Search Results (5,102)

This paper presents a robust and efficient mmWave radar-based human activity recognition (HAR) framework optimized for practical real-time indoor deployment. Addressing computational inefficiencies and limited recognition scopes in existing systems, the framework introduces two core contributions: Multi-class Spatio-Temporal Network (MuST-Net), a lightweight, multi-class network, and an online detection process for enhanced temporal stability. MuST-Net utilizes a hybrid 2D convolutional neural network and temporal convolutional network architecture to recognize seven distinct classes, significantly broadening the system’s recognition repertoire. The online detection process implements a novel sliding-window post-processing chain that employs an activity-buffering mechanism, which maintains temporal continuity and effectively suppresses spurious detections at activity boundaries. Experimental results demonstrate the superior performance of our unified framework, attaining over 98.6% accuracy for multi-class classification by MuST-Net and achieving at least 97% accuracy for activity detection and a crucial 100% recall for fall detection. Robustness is validated across three distinct indoor environments and nine subjects—with two of the three sites entirely unseen during training—confirming strong generalization under installation, environment, and subject variations. Full article

Aiming at the precise modeling demand of high-gain parabolic antennas for 6G and terahertz wireless communications, this study implements and systematically validates a high-precision, self-developed full-wave electromagnetic analysis framework based on the 3D vector finite element method (VFEM). The weak form of the vector Helmholtz equation is rigorously derived to ensure the discrete system is consistent with Maxwell’s equations physically. First-order tetrahedral edge elements are adopted to suppress spurious modes, and a computationally robust implementation of the Silver–Müller absorbing boundary condition (ABC) is carried out for accurate open-domain truncation. Four progressive test cases (parallel-plate waveguide, free-space dipole, finite planar reflector, and parabolic antenna) validate the algorithm’s performance: the relative error of the parabolic antenna’s gain is only 3.39%, with the L2-norm error well constrained in all cases. The self-developed VFEM achieves precision comparable to commercial software with a transparent underlying architecture. Future research will focus on high-order basis functions, AI-based intelligent ABCs, and the domain decomposition method (DDM) for billion-level-degree-of-freedom simulations. This work lays a solid algorithmic foundation for the forward design of high-throughput communication antennas. Full article

Aiming at the problems that existing detection methods struggle to accurately identify early insulation faults of induction motors, are susceptible to interference, and have poor installation adaptability, a non-intrusive detection method for early insulation faults of induction motors based on a microstrip antenna array is proposed. Relying on the low-loss electromagnetic wave transmission characteristic of the heat dissipation hole at the tail of the induction motor, a four-element microstrip antenna array with multiple narrow beams and dual detection frequencies is designed, with the detection frequencies accurately set at 1.14 GHz and 2.23 GHz, which effectively avoids the motor operation noise frequency band (≤300 MHz) and the strong interference frequency band of mobile base stations (900 MHz, 1.8 GHz, 2.4 GHz). Utilizing the high gain and strong directivity of the array antenna, the accurate extraction and amplification of weak electromagnetic wave signals from early insulation fault discharge penetrating through the heat dissipation hole are realized. The full-dimensional simulation design of the antenna array is completed by using HFSS electromagnetic simulation software, and an industrial-grade experimental platform is built to carry out multi-condition verification experiments. The results show that the proposed detection system can realize non-intrusive, non-stop, and non-disassembly identification of early insulation discharge faults in induction motors, with a fault recognition rate of 94% for single faults and 90% for composite faults, and the average signal-to-noise ratio reaches 31.6–35.2 dB. Even under strong industrial electromagnetic interference, the recognition rate remains above 85%. This method overcomes the problems of traditional methods such as severe noise interference, difficult installation, and inability to monitor online, providing a high-efficiency scheme for real-time insulation state monitoring of industrial induction motors with good engineering application value. Full article

