We developed a strategy involving an electroactive biofiltration dynamic membrane(EBDM)for wastewater treatment and membrane fouling mitigation.This approach utilizes a cathode potential within an anaerobic dynamic me...We developed a strategy involving an electroactive biofiltration dynamic membrane(EBDM)for wastewater treatment and membrane fouling mitigation.This approach utilizes a cathode potential within an anaerobic dynamic membrane bioreactor to establish a growth equilibrium electroactive fouling layer.Over a 240 day operation period,the EBDM exhibited outstanding performance,characterized by an ultralow fouling rate(transmembrane pressure<2.5 kPa),superior effluent quality(chemical oxygen demand(COD)removal>93%and turbidity 2 nephelometric turbidity units(NTU)),and a 7.2%increase in methane(CH4)productivity.Morphological analysis revealed that the EBDM acted as a biofilter consisting of a structured,interconnected,multilevel dynamic membrane system with orderly clogging.In the EBDM system,the balanced-growth fouling layers presented fewer biofoulants and looser secondary protein structures.Furthermore,the applied electric field modified the physicochemical properties of the biomass,leading to a decrease in fouling potential.Quartz crystal microbalance with dissipation monitoring analysis indicated that growth equilibrium promoted a looser fouling layer with a lower adsorption mass than did the denser,viscoelastic fouling layer observed in the control reactor.Metagenomic sequencing further demonstrated that continuous electrical stimulation encouraged the development of an electroactive fouling layer with enhanced microbial metabolic functionality on the EBDM.This approach selectively modifies metabolic pathways and increases the degradation of foulants.The EBDM strategy successfully established an ordered-clogging,step-filtered,and balanced-growth electroactive fouling layer,achieving a synergistic effect in reducing membrane fouling,enhancing effluent quality,and improving CH_(4)productivity.展开更多
The perfluorosulfonic acid(PFSA) membrane doped with two-dimensional conductive filler Ti_(3)C_(2)T_(x) is a fuel cell proton exchange membrane with high application potential. Experimental studies showed that the pro...The perfluorosulfonic acid(PFSA) membrane doped with two-dimensional conductive filler Ti_(3)C_(2)T_(x) is a fuel cell proton exchange membrane with high application potential. Experimental studies showed that the proton conductivity of Nafion/Ti_(3)C_(2)T_(x) composite membrane is improved significantly compared with that in pure Nafion. However, the microscopic mechanism of doping on the enhancement of membrane performance is remain unclear now. In this work, molecular dynamics simulation was used to investigate the microscopic morphology and proton transport behaviors of Nafion/Ti_(3)C_(2)T_(x) composite membrane at the molecular level. The results shown that there were significant differences about the diffusion kinetics of water molecules and hydroxium ions in Nafion/Ti_(3)C_(2)T_(x) at low and high hydration levels in the nanoscale region.With the increase of water content, Ti_(3)C_(2)T_(x) in membrane was gradually surrounded by ambient water molecules to form a hydration layer, and forming a relatively continuous proton transport channel between Nafion polymer and Ti_(3)C_(2)T_(x) monomer. The continuous proton transport channel could increase the number of binding sites of proton and thus achieving high proton conductivity and high mobility of water molecules at higher hydration level. The current work can provide a theoretical guidance for designing new type of Nafion composite membranes.展开更多
Because of the small stiffness and high flexibility, the tension membrane structure is easy to relax and damage or even destroy under the action of external load, which leads to the occurrence of engineering accidents...Because of the small stiffness and high flexibility, the tension membrane structure is easy to relax and damage or even destroy under the action of external load, which leads to the occurrence of engineering accidents. In this paper, the damped nonlinear vibration of tensioned membrane structure under the coupling action of wind and rain is approximately solved, considering the geometric nonlinearity of membrane surface deformation and the influence of air damping. Applying von Karman’s large deflection theory and D’Alembert’s principle, the governing equations are established for an analytical solution, and the experimental results are compared with the analytical results. The feasibility of this method is verified, which provides some theoretical reference for practical membrane structure engineering design and maintenance.展开更多
The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for...The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for hydrogen production.Despite remarkable advancements in this field,confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle.This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment.To address these challenges,we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system.Compared to constant voltage electrolysis(hydrogen production rate:51.6 m L h^(-1),energy consumption:5.37 kWh Nm-^(3)H_(2)),this strategy(hydrogen production rate:66 m L h^(-1),energy consumption:3.83 kWh Nm-^(3)H_(2))increases the hydrogen production rate by approximately 27%and reduces the energy consumption by about 28%.Furthermore,we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic(PV)system designed for outdoor operation,successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V.The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism:pulsed dynamic electrolysis(PDE)dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface.As such,PDE-enhanced PEMWE represents a synergistic advancement,concurrently enhancing both the hydrogen generation reaction and associated transport processes.This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.展开更多
