Abstract Understanding the hydro‐mechanical behavior of faults in clay‐rich formations is essential for earthquake mechanics and underground storage applications. We conducted fully hydro‐mechanically coupled triaxial tests on preserved fault material from scaly clay sections of the Opalinus Clay formation. The faulted rock exhibits no post‐peak weakening and maintains distributed strain accommodation through the reactivation of multiple, sub‐parallel tectonic micro‐shears. The hydro‐mechanical response is stress‐dependent, transitioning from dilative shearing at lower effective consolidation stresses to constant volumetric shearing at higher effective consolidation stresses, eventually resulting in critical state conditions. Shear strength analysis revealed the absence of cohesion in the scaly clay fabric, which reduces the rock's shear strength to below the residual strength of the intact rock. These findings provide direct experimental evidence for distributed, steady‐state shearing in naturally faulted clay shale and highlight the need to incorporate fabric‐dependent behavior into models of fault mechanics.
Yingjun Zhang, Brian B. Barnes, Dennis J. McGillicuddy Jr.
et al.
Abstract Pelagic Sargassum has increased dramatically in the past decade, primarily in the annually recurrent Great Atlantic Sargassum Belt (GASB) that extends from the coast of West Africa to the Gulf of Mexico. Using satellite observations of Sargassum density and mesoscale eddies from 2011 to 2023, we investigate whether more Sargassum can be found in mesoscale eddies. Cyclonic eddies were found to contain 6%–47% more Sargassum (relative to eddy‐free waters) across all selected regions within the GASB, with the highest Sargassum density in their inner cores (<0.5 eddy radius). Impacts of anticyclonic eddies were weaker and varied between regions. In addition, Sargassum enrichment tended to be higher in eddies with greater size or amplitude, such as the North Brazil Current rings and those in the Caribbean Sea. These findings may inform Sargassum mitigation strategies, for example, through physical removal in targeted locations.
Underwater image enhancement techniques typically rely on multiscale feature extraction to restore images degraded by light absorption and scattering. This article challenges that dominant paradigm by demonstrating that a meticulously designed single-scale architecture can achieve highly comparable performance to multiscale counterparts, while significantly reducing model complexity. We propose the single-scale decomposition network (SSD-Net), an innovative framework that explores the full potential of single-scale representations. SSD-Net introduces an asymmetric pipeline to decouple the input into a scene-intrinsic clean layer and a medium-induced degradation layer. This is achieved through two core synergistic modules: first, the parallel feature decomposition block, which utilizes a sparse Transformer and CNNs for dual-branch feature disentanglement, and second, the bidirectional feature communication block, which enables cross-layer residual interactions for mutual refinement. This design preserves decomposition independence while establishing dynamic information pathways, maximizing the efficacy of single-scale features. Compared to state-of-the-art multiscale approaches, SSD-Net achieves superior enhancement quality with substantially fewer parameters and computations.
In practical applications of aerial object detection, real-time uncrewed aerial vehicle (UAV) imagery is often affected by noise, low light, and cloud occlusion, leading to poor image quality. The performance of mainstream UAV object detection algorithms tends to degrade when applied to such imagery, as these models are typically trained and evaluated on clean datasets. To address these challenges, we propose a robust YOLO-based network, YOLO-atrous feature pyramid (AFP), which integrates an AFP module. This allows the model to generalize effectively under various corrupted conditions, despite being trained only on clean data. First, we introduced AFP module, which employs atrous convolutions with varying dilation rates, and integrate it into the path aggregation network to expand the receptive field. This enhancement allows the model to better capture object-background relationships and reduce feature corruption caused by local pixel changes. Second, we propose a robust ResNet-spatial pyramid pooling fast (SPPF) as the backbone network, which retains strong feature extraction capabilities while having fewer residual connections compared to YOLO’s Darknet. This design effectively mitigates the impact of corrupted image features on subsequent feature extraction. To validate the effectiveness of our method, we constructed two new datasets based on the DOTAv1.0 dataset, named DOTA-HC and DOTA-HCloud. Experimental results demonstrate that on the DOTA-HC dataset, YOLO-AFP achieved an mean performance under corruption of 60.8% and an relative performance under corruption (rPC) of 80.3%, outperforming the best real-time detection model by 1.5% and 2%, respectively. On the DOTA-HCloud dataset, YOLO-AFP achieved an rPC of 88.5%, surpassing the top model by 1.1% .
