Search Results (103)

Understanding the absorption and desorption behavior of superabsorbent polymers (SAPs) in ionic environments is critical for their practical applications. Ion exchange between monovalent counterions within the SAP and multivalent cations (e.g., Ca²⁺) in solution not only induces macroscopic desorption but also generates non-uniform internal strain, creating a complex feedback loop with ion transport. This study establishes a phenomenological coupled model that integrates Fickian diffusion for ion transport with an elastic wave equation for SAP deformation. The coupling is realized through deformation-dependent diffusion coefficients and an ion-concentration-modulated elastic modulus, with the latter described by a first-order linear relationship over a limited range. Taking Ca²⁺ as a representative divalent cation, we systematically investigate the effects of solution concentration, SAP particle size, and ion dissociation degree. The model predicts several non-intuitive phenomena, including transient internal free Ca²⁺ concentrations exceeding the boundary concentration by up to ~15% and concentration gradient inversions for small SAP particles (radius 75 μm) at later times. Characteristic absorption time constants τ_a range from 98 s to 179 s depending on particle size and Ca²⁺ level. Simulated total Ca²⁺ uptake agrees with experimental data within an 8% mean relative error. The model is validated against macroscopic absorption/desorption curves and total Ca²⁺ uptake, while the predicted internal concentration and strain fields remain to be confirmed by spatially resolved experiments. These findings provide new mechanistic insights into the chemo-mechanical coupling in SAPs and offer guidance for their tailored design. Full article

Low-melting-point impurities in powder feedstock can trigger local melting phenomena in laser powder bed fusion (LPBF) parts and may initiate defects in printed components. Here, we combine bulk chemistry with automated, high-throughput particle-by-particle SEM/EDS to identify and quantify Sn-containing impurity particles in two gas-atomized Al–Mg–Zr powder batches with different bulk Sn levels. The aim was not to establish a direct batch-to-batch performance comparison, but to clarify whether Sn was uniformly distributed among the powder particles or concentrated in rare impurity particles. Although ICP analysis indicated only 0.07 ± 0.02 wt.% Sn in the Sn-higher batch and <0.01 wt.% Sn in the Sn-lower batch, automated SEM/EDS screening of 20,001 particles per batch revealed that Sn was present as a very small number of highly enriched particles with Sn > 45 wt.% (eight particles in the Sn-higher batch and three particles in the Sn-lower batch). In the Sn-higher batch, Sn-rich particles were predominantly spherical and fell within the LPBF feedstock size window (Dmax ≈ 25–40 μm), implying that standard sieving would not remove them. BSE imaging and EDS mapping of polished sections and fracture surfaces of LPBF specimens built from the Sn-higher batch revealed spatially localized Sn-rich features associated with pores and Sn-rich phases on the fracture surface, supporting a direct powder-to-part transfer. These results demonstrate that low bulk impurity levels can mask highly localized, particle-scale contamination and highlight the need for particle-level compositional screening to support robust powder qualification and reuse decisions in LPBF. Full article

Tri-reforming of methane (TRM) has emerged as a promising pathway for low-carbon syngas production by integrating steam reforming, dry reforming, and partial oxidation within a single process. This coupling enables simultaneous CH₄ utilization and CO₂ valorization while enabling internal heat generation and flexible adjustment of the H₂/CO ratio for downstream synthesis. However, TRM performance cannot be adequately evaluated using conversion or energy efficiency alone, because the process involves complex interactions among competing reaction pathways, transport phenomena, catalyst stability, and thermodynamic irreversibility. This review provides a multiscale critical assessment of TRM from both first-law energy and second-law exergy perspectives, linking reaction-network fundamentals to reactor-level behavior and system-level performance. The literature evidence shows that although high temperatures and near-autothermal operation can enhance CH₄ conversion and reduce external heat demand, these conditions may simultaneously intensify deep oxidation, hotspot formation, carbon-forming tendencies, and exergy destruction. While equilibrium analyses help define feasible operating windows, they are insufficient without kinetic modeling and reactor-scale studies that capture spatial non-uniformities and pathway competition. Across reported TRM systems, exergy destruction is consistently concentrated within the reformer, identifying the reacting core as the dominant thermodynamic bottleneck. Accordingly, the key challenge in TRM is not simply to maximize conversion but to preserve chemical work potential while maintaining syngas quality and operational stability. Viewed from this perspective, TRM is better understood as an irreversibility-aware multiscale design problem in which optimal performance depends on the integrated optimization of catalyst functionality, reactor architecture, heat management, and system-level operation. Full article

