Search Results (1,347)

Accurate localization and mapping are essential for autonomous mobile robots operating in unknown environments. This study investigates the impact of Extended Kalman Filter (EKF)-based sensor fusion on the performance of three widely used two-dimensional (2D) LiDAR Simultaneous Localization and Mapping (SLAM) algorithms: GMapping, Karto SLAM, and SLAM Toolbox. Wheel encoder longitudinal velocity and inertial measurement unit (IMU) yaw angular velocity were fused using an EKF and compared with raw wheel odometry using the MIT Stata Center dataset. Localization performance was evaluated both before and after SLAM using translational and rotational Absolute Pose Error (APE) across multiple trajectory segments. Five repeated executions were performed for each SLAM configuration to characterize run-to-run variability. Prior to SLAM, EKF-filtered odometry reduced translational APE root mean square error (RMSE) by approximately 61–75% and rotational APE RMSE by approximately 65–77% relative to raw odometry. After SLAM, translational differences between the two odometry sources were substantially smaller and varied according to the evaluated algorithm and trajectory, while rotational performance exhibited larger and less consistent changes. These results demonstrate that substantial improvements in upstream odometry accuracy do not necessarily produce proportional improvements in final SLAM localization and that the influence of sensor fusion varied across the evaluated SLAM algorithm and trajectory segments, providing practical guidance for selecting localization strategies in autonomous mobile robots. Full article

Industrial IoT sensor nodes face a triple burden—sampling, compression, and security—under severe resource constraints; yet, the question of which signals can actually benefit from compressed sensing (CS) remains largely implicit in the literature. SCCS answers this question by unifying compression, chaotic obfuscation, and authentication within a single CS measurement and deriving an empirical deployability rule consisting of the PCA energy concentration ratio $\rho$. When $\rho$ exceeds 80%, signals reconstruct at high fidelity; when $\rho$ falls below 50%, they are intrinsically incompressible; and in the intermediate 50–80% band, reconstruction is uncertain and may fail outright rather than degrading gracefully (as shown on CWRU). This empirical deployability rule is supported by evaluation on three real datasets: high-fidelity reconstruction is confirmed on CBM ($\rho =99.9\%$), while CWRU ($\rho =65.9\%$) and CCPP ($\rho =15.4\%$) establish the applicability boundaries and validate the $\rho$-based screening criterion. The enabling system integrates a block-circulant chaotic measurement matrix (BCCM, from a two-dimensional sine-logistic iteration mapping (2D-SLIM) map) that compresses and obfuscates in one operation (online measurement seed 0.84 KB, down from a 512 KB dense matrix; the full reference implementation requires 185 KB Flash, including a 160 KB decoder dictionary); an offline principal component analysis (PCA) dictionary that lifts reconstruction signal-to-noise ratio (SNR) from 5.36 to 33.52 dB at CR = 4 (+28.16 dB over the fixed-basis configuration; Wilcoxon $p<0.001$, 30 independent trials); and a dual-layer authentication scheme combining always-on hash-based message authentication code (HMAC) with adaptive reconstruction-based implicit authentication (RBIA), the latter providing zero-overhead tamper pre-screening that reuses the decoder’s reconstruction residual and automatically falls back to HMAC-only under channel noise. Security boundaries are explicitly disclosed: the chaotic measurement resists known-plaintext attacks but is vulnerable to chosen-plaintext recovery (N plaintexts recover the linear matrix), and 1.13 bits of amplitude side-channel leakage exist. The SCCS framework demonstrates that the three functions need not be separate serial stages, provided the target signals satisfy the $\rho$ screening rule. Full article

Automated wildlife monitoring systems are essential for studying bat populations in natural environments, where nocturnal behavior, high flight speeds, and limited illumination make conventional observation difficult. This paper presents a modular multi-sensor vision system that integrates RGB, near-infrared (NIR), and depth cameras for automated bat monitoring. The proposed architecture consists of one main module and two secondary modules that can be configured into multiple operating modes according to monitoring requirements. The main module operates independently to perform real-time habitat reconstruction using an integrated depth camera or bat detection using a YOLO-based model. When combined with one secondary module, it forms a stereo vision system for three-dimensional localization; when combined with both secondary modules, it generates panoramic images that substantially expand the field of view for monitoring large cave entrances and other complex environments. The proposed modular architecture enables flexible deployment while supporting multiple sensing configurations within a single platform. The modular design provides scalability, geometric consistency through multi-sensor calibration, and flexible deployment, enabling accurate bat detection, habitat reconstruction, and wide-area monitoring within a unified sensing framework. The proposed system provides a versatile and scalable solution for adapting wildlife monitoring to different environmental conditions and observation scenarios. Experimental results demonstrate a detection precision of 0.893, a panoramic field of view of 119°, and real-time processing at 60 fps, validating the effectiveness of the proposed modular architecture. Full article

