Search Results (98)

The rapid expansion of tunnel construction in mountainous regions faces significant challenges due to the heterogeneity of surrounding rocks caused by faults, fractures, and karst features, which strongly affect groundwater seepage. Traditional homogeneous assumptions are inadequate for accurately predicting tunnel water inflow, while current heterogeneous assumptions primarily focus on the permeability of the medium near a single tunnel. This study employs 2D numerical modeling based on the Kexuecheng Tunnel in Chongqing, China, to investigate the effects of geological heterogeneity on tunnel discharge and groundwater drawdown. A methodological advancement of this work lies in the quantification of the impact of non-permeability heterogeneity, stratigraphic continuity, and dip angles on groundwater under multi-tunnel conditions. Four stratigraphic continuities (R = 60 m, 120 m, 180 m, 240 m) and four dip angles (θ = 0°, 30°, 60°, 90°) are considered for permeability variations. Results demonstrate that heterogeneous formations produce irregular discharge and non-uniform groundwater drawdown, closely reflecting field conditions. Increased stratum continuity intensifies discharge and drawdown at smaller dip angles, while combined variations yield complex hydraulic responses. In multi-tunnel settings, reduced spacing amplifies discharge and drawdown, exacerbating groundwater impacts. Compared with homogeneous conditions, heterogeneous formations yield higher water inflow and uneven drawdown. The findings underscore the necessity of accounting for geological heterogeneity and tunnel interactions in hydrogeological evaluations and design. In addition to permeability, stratigraphic continuity and dip angles during simulation validation, especially in multi-tunnel configurations, enhance safety and reduce engineering risks. Full article

This study investigates the impact of the expansion ratio on combustion oscillation phenomena and their driving mechanisms in a solid-fuel ramjet (SFRJ) through experimental and numerical simulations. By analyzing flow characteristics, combustion oscillations at varying expansion ratios, heat release patterns, and species distribution within the engine, the following key conclusions are drawn: Ground tests revealed first-order pressure oscillations with a dominant frequency of approximately 600 Hz, exhibiting a half-wavelength oscillation pattern. As the expansion ratio increased from 1.75 to 2.25, the amplitude of the first-order oscillation increased by 21%, from 1.89 kPa, while the dominant frequency initially rose and then decreased, peaking at an expansion ratio of 2. The shear-induced downstream of the step was identified as a critical factor influencing heat release and acoustic pressure oscillations in the combustion chamber, which led to periodic unstable heat release that amplified combustion oscillation amplitudes. The numerical results show that the periodic motion of vortices induced by flow shear downstream of the sudden expansion step causes oscillations in the temperature distribution on the propellant surface, which is one of the key factors contributing to combustion instability and pressure oscillations. When the expansion ratio is increased to 2.0 and 2.25, the dominant frequency of pressure oscillations increases by 15.2% and 13.2%, respectively, while the amplitude rises by 7.9% and 30%, respectively. The vortice development blurs the oxygen-rich and fuel-rich zones, enhancing the mixing of oxygen and fuel-rich gases and exacerbating the instability of heat release. Larger expansion ratios further extended the axial range of unstable species distribution, increasing nonuniformity within the combustion region. Full article

The rapid expansion of mobile user behavior data has made next-Point-of-Interest (POI) recommendation increasingly vital for enhancing personalized location-based services. However, the non-uniform spatio-temporal distribution of user behavior poses significant challenges to recommendation performance. Most existing methods neglect this fundamental issue at the distribution level, while conventional data augmentation strategies fall short in optimizing spatio-temporal distribution properties. To tackle this problem, we propose a spatio-temporal Distribution Calibration framework for next-POI Recommendation (DCal-Rec), which optimizes behavioral sequence distributions through disentangled spatial and temporal operator pools. This is combined with a dual-constraint mechanism that incorporates both distribution and interest information to maintain semantic consistency. Furthermore, a multi-channel contrastive learning paradigm is introduced to jointly optimize the recommendation and contrastive tasks under a unified training objective, thereby improving the model’s generalization capability. Experimental results on three public real-world datasets demonstrate that DCal-Rec significantly outperforms baseline methods across various evaluation metrics. Full article

