Search Results (123)

Accurate cladding segmentation is essential for quantitative quality assessment of stainless-steel/carbon-steel clad wire rods used in bridge cables, yet remains challenging because of weak core–cladding contrast, narrow interfacial transition zones, local cladding-thickness fluctuations, and limited repeatability of manual inspection. This study proposes an improved U-Net framework that integrates residual feature extraction, multi-scale contextual perception, and attention-guided feature refinement for robust cladding identification. A cross-sectional image dataset comprising 18,566 samples was constructed through standardized specimen preparation, chemical color development, image acquisition, pixel-level annotation, and data augmentation. In the proposed model, the original U-Net encoder is replaced with ResNet50 to enhance deep semantic representation, while atrous spatial pyramid pooling and a convolutional block attention module are embedded into the feature-fusion stage to improve boundary discrimination and thin-cladding recognition. On the test set, the model achieved a mean pixel accuracy of 97.29%, cladding intersection over union of 88.82%, and mean intersection over union of 93.72%, outperforming the baseline U-Net by 1.38, 9.19, and 5.17 percentage points, respectively. Ablation and comparative experiments further demonstrate improved boundary continuity, local-detail preservation, and segmentation stability compared with representative CNN-based segmentation models. These findings suggest that the proposed framework provides a practical and reliable vision-based approach for cladding-thickness measurement, eccentricity evaluation, uniformity assessment, and batch quality inspection of clad wire rods. Full article

As an active reinforcement technology, prestressed anchor cables are susceptible to environmental corrosion during long-term service. Corrosion occurs and progresses more rapidly, especially in an alternating wet–dry environment, which can degrade the mechanical properties of prestressed anchor cables and may ultimately lead to failure. Current methods typically evaluate the mechanical properties of anchor cables based on cross-sectional loss calculated from the average weight loss ratio. However, this uniform-corrosion assumption may underestimate the effect of corrosion on mechanical performance. In this study, a testing apparatus for corroding prestressed anchor cables under alternating wet–dry conditions was developed. The apparatus enabled accurate loading and nondestructive sampling. Using this apparatus, alternating wet–dry corrosion tests and mechanical tensile tests were conducted on anchor cables under different stress levels. The relationship between weight loss ratio and mechanical properties was then analyzed. Based on this relationship, an equation was derived to calculate the breaking strength of corroded anchor cables in alternating wet–dry environments. The service life estimated using this equation was closer to that observed in actual anchor cable failure cases. This indicates that the proposed equation provides more accurate predictions than methods based on the uniform-corrosion assumption. Full article

Abnormal circulating current induced by sheath grounding faults in cross-bonded high-voltage cables is a major cause of single-phase grounding faults. For the early detection and localization of sheath grounding faults, this paper constructs an equivalent circuit model for three-phase nine-section cross-bonded cables. Circuit model parameters are estimated via online monitoring data. The relational equation between sheath electrical quantities, fault impedance, and distance is derived for typical sheath grounding faults. Using the Adam algorithm, the solution of fault impedance and location is converted into the minimization of an optimization objective function. Simulation results show that under the influences of phase current imbalance, measurement error, and fault impedance fluctuation, the Adam algorithm exhibits superior optimization accuracy and computational efficiency in comparison with the ED and GA algorithms. Experimental results show that for low-resistance sheath grounding, the proposed method has a fault impedance calculation error ≤ 0.59% and a fault positioning error ≤ 1.89%. For metallic sheath grounding with zero resistance, the positioning error is ≤1.37%. Field test results demonstrate that the proposed method performs similarly to the time-domain reflectometry method, with a positioning deviation ≤ 0.15 m, and can meet online monitoring requirements. Full article

Addressing the challenges of topological design and the limitations of global optimization for large-scale photovoltaic (PV) plants in complex terrains, this paper proposes a topology optimization method based on mixed-integer linear programming (MILP). The innovation of the proposed method lies in its use of a MILP framework to integrate complex terrain modeling, quantification of construction difficulty, and coordinated configuration of conductor cross-sections into a single equivalent annual cost optimization model. First, equivalent mathematical models tailored to diverse environmental features—including flat, mountainous, and hilly terrains—are developed to enable accurate spatial identification. Second, aimed at minimizing the total equivalent annual cost (EAC), a MILP model is formulated. This model comprehensively incorporates physical construction difficulties and strict electrical constraints, such as active power flow balance, cable current-carrying capacity, and node voltage deviations. A high-performance solver is then utilized to achieve global optimization for radial topologies. Furthermore, the cross-sectional areas of the conductors are dynamically configured to compensate for power quality losses caused by path detours. Case studies demonstrate that the proposed method significantly reduces the EAC and enhances the overall economic benefits of PV plants while ensuring strict electrical safety across various complex environments. Full article

