“9·11”事件前后美国轨道交通的安全情况

2001年发生的9·11事件,不可逆转地改变了美国人对安全准备工作的内涵与认识。虽然新安保措施的着重点主要放在航空运输方面,但人们也更加注重陆地公共交通系统的安全形势,因为公众关注的焦点从9·11之前的私人财产犯罪转变为恐怖主义活动。然而,美国的铁路运营安全却被现实的情况所限制:当前紧缩的财政预算无法构建一个巨大的、均匀分级的保安网络。上述的两种形势相互作用,促使有关部门在9·11之后采取更为合理和实际的铁路安全措施,并由此催生了一些新方法来解决在根基上原本就脆弱的网络体系问题。交通安全部门和民间研究小组的结论是:对所有公共交通基础设施提供一整套安全设施是不必要的。     

建设广西和谐水运的思考

“十一五”时期是我区经济由艰难爬坡向经济起飞转变的重要时期,也是我区加强加快建设、深化改革、加快航运事业发展的黄金发展期,更是我区实现由传统航运向现代航运转变的战略机遇期。文章回顾了“十五”期间广西水运建设的发展,提出“十一五”时期广西建设和谐水运应重点关注的若干问题。     

Congestion tolling in the bottleneck model with heterogeneous values of time

When analysing the effects of transport policies it is important to adequately control for heterogeneity: previous studies note that ignoring heterogeneity biases the estimated welfare effects of tolling. This paper examines the effects of tolling, in a bottleneck model, with a continuously distributed value of time. With homogeneous users, first-best public tolling has no effect on prices. With heterogeneity it does: low values of time lose, and high values of time gain. The average congestion externality decreases with the heterogeneity in the value of time. Consequently, the welfare gain of first-best tolling also decreases. The more heterogeneous the value of time is, the lower the relative efficiency of a public pay-lane. This finding contrasts with the previous literature. Earlier studies, using static flow congestion, conclude that the relative efficiency increases with this type of heterogeneity. With more heterogeneity in the value of time, the relative efficiency of a private pay-lane is also lower, while that of a public time-invariant toll is higher. Our results suggest that the welfare gains of different tolling schemes are affected differently by heterogeneity. Further, the impact of heterogeneity on the effects of a policy also depends on the type of congestion considered.     

基于西门子802D系统的磨床数控化改造

介绍利用西门子公司的数控设备SINUMERIK 802D数控系统对SS-13缓进磨床进行数控改造的方案以及设计内容.     

船舶电力系统同步相量测量装置的研制

实现一种适用于船舶电力系统的同步相量测量装置,介绍了时钟同步模块、数据采集模块和数据处理模块。采用基于Nuttall窗函数的双谱线插值FFT算法对电力谐波进行分析,并对IEEE C37.118协议进行扩展,使之适用于船舶电力系统同步相量参数测量。用标准信号源对装置进行测试,相量幅值误差小于0.2%,相位误差小于0.2°。满足电力系统实时监控的要求。     

无线局域网技术特征与铁路行业无线应用前景的研究

主要介绍了无线局域网的概念、技术特点、协议标准、网络结构和安全技术,并对其在铁路行业的应用前蒂作了初步阐述。     

高速网络用户接入认证技术研究

自网络诞生以来,认证（authentication）、授权（authorization）和计费（accounting）体制（AAA）成为其运营的基础.网络中各类资源的使用,都由认证,授权,计费来管理.随着网络规模的扩大,传统的认证方式已不能适应用户数量的急增和宽带业务多样化的要求,需要采用新方法对用户的接入进行控制和配置.因此,针对不同的网络环境,提出了不同的网络用户接入认证技术.通过分析和比较,阐明了各种高速网络用户接入认证技术的特点.     

边际油田-WZ11—1N开发的工程策略

讨论了北部湾边际油田-WZ11-1N油田开发的工程策略，通过技术和经济上的综合分析，WZ11-1N油田采用了“三一”模式依托开发的成果，在应用涠洲地区成熟的、较先进的工程技术和开发经验的基础上，对依托平台／管线的处理工艺和寿命进行了详细的优化和校核，同时采用了电力组网新技术，达到了降低工程投资，提高油田收益的目的。另外在总体布置上为未来油田的依托开发预留了空间。     

液相色谱-离子阱质谱联用法测定西洋参药材中p-F_(11)含量

目的　建立液相色谱 离子阱质谱联用法 ,测定西洋参特有指标成分拟人参皂苷 p F11含量。方法　通过固相萃取小柱预处理样品 ,电喷雾质谱正离子模式全扫描法检测 ,选择离子法定量 ,用液相色谱 蒸发光散射法对该定量方法进行了佐证。结果　线性范围为 0 .4 5～ 7.2 0 μg ,回收率为 98.7% ,精密度和重现性实验RSD值分别为 2 .5 %和2 .8% ,样品在 4 8h内稳定性良好。该方法测得 p F11质量浓度为 3.0 1mg·g-1。结论　该方法有良好的精密度和重现性 ,能准确分析、测定西洋参药材中 p F11含量     

A simulation study of service differentiation for the bandwidth request scheme in fixed IEEE 802.16 network

Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better. Foundation item: the National Basic Research Program (973) of China (No. 2005C13321804)