Remote sensing (RS) imagery often suffers from non-uniform atmospheric scattering, resulting in severe contrast degradation, detail blurring, and spectral distortion. While recent advanced State Space Models (SSMs) offer efficient long-range modeling, they frequently struggle with spectral–spatial coupling interference and lack explicit physical constraints, leading to over-smoothed textures and color biases in high-reflectance regions. In this paper, we propose PhysWave-SSN, a Physics-Inspired Frequency-Decoupled Network specifically designed for high-fidelity RS image dehazing. The architecture employs a task-adaptive frequency-specific screening strategy to effectively isolate structural details from atmospheric interference. Specifically, we first introduce a Frequency-Aware Selection Gate (FASG) that unifies adaptive channel screening with physical transmission estimation, enabling precise recalibration of frequency components. To bridge the gap between physical scattering principles and state space representation learning, we develop a Physics-Informed SSM (PI-SSM), where the discretization step size of Mamba is dynamically modulated by the estimated haze density. This mechanism allows the model to adaptively adjust its spatial receptive field according to local degradation levels, enhancing physical interpretability. Furthermore, a Luminance-Adaptive Fusion Module (LAFM) is presented to protect high-reflectance land covers and maintain spectral consistency. Extensive experiments on multiple RS datasets demonstrate that PhysWave-SSN achieves superior performance, notably attaining a maximum PSNR gain of 2.49 dB while ensuring high structural and spectral fidelity. Full article

Understanding the anisotropy in the physical and mechanical properties of layered rocks is essential for predicting and preventing instability in layered rock masses. However, in-situ sampling is often hindered by the difficulty of obtaining specimens with controlled bedding orientations. Cement-based 3D printing (3DP) offers an efficient approach for fabricating rock analogues, yet the inherent anisotropy induced by the layer-by-layer deposition process has not been well characterized, hindering its broader application. The objectives of this study are (i) to systematically evaluate the intrinsic anisotropy of cement-based 3DP rocks and (ii) to compare the mechanical anisotropy and failure modes of 3DP layered rocks with those of natural layered sandstone. The key findings are as follows: (1) The uniaxial compressive strength (UCS), P-wave velocity, and computed tomography (CT) number of the 3DP rock vary by less than 6% among the X-, Y-, and Z-directions, indicating lower intrinsic anisotropy compared to typical sandstones and several other natural rocks. (2) The UCS, elastic modulus, and secant modulus of the 3DP layered rocks all decrease initially and then increase with bedding dip angle, reaching a minimum at 60°. (3) The main fracture characteristics of the 3DP layered rocks are similar to those of layered sandstone; notably, the 3DP layered soft rock exhibits the most pronounced shear failure features. This study quantifies the low intrinsic anisotropy of cement-based 3DP rocks and validates their similarity to natural layered sandstone in both mechanical anisotropy and failure modes. It thereby provides a reliable, reproducible basis for physical modeling of layered rock masses using 3DP, offering a new approach for laboratory-scale investigations of layered rocks. Full article

To optimize the electromagnetic and mechanical properties, a resin-based coating with a bionic helical structure made by carbonyl iron fibers (CIF) was prepared by alternating spray and brushing with 0°/45°/90°. The morphologies of CIP and CIF were characterized by a scanning electron microscope (SEM). The electromagnetic parameters of CIP were measured in the frequency range of 2–18 GHz by the coaxial ring method, and microwave absorption properties of the coating were evaluated by reflection loss (RL). The mechanical properties of the coating with the bionic helical structure were investigated by the pull-off method. The effects of the CIP ratio, CIF content, and thickness on the microwave absorption were discussed, respectively. The results show that 6.5:3.5 is the optimal CIP-to-paraffin ratio with superior electromagnetic performance and RL. The coating with the triple helical structure, fiber content of 3 wt% and free of CIP (C4) exhibits optimal electromagnetic wave absorption performance with a minimum RL value of −10.66 dB and wide effective absorbing bandwidth (EAB) of 10.58 GHz at a thickness of 0.6 mm. Moreover, the adhesion strength of C4 reaches 13.52 MPa. The excellent absorption performance and mechanical properties of the resin-based coating with the bionic helical structure indicate that it has potential application value in the field of stealth materials. Full article

