Search Results (627)

This paper presents a systematic experimental and computational investigation of the free-vibration characteristics of a Laser Powder Bed Fusion (LPBF) AlSi10Mg thick-walled cylinder, a geometry relevant to electric-machine housings, hydraulic sleeves, and pressure-carrying components exposed to resonance-critical service loads. The specimen has an outer diameter of 94 mm, an inner diameter of 64 mm, a wall thickness of 15 mm, and a height of 90 mm, placing it firmly in the thick-walled regime ($d/D=0.68$). A three-dimensional finite element model comprising 23,864 total elements (23,236 SOLID186 solid elements and 628 surface/contact elements) and 106,015 nodes was constructed in Ansys Mechanical using the AlSi10Mg material database entry (E = 75 GPa, $\rho$ = 2670 kg/m³, $\nu$ = 0.33) and solved with the Block Lanczos eigensolver under free–free boundary conditions. Experimental modal analysis (EMA) was conducted using Brüel & Kjær software with an impact hammer with a 260-node measurement grid covering the outer surface and both end rings; frequency response functions were acquired over 0–22,500 Hz. Fourteen flexible modes were identified in simulation; nine corresponding experimental modes were resolved with frequency deviations ranging from 0.13% to 1.10%. In addition to frequency correlation, this paper introduces a non-conservative damping characterization framework comprising: (i) Rayleigh (proportional) damping coefficient extraction from EMA data and assessment of its frequency-domain validity; (ii) a viscoelastic complex-modulus model relating the real storage modulus $E^{\prime }$ and imaginary loss modulus $E^{″}$ to the modal loss factor $\eta$ and damping ratio $\zeta$; and (iii) a practical design workflow for resonance mitigation of future AM structures including electric machine frames. Experimental damping ratios ($\zeta =0.013$–$0.311\%$) are converted to per-mode $E^{″}$ values and loss factors, revealing that energy dissipation in LPBF AlSi10Mg is strongly mode-shape-dependent and cannot be accurately represented by a single Rayleigh model. Full article

Against a backdrop of tightening environmental regulations and escalating climate-related risks, the construction sector faces mounting pressure to improve both its sustainability performance and long-term resilience. As a market-oriented institutional tool, green finance policy has been widely identified as a pivotal lever for advancing corporate green innovation; nevertheless, its causal impact on green innovation in construction enterprises—an essential foundation for sustained industry resilience—has Iyet to be fully examined in empirical research. Capitalizing on the exogenous variation introduced by China’s Green Finance Reform and Innovation Pilot Zone (GFRIPZ) initiative, this study investigates 105 construction enterprises listed on the Chinese stock market from 2010 to 2020. Employing a Difference-in-Differences (DiD) estimation strategy, we find that the GFRIPZ initiative significantly boosts green innovation among construction enterprises. This positive association persists after a series of robustness assessments. Channel analysis identifies financing conditions as a key pathway linking the GFRIPZ initiative to green innovation. Reduced financing frictions allow construction enterprises to increase investment in environmentally oriented technological activities. Additional sub-sample analysis corroborates that the GFRIPZ policy exerts a far more salient innovation incentive effect on non-state-owned construction firms, which aligns with the stronger impetus for in-house R&D under competitive market conditions. These findings offer empirical evidence that well-designed green finance policies can serve as effective institutional enablers of green innovation, thereby contributing to the sustainable resilience of the construction sector. The findings offer actionable guidance for regulators on incorporating financial instruments into governance frameworks that support sustainable construction. Full article

