Search Results (617)

(1) Background: The issue of providing evidence for some electromagnetic phenomena occurring with strong earthquakes has not yet received a conclusive response. Here, long-term continuous monitoring of electromagnetic signals detected by the Central Italy Electromagnetic Network in the atmosphere was reported, and data from the Avigliano Umbro station from the beginning of October 2013 to early January 2015 were analysed. (2) Methods: Spectrogram recordings of extremely low-frequency electric fluctuations were analysed for frequency-time well-defined structures. Electrical oscillations with intensities exceeding a threshold were extracted and compared with moderate earthquakes using Pearson correlations. (3) Results: The cross-correlation between the electric activity of non-meteorological origin and the seismic activity observed within 70 km around the station during the same period was calculated. A correlation peak at +7 days emerged, suggesting that the electric phenomenon occurs mainly 7 days before earthquakes, which has a probability < 1% of being due to chance. (4) Conclusions: The electric oscillation phenomenon is concluded to have a relationship with moderate seismic activity. They show moderate predictive skill. A possible interpretation relates to fluids escaping from the ground. These results are useful for risk mitigation by enabling the computation of the conditional occurrence probability of a seismic event. Full article

Global warming poses a serious environmental challenge worldwide. Agriculture, as a significant source of greenhouse gas (GHG) emissions, exerts considerable influence on the atmospheric environment. Chengdu, renowned for its thriving agricultural sector, serves as a key grain production center in China. Reducing agricultural greenhouse gas (AGHG) emissions is essential for mitigating the impact of climate change on Chengdu. Firstly, this paper employed the IPCC (Intergovernmental Panel on Climate Change) coefficient method and the Super-SBM-Undesired model to calculate the AGHG emissions and emission efficiency in Chengdu, respectively. Then, center of gravity shift analysis, kernel density estimation and spatial autocorrelation theory were used to analyze the spatial–temporal evolution characteristics of AGHG emissions. Finally, this paper conducted an in-depth analysis based on the STIRPAT model to identify key factors affecting AGHG emissions. The results show that: (1) From 2007 to 2021, Chengdu experienced an overall decline in both AGHG emissions and emission intensity, with reductions of 22.32% and 66.20%, respectively. And the AGHG emission efficiency was largely low. (2) AGHG emissions display regional variations and spatial clustering phenomena, characterized by a pattern of “high in the east, low in the west, high outside and low inside”. (3) AGHG emissions are highly increased by the sown area (S) and pesticide and fertilizer utilization (F) and may be reduced by the agricultural industrial structure (V) and the urbanization rate (U). These findings provide valuable scientific insights into the spatial–temporal dynamics of regional agricultural emissions. Furthermore, this study offers practical references for local governments to optimize agricultural resource allocation, formulate tailored low-carbon agricultural policies, and promote sustainable rural development. Full article

While Thermal Infrared (TIR) sensors are standard for monitoring volcanic activity, their efficacy is severely compromised by meteorological clouds and dense volcanic ash. To overcome these optical limitations, we present the first ground-based application of a passive microwave radiometer for continuous volcano monitoring. Operating in the 10–12 GHz band, our Total Power Microwave Receiver is stationed 12 km from Mount Etna’s active craters to measure thermal emissions from eruptive hotspots. Unlike traditional TIR imaging, this low-cost, automated system exploits the atmospheric transparency of microwave wavelengths, enabling uninterrupted observation regardless of weather or solar illumination. We detail the system’s design and report its successful detection of volcanic phenomena during the 2023–2025 eruptive cycles, including the transit of a high-temperature ash cloud that triggered a significant radiometric peak. Our findings demonstrate that fixed-point microwave radiometry provides a reliable thermal signature of eruptive activity, offering a pioneering and highly accessible tool for the next generation of global volcanic early warning systems. Full article

