一种交直流混合输电系统直流侧双极故障保护策略

为进一步分析含柔性直流输电(MMC-HVDC)的交直流混合输电系统的故障特征,基于交直流混合输电系统和模块化多电平换流器(MMC)的拓扑结构,推导了MMC的数学模型,研究了直流系统双极短路的故障机理和故障特征,针对含MMC-HVDC的交直流混合输电系统的双极短路故障,设计了限流电路及闭锁换流站与交流断路器跳闸相结合的故障保护方案。以厦门市柔性直流输电系统为例,在PSCAD/EMTDC中搭建了交直流混合系统,并对保护方案进行了仿真验证。结果表明,提出的保护策略能有效地降低故障电流,提高系统稳定性。     

Functional organisation of the endomembrane network in the digestive gland of the Venus flytrap: revisiting an old story with a new microscopy toolbox

Up-to-date imaging approaches were used to address the spatiotemporal organisation of the endomembrane system in secretory cells of Dionaea muscipula. Different ‘slice and view’ methodologies were performed on resin-embedded samples to finally achieve a 3D reconstruction of the cell architecture, using ultrastructural tomography, array tomography, serial block face-scanning electron microscopy (SBF-SEM), correlation, and volume rendering at the light microscopy level. Observations of cryo-fixed samples by high-pressure freezing revealed changes of the endomembrane system that occur after trap activation and prey digestion. They provide evidence for an original strategy that adapts the secretory machinery to a specific and unique case of stimulated exocytosis in plant cells. A first secretion peak is part of a rapid response to deliver digestive fluids to the cell surface, which delivers the needed stock of digestive materials ‘on site’. The second peak of activity could then be associated with the reconstruction of the Golgi apparatus (GA), endoplasmic reticulum (ER) and vacuolar machinery, in order to prepare for a subsequent round of prey capture. Tubular continuum between ER and Golgi stacks observed on ZIO-impregnated tissues may correspond to an efficient transfer mechanism for lipids and/or proteins, especially for use in rapidly resetting the molecular GA machinery. The occurrence of one vacuolar continuum may permit continuous adjustment of cell homeostasy. The subcellular features of the secretory cells of Dionaea muscipula outline key innovations in the organisation of plant cell compartmentalisation that are used to cope with specific cell needs such as the full use of the GA as a protein factory, and the ability to create protein reservoirs in the periplasmic space. Shape-derived forces of the pleiomorphic vacuole may act as signals to accompany the sorting and entering flows of the cell.     

基于等切共轭的弧齿锥齿轮差曲面建立与解析

对弧齿锥齿轮提出了一种新的共轭求解方法，来更方便地求解共轭小轮的齿面方程，在此基础上进行了齿面接触分析。在分析过程中提出了一种新的ease-off差曲面计算方法，即用对应点的转角误差替代直线误差进行差曲面求解，使得传动误差解析、齿面修形量的确定更为直观和准确。提取了ease-off曲面上的差曲线，以方便地确定出接触路径和边缘接触点。根据全程差曲线得到了齿面接触印痕分布情况。     

Robust predictive extended state observer for a class of nonlinear systems with time-varying input delay

ABSTRACT

This paper deals with asymptotic stabilisation of a class of nonlinear input-delayed systems via dynamic output feedback in the presence of disturbances. The proposed strategy has the structure of an observer-based control law, in which the observer estimates and predicts both the plant state and the external disturbance. A nominal delay value is assumed to be known and stability conditions in terms of linear matrix inequalities are derived for fast-varying delay uncertainties. Asymptotic stability is achieved if the disturbance or the time delay is constant. The controller design problem is also addressed and a numerical example with an unstable system is provided to illustrate the usefulness of the proposed strategy.     

无人机在输电线路巡检中的多种应用

无人机技术目前的快速发展使得我们国家输电线路自身的巡检能力得到了持续的提升,基于此本文在对无人机技术给予认识的情况下,在了解了输电线路巡检过程中的使用优势之后,还总结了无人机技术在当前我国线路巡检过程中的应用路径以及应用方法;之后使用案例分析的方式分析了无人机技术在当前输电线路巡检过程中的应用方法。     

Fast Transmission Photothermal Radiometry via Sampling by an Internal Computer Sound Card

During the last few decades, photothermal radiometry (PTR) has been greatly developed and widely applied in the field of nondestructive testing. However, the traditional PTR system employs an expensive lock-in amplifier to detect the weak photothermal signal, which leads to high cost and long test time. In this paper, a fast transmission PTR system based on sampling by using an internal computer sound card was developed to lower the system cost and shorter the test time. A piece of amorphous silicon (a:Si) thin film solar cells with artificial defects was prepared and tested by the system. The results show that the sharpened defects can be identified easily and quickly according to the significant peaks of the original infrared signal sampled by the internal computer sound card. Furthermore, more detailed defects can be investigated by processing the infrared signal. These validate the effectiveness of the proposed transmission PTR system as a low cost and efficient non-destructive test technique.     

基于关键路径延时检测的自适应电压缩减技术

为了减小传统的最差情况设计方法引入的电压裕量,提出了一种变化可知的自适应电压缩减(AVS)技术,通过调整电源电压来降低电路功耗.自适应电压缩减技术基于检测关键路径的延时变化,基于此设计了一款预错误原位延时检测电路,可以检测关键路径延时并输出预错误信号,进而控制单元可根据反馈回的预错误信号的个数调整系统电压.本芯片采用SMIC180 nm工艺设计验证,仿真分析表明,采用自适应电压缩减技术后,4个目标验证电路分别节省功耗12.4％,11.3％,10.4％和11.6％.     

“聚龙一号”装置四层圆盘锥磁绝缘传输线的三维粒子模拟研究

介绍了"聚龙一号"中四层圆盘锥磁绝缘传输线(MITL)的基本理论。在CPIPIC平台上,采用非均匀网格和周期性对称边界条件,建立了"聚龙一号"的四层圆盘锥MITL的三维粒子模拟模型。设置相应的参数并用并行算法模拟得到了该器件中各层在绝缘堆上和MITL中间位置的电流和汇流后的电流,并与理论和实验数据进行相互对比验证。模拟结果表明整个器件在达到磁绝缘状态后具有很高的传输效率,并与实验结果相互验证,为以后进一步的研究提供了保证。     

TR180旋挖钻机动力头结构设计

动力头是旋挖钻机的关键部件,其性能好坏直接影响钻机整机性能的。文中介绍了TR 180旋挖钻机动力头的结构设计,着重分析了齿轮箱传动系统、滑动支架总成和缓冲装置。     

Alloying behavior and novel properties of CoCrFeNiMn high-entropy alloy fabricated by mechanical alloying and spark plasma sintering

An equiatomic CoCrFeNiMn high-entropy alloy was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). During MA, a solid solution with refined microstructure of 10 nm which consists of a FCC phase and a BCC phase was formed. After SPS consolidation, only one FCC phase can be detected in the HEA bulks. The as-sintered bulks exhibit high compressive strength of 1987 MPa. An interesting magnetic transition associated with the structure coarsening and phase transformation was observed during SPS process.