This paper deals with power regulation in variable speed wind energy conversion systems. The importance of power control in the stall region is stressed. This mode of operation is characterized by a non-minimum phase behaviour. A variable structure controller is described that provides stability by
Conformally invariant powers of the Dirac operator in Clifford analysis
✍ Scribed by David Eelbode; Vladimír Souček
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 252 KB
- Volume
- 33
- Category
- Article
- ISSN
- 0170-4214
- DOI
- 10.1002/mma.1268
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✦ Synopsis
The paper deals with conformally invariant higher-order operators acting on spinor-valued functions, such that their symbols are given by powers of the Dirac operator. A general classification result proves that these are unique, up to a constant multiple. A general construction for such an invariant operators on manifolds with a given conformal spin structure was described in (Conformally Invariant Powers of the Ambient Dirac Operator. ArXiv math.DG/0112033, preprint), generalizing the case of powers of the Laplace operator from (J. London Math. Soc. 1992; 46:557-565). Although there is no hope to obtain explicit formulae for higher powers of the Laplace or Dirac operator on a general manifold, it is possible to write down an explicit formula on Einstein manifolds in case of the Laplace operator (see Laplacian Operators and Curvature on Conformally Einstein Manifolds. ArXiv: math/0506037, 2006). Here we shall treat the spinor case on the sphere. We shall compute the explicit form of such operators on the sphere, and we shall show that they coincide with operators studied in (J. Four. Anal. Appl. 2002; 8(6):535-563). The methods used are coming from representation theory combined with traditional Clifford analysis techniques.
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