The turbulence structures near a sheared air-water interface were experimentally investigated with the hydrogen bubble visualization technique. Surface shear was imposed by an airflow over the water flow which was kep...The turbulence structures near a sheared air-water interface were experimentally investigated with the hydrogen bubble visualization technique. Surface shear was imposed by an airflow over the water flow which was kept free from surface waves. Results show that the wind shear has the main influence on coherent structures under air-water interfaces. Low- and high- speed streaks form in the region close to the interface as a result of the imposed shear stress. When a certain airflow velocity is reached, “turbulent spots” appear randomly at low-speed streaks with some characteristics of hairpin vortices. At even higher shear rates, the flow near the interface is dominated primarily by intermittent bursting events. The coherent structures observed near sheared air-water interfaces show qualitative similarities with those occurring in near-wall turbulence. However, a few distinctive phenomena were also observed, including the fluctuating thickness of the instantaneous boundary layer and vertical vortices in bursting processes, which appear to be associated with the characteristics of air-water interfaces.展开更多
It is the traditional belief that sound transmission from water to the air is very weak due to a large contrast between air and water impedances. Recently, the enhanced sound transmission and anomalous transparency of...It is the traditional belief that sound transmission from water to the air is very weak due to a large contrast between air and water impedances. Recently, the enhanced sound transmission and anomalous transparency of air-water interface have been introduced. Anomalous transparency of air-water interface states that the sound generated by a submerged shallow depth monopole point source localized at depths less than 1/10 sound wavelength, can be transmitted into the air with omni-directional pattern. The generated sound has 35 times higher power compared to the classical ray theory prediction. In this paper, sound transmission through air-water interface for a localized underwater shallow depth source is examined. To accomplish this, two-phase coupled Helmholtz wave equations in two-phