Search Results (60)

Phase stability at low radio frequencies is severely impacted by ionospheric propagation delays. Radio interferometers such as the giant metrewave radio telescope (GMRT) are capable of detecting changes in the ionosphere’s total electron content (TEC) over larger spatial scales and with greater sensitivity compared to conventional tools like the global navigation satellite system (GNSS). Thanks to its unique design, featuring both a dense central array and long outer arms, and its strategic location, the GMRT is particularly well-suited for studying the sensitive ionospheric region located between the northern peak of the equatorial ionization anomaly (EIA) and the magnetic equator. In this study, we observe the bright flux calibrator 3C48 for ten hours to characterize and study the low-latitude ionosphere with the upgraded GMRT (uGMRT). We outline the methods used for wideband data reduction and processing to accurately measure differential TEC ($\delta \mathrm{TEC}$) between antenna pairs, achieving a precision of< mTECU (1 mTECU = ${10}^{-3}$ TECU) for central square antennas and approximately mTECU for arm antennas. The measured $\delta \mathrm{TEC}$ values are used to estimate the TEC gradient across GMRT arm antennas. We measure the ionospheric phase structure function and find a power-law slope of $\beta =1.72\pm 0.07$, indicating deviations from pure Kolmogorov turbulence. The inferred diffractive scale, the spatial separation over which the phase variance reaches $1{\mathrm{rad}}^2$, is ∼6.66 km. The small diffractive scale implies high phase variability across the field of view and reduced temporal coherence, which poses challenges for calibration and imaging. Full article

The Qigebulake Formation in the northwestern Tarim Basin records high-frequency oolitic tidal flat cycles formed during the Upper Ediacaran, a period marked by tectonic, volcanic, and hydrothermal events. This study presents a detailed petrographic and geochemical characterization of these cycles, focusing on their lithofacies development and implications for regional geological processes. Seven microfacies were identified, ranging from oolitic dolostone and dolothrombolite to siliciclastic dolomudstone and mudstone. Elemental trends indicate a systematic decline in SiO₂, Al₂O₃, and TiO₂ content with decreasing siliciclastic input, suggesting a shallowing-upward sequence. Volcaniclastic quartz grains, exhibiting embayed textures and bright-blue cathodoluminescence, are reported here for the first time in the Ediacaran of Tarim, supporting synsedimentary volcanic input. Positive δEu anomalies, coupled with low Al/(Al+Fe+Mn) and elevated Fe₂O₃/TiO₂ and MnO/TiO₂ ratios, reveal hydrothermal influence in upper-cycle dolostones. These signatures, combined with regional stratigraphy, suggest that the Qigebulake tidal flat records the interplay between deposition, volcanism, and fluid migration during the late Ediacaran. The findings provide new constraints on the evolution of peritidal environments and inform deep carbonate reservoir assessments in Tarim and similar cratonic basins. Full article

The accurate identification of coal and rock at the mining face is often hindered by adverse underground imaging conditions, including poor lighting and strong reflectivity. To tackle these issues, this work introduces a recognition framework specifically designed for underground environments, leveraging joint migration and enhancement of multidimensional and full-scale visual representations. A Transformer-based architecture is employed to capture global dependencies within the image and perform reflectance component denoising. Additionally, a multi-scale luminance adjustment module is integrated to merge features across perceptual ranges, mitigating localized brightness anomalies such as overexposure. The model is structured around an encoder–decoder backbone, enhanced by a full-scale connectivity mechanism, a residual attention block with dilated convolution, Res2Block elements, and a composite loss function. These components collectively support precise pixel-level segmentation of coal–rock imagery. Experimental evaluations reveal that the proposed luminance module achieves a PSNR of 21.288 and an SSIM of 0.783, outperforming standard enhancement methods like RetinexNet and RRDNet. The segmentation framework achieves a MIoU of 97.99% and an MPA of 99.28%, surpassing U-Net by 2.21 and 1.53 percentage points, respectively. Full article

