Analytical evaluation of steady-state solute distribution in through- diffusion and membrane behavior test under non-perfectly flushing boundary conditions

The through-diffusion and membrane behavior testing procedure using a closed-system apparatus has been widely used for concurrent measurement of diffusion and membrane efficiency coefficients of low-permeability clay-based barrier materials.However,the common assumption of perfectly flushing conditions at the specimen boundaries could induce errors in analyses of the diffusion coefficients and membrane efficiencies.In this study,an innovative pseudo three-dimensional(3D)analytical method was proposed to evaluate solute distribution along the boundary surfaces of the soil-porous disks system,considering the non-perfectly flushing conditions.The results were consistent with numerical models under two scenarios considering different inflow/outflow positions.The proposed model has been demonstrated to be an accurate and reliable method to estimate solute distributions along the bound-aries.The calculated membrane efficiency coefficient and diffusion coefficient based on the proposed analytical method are more accurate,resulting in up to 50%less relative error than the traditional approach that adopts the arithmetic mean value of the influent and effluent concentrations.The retar-dation factor of the clay specimen also can be calculated with a revised cumulative mass approach.Finally,the simulated transient solute transport matched with experimental data from a multi-stage through-diffusion and membrane behavior test,validating the accuracy of the proposed method.

Optimization of anchorage support parameters for soft rock tunnel based on displacement control theory

In the construction of a soft rock tunnel,it is critical to accurately estimate the pre-stressed anchor support parameters for surrounding rock reinforcement;otherwise,engineering disasters may occur.This paper presents a support parameter selection method that aims to allow deformation as a control objective,which was applied to the tunnel located in Muzailing Highway,Min County,Dingxi City,Gansu Province,China.Through theoretical analysis,we have identified five factors that influence pre-stressing anchorages.The selection of mechanical parameters for the rock mass was carried out using an inverse analysis method.Compared with the measured data,the maximum displacement error of the numerical simulation results was only 0.07 m.The length of anchor cable,circumferential spacing of anchor cable,longitudinal spacing,and pre-stress index are adopted as the input parameters for the support vector machine neural network model based on particle swarm optimization(PSO-LSSVM).Besides,the vault subsidence and the maximum deformation of surrounding rock are considered as output values(performance indices).The goodness of fit between the predicted values and the simulated values exceeds 0.9.Finally,all support parameters within the acceptable deformation range are calculated.The optimal support variables are derived by considering the construction cost and duration.The field application results show that it is feasible to construct the sample database utilizing the numerical simulation approach by taking the displacement as the control target and using the neural network to specify the appropriate support parameters.

Artificial Neural Network Methods for the Solution of Second Order Boundary Value Problems

We present a method for solving partial differential equations using artificial neural networks and an adaptive collocation strategy.In this procedure,a coarse grid of training points is used at the initial training stages,while more points are added at later stages based on the value of the residual at a larger set of evaluation points.This method increases the robustness of the neural network approximation and can result in significant computational savings,particularly when the solution is non-smooth.Numerical results are presented for benchmark problems for scalar-valued PDEs,namely Poisson and Helmholtz equations,as well as for an inverse acoustics problem.

Numerical simulation of flocculation and settling behavior of whole-tailings particles in deep-cone thickener

Rapid dewatering and thickening of whole-tailings with ultrafine particles is one of the most important processes for the whole-tailings paste preparation. Deep-cone thickener, a kind of such process for the flocculation and settling of whole-tailings, is particularly necessary to study. However, there exist many problems in observing the flocculation and settling process of whole-tailings, as well as the particle size distribution(PSD) of whole-tailings floccules in deep-cone thickener. Population balance model(PBM) is applied to predict the PSD in deep-cone thickener, and LUO model and GHADIRI model are employed to study the aggregation and fragmentation mechanism of the whole-tailings particles, respectively. Through three-dimensional numerical simulation on the whole-tailings flocculation and settling in deep-cone thickener using computational fluid dynamics(CFD)-PBM, the distribution of density and turbulent kinetic energy in deep-cone thickener were obtained, at the same time the spatio-temporal changes of whole-tailings floccules particle size distribution are analyzed. Finally, the major flocculation position in deep-cone thickener is found and the flocculation settling rules of whole-tailings are achieved.

