膏溶角砾岩条件下铁路单线隧道断面形式分析

采用偏心距为准则,对膏溶角砾岩条件下的某铁路单线隧道采用的断面形式与高速铁路隧道规范和专家推荐的比选断面在不同侧压力系数条件下的结构受力特性进行了比较,并依据隧道二次衬砌接触压力及其应力监测数据对选用的断面形式的适用性进行了分析.分析表明,隧道断面形式的适用性具有限定条件,侧压力系数是主要影响因素之一;侧压力系数变化时,衬砌的受力控制截面可能相应发生改变.     

砂卵石地层水泥盾构泥浆渗透试验分析

采用自制试验仪器,通过渗透试验研究泥浆对地层的适应性.试验表明,泥浆相对密度越大,泥膜质量越好,在相对密度达到1.08时,增大泥浆的黏度并不能有效减少泥浆的渗流量.泥膜的抗渗性与泥膜形成时的压差以及渗透时间密切相关,渗透成膜的压差越大,泥膜破坏需要的渗透压力也越大,而渗透时间长短决定泥膜凝胶强度的大小以及致密性.     

我省高速公路运营管理机构和人员情况调研分析

通过对全省高速公路运营管理机构设置和人员编制情况进行调研统计,为科学设置高速公路运营管理机构、合理配置各类人员提供依据.     

铁路给水降低水损的实践和探索

铁路给水是一个复杂的系统,水损是反映供水企业管理水平的重要标志,也是设备质量状况的具体体现。降低水损是提高效益和保证水质安全的有效途径,供水管网水损的因素很多,一直以来降水损工作都是铁路给水面临的一个难题。以往降水损只是形成思想上的＂共识＂而不能实现行动上的＂共振＂,这也同时成为从业人员潜意识中回避的问题。然而随着铁路给水改革的发展,这恰恰是奠定整体基础、增强发展后劲的必然选择,同时也是一个复杂而非常有意义的研究课题。2008年至今我单位结合公司发展实际,全面开展降损攻关活动,取得了一定的成绩。     

基于激光监测传感器的列车超限监测报警系统设计

列车超限监测报警系统利用激光监测传感器的"监测区"测量功能,根据场地、空间等实际需求,可悬空调节监测超限列车有效区域。该系统由激光监测传感器、激光监测信号处理控制、GPS卫星定位仪和电源控制4部分组成,可无接触测量运行中的列车货物超限并报警。     

我国电子商务相关产业发展规划

本对电子商务相关产业从功能角度进行了分类，并对各产业类的发展现状、国内外的差距、新兴的产业生长点等作了简要的分析。在此基础上，本针对上述产业结构划分提出了一种适合我国具体情况的可行的产业发展策略及规划，从产业体系及相关的科研、管理体系构建三个角度进行了分析。     

Free-riders impact on throughputs of peer-to-peer file-sharing systems

In a peer-to-peer file-sharing system, a free-rider is a node which downloads files from its peers but does not share files to other nodes. Analyzing the free-riders’ impact on system throughputs is essential in examining the performance of peer-to-peer file-sharing systems. We find that the free-riders’ impact largely depends on nodes behavior, including their online time and greed of downloading files. We extend an existing peer-to-peer system model and classify nodes according to their behavior. We focus on two peer-to-peer architectures: centralized indexing and distributed hash tables. We find that when the cooperators in a system are all greedy in downloading files, the system throughput has little room to increase while the cooperators throughput degrade badly with the increasing percent of greedy free-riders in the system. When all the cooperators are non-greedy with long average online time, the system throughput has much room to increase and the cooperators throughput degrade little with a high percent of greedy free-riders in the system. We also find that if a system can tolerate a high percent of greedy free-riders without suffering much throughput degradation, the system must contain some non-greedy cooperators that contribute great idle service capacity to the system. Foundation item: the National High Technology Research and Development Program (863) of China (No. 2007AA01Z457), and the Shanghai Science and Technology Development Funds (No. 07QA14033)     

An authenticated group key distribution scheme for wireless sensor networks

In wireless sensor networks (WSNs), group key distribution is the core of secure communications since sensor nodes usually form groups and cooperate with each other in sensing data collection and in-network processing. In this paper, we present a scalable authenticated scheme for group key distribution based on a combinatorial exclusion basis system (EBS) for efficiency and one-way hash chains for authentication. The proposed scheme guarantees a lightweight authenticated group key updating procedure and is efficient in terms of storage, communication and computation overheads. Foundation item: the National High Technology Research and Development Program (863) of China (Nos. 2006AA01Z436, 2007AA01Z455, and 2007AA01Z473).     

繁华城区大直径泥水盾构掘进沉降控制及对周边环境影响分析

结合北京站—北京西站地下直径线工程实践,介绍大直径泥水盾构在繁华城区施工对地表沉降及周边环境的影响因素,对监测结果进行分析,并提出控制施工沉降的措施,以期为类似工程提供借鉴。