NUI Maynooth Eprint Archive
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Receding-Horizon Pseudospectral Control for Energy Maximization of Oscillating-Water-Column Wave Energy Systems
No full textWave energy, harnessed by wave energy converters
(WECs), has the potential to significantly contribute to the
renewable energy mix. To improve the commercial viability
of WECs, the design of control strategies for maximizing the
produced energy is vital. This work specifically focuses on
energy maximizing control for oscillating-water-column (OWC)
WECs, using a receding-horizon pseudospectral (RHPS) optimal
control method. With pseudospectral control, the continuous
time OWC energy maximizing optimal control problem is
directly transcribed, by discretizing both state, and control,
variables, into a finite-dimensional nonlinear program. Due to
the importance of turbine performance, OWC control typically
aims to maximize turbine efficiency, albeit ignoring the impact
of rotational speed on hydrodynamic performance. With the
RHPS optimal control approach developed in this paper, a better trade-off between turbine and hydrodynamic performance
is achieved and, therefore, energy production is improve
Numerical and experimental multi-linear modelling of wave energy devices
No full textThe escalating demand in global energy requirements and the soaring price of traditional
fossil fuels, in combination with global awareness to follow a pathway toward
decarbonisation, are fuelling research and development into novel technologies to
harness renewable energy sources. Ocean wave energy, a significant and untapped
source of renewable energy, if economically viable, can make a promising avenue for
sustainable energy generation. In the drive for the development and more efficient
operation of wave energy converters (WECs), effective control systems, which can
maximise converted energy for a given capital cost, are crucial. Model-based control
systems contribute to the majority of energy-maximising control systems of WECs,
with a need for a suitable mathematical model. Physics-based models, numerical
simulations, full-scale tests, or laboratory-scale tests can be used to develop WEC
models, each presenting distinct methodologies and challenges, yielding models
with a diverse range of accuracy. The effectiveness of model-based control relies on
the precision of the WEC model upon which the controller is based, given that WEC
controllers have shown considerable sensitivity to inaccuracies in their underlying
models. Among the distinct WEC modelling techniques, the determination of
models from data (using either physical or numerical experiments) is an effective
route to derive representative (linear and nonlinear) WEC models. In this thesis,
both numerical wave tank (NWT) and physical wave tank (PWT) experiments are
considered to estimate a range of adequate linear WEC models capable of meeting
the requirements of a control system by the employment of the proper test signals
(specific to each test setup) to cover the full operational space of the system. Many
uncertainty parameters in the data-driven models with sources differing significantly
in NWT and PWT experiments, may hinder accurate WEC model determination
for efficient (model-based) control strategies. Within this scope, the current study
considers the range of tests that can be performed, the uncertainty sources, and
the range of post-processing techniques that can be applied in NWT and PWT tests
for a point-absorber type system, with an aim to get the most realistic hydrodynamic
WEC models. Moreover, in NWT testing, a comprehensive representation of input
signal synthesis and characterisation is carried out, to provide sufficient fidelity
in Computational Fluid Dynamics (CFD)- based NWT tests and, in PWT testing,
specific focus is directed towards the quantification of uncertainty and external
disturbance, specifically tailored to the PWT under study, with the corresponding
effects are mitigated by applying effective data-processing steps.
Multi-linear hydrodynamic WEC models (obtained either from NWT or PWT
testing), serve as a starting point for model-based linear WEC controller synthesis.
Finally, with a view to robust WEC control, a (single) nominal model and uncertainty
bound are quantified from multi-linear models obtained from NWT tests, and robust
control results are provided to demonstrate the efficacy of the modelling and
control philosophy
The Effect of Eccentric or Isometric Training on Strength, Architecture, and Sprinting across an Australian Football Season
No full textThis study aimed to investigate the effect of an isometric (ISO) or Nordic hamstring exercise (NHE) intervention, alongside a sprint training program on hamstring strength, architecture, and sprinting performance in Australian footballers.