Fine-scale urban underground exploration is vital for geological safety and hydrogeological protection. In spring-rich cities like Jinan, shallow structures—such as sedimentary layers and fault systems—act as critical regulators of groundwater migration and spring formation. Yet, traditional seismic methods are often hindered by high costs and complexity. While Distributed Acoustic Sensing (DAS) offers a solution, its effectiveness is frequently limited by the poor coupling and coherent signal loss of existing cables in pipes. This study proposes an efficient alternative using mobile, unburied surface fiber-optic cables. Ten temporary DAS experiments were conducted along a 23 km line in Jinan, accompanied by nodal seismometers. Stable dispersion curves along the line can be extracted by subarray ambient noise interferometry with short-duration urban traffic noise DAS recording, and finally a high-resolution 2D S-wave velocity profile was mapped. The result shows that the profile has pronounced subsurface lateral heterogeneity, characterized by the alternation between two uplift zones and two grabens, which is highly consistent with H/V results from nodal seismometers. This confirms that mobile surface-cable DAS provides a rapid, reliable, and cost-effective imaging solution for characterizing complex urban subsurface structures, providing essential data for both geohazard assessment and the protection of groundwater transport pathways. Full article

A wideband linearly polarized over-2-bit transmitarray antenna (TA) using the receiving-transmitting (R-T) scheme in the millimeter-wave band is presented in this work. The TA unit consists of two rectangular patches with a pair of bent branches, and the patches are connected by a metalized via. Two methods are used in this TA to obtain an over-2-bit phase shift of 0–${90}^{\circ }$ and 180–${270}^{\circ }$ from 18 GHz to 30 GHz. Firstly, ${180}^{\circ }$ phase resolution is obtained by rotating the receiving patch around via by ${180}^{\circ }$. Secondly, by tuning the connection position between the branches and rectangular patch of the TA unit cell, a continuous ${90}^{\circ }$ phase shift is further achieved. A TA prototype with $20\times 20$ units is designed, fabricated, and measured. The measured 1 dB and 3 dB gain bandwidth is 24.9% (24.47–31.43 GHz) and 46.96% (20.45–33 GHz) respectively, with a peak gain of 25.17 dBi and a peak aperture efficiency of 55.2%. The measured results agree well with the simulated ones. Full article

In this work, we examine viable models of $f(Q,T)$ gravity theories against observational data with the aim to constrain the parameter space of these models. We have analyzed four different models of $f(Q,T)$ gravity and tested them against against late-time background probes: Cosmic Chronometer (CC), Baryon Acoustic Oscillations (DESI BAO), $Pantheo{n}^{+}$ and Gravitational wave(GWTC-3) data. We put stringent constraints on the $f(Q,T)$ gravity models, $f(Q,T)=\alpha Q+\beta T$, $f(Q,T)=\alpha Q^n+\beta T$, $f(Q,T)=-\alpha Q-\beta T^2$ and $f(Q,T)=\alpha Q^{-2}{T}^2$ along with other late-time cosmological parameters such as deceleration parameter ($q_0$), equation of state parameter ($w_0$), sound horizon distance ($r_d$) and demonstrate their alignment with the $\mathrm{\Lambda }CDM$ model and the observational data. We show that these models have the capability to alleviate the Hubble tension in late time universe, by predicting the present value of the Hubble parameter close to 74 km/s/Mpc. $f(Q,T)$ gravity theory introduces alterations in the background evolution and imposes a friction term in the propagation of gravitational waves, this phenomenon has also been examined. We have shown their agreement with the Gravitational Wave (GW) luminosity distance with the Electromagnetic (EM) counter part GWTC-3 data from Advanced LIGO and Advanced VIRGO across different observing runs capturing coalescence of Binary Neutron Stars (BNS), mergers of Binary Black Holes (BBHs), and Neutron Star-Black Hole (NSBH) binaries with EM counterparts. Full article