Advances in artificial intelligence models offer promising approaches for intelligent convection initiation (CI) identification—a critical step in severe weather nowcasting—thereby driving demand for high-quality, long-term labeled datasets. Accordingly, this study develops a CI identification technique using quality-controlled, gridded composite reflectivity data from the weather radar and CMA global atmospheric reanalysis wind data over central-eastern China (2018–2023) to construct a labeled dataset. The proposed CI identification method integrates a “forward-time search and backward-time verification” strategy, which involves three key steps: screening grid points with absent or weak convection; monitoring these points for convective development within 30 min; and finally, confirming the first occurrence of convection. Additionally, quality control is applied to eliminate the influence of outliers and anomalous radar data. The resulting dataset constructed from 829 severe convective processes comprises ~25.6 million grid points labeled for CI occurrences at one or more lead times of 10, 20, or 30 min to resolve spatiotemporal evolution. Of these, 71.90% are accompanied by surface weather phenomena. This study provides a reliable dataset to support the learning of intelligent identification and nowcasting models for CI events. Furthermore, based on this dataset, the spatiotemporal distribution characteristics of warm-season CI over central-eastern China are delineated. Full article

Tropospheric refraction significantly impacts the propagation of ultrashort- and microwave-frequency radio waves over marine environments. Atmospheric ducting, the most common super-refractive structure, allows radio waves to travel over the horizon. This holds significant practical value for applications such as maritime communication, remote radar monitoring, and navigation systems. However, atmospheric ducts can also present challenges, especially under unstable meteorological conditions. Atmospheric ducts may cause signal attenuation and even severe interference. Therefore, the detection of atmospheric ducting phenomena is crucial for ensuring the reliability of maritime communication systems and the accuracy of radar monitoring. This paper provides a comprehensive and systematic review of the current state of research on atmospheric duct detection, presenting a detailed analysis of several key methodologies. These include direct measurement techniques, model estimation approaches, numerical forecasting methods, and remote sensing inversion techniques. Additionally, the paper offers an in-depth examination of the strengths and limitations of each method in practical applications, while also highlighting the ongoing challenges within the field. In conclusion, this work aims to provide theoretical foundations and practical guidance for the future development of atmospheric duct detection technologies, fostering further advancements in both theoretical research and technical applications in the field. Full article

Extreme atmospheric events are rare phenomena characterized by unusual intensity or chemical composition compared to the atmospheric background state. Many such events, in the context of global warming, pose threats to human health, thereby making their early detection and monitoring essential. The Infrared Atmospheric Sounding Interferometer (IASI), able to measure more than 30 atmospheric chemical species on a global scale, offers strong potential in this context. However, the large volume of current and upcoming satellite observations makes intelligent data screening more and more challenging. This work aims to overcome this limitation by developing a dedicated algorithm based on Principal Component Analysis (PCA) of Level 1C IASI spectra. Named IASI-PCA, it is designed for the systematic detection of fires, volcanic eruptions, dust storms, pollution plumes, and other extreme atmospheric events that remain unclassified. The detected events are defined as spectral outliers relative to the representative global variability of IASI observations under normal or unperturbed conditions. The detection of an individual spectrum is driven by its anomalous behavior in selected spectral domains, where a set of optimized indicators corresponding to more than 10 species has been defined to discriminate events according to their chemical signatures. This methodology has been implemented in a near-real-time operational system providing detection and classification products within one hour and one day, respectively. The IASI-PCA approach has been applied to multiple case studies demonstrating that it is a powerful tool for: (1) efficiently detecting and monitoring fires, whether isolated sources or extended plumes; (2) handling both clear and cloudy conditions; (3) detecting dust plumes predominantly associated with calcite; (4) identifying pollution sources; and (5) detecting volcanic events. The consistency of our results with those obtained with the EUMETSAT Principal Component Compression (PCC) is also illustrated through the processing of a representative study period. Full article

Enhancement behavior on saturation current of output characteristics in amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors under positive bias stress (PBS) is investigated. The threshold voltage (V_th) of the a-IGZO TFT demonstrates a typical positive shift during PBS. Notably, the output current at an identical overdrive voltage (V_ov) initially rises with increasing bias stress duration. The observed phenomena are elucidated by the detrapping of positively charged defects situated at the interface between the dielectric and active layer due to electrons induced by bias stress during PBS, which diminishes carrier scattering at the channel interface. Following the full release of positive interface charge, additional electron trapping states emerge. The presence of trapped electrons intensifies carrier scattering at the channel interface, leading to a degradation in drive current. Low-frequency noise (LFN) measurements are conducted to verify the suggested mechanism of PBS instability in a-IGZO TFTs. Moreover, the energy distribution of PBS-induced traps is shown by C-V characterization to be exponential, dominated by shallow traps. Passivation greatly enhanced the PBS stability, which is attributed to hydrogen doping-induced defect passivation and the shielding of the back-channel interface from the air atmosphere. Full article

