1,721,015 research outputs found
Optimal Path Planning for Autonomous Spraying UAS framework in Precision Agriculture
Full text linkThis paper presents a novel guidance and control strategy for multirotor Unmanned Aerial Systems (UASs) which aims to provide an autonomous and safe mission in precision agriculture applications.
In the last few years, the research in this field has always improved thanks to the advent of new technologies and with the launch of the first smart farms. Precision aerial spraying of Plant Protection Products (PPP) in vineyards is the focus of this work, highlighting several advantages in terms of quality management, time and cost. In particular, we propose a combination of a Traveling Salesman Problem (TSP) solver with the well-know Theta* algorithm to investigate optimal UAS trajectories in order to visit a specific number of plants that require intervention. The final goal is to demonstrate the fulfillment of the evaluated trajectory with the on-board control system of the vehicle in provision for UAS field testing.
Finally, the planning strategy is applied to two case studies so as to present the feasibility of a more efficient autonomous UAS path planning
Biomaterials for Bone Tissue Engineering 2020
No full textOver the last few decades, a variety of tissue engineering strategies have been developed to improve the regenerative properties of bone biomaterials (e.g., osteoinduction and osteoconduction). This Special Issue on “Biomaterials for Bone Tissue Engineering” will provide an overview of the recent advances and cutting-edge approaches in the field of bone biomaterials and bone tissue engineering, including the new molecular insights on the various aspects of the interaction of bone substitutes with cells and tissues. Contributions reporting innovative materials, osteoinduction and osteoconduction approaches, and examples of combination with biochemical and/or physical stimuli and/or different cell types (e.g., stem cells, macrophages, endothelial cells) tested for their application in bone tissue regeneration and engineering are welcome
Proximity operations with obstacles avoidance based on artificial potential field and sliding mode control
No full textThis paper combines Guidance and Control (GC) algorithms for spacecraft proximity operations in presence of multiple obstacles. The proposed guidance algorithm is based on Artificial Potential Field (APF) theory, while the adopted control strategies are first-order Sliding Mode Control (SMC) algorithms. The position control problem is addressed by considering two different first-order methods: the simplex-based and the component-wise SMC. Both control strategies result to be effective and suitable to be implemented by the mono-directional actuation system. These algorithms are suitably designed for a ground test-bed for spacecraft rendezvous and docking experiments, developed within the STEPS project (Systems and Technologies for Space Exploration). The selected algorithms are suitable for autonomous, real-time control of proximity maneuvers with a minimum on-board computational effort. Moreover, the presented strategy is able to avoid obstacles and to manage issues related to the presence of local minima in APF algorithms
Numerical Analysis and Wind Tunnel Validation of Droplet Distribution in the Wake of an Unmanned Aerial Spraying System in Forward Flight
Full text linkRecent developments in agriculture mechanization have generated significant challenges towards sustainable approaches to reduce the environmental footprint and improve food quality. This paper highlights the benefits of using unmanned aerial systems (UASs) for precision spraying applications of pesticides, reducing the environmental risk and waste caused by spray drift. Several unmanned aerial spraying system (UASS) operation parameters and spray system designs are examined to define adequate configurations for specific treatments. A hexarotor DJI Matrice 600 equipped with T-Motor “15 × 5” carbon fiber blades is tested numerically using computational fluid dynamics (CFD) and experimentally in a wind tunnel. These tests assess the aerodynamic interaction between the wake of an advancing multicopter and the fine droplets generated by atomizers traditionally used in agricultural applications. The aim of this research is twofold. First, we analyze the effects of parameters such as flight speed (0, 2, and 3 m·s (Formula presented.)), nozzle type (hollowcone and fan), and injection pressure (2–3 bar) on spray distribution. In the second phase, we use data from the experimental campaign to validate numerical tools for the simulation of rotor–droplet interactions necessary to predict spray’s ground footprint and to plan a precise guidance algorithm to achieve on-target deposition and reduce the well-known droplet drift problem
Toward Virtual Testing of Unmanned Aerial Spraying Systems Operating in Vineyards
Full text linkIn recent times, the objective of reducing the environmental impact of the agricultural industry has led to the mechanization of the sector. One of the consequences of this is the everyday increasing use of Unmanned Aerial Systems (UAS) for different tasks in agriculture, such as spraying operations, mapping, or diagnostics, among others. Aerial spraying presents an inherent problem associated with the drift of small droplets caused by their entrainment in vortical structures such as tip vortices produced at the tip of rotors and wings. This problem is aggravated by other dynamic physical phenomena associated with the actual spray operation, such as liquid sloshing in the tank, GPS inaccuracies, wind gusts, and autopilot corrections, among others. This work focuses on analyzing the impact of nozzle position and liquid sloshing on droplet deposition through numerical modeling. To achieve this, the paper presents a novel six degrees of freedom numerical model of a DJI Matrice 600 equipped with a spray system. The spray is modeled using Lagrangian particles and the liquid sloshing is modeled with an interface-capturing method known as Volume of Fluid (VOF) approach. The model is tested in a spraying operation at a constant velocity of 2 m/s in a virtual vineyard. The maneuver is achieved using a PID controller that drives the angular rates of the rotors. This spraying mission simulator was used to obtain insights into optimal nozzle selection and positioning by quantifying the amount of droplet deposition
Editorial: Cells, biomaterials, and biophysical stimuli for bone, cartilage, and muscle regeneration, volume II
No full textPreliminary Design of a Remotely Piloted Aircraft System for Crop-Spraying on Vineyards
Full text linkThis paper describes the preliminary design of an innovative concept rotary-wing Unmanned Aircraft System (UAS) for precision agriculture and aerial spraying applications. Aerial spraying of plant protection products and pesticides shows open challenges in terms of performance and regulatory requirements. In particular*the focus here is on highlighting the advantages of the proposed solution in performing precise and expeditious interventions, coping with the spray drift problem (i.e. minimization of drift). Flight performances and agronomists' requirements are combined to define the mission and the aerial vehicle and spray system design
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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