一些改进措施。     

装配式公路钢桥承载力的有限元分析

指出装配式公路钢桥设计中所采用的简化计算方法的不足,使用大型有限元软件ANSYS对其受力情况和承载力进行了分析,并与简化计算方法作了对比,得出了一些规律性的结论,对实际应用具有指导意义。     

对我国建设工程索赔机制运行有关问题的探讨

索赔机制及其运行是实现索赔的重要保证。文章通过对索赔机制的定义及构成分析,阐释了索赔机制的本质及运行影响因素。据此,对我国索赔机制运行中的困境及原因做了剖析,提出了完善我国索赔机制、改善索赔环境的具体措施和建议。     

阜朝高速公路湿陷性黄土段小桥涵地基的处治

湿陷性黄土易产生沉降变形,且承载力低。本文介绍阜朝高速公路湿陷性黄土段小桥涵地基处治的一些方法。