on the inequivalence of generalized preparata codes if m is odd and sigma in aut gf 2 m is such that x rightarrow x sigma 2 1 is 1 1 there is a 2 m 1 1 2 m l 2m 2 nonlinear binary code p sigma having minimum distance 5 all the codes p sigma have the same distance and weight enumerators as the usual preparata codes which rise as p sigma when x sigma x 2 it is shown that p sigma and p tau are equivalent if and only if tau sigma pm 1 and aut p sigma is determined

super critical free surface flow over a trapezoidal obstacle a numerical method based on series truncation is presented to solve the problem of an irrotational inviscid incompressible and steady flow over a two dimensional trapezoidal obstacle with obstacle height w lying on the bottom of the running stream the suggested numerical method for the solution of the fully nonlinear problem is presented for which the flow is super critical both upstream and downstream it is found that solutions exist for symmetric trapezoidal for arbitrary size the results are plotted for different trapezoidal shapes and different values of froude number f 1 the effect of the froude number the bottom height and the shape of the bottom are discussed

on the extended error correcting capabilities of the quaternary preparata codes we prove extended error correcting capabilities of the quaternary preparata codes these are metrically reflected by a slight and simple modification of the lee distance on z sub 4 we change the weight of the element 2 to 4 3 and leave all remaining weights untouched

weight distributions of cosets of two error correcting binary bch codes extended or not let b be the binary two error correcting bch code of length 2 sup m 1 and let b spl circ be the extended code of b we give formal expressions of weight distributions of the cosets of the codes b spl circ only depending on m we can then deduce the weight distributions of the cosets of b when m is odd it is well known that there are four distinct weight distributions for the cosets of b so our main result is about the even case camion courteau and montpetit see ibid vol 38 no 7 p 1353 1992 observe that for the lengths 15 63 and 255 there are eight distinct weight distributions we prove that this property holds for the codes b spl circ and b for all even m

soft decoding techniques for codes and lattices including the golay code and the leech lattice two kinds of algorithms are considered 1 if is a binary code of length n a soft decision decoding algorithm for changes an arbitrary point of r n into a nearest codeword nearest in euclidean distance 2 similarly a decoding algorithm for a lattice lambda in r n changes an arbitrary point of r n into a closest lattice point some general methods are given for constructing such algorithms ami are used to obtain new and faster decoding algorithms for the gosset lattice e 8 the golay code the leech lattice

robust spl hscr sub spl infin filtering for uncertain discrete time state delayed systems this paper addresses the problem of robust spl hscr sub spl infin filtering for linear discrete time systems subject to parameter uncertainties in the system state space model and with multiple time delays in the state variables the uncertain parameters are supposed to belong to a given convex bounded polyhedral domain a methodology is developed to design a stable linear filter that assures asymptotic stability and a prescribed spl hscr sub spl infin performance for the filtering error irrespective of the uncertainty and the time delays the proposed design is given in terms of linear matrix inequalities which has the advantage in that it can be implemented numerically very efficiently

fuzzy h_ infty filter design for a class of nonlinear discrete time systems with multiple time delays this paper studies the fuzzy hinfin filter design problem for signal estimation of nonlinear discrete time systems with multiple time delays and unknown bounded disturbances first the takagi sugeno t s fuzzy model is used to represent the state space model of nonlinear discrete time systems with time delays next we design a stable fuzzy hinfin filter based on the t s fuzzy model which guarantees asymptotic stability and a prescribed hinfin index for the filtering error system irrespective of the time delays and uncertain disturbances a sufficient condition for the existence of such a filter is established by using the linear matrix inequality lmi approach the proposed lmi problem can be efficiently solved with global convergence guarantee using convex optimization techniques such as the interior point algorithm simulation examples are provided to illustrate the design procedure of the present method

