Asymptotic and spectral properties of operator‐valued functions generated by aircraft wing model

The present paper is devoted to the asymptotic and spectral analysis of an aircraft wing model in a subsonic air flow. The model is governed by a system of two coupled integro‐differential equations and a two parameter family of boundary conditions modelling the action of the self‐straining actuators. The differential parts of the above equations form a coupled linear hyperbolic system; the integral parts are of the convolution type. The system of equations of motion is equivalent to a single operator evolution–convolution equation in the energy space. The Laplace transform of the solution of this equation can be represented in terms of the so‐called generalized resolvent operator, which is an operator‐valued function of the spectral parameter. More precisely, the generalized resolvent is a finite‐meromorphic function on the complex plane having a branch‐cut along the negative real semi‐axis. Its poles are precisely the aeroelastic modes and the residues at these poles are the projectors on the generalized eigenspaces. The dynamics generator of the differential part of the system has been systematically studied in a series of works by the second author. This generator is a non‐selfadjoint operator in the energy space with a purely discrete spectrum. In the aforementioned series of papers, it has been shown that the set of aeroelastic modes is asymptotically close to the spectrum of the dynamics generator, that this spectrum consists of two branches, and a precise spectral asymptotics with respect to the eigenvalue number has been derived. The asymptotical approximations for the mode shapes have also been obtained. It has also been proven that the set of the generalized eigenvectors of the dynamics generator forms a Riesz basis in the energy space. In the present paper, we consider the entire integro‐differential system which governs the model. Namely, we investigate the properties of the integral convolution‐type part of the original system. We show, in particular, that the set of poles of the adjoint generalized resolvent is asymptotically close to the discrete spectrum of the operator that is adjoint to the dynamics generator corresponding to the differential part. The results of this paper will be important for the reconstruction of the solution of the original initial boundary‐value problem from its Laplace transform and for the analysis of the flutter phenomenon in the forthcoming work. Copyright © 2004 John Wiley & Sons, Ltd.     

Asymptotic analysis of aircraft wing model in subsonic air flow

This paper is the first in a series of several works devotedto the asymptotic and spectral analysis of an aircraft wingin a subsonic air flow. This model has been developed in theFlight Systems Research Center of UCLA and is presented in theworks of Balakrishnan. The model is governed by a system oftwo coupled integro-differential equations and a two parameterfamily of boundary conditions modelling the action of the self-strainingactuators. The unknown functions (the bending and the torsionangle) depend on time and one spatial variable. The differentialparts of the above equations form a coupled linear hyperbolicsystem; the integral parts are of convolution type. The systemof equations of motion is equivalent to a single operator evolution–convolutiontype equation in the state space of the system equipped withthe so-called energy metric. The Laplace transform of the solutionof this equation can be represented in terms of the so-calledgeneralized resolvent operator. The generalized resolvent operatoris an operator-valued function of the spectral parameter. Thisgeneralized resolvent operator is a finite meromorphic functiondefined on the complex plane having the branch cut along thenegative real semi-axis. The poles of the generalized resolventare precisely the aeroelastic modes, and the residues at thesepoles are the projectors on the generalized eigenspaces. Inthis paper, our main object of interest is the dynamics generatorof the differential parts of the system. It is a non-selfadjointoperator in the state space with a pure discrete spectrum. Inthe present paper, we show that the spectrum consists of twobranches, and we derive their precise spectral asymptotics.Based on these results, in the next paper we will derive theasymptotics of the aeroelastic modes and approximations forthe mode shapes.     

广义算子半群与广义分布参数系统的适定性

首先,针对广义分布参数系统的求解问题,提出了由Hilbert空间中有界线性算子所引导的广义算子半群和广义积分半群;其次,讨论了广义预解算子的性质、广义算子半群与广义积分半群的性质;最后,研究了广义分布参数系统的适定性问题.     

