Polytechnic University of Milan

About: Polytechnic University of Milan is a education organization based out in Milan, Italy. It is known for research contribution in the topics: Computer science & Finite element method. The organization has 18231 authors who have published 58416 publications receiving 1229711 citations. The organization is also known as: PoliMi & L-NESS.

Leader-follower strategies for robotic patrolling in environments with arbitrary topologies

Abstract: Game theoretic approaches to patrolling have become a topic of increasing interest in the very last years. They mainly refer to a patrolling mobile robot that preserves an environment from intrusions. These approaches allow for the development of patrolling strategies that consider the possible actions of the intruder in deciding where the robot should move. Usually, it is supposed that the intruder can hide and observe the actions of the patroller before intervening. This leads to the adoption of a leader-follower solution concept. In this paper, mostly theoretical in its nature, we propose an approach to determine optimal leader-follower strategies for a mobile robot patrolling an environment. Differently from previous works in literature, our approach can be applied to environments with arbitrary topologies.

Model-based control of FES-induced single joint movements

Abstract: A crucial issue of functional electrical stimulation (FES) is the control of motor function by the artificial activation of paralyzed muscles. Major problems that limit the success of current FES systems are the nonlinearity of the target system and the rapid change of muscle properties due to fatigue. In this study, four different strategies, including an adaptive algorithm, to control the movement of the freely swinging shank were developed on the basis of computer simulations and experimentally evaluated on two subjects with paraplegia due to a complete thoracic spinal cord injury. After developing a nonlinear, physiologically based model describing the dynamic behavior of the knee joint and muscles, an open-loop approach, a closed-loop approach, and a combination of both were tested. In order to automate the individual adjustments cited, we further evaluated the performance of an adaptive feedforward controller. The two parameters chosen for the adaptation were the threshold pulse width and the scaling factor for adjusting the active moment produced by the stimulated muscle to the fitness of the muscle. These parameters have been chosen because of their significant time variability. The first three controllers with fixed parameters yielded satisfactory result. An additional improvement was achieved by applying the adaptive algorithm that could cope with problems due to muscle fatigue, thus permitting on-line identification of critical parameters of the plant. Although the present study is limited to a simplified experimental setup, its applicability to more complex and functional movements can be expected.

Enhanced solar cell stability by hygroscopic polymer passivation of metal halide perovskite thin film

Abstract: Long-term device stability is one of the most critical issues that impede perovskite solar cell commercialization. Here we show that a thin layer of a functional hygroscopic polymer, poly(ethylene oxide), PEO, on top of the perovskite thin film, can make perovskite-based solar cells highly stable during operation and in a humid atmosphere. We prove that PEO chemically interacts with lead ions on the perovskite surface, and thus passivates undercoordinated defect sites. Importantly, defect healing by PEO not only results in an improvement of the photo-voltage but also makes the perovskite thin film stable. We demonstrate that the hygroscopic PEO thin film can prevent water inclusion into the perovskite film by screening water molecules, thus having a multi-functional role. Overall, such interface engineering leads to highly durable perovskite solar cells, which, in the presence of PEO passivation, retained more than 95% of their initial power conversion efficiency over 15 h illumination, under load, in ambient atmosphere without encapsulation. Our findings experimentally reveal the role of interface engineering in mastering the instability of perovskite materials and propose a general approach for improving the reliability of perovskite-based optoelectronic devices.

Opening the Black Box of Food Waste Reduction

Abstract: Surplus food management plays a key role in sustainable development, because effective management of food resources and products can reduce food waste and food poverty. This paper addresses the multifaceted concept of food supply chain sustainability by presenting a model of surplus food generation and management (called ASRW, Availability-Surplus-Recoverability-Waste), which encompasses the integrated food supply chain (i.e. business, environmental and social players). The model was developed using a bottom-up approach, by conducting 30 exploratory case studies and iterating theory development and data analysis. Three confirmatory case studies, from different food supply chain stages, are also presented to show the suitability of the model in the identification of food waste reduction strategies.