Search Results (269)

Many challenges are commonly encountered in the underground mining of steeply dipping thin-to-medium-thick orebodies associated with weak hanging wall rockmass, such as stope back collapse, high ore dilution, and poor stoping stability. To address these issues, a synergistic mining method combining sidewall retaining and open stoping with a delayed backfilling method is proposed. Taking the north wing orebody of the Erlihe lead–zinc mine as the engineering background, a 3D finite element numerical simulation model was established using MIDAS GTS(2026 version) to conduct a comparative analysis between the proposed mining method and the current mining method. The mechanical response characteristics of crown pillar stress, crown pillar settlement, hanging wall displacement, and plastic zone evolution were systematically investigated under different mining stages. The results show that the proposed method improves the stress and deformation distribution at the bottom of the crown pillar. The peak stress decreases from 13.72 MPa to 12.86 MPa, and the spatial extent of the high-stress zone is noticeably reduced. Meanwhile, the maximum crown pillar subsidence decreases, while the width of the main subsidence zone decreases from 11 nodes to 9 nodes, and the settlement of the end region decreases by 6.05%. In terms of hanging wall response, the maximum displacement is reduced by 9.3–26.5% during the stope extraction stage and 9.6–10.0% during the inter-pillar recovery stage, with an overall average reduction of approximately 14.0%. Furthermore, the plastic zone in the hanging wall surrounding rock becomes smaller and develops later under the proposed mining method. Our findings demonstrate that the new proposed mining method effectively modifies the stress transfer path, mitigates deformation of both the crown pillar and hanging wall rock, and delays the development of plastic failure, thereby improving stope stability under weak hanging wall rockmass conditions. The proposed method provides a practical technical solution for the safe and efficient extraction of steeply dipping thin-to-medium-thick orebodies. Full article

This study presents a pilot methodological investigation of the thermal performance of a Najdi mudbrick dwelling in Ushaiger, Saudi Arabia, using short-term field monitoring and a preliminary digital-twin inspired workflow. Two field campaigns in August and September 2025 measured indoor and outdoor conditions with a portable weather station under severe site constraints, including lack of electrical infrastructure, restricted access, and the use of consumer-grade sensors. The monitored results indicate that the massive earthen walls attenuated part of the outdoor daily temperature swing, but indoor conditions remained very hot: in August, indoor temperatures averaged 38.1 °C, compared with 40.2 °C outdoors, and in September, indoor temperatures averaged 36.3 °C, compared with 36.1 °C outdoors. A simplified IDA ICE model was compared with the monitored indoor temperature over the available windows, and a post-processing affine bias adjustment was tested only as a diagnostic short-window correction rather than as a transferable calibration. Monte Carlo sensitivity analysis was used in an exploratory way. It examined how passive envelope and boundary-related parameters influenced simulated indoor relative humidity, with infiltration emerging as the dominant factor affecting relative humidity dynamics; peak indoor relative humidity increased from about 67% at 0.15 air changes per hour (ACH) to more than 74% at 0.60 ACH, whereas wall thickness had a modest buffering effect. Given the short monitoring duration and field limitations, the study is not presented as a fully validated digital twin but as a feasibility-oriented workflow that combines constrained in situ monitoring with exploratory simulation to support future, longer-term conservation and adaptive reuse research on earthen heritage in hot–arid climates. Full article

This study investigates the sound insulation performance of an anechoic chamber, exploring the influence patterns of different multilayer material combinations on wall sound insulation characteristics. Based on sound transmission theory, a predictive model for multilayer material wall sound insulation was established. The finite element method was employed to simulate the sound propagation characteristics of walls and glass doors with various material combinations. After validating the simulation results through a double-room method experiment, the material combination scheme for the anechoic chamber walls and glass doors was optimized. Based on this, a 1000 mm × 1000 mm × 2300 mm soundproof room prototype was designed and constructed. Its sound insulation performance under reverberant conditions was tested using the insertion loss method and compared with simulation data. Simultaneously, a hybrid calculation method combining low-frequency finite element analysis with high-frequency statistical energy analysis enabled precise and efficient prediction of the overall sound insulation performance of the soundproof room. Research revealed that single-pane glass with thicknesses between 5 and 20 mm conformed to the mass law, with sound insulation increasing by an average of 0.8 dB per additional millimeter. The 10 mm single-pane glass emerged as the optimal choice for the soundproof room’s glass door due to its ideal thickness and excellent low-to-mid-frequency sound insulation. The optimized wall structure featured compact thickness, outstanding low-frequency sound insulation, and balanced mid-to-high-frequency performance. Simulation and experimental results for the core frequency range of 63–1000 Hz showed high consistency, which validates the reliability of the theoretical model and simulation methodology within this frequency band. The deviation of simulation results from experimental data in the frequency range above 1000 Hz is mainly caused by acoustic leakage due to experimental sealing defects, and the high-frequency simulation results are only used for trend analysis rather than conclusion support. This study identifies the optimal multi-layer material combination for soundproof rooms, providing practical material strategies for acoustic design. It also reveals the sound insulation mechanisms of multi-layer composite structures. The findings offer significant reference for optimizing soundproofing materials and structures in architectural acoustics and transportation noise control. Full article