Riesz basis property of the generalized eigenvector system of a Timoshenko beam

The Riesz basis property of the generalized eigenvector system of a Timoshenko beam with boundary feedback controls appliedto two ends is studied in this paper. The spectral property of the operator A determined by the closed loop system is investigated.It is shown that operator A has compact resolvent and generatesa C₀ semigroup, and its spectrum consistsof two branches and has two asymptotes under some conditions.Furthermore it is proved that the sequence of all generalizedeigenvectors of the system principal operator forms a Rieszbasis for the state Hilbert space.     

Properties of eigenvalues and spectral singularities for impulsive quadratic pencil of difference operators

In this paper, we investigate the spectral analysis of impulsive quadratic pencil of difference operators. We first present a boundary value problem consisting one interior impulsive point on the whole axis corresponding to the above mentioned operator. After introducing the solutions of impulsive quadratic pencil of difference equation, we obtain the asymptotic equation of the function related to the Wronskian of these solutions to be helpful for further works, then we determine resolvent operator and continuous spectrum. Finally, we provide sufficient conditions guarenteeing finiteness of eigenvalues and spectral singularities by means of uniqueness theorems of analytic functions. The main aim of this paper is demonstrating the impulsive quadratic pencil of difference operator is of finite number of eigenvalues and spectral singularities with finite multiplicities which is an uninvestigated problem proposed in the literature.     

Exact controllability of damped coupled Euler-Bernoulli and Timoshenko beam model

^** Email: marianna.shubov{at}euclid.unh.edu The zero controllability problem for the system of two coupledhyperbolic equations which governs the vibrations of the coupledEuler–Bernoulli and Timoshenko beam model is studied inthe paper. The system is considered on a finite interval witha two-parameter family of physically meaningful boundary conditionscontaining damping terms. The controls are introduced as separableforcing terms g_i(x)f_i(t), i = 1, 2, on the right-hand sidesof both equations. The force profile functions g_i(x), i = 1,2, are assumed to be given. To construct the controls f_i(t),i = 1, 2, which bring a given initial state of the system tozero on the specific time interval [0, T], the spectral decompositionmethod has been applied. The approach, used in the present paper,is based on the results obtained in the recent works by theauthor and the collaborators. In these works, the detailed asymptoticand spectral analyses of the non-self-adjoint operators generatingthe dynamics of the coupled beam have been carried out. It hasbeen shown that for each set of the boundary parameters, theaforementioned operator is Riesz spectral, i.e. its generalizedeigenvectors form a Riesz basis in the energy space. Explicitasymptotic formulas for the two-branch spectrum have also beenderived. Based on these spectral results, the control problemhas been reduced to the corresponding moment problem. To solvethis moment problem, the asymptotical representation of thespectrum and the Riesz basis property of the generalized eigenvectorshave been used. The necessary and/or sufficient conditions forthe exact controllability are proven in the paper and the explicitformulas for the control laws are given. The case of the approximatecontrollability is discussed in the paper as well.     

Asymptotic distribution of the eigenvalues of the bending-torsion vibration model with fully nondissipative boundary feedback

Asymptotic and spectral results on the initial boundary-value problem for the coupled bending-torsion vibration model (which is important in such areas of engineering sciences as bridge and tall building designs, aerospace and oil pipes modeling, etc.) are presented. The model is given by a system of two hyperbolic partial differential equations equipped with a three-parameter family of non-self-adjoint (linear feedback type) boundary conditions modeling the actions of self-straining actuators. The system is rewritten in the form of the first-order evolution equation in a Hilbert space of a four-component Cauchy data. It is shown that the dynamics generator is a matrix differential operator with compact resolvent, whose discrete spectrum splits asymptotically into two disjoint subsets called the α-branch and the β-branch, respectively. Precise spectral asymptotics for the eigenvalues from each branch as the number of an eigenvalue tends to ∞ have been derived. It is also shown that the leading asymptotical term of the α-branch eigenvalue depends only on the torsion control parameter, while of the β-branch eigenvalue depends on two bending control parameters.     