Landslide susceptibility analysis of Karakoram highway using analytical hierarchy process and scoops 3D

Landslides are prevalent,regular,and expensive hazards in the Karakoram Highway(KKH)region.The KKH connects Pakistan with China in the present China-Pakistan Economic Corridor(CPEC)context.This region has not only immense economic importance but also ecological significance.The purpose of the study was to map the landslide-prone areas along KKH using two different techniquesAnalytical Hierarchy Process(AHP)and Scoops 3 D model.The causative parameters for running AHP include the lithology,presence of thrust,land use land cover,precipitation,and Digital Elevation Model(DEM)derived variables(slope,curvature,aspect,and elevation).The AHP derived final landslide susceptibility map was classified into four zones,i.e.,low,moderate,high,and extremely high.Over 80%of the study area falls under the moderate(43%)and high(40%)landslide susceptible zones.To assess the slope stability of the study area,the Scoops 3 D model was used by integrating with the earthquake loading data.The results of the limit equilibrium analysis categorized the area into four groups(low,moderate,high,and extremely high mass)of slope failure.The areas around Main Mantle Thrust(MMT)including Dubair,Jijal,and Kohistan regions,had high volumes of potential slope failures.The results from AHP and Scoops 3 D techniques were validated with the landslides inventory record of the Geological Survey of Pakistan and Google Earth.The results from both the techniques showed similar output that coincides with the known landslides areas.However,Scoops 3 D provides not only susceptible zones but also the range of volume of the potential slope failures.Further,these techniques could be used in other mountainous areas,which could help in the landslide mitigation measures.

On the Application of the Lattice Boltzmann Method to Predict Soil Meso Seepage Characteristics

In this study,a two-dimensional approach is elaborated to study with the lattice Boltzmann method(LBM)the seepage of water in the pores of a soil.Firstly,the D2Q9 model is selected to account for the discrete velocity distribution of water flow.In particular,impermeability is considered as macroscopic boundary condition for the left and right domain sides,while the upper and lower boundaries are assumed to behave as pressure boundaries controlled by different densities.The micro-boundary conditions are implemented through the standard rebound strategy and a non-equilibrium extrapolation scheme.Matlab is used for the development of the related algorithm.Finally,the influence of porosity,permeability,osmotic pressure and other factors is assessed with regard to seepage characteristics and the ensuing results are compared with Darcy’s law.The computations show that,for fixed initial conditions,the pore structure has a certain influence on the local velocity of seepage,but the overall state is stable,and the average velocity of each layer is the same.The larger the pore passage is,the faster the flow velocity is,and vice versa.For low permeability,the numerical results are consistent with the Darcy's law.The greater the pressure difference between the inlet and outlet of seepage,the greater the seepage rate.The relationship between them is linear(yet in good agreement with Darcy’s law).

Frost susceptibility of soils——A confusing concept that can misguide geotechnical design in cold regions

Frost susceptibility is a concept widely used in cold region geotechnical design, to quantify the capacity of a soil in generating frost heave and frost damage. The laboratory test used to verify frost susceptibility of a soil is based on the measurement of frost heave generated in the soil under specific conditions. In reality this concept is, however, more related to the soil's potential to thaw weakening than to frost heave. Recent experimental studies show that frost non-susceptible soils like clean sand and clean gavel can also generate much ice segregation and frost heave if the conditions are favourable, hence challenging the usefulness and suitability of soil classification based on frost susceptibility. It is further shown that the concept is not suitable for design scenarios where frost heave itself is a serious hazard, such as in high-speed rail embankments.

