Search Results (2,249)

In this paper, a comprehensive investigation into the single-mode capability of curved sapphire fiber is performed, ranging from theoretical simulation to experimental verification. The equivalent refractive index theoretical model for curved sapphire fiber is proposed based on stress–optic effects and the conformal mapping technique. According to the finite element method, when the radius of curvature is 0.02 m, the curved losses’ difference between high-order modes and the fundamental mode is as high as five orders of magnitude, demonstrating the best single-mode potential. In addition, the curving experiments of sapphire fiber and sapphire fiber Bragg grating are completed. The transmission spectrum of the curved sapphire fiber with a curving radius of 0.02 m is the closest to that of the single-mode fiber. As for curved sapphire fiber Bragg grating (CSFBG), the 3 dB bandwidth of reflection spectrum with the same radius of curvature is also the smallest, with a value of 3.7 nm. Furthermore, the temperature performance of the proposed CSFBG is measured from 22 °C to 1600 °C. The sensitivity is 37.88 pm/°C (@1600 °C), and the measurement accuracy is ±2.98 °C. This study provides theoretical support for single-mode signal transmission of curved sapphire fibers and facilitates high-precision sensing applications under extreme high-temperature conditions. Full article

Friction at the cold rolling interface is affected jointly by the surface roughness, lubrication state, local pressure, and relative sliding. A constant friction coefficient is therefore insufficient to describe its non-uniform distribution along the contact arc. Accordingly, this study proposes a macro–micro two-scale mixed-lubrication and dynamic friction model based on the measured roll roughness. First, the measured roll roughness profile was represented within a finite effective scale interval by a scaled and truncated Weierstrass–Mandelbrot (W–M) function. The parameters D and G were obtained as finite-scale W–M roughness parameters and were introduced into a mixed-lubrication load-sharing model to calculate the local mixed-lubrication friction coefficient. The pressure distribution along the contact arc was calculated using the Karman equation, and the local macroscopic pressure was mapped to a representative microscopic contact load. Finally, the mixed-lubrication friction coefficient was used to calibrate the dynamic friction factor separately in the forward-slip and backward-slip zones, and the friction stress distribution along the contact arc was calculated. For the selected effective scale interval and preprocessing procedure, the fitted W–M roughness parameters were D = 1.528 and G = 9.15 × 10⁻⁸ m. The W–M parameter D had a more significant influence on the mixed-lubrication friction coefficient and load-sharing behavior than the scale parameter G. Increasing the rolling speed strengthened the oil-film load-carrying effect and reduced the equivalent interfacial friction coefficient. The friction stress was positive in the backward-slip zone and negative in the forward-slip zone, with a direction reversal near the neutral point. Field forward-slip inversion showed that both the simulated and measured equivalent friction coefficients decreased with increasing rolling speed, with a difference of approximately 0.009~0.017. The proposed model can capture the main trend of cold rolling interfacial friction with variations in the rolling speed and contact state. Full article

This study investigates the side-impact crashworthiness of a low-floor electric bus with traction batteries integrated into the inter-window pillars of the body structure. A finite-element model of the bus body was developed in Ansys and used to evaluate six impact scenarios involving conventional diesel and battery-integrated configurations. The analysis included evaluation of von Mises stresses, structural safety margins, deformation fields, strain energy, and transient nodal velocity response. The battery-integrated configuration demonstrated improvements in key crashworthiness indicators across the investigated impact scenarios, with both the average maximum deformation and the averaged equivalent stress reduced by approximately one quarter compared with the conventional configuration. The stress state of the inter-window pillars remained below the local structural failure levels observed in the conventional configuration, with the maximum pillar stress criterion reduced by more than half. Simultaneously, lower transient nodal velocities indicated reduced transmission of impact momentum toward the occupant compartment and more efficient redistribution of impact energy through the body structure. The results demonstrate the feasibility of using battery-integrated inter-window pillars as multifunctional structural members that simultaneously serve as energy storage and enhance the side-impact crashworthiness of low-floor electric buses. Full article

