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AbstractLaser-induced breakdown spectroscopy (LIBS) technology has been widely used in many fields including industrial production, space exploration, medical analysis, environmental pollution detection, etc. However, the stability problem of LIBS is one of the core problems for its further development. Solutions in the LIBS field in recent decades were summarized and classified from the physical mechanism and analysis method. In particular, the processing methods based on the features of the plasma image and reconstructed image were analyzed and expounded. At the physical mechanism level, the system improvement strategy, environmental modulation strategy, and sample pretreatment improvement strategy were summarized and classified as a pre-improvement strategy. At the analysis method level, two kinds of correction strategies were concluded according to the difference between the feature mediums of the plasma spectrum and image, which were classified as a later improvement strategy. Strategies and methods were discussed in detail, which can provide a basic architecture and reference for the research of LIBS stability improvement. Moreover, the potential developing trend for this topic was proposed. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Earthquake Sciences is the property of China Earthquake Administration, Institute of Geophysics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In February 2024, Hunan encountered two regional rainfall/snowfall and freezing events with low temperatures, one in northern Hunan from February 2 to 6 (hereinafter referred to as the“2.02”event), and the other across the whole province from February 21 to 26 (hereinafter referred to as the“2.21”event). Using conventional upper-air and surface weather observations, regional automatic weather station data, and NCEP reanalysis data, we conducted a comparative analysis of the circulation background, cooling mechanism, and water vapor transport characteristics of the two events. The results are as follows. (1) There are obvious differences in the circulation background between the two events. The“2.02”event occurred in the background with eastward movement of both the southern branch trough and westerly trough overlapping in phase. However, the“2.21”event occurred under the cold wave caused by the collapse of the blocking high, with the transition of rain and snow phases appearing multiple times due to the small influence on the southern branch trough. (2) There were the strong low-level frontal zone in both events. A rare north-south temperature gradient greater than 26 ℃ was observed in the“2.21”event, which may be an important indication of this extreme cold wave weather. (3) Temperature advection played an important role in the transition of rain and snow phases. In the“2.02”event, the strong cold advection intrusion in the middle level was driven by the westerly trough, causing a temperature decrease across the whole layer. In the“2.21”event, the continuous input of the ultra-low-level strong cold advection was one of the important cooling mechanisms. In addition, the strongest transport layer of warm advection corresponded to the negative center of vertical velocity, and the stronger vertical wind shear in the middle and lower troposphere resulted in stronger rain and snow intensity. (4) The Arabian Sea was the main source of water vapor for both events. Southwest warm and wet airflow in the middle troposphere moved with the low trough at 500 hPa or the small trough from it, with the highest contribution of specific humidity and water vapor flux to both events. The low troughs provided both favorable dynamical conditions and abundant water vapor for the occurrence of rain and snow weather. In the “2.21”event, the warm and wet air carried by three combined channels from the South China Sea channel, the Arabian Sea channel and the low latitude inland regions provided water vapor and warm layer conditions for the freezing area in the southern Hunan, which was an important reason for the severe freezing in this area.

Based on the observation data collation, data quality and interference analysis of the geoelectric field of Tengchong center station from 2018 to 2022, it is considered that the geoelectric field data of Tengchong center station has good correlation with the long and short polar distances in the same direction without interference, with clear diurnal variation and high data reliability. The interference types can be roughly divided into two categories: natural environment interference and artificial interference. Among them, the interference of geoelectric storm, lightning and rainfall belongs to natural environment interference, and the interference of artificial power supply and site leakage belongs to artificial interference. The interference changes caused by geoelectric storm are mainly characterized by large amplitude sharp pulse jumps similar to earthquake waveforms. The interference changes caused by lightning are mainly characterized by typical large amplitude distortions. The interference changes caused by rainfall are mainly characterized by large decreases. The interference changes caused by ground resistivity power supply in the same observation site are mainly characterized by regular pulse jumps. The interference caused by street lamp leakage mainly exhibit a step-type periodic variation change. By analyzing the forms and physical mechanisms of changes in the geoelectric field caused by different types of interference sources, methods to solve the interference are proposed to improve the quality of geoelectric field observation and provide a basis for the effective identification of geoelectric field interference and earthquake prediction.

Due to the relatively different mechanical and physical properties of soils and structures, the interface plays a critical role in the transfer of stress and strain between them. The stability and safety of geotechnical structures are thus greatly influenced by the behavior at the soil–structure interface. It is therefore important to focus on the unique characteristics that set the interface apart from other geomaterials while examining the interface behaviour. Understanding the physical mechanism and modelling principles of these interfaces becomes a crucial step for the secure design and investigation of soil-structure interaction (SSI) issues. Moreover, to deal with this soil-environment interaction problem, the classical soil mechanics formulation must be progressively generalised in order to incorporate the effects of new phenomena and new variables on SSI behaviour. Considering the variety of energy geostructures that are emerging nowadays, it is crucial to comprehend the thermo-hydro-mechanical (THM) behaviour of the interface. The objective of this study is to fill this information gap as concisely as possible. A critical review is provided along with the state-of-the-art information on the thermo-hydro-mechanical behaviour of the soil-structure interface, including testing tools and measurement methods, basic principles and deformation mechanisms, constitutive models, as well as their applications in numerical simulations. This study explains how loading influences the mechanisms at the interface and critically examines the effects of boundary conditions, soil properties, environmental factors, and structure type on the THM behaviour of interface zones between soils and structural elements. The validity and reliability of the interface shear stress-displacement models are also covered in this paper. Lastly, the trends and recent advancements are also recommended for the interface research. [ABSTRACT FROM AUTHOR]

The Ranque-Hilsch vortex tube (RHVT) is a device which can separate compressed gas into high and low energy flows only through its own fluid motion by generating a high-speed swirling flow inside a cylindrical vortex chamber. The energy separation phenomenon of RHVT is called the Ranque-Hilsch effect (RH effect). Although numerous studies have been conducted over the past 90 years since the discovery of the RH effect (1933), the energy separation mechanism has not been elucidated. Previous studies have suggested that the RH effect is caused by the unsteadiness of a high-speed swirling flow inside the cylinder, such as turbulence and acoustic phenomena. However, the unsteady characteristics have not been clarified because it is difficult to obtain time evolution data sufficiently guaranteed physical reliability. In this paper, high-speed unsteady swirling flow inside the cylindrical vortex chamber of RHVT is calculated by direct numerical simulation for the first time. Because the Reynolds number of the flow inside RHVT is high, it is difficult to use direct numerical simulation due to the high computational costs. To reduce the computational costs, we performed direct numerical simulation by setting the viscosity of the working fluid higher than the air. The viscous coefficient of the working fluid is set equal to or larger than 100 times that of the air. We find out that the turbulence intensity is axisymmetric, and the closer to the axial position of inlet, the stronger turbulence occurs. By comparing flows with different viscosities of the working fluid, we also find out that there is a relationship between the RH effect and turbulence in a high-speed swirling flow inside the cylinder, as the energy separation effect increases with increasing turbulence intensity.

