Search Results (252)

Between April and May 2025, an outbreak of travel-associated Legionnaires’ disease (TALD) occurred, involving six cases at a hotel in Crete, Greece. Including two cases reported in 2023 and two additional cases from 2016 to 2017, ten cases were associated with this accommodation site. All TALD cases were reported by the European Legionnaires’ Disease Surveillance Network (ELDSNet). In compliance with the European Centre for Disease Prevention and Control (ECDC) surveillance and investigation protocols for hotels associated with the patient’s stay, local public health authorities conducted on-site inspections at the hotel by collecting water samples and performing risk assessments, while simultaneously recording the required epidemiological, environmental, and physicochemical data. A total of 181 statistically analyzed water samples showed positive rates for L. pneumophila of 12.71% (95% CI: 7.86–17.56) for (≥50 CFU/L) and 6.08% (95% CI: 2.60–9.56) for (≥1000 CFU/L). Risk assessments identified 18 stagnation points, systemic maintenance deficiencies, and high cumulative structural (30/52) and water (36/71) system risk scores. Low microbiological positivity of water samples does not necessarily equate to low risk, thus necessitating continuous risk assessment, implementation of Water Safety Plans (WSPs), and integrated monitoring by accommodation facilities to prevent LD cases. Full article

This research examines the ongoing challenge of depopulation in rural areas, focusing on the municipality of Buenavista del Norte in the Canary Islands. The objective is to analyse how governance and local community participation can contribute to reversing rural decline and to identify concrete strategies for sustainable development. Depopulation significantly impacts the social and economic viability of small rural municipalities, exacerbating marginalisation and isolation. The study applies a qualitative methodology, including interviews with public representatives, key strategic sector informants, and participatory group dynamics, to identify projects and resources that could foster local development. A core focus is placed on the integration of tourism, particularly wine tourism, as a tool for economic diversification and combating rural decline. Despite the Canary Islands’ status as a mature tourist destination, rural areas have not equally benefited, with some experiencing stagnation. Results point to the relevance of public–private collaboration, community-based innovation, and participatory approaches that engage key actors from various sectors. These processes facilitate the identification of viable projects and reveal the potential of tourism and sustainable community initiatives to reduce regional disparities. The implications of this research highlight the need for integrated local development strategies, improved infrastructure, and quality public services as essential measures to confront demographic challenges in remote areas. The inclusive governance, combined with strategic planning and tourism-based innovation, offers a viable roadmap for revitalising rural municipalities and ensuring their long-term resilience. Full article

The present paper treats the problem of steady laminar MHD flow of an incompressible viscous fluid for mixed convection stagnation-point flow over a vertical stretching sheet in the presence of an externally magnetic field. By means of the Optimal Auxiliary Functions Method (OAFM), the resulting nonlinear ODEs are semi-analytically solved. The impact of various physical parameters, such as the velocity ratio parameter A, the Prandtl number $Pr$, and the Hartmann number $Ha$, on the behavior of velocity and temperature profiles is analyzed. Both assisting ($\lambda >0$) and opposing ($\lambda <0$) flows are considered. The influence of these parameters is tabulated and graphically presented. The originality of this work lies in the development of effective semi-analytical solutions and in the excellent agreement between these solutions and the corresponding numerical solutions. This highlights the accuracy of the proposed method applied to steady laminar MHD flow. A comparative analysis underlines the advantages of the OAFM compared to the iterative method. The obtained results confirm that the OAFM represents a competitive mathematical tool to explore a large class of nonlinear problems with applications in engineering. Full article

Over the past several decades, old industrialized regions worldwide have faced immense pressure to adapt to global economic shifts. Using one of China’s major industrial provinces, Hebei, as a representative case study, this study examines how the evolution of one of China’s old industrial provinces, Hebei’s industrial structure has influenced its economic growth from 1990 to 2023. Drawing on theories of structural transformation and endogenous growth, we argue that the reallocation of resources from lower-productivity sectors (e.g., agriculture) to higher-productivity sectors (manufacturing and services) can act as an engine of growth. We employ a shift-share analysis (SSA) to decompose Hebei’s economic growth into components attributable to national trends, industrial structure, and regional competitive performance. The results reveal a globally relevant pattern of stagnation: while Hebei’s growth largely benefited from nationwide economic expansion (national effect), its heavy industrial structure initially posed a drag on growth (negative structural effect) and its regional competitive advantage in steel and energy sectors has eroded over time (weakening competitive effect). Our regression analysis further shows that growth was overwhelmingly dependent on capital accumulation while the contribution of labor was statistically insignificant, pointing to a low-productivity trap common in such regions. By integrating these methods, this study provides a robust diagnostic framework for identifying the root causes of economic distress in legacy industrial regions both within and outside China. These findings underscore the importance of structural upgrading for sustainable growth and offer critical lessons for policymakers globally, highlighting the necessity of moving beyond extensive, capital-driven growth toward an intensive model focused on industrial diversification, innovation, and human capital to ensure the sustainable revitalization of post-industrial economies. Full article

