Indoor Experiments Research Articles

Direction of Arrival Estimation for Single Microelectromechanical Systems Vector Hydrophone Using Modified Wavelet Packet De-Noising

The complex and variable ocean environment introduces complex noise to the signal received by microelectromechanical systems (MEMS) vector hydrophones, which seriously affects target location. To improve the detection efficiency and broaden the application range of vector hydrophone, this paper proposed a novel modified Wavelet packet de-noising method, known as the Wavelet packet energy (WPE) de-noising method. This method utilizes Shannon entropy to determine the optimal decomposition levels of Wavelet packets, and calculates the energy of reconstructed signals in each frequency band to construct feature vectors. The Wavelet packet with the larger energy is selected to reconstruct the signal until the root mean square error of the original signal and the reconstructed signal is minimized. thereby obtaining an optimal solution. The performance of this proposed method is evaluated through both indoor and outdoor experiments. The experimental results demonstrate that the developed method is effective in Direction of Arrival (DOA) estimation of single frequency signals and is feasible in low signal-to-noise ratio situations. The method improves the azimuth discrimination ability of the Minimum Variance Distortionless Response algorithm, and DOA estimation errors are all within 1°. Furthermore, the indoor and outdoor experiments also demonstrate that the WPE de-noising method solves the group delay and distortion of signals caused by conventional filtering.

Belowground facilitation of plant mixtures on rhizosphere soil of Commelina communis grown on extremely Cu- and Cd-contaminated mine: From soil quality to bacterial community

Plant–plant interactions exert positive effects under stress conditions, but their impact on heavy metal-contaminated rhizosphere soil quality and bacterial community remains unclear. In this work, the rhizospheric soil of Cu-accumulator Commelina communis and neighboring plants grown in a heavily contaminated copper mine was analyzed to elucidate such belowground facilitation. Physicochemical properties and microbial characteristics of rhizospheric soil of control C. communis (far from neighboring plants), facilitated C. communis (near neighboring plants), and neighboring plants were compared. The average values of total organic carbon, NH4+-N, NO2−-N, NO3−-N, available phosphorus, urease, and phosphatase in the C. communis rhizosphere increased by 0.82-, 0.64-, 0.44-, 0.06-, 0.10-, 0.36-, and 0.30-fold in the presence of surrounding plants, respectively. The relative abundance of oligotrophic bacteria (Chloroflexi) decreased, whereas copiotrophic bacteria (Proteobacteria) increased in plant species mixtures. Venn graph and partial least squares discriminant analysis indicated that the composition of the bacterial community in the facilitated C. communis rhizosphere showed higher similarity to neighboring plants than to control C. communis. Among 49 predicted functional groups analyzed by FAPROTAX analysis, chemoheterotrophy (36.04 %) involved in carbon cycles had the highest relative abundance and increased in the facilitated C. communis rhizosphere due to the positive response of 193 OTUs (mainly belonging to Proteobacteria and Actinobacteriota) under plant–plant interactions. The increased relative abundance of Methylocella and Bradyrhizobium resulted in improved nitrogen fixation in the C. communis rhizosphere, whereas nitrate reduction with its main performer Rubrobacter was inhibited. The ecological function of rhizobiomes of the facilitated C. communis and neighbors also showed higher similarity compared with that of the control C. communis. These results show the role of neighboring plants in modulating soil quality and rhizobiomes of plant remediators under stress and more indoor garden experiments need to be conducted to verify such belowground facilitation.