This paper demonstrates a comprehensive assessment of bibliometric analysis of published research on the global impact of urbanization on environmental consequences. Scopus database was used to collect data on the global impact of urbanization on ecosystem research from 2000 to 2023 and scrutinizes the progression of publications, keyword analysis, co-citation of authors, citation of documents, co-authorship of authors, and most efficient and influential authors, countries, and institutions. A total of 4322 research papers (journals) were published during the period (2000–2023). This bibliometric study was carried out with the Vos Viewer software. The study's findings demonstrate that the number of publications has continuously increased between 2000 and 2023. In 2020 and 2022, there were 396 and 635 publications, respectively. The top three influential journals in terms of citations are Remote Sensing of Environment (2415 citations), Ecological Economics (1456 citations), and PLoS (1410). From 2000 to 2023, the most often appearing terms were urbanization (3028), urban area (1111), people (853), land use (769), environmental monitoring (594), environmental effect (570), sustainable development (567), and climate change (534). We created a time series with four periods (2000–2005, 2006–2011, 2012–2017, and 2018–2023) based on the periodic changes, which also shows the trend. In more specific terms, this study demonstrates not just a logical structure but also the development of keywords throughout time. The empirical evidence also shows that while this field initially focused on a few themes, it has since broadened to include the many aspects of urban sustainability. This analysis also identifies the most efficient and influential authors, institutions, and nations in terms of total publishing (TP), proportion of cited publications (PCP), total citation (TC), h-index, and g-index. Yang K is the most prominent author, China and the United States are the most efficient nations, and the Chinese Academy of Science is the most powerful organization. The top two nations by co-authorship are China (40 695 citations and 1527 publications) and the United States (41 119 citations and 833 publications). Additionally, it is noted that while environmental concerns continue to dominate, basic socioeconomic problems like equality, justice, and public participation are underrepresented. Sustainable development indicators, energy, ecologically friendly infrastructure, water, the use of land, and urban planning are prominent subject topics, with the first three exerting a larger influence in shaping the field's growth. This research may be utilized as a resource for people intrigued in learning more about the evaluation of urban sustainability and its advancement.
Hyperspectral image (HSI) band selection (BS) plays a crucial role in HSI dimensionality reduction, aiming to identify a representative subset of bands with minimal redundancy. However, conventional BS approaches primarily operate in the Euclidean domain, often overlooking the structural characteristics of pixels and spectral bands, such as spatial continuity and spectral dependencies. In addition, they handle each HSI as an integrated unit to harness implicit spatial information, disregarding spatial distribution variations across different homogeneous regions. To fully leverage structural information, this study introduces a novel BS method, termed the dual heterogeneous graph convolutional network with enhanced self-representation (ESR-HGCN), for HSI BS. The heterogeneous graph convolutional network (HGCN) and enhanced self-representation (ESR) serve as the two essential components of the proposed ESR-HGCN. To explore spatial features and the potential hidden interactions among spectral bands, we use the HGCN as the backbone network for heterogeneous graph-based HSI BS. Dual graphs at the pixel and band levels are separately constructed and integrated into the ESR module, where a sparsity constraint is enforced and the original Frobenius norm is replaced with <inline-formula><tex-math notation="LaTeX">$\ell _{1}$</tex-math></inline-formula>- and <inline-formula><tex-math notation="LaTeX">$\ell _{2,1}$</tex-math></inline-formula>-norm regularizations to achieve robust BS. Meanwhile, dual graph convolution operations are performed to separately extract spatial and spectral features, thereby seamlessly integrating spectral, spatial, and geometric information, offering significant advantages for HSI BS. Finally, an effective optimization scheme is developed to refine the proposed approach. Experimental findings on representative HSI datasets highlight the superiority of ESR-HGCN over state-of-the-art methods.
