Search Results (195)

The interlayer oxidation zone-type Mengqiguer uranium deposit in the southern Yili Basin is a typical sandstone-hosted uranium deposit in northwest China, and the lower member of the Jurassic Xishanyao Formation is its main ore-hosting stratum. However, mineralogical and geochemical responses to redox evolution in the deposit have not been systematically constrained. In this study, we carried out detailed petrographic observation, X-ray diffraction analysis, electron probe microanalysis, and whole-rock geochemical analyses on samples from the interlayer oxidation zone in the lower member of the Xishanyao Formation. Kaolinite and illite are the dominant clay minerals in the deposit, with higher contents in oxidation zones than in transition and unaltered zones, while the illite–smectite mixed-layer content shows the opposite trend. The main uranium minerals are uranium oxides and coffinite. U, S and organic carbon are enriched in the transition zone, while the Fe³⁺/Fe²⁺ ratio increases with the oxidation degree. Comprehensive analysis on clay minerals shows that the ore-forming fluids evolved from acidic oxidized meteoric fluids to weakly alkaline reduced fluids; the uranium was mainly derived from the leaching of uraniferous sandstone. The formation of the deposit is controlled by sedimentary facies, tectonic uplift, organic–inorganic fluid interaction and redox reaction. This study provides detailed mineralogical and geochemical evidence for the metallogenic mechanism of interlayer oxidation zone-type uranium deposits, and has important guiding significance for uranium prospecting in the Yili Basin. Full article

Electrohydrodynamic effects can significantly alter transport processes in reacting flows, even when the plasma is weakly ionized. However, predictive modeling of such plasma–flame interactions remains challenging due to the multiscale coupling among charge transport, fluid motion, and chemical kinetics. This study presents a charge-transport closure model to investigate electrohydrodynamic influences on laminar non-premixed flames. A two-dimensional computational framework in cylindrical coordinates is used to simulate plasma-assisted methane–air diffusion flames under weak electric-field conditions representative of practical combustion environments. To represent plasma–flow coupling in a computationally feasible yet physically consistent manner, a charge-transport formulation based on the drift–diffusion approximation is employed. The model solves transport equations for representative positive and negative charge carriers coupled with Poisson’s equation for the electric potential to obtain a self-consistent electric field. This formulation assumes a weakly ionized regime for low-temperature plasma-assisted combustion, in which neutral species dominate the mass and momentum transport, while ionization chemistry is simplified and charge transport primarily influences the flow through electrohydrodynamic body forces and Joule heating. Assuming a weak electric field, the steady flamelet model is applied, in which plasma effects primarily influence scalar transport and local thermal balance rather than inducing significant bulk ionization dynamics. The governing equations are discretized using a high-order compact finite-difference scheme that provides improved resolution of steep gradients in temperature, species concentration, and space-charge density near thin reaction zones. The canonical laminar flame model configuration was validated using the established laminar methane–air diffusion flame benchmark, and steady-state spatial profiles of key transport properties were evaluated. Two-dimensional analysis identified the discharge coupling location as an important factor. The application of discharge in the fuel-air mixing region leads to a clear restructuring of the flame. When the discharge is activated, electrohydrodynamic forcing and ion-driven momentum transfer produce a highly localized, columnar flame with sharp gradients and a confined reaction zone. Compared with the baseline case, the plasma-assisted flame localizes the OH-rich reaction zone, confines the high-temperature region into a narrow column, and enhances downstream H₂O formation. Full article