Seismic-induced permanent displacement estimation combining acceleration and computer vision measurements

In this study, a seismic-induced permanent displacement estimation technique that combines acceleration and computer vision measurements was proposed. The proposed technique involves installing a vision camera and an accelerometer on a target building, with the vision camera capturing the change in the position of surrounding objects after a seismic event to estimate the permanent displacement of the target building. During the installation, the vision camera and accelerometer were vibrated in a controlled manner using a shaker on the target building. Then, in the absence of any artificial target or prior knowledge of the size of natural targets, an automatic scale factor map was generated, which converts a translation of an image (in pixels) into a physical displacement. After an earthquake, a displacement map was constructed to estimate the relative movement of the target building to the natural targets and then clustered using Gaussian mixture modeling. Finally, the undeformed portions of the natural targets were retrieved to estimate the permanent displacement of the target building with respect to the distribution of the natural target movement. Both indoor and outdoor experiments were conducted to validate the performance of the proposed technique. The results demonstrate the improved performance of the proposed technique compared with the previous technique.

The different expression patterns of cytokines in Pacific oyster Crassostrea gigas response against bacterial stimulation

Cytokines can be induced by pathogen stimulation for the information exchange between cells, and their expression patterns indicate the response status of cells. In the present study, the expression patterns of ten cytokines (CgIL17–1, −2, −3, −4, −5, −6, CgTNF-1/2, CgTGF-β and CgIFNLP) in haemocytes were analyzed in the Pacific oyster Crassostrea gigas after Vibrio splendidus stimulation in the indoor and outdoor experiments to compare the induction patterns of different cytokines and evaluate the response status of haemocytes. After the indoor V. splendidus immersion stimulation, the mRNA abundances of six cytokines (CgIL17–1, −3, −4, −5, CgTGF-β and CgIFNLP) in haemocytes were significantly downregulated at 48 h compared with that in the control group, among which CgIL17–4 was the most down-regulated with 0.009-fold of that in the control group (p < 0.05). The mRNA abundances of CgIL17–2, CgIL17–6, CgTNF-1 and CgTNF-2 showed no significant change at 48 h compared with that in the control group. The apoptosis rate of haemocytes reached the maximum level of 1.138% at 48 h after the stimulation. In the oysters cultured outdoor from April to September 2021, the mRNA abundances of all ten cytokines in haemocytes were found to decrease in June (0.270-fold on average) and increase in July (5.402-fold on average) compared with those in May. After the in situ V. splendidus immersion stimulation in the outdoor cultured oysters in June and July, seven cytokines (CgIL17–1, CgIL17–2, CgIL17–4, CgIL17–5, CgTNF-1, CgTGF-β and CgIFNLP) exhibited upregulated mRNA abundance in June, while in July, the mRNA abundances of five cytokines (CgIL17–1, CgIL17–3, CgTNF-2, CgTGF-β, and CgIFNLP) remained constant, and four cytokines (CgIL17–2, CgIL17–4, CgIL17–5 and CgTNF-1) were suppressed after the stimulation. CgIL17–4 had the highest fold-change in mRNA abundance among all cytokines in June after the stimulation, which was 85.599-fold compared with that in the control group (p < 0.05). The score of haemocyte response status (SH) was evaluated using the mRNA abundance database of all ten cytokines. It decreased to 124.860 at 48 h after the indoor V. splendidus stimulation, and it decreased to 66.793 in June and increased to 451.092 in July in the cultured oysters prior to the stimulation. Collectively, the expression patterns of ten cytokines in haemocytes varied against bacterial stimulation, among which CgIL17–4 was found to response the most significantly, and SH indicated by the mRNA abundances of cytokines suggested an abnormal response status of haemocytes in the oysters at 48 h after indoor V. splendidus stimulation and the oysters cultured outdoor during June and July. These findings will further our understanding of the cytokine variation and haemocyte response of the Pacific oyster against bacterial stimulation.

