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Nanoscale surfactant transport: bridging molecular and continuum models
Get PDFJFM classification:
Interfacial Flows (free surface): Capillary flows;
Interfacial Flows (free surface): Thin films;
Micro-/Nano-fluid dynamics: Microscale transport.Data availability:
Codes to reproduce the data, and the force field parameters are available in: https://github.com/MuhammadRRahman/Nanoscale-Surfactant-Transport.gitSupplementary material is available online at https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/nanoscale-surfactant-transport-bridging-molecular-and-continuum-models/6549A8BA9E8CF5C5A9E484A13DB4D416#s5 .A preprint version of the article is available at arXiv:2408.08327v1 [cond-mat.soft], https://arxiv.org/abs/2408.08327, under a CC BY licence. It has not been certified by peer review.Surfactant transport is central to a diverse range of natural phenomena with numerous practical applications in physics and engineering. Surprisingly, this process remains relatively poorly understood at the molecular scale. Here, we use non-equilibrium molecular dynamics (NEMD) simulations to study the spreading of sodium dodecyl sulphate on a thin film of liquid water. The molecular form of the control volume is extended to a coordinate system moving with the liquid–vapour interface to track surfactant spreading. We use this to compare the NEMD results to the continuum description of surfactant transport on an interface. By including the molecular details in the continuum model, we establish that the transport equation preserves substantial accuracy in capturing the underlying physics. Moreover, the relative importance of the different mechanisms involved in the transport process is identified. Consequently, we derive a novel exact molecular equation for surfactant transport along a deforming surface. Close agreement between the two conceptually different approaches, i.e. NEMD simulations and the numerical solution of the continuum equation, is found as measured by the surfactant concentration profiles, and the time dependence of the so-called spreading length. The current study focuses on a relatively simple specific solvent–surfactant system, and the observed agreement with the continuum model may not arise for more complicated industrially relevant surfactants and anti-foaming agents. In such cases, the continuum approach may fail to predict accompanying phase transitions, which can still be captured through the NEMD framework.M.R.R. was supported by Shell, and the Beit Fellowship for Scientific Research. J.P.E. was supported by the Royal Academy of Engineering (RAEng). L.S. thanks EPSRC for a Postdoctoral Fellowship (EP/V005073/1). D.D. acknowledges a Shell/RAEng Research Chair in Complex Engineering Interfaces and EPSRC Established Career Fellowship (EP/N025954/1). The authors are grateful to UK Materials and Molecular Modelling Hub for computational resources funded by EPSRC (EP/T022213/1, EP/W032260/1 and EP/P020194/1)
The Effectiveness of Physical Activity and Nutrition Interventions for Children and Adolescents With Cerebral Palsy to Improve Physical Health and Cognitive Outcomes: A Systematic Review
Get PDFPurpose: Using systematic review methodology, we set out to describe the evidence for physical activity and nutrition interventions for children and adolescents with cerebral palsy (CP) as compared with no intervention or exposure that reports physical health and cognitive outcomes. Method: Quantitative, primary studies that explored the effectiveness of these interventions, replicable in school and home contexts, in comparison to any other or no intervention or exposure in children and adolescents between the ages of 6–18 years old with a diagnosis of cerebral palsy were included (PROSPERO CRD42022322143). Risk of bias was assessed by Joanna Briggs Institute and QualSyst. Results: A total of 16 international heterogeneous studies (13 physical activity and 3 nutrition) with interventions ranging from a single exposure to 8 months, with quality 58% to 89% and effectiveness, D = 0.03 to 0.97, were included. Outcome measures were varied. Conclusion: The review brings together a number of high-quality studies on physical activity and nutrition interventions and promising findings of impact on cardiovascular, musculoskeletal, and cognitive outcomes. Evidence supports implementation of these interventions in community contexts. Future research would benefit from agreement on the use of core outcome measures for meta-synthesis
A Novel Particle Swarm Optimizer with Randomly Occurring Uncertainty