Stay cables are critical load-bearing components in cable-stayed structures, making corrosion distribution vital for damage diagnosis and maintenance. To address the insufficient characterization of circumferential multi-point corrosion distribution in stay cables, a theoretical model of circumferential multi-point defect magnetic charge for the stay cables was established, and a self-magnetic flux leakage experiment was conducted on 37-wire steel specimens with circumferential corrosion. The effects of corroded wire number (N), corrosion time (T), and circumferential angle number (K) on the axial B_x component of the magnetic flux leakage signal were analyzed. The relationship between the θ-B_x-max peak distribution and corrosion patterns was clarified. Quantitative models for corrosion number (c), center (θ_c), and the cross-sectional corrosion rate (α) were established. The results indicate that c improves the determination of the number of concentrated corrosion sites in the ‘peak platform’ corrosion distribution type. Based on the Lorentz fitting, the maximum prediction error of θ_c is 15.1%, and the prediction accuracy of the cross-sectional corrosion rate α exceeds 90%. The study provides a reference for the quantifiable characterization and evaluation methods of the circumferential multi-point defect distribution in stay cables. Full article

Parallel laying of high-voltage cables will generate a zero-sequence current, due to spatial electromagnetic induction, which reduces the cable’s current-carrying capacity, causing heating and corrosion of the grounding points and deteriorating grounding performance. Currently, there is a lack of effective control measures. This article establishes a calculation model for the cable sheath current under the condition of double circuit cable cross interconnection grounding, analyzes the causes of a zero-sequence grounding current in a double circuit cable sheath, and proposes an optimal phase sequence selection method, considering load changes with the goal of maximizing the probability of the cable sheath current, not exceeding the standard. The results show that when the double circuit cable is evenly distributed in the cross interconnection section, the zero-sequence grounding current will be generated on the metal sheath of the cable, causing an excessive total grounding current. By applying the proposed probability-based phase-sequence optimization, the likelihood that both circuits simultaneously satisfy the sheath-current criterion can be significantly improved; for example, under representative layouts and load distributions, the “both-within-limit” probability can reach 53.3% (horizontal layout), 76.2% (horizontal equilateral triangle layout), 90.5% (vertical layout), and 81.6% (vertical equilateral triangle layout). For different working conditions, selecting the optimal load phase sequence combination by maximizing the probability of the sheath current and not exceeding the standard within the current carrying area can help to reduce the cable sheath current. Full article

The measured standard resistance at 20 °C ($R_{20}$) is a critical indicator for evaluating the quality of electric cables. Utilizing a thermal circuit model allows for the rapid determination of $R_{20}$. Focusing on civil electrical cables, this study constructs a thermal circuit model based on an equivalent circuit. Through mathematical derivation, model parameters are expressed as functions of the insulation cross-sectional area and conductor specification. Subsequently, the insulation area is fitted to the conductor specification, establishing a universal analytical thermal circuit model with the conductor specification as the sole variable. Ambient temperatures measured under specific operating conditions showed exponential variation. Using corresponding simulated conductor temperatures, the Differential Evolution algorithm was employed to train the model, achieving a training standard deviation of 0.0184 °C. Validation under different conditions demonstrated that for various cable specifications, the conductor temperature prediction deviation within 300 s remained within 0.368 °C, and the maximum estimation error for $R_{20}$ was less than 0.148%. These results indicate that the established model possesses high calculation accuracy and strong universality, offering a valuable tool for researchers and practitioners in fields relevant to civil electrical cables. Full article

Electrical strain gauges are essential for monitoring wind turbine tower loads and fatigue, but accurate load measurements from these sensors require calibration over time to correct the zero-drift found in long-term measured signals. Calibration is often performed using nacelle rotation events for cable untwisting, where the tower mechanical load is known; however, non-uniform solar heating during these events can introduce thermal stresses that are misinterpreted as drift, causing systematic errors. This study evaluates six preprocessing methods for correcting zero-drift and thermal stresses in strain gauges, using measurements from two tower cross-sections—one with temperature sensors and one without. Performance is quantified using the scatter of the 10 min mean bending moments in the fore–aft and side-to-side directions and the cumulative fatigue damage over the monitoring periods. Results show that modelling the thermal stresses using a linear regression model with temperature measurements as inputs yields the most physically consistent load curves. If temperature measurements are unavailable, the effects of thermal stresses can be partly mitigated by restricting calibration to nighttime events or using solar-position variables in a regression model (instead of temperatures). As expected, the choice of preprocessing method significantly impacts load curves, but its influence on fatigue damage estimates is limited. Full article

