Search Results (2,163)

With the increasing demand for sustainable building materials, it is essential to investigate the durability of recycled fine aggregate concrete (RFAC) under corrosive environmental conditions. This study systematically assessed the performance of RFAC with three compressive strengths after dry–wet cycles in chloride and sulfate environments, respectively. The experimental program encompassed measurements of compressive strength, mass variation, porosity, ion penetration depth, and free ion content, complemented by comprehensive microstructural characterization. Results show that under sulfate exposure, 20 MPa and 40 MPa RFAC suffered significant strength losses of 60.1% and 18.0% after 70 cycles, while 60 MPa RFAC gained 2.5% strength. In chloride environments, 20 MPa and 40 MPa RFAC experienced strength reductions of 30.7% and 6.9%, whereas 60 MPa RFAC increased in strength by 6.6%. Compared to sulfate exposure, all groups exhibited slight mass increases or porosity reduction under chloride exposure, with high-strength RFAC showing the most noticeable densification. The chloride penetration depth in RFAC of 60 MPa was measured at 14.65 mm, representing a 41.0% reduction compared to RFAC of 20 MPa; sulfate penetration depth was 17.84 mm, which is 44.6% lower than that of the 20 MPa counterpart. Microstructural analysis revealed that sulfate-induced ettringite and gypsum formation triggered crack propagation, while chloride mainly affected pore structure through crystallization and filling, and the formation of C-S-H in high-strength RFAC inhibits pore expansion and mitigates deterioration. Full article

Kinetic façades represent a climate-responsive design solution that improves building adaptability by responding to seasonal needs such as daylighting and shading. They offer an attractive retrofit strategy that improves both the esthetics and environmental performance of buildings. This study investigated the integration of an origami-inspired kinetic façade into a student dormitory building located in Dhahran, Saudi Arabia. Using numerical simulations, 35 façade configurations were analyzed under varying conditions of façade orientations, closure ratios (from 5% to 95%), and cavity depths (from 20 cm to 100 cm). The findings highlight the critical impact of kinetic façade design characteristics on daylight availability and solar exposure and the required trade-off between these two variables. In this context, this study observed that at higher façade closure ratios, increasing cavity depth could effectively mitigate daylight reduction by promoting reflected daylight penetration inside the cavity. As for heat gains and cooling load reduction, mid-range façade closure, 50 cm in this study, achieved balanced performance across the three examined orientations. However, the southern façade showed slightly higher efficiency compared to the eastern and western façades, which achieved lower cooling reductions and showed a similar UDI compromise. Thus, a dynamic façade operation is recommended, where higher closure ratios could be applied during peak solar hours on the east in the morning and the west in the afternoon to maximize cooling savings, while moderate closure ratios can be maintained on the south to preserve daylight. Future work should incorporate real-time climatic data and smart control technologies to further optimize kinetic façade performance. Full article

Titanium (Ti) alloy sheets are important mechanical and structural components. However, thickness deviations may occur during the production of Ti-alloy sheets, significantly compromising product quality and structural safety. Eddy current testing (ECT) is a common method for measuring the thickness deviation of metal sheets. Nevertheless, conventional ECT methods often rely on complex calibration procedures or iterative inversion algorithms, thereby limiting their applicability. It was found that when low-frequency ECT excitation is used, such that the eddy current penetration depth exceeds three times the maximum target thickness of the Ti-alloy sheet, the tangent of the ECT coil impedance phase exhibits a linear relationship with the thickness. Based on this observation, by analyzing the low-frequency ECT response of Ti-alloys and separating the real and imaginary parts of the impedance under approximate conditions, a phase feature model was developed. The model effectively describes the linear dependence of the phase tangent on the thickness of the Ti-alloy sheet, offering a succinct characterization. The measurement method based on this model thereby allows for direct thickness calculation from the measured coil impedance without requiring master-curve calibration or iterative computation. Experiments were conducted using a custom-designed ECT coil and impedance analyzer to measure different Ti-alloy specimens. The results indicate that the measurement error was less than 3.5%. This research provides a theoretical foundation as well as a straightforward engineering solution for online, high-speed thickness measurement of Ti-alloy sheets. Full article

Background: Hollow posts have been introduced in clinical practice, providing the possibility of injecting luting resin directly into the post. The aim of our study was to compare quartz fiber hollow posts with solid posts. Methods: In total, 20 human teeth with straight single root canals were utilized for this study, divided into two groups with 10 elements each, one restored with radiopaque quartz fiber hollow posts and the other with radiopaque quartz fiber solid posts. In total, two micro-CT (micro-computerized tomography) analyses allowed us to evaluate both the presence of air voids in the luting resin and the different capacities of posts to penetrate until full depth into the post space. Results: The authors observed that hollow quartz fiber posts create a smaller volume of air voids in the luting resin (p < 0.01) and better fit (p < 0.05) the post space compared to the solid posts. Conclusions: Hollow posts can promote retention. Future studies with larger samples are encouraged to confirm these findings and provide possible better long-term results for post-endodontic reconstructions in vivo. Full article

