A DOUBLE TIME—SCALE CNN FOR SOLVING TWO-DIMENSIONAL NAVIER—STOKES EQUATIONS

A practical cellular neural network (CNN) approximation to the Navier–Stokes equation describing the viscous flow of incompressible fluids is presented. The implementation of the CNN templates based on a finite-difference discretization scheme, including the double-timescale CNN dynamics and the treatment of various types of boundary conditions are explained. The operation of the continuous-time model is demonstrated through several examples.     

工程中混沌现象及混沌应用的研究现状与展望

混沌广泛存在,工程领域的混沌现象和混沌应用正在引起广大工程学者的关注。本文概述了工程中的混沌现象及混沌应用研究的主要进展和研究现状,并展望了它们的发展前景。     

光伏微逆变器中Boost变换器的混沌现象分析与控制研究

由于光伏并网微逆变器中Boost变换器存在着混沌现象,易造成微电网系统的不稳定。故引入两级式微逆变器,通过建立Boost变换器模型分析混沌现象产生机理,参考电流参数是造成混沌的重要因素。提出一种基于参数共振微扰法的Boost变换器混沌动力学控制方法,以参考电流作为微扰参数,推导出最优控制计算公式。通过实例验证,参数共振微扰法可以有效抑制Boost变换器的混沌现象。结果表明该控制算法对研究光伏微逆变器具有有效性和可行性。     

Rogowski线圈的动模实验研究

介绍了基于Rogowsk i线圈传感的电子式电流互感器在与电磁式电流互感器并联运行时的实验结果,并以变压器差动保护为例对两种传感器的保护特性进行了比较分析研究。实验结果表明:在保证传感器绕制工艺和合理选择信号处理电路结构参数的情况下,与电磁式电流互感器相比,基于Rogowsk i线圈原理的电子式电流互感器能准确反映一次侧暂态电流的变化情况,具有无饱和、测量准确、响应速度快的特点,完全满足电力系统的保护和控制对电流信号采样的要求。     

多通道蛇形流场PEMFC内传递现象的数值模拟

电极板上的流场构型对质子交换膜燃料电池的流动特性和电池效率有重要的影响。为研究多通道蛇形流场设计质子交换膜燃料电池的局部流场、电流密度和组分浓度等的空间分布,应用作者前期发展的基于计算流体力学的三维稳态数学模型,对一个小型电池单体(电极面积大小为5.9cm×6.1cm)进行了详细的数值模拟,讨论和分析了该设计的流动特性和传输机理。结果表明:电池的电流密度分布比较均匀,阴极的压力损失要比阳极大得多,阳极氢的质量分数从流动入口到出口基本呈现增大趋势。     

Monte Carlo simulation for stochastic calculus of far‐field radiation from open‐ended waveguide arrays

In this paper, Monte Carlo (MC) simulation has been applied for the analysis and stochastic calculus of far‐field radiation from the small, large, and infinite open‐ended waveguide arrays. Elements of the arrays are excited by the fundamental TE₁₀ mode and with equal amplitude and linear phase. The simulated results from MC are compared closely with the finite element method (FEM). Numerical analysis based on FEM is performed using Ansoft High Frequency Structural Simulator to calculate the far‐field radiation characteristics of the arrays. The accuracy and the effectiveness of the aforesaid method, which is based on Monte Carlo integration technique, are also demonstrated in uniformly and nonuniformly spaced waveguide arrays for pattern synthesis or achieving side lobe level reduction. The arrays with arbitrary shapes are simply evaluated by MC method in equal spacing array. It is found that by applying MC simulation, the open‐ended waveguide arrays have the ability to produce the desired radiation pattern and could satisfy requirements for many applications. Copyright © 2016 John Wiley & Sons, Ltd.     

混合编程在Lorenz混沌系统动力学行为仿真中应用

Lorenz混沌系统的动力学行为是由控制参数决定。以Lorenz混沌系统的动力学行为为实例,采用更加直观的相图和时域图并借助于Lab VIEW与MATLAB软件对之进行仿真,实现系统的动力学行为。分析了Lab VIEW与MATLAB两种编程语言的特点和混合编程技术,采用两者混合编程技术实现了有效仿真,给出了混合编程的具体实现过程。实践证明,Lab VIEW与MATLAB的结合运用,简单可行,相互补充,有利于程序的仿真,提高编程效率。     

