Search Results (9,434)

Low-velocity impacts during manufacturing and maintenance (e.g., tool drops) can induce barely visible impact damage in composite aircraft structures, motivating sensing-assisted approaches for rapid post-event assessment. This study proposes and validates a strain-based structural health monitoring framework for carbon-fiber-reinforced polymer (CFRP) panels by combining surface-mounted strain gauges with explicit finite element analysis (FEA). Drop-weight tests were con-ducted in accordance with ASTM D7136 using a 1.0 kg hemispherical impactor at drop heights of 250–400 mm. Three strain gauges were positioned at 1.25 mm, 32.5 mm, and 52.5 mm from the impact point to quantify the spatial attenuation of peak surface strain. The measured peak strains exhibited clear-dependent decay and increased with impact energy up to 350 mm, whereas the 400 mm case showed a non-monotonic response and a pronounced deviation from an elastic energy-scaling baseline, consistent with a transition to damage-dominated energy dissipation. Dedicated MSC Apex/Nastran Implicit simulations reproduced experimental trends and provided a physics-based digital twin for interpreting strain signatures in elastic regions, correlating them with likely damage states. Full article

Lightning-induced breaking accidents of medium-voltage insulated conductors pose a serious threat to the safety of distribution networks, and the key cause lies in the establishment and sustained combustion of the power-frequency follow-current arc after lightning overvoltage breakdown. This paper systematically investigates the formation mechanism and critical conditions of power-frequency follow-current arcs using combined simulation and experimental approaches. Based on the streamer discharge theory, a lightning breakdown model was established and combined with the arc energy balance equation, revealing that the establishment of power-frequency follow-current arcs is essentially determined by the post-breakdown energy competition process. The simulation results show that the required anode electric field strength for lightning breakdown is not less than 3 kV/mm. When the power-frequency voltage reaches 10 kV, Joule heating of the arc continuously exceeds heat dissipation loss, enabling restrike after zero-crossing and sustaining stable burning. Experiments verified this voltage threshold and further revealed that the arc establishment rate exhibits nonlinear growth with increasing power-frequency voltage, exceeding 90% at power-frequency voltages ≥ 10 kV. The study also reveals that increased gap distance reduces the arc establishment rate, while the introduction of insulators can enhance it by approximately 20%. This study clarifies the energy criterion for power-frequency follow-current arc establishment and the influence patterns of key parameters, providing theoretical basis and engineering reference for lightning protection design and arc suppression in medium-voltage insulated lines. Full article

Thermal stress is an important factor affecting the long-term performance of solid insulation in GIS/GIL, and the physicochemical properties of insulating materials play a crucial role in governing surface charge dynamics. This study investigates the influence of accelerated thermal aging on the surface charge behavior of Al₂O₃-doped epoxy resin insulators. Different aging severities were applied to simulate long-term service conditions, and charge accumulation and dissipation characteristics were correlated with physicochemical evolution revealed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results indicate that increasing aging severity reduces the charge accumulation rate while increasing the saturated surface charge density. Voltage polarity significantly influences surface charge behavior: a relatively uniform distribution is observed under positive polarity, whereas localized charge clusters are more likely to form under negative polarity. Thermal aging also accelerates the development of surface defects and increases polar functional groups, resulting in degraded insulating performance. These findings clarify the relationship between thermal aging, physicochemical evolution, and surface charge dynamics in epoxy-based insulation systems. Full article

Beam-to-column connections govern both seismic performance and post-earthquake repairability of steel moment-resisting frames. Yet direct, apples-to-apples comparisons among welded, bolted, and repair-oriented replaceable-fuse moment connections are still scarce, which hinders rational selection for resilient construction. This study conducts a unified finite-element comparison of three representative joint archetypes—W-RBS, Bolted, and Prefab-web-fuse—under monotonic and cyclic loading. Consistent moment-rotation definitions are adopted, and normalized indices are introduced to compare hysteresis shape, degradation, and energy dissipation across joint concepts with different strength scales. Component-wise plastic dissipation is also extracted to quantify damage localization and assess main-frame protection and replaceability. Results reveal clear trade-offs: W-RBS provides the highest strength and dissipation but degrades most in stiffness; the bolted joint shows pinching due to interface compliance; and the web-fuse concept concentrates inelastic demand in a replaceable segment, supporting repairability-oriented design. The proposed framework offers mechanism-based guidance for selecting steel moment connections toward resilient and repairable frames. Full article

