The interaction between surrounding rock and support structure is fundamental for support structure design and tunnel stability evaluation, closely related to underground engineering safety and economy. A strain-softening model based on Unified Strength Criteria (USC) is employed to characterize deep rock masses, considering intermediate principal stress effects on rock mechanical behavior. Under the assumption of axisymmetric plane strain, a new mechanical model for rock-support interaction is established. A corresponding solution method is proposed and validated by numerical simulation results, existing analytical models and field datasets. Parameter studies were conducted to investigate the effects of intermediate principal stress and supporting time on rock-support interaction. The findings indicate that the intermediate principal stress has a significant impact on the stability of the surrounding rock and the load-sharing behavior of the support structure. The increasing intermediate principal stress significantly reduces both tunnel wall displacement and support load, with a Stress Effect Factor (SEF) demonstrating up to a 28.1% reduction in tunnel wall deformation and a 12.6% reduction in support load when transitioning from the traditional Mohr-Coulomb criterion (the intermediate principal stress effect coefficient b =0) to a double shear strength criterion ( b =1). The proposed model and solution method provide a comprehensive and accurate approach to analyzing rock-support interaction in deep tunnels, offering valuable insights for tunnel design and support structure optimization.

The study of corrosion damage mechanisms in high-strength steel (HSS) has important theoretical value and engineering significance, as HSS is the core material of modern steel structure engineering. In this paper, Q690D HSS specimens with different degrees of corrosion damage were prepared through salt spray and dry and wet cyclic accelerated corrosion tests. Combined with 3D scanning-based reverse modeling and numerical simulation method, the degradation law of tensile mechanical properties of Q690D HSS under a corrosive environment is systematically revealed. The results of the study show that the surface of corroded HSS is uneven, with pits of different sizes distributed. With the increase of corrosion degree, the strength and ductility of HSS gradually decreased, and the maximum tensile strength and elongation decreased by 8.78% and 35.47%, respectively. It shows that the corrosion damage has a more significant effect on the ductility of HSS. As the degree of corrosion increases, the stress concentration effect on the surface of the specimen increases significantly, the critical displacement corresponding to the moment of initial damage occurrence decreases, and the fracture mode shows a clear trend of brittle transition. The numerical simulation results of the finite element (FE) analysis method based on 3D scanning-based reverse modeling are highly consistent with the test data. The reliability and applicability of the method in the assessment of mechanical properties of corroded HSS are verified.

A physics-informed coupled residual-Fourier neural network for multi-physics field prediction in laser manufacturing

Dampers are key energy-dissipating components in structural seismic systems. They can effectively dissipate seismic energy, control structural dynamic responses, and mitigate damage to primary structural members. Thus, they play an important role in improving structural seismic resilience and mitigating seismic hazards. By integrating multiple units with different yield thresholds or energy-dissipating mechanisms, multi-stage energy-dissipating dampers realize sequentially activated energy dissipation under varying seismic intensities and spectral characteristics. They broaden the energy dissipation range under varying seismic intensities and enhance cyclic stability and fatigue resistance. They provide an effective technical approach to overcome the inherent limitations of traditional single-stage dampers, such as insufficient energy dissipation capacity and poor cyclic fatigue performance. This study systematically reviews the recent research progress on multi-stage energy-dissipating dampers, focusing on the structural configurations and seismic performance studies of four typical types: stage-yielding metallic dampers, stage-friction dampers, metal-friction hybrid dampers, and metal-viscoelastic hybrid dampers. Relevant numerical simulation and experimental research results are summarized, and the key issues that require further in-depth exploration in this field are prospected.

