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Numerical simulations of flow boiling in constricted microchannels: Bubble dynamics and heat transfer characteristics
Get PDFFlow boiling in microchannels as a method for cooling electronic systems is constrained by inherent boiling instabilities. These instabilities are largely caused by the sudden expansion of bubbles inside the channels resulting in reversed flow and flow maldistribution. One approach which has been suggested to mitigate flow reversal is to add a restriction at the channel inlet. However, the impact of this inlet restriction on bubble growth dynamics remains largely unexplored. This article presents a numerical study of the effect of restrictions at microchannel inlets on bubble growth dynamics and associated heat transfer characteristics. We consider a refrigerant, R245fa, as the fluid flowing inside a microchannel of hydraulic diameter 100μm. The mass flux range considered is 500−1900kg/m2s (Reynolds number, Rel=130−505) and a constant heat flux of 150kW/m2 is applied at the base of the evaporator. We carry out transient, three-dimensional numerical simulations using boilingFOAM, a custom version of OpenFOAM which utilises the volume-of-fluid method to capture the dynamics of the liquid–vapour interface accounting for heat transfer, phase change and also incorporates conjugate heat transfer through the evaporator wall. Our results demonstrate that the bubble nucleation location exerts a significant influence over the bubble growth rate, heat transfer, and pressure fluctuations. Further, with an increase in Reynolds number, we observe a breakdown in the symmetry of the fluid flow giving rise to asymmetric bubble growth inside the channel. Finally, we demonstrate that reducing the restriction ratio from 0.5 to 0.2 leads to an increase in inlet pressure, and a marked rise in the Nusselt number
The PMDWell framework: A confirmatory factor analysis of video game players’ wellbeing
Get PDFDespite the video game moral panics that have sprung up since the early 1990s, videogames remain a popular medium, increasing in capacity and market value every year. With the growth in the number of digital game players came the growth of uncertainty over the impacts of video games on wellbeing. The new generations are growing upsurrounded by ubiquitous, always-available digital technology and increasingly practice digitally mediated socialisation. The cultural shift suggests a change in the conceptualisation of wellbeing that can explain the phenomena of video game playing deaths.A Player Multidimensional Wellbeing scale (PMDWell) is presented. The scale was derived from a conceptual framework drawn from existing literature on video game specific influences on wellbeing, and tested of 443 participants aged 13 to 65 worldwide. Teenagers were included due to the prevalence of gamers in the younger population. The scale constructs were validated using confirmatory factor analyses, ranging from good to excellent model fits, validity and reliability. We concluded that player wellbeing is a multidimensional construct with internal (social functioning, mental health) and external (physical health, life circumstances) dimensions.Compared to other measures of wellbeing, PMDWell offers a broader understanding of wellbeing in the digital era that can be used to promote and maintain good health and perhaps highlight the lifestyle changes needed to optimise wellbeing and improve mental health. Future research could seek to replicate our validation in wider populations to enable demographic comparisons, especially comparing adolescents and young adults
Belowground Interactions in a Barley Cultivar Mixture: Root Distribution and Arbuscular Mycorrhizal Contributions to Uptake of Heterogeneous Phosphorus
Get PDFCultivar mixtures have the potential to mitigate abiotic stress and stabilize crop yields, but their belowground dynamics remain poorly understood. We evaluated phosphorus (P) uptake by two contrasting spring barley (Hordeum vulgare L.) cultivars (“Anneli” and “Feedway”), grown either in 50:50 mixture or as pure stand. The cultivars were grown in mesocosms under four P fertilization treatments: low-P, homogeneous high-P (90 mg P/kg), and localized P hotspots (100 mg P) placed either in the topsoil (5 cm) or subsoil (35 cm). To trace P uptake pathways, the hotspots were labeled with 33P and enclosed in mesh bags allowing only mycorrhizal hyphae (25 μm) or both roots and hyphae (2 mm) to access the hotspot. After 35 days, we measured aboveground biomass, total P content, 33P specific activity, and root biomass, length, diameter, and arbuscular mycorrhiza fungi (AMF) root colonization. In the mixture, reduced P uptake by “Feedway” led to lower overall performance compared to pure stand. Root modifications in the mixture did not enhance biomass or P acquisition, potentially due to decreased AMF colonization. Although different P placements altered P uptake patterns, they did not increase total P uptake. Roots accessed the P hotspots and acquired 33P without notable proliferation in the enriched zones. Our findings underscore the complexity of belowground interactions involving root distribution, competition for P, and AMF, and highlight the need for future research to optimize nutrient acquisition and performance in cultivar mixtures
Understanding Online Registered Nursing Students’ Attitudes Towards Environmentally Sustainable Healthcare
