Push & Pull: autonomous deployment of mobile sensors for a complete coverage

Mobile sensor networks are important for several strategic applications devoted to monitoring critical areas. In such hostile scenarios, sensors cannot be deployed manually and are either sent from a safe location or dropped from an aircraft. Mobile devices permit a dynamic deployment reconfiguration that improves the coverage in terms of completeness and uniformity. In this paper we propose a distributed algorithm for the autonomous deployment of mobile sensors called Push&Pull. According to our proposal, movement decisions are made by each sensor on the basis of locally available information and do not require any prior knowledge of the operating conditions or any manual tuning of key parameters. We formally prove that, when a sufficient number of sensors are available, our approach guarantees a complete and uniform coverage. Furthermore, we demonstrate that the algorithm execution always terminates preventing movement oscillations. Numerous simulations show that our algorithm reaches a complete coverage within reasonable time with moderate energy consumption, even when the target area has irregular shapes. Performance comparisons between Push&Pull and one of the most acknowledged algorithms show how the former one can efficiently reach a more uniform and complete coverage under a wide range of working scenarios.Comment: Technical Report. This paper has been published on Wireless Networks, Springer. Animations and the complete code of the proposed algorithm are available for download at the address: http://www.dsi.uniroma1.it/~novella/mobile_sensors

Rule-based Handling of Hazardous Nitrogen

A rule-based, recursive framework is an ideal approach to support the design of cropping systems (CS). A framework of this type was proposed, arranged into three stages (Silvestri and Bellocchi, 2007): (phase I) prior evaluation (technical, problem-solving, farmer-driven stage), (phase II) posterior evaluation (institutional, environmental monitoring implemented when CS response deviates from expected behaviour), and (phase III) managing the change (participatory, dynamic rearrangement of CS). This sequence is meant to evolve and grow over time through reiterations (Fig. 1), allowing for a continuous adaptation of agricultural productions systems as the business environment and society change. The same procedure was applied in this study to assess the behaviour of an array of CS run in the proximity of Lake Massaciuccoli - an area of Central Italy currently defined as “vulnerable area” under EU Directive 676/91 - as part of an action aimed at identifying possible responsibilities of farmers in NO3 contamination of waters (research developed in 2005-2006 under the Italian Ministry of Education, University and Research)

Reflecting on and Embracing the Complexity of Literacy Theories in Practice

This paper responds to the need to support complexities of literacy instruction by identifying and illustrating teaching strategies used by a practicing special education teacher rooted in a multi-theoretical approach to teaching literacy. We argue the importance of teaching from multiple theoretical standpoints and utilizing student-centered, asset-based approaches to pedagogy, assessment, and learning relating to literacy. We share our multi-theoretical approach to understanding and teaching literacy, defining literacy and its complexities. Then, we illustrate several teaching practices including using growth mindset, implementing asset-based data collection, utilizing feedback, and integrating inquiry-based learning that ultimately supports the cultivation of empowered literacy learners who deem learning as both interesting and valuable. Finally, we discuss tensions and challenges inherent to implementing a multi-theoretical approach. Throughout, we provide reflection points to empower teachers to rely on their agency, self-efficacy, and expertise and to feel capable in their knowledge and agency in an era where teachers are increasingly experiencing deprofessionalization through disempowering factors