Search Results (377)

This study evaluates the effect of copper-containing composite nanopowders on the antiwear properties of additive-free I-20A mineral oil. The powders were produced by the same electron-beam evaporation route in argon under different current–time regimes and differed in phase composition and particle characteristics. N1 was synthesized at 1.4 MeV and 20 mA for 15 min and contained 91 wt.% Cu, 2 wt.% Cu₂O, and 7 wt.% CuO (mean particle size 140 nm), whereas N2 was synthesized at 1.4 MeV and 15 mA for 25 min and contained 38 wt.% Cu, 48 wt.% Cu₂O, and 14 wt.% CuO (187 nm). Six separate oil suspensions containing 0.01, 0.1, or 1 wt.% N1 or N2 were evaluated in block-on-ring tests; three independent tests were performed for each lubricant condition (21 individual measurements in total). The lowest mean mass loss was obtained with 1 wt.% N2 (0.00290 ± 0.00015 g), representing a 43.1% decrease relative to pure I-20A oil (0.00510 ± 0.00026 g; Holm-adjusted p = 0.0045). The 0.01 and 0.1 wt.% N2 formulations did not differ significantly from pure oil, whereas 0.01 and 1 wt.% N1 significantly increased mass loss. In selected SEM/EDS regions, the wear scar produced with 1 wt.% N1 showed deeper longitudinal grooves and no detectable Cu, whereas the scar produced with 1 wt.% N2 showed a smoother local morphology and 0.58 wt.% Cu. These local observations are consistent with different particle–surface interactions and greater local retention of Cu-containing material for N2, but they do not identify the copper oxidation state or prove formation of a continuous tribofilm. Overall, the powders exhibited formulation- and concentration-dependent antiwear behavior: 1 wt.% N2 was beneficial, whereas 1 wt.% N1 was strongly detrimental. Because the synthesis regime, phase composition, particle size, and morphology varied together, the observed difference cannot be attributed exclusively to the Cu/Cu₂O/CuO ratio. Full article

To simulate the fracture behavior of members during structural collapse, this paper proposes a member fracture simulation algorithm that integrates the plastic hinge model with a ductile fracture damage model within the member discrete element method (MDEM) framework. The coupling is achieved by computing stresses at the four most unfavorable edge points of the contact section and using the minimum fracture strain as the section-level failure criterion. The algorithm is validated against a cantilever beam fracture example, yielding results in good agreement with reference data under two yield stress conditions. The fracture algorithm is then embedded as a self-contained module into an adaptively coupled DEM/FEM algorithm and applied to simulate the shaking table collapse test of a single-layer spherical reticulated shell. The simulation predicts structural collapse at a peak ground acceleration (PGA) of 2268 gal—consistent with the experimental value—with 126 members fractured at collapse onset, and reproduces the observed fracture sequence in which first-ring diagonal members near the supports fail progressively from the bottom upward. The proposed framework provides a computationally robust and practically deployable tool for collapse analysis of large-span reticulated structures, with direct implications for progressive-collapse prevention in seismic design and post-event structural forensic investigation of collapse mechanisms. Full article

Existing long-wave infrared (LWIR) BaGa₄Se₇ optical parametric oscillators (BGSe-OPOs) adopt linear-cavity configurations yet struggle to balance high beam quality and high output energy. To overcome this limitation, we report a compact Type I phase-matched ring cavity BGSe-OPO pumped by a 1.06 μm laser. Operating at 8.5 μm, the OPO generates 1.2 mJ single pulses with a peak power of 0.25 MW and an optical-to-optical conversion efficiency of 2%. The estimated beam quality factor M² is 9, representing a threefold enhancement relative to linear-cavity under identical pump conditions. The system features a compact footprint of 400 × 200 mm² and a far-field divergence angle of 4 mrad after 6× beam expansion, enabling practical applications in far-field monitoring. Full article

