Search Results (1,538)

Hydropower is a crucial component of renewable energy, and sediment erosion is a key factor affecting the operation of impulse turbines, with erosion inside the nozzle being particularly prominent and leading to reduced unit efficiency. This paper investigates the distribution patterns of energy dissipation and erosion locations inside the nozzle under varying particle sizes, based on numerical simulation and entropy production theory. The results indicate that small particle sizes (0.02 mm) exhibit good fluidity, uniform flow velocity distribution, and a small high-entropy-production region. As particle size increases (0.1 mm, 0.3 mm), fluidity gradually deteriorates, the flow field becomes more turbulent, and the high-entropy-production region expands. When the turbulent kinetic energy exceeds 10 m²/s², the entropy production rate increases sharply. A significant negative correlation is observed between entropy production rate and erosion rate; smaller particle sizes correspond to more severe erosion. Erosion on the needle is primarily due to friction, while erosion on the nozzle is primarily due to impact. High erosion levels on both the nozzle and needle are concentrated within a particle velocity range of [80, 100], and the erosion rate within this speed range shows a sharp upward trend. Full article

Airflow is widely used in grain cleaning and sorting processes to separate grains according to their aerodynamic properties. However, separation efficiency depends on airflow parameters and grain physical characteristics. The aim of this study was to evaluate the movement and sorting of wheat grains under different airflow conditions and to compare the effects of vertical and horizontal airflows on grain separation efficiency. A theoretical analysis was conducted to investigate grain motion in laminar and turbulent airflows by determining grain displacement and displacement differences. Theoretical calculations were used to predict the displacement behavior and separation potential of grains with different critical velocities under various airflow conditions. To evaluate these predictions, laboratory experiments were conducted in a horizontal airflow sorting chamber at grain feed rates of 1 and 2 kg min⁻¹. The experimentally observed grain distributions were then compared with the theoretical predictions, allowing comparison between predicted and experimentally observed grain movement patterns. The average critical velocity of wheat grains was found to be 10.35 m s⁻¹ at 14.2% moisture content, while the floating coefficient was approximately 0.092. The theoretical analysis showed that displacement differences between grains with different aerodynamic properties ranged from 0.103 to 0.185 m within 1 s, depending on airflow conditions. Experimental results revealed a non-uniform distribution of grains within the sorting chamber, with the majority of grains collected in the first boxes. Increasing the grain feed rate reduced separation efficiency to approximately 55%, indicating a significant influence of grain flow intensity on the separation process. The results demonstrate that efficient grain sorting requires the optimization of both airflow parameters and grain feeding conditions. The findings of this study may contribute to the design and improvement of grain cleaning and sorting equipment. Full article

Urbanization and rapid economic growth have exacerbated urban heat effects, increasing the frequency of heat-related disasters and intensifying human health risks. Urban traffic generates substantial carbon emissions and associated heat, which significantly alter roadside thermal environments and impact human activities. Numerous previous studies have investigated urban thermal environments and their influencing mechanisms. However, the relationships between road-level traffic carbon emission (TCE) and road surface temperature (RST) remain insufficiently explored. In this study, roadway segment-based TCE and RST were acquired by integrating hourly traffic flow information, localized vehicle carbon emission factors, high-resolution Landsat-8 remote sensing datasets, and the road network. Three commonly used linear regression models and an improved Random Forest (RF) model were utilized to assess the impact of TCE on RST for different grades of roads. The study showed that carbon emissions from road traffic exhibit a locally focused distribution pattern in space. Compared to other grades of roads, higher levels of TCE were observed in urban main roads. In summer, roads (e.g., minor arterials) with lower grades tended to have a higher thermal risk, with freeways having the lowest TCE and urban expressways experiencing the greatest TCE fluctuations. An improved RF model integrating the spatial weight matrix and Gaussian process could more efficiently identify the nonlinear effects of TCE on RST. The contributions of TCE to summer RST were 0.4, 0.37, 0.54, and 0.56 for freeways, urban expressways, main roads, and minor arterials, respectively. The relative impact of road TCE with lower grades on RST becomes more significant, while the impact of surrounding buildings and green areas tends to decrease. Our findings provide valuable insights for reducing urban carbon emissions and thermal risks. Full article