This study proposes a semi-analytic harmonic modeling method that significantly improves the accuracy and efficiency of complex magnetic field modeling by integrating numerical and analytical approaches. Compared to traditional methods such as the equivalent charge method and finite element method, this approach optimizes the distribution of surface and body charges in the magnetic dipole model and introduces a finite and variable permeability model to accommodate material non-uniformity. Through harmonic expansion and analytical optimization, the method more accurately reflects the characteristics of real magnets, providing an efficient and precise solution for complex magnetic field problems, particularly in the design of high-performance magnets such as Halbach arrays. In this study, the effectiveness of the new modeling method is verified through the combination of simulation and experiment: the magnetic field distribution of the new Halbach array is accurately simulated, and the applicability of the model in the description of complex magnetic fields is analyzed. The dynamic response ability of the optimized model is verified by modeling and simulating the variation of the permeability under actual conditions. The distribution of scalar potential energy with permeability was simulated to evaluate the adaptability of the model to the real physical field. Through the comparative analysis of simulation and experimental results, the advantages of the new method in modeling accuracy and efficiency are clearly pointed out, and the effectiveness of the semi-analytic harmonic modeling method and its wide application potential in the design of new magnetic fields are proved. In this study, a semi-analytic harmonic modeling method is proposed by combining numerical and analytical methods, which breaks through the efficiency bottleneck of traditional modeling methods, and achieves the unity of high precision and high efficiency in the magnetic field modeling of the new Halbach array, providing a new solution for the study of complex magnetic field problems. Full article

Addressing the core issue of rock mass failure and deformation induced by local water-induced uneven expansion in expansive soft rock tunnels, this study systematically analyzes the stress–displacement response of the rock mass under various working conditions. This analysis integrates physical model testing with FLAC3D 6.0 numerical simulation and covers four typical expansion zone configurations (vault, spandrel, haunch, invert) as well as multiple stages of stress loading. Leveraging the mathematical analogy between heat conduction and fluid seepage and combining it with a thermo-hydraulic coupling approach, the FLAC3D temperature field module precisely simulates the moisture-induced stress field. This overcomes the limitations of traditional tools for direct moisture field simulation and enables quantitative assessment of how localized expansion impacts tunnel lining failure. The study reveals that horizontal expansion zones significantly increase the risk of shear failure in tunnel structures. Expansion zones at the tunnel crown and base (invert) pose critical challenges to overall safety and exhibit a pronounced nonlinear relationship between stress loading and displacement. This research deepens the theoretical understanding of the interaction between localized non-uniform expansion and the surrounding rock mass and provides crucial technical guidance for optimizing tunnel support systems and improving disaster monitoring and prevention measures. Full article

In deepwater oil and gas transportation, Pipe-in-Pipe (PIP) systems are an effective solution for mitigating external loads while preserving internal thermal integrity. A finite element model with ITT elements and nonlinear spring contacts was developed in ABAQUS to simulate thermal expansion and contraction under extreme conditions. The coupled mechanical response of double-layer pipelines under non-uniform temperature fields and internal pressure was analyzed, focusing on stress distribution and deformation coordination between the inner and outer pipes. The inner pipe primarily sustains compressive or tensile stress depending on the thermal load direction, while the outer pipe experiences opposing stresses due to mechanical coupling. Distinct stress transfer zones are present near the pipe ends, governed by pipe-soil interaction and internal bending moments. The proposed model for double-layer pipelines under coupled thermal and internal pressure loads demonstrates a prediction accuracy within 5% as compared with benchmark numerical solutions. The simulations capture axial stress variations of up to 68% between extreme thermal expansion and contraction scenarios, with radial deformation ranging from 0.9 mm to 3.4 mm. These findings provide valuable insights into the safe and efficient design of subsea PIP systems, particularly for optimizing material selection and structural configuration in high-temperature, high-pressure environments. Full article