Membrane electrode assembly(MEA)is widely considered to be the most promising type of electrolyzer for the practical application of electrochemical CO_(2) reduction reaction(CO_(2)RR).In MEAs,a square-shaped cross-sec...Membrane electrode assembly(MEA)is widely considered to be the most promising type of electrolyzer for the practical application of electrochemical CO_(2) reduction reaction(CO_(2)RR).In MEAs,a square-shaped cross-section in the flow channel is normally adopted,the configuration optimization of which could potentially enhance the performance of the electrolyzer.This paper describes the numerical simulation study on the impact of the flow-channel cross-section shapes in the MEA electrolyzer for CO_(2)RR.The results show that wide flow channels with low heights are beneficial to the CO_(2)RR by providing a uniform flow field of CO_(2),especially at high current densities.Moreover,the larger the electrolyzer,the more significant the effect is.This study provides a theoretical basis for the design of high-performance MEA electrolyzers for CO_(2)RR.展开更多
The formation of donut-shaped penetration pore upon membrane fusion in a closed lipid membrane system is of biological significance,since such the structures extensively exist in living body with various functions.How...The formation of donut-shaped penetration pore upon membrane fusion in a closed lipid membrane system is of biological significance,since such the structures extensively exist in living body with various functions.However,the related formation dynamics is unclear because of the limitation of experimental techniques.This work developed a new model of intra-vesicular fusion to elaborate the formation and stabilization of penetration pores by employing molecular dynamics simulations,based on simplified spherical lipid vesicle system,and investigated the regulation of membrane lipid composition.Results showed that penetration pore could be successfully formed based on the strategy of membrane fusion.The ease of intra-vesicular fusion and penetration pore formation was closely correlated with the lipid curvature properties,where negative spontaneous curvature of lipids seemed to be unfavorable for intra-vesicle fusion.Furthermore,the inner membrane tension around the pore was much larger than other regions,which governed the penetration pore size and stability.This work provided basic understanding for vesicle penetration pore formation and stabilization mechanisms.展开更多
Membrane fusion is essential for many cellular physiological functions,which is modulated by highly precise molecular mechanism involving multiple energy barriers.Nanoparticles(NPs),which exhibit immense potential in ...Membrane fusion is essential for many cellular physiological functions,which is modulated by highly precise molecular mechanism involving multiple energy barriers.Nanoparticles(NPs),which exhibit immense potential in the field of biomedical applications,can act as fusogen proteins to initiate and regulate membrane fusion.However,the underlying mechanisms of NP-induced membrane fusion and the molecular details involved remain largely elusive.Here,using coarse-grained molecular dynamics simulations,we systematically investigate the NP-induced membrane fusion behaviors and the influences of NP properties(size,hydrophobicity and hydrophilicity).Our results show that the vesicle-bilayer fusion induced by a hydrophobic NP is an intricately state-wise process,involving the approach and local deformation of the vesicle and bilayer bridging by the NP,the flip-flop of lipids from proximal leaflets and the formation of a fusion stalk,as well as further lipid interactions between distal leaflets and complete fusion.Moreover,we find that NP properties have distinct effects on membrane fusion and thus the optimal NP conditions for facilitating membrane fusion are obtained.Our work provides a mechanistic understanding of NP-induced membrane fusion and offers useful insights for efficient and controlled regulation of membrane fusion.展开更多
Polymer fibers are an important class of materials throughout human history,evolving from natural fibers such as cotton and silk to modern synthetic fibers such as nylon and polyester.With the advancement of materials...Polymer fibers are an important class of materials throughout human history,evolving from natural fibers such as cotton and silk to modern synthetic fibers such as nylon and polyester.With the advancement of materials science,the development of new fibers is also advancing.Polymer fibers based on dynamic covalent chemistry have attracted widespread attention due to their unique reversibility and responsiveness.Dynamic covalent chemistry has shown great potential in improving the spinnability of materials,achieving green preparation of fibers,and introducing self-healing,recyclability,and intelligent response properties into fibers.In this review,we divide these fiber materials based on dynamic covalent chemistry into monocomponent fibers,composite fibers,and fiber membranes.The preparation methods,structural characteristics,functional properties,and application performance of these fibers are summarized.The application potential and challenges of fibers based on dynamic covalent chemistry are discussed,and their future development trends are prospected.展开更多
The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pol...The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.展开更多
