A new framework for understanding educational digital library use: re-examining digital divides in U.S. schools

Despite their decade of deployment, educational digital libraries have not achieved sustained use in elementary and secondary schools in the United States. Barriers to accessing the Internet and computers have been widely targeted by myriad initiatives, but efforts aimed at bridging this first-level “digital divide” have not led to increased use of the Internet and digital library resources in U.S. classrooms. In fact, such programs have revealed additional divides that affect educators’ use. This paper examines the additional digital divide levels and proposes a new framework for understanding technology innovation in schools that can improve development and outreach approaches by digital library developers.     

Electrospinning hollow and core/sheath nanofibers using hydrodynamic fluid focusing

Hollow poly (vinylpyrrolidone) (PVP) + TiO₂ and polypyrrole (core)/PVP (sheath) nanofibers were successfully electrospun using hydrodynamic fluid focusing. Utilizing a two-dimensional fluid focusing technique previously applied to aqueous solutions, intersecting microchannels cast in (poly)dimethylsiloxane were utilized to dynamically center core fluids in immiscible sheath fluids prior to electrospinning at the channel outlet. Advantages of using microfluidic channel networks for the electrospinning of composite nanofibers include spatiotemporal control over input reagents, ease of fabrication and the ability to focus the core stream into sheath layer without the need of complex co-annular nozzles.     

Modeling expert problem solving in a game of chance: a Yahtzee© case study

Although developments on software agents have led to useful applications in automation of routine tasks such as electronic mail filtering, there is a scarcity of research that empirically evaluates the performance of a software agent versus that of a human reasoner, whose problem-solving capabilities the agent embodies. In the context of a game of a chance, namely Yahtzee©, we identified strategies deployed by expert human reasoners and developed a decision tree for agent development. This paper describes the computer implementation of the Yahtzee game as well as the software agent. It also presents a comparison of the performance of humans versus an automated agent. Results indicate that, in this context, the software agent embodies human expertise at a high level of fidelity.     

基于FPGA的VPN网关设计方案研究*

提出了一种基于FPGA的高速VPN网关的设计方案。它的特点是用FPGA方式完成VPN网关的实时处理,而将通用处理机置于数据通路之外,完成系统配置和管理功能。这种构架的VPN实时性好,可以线速处理IP包,而且易于管理。     

建设项目设计阶段投资控制系统的建立与分析

针对建设设计阶段独立使用价值工程、优化设计和限额设计等方法进行投资控制的局限性,借鉴系统论、控制论、信息论等思想和方法,建立了设计阶段投资控制系统。系统主要由探测元件、控制元件和执行元件组成,探测元件进行设计阶段的信息收集;控制元件通过审核将各项投资控制活动与投资控制目标进行对比,提出应对策略;执行元件完成应对策略。通过投资控制系统的执行,实现对设计阶段各项活动的全面系统控制,从管理层面上解决设计阶段投资控制活动割裂问题,进而改善设计阶段整体投资控制效果。     

划子口河闸弧形钢闸门三维有限元分析与安全评估

划子口河闸拆建工程闸门为"Π"型弧形钢闸门,为掌握不同工况下的结构变形和应力分布,需要建立三维有限元整体模型进行分析.采用ANSYS有限元计算软件建立模型,按不同工况分别施加荷载.计算结果表明,5种工况下弧形钢闸门的结构变形都在允许范围内,应力值都在钢材的屈服应力以下.采用结构线性屈曲分析闸门结构稳定性,用有限元法求出结构的稳定安全系数,结果表明大部分工况下的稳定安全系数大于4,最先失稳的部位在跨中水平次梁处,建议适当加密跨中纵梁,以减小水平次梁计算长度,提高稳定性.     

枕头坝电站大型轴流转桨机组快速装机对标研究

为了实现枕头坝一级水电站首台机快速装机并提前投产发电的目标,采用对标管理方式,以深溪沟水电站的快速装机技术参照体系,提出了枕头坝电站轴流转桨机的具体装机措施。介绍了深溪沟电站机组各主要部件的具体安装工序,并对安装过程中所遇到的问题和相应的处理措施进行了总结。在此基础上提出,枕头坝一级水电站必须采用构建强有力的组织协调机构、紧抓机组安装关键线路和确保设备图纸及时供应等措施,加速推进机组安装进程,以期实现提前投产发电的目标。     

砂砾层复合防渗体的研究与应用

哈达山水利枢纽工程防护区堤基的卵石有局部集中现象,见有超径卵石(大于110mm),地质条件复杂。施工中堤基防渗处理措施采用复合防渗体形式的截渗墙。文中针对施工中因地层受阻,造成相邻水泥土成墙单元间存在缺漏或水泥土截渗墙底呈现台阶状无法形成连续整齐的水泥土截渗墙,进行有效的处理。复合防渗体达到了哈达山水利枢纽防护区的防渗要求,为社会经济发展提供了保障。     

电熨斗在线温度检测系统的设计

针对电熨斗生产线上工人调温不准确且效率低下的问题,研发了一种电熨斗在线温度检测系统。介绍了该系统的硬件电路原理图和软件设计流程框图,并对其进行了误差修正,误差在1℃范围之内。利用该系统不仅能显示实时温度,还能显示周期性的最高、最低温度,利于生产线上进行多工位快速准确调温;实现与上位机的通信,方便厂家进行品质管理。