Showing papers by "National Technical University of Athens published in 1971"

Two families of simply symmetric orbits in E3

Abstract: Numerical processes are applied to the classical formulation of the restricted problem of three bodies in order to compute families of periodic orbits that exist inE3 and are symmetric with respect to a plane that contains the two primaries and their axis of angular velocity. Two such families are found and their stability numbers are computed. In general, the discovery of such families proves to be extremely difficult.

A contribution to the gamma radiography of reinforced concrete structures

Abstract: A systematic presentation of arrangements and materials for detection of reinforced concrete by means of gamma-radiography is the first aim of this paper. New proposals concerning auxiliary techniques in gamma-radiography have been investigated: a) Photometric measurements on simple gamma-radiographies have been applied, in order to estimate the diameter of an embedded bar, on the basis of the difference in film density, between the image of the bar and its surrounding area. b) Ordinary photogrammetric apparatuses have been used on twin stereo-radiographies for direct discrimination of complicated bars of concrete reinforcements. The same method has been applied for a direct reading of the position and diameter of every bar simultaneously, instead of repetitive application of two-equations systems for each bar in conventional stereo-radiography.