Search Results (972)

Efficient modeling of acoustic scattering from water-filled thin shells remains challenging due to prohibitive computational costs of rigorous methods and oversimplifications in ray-based approximations. This paper develops an iterative physical acoustics (IPA) method, presenting simple and explicit formulations for scattering by penetrable objects immersed in fluids. The method combines Kirchhoff integral frameworks with thin-plate effective boundary conditions, discretizes mid-surfaces into triangular facets, and iteratively converges pressure fields to characterize the mechanisms of multiple reflections and transmissions. Validated against analytical solutions, numerical simulations, and scaled experiments, IPA provides comprehensive field predictions encompassing internal cavity fields, external near-fields, and far-field scattering patterns within a unified framework. It achieves significant computational efficiency gains while maintaining engineering practicality, successfully reproducing distant-range highlights from these mechanisms in time-domain spectra. Limitations are observed at low frequencies and high-curvature regions where elastic-wave effects become significant. The IPA framework enables engineering-efficient scattering analysis for complex thin-shell structures. Full article

Road extraction from remote sensing imagery plays a critical role in applications such as autonomous driving, urban planning, and infrastructure development. Although deep learning methods have achieved notable progress, current approaches still struggle with complex backgrounds, varying road widths, and strong texture interference, often leading to fragmented road predictions or the misclassification of background regions. Given that roads typically exhibit smooth low-frequency characteristics while background clutter tends to manifest in mid- and high-frequency ranges, incorporating frequency-domain information can enhance the model’s structural perception and discrimination capabilities. To address these challenges, we propose a novel frequency-aware road extraction network, termed PWFNet, which combines frequency-domain modeling with multi-scale feature enhancement. PWFNet comprises two key modules. First, the Pyramidal Wavelet Convolution (PWC) module employs multi-scale wavelet decomposition fused with localized convolution to accurately capture road structures across various spatial resolutions. Second, the Frequency-aware Adjustment Module (FAM) partitions the Fourier spectrum into multiple frequency bands and incorporates a spatial attention mechanism to strengthen low-frequency road responses while suppressing mid- and high-frequency background noise. By integrating complementary modeling from both spatial and frequency domains, PWFNet significantly improves road continuity, edge clarity, and robustness under complex conditions. Experiments on the DeepGlobe and CHN6-CUG road datasets demonstrate that PWFNet achieves IoU improvements of 3.8% and 1.25% over the best-performing baseline methods, respectively. In addition, we conducted cross-region transfer experiments by directly applying the trained model to remote sensing images from different geographic regions and at varying resolutions to assess its generalization capability. The results demonstrate that PWFNet maintains the continuity of main and branch roads and preserves edge details in these transfer scenarios, effectively reducing false positives and missed detections. This further validates its practicality and robustness in diverse real-world environments. Full article

Energy raw materials are the basis of the economic system. From this emerges the need to examine in more detail how various uncertainty indices interact with the dynamic of spillover connectedness among energy markets. The TVP-VAR model is used to investigate connectedness among US, European, and Indian oil and gas markets and the S&P carbon allowances Eua index. Following this, the wavelet decomposition technique is used to capture the dynamic correlations between uncertainty indices (GPR and VIX) and connectedness indices. First, the results indicate that energy market spillovers are time-varying and crisis-sensitive. Second, the time–frequency dependence among uncertainty indices and connectedness indices is more marked and can change with the occurrence of unexpected events and geopolitical conflicts. The VIX index shows a positive dependence on total dynamic connectedness in the mid-long-term, while the GPR index has a long-term effect only after 2020. The analysis of the interdependence among the connectedness of each market and the uncertainty indices is more heterogeneous. Political tensions and geopolitical risks are, therefore, causal factors of energy prices. Given their strategic and economic importance, policy makers and investors should establish a risk warning mechanism and try to avoid the transmission of spillovers as much as possible. Full article