Get PDFBackground/Objectives: The healthcare sector is a significant source of pollution, and it is widely acknowledged that changes are required to transition to more sustainable healthcare practice. Nurses represent more than half of the sector's workforce and are uniquely positioned to enact change. However, expertise on environmental sustainability within the nursing field is a barrier despite the topic being positively embraced by students. Methods: This research employed a cross-sectional design using an anonymous online survey with convenience sampling from registered nursing students studying online to understand their attitudes towards environmentally sustainable healthcare. Data were collected between April 2023 and January 2024 with quantitative results analysed using descriptive statistics and qualitative results using thematic analysis. Results: Results show that registered nursing students are aware of the negative environmental impact of healthcare practice, realise the importance of working more sustainably and understand the value and role of education to facilitate meaningful change in the sector. However, they called for more educational content, specifically on carbon footprints, waste management, and resource use, paired with organisational leadership support and workplace training in healthcare settings. Conclusions: Adopting these recommendations endorsed by student nurses in practice could support nurses to reduce the environmental burden of the healthcare sector and contribute to both net zero and the United Nations Sustainable Development Goals
It’s Hey Jude, not Hey Jade: Input Variation and the Emergence of the Infant Lexicon
Get PDFA growing literature explores the representational detail of infants’ early lexical representations, but no study has investigated how exposure to real-life acoustic-phonetic variation impacts these representations. Indeed, previous experimental work with young infants has largely ignored the impact of accent exposure on lexical development. We ask how routine exposure to accent variation affects 6-month-olds’ ability to detect mispronunciations. Forty-eight monolingual English-learning 6-month-olds participated. Mono-accented infants, exposed to minimal accent variation, detected vowel mispronunciations in their own name. Multi-accented infants, exposed to high levels of accent variation, did not. Accent exposure impacts speech processing at the earliest stages of lexical acquisition
Distributed Reputation for Accurate Vehicle Misbehavior Reporting (DRAMBR)
Get PDFVehicle-to-Vehicle (V2V) communications technology offers enhanced road safety, traffic efficiency, and connectivity. In V2V, vehicles cooperate by broadcasting safety messages to quickly detect and avoid dangerous situations on time or to avoid and reduce congestion. However, vehicles might misbehave, creating false information and sharing it with neighboring vehicles, such as, for example, failing to report an observed accident or falsely reporting one when none exists. If other vehicles detect such misbehavior, they can report it. However, false accusations also constitute misbehavior. In disconnected areas with limited infrastructure, the potential for misbehavior increases due to the scarcity of Roadside Units (RSUs) necessary for verifying the truthfulness of communications. In such a situation, identifying malicious behavior using a standard misbehaving management system is ineffective in areas with limited connectivity. This paper presents a novel mechanism, Distributed Reputation for Accurate Misbehavior Reporting (DRAMBR), offering a fully integrated reputation solution that utilizes reputation to enhance the accuracy of the reporting system by identifying misbehavior in rural networks. The system operates in two phases: offline, using the Local Misbehavior Detection Mechanism (LMDM), where vehicles detect misbehavior and store reports locally, and online, where these reports are sent to a central reputation server. DRAMBR aggregates the reports and integrates DBSCAN for clustering spatial and temporal misbehavior reports, Isolation Forest for anomaly detection, and Gaussian Mixture Models for probabilistic classification of reports. Additionally, Random Forest and XGBoost models are combined to improve decision accuracy. DRAMBR distinguishes between honest mistakes, intentional deception, and malicious reporting. Using an existing mechanism, the updated reputation is available even in an offline environment. Through simulations, we evaluate our proposed reputation system’s performance, demonstrating its effectiveness in achieving a reporting accuracy of approximately 98%. The findings highlight the potential of reputation-based strategies to minimize misbehavior and improve the reliability and security of V2V communications, particularly in rural areas with limited infrastructure, ultimately contributing to safer and more reliable transportation systems
Investigation of the Effect of Copper Nanoparticle Deposition on Low-Carbon Steel using Physical Vapor Deposition for Solar Cooling Application
Get PDFThe use of nanomaterials in solar cooling applications has gained significant attention in recent years. This study aimed to increase thermal conductivity by depositing copper nanoparticles (Cu-NP) on low-carbon steel using thermal evaporation and a physical vapor deposition (PVD) method. Low-carbon steel was selected as the substrate due to its wide use in thermal applications and strong absorption properties. The presence of Cu-NP on the surface was analysed using XRD and thermal characteristics of the thin layer were determined using Thermal Constant Analyzer (TCA) and Transient Plane Source (TPS) measurements. Results showed that the copper nanoparticle coating sample on the carbon steel substrate had better heat emission and absorption compared to the carbon steel alone. It also shows some improvement of around 1% in the thermal conductivity results. This study demonstrates the potential of using Cu-NP deposited on low-carbon steel as a promising material for solar thermal/cooling applications
