Search Results (11,506)

The non-uniform temperature distribution in ballastless track slabs under complex meteorological conditions can induce structural defects, threatening the safety of high-speed railways. Existing temperature field models often rely on idealized geometric and meteorological assumptions, thereby constraining a fine-grained and quantitative resolution of the independent thermal effects governed by key boundary conditions. To address this, the current study proposes a temperature field analysis method integrating high-precision geometry and physical processes: the actual track geometry is reconstructed via 3D laser scanning point clouds, and a 3D transient heat conduction finite element model is developed by incorporating measured meteorological data and an astronomical model for dynamic solar radiation calculation. Results demonstrate close agreement between simulations and field measurements (MAPE < 5%, R² > 0.92), validating the model’s accuracy. Further analysis reveals that the box girder substructure, due to the “air cavity heat accumulation effect,” causes greater temperature fluctuations at the slab bottom compared to the subgrade, increasing the maximum positive temperature gradient by approximately 9%. The track alignment significantly influences temperature distribution, with the east–west alignment (0°) exhibiting a peak surface temperature 1.30 °C higher than the north–south alignment (90°) and instantaneous temperature differences reaching up to 2.4 °C. This study delivers the first dedicated, quantitative analysis of the impact of track substructure and alignment on the temperature field of the slab, providing a theoretical basis for the differentiated design of ballastless tracks and the revision of temperature load standards. Full article

As the complexity of modern engineering systems continues to increase, traditional reliability analysis methods still face challenges regarding computational efficiency and reliability in scenarios where the distribution information of random variables is incomplete and samples are sparse. Therefore, this study develops a data-driven polynomial chaos expansion (DD-PCE) model for scenarios with limited samples and applies it to reliability-based robust design optimization (RBRDO). The model directly constructs orthogonal polynomial basis functions from input data by matching statistical moments, thereby avoiding the need for original data or complete statistical information as required by traditional PCE methods. To address the statistical moment estimation bias caused by sparse samples, kernel density estimation (KDE) is employed to augment the data derived from limited samples. Furthermore, to enhance computational efficiency, after determining the DD-PCE coefficients, the first four moments of the DD-PCE are obtained analytically, and reliability is computed based on the maximum entropy principle (MEP), thereby eliminating the additional step of solving reliability as required by traditional PCE methods. The proposed approach is validated through a mechanical structure and five mathematical functions, with RBRDO studies conducted on three typical structures and one practical engineering case. The results demonstrate that, while ensuring computational accuracy, this method saves approximately 90% of the time compared to the Monte Carlo simulation (MCS) method, significantly improving computational efficiency. Full article

To assess UAV (Unmanned Aerial Vehicle) flight stability in urban wind fields, this study conducted numerical simulations of urban scene and logistics UAV models and developed a wind field safety level evaluation model for UAV flight paths. First, urban wind field structures were analyzed with simulations of typical building clusters. Second, the UAV’s aerodynamic characteristics under vertical balance were elaborated. Third, sideslip angles and wind speeds were adjusted based on the UAV’s maximum wind resistance to explore aerodynamic performance variations across conditions. Finally, a safety level calculation method was proposed to determine the wind field safety distribution along target paths. The results show that building layouts significantly affect urban wind fields, forming wind acceleration zones beside high-rises and between some buildings. The acceleration effect at 25 m is stronger than at 10 m and 50 m. UAV aerodynamic moments vary greatly with wind sideslip angles, with the dangerous angle being around 150°. Flight stability and wind field structures differ notably by path and height. This evaluation method enables UAVs to avoid high-risk areas, improving urban flight stability. Full article

Oil–paper insulation in oil-immersed transformers undergoes a concealed degradation process that is difficult to detect during operation. To understand its discharge behavior, this study examines partial discharge characteristics under controlled moisture absorption and thermal aging. Experiments on S-PD (Surface Partial Discharge) and N-PD (Needle Partial Discharge) were carried out, and partial discharge patterns, discharge frequency, and breakdown voltage were collected to analyze discharge evolution. The results show that partial discharge develops through three stages: initiation, development, and pre-breakdown. In the initiation stage, pulses are sparse with low amplitudes and appear near the voltage peak. During development, both amplitude and discharge frequency increase, and the phase range expands. As breakdown approaches, pulse amplitude rises sharply, the phase distribution covers almost the full cycle, and conductive channels begin to form. Skewness, Peak Degree, and Maximum Steepness were extracted from statistical discharge maps to compare moisture-affected and aged samples. The findings provide experimental support for developing state-evolution-based failure warning models and diagnostic criteria, contributing to improved operational safety of oil–paper insulation systems. Full article

