bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimum output variance control for FSN models: Continuous‐time case
Authors: Shi Guojun , Skelton Robert E. , Grigoriadis Karolos M.
Published: September 2005

In this paper we consider the Finite Signal‐to‐Noise ratio model for linear stochastic systems. It is assumed that the intensity of noise corrupting a signal is proportional to the variance of the signal. Hence, the signal‐to‐noise ratio of each sensor and actuator is finite – as opposed to the infinite signal‐to‐noise ratio assumed in LQG theory. Computational errors in the controller implementation are treated similarly. The objective is to design a state feedback control law such that the closed loop system is mean square asymptotically stable and the output variance is minimized. The main result is a controller which achieves its maximal accuracy with finite control gains – as opposed to the infinite controls required to achieve maximal accuracy in LQG controllers. Necessary and sufficient conditions for optimality are derived. An optimal control law which involves the positive definite solution of a Riccati‐like equation is derived. An algorithm for solving the Riccati‐like equation is given and its convergence is guaranteed if a solution exists.
Weighted multirate q‐Markov Cover identification using PRBS – an application to engine systems
Authors: Zhu G. George
Published: September 2005

The q‐Markov COVariance Equivalent Realization (q‐Markov Cover) method for identification uses either pulse, white noise or PRBS (Pseudo‐Random Binary Signal) as test excitation. This paper extended the q‐Markov Cover using PRBS to the weighted multirate case, that is, the sample rate of the PRBS signal is different from the system output one. Then, the multirate PRBS q‐Markov Cover is applied to identify a diesel engine model from the fuel command input to the engine speed output. The identified engine model has order of two and approximates the pure fuel system time delay using a first‐order transfer function with a non‐minimum phase numerator. Finally, the identified engine model was successfully used for designing engine idle speed governor and obtained satisfactory performance in the first try.
Improvability of assembly systems II: Improvability indicators and case study
Authors: Chiang S.-Y. , Kuo C.-T. , Lim J.-T. , Meerkov S. M.
Published: September 2005

Based on the performance analysis technique developed in Part I, this paper presents improvability indicators for assembly lines with unreliable machines. In particular, it shows that assembly lines are unimprovable with respect to workforce re‐distribution if each buffer is, on the average, close to being half full. These lines are unimprovable with respect to buffer capacity re‐distribution if each machine is starved and blocked with almost equal frequency. In addition, the paper provides indicators for identification of bottleneck machines and bottleneck buffers. Finally, the paper reports on an application of these improvability indicators in a case study at an automotive components plant.
Two (multi) point nonlinear Lyapunov systems associated with an nth order nonlinear system of differential equations – existence and uniqueness
Authors: Murty K. N. , Howell G. W. , Sarma G. V. R. L.
Published: September 2005

This paper presents a criterion for the existence and uniqueness of solutions to two and multipoint boundary value problems associated with an nth order nonlinear Lyapunov system. A variation of parameters formula is developed and used as a tool to obtain existence and uniqueness. We discuss solution of the second order problem by the ADI method and develop a fixed point method to find the general solution of the nth order Lyapunov system. The results of Barnett (SIAM J. Appl. Anal. 24(1), 1973) are a particular case.
H2 guaranteed cost control of discrete linear systems
Authors: Colmenares W. , Tadeo F. , Granado E. , Pérez O. , Valle F. Del
Published: September 2005

This paper presents necessary and sufficient conditions for the existence of a quadratically stabilizing output feedback controller which also assures H2 guaranteed cost performance on a discrete linear uncertain system where the uncertainty is of the norm bounded type. The conditions are presented as a collection of linear matrix inequalities.The solution, however requires a search over a scalar parameter space.
Fluid queues driven by an M/M/1/N queue
Authors: Lenin R. B. , Parthasarathy P. R.
Published: September 2005

In this paper, we consider fluid queue models with infinite buffer capacity which receives and releases fluid at variable rates in such a way that the net input rate of fluid into the buffer (which is negative when fluid is flowing out of the buffer) is uniquely determined by the number of customers in an M/M/1/N queue model (that is, the fluid queue is driven by this Markovian queue) with constant arrival and service rates. We use some interesting identities of tridiagonal determinants to find analytically the eigenvalues of the underlying tridiagonal matrix and hence the distribution function of the buffer occupancy. For specific cases, we verify the results available in the literature.
Robust stabilization of nonlinear systems: The LMI approach
Authors: Šiljak D. D. , Stipanović D. M.
Published: September 2005

This paper presents a new approach to robust quadratic stabilization of nonlinear systems within the framework of Linear Matrix Inequalities (LMI). The systems are composed of a linear constant part perturbed by an additive nonlinearity which depends discontinuously on both time and state. The only information about the nonlinearity is that it satisfies a quadratic constraint. Our major objective is to show how linear constant feedback laws can be formulated to stabilize this type of systems and, at the same time, maximize the bounds on the nonlinearity which the system can tolerate without going unstable.