Spectral remote sensing enables efficient acquisition of large-scale land surface information and is a key approach for monitoring soil salinity content (SSC). However, surface mulching significantly alters the spectral reflectance responses of croplands, increasing the uncertainty of SSC retrieval using remote sensing. This study aimed to systematically identify SSC-sensitive spectral features under different mulching conditions and to evaluate the effects of spatial resolution on SSC–spectral relationships. Multi-resolution datasets were constructed based on plastic mulch geometric parameters, and SSC–spectral relationships were analyzed using correlation methods and recursive feature elimination (RFE). Results indicate that under near-ground ultra-high-resolution conditions, the correlation between inter-mulch bare soil spectral features and SSC was weakly influenced by mulch type, and distinguishing mulch types provides limited improvement in inter-variable relationships. Pearson’s r exceeded 0.40 for both white- and black-mulched samples, and distinguishing mulch types provided only marginal gains in model accuracy (RFR–RFE R² = 0.9524 for white-mulched and 0.9252 without distinguishing; R² = 0.9387 for black-mulched). In contrast, under multi-resolution settings at the field scale, separating black-mulched, white-mulched, and non-mulched fields significantly enhanced the correlation between spectral indices (SIs) and SSC, with the coefficient of determination (R²) based on the recursive feature elimination (RFE) algorithm increasing by up to 0.28. The highly sensitive SIs of non-mulched farmland are generally consistent with those of white-mulched farmland but differ markedly from those of black-mulched farmland. Scale optimization analysis further indicated that the optimal spatial resolution was 1.35 m for white-mulched and non-mulched farmland. Black-mulched farmland performed best at 5.4 m, likely because stronger spectral masking by black mulch increases mixed-pixel dominance and benefits from spatial aggregation. These findings provide methodological guidance and practical approaches to accurately retrieve SSC in plastic-mulched croplands and to determine the optimal image spatial resolution. Full article

To address the imbalance between the shearing–mixing quality and energy efficiency of deepwater drilling mud mixers and breakthrough the limitations of existing independent single-objective analytical perspectives, the Eulerian solid–liquid two-phase numerical simulation was adopted in this study. Combined with a modified shear rate algorithm and a triple energy coupling analysis of shear rate, Lamb vortex energy and Enstrophy, the energy conversion and particle dispersion mechanisms inside the mixer under variable flow rates and solid concentrations were systematically investigated, and the performance differences between the first-generation and optimized mixers were clarified. Structural optimizations including an additional modular stator with a designed shear gap of 2 mm, improved blade profiles and shear angles to 14.2°, and miniaturized radial dimensions of the impeller and volute were implemented to achieve compact structural upgrading. The results demonstrate that high-energy regions are concentrated in the rotor–stator gap. After optimization, the peak shear rate increases from 12,010 s⁻¹ to 17,092 s⁻¹, representing a 42.3% enhancement. The peak Lamb vortex energy and the mean Enstrophy rise by 8.6% and 18.9%, respectively. Shear rate correlates weakly positively with Lamb vortex energy and strongly negatively with Enstrophy, revealing vortex sensitivity to flow velocity and tight coupling of viscous dissipation to particle concentration. The outlet coefficient of variation C_v decreases by 59.6%. Higher flow rates strengthen the coupling of shear and vortex energy, and higher solid concentrations weaken stator shear performance. The optimized mixer achieves synergistic improvements in shear efficiency and mixing quality, with over 50% enhancement in mud dispersion stability and more than 15%. Full article

Neoproterozoic iron formations (NIFs), deposited during Cryogenian glaciation events, are critical for understanding early Earth oxidation events and the evolution of glacial–interglacial environments. Apatite, a common accessory mineral in iron formations, holds significant implications for sedimentary environments and diagenetic processes, but these aspects remain underexplored. This study focuses on the Hengyang NIF in the Nanhua Basin, South China. Using whole-rock geochemistry and major and trace element analysis of apatite, we investigate the environmental significance of apatite and associated diagenetic processes. Our results show that the Hengyang NIF are formed through the mixing of low-temperature hydrothermal fluids, seawater, and terrigenous detrital materials, with hydrothermal contributions increasing progressively from the bottom to the top of the iron formation layers. Whole-rock geochemical proxies indicate that the depositional water column evolved from relatively oxidizing to weakly oxidizing conditions. The study further demonstrates that the rare earth element patterns in apatite, characterized by middle rare earth element enrichment, are primarily controlled by porewater chemistry during diagenesis. In contrast, Ce anomalies and the V/Cr and V/(V + Ni) ratios in apatite, which are strongly influenced by fluid–rock interactions and magnetite recrystallization, no longer reliably reflect the primary depositional environment. The Th/U ratio in apatite, due to its geochemical stability, aligns with whole-rock trends and serves as a more reliable redox proxy. Based on these findings, we propose a three-stage depositional-diagenetic model: the early and late stages are characterized by high-energy, rapid sedimentation with minimal diagenetic modification, while the middle stage is dominated by low-energy, stagnant conditions with slow sedimentation rates, leading to prolonged diagenesis and significant decoupling of mineral geochemical signatures. This study emphasizes the need to distinguish between sedimentary and diagenetic signals when using mineral geochemical proxies to reconstruct paleoenvironments and provides new insights into the genesis of Neoproterozoic iron formations. Full article

