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A novel unified data-based approach for determining the material constants in complex unified constitutive equations
Get PDFIn the hot metal forming processes, materials deform viscoplastically and the microstructure changes dynamically, and constitutive equations used to characterize the material flow and microstructure evolution can be complicated. Although different types of constitutive equations have been proposed by many researchers, due to the strong non-linear relationship and interconnectivity between the variables, determining the material constants could be complex, and it lacks a unified optimization method and program for these problems. This work will develop a groundbreaking step-by-step optimization methodology to determine the material constants in constitutive equations effectively and efficiently. Relationships between the variables will be analyzed, and the computational complexity and cost will be reduced by dividing the whole optimization process into several steps and considering only one or several variables in each step. Five different sets of experimental data for different materials and forming conditions will be considered in this work for demonstration, and different constitutive equations will be used to describe the material flow behaviors and microstructure evolution, where the material constants will be determined using the proposed optimization method. Instead of taking days, weeks or even months to accurately determine the large number of material constants, the proposed unified data-based optimization method only took less than 7 min even for the most complex case, using a conventional personal desktop computer. This transformative optimization method will significantly improve the accuracy and efficiency of viscoplastic constitutive models’ development, enabling more complex microstructure behaviors e.g., phase transformation, void reduction, solid welding quality to be incorporated and reliably modelled
Operationalising an ecosocialist approach to sustainability transition : a socio-metabolic analytical framework
No full textIn recent years, ecosocialist scholars have revived Marx's conceptual framework of metabolisms, thereby contributing to the conceptualisation of a radical sustainability transition that is both socially and environmentally committed. However, further research is needed to clarify what a sustainability transition entails from an ecosocialist theoretical position and how it can be promoted and assessed. This paper develops an innovative socio-metabolic analytical framework that integrates four key dimensions of ecosocialist theory: (i) the use-value of goods and services; (ii) their social distribution/access; (iii) the standard of working conditions; and (iv) the standard of care for nature. This model offers theoretical and methodological advancements that bring the ends and means of productive systems into focus to simultaneously challenge the root causes of wasteful production, social inequality, labour exploitation, and environmental degradation. It contributes to an ecosocialist theoretical approach in sustainability studies by effectively integrating social and environmental issues and targeting deep leverage points of system change
Sacrificial biofabrication for vascularization : concept, materials, technologies, and applications
Get PDFVasculature plays a crucial role in tissue engineering since it is essential for maintaining tissue viability by efficient nutrient and oxygen exchange as well as waste removal. The creation of biomimetic vascular networks is therefore critical for the development of functional tissue constructs. Sacrificial biofabrication has emerged as an effective method for engineering vascular structures by creating temporary templates that are subsequently removed to form well-defined vascular channels. In this review, the concept of sacrificial biofabrication is introduced and defined, with a focus on vascularization. Then, a comprehensive overview of the commonly used sacrificial materials based on different types of external stimuli is provided, and the classification and design principles of surrounding materials are briefly introduced. Additionally, various fabrication technologies employed to process sacrificial materials are summarized, and the diverse applications of sacrificial biofabrication in disease models and regenerative medicine are discussed. Finally, the current challenges are highlighted, and the future perspectives for advancing sacrificial biofabrication are explored to address the demand for vasculature manufacturing
Numerical investigations of aerodynamic performance for flettner rotors in the presence of full-scale ship-rotor interaction
Get PDFThis study presents numerical investigations of aerodynamic characteristics (lift and drag coefficients) for Flettner rotors in the presence of the interaction between the rotor and the full-scale merchant ship. For this purpose, several numerical investigations have been conducted for two different isolated rotors in model and full-scale conditions using Reynolds Averaged Navier-Stokes (RANS) based Computational Fluid Dynamics (CFD) approaches. The effects of different turbulence models, mesh types and sizes, and boundary conditions on the domain's bottom surface have been investigated for a reference rotor in isolation and model-scale conditions. After that, selected methods were implemented on a full-scale isolated rotor geometry. The results of the computations were compared with experimental and computational results from the open literature and showed good agreement. As a result of the validation studies in isolated conditions, a similar CFD approach was applied on a full-scale rotor, which is operating on a capsize bulk carrier (merchant ship) to investigate the interaction between the rotor and the ship. During these numerical calculations, different ship and wind speeds, rotation rates for rotor and Thom, and also different wind profiles such as Straight and Atmospheric Boundary Layer (ABL) were investigated for the Flettner rotors in interaction with the full-scale ship. In conclusion, not only the aerodynamic characteristics of the Flettner rotor but also the effects of this complex interaction between the rotor and ship were analysed and investigated computationally. Results show that rotor-ship interaction significantly affects aerodynamic performance at spin ratios above 3, with drag forces increasing and lift forces decreasing compared to isolated conditions. Moreover, ABL profiles consistently led to lower lift coefficients than uniform wind conditions, underlining the importance of realistic environmental modeling
