University of Limerick Research Repository

Recent Submissions

  • PublicationOpen Access
    EvoDropX: Evolutionary optimization of feature corruption sequences for faithful explanations of transformer models
    (MDPI, 2026-03-02) Singh, Dhiraj Kumar; Ryan, Conor
    As deep learning models become increasingly integrated into critical decision-making systems, the need for explainable Artificial Intelligence (xAI) has grown paramount to ensure transparency, accountability, and trust. Post hoc explainability methods, which analyse trained models to interpret their predictions without modifying the underlying architecture, have become increasingly important, especially in fields such as healthcare and finance. Modern xAI techniques often produce feature importance rankings that fail to capture the true causal influence of features, particularly in transformer-based models. Recent quantitative metrics, such as Symmetric Relevance Gain (SRG), which measures the area between the feature corruption performance curves of the Most Important Feature (MIF) and the Least Important Feature (LIF), provide a more rigorous basis for evaluating explanation fidelity. In this study, we first show that existing xAI methods exhibit consistently poor performance under the SRG criterion when explaining transformer-based text classifiers. To address these limitations, we introduce EvoDropX, a novel framework that formulates explanation as an optimisation problem. EvoDropX leverages Grammatical Evolution (GE) to evolve sequences of feature corruption with the explicit objective of maximising SRG, thereby identifying features that most strongly influence model predictions. EvoDropX provides interventional, input–output (behavioural) explanations and does not attempt to infer or interpret internal model mechanisms. Through comprehensive experiments across multiple datasets (IMDb movie reviews (IMDB), Stanford Sentiment Treebank (SST-2), Amazon Polarity (AP)), multiple transformer models (Bidirectional Encoder Representations from Transformers (BERT), RoBERTa, DistilBERT), and multiple metrics (SRG, MIF, LIF, Counterfactual Conciseness (CFC)), we demonstrate that EvoDropX significantly outperforms all state-of-the-art (SOTA) xAI baselines including Attention-Aware Layer- Wise Relevance Propagation for Transformers (AttnLRP), SHapley Additive exPlanations (SHAP), and Local Interpretable Model-agnostic Explanations (LIME), when evaluated using intervention-based faithfulness criteria. Notably, EvoDropX achieves 74.77% improvement in SRG than the best-performing baseline on the IMDB dataset with the BERT model, with consistent improvements observed across all dataset-model pairs. Finally, qualitative and linguistic analyses reveal that EvoDropX captures both sentiment-bearing terms and their structural relationships within sentences, yielding explanations that are both faithful and interpretable.
  • PublicationOpen Access
    Supercritical CO2-assisted spray-dried drug particle production
    (Elsevier, 2026-05-01) Baassiri, Mohamad; Ranade, Vivek; Padrela, Luis
    In this work, we have investigated supercritical CO2(scCO2)-assisted spray drying for the production of drug particles using ketoprofen as a model Active Pharmaceutical Ingredient (API). We have used an experimental and Computational Fluid Dynamics (CFD) simulations approach to explore the hydrodynamics and particle formation pathways of a scCO2-assisted spray drying. The Eulerian-Lagrangian CFD framework was developed to describe the scCO2-assisted atomization of a drug solution through a micro-orifice two-fluid nozzle structure. The commercial CFD code, Ansys FLUENT (2024R2) was used. The relevant thermodynamic sub-models were integrated via user-defined functions. Experimental validation and calibration were guided by real-time laser-diffraction based particle sizing methods as well as offline dynamic light scattering measurements. The comparison of simulated and experimentally measured average particle sizing data showed good agreement across three different feed solution concentrations at an injection pressure of 110 bar and feed solution flow rate of 1 mL/min. The developed model offers a cost-effective tool for design, simulation and optimization of relevant drug particle production setups.
  • PublicationOpen Access
    Early antidepressant effects of supervised Nordic walking in adults with moderate to severe depression: A randomized controlled trial
    (Elsevier, 2026-07-01) Ginoux, Clément; Stubbs, Brendon; Herring, Matthew P.; Abdullah, Mohammad Farris Iman Leong Bin; Legrand, Fabien D.
