Search Results (171)

Rockfalls, among the most common natural disasters, pose risks such as traffic congestion, casualties, and substantial property damage. Guizhou Province, with China’s fourth-longest highway network, features mountainous terrain prone to frequent rockfall incidents annually. Consequently, assessing highway rockfall risks in Guizhou Province is crucial for safeguarding the lives and travel of residents. This study evaluates highway rockfall risk through three key components: susceptibility, hazard, and vulnerability. Susceptibility was assessed using information content and logistic regression methods, considering factors such as elevation, slope, normalized difference vegetation index (NDVI), aspect, distance from fault, relief amplitude, lithology, and rock weathering index (RWI). Hazard assessment utilized a fuzzy analytic hierarchy process (AHP), focusing on average annual rainfall and daily maximum rainfall. Socioeconomic factors, including GDP, population density, and land use type, were incorporated to gauge vulnerability. Integration of these assessments via a risk matrix yielded comprehensive highway rockfall risk profiles. Results indicate a predominantly high risk across Guizhou Province, with high-risk zones covering 41.19% of the area. Spatially, the western regions exhibit higher risk levels compared to eastern areas. Notably, the Bijie region features over 70% of its highway mileage categorized as high risk or above. Logistic regression identified distance from fault lines as the most negatively correlated factor affecting highway rockfall susceptibility, whereas elevation gradient demonstrated a minimal influence. This research provides valuable insights for decision-makers in formulating highway rockfall prevention and control strategies. Full article

Currently, chimney technology is looking for new materials with improved thermal insulation properties and, at the same time, adequate durability. The use of concretes based on lightweight aggregates, such as expanded perlite, is capable of meeting such a challenge, provided that the composition of the concrete mixes is appropriately modified. The main research challenge when designing chimney system casing elements lies in ensuring adequate resistance to moisture penetration (maximum water absorption of 25%), while achieving the lowest possible bulk density (below 1000 kg/m³), sufficient compressive strength (minimum 3.5 MPa), and capillary water uptake not exceeding 0.6%. In the present research, laboratory tests were conducted to improve the fundamental technical properties of lightweight perlite-based concrete to meet the aforementioned requirements. Laboratory tests of perlite concrete were carried out by adding eight chemical admixtures with a hydrophobic effect and the obtained results were compared with a reference concrete (without admixtures). However, the positive results obtained under laboratory conditions were not confirmed under actual production conditions. Therefore, further tests were conducted on chimney casings taken directly from the production line. Subsequent chemical admixtures with a hydrophobic effect, based on silane/siloxane water emulsions, were applied to determine the concrete mix’s optimal composition. The results of the tests carried out on perlite concrete chimney casings from the production line confirm the effectiveness of the applied chemical admixtures with a hydrophobic effect in improving the moisture resistance. This was further supported by the outcomes of the so-called ‘drop test’ and capillary uptake test, with the suitable bulk density and compressive strength being maintained. Full article

Snow water equivalent (SWE) can be estimated using Differential SAR Interferometry (DInSAR), which captures changes in snow depth and density between two SAR acquisitions. However, challenges arise due to SAR signal penetration into the snowpack and the intrinsic limitations of DInSAR measurements. This study addresses these issues and explores the use of multi-band SAR data to derive SWE maps in alpine regions characterized by steep terrain, small spatial extent, and a potentially heterogeneous snowpack. We first conducted a performance analysis to assess SWE estimation precision and the maximum unambiguous SWE variation, considering incidence angle, wavelength, and coherence. Based on these results, we selected C-band Sentinel-1 and L-band SAOCOM data acquired over alpine areas and applied tailored DInSAR processing. Atmospheric artifacts were corrected using zenith total delay maps from the GACOS service. Additionally, sensitivity maps were generated for each interferometric pair to identify pixels suitable for reliable SWE estimation. A comparative analysis of the C- and L-band results revealed several critical issues, including significant atmospheric artifacts, phase decorrelation, and phase unwrapping errors, which impact SWE retrieval accuracy. A comparison between our Sentinel-1-based SWE estimations and independent measurements over an instrumented site shows results fairly in line with previous works exploiting C-band data, with an RSME in the order of a few tens of mm. Full article