Mixed Heat Transfer in a Double Barrel with Differential Velocity based on CFD-DEM and Experiment

Abstract A double barrel with differential velocity (DBDV) was proposed to improve the mixture quality. Temperature is one of the indexes to evaluate the mixture quality. At present, there are few studies on the heat transfer of DBDV. The heat transfer of particles in DBDV was studied by CFD-DEM to deeply understand the proposed DBDV. The heat transfer process in DBDV was analyzed. The distribution law of temperature field under the coupling effect of particles and fluid was obtained. The influence of fluid speed on particle temperature and the regeneration proportion in DBDV were analyzed and compared with the existing double barrel. And the main heat transfer mode of particles in DBDV was to be obtained. The results show that the mixture temperature in the proposed DBDV is generally higher than that in the existing DB. And the mixture produced by DBDV is not only friendly to the environment, but also the mixture temperature can meet the construction requirements even if more than half of the RAP materials are added to the mixture. Compared with DB, the addition proportion of DBDV is increased by 9.38% - 20.70%. And the reliability of the simulation work was verified by the indoor experiment platform, which lays a foundation for the application of DBDV.

Simulation of fracture propagation law in fractured shale gas reservoirs under temporary plugging and diversion fracturing

Natural fractures (NFs) are developed in shale gas reservoirs, which can easily cause frac hits during hydraulic fracturing and reduce the productivity of infill wells and parent wells. Temporary plugging diverting fracturing (TPDF) can hinder the single forward extension of fracture transition and avoid the communication of hydraulic fractures (HFs) or NFs adjacent to wells. In order to explore the fracture propagation law of TPDF in fractured shale gas reservoirs, this study systematically evaluates the main factors such as stress difference, displacement, and fracturing fluid viscosity on the fracture temporary plugging diversion (TPD) law by means of true triaxial hydraulic fracturing simulation device and cohesive element model in ABAQUS. The findings reveal that (1) the law of fracture initiation and propagation at the engineering scale is similar to that in indoor experiments. Upon the primary fracturing (PF), the smaller the horizontal stress difference, the larger the pumping displacement, and the smaller the viscosity of the fracturing fluid is, the greater the corresponding fracture breakdown pressure and the stronger the rock compression resistance. (2) After TPD secondary fracturing, a small horizontal stress difference and a large pumping displacement facilitate the formation of a vertical complex fracture network structure on the primary fracture. Because of the small size of the indoor rock, viscosity has little effect on the fracture propagation of the TPDF, but the numerical simulation results reveal that the higher the viscosity, the greater the width of the new fracture. In addition, (3) the smaller the angle between the new fracture opened after PF and TPDF, the better the propagation effect of the new fracture. Meanwhile, the farther the temporary plugging zone is from the fracture front end, the wider the new fracture opened after TPDF. The field construction results reveal that the TPDF technology can avoid the effect of HFs, thus preventing frac hits during shale gas reservoir reconstruction. This study not only posits a physical and numerical simulation method for simulating the fracture propagation law of TPDF in fractured shale gas reservoirs but also provides theoretical guidance for applying TPDF to field construction.

Retention and loss pathways of soluble nutrients in biochar-treated slope land soil based on a rainfall simulator

Global food crisis makes intense agricultural activity necessary, which accelerates soil degradation and increases pollution risk to nearby catchments. Application of biochar can effectively retain plant-required nutrients in soils. However, the linkage between retention and loss pathways of nutrients is still unclear, particularly at slope lands. Therefore, a simulated rainfall experiment (rainfall intensity ​= ​50 ​mm ​h−1) was conducted in a sandy soil with 10° gradient slope (indoor experiment) to clarify loss pathways of soluble C, N, P and K in biochar-amended soils. Wood biochar pyrolized at 300 ​°C (LWB) or 600 ​°C (HWB) was applied at 1% (LWB1; HWB1) or 2% (LWB2; HWB2). Our results show that the pathways for C, N, P and K loss was percolation ​> ​surface runoff ​> ​soil erosion. Compared to control, HWB2 treatment had a 2–4 times higher infiltration amount but 5–6 times lower surface runoff and soil loss, indicating that this treatment alleviated nutrient loss via erosion and runoff in the sloped soil. Among all treatments, HWB2 treatment was the most effective for retaining organic C, dissolved organic C, total N, and exchangeable K through various pathways. However, a substantial amount of soluble P was lost through percolation. Therefore, the potential pollution of groundwater by P through percolation pathway should be considered during biochar application.

