Search Results (5,667)

This study investigates the mechanical behavior of jointed rock mass tunnels through numerical simulations using UDEC software. Focusing on the time-dependent variation in joint shear stiffness, a theoretical model is proposed to characterize the evolution of shear stiffness over time. Based on this model, numerical simulations are conducted to analyze tunnel stability and associated deformation patterns. A variable shear stiffness model is first established in UDEC, which effectively captures the evolution of shear creep displacement along rock joints. Incorporating this model, an adaptive support scheme involving locally extended rock bolts is introduced to improve long-term tunnel stability. The proposed approach is further validated through a comparative analysis with field monitoring data obtained from a tunnel in Yunnan Province. The results indicate that creep effects significantly influence tunnel behavior, leading to rapid increases in crown settlement and expansion of the surrounding rock disturbance zone during the early stages following excavation. Optimizing the bolt layout is shown to effectively reduce the extent of the disturbed zone and enhance the tunnel’s load-bearing capacity. Finally, a novel reinforcement optimization method for jointed rock mass tunnels is proposed, along with a key threshold value for assessing tunnel stability, thereby providing theoretical support for practical engineering applications. Full article

With the growth of urban zones and the increasing need for energy, the use of renewable energy solutions in the built environment becomes a must. Due to their small size and the ability to capture wind from any direction, vertical-axis wind turbines are an alternative to conventional wind energy generators. However, the use of these turbines in the built environment faces difficulties due to performance inefficiencies, particularly because of the intricate aerodynamic characteristics of the blades. This work investigates a method for increasing the efficiency of VAWTs by addressing blade-to-blade interactions using Computational Fluid Dynamics simulations. The research aims to improve turbine design for urban locations, which motivates the application context of the study. The present numerical model employs a uniform inflow to isolate blade–blade interaction mechanisms under controlled conditions. The paper presents a design that minimizes aerodynamic losses, decreases turbulence-induced drag, and increases overall energy capture efficiency by modeling different blade configurations and their interactions. The performance of four asymmetric configurations of blade chord and radius was numerically studied and compared to a symmetric configuration. Full article

This study investigates the feasibility of incorporating recycled concrete aggregate (RCA) as a full replacement for fine aggregate in high-performance concrete (HPC). Five mixtures containing 0%, 25%, 50%, 75%, and 100% RCA were experimentally evaluated. Hardened density, compressive strength, splitting tensile strength, flexural strength, water absorption, microstructure (SEM), and carbon footprint were analyzed. Results showed a near-linear density reduction of 5.8% at 100% RCA due to lower specific gravity and higher porosity of RCA. Mechanical performance decreased with RCA content: compressive strength reduced from 78 MPa to 53 MPa (−32%), splitting tensile strength from 6.2 to 4.2 MPa, and flexural strength from 7.6 to 5.0 MPa. Water absorption increased by 42%, indicating increased permeability. SEM analysis revealed a weakened and porous interfacial transition zone (ITZ) surrounding RCA particles, explaining strength reduction. Carbon footprint analysis showed a slight increase in emissions with RCA due to cement dominance and RCA processing energy. Results confirm that RCA enhances material circularity but introduces a performance–durability trade-off, requiring optimized mix design and SCM integration for structural applications. Full article