2001—2014年阿克苏河流域山区积雪时空变化分析

Mountain snow is one of the main water source for the Aksu River in Xinjiang. A comprehensive analysis of spatio-temporal variations in the mountain snow in the Aksu River basin can provide a basic support for runoff analysis. In this paper, the snow products of Moderate Resolution Imaging Spectroradiometer (MODIS) during the period of 2001-2014 were used to analyze the snow cover area and its spatio-temporal variations in the Aksu River basin. Results show that in this period of 14 years, the snow cover area took a decreasing trend in the annual, seasonal and monthly scales, with particularly significant decreasing in the annual maximum snow cover and the snow cover in summer. The major significant changes of snow cover occurred in Tuoshigan River mountainou area, mountainous border region and the west of Kumalake River mountain area in the winter and summer, and significant reduction in permanent snow area occurred in the east of Kumalake River mountain area. Without considering other meteorological factors, temperature rising could be a major cause for reduction in the snow cover.     

电网故障仿真实验装置的设计

应高校继电保护实验的要求,设计用于继电保护实验的电网故障仿真实验装置。根据高校继电保护教育中的典型回路、典型故障,实现简单电网相应短路故障过程的简单模拟。介绍了其硬件结构和软件仿真。装置以TI公司的MSP430系列单片机为控制核心,经D/A转换、低通滤波后,由功率放大模块对信号进行放大输出。上位机采用VC 6.0完成上位机仿真软件模块的编写,主要实现电气接线图形化操作与短路计算模块功能。该装置能灵活地仿真故障时保护安装处电流、电压的实际动态过程,为继电保护实验的深入推广打下了基础。     

电网故障仿真实验装置的设计

应高校继电保护实验的要求,设计用于继电保护实验的电网故障仿真实验装置.根据高校继电保护教育中的典型回路、典型故障,实现简单电网相应短路故障过程的简单模拟.介绍了其硬件结构和软件仿真.装置以TI公司的MSP430系列单片机为控制核心,经D/A转换、低通滤波后,由功率放大模块对信号进行放大输出.上位机采用VC ++6.0完成上位机仿真软件模块的编写,主要实现电气接线图形化操作与短路计算模块功能.该装置能灵活地仿真故障时保护安装处电流、电压的实际动态过程,为继电保护实验的深入推广打下了基础.     

恒定有压扩散流局部非稳态现象数值模拟研究

三维数值模拟采用大涡模拟(LES)方法,小尺度涡的影响采用RNG亚格子模型。通过瞬时流场结构分析,发现在恒定流状态下扩散段内存在流动的局部非稳态(流动)现象。结合速度历时过程及其频谱分析,探讨了此现象产生的原因,指出扩散段内水流运动由低频摆动运动和高频脉动运动组成,主流的低频摆动是由分离区漩涡的横向振荡诱发的。基于不同雷诺数(Re=500~56000)及边壁扩散角度(5~10度)扩散段内水流运动局部非稳态现象的统计特征,指出对称边界条件下主流在扩散段内做准周期摆动,高雷诺数(Re7000)时其摆动的统计特征不受雷诺数影响;水平扩散段不产此现象的极限扩散角为7度。壁面压强历时过程的频谱分析表明,对称边界条件下扩散段内产生局部非稳态现象时,边壁压强的时域过程并不对称,但频域过程基本对称。计算结果和试验结果基本吻合。     

Trajectory control of controlled-PM linear synchronous motor magnetic levitation vehicle—FEM dynamics simulations and experiments in mass-reduced-control mode

A novel magnetic levitation train system can be constructed by using a long-stator controlled-PM linear synchronous motor having propulsion and attractive-mode levitation functions and minimum loss. Realizing this system requires simplifying manufacture of the long-stator guideway. In the long-stator on the ground, semiclosed large slots are adapted and designed for one-turn coils of a waveform to be easily installed. The large slots cause the PM LSM detent forces to give strong influences on dynamic operations of the running vehicle. A two-dimensional FEM used for the dynamics simulations is capable of precisely analyzing the detent forces produced between the stator teeth and the PMs. This paper presents FEM dynamics simulations and experiments in mass-reduced-control mode of a 1/2 scale model magnetic levitation vehicle supported by small rubber rollers. The simulation model developed here includes the vehicle speed performance, position sensors and drag force due to friction between rubber roller and rail. The detent force problem in propulsion motion is successfully solved by adapting the feedback control of the vehicle propulsion based on the I₁₀-controlled method. The trajectory control is thus accomplished for the vehicle to follow speed and position patterns. The dynamics simulations are verified from the experiments. The simulation program proposed here enables us to investigate the magnetic levitation train system, including LSM design and vehicle dynamic operations.     