In the forefront of quantitative solar physics research using large-aperture ground-based solar optical telescopes, high-contrast observation along with high-accuracy polarimetric measurement in the solar active region are required. In this paper, we propose a novel high-contrast imaging telescope construction with a 60 cm medium aperture, namely, the PAthfinder in Solar Adaptive Telescope (PASAT), in which a deformable secondary mirror is used as the adaptive optical correction device and a symmetrical optical path design is employed, leading to the least Muller matrix polarization instruments. The telescope can provide a high-resolution magnetic field with high accuracy for the solar active regions, as well as high-contrast images with a superior signal-to-noise ratio and photometric accuracy of the solar photosphere and chromosphere. These data will be directly used for a better understanding of the evolution and release of magnetic energy, which will help in improving space weather forecasting. Meanwhile, PASAT will accumulate the relevant techniques for constructing similar, larger solar telescopes in the future.
Anindita Patra, Guillaume Dodet, Seung‐Ki Min
et al.
Abstract This study investigates the contribution of external forcings on global and regional ocean wave height change during 1961–2020. Historical significant wave height (Hs) produced for different CMIP6 external forcings and preindustrial control conditions following the Detection and Attribution Model Intercomparison Project (DAMIP) are employed. The internal variability ranges are compared with different external forcing scenario. Statistically significant linear trends in Hs computed over regional ocean basins are found to be mostly associated with anthropogenic forcings: greenhouse gas‐only (GHG) and aerosol‐only (AER) forcing. For Hs, GHG signals are robustly detected and dominant for most of the global ocean, except over North pacific and South Atlantic, where AER signals are dominant. These results are supported by multi‐model analysis for wind speed. The remarkable increase in Hs over the Arctic (22.3%) and Southern (8.2%) Ocean can be attributed to GHG induced sea‐ice depletion and larger effective fetch along with wind speed increase.
Abstract Polarities of seismic reflections at the discontinuity atop the D" region (PdP and SdS) indicate the sign of the velocity contrast across the D" reflector. Recent studies found PdP polarities matching and opposite those of P and PcP. While anisotropy could explain this behavior, we find that the ratio of the change in S wave velocity over change in P wave velocity (R‐value) can influence polarity behavior of D" reflected P waves. For R‐values exceeding 3, the P wave reverses polarity in the absence of anisotropy while S wave polarity is not influenced by the R‐value. Using sets of one million models for normal mantle and MORB with varying minerals and processes across the boundary, we carry out a statistical analysis (Linear Discriminant Analysis) finding that there is a marked difference in mantle mineralogy to explain R‐values larger and smaller than 3, respectively. Based on our results we can attribute different mineralogy to a number of cases. In particular, we find that when velocities increase across D" and polarities of PdP and SdS are opposite the post‐perovskite phase transition is still the best explanation whereas MORB is the best explanation when PdP and SdS are the same. When the velocities are decreasing, the post‐perovskite phase transition within MORB is the best explanation if PdP and SdS polarities are the same but if PdP and SdS are opposite, our results indicate that primordial material or mantle enriched in bridgmanite can explain the polarity behavior, further constraining mineralogy within the large low seismic velocity provinces.
A marine oil spill is an environmental pollution incident that generally has the attributes of a high speed, widespread, and long duration. It seriously threatens the marine ecological environment and related industries. It is vital to determine the source of the oil leakage so that it may be stopped and related hazards can be reduced. Oil spill accidents in the sea are generally located in offshore and navigation channels. With the rapid development of remote-sensing techniques, oil leak extraction using remote-sensing data has played an essential role in oil spill research. This article proposes a Monte Carlo-based deep Q-transfer-learning network (DQTN) offshore oil leak detection method that uses remote-sensing data. Remote-sensing data are utilized to continuously monitor a marine oil spill on the surface. The estuarine and coastal ocean model is utilized to simulate a marine oil spill event. The deep-Q-network method with offline transferred knowledge is then utilized to determine the marine oil spill source location. In an experiment, based on the Bohai oil spill incident on June 2, 2011, the effectiveness of the remote-sensing-based DQTN marine oil spill search algorithm is verified. The accuracy of the targeted oil spill point is up to 98.97%.
A possibility is that in cosmic background, primordial photon lattice where emerges a way to mass conservation, a photon was disturbed to create a spin then lead to its neighbors consecutively avalanching -- CMB -- into this a small ripple, which inverse spin directions pointing to a world was made of matter or antimatter whichever is parity violation; now cosmos was like an expanding hole -- an isotropic gravity field -- in photon lattice that influenced on everything, so inertia will be partly clarified.