We analyze the spectral stability of travelling waves in a $\delta$-regularized dissipative sine-Gordon equation modelling refined long Josephson junction dynamics. Linearization about a wave yields a singularly perturbed fourth-order spectral problem with intrinsic slow–fast spatial structure. Using an Evans-function formulation on a domain of consistent spatial splitting, we establish a local factorization separating slow and fast modes and prove that the $\delta$-induced fast subsystem remains uniformly hyperbolic and does not generate an additional point spectrum near $\lambda =0$. Hence, the local point spectrum coincides with that of the classical dissipative sine-Gordon equation. Numerical computations of the essential spectrum and Evans winding numbers confirm the analysis and show that the higher-order terms enhance high-frequency damping without altering low-frequency spectral stability. Full article

To investigate the interlayer contact mechanism of foamed cold-recycled asphalt mixture under static loads, a three-layer asphalt pavement discrete element model (DEM) was established, with the surface layer composed of asphalt concrete-13 (AC-13), asphalt concrete-20 (AC-20) and asphalt-treated base-25 (ATB-25) foamed cold-recycled asphalt mixture and cement-stabilized macadam as the base. Based on mortar theory, the pavement was divided into coarse aggregate, asphalt mastic and air void phases, and the Burgers Model, Linear Parallel Bond Model and Linear Model were adopted to characterize the bonding of asphalt-aggregate, cement contact interface and subgrade-surface layer, respectively. Static loads of 0.7 MPa, 1.1 MPa, 1.5 MPa and 1.9 MPa were applied to analyze the mechanical responses of asphalt-based and cement-based pavement systems from tensile strain, vertical compressive stress and vertical displacement. Results showed that mechanical indices of the pavement increase monotonically with static load and present obvious layered distribution. The cement-stabilized macadam base provides rigid support, significantly reducing tensile strain (TS) and vertical displacement (VD) of asphalt layers, while the asphalt-based system has flexible stress transfer and superior stress dissipation in the bottom layer. The two systems exhibit respective structural advantages, with the cement-based system outstanding in deformation control and the asphalt-based system suitable for flexible stress adaptation working conditions. Full article

Hafnium oxide (HfO₂) is predominantly used as a high-index material in multi-layer dielectric coatings for high-peak- and high-average-power lasers, but laser damage often initiates within the HfO₂ layers despite their wide bandgap. Oxygen deficiency during deposition can introduce vacancy-related sub-bandgap states and absorptive defects, lowering damage resistance. This study investigates how oxygen flow during HfO₂ deposition with ion beam sputtering (IBS) affects its stoichiometry, defect formation, and nanosecond laser-induced damage threshold (LIDT) and whether single-layer trends predict multilayer performance. Single layers were deposited at varying oxygen flows, characterized for optical and structural properties, and tested for the LIDT at 1064 nm and 355 nm. Increasing oxygen flow drove the layer toward near-stoichiometric HfO₂, reduced the refractive index, and altered the density of surface pinhole-like features. The single-layer LIDT at 355 nm increased with oxygen, whereas the 1064 nm LIDT was comparatively less sensitive to oxygen flow, consistent with the wavelength-dependent roles of absorptive precursors and microstructural defects. In contrast, a HfO₂-based high-reflector (HR) showed a higher LIDT at lower oxygen flow, indicating that the family of damage precursors changes between single layers and multilayers; in stacks, structural properties such as stress, gas entrapment and thermal dissipation may outweigh the isolated absorptive defects found in single layers. These results demonstrate that the optimal oxygen flow condition depends on both LIDT wavelength and film architecture. We identified, for single layers, a 15–35 sccm window for maximizing the 1064 nm LIDT and a high-flow optimum (45 sccm) for the 355 nm LIDT and, for 355 nm HR stacks, a distinct lower-flow regime (~10 sccm). Full article

This paper presents the analysis, design, and experimental validation of a Partial Power Processing (PPP) Single-Ended Primary Inductor Converter (SEPIC) for photovoltaic (PV) applications. The proposed topology limits the fraction of processed power through the active switching stage, thereby reducing MOSFET RMS current and associated conduction losses and improving overall conversion efficiency. A complete analytical framework is developed, including steady-state modeling, state-space formulation, and small-signal analysis. The theoretical results are validated through MATLAB/Simulink simulations and laboratory-scale experimental tests under multiple loading conditions. Comparative analysis against a conventional Full Power Processing (FPP) SEPIC converter demonstrates that the proposed PPP configuration achieves efficiencies up to 95% in simulation and up to 93% experimentally, compared to 87% for the FPP counterpart under identical nominal conditions ($V_{\mathrm{in}}=18$ V, $f_{\mathrm{s}}=70$ kHz). Additionally, the PPP approach reduces the MOSFET RMS current by more than 50%, which directly translates into lower conduction losses and reduced device power dissipation. The results confirm that the proposed PPP-SEPIC converter constitutes a technically viable and energy-efficient solution for photovoltaic DC–DC power conversion systems. Full article