Uranium tailings, the primary solid waste from uranium production, are characterized by vast quantity, high radioactivity, and substantial environmental risks. This study systematically investigated a combined magnetic separation–reverse flotation process for extracting quartz from uranium tailings. Process mineralogical analyses, including XRD, MLA, and XRF, revealed that the tailings are mainly composed of quartz, potassium feldspar, albite, and almandine, with quartz accounting for approximately 43% and non-magnetic/weakly magnetic materials making up 91.06% of the total. The experimental results showed that after high-intensity magnetic separation at 1.8 T, the SiO₂ grade increases to 76.36%. Under the conditions of pH 2, a mixed collector system of sodium oleate and dodecylamine at a mass ratio of 1:7, and a total dosage of 2000 g/t, the SiO₂ grade further rises to above 90%. This work proposes a green process route for extracting quartz from uranium tailings, which not only achieves a reduction in radioactive tailings but also successfully obtains high-grade quartz products. Full article

Motivated by the persistent short-baseline anomalies that hint at the possible existence of physics beyond the standard three-flavor paradigm, we study the phenomenology of light sterile neutrinos in the minimal (3 + 1) framework using two future experiments: the MuOn-decay MEdium-baseline NeuTrino beam experiment (MOMENT) and the Deep Underground Neutrino Experiment (DUNE). We place constraints on active–sterile mixing parameters, probe CP-violation discovery potential, and examine correlations between the standard Dirac CP phase and the additional CP phases arising from active–sterile mixing to quantify phase degeneracies. We present exclusion limits and demonstrate the crucial role of the near detector in improving sensitivities by one or two orders of magnitude compared to a configuration with only the far detector. We find that the presence of sterile neutrinos can reduce the CP-violation sensitivity in long-baseline neutrino oscillation experiments. For large sterile mass splittings, the rapid oscillations average out, leading to strong parameter degeneracies in DUNE. In contrast, MOMENT retains strong sensitivity to CP violation and efficiently disentangles the standard and sterile CP phases. Our results highlight the strong complementarity between DUNE and MOMENT and show that their combined capabilities provide a powerful test of the light sterile neutrino hypothesis in regions of the parameter space that remain weakly constrained by current data. Full article

In this study, we investigate a class of mixed fractional partial integro-differential equations (FrPI-DE) involving symmetric singular kernels. The considered model problem involves Caputo fractional derivatives and integral operators that describe spatial interactions in a bounded domain. For the purpose of analysis, the original problem is reformulated in the form of a nonlinear Volterra–Fredholm integral equation (NV-FIE). The existence and uniqueness of the solution are established by the Banach fixed point theorem. To compute numerical solutions, a modified Toeplitz matrix method (TMM) is proposed to handle the singular kernel efficiently. The method transforms the integral equation to a system of nonlinear algebraic equations, which can be solved numerically. The convergence properties of the resulting numerical scheme are analyzed and illustrate the effectiveness of the method by providing numerical examples involving logarithmic, Cauchy-type, and weakly singular kernels. Numerical results indicate that the proposed method provides highly accurate approximations and exhibits stable convergence behavior for different parameter values. Furthermore, these results confirm the effectiveness and reliability of the proposed method for solving fractional integro-differential equations that include symmetric singular kernels. Full article

