Search Results (539)

Accurately characterizing the structural state of membrane reflector antennas (MRA) remains challenging due to the difficulty in determining stress distribution through geometric measurement alone. Although photogrammetry provides high-precision geometric data, it falls short of capturing mechanical pre-tension and is notably influenced by gravity, which limits its utility in guiding surface accuracy adjustments. This paper proposed an integrated approach combining photogrammetry with a nonlinear finite element method (NFEM) to achieve high-fidelity imaging and effective shape adjustment of electrostatically formed MRA, explicitly accounting for gravity effects during ground-based measurement and shape control. The proposed method establishes a mechanical model that incorporates real-world geometric data under gravity and performs force–shape matching to reconcile discrepancies between physical and simulation models. Experimental validation demonstrates that the gravity-corrected NFEM model closely aligns with the physical antenna, with a deviation in surface accuracy within 9.9%. Using this refined model, we successfully optimized electrode voltages and cable tensions, improving the surface accuracy of the physical model from an initial 0.7033 mm to 0.5723 mm. This work provides a reliable and efficient strategy for the shape control and adjustment of membrane space structures under gravity, with potential applications in large deployable antennas, solar sails, and other tension-controlled flexible systems. Full article

Large-scale frames are increasingly used in engineering structures, particularly in aerospace structures. Among them, planar phased array satellite antennas used for global observations and target tracking have received much attention. Considering that structural deformation will degrade the coherence of antennas, a frame with inherent diagonal cables that serves to control the antennas’ static configuration is thoroughly studied. These inherent cables of planar phased arrays are pre-tensioned to preserve the structural integrity and increase the stiffness of the antenna. However, they are also used as actuators in our research; in this way, additional control devices are not needed. As a result, the antenna’s mass will decrease, and its reliability will increase. For high observation accuracy, the antennas tend to be very large. Accordingly, there is a significant deformation of space antennas when they are loaded. For this reason, a nonlinear finite element method is used to consider the structures’ geometrical nonlinearity. In order to achieve shape adjustment, the difference between active and passive cables must be carefully investigated. Furthermore, for the nonlinear structure in this paper, the active cables will deform in tandem with the structure as a whole so that the direction of the active cables’ control forces will also change during the entire control process. This paper elaborates on this problem and proposes a nonlinear optimization method considering this characteristic of the cables. Simulations of a simplified 2-bay and 18-bay satellite antenna are performed to validate the proposed method. Results of the numerical simulation demonstrate that the proposed method can successfully adjust the large-scale antenna’s static shape and achieve high precision. Full article

To address the dual challenges of improving precast cable trench joint performance and promoting solid waste recycling for carbon neutrality, this study developed a jute fiber-reinforced recycled aggregate concrete (JFRAC) and established a complete technical chain via experiments and numerical simulations. Compressive strength tests were conducted on JFRAC with varying jute fiber volume content and recycled coarse aggregate (RCA) replacement ratio to obtain their influence on the stress–strain relationship. A modified Concrete Damaged Plasticity (CDP) model was proposed by introducing correction coefficients for compressive strength and elastic modulus, achieving over 95% agreement with experimental data. Finite element simulations of cable trench joints showed that JFRAC outperforms C30 concrete, with the same compressive strength, in ultimate bearing capacity (↑4.17%), peak displacement (↑18.78%), and ductility (↑14.66%). JFRAC provides substantial environmental and economic advantages by reducing carbon emissions by 2.29% and saving costs of CNY 62.43 per meter of precast cable trench. Parametric studies indicated bolt grade and number are the primary performance influencers. Bolt grade’s impact diminishes as it increases from 8.8 to 10.9, while bolt number linearly enhances load-bearing capacity. This study provides a feasible path for JFRAC to replace conventional concrete in cable trenches, realizing both economic and environmental benefits. Full article

Low-frequency alternating-current (LFAC) transmission has attracted significant attention for medium- and long-distance offshore wind integration due to its ability to mitigate the substantial charging currents and reactive power burdens associated with long submarine cables. This paper investigates the frequency-dependent electrothermal behaviors of a 500 kV three-core XLPE submarine cable using a coupled electromagnetic–thermal finite-element model. The simulation framework evaluates the current distribution, power losses in metallic components, temperature rise, and ampacity across various frequency regimes. To validate the numerical model, a thermal-circuit approach based on the IEC 60287 standard is developed, with comparisons confirming that deviations remain within acceptable engineering margins. The study reveals that operating at lower frequencies effectively mitigates skin and proximity effects, leading to reduced conductor and sheath losses. Quantitative results demonstrate that reducing the operating frequency from 50 Hz to 5 Hz results in a 30.6% reduction in total power losses and a 14.2% increase in current-carrying capability. These findings confirm that LFAC transmission offers a viable pathway to enhance the efficiency and capacity of submarine power transmission systems. Full article