robust mixed h_2 h_infty filtering for time delay fuzzy systems in this paper a robust mixed h2 hinfin filtering problem for continuous time fuzzy systems subject to parameter uncertainties and multiple time varying delays in state variables is addressed the uncertain systems are expressed as takagi sugeno fuzzy models with linear nominal parts and norm bounded uncertainties the main objective is to design stable filters that minimize a guaranteed cost index and achieve a prescribed hinfin performance under worst case disturbance based on lyapunov theory both delay independent and delay dependent sufficient conditions guaranteeing stability and achieving prescribed performances are stated in terms of linear matrix inequalities therefore stable filters can be obtained easily with existing convex algorithms lastly two examples are given to illustrate the proposed design methodology

weight distribution of cosets of 2 error correcting binary bch codes of length 15 63 and 255 the weight distributions of cosets are not known for the class of binary 2 error correcting bch codes of length n 2 sup m 1 m even the nonuniformly packed case by using the graph theoretical concepts of the combinatorial matrix of a code and an r partition design introduced in previous works the authors obtain these distributions of cosets in the three particular cases of length 15 63 and 255 it is observed that in these three cases the number of distinct weight distributions is a constant equal to 8

binary sequences with gold like correlation but larger linear span a new construction of optimal binary sequences identical to the well known family of gold sequences in terms of maximum nontrivial correlation magnitude and family size but having larger linear span is presented the distribution of correlation values is determined for every odd integer spl tau spl ges 3 the construction provides a family that contains 2 sup spl tau 1 cyclically distinct sequences each of period 2 sup spl tau 1 the maximum nontrivial correlation magnitude equals 2 spl tau 1 sup 2 1 with one exception each of the sequences in the family has linear span at least spl tau sup 2 spl tau 2 compared to 2 spl tau for gold sequences the sequences are easily implemented using a quaternary shift register followed by a simple feedforward nonlinearity

p adic valuation of weights in abelian codes over spl zopf p sup d counting polynomial techniques introduced by wilson are used to provide analogs of a theorem of mceliece mceliece s original theorem relates the greatest power of p dividing the hamming weights of words in cyclic codes over gf p to the length of the smallest unity product sequence of nonzeroes of the code calderbank li and poonen presented analogs for cyclic codes over zopf 2d using various weight functions hamming lee and euclidean weight as well as count of occurrences of a particular symbol some of these results were strengthened by wilson who also considered the alphabet zopf pd for p an arbitrary prime these previous results new strengthened versions and generalizations are proved here in a unified and comprehensive fashion for the larger class of abelian codes over zopf pd with p any prime for abelian codes over zopf 4 combinatorial methods for use with counting polynomials are developed these show that the analogs of mceliece s theorem obtained by wilson for hamming weight lee weight and symbol counts and the analog obtained here for euclidean weight are sharp in the sense that they give the maximum power of 2 that divides the weights of all the codewords whose fourier transforms have a specified support

brief paper robust h filtering for a class of uncertain linear systems with time varying delay this paper deals with the problem of delay dependent robust h filtering for uncertain linear systems with time varying delay two cases of time varying delays are fully considered one is the time varying delay being continuous uniformly bounded while the other is the time varying delay being differentiable uniformly bounded with delay derivative bounded by a constant a stable linear filter is designed to ensure that the filtering error system is asymptotically stable with a prescribed level of h noise attenuation based on a new integral inequality delay dependent sufficient conditions for the existence of such a filter are established in terms of linear matrix inequalities lmis through deriving these conditions neither model transformation nor bounding technique for cross terms is employed moreover the relationship between the sufficient conditions for the two cases of time varying delay is disclosed finally two examples are also given to illustrate the effectiveness of the proposed methodology

robust h sub spl infin filter design of uncertain descriptor systems with discrete and distributed delays the robust h sub spl infin filtering problem for a class of continuous time uncertain linear descriptor systems with time varying discrete and distributed delays is investigated the time delays are assumed to be constant and known the uncertainties under consideration are norm bounded and possible time varying uncertainties sufficient condition for the existence of an h sub spl infin filter is expressed in terms of strict linear matrix inequalities lmis instead of using decomposition technique a unified form of lmis is proposed to show the exponential stability of the augmented systems the condition for assuring the stability of the fast subsystem is implied from the unified form of lmis which is shown to be less conservative than the characteristic equation based conditions or matrix norm based conditions the suitable filter is derived through a convex optimization problem a numerical example is given to show the effectiveness of the method

