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Modelling thermal conductivity of porous core systems for vacuum insulation panels
No full textThis thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonVacuum insulation panels (VIPs) are one of the most advanced and expensive insulation technologies, which achieve exceptionally low thermal conductivities of up to 0.004 W/(m·K) within a compact space. Modelling the thermal conductivity of core materials is essential for understanding their internal heat transfer mechanisms, enabling the development and optimisation of low-cost, sustainable, and durable cores of VIPs.
The core material of VIPs is typically made of porous media since the voids within the porous structure not only reduce the density but also restrict both gaseous and solid heat transfer within the core. Existing models often fall short in efficiently capturing the complex interplay of heat transfer mechanisms within diverse porous structures, particularly across a wide range of pressure and for non-ideal porous structures.
The particles forming the core are generally spherical or flaky in shape. Therefore, this study designs a two-dimensional Voronoi structure and a set of three-dimensional granular structures to construct physical models for analysing heat transfer. The proposed structures can be customised to reflect the morphological characteristics. The modelling work includes three components: conduction, convection, and radiation. For solid thermal conduction, this study employs either the Lattice Boltzmann method (LBM) or the finite element method (FEM), depending on the characteristic length of the solid skeleton. Then, a multiscale analytical model and numerical models are developed for calculating gas conduction and convection. Finally, the Rosseland approximation is applied to materials when FTIR data is available; If not, an improved radiation model combining the Watson model and physical structures is developed in this study to predict the radiative thermal conductivity of porous media.
This study first examines the thermal conductivity variations of multiscale porous media, using fumed silica as a case study, with gas pressure as the primary variable. The model effectively captures the morphological characteristics of the material and has been validated across a full range of pressure conditions. Compared to existing studies on fumed silica, the proposed model achieves more accurate and reasonable predictions. In the pressure range from 0.01 to 0.8 atm, where thermal conductivity
changes sharply, the model maximum error does not exceed 3%. This study further investigates the heat transfer behaviour of flaky porous media, exemplified by expanded perlite powder, by developing an innovative hybrid model to achieve a balance between predictive accuracy and computational complexity from vacuum to atmospheric pressure. At higher pressures (0.0001 to 0.05 atm, where Knudsen number 0.05 atm, where Knudsen number > 0.1), the analytical model demonstrates deviations from the experimental values ranging between 5% and 17%. Subsequently, the model is applied to investigate the effects of morphological parameters on the effective thermal conductivity and offers practical advice into optimising the thermal performance of flaky porous media.
Finally, this study develops a thermal conductivity model for granular porous media, using glass beads as an example, under vacuum conditions to investigate the influence of morphological characteristics on effective thermal conductivity and identify the most suitable three-dimensional geometric structure to represent their solid skeleton. A scaling model is first introduced by analysing the nonlinear relationship between contact thermal conduction and contact radius, significantly reducing the computational complexity with a maximum error of 1%. Five geometric structures are then employed to predict the conductive and radiative thermal conductivity with varying porosities. The results show that the aggregation structure provides the most accurate predictions for high-porosity (> 47.6%, porosity of simple cubic packing) structures with an average error of 12.7%; the dumping structure is optimal for packed beds (≈ 40%) with an average error of 9.2%, particularly for radiative thermal conductivity,
In conclusion, this thesis presents a comprehensive modelling framework that addresses critical gaps in the thermal conductivity modelling of porous VIP core materials. By integrating analytical and numerical methods with advanced material characterisation and physical representation techniques, this study provides practical approaches for calculating the thermal conductivity of porous media cores. The developed modelling framework offers a powerful tool for the rational design and optimisation of VIP core materials with tailored thermal performance, which can contribute to the development of more energy-efficient and cost-effective insulation solutions for the industries
’We are teachers too’: reclaiming professionalism in early childhood education from within
Get PDFThe professionalisation of Early Childhood Education and Care (ECEC) has gained international prominence due to its role in fostering children’s lifelong learning and contributing to societal economic growth. This paper explores professionalism in the ECEC workforce in England, focusing on tensions between policy, qualifications and the experiences of early years educators. Drawing on critical pedagogy and Bernstein’s pedagogic device, we explore how power dynamics and inequalities have led to the de-professionalisation of early years educators, positioning them as subordinate to teachers in compulsory education. Through narrative inquiry with 15 participants, we highlight the challenges and opportunities for early years educators to reclaim agency, foster criticality and transform their professionalism. The findings highlight a need to re-conceptualise ECEC professionalism, to prioritise practitioner autonomy, equitable policies and develop an integrated approach to workforce development through a sector-wide commitment to change that empowers early years educators as agents of pedagogic and policy innovation
Ex vivo expanded human regulatory T cells promote cholesterol efflux and PON1 expression in oxLDL-exposed macrophages via gap junction-mediated cAMP transfer
Get PDFData availability statement:
