一类多滞量周期扰动非线性系统的周期解

采用更精确的先验估计，利用拓扑度讨论了一类具有多滞量的周期扰动非线性系统的T-周期解，得到了系统存在T-周期解的充分条件．证明了具有滞后的单种群对数模型在一定条件下存在的正周期解．     

多机系统在参数扰动下的周期解

研究了多机系统受到功率或线路阻抗扰动时的周期解，建立了相应的数字模型，利用空间周期解理论导出了多机系统产生周期解的一些条件。文中所讨论的扰动可以是强振性的，这为研究机互联系统所产生的低频振荡现象提供了理论分析基础。     

防振锤的动力响应及能量消耗

此文给出防振锤在周期激励和非周期激励的统一解，并讨论了上述两种情形下防振锤的能量消耗。     

一类二元具时滞的神经网络概周期解的存在性和全局吸引性

通过构造Liapunov泛函，研究如下二元神经网络{dx/dt=-x(t) atanh[y(t)-by(t-τ)] I1(t) dy/dt=-y(t) atanh[x(t)-bx(t-τ)] I2(t)解的存在性和全局吸引性，获得了该网络存在唯一概周期解的充分条件和所有解收敛于此概周期解的充分条件。     

三电平逆变器SHEPWM多组解特性比较及实验

研究了应用于三电平NPC逆变器的特定消谐(Selective Harmonic Eliminated PWM, SHEPWM)技术.传统SHE均假设波形1/4周期对称,这有助于减小方程组的维数,但同时也减少了可行解的空间,而消除低次谐波并不严格要求波形1/4周期对称.针对1/4周期对称SHE,以N=7为例给出四组解,然后进一步研究1/2周期对称下的解,从理论上证明可以存在无数组解,进一步将其分为两种不同的类型.分析和比较了1/4周期对称解和1/2周期对称解的区别和联系,以及不同类型的解在谐波特性方面的差异,并通过实验进行了验证.     

The Periodicity of Rational Recursive Sequencexn＋1＝f（xn）xn－1

通过有理递归序列周期性的探讨，给出了差分方程ｘｎ＋１＝ｆ（ｘｎ）ｘｎ－１（假定ｆ∈Ｃ［（０，∞），（０，∞）］且ｐ≥５的正整数）每一正解必是周期解一个充分必要条件，从而解决了ＬａｄａｓＧ．公开提出的问题．     

非线性电容双涡卷混沌电路的Hopf分岔

对一个非线性电容双涡卷混沌电路的方程 ,利用中心流形定理和Hopf分岔理论讨论了电路产生Hopf分岔的条件 ,得到中心流形、小振幅周期解的渐近表达式 ,同时给出了周期解稳定性判据。     

具复杂偏差变元的Rayleigh方程的周期解

利用k-集压缩算子拓扑度抽象连续定理,研究了一类具复杂偏差变元的Rayleigh方程周期解的存在性,并获得了此类方程周期解存在的充分条件。本文的结果推广并改进了已有的结果。     

转子碰摩故障振动特征的数值分析与辨识方法

为一类集中参数非线性转子碰摩行为进行了数值仿真，获得了各种响应解形态，同时获得了两类混沌路径，即拟周期进入混沌路长和混沌运动突发到周期运动路径，以数值分析结果为基础开展试验研究，观测到的响应形态与仿真结果定性一致，最后，对碰摩故障的振动特征进行了总结并提出了相应的辨识方法，这些结果对工程实际具有一定的参考价值。     

Chemostat系统周期解的渐近性态

使用上、下解的方法证明Chemostat系统周期解的存在性和稳定性.     

抑制局部放电信号中周期性窄带干扰的子空间重构方法

为有效提取局部放电信号,提出一种基于子空间重构的窄带干扰抑制方法。对局部放电信号数据形成的HANKEL矩阵进行奇异值分解,将信号划分为窄带干扰子空间和局部放电信号子空间。利用子空间数据重构窄带干扰波形,然后与原始数据相减,得到抑制干扰后的局部放电信号。该方法能在保证局部放电信号失真较小的同时有效去除窄带干扰,抗随机干扰能力较强。仿真和实测信号的处理结果验证了其有效性。     

Convergence analysis of general neural networks under almost periodic stimuli

In this paper, we investigate the convergence dynamics of 2^N almost periodic encoded patterns of general neural networks subjected to external almost periodic stimuli, including almost periodic delays. Invariant regions are established for the existence of 2^N almost periodic encoded patterns under two classes of activation functions. By employing the property of ??‐cone and inequality technique, attracting basins are estimated and some criteria are derived for the networks to converge exponentially toward 2^N almost periodic encoded patterns. The results obtained are new; they extend and generalize the corresponding results existing in the previous literature. Copyright © 2008 John Wiley & Sons, Ltd.     

Harmonic balance‐based control of a boost DC/AC converter

The achievement of step‐up inversion with a boost DC/AC converter requires appropriate periodic references for inductor currents, which have to satisfy ordinary differential equations (ODE) of the Abel type. These are equations with highly unstable solutions for which the existence of periodic solutions remains unproved. Hence, the studies reported so far in this subject obtain periodic output voltages that approximately track the expected profile using different periodic current references that do not exactly satisfy the Abel ODE. However, neither an explanation of why are periodic output voltages still obtained, nor an assessment of the output voltage error is provided. This paper analyzes the effect of using periodic current references in a Lyapunov‐based controlled boost DC/AC converter performing step‐up inversion tasks. It is shown that, for sufficiently accurate current references, the system exhibits asymptotically stable periodic solutions with bounded error. Moreover, the paper propounds the use of Harmonic Balance (HB)‐based techniques to obtain such current references. Simulation and experimental results confirm that this choice yields periodic output voltages with an error that may be lowered using higher HB approximations. Copyright © 2011 John Wiley & Sons, Ltd.     

