Causality,stability and inverse systems

A definition of linear systems is given in terms of convolution operations using a sequence of Markov matrices. A sequence of (block) Toeplitz matrices is constructed from the set of Markov matrices and is shown to act as a sequence of input-output maps for system records. Inverse systems and minimum phase systems are defined and properties including causality and stability established. These results are used to examine system input sequences which produce zero output sequences. Applications in identification theory are indicated.     

Strategic justification of advanced automated technology systems using an expert system

This paper presents an application of expert systems for the strategic justification of advanced automated technology systems. This expert system is developed using the EXSYS expert system shell in the VAX-VMS mainframe environment. It considers important attributes such as suitability (measure of the AMT's compliance with corporate strategy); system capability; performance of the AMT system; and productivity including the financial benefits of the AMT.     

Practice, systems and technology for seniors

This paper explores how research teams in Intel’s Digital Health Group are using ethnography to identify ‘designable moments’—spaces, times, objects, issues and practices which suggest opportunities for appropriate interventions. It argues that technology innovation should aim to incorporate the views, experiences and practices of users from the start of the design process to support independent living and develop culturally sensitive enhancements that contribute towards wellbeing and a life of quality for local older populations.     

On stability, -gain and control for switched systems

This paper addresses the issues of stability, L₂-gain analysis and H_∞ control for switched systems via multiple Lyapunov function methods. A concept of general Lyapunov-like functions is presented. A necessary and sufficient condition for stability of switched systems is given in terms of multiple generalized Lyapunov-like functions, which enables derivation of improved stability tests, an L₂-gain characterization and a design method for stabilizing switching laws. A solution to the H_∞ control problem for switched systems is also provided.     

Equilibria, stability and reachability of Leslie systems withnonnegative inputs

Leslie systems, a particular class of positive systems used in population dynamics and control, are defined and analyzed. A simple property relating sign and stability of their equilibria, and some geometric characteristics of their reachability set (in cases of bounded and unbounded inputs) are proved. All the properties do not hold, in general, in other classes of positive systems. It is shown that Leslie systems have strictly positive equilibria if and only if they are asymptotically stable. Their reachability set in the case of unbounded inputs is the positive cone generated by the reachability vectors, while in the case of bounded inputs, it is a polyhedron whose vertices can be easily computed. All of these properties follow from the nonpositiveness of the coefficients of the characteristic polynomial of the system     

离散区间系统的二次稳定性及其稳定裕度分析

研究了动态离散区间系统的鲁棒稳定性问题,提出了系统二次稳定的充分与必要条件,以及相应的稳定裕度的计算方法,并推广到离散参数不确定系统.所有结论以线性矩阵不等式(LMI)的形式给出.利用功能强大的LMI工具,求解非常方便.所给实例表明,该方法用于确定动态离散区间系统的鲁棒稳定性及其稳定裕度,非常有效.     

The existence of solutions,stability, and linearization of volterra systems

LetB be a Banach space ofR _n valued continuous functions on [0, ) withfB. Consider the nonlinear Volterra integral equation (^*)x(t)+ _o ^t K(t,s,x(s))ds. We use the implicit function theorem to give sufficient conditions onB andK (t,s,x) for the existence of a unique solutionxB to (^*) for eachf B with f ^B sufficiently small. Moreover, there is a constantM>0 independent off with Mf^B.Part of this work was done while the author was visiting at Wright State University.     

On graphs, conic relations, and input-output stability of nonlinearfeedback systems

This paper presents necessary and sufficient conditions for the stability of general interconnected dynamical systems. The results are expressed in terms of the graphs of the interconnection's subsystems. Conditions for robustness of stability for an interconnection with additive disturbances are also provided. Finally, the paper gives sufficient conditions for stability using conic sector conditions that generalize earlier conditions and that incorporate a recent nonlinear small gain idea     

Excitability, stability, and sign of equilibria in positive linear systems

The relationship between sign and stability of equilibria in positive linear systems is investigated in this paper. In particular it is proved that the well-known result “stability and irreducibility imply strict positivity” can be better specified by introducing the notion of excitability. In fact stability, excitability and strict positivity of the equilibria are three perfectly balanced properties since any one of them is implied by the two others.     

International and Turkish information technology standardization

The International Organization for Standardization (ISO) is working towards establishing worldwide concensus-oriented standards in information technology. The report reviews the state-of-the-art in information technology standardization. It establishes that the current trend in both hardware and software is towards open platforms and open distributed systems. Networks are evolving towards intelligent networks. Financial institutions and network operating companies are cooperating in ISO committees to prepare security standards. In Turkiye the Turkish Standards Institute (TSE) is active more than ever in promoting the cause of standards. It is recognized that in the information technology area TSE's activities are limited to trying to have the product conformity to the Latin Alphabet No. 5 which includes Turkish characters at all levels. It is the wish of the industry leaders to introduce the present ISO information technology standards and contribute to the future standards. Various mechanisms are discussed on how this can be established.     

Output-input stability and minimum-phase nonlinear systems

This paper introduces and studies the notion of output-input stability, which represents a variant of the minimum-phase property for general smooth nonlinear control systems. The definition of output-input stability does not rely on a particular choice of coordinates in which the system takes a normal form or on the computation of zero dynamics. In the spirit of the "input-to-state stability" philosophy, it requires the state and input of the system to be bounded by a suitable function of the output and derivatives of the output, modulo a decaying term depending on initial conditions. The class of output-input stable systems thus defined includes all affine systems in global normal form whose internal dynamics are input-to-state stable and also all left-invertible linear systems whose transmission zeros have negative real parts. As an application, we explain how the new concept enables one to develop a natural extension to nonlinear systems of a basic result from linear adaptive control     

Equivalence of input-output stability and exponential stability for infinite-dimensional systems

For a wide class of infinite-dimensional linear systems it is shown that if the state-space realization is exponentially stabilizable and detectable then exponential stability is equivalent to input-output stability of the transfer function. Exponential stabilizability (or detectability) is a strong assumption as it implies that the system operator satisfies the spectrum decomposition assumption and has finitely many unstable eigenvalues of finite multiplicity. In addition, the finite-dimensional unstable projection of the system is controllable (or observable).     

Modeling in advanced systems engineering

Software and Systems Modeling -