1,721,007 research outputs found
Lessons learnt from 12 years experience of the launch and recovery of Autosub
No full textThe Autosub AUV project, funded by the Natural Environment Research Council (NERC) has been used worldwide over the last twelve years, for the most part, using a purpose made gantry on a variety of ships for launch and recovery. Over this time, a history has accumulated of the system strengths, weaknesses, and maintenance and refit costs. We require a second system to allow simultaneous AUV use on separate ships. This will be designed to be a more compliant system, tolerant of high dynamic loads. We will also review the positioning of the system on the ship to minimise pitch and roll movements. The inherent dynamic difficulties in recovering AUVs are similar to those of ROVs and we would consider whether a common crane system with interchangeable lift heads would be feasible for use with either AUVs or ROVs, thus creating the benefits of a shared infrastructure
Air launched platforms - a new approach for underwater vehicles
No full textThe economics of expediting wide area, synoptic surveys of the oceans often limit the extent and frequency of such work. The concept of Air Launched Platforms addresses the question of how to carry out this work more effectively using small and affordable submersible autonomous vehicles launched from fixed or rotary wing aircraft. With relatively recent developments of mass market GPS receivers, processors, attitude sensors and micro machines, there is the possibility developing new platforms and methods to carry out wide area survey work in a very different way
AUV design – shape, drag and practical issues
No full textTwenty years ago, Autonomous Underwater Vehicles (AUVs) were an infant technology and there was an absence of evolution to guide designers in deciding the fundamental shape and size of their craft. Since this period there have been a wide variety of AUV shapes and sizes tried, these include torpedo shapes, (e.g. Autosub, Remus), laminar flow bodies (early Hugin vehicles), streamlined rectangular styles (e.g. Maridan), and multi hull vehicles, (ABE). Each came with a vision of fulfilling a certain set of requirements and oceanographic niche
AUV design – shape, drag and practical issues. Looking to combine the practical and hydrodynamic considerations
No full textThis paper reports on recent Computational
Fluid Dynamics (CFD) work, revisiting the concept of the
tear drop shaped laminar flow hull and compares it with
practical drag data, both laminar body and torpedo
shape, that has been accumulated over the years. A short
vehicle of length /diameter ratio 3 to 4 can be a more
practical proposition with little if any increase in drag
coefficient (Cd. The laminar flow body, an idea largely
discarded in the 1990s due to practical build difficulties
and shortfall in expected performance, may still have a
lower Cd if care is taken with the placement of external
ancillaries
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
Autosub6000: results of its engineering trials and first science missions
Full text linkIn September 2007 on RRS Discovery, the Autosub6000 Autonomous Underwater Vehicle (AUV)
completed its first deep water engineering trials, and less than a year later, fitted with a multibeam
bathymetric mapping sonar, carried out its first science missions, as part of a geology and
geophysics science cruise onboard the RRS James Cook to investigate potential geo-hazards
(such as tsunami generating landslides) on the European and North African margin. In the spirit of
true AUV autonomy, while the AUV was deployed, we used the ship for seabed coring operations,
and once the AUV was recovered, the high resolution bathymetry which it had obtained guided
the next coring operations. In this paper we will describe how we are tackling the issues that
specifically affect a deep diving AUV capable of operating with true autonomy, and independently
of the mother ship: How to carry enough energy for long endurance and range? How to operate
safely and efficiently with varying buoyancy? How to maintain accurate navigation throughout
missions lasting up to several days
Draft: thruster interactions on autonomous underwater vehicles
No full textAutonomous underwater vehicles are a developing technology capable of undertaking a wide variety of different tasks. The development of these vehicles is aided by the use of simulations of their performance. For simulations to calculate the response of these vehicles to different situations and control strategies requires accurate modelling of the propulsion and control devices employed. Simulations of underwater vehicles tend to employ models of the dynamic performance of the thrusters employed however the simulations neglect some of the hydrodynamic interaction effects. These interaction effects include thruster – hull and thruster – thruster interactions similar to those encountered on dynamic positioning surface vessels. This paper assesses these effects for autonomous underwater vehicles and, where appropriate, suggests models for use in simulations.<br/
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