Abstract: According to the invention, the object (34) is brought to a first inspection station (I to IV) in which the object is irradiated by thermal neutrons, the capture gamma radiation then liable to be emitted by the object and characterizing a chemical element of the substance to be detected is detected, if the intensity of said radiation exceeds a predetermined threshold, the object is brought to a second inspection station (V,VI), in which the object is irradiated by fast neutrons and the prompt gamma radiation then liable to be emitted by the object and characterizing the chemical element is detected, the energy of the fast neutrons being at least equal to that of prompt gamma radiation, in order to confirm or disprove the information obtained in the first station.

Abstract: A device for examining objects by ultrasonic echography comprising a focusing network of n ultrasonic transducers and in which the ultrasonic transducers (a,b,c, . . . i, . . . , n-1,n) are made of an electrostrictive material with non-remanent polarization, and the said polarization is effected by a polarization stage comprising: (1) a source (501) of p polarization direct voltages, (2) a demultiplexing and branching circuit (502) receiving, on the one hand, the p polarization voltages and, in the other, combinations of m bits selecting the said voltages in order to supply them to the transducers, (3) a circuit for the determination of a law of sensitivity (503), consisting of a counter (522) whose number of states corresponds at least to the numbers of directions to be explored and of a memory (521), intended to provide the n respective digital combinations corresponding to each state of the counter, and (4) a sequencer (520).

Abstract: An ultrasonic transducer comprising a network of parallel piezoelectric transducer elements having a width W or in the form of a parallelepipedon having a length H and a width W, characterized in that the thickness T of the said transducer elements is equal to half the wavelength corresponding to a frequency F which is equal to the average value of at least two of the successive piezoelectric resonance frequencies of the piezoelectric material concerned, the products of the thickness and the resonance frequencies framing at least two successive vibratory modes of this material in the bidimensional diagram of the curves F.multidot.T=f(W/T) of the spread of the resonance frequencies relating to the piezoelectric material concerned or in the tridimensional diagram of the curves F.multidot.T=f(W/T, H/T).

Abstract: A device for determining preferred directions in biological structures by ultrasonic examination. The device comprises an electroacoustic converter which is sub-divided into at least four sectors and which comprises transducers which are combined in groups in sectors which are diametrically situated with respect to the center. The transducers of each group are connected to the inputs of an adder. The outputs of the adders are connected to an arithmetic circuit which is adapted to form a first signal which is dependent of the sum of all signals generated by the transducers, and to form also a number of second signals which are dependent of the differences between signals generated by different transducer groups. The arithmetic circuit is connected to a display device for color images in a manner so that the first signals determines the brightness of the image, while the second signals determine the color information.