statement of problem: acrylic teeth of dentures are prone to discoloration due to frequent exposure to different colouring solutions in the oral environment. thus, in order to maintain their aesthetic appearance, they must possess high colour stability while exposed to colorant solutions. objectives: to compare the colour stability of three different brands of acrylic teeth following immersion ...

The 3-Colouring of a graph is a classic NP-complete problem. We show that some solutions for the 3-Colouring can be built in polynomial time based on the number of basic cycles existing in the graph. For this, we design a reduction from proper 3-Colouring of a graph G to a 2-CF Boolean formula FG, where the number of clauses in FG depends on the number of basic cycles in G. Any model of FG prov...

In this paper we present a random iterative graph based hyper-heuristic to produce a collection of heuristic sequences to construct solutions of different quality. These heuristic sequences can be seen as dynamic hybridisations of different graph colouring heuristics that construct solutions step by step. Based on these sequences, we statistically analyse the way in which graph colouring heuris...

The purpose of this paper is twofold. First, it explores the issue of producing valid, compact round-robin sports schedules by considering the problem as one of graph colouring. Using this model, which can also be extended to incorporate additional constraints, the difficulty of such problems is then gauged by considering the performance of a number of different graph colouring algorithms. Seco...

The graph colouring problem and its derivatives have been notoriously known for their inherent intractability. The difficulty seems to stem from the fact that we want a solution for any given graph, however complex it may be. One of the ways how to overcome this difficulty is to restrict possible inputs to the problem; that is, we ask for a solution only for graphs having some special structure...

Grouping problems are hard to solve combinatorial optimisation problems which require partitioning of objects into a minimum number of subsets while a given objective is simultaneously optimized. Selection hyper-heuristics are high level general purpose search methodologies that operate on a space formed by a set of low level heuristics rather than solutions. Most of the recently proposed selec...