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We consider positivity preserving model order reduction of SISO linear systems. Whereas well-established model reduction methods usually do not result in a positive approximation, we show that a symmetry characterization of balanced truncation can be used to preserve positivity after performing balanced truncation. As a consequence, the method is independent of the initial realization and always r
Biological invasions offer fertile grounds for studying evolutionary ecology because species’ contact histories are uncharacteristically well-defined. As a result, invasions can be used to gain glimpses of the earliest micro-evolutionary responses of natural populations to new species’ interactions by studying changes in behaviour, physiology or morphology in space and time. Here, the known histor
During the 1990s public services have to a great extent reorganised according to the idea of market economy and new management ideas. An example that illustrates these processes is the home care organisations. Private companies, new management strategies and special need assessment officials have been introduced. In a longitudinal study we have focused on the fate of the working teams as it is sho
I understand patronage principally as a work of cultural and material support - the support shich was necessary to stage the performance of a piece of music in mayn different contexts. I focus on the fate of an opera, Richard Wagner's Parsifal, a work which was not performed at the Bayreuth festival between 1939 and 1944 because of its emphasis on reconciliation, non-violence and faith, but which
This paper concerns the unifying framework to strictly contractive extension problems, which is usually referred to as the band method. The solution to the so-called strictly contractive extension problem in this abstract framework, when applied to a certain concrete case, yields a complete characterization of solutions to the sub-optimal Nehari problem. The sub-optimal Hankel norm approximation p
A common approach to distributed control design is to impose sparsity constraints on the controller structure. Such constraints, however, may greatly complicate the control design procedure. This paper promotes an alternative structure, which is not sparse, yet might nevertheless be well suited for distributed control purposes. The structure appears as the optimal solution to a class of coordinati