This study presents a comprehensive computational evaluation of radiofrequency (RF) ablation efficacy and the spatial formation of thermal ablation zones within a 3D model of a liver tumor. By systematically comparing these configurations, the study aims to elucidate the physical mechanisms governing electromagnetic (EM) energy dissipation in hepatic tissue and to provide clear engineering guidelines for optimizing RF applicator selection and treatment planning in clinical practice. To reliably simulate the biophysical phenomena of the RF ablation procedure, a coupled electro-thermal model based on the finite element method and the Pennes bioheat equation was implemented. The research investigates six distinct applicator variants: conventional needle-type applicators and advanced expandable umbrella-type RF applicators equipped with four- and eight-tine electrodes, each evaluated in both monopolar and bipolar configurations. Numerical simulations were conducted for a standard 10 min ablation procedure at varying applied voltages to assess the specific absorption rate (SAR) distribution, transient heating dynamics, and the exact volumes of the resulting coagulation necrosis which were quantified using rigorous isotherms and the cumulative equivalent minutes at 43 °C (CEM₄₃) thermal dose index. Volumetric analysis of the ablation zones revealed that bipolar multi-tine electrodes induce highly localized heat concentration. Conversely, monopolar multi-tine setups strongly disperse EM energy. The results demonstrated that, for conventional needle applicators, the monopolar configuration generated significantly larger necrosis zones than the bipolar operating mode. The RF applicator geometry and its operating mode directly dictate the spatial extent of liver tissue necrosis. Moreover, advanced numerical treatment planning is essential for optimizing SAR and CEM₄₃ distributions and ensuring safe and complete hepatocellular carcinoma eradication. Full article

This study utilizes a large-scale numerical simulation model to investigate the hydrodynamic behavior and particle transport characteristics of gas–liquid–solid three-phase flow in vertical wellbores featuring multi-source confluence and curved geometries. Simulation results indicate that increasing flow velocity shifts the dominant control mechanism from surface tension to inertial forces, transitioning the flow pattern from slug flow to churn flow. In curved pipe sections, centrifugal phase separation and geometric shielding effects cause significant flow asymmetry and maintain large bubble stability at the inner wall. Additionally, the multi-inlet structure induces shear rate gradients that result in the spatial coexistence of two distinct bubble scales. Furthermore, localized gas concentrations exceeding 70% at the upper inlet can trigger severe gas-locking phenomena and intense pressure pulsations. Full article

Floods remain one of the most frequent and destructive natural phenomena, the scale and consequences of which are exacerbated by climate variability and anthropogenic pressure on river systems. The Yertis water basin (Kazakhstan) is an area with high exposure to flood risks, where the dense concentration of settlements and infrastructure is within floodplain areas. This study applies an integrated approach based on the integration of statistical methods for hydrological analysis and GIS-based spatial modeling to assess and delimit potential flood zones. Long-term series of maximum water levels and discharges from hydrological stations for the period 1974–2025 were analyzed using probability distribution functions, including the log-normal, Pearson Type III, and Gumbel distributions. The optimal distribution model for each station was selected based on the Kolmogorov–Smirnov goodness-of-fit test and the Akaike information criterion. Exceedance-probability curves for extreme hydrological events were constructed for 0.1%, 1%, and 10% probabilities. Spatial flood modeling was performed in the ArcGIS 10.8 environment using a hydrologically corrected digital elevation model and interpolated flood levels. The resulting flood zone maps allow for the identification of the highest-risk areas and serve as a tool for scientifically based planning of emergency prevention measures and floodplain area management. The study contributes to the methodological development of probabilistic floodplain mapping through the integration of statistical frequency analysis and GIS technologies and demonstrates the applicability of this approach for flood hazard assessment in large transboundary river systems under conditions of climatic and hydrological variability. Full article

