Search Results (376)

High-speed jet-in-crossflow (JICF) configurations are central to several aerospace applications, including turbine-blade film cooling, thrust vectoring, and fuel or hydrogen injection in combusting or reacting flows. This study employs high-fidelity direct numerical simulations (DNS) to investigate the dynamics of a supersonic jet (Mach 3.73) interacting with a subsonic crossflow (Mach 0.8) at low Reynolds numbers. Three momentum-flux ratios (J = 2.8, 5.6, and 10.2) are considered, capturing a broad range of jet–crossflow interaction regimes. Turbulent inflow conditions are generated using the Dynamic Multiscale Approach (DMA), ensuring physically consistent boundary-layer turbulence and accurate representation of jet–crossflow interactions. Modal decomposition via proper orthogonal decomposition (POD) and spectral POD (SPOD) is used to identify the dominant spatial and spectral features of the flow. Across the three configurations, near-wall mean shear enhances small-scale turbulence, while increasing J intensifies jet penetration and vortex dynamics, producing broadband spectral gains. Downstream of the jet injection, the spectra broadly preserve the expected standard pressure and velocity scaling across the frequency range, except at high frequencies. POD reveals coherent vortical structures associated with shear-layer roll-up, jet flapping, and counter-rotating vortex pair (CVP) formation, with increasing spatial organization at higher momentum ratios. Further, POD reveals a shift in dominant structures: shear-layer roll-up governs the leading mode at high J, whereas CVP and jet–wall interactions dominate at lower J. Spectral POD identifies global plume oscillations whose Strouhal number rises with J, reflecting a transition from slow, wall-controlled flapping to faster, jet-dominated dynamics. Overall, the results demonstrate that the momentum-flux ratio (J) regulates not only jet penetration and mixing but also the hierarchy and characteristic frequencies of coherent vortical, thermal, and pressure and acoustic structures. The predominance of shear-layer roll-up over counter-rotating vortex pair (CVP) dynamics at high J, the systematic upward shift of plume-oscillation frequencies, and the strong analogy with low-frequency shock–boundary-layer interaction (SBLI) dynamics collectively provide new mechanistic insight into the unsteady behavior of supersonic jet-in-crossflow flows. Full article

Ecosystem vulnerability assessment is paramount for local environmental stability and lasting economic progress. This study selects Hubei Province as the research area, applying multi-source spatiotemporal datasets spanning the period 2000–2023. A pressure–state–response (PSR) framework, incorporating 14 distinct indicators, was developed. The selection criteria for these indicators adhered to principles of scientific rigor, all-encompassing scope, statistical representativeness, and practical applicability. The chosen indicators effectively encompass natural, anthropogenic, and socio-economic drivers, aligning with the specific ecological attributes and key vulnerability factors pertinent to Hubei Province. The analytic network process (ANP) method and entropy weighting (EW) method were integrated to ascertain comprehensive weights, thereby computing the ecological vulnerability index (EVI). In the meantime, we analyzed temporal and spatial EVI shifts. Spatial autocorrelation analysis, the geodetic detector, the Theil–Sen median, the Mann–Kendall trend test, and the Grey–Markov model were employed to elucidate spatial distribution, driving factors, and future trends. Results indicate that Hubei Province exhibited mild ecological vulnerability from 2000 to 2023, but with a notable deteriorating trend: extreme vulnerability areas expanded from 0.34% to 0.94%, while moderate and severe vulnerability zones also increased. Eastern regions demonstrate elevated vulnerability, but they were lower in the west, correlating with human activity intensity. The global Moran’s I index ranged from 0.8579 to 0.8725, signifying a significant positive spatial correlation of ecological vulnerability, with the highly vulnerable areas concentrated in regions with intense human activities, while the less vulnerable areas are located in ecologically intact areas. Habitat quality index and carbon sinks emerged as key drivers, possibly stemming from the forest–wetland composite ecosystem’s high dependence on water conservation, biodiversity maintenance, and carbon storage functions. Future projections based on Grey–Markov models indicate that ecological fragility in Hubei Province will exhibit an upward trend, with ecological conservation pressures continuing to intensify. This research offers a preliminary reference basis of grounds for ecological zoning, as well as sustainable regional development in Hubei Province, while also providing a theoretical and practical framework for constructing an ecological security pattern within the Yangtze River Economic Belt (YREB) and facilitating ecological governance in analogous river basins globally, thereby contributing to regional sustainable development goals. Full article

