Torbjørn Pedersen

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By measuring the current through the coil of the actuators in the optical pickup in a compact disk player, open loop para-metric system identification can be performed. The parameters are identified by minimizing the least-squares loss function of the ARX model. The only parameter which cannot be identified in open loop is the optical gain. This is(More)
Motivated by the rapid increase in atmospheric CO2 due to human activities since the Industrial Revolution, several international scientific research programs have analyzed the role of individual components of the Earth system in the global carbon cycle. Our knowledge of the carbon cycle within the oceans, terrestrial ecosystems, and the atmosphere is(More)
Increasing quantities of atmospheric anthropogenic fixed nitrogen entering the open ocean could account for up to about a third of the ocean's external (nonrecycled) nitrogen supply and up to approximately 3% of the annual new marine biological production, approximately 0.3 petagram of carbon per year. This input could account for the production of up to(More)
— The design of the positioning controllers in Optical Disk Drives are today subjected to a trade off between an acceptable suppression of external disturbances and an acceptable immunity against surfaces defects. In this paper an algorithm is suggested to detect defects of the disk surface combined with an observer and a Linear Quadratic Regulator. As a(More)
High resolution measurements on the Alcator C-Mod tokamak [I.H. Hutchinson et al, of the transport barrier in the " Enhanced D α " (EDA) regime, which has increased particle transport without large edge localized modes, show steep density and temperature gradients over a region of 2-5 mm, with peak pressure gradients up to 12 MPa/m. Evolution of the(More)
Control of compact disc mechanisms is highly challenging not least due to the many conflicting control objectives arising from a large number of disturbances of rather different physical natures. A method is proposed which enables the control system to distinguish between some of the disturbance classes. A significant robustness problem is solved by a(More)
Trace non-recycling impurities (Sc and CaF 2) have been injected into Alcator C-Mod plasmas in order to determine impurity transport coefficient profiles in a number of operating regimes. Recycling Ar has also been injected to characterize steady state impurity density profiles. Subsequent impurity emission has been observed with spatially scanning x-ray(More)
Part of Special Issue " Atmospheric studies by optical methods " Abstract. High-power high-frequency radio waves beamed into the ionosphere cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutral oxygen causing artificial optical emissions identical to natural aurora. Pumping at electron gyro-harmonic(More)
Observations of airglow at 630 nm (red line) and 557.7 nm (green line) during HF modification experiments at the High Frequency Active Auroral Research Program (HAARP) heating facility are analyzed. We propose a theoretical framework for understanding the generation of Lang-muir and ion acoustic waves during magnetic zenith injections. We show that(More)