FFT与小波分析应用于抑制局部放电窄带干扰

局部放电极易被噪声污染,众多干扰中载波通讯、高频保护、无线电广播等周期干扰尤其严重,而窄带干扰严重时可能完全淹没局部放电信号,这给局部放电的检测工作带来了巨大困难。为了从强的窄带干扰背景中有效提取局部放电信号,在基于FFT与小波分析理论的基础上,根据窄带干扰与局部放电信号具有不同频谱的特性,提出了抑制局部放电信号窄带干扰的新方法。考虑FFT处理方法的频谱泄漏性,再用小波变换对FFT处理后的局部放电信号进行进一步消噪,由此能够取得很好的消噪效果。仿真结果表明,此方法对窄带干扰去噪要比FFT、小波及小波模极大值去噪效果好,且得到的局部放电信号失真小。     

RTU自动在线检测技术探讨

对RTU的周期检定问题提出解决方案,促使RTU的周期检定与RTU在线运行之间没有影响正常生产因数存在,从而实现用最先进和最有效的检定方法来满足RTU的周期检定,满足数字变电站智能测量设备的需要。     

周期误差自适应分离算法研究

动态测量误差信号通常为多分量的非平稳信号,可能包含非周期性趋势项误差、周期性误差、随机误差等分量,为了更精确的修正误差,需将各误差分量分离出来.主要研究周期性误差的分离,分别使用LMS算法和RLS算法构成神经网络自适应线性元件模型,实现周期性误差成分的分离,通过1个动态测试仿真系统进行验证,得出基于RLS算法的神经网络...     

环境激励下基于频域特征的扰动源定位方法

环境激励下小幅周期性扰动容易被淹没在类噪声信号中,从时域角度很难实现小幅周期性扰动的检测及扰动源定位。在分析环境激励下电力系统类噪声信号频域特征的基础上,提出了基于频域特征的小幅周期性扰动的检测与扰动源定位方法。环境激励下周期性扰动的频域表征为振荡恒定、阻尼比近似为0的振荡模式,且在该模式中扰动源所在机组的模态相位超前于其他机组。利用随机子空间辨识算法对环境激励下的类噪声响应信号进行分析,提取振荡模态及参数,根据模态个数及特征参数实现小幅周期性扰动的检测,检测到周期扰动后,根据阻尼比近似为0的周期性振荡模式的模态相位关系即可定位扰动源所在机组。IEEE 4机2区域系统和IEEE 16机68节点系统的算例结果验证了所提方法的有效性和可行性。     

直埋电缆周期性负荷载流量的计算分析*

载流量是电缆工程设计和运行的重要参数之一,其值是在负荷电流恒定的条件下得到的。电力系统实际运行时负荷电流通常是周期性变化的。为研究电缆在周期性负荷下的输送能力,本文基于有限差分法编制了电缆暂态温度场数值计算程序,并对直埋电缆进行大电流温升试验,试验结果和数值计算结果吻合。采用该暂态计算程序计算24h周期负荷下缆芯温升,确定周期负荷载流量,对现有的周期负荷载流量解析计算公式进行误差研究,并给出了计算简便的直埋电缆周期性负荷载流量的解析计算公式,提高了解析计算周期性负荷载流量的计算精度。     

APPLICATION OF WAVELETS TO THE ANALYSIS OF ARBITRARY THIN-WIRE LOOP ANTENNAS AND SCATTERERS

An analysis of arbitrary thin-wire loop antennas and scatterers using periodic orthogonal wavelets is presented. The periodic orthogonal wavelet expansion is applied to solve the thin-wire version of the electric-field integral equation (EFIE). The curved solution domains are mapped into the definition domain [0, 1] of the periodic wavelets. The unknown current over each loop wire is expanded in terms of a basis derived from a periodic orthogonal wavelet through the maps between the curved integration domains and the interval [0,1]. The integral equation under study is converted into a sparse matrix equation by this technique. Numerical examples are provided for a variety of thin-wire loop antennas and scatterers. © 1997 John Wiley & Sons, Ltd.     

A switching periodic adaptive control approach for time‐varying parameters with unknown periodicity

Periodic variations are encountered in many real systems, which can exist in the system parameters, as a disturbance or as the tracking objective. However, there exist a great number of situations where the periodicity is not known in advance. Hence, how to compensate for the effects of time‐varying parameters with unknown periodicity remains a challenge for the controller design. In this paper, we proposed a switching periodic adaptive control approach for continuous‐time nonlinear parametric systems with periodic uncertainties in which the period and bound are not known in advance. We utilized a fully saturated periodic adaptation law to identify the unknown periodic parameters in a pointwise manner. In addition, we provided a logic‐based switching scheme to estimate the unknown period and bound online simultaneously. By virtue of Lyapunov stability analysis, we show that the asymptotic convergence can be guaranteed irrespective of the initial conditions. Finally, we carried out numerical simulations to demonstrate the efficacy of the switching periodic adaptive control algorithm. The proposed approach can be applied to parametric nonlinear systems with time‐varying parameters of unknown periodicity irrespective of the types of periodic uncertainties. Copyright © 2015 John Wiley & Sons, Ltd.