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Influence of grain morphology on strengthening of aluminium and magnesium alloys
Get PDFThis thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe Hall-Petch equation is commonly employed to establish a connection between the yield strength/hardness of metallic materials and the grain diameter (d). However, for alloys having grains with dendritic morphology, a more accurate representation of the Hall-Petch equation involves substituting d with the secondary dendritic arm spacing (SDAS), denoted as λ2. This thesis underscores the significance of considering a perimeter-associated parameter, rather than relying solely on d or λ2, to account for strength contribution from morphological changes in various alloys. To express the complexity of dendritic / grain morphology in 2 dimension, a perimeter associated parameter (p') has been proposed. And, a comprehensive generic Hall-Petch relation expressed as =o+′′√′, where p' signifies the area per unit perimeter which can be accurately measured using digital imaging tools and ′′ is the slope representing Hall-Petch constant, is being proposed. To substantiate the validity of this proposed relation, controlled solidification experiments were conducted on Al-Si and Al-Ce binary alloys, encompassing a range of cooling rates from 0.000167 °C/s to 0.34 °C/s. The degree of dendritic structure in primary α-Al was deliberately manipulated through solute content, such as the addition of Si or Ce. Notably, the relationship between λ2 and the corresponding p' is observed to be non-linear, both experimentally and theoretically. This underscores the critical importance of incorporating the perimeter-associated parameter p' as a fundamental strength metric in the Hall-Petch relation. The resulting changes in hardness, in conjunction with evolving grain morphologies, were meticulously analysed. The experimental data from a spectrum of observed morphologies (facetted, rosette, and dendritic) fit more effectively with our proposed generic Hall-Petch relationship compared to conventional representations.
To assess the applicability of the new Hall-Petch relationship across different alloy systems, magnesium (Mg) alloys were also investigated. Wedge mould castings of commercially available AZ91D alloy and Mg-5 and 9 wt.% binary alloys were examined. The diverse cooling rates induced by the wedge mould, along with varying solute content, led to a range of morphologies in the magnesium grains. Tensile tests were conducted on both as-cast and solution-treated AZ91D alloy to examine the relationship between d, λ2, p', and yield strength (YS). The proposed generic Hall-Petch relationship yields better coefficient of regression when p' is considered instead of d or λ2. This underscores the significance of incorporating perimeter-associated parameters to accurately quantify the variation in the morphology of grain structures across different alloys.
During the examination of dendritic structure morphology in Al-Ce binary alloys, high thermal stability of Al11Ce3 was recognised. Spheroidization experiments were conducted to evaluate the coarsening resistance of the Al11Ce3 phase in Al-5Ce alloy, with comparisons made to Al-5Si alloy through circularity measurements. The circularity of Al11Ce3 changed from 0.64 to 0.66, while the circularity of eutectic Si changed from 0.55 to 0.8 during isothermal annealing at 400°C. To exploit the superior thermal stability of Al-Ce alloys, new alloys incorporating various compositions of Sc, Zr, Si and Mg for their mechanical properties at elevated temperatures. Specimens were fabricated using gravity and high-pressure die casting techniques. The addition of 0.2 wt.% Sc and 0.2 wt.% Zr resulted in the formation of nanoscale Al3Sc,Zr precipitates with an average particle size of approximately 3 nm at the peak aged condition of 300°C. Moreover, the addition of 0.4 wt.% Sc and 0.2 wt.% Zr refined the grain structure, leading to the formation of grains with an average size of approximately 20 μm. Specimens cast through HPDC were tested at room and elevated temperatures ranging from 150 to 300°C. The yield strength (YS) of Al-10Ce-0.2Sc-0.2Sc was measured to be 115 MPa with a retention factor of 0.9 at 300°C
Sustainable Development Goals in a regional context: conceptualising, measuring and managing residents’ perceptions
No full textData Availability Statement: The data supporting the findings of this study are available from the corresponding author upon reasonable request.Supplemental material: Supplemental data for this article can be accessed online at https://doi.org/10.1080/00343404.2024.2373871 .JEL: C83.This study explores how national-level Sustainable Development Goals (SDGs) are implemented at the regional level in Italy by achieving three objectives: (1) conceptualising local residents’ perceptions of the SDGs; (2) creating a scale to measure these perceptions; and (3) validating this scale across Italian regions. Using a six-step methodology, including panel data analysis and surveys with 2303 respondents, this research validates key SDGs significant to Italian regions. The results provide policymakers with a framework to tailor regional policies that resonate with residents’ views on SDGs
The Defence Intelligence Daily Update: Current Intelligence as Public Service Announcement
No full textSince the outbreak of the Russo-Ukraine war the UK’s defence intelligence organisation, slightly unhelpfully branded simply ‘Defence Intelligence’ (DI) has been turning out a daily Intelligence Update. The Update has received considerable press attention and has even become the basis of a nearly daily item in the Evening Standard newspaper. Reactions have been varied, from cynical dismissal of yet another information and influence operation by His Majesty’s Government through technical dissatisfaction with the analytical quality of the Update to breathless enthusiasm for yet another British leap forward in transparency and open government. ..
