Search Results (208)

Water leakage in water supply pipeline networks leads to water resource loss, drinking water contamination, and ground subsidence. The existing acoustic leak detection techniques are constrained by low signal-to-noise ratios of leakage signals, difficulties in wave velocity estimation, and rapid signal attenuation, often resulting in localization errors of several meters. This study proposes a “wavenumber–frequency spectrum filtering and phase analysis” method for leak source localization, achieving precise positioning of underground water pipeline leaks through surface-mounted sensor array sampling. Based on the numerical simulation results, this research reveals the wavenumber–frequency spectrum characteristics of leakage noise on the ground surface, analyzes the impact of the sampling strategies on the wavenumber extraction, and ultimately constructs a localization model suitable for near-field array sampling. A mean localization error of 0.0374 m was achieved in a controlled experiment under single-layer sandy soil conditions, demonstrating the feasibility and accuracy of the proposed method under these tested conditions and providing a promising basis for precise leak localization in water supply networks that warrants further field validation. Full article

Sunscreen-derived ultraviolet (UV) filters are emerging pollutants of increasing concern in coastal ecosystems. This study presents the development, optimization, and field validation of Mar_Spectra, a compact spectroradiometric system mounted on an unmanned aerial vehicle (UAV) designed to detect sunscreen UV filters in surface waters. The system integrates an Ocean Optics microspectrometer with a Raspberry Pi microprocessor, a GPS receiver, an altimeter, and an RGB camera for synchronized image acquisition. Spectral measurements were processed to derive remote sensing reflectance ($R_{rs}$) using a Zenith Lite reference panel. Controlled calibration experiments confirmed the system’s sensitivity in the 300–380 nm range and allowed the definition of a convenient index $\left(i_S\right)$ exhibiting a strong linear relationship with total UV-filter concentration (R² = 0.964). Environmental tests indicated that wind, turbidity, and algal presence reduced detection capacity, while stable solar conditions improved spectral consistency. Despite its sensitivity to environmental variability, the Mar_Spectra device demonstrated consistent and reproducible performance under real field conditions, providing a cost-effective and scalable approach for near-real-time monitoring of UV filters and enhancing spatially resolved coastal pollution surveillance Full article

Existing analytical models for Fiber-Reinforced Polymer (FRP)-strengthened timber beams are generally limited to individual strengthening techniques and cannot readily accommodate hybrid reinforcement systems. This study develops a generalized analytical model to predict the flexural capacity of timber beams strengthened with near-surface-mounted (NSM) FRP bars, externally bonded FRP sheets, or their hybrid combination within a unified theoretical framework. The model is formulated based on internal force equilibrium and strain compatibility, incorporating a constitutive model for timber with linear elastic tensile behavior and a bilinear compressive stress–strain relationship including post-peak softening. The generalized formulation can be readily adapted to different strengthening configurations through appropriate simplifications. The proposed model was validated against experimental results obtained from four-point bending tests on small-scale timber beams strengthened with NSM GFRP bars and externally bonded GFRP sheets. The analytical predictions showed good agreement with the experimental results, with differences generally ranging from 2% to 23%, demonstrating satisfactory predictive accuracy. The experimental results further showed that the hybrid strengthening system increased the flexural capacity of the timber beams by up to 84% compared with the unstrengthened control beams, while also improving stiffness, ductility, and overall structural response. Failure was primarily due to timber tensile rupture and longitudinal splitting, whereas the GFRP reinforcement remained effective without rupture, indicating efficient utilization of the strengthening system. The proposed generalized analytical model provides a practical and reliable design tool for predicting the flexural strength of timber beams strengthened with various FRP reinforcement configurations, thereby supporting the structural rehabilitation and sustainable retrofitting of timber structures. Full article

The performance degradation of Permanent Magnet Synchronous Motors (PMSMs) is caused by nonlinear friction torque during low-speed operation, a phenomenon known as low-speed crawling. To address this issue, a composite compensation strategy based on a piecewise modeling approach is proposed in this paper. To accurately characterize the friction behavior, a dynamic learning rate neural network (DLRNN) is utilized for the ultra-low-speed region, while an optimal 5th-order polynomial model is established for the low-speed region. Building on this piecewise modeling, a composite control strategy with friction compensation is studied. This strategy employs a friction compensator for the feedforward compensation of the deterministic friction torque components. Furthermore, a reduced-order extended state observer (RESO) is designed to estimate and compensate for residual friction errors and random disturbance torques, thereby achieving high-precision motor control. Finally, experimental results on a surface-mounted PMSM validate that the proposed strategy effectively improves tracking accuracy and suppresses torque ripple near zero-speed, all while remaining within the computational constraints of standard industrial control hardware. Full article