The beef production chain plays a strategic role in Brazilian and global agri-food systems and faces growing demands for sustainability, transparency, and traceability. Building on official Animal Transit Guide (GTA) records from Mato Grosso do Sul, Brazil, this study examines whether a parsimonious agent-based model (ABM) can generate the main structural signatures of an observed cattle-trade network. The empirical benchmark is a directed and weighted network with 20,827 nodes and 258,120 weighted edges. The ABM represents producers and slaughterhouses as spatial agents connected by trade decisions based on three mechanisms: destination attractiveness, defined as the accumulated pull of a slaughterhouse based on previous simulated throughput; geographic distance, representing spatial friction; and relational memory, representing the tendency to repeat previous commercial ties. Producer choice is formalized through a local utility function that combines attractiveness, distance penalty, and relational memory under capacity, sourcing-radius, and saturation constraints. In the simulated scenarios, the top-five slaughterhouses accounted for 38.49 ± 2.56% of throughput at reduced scale and 14.40 ± 0.65% at intermediate scale, while weighted mean distances were 11.94 ± 0.56 and 9.07 ± 0.39 model units, respectively. The model reproduced, in structural and mechanistic terms, the emergence of dominant hubs, the concentration of flows, and the bounded increase in transaction distance with connectivity around the empirical threshold of kw ≈ 256. Sensitivity analyses indicated that attractiveness increases concentration, distance localizes transactions, and relational memory can stabilize repeated ties when recurrent activation is represented. Rather than reconstructing individual transactions, estimating policy impacts, or identifying a unique parameter vector, the model provides a generative explanation of how local trade rules can produce macro-level network patterns consistent with the observed cattle-trade regime. These findings support future prospective analyses of cattle governance, traceability, and sustainability within the broader context of Livestock 4.0. Full article

Climate-related disasters are escalating in frequency and severity, yet global adaptation finance remains critically insufficiently structured to respond after disasters occur rather than before. This study empirically examines disaster loss data, climate finance flows, and financial instrument evidence to test two hypotheses: whether climate finance is disaster-reactive, and whether policy uncertainty constrains it. We integrate data from the Emergency Events Database (EM-DAT), covering seven climate-induced hazard types (droughts, extreme temperatures, floods, glacial lake outburst floods, wet mass movements, storms, and wildfires), in addition to the OECD Creditor Reporting System (CRS), the World Uncertainty Index (WUI), the ND-GAIN vulnerability index, and the World Governance Indicators, the Green Climate Fund Open Data Library, and the Artemis Deal Directory across 131 countries (2011–2024) for Hypothesis 1 and 100 countries (2012–2024) for Hypothesis 2. Fixed-effects panel regressions with Driscoll–Kraay standard errors confirm that prior-year disaster losses significantly predict subsequent climate finance flows (β = 0.040, p = 0.009; N = 1769 country-year observations), establishing a reactive financing pattern. Policy uncertainty interacting with high vulnerability is found to suppress adaptation finance flows (β = −2.587, p = 0.080, N = 878 country-year observations), with the effect concentrated among the most climate-exposed economies. We propose a risk-layered climate finance architecture aligning instruments with distinct hazard tiers across the Global South. Credible policy signals, strategic public investment, and systematic integration of insurance mechanisms are essential preconditions for unlocking scalable, forward-looking resilience finance. Full article