We shall broaden the new setting to include design of decentralized control laws for robust stabilization of interconnected systems. Again, the LMI methods will be used to maximize the class of uncertain interconnections which leave the overall system connectively stable. It is useful to learn that the proposed LMI formulation “recognizes” the matching conditions by returning a feedback gain matrix for any prescribed bound on the interconnection terms. More importantly, the new formulation provides a suitable setting for robust stabilization of nonlinear systems where the nonlinear perturbations satisfy the generalized matching conditions.
On an M1,M2/Gr/1 queueing system
Authors: Tadj Lotfi
Published: September 2005

The author studies a service delayed queueing system with priority discipline. The joint queue size distribution is derived in the steady state.
Modular production line optimization: The exPLORE architecture
Authors: Spinellis Diomidis D. , Papadopoulos Chrissoleon T.
Published: September 2005

The general design problem in serial production lines concerns the allocation of resources such as the number of servers, their service rates, and buffers given production‐specific constraints, associated costs, and revenue projections. We describe the design of exPLOre: a modular, object‐oriented, production line optimization software architecture. An abstract optimization module can be instantiated using a variety of stochastic optimization methods such as simulated annealing and genetic algorithms. Its search space is constrained by a constraint checker while its search direction is guided by a cost analyser which combines the output of a throughput evaluator with the business model. The throughput evaluator can be instantiated using Markovian, generalised queueing network methods, a decomposition, or an expansion method algorithm.
Explicit solution of the jump problem for the Laplace equationand singularities at the edges
Authors: Krutitskii P. A.
Published: September 2005

The boundary value problem for the Laplace equation outside several cuts in a plane is studied. The jump of the solution of the Laplace equation and the jump of its normal derivative are specified on the cuts. The problem is studied under different conditions at infinity, which lead to different uniqueness and existence theorems. The solution of this problem is constructed in the explicit form by means of single layer and angular potentials. The singularities at the ends of the cuts are investigated.
A generalized regular form for multivariable sliding mode control
Authors: Perruquetti W. , Richard J. P. , Borne P.
Published: September 2005

The paper shows how to compute a diffeomorphic state space transformation in order to put the initial mutivariable nonlinear model into an appropriate regular form. This form is an extension of the one proposed by Lukyanov and Utkin [9], and constitutes a guidance for a “natural” choice of the sliding surface. Then stabilization is achieved via a sliding mode strategy. In order to overcome the chattering phenomenon, a new nonlinear gain is introduced.
On exponential stabilizability of linear neutral systems
Authors: Dusser Xavier , Rabah Rabah
Published: September 2005

In this paper, we deal with linear neutral functional differential systems. Using an extended state space and an extended control operator, we transform the initial neutral system in an infinite dimensional linear system. We give a sufficient condition for admissibility of the control operator B, conditions under which operator B can be acceptable in order to work with controllability and stabilizability. Necessary and sufficient conditions for exact controllability are provided; in terms of a gramian of controllability N(μ). Assuming admissibility and exact controllability, a feedback control law is defined from the inverse of the operator N(μ)
in order to stabilize exponentially the closed loop system. In this case, the semigroup generated by the closed loop system has an arbitrary decay rate.
The strong law of large numbers for dependent vector processeswith decreasing correlation: “Double averaging concept”
Authors: Poznyak Alex S.
Published: September 2005

A new form of the strong law of large numbers for dependent vector sequences using the “double averaged” correlation function is presented. The suggested theorem generalizes the well‐known Cramer–Lidbetter′s theorem and states more general conditions for fulfilling the strong law of large numbers within the class of vector random processes generated by a non stationary stable forming filters with an absolutely integrable impulse function.
Identification of an unstable ARMA equation
Authors: Gel Yulia R. , Fomin Vladimir N.
Published: September 2005

Usually the coefficients in a stochastic time series model are partially or entirely unknown when the realization of the time series is observed. Sometimes the unknown coefficients can be estimated from the realization with the required accuracy. That will eventually allow optimizing the data handling of the stochastic time series.

Here it is shown that the recurrent least‐squares (LS) procedure provides strongly consistent estimates for a linear autoregressive (AR) equation of infinite order obtained from a minimal phase regressive (ARMA) equation. The LS identification algorithm is accomplished by the Padé approximation used for the estimation of the unknown ARMA parameters.
Modelling the electromagnetic behaviour of sife alloys using thePreisach theory and the principle of loss seperation
Authors: Dupré L. , Van Keer R. , Melkebeek J.
Published: September 2005

In this paper we present 2 simplified methods for the evaluation of magnetisation loops in laminated SiFe alloys, using the Preisach theory and the statistical loss theory. These methods are investigated in detail as a practical alternative for a very accurate, but much involved numerical approach, viz a combined lamination model – dynamic Preisach model earlier developed by the authors. Particularly, one of the 2 methods provides accurate results inspite of a dramatic reduction of the CPU‐time in comparison with the earlier developed combined model. For the other simplified method, the reduction of CPU‐time is less pronounced but still considerable and the results are fairly good.
An optimal control approach to manpower planning problem
Authors: Lee H. W. J. , Cai X. Q. , Teo K. L.
Published: September 2005