Student retention analytics often treats withdrawal as a single outcome, although students may attribute dropout intention to personal, socioeconomic, and academic pressures simultaneously. We benchmarked nine supervised classifiers for identifying a concurrent three-domain attribution profile in a cross-sectional survey of 333 undergraduates at a Colombian public university campus. The response came from a semi-structured weight-allocation item; an audit found that literal label matching altered 21 classifications because of spelling variants and decimal notation. Nine classifiers—logistic regression, decision tree, random forest, neural network, Gaussian Naïve Bayes, k-nearest neighbors, AdaBoost, gradient boosting, and XGBoost—were fitted using six pre-specified predictors. Models were compared by repeated nested stratified cross-validation (five outer folds, three repeats), inner tuning, fold-contained preprocessing, and training-only threshold selection. The concurrent profile occurred in 256 students (76.9%). Logistic regression achieved the highest mean held-out ROC AUC (0.674, 95% CI 0.644–0.704), closely followed by random forest (0.671, 0.641–0.702); their paired difference was nonsignificant after Holm adjustment. Logistic regression had the highest F1 score (0.788), whereas random forest had the highest balanced accuracy (0.617). AdaBoost did not retain its apparent single-holdout advantage. Housing and financial aid had the largest held-out permutation importance. The predictors provided moderate discrimination of a perceptual profile, not a validated prediction of future dropout. Outcome auditing and leakage-free validation materially changed the model ranking. Full article

This study analyses, within the post-pandemic tourism context, whether differences in degree and stage of tourism development in heritage historic centres shape the nature and direction of the social, demographic, and economic transformations they undergo. To this end, using Angra do Heroísmo (Azores, Portugal) and Vegueta–Triana (Canary Islands, Spain) as comparative study areas, a mixed-methods approach is applied, based on official statistics and accommodation records for the period 2018–2025, as well as fieldwork conducted between June and August 2024 and between July and September 2025, including 31 semi-structured interviews with key informants. The results show a recent intensification of touristification in both Macaronesian island spaces, although its forms and perceived effects differ according to their previous tourism trajectories and residential conditions. In Vegueta–Triana, it is more clearly associated with saturation, commodification of space, housing pressure, and weakening of the residential function, whereas in Angra do Heroísmo, it is more closely linked to heritage-based hotel development and functional revitalisation, although concerns about housing and population loss are also emerging. The comparison shows that the effects of post-pandemic tourism growth depend not only on visitor volumes, but also on the depth and speed of change and on local governance capacity. Full article

Magnetorheological elastomers (MREs) exhibit magnetic-field-dependent stiffness and can, therefore, be used to tune the natural frequency of a dynamic vibration absorber through the applied coil current. This study evaluates the extension of a previously developed MRE-based semi-active absorber to two automotive noise, vibration, and harshness transmission paths: road-input-related subframe vibration and engine-induced seat vibration. A standard cylindrical actuator was installed below the subframe of a passenger vehicle and tested on a rough road at 10, 20, and 30 km/h. Vehicle speed was used as the operating-condition feedback variable for current selection, while additional fixed-current measurements were conducted to characterize the current-dependent response. Cabin sound pressure was measured simultaneously. A compact actuator with a lightweight resin housing was also developed for the seat application; engine speed was used as the feedback variable, and the current was selected with reference to the second-order engine excitation. The natural frequencies of both actuators increased with current, although the compact actuator had a smaller tuning range. The actuator-installed conditions produced local, current-dependent reductions in subframe and seat vibration spectra. Changes in cabin sound pressure were smaller, frequency-dependent, and not uniform. The results demonstrate the feasibility of the operating-condition-based tuning of MRE dynamic absorbers for local automotive vibration paths, while also identifying limitations associated with passive installation effects, magnetic-circuit efficiency, packaging, and multi-path cabin acoustics. Full article

