高精度车载导航定位系统的研究

通过对车载导航系统结构、功能的分析，对车辆的高精度导航定位进行了研究。在常见的卫星导航（GPS）、航位推算（DR）等导航定位的基础上，进一步研究并实现了地图匹配算法，克服了GPS信号受阻时定位间断或失效的缺点，避免了航位推算定位误差随时间的积累。通过大量的跑车试验表明，基于GPS／DR／MM的车辆导航系统，可以高精度地实现车辆定位，进而可以实现地理信息的查询、交通诱导等功能。具有重要的实际应用价值。     

What do people know about their public transport options?

This paper studies the memory representations of residents regarding the public transport system in their city. Telephone interviews were conducted with a representative sample of 204 inhabitants in a selected residential inner-city area in Stockholm. Route knowledge questions, recognition tasks, free-recall tasks and estimations of service frequency were used to explore memory representations. The results showed that, in general, residents in metropolitan areas have good knowledge of the public transport options along well-known transport corridors. The memory representation of lesser-known transport corridors tends to be of a poorer quality. In the results presented here, the variables gender, age, employment status, level of education and car availability had no correlation with the quality of the memory representation, but experience increased knowledge. Although frequent users of public transport had a more detailed representation of the system, the less frequent users also had a considerable- and good-memory representation. An explorative hierarchy for representation of public transport lines in the memory is proposed. It is hypothesised that memory representations of a transport line can be affected by the following three factors: the extent to which a line is visible in the urban area, the straightness of the routes and whether or not stops are labelled, for example, by destination area. Simply put, these factors determine how well a person knows a line. It was found that people first remember a commuter train and a trunk bus line, followed by metro lines and suburban buses and finally normal inner-city buses with the poorest anchorage in memory.

Behavior of the cell transmission model and effectiveness of ramp metering

The paper characterizes the behavior of the cell transmission model of a freeway, divided into N sections or cells, each with one on-ramp and one off-ramp. The state of the dynamical system is the N-dimensional vector n of vehicle densities in the N sections. A feasible stationary demand pattern induces a unique equilibrium flow in each section. However, there is an infinite set—in fact a continuum—of equilibrium states, including a unique uncongested equilibrium n^u in which free flow speed prevails in all sections, and a unique most congested equilibrium n^con. In every other equilibrium n^e one or more sections are congested, and n^u  n^e  n^con. Every equilibrium is stable and every trajectory converges to some equilibrium state.Two implications for ramp metering are explored. First, if the demand exceeds capacity and the ramps are not metered, every trajectory converges to the most congested equilibrium. Moreover, there is a ramp metering strategy that increases discharge flows and reduces total travel time compared with the no-metering strategy. Second, even when the demand is feasible but the freeway is initially congested, there is a ramp metering strategy that moves the system to the uncongested equilibrium and reduces total travel time. The two conclusions show that congestion invariably indicates wastefulness of freeway resources that ramp metering can eliminate.     

混沌扩频通信系统仿真

码分多址（CDMA）扩频通信系统的关键问题之一是如何选择优质的扩频码。文章采用Logistic映射方程产生混沌序列,对基于混沌序列的CDMA扩频通信系统进行仿真研究。结果表明,混沌序列具有生成简单,可用码组数目多、保密性能高等优点,可以很好地应用于扩频通信系统。     

基于改进遗传算法的出租车共乘线路规划研究

常规出租车运行模式效率低,增加了城市的拥堵. 针对兰州市出租车搭载率低和行驶路线规划不合理等问题,设计一种以最高搭载率、最短行驶距离为目标的函数,考虑出租车的容量限制、车辆行驶距离限制及上下车人数约束等问题的共乘模式. 建立基于改进遗传算法的出租车共乘线路规划模型. 通过采用锦标赛选择策略、站点片段交叉设计和站点监督式变异等操作对模型进行求解. 最后用兰州市出租车历史轨迹数据进行实验分析,结果表明,运用设计的出租车线路规划模型及改进的遗传算法,能够快速地得到优化路径,实现多辆出租车的规划路径满足最高搭载率及最短距离的要求.     

基于OpenGL的虚拟现实地图实现方法研究

着重讨论了3D GIS环境下的三维建模及如何利用OpenGL标准图形接口实现虚拟现实地图的方法.提出先利用3D Studio VIZ构建复杂物体三维景观,然后在OpenGL中导出三维模型,最后在编程的基础上实现了某一实验区的虚拟现实地图.     

在微型计算机上自动绘制坡度图

坡度是地形的一个重要特征信息,它在工程设计中有着极其重要的意义。本文论述了利用DEM (DigitaiElevationModel)数据获取地面坡度值的方法;提出了一种自动生成和识别某一坡 度范围区域边界线的方法,根据该方法在IBM一PC/XT微型计算机上编制了利用DEM数据 自动绘制坡度图的程序,并用该程序绘制出了某一实验区域的坡度图。      

基于技术预见方法的海上浮动核电站关键技术

在对海上浮动核电站科研论文和专利文献进行分析的基础上,结合德尔菲法对海上浮动核电站关键技术进行分析研究,最终确定了小型模块化核反应堆设计等16项关键技术为海上浮动核电站关键技术。研究结果可以为后期海上浮动核电站产业政策制定和技术路线图规划提供相关参考。     

混沌映射的保密性能分析

通过实例说明两个具有拓扑共轭关系的混沌映射具有相同的Lyapunov指数.指出了仅仅使用Lyapunov指数作为混沌映射的密码学特性描述,具有一定的局限性.并利用混沌序列的伪随机特性,通过计算映射的自相关函数、互相关函数等随机数值特性,结合Lyapunov指数,分析了混沌序列的保密性能.     

基于因子图优化的众包高精度地图云端融合方法

针对高精度地图传统云端融合方法生成的地图置信度较低、误差较大的问题,提出了一种基于因子图优化的众包高精度地图云端融合方法。利用RTK-GPS数据对车端上传的局部语义地图进行全局化处理;对地图片段进行匹配,并利用一致性筛选流程提高匹配精度;以车道线匹配对构建约束地图间变换关系矩阵的因子图优化模型;利用某城市道路真实多车轨迹数据进行测试。结果表明,相较于传统方法,该算法对于优化初值的依赖性较低,对于地图间聚集度提升了44.7%;与车道线数据真值相比,该算法绝对误差均在1 m以内,具有较高的实用价值。