Groundwater is a strategic resource for maintaining ecological balance and supporting human development in arid inland basins. However, under the dual pressures of climate change and human activities, it faces threats in both quantity and quality. This study selects the Chahan Usu River watershed in the eastern Qaidam Basin, a typical arid inland basin on the Tibetan Plateau, to assess the current quality of groundwater resources and reveal the formation mechanisms and material sources of its hydrochemistry. The results show that the groundwater in the watershed is generally weakly alkaline, with some areas exhibiting high salinity. The dominant cations and anions are Na⁺ and Cl⁻, respectively. The hydrochemical type is mainly Cl-Na, with a minority being mixed Cl-Mg·Ca. Overall, the groundwater in the watershed is suitable for domestic use. However, in the middle and lower reaches of the Chahan Usu River, nitrate and ammonia nitrogen contamination reduce its suitability. Meanwhile, although long-term use of this groundwater would not lead to soil degradation, its widespread high salinity and high sodium content make it unsuitable for irrigation. Water–rock interactions with evaporites and silicate rocks are the main mechanisms controlling groundwater chemistry in the watershed. Among them, halite minerals contribute most of the Na⁺ and Cl⁻, while sulfate minerals provide Ca²⁺ and SO₄²⁻. In addition, cation exchange is widespread. This study provides a reference for ensuring the security and sustainable development of groundwater resources on the plateau. Full article

This study addresses the challenges posed by weakly cemented strata in mine tunnels, where surrounding rock softens and deforms upon water exposure, which promotes the development of seepage pathways, and exhibits insufficient stability in bolt (cable) support systems. This study conducts laboratory grouting tests using silica sol on typical weakly cemented sandstone from Xinjiang mining areas. The mineral composition and pore structure were characterized using XRD, SEM, and mercury porosimetry. The injectable mixing ratio parameters for silica sol and the catalyst were determined through viscosity-time evolution tests. Grouting was performed using a custom-built constant-pressure grouting apparatus. After curing, unconfined compressive strength (UCS) and porosity-permeability tests were conducted to evaluate the micro-mechanism of grouting effects on the mechanical and permeability properties of weakly cemented sandstone. The results indicate: (1) The sandstone exhibits a high clay mineral content of 39.8%, dominated by illite. Its pores are primarily small-scale (10–100 nm), accounting for 79.31% of the total pore volume. This scale matches that of silica sol nanoparticles (approximately 9–20 nm), facilitating slurry penetration into micro-pores; (2) microscopic analyses reveal that silica sol effectively reconstructs pore structures through permeation filling and surface coating. Compared to KCl-induced gelation (with approximately 8% gel coverage), NaCl-induced gelation forms a more continuous gel film with more complete pore filling, achieving coverage of around 22%. Furthermore, the larger surface area of the gel aggregates indicates a more thorough filling of micro- and nano-pores, effectively enhancing rock mass compactness. (3) Permeability decreased from 6.91 mD to 3.55 mD, a reduction of 48.6%, while porosity decreased from 16.94% to 13.55%, showing a phased reduction during the grouting process; (4) following pressure grouting stabilization, the uniaxial compressive strength of sandstone increased appropriately by approximately 7–14%, while the elastic modulus rose by about 18–28%. The failure mechanism shifted from shear brittleness to a shear-tension composite state, with enhanced post-peak bearing capacity. These findings provide support for optimizing silica sol grouting parameters in weakly cemented strata tunnels and for the synergistic reinforcement of rock mass permeability and strength. Full article

