Abstract: A ceramic heat exchanger element comprises a ceramic honeycomb body, fluid passages formed in the ceramic honeycomb body and ceramic tubes extending through and fixed to the ceramic honeycomb body so as to intersect the fluid passages. The ceramic of the honeycomb body, the fluid passages therein, and the tubes extending through and fixed thereto preferably have a thermal conductivity of 15 Kcal/m/hr/.degree.C. or higher.

Abstract: The present invention relates to a beam forming device for forming a uniform radiation beam and/or a reception beam. In radiation, the transducer is vibrated in such a way that the pressure of a sound wave produced from each point of the vibrating surface of the transducer is determined based on a weight function, thereby forming a radiation beam. In reception, electric signals are derived based on the sound energy received in a manner that the amplitude level of an electric signal produced based on the sound energy received by each point of the vibrating surface of the transducer is determined based on a weight function, and the derived signals are combined with one another to form a reception beam.

Abstract: An underwater detection system which has a transmitting and receiving unit for radiating an ultrasonic wave pulse into the water within a narrow sector and receiving echo signals by a plurality of reception beams, and turns the transmitting and receiving unit by a predetermined angle to search another narrow sector each time the search within the narrow sector is completed, thereby searching the water within a wide angular range.

Abstract: A multicellular monolithic ceramic body having many gas passages partitioned by thin walls is made of aluminum titanate as a major cnstituent and has less than 0.15% of a thermal expansion coefficient at 1000.degree. C. and higher than 350 kg./cm.sup.2 of a compressive strength as zero of an open frontal area as the properties in the direction along the gas passages and more than 35% of a porosity.