A Quantitative Evaluation of the Performance of the Low-Cost AudioMoth Acoustic Recording Unit.

The AudioMoth is a popular autonomous recording unit (ARU) that is widely used to record vocalizing species in the field. Despite its growing use, there have been few quantitative tests on the performance of this recorder. Such information is needed to design effective field surveys and to appropriately analyze recordings made by this device. Here, we report the results of two tests designed to evaluate the performance characteristics of the AudioMoth recorder. First, we performed indoor and outdoor pink noise playback experiments to evaluate how different device settings, orientations, mounting conditions, and housing options affect frequency response patterns. We found little variation in acoustic performance between devices and relatively little effect of placing recorders in a plastic bag for weather protection. The AudioMoth has a mostly flat on-axis response with a boost above 3 kHz, with a generally omnidirectional response that suffers from attenuation behind the recorder, an effect that is accentuated when it is mounted on a tree. Second, we performed battery life tests under a variety of recording frequencies, gain settings, environmental temperatures, and battery types. We found that standard alkaline batteries last for an average of 189 h at room temperature using a 32 kHz sample rate, and that lithium batteries can last for twice as long at freezing temperatures compared to alkaline batteries. This information will aid researchers in both collecting and analyzing recordings generated by the AudioMoth recorder.

Pressure amplification effect of initial compression waves in circumferential cracks of high-speed railway tunnel linings

Spalling of concrete blocks from tunnel linings is a severe defect in high-speed railway tunnels (HSRTs). The amplified initial compression wave (ICW) in circumferential cracks induced by high-speed trains may be the main cause of crack propagation and concrete block formation. To investigate the aerodynamic amplification effect of the ICW in circumferential cracks, tunnel-crack models are established and solved based on the unsteady viscous k–ε turbulence method. A scaled indoor experiment is carried out to verify the reliability of the calculation method. The characteristics of amplified pressure and corresponding mechanisms are analyzed and revealed. Three influential parameters, including the crack width, crack depth, and train velocity, are analyzed and discussed in detail. The main conclusions are as follows: (1) the maximum amplified pressure in a typical circumferential crack is 5.68 times that of the ICW. (2) The maximum power spectrum density (PSD) of the aerodynamic pressure at the crack tip is 91.04 times that at the crack mouth. The crack tip suffers most from the aerodynamic impact of the fluctuating component of pressure waves, whereas the crack mouth is most susceptible to the average component. (3) The train velocity is the most influential parameter on the maximum pressure at the crack tip, followed by the crack depth. The power function with an exponent of 2.3087 is applicable for evaluating the relationship between the maximum pressure and train velocities. (4) The train velocity and crack depth are most influential parameters to the maximum PSD. The relationship between the maximum PSD and the crack widths, crack depths, and train velocities can be reasonably described by the power function. (5) The mechanism of pressure amplification is as follows: first, the superposition of the internal energy possessed by air molecules near crack surfaces. Second, the increase in the internal energy of air near the crack tip because of the gradually narrowing space. The results of our research may be applicable in analyzing the cracking behavior of tunnel lining cracks and preventing the spalling of concrete blocks in HSRTs.