Late gadolinium enhancements (LGEs) appear in asymptomatic individuals as septal stripes, which mimic abnormal LGEs in patients with dilated cardiomyopathy (DCM). We aimed to evaluate the frequency and extent of LGE variation in asymptomatic individuals and to compare it with those of DCM group. This retrospective study included asymptomatic and DCM groups who underwent CMR imaging. LGE was defined as a myocardial signal intensity higher than five standard-deviations of normal myocardium. LGE was evaluated in right ventricular insertion points (RVIPs) and mid-interventricular septum. A total of 273 asymptomatic individuals (age, 54.3 ± 5.8 years, 209 males) and 100 patients with DCM (age, 55.3 ± 4.9 years, 73 males) were included. LGE was observed in 99.3% of asymptomatic and 100% of DCM groups. The average number of myocardial segments with LGE was distinguishable between asymptomatic and DCM groups (5.5 ± 1.7 vs. 7.6 ± 2.2; p < 0.001). The thickness of LGE differed between two groups in mid-septum (4.5 ± 1.3 mm vs. 5.7 ± 1.8 mm; p < 0.001), upper RVIP (6.1 ± 1.9 mm vs. 8.7 ± 2.7 mm; p < 0.001), and lower RVIP (6.4 ± 2.3 mm vs. 8.6 ± 2.8 mm; p < 0.001). Considerable overlap was observed in LGE between asymptomatic and DCM groups despite different LGE characteristics between them. LGEs within normal range should not be interpreted as abnormal findings in the evaluation of myocardial diseases including DCM. Full article

Whispering-gallery-mode (WGM) microresonators are amongst the most promising optical sensors for detecting bio-chemical targets. A number of laser interrogation methods have been proposed and demonstrated over the last decade, based on scattering and absorption losses or resonance splitting and shift, harnessing the high-quality factor and ultra-small volume of WGMs. Actually, regardless of the sensitivity enhancement, their practical sensing operation may be hampered by the complexity of coupling devices as well as the signalprocessing required to extract the WGM response. Here, we use a silica microsphere immersed in an aqueous environment and efficiently excite optical WGMs with a free-space visible laser, thus collecting the relevant information from the transmitted and back-scattered light without any optical coupler, fiber, or waveguide. We show that a 640-nm diode laser, actively frequency-locked on resonance, provides real-time, fast sensing of dielectric nanoparticles approaching the surface with direct analog readout. Thanks to our illumination scheme, the sensor can be kept in water and operate for days without degradation or loss of sensitivity. Diverse noise contributions are carefully considered and quantified in our system, showing a minimum detectable particle size below 1 nm essentially limited by the residual laser microcavity jitter. Further analysis reveals that the inherent laserfrequency instability in the short, -mid-term operation regime sets an ultimate bound of 0.3 nm. Based on this work, we envisage the possibility to extend our method in view of developing new viable approaches for detection of nanoplastics in natural water without resorting to complex chemical laboratory methods. Full article

This study explores the aeroacoustic influence of leading-edge serrations applied to stator blades subjected to turbulent inflow, which is representative of rotor–stator interaction in turbomachinery. A set of serrated geometries—75 mm span, with up to 9 teeth corresponding to 10% chord amplitude—was fabricated via 3D printing and tested experimentally in a dedicated aeroacoustic facility at COMOTI. The turbulent inflow was generated using a passive grid, and far-field acoustic data were acquired using a semicircular microphone array placed in multiple inclined planes covering 15°–90° elevation and 0–180° azimuthal angles. The analysis combined power spectral density and autocorrelation techniques to extract turbulence-related quantities, such as integral length scale and velocity fluctuations. Beamforming methods were applied to reconstruct spatial distributions of sound pressure level (SPL), complemented by polar directivity curves to assess angular effects. Compared to the reference case, configurations with serrations demonstrated broadband noise reductions between 2 and 6 dB in the mid- and high-frequency range (1–4 kHz), with spatial consistency observed across measurement planes. The results extend the existing literature by linking turbulence properties to spatially resolved acoustic maps, offering new insights into the directional effects of serrated stator blades. Full article