Corrosion-induced cracking of reinforced-concrete (RC) covers is well known, yet key knowledge gaps persist. Most studies isolate uniform corrosion or a single non-uniform corrosion pattern and ignore the effects of boundary restraint and structural configurations, leading to inaccurate predictions of cracking thresholds and crack propagation patterns. This study systematically investigates the influence mechanisms of constraint conditions and structural configurations on corrosion-induced cracking behavior using the phase-field model. The results indicate that the non-uniformity of steel corrosion is a critical factor governing cover cracking. As the corrosion non-uniformity coefficient increases, the critical corrosion level exhibits a monotonic decreasing trend—from 0.95% to 0.15% under strong constraints and from 0.52% to 0.15% under weak constraints. Concurrently, the crack morphology evolves from a single radial crack to a wedge-shaped crack oriented toward the peak corrosion side. The influence of constraint conditions is dualistic, while strong constraints enhance the failure threshold, their mitigating effect diminishes markedly under highly non-uniform corrosion. The critical corrosion threshold for eccentrically arranged corner reinforcement is significantly lower than that for centrally arranged reinforcement; the corrosion angle only induces slight crack deflection and minor threshold fluctuations; and the curved top section, due to its weaker equivalent constraint, exhibits inferior crack resistance compared to the linear top section. Three-dimensional analysis reveals a pronounced longitudinal discreteness effect, which not only substantially elevates the critical corrosion threshold but also leads to diverse spatial failure modes. This work links rust-expansion eigen-displacement to crack propagation within a unified phase-field framework, providing materials-level criteria for evaluating corrosion tolerance and guiding the design of cover materials and reinforcement layouts to enhance durability. Full article

The persistent challenge of fracture-driven interference (FDI) during large-scale hydraulic fracturing in the southern Sichuan Basin has severely compromised shale gas productivity, while the existing research has inadequately addressed both FDI risk reductions and the optimization of reservoir stimulation. To bridge this gap, this study developed a mechanistic model of the competitive multi-cluster fracture propagation under non-uniform perforation conditions and established a perforation-based design methodology for the mitigation of horizontal well interference. The results demonstrate that spindle-shaped perforations enhance the uniformity of fracture propagation by 20.3% and 35.1% compared to that under uniform and trapezoidal perforations, respectively, with the perforation quantity (48) and diameter (10 mm) identified as the dominant control parameters for balancing multi-cluster growth. Through a systematic evaluation of the fracture communication mechanisms, three distinct inter-well types of FDI were identified: Type I (natural fracture–stress anisotropy synergy), Type II (natural-fracture-dominated), and Type III (stress-anisotropy-dominated). To mitigate these, customized perforation schemes coupled with geometry-optimized fracture layouts were developed. The surveillance data for the offset well show that the pressure interference decreased from 14.95 MPa and 6.23 MPa before its application to 0.7 MPa and 0 MPa, achieving an approximately 95.3% reduction in the pressure interference in the application wells. The expansion morphology of the inter-well fractures confirmed effective fluid redistribution across clusters and containment of the overextension of planar fractures, demonstrating this methodology’s dual capability to enhance the effectiveness of stimulation while resolving FDI challenges in deep shale reservoirs, thereby advancing both productivity and operational sustainability in complex fracturing operations. Full article

