基于留数定理的VSC锁相环频率估计算法研究

在柔性直流输电系统中,锁相环对控制电压源型换流器(VSC)的电压和功率稳定具有重要作用。针对连接弱交流系统下VSC锁相环性能恶化和稳定性差的缺点,提出了一种基于留数定理的VSC锁相环频率估计算法,该算法利用留数定理,将交流电压信号由时域转换为复变域,通过求解电压复变函数的闭合路径积分对频率进行估计,实现了三相平衡和不平衡情况下交流电网频率的精确估计和快速追踪,具有良好的暂态特性和稳定性。以一个单端VSC系统为例,仿真结果验证了该算法的有效性和正确性。     

具有输入时滞和外部扰动的线性系统的过渡过程估计

给同了具有输入时滞和外部扰动的一类线性系统的过渡过程的估计,理论分析和仿真结果表明,文中的主要结论为时滞系统稳定性的定量分析提供了一种有效的分析方法。     

关于时延参量估计的研究

应用随机信号的二阶和三阶统计特性，对被动系统两个接收机所接收信号的时间延迟参量进行估计，并对高斯白噪声中低通和带通两种信源信号，在不同信噪比情况下的时延参量估计性能进行了试验。结果表明，基于三阶特性的时延估计优于二阶统计特性的性能。     

多维ARMA模型的新息定理及预测

利用线性最小方差估计方法,推导出多维ＡＲＭＡ模型的新息定理,并依据该定理得出仅需ＡＲ参数的线性最小方差新息预测公式,这在计算上大为简化,同时又保证有一定的精度。最后给出了仿真实例。     

基于余弦函数局部特征的时间衰变模式

数据流具有无限增长的特征,目前的计算系统无法在线处理整个数据集,只能在有限空间内对部分数据进行处理。为了能够得到尽可能合理的结果,数据流系统常常采用单调递减函数由数据的时间戳来确定数据的权值,根据权值选择数据。广泛使用的单调函数是指数函数和多项式函数,但它们存在衰变速度太快或太慢等问题。提出一种新的时间衰变模式——使用余弦函数的局部衰变速度介于指数和多项式之间的特征来确定数据的权值。实验结果显示相对于指数和多项式衰变,局部余弦衰变具有衰变速度合理、参数易于确定、适用于乱序数据流等优势。     

关于遗传算法图式定理的分析研究

遗传算法的基本定理－－图式定理给出了某一图式经过一步迭代后生存的数目的下界值。对这一定理进行详细分析，给出具有选择、变异两种算子的图式定理的精确表达式，并从理论上证明选择算子能使整个群体点的质量得以改进。     

参数估计定理

空间信息论是关于雷达等目标参数估计系统信息获取一般规律的基本理论,这里的空间信息指被测目标相对于雷达的距离、方向和散射信息。参数估计定理是空间信息论的重要组成部分,本文提出参数估计定理的证明框架,该框架由3个原创性概念和1个定理构成,其中3个概念是空间信息、熵误差和抽样后验概率估计。参数估计定理证明,熵误差是可达的,反之,任何估计器的熵误差不低于熵误差。空间信息论的建立将对雷达探测的系统理论和方法产生巨大的推动作用。     

考虑估计方差的软件可靠性估计

软件可靠性是软件质量保证（SQA）工程的关键。本文分析现有的软件组件可靠性估计的参数模型,在考虑组件可靠性估计方差的基础上,提出一种系统可靠性估计的非参数模型。     

关于Fuzzy推理式的可信度估计

众所周知,Fuzzy逻辑比古典逻辑更为充分更为合理地反映了我们的客观世界。在Fuzzy逻辑中,公式的值可取为[0,1]中的任一实数。这一值可看作是该公式的可信度。若S为一公式,则T(S)代表S的可信度,在[1]中,已经对Fuzzy逻辑中的基本子句的归结式的值做了估计:设C_1,C_2为两个Fuzzy逻辑下的基本子句,R(C_1,C_2)为它们的任一归结式.max[T(C_1),T(C_2)]=b,min[T(C_1),T(C_2)]=a>0.5,b≥a,则     

Vague软集的分解定理、表现定理和扩张原理

基于现有关于Vague软集的研究以及Fuzzy集与经典集合之间的关系,定义了Vague软集截集和集合套的概念。进而给出Vague软集的分解定理、表现定理和扩张原理的定义,以及其相关性质的数学证明。由此构建出Vague软集与经典软集之间的联系。     

Designing Mathematical Libraries Based on Requirements for Theorems

Theorems can be considered independent of abstract domains; a theorem rather depends on a set of properties necessary to prove the theorem correct. Following this observation theorems can be formulated and proven more generally thereby improving reuse of mathematical theorems. We discuss how this view influences the design of mathematical libraries and illustrate our approach with examples written in the Mizar language. We also argue that this approach allows for both stating requirements of generic algorithms and checking whether particular instantiations of generic algorithms are semantically correct.     