Ion irradiation of semiconductors has emerged as a promising approach for fabricating self-organized nanosystems with high atomic precision, despite often being accompanied by undesirable phenomena. Exploring the mechanisms underlying structural transformations is crucial for assessing nanostructure array types under complex irradiation environments. By quantitatively calculating the thermodynamically driven processes and analyzing the impact of intrinsic structural parameters, distinct structural transformations in response to intense electronic excitation are systematically investigated in gallium antimonide (GaSb) and gallium arsenide (GaAs) systems. In high-energy regimes, the nanofibers layer of GaSb exhibits intriguing structural discrepancy, characterized by partial nanofibers with coherent boundaries, interspersed nanopores accompanied by antisite defects and Ga precipitates, distinguishing to a series of discontinuous latent tracks that emerged within cylindrical trajectories in GaAs. Furthermore, significant diffusion behaviors of the nanohillocks are discovered in GaAs, with higher average roughness than GaSb, driven by the gradient stress distribution influenced by the free-surface effects. The deposition energy for melting phase formation, Gibbs free energy, and Ga diffusion coefficients contribute to the distinctive structural features, evidencing relatively stable morphological configurations and higher irradiation resistance in GaAs. Consequently, special optoelectronic properties associated with structural discrepancies facilitate the design and optimization of material functionalities by irradiation technologies.

This study discusses the interannual variability and influencing mechanisms of the summer precipitation dipole pattern in Northeast China from 1961 to 2020 based on observation data and reanalysis data. Results indicate that the second mode of empirical orthogonal function (EOF2) mode of summer (June–August) precipitation in Northeast China presents a dipole pattern with opposite trends in the north and south, and its time series (PC2) demonstrates significant interannual variations. The South-North dipole pattern in summer precipitation over Northeast China are significantly correlated with the tropical sea surface temperature, Arctic sea ice, and Eurasian snow cover in the preceding spring (March–May) on an interannual scale. In the preceding spring, the rise in sea temperature in the eastern equatorial Pacific and the decline in the western equatorial Pacific can stimulate EAP and EU teleconnections, positioning a cyclonic center over Northeast China, thereby influencing the dipole pattern of precipitation in Northeast China. Furthermore, the anomalies in European snow cover and Arctic sea ice can lead to an increase in albedo and a decrease in upward heat flux, causing the lower atmospheric temperature to drop and persist into the summer. This triggers the eastward propagation of atmospheric Rossby waves at mid-high latitudes, which promotes precipitation in Northeast China through the occurrence of negative potential height anomalies. These conditions influence the anomalies in the atmospheric circulation over the Eurasian continent, regulate moisture transport and vertical motion, and collectively contribute to the dipole pattern of summer precipitation in Northeast China over the past 60 years, with opposite trends in the north and south. [ABSTRACT FROM AUTHOR]

In this paper, a technology named SCM−ANN combining physical scattering mechanisms and artificial intelligence is proposed to realize radar cross-section (RCS) extrapolation of non-cooperative conductor targets with higher efficiency. Firstly, an adaptive scattering center (SC) extraction algorithm is used to construct the scattering center model (SCM) for non-cooperative targets from radar echoes in the low-frequency band (LFB). Secondly, an artificial neural network (ANN) is constructed to capture the nonlinear relationship between the real LFB echoes and those reconstructed from the SCM. Finally, the SCM is used to reconstruct echoes in the high-frequency band (HFB), and these reconstructions, together with the trained ANN, optimize the extrapolated HFB RCS. For the SCM−ANN technology, physical mechanistic modes are used for trend prediction, and artificial intelligence is used for regression optimization based on trend prediction. Simulation results show that the proposed method can achieve a 50% frequency extrapolation range, with an average prediction error reduction of up to 40% compared with the traditional scheme. By incorporating physical mechanisms, this proposed approach offers improved accuracy and an extended extrapolation range compared with the RCS extrapolation techniques relying solely on numerical prediction. [ABSTRACT FROM AUTHOR]

This article presents the gettering mechanism and the physical model of impurity Ni atom clusters in the Si crystal lattice. The study finds out that the formed Ni atom clusters lead to gettering various rapidly diffusing impurities, both present in the Si lattice and introduced, as well as oxygen atoms, by stimulating generation of recombination centers of thermal and radiation defects. [ABSTRACT FROM AUTHOR]

