NUI Maynooth Eprint Archive
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Constraint handling in extremum-seeking control for wave energy systems: A case study
No full textWave energy converters (WECs) are a promising
technology aimed at harvesting energy by converting the device
motion induced by ocean and sea waves. The control strategy
adopted to guide the power take-off (PTO) system is among
the most crucial aspects in the energy conversion process.
Indeed, the solution of such an energy-maximizing optimal control
problem is fundamental for the economic viability of this type of
emerging technology. State-of-the-art WEC control technology
can be almost fully enclosed within the family of model-based
control strategies: The optimal control law, which maximizes
energy absorption, is computed based upon knowledge of a
dynamical model of the device, able to predict the associated
motion. Nonetheless, models constructed for WEC control purposes are inherently affected by several sources of uncertainty,
especially in terms of the associated hydrodynamic effects. As
a consequence, there is a significant appetite to adopt model free control strategies to overcome this issue. In this study, we
propose a perturbation-based extremum-seeking control (ESC) in
which a class of soft-constraint handling has been introduced to
deal with excessive motion values for a heaving point absorber
WEC. We test such a strategy in different operating conditions
to highlight the influence of the soft constraint mechanism on
power absorption, applied control action, and WEC velocity
A review of wave energy technology from a research and commercial perspective
No full textAlthough wave energy prototypes have been proposed for more than 100 years, they have
still not reached full commercialisation. The reasons for this are varied, but include the
diversity of device operating principles, the variety of onshore/nearshore/offshore deployment possibilities, the diversity of the wave climate at various potential wave energy sites,
and the consequent lack of convergence in technology and consensus. This distributed
effort has, in turn, lead to a slow rate of progression up the learning curve, with a significant number of wave energy company liquidations and technical setbacks dampening
investor confidence. Although a number of reviews on wave energy technology are already
in the published literature, such a dynamic environment merits an up-to-date analysis and
this review examines the wave energy landscape from a technological, research and commercial perspectiv
Cyclosporine A and IFNγ licencing enhances human mesenchymal stromal cell potency in a humanised mouse model of acute graft versus host disease
No full textImmunosuppressive ability in human MSC donors has been shown to be variable and may be a limiting factor in
MSC therapeutic efficacy in vivo. The importance of cytokine activation of mesenchymal stromal cells (MSCs) to
facilitate their immunosuppressive function is well established. This study sought to further understand the
interactions between MSCs and the commonly used calcineurin inhibitor cyclosporine A (CsA). The existing
literature regarding approaches that use MSCs and cyclosporine are conflicting regarding the effect of CsA on MSC
potency and function. Here, we clearly demonstrate that when added at the same time as MSCs, CsA negatively
affects MSC suppression of T cell proliferation. However, licencing MSCs with IFNγ before addition of CsA protects
MSCs from this negative effect. Notably, adding CsA to MSCs after IFNγ pre-stimulation enhances MSC production
of IDO. Mechanistically, we identified that CsA reduces SOCS1 expression to facilitate enhanced IDO production in
IFNγ pre-stimulated MSCs. Importantly, CsA exposure to IFNγ pre-stimulated MSC before administration, significantly
enhanced the potency of MSCs in a human relevant humanised mouse model of acute Graft versus Host Disease.
In summary, this study identified a novel licencing strategy to enhance MSC potency in vitro and in vivo
Mesenchymal stem/stromal cell-based therapies for severe viral pneumonia: therapeutic potential and challenges
No full textSevere viral pneumonia is a significant cause of morbidity and mortality globally,
whether due to outbreaks of endemic viruses, periodic viral epidemics, or the rarer but
devastating global viral pandemics. While limited anti-viral therapies exist, there is a
paucity of direct therapies to directly attenuate viral pneumonia-induced lung injury,
and management therefore remains largely supportive. Mesenchymal stromal/stem
cells (MSCs) are receiving considerable attention as a cytotherapeutic for viral pneumonia. Several properties of MSCs position them as a promising therapeutic strategy for
viral pneumonia-induced lung injury as demonstrated in pre-clinical studies in relevant
models. More recently, early phase clinical studies have demonstrated a reassuring
safety profile of these cells. These investigations have taken on an added importance
and urgency during the COVID-19 pandemic, with multiple trials in progress across the
globe. In parallel with clinical translation, strategies are being investigated to enhance
the therapeutic potential of these cells in vivo, with different MSC tissue sources,
specific cellular products including cell-free options, and strategies to ‘licence’ or ‘pre-activate’ these cells, all being explored. This review will assess the therapeutic potential
of MSC-based therapies for severe viral pneumonia. It will describe the aetiology and
epidemiology of severe viral pneumonia, describe current therapeutic approaches, and
examine the data suggesting therapeutic potential of MSCs for severe viral pneumonia
in pre-clinical and clinical studies. The challenges and opportunities for MSC-based
therapies will then be considered
A control design framework for wave energy devices
No full textThis paper presents an integrated framework
for the design of wave energy control systems, considering
the totality of the design process as well as any ancillary
functions required, such as model reduction, excitation force
estimation, etc. In particular, we propose the moment-based
mathematical framework as an integrated environment
which allows a smooth transition between modelling and
control activities, as well as providing a framework to
consider optimal rejection of modelling errors or errors in
excitation force estimation. The paper provides an overview
of the framework, also containing an illustrative case study
to demonstrate a likely pathway through the framewor
Quantifying hydrodynamic model uncertainty for robust control of wave energy devices
No full textWave energy converter (WEC) modelling attracts significant uncertainty, often due to the need to
develop compact parametric models for simulation, optimisation and control design. For linear models, which
form the basis of many WEC control philosophies, this
uncertainty can be as a result of real system nonlinearity, particularly as a result of control action, as well as
more general uncertainty in the hydrodynamic modelling
process. Recent developments in WEC control include the
development of robust control algorithms, which utilise a
nominal linear model, but tolerate a level of uncertainty in
the model parameters. This study develops a framework
for identifying a nominal model plus model uncertainty
bounds, which uses data from nonlinear computational
fluid dynamics (CFD) simulation. Two robust control solutions are developed, one with an analytical approach, for
circular uncertainty boundaries, and a further numerical
approach, considering uncertainty sets of arbitrary shape.
