A multiphysical-geochemical coupling model for caprock sealing efficiency in CO_(2) geosequestration

Precipitation or dissolution due to geochemical reactions has been observed in the caprocks for CO_(2) geosequestration.Geochemical reactions modify the caprock sealing efficiency with self-limiting or self-enhancement.However,the effect of this modification on the caprock sealing efficiency has not been fully investigated through multiphysical-geochemical coupling analysis.In this study,a multiphysical-geochemical coupling model was proposed to analyze caprock sealing efficiency.This coupling model considered the full couplings of caprock deformation,two-phase flow,CO_(2) concentration diffusion,geochemical reaction,and CO_(2) sorption.The two-phase flow only occurs in the fracture network and the CO_(2) may partially dissolve into water and diffuse through the concentration difference.The dissolved CO_(2) has geochemical reactions with some critical minerals,thus altering flow channels.The CO_(2) in the fracture network diffuses into matrix,causing the matrix swelling.This fully coupling model was validated with a penetration experiment on a cement cube and compared with two other models for CO_(2) storage plumes.Finally,the effects of geochemical reactions on penetration depth and pore pressure were studied through parametric study.The numerical simulations reveal that the coupling of geochemical reactions and matrix diffusion significantly affect the caprock sealing efficiency.Geochemical reactions occur at a short time after the arrival of CO_(2) concentration and modify the fracture porosity.The CO_(2) diffusion into the matrix requires a much longer time and mainly induces matrix swelling.These effects may produce selfenhancement or self-limiting depending on the flow rate in the fracture network,thus significantly modifying caprock sealing efficiency.

Precise robust motion control of cell puncture mechanism driven by piezoelectric actuators with fractional-order nonsingular terminal slidingmode control

A novel robust controller is proposed in this study to realize the precise motion control of a cell puncture mechanism(CPM)driven by piezoelectric ceramics(PEAs).The entire dynamic model of CPM is constructed based on the Bouc–Wen model,and the nonlinear part of the dynamic model is optimized locally to facilitate the construction of a robust controller.A model-based,nonlinear robust controller is constructed using time-delay estimation(TDE)and fractional-order nonsingular terminal sliding mode(FONTSM).The proposed controller does not require prior knowledge of unknown disturbances due to its real-time online estimation and compensation of unknown terms by using the TDE technology.The controller also has finite-time convergence and high-precision trajectory tracking capabilities due to FONTSM manifold and fast terminal sliding mode-type reaching law.The stability of the closed-loop system is proved by Lyapunov stability theory.Computer simulation and hardware-in-loop simulation experiments of CPM verify that the proposed controller outperforms traditional terminal sliding mode controllers,such as the integer-order or model-free controller.The proposed controller can also continuously output without chattering and has high control accuracy.Zebrafish embryo is used as a verification target to complete the cell puncture experiment.From the engineering application perspective,the proposed control strategy can be effectively applied in a PEA-driven CPM.

Analyzing the formation cause of Xidatan drinking mineral springs in island permafrost area on north slope of the Kunlun Mountains

The replenishment source of Xidatan drinking mineral springs in island permafrost area on north slope of the Kunlun Mountains are mainly the melting water from the modern glaciers bottom, snow and ice melting water, atmospheric precipitation, and surface water in Yuzhu Peak area on the Kunlun Mountains. This scenario is based on the survey of hydrogeology, water-conducting and water-controlling faults, and water chemistry, and on the EH-4 high-frequency electronic deep exploration. The original water recharges the deep groundwater at fracture zone of active normal faults F3 and F4 , then groundwater enriches at normal faults F2 and F2-1,2 , and then run northward. A water-rich triangle area is formed when groundwater reach the active reverse fault F1 . Groundwater then discharges through fracture zone of F1 , which is the major cause of the Xidatan mineral springs formation.

Human-robot interface based on sEMG envelope signal for the collaborative wearable robot

Surface electromyography(sEMG)control interface is a common method for human-centered robotics.Researchers have frequently improved the recognition accuracy of sEMG through multichannel or high-precision signal acquisition devices.However,this increases the cost and complexity of the control system.Therefore,this study developed a control interface based on the sEMG enveloped signal for a collaborative wearable robot to improve the accuracy of sEMG recognition based on the time-domain(TD)features.Specifically,an acquisition device is developed to obtain the sEMG envelope signal,and 11 types of TD features are extracted from the sEMG envelope signal acquired from the upper limb.Furthermore,a dimension reduction method based on the correlation coefficient is proposed,transforming the 11-dimensional feature into a five-dimensional envelope feature set without decreasing the accuracy.Moreover,a recognition algorithm based on a neural network has also been proposed for gesture classification.Finally,the recognition accuracy of the proposed method,principal component analysis(PCA)feature set,and Hudgins TD feature set is compared,with their accuracy at 84.39%,72.44%,and 70.89%,respectively.Therefore,the results indicate that the envelope feature set performs better than the common gesture recognition method based on signal channel sEMG envelope signal.

The effect of dolomite amendment on soil organic carbon mineralization is determined by the dolomite size

Background:The size of lime material is vital for the efficiency of ameliorating soil acidity,thereby influencing soil biochemical processes.However,the effects of different sized lime material application on soil organic carbon(SOC)mineralization are yet to be elucidated.Therefore,a 35-day incubation experiment was conducted to determine the effects of three particle size fractions(0.5 to 0.25,0.25 to 0.15,and<0.15 mm)of dolomite on SOC mineralization of two acidic paddy soils.Results:CO_(2) emission was increased by 3–7%,11–21%,and 32–49%for coarse-,medium-,and fine-sized dolomite treatments,respectively,compared to the control in both soils.They also well conformed to a first-order model in all treatments,and the estimated decomposition rate constant was significantly higher in the fine-sized treatment than that of other treatments(P<0.05),indicating that SOC turnover rate was dependent on the dolomite size.The finer particle sizes were characterized with higher efficiencies of modifying soil pH,consequently resulting in higher dissolved organic carbon contents and microbial biomass carbon,eventually leading to higher CO_(2) emissions.Conclusions:The results demonstrate that the size of dolomite is a key factor in regulating SOC mineralization in acidic paddy soils when dolomite is applied to manipulate soil pH.