Soil moisture can significantly influence weather and climate via land‒atmosphere interactions over the Tibetan Plateau. However, the temporal and spatial preferences of precipitation for soil moisture anomalies and the underlying mechanisms over the plateau have not been determined. Using multiple satellite data sets (including Global Precipitation Measurement precipitation data and Soil Moisture Active Passive and Advanced SCATterometer soil moisture data) and ERA5 reanalysis data, the temporal and spatial soil moisture–precipitation coupling (SMPC) relationships in seven summers during 2015–2021 over the plateau are quantified based on a percentile‐based method. The satellite observations show prevalent positive temporal SMPC across the plateau, indicating that wetter‐than‐normal soil conditions tend to lead to more afternoon precipitation. While ERA5 generally aligns with satellite findings, it underestimates areas with positive temporal SMPC. Both the satellite and ERA5 data show that spatial SMPC relationships are usually statistically insignificant, but a few regions show significant positive relationships, that is, precipitation is more likely to occur over soils wetter than the surrounding soils. Moreover, the satellite observations suggest an inter‐event positive correlation between the temporal and spatial SMPC relationships. ERA5 agrees with the satellite‐based results over the western plateau but shows discrepancies over the eastern plateau. The temporal and spatial variations in soil moisture modulate the partitioning of surface heat fluxes, planetary boundary layer height, and lifting condensation level, promoting moist convection and afternoon precipitation. The findings from this study shed new light on SMPC and have important implications for precipitation forecasting over the plateau. Plain Language Summary: Soil moisture can influence precipitation via land–atmosphere water and energy exchanges over the Tibetan Plateau. Such impacts manifest itself in different ways. Temporally, precipitation could preferentially occur on antecedent soils that are either wetter or drier than normal. Spatially, precipitation could preferentially occur on antecedent soils that are either wetter or drier than the surrounding soils. In this study, we investigate the effects of soil moisture on precipitation in summer over the plateau from separate temporal and spatial perspectives using satellite and reanalysis data sets. Satellite data suggest that wetter‐than‐normal soil conditions often lead to more afternoon precipitation. While the ERA5 generally supports satellite findings, they underestimate areas with a positive temporal relationship. Both the satellite and ERA5 data show that in many areas, the spatial relationship between soil moisture and precipitation is not statistically significant. However, in a few regions, precipitation is more likely to occur over soils wetter than the surrounding soils. Soil moisture‐induced changes in surface energy and water fluxes influence the atmospheric boundary layer, leading to the spatiotemporal preference of afternoon precipitation over soil moisture anomalies. This work helps improve our understanding of the effects of soil moisture on precipitation over the plateau. Key Points: The temporal and spatial preferences of afternoon precipitation over soil moisture anomalies over the Tibetan Plateau are investigatedPrecipitation preferentially occurs over antecedent soil that is wetter than normal and wetter than the surrounding soilsSoil moisture changes the surface energy partitioning and affects subsequent precipitation by adjusting the atmospheric boundary layer [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fibre-reinforced sand (FRS) is a multiphase and multiscale geo-material, which is widely used in geotechnical engineering as supporting structure of excavation of underground space and reinforcement of foundation of underground structures, and its strength is determined by the properties of the heterogeneous substances of the FRS and their coupling mechanical responses. In order to investigate the influence of fibre characteristics and mechanical properties on the shear strength of the FRS, according to the microscopic interface slip effect generated by the interaction between sand particles and the interaction between these particles and fibre, the material phase of the FRS is divided to conceptualize a micro cell element of the FRS that is capable of reflecting the internal material characteristic information of the FRS. Moreover, based on the coordinated deformation condition between fibres and sand particles at the microscale and the couple stress theory that is capable of effectively describing the discontinuous mechanical responses at the sand-fibre interface, a mesomechanism-based multiscale Mohr–Coulomb shear strength criterion of the FRS is derived, and the yield locus of the FRS is also drawn on the π plane. Furthermore, a series of FRS samples with different fibre content and fibre length were prepared by adopting the freezing method, and consolidated and drained triaxial compression tests were conducted on these samples to validate the proposed multiscale coupled Mohr–Coulomb shear strength criterion. Results show that the multiscale coupled Mohr–Coulomb shear strength criterion is capable of effectively reproducing and predicting the yield strength of the FRS. The yield locus of the FRS extends outwards as fibre content and fibre length increase. The yield stress of the FRS predicted by the proposed multiscale coupled Mohr–Coulomb shear strength criterion is in good agreement with that of the test result.

Currently, the spectra-based physical models and deep learning methods are frequently used to detect wildfires from remote sensing data. However, physical algorithms mainly rely on radiative transfer processes, which limit their effectiveness in detecting small and weak fires. On the other hand, deep learning methods usually lack mechanism constraints, thus generally resulting in false alarms of bright surfaces. It is promising to combine the advantages of them and correspondingly reduce the inherent error of a single algorithm. To this end, in this paper, both the local contextual and the global index method based on physical mechanisms are optimized, simultaneously, a new U-Net model is also establish to accurately detect fires. Moreover, YOLO v5 is incorporated for the first time to extract and remove the false alarms of objects with high exposure. Based on the above series of novel works, a self-adaptive fusing algorithm is finally proposed. Our results reveal that: (1) Short-wave infrared band of about 2.15 μm is crucial in fire detection for data with moderate-to-high resolutions. Taking Landsat 8 as an example, the band combinations of 7, 6, 2(SWIR + VI), 7, 6, 5(SWIR + NIR), and 7, 5, 3(SWIR + VI + NIR) show reasonable accuracy, with recall rate of greater than 81 %. The thermal infrared band can be used to assist in detecting the general location of the fire and serve as alternative choice in extreme cases. (2) The optimized physical algorithm can reduce false alarms and predict more accurate fire positions. (3) It is very effective to introduce the YOLO v5 framework to remove false alarms with high exposure in urban and suburban regions. (4) The proposed self-adaptive fusion algorithm integrates the advantages of various schemes, proving its better performance in terms of robustness, stability and generality compared to any single method. Even in extreme situations such as the Gobi Desert, thin cloud edges, and mountain shadow areas, the fusion algorithm still works well. The generality tests based on Sentinel-2A, WorldView-3, and SPOT-4 reveal the potential applicability of the newly proposed fusing algorithm, especially for data with fine spatial and spectral resolutions.

Gully erosion can usually cause the serious environmental damage and economic losses. Susceptibility assessment and spatial distribution of gully erosion can provide a strong references for the targeted measures, decision-making on environmental protection, geologic disaster prevention, water resource management, and infrastructure planning. It is of great significance to better understand and manage the gully system, and then reduce potential risks and losses. The regional environment can be improved to maintain the regional food production in sustainable economic development. Much effort has focused on the prediction models of soil erosion over the past few decades. The amount of erosion on slopes has been predicted from both empirical statistical and physical genesis models. However, few models have been developed to predict the development of erosion gullies. Gully erosion is more complicated than slope erosion. Furthermore, the modeling has only focused on the shallow gully erosion. Only a few studies have been conducted on the topographic, critical and empirical model of gully morphologic features, the gully erosion prediction, and the landscape evolution. It is still lacking on general extrapolation of these models, even the susceptibility of gully erosion. Multiple factors can also be considered, such as the topography, geomorphology, soil, climate, vegetation and anthropogenic factors. A comprehensive and quantitative analysis of the influencing factors can be expected with the remote sensing satellites, resource and environmental surveys. A large amount of gully-erosion data has been accumulated to statistically modeling in this field. The susceptibility assessment of gully erosion aims to calculate the importance of the influencing factors on the occurrence of gully erosion and the prediction performance between different algorithms. It is still lacking on the innovative and promotional research in this field. In this review, the flow of research in this direction was systematically introduced to summarize the strengths and weaknesses of the statistical models under various classifications. The advance in this direction was proposed to compare the commonalities and differences in the application conditions from three aspects: the process of gully erosion, the data construction, and the application of statistical model. At the same time, future research needs to realize the application of transfer learning and time series models in the susceptibility assessment on gully erosion. The deep learning and physical mechanisms can be integrated to clarify the erosion gully development, in order to improve and strengthen the cross-disciplinary application of statistical models in soil erosion. The finding can lay the theoretical and technical foundation for regional development planning. [ABSTRACT FROM AUTHOR]

