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- M Taylor-Teeples, L Lin, +24 authors SM Brady
- Nature
- 2015

The plant cell wall is an important factor for determining cell shape, function and response to the environment. Secondary cell walls, such as those found in xylem, are composed of cellulose, hemicelluloses and lignin and account for the bulk of plant biomass. The coordination between transcriptional regulation of synthesis for each polymer is complex and… (More)

- Wolfram Wiesemann, Angelos Tsoukalas, Polyxeni-Margarita Kleniati, Berç Rustem
- SIAM Journal on Optimization
- 2013

We study a variant of the pessimistic bilevel optimization problem, which comprises constraints that must be satisfied for any optimal solution of a subordinate (lower-level) optimization problem. We present conditions that guarantee the existence of optimal solutions in such a problem, and we characterize the computational complexity of various subclasses… (More)

- Alexander Mitsos, Angelos Tsoukalas
- J. Global Optimization
- 2015

The algorithm proposed in [Mitsos Optimization 2011] for the global optimization of semi-infinite programs is extended to the global optimization of generalized semi-infinite programs (GSIP). No convexity or concavity assumptions are made. The algorithm employs convergent lower and upper bounds which are based on regular (in general nonconvex) nonlinear… (More)

- Angelos Tsoukalas, Berç Rustem, Efstratios N. Pistikopoulos
- J. Global Optimization
- 2009

We study the solution of non-convex, pessimistic bi-level problems. After providing several motivating examples, we relate the problem to existing research in optimisation. We analyse key properties of the optimisation problem, such as closedness of the feasible region and computational complexity. We then present and investigate a semiinfinite solution… (More)

- Angelos Tsoukalas, Berç Rustem
- Optimization Letters
- 2011

- Natashia Boland, Andrew C. Eberhard, Faramroze G. Engineer, Matteo Fischetti, Martin W. P. Savelsbergh, Angelos Tsoukalas
- Math. Program. Comput.
- 2014

The Feasibility Pump (FP) has proved to be an effective method for finding feasible solutions to mixed integer programming problems. FP iterates between a rounding procedure and a projection procedure, which together provide a sequence of points alternating between LP relaxation feasible but fractional solutions, and integer but LP relaxation infeasible… (More)

- Natashia Boland, Andrew C. Eberhard, Faramroze G. Engineer, Angelos Tsoukalas
- SIAM Journal on Optimization
- 2012

The feasibility pump is a recent, highly successful heuristic for general mixed integer linear programming problems. We show that the feasibility pump heuristic can be interpreted as a discrete version of the proximal point algorithm. In doing so, we extend and generalize some of the fundamental results in this area to provide new supporting theory. We show… (More)

- Angelos Tsoukalas, Panos Parpas, Berç Rustem
- Optimization Letters
- 2009

We generalize a smoothing algorithm for finite min–max to finite min– max–min problems. We apply a smoothing technique twice, once to eliminate the inner min operator and once to eliminate the max operator. In mini–max problems, where only the max operator is eliminated, the approximation function is decreasing with respect to the smoothing parameter. Such… (More)