Nowcasting economic activity in European regions using a mixed-frequency dynamic factor model
Get PDFTimely and accurate information about regional economic conditions can be essential for planning, implementing, and evaluating locally targeted economic policies. However, European regional accounts for output are published at an annual frequency with a two-year delay. To obtain robust and more timely measures in a computationally efficient manner, we propose a mixed-frequency dynamic factor model that accounts for national information to produce high-frequency estimates and reliable nowcasts of regional gross value added (GVA) in more than 150 regions across 13 European countries
Challenges regarding the provision of antibiotics via the informal sector across low- and middle-income countries and potential ways forward
No full textAntimicrobial resistance (AMR) is a global public health threat in view of its impact on morbidity, mortality and costs. AMR rates are highest in low- and middle-income countries (LMICs), including among children, driven by high rates of inappropriate prescribing and dispensing of antibiotics. By 2050 unless addressed, it is envisaged that there will be 1·91 million deaths attributable to AMR, and 8·22 million deaths associated with AMR, with the greatest burden among African and Asian countries. The estimate for sub-Saharan Africa is 4.1 million AMR-related deaths annually by 2050 unless urgent activities are undertaken
Crystallographic and morphological characteristics of acicular ferrite and their formation mechanisms in HSLA steels
Get PDFThe crystallographic and morphological characteristics of acicular ferrite (AF) and their formation mechanisms were investigated in this research. A high-strength low-alloy steel was processed to promote AF formation, and a numerical fitting method was employed to reconstruct the deformed austenite orientations. Comprehensive crystallographic analysis revealed that the crystallographic characteristics of AF are manifested in the selection of variants from multiple close-packed planes (CP) and Bain groups and the near-random variant pairing. This is distinct from those observed in other bainitic microstructures in the literature, exhibiting variants selected from either the same CP or the same Bain group and the preferential variant pairing. These unique crystallographic features arise from multi-variant intragranular nucleation, arrest of lengthening laths and self-accommodation of the transformation shape strain, driven by austenite deformation and proper cooling. Correlative morphology characterization and three-dimensional atom probe results indicate that the boundaries between AF laths become metallographically distinguishable through crystal faceting, martensite/austenite constituent delineating, and surface protrusions induced by carbon segregation at grain boundaries. The morphological features of AF—chaotic grain arrangements and irregular grain shapes—are direct consequences of AF’s distinct crystallographic characteristics and the above boundary revelation mechanisms. These findings advance the understanding and characterization of AF and provide insight into weakening variant selection and forming random variant pairing by austenite deformation and appropriate cooling
Stochastic modeling of EV on-board chargers for fast frequency response under communication delays
Get PDFThe rapid electrification of the transportation sector offers a promising avenue for ancillary services through Vehicle-to-Grid (V2G) applications. This is particularly critical for low-inertia systems, such as the U.K. grid, where the transition toward converter-based renewable generation necessitates very fast frequency response. Therefore, the viability of V2G for high-value frequency markets is constrained by strict latency requirements (e.g. one second)). Existing literature has predominantly focused on high-level economic aggregation models or communication network delays, largely neglecting the stochastic physical response dynamics of the EV On-Board Charger (OBC). This paper addresses this gap by developing a discrete-time Markov chain model that specifically characterizes the internal dynamics and response latency of OBC hardware. We integrate this model into a discrete-event simulation framework to evaluate end-to-end system latency, coupling stochastic OBC constraints with Over-the-Air (OTA) communication delays. We analyze the performance of fleets comprised of three common OBC ratings: 10 kW, 22 kW, and 43 kW. Contrary to the intuition that higher power ratings yield superior agility, our results demonstrate that high-capacity chargers may exhibit lower success rates in fast frequency markets due to insufficient ramp-rate-to-capacity ratios. Furthermore, we demonstrate that the frequency of mode switching events (switching between charging and discharging) is a dominant factor in performance degradation due to hardware hysteresis. These findings underscore that the efficacy of V2G applications requires precise EV-level control logic rather than relying solely on fleet-level optimization. Finally, the proposed models are evaluated against the PJM interconnection’s composite score methodology. The results demonstrate high accuracy, suggesting the proposed framework can serve as a preliminary, EV-specific V2G assessment tool for market operators
Machine Tools, Advanced Manufacturing, and Precision Manufacturing
Get PDFModern industries impose numerous challenges on manufacturing technologies and systems due to stringent quality requirements, the adoption of difficult-to-machine materials, high demands on miniaturization, mass customization, high productivity, and sustainability targets [...
Editorial: Open quantum systems in quantum technologies
Get PDFEditorial on the Research Topic Open quantum systems in quantum technologie
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