6,957 research outputs found
The evaluation of the rolling moments induced by wraparound fins
A possible reason is suggested for the induced rolling moments occurring on wraparound-fin configurations in subsonic flight at zero angle of attack. The subsonic potential flow over the configuration at zero incidence is solved numerically. The body is simulated by a distribution of sources along its axis, and the fins are described by a vortex-lattice method. It is shown that rolling moments can be induced on the antisymmetric fins by the radial flow generated at the base of the configuration, either over the converging separated wake, or over the diverging plume of a rocket motor
Compact coalgebras, compact quantum groups and the positive antipode
In this article -that has also the intention to survey some known results in
the theory of compact quantum groups using methods different from the standard
and with a strong algebraic flavor- we consider compact o-coalgebras and Hopf
algebras. In the case of a o-Hopf algebra we present a proof of the
characterization of the compactness in terms of the existence of a positive
definite integral, and use our methods to give an elementary proof of the
uniqueness - up to conjugation by an automorphism of Hopf algebras- of the
compact involution appearing in [4]. We study the basic properties of the
positive square root of the antipode square that is a Hopf algebra automorphism
that we call the positive antipode. We use it -as well as the unitary antipode
and the Nakayama automorphism- in order to enhance our understanding of the
antipode itself
- …