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

h sub infinity minimum error state estimation of linear stationary processes a state estimator is derived which minimizes the h sub infinity norm of the estimation error power spectrum matrix two approaches are presented the first achieves the optimal estimator in the frequency domain by finding the filter transfer function matrix that leads to an equalizing solution the second approach establishes a duality between the problem of h sub infinity filtering and the problem of unconstrained input h sub infinity optimal regulation using this duality previously published results for the latter regulation problem are applied which lead to an optimal filter that possess the structure of the corresponding kalman filter the two approaches usually lead to different results they are compared by a simple example which also demonstrates a clear advantage of the h sub infinity estimate over the conventional l sub 2 estimate

bounded real criteria for linear time delay systems considers the problem of finding the h sub spl infin norm of a linear time varying system having a delayed state and with an output that comprises a linear combination of the current state as well as of the delayed state both delay independent and delay dependent bounded real criteria are derived which provide sufficient conditions for the system to possess an h sub spl infin norm which is less than or equal to a prescribed bound the stationary case for time invariant systems is also tackled and in this situation the proposed bounded real criteria are given in terms of linear matrix inequalities two examples are presented which compare the guaranteed bounds that are achieved by our results with the actual h sub spl infin norm of the system

the z sub 4 linearity of kerdock preparata goethals and related codes certain notorious nonlinear binary codes contain more codewords than any known linear code these include the codes constructed by nordstrom robinson 1967 kerdock 1972 preparata 1968 goethals 1974 and delsarte goethals 1975 it is shown here that all these codes can be very simply constructed as binary images under the gray map of linear codes over z sub 4 the integers mod 4 although this requires a slight modification of the preparata and goethals codes the construction implies that all these binary codes are distance invariant duality in the z sub 4 domain implies that the binary images have dual weight distributions the kerdock and preparata codes are duals over z sub 4 and the nordstrom robinson code is self dual which explains why their weight distributions are dual to each other the kerdock and preparata codes are z sub 4 analogues of first order reed muller and extended hamming codes respectively all these codes are extended cyclic codes over z sub 4 which greatly simplifies encoding and decoding an algebraic hard decision decoding algorithm is given for the preparata code and a hadamard transform soft decision decoding algorithm for the i kerdock code binary first and second order reed muller codes are also linear over z sub 4 but extended hamming codes of length n spl ges 32 and the golay code are not using z sub 4 linearity a new family of distance regular graphs are constructed on the cosets of the preparata code

4 phase sequences with near optimum correlation properties two families of four phase sequences are constructed using irreducible polynomials over z sub 4 family a has period l 2 sup r 1 size l 2 and maximum nontrivial correlation magnitude c sub max

a game theoretic approach to a finite time disturbance attenuation problem a disturbance attenuation problem over a finite time interval is considered by a game theoretic approach where the control restricted to a function of the measurement history plays against adversaries composed of the process and measurement disturbances and the initial state a zero sum game formulated as a quadratic cost criterion subject to linear time varying dynamics and measurements is solved by a calculus of variation technique by first maximizing the quadratic cost criterion with respect to the process disturbance and initial state a full information game between the control and the measurement residual subject to the estimator dynamics results the resulting solution produces an n dimensional compensator which expresses the controller as a linear combination of the measurement history a disturbance attenuation problem is solved based on the results of the game problem for time invariant systems it is shown that under certain conditions the time varying controller becomes time invariant on the infinite time interval the resulting controller satisfies an h sub infinity norm bound