The increasing penetration of renewable energy sources and converter-interfaced loads has intensified the need for fast and reliable grid-support services. Although electric vehicle (EV) battery chargers have emerged as promising resources for Vehicle-to-Grid (V2G) applications, existing solutions typically focus on individual services such as virtual inertia or frequency regulation, while limited attention has been given to the coordinated provision of multiple ancillary services within a unified framework. Furthermore, the use of batteries alone for fast frequency support may accelerate battery degradation due to frequent high-power transients. To address these challenges, this paper proposes a hybrid energy storage-based EV battery charger architecture and a coordinated multi-timescale control strategy capable of simultaneously providing virtual inertia support, long-term frequency regulation, reactive power compensation, and harmonic mitigation. The proposed approach utilizes a DC-link capacitor to deliver fast inertial response while the battery supplies sustained frequency support, thereby reducing battery stress and improving energy management efficiency. An enhanced frequency estimation method based on a phase-locked loop combined with a low-pass filter is also introduced to improve dynamic performance. Simulation results demonstrate the effectiveness of the proposed strategy under various grid disturbances. The system achieves an equivalent virtual inertia constant of approximately 1.85 s and delivers up to 786 W of transient inertial support within 80 ms during frequency events. The enhanced frequency estimation method significantly reduces transient overshoot, while harmonic compensation limits the grid current and voltage total harmonic distortion to 1.50% and 3.23%, respectively. In addition, the controller provides up to 400 VAR of reactive power support during voltage disturbances while maintaining stable battery operation. These results demonstrate that the proposed EV battery charger can function as a multifunctional grid-support resource, enhancing frequency stability, voltage regulation, power quality, and overall V2G capability in future smart grids. Full article

To establish a quantitative mapping relationship between macro- and micro-parameters in the PFC^2D parallel bonding model, and in view of the inherent complexity of the mutual validation process between laboratory experiments and parameter calibration, this paper takes uniaxial compression tests as the mechanical reference. By combining orthogonal experimental design, Pearson correlation analysis and multivariate analysis of variance, this study systematically investigates the effects of 10 micro-parameters on 6 macro-mechanical indicators (modulus of elasticity E, Poisson’s ratio ν, uniaxial compressive strength ${\sigma }_c$, friction-to-cohesion ratio FCR, crack initiation strength ${\sigma }_{ci}$ and crack damage stress ${\sigma }_{cd}$). To reduce the coupling dimension between cohesion and internal friction angle in the calibration of PFC macro–micro parameters, this paper defines the Friction-to-Cohesion Ratio (FCR) as the ratio of the equivalent macroscopic angle of internal friction to the equivalent macroscopic cohesion, and systematically conducts sensitivity analyses of uniaxial compression simulations. The results indicate that the elastic modulus E is primarily governed by $E^{*}$, ${\overline{E}}^{*}$, ${\overline{k}}^{*}$ and $R_f$; the Poisson’s ratio ν is mainly influenced by $E^{*}$, $k^{*}$, ${\overline{E}}^{*}$, ${\overline{k}}^{*}$ and $R_f$; the uniaxial compressive strength ${\sigma }_c$, the crack initiation strength ${\sigma }_{ci}$ and the crack damage stress ${\sigma }_{cd}$ are primarily regulated by ${\overline{\sigma }}_c$ and $R_f$; whilst the Friction-to-Cohesion Ratio (FCR) is mainly affected by ${\overline{\sigma }}_c$, $\overline{\phi }$, $R_f$, $\overline{c}$ and $\beta$; Elasticity parameters and strength parameters are governed by different micro-mechanisms, reflecting the fundamental decoupling of stiffness and strength in the PFC model. This study established a progressive ‘screening–validation–quantification’ sensitivity analysis framework, revealing the directional regulation patterns of various micro-parameters on macroscopic responses, thereby providing a theoretical basis for the targeted optimisation and efficient calibration of micro-parameters in PFC discrete element simulations. Full article

Quantum machine learning (QML) provides a framework for benchmarking wearable biosignal classification relevant to stress detection. Motivated by the burden of stress-related conditions, this study compares three quantum classifiers with seven classical baselines using heart rate and respiration rate features as inputs under noise-free and noisy conditions. Uncertainty was quantified using Nadeau–Bengio-corrected confidence intervals and percentile bootstrap ($B=1000$). The variational quantum classifier (VQC) achieved an accuracy of $99.47\%/97.30\%$ (noise-free/noisy), the quantum support vector classifier (QSVC) achieved $99.90\%/99.37\%$, and PegasosQSVC achieved $99.80\%/99.70\%$. Additionally, under the assessed proof-of-concept conditions, statistical equivalence between the QSVC and the best-performing classical model was established at $\Delta =1$ pp; PegasosQSVC under noise achieved equivalence at $\Delta =2$ pp with accuracy degradation of less than $0.10$ pp. The time feature was identified as the primary separability driver in a post hoc classical ablation. Tree-based models were robust on physiological features alone. The surveyed methods provide a reproducible, noise-aware benchmark for wearable physiological signal classification; however, the reported high accuracies are based on a deliberately separable proof-of-concept benchmark and do not demonstrate clinical utility or a quantum advantage. Full article

