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Re: Abstract

An interesting abstract. In my own work on KJ1 and KJ2, I've been careful to explicitly point out that there is no fossil evidence that the crest supported a membrane, and have just looked at the potential impact if there were one, without implying that one did indeed exist. The hypothetical membrane would be stable in flight, but there are only three ways to use it to generate thrust during flight. One is by flying through a regularly repeating sinusoidal windfield (which doesn't exist in nature), the second is by a repeated sinusoidal lateral weaving back and forth of the neck, and the third is during sustained winds on the order of 7 knots or more when some portion of the animal's body is in also in contact with a seperate fluid surface (water). The latter was the subject of a presentation at the annual conference of the Advanced Physics Society a few years back. I note in passing that the mean annual windfield on the Western Interior Seaway at the time of Nyctosaurus has been reported in the literature as 8 knots.
JimC

----- Original Message ----- From: "Jiří Meixner" <JiriMeixner@seznam.cz>
To: <dinosaur@usc.edu>
Sent: Friday, January 16, 2009 12:44 AM
Subject: Abstract


Could I add by this way this Nyctosaurus abstract to DML? Jiri Meixner.... it´s from Lida Xing´s page:

Abstract: The Nyctosaurus specimen KJ1 is reconstructed under the hypothesis that there is a membrane attached to the crest, the so-called headsail crest. The aerodynamic forces and moments acting on headsail crest are then analyzed. It is shown that KJ1 might adjust the angle of the headsail crest relative to the air current as one way to generate thrust (one of the aerodynamic forces, used to overcome body drag in forward flight) and that the magnitude of the thrust and moment could vary with the gesture angle and the relative location between the aerodynamic center of headsail crest and bodyˇŻs center of gravity. Three scenarios are tested for comparison to each other: the crest with membrane attachment, the crest without membrane attachment and the absence of cranial crest. It is shown that the aerodynamic characteristics (increasing, maintaining and decreasing thrusts and moments) would almost disappeared in flight for the crest without membrane attachment and none existent
without the cranial crest. It is suggested from aerodynamics evidence alone that Nyctosaurus specimen KJ1 had membrane attached to the crest and used this reconstructed form for auxiliary flight control.

http://www.xinglida.net/indexe.htm

Thanks for upload.... Jiri