Modification and Application of Materials for Strong Inhibitory Drilling Fluid

Due to the strong inhibition of drilling fluid, many polymer fluid loss additives can not play their role. Therefore, it is necessary to develop some water loss reducing materials that can withstand the strong inhibition environment. In this paper, the surface of asbestos fiber was modified and treated by indoor experiments. The physical and chemical properties of the obtained drilling fluid treatment samples were evaluated to optimize the appropriate amount of reagents used for surface treatment of asbestos. Subsequently, the drilling fluid performance of the obtained treatment agent samples were evaluated at different temperatures to analyze the effect of temperature on the drilling fluid performance. The surface of asbestos fiber was modified by adsorbed cationic surfactant CTAC which better solved the problem of entanglement of asbestos fiber in drilling fluid. The mechanism of the action of the surface of asbestos fiber was analyzed by scanning electron microscope observation experiments. Subsequently, different amounts of modified asbestos fiber was added to the drilling fluid and the performance of drilling fluid was evaluated at different temperatures. The experimental results showed that the modified asbestos fiber reduced the filtration loss of drilling fluid and still maintained good filtration loss reduction effect at 200°C.

Echo State Neural Network Based on an Improved Gray Wolf Algorithm Predicts Porosity through Logging Data.

In oil exploration and development, many reservoir parameters are very essential for reservoir description, especially porosity. The porosity obtained by indoor experiments is reliable, but human and material resources will be greatly invested. Experts have introduced machine learning into the field of porosity prediction but with the shortcomings of traditional machine learning models, such as hyperparameter abuse and poor network structure. In this paper, a meta-heuristic algorithm (Gray Wolf Optimization algorithm) is introduced to optimize the ESN (echo state neural) network for logging porosity prediction. Tent mapping, a nonlinear control parameter strategy, and PSO (particle swarm optimization) thought are introduced to optimize the Gray Wolf Optimization algorithm to improve the global search accuracy and avoid local optimal solutions. The database is constructed by using logging data and porosity values measured in the laboratory. Five logging curves are used as model input parameters, and porosity is used as the model output parameter. At the same time, three other prediction models (BP neural network, least squares support vector machine, and linear regression) are introduced to compare with the optimized models. The research results show that the improved Gray Wolf Optimization algorithm has more advantages than the ordinary Gray Wolf Optimization algorithm in terms of super parameter adjustment. The IGWO-ESN neural network is better than all machine learning models mentioned in this paper (GWO-ESN, ESN, BP neural network, least squares support vector machine, and linear regression) in terms of porosity prediction accuracy.

Detection and mitigation of antibiotic residues in poultry products and byproducts

Majority of the people in Bangladesh are still not aware about the health hazards of antibiotic residues. In this research, farmer’s awareness has been investigated by a questionnaire in different poultry farms, retail sellers and poultry markets and spread out the knowledge of public health hazards of antibiotics residues. Poultry farmers were found well educated about health hazards of antibiotic residues and aware about the judicial use of antibiotics before selling the poultry for human consumptions. During this survey, sufficient samples (thigh muscle, breast muscle, liver etc., n=100) were collected from different poultry farms, retail sellers and poultry markets. Randomly 50 livers, 50 thigh muscle and 50 breast muscle samples respectively were evaluated by TLC analysis. Out of 50 samples for each 2 liver, 2 breast muscle and 2 thigh muscle samples were found positive for Amoxicillin antibiotic; 5 liver, 3 breast muscle and 3 thigh muscle samples were found positive for Ciprofloxacin; 3 liver, 3 breast muscle and 3 thigh muscle samples were found positive for Cefalexin; 2 liver, 2 breast muscle and 2 thigh muscle samples were found positive for Enrofloxacin; 4 liver, 2 breast muscle and 2 thigh muscle samples were found positive for Oxytetracycline. Gentamicin and Neomycin were found negative for any samples. Further investigation was done in indoor discriminate and indiscriminate use of antibiotics (Cefalexin) in broilers. Indoor experiment was investigated in poultry chicks. Day old chicks were collected and reared up to 30 days. On day 14th, the chicks were randomly divided into three groups namely control group (n=10), discriminate antibiotic group (n=10) and indiscriminate antibiotic group (n=10). Discriminate antibiotic group was treated with antibiotics (Cefalexin) for one week followed by withdrawal period for one week, whereas; indiscriminate antibiotic group was treated with antibiotic (Cefalexin) for two weeks until the day of sacrifice. Liver, thigh muscle and breast muscle samples were collected and evaluated by TLC method. Control and discriminate antibiotics birds were found negative for any antibiotics residues. On the other hand, ten liver samples, eight thigh muscles and eight breast muscles were found positive for Cefalexin in indiscriminate group. Indiscriminate uses of antibiotic indicated that antibiotic residue mitigation for human safe meat production depends on withdrawal period and farmers awareness. Therefore, poultry treated with antibiotics are required for specific withdrawal period until all residues are depleted to safe levels before human consumption. Asian Australas. J. Food Saf. Secur. 2023, 7 (1), 33-39

