A hybrid system of neural networks and rough sets for road safety performance indicators

Road safety performance indicators are comprehensible tools that provide a better understanding of current safety conditions and can be used to monitor the effect of policy interventions. New insights can be gained in case one road safety index is composed of all risk indicators. The overall safety performance can then be evaluated, and countries ranked. In this paper, a promising structure of neural networks based on decision rules generated by rough sets—is proposed to develop an overall road safety index. This novel hybrid system integrates the ability of neural networks on self-learning and that of rough sets on automatically transforming data into knowledge. By means of simulation, optimal weights are assigned to seven road safety performance indicators. The ranking of 21 European countries in terms of their road safety index scores is compared to a ranking based on the number of road fatalities per million inhabitants. Evaluation results imply the feasibility of this intelligent decision support system and valuable predictive power for the road safety indicators context.     

PostgreSQL数据库运行状态数据的统计收集机制分析

对象关系数据库是新一代的数据库管理系统,它将关系数据库系统与面向对象数据库系统两方面的特征相结合,不仅能很好地支持对象管理和规则管理,而且能更好地支持原有的关系数据管理.要维护一个对象关系数据库管理系统长期正常有效地运行,其中一个不可忽略的机制就是数据库的清理机制.PostgreSQL是一个面向公众的、开放源代码的对象关系数据库管理系统,受到了人们的普遍认可和欢迎.对该系统数据清理机制的一个重要组成部分--数据库运行状态的数据统计收集机制进行了全面分析,给出了统计收集信息的种类、主要函数、数据结构和实现算法,这将有助于维护和完善该数据库系统.     

Adaptive prefetching and storage reorganization in a log-structuredstorage system

We present a storage management system that has the ability to adapt to the data access characteristics of the application that uses it based on collection and analysis of runtime statistics. This feature is especially useful in the storage management layer of database systems, where applications exhibit relatively predictable access patterns. Adaptive reorganization is performed by the storage management system in a manner that optimizes the access patterns of the system for which it is used. We enhance the log-structured storage system that naturally caters for write optimization, with the addition of a statistics collection mechanism to determine data access patterns of applications. The storage system can serve as a testbed for a variety of statistics analysis and clustering mechanisms. Higher level application-specific data clustering mechanisms can be used to override the storage system's low-level clustering mechanisms. In addition, the analysis techniques and reorganization scheme can be used in other storage systems. Performance results from our prototype show potential response time speedups of up to 83 percent over the basic log-structured file system in the best case, using a combination of storage reorganization and prefetching     

Discovering structural association of semistructured data

Many semistructured objects are similarly, though not identically structured. We study the problem of discovering “typical” substructures of a collection of semistructured objects. The discovered structures can serve the following purposes: 1) the “table-of-contents” for gaining general information of a source, 2) a road map for browsing and querying information sources, 3) a basis for clustering documents, 4) partial schemas for providing standard database access methods, and 5) user/customer interests and browsing patterns. The discovery task is affected by structural features of semistructured data in a nontrivial way and traditional data mining frameworks are inapplicable. We define this discovery problem and propose a solution     

Scalable, Distributed, Real-Time Map Generation

In this application, many vehicles participate in the collection, processing, and dissemination of data to automatically generate digital road maps. Details about new roads and the modification or closure of existing roads must be incorporated into the databases in a timely fashion. Mapping organizations obtain data about road network changes from various sources, including local authorities and building contractors, but this data tends to be highly inaccurate. To simplify mapmaking process, vehicles could use their computational resources to directly generate accurate map data. We envisage vehicles on the road network forming a wide-scale mobile sensing and computing platform. Toward that goal, we've developed an algorithm for keeping digital maps up-to-date, using ordinary vehicles making normal journeys rather than fleets of dedicated probe vehicles. However, further development is required to address several remaining challenges, including the choice of architecture to support the algorithm     

利用VB实现WinCC归档数据处理

WinCC是一款功能强大的HMI系统,它可以组态界面并可以对数据进行归档,但是对于一些复杂的数据处理如数据查询,计算和统计,就显得力不从心．文章利用VB编程工具建立了WinCC的归档数据库与Access数据库和EXCEL的连接,并生成了．exe文件,通过WinCC的直接调用,实验人员可以根据自己的喜好去选择数据存储方法和路径,实现数据的有条件查询和复杂处理．     

柔性转子动平衡测试数据库系统开发与验证

为提高航空发动机柔性转子动平衡效率,建立动平衡数据库,用于整理、处理、归纳动平衡试验数据,为发动机的后期维护和新机研制提供技术依据.采用LabWindows/CVI软件开发平台,与MicrosoftAccess建立数据接口,设计开发了柔性转子动平衡数据库系统,对设计要求、数据来源、模块设计及其实验应用等进行了阐述,对历史数据进行管理、统计、比较以及趋势分析,为柔性转子动平衡提供数据支持.实验结果表明,试重相角、试重大小、支承方式以及转速等因素对影响系数的影响程度不同;动平衡数据库系统结构合理、运行可靠、操作方便,能够提高影响系数精度和动平衡的效率,具有一定的工程应用价值.     

