139585 research outputs found
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Towards an analysis framework for operational risk coupling mode : A case from MASS navigating in restricted waters
No full textPublisher Copyright: © 2024 Elsevier LtdMaritime Autonomous Surface Ships (MASSs) constitute highly interconnected and tightly coupled multistate systems. Incorporating the coupling effects of both interactions and dependencies is centrally important to ensure navigation safety of MASSs. This paper proposes a framework for examining the coupling effects in the operational modes (OM) of MASSs. Failure Modes (FMs) of MASSs related to interactions with the environment and subsystems are identified using 24Model developed based on conventional ship accidents involving grounding in the west of Shenzhen port, China. FMs related to grounding are classified into the five risk types of human, organization, ship, environment, and technology, considering three OMs (states), i.e., manual control, remote control, and autonomous control. Based on this classification, the N-K model is applied to calculate the risk coupling values of scenarios involving multiple risk types. These scenarios are then ranked by the risk coupling values of the three OMs, and values are compared among different OMs. The results indicate that for grounding in the west of Shenzhen port most risk coupling values increase with increasing risk type diversity. Furthermore, the risk coupling mechanism in remote control differs significantly from that in manual control and autonomous control, thus risk management of MASS OMs should vary.Peer reviewe
Evaluating numerical simulation accuracy for full-scale high-strength steel ship structures : Insights from the ISSC 2025 Ultimate Strength Committee benchmark on transversely stiffened panels
No full textPublisher Copyright: © 2025 The Author(s).The demand for sustainable ship design has driven the use of high-strength steel to reduce structural weight, although this introduces buckling challenges due to unchanged elastic properties. Supported by the ISSC 2025 Ultimate Strength Committee, this study evaluated the ability of numerical simulations to predict the nonlinear response and ultimate strength of stiffened panels subjected to transverse compression. The benchmark consisted of full-scale blinded experimental tests that were conducted in parallel using a deck-like structure with thin plating prone to elastic buckling. The finite element models produced by participating researchers were compared, focusing on the complete end-shortening curve rather than just ultimate strength. Despite identical input geometry and minimal modeling guidance, results varied widely, revealing the significant influence of user-defined assumptions. The inclusion of additional data on material properties in the second study phase led to greater result dispersion due to the different strategies adopted for the hardening model. Key variability sources included the modeling of initial imperfections, material constitutive laws, and residual stresses from welding. The study highlights the need for consistent modeling and improved experimental data collection, particularly regarding boundary conditions and residual stress effects. While including welding stresses improved stiffness predictions, uncertainty in boundary behavior limited the assessment of ultimate strength impacts. The study also evaluated compliance with classification society rules (e.g., CSR, DNV, UR-S35), offering insights into how nonlinear numerical analyses complement or challenge regulatory frameworks based on closed-form expressions. Recommendations are made for improving simulation reliability and result validation.Peer reviewe
AI makes you smarter but none the wiser: The disconnect between performance and metacognition
No full textPublisher Copyright: © 2025Optimizing human–AI interaction requires users to reflect on their performance critically, yet little is known about generative AI systems’ effect on users’ metacognitive judgments. In two large-scale studies, we investigate how AI usage is associated with users’ metacognitive monitoring and performance in logical reasoning tasks. Specifically, our paper examines whether people using AI to complete tasks can accurately monitor how well they perform. In Study 1, participants (N = 246) used AI to solve 20 logical reasoning problems from the Law School Admission Test. While their task performance improved by three points compared to a norm population, participants overestimated their task performance by four points. Interestingly, higher AI literacy correlated with lower metacognitive accuracy, suggesting that those with more technical knowledge of AI were more confident but less precise in judging their own performance. Using a computational model, we explored individual differences in metacognitive accuracy and found that the Dunning–Kruger effect, usually observed in this task, ceased to exist with AI use. Study 2 (N = 452) replicates these findings. We discuss how AI levels cognitive and metacognitive performance in human–AI interaction and consider the consequences of performance overestimation for designing interactive AI systems that foster accurate self-monitoring, avoid overreliance, and enhance cognitive performance.Peer reviewe