Motivated by recent experimental observations that carbon nanotubes （CNT） can enter animal cells, here we conduct coarse grained molecular dynamics and theoretical studies of the intrinsic interaction mechanisms bet...Motivated by recent experimental observations that carbon nanotubes （CNT） can enter animal cells, here we conduct coarse grained molecular dynamics and theoretical studies of the intrinsic interaction mechanisms between CNT＇s and lipid bilayer. The results indicate that CNT-cell interaction is dominated by van der Waals and hydrophobic forces, and that CNT＇s with sufficiently small radii can directly pierce through cell membrane while larger tubes tend to enter cell via a wrapping mechanism. Theoretical models are proposed to explain the observed size effect in transition of entry mechanisms.展开更多
Detailed atomistic structures are constructed for polydopamine membranes containing different amounts of catechol and quinone groups to investigate the effect of p H value in the membrane casting solution on sorption ...Detailed atomistic structures are constructed for polydopamine membranes containing different amounts of catechol and quinone groups to investigate the effect of p H value in the membrane casting solution on sorption and diffusion of small gas molecules(water and propylene) in the membranes. Interactions between dopamine oligomers are calculated, and it is found that the interactions decrease from- 2356.52 k J·mol-1in DOP-1 to-1586.69 k J·mol-1in DOP-3 when all of the catechol groups are converted to quinone groups. The mobility of polymer segments and free volume properties of polydopamine membranes are analyzed. The sorption quantities of water and propylene in the membrane are calculated using Grand Canonical Monte Carlo method. The sorption results show that water adsorbed in DOP-1, DOP-2 and DOP-3 are 17.3, 18.6 and 20.0 mg water per gram polymer, respectively, and no propylene molecule can be adsorbed. The diffusion behavior of water molecules in the membrane is investigated by molecular dynamics simulation. The diffusion coefficients of water molecules in DOP-1, DOP-2 and DOP-3 membranes are(1.80 ± 0.52) × 10-11,(3.40 ± 0.64) × 10-11and(4.50 ± 0.92) × 10-11m2·s-1, respectively. The predicted sorption quantities and diffusion coefficients of water and propylene in the membrane present the same trends as those from experimental results.展开更多
In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR usi...In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge <sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.展开更多
Membrane fouling is often considered as a hindrance for the application of microfiltration/ultrafiltration(MF/UF) for drinking water production. A novel process of photocatalytic membrane reactor/dynamic membrane(PMR/...Membrane fouling is often considered as a hindrance for the application of microfiltration/ultrafiltration(MF/UF) for drinking water production. A novel process of photocatalytic membrane reactor/dynamic membrane(PMR/DM), operating in a continuous mode under sub-critical flux, was proposed for the mitigation of membrane fouling caused by humic acids(HAs) in water. The mechanism of membrane fouling alleviation with synergistic photocatalytic oxidation and dynamic layer isolating effect was comprehensively investigated from the characterization of foulant evolution responsible for the reversible and irreversible fouling. The results showed that the PMR/DM utilized photocatalytic oxidation to enhance the porosity and hydrophilicity of the fouling layer by converting the high molecular weight(MW) and hydrophobic HA molecules with carboxylic functional groups and aromatic structures into low-MW hydrophilic or transphilic fractions, including tryptophan-like or fulvic-like substances. The fouling layer formed in the PMR/DM by combination of photocatalytic oxidation and DM running at a sub-critical flux of 100 L·h^-1·m^-2, was more hydrophilic and more porous, resulting in the lowest trans-membrane pressure(TMP) growth rates, as compared to the processes of ceramic membrane(CM), DM and PMR/CM.Meanwhile, the dynamic layer prevented the foulants, particularly the high-MW hydrophobic fractions,from contacting the primary membrane, which enabled the membrane permeability to be restored easily.展开更多
Based on energy equilibrium,a new procedure called the Membrane Factor Method is devel- oped to analyze the dynamic plastic response of plates with deflections in the range where both bending mo- ments and membrane fo...Based on energy equilibrium,a new procedure called the Membrane Factor Method is devel- oped to analyze the dynamic plastic response of plates with deflections in the range where both bending mo- ments and membrane forces are important.The final deflection of a simply -supported circular rigid-plastic plate loaded by a uniformly distributed impulse is obtained.In comparison with other approximate solutions, the present results are found to be simpler and in better agreement with the corresponding experimental values reoorded by Florence.展开更多
In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inn...In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inner surface. A second-order nonlinear ordinary differential equation that approximately describes the radial oscillation of the inner surface of the membrane with respect to time is obtained. Some interesting conclusions are proposed for different materials, such as the neo-Hookean material, the Mooney-Rivlin material and the Rivlin-Saunders material. Firstly, the bifurcation conditions depending on the material parameters and the pressure loads are determined. Secondly, the conditions of periodic motion are presented in detail for membranes composed of different materials. Meanwhile, numerical simulations are also provided.展开更多
A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain p...A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.展开更多
