Power Electronic Devices for Damping Torsional Vibrations
Torsional vibrations and resonance problems with synchronous machines are most frequently encountered in rotor systems with long shafts and large inertias constituting a weakly damped mechanical resonator which exhibits a low resonance frequency. It is impossible to obtain a effective mechanical damping for these torsional vibrations, but by using a power electronics device and an inductive or capacitive energy storage which is connected to the stator winding of the synchronous machine, which produce the same effect as an increased natural damping for oscillation mode in the rotating shaft assembly. This electrical method is applicable to torsional vibration problems in generators and electrical drive systems. The paper presents examples for the successful suppression of torsional resonances in synchronous machines of an isolated power system based on flywheel generators and by three phase fault in the second benchmark model of the IEEE.
Fusion as a Future Power Source: Recent Achievements and Prospects
Recent advances in high energy plasma physics show that nuclear fusion the energy source of the sun and the stars [1] may provide the corner-stone of a future sustainable energy system. Such power plants would be safe and environmentally friendly. In particular, one of the main problems of fission reactors, namely that of a possible uncontrollable nuclear reaction is banished; also the problem of radiotoxic waste is reduced by many orders of magnitude. Fusion reactors would have almost limitless supplies of fuel and could be sited anywhere in the world. Fusion is, however, still in the development stage and it is not expected that commercial power plants will start operation before the middle of this century.
Air scrubbing techniques for ammonia and odor reduction at livestock operations : review of on-farm research in the Netherlands
Acid scrubbers and biotrickling filters have been developed for ammonia (NH3) removal at pig and poultry houses 
in The Netherlands over the last 20 years to prevent acidification and eutrophication of soils. Because of growing 
suburbanization, odor removal is increasingly considered important as well. In this review, we report the results of the on-farm 
research on full-scale operated scrubbers for treatment of exhaust air from animal houses with regard to NH3 and odor 
removal in The Netherlands. The NH3 removal of acid scrubbers ranged from 40% to 100% with an overall average of 96%. 
The NH3 removal of biotrickling filters ranged from -8% to +100% with an overall average of 70%. Minimum empty bed air 
residence times (EBRTs) were 0.4 to 1.1 s. For acid scrubbers, process control with pH measurement and automatic water 
discharge is sufficient to guarantee sufficient NH3 removal. For biotrickling filters, however, improvement of process control 
is necessary to guarantee sufficient NH3 removal. The odor removal of acid scrubbers ranged from 3% to 51% with an overall 
average of 27%. The odor removal of biotrickling filters ranged from -29% to +87% with an overall average of 51%. 
Minimum EBRTs were 0.5 to 2.3 s. Further research is necessary to explain this variation and to improve the odor removal 
efficiency of both acid scrubbers and biotrickling filters.