In this investigation, we introduce a new meromorphic operator defined by meromorphic univalent functions. A new class of meromorphic functions is introduced by this operator, which can generate several distinct subclasses depending on the values of its parameters. Within the framework of this class of functions, we obtain several significant algebraic and geometric properties, including coefficient estimates, distortion theorems, the radius of starlikeness, convex combination closure, extreme point characterization, and neighborhood structure. Our findings are sharp, offering accurate and significant insights into the mathematical structure and behavior of these functions. In addition, we present several applications of these results in fluid mechanics, like identifying stagnation points in vortex flows, predicting velocity decline in source/sink systems, and determining stability thresholds that protect crucial streamlines from perturbations, which demonstrates that the introduced operator and class characterize critical properties of 2D potential flows. Full article

Preserving historical porous materials requires careful monitoring of surface humidity to mitigate deterioration processes like salt crystallization, mold growth, and material decay. While microclimate monitoring is a recognized preventive conservation tool, its role in detecting surface-specific moisture risks remains underexplored. This study evaluates the relationship between indoor microclimate fluctuations and surface moisture dynamics across 13 historical sites in Northern Italy (Lake Como, Valtellina, Valposchiavo), encompassing diverse masonry typologies and environmental conditions. High-resolution sensors recorded temperature and relative humidity for a minimum of 13 months, and eight indicators—including dew point depression, critical temperature–humidity zones, and damp effect indices—were analyzed to assess the moisture risks. The results demonstrate that multivariate microclimate data could effectively predict humidity accumulation. The key findings reveal the impact of seasonal ventilation, thermal inertia, and localized air stagnation on moisture distribution, with unheated alpine sites showing the highest condensation risk. The study highlights the need for integrated monitoring approaches, combining dew point analysis, mixing ratio stability, and buffering performance, to enable early risk detection and targeted conservation strategies. These insights bridge the gap between environmental monitoring and surface moisture diagnostics in porous heritage materials. Full article

Thermochemical nonequilibrium significantly affects the accurate simulation of the aerothermal environment surrounding a hypersonic reentry vehicle entering Earth’s atmosphere during deep space exploration missions. The different heat transfer modes corresponding to each internal energy mode and chemical diffusion have not been sufficiently analyzed. The existing dimensionless correlations for stagnation point aerodynamic heating do not account for thermochemical nonequilibrium effects. This study employs an in-house high-fidelity solver PHAROS (Parallel Hypersonic Aerothermodynamics and Radiation Optimized Solver) to simulate the hypersonic thermochemical nonequilibrium flows over a standard sphere under both super-catalytic and non-catalytic wall conditions. The total stagnation point heat flux and different heating modes, including the translational–rotational, vibrational–electronic, and chemical diffusion heat transfers, are all identified and analyzed. Stagnation point aerodynamic heating correlations have been modified to account for the thermochemical nonequilibrium effects. The results further reveal that translational–rotational and chemical diffusion heat transfers dominate the total aerodynamic heating, while vibrational–electronic heat transfer contributes only about 5%. This study contributes to the understanding of aerodynamic heating principles and thermal protection designs for future hypersonic reentry vehicles. Full article

Efficient scheduling in industrial prefabrication environments—such as Prefabricated Bathroom Unit (PBU) production—faces increasing challenges due to resource limitations, overlapping projects, and complex task dependencies. To address these challenges, this paper presents a Learning-Enhanced Differential Evolution (LEDE) framework for solving the Multi-Mode Resource-Constrained Multi-Project Scheduling Problem (MRCMPSP). The MRCMPSP models the operational difficulty of coordinating interdependent activities across multiple PBU projects under limited resource availability. To address the computational intractability of this NP-hard problem, we first formulate a mixed-integer linear programming (MILP) model, and then develop an adaptive DE-based metaheuristic. The proposed LEDE method co-evolves activity sequencing and mode assignment using floating-point encodings, incorporating strategy switching, parameter adaptation, elitism, stagnation handling, and rank-based crossover control. Evaluated on real-world production data from the PBU industry, the algorithm produces high-quality solutions with strong scalability. These results demonstrate its practical potential as a decision-support tool for dynamic, resource-constrained industrial scheduling. Full article