Compared with conventional cylinder airlift bioreactors(CCABs)that produce coarse bubbles,a novel rectangular dynamic membrane airlift bioreactor(RDMAB)developed in our lab produces fine bubbles to enhance the volumet...Compared with conventional cylinder airlift bioreactors(CCABs)that produce coarse bubbles,a novel rectangular dynamic membrane airlift bioreactor(RDMAB)developed in our lab produces fine bubbles to enhance the volumetric oxygen mass transfer coefficient(k_(L)a)and gas holdup,as well as improve the bioprocess in a bioreactor.In this study,we compared mass transfer,gas holdup,and batch and con-tinuous fermentation for RNA production in CCAB and RDMAB.In addition,unstructured kinetic models for microbial growth,substrate utilization,and RNA formation were established.In batch fermentation,biomass,RNA yield,and substrate utilization in the RDMAB were higher than those in the CCAB,which indicates that dynamic membrane aeration produced a high k_(L)a by fine bubbles;a higher k_(L)a is more bene-ficial to aerobic fermentation.The starting time of continuous fermentation in the RDMAB was 20 h ear-lier than that in the CCAB,which greatly improved the biological process.During continuous fermentation,maintaining the same dissolved oxygen level and a constant dilution rate,the biomass accumulation and RNA concentration in the RDMAB were 9.71% and 11.15% higher than those in the CCAB,respectively.Finally,the dilution rate of RDMAB was 16.7% higher than that of CCAB during con-tinuous fermentation while maintaining the same air aeration.In summary,RDMAB is more suitable for continuous fermentation processes.Developing new aeration and structural geometry in airlift bioreac-tors to enhance k_(L)a and gas holdup is becoming increasingly important to improve bioprocesses in a bioreactor.展开更多
A simple harmonic motion is proposed to make the membrane move in a simpleharmonic way so as to enhance the membrane filtration, and minimize the membrane fouling andconcentration polarization. The velocity distributi...A simple harmonic motion is proposed to make the membrane move in a simpleharmonic way so as to enhance the membrane filtration, and minimize the membrane fouling andconcentration polarization. The velocity distribution and pressure distribution are deduced from theNavier-Stokes equation on the basis of a laminar flow when the membrane rotates at the speed of Asin(αt). And then the shear stress, shear force, moment of force on the membrane surface and powerconsumed by viscous force are calculated. The velocity distribution demonstrates that the phase ofmembrane velocity does not synchronize with that of shear stress. The simple harmonic motion canresult in self-cleaning, optimize energy utilization, provide the velocity field with instability,and make the feed fluid fluctuation. It also results in higher shear stress on the membrane surfacethan the constant motion when they consume the same quantitative energy.展开更多
The present paper covers the response dynamics of a gas-sensing membrane probe, which is described by the dynamic differential equation based upon a steady-state diffusion process. The theoretical results indicate tha...The present paper covers the response dynamics of a gas-sensing membrane probe, which is described by the dynamic differential equation based upon a steady-state diffusion process. The theoretical results indicate that the response time is dependent upon membrane properties, membrane geometry, internal electrolyte composition, the dissociation constant of the conjugate reaction, the initial gas concentration in the internal electrolyte, and the gas concentration in the evaluation sample. The theoretical prediction is in good agreement with the experimental result. A method for determining a gas-sensing probe' s dynamic parameter is proposed in this paper also.展开更多
基金Financial support by Natural Science Foundation of China(52430001)is acknowledged.
文摘We developed a strategy involving an electroactive biofiltration dynamic membrane(EBDM)for wastewater treatment and membrane fouling mitigation.This approach utilizes a cathode potential within an anaerobic dynamic membrane bioreactor to establish a growth equilibrium electroactive fouling layer.Over a 240 day operation period,the EBDM exhibited outstanding performance,characterized by an ultralow fouling rate(transmembrane pressure<2.5 kPa),superior effluent quality(chemical oxygen demand(COD)removal>93%and turbidity 2 nephelometric turbidity units(NTU)),and a 7.2%increase in methane(CH4)productivity.Morphological analysis revealed that the EBDM acted as a biofilter consisting of a structured,interconnected,multilevel dynamic membrane system with orderly clogging.In the EBDM system,the balanced-growth fouling layers presented fewer biofoulants and looser secondary protein structures.Furthermore,the applied electric field modified the physicochemical properties of the biomass,leading to a decrease in fouling potential.Quartz crystal microbalance with dissipation monitoring analysis indicated that growth equilibrium promoted a looser fouling layer with a lower adsorption mass than did the denser,viscoelastic fouling layer observed in the control reactor.Metagenomic sequencing further demonstrated that continuous electrical stimulation encouraged the development of an electroactive fouling layer with enhanced microbial metabolic functionality on the EBDM.This approach selectively modifies metabolic pathways and increases the degradation of foulants.The EBDM strategy successfully established an ordered-clogging,step-filtered,and balanced-growth electroactive fouling layer,achieving a synergistic effect in reducing membrane fouling,enhancing effluent quality,and improving CH_(4)productivity.
