139585 research outputs found
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Besov–Triebel–Lizorkin-type spaces with matrix A∞ weights
No full textPublisher Copyright: © Science China Press 2025.Introduced by A. Volberg (1997), matrix Ap,∞ weights provide a suitable generalization of Muckenhoupt A∞ weights from the classical theory. In our previous work, we established new characterizations of these weights. Here, we use these results to study inhomogeneous Besov-type and Triebel–Lizorkin-type spaces with such weights. In particular, we characterize these spaces, in terms of the φ-transform, molecules, and wavelets, and obtain the boundedness of almost diagonal operators, pseudo-differential operators, trace operators, pointwise multipliers, and Calderón–Zygmund operators on these spaces. This is the first systematic study of inhomogeneous Besov–Triebel–Lizorkin-type spaces with Ap,∞-matrix weights, but some of the results are new even when specialized to the scalar unweighted case.Peer reviewe
High energy density long-term thermochemical energy storage composite based on salt and wood-derived activated biochar
No full textPublisher Copyright: © 2025 The Author(s)Hygroscopic salts as thermochemical energy storage materials stand out for their substantial energy storage density and long-term storage capability, but challenges like agglomeration, deliquescence, and mass transfer issues during sorption hinder their practical application. To resolve these problems, a nature-inspired, sustainable, and inexpensive composite composed of a wood-derived porous activated biochar matrix and CaCl2 as active component is developed through an impregnation method. This study investigates how matrix particle size affects the energy storage density and cyclic stability of the composite. In addition, this research analyzes the salt leakage and evaluates the stability of the composite by using an accurate quantitative method. A simultaneous thermal analyzer coupled with a humidifier was used to analyze the energy storage density. Scanning electron microscopy and X-ray micro-computed tomography were used to analyze salt deposition on the outer surface and inner porous structure of the matrices. The surface area and porosity of the matrix and composite samples were characterized by analyzing nitrogen adsorption/desorption isotherms. Derived from cellular and vascular channels of wood, the activated biochar matrix shows a multi-scale porous structure that not only has exceptional surface area but also facilitates mass transfer as well as successful salt impregnation. A particle diameter between 354 to 595 µm leads to synthesis of the composite with optimal performance, exhibiting an initial energy storage density of approximately 2480 J/g. The energy storage density of this composite remains stable at 2310 J/g and 1780 J/g after 10 consecutive hydration/dehydration and 5 leakage test cycles respectively.Peer reviewe
Marine Thruster Lip Seals : A Comparative Study of Frictional Behavior and a Condition-Based Monitoring Approach
No full textPublisher Copyright: Copyright © 2025 by ASME.The present work studies the behavior of a polyurethane (PU) seal and a hybrid seal design with a PU body with a polytetrafluoroethylene (PTFE) insert, and compares it to a conventional nitrile butadiene rubber (NBR) seal used in marine thrusters. The seals had a 300 mm diameter. Three samples of each seal were tested under 27 operating condition combinations, and were characterized by the frictional torque and subsurface temperature. The PU seal had the highest frictional torque and subsurface temperature, followed by the NBR seal, then the PTFE seal. The contact temperature was estimated with a simplified conjugate heat transfer model, and a condition-based monitoring approach was proposed based on the results of the model and online measurement of near-lip temperature.Peer reviewe
Data-driven surface reconstruction for assessing welding-induced distortions in ship-deck panels
No full textPublisher Copyright: Copyright © 2025. Published by Elsevier Ltd.Increasingly stringent regulations on greenhouse gas emissions have sparked interest in lightweight, thin-walled deck panels for cruise ship superstructures. Throughout the ship assembly, irregular welding-induced distortions accumulate on thin plates, affecting their load-carrying capacity significantly. Due to complex geometries, the assessment of distorted thin-walled panel units relies on accurate finite element modeling based on high-density optical scanning measurements, provided as unorganized point clouds (PC). This poses challenges in terms of processing of the data for surface reconstruction and data storage. This paper presents a