In cold regions with prolonged subzero temperatures and abundant solar radiation, Trombe walls serve as high-efficiency passive solar building envelopes for improving indoor thermal comfort. This study aims to optimize the thermal performance of Trombe walls via a multimodal data analysis framework and a multiview measurement algorithm. Three distinct Trombe wall configurations were constructed and continuously monitored for 60 consecutive days under typical winter conditions (average temperature: −15 °C; solar radiation intensity: 800–1100 W/m²). Field-measured datasets, including solar radiation intensity, hourly air temperature distribution, and heat exchange efficiency, were systematically analyzed to quantify the impacts of ventilation mode, air gap width, and insulation thickness on thermal performance. The results demonstrate that the hourly peak surface temperature of the optimized Trombe wall reaches 25.7 °C at 13:00, which significantly improves indoor thermal comfort compared with conventional buildings. An air gap width of 6 cm minimizes indoor temperature fluctuations (fluctuation coefficient = 0.08), while a 20 mm insulation layer stabilizes heat loss reduction at 31.1% relative to non-insulated walls. The optimal operational parameter combination (6 cm air gap, 16 °C indoor set temperature) was determined based on the lowest temperature fluctuation and highest thermal efficiency, with experimental results deviating by less than 5% from established analytical models. This study verifies the reliability of the multimodal data analysis framework for Trombe wall performance evaluation, providing practical design guidelines for passive solar building envelopes in cold regions. Full article

Shell-and-tube falling film condensers are critical in fields like energy, petrochemicals, and waste heat recovery. Their operation predominantly involves the complex mixed condensation of steam and non-condensable gases. This process couples multi-physical phenomena—gas flow, liquid film dynamics, phase change, and non-condensable gas accumulation—making accurate prediction challenging. To better understand the underlying mechanisms, this paper develops a practical CFD simulation scheme. The scheme strongly couples the Species Transport model and the Eulerian-wall-film (EWF) model via User-Defined Functions (UDFs) to simulate condensate generation, inter-tube migration, and interphase transfer. Its reliability is validated through grid independence tests and comparisons with theoretical and experimental data. Using this model, the effects of inlet velocity, temperature difference, and non-condensable gas mass fraction are analyzed. Results indicate that higher inlet velocity significantly enhances heat and mass transfer, with the average wall heat transfer coefficient stabilizing at high velocities. While a larger temperature difference increases total heat transfer, its marginal benefit decreases, accompanied by reduced efficiency. A high non-condensable gas mass fraction severely inhibits condensation. Furthermore, the outer wall heat transfer coefficient of the tube bundle is highly non-uniform, with the liquid film thickness varying by over two orders of magnitude. This study provides theoretical and numerical insights for the optimal design and operation of falling film condensers. Full article

The use of appropriate thermal insulation is one of the fundamental methods for reducing a building’s energy demand. The article aims to assess the ecological effectiveness of reducing thermal energy losses through the external brick walls of a model single-family building. Environmental impacts resulting from the use of three alternative heat sources (a condensing gas boiler, an oil boiler, and a brine-to-water heat pump) and two types of insulation materials (EPS with recycled material and mineral wool) were determined. Oil heating has the highest combined environmental impact (EUR 4.392). Using EPS as an insulating material generates a lower environmental impact compared to mineral wool (EUR 2.846 vs. EUR 3.775). The impact of climatic conditions was also considered, taking into account seven building locations that correspond to the diverse climatic conditions found in different regions of Poland. The obtained values indicate a clear impact of both the thickness of the thermal insulation layer and the building’s location on the amount of heat loss and, consequently, environmental costs. In locations with higher average annual outdoor temperatures, the determined heat losses are approximately 20% lower. The most significant environmental benefits are observed when switching from no insulation to 150–200 mm of insulation. The results indicate that the environmental benefits resulting from reduced heat losses achieved through the use of thermal insulation are quickly offset by the externalities associated with the production of the insulation. For a thickness of 50 mm, the benefit–cost ratio (B/C) ranges from 1.7 to 8.4, indicating that the environmental benefits achieved by reducing heat loss are approximately two to eight times greater than the costs associated with producing the material. The B/C ratio decreases with increasing insulation thickness, regardless of the building’s location and the type of heat source. As the thickness increases to 100 mm, the ratio drops to 1–5. In the temperate climate zone, where Poland and others UE’s countries are located, a 100–150 mm layer of insulation offers the best compromise between environmental benefits and environmental costs. The results demonstrate the validity of using building insulation and may serve as an argument in environmental policy for supporting it with budgetary funds in Poland and the European Union. Full article