The response mechanism of microorganisms to the organic carbon-driven formation of black and odorous water

The formation of black and odorous water is a complex process influenced by various factors such as organic matter and environmental conditions. However, there are limited studies on the role of microorganisms in water and sediment during the blackening and odorization process. In this study, we investigated the characteristics of black and odorous water formation by simulating organic carbon-driven black and odorous water through indoor experiments. The study revealed that the water turned black and odorous when DOC reached 50 mg/L and the microbial community structure in the water changed significantly during this process, with the relative abundance of Desulfobacterota increasing significantly and Desulfovibrio being the main dominant genus in Desulfobacterota. Additionally, we observed a notable decrease in the α-diversity of the microbial community in water and a considerable increase in microbial function of sulfur compounds respiration in water. In contrast, the sediment microbial community changed slightly, and the main functions of the sediment microbial community remained unchanged. The partial least squares path model (PLS-PM) suggested that organic carbon will drive the blackening and odorization process by affecting DO levels and microbial community structure and that the contribution of Desulfobacterota in water to the formation of black and odorous water was higher than that in sediment. Overall, our study provides insights into the characteristics of black and odorous water formation and suggests potential ways to prevent its formation by controlling DOC and inhibiting the growth of Desulfobacterota in water bodies.

Experimental development of a gated UV-induced spectroscopic lidar for the daytime study of plant ecology and photosynthesis: multi-modal measurement of fluorescence of trees growing in a field and Mie-Raman-fluorescence of the surrounding atmosphere.

A gated UV-induced spectroscopic lidar operational during daylight was developed to better understand the plant growth status in real time and the influence from the surrounding atmosphere chemical environment. Initial indoor experiments and short-range (100m) field measurements were very positive. The lidar worked as a vegetation fluorescence lidar, as well as an atmospheric Mie-Raman-fluorescence lidar. A UV (355nm) laser was effective to induce fluorescence and Raman scattering, and a synchronous detection technique made it possible to detect weak signals, even in daytime. Tree spectra containing chlorophyll fluorescence of tree leaves offered information about the growth status of trees. Atmospheric spectra containing aerosol Mie scattering, N 2, O 2, H 2 O Raman scattering, and pollutant fluorescence helped us to learn about atmospheric circumstances surrounding trees. The multi-modal information is useful for comprehensive understanding of plant ecology.

Experimental study on evaluation of conglomerate reservoir support-type fracture conductivity in Xinjiang oilfield

The volume fracturing in the Mahu conglomerate reservoir, double-wing fractures are generated, resulting in inadequate proppant laying effect and low fracture conductivity. Experiments are designed to explore methods for improving the conductivity of conglomerate-supported fractures. Real triaxial indoor experiments are conducted to explore the effects of displacement, stress difference, and weak surfaces. The proppant diversion experiment explores the diversion ability under the conditions of single proppant, mixed proppant, and multiple sand-laying concentrations. Attention is focused on the impact of proppant embedding and fragmentation on conductivity. Research has shown that (1) stepped variable displacement fracturing is beneficial for controlling the generation of fractures. High displacement is beneficial for activating naturally weak surfaces. Small displacements are beneficial for identifying naturally weak surfaces and controlling the speed of crack extension. (2) Embedding of proppants mainly affects the conductivity of mixed base-supported conglomerates. Crushing mainly affects the conductivity of particles supporting conglomerate fractures. (3) Quartz sand or quartz sand-mixed ceramsite is used for conglomerate reservoirs with low effective closure stress and a complex matrix. Ceramic particles can are reduce the impact of fragmentation on the conductivity of particle-supported conglomerate reservoirs. Study aims to provide scientific guidance for the efficient development of the Mahu reservoir.