The Soybean aphid (Aphis glycines) is a destructive pest that threatens soybeans. In order to develop green and effective control strategies, we propose an EQPAL epidemic model that integrates four developmental stages (1st–2nd stage nymphs, 3rd stage nymphs, 4th stage nymphs, and adults) and a ladybug (Harmonia axyridis) compartment. This model achieves green pest control by artificially releasing a natural enemy of soybean aphids to prey on adult soybean aphids. We analyzed the dynamic behavior of the model and derived the basic reproduction number R0. Using field monitoring data from Changchun City, Jilin Province, China in 2025, the segmented nonlinear least squares method was used for parameter estimation and fitting, resulting in an overall determination coefficient of R2=0.8204. The numerical simulation results showed that the release of ladybugs significantly reduced the density and peak value of soybean aphid adults, and the predation rate β, predation conversion rate c, and ladybug migration rate ω were identified as key regulatory parameters. In addition, a cost–benefit analysis was conducted to determine the most cost-effective control measures.

Joint modulation format identification (MFI) and optical signal-to-noise ratio (OSNR) monitoring constitutes one of the most critical functions integrated in digital coherent receivers, ensuring high flexibility and stability in elastic optical networks (EONs). Since signal amplitude information captures inherent characteristics associated with modulation formats and fluctuations induced by OSNR variations, a simple and effective optical performance monitoring (OPM) scheme based on an amplitude-analytic complex plane is proposed. By employing a multi-task learning algorithm incorporating the multi-order gated aggregation (MOGA) module, the proposed scheme enables simultaneous MFI and OSNR monitoring for polarization division multiplexed (PDM)-QPSK/-16QAM/-32QAM/-64QAM/-128QAM signals. The performance of the proposed scheme is numerically verified in 28 GBaud coherent optical communication systems of various configurations. Numerical simulation results show that 100% identification accuracy is obtainable for all five modulation formats, even at OSNR values lower than the corresponding theoretical 20% forward error correction (FEC) limit. Meanwhile, the mean absolute error (MAE) of OSNR monitoring for QPSK, 16QAM, 32QAM, 64QAM, and 128QAM are 0.16 dB, 0.15 dB, 0.17 dB, 0.28 dB, and 0.33 dB, respectively. Furthermore, simulation results show that the proposed scheme is robust to residual chromatic dispersion (CD) and the nonlinear effects with strong generalization capability. These results suggest that the proposed scheme is promising for applications in next-generation EONs.

Precise and fast motion trajectory tracking response for rigid robot manipulator systems (RRMSs) pose a significant challenge due to the system uncertainties and unknown disturbances during operation. Despite extensive research, the varied and fluctuating factors in these harsh conditions consistently degrade the trajectory tracking performance of RRMSs. To address this issue, a fixed-time sliding mode control (FSMC) with an adaptive fixed-time disturbance observer (AFDO) offers an effective solution. Firstly, an improved FSMC method using a new sliding mode manifold is proposed, which can eliminate the dependence of the settling time on initial values of system and avoid singularity. Subsequently, a AFDO based on the equivalent input is presented to estimate the lump disturbances in real time, which introduce adaptive gain to further mitigate the effects of disturbances. Finally, the sufficient conditions for establishing the fixed-time stability of RRMSs are derived via Lyapunov theory. The results of numerical simulations and control experiments show that the proposed method can enhance the global fixed-time stability and reduce the high-frequency chattering. Compared with existing methods, it exhibits superior trajectory tracking control accuracy for RRMSs.

A novel polynomial guidance law is proposed for flight vehicle terminal guidance, subject to multiple constraints including launch angle, impact angle, impact time, and zero terminal acceleration. This approach reconstructs the flight path angle profile into two components. One component satisfies the constraints. The other ensures target interception. The constraint-oriented component is formulated as a polynomial function of the relative range-to-go. Based on this reconstruction framework, a new linearization approach is introduced to handle the nonlinear engagement kinematics. A closed-form guidance law is then derived to satisfy multiple constraints, and its convergence is analyzed theoretically. To optimize the control effort, a data-driven method is subsequently incorporated into the framework. Numerical simulation results show that the proposed guidance law achieves multiple constraints with high precision. Compared with existing methods, it also requires less control effort. Specifically, the impact angle error is within 0.02°, and the impact time error is within 0.05 s.