Weather-related hazards cause significant societal impacts, yet systematic long-term analyses linking these events to all levels of impact severity remain limited. This study investigates weather-related events and their associated impacts in Greece (2000–2025) using the High-Impact Weather Events Database (HIWE-DB). The HIWE-DB records 626 events, corresponding to 1871 localized records and includes 269 confirmed fatalities. Flood-related hazards are dominant, followed by windstorms, while one-third of all events involve multiple hazardous phenomena. A multilevel analysis, independently assessing weather intensity (W) and impact severity (I), reveals a statistically significant annual increase in the total number of events, driven mainly by low- to moderate-impact events (I1-I2), alongside an increase in high-intensity events (W3). While the most severe events (I3) show high annual variability, they exhibit a 38% increase in the second half of the study period compared to the first. Spatially, societal impacts are predominantly concentrated in major metropolitan areas, whereas the highest per capita fatality rates occur in specific regions, such as West Attica. The findings demonstrate how the independent indicators of intensity and severity contribute to understanding the link between weather hazards and societal exposure, providing an empirical basis for evidence-based risk assessment and impact-based early warnings. Full article

Coal-mine-gas-monitoring data exhibits missing phenomena due to the harsh underground operating environment. Accurate imputation of missing values in gas-monitoring sequences serves as a key data foundation for guaranteeing the continuity of gas data, enhancing the reliability of disaster early warning, and improving the accuracy of mine safety situation analysis and judgment. Aiming at the prevalent random and segmented missing issues in coal-mine-gas-monitoring time-series data, and the limitation that existing imputation methods struggle to accurately capture the nonlinear spatiotemporal correlations and long-range temporal dependencies of such data, this study proposes a missing data imputation method for coal mine gas time-series data based on the Spatio-Temporal Graph Attention Network—Echo State Network (ST-GAT-ESN). Firstly, this method extracts temporal features of the gas concentration sequence using a Gated Recurrent Unit (GRU). Subsequently, it models multiple monitoring points as graph nodes through a Graph Attention Network (GAT), constructs an adjacency matrix based on airflow propagation relationships, and adaptively learns the spatial dependency weights between monitoring points to realize the deep fusion of spatiotemporal features. Finally, it designs a dual-channel Echo State Network (ESN), synchronously inputs the spatiotemporal fusion features of the missing regions before and after, efficiently fits the nonlinear evolutionary trend of the data by virtue of the echo state property of the reservoir, and solves the output layer weights through ridge regression to achieve accurate imputation of missing values. Experimental results demonstrate that, compared with the single-ST-GAT-ESN, ESN, and ARIMA models, the proposed method achieves the optimal imputation performance in both random and segmented missing scenarios within the missing rate range of 5–50%. The three evaluation metrics—Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Mean Absolute Percentage Error (MAPE)—are reduced by 30–80% compared with the benchmark models. Moreover, the imputation curve achieves the best fitting performance with the ground-truth curve at a 50% segmented missing rate. This study confirms that the ST-GAT-ESN model effectively enhances the adaptability and robustness to complex missing patterns via spatiotemporal collaborative modeling and a dual-channel fusion mechanism, providing a high-precision and highly stable technical solution for ensuring the integrity of coal-mine-gas-monitoring data, and also provides theoretical references and engineering insights for the missing-value processing of industrial time-series monitoring data. Full article

Although the molecular pathogenesis of bilirubin-induced neuronal cell injury is not completely understood, certain recurrent themes resonate in the literature on this topic and include the generally untoward effects of high unconjugated bilirubin (UCB) concentrations on membranes (plasma, mitochondrial, and endoplasmic reticulum (ER)), cellular bioenergetics, and intracellular calcium homeostasis. Only in the last decade, ER was discovered as an early target of bilirubin neurotoxicity. We will review the main features of bilirubin neurotoxicity from the point of view of ER and bilirubin-induced ER stress. Neuronal excitotoxicity, mitochondrial energy failure, and increased intracellular calcium concentration are three phenomena linked spatially and temporally in the pathogenesis of bilirubin-induced neurotoxicity. ER, being the main intracellular calcium storage organelle, is involved in the increase in the universal second messenger, calcium. This event leads to the activation of proteolytic enzymes, apoptotic pathways, and necrosis, the occurrence of which is likely a function of the degree and duration of bilirubin exposure. Full article