Future lunar missions, like the International Lunar Research Station (ILRS), demand single-launch multi-point operations, urgently requiring reusable energy-absorbing structures. Integrating shape memory alloy (SMA) into honeycombs offers a promising solution; however, deformation exceeding the SMA’s recoverable limit induces structural residual deformation, altering the configuration and degrading subsequent energy absorption. To address this, we propose a semi-analytical, data-calibrated hybrid model predicting SMA honeycomb residual deformation. A four-stage linear constitutive model is established capturing superelasticity and martensitic yielding. Cell walls are idealized as equivalent beams. Using layered fiber integration and numerical interpolation, a nonlinear moment–curvature relationship is constructed, enabling rapid structural residual deflection evaluation from material residual strains. Finite element results confirm that initial residual deformation stabilizes the honeycomb into a reusable configuration, governing subsequent plateau stresses. Calibrated by uniaxial test data, the proposed model accurately predicts residual deformation ratios and reusable plateau stresses with errors within 8%. By bridging material-level strain with structural-level deformation, this approach circumvents computationally expensive full-scale simulations and costly experimental trials, providing a highly efficient tool for designing reusable SMA absorbers. Full article

Rainfall-induced delayed instability of fractured rock slopes is strongly affected by fracture preferential flow, hydro-mechanical coupling, and spatial matrix heterogeneity. However, the coupled influence of stress-dependent fracture aperture evolution and heterogeneous matrix properties on delayed slope deformation remains insufficiently quantified. In this study, a two-dimensional discrete fracture network (DFN)–equivalent continuum coupled model was established using spectral random field theory and a representative Monte Carlo-generated fracture geometry. The spectral exponent β = 1.0–2.5 was adopted to characterize different degrees of matrix heterogeneity, and rainfall infiltration–stress coupling simulations were conducted under an extreme rainfall scenario followed by drainage. The results indicate that the wetting front advances irregularly in the heterogeneous matrix, while fracture preferential flow accelerates rainwater infiltration and promotes local pore-pressure accumulation near the phreatic surface. After rainfall cessation, water stored in fractures continues to recharge the deep matrix, leading to delayed pore-pressure increase and post-rainfall deformation. The simulated fracture aperture shows an initial closure followed by gradual dilation, which is controlled by the competition between saturation-induced stress redistribution and pore-pressure-driven effective stress reduction. Under a common strength reduction factor of FOS = 1.4, stronger matrix heterogeneity results in more pronounced plastic strain concentration and larger displacement amplitude along the potential slip zone. These findings suggest that fracture aperture evolution and matrix heterogeneity jointly influence delayed deformation and potential failure-zone development in rainfall-affected fractured rock slopes. The conclusions should be interpreted within the scope of a two-dimensional DFN–equivalent continuum numerical framework with prescribed rainfall conditions and representative fracture/random-field realizations. Full article

Circular tunnel linings are geometrically symmetric structures, whereas non-uniform external pressure and different steel–concrete layer arrangements may induce asymmetric stress redistribution. To distinguish the axisymmetric response from the asymmetric harmonic response, this study develops an analytical solution for a two-layer corrugated steel–concrete composite tunnel lining subjected to equivalent external pressure. The concrete layer is modeled as an isotropic elastic material, while the corrugated steel layer is represented as an equivalent cylindrically orthotropic material. The governing equations are formulated in polar coordinates under plane-strain conditions, and the solution is obtained by superposing the axisymmetric component and the harmonic component. Perfect bonding is assumed at the steel–concrete interface, where displacement, radial stress, and shear stress are continuous. The proposed analytical solution is verified using finite element models for three cases: a single-layer homogeneous lining under uniform pressure, a two-layer composite lining under uniform pressure, and a two-layer composite lining under non-uniform pressure. The analytical and finite element results show good agreement, confirming the mathematical consistency and implementation accuracy of the proposed formulation. Based on the verified solution, the effects of layer arrangement, corrugated steel stiffness ratio, and burial depth are investigated. The results show that the corrugated steel layer carries the dominant hoop stress in both layer arrangements. The inner corrugated steel arrangement may be more relevant to internal strengthening of existing tunnels, whereas the outer corrugated steel arrangement provides a useful reference for new composite linings dominated by external ground pressure. Increasing the stiffness ratio transfers more hoop stress to the steel layer and reduces the elastic stress and displacement responses of the concrete layer, although improvement becomes less significant at large stiffness ratios. Increasing burial depth mainly amplifies the response magnitude without changing the overall symmetry pattern. The proposed solution provides a closed-form benchmark for evaluating symmetry-related stress redistribution in corrugated steel–concrete composite tunnel linings within the linear-elastic range. Full article