Aim. Verification of local similarity method for calculating the aerodynamics of aircraft at low supersonic speeds. Methodology. The primary criterion for developing this method is minimal computation time. The method is based on the hypothesis of locality, i. e. aerodynamic characteristics of each surface element are calculated independently. The proposed technique for aerodynamics calculation is a combination of well-known methods widely-used in supersonic flow around a thin plate and a flexible mechanism for their application taking into account the curvature of the aircraft surface. Results. The technique proposed has been verified on s cone, a slender body of revolution and a thin straight wing. The verification has been carried by comparing with numerical simulation results and existing techniques of aerodynamics calculation. Good agreement between the aerodynamic coefficient values and the numerical calculation results was demonstrated. Research implications. The technique considered is supposed to be used to make preliminary assessment of the aerodynamics of an aircraft at low supersonic flight speeds, followed by their refinement using more accurate methods.

Abstract The influence of vertical surface-open crack depth on the spectral characteristics of scattered Rayleigh waves are investigated theoretically and a quantitative method is proposed for determining crack depth based on characteristic frequency. A broadband Rayleigh wave is introduced, and in the frequency domain, the wave signal is convolved with transmission coefficients corresponding to cracks of varying depths, allowing the spectral characteristics of the transmitted Rayleigh waves to be obtained. The numerical simulation results show that distinct characteristic frequencies exist in the transmitted wave spectra, which are closely correlated with crack depth. The underlying mechanism responsible for the emergence of these characteristic frequencies is further explained by examining the crack depth-dependent transmission coefficient, enabling the establishment of a theoretical quantitative calibration curve that relates characteristic frequency to crack depth. Experiments are conducted on aluminum specimens containing artificial cracks of varying depths. The results demonstrate that crack depths can be accurately evaluated using the extracted characteristic frequencies in conjunction with the proposed theoretical curve, thereby validating the effectiveness of the method for assessing surface vertical cracks. Compared with existing frequency-spectrum-based techniques, the range of crack depths that can be quantitatively evaluated has been extended to the Rayleigh wavelength scale with the support of a rigorous theoretical analysis, providing a novel technical route and theoretical basis for high-precision characterization of surface-breaking cracks.

The article presents the results of numerical simulation of unsteady gas-dynamic and thermal processes occurring during combustion of a stoichiometric mixture of heptane vapors with air in a semi-closed cylindrical tube simulating the gas-generating cavity of a pulse-action fire extinguishing device. The relevance of the study is determined by the need to create a reliable physical and mathematical basis for describing the working process of gas generation, which is a prerequisite for designing fire extinguishing devices with enhanced characteristics. The simulation was performed in the ANSYS Fluent 2023 R1 software package using unsteady Navier-Stokes equations for a compressible reacting multicomponent gas, a k-ε realizable turbulence model and a Species Transport combustion model with oxidation kinetics according to the Arrhenius law.Based on the calculation results, the spatial and temporal distributions of temperature and pressure at five characteristic stages of the process are obtained. It is shown that the gas temperature in the reaction zone increases from 1 653 K at initiation to 4 884 K at the stage of advanced combustion at the closed end, and then stabilizes at the level of ~3 100K by the time the mixture is completely burned out.Gorenje. The maximum pressure at the closed end reaches 4,2 atm with an increase rate of ~5,1 atm/s. It is established that the acceleration of the flame front is realized by the Shelkin mechanism due to the interaction of expanding combustion products with an unburned mixture. The velocity of hot gases escaping from the open end in the initial phase of the ejection reaches sound values. The data obtained are verified based on analytical estimates of the adiabatic gorenje temperature and the normal velocity of the laminar front and form the basic boundary conditions for subsequent calculation stages.

The nonlinear problem of controlling the attitude of a suspended cargo during transportation and various flight phases of an aerial vehicle is considered. The control system requirement is to provide independent cargo attitude control relative to the aerial vehicle. The suspension is done by a cable and a pair of spherical joints on both sides, resulting in a system containing two oscillations of the cable and a two-dimensional rotation of cargo, simplified as a double spherical pendulum model. The technical solution is obtained by a reaction wheel system installed in the cargo and an Omni wrist at the pivot point. Different stages of flight, agile movement of the drone, and highly perturbed environments require a robust control capable of being adjusted rapidly to new operating conditions. Attitude control algorithms are synthesized based on the newly developed optimized integral sliding mode, and the sufficient conditions of reachability and convergence for the nonlinear case are derived. The efficiency of the algorithm is confirmed by the results of numerical simulation.

