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Gaussian process latent variable model and Bayesian inference for non-parametric failure modeling applied to ship engine
No full textPublisher Copyright: © 2025 The AuthorsUnnecessary early maintenance is especially critical for high-value or essential components whose unexpected failures could disrupt the entire operational process of the system. The uncertainties inherent in facility deterioration necessitate a robust framework that accurately assesses system health and guides optimal maintenance scheduling. To this end, this paper proposes a probabilistic machine learning framework based on a Gaussian Process Latent Variable Model (GPLVM) combined with Bayesian Inference (BI) to dynamically assess the health state of system and predict failure risk. The model integrates uncertainty quantification through BI, providing a non-parametric hazard rate estimate at each time step, which enables a precise and adaptive maintenance planning strategy. To verify the proposed model, a critical component of an engine – spark ignition, is considered as the case study. Herein, ignition voltage is monitored as the primary indicator of spark health, with degradation thresholds and safety thresholds explicitly modeled to capture degradation trends accurately. The results indicate that 96.5 % of the observations fell within precise predictive range (according to Pareto Diagnostics values), underscoring the model's promise for maintenance planning. This approach has the potential not only to improve predictive accuracy and decision confidence but can also provide a flexible, non-parametric solution adaptable to various high-stakes maintenance applications.Peer reviewe
Boundary conditions for studying branch-scale tree growth strategies using tree quantitative structure model time series
No full textAdvances in Light Detection and Ranging (LiDAR) technology, along with point cloud modeling techniques like Quantitative Structure Models (QSM), have improved the accuracy of non-destructive above-ground tree biomass estimation. However, branch-level tree growth analysis using QSM time series remains underexplored due to challenges in data quality and methodology. This study investigates the boundary conditions in terms of data and species to facilitate robust QSM generation, which could enable branch-level growth analysis using multi-temporal LiDAR data and QSM. A multi-scan terrestrial laser scanning dataset and a dataset from a tower-based system were used to assess the impact of data acquisition setup and data quality on QSM reconstruction for birch (Betula pendula), pines (Pinus sylvestris), and spruces (Picea abies). The results show that reliable QSMs for detecting branch-level growth require a minimum spatial resolution of approximately 500 pts./m3 with a uniform point density, a maximum uniform 3D point distance of 2 cm, and gaps smaller than around 20 cm. Although smaller spherical noise clusters can be removed using denoising techniques, larger and denser noise clusters (e.g., > 9500 points within 1 m radius) are more likely to be misidentified as additional branches. Foliage removal methods risk modeling accuracy by inadvertently removing woody points. Regarding species, birches were more accurately modeled than pines and spruces. While QSMs are reproducible for single time points, comparing branches over time is challenging due to inconsistencies in modeled branching order and scanner positioning. Nonetheless, tree-level QSM metrics remain statistically consistent, revealing diverse growth strategies within and across speciesPeer reviewe
A CCP-Based Distributed Cooperative Operation Strategy for Multi-Agent Energy Systems Integrated with Wind, Solar, and Buildings
No full textTo explore the bidirectional interaction between renewable energy and buildings in multi-agent energy systems, this paper proposes a distributed cooperative operation strategy for multi-agent energy systems integrated with wind, solar, and buildings based on chance-constrained programming (CCP). First, the multi-agent energy system integrated with wind, solar, and buildings is comprehensively modeled with detailed electric and thermal characteristics for flexibility enhancement. Then for maximizing the profits of the cooperative energy system and each engaged agent, a Nash bargaining model is presented and is divided into two subproblems: the coalition income and the power payment. To preserve the privacy of agents, the adaptive alternating direction method of multipliers (ADMM) is exploited to solve both subproblems. Meanwhile, the CCP method is applied to address diverse uncertainties from wind and solar power generation as well as outdoor temperature. Finally, the effectiveness of the proposed strategy is validated. The simulation results show that, besides the privacy of information among all agents being well preserved, our strategy enhances the profits not only for the energy system but also for all engaged agents.Peer reviewe
ConfermentSampo - A Knowledge Graph, Data Service, and Semantic Portal for Intangible Academic Cultural Heritage 1643-2023 in Finland
No full textThis article presents a model for representing and studying academic intangible cultural heritage pertaining to conferment ceremonies organized by universities in Europe since the 1100’s. A new Linked Open Data (LOD) service and semantic portal on top of it in-use called ConfermentSampo – 100 conferments of the Faculty of Philosophy at the University of Helsinki 1643–2023 is introduced. It allows data related to conferment celebrations, rituals, and academics involved in different roles to be published, stored, and researched using Semantic Web technologies. A goal of our work is to preserve and foster conferment traditions for the future generations of academics.Peer reviewe
Analysing ship emissions under complex operating conditions : Insights from onboard measurement data
No full textPublisher Copyright: © 2024This research evaluated the emission characteristics of old ships during typical operations, under varying cruising speeds, and during lock transit, using a shaft power meter and PEMS. The research revealed that upstream and downstream low-load voyages accounted for 67.9 % and 65.4 % of the total voyage, respectively. The average emission factors of CO, NOX and CO2 were highest under lock transit with 17.13±0.51 g/kWh, 16.2±0.62 g/kWh and 1075.37±5.72 g/kWh, respectively, while SO2 was highest under manoeuvring with 0.46 ± 0.001 g/kWh. Emissions are closely correlated with engine speed, with the largest emissions at cruising, and emissions at departure and docking significantly concentrated in the 10–15 % and 5–10 % loads. This research emphasizes the importance of considering low-load operating conditions in engine test cycles and provides data support for maritime decarbonization and emission reduction strategies. Future research should continue to explore the emission characteristics of old ships.Peer reviewe