Tam Quan Inlet, a monsoon-driven asymmetric entrance on the south-central coast of Vietnam, has experienced persistent shoaling and severe downdrift erosion despite jetty construction and repeated maintenance dredging. This study investigates the unresolved linkage between seasonal circulation reorganization, inlet-directed sediment convergence, channel infilling, and southern-beach erosion. A coupled Delft3D-FLOW/WAVE model, constrained by field observations from May 2022 and November–December 2022, was used to diagnose hydrodynamic controls and compare alternative management layouts. The model satisfactorily reproduced the dominant variability of water level, wave conditions, and depth-averaged currents during calibration and independent validation, providing a suitable basis for process diagnosis and comparative layout assessment. The simulations identify four recurrent circulation modes: a cape-crossing north-to-south longshore jet, flow acceleration and deflection near the southern jetty, a northeast-monsoon recirculation cell that promotes inlet-directed convergence from the southern beach, and a partial summer reversal under SE-sector waves. These modes explain why shoaling persists after one-sided intervention and why the southern shoreline functions simultaneously as an eroding downdrift beach and a seasonal sediment source to the inlet. Among the tested layouts, PA2 most effectively concentrates flow through the inner throat while relocating sediment retention to an external storage basin, supporting controlled trapping and periodic bypassing. The results support a sediment-balanced management strategy that integrates controlled trapping, maintenance dredging, and sediment bypassing to improve navigation reliability and reduce the sediment deficit along the downdrift shoreline. Full article

Shallow shear-wave velocity structures provide useful constraints on sedimentary architecture in coastal abandoned-estuary settings, yet laterally continuous velocity information remains limited in the Paleo-Yellow River Estuary, Yancheng, Eastern China. In this study, vertical-component ambient noise recorded by a dense linear array of 102 short-period stations over 27 days was used to derive Rayleigh-wave phase-velocity dispersion curves by the modified frequency-Bessel (MFJ) method. Sequential 1D S-wave velocity models were inverted beneath moving subarrays and interpolated to construct a pseudo-2D velocity profile along the survey line. For comparison, the conventional spatial autocorrelation (SPAC) method was applied to the same dataset using the same subarray length, usable frequency band, and inversion-layer parameterization. The MFJ method produces clearer and more concentrated fundamental-mode dispersion energy and suppresses high-frequency crossed artefacts more effectively than SPAC, which improves the stability of dispersion picking. The resulting velocity model reveals a laterally heterogeneous shallow sedimentary system and outlines a U-shaped low-velocity zone that is spatially consistent with the mapped paleochannel boundary. These results indicate that MFJ-based ambient-noise imaging can provide useful complementary geophysical constraints for paleochannel mapping and shallow sedimentary characterization in coastal abandoned-estuary settings. Full article

The rapid advancement of high-performance computing has spurred growing demand for miniaturized, high-density, high-power, and highly reliable electronic packaging. Through-silicon via (TSV), as a pivotal technology enabling high-density integrated packaging, achieves vertical interconnection that reduces signal latency and power consumption while substantially improving system integration. However, inherent challenges persist due to coefficient of thermal expansion mismatches among heterogeneous materials in TSV and parasitic effects introduced by high-density TSV arrays, leading to critical concerns regarding thermomechanical reliability and signal integrity. This study focuses on TSV structures, investigating their thermomechanical reliability and electrical performance. First, the macro–micro model of 2.5D package structure was established to address cross-scale challenges based on Representative Volume Element (RVE) homogenization and sub-model technique. Then, an equivalent circuit model integrating transmission line network theory was developed and validated through full-wave electromagnetic simulations using S-parameter analysis to analyze signal transmission characteristics. Finally, by introducing an improved multi-objective grasshopper algorithm, the structural parameters of TSV are co-optimized using a genetic algorithm back propagation network (GA-BP) and an improved multi-objective grasshopper algorithm (IMOGOA) to enhance both thermomechanical reliability and electrical characteristics simultaneously. The proposed approach offers a practical and effective solution for improving the reliability and performance of high-density integrated packaging, providing valuable insights for future packaging design and optimization. Full article

