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This study conducts a series of large-scale pullout tests to explore the pullout behavior of the biaxial geogrid-calcareous sand interface. It investigates the effects of normal stress, relative density, and embedded length on the interface pullout behavior of geogrid reinforcement in calcareous sand. In addition, this research examines changes in interface shear strength and the interface friction coefficient. The interface interaction mechanism of geogrid reinforcement in calcareous sand and the evolution of pullout force-clamp displacement curves are determined. The results indicated that the pullout force-clamp displacement curve primarily exhibits softening and hardening behaviors. The passive resistance of the geogrid mesh significantly influences the softening behavior, while shear friction predominantly affects the hardening behavior. The interface friction coefficient ranged from 0.28 to 0.88 for embedded lengths of 300 − 460 mm. The effects of relative density and embedded length on interface cohesion are more pronounced than those on the interface friction angle. When the embedded length increased from 300 to 460 mm, the rise in interface cohesion ranged from 42.0% to 47.7%, whereas the increase in internal friction angle ranged from 9.5% to 14.5%. [ABSTRACT FROM AUTHOR]

Ultra-long-distance and high-precision lightning location technology is an important means to realize low-cost and wide-area lightning detection. This paper carried out research on the high-precision location technology of very-low-frequency (VLF) lightning electromagnetic pulse based on the Asia-Pacific Lightning Location Network (APLLN) deployed in 2018. Two key technologies are proposed in this paper: one is the calculation method of signal arrival time using very-low-frequency lightning electromagnetic pulse waveform, and the other is the compression transmission technology of lightning electromagnetic pulse waveform based on a signal principal component analysis. The results of a comparison and evaluation of the improved APLLN with the ADTD system show that the APLLN has a relative location efficiency of 69.1% and an average location error within the network of 4.5 km. [ABSTRACT FROM AUTHOR]

To assess the impact of solid waste phosphogypsum on the road performance of lime-fly ash-stabilized red clay, we conducted comprehensive tests on the road performance, swelling and shrinkage characteristics, and mechanical properties of lime-fly ash soil with varying phosphogypsum content and curing age. Additionally, we analyzed the microstructure and composition changes using scanning electron microscopy and X-ray diffraction tests. The results revealed that phosphogypsum significantly enhances the early strength and moisture stability of lime-fly ash soil. The mechanical properties of lime-fly ash soil continue to improve with increased curing age, with performance improvements tapering off after 60 days and eventually stabilizing. Moreover, as the phosphogypsum content increases, the unconfined compressive strength (UCS), splitting strength, and CBR value of the lime-fly ash soil initially increase and then decrease. The optimal mixing ratio was determined to be 4% phosphogypsum, resulting in a 7-day UCS increase of 67.2%, a 28-day UCS increase of 3 times, and a 28-day splitting strength increase of 4.3 times. The moisture stability coefficient also exhibited a 43% increase after 7 days, and its anti-disintegration ability was enhanced, reaching 0.91 after 28 days, which meets the specified standards. Microscopic analysis revealed that the addition of phosphogypsum improved the overall integrity of the lime-fly ash soil, and the formation of ettringite effectively filled the soil's pores. However, excessive ettringite caused increased expansion and deformation. To optimize the use of phosphogypsum-modified lime-fly ash-stabilized red clay as subgrade filler, it is advisable to incorporate additives to further reduce swelling deformation. [ABSTRACT FROM AUTHOR]