When operating in the marine environment, floating offshore wind turbines (FOWTs) are subjected to various inflow conditions such as wind, waves, and currents. To investigate the effects of complex inflow conditions on offshore wind farms, an integrated fluid-structure interaction computational and coupled dynamic analysis method for FOWTs is employed. An aero-hydro-servo-elastic coupled analysis model of the NREL 5 MW semi-submersible wind turbine array based on the OC4-DeepCwind platform is established. The study examines the variations in power generation, platform motion, structural loads, and flow field distribution of the FOWT array under different wave incident angles and yaw angles of the first column turbines. The results indicate that the changes in power generation, platform motion, and flow field distribution of the wind farm are significantly influenced by the yaw angle. The maximum tower top yaw bearing torque and the tower base Y-direction bending moment of the wind turbines undergo significant changes with the increase in the angle between wind and wave directions. The study reveals the mechanism of power generation and load variation during yaw control of the FOWT array under misaligned wind and wave conditions, providing a theoretical basis for the future development of offshore floating wind farms. Full article

A macrotidal estuary with mountain-stream inputs (MEMSs) is characterized by strong hydrodynamic forcing, high turbidity, and complex channel morphology. This study combines field measurements (2005–2020) with a 2D hydrodynamic–sediment model to examine estuarine turbidity maximum (ETM) dynamics, erosion–deposition patterns, and the effects of engineering interventions in the Jiaojiang Estuary (JJE). Results show that the coupled influence of upstream floods and downstream macrotides produces highly seasonal and spatially variable water–sediment processes: mountain-stream floods exhibit sharp hydrodynamic fluctuations, and the estuary displays pronounced tidal-wave deformation. Over the 15-year observation period, the riverbed experienced alternating erosion (up to −3.5 m) and deposition (up to +4.2 m), with net erosion of 0.5–1.2 m occurring in most Ling River sections during high-discharge years. The ETM migrated about 30 km during spring tides, with near-bed suspended sediment concentrations reaching 50–60 kg/m³. Human activities—particularly historical sand mining—modified channel geometry and sediment composition, intensifying the exchange between bed material and suspended sediment and facilitating the formation and migration of the ETM. Extreme events further enhanced geomorphic adjustment: the post-Lekima (2019) flood produced maximum scour of −5.8 m in the upper Ling River and deposition of +3.2 m in the Jiaojiang main channel within weeks. Channel curvature and junction morphology strongly controlled flood-level distribution. Model experiments indicate that lowering shoal elevations and widening the cross-section at key constrictions can effectively reduce flood levels. Collectively, these findings clarify the morphodynamic evolution mechanisms of a MEMS system and provide quantitative guidance for flood-mitigation and estuarine-management strategies. Full article

