混合二极管箝位多电平变换器的拓扑结构研究

二极管箝位多电平变换器在控制功率的双向流动方面有优势．因而在中压变频调速领域和交流柔性供电系统中有着良好的应用前景。将经典二极管箝位多电平变换器中的每个箝位二极管中性点，用1个两电平逆变器桥臂和电容并联单元代替，得到了所谓的混合二极管箝位多电平变换器，在相同电平数的条件下，所使用的箝位二极管的数目有所减少，适用于对波形质量要求较高的中压功率变换场合。分析了电路的工作机理，采用电力电子专用仿真软件PSIM6和特定谐波消除脉宽调制控制策略，对所提的混合二极管箝位多电平变换器进行了仿真研究．仿真结果证明了所提拓扑的有效性。     

隔爆型设备的新型材料--为安全避免火焰传播,采用多孔材料

用于危险场所的电气设备和保护系统按指令94／9／EC要求，必须设计为防爆型。按防爆要求，设备或保护系统，无论是在正常运行时或故障状态下，不能成为点燃源。在防爆技术发展的进程中，研究出了各种各样的保护方式，这些保护方式在欧洲协调标准中都有相应的规定。在一些保护方式中，如浇封型“m”，充砂型“q”，正压型“p”和油浸型“o”，采用适当的设计方法(保护措施)可以阻止可能产生点燃源的电气装置的部件与爆炸性环境接触；在增安型“e”和本安型“i”中，     

一种适用于模块并联的同步整流驱动电路

该文提出一种适用于模块并联工作的高效率的同步整流驱动电路。采用这种驱动电路，同步整流的波形和驱动损耗可以做到和自驱动一样的效果，同时又解决了多个模块并联时会产生短路的问题。此外，采用这种驱动电路还可以调节驱动电压幅度的高低。文中从时域和频域两个角度对此电路进行了详细的原理分析。采用所推荐驱动电路的36～75V输入，1．8V／60A输出，四分之一砖标准的模块电源效率高达90％以上。最后，仿真结果验证了该电路调节同步整流驱动电压幅度的功能。     

多环电网方向保护整定计算中形成有向简单回路的新方法

在高压或超高压电网的距离保护和零序保护的整定计算过程中，首先要确定全网的最小断点集(MBPS)，然后在断点集的保护安装处打开断点，使得全网变为辐射网络。其中，多环复杂电网中有向简单回路的确定是求解最小断点集的关键，也是其必要步骤之一。为了最大限度地减少多环复杂电网中有向简单回路的计算复杂性，该文提出了一种保护依赖度和主／后备保护依赖集的新概念：将所有有向简单回路的形成过程归结为环网中所有保护依赖度大小的比较和保护依赖集的不完全深度优先搜寻过程。通过比较保护依赖度的大小来确定每次方向回路搜索的起始点，并通过对保护依赖集的深度优先搜索来确定所有有向简单回路。该方法能统一处理环网中的‘T’形接线、辐射线路等保护的配合问题。算例表明该方法简单有效，显著地降低了计算的复杂性，可方便地应用于高压或超高压电网的距离保护和零序保护的整定计算。     

From LDPE to XLPE: investigating the change of electrical properties. Part I. space charge, conduction and lifetime

This paper discusses the results of space charge, conduction current and electrical lifetime measurements performed on widely-used materials for electrical insulation, that is, low density polyethylene (LDPE) and cross-linked polyethylene (XLPE). Space charge accumulation profiles were compared in LDPE, low density polyethylene plus antioxidant (LDPE+AO) and XLPE, with consideration of thermal treatment effects in LDPE and XLPE. Significant variation (decrease) of accumulated space charge and apparent mobility, as well as slight decrease of conduction current, can be seen going from LDPE to LDPE+AO and XLPE, which may be associated with formation of deeper trap levels (or an increase of their density). On the contrary, electrical life under AC voltage does not show significant differences from LDPE to XLPE. This latter result underlines that life under high AC electrical stress is mostly determined by defects (weak points) rather than material characteristics associated with charge injection and transport.     

A multilevel relaxation algorithm for simultaneous localization and mapping

This paper addresses the problem of simultaneous localization and mapping (SLAM) by a mobile robot. An incremental SLAM algorithm is introduced that is derived from multigrid methods used for solving partial differential equations. The approach improves on the performance of previous relaxation methods for robot mapping, because it optimizes the map at multiple levels of resolution. The resulting algorithm has an update time that is linear in the number of estimated features for typical indoor environments, even when closing very large loops, and offers advantages in handling nonlinearities compared with other SLAM algorithms. Experimental comparisons with alternative algorithms using two well-known data sets and mapping results on a real robot are also presented.     

Path-following control of mobile robots in presence of uncertainties

This paper presents, in detail, the implementation of a new control strategy, Kalman-based active observer controller (AOB), for the path following of wheeled mobile robots (WMRs) subject to nonholonomic constraints. This control strategy presents some particularities as being used in discrete mode, and being robust against uncertainties and disturbances such as the ones due to the use of the input-output feedback-linearization method in discrete mode, while it was developed to be used in continuous mode. The performance of the proposed control algorithm is verified via computer simulation, and is compared with other control strategies, such as pole placement controller (PPC) and PPC with a Kalman filter observer (CKF).     

EICAR 2005

The European Institute Center for Anti-Virus Research (EICAR; www.eicar.org) held its 14th annual conference and attracted about 100 researchers, vendors, users, and government representatives interested in discussing the field’s latest developments. This report presents a brief overview of what went on at the invited talks, paper presentations, and industry sessions.     

Selective and in-situ determination of carbonate and oxide particles in aqueous solution using laser-induced breakdown spectroscopy (LIBS) for wearable information equipment

Laser-induced breakdown spectroscopy (LIBS) has been applied for quantitative analysis of Al₂O₃, CaCO₃ and MgO particles suspended in water. In the single elemental system, the plasma emission intensities of Al, Ca and Mg were linearly increased with concentration of elements in the range of 1.0×10^?5–1.0×10^?3  M, 1.0×10^?4–2.0×10^?3 M and 8.0×10^?5 –4.0×10^?3 M, respectively. We also investigated the concentration dependence of breakdown spectra for suspended mixtures of Al₂O₃, CaCO₃ and MgO particles. The emission lines, such as Al I, Ca I, Ca II and Mg I, were appeared in the LIBS spectrum simultaneously, and each emission peak could be deconvoluted. The plasma emission intensities of Al, Ca and Mg in the multielemental system were also linearly increased with their concentrations in the range of 1.0×10^?5–1.0×10^?3 M, 1.0×10^?4–2.0×10^?3 M and 4.0×10^?4–2.0×10^?3 M, respectively. LIBS was found to be available for quantitative and qualitative measurement of the concentrations of Al₂O₃, CaCO₃ and MgO particles suspended in water. The present results suggest that LIBS is a potentially useful tool for in-situ analysis on particles composition and concentrations for environmental monitoring by the wearable information equipments.