Rare earths are a strategically vital mineral resource on a global scale; the security of their supply chain and their recycling face severe challenges amid dual pressures of resource scarcity and environmental protection. This study focuses on the reverse supply chain for rare earth permanent magnet materials—specifically those based on praseodymium and neodymium—constructing a two-level game model comprising a rare earth oligopoly (Stackelberg leader) and two recyclers (Cournot followers). It systematically analyzes the dual decision-making behavior of recyclers between “recycling and selling” and “in-house remanufacturing”, and examines the impact of two policy instruments—government subsidies and environmental taxes—on the supply chain equilibrium. The study employs reverse induction to solve the game equilibrium and combines this with numerical simulation methods to compare the differing effects of the two policies on key indicators such as product output, market share, profit distribution, waste recovery volume, and recycling rates. The results indicate that there is strategic coordination and resource competition in recyclers’ decisions regarding recycling and remanufacturing, causing them to assume dual roles as both “suppliers” and “competitors” within the supply chain. Subsidy policies significantly incentivize recycling and remanufacturing activities, thereby increasing the recycling rate, but exert a slight squeeze on the profits of rare earth conglomerates. Environmental tax policies effectively curb primary mining and promote resource circulation, but may have a negative impact on the remanufacturing industry. Currently, value within the closed-loop rare earth supply chain is highly concentrated among upstream oligopolistic enterprises, whilst the recycling segment suffers from insufficient economic incentives and significant policy dependency. This study provides theoretical support and decision-making references for the government to optimize policy combinations and promote the high-quality development of the rare earth recycling industry. Full article

The increase in global carbon dioxide emissions is intensifying climate change and severely affecting diverse communities. Addressing these impacts requires sustainable planning approaches that promote environmental and social balance. This research aims to develop a transferable planning methodology incorporating ex ante evaluation for sustainable productive rural settlements, the application of which is examined through a design proposal in Pocollay, Tacna, used as a case study. The methodology comprises six sequential phases: integrated territorial diagnosis, construction of the multicriteria evaluation model, assessment of the baseline scenario, formulation of the planning model, application of the methodology to the case study, and comparative multicriteria evaluation of the projected scenario. As an application of the methodology, a Master Plan and a productive housing module were developed, integrating the proposed planning principles within a circular economy approach, together with bioclimatic design strategies aimed at resource efficiency, passive comfort, water management, renewable energy integration, and reduced environmental pressure. Compared with the baseline scenario, the projected scenario obtained higher potential performance scores across the architectural, environmental, productive, and socioeconomic indicators evaluated. These results represent expected performance according to predefined criteria rather than impacts observed after construction. In conclusion, the main contribution of the research is the proposed planning and evaluation methodology, which can be replicated or adapted in future applications by recalibrating its indicators, weights, climatic parameters, productive systems, material strategies, and community priorities. Full article

Countries face interconnected policy challenges: population aging, fertility change, migration, urbanization, labor transitions, food and water security, climate risk, health-system demand, school planning, housing pressure, consumption planning, and spatial inequality. Yet planning evidence is often fragmented across ministries, statistical offices, surveys, administrative systems, research projects, and dashboards. This paper proposes the Population-Based Systems Model, or PopSyM, as a country-owned analytical infrastructure that places population dynamics at the center of integrated policy planning. PopSyM begins with a demographic spine by age, sex, location, year, and scenario, then links that spine to modules for health, education, food, labor, housing, social protection, environment, and local infrastructure. Its purpose is not projection for its own sake, but the measurement and improvement of population well-being: longer and healthier lives, adequate material conditions, skills, meaningful work, security, dignity, and country-specific dimensions of a good life. Nepal is used as a motivating example, but the proposed architecture is general. The paper argues that the population should be treated not only as a denominator for indicators but also as the organizing framework through which countries understand future demand, vulnerability, consumption needs, policy trade-offs, and feedback between people and systems. Full article

Growing urbanization, housing affordability pressures, and increasing sustainability demands have positioned modular and flexible design strategies as central approaches in contemporary residential architecture. Modularity enhances construction efficiency, reduces material waste, and accelerates delivery through the use of prefabricated, standardized components. Flexibility, in turn, enables spaces to adapt in configuration and function over time, responding to the evolving needs of occupants and communities. Following PRISMA 2020 guidance, a systematic search was conducted across Web of Science, Scopus, and ScienceDirect academic databases resulting in 2140 records. After duplicate removal and sequential screening, 98 studies were included in the final review. The selected literature spans peer-reviewed journal articles and documented case studies, with emphasis on publications from 2015 onwards. The review identifies key advantages of modular and flexible residential systems, including cost-effectiveness, reduced environmental impact, and improved user satisfaction, while also highlighting persistent challenges such as regulatory barriers, standardization constraints, and limited interdisciplinary integration. The review contributes three synthesis outputs: a typology of modular residential systems, a critical comparison of modular–flexible strategies, and a cross-scale conceptual framework linking production logic, occupant adaptation, and sustainability outcomes. The findings underscore the potential of hybrid strategies that combine modular construction with flexible design principles to produce residential environments that are resilient, adaptable, and sustainable. The review provides structured insights and evidence-based recommendations for architects, planners, and policymakers involved in the development of future housing systems. Full article

