new criteria of passivity analysis for fuzzy time delay systems with parameter uncertainties this paper investigates the passivity problem for a class of uncertain stochastic fuzzy nonlinear systems with mixed delays and nonlinear noise disturbances by employing an improved free weighting matrix approach the fuzzy system is based on the takagi sugeno model that is often used to represent the complex nonlinear systems in terms of fuzzy sets and fuzzy reasoning to reflect more realistic dynamical behaviors of the system the parameter uncertainties the stochastic disturbances and nonlinearities are considered where the parameter uncertainties enter into all the system matrices the stochastic disturbances are given in the form of a brownian motion the mixed delays comprise both discrete and distributed time varying delays by taking the relationship among the time delays their lower and upper bounds into account some less conservative linear matrix inequality based delay dependent passivity criteria are obtained without ignoring any useful terms in the derivative of lyapunov functional finally numerical examples are given to demonstrate the effectiveness and merits of the proposed methods

dissipativity analysis for singular systems with time varying delays this paper is concerned with the dissipativity analysis problem for singular systems with time varying delays a delay dependent criterion is established to guarantee the dissipativity of the underlying systems using the delay partitioning technique all the results given in this paper are not only dependent upon the time delay but also dependent upon the number of delay partitions the effectiveness and the reduced conservatism of the derived results are demonstrated by two illustrative examples

efficient algorithms for membership in boolean hierarchies of regular languages this paper provides efficient algorithms that decide membership for classes of several boolean hierarchies for which efficiency or even decidability were previously not known we develop new forbidden chain characterizations for the single levels of these hierarchies and obtain the following results the classes of the boolean hierarchy over level 1 of the dot depth hierarchy are decidable in nl previously only the decidability was known the same remains true if predicates mod d for fixed d are allowed if modular predicates for arbitrary d are allowed then the classes of the boolean hierarchy over level 1 are decidable for the restricted case of a two letter alphabet the classes of the boolean hierarchy over level 2 of the straubing therien hierarchy are decidable in nl this is the first decidability result for this hierarchy the membership problems for all mentioned boolean hierarchy classes are logspace many one hard for nl the membership problems for quasi aperiodic languages and for d quasi aperiodic languages are logspace many one complete for pspace

an optimal fault detection approach for piecewise affine systems via diagnostic observers abstract in this paper the design issues of diagnostic observer based fault detection fd for piecewise affine systems are investigated to be specific the diagnostic observer based fd approaches are developed to satisfy the specified disturbance attenuation and optimize the fault detectability at the same time considering the fact that the measurements are generally corrupted with noises or disturbances the proposed approaches are mainly dedicated to the case that the process and its fd system are non synchronous in transition from one region to another moreover aiming at improving the fd performance a mode observer is integrated to relax the design condition for the residual generator an example is given in the end to show the effectiveness of the proposed approaches

observer based h control of discrete time delay systems with random communication packet losses and multiplicative noises this paper investigates the observer based h control problem for a class of discrete time mixed delay systems with random communication packet losses and multiplicative noises where the mixed delays comprise both discrete and distributed time varying delays the random packet losses are described by a bernoulli distributed white sequence that obeys a conditional probability distribution and the multiplicative disturbances are in the form of a scalar gaussian white noise with unit variance in the presence of mixed delays random packet losses and multiplicative noises sufficient conditions for the existence of an observer based feedback controller are derived such that the closed loop control system is asymptotically mean square stable and preserves a guaranteed h performance then a linear matrix inequality lmi approach for designing such an observer based h controller is presented finally a numerical example is provided to illustrate the effectiveness of the developed theoretical results

asymptotic theory and deficiency indices for differential equations of odd order an asymptotic theory is developed for linear differential equations of odd order the theory is applied to the evaluation of the deficiency indices n and n associated with symmetric differential expressions of odd order general conditions on the coefficients are given under which all possible values of n and n subject to n n 1 are realized

regular languages defined with generalized quantifiers we study an extension of first order logic obtained by adjoining quantifiers that count with respect to an integer modulus it is shown that the languages definable in this framework are precisely the regular languages whose syntactic monoids contain only solvable groups we obtain an analogous result for regular languages and establish some connections with complexity theory for fixed depth families of circuits

a generalization of the schutzenberger product of finite monoids for each n 1 an n ary product on finite monoids is constructed this product has the following property let be a finite alphabet and the free monoid generated by for i 1 n let ai be a recognizable subset of m ai the syntactic monoid of an and m a1 an the syntactic monoid of the concatenation product a1 an then m a1 an m a1 m an the case n 2 was studied by schutzenberger as an application of the generalized product i prove the theorem of brzozowski and knast that the dot depth hierarchy of star free sets is infinite