The worldwide spread of semiconductor devices has driven a surge in electronic waste (e-waste), which reached 62 million metric tons in 2022 and is projected to exceed 80 million metric tons by 2030. E-waste contains hazardous substances such as cadmium and mercury, yet also represents a $57 billion annual opportunity through the recovery of valuable and critical raw materials (CRMs). However, formal recycling rates remain stagnant at 22.3%, largely due to limitations of current automated sorting methods. These systems primarily rely on visible-light (RGB) imaging, which lacks the spectral resolution needed to distinguish chemically similar polymers, complex metal alloys, and composite substrates on printed circuit boards (PCBs). This paper presents a multidisciplinary synthesis of AI-driven detection and classification for e-waste, bridging materials science and computer vision through three interconnected themes. 1. Material and Economic Context: The toxicological risks and economic drivers of semiconductor recycling are characterized, framing fine-grained material identification as essential for a circular economy. 2. Multispectral Sensing & Fusion: Sensing modalities such as near-infrared (NIR), hyperspectral imaging (HSI), and X-ray fluorescence (XRF) are assessed, and sensor fusion strategies, including early, late, and intermediate fusion, are reviewed for high-throughput industrial settings. 3. Deep Learning Benchmarking: 11 publicly available PCB datasets are analyzed, and the YOLO series (YOLOv3–YOLOv12) is compared with leading non-YOLO detectors, including Faster R-CNN, RT-DETR-L, and RetinaNet. The results show that while YOLOv9s achieves a peak mAP@0.5 of 56.5% and YOLOv11s offers an optimal industrial profile (37.2% mAP@0.5:0.95 at 115 ms edge inference), all RGB-based models fail to detect visually ambiguous surface-mount devices (SMDs), with mAP values below 12%. This confirms a performance ceiling for purely visual systems. The review concludes that transitioning from RGB-centric to multispectral fusion architectures is the primary research frontier and proposes a roadmap for standardized multimodal datasets and edge-deployable fusion models to enable next-generation, high-recovery automated recycling. Full article

This paper presents a novel design approach for mitigating the adverse effects of antenna mountings on the radiation pattern of GNSS antennas. By employing a resistive structure integrated into the ground plane, the proposed solution suppresses unwanted edge diffraction and near-field reflections caused by nearby mounting hardware. The design is developed using the concept of tapered resistive sheets and optimized using a customized cost function that accounts for pattern degradation across multiple realistic mounting configurations, ensuring robust performance under varying installation conditions. The resulting structure is fabricated using additive manufacturing (AM), enabling precise realization of complex resistive profiles with tailored surface impedance. Comprehensive validation through both electromagnetic simulations and experimental measurements demonstrates significant improvements in radiation pattern stability and reduced sensitivity to near-field objects, particularly in critical GNSS bands such as E5a/L5 and E1/L1. The results demonstrate that the proposed structure significantly enhances antenna reliability and calibration integrity in real-world deployments, offering a practical, hardware-based solution to a persistent challenge in high-precision GNSS systems. Full article

A complex curved reflector made from a 40% silicon–aluminum alloy (AlSi40) can meet the requirements of optical systems operating across the infrared, near-infrared, and visible bands. It enables an athermalization design with simplified alignment and assembly, while offering high manufacturing efficiency and low costs. This makes it ideal for widespread use in high-end optical systems. As an enabling technology for the fabrication of AlSi40 freeform mirrors, error compensation in ultra-precision (UP) diamond turning is currently a research hotspot; however, current error compensation methods still have considerable room for improvement in terms of both accuracy and manufacturing efficiency. To address this issue, this study proposes an efficient and highly accurate method: a polar grid is defined in the machining coordinate system, and the corresponding surface point cloud is calculated. Using measured point clouds from reference spheres and freeform form error in the measurement coordinate system, mounting pose errors and form error with measurement error removed are determined via least squares. Machining error at grid points is then calculated via coordinate transformations and bicubic spline interpolation, and applied to correct cutter contact points (CCPs). Cutter location points (CLPs) are finally obtained using piecewise cubic spline fitting and a bisection method. With this method, average form error of four AlSi40 substrates improved from RMS 114.8 nm to 47.9 nm, and for four AlSi40 substrates with nickel–phosphorus (NiP)-plated surfaces, from RMS 71.3 nm to 31.1 nm. The compensated accuracy meets near-infrared stellar tracker requirements without polishing, greatly enhancing freeform mirror manufacturing efficiency. Full article