Existence Theorems for Nonconvex Problems of Variational Calculus

A solution to a variational calculus problem is studied under the conditions of integrant convexity. The existence theorem is proved. As an example, a function is given, which satisfies all the conditions of the theorem but is not convex.     

相依线性回归系统回归系数协方差改进估计的收敛性及其计算机求解

本文在较弱条件下给出β_i的协方差改进估计β_i~*及两步改进估计的收敛性质,将[1]中的结果推广到一般截尾随机变量的情形。最后通过实例,应用SPSS/PC 2.0统计软件包及自行开发的程序给出相应的回归方程的计算机求解方法,并作了比较。     

On the output feedback stabilization for distributed semilinear systems

The output stabilization for a class of distributed semilinear system is obtained with stabilizing controls that depend on the output operator. Then, we give sufficient conditions for exponential, strong and weak stabilization. The obtained results are illustrated by examples and simulations.     

遗传规划模式理论的研究进展

模式定理是遗传规划的理论基础,主要解释群体在遗传进化过程中动态变化的情况,希望能够预测下一代属于某个模式的实例数,为改进遗传规划的性能提供理论上的指导。以介绍悲观模式定理和精确模式定理这两类模式的形式分析了近年来模式理论的研究进展。     

Decay Rates for a Beam with Pointwise Force and Moment Feedback

We consider the Rayleigh beam equation and the Euler–Bernoulli beam equation with pointwise feedback shear force and bending moment at the position ξ in a bounded domain (0,π) with certain boundary conditions. The energy decay rate in both cases is investigated. In the case of the Rayleigh beam, we show that the decay rate is exponential if and only if ξ/π is a rational number with coprime factorization ξ/π=p/q, where q is odd. Moreover, for any other location of the actuator we give explicit polynomial decay estimates valid for regular initial data. In the case of the Euler–Bernoulli beam, even for a nonhomogeneous material, exponential decay of the energy is proved, independently of the position of the actuator. Date received: October 30, 2000. Date revised: December 20, 2001.     

Fidelity Decay Saturation Level for Initial Eigenstates

We show that the fidelity decay between an initial eigenstate evolved under a unitary chaotic operator and the same eigenstate evolved under a perturbed operator saturates well before the 1/N limit expected for a generic initial state, where N is the dimension of the Hilbert space. We provide a theoretical argument and numerical evidence that, for perturbations of intermediate strength, the saturation level depends quadratically on the perturbation strength. PACS: 05.45.Mt; 03.67.Lx     

Central Limit Theorems for Stochastic Optimization Algorithms Using Infinitesimal Perturbation Analysis

Central limit theorems are obtained for the perturbation analysis Robbins-Monro single run (PARMSR) optimization algorithm, with updates either after every L customers or after every busy period, in the context of the optimization of a GI/GI/1 queue. The PARMSR algorithm is a stochastic approximation (SA) method for the optimization of infinite-horizon models. It is shown that the convergence rate and the asymptotic variance constant of the optimization algorithm, as a function of the total computing budget (i.e., total number of customers), are the same for both updating methods, and independent of L, provided that the step sizes of SA are chosen in the (asymptotically) optimal way for each method.     

衰减湮灭的状态方程及状态控制

根据衡敛状态方程,系统输入或边界条件的变化能够影响系统状态,对于系统状态出现的衰减湮灭,推导了系统衰减湮灭的状态方程、衰灭平衡方程。得出,当系统状态发生衰减湮灭,系统状态值、系统输入值、边界条件之间相互作用,改变系统的输入或边界条件能够恢复系统。应用系统衰灭状态方程及衰灭平衡方程,对系统状态变化进行分析,是研究系统状态演变,系统控制,状态时滞、预防系统性衰减的方法。     

Strong stabilisation and decay estimate for unbounded bilinear systems

In this article, we deal with distributed bilinear systems, where the operator of control is supposed to be unbounded in the sense that it is bounded from the state space into some extension. Then we give sufficient conditions for strong stabilisation. Also the rate of convergence of the state is estimated. An illustrating example is given.