This study presents a case-specific joining method for modular, large-scale components manufactured using Selective Laser Sintering (SLS). A T-slot joint reinforced with a pultruded carbon fiber rod was developed to enable the segmental assembly of polymer fan blades that exceed the build volume of common SLS printers. Through an iterative design process, five joint variations were investigated, focusing on the optimization of slot geometry (fillet radii and wall thickness) and the integration of carbon fiber reinforcements to create a high-strength hybrid connection. The experimental findings were validated using a non-linear finite element analysis (FEA) utilizing an iteratively calibrated Young’s modulus of 710 MPa, which accounts for the 50/50 virgin-to-reused PA2200 powder ratio employed in the study. The numerical model identified that the primary sites for crack initiation were the fillet radii of the female slot, where localized equivalent plastic strains reached critical levels of up to 84% in tension and 78% in bending. The final design achieved an average tensile strength of 27.6 MPa, exceeding the design threshold of 21.9 MPa with a safety factor of 2.5. While unreinforced joints showed a 73.4% reduction in bending strength compared to solid specimens, the addition of an 8 mm carbon rod increased performance by 238.7%, restoring over 90% of the monolithic material’s strength. Numerical results confirmed that the reinforcement assumed the primary load-bearing role, effectively mitigating stresses in the polymer matrix below the ultimate tensile strength. Failure analysis clarified that the observed audible failure originated from internal fiber breakage within the rod at stresses between 900–1050 MPa. This work demonstrates that a segmental, reinforcement-based joining method can effectively overcome size constraints in polymer additive manufacturing, providing a robust and repeatable solution for rotating components subject to complex loading conditions. Full article

Hydroforming has become an effective manufacturing technique for asymmetric corrugated thin-walled tubular components in lightweight automotive structures, owing to its capability to integrally form complex geometries. In this study, a finite-element model of the hydroforming process for 316L stainless-steel asymmetric corrugated thin-walled tubes was established, and three representative internal pressure loading paths—pulsating, linear, and stepped—were investigated using the DYNAFORM/LS-DYNA platform. The effects of different loading paths on material flow behavior, strain evolution, and forming quality, particularly wall-thickness distribution, were systematically compared. Among the three loading strategies, the pulsating pressure path exhibited the most balanced forming performance for asymmetric thin-walled tubes in terms of overall forming quality and wall-thickness control, although limited forming stability was observed in the initial pulsation scheme. To address this limitation, a dual-window orthogonal pulsation strategy was employed to optimize the initial pulsating loading path and further enhance its forming performance. The optimized pulsating curve completely eliminated the wrinkling tendency in the corrugated regions and reduced the maximum wall-thickness thinning ratio from 21.8% to 19.6%. Furthermore, the numerical simulation results show good agreement with experimental observations, with both the average wall-thickness deviation and the minimum wall-thickness error calculated using the interpolation method remaining within 2%. These results confirm the effectiveness of the optimized pulsating loading path for the hydroforming process design of asymmetric corrugated thin-walled tubes. Full article

To study the forming, microstructures, and mechanical properties of high-speed laser cladding thin-walled tube, 1Cr17Ni2 powder was used to perform high-speed laser cladding on a 1Cr17Ni5 stainless steel tube with a thickness of 1 mm. The effects of powder feeding rate, laser power, rotation speed, protective gas flow rate, powder defocusing amount, and powder feeding gas flow rate on the width, height, and penetration depth of the weld beads were investigated. Subsequently, the cladding of multi-pass was carried out, and the microstructures and microhardness of the cladding layer were studied. The results showed that laser power had the most significant effect on the width of the weld bead, and the width gradually increased with the increase in power. The powder feeding rate had the most significant effect on the height of the weld bead, and the height gradually increased with the increase in powder feeding speed. The powder feeding rate also had the most significant effect on the penetration depth, and the penetration depth gradually decreased with the increase in powder feeding speed. When multiple passes overlap, the microstructure of the cladding layer exhibits a distinct periodic distribution. Large-sized primary austenite columnar crystals exist in the cladding layer, and the main microstructure in the columnar crystals is martensite and possesses a small amount of residual austenite. The base material is composed of austenite and a small amount of martensite. The average microhardness of the substrate is 366 HV, and the microhardness of the cladding layer gradually decreases with increasing distance from the fusion line, from 562 HV to 532 HV. Due to the heat effect of the cladding on the substrate, the microhardness of the substance near the fusion line is only 239 HV. As the distance from the fusion line increases, the influence of heat effect decreases, and the microhardness gradually increases. Full article