Landslide detection has largely relied on supervised learning or DEM-based representations, which can limit rapid deployment and generalization across heterogeneous terrain. In this work, we present a zero-shot, fully unsupervised framework that identifies landslide-like geomorphic instability candidates from raw UAV-mounted LiDAR, removing the need for labeled data, pre-event baselines, or rasterized terrain abstractions. Our approach is motivated by the observation that landslides manifest as localized geometric inconsistencies in the terrain surface. We capture this through a multi-scale formulation that combines point-level and cluster-level indicators of instability. At the point level, a PCA-based residual depth metric reduces slope-induced bias and highlights surface discontinuities, while local concavity captures terrain depletion patterns. At the cluster level, geomorphometric descriptors such as curvature concentration, surface roughness, elevation discontinuity, and slope variation are extracted using density-aware 3D clustering and integrated through adaptive feature fusion. The resulting probabilistic instability field enables spatially coherent delineation of landslide scars, including rupture boundaries, displaced material, and emerging failure regions. In addition, the detected patches provide useful priors for post-event susceptibility analysis without requiring temporal observations. Experiments across diverse geomorphic settings show that the proposed method improves detection of subtle terrain disturbances compared to DEM-based pipelines and supervised learning approaches, while remaining robust to noise and terrain variability. Overall, this work demonstrates that geometry-driven, unsupervised inference on raw 3D data can serve as a practical and scalable alternative for near real-time landslide detection using UAV-based systems. Full article

This paper presents research on reinforced concrete beams strengthened with non-pretensioned and pretensioned near-surface-mounted (NSM) carbon fibre-reinforced polymer (CFRP) strips under self-weight and external preloading. The first part of this paper briefly describes and discusses the results of experimental tests performed on six beams with different reinforcing steel ratios, preloading levels, and strengthening-system configurations. Next, three-dimensional (3D) numerical models of the tested specimens were developed. The models consider the nonlinear behavior of concrete (both in tension and compression), steel bars, and the interface between concrete and CFRP laminates. For these models, the material parameters were established based on experiments and recommendations from the literature. Furthermore, a sensitivity analysis was conducted with respect to the material parameters of the model that were not directly obtained from experimental measurements. The analyses validated the applicability of the numerical model in predicting the flexural behavior of reinforced concrete (RC) members strengthened with near-surface-mounted (NSM) CFRP materials over the full loading range. Furthermore, the developed models were employed to assess the effectiveness of active strengthening relative to passive strengthening methods (i.e., without pretensioning of the laminate). A comparison study of actively and passively strengthened elements indicates that prestressing does not affect the ultimate limit state but enhances serviceability limit states. The presented computational model, together with the adopted computational strategy, demonstrates its effectiveness for analyzing realistic scenarios involving RC beams that are damaged and subjected to loading during the strengthening process. Full article

This study presents a mechanics based analytical framework for predicting the flexural–shear capacity of reinforced concrete (RC) beams strengthened with Engineered Cementitious Composites (ECCs) and a hybrid ECC–GFRP near surface mounted (NSM) system. Building upon previously reported experimental observations, the present work aims to establish rational prediction models capable of capturing the interaction between flexural and shear mechanisms in strengthened beams. The analytical approach integrates sectional analysis for flexural capacity with a modified truss analogy for shear resistance, explicitly incorporating the strain hardening tensile contribution of ECC and the tensile and confinement effects of GFRP reinforcement. An interaction based failure criterion is subsequently employed to identify the governing failure mode under combined flexural shear actions. The proposed model is validated against experimental results obtained from twenty seven beam specimens with varying flexural and shear reinforcement ratios and strengthening configurations. The predicted ultimate loads show good agreement with experimental values, with an average deviation within ±10%. The analytical framework accurately captures the transition between flexural dominated, combined flexural–shear, and diagonal tension failures observed experimentally. Results demonstrate that ECC significantly enhances ductility and shear crack control, while the hybrid ECC–GFRP system provides substantial strength enhancement with a controlled shift in failure mode. Overall, the developed analytical models offer a reliable and computationally efficient tool for predicting the flexural–shear capacity and failure behavior of ECC and hybrid ECC–GFRP-strengthened RC beams, supporting performance based design and practical strengthening applications. Full article

The near-surface mounted (NSM) technique with carbon fibre-reinforced polymer (CFRP) composites has been proven to be one of the most effective alternatives for the flexural strengthening of existing reinforced concrete (RC) members. However, several issues remain unresolved, including the effects of elevated temperatures on the performance of these strengthened RC elements. This study experimentally investigates the mechanical performance of RC slabs strengthened with NSM-CFRP systems under elevated temperatures, using both (i) steady-state and (ii) transient heating under applied loads. The steady-state tests were conducted at 20, 40, 50, 70, and 80 °C, while the transient tests were performed at 20 and 80 °C. Deflections, strains, temperatures and loads were registered during the heating phase and during the flexural tests up to failure. These measurements were used to analyse the system response in terms of load–deflection curves, evolution of concrete and CFRP strains, and bond stresses between the epoxy adhesive and CFRP. At 80 °C, the NSM-CFRP-strengthened RC slabs exhibited an average reduction of 12.1% (steady-state) and 2.3% (transient) in ultimate strength. Moreover, the concrete crushing failure mode governed up to 70 °C, despite passing the epoxy’s glass transition temperature (54 °C), while cohesive failure of the adhesive governed the failure at 80 °C. Full article

