1,720,956 research outputs found
Constrained path planning for manned–unmanned rotorcraft teaming in emergency medical service missions
Get PDFThis paper investigates the path-planning problem applied to an innovative Unmanned Air Vehicle teaming with a helicopter to increase safety during Helicopter Emergency Medical Services operations. The unmanned vehicle, a drone that optionally can be launched from the helicopter, has the mission to explore the area of operation to determine the meteorological and environmental conditions and to detect physical obstacles. It is initially found that the combination of probabilistically optimal Rapidly-exploring Random Tree (RRT*) as the global planner and of Bidirectional Rapidly-exploring Random Tree (BiRRT) as the local planner provides a nearly optimal global path and a rapid replanning in case new obstacles are detected. Adopting a Savitzky–Golay filter in an optional post-processing phase enables trajectory smoothing, thus improving its practicability. The feasibility of the identified trajectory for a rigid-body helicopter model is assessed by computing a first estimate of attitude, forces, control inputs, and rotor power from the trajectory points and curvature. This assessment shows that the RRT* used as a local planner provides replanned trajectories more feasible than BiRRT with comparable computational times
A SysML-based framework towards EASA CS-23 digitalization: An MBSE approach
Get PDFThe general aviation sector is undergoing rapid transformation, driven by technological innovation and increasing market demand. However, certification frameworks remain predominantly document-based, resulting in inefficiencies and elevated costs. This study presents a digital certification framework grounded in Model-Based Systems Engineering (MBSE), utilizing the Systems Modeling Language (SysML) to encode the European Union Aviation Safety Agency (EASA) Certification Specifications (CS-23) and Acceptable Means of Compliance (AMC) into a structured, machine-readable model. The proposed methodology enables automated verification and validation, report generation, and traceability across regulatory artifacts. Beyond its technical contributions, the framework addresses interdisciplinary challenges in the present regulatory landscape, systems engineering, and organizational communication. It highlights the complexity of certification processes, emphasizing the need for coherent information exchange among stakeholders with varying levels of technical proficiency. The study contributes to ongoing discussions in the social sciences regarding institutional adaptation, digital transformation, and collaborative governance in high-reliability sectors. The framework’s scalability to commercial aviation and its potential to support emerging aircraft architectures underscore its relevance to both industry and regulatory bodies
Scout Drone: a Drone-Helicopter Collaboration to Support HEMS Missions
Get PDFThe paper presents the idea to exploit the collaboration between unmanned VTOL drones and helicopters to increase the situational awareness of helicopter employed in emergency, medical or search and rescue missions. The need for this collaboration is initially presented in the introduction. Then, after performing a review of the current state of the art that indicates that no system of this type is currently under development, the principles of operation of such a system are expressed together with a first brief description of possible concepts of operation. Finally, some preliminary thought on two of the most relevant elements of this system, the drone and the control station are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Nonlinear dynamic model of an unmanned rotorcraft : implementation and validation
Get PDFLAUREA MAGISTRALEIn questa tesi viene trattato lo sviluppo del modello non lineare della dinamica di un elicottero a pilotaggio remoto, utilizzabile anche per il volo automatico. Il modello, implementato in ambiente Simulink-Matlab, riceve in ingresso i comandi di collettivo, ciclico e coda generati dal controllore o dal pilota tramite il radiocomando e fornisce in uscita la posizione, la velocità e l'assetto del velivolo.
Nella prima parte della tesi è descritta la realizzazione del modello. Il modello è organizzato sotto forma di schema a blocchi in cascata composto da quattro sistemi: il primo contiene il modello del cinematismo degli attuatori che convertono i comandi in variazioni del passo delle pale; il secondo contiene la dinamica del rotore, e fornisce in uscita l'angolo di incidenza, la velocità all'aria e le accelerazioni degli elementi di pala; nel terzo blocco vengono modellate le forze ed i momenti trasmessi al corpo dell'elicottero e nel quarto sono contenute le equazioni del corpo rigido per la dinamica del velivolo.
Una particolare attenzione in questo lavoro di tesi è dedicata alla modellazione dell'aerodinamica del rotore, con una trattazione sui modelli di influsso provenienti dalla Momentum Theory, dalla BEMT ( Blade Element Momentum Theory) e dalla teoria dell'influsso dinamico di Pitt e Peters. La BET (Blade Element Theory) è utilizzata per modellare le forze ed i momenti di pala. La dinamica del flappeggio è trattata ampiamente, insieme a metodi sperimentali per determinare la posizione della cerniera di flappeggio e la frequenza naturale del fenomeno.
Nella seconda parte della tesi si descrive il processo di validazione tramite simulazioni in anello chiuso col controllore, i cui risultati vengono comparati con quelli del modello lineare del velivolo identificato tramite prove di volo. Le simulazioni danno risultati soddisfacenti e confrontabili con quelli del modello identificato, tranne per alcuni aspetti quali oscillazioni più accentuate ed un angolo di rollio maggiore in tutte le fasi della missione simulata. Queste discrepanze conducono all'elaborazione di alcune raccomandazioni per gli sviluppi futuri del modello.The present thesis treats the development and validation of a nonlinear dynamic model for an unmanned rotorcraft. The model, implemented in the Simulink-Matlab environment, receives as input the collective, tail and cyclic commands generated by the controller or by the pilot through the radio control and provides as output the velocities, positions and attitude of the aircraft.
In the first part of the thesis, the implementation of the model is described. The model is organized as a cascade block diagram composed by four blocks: the first one contains the servo model, which computes the collective and cyclic pitch variation on the blades depending on the commands received; the second block includes the rotor dynamics, and provides the angle of attack, the airspeed and the acceleration of the blade; the third block computes the forces generated on the rotorcraft and the fourth block contains the rigid body motion equations.
A particular attention in the thesis is dedicated to the rotor aerodynamics, with a discussion on the inflow models coming from the momentum theory, the BEMT (Blade Element Momentum Theory) and the Pitt-Peters dynamic inflow theory. The BET (Blade Element Theory) is used to compute the blade forces and moments. The flapping dynamics modelling is widely treated, along with experimental methods to obtain the flapping hinge offset and the flapping frequency.
In the second part of the thesis the process of validation carried out with closed-loop simulations is described. The results of the simulations are compared to the ones of the linear in-flight identified model of the helicopter. The simulations provide satisfactory results comparable to the ones provided by the identified model except for some aspects as the emphasized oscillations or greater roll angle in all the phases of the mission simulated. These discrepancies lead to the production of some recommendations for the future developments of the model
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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