Background/Objectives: Trauma triggers complex early immune responses. However, the relationship among trauma severity, changes in immune cell survival, and circulating inflammatory mediators remains unclear. This study compared early cell viability and death patterns in CD66b⁺ granulocytes, total T lymphocytes, and CD4⁺ and CD8⁺ T-cell subsets as well as inflammatory mediator levels between patients with non-severe and severe trauma. Methods: This single-center prospective observational study included 67 adult patients with trauma who were classified into non-severe and severe trauma groups according to the Injury Severity Score (ISS < 15 vs. ISS ≥ 15). Blood samples were obtained within 1 h of arrival at the emergency department. Flow cytometry was used to assess the viability, early apoptosis, late apoptosis, and necrosis in the leukocyte subsets. Serum concentrations of intercellular adhesion molecule-1 (ICAM-1), macrophage migration inhibitory factor (MIF), CD40 ligand (CD40L), and interleukin-1 receptor antagonist (IL-1ra) were measured using enzyme-linked immunosorbent assays. Results: The severe trauma group had a significantly lower proportion of early apoptotic CD66b⁺ granulocytes than the non-severe trauma group (2.9% [1.4–6.7] vs. 6.3% [3.7–10.9], p = 0.001), whereas the live, late apoptotic, and necrotic CD66b⁺ granulocyte fractions did not differ significantly between the two groups. Most T-cell death parameters were similar between the groups, although an exploratory increase in necrotic CD4⁺ T lymphocyte abundance was observed in the severe trauma group. IL-1ra levels were significantly higher in the severe trauma group than in the non-severe trauma group and were associated with ISS in both mediator-only and adjusted sensitivity regression analyses. Conclusions: Severe trauma was associated with reduced early apoptosis in the CD66b⁺ granulocyte compartment and elevated IL-1ra levels shortly after injury compared with non-severe trauma. These findings suggest that early immune alterations after severe trauma may involve compartment-specific granulocyte death patterns and counter-regulatory inflammatory responses rather than generalized changes across leukocyte populations. Full article

Cycas is one of the most ancient extant seed plant lineages on Earth, with a fossil record and evolutionary history dating back to the Carboniferous period. In this study, six screened SSR primer pairs were used to analyze the genetic diversity and population structure of 640 samples from 41 populations representing eight Cycas species collected from Guangxi, with the aim of providing a theoretical basis for the conservation of wild cycad resources in this region. The results showed that the average number of alleles (Na) across the eight species ranged from 1.945 to 3.643, the average effective number of alleles (Ne) ranged from 1.548 to 2.245, Shannon’s information index (I) ranged from 0.446 to 0.824, observed heterozygosity (Ho) ranged from 0.222 to 0.453, and expected heterozygosity (He) ranged from 0.293 to 0.443, indicating a moderate overall level of genetic diversity. Among the species, C. sexseminifera exhibited the highest genetic diversity (I = 0.824, He = 0.443), whereas C. guizhouensis showed the lowest (I = 0.446, He = 0.293). In addition, the interspecific genetic differentiation coefficient (F_st) ranged from 0.047 to 0.354, and gene flow (N_m) ranged from 0.456 to 5.094. Except for C. guizhouensis, relatively high levels of gene flow were detected among species. Principal Coordinates Analysis (PCoA) revealed that the 640 samples could be divided into three genetic clusters, which were not strictly consistent with species boundaries. AMOVA further indicated that 78% of the total genetic variation was distributed within populations, including 60% within individuals and 18% among individuals within populations. These findings provide important insights into the genetic diversity and differentiation patterns of Cycas species distributed in Guangxi and offer a theoretical foundation for their introduction, ex situ conservation, and scientific management of genetic resources. Full article

