Abstract: Provided are a method and an apparatus for modifying particle size of powders in closed items, comprising the exposure of said items to external electric field of suitable parameters. The degree of agglomeration of the particles can be increased or decreased. Applications to neutralization of harmful powders in mails, to dry agglomeration and to volatilization of powders in food industry and in pharmacology are described.

Abstract: A transducer has natural unidirectionality for surface acoustic waves. An interdigital electrode structure is arranged on a piezoelectric crystal substrate and is constructed with interdigital transducers including collecting electrodes and fingers. At least two of the fingers form a transducer cell, which includes at least one excitation center for exciting an electrical potential wave and at least one reflection center for reflecting electrical potential waves. The fingers are oriented perpendicularly to a direction R parallel to a 1- or 3-fold rotational axis of the substrate crystal and the derivative dv/d?=0 applies to R, wherein v is the phase velocity of the surface wave and ? is an angular deviation of the perpendicular to the finger direction from the direction R.

Abstract: Provided are a method and an apparatus for modifying particle size of powders in closed items, comprising the exposure of said items to external electric field of suitable parameters. The degree of agglomeration of the particles can be increased or decreased. Applications to neutralization of harmful powders in mails, to dry agglomeration and to volatilization of powders in food industry and in pharmacology are described.

Abstract: The invention relates to a transducer having natural unidirectionality for surface acoustic waves, wherein an interdigital electrode structure is arranged on a piezoelectric crystal substrate and is constructed with interdigital transducers comprising collecting electrodes and fingers, wherein at least two of the fingers form a transducer cell, which comprises at least one excitation center for exciting an electrical potential wave and at least one reflection center for reflecting electrical potential waves. The invention is based on the problem of finding materials, material sections, and propagation directions for transducers having natural unidirectionality that result in a low insertion loss even in broadband transducers, and for which the frequency position is not affected or is affected only slightly by errors in the orientation of the electrode structure on the substrate despite the unidirectional characteristics of the transducers.

Abstract: The invention relates to waveguide components based on acoustic surface waves, comprising at least one interdigital converter for exciting acoustic surface waves in a piezoelectric substrate or a piezoelectric layer. The object of the invention is to change known waveguide components, comprising at least one interdigital converter for exciting acoustic surface waves in a piezoelectric substrate or a piezoelectric layer, such that no reflectors are necessary with an otherwise equivalent function. The inventive waveguide components are characterized in that the interdigital converter(s) a) is or are disposed at a defined distance over the piezoelectric substrate or the piezoelectric layer for exciting wave fields, or b) is or are in contact with the piezoelectric substrate or the piezoelectric layer, wherein in version a) the piezoelectric substrate is designed as a ring and the piezoelectric layer is designed as a circular region.

Abstract: The invention relates to waveguide components based on acoustic surface waves, comprising at least one interdigital converter for exciting acoustic surface waves in a piezoelectric substrate or a piezoelectric layer. The object of the invention is to change known waveguide components, comprising at least one interdigital converter for exciting acoustic surface waves in a piezoelectric substrate or a piezoelectric layer, such that no reflectors are necessary with an otherwise equivalent function. The inventive waveguide components are characterized in that the interdigital converter(s) a) is or are disposed at a defined distance over the piezoelectric substrate or the piezoelectric layer for exciting wave fields, or b) is or are in contact with the piezoelectric substrate or the piezoelectric layer, wherein in version a) the piezoelectric substrate is designed as a ring and the piezoelectric layer is designed as a circular region.