The Palu MW7.4 earthquake occurred on September 28, 2018, with the epicenter at 119.86°, 0.72°. The severe shaking caused severe damage in Central Sulawesi, especially in Palu. We conducted a postseismic deformation study to determine the deformation pattern and reduce future earthquakes' impact. Interferometric Synthetic Aperture Radar (InSAR) data were processed using LiCSBAS to get the time series. The time series data were fitted to exponential and logarithmic functions to determine the mechanism of postseismic deformation. The exponential model identified the influence of the viscoelastic mechanism, and the logarithm identified the afterslip mechanism. The Palu earthquake was fitted to logarithmic and exponential, but the logarithmic was more significant than an exponential function. Afterslip mechanism predominates, and viscoelastic mechanisms play a minor role in this postseismic deformation.

In recent years, deep learning methods have shown significant potential in soil moisture modeling. However, a prominent limitation of deep learning approaches has been the absence of physical mechanisms. To address this challenge, this study introduces two novel loss functions designed around physical mechanisms to guide deep learning models in capturing physical information within the data. These two loss functions are crafted to leverage the monotonic relationships between surface water variables and shallow soil moisture as well as deep soil water. Based on these physically-guided loss functions, two physically-guided Long Short-Term Memory (LSTM) networks, denoted as PHY-LSTM and PHYs-LSTM, are proposed. These networks are trained on the global ERA5-Land dataset, and the results indicate a notable performance improvement over traditional LSTM models. When used for global soil moisture forecasting for the upcoming day, PHY-LSTM and PHYs-LSTM models exhibit closely comparable results. In comparison to conventional data-driven LSTM models, both models display a substantial enhancement in various evaluation metrics. Specifically, PHYs-LSTM exhibits improvements in several key performance indicators: an increase of 13.6% in Kling-Gupta Efficiency (KGE), a 20.7% increase in Coefficient of Determination (R2), an 8.2% reduction in Root Mean Square Error (RMSE), and a 4.4% increase in correlation coefficient (R). PHY-LSTM also demonstrates improvements, with a 14.8% increase in KGE, a 19.6% increase in R2, an 8.2% reduction in RMSE, and a 4.4% increase in R. Additionally, both models exhibit enhanced physical consistency over a wide geographical area. Experimental results strongly emphasize that the incorporation of physical mechanisms can significantly bolster the predictive capabilities of data-driven soil moisture models.

Seismic isolation can significantly improve the seismic resilience of buildings, resulting in a growing demand for seismic isolation designs. Meanwhile, the deep generative network‐based intelligent design can significantly increase scheme design efficiency. However, the performance of existing intelligent scheme designs is constrained by data quality and quantity. The limited availability of isolation design data hinders the development of intelligent seismic isolation design. Therefore, there is an emerging demand to establish an intelligent scheme design method that is free from data constraints and that can learn the physical mechanism and design rules. Consequently, this study proposes a physics‐rule‐co‐guided self‐supervised generative adversarial network (GAN) that can generate the layout and parameters of seismic isolation bearings by inputting the layout drawings of the shear wall structures. The critical physics‐rule‐co‐guided network model consists of a physics estimator, rule evaluator, discriminator, and design generator. The physics estimator is a deep neural network‐based surrogate model for predicting the mechanical response of an isolated structure, whereas the rule evaluator is a tensor operation‐based loss calculator that considers design rules. Furthermore, the proposed GAN model masters the schematic design ability of the seismic isolation of shear wall structures through multiphase hybrid learning of the pseudo‐labels, physical mechanism, and isolation design rules, obviating the need for ground‐truth data. Case studies also prove the rationality of the method, where the design results can effectively meet the code requirements and reduce the seismic response of the structure. [ABSTRACT FROM AUTHOR]

The observation-based air pollution forecasting method has high computational efficiency over traditional numerical models, but a poor ability in long-term (after 6 h) forecasting due to a lack of detailed representation of atmospheric processes associated with the pollution transport. To address such limitation, here we propose a novel real-time air pollution forecasting model that applies a hybrid graph deep neural network (GNN_LSTM) to dynamically capture the spatiotemporal correlations among neighborhood monitoring sites to better represent the physical mechanism of pollutant transport across the space with the graph structure which is established with features (angle, wind speed, and wind direction) of neighborhood sites to quantify their interactions. Such design substantially improves the model performance in 72-hour PM2.5 forecasting over the whole Beijing-Tianjin-Hebei region (overall R2 increases from 0.6 to 0.79), particularly for polluted episodes (PM2.5 concentration > 55 µg/m3) with pronounced regional transport to be captured by GNN_LSTM model. The inclusion of the AOD feature further enhances the model performance in predicting PM2.5 over the sites where the AOD can inform additional aloft PM2.5 pollution features related to regional transport. The importance of neighborhood site (particularly for those in the upwind flow pathway of the target area) features for long-term PM2.5 forecast is demonstrated by the increased performance in predicting PM2.5 in the target city (Beijing) with the inclusion of additional 128 neighborhood sites. Moreover, the newly developed GNN_LSTM model also implies the “source”-receptor relationship, as impacts from distanced sites associated with regional transport grow along with the forecasting time (from 0% to 38% in 72 h) following the wind flow. Such results suggest the great potential of GNN_LSTM in long-term air quality forecasting and air pollution prevention.

