基于高分辨率SAR影像的高压输电线路杆塔检测方法

高压输电杆塔是电力系统中最重要的基础设施之一,其运行状态决定着整个电网的运行稳定和安全,对其运行状态的监测是高压输电线路监测的重要部分.提出利用高分辨率合成孔径雷达图像检测高压输电线路杆塔目标.由于在高分辨率SAR图像中,输电杆塔目标表现出明显的轮廓信息,利用G0分布参数模型和自相似性特征对输电杆塔目标进行检测分类.实验结果表明,该方法能够很好地实现在复杂场景中输电杆塔的目标检测分类.     

浅谈水暖地热的盘管设计

介绍了水暖地热的优点,对盘管的材料进行了比较选择,对房问的散热损失进行了分析和计算,对地板辐射采暖传热机理进行了研究,计算出盘菅需求量.     

Integrated assessment modelling for water resource allocation and management: A generalised conceptual framework

Nodal network approaches are a common framework for considering water allocation in river basins. In this type of model framework, a river basin is represented as a series of nodes, where nodes generally represent key points of extraction or instream use. When considering water allocation, agricultural production and other water use decisions generally interact with the stream system in two ways: they can affect the generation of runoff and thus the volume of water reaching the stream; or, they may involve direct extraction or use of water once it has reached the stream. Models are generally required to consider the influence of these decisions on flows and downstream water availability, as well as the influence of flows on the productive, passive use and environmental values of water. This paper provides a generalised conceptual framework for considering these types of interactions and their representation in integrated water allocation models. Applications of this framework to three very different case studies are outlined.     

输电线主动除冰机器人后台监控系统的设计与实现

输电线路覆冰在秋冬季节较为常见,人工除冰效率低且危险性较高,而现有的除冰机器人设计上更注重于除冰的机械性能忽略了在覆冰初期主动除冰的重要性导致除冰效果不佳,本文设计一种主动除冰机器人后台监控系统能够在覆冰初期智能预测主动除冰作业,能大幅降低覆冰可能和除冰难度,实现智能化除冰.该系统由除冰机器人本体、数据采集装置、通信模...     

Mn/Co oxide on Ni foam as a bifunctional catalyst for Li–air cells

Binary Mn/Co oxide sheets with spherical flower-like hierarchical structure are grown directly on the surface of a Ni foam skeleton as a cathode for Li–O₂ batteries using a hydrothermal method. This integrated cathode architecture eliminates the negative effects of a conductive carbon additive and binder on the electrochemical performance of Li–O₂ batteries and minimizes the processing steps in fabrication of cathodes for Li–O₂ batteries. The porous Ni foam acts as a scaffold and current collector, and the highly hierarchical porous flower-like structure of the binary Mn/Co oxide sheet acts as a highly active catalyst. Together, they facilitate effective diffusion of oxygen gas as well as rapid ion and electron conduction during electrochemical reactions. When assembled in Li–O₂ cells, the prepared catalyst exhibits excellent catalytic activities, including the oxygen reduction and oxygen evolution reactions. In particular, the Li–O₂ cell using the cathode delivers an extremely high specific discharge capacity of 9690 mAh g^-1 under a applied specific current of 200 mA g^-1 and operate successfully in a long lifespan of 66 cycles even under a high specific current of 600 mA g^-1 and a limited discharge-charge capacity mode of 1000 mAh g^-1. The simultaneous effect of the fast electron transport kinetics provided by the free-standing structure and the high catalytic activity of the binary Mn/Co oxide show promise for use in air electrodes for Li–O₂ batteries.     