Methane cracking has emerged as a promising route for sustainable hydrogen production because it avoids direct carbon dioxide emissions while simultaneously enabling carbon sequestration in the form of solid carbon. In this work, a comprehensive and systematic experimental investigation of catalytic methane cracking was performed by directly comparing a commercial nickel catalyst (KATALCO™ 25-4MQ), an in-house catalyst prepared by wet impregnation using Fe(NO₃)₃·9H₂O as the iron precursor and Puralox SCFa-160 Ce20 as the support, and non-catalytic thermal conditions under identical operating parameters. Experiments were carried out in a laboratory-scale fixed-bed reactor at atmospheric pressure by varying methane partial pressure (0.1–0.2 atm) and operating temperature (600–800 °C), while maintaining a constant methane-specific WHSV of 0.3 h⁻¹. Continuous online gas analysis was employed to monitor reactor performance, and a dedicated post-processing methodology, including nitrogen-tracer-based carbon balance calculations, was developed to validate the experimental results. The results demonstrated the strong beneficial effects of both temperature and catalytic materials on methane decomposition. The Fe-based catalysts exhibited the highest performance, achieving average methane conversions and hydrogen yields approaching 50%, with peak values exceeding 90% under the most favorable conditions. Commercial Ni catalysts also showed promising activity, although a more pronounced deactivation tendency was observed during prolonged operation. Conversely, non-catalytic tests resulted in substantially lower performance. Overall, this work provides an experimentally assessed and integrated methodology together with benchmark performance indicators that may serve as useful guidance for researchers, process designers, and practitioners involved in the development, optimization, and future scale-up of methane cracking technologies for turquoise hydrogen production. Full article

Contemporary urbanization, particularly in the suburban zones of major cities, intensifies conflicts at the interface between forested and developed areas. Forests, as critical components of municipal functional and spatial structures, face increasing development pressure, primarily driven by escalating social demands for housing. This study evaluates the effectiveness of spatial policy implementation in safeguarding and maintaining forested areas, taking into account their distinct environmental and functional characteristics. The research focuses on selected municipalities near Warsaw: Izabelin, Jabłonna, Wiązowna, Lesznowola, and Podkowa Leśna, all of which experience significant investment pressure and possess a high proportion of forest cover. The analysis utilizes qualitative and comparative research methods. A Forest Planning Protection Quality Index (FPPQI) was developed through expert-based assessment of local spatial development plans to evaluate the quality of planning solutions for forest protection. The results were compared with the degree of forest fragmentation identified through GIS analyses. The expert method was used to evaluate selected local plans for the quality of planning protection of forest areas. Additionally, spatial analyses in a GIS environment assessed whether municipalities with a low FPPQI, resulting from ongoing suburbanization, also exhibit increasing forest fragmentation. The findings demonstrate that forest protection effectiveness is determined primarily by the quality of planning provisions in local spatial development plans, rather than by the extent of planning coverage. Municipalities experiencing high suburbanization pressure and lower FPPQI values exhibited increased forest fragmentation, while those with more restrictive planning regulations preserved greater spatial continuity of forest complexes. Full article