路面破损状况检测、评价、预测与管理系统研究进展

高效而准确地对路面破损状况进行评价分析,是路面养护管理的基础和关键。本文对路面破损的数据采集关键技术、评价指标与方法、预测和数据库决策支持系统4个方面进行综述,分析了现有技术和方法的利弊,指出了粗放化管理的问题,提出了建立路面破损状况信息环境的展望。该法有利于建立从数据采集、破损评价分析到预测管理的一整套有机体系,全面准确地掌握路面破损状况。

Theoretical Analysis on Deflection and Bearing Capacity of Prestressed Bamboo-Steel Composite Beams

A theoretical analysis of upward deflection and midspan deflection of prestressed bamboo-steel composite beams is presented in this study.The deflection analysis considers the influences of interface slippage and shear deformation.Furthermore,the calculation model for flexural capacity is proposed considering the two stages of loading.The theoretical results are verified with 8 specimens considering different prestressed load levels,load schemes,and prestress schemes.The results indicate that the proposed theoretical analysis provides a feasible prediction of the deflection and bearing capacity of bamboo-steel composite beams.For deflection analysis,the method considering the slippage and shear deformation provides better accuracy.The theoretical method for bearing capacity matches well with the test results,and the relative errors in the serviceability limit state and ultimate limit state are 4.95%and 5.85%,respectively,which meet the accuracy requirements of the engineered application.

Electrochemistry-stimulated environmental bioremediation:Development of applicable modular electrode and system scale-up

Bioelectrochemical systems(BESs)have been studied extensively during the past decades owing primarily to their versatility and potential in addressing the water-energy-resource nexus.In stark contrast to the significant advancements that have been made in developing innovative processes for pollution control and bioresource/bioenergy recovery,minimal progress has been achieved in demonstrating the feasibility of BESs in scaled-up applications.This lack of scaled-up demonstration could be ascribed to the absence of suitable electrode modules(EMs)engineered for large-scale application.In this study,we report a scalable composite-engineered EM(total volume of 1 m^(3)),fabricated using graphite-coated stainless steel and carbon felt,that allows integrating BESs into mainstream wastewater treatment technologies.The cost-effectiveness and easy scalability of this EM provides a viable and clear path to facilitate the transition between the success of the lab studies and applications of BESs to solve multiple pressing environmental issues at full-scale.

Remarkable low-temperature hydrogen cycling kinetics of Mg enabled by VH_(x) nanoparticles

Nanoscaled catalysts have attracted much more attention due to their more abundant active sites and better dispersion than their bulky counterparts.In this work,VH_(x) nanoparticles smaller than 10 nm in average size are successfully synthesized by a simple solid-state ball milling coupled with THF washing process,which are proved to be highly effective in enhancing the hydrogen absorption/desorption kinetics of MgH_(2) at moderate temperatures.The nano-VH_(x)-modified MgH_(2) releases hydrogen from 182℃,which is 88℃ lower than additive-free MgH_(2).The release of hydrogen amounts to 6.3 wt%H within 10 min at 230℃ and 5.6 wt%H after 30 min at 215℃ with initial vacuum.More importantly,the dehydro-genated MgH_(2)+10 wt.%nano-VH_(x) rapidly absorbs 5.2 wt%H within 3 min at 50℃ under 50 bar H_(2).It even takes up 4.3 wt%H within 30 min at room temperature(25℃)under 10 bar H_(2),exhibiting supe-rior hydrogenation kinetics to most of the previous reports.Mechanistic analyzes disclose the reversible transformation between V and V-H species during the hydrogen desorption-absorption process.The ho-mogeneously distributed V-based species is believed to act as hydrogen pump and nucleation sites for MgH_(2) and Mg,respectively,thus triggering fast hydrogenation/dehydrogenation kinetics.