Butidae is a family of teleost fishes with diverse morphological and ecological adaptations, including the marbled goby (Oxyeleotris marmorata), a large species of high economic value in Southeast and East Asia. The previous mitogenomic studies on cultured populations of O. marmorata from non-native habitats have provided limited insights into genetic divergence, structural variation, and evolutionary relationships. Hence, this study presented the complete mitochondrial genome of O. marmorata from its native habitat in Indonesia, providing structural characterization, assessment of genetic diversity, and matrilineal phylogenetic analysis. The circular mitogenome was 16,525 bp, comprising 37 genes and a non-coding control region (CR). The gene organization and strand distribution were conserved among Oxyeleotris species, with 28 genes on the heavy strand and nine on the light strand, and a pronounced A+T compositional bias. The comparative analyses of O. marmorata (from both native and cultured habitats) and Oxyeleotris lineolata mitogenomes revealed minor variations in intergenic spacers, gene overlaps, protein-coding gene (PCGs) lengths, and codon usage patterns. Conversely, the nonsynonymous and synonymous substitution ratios observed in species of the family Butidae and its closest related family (Eleotridae) indicate strong purifying selection in the present dataset. Notably, the ATG was the predominant start codon, whereas the COI gene utilized GTG, and amino acid composition analysis demonstrated high frequencies of arginine, leucine, and serine. Most transfer RNAs retained the canonical cloverleaf secondary structure except for trnS1, which lacked a functional dihydrouridine arm, whereas the CR contained four conserved sequence blocks with variable nucleotide motifs and no detectable tandem repeats. The haplotype analysis of native (Indonesia) and introduced populations (China) highlighted three haplotypes with high diversity (Hd = 1.0000) and substantial nucleotide variation (π = 0.6667). The genetic divergence across 13 PCGs was gene-specific, with COI and ND5 showing the highest variation, while ND4L and ATP8 were highly conserved. The phylogenetic analyses based on concatenated 13 PCGs using both Bayesian Inference and Maximum Likelihood methods revealed that Oxyeleotris forms a monophyletic clade and is closely related to Bostrychus sinensis. In addition, the broader phylogenetic framework inferred the matrilineal relationships within the family Butidae and its closest related family, Eleotridae. This study also recommends expanding analyses to include the mitogenomes of the remaining 17 Oxyeleotris species, together with comprehensive genomic data, to further elucidate their genetic architecture, evolutionary history, and ecological adaptability across diverse aquatic ecosystems. Full article

To address the issue that distributed renewable energy grid-connected Virtual Synchronous Generator (VSG) systems are prone to significant power and frequency fluctuations under changing operating conditions, this paper proposes a multi-parameter coordinated control strategy for VSGs based on a fusion framework of fuzzy logic and the Soft Actor–Critic (SAC) algorithm, termed Improved SAC-based Virtual Synchronous Generator control (ISAC-VSG). First, the method uses fuzzy logic to map the frequency deviation and its rate of change into a five-dimensional membership vector, which characterizes the uncertainty and nonlinear features during the transient process, enabling segmented policy optimization for different transient regions. Second, a stage-based guidance mechanism is introduced into the reward function to balance the agent’s exploration and stability, thereby improving the reliability of the policy. Finally, the action space is expanded from inertia–damping to the coordinated regulation of inertia, damping, and active power droop coefficient, achieving multi-parameter dynamic optimization. MATLAB/Simulink R2022b simulation results indicate that, compared with the traditional SAC-VSG and DDPG-VSG method, the proposed strategy can reduce the maximum frequency overshoot by up to 29.6% and shorten the settling time by approximately 15.6% under typical operating conditions such as load step changes and grid phase disturbances. It demonstrates superior frequency oscillation suppression capability and system robustness, verifying the effectiveness and application potential of the proposed method in high-penetration renewable energy power systems. Full article

This research presents a detailed assessment of the wind power potential in six Palestinian cities—Bethlehem, Jericho, Jenin, Nablus, Ramallah, and Tulkarm—utilizing daily wind speed data from the years 2015 to 2021. The primary goal of this study is to formulate a robust, data-driven framework for the strategic placement of turbines and the economical production of energy in areas with limited wind resources. A critical aspect of this research is the application of nine numerical methods, including the Maximum Likelihood Method (MLM) and the Energy Pattern Factor Method (EPF), to analyze the wind data. These methods were employed to estimate the shape and scale parameters of the Probability Distribution Function (PDF) that represents the Weibull distribution for various shape factor values. The accuracy of the numerical methods was validated through five statistical tools, including the Root Mean Square Error (RMSE) and Chi-square tests (X²). The Weibull parameters obtained from the numerical techniques indicated shape factors ranging from 1.27 to 1.96 and scale factors between 1.16 and 3.21 m/s. The energy output was calculated based on the swept area of the wind turbine, following Betz’s limit. The estimated annual energy production per square meter in the six cities is as follows: Ramallah—123 kWh/m², Bethlehem—24.42 kWh/m², Jenin—31.12 kWh/m², Nablus—22 kWh/m², Tulkarm—15.5 kWh/m², and Jericho—10.36 kWh/m². A 5 kW small-scale wind turbine was utilized to evaluate the technical feasibility, sustainability, and economic viability of small-scale wind energy applications. The anticipated energy output from the proposed wind turbine is 2054 kWh, with an estimated payback period of approximately 11.6 years. Full article