The bedding structure of shale is generated during the deposition and formation, which results in shales with prominent anisotropic characteristics. It depends on stability, control of oil and gas storage, and deep exploitation. In addition, the mechanical and permeability parts of bedding shale are very complex when it is under deep underground space with coupled high stress and high seepage. In this study, the black bedding shale was used as the research object, and a series of triaxial shear-seepage coupling tests were carried out. Firstly, the triaxial shear stress-shear strain curves and permeability-shear stress curves of different bedding shales under other triaxial shear-seepage coupling conditions were obtained. Secondly, the failure characteristics and shear deformation characteristics of shale under the shear-seepage coupling effect were explored. The shear stress threshold and permeability evolution law at each stage of shear failure were discussed. Thirdly, the shear strength, failure mode, and mechanism parameters of the black bedding shale under different normal stress and seepage pressure were studied. Fourthly, the linear M-C criterion, Ramamurthy criterion, and Hoek-Brown criterion characterize the variation of damage strength of shale with bedding orientation under triaxial shear-seepage coupling. Those results provide an experimental basis for exploring the anisotropic mechanical characteristics and failure mechanism of bedding shale under shear-seepage coupling. [ABSTRACT FROM AUTHOR]

Converting more CO2 absorbed by plant photosynthesis into biomass-activated carbon effectively reduces carbon emissions. In this study, we used a one-step preparation of biomass-activated carbon loaded with MgO nanoparticles to investigate the effect of Mg loading on the catalytic pyrolysis process. The influences of magnesium loading on biochar yield and fixed carbon production were assessed. The addition of 1% Mg weakened the carbonyl C=O, inhibited the dehydroxylation reaction, enhanced the C-H signal strength, and the formation of MgO inhibited the weaker- bound substituent breakage. Additionally, the addition of magnesium altered the morphological features and chemical composition of the biochar material. It also increased the activated carbon mesoporosity by 3.94%, biochar yield by 5.55%, and fixed carbon yield by 12.14%. The addition of 1% Mg increased the adsorption capacity of the activated carbon to potassium dichromate, acid magenta, methylene blue, and tetracycline effluents by 8.71 mg, 37.15 mg, 117.68 mg, and 3.53 mg, respectively. The results showed that MgCl2 played a significant role in promoting the thermal degradation of biomass and improving the solid yield and adsorption performance of activated carbon. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of a closed-cycle evaporation system for the desalination of seawater. The system couples the condensing end of a heat pump with a humidifier, where the air is dehumidified in the heat pump evaporator. First, the mechanism of action of the closed-cycle evaporation system was analyzed from the perspective of heat transfer, and the control equations for the heat and mass transfer of the system were investigated. In addition, a mathematical model of the system was developed and validated. The influence of several important parameters of the air and seawater entering the system on the system's performance under the design conditions was investigated numerically. The parametric analysis showed that the effect of the seawater mass flow rate on the system's productivity was not significant. As the air mass flow rate increases, the freshwater production rate increases and then decreases. The output ratio (GOR) of the system was estimated and found to be competitive with other reported HDH systems. [ABSTRACT FROM AUTHOR]

Advances in technology have facilitated the development of lightning research and data processing. The electromagnetic pulse signals emitted by lightning (LEMP) can be collected by very low frequency (VLF)/low frequency (LF) instruments in real time. The storage and transmission of the obtained data is a crucial link, and a good compression method can improve the efficiency of this process. In this paper, a lightning convolutional stack autoencoder (LCSAE) model for compressing LEMP data was designed, which converts the data into low-dimensional feature vectors through the encoder part and reconstructs the waveform through the decoder part. Finally, we investigated the compression performance of the LCSAE model for LEMP waveform data under different compression ratios. The results show that the compression performance is positively correlated with the minimum feature of the neural network extraction model. When the compressed minimum feature is 64, the average coefficient of determination R 2 of the reconstructed waveform and the original waveform can reach 96.7%. It can effectively solve the problem regarding the compression of LEMP signals collected by the lightning sensor and improve the efficiency of remote data transmission. [ABSTRACT FROM AUTHOR]

