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Model Reduction of Spatially Distributed Systems Using Coprime Factors and Semidefinite Programming

In this paper an order reduction method for spatially distributed models is presented. Such systems may be modeled as two nodes interacting with each other through feedback. A model of one of the nodes reduced in such a way, that the closed loop performance is approximated. The method exploits a coprime factor description of the closed loop model and semidefinite programming. The method is related

Diversity performance of multiband antennas for compact mobile terminals

Spatial diversity is a popular multiple antenna system technique, due to simplicity in implementation. However, its application has thus far been limited to systems where the electrical separation between adjacent antennas typically exceeds half a wavelength. This is because a more compact design induces higher antenna correlation and impedance mismatch, which results in lower diversity gains. In

Operational Experience of Load Shedding and new Operational Requirements on Frequency Relays

This paper summarises experience and analysis of under-frequency load shedding and power generator islanding. Most power systems can withstand the loss of a single generating unit or a single transmission line. Simultaneous loss of several power system components may cause a severe deficit in active and reactive power. The action of overexcitation limiters on the remaining generators may further a

Algebraic Properties of Ore Extensions and Their Commutative Subrings

This thesis deals with a class of rings known as Ore extensions. An Ore extension can be described as a noncommutative ring of polynomials in one variable. A special focus of the thesis is the study of commuting elements in Ore extensions. In the first two papers in the thesis we prove that commuting elements of Ore extensions are in many cases algebraically dependent. In doing this we extend a