Groundwater discharge drives water quality and greenhouse gas emissions in a tidal wetland

Wetlands play an important role in the global carbon cycle as they can be sources or sinks for greenhouse gases.Groundwater discharge into wetlands can affect the water chemistry and act as a source of dissolved greenhouse gases,including CO_(2)and CH_(4).In this study,surface water quality parameters and CO_(2)and CH_(4)concentrations were evaluated in a tidal wetland(Hunter Wetlands National Park,Australia)using time series measurements.Radon(^(222)Rn),a natural ground water tracer,was used to investigate the role of groundwater as a pathway for transporting dissolved CO_(2)and CH_(4)into the wetland.In addition,water-to-air CO_(2)and CH_(4)fluxes from the wetland were also estimated.The results showed a high concentration of radon in wetland surface water,indicating the occurrence of ground water discharge.Radon concentration had a strong negative relationship with water depth with a determination coefficient(R^(2))of 0.7,indicating that tidal pumping was the main driver of groundwater discharge to the wetland.Radon concentration also showed a positive relationship with CO_(2)and CH_(4)concentrations(R^(2)=0.4 and 0.5,respectively),while the time series data revealed that radon,CO_(2),and CH_(4)concentrations peaked concurrently during low tides.This implied that groundwater discharge was a source of CO_(2)and CH_(4)to the wetland.The wetland had an average water-to-air CO_(2)flux of 99.1 mmol/(m^(2)·d),twice higher than the global average CO_(2)flux from wetlands.The average CH_(4)flux from the wetland was estimated to be 0.3 mmol/(m^(2)d),which is at the higher end of the global CH_(4)flux range for wetlands.The results showed that groundwater discharge could be an important,yet unaccounted source of CO_(2)and CH_(4)to tidal wetlands.This work has implications for tidal wetland carbon budgets and emphasizes the role of groundwater as a subsurface pathway for carbon transport.

Fabrication of monodispersed B,N co-doped hierarchical porous carbon nanocages through confined etching to boost electrocatalytic oxygen reduction

Dual heteroatom-doped carbons have attracted widespread research attention as catalysts in the field of energy storage and conversion due to their unique electronic structures and chemical tunability.In particular,boron and nitrogen co-doped carbon(B,N@C)has shown great potential for photo/electrocatalytic applications.However,more needs to be done for rational designing and regulating the structure of these materials to improve their catalytic performance.Herein,monodispersed hierarchical porous B,N@C nanocages were fabricated by pyrolyzing zeolite imidazole framework(ZIF)which was treated with ammonia borane or boric acid via an integrated double-solvent impregnation and nanocofined-etching method.The treated ZIF-8 provided an essential structural template to achieve B,N co-doped hierarchical structures with micro/meso/macro multimodal pore size distributions.The resultant B,N@C nanocages displayed high catalytic activities for electrochemical oxygen reduction reaction(ORR)in alkaline media,outperforming most carbon-based catalysts,particularly from the perspective of the half-wave potentials.Such high catalytic performance is due to the enhanced activity by the coexistence of B and N and the mass transfer promoted by the unique hierarchical porous structure.

Numerical investigation of the effect of geosynthetic clay liner chemical incompatibility on flow and contaminant transport through a defective composite liner

A composite liner consisting of a geomembrane(GMB)and a geosynthetic clay liner(GCL)can be compromised by inorganic contaminants because of a defective GMB.When the composite liner with defective GMB is exposed to aggressive leachate conditions,the neglect of the chemical incompatibility of the GCL can potentially result in an underestimation of the leakage rate and flux through the composite liner.This paper proposed a numerical investigation on the effect of chemical incompatibility of GCL on the barrier performance of the composite liner with hole defect.Four cases with leachate solutions having varied cation valencies and ionic strengths were analyzed,in which the hydraulic conductivity of GCL was concentrationdependent.Both the effect of the chemical incompatibility of GCL and the mechanisms were analyzed.The incompatibility of GCL resulted in significant increases in leakage rate and flux through the composite liner by factors of up to 4.9 and 5.0,respectively.The incompatibility-affected area in GCL is located within 0.1 m from the center of the hole in the GMB.The coupled increase in the hydraulic conductivity of GCL and pore water concentration impacts the flux and leakage in a short period of time.With GCL chemical incompatibility considered,advection may dominate the contaminant transport through GCL.

