Search Results (36,057)

This Special Issue (SI) was intended to gather high-quality original research articles and reviews on the above topic, with an emphasis on the essential role of VLF (very low frequency, 3–30 kHz)/ELF (extremely low frequency, 1 Hz–3 kHz) wave phenomena in a wide range of scientific fields from astrophysics, space physics, ionospheric physics, atmospheric electricity, and seismo-electromagnetics [...] Full article

To address the low mechanization level, high labor intensity, and severe substrate disturbance in intertidal shellfish harvesting, a vibratory harvesting method based on local vibration-induced substrate fluidization was proposed, and a vibratory harvesting device for Mactra veneriformis was developed. Bench and intertidal field tests were conducted to systematically investigate the effects of vibration frequency, vibration pressure, and vibration amplitude on substrate fluidization, clam uplift, and harvesting performance. The single-factor results showed that all three parameters significantly affected the pore water pressure ratio, substrate viscosity, uplift distance, and harvesting rate, with better fluidization obtained at 8 Hz, 30 kPa, and 25 mm. A Box–Behnken response surface design was further used to establish quadratic regression models for these responses, and all models were highly significant with a non-significant lack of fit. The optimized parameter combination was 10 Hz, 35 kPa, and 25 mm, under which the predicted pore water pressure ratio and uplift distance were 101.3% and 97.2 mm, respectively, and the substrate viscosity was 1364 Pa·s. Field tests showed that the pore water pressure ratio remained above 85.3%, viscosity decreased to 1331–2639 Pa·s, shear strength decreased by 57.2–64.9%, and the average uplift distance at 100 mm burial depth reached 80–92 mm. The results indicate that vibratory harvesting can effectively promote substrate fluidization and reduce clam uplift resistance, providing a reference for the development of low-disturbance mechanized harvesting equipment for intertidal shellfish. Full article

Background: Previous research on diet and age-related macular degeneration (AMD) has emphasized primarily particular nutrients or foods, and the influence of comprehensive dietary patterns that represent actual eating behaviors is largely unknown. Objective: The aim of this study was to assess the association between dietary patterns and the odds of AMD. Methods: A case–control study involving 246 participants with AMD and 246 controls are individually matched by age and gender. Dietary patterns were identified through principal component analysis using a validated food frequency questionnaire. Multivariable conditional logistic regression models were applied to examine the association between the extracted dietary patterns and the likelihood of AMD. Results: Three major dietary patterns were found, accounting for 50.59% of the total variance explained. The prudent dietary pattern represented a high intake of vegetables, fruits, soybeans and its products, edible fungi and algae, and nuts were associated with reduced odds ratios (ORs) of the highest tertile compared to the lowest tertile (OR, 0.29, 95% confidence interval [CI], 0.14−0.59, p for trend = 0.001). The estimated likelihood for AMD in the highest tertile of egg and milk dietary pattern intake, which is characterized by a high intake of eggs, milk and dairy products, and refined grains, was 0.40 (95% CI, 0.23−0.67, p for trend <0.001) compared with those in the lowest tertile. No association with AMD was identified for the animal dietary pattern (p > 0.05). Conclusions: Adherence to dietary patterns rich in fruits, vegetables, nuts, refined grains, eggs, milk and dairy products is associated with reduced odds of AMD, emphasizing the potential relevance of dietary habits to visual health among middle-aged and elderly adults. Full article