Local spectral theory for normal operators in Krein spaces

Sign type spectra are an important tool in the investigation of spectral properties of selfadjoint operators in Krein spaces. It is our aim to show that also sign type spectra for normal operators in Krein spaces provide insight in the spectral nature of the operator: If the real part and the imaginary part of a normal operator in a Krein space have real spectra only and if the growth of the resolvent of the imaginary part (close to the real axis) is of finite order, then the normal operator possesses a local spectral function defined for Borel subsets of the spectrum which belong to positive (negative) type spectrum. Moreover, the restriction of the normal operator to the spectral subspace corresponding to such a Borel subset is a normal operator in some Hilbert space. In particular, if the spectrum consists entirely out of positive and negative type spectrum, then the operator is similar to a normal operator in some Hilbert space. We use this result to show the existence of operator roots of a class of quadratic operator polynomials with normal coefficients.     

Asymptotic analysis of nonselfadjoint operators generated by coupled Euler‐Bernoulli and Timoshenko beam model

In the current paper, we present a series of results on the asymptotic and spectral analysis of coupled Euler‐Bernoulli and Timoshenko beam model. The model is well‐known in the different branches of the engineering sciences, such as in mechanical and civil engineering (in modelling of responses of the suspended bridges to a strong wind), in aeronautical engineering (in predicting and suppressing flutter in aircraft wings, tails, and control surfaces), in engineering and practical aspects of the computer science (in suppressing bending‐torsional flutter of a new generation of hard disk drives, which is expected to pack high track densities (20,000+TPI) and rotate at very high speeds (25,000+RPM)), in medical science (in bio mechanical modelling of bloodcarrying vessels in the body, which are elastic and collapsible). The aforementioned mathematical model is governed by a system of two coupled differential equations and a two parameter family of boundary conditions representing the action of the self‐straining actuators. This linear hyperbolic system is equivalent to a single operator evolution equation in the energy space. That equation defines a semigroup of bounded operators and a dynamics generator of the semigroup is our main object of interest. We formulate and proof the following results: (a) the dynamics generator is a nonselfadjoint operator with compact resolvent from the class ??p with p > 1; (b) precise spectral asymptotics for the two‐branch discrete spectrum; (c) a nonselfadjoint operator, which is the inverse of the dynamics generator, is a finite‐rank perturbation of a selfadjoint operator. The latter fact is crucial for the proof that the root vectors of the dynamics generator form a complete and minimal set. In our forthcoming paper, we will use the spectral results to prove that the dynamics generator is Riesz spectral, which will allow us to solve several boundary and distributed controllability problems via the spectral decomposition method. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Some Local Properties of Spectrum of Linear Dynamical Systems in Hilbert Space

We prove some local properties of the spectrum of a linear dynamical system in Hilbert space. The semigroup generator, the control operator and the observation operator may be unbounded. We consider (i) the PBH test, (ii) the correspondence between the poles of the resolvent of the semigroup generator and the poles of the transfer function, and (iii) pole-zero cancellation between two transfer functions of the cascade connection of two dynamical systems. For our investigation we take well-posed linear systems and a subclass of them called weakly regular systems as the most general setting.     

复合结构可修复系统口香糖算子的性质

研究了有15个部件串并联工作的多状态口香糖生产可修复系统.运用C_0半群的理论,证明了系统算子是稠定的预解正算子,得出了系统算子的共轭算子及其定义域,并证明了系统算子的增长界为0.最后运用了预解正算子中共尾的概念及相关理论,证明了系统算子的谱上界也是0.     

Lipschitz-α算子的M-谱理论

本文运用一个选定的可逆Lip-α算子M作为尺度算子(称为谱尺度),引入两个Banach空间之间的非线性Lip-α算子的M-豫解集、M-谱集、M-谱半径、豫解集、谱集及谱半径,证明了它们的一列系重要性质,给出了M-谱的一个摄动定理,初步建立了Lip-α算子的M-谱理论,使得现有的谱理论成为其特例.     