Get PDFParticle Swarm Optimization (PSO) has been widely applied due to its simplicity and effectiveness in solving optimization problems. However, PSO often suffers from premature convergence and stagnation in local optima, especially in complex search spaces. This paper proposes a novel PSO algorithm by incorporating stochastic perturbations into the velocity updating mechanism. Specifically, the acceleration coefficients are perturbed by the introduced randomly occurring uncertainty to improve the search ability of the entire swarm. Experimental results on representative CEC benchmark functions demonstrate that the proposed algorithm outperforms several existing PSO variants
A comprehensive survey on domain adaptation for intelligent fault diagnosis
No full textData availability:
Data will be made available on request.Deep learning-based intelligent fault diagnosis methods have typically been developed under the assumption that an abundant and diverse set of training samples and labels is available. Thus, it is crucial to develop models capable of generalizing effectively to distributions characterized by limited samples and insufficient labels. The transfer of knowledge from semantically related but distributionally different source domains has been recognized as an effective approach; however, discrepancies between distributions may result in negative transfer issues. Domain adaptation (DA), as a prominent research area within transfer learning, has been extensively studied to enhance generalization performance on target tasks. In this survey, the various concepts, formulations, algorithms, and applications of DA in industrial fault diagnosis are thoroughly reviewed. Broader DA solutions are covered, including (a) metric learning, adversarial adaptation, reconstruction, and generation within a homogeneous setting, and (b) source-free domain adaptation, domain generalization, partial domain adaptation, open-set domain adaptation, and universal domain adaptation within a heterogeneous setting, all of which extend beyond the traditional divisions of semi-supervised and unsupervised learning. This survey allows researchers to quickly and comprehensively grasp the research foundation, current status, theoretical limitations, and under-explored directions in the field, thereby facilitating the achievement of universally applicable methods in diverse industrial scenarios.This work was supported in part by the European Union’s Horizon 2020 Research and Innovation Programme under Grant 820776 (INTEGRADDE), the National Natural Science Foundation of China under Grants U21A2019 and 62403119, the Hainan Province Science and Technology Special Fund of China under Grant ZDYF2022SHFZ105, the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation (CPSF) under Grant Number GZB20240136, the China Postdoctoral Foundation under Grant Number 2024MD753911, the Heilongjiang Provincial Postdoctoral Science Foundation of China under Grant Number LBH-TZ2405, the Engineering and Physical Sciences Research Council (EPSRC) of the UK, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany
Unveiling heatwave events in Bangladesh: Insights from observational records and ERA5 reanalysis data
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Data will be made available on request.Supplementary data are available online at: https://www.sciencedirect.com/science/article/pii/S2405880725000706?via%3Dihub#m0005 .Heatwaves (HWs) are escalating in frequency and intensity, posing serious risks to human health, agriculture, and infrastructure worldwide. However, the lack of a universally accepted definition of HWs complicates consistent characterization across regions. In Bangladesh, a subtropical country increasingly vulnerable to extreme heat, the dynamics of HWs remain insufficiently understood. This study aims to bridge that knowledge gap by analyzing three decades of observational data to characterize HWs in Bangladesh, using ambient and apparent temperature metrics. Five HW indices were employed to assess 24-hour (EHF), daytime (CTX90pct, TX90), and nocturnal (CTN90pct, TN90) HW patterns, with humidity effects incorporated through apparent temperature-based indices. HWs were defined as events lasting at least three consecutive days, reflecting the heightened health risks of prolonged exposure. HWs were evaluated in terms of frequency, duration, intensity, and early onset patterns. Station-based observations were compared against corresponding estimates derived from ERA5 reanalysis data. The 90th percentile of daily temperature emerged as a robust operational threshold for HW characterization in Bangladesh. Declines in temperature variability during HW events were linked to reduced intensities for indices sensitive to short-term variability or independent of seasonality. Humidity exerted a stronger influence on nocturnal HWs than on daytime events, while seasonal variations in temperature and humidity during the pre- and post-monsoon periods significantly shaped HW characteristics. These findings provide new insights into the spatiotemporal dynamics of HWs in Bangladesh, offering an evidence base to inform adaptation strategies in other subtropical regions facing similar climate threats.
