Search Results (983)

Existing target sorting methods suffer severe performance degradation or even failure under inherent severe spectrum overlap, homogeneous protocol parameters, and scarce single-source points in Synchronous Non-Orthogonal Frequency Hopping (SNOFH) scenarios. To address this challenge, this paper proposes a passive sorting framework for SNOFH UAV swarm signals based on multi-station relative hopping time difference. The proposed framework constructs a spatial-location-driven sorting feature system, designs a kernel joint distribution adaptation module to eliminate inter-station measurement discrepancies, and develops a multi-scale wavelet-based method to achieve sub-sampling level hopping time extraction, reducing the dependence on prior FH parameters and hardware radio frequency fingerprints. Experimental comparisons between the proposed and reference sorting methods are conducted on a simulated SNOFH dataset to validate the performance of the proposed sorting framework. The experimental results show that the proposed method achieves the highest sorting accuracy of 98%, outperforming adopted baselines in most SNOFH cases. The proposed method exhibits favorable robustness with noise interference, clock-synchronization error, carrier-frequency offset and multipath influence. It is a suitable choice for UAV swarm sorting under regular and slow-varying UAV formations. Full article

Energy-efficient renovation of existing buildings is one of the important approaches to achieving sustainable development. This study takes a naturally ventilated sports hall (without heating or air conditioning systems) at a university in Weifang, Shandong Province, as the research object, where indoor thermal comfort levels remain low throughout most of the year. Adopting passive optimization as the core approach, the study aims to improve natural daylighting and winter thermal environment by adjusting window-to-wall ratio (WWR), window-to-floor ratio (WFR), skylight height, and glass thermal–optical parameters. The research methodology consists of two main stages: field measurement and multi-scenario simulation. On-site measurements were first conducted to ascertain the building’s actual usage patterns, existing daylighting conditions, and temperature distribution characteristics. Subsequently, six scenarios—including the original design, the current condition, and four differentiated optimization schemes (Schemes A, B, C, and D)—were quantitatively evaluated for indoor daylighting and thermal performance using Ecotect Analysis 2011 and eQUEST 3.65. The simulation models were calibrated against field measurement data to ensure result reliability. Key findings are as follows. In terms of daylighting, daylight factor and indoor average illuminance increase significantly with higher WFR, with this growth trend noticeably plateauing around a WFR of 0.7. Illuminance uniformity should be comprehensively assessed using both of its calculation methods; skylights provide more balanced daylighting than side windows, and combined side-window and skylight schemes yield far superior illuminance uniformity compared to single-type window arrangements. Regarding thermal performance, in schemes incorporating skylights, indoor temperature rises with increasing glazing area when WFR is below 0.7; however, when WFR exceeds 0.7, building heat dissipation surpasses solar heat gain, causing indoor temperature to decrease. Considering annual thermal comfort performance, Scheme C achieves the longest cumulative comfort hours and the most balanced year-round thermal performance, making it suitable for renovation projects pursuing stable indoor environments. Scheme A demonstrates significant winter warming effects but suffers from overheating defects during summer and transition seasons, thus requiring enhanced ventilation measures. After implementing increased ventilation (5 air changes per hour), Schemes A and C achieve 36.7% and 37.2% more comfortable hours during the building’s 10-month usage period, respectively, compared to the current condition. In conclusion, for large-space buildings such as sports halls, relying solely on increasing WFR and WWR for passive winter warming yields limited effects, and coordinated optimization of glass thermal–optical properties and ventilation strategies should be adopted. Full article

Background: Pes planus is a common foot deformity that may lead to both structural and functional consequences. This alteration in foot morphology has been associated with changes in neurosensory mechanisms such as proprioception and balance. This study aims to evaluate proprioception and balance parameters in young adults with pes planus by comparing them with healthy individuals. Methods: This case–control study, which had a quantitative and cross-sectional design, included a total of 90 volunteer university students aged 18–30. The presence of pes planus was assessed using the Navicular Drop Test. Proprioception assessment was performed using a digital goniometer to measure active and passive joint position sense, while balance assessment was performed using the Y Balance Test. Results: The groups were similar in terms of demographic and anthropometric characteristics (p > 0.05). In the proprioception assessment, a significant difference was observed in active joint position sense scores in individuals with pes planus (p = 0.032). In contrast, no significant difference was found between the two groups in terms of passive joint position sense (p = 0.769). According to the Y Balance Test results, no difference was observed in the anterior and posteromedial directions (p = 0.690 and p = 0.806). At the same time, the balance performance of individuals with pes planus was significantly lower in the posterolateral direction (p = 0.045). Conclusions: Young individuals with flexible pes planus showed differences in active joint position sense and balance performance in the posterolateral direction. This situation shows that pes planus may be associated with not only structural but also neurosensory functions. The findings highlight the importance of planning protective interventions early. In the future, there is a need for longitudinal studies conducted with larger and more heterogeneous samples, including rigid type pes planus. Full article

