Search Results (137)

Groundwater is an important factor for the stability of the subway station pit constructed in the offshore area. To reflect the effects of groundwater drawdown on the stability of the station pit, this work uses a surface settlement formula based on Rayleigh distribution to construct a continuous deformation velocity field based on Terzaghi's mechanism, so as to derive a theoretical calculation method for the safety factor of the deep station pit anti-uplift considering the effect of seepage force. Taking the seepage force as an external load acting on the soil skeleton, a simplified calculation method is proposed to describe the variation in shear strength with depth. Substituting the external work rate induced by self-weight, surface surcharge, seepage force, and plastic shear energy into the energy equilibrium equation, an explicit expression of the safety factor of the station pit is obtained. According to the parameter study and engineering application analysis, the validity and applicability of the proposed procedure are discussed. The parameter study indicated that deep excavation pits are significantly affected by construction drawdown and seepage force; the presence of seepage, to some extent, reduces the anti-uplift stability of the station pit. The calculation method in this work helps to compensate for the shortcomings of existing methods and has a higher accuracy in predicting the safety and stability of station pits under seepage situations. Full article

Background: The diameter of mature follicles in donkeys is several times larger than in cattle and sheep, but the key genes responsible for maintaining follicular development and preventing apoptosis remain unclear. Methods: This study observed the process of donkey follicular development using ultrasound and analyzed the changes in common reproductive hormones in serum. Granulosa cells (GCs) were collected from large (mature follicles, diameter ≥ 37 mm) and small (atretic follicles, diameter 10–25 mm) follicles for sequencing to screen differentially expressed genes (DEGs) and signaling pathways influencing the development of mature follicles. The roles of selected genes were further validated in in vitro cultured GCs. Results: Donkey follicles exhibited rapid growth 5–7 days before ovulation, reaching maturity at a diameter of 37 mm. The maximum diameter of ovulatory follicles was approximately 40.7 mm, while non-ovulatory follicles began to undergo atresia when reaching about 25 mm. Serum reproductive hormone levels aligned with follicular developmental status. RNA sequencing identified 3291 DEGs between large and small follicles, with KEGG analysis highlighting enrichment in the PI3K-Akt signaling pathway, focal adhesion, amoebiasis, and cancer pathways. Lentiviral overexpression and interference assays targeting the DEGs EMCN and SYT12 revealed that EMCN positively regulates FOXO3, a key gene in the PI3K-Akt pathway. Conclusions: The EMCN gene in mature donkey follicles regulates FOXO3 in the PI3K-Akt signaling pathway, potentially inhibiting apoptosis in follicular granulosa cells and sustaining follicular development until ovulation. This study provides insights into the mechanisms underlying follicular development in donkeys. Full article

Influenced by a warm and humid climate, the permafrost on the Qinghai–Tibet Plateau is undergoing significant degradation, leading to the occurrence of extensive thermokarst landforms. Among the most typical landforms in permafrost areas is thaw slump. This study, based on three periods of data from keyhole images of 1968–1970, the fractional images of 2006–2009 and the Gaofen (GF) images of 2018–2019, combined with field surveys for validation, investigates the distribution characteristics and spatiotemporal variation trends of thaw slumps in the Hoh Xil area and evaluates the susceptibility to thaw slumping in this area. The results from 1968 to 2019 indicate a threefold increase in the number and a twofold increase in total area of thaw slumps. Approximately 70% of the thaw slumps had areas less than 2 × 10⁴ m². When divided into a grid of 3 km × 3 km, about 1.3% (128 grids) of the Hoh Xil region experienced thaw slumping from 1968 to 1970, while 4.4% (420 grids) showed such occurrences from 2018 to 2019. According to the simulation results obtained using the informativeness method, the area classified as very highly susceptible to thaw slumping covers approximately 26% of the Hoh Xil area, while the highly susceptible area covers about 36%. In the Hoh Xil, 61% of the thaw slump areas had an annual warming rate ranging from 0.18 to 0.25 °C/10a, with 70% of the thaw slump areas experiencing a precipitation increase rate exceeding 12 mm/10a. Future assessments of thaw slump development suggest a possible minimum of 41 and a maximum of 405 thaw slumps occurrences annually in the Hoh Xil region. Under rapidly changing climatic conditions, apart from environmental risks, there also exist substantial potential risks associated with thaw slumping, such as the triggering of large-scale landslides and debris flows. Therefore, it is imperative to conduct simulated assessments of thaw slumping throughout the entire plateau to address regional risks in the future. Full article