The Loess Plateau, possessing the world’s most extensive loess deposits, is highly vulnerable to accelerated soil erosion and vegetation loss triggered by extreme hourly rainfall (EHR) events due to the inherently erodible nature of its porous, weakly cemented sediment structure. EHR exacerbates soil erosion, induces flash flooding, compromises power infrastructure, and jeopardizes agricultural productivity. Through analysis of 43 years (1981–2023) of station observational data and ERA5 reanalysis, we present the first comprehensive assessment of EHR characteristics across the plateau. Results reveal pronounced spatial heterogeneity, with southeastern regions exhibiting higher EHR intensity thresholds and frequency compared to northwestern areas. EHR frequency correlates positively with elevation, while intensity decreases with altitude, demonstrating orographic modulation. Synoptic-scale background environment of EHR events is characterized by upper-level divergence, mid-tropospheric warm advection, and lower-tropospheric convergence, all of which are linked to summer monsoon systems. Temporally, EHR peaks in July during the East Asian summer monsoon and exhibits a bimodal diurnal cycle (0700/1700 LST). Long-term trends reveal a significant overall increase in the frequency of EHR events (~0.82 events a⁻¹). While an overall increase in EHR intensity is also observed, it fails to achieve statistical significance due to opposing regional signals. Collectively, these trends elevate the risks of slope failures and debris flows. Our findings highlight three priority interventions: (i) implementation of elevation-adapted early warning systems, (ii) targeted agricultural soil conservation practices, and (iii) climate-resilient infrastructure design for high-risk valleys—all essential for safeguarding this ecologically sensitive region against intensifying hydroclimatic extremes. Full article

In practical applications, precise tuning of current controllers is essential for achieving desirable dynamic performance and stability margins. Traditional tuning techniques rely heavily on accurate plant parameter identification. However, this process is often challenged by inherent nonlinearities and unmodeled dynamics in motor systems. To address this issue, this paper proposes a current loop parameter tuning algorithm based on open-loop frequency sweeping. As the swept Bode diagram reveals nonlinear factors typically neglected during modeling, it provides a basis for control parameter correction. A pulse-sine voltage injection method is first introduced to identify motor parameters, serving as initial values for the controller. By analyzing the magnitude and phase characteristics of the open-loop transfer function, the delay time constant in the high-frequency range can be accurately identified, and mismatched parameters in the low-to-mid frequency range can be corrected. This method does not rely on complex model structures or extensive online adaptation mechanisms. Experimental results on a mechanical test platform demonstrate that the proposed tuning strategy significantly enhances the current loop’s closed-loop bandwidth and dynamic performance. Full article

This study aimed to elucidate stage-specific dynamics, assembly mechanisms, and functional roles of bacterial communities during Macrobrachium rosenbergii larval development through high-resolution microbiota profiling. A high-frequency sampling strategy (126 samples across 11 zoeal stages and 1 post-larval stage within 21 days) and 16S rRNA absolute quantification sequencing were employed. Bacterial succession, persistent taxa, and ecological processes were analyzed using abundance-occupancy modeling, neutral community modeling, and PICRUSt2-based functional prediction. Absolute bacterial abundance exhibited a triphasic abundance trajectory. Initial accumulation: Linear increase (Dph 1–5, peak Δlog10 = +1.7). Mid-stage expansion: Peak abundance (log10 = 7.5 copies/g, Dph 7–8). Late-stage remodeling: Secondary peak (log10 = 7.1 copies/g, Dph 19). Eighty dominant amplicon sequence variants (ASVs) (dominant taxa: Herminiimonas, Maritalea, and Enterobacteriaceae) comprised > 95% of the total abundance and coexisted via niche partitioning. Community construction was dominated by ecological drift/dispersal limitation (neutral model R² = 0.16, p < 0.01). Metabolic pathways (e.g., nutrient metabolism) shifted with dietary transition. “Phylogenetic replacement” underpinned microbiota resilience against environmental perturbations. Optimizing aquaculture environments offers a viable antibiotic-free strategy for microbial management, advancing our understanding of host microbe interactions and ecological niche differentiation in aquatic animals. Full article