基金financially supported by the National Key R&D Program of China (Nos.2020YFB1505500 and 2020YFB1505503)。
文摘The perfluorosulfonic acid(PFSA) membrane doped with two-dimensional conductive filler Ti_(3)C_(2)T_(x) is a fuel cell proton exchange membrane with high application potential. Experimental studies showed that the proton conductivity of Nafion/Ti_(3)C_(2)T_(x) composite membrane is improved significantly compared with that in pure Nafion. However, the microscopic mechanism of doping on the enhancement of membrane performance is remain unclear now. In this work, molecular dynamics simulation was used to investigate the microscopic morphology and proton transport behaviors of Nafion/Ti_(3)C_(2)T_(x) composite membrane at the molecular level. The results shown that there were significant differences about the diffusion kinetics of water molecules and hydroxium ions in Nafion/Ti_(3)C_(2)T_(x) at low and high hydration levels in the nanoscale region.With the increase of water content, Ti_(3)C_(2)T_(x) in membrane was gradually surrounded by ambient water molecules to form a hydration layer, and forming a relatively continuous proton transport channel between Nafion polymer and Ti_(3)C_(2)T_(x) monomer. The continuous proton transport channel could increase the number of binding sites of proton and thus achieving high proton conductivity and high mobility of water molecules at higher hydration level. The current work can provide a theoretical guidance for designing new type of Nafion composite membranes.
文摘Because of the small stiffness and high flexibility, the tension membrane structure is easy to relax and damage or even destroy under the action of external load, which leads to the occurrence of engineering accidents. In this paper, the damped nonlinear vibration of tensioned membrane structure under the coupling action of wind and rain is approximately solved, considering the geometric nonlinearity of membrane surface deformation and the influence of air damping. Applying von Karman’s large deflection theory and D’Alembert’s principle, the governing equations are established for an analytical solution, and the experimental results are compared with the analytical results. The feasibility of this method is verified, which provides some theoretical reference for practical membrane structure engineering design and maintenance.
基金National Natural Science Foundation of China(No.52476192,No.52106237)Natural Science Foundation of Heilongjiang Province(No.YQ2022E027)。
文摘The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for hydrogen production.Despite remarkable advancements in this field,confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle.This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment.To address these challenges,we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system.Compared to constant voltage electrolysis(hydrogen production rate:51.6 m L h^(-1),energy consumption:5.37 kWh Nm-^(3)H_(2)),this strategy(hydrogen production rate:66 m L h^(-1),energy consumption:3.83 kWh Nm-^(3)H_(2))increases the hydrogen production rate by approximately 27%and reduces the energy consumption by about 28%.Furthermore,we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic(PV)system designed for outdoor operation,successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V.The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism:pulsed dynamic electrolysis(PDE)dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface.As such,PDE-enhanced PEMWE represents a synergistic advancement,concurrently enhancing both the hydrogen generation reaction and associated transport processes.This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.
基金the National Key R&D Program of China(No.2021YFA1501503)the National Natural Science Foundation of China(Nos.22250008,22121004,22108197)+3 种基金the Haihe Laboratory of Sustainable Chemical Transformations(No.CYZC202107)the Natural Science Foundation of Tianjin City(No.21JCZXJC00060)the Program of Introducing Talents of Discipline to Universities(No.BP0618007)the Xplorer Prize for financial support。
文摘Membrane electrode assembly(MEA)is widely considered to be the most promising type of electrolyzer for the practical application of electrochemical CO_(2) reduction reaction(CO_(2)RR).In MEAs,a square-shaped cross-section in the flow channel is normally adopted,the configuration optimization of which could potentially enhance the performance of the electrolyzer.This paper describes the numerical simulation study on the impact of the flow-channel cross-section shapes in the MEA electrolyzer for CO_(2)RR.The results show that wide flow channels with low heights are beneficial to the CO_(2)RR by providing a uniform flow field of CO_(2),especially at high current densities.Moreover,the larger the electrolyzer,the more significant the effect is.This study provides a theoretical basis for the design of high-performance MEA electrolyzers for CO_(2)RR.
基金supported by the National Natural Science Foundation of China(Grants Nos.T2394512,32130061,and 12172366)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant No.GJJSTD20220002).