Lentinan is one of the main metabolites of Lentinula edodes and exhibits numerous biological properties, such as antitumor and antioxidant activity. Despite recent advancements, its commercialization remains constrained by a lengthy cultivation cycle, low yield, and high cost. Therefore, screening strains with high polysaccharide production or enhanced bioactivity at the mycelial fermentation stage is of significant importance. In this study, the mycelial polysaccharide content and in vitro antioxidant activity of 18 L. edodes strains were evaluated under shaking and static culture conditions. The total polysaccharide content and IC₅₀ values under both culture conditions served as indicators for screening high-yielding and high in vitro antioxidant activity strains. Strain XG21 demonstrated superior polysaccharide production, with a total polysaccharide content of 78.80 mg in 50 mL of culture medium, which was 1.82 times higher than that of the main cultivated strain Xin808 (43.30 mg). Additionally, strain XG19 was identified for its high in vitro antioxidant activity, with total IC₅₀ values of 3.11 and 3.38 mg mL⁻¹ under shaking and static culture conditions, respectively. Further analyses on polysaccharide components, molecular weight, and enzyme activities were conducted on strains XG19, XG21, and Xin808. The results reveal that the polysaccharide from strain XG19 exhibited high uronic acid content and a significant weight-average molecular weight. Specifically, the intracellular polysaccharide uronic acid content (2.96%) was 2.22 and 1.14 times higher than that of Xin808 and XG21, respectively, while its weight-average molecular weight (Mw, 702.924 kDa) was 2.60 and 1.28 times greater than that of Xin808 and XG21. While the uronic acid content in its extracellular polysaccharides (EPSs) (8.26%) was similar to Xin808 and XG21, the Mw (83.894 kDa) was 1.56 times greater than that of XG21. Correlation analysis revealed that the content of extracellular polysaccharides and total polysaccharides was positively correlated with phosphoglucose isomerase (PGI) activity but negatively correlated with phosphoglucomutase (PGM) activity. These findings provide valuable strain information for the screening of mycelial polysaccharides with high yields and bioactivities. Full article

This study employed low-pressure chemical vapor deposition (LPCVD) SiN_x as both the gate dielectric layer and surface passivation layer, systematically investigating the effects of different growth conditions on the dielectric layer quality, two-dimensional electron gas (2DEG) characteristics, interface trap density, and devices’ performance, thereby optimizing the growth parameters of LPCVD SiN_x. The experiment investigated the effects of growth parameters such as the growth temperature, chamber pressure, and gas flow ratio on the growth rate of SiN_x during the process of growing SiN_x using the LPCVD technique. Further studies were performed to analyze the impact of SiN_x introduction on the 2DEG performance. The results indicated that both Si-rich and N-rich SiN_x compositions could enhance the 2DEG density improvement induced by SiN_x passivation. The impact of the gas flow ratio on the interface trap density is studied. Through the quantitative characterization of the interface trap density using the pulse-mode I_DS-V_GS method and frequency-dependent capacitance–voltage (C-V) measurement, the results show that the interface trap density decreases with an increased Si-to-N ratio. Full article

