Abstract: Stress in a substance is measured by utilizing the transfer characteristics of elastic waves, such that elastic waves input to a substance are displaced by the stress load within the substance. Waves input to the substance and output therefrom by transmission or reflection are compared by fast fourier transform analysis, obtaining a wave attenuation factor quantifying the magnitude of stress in the substance.

Abstract: A non-destructive, non-invasive arrangement is provided for detecting defects, such as voids, or poorly adhering layers in solid objects and laminated materials. A sensing signal is emitted by one transducer and received by two others. All of the sensors are disposed in a housing unit. The difference between the received signals is used to indicate a defect in the work piece proximate one of the transducers.

Abstract: In a functional evaluation device for use in evaluating functional degradation of an artificial device buried in a living body, frequency zones of acoustic emission are detected by the use of the fact that the functional degradation brings about variation of the frequency zones. The acoustic emission may be measured at two different positions adjacent to the artificial device so as to detect an arrival time difference of the acoustic emission and to thereby locate the functional degradation. The acoustic emission is therefore picked up by a pair of transducers placed at the two positions and is processed by a processing circuit for detecting whether or not the functional degradation takes place and by a determining circuit for locating the functional degradation.

Abstract: A code system comprising a temperature-resistance conversion element the change of electric resistance value of which describes a hysteresis loop with respect to a temperature change; a means for changing the temperature of said temperature-resistance conversion element; a means for detecting the change of the electric resistance of said conversion element; and a time counting means of counting the actuation time of said temperature changing means. A hard lock device for use in the code system is also disclosed.