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The problem of maximizing the range of a propeller-driven aircraft in a level flight cruise is analyzed within the framework of optimal control. The specific fuel consumption and propeller efficiency of its propulsive system are characterized by functions of the velocity and engine power (full model), in contrast to previous works, where they were considered to be constant. To conduct the study, a notional Piper Cherokee PA-28 is selected as representative of light aircraft, defining both the airplane and mission features. Two simplified models are also derived: the Von Mises model, with constant specific fuel consumption and propeller efficiency, and the Parget and Ardema model, defined by constant specific fuel consumption and propeller efficiency depending on the velocity. The problem is solved numerically by means of a direct transcription method. Since the optimal problems of the Von Mises and Parget and Ardema models are singular, it is necessary to incorporate a regularization term. Such a numerical algorithm is validated against the analytical solution given by the Breguet formulation. In this context, the velocity and mass (state variables), the power throttle (control), and the best range are determined. The full model provides a maximum range of 1492 km. The differences between the Von Mises and Parget and Ardema models are about 24 km and 1 km, respectively. A non-optimal steady cruise is also analyzed, providing a significant reduction in the flight time, with a decrease of about 2% of the range. The evolution of the state variables and control in the steady cruise, however, separates from the full model. On the other hand, the Parget and Ardema model almost reproduces the full model results, leading to a clear image of the physics involved: the best range comes from maximizing the product of the propeller and aerodynamic efficiencies with respect to the velocity, which determines the optimal arc.

Despite over two decades of intense research into bioelectrochemical systems (BESs), their practical implementation remains unrealized, partly due to the low performance of bioelectrodes. With the introduction of additive manufacturing techniques, the development of a new generation of bioelectrodes with custom-shaped geometries using conductive composites has become feasible. This study examines the potential of using two conductive composites, Poly-lactic acid (PLA) and thermoplastic polyurethane (TPU), for 3D-printed electrodes. Electrochemical characterization reveals that TPU has a charge transfer resistance approximately two orders of magnitude higher than PLA, rendering it unsuitable for bioelectrodes. The presence of triangular patterns enhances the performance of planar electrodes, with optimal results observed for PLA-based electrodes with surface pattern depths between 0.6 and 1.4 mm. Additionally, electrodeposition (ED) of graphene oxide (GO) further improves performance across all cases. During the subsequent biotic start-up, patterned PLA electrodes with a depth of 1.4 mm exhibit higher current. However, these 3D-printed electrodes exhibit degradation after 56 days of operation.

This study explores the possibility of utilising electrochemically assisted anaerobic digestion supplemented with carbon-based materials to stimulate methanogenesis. Two different carbonaceous materials—commercial activated carbon (AC), and pyrolysed argan (PA, derived from argan shells)—were employed as supplements, with cheese whey (CW) being used as the substrate. Methane production slightly increased in the electrochemically assisted digesters, potentially translating into a 2–4% increase in the output of industrial digesters. In addition, reactors supplemented with PA also exhibited better production rates (496–508 L·kgVS−1), although there was no observed improvement in the quantity of biogas at the end of the biodegradability experiment. In contrast, when commercial AC was used as the supplement, the start-up phase was accelerated (5 days), although methane productivity decreased (273–352 L·kgVS−1). These observations were supported by microbiological analyses, demonstrating that the reactors with the poorest performance (those supplemented with AC) experienced the most significant decrease in both archaeal and bacterial populations.