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Self-similar factor approximants for evolution equations and boundary-value problems
The method of self-similar factor approximants is shown to be very convenient
for solving different evolution equations and boundary-value problems typical
of physical applications. The method is general and simple, being a
straightforward two-step procedure. First, the solution to an equation is
represented as an asymptotic series in powers of a variable. Second, the series
are summed by means of the self-similar factor approximants. The obtained
expressions provide highly accurate approximate solutions to the considered
equations. In some cases, it is even possible to reconstruct exact solutions
for the whole region of variables, starting from asymptotic series for small
variables. This can become possible even when the solution is a transcendental
function. The method is shown to be more simple and accurate than different
variants of perturbation theory with respect to small parameters, being
applicable even when these parameters are large. The generality and accuracy of
the method are illustrated by a number of evolution equations as well as
boundary value problems.Comment: Latex file, 27 pages, 2 figures, 5 table
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A Framework for Globally Optimizing Mixed-Integer Signomial Programs
Mixed-integer signomial optimization problems have broad applicability in engineering. Extending the Global Mixed-Integer Quadratic Optimizer, GloMIQO (Misener, Floudas in J. Glob. Optim., 2012. doi:10.1007/s10898-012-9874-7), this manuscript documents a computational framework for deterministically addressing mixed-integer signomial optimization problems to ε-global optimality. This framework generalizes the GloMIQO strategies of (1) reformulating user input, (2) detecting special mathematical structure, and (3) globally optimizing the mixed-integer nonconvex program. Novel contributions of this paper include: flattening an expression tree towards term-based data structures; introducing additional nonconvex terms to interlink expressions; integrating a dynamic implementation of the reformulation-linearization technique into the branch-and-cut tree; designing term-based underestimators that specialize relaxation strategies according to variable bounds in the current tree node. Computational results are presented along with comparison of the computational framework to several state-of-the-art solvers. © 2013 Springer Science+Business Media New York
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