Geophysical techniques are a core toolkit of modern archeology, thanks to their effectiveness in reconstructing important pieces of evidence for buried ruins, which are relics of the past usage of an inspected site. Some methodological approaches and advancements are proposed for investigating the site of Gela, which was one of the most important western Greek colonies, founded in 689–688 BC on the southern coast of Sicily, Italy. The ancient settlement was developed on a hill, mostly flat on the top, and over its sides. The archeological evidence discovered so far in the acropolis of the city can be attributed to two main architectural typologies: urban blocks and archaic temples. Based on these targets, a geophysical protocol has been tested, utilizing passive seismic, electrical resistivity tomography (ERT), and ground-penetrating radar (GPR) methods. Where the lowest physical contrast was expected among possible archeological remains and burying soil (close to the urban blocks area), the three geophysical techniques have been jointly applied, while an innovative support-to-interpretation approach for GPR datasets is proposed and developed over both kinds of archeological targets. Our experimental outcomes underline the effectiveness (and possible weaknesses) of the two geophysical investigation strategies against various targets producing different signal-to-noise responses, thanks to the synergistic contributions from multi-method and multi-depth approaches. The integrated use of GPR, ERT, and passive seismic methods allowed the reconstruction of complementary information, with each method compensating for the limitations of the others. This combined approach provided a more robust and comprehensive understanding of the subsurface features than would have been achieved through the application of any single technique. Full article

The displacement of synchronous machines by inverter-based resources raises critical concerns regarding the stability of future low-inertia power systems. Grid-forming (GFM) inverters offer a pathway to address these challenges by autonomously establishing voltage and frequency while emulating inertia and damping. This paper investigates the feasibility of operating a transmission-scale network with 100% GFM penetration by fully replacing all synchronous generators in the IEEE 39-bus system with a heterogeneous mix of droop, virtual synchronous machine (VSM), and synchronverter controls. System stability is assessed under a severe fault-initiated separation, focusing on frequency and voltage metrics defined through center-of-inertia formulations and standard acceptance envelopes. A systematic parameter sweep of virtual inertia (H) and damping ($D_p$) reveals their distinct and complementary roles: inertia primarily shapes the Rate of Change in Frequency and excursion depth, while damping governs convergence speed and steady-state accuracy. All tested parameter combinations remain within established stability limitations, confirming the robust operability of a fully inverter-dominated grid. These findings demonstrate that properly tuned GFM inverters can enable secure and reliable operation of future power systems without reliance on synchronous machines. Full article

Transcranial focused ultrasound is a promising noninvasive technique for neuromodulation in neurological and psychiatric disorders, but accurate prediction of acoustic transmission through the skull remains a major challenge. In this study, we present a five-layer numerical human head model that integrates frequency-dependent acoustic parameters with nonlinear time-explicit dynamics to realistically capture ultrasound propagation. The model explicitly represents skin, trabecular bone, cortical bone, and brain, each assigned experimentally derived acoustic properties across a clinically relevant frequency range (0.5–5 MHz). Numerical simulations were performed in the frequency domain and time-explicit to quantify sound transmission loss and focal depth under high-intensity and high-frequency stimulation. The results show the effect of frequency, radius of curvature, and skull thickness on maximum pressure ratio, focal depth, and focus zone inside the brain tissue. Findings indicate that skull geometry, particularly radius of curvature and thickness, strongly influences the focal zone, with thinner skull regions allowing deeper penetration and reduced transmission loss. Comparison of the frequency-domain model with the time-explicit model demonstrated broadly similar trends; however, the frequency-domain approach consistently underestimated transmission loss and was unable to capture nonlinear effects such as frequency harmonics. These findings highlight the importance of nonlinear, time-explicit modeling for accurate transcranial ultrasound planning and suggest that the proposed framework provides a robust tool for optimizing stimulation parameters and identifying ideal target zones, supporting the development of safer and more effective neuromodulation strategies. Full article