Vortex generators (VGs) are considered in this study as an effective means of controlling the boundary-layer structure and suppressing flow separation on the suction sides of wind turbine blades. An original geometry of a surface-mounted VG has been developed and experimentally investigated, providing a stable modification of the near-wall flow over a wide range of incoming flow velocities. The aerodynamic effect is attributed to the formation of spatially diverging vortex structures that enhance momentum transfer from the outer flow region toward the near-wall layer, thereby increasing the energy level of the boundary layer. This results in an extension of the attached-flow region and an increase in the mean flow velocity over the suction side of the airfoil by up to 6.5%. The proposed configuration enables a 15% increase in the installation spacing of surface-mounted VGs without loss of control efficiency. Experimental investigations were carried out in a subsonic aerodynamic facility using the Particle Image Velocimetry (PIV) method at free-stream velocities of up to 30 m/s. The obtained data will be used for the development and validation of a mathematical model intended for parametric studies of the influence of surface-mounted VGs on various wind turbine blade airfoils under a wide range of atmospheric turbulence conditions. Full article

This study investigates the shear performance of reinforced concrete (RC) beams strengthened with near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) ropes under ambient and elevated temperature conditions. An experimental program comprising twelve RC beams was conducted, including both normal- and high-strength concrete specimens. The beams were strengthened using CFRP ropes installed at two orientations (45° and 90°) and two spacing configurations (150 mm and 200 mm). Ten specimens were exposed to a temperature of 600 °C prior to shear testing. The experimental results were evaluated against finite element (FE) simulations and shear strength predictions obtained from ACI 440.2R provisions. The FE models demonstrated close agreement with the observed experimental response, whereas ACI 440.2R consistently yielded conservative shear strength estimates, particularly for high-strength concrete beams. The results confirm that inclined CFRP configurations and reduced rope spacing significantly enhance shear capacity, even after severe thermal exposure, with measured strength gains reaching approximately 75% relative to unheated control beams and up to 135% compared to heated control specimen. The findings emphasize the sensitivity of NSM CFRP in terms of strengthening effectiveness to elevated temperature and highlight the limitations of existing design provisions when applied to fire-damaged RC members. Full article

Sui–Tang Luoyang represents a classic achievement in Chinese capital planning, yet research remains dominated by archaeological and historical–geographical approaches, lacking a unifying theoretical framework. This research addresses this gap by applying the Historic Urban Landscape (HUL) approach to systematically interpret the city’s integration of built form and natural landscape. This research developed a three-dimensional analytical scheme comprising spatial structure, visual axis, and borrowed scenery and implemented it using historical documents, archaeological data, GIS, and cross-validation methods. The results reconstruct the city’s triple spatial structure (Palace City, Imperial City, Outer City) and identify a near-north–south central axis that connects the palace with the Longmen Yique and Mount Mang, forming a dominant view corridor and ritual sequence. Further analysis examines how multi-layered borrowed scenery embodies and articulates the traditional “Harmony of Nature and Humanity” philosophy. This research supports the plausibility of the applicability of HUL to sites with scarce surface remains and provides a transferable framework for the holistic conservation, view-corridor management, and digital reconstruction of historic cities. Full article

The strengthening of reinforced concrete (RC) beams requires repair systems that can enhance strength, stiffness, and energy dissipation without significantly increasing self-weight or compromising durability. This study explores the structural response of RC beams strengthened using an integrated shear–flexure system combining near-surface-mounted carbon fiber-reinforced polymer (NSM-CFRP) ropes and steel-reinforced geopolymer overlays in the compression zone. Monotonic three-point bending tests were performed on two RC beam specimens, one unstrengthened control and one strengthened beam, to obtain preliminary observations of load–deflection behavior, stiffness, ductility, and energy absorption. The strengthened specimen exhibited increases in ultimate load (28.6%), stiffness (13.6%), and energy absorption (7.65%) relative to the control beam, suggesting the potential for effective composite action between the CFRP ropes and geopolymer material. A three-dimensional nonlinear finite element model was developed using ATENA to support interpretation of the experimental response, incorporating detailed constitutive models for concrete, steel reinforcement, and CFRP ropes. The numerical predictions showed reasonable agreement with the experimental results. Within the limitations of the test matrix, the results indicate that the proposed dual strengthening system may offer a viable and sustainable approach for enhancing the shear–flexural performance of RC beams. Full article