As a natural building material, rammed earth has gained significant attention due to its environmental friendliness, low cost, and sustainability. This study conducted a dynamic simulation of heat and moisture transfer in rammed earth and brick buildings to compare their energy performance under identical conditions. The results indicated that the annual minimum indoor temperature in rammed earth buildings was 0.7 °C higher, while the maximum was 0.4 °C lower than that in brick buildings. The minimum and maximum indoor relative humidities were 11.4% higher and 9.6% lower, respectively, in rammed earth buildings, with an annual average of 69.2%, which is slightly lower than that of brick buildings. The annual heating and cooling energy consumption in brick buildings was 1.37 and 1.2 times greater, respectively, than in rammed earth buildings, and their monthly dehumidification demands were consistently higher. The effect of wall thickness on energy consumption revealed that increasing the thickness from 200 to 250 mm reduced energy use by 9.3%, whereas an increase from 450 to 500 mm yielded a 4.2% reduction. When the wall thickness exceeded 400 mm, the energy savings were marginal (<5%), whereas the construction costs and space occupancy increased. Therefore, a wall thickness of 350–400 mm is recommended to optimize the trade-off between energy efficiency, thermal-moisture performance, and cost-effectiveness. Full article

This paper proposes a novel mortise-and-tenon grouted masonry (MTGM) structure to enhance the mechanical performance and engineering applicability of masonry. The axial and eccentric compressive behavior of the system was systematically investigated through experimental testing and numerical simulation. A refined three-dimensional finite element model, developed in DIANA, effectively accounted for material nonlinearity and interfacial contact, with its high accuracy confirmed by experimental results. The parametric analysis of 52 numerical models elucidated the influence of block strength, core material type, wall thickness, steel fiber content, and geometric ratios on the compressive strength, deformation capacity, and failure modes. The results demonstrate that using steel fiber-reinforced concrete (SFRC) as the core filling material significantly enhances ductility and toughness; an SFRC content of 1.6% increased the ultimate strain by approximately 37%. Furthermore, increasing the eccentricity from 0.1 to 0.3 led to an average 40% reduction in load-bearing capacity. Theoretical analysis led to the derivation of calculation formulae relating to key axial compression parameters. Furthermore, a stress–strain constitutive relationship suitable for MTGM was established, featuring a parabolic ascending branch and a linear descending branch (R² = 0.992). For eccentric compression, a practical design method was developed based on the plane section assumption, which demonstrated superior predictive accuracy compared to existing code provisions. This study provides a reliable theoretical foundation and practical computational tools for the structural design and application of MTGM. Full article

Accurate measurement of wall shear stress (WSS) is essential for both fundamental and applied fluid dynamics, where it governs boundary-layer behavior, drag generation, and the performance of flow-control systems. Yet, existing WSS sensing methods remain limited by low spatial resolution, complex instrumentation, or the need for user-dependent calibration. This work introduces a method based on artificial intelligence (AI) and Oil-Film Interferometry, referred to as AI-OFI, that transforms a classical optical technique into an automated and sensor-like platform for local WSS detection. The method combines the non-intrusive precision of Oil-Film Interferometry with modern deep-learning tools to achieve fast and fully autonomous data interpretation. Interference patterns generated by a thinning oil film are first segmented in real time using a YOLO-based object detection network and subsequently analyzed through a modified VGG16 regression model to estimate the local film thickness and the corresponding WSS. A smart interrogation-window selection algorithm, based on 2D Fourier analysis, ensures robust fringe detection under varying illumination and oil distribution conditions. The AI-OFI system was validated in the high-Reynolds-number Long Pipe Facility at the Centre for International Cooperation in Long Pipe Experiments (CICLoPE), showing excellent agreement with reference pressure-drop measurements and conventional OFI, with an average deviation below 5%. The proposed framework enables reliable, real-time, and operator-independent wall shear stress sensing, representing a significant step toward next-generation optical sensors for aerodynamic and industrial flow applications. Full article