A taxometric analysis of developmental prosopagnosia: Evidence for a categorically distinct impairment
Get PDFPoor performance on cognitive assessment tasks may indicate a selective ‘impairment’. However, it is unclear whether such difficulties separate the individual from the general population qualitatively (i.e., they form a discrete group) or quantitatively (i.e., they represent the lower end of a continuous distribution). Taxometric methods address this question but have rarely been applied to cognitive disorders. This study examined the latent structure of developmental prosopagnosia (DP) – a relatively selective deficit in face recognition that occurs in the absence of neurological injury. Multiple taxometric procedures were applied to dominant diagnostic indices of face recognition ability across two independent datasets. All analyses supported a categorical outcome, even for mild cases of DP, suggesting that it is a qualitatively distinct condition. This finding has significant implications for our understanding of DP given it has traditionally been viewed as a continuous impairment. In particular, existing (arbitrary) diagnostic cut-offs may be too conservative, underestimating prevalence rates and prohibiting big-data approaches to theoretical study. More broadly, these conclusions support application of the taxometric method to many other cognitive processes where weaknesses are predominantly assumed to reside on a continuous distribution
Introduction – Performance and Political Economy: Bodies, Politics, and Well-Being
No full textIn this article, Katerina Paramana introduces Lateral's special section, “Political Economy and the Arts,” and its first set of articles, “Performance and Political Economy: Bodies, Politics, and Well-Being,” and provides the rationale and context for this section’s topic. In the face of a multiplicity of world-wide problems and suffering, this special section aims at a reinvestment in desire for change in order to resuscitate and reinvest in hope. The articles therein provide insights into the current relationship between politics, human and non-human bodies, and their well-being (and why it is necessary we take action to change it) which might help us steer the wheel before we drive off the cliff.Brunel University London Research Seminar Series Award
Conversion of Aluminum to Hydrogen: A Metallurgical Point of View
Get PDFPerspective.Transition to the Net-Zero economy requires new sources of energy. Hydrogen is one of the promising candidates to replace carbohydrates. Emission-free technologies for hydrogen production are pivotal for this transition. However, the existing technologies to produce hydrogen are either polluting or energy-intensive. In recent years, a reaction of aluminum with water generating hydrogen has attracted a lot of attention. Most of the research is done with solid aluminum and analyzed mostly from the chemical and energy points of view. In this overview paper, rarely mentioned metallurgical aspects of this reaction are considered, as well as potential integration of the related technology into a green aluminum production cycle. The advantages of using liquid aluminum as well as related safety aspects are highlighted.This analysis was done within the framework of Circular Metals Centre funded by a UKRI/EPSRC grant EP/V011804/1
Effect of Protic and Aprotic Formamide-Based Organic Electrolytes for Rechargeable Zinc/MnO2 Battery
Get PDFData Availability Statement: The data that support the findings of this study are openly available in Brunel Figshare at https://doi.org/10.17633/rd.brunel.25093388.v1.Zinc ion batteries (ZIBs) are emerging as a promising and cost-effective alternative energy storage system compared to other metal-ion batteries. Aqueous electrolytes have been extensively studied in Zn-ion batteries which has shown issues related to cathode dissolution. In comparison, little has been looked into the use of organic electrolytes in ZIBs. Here, we have studied both protic and aprotic forms of formamide-based organic electrolytes containing Zn trifluoromethanesulfonate and their influence on the Zn solvation chemistry, electrochemistry, and performance of Zn-MnO2 battery. It was observed that protic-based electrolytes gave a much better capacity and stability for the Zn-MnO2 battery. A capacity close to 150 mAh g−1 was obtained with formamide electrolyte at a current density of 0.25 A g−1. For all the other formamide-based electrolytes tested, the capacity was lower. After 100 cycles, an average capacity retention of 72 % was obtained for formamide-based electrolyte. This study shows that protic-based electrolytes might be a suitable option for non-aqueous-based Zn-ion batteries.This research was funded, in whole by EPSRC. Grant Number: EP/W015129/
Breathable Cities: Dynamic Machine Learning Modelling Approaches for Advanced Air Pollution Control
Get PDFData Availability Statement: The data that support the findings of this study are available from the corresponding author, M.A., upon reasonable request.first_pageDownload PDFsettingsOrder Article Reprints
Open AccessArticle
Breathable Cities: Dynamic Machine Learning Modelling Approaches for Advanced Air Pollution Control
by Roba Zayed andMaysam Abbod *ORCID
Department of Electronic and Electrical Engineering, Brunel University London, London UB8 3PH, UK
*
Author to whom correspondence should be addressed.