Additive Manufacturing (AM) for jewelry applications is increasingly adopting Binder Jetting (BJ) to overcome the fusion-related limitations associated with precious metals, including unstable melt pools, excessive reflectivity, and high thermal conductivity. In this context, the present review establishes a thermophysical and manufacturability-oriented framework that redefines thermal management beyond localized melt-pool stabilization toward the furnace-scale control of densification kinetics, shrinkage evolution, atmosphere-assisted sintering, and viscoplastic deformation. Particular emphasis is placed on gold-, silver-, and platinum-based jewelry alloys, with a specific focus on the thermal, mechanical, and chemical phenomena governing Binder Jetting sintering. During consolidation, low-density green bodies (~40–65% relative density) must transform into highly dense components through extensive volumetric shrinkage and gravity-driven deformation, creating major challenges in dimensional fidelity and surface quality. The review further examines predictive viscoplastic constitutive models (SOVS/ROH), reversed-deformation compensation strategies, and atmosphere-engineering approaches for oxide reduction, pore-pressure regulation, and residual-porosity control. By linking thermophysical consolidation, dimensional fidelity, polishability, and jewelry-grade manufacturability within a hierarchical framework, this review provides a structured basis for the development of high-precision and low-waste precious-metal additive manufacturing. Full article

Pressurized pipelines are critical components in hydraulic engineering systems, including urban water supply networks and hydroelectric power plants. These systems are susceptible to air entrapment during operations such as filling and emptying, which can reduce the effective flow area and trigger critical pressure surges or sub-atmospheric conditions. One-dimensional approaches, namely the Rigid Water Column (RWC) and Elastic Water Column (EWC) models, are the most widely used due to their balance between physical accuracy and computational practicality. EWC models have been widely used to analyze transient phenomena in pipe filling and water hammer processes; however, their application to emptying operations is limited. For this reason, this study develops an EWC-based formulation for emptying operations and assesses pressure behavior through a dimensionless analysis for different air pocket configurations. The developed model couples the Method of Characteristics (MOC) with a polytropic air pocket model, enabling the representation of wave propagation effects that RWC-based models cannot capture. The formulation is verified against 24 experimental cases, yielding a mean absolute error of 0.35% in minimum pressure prediction. The results show that dimensionless air pocket ratios $x_0/L_T$ between 0.17 and 0.83 produce minimum pressures between 0.309 and 0.877 $p_{atm}^{*}$, confirming that smaller initial air pocket volumes generate the most severe depressurization conditions. The inclusion of an air valve in the most critical scenario effectively prevents sub-atmospheric pressure development, underscoring the protective role of air admission devices. These findings provide a dimensionless framework for characterizing transient pressure risk during pipeline emptying across different operational conditions. Full article

This study assesses the technical feasibility of using polar orbiting satellite constellations to generate temperature profiles in the middle atmosphere, based on image analysis from the UVSQ-Sat NG nanosatellite. We first identified the phenomena influencing the temperature of this layer of the atmosphere, specifying their amplitudes and spatio-temporal resolutions. We then present the UVSQ-Sat NG nanosatellite and its Nanocam instrument, whose images of the Earth’s limb served as the basis for our processing. Finally, we detail the processing methodology, demonstrating its applicability to any image of the Earth’s limb acquired in the spectral range from near-UV to near-IR, subject to the following strict conditions: a measurement dynamic range greater than 1000 and rigorous control of instrumental noise. This approach paves the way for continuous, global monitoring of the middle atmosphere, which is essential for improving climate and weather models. Full article