The giant atom paradigm, where a single quantum emitter couples to a continuum at multiple discrete points, has enabled unprecedented control over light-matter interactions, including decoherence-free subspaces and chiral emission. However, realizing these non-local effects beyond the microwave regime remains a significant challenge due to the diffraction limit. Here, we theoretically propose a photonic analog of giant atoms operating at optical frequencies, utilizing a quantum emitter resonantly coupled to a pair of spatially separated single-mode cavities interacting with a common 1D photonic continuum. By rigorously deriving the effective non-Hermitian Hamiltonian and integrating out the bath degrees of freedom, we demonstrate that the interference between cavity-mediated emission pathways leads to the formation of robust Bound States in the Continuum (BICs). These interference-induced dark states allow for the infinite trapping of excitation within the emitter-cavity subsystem, effectively shielding it from radiative decay. Our results extend the giant atom toolbox to the optical domain, offering a scalable architecture for integrated quantum photonics and quantum interconnects. Full article

The “Anthropocene” has witnessed unprecedented challenges to the sustainability of human development. Resolving the contradiction between humans and land and achieving coordinated development has become a pressing issue across many disciplines in the era of ecological civilization. This study adopts an ecological perspective to investigate the symbiotic relationship between humans and land in the “Five Poles” urban agglomerations of the Yellow River Basin. In this framework, ecosystem service value and human well-being are employed to quantify “human” and “land,” respectively. The Lotka–Volterra model is then applied as a structural analogy to quantify the dynamic interactions within this symbiotic relationship, treating ecosystem service value and human well-being as two interdependent systems with feedback mechanisms. For the “Five Poles” urban agglomerations in the Yellow River Basin, the ecosystem service and human well-being pressures, along with the symbiosis indices for the period 2011–2020, were calculated and categorized. The results were first subjected to a visual analysis to describe the spatial patterns. Subsequently, spatial autocorrelation analysis was employed to quantitatively investigate the clustering and heterogeneity of these patterns, thereby systematically elucidating the spatial characteristics of human–land symbiosis in the Yellow River Basin. The findings indicate that: (1) the human–land relationship in the Yellow River Basin has evolved from partial interaction to mutualism, reflecting improved coordination within the regional human–land system. (2) The evaluation of this relationship improved between 2011–2015 and 2016–2020. (3) High-evaluation areas have shifted from east to west, exhibiting distinct agglomeration characteristics. Full article

Soil heavy metal contamination poses significant risks to ecological safety and human health, particularly in rapidly industrializing cities. Effectively identifying pollution sources is crucial for risk management and remediation. GIS coupled with data mining techniques, provide a powerful tool for quantifying and visualizing these sources. This study investigates the concentration, spatial distribution, and sources of heavy metals in urban soils of Bengbu City, an industrial and transportation hub in eastern China. A total of 139 surface soil samples from the urban core were analyzed for nine heavy metals. Using integrated GIS and PCA-APCS-MLR data mining techniques, we systematically determined their contamination characteristics and apportioned sources. The results identified widespread Hg enrichment, with concentrations exceeding background levels at all sampling sites, and a Cd exceedance rate of 28.06%, leading to a moderate ecological risk level overall. Spatial patterns revealed significant heterogeneity. Quantitative source apportionment identified four primary sources: industrial source (37.1%), which was the dominant origin of Cr, Cu, and Ni, primarily associated with precision manufacturing and metallurgical activities; mixed source (26.7%) governing the distribution of Mn, As, and Hg, mainly from coal combustion and the natural geological background; traffic source (22.3%) significantly contributing to Pb and Zn; and a specific cadmium source (13.9%) potentially originating from non-ferrous metal smelting, electroplating, and agricultural activities. These findings provide a critical scientific basis for targeted pollution control and sustainable land-use management in analogous industrial cities. Full article