In response to the current limitation where conventional constant volume combustion apparatuses are generally confined to pressure ratings of 5–20 MPa, insufficient for the demands of ultra-high-pressure combustion fundamental research, this study designs and verifies a high-pressure-resistant constant volume combustion apparatus with a rated working pressure of 250 MPa. The strength design and safety factor calculation for the combustion chamber main body were conducted based on the Lame thick-walled cylinder elastic theory. A finite element numerical simulation method was systematically employed to perform static analysis, transient impact response analysis, and high-cycle fatigue-life assessment of the key components of the apparatus. The results indicate that under a 250 MPa design internal pressure load, the maximum circumferential stress at the inner wall of the combustion chamber main body is 328.0 MPa, with a safety factor greater than 1.5, complying with relevant safety codes for high-pressure vessels. Under transient loading simulating combustion impact, the maximum equivalent stress of all structural components is below the material yield strength, with a maximum elastic deformation of less than 0.06 mm, demonstrating excellent structural stiffness and impact resistance. Fatigue assessment with a design-life target of 1.0 × 10⁶ pressure cycles shows that the cumulative damage values for all components are significantly less than 1.0, meeting the reliability requirements for long-term cyclic service. This apparatus integrates functional modules such as high-pressure precision gas mixing, high-energy reliable ignition, high-speed transient parameter acquisition, and safe product collection, providing a stable, controllable, and safe experimental platform for in-depth research on the combustion mechanisms of gaseous fuels under ultra-high-pressure conditions. Full article

We propose an exploratory framework for a Bohmian model of quantum matter propagating on a classical curved spacetime background. The gravitational sector is governed by classical Einstein field equations throughout; no quantisation of spacetime is attempted. The wave function emerges as the scalar contraction $\mathrm{\Psi }={\psi }_{\nu }{\psi }^{\nu }\in \mathbb{C}$ of a complex-valued tensorial field ${\psi }^{\mu }$, encoding quantum dynamics in a geometric object. The wave tensor interacts with spacetime via the stress–energy tensor $T_{\mu \nu }$, mediated by a real scalar field a of dimension volume, so that $a{T}_{\mu \nu }{\psi }^{\mu }{\psi }^{\nu }$ yields the correct potential energy. We derive a covariant Adapted Schrödinger Equation as the unique minimal covariant lift of the standard equation, justify it from four guiding principles, and verify three internal consistency checks. Under seven explicit approximations the framework reproduces the Schrödinger equation with Coulomb potential for the hydrogen atom. We also derive a dynamical equation for ${\psi }^{\mu }$ that entails the Adapted Schrödinger Equation by contraction. Two open problems are then resolved. First, a complete Lagrangian formulation is provided: a real-valued action for $\mathrm{\Psi }$ yields the Adapted Schrödinger Equation via the Euler–Lagrange equations; a separate action for ${\psi }^{\mu }$, extended by a non-polynomial term, yields the full dynamical equation variationally. Second, two experimental predictions are derived. Expanding to first post-Newtonian order, the perturbation Hamiltonian has coefficients $(3, 1)$ on the kinetic and potential operators; via the virial theorem these produce a coordinate-time blueshift, which after photon propagation yields the universal Einstein gravitational redshift $\delta \nu /\nu =\mathrm{\Phi }/c^2$, confirming consistency with the equivalence principle. The same kinetic coefficient independently predicts that free quantum wave packets spread more slowly by the fractional amount $3\left|\mathrm{\Phi }\right|/c^2$, a correction absent in standard non-relativistic quantum mechanics. Full article