High-precision two-dimensional intermolecular potential energy surfaces (PESs) for Rg–CuF (Rg = Ar, Kr, Xe) were constructed at the coupled-cluster singles and doubles with non-iterative triples [CCSD(T)] level by employing aug-cc-pVXZ (X = D, T, Q) basis sets, and the energies were extrapolated to the complete basis set (CBS) limit. All three complexes exhibit a consistent topological pattern: the global minimum corresponds to a collinear Rg–Cu–F configuration, and the local minimum corresponds to an anti-linear Rg–F–Cu configuration. As the atomic number of noble gas increases, the Rg–Cu equilibrium distance lengthens while the binding strength remarkably enhances. Bound state calculations were performed based on these PESs to yield rotational levels, which can be used to derive the intermolecular vibrational frequencies, molecular structures and spectroscopic parameters for all primary isotopologues. The predicted rotational constants B are in excellent agreement with the experimental observations, attaining a sub-MHz accuracy at the AVTZ level for Kr–CuF and at the CBS limit for Ar–CuF and Xe–CuF. Vibrational wavefunction analysis reveals that the intermolecular vibrational modes of Kr–CuF and Xe–CuF are highly localized, consistent with the pronounced molecular rigidity observed experimentally. Isotopic effect analysis reveals a well-defined linear relationship between the changes in the rotational constant B and the intermolecular vibrational frequency in relation to the reduced mass of the complex, which provides a reliable basis for predicting spectroscopic parameters of unobserved isotopologues. Symmetry-adapted perturbation theory (SAPT) energy decomposition further demonstrates that the Rg–Cu interaction is dominated by induction forces, with significant contributions from dispersion and electrostatics, and exhibits notable charge transfer character. This polarization and orbital overlap transcend the conventional van der Waals picture and reveal a partially covalent nature in noble gas transition metal interactions. Full article

In this work, a novel all-optical 4-to-2 encoder employing nonlinear resonant cavities in a two-dimensional photonic crystal is proposed and numerically investigated. The encoder consists of a lattice of chalcogenide rods incorporating nonlinear Kerr-effect cavities, enabling selective wavelength coupling through intensity-controlled resonance. By assigning three distinct optical input power levels, the proposed architecture successfully realizes all encoding states without requiring additional control signals or complex resonator configurations. Numerical results demonstrate correct encoding functionality with normalized logic-1 output powers ranging from 0.89 to 1.71 and logic-0 levels below 0.013, yielding a high contrast ratio of 18.35 dB. The encoder exhibits ultrafast temporal performance with a maximum rise time of only 108 fs, corresponding to a data transmission capability of 4.63 Tbit/s, while maintaining a low insertion loss of 3.73 dB. Furthermore, the proposed structure occupies an ultra-compact footprint of only 95 μm², outperforming previously reported photonic crystal encoders in terms of integration density and speed. With regard to its compactness, high switching speed, excellent signal discrimination, and compatibility with current nanofabrication technologies, the proposed encoder represents a promising building block for future photonic integrated circuits, optical computing systems, and high-capacity optical communication networks. Full article

Amplitude-modulation magnetic particle imaging (AM-MPI) has strong potential for real-time navigation of magnetic nanoparticles because it provides tracer-specific spatial feedback using a narrowband acquisition scheme with relatively low excitation power and simplified signal detection. However, improving spatial resolution by increasing the selection-field gradient becomes increasingly difficult as scanner dimensions increase. This study investigates whether field orientation can be used to improve and control the spatial resolution of three-dimensional AM-MPI with field-free-point (FFP) and field-free-line (FFL) encoding. Four scan-receive configurations were analyzed using a matrix point-spread-function (PSF) model, followed by two-point phantom simulations at equal physical and FWHM-normalized source separations. With a common y-directed scan, FFP-y produced a single-peaked collinear h_yy response with FWHM values of 1.29 mm along y and 5.89 mm along x and z. FFL-y retained the same y-direction FWHM while reducing the z-direction FWHM to 2.94 mm. FFP-x selected the transverse h_xy component, producing a central null and a multi-lobe response, whereas FFL-x was a null channel for the adopted field geometry. At equal physical spacing, the first tested separation satisfying the adopted Rayleigh-type criterion (M ≥ 0.26) was 3 mm along y for both FFP-y and FFL-y, 5 mm along z for FFL-y, and 7 mm along x and z for FFP-y. FFL-y also provided better z-direction separability than FFP-y. After normalization by the corresponding directional FWHM, the single-peaked responses showed similar two-point separability, indicating that the differences observed at equal physical spacing were mainly associated with directional PSF width. These results show that field orientation affects both the topology and directional resolution of the AM-MPI response and can be considered together with selection-field design when optimizing AM-MPI systems for nanoparticle navigation. Full article