Against the backdrop of intensifying global climate change and expanding human encroachment into mountainous regions, landslides have increased markedly in both frequency and destructiveness, emerging as a key risk to socio-ecological security and development in mountain areas. Rigorous assessment and forward-looking prediction of landslide disaster vulnerability (LDV) are essential for targeted disaster risk reduction and regional sustainability. However, existing studies largely center on landslide susceptibility or risk, often overlooking the dynamic evolution of adaptive capacity within affected systems and its nonlinear responses across temporal and spatial scales, thereby obscuring the complex mechanisms underpinning LDV. To address this gap, we examine Yunnan Province, a landslide-prone region of China where intensified extreme rainfall and the expansion of human activities in recent years have exacerbated landslide risk. Drawing on the vulnerability scoping diagram (VSD), we construct an exposure–sensitivity–adaptive capacity assessment framework to characterize the spatiotemporal distribution of LDV during 2000–2020. We further develop a multi-model, multi-scale integrated prediction framework, benchmarking the predictive performance of four machine learning algorithms—backpropagation neural network (BPNN), support vector machine (SVM), random forest (RF), and XGBoost—across sample sizes ranging from 2500 to 360,000 to identify the optimal model–scale combination. From 2000 to 2020, LDV in Yunnan declined overall, exhibiting a spatial pattern of “higher in the northwest and lower in the southeast.” High-LDV areas decreased markedly, and sustained enhancement of adaptive capacity was the primary driver of the decline. At approximately the 90,000-cell grid scale, XGBoost performed best, robustly reproducing the observed spatiotemporal evolution and projecting continued declines in LDV during 2030–2050, albeit with decelerating improvement; low-LDV zones show phased fluctuations of “expansion followed by contraction”, whereas high-LDV zones continue to contract northwestward. The proposed multi-model, multi-scale fusion framework enhances the accuracy and robustness of LDV prediction, provides a scientific basis for precise disaster risk reduction strategies and resource optimization in Yunnan, and offers a quantitative reference for resilience building and policy design in analogous regions worldwide. Full article

Fin-de-siècle decadence—marked by symbolism, dandyism, aesthetic withdrawal, and defiance of bourgeois norms—has long been reimagined beyond its original European contours. Vladimir Nabokov’s Ada or Ardor: A Family Chronicle exemplifies this transformation by extending decadent aesthetics into the domains of modern physics, perception, and experimental temporality. While Ada is often read as a retreat into aestheticism, this paper argues that Nabokov reconfigures decadence through a radical engagement with time, science, and sensual consciousness. Through Van Veen’s philosophical treatise “The Texture of Time”—a burlesque of Bergsonian introspection—Nabokov constructs a vision of purified, de-spatialized, and self-reflexive time that destabilises the boundary between decadent and modernist aesthetics. The novel fuses metaphysical decadence with Bergsonian duration, creating a poetic meditation on temporality as both perceptual and sensual experience. Through intricate linguistic play—anagrams, palindromes, and recursive narrative structures—Nabokov fashions a labyrinthine temporality that mirrors the paradoxes of the decadent imagination: time that is linear yet cyclical, finite yet infinitely recurrent. Positioning Ada within broader debates on the afterlife of decadence, this paper examines how Nabokov preserves the movement’s aesthetic essence while transforming it through scientific analogy and linguistic experimentation. Ada simultaneously honours and subverts decadence, reimagining its hedonism and nostalgia within a cosmological framework that renders temporality itself a site of aesthetic play and metaphysical desire. Full article

How does digital technology mediate decision-making and shape our understanding of disaster recovery? I address this question by examining both the administrative and cinematic uses of digital images in the reconstruction process following the 2011 Great East Japan Earthquake. Post-disaster digital mediation is characterized by the administrative use of what has been termed “operational images,” designed not for interpretation but for action, particularly in disaster response and prevention. I connect the social and ethical dimensions of post-disaster recovery with the ontological dimensions of the technological characteristics of digital photography. By comparing Japanese independent filmmaker Haruka Komori’s digital filmmaking practice with the operational images utilized by administrative and research bodies, I aim to demonstrate how her particular digital aesthetics elicit the latent capacity of the “digital unconscious” and offer new modes of perceiving post-disaster recovery, in contrast to both other forms of post-disaster digital mediation and to analog photography. Through close analyses, I argue that her work articulates an alternative vision of recovery—one rooted not in spatial management or predictive planning, but in physical attachment to place, trust in the future, and imaginative engagement with survivors and the dead. Full article