Single-story unreinforced masonry rural houses along the Tanlu Earthquake Belt in Anhui Province are generally constructed without ring beams and tie columns, resulting in poor structural integrity and low seismic performance. This paper proposes a convenient single-sided High-Ductility Concrete Strip (HDCS) retrofitting method. Two 1:2 scaled test specimens, namely the unretrofitted model M1 and HDCS single-side retrofitted model M2, were fabricated for shaking table tests. Systematic analyses were carried out based on white noise sweep tests, failure modes, acceleration responses and inter-story displacement responses. The test results show that HDCS possesses excellent tensile capacity, which forms continuous confinement at wall joints and openings to boost structural stiffness and greatly restrain post-seismic stiffness degradation, as well as achieve more uniform structural deformation distribution. Under strong seismic excitations, the unretrofitted model suffers severe damage, including penetrating diagonal shear cracks and separation between gable walls and lower walls. In contrast, damage of the retrofitted model is concentrated within the HDCS overlay, realizing damage redistribution and preventing brittle failure of the main masonry. HDCS stabilizes the distribution of acceleration amplification factors and restrains wall rocking and stress concentration around openings. Although single-sided strengthening induces slight out-of-plane effects, its adverse influence is acceptable. Full article

A critical research gap persists in modular steel construction regarding the seismic behavior of inter-module connections between square steel tubular columns and H-shaped steel beams. While numerous connection systems have been proposed, two fundamental challenges remain unresolved: the inherent conflict between construction efficiency and mechanical performance, and the insufficiency of restoring force models that systematically describe hysteretic characteristics and stiffness degradation under cyclic loading. To address these issues, a novel box-type modular connection between square steel tubular columns and H-shaped steel beams is proposed. A finite element model was established using ABAQUS, and the modeling methodology was validated against experimental results from the literature. The seismic behavior was systematically investigated, and a restoring force model with theoretical saturation and linear degradation was developed. Results show that the novel joint is a semi-rigid connection that satisfies the “strong column–weak beam” design principle. The outer ring plate shifts the plastic hinge away from the vulnerable beam end region, preventing failure at the beam–column connection. Among the detrimental factors identified, the insert-to-column gap has the most severe impact, causing up to a 49.5% reduction in energy dissipation and a 6.5% reduction in initial stiffness; the outer ring plate thickness below the beam flange thickness causes a 44.6% drop in energy dissipation. The proposed restoring force model, validated against nine calibration specimens and one independent specimen, predicts peak load with a deviation of only 1.14% and the equivalent viscous damping coefficient with a relative error of 14.7%, confirming its reliability in capturing the cyclic behavior of the joint. This study provides both design recommendations for engineering practice and a theoretical foundation for elasto-plastic analysis of modular frames with this connection type. Full article

To investigate the evolution of acoustic emission (AE) parameters during the flexural failure of reinforced concrete (RC) beams subjected to freeze–thaw and corrosion, four RC beams were fabricated and assigned to four conditioning regimes: no deterioration, freeze–thaw only (75 cycles), corrosion only (4.8% mass loss), and combined. Three-point bending tests were conducted, combining AE and digital image correlation (DIC) techniques. The damage process was divided into four stages: micro-crack initiation, stable crack propagation, unstable crack propagation, and failure. The evolution of AE parameters including ring count, energy, amplitude, peak count, and duration was analyzed. Each parameter is positively correlated with load level and rises as the damage stage advances. The slope of cumulative parameters reflects crack development more reliably than instantaneous values. The effect of corrosion on these parameters is significantly greater than that of freeze–thaw. For corroded beams, AE parameter levels are higher during the micro-crack initiation stage but lower during the stable crack propagation stage. The overall AE activity decreases with increasing deterioration degree. High-amplitude events increase with damage progression, but fewer high-amplitude events are observed at the failure stage of severely deteriorated beams. This study reveals the correspondence between AE parameters and damage stages, providing an experimental basis for damage assessment using AE techniques. Full article