Vegetation phenology refers to the cyclical growth patterns of vegetation in nature, which are influenced by climatic conditions, human activities, and genetic factors. It plays an irreplaceable role in regulating carbon cycling and energy flow within natural ecosystems. However, the combination of a cloudy and rainy climate with a landscape characterized by the interplay of land and water and fragmented patches has long posed challenges for remote sensing phenological monitoring data, including a scarcity of valid observations, frequent temporal gaps, and spectral distortion in mixed pixels. These issues make it difficult to reliably support the needs of wetland phenological inversion and mapping. To address this issue, this study uses vegetation inversion in the Poyang Lake wetlands as a case study and reconstructs high-spatiotemporal-resolution time-series kNDVI data based on multi-source remote sensing data. Methodologically, we propose an improved and enhanced spatiotemporal adaptive reflectance fusion model, IESTARFM. This model enhances the homogeneity of similar pixel selection through adaptive matching windows and land cover constraints. Additionally, it explicitly incorporates cloud probability and time-lag factors into the weighting structure to systematically downweight unreliable observations, and further employs quadratic term corrections to account for the nonlinear growth response of kNDVI. Using the reconstructed dataset, key phenological information is extracted by combining third-order harmonic analysis with a dynamic thresholding method, thereby enhancing the robust characterization of seasonal trajectories under conditions of missing data and noise. Accuracy evaluation results show that the 10m/8d high-frequency kNDVI dataset reconstructed by IESTARFM achieves at least a 12.61% improvement in fusion accuracy compared to classical methods such as ESTARFM, STARFM, and FSDAF, with a maximum reduction in RMSE of 0.026, and effectively restores details in areas with thin cloud cover. The reconstructed kNDVI series achieved a coefficient of determination $R^2$ = 0.875 and RMSE = 0.066 relative to Sentinel-2 observations, indicating that the reconstructed series closely reproduces the reference imagery in both amplitude and spatial structure. The phenological parameters derived from kNDVI exhibit an RMSE of 4.81 days compared to field observations, demonstrating that the reconstructed time series reliably captures the timing of key phenological events. It should be noted that the proposed approach is designed for post-event time-series reconstruction and is not intended for real-time forecasting. In summary, this study collaboratively enhanced the reliability of high-resolution index time-series reconstruction and phenological identification in cloudy and rainy wetlands through three key aspects: cloud noise suppression, heterogeneous boundary preservation, and nonlinear growth characterization. It provides a generalizable technical foundation for dynamic monitoring of wetland vegetation, ecological restoration assessment, and refined management in regions with frequent cloud and rainfall. Full article

The Arabian Sea is a key region for global marine biogeochemical research, yet the distribution characteristics and influencing factors of dissolved oxygen and chlorophyll a concentration in its central oxygen minimum zone still require further in-depth investigation. Based on survey data and reanalysis data from 2024, this paper analyzes the distribution characteristics and underlying causes of chlorophyll a concentration and dissolved oxygen using empirical orthogonal function (EOF) decomposition of chlorophyll a concentration and dissolved oxygen saturation along the depth direction, combined with the distribution of the barrier layer, Ekman pumping induced by wind fields, and the diagnostic vertical velocity distribution calculated from ADCP-observed flow velocities. Taking approximately 10° N as the boundary, the chlorophyll a concentration in the layer shallower than 35 m exhibits a distribution pattern of high in the northwest and low in the southeast, while the water layer between 45 m and 95 m shows a pattern of low in the northwest and high in the southeast. A thick barrier layer exists in the southeastern region, whereas the barrier layer in the northwestern region is thinner or absent, resulting in lower surface chlorophyll a concentration in the southeast. ADCP observations indicate that horizontal flow velocities are higher in the south, bringing oxygen-rich water from the south, which leads to higher dissolved oxygen saturation in the southern region compared to the northern region in water shallower than 45 m. At the 65 m water layer, the higher chlorophyll a concentration in the south may result in relatively low dissolved oxygen. The hypoxic zone (dissolved oxygen saturation less than 30%) begins to appear at depths below 105 m, with its southern boundary located between 9° N and 11° N, and this boundary gradually shifts northward as depth increases. The diagnostic vertical velocity between 9° N and 11° N is higher than that in other regions, which may hinder the northward movement of oxygen-rich water from the south. In the southern region, influenced by wind stress, the vertical water movement induced by Ekman pumping is relatively significant, which may lead to a slight increase in dissolved oxygen saturation in water layers with a depth below 125 m. Full article

To investigate the flow pattern evolution and phase-change characteristics of a two-phase loop thermosyphon under high heat flux conditions with different filling ratios, a visual experimental study was conducted. The filling ratio ranged from 36.8% to 92.3%, with a maximum heat flux of 240 W/cm². The results indicate that at a filling ratio of 81.6%, bubbly flow is observed under low heat flux (30–60 W/cm²), with a bubble detachment size of approximately 2 mm. When the heat flux increases to 90–180 W/cm², intermittent boiling occurs, and the flow pattern cycle shifts from bubbly flow to single-phase flow and back to bubbly flow, with the period shortening from 5.92 s to 4.92 s. At heat fluxes ≥ 200 W/cm², intermittent boiling disappears, transitioning to stable high-velocity subcooled flow boiling, and the detachment size decreases from 1951 μm to 762 μm. At a filling ratio of 65.3%, bubbly and slug flow are observed under low heat flux (30–120 W/cm²). Intermittent boiling appears at heat fluxes ≥ 150 W/cm², characterized by a cycle of “churn flow–bubbly flow–single-phase flow–bubbly flow–churn flow”. This intermittent boiling persists under high heat flux (200–220 W/cm²) without transitioning to stable flow boiling. At a filling ratio of 36.8%, large-scale slug bubbles (maximum 37 cm) form under 30–60 W/cm², transitioning to churn flow at 90–120 W/cm². Instantaneous dryout occurs at 150 W/cm², followed by complete dryout at 180 W/cm². The visualization results reveal the critical heat flux for flow pattern transitions and the periodic characteristics of intermittent boiling under different filling ratios. Full article