Polarity reversal changes not only the instantaneous electric field in a needle–plane air gap but also the subsequent field–particle coupling through the charged-particle distribution established before reversal. For a configuration in which the grounded needle and grounded lower plate share the same return path, it remains unclear to what extent this local history-dependent state is transferred to the complete grounded conductor and its externally measurable current. Here, a two-dimensional axisymmetric electrostatic model (ES) and a drift–diffusion–reaction–Poisson–discharge-fluid model (EDIS) were established for a 50 mm needle–plane air gap. Positive-to-negative (P2N)/negative-to-positive (N2P) reversals and history-retained/history-reset (H/R) controls were used to separate the effects of reversal path and pre-existing charged-particle state. Over the tested 0–2τ reset-hold range, the representative near-tip electron density in H remained approximately 15–16% higher than that in the corresponding R case, whereas the H/R conductor-integrated response of the complete common-ground assembly was indistinguishable at the present numerical resolution. Outer-domain analysis further showed that for the representative 15 kV case in the 300 mm reference domain, the EDIS and ES common-ground integrated responses differed by approximately 3.3%. Experimentally, P2N and N2P reversals were repeated at 5, 10, and 15 kV, yielding 120 events. The main common-ground current pulse increased with voltage magnitude and maximum voltage slew rate, and the median event-level Pearson correlation with signed dV/dt was approximately 0.989. Different capacitance-baseline constructions yielded central residual-integral levels of approximately 18–19%; after multiplicity correction, the 15 kV fixed-window absolute integral was the direction-sensitive terminal metric with the strongest statistical support. Under the investigated conditions—a nominal 0.5 mm tip radius, 50 mm gap, approximately 3 ms reversal time, and weak-discharge regime—the reversal path and particle history primarily reorganize the near-tip charged-particle state, whereas the dominant scale of the common-ground transient remains closely associated with the applied-voltage variation and the capacitive response of the system. Full article

This study presents a comprehensive experimental and theoretical investigation into dual-gate field-emission devices fabricated using a standard 0.35 µm CMOS-MEMS process. Two emitter configurations, the concave-tip and triangular-tip, are characterized, and their performance is rigorously analyzed using three-dimensional simulations based on Fowler–Nordheim emission theory. To account for discrepancies between initial designs and fabricated devices, the influence of critical geometric parameters, including tip apex radius, cathode-anode spacing, and tip sharpness, is systematically evaluated regarding emission current and threshold voltage. Compared to the floating-gate baseline (~38 V), dual-gate (DG) operation lowers the threshold voltage by ~70% (~10 V), enhances low-voltage emission over tenfold, and provides a 3.4-fold boost in differential output conductance. Simulation analysis indicates this improvement stems from enhanced electrostatic field distribution governed by the gates. Furthermore, the top gate, due to its proximity to the emitter tip relative to the bottom gate, provides superior control over emission current at lower operating voltages. Three-dimensional simulations corroborate these findings, revealing that minimizing both the tip radius and cathode-anode spacing substantially enhances tunneling electron flow. Additionally, gate voltage sweeps confirm that electron trajectories are effectively directed by electrostatic steering. These findings establish critical design guidelines for integrating field-emission devices into standard CMOS platforms, facilitating the development of on-chip electrostatically controlled electron sources for integrated vacuum microelectronics. Full article

Improving the conversion of incident wave energy into useful pneumatic power requires a clear understanding of the coupling among floating body motions, internal water column oscillation, air compression, and pneumatic damping in oscillating water column (OWC) systems. In this study, a coupled multi degree of freedom (MDOF) analytical framework is developed by incorporating the surge, heave, and pitch motions of the floating body together with internal water column oscillation and compressible chamber air dynamics. A distinctive feature of the framework is the direct comparison between a simplified single degree of freedom (SDOF) configuration and the coupled MDOF configuration, which enables the contribution of body motion coupling to pneumatic energy conversion to be explicitly identified. Based on potential flow theory, frequency-domain hydrodynamic characteristics are coupled with the pneumatic response to evaluate added mass, radiation damping, hydrodynamic impedance, chamber pressure, pneumatic power, and capture width ratio (CWR). The MDOF results exhibit two distinct pneumatic power peaks. The dominant peak reaches a non-dimensional pneumatic power coefficient P* of approximately 0.88 at ω ≈ 0.4 (kh ≈ 0.13), whereas a secondary peak of approximately 0.06 appears in the higher frequency regime (kh ≈ 2.2), reflecting the primary water column resonance and the contribution of coupled structural responses, respectively. Comparison with wave-basin measurements reproduces the principal CWR trend and resonance peak location, although the peak magnitude is overpredicted near resonance. The results clarify how body motion coupling and pneumatic damping jointly govern the transfer of incident wave energy into pneumatic power and provide a practical framework for resonance tuning and preliminary performance optimization of OWC systems. Full article