Downhole vibration characteristics of 3D curved well under drillstring–bit–rock interaction

Understanding the characteristics of downhole vibration helps optimize the drilling parameters and improve the rate of penetration (ROP). This work establishes a nonlinear drillstring–bit–rock model to predict the downhole vibration behavior of 3D curved wells. The main novelty of this model is to consider the complex nonlinear bit–rock interaction and well trajectory. The model is solved by the Newmark method and verified by an indoor experiment and field data. The drillstring dynamics and effects of the main working parameters on the vibration characteristics are obtained and analyzed. Results show that, in the horizontal section, the drillstring motion and shape deformation are stable, and radial vibration is dominant. In the buildup section, the drillstring motion is irregular and messy, shape deformation becomes large, and radial vibration is significant but tangential vibration starts to become intense. In the vertical section, the drillstring motion is small in wellbore center, shape deformation is stable, and vibration severity reduces. The weight on bit (WOB) only affects drillstring vibration near the bit, and radial, tangential, and axial accelerations intensify as WOB increases. RPM has little effect on the drillstring vibration in 3D curved wells. In the buildup and horizontal sections, as the coefficient of friction (COF) increases, the radial and tangential accelerations rise while the axial vibration obviously weakens. When drilling in 3D curved wells, small WOB and large RPM can be adopted to reduce downhole vibration and increase ROP. The safety of drillstring and downhole tool also needs more attention when drilling in formations with large COF, such as gravel stone and sandstone. Large oil/water ratio or lubricant is recommended to improve the lubricity of drilling fluid. The research results could provide a valuable and useful guidance for drilling engineers to improve ROP and reduce downhole accidents.

Development of an expendable current profiler and simulation of passive sources

A common approach to ocean current measurement is to use a motion-induced electric field; this is the basic principle of the expendable current profiler (XCP). However, existing studies into XCPs have not explored indoor simulations of the ocean current environment or the implementation of attitude correction in the hardware. The accuracy of XCPs can be verified via indoor experiments and is affected by the sinking attitude. Therefore, in this study, we develop an XCP to measure ocean information in real time, and we correct the data for different XCP sinking attitudes. Furthermore, we design electromagnetic-induction-based laboratory measurements of simulated dynamic ocean currents. The signals collected by the XCP are linearly related to the copper-plated-power-supply signal. The processed data are compared and the feasibility of extracting ocean current signals via electrodes is verified through laboratory simulations of XCPs. Furthermore, we performed marine experiments in the South China Sea; the results indicate that the system is stable and easy to use. We implemented an expendable conductivity-temperature-depth system at the same location; the curve trends measured by the two probes were consistent, and the maximum error was found to be 0.5 °C. We expect this work to improve the quality of ocean current measurements and subsequent monitoring capabilities.

Technical Note: Combining undisturbed soil monoliths for hydrological indoor experiments

Abstract. An important decision in soil hydrological research is whether to conduct experiments outdoors or indoors. Both approaches have their advantages and trade-offs. Using undisturbed soil monoliths combines some of the advantages of outdoor and indoor experiments; however, there are often size limitations. Acquiring large monoliths necessitates heavy machinery, which is time-, cost-, and labor-intensive. Small- to medium-sized soil blocks, however, can be obtained using less demanding methods. A promising approach is the combination of smaller blocks to form a single large monolith, thereby optimizing cost and labor efficiency as well as representativity and upscaling potential. To this end, we compared the runoff properties of medium-sized (1×0.5×0.35 m) grassland soil monoliths cut in half and recombined with uncut blocks. We conducted artificial runoff experiments and analyzed the chemical composition and amount of outflow from four flow pathways (surface runoff, subsurface interflow, percolating water, lateral flow). Furthermore, we studied surface runoff velocity parameters using a salt tracer. Our results suggest that the effects of the recombination procedure are negligible compared to the variation in the data caused by the inherent soil heterogeneity. We propose that the benefits of combining soil monoliths outweigh the potential disadvantages.