The presence of fissures poses significant threats to tunnel-lining structures, and the interaction between tunnels and linings under complex stress conditions remains poorly understood. This study investigated the failure modes of tunnel-lining structures with prefabricated fissures via 3D-printed samples, uniaxial compression experiments using DIC technology for full-field strain monitoring, and a particle-based meshless (SPH) numerical method to simulate tunnel–fissure interactions. The results show that under uniaxial compression, three crack types (main, upper/lower side cracks) initiate from the tunnel, while only wing cracks form at pre-existing fissures; wing crack initiation suppresses upper-side cracks, whereas more lining cracks (upper, middle, lower, corner, bottom) emerge without fissure-induced propagation. Fissure orientation (β) and inclination (α) significantly affect crack distributions: β = 90° induces maximum stress concentration and asymmetric deformation, while α ≥ 45° promotes wing crack initiation and reduces lining crack density. Along with our findings, we offer design recommendations to prioritize fissure orientation in tunnel engineering and expand SPH applications for predicting crack propagation in underground structures with complex fissures. Full article

The assessment of the maximum snow-water equivalent in mountains is important for understanding the mechanism of their formation, as well as for hydrological calculations. The low density of the observation network and the high complexity of ground-based snow-measuring operations have led to the widespread use of remote methods to obtain such data. In this study, the maximum water reserve of the Uba River basin was calculated for the period of 2020–2023, based on data from the Sentinel-2 satellite regarding the position of the seasonal snow line, obtained using the temperature-based melt-index method. This study determined the snowmelt coefficients for the meteorological stations at Zmeinogorsk, Shemonaikha, and Ridder. Maps were constructed to show the distribution of the maximum snow-water equivalent in the Uba River basin. The spatial differentiation features of the snow cover were revealed, depending on the elevation, slope exposure, and distance from the watersheds. It was established that the altitudinal distribution of snow cover on the northern and southern macro-slopes of the ridges is asymmetric: in the western part of the basin, within the elevation range of 500–1200 m, the maximum water reserves of snow cover are greater on the southern slopes, but they become higher on the northern slopes above 1200 m. In the eastern part of the basin, they are always larger on the northern slopes. The greatest differences in the distribution of snow cover between the slopes occur near the watersheds. Full article

This paper investigates the effects of initial porosity index and load range on the shear strength of a sand sample using direct shear tests performed with a standard direct shear apparatus under varying densities, from loose to compacted. This study focuses on the distinction between the peak $\left({\varphi }_p\right)$ and critical $\left({\varphi }_{cv}\right)$ internal friction angles and their variation with stress level and initial porosity. Results show that the internal friction angle of sand depends on the stress state and initial porosity, reaching a peak value at maximum shear stresses and a critical value at constant sample volume. Higher initial compaction increases the peak friction angle, while higher effective stresses reduce the critical porosity index. The critical state line (CSL) defines the contraction and dilation behaviour of soils, with the critical porosity index varying with average soil stress. The analysis confirmed Bolton’s empirical relationship, linking the peak friction angle with the critical state angle and the dilation angle. This study emphasizes the importance of accurately defining the internal friction angle and considering the nonlinear relationship between shear strength and normal stresses. These findings are significant for geotechnical engineering, particularly in foundation bearing capacity, earth pressure, and slope stability analysis. Full article

The study investigates the spectral, structural, and phase changes occurring in austenitic steel 12Kh18N10T during cathodic electrolytic plasma nitriding (EPN) in a Na₂CO₃–CO(NH₂)₂–NH₄Cl electrolyte at 550 °C for 10 min. Emission spectroscopy revealed active plasma components: N₂⁺, N I, Hα, and O I. The electron density, calculated from the Hα line broadening, was approximately 8.5 × 10¹⁸ cm⁻³. X-ray phase analysis revealed the formation of CrN, Fe₃N phases, and a solid solution of nitrogen in γ-Fe. SEM analysis revealed a three-layer structure of the nitrided layer: a nitride zone, a transition region, and the austenitic matrix. The EDS profile confirmed a decrease in nitrogen concentration, accompanied by a reduction in microhardness from a maximum of 480 HV at the surface, both gradually decreasing with depth. The friction coefficient decreased from ~0.8 (in the initial state) to ~0.6 after EPN. The results confirm the effectiveness of EPN in strengthening and improving the wear resistance of stainless steel. Full article

