Continuous formulations and analytical properties of the link transmission model

The link transmission model (LTM) has great potential for simulating traffic flow in large-scale networks since it is much more efficient and accurate than the Cell Transmission Model (CTM). However, there lack general continuous formulations of LTM, and there has been no systematic study on its analytical properties such as stationary states and stability of network traffic flow. In this study we attempt to fill the gaps. First we apply the Hopf–Lax formula to derive Newell’s simplified kinematic wave model with given boundary cumulative flows and the triangular fundamental diagram. We then apply the Hopf–Lax formula to define link demand and supply functions, as well as link queue and vacancy functions, and present two continuous formulations of LTM, by incorporating boundary demands and supplies as well as invariant macroscopic junction models. With continuous LTM, we define and solve the stationary states in a road network. We also apply LTM to directly derive a Poincaré map to analyze the stability of stationary states in a diverge-merge network. Finally we present an example to show that LTM is not well-defined with non-invariant junction models. We can see that Newell’s model and continuous LTM complement each other and provide an alternative formulation of the network kinematic wave theory. This study paves the way for further extensions, analyses, and applications of LTM in the future.     

新旧路基结合部变形特性有限元分析

针对旧路拓宽工程中新旧路基结合部的变形问题,以Mohr．Coulomb模型为基础,采用有限元方法对路基结合部的变形性状进行计算分析,为旧路拓宽工程中新旧路基结合部的处治提供理论依据。     

A kinematic wave approach to traffic statics and dynamics in a double-ring network

Recently there has been much interest in understanding macroscopic fundamental diagrams of stationary road networks. However, there lacks a systematic method to define and solve stationary states in a road network with complex junctions. In this study we propose a kinematic wave approach to defining, analyzing, and simulating static and dynamic traffic characteristics in a network of two ring roads connected by a 2 × 2 junction, which can be either an uninterrupted interchange or a signalized intersection. This study is enabled by recently developed macroscopic junction models of general junctions. With a junction model based on fair merging and first-in-first-out diverging rules, we first define and solve stationary states and then derive the macroscopic fundamental diagram (MFD) of a stationary uninterrupted network. We conclude that the flow-density relationship of the uninterrupted double-ring network is not unique for high average network densities (i.e., when one ring becomes congested) and unveil the existence of infinitely many stationary states that can arise with a zero-speed shockwave. From simulation results with a corresponding Cell Transmission Model, we verify that all stationary states in the MFD are stable and can be reached, but show that randomness in the retaining ratio of each ring drives the network to more symmetric traffic patterns and higher flow-rates. Furthermore we model a signalized intersection as two alternate diverge junctions and demonstrate that the signalized double-ring network can reach asymptotically periodic traffic patterns, which are therefore defined as “stationary” states in signalized networks. With simulations we show that the flow-density relation is well defined in such “stationary” states, and asymptotic traffic patterns can be impacted by signal cycle lengths and retaining ratios. But compared with uninterrupted interchanges, signalized intersections lead to more asymmetric traffic patterns, lower flow-rates, and even gridlocks when the average density is higher than half of the jam density. The results are consistent between this study and existing studies, but the network kinematic wave model, with appropriate junction models, is mathematically tractable and physically meaningful. It has offered a more complete picture regarding the number and type of stationary states, their stability, and MFD in freeway and signalized networks.     

新丰镇编组站GSM-R数字移动通信系统设计

目前青藏、大秦、胶济、石太等线已开通了GSM-R系统,长大干线GSM-R系统的设计已经积累了一定经验。而大型编组站地区GSM-R系统的设计则处于起步阶段,介绍新丰镇编组站前期的GSM-R试验系统设计情况,提出解决编组站地区GSM-R系统设计难点的一些可能方案。     

京沈客运专线引入沈阳铁路枢纽桥梁工程过渡与防护设计

京沈客运专线引入沈阳铁路枢纽工程的引入通道和施工场地空间狭小,需跨越秦沈客运专线和多条普速铁路、河流、市政道路与管线等。通过科学、合理、严密地编制京沈客运专线引入沈阳铁路枢纽桥梁工程过渡与防护设计解决了桥梁特殊工点多、过渡方案复杂施工难度大;临近既有设备安全防护压力大、公铁立交桥改建交通疏解难;敏感点多、高程要求苛刻、相互干扰大;自动化沉降和变形监测秦沈客运专线标准高等诸多困难。保证了既有设备正常运营和安全,确定了经济合理的桥梁过渡与防护设计方案,使京沈客运专线在狭小空间成功引入沈阳铁路枢纽。     

杭长客专引入长沙南枢纽RBC设置方案探讨

主要介绍杭长客专引入长沙南枢纽2种RBC设置方案,通过对这2种RBC设置方案优、缺点的比较、分析,得到最优方案。     

EFFECTS OF MANGANESE ON NEUROMUSCULAR JUNCTION TRANSMISSION

ＥＦＦＥＣＴＳＯＦＭＡＮＧＡＮＥＳＥＯＮＮＥＵＲＯＭＵＳＣＵＬＡＲＪＵＮＣＴＩＯＮＴＲＡＮＳＭＩＳＳＩＯＮＣａｏＹｏｎｇｘｉａｏ；ＣｈｅＸｉｐｉｎｇ；ＷａｎｇＣｈａｎｇｊｉａｎｇＬｉＷｅｉｈｏｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈａｒｍａｃｏｌｏｇｙ，Ｆ...     

先天性肾积水患者的超微结构病理及临床分析

对38例单纯先天性肾积水肾盂输尿管连接部（UPJ）组织作透射电镜观察，结果：其主要超微结构病理改变是平滑肌细胞间有大量胶原料堆组织堆积，平滑肌细胞相互分离，肌细胞本身发育不良，胞膜皱折、锯齿状、指状突起，线粒体肿胀破坏。提示积水的原因是UPJ部位功能性梗阻。     

公路路基填挖交界处不均匀沉降原因及防治

道路填挖交界处出现不均匀沉降,是一个需要加强管理的质量问题。采用水稳定性好的填筑材料和相应的加固措施,可减小不均匀沉降量,保证路基的稳定性,延长道路的使用期限。     

福仕达前舱线束电气盒电路图解

介绍海马福仕达豪华型微型客车的线束部件配置明细,并根据全车线束产品图纸,对前舱线束中电气盒的连接电路作出图解。当车载某电气设备不能正常工作时,本文可以作为参照,便于对连接电器设备的线束电路进行查找及故障的排除。