Extended operation in complex environments characterized by high temperatures, pressures, and hydrogen exposure can lead to performance degradation for S32168 stainless steel welds of hydrogenation reactors, which significantly impacts the reliability of hydrogenation reactors. The impact of the grinding process on the grinding temperature and force of S32168 steel welds is studied in this paper based on the W-M fractal dimension. A multi-grain grinding simulation model was built, and grinding experiments were conducted. The results show that the grinding speed and depth increased as the grinding temperature increased. At a speed of 20 m/s and depth of 15 μm, the temperature peaked at 1073 °C. Increasing the grinding depth increased both the temperature and force, while increasing the speed increased the temperature but reduced the force. When the depth was 15 μm and speed was 20 m/s, the maximum temperature was 939.1 °C. At a 15 μm depth and 10 m/s speed, the normal and tangential grinding forces peaked at 11.68 N and 9.33 N, respectively. When the depth was 5 μm and the speed was 20 m/s, the grinding forces were the lowest with normal and tangential forces of 0.93 N and 1.72 N, respectively. Comparing the simulated and experimental temperature results through nine sets of experiments, the error range was 6.97–14.2% with an average of 9.37%. The simulation model effectively simulated the grinding process. Full article

Vibrio parahaemolyticus is an aquatic animal pathogen. Recently, the detection rate of V. parahaemolyticus in freshwater products has exceeded that in seafood products, and the strains isolated from freshwater products exhibit better growth conditions in low-salinity environments. This study is based on a food risk detection activity in Changzhou, Jiangsu Province, China, investigating the variation of halophilism and the virulence of two groups of strains under different salt concentrations. Under 0%, 0.5%, and 1% salt, the strains from the freshwater showed faster growth than those from the seawater. In comparison, the strains from the seawater group under 2% and 3% salt grew faster than the growing status under the foregoing low-salt concentration environment. The cytotoxicity produced by the two strains was approximately 1.4 times higher in the 0.5% and 1% salt concentration groups compared to the 3% corresponding experimental group. Under the 0%, 0.5%, and 1% salt, the cytotoxicity of strains in the freshwater group increased by nearly 20% compared to that in the seawater groups. The freshwater strains showed altered halophilism and adapted to the low-salt environment. This research will be helpful in establishing a local and global control strategy against the diseases resulting from V. parahaemolyticus. Full article

The wet carbonation of coal gangue-based backfilling slurry (CGBS) is considered to be an effective method for the resource utilization of coal gangue solid waste and CO₂ sequestration, but CO₂ sequestration has a negative impact on the rheological properties of CGBS. This investigation explores the effect of carbonization pressure on the rheological properties and CO₂ sequestration properties of CGBS by using a carbonization reactor, a rheometer, X-ray diffraction, a nitrogen adsorption–desorption instrument, a scanning electron microscope and other testing methods. The results show that increasing the carbonization pressure can increase the CO₂ sequestration capacity of CGBS, and the carbonization products produced make the pores of CGBS smaller and the structure more compact; however, increasing the carbonization pressure will reduce the rheological properties of the slurry, and the optimal carbonization pressure is 0.7 MPa. At this time, the yield stress, plastic viscosity and hysteresis loop area of CGBS are 171.66 Pa, 0.0998 Pa·s and 1376 Pa/s, respectively. However, when the carbonization pressure is further increased, the CO₂ sequestration capacity tends to remain unchanged. This is mainly because the carbonization pressure causes the carbonization reaction to intensify, forming a calcified layer on the particle surface, which hinders the penetration of CO₂ into the particles. This study is of great significance for improving the utilization rate of gangue solid waste and CO₂ sequestration. Full article

Manganese-based oxides with good redox properties exhibit high soot oxidation activity. To further enhance their catalytic performance, introducing additional metal elements into manganese-based oxides is considered an effective approach. Herein, two rare earth elements (Sm and Ce)-modified MnO_x catalysts were prepared by the co-precipitation method. The synthesized MnO_x catalyst primarily consists of the Mn₃O₄ phase, with trace amounts of Mn₅O₈. The addition of Sm or Ce maintains the predominance of the Mn₃O₄ phase, increases the proportion of Mn₅O₈, and enhances the redox properties, thereby boosting the catalytic activity for NO and soot oxidation. Notably, the coexistence of Sm and Ce achieves optimal soot oxidation activity, with T₁₀ reaching 306 °C. Comprehensive physicochemical characterization elucidates the underlying structure–performance relationships of these catalysts. Full article

