52,117 research outputs found
Risk Analysis for Autonomous Underwater Vehicle Operations in Extreme Environments
No full textAutonomous underwater vehicles (AUVs) are used increasingly to explore hazardous marine environments. Risk assessment for such complex systems is based on subjective judgment and expert knowledge as much as on hard statistics. Here, we describe the use of a risk management process tailored to AUV operations, the implementation of which requires the elicitation of expert judgment. We conducted a formal judgment elicitation process where eight world experts in AUV design and operation were asked to assign a probability of AUV loss given the emergence of each fault or incident from the vehicle's life history of 63 faults and incidents. After discussing methods of aggregation and analysis, we show how the aggregated risk estimates obtained from the expert judgments were used to create a risk model. To estimate AUV survival with mission distance, we adopted a statistical survival function based on the nonparametric Kaplan-Meier estimator. We present theoretical formulations for the estimator, its variance, and confidence limits. We also present a numerical example where the approach is applied to estimate the probability that the Autosub3 AUV would survive a set of missions under Pine Island Glacier, Antarctica in January–March 2009
Eliciting expert judgement for the probability of AUV loss in contrasting operational environments
No full textEach time an autonomous underwater vehicle (AUV)
is used in the sea there is a non-zero probability of
loss. Quantifying probability of loss is not an exact
science; therefore much depends on the fault history
of the vehicle, the operational environment and the
complex relationships between the consequences of
faults or incidents and the environment. While this
problem may be stated in scientific terms, in practice,
there is no solution through scientific means alone.
This is an example of ‘trans-science’. We suggest that
an approach based on the formal process of eliciting
expert judgement may be an effective means of
approaching this problem, as the process has been
used successfully for other trans-scientific questions.
The paper provides an introduction to the process of
eliciting expert judgement, outlines four exemplar
environments: coastal, open water, under sea ice and
under shelf ice, and gives a worked example of one
expert’s judgement on the probability of loss in the
four environments arising from a real fault with the
Autosub1 AUV. Using the fault history of the
Autosub3 AUV, included in the Annex, we ask
experts from among UUST attendees (and others) to
take part in this expert judgement elicitation. Based
on the results of this elicitation we aim to publish a
paper in the peer-reviewed literature
The productive ward: releasing time to care - learning and impact review
No full textThe Productive Ward: Releasing time to care™ programme aims to empower ward teams to identify areas for improvement by giving staff the information, skills and time they need to regain control of their ward and the care they provide.The NHS Institute for Innovation and Improvement commissioned Kings College London to undertake a review of the Productive Ward programme. This review (undertaken February-June 2009) set out to establish the overall learning from and impact of The Productive Ward programme since its conception in 2005, and to suggest how this can be spread and sustained.The review applies an evidence-based Diffusion of Innovation framework to The Productive Ward programme to examine multi-level perspectives (national, regional, local) of learning and impact. The findings are informed by in-depth interviews with national and regional stakeholders, a national online-survey of frontline staff, and case studies of implementation within five NHS acute Trusts.Overall, this review finds The Productive Ward programme has been successfully framed and communicated in a way that connects with frontline NHS staffs’ need and will for change, and that it thrives where local leadership and ownership are strong. The review suggests 15 ‘top tips’, which comprise of key lessons from the programme to date that will assist trusts in local implementation in the future
Engineering geomorphology- theory and practice
No full textThe article reviews the book "Engineering Geomorphology- Theory and Practice," edited by P. G. Fookes, E. M. Lee, and J. S. Griffiths
Results of expert judgments on the faults and risks with Autosub3 and an analysis of its campaign to Pine Island Bay, Antarctica, 2009
No full textProbabilistic risk assessment is a methodology that can be systematically applied to estimate the risk associated with the design and operation of complex systems. The National Oceanography Centre, Southampton, UK has developed a risk management process tailored to the operation of autonomous underwater vehicles. Central to the application of the risk management process is a probabilistic risk assessment. The risk management process was applied to estimate the risk associated with an Autosub3 science campaign in the Pine Island Glacier, Antarctica, and to support decision making. The campaign was successful. In this paper we present the Autosub3 risk model and we show how this model was used to assess the campaign risk