Appl. Sci. 2024, 14(13), 5581; https://doi.org/10.3390/app14135581
Submission received: 20 May 2024 / Revised: 19 June 2024 / Accepted: 24 June 2024 / Published: 27 June 2024
(This article belongs to the Special Issue Air Quality Prediction Based on Machine Learning Algorithms II)
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Abstract
This paper discusses air quality index (AQI) representation using a fuzzy logic framework to cover the blurry areas of AQI where indices are in between ranges of values. After studying several standards for air quality prediction (AQP), this research suggested the use of fuzzy logic as an extended method to cover some limitations found in several standards, in which the fuzzy logic represents a more dynamic way to support cross-country comparisons as well. This research expanded upon the United States Environmental Protection Agency (USEPA) standards to address their acknowledged limitations by constructing a fuzzy air quality levels prediction (FAQLP) model, which categorizes air quality into corresponding ranges (actual levels) and classifies new fuzzy levels (predicted levels), using a fuzzy logic model (to enforce more realistic predictions). This model can solve the issue of values at or near boundaries when there is uncertainty about air quality levels. The study aims to incorporate a comparative study of two urban settings providing dynamic machine-learning modeling approaches for advanced air pollution control. The DNN–Markov model is presented in this paper as the selected hybrid model for AQI prediction, and the adaptive neuro-fuzzy inference system (ANFIS) was used to represent AQI. This work presents a novel air quality index framework that consists of a DNN–Markov model for accurate hourly predictions and air quality level representations using ANFIS.This research received no external funding. The APC was funded by Brunel University London
Highly Efficient Hybrid Reconfigurable Intelligent Surface Approach for Power Loss Reduction and Coverage Area Enhancement in 6G Networks
Get PDFData Availability Statement: Derived data supporting the findings of this study are available from the corresponding author upon request.This paper introduces a novel efficient hybrid reconfigurable intelligent surface (RIS) approach designed to significantly reduce power loss and enhance coverage area in 6G networks. The core innovation of this approach lies in an advanced iterative algorithm introduced as the Hybrid reconfigurable intelligent surface decision-making algorithm (HRIS-DMA) that integrates precise user location data into the RIS configuration process. By dynamically adjusting RIS elements to reflect and direct signals based on real-time user positions, this method minimises signal attenuation and optimises signal propagation. The mechanism driving the performance gains includes precise beamforming and intelligent reflection, continuously refined through iterative updates. This technique ensures robust signal strength and expanded coverage, addressing the challenges of dense and diverse deployment scenarios in 6G networks. The proposed scheme’s application in 6G networks demonstrates substantial improvements in signal quality and network reliability, paving the way for enhanced user experiences and efficient communication infrastructures. This novel approach was tested using MATLAB R2023a, and its performance was evaluated using three downlink scenarios: zero to few, few to moderate, and moderate to many obstacles. The three scenarios show higher coverages than conventional simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) and base station (BS) handover. Based on the evaluation metrics, the analysis results of the novel HRIS-DMA show 70% less signal power loss, 0.17 (Formula presented.) s less system delay, 25 dB and 12 dB channel gain compared with the conventional STAR-RIS and BS handover, respectively, and 95% improvement in the overall system’s efficiency compared to STAR-RIS and 13% compared to BS-BS handover.This research received no external funding
Web accessibility barriers and their cross-disability impact in eSystems: A scoping review
Get PDFData availability: No data was used for the research described in the article.Accessibility is an important component in the implementation of Web systems to ensure that these are usable, engaging, and enjoyable by all regardless of the level of ability, condition, or circumstances. Despite manifold efforts, the Web is still largely inaccessible for a plurality of reasons (e.g. poor navigation, lack of/unsuitable alternative text, complex Web forms) with significant impact on disabled users. The impact of Web accessibility barriers varies per disability, but current measures for the impact of barriers treat disabilities as a homogeneous group. In this work, we present a scoping review of the Web accessibility research landscape. Following a structured approach, 112 studies were reviewed, and findings are reported on common Web accessibility barriers and practices within the Web Accessibility Lifecycle. An assessment framework is further proposed to measure the impact of such barriers across disabled groups. Finally, the need for extensive qualitative research into organizational change and multinational studies on Web activity and disturbance by barriers per disabled user group are discussed as future avenues for accessibility research
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