An empirical study of hyperheuristics for managing very large sets of low level heuristics

Hyperheuristics give us the appealing possibility of abstracting the solution method from the problem, since our hyperheuristic, at each decision point, chooses between different low level heuristics rather than different solutions as is usually the case for metaheuristics. By assembling low level heuristics from parameterised components we may create hundreds or thousands of low level heuristics, and there is increasing evidence that this is effective in dealing with every eventuality that may arise when solving different combinatorial optimisation problem instances since at each iteration the solution landscape is amenable to at least one of the low level heuristics. However, the large number of low level heuristics means that the hyperheuristic has to intelligently select the correct low level heuristic to use, to make best use of available CPU time. This paper empirically investigates several hyperheuristics designed for large collections of low level heuristics and adapts other hyperheuristics from the literature to cope with these large sets of low level heuristics on a difficult real- world workforce scheduling problem. In the process we empirically investigate a wide range of approaches for setting tabu tenure in hyperheuristic methods, for a complex real-world problem. The results show that the hyperheuristic methods described provide a good way to trade off CPU time and solution quality

Comparative investigation on the effect of a herbecide on aquatic organisms in single species tests and aquatic microcosms

Schäfer H, Remde A, Traunspurger W. Comparative investigation on the effect of a herbecide on aquatic organisms in single species tests and aquatic microcosms. Chemosphere. 1996;33:1129-1141

Kleinräumige Bodencharakterisierung mittels Mikromethoden

Kördel W, Klöppel H, Remde A, Rüdel H, Traunspurger W, Wahle U. Kleinräumige Bodencharakterisierung mittels Mikromethoden. Texte 30/92. Umweltbundesamt; 1992

Verfahren zur Herstellung von Cellulosefasern und die mit diesem Verfahren hergestellten Fasern

Production of flexible cellulose fibres involves spinning cellulose solutions through spinnerets through an air gap into an aqueous and/or alcoholic coagulation bath containing amine oxide and then drying. The novelty is that, before drying, the moist spun fibre is passed through after-treatment bath(s) containing water and water-miscible alcohol(s), diol(s) and/or triol(s) and washing bath(s) containing water, an alkanol, a diol or a triol. Also claimed are cellulose fibres made by this method, which have an initial modulus < 1500 cN/tex. Preferably the after-treatment bath is alkaline and especially consists of a mixture of alkanol and aqueous sodium hydroxide (NaOH) solution, more especially ethanol (EtOH) and 1-30% aqueous NaOH solution. The washing bath contains EtOH. ADVANTAGE - The orientation, modulus, brittleness and tendency of the fibres to fibrillate are all reduced compared with the usual fibres spun from solutions in amine oxides, especially N-methylmorpholine N-oxide (NM MNO), or aqueous NMMNO