This work presents the Theory of Spacetime Impedance (TSI), a phenomenological framework in which the vacuum is modeled as a distributed reactive medium with an effective RLC structure. At the classical level, the vacuum is characterized by permeability, ${\mu }_0$, permittivity, ${\epsilon }_0$, and impedance, $Z_0$, so that the speed of light follows from the vacuum’s constitutive reactive properties. The TSI introduces a reactive–dissipative term, $R_H$, as an effective mechanism associated with irreversibility, decoherence, and entropy production, providing a physical basis for the arrow of time. At the quantum level, TSI incorporates a quantum RLC triad associated with the electron, defined by quantum inductance, $L_K$, quantum capacitance, $C_K$, and von Klitzing resistance, $R_K$. When normalized by the Compton wavelength, these quantities admit a direct comparison with ${\mu }_0$ and ${\epsilon }_0$, identifying the fine-structure constant as an impedance scaling factor between classical and quantum regimes. Within this unified reactive picture, inductive, capacitive, and resistive responses are respectively associated with gravitation, electromagnetism, and thermodynamic irreversibility, offering a complementary bridge across quantum, relativistic, and macroscopic domains. Full article

Pulsating heat pipes (PHPs) are promising passive heat-transfer devices for compact thermal management; however, their performance is highly sensitive to channel geometry. In particular, the operating-condition-dependent influence of sinusoidal corrugation amplitude on the condenser side remains unclear, despite its importance for oscillation regulation and heat dissipation. This numerical study investigates a single-loop PHP with sinusoidally corrugated condensers (A = 0.25 and 0.5 mm) under heat fluxes of 5000–12,500 W/m² and filling ratios of 40–60%, using a uniform-diameter PHP as the baseline. The results show that the configuration with A = 0.25 mm exhibits better start-up performance, especially at low heat fluxes, whereas both corrugated configurations provide better thermal performance than the baseline. At a filling ratio of 50%, the thermal-resistance reductions for A = 0.25 and A = 0.5 mm are 14.5% and 9.2% at 5000 W/m² and 8.4% and 10.5% at 12,500 W/m², respectively. An operating-condition-dependent amplitude-matching relationship is identified: The smaller amplitude is more favorable for start-up under weak driving conditions, whereas the larger amplitude tends to provide lower thermal resistance and higher equivalent thermal conductivity under strong driving conditions. These findings provide useful guidance for condenser-geometry optimization in single-loop PHPs. Full article

Icing poses significant operational and safety risks in aviation, especially for engine components such as cowls and baffles. This study explores the potential of a chemically exfoliated graphene-rich carbon platelet epoxy coating to improve the anti-icing and de-icing performance of 3003-H14 aluminum alloy, which is widely used in such applications. Chemically exfoliated graphite was incorporated into an epoxy resin, then applied to aluminum substrates. Characterization of the coated samples revealed ~30% improvement in surface Vickers hardness (HV) (HV 75.6 ± 1.15 vs. HV average of 98.3 ± 1.5) and enhanced thermal dissipation, with coated surfaces cooling from 104 °C to 22 °C in 530 s compared to 870 s for uncoated samples. While anti-icing performance was not directly evaluated, the observed improvements in thermal dissipation and surface hardness suggest that chemically exfoliated graphene-rich carbon platelet coatings could be promising for passive anti-icing applications. The literature suggests that graphene coating improves hydrophobicity, reducing ice adhesion and delaying nucleation due to its low surface energy and nanoscale roughness, thereby supporting potential passive anti-icing functionality for aircraft engine components. SEM analysis confirmed a uniform, compact coating layer. These preliminary findings indicate that chemically exfoliated graphene-rich carbon platelet coatings can deliver multifunctional performance—mechanical, thermal, and surface—making them promising candidates for passive anti-icing/de-icing solutions in engine components where conventional systems are ineffective. Full article