ANÁLISIS DE LA CAPACIDAD DE ABSORCIÓN DE ENERGÍA DEL HORMIGÓN LIGERO DE FIBRAS (MLWC) EN EL ENSAYO DE BARRA DIVIDIDA DE PRESIÓN HOPKINSON (SHPB) POR CONDUCCIÓN ELECTROMAGNÉTICA

To investigate the energy absorption capacity of the mixed lightweight aggregate concrete (MLWC), a new device of electromagnetic driving split Hopkinson pressure bar (SHPB) was self-developed, and the numerical model of electromagnetic driving SHPB and the mesoscale model of MLWC were established. Some simulations of electromagnetic driving SHPB impact for MLWC with different gravel replacement rates under different initial voltages were carried out, which were verified by the indoor experiments. Results show that the peak velocity of the bullet is exponentially related to the initial voltage, and the peak velocity has a power function relationship with the power-off time when the bullet reaches the peak velocity. With the increase of gravel replacement rate, the peak value of specific energy absorption for MLWC and the dynamic compressive strength increase gradually, while the absorbed energy density decreases. When the gravel replacement rate is 25-35%, the strength of MLWC is effectively improved on the premise of ensuring its energy absorption capacity. The obtained conclusions can provide a reference for the application of MLWC. Keywords: Electromagnetic drive, Mixed aggregate concrete, Simulation modelling, Split Hopkinson pressure bar (SHPB), Energy absorption

Study on Compaction Characteristics and Compaction Process of an Unsaturated Silt Based on PFC3D

In order to reduce the construction cost of excessively wet silt roadbeds and improve the compaction quality, this paper studies the compaction characteristics and compaction technology of excessively wet silts through theoretical derivation, indoor experiments, numerical simulation, engineering verification, and other research methods. Based on the pendulum-type liquid bridge structure, this paper uses the Hertz–Mindlin theory, particle motion equation of state, and other theories to modify the force between particles of an unsaturated soil. Through the contact angle, which is a medium, the matrix suction is linked to the water content and is used to approximate the water content state of soil samples. Using PFC3D (particle flow code 3D) numerical simulation software, an unsaturated silt model was established based on Hill contact, and the model parameters were calibrated through basic geotechnical tests and triaxial compression tests. The correctness of the theory is verified by comparing the simulated triaxial compression test of wet silts with the indoor test. By simulating subgrade rolling, considering factors such as the distribution of contact force chain and the variation of compaction degree, the effects of rolling times, strong vibration, and weak vibration on the compaction effect were compared and analyzed. Finally, the optimal rolling and compaction process under the optimal water content is obtained through on-site engineering tests. The results show that: (1) The Hill contact model is reasonable for simulating the wet silt. (2) During the simulation of the roadbed compaction process using PFC3D software, it was found that the compaction degree change during the entire compaction process can be roughly divided into the initial compaction stage and the re-compaction stage. The reasonable number of compaction times was determined to be five through discrete element simulation. (3) It is found from the numerical simulation results that compared to static compaction, both strong and weak vibration compaction can effectively improve the compaction effect of subgrade compaction. The larger the vibration amplitude, the more obvious the improvement of the compaction effect. The compaction effect of strong vibration followed by weak vibration is stronger than that of weak vibration followed by strong vibration. (4) The optimal compaction process obtained under the optimal moisture content of 15% is static pressure once + strong vibration twice + weak vibration twice.