A manpower planning problem is studied in this paper. The model includes scheduling different types of workers over different tasks, employing and terminating different types of workers, and assigning different types of workers to various trainning programmes. The aim is to find an optimal way to do all these while keeping the time‐varying demand for minimum number of workers working on each different tasks satisfied. The problem is posed as an optimal discrete‐valued control problem in discrete time. A novel numerical scheme is proposed to solve the problem, and an illustrative example is provided.
Stability and stabilization of nonlinear systems andTakagi‐Sugeno′s fuzzy models
Authors: Blanco Yann , Perruquetti Wilfrid , Borne Pierre
Published: September 2005

This paper outlines a methodology to study the stability of Takagi‐Sugeno′s (TS) fuzzy models. The stability analysis of the TS model is performed using a quadratic Liapunov candidate function. This paper proposes a relaxation of Tanaka′s stability condition: unlike related works, the equations to be solved are not Liapunov equations for each rule matrix, but a convex combination of them. The coefficients of this sums depend on the membership functions. This method is applied to the design of continuous controllers for the TS model. Three different control structures are investigated, among which the Parallel Distributed Compensation (PDC). An application to the inverted pendulum is proposed here.
Robust stability and ℋ∞‐estimation for uncertain discrete systems with state‐delay
Authors: Mahmoud Magdi S.
Published: September 2005

In this paper, we investigate the problems of robust stability and ℋ∞‐estimation for a class of linear discrete‐time systems with time‐varying norm‐bounded parameter uncertainty and unknown state‐delay. We provide complete results for robust stability with prescribed performance measure and establish a version of the discrete Bounded Real Lemma. Then, we design a linear estimator such that the estimation error dynamics is robustly stable with a guaranteed ℋ∞‐performance irrespective of the parameteric uncertainties and unknown state delays. A numerical example is worked out to illustrate the developed theory.
Transient analysis of a queue where potential customers arediscouraged by queue length
Authors: Parthasarathy P. R. , Selvaraju N.
Published: September 2005

The transient solution is obtained analytically using continued fractions for a state‐dependent birth‐death queue in which potential customers are discouraged by the queue length. This queueing system is then compared with the well‐known infinite server queueing system which has the same steady state solution as the model under consideration, whereas their transient solutions are different. A natural measure of speed of convergence of the mean number in the system to its stationarity is also computed.
Existence criteria for singular initial value problems with signchanging nonlinearities
Authors: Agarwal Ravi P. , O′Regan Donal , Lakshmikantham V.
Published: September 2005

A general existence theory is presented for initial value problems where our nonlinearity may be singular in its dependent variable and may also change sign.
A general theory of rotorcraft trim
Authors: Peters David A. , Barwey Dinesh
Published: September 2005

In this paper we offer a general theory of rotorcraft trim. The theory is set in the context of control theory. It allows for completely arbitrary trim controls and trim settings for multi‐rotor aircraft with tests to ensure that a system is trimmable. In addition, the theory allows for “optimal trim” in which some variable is minimized or maximized rather than set to a specified value. The theory shows that sequential trim cannot work for free flight. The theory is not tied to any particular trim algorithm; but, in this paper, it is exercised with periodic shooting to show how free‐flying rotorcraft can be trimmed in a variety of ways (zero yaw, zero pitch, zero roll, minimum power, etc.) by use of the general theory. The paper also discusses applications to harmonic balance and
auto‐pilot trim techniques.
A note on the convergence of quantizers
Authors: Hall Eric B.
Published: September 2005

Several questions concerning the convergence of quantized estimators are considered based upon points of accuracy. Examples are considered in which quantizers converge and in which they fail to converge, and points of accuracy are shown to provide explanations for both types of behavior.
Partial least‐squares: Theoretical issues and engineering applications in signal processing
Authors: Ham Fredric M. , Kostanic Ivica
Published: September 2005

In this paper we present partial least‐squares (PLS), which is a statistical modeling method used extensively in
analytical chemistry for quantitatively analyzing spectroscopic data. Comparisons are made between classical
least‐squares (CLS) and PLS to show how PLS can be used in certain engineering signal processing applications.
Moreover, it is shown that in certain situations when there exists a linear relationship between the independent
and dependent variables, PLS can yield better predictive performance than CLS when it is not desirable to use
all of the empirical data to develop a calibration model used for prediction. Specifically, because PLS is a factor analysis method, optimal selection of the number of PLS factors can result in a calibration model whose
predictive performance is considerably better than CLS. That is, factor analysis (rank reduction) allows only those features of the data that are associated with information of interest to be retained for development of the calibration model, and the remaining data associated with noise are discarded. It is shown that PLS can yield physical insight into the system from which empirical data has been collected. Also, when there exists a non‐linear cause‐and‐effect relationship between the independent and dependent variables, the PLS calibration model can yield prediction errors that are much less than those for CLS. Three PLS application examples are given and the results are compared to CLS. In one example, a method is presented using PLS for parametric system identification. Using PLS for system identification allows simultaneous estimation of the system dimension and the system parameter vector associated with a minimal realization of the system.
Vibration suppression in a flexible gyroscopic system using modal coupling strategies
Authors: Siddiqui Sultan A. Q. , Golnaraghi M. Farid
Published: September 2005

