变电站三维交互场景仿真关键技术研究

应用三维图形技术为变电站仿真系统构造虚拟环境能大大提高变电站场景的真实感,为变电站培训仿真工作带来技术飞跃.文章研究了基于三维图形技术的变电站交互场景仿真的关键技术,给出了基于电气连接特性构造虚拟场景树型层次组织的方法,即"以母线为纬、以单元为经、以断路器为基准,按电气接线顺序排列";提出了基于特征的实时层次细节模型生成方法和基于虚拟漫游上下文情景的碰撞检测加速算法,并已成功应用于变电站虚拟现实仿真系统中.     

Effect of Scandium on Corrosion Resistance of Welded Joint of Al-6Mg-Zr Alloy

Al Mgalloyshavebeenwidelyusedinmanyin dustries,especiallyinmarineandaircraftapplica tions,duetotheirgoodweldability,ductilityandex cellentcorrosionresistance.Beingthenon heattreat ablealloys,thesematerialsderivetheirstrengthpri marilyfromsolidsolutio…     

校园社区网页登录的交互界面设计研究

良好的交互界面设计可有效提高网页的登录效率,并能传递网站的定位与文化属性,形成较好的用户体验.以在校大学生为社区网用户群,通过问卷调查方法分析了登录操作行为过程中的用户需求偏好,提出了针对登录表单的3个可用性问题.结合大学生互动社区“易班”的登录界面进行了案例分析,归纳总结出校园社区网页登录界面在导航、布局、背景和文化诉求等方面的界面视觉设计元素.     

基于ANSYS Workbench水轮发电机螺栓法兰连接有限元分析

根据机械设计理论,分析了只承受预紧力和预紧力与工作载荷同时作用两种情况下螺栓连接的受力情况,并利用ANSYS Workbench对水轮发电机螺栓法兰连接结构进行模拟,创建了有限元模型,施加了相应的约束、预紧载荷与工作载荷,进行了结构静力学分析.有限元分析结果与理论运算结果进行比较,有限元模型的正确性、可靠性得到验证.该模拟分析结果为螺栓的选用与装配提供了依据,提高了产品的可靠性和设计水平.     

移动智能终端操作系统网络流量控制策略研究

从智能终端对移动网络数据流量和信令流量的影响出发,总结主流操作系统和应用对网络流量的需求特点。然后从操作系统、移动网络和应用开发三个层面分析终端侧流量管控技术策略,就PUSH中心、网络连接请求管理、自动识别、平滑切换、网络快速休眠、连续分组连接等关键技术引入作了详细论证。最后提出手机操作系统流量管控建议,包括建设公共测试平台、加大管控技术研发和加快流量管控技术标准化。     

A dead-time minimization algorithm for improving the output characteristics of the PWM inverter

The dead time in an inverter is necessary to prevent the short circuit of the DC source. However, the dead time may cause serious problems such as waveform distortion, voltage drop, increased torque ripple and heating of the motors. In this paper, a dead-time minimization algorithm is proposed for improving the inverter output performance. The adverse effects of the dead time are investigated, focusing on the voltage drop and the distortion factor of inverter output current. The proposed algorithm consists of forbidding unnecessary triggers for the inverter switches that are not turned on although the gate drive signal is impressed. The proposed algorithm is explained in terms of the conduction modes of the output currents. The validity of the proposed method is verified by comparing the simulated and experimental results with those of the conventional methods. It is concluded from the results that the proposed algorithm can reduce the output current harmonics. Further, the output voltage can be equal to the reference value and the number of inverter switchings can also be reduced to 50% compared with those of conventional methods.     

非对称路由环境下SYN flood攻击防御方法

针对现有网络安全设施无法有效防御非对称路由环境下流量规模较大的SYN flood攻击的问题,对SYN flood攻击检测技术和TCP连接管理策略进行研究,提出了一种轻量级攻击检测和混合连接管理策略相结合的防御方法,利用SYN分组比例和目的地址熵进行攻击检测,并根据检测结果对基于SYN的连接管理策略和基于数据的连接管理策略进行灵活切换。实验证明该防御方法能有效地减轻SYN flood攻击对网络安全设施的影响。     

热电偶串并联在工程检测中的应用

本文分别对几种特定情况下热电偶串、并联的工作状况进行了分析,并讨论了如何对热电偶在某些特定情况下的串、并联加以应用。     

Conditions and costs for renewables electricity grid connection: Examples in Europe

This paper compares conditions and costs for RES-E grid connection in selected European countries. These are Germany, the Netherlands, the United Kingdom, Sweden, Austria, Lithuania and Slovenia. Country specific case studies are presented for wind onshore and offshore, biomass and photovoltaic power systems, as based on literature reviews and stakeholder interviews. It is shown that, especially for wind offshore, the allocation of grid connection costs can form a significant barrier for the installation of new RES-E generation if the developer has to bear all such costs. If energy policy makers want to reduce the barriers for new large-scale RES-E deployment, then it is concluded that the grid connection costs should be covered by the respective grid operator. These costs may then be recouped by increasing consumer tariffs for the use of the grid.     

整流变压器改变接线方式的实践与思考

叙述了为适应生产规模的改变对整流变压器进行的吊芯、改造过程。节约了投资,保证了整流系统改造过渡时期的安全生产。