Beaver dams can substantially modify flow conditions and increase local water retention, particularly in small urban and peri-urban streams exposed to hydrological alterations and increasing water deficits. This study evaluates the influence of beaver dams on hydraulic conditions, retention capacity, and water resources in the Junikowski Stream in Poznań, Poland. Field surveys, geodetic measurements, and spatial data were used to develop a one-dimensional hydraulic model in HEC-RAS. Three management scenarios were analysed: a channel without impoundment structures, the 2022 configuration including beaver dams and two artificial weirs, and the 2025 configuration representing a more developed beaver-dam cascade together with the functioning weirs. Simulations were conducted for a range of characteristic and probability flows to assess changes in water levels, inundation extent, and retained water volume. The results show that beaver dams exert the strongest effect under low-flow conditions, when they significantly increase water levels and improve local retention. Their hydraulic influence decreases with increasing discharge, although they continue to affect the spatial distribution of water in the valley. The proposed artificial structure may partly maintain retention benefits in the event of beaver dam degradation or removal. The findings demonstrate that beaver dams may function as effective nature-based solutions supporting water retention and potentially contributing to drought resilience and sustainable management of urban stream valleys. Full article

Learning environments are typically designed according to nominal seating capacity, yet their actual visual performance often falls well below this figure—a discrepancy defined here as an illusion of capacity. Conventional two-dimensional sightline analysis, the standard method for assessing visibility, cannot fully capture the three-dimensional effects of human occlusion or the influence of room scale on visual performance. To address this gap, the study evaluates three higher-education classroom typologies—a flat-floor classroom, a terraced classroom, and a constant-slope auditorium—using a Python-based three-dimensional ray-casting framework. Each seating position is assessed against four criteria: horizontal legibility, vertical strain, two-dimensional sectional clearance, and three-dimensional functional visibility. The results reveal marked differences between the two analytical approaches. In the smaller configuration, the three-dimensional analysis uncovered visible areas overlooked by sectional analysis: effective capacity in the flat-floor classroom increased from 12.50% to 29.16%, and total obstruction in the terraced classroom fell from 45.45% to 36.36%. The large auditorium showed the opposite trend—owing to cumulative shoulder overlap and a phenomenon termed perspective closure, its effective capacity dropped to 6.42% (versus 9.28% by sectional analysis), with 73.57% of seats fully obstructed. Full article

Three-dimensional Dirac semimetal (3D DSM), characterized by linear band dispersion and strong terahertz nonlinear optical responses, has attracted increasing interest as promising materials for compact nonlinear photonic devices. Optical bistability (OB), which enables two stable output states under the same input condition, is of particular importance to all-optical switching, optical logic gates, and optical memory. However, achieving OB with a sufficiently low switching threshold remains a key challenge. Here, we propose a prism-coupled multilayer structure incorporating 3D DSMs to realize low-threshold, tunable OB by exciting the surface plasmon polaritons (SPPs). The prism-coupling configuration enables efficient excitation of SPPs, producing strong local-field enhancement around the nonlinear 3D DSM layer. This enhanced light–matter interaction, together with the large nonlinear refractive index of the 3D DSM, substantially reduces the electric-field threshold required for bistable switching. Numerical results show that OB can be achieved with an incident electric-field threshold on the order of 10⁵ V/m through optimizing the material and structural parameters. Moreover, the switching threshold and hysteresis loop width can be flexibly controlled by varying the Fermi energy, relaxation time, and geometric parameters of the 3D DSM multilayer structure. These results suggest that SPP-assisted 3D DSM structures provide an effective platform for low-threshold, actively tunable optical bistable devices in integrated terahertz photonic systems. Full article