To address the lack of comprehensive quality evaluation indicators for heat treatment after bilateral induction hardening of high-speed linear guide rails, this study draws on the concept of geometric tolerance to innovatively propose a quantitative evaluation indicator for the “symmetry” of the hardening layer depth profile, and conducts non-destructive evaluation research based on ultrasonic transverse wave backscattering technology. Aiming at the complex cross-sectional profile of the guide rail and the problem of anisotropic acoustic scattering, a multi-dimensional symmetry characterization framework driven jointly by “local pair-wise tolerance zone constraints” and a “global equivalent case depth metric” was established. This dual-driven evaluation framework effectively eliminates the evaluation loophole of “false symmetry” caused by the mutual cancellation of opposite positive and negative local deviations. By constructing an equivalent hardened layer model based on discrete feature point mapping, the interference of non-parallel complex curved surfaces on traditional continuous B-scan imaging is successfully circumvented, achieving stable characterization of the overall hardening layer coverage under specific process parameters. A 15 MHz water-immersed point-focusing ultrasonic transverse wave oblique incidence detection system was developed, paired with a self-designed spring-loaded passive conformal tracking clamping mechanism for continuous automated scanning. Experimental results demonstrate that the overall equivalent symmetry of the tested guide rail specimens remains above 98%. Verified by the metallographic Vickers hardness gradient method, the equivalent relative error between the ultrasonically measured case depth and the physical case depth is only 1.0% and 1.6%. This proves that this non-destructive evaluation method possesses excellent measurement accuracy and holds significant industrial value for online non-destructive monitoring. Full article

During the meshing process of plastic gears, inhomogeneous thermal deformation is prone to occur due to the coupling effect of frictional heat generation and material thermal sensitivity, leading to contact misalignment on tooth surfaces. Traditional modification designs mostly rely on empirical approaches or merely compensate for static elastic deformation, which cannot adequately address thermo-mechanical interactions. In this paper, an active modification method based on the identification of thermal deformation regions is proposed. First, a thermo-structural coupling finite element model of polyoxymethylene (POM) gears is established, taking into account the temperature-dependent modulus. The steady-state temperature field is obtained through ANSYS 2024 R1 simulations, and its accuracy is verified against experimental measurements. Subsequently, the thermal deformation distribution is acquired by coupling the structural field. The cumulative deformation energy function is introduced, and the modification length is objectively determined as L = 0.35 mm by adopting the extreme point of the second derivative of the normalized cumulative energy. Three modification strategies, namely linear modification, Walker curve modification, and Mingchuan curve modification, are designed. Simulation results demonstrate that all three strategies effectively reduce the thermal deformation, steady-state temperature, and contact pressure of the gears, among which the Walker curve modification exhibits the best performance. After modification, the maximum thermal deformation is reduced by 44.14%, the maximum contact pressure by 16.2%, and the maximum steady-state temperature by 9.5%. The proposed method transforms thermal deformation from a “passive response” into an “active design input”, verifies the feasibility of thermally driven modification, and thereby establishes a quantifiable thermally adaptive modification approach for plastic gears. Full article