The Siberian moth, Dendrolimus sibiricus Tschetverikov, is one of the most destructive conifer pests in Northern Asia, causing severe ecological and economic losses. In Russia, its range overlaps with that of the closely related pine-tree lappet Dendrolimus pini (L.), and this raises the potential for hybridization and complicates accurate identification, particularly in the context of the potential westward expansion of D. sibiricus. Here, we present the first comprehensive morphometric analysis of male genitalia aimed at distinguishing these two major forest pests and their hybrids. The study was based on D. sibiricus and D. pini specimens collected during the last 130 years (1894–2024) across Europe and Asia, including their hybrids reared indoors by crossing D. pini females with D. sibiricus males in 1956 and preserved in the collection of the Zoological Institute of the Russian Academy of Sciences (St. Petersburg, Russia). Overall, 70 permanent genitalia slides were prepared (33 D. sibiricus, 33 D. pini, and 4 hybrids), and the following genital structures were measured: valva and harpe length, aedeagus width and length, and cornuti length. Dendrolimus sibiricus had significantly larger genital structures compared to D. pini: 74% longer harpe, 32% longer valva, and a 28% wider and longer aedeagus. In contrast, in D. sibiricus cornuti were 21% shorter than in D. pini. Hybrids displayed intermediate values for valva, harpe, and aedeagus lengths, and for these parameters, they significantly differed from both parental species. The following diagnostic indices were suggested to distinguish between the two species and their hybrids: Harpe Length/Valva Length Index (HL/VL) and Cornuti Length/Aedeagus Length Index (CL/AL). Decision-tree analysis identified HL/VL as the strongest predictor for separating the parental species and the Combined Genital Proportion Index (CGPI), which integrates harpe, valva, aedeagus, and cornuti lengths, as the strongest predictor for identifying hybrids. The morphometric criteria developed here have practical applications for monitoring programs and quarantine diagnostics, particularly in sympatric zones and regions at risk of D. sibiricus expansion. Full article

Nickel-titanium (NiTi) alloys are attractive for functional and biomedical applications due to their shape memory effect, superelasticity, and favorable corrosion resistance and biocompatibility. In this work, the influence of strut size on the compressive response of laser-based powder bed fusion (PBF-LB/M) fabricated NiTi ortho-octahedral porous scaffolds was systematically investigated using combined experiments and finite element simulations. Four scaffold designs with identical unit-cell size (2 mm) but different strut sizes (280, 320, 360, and 400 μm) were fabricated, and their forming quality and deformation behaviors were examined. The as-built scaffolds exhibited high geometric fidelity to the CAD models and stable manufacturability across the investigated parameter range. Quasi-static compression tests revealed a typical three-stage response (linear-elastic regime, plateau/collapse regime, and densification), with both elastic modulus and compressive strength increasing markedly with strut size. Specifically, the modulus increased from 1.17 to 4.28 GPa and the compressive strength increased from 155 to 564 MPa as the strut size increased from 280 to 400 μm. A pronounced oscillatory plateau was observed for the 280 μm scaffolds, indicating progressive layer-by-layer collapse, whereas larger struts promoted a shear-band-dominated failure mode characterized by an approximately 45° fracture zone. Explicit quasi-static simulations reproduced the experimentally observed collapse sequence and demonstrated that stress preferentially concentrates at nodal junctions, with load transfer dominated by struts aligned with the loading direction. The agreement between experiments and simulations confirms the predictive capability of the proposed modeling framework and provides mechanistic insights into geometry-controlled failure. These findings establish a structure-property-failure relationship for PBF-LB/M-fabricated NiTi octahedral scaffolds and offer practical guidance for tailoring stiffness, strength, and collapse mode through strut-size design. Full article

Global water scarcity is intensifying, and agriculture remains the main consumer of freshwater. Many studies have assessed agricultural water productivity (WP) in major farming regions. While previous studies have mainly assessed overall efficiency or single crops, crop-specific dynamics within double-cropping systems remain insufficiently understood. This study quantifies the spatial patterns and stage-wise changes in winter wheat and summer maize WP in the North China Plain based on five representative years (2000, 2005, 2010, 2015, and 2019) and examines their climatic and anthropogenic drivers. The Optimal Parameter-Based Geographical Detector (OPGD) model was used to assess the explanatory power of influencing factors, and the Multi-scale Geographically Weighted Regression (MGWR) model was applied to capture spatially heterogeneous relationships. Wheat WP ranged from 0.56 to 1.30 kg m⁻³ and showed a significant increasing trend, whereas maize WP ranged from 0.89 to 1.72 kg m⁻³. Both climatic and anthropogenic factors exhibited pronounced spatial heterogeneity. Beijing and Tianjin were classified as anthropogenic-dominated zones, while several cities in Henan displayed crop-specific dominant drivers. Fertilizer application was negatively associated with WP in multiple regions, indicating declining input efficiency under intensive management. These findings support irrigation zoning and differentiated water allocation strategies, contributing to sustainable intensification and progress toward water-related (SDG 6) and food security (SDG 2) goals in intensive double-cropping regions. Full article

