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-...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.展开更多
Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submer...Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submerged piles that are determined by solving the Navier-Stokes equations with the improved delayed detached eddy simulation model.This model is verified by comparing experimental and numerical results for hydrodynamic parameters with the literature for both square-crossing piles(SCPs)and circular-crossing piles(CCPs).Original topographies of flat and scoured beds(i.e.,the initial and equilibrium scouring stages)are based on experimental results obtained by the authors in the present paper.SCP and CCP flow features in the scouring process are discussed.The results indicate that during the scouring process,the time-averaged drag coefficient and root mean square(rms)of the lift coefficient increase linearly in the CCP test,while the rms of the lift coefficient in the SCP test decreases linearly.Moreover,the minimum pressure coefficient is always located in the upstream corners in the SCP case but moves from 72.5°to 79.5°when the scour hole is completely developed in the CCP case.Downward flow behind the pile,which is generated by separated boundary layers above the top face of the pile,can reach the sand bed and turn the separated shear layers into patches of small vortices in the near-wake regions.Thus,the high shear stress zones are mainly at the scour edges under scoured-bed conditions.展开更多
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 shea...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.展开更多
In the bridge technical condition assessment standards,the evaluation of bridge conditions primarily relies on the defects identified through manual inspections,which are determined using the comprehensive hierarchica...In the bridge technical condition assessment standards,the evaluation of bridge conditions primarily relies on the defects identified through manual inspections,which are determined using the comprehensive hierarchical analysis method.However,the relationship between the defects and the technical condition of the bridges warrants further exploration.To address this situation,this paper proposes a machine learning-based intelligent diagnosis model for the technical condition of highway bridges.Firstly,collect the inspection records of highway bridges in a certain region of China,then standardize the severity of diverse defects in accordance with relevant specifications.Secondly,in order to enhance the independence between the defects,the key defect indicators were screened using Principal Component Analysis(PCA)in combination with the weights of the building blocks.Based on this,an enhanced Naive Bayesian Classification(NBC)algorithm is established for the intelligent diagnosis of technical conditions of highway bridges,juxtaposed with four other algorithms for comparison.Finally,key defect variables that affect changes in bridge grades are discussed.The results showed that the technical condition level of the superstructure had the highest correlation with cracks;the PCA-NBC algorithm achieved an accuracy of 93.50%of the predicted values,which was the highest improvement of 19.43%over other methods.The purpose of this paper is to provide inspectors with a convenient and predictive information-rich method to intelligently diagnose the technical condition of bridges based on bridge defects.The results of this research can help bridge inspectors and even non-specialists to better understand the condition of bridge defects.展开更多
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 s...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.展开更多
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 imm...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.展开更多
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 flocculat...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.展开更多
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...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).展开更多
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 presen...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.展开更多
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 ...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.展开更多
The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation.Herein,we demonstra...The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation.Herein,we demonstrate a unique organic/inorganic hybrid binder system that enables an efficient in situ crosslinking of aqueous binders(e.g.,sodium alginate(SA)and carboxymethyl cellulose(CMC))by reacting with an inorganic crosslinker(sodium metaborate hydrate(SMH))upon vacuum drying.The resultant 3D interconnected networks endow the binders with strong adhesion and outstanding self-healing capability,which effectively improve the electrode integrity by preventing fracturing and exfoliation during cycling and facilitate Li^(+)ion transfer.SiO anodes fabricated from the commercial microsized powders with the SA/0.2SMH binder maintain 1470 mAh g^(-1)of specific capacity at 100 mA g^(-1)after 200 cycles,which is 5 times higher than that fabricated with SA binder alone(293 mAh g^(-1)).Nearly,no capacity loss was observed over 500 cycles when limiting discharge capacity at 1500 mAh g^(-1).The new binders also dramatically improved the performance of Fe_(2)O_(3),Fe_(3)O_(4),NiO,and Si electrodes,indicating the excellent applicability.This finding represents a novel strategy in developing high-performance aqueous binders and improves the prospect of using high-capacity anode materials in Li-ion batteries.展开更多