面向混合数据源的企业数据库私有云设计

针对混合数据源的采集、集成和应用问题,提出一种面向混合数据源的数据库私有云设计,针对混合数据源的不同结构化程度,将数据源分成结构化、半结构化和非结构化;针对混合数据源不同的不同时序特点,数据库私有云设计定时采集和实时采集两种采集方式;为了提高混合数据源的存取效率,数据库私有云将非结构化和半结构化数据存储在分布式文件系统,将结构化数据存储在分布式数据库;针对混合数据源的大数据应用需求,数据库私有云的计算层由数据仓库、实时数据处理、机器学习和数据查询服务组成;数据库私有云通过服务使能系统辅助用户开发具体应用程序,通过服务管理系统管理和监控这些具体应用程序。数据库私有云设计可以有效提供企业采集、集成和应用混合数据源的效率和效益。     

基于GPS和DR的公路数据采集GIS系统

该文介绍了一个新型的基于GPS和DR的公路数据采集GIS系统,它以GPS动态差分定位为主,辅以陀螺仪和里程计的航位推测法,可以高效准确地采集到现有公路的空间和属性数据信息。系统采用了GIS技术以增加地图和GIS功能,同时采用ArcSDE构建路况数据库。对路况数据信息的分析评价,将指导公路的养护管理和未来规划。实际应用表明,采用GPS和DR组合定位后的该GIS系统有效地克服了GPS定位的局限性,能够采集到连续精确的测量数据。     

基于UE4的在线驾驶仿真系统设计与实现

驾驶仿真系统在交通安全研究中发挥着重要作用,但目前仍存在三维道路建模受限、仿真场景还原度不高等问题;研究采用虚幻引擎开发仿真功能模块,根据道路几何线形与交通流原始资料,能高效搭建出驾驶仿真场景;采用像素流送技术将视频帧发送到前端,设置硬件设备的轴属性映射,支持模拟驾驶外部信号输入,并实时将驾驶行为数据存入数据库,设计了一种轻量化、自动化、智能化的在线驾驶仿真信息管理与可视化系统;系统主要实现了道路自动化建模、人-车-路-环境信息管理、车道级真实交通流场景还原、在线模拟驾驶与数据可视化等功能;经测试,系统部署后能在Web端稳定运行,弥补了现有驾驶仿真系统的不足,为实验人员提供轻量高效的驾驶仿真服务。     

试验评估系统中快速实时数据统计方法的实现

试验评估系统中,快速完成数据统计是关键。试验设备运行源源不断产生的数据,以及试验评估数据库中存在日积月累的大量数据,给数据统计带来了极大的困难。传统数据统计方法以人为操作为触发,需要一次性遍历所需的所有数据,完成统计特征值的计算。该方法容易造成计算速度缓慢、计算资源不足等现象。文章研究并实现了一种快速实时数据统计的方法,提高了试验评估数据库千万条及以上量级数据统计特征值的计算效率,且占用资源少,模块运行可靠、稳定,同时能够灵活适应不同装备指标数据的统计分析处理。     

Spark Streaming框架下的气象自动站数据实时处理系统

针对现有气象自动站业务平台面临处理数据不及时、交互式响应慢、统计时效差等问题,提出了使用Spark Streaming技术和HBase解决该问题的方法,将实时计算框架和分布式数据库系统结合起来实现大规模流式数据处理。使用Flume收集自动站数据,Spark Streaming对数据进行流式处理并存储到HBase数据库中,并设计Spark框架下的自动站数据流式入库处理算法和要素极值的实时统计算法,在Cloudera平台下实现了一个高速可靠的实时采集、处理、统计的应用系统。通过对比分析和性能监测,验证了该系统具有低延迟和高吞吐量的优势,运行状况良好,负载均衡。实验结果表明,Spark Streaming用于气象自动站的实时业务处理,数据并行写入HBase、基于HBase的查询和各类要素统计均能达到毫秒级响应,完全能满足自动站数据的应用需求,有效地支撑天气预报业务。     

基于LINQ的人事档案管理系统的设计与实现

介绍在ASP.NET编程中使用LINQ技术开发人事档案管理系统。LINQ通过将查询语法嵌入到编程语句中,增强了程序的语义性和安全性,减少了编程错误。LINQ技术可以实现数据的查询、新增、修改、删除等操作而无需开发人员直接访问数据库。此外,LINQ还可以支持.NET集合类、XML文档、ADO.NET数据集等多种数据源,实现程序的通用性。     

Automating statistics management for query optimizers

Statistics play a key role in influencing the quality of plans chosen by a database query optimizer. In this paper, we identify the statistics that are essential for an optimizer. We introduce novel techniques that help significantly reduce the set of statistics that need to be created without sacrificing the quality of query plans generated. We discuss how these techniques can be leveraged to automate statistics management in databases. We have implemented and experimentally evaluated our approach on Microsoft SQL Server 7.0     

