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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]

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]

A rectangular double chamber with trivalent arsenic as the electron donor of the biological anode was constructed by microbial fuel cells (MFC), and the feasibility of the MFC simultaneous degradation of trivalent arsenic and nitrate was studied. Experimental results show that the co-matrix-coupled MFC reactor oxidizes trivalent arsenic in an anode chamber and degrades nitrate in the cathode chamber. The removal rate of trivalent arsenic is about 63.35%, and the degradation rate of nitrate is about 55.95% during the complete and stable operation period. MFC can continuously output electric energy, and the maximum output voltage is 388 mV. We compared and analyzed the main functional microflora of biofilm microorganisms in an anode chamber. In the long-term arsenic-polluted environment, the activity of Acinetobacter, Pseudomonas bacteria with arsenic resistance, was improved. It is inferred that a fraction of trivalent arsenic was oxidized to pentavalent arsenic by electrode-attached microorganisms. While remaining trivalent, arsenic was taken up by the suspended bacterial biomass and converted into stable arsenide. The results of this study have theoretical reference value for the expansion of the MFC application scope. [ABSTRACT FROM AUTHOR]

Industrial wastewater contains high concentrations of inorganic salts and organic matter. This experiment studied a system for treating wastewater containing high concentrations of inorganic salts and organic matter. The setup consists of a closed-cycle humidification and dehumidification system and a filter press. Chemical wastewater was used as the treatment solution, and the treatment performance of the system was tested and analyzed. The system effectively reduced the chemical oxygen demand (COD), electric conductivity (EC), total nitrogen (TN), and ammonia nitrogen (NH4-N) in the wastewater and, at the same time, dehydrated sludge was obtained through a filter press. The system maintains a stable removal rate of each index (COD, EC, TN, and NH4-N) in wastewater and can remove inorganic salts and organic matter from wastewater. The system can successfully treat industrial wastewater containing high concentrations of inorganic salts and organic matter. [ABSTRACT FROM AUTHOR]

The use of seawater desalination technology to solve water shortages in energy- and resource-scarce regions has attracted widespread attention worldwide. In this paper, the performance of a closed-cycle humidification–dehumidification desalination system with a heat pump was experimentally investigated. The system is a closed-cycle system, which includes humidifiers, a heat pump, dehumidifiers, and an air heat exchanger. The heat pump is used by the system to carry energy. The effects of different parameters on the system performance were studied. Scale and economic analyses of the system were conducted to explore the application prospects of the system. The maximum gained output ratio of the system was 4.82. The maximum freshwater production was 960 kg/h, and the cost per kilogram of freshwater was USD 0.03, which are more considerable compared with other systems. This system provides an effective way to save energy in remote areas with energy shortages and freshwater resource shortages. [ABSTRACT FROM AUTHOR]

The Asia-Pacific Lightning Location Network (APLLN) is a lightning location system consisting of a series of very low-frequency signal detection sites. Since 2018, 16 detection sites have been deployed with an average baseline longer than 1000 km. The detection site used a trigger sampling method to record the lightning signal with a duration of 2 ms and calculates the lightning arrival time based on digital filtering and the Hilbert envelope method. APLLN used a time difference location algorithm and improved Levenberg–Marquardt non-linear least squares iterative algorithm to calculate and optimize the lightning location results. The analysis results of a strong thunderstorm process show that the average detection efficiency of APLLN was 55.34% for intracloud (IC) strokes, 63.55% for cloud-to-ground (CG) strokes and 61.83% for all strokes (IC + CG). The average location error of APLLN for this thunderstorm is 5–10 km. [ABSTRACT FROM AUTHOR]

Lightning waveform plays an important role in lightning observation, location, and lightning disaster investigation. Based on a large amount of lightning waveform data provided by existing real-time very low frequency/low frequency (VLF/LF) lightning waveform acquisition equipment, an automatic and accurate lightning waveform classification method becomes extremely important. With the widespread application of deep learning in image and speech recognition, it becomes possible to use deep learning to classify lightning waveforms. In this study, 50,000 lightning waveform samples were collected. The data was divided into the following categories: positive cloud ground flash, negative cloud ground flash, cloud ground flash with ionosphere reflection signal, positive narrow bipolar event, negative narrow bipolar event, positive pre-breakdown process, negative pre-breakdown process, continuous multi-pulse cloud flash, bipolar pulse, skywave. A multi-layer one-dimensional convolutional neural network (1D-CNN) was designed to automatically extract VLF/LF lightning waveform features and distinguish lightning waveforms. The model achieved an overall accuracy of 99.11% in the lightning dataset and overall accuracy of 97.55% in a thunderstorm process. Considering its excellent performance, this model could be used in lightning sensors to assist in lightning monitoring and positioning. [ABSTRACT FROM AUTHOR]

In order to realize the resource utilization of bloom algae from Lake Chao, this study presents the use of fresh algae to improve the mechanical and biological properties of low-density polyethylene (LDPE). In this study, the algae and LDPE were used as raw materials, maleic anhydride grafted polyethylene (PE-g-MAH), polyethylene wax (PE-wax) and white oil, and glycerin were used as the compatibilizer, lubricant, and plasticizer, respectively. The single factor experiments were conducted with these three individual factors, and the response surface methodology technique was used to optimize the process conditions. In the single factor experiments, the mechanical properties of the composites increased with additions of PE-g-MAH, PE-wax/white oil, and glycerin. Both flexural strength and flexural modulus were maximized to optimize the preparation conditions. The optimum preparation conditions were found as follows: algae powder of 15.00 wt%, LDPE of 85.00 wt%, PE-g-MAH of 4.00 wt%, lubricant of 2.67 wt%, and glycerin of 3.00 wt%. This resulted in 11.60 MPa of tensile strength, 9.95 MPa of flexural strength, and 241.00 MPa of flexural modulus. The mechanical properties of composites were greatly improved compared with the absence of additives. In addition, compared with LDPE resin, the degradability of the composite was improved, and the weight loss rate was 7.73% after 6 months. The results recommended that the composites of the algae from Lake Chao and LDPE resin could be a useful material in the packaging field. Generally, the prepared composite particles can be used to produce foam products, packaging bags, or hard packing boxes with special shapes. It is more environmentally friendly, and more able to meet the challenges of sustainable development. [ABSTRACT FROM AUTHOR]