Accurate prediction of the rate of penetration (ROP) in deep and ultra-deep wells remains a major challenge due to complex downhole conditions and limited real-time data. To address the issues of physical inconsistency and weak generalization in conventional da-ta-driven approaches, this study proposes a mechanism-guided and attention-enhanced deep learning framework. In this framework, drilling physical principles such as energy balance are reformulated into differentiable constraint terms and directly incorporated in-to the loss function of deep neural networks, ensuring that model predictions strictly ad-here to drilling physics. Meanwhile, attention mechanisms are integrated to improve feature selection and temporal modeling: for tree-based models, we investigate their implicit attention to key parameters such as weight on bit (WOB) and torque; for sequential models, we design attention-enhanced architectures (e.g., LSTM and GRU) to capture long-term dependencies among drilling parameters. Validation on 49,284 samples from 11 deep and ultra-deep wells in China (depth range: 1226–8639 m) demonstrates that the synergy between mechanism constraints and attention mechanisms substantially improves ROP prediction accuracy. In blind-well tests, the proposed method achieves a mean absolute percentage error (MAPE) of 9.47% and an R² of 0.93, significantly outperforming traditional methods under complex deep-well conditions. This study provides reliable intelligent decision support for optimizing deep and ultra-deep well drilling operations. By improving prediction accuracy and enabling real-time anomaly detection, it enhances operational safety and efficiency while reducing drilling risks. The proposed approach offers high practical value for field applications and supports the intelligent development of the oil and gas industry. Full article

Carbon-fiber-reinforced plastic (CFRP) machining by ultrashort-pulse lasers promises high precision but is limited due to the heterogeneous epoxy–carbon fiber structure, which creates heat-affected zones and variable kerf quality. This work investigates synthesized copper hydroxyphosphate as a laser-absorbing additive to improve femtosecond (1030 nm) laser ablation of CFRP. Copper hydroxyphosphate particles were synthesized hydrothermally and incorporated into an epoxy matrix to produce single-ply CFRP laminates. Square patterns (0.5 × 0.5 mm) were ablated with a pulse energy of 0.5–16 μJ. Then, ablated volumes were profiled and materials characterized by SEM and EDS. In neat epoxy the copper additive reduced optimum ablation efficiency and decreased penetration depth, while producing smoother, less porous surfaces. In contrast, CFRP with copper hydroxyphosphate showed increased efficiency and higher penetration depth. SEM and EDS analyses indicate more uniform matrix removal and retention of resin residues on fibers. These results suggest that copper hydroxyphosphate acts as a local energy absorber that trades volumetric removal for improved surface quality in epoxy and enhances uniformity and process stability in CFRP femtosecond laser machining. Full article

Pulse wave velocity (PWV) is a useful biomarker in the monitoring and risk stratification of various cardiovascular diseases including hypertension. The current gold standard for non-invasive measurement is carotid-femoral PWV (cfPWV) measurement via direct tonometry. However, cfPWV provides only a global PWV measure, which emphasises the need for an alternative capable of local PWV assessment. There are several alternatives for local PWV measurement proposed in the literature and one promising alternative is ultrasound, which offers good penetration depth, accessibility, and a relatively low cost, making it well-suited for non-invasive, real-time acquisition of haemodynamic parameters for PWV estimation. This paper aims to evaluate the different approaches for ultrasound-based acquisition while considering technical and physiological constraints to optimise the accuracy, reliability, and reproducibility of the parameters collected for estimation. In particular, this paper focuses on the flow-area (QA) and lnDiameter-velocity (lnDU) methods, which require local area and velocity data for PWV estimation. Accordingly, this paper discusses the use of ultrasound imaging in vessel data acquisition, highlights various challenges and considerations to be managed during acquisition and processing, outlines the different ultrasound-based imaging modalities for acquiring area and velocity data, and compares the simultaneous and non-simultaneous acquisition of data for PWV estimation. Full article

Cofferdams provide dry, stable working conditions for construction in marine environments. However, conventional methods often require significant time and cost for installation and removal, and are prone to leakage. This study proposes a novel method for the rapid and efficient construction of a large-diameter circular cofferdam using suction-driven installation and extraction. As opposed to conventional suction bucket foundations, the upper part of the cofferdam remains exposed above the water surface, and several prefabricated segments are assembled to form a single suction unit. A full-scale field test was conducted in Jebudo, Republic of Korea, using a 20 m-diameter, 13 m-high circular steel cofferdam. The test program included the design and fabrication of a suction cover and an optimized piping system. The key measurements during installation included the suction pressure variation with the penetration depth, leakage at the segmental joints, structural deformations, and inclination. The cofferdam successfully penetrated to a target embedment depth of 5 m at an average rate of 1.83 m/h and was safely removed using reverse suction. Although suction technology has been widely applied to offshore foundations and anchors, this study is the first to demonstrate its feasibility for large cofferdams. These results provide a foundation for future offshore applications of suction-driven cofferdam installations. Full article

