Abstract: A voltage surge damping device for electromagnets is provided which applies more particularly to electromagnets of the type comprising a fixed magnetic circuit and a mobile magnetic circuit cooperating with the fixed magnetic circuit and forming therewith, in the "closed" position, at least one air gap. Said device comprises at least one short circuiting ring mounted on the fixed magnetic circuit and formed by a good electrically conducting and a magnetic metal sheet, and having at least one part shaped so as to extend into said air gap.

Abstract: The method comprises the following steps: depositing the coating (20) to be treated on a first face (11) of the dielectric support (10); depositing a layer (30) of electrically conductive material on a second face (12) of the dielectric support (10) opposite to the first face and generally parallel thereto, the thickness of said layer (30) being of the same order as the penetration depth .delta. in the material thereof of the selected electromagnetic wave; and applying microwave energy to the assembly thus constituted in such a manner that the direction of vibration of the electric field is substantially parallel to the coating (20) to be treated and to the layer (30) of conductive material.

Abstract: A process for producing fritted alumina members having a high optical transparency and a high mechanical strength of the type involving the production of the members from a high purity alumina powder to which has been added an organic binder and a small percentage of oxide, particularly of magnesium and/or rare earth, followed by the shaping thereof and subjecting them to two successive heat treatments, namely a first treatment in an oxidizing atmosphere to remove the binder and consolidate the particles and a second treatment at a higher temperature and in a hydrogen-rich atmosphere for obtaining fritting, wherein the second heat treatment takes place by continuously passing the said members through a kiln kept at a temperature between 1820.degree. and 1970.degree. C.