With the increasing demand for precise identification of underwater targets, the development of advanced underwater detection technologies has become a pivotal area of research. This study presents the design and implementation of a laser-based underwater detection system that leverages polarization characteristics to significantly enhance detection accuracy and target identification capabilities in complex aquatic environments. A key innovation of this research lies in the application of a dual-frequency modulation technology using a 532 nm pulsed laser. By modulating the high-frequency characteristics of the laser, this technique effectively suppresses backscattering interference within the water medium, improves the efficiency of target signal extraction, and exhibits exceptional performance, particularly in long-range detection and highly turbid water conditions. This paper elucidates the principles of underwater laser detection and polarization measurement, outlines the design of an integrated optical and mechanical system for laser transmission and reception, and introduces an optimized signal processing methodology. Experimental results demonstrate that the proposed system can reliably distinguish targets composed of different materials while maintaining high detection accuracy across a range of challenging environmental conditions. A comparative analysis further highlights the system’s significant advantages over traditional technologies, including enhanced noise suppression and greater detection depth. These findings establish a solid foundation for advancing underwater detection technologies and broadening their practical applications. Full article

Buried pipes are widely used for submarine water transportation, but the complex operating conditions in the seabed pose challenges for the modeling of buried pipes. In order to more accurately capture the dynamic behavior of the buried pipes in the seabed, in this study, considering the pipeline and soil as a systematic structure is proposed, improving the fluid–structure interaction four-equation model to make it applicable for the calculation of buried pipe system modes. After verifying the practicality of the model, considering the external seawater as uniform pressure, the coupling at the joints, and the Poisson coupling of submarine pipelines during transient processes are discussed, revealing that structural vibrations under both forms of coupling will cause greater hydraulic oscillations. The impact of soil elastic modulus on the system’s response is further discussed, revealing that increasing the modulus from 0 to 10¹⁵ Pa raises the wave speed from 498 m/s to 1483 m/s, causing a 40% increase in the amplitude of pressure oscillations. Finally, the vibration modes of the combined structure of pipe wall and soil are discussed, revealing that the vibration modes are mainly dominated by water hammer pressure, with the superposition of pipeline stress waves and soil stress waves. In this study, the dynamic behavior of submarine pipelines is elucidated, providing a robust foundation for regulating and mitigating fatigue failures in such systems. Full article

During the heat treatment process, bearing rings are subjected to drastic temperature variability and complex microstructural evolution, which result in deformation, high residual stresses, operational instability and a limited operating life. However, the underlying relationship between temperature, phase transformation, and deformation has not been fully revealed in previous research. As a result, it is difficult to accurately control the roundness of bearing rings during the heat treatment process. Therefore, a combination of numerical simulations and experimental methods was employed to analyze the heat treatment process of the rings of angular-contact ball bearings (ACBB) (7008C). Firstly, according to the multiple coupling theory of thermal, phase-transition, and stress–strain fields, a model for the numerical simulation of the quenching and tempering process was established. Secondly, the thermal–physical properties of the material were calculated using the Jmatpro 7.0 software, and the quenching and tempering processes were numerically simulated using the Deform software. Subsequently, the evolution of the stress, phase-transformation, and deformation behaviors of bearing rings during the quenching and tempering were studied in detail. Finally, the roundness errors of the bearing rings were obtained by a coordinate-measuring machine (CMM). The results showed that the axial and radial stress distributions at the surface and center of the bearing rings were significantly different. The bearing rings experienced uneven expansion and deformation. The roundness errors of the inner diameter and outer diameter of the inner ring were 0.0386 mm and 0.0423 mm, respectively. The roundness errors of the inner diameter and outer diameter of the outer ring were 0.0202 mm and 0.0180 mm, respectively. In this study, the mechanism of the effect of the temperature variation and phase transformation on deformation during the quenching and tempering process was revealed in detail. This provides a reference for controlling the roundness of bearing rings in actual production processes. Full article

