Descriptor systems consisting of a large number of differential-algebraic equations (DAEs) usually arise from the discretization of partial differential-algebraic equations. This paper presents an efficient algorithm ...
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Descriptor systems consisting of a large number of differential-algebraic equations (DAEs) usually arise from the discretization of partial differential-algebraic equations. This paper presents an efficient algorithm for solving the coupled Sylvester equation that arises in converting a system of linear DAEs to ordinary differential equations. A significant computational advantage is obtained by exploiting the structure of the involved matrices. The proposed algorithm removes the need to solve a standard Sylvester equation or to invert a matrix. The improved performance of this new method over existing techniques is demonstrated by comparing the number of Floating-point operations and via numerical examples. (C) 2010 Elsevier Ltd. All rights reserved.
In this paper, a constitutive model for the unified description of rate dependent and rate independent material behavior is proposed. It is applicable to isotropic metals subjected to arbitrary thermomechanical loadin...
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In this paper, a constitutive model for the unified description of rate dependent and rate independent material behavior is proposed. It is applicable to isotropic metals subjected to arbitrary thermomechanical loading conditions at small strains. The focus of the model formulation is its validity for the full range of thermal and mechanical loading conditions to be covered in an industrial context by e.g. modern aero-engine designs. Consequently, the proposed model describes the material behavior on a macroscopic level covering the full temperature range from room temperature to the upper application limit under monotonic as well as cyclic loading. Special emphasis is also put on the correct representation of the observed ratcheting behavior. The most prominent features of the model are the combined treatment of both, rate dependent, as well as rate independent inelasticity through a limit surface concept, the description of primary, secondary and tertiary creep behavior and the application of an appropriate backstress evolution equation. A fully implicit integration algorithm for the proposed model is developed and implemented in connection with uniaxial integration point drivers as well as three alternative Finite Element packages. The parameters of the proposed model can be identified based on a limited number of complex cyclic tests and monotonic creep tests. After reporting on the fitting results for such tests for the Nickel-base superalloy IN718 the predictive capabilities of the proposed model are assessed for a number of isothermal and nonisothermal tests. Finally, the performance of the algorithmic implementation into the Finite Element packages is briefly addressed. (C) 2010 Elsevier Ltd. All rights reserved.
A new numerical procedure is proposed for the reconstruction of the shape and volume of unknown objects from measurements of their radiation in the far field. This procedure is a variant and the linear sampling method...
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A new numerical procedure is proposed for the reconstruction of the shape and volume of unknown objects from measurements of their radiation in the far field. This procedure is a variant and the linear sampling method has a very acceptable computational load and is fully automated. It is based on exploiting an iteratively computed truncated singular-value decomposition and heuristics to extract the desired signal from the background noise. Its performance on a battery of examples of different types is shown to be promising. Copyright (C) 2010 John Wiley & Sons, Ltd.
The problem of computation of the joint (generalized) spectral radius of matrix sets has been discussed in a number of publications. In this paper, an iteration procedure is considered that allows to build numerically...
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The problem of computation of the joint (generalized) spectral radius of matrix sets has been discussed in a number of publications. In this paper, an iteration procedure is considered that allows to build numerically Barabanov norms for the irreducible matrix sets and simultaneously to compute the joint spectral radius of these sets.
This work concentrates on the role of nonlinear models in engineering and science. The emphasis is primarily on engineering models with some comparisons between engineering models and scientific models. Several genera...
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ISBN:
(纸本)9781936338207
This work concentrates on the role of nonlinear models in engineering and science. The emphasis is primarily on engineering models with some comparisons between engineering models and scientific models. Several general principles and approaches used in solving nonlinear models are presented. Specific examples of nonlinear engineering models are used to illustrate the development and application of the general approaches.
A procedure for free-return trajectory generation in a simplified Earth-moon system is presented. With two-body and circular restricted three-body models, the algorithm constructs an initial guess of the translunar in...
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A procedure for free-return trajectory generation in a simplified Earth-moon system is presented. With two-body and circular restricted three-body models, the algorithm constructs an initial guess of the translunar injection state and time of flight. Once the initial trajectory is found, the Jacobian of the constraints is derived analytically using linear perturbation theory, and a square system of nonlinear equations is solved numerically to target Earth entry interface conditions leading to feasible free-return trajectories. No trial and error is required to generate the initial guess. Possible free returns include departures from both posigrade and retrograde Earth orbits coupled with circumlunar or cislunar flight, in and out of the Earth-moon plane.
Abstract We discuss the solution of the fault detection problem in presence of parametric uncertainties. The basic approach is an extension of the nullspace method for constant systems to the case of linear parameter ...
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Abstract We discuss the solution of the fault detection problem in presence of parametric uncertainties. The basic approach is an extension of the nullspace method for constant systems to the case of linear parameter varying (LPV) models. In a general setting, we consider the case when part of the unknown parameters are non-measurable and part of them are measurable. The resulting LPV-gain scheduled fault detection filter provides robustness with respect to both types of parametric uncertainties. Symbolic and numerical computational procedures which underlie the proposed synthesis approach are discussed.
Abstract We consider a dynamic programming approach for solving optimal control problems of sampled continuous-time systems. Robustness to bounded noise and model uncertainties is provided by formulating the problem i...
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Abstract We consider a dynamic programming approach for solving optimal control problems of sampled continuous-time systems. Robustness to bounded noise and model uncertainties is provided by formulating the problem in the framework of differential games. We use a semi-Lagrangian scheme for the computation of the value function and the state feedback control law for constrained infinite horizon optimal control problems. The approach is illustrated with the optimal control of linear systems and nonlinear systems subject to bounded disturbances.
Abstract The synthesis problem of fault detection and isolation (FDI) filters can be formulated as a model matching problem and solved using an H ∞ -norm optimization approach. A systematic procedure is proposed to c...
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Abstract The synthesis problem of fault detection and isolation (FDI) filters can be formulated as a model matching problem and solved using an H ∞ -norm optimization approach. A systematic procedure is proposed to choose appropriate filter specifications which guarantee the existence of proper and stable solutions of the model matching problem. This selection is integral part of a numerically reliable computational method to design H ∞ -optimal FDI filters. The proposed design approach is completely general, being applicable to both continuous- and discrete-time systems, and can easily handle even unstable and/or improper systems.
A new method is introduced for solving equality constrained nonlinear optimization problems. This method does not use a penalty function, nor a filter, and yet can be proved to be globally convergent to first-order st...
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A new method is introduced for solving equality constrained nonlinear optimization problems. This method does not use a penalty function, nor a filter, and yet can be proved to be globally convergent to first-order stationary points. It uses different trust-regions to cope with the nonlinearities of the objective function and the constraints, and allows inexact SQP steps that do not lie exactly in the nullspace of the local Jacobian. Preliminary numerical experiments on CUTEr problems indicate that the method performs well.
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