Abstract: A piezoelectric composite material including an organic matrix, and 72-78 % by volume of a piezoelectric ceramic powder dispersed in the matrix and consisting of 25-41.6 % by weight of a first group of lead titanate particles having a first average particle size, 25-41.6 % by weight of a second group of lead titanate particles having a second average particle size and 25-41.6 % by weight of a third group of lead titanate particles having a third average particle size. The first, second and third average particle sizes are different from each other and generally 2.5-4.5 .mu.m, 5-10 .mu.m and 20-40 .mu.m, respectively. At least a portion of the lead titanate particles of one of the first to third groups may be substituted with lead titanate zirconate having a similar particle size.

Abstract: A piezoelectric cable for use in detecting under water acoustic wave while being trailed by a boat is disclosed, which includes a core electrode, an outer electrode surrounding the core electrode, a piezoelectric layer disposed between the core electrode and the outer electrode, a sheath surrounding the outer electrode, and a shape retaining member extending axially within the cable and formed of a shape memory alloy whose phase is transformed between an austenite phase and a martensite phase by changing the temperature thereof and memorizing a predetermined shape in the austenite phase of the alloy. One of the core and outer electrodes may be formed of the shape memory alloy and, in this case, the shape retaining member can be omitted.

Abstract: A high unidirectivity piezoelectric element whose d.sub.31, d.sub.33 or d.sub.h is substantially zero. The element may be in the form of a sheet or a cable and includes a pair of electrodes, and a piezoelectric layer interposed between the pair of electrodes and containing two, first and second inorganic piezoelectric materials which have different coercive forces from each other and which are polarized in opposite directions. The element may be obtained by first applying a direct current voltage to a layer containing the first and second piezoelectric materials to polarize the both piezoelectric materials in one direction, and then applying a reverse direct current voltage thereto so that one of the piezoelectric materials having a smaller coercive force is selectively polarized in the other direction.

Abstract: A high d.sub.h piezoelectric composite material useful for utilization for hydrophones is disclosed which includes a matrix of an organic polymeric material and two different inorganic piezoelectric powders dispersed in the matrix. One of the piezoelectric powders has a large .vertline.d.sub.31 /d.sub.33 .vertline. value, such as lead titanate zirconate, and the other piezoelecctric powder has a low .vertline.d.sub.31 /d.sub.33 .vertline. value, such as lead titanate. The average particle size of one of the two piezoelectric powders is at least two times that of the other. The total amount of the two piezoelectric powders is 65-75% by volume based on the total volume of the matrix and the two piezoelectric powder. The volume ratio of the high .vertline.d.sub.31 /d.sub.33 .vertline. piezoelectric powder to the low .vertline.d.sub.31 /d.sub.33 .vertline. piezoelectric powder is in the range of 3:2 to 9:1.

Abstract: A piezoelectric type pager comprises at least one piezoelectric vibrator which has one end fixed on a portion of a casing and the other end fixed on another portion of the casing and can generate a vibration which has a frequency suitable to attract a user's attention without causing any trouble for those around one carrying the pager.

Abstract: A video codec system inputs consecutively frame after frame of sub-sampled video data obtained by sub-sampling video data in units of frames. The video data is coded in parallel by internal coding circuits. This averages the numbers of significant pixels in the sub-sampled video data to be processed. The coded video data is composed so as to comply with specifications of the receiving equipment. Upon transmission, the data is again sub-sampled depending on the number of coding circuits on the receiving side. Each piece of the sub-sampled data is given a header for consecutive transmission. This allows for a certain period of time between pieces of data that arrive at the receiving side, thereby eliminating time differences in receiving and coding.

Abstract: A towed piezoelectric cable having a plurality of receiver element units which are arranged on a nonshrinking flexible core with leaving a buffer zone therebetween, each of said receiver element units having two piezoelectric elements which are polarized in a predetermined direction, and are provided with inner electrodes connected to each other and outer electrodes between which an output signal is produced, respectively, the assembly of said receiver element units and said flexible core being contained in a flexible tube which is filled with an insulating oil.

Abstract: A cyclic fatigue testing apparatus intended for testing the cyclic fatigue of samples such as ceramic or the like, in which it comprises a vibration plate assembly comprising a flex plate provided with piezoelectric element layer(s) on at least one surface thereof, a sample supporting member disposed on the vibration plate for supporting the sample and a loading member for forcing the samnple onto the supporting member. The apparatus can operate over a wide frequency range by adjusting the position of the sample supporting member with respect to the flex plate and selecting the frequency of an alternating voltage to be applied to each piezoelectric element layer.