In the past two decades, there has been a tremendous increase in demand for services requiring a high bandwidth, a low latency, and high data rates, such as broadband internet services, video streaming, cloud computing, IoT devices, and mobile data services (5G and beyond). Optical wireless communication (OWC) technology, which is also envisioned for next-generation satellite networks using laser links, offers a promising solution to meet these demands. Establishing a line-of-sight (LOS) link and initiating communication in laser links is a challenging task. This process is managed by the acquisition, pointing, and tracking (APT) system, which must deal with the narrow beam divergence and the presence of satellite platform vibrations. These factors increase acquisition time and decrease acquisition probability. This study presents a framework for evaluating the acquisition time of four different scanning methods: spiral, raster, square spiral, and hexagonal, using a probabilistic approach. A satellite platform vibration model is used, and an algorithm for estimating its power spectral density is applied. Maximum likelihood estimation is employed to estimate key parameters from satellite vibrations to optimize scan parameters, such as the overlap factor and beam divergence. The simulation results show that selecting the scan path, overlap factor, and beam divergence based on an accurate estimation of satellite vibrations can prevent multiple scans of the uncertainty region, improve target satellite detection, and increase acquisition probability, given that the satellite vibration amplitudes are within the constraints imposed by the scan parameters. This study contributes to improving the acquisition process, which can, in turn, enhance the pointing and tracking phases of the APT system in laser links. Full article

To ensure the sustainable development of the surrounding environment and the sustainable operation of landfills, detecting landfill leakage is of great significance. In landfills lacking a leakage monitoring system, the inability to detect and locate damaged High-Density Polyethylene (HDPE) membranes can lead to the contamination of soil and groundwater by landfill leachate. To address this issue, this study proposes a resistivity tomography inversion model based on the external-electrode power supply mode. Utilizing the resistivity difference between the leakage zone and the surrounding soil, electrodes are arranged symmetrically for both power supply and measurement. Upon applying direct current (DC) excitation, potential data are collected, with the finite volume method employed for inversion and the Gauss–Newton method integrated with an adaptive particle swarm optimization algorithm for parameter fitting. Experimental results show that the combined algorithm provides better clarity in edge recognition of low-resistance models compared with single algorithms. The maximum deviation between inferred leakage coordinates and the actual location is 10.1 cm, while the minimum deviation is 6.4 cm, satisfying engineering requirements. This method can effectively locate point sources and line sources, providing an accurate solution for subsequent leakage point filling and improving repair efficiency. Full article

This study focuses on a 4FSK-modulated ultraviolet (UV) communication system, introducing an innovative symbol-level maximum likelihood decoding approach based on Poisson statistics. A forward error correction (FEC) coding mechanism is integrated to enhance system robustness. Through Monte Carlo simulations, the proposed decoding scheme and the error correction performances of Reed–Solomon (RS) and Low-Density Parity-Check (LDPC) codes are evaluated in UV channels. Both RS and LDPC codes significantly improve the Bit Error Rate (BER), with LDPC codes achieving superior gains under low SNR conditions. Hardware implementation and field tests validate the decoding algorithm and LDPC-optimized 4FSK system. Under non-line-of-sight (NLOS) conditions (10–45° transmit elevation angle), stable 60 m communication with BER < 10⁻³ is achieved. In line-of-sight (LOS) scenarios, the system demonstrates 900 m range with BER < 10⁻³, highlighting practical applicability in challenging atmospheric environments. Full article

Aiming at the problems of poor image quality of traditional cameras and serious noise interference of event cameras under complex lighting conditions in coal mines, an event denoising algorithm fusing spatio-temporal information and a method of denoising event target pose estimation is proposed. The denoising algorithm constructs a spherical spatio-temporal neighborhood to enhance the spatio-temporal denseness and continuity of valid events, and combines event density and curvature to achieve event stream denoising. The attitude estimation framework adopts the noise reduction event and global optimal perspective-n-line (OPNL) methods to obtain the initial target attitude, and then establishes the event line correlation model through the robust estimation, and achieves the attitude tracking by minimizing the event line distance. The experimental results show that compared with the existing methods, the noise reduction algorithm proposed in this paper has a noise reduction rate of more than 99.26% on purely noisy data, and the event structure ratio (ESR) is improved by 47% and 5% on DVSNoise20 dataset and coal mine data, respectively. The maximum absolute trajectory error of the localization method is 2.365 cm, and the mean square error is reduced by 2.263% compared with the unfiltered event localization method. Full article

On 1 December 2023, a strong geomagnetic storm was triggered by an interplanetary shock caused by a coronal mass ejection (CME). This study used data from 193 Global Navigation Satellite System (GNSS) observation stations in China to study the three-dimensional morphological total electron content (TEC) disturbances during this storm. By analyzing GNSS TEC data from 15 GNSS stations along the magnetic field lines, it was found that TEC disturbances spread from low to high latitudes, confirmed by ionosonde NmF2 data. The TEC disturbance first appeared at the LJHP station, (21.68° N) at 11:30 UT and propagated to the BJFS station (39.60° N) at 13:30 UT with a propagation speed of about 217 m/s and maximum amplitude of ±0.2 m. The TEC disturbance lasted the longest, approximately 4 h, between latitudes 25° N and 32° N. Additionally, this study investigated the ionosphere’s three-dimensional electron density distribution in the Guangxi region using an ionospheric tomography algorithm. Results showed that the TEC disturbances were mainly concentrated between 450 and 580 km in altitude. At 12:00 UT, the maximum change in electron density occurred at a 580 km height at 26° N, 112° E, increasing by 20.54 total electron content unit (TECU). During the main phase of the geomagnetic storm, the electron density expanded from higher to lower layers, while during the recovery phase, it recovered from the lower layers to the higher layers. Full article