The RNA sequencing data has been deposited in GEO database (GSE265832).Supplementary material:
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fimmu.2025.1662925/full#supplementary-materialLipid-driven inflammation contributes to the development of atherosclerosis, and regulatory T cells (Tregs) have been proposed to influence macrophage responses to lipid stress. While adoptive Treg transfer has been shown to be safe in clinical studies, the mechanisms by which Tregs modulate macrophage lipid handling remain incompletely understood. In this study, we investigated the effects of ex vivo–expanded human Tregs on primary monocyte-derived M2-like macrophages exposed to oxidized low-density lipoprotein (oxLDL) in an in vitro coculture system. We assessed macrophage phenotype, gene expression, and cholesterol accumulation using flow cytometry, RNA sequencing, and western blotting. Our data show that coculture with Tregs attenuated oxLDL-induced pro-inflammatory responses and reduced intracellular lipid accumulation in macrophages. Mechanistically, we found evidence that Tregs transfer cyclic AMP (cAMP) into macrophages, which enhanced the ABCA1-mediated cholesterol efflux pathway and increased expression of paraoxonase-1 (PON1). These findings provide mechanistic insight into how Tregs modulate macrophage responses to oxLDL under controlled in vitro conditions. They highlight potential pathways through which Tregs may regulate macrophage lipid metabolism and inflammatory activity. Further in vivo studies will be essential to determine the physiological significance and therapeutic potential of these mechanisms.The author(s) declare financial support was received for the research and/or publication of this article. This research was supported by the British Heart Foundation PhD studentship (grant number FS/16/57/32733), Wellcome Trust PhD studentship (grant number 108874/B/15/Z), Lupus UK, King’s Health Partners, BD Biosciences Research Program Award, National Institute for Health Research (NIHR) Biomedical Research Centre based at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London and the NIHR Clinical Research Facility
Maximum correntropy state estimation for complex networks with uncertain inner coupling and amplify-and-forward relays
No full textIn this paper, the remote state estimation problem is addressed for a class of discrete time-varying nonlinear complex networks subject to non-Gaussian noises, uncertain inner coupling, and amplify-and-forward (AF) relays. The coupling strengths are unknown but belong to predefined intervals, and the measurement signals are transmitted to the remote estimator via AF relays with stochastic channel gains. To effectively deal with the non-Gaussian noises, a novel correntropy-based estimator design index is proposed considering the uncertain inner coupling and the AF relays, and the parameters of the estimator are obtained via recursively maximizing the index through a fixed-point iterative update rule. Furthermore, sufficient conditions are established to guarantee the convergence of the fixed-point approach. Finally, a simulation example is used to demonstrate the effectiveness of the proposed estimation scheme.This work was supported in part by the National Natural Science Foundation of China under Grants 62476039, the National Science and Technology Major Project of China under Grant 2019-I-0019-0018, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany
An investigation of the corporate accountability for human rights violations under exisitng regulations
No full textThis thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonAs a result of the abnormal control and enormous influence of transnational corporations
(TNCs) within the corporate world, the international community has become aware of the
potential damage TNCs may cause to the subjects and the impacts they may have on local
cultures and initiatives. For example, many TNCs are involved in transgressive activities by
operating in developing states and violating human rights such as right to life, right to clean
water, right to health environment, etc. Disappointingly, states are often implementing
effective enforcing mechanisms for the corporate human rights accountability because they
heavily rely upon these global giants for their economic prosperity, i.e., resources extracted
by the TNCs for generating profit. Thus, states tend to lack the political will and economic
competence to successfully regulate the unethical and illegal operations performed by
TNCs, providing the TNCs with an almost free pass to impede human rights and violate
them with the vicinity of their performance. Efforts to address human rights abuses by TNCs
go back to the early twentieth century, but it was not until the 1970s that the concept of
corporate social responsibility (CSR) began to gain prominence. Since putting the concept
into practice, several major international regulatory initiatives have been adopted to fill the
accountability gap. For example, the UN Global Compact, the United Nations Guiding
Principles on Business and Human Rights, OECD Guidelines for Multinational Enterprises,
International Labour Organisation, Extractive Industries Transparency, and Alien Tort
Claims Act 1789. Unfortunately, all these initiatives have proved inadequate in both form
and effect in tackling the issue of human rights abuses attributed to TNCs. This is because
of their non-voluntary nature, limited scope, and the extent of implementation. These
instruments were criticised as merely political commitments lacking the legal binding force
for their enforcement and implementation. Thus, this thesis calls for a widely ratified treaty
on businesses and human rights and comprehensively analyses recent work by the
Intergovernmental Working Group (IGWG) in this regard; specifically, the formation of the
Zero Draft 2018, Second Revised Draft 2020, and the Third Revised Draft 2021 of the
binding treaty. Primarily, the thesis will focus on analysing the provisions of these drafts,
which can become the content of the much awaited legally binding mechanism (treaty),
filling the vacuum created by the preceding regulatory mechanisms on businesses and
human rights and regulate human rights abuses. This thesis also critically analyses the
alternatives to the binding treaty and makes recommendations for the formation of an