This study presents the digitization and integration of Kazakhstan’s legacy gravimetric maps at a scale of 1:200,000 into a modern geospatial database using ArcGIS. The primary objective was to convert analog gravity data into a structured, queryable, and spatially analyzable digital format to support contemporary geoscientific applications, including geoid modeling and regional geophysical analysis. The project addresses critical gaps in national gravity coverage, particularly in underrepresented regions such as the Caspian Sea basin and the northeastern frontier, thereby enhancing the accessibility and utility of gravity data for multidisciplinary research. The methodology involved a systematic workflow: assessment and selection of gravimetric maps, raster image enhancement, georeferencing, and digitization of observation points and anomaly values. Elevation data and terrain corrections were incorporated where available, and metadata fields were populated with information on the methods and accuracy of elevation determination. Gravity anomalies were recalculated, including Bouguer anomalies (with densities of 2.67 g/cm³ and 2.30 g/cm³), normal gravity, and free-air anomalies. A unified ArcGIS geodatabase was developed, containing spatial and attribute data for all digitized surveys. The final deliverables include a 1:1,000,000-scale gravimetric map of free-air gravity anomalies for the entire territory of Kazakhstan, a comprehensive technical report, and supporting cartographic products. The project adhered to national and international geophysical mapping standards and utilized validated interpolation and error estimation techniques to ensure data quality. The validation process by the modern gravimetric surveys also confirmed the validity and reliability of the digitized historical data. This digitization effort significantly modernizes Kazakhstan’s gravimetric infrastructure, providing a robust foundation for geoid modeling, tectonic studies, and resource exploration. Full article

During preliminary reconnaissance at a hydropower station site in Southwestern China, a unique phenomenon of deep-seated fractures was identified within the slopes, which were symmetrically developed on both banks. These features occur within unloading zones and manifest as tensile fractures with deep-seated fractures exhibiting unloading characteristics. This study systematically analyzes the spatial distribution, developed patterns, and structural attributes of these deep fractures. Through numerical model of stress field dynamics during valley evolution, we investigate the relationship between stress states and deep fracture formation. Research demonstrates that these fractures result from energy release through unloading at stress-concentration zones in slope interiors, driven by rapid valley incision under high in situ stress conditions. This process is further conditioned by specific slope geometries, rock mass structures, and geomorphic settings. Crucially, river incision rate governs fracture depth, while the number of incision cycles significantly controls fracture aperture. These findings provide a theory for understanding deep-seated slope failure mechanisms and engineering mitigation in analogous geological environments. Full article

Background: Tracheal breathing sounds (TBS) have demonstrated strong potential as a non-invasive, wakefulness-based diagnostic tool for obstructive sleep apnea (OSA); yet the relationship between specific upper airway anatomical features and the resulting TBS spectra remains insufficiently understood. This study aims to enhance the diagnostic utility of TBS in OSA by investigating how the upper airway anatomy influences TBS spectral characteristics. Method: Patient-specific computational models of the upper airway were reconstructed from high-resolution CT scans of a healthy subject and an individual with OSA. Additional variants were generated with targeted constrictions at the velopharynx, oropharynx, and trachea, based on clinically reported anatomical ranges. Airflow dynamics were simulated using Large Eddy Simulation (LES), and the resulting acoustic responses were computed via Lighthill’s acoustic analogy within a hybrid aero-acoustic framework. Results: Oropharyngeal constriction generated the most spatially concentrated vorticity patterns among single-region constricted models. Airway Resistance analysis revealed that severe velopharyngeal and oropharyngeal constrictions contributed most to regional airway resistance. Spectral analysis showed that velopharyngeal narrowing produced a progressive downward shift in the third resonance peak (1000–1700 Hz), while oropharyngeal narrowing induced an upward shift of the third peak and a downward shift of the fourth peak (1700–2500 Hz). These frequency shifts were attributed to the effective role of acoustic mass and airway compliance. Conclusions: Anatomical modifications of the upper airway produce region-specific changes in both flow and acoustic responses. These findings support the use of TBS spectral analysis for non-invasive localization of airway obstructions in OSA. Full article

Low-frequency noise, the most critical noise frequency band affecting human physical and mental health, poses a significant challenge for effective control in spatially constrained building environments. The shunt loudspeaker offers a novel solution to control low-frequency noise. Unlike traditional methods, it does not rely on large cavity depth but only requires the adjustment of parameters or structure of the shunt circuit. However, most shunt loudspeakers utilize analog shunt technology, which leads to instability and inaccuracy owing to the negative impedance converter circuit and parasitic impedance in analog electronic components. The paper proposes a tunable low-frequency sound absorber utilizing a combined array of hybrid digital–analog shunt loudspeakers. The theoretical model was established based on the electro-mechanical–acoustic analogy method and parallel impedance method. Numerical simulations and experimental studies were performed to verify the proposed model. The results demonstrate that the proposed absorber can achieve excellent low-frequency sound absorption capability by designing only a few digital filter parameters, while simultaneously enhancing the stability and accuracy of the system. This study presents a promising innovative method for low-frequency noise control at sub-wavelength scales, providing a space-efficient solution. Full article

