The protection of forests is crucial to providing important ecosystem services, such as supplying clean air and water, safeguarding critical habitats for biodiversity, and reducing global greenhouse gas emissions. Despite this importance, global forest loss has steadily increased in recent decades. Protected Areas (PAs) currently account for almost 15% of Earth’s terrestrial surface and protect 5% of global tree cover and were developed as a principal approach to limit the impact of anthropogenic activities on natural, intact ecosystems and habitats. We assess global trends in forest loss inside and outside of PAs, and land cover following this forest loss, using a global map of tree cover loss and global maps of land cover. While forests in PAs experience loss at lower rates than non-protected forests, we find that the temporal trend of forest loss in PAs is markedly similar to that of all forest loss globally. We find that forest loss in PAs is most commonly—and increasingly—followed by shrubland, a broad category that could represent re-growing forest, agricultural fallows, or pasture lands in some regional contexts. Anthropogenic forest loss for agriculture is common in some regions, particularly in the global tropics, while wildfires, pests, and storm blowdown are a significant and consistent cause of forest loss in more northern latitudes, such as the United States, Canada, and Russia. Our study describes a process for screening tree cover loss and agriculture expansion taking place within PAs, and identification of priority targets for further site-specific assessments of threats to PAs. We illustrate an approach for more detailed assessment of forest loss in four case study PAs in Brazil, Indonesia, Democratic Republic of Congo, and the United States.

For many of us in emergency medicine, rising to the challenge of the COVID-19 crisis will be the single most exciting and challenging episode of our careers. Lessons have been learnt on how to make quick and effective changes without being hindered by the normal restraints of bureaucracy. Changes that would normally have taken months to years to implement have been successfully introduced over a period of several weeks. Although we have managed these changes largely by command and control, compassionate leadership has identified leaders within our team and paved the way for the future. This article covers the preparation and changes made in response to COVID-19 in a London teaching hospital.

In this paper, two alternative modelling approaches for a one-way mechanical coupling device known as a free-wheeling clutch are considered. Unlike existing mathematical models which account for variables primarily aimed at design and life expectancy calculations, a simple model capturing the essential couple-decouple behaviour is sought for future use in control design. The bond graph methodology is used as a framework in which to examine two alternative models for the clutch: a semi-ideal model involving non-linear resistance and an ideal model introducing hybrid-dynamical behaviour. Some properties of each model are made explicit and their desirable and undesirable features highlighted. Experimental verifications using a twin electric motor drive are conducted to validate the models and then used to evaluate their practical usefulness. The ideal model is then used to characterize the behaviour of a typical two-driver transmission. Finally, preliminary considerations are discussed regarding the use of the ideal model in subsequent control designs.

A portable testbed is designed and built to demonstrate attitude control using cold gas thrusters. The main components are a high-pressure Nitrogen tank, solenoid valves, nozzles and a data acquisition and control interface. The device is small enough to be operated on a desktop, facilitating classroom demonstrations. The device can be commanded from a laptop computer having the necessary interfacing software. A rotary encoder provides angular position information for use in model generation and calibration or in feedback control evaluations. Only bang-bang, pulse-width modulation and similar control strategies are possible to be implemented in this system due to the on/off nature of thruster operation. The paper describes the design and construction of the platform, the procedures followed to estimate key dynamic parameters and includes a sample run using a time-fuel optimal control law based on a nominal double integrator plant.

This paper discusses modeling approaches for mechanical systems which may be driven from more than one source of power and which include unidirectional coupling elements. These systems arise in various settings, including heavy-lift helicopters and hybrid automobiles. In this paper, two kinds of mathematical model are examined for the free-wheeling clutch, a key element in these systems. It is shown that it is not possible to define transition rules between coupled and decoupled states using only relative speed or only torque if idealized models are used. A model involving a mixed torque-velocity transition rule is shown to capture the essential switching behavior. By using the bond graph formalism, the inclusion of realistic continuous effects such as inertia and friction becomes simple by modular cascading. A simplified two-driver hybrid dynamical model is constructed and characterized using the mixed model and the concept of clutch line is introduced to characterize the dynamic behavior. This work serves as a basis for subsequent controllability studies and selection of feedback control strategies.