Climate change has led to an increase in the frequency of extreme events, such as droughts and floods. This study aims to review the literature on the newly proposed phenomenon known as drought-flood abrupt alternation (DFAA). A comprehensive summary is provided to round up the numerous approaches employed to identify DFAA events, as well as its mechanisms and impacts. To provide a reference for responding and managing the emerging intensity and frequency of DFAA events, we conclude the paper by listing the insufficiency of current research and suggesting possible future research directions. As for the impact of DFAA, besides the loss of life and property which can be caused by any natural disaster, a DFAA event severely threatens food security by making a lasting and profound impact on the land productivity through the alteration of the combining conditions of water, soil, and temperature. As for the future research directions, existing indexes developed for DFAA identification should be improved by downscaling the temporal and spatial scale, with interactions of neighboring drought and flood events taken into consideration. What’s more, to better protect human society from the losses caused by DFAA, researches on accurate DFAA prediction are encouraged.

With the rapid development of emerging artificial intelligence technology, brain–computer interfaces are gradually moving from science fiction to reality, which has broad application prospects in the field of intelligent robots. Looking for devices that can connect and communicate with living biological tissues is expected to realize brain–computer interfaces and biological integration interfaces. Brain‐like neuromorphic devices based on memristors may have profound implications for bridging electronic neuromorphic and biological nervous systems. Ultra‐low working voltage is required if memristors are to be connected directly to biological nerve signals. Therefore, inspired by the high‐efficient computing and low power consumption of biological brain, memristors directly driven by the electrical signaling requirements of biological systems (bio‐voltage) are not only meaningful for low power neuromorphic computing but also very suitable to facilitate the integrated interactions with living biological cells. Herein, attention is focused on a detailed analysis of a rich variety of physical mechanisms underlying the various switching behaviors of bio‐voltage memristors. Next, the development of bio‐voltage memristors, from simulating artificial synaptic and neuronal functions to broad application prospects based on neuromorphic computing and bio‐electronic interfaces, is further reviewed. Furthermore, the challenges and the outlook of bio‐voltage memristors over the research field are discussed. [ABSTRACT FROM AUTHOR]

We take red sandstone as the research object and apply the freeze-thaw cycles, CT scans and mechanical properties experiments. We use image processing technology combined with genetic algorithm optimization model to achieve the denoise, enhancement, segmentation and three-dimensional reconstruction of CT scan images after 0, 5, 10, 20, and 40 freeze-thaw cycles. With the damage identification and comparative study of the same object across scales, we established a prediction formula of elastic modulus deterioration based on mesoscopic damage. Therefore, the macroscopic mechanical behavior of freeze-thaw red sandstones can be interpreted from the physical nature of the material meso-structure. The results show that genetic algorithm based on image maximum entropy can quickly and accurately select the threshold for image segmentation, and achieve the recognition of matrix and defects in rock meso-structure. With the increase of freezing and thawing cycles, the porosity of rock increases, and the fractal dimension of pore decreases. On the meso-scale, the evolution shows that the pores expand and the number increases, but the structural complexity decreases. The macroscopic and mesoscopic damage variables defined by the traditional methods are based on the effective bearing area and elastic modulus, and they fail to fully consider the damage physical mechanism and the internal structure information of the material. The damage evolution curves are different. Based on the two physical mechanisms, we define the meso-damage variable and the macro-damage variable that considers the natural rock damage, which achieves the combination of macroscopic and mesoscopic damages. Finally, according to the relationship between meso-structure evolution and macroscopic mechanical response in the process of freeze-thaw cycles, we propose a prediction formula of elastic modulus degradation, and analyze the different dominant roles of pore size and pore structure morphology through the damage process. We interpret the mechanical mechanism of macroscopic sandstone freeze-thaw damage based on the meso-structure physical mechanisms.

• The micro-nano structure response of Zr-based alloys with different crystallinity when subjected to nanosecond pulsed laser irradiation was investigated. • The microstructural transformation between micro-concave and micro-convex was independent of the arrangement of the internal atomic structure of the Zr-based alloy. • The geometrical dimension of the laser-induced micro-nano structures was strongly dependent on the crystallinity of Zr-based alloys. • A point-by-point laser patterning technique was developed for achieving flexible preparation of micro-nano patterns, which exhibited an ultra-high processing efficiency with a material accumulation rate of more than 1012 μm3/s. Understanding the processes and mechanisms of laser-matter interaction is fundamental to the treatment of materials by using laser-based methods, but it is quite challenging because the response of matter to laser irradiation is influenced by many factors, especially the intrinsic properties of the matter. In this study, the influence of crystallinity on micro-nano structure response of Zr-based alloys (Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5) treated by nanosecond laser is investigated. The microscopic topographies and geometrical dimensions of the laser-induced micro-nano structures formed on the surface of Zr-based alloys with different crystallinity have been explored and compared. The experimental results indicate that the microstructural transformation between micro-concave and micro-convex is observed for both amorphous and crystallized Zr-based alloys, i.e., independent of the arrangement of the internal atomic structure. The geometrical dimensions of the laser-induced micro-nano structures and the critical peak laser power intensity required for the microstructural transformation are different, which can be attributed to the difference in thermal conductivity. Inspired by laser-induced micro-convex, a point-by-point laser patterning technique has been proposed for highly efficient and flexible preparation of micro-nano patterns. Importantly, this patterning technique exhibits ultra-high processing efficiency with a material accumulation rate of more than 1012 μm3/s. This work paves an avenue for understanding the laser-matter interaction and is expected to facilitate the advanced functional applications of Zr-based alloys in many fields. [ABSTRACT FROM AUTHOR]

The intrinsic connection between the transverse photonic spin Hall effect (PSHE) and the Imbert–Fedorov shift has been well characterized. However, physical insights into the longitudinal photonic spin splitting associated with the Goos-Hänchen (GH) shift remain elusive. This paper aims to expand the theory of the PSHE generation mechanism from the transverse to the longitudinal case by examining the reflection of each spin component from an arbitrarily linearly polarized incident Gaussian beam on the air-dielectric interface. Unlike the transverse case, both spin-maintained and spin-flipped modes exhibit non-zero longitudinal displacements, with the latter being affected by the second-order expansion term of the Fresnel reflection coefficient with respect to the in-plane wave-vector component. Meanwhile, the polarization angle plays a crucial role in determining the longitudinal PSHE since each reflected total spin component is a coherent superposition of these two corresponding modes. Remarkably, the imaginary part of the relative permittivity of the dielectric significantly affects the symmetry of the longitudinal PSHE. Furthermore, the GH shift results from a superposition of individual spin states’ longitudinal displacements, taking into account their energy weights. By incorporating the corresponding extrinsic orbital angular momentum, we explore the generation mechanism of the symmetric/asymmetric longitudinal PSHE. The unified physical framework elucidating the longitudinal photonic spin splitting and GH shift provides a comprehensive understanding of the fundamental origin of the PSHE and beam shifts, paving the way for potential applications in spin-controlled nanophotonics.