To meet the growing requirements of agricultural mechanization, a newly designed 9.5 m span frame has been introduced to replace the traditional 8.0 m span frame, which is constrained by limited internal space. However, as the structural dimensions increase, the failure mechanisms of arch frames under wind loads remain insufficiently understood. In particular, the influences of crop loads, initial geometric imperfections, pipe cross-sectional properties, and cable reinforcement on these failure mechanisms have not yet been systematically investigated. This study aims to reveal the mechanical mechanisms governing the wind-bearing capacity of standard 8.0 m span and newly designed 9.5 m span frames through comparative analysis, and to further investigate how crop loads, initial geometric imperfections, pipe cross-sectional properties, and cable reinforcement modify these mechanisms. The load combinations considered included the following: (1) permanent load + wind load and (2) permanent load + crop load + wind load. The crop load was applied to the frames via a 5-point hanging system. Simulation results indicate that the 9.5 m span frame exhibits a lower allowable wind speed (v_a) than the 8.0 m span frame due to strength failure. Further analysis reveals that the failure is governed by decreased stiffness resulting from the dimensional expansion. Notably, crop loads and initial geometric imperfections were found to amplify second-order bending moments, thereby further decreasing v_a. Moreover, a positive linear correlation is observed between the section modulus of pipes and v_a. However, replacing the circular pipe with rectangular, oval, or elliptical pipes of a similar cross-sectional area does not increase the v_a of the 9.5 m span frame. Conversely, reinforcing the 9.5 m span frame with cables provides strong lateral constraints and effectively suppresses the amplification of bending moments arising from crop loads and initial geometric imperfections. Thus, limiting lateral displacement through reinforcement measures can markedly increase the wind-bearing capacity of frames. The reinforced 9.5 m span frame proves to be a viable replacement for the 8.0 m span frame, meeting the modern demands of facility agriculture in Southern China. Full article

Aluminum alloys offer advantages such as lightweight properties, high strength, and excellent corrosion resistance. To expand their application in long-span spatial structures, prestressed cables have been introduced into aluminum alloy structural systems, forming a new type of string-beam structure. To further investigate the static performance of aluminum alloy string-beam structures, a static analysis was conducted based on the greenhouse project for the archaeological site of the Qin Eastern Mausoleum. This analysis examined the structural response under various load combinations, as well as the effects of the number of struts, cross-sectional area of the cables, prestress level in the cables, and the sag-to-span ratio of the cables. The results indicate that the incorporation of prestressed cables significantly enhances the static performance of aluminum alloy string-beam structures. Under the most critical load combination, the maximum stress observed was 189.45 MPa, and the maximum vertical displacement was 137.31 mm, both of which comply with design specifications. The structure was found to be most sensitive to temperature load. From the perspectives of structural performance and construction economy, setting the number of struts between five and seven is optimal. Increasing the cross-sectional area of the cables effectively reduces structural deflection but leads to an increase in internal stress. Similarly, increasing the prestress level effectively reduces structural displacement. The sag-to-span ratio of the cables has the most pronounced effect on structural stiffness: when the ratio increases from 0.025 to 0.065, the mid-span displacement increases by 33.51%. These findings demonstrate that aluminum alloy beam-string structures are suitable for long-span spatial structures. Full article

The flow mechanism around a yawed cylinder is highly complex. While previous research has confirmed the limitation of the Independence Principle at high yaw angles, the specific flow phenomena beyond 20° yaw remain poorly understood, particularly concerning the spanwise development of the critical regime and the mechanism behind asymmetric surface pressure. Most studies have focused on spatially averaged forces or specific angles, lacking a systematic investigation of the inherent flow characteristics in the intermediate region of finite-length cylinders. To bridge this gap, the present study conducts a detailed wind tunnel test on a yawed cylinder across a wide range of yaw angles (0–60°). By analyzing the pressure distribution and aerodynamic forces in the mid-span region, this study yields the following core findings of universal significance: (1) As the yaw angle increases, the critical flow regime in the intermediate section occurs prematurely. This leads to a decrease in the Reynolds number at which the critical region begins, resulting in the formation of separation bubbles and consequent localized negative-pressure zones on either the upper or lower windward surface of the cylinder. (2) When the yaw angle β ≤ 17.4°, the mean drag and lift in the middle region resemble those of a straight cylinder. However, as the yaw angle increases further, the drag coefficient decreases beyond a certain critical Reynolds number, which itself decreases with increasing yaw angle. (3) At β = 0°, the circumferential mean pressure distribution is symmetric about the cross-sectional axis and remains largely uniform along the span. High yaw angles disrupt this symmetry and uniformity, leading to complex three-dimensional flow structures. These findings have critical implications for the design of structures like inclined bridge towers and cables under oblique winds. Full article