Cross-view geo-localization (CVGL) between unmanned aerial vehicle (UAV) imagery and satellite imagery is a key technique for autonomous UAV navigation in Global Navigation Satellite System (GNSS)-denied environments. However, most existing methods rely on energy-intensive Artificial Neural Networks (ANNs), making them difficult to deploy on resource-constrained edge computing platforms. Spiking Neural Networks (SNNs) provide a promising alternative for energy-efficient inference, but their application to CVGL still faces two challenges that remain insufficiently addressed. First, the isotropic computation used by existing SNN backbones is mismatched with the directional characteristics of spike activations. Spike activations tend to form oriented aggregation patterns along elongated geographic structures, and isotropic computation can therefore dilute directional signals. Second, the limited representational capacity of SNNs further increases the sensitivity during training optimization. However, the standard triplet loss adopts a static weighting strategy and assigns the same weight to all triplets that violate the margin constraint, which is unfavorable for learning from hard negatives. To address these challenges, we propose a framework with two core contributions. At the feature extraction level, the Directional Adaptive Convolution Module (DACM) processes spike feature maps by sequentially performing horizontal strip convolution and vertical strip convolution, thereby capturing a more complete geometric structure of directional spike clusters. At the training supervision level, we propose a Dual-dimensional Progressive Reweighting (DPR) loss, which jointly characterizes sample difficulty from pairwise difficulty and positive-pair quality difficulty. A learnable fusion parameter is used to adaptively balance these two types of difficulty information. Experimental results on the University-1652 and SUES-200 benchmarks show that the proposed framework, when equipped with the same representation learning head as its ANN counterparts, achieves competitive and, in many settings, superior performance. In terms of energy efficiency, its estimated theoretical energy consumption is over $8.8\times$ lower than that of published ANN methods under their original configurations. Under a more rigorous matched ANN control that shares the identical architecture, the estimated energy is reduced from 29.84 mJ to 6.36 mJ, an approximately $4.7\times$ reduction obtained at a cost of only 2.29 percentage points in R@1. Full article

Overhead-line sensor platforms must satisfy electrical and mechanical installation constraints that vary with the operating scenario. This study evaluates separate phase-conductor electrostatic and 9 mm optical ground wire (OPGW) vibration-test scenarios for the same platform. A full Maxwell potential-coefficient matrix provides an analytical reference for a 500 kV line-to-line RMS four-bundle conductor. A three-dimensional COMSOL Multiphysics 6.3 model compares the prototype enclosure scale and fastening-hole configurations. The matrix gives a maximum bare-conductor surface field of 14.33 kV/cm RMS. The phase-RMS values for the hole-free, single-hole, and double-hole cases are 8.05, 12.27, and 12.91 kV/cm RMS, respectively. These values quantify local field enhancement at the hole edge and support geometry comparison. Under a 16.5 kN tensile load, 47.71 Hz vibration, ±2.4 mm cable amplitude, and 1 × 10⁷ cycles, the OPGW test showed no visually detectable slippage or cable damage. The two scenarios provide electrical-geometry and mechanical-interface evidence under the specified analysis and test conditions. Full article

When large liquefied natural gas (LNG) storage tanks are constructed on deep non-rock sites, soil–foundation–structure interaction (SFSI) alters the dynamic characteristics of the system and affects the actual control effectiveness of the isolation layer. However, the current understanding of the coupling mechanism between the two remains insufficient. This paper takes a 220,000 m³ full-containment LNG storage tank as the study object and establishes a three-dimensional finite element model of the tank-pile group-site system in ABAQUS. Through comparative analyses of three model configurations, namely a rigid foundation model, a non-isolated model considering SFSI, and a lead-rubber bearing (LRB) isolated model considering SFSI, the SFSI effects and LRB isolation effectiveness are systematically separated. For the SFSI effects, the deep site attenuates medium- and high-frequency content while amplifying the response around approximately 1.6 Hz through site–foundation flexibility, transforming the heightwise acceleration amplification profile from an approximately linear pattern to a curvilinear one that bulges at mid-height, with peak pile-cap accelerations increasing by 25.1–76.9% relative to the rigid-base values. For the LRB isolation performance, the introduction of LRBs shifts the dominant system frequency below 1.0 Hz and reduces the maximum tank-wall acceleration amplification factor from 2.64 to 0.81. The resulting attenuation of superstructural inertial forces leads to reductions of 49.6–82.0% in pile-head shear and 57.4–78.0% in near-head bending moment, while the outer-to-inner pile-head moment ratio decreases from 2.94 to 1.13, indicating substantially improved pile-group force uniformity. Nevertheless, the beneficial effect of isolation diminishes with depth, and internal forces at abrupt soil-stiffness interfaces remain governed by kinematic interaction that the isolation layer cannot mitigate. The findings of this study can provide references for the seismic isolation design and pile foundation seismic optimization of super-large LNG storage tanks on deep overburden sites. Full article