Concrete-encased steel (CES) bridge piers can be considered as a robust alternative to traditional reinforced concrete sections, especially in regions prone to seismic activity. CES piers combine the ductility of steel with the compressive strength of concrete, offering improved energy dissipation and resilience during earthquakes. Given the lack of CES design specifications in the Canadian design code, it is crucial to compile a body of knowledge describing the behavior of the CES bridge pier in order to facilitate the codification of the design guide. This study assesses the seismic performance of CES rectangular bridge piers with a focus on how variations in the steel section configuration affect the pier’s overall behavior under seismic loads. To conduct this assessment, a fiber element model was employed to model CES bridge piers subjected to seismic loading. The thickness and height of the web and the width and the thickness of the flanges of the I-shape steel section were varied to understand their impact on the bridge’s seismic performance. In addition to the I-shape sections, a crossed two-I-shape section was also studied. Spectral analysis, nonlinear pushover analysis and nonlinear time-history analysis was performed on the bridge models in order to better understand the seismic performance of the studied bridge piers. Simulation results indicate that larger flanges increase the pier’s bending moment capacity, allowing it to absorb greater seismic energy and undergo larger deformations without failing. This increases the overall ductility of the pier and enhances its ability to dissipate seismic energy. However, excessively large flanges or web can reduce the concrete cover and reduce the durability of the pier in the context of Canadian extreme-winter conditions. The study concludes that a balance between web thickness and flange width must be achieved to ensure the bridge can resist seismic forces while maintaining sufficient ductility and energy dissipation. Therefore, an optimized design, according to seismic demands, enhances the overall resistance of CES bridge piers. Full article

This research addresses a structural cybernetic anomaly within strategic management precipitated by the integration of artificial intelligence into the organizational core. Traditional paradigms, specifically the resource-based view and the dynamic capabilities framework, operate under closed-system, first-order cybernetic assumptions that fail to capture the dissipative nature of algorithmic agents. By conceptualizing the enterprise as a complex adaptive system operating far from thermodynamic equilibrium, this study introduces the theory of dynamic cognitive advantage. Grounded in second-order cybernetics, the framework posits that competitive differentiation emerges from the historical, recursive, structural coupling of human semantic intent and machine syntactic processing. This research formalizes this co-evolutionary dynamic utilizing coupled non-linear differential equations and time decay integrals. Furthermore, it operationalizes the central mechanism of this capability—the cognitive flywheel—and proposes a fractal governance architecture to mitigate systemic vulnerabilities such as automation bias. To transition these propositions into management science, a proposed mixed-methods empirical research agenda is presented. It outlines a future partial least squares–structural equation modeling (PLS-SEM) approach to test the mediating role of the cognitive flywheel and the moderating effect of fractal governance on organizational resilience. This research provides a mathematically formalized, empirically testable architecture for navigating the artificial intelligence economy. Full article

This study proposes a comprehensive framework, based on an upper-bound approach, for assessing how vegetation enhances wall stability through two primary mechanisms. The two mechanisms are reinforcement from root systems and hydrological reinforcement through transpiration-induced soil suction. Both contributions are integrated as additional internal energy dissipation terms within a logarithmic-spiral failure model. New expressions of earth pressure in unsaturated soil are derived, considering the influence of vegetation. The active earth pressure acting on the retaining wall is obtained using sequential quadratic programming. The proposed method is validated against classical non-vegetated solutions, confirming its accuracy. The results show that vegetation significantly reduces active earth pressure, with the extent of reduction depending on soil type, root distribution, and transpiration rate. In clay soils, both mechanical and hydrological effects are important, while in sandy soils, mechanical root reinforcement plays the dominant role. The effectiveness of vegetation is influenced by root depth, density, and diameter, with practical design insights provided through parametric charts. This work offers a theoretically consistent and design-oriented tool for evaluating vegetated retaining walls, emphasizing the coupled hydro-mechanical interactions between plants and soil. Full article

Wind-induced noise remains a critical engineering challenge for MEMS microphones in compact consumer electronics such as smartphones, where spatial constraints limit conventional noise control solutions. This study experimentally investigates the suppression of flow-induced wind noise by a straight tube serving as the front cavity of a microphone, using a precision measurement microphone for data acquisition. Controlled experiments were conducted in both a flow duct for parametric isolation and an anechoic chamber for real-world validation. Results demonstrate a strong diameter-dependent effect: for a 1 mm diameter, increasing tube length significantly reduces noise power spectral density and steepens high-frequency roll-off via enhanced internal viscous and thermal dissipation. This effect weakens for a 2 mm diameter and becomes negligible for a 3 mm diameter, where noise is dominated by external flow excitation at the tube inlet rather than internal propagation. Therefore, extending tube length is an effective noise control strategy only for small-diameter cavities. Furthermore, while increased wind speed and oblique incidence elevate PSD, a longer tube reduces this sensitivity. Because acoustic transmission loss—including potential effects like aperture diffraction and impedance mismatch—was not measured, any resulting improvement in the effective signal-to-noise ratio is strictly presented as a hypothesis requiring future electroacoustic validation. The consistent findings across both experimental environments provide clear design guidance: for compact MEMS microphone systems in portable devices, elongating the front cavity is a viable passive noise control method only when the cavity diameter is sufficiently small (<2 mm). This offers a practical, space-efficient alternative to traditional windscreen-based approaches in portable devices. Full article