Under drip irrigation conditions, the transport pattern of soil water in the root zone directly affects the water use efficiency of crops. The type of soil matrix, initial moisture content, and irrigation water quality jointly determine the hydrodynamic process of water infiltration. However, as a special type of irrigation water, the water movement mechanism of biogas slurry under drip irrigation in soilless cultivation substrates still lacks systematic investigation. In this study, transparent soil column infiltration experiments were conducted using two types of cultivation substrates—organic (coconut coir) and inorganic (desert sand)—under controlled facility conditions. Three initial moisture contents (10%, 15%, and 20%) and two irrigation water qualities (tap water and diluted biogas slurry) were combined to form twelve treatment groups. Soil moisture sensors and visualization techniques were employed to quantitatively analyze the wetting front morphology, vertical and horizontal infiltration rates, wetting ratio, and soil moisture profile distribution under different treatments. The results showed that the initial moisture content significantly influenced the advancement pattern of the wetting front. Higher initial moisture levels promoted the transformation of the wetting front shape from a “semi-pear” form to a “hemispherical” one and reduced the rate of infiltration decline. The coconut coir substrate exhibited stronger vertical infiltration capacity and a central water aggregation characteristic, whereas the desert sand demonstrated a wider horizontal expansion range. Under low and moderate initial moisture conditions, the application of biogas slurry enhanced horizontal water diffusion and improved the uniformity of the wetted zone, with the wetting ratio increasing by more than 6% compared with high moisture conditions. In addition, the power function model provided an excellent fit for the cumulative infiltration process across all treatments (R² > 0.96), indicating its suitability for describing the water transport process in facility cultivation substrates. This study provides theoretical support for precise water and fertilizer management and the efficient utilization of biogas slurry in soilless cultivation systems. Full article

This study aims to clarify the influence mechanism of air–water–mineral three-phase flow behavior on separation efficiency in a graphite flotation column, addressing the issues of over-breaking of coarse graphite flakes and low recovery of fine particles caused by mismatched flow fields and operating parameters in traditional flotation columns. Using CFD numerical simulations based on the Eulerian multiphase flow model, the standard k-ε turbulence model, and scalable wall functions, the effects of feed velocity (0.8–2.4 m/s) and aeration velocity (1–5 m/s) on the flow field structure, gas holdup distribution, and weighted average bubble–particle collision probability inside the column were systematically analyzed. Key quantitative results show that under the synergistic condition of a feed velocity of 2 m/s and an aeration velocity of 3 m/s, an internal circulation flow field conducive to particle retention is formed. Under these conditions, the gas holdup in the collection zone reaches an optimal range (0.26–0.27), and the weighted average collision probability increases by approximately 22% compared to the baseline condition. Aeration velocity shows a significant positive correlation with gas holdup in the collection zone (~0.235 at 1 m/s, rising to ~0.285 at 5 m/s). While an increase in feed velocity reduces the overall gas volume fraction, it enhances turbulence and promotes uniform bubble dispersion through the spatial distribution of regions with high collision probability from the upper part to the upper–middle part of the column and improves the uniformity of distribution. The novelty of this study lies in being the first to quantitatively reveal, through CFD simulation, the coupled regulatory effects of feed velocity and aeration velocity on the stratified flow field structure and mineralization probability in a flotation column and to identify the key optimization threshold of “2 m/s feed velocity”. The practical significance is that it provides a clear theoretical basis and operational window for energy saving, consumption reduction, and process intensification in industrial flotation columns. It offers directly applicable parameter optimization strategies for the efficient recovery of fine-flake graphite and the protection of coarse flakes. 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