The article analyses the hosting capacity of low-voltage (LV) power grids for connecting distributed energy sources (DER), mainly photovoltaic installations (PV), considering technical limitations imposed by power system operating conditions. The main objective of the research was to develop a simple equation that enables the quick estimation of the maximum power of an energy source that can be safely connected at a given point in the network without causing excessive voltage rise or overloading the transformer and line cable. The analysis was performed on the basis of relevant calculation formulas and simulations carried out in DIgSILENT PowerFactory, where a representative low-voltage grid model was developed. The network model included four transformer power ratings (40, 63, 100, and 160 kVA) and four cable cross-sections (25, 35, 50, and 70 mm²), which made it possible to assess the impact of these parameters on grid hosting capacity as a function of the distance from the transformer station. Based on this, the P_HCI indicator was developed to determine the hosting capacity of a low-voltage network, using only the transformer rating and the length and cross-section of the line for the calculations. A comparison of the results obtained using the proposed equation with detailed calculations showed that the approximation error does not exceed 15%, which confirms the high accuracy and practical applicability of the proposed approach. Full article

Scholte wave surveys were conducted at both the laboratory and field scales to evaluate the reliability of distributed acoustic sensing (DAS) with a fiber-optic cable resting on top of unconsolidated sedimentary deposits to determine the distribution of S-wave velocity underneath. Laboratory measurements performed in a controlled environment at the Deltares Laboratory facility demonstrated that DAS retrieves low- and high-frequency energy associated with Scholte and guided waves. The recorded DAS signals provided consistent Scholte wave signals, which depicted coherent phase velocity energy that was used to accurately depict S-wave velocity layering. We observed the presence of guided waves at higher frequencies, which appeared to be enhanced as the source position was moved away from the fiber-optic cable. A field survey was carried out using a linear set-up in a shallow lake, where a fiber-optic cable was placed on top of a sediment layer with a thickness of 5–10 m. The results from DAS were validated using standard hydrophone measurements performed simultaneously. The 2D S-wave velocity cross-section retrieved by DAS appeared to be in good agreement with the results obtained from hydrophone measurements, especially when detecting the main velocity transition occurring at a 7–10 m depth from the free surface. Full article

The demand for a reliable power supply is growing. Non-linear loads are becoming more numerous, so supply cables must be carefully selected to consider the skin effect. This article calculates the power losses and cable temperature for different cable arrangements supplying non-linear loads. Power losses are determined using the fast Fourier transform (FFT) of the distorted current signal and the current penetration depth method. The temperature distribution is then calculated using finite element analysis (FEA) for selected cases. The results show that cable bundles can be used instead of single cables with a large cross-sectional area because of lower conductor temperatures, lighter cable arrangements, and reduced installation costs. These aspects are important for the sustainable development of the economy, particularly with regard to material usage. Full article

In order to determine appropriate anchoring parameters after enlarging the cross-section of the mining roadway, a comprehensive study was conducted to investigate the development of deformation and failure characteristics in the surrounding rock. The mechanical behavior of rock failure under high-stress conditions and the progressive evolution of deformation and failure from shallow to deep zones were thoroughly analyzed. It was proposed that the primary function of bolt support in mining roadways is to guide the surrounding rock to form a stable compressive arch or ring structure. The mechanical mechanism underlying the formation of such an arch under bolt guidance, along with the stability characteristics during this process, was investigated. The principles for determining bolt support parameters were established as follows: (a) ensuring the formation of a closed compressive ring within the anchorage zone around the roadway; (b) preventing shear failure at the roadway corners; and (c) controlling the extent of roof subsidence under gravitational loading. Design methodologies for determining rock bolt and anchor cable length and spacing were formulated and implemented in the support design of large-section mining roadways within million-ton fully mechanized mining faces. The cross-sectional dimensions of the supported roadway are 5.8 × 4.0 m. Field monitoring results indicate that, after stabilization of the surrounding rock deformation, the maximum convergence between both sides does not exceed 140 mm, the maximum roof subsidence remains below 40 mm, and the maximum roof separation is limited to within 4 mm. These findings provide strong evidence that the selected design parameters fully meet the engineering requirements for roadway support. Full article