Non-uniform temperature fields are developed during the welding of studs in steel–concrete composite bridges. Due to uneven thermal expansion and reversible solid-state phase transformations between ferrite/martensite and austenite structures within the materials, residual stresses are induced, which ultimately degrades the mechanical performance of the structure. For a better understanding of the influence on steel–concrete composite bridges’ structural behavior by residual stress, accurate simulation of the spatio-temporal temperature distribution during stud welding under practical engineering conditions is critical. This study introduces a precise simulation method for temperature evolution during stud welding, in which the Gaussian heat source model was applied. The simulated results were validated by real welding temperature fields measured by the infrared thermography technique. The maximum error between the measured and simulated peak temperatures was 5%, demonstrating good agreement between the measured and simulated temperature distributions. Sensitivity analyses on input current and plate thickness were conducted. The results showed a positive correlation between peak temperature and input current. With lower input current, flatter temperature gradients were observed in both the transverse and thickness directions of the steel plate. Additionally, plate thickness exhibited minimal influence on radial peak temperature, with a maximum observed difference of 130 °C. However, its effect on peak temperature in the thickness direction was significant, yielding a maximum difference of approximately 1000 °C. The thermal influence of group studs was also investigated in this study. The results demonstrated that welding a new stud adjacent to existing ones introduced only minor disturbances to the established temperature field. The maximum peak temperature difference before and after welding was approximately 100 °C. Full article

The rapid spread of COVID-19 increased the need for speedy diagnostic tools, which led scientists to conduct extensive research on deep learning (DL) applications that use chest imaging, such as chest X-ray (CXR) and computed tomography (CT). This review examines the development and performance of DL architectures, notably convolutional neural networks (CNNs) and emerging vision transformers (ViTs), in identifying COVID-19-related lung abnormalities. Individual ResNet architectures, along with CNN models, demonstrate strong diagnostic performance through the transfer protocol; however, ViTs provide better performance, with improved readability and reduced data requirements. Multimodal diagnostic systems now incorporate alternative methods, in addition to imaging, which use lung ultrasounds, clinical data, and cough sound evaluation. Information fusion techniques, which operate at the data, feature, and decision levels, enhance diagnostic performance. However, progress in COVID-19 detection is hindered by ongoing issues stemming from restricted and non-uniform datasets, as well as domain differences in image standards and complications with both diagnostic overfitting and poor generalization capabilities. Recent developments in COVID-19 diagnosis involve constructing expansive multi-noise information sets while creating clinical process-oriented AI algorithms and implementing distributed learning protocols for securing information security and system stability. While deep learning-based COVID-19 detection systems show strong potential for clinical application, broader validation, regulatory approvals, and continuous adaptation remain essential for their successful deployment and for preparing future pandemic response strategies. Full article

Steel pipes, while essential for modern infrastructure due to their high strength and load-bearing capacity, are prone to corrosion in the marine environment, leading to material degradation, compromised structural integrity, and elevated safety risks and economic losses. In this study, distributed fiber-optic sensors were deployed on steel pipe surfaces to monitor corrosion in the splash zone (a region particularly vulnerable to cyclic wet–dry conditions). The sensors were engineered to withstand aggressive marine exposure. Strain variations induced by expansive corrosion products were detected via the fiber-optic array and used to calculate localized mass loss. Color-coded corrosion severity maps were generated to visualize the non-uniform corrosion distribution. Experimental results demonstrate that sensor-derived mass loss values align with 3D laser scanning measurements, validating the operational efficacy of distributed fiber-optic sensing for marine corrosion monitoring. This approach provides quantitative insights into the field applicability of optical sensing in structural health monitoring. Full article

Wolfberry (Lycium barbarum L.) is a valued traditional medicinal plant and dietary supplement in China. The basic leucine zipper (bZIP) transcription factor (TF) family is a multifunctional group of regulatory proteins critical to plant biology, orchestrating processes such as growth and development, secondary metabolite biosynthesis, and stress responses to abiotic conditions. Despite its significance, limited information about this gene family in wolfberry is available. In this study, a total of 66 LbabZIP genes were identified, exhibiting a non-uniform distribution across all 12 chromosomes. Phylogenetic analysis divided these genes into 13 subgroups based on comparison with Arabidopsis bZIP proteins. Analysis of gene structures and conserved motifs revealed high similarities within individual subgroups. Gene duplication analysis indicated that dispersed duplication (DSD) and whole-genome duplication (WGD) events were the primary drivers of LbabZIP gene family expansion, with all duplicated genes subject to purifying selection. Cis-regulatory element (CRE) analysis of LbabZIP promoter regions identified numerous elements associated with plant growth and development, hormone signaling, and abiotic stress responses. Gene Ontology (GO) annotation further indicated that the LbabZIP genes are involved in transcriptional regulation, metabolism, and other biological processes. Transcriptome data and quantitative real-time PCR (qRT-PCR) analysis demonstrated tissue-specific expression patterns for several LbabZIP genes. Notably, LbaZIP21/40/49/65 showed significant involvement in wolfberry fruit development. Subcellular localization assays confirmed that these four proteins are nucleus-localized. This comprehensive analysis provides a theoretical foundation for future studies investigating the biological functions of LbabZIP genes, especially their role in wolfberry fruit development. Full article