state feedback and output feedback control of a class of nonlinear systems with delayed measurements this paper is concerned with the problem of state feedback and output feedback control of a class of nonlinear systems with delayed measurements this class of nonlinear systems is made up of continuous time linear systems with nonlinear perturbations the nonlinearity is assumed to satisfy a global lipschitz condition and the time delay is assumed to be time varying and have no restriction on its derivative on the basis of the lyapunov krasovskii approach sufficient conditions for the existence of the state feedback controller and the output feedback controller are derived in terms of linear matrix inequalities methods of calculating the controller gain matrices are also presented two numerical examples are given to illustrate the effectiveness of the proposed methods c 2006 elsevier ltd all rights reserved

orbit and coset analysis of the golay and related codes let b be a code of length n over a field f with automorphism group g b sub w denotes the subset of codewords of weight w the goal is to classify the vectors of f sup n into orbits under g and to determine their distances from the various subcodes b sub w this is done for the first order reed muller nordstrom robinson and hamming codes of length 16 the golay and shortened golay codes of lengths 22 23 24 and the ternary golay code of length 12

translates of linear codes over z sub 4 we give a method to compute the complete weight distribution of translates of linear codes over z sub 4 the method follows known ideas that have already been used successfully by others for hamming weight distributions for the particular case of quaternary preparata codes we obtain that the number of distinct complete weights for the dual preparata codes and the number of distinct complete coset weight enumerators for the preparata codes are both equal to ten independent of the code length

robust h spl infin filter design for uncertain linear systems with multiple time varying state delays the problem of robust h spl infin filtering for continuous time uncertain linear systems with multiple time varying delays in the state variables is investigated the uncertain parameters are supposed to belong to a given convex bounded polyhedral domain the aim is to design a stable linear filter assuring asymptotic stability and a prescribed h spl infin performance level for the filtering error system irrespective of the uncertainties and the time delays sufficient conditions for the existence of such a filter are established in terms of linear matrix inequalities which can be efficiently solved by means of powerful convex programming tools with global convergence assured an example illustrates the proposed methodology

filtering continuous time linear systems with time varying measurement delay we consider the filtering problem of lti continuous time systems with known and bounded measurement delays the aim of the technical note is the design of a finite dimensional sub optimal filter whose performance in terms of the estimation error is comparable to optimal infinite dimensional approaches we show that the proposed approach allows for a precise characterization of the relationship between measurement delay and the covariance of the estimation error in the time varying case no restrictive hypotheses on the delay function are needed the proposed filter can therefore be applied to delay functions for which traditional infinite dimensional approaches cannot be straightforwardly applied

nonlinear transient gravity waves due to an initial free surface elevation over a topography the behavior of nonlinear two dimensional transient gravity waves inside an incompressible nonviscous and homogeneous fluid is predicted these waves are the response of an initial free surface elevation in an infinite channel with a general topography a perturbation technique is used for the investigation in contrast to the limitations made on the horizontal extent of the topography by the shallow water theory the present approach necessitates small vertical extent of the topography relative to its horizontal extent and to the mean water s depth as well the same limitation is assumed satisfied by the initial free surface elevation solutions up to the second order are obtained discussed and illustrated the asymptotic behavior of the solutions is obtained and discussed the expressions for the right going and the left going waves are separated the case of a very shallow fluid is deduced and analyzed for such a model which is free from the limitations assumed by the shallow water theory the validity of the obtained solution is tested by comparing the lowest streamline with the bottom topography the difference between the linear and the nonlinear theories and the effect of the bottom topography on the resulting flow are illustrated

brief paper robust h filtering for nonlinear stochastic systems with uncertainties and markov delays this paper investigates the h filtering problem for a class of general nonlinear stochastic systems considering model uncertainties and random time delays governed by markov chains simultaneously the general algebraic hamilton jacobi inequality hji is established first for general nonlinear stochastic systems with uncertainties and random markovian delays then a set of sufficient conditions are derived for the filtering system to achieve stochastic stability in the sense of mean square and the prescribed disturbance attenuation level moreover the developed results are specialized for a special class of nonlinear stochastic systems by presenting the sufficient conditions in terms of matrix inequalities simulation results demonstrate the effectiveness of the proposed approach

