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Authors propose the use of an ultrasonic transducer to achieve a passive safety system for a collision using a corner sensor. However, the sensitivity of the transducer decreases owing to Doppler shift in the case of a travelling car. On the contrary, authors also propose a resonance control method for the transducer using a generalized impedance converter (GIC) circuit. In this study, the resonance control frequency method is used to correct the sensitivity of the transducer. In the sensitivity control, the input impedance control of the GIC circuit is tried using a voltage-controlled resistance. The automatic sensitivity correction control is expected to be realized by a combination of the GIC circuit and frequency-voltage (F/V) converter. As a result, the sensitivity of a Langevin transducer with a GIC circuit as a receiver is slightly improved, compared with that of a retailed transducer. Moreover, the resonance frequency of the transducer can be controlled in the range of about 3 kHz using the GIC circuit and F/V converter.

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The semiclassical nuclear properties have been studied in the framework of the energy density formalism by choosing two energy densities, one containing derivative terms up to second order and the other also containing fourlh-order derivative terms. The surface energy density in each of the two cases can be suitably approximated so that the Euler-Lagrange (EL) equations in a semi-infinite nuclear medium (SINM) lead to a pure Fermi distribution (F-1) for the density. The importance of the inclusion of the fourth-order derivative terms in the energy density to reproduce the correct surface energy and the correct behaviour of the density in the outer part of the surface has been shown explicitly. The variations of lhe central density pa and lhe surface thickness (I with the sue of the nucleus have been studied under the assumption that the departures E and A of these quantities from their respective SINM values are small. The restricted simple nature of the surface energy density resulting from the imposition of an F-1 distribution of density in a SMM has the advantage of describing the variations E and A in terms of the small ratio ( I between the surface thickness and the half-density radius in a general way, independent of the charactefistics of the energy density used. This study shows that the correct behaviour oi the variations of E and h cannot be reproduced in an expansion in powers of ( I and retaining the first few terms. It is further observed that the lower-order terms in the energy in an expansion in powers of ( I are quite important for a correct description of the departures E and A, at least in the region ( I aO.1, although these lower-order terms are not so important as far as the total energy is concerned. A comparison of the variations of the surface thickness with the size of the nucleus for the two different energy densities shows that the variation h is much smaller for the fourth-order case, in conformity with the fact that the surlace thickness is almost independent of the sue of the nucleus and thereby favours an energy density containing derivative terms up to fourth order over an energy density having only second-order derivative terms.A-"'. In the work of Brack el a/ (1985), the energy density lunctional resulting from the semiclassical expansion upto A4 t e r m has been used for the leptodermous expansion of the total energy. However, in their work, they have not considered the variation of a and v , and have taken fixed values for them. On the other hand, the B Behera and T R Routray

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