The cloud spatial uniformity in the test section is crucial for icing wind tunnels in aircraft icing research and airworthiness certification. To achieve uniform supercooled large droplet (SLD) icing conditions, both the spatial variation in droplet size distribution and the concentration should be considered. In this study, the spatial distribution of droplets under three SLD conditions is explored in the Aviation Industry Corporation of China Aerodynamics Research Institute (AVICARI)’s FL-61 icing wind tunnel. Measurements are conducted at 12 test points in vertical and horizontal directions using the holographic airborne cloud particle imager (HACPI) in conjunction with a two-axis traversing system. The droplet images obtained at specific test points below the test section centerline show deformation phenomena for droplets larger than 400 $\mathsf{\mu }$m. Additionally, the aspect ratio of deformed droplets increases with droplet size. The spatial evolution of the median volume diameter (MVD) and liquid water content (LWC) is examined. For two spray arrangements where the activated nozzles are positioned close, the test point where the LWC peak in the vertical direction occurs is higher than that of the MVD peak. Further analysis focuses on the size distribution of droplets in the vertical direction. The results show that the settling effect of the droplets larger than 50 $\mathsf{\mu }$m is evident under a flow velocity of 78 m/s. Meanwhile, the position where large droplets tend to appear lowers as the droplet size increases. Finally, the spatial uniformity of droplet size distributions at the same radial distance is discussed. Full article

Atmospheric contamination and thermal pollution are two phenomena that impact negatively on the quality of life of residents in a city. Furthermore, exposure to these phenomena has a differential impact on socioeconomic strata, with the poorest being the most affected. Spatial and temporal analyses were conducted of PM_2.5 pollution and air temperature, as well as socioeconomic variable. This characterization revealed that low-income people are more exposed to thermal pollution during the warm season with temperatures up to 32.6 °C, and to PM_2.5 pollution with concentrations up to 205 µgm⁻³ during the cold season, focusing on the eastern part of the Metropolitan Area of Mexico City (MAMC). High temperatures can persist for up to 6 h, while PM_2.5 concentrations can persist for up to 5 h. The social backwardness index is a fixed variable that can change in the long term and is related to thermal pollution. This study will allow us to understand social and environmental vulnerability and, thus, to develop an appropriate mitigation methodology for these two phenomena and their impact on human health, with special attention to environmental justice issues. Full article

(1) Studying the spatial distribution of wingless arthropods restricted to the Earth’s surface presents numerous challenges. In this study, we focused on the spatial distribution of terrestrial isopods (Oniscidea) within a managed forest ecosystem, examining relationships among abundance, variance, occupancy, and clumpiness (i.e., aggregation) to highlight their significant roles in the observed phenomena. (2) Terrestrial isopods were collected using pitfall traps along a gradient spanning deforested and forested areas. For analysis, we employed summary statistics to describe the community using 18 different coefficients. Abundance–variance and abundance–occupancy models, together with Taylor’s power law and ordination symbol plots were performed. (3) Nearly 1000 individuals representing 8 species were identified and analyzed. All species exhibited a clumped distribution; however, Ligidium hypnorum displayed the highest degree of clumpiness, which resulted in notably low frequency and constancy despite its high overall abundance. Shrubs were the habitat with the highest rate of aggregation. Most species concentrated their individuals in just up to 5 of the 75 pitfall traps, with the remaining traps typically containing fewer or no individuals. (4) Species that are highly abundant on a local scale can be surprisingly limited in their spatial distribution, making their assumed dominance questionable and causing them to deviate from established trends. Awareness of species-specific traits and attention to such details can progressively improve the interpretation of observed ecological patterns. Full article