Controlled synthesis of MOF-derived hollow and yolk–shell nanocages for improved water oxidation and selective ethylene glycol reformation

Delicately designed metal–organic framework(MOF)-derived nanostructured electrocatalysts are essential for improving the reaction kinetics of the oxygen evolution reaction and tuning the selectivity of small organic molecule oxidation reactions.Herein,novel oxalate-modified hollow CoFe-based layered double hydroxide nanocages(h-CoFe-LDH NCs)and yolk–shell ZIF@CoFe-LDH nanocages(ys-ZIF@CoFe-LDH NCs)are developed through an etching–doping reconstruction strategy from a Co-based MOF precursor(ZIF-67).The distinctive nanostructures,along with the incorporation of the secondary metal element and intercalated oxalate groups,enable h-CoFe-LDH NCs and ys-ZIF@CoFe-LDH NCs to expose more active sites with high intrinsic activity.The resultant h-CoFe-LDH NCs exhibit outstanding OER activity with an overpotential of only 278 mV to deliver a current density of 50 mA cm^(-2).Additionally,controlling the reconstruction degree enables the formation of ys-ZIF@CoFe-LDH NCs with a yolk–shell nanocage nanostructure,which show outstanding electrocatalytic performance for the selective ethylene glycol oxidation reaction(EGOR)toward formate,with a Faradaic efficiency of up to 91%.Consequently,a hybrid water electrolysis system integrating the EGOR and the hydrogen evolution reaction using Pt/C||ys-ZIF@CoFe-LDH NCs is explored for energy-saving hydrogen production,requiring a cell voltage 127 mV lower than water electrolysis to achieve a current density of 50 mA cm^(-2).This work demonstrates a feasible way to design advanced MOF-derived electrocatalysts toward enhanced electrocatalytic reactions.

Reliability of electric vehicle charging infrastructure:A cross-lingual deep learning approach

Vehicle electrification has emerged as a global strategy to address climate change and emissions externalities from the transportation sector.Deployment of charging infrastructure is needed to accelerate technology adoption;however,managers and policymakers have had limited evidence on the use of public charging stations due to poor data sharing and decentralized ownership across regions.In this article,we use machine learning based classifiers to reveal insights about consumer charging behavior in 72 detected languages including Chinese.We investigate 10 years of consumer reviews in East and Southeast Asia from 2011 to 2021 to enable infrastructure evaluation at a larger geographic scale than previously available.We find evidence that charging stations at government locations result in higher failure rates with consumers compared to charging stations at private points of interest.This evidence contrasts with predictions in the U.S.and European markets,where the performance is closer to parity.We also find that networked stations with communication protocols provide a relatively higher quality of charging services,which favors policy support for connectivity,particularly for underserved or remote areas.

Effective electrocatalytic hydrodechlorination of 2,4,6-trichlorophenol by a novel Pd/MnO_(2)/Ni foam cathode