Several recent studies have shown that vibrations in a two‐degree‐of‐freedom system can be suppressed by using modal coupling based control techniques. This involves making the first two natural frequencies commensurable (e.g, in a ratio of 1:1 or 1:2) to establish a state of Internal Resonance (IR). When the system exhibits IR, vibrations in the two directions are strongly coupled resulting in a beat phenomenon. Upon introducing damping in one direction, oscillations in both directions can be quickly suppressed. In this paper we consider vibration suppression of a flexible two‐degree‐of‐freedom gyroscopic system using 1:1 and 1:2 IR. The possibility of using 1:1 and 1:2 IR to enhance the coupling in the system is established analytically using the perturbation method of multiple scales. The results of IR based control strategy are compared with a new method, which is based on tuning the system parameters to make the mode shapes identical. Results indicate that this new technique is more efficient and easy to implement than IR based control strategies. Another advantage of this method is that there is no restriction on the frequencies as in the case of IR. Finally, a control torque is obtained which on application automatically tunes the system parameters to establish modal coupling.
Discrete‐time adaptive control using a sliding mode
Authors: Semba Tetsuo , Furuta Katsuhisa
Published: September 2005

Adaptive control using a sliding mode in discrete time systems is proposed as a means of achieving robustness with respect to parameter variations, fast tracking to a desired trajectory, and fast parameter convergence, without increasing the chattering of the control inputs. We first prove the stability of a system in which the control inputs consist of equivalent control driven by the adaptive control law and bounded discontinuous control. The discontinuous control driven by the sliding control law is then obtained so that the output error quickly converges to zero. Finally, the performance improvements obtained by adding the sliding mode control input are shown through computer simulations.
Asymptotic performance characteristics of CSMA and CSMA ← CD → CSMA/CD networks
Authors: Lim J.-T
Published: September 2005

This paper presents analytical formulae for performance evaluation of CSMA and CSMA/CD networks with a finite number of buffered users. The asymptotic theory developed in [1] is extended to local area networks so as to investigate the resulting steady state throughput, time delay, probability of blocking, and local stability of each equilibrium. In particular, the stabilization of CSMA and CSMA/CD networks is considered, i.e., how to choose the transmission probability so that a unique steady state with relatively high performance characteristics is achieved.
Impulsive controllability of linear dynamical systems with applications to maneuvers of spacecraft
Authors: Liu Xinzhi , Willms Allan R.
Published: September 2005

Necessary and sufficient conditions for impulsive controllability of linear dynamical systems are obtained, which provide a novel approach to problems that are basically defined by continuous dynamical systems, but on which only discrete‐time actions are exercised. As an application, impulsive maneuvering of a spacecraft is discussed.
Nonlinear filtering for LIDAR signal processing
Authors: Lainiotis D. G. , Papaparaskeva Paraskevas , Plataniotis Kostas
Published: September 2005

LIDAR (Laser Integrated Radar) is an engineering problem of great practical importance in environmental monitoring sciences. Signal processing for LIDAR applications involves highly nonlinear models and consequently nonlinear filtering. Optimal nonlinear filters, however, are practically unrealizable. In this paper, the Lainiotis′s multi‐model partitioning methodology and the related approximate but effective nonlinear filtering algorithms are reviewed and applied to LIDAR signal processing. Extensive simulation and performance evaluation of the multi‐model partitioning approach and its application to LIDAR signal processing shows that the nonlinear partitioning methods are very effective and significantly superior to the nonlinear extended Kalman filter (EKF), which has been the standard nonlinear filter in past engineering applications.
Accommodation of zero‐valued characteristic roots in the classical solution expression for linear, homogeneous, constant‐coefficient difference equations
Authors: Johnson C. D.
Published: September 2005

Linear, constant‐coefficient difference equations play a central role in many areas of engineering, where cases involving repeated zero-valued characteristic roots are sometimes of particular interest. Unfortunately, the classical solution expression presented in the mathematical literature of difference equations is not valid for this latter case. In this paper we develop a unique generalization of the classical solution expression for linear, constant‐coefficient, homogeneous difference equations that accommodates the most general case of repeated zero‐valued characteristic roots, thereby “completing” the classical theory. A worked example is presented to illustrate our result.
On the structure of the deflagration for the generalized reaction‐rate model
Authors: Bush W. B. , Krishnamurthy L.
Published: September 2005

