Characterizations of the solution sets of pseudoinvex programs and variational inequalities

Author name used in this publication: Heungwing Lee2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Optimality conditions for approximate solutions in multiobjective optimization problems

Version of RecordPublishe

Strong and Δ-convergence for mixed type total asymptotically nonexpansive mappings in CAT(0) spaces

2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

On the equivalence between some kinds of implicit and explicit iterations with applications

Author name used in this publication: HW Joseph LeeVersion of RecordPublishe

Strong and weak convergence theorems for an infinite family of lipschitzian pseudocontraction mappings in banach spaces

Author name used in this publication: H. W. Joseph Lee2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A generalization and improvement of Chidume theorems for total asymptotically nonexpansive mappings in Banach spaces

Author name used in this publication: HW Joseph LeeVersion of RecordPublishe

Coherent feedback control of linear quantum optical systems via squeezing and phase shift

2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordRGC5203/10EPublishe

A Hybrid Time-Scaling Transformation for Time-Delay Optimal Control Problems

In this paper, we consider a class of nonlinear time-delay optimal control problems with canonical equality and inequality constraints. We propose a new computational approach, which combines the control parameterization technique with a hybrid time-scaling strategy, for solving this class of optimal control problems. The proposed approach involves approximating the control variables by piecewise constant functions, whose heights and switching times are decision variables to be optimized. Then, the resulting problem with varying switching times is transformed, via a new hybrid time-scaling strategy, into an equivalent problem with fixed switching times, which is much preferred for numerical computation. Our new time-scaling strategy is hybrid in the sense that it is related to two coupled time-delay systems—one defined on the original time scale, in which the switching times are variable, the other defined on the new time scale, in which the switching times are fixed. This is different from the conventional time-scaling transformation widely used in the literature, which is not applicable to systems with time-delays. To demonstrate the effectiveness of the proposed approach, we solve four numerical examples. The results show that the costs obtained by our new approach are lower, when compared with those obtained by existing optimal control methods