Abstract With the rapid development of emerging artificial intelligence technology, brain–computer interfaces are gradually moving from science fiction to reality, which has broad application prospects in the field of intelligent robots. Looking for devices that can connect and communicate with living biological tissues is expected to realize brain–computer interfaces and biological integration interfaces. Brain‐like neuromorphic devices based on memristors may have profound implications for bridging electronic neuromorphic and biological nervous systems. Ultra‐low working voltage is required if memristors are to be connected directly to biological nerve signals. Therefore, inspired by the high‐efficient computing and low power consumption of biological brain, memristors directly driven by the electrical signaling requirements of biological systems (bio‐voltage) are not only meaningful for low power neuromorphic computing but also very suitable to facilitate the integrated interactions with living biological cells. Herein, attention is focused on a detailed analysis of a rich variety of physical mechanisms underlying the various switching behaviors of bio‐voltage memristors. Next, the development of bio‐voltage memristors, from simulating artificial synaptic and neuronal functions to broad application prospects based on neuromorphic computing and bio‐electronic interfaces, is further reviewed. Furthermore, the challenges and the outlook of bio‐voltage memristors over the research field are discussed.

In the early 1960s, Tóth obtained hierarchical groundwater flow systems by using analytical solution based on given-head upper boundary, which is a milestone breakthrough in hydrogeology and successfully solved a series of theoretical and practical problems.However, the defects of Tóth's analytical solution have been followed for a long time such as focusing solely on mathematical simulation and ignoring the physical mechanism; taking terrain control of water table as a universal law; and ignoring the distortion of the mathematical simulation based on given-head upper boundary.These shortcomings, especially the lack of the physical mechanisms exploration, not only hindered the development of Tótian theory itself, but also made the theory difficult to be understood, so that the theory has not being widely applied yet by the international hydrogeological community.This paper proposes an expression for the minimum energy consumption rate of groundwater flow referring to the principle of minimum energy consumption rate applied in river dynamics.Based on the exited results of "numerical simulation of groundwater flow patterns using flux as upper boundary", the physical mechanism is further explored, and it is concluded that groundwater flow follows the principle of minimum energy consumption rate.

Owing to global warming, extreme precipitation events in the arid regions of Central Asia have increased, resulting in significant consequences for water resources and ecosystems. Hence, to address the features and corresponding physical mechanisms of these rainstorms, we examined the rainstorm that occurred in Hotan, Xinjiang in June 2021 as a case study. We employed multiple datasets, including meteorological stations, sounding observations, satellite precipitation data, and reanalysis datasets. The results indicate that the Global Precipitation Measurement satellite precipitation product accurately captured the temporal and spatial variations in this rainstorm, as verified against hourly in situ observation data. Some meteorological stations recorded values greater than twice their historical records, such as Luopu, Pishan, Moyu, and Hotan. Moreover, the duration of the precipitation was longer than 2 days. For the physical mechanisms of this rainstorm, the water vapor in this rainstorm is sourced from the 45°–65°N region of the North Atlantic Ocean crosses the Ural Mountains and the West Siberian Plain to southern Xinjiang. The low-pressure levels (e.g., 700 hPa and 850 hPa) have the more water vapor flux and specific humidity than the high-pressure levels. Our findings can aid the understanding of extreme precipitation events in Central Asia and provide a reference for dealing with meteorological disasters, including extreme precipitation, in the context of global climate change.

The giant electrocaloric effect (ECE) in ferroelectrics arouses enthusiasm on the electrocaloric refrigeration for its zero global-warming-potential. Previous studies have observed that large ECE response occurs around ferroelectric-paraelectric phase transition in BaTiO 3 -based ferroelectrics. However, few attention is paid to the effect of phase fraction on ECE performance. In this work, Ba 1- x Sr x Ti 0.95 Sn 0.05 O 3 ceramics which display varied phase fraction of orthorhombic and tetragonal (O and T) phase at room temperature, are developed to reveal the influence of phase fraction on the electric properties, especially ECE performance. The electrocaloric temperature change (Δ T) is enhanced in composition with equal phase fraction of O and T, which also shows excellent piezoelectric property. Intrinsically, a number of nanodomains are formed due to the incorporation of Sr2+, greatly benefiting the invertibility of domains under the electric field. It is believed that this study opens a new way for designing and understanding of ECE in BT-based ceramics. [ABSTRACT FROM AUTHOR]

The Asian-Pacific Oscillation (APO), featuring a seesaw pattern in the upper-tropospheric temperatures between Asia and the North Pacific, plays profound roles in the Northern Hemispheric climate anomalies. So, its variability and associated physical mechanisms are of great interest. Although progress has been achieved for the APO variability at the interannual time scale, the understanding of its interdecadal variability remains relatively poor. Based on the twentieth-century reanalysis and the simulations of the preindustrial control, Pacific pacemaker, and large ensemble experiments, this study reports a salient contribution of the Pacific Decadal Oscillation (PDO) to the interdecadal variability of the APO during summer, featured as a warm (cold) PDO phase accompanying a negative (positive) APO polarity. During the warm PDO phase, the sea surface temperature (SST) warming over the eastern Pacific is conducive to local ascending anomalies, which teleconnect with descending anomalies over the Tibetan Plateau through zonal vertical circulations. The anomalous ascent (descent) over the eastern Pacific (Tibetan Plateau) tends to strengthen (weaken) the atmospheric heating, beneficial for a warming (cooling) of the troposphere in situ. In addition, the PDO-related meridional SST gradient anomalies favor a southward shift of the subtropical jet stream, weakening the South Asian high and the North Pacific trough in the upper troposphere, which corresponds to the atmospheric situation of a negative APO phase. Quantitative analysis from the large ensemble simulations indicates that the PDO may contribute to approximately 48% of recent APO interdecadal variation from the negative phase to the positive phase in the late 1990s. • PDO and APO in summer are significantly and negatively correlated at the interdecadal time scale. • PDO may contribute to approximately 48% of APO interdecadal variation occurring in the late 1990s by the CESM-LE simulations. • PDO relates to APO through its influence on the zonal-vertical circulation and upper-tropospheric atmospheric circulation. [ABSTRACT FROM AUTHOR]

