用LIFBASE分析高压脉冲放电过程OH自由基的转动温度

为探讨低温放电等离子体特性,研究高压脉冲放电过程中的气体温度,采用喷嘴-筒式放电极结构分析OH自由基在高压负脉冲放电过程中的发射光谱,并利用LIFBASE估算OH自由基的转动温度.通过模拟,得到放电脉冲频率和喷嘴直径的变化对OH自由基的转动温度的影响:OH自由基的转动温度随高压脉冲频率的升高或放电喷嘴直径的增大而降低;当脉冲峰值电压为-32 k V,放电喷嘴外直径为3 mm时,改变脉冲频率,OH自由基转动温度变化范围为200~500 K;当脉冲峰值电压为-30 k V,脉冲频率为50 Hz时,改变喷嘴直径,OH自由基转动温度变化范围为400~600 K.     

Increasing Student Engagement,Self-Efficacy,and Meta-Cognitive Self-Regulation in the High School Geometry Classroom: Do iPads Help?

Teachers are increasingly integrating mobile digital technology into the classroom. The purpose of this study was to assess the effect of incorporating iPads in a secondary-level geometry course on academic achievement, student engagement, self-efficacy, and meta-cognitive self-regulation. Students in the iPad-using classroom experienced lower levels of geometry proficiency scores, higher levels of off-task behaviors, and similar levels of self-efficacy and meta-cognitive self-regulation compared to the non-iPad group. However, the results may have been affected by several latent variables that can be controlled for in future research.     

新工科背景下环境工程专业课程教学改革探讨——以画法几何及工程制图课程教学为例

画法几何及工程制图课程是环境工程专业一门既有系统理论又有较强实践性的专业基础课,能够培养学生的绘图读图能力和空间想象能力,使学生运用现代化绘图手段解决复杂环境工程问题。文章介绍了画法几何及工程制图课程教学内容,并基于该课程的实际教学情况、结合环境工程专业的实际教学需求,提出从高校和教师两个层面对该课程进行教学改革的建议,以期为新工科背景下的工程制图教学提供一些建议与思考。     

激光焊接保护气嘴结构设计

针对高功率激光焊接过程中的气体保护问题,设计了三管组合保护气嘴结构。对保护气嘴的倾角以及三管气嘴的间距进行精确设计,三管组合保护气嘴通过三向活动导向臂与焊接头固定,并且可以很方便的调节气管方向及与焊缝的位置。通过和单管及双管保护气管的焊接效果相比较,三管组合保护气嘴结构可以得到光亮、平整的焊缝效果。     

Influence of Diesel Nozzle Geometry on Cavitation Using Eulerian Multi-Fluid Method

Dependent on automatically generated unstructured grids, a comprehensive computational fluid dynamics(CFD)numerical simulation is performed to analyze the influence of nozzle geometry on the internal flow characteristics of a multi-hole diesel injector with the multi-phase flow model based on Eulerian multi-fluid method.The diesel components in nozzle are considered as two continuous phases, diesel liquid and diesel vapor respectively.Considering that both of them are fully coupled and interpenetrated, sepa...     

同途殊归:几何学的例证意义——胡塞尔和德里达对几何学例证的不同解读

面对欧洲科学文化和人性的危机,胡塞尔运用历史现象学的方法 ,以对几何学起源的回溯为例证,试图赋予他的超文化的生活世界以超越的意义。德里达通过解构历史现象学方法论的合法性指出历史性的不可回溯性和延异性,指出回溯几何学起源的运动只不过是实现历史现象学目的论的例证。     

Web geometry laboratory: case studies in Portugal and Serbia

The role of information and communication technologies (ICT) in education is well recognised – learning environments where the ICT features included are being proposed for many years now. The Web Geometry Laboratory (WGL) innovates in proposing a blended learning, collaborative and adaptive learning Web-environment for geometry. It integrates a well-known dynamic geometry system providing an adaptive environment where face-to-face activities can be combined with computer-mediated activities, in a collaborative or stand-alone, synchronous or asynchronous, classroom or homework way. The WGL collaborative environment allows each student to capitalise on one another's resources and skills. Its adaptive module gives to each teacher the ability to assess the geometric level of each student, allowing the teacher to build the individual profile and/or learning paths. In this paper we begin describing what are the goals that support the development of such an environment, the goals that support our beliefs in the usefulness of such an environment for the teaching and learning of geometry, after which we describe the environment and the case studies already conducted.     

基于Matern硬核点过程的无人机辅助蜂窝网络吞吐量分析

无人机与传统的地面蜂窝基站混合组网有望成为一种实现数据高速传输的重要手段。针对这一场景,提出一种针对下行双层异构网络吞吐量性能的分析框架,采用泊松点过程对地面基站的位置进行建模,同时考虑到无人机之间存在的最小安全距离约束,采用Matern硬核点过程对无人机的位置进行建模,利用随机几何工具推导得到用户平均数据速率的简易表达式。根据得到的解析表达式,进而讨论无人机高度和功率控制因子的最优参数组合。结果表明,在提出的网络模型下选择适当的功率控制因子可以在保证地面基站用户速率的同时,有效地提高无人机用户的平均数据速率。     

同步发电机线性多变量与PID结合的励磁控制

提出一种用于同步发电机新型励磁控制方法———PID 线性多变量反馈励磁控制器.该控制器将PID的调节输出和线性多变量反馈励磁控制器的输出进行综合.针对单机无穷大系统运用微分几何精确反馈线性化理论进行线性多变量励磁控制器的设计,设计方法简单.Matlab/Simulink仿真结果表明该励磁控制器在提高电力系统的稳定性以及稳定机端电压方面比线性多变量励磁控制器和常规PID控制器更有效.