面向新型电力系统物理模拟实验的快速系统原型技术

新型电力系统对电力系统物理模拟实验提出了很高的要求,原有的物理模拟技术已难以满足。通过借鉴控制领域常用的快速控制原型（RCP）技术思想,提出了快速系统原型（RSP）技术,包括数字仿真器、快速原型控制器和快速原型被控对象（ROP）3个部分,解决了传统物理模拟技术费时费力和难以满足新型电力系统快速演进需求的缺陷。RSP技术用于科学研究、产品开发和入网验证时,研究成果和产品可直接用于工程实际。首先介绍了RSP的思想及具体实现方案,并阐述了其“所见即所得”的动模实验理念,最后以柔直输电动模实验为例,验证了基于RSP理念和技术可建成一个企业级别的仿真环境及工程技术实践平台,并能真实灵活仿真新型电力系统的各种特性。     

Suppressing harmonics in four‐quadrant AC‐DC converters with chaotic SPWM control

In this paper, a new chaotic sinusoidal pulse width modulation (chaotic SPWM) control is proposed and implemented in a four‐quadrant AC‐DC converter for harmonics suppression, where a chaotic carrier plays a key role. Further, the relationship of the harmonic distribution and carrier frequency is derived by analyzing the harmonic components of the AC‐DC converter, which is useful for revealing the operation principle of the chaotic SPWM control for harmonic suppression. Finally, the simulation and experimental results illustrate the effectiveness of the proposed chaotic SPWM control on harmonics reduction. Copyright © 2012 John Wiley & Sons, Ltd.     

Numerical simulation and design of a new microwave annular waveguide plasma source—I: Simulations without the plasma parameters

A new microwave annular waveguide plasma source with slot antennas is introduced in this paper. The distributions of electromagnetic field within the rectangular waveguide and the annular waveguide are simulated and analyzed, and the relationship between the distributions of the electromagnetic field and the radius of the microwave reactor is investigated. In addition, HFSS microwave studio simulator is applied to carry out the final design. Both analysis calculation and numerical simulation of the electromagnetic field distributions for the waveguide and microwave annular waveguide plasma source are presented and they are in good agreement. Copyright © 2010 John Wiley & Sons, Ltd.     

High‐order harmonic resonance phenomena of a voltage‐sourced converter in cable system

This paper presents high‐order harmonic resonance phenomena of voltage‐sourced converters (VSC). When a voltage‐sourced converter is connected to a power system with cables, there is a possibility that minute high‐order harmonic voltages of a voltage‐sourced converter are magnified by a series resonance and a parallel resonance, and high‐order harmonic resonance phenomena are determined by this study. The cause of high‐order harmonic resonance phenomena is investigated and elucidated by the analysis using EMTP. In addition, it is verified that high‐order harmonic resonance phenomena occur as a practical matter. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 26–35, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20054     

A study of three‐dimensional observation of prebreakdown phenomena in dielectric liquids

This paper presents a new method which visualizes the high‐speed three‐dimensional images of prebreakdown streamers in dielectric liquids. A new optical system, having two crossed light axes to observe the needle tip from different directions, was designed. The shadowgraphic images from these two directions were combined through a beam splitter and focused on the photo‐cathode of an image converter camera. The photograph taken by this high‐speed shadowgraph system was reconstructed to three‐dimensional images using an image scanner and a computer. Using this system, the growth and decay processes of the streamer in cyclohexane were investigated. © 1999 Scripta Technica, Electr Eng Jpn, 128(4): 9–15, 1999     

Novel chaotic behavior in the Muthuswamy–Chua system using Chebyshev Polynomials

In this paper, three kinds of memristors with memristance functions obtained from the Chebyshev polynomials are used in the Muthuswamy–Chua system, which has only three circuit elements: a linear passive inductor, a linear passive capacitor and a nonlinear active memristor. We use multivariable second‐order polynomial functions of current and memristor state for the internal state function of the memristor. This enables our system to generate not only double‐scroll but also four‐scroll attractors. Systematic studies of chaotic behavior in these systems are performed using phase portraits, bifurcation diagrams and Lyapunov exponents. Simulation results show that all these systems exhibit chaotic behavior over a range of control parameters. Copyright © 2014 John Wiley & Sons, Ltd.