Practical implications:
This study provides critical insights into the growing challenges of HWs in Bangladesh, highlighting their increasing frequency, duration, intensity, and earlier onset. The findings underscore the importance of adopting the 90th percentile of daily temperature as a reliable threshold for HW characterization, tailored to Bangladesh’s subtropical climate. The study reveals distinct regional and seasonal patterns, with coastal areas experiencing prolonged HWs and humidity-driven nocturnal events, which significantly disrupt nighttime recovery and productivity. Policymakers can leverage these insights to develop localized mitigation strategies, such as early warning systems, urban heat management plans, and infrastructure adaptations to reduce HW impacts. The results emphasize the role of humidity in intensifying heat stress, calling for integrated approaches that consider both ambient temperature and apparent temperature metrics in HW assessments. Furthermore, the methodology used in this study is transferable to other similar climatic contexts, making the results valuable for informing policy in regions beyond Bangladesh that face comparable challenges. By addressing gaps in observational data and incorporating indoor heat stress and continuous surface data in future research, the findings offer a pathway to designing more robust climate resilience frameworks. These measures are essential for safeguarding vulnerable populations, ensuring public health, and minimizing socio-economic losses from extreme heat events both locally and globally.Mohammed Sarfaraz Gani Adnan acknowledges support from the Leverhulme Trust through an Early Career Fellowship [grant reference ECF-2023-074]
CSM proposal for predicting buckling resistance of stainless steel CHS beam-columns
No full textData availability:
Data will be made available on request.Stainless steel is increasingly being utilized to enhance the sustainability and long-term performance of structures owing to its exceptional corrosion resistance and excellent material propreties. However, most global design standards incorporate cross-section classification into the design procedures, limiting the load-bearing capacity of sections to the 0.2 % proof stress. This approach prevents the full utilization of the significant strain hardening capacity of stainless steel, leading to overly conservative predictions. Therefore, there is a real need to develop a more advanced analytical design approach. This study presents the first systematic extension of the Continuous Strength Method to stainless steel circular hollow sections under combined axial compression and bending, addressing a key gap in current design guidance. For this purpose, a finite element model is developed and used to conduct a parametric study for assessing the proposed CSM approach. The existing interaction factors are evaluated, and a revised interaction factor is proposed based on the findings. A comparative analysis with design rules given Eurocode 3 is presented. The results demonstrate that implementing the proposed CSM method with the revised interaction factor leads to more accurate resistance predictions for stainless steel CHS under combined axial compression and bending. Finally, the safety of the proposed CSM method is evaluated through a reliability analysis
Gradient-Based Calibration of a Precipitation Hardening Model for 6xxx Series Aluminium Alloys
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The original contributions presented in this study are included in the article/Supplementary Material . Further inquiries can be directed to the corresponding authors.Supplementary Materials:
The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/met15091035/s1. GIF S1: Gradient-based calibration of the predicted yield strength curve using the ADAM optimiser. The model iteratively adjusts parameters to minimise the loss, with a stopping criterion set to a function tolerance of 1 × 10^−6. The convergence towards the interpolated experimental data is shown across successive iterations.Precipitation hardening is the primary mechanism for strengthening 6xxx series aluminium alloys. The characteristics of the precipitates play a crucial role in determining the mechanical properties. In particular, predicting yield strength (YS) based on microstructure is experimentally complex and costly because its key variables, such as precipitate radius, spacing, and volume fraction (VF), are difficult to measure. Physics-based models have emerged to tackle these complications utilising advancements in simulation environments. Nevertheless, pure physics-based models require numerous free parameters and ongoing debates over governing equations. Conversely, purely data-driven models struggle with insufficient datasets and physical interpretability. Moreover, the complex dynamics between internal model variables has led both approaches to adopt heuristic optimisation methods, such as the Powell or Nelder–Mead methods, which fail to exploit valuable gradient information. To overcome these issues, we propose a gradient-based optimisation for the Kampmann–Wagner Numerical (KWN) model, incorporating CALPHAD (CALculation of PHAse Diagrams) and a strength model. Our modifications include facilitating differentiability via smoothed approximations of conditional logic, optimising non-linear combinations of free parameters, and reducing computational complexity through a single size-class assumption. Model calibration is guided by a mean squared error (MSE) loss function that aligns the YS predictions with interpolated experimental data using L2 regularisation for penalising deviations from a purely physics-based modelling structure. A comparison shows that the gradient-based adaptive moment estimation (ADAM) outperforms the gradient-free Powell and Nelder–Mead methods by converging faster, requiring fewer evaluations, and yielding more physically plausible parameters, highlighting the importance of calibration techniques in the modelling of 6xxx series precipitation hardening.This work was supported by UK Research and Innovation under funding code EP/V061798/1
The ePIC Silicon Vertex Tracker IB-OB: Design and thermal-mechanical simulations
Get PDFThe future Electron–Ion Collider (EIC) will offer a unique opportunity to explore the parton distributions inside nucleons and nuclei thanks to an unprecedented luminosity, a wide range of energies, a large choice of nuclei and polarization of both beams. The Electron–Proton/Ion Collider (ePIC) detector will be capable of precise determination of the position of primary and secondary vertexes, essential e.g. for the identification of charm hadrons, giving access to the gluon distribution inside hadrons. This measurement capability is achieved with a Silicon Vertex Tracker (SVT) placed as the innermost device in the ePIC experiment. The SVT Inner and Outer Barrel (IB, OB), developed by a collaboration of Italy-UK-USA institutes, provide five detecting layers made of silicon detectors, using the 65 nm Monolithic Active Pixel Sensor (MAPS) technology with stitching, pioneered by the ALICE collaboration for the Inner Tracking System 3 (ITS3) upgrade. The IB main focus is on vertexing performance. It is made of three layers of wafer-scale sensors bent to a cylindrical shape. The OB, composed of two layers, mainly contributes to the particle momentum measurement and it is equipped with a smaller version of the IB sensor mounted in a typical stave configuration.
