树的最大特征值的上界的一个注记

设T是一个树,V是T的顶点集．记dv是υ∈V的度,△是T的最大顶点度．设υ∈V且dw=1．记k=ew+1,这里ew是w的excentricity．设δj′= max{dυ:dist(υ,w)=j},j=1,2,…,k-2,我们证明和这里μ1(T)和λ1(T)分别是T的Laplacian矩阵和邻接矩阵的最大特征值．特别地,记δo′=2．     

乘方的指数与其幂的位数的关系

为了探究乘方的指数与其幂的位数的关系,定义了几个有关的新概念,并且证明了两个关于乘方以及进制进位的定理,由此建立起关于乘方以及进制进位的理论体系,其中包括进位理论中判定乘方的指数与其幂的位数是否存在周期规律的判别法,以及进位规律的求解法和四条相关的性质.     

一类具有转向点的三阶微分方程的边值问题的解的高阶渐近展开

利用上下解方法,研究如下一类具有转向点的三阶微分方程的边值问题{ε~2y″′=f(t,y,ε)y″ g(t,y,ε)y′ h(t,y,ε),a相似文献   

计算Hamilton矩阵特征值的一个稳定的有效的保结构的算法

提出了一个稳定的有效的保结构的计算Hamilton矩阵特征值和特征不变子空间的算法,该算法是由SR算法改进变形而得到的。在该算法中,提出了两个策略,一个叫做消失稳策略,另一个称为预处理技术。在消失稳策略中,通过求解减比方程和回溯彻底克服了Bunser Gerstner和Mehrmann提出的SR算法的严重失稳和中断现象的发生,两种策略的实施的代价都非常低。数值算例展示了该算法比其它求解Hamilton矩阵特征问题的算法更有效和可靠。     

自由群的直积的检验元素的注记

本文研究了自由群的直积的检验元素,通过对直积的自同态的分解,得到了直积中的元素为检验元素的充分必要条件,改进了O'neill和Turner的结果.此外,构造了两类具体的检验元素.     

与一类算术函数关联的矩阵的行列式的下界

设f为一个算术函数,S={x 1,…,x n}为一个n元正整数集合.称S为gcd-封闭的, 如果对于任意1 i,j n,均有(x i,x j)∈S.以 ={y 1,…,y m}表示包含S的最小gcd-封闭的正整数集合. 设(f(x i,x j))表示一个n×n矩阵, 其(i,j)项为f在x i与x j的最大公因子(x i,x j)处的值. 设(f[x i,x j])表示一个n×n矩阵, 其(i,j)项为f在x i与x j的最小公倍数[x i.xj]处的值. 本文证明了: (i) 如果f∈C s ={f:(f*μ)(d)>0, x∈S,d|x},这里f*μ表示f与μ的Dirichlet乘积,μ表示M bius函数,那么 并且(1)取等号当且仅当S=;(ii)如果f为乘法函数,并且 ∈Cs,那么 并且(2)取等号当且仅当S= .不等式(1)和(2)分别改进了Bourque与Ligh在1993年和1995年所得到的结果.     

数的蒙蔽与形的误导

数与形是一个数学问题的两个层面,数能精细,形可直观,但同学们也须注意,如果你在解题时,出现了疏漏,数也可能出现貌似精细的蒙蔽,形也可以导致似乎明了的误导.本文通过两个典型例子,提醒同学们在学习     

函数的对称性和周期性的关系

“函数”一章的内容贯穿于高中数学的始终,历来是数学高考考查的一个难点和热点,要求学生熟练掌握函数的性质．但在学习这一章过程中,许多同学被函数的若干性质弄的头昏脑涨．事实上,只要把握其中的关系,也就不困难了．     

一个问题的争论引发的思考

最近在网上看到这样一个题目：“王师傅是卖鱼的,一斤鱼进价45元,现亏本大甩卖,顾客35元买了一公斤,给了王师傅100元假钱,王师傅没零钱,于是找邻居换了100元.事后邻居存钱过程中发现钱是假的,被银行没收了,王师傅又赔了邻居100,请问王师傅一共亏了多少？”笔者把题目抛给办公室的老师们：谢老师：“55＋65＋100.”     

由自然数的因子构成的半群

本文首先介绍了半群、群的定义,研究了自然数n取何值时,通过定义相应的代数运算,使得它的因子集构成半群、群,从而为半群的代数理论提供了一个有趣的实例.     

Design of sliding mode controller for a class of fractional-order chaotic systems

In this paper, a sliding mode control law is designed to control chaos in a class of fractional-order chaotic systems. A class of unknown fractional-order systems is introduced. Based on the sliding mode control method, the states of the fractional-order system have been stabled, even if the system with uncertainty is in the presence of external disturbance. In addition, chaos control is implemented in the fractional-order Chen system, the fractional-order Lorenz system, and the same to the fractional-order financial system by utilizing this method. Effectiveness of the proposed control scheme is illustrated through numerical simulations.     