(1) Background: Cultural heritage plays a vital role in shaping collective identity and supporting tourism, yet it faces increasing threats from natural and human-induced disasters. As a response, digital technologies—especially drone-based monitoring systems—are being explored for disaster prevention. This study examines whether a Genetic Algorithm can effectively optimize the placement of drone stations for the economic protection of cultural heritage. (2) Method: A simulation was conducted in a 2500 km² virtual space divided into 25 km² grid units, each assigned a random land price. Drone stations have an operational radius of 40 km. GA optimization uses a fitness function based on the ratio of cultural artifacts covered to installation cost. To prevent premature convergence, multi-point crossover and roulette wheel selection are employed. Key GA parameters were fine-tuned through repeated simulations. (3) Results: The optimal parameter set—population size of 300, mutation rate of 0.2, mutation strength of ±5 km, and crossover ratio of 0.3—balances exploration and convergence. The results show convergence toward low-cost, high-coverage locations without premature stagnation. Visualization clearly illustrates the optimization process. (4) Conclusions: GA proves effective for economically optimizing drone station placement. Though virtual, this method offers practical implications for real-world cultural heritage protection strategies. Full article

Wind turbine blades are prone to icing in cold environments, which leads to decreased aerodynamic performance, increased power loss, and even endangers the safe and stable operation of wind turbines. Electric heating anti-deicing method is the most effective solution because of its flexible control, rapid response, and high deicing efficiency. However, in the process of blade high-speed rotation, the complex flow field effect significantly affects the blade heat transfer performance, which leads to the problems of high energy consumption, low heat utilization, and uneven heating of traditional electric heating anti-icing/deicing methods, limiting their application effect in complex working conditions. Based on the physical mechanism and heat exchange characteristics of electric heating deicing of wind turbine blades, a coupled flow–heat transfer numerical model suitable for complex flow field conditions was constructed in this study, aiming to realize the dynamic simulation of the global temperature field and the phase transition process of ice sheets under different heating modes. Furthermore, the deicing efficiency characteristics of continuous heating and cyclic heating modes were compared and analyzed. The blade tip section of a Sinoma87.5 was taken as the experimental object, and the deicing experiment of blade by electric heating was carried out under artificial ice-covering laboratory conditions. The simulation and experimental results show that the deicing process by electric heating can be divided into three typical stages: initial temperature rise, stagnation, and rapid temperature rise. Under the influence of incoming flow conditions, the temperature rise of the front stagnation point region lags behind that of the windward side, and the steady-state peak temperature is lower. Compared with the cyclic heating mode, the continuous heating mode can enter and cross the stagnation period more quickly. The peak steady-state temperature of the continuous heating mode is 24.2 °C, and the deviation from the simulation result is only 2.8 °C, which is within the acceptable error range, effectively verifying the reliability of the numerical calculation model established. Full article

Drinking water treatment, from a microbiological perspective, efficiently removes hygienically relevant microorganisms, making the water safe for human consumption. The water quality is strictly regulated. An aspect that is often overlooked, however, is biological stability. In this study, we assessed the effect of drinking water treatment of surface waters on biological stability. Biological stability was assessed as the difference between the actual cell concentrations naturally contained in the water at the time point of sampling and the maximal cell concentrations in the same sample obtained after a batch growth assay. Whereas raw waters were biologically stable, treatment resulted in a loss of biological stability and also partly in an increase in the maximal cell numbers. Treatment steps reducing biological stability resulted in the conversion of biologically fixed nutrients to dissolved nutrients. The stabilizing effect of biologically active filters was annihilated by disinfection at the end of treatment. The lack of biological stability was especially evident when distributing chlorinated water, where actual cell numbers and, in part, regrowth potentials tended to increase throughout transport with strong seasonal variations. Comparing cold drinking water at house entrances in different buildings across Germany, regrowth tests resulted in an average regrowth factor of 54 with high spatial and temporal variability. Biological instability was further increased in drinking water installations during water heating, which contributed to an additional shift towards dissolved nutrients, giving room to microbiological changes once the water cools down and stagnates. It remains to be determined whether the biological stabilization of drinking water can increase its microbiological resilience towards the growth of hygienically relevant bacteria. Full article