Ground-based remote sensing of seismic and geophysical displacements remains a major challenge due to environmental hazards, signal attenuation, and practical deployment limitations of traditional seismometers. In this study, we present a detailed design, implementation, and performance evaluation of a Moiré-based apparatus for remote ground displacement measurement. The system operates by detecting fringe shifts formed between a fixed and a displaced grating, with displacement magnified through controlled angular superposition. We systematically assess each component of the system, including telescope optics, imaging sensors, and grating configurations, to optimize spatial resolution, contrast, and robustness under varying environmental conditions. A digital approach for fringe generation was employed, allowing controlled magnification and improved sensitivity without the need for physical alignment of dual gratings. Indoor experiments under low-turbulence conditions validated the system’s capability to detect displacements as small as $50\mathsf{\mu }\mathrm{m}$. Subsequent outdoor trials at different distances demonstrated successful measurement of both square-wave and seismic-like displacements despite increased atmospheric turbulence and wind. The results confirm the system’s ability to perform real-time, long-range, non-contact displacement monitoring with high accuracy and resilience to environmental variability. This study establishes a foundation for the application of Moiré-based sensing in challenging field conditions, including volcanic and seismic zones. Full article

Stilling basins are critical energy-dissipating structures in high-head hydraulic projects, yet conventional stilling basins often face challenges of insufficient energy dissipation and excessive bottom pressure under high water head and large unit discharge conditions. The integration of sudden expansion and drop sill into stilling basin design has emerged as a potential solution, but its hydraulic characteristics and the specific impact of sudden expansion remain inadequately quantified and understood. To address this research gap, this study experimentally investigates the hydraulic performance of stilling basins with sudden expansion and drop sill, conducting physical model tests on nine design schemes that contrast basins with and without sudden expansion. The tests measure time-averaged pressure, fluctuating pressure, and aeration concentration at key positions of the basin floor. The results demonstrate that the drop sill stilling basin with sudden expansion is technically feasible for application under conditions of high water head and large unit discharge. In the direction perpendicular to the flow, the distributions of time-averaged pressure, fluctuating pressure, and aeration concentration are non-uniform, generally exhibiting a decreasing trend in the order of the 1/4 centerline, chute extension line, 1/2 centerline, and near-sidewall line. Specifically, the time-averaged pressure, fluctuating pressure, and aeration concentration at the bottom of the sudden-expansion basin are, respectively, lower than those of the non-sudden-expansion basin. Notably, the primary protection zones of the sudden-expansion and drop sill stilling basin are situated between the chute extension line and the 1/4 centerline, as well as in the region ranging from the drop sill to 0.4l (with l denoting the stilling basin length). These findings verify that sudden expansion significantly modifies the hydraulic characteristics of stilling basins by reducing pressure and aeration concentration in key areas, and further provide quantitative design parameters and theoretical support for the optimization of sudden-expansion and drop sill stilling basins in high-head hydraulic engineering projects. Full article

High-strength concrete (HPC/UHPC) provides a new way to optimize the performance of nuclear power containment, but the mechanism of its application in the bi-directional dense anchorage zone is not clear. In this paper, a three-dimensional nonlinear model was established by ABAQUS to systematically study the effects of concrete strength, cylinder thickness and other parameters on the local pressure-bearing performance of the anchorage zone. The study shows that the use of C80-C120 concrete can thin the thickness of the containment by 30–40% and significantly enhance the pre-compressive stress safety reserve. Comparison of the existing design codes (e.g., Kim’s formula, Highway Bridge Specifications and UHPC-related regulations) reveals that the prediction results have a non-conservative or over-conservative tendency, which restricts the full utilization of the material performance. This study reveals the working mechanism of bi-directional multiple anchorage zones, demonstrates the advantages of high-strength concrete containment in terms of safety and economy, and provides a theoretical basis for the design of advanced nuclear power structures. Full article

Thermal conductivity and specific heat capacity are key parameters controlling heat transfer and temperature distribution in road pavement structures. Although transient methods are increasingly used in laboratory testing, the thermal properties of asphalt mixtures have not been sufficiently studied using these methods, and no dedicated standards exist for road materials. This creates uncertainty in test procedures, specimen geometry, surface preparation, measurement location, and data interpretation, which may lead to significant errors, especially for massive and heterogeneous mixtures. The objective of this study is to systematically quantify the edge zone effect and assess its influence on the determined thermal parameters of a selected heterogeneous asphalt mixture. The study focuses on the quantitative determination of the edge zone effect, practical identification of its width in slab-shaped specimen, and the identification of scientific and practical methodological consequences, as well as the risks and limitations of applying the Modified Transient Plane Source (MTPS) method in the absence of standards. Laboratory measurements demonstrate a clear edge zone effect, with thermal conductivity and thermal diffusivity differing by up to 17% and 18%, respectively, near the specimen edges. These findings highlight the importance of methodological guidelines for slab-shaped asphalt mixture specimens and provide both scientific insight and practical guidance for the reliable application of transient method. They may also support the development of standardized testing procedures for asphalt mixtures. Full article