Under climate warming, frequent short-duration extreme precipitation events in coastal megacities exacerbate urban waterlogging, whereas the associated convective mechanisms over complex underlying surfaces remain poorly understood. On 21 July 2023, an extreme short-duration rainfall event (14:00–19:00 LST, peak intensity 127.3 mm h⁻¹) struck Shanghai under weak vertical wind shear (VWS) conditions that cannot be fully explained by classic storm dynamics. Based on multi-source observations, this study shows that the middle and lower troposphere was controlled by warm, moist southwesterly flows, with highly favorable thermodynamic conditions (CAPE ~3300 J kg⁻¹, CIN near zero) that only required weak local lifting to trigger convection. Both 0–1 km and 0–6 km VWS were below 7 m s⁻¹, maintaining stable, upright updrafts that favored high precipitation efficiency. The formation and maintenance of the quasi-linear convective system and the resultant extreme precipitation depended critically on the southerly sea breeze, local mesoscale convergence, and cold pool feedback. Convergence induced by the complex underlying surface (urban friction, high-rise building blocking) played important roles in initiating convective cells, while the interaction between cold pool outflows and the sea breeze from the East China Sea and Hangzhou Bay sustained the system, which evolved into a unique “fish-shaped” rainstorm. Driven by dominant convective propagation toward unstable inland areas, the system moved west–southwestward across the coastal zone into central urban Shanghai. This mechanism differs from both the cold pool–VWS balance under strong shear and the urban convective relay propagation mode under weak VWS documented in previous studies. These findings provide new observational insights into the formation and maintenance of weak-shear, short-duration extreme rainfall in coastal megacities, and carry important implications for identifying convectively prone zones, optimizing spatial development patterns, and improving climate-resilient land management and urban planning practices. Full article

China is at a critical stage in the coordinated promotion of ecological civilization construction, rural revitalization, and new urbanization strategies. How to scientifically coordinate the transformation of territorial spatial utilization (TSU), such as that of ecology–agriculture–urban spaces, and to build an ecological security pattern (ESP) has emerged as a critical task facing regional sustainability. To address the above problem, this study constructs a research framework to reveal the response characteristics of ESP to TSU transformation by adopting the source–surface–flow continuous field model and geographic grid analysis methods. Taking the Qinba–Dabie convergence area in China, with typical transitional characteristics and regional representativeness, as the study area, this study quantitatively analyzes the spatiotemporal evolution of the comprehensive index of TSU degree, as well as the ecological source, resistance, and flow indices across the whole territory. With the geographic grid method adopted to unify the spatial analysis grain between ESP and TSU transformations, this study further explores the response characteristics of ESP under TSU transformation. The main study findings are presented as follows: With the transformation of TSU, ESP elements such as the ecological source index, resistance index, and flow index exhibited significant spatial differentiation, and a nonlinear relationship could be observed between the TSU degree index and the ESP elements. On this basis, this study further explores and constructs a zoning method system for regional TSU control oriented to ESP, formulates targeted protection and restoration strategies, offering theoretical and practical references for the scientific compilation of territorial spatial planning and the conservation and restoration of ESP. Full article