The structure of the deflagration is examined by means of an asymptotic analysis of the physical‐plane boundary‐value problem, with Lewis‐Semenov number unity, in the limit of the activation‐temperature ratio, β = Ta/Tb, greater than order unity, for the generalized reaction‐rate‐model case of (1) the heat‐addition‐temperature ratio, α = (Tb − Tu)/Tu, of order unity [where Ta, Tb, and Tu are the activation, adiabatic‐flame (and/or burned‐gas), and unburned‐gas temperatures, respectively]; and (2) the exponent, a, which characterizes the pre‐exponential thermal dependence of the reaction‐rate term, unity. This examination indicates that the deflagration has a four‐region structure. To obtain a uniformly valid solution of the problem,
in addition to the (classical) upstream diffusion‐convection and downstream diffusion‐reaction regions, a far‐upstream (or cold‐boundary) region and a far‐downstream (or hot‐boundary) region must be introduced.
Linear programming with positive semi‐definite matrices
Authors: Lasserre J. B.
Published: September 2005

We consider the general linear programming problem over the cone of positive semi‐definite matrices. We first provide a simple sufficient condition for existence of optimal solutions and absence of a duality gap without requiring existence of a strictly feasible solution. We then simply characterize the analogues of the standard concepts of linear programming, i.e., extreme points, basis, reduced cost, degeneracy, pivoting step as well as a Simplex‐like algorithm.
Stability of stochastic systems with jumps
Authors: Boukas E. K. , Yang H.
Published: September 2005

This paper deals with stochastic stability of systems with Markovian jumps and Brownian motion. Mainly, we present sufficient conditions for quadratic stabilization of Ito type stochastic linear and nonlinear systems with Markovian jumps and Brownian motion using state feedback control. We also prove the guaranteed cost property of the proposed control strategy for the linear case.
Robust stability of nonlinear piecewise deterministic systems under matching conditions
Authors: Boukas E. K. , Yang H.
Published: September 2005

This paper deals with the robustness of the class of nonlinear piecewise deterministic systems with unknown but bounded uncertainties. Under the assumption that all the modes of the markovian jump process (disturbance) communicate, the complete access to the system state and the boundedness of the uncertainties, a sufficient condition for stochastic stability of this class of systems is given. An example is presented to validate the proposed results.
Nonlinear unsteady supersonic flow analysis for slender bodies of revolution: Theory
Authors: Panayotounakos D. E. , Markakis M.
Published: September 2005

We construct analytical solutions for the problem of nonlinear supersonic flow past slender bodies of revolution due to small amplitude oscillations. The method employed is based on the splitting of the time dependent small perturbation equation to a nonlinear time independent partial differential equation (P.D.E.) concerning the steady flow, and a linear time dependent one, concerning the unsteady flow. Solutions in the form of three parameters family of surfaces for the first equation are constructed, while solutions including one arbitrary function for the second equation are extracted. As an application the evaluation of the small perturbation velocity resultants for a flow past a right circular cone is obtained making use of convenient boundary and initial conditions in accordance with the physical problem.
M/G/1 vacation model with limited service discipline and hybrid switching‐on policy
Authors: Babitsky Alexander V.
Published: September 2005

The author studies an M/G/1 queueing system with multiple vacations. The server is turned off in accordance with the K‐limited discipline, and is turned on in accordance with the T‐N‐hybrid policy. This is to say that the server will begin a vacation from the system if either the queue is empty or K
customers were served during a busy period. The server idles until it finds at least N waiting units upon return from a vacation.

Formulas for the distribution generating function and some characteristics of the queueing process are derived. An optimization problem is discussed.
A 2D finite element procedure for magnetic field analysis taking into account a vector Preisach model
Authors: Dupré Luc R. , Van Keer Roger , Melkebeek Jan A. A.
Published: September 2005

The main purpose of this paper is to incorporate a refined hysteresis model, viz. a vector Preisach model, in 2D magnetic field computations. To this end the governing Maxwell equations are rewritten in a suitable way, which allows to take into account the proper magnetic material parameters and, moreover, to pass to a variational formulation. The variational problem is solved numerically by a FE approximation, using a quadratic mesh, followed by the time discretisation based upon a modified Cranck Nicholson algorithm. The latter includes a suitable iteration procedure to deal with the nonlinear hysteresis behaviour. Finally, the effectiveness of the presented mathematical tool has been confirmed by several numerical experiments.
Identification of hysteretic control influence operators representing smart actuators part I: Formulation
Authors: Banks H. T. , Kurdila A. J. , Webb G.
Published: September 2005