Hot forging of Ti-6Al-4V is extensively utilized in the manufacture of orthopedic implants; however, the coupled influence of strain rate and temperature on ductile damage evolution during the forging of femoral stems remains insufficiently quantified. In this study, a finite element framework is developed to analyze and optimize the hot forging process, incorporating strain rate- and temperature-dependent plasticity, as well as the Johnson–Cook damage criterion. Mesh convergence is established, and the assumption of quasi-adiabatic conditions is substantiated via Péclet number analysis. A full factorial design is implemented by varying the ram velocity (0.1–0.5 m/s) and initial billet temperature (850–950 °C) to evaluate the forging load, stress triaxiality, equivalent plastic strain, and damage accumulation. Results indicate that process kinetics govern the mechanical response: increasing the ram velocity enhances strain-rate hardening, resulting in higher peak loads, while explicitly reducing stress triaxiality and suppressing ductile damage evolution. Conversely, temperature exhibits a secondary influence within the investigated domain. Validation of the damage criterion confirms safe operating windows, identifying low-velocity forging as a high-risk condition for localized defect formation. These findings provide practical guidelines for the strain-rate-based optimization of thermomechanical processing parameters for Ti-6Al-4V femoral stems. Full article

This paper proposes a mathematical co-design framework for synchronous Boost DC-DC converters and their PI voltage controllers. In contrast to the conventional sequential design approach, where the power stage is sized first and the controller is tuned afterward, the proposed method treats the converter and the controller as a single coupled design problem. A nonlinear averaged model of the synchronous boost converter operating in continuous conduction mode is considered, explicitly incorporating the inductor series resistance, the capacitor equivalent series resistance, and the on-state resistances of the active switches. In addition, a simplified but physically interpretable loss model is included in order to capture inductor copper loss, capacitor ESR loss, semiconductor conduction loss, and switching loss. Based on this formulation, the joint design of the power stage and the PI controller is cast as a constrained multi-objective optimization problem whose decision variables include the inductance, capacitance, switching frequency, and controller gains. The optimization criteria account for output-voltage ripple, settling time, total losses, and current stress, while practical constraints related to duty cycle, current limits, ripple bounds, and closed-loop feasibility are enforced. The proposed framework makes it possible to compute Pareto-efficient designs and to reveal trade-offs that remain hidden under classical decoupled design procedures. Numerical case studies are structured to compare the proposed co-design strategy with a conventional sequential-design baseline. An optional technology-aware extension is also considered, allowing the influence of different semiconductor classes, such as Si, SiC, and GaN, to be assessed through technology-dependent loss and switching-frequency assumptions. The results indicate that the proposed framework provides a mathematically grounded and practically useful basis for integrated converter–controller synthesis in nonideal power electronic systems. Full article

This paper presents a preliminary numerical investigation on the mechanical behavior under eccentric compression of T-shaped steel tube-steel reinforced concrete columns. A refined finite element (FE) model was developed in ABAQUS 2021 and validated against published axial compression test results. The effects of three key parameters (eccentricity, outer steel tube thickness, and built-in steel skeleton size) on the bearing capacity, failure mode, stiffness degradation, and stress distribution of the studied members were systematically analyzed via finite element analysis, followed by comparative calculations and an applicability analysis of the calculation of eccentric compression bearing capacity. All eccentric compression results presented herein were obtained through numerical simulation and have not been directly verified by physical tests. The results show that the ultimate bearing capacity decreases by more than 57% as the eccentricity increases from 0 mm to 75 mm, with the failure mode transitioning from axial compression failure to flexural failure. Within the studied parameter range, the 4 mm-thick outer steel tube exhibits superior comprehensive performance, including bearing capacity, stiffness, and ductility. Increasing the built-in steel skeleton size effectively enhances the flexural stiffness and ductility, and delays stiffness degradation. The existing code-specified formula demonstrates good accuracy (relative error < 6%) for e ≤ 50 mm but yields significant errors for e = 75 mm. An empirical expression for the equivalent eccentricity influence coefficient α is proposed, which reduces the overall average error from 4.89% to 2.26% within the parameter scope of this study. Full article

Based on the viscoelastic artificial boundary theory and the equivalent seismic load input method, this study develops a three-dimensional time-domain input method for obliquely incident SV waves; the validation of this input method was verified, and seismic response analysis was conducted on a biased rock tunnel. The results indicate that the structural seismic response under oblique wave incidence differs significantly from that under vertical incidence. With an increase in the incidence angle, the tunnel’s stress, acceleration, and damage zones all tend to concentrate toward the left arch foot and waist. At different times during the earthquake, stresses and plastic zones develop at the tunnel shoulder, along with the obliquely incident seismic wave propagation, and the stresses and plastic zones gradually concentrate in the direction facing the waves, causing damage at the tunnel foot near the earthquake source. Therefore, in tunnel structures located near the epicenter of an earthquake, the damage evolution at the foot of the tunnel facing the seismic waves should garner more attention. Full article