We develop a data-driven framework for analyzing how scientific concepts evolve through their empirical in-text frequency distributions in large text corpora. For each concept, the observed distribution is paired with a maximum entropy equilibrium reference, which takes a generalized Boltzmann form determined by two measurable statistical moments. Using data from more than 500,000 physics papers (about 13,000 concepts, 2000–2018), we reconstruct the temporal trajectories of the associated MaxEnt parameters and entropy measures, and we identify two characteristic regimes of concept dynamics, stable and driven, separated by a transition point near criticality. Departures from equilibrium are quantified using a residual-information measure that captures how much structure a concept exhibits beyond its equilibrium baseline. To analyze temporal change, we adapt the Hatano–Sasa and Esposito–Van den Broeck decomposition to discrete time and separate maintenance-like contributions from externally driven reorganization. The proposed efficiency indicators describe how concepts sustain or reorganize their informational structure under a finite representational capacity. Together, these elements provide a unified and empirically grounded description of concept evolution in scientific communication, based on equilibrium references, nonequilibrium structure, and informational work. Full article

This study analyses the operational efficiency of urban loading and unloading zones (LUZs) by applying queuing theory without waiting (Erlang B model) and incorporating weighted occupancy time as a fundamental metric. Six scenarios were evaluated in an urban block in Zaragoza, Spain: three using field data obtained through real world observation and three simulated. The system’s performance was compared under conditions of free access with a model that strictly enforces the municipal ordinance for Urban Goods Distribution, restricting access to authorized vehicles and maximum dwell times. The objective of this study is to evaluate the operational performance of different LUZ configurations, assessing how real versus regulation-compliant usage affects system capacity, estimated loss rates, and the spatial temporal productivity of the zones. The M/M/1/1 model in Kendall notation is suitable for representing this type of queuing-free urban environment, and weighted occupancy time proves to be a robust indicator for evaluating the performance of heterogeneous zones. The scenario assessment confirms that the sizing of these zones is correct if their proper use is guaranteed. The study concludes with recommendations and best practices for city governance in formulating urban policies aimed at developing more efficient and sustainable logistics to control land use in the LUZ. Full article

Wind disturbance is one of the key factors affecting the high-precision pointing of large-aperture radio telescopes. Therefore, it is indispensable to monitor the wind environment of the site. This enables the acquisition of wind environment data, facilitating targeted wind-resistant design to maintain the observational performance of the radio telescope. A 60 m high wind tower is located within the QTT (QiTai Radio Telescope, 110 m) site. This study investigates the wind environment characteristics based on the wind data for the entire year of 2021. The analysis of anomalous data from the wind tower indicates that these are mainly caused by local freezing rain and snow conditions. The temporal variations and vertical distribution characteristics of the wind environment were analyzed. On an annual basis, winds predominantly originate from north–south, while those from east–west are relatively less frequent; 90% of the winds are less than 4 m/s; the maximum recorded wind speed is 22.29 m/s; the prevailing winds are from the SSE (south-southeast) direction. On a monthly basis, the distributions of wind direction and speed exhibit a distinct seasonal cycle, with wind speeds being relatively lower in winter. On a diurnal basis, the wind direction undergoes a reversal, with northerly winds prevailing during the day and southerly winds at night; the diurnal wind speed distribution shows that nocturnal wind speeds are relatively stable and lower. Daily wind speed statistics indicate that there were 79 days on which 90% of wind speeds throughout the day were less than or equal to 2 m/s. Compared to sites of other telescopes of a similar class, the wind environment at the QTT site is relatively favorable. Full article