A large class of emerging actuation devices and materials exhibit strong hysteresis characteristics during their routine operation. For example, when piezoceramic actuators are operated under the influence of strong electric fields, it is known that the resulting input–output behavior is hysteretic. Likewise, when shape memory alloys are resistively heated to induce phase transformations, the input–output response at the structural level is also known to be strongly hysteretic. This paper investigates the mathematical issues that arise in identifying a class of hysteresis operators that have been employed for modeling both piezoceramic actuation and shape memory alloy actuation. Specifically, the identification of a class of distributed hysteresis operators that arise in the control influence operator of a class of second order evolution equations is investigated. In Part I of this paper we introduce distributed,hysteretic control influence operators derived from smoothed Preisach operators and generalized hysteresis operators derived from results of Krasnoselskii and Pokrovskii. For these classes, the identification problem in which we seek to characterize the hysteretic control influence operator can be expressed as an ouput least square minimization over probability measures defined on a compact subset of a closed half‐plane. In Part II of this paper, consistent and convergent approximation methods for identification of the measure characterizing the hysteresis are derived.
Robust performance results for discrete‐time systems
Authors: Mahmoud Magdi S.
Published: September 2005

The problems of robust performance and feedback control synthesis for a class of linear discrete‐time systems with time‐varying parametric uncertainties are addressed in this paper. The uncertainties are bound and have a linear matrix fractional form. Based on the concept of strongly robust H∞‐performance criterion, results of robust stability and performance are developed and expressed in easily computable linear matrix inequalities. Synthesis of robust feedback controllers is carried out for several system models of interest.
On a bulk queueing system with impatient customers
Authors: Tadj Lotfi , Benkherouf Lakdere , Aggoun Lakhdar
Published: September 2005

We consider a bulk arrival, bulk service queueing system. Customers are served in batches of r
units if the queue length is not less than r. Otherwise, the server delays the service until the number of units in the queue reaches or exceeds level r. We assume that unserved customers may get impatient and leave the system. An ergodicity condition and steady‐state probabilities are derived. Various system characteristics are also computed.
Antioptimization of earthquake exitation and response
Authors: Zuccaro G. , Elishakoff I. , Baratta A.
Published: September 2005

The paper presents a novel approach to predict the response of earthquake‐excited structures. The earthquake excitation is expanded in terms of series of deterministic functions. The coefficients of the series are represented as a point in N‐dimensional space. Each available ccelerogram at a certain site is then represented as a point in the above space, modeling the available fragmentary historical data. The minimum volume ellipsoid, containing all points, is constructed. The ellipsoidal models of uncertainty, pertinent to earthquake excitation, are developed. The maximum response of a structure, subjected to the earthquake excitation, within ellipsoidal modeling of the latter, is determined. This procedure of determining least favorable response was termed in the literature (Elishakoff, 1991) as an antioptimization. It appears that under inherent uncertainty of earthquake excitation, antioptimization analysis is a viable alternative to stochastic approach.
Time‐delay polynomial networks and rates of approximation
Authors: Sandberg Irwin W.
Published: September 2005

We consider a large family of finite memory causal time‐invariant maps G from an input set S to a set of
ℝ‐valued functions, with the members of both sets of functions defined on the nonnegative integers, and we give an upper bound on the error in approximating a G using a two‐stage structure consisting of a tapped delay line and a static polynomial network N . This upper bound depends on the degree of the multivariable polynomial that characterizes N. Also given is a lower bound on the worst‐case error in approximating a G using polynomials of a fixed maximum degree. These upper and lower bounds differ only by a multiplicative constant. We also give a corresponding result for the approximation of not‐necessarily‐causal input–output maps with inputs and outputs that may depend on more than one variable. This result is of interest, for example, in connection with image processing.
Stability of suspension bridge I: Aerodynamic and structural damping
Authors: Ahmed N. U. , Harbi H.
Published: September 2005

In this paper we consider a few dynamic models of suspension bridge described by partial differential equations with linear and nonlinear couplings. We study analytically the stability properties of these models and the relative effectiveness of aerodynamic and structural damping. Increasing aerodynamic or structural damping indefinitely does not necessarily increase the decay rate indefinitely. In view of possible disastrous effects of high wind, structural damping is preferable to aerodynamic (viscous) damping. These results are illustrated by numerical simulation.
On a numerical model for diffusion‐controlled growth and dissolution of spherical precipitates
Authors: Van Keer R. , Kačur J.
Published: September 2005

This paper deals with a numerical model for the kinetics of some diffusion‐limited phase transformations. For the growth and dissolution processes in 3D we consider a single spherical precipitate at a constant and uniform concentration, centered in a finite spherical cell of a matrix, at the boundary of which there is no mass transfer, see also Asthana and Pabi [1] and Caers [2].