Measuring biogas venting from over-pressurisation of household scale dome biogas digesters: A case study in Kenya and Uganda
No full textMethane emissions from household-scale biogas digesters represent a potentially significant climate concern that has been largely overlooked in rural energy access programmes. This study presents the first assessment of biogas venting patterns, resulting from over-pressure, across 53 household-scale biogas digesters in Kenya and Uganda. We develop and apply a methodology for estimating venting using digital monitoring technology known as 'Smart Biogas', which continuously measures pressure and flow data to quantify both the volume and timing of biogas loss.Our findings reveal a complex picture of household biogas use. By measuring the Biogas Utilisation Factor (BUF) - the ratio of consumed to generated biogas, where a lower BUF indicates higher venting rates - we found that households can achieve excellent performance during optimal periods, with venting rates below 3% across all digester sizes, which demonstrates the potential for optimised biogas use. However, although most households maintain good biogas utilisation most of the time, periodic episodes of underuse significantly impact overall performance. The mean pressure-driven venting rates ranged from 10.8% ± 12.7% for 10m³ digesters to 20.9% ± 20.9% for 6m³ digesters (overall mean: 15.9% ± 20.2%). Temporal patterns also emerge, with increased venting likely during afternoon and nighttime hours, and during agricultural planting seasons when cooking patterns change. Drawing from these insights, we propose strategies to help households maintain the consistent high biogas utilisation they achieve during optimal periods.The methodology developed in this paper can be applied across other biogas programmes to build a broader understanding of patterns of biogas use and the likelihood of venting. These findings have implications for biogas programme design, carbon credit methodologies, and efforts to maximise both the climate benefits and household value of small-scale biogas systems
Understanding influence and action in Learning and Action Alliances: Experience from the Newcastle Blue‐Green vision
Get PDFThe Learning and Action Alliance (LAA) framework is increasingly valued as an approach to facilitate social learning and action by enabling collaboration within and between organisations, breaking down barriers to information sharing and facilitating co‐development of innovative visions to address key environmental and societal challenges. While the social learning potential of LAAs has been documented in detail, the role of ‘action’ is relatively unexplored and there is little research into how LAAs might evolve over time to ensure longevity. Here, we explore the key achievements and limitations of the Newcastle LAA (established in 2014) through interviews with 15 LAA members. We find that interpretations of the concept of ‘action’ influences perceptions of the LAA's success. We update the structural framework of the LAA and expand the implementation phase to better reflect the agents of change that impact the LAAs' ability to apply their vision to demonstration projects. Finally, we explore the longevity of the Newcastle LAA and conclude that after running for 8 years, there may be a cyclical nature to whole‐group visioning and a move towards greater intra‐organisational learning. This demonstrates a shift in the primary role of the LAA over time, from learning towards greater influence and action
De Novo Designed β-Hairpin Peptides Mimicking the Copper-Binding Histidine Brace Motif of Lytic Polysaccharide Monooxygenases
Get PDFLytic polysaccharide monooxygenases (LPMOs) are Cu-containing enzymes that play a crucial role in lignocellulosic biomass degradation for use in biofuel production. These enzymes carry out the selective oxidation of C─H bonds in the sugar units, leading to the cleavage of the glycosidic bond. Creating LPMO mimics facilitates the study of the mechanism of action, the characterisation of the reactive species responsible for the C─H bond activation and the potential scale up for industrial application. Here, we report the design, structural and functional characterisation of two novel Cu-binding β-hairpin peptides, called HisPins, that mimic the Histidine-brace site of LPMOs. Activity assays were conducted with p-nitrophenyl-β-d-glucopyranoside (PNPG) and demonstrate that the Cu-HisPins show LPMO-like activity on the model substrate. Furthermore, the Cu-HisPins can also perform light-driven oxidation of phosphoric acid swollen cellulose (PASC) in the presence of melanin, similarly to some LPMO enzymes. Hence, the Cu-HisPins represent the first structural and functional LPMO mimics based on short, folded peptide sequences and show a light-stimulated melanin-mediated oxidative activity, which is unreported for any LPMO mimic characterised so far. Thus, this work paves the way to further exploration of LPMO mechanism, structure-activity relationship and substrate scope expansion
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