为了消除路面裂缝图像中的孤立噪声并保护裂缝边缘的细致特征,本文基于像素和裂缝子块两个层级的连通性检测设计了去噪算法,主要包括3个部分：（1）像素连通性检测,剔除连通性差的像素;（2）孤岛噪声消除算法,删除相对孤立的目标区域;（...为了消除路面裂缝图像中的孤立噪声并保护裂缝边缘的细致特征,本文基于像素和裂缝子块两个层级的连通性检测设计了去噪算法,主要包括3个部分：（1）像素连通性检测,剔除连通性差的像素;（2）孤岛噪声消除算法,删除相对孤立的目标区域;（3）8×8裂缝子块去噪算法。然后,提出了算法流程并探讨参数的选择。最后,应用Visual Studio 2008和Open CV编程对本文算法、常用的中值滤波去噪法、长线段和黑色像素比例法进行性能测试,结果表明,本文算法可有效消除孤立噪声并保持边缘连续性,具有更高的准确率（85.06%）和召回率（85.80%）,综合性能指标F1值比后两者分别高0.74%~19.19%和0.20%~12.06%。展开更多
Causality,the science of cause and effect,has made it possible to create a new family of models.Such models are often referred to as causal models.Unlike those of mathematical,numerical,empirical,or machine learning(M...Causality,the science of cause and effect,has made it possible to create a new family of models.Such models are often referred to as causal models.Unlike those of mathematical,numerical,empirical,or machine learning(ML)nature,causal models hope to tie the cause(s)to the effect(s)pertaining to a phenomenon(i.e.,data generating process)through causal principles.This paper presents one of the first works at creating causal models in the area of structural and construction engineering.To this end,this paper starts with a brief review of the principles of causality and then adopts four causal discovery algorithms,namely,PC(Peter-Clark),FCI(fast causal inference),GES(greedy equivalence search),and GRa SP(greedy relaxation of the sparsest permutation),have been used to examine four phenomena,including predicting the load-bearing capacity of axially loaded members,fire resistance of structural members,shear strength of beams,and resistance of walls against impulsive(blast)loading.Findings from this study reveal the possibility and merit of discovering complete and partial causal models.Finally,this study also proposes two simple metrics that can help assess the performance of causal discovery algorithms.展开更多
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 significa...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.展开更多
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 green...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.展开更多
Urban terrorism is a significant global concern,prompting extensive scholarly inquiry into its underlying causes and effects.However,a comprehensive literature review summarizing this body of knowledge is notably abse...Urban terrorism is a significant global concern,prompting extensive scholarly inquiry into its underlying causes and effects.However,a comprehensive literature review summarizing this body of knowledge is notably absent.Thus,this study seeks to address this gap by conducting a thorough examination of existing literature on terrorism,particularly focusing on urban contexts,to identify key patterns and recurring themes.The study identified 515 research articles using the keywords"urban"and"terrorism"through the Web of Science and Scopus databases.A bibliometric review was conducted,which included a historical background,author keywords,country and institution,citation,and co-citation analyses.The findings revealed an increase in the number of studies on urban terrorism following the 9/11 attacks in the United States,which accounted for the highest number of publications in the country.Most studies were conducted in government law,international relations,and urban studies.Keyword analysis revealed that counterterrorism,security,and disasters were more closely linked to terrorism.Thematic analysis identified six main themes related to urban spaces and terrorism:tourism,governance,resilience,public health,economy,security,and counterterrorism.This study emphasizes the importance of involving the public in counterterrorism efforts in addition to traditional approaches to addressing urban terrorism.展开更多
Liquid-liquid solvent extraction,commonly used for high purity Co(Ⅱ)extraction,suffers from drawbacks such as environmental pollution and high cost.To overcome these challenges,a novel Cyanex 272(bis(2,4,4-trimethyl ...Liquid-liquid solvent extraction,commonly used for high purity Co(Ⅱ)extraction,suffers from drawbacks such as environmental pollution and high cost.To overcome these challenges,a novel Cyanex 272(bis(2,4,4-trimethyl pentyl)phosphinic acid,HCyanex)adsorptive membrane(CAM)was synthesized using the phase inversion method with varied Cyanex 272 loadings(0–52.5%)to extract Co(Ⅱ)from cobalt-nickel mixed sulfate solution.Fourier transform infrared(FTIR)spectrometer,Scanning electron microscopy(SEM),and Energy dispersive X-ray spectroscopy(EDX)of asprepared CAMs confirmed the successful and homogeneous blending of Cyanex 272 with poly(vinylidenefluoride)(PVDF),and increased pore sizes were observed with the addition of Cyanex 272.The highest Co(Ⅱ)removal was achieved by the CAMs containing 33.2%weight percentage of Cyanex 272 to PVDF with a Langmuir sorption capacity of 1.42 mg/g.The extraction process for Co(Ⅱ)and Ni(Ⅱ)by CAMs was sensitive to pH and temperature,with an optimal separation factor of 209.5 at pH 6.8 and 75°C.The adsorption process is endothermic.Additionally,the membrane exhibited excellent stability and durability,maintaining around 98%adsorption capacity after 20 cycles in the recycling process.These findings suggest that the as-prepared CAMs are a promising technology for the separation of Co(Ⅱ)from Ni(Ⅱ)in the recycling process of lithium-ion batteries.展开更多
