Restricted Power - Computational Complexity Results for Strategic Defense Games

We study the game Greedy Spiders, a two-player strategic defense game, on planar graphs and show PSPACE-completeness for the problem of deciding whether one player has a winning strategy for a given instance of the game. We also generalize our results in metatheorems, which consider a large set of strategic defense games. We achieve more detailed complexity results by restricting the possible strategies of one of the players, which leads us to Sigma^p_2- and Pi^p_2-hardness results

Hydraulische invloed van structurele ingrepen tegen de verzanding van het Zwin

The specific fauna and flora of the natural reserve "Het Zwin" are generated by the seawater that streams in and out of the channels of the reserve at each tide. This water transports sand and mud, that are deposited in the channels and on the inundated surfaces. This way the chanels and saltmarshes are silting up gradually.The international Belgian-Dutch Commission of the Zwin has decided to stop the silting up and to maintain the Zwin as a salty tidal area.In 1987 a technical committee was established to deliberate on the mesures that had to be taken. In 1989 the main channel was deepened and a sandtrap introduced.This article represents mainly the calculations on mathematical model by Flanders Hydraulics to estimate the influence of different proposed solutions.Alternative managements are examined concerning their effect on the ecological values, the landscape and the recreational values of the Zwin.The international Commission of the Zwin has approuved a project in phases, where alternatives are combined to maintain and fortify the natural values of the Zwin