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Influence of water saturation duration on the mechanical properties and toughness index of Australian coal
No full textThe coal seam water infusion technique is recognized as a successful method for mitigating the occurrence of rock and coal bursts. As coal burst is a process of energy accumulation and release, the mechanical properties of coal, such as Uniaxial Compressive Strength (UCS), toughness, and elastic modulus, play a significant role. The water infusion method is already an industry-practiced technique to control the accumulation and release of energy by reducing compressive strength and elasticity. However, its effectiveness is potentially specific to each case and subject to the properties of the rock and coal. Several parameters influence the efficacy of this method, including infusion time, lithology, and coal properties. In this study, four groups of specimens were selected for the water saturation test and the Uniaxial Compressive Strength (UCS) and the coal toughness index method were employed to assess coal strength. Specimens underwent water saturation for 0, 5, 10, and 15 days. Results indicate decreasing compressive strength, toughness index, and elastic modulus with prolonged saturation. Scanning Electron Microscope (SEM) analysis was conducted to observe the micro-cracking behaviour of the coal surface at various saturation times, revealing an increased development of internal micro-cracks as the saturation time extends. This comprehensive study offers compelling evidence that water saturation time significantly influences both the strength and micro-cracking behaviour of coal
Linearly Interlinked Fe-Nx-Fe Single Atoms Catalyze High-Rate Sodium-Sulfur Batteries
No full textLinearly interlinked single atoms offer unprecedented physiochemical properties, but their synthesis for practical applications still poses significant challenges. Herein, linearly interlinked iron single-atom catalysts that are loaded onto interconnected carbon channels as cathodic sulfur hosts for room-temperature sodium-sulfur batteries are presented. The interlinked iron single-atom exhibits unique metallic iron bonds that facilitate the transfer of electrons to the sulfur cathode, thereby accelerating the reaction kinetics. Additionally, the columnated and interlinked carbon channels ensure rapid Na+ diffusion kinetics to support high-rate battery reactions. By combining the iron atomic chains and the topological carbon channels, the resulting sulfur cathodes demonstrate effective high-rate conversion performance while maintaining excellent stability. Remarkably, even after 5000 cycles at a current density of 10 A g−1, the Na-S battery retains a capacity of 325 mAh g−1. This work can open a new avenue in the design of catalysts and carbon ionic channels, paving the way to achieve sustainable and high-performance energy devices
Effects of TiB2 content on microstructural evolution, microhardness and tribological behaviours of Al matrix composites reinforced with TiB2 particles
No full textIn this study, Al2024/TiB2 composites with different TiB2 fractions (5, 10 and 15 vol%) were fabricated by high-energy ball milling and spark plasma sintering. The effects of TiB2 fraction on the microstructure, hardness and wear resistance of the composites were explored to determine the optimal TiB2 content in the composite with optimal properties. An increase in Vickers hardness of the composites correlates with the increased TiB2 content, and the Al2024-15TiB2 composite exhibits the highest hardness. The wear rate of the composite initially increases and then decreases with higher TiB2 content. Notably, the Al2024-10TiB2 composite demonstrates the best wear resistance with a wear rate of 1.14 × 10−4 mm³/Nm, representing a 96.81 % reduction compared to the unreinforced Al2024. The deteriorated wear resistance of the Al2024-15TiB2 composite was attributed to the decreased toughness and severe three-body abrasion caused by the excessive TiB2 particles
Wear prediction model of hot rolling backup roll based on FEM + ML algorithm
No full textThe wear of backup rolls will have a great impact on the quality of the shape of hot rolled strip sheet. In order to overcome the limitations of the finite element method (FEM) in calculating backup roll wear in terms of efficiency and accuracy, this paper proposes a tandem FEM + ML hybrid model to optimise the predictive effect of the finite element method (FEM) on backup roll wear. Firstly, a backup roll wear model based on FEM is established. Secondly, in order to select the optimal machine learning (ML) algorithm as the finite element error compensation model, three types of finite element error compensation models were established based on the random forest (RF) algorithm, the radial basis function (RBF) neural network algorithm, and the particle swarm optimisation support vector machine (PSO-SVM) algorithm. Finally, the three types of finite element error compensation models were connected in series with the FEM model to compare the prediction performance of the three types of FEM + ML models on backup roll wear. The numerical experimental results show that the FEM + PSO-SVM model can better predict the wear of the backup roll, and the PSO-SVM algorithm is the most suitable for building the finite element error compensation model. It is proved that the FEM + ML model proposed in this paper can effectively improve the accuracy and computational efficiency of the FEM model for predicting backup roll wear without adding microelements. In addition, among the hot rolling parameters, the rolling force has the greatest influence on the backup roll wear, and excessive rolling force for a single pass should be avoided to slow down the backup roll wear
Role of texture before rolling: a research based on texture and magnetic properties of 4.5 wt.% Si non-oriented electrical steel
No full textThe evolution of microstructure, texture, and magnetic properties with random texture, near-copper texture, weak near-cube texture, and strong λ fiber (//ND (normal direction)) before rolling of non-oriented electrical steel was studied. Three recrystallized hot bands with different textures but similar grain sizes were prepared by pre-annealing at low-temperature and high-temperature normalization annealing. It was observed that the final annealed products exhibited similar recrystallized microstructures. By contrast, the final annealed product with more λ fiber before rolling exhibited a stronger cube texture. With the λ fiber before rolling becoming stronger, the proportion of {111} deformed matrices became larger, which could be observed in the early recrystallization stage. The overwhelmingly dominant λ orientation nuclei are formed in the {111} deformed matrix and become the dominant texture. Eventually, the best magnetic properties are obtained in the products with strong λ fiber before rolling, corresponding to the strong cube texture and low anisotropy parameter
Understanding risk and causal mechanisms for developing obesity in infants and young children: A National Institutes of Health workshop