quaternary quadratic residue codes and unimodular lattices we construct new self dual and isodual codes over the integers module 4 the binary images of these codes under the gray map are nonlinear but formally self dual the construction involves hensel lifting of binary cyclic codes quaternary quadratic residue codes are obtained by hensel lifting of the classical binary quadratic residue codes repeated hensel lifting produces a universal code defined over the 2 adic integers we investigate the connections between this universal code and the codes defined over z sub 4 the composition of the automorphism group and the structure of idempotents over z sub 4 we also derive a square root bound on the minimum lee weight and explore the connections with the finite fourier transform certain self dual codes over z sub 4 are shown to determine even unimodular lattices including the extended quadratic residue code of length q 1 where q spl equiv 1 mod8 is a prime power when q 23 the quaternary golay code determines the leech lattice in this way this is perhaps the simplest construction for this remarkable lattice that is known

robust h exponential filtering for uncertain stochastic time delay systems with markovian switching and nonlinearities in this paper we deal with the robust h exponential filtering problem for a class of uncertain stochastic time delay systems with markovian switching and nonlinear disturbances the system under consideration involves parameter uncertainties ito type stochastic disturbances markovian jump parameters unknown nonlinear disturbances as well as time varying delays which vary in a range and dependent on the mode of the operation the aim of this problem is to design a markovian jump exponential filter such that the filtering error system is robustly stochastically exponentially mean square stable and a prescribed h disturbance attenuation level is guaranteed novel delay range dependent sufficient conditions are proposed to guarantee the existence of the desired robust exponential filter which are derived in terms of linear matrix inequalities lmis then the explicit expression of the desired filter parameters is characterized an illustrative numerical example is provided to demonstrate the effectiveness of the proposed method

monotonicity of maximal solutions of algebraic riccati equations abstract a monotonicity result for the maximal solution of the equation xbb x a x xa q 0 q q a b stabilizable is proved

delay range dependent robust h filtering for uncertain stochastic systems with mode dependent time delays and markovian jump parameters abstract this paper investigates the problem of robust h filtering for uncertain stochastic time delay systems with markovian jump parameters both the state dynamics and measurement of the system are corrupted by wiener processes the time delay varies in an interval and depends on the mode of operation a markovian jump linear filter is designed to guarantee robust exponential mean square stability and a prescribed disturbance attenuation level of the resulting filter error system a novel approach is employed in showing the robust exponential mean square stability the exponential decay rate can be directly estimated using matrices of the lyapunov krasovskii functional and its derivative a delay range dependent condition in the form of lmis is derived for the solvability of this h filtering problem and the desired filter can be constructed with solutions of the lmis an illustrative numerical example is provided to demonstrate the effectiveness of the proposed approach

observation and stabilization of ltv systems with time varying measurement delay abstract this work deals with observer based output feedback stabilization of linear time varying ltv systems with time varying measurement delay the delay is modeled by a first order hyperbolic partial differential equation pde whose boundary condition evolves according to an ordinary differential equation ode namely the plant the overall system is thus represented by an ode pde cascade which is also the structure of the proposed observer the exponential stability of the estimation error is established for arbitrarily large time varying delays an observer based controller is also introduced and the closed loop stability is proved the separation principle holds and the design of both the observer and controller gains can be done as if there was no delay some simulations illustrate the feasibility of this approach

a delay dependent approach to robust h sub spl infin filtering for uncertain distributed delay systems this paper is concerned with the problem of robust h sub spl infin filtering for linear systems with both discrete and distributed delays which are subject to norm bounded time varying parameter uncertainties both the state and measurement equations are assumed to have discrete and distributed delays a delay dependent condition for the existence of h sub spl infin filters is proposed which is less conservative than existing ones in the literature via solutions to certain linear matrix inequalities general full order filters are designed that ensure asymptotic stability and a prescribed h sub spl infin performance level irrespective of the parameter uncertainties an illustrative example is provided to demonstrate the effectiveness and the reduced conservatism of the proposed method