The "method of overlap" replaces traditional welding to solve the problem of how the geosynthetic-encased stone column is limited by the welding frame during site construction, making the site construction simplified and economical, but its bearing mechanism is not clear. Therefore, the bearing mechanism and failure mode of the stone column was studied through the compression test of the multi-layer geosynthetic-encased stone column under dynamic and static loading. The research shows that the multi-layer encasement improves the modulus and lateral restraint of the stone column, which increases the stress transfer rate and reduces the damage degree of the stone column. The vertical ultimate bearing capacity increase in multi-layer geosynthetic-encased stone columns under dynamic and static loading is significantly different, and the difference can be up to 47.1%; the corresponding number of encasement layers should be selected according to the actual situation. The influence of the difference between dynamic and static loading on the location of the main radial strain of the stone column can be ignored, but the lateral restraint of the stone column under dynamic loading is weakened, the stress transfer rate is reduced, and the radial strain is reduced and more uniform along the stone column height. The vertical ultimate bearing capacity of the one- and two-layer geogrid-encased stone column under dynamic loading is lower than that of static loading. When treating soft foundations, the influence of traffic loads should be considered, and the bearing capacity of the geosynthetic-encased stone column should be appropriately increased in design value. [ABSTRACT FROM AUTHOR]

In order to obtain the optimal spacing of closely spaced footings under cyclic dynamic loading, dynamic model tests of closely spaced footings were carried out on unreinforced and reinforced sand foundations. The influence of the center point spacing (S) of closely spaced footings on the bearing capacity of the foundation under cyclic dynamic load is discussed. The test results show the following: (1) The dynamic load peak of the unreinforced and reinforced sand foundation is the largest when S/B = 2.0 (B is the width of footing), and the ultimate bearing capacity of the reinforced sand foundation is 20% higher than that of unreinforced sand foundation. (2) The vertical soil pressure at different positions of closely spaced footings with different spacing ratios (S/B) on the reinforced sand foundation is lower than that of unreinforced sand foundation, and the vertical soil pressure at different buried depths ('1-3', '2-3', '3-3' positions) at the center of closely spaced footings are smaller than that below the footings ('1-2', '2-2', '3-2' positions). (3) When S/B = 2.0, the strain of geogrid and the peak acceleration at the center of the closely spaced footings are the smallest, indicating that the sand foundation has little transient change under this spacing. From the aspects of ultimate bearing capacity design and engineering economic benefits, it is suggested that the spacing between closely spaced footings should be arranged according to two times the width of the footing (S/B = 2.0). [ABSTRACT FROM AUTHOR]

Modular Geogrid Reinforced Soil (GRS) retaining walls, as flexible structures, usually have a certain deformation capacity. However, the deformation damage of the facing panels will directly affect the durability performance of the retaining wall and pose a threat to the safety and operation of the road and related facilities. In order to study the influence of different load factors on the deformation mode and failure characteristics of the retaining wall, an indoor large-scale model test was carried out. The test load considers the average load, peak value, amplitude and frequency of load under traffic load. The changes in settlement and horizontal deformation, geogrid strain and acceleration response of the GRS retaining wall are compared and analyzed. The results show that in the dynamic test, the two wall damage modes are "wall facing outward tilt" and "wall facing outward curved". The maximum strain of the geogrid was 4.5% and 3.6%, respectively, which did not reach the damage strain. The peak load is the largest mechanical response of all load factors, followed by the load magnitude and average value, and finally the load frequency. In addition, combining the existing GRS retaining wall deformation and earth pressure calculation theory, a set of calculation methods for the strain of tendons under external load is proposed. [ABSTRACT FROM AUTHOR]

