Finding the "right-size" physical therapy workforce is an increasingly important issue, but it has had limited study, particularly across nations. This perspective article provides a comprehensive examination of physical therapy workforce issues across 4 countries (United States, Singapore, Portugal, and Bangladesh), which were deliberately selected to allow consideration of key contextual factors. This investigation provides a theoretical model uniquely adapted to focus on variables most likely to affect physical therapy workforce needs. This theoretical model was used to guide acquisition of public domain data across the respective countries. The data then were used to provide a contextualized interpretation about the physical therapy workforce supply (ie, physical therapists per capita) across the 4 countries in light of the following factors: indicators of physical therapy need, financial and administrative barriers affecting physical therapy access and demand, the proportion of physical therapy graduates (with varying trends over time across the countries), and the role of emigration/immigration in supply inequalities among countries of lower and higher income. In addition, both the physical therapy workforce supply and scope of practice were analyzed in the context of other related professions across the 4 countries. This international comparison indicated that there may not be a "one-size-fits-all" recommendation for physical therapy workforce supply across countries or an ideal formula for its determination. The optimal, country-specific physical therapy workforce supply appears to be affected by discipline-specific health care and contextual factors that may vary across countries, and even within the same country. This article provides a conceptual framework and basis for such contextualized evaluations of the physical therapy workforce.

A large quantity of recent research into the harvesting of electrical energy from ambient vibration sources has been focused on the improvement of device performance via the deliberate introduction of dynamic nonlinearities. In addition to this, the realisation that most of these kinetic energy sources are stochastic in nature has led to many studies focusing on the response of energy harvesters to random vibrations (often Gaussian white noise). This differs from early studies in which it was assumed that ambient vibration sources were sinusoidal. The aim of the present study is to take current nonlinear energy harvesting solutions and to numerically analyse their effectiveness when two real ambient vibration sources are used: human walking motion and the oscillation of the midspan of a suspension bridge. This study shows that the potential improvements that can be realised through the introduction of nonlinearities into energy harvesters are sensitive to the type of ambient excitation to which they are subjected. Additionally, the need for more research into the development of low-frequency energy harvesters is emphasised.

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Linear energy harvesters can only produce useful amounts of power when excited close to their natural frequency. Due to the uncertain nature of ambient vibrations, it has been hypothesised that such devices will perform poorly in realworld applications. To improve performance, it has been suggested that the introduction of non-linearities into such devices may extend the bandwidth over which they perform effectively. In this study, a magnetic levitation device with non-linearities similar to the Duffing oscillator is considered. The governing equations of the device are formed in which the effects of friction are considered. Analytical solutions are used to explore the effect that friction can have on the system when it is under harmonic excitations. Following this, a numerical model is formed. A differential evolution algorithm is used alongside experimental data to identify the relevant parameters of the device. The model is then validated using experimental data. Monte Carlo simulations are then used to analyse the effect of coulomb damping and Duffingtype non-linearities when the device is subjected to broadband white noise and coloured noise excitations.