Understanding how ecological dominance aligns with culturally and economically valued plant use is critical for participatory forest management. This study integrated vegetation structure and ethnobotanical valuation to assess angiosperm importance across three forest strata (Mixed Deciduous Forest (MDF), Dry Dipterocarp Forest site 1 (DDF1), and Dry Dipterocarp Forest site 2 (DDF2)) within the Ngao Model Forest, Northern Thailand. Fifteen 10 × 10 m vegetation plots (five per forest stratum) were surveyed to calculate the Importance Value Index (IVI), and 198 semi-structured interviews were conducted to derive the Use Value Index (UVI) and a standardized Socio-Economic Value Index (SEVI). A total of 112 angiosperm species were recorded across forest types, with strong structural dominance by dipterocarps in DDF sites and greater compositional heterogeneity in MDF. Spearman rank correlation analysis supported the working hypothesis that ecological dominance is only weakly associated with cultural and socio-economic importance. IVI showed weak but significant positive correlations with UVI (ρ = 0.288, p < 0.05) and SEVI (ρ = 0.300, p < 0.05), indicating partial but limited alignment between structural abundance and livelihood value. Several species with moderate or low IVI exhibited disproportionately high UVI and SEVI scores, reflecting their importance in food, medicinal, and commercial use categories. Conversely, certain canopy dominants showed limited ethnobotanical significance. These findings demonstrate that ecological abundance alone is an insufficient proxy for community-defined species value. Integrating structural, cultural, and socio-economic indices provides a more comprehensive framework for identifying priority species in community-managed forest systems. The IVI–UVI–SEVI comparative approach offers practical insights for model forest governance by distinguishing ecological dominants, multipurpose livelihood species, and culturally significant taxa occurring outside forest interiors. This multidimensional valuation framework strengthens participatory forest management and biodiversity prioritization in heterogeneous tropical landscapes. Full article

This study explores the hydrochemical and thermal characteristics of a fault-controlled geothermal field within the Northern Qinghai Lake Coalfield Area on the northeastern Qinghai–Tibetan Plateau (QTP). This research integrates hydrochemical analyses, isotopic tracers, and the regional geological framework to define hydrochemical signatures, identify recharge sources and flow paths, assess cold–hot water mixing, estimate reservoir temperatures, determine circulation depths and residence times, and explain the geothermal system’s formation. Systematic sampling included geothermal waters, cold springs, and surface waters, followed by laboratory analysis of major ions, stable isotopes (δ²H, δ¹⁸O), radiocarbon (¹⁴C), and tritium (³H). The geothermal water is categorized as a low-temperature, weakly acidic to near-neutral HCO₃-Ca•Mg type, exhibiting temperatures from 35.6 to 46.2 °C. Isotopic analyses indicate that cold spring and river waters align with the local meteoric water line, while geothermal waters display distinct isotopic signatures, suggesting deeper circulation. A silica–enthalpy mixing model reveals substantial cold-water mixing during upwelling, with mixing ratios between 74.5% and 85.6%. The corrected recharge elevation is estimated to be 4378–4456 amsl, implying a primary recharge zone in the branch of the Qilian mountains—the middle section of Datong Mountain to the northeast. Geothermometry, employing quartz and chalcedony temperature scales and accounting for mixing, estimates reservoir temperatures of 150–202 °C. The calculated circulation depth spans 3211–4291 amsl. Low tritium levels and carbon dating suggest a deep-cycling system predating 1952, characterized by deeply circulating “ancient water”. The geothermal system’s development is associated with regional tectonics, fault systems, and the Kesuer Formation (J_xk) acting as the reservoir. This study provides a scientific foundation for the development and sustainable use of geothermal resources in the northern Qinghai Lake region and offers insights applicable to comparable fault-controlled geothermal systems across the QTP. Full article