This paper introduces a method of monitoring infrared channel calibration stability through direct comparison of calibrated radiances by two Advanced Baseline Imager (ABI) on two geostationary (GEO) platforms. This GEO-GEO comparison is based on radiances in the overlapping area observed by the two ABIs, pixel by pixel, at approximately the same time, location, spectrum, and viewing zenith angle. It was initially developed for GOES-17 and subsequent GOES missions to validate the ABI’s calibration around its local midnight—a subject of particular interest for instruments on three-axis stabilized geostationary satellites. With the cryocooler anomaly of the GOES-17 ABI, however, the GEO-GEO comparison became an indispensable tool to characterize GOES-17 ABI infrared (IR) channel calibration with high frequency, low uncertainty, and in near real time, providing critical feedback to root cause investigation and mitigation options. Later, the GEO-GEO comparison was applied to the GOES-18 ABI as originally intended and was proved successful. It confirms that, with few exceptions, radiometric calibration for all ABIs is stable to within 0.1 K when the radiance fluctuation is converted to the brightness temperature at 300 K. Full article

In the process of mosaicking regional synthetic aperture radar (SAR) intensity images, multiple images with significant brightness anomalies can cause a considerable number of pixels to exceed the grayscale quantization range. Applying traditional color harmonization methods increases this issue, causing a loss of brightness information. We propose a multi-objective gray consistency correction method designed explicitly for mosaicking regional SAR intensity images with brightness anomalies to address this. We constructed a two-objective optimization model to ensure regional image gray consistency and mitigate brightness information loss. The truncation values of brightness anomaly images were selected as decision variables, maximizing the overall gray consistency of overlapping image pairs and minimizing the number of pixels with grayscale values that were out of bounds as the objective functions. To synchronously solve the truncation values of brightness anomaly images and linear stretch parameters of all images, a hybrid framework that combines the non-dominated sorting genetic algorithm II (NSGA-II) with the quadratic programming (QP) algorithm was proposed. Two large-area experimental results show that the proposed method achieves a balanced optimization between gray consistency and brightness information loss for regional SAR intensity image mosaicking. Compared with the traditional method, our method reduces brightness information loss by 99.552–99.647% and 99.973–99.969%, respectively, while maintaining better peak signal-to-noise ratio performance. Full article

Lunar swirls are enigmatic features on the Moon’s surface, and their formation remains debated. Previous studies suggest that the distinctive spectral characteristics of lunar swirls result from the asymmetric space weathering between their bright markings (on-swirl) and dark surrounding background (off-swirl) regions. Nanophase iron (npFe⁰), as the product of space weathering, directly reflects this varying degree of space weathering. In this study, we investigated the formation of lunar swirls from the perspective of the npFe⁰ distribution across five lunar swirls using Chang’e-1 (CE-1) Interference Imaging Spectrometer (IIM) data. Our results show that (1) on-swirl regions exhibit an obvious lower npFe⁰ abundance compared to their backgrounds; (2) the relationship between the npFe⁰ abundance in swirl dark lanes and the off-swirl regions is associated with different stages of space weathering; (3) the difference in the npFe⁰ abundance between on-swirl regions and off-swirl fresh craters could be due to their different weathering processes; and (4) there is a correlation between npFe⁰, water content, and the strength of magnetic anomalies related to lunar swirls. These findings support the view that the process of solar wind deflection leads to the preservation of swirl surfaces with reduced space weathering and provide a new perspective for comparing different swirl formation models. Full article

Effectively identifying and preventing anomalies in the melt process significantly enhances production efficiency and product quality in industrial manufacturing. Consequently, this paper proposes a study on a melt anomaly identification system for pelletizers using autoencoder technology. It discusses the challenges of detecting anomalies in the melt extrusion process of polyester pelletizers, focusing on the limitations of manual monitoring and traditional image detection methods. This paper proposes a system based on autoencoders that demonstrates effectiveness in detecting and differentiating various melt anomaly states through deep learning. By randomly altering the brightness and rotation angle of images in each training round, the training samples are augmented, thereby enhancing the system’s robustness against changes in environmental light intensity. Experimental results indicate that the system proposed has good melt anomaly detection efficiency and generalization performance and has effectively differentiated degrees of melt anomalies. This study emphasizes the potential of autoencoders in industrial applications and suggests directions for future research. Full article

The spatiotemporal and cloud features of the extreme rainfall under the warm and cold upper-level anomalies over the central Yungui Plateau (YGP) were investigated using the hourly rain gauge records, ERA5 reanalysis data, TRMM, and Fengyun satellite data, aiming to refine the understanding of different types of extreme rainfall. Extreme rainfall under an upper-level negative temperature anomaly (cold events) presents stronger convective cloud features when compared with the positive temperature anomaly (warm events). The maximum rainfall intensity and duration in cold events is much larger than that of warm events, while the brightness temperature of the cloud top is lower, and the ratio of convective rainfall is higher. In cold events, the middle-to-upper troposphere is dominated by a cold anomaly, and an unstable configuration with upper (lower) cold (warm) anomalies is observed around the central YGP. Although the upper-level temperature anomaly is positive, the anomalous divergence and convergence of southerly and northerly winds, as well as the strong moisture center and upward motions, are also found over the central YGP in warm events. The stronger atmospheric instability and higher convective energy under the upper-level cold anomalous circulation are closely associated with the rainfall features over the central YGP. The results indicate that the upper tropospheric temperature has significant influences on extreme rainfall, and thus more attention should be paid to the upper tropospheric temperature in future analyses. Full article