Background/Objectives: Intramedullary tumors are uncommon spinal cord lesions that account for a small proportion of central nervous system neoplasms but are associated with a high risk of neurological morbidity. Accurate preoperative characterization is essential because therapeutic strategies, surgical planning, and functional prognosis depend strongly on tumor biology and growth behavior within the confined spinal cord environment. This study aims to characterize the radiological phenotype of intramedullary tumors and to identify imaging patterns that may assist in lesion characterization and diagnostic stratification. Methods: A retrospective analysis of preoperative MRI findings in patients with histopathologically confirmed intramedullary tumors was performed. Preoperative MRI examinations were systematically analyzed to describe imaging features according to tumor histology using conventional sequences (T1-weighted, T2-weighted, and contrast-enhanced imaging). Results: Distinct radiological phenotypes were observed across a wide spectrum of lesions. Glial tumors, including subependymoma, ependymoma, pilocytic astrocytoma, diffuse midline glioma H3K27M, glioblastoma, high-grade astrocytoma with piloid features, ganglioglioma, and diffuse leptomeningeal glioneural tumors, demonstrated variable combinations of cord expansion, margin definition, enhancement patterns, and tract involvement, reflecting differences between expansile and infiltrative growth. Secondary tumors such as metastases frequently exhibited aggressive imaging features, including extensive edema and intense or heterogeneous enhancement. Vascular lesions, including hemangioblastoma and cavernoma, showed characteristic vascular signatures, such as nodular enhancement with flow voids or susceptibility-related signal changes. Developmental lesions, such as epidermoid cysts, neurenteric cysts, and lipoma, displayed distinctive signal characteristics, especially on diffusion and T1, that aided differentiation from neoplastic processes. Conclusions: In conclusion, the structured radiological interpretation functions proposed herein are not only useful for diagnostic purposes, but could also be useful for risk stratification and therapeutic guidance. Full article

Multisource remote sensing data is utilised for the purpose of monitoring annual and interannual changes associated with climate change in the water bodies of the Chotts of Merouane and Melrhir, which are located in the Zone of Chotts in North Africa. These endorheic depressions are distinguished by recurrent flooding events of varying magnitude and frequency, which are contingent on fluctuations in climate parameters. It has been determined that certain cities located within the surrounding watersheds, such as Biskra, are subject to the intermittent threat of severe flooding. This has been shown to result in land degradation and soil salinisation during the drying-up process. A detailed examination of chronological data from the 1960s onwards reveals a decline in the frequency of flooding in Chott Melrhir in recent years. It is noteworthy that the region has not experienced any substantial flooding since 2020. This phenomenon is concomitant with the marked decline in precipitation levels observed in the region. Since 1980, there have been at least ten significant floods, resulting in varying degrees of damage and disruption. In contrast, Chott Merouane exhibits a more consistent hydrological pattern, with water flowing almost year-round due to wastewater and the drainage of the palm groves by the Oued Righ. Until the 1970s, the occurrence of flooding in the region was exclusively attributable to the direct overflow of the Biskra River and its tributaries. However, from the 1980s onwards, a new type of flooding emerged, linked to insufficient infiltration and drainage capacity in the soil and sewage systems during rainfall that was sometimes considered normal. The hydrological regime in the area has severe ramifications for the water supply and the state of the oases, which are vulnerable to salinisation. Full article

The rim-driven thruster (RDT) adopts a shaftless design, thus eliminating the mechanical excitation and frictional noise caused by shaft movement. In this study, dynamic and noise prediction models of the composite-material RDT have been developed, and numerical examples are given to study the characteristics of radiated-noise RDTs. Studies have shown that the layup method of composite materials has a significant impact on the natural frequency of the blade’s free vibration and further affects the spectral characteristics of the RDT flow-induced noise. In the low-frequency range, the flow-induced load has not yet caused the blade to vibrate, and the noise is mainly hydrodynamic noise. As the frequency increases, the blade starts to vibrate, and a distinct flow-induced vibration spectral pattern is observed. Compared with metal blades, composite material blades can effectively suppress the amplitude of the flow-induced noise spectrum and reduce the total noise of the propeller. The composite RDT generally exhibits lower noise levels than the metal RDT, with a difference of approximately 10 dB observed at the resonance frequency. By comparing the three RDTs with different fiber layer-ups, it can be observed that the fiber-laying angles have a direct impact on the resonance characteristics of the blade and its flow-induced noise. It can be concluded that composite materials have significant potential in the low-noise design of RDT, and a reasonable layup design of the blades can achieve excellent noise-control effects. Full article