Abstract: A vehicle comprising at least one pressure-drag-reducing apparatus (1) for reducing the pressure drag on the vehicle. The apparatus comprises: a housing (31) at least partly defining a cavity (34) and an aperture (35) in the housing (31), the cavity (34) in fluid communication via the aperture (35) with the environment surrounding the vehicle; and oscillating means (32, 36) for creating an oscillation in pressure across the aperture between the cavity and the environment. The cavity volume, the frequency of oscillation, the aperture size and the amplitude of oscillation are arranged to cause fluid to be alternately drawn into, and ejected from, the cavity through the aperture. The apparatus is positioned relative to the remainder of the vehicle such that the ejected fluid entrains fluid from the environment to reduce pressure drag on the vehicle.

Abstract: A vehicle comprising at least one pressure-drag-reducing apparatus (1) for reducing the pressure drag on the vehicle. The apparatus comprises: a housing (31) at least partly defining a cavity (34) and an aperture (35) in the housing (31), the cavity (34) in fluid communication via the aperture (35) with the environment surrounding the vehicle; and oscillating means (32, 36) for creating an oscillation in pressure across the aperture between the cavity and the environment. The cavity volume, the frequency of oscillation, the aperture size and the amplitude of oscillation are arranged to cause fluid to be alternately drawn into, and ejected from, the cavity through the aperture. The apparatus is positioned relative to the remainder of the vehicle such that the ejected fluid entrains fluid from the environment to reduce pressure drag on the vehicle.

Abstract: The invention provides a method for the production of a photonic device comprising providing a substrate, forming in the substrate substantially straight pores, lining or filling the pores with a material having voltage-dependent index of refraction, and removing part but not all of the substrate materials so that an array remains of tubes or rods of material having. voltage-dependent index of refraction. In a variant of the method the deposited material is piezoelectric and the substrate is completely removed, resulting in piezoelectric tubes or rods of small diameter, generally below 10 ?m.

Abstract: According to the invention we provide a process for filling or lining the pores of a porous silicon, silica or alumina substrate with a material which exhibits voltage-dependent index of refraction n comprising providing precursors for the deposited material as a precursor solution, forming a fine mist of droplets of precursor solution and applying the droplets to the porous substrate. The invention provides for the first time porous silicon, silica and alumina substrates having fill fraction at least 60%. Fill fractions of close to 100% can be achieved. When provided with top and bottom electrodes, filled porous silicon, silica and alumina wafers can be used as voltage-dependent photonic devices. The same process can be used for lining trenches in the surface of a silicon substrate, for instance for use in production of microelectronic devices such as random access memories.