This work proposes a novel multi-objective genetic algorithm to solve the Periodic Vehicle Routing Problem with Time Windows (PVRPTWs) tailored for sales teams with diverse geographic scales and visit frequency requirements. Unlike existing models, our approach incorporates workload balancing and applies a clustering-based preprocessing step for long-distance routes using multidimensional scaling and fuzzy clustering, improving initial route grouping. When tested on three salesperson profiles (short-, mid-, and long-distance), the model achieved up to a 69% reduction in total travel time compared to a nearest neighbor baseline. These results demonstrate substantial improvements over existing methods and underscore the model’s flexibility and potential for extension to dynamic or real-time sales routing applications. Full article

With the continuous exploration and advancement of communication frequency bands, terahertz and mid-to-far-infrared communication systems have attracted significant attention in recent years. Modulators are essential components in these systems, making the enhancement of modulator performance in the infrared and terahertz bands a prominent research focus. In this study, we propose a high-performance infrared transmission-type modulator based on the plasmon resonance effect of graphene nanoribbons. This design synergistically exploits near-field enhancement from metal slits and defect states in one-dimensional photonic crystals to strengthen light–graphene interactions. The modulator achieves a modulation depth exceeding 80% and an operating bandwidth greater than 4 THz in the mid-infrared range, enabling efficient signal modulation for free-space optical communication. Importantly, the proposed design alleviates experimental challenges typically associated with the need for high graphene mobility and a wide Fermi energy tuning range in conventional approaches, thereby improving its practical feasibility. Moreover, the approach is scalable to far-infrared and terahertz bands, offering valuable insights for advancing signal modulation technologies across these spectral regions. Full article

The Earth’s Radiation Budget (ERB) is a critical component for understanding the planet’s climate system, as it governs the balance between incoming solar energy and outgoing thermal radiation. Accurate monitoring of the ERB, combined with Ocean Heat Content (OHC) measurements, is essential to assess Earth’s Energy Imbalance (EEI) and its implications for global warming. This paper presents new results on the ERB based on data from the Uvsq-Sat and Inspire-Sat nanosatellite missions, which operated from 2021 to 2024. These satellites constitute the first European constellation demonstrator designed for broadband, Wide Field-Of-View (WFOV) measurements of the ERB. While WFOV instruments provide enhanced temporal and spatial coverage, they do not replace the need for Narrow Field-Of-View (NFOV) measurements, such as those provided by the established Clouds and the Earth’s Radiant Energy System (CERES) instruments. Instead, they are designed to complement them. By using data from both the WFOV constellation and CERES instruments to measure Reflected Solar Radiation (RSR) and Outgoing Longwave Radiation (OLR), we estimate the EEI and monitor its evolution. Our analysis reveals a generally good agreement between Uvsq-Sat and CERES data for EEI from 2021 through the end of 2024. Over this period, EEI derived from Uvsq-Sat averaged +0.87 ± 0.23 ${\mathrm{Wm}}^{-2}$, closely matching the recent CERES trend. Both datasets indicate a peak in EEI in mid-2023, followed by a decline throughout 2024, likely reflecting stabilizing feedbacks triggered by the 2023 El Niño event. Importantly, this short-term decline occurred within a sustained upward trend in EEI since 2013, as shown by CERES observations, with solar activity having a negligible impact. Comparisons with OHC measurements confirm ongoing ocean heat accumulation, consistent with the rising decadal trend in EEI. These insights underscore the importance of continuous, high-frequency observations to capture the complex and rapidly evolving processes influencing Earth’s energy balance. Demonstrations using nanosatellites at different local times illustrate the advantages of small satellite constellations for improved monitoring frequency and coverage, particularly for variables that change over short time scales, such as RSR, also known as Outgoing Shortwave Radiation (OSR). Full article

