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11
Validated solutions of initial value problems for parametric ODEs
 Appl Num Math
"... Accepted for publication in Applied Numerical Mathematics In initial value problems for ODEs with intervalvalued parameters and/or initial values, it is desirable in many applications to be able to determine a validated enclosure of all possible solutions to the ODE system. Much work has been done ..."
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Cited by 27 (10 self)
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Accepted for publication in Applied Numerical Mathematics In initial value problems for ODEs with intervalvalued parameters and/or initial values, it is desirable in many applications to be able to determine a validated enclosure of all possible solutions to the ODE system. Much work has been done for the case in which initial values are given by intervals, and there are available software packages that deal with this case. However, less work has been done on the case in which parameters are given by intervals. We describe here a new method for obtaining validated solutions of initial value problems for ODEs with intervalvalued parameters. The method also accounts for intervalvalued initial values. The effectiveness of the method is demonstrated using several numerical examples involving parametric uncertainties.
Linear systems with large uncertainties, with applications to truss structures
, 2006
"... Linear systems whose coefficients have large uncertainties arise routinely in finite element calculations for structures with uncertain geometry, material properties, or loads. However, a true worst case analysis of the influence of such uncertainties was previously possible only for very small sys ..."
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Cited by 20 (6 self)
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Linear systems whose coefficients have large uncertainties arise routinely in finite element calculations for structures with uncertain geometry, material properties, or loads. However, a true worst case analysis of the influence of such uncertainties was previously possible only for very small systems and uncertainties, or in special cases where the coefficients do not exhibit dependence. This paper presents a method for computing rigorous bounds on the solution of such systems, with a computable overestimation factor that is frequently quite small. The merits of the new approach are demonstrated by computing realistic bounds for some large, uncertain truss structures, some leading to linear systems with over 5000 variables and over 10000 interval parameters, with excellent bounds for up to about 10 % input uncertainty. Also discussed are some counterexamples for the performance of traditional approximate methods for worst case uncertainty analysis.
Exclusion Regions for Systems of Equations
 SIAM J. NUM. ANALYSIS
, 2003
"... Branch and bound methods for finding all zeros of a nonlinear system of equations in a box frequently have the difficulty that subboxes containing no solution cannot be easily eliminated if there is a nearby zero outside the box. This has the effect that near each zero, many small boxes are created ..."
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Cited by 11 (7 self)
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Branch and bound methods for finding all zeros of a nonlinear system of equations in a box frequently have the difficulty that subboxes containing no solution cannot be easily eliminated if there is a nearby zero outside the box. This has the effect that near each zero, many small boxes are created by repeated splitting, whose processing may dominate the total work spent on the global search. This paper discusses the reasons for the occurrence of this socalled cluster effect, and how to reduce the cluster effect by defining exclusion regions around each zero found, that are guaranteed to contain no other zero and hence can safely be discarded. Such exclusion regions are traditionally constructed using uniqueness tests based on the Krawczyk operator or the Kantorovich theorem. These results are reviewed; moreover, refinements are proved that significantly enlarge the size of the exclusion region. Existence and uniqueness tests are also given.
Interval Methods for Nonlinear Equation Solving Applications
"... Interval analysis provides techniques that make it possible to determine all solutions to a nonlinear algebraic equation system and to do so with mathematical and computational certainty. Such methods are based on the processing of granules in the form of intervals and thus can be regarded as one f ..."
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Cited by 3 (0 self)
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Interval analysis provides techniques that make it possible to determine all solutions to a nonlinear algebraic equation system and to do so with mathematical and computational certainty. Such methods are based on the processing of granules in the form of intervals and thus can be regarded as one facet of granular computing. We review here some of the key concepts used in these methods and then focus on some specific application areas, namely ecological modeling, transition state analysis, and the modeling of phase equilibrium. 1
Interval Computations as an Important Part of Granular Computing: An Introduction
 in Handbook of Granular Computing, Chapter 1
, 2008
"... This chapter provides a general introduction to interval computations, especially to interval computations as an important part of granular computing. ..."
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Cited by 3 (1 self)
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This chapter provides a general introduction to interval computations, especially to interval computations as an important part of granular computing.
Improving interval enclosures
, 2009
"... This paper serves as background information for the Vienna proposal for interval standardization, explaining what is needed in practice to make competent use of the interval arithmetic provided by an implementation of the standard to be. Discussed are methods to improve the quality of interval encl ..."
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Cited by 2 (0 self)
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This paper serves as background information for the Vienna proposal for interval standardization, explaining what is needed in practice to make competent use of the interval arithmetic provided by an implementation of the standard to be. Discussed are methods to improve the quality of interval enclosures of the range of a function over a box, considerations of possible hardware support facilitating the implementation of such methods, and the results of a simple interval challenge that I had posed to the reliable computing mailing list on November 26, 2008. Also given is an example of a bound constrained global optimization problem in 4 variables that has a 2dimensional continuum of global minimizers. This makes standard branch and bound codes extremely slow, and therefore may serve as a useful degenerate test problem.
SOME IDEAS TOWARDS GLOBAL OPTIMIZATION OF IMPROVED EFFICIENCY
"... Scope of the talk. The problem is in a rather general form: (P) minimize 0 ( ) x ϕ ..."
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Scope of the talk. The problem is in a rather general form: (P) minimize 0 ( ) x ϕ
approximation errors
, 2010
"... For purposes of actual evaluation, mathematical functions f are commonly replaced by approximation polynomials p. Examples include floatingpoint implementations of elementary functions, quadrature or more theoretical proof work involving transcendental functions. Replacing f by p induces a relative ..."
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For purposes of actual evaluation, mathematical functions f are commonly replaced by approximation polynomials p. Examples include floatingpoint implementations of elementary functions, quadrature or more theoretical proof work involving transcendental functions. Replacing f by p induces a relative error ε = p/f −1. In order to ensure the validity of the use of p instead of f, the maximum error, i.e. the supremum norm ‖ε‖ ∞ must be safely bounded above. Numerical algorithms for supremum norms are efficient but cannot offer the required safety. Previous validated approaches often require tedious manual intervention. If they are automated, they have several drawbacks, such as the lack of quality guarantees. In this article a novel, automated supremum norm algorithm with a priori quality is proposed. It focuses on the validation step and paves the way for formally certified supremum norms.
and
, 2006
"... Linear systems with large uncertainties, with applications to truss structures ..."
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Linear systems with large uncertainties, with applications to truss structures
On solving mixedinteger constraint satisfaction problems
"... with unbounded variables ..."
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