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 ...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.展开更多
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 form...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.展开更多
基金The financial support received from the Ministry of Science and Technology of the People’s Republic of China(Grant No.2019YFC1806002)National Natural Science Foundation of China(Grant Nos.42107174,42077241)is gratefully acknowledged.
文摘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.
基金support from the National Natural Science Foundation of China (Nos.52301324 and 52001276)the Natural Science Foundation of Zhejiang Province (No.LQ24E090001)+2 种基金the Open Fund of Key Laboratory of Estuary and Coast of Zhejiang Province (No.ZIHE21005)the Natural Science Foundation of Ningbo (No.2021J096)the Zhejiang Transportation Science and Technology (No.2021064)。
文摘Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submerged piles that are determined by solving the Navier-Stokes equations with the improved delayed detached eddy simulation model.This model is verified by comparing experimental and numerical results for hydrodynamic parameters with the literature for both square-crossing piles(SCPs)and circular-crossing piles(CCPs).Original topographies of flat and scoured beds(i.e.,the initial and equilibrium scouring stages)are based on experimental results obtained by the authors in the present paper.SCP and CCP flow features in the scouring process are discussed.The results indicate that during the scouring process,the time-averaged drag coefficient and root mean square(rms)of the lift coefficient increase linearly in the CCP test,while the rms of the lift coefficient in the SCP test decreases linearly.Moreover,the minimum pressure coefficient is always located in the upstream corners in the SCP case but moves from 72.5°to 79.5°when the scour hole is completely developed in the CCP case.Downward flow behind the pile,which is generated by separated boundary layers above the top face of the pile,can reach the sand bed and turn the separated shear layers into patches of small vortices in the near-wake regions.Thus,the high shear stress zones are mainly at the scour edges under scoured-bed conditions.
基金supported by the National Natural Science Foundation of China(51978345,52278264).
文摘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.
基金financially supported by the National Natural Science Foundation of China(No.51808301)the Scientific Research Fund of Zhejiang Provincial Education Department(No.Y202248860)the National“111”Centre on Safety and Intelligent Operation of Sea Bridge(D21013).
文摘In the bridge technical condition assessment standards,the evaluation of bridge conditions primarily relies on the defects identified through manual inspections,which are determined using the comprehensive hierarchical analysis method.However,the relationship between the defects and the technical condition of the bridges warrants further exploration.To address this situation,this paper proposes a machine learning-based intelligent diagnosis model for the technical condition of highway bridges.Firstly,collect the inspection records of highway bridges in a certain region of China,then standardize the severity of diverse defects in accordance with relevant specifications.Secondly,in order to enhance the independence between the defects,the key defect indicators were screened using Principal Component Analysis(PCA)in combination with the weights of the building blocks.Based on this,an enhanced Naive Bayesian Classification(NBC)algorithm is established for the intelligent diagnosis of technical conditions of highway bridges,juxtaposed with four other algorithms for comparison.Finally,key defect variables that affect changes in bridge grades are discussed.The results showed that the technical condition level of the superstructure had the highest correlation with cracks;the PCA-NBC algorithm achieved an accuracy of 93.50%of the predicted values,which was the highest improvement of 19.43%over other methods.The purpose of this paper is to provide inspectors with a convenient and predictive information-rich method to intelligently diagnose the technical condition of bridges based on bridge defects.The results of this research can help bridge inspectors and even non-specialists to better understand the condition of bridge defects.