Acid Mine Drainage (AMD) is unique acidic wastewater produced in the process of iron mining and utilization. The soil and wetland contaminated by AMD in a mining area in Ma'anshan were studied in this paper. The physical and chemical characteristics and microbial community structure of the samples were analyzed to evaluate the resident soil pollution. The results showed that the soil around the acid reservoir was seriously polluted by metals such as Fe, Mn, Cd, and sulfate, and the loss of organic matter and total nitrogen was serious. With the increased distance between soil samples and the acid reservoir, the pollution degree of AMD decreased, the soil pH, organic matter and total nitrogen contents increased gradually, the soil microbial species increased slightly, and the diversity index increased. Bacillus, Lactococcus, and other bacteria with hydrolytic acid-producing functions accounted for more than 55.0% of the total bacterial community. Desulfuromonas, Desulfobulbus, and other genes involved in sulfur metabolism accounted for more than 24.0% of the total microbial community. In addition, Nitrosophaera, Nitrosopumilus, Methanoregula, and Methanosphaerula, which were involved in nitrogen cycling, were the dominant bacteria in the sampled soil. Our findings provide the basic data to support the mineral industry in China as well as for ecological functional evaluation based on species differences. [ABSTRACT FROM AUTHOR]

Hai‐Nan Lightning Detection Network (HNLDN) is composed of seven sites that accept very low frequency/low frequency (VLF/LF) signals. A total of seven sites are evenly distributed on Hai‐Nan Island. The baseline distance is between 50 and 150 km, which is about five times longer than in typical short‐baseline VLF/LF imaging networks. Each detection station uses zero‐phase digital filtering to avoid the phase deviation caused by filtering. HNLDN uses an improved peak search method to increase the number of detected of lightning waveforms, applies a One‐dimensional convolutional neural network (1D‐CNN) to identify and classify the waveforms, and to the increase the detection efficiency of intracloud lightning. This article analyzes three typical thunderstorm processes. From inside to outside the network, the detection efficiency of HNLDN relative to the advanced direction‐time lightning detection system (ADTD) is 239%, 181%, and 19%, respectively. It can be seen that the detection efficiency is negatively correlated with the distance from the thunderstorm to HNLDN. The average location error of HNLDN inside the network is 190 m. Key Points: Use very low frequency/low frequency network locationDepiction of a wide range of lightning in spaceThe new method improves the detection efficiency of cloud lightning and increases the number of lightning locations [ABSTRACT FROM AUTHOR]

One of the NHC–iridium coordination assemblies containing 1,5‐cyclooctadiene (COD) and iodide ion has been demonstrated as robust, efficient, recyclable solid molecular catalyst for N‐formylation of diverse primary and secondary amines with CO2 and H2 under mild reaction conditions. Remarkably, in the case of N,N‐dimethylformamide production, even at 0.1 mol % catalyst loading under solvent‐free conditions, the solid catalyst can be readily recovered by simply filtration and reused more than 10 runs without noticeable loss of activity. One of the NHC–iridium coordination assemblies containing 1,5‐cyclooctadiene (COD) and iodide ion has been demonstrated as a robust, efficient and recyclable solid molecular catalyst for N‐formylation of various primary and secondary amines with H2 and CO2 under mild reaction conditions at catalyst loadings as low as 0.1 mol %. [ABSTRACT FROM AUTHOR]

Abstract: By using the commercially available ruthenium pincer complex (Ru‐MACHO‐BH) as a catalyst, the challenging direct hydrogenation of lactams and analogues has been successfully accomplished to deliver corresponding value‐added amino alcohols in good‐to‐excellent yields under mild reaction conditions. Remarkably, in addition to N‐protected lactams, unprotected ones could also be readily reduced in the presence of a catalytic amount of weak base or even under neutral reaction conditions, which further highlights the broad substrate scope and the protocol efficiency. [ABSTRACT FROM AUTHOR]

This study systematically assessed the inactivation mechanism on Staphylococcus aureus biofilms by a N2 atmospheric-pressure plasma jet and the effect on the biofilm regeneration capacity from the bacteria which survived, and their progenies. The total bacterial populations were 7.18 ± 0.34 log10 CFU ml−1 in biofilms and these were effectively inactivated (>5.5-log10 CFU ml−1) within 30 min of exposure. Meanwhile, >80% of the S. aureus biofilm cells lost their metabolic capacity. In comparison, ∼20% of the plasma-treated bacteria entered a viable but non-culturable state. Moreover, the percentage of membrane-intact bacteria declined to ∼30%. Scanning electron microscope images demonstrated cell shrinkage and deformation post-treatment. The total amount of intracellular reactive oxygen species was observed to have significantly increased in membrane-intact bacterial cells with increasing plasma dose. Notably, the N2 plasma treatment could effectively inhibit the biofilm regeneration ability of the bacteria which survived, leading to a long-term phenotypic response and dose-dependent inactivation effect on S. aureus biofilms, in addition to the direct rapid bactericidal effect. [ABSTRACT FROM AUTHOR]