This work presents the experimental and numerical investigation of a novel acoustic metamaterial based on sustainable and biodegradable components: cork membranes and honeycomb cores made from treated aramid paper. The design exploits the principle of localized resonance induced by tensioned membranes coupled with subwavelength cavities, aiming to achieve high sound absorption at low (250–500 Hz) and mid frequencies (500–1400 Hz) with minimal thickness and environmental impact. Three configurations were analyzed, varying the number of membranes (one, two, and three) while keeping a constant core structure composed of three stacked honeycomb layers. Acoustic performance was measured using an impedance tube (Kundt’s tube), focusing on the normal-incidence sound absorption coefficient in the frequency range of 250–1400 Hz. The results demonstrate that increasing the number of membranes introduces multiple resonances and broadens the effective absorption bandwidth. Numerical simulations were performed to predict pressure field distributions. The numerical model showed good agreement with the experimental data, validating the underlying physical model of coupled mass–spring resonators. The proposed metamaterial offers a low-cost, modular, and fully recyclable solution for indoor sound control, combining acoustic performance and environmental sustainability. These findings offer promising perspectives for the application of bio-based metamaterials in architecture and eco-design. Further developments will address durability, high-frequency absorption, and integration in hybrid soundproofing systems. Full article

This study investigates the propagation characteristics and field distribution of photonic crystals composed of epsilon-near-zero (ENZ) materials and metal cylinders. The research reveals that the cutoff frequency of the photonic crystal formed by combining metal cylinders with an ENZ background is independent of the volume fraction of the metal cylinders and exhibits a stop-band profile within the measured frequency range. This unique behavior is attributed to the scattering of long-wavelength light when the wavelength approaches the effective wavelength range of the ENZ material. Taking advantage of this feature, the study selectively filters specific wavelength ranges from the mid-frequency band by varying the ratio of cylinder radius to lattice constant (R/a). Decreasing the R/a ratio enables the design of waveguide devices that operate over a broader guided wavelength range within the intermediate-frequency band. The findings emphasize the importance of the interaction between light and ENZ materials in shaping the transmission characteristics of photonic crystal structures. Full article

This study aims to develop an integrated wireless monitoring system named MANTiS-32, which leverages an open-source platform to enable autonomous modular operation, high-speed large-volume data transmission via Wi-Fi, and the integration of multiple complex sensors. The MANTiS-32 system is composed of ESP32-based MANTiS-32 hubs connected to eight MPU-6050 sensors each via RS485. Four MANTiS-32 hubs transmit data to a main PC through an access point (AP), making the system suitable for real-time monitoring of modal information necessary for structural performance evaluation. The fundamental performance of the developed MANTiS-32 system was validated to demonstrate its effectiveness. The evaluation included assessments of acceleration and frequency response measurement performance, wireless communication capabilities, and real-time data acquisition between the MANTiS-32 hub and the eight connected MPU-6050 sensors. To assess the feasibility of using MANTiS-32 for performance monitoring, a flexible model cable-stayed bridge, representing a mid- to long-span bridge, was designed. The system’s ability to perform real-time monitoring of the dynamic characteristics of the bridge model was confirmed. A total of 26 MPU-6050 sensors were distributed across four MANTiS-32 hubs, and real-time data acquisition was successfully achieved through an AP (ipTIME A3004T) without any bottleneck or synchronization issues between the hubs. Vibration data collected from the model bridge were analyzed in real time to extract dynamic characteristics, such as natural frequencies, mode shapes, and damping ratios. The extracted dynamic characteristics showed a measurement error of less than approximately 1.6%, validating the high-precision performance of the MANTiS-32 wireless monitoring system for real-time structural performance evaluation. Full article