A new mathematical method for sound speed profile calculation in the ocean is proposed in this paper. Because we are taking account of the characteristics of the sound speed profiles in the middle latitude ocean, this method computes various sound speed distribution curves much easier than by the conventional method. In order to confirm the validity of this method, typical profiles are calculated using the actual measured average temperature data. The difference of propagation sound characteristics is also estimated between under normal condition and under eddy current by the sound ray theory.
The giant magnetostrictive material, of which maximum strain is very large has been useful for many applications. That material has characteristics of large 'd constant', low Young's modulus and low mechanical quality factor. But magnetostriction and magnetization of the material have large hysteresis, so it seems that above mentioned characteristics are depend on the amplitude of exciting magnetic field. That is the reason of necessity of intellectual and complex design for the practical useful application. In this paper, we explained the electric equivalent circuit of giant magnetostrictive vibrator at first. Next, we calculated exciting current dependency of the lumped parameters for the equivalent circuit based on measured impedance data of our developed vibrator, and also derived simple empirical equations of the parameters as a function of input current into the exciting solenoid coil. From these results, it was clarified that larger 'd constant' and higher elasticity can be realized by larger magnetic field into the magnetostrictive rod along the axial direction. Electro-mechanical coupling factor and electro-mechanical efficiency of the vibrator reached to large values, 76% and 90.7% respectively when the input current is 1 ampere. After all, it was verified that the developed vibrator is designed under adequate and excellent combination of magnetic bias and pre-stress.
Lofargram is a processing method for analyzing the temporal structure of passive sonar signals by spectral analysis. The authors have proposed to suppress the impulse noise on lofargram using morphological opening filter instead of averaging procedure which has been used generally. In our experimental results, the effective improvements of the processing gain and the time resolution have been obtained as compared with averaging procedure. However, a large amount of the calculation time of morphological opening filter occurred by the memory access bottleneck with software implementation has been an obstacle to the real-time processing. In this paper, the parallel algorithm of morphological opening filter for lofargram using the distributivity by the structuring element is proposed for the high speed calculation. This algorithm is inspected by the execution results using MIMD parallel machine. Then, the limitation of this method and the performance of the processor node for the real-time smoothing of lofargram are estimated.