Fast pyrolysis pathway for production of sustainable aviation fuel (SAF) from demolition wood : Experimental and process simulation approach
No full textPublisher Copyright: © 2025 The AuthorsThe escalating adverse climate impacts of aviation industry have attracted the attention of research towards the production of sustainable aviation fuels (SAF) for mitigating the climate change. This study aims to investigate the demolition wood as a potential feedstock to produce SAF through fast pyrolysis process. A steady-state process simulation model was developed in Aspen Plus® and validated experimentally. The simulation model developed for SAF production comprises pyrolysis process, hydrotreating of bio-oil, fractionation of hydrotreated-oil, production of H2 gas through Proton exchange membrane (PEM) electrolyzer, purification of aqueous stream, and combustion of char blocks. The process simulation model has produced 52.8 wt% bio-oil, 20.5 wt% char, and 10.8 wt% gases by using yield-based pyrolysis reactor at operating temperature of 500 °C. Experimental results have demonstrated 49.9 wt% bio-oil yield at 500 °C pyrolysis temperature and 1 s reactants residence time. The simulation model indicated 12.2 wt% SAF yield, and physiochemical properties of SAF were also found consistent with the ASTM D7566 standard. It was also indicated that around 0.07 kg of H2 per kg of bio-oil is needed for hydro-processing reactions at 99.9 % purity of H2 gas. The process simulation model also estimated that 36.3 MW of electrical power, 6.9 MW of external heating utility and 11.7 MW of external cooling utility were required to produce 0.12 kg of SAF per kg of feedstock. Overall, the research provides a platform to examine the development of SAF production process through the fast pyrolysis of demolition wood, followed by hydro-processing and fractionation.Peer reviewe
Relaxation time effect on NMC811 equivalent circuit models for marine duty cycle simulation
No full textPublisher Copyright: © 2025 The AuthorsPulse experiments such as the galvanostatic intermittent titration technique (GITT) are commonly used to parameterize lithium-ion batteries (LIBs) in physics-based models, but have recently been adapted to parameterize equivalent circuit models (ECMs). This study investigates the impact of GITT relaxation time on the accuracy of ECMs for LIBs in marine duty cycles, using nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) with LixWyOz coating (LWO-NMC811) as a cathode material. GITT was performed with varying relaxation times to collect state-of-charge vs open-circuit voltage (SOC-OCV) curves and ECM parameters. The results show that longer relaxation times improve the accuracy of SOC-OCV curves and ECM parameter fit. However, shorter relaxation times may better replicate real-world battery discharge cycles, so subsequent model validation was performed. Validation experiments using constant current discharge and ship cycle profiles demonstrate that ECMs built with longer relaxation times have lower root mean square error, indicating better accuracy. However, 1-hour relaxation time experiments provide a balanced approach, with an average error difference of 7.54 mV and 80% less experiment time versus 5-hour relaxation time experiments for cells cycled within 90% to 10% SOC. This study suggests potential for optimizing relaxation times based on specific application needs and highlights the importance of supplementing continuous efforts to improve NMC811 cycling stability in high-voltage windows with parallel modeling studies.Peer reviewe
Sidestepping Intermolecular Hydrogen Bonds : How Single Water Molecules Adsorb and Assemble on the Calcite(104)-(2 × 1) Surface
No full textThe adsorption of water on mineral surfaces has a decisive impact on processes in the geological, geochemical, biological, and technological contexts. In this work, we investigate the water/calcite(104)-(2 × 1) interface at the single-molecule level by direct imaging with CO-tip-assisted noncontact atomic force microscopy (NC-AFM) and by density functional theory (DFT) calculations combined with NC-AFM image simulations. For single water molecules, the adsorption geometries within the (2 × 1) calcite unit cell are consistently identified by experiments and simulations. The energetic difference between the energetically most favorable adsorption position next to a bulk-like carbonate row (QS water) and the less favorable adsorption geometry next to a reconstructed carbonate row (PR water) can be explained by the local relaxation of the calcite(104) surface nearby a PR water molecule that locally restores the unreconstructed (1 × 1) surface structure. Different combinations of QS and PR water molecules yield a variety of water dimer configurations. We find that the dimer adsorption energy is mostly identical to the sum of the individual molecule energies. From successively raising the sample temperature up to 170 K at half monolayer coverage, we observe that all water molecules move to the most favorable QS position. Overall, the first layer of water molecules on the calcite(104) surface is strongly bound to the substrate in the absence of intermolecular hydrogen bonds.Peer reviewe
Beliefs about beta : upside participation and downside protection
