In this work we deal primarily with the derivation of various convergence estimates for some semidiscrete and fully discrete procedures which might be used in the approximation of exact solutions of initial-boundary v...
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In this work we deal primarily with the derivation of various convergence estimates for some semidiscrete and fully discrete procedures which might be used in the approximation of exact solutions of initial-boundary value problems with homogeneous Dirichlet boundary conditions for the Euler–Poisson–Darboux equation. These procedures include the ordinary Galerkin method based on conforming finite element subspaces as well as certain methods which do not require such restrictions. Although the equation is of hyperbolic type, the results are somewhat analogous to those known for parabolic equations. This is due to the presence of a limited “smoothing” property. This paper contains $L_2 $ estimates, maximum norm estimates, negative norm estimates, interior estimates of difference quotients and superconvergence estimates of the error. Most of the proofs are based on different modifications of an energy method, some of them intrinsically depend on the Weinstein recursion formulae and on known results for the associated elliptic problem. Several of these estimates are obtained for positive time under weak assumptions on the initial data.
作者：
Giona, MUniv Rome La Sapienza
Dipartimento Ingn Chim Ctr Interuniv Sistemi Disordinati & Frattali Ingn I-00184 Rome Italy
This article develops the definition of contour integrals over fractal curves in the plane by introducing the notion of oriented Iterated Function Systems and directional pseudo-measures. An expression for the contour...
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This article develops the definition of contour integrals over fractal curves in the plane by introducing the notion of oriented Iterated Function Systems and directional pseudo-measures. An expression for the contour integral of continuous functions over fractal interfaces is obtained through renormalization. As a result, a vector calculus on fractal interfaces which are boundaries of regular two-dimensional domains is developed by extending Green's theorem in the plane, also to fractal curves. The use of moment analysis makes it possible to obtain recursive relations and closed-form expressions for contour integrals of algebraic functions. Several physical applications are analyzed, including the properties of double-layer potentials and connections with the solution of the Dirichlet problem on bounded two-dimensional domains possessing fractal boundaries. (C) 1999 Elsevier Science Ltd. All rights reserved.
The model checking tools Uppaal and VerICS accept a description of a network of Timed Automata with Discrete Data (TADDs) as input. Thus, to verify a concurrent program written in Java by means of these tools, first a...
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The model checking tools Uppaal and VerICS accept a description of a network of Timed Automata with Discrete Data (TADDs) as input. Thus, to verify a concurrent program written in Java by means of these tools, first a TADD model of the program must be build. Therefore, we have developed the J2TADD tool that translates a Java program to a network of TADDs;the paper presents this tool. The J2TADD tool works in two stages. The first one consists in translation of a Java code to an internal assembly language (IAL). Then, the resulting assembly code is translated to a network of TADDs. We exemplify the use of the translator by means of the following well-known concurrency examples written in Java: race condition problem, dining philosophers problem, single sleeping barber problem and readers and writers problem.
A continuous recursive sliding mode controller (CRSMC) with extended disturbance observer (EDO) is proposed for the longitudinal dynamics of a generic hypersonic flight vehicle (HFV) in the presence of multiple uncert...
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A continuous recursive sliding mode controller (CRSMC) with extended disturbance observer (EDO) is proposed for the longitudinal dynamics of a generic hypersonic flight vehicle (HFV) in the presence of multiple uncertainties under control constraints. Firstly, sliding mode tracking controller based on a set of novel recursive sliding mode manifolds is presented, in which the chattering problem is reduced. The CRSMC possesses the merits of both nonsingular terminal sliding mode controller (NTSMC) and high-order sliding mode controller (HOSMC). Then antiwin dup controller is designed according to the input constraints, which adds a dynamic compensation factor in the CRSMC. For the external disturbance of system, an improved disturbance observer based on extended disturbance observer (EDO) is designed. The external disturbance is estimated by the disturbance observer and the estimated value is regarded as compensation in CRSMC for disturbance. The stability of the proposed scheme is analyzed by Lyapunov function theory. Finally, numerical simulation is conducted for cruise flight dynamics of HFV, where altitude is 110000 ft, velocity is 15060 ft/s, and Mach is 15. Simulation results show the validity of the proposed approach.