No full textObesity in children remains a major public health problem, with the current prevalence in youth ages 2–19 years estimated to be 19.7%. Despite progress in identifying risk factors, current models do not accurately predict development of obesity in early childhood. There is also substantial individual variability in response to a given intervention that is not well understood. On April 29–30, 2021, the National Institutes of Health convened a virtual workshop on “Understanding Risk and Causal Mechanisms for Developing Obesity in Infants and Young Children.” The workshop brought together scientists from diverse disciplines to discuss (1) what is known regarding epidemiology and underlying biological and behavioral mechanisms for rapid weight gain and development of obesity and (2) what new approaches can improve risk prediction and gain novel insights into causes of obesity in early life. Participants identified gaps and opportunities for future research to advance understanding of risk and underlying mechanisms for development of obesity in early life. It was emphasized that future studies will require multi-disciplinary efforts across basic, behavioral, and clinical sciences. An exposome framework is needed to elucidate how behavioral, biological, and environmental risk factors interact. Use of novel statistical methods may provide greater insights into causal mechanisms
Topological nodal-point phononic systems
No full textTopological phonons in materials are associated with specific atomic lattice vibrations around the terahertz frequency ranges, offering a rich platform for studying various boson-related quasiparticles. Recently, researchers in topological physics have prioritized the search for materials that exhibit topological phonons. This review focuses on topological nodal-point phononic systems in three dimensions. On the one hand, the review highlights the classification, symmetry conditions, material realizations, unique properties, and potential applications of these topological nodal-point systems. On the other hand, it summarizes our guidelines for predicting such materials in three and two dimensions. This review can serve as a scholarly survey of recent developments in topological nodal-point phononic systems over the past 5 years as well as a guide for achieving other and designing new topological nodal-point phononic states in the future. It will undoubtedly benefit academic communities interested in materials science and condensed matter physics
Electrochemical coupling in subnanometer pores/channels for rechargeable batteries
No full textSubnanometer pores/channels (SNPCs) play crucial roles in regulating electrochemical redox reactions for rechargeable batteries. The delicately designed and tailored porous structure of SNPCs not only provides ample space for ion storage but also facilitates efficient ion diffusion within the electrodes in batteries, which can greatly improve the electrochemical performance. However, due to current technological limitations, it is challenging to synthesize and control the quality, storage, and transport of nanopores at the subnanometer scale, as well as to understand the relationship between SNPCs and performances. In this review, we systematically classify and summarize materials with SNPCs from a structural perspective, dividing them into one-dimensional (1D) SNPCs, two-dimensional (2D) SNPCs, and three-dimensional (3D) SNPCs. We also unveil the unique physicochemical properties of SNPCs and analyse electrochemical couplings in SNPCs for rechargeable batteries, including cathodes, anodes, electrolytes, and functional materials. Finally, we discuss the challenges that SNPCs may face in electrochemical reactions in batteries and propose future research directions
Impacts of Climate Change on Marine Foundation Species
No full textMarine foundation species are the biotic basis for many of the world's coastal ecosystems, providing structural habitat, food, and protection for myriad plants and animals as well as many ecosystem services. However, climate change poses a significant threat to foundation species and the ecosystems they support. We review the impacts of climate change on common marine foundation species, including corals, kelps, seagrasses, salt marsh plants, mangroves, and bivalves. It is evident that marine foundation species have already been severely impacted by several climate change drivers, often through interactive effects with other human stressors, such as pollution, overfishing, and coastal development. Despite considerable variation in geographical, environmental, and ecological contexts, direct and indirect effects of gradual warming and subsequent heatwaves have emerged as the most pervasive drivers of observed impact and potent threat across all marine foundation species, but effects from sea level rise, ocean acidification, and increased storminess are expected to increase. Documented impacts include changes in the genetic structures, physiology, abundance, and distribution of the foundation species themselves and changes to their interactions with other species, with flow-on effects to associated communities, biodiversity, and ecosystem functioning. We discuss strategies to support marine foundation species into the Anthropocene, in order to increase their resilience and ensure the persistence of the ecosystem services they provide
Interpersonal Violence and Gender Inequality in Adolescents: A Systematic Analysis of Global Burden of Disease Data From 1990 to 2019
No full textPurpose: Interpersonal violence is a leading cause of adolescent deaths and disability. This study investigates sex differences in burden of interpersonal violence for adolescents and explores associations with gender inequality. Method: Using data from the 2019 Global Burden of Disease study, we report numbers, proportions, rates of interpersonal violence deaths and disability adjusted life years (DALYs) for all ages, and rate of change (from 1990 to 2019) in adolescents aged 10–24 years disaggregated by sex and geography. We explored associations with gender inequality using gender inequality index. Results: One in four (24.8%) all-age interpersonal violence deaths are in adolescents. In 2019, the rate of deaths in adolescent males was almost six times higher than females (9.3 vs. 1.6 per 100,000); and since 1990, the rate of decline in DALYs for females was double than that for males (−28.9% vs. −12.7%). By contrast, the burden of sexual violence is disproportionately borne by adolescent females, with over double the rate than males (DALYs: 42.8 vs. 17.5 per 100,000). In countries with greater gender inequality, the male-to-female ratio (deaths and DALYs) was increased among older adolescents, pointing to benefits for males in more gender equal settings. Discussion: Social identities, relationships, and attitudes to violence are established in adolescence, which is an inflection point marking the emergence of disproportionate burdens of interpersonal violence. Our findings affirm that global agendas must be expanded to address interrelated factors driving multiple forms of interpersonal violence experienced by adolescents and reverberating to the next generation