filtering and smoothing in an h sup infinity setting the problems of filtering and smoothing are considered for linear systems in an h sup infinity setting i e the plant and measurement noises have bounded energies are in l sub 2 but are otherwise arbitrary two distinct situations for the initial condition of the system are considered the initial condition is assumed known in one case while in the other the initial condition is not known but the initial condition the plant and measurement noise are in some weighted ball of r sup n xl sub 2 finite horizon and infinite horizon cases are considered necessary and sufficient conditions are presented for the existence of estimators both filters and smoothers that achieve a prescribed performance bound and algorithms that result in performance within the bounds are developed in case of smoothers the optimal smoother is also presented the approach uses basic quadratic optimization theory in a time domain setting as a consequence of which both linear time varying and time invariant systems can be considered with equal ease in the smoothing problem for linear time varying systems one considers only the finite horizon case

covering radius survey and recent results all known results on covering radius are presented as well as some new results there are a number of upper and lower bounds including asymptotic results a few exact determinations of covering radius some extensive relations with other aspects of coding theory through the reed muller codes and new results on the least covering radius of any linear n k code there is also a recent result on the complexity of computing the covering radius

spl hscr sub spl infin filtering for continuous time linear systems with delay the problem of spl hscr sub spl infin filtering for continuous time linear systems with time delayed measurement is investigated the authors develop a methodology for designing linear filters which ensure a prescribed bound on the spl lscr sub 2 induced gain from the noise signals to the estimation error filtering problems for time varying systems over a finite horizon as well as stationary infinite horizon filtering for time invariant systems are tackled in the finite horizon case our estimation procedure entails an overdesign that stems from the last d seconds of the time interval 0 t where d is the delay length this overdesign becomes smaller as t increases and it vanishes in the infinite horizon case

a linear construction for certain kerdock and preparata codes the nordstrom robinson kerdock and slightly modified preparata codes are shown to be linear over z4 the integers mod 4 the kerdock and preparata codes are duals over z4 and the nordstrom robinson code is self dual all these codes are just extended cyclic codes over z4 this provides a simple definition for these codes and explains why their hamming weight distributions are dual to each other firstand second order reed muller codes are also linear codes over z4 but hamming codes in general are not nor is the golay code

an innovation approach to h prediction for continuous time systems with application to systems with delayed measurements this paper studies the problem of h prediction for linear continuous time systems by developing a new method of characterizing the innovation process and applying a novel innovation analysis approach in krein space a necessary and sufficient condition for the existence of a finite horizon h predictor is derived the solution to the h prediction is given in terms of solutions of riccati and matrix differential equations we further extend our study to give a necessary and sufficient condition for the h filtering of linear continuous time systems with both instantaneous and delayed measurements

fast ml decoding algorithm for the nordstrom robinson code corresp the extended nordstrom robinson code is an optimum nonlinear double error correcting code of length 16 with considerable practical importance this code is also useful as a rate 1 2 vector quantizer for random waveforms such as speech linear predictive coding lpc residual a fast decoding algorithm is described for maximum likelihood decoding or nearest neighbor search in the squared error sense with 304 additions and 128 comparisons

an exponential number of generalized kerdock codes if n 1 is an odd composite integer then there are at least 2 1 2 n pairwise inequivalent binary error correcting codes of length 2 n size 2 2 n and minimum distance 2 n 1 2 1 2 n 1

h sub spl infin filtering for multiple time delay measurements the aim of this paper is to study the h sub spl infin filtering problem for linear continuous time systems with both current and multiple time delay measurements the key technique applied for deriving the filter is the reorganized innovation analysis approach in krein space a necessary and sufficient condition for the existence of an h sub spl infin filter is derived and the solution to the h sub spl infin filter is given in terms of solutions of riccati and matrix differential equations an example is finally presented to show the effectiveness of the proposed approach

cocyclic simplex codes of type spl alpha over z sub 4 and z sub 2 sup s over the past decade cocycles have been used to construct hadamard and generalized hadamard matrices this in turn has led to the construction of codes self dual and others here we explore these ideas further to construct cocyclic complex and butson hadamard matrices and subsequently we use the matrices to construct simplex codes of type spl alpha over z 4 and z 2 sup s respectively

