Abstract: The present invention relates to a controllable barrier layer against electromagnetic radiation, to be used, inter alia, as a radome for a radar antenna for instance. The barrier layer comprises a first frequency selective layer (4) of a given geometric shape, said frequency selective layer transmitting radiation of a certain polarization within a desired frequency band and reflecting radiation of a different polarization and radiation outside said band and at least a second identical frequency selective layer, which is placed close to or in connection with the first layer in the radiation direction. The layers are configured to be placed in a first position relative to each other so that they together obtain transmission properties similar to those of the first layer alone and in a second position relative to each other so that they together reflect radiation of said certain polarization within said desired frequency band.

Abstract: A method of preparing salt of dinitramidic acid, comprising nitration of an initial compound with a nitrating acid mixture to form dinitramidic acid in a reaction mixture. A positive ion is added to the reaction mixture and forms with the dinitramide ion an ion pair complex which precipitates in the acidic reaction mixture, and the precipitate is separated from the mixture. The remaining spent acid can be reprocessed for recovery of acid for preparation of a new nitrating acid mixture. The preferred positive ion is the guanylurea ion which gives a precipitate of guanylurea dinitramide. The precipitate can be used as starting material for preparation of other dinitramide salts, such as KDN and ADN. The guanylurea ion can be formed in situ in the process by cyanoguanidine being reacted with the reaction mixture.

Abstract: An interactive method of presenting information in an image to a user, who carries a head-mounted display device that presents an image of the surroundings. The user's head position and direction are established in relation to the surroundings and a calculating device establishes, based on this, which part of the surroundings is positioned in front of the user's head. Furthermore, the calculating device establishes where in a chain of information the user is positioned and, based on this, presents information in the form of a virtual image which is mixed with the real image. A central part of the image is then defined and fields and/or objects outside this area are shown in a non-disturbing way until the user's gaze has left the central part. The user informs the calculating device that he/she has received the information and, respectively, performed the current operations by looking at the fields/objects.