This study presents the spatio–temporal evolution of the electric and magnetic fields recorded by the China Seismo–Electromagnetic Satellite (CSES) and the thermal infrared remote sensing data observed by the Chinese stationary meteorological satellites Feng Yun–2G (FY–2G) associated with the 2021 Mw7.3 Maduo earthquake. Specifically, we analyzed the power spectrum density (PSD) data of the electric field in the extremely low frequency (ELF) band, the geomagnetic east–west vector data, and the temperature of brightness blackbody (TBB) data to investigate the spatio–temporal evolution characteristics under quiet space weather conditions (Dst > −30 nT and Kp < 3). Results showed that (1) the TBB radiation began to increase notably along the northern fault of the epicenter ~1.5 months prior to the occurrence of the earthquake. It achieved its maximum intensity on 17 May, and the earthquake occurred as the anomalies decreased. (2) The PSD in the 371 Hz–500 Hz and 700 Hz–871 Hz bands exhibited anomaly perturbations near the epicenter and its magnetic conjugate area on May 17, with particularly notable perturbations observed in the latter. The anomaly perturbations began to occur ~1 month before the earthquake, and the earthquake occurred as the anomalies decreased. (3) Both the magnetic –east–west component vector data and the ion velocity Vx data exhibited anomaly perturbations near the epicenter and the magnetic conjugate area on 11 May and 16 May. (4) The anomaly perturbations in the thermal infrared TBB data, CSES electric field, and magnetic field data all occurred within a consistent perturbation time period and spatial proximity. We also conducted an investigation into the timing, location, and potential causes of the anomaly perturbations using the Vx ion velocity data with magnetic field –east–west component vector data, as well as the horizontal –north–south and vertical component PSD data of the electric field with the magnetic field –east–west component vector data. There may be both chemical and electromagnetic wave propagation models for the “lithosphere—atmosphere—ionosphere” coupling (LAIC) mechanism of the Maduo earthquake. Full article

The Ordovician thick dolostone in Shuntogol area of the Tarim Basin has the potential to form a large-scale reservoir, but its genesis and reservoir development model are still unclear. Starting from a sedimentary sequence, this study takes a batch of dolostone samples obtained from new drilling cores in recent years as the research object. On the basis of core observation and thin section identification, trace elements, cathodoluminescence, carbon and oxygen isotopes, rare earth elements, and X-ray diffraction order degree tests were carried out to discuss the origin of the dolomite and summarize the development model of the dolostone reservoir. The analysis results show that the Ordovician dolomite in the study area had a good crystalline shape, large thickness, high Fe and Mn values, and mostly showed bright red light or bright orange–red light under cathode rays. The ratio of δ¹⁸O values to seawater values at the same time showed a negative bias; the δCe values were negative anomalies, the δEu values were positive anomalies, and the order degree was high. This indicates that the dolomitization process occurred in a relatively closed diagenetic environment. The Ordovician carbonate rocks in the study area were low-lying during the sedimentary period, and with the rise of sea level, the open platform facies continued to develop. When the Middle and Lower Ordovician series entered the burial stage, the main hydrocarbon source rocks of the lower Cambrian Series entered the oil generation peak, and the resulting formation overpressure provided the dynamic source for the upward migration of the lower magnesium-rich fluid, and the dolomitization fluid entered the karst pore system in the target layer to produce all the dolomitization. This set of dolostone reservoirs is large in scale and can be used as a favorable substitute area for deep carbonate exploration for continuous study. Full article