Pd modified electrodes possess problems such as easy agglomeration and low electrolytic ability,and the use of manganese dioxide(MnO_(2)) to facilitate Pd reduction of organic pollutants is just started.However,there is still a limited understanding of how to match the Pd load and MnO_(2) to realize optimal dechlorination efficiency at minimum cost.Here,a Pd/MnO_(2)/Ni foam cathode was successfully fabricated and applied for the efficient electrochemical dechlorination of 2,4,6-trichlorophenol(2,4,6-TCP).The optimal electrocatalytic hydrodechlorination(ECH)performance with 2,4,6-TCP dechlorination efficiency(92.58%in 180 min)was obtained when the concentration of PdCl_(2) precipitation was 1 mmol/L,the deposition time of MnO_(2) was 300 s and cathode potential was-0.8 V.Performance influenced by the exogenous factors(e.g.,initial pH and coexisted ions)were further investigated.It was found that the neutral pH was the most favorable for ECH and a reduction in dechlorination efficiency(6%~47.6%)was observed in presence of 5 mmol/L of NO_(2)^(-),NO_(3)^(-),S^(2-)or SO_(3)^(2-).Cyclic voltammetry(CV)and quenching experiments verified the existence of three hydrogen species on Pd surface,including adsorbed atomic hydrogen(H^(*)_(ads)),absorbed atomic hydrogen(H^(*)_(abs)),and molecular hydrogen(H_(2)).And the introduction of MnO_(2)promoted the generation of atomic H^(*).Only adsorbed atomic hydrogen(H^(*)_(ads)) was confirmed that it truly facilitated the ECH process.Besides H^(*)_(ads) induced reduction,the direct reduction by cathode electrons also participated in the 2,4,6-TCP dechlorination process.Pd/MnO_(2)/Ni foam cathode shows excellent dechlorination performance,fine stability and recyclable potential,which provides strategies for the effective degradation of persistent halogenated organic pollutants in groundwater.

Photocatalytic degradation of methyl orange using ZnO/TiO_(2) composites

ZnO/TiO_(2)composites were synthesized by using the solvothermal method and ultrasonic precipitation followed by heat treatment in order to investigate their photocatalytic degradation of methyl orange(MO)in aqueous suspension under UV irradiation.The composition and surface structure of the catalyst were characterized by X-ray diffraction(XRD),field emission scanning electron microscope(FE-SEM),and transmission electron microscopy(TEM).The degradation efficiencies of MO at various pH values were obtained.The highest degradation efficiencies were obtained before 30 min and after 60 min at pH 11.0 and pH 2.0,respectively.A sample analysis was conducted using liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry.Six intermediates were found during the photocatalytic degradation process of quinonoid MO.The degradation pathway of quinonoid MO was also proposed.

The effect of various cations/anions for MgH_(2) hydrolysis reaction

MgH_(2) is regarded as a potential hydrolysis material for the hydrogen generation due to its high theoretical hydrogen yield,abundant source on earth and environmentally friendly hydrolysates.However,the quickly formed passive magnesium hydroxide layer on the surface of MgH_(2) will hinder its further hydrolysis reaction,leading to sluggish reaction kinetics and low H_(2) yield.In this paper,we explore the improvement of different anions and cations in solutions for the hydrolysis of MgH_(2).It is found that the cations in the solution promote the reaction rate of MgH_(2) hydrolysis through the hydrolysate-induced growth effect,among which the fastest hydrogen yield can get 1664 m L/g within a few minutes in the Fe_(2)(SO_(4))_(3) solution.As for the anions,it enables different microstructures of the Mg(OH)_(2) hydrolysate which give rise to enhanced water utilization.Specially,for the mixed 0.5 M MgCl_(2)+0.05 M MgSO_(4) solution,the water utilization rate attains the optimum value of 51.3%,much higher than that of the single MgCl_(2) or MgSO_(4) solutions.These findings are of great significance for the application of MgH_(2) hydrolysis as hydrogen generation.

Early construction cost and time risk assessment and evaluation of large-scale underground cavern construction projects in Singapore

The applicability of the Decision Aids for Tunneling(DAT)as an early construction cost and time predicting tool for large-scale underground cavern construction projects is investigated in this study.For this purpose,three large-scale underground cavern construction projects in Singapore are presented using the proposed framework.The data from Project A,which is already completed,are used to validate the prediction outcomes.The results show that the proposed workflow can well estimate the construction cost and time at the 95%confidence level.The DAT simulation results of the other two projects,which are in the early planning stages,are compared with Project A to assess the accuracy of the predicted cost and time.The results show that the proposed workflow with the DAT as a predictor is a valuable tool in estimating construction cost and time for large-scale underground cavern projects,particularly for feasibility studies.