This article employs exploratory data-driven modeling to examine the relationships between selected macroeconomic indicators, residential property prices, and housing affordability pressures in Poland between 2020 and 2024. This turbulent period was selected for analysis because of the unprecedented volatility triggered by the COVID-19 pandemic and the geopolitical shocks associated with the war in Ukraine, both of which severely disrupted macroeconomic stability and construction supply chains. The study examines how key economic variables—including inflation, gross domestic product (GDP), unemployment, and average and minimum wage dynamics—are associated with residential property price dynamics within the framework of construction economics. Using statistical modeling techniques, including linear regression and Pearson correlation analysis, the study quantifies the strength, direction, and dynamics of these relationships across primary and secondary housing sectors. Our findings reveal a distinct comparative pattern of associations: average wage growth and inflation emerge as the macroeconomic indicators most strongly associated with property valuations, while macroeconomic growth and unemployment dynamics exhibit asymmetric associations across market segments. Notably, the findings suggest that the primary sector may be more sensitive to credit-related demand shocks and policy interventions, whereas the secondary sector appears to respond more directly to broader consumer trends and household purchasing capacity. By integrating macroeconomic data into a sectoral analysis, this study provides an exploratory empirical basis for discussing sustainable housing strategies. The results underscore the necessity of aligning investment and production cycles in the construction sector with macroeconomic stability to maintain long-term residential purchasing capacity and support resilient urban development. Full article

This article examines the relationship between tourism dynamics and housing systems in large urban municipalities, combining three complementary analytical dimensions: statistical indicators, correlation analysis, and resident survey data. The study explores how tourism growth, platform-mediated accommodation, and real estate pressures interact with housing affordability and availability. By triangulating municipal statistical indicators and residents’ perceptions, the article contributes to current debates on touristification, housing assetisation, and platform urbanism. The findings suggest that tourism–housing pressures are multidimensional and uneven, requiring integrated regulatory and planning responses that address both supply constraints and demand-side transformations linked to tourism economies. Full article

Extensometers housed in vaults are capable of resolving strain changes of less than a nanostrain; however, they are differently distorted by variations in barometric pressure at different frequencies, which may result in complicated strain noise. Therefore, how to quantify the barometric effects in different frequency bands is a perennial challenge in extensometric observation and research. Since the first strain observations at the Geodynamical Observatory Jingyuan (NW China) in 2007, the barometric effect has proven significant. Nevertheless, the frequency dependence and underlying mechanism of this effect remain unknown. With targeted research lacking at present, this study attempts to adopt the transfer function method to provide a systematic diagnosis. The results indicate that (1) the North–South (NS) component responds significantly to low-frequency pressure waves, with a slight phase shift leading the phenomenon; (2) the East–West (EW) component responds well to pressure waves in high-, medium-, and low-frequency bands, and the frequency dependence of the barometric coefficient spectrum and phase shift spectrum is strong; (3) the frequency-dependent response effect of the EW component may be related to factors such as horizontal pressure gradient force, topography, and fracture medium. These findings not only contribute to sub-frequency band correction of the barometric effect at the Geodynamical Observatory Jingyuan but also deepen our understanding of the ground–atmosphere coupling mechanism in the fault zone. Full article

This research examines the tourism structure of Santorini within the framework of the Triple Layered Business Model Canvas (TLBMC) and evaluates how circular tourism principles can be integrated into the value creation process across the TLBMC layers. The study utilizes secondary sources such as tourism reports, policy documents, corporate publications, and previous academic studies. Conducted using qualitative case study principles, this study employs PESTLE analysis, stakeholder analysis, TLBMC framework analysis, alignment analysis, and SWOT–CAME analysis. The research concludes that tourism in Santorini is highly dependent on a premium positioning strategy and characterized by a cruise- and experience-oriented visitor structure. Furthermore, the existing tourism structure exhibits both environmental and social vulnerabilities, including water scarcity, overtourism, seasonal demand concentration, and housing pressure. The destination possesses significant potential for stronger alignment among economic, environmental, and social layers, particularly through the introduction of alternative tourism activities. This research provides significant contributions to the literature and offers recommendations for all stakeholders, especially local actors, to establish a resilient tourism model that supports long-term alignment among the layers. Full article