TP2紫铜管弯制开裂原因分析

TP2紫铜管在进行弯制时开裂,为找到原因,用退火试验模拟生产中的退火工艺。试验数据表明,铜管经多道次拉拔产生加工硬化,其外表面金相组织和内部金相组织不均匀,导致在进行弯制时铜管产生开裂。通过对比试验,找到铜管弯制的最佳退火温度区间为550～580℃,为铜管弯制退火工艺提供指导。     

智能网联环境下复杂异质交通流稳定性解析

针对网联车辆与普通车辆构成的异质交通流，考虑网联车辆车对车(V2V)、车对基础设施(V2I)不同通信技术，研究复杂异质交通流稳定性.基于李雅普诺夫理论，分析对比不同通信技术下网联车辆与普通车辆构成的异质交通流稳定性；基于V2V、V2V/V2I的网联车辆和普通车辆以不同比例混合时，进行异质交通流稳定性判别及稳定域解析.通过数值仿真，验证理论解析的正确性.研究结果表明，基于V2V/V2I的网联车辆比基于V2V的网联车辆混入对异质交通流稳定性改善效果更显著.基于V2V、V2V/V2I的网联车辆同时汇入普通车辆交通流的情况下，当基于V2V的网联车辆比例较低时，不会明显提高异质交通流稳定性；而基于 V2V/V2I的网联车辆即使在低比例时，也会显著改善交通流稳定性；且基于V2V网联车辆比例较低时，平衡态临界速度值随着基于V2V/V2I网联车辆的比例增加近似呈线性减小.     

基于二乘二取二架构的安全扩展平台研究

为节约时间和资金成本,在不改变既有CTCS-2/3级列控系统的前提下,进一步修改完善扩展其系统功能,提出采用二乘二取二架构安全扩展平台.平台内部双CPU之间采用时钟同步机制进行实时自检、互检,大大提高了安全扩展平台的安全性、可靠性和可用性.     

A network level connectivity robustness measure for connected vehicle environments

This study introduces a new CONnectivity ROBustness model (CONROB) to assess vehicle-to-vehicle communication in connected vehicle (CV) environments. CONROB is based on Newton’s universal law of gravitation and accounts for multiple factors affecting the connectivity in CV environments such as market penetration, wireless transmission range, spatial distribution of vehicles relative to each other, the spatial propagation of the wireless signal, and traffic density. The proposed methodology for the connectivity robustness calculation in CONROB accounts for the Link Expiration Time (LET) and the Route Expiration Time (RET) that are reflected in the stability of links between each two adjacent vehicles and the expiration time of communication routes between vehicles. Using a 117 sq-km (45-square mile) network in Washington County, located west of Portland city, Oregon, a microscopic simulation model (VISSIM) was built to verify CONROB model. A total of 45 scenarios were simulated for different traffic densities generated from five different traffic demand levels, three levels of market penetration (5%, 15%, and 25%), and three transmission range values [76 (250), 152 (500), and 305 (1000) m (ft)]. The simulation results show that the overall robustness increases as the market penetration increases, given the same transmission range, and relative traffic density. Similarly, the overall connectivity robustness increases as the relative traffic density increases for the same market penetration. More so, the connectivity robustness becomes more sensitive to the relative traffic density at higher values of transmission range and market penetration. Multiple regression analysis was conducted to show the significant effect of relative traffic density, transmission range, and market penetration on the robustness measure. The results of the study provide an evidence of the ability of the model to capture the effect of the different factors on the connectivity between vehicles, which provides a viable tool for assessing CV environments.     

智能网联环境下复杂异质交通流稳定性解析

针对网联车辆与普通车辆构成的异质交通流,考虑网联车辆车对车(V2V)、车对基础设施(V2I)不同通信技术,研究复杂异质交通流稳定性.基于李雅普诺夫理论,分析对比不同通信技术下网联车辆与普通车辆构成的异质交通流稳定性;基于V2V、V2V/V2I的网联车辆和普通车辆以不同比例混合时,进行异质交通流稳定性判别及稳定域解析.通过数值仿真,验证理论解析的正确性.研究结果表明,基于V2V/V2I的网联车辆比基于V2V的网联车辆混入对异质交通流稳定性改善效果更显著.基于V2V、V2V/V2I的网联车辆同时汇入普通车辆交通流的情况下,当基于V2V的网联车辆比例较低时,不会明显提高异质交通流稳定性;而基于 V2V/V2I的网联车辆即使在低比例时,也会显著改善交通流稳定性;且基于V2V网联车辆比例较低时,平衡态临界速度值随着基于V2V/V2I网联车辆的比例增加近似呈线性减小.     

Development of 2D hybrid equilibrium elements in large increment method

As a force-based finite element method (FEM), large increment method (LIM) has been developed in recent years. It has been shown that LIM provided prominent advantage of parallel computation with high efficiency and low time consumption for member structural system. To fully utilize its advantage in parallel computation, it is the time to extend LIM to 2D and 3D continua analysis. In this paper, a 2D finite element library with the capability of modeling arbitrary configurations is developed. Some illustrative numerical examples are solved by using the proposed library; the obtained results are compared with those obtained from both traditional displacement-based FEM and analytical solutions, which has clearly shown the advantages of LIM.     

Simulation study of foundations reinforced with horizontal-vertical inclusions using particle flow code

A two-dimensional discrete element code, particle flow code (PFC2D), is employed to investigate foundations reinforced with horizontal-vertical (H-V) inclusions. The initial states and loading processes of both unreinforced and H-V reinforced foundations are simulated by PFC 2D method. The interface between particles and reinforcements, and the reinforcement mechanism of the H-V reinforced foundations are studied through stress distribution graphs, displacement vector graphs and contact force graphs. The simulation results demonstrate that the vertical elements of the H-V reinforcement keep the particles from being displaced under the applied load. The H-V reinforcement can distribute the load uniformly over a wider area, thereby improving the bearing capacity of soil foundation.     

基于效能及可靠性的车辆资产全寿命周期成本评估模型及应用系统

车辆资产管理是道路运输企业管理的重点内容,本文提出一种基于效能及可靠性的LCC评估算法,并在该评估模型基础上建立计算机管理系统。系统对车辆可靠性,成本、效能进行识别、量化和平衡,为企业在车辆购置、运行维护、报废淘汰等过程提供效益最优的决策方案。     

纳米TiO_2材料对沥青抗紫外光老化的作用

把纳米TiO2作为紫外线吸收抗老化剂加入到沥青中,根据紫外线老化前后沥青针入度、软化点、延度的试验结果,分析纳米TiO2及其掺量对沥青抗紫外线老化能力的影响。结果表明:掺入纳米TiO2的沥青,其紫外线老化后的针入度、延度都有所增加,软化点明显减小;针入度指数的增加程度降低;针入度、延度、软化点损失率均明显降低;纳米TiO2的最佳掺量为1%。纳米TiO2作为紫外线吸收抗老化剂在一定程度上提高了沥青抗紫外线的能力。     

二次变形模量EV2试验的尺寸效应研究

提出了承载板直径分别为400,600 mm的二次变形模量EV2的试验方法,通过对京沪高速、京石客运专线铁路路基施工现场试验数据的分析,得出承载板直径分别为300,400,600 mm的二次变形模量EV2试验结果之间的相关关系,并分析了填料最大粒径对试验结果的影响。