To address the limitations of existing cable damage identification methods in terms of environmental robustness and measurement dependency, this study proposes a novel damage identification approach based on the second-order difference characteristics of main beam deflection. Through theoretical derivation, the intrinsic relationship between cable damage and local deflection field disturbances in the main beam was revealed, leading to the innovative definition of a second-order difference of deflection (DISOD) index for damage localization. By analyzing the second-order deflection differences at the anchorage points of a three-cable group (a central cable and its two adjacent cables), the damage status of the central cable can be directly determined. The research comprehensively employed finite element numerical simulations and scaled model experiments to systematically validate the method’s effectiveness in identifying single-cable and double-cable (both adjacent and non-adjacent) damage scenarios under various noise conditions. This method enables damage localization without direct cable force measurement, demonstrates anti-noise interference capability, achieves rapid and accurate identification, and provides a technically promising solution for the health monitoring of long-span cable-stayed bridges. Full article

High-temperature superconducting (HTS) DC power devices operate at cryogenic temperatures to achieve high power density for aviation applications. Ensuring reliable operation requires an optimized insulation system capable of withstanding cryogenic DC stress. In this study, finite element numerical simulations were conducted to investigate the transient behavior of electric fields in HTS cable insulation under DC stress at cryogenic temperatures. The results demonstrate that the transient field distribution is strongly temperature-dependent, leading to prolonged high-field exposure near ground terminations. Strategies to mitigate electric field enhancement are proposed to improve insulation reliability, supported by a comparative evaluation of various insulating materials. The simulation-based insights provide design guidance for developing resilient insulation systems for HTS and other cryogenic DC devices. Full article

Flexible photovoltaic (PV) support systems, referring to cable-supported structural systems that carry conventional rigid PV modules rather than flexible thin-film modules, have attracted increasing attention as a promising solution for photovoltaic construction in complex terrains due to their advantages of broad-span design and simplified installation. However, the deformation behavior of flexible PV supports remains insufficiently understood, which restricts its application and engineering optimization. To address this issue, a three-dimensional finite element model of a flexible PV support system was developed using an in-house Python code to investigate its deformation characteristics. The model discretizes the structure into beam and cable elements according to their mechanical properties, and the coupling relationship between their degrees of freedom is established by means of a multi-point constraint. The validation of the proposed model is confirmed by comparison with theoretical solutions. Simulation results reveal that the deformation of flexible PV supports is more sensitive to horizontal loads, indicating that their overall deformation performance is primarily governed by lateral rather than vertical loading. Furthermore, dynamic analyses show that higher loading frequencies induce noticeable torsional de-formation of the structure, which may compromise the stability of the PV panels. These findings provide valuable theoretical guidance for the design and optimization of flexible PV support systems deployed in complex terrains. Full article

Electrical energy in urban and industrial power supply networks is mainly transmitted through 6–10-kV cable networks with an isolated neutral, where most lines are made as bunches of cables. Up to 75–90% of electrical faults in these cable networks belong to single-phase ground faults (SGFs), which can cause more severe accidents accompanied by significant economic damage. Widely known simple and directional protections against SGFs are relatively selective and, hence, often incapable of properly responding to SGFs in a network with such lines and detecting a cable with SGFs in the bunch of a damaged line. These disadvantages can be eliminated by using new, simple, and inexpensive, absolutely selective protections capable of detecting a cable with SGFs in a damaged line. We suggest the techniques and devices based on zero-sequence current transformers and ring measuring converters for building up such protection systems. The methods for calculating zero-sequence currents in cables of a bunched cable line, depending on the SGF point and the currents in the responding elements, are developed, as well as a procedure for determining a damaged cable and methods for estimating the responding element thresholds and the length of the protection dead zone. Full article