Dog parks are widely used recreational spaces for human–dog interaction, yet there is little empirical data about how surface materials influence dogs’ behavior and welfare. This study evaluated dogs’ behavior on three surfaces commonly used in outdoor dog recreation areas. Ten dogs (N = 10) participated in ten structured play sessions in an experimental area with unrestricted access to all surfaces. The testing area consisted of a 12.2 m² playground divided into nine plots of equal size. Each plot was randomly assigned a surface material (i.e., natural grass, stabilized grass, or artificial turf) in a 3 × 3 block design. Environmental and surface temperatures were recorded in each session. Dog behavior was recorded during a pre- and post-play period and measured using a 10 s scan sampling technique. In addition, surface characteristic measures were collected throughout the study to evaluate differences in their tolerance to weather conditions and usage. Artificial turf consistently reached a higher temperature (25.2 °C; 95% CI: 24.5–25.8 °C) than natural (19.4 °C; 95% CI: 18.7–20.1 °C) and stabilized (20.0 °C; 95% CI: 19.3–20.6 °C). In this study, the artificial turf reached temperatures as high as 63.8 °C while, under the same environmental conditions, the surface temperature of both natural turfgrass treatments remained below 40 °C. During the pre-play period, dogs showed more active than passive behaviors on the stabilized surface (35.03%; 95% CI: 30.58–39.80%) compared to the natural (27.86%; 95% CI: 23.94–32.10%) and artificial turf (23.31%; 95% CI: 19.81–27.20%). During the post-play period, activity levels decreased across all surfaces, while the occurrence of passive behaviors increased and was observed more frequently on the natural turfgrass surfaces (27.30% on stabilized and 15.52% on natural) than on artificial turf (2.41%). Artificial turf was less affected by dog traffic and seasonal changes; however, its surface was harder than both natural turfgrass treatments. The addition of the stabilizing grid failed to reduce soil compaction as anticipated. Overall, dogs spent more time on both natural turfgrass surfaces than artificial turf. However, a potential confounding effect of location could have influenced dog behavior. Nonetheless, our findings show that dog owners should be cautious when using artificial turf areas when environmental temperatures are above 25 °C when the turf temperature is above the safety threshold for burn injuries. These findings highlight the importance of carefully selecting surface materials for outdoor dog spaces to ensure dogs’ safety and comfort. Full article

A reconfigurable intelligent surface (RIS) is a promising technology for beyond-fifth-generation (B5G) and sixth-generation (6G) wireless communications, but its passive reflection and two-hop double-fading structure make cascaded channel estimation challenging. Conventional convolutional neural network (CNN) estimators require many trainable parameters, while a single shallow parameterized quantum circuit (PQC) may have limited feature representation. Deep quantum circuits can also suffer from noise and barren-plateau effects on noisy intermediate-scale quantum (NISQ) devices. To address these issues, this paper proposes a multi-filter quantum convolutional neural network (MF-QCNN) for cascaded channel estimation in RIS-assisted multi-user uplink systems. The proposed model uses multiple independent shallow PQC filters in parallel, concatenates their measured features, and estimates the cascaded channel through a compact classical dense head, with the total trainable-parameter count scaling as $182F+696$ for F parallel filters. Simulation results, compared with a single-filter quantum convolutional neural network (QCNN), CNN, and multilayer perceptron (MLP) baselines, show that at a signal-to-noise ratio (SNR) of 20 dB, the 3-filter MF-QCNN reduces the normalized mean squared error (NMSE) by approximately 22.9, 8.1, and 4.6 dB relative to the single-filter QCNN, CNN, and MLP baselines, respectively, while using only about 19.3% of the CNN trainable parameters. Under zero-forcing (ZF) precoding, it achieves the highest achievable sum rate among the learning-based estimators; at SNR = 30 dB, it improves the achievable sum rate by approximately 17.4% and 12.8% over the CNN and MLP baselines, respectively. These simulation results suggest that the parallel shallow-PQC design can serve as a compact quantum-aided estimator for RIS channel estimation and may provide a useful basis for future studies on AI-native transceiver design in B5G/6G networks. Full article

Human gait analysis is a key component of rehabilitation medicine, enabling objective assessment of patient recovery. In crutch-assisted locomotion, however, conventional forearm crutches operate as passive devices, providing no quantitative information on load distribution or patient adherence to partial weight-bearing (PWB) prescriptions. This work presents the design and dynamic validation of a sensorized forearm crutch system for biomechanical monitoring during assisted gait. The proposed device combines a force-sensing module based on a full Wheatstone bridge strain-gauge configuration with a 6-axis inertial measurement unit (IMU) to capture both axial load and crutch orientation. Sensor fusion was implemented through a complementary filter to estimate pitch and roll angles under dynamic conditions. The system was calibrated through static loading procedures and validated against reference instrumentation, including an optoelectronic motion capture system and an instrumented dual-belt treadmill with force platforms. Unlike previous studies relying on stationary force platforms that capture discrete steps and may alter natural gait, this validation approach enabled continuous, stride-by-stride force and orientation measurements without restricting foot placement. Experimental trials were conducted with unimpaired participants performing assisted gait using 2-point and 3-point patterns at two partial weight-bearing levels (20% and 40% body weight) and two walking speeds (0.80 m/s and 1.20 m/s). Dynamic validation showed good agreement with the treadmill reference, with force RMSE values of $9.33\pm 1.70$ N for the left crutch and $12.90\pm 2.85$ N for the right crutch, and with coefficients of determination of $R^2=0.9956$ and $R^2=0.9927$, respectively. Orientation RMSE values were $1.08\pm 0.44$° (roll, right), $2.06\pm 0.56$° (roll, left), $1.79\pm 0.55$° (pitch, right), and $1.66\pm 0.37$° (pitch, left). Beyond validation accuracy, the system enabled extraction of a set of quantitative biomechanical descriptors directly from crutch signals, axial load, cadence, crutch contact variability, load asymmetry, pitch asymmetry, and crutch stance/swing asymmetries, characterizing walking stability, bilateral coordination, and gait regularity during continuous assisted locomotion. These results demonstrate the feasibility of integrating force and inertial sensors into forearm crutches to enable quantitative monitoring of assisted gait, with potential applications in rehabilitation assessment and real-time feedback. Full article

