Abstract: The invention relates to a method enabling the existence of a biological activity of microorganisms to be determined quickly by applying an electric field. The inventive method includes the following: the microorganisms are placed in a suspension in a dielectric oil, an electric field is applied to said suspension and variations in the strength of the leakage current induced as a function of the applied electric field are measured. The device according to the invention comprises a container which is fitted with electrodes (2), whereby the suspension (3) of microorganisms in a dielectric oil is placed therein, in addition to means for generating an electric field between two or several electrodes, measuring means and means for recording the induced leakage current.

Abstract: A triboelectric device includes a voltage source, a polarizing amplifier, and electrodes to apply a polarizing voltage to a first material of the device. The electrodes are not fixed to the first material, allowing relative rubbing displacement between the electrodes and the first material. Preferably, a conductive second material, such as petrolatum, is provided between the first material and the electrodes. Such a device can have its properties change while in service. To accommodate this, the voltage source preferably provides an adjustable polarization voltage. The triboelectric device is useful as a transducer, and particularly useful as a hydrophone used in sonar antenna, as its mode type can be changed in the field during service to correct spurious signals or interferring noises.

Abstract: A piezosensitive device includes a material and a device that applies a polarizing voltage to the material. Embodiments of the material are piezosensitive only when a polarizing voltage is applied to them. The device can be used, for example, in electromechanical transducers of sonar antennas.

Abstract: A method is disclosed for producing magnetic or piezoelectric particles consisting of dried microorganisms which contain fixed magnetic or piezoelectric powder. The microorganisms are cultured in a nutrient medium containing the magnetic or piezoelectric powder which is then fixed or ingested by the microorganism. The microorganisms containing the magnetic or piezoelectric powder are then extracted from the nutrient medium and dehydrated to obtain dry particles. The dry particles may be compacted or inserted into a matrix to form a composite material.

Abstract: The invention relates to the areas of piezoelectricity and magnetism, and relates in particular to a composite material having piezoelectric or magnetic properties and a method for manufacturing the same. The composite material can be used, for example, in piezosensitive sensors or in magnetic sensors. The method according to the invention includes culturing microorganisms in a nutrient medium in the presence of a piezoelectric powder or magnetic powder. The microorganisms fix or ingest the powder, and are subsequently extracted from the nutrient medium and dehydrated to obtain dry particles. The dry particles are then compacted or inserted into a matrix to constitute the composite material. The microorganisms can optionally be separated from the particles prior to compaction of the particles or insertion of the particles into the matrix.

Abstract: A transducer includes at least one cylindrical driving assembly and at least one headmass coupled to an end of the cylindrical driving assembly. The headmass has an external ring that surrounds a core. The core is made from a core material that is less dense than the material from which the external ring is made. The headmass is dimensioned to occupy a predetermined volume so as to transmit waves within a predetermined frequency range. As a result, the transducer provides higher power waves, yet occupies the same volume as the transducers of the prior art.

Abstract: A transducer includes one or more electro-acoustic motors located on a same internal plane or as a peripheral ring of a flexible envelope to which they are interdependent by at least one-of their ends by an assembling device and to which they transmit their vibrations, the flexible envelope being in contact with the liquid and constituting the acoustic waves emitting surface. The flexible envelope is shaped such that the amplitude of the vibrations is increased in a range of very low frequency. The envelope includes at least one orifice allowing the liquid to enter the whole internal cavity delimited by the envelope and a baffle made up of alveolar material that resists the immersion pressure and fills most of the cavity volume. The external surface of the baffle is at a constant distance from that of the interior of the envelope and is interdependent to the assembling device of the acoustic motors.