state space solutions to standard h sub 2 and h sub infinity control problems simple state space formulas are derived for all controllers solving the following standard h sub infinity problem for a given number gamma 0 find all controllers such that the h sub infinity norm of the closed loop transfer function is strictly less than gamma it is known that a controller exists if and only if the unique stabilizing solutions to two algebraic riccati equations are positive definite and the spectral radius of their product is less than gamma sup 2 under these conditions a parameterization of all controllers solving the problem is given as a linear fractional transformation lft on a contractive stable free parameter the state dimension of the coefficient matrix for the lft constructed using the two riccati solutions equals that of the plant and has a separation structure reminiscent of classical lqg i e h sub 2 theory this paper is intended to be of tutorial value so a standard h sub 2 solution is developed in parallel

linear quadratic regulators with eigenvalue placement in a vertical strip a computational method is presented for finding the linear quadratic regulator such that the optimal closed loop system has eigenvalues lying within a vertical strip in the complex plane the proposed method is suitable for the two stage optimal design of two time scale systems

reduction for the nonlinear problem of fluid waves to a system of integro differential equations with an oceangraphical application a numerical procedure for the solution of the nonlinear problem of irrotational wave propagation inside a finite or an infinite homogeneous fluid mass is proposed this procedure is applied to calculate the fluid gravity waves resulting from certain prescribed varying pressure applied to the free surface of an infinite fluid mass with finite or infinite depth these waves also are calculated analytically within the frame of the linear theory of motion the variation of the fluid s constant depth for this application is found to have no influence on the resulting flow a slight agreement between the numerical solution of the nonlinear problem and the analytical solution of the corresponding linearized problem is noticed in a narrow interval of time following the start of the motion in the course of time a significant divergence between the two theories is found and the nonlinear theory is therefore indispensable for the theoretical prediction of this phenomenon the proposed procedure can be applied to problems with more complicated geometry

robust switching type h filter design for linear uncertain systems with time varying delay this paper is concerned with the problem of robust h filter design for a class of linear uncertain systems with time varying delay the uncertainty parameters are supposed to be time varying unknown but bounded which appear affinely in the matrices of the considered system model based on linear matrix inequality lmi method and switching laws a new switching type filter is designed to guarantee the asymptotic stability and h performance level of the filtering error systems the key feature is that the new proposed filter parameters are switching between certain fixed gains automatically via the designed switching law it is shown that the new filter design method is less conservative than the traditional fixed gain filter design method an example is given to illustrate the validity of the proposed design

robust h infinity filtering for a class of non linear systems with state delay and parameter uncertainty this paper deals with the problem of robust h infinity filtering for a class of state delayed non linear systems with normbounded parameter uncertainty appearing in all the matrices of the linear part of the system model the non linearities are assumed to satisfy the global lipschitz conditions and appear in both the state and measured output equations attention is focused on the design of a non linear filter which ensures both the robust stability and a prescribed h infinity performance of the filtering error dynamics for all admissible uncertainties a sufficient condition for the existence of such a filter is given in terms of a linear matrix inequality lmi when this lmi is feasible the expression of a desired h infinity filter is also presented a numerical example is provided to demonstrate the applicability of the proposed approach

approximate solution of a flow over a ramp for large froude number abstract an approximate method is presented to solve the problem of steady free surface flow of an ideal fluid over a semi infinite ramp in the bottom schwartz christoffel transformation is used to map the region of flow in the complex potential plane onto the upper half plane the hilbert transformation as well as the perturbation technique are used as a basis for the approximate solution of the problem for large froude number and small inclination angle of the ramp general equations in integral form for any order of approximation are obtained solution up to first order approximation is discussed and illustrated elevation of the free surface for different ramp heights different inclination angles of the ramp and different froude numbers are plotted an approximate formula of maximum elevation of the free surface in terms of the ramp heights and its inclination angle is found