No full textIn four large online experiments, we study how investors assess the relationship between stock portfolios and the market. Participants select or are randomly assigned a portfolio of stocks from a market index. They state portfolio return expectations conditional on different market outcomes, revealing implied beliefs about portfolio beta. We find general underestimation of beta which is stronger for downside beta. This asymmetry is amplified for participants who select their portfolio. They believe their portfolio goes up with the market but does not come down with it. We confirm biased beliefs about beta with financial professionals, monetary incentives, and alternative belief elicitation methods.Peer reviewe
Perceptions of home-country institutions, decision-making logics, and international performance of SMEs
No full textIn today's complex and uncertain world, entrepreneurs, especially those leading small- and medium-sized enterprises (SMEs), play a crucial role in societal development. The international growth of SMEs not only drives macroeconomic progress but also addresses significant global challenges. However, rising tensions, risks, and regulations in international business often create more losers than winners, despite governmental support. Our study of 210 international SMEs from Finland seeks to identify factors that differentiate better-performing SMEs. We theorise and empirically examine how perceptions of home country institutions and decision-making logic influence international performance. Our findings reveal that while perceptions of the institutional environment do not directly impact international performance, the regulatory dimension of institutions fosters flexibility in decision-making, which in turn enhances SMEs' international success. Specifically, SMEs that perceive their home-country regulatory environment as supportive tend to adopt a more flexible decision-making approach, which positively affects their international performance. By linking the understanding of the institutional environment with entrepreneurial choices, our research offers valuable insights for global strategy, and international entrepreneurship research, and provides guidance for entrepreneurs, investors, and policymakers.Peer reviewe
Clustering energy performance certificates : a methodology for selecting representative buildings in scalable energy simulations
No full textPublisher Copyright: © 2025 The Author(s).This study presents a methodology for selecting representative buildings through clustering of Energy Performance Certificate (EPC) features. The six-phase workflow includes EPC attribute preparation, clustering with K-Medoids, Agglomerative clustering, and Gaussian Mixture Model (GMM), and internal validation using Silhouette, Calinski-Harabasz, and Davies-Bouldin indices. An EPC database of educational buildings in Helsinki is utilised to demonstrate the applicability of scalable energy simulations. To assess thermal validity, regression models: Linear, Random Forest, and XGBoost were trained within clusters to predict District Heating (DH) demand from outdoor temperature, achieving higher accuracy than global models. Additionally, DH clustering was compared to EPC-derived labels using the Adjusted Rand Index (ARI) and Normalized Mutual Information. Formal statistical differentiation tests: ANOVA and Kruskal–Wallis with FDR correction confirmed that EPC attributes differ significantly between clusters, and medoid buildings were shown to represent cluster means, with r ranging from 0.92 to 0.98. Results show that EPC-based clusters capture thermal behaviour, enabling the selection of representative buildings without continuous monitoring. Across internal cluster validity indices, Agglomerative clustering often performed best, while externally, GMM showed the strongest alignment with DH-based clusters with ARI = 0.555 and NMI = 0.571. Four clusters were identified from linkage distance and thermal performance. Feature importance analysis highlighted air leakage rate as the dominant predictor, with UA value and EP value also influential. This generalizable methodology enables meaningful building grouping and simulation targeting without detailed metering, supporting energy policy and retrofit planning.Peer reviewe
Dynamics of convivial affective atmospheres
No full textFunding Information: The authors wish to extend their thanks to all Lifestyle Research Center members and our students who took part in Club Med fieldwork and related discussions over the years. In addition, we wish to warmly thank Club Med for making this research possible. Publisher Copyright: © 2023 Elsevier LtdThis article examines the dynamics of affective atmospheres in explaining compelling touristic service experiences. Extending affect-theoretical research, we theorize and examine the role of affective bodily encounters through which convivial atmospheres are (re)produced. Based on multi-sited ethnographic research in iconic Club Med resorts, our findings emphasize the spontaneity and fragility of convivial affective atmospheres, meaning they are difficult to control, but also how their ongoing “bubbling” is shaped by materiality, ritual activities, and temporality. We contribute by (1) developing the concept of convivial affective atmosphere, and by (2) offering a theoretical framework that helps advance research into the affective entanglement and dynamics of atmospheres in tourism. Finally, we critically discuss what service providers can do to facilitate and re-produce convivial atmospheres.Peer reviewe