Debris-flow disaster has caused large casualties and tremendous economic loss. Check dams, flexible barriers, silt dams and baffle arrays are most used disaster prevention countermeasures. For a better design strategy, we made a thorough review and discussion about the achievements and challenges in four important aspects, including impact force estimation, run-up height prediction, failure analysis and plain configuration planning. The impact force exerted by debris flow on structures is the most crucial design parameter, while most widely used models are based on hydraulic theory and lack physical mechanisms, especially in accounting for the effect of nonstationary flow regimes, impact patterns and barrier characteristics. Current methods of designing protection structures mainly depend on static and deterministic theory to address dynamic problems that are highly stochastic, which reveals a great research gap in understanding the response and failure under impact of structures. In future, physically based design strategy should be highlighted, for which robust physical modelling methods and numerical simulation tools are needed for the better understanding of flow–structure interaction mechanism and the verification of structure design strategy. Furthermore, the resilience-based disaster prevention concept should be highlighted for its outstanding ability in preparedness, response, and recovery when threatened by unknown disasters. [ABSTRACT FROM AUTHOR]

Abstract With the continuous decreasing in sizes of functional materials and devices, people are being asked to perform a flexible, accurate, in-situ and non-thermal welding of nanowires at the nanoscale. In this work, a well deliberated procedure including three typical stages: sharpening, hooking and welding, was carried out in sequence by in-situ TEM to realize the high demand welding of SiOx nanowire to macroporous carbon film. It was found that the brittle SiOx nanowire was non-thermally softened under energetic e-beam irradiation, and the flexibility and accuracy of welding could be achieved by adjusting the beam spot size, irradiation location and irradiation time. It was demonstrated that the nanocurvature effect of SiOx nanowire and the ultra-fast energy deposition effect induced by energetic e-beam irradiation dominated the diffusion, evaporation and plastic flow of atoms and the resulting nanowire re-shaping and nanowelding processes. In contrast, the traditional knock-on mechanism and e-beam heating effect are inadequate to explain these phenomena. Therefore, such a study is crucial not only to the flexible technical controlling but also to the profound fundamental understanding of energetic e-beam-induced nanowire re-shaping and nanowelding.

Terahertz band in electromagnetic spectrum has many properties than traditional light source, which has very important research value in biology, material, security, communication and other fields. The high power and high efficiency terahertz radiation source is an important factor and prerequisite for the transformation of terahertz technology into actual productivity. In this paper, the research progress of terahertz wave generated by laser interacting with different excitation media is summarized from the perspective of gas, solid and liquid as excitation media. The physical mechanism of four-wave mixing, mass-dynamic, cherenkov and photocurrent models commonly used in gas media, as well as the physical mechanism of photo-conductance and photorectification models in solid media are described in detail, and the factors affecting the generation of terahertz waves by these excitation media are analyzed and summarized. Finally, the methods of producing terahertz radiation source by liquid excited medium are prospected.

In this article, characterization of fully patterned zinc-tin oxide (ZTO)-based memristive devices with feature sizes as small as 25 µm2 is presented. The devices are patterned via lift-off with a platinum bottom contact and a gold-titanium top contact. An on/off ratio of more than two orders of magnitude is obtained without the need for electroforming processes. Set operation is a current controlled process, whereas the reset is voltage dependent. The temperature dependency of the electrical characteristics reveals a bulk-dominated conduction mechanism for high resistance states. However, the charge transport at low resistance state is consistent with Schottky emission. Synaptic properties such as potentiation and depression cycles, with progressive increases and decreases in the conductance value under 50 successive pulses, are shown. This validates the potential use of ZTO memristive devices for a sustainable and energy-efficient brain-inspired deep neural network computation.

Many studies have examined elevation-dependent warming in mountain regions of the world, yet little attempt has been undertaken to examine the relationship of the observed warming with both altitude and latitude on a regional scale. Here, based on the mean temperature series (1961–2015) of 105 stations in the Tibetan Plateau, the signals of warming amplification with these two factors are quantified using four groups of methods. The results, highly consistent for the different methods, confirm that the warming for the Tibetan Plateau is not only elevation-dependent, but also latitude-dependent, and the magnitude of altitudinal amplification trend is two orders of magnitude larger than that of latitudinal amplification trend on the annual and seasonal scales over the period 1961–2015. The annual warming is amplified by 0.066°C 10 year−1·km−1 of altitude and 0.016 × 10−2°C 10 year−1·km−1 of latitude (or 0.018°C 10 year−1·degree−1 of latitude), with the highest altitudinal (latitudinal) amplification in winter (autumn), followed by autumn (winter) and the lowest in spring and summer. Meanwhile, the estimates of altitude and latitude components of the regional warming shows that the contribution of latitude to the regional warming is larger than that of altitude on the annual scale and for all seasons excepting summer, due primarily to the much larger range of latitude than the range of altitude covered by all the stations used. Moreover, analysis of the number of snow cover days demonstrates that the snow albedo feedback has played a significant role in enhancing the warming in the Tibetan Plateau during the recent sub-period 1996–2015, due to the decrease of snow cover days in the spring, autumn and winter seasons. These results highlight an integrated picture of Tibetan Plateau warming amplification, and a clear snow albedo feedback effect on the regional amplification, allowing better investigation of impacts andmechanisms. [ABSTRACT FROM AUTHOR]