The governing equations are the diffusion equation (2nd Fick′s law) for the concentration of dissolved element in the matrix, with a known value at the precipitate‐matrix interface, and the flux balans (1st Fick′s law) at this interface. The numerical method, outlined for this free boundary value problem (FBP), is based upon a fixed domain transformation and a suitably adapted nonconforming finite element technique for the space discretization. The algorithm can be implemented on a PC. By numerous experiments the method is shown to give accurate numerical results.
Design of robust controller for linear systems with Markovian jumping parameters
Authors: Benjelloun K. , Boukas E. K. , Costa O. L. V. , Shi P.
Published: September 2005

This paper deals with the robustness of the class of uncertain linear systems with
Markovian jumping parameters (ULSMJP). The uncertainty is taken to be time‐varying norm bounded. Under the assumptions of the boundedness of the uncertainties and the complete access to the system′s state and its modes, a sufficient condition for stochastic stabilizability of this class of systems is established. An example is provided to demonstrate the usefulness of the proposed theoretical results.
A representation theorem for linear discrete‐space systems
Authors: Sandberg Irwin W.
Published: September 2005

The cornerstone of the theory of discrete‐time single‐input single‐output linear systems is the idea that every such system has an input–output map H that can be represented by a convolution or the familiar generalization of a convolution. This thinking involves an oversight which is corrected in this note by adding an additional term to the representation.
Torsional and longitudinal vibration of suspension bridge subject to aerodynamic forces
Authors: Ahmed N. U. , Harbi H.
Published: September 2005

In this paper we consider a dynamic model of suspension bridge governed by a pair of coupled partial differential equations which describe both torsional and longitudinal vibration of the road bed. The vertical and torsional motions are coupled through a nonlinear operation with the nonlinearity arising from loss of tension in the vertical cables supporting the decks. We study the impact of wind forces on the stability of motion of this system both in the absence and presence of viscous and structural damping. The results are illustrated by numerical simulation.
Adaptive filters for color image processing
Authors: Papanikolaou V. , Plataniotis K. N. , Venetsanopoulos A. N.
Published: September 2005

The color filters that are used to attenuate noise are usually optimized to perform extremely well when dealing with certain noise distributions. Unfortunately it is often the case that the noise corrupting the image is not known. It is thus beneficial to know a priori the type of noise corrupting the image in order to select the optimal filter. A method of extracting and characterizing the noise within a digital color image using the generalized Gaussian probability density function (pdf) (B.D. Jeffs and W.H. Pun, IEEE Transactions on Image Processing, 4(10), 1451–1456, 1995 and Proceedings of the Int. Conference on Image Processing, 465–468, 1996), is presented. In this paper simulation results are included to demonstrate the effectiveness of the proposed methodology.
A model discrimination method for processes with different memory structure
Authors: Freidlin Mark , Pfeiffer Ruth
Published: September 2005

In this paper we develop a test for determining whether the observed sample path comes from a system with hysteresis perturbed by noise, or if it arises from a system governed by an ordinary differential equation with the same noise. A large sample size test is constructed, which is appropriate in many practical situations. Two models are
considered as alternatives to the hysteresis model. An asymptotic expression for the
cutoff point of the test is found using a version of the central limit theorem.
Boundary element method for internal axisymmetric flow
Authors: Gokhman Alexander , Gokhman Dmitry
Published: September 2005

We present an accurate fast method for the computation of potential internal axisymmetric flow based on the boundary element technique. We prove that the computed velocity field asymptotically satisfies reasonable boundary conditions at infinity for various types of inlet/exit. Computation of internal axisymmetric potential flow is an
essential ingredient in the three‐dimensional problem of computation of velocity fields
in turbomachines. We include the results of a practical application of the method to
the computation of flow in turbomachines of Kaplan and Francis types.
A problem related to the hall effect in a semiconductor with anelectrode of an arbitrary shape
Authors: Krutitskii P. A. , Krutitskaya N. Ch. , Malysheva G. Yu.
Published: September 2005

A problem on electric current in a semiconductor film from an electrode of an arbitrary shape is studied in the presence of a magnetic field. This situation describes the Hall effect, which indicates the deflection of electric, current from electric field in a semiconductor. From mathematical standpoint we consider the skew derivative problem for harmonic functions in the exterior of an open arc in a plane. By means of potential theory the problem is reduced to the Cauchy singular integral equation and next to the Fredholm equation of the 2nd kind which is uniquely solvable. The solution of the integral equation can be computed by standard codes by discretization and inversion of the matrix. The uniqueness and existence theorems are formulated.
Multidisciplinary design optimization of film‐cooled gas turbineblades
Authors: Talya Shashishekara S. , Rajadas J. N. , Chattopadhyay A.
Published: September 2005

Design optimization of a gas turbine blade geometry for effective film cooling toreduce the blade temperature has been done using a multiobjective optimization formulation. Three optimization formulations have been used. In the first, the average blade temperature is chosen as the objective function to be minimized. An upper bound constraint has been imposed on the maximum blade temperature. In the second, the maximum blade temperature is chosen as the objective function to be minimized with an upper bound constraint on the average blade temperature. In the third formulation, the blade average and maximum temperatures are chosen as objective functions.
Shape optimization is performed using geometric parameters associated with film
cooling and blade external shape. A quasi‐three‐dimensional Navier–Stokes solver for turbomachinery flows is used to solve for the flow field external to the blade with
appropriate modifications to incorporate the effect of film cooling. The heat transfer
analysis for temperature distribution within the blade is performed by solving the heat
diffusion equation using the finite element method. The multiobjective Kreisselmeier–Steinhauser function approach has been used in conjunction with an approximate
analysis technique for optimization. The results obtained using both formulations are
compared with reference geometry. All three formulations yield significant reductions
in blade temperature with the multiobjective formulation yielding largest reduction in
blade temperature.
A model of frontal polymerization using complex initiation
Authors: Goldfeder P. M. , Volpert V. A.
Published: September 2005