文摘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.
文摘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.
基金Project(51174032)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0225)supported by the Program for New Century Excellent Talents in University,ChinaProject(FRF-TP-09-001A)supported by the Fundamental Research Funds for the Central Universities,China
文摘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.
文摘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).
基金supported by the Open Fund of State Key Laboratory of High speed Railway Track Technology(2022YJ127-1)National Natural Science Foundation of China(52104125,41941018)+1 种基金the Natural Science Basic Research Plan in Shaanxi Province of China(2022JQ-304)the Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)。
文摘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.
文摘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.
基金support from the National Outstanding Youth Foundation of China(52125104)the National Natural Science Foundation of China(52071285 and 51831009)+1 种基金the Fundamental Research Funds for the Central Universities(2021FZZX001-09)the National Youth Top-Notch Talent Support Program.Z.H.acknowledges support under the Australian Research Council's Future Fellowship(FT190100658).
文摘The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation.Herein,we demonstrate a unique organic/inorganic hybrid binder system that enables an efficient in situ crosslinking of aqueous binders(e.g.,sodium alginate(SA)and carboxymethyl cellulose(CMC))by reacting with an inorganic crosslinker(sodium metaborate hydrate(SMH))upon vacuum drying.The resultant 3D interconnected networks endow the binders with strong adhesion and outstanding self-healing capability,which effectively improve the electrode integrity by preventing fracturing and exfoliation during cycling and facilitate Li^(+)ion transfer.SiO anodes fabricated from the commercial microsized powders with the SA/0.2SMH binder maintain 1470 mAh g^(-1)of specific capacity at 100 mA g^(-1)after 200 cycles,which is 5 times higher than that fabricated with SA binder alone(293 mAh g^(-1)).Nearly,no capacity loss was observed over 500 cycles when limiting discharge capacity at 1500 mAh g^(-1).The new binders also dramatically improved the performance of Fe_(2)O_(3),Fe_(3)O_(4),NiO,and Si electrodes,indicating the excellent applicability.This finding represents a novel strategy in developing high-performance aqueous binders and improves the prospect of using high-capacity anode materials in Li-ion batteries.
文摘为了消除路面裂缝图像中的孤立噪声并保护裂缝边缘的细致特征,本文基于像素和裂缝子块两个层级的连通性检测设计了去噪算法,主要包括3个部分：（1）像素连通性检测,剔除连通性差的像素;（2）孤岛噪声消除算法,删除相对孤立的目标区域;（3）8×8裂缝子块去噪算法。然后,提出了算法流程并探讨参数的选择。最后,应用Visual Studio 2008和Open CV编程对本文算法、常用的中值滤波去噪法、长线段和黑色像素比例法进行性能测试,结果表明,本文算法可有效消除孤立噪声并保持边缘连续性,具有更高的准确率（85.06%）和召回率（85.80%）,综合性能指标F1值比后两者分别高0.74%~19.19%和0.20%~12.06%。
文摘Causality,the science of cause and effect,has made it possible to create a new family of models.Such models are often referred to as causal models.Unlike those of mathematical,numerical,empirical,or machine learning(ML)nature,causal models hope to tie the cause(s)to the effect(s)pertaining to a phenomenon(i.e.,data generating process)through causal principles.This paper presents one of the first works at creating causal models in the area of structural and construction engineering.To this end,this paper starts with a brief review of the principles of causality and then adopts four causal discovery algorithms,namely,PC(Peter-Clark),FCI(fast causal inference),GES(greedy equivalence search),and GRa SP(greedy relaxation of the sparsest permutation),have been used to examine four phenomena,including predicting the load-bearing capacity of axially loaded members,fire resistance of structural members,shear strength of beams,and resistance of walls against impulsive(blast)loading.Findings from this study reveal the possibility and merit of discovering complete and partial causal models.Finally,this study also proposes two simple metrics that can help assess the performance of causal discovery algorithms.