This study elucidates the underlying formation mechanisms and mitigation strategies for the W-shaped solidification profile in slab continuous casting. Through the development of a multiphysics coupling numerical model, integrated with measured nozzle cooling characteristics in the secondary cooling zone, the effect of steel flow patterns in mold and non-uniform cooling conditions in the secondary cooling zone on solidifying shell evolution is systematically studied. A principal finding is that wide-face shell erosion, induced by both the radial expansion jet and the lower recirculation, constitutes the primary determinant of uneven shell thickness. An increase in the immersion depth and inclination angle of the nozzle side-hole exacerbates the non-uniformity of the solidified shell. Non-uniform cooling in the secondary cooling zone further amplifies the shell thickness differences, culminating in characteristic dumbbell-shaped solidified shell geometry. Strategic implementation of localized enhanced cooling on the wide face in the secondary cooling zone demonstrates significant improvement in shell uniformity, with implementation efficacy contingent upon a critical process window (Segments 1–6). These findings establish mechanistic foundations and deliver practical guidance for minimizing centerline segregation through optimized continuous casting parameter configuration. Full article

Compartment boundaries divide the embryo into segments with distinct fates and functions. In the vascular system, compartment boundaries organize endothelial cells into arteries, capillaries, and veins that are the fundamental units of a circulatory network. For vascular smooth muscle cells (SMCs), such boundaries produce mosaic patterns of investment based on embryonic origins with important implications for the non-uniform distribution of vascular disease later in life. The morphogenesis of blood vessels requires vascular cell movements within compartments as highly-sensitive responses to changes in fluid flow shear stress and wall strain. These movements underline the remodeling of primitive plexuses, expansion of lumen diameters, regression of unused vessels, and building of multilayered artery walls. Although the loss of endothelial compartment boundaries can produce arterial–venous malformations, little is known about the consequences of mislocalization or the failure to form SMC-origin-specific boundaries during vascular development. We propose that the failure to establish a normal compartment boundary between cardiac neural-crest-derived SMCs of the 6th pharyngeal arch artery (future ductus arteriosus) and paraxial-mesoderm-derived SMCs of the dorsal aorta in mid-gestation embryos leads to aortic coarctation observed at birth. This model raises new questions about the effects of fluid flow dynamics on SMC investment and the formation of SMC compartment borders during pharyngeal arch artery remodeling and vascular development. Full article

This paper proposes an improved RRT*-Connect algorithm (IRRT*-Connect) for robotic arm path planning in narrow environments with multiple obstacles. A heuristic sampling strategy is adopted with the integration of the ellipsoidal subset sampling and goal-biased sampling strategies, which can continuously compress the sampling space to enhance the sampling efficiency. During the node expansion process, an adaptive step-size method is introduced to dynamically adjust the step size based on the obstacle information, while a node rejection strategy is used to accelerate the search process so as to generate a near-optimal collision-free path. A pruning optimization strategy is also proposed to eliminate the redundant nodes from the path. Furthermore, a cubic non-uniform B-spline interpolation algorithm is applied to smooth the generated path. Finally, simulation experiments of the IRRT*-Connect algorithm are conducted in Python and ROS, and physical experiments are performed on a UR5 robotic arm. By comparing with the existing algorithms, it is demonstrated that the proposed method can achieve shorter planning times and lower path costs of the manipulator operation. Full article