文摘The formation of donut-shaped penetration pore upon membrane fusion in a closed lipid membrane system is of biological significance,since such the structures extensively exist in living body with various functions.However,the related formation dynamics is unclear because of the limitation of experimental techniques.This work developed a new model of intra-vesicular fusion to elaborate the formation and stabilization of penetration pores by employing molecular dynamics simulations,based on simplified spherical lipid vesicle system,and investigated the regulation of membrane lipid composition.Results showed that penetration pore could be successfully formed based on the strategy of membrane fusion.The ease of intra-vesicular fusion and penetration pore formation was closely correlated with the lipid curvature properties,where negative spontaneous curvature of lipids seemed to be unfavorable for intra-vesicle fusion.Furthermore,the inner membrane tension around the pore was much larger than other regions,which governed the penetration pore size and stability.This work provided basic understanding for vesicle penetration pore formation and stabilization mechanisms.
基金supported by the National Natural Science Foundation of China (Nos.22303060,12274307,32230063,12347102 and 22203059)Natural Science Foundation of Jiangsu Province (Nos.BK20230470 and BK20210100)+2 种基金the Natural Science Foundation of Guangdong Province of China (No.2023A1515011610)the Program of Jiangsu Provincial Key Lab of Thin Films (No.KJS2131)the open research fund of State Key Laboratory of Surface Physics of Fudan University (No.KF2023_03)
文摘Membrane fusion is essential for many cellular physiological functions,which is modulated by highly precise molecular mechanism involving multiple energy barriers.Nanoparticles(NPs),which exhibit immense potential in the field of biomedical applications,can act as fusogen proteins to initiate and regulate membrane fusion.However,the underlying mechanisms of NP-induced membrane fusion and the molecular details involved remain largely elusive.Here,using coarse-grained molecular dynamics simulations,we systematically investigate the NP-induced membrane fusion behaviors and the influences of NP properties(size,hydrophobicity and hydrophilicity).Our results show that the vesicle-bilayer fusion induced by a hydrophobic NP is an intricately state-wise process,involving the approach and local deformation of the vesicle and bilayer bridging by the NP,the flip-flop of lipids from proximal leaflets and the formation of a fusion stalk,as well as further lipid interactions between distal leaflets and complete fusion.Moreover,we find that NP properties have distinct effects on membrane fusion and thus the optimal NP conditions for facilitating membrane fusion are obtained.Our work provides a mechanistic understanding of NP-induced membrane fusion and offers useful insights for efficient and controlled regulation of membrane fusion.
基金financially supported by the National Natural Science Foundation of China(Nos.52203169,52203135 and 52403153)foundation of Yangtze Delta Region Institute(Huzhou)of UESTC(No.U03220149)+2 种基金Huzhou Science and Technology Program Projects(No.2023GZ18)Zhejiang Postdoctoral Research Project(No.ZJ2023133)Science and Technology Cooperation Fund Program of Chengdu-Chinese Academy of Sciences(2023-2025).
文摘Polymer fibers are an important class of materials throughout human history,evolving from natural fibers such as cotton and silk to modern synthetic fibers such as nylon and polyester.With the advancement of materials science,the development of new fibers is also advancing.Polymer fibers based on dynamic covalent chemistry have attracted widespread attention due to their unique reversibility and responsiveness.Dynamic covalent chemistry has shown great potential in improving the spinnability of materials,achieving green preparation of fibers,and introducing self-healing,recyclability,and intelligent response properties into fibers.In this review,we divide these fiber materials based on dynamic covalent chemistry into monocomponent fibers,composite fibers,and fiber membranes.The preparation methods,structural characteristics,functional properties,and application performance of these fibers are summarized.The application potential and challenges of fibers based on dynamic covalent chemistry are discussed,and their future development trends are prospected.
基金supported by the National Natural Science Foundation of China (Nos.51778522,and 51508450)the Program for Innovative Research Team in Shaanxi (No.IRT2013KCT-13)
文摘The effects of powdered activated carbon(PAC) addition on sludge morphological, aggregative and microbial properties in a dynamic membrane bioreactor(DMBR) were investigated to explore the enhancement mechanism of pollutants removal and filtration performance. Sludge properties were analyzed through various analytical measurements. The results showed that the improved sludge aggregation ability and the evolution of microbial communities affected sludge morphology in PAC-DMBR, as evidenced by the formation of large, regularly shaped and strengthened sludge flocs. The modifications of sludge characteristics promoted the formation process and filtration flux of the dynamic membrane(DM) layer. Additionally, PAC addition did not exert very significant influence on the propagation of eukaryotes(protists and metazoans)and microbial metabolic activity. High-throughput pyrosequencing results indicated that adding PAC improved the bacterial diversity in activated sludge, as PAC addition brought about additional microenvironment in the form of biological PAC(BPAC), which promoted the enrichment of Acinetobacter(13.9%), Comamonas(2.9%), Flavobacterium(0.31%) and Pseudomonas(0.62%), all contributing to sludge flocs formation and several(such as Acinetobacter) capable of biodegrading relatively complex organics. Therefore, PAC addition could favorably modify sludge properties from various aspects and thus enhance the DMBR performance.
