Risto Hänninen

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The phonemic errors of three Finnish Broca's aphasics were analyzed according to various phonological features, frequency of segments, syllable, word, and stress positions, as well as for the phonotactic structure of the uncanonical products. It was found, e.g., that the distance between the syntagmatic error and its source could not be satisfactorily(More)
We investigate the decay of vortices in a rotating cylindrical sample, after rotation has been stopped. With decreasing temperature vortex annihilation slows down, as the damping in vortex motion, the mutual friction dissipa-tion α(T), decreases exponentially. Remnant vortices then survive for increasingly long periods, while they move towards annihilation(More)
New techniques, both for generating and detecting turbulence in the helium su-perfluids 3 He-B and 4 He, have recently given insight in how turbulence is started, what the dissipation mechanisms are, and how turbulence decays when it appears as a transient state or when externally applied turbulent pumping is switched off. Important simplifications are(More)
Rapid new developments have occurred in superfluid hydrodynamics since the discovery of a host of unusual phenomena which arise from the diverse structure and dynamics of quantized vortices in 3 He superfluids. These have been studied in rotating flow with NMR measurements which at best provide an accurate mapping of the different types of topological(More)
Kinetic helicity is one of the invariants of the Euler equations that is associated with the topology of vortex lines within the fluid. In superfluids, the vorticity is concentrated along vortex filaments. In this setting, helicity would be expected to acquire its simplest form. However, the lack of a core structure for vortex filaments appears to result in(More)
Name of the doctoral dissertation Approaching the zero-temperature limit in superfluid dynamics and dissipation Abstract Most collective physical systems freeze and become immobile at zero temperature. Thus, there exist few systems where hydrodynamics can be experimentally studied in the zero-temperature limit. Most notable among these are the helium(More)
We study a twisted vortex bundle where quantized vortices form helices circling around the axis of the bundle in a "force-free" configuration. Such a state is created by injecting vortices into a rotating vortex-free superfluid. Using continuum theory we determine the structure and the relaxation of the twisted state. This is confirmed by numerical(More)
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