硅溶胶型壳熔模铸件毛刺缺陷的研究

熔模铸造中经常出现毛刺缺陷,是造成铸件次品的重要原因.毛刺的出现与制壳过程中面层型壳的开裂有关.讨论了型壳间温湿度、风力对型壳开裂的影响,并提出了监控的具体措施.使用快干增强硅溶胶也有助于降低毛刺缺陷.     

求解带时间窗车辆路径问题的动态混合蚁群优化算法

为求解带时间窗车辆路径问题,针对传统蚂蚁遗传混合算法中参数静态设置、冗余迭代及收敛速度慢等缺点,提出一种动态混合蚁群优化算法( DHACO)。该算法首先借助最大最小蚁群得到初始解,利用蚁群优化算法求解带时间窗车辆路径问题的基本可行解。然后采用遗传算法交叉和变异操作对局部解和全局最优解进行二次优化,从而得到最优解。最后利用蚂蚁遗传混合算法融合策略,动态交叉调用蚂蚁算法、遗传算法,根据云关联规则自适应控制蚁群算法参数。 DHACO有效减少无效迭代次数,加快收敛速度。仿真结果表明,与其他相关的启发式算法相比,DHACO优于某些实例的已知最优解。     

基于Windows XPE的水下航行器航行操纵系统多任务软件设计

航行操纵系统是水下航行器控制系统的重要组成部分;为了保证航行操纵系统的实时性与可靠性,鉴于其硬件板卡驱动支持Windows平台,故软件采用了一种基于Windows XPE实时嵌入式系统的设计方法,根据操纵要求对航行操纵系统实时多任务进行了划分,诸如手柄信息处理任务、自动控制任务和网络通信任务等,介绍了多任务执行实体—线程(thread)的优先级的设置和线程同步工具的选取,并分析了Windows的多线程调度策略,然后详细阐述了航行操纵系统各任务的执行流程以及实现方法;最后,对航行操纵系统进行了实验室仿真测试,结果表明该系统实时性和控制精度达到了设计要求,操纵系统性能良好.     

Tackling the Password Problem: Image- and Gesture-Based Alternatives to Alphanumeric Passwords

Abstract

Alphanumeric passwords remain a ubiquitous means of user authentication, yet they are plagued by a fundamental problem: Secure passwords are difficult to create and remember. This paper suggests that image- or gesture-based passwords might strike a better balance between security and usability. It examines two such systems that are currently in widespread commercial use and examines alternative approaches that may offer insights for future improvements. Finally, it considers the possibility that touch-screen gesture passwords may become a viable biometric measure, which may allow them to provide multi-factor gesture-based authentication.     

Optimal blank design based on finite element method for blades of large Francis turbines

Metal pressing process that is widely used in industries has advantages over casting process for producing large Francis turbine blades from thick plates. Prior to the pressing process, blank design is firstly performed to determine flat blanks. The traditional trial and error approach is not applicable to blade design for Francis turbines that are not standard due to hydraulic characteristics of power plant sites. The rapid development of computing technology makes it possible to obtain optimal flat blanks by numerical modelling and simulation. In this paper, inverse finite element approach is investigated for blank design and an elasto-plastic model has been built using the well-known commercial software ANSYS. Numerical simulations for blade unfolding models with thick shell elements, solid elements and shell elements have given results with negligible differences. Unfolding tests with simple geometries have been carried out and the numerical results agree well with the analytical solutions. A large and thick shape of a Francis turbine blade for a hydropower plant has been successfully unfolded by inverse FE model. Sensibility analysis shows that the middle surface of the flat blank is independent of blade thickness. For ensuring the machining of the blade after the pressing process, a new contour is obtained by extending the boundary of the flat blank provided by the numerical model. This research may provide a useful tool for optimal blank design of Francis turbine blades.     

基于Windows Azure平台的虚拟化技术研究

随着云计算的发展,各种云计算平台也像雨后春笋般萌生。虚拟化技术作为云计算的关键技术成为各大云计算平台的核心,Windows Azure云计算平台同样也离不开虚拟化技术的支持。本文以微软Windows Azure平台作为研究对象,分析Windows Azure云计算平台使用虚拟化技术的必要性,研究Windows Azure云计算平台虚拟化技术,从Windows Azure架构上探索虚拟化技术。     

用脚本实现计算机管理的自动化

脚本以其易用,功能丰富的特点,在计算机日常管理中发挥着重要作用。脚本结合了Windows脚本宿主后,可以调用COM对象,可以使用WMI,功能更是强大。文中介绍了Windows脚本编程的基本技术,并对常用的计算机管理任务给出了脚本代码。     

基于Windows脚本技术的计算机信息采集 方案实现①

使用Windows脚本编程,并结合数据库实现C/S模式下的网络内计算机设备信息的获取,展示了在网络环境下Windows脚本结合数据库编程技术的强大功能,善用Windows脚本编程技术将提高系统管理员日常管理和维护效率。     

Windows CE.NET与桌面Windows应用程序开发差异研究

根据实际经验,从开发环境、字符集、编程接口及硬件平台等多方面,分析Windows CE.NET应用程序与一般桌面Windows应用程序开发的差异,为开发人员快速从桌面转到Windows CE.NET嵌入式开发提供参考.     

一种基于磁盘块的持续数据保护系统

数据重要性不断提高,对数据保护提出了越来越高的要求。基于数据的细粒度保护,以最小的时间代价和存储代价来保护数据,并以最少的数据损失量来恢复数据,则是数据保护的追求目标。针对此需求,提出并设计实现了一套基于磁盘块的持续数据保护系统。该系统高效而灵活地实现了Windows操作系统下的磁盘数据的保护。测试表明,该系统在使用时对正常的业务影响很小;在灾难发生后可以在较短的时候内将数据恢复至可用状态。