基金financially supported by the NSFC-EU Environmental Biotechnology joint program(No.31861133001).
文摘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.
文摘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.
文摘Urban terrorism is a significant global concern,prompting extensive scholarly inquiry into its underlying causes and effects.However,a comprehensive literature review summarizing this body of knowledge is notably absent.Thus,this study seeks to address this gap by conducting a thorough examination of existing literature on terrorism,particularly focusing on urban contexts,to identify key patterns and recurring themes.The study identified 515 research articles using the keywords"urban"and"terrorism"through the Web of Science and Scopus databases.A bibliometric review was conducted,which included a historical background,author keywords,country and institution,citation,and co-citation analyses.The findings revealed an increase in the number of studies on urban terrorism following the 9/11 attacks in the United States,which accounted for the highest number of publications in the country.Most studies were conducted in government law,international relations,and urban studies.Keyword analysis revealed that counterterrorism,security,and disasters were more closely linked to terrorism.Thematic analysis identified six main themes related to urban spaces and terrorism:tourism,governance,resilience,public health,economy,security,and counterterrorism.This study emphasizes the importance of involving the public in counterterrorism efforts in addition to traditional approaches to addressing urban terrorism.
基金partially supported by the U.S.Department of Agriculture Grants:2018-68011-28371 and 2022-05735.Lastly。
文摘Liquid-liquid solvent extraction,commonly used for high purity Co(Ⅱ)extraction,suffers from drawbacks such as environmental pollution and high cost.To overcome these challenges,a novel Cyanex 272(bis(2,4,4-trimethyl pentyl)phosphinic acid,HCyanex)adsorptive membrane(CAM)was synthesized using the phase inversion method with varied Cyanex 272 loadings(0–52.5%)to extract Co(Ⅱ)from cobalt-nickel mixed sulfate solution.Fourier transform infrared(FTIR)spectrometer,Scanning electron microscopy(SEM),and Energy dispersive X-ray spectroscopy(EDX)of asprepared CAMs confirmed the successful and homogeneous blending of Cyanex 272 with poly(vinylidenefluoride)(PVDF),and increased pore sizes were observed with the addition of Cyanex 272.The highest Co(Ⅱ)removal was achieved by the CAMs containing 33.2%weight percentage of Cyanex 272 to PVDF with a Langmuir sorption capacity of 1.42 mg/g.The extraction process for Co(Ⅱ)and Ni(Ⅱ)by CAMs was sensitive to pH and temperature,with an optimal separation factor of 209.5 at pH 6.8 and 75°C.The adsorption process is endothermic.Additionally,the membrane exhibited excellent stability and durability,maintaining around 98%adsorption capacity after 20 cycles in the recycling process.These findings suggest that the as-prepared CAMs are a promising technology for the separation of Co(Ⅱ)from Ni(Ⅱ)in the recycling process of lithium-ion batteries.
基金supported by the National Out-standing Youth Foundation of China (No.52125104)the Natural Science Foundation of Zhejiang Province (No.LD21E010002)+2 种基金the National Natural Science Foundation of China (No.52001277)the Fundamental Research Funds for the Central Universities (No.2021FZZX001-09)the National Youth Top-Notch Talent Support Program.
文摘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.
基金supported by the National Key Research and Development Program of China(2017YFA0204600)the National Science Fund for Distinguished Young Scholars(51625102)+2 种基金the National Natural Science Foundation of China(51971065)the Innovation Program of Shanghai Municipal Education Commission(2019–01–07–00–07-E00028)the financial support from ARC(DP170101773)。
文摘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.