Pulse-modulation eddy current inspection of subsurface corrosion in conductive structures

Due to corrosive and hostile environment, in-service conductive structures are prone to subsurface corrosion which has posed a severe threat to structural integrity and safety. Although Pulsed eddy current testing (PEC) has been found advantageous over other Electromagnetic Non-destructive Evaluation (ENDE) techniques particularly in detection and characterisation of subsurface defects in conductive structures, it is subject to technical drawbacks. In light of this, in this paper, Pulse-modulation eddy current technique (PMEC) is proposed in an effort to enhance the inspection sensitivity to subsurface corrosion and quality of corrosion imaging. Closed-form expressions of PMEC responses to subsurface corrosion are formulated via the Extended Truncated Region Eigenfunction Expansion (ETREE) modelling. A series of simulations are subsequently conducted to analyse the characteristics of PMEC signals and inspection sensitivity. Following this, experiments of PMEC for evaluation and imaging of subsurface corrosion are carried out. Through theoretical and experimental investigation, it has been found that PMEC is advantageous over PEC in terms of evaluation sensitivity and quality of corrosion imaging.     

Numerical analysis of geocell-reinforced retaining wall failure modes

Numerical analyses on the failure mode of geocell-reinforced retaining walls by the finite element strength reduction technique are reported. The effectiveness of the numerical model was validated by the centrifuge model test results. Parametric studies were conducted using the calibrated finite element procedure to investigate the effects of the apparent cohesion of geocell-reinforced soil, the friction between the wall base and the footing, the weak interlayer in the wall, and the layout of the two-tiered geocell-reinforced retaining wall on the failure surface and the factor of safety. The study results indicated that when the apparent cohesion was very large, or the friction between the wall and the footing was small, or there existed a weak interlayer in the wall, sliding failure was found to occur in geocell-reinforced retaining walls, similar to the failure mode of rigid retaining walls. Coulomb's wedge theory was suitable for the stability analysis of geocell-reinforced retaining wall in these conditions. However, in other conditions, which are more relevant in engineering applications, the failure mode of geocell-reinforced retaining walls was similar to that of slopes and the strength reduction technique for the stability analysis of slope may be suitable to analyze the stability of geocell-reinforced retaining walls.     

电网安全和调度公平性的新能源发电计划研究

  目的  随着风电场、光伏电站不断并网,地区电网网架结构发展跟不上新能源机组容量的增长速度,多能源混合的特点以及断面分层的特征给日前发电计划制定带来困难,为此提出一种考虑断面安全约束和调度公平性的多层次多能源日前发电计划方法。  方法  一是深度优先搜索越限断面,二是提出基于信息熵的出力受限分配策略,利用经济学领域中信息熵的概念指导评价调度公平性的量化指标,构造一种公平性计算方法。  结果  在保证断面潮流接近稳定极限的情况下,合理公平进行各个电厂的有功功率分配,实现电网安全稳定运行条件下的风光资源充分利用。  结论  通过某地区电网实际算例进行验证,该方法可以解决目前新能源发电计划制定存在的问题,具有很好的实际应用价值。     

基于改进小波阈值函数和奇异值分解的电能质量扰动检测定位

为了在噪声环境下准确提取电能质量扰动特征,本文提出基于改进小波阈值函数去噪和奇异值分解的电能质量扰动检测定位方法。首先构建改进小波阈值函数对含噪电能质量扰动信号降噪,利用经验模态分解的信号频带划分能力,实现降噪后扰动信号各模态的有效分离,再采用希尔伯特变换提取各模态幅值、频率等特征信息,同时基于奇异值分解实现对扰动信号的起止时刻的有效定位。最后分别采用不同类型的电能质量扰动信号进行仿真实验,实验证明本文提出的算法不仅具有良好的抗噪性能,同时具有较高的定位准确度和良好的鲁棒性。     

二级式三电平逆变器不连续调制及中点电位平衡策略

针对常见的前置TL-Boost变换器的二级式三电平逆变器,为降低逆变器开关损耗,同时控制中点电位平衡,文中提出了一种空间矢量不连续调制及其中点电位平衡策略。首先设计了不连续调制算法,分析不连续调制下逆变器中点电位波动情况;然后基于电荷平衡原理,定量计算TL-Boost变换器电荷补偿量,推导变换器占空比调整量表达式,控制流经中点的总电荷量为零。通过两级系统协调控制,不仅可发挥逆变器不连续调制低开关损耗的优势,同时可实现中点电位平衡控制,降低逆变器调制策略复杂度。该控制策略适用于二级式三电平逆变器,可有效提高系统效率,同时保证输出波形质量。