Wave Field Decomposition in Anisotropic Fluids: A Spectral Theory Approach

An extension of directional wave field decomposition in acoustics from heterogenous isotropic media to generic heterogenous anisotropic media is established. We make a connection between the Dirichlet-to-Neumann map for a level plane, the solution to an algebraic Riccati operator equation, and a projector defined via a Dunford–Taylor type integral over the resolvent of a nonnormal, noncompact matrix operator with continuous spectrum.In the course of the analysis, the spectrum of the Laplace transformed acoustic system's matrix is analyzed and shown to separate into two nontrivial parts. The existence of a projector is established and using a generalized eigenvector procedure, we find the solution to the associated algebraic Riccati operator equation. The solution generates the decomposition of the wave field and is expressed in terms of the elements of a Dunford–Taylor type integral over the resolvent.     

A new concept for block operator matrices:the quadratic numerical range

In this paper a new concept for 2×2-block operator matrices – the quadratic numerical range – is studied. The main results are a spectral inclusion theorem, an estimate of the resolvent in terms of the quadratic numerical range, factorization theorems for the Schur complements, and a theorem about angular operator representations of spectral invariant subspaces which implies e.g. the existence of solutions of the corresponding Riccati equations and a block diagonalization. All results are new in the operator as well as in the matrix case.     

一类新的含（A，η）-增生算子的广义混合拟-似变分包含组

介绍和研究了实q-一致光滑Banach空间中一类新的具（A,η）一增生算子的广义混合拟一似变分包含组,利用（A,η）一增生算子的预解算子技巧,证明了解的存在性及由新的P步迭代算法所生成序列的收敛性．     

Banach空间中的广义Hη增生算子及其在变分包含中的应用

在Banach空间中,引入和研究了新的广义H-η-增生算子,对广义m-增生算子与H-η-单调算子提供了一个统一的框架．还定义了广义H-η-增生算子相应的预解算子,并且证明了其Lipschitz连续性．作为应用,考虑了涉及广义H-η-增生算子的一类变分包含问题的可解性．利用预解算子方法,构造了一个求解变分包含的迭代算法．在适当假设下,证明了变分包含解的存在性和由算法生成的迭代序列的收敛性．     

广义p-Laplace算子相关的非线性边值问题解的存在性

本文首先把p-Laplace算子推广为广义p-Laplace算子,然后利用非线性增生映射值域的扰动理论研究了与广义p-Laplace算子相关的具有牛曼边值的非线性椭圆问题在LP(Ω)空间中解的存在性,其中2≤p< ∞．本文所讨论的方程及所用的方法是对以往一些工作的补充和延续．     

可修复人机系统的指数稳定性

研究了两相同部件温储备可修的人机系统,运用C_0半群的相关理论,对系统主算子的谱界进行估值.估算系统的算子产生的半群的增长界,然后运用了共尾的概念及相关的理论,得到了系统算子A+B的谱界与系统算子产生的半群的增长界相同.进而运用相关代数知识证得,0为系统算子的简单本征值,并分析了系统算子的谱分布,得到系统的指数稳定性.并研究了系统算子预解式的特性.对任意给定的δ0,γ=a+bi,-μ+δa_1≤a≤a_2,得到lim|b|→∞‖R(γ;A+B)‖=0.进而得到在~sRγ≥a_1的右半平面内相应于系统算子A+B的谱点由有限个本征值组成.     

Banach空间中广义集值拟变分包含的灵敏性分析

研究了Banach空间中一类广义集值拟变分包含问题的灵敏性分析．利用预解算子的技巧,在对给定条件没有假设可微性和单调性下,建立了这类问题与广义预解方程类的等价性．     

两同型部件温贮备可修系统算子性质

研究了两同型部件温贮备可修系统,此系统由2个同型部件及一个修理设备构成.其中一个部件工作,另一个部件温储备.运用C_o半群的理论,证明系统算子是稠定的预解正算子,得出系统算子的共轭算子及其定义域,并证明了系统算子的增长界为O.最后运用了预解正算子中共尾的概念及相关理论,证明系统算子的谱上界也是0.