computationally efficient, iterative B-spline surface fitting procedure for surface reconstruction from an unorganized 3D PC for the finite element analysis of distorted thin-deck panels. The method achieves a minimum geometric reconstruction accuracy of 0.08 mm and structural strain predictions mostly within 89% accuracy, validated against uni-axial monotonic tensile experiments on full-scale panels. Additionally, the proposed procedure reduces the file size to less than 1% of the original, thus representing a valuable solution for the handling of large sets of data from the scanning of multiple decks in ship superstructures. These results highlight the method’s potential for improving the assessment and quality control of thin-walled ship superstructures.Peer reviewe
Circular supply chains for sustainable use of biomass
No full textPublisher Copyright: © 2025 The AuthorsA significant impediment to sustainable biofuel and bioenergy production is deciding between various supply chain designs, available resources, and process technologies, especially when sustainability is a key criterion. To simultaneously address the challenge of continuous waste generation, increasing energy demand, high natural resource consumption, and increasing greenhouse gas emissions, the use of biobased waste should be enhanced. Providing economical and environmentally sustainable solutions for biowaste processing necessitates developing an optimization model for the associated supply chain network. This study creates a mathematical model to optimally plan and integrate biobased waste supply chain components into a coordinated system. The model aligns the purchasing and supply with varying demands, effectively assigns resources to operations, optimizes the production levels, plans delivery through optimal transportation networks, and reduces operational CO₂ emissions from transport and conversion stages in biomass systems. The results indicate that a well-designed supply chain is more cost-effective and efficient, reduces wasted materials, and keeps up with demand fluctuations. It also diminishes the existing risks and identifies the bottlenecks in the network. Furthermore, decentralized biomass treatment allows localized resource valorization and improves supply chain flexibility by lowering emissions and transportation costs. Using smaller geographically dispersed processing units increases system adaptability and mitigates feedstock variability risks. By optimizing energy efficiency and economic viability, this strategy not only reinforces the circular bioeconomy principles but also makes sustainable biomass consumption more feasible and scalable.Peer reviewe
Leveraging Generative Design for Industrial Layout Planning : SWOT Analysis Insights from a Practical Case of Papermill Layout Design
No full textLayout design is a complex problem requiring significant expertise and considerable effort. Digital tools and Generative Design (GD) concepts provide opportunities for improving and automating the layout design process. However, the adoption of GD concepts in practice still needs to be improved. Hence, case studies where GD has been used in practice can offer critical insights into GD implementation. This research presents the findings from the SWOT (Strengths-Weaknesses-Opportunities-Threats) analysis of such a case study. The industry commissioned the researchers to develop a GD tool for layout design optioneering for paper mills. Thus, the findings are based on action research, which provided the authors with first-hand insights into the practical challenges and opportunities for GD implementation in industrial facility layout problems (FLP). Findings suggest that the objectives and technical rules governing industrial layouts make a strong case for GD implementations. However, the lack of established digital workflow, the need for GD expertise and experience within client teams, and the lack of GD best practices are the major threats and weaknesses limiting GD adoption and implementation. Based on the findings, implications for GD research and practice are discussed.Peer reviewe
A cobalt-free Pr6O11–BaCe0.2Fe0.8O3-δ composite cathode for protonic ceramic fuel cells with promising oxygen reduction activity and hydration ability