An improved generalized predictive control algorithm based on the difference equation CARIMA model for the SISO system with known strong interference

ABSTRACT

The single input single output (SISO) system with known strong interference is widely used in various occasions. Due to its strong interference, the control accuracy is hard to guarantee. To solve this problem, an improved generalized predictive control (IGPC) algorithm is developed. The IGPC firstly builds the difference equation CARIMA (Controlled Auto-Regressive Integrated Moving-Average) model of the SISO system and then treats the system as a two input single output (TISO) system and calculates its predictive vector, then transforms it into a SISO system and uses the TISO system predictive vector to calculate the SISO system control increment. A new parameter called phase coefficient is added to inhibit the control lag. Simulations are performed to make the comparison among the traditional GPC, PID control, velocity synchronization control (VSC), fuzzy adaptive PID control (FAPID), model-based robust PID control (BPID) and the IGPC. Results show that IGPC has best performance compared to the others. Finally, experiments are developed which proved that the IGPC algorithm has a higher accuracy in the SISO system with known strong interference than that of VSC.     

一类时滞非线性系统的自适应模糊控制

对于一类SISO输入时滞已知,状态时滞不确定但有上界的能采用后推设计方法的非线性系统提出一种基于后推设计、自适应模糊控制和滑模控制的控制方案.通过状态变换,把输入时滞系统转化为无输入时滞的系统.用模糊系统来估计系统的未知连续函数,对转化后的新系统设计自适应滑模控制器,使得新系统的状态有界,通过递推证得原系统的状态半全局一致有界.     

Lur''''e系统稳定与同步的脉冲控制

提出了Lur’e系统的脉冲控制系统，利用关于脉冲系统稳定的几个定理，得到了具变化的脉冲区间的Lur'e系统镇定的充分条件；并且给出了Lur'e系统的适当参数与脉冲控制律，使得两个Lur'e系统脉冲同步。最后，给出数值例子说明本结论的有效性。     

年龄相关的半线性种群扩散系统的最优收获控制

研究年龄相关的半线性种群扩散系统的最优收获控制问题，证明了最优收获控制的存在性，得到了收获控制为最优的必要条件和由偏微分方程与变分不等式所构成的最优性组，由最优性组确定最优控制．     

一种改进的基于再励学习算法的模糊神经BOXES控制系统

本文给出了一种改进的基于再励算法的神经网络ＢＯＸＥＳ控制系统,引入超维椭球体模糊划分状态空间的概念,并且通过神经网络的再励学习邮对状态空间的自动划分。最后,应用到倒立摆控制中的仿真结果展示了控制系统的有效性。     

Adaptive Predictor-Based Output Feedback Control for a Class of Unknown MIMO Linear Systems

In this paper, the problem of characterizing adaptive output feedback control laws for a general class of unknown MIMO linear systems is considered. Specifically, the presented control approach relies on three components, i.e., a predictor, a reference model and a controller. The predictor is designed to predict the system’s output with arbitrary accuracy, for any admissible control input. Subsequently, a full state feedback control law is designed to control the predictor output to approach the reference system, while the reference system tracks the desired trajectory. Ultimately, the control objective of driving the actual system output to track the desired trajectories is achieved by showing that the system output, the predictor output and the reference system trajectories all converge to each other.     

重复结构振动控制的降维方法

提出了对称结构、旋转周期结构和链式结构的振动控制的降维方法．以某种对称的方式设置广义坐标的凝聚、传感器、驱动器的位置以及输入与控制力的关系,即可使控制系统具有和结构同样的重复性．对凝聚了的广义坐标和系统输入采用适当的变换,即可通过执行一些子结构的控制问题实现整体系统的振动控制,从而使控制问题的维度显著降低．     

Direct model reference adaptive control (MRAC) design and simulation for the vibration suppression of piezoelectric smart structures

The paper presents control system design based on a non-linear model reference adaptive control law (MRAC) used for the vibration suppression of a smart piezoelectric mechanical structure. Numerical simulation of the proposed control system is performed based on the finite element (FE) model of the structure, modally reduced in order to meet the requirements of the control system design. First the MRAC problem is defined and a direct control algorithm described in the paper is suggested as a solution to the control problem. The basic MRAC algorithm is modified by augmenting the integral term of the control law in order to provide the robustness of the control system with respect to the stability. This approach provides preserving the boundness of the system states and adaptive gains, with small trackings error over large ranges of non-ideal conditions and uncertainties. The efficiency of the suggested control for the vibration suppression is tested and shown through a numerical simulation of the funnel-shaped piezoelectric structure.     

Effects of Divert-Thrusters on Homing Performance of Endo-atmospheric Interceptors

A new guidance law is proposed for interceptor missiles by using a differential game formulation with bounded controls. The interceptor is steered by the aerodynamic-lift control system and the divert-thrusters control system. By using game space decomposition, the parameter effects of divert-thrusters control system on homing performance are investigated. Under propellant limits and given the time constant of the divert-thrusters control system, the hit-to-kill performance requires the following conditions. Firstly, the maximum acceleration generated by the divert-thrusters control system is greater than a critical value. Secondly, the thrusters close after interception terminates. Thirdly, the operation time of the divert-thrusters control system is sufficient long to cancel the miss distance. These results are also demonstrated by a realistic ballistic missile-defense simulation program.