Modelling the input-output behaviour of piezoelectric structural health monitoring systems for composite plates

This paper investigates the input-output characteristics of structural health monitoring systems for composite plates based on permanently attached piezoelectric transmitter and sensor elements. Using dynamic piezoelectricity theory and a multiple integral transform method to describe the propagating and scattered flexural waves an electro-mechanical model for simulating the voltage input-output transfer function for circular piezoelectric transmitters and sensors adhesively attached to an orthotropic composite plate is developed. The method enables the characterization of all three physical processes, i.e. wave generation, wave propagation and wave reception. The influence of transducer, plate and attached electrical circuit characteristics on the voltage output behaviour of the system is examined through numerical calculations, both in frequency and the time domain. The results show that the input-output behaviour of the system is not properly predicted by the transducers' properties alone. Coupling effects between the transducers and the tested structure have to be taken into account, and adding backing materials to the piezoelectric elements can significantly improve the sensitivity of the system. It is shown that in order to achieve maximum sensitivity, particular piezoelectric transmitters and sensors need to be designed according to the structure to be monitored and the specific frequency regime of interest.

Some economic dimensions of the mental health jigsaw in Australia

The purpose of this paper is to demonstrate that, although there are some unique features associated with mental illness, such special features do not preclude economic analysis. As a mechanism for understanding how individual economic studies fit into the mental health sector, a conceptual framework of the components of mental health service provision is outlined. Emphasis is placed on, not simply institutional and market resources, but also on the services provided by relatives, self-help groups, etc. Australian data on parts of the mental health sector are employed to illustrate that some (and different) economic analyses can be undertaken in mental health. First, time-series data on public psychiatric hospitals are employed to demonstrate trends associated with deinstitutionalisation. Other data (for Queensland alone) indicate that there are state-based differences in the provision of such services. Second, attention is then directed to the analysis of time-series data on private fee-for-service psychiatric services. Various concepts and measures from industrial economics are applied to analyse the relative size of this service industry, the pricing behaviour of the profession, the service-mix of "the psychiatry firms" operating in Australia.