Frontal polymerization is a process in which a spatially localized reaction zone propagates into a monomer, converting it into a polymer. In the simplest case of free‐radical polymerization, a mixture of monomer and initiator is placed in a test tube. A reaction is then initiated at one end of the tube. Over time, a self‐sustained thermal wave, in which chemical conversion occurs, is produced. This phenomenon is possible because of the highly exothermic nature of the polymerization reactions.

Though there are certain advantages to this polymerization process over the more traditional methods, one of the drawbacks is that conversion tends to be incomplete. One way to increase conversion is by using greater amounts of initiator. The disadvantage to using this method is that more initiator results in the production of more free radicals, leading to large numbers of undesirably short polymer chains. A second method is to use a mixture of unstable and stable initiators. In this paper we develop and study a mathematical model of the propagation of free‐radical polymerization fronts using such a complex initiation. We compare the propagation velocity, maximum temperature and degree of conversion of fronts with a stable initiator, an unstable initiator and a mixture of the two. In addition, we examine how altering the stability of the stable initiator affects these quantities. We show that it is indeed the case that a mixture of unstable and stable initiators does have many advantages over using either type of initiator individually, in agreement with the existing experimental data.
Some insights into the regularization of III‐posed problems
Authors: Hańćkowiak J.
Published: September 2005

In this paper a simple introduction to the problem of the regularization of ill‐posed problems (IPP) is presented. We describe three regularization methods with simple examples which illustrate the principle that for “bad” equations it is unprofitable to
carry out exact computations.
Method of interior boundaries in a mixed problem of acoustic scattering
Authors: Krutitskii P. A.
Published: September 2005

The mixed problem for the Helmholtz equation in the exterior of several bodies (obstacles) is studied in 2 and 3 dimensions. The Dirichlet boundary condition is given on some obstacles and the impedance boundary condition is specified on the rest. The problem is investigated by a special modification of the boundary integral equation method. This modification can be called ‘Method of interior boundaries’, because
additional boundaries are introduced inside scattering bodies, where impedance
boundary condition is given. The solution of the problem is obtained in the form of
potentials on the whole boundary. The density in the potentials satisfies the uniquely
solvable Fredholm equation of the second kind and can be computed by standard
codes. In fact our method holds for any positive wave numbers. The Neumann,
Dirichlet, impedance problems and mixed Dirichlet–Neumann problem are particular
cases of our problem.
Linear‐quadratic optimization and some general hypotheses onoptimal control
Authors: Rozonoer L. I.
Published: September 2005

Necessary and sufficient conditions for existence of optimal control for all initial data are proved for LQ‐optimization problem. If these conditions are fulfilled, necessary and sufficient conditions of optimality are formulated. Basing on the results, some general hypotheses on optimal control in terms of Pontryagin′s maximum condition and Bellman′s equation are proposed.
Monotone methods for solving a boundary value problem of secondorder discrete system
Authors: Wang Yuan-Ming , Agarwal Ravi P.
Published: September 2005

A new concept of a pair of upper and lower solutions is introduced for a boundary value problem of second order discrete system. A comparison result is given. An existence theorem for a solution is established in terms of upper and lower solutions. A monotone iterative scheme is proposed, and the monotone convergence rate of the iteration is compared and analyzed. The numerical results are given.
Vortex formation and stability analysis for shear flows overcombined spatially and temporally structured walls
Authors: Riahi D. N.
Published: September 2005

Benney′s theory of evolution of disturbances in shear flows over smooth and flat boundary is extended to study for shear flows over combined spatially and temporally corrugated walls. Perturbation and multiple‐scales analyses are employed for the case where both amplitude of the corrugations and the amplitude of wave motion are small. Analyses for instability of modulated mean shear flows with respect to spanwise‐periodic disturbance rolls and for the subsequent vortex formation and vortex stability
are presented, and the effects of the corrugated walls on the resulting flow and vortices are determined. It is found that particular corrugated walls can originate and control the longitudinal vortices, while some other types of corrugated walls can enhance instability of such vortices.
A queueing model for error control of partial buffer sharing inATM
Authors: Ahn Boo Yong , Lee Ho Woo
Published: September 2005

We model the error control of the partial buffer sharing of ATM by a queueing system M1, M2/G/1/K + 1 with threshold and instantaneous Bernoulli feedback. We first derive the system equations and develop a recursive method to compute the loss probabilities at an arbitrary time epoch. We then build an approximation scheme to compute the mean waiting time of each class of cells. An algorithm is developed for finding the optimal threshold and queue capacity for a given quality of service.