文摘Motivated by recent experimental observations that carbon nanotubes （CNT） can enter animal cells, here we conduct coarse grained molecular dynamics and theoretical studies of the intrinsic interaction mechanisms between CNT＇s and lipid bilayer. The results indicate that CNT-cell interaction is dominated by van der Waals and hydrophobic forces, and that CNT＇s with sufficiently small radii can directly pierce through cell membrane while larger tubes tend to enter cell via a wrapping mechanism. Theoretical models are proposed to explain the observed size effect in transition of entry mechanisms.
基金Supported by the National Science Fund for Distinguished Young Scholars(21125627)the National Natural Science Foundation of China(21306131)+2 种基金Specialized Research Fund for the Doctoral Program of Higher Education(20120032120009)Seed Foundation of Tianjin Universitythe Programme of Introducing Talents of Disciplineto Universities(B06006)
文摘Detailed atomistic structures are constructed for polydopamine membranes containing different amounts of catechol and quinone groups to investigate the effect of p H value in the membrane casting solution on sorption and diffusion of small gas molecules(water and propylene) in the membranes. Interactions between dopamine oligomers are calculated, and it is found that the interactions decrease from- 2356.52 k J·mol-1in DOP-1 to-1586.69 k J·mol-1in DOP-3 when all of the catechol groups are converted to quinone groups. The mobility of polymer segments and free volume properties of polydopamine membranes are analyzed. The sorption quantities of water and propylene in the membrane are calculated using Grand Canonical Monte Carlo method. The sorption results show that water adsorbed in DOP-1, DOP-2 and DOP-3 are 17.3, 18.6 and 20.0 mg water per gram polymer, respectively, and no propylene molecule can be adsorbed. The diffusion behavior of water molecules in the membrane is investigated by molecular dynamics simulation. The diffusion coefficients of water molecules in DOP-1, DOP-2 and DOP-3 membranes are(1.80 ± 0.52) × 10-11,(3.40 ± 0.64) × 10-11and(4.50 ± 0.92) × 10-11m2·s-1, respectively. The predicted sorption quantities and diffusion coefficients of water and propylene in the membrane present the same trends as those from experimental results.
基金supported by the National Natural Science Foundation of China(Nos.51778522,and 51508450)the Science Foundation for Fostering Talents of Xi'an University of Architecture and Technology(No.RC1710)the Program for Innovative Research Team in Shaanxi(No.IRT2013KCT-13)
文摘In dynamic membrane bioreactors(DMBRs), a dynamic membrane(DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh(25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process(within 240 min). Furthermore, the extended Derjaguin–Landau–Verwey–Overbeek(XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process(including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time(permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge <sludge with poor flocculability. Moreover, normal sludge(regarding settleability, dewaterability,flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance(short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid–based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.
基金Supported by the National Natural Science Foundation of China(21566013,51562016)Youth Science Foundation of Jiangxi Provincial Department of Education,China(GJJ170970)the Natural Science Foundation of Jiangxi Province(20171BAB206015)
文摘Membrane fouling is often considered as a hindrance for the application of microfiltration/ultrafiltration(MF/UF) for drinking water production. A novel process of photocatalytic membrane reactor/dynamic membrane(PMR/DM), operating in a continuous mode under sub-critical flux, was proposed for the mitigation of membrane fouling caused by humic acids(HAs) in water. The mechanism of membrane fouling alleviation with synergistic photocatalytic oxidation and dynamic layer isolating effect was comprehensively investigated from the characterization of foulant evolution responsible for the reversible and irreversible fouling. The results showed that the PMR/DM utilized photocatalytic oxidation to enhance the porosity and hydrophilicity of the fouling layer by converting the high molecular weight(MW) and hydrophobic HA molecules with carboxylic functional groups and aromatic structures into low-MW hydrophilic or transphilic fractions, including tryptophan-like or fulvic-like substances. The fouling layer formed in the PMR/DM by combination of photocatalytic oxidation and DM running at a sub-critical flux of 100 L·h^-1·m^-2, was more hydrophilic and more porous, resulting in the lowest trans-membrane pressure(TMP) growth rates, as compared to the processes of ceramic membrane(CM), DM and PMR/CM.Meanwhile, the dynamic layer prevented the foulants, particularly the high-MW hydrophobic fractions,from contacting the primary membrane, which enabled the membrane permeability to be restored easily.