Effect of solution conditions (such as contact time, solution pH, ionic strength, reaction temperature, solid-liquid ratio and humic acid (HA)) on U(VI) immobilization on montmorillonite from Huangshan, China in environment was investigated by batch technique. U(VI) adsorption on montmorillonite is fairly affected by the solution pH and the ionic strength. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) suggest that U(VI) adsorption on montmorillonite shows a spontaneous and endothermic process. The coexisted HA in solution could promote the U(VI) adsorption on montmorillonite. Notably, Huangshan montmorillonite has the potential in enrichment and solidification of U(VI) ions under environmental conditions. [ABSTRACT FROM PUBLISHER]

Different types of acid pretreatment are known to influence the removal of certain components from pine wood sawdust, due to differences in the acid hydrolysis, which also predetermine the final formation and adsorptive properties of the produced activated carbon (AC) through subsequent potassium hydroxide activation. AC made by using phosphorous acid as an acid pretreatment had the largest absorption capacity of methylene blue (MB) dye due to its highest acidity. Subsequently, the effects on the adsorption variables for this AC such as initial pH, MB concentration, contact time and temperature were investigated. The resulting adsorption process was classified as pseudo-second-order kinetic model, and the Langmuir isotherm model better described the equilibrium data in comparison with the Freundlich isotherm model. The outcome showed that a lower temperature had an increased adsorption capacity of sawdust-derived AC pretreated with phosphorous acid, which allowed maximum adsorption capacities of 303.03 mg/g at 30 °C, implying that the adsorption was an endothermic process. Phosphorous acid pretreatment and activation processes proved to be an effective strategy to prepare highly porous AC from sawdust, with high potential to cationic dye removal from liquid phases. [ABSTRACT FROM AUTHOR]

Dry anaerobic digestion of sewage sludge can recover biogas as energy; however, its low C/N ratio limits it as a single substrate in the anaerobic digestion. Rice straw is an abundant agricultural residue in China, which is rich in carbon and can be used as carbon source. In the present study, the performance of dry co-digestion of sewage sludge and rice straw was investigated under mesophilic (35 °C) and thermophilic (55 °C) conditions. The operational factors impacting dry co-digestion of sewage sludge and rice straw such as C/N ratio, moisture content, and initial pH were explored under mesophilic conditions. The results show that low C/N ratios resulted in a higher biogas production rate, but a lower specific biogas yield; low moisture content of 65 % resulted in the instability of the digestion system and a low specific biogas yield. Initial pH ranging 7.0-9.0 did not affect the performance of the anaerobic digestion. The C/N ratio of 26-29:1, moisture content of 70-80 %, and pH 7.0-9.0 resulted in good performance in the dry mesophilic co-digestion of sewage sludge and rice straw. As compared with mesophilic digestion, thermophilic co-digestion of sewage sludge and rice straw significantly enhanced the degradation efficiency of the substrates and the specific biogas yield ( p < 0.05) at the conditions of C/N ratio 26:1, moisture content 80 %, and natural initial pH. Although high concentrations of ammonia-nitrogen (NH-N, 1500 mg/kg wet weight) were formed during thermophilic digestion, there was no obvious inhibition occurred. The results indicated that rice straw can be used as carbon source for the dry co-digestion of sewage sludge under mesophilic and thermophilic conditions. [ABSTRACT FROM AUTHOR]