A new approach to optical single-channel encryption that utilizes biometric random phase mask fusion and modulation, as well as LU decomposition in gyrator transform domains, is proposed. In this method, the colour palmprint is decomposed into R, G and B channels. Each channel is encoded and modulated individually by a random phase mask to produce a biometric random phase mask (BRPM). An original colour image is split into R, G and B channels. R-channel BRPM, R, G and B channels of the original image are fused and then inverse discrete wavelet transformed to produce a single covered image, which is used as an input image. The covered image is modulated with G-channel BRPM, and then gyrator transformed. The gyrator spectrum is decomposed by LU decomposition. L and U are utilized as the preliminary encrypted image and the first decryption key, respectively. L is phase- and amplitude-truncated to produce the second encrypted image and the second decryption key. The encrypted image is modulated with B-channel BRPM, and then gyrator transformed. The gyrator spectrum is decomposed by LU decomposition. L and U are exploited as the third encrypted image and the third decryption key, respectively. L is phase- and amplitude-truncated to generate the final encrypted image and the fourth decryption key. For the first time to the author’s knowledge, a colour image is hidden in the R-channel BRPM. The proposed cryptosystem has three primary advantages. First, the R-channel BRPM with a unique palmprint image conceals the R, G and B channels of a colour image. Second, G-channel BRPM and B-channel BRPM are exploited as unique encryption keys. Finally, the four different decryption keys increase security layers against various types of attacks. A hybrid optoelectronic system can be utilized to implement the proposed method. Numerical simulation results show the feasibility, effectiveness and security of the proposed system.

Current sensors based on permanent magnet synchronous motor (PMSM) may face various unanticipated faults (UFs) that can degrade the operation performance and safety of the 14.5-meter telescope drive system, resulting in distorted current and highly fluctuating speed, etc. To enhance the reliability of the drive system, it is significant to develop an accurate and fast fault diagnosis and compensation (FDC) approach. The proposed technology incorporates several prominent aspects, such as fault diagnosis block, fault isolation algorithm and compensation unit. A signal processing-based diagnosis scheme is adopted in this research, using three cascade difference operator (TCDO) to detect abnormal changes in the current signals and generate high-amplitude pulses. This method demonstrates excellent robustness, even for minor faults. Fault isolation dictates whether to activate the isolation signals based on the comparison between high-amplitude pulses and the preset threshold. To accomplish satisfactory post-fault operation of the PMSM drive, a compensation unit based on coordinate rotation estimating phase currents is applied. Finally, the effectiveness of the proposed FDC method is demonstrated through numerical simulation results.

Abstract Stress-induced anisotropy is prevalent in the subsurface and has a significant impact on seismic wave propagation. Employing the framework of acoustoelastic theory, we establish velocity-stress formulations in the first-order form tailored for media exhibiting stress-induced anisotropy. A numerical implementation based on high-order staggered-grid finite-difference is proposed for wavefield simulation. The study demonstrates that isotropic media subjected to overburden stress exhibit an effective elastic stiffness tensor with VTI (Vertical Transverse Isotropy) symmetry, and the degree of anisotropy scales proportionally with the applied stress level. Numerical simulation results indicate that as the overburden stress increases, the wavefront morphology gradually transitions from circular (isotropic) to elliptical (anisotropic). This research provides a theoretical foundation for understanding seismic wave propagation in stressed media and for subsequent inversion of stress parameters.

