高精度分体式多通道超声波温度计的设计

针对传统的温度传感器在极端与特殊条件下无法满足测量的要求,设计了分体式多通道的超声波温度计。将多对测量头均匀布置在装有被测介质的容器外侧的各个方位,利用FPGA的控制驱动信号精确确定超声波传播的起点时刻,通过分块查找的特征波查找算法、高速高分辨率的信号采样电路和直线插补算法相结合,利用过零点两侧的采样点来实现对超声波传播时间终点时刻的高精度检测,进而精确计算出超声波传输时间。在传播距离一定的条件下,以水为介质为例进行模拟实验。结果表明：分体式多声道超声波温度计能够实现对超声波传输时间的分辨率ns级的测量,从而确保了对温度的高精度测量。     

一种新型相移场探头改变导体涡电流分布的理论验证

涡流检测方法广泛应用于导电材料的缺陷检测和无损评价中。受趋肤效应的影响,常规涡流检测法通常只能检测导体表面缺陷。有学者提出了一种相移场探头,并通过实验验证了该探头在满足一定激励条件时,可以达到抑制导体表面涡电流密度,而增加导体深处涡电流密度的效果,从而可以检测导体更深处缺陷。但该结论仅有实验结果,还没有理论方面的验证。本文采用解析方法研究了该相移探头与导体的相互作用,推导出导体中涡电流分布的精确理论表达式,然后分析相位、激励频率对涡电流分布的影响,并计算了导体不同深度涡电流密度分布。从理论上验证了该探头设计及激励方法具有改变导体涡电流密度分布,增加导体深处涡电流密度的效果。     

A novel algorithm for selective current limit used in AMOLED panel

A selective current limit algorithm based on color space conversion is proposed in this paper. There are mainly two advantages for this algorithm. Firstly, only the luminance component Y is decreased, and the color component Cb or Cr is not changed; thus, the color distortion is avoided in the process of current limit. Secondly, the current of pixels with high luminance is limited while that of those pixels with low luminance is not, which means current limit is executed selectively. For the same value of mean square error, the simulation results show that the ratio of pixels with high luminance of the image processed by the proposed algorithm is zero, and that processed by the net power control and the algorithm based on color space conversion is 0.081 and 0.0854, respectively. This algorithm is implemented on a field‐programmable gate array to drive the image display on the AMOLED panel.     

A Lyapunov‐based small‐gain approach on design of triggering conditions in event‐triggered control systems

This paper studies a Lyapunov‐based small‐gain approach on design of triggering conditions in event‐triggered control systems. The event‐triggered control closed‐loop system is formulated as a hybrid system model. Firstly, by viewing the event‐triggered control closed‐loop system as a feedback connection of two smaller hybrid subsystems, the Lyapunov‐based small‐gain theorems for hybrid systems are applied to design triggering conditions. Then, a new class of triggering condition, the safe, adjustable‐type triggering condition, is proposed to tune the parameters of triggering conditions by practical regulations. This is conducive to break the restriction of the conservation of theoretical results and improve the practicability of event‐triggered control strategy. Finally, a numerical example is given to illustrate the efficiency and the feasibility of the proposed results. Copyright © 2015 John Wiley & Sons, Ltd.     

Agro-ecosystem modeling can aid in the optimization of biomass feedstock supply

Recent European Directives promoted the development of biofuels, requesting mandatory limits to their emissions ot greenhouse gases (GHG). Second-generation biofuels based on lignocellulosic biomass are prime candidates but their GHG emissions are variable and uncertain. Agro-ecosystem modeling can capture them and the performance of biofuel feedstocks.This study aimed at optimizing feedstock supply for a bioethanol unit in France, from agricultural residues, annual and perennial crops. Their productivity and environmental impacts were modelled on a regional scale using geo-referenced data on soil properties, crop management, land-use and future weather data. Several supply scenarios were tested. Cereal straw was the most efficient feedstock but had a low availability, and only miscanthus could meet the bioethanol plant's demand. Sorghum combined poor yields and high GHG emissions compared by miscanthus and triticale. A mix of three biomass sources used less than 3% of the regional agricultural land while abating GHG emissions by 60%.     

用于单个纳米颗粒检测的固态纳米孔器件的仿真与优化

基于固态纳米孔器件的检测技术是近年来的研究热点,它可广泛用于各种纳米颗粒、生物分子检测及DNA测序等各个领域.采用数值方法对两种常用的纳米孔器件,即圆柱形纳米孔和棱台形纳米孔器件在检测纳米颗粒穿过时的局部电场变化以及离子电流特性进行了系统性的仿真和分析,提出了采用纳米孔阻塞电流因子,来评估器件性能.在此基础上,深入分析和讨论了纳米孔的孔径和孔深等参数的变化对检测纳米粒子性能的影响,并提出了优化的纳米孔器件设计方案.研究结果对纳米孔器件的制备,以及其在检测纳米颗粒的应用实践中提供了理论指导.     

基于科赫雪花图形激励装置的涡流传感器工作原理分析

首次提出并设计了一种基于分形理论自相似结构的科赫雪花图形激励装置涡流传感器,对这种传感器的工作原理和物理模型进行了深入的分析,分析表明,基于分形结构激励线圈的涡流传感器,在多处具有涡流叠加效应,随着科赫雪花图形阶次的提高,这种涡流叠加效应越来越明显,分布密度不断增加,可以显著提高涡流传感器激励效果和检测灵敏度,从而提高对微小裂纹缺陷的检测能力.研制了实际装置,通过实验证了这一结论.     

基于WSN定位算法的井下单相接地故障研究

由于井下配电网的布线很复杂,故障检测传感器节点的分布却很分散,在故障信号传输过程中如果受到井下环境的干扰,容易造成消弧线圈的故障特征电流很小。传统的故障检测模型针对小电流故障特征很难进行高效准确采集,无法提供准确的故障检测,提出了一种Zigbee改进Music故障定位算法,采用Zigbee网络技术对故障区域进行定位,建立了多通道数据传输机制。改进Music算法通过对阵列输出扩展虚拟矩阵,解决了传统算法只能估计出少于阵元数信号方向的问题,将共轭信息引入到了Music算法中,利用二阶共轭增强法大幅度降低了算法的运算量。仿真结果表明,在相同锚节点密度的情况下,定位精度和定位覆盖率都得到了显著提高。通过单相接地故障电路实验对线路的零序电流进行了实际测量分析,验证了上述方案的可行性,可以有效地解决由于单相接地引起的井下故障问题。     

关于110 kV线路重合闸的探讨

重合闸在110 kV线路供电过程中起到了非常重要的作用,它关系着电力系统运行的安全性和可靠性。在重合闸投运前,需要模拟系统的运行情况,事前试验可能存在的重合闸形式,及时发现、排除其中存在的问题,确保重合闸能够正确动作。分析了110 kV线路重合闸的原理、功能,并以某案例分析为基础,简要探讨了对110 kV线路重合闸控制的相关认识。     

浅谈110 kV变压器的维护与检修

作为电网的核心电气设备,变压器会对电网的运行产生重大影响。为了确保变压器的可靠、安全运行,电力企业需要对变压器进行日常维护与检修。阐述了变压器常见异常状况和日常维护的具体内容,以供参考。