Electro-hydraulic servo systems are widely used in industrial machinery and automation due to their high power density and fast dynamic response; however, their achievable positioning accuracy is often limited by nonlinear friction effects. In many robust control strategies, including sliding mode control and its multi-surface variants, friction is commonly treated as a lumped bounded disturbance. This simplification neglects the dynamic and operating condition-dependent nature of friction, leaving the practical value of explicit friction compensation insufficiently clarified, especially for electro-hydraulic actuators operating near their bandwidth limits. This paper presents an experimental evaluation of LuGre-based dynamic friction compensation integrated into a multi-surface sliding mode control framework for electro-hydraulic actuators. Rather than proposing a new control methodology, the study focuses on clarifying, from a control-oriented mechanical engineering perspective, how friction compensation influences closed-loop tracking performance under different operating regimes. The proposed scheme is implemented on a laboratory-scale electro-hydraulic test bench and evaluated using step and sinusoidal reference motions over a wide range of excitation frequencies, from low-speed operation to the practical bandwidth limit of the actuator. Comparative experiments with a conventional proportional–integral–derivative controller and a multi-surface sliding mode controller without friction compensation are conducted to isolate the effect of explicit friction modeling. The experimental results reveal a strongly frequency-dependent influence of friction on tracking performance. At low excitation frequencies (e.g., 0.1 Hz), friction compensation provides only marginal improvement in root mean square (RMS) tracking errors. In contrast, as the excitation frequency approaches the actuator bandwidth limit (1 Hz), explicit LuGre-based friction compensation reduces the relative RMS tracking error by approximately 57% compared with the baseline MSSM controller and by up to 82% relative to a conventional PID controller. These results demonstrate that the effectiveness of friction compensation is highly dependent on operating conditions, providing experimentally grounded guidance for the design of control strategies for bandwidth-limited electro-hydraulic machines. Full article

Optical and Synthetic Aperture Radar (SAR) sensors capture complementary and consistent information, and their fusion enhances remote sensing image quality. Existing pyramid decomposition-based methods suffer from insufficient texture–edge discrimination. Additionally, the manual setting of parameters during pyramid decomposition introduces uncertainty in the fusion results. To address this problem, we propose an optical and SAR image fusion framework based on local extrema adaptive pyramid decomposition (LEAPFusion), which enhances edge preservation and improves parameter adaptability. Specifically, by leveraging the edge-preserving properties of local extrema, we introduce them into the image pyramid decomposition framework to construct complementary local extrema and Laplacian pyramids. Then, we introduce an explicit parameter adaptation strategy in which the decomposition levels and local extrema kernel sizes are automatically determined from image size and pyramid scale, enabling consistent multi-scale representation and reducing parameter sensitivity compared to empirically tuned settings. Finally, by exploiting the complementary properties of the two pyramids, we implement a multi-type fusion strategy: weighted averaging for low-frequency components and parameter-adaptive pulse-coupled neural network (PAPCNN) for high-frequency details. Our decomposition framework seamlessly integrates three representative edge-preserving filters—a median filter, a guided filter, and a rolling guidance filter—demonstrating strong generalization capability across different filtering paradigms. Extensive experiments on two benchmark datasets demonstrate that our method outperforms seven state-of-the-art algorithms, achieving the best results across diverse scenes with improvements of up to 13.38% in SF and 18.90% in SCD compared to the second-best methods. Full article

The study of genetic effects induced by low-dose alpha radiation associated with radon and its decay progeny is critically important for assessing radiation risks in regions with elevated natural background levels. The aim of this study was to evaluate the mutagenic effects (in germline cells) and teratogenic effects (in somatic tissues) of alpha radiation using the D. melanogaster model. To differentiate between these effects, teratogenic outcomes were analyzed in directly exposed individuals (phenotypic analysis of adults that developed from irradiated larvae), whereas mutagenic effects were assessed in the progeny of irradiated flies. Larvae and adult flies were exposed to calibrated alpha-particle sources with energies ranging from 4.8 to 7.7 MeV and absorbed doses of 1.90–44.96 mGy. The results demonstrated a statistically significant increase in the frequency of morphological abnormalities in the exposed groups, including melanotic masses and deformities of the wings, thorax, and tergites. Under 72 h exposure, a strong correlation between absorbed dose and abnormality frequency was observed (r = 0.98). In the reporter system, induction of GFP expression was detected in imaginal discs at doses above 10 mGy, indicating threshold activation of the cellular stress response. The obtained data demonstrate that chronic low-dose α-irradiation leads to an increased frequency of morphological abnormalities (indirect phenotypic manifestations of compromised genetic stability) in D. melanogaster, with the most pronounced effects observed at the level of morphogenesis. The high sensitivity of the applied test systems was confirmed, supporting the use of D. melanogaster as a bioindicator for ecogenetic monitoring of radon-prone areas, including regions of Kazakhstan. Full article

