明渠非恒定流的特征线解法

长距离输水明渠中,常遇到闸门启闭过程中,渠中水面波动比较剧烈,导致漫堤的情况,严重的可能会引起渠堤失稳滑坡.利用特征线法对描述明渠中水流运动状态的圣维南方程组进行求解,编制程序求解了简单输水模型中,闸门启闭情况下渠中各断面水深的变化情况,为分析复杂情况提供参考.     

Solution for the Closed-Loop Problem in Pressurized Multipipe Systems

The fundamental background of the solution for the steady-state flow in pressurized water closed-loop pipe systems, without any reservoirs in-between, is presented in this paper. The use of the steady-state mass balance and energy equations to calculate discharges and heads in this type of hydraulic system leads to an undetermined problem. The way to solve this indeterminacy is to consider an additional continuity equation associated with the difference between initial and final conditions, taking into account fluid compressibility and pipe-wall deformability. A complete formulation is derived considering pressure and temperature changes in the hydraulic system. Simplified formulae are presented for isothermal flows in simple systems and multiple closed-loops with pipes in series and in parallel. This problem can also be solved by a pseudotransient analysis technique applied to steady-state conditions. Proposed solutions for this problem are applied to steady-state flows and tested for different system configurations.     

特高压交/直流电网仿真技术研究

电力系统的规模日趋扩大，复杂程度不断增加，迫切需要建立与特高压电网发展形势相适应的特高压电网仿真系统。首先分析了各种仿真系统的特点及其适用范围，然后结合我国特高压电网研究对仿真系统的要求，讨论了可用来对大规模交/直流电网的机电暂态与电磁暂态现象进行实时仿真的全数字实时仿真系统与数模混合仿真系统的原理、功能、特点、发展现状及适用范围，指出了其现存的局限性，提出了改进与完善的思路。     

基于小波能谱矩阵相似度的电力暂态信号识别

暂态保护技术正呈现加速发展态势,但如何正确识别各类故障和非故障暂态,是暂态保护实用化必须解决的一个最大难题.信号经过小波分析之后得到的小波能谱能很好的反映信号不同时间的能量分布.电力系统中,不同电力暂态信号其时频特性必然不同,其在多个尺度下的小波能谱的分布必然存在差异,因此,在构造小波能谱矩阵的基础上,借鉴数字图像处理中的相似度的思想,提出基于小波能谱矩阵相似度的分类方法.建立各种电力暂态的标准能谱矩阵,计算测试样本的能谱矩阵与各种标准能谱矩阵的相似度,按照相似度最大原则实现分类.对电力系统单相接地故障暂态、线路正常开关操作暂态、电容投切操作暂态和雷电扰动暂态的仿真分析表明,该方法对电力暂态的识别率高.     

A support vector machine integrated system for the classification of operation anomalies in nuclear components and systems

A support vector machine (SVM) approach to the classification of transients in nuclear power plants is presented. SVM is a machine-learning algorithm that has been successfully used in pattern recognition for cluster analysis. In the present work, single- and multiclass SVM are combined into a hierarchical structure for distinguishing among transients in nuclear systems on the basis of measured data. An example of application of the approach is presented with respect to the classification of anomalies and malfunctions occurring in the feedwater system of a boiling water reactor. The data used in the example are provided by the HAMBO simulator of the Halden Reactor Project.     

Hyperreal transients in transfinite RLC networks

Up to the present time, there have been no transient analyses of RLC transfinite networks. Standard analyses of transfinite networks have been restricted to purely resistive ones. In this paper, it is shown how non‐standard analysis can be used to examine the transient behaviour of transfinite networks having lumped resistors, inductors, and capacitors. To do so, the time line is expanded into the hyperreal time line, and the transients obtained take on hyperreal values. It is also shown how the diffusion of signals on artificial RC cables and the propagation of waves on artificial RLC transmission lines can ‘pass through infinity’ and penetrate transfinite extensions of those cables and lines. Less precisely but more suggestively, we can say that diffusions and waves can reach—with appreciable values—nodes that are transfinitely far away from their starting points, but that it will take infinitely long times in order to get there. Copyright © 2001 John Wiley & Sons, Ltd.     

时间相关单光子计数记录快速荧光寿命图像

基于时间相关单光子计数(TCSPC)的荧光寿命成像(FLIM)的获取时间取决于成像的图像尺寸、样品寿命的精度及样品计数率.对于高密度荧光团样品,如染色组织或植物细胞,当前可用的样品计数率与TCSPC荧光寿命成像技术最高的计数率接近.该文描述了在高计数率下TCSPC性能,并估计计数损失及堆积效应.结果表明,整个体系的寿命误差比预料的要小.因此,TCSPC FLIM可在获取时间低于1 s的情况下记录寿命图像.为增加FLIM时间序列记录,利用存储交换技术,在采集下一个光子期间读取正在记录的数据,使用两个平行TCSPC模块,可以每秒两幅图像记录荧光寿命时间序列.该技术可应用于活体植物组织叶绿素的瞬态测量.     

Calibration of viscoelastic parameters by means of transients in a branched water pipeline system

In this paper, different arrangements of Kelvin–Voigt elements are implemented in an admittance matrix model to investigate the transient modeling of water distribution systems. The viscoelastic parameters are calibrated by experimental data acquired during a transient in a branched system of three HDPE pipes at the Water Engineering Laboratory of the University of Perugia, Italy. The dependence of the viscoelastic parameters on the branch characteristic time is investigated. Models with a single set of elements for all branches are compared with models with different sets of elements for each branch. When the same number of parameters is used, the former perform better than the latter. No evident correlation is found between the retardation times of the viscoelastic parameters and the branch characteristic times. The use of two measurement sections instead of one does not modify the calibration results significantly.     

采用高斯脉冲函数计算电路的冲激响应

电路的单位冲激响应是研究电路暂态性质的重要工具之一。为了建立电路冲激响应的物理图景,本文以高斯冲击函数作为激励源,对储能元件采用伴随模型,对一阶RC电路的响应进行仿真计算。由于考虑了冲激函数的作用过程,电压和电流是时间的连续函数,从而为理解冲激响应的物理过程提供一个正确的物理描述。同时,本文给出的数值算法亦可应用于高阶电路的暂态仿真中。     

电力系统机电暂态和电磁暂态数字混合仿真研究

机电暂态与电磁暂态混合仿真避免了机电暂态仿真对电力电子器件及其控制保护模型只能粗略模拟的不足,克服了电磁暂态仿真规模过小和仿真效率低的缺点,是解决交直流大电网仿真计算难题的重要技术方案。混合仿真的重点是机电暂态和电磁暂态的接口设计,在对比两类仿真差异性的基础上,就接口位置的选择、等值电路的形成和接口交互时序等方面内容进行了总结评述。指出当前接口技术基本框架已经成型,研究难点在于等值电路类型及其参数的快速求取,最后对混合仿真的发展做了简要展望。