    Background: Physical exercise is an effective treatment for depression, yet little is known about the temporal dynamics of symptom improvement during exercise interventions. Methods: In this randomized controlled trial, 64 adults with moderate to severe depressive symptoms were allocated to a 10-week supervised Nordic walking (NW) program (n = 48) or a non-active control condition (n =16). The NW group completed two weekly training sessions at moderate intensity(65-75%HRmax).Depressive symptoms were assessed at baseline, mid-intervention (Week 5), and post-intervention (Week 10) using the Beck Depression Inventory-II. Primary analyses examined Group × Time effects on symptom severity. Secondary analyses explored (via a Group × Depression intensity × Time ANOVA) whether baseline depression intensity moderated treatment response. Results: A significant Group × Time interaction indicated greater reductions in depressive symptoms in the NW group compared with controls. Symptom improvement was most pronounced during the first half of intervention (Hedges's g = _ 0.98), with smaller changes thereafter (Hedges's g = _ 0.40 from mid- to post-intervention). In addition, a significant Group × Depression intensity × Time interaction suggests that participants with severe baseline depression experienced larger and more rapid improvement than those with moderate symptoms in the first five weeks. Conclusions: Supervised Nordic walking was found to be associated with substantial reductions in depressive symptoms within five weeks, particularly among individuals with severe depression. Implications of our findings and study's limitations are discussed.
  • PublicationOpen Access
    Thermally induced multistability in cured shapes of hybrid composite laminates
    (Elsevier, 2026-06-01) Anilkumar, P.M.; Bashir, Danish; Weaver, P.M.
    Compliant structures derived from multistable laminates have attracted significant research interest due to their ability to transition between multiple equilibrium shapes. However, most existing designs are limited to bistable behavior or rely on the assembly of multiple elements to achieve higher-order multistability, which restricts their applicability in continuous morphing structures. These structures can exhibit symmetrically or anti symmetrically curved configurations depending on geometry and layup, with square laminates typically showing symmetrically curved bistable shapes and rectangular laminates exhibiting anti symmetrically curved bistable shapes. Symmetric curved shapes in rectangular bistable laminates can be achieved by tailoring the stiffness distribution through additional plies. Laminates designed with such customized layups are referred to as hybrid bistable symmetric laminates (HBSLs). Most center-fixed HBSLs reported in the literature exhibit two symmetric stable shapes, along with several intermediate unstable configurations influenced by boundary conditions and material properties. However, bistable behavior alone does not satisfy the requirements of continuous shape-changing structures, which demand more than two stable configurations. This study investigates selected HBSL layups with a center-fixed boundary condition that exhibit more than two equilibrium configurations, enabled by a tailored hybrid composite aluminum layup. A fully nonlinear finite element framework is first employed to characterize the cured multi stable shapes. The presence of multi stability is then further confirmed using a Rayleigh–Ritz-based semi-analytical approach. Finally, experimental results are used to validate the predicted multistable behavior of HBSLs through comparisons of displacement profiles. The results demonstrate that the proposed laminates can achieve up to four stable configurations, with good agreement between numerical, semi-analytical, and experimental predictions, showing discrepancies generally within 6% for the primary shapes, with slightly larger errors observed for the intermediate shapes. The findings highlight the potential of HBSLs for highly flexible morphing structures with smooth shape transitions, offering promising applications in adaptive structures, deployable systems, and advanced shape-morphing components.
  • PublicationOpen Access
    Strategies supporting women’s engagement with specialist perinatal mental health services after traumatic pregnancy or birth: A qualitative study
    (Elsevier, 2026-04-01) Gibbons, Maria; Atkinson, Sandra; Mohamad, Mas; Imcha, Mendinaro; Noonan, Maria
    Problem: Limited research has explored women’s experiences of engaging with specialist perinatal mental health services for trauma. Background: Perinatal psychological trauma is common and impacts the woman, her baby and family. Engagement with services is a critical first step in receiving interventions that support recovery. Aim: This study aimed to explore women’s experience of accessing specialist perinatal mental health services following a psychologically traumatic pregnancy or birth, and to identify strengths and areas for improvement in service delivery. Methods: This qualitative descriptive study employed in-depth interviews with a purposeful sample of nine women to explore their experiences. Findings: Two themes were developed: seeking perinatal trauma support and healing trauma through compassionate encounters. Women experienced a wide variety of traumatic events that affected their physical and mental wellbeing, relationships and subsequent pregnancy planning. They described overcoming initial reluctance to engage with the service due to fear of judgement and perceived stigma associated with perinatal mental health. The therapeutic relationship formed with a known healthcare professional was instrumental in helping women to address their trauma. Conclusion: Compassionate care from non-judgemental and consistent specialist perinatal mental health clinicians is central to sustained engagement with SPMHS and perinatal trauma recovery. Advocacy within the therapeutic relationship plays a pivotal role in helping women with trauma histories navigate the maternity healthcare system during current or subsequent pregnancies. These findings provide further evidence for the role of specialist perinatal mental health services in supporting women with perinatal psychological trauma and can inform future policy and service design.