This paper investigates the impact of atmospheric conditions on distance determination accuracy in the VDES R-Mode system, based on system development and long-term analytical work conducted within the ORMOBASS project. A dedicated VDES R-Mode transmitter and monitoring station were developed and deployed in Poland, in the Port of Gdynia and at the boatswain’s office in the port of Jastarnia, respectively. Both stations were synchronized in time and frequency using a fiber-optic link and White Rabbit technology, ensuring high-precision and stable operation during long-term measurements. Based on a one-year stationary measurement campaign, a comprehensive dataset combining ranging results and meteorological observations was collected and analyzed. Statistical evaluation demonstrated that atmospheric conditions—particularly rainfall intensity and water vapor density—have a measurable impact on ranging accuracy. These findings motivated the development of a mathematical model describing the relationship between atmospheric conditions and distance measurement errors. The proposed logarithmic regression-based approach was validated using real measurement data; the authors also demonstrated its ability to reduce error variability during changing weather conditions, indicating its potential for future implementation in VDES R-Mode receivers. Full article

Series arc faults on the DC side of photovoltaic (PV) systems are a critical hazard that can trigger system fires. Conventional contact-based detection methods suffer from cumbersome installation and high retrofit cost, whereas existing non-contact approaches mostly rely on megahertz-level high-frequency sampling and therefore require expensive radio-frequency instrumentation or high-performance computing platforms. As a result, it remains difficult to simultaneously achieve strong interference immunity and real-time performance on low-cost embedded devices with limited resources. To address this engineering paradox between high-frequency sampling and constrained computational capability, this paper proposes a fully embedded, non-contact arc fault detection system based on a 12–80 kHz low-frequency sub-band selection strategy. By exploiting the physical characteristic of broadband energy elevation induced by arc faults, the proposed strategy avoids dependence on high-bandwidth hardware. Guided by this strategy, a Moebius-topology coaxial shielded loop antenna is employed as the near-field sensor, while an ultra-simplified passive analog front end is constructed directly by using the on-chip programmable gain amplifier and analog-to-digital converter of the microcontroller unit, enabling efficient signal acquisition and fast Fourier transform processing within the target sub-band. To cope with complex background noise in the low-frequency range, an environment-adaptive baseline mechanism based on exponential moving average and exponential absolute deviation is developed for dynamic decoupling. In addition, a lightweight INT8-quantized multilayer perceptron is introduced as a nonlinear auxiliary module, thereby forming a robust hybrid decision architecture with complementary rule-based and artificial intelligence components. Experimental results show that, under the tested household, laboratory, and PV-site conditions, the proposed system achieved an overall detection rate of 97%, while the remaining 3% mainly corresponded to failed ignition or non-sustained arc attempts rather than persistent false triggering during normal monitoring. Full article

Stiffened plate structures widely used in military aircraft are frequently subjected to severe shock environments, such as those generated by gunfire or explosive blasts, which can significantly compromise the integrity and reliability of onboard equipment and devices. Accurate characterization and prediction of the shock response, especially the damping behavior of such structures, remains a critical yet challenging problem in aeronautical engineering. This study presents an integrated experimental–numerical framework for analyzing the shock response and damping characteristics of representative stiffened plates under shock wave excitation. Controlled shock loading is applied using a shock tube, with real-time acceleration responses measured at multiple locations on both plain and rib-reinforced plates. A high-fidelity finite element model is developed, and three commonly used damping models—Rayleigh Damping, wave attenuation Model, and Maximum Loss Factor Model—are systematically evaluated. Damping parameters are identified through a Particle Swarm Optimization (PSO) algorithm, using the shock response spectrum (SRS) as the performance metric. Experimental results reveal that the incorporation of reinforcing ribs can reduce peak acceleration responses and significantly enhance the damping performance, particularly in the mid-to-high frequency range. The identified damping parameters further show that the maximum loss factor model provides superior agreement with experimental SRS data compared to traditional approaches. The proposed methodology offers a robust method for modeling damping behavior in stiffened plates, providing practical insights for the design of aircraft structures exposed to shock environments. Full article