Methods
Twenty-five male athletes undertook NHE ( n = 13) or ISO ( n = 12) training across a 38-wk period (including preseason and in season). Biceps femoris long head (BFlh) architecture, ISO, and eccentric knee flexor strength were assessed at baseline, at the end of preseason (14 wk), and at the conclusion of the intervention. Sprint times and force–velocity profiles were determined at baseline and at the end of preseason.
Results
After the intervention, both groups had significant improvements in BFlh fascicle length (NHE: 1.16 cm, 95% CI = 0.68 to 1.63 cm, d = 1.88, P < 0.001; ISO: 0.82 cm, 95% CI = 0.57 to 1.06 cm, d = 1.70, P < 0.001), muscle thickness (NHE: 0.11 cm, 95% CI = 0.01 to 0.21 cm, d = 0.51, P = 0.032; ISO: 0.21 cm, 95% CI = 0.10 to 0.32 cm, d = 0.86, P = 0.002), and eccentric strength (NHE: 83 N, 95% CI = 53 to 114 N, d = 1.79, P < 0.001; ISO: 83 N, 95% CI = 17 to 151 N, d = 1.17, P = 0.018). Both groups also finished the intervention weaker isometrically than they started (NHE: −45 N, 95% CI = −81 to −8 N, d = −1.03, P = 0.022; ISO: −80 N, 95% CI = −104 to −56 N, d = −3.35, P < 0.001). At the end of preseason, the NHE group had improved their 5-m sprint time by 3.3% ± 2.0%), and their maximum horizontal velocity was 3% ± 2.1% greater than the ISO group who saw no changes.
Conclusions
Both ISO and NHE training with a periodized sprinting program can increase BFlh fascicle length, thickness, and eccentric strength in Australian footballers. NHE training also improves 5-m sprint time and maximum velocity. However, both interventions reduced ISO strength. These findings provide unique, contextually relevant insights into the adaptations possible in semiprofessional athletes
The Structure, Function, and Adaptation of Lower-Limb Aponeuroses: Implications for Myo-Aponeurotic Injury
No full textThe aponeurosis is a large fibrous connective tissue structure within and surrounding skeletal muscle and is a critical component of the muscle–tendon unit (MTU). Due to the lack of consensus on terminology and the heterogeneous nature of the aponeurosis between MTUs, there are several questions that remain unanswered. For example, the aponeurosis is often conflated with the free tendon rather than being considered an independent structure. This has subsequent implications when interpreting data regarding the structure, function, and adaptation of the aponeuroses from these studies. In recent years, a body of work has emerged to suggest that acute injury to the myo-aponeurotic complex may have an impact on return-to-sport timeframes and reinjury rates. Therefore, the purpose of this review is to provide a more detailed understanding of the morphology and mechanical behaviour common to all aponeuroses, as well as the unique characteristics of specific lower-limb aponeuroses that are commonly injured. This review provides the practitioner with a current understanding of the mechanical, material, and adaptive properties of lower limb aponeuroses and suggests directions for future research related to the myo-aponeurotic complex
Resilience, resistance and ‘giving back’: teachers from working class backgrounds and their journeys to teaching
No full textPrecipitated by a recent policy focus on diversifying Ireland’s homogeneous teaching profession, there is an emerging research base focused on the experiences of teachers from under-represented groups. However, the life stories of teachers from lower socio-economic groups remain underexplored. Responsive to the mostly atheoretical nature of research on initial teacher motivation and employing a narrative life history methodology grounded in phenomenology, interviews were conducted with six teachers from working class backgrounds. Consistent with the generative capacity of habitus, the participants’ stories of becoming a teacher are ones of resilience, resistance, and aspiration to make a difference in their local communities. Their experiences of schooling and initial teacher education and the various challenges they encountered, highlights the systemic and cultural change required to ensure not only a more diverse and representative teaching profession, but one that is also critically conscious and culturally responsiv
Los Vínculos entre el Partido y la Base, la Movilización Contestataria y las “Tensiones Creativas” en Bolivia
No full textThe abstract is included in the text
Exploiting Fano resonance in wave energy systems