The superconducting properties of YBa₂Cu₃${\mathrm{O}}_{7-\delta }$ thin films were investigated by conducting 1.7 MeV proton irradiations with a total fluence of $2.64\times {10}^{17}$${\mathrm{p}/\mathrm{cm}}^2$. The superconducting critical temperature ($T_c$) was reduced from 89.4 K to 10.1 K. The experimental procedure was similar to a previous study (0.6 MeV proton irradiation). We compared the effectiveness of $T_c$ suppression by varying the proton energy from 0.6 to 1.7 MeV and found that in general both protons of 1.7 MeV and 0.6 MeV were effective in suppressing the $T_c$ of YBCO. In particular, both results were consistent with the theoretical expectation (generalized d-wave AG theory) when a zero-temperature London penetration depth (${\lambda }_0$) = 215 nm is assumed for thin-film YBCO. For heavily irradiated cases (more than 80% $T_c$ suppression), however, 1.7 MeV protons were more effective in suppressing $T_c$ than 0.6 MeV protons. This can be understood by the fact that in the thin-film limit, higher-energy protons tend to produce less clustered point defects while lower-energy protons tend to create agglomeration of point defects. Full article

Submarine power cables (SPCs), as critical infrastructure for offshore wind farms, are the primary conduits for transmitting electricity from turbines to the grid. Actions such as seabed friction can cause damage to the submarine power cable’s outer sheath, accelerating the penetration of seawater corrosion media. This subsequently leads to corrosion fatigue or excessive loading in the tensile armor layer, which seriously threatens the long-term operational reliability of SPCs and the security of energy transmission. Based on homogenization theory and periodic boundary conditions, a repetitive unit cell (RUC) ABAQUS finite element model for a single-core submarine power cable (SPC) was established in this paper. And the mechanical response of the single-core SPC with the corroded tensile armor layers under tensile loading condition were systematically investigated. By comparing with a full-scale model, the feasibility and accuracy of the cable RUC damaged model proposed in this paper were effectively verified. It was found that the RUC damaged model exhibits significant stress concentration phenomena due to localized corrosion damage in the tensile armor layers, with its maximum von Mises stress being considerably higher than that of the RUC intact model; the elastic tensile stiffness of the SPC continuously decreases with increasing corrosion damage depth, but the magnitude of this reduction is small. This is because the corroded region is relatively small compared to the entire cable model dimension. This research reveals the potential impact of localized corrosion on the mechanical performance of the tensile armor layer, which can hold significant engineering importance for assessing the remaining load-bearing capacity of in-service SPCs and ensuring the reliability of subsea energy transmission corridors. Full article

The focus of this study was the investigation of the quasi-simultaneous laser welding (QSW) technique of polymethyl methacrylate (PMMA) and acrylonitrile butadiene styrene (ABS) in a T-joint configuration using a circular wobble laser path. The main aim was to find how laser parameters, such as scanning speed, number of scans, and laser power, influence key indicators of weld quality: penetration depth and weld strength. A range of scanning speeds (1–2 m/s) and scan repetitions (20–70) was explored, with the goal of keeping the total welding time around 1 s, a time compatible with industrial mass production. The results demonstrated a clear correlation between linear energy density and penetration depth. Deeper penetrations were achieved at higher energy levels. Weld strength was maximized with a lower number of scans (20) and higher powers (above 130 W). The configuration offering the best combination of weld strength (1137 N) and total welding time (0.8 s) was identified, demonstrating the suitability of QSW for mass production. Full article

Underground pipelines form a critical part of urban infrastructure, yet their complex configurations and fragmented documentation hinder efficient maintenance and risk management. Ground-penetrating radar provides a non-invasive method for subsurface inspection; however, traditional interpretation of B-scan data relies heavily on manual analysis, which is time-consuming and prone to error. This research proposes a two-step automated system for the detection and quantitative characterization of underground pipelines from GPR B-scans. In the first step, hyperbolic reflections are automatically detected and localized using state-of-the-art object detection algorithms, where YOLOv11x achieved superior stability compared to RT-DETR-X. In the second step, detected hyperbolic reflections are processed in order to estimate key parameters, including two-way travel time, burial depth, pipeline diameter, and the angle between GPR survey line and pipeline. Experimental results from 5-fold cross-validation demonstrate that TWTT and burial depth can be estimated with high performance, while pipeline diameter and angle exhibit moderate performance, reflecting their higher complexity and sensitivity to noise. According to the experimental results, EfficientNetV2L consistently produced the best overall performance. The proposed automated system reduces reliance on manual inspection, improves efficiency, and establishes a foundation for real-time, autonomous GPR-based underground infrastructure assessment. Full article