1,720,959 research outputs found
Modelling and analysis of a single gimbal gyroscopic energy harvester
No full textThis work investigates the non-linear dynamicsof a single gimbal gyroscopic energy harvester,excited by a harmonic moment about 1 and 2 axes simultaneously. The governing equations of motion arederived and a numerical model is developed to analysethe forced system response in all three rotationaldegrees of freedom. Simulations showing the effectof the harmonic forcing frequency and the gyroscopicdamping are presented. The results identify the characteristic motion responses and available power of asingle gimbal gyroscopic energy harvester includingthe development of the non-linear responses
Recharging autonomous underwater vehicles from ambient wave induced motions
No full textIn this paper a novel gyroscopic system capable of recharging an autonomous underwater vehicle (AUV) using wave energy is proposed. The system, which is based on control moment gyroscope (CMG) principles, utilises the gyroscopic response of a gimballed flywheel mounted within an AUV body to generate energy from the wave induced rotational motions of the vehicle. By utilising the wave induced rotational motions of an AUV and the relative motion/torque created by a precessing gimballed flywheel promises to enable AUVs to generate energy in-situ and from a renewable source. This novel approach has several advantages. As the system is housed internally it is not exposed to the harsh underwater environment, is not susceptible to bio-fouling and does not add any hydrodynamic drag. In addition, the system can be positioned anywhere within the AUV body and the technology has the potential to be developed into an integrated energy harvesting, storage and motion control system; whereby the wave induced gyroscopic precession of the flywheel can be used to generate energy, the flywheel kinetic energy (spin) can be utilised for energy storage (similar to Kinetic Energy Recovery Systems or KERS) and motion control can be provided by precession control of the flywheel (providing a stable platform for improved monitoring/recording capabilities). In this paper a theoretical description of the system is provided including a derivation of the governing equations of motion following a momentum (Newton-Euler) approach. A numerical model is also described and simulation results for a pitching 2m AUV system are presented. The results show that the system could be used to periodically recharge an AUV remotely, enabling longer AUV deployments at sea<br/
Gyrostabilizer vehicular technology
No full textThis paper examines the current state of gyrostabilizer vehicular technology. With no previous description of the wide range and variety of gyrostabilizer technology, this paper provides a review of the current state of the art. This includes a detailed examination of gyrostabilizer vehicular systems, dynamics and control. The present review first describes the historical development of gyroscopic systems before going on to describe the various system characteristics, including an overview of gyrostabilizer vehicular applications and system designs for land, sea and spacecraft. The equations of motion for generic gyroscopic systems are derived following momentum (Newton-Euler) and energy (Lagrange) based approaches and examples provided. The derivations are made generically for individual components, enabling direct application for a wide variety of systems. In the final section, a review of gyrostabilizer control strategies is presented and the remaining challenges are discussed. Gyrostabilizer systems are anticipated to become more widely adopted as they provide an effective means of motion control with several significant advantages for land, sea and spacecraft.(101 references
Experimental investigations into the current-induced motion of a lifeboat at a single point mooring
No full textThis paper presents a series of model experiments on the current-induced motions of a 1:40 scale lifeboat at a single point mooring (SPM). The influence upon vessel and buoy motion of the mooring configuration factors of (a) three mooring line (hawser) lengths, (b) four buoy shapes and (c) two buoy sizes have been investigated.A motion tracking algorithm was successfully employed and validated against data from an inertial measuring unit allowing small scale testing without the influence of instrument cabling. The results show that the dominanttranslational motion, of the model lifeboat at a SPM, is sway and the rotational motion is yaw, with double pendulum-like fishtailing behaviour prevalent. Increasing the hawser length, when no buoy was present, resulted in an increase in the vessel's sway velocity. No significant effects on vessel motion were observed from changes in the shape of the 1:40 and 1:20 scale buoys. However, the presence and increasing size of the buoy was found to increase the sway velocity of the buoy and reduce the motions of the model lifeboat. These results suggest that changes in buoy size influence the motions of the model lifeboat which may enable mooring efficacy to be improved
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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