The DC and AC performances of proton radiated Silicon-Germanium (SiGe) Heterojunction Bipolar Transistors (HBTs) with different emitter areas at liquid nitrogen temperature (77 K), room temperature and heating hotplate (393 K) were presented in this work. Performance dependence on the emitter area and temperature was investigated. Results showed that SiGe HBTs with a large emitter area had more damage by proton radiation. Furthermore, the SiGe HBTs showed better tolerance to proton radiation at extreme temperatures than at room temperature. To reveal the underlying mechanism, the radiated SiGe HBTs were modeled based on the device structure and parameters. The electron density, Shockley–Read–Hall (SRH) recombination and carrier mobility were extracted from the device model and demonstrated to have major impacts on the performance dependence of the radiated SiGe HBTs. The results provide useful guidance for the application of SiGe HBTs at extreme environments. [ABSTRACT FROM AUTHOR]

• The BNT-BT- x BFOMT polycrystalline thin films were successfully prepared on Pt (111)/Ti/SiO 2 /Si (100) substrates by the sol-gel method. • The coexistence of long-range ordered and short-range disordered nanodomains is realized in the multi-phase BNT-0.06BT-0.01BFOMT thin film. • This kind of coexisting domain structure can reduce the potential barrier and the hysteresis, and improve the piezoelectric properties significantly. • The piezoelectric properties of the BNT-BT thin films are enhanced nearly 2.3 times. Although the multi-phase coexistence makes Bi 0.5 Na 0.5 TiO 3 -based piezoelectric thin films possess stronger piezoelectric properties and more spacious application prospects in electronic devices, the domain reversal mechanism of Bi 0.5 Na 0.5 TiO 3 -based thin films cannot be accurately understood due to the size effect. In this study, the relationship between domain structure and piezoelectric properties of the (0.94-x)Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 -xBi(Fe 0.95 Mn 0.03 Ti 0.02)O 3 thin films are studied by using visualization technology PFM, structure and electrical properties characterizations. The results show that the addition of Bi(Fe 0.95 Mn 0.03 Ti 0.02)O 3 creates a long-range ordered/short-range disordered nanodomain coexisting structure. This kind of coexisting domain structure can realize the long-range reversal driven by disordered nanodomains under the external electric field, reduce the potential barrier and the hysteresis, and significantly enhance the piezoelectric properties of the thin films. Under the same conditions, the piezoelectric properties of the 0.94Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 thin films are enhanced nearly 2.3 times. This provides a reference for exploring the physical mechanism of high performance lead-free piezoelectric thin films. [ABSTRACT FROM AUTHOR]

Magnetic viscosity (MV) effect is a disturbance to the transient electromagnetic method (TEM). This effect will cause slow decay at the intermediate-late time of the TEM responses, leading to erroneous interpretation. Although there are extensive researches on the MV distortion to TEM data, they are focused on conventional loop source configuration, while little has been studied for grounded-wire source configuration that has become the essential role for relatively deep-buried targets. Hence, we present the study of MV effect on the grounded-wire source TEM data. We first derived the formulas for calculating the secondary field due to MV effect, based on the Chikazumi model. The dependence of the MV effect on model parameters, such as resistivity, susceptibility, offset and geometry of the superparamagnetic layer, is then examined to illustrate the intrinsic physical mechanism of MV effect. We find that the MV effect on the grounded-wire source TEM data can be suppressed by adjusting the parameters of the survey design. Thereafter, we propose the method to quantify the MV effect when estimates of resistivity and susceptibility are available. Finally, the method for choosing the optimal offset to suppress the MV effect is proposed, which can be used as a guide for the installation of fieldwork of grounded-wire TEM survey.

The frequently observed tropospheric warm cores over the Tibetan Plateau (TP) are unique climate phenomena and are crucial to the Asian summer monsoon development. However, their climatological structure and formation mechanisms remain elusive and inconsistent among previous studies. In this work, two vertically separated warm cores, the upper-level warm cores (ULWCs) and lower-level warm cores (LLWCs), are identified based on the zonal temperature deviation. The LLWCs are basically confined below 450 hPa, and the ULWCs are mostly observed at 200–400 hPa. The active region of the LLWCs is generally within the TP domain and characterized by regional patches with high frequency occurrences. In contrast, the active region of the ULWCs is featured by a zonally elongated band along the southern TP. The physical mechanisms for the formations of these two distinct types of warm cores are revealed: the LLWCs are mainly generated and maintained by the surface diabatic heating, while the ULWCs are dominated by the large-scale circulation associated with the convection over the Indo-Pacific warm pool. During March–June, the ULWCs within the TP domain occur most frequently and the intensities attain their maxima. In March–April, the ULWCs are mainly determined by the TP adiabatic subsidence induced by the convection over the Indo-Pacific warm pool. In May–June, the warm advection induced by westerlies generates the downstream ULWCs and enhances the ULWCs formed in previous months. Hence it might be inappropriate in traditional view to attribute the tropospheric warm cores around the TP solely to the direct thermal effect of the elevated topography. [ABSTRACT FROM AUTHOR]

A significant number of modern earthquake prediction algorithms are based on general signs of loss of stability by the system, without reference to the physical mechanism behind the development of seismic instability. Considerations have been repeatedly expressed that such an approach is unlikely to lead to a completely satisfactory forecast. New geophysical evidence in favor of a fluid metamorphogenic model of the earthquake mechanism and data on the typical nature of the precursor seismic process are presented. The use of these new data for earthquake prediction is discussed. [ABSTRACT FROM AUTHOR]

This paper proposes a double-heterostructure (DH) GaN/AlGaN epitaxial layer that contains an AlGaN interlayer. The electrical properties are characterized and compared with conventional single-heterostructure (SH) GaN/AlGaN epitaxial layers. The Hall effect measurement shows that the DH GaN/AlGaN epitaxial layer has a carrier mobility of 1815 cm2 V−1 s−1, which is approximately 20.37% higher than the SH GaN/AlGaN epitaxial layer. The weak-beam dark-field images taken by transmission electron microscopy show that the AlGaN interlayer in the DH GaN/AlGaN epitaxial layer can block dislocations. The full widths at half maximum results show that there is no significant difference in the screw dislocation density between the SH and DH GaN/AlGaN epitaxial layers. However, the edge dislocation density and the overall internal stress in the DH GaN/AlGaN epitaxial layer are less than those in the SH GaN/AlGaN epitaxial layer. Finally, the physical mechanism of how edge dislocations impact the electrical properties of a DH GaN/AlGaN epitaxial layer is discussed. [ABSTRACT FROM AUTHOR]