robust passivity and passification of stochastic fuzzy time delay systems in this paper the passivity and passification problems are investigated for a class of uncertain stochastic fuzzy systems with time varying delays the fuzzy system is based on the takagi sugeno t s model that is often used to represent the complex nonlinear systems in terms of fuzzy sets and fuzzy reasoning to reflect more realistic dynamical behaviors of the system both the parameter uncertainties and the stochastic disturbances are considered where the parameter uncertainties enter into all the system matrices and the stochastic disturbances are given in the form of a brownian motion we first propose the definition of robust passivity in the sense of expectation then by utilizing the lyapunov functional method the ito differential rule and the matrix analysis techniques we establish several sufficient criteria such that for all admissible parameter uncertainties and stochastic disturbances the closed loop stochastic fuzzy time delay system is robustly passive in the sense of expectation the derived criteria which are either delay independent or delay dependent are expressed in terms of linear matrix inequalities lmis that can be easily checked by using the standard numerical software illustrative examples are presented to demonstrate the effectiveness and usefulness of the proposed results

reliable state feedback control of t s fuzzy systems with sensor faults this paper is concerned with reliable state feedback control synthesis for takagi and sugeno t s fuzzy systems with sensor multiplicative faults by considering the influence of sensor faults on both the system states and premise variables of fuzzy controllers a class of new convex reliable stabilization conditions are proposed for t s fuzzy systems using the properties of fuzzy product inference engines furthermore the obtained result is extended to the h infty reliable control case the resulting controllers are reliable in that they provide guaranteed asymptotic stability and h infty performance when all sensors are operational as well as when some sensor experiences failures different from the proposed approach the influence of sensor faults on premise variables is not considered in the existing results then it might not guarantee the stability and control performance for t s fuzzy systems with premise variables dependent on the system states a numerical example is given to illustrate the effectiveness of the proposed method

descriptional and computational complexity of finite automata a survey finite automata are probably best known for being equivalent to right linear context free grammars and thus for capturing the lowest level of the chomsky hierarchy the family of regular languages over the last half century a vast literature documenting the importance of deterministic nondeterministic and alternating finite automata as an enormously valuable concept has been developed in the present paper we tour a fragment of this literature mostly we discuss developments relevant to finite automata related problems like for example i simulation of and by several types of finite automata ii standard automata problems such as fixed and general membership emptiness universality equivalence and related problems and iii minimization and approximation we thus come across descriptional and computational complexity issues of finite automata we do not prove these results but we merely draw attention to the big picture and some of the main ideas involved

stability analysis of piecewise discrete time linear systems presents a stability analysis method for piecewise discrete time linear systems based on a piecewise smooth lyapunov function it is shown that the stability of the system can be established if a piecewise lyapunov function can be constructed and moreover the function can be obtained by solving a set of linear matrix inequalities lmis that is numerically feasible with commercially available software

technical communique reliable h control for discrete time piecewise linear systems with infinite distributed delays in this paper the reliable h control problem is investigated for discrete time piecewise linear systems with time delays and actuator failures the time delays are assumed to be infinitely distributed in the discrete time domain and the possible failure of each actuator is described by a variable varying in a given interval the aim of the addressed reliable h control problem is to design a controller such that for the admissible infinite distributed delays and possible actuator failures the closed loop system is exponentially stable with a given disturbance attenuation level c the controller gain is characterized in terms of the solution to a linear matrix inequality that can be easily solved by using standard software packages a simulation example is exploited in order to illustrate the effectiveness of the proposed design procedures

robust h sub spl infin filtering for stochastic time delay systems with missing measurements in this paper the robust hinfin filtering problem is studied for stochastic uncertain discrete time delay systems with missing measurements the missing measurements are described by a binary switching sequence satisfying a conditional probability distribution we aim to design filters such that for all possible missing observations and all admissible parameter uncertainties the filtering error system is exponentially mean square stable and the prescribed hinfin performance constraint is met in terms of certain linear matrix inequalities lmis sufficient conditions for the solvability of the addressed problem are obtained when these lmis are feasible an explicit expression of a desired robust hinfin filter is also given an optimization problem is subsequently formulated by optimizing the hinfin filtering performances finally a numerical example is provided to demonstrate the effectiveness and applicability of the proposed design approach

robust estimation for neural networks with randomly occurring distributed delays and markovian jump coupling this paper studies the issue of robust state estimation for coupled neural networks with parameter uncertainty and randomly occurring distributed delays where the polytopic model is employed to describe the parameter uncertainty a set of bernoulli processes with different stochastic properties are introduced to model the randomly occurrences of the distributed delays novel state estimators based on the local coupling structure are proposed to make full use of the coupling information the augmented estimation error system is obtained based on the kronecker product a new lyapunov function which depends both on the polytopic uncertainty and the coupling information is introduced to reduce the conservatism sufficient conditions which guarantee the stochastic stability and the l 2 l infty performance of the augmented estimation error system are established then the estimator gains are further obtained on the basis of these conditions finally a numerical example is used to prove the effectiveness of the results

languages and formations generated by d4 and q8 abstract we describe the two classes of languages recognized by the groups d 4 and q 8 respectively then we show that the formations of languages generated by these two classes are the same we also prove that these two formations are closed under inverses of morphisms which yields a language theoretic proof of the fact that the group formations generated by d 4 and q 8 respectively are two equal varieties

classification of finite monoids the language approach abstract the concept of a variety of congruences is introduced and related to variety of languages and variety of monoids a systematic construction of increasingly complex varieties of congruences is presented this construction is powerful enough to generate all monoids containing solvable groups some hierarchies occurring through this process are shown to correspond to well known hierarchies of monoids thus indicating that our construction is natural from an algebraic point of view some problems that remain open are also discussed