Hydrodynamics-based analysis and physics-guided prediction of energy saving and emission reduction in longitudinal heterogeneous ship formations

Abstract To study the instability deformation law and acoustic emission response characteristics of rocks under loading, compression experiments were conducted on the rock specimens under single-axis loading. The mechanical parameters of rock failure and the characteristic parameters of AE (acoustic emission) response were recorded by a full-information acoustic emission instrument. The numerical simulation of this process was carried out with PFC. The research results show that the evolution traits of the number of acoustic emission location events can reflect the degree of rock damage and failure, and the spatio-temporal evolution characteristics can reflect the actual failure process of rocks. During the loading process, there is a good correspondence between the failure process of the rock specimen and the acoustic emission response characteristics. When the stress changes suddenly (suddenly increases or decreases), the accumulated number of AE ring count and the cumulative energy of acoustic emission both increase sharply. The cumulative ringing count and cumulative energy of acoustic emission increase sharply, but the stress does not necessarily change suddenly. The results of laboratory experiments and numerical simulations were compared and verified to explain in depth the failure and deformation laws of rocks and the acoustic emission response characteristics. According to the acoustic emission response characteristic parameters, a quantitative model of acoustic emission signals and damage was established, further revealing the failure behavior of rocks. The research results provide a new idea for the study of rock damage mechanisms and offer references and inspirations for other geotechnical engineering fields or similar problem areas.

This work aims to study the influencing factors and spatial distribution characteristics of wind parameters in typical steep escarpment terrain. The narrowband synthetic random flow generation (NSRFG) method is employed to set target turbulent wind parameters, and large eddy simulations (LES) are performed on terrain models of varying scales. The relationship among the fluctuating wind spectrum function, turbulent kinetic energy resolution ratio, and grid size is established. The combined correction method using power and linear functions can quickly achieve the target wind profile. To reduce the output time of numerical simulation results, a Python program is developed to extract and reconstruct transient data in a user-defined subdomain of the computational domain. The results indicate that the wind parameters of the steep escarpment exhibit significant spatial variations and are significantly influenced by the direction of incoming flow and local terrain. The terrain scale impacts the results of wind parameters in numerical simulations. However, the overall characteristics of the numerical simulation results for the central region of terrain models at different scales are consistent. Regardless of the incoming wind direction, the maximum wind speed is always observed at the mountaintop. The turbulence intensity and wind attack angle at the junction of the escarpment are greater than those in homogeneous areas. The fluid vortices are compressed on the windward side of high mountains and generate rotating vortices at steep escarpments on the leeward side.

This paper addresses the impact of turbulence models on the numerical performance of airflow around the NACA 0012 airfoil. For this purpose, a series of numerical results were conducted using three computational grids — one structural and two hybrid — for six turbulence models: Spalart-Allmaras, k-ε Standard, k-ε Realizable, k-ω Standard, k-ω SST and Transition SST. The simulations were performed using Ansys Fluent software and involved determining the aerodynamic coefficients of the NACA 0012 airfoil and comparing them with experimental data. The numerical simulations were performed at a Reynolds number of 2 000 000 and a Mach number of 0.09, which corresponded to the conditions performed in the experiment. The analyses made it possible to assess the impact of the selected turbulence model on the reliability of numerically obtained results and to identify the optimal model for future studies of similar aerodynamic cases.

Stability of the excavation face is paramount for the safe construction of subsea shield tunnels traversing upper-soft and lower-hard strata. Existing theoretical models are predominantly developed for homogeneous conditions, leaving a significant gap in addressing the coupled effects of stratum heterogeneity and high hydraulic pressure seepage. This study bridges this gap by integrating numerical simulation and theoretical analysis. First, finite difference numerical simulations are conducted using FLAC3D, aiming to investigate how permeability differences between soft and hard strata affect the hydraulic head distribution around the tunnel face. The simulations reveal that the permeability coefficient ratio is the dominant factor, leading to a modification of the existing hydraulic head calculation formula. Subsequently, a novel three-dimensional limit equilibrium model, characterized by a log-spiral slip surface in the soft soil layer and an inverted rounded-platform failure zone in the overburden, is proposed. This model facilitates the derivation of an analytical solution for the limit support pressure. The validity of the proposed model is demonstrated by favorable comparisons with numerical simulation results and existing theoretical models, showing consistent trends and providing conservative estimates for cases with a large proportion of soft soil. This research provides a practical theoretical framework for assessing face stability in subsea shield tunnels under similar complex geological and hydrological conditions.