To address the longitudinal vibration issues in high-speed elevators induced by external excitations, this study constructs a high-precision multi-degree-of-freedom (MDOF) dynamic model to systematically analyze vertical dynamic response characteristics. Utilizing the substructure method, the complex traction system is decomposed into several subsystems, including the traction device, tensioning device, car and car frame, counterweight system, and segmented wire ropes. By integrating Lagrange’s equations with Newton’s second law, the governing differential equations of motion for each component are derived, establishing an adaptable global dynamic model. The forced vibration analysis focuses on the impacts of periodic excitation from traction sheave eccentricity, piecewise reverse braking torque, and vertical impacts from guide rail joints on car vibration response and wire rope dynamic stress. The results indicate that: traction sheave eccentricity leads to periodic fluctuations in car acceleration, with vibration peaks decreasing as the payload increases; reverse braking torque triggers impulsive acceleration overshoots, where the peak value under full-load conditions increases by approximately 15% compared to the no-load condition, accompanied by a longer duration of low-frequency vibrations; guide rail joint impacts produce instantaneous acceleration spikes, which increase by about 18% under high-speed operating conditions; and the wire rope stress exhibits significantly higher sensitivity to load variations within the low-load range of 0–0.2. Full article

In this work, high-resolution sparse channel estimation in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems is addressed. Firstly, a block-structured compressed channel sensing (CCS) model with high spectral efficiency and high delay resolution is constructed. Then, by fully exploiting the temporal correlation and joint sparsity of the channels, a novel two-stage prior delay support-aided delay tracking and block residual norm minimization (PDSA-DT-BRNM) algorithm is proposed. In the first stage, with a limited number of pilots for each antenna and the delay grids within the prior delay support, an efficient delay tracking and block norm minimization algorithm is put forward to choose the common delay grids and estimate each block gain iteratively. In the second stage, by comprehensively utilizing the intermediate channel estimation results of the first stage and the prior delay support, an optimized channel estimation strategy is developed based on the block residual norm minimization (BRNM) criterion. Simulation results and theoretical analysis show the effectiveness of the proposed channel estimation scheme in terms of channel estimation performance, spectral efficiency and computational complexity. Full article

Geothermal energy extraction, hydrocarbon recovery, and CO₂ geological sequestration are frequently hindered by interfacial barriers and slow mass transfer. While high-power ultrasound offers a sustainable, purely physical method for reservoir stimulation, its field effectiveness remains debated because traditional macroscopic experiments fail to isolate mechanisms like acoustic streaming and cavitation. This review systematically examines acoustic mechanisms in porous media via microfluidic visualization, focusing on pore-scale fluid dynamics during enhanced oil recovery, hydrate dissociation, and CO₂ sequestration. Microscopic evidence reveals that fluid transport mechanisms depend heavily on pore geometry and local acoustic intensity. In wider channels, nonlinear acoustic flow provides sustained, directed convection to strip away concentration boundary layers; in narrow throats, microjets and pulsed stresses generated by transient cavitation are responsible for physically breaking capillary barriers. The spatiotemporal synergy of these mechanisms is critical for multiphase fluid transport in tight porous networks. Pore geometry serves not only as the application context but also as a core physical variable. To translate microfluidic results into reservoir-scale applications, future research must address two-dimensional simplifications, thermodynamic discrepancies under high-temperature and high-pressure conditions, and bubble cluster interactions, alongside the development of adaptive frequency-modulated control and multiscale computational models. Full article