Maintaining the stability of the mine roadway is of paramount importance, as it is critical in ensuring the daily operational continuity, personnel safety, long-term economic viability, and sustainability of the entire mining operation. Significant instability can trigger serious disruptions—such as production stoppages, equipment damage, and severe safety incidents—which ultimately compromise the project’s financial returns and future prospects. Therefore, the proactive assessment and rigorous control of roadway stability constitute a foundational element of successful and sustainable resource extraction. In China, thick and extra-thick coal seams constitute over 44% of the total recoverable coal reserves. Consequently, their safe and efficient extraction is considered vital in guaranteeing energy security and enhancing the efficiency of resource utilization. The surrounding rock of gob-side roadways in typical coal seams is often fractured due to high ground stress, intensive mining disturbances, and overhanging goaf roofs. Consequently, asymmetric failure patterns such as bolt failure, steel belt tearing, anchor cable fracture, and shoulder corner convergence are common in these entries, which pose a serious threat to mine safety and sustainable mining operations. This deformation and failure process is associated with several parameters, including the coal seam thickness, mining technology, and surrounding rock properties, and can lead to engineering hazards such as roof subsidence, rib spalling, and floor heave. This study proposes countermeasures against asymmetric deformation affecting gob-side entries under intensive mining pressure during the fully mechanized caving of extra-thick coal seams. This research selects the 8110 working face of a representative coal mine as the case study. Through integrated field investigation and engineering analysis, the principal factors governing entry stability are identified, and effective control strategies are subsequently proposed. An elastic foundation beam model is developed, and the corresponding deflection differential equation is formulated. The deflection and stress distributions of the immediate roof beam are thereby determined. A systematic analysis of the asymmetric deformation mechanism and its principal influencing factors is conducted using the control variable method. A support approach employing a mechanical constant-resistance single prop (MCRSP) has been developed and validated through practical application. The findings demonstrate that the frequently observed asymmetric deformation in gob-side entries is primarily induced by the combined effect of the working face’s front abutment pressure and the lateral pressure originating from the neighboring goaf area. It is found that parameters including the immediate roof thickness, roadway span, and its peak stress have a significant influence on entry convergence. Under both primary and secondary mining conditions, the maximum subsidence shows an inverse relationship with the immediate roof thickness, while exhibiting a positive correlation with both the roadway span and the peak stress. Based on the theoretical analysis, an advanced support scheme, which centers on the application of an MCRSP, is designed. Field monitoring data confirm that the peak roof subsidence and two-side closure are successfully limited to 663 mm and 428 mm, respectively. This support method leads to a notable reduction in roof separation and surrounding rock deformation, thereby establishing a theoretical and technical foundation for the green and safe mining of deep extra-thick coal seams. Full article

To investigate the anti-slip characteristics of the main cables in a three-tower suspension bridge with spatial cable systems, this paper proposes an analytical calculation method for the anti-slip safety factor of the main cables and establishes an equivalent mechanical analysis model for multi-tower suspension bridges with spatial cable systems. Based on the deformation of the towers and cables under live load, as well as the equilibrium relationship of the main cable forces in loaded and unloaded spans, analytical formulas for the anti-slip safety factor of the main cables at the middle tower saddle are derived. A finite element model is developed to validate the formulas. The influence of parameters such as the spatial cable inclination angle, tower-to-cable stiffness ratio, dead-to-live load ratio, sag-to-span ratio, span length, and friction coefficient between the main cable and saddle on the anti-slip safety factor is analyzed. The results indicate that the formula proposed in this paper provides a highly accurate estimation of the slip resistance safety factor for main cables in spatial cable multi-tower suspension bridges. The adoption of spatial main cable configuration enhances the stability of the slip resistance safety factor at the intermediate tower saddle. The slip resistance safety factor of the main cable decreases with the increase in the tower-to-cable stiffness ratio, while it increases with the rise in the sag-to-span ratio. Moreover, the influence of the sag-to-span ratio on the slip resistance stability of the main cable becomes more pronounced with higher tower stiffness. The slip resistance safety factor of the main cable exhibits an approximately linear increase with the rise in the dead-to-live load ratio and the coefficient of friction. Furthermore, the slip resistance safety factor increases with the span length, and this rate of increase becomes more pronounced with smaller sag-to-span ratios. The research findings presented in this paper provide a theoretical basis for the design of spatial cable multi-tower suspension bridges. Full article

The outer sheaths of cables can be damaged by factors, such as mechanical stress, chemical corrosion, and aging, leading to moisture intrusion. This seriously threatens cable insulation performance and may even induce discharge accidents. Based on the corrugated aluminum sheath structure of the cables and moisture diffusion mechanism, the moisture intrusion (moisture absorption) process can be divided into three stages: water-blocking tape adsorption, air-gap wetting, and main insulation diffusion. First, through experimental tests, key electrical parameters such as capacitance, dielectric constant, and dielectric loss of 66 kV cables and XLPE main insulation samples in different moisture absorption stages were obtained. Furthermore, using finite element simulation, theoretical analysis and verification of the parameter variation characteristics of the cable were conducted by adjusting the moisture content and varying the moisture-affected positions. The results show that the electrical parameters of the cable body change most significantly in the third stage of moisture absorption: when the moisture absorption degree increases by 0.01%, the cable body capacitance increases by 1.2% and the insulation resistance decreases by 3.7%; for the XLPE insulation samples, when the moisture absorption degree increases by 0.25%, the relative dielectric constant increases by 0.7%, the conductivity increases by 1.4%, and the dielectric loss increases by a factor of 1.6 times at lower frequencies. In addition, the changes in the main insulation parameters were only related to the moisture content and were not affected by moisture distribution. Full article