Finally, the comparative controller performance, based on
the appropriate selection of a nominal model and uncertainty bound, compared to a non-robust nominal controller,
is shown
“They were having so much fun, so genuinely..”: K-pop fan online affect and corroborated authenticity
No full textThis article examines the relationship between K-pop boybands and their fandoms
in the West as mediated by digital streaming performances. It investigates the socio-emotional organization of online interaction orders in K-pop fan communities,
the emotional forms of expression, and the social assessment of their authenticity.
The article asks two questions. First, how is the loyalty of fans elicited through the
emotional experiences of fandom online? Second, how are these emotions validated
by fans as “authentic”? The article argues that the experience of “liveness” is central
to the process through which fans feel emotionally close to their K-pop idols and this
facilitates investment by fans in emotional interactions “in real life” with other fans. Fans
also rely on “corroborated authenticity.” This corroboration of internal interactions
comes from two sources: (1) the presence of related/similar content on the other
digital platforms and (2) the connection of the apparently “placeless” digital platforms
to a particular ethnic place, Korea
Model exploration using conditional visualization
No full textIdeally, statistical parametric model fitting is followed by various summary tables which show predictor contributions, visualizations which assess model assumptions and goodness of fit, and test statistics which compare models. In contrast, modern machine-learning fits are usually black box in nature, offer high performing predictions but suffer from an interpretability deficit. We examine how the paradigm of conditional visualization can be used to address this, specifically to explain predictor contributions, assess goodness of fit, and compare multiple, competing fits. We compare visualizations from techniques including trellis,
condvis, visreg, lime, partial dependence, and ice plots. Our examples use random forest fits, but all techniques presented are model agnostic. This article is categorized under: Statistical and Graphical Methods of Data Analysis > Statistical Graphics and Visualization Statistical Learning and Exploratory Methods of the Data Sciences > Exploratory Data Analysis Statistical Learning and Exploratory Methods of the Data Sciences > Modelling Method
Productively Undoing a Doctoral Study: Ethically Researching Early Childhood Education and Care in the Majority World
No full textThis thesis productively undoes (Spivak, 2012) a doctoral study in the early childhood education and care classes of an NGO run school in Pune, India. I tell the story of my original research project that intended to develop a rich understanding of children’s play and early learning in an early childhood education and care setting through a children’s rights lens within in a marginalised community, while also problematising the universal application of dominant Minority world discourses to the lives of young children living diverse childhoods in the Majority world. Using a combination of Bronfenbrenner’s bio-ecological systems theory, Vygotsky’s socio-cultural historical theory, and post-colonial theory the study was designed to collect data by ethnographic observations in the school and wider society, along with participatory methods with the children (such as drawings and photovoice), and interviews with teachers and parents. However, Spivak stepped into the process, interrupted me, and stopped the research study in its tracks after the last trip to the school by asking if the subaltern could speak (1992). Rather than analysing the data for themes, trends and results, the data and individual pieces of the research study are taken apart and played with. I push them, pull them, unthread them, rip them, add new threads, braid them, and re-rupture them. I then view them from different theoretical perspectives (Jackson and Mazzei; 2012) and interdisciplinary perspectives, before gently, and with productive intention, attempt to put them back together to offer possible insights and considerations for more ethical possibilities when researching in the Majority world for educational researchers, and for those working in early childhood education and care alike. Format, form, and voice are played with using a narrative approach to the writing process allowing the authority of my voice to be interrupted, challenged, or joined by the voices of children and the interpreter with whom I co-researched. Whispers of conversations, social media posts, news, song lyrics, and stories that surrounded me, interrupted me, or spoke to me during the writing process weave in and out of the story at different times and in different voices
Benchmarking seasonal forecasting skill using river flow persistence in Irish catchments
No full textThis study assesses the seasonal forecast skill of river flow persistence in 46 catchments representing a range of hydrogeological conditions across Ireland. Skill is evaluated against a climatology benchmark forecast and by examining correlations between predicted and observed flow anomalies. Forecasts perform best when initialized in drier summer months, 87% of which show greater skill relative to the benchmark at a 1-month horizon. Such skill declines as forecast horizon increases due to the longer time a catchment has to “forget” initial anomalous flow conditions and/or to be impacted by “new” events. Skill is related to physical catchment descriptors such as the baseflow index (correlation ρ = 0.86) and is greatest in permeable high-storage catchments. The distinct seasonal and spatial variations in persistence skill allow us to pinpoint when and where this method can provide a useful benchmark in the future development of more complex seasonal hydrological forecasting approaches in Ireland