基金The project supported by a fund from the National Educational Committee.
文摘Based on energy equilibrium,a new procedure called the Membrane Factor Method is devel- oped to analyze the dynamic plastic response of plates with deflections in the range where both bending mo- ments and membrane forces are important.The final deflection of a simply -supported circular rigid-plastic plate loaded by a uniformly distributed impulse is obtained.In comparison with other approximate solutions, the present results are found to be simpler and in better agreement with the corresponding experimental values reoorded by Florence.
基金Project supported by the National Natural Science Foundation of China (Nos. 10872045 and 10772104)the Program for New Century Excellent Talents in University (No. NCET-09-0096)the Fundamental Research Funds for the Central Universities (No. DC10030104)
文摘In this paper, the dynamic characteristics are examined for a cylindrical membrane composed of a transversely isotropic incompressible hyperelastic material under an applied uniform radial constant pressure at its inner surface. A second-order nonlinear ordinary differential equation that approximately describes the radial oscillation of the inner surface of the membrane with respect to time is obtained. Some interesting conclusions are proposed for different materials, such as the neo-Hookean material, the Mooney-Rivlin material and the Rivlin-Saunders material. Firstly, the bifurcation conditions depending on the material parameters and the pressure loads are determined. Secondly, the conditions of periodic motion are presented in detail for membranes composed of different materials. Meanwhile, numerical simulations are also provided.
文摘A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller.
基金supported by National Key Research and Development Program of China (2020YFE0100100, 2021YFC21041002018YFA0901500)+1 种基金Basic Science (Natural Science) Research Project of Jiangsu Province Colleges and Universities(21KJB530014)Jiangsu Synergetic Innovation Center for Advanced Bio-Manufacture
文摘Compared with conventional cylinder airlift bioreactors(CCABs)that produce coarse bubbles,a novel rectangular dynamic membrane airlift bioreactor(RDMAB)developed in our lab produces fine bubbles to enhance the volumetric oxygen mass transfer coefficient(k_(L)a)and gas holdup,as well as improve the bioprocess in a bioreactor.In this study,we compared mass transfer,gas holdup,and batch and con-tinuous fermentation for RNA production in CCAB and RDMAB.In addition,unstructured kinetic models for microbial growth,substrate utilization,and RNA formation were established.In batch fermentation,biomass,RNA yield,and substrate utilization in the RDMAB were higher than those in the CCAB,which indicates that dynamic membrane aeration produced a high k_(L)a by fine bubbles;a higher k_(L)a is more bene-ficial to aerobic fermentation.The starting time of continuous fermentation in the RDMAB was 20 h ear-lier than that in the CCAB,which greatly improved the biological process.During continuous fermentation,maintaining the same dissolved oxygen level and a constant dilution rate,the biomass accumulation and RNA concentration in the RDMAB were 9.71% and 11.15% higher than those in the CCAB,respectively.Finally,the dilution rate of RDMAB was 16.7% higher than that of CCAB during con-tinuous fermentation while maintaining the same air aeration.In summary,RDMAB is more suitable for continuous fermentation processes.Developing new aeration and structural geometry in airlift bioreac-tors to enhance k_(L)a and gas holdup is becoming increasingly important to improve bioprocesses in a bioreactor.
文摘A simple harmonic motion is proposed to make the membrane move in a simpleharmonic way so as to enhance the membrane filtration, and minimize the membrane fouling andconcentration polarization. The velocity distribution and pressure distribution are deduced from theNavier-Stokes equation on the basis of a laminar flow when the membrane rotates at the speed of Asin(αt). And then the shear stress, shear force, moment of force on the membrane surface and powerconsumed by viscous force are calculated. The velocity distribution demonstrates that the phase ofmembrane velocity does not synchronize with that of shear stress. The simple harmonic motion canresult in self-cleaning, optimize energy utilization, provide the velocity field with instability,and make the feed fluid fluctuation. It also results in higher shear stress on the membrane surfacethan the constant motion when they consume the same quantitative energy.
文摘The present paper covers the response dynamics of a gas-sensing membrane probe, which is described by the dynamic differential equation based upon a steady-state diffusion process. The theoretical results indicate that the response time is dependent upon membrane properties, membrane geometry, internal electrolyte composition, the dissociation constant of the conjugate reaction, the initial gas concentration in the internal electrolyte, and the gas concentration in the evaluation sample. The theoretical prediction is in good agreement with the experimental result. A method for determining a gas-sensing probe' s dynamic parameter is proposed in this paper also.