With the increasing demand for flexible electric vehicle charging and grid-interactive energy utilization, wireless power transfer (WPT) systems with high efficiency, bidirectional power flow capability, and controllable charging characteristics have attracted growing attention. However, existing WPT systems for electric vehicles still suffer from challenges including low adaptability to multiple operating modes, difficulty in achieving stable constant-current/constant-voltage output, and limited bidirectional power transfer capability under weak-coupling conditions. To address these issues, two relay-based four-coil WPT topologies, namely S-SS-LCC and LCC-SS-LCC, are proposed for electric vehicle charging and bidirectional energy transfer applications. Based on fundamental frequency analysis, frequency-domain models of the two topologies are established to reveal the relationships among resonant characteristics, output behavior, and power transfer direction. The results show that the S-SS-LCC topology can achieve constant-current and constant-voltage output in the forward grid-to-vehicle charging mode, as well as constant-voltage output in the reverse vehicle-to-grid mode. In contrast, the symmetrical LCC-SS-LCC topology can achieve bidirectional constant-current power transfer, making it suitable for vehicle-to-vehicle emergency charging scenarios. Under weak-coupling conditions (k = 0.1), the S-SS-LCC system delivers an output current of approximately 12 A at 85.2 kHz and an output voltage of about 612 V at 87.7 kHz, with a peak efficiency of 91.63%. The LCC-SS-LCC system achieves bidirectional constant-current output at 87.7 kHz with a maximum efficiency of 92.23%. Low-power experimental results further verify the predicted constant-current and constant-voltage characteristics. The proposed topologies provide a promising solution for efficient electric vehicle wireless charging and flexible bidirectional energy interaction in future smart charging systems. Full article

The high-density integration of low-temperature co-fired ceramic (LTCC) filters inevitably induces complex parasitic coupling. Traditional designs rely on forced isolation to mitigate this issue, often at the expense of increased physical footprints. To overcome this limitation, this paper proposes a strategy for the controlled utilization of parasitic effects. Methodologically, localized grounding structures are introduced to construct a controlled electromagnetic boundary. The system’s main path exhibits alternating inductive-capacitive (L-C) coupling, with a single explicit capacitive cross-coupling introduced between specific nodes (resonators 2 and 5). Based on the principle of multi-path signal cancellation, this explicit path synergizes with the implicit parasitic environment. By satisfying conditions of equal amplitude and a 180° phase difference at specific frequencies, a high-order hybrid network is equivalently reconstructed, generating four transmission zeros (TZs). A compact sixth-order LTCC filter was fabricated and tested. Measured results demonstrate a fractional bandwidth (FBW) of 38.6%, a shape factor of 1.16 (based on the 20-dB/3-dB bandwidth ratio), and a 20-dB upper stopband extending beyond $4.28f_0$. In conclusion, the rational utilization—rather than forced isolation—of inherent parasitic effects provides an effective solution for enhancing frequency selectivity and stopband performance in high-density integrated RF front-ends. Full article

Self-efficacy is a person’s belief in their ability to perform a task effectively despite difficulties and predicts future willingness to undertake similar tasks. The study’s aim was to determine the extent to which undergraduate nursing students develop their clinical performance self-efficacy beliefs throughout their degree. Using a cross-sectional survey design, Year 1, 2 and 3 students from a three-year undergraduate nursing program completed a clinical performance self-efficacy scale, comprising the domains of assessment, planning, implementation and evaluation. Welch’s one-way ANOVA and Games–Howell post hoc analyses compared self-efficacy scores across year levels. Self-efficacy predictors were identified with multiple linear regression. Descriptive statistics determined students’ confidence with clinical activities. Participants’ self-efficacy scores increased significantly from Year 1 to 2 and Year 2 to 3. Year level of study was the only unique positive predictor of scores. Over the years, participants were most confident implementing care and least confident planning and evaluating care. Given that clinical placement frequency was not a unique significant predictor of self-efficacy, but rather weakly correlated, future studies should examine if other learning activities such as high-fidelity simulation may play a greater role in its development. The lower confidence with planning and evaluation underscores the need for curricula that scaffold higher-order skills like critical thinking and reflection. Full article