Plane geometry and convexity of polynomial stability regions

The set of controllers stabilizing a linear system is generally non-convex in the parameter space. In the case of two-parameter controller design (e.g. PI control or static output feedback with one input and two outputs), we observe however that quite often for benchmark problem instances, the set of stabilizing controllers seems to be convex. In this note we use elementary techniques from real algebraic geometry (resultants and Bezoutian matrices) to explain this phenomenon. As a byproduct, we derive a convex linear matrix inequality (LMI) formulation of two-parameter fixed-order controller design problem, when possible

Complex Rotating Waves and Long Transients in a Ring-Network of Electrochemical Oscillators with Sparse Random Cross-Connections

We perform experiments and phase model simulations with a ring network of oscillatory electrochemical reactions to explore the effect of random connections and non-isochronocity of the interactions on the pattern formation. A few additional links facilitate the emergence of the fully synchronized state. With larger non-isochronicity, complex rotating waves or persistent irregular phase dynamics can derail the convergence to global synchronization. The observed long transients of irregular phase dynamics exemplify the possibility of a sudden onset of hyper synchronous behavior without any external stimulus or network reorganization.Comment: 4 pages main text and 4 pages supplemental materia

12% minder ammoniakemissie in 2010? Met BEA kan dat!

Voor 2010 moet de ammoniakemissie van de melkveehouderij met 12% verminderen ten opzichte van 2005. Kort dag dus. Maar het kan door gebruik te maken van de Bedrijfsspecifieke Emissie Ammoniak (BEA). Onderzoek op Koeien & Kansenbedrijven toont aan dat zelfs 20% haalbaar is

Water Attaining Capability of the Leaves in Autochthonous Plum Cultivars as an Indicator of their Resistance to Drought

The results of this research show that the plant height, stem diameter, branching and uniformity of one-year old seedlings of autochthonous plum cultivars are genetic characteristics of autochthonous plum cultivars, from which rapid growth and uniformity of scions depend. Out of the studies of one-year old seedlings of autochthonous plum cultivars, the highest water attaining capability had the leaves of cultivar ʽCrvena rankaʼ . Over the monitored time interval (8 hours upon sample taking), leaves taken from the annual twigs of the studied cultivars (one-year old seedlings) lost on average 33,54% of water. The lowest level of the stated capability was recorded with the leaves of cultivar ʽObični piskavacʼ (41.74%)