algebraic tools for the concatenation product this paper is a contribution to the algebraic study of the concatenation product in the first part of the paper we extend to the ordered case standard algebraic tools related to the concatenation product like the schutzenberger product and the relational morphisms we show in a precise way how the ordered schutzenberger product corresponds to polynomial operations on languages in the second part of the paper we apply these results to establish a bridge between the three standard concatenation hierarchies namely the straubing therien hierarchy the brzozowski s or dot depth hierarchy and the group hierarchy

languages defined with modular counting quantifiers we prove that a regular language defined by a boolean combination of generalized 1 sentences built using modular counting quantifiers can be defined by a boolean combination of 1 sentences in which only regular numerical predicates appear the same statement with 1 replaced by first order is equivalent to the conjecture that the nonuniform circuit complexity class acc is strictly contained in nc1 the argument introduces some new techniques based on a combination of semigroup theory and ramsey theory which may shed some light on the general case

products of languages with counter abstract it is well known that varieties of rational languages are in one to one correspondence with varieties of finite monoids this correspondence often extends to operations on languages and on monoids we investigate the special case of the product of languages with counter and describe the associated operations on monoids and varieties

on joint design of intentionally introduced delay and controller gain for stabilization of second order oscillatory systems this paper focuses on stabilization of second order oscillatory systems using both feedback control and intentionally introduced time delay the argument principle is employed as a key technique to divide the parameter space of time delay and controller gain into several regions every admissible value in these regions moves the poles of the closed loop system towards the left of the complex plane such that stability improvement is achieved the concept of potent asymptotic stability is first introduced referring to the property that all the poles of the closed loop system are stable and lie on the left of open loop system poles in the complex plane analytical characterizations on parameter pairs of time delay and controller gain that result in potent asymptotic stability are established all the poles and corresponding root locus with respect to gain are examined numerical examples and simulations are given to illustrate the usefulness and merits of the theoretical results

deficiency indices of an odd order differential operator we obtain asymptotic solutions of odd order formally self adjoint differential equations with power coefficients and discuss possible values for the deficiency indices of the associated operators

a delay dependent approach to robust h sub spl infin filtering for uncertain discrete time state delayed systems a delay dependent approach to robust h sub spl infin filtering is proposed for linear discrete time uncertain systems with multiple delays in the state the uncertain parameters are supposed to reside in a polytope and the attention is focused on the design of robust filters guaranteeing a prescribed h sub spl infin noise attenuation level the proposed filter design methodology incorporates some recently appeared results such as moon s new version of the upper bound for the inner product of two vectors and de oliveira s idea of parameter dependent stability which greatly reduce the overdesign introduced in the derivation process in addition to the full order filtering problem the challenging reduced order case is also addressed by using different linearization procedures both full and reduced order filters can be obtained from the solution of convex optimization problems in terms of linear matrix inequalities which can be solved via efficient interior point algorithms numerical examples have been presented to illustrate the feasibility and advantages of the proposed methodologies

asymptotic theory for a critical class of fourth order differential equations a recently formulated asymptotic theory for differential equations with large coefficients that are like powers of the independent variable is developed here for fourth order equations with general coefficients in this general approach a critical case is identified that forms a borderline between situations where all solutions have asymptotically a certain exponential character in terms of the coefficients and where only two solutions have this character the asymptotic forms of a fundamental set of solutions are obtained in the critical case

asymptotics and deficiency indices for certain pairs of differential operators asymptotic approximations to solutions of perturbations of meijer s differential equation are derived these are used to determine deficiency indices for certain subspaces associated with related pairs of symmetric differential expressions

reliable h_ infty control for discrete time fuzzy systems with infinite distributed delay in this paper the problem of reliable h control is investigated for discrete time takagi sugeno t s fuzzy systems with infinite distributed delay and actuator faults a discrete time homogeneous markov chain is used to represent the stochastic behavior of actuator faults in terms of a stochastic fuzzy lyapunov functional a sufficient condition is proposed to ensure that the resultant closed loop system is exponentially stable in the mean square sense with an h performance index based on the derived condition the reliable h control problem is solved and an explicit expression of the desired controller is also given the case of no failure in the actuator is also considered a numerical example is given to demonstrate that our results are effective and less conservative

improved criteria for the stabilization of t s fuzzy systems with actuator failures via a sampled data fuzzy controller abstract this paper studies a problem of the sampled data stabilization for takagi sugeno fuzzy systems with actuator failures an improved lyapunov functional is constructed which is dependent on the fuzzy membership functions fmfs and includes the sampling states with two sampling instants a new integral term including the fmfs is introduced into this lyapunov functional for the first time each term in this lyapunov functional need not be positive but it should be positive at sampling instants the variation range of the fmfs is taken into account in dealing with the derivative of this lyapunov functional as well then improved stabilization criteria guaranteeing a larger sampling interval are obtained by applying the developed fuzzy controller simulation examples are given to illustrate the effectiveness and less conservatism of the proposed method