Abstract: The effective area of a solar cell unit may be enlarged or increased considerably relative to its physical area by providing its exposed surface layer with a periodic structure or pattern, by which a local field is generated, a so-called Hartree harmonics field. The periodic structure is preferably a grating structure or pattern, and by orienting the solar cell edgewise so that the sunlight is grazing rather than oblique or directly perpendicular to the surface, its response factor may be increased up to a factor 11 theoretically.

Abstract: A sound-absorbing structure comprising a plurality of linear and parallel grooves in the surface of the structure and ribs between the grooves. The structure is employed to damp, in a semi-space which is delimited by a substantially plane surface, e.g. a ground surface, a sound field propagating essentially in parallel with said surface. The sound field originates in for instance traffic on a motorway or an airport. The grooves of the structure are arranged in such manner, that a sound attenuation is obtained, in terms of the direction of propagation of the sound field, behind the structure by means of an acoustic coupling between adjoining grooves at the sound frequencies to be damped. The surface of the sound-absorbing structure is situated substantially in the surface delimiting the above mentioned semi-space. The cross-section of the structure has an outline similar to a square wave or a sine curve.