No full textEnergy maximising control of wave energy converters (WECs) typically results in exaggerated motion of the device, with consequent increases in mooring and other forces which can adversely affect WEC lifetime. In addition, the exaggerated motion typically increases the incidence of nonlinear hydrodynamic effects, confounding linear analysis upon which many WEC control design paradigms are based. This paper explores the potential to exploit Fano resonance in a wave energy context, where the WEC body remains relatively stationary, while the active power take-off elements are well exercised. Preliminary results suggest that significant WEC body motion reduction is possible, with a modest reduction in energy capture
New opportunities for discourse studies: combining Discourse Theory, Critical Discourse Studies and Corpus Linguistics
No full textThis paper proposes a methodological framework that integrates poststructuralist Discourse Theory (DT), Critical Discourse Studies (CDS) and Corpus Linguistics (CL). While previous research has discussed potential compatibility between combinations of these approaches, there have been few attempts to bring them all together into a cohesive research programme. Fostering dialogue between diverse methodological perspectives can facilitate multi-level analysis to capture the complex dynamics of sociopolitical issues. In this vein, the article presents the methodological tree, an analogy used to illustrate how these traditions may come together to complement one another. This foundation lays the groundwork for practical application in discursive analysis, with a flexible analytical structure proposed and examples provided to illustrate its implementation. It is hoped that the article can stimulate further discussion around how DT, CDS and CL can be brought together to harness their strengths
The next frontier for climate change science – Insights from the authors of the IPCC 6th assessment report on knowledge gaps and priorities for research
No full textAs climate change impacts intensify globally in both frequency and magnitude, and with scientific consensus on what is yet to come if the world fails to act, the imperative to step up our collective response has never been more pressing. By providing the knowledge necessary to formulate effective mitigation and adaptation strategies, climate science serves as a critical enabler of climate action and a vital input to evidence-based policymaking. Bridging the knowledge gaps in climate change research is crucial for guiding the transition towards a low-carbon climate resilient future, for fostering consensus and alliances, for empowering global cooperation and for mobilising stakeholders across the society. This report draws attention to where additional research is required to effectively and adequately address climate change, aiming to inform future calls under the EU Horizon Europe R&I Programme and beyond
A speleothem record of hydroclimate variability in northwestern Madagascar during the mid-late Holocene
No full textWe present a continuous high-resolution precisely dated multiproxy record of hydroclimate variability at Anjohibe cave in northwestern Madagascar using speleothem AB13. The record spans from ~4484 y BP to ~2863 y BP. Stalagmite δ18O, δ13C and Sr/Ca ratios show very similar changes in hydroclimate. The mechanism controlling Sr/Ca changes, however, from prior calcite precipitation to degree of dolomite dissolution at about 4 ky BP. Our record is also in good agreement with previously published speleothem records from the same area. This agreement and multiproxy consensus indicate that AB13 provides a robust record of hydroclimate variability, including a continuous record of hydroclimate variability across the 4.2 ka event. This 4.2 ka event in Madagascar is marked by two distinct periods of drying between ~3900 y BP to 4300 y BP. A dry 4.2 ka event at this Southern Hemisphere site helps limit possible mechanisms for the event, indicating that a meridional shift to the south in the ITCZ is not responsible for the 4.2 ka event. In addition, the 4.2 ka event does not stand out as a unique dry period in our record. The longest and driest period of the record lasted ~300 years with peak dryness at ~3000 y BP. Our record differs significantly from a speleothem record from Rodrigues Island, located ~1800 km to the east of our study area in Madagascar suggesting different climatological controls on northwest Madagascar and more oceanic sites to the east