Generically, in a system with more than three point vortices, there exist regions of stability around each vortex, even if the system is chaotic. These regions are usually called stability islands, and they have a morphology that is hard to characterize. In a system of two or three point vortices, these stability islands are better named vortex atmospheres or atmospheric islands, since the whole system is regular. In this work, we present an analytical study to characterize these atmospheres in two point vortex systems for arbitrary values of the circulations ${\mathrm{\Gamma }}_1$ and ${\mathrm{\Gamma }}_2$ in the infinite two-dimensional plane $\left(x,y\right)\in {\mathbb{R}}^2$—the simplest scenario—by studying the dynamics of passive particles in these environments. We use the trajectories of passive particles to find the stagnation points of these systems, the special trajectories that partition ${\mathbb{R}}^2$ in different regions and the analytical expressions that define the boundary of the atmospheric islands. In order to characterize the geometry of these atmospheres, we compute their perimeter and area as a function of $\gamma ={\displaystyle \frac{{\mathrm{\Gamma }}_1}{{\mathrm{\Gamma }}_1+{\mathrm{\Gamma }}_2}},$ if ${\mathrm{\Gamma }}_1+{\mathrm{\Gamma }}_2\ne 0.$ The case ${\mathrm{\Gamma }}_1+{\mathrm{\Gamma }}_2=0$ is treated separately, as the perimeter and area of the atmospheres do not depend on the circulations. Furthermore, in this latter case, we observe that the atmospheric island has a very similar morphology to an ellipse, only differing from the ellipse that best approximates the atmosphere by a relative error of $\approx$3.76‰ in area. Full article

This research investigates the impact of second-order slip conditions, Stefan flow, and convective boundary constraints on the stagnation-point flow of couple stress nanofluids over a solid sphere. The nanofluid density is expressed as a nonlinear function of temperature, while the diffusion-thermo effect, chemical reaction, and thermal radiation are incorporated through linear models. The governing equations are transformed using appropriate non-similar transformations and solved numerically via the finite difference method (FDM). Key physical parameters, including the heat transfer rate, are analyzed in relation to the Dufour number, velocity, and slip parameters using an artificial neural network (ANN) framework. Furthermore, response surface methodology (RSM) is employed to optimize skin friction, heat transfer, and mass transfer by considering the influence of radiation, thermal slip, and chemical reaction rate. Results indicate that velocity slip enhances flow behavior while reducing temperature and concentration distributions. Additionally, an increase in the Dufour number leads to higher temperature profiles, ultimately lowering the overall heat transfer rate. The ANN-based predictive model exhibits high accuracy with minimal errors, offering a robust tool for analyzing and optimizing the thermal and transport characteristics of couple stress nanofluids. Full article

This work results from a numerical investigation of the thermochemical non-equilibrium effects on the surface properties of a hypersonic body. Non-equilibrium within an air mixture composed of 11 chemical species was considered when solving the Navier–Stokes–Fourier equations using a density-based algorithm in OpenFOAM. The influence of thermal and chemical non-equilibrium on the surface properties of a hypersonic double-cone test body was studied by considering two types of surfaces. It was found that the heat flux and pressure distribution along the surface are higher under non-equilibrium free-stream conditions. Unlike what was observed at the impingement point, where the vibrational non-equilibrium effects on the surface properties are almost independent of the surface type, at the stagnation point, these effects are highly dependent on the catalytic activity of the surface. At the stagnation point, the vibrational non-equilibrium effects are more pronounced on a fully catalytic surface than on a non-catalytic surface. Under the studied conditions, the vibrational non-equilibrium reduces the heat flux by 18% for a non-catalytic surface, while for a fully catalytic surface, it reduces the heat flux by 38%. Additionally, the presence of vibrational non-equilibrium in the free-stream reduces the pressure by 24% for a non-catalytic surface, while for a fully catalytic surface, it is reduced by 42%. Full article

This study investigates the numerical modeling of a high-velocity circular free-water jet impinging into a plunge pool, focusing on the simulation and validation of mean and fluctuating dynamic pressures on the pool floor. Numerical simulations were performed using two different computation methods, two-phase volume-of-fluid and Euler–Euler, under conditions replicating experimental data obtained at a jet velocity of 7.4 m/s and plunge pool depth of 0.8 m. The models, based respectively on the Volume of Fluid (VoF) and Euler–Euler methods, were evaluated for accuracy in replicating experimentally measured pressures and air concentration values. The Euler–Euler solver, coupled with the k-Omega SST turbulence model, demonstrated mesh independence for mean dynamic pressures with a mesh resolution of 24 cells across the jet diameter. In contrast, two-phase volume-of-fluid exhibited mesh dependency, particularly near the jet stagnation point and pressure values higher than the experimental ones. While the Euler–Euler accurately captured mean pressures and air concentration in close agreement with experimental data, its Reynolds-Averaged Navier–Stokes (RANS) formulation limited its ability to simulate pressure fluctuations directly. To approximate these fluctuations, turbulent kinetic energy values were used to derive empirical estimates, yielding results consistent with experimental measurements. This study demonstrates the efficacy of the Euler–Euler method with the k-Omega SST model in accurately capturing key dynamic pressures and air entrainment in plunge pools while highlighting opportunities for future work on pressure fluctuation modeling across a broader range of jet conditions. Full article