The Griffiths bundle is generated by groups
No full textFirst the Griffiths line bundle of a Q-VHS V is generalized to a Griffiths character grif(G, mu, r) associated to any triple (G, mu, r), where G is a connected reductive group over an arbitrary field F, mu is an element of X-*(G) is a cocharacter (over (F) over bar) and r : G -> GL(V) is an F-representation; the classical bundle studied by Griffiths is recovered by taking F = Q, G the Mumford-Tate group of V, r : G -> GL(V) the tautological representation afforded by a very general fiber and pulling back along the period map the line bundle associated to grif(G, mu, r). The more general setting also gives rise to the Griffiths bundle in the analogous situation in characteristic p given by a scheme mapping to a stack of G-Zips. When G is F-simple, we show that, up to positive multiples, the Griffiths character grif(G, mu, r) (and thus also the Griffiths line bundle) is essentially independent of r with central kernel, and up to some identifications is given explicitly by -mu. As an application, we show that the Griffiths line bundle of a projective G-Zip(mu)-scheme is nef.</p
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Theoretical Loss and Gambling Intensity (Revisited): A Response to Braverman et al. (2013)
No full textIn this paper, we provide a brief response to Braverman and colleagues’ (2013) critique of our ‘Theoretical Loss’ metric as a measure of monetary gambling intensity (Auer & Griffiths, 2013; Auer, Schneeberger & Griffiths, 2012). We argue that ‘gambling intensity’ and ‘gambling involvement’ are essentially the same construct as descriptors of monetary gambling activity. Additionally, we acknowledge that playing duration (i.e., the amount of time – as opposed to money – actually spent gambling) is clearly another important indicator of gambling involvement – something that we have consistently noted in our previous studies including our empirical studies on gambling using behavioural tracking data. Braverman and colleagues claim that the concept of Theoretical Loss is nullified when statistical analysis focuses solely on one game type as the house edge is constant across all games. In fact, they state, the correlation between total amount wagered and Theoretical Loss is perfect. Unfortunately, this is incorrect. To disprove the claim made, we demonstrate that in sports betting (i.e., a single game type), the amount wagered does not reflect monetary gambling involvement using actual payout percentage data (based on 52,500 independent bets provided to us by an online European bookmaker). After reviewing the arguments presented by Braverman and colleagues, we are still of the view that when it comes to purely monetary measures of ‘gambling intensity’, the Theoretical Loss metric is a more robust and accurate measure than other financial proxy measures such as ‘amount wagered’ (i.e., bet size) as a measure of what players are prepared to financially risk while gambling
On the reliability of the Autosub autonomous underwater vehicle
No full textAs autonomous underwater vehicles (AUVs) enter operational service an assessment of their reliability is timely. Using the Autosub AUV as an example, several design issues affecting reliability are discussed, followed by an analysis of recorded faults. Perhaps contrary to expectations, failures rarely involved the autonomous nature of the vehicle. Rather, faults were typical of those that occur with any complex item of marine electromechanical equipment. A statistical analysis showed that the failure rate decreased with distance travelled- an indicator that an AUV underway, submerged, is at less risk of a fault developing than during other phases of a mission. 1
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Gaming addiction in adolescence (revisited)
No full textGaming addiction has become a topic of increasing research interest. Over the last 25 years, I have written many articles on adolescent video gaming for Education and Health as it is one of the research fields that is constantly evolving. In fact, over the last decade, there has been a significant increase in the number of scientific studies examining various aspects of online addiction particularly among adolescents and young adults (Kuss & Griffiths, 2012; Kuss, Griffiths, Karila & Billieux, 2014). Although the amount and the quality of research in the field has progressed much over this period, it is still in its infancy compared to other more established behavioural addictions (such as pathological gambling). This article briefly examines (i) how adolescent gaming addiction research has changed over the last three decades, (ii) how online gaming addiction has gained genuine psychiatric status, (iii) excessive gaming as an addiction, and (iv) where the gaming addiction field is going
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