effective widely ratified treaty on businesses and human rights
Inverter-Side Current Feedback Active Damping Based on Phase-Lead Compensation for Grid-Connected Inverter
Get PDFTo suppress the resonance in LCL-type grid-connected inverter (GCI), various active damping (AD) methods have been developed. In this article, an inverter-side current feedback active damping (ICFB-AD) strategy with phase-lead compensation is proposed, which achieves both resonance attenuation and accurate current control. A second-order unstable phase-lead filter is introduced in series with the ICFB loop to enhance the stability and robustness of the GCI. Design guidelines for the second-order unstable PLF are also presented. The proposed system ensures stability across a wide range of LCL resonance frequencies and exhibits strong robustness against variations in the filter inductance and grid impedance. Finally, the effectiveness of the proposed ICFB-AD strategy, along with its z-domain design methodology, is validated by experimental results.10.13039/501100001809-National Natural Science Foundation of China;
10.13039/501100004608-Natural Science Foundation of Jiangsu Provinc
Titanium Dioxide for Improved Performance of Reclaimed Asphalt Pavement Aggregates in Concrete
Get PDFData Availability Statement:
Data will be available upon request.This work presents an innovative approach to enhancing the performance of concrete with reclaimed asphalt pavement (RAP) aggregates using titanium dioxide (TiO2) nanoparticles. Traditional limestone coarse aggregates were partially replaced with 30% and 50% RAP aggregates; a subset of mixtures containing RAP aggregates was treated with TiO2 nanoparticles. The rheological, mechanical, and long-term properties of concrete, along with changes in its chemical composition following the addition of RAP and TiO2, were evaluated. Results revealed that using 30% and 50% RAP in concrete mixtures reduced their compressive strength by 18% and 27%, respectively. However, using TiO2 in those mixtures enhanced their compressive strength by 8.7% and 6.3%. Moreover, concrete with 50% RAP exhibited an 85% increase in water absorption (the highest among all mixtures) compared to the control. TiO2 treatment was most beneficial in the 30% RAP mixture, reducing its water absorption by 32.5% compared to its untreated counterpart. Additionally, the 30% RAP mixture treated with TiO2 showed the highest resistance to sulfates among modified mixtures, as its compressive strength decreased by 10.4% compared to a decrease of 23% in the strength of the untreated 30% RAP mixture. Statistical analysis using single-factor ANOVA showed that integrating RAP aggregates with or without the presence of TiO2 particles would significantly affect the concrete properties in terms of their population means. The t-test analysis, on the other hand, proved sufficient evidence that the mean values of the 30% RAP mixture treated with TiO2 would not differ significantly from the control in terms of its slump and water absorption properties. The chemical structure analysis revealed an increase in the Si-O-Si and Si-O functional groups when using TiO2 in RAP mixtures, suggesting improved hydration activity and accelerated C-S-H formation in the treated RAP mixtures. Moreover, distinct C-H peaks were witnessed in concrete with untreated RAP aggregates, resulting from the aged asphalt coating on the RAP, which weakened the bond between the RAP and the cementitious matrix.This research received no external funding
A Collaborative Rapid Response to Abuse in U.K. Gymnastics Using Group Focused Acceptance and Commitment Therapy-Based Program
No full textAlthough abuse is commonplace within sport, the abuse scandal in gymnastics has left many current and ex-gymnasts traumatized by their experiences. When the scandal emerged, we recognized an immediate need for support for survivors of this abuse within British Gymnastics; this paper documents our response. This paper presents practice-based evidence on how a focused acceptance and commitment therapy-based intervention program was designed and delivered to four different groups: parents/guardians, older ex-gymnasts, adolescent gymnasts (13–18 years), and younger gymnasts (9–12 years). In total, 90 individuals attended the group sessions across a period of 7 months. The intervention was found to be helpful in helping the group members to overcome current and historical traumas resultant from their experiences in gymnastics. The group program was efficacious in establishing psychological safety, imparting acceptance and commitment therapy-based skills, improving family relationships, and providing a healing group experience
Rethinking Gender Equality Policies in Indian Higher Education: A Critical Analysis of the National Education Policy
No full text..
Unveiling AI Perceptions: How Student Attitudes Towards AI Shape AI Awareness, Usage, and Conceptions
Get PDFAcknowledgements:
We would like to thank Ms D. Bejenaru-Burlacu, Ms P. Uppal and Ms M. Kaur for their support with data collection.This study examines the relationship between students’ attitudes toward artificial intelligence (AI) and both AI competence and conceptions. 176 UK university students completed a survey where they were asked to rate statements in relation to their attitudes towards AI, their AI competence and their conceptions about AI using 5-point Likert-type scales. In relation to AI competence, results indicate that affective attitudes predicted awareness and usage, leading to information avoidance and disengagement. Cognitive attitudes positively predicted AI awareness and usage. Behavioural attitudes, however, did not predict awareness or usage, suggesting that individuals may engage with AI technology without deeper understanding. For AI conceptions, behavioural attitudes were more closely linked to conceptions of AI in educational contexts. Positive behavioural attitudes predicted students’ conceptions of AI’s role in intelligent tutoring systems, retentions, drop-out reduction, recommendation systems, and personalised learning. In contrast, affective attitudes predicted conceptions of AI’s use in classroom monitoring and performance prediction, while cognitive attitudes had little influence. These are areas educators can focus on when designing teaching & assessment strategies in relation to AI
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