Naples is the most densely populated Italian city (7744 inhabitants per km²). It is located in a particular geological context: the presence of Mt Vesuvius characterizes the eastern part, and the western part is characterized by the presence of the Phlegrean Fields, making Naples a high-geothermal-gradient region. This endogenous heat, combined with the anthropogenic heat due to intense urbanization, has defined Naples as an ideal location for Surface Urban Heat Island (SUHI) analysis. SUHI analysis was effectuated by acquiring the Land Surface Temperature (LST) over Naples municipality by processing Landsat 8 (L8) Thermal Infrared Sensor (TIRS) images in the 2013–2023 time series by employing Google Earth Engine (GEE). In GEE, two different approaches have been followed to analyze thermal images, starting from the Statistical Mono Window (SMW) algorithm, which computes the LST based on the brightness temperature (Tb), the emissivity value, and the atmospheric correction coefficients. The first one is used for the LST retrieval from daytime images; here, the emissivity component is derived using, firstly, the Normalized Difference Vegetation Index (NDVI) and then the Vegetation Cover Method (VCM), defining the Land Surface Emissivity (LSɛ), which considers solar radiation as the main source of energy. The second approach is used for the LST retrieval from nighttime images, where the emissivity is directly estimated from the Advance Spaceborne Thermal Emission Radiometer database (ASTER-GED), as, during nighttime without solar radiation, the main source of energy is the energy emitted by the Earth’s surface. From these two different algorithms, 123 usable daytime and nighttime LST images were downloaded from GEE and analyzed in Quantum GIS (QGIS). The results show that the SUHI is more concentrated in the eastern part, characterized by intense urbanization, as shown by the Corine Land Cover (CLC). At the same time, lower SUHI intensity is detected in the western part, defined by the Land Cover (LC) vegetated class. Also, in the analysis, we highlighted 40 spots (10 hotspots and 10 coldspots, both for daytime and nighttime collection) that present positive or negative temperature peaks for all the time series. Due to the huge amount of data, this work considered only the five representative spots that were most representative for SUHI analysis and determination of thermal anomalies in the urban environment. Full article

Delineating the process of hydrothermal alteration is crucial for effectively enhancing exploration strategies and better understanding the gold mineralization process. Rutile, with its capacity to accommodate a wide range of trace elements including high-field-strength elements and base metals, serves as a reliable fluid tracer in ore systems. As one of the most significant gold ore concentrations globally, Jiaodong boasts a gold reserve exceeding 5500 t. The Xincheng gold deposit is a world-class high-grade mine, boasting a proven gold reserve exceeding 200 t, and stands as one of the largest altered-type gold deposits in the vast gold province of the Jiaodong Peninsula, Eastern China. In this study, rutile (Rt1,2,3) was identified in the K-feldspar alteration, sericitization, and pyrite–sericite–quartz alteration stages of the Xincheng gold deposit in Jiaodong based on petrographic characteristics. Rt1 coexists with hydrothermal K-feldspar and quartz, while Rt2 coexists with minerals such as sericite, quartz, muscovite, and pyrite. Rt3 is widely distributed in hydrothermal veins and is primarily associated with minerals including quartz, pyrite, chalcopyrite, and sericite. Raman spectroscopy, EPMA, and LA-ICP-MS analysis were conducted to investigate the characteristics and evolution of altered hydrothermal fluids. This study indicates that the Zr vs. W and Nb/V vs. W diagrams suggest that Rt1 is of magmatic–hydrothermal origin, while Rt2 and Rt3 are of metamorphic–hydrothermal origin. Notably, the W content in Rt2 and Rt3 is significantly higher than in Rt1 (<100 ppm), suggesting a close relationship between the W content in rutile and mineralization. The three types of rutile exhibit significantly different concentrations of trace elements such as W, V, Nb, Zr, Sn, and Fe, displaying distinct bright spots and elemental zoning characteristics in backscattered electron images and surface scans. These features arise from the isomorphic substitution of Ti⁴⁺. While Rt1 exhibits no significant element exchange with the hydrothermal fluids, Rt2 and Rt3 show a stronger substitution of W, Nb, V, and Fe, indicating a gradual enrichment of F and Cl in the fluids. This process activates and transports these elements into the fluids, leading to their continuous accumulation within the system. From Rt1 to Rt3, the increasing concentrations of Fe and W, along with the negative Eu anomaly, suggest a decrease in fluid temperature and oxygen fugacity during the alteration and mineralization process. The gradual increase in the contents of REEs and high-field-strength elements such as W, V, Nb, and Sn indicates that the hydrothermal fluids are enriched in F and Cl, exhibiting weak acidity. The nature of the fluids during hydrothermal alteration is closely related to the composition of rutile, making it a promising tool for studying hydrothermal alteration and related mineralization processes. Full article