The method of matched asymptotic expansions is applied to analyze the meniscus around a floating particle. The asymptotic solutions, derived while considering Fraenkel’s warning, are expressed as functions of the filling angle and contact angle. The analytical solutions accurately predict both the filling angle and the position of the three-phase contact line, even for larger $ϵ$ values. The deformed free surface profile around a single floating particle shows excellent agreement with numerical results obtained from transformed equations using the inclination angle of the deformed surface. The matched asymptotic solutions reveal two distinct steady-state interface configurations, with one stable configuration identified through vertical stability analysis. This asymptotic approach enables the construction of stability diagrams for floating conditions, helping determine the maximum floatable particle size or density ratio for sustained flotation. The methodology developed here provides a foundation for future research on buoyancy for particles of various shapes and stability under dynamic conditions. Full article

The stay-green (SG) trait enhances photosynthetic activity during the late grain-filling period, benefiting grain yield under drought and heat stresses. CH7034 is a wheat breeding line with SG. To clarify the SG loci carried by CH7034 and obtain linked molecular markers, in this study, a recombinant inbred line (RIL) population derived from the cross between CH7034 and non-SG SY95-71 was genotyped using the Wheat17K single-nucleotide polymorphism (SNP) array, and a high-density genetic map covering 21 chromosomes and consisting of 2159 SNP markers was constructed. Then, the chlorophyll content of flag leaf from each RIL was estimated for mapping, and one QTL for SG on chromosome 7D was identified, temporarily named QSg.sxau-7D, with the maximum phenotypic variance explained of 8.81~11.46%. A PCR-based diagnostic marker 7D-16 for QSg.sxau-7D was developed, and the CH7034 allele of 7D-16 corresponded to the higher flag leaf chlorophyll content, while the 7D-16 SY95-71 allele corresponded to the lower value, which confirmed the genetic effect on SG of QSg.sxau-7D. QSg.sxau-7D located in the 526.4~556.2 Mbp interval is different from all the known SG loci on chromosome 7D, and 69 high-confidence annotated genes within the interval expressed throughout the entire period of flag leaf senescence. Moreover, results of an association analysis based on the diagnostic marker showed that there is a positive correlation between QSg.sxau-7D and thousand-grain weight. Our results revealed a novel QTL QSg.sxau-7D whose CH7034 allele had a strong effect on SG, which can be applied in further wheat molecular breeding. Full article

Sustainable management of forest ecosystems requires assessing forest dynamics and project stand growth and yield in order to make strategic decisions. The size–density relationship is one of the most important measures in quantifying the carrying capacity of a forest ecosystem and determining appropriate silvicultural decisions. In this study, the maximum stand density index (SDI_max) was estimated for three common pine species in seven different ecological regions across Türkiye. Observations from 14,413 sample plots, including Calabrian pine (Pinus brutia Ten.; 6266 plots from five regions), Black pine (Pinus nigra J.F. Arnold; 6106 plots from five regions) and Scots pine (Pinus sylvestris L.; 2041 plots from three regions) forests were used in this study, covering the entire natural range of these three pine species. A mixed model with region as a random effect was developed for each species to estimate SDI_max. Results show that the slope coefficients of the self-thinning lines vary by species and are significantly different from −1.605. The Scots pine stands exhibited the highest SDI_max, followed by Black pine and Calabrian pine stands. Across seven ecological regions, the highest SDI_max was observed in the Aegean region for Calabrian and Black pine and in the East Anatolia region for Scots pine. The arid Inner Anatolia region yielded the lowest SDI_max for Black pine and Scots pine. The humid and semi-humid regions showed a higher SDI_max compared to arid regions. The three pine species studied make up almost half of the total forest area in Türkiye. The results of the study are therefore very important in terms of quantitative assessment of the country’s forests. The differences in stand dynamics of these three pine species, which are also widely distributed outside Türkiye under different ecological conditions, may also be a relevant source of information for other regions. Moreover, considering that pine stands in dry environments have a lower carrying capacity than those in humid conditions, it seems likely that pine forests in Türkiye will be affected by increasing global warming. Full article