On cardinality constrained cycle and path polytopes

Given a directed graph D = (N, A) and a sequence of positive integers 1 <= c_1 < c_2 < ... < c_m <= |N|, we consider those path and cycle polytopes that are defined as the convex hulls of simple paths and cycles of D of cardinality c_p for some p, respectively. We present integer characterizations of these polytopes by facet defining linear inequalities for which the separation problem can be solved in polynomial time. These inequalities can simply be transformed into inequalities that characterize the integer points of the undirected counterparts of cardinality constrained path and cycle polytopes. Beyond we investigate some further inequalities, in particular inequalities that are specific to odd/even paths and cycles.Comment: 24 page

Shoreline Sand Waves. A Nonlinear One-Line Model

The morpho-dynamic model presented in this paper finds its application in the large time and length scale prediction of wave-driven along-shore sediment transport. It employs an extended version of the well established one-line concept. The model uses a nonlinear wave-field evaluation projecting the curvature of coastline to the bathymetric topography. A new quasi-perpendicular equilibrium profile is applied. Coastline changes are accounted until a finite distance from the averaged shoreline. The methods employed allow the model computation of high and low angle waves at stronger perturbations from rectilinear coastline. The mentioned bathymetric feedback allows to predict sand wave formation, movement, diffusion and high angle wave instability. The effects of changing wave properties, bathymetric parameters and initial shoreline conditions are investigated by numerical experiments. The formation of sand waves is studied using a random initial shore shape

Constitutional Design: Separation of Financing and Project Decision

We examine the provision of public projects under separate tax and subsidy rules. We find that tax rules separated from project cum subsidy decisions exhibit several advantages when incentive problems of the agenda-setter are taken into account. In particular, tax rules may prevent the proposal of inefficient projects which benefit only a small lobby group. We propose “redistribution efficiency” as a socially desirable property of proposals and find that tax rules always guarantee redistribution efficiency. We show that rules on subsidies combined with discretion regarding taxes always yield socially inferior proposals. Finally, tax rules induce the agenda-setter to look for potential improvements of public projects.constitutional design, provision of public projects, voting, taxes and subsidies

Virtual Integration Platforms (VIP) –A Concept for Integrated and Interdisciplinary Air Transportation Research and Assessment

The paper descibes a new methodology for a holistic development of air transportation concepts. The Virtual Integration Plattform (VIP) concept is based on an IT tool chain as well as human collaborative methods to deal with complex systems. As a result the definitions of future air transportation concepts for short range "Quiet and Clean", long range "Comfortable and Clean" and individual transport "Fast and Flexible" are presente