To address the poor thermal insulation and freeze resistance of rural outdoor toilets in cold regions—key obstacles to achieving the UN Sustainable Development Goal (SDG) 6.2 and popularizing rural sanitary toilets—this study fills the literature gap of insufficient research on passive solar heating systems tailored for rural toilets in cold climates. Using TRNSYS simulation, Plackett–Burman key factor screening, single-factor experiments, and Box–Behnken response surface methodology, we optimized the system with building envelope thermal parameters and Beijing’s typical meteorological year data as inputs, taking January’s average indoor temperature as the core evaluation index. Results indicated six parameters (solar wall area, air cavity thickness, vent area ratio, vent spacing, exterior wall insulation thickness, and heat-gain window-to-wall ratio) significantly influence indoor temperature (p < 0.05). The optimal configuration was as follows: solar wall area 3.45 m², window-to-wall ratio 30%, exterior wall insulation thickness 200 mm, vent spacing 1800 mm, air cavity thickness 43 mm, and vent area ratio 5.7%. Post-optimization, the average temperature during the heating season reached 10.81 °C (79.5% higher than baseline), with January’s average, maximum, and minimum temperatures at 7.95 °C, 20.47 °C, and −1.42 °C, respectively. This solution effectively prevents freezing of flushing fixtures due to prolonged low temperatures, providing scientific support for the application of passive rural toilets in China’s cold regions. Full article

With the increasing functional and geometric complexity of modern steel buildings, irregular-shaped beam-to-column joints are becoming common in engineering practice. However, their seismic behavior remains insufficiently understood, particularly for configurations with geometric asymmetry and complex stress transfer mechanisms. This study experimentally investigates the seismic performance of irregular steel-beam-to-concrete-filled steel tube (CFST) column joints incorporating inclined internal diaphragms (IIDs), taking unequal-depth beam (UDB) and staggered beam (SB) joints as representative cases. Two full-scale joint specimens were designed and tested under cyclic loading to evaluate their failure modes, load-bearing capacity, stiffness/strength degradation, energy dissipation capacity, strain distribution, and panel zone shear behavior. Both joints exhibited satisfactory strength and initial stiffness. Although diaphragm fracture occurred at approximately 3% drift, the joints retained 45–60% of their peak load capacity, based on the average strength of several loading cycles at the same drift level after diaphragm failure, and maintained stable hysteresis with average equivalent damping ratios above 0.20. Final failure was governed by successive diaphragm fracture followed by the tearing of the column wall, indicating that the adopted diaphragm thickness (equal to the beam flange thickness) was insufficient and that welding quality significantly affected joint performance. Refined finite element (FE) models were developed and validated against the test responses, reasonably capturing global strength, initial stiffness, and the stress concentration patterns prior to diaphragm fracture. The findings of this study provide a useful reference for the seismic design and further development of internal-diaphragm irregular steel-beam-to-CFST column joints. Full article

Honey authenticity, including its botanical origin, is traditionally assessed by melissopalynology, a labour-intensive and expert-dependent method. This study reports the final validation of a deep learning model for pollen grain classification in honey, developed within the NUTRITECH.I-004A/22 project, by comparing its performance with that of an independent palynology expert. A dataset of 5194 pollen images was acquired from five unifloral honeys, rapeseed (Brassica napus), sunflower (Helianthus annuus), buckwheat (Fagopyrum esculentum), phacelia (Phacelia tanacetifolia) and linden (Tilia cordata), under a standardized microscopy protocol and manually annotated using an extended set of morphological descriptors (shape, size, apertures, exine ornamentation and wall thickness). The evaluation involved training and assessing a deep learning model based solely on the ResNet152 architecture with pretrained ImageNet weights. This model was enhanced by adding additional layers: a global average pooling layer, a dense hidden layer with ReLU activation, and a final softmax output layer for multi-class classification. Model performance was assessed using multiclass metrics and agreement with the expert, including Cohen’s kappa. The AI classifier achieved almost perfect agreement with the expert (κ ≈ 0.94), with the highest accuracy for pollen grains exhibiting spiny ornamentation and clearly thin or thick walls, and lower performance for reticulate exine and intermediate wall thickness. Misclassifications were associated with suboptimal image quality and intermediate confidence scores. Compared with traditional melissopalynological assessment (approx. 1–2 h of microscopic analysis per sample), the AI system reduced the effective classification time to less than 2 min per prepared sample under routine laboratory conditions, demonstrating a clear gain in analytical throughput. The results demonstrate that, under routine laboratory conditions, AI-based digital palynology can reliably support expert assessment, provided that imaging is standardized and prediction confidence is incorporated into decision rules for ambiguous cases. Full article