This study focuses on a large-span highway tunnel in argillaceous soft rock. Numerical simulations were conducted to investigate the mechanical characteristics of the tunnel, constructed using the Double Side Drift Method (DSDM), and the effects of the offset distance between drift faces. Subsequently, field monitoring was performed to analyze the deformation patterns of the primary support at typical cross-sections. The results indicate the following: (1) During DSDM construction in argillaceous soft rock, the crown settlement of the left drift is the largest, while that of the central drift is the smallest. The left and right drifts converge inward, whereas the central drift expands outward, resulting in overall inward convergence of the tunnel section, with the left drift exhibiting a larger convergence. The crown settlement and horizontal convergence induced by excavation of the upper benches of each drift are greater than those caused by the lower benches. (2) The stresses in the primary support increase rapidly after excavation of each segment and then tend to stabilize. The maximum tensile stress occurs at the left haunch, reaching 0.41 MPa, while the maximum compressive stress occurs at the left arch waist, reaching 14.56 MPa. After the tunnel excavation is completed and the section is enclosed, the stress on the left side is significantly higher than that on the right, indicating an eccentric stress state. The plastic zones in the surrounding rock exhibit a butterfly-shaped distribution, mainly concentrated at the haunches and arch springings on both sides. (3) As the offset distance decreases, the deformation of the primary support reduces, whereas the stress and the area of the surrounding rock plastic zones increase. When the offset distance is less than 15 m, both the stress in the primary support and the plastic zone area increase sharply, suggesting that the drift face offset distance should not be less than 15 m. (4) Field monitoring shows that the maximum cumulative crown settlement of the primary support reaches 30.2 mm, and the cumulative horizontal convergence of the section is 35.6 mm, both of which are below the reserved deformation allowance. Full article

(1) Background: Intra-articular injection is a fundamental technique in preclinical research for evaluating therapeutics and inducing joint disease models in rodents. However, the absence of standardized and validated protocols compromises reproducibility and translational validity. (2) Methods: This study establishes and experimentally validates a refined protocol for precise intra-articular injection in the knee of adult male Wistar rats. The comprehensive procedure specifies anatomical landmarks (medial border of the patellar tendon), instrumentation (27 G needle, 100 µL Hamilton syringe), a maximum volume of 35 µL, and operative verification criteria based on tactile feedback. Experimental validation was performed by administering a suspension of wear particles (2.35 mg/mL) generated from tribocorrosion tests of CoCr surfaces biofunctionalized with graphene oxide-hyaluronic acid (GO-HA) into the left knee of five rats. (3) Results: Histological analysis using the cutting–grinding technique and Toluidine Blue staining confirmed the exclusive intra-articular localization of particles in all injected animals (5/5 success rate). Qualitative assessment revealed abundant particulate distribution within the synovial space, with numerous individual particles and multiple aggregates observed per high-power field, without evidence of extravasation in any case. (4) Conclusions: The protocol demonstrated high intra-operator repeatability and provides a reliable, ethically refined tool for precise intra-articular administration of nanomaterials and for generating robust joint disease models, thereby enhancing reproducibility and animal welfare in preclinical research. Full article

This study investigates the settlement characteristics of overlying strata in backfilled stopes at the Sanshandao Gold Mine, focusing on the compaction behavior of backfill materials. Integrating laboratory tests, numerical modeling, and field monitoring, we analyzed the particle size distribution and fractal dimensions of tailings (2.1525) and C material (2.1994), with tailings showing better gradation. Systematic compaction tests examined the effects of mix ratio, water content, and curing time. Results indicate that compression follows a viscous sliding model with exponential curves, progressing through three stages—pore compaction, structural deformation, and elastic/plastic deformation—with energy dissipation ratios of 1:5:18. Water content was the most influential factor, with optimal compaction occurring at 5~8%. Coupled Midas-Flac3D simulations estimated a theoretical compaction rate of 0~2% in filled stopes, excluding seepage and equipment effects. Field monitoring at the −480 m level revealed non-uniform settlement, with maximum subsidence of 63.75 mm above stopes and initial settlement rates of 12~20 mm/month. At the −520 m mining level, the backfill compaction rate reached 0.31%, with minor future increases expected. These findings offer valuable guidance for backfill mixture design and strata control in mining engineering. Full article