Given the imaging characteristics of synthetic aperture radar (SAR) images and the inherent speckle noise in them, scale-invariant feature transform based algorithms are unable to perform satisfactorily. To improve registration efficiency between SAR images, we propose a robust and efficient registration method with three main contributions. First, considering sudden dark patches appearing in SAR images, we propose the ratio of exponentially weighted average blocks to suppress the sudden dark patches and better adapt to different test images. This new operator called blocks of the ratio of exponentially weighted averages (ROEWA-B) divides the processing windows of ROEWA into blocks, which can not only reduce speckle noise but also retain more edge details compared to ROEWA when sudden dark patches appear. Second, for outlier removal, we present an approach using the minimum moment map to remove erroneous keypoints. Finally, based on the gradient location orientation histogram descriptor, we propose a novel multiscale circle descriptor, which combines scale change information to give weights to feature points at different scales. Experimental results for various thresholds and evaluations demonstrate the advantage and robustness of our method in registration.
<p>Identification of a large-amplitude Alfvén wave decaying into a pair of
ion-acoustic and daughter Alfvén waves is one of the major goals in the
observational studies of space plasma nonlinearity. In this study, the decay
instability is analytically evaluated
in the 2-D wavenumber domain
spanning the parallel and perpendicular directions to the mean magnetic field. The growth-rate determination of
the density perturbations is based on the Hall MHD (magnetohydrodynamic) wave–wave coupling theory for circularly polarized Alfvén waves.
The diagrams of the growth rates versus the wavenumber and propagation angle
derived in analytical studies are replaced by 2-D wavenumber distributions
and compared with the
corresponding wavevector spectrum of density and magnetic field
fluctuations.
The actual study reveals a perpendicular spectral pattern consistent with the result of a previous study based on 3-D hybrid numerical simulations.
The wavevector signature of the decay instability observed in the
two-dimensional wavenumber domain ceases at values of plasma beta
larger than <span class="inline-formula"><i>β</i>=0.1</span>. Growth-rate maps
serve as a useful tool for predictions of the wavevector spectrum of density
or magnetic field fluctuations in various scenarios for the
wave–wave coupling processes developing at different stages in
space plasma turbulence.</p>
The Wufeng-Longmaxi shale in the Sichuan Basin is the only stratum in China to realize commercial development of shale gas. There are some differences in shale gas generation and a lack of direct experimental evidence of the reasons for these differences. Hydrocarbon generation experiments using pyrolysis in a gold tube with low and medium maturity shale and graptolite of O3-S1 were carried out. Gas from remaining oil produced by hydrogen-rich and lipid-rich organic matter such as planktonic algae is the main contributor of shale gas in the Wufeng-Longmaxi formations. The oil generation ability of graptolite is poor, and it can produce gas during the high-maturity and over-mature stages, up to about 20% of the hydrogen-rich and lipid-rich organic matter such as algae. The lower layer of the Wufeng-Longmaxi shale in the Sichuan Basin is superior to the upper layer, which is mainly composed of graptolite, because of abundant hydrogen-rich and lipid-rich organic matter such as phytoplankton. Pure thermal evolution fractionation and the mixture of primary (from kerogen) and secondary (from oil) gas do not cause hydrocarbon gas isotopes to "reverse". Formation uplift, formation water, minerals, metals and other late transformation of hydrocarbons in shale gas may be an important cause of shale gas isotopic "inversion". Carbon isotope "inversion" may be more of a reflection of the later shale gas preservation process.
The discovery of the 2012 extreme melt event across almost the entire surface of the Greenland ice sheet is presented. Data from three different satellite sensors – including the Oceansat‐2 scatterometer, the Moderate‐resolution Imaging Spectroradiometer, and the Special Sensor Microwave Imager/Sounder – are combined to obtain composite melt maps, representing the most complete melt conditions detectable across the ice sheet. Satellite observations reveal that melt occurred at or near the surface of the Greenland ice sheet across 98.6% of its entire extent on 12 July 2012, including the usually cold polar areas at high altitudes like Summit in the dry snow facies of the ice sheet. This melt event coincided with an anomalous ridge of warm air that became stagnant over Greenland. As seen in melt occurrences from multiple ice core records at Summit reported in the published literature, such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the Medieval Warm Period. Given its rarity, the 2012 extreme melt across Greenland provides an exceptional opportunity for new studies in broad interdisciplinary geophysical research.