In the Republic of Korea, the problems of low birth rate and population aging are accelerating population decline at the regional level, leading to the phenomena of local extinction and urban shrinkage. These phenomena, coupled with the projected nationwide population decline, pose a fundamental threat to the sustainability of essential infrastructure such as urban parks. The conventional growth-oriented paradigm of urban planning has shown clear limitations in quantitatively forecasting future demand, constraining proactive management strategies for the era of population decline. To address this gap, this study develops a policy-decision-support framework that integrates long-term population projections, grid-based population data, the DEGURBA urban classification system—a global standard for delineating urban and rural areas— and network-based accessibility analysis. For the entire Republic of Korea, we (1) constructed a 1 km resolution time-series population dataset for 2022–2072; (2) applied DEGURBA to quantify transitions among urban, semi-urban, and rural types; and (3) assessed changes in potential user populations within the defined service catchments. The results indicate that while population concentration in the Seoul Capital Area persists, under the low-variant scenario, a projected average decline of 40% in potential user populations by 2072 will lead to significant functional changes, with 53.6% of municipalities nationwide transitioning to “semi-urban” or “rural” areas. This spatial shift is projected to decrease the proportion of urban parks located in “urban” areas from 83.3% to 75.0%, while the total potential user population is expected to plummet from approximately 44.4 million to 25.8 million, a 42.0% reduction. This study underscores the need for urban park policy to move beyond quantitative expansion and toward quality-oriented management based on selection and concentration. By uniquely integrating long-term demographic scenarios, the Degree of Urbanization (DEGURBA), and spatial accessibility analysis, this study provides a foundational scientific basis for forecasting future demand and supports the formulation of sustainable, data-driven strategies for urban park restructuring under conditions of demographic change. Full article

Recent studies on semi-dilute Calf-Thymus DNA (CT-DNA) solutions have revealed the presence of birefringence and small-scale textures influenced by shear and ionic strength. In this study, we investigate these phenomena on the same solutions to elucidate the underlying shear-induced supramolecular organization and relaxation dynamics using rheo-birefringence, rheology, and rheo-SAXS (small-angle X-ray scattering). Static SAXS confirmed concentration-dependent inter-chain correlations in the 15–25 nm range, while rheology revealed a slipping yield-stress behavior. Oscillatory strain sweep and steady state rheo-birefringence experiments correlated the appearance of textures with the onset of flow and a stress plateau observed over a shear rate range from approximately 1 to 1000 s⁻¹. Transient rheo-birefringence and rheo-SAXS revealed two distinct relaxation mechanisms on well-separated time scales: a fast process lasting a few seconds, inversely proportional to the shear rate, consistent with the orientational relaxation of DNA segments on a ~20 nm scale; and a slower relaxation over tens of seconds, independent of the shear rate, associated with the disappearance of textures, and attributed to a diffusive process. These findings provide significant insights into the mechanisms governing DNA organization and dynamics in semi-dilute solutions under flow and highlight the need for temporally resolved start-up rheo-SAXS and rheo-birefringence measurements, as well as theoretical models describing these processes across various spatial and temporal scales. Full article

With the impact of fossil energy on the climate environment and the development of energy technologies, new energy vehicles, represented by electric cars, have begun to receive increasing attention and emphasis. The rapid proliferation of public charging infrastructure for NEVs has concurrently influenced traditional petrol station networks, creating measurable disparities in their spatial distributions that warrant systematic investigation. This research examines Wenzhou City, China, as a representative case area, employing multi-source Point of Interest (POI) data and spatial analysis models to analyse differential characteristics in spatial layout accessibility, service equity, and underlying driving mechanisms between public electric vehicle charging stations (EV) and traditional gas stations (GS). The findings reveal that public electric vehicle charging stations exhibit a pronounced “single-centre concentration with weak multi-centre linkage” spatial configuration, heavily reliant on dual-core drivers of population density and economic activity. This results in marked service accessibility declines in peripheral areas, resembling a cliff-like drop, and a relatively low spatial equity index. In contrast, traditional gas stations demonstrate a “core-axis linkage” diffusion pattern with strong coupling to urban road networks, showing gradient attenuation in service coverage efficiency along transportation arteries, fewer suburban service gaps, and more gradual accessibility reductions. Location entropy analysis further indicates that charging station deployment shows significant capital-oriented tendencies, with certain areas exhibiting paradoxical “excess facilities” phenomena, while gas station distribution aligns more closely with road network topology and transportation demand dynamics. Furthermore, the layout characteristics of public charging stations feature a more complex and diverse range of land use types, while traditional gas stations have a strong dependence on industrial land. This research elucidates the spatial distribution patterns of emerging and legacy energy infrastructure in the survey regions, providing critical empirical evidence for optimising energy infrastructure allocation and facilitating coordinated transportation system transitions. The findings also offer practical insights for the construction of energy supply facilities in urban development frameworks, holding substantial reference value for achieving sustainable urban spatial governance. Full article