1,720,969 research outputs found
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
Adaptive backstepping control design for mass estimation and trajectory control of quadrotor with spherical pendulum
No full textThis study focuses a trajectory control problem of a quadrotor, created by combining the dynamics of a spherical pendulum with the dynamics of a quadrotor. A spherical pendulum is a physical system comprising a mass suspended by a string or rod that has the freedom to swing in any direction. During the operation of a quadrotor, the payload connected to it behaves similar to the dynamics of a spherical pendulum. Consequently, it is essential to design a trajectory control problem by considering both quadrotor and spherical pendulum dynamics together, as this constitutes a significant aspect. Due to the varying masses of the payload that are attached to the quadrotor during each take off, the adaptability of the total mass in model-based control design poses a significant challenge. In addition, it is crucial to consider mass adaptation when the payload attached to the quadrotor is released during flight. The proposed Lyapunov based adaptive backstepping controller algorithm can predict the total mass of the quadrotor without prior knowledge of the actual payload. The ability to estimate varying payload masses is crucial for enhancing the quadrotor's operational flexibility and reliability, particularly in real-world applications where payloads may change dynamically. This innovation paves the way for more versatile, real-world deployment of quadrotor systems in scenarios requiring precise and adaptive control
A vertical take-off and landing (VTOL) unmanned aircraft vehicle trajectory control model with air-launched missiles
No full textPurposeIn today's technology, the significance of unmanned aerial vehicles is steadily increasing. Many unmanned aerial vehicles design, especially those used for military purposes, have achieved autonomy from human operators. Undoubtedly, one of the most crucial features of these aircraft is their vertical take-off and landing (VTOL) capability. Inspired by quadrotor methodology, this paper aims to conduct, a modeling of an aircraft with VTOL capabilities.Design/methodology/approachThe impact of releasing air-launched missiles, considered as the useful payload carried during the flight of the aircraft, has been taken into account in this modeling. The release of air-launched missiles disrupts both the symmetric structure of the system and alters the mass and inertia parameters. Simulations were conducted to investigate scenarios involving the simultaneous release of all air-launched missiles and their release at different times.FindingsThe investigation focused on determining how quickly an aircraft, aiming to consecutively hit targets, can return to its desired trajectory. The time interval between the consecutive releases of two air-launched missiles has been identified.Originality/valueIt is crucial for a VTOL-capable aircraft to possess a unique modeling structure to examine its capability of releasing air-launched missiles in various scenarios. This entails understanding not only the aircraft's VTOL functionality but also its ability to effectively release missiles in different operational conditions
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
Levitation force analysis of ring and disk shaped permanent magnet-high temperature superconductor
Get PDF261-268In superconducting magnetic levitation systems, interaction models between a high temperature superconductor and a permanent magnet are useful to analyze the dynamics of the levitated system. In this study, stiffness equations of a superconducting levitation system using a disk and a ring permanent are obtained using frozen image concept. The variation of the stiffness has been analyzed for vertical movements of the PMs. For engineering applications, accuracy of such models should be tested experimentally. An experimental PM-HTS setup has been built to verify the obtained models for different cooling height conditions. Levitation forces computed using the frozen image approach for the disk and ring PMs are converged to the experimental results when the cooling heights are smaller values
Novel repulsive magnetic bearing flywheel system with composite adaptive control
Get PDFHere, a novel flywheel structure is proposed with passive permanent magnet (PM) bearings in the radial and axial directions and an active magnetic bearing (AMB) in the axial direction. In the proposed structure, passive magnetic bearings do not provide a stable magnetic levitation in all directions, but it is possible to maintain the dynamic stability of the flywheel by using AMB in the axial direction. In the proposed bearing structure, radial repulsive magnetic bearings (RMBs) reduce the power consumption with less complexity in the bearing structure but impose disturbance forces that deteriorate the stability of the actively controlled flywheel system. A complete model of the flywheel system is derived and transformed for a control design. A Lyapunov-based composite adaptive feedback control is designed for maintaining the stability under disturbances and a close convergence to the desired trajectory with fast parameter estimation. The performance of the composite adaptive control was experimentally verified for different cases using the RMB flywheel system. Additionally, a PID control was experimentally verified to demonstrate the usefulness of parameter estimation.Scientific and Technological Research Council of Turkey [214M284]This work was supported by The Scientific and Technological Research Council of Turkey through grant no 214M284 under the research projects funding program
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