This paper will present the design of SVT Inner and Outer Barrel and the first Finite Element Analysis (FEA) simulations for mechanical and thermal studies.SCOAP3
On K-stability of One-nodal Prime Fano Threefolds of Genus 12
No full textA preprint version of the article is available at arXiv:2506.17649v2 [math.AG], https://arxiv.org/abs/2506.17649 ([v2] Fri, 10 Oct 2025 21:53:54 UTC (59 KB)), under a CC BY license (https://creativecommons.org/licenses/by/4.0/). It has not been certified by peer review.Subjects:
Primary: 14E05 , 14J10 , 14J45.We show that general one-nodal prime Fano threefolds of genus 12 are K-polystable.Anne-Sophie Kaloghiros was supported by EPSRC grant EP/V056689/1, Elena Denisova is a PhD student at the University of Edinburgh supported by the School of Mathematics Studentship (funded via EPSRC DTP).Denisova was supported by a University of Edinburgh School of Mathematics EPSRC DTP Studentship, Kaloghiros was supported by EPSRC grant EP/V056689/1
Evaporation and micro-explosion characteristics of oxymethylene dimethyl ether–diesel binary droplet
No full textData Availability:
The data that support the findings of this study are available from the corresponding author upon reasonable request.Supplementary Material:
See the supplementary material for the ImageJ scripts used in data processing and analysis at https://doi.org/10.60893/figshare.pof.c.8084863 .This study investigates evaporation behavior, puffing, and micro-explosion in droplets of pure diesel, oxymethylene ether (OME1), and diesel/OME1 blends (20%–90% OME1 by volume) using high-speed backlighting imaging. While the 50% OME1 blend exhibits micro-explosions, the 60% and 70% blends show only puffing, and higher or lower OME1 fractions primarily undergo smooth evaporation. The findings indicate that increasing the OME1 concentration accelerates droplet evaporation. Moreover, the evaporation process exhibits universal behavior when droplet lifetimes are scaled by the characteristic evaporation time scale and the binary mixtures show a behavior similar to a homogenous single-component fuel. A modified D2-law has been proposed to account for binary mixture composition. Morphological observations reveal two dominant pathways: strong micro-explosions, which lead to explosive disintegration and rapid ligament growth, while weak micro-explosions involve mild puffing, and smooth ligament formation culminating in larger droplets. We further analyze this ligament evolution through a breakup regime map, constructed using non-dimensionalized ligament neck diameter, gamma distribution shape parameter, and ligament aspect ratio. Results show a strong correlation between these parameters, indicating a statistical transition in ligament-to-droplet fragmentation modes. An analysis of the dominated time scales shows that strong micro-explosions occur in an inertial-dominated regime, where the ligament stretching time is relatively much shorter than the capillary time scale, while weak micro-explosions occur at relatively higher time scale ratios, suggesting capillary-dominated breakup. The drop size distribution, driven by inertial-dominated regime, is well described by a gamma distribution. These findings enhance our understanding of multicomponent droplet atomization and its relevance to spray-driven combustion.We acknowledge the financial support provided by the Engineering and Physical Sciences Research Council (EPSRC), UK, under Grant No. EP/X019578/1
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