The Gulf of Mexico Hydrates Research Consortium selected the Mississippi Canyon Lease Block 118 (MC118) as a multi-sensor, multi-discipline seafloor observatory for gas hydrate research with geochemical, geophysical, and biological methods. Woolsey Mound is a one-kilometer diameter hydrate complex where gas hydrates outcrop at the sea floor. The hydrate mound is connected to an underlying salt diapir through a network of shallow crestal faults. This research aims to identify the base of the hydrate stability zone without regionally extensive bottom simulating reflectors (BSRs). This study analyzes two collocated 3D seismic datasets collected four years apart. To identify the base of the hydrate stability zone in the absence of BSRs, shallow discontinuous bright spots were targeted. These bright spots may mark the base of the hydrate stability field in the study area. These bright spots are hypothesized to produce an amplitude versus offset (AVO) response due to the trapping of free gas beneath the gas hydrate. AVO analyses were conducted on pre-stacked 3D volume and decreasing amplitude values with an increasing offset, i.e., Class 4 AVO anomalies were observed. A comparison of a time-lapse analysis and the AVO analysis was conducted to investigate the changes in the strength of the AVO curve over time. The changes in the strength are correlated with the decrease in hydrate concentrations over time. Full article

The Xiangzhong district is the largest low-temperature W-Au-Sb metallogenic area in the world. The Darongxi skarn W deposit in the north of the Xiangzhong district is closely related to biotite monzonite granite, muscovite monzonite granite, and felsophyre, but the nature of granitic magma and its relationship with mineralization is relatively weak. In this paper, U-Pb dating, Lu-Hf isotope, the in situ composition of zircon, and the apatite of biotite monzonite granite, muscovite monzonite granite, and felsophyre in the Darongxi mining area are systematically studied, and the formation age, magma property and source, and their relationship with mineralization are discussed. The values of zircon U-Pb age and the ε_Hf(t) of biotite monzonite granite are 222.2 ± 0.54 Ma and −2.9~−6.4, respectively. The values of zircon U-Pb age and the ε_Hf(t) of muscovite monzonite granite are 220.8 ± 0.58 Ma and −2.7 to −8.1, respectively. The values of zircon U-Pb age and the ε_Hf(t) of felsophyre are 222.3 ± 2.20 Ma and −2.2~−5.4, respectively. Magmatic apatite grains from biotite monzonite granite and muscovite monzonite granite show distinctive core–rim and oscillatory zoning textures in CL images, and demonstrate a bright yellow in colorful CL images. The magmatic apatite has a total rare earth concentration (3766~4627 ppm), exhibiting right-inclined nomorlized rare earth element patterns and obvious negative Eu anomalies. The geochemical data of magmatic zircon and apatite indicate that magma sources are responsible for these intrusions in the Darongxi mining area, mainly derived from the partial melting of the Mesoproterozoic crust, which is rich in W; the magma is rich in F and poor in Cl (F = 2.4~3.3 wt%, Cl = 0.0024~0.0502 wt%). The oxygen fugacity of magmatic zircon (ΔFMQ_AVG = −4.02~−0.26), the high negative Eu anomaly (δEu = 0.06~0.12) and the low positive Ce anomaly (δCe = 1.09~1.13) of magmatic apatite, and the occurrence of ilmenite all indicate that the redox condition of magma from the Darongxi mining area is reduced. The reduced F-rich crust-source granitic rock and W-rich source provide favorable conditions for the mineralization of the Darongxi reduced skarn W deposit. Full article

This study develops a wavelet maxima-based methodology to extract anomalous signals from microwave brightness temperature (MBT) observations for seismogenic activity. MBT, acquired via satellite microwave radiometry, enables subsurface characterization penetrating clouds. Five surface categories of the epicenter area were defined contingent on position (oceanic/terrestrial) and ambient traits (soil hydration, vegetal covering). Continuous wavelet transform was applied to preprocess annualized MBT readings preceding and succeeding prototypical events of each grouping, utilizing optimized wavelet functions and orders tailored to individualized contexts. Wavelet maxima graphs visually portraying signal intensity variations facilitated the identification of aberrant phenomena, including pre-seismic accrual, co-seismic perturbation, and postseismic remission signatures. The casework found 10 GHz horizontal-polarized MBT optimally detected signals for aquatic and predominantly humid/vegetative settings, whereas 36 GHz horizontal-polarized performed best for arid, vegetated landmasses. Quantitative machine learning methods are warranted to statistically define selection standards and augment empirical forecasting leveraging lithospheric stress state inferences from sensitive MBT parametrization. Full article