To investigate the impact of continuous leading-edge curvature on the aerodynamic performance of transonic compressor blade profiles, schlieren observations and surface pulsating pressure measurements were conducted on the baseline profile CM1.2 and its optimized variant CM1.2-Y. The results indicate that the optimized profile can effectively reduce unsteady pressure pulsations at Mach numbers of 0.8 and 1.05, with a maximum reduction of 14.6 dB. At Mach number 0.95, the optimized design eliminates high-pressure pulsation regions on the pressure surface but intensifies local loading on the suction surface. The optimization of leading-edge curvature effectively reduces the extreme pulsations on the suction surface caused by shock wave interference under most operating conditions, and significantly improves the wave structure on the pressure surface, thereby comprehensively reducing the pressure pulsation level of the blade profile. Full article

Developing lightweight materials that simultaneously achieve efficient electromagnetic wave absorption and robust corrosion resistance remains a significant challenge for marine stealth and electromagnetic protection applications. The main obstacle lies in the rational integration of electromagnetic attenuation capability, impedance matching, and corrosion protection. In this work, a multilayer carbon-structured BaTiO₃@C nanocomposite (CSTB-x) was successfully fabricated via freeze-drying combined with in situ pyrolysis. During the carbonization process, chitosan (CS) was transformed into a nitrogen-doped multilayer porous carbon framework, while BaTiO₃ particles were embedded into the carbon matrix to construct a BaTiO₃@C heterostructure. Benefiting from optimized impedance matching and the synergistic contributions of conduction loss, dipolar polarization, and interfacial polarization, CSTB-1.0 delivered a minimum reflection loss (RL_min) of −48.07 dB at 6.16 GHz with a thickness of 3.32 mm, and achieved a maximum effective absorption bandwidth (EAB) of 7.04 GHz at a thickness of 1.88 mm. In addition, CSTB-1.0 exhibited a low corrosion current density (8.93 × 10⁻⁶ A/cm²) and a high polarization resistance (7.87 × 10³ Ω∙cm²), indicating excellent corrosion protection performance. The enhanced corrosion resistance is mainly attributed to the barrier effect of the multilayer carbon framework and the tortuous diffusion pathways generated by the porous and core–shell structures. Moreover, the material showed a minimum radar cross-section (RCS) value of −41.25 dBsm, demonstrating remarkable electromagnetic scattering suppression capability. These results provide a feasible strategy for the design and fabrication of marine stealth materials with integrated microwave absorption and corrosion resistance. Full article

To address the challenge of balancing high density with low elastic modulus in physical model tests of liquefiable foundations, this study proposes a novel concrete similitude material and numerically investigates the dynamic response of saturated silt-pile systems. Based on Buckingham π theorem, the mixture of barium sulfate and blast furnace slag was optimized by changing the ratio of sand to stone powder under the condition of 1 g, with Portland cement, natural sand, barium sulfate powder and blast furnace slag powder as raw materials. Subsequently, 3D numerical simulations using MIDAS GTS NX 2023 v1.1 evaluated pile-soil interactions under varying seismic intensities. The results show that the optimal mixture achieves a density of 2.083 g/cm³ and an elastic modulus of 0.65 GPa, accurately simulating C30 concrete at a 1:30 scale. Simulations indicate that shallow soils liquefy first under 0.2 g seismic loading. Pile groups significantly delay liquefaction and reduce excess pore water pressure by 15–20% compared to free-field conditions. Furthermore, they regulate acceleration bilaterally: before liquefaction, piles restrict soil shear deformation, reducing surface acceleration amplification from 6.0 to 3.2; after liquefaction, their rigidity alters wave propagation, diminishing the soil’s vibration isolation effect. These material innovations and elucidated anti-liquefaction mechanisms provide a robust scientific foundation for large-scale shaking table tests and the seismic resilience evaluation of pile-supported structures. Full article