Query processing techniques for arrays

Arrays are a common and important class of data. At present, database systems do not provide adequate array support: arrays can neither be easily defined nor conveniently manipulated. Further, array manipulations are not optimized. This paper describes a language called the Array Manipulation Language (AML), for expressing array manipulations, and a collection of optimization techniques for AML expressions. In the AML framework for array manipulation, arbitrary externally-defined functions can be applied to arrays in a structured manner. AML can be adapted to different application domains by choosing appropriate external function definitions. This paper concentrates on arrays occurring in databases of digital images such as satellite or medical images. AML queries can be treated declaratively and subjected to rewrite optimizations. Rewriting minimizes the number of applications of potentially costly external functions required to compute a query result. AML queries can also be optimized for space. Query results are generated a piece at a time by pipelined execution plans, and the amount of memory required by a plan depends on the order in which pieces are generated. An optimizer can consider generating the pieces of the query result in a variety of orders, and can efficiently choose orders that require less space. An AML-based prototype array database system called ArrayDB has been built, and it is used to show the effectiveness of these optimization techniques. Edited by M. Carey. Received: 10 August 2001 / Accepted: 11 December 2001 Published online: 24 May 2002     

异构数据源的集成与访问

1 引言近年来,Internet/Web技术和计算机硬件的迅速发展对数据库研究领域产生了巨大的影响,提出了新的挑战性问题:一是如何使数据库系统和技术成为Web的有机组成部分,而不仅仅充当Web体系的外围角色;二是如何实现Web动态信息的管理,完成日益增多的新一代Web应用等。人们已认识到Web正在逐渐成为全球性的自主分布式计算环境,Web上的多数站点都具有丰富的数据资源。如果能够把遍及全球的Web数据源集成起来,Web将成为一个全球统一的数据库,由全世界共享。然而Web数据源的集成并非易事,数据源的异构问题是影响Web数据源集成的最大障碍。Web数据源的异构问题主要包括三个方面:第一是模式异构,表现在不     

Formal Representation of Summary Tables for Health Care Statistical Database Management

There is an ever-increasing demand for statistical information in health-care societies, and voluminous statistics are collected every year. When one needs information on survey results, it is generally not allowed to access the original data, and the summary tables are the most important source of information which can be shared. In order to store summary tables as a well-organized database and to perform flexible retrieval, a formal study has been made on the structure of summary tables. We introduce the notion of summary table scheme and define the operations called table transformation. A statistical database management system has been implemented based on the study. In our study, a statistical database is a collection of summary tables obtained from a survey. If a survey is conducted periodically, a database consists of all the tables obtained in the past. System utilities have been implemented for handling time-oriented information.     

3D road traffic situation simulation system

The 3D traffic situation simulation system combines the multibody based mathematical model of a vehicle, the multibody mathematical model of human body, the database of vehicle and human body data and the display subsystem. Together with the model of driving surface the system can be used to simulate and analyse vehicle and its occupant behaviour under different road conditions and different driving regimes. The result obtained this way can be used to investigate safety related parameters and optimise the driver–vehicle–road system regarding to arbitrary criteria (safety, comfort, speed, etc.). The results of simulations are available as numerical data as well as animations in virtual 3D environment.     

Timeliness-Accuracy Balanced Collection of Dynamic Context Data

In the future, we are likely to see a tremendous need for context-aware applications which adapt to available context information such as physical surroundings, network, or system conditions. We aim to provide a fundamental support for these applications - a real-time context information collection service. This service delivers the right context information to the right user at the right time. The complexity of providing the real-time context information service arises from 1) the dynamically changing status of information sources, 2) the diverse user requirements in terms of data accuracy and service latency, and 3) constantly changing system conditions. In this paper, we take into consideration these dynamics and focus on addressing the trade-offs between timeliness, accuracy, and cost for information collection in distributed real-time environments. We propose a middleware-based approach to enable a judicious composition of services for accuracy-aware scheduling and cost-aware database maintenance. Specifically, we characterize the problem in terms of quality-of-service satisfaction (QoSSat), quality-of-data satisfaction (QoDSat), and cost. We propose a middleware framework for the real-time information collection process, where the information mediator coordinates and facilitates communication between information sources and consumers. We design a family of algorithms for real-time request scheduling, request servicing, and directory service maintenance to be implemented at the mediator to support QoSSat and QoDSat. Our studies indicate that the composition of our proposed scheduling algorithm and directory service maintenance policy can improve the overall efficiency of the system. We also observe that the proposed policies perform very well as the system scales in the number of information sources and consumer requests     

.基于GIS的城市道路交通流信息发布系统应用研究*

根据基于GPRS/GPS/GSM浮动车交通流信息采集系统实时采集的交通流瞬时速度、路段速度、车辆定位等信息,借助面向对象技术、GIS技术、数据库技术设计、开发了基于GIS的城市交通流信息发布系统,系统采用数据库中的存储过程技术处理海量交通流信息与GIS信息等数据表的多表连接,实现了高效率信息查询,并融合GIS专题地图技术和数据库技术实现浮动车辆历史轨迹动态回放、交通流路段速度查询、可视化显示。开发的系统在天津市部分路段进行试验,系统能稳定、可靠地实现交通流信息发布,并能快速有效查询城市道路交通流信息及识别城市道路网络路况瓶颈,可以辅助交通管理者进行交通管理决策。