Erosive rainfall is essential for initiating surface runoff and soil erosion to occur. The analysis on its temporal and spatial distribution characteristics is crucial for calculating rainfall erosivity, predicting soil erosion, and implementing soil and water conservation. This study utilized daily rainfall observation data from 90 meteorological stations in Henan from 1981 to 2020, and conducted geostatistical analysis, M-K mutation test analysis, and wavelet analysis on erosive rainfall to reveal the spatiotemporal distribution characteristics over the past 40 years. Building on this foundation, the correlation between erosive rainfall, rainfall, and rainfall erosivity were further explored. The findings indicated that the average annual rainfall in Henan Province varied between 217.66 mm and 812.78 mm, with an average yearly erosive rainfall of 549.24 mm and a standard deviation of 108.32 mm. Erosive rainfall constitutes for 77% of the average annual rainfall on average, and the analysis found that erosive rainfall is highly correlated with rainfall volume. The erosive rainfall increased from northwest to southeast, and had the same spatial distribution characteristics as the total rainfall. The number of days with erosive rainfall was 20.5 days and the annual average sub-erosive rainfall was 26.86 mm. The average annual rainfall erosivity in Henan Province ranged from 1341.81 to 6706.64 MJ·mm·ha⁻¹·h⁻¹, averaging at 3264.63 MJ·mm·ha⁻¹·h⁻¹. Both the erosive rainfall and the rainfall erosivity are influenced by the monsoon, showing a unimodal trend, with majority of the annual total attributed to rainfall erosivity from June to September, amounting to 80%. The results can provide a basis for forecasting of heavy rainfall events, soil conservation and planning, ecological treatment, and restoration. Full article

Global warming has led to an increasing frequency and intensity of extreme precipitation events worldwide. The extreme precipitation of Henan Province in central China usually occurs in summer, with the climate transition from the northern subtropical to the warm temperate climate. Compared with the study of extreme precipitation events in other regions, the study of Henan Province pays less attention. In order to systematically understand the spatial and temporal characteristics of extreme precipitation in Henan Province, this study applied RClimDex model to obtain nine extreme precipitation indices based on daily precipitation data from 90 meteorological stations from 1981 to 2020. Linear propensity estimation, M-K mutation test, Morlet wavelet analysis, and geostatistical analysis were used to investigate the spatial and temporal variation characteristics of the extreme precipitation indices in the region. The results indicated that continuous dry days (CDD), number of heavy rain days (R20mm), maximum daily precipitation (Rx1day), maximum precipitation for 5 consecutive days (Rx5day), and precipitation intensity (SDII) showed an overall increasing trend, but none passed the significance test (p > 0.01). Extremely strong precipitation (R99p) and Rx5day changed abruptly in 1994, and Rx1day and SDII changed abruptly in 2004. The seven extreme precipitation indices, except CDD and continuous wet days (CWD), had a 30-year cyclical pattern. The multi-year average of extreme precipitation indices showed that the CDD gradually decreased from north to south, CWD and R20mm gradually increased from north to south. Rx1day and Rx5day gradually increased from northwest to southeast, and SDII increased from west to east. The results can contribute valuable insights to extreme precipitation trends and future climate predictions in Henan Province and provide scientific support for coping with extreme precipitation changes and disaster prevention. Full article

Global climate change exerts great effects on plant distributions. However, the response of Prunus mira Koehne, one of the most important species for ecological protection in the southeast of the Qinghai–Tibet Plateau, to climate change remains unclear. To explore the ecological factors affecting the distribution of P. mira in the context of global climate change, the MaxENT model is used to predict suitable habitats for P. mira. Our study indicated that the distribution of Prunus mira Koehn is primarily influenced by temperature rather than precipitation, and warming can facilitate the growth of P. mira. When the temperature seasonality (bio4) ranges from 134 to 576 and the mean temperature of the coldest quarter (bio11) ranges from −2.6 °C to 2.7 °C, it is most conducive to the growth of P. mira. Among the four climate scenarios, the optimal habitat for P. mira is predominantly concentrated in river valley areas and is expected to expand into higher altitude regions, particularly in the north and southeast. SSP245 and SSP370 climate pathways are conducive to the growth and spatial expansion of P. mira. Our findings highlight the significant impact of temperature not precipitation on the distribution of P. mira, and this insight is crucial for the stability and conservation of this ecologically significant plant species. Full article