A robust metaheuristic framework based on a sequential hybrid of Artificial Rabbits Optimisation (ARO) and the Grey Wolf Optimiser (GWO) is proposed for the synthesis of linear (20 elements) and concentric circular (three rings, 4, 6, and 10 elements) antenna arrays. The optimisation strategy is applied to two distinct excitation scenarios—amplitude-only and complex amplitude–phase—to synthesise radiation patterns for both broadside and 30° tilted beams. The hybrid TSARO–GWO algorithm aims to minimise the sidelobe level (SLL) while ensuring compliance with design constraints on HPBW, directivity, and DRR. Experimental results validate the hybrid’s superior efficacy, yielding SLLs as low as −34.8 dB and −38.4 dB for the LAA, and −35.9 dB and −45 dB for the CCAA, respectively, while strictly satisfying half-power beamwidth (HPBW), high directivity, and dynamic range ratio (DRR) constraints. Comparative benchmarks against contemporary optimisers (CTPOA, MVO, FPA, DO, SPS-JADE, AHA, HKOA, SSA, and ALO-SQP) demonstrate that TSARO-GWO achieves SLL values that are competitive with or superior to these recent methods across all six synthesis cases, establishing it as a promising framework for complex array synthesis problems. Full article

Severe shocks and vibrations are common in industrial settings (such as oil drilling at 200–300 °C and heavy machinery); high-temperature piezoelectric gyroscopes’ solid-state architecture provides remarkable shock and vibration tolerance as well as great reliability. This review covers the most recent advances in the creation of high-temperature piezoelectric gyroscopes from three angles: materials, structural design, and circuit design. First, it emphasises how optimising microstructures can greatly improve the materials’ temperature stability (e.g., PZT with d₃₃ = 562 pC/N and LiNbO₃ with Curie temperature ~1210 °C) and piezoelectric coefficient; second, it examines the structural design of piezoelectric gyroscopes based on MEMS/NEMS technology (such as disc-type, ring-type, and beam-type), showing that optimising resonance frequency matching and modal isolation techniques greatly improves the gyroscope’s zero-bias stability (down to 5°/h) and immunity to interference; and third, it summarises the efficacy of optimisation techniques like temperature self-compensation circuit design and structural symmetry design. According to research, problems like high-temperature material ageing (e.g., degradation above 120 °C for silicon-based devices) and the difficulty of system integration continue to limit current technology; in the future, performance bottlenecks will need to be removed through advancements in cross-scale manufacturing technologies and intelligent sensor fusion design. From a multidisciplinary standpoint, this study offers theoretical references and technical recommendations for the industrial use of high-temperature piezoelectric gyroscopes. Full article

To achieve rapid and nondestructive evaluation of subgrade compaction quality, this study proposes a subgrade compaction quality evaluation method based on the dynamic modulus obtained from a portable falling weight deflectometer (PFWD), and field experiments were conducted relying on the Gaoyi North Connection Line Project of the Hengxi Expressway in Hebei Province. PFWD tests were carried out on the roadbed under different compaction passes, combined with compaction degree tests using the cutting ring method (CRM) and falling weight deflectometer (FWD) tests, to systematically analyze the evolution law and spatial uniformity of dynamic modulus during the subgrade compaction process. The results indicate that the PFWD dynamic modulus (E_PFWD) exhibits a staged variation characteristic of “rapid increase—slow increase—tending to stability” with increasing compaction passes, and becomes basically stable after the eighth compaction pass. The overall longitudinal compaction quality of the subgrade is relatively uniform, while certain discreteness still exists among different lanes and local areas. The E_PFWD shows good linear correlations with both compaction degree and the equivalent Benkelman Beam deflection values derived from FWD measurements, among which the correlation with FWD results is stronger. The study demonstrates that PFWD can effectively characterize the overall structural stiffness and compaction uniformity of subgrade, providing a reliable basis for rapid detection and uniformity evaluation of subgrade construction quality. Full article

