Engineering Planar-Separator and Shortest-Path Algorithms

"Algorithm engineering" denotes the process of designing, implementing, testing, analyzing, and refining computational proceedings to improve their performance. We consider three graph problems -- planar separation, single-pair shortest-path routing, and multimodal shortest-path routing -- and conduct a systematic study in order to: classify different kinds of input; draw concrete recommendations for choosing the parameters involved; and identify and tune crucial parts of the algorithm

Multi-Head Finite Automata: Characterizations, Concepts and Open Problems

Multi-head finite automata were introduced in (Rabin, 1964) and (Rosenberg, 1966). Since that time, a vast literature on computational and descriptional complexity issues on multi-head finite automata documenting the importance of these devices has been developed. Although multi-head finite automata are a simple concept, their computational behavior can be already very complex and leads to undecidable or even non-semi-decidable problems on these devices such as, for example, emptiness, finiteness, universality, equivalence, etc. These strong negative results trigger the study of subclasses and alternative characterizations of multi-head finite automata for a better understanding of the nature of non-recursive trade-offs and, thus, the borderline between decidable and undecidable problems. In the present paper, we tour a fragment of this literature

Condition-dependent signaling affects male sexual attractiveness in field crickets, Gryllus campestris

The condition dependence of sexually selected traits is an important assumption of sexual selection theory. Several laboratory studies have documented a positive relationship between food availability, body condition, and sexual display. However, these studies might not reflect the resource allocation between body maintenance, reserves, and the sexually selected trait under natural conditions. Further, the effect of condition-dependent signaling on female mate choice has hardly been investigated experimentally in the field. We therefore investigated the effect of food availability on body condition, calling behavior, and sexual attractiveness of male field crickets, Gryllus campestris, under field conditions. Food availability was manipulated for individual males by supplementing food in a confined area close to the burrow. Food-supplemented males showed a significant increase in body condition, whereas the opposite was found in the control males. Males receiving extra food called more frequently, whereas the calling-song characteristics were not affected by the treatment. Further, food-supplemented males attracted more females than did control males, and their higher attractiveness was partly explained by their superior calling rate. Our study thus indicates condition-dependent signaling as an important determinant of the sexual attractiveness of males to females under natural conditio

Towards Collaborative Conceptual Exploration

In domains with high knowledge distribution a natural objective is to create principle foundations for collaborative interactive learning environments. We present a first mathematical characterization of a collaborative learning group, a consortium, based on closure systems of attribute sets and the well-known attribute exploration algorithm from formal concept analysis. To this end, we introduce (weak) local experts for subdomains of a given knowledge domain. These entities are able to refute and potentially accept a given (implicational) query for some closure system that is a restriction of the whole domain. On this we build up a consortial expert and show first insights about the ability of such an expert to answer queries. Furthermore, we depict techniques on how to cope with falsely accepted implications and on combining counterexamples. Using notions from combinatorial design theory we further expand those insights as far as providing first results on the decidability problem if a given consortium is able to explore some target domain. Applications in conceptual knowledge acquisition as well as in collaborative interactive ontology learning are at hand.Comment: 15 pages, 2 figure