No full textPublisher Copyright: © 2024 Elsevier B.V.Oxygen reduction and proton conduction originated from hydration are two key steps in the cathode process of protonic ceramic fuel cells. In this work, Pr6O11 is impregnated into a cobalt-free BaCe0.2Fe0.8O3-δ cathode, resulting in an improved activity of lattice oxygen and a moderate enhancement of the electrical conductivity, both of which are beneficial for charge transfer, the rate-determining step of oxygen reduction process at the cathode. The polarization resistance of bare BaCe0.2Fe0.8O3-δ cathode for oxygen reduction is 0.115 Ω cm2 at 700 °C, which is reduced significantly to 0.039 Ω cm2 with the addition of 30 wt% Pr6O11. Besides, the hydration ability of the cathode is also improved with Pr6O11, and thus the combination of proton and oxygen is facilitated. A single cell with 30 wt% Pr6O11-70 wt% BaCe0.2Fe0.8O3-δ composite cathode exhibits the highest maximum power density of 1406 mW cm−2 at 700 °C. The composite cathode also shows a good stability.Peer reviewe
Air speed needs and local sensitivity of non-frail and pre-frail older adults : A lab study in China
No full textPublisher Copyright: © 2025 Elsevier LtdIn China's hot summers and cold winters regions, older individuals often use fans or fan-AC combinations for thermal comfort in warm environments. However, there is a lack of research on the preferred air speed settings for varying levels of frailty and the reasons behind their sensitivity to airflow. This study, using the Fried frailty classification method, involved 12 non-frail and 12 pre-frail older participants in experiments conducted at warm temperatures of at 28 °C, 30 °C, and 32 °C. Different air speeds were set to examine subjective air speed needs, physiological changes, and sensitive body areas. Results showed that pre-frail older persons had lower thermal sensation votes in a situation without air speed, and experienced higher air speed sensation votes at the head, calves, and feet. As air speed increased, skin temperatures decreased, with the most significant changes observed in the head, which was also the most sensitive area. Pre-frail individuals also required more time for skin temperatures to stabilize and exhibited lower sweat production in distal limbs, excluding hands. No significant differences were observed in cardiovascular parameters. Comfortable air speed limits for pre-frail individuals were lower across the research temperature range: at 28 °C [0.12, 0.63] m/s, at 30 °C [0.36, 0.76] m/s, and at 32 °C [0.47, 0.78] m/s, compared to non-frail individuals at 28 °C [0.23, 0.89] m/s, at 30 °C [0.54, 1.01] m/s, and at 32 °C [0.65, 1.25] m/s. When creating airflow in warm conditions, it is crucial to consider the frailty level of older individuals to ensure appropriate age-friendly environmental control.Peer reviewe
Complete flux scheme for variable velocity fields : Coupling between the advection–diffusion equation and the Poisson equation for the velocity field
No full textPublisher Copyright: © 2025 The AuthorsIn this work, we consider an advection–diffusion equation, coupled to a Poisson equation for the velocity field. This type of coupling is typically encountered in models arising from plasma physics or porous media flow. The aim of this work is to build upon the complete flux scheme (an improvement over the Scharfetter–Gummel scheme by considering the contribution of the source term), so that its second-order convergence, which is uniform in Péclet numbers, carries over to these models. This is done by considering a piecewise linear approximation of the velocity field, which is then used for defining upwind-adjusted Péclet numbers. Numerical results show that the usage of upwind-adjusted Péclet numbers result in a second-order scheme, even for extreme tests for which the Poisson equation has a very steep source term.Peer reviewe
Another set of eyes: The role of intermediaries in doing qualitative research in low-income settings in emerging markets
No full textPublisher Copyright: © The Editor and Contributors Severally 2025. All rights reserved.The involvement of various intermediaries - i.e., facilitators that mediate the relationship between the researcher, the research participants, and the research site - has been acknowledged in previous work. Yet, their role is either overlooked or glossed over. Furthermore, it is often assumed that only researchers who are outsiders in relation to the site and the research participants require intermediaries. In contrast, we show that researchers who are insiders may also need intermediaries in the field and conceptualise the researcher's degree of insidership versus outsidership along a continuum. Arguing for the hidden but strategically vital role of intermediaries for access, data collection, and even knowledge production, we invite a more explicit and faithful account of the use of intermediaries in research. We present a typology of intermediaries, discuss their roles, and provide recommendations regarding their use including potential pitfalls and solutions for managing their involvement. Finally, we propose guidelines for reporting the use of intermediaries.Peer reviewe