Background: Electromagnetic compatibility (EMC) challenges in 2.5D/3D semiconductor packaging arise from the complex coupling between device, interposer, board, and cable domains, which are insufficiently captured by conventional board-level analysis. Method: This study proposes HiPAC-EMC, a packaging-aware EMC workflow that integrates the device, package, PCB, cable harness, line impedance stabilization network (LISN), and receiver elements into an isomorphic co-model. The model mirrors the entire measurement chain and links simulation to real conducted and radiated tests. Validation: The workflow was verified using CISPR-25-compliant conducted measurements, magnetic near-field mapping, and key-point radiated checks at 3 m and 10 m, ensuring model–measurement consistency within ±2–3 dB (1σ ≈ 3.1 dB). Results: Two quantitative indices—the mitigation efficiency (η) and the common-mode hot-spot headroom (CMH)—enabled the traceable evaluation of suppression effectiveness, achieving up to 22–25 dB reduction across dominant 300–800 MHz bands. Significance: The HiPAC-EMC workflow establishes a traceable, reproducible, and measurement-faithful design methodology, providing a practical tool to de-risk EMC during early design and reduce full-band chamber time for advanced semiconductor packaging. Full article

The boundary of a submerged floating tunnel (SFT) is flexible, and ignoring the influence of boundary and pipeline connections may reduce its structural performance. Therefore, this study uses rotating springs and linear springs to simulate the flexible boundary. Joints are simplified as shear springs and bending springs. A multi-span SFT model on discrete elastic supports is established, and its seismic response is evaluated using the transfer matrix method and the modal superposition method. The proposed method is validated by comparing it with finite element results, and the vertical mechanical response of the SFT when the cable relaxes or fractures under earthquake action is analyzed. The results indicate a significant deviation between the seismic response of flexible constraints and those modeled as simple hinged or fixed connections, and the lower boundary constraint stiffness is beneficial to the seismic response of the SFT. Introducing flexible joints can effectively reduce the internal force response of the structure, and a bending stiffness ratio of 0.01 to 0.03 for the joints is considered reasonable. In contrast, variations in the shear stiffness of the joints have a relatively small impact on the seismic response. Full article

Transmission tower guy wires are critical flexible tension members ensuring the stability and safe operation of overhead power transmission networks. However, these components are vulnerable to external impacts from falling rocks, ice masses, and other natural hazards, which can cause excessive deformation, anchorage loosening, and catastrophic failure. Current design standards primarily consider static loads, lacking comprehensive models for predicting dynamic impact responses. This study presents a theoretical model for predicting the peak impact response of guy wires by modeling the impact process as a point mass impacting a nonlinear spring system. Using an energy-based elastic potential method combined with cable theory, analytical solutions for axial force, displacement, and peak impact force are derived. Newton–Cotes numerical integration solves the implicit function to obtain closed-form solutions for efficient prediction. Validated through finite element simulations, deviations of peak displacement, peak impact force, and peak axial force between theoretical and numerical results are within ±4%, ±18%, and ±4%, respectively. Using the validated model, parametric studies show that increasing the inclination angle from 15° to 55° slightly reduces peak displacement by 2–4%, impact force by 1–13%, and axial force by 1–10%. Higher prestress (100–300 MPa) decreases displacement and impact force but increases axial force. Longer lengths (15–55 m) cause linear displacement growth and nonlinear force reduction. Impacts near anchorage points help control displacement risks, and impact velocity generally has a more significant influence on response characteristics than impactor mass. This model provides a scientific basis for impact-resistant design of power grid infrastructure and guidance for optimizing de-icing strategies, enhancing transmission system safety and reliability. Full article

The study presents a comprehensive analysis of the effects of high temperatures (500 °C and 700 °C) on the microstructure, mechanical properties, and acoustic emission (AE) parameters of cold-drawn prestressing steel. The investigations included mechanical testing, AE signal acquisition, and numerical verification using the finite element method (FEM). It was demonstrated that increasing temperature leads to significant microstructural changes (pearlite spheroidisation, carbide coarsening), resulting in strength degradation and a shift in the failure mechanism from quasi-brittle (initial state) to transitional (500 °C), and finally to ductile (700 °C). For the first time, AE parameters (Counts to Peak and RA-value) were correlated with local axial strains ε₂₂ and von Mises equivalent stress, enabling the identification of the moment of onset load-bearing capacity loss and the determination of critical material damage thresholds. A multi-criteria diagnostic indicator was proposed to assess the condition of prestressing steel after fire exposure. The results confirm the high potential of AE as a non-invasive tool for evaluating the safety of prestressing tendons and cables in reinforced concrete structures subjected to overheating or fire. Full article