作者：
Symons, PR2
Manor Park Drive Finchampstead Wokingham Berkshire RG40 4XE England
This article presents a precise method for determining the instantaneous phase of a discrete-time (DT) sinusoid at any sample point and develops initial conditions (IC) functions supporting constant-amplitude, phase-c...
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This article presents a precise method for determining the instantaneous phase of a discrete-time (DT) sinusoid at any sample point and develops initial conditions (IC) functions supporting constant-amplitude, phase-continuous frequency changes. The direct-form, second-order recursive oscillator is a widely applied digital frequency synthesis technique. Phase is defined with respect to the most recent zero-phase point in the sinusoidal sequence. However, the trigonometric functions are not one-to-one on their whole domains. To obtain inverse functions, each trigonometric function is restricted to a subset of the domain where it is one-to-one. Contour lines represent lines of constant amplitude. As the starting phase varies, the fixed-transition sample index causes frequency transition to occur at all possible phase values. The error magnitude can be reduced by increasing sample word length and thereby reducing the quantization interval. Alternative recursive oscillator forms, such as the amplitude-normalized digital waveguide oscillator and modified coupled-form, offer intrinsically phase-continuous frequency transitions but greater arithmetic overhead in the kernel-recursive computations.
The purpose of this paper is to show the existence of a unique solution for some non-linear time-independent transport equations and to present a recursion formula for the construction of the solution by successive ap...
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The purpose of this paper is to show the existence of a unique solution for some non-linear time-independent transport equations and to present a recursion formula for the construction of the solution by successive approximations. An error estimate for the approximate solutions is given. The approach to the problem entails the use of a semi-inner product in a Banach space together with the contraction mapping theorem. Particular attention is given to the linear transport problem and a recursion formula for the construction of the solution is included.
A calculus and a model for a first-order functional language with sharing is presented. In most implementations of functional languages, argument subexpressions in a function application are shared to avoid their repe...
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A calculus and a model for a first-order functional language with sharing is presented. In most implementations of functional languages, argument subexpressions in a function application are shared to avoid their repeated evaluation. recursive functions are typically implemented using graphs with cycles. Compilers for these languages sometimes employ non-left-linear and left-cyclic rules for optimizations. A graph rewriting system (GRS) to address these concerns is developed. It is shown that a GRS without interfering rules is confluent. Along the lines of Levy's term model for the lambda-calculus, a semantics of such a GRS is also presented. An application of the term model to compiler optimizations is discussed.
Many physical systems can be modeled by a Wiener nonlinear model, which consists of a linear dynamic system followed by a nonlinear static function. This work is concerned with the identification of Wiener systems who...
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Many physical systems can be modeled by a Wiener nonlinear model, which consists of a linear dynamic system followed by a nonlinear static function. This work is concerned with the identification of Wiener systems whose output nonlinear function is assumed to be continuous and invertible. A recursive least squares algorithm is presented based on the auxiliary model identification idea. To solve the difficulty of the information vector including the unmeasurable variables, the unknown terms in the information vector are replaced with their estimates, which are computed through the preceding parameter estimates. Finally, an example is given to support the proposed method. (C) 2016 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.
We suggest an approach to provide time-varying parameter estimates in ARMA (Auto Regression Moving Average) models of a stochastic nature based on the use of the recursive version of the Instrumental Variable Method (...
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We suggest an approach to provide time-varying parameter estimates in ARMA (Auto Regression Moving Average) models of a stochastic nature based on the use of the recursive version of the Instrumental Variable Method (IVM) with a Matrix Forgetting Factor (MFF). We demonstrate that there exists the best selection of MFF minimizing the error strip bound. This optimal MFF depends in a complex manner on a group of unknown parameters. An adaptation procedure is suggested to obtain asymptotically this optimal value using only the available measurements. The adaptation procedure is based on one Gaussian smoothing technique. The combination of IVM with adaptive MFF is a tool for estimating the entries of a non-stationary parameter matrix involved in the ARMA model. An asymptotic analysis of the error matrix is presented. Simulation results demonstrate the effectiveness of the suggested approach.
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