The Tawenchahanxi mining area, situated in the southeastern Qimantagh region of the East Kunlun Orogenic Belt, hosts a skarn-type Fe–polymetallic deposit associated with acidic granitic intrusions. Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating yields ages of 233.3 ± 1.2 to 234.3 ± 1.1 Ma for a granodiorite and 397.7 ± 1.4 Ma for a quartz porphyry, indicating two magmatic intrusive events during the Early Devonian and Late Triassic. The Early Devonian quartz porphyry is characterized by high ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ (72.39%–74.04%), high total alkalis (7.81%–7.83%), high TFeO (>1.0%) and high crystallization temperatures (~865 °C), together with low CaO (1.64%–1.70%) and MgO (0.61–0.65%), which are all consistent with A-type granite affinity. The granodiorite exhibits aluminum saturation index (A/CNK) values of 0.67–1.07 (metaluminous to weakly peraluminous) and belongs to the high-K calc-alkaline series. It exhibits moderate negative Eu anomalies (δEu = 0.71–0.83), and zircon saturation temperatures of ~748 °C, collectively indicative of I-type granite affinity. Both rock suites display depletion in Nb, Ta, and Sr and enrichment in Rb and LREEs. Zircon Hf isotopic data show εHf(t) values of −0.64 to 0.57 for the quartz porphyry and −4.37 to −1.06 for the granodiorite, indicating derivation primarily from partial melting of ancient crust with variable mantle contributions. These intrusions formed during post-collisional extensional (Early Paleozoic) and collisional to post-collisional (Late Paleozoic–Early Mesozoic) stages, respectively, associated with mantle magma underplating and crust–mantle mixing. Such processes formed the material basis for the polymetallic mineralization in the Tawenchahanxi district by providing Fe–Cu–Pb–Zn and other ore-forming elements from deeper crust. Full article

Addressing the challenge of stable cloud velocity field estimation under complex sky conditions in ground-based cloud imaging, this paper proposes a comprehensive 3D cloud velocity calculation framework. The methodology integrates binocular stereo vision geometry, self-supervised deep feature learning, and graph attention-based matching. First, a self-supervised feature detection and description model tailored to the radiometric characteristics of cloud images is developed. By incorporating a homography adaptation strategy constrained by physical priors, the model acquires robust feature representations for weakly textured and highly deformable cloud masses without requiring labeled datasets. Subsequently, a Transformer-based graph neural network matcher is employed to establish global feature correspondences across both cross-view and cross-temporal dimensions, thereby substantially augmenting matching robustness. On this basis, the framework establishes a rigorous calibration model for fisheye cameras to derive cloud base height (CBH) via binocular geometry. These geometric constraints are then coupled with sequential feature tracking results to construct 3D velocity inversion equations, enabling an end-to-end mapping from 2D pixel coordinates to 3D physical space and providing direct estimation of physical cloud motion velocity in meters per second (m/s). The experimental results show that the proposed method extracts 4.5 times more feature points than the traditional SIFT method. Furthermore, the Pearson correlation coefficient for cloud motion trends in continuous sequences reaches 0.662 relative to baseline models, indicating good relative consistency in motion estimation. The framework achieves high-precision and stable velocity estimation across diverse cloud types, including cirrus, cumulus, stratus, and mixed clouds. Full article

Given the concurrent challenges of declining participation rates in STEM education and the growing societal demand for STEM expertise, understanding and implementing motivation-enhancing interventions is essential for safeguarding the future STEM workforce and enabling societies to respond to technological and societal challenges. This narrative literature review synthesized studies published between 2014 and 2025 and aimed to elucidate the underlying rationales and drivers of motivation-focused STEM research, as well as to identify and evaluate interventions designed to increase students’ motivation for STEM. The synthesis identified four recurring drivers of motivation-focused STEM research: increasing demand for the STEM workforce, inequities in STEM participation, the strategic socioeconomic importance of STEM and declining student motivation over time. Interventions were analytically grouped into six categories: motivational STEM interventions/programs, community engagement initiatives, hands-on learning approaches, supportive instructional materials and educational technologies, extracurricular interventions, and interventions leveraging social support. Overall, the synthesis indicated that motivational effects were shaped less by the setting of an intervention and more by its implementation characteristics, including duration, intensity, pedagogical integration and alignment with students’ motivational needs. Interventions that were sustained and well-integrated tended to have more positive effects, whereas short or weakly embedded approaches yielded mixed or transient outcomes. The insights presented here provide structured guidance for educators and policymakers seeking to foster more motivated STEM learners, with potential implications for improving retention in STEM pathways and addressing the growing societal demand for STEM professionals. Full article