Atmospheric microplastics (AMPs), as a globally prevalent environmental pollutant, have attracted increasing attention from the academic community in the past decade. This study aims to systematically explore the historical background, development trajectory, and evolutionary trends of global atmospheric microplastic research through bibliometric analysis. Based on 1385 relevant studies retrieved from the Web of Science core collection, knowledge graph analysis was conducted using the CiteSpace and VOSviewer tools. The results indicate that research on AMPs has gone through three distinct stages: the budding exploration period (2014–2016), the steady growth period (2016–2019), and the explosive expansion period (2020–2025). In the initial stage, people lacked understanding of AMPs, with a low publication volume and research focused on “occurrence and source”. During the steady growth stage, the number of publications increased, and researchers’ research areas focused on source analysis. During the explosive growth stage, the number of publications reached its peak, and research on AMPs gradually developed from the initial description of phenomena and method development to a comprehensive research direction involving multiple regions, media, and methods. It is worth noting that China has the highest research output on AMPs globally and occupies a dominant position in atmospheric microplastics research. Therefore, this study establishes a knowledge framework for global atmospheric microplastics research, identifies current research gaps, and provides comprehensive references for subsequent academic exploration and environmental governance practices. Full article

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

Low-temperature atmospheric plasma (LTP) is widely used in industrial processes, such as disinfection, surface modification and wastewater treatment. The dielectric barrier discharge (DBD) is regarded as one of the most robust and reliable methods for generating LTP in ambient air. Compared to conventional AC excitation, pulsed powering offers several advantages (i.e., lower energy use and heat production). The present trend is to use short and fast pulses (in the nano- and picosecond range). In this review, the key design parameters of a DBD (barrier thickness, relative permittivity and gap distance) are discussed. Material-specific phenomena like surface charging and degradation are analyzed. The complex interactions between the pulse source and DBD are examined. By mapping the interdependencies, this review aims to support the rational design and optimization of pulsed DBD systems, and to facilitate their broader industrial use. Full article

The high emissions of carbon dioxide (CO₂) into the atmosphere have driven the development of carbon capture, transport, and storage (CCTS) technologies. These focus on capturing CO₂ from industrial exhaust gases and transporting it through existing pipeline networks. Although various capture techniques are available, they may introduce impurities such as O₂, N₂, Ar, H₂O, NH₃, and others into the CO₂ stream. These contaminants can significantly alter the thermophysical behaviour of the fluid, making the phase behaviour predictions, reliable for pure CO₂, much more complex. Pressure and temperature variations along pipelines can induce unexpected phase transitions, affecting fluid composition and potentially triggering corrosion. This review examines the formation of condensates within pipelines and their role in initiating corrosion phenomena, with a focus on top of the line corrosion (TLC) and conventional CO₂-induced corrosion (sweet corrosion). The main literature findings highlight how phase changes and altered fluid composition due to corrosion processes can significantly intensify degradation mechanisms during CO₂ transport. Full article

This study investigates the synthesis and kinetic behavior of a magnetic biochar derived from avocado seed biomass for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. Magnetite (Fe₃O₄) was synthesized through different routes, including nitrogen-assisted coprecipitation, redox-controlled coprecipitation, polyol, sol–gel, and sonochemical methods, to evaluate their structural properties and iron incorporation efficiency. Based on compositional and crystallographic analyses, the coprecipitation under an inert atmosphere exhibited improved phase purity and higher Fe₃O₄ content, which was selected for in situ incorporation onto biochar produced by pyrolysis at 450 °C. The resulting magnetic material and composite were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS), confirming the suitability of the synthesis method and the successful deposition of magnetite onto the porous carbon matrix while preserving its structural integrity. Batch adsorption experiments were conducted at pH 2.0 to evaluate the effect of adsorbent dose and initial Cr(VI) concentration. The adsorption process reached equilibrium within 120 min and was better described by the pseudo-second-order kinetic model (R² ≥ 0.98), suggesting that chemisorption governs the rate-controlling step, with diffusion phenomena contributing but not dominating the overall mechanism. The maximum adsorption capacity predicted by the kinetic model reached 42.49 mg g⁻¹ at an initial concentration of 100 mg L⁻¹. The results demonstrate that avocado-seed-derived magnetic biochar represents a sustainable and effective material for chromium-contaminated water treatment, integrating agro-industrial waste valorization with enhanced adsorption performance and magnetic separability. Full article