Urbanization in Northern Nigeria has accelerated the adoption of modern architectural forms that often neglect climatic responsiveness and indigenous cultural values. This study examines how vernacular architectural principles can be integrated into contemporary urban development to enhance climate resilience. Focusing on Sokoto, Katsina, and Kano, the research adopts a mixed-methods approach combining field measurements, simulation modeling, structured interviews, and policy analysis. Findings indicate that traditional Hausa architecture achieves indoor temperature reductions of 4–6 °C compared to ambient outdoor conditions. This is primarily due to courtyard configurations, high thermal mass, and passive ventilation strategies associated with the architecture. Life-cycle assessment reveals that vernacular materials exhibit 60–75% lower embodied energy than modern buildings. Despite these advantages, policy frameworks inadequately support their integration. This study proposes an integrative model combining vernacular strategies with modern technologies and policy reforms. The findings contribute to sustainable urban design discourse and align with global sustainability goals. Full article

ETFE (EthylenTetraFluoroEthylen) cushion facade systems are increasingly adopted in contemporary architecture due to their lightweight properties and design flexibility. However, their thin, meltable structures present persistent uncertainties in fire safety. Specifically, the quantitative effects of fire origin, facade location, and passive–active fire protection measures on structural integrity, toxicity, and secondary fire risks remain underexplored. This study evaluates the fire performance of 15 ETFE cushion facade typologies under 135 scenarios, including fires originating externally, internally, and within the cushion, across middle, corner, and recessed facade locations. Simulations are conducted using artificial intelligence-based code generation to address the limitations of conventional fire modeling. Fire behavior is quantified via time to structural failure, burning duration, CO toxic gas production, dripping onset and mass, and normalized fire and dripping performance indices. Results show that passive measures provide limited structural delay and often increase burning duration and toxicity. Conversely, active systems demonstrate more balanced, scenario-dependent performance, reducing fire intensity, toxic gas emission, and melt-induced secondary risks. These findings highlight that effective fire safety in ETFE cushion facades requires holistic, location-sensitive and scenario-sensitive integration of passive and active measures rather than reliance on singular strategies, ensuring property protection and life safety in buildings. Full article

This study examines the influence of device architecture and substrate materials on the external quantum efficiency (EQE) of high-performance solar cells. A diverse array of photovoltaic technologies was evaluated, including formamidinium lead iodide CH₅N₂PbI₃ (FAPI) perovskite cells and various silicon-based designs, such as Passivated Emitter and Rear Cell (PERC), Back Integrated Contact (BIC), and Bifacial structures. Quantum characteristics were determined through wavelength-dependent photocurrent measurements utilizing a precision monochromator system. Our results reveal that device structure is a primary determinant of charge carrier collection efficiency; specifically, Bifacial and PERCs achieved superior short-circuit current densities (J_sc) of 40.98 mA/cm² and 39.42 mA/cm², respectively. Notably, the EQE(λ) profile of Bifacial cells under n-side illumination exhibits a near-ideal rectangular shape, indicating an optimized spectral response throughout the operating spectrum. Furthermore, the analysis investigates the role of surface recombination velocity and the efficacy of advanced passivation layers—specifically Al₂O₃ and SiN_x—in enhancing quantum performance by mitigating recombination state density. Our findings demonstrate that the strategic integration of advanced passivation layers (Al₂O₃ and SiN_x) with optimized architectures, such as PERC and Bifacial designs, is paramount for maximizing charge carrier collection and achieving record-high current densities reaching 40.98 mA/cm². A comprehensive analysis of solar cell performance involves spectral response (SR) and external quantum efficiency (EQE) as functions of wavelength. Additionally, SR-based current density analysis enables more accurate evaluation of cell parameters than standard I–V characterization. Full article

