The single-depot multiple TSP (SD-MTSP) is a simple extension of the standard TSP, in which more than one salesman is allowed to visit the set of interconnected cities, such that each city is visited exactly once (by a single salesman) and the total cost of the traveled subtours is minimized. Although Ant Colony Systems (ACSs) are a natural choice for shortest-path problems, with TSP at its core, the application of ACS on this straightforward extension is not properly explored. The reasons may lie in the bi-criteria nature of the problem (shortest cost versus balanced subtours) and the lack of dedicated benchmarks exposing optimal solutions. This paper attempts at proposing and evaluating from a bi-criteria perspective several multiobjective ACSs to tackle SD-MTSP when two objectives need to be simultaneously optimized: minimizing the total cost of traveled subtours while achieving balanced subtours. Experiments are conducted towards investigating the efficiency of the algorithms in a multi-objective setting.
PurposePer capita meat consumption in Switzerland has been rather consistent for decades, although the percentage of vegetarians has risen to 14 per cent according to a recent survey. This study tries to resolve this apparent contradictionDesign/methodology/approachThe study is based on household consumption data from Switzerland and focuses on the distribution of consumption rather than on average amounts, using descriptive statistics and a mixed-effects model which explains the coefficient of variation between single consumer consumption amounts.FindingsVegetarianism and veganism are not only overestimated through surveys but also associated with a segment of the population that is consuming increasing amounts of meat. This dual development leads to a stable per capita meat consumption.Originality/valueOur results indicate that greater scientific attention should be paid to this segment of heavy meat eaters.
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