Abstract: A method of shaping an aspherical optical element is provided that includes the steps of fastening an optical element blank to a ring, the blank presenting an optical surface that is to be shaped and a surface referred to as a rear surface; applying forces and moments to the ring in order to deform the optical element and its optical surface, which element is fastened to the ring; using abrasion to shape said deformed optical surface so as to restore a spherical or planar shape thereto; and extracting the blank from the ring so as to release the stresses deforming said shaped optical surface so as to allow it to acquire the desired aspherical shape. The method also includes the step of fastening the blank to the ring is performed by bonding the optical surface or the rear surface to a surface of the ring with a layer of adhesive.

Abstract: A method of shaping an aspherical optical element is provided that includes the steps of fastening an optical element blank to a ring, the blank presenting an optical surface that is to be shaped and a surface referred to as a rear surface; applying forces and moments to the ring in order to deform the optical element and its optical surface, which element is fastened to the ring; using abrasion to shape said deformed optical surface so as to restore a spherical or planar shape thereto; and extracting the blank from the ring so as to release the stresses deforming said shaped optical surface so as to allow it to acquire the desired aspherical shape. The method also includes the step of fastening the blank to the ring is performed by bonding the optical surface or the rear surface to a surface of the ring with a layer of adhesive.

Abstract: A method of shaping an aspherical optical element, such as a composite mirror element, the method comprising the following steps: fastening, preferably by adhesive, an optical element blank, presenting an optical surface that is to be shaped, to the inside of a ring, the optical surface of the blank projecting beyond an edge of said ring; applying forces and moments to the perimeter of the ring in such a manner as to deform it in controlled manner, thereby also deforming the optical surface of the blank fastened to its inside; shaping said deformed optical surface by abrasion so as to restore it to a shape that is spherical or planar; and extracting the blank from the ring so as to release the stresses deforming said shaped optical surface, thereby enabling it to acquire the desired aspherical shape.

Abstract: A method of shaping an aspherical optical element, such as a composite mirror element, the method comprising the following steps: fastening, preferably by adhesive, an optical element blank, presenting an optical surface that is to be shaped, to the inside of a ring, the optical surface of the blank projecting beyond an edge of said ring; applying forces and moments to the perimeter of the ring in such a manner as to deform it in controlled manner, thereby also deforming the optical surface of the blank fastened to its inside; shaping said deformed optical surface by abrasion so as to restore it to a shape that is spherical or planar; and extracting the blank from the ring so as to release the stresses deforming said shaped optical surface, thereby enabling it to acquire the desired aspherical shape.

Abstract: A niobium and titanium based alloy having a density less than 6.5 and possessing a high resistance to oxidation at high temperatures in the region of 900.degree. C. has a chemical composition comprising, in atomic percentages:more than 24% Nbfrom 30 to 48% Tifrom 21 to 38% Aland possibly up to 8% of at least one of Cr, Mo, V and Zr.

Abstract: In a method of remelting metallic materials, particularly nickel-based superalloys, in which the melting operation is carried out in a cooled copper crucible under clean vacuum conditions by means of electromagnetic inductors, the magnetic field applied to the mass of molten metal has a frequency between 50 Hz and 5.times.10.sup.6 Hz, preferably between 5.times.10.sup.3 Hz and 5.times.10.sup.5 Hz, so as to effect simultaneously electromagnetic stirring of the liquid metal and a surface concentration at the cold walls of the mass to be recast of all the non-conductive particles, especially ceramic inclusions, thereby achieving an inclusion decanting.

Abstract: A dispenser is provided which is adapted to be used in connection with a hopper for distribution of a granular and/or powdered product, said dispenser having a rotary star-shaped distributor on which is mounted a plurality of crenellated radial blades which upon rotation move between two parallel walls at right angles to the axis of rotation, one wall being an upstream wall and the other a downstream wall, each having at least one cut-out nonaligned with the cut-out in the other, one cut-out being an inlet on the upstream wall and another one an outlet on the downstream wall, the upstream wall having on its inner face at least one stud which is disposed in line with the outlet and the edge of each crenellated radial blade being so crenellated that the recessed surface of the crenellation matches the projecting stud or studs of the upstream wall whereby a constant measured quantity of granular and/or powdered product is dispensed.