Reliable radio coverage is essential for the deployment of 5G for railway (5G-R) communication systems in complex railway-line environments. Previous simulation- and measurement-based studies have mainly focused on main-track railway scenarios, while the propagation characteristics in railway-side obstructed environments remain insufficiently characterized. To address this gap, this paper investigates large-scale propagation characteristics using passive synchronization signal reference signal received power (SS-RSRP) measurements collected from a 5G-R test network. Typical railway-line scenarios, including open line-of-sight (LOS) propagation, building-obstructed railway-side sections, viaduct-blocked regions, and depot-like environments, are analyzed to reveal the influence of railway-side structures on large-scale signal behavior. A floating-intercept (FI) model is adopted to characterize scenario-dependent path loss, and a height-corrected FI refinement is further introduced for building-obstructed sections. The results show that local railway-side structures introduce distinct and quantifiable excess propagation loss beyond conventional distance-dependent path loss. The obtained model parameters can support large-scale propagation modeling, link-budget margin design, coverage-hole identification, and wireless coverage evaluation for 2100 MHz 5G-R systems in obstructed railway-side environments. Full article

Saturable absorbers (SAs) are critical for passive mode-locking in ultrafast fiber lasers. Although many materials have been studied as SAs, new candidates with broadband and stable performance are still needed. In this work, we report the synthesis and fabrication of Ti₂O-based SAs and present the first systematic investigation of their performance in broadband ultrafast fiber lasers. Specifically, phase-pure Ti₂O crystals were synthesized via solid-state sintering. High-performance Ti₂O SAs were then fabricated through a photodeposition method. The balanced synchronous twin-detector measurement method demonstrated that Ti₂O exhibited obvious and stable saturable absorption behavior. To validate their broadband mode-locking capability, the as-prepared Ti₂O SAs were integrated into the Yb-doped and Er-doped fiber lasers, respectively. Experimental results show that both laser systems deliver stable pulsed output, with pulse durations of 441.7 ps at 1 μm and 522.5 fs at 1.5 μm. This work pioneers the application of Ti₂O in ultrafast photonics, and provides an important reference and novel research insights for the design and development of advanced broadband optical devices and systems. Full article

In wind tunnel testing, an active vibration suppression system based on piezoelectric actuators is an effective means to ensure stable operation. However, in a cryogenic wind tunnel testing environment, the performance of piezoelectric actuators degrades significantly when they are exposed to cold temperatures and subjected to uneven cooling. This is particularly problematic during real-time changes in the attack angle of a test model. To ensure the reliable operation of wind tunnel tests, an active–passive hybrid thermal control method is proposed in this paper. First, the insulation and heating structure was designed based on the thermal analysis results. Then, combining simulation and measured data, the temperature field was reconstructed in real time using a recurrent neural network algorithm. Next, considering the non-uniform heat dissipation of the system, a thermal allocation module was designed based on digital–physical integration to actively control the overall and localized heat. Finally, a heat preservation performance test platform was established to conduct cooling experiments in a small-scale cryogenic wind tunnel. The results indicated that the proposed thermal control method reduced the average cooling rate of the system by 97% and improved the overall temperature uniformity by approximately 94.23%. Full article

To address the difficulty in controlling the filtration performance of water-based drilling fluids under high-temperature and high-salinity conditions during the drilling of deep and ultra-deep wells, a salt-responsive micro-crosslinked polymer gel filtration loss reducer, designated LZX, was developed. The synthesis employed 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N,N-dimethylacrylamide (DMAA), dimethyldiallylammonium chloride (DMDAAC), and a betaine monomer containing an unsaturated double bond as monomers, with polyethylene glycol diacrylate (PEGDA) introduced as a crosslinker. Experimental results showed that the product structure matched the design expectations, and the thermal decomposition temperature of the main molecular chain exceeded 290 °C, indicating good thermal stability. At 220 °C under saturated salt conditions, a dosage of 2.5 wt% LZX maintained the API filtration loss at 5.8 mL and the HPHT filtration loss at 28.6 mL. Comparative experiments at different temperatures demonstrated that LZX exhibited superior filtration control performance compared to the commercial high-temperature filtration reducer Driscal Temp and Driscal D. The micro-crosslinked structure of LZX enhanced the rigidity of the molecular chains, raising the upper limit of its thermal resistance. Rheological and viscosity-average molecular weight measurements revealed that LZX exhibited typical antipolyelectrolyte behavior in high-salinity environments—the molecular chains tended to extend and the filtration reduction capability was accordingly maintained—preliminarily achieving a functional transition from passive salt tolerance to active salt responsiveness. LZX is expected to support the construction of high-performance water-based drilling fluids with high temperature and high salt resistance for future deep-earth drilling. Full article