This study investigated the compatibility of lead with distinct crystal planes of Fe with a body-centered cubic (bcc) crystal structure and Ni with a face-centered cubic (fcc) crystal structure using molecular dynamics (MD) simulation. It was found that corrosion anisotropy depends mainly on the role of different crystal planes in regulating the spatial distribution of liquid lead. The essence of this regulation can be attributed to the interaction between the crystal plane and the liquid lead atoms. In consequence of the periodic arrangement of the crystal planes, the close-packed plane exhibits the highest atomic density and the widest interplanar distance. This configuration minimizes the interaction of the liquid lead atoms with the other crystal planes, thereby maximizing the regulatory effect on the distribution of the liquid lead atoms. The regulatory effect results in the formation of a regular layer-like distribution of the lead atoms, with a spacing between layers that is analogous to the crystal planes. This distribution mechanism effectively prevents the dissolution of atoms on the crystal surface into the liquid lead side by separating the atoms of the solid–liquid system from each other. Accordingly, for pure metals with a bcc crystal structure, corrosion resistance anisotropy indicates that the (111) plane is the most susceptible to corrosion, followed by the (001) plane, and the close-packed plane of (110) exhibits the most corrosion-resistant properties. As for fcc crystals, the corrosion resistance of the distinct planes is ordered as follows: (111) > (001) > (110). Full article

Background: Tinnitus has been increasingly reported during the COVID-19 pandemic, following both infection and vaccination. While these reports suggest that pandemic-related factors may influence the onset or worsening of tinnitus, the perceptual characteristics and functional consequences of such cases remain poorly understood. This study examined the nature, severity, and communication-related impact of self-reported tinnitus following COVID-19 vaccination. Methods: A total of 770 adults who self-reported new or worsened tinnitus after vaccination completed a structured online survey between August 2021 and May 2023. Standardized instruments included the Tinnitus Functional Index (TFI), the Speech, Spatial and Qualities of Hearing Scale (SSQ), and visual analog scales assessing loudness discomfort and hyperacusis-related symptoms. Analyses included descriptive statistics, chi-square tests, t-tests, and correlation matrices. Results: Respondents reported moderate to severe tinnitus-related distress, with the greatest impacts on emotional control, sleep, and relaxation. Many described communication difficulties in noisy or multi-talker environments, despite relatively preserved spatial hearing and sound quality. A substantial subset endorsed hyperacusis symptoms, including sound-induced annoyance, fear, and intolerance. Correlation analyses revealed strong associations between emotional, cognitive, and auditory domains, underscoring the multidimensional burden of tinnitus in this population. Conclusions: Self-reported tinnitus after COVID-19 vaccination was associated with distress, sleep disruption, and communication difficulties, mirroring patterns commonly observed in tinnitus more broadly. Although causality cannot be determined, these findings highlight the importance of comprehensive audiological and psychological assessment for individuals reporting auditory complaints after vaccination and support the inclusion of functional hearing outcomes in tinnitus evaluation protocols. Full article

Massive Multiple-Input Multiple-Output (MIMO) systems with hundreds or thousands of antenna elements are fundamental to next-generation wireless networks, promising unprecedented spectral efficiency through spatial multiplexing and beamforming. However, the computational burden of channel state information (CSI) acquisition and processing scales dramatically with array size, creating a critical bottleneck for practical deployments. While previous works demonstrated that Fast Fourier Transform (FFT)-based beamspace processing can exploit the inherent angular sparsity of wireless channels to compress CSI feedback, the digital implementation requires intensive computations that become prohibitive for ultra-large arrays. This paper presents an analog alternative using Butler matrices—passive beamforming networks that realize the Discrete Fourier Transform in hardware—combined with RF switching circuits to select only dominant angular components. We provide a comprehensive analysis of Butler matrix architectures for arrays up to 32 × 32 elements, characterizing insertion losses across different technologies (microstrip, substrate-integrated waveguide, and waveguide) and operating frequencies (10–30 GHz). The proposed system incorporates parallel power sensing with Winner-Take-All circuits for sub-microsecond beam selection, drastically reducing the number of active RF chains. Full-wave simulations and capacity evaluations at 12 and 30 GHz demonstrate that the Butler-based approach achieves comparable performance to FFT methods while offering significant advantages in power consumption and processing latency. For a 256 × 256 array, FFT computation requires 0.36 ms compared to near-instantaneous analog processing, making Butler matrices particularly attractive for real-time massive MIMO systems. These findings establish Butler matrix front-ends as a practical pathway toward scalable, energy-efficient beamspace processing in 6G networks. Full article