Nonlinear kickers (NLKs) enable off-axis injection in ultralow-emittance storage rings by providing a strong kick to the injected beam while remaining nearly transparent to the stored beam. In hybrid schemes, a conventional four-kicker bump defines the injected trajectory, and the NLK reduces the first-turn action under constrained beam offset and optics conditions. Effective operation additionally requires stable and reproducible first-turn injection trajectories. We develop a compact action–angle framework that expresses NLK dynamics in terms of Courant–Snyder invariants and yields an analytical bound on achievable action reduction. This formulation provides direct design rules for NLK placement, phase advance, injected-beam offset, and kicker field profile. Within this framework, we identify the 8-wire NLK as a practical baseline and extend its design by relaxing the square-geometry constraint, enabling inward shifting of the off-axis field peak while preserving on-axis field and gradient cancellation. Application to the NSLS-II lattice shows how aperture, pulsed-power, and mechanical constraints combine to determine a coupled design solution. Multi-turn tracking confirms that candidate NLK locations maintain sufficient stay-clear (aperture-clearance) margin, while the optimized wire geometry reduces the required current and Lorentz force load. The results establish a unified approach for NLK-assisted injection design and provide a practical pathway for upgrades in diffraction-limited storage rings. Full article

This paper presents a co-optimization framework for sparse concentric ring arrays based on an improved Dueling Deep Q-Network (DDQN) with a two-tier adaptive step-size strategy. The method aims at joint sidelobe suppression and structural optimization under non-ideal conditions. A tri-domain stochastic error model is introduced to characterize position, phase, and amplitude perturbations, and atmospheric-effect-aware evaluation is incorporated for high-frequency propagation scenarios. For a six-ring sparse array, radius-only optimization achieves a PSLL of $-24.4810$ dB, corresponding to an average improvement of $5.809$ dB over the initial array and an additional reduction compared with the baseline DDQN method. Extending the design to joint optimization of ring radii and element counts further reduces the PSLL to $-30.629$ dB, demonstrating the effectiveness of combined geometric and sparsity control. Monte Carlo simulations show that the optimized array maintains stable sidelobe performance under tri-domain stochastic perturbations, with an average PSLL of $-26.758$ dB. Further analysis using real meteorological data indicates that atmospheric effects introduce moderate variations in the normalized beam pattern, while the overall performance remains primarily influenced by stochastic perturbations under the considered modeling conditions. The proposed framework provides an effective and robust optimization approach for sparse concentric ring arrays in practical high-frequency scenarios. Full article

One of the bottlenecks in realizing all-optical computing is the lack of on-chip all-optical logic devices that combine compactness, low loss, and high robustness. Valley photonic crystals (VPCs) have become an important solution for realizing such devices, relying on the excellent transmission characteristics of topological valley states. However, existing structures still face issues such as limited design flexibility. In this paper, a high-performance topological all-optical logic device based on VPCs consisting of circular ring dielectric columns is designed and demonstrated. By introducing the inner radius as an independent design parameter, we construct a new type of VPC and systematically investigate its influence on the photonic band gap. Based on this, we design a beam splitter with high operational bandwidth and low insertion loss (<0.5 dB) and then realize fundamental OR and XOR logic gates, achieving extinction ratios of 18.9 dB for the OR gate and up to 44 dB for the XOR gate at an operating frequency of 193.5 THz. The platform also supports the NOT gate and, through cascading, can implement more logic functions such as the AND gate. Full article