The high-temperature engine nozzle is a critical component of a rocket motor, and its stability and performance are significantly influenced by internal high-temperature gas radiative heat transfer. Due to the non-gray nature of the nozzle medium and the complexity of the Radiative Transfer Equation (RTE), rapid and accurate simulation of radiative heat transfer is crucial for engineering applications. This paper presents a high-efficiency solution coupling the Full-Spectrum Correlated k-Distribution (FSCK) model with the Null-Collision Monte Carlo Method (NCMCM). To address the inherent computational bottleneck of linear traversal in unstructured grids, a hybrid ray-localization model integrating KD-tree and Bounding Volume Hierarchy (BVH) is proposed. This model shifts the search mechanism from element-wise iteration to spatial topological indexing, achieving logarithmic search complexity and significantly mitigating the sensitivity of computational cost to grid scale. Furthermore, a collaborative MPI–OpenMP parallel framework is established to maximize hardware utilization, where an optimized guided scheduling strategy effectively counteracts the stochastic load imbalances encountered in traditional static schemes. Results indicate that the proposed method reduces the total execution time to approximately 1/4 compared to traditional models. Simulations identify the convergent section as the primary radiation zone, where CO₂ contributes less to the radiative source term than H₂O under high-temperature conditions. Full article

This study develops a conceptual framework for characterizing reservoir architecture in multi-component, discrete systems using pressure transient analysis (PTA), aimed at calibrating inflow geometry prior to full-field dynamic simulation for subsurface gas storage applications such as CO₂ and hydrogen. A secondary objective is to identify variations in permeability over time by analyzing flow capacity trends and evaluating the dynamic influence of faults and fractures. The analysis is based on a gas-condensate field comprising seven wells and four zones (A, B, C, D), using integrated dynamic datasets including extended well tests (EWTs), mud loss, production logs, and production data. Detailed interpretation of PX-1’s EWT indicated delayed re-pressurization and persistent under-pressure, suggesting a compartmentalized or transient system with limited gas-in-place connectivity. Four reservoir architecture concepts were developed: (1) lithology-dominated inflow, (2) structurally controlled inflow, (3) discrete, weakly connected compartments, and (4) transient-dominated systems with tight matrix GIIP. These concepts informed four reservoir models: matrix-only (M), areal heterogeneity (A), sparse bodies (B), and sparse networks (S). Application of these models across other wells revealed consistent localized KH (permeability–thickness product) behavior, with all models fitting short-duration data comparably. However, only sparse drainage models (B/S) adequately matched PX-1’s EWT response. PTA results confirm that well tests constrain KH locally but provide limited insight into large-scale reservoir architecture. EWTs may reach ~1 km, while shorter tests are confined to ~200–400 m, typically within one to two simulation grid blocks. This study demonstrates how integrating PTA with multi-scale data improves characterization of naturally fractured, tight carbonate reservoirs and supports reservoir simulation and history matching for hydrogen storage evaluation. Based on reservoir simulations, this study concluded that naturally fractured carbonate gas reservoirs can provide significant storage and injection capacities for underground hydrogen storage. This study exemplifies how to characterize the naturally fractured tight carbonate reservoirs by integrating multi-scale and multi-dimensional data such as PTA. Furthermore, this study assists in gridding for full-field reservoir models, for history matching and quantifying the potential of hydrogen storage in these complex reservoirs. The proposed workflow provides an uncertainty-bounded reservoir characterization framework and should not be interpreted as a complete field-design methodology for hydrogen storage. The modeling does not explicitly couple geomechanical fracture growth, hydrogen diffusion, long-term geochemical reactions, or caprock integrity degradation. Therefore, the presented storage scenarios represent technically feasible cases under defined assumptions. Comprehensive site-specific geomechanical and containment assessments are required prior to field-scale implementation. Full article