Unleashing novel configurations of gravitational water vortex thermal energy exchanger
No full textPublisher Copyright: © 2024 Elsevier LtdThis study presents thermal and hydrodynamics investigations for novel configurations of gravitational water vortex heat exchanger (GWVHE). The proposed novel configurations of GWVHE include SWB (shell with baffles), CSFH (circular spiral flow helix) and RSFC (rectangular spiral flow channel). The thermal energy balance between two fluid domains has been calculated numerically for various operational conditions. An analytical model is developed using the Kern's approach, the effectiveness-NTU method, and the LMTD method for heat exchangers to calculate the heat transfer characteristics of two fluids to validate numerical results. Moreover, a transient two-phase flow numerical model has been solved to investigate the volume fraction of air and water during the development of the vortex at the center of the basin. The results show that a convincing thermal energy balance is present between both fluid streams for all the proposed configurations of GWVHE. However, the heat exchange rate for the RSFC configuration of GWVHE is higher than the SWB and CSFH of GWVHE. Because it has maximum heat exchange surface area of 1.08 m2 and thermal losses in RSFC are significantly lower than those computed in CSFH and SWB at different operating conditions. The thermal losses reported for RSFC are just 1 % compared to CSFH and SWB thermal losses of 2 % and 5 %, respectively. Moreover, the maximum volume fraction of air obtained at the center of basin during vortex formation is 18 %, indicating an effective vortex air core.Peer reviewe
Comparing ICT-related future development trends in shrinking cities : resident and decision-maker perceptions
No full textPublisher Copyright: © 2024 Informa UK Limited, trading as Taylor & Francis Group.Digitalization and the widespread adoption of novel Information and Communication Technologies (ICT) has transformed almost all aspects of society. Remote working, e-commerce and remote services have had a major impact on the lives of individuals, and they increasingly enable individuals to choose their place of residence regardless of geographical constraints. These trends also have a considerable impact on urban spatial structure and regional development. This study examines and compares the probability and desirability of how residents and decision-makers perceive the development trends influenced by ICT and digitalization in shrinking cities and regions. Based on the results the perceptions of residents and decision-makers regarding the desirability of analysed future scenarios are quite well in line, but there exists significant differences regarding the probability of these trends. The results and methodology provide valuable insights for policymakers and other decision-makers to make informed and more participatory decisions regarding future regional development.Peer reviewe
The application of graphitic nitrogen from corn stover for the selective catalytic oxidation of 5-hydroxymethyl furfural
No full textPublisher Copyright: © 2024Nitrogen atom-doped biomass carbon prepared from corn stover is a newly discovered metal-free catalyst that shows good activity on the selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF). Here, the presence of graphitic nitrogen on the catalyst surface activated the oxygen adsorbed on the carbon sites next to the graphitic nitrogen in the carbon material and promoted the formation of oxygen radicals on the surface-active sites, improving the HMF oxidation process. The results show that the catalyst NC-800 reacted with acetonitrile as the reaction solvent at 110 °C and 1.0 MPa O2 for 8 h to obtain 93.0 % HMF conversion and 94.4 % DFF selectivity, and the 5-HMF conversion and DFF selectivity were maintained at more than 85 % after five cyclic tests, with excellent cyclic stability. One of the main factors influencing the material flaws is the variation in pyrolysis temperature. Using maize stover, a readily available and renewable biomass, in the catalytic oxidation of biomass platform compounds may improve biomass utilization more extensively.Peer reviewe
ArtSampo – Finnish Art on the Semantic Web
No full textPublisher Copyright: © The Author(s), under exclusive license to Springer Nature Switzerland AG 2025.This paper presents first results of ArtSampo, a collaborative Finnish Linked Open Data (LOD) infrastructure for publishing fine art collections on the Semantic Web and for facilitating Digital Humanities (DH) research. The infrastructure consists of a Knowledge Graph (KG) whose initial version was compiled from the metadata of the three art museums of the Finnish National Gallery. A semantic ArtSampo portal was built on top of the KG for searching, browsing, and analyzing the underlying data. The Finnish ontology infrastructure and international datasets are used for harmonizing and enriching the data.Peer reviewe
A novel Cr2O3/Cr-doped g-C3N4 photocatalyst with a narrowed band gap for efficient photodegradation of tetracycline
No full textPublisher Copyright: © 2024Two significant strategies for enhancing photocatalyst performance are heterojunction construction and band gap modulation, but up until now, these methods have typically been treated separately. This work examines a strategy combining the heterojunction with a mid-gap state to prepare a novel Cr2O3 modified Cr-doped g-C3N4 photocatalyst for antibiotics degradation. According to the characterization results, the integration of Cr 3d orbital energy level into the original band gap of g-C3N4 results in the formation of Cr-doped g-C3N4, leading to a reduction in the band gap from 2.80 eV to 2.36 eV. Besides, the constructed Z-type heterojunction enhances the separation of photoinduced carriers. The degradation experiments of tetracycline proved the significant enhancement in the photocatalytic performance of the prepared catalyst. In addition, the degradation effect of the prepared catalyst on tetracycline in micro-polluted lake water was also investigated, revealing the applicability of the catalyst in the purification of natural water environments.Peer reviewe