Real-time monitoring of surface cracks in reinforced concrete (RC) beams is critical to structural safety and service performance evaluation. Current structural crack monitoring still faces prominent scientific and technical bottlenecks: conventional unidirectional sensors cannot achieve multi-directional collaborative sensing, rigid piezoelectric materials exhibit poor compatibility with the large deformation of concrete, and there is a lack of quantitative mapping relationships from sensing signals to crack parameters, making it difficult to simultaneously measure crack width, angle, and morphology. This paper presents a novel ring-shaped piezoelectric sensor based on polyvinylidene fluoride (PVDF) and an annular piezoelectric sensing mechanism for real-time monitoring of crack angle, width, and morphology. The sensor incorporates a laminated structure with four strip sensing units for multi-directional strain detection. Experiments were conducted on RC beams under various loading conditions, and finite element analysis was performed using COMSOL Multiphysics. An innovative crack damage index (B) was introduced to assess structural damage quantitatively. Results demonstrate high sensor sensitivity and stable output. Voltage signals increase both with crack width and crack angle, showing responses of 0.045 mV, 0.041 mV, and 0.023 mV for crack angles of 60°, 45°, and 30°, respectively, at a crack width of 9 mm. Strong consistency between experimental and simulation data validates the effectiveness of the mechanism in monitoring the direction, width, and types of cracks. The crack damage index B exhibits a positive correlation with the structural stress response, enabling a quantitative assessment of damage. This study is applicable to the prestressed concrete box girders and T-beams commonly used in large-span bridges, which are typically with a main span of 20–50 m, a beam length of 6–30 m, a section height of 1.2–2.5 m, and designed for Grade C35–C50 concrete. The findings provide a practical foundation for real-time crack monitoring in large-scale bridge beam members. Full article

This work presents a refined theoretical and numerical framework for shaping the axial intensity of finite-energy Bessel–Gaussian beams through programmable nonlinear phase modulation. Starting from the scalar Fresnel diffraction integral, we reformulate the propagation of a Gaussian-apodized axicon beam using a dimensionally consistent stationary-phase method. This analysis directly relates the radial phase gradient to the saddle-point trajectory, phase curvature, and on-axis intensity distribution. A Gaussian phase modulation (GPM) serves as a reference design to achieve a flattop axial profile while preserving the characteristic transverse Bessel ring structure. This work is validated against beam propagation simulations and previously reported spatial light modulator (SLM) experiments, confirming its accuracy within the paraxial regime. A parametric study then clarifies the scaling of wavelength, beam waist, axicon angle, and refractive index for extended focusing. Beyond standard GPM, several alternative nonlinear phase functions are systematically compared. High-performing profiles must replicate not only the amplitude scale but, more importantly, the radial phase-gradient structure of the Gaussian reference, which governs energy redistribution from annular regions to the axis. The results identify smooth, localized nonlinear functions as promising candidates for stable flattop Bessel beam generation. The proposed framework offers a flexible optical design for applications such as through-glass via (TGV) micromachining and light-sheet illumination, while prospective high-intensity laser plasma uses remain beyond the present linear model. Full article

Pulsed laser-induced phase change in silicon underpins applications from photonic device trimming to stealth dicing, yet predictive models that capture the non-equilibrium kinetics governing the competition between epitaxial recrystallization and amorphization remain limited. In this work, we developed a two-dimensional axisymmetric numerical model at the continuum level for picosecond laser-induced melting, resolidification, and amorphization of crystalline silicon at 532 nm laser wavelength, coupling transient heat conduction with Wilson–Frenkel interface kinetics and Lagrangian marker-based interface tracking. The model predicts a bounded amorphization window defined by lower and upper fluence thresholds, within which the central amorphous thickness exhibits a bell-shaped fluence dependence. Under a Gaussian beam, this window governs a morphological transition from a central amorphous spot to an amorphous ring. The predicted amorphization threshold of ≈0.22 J/cm² agrees with published experimental data for 20 ps, 532 nm irradiation. Parametric studies reveal that reducing the spot diameter or substrate temperature shifts or eliminates the upper threshold, transforming the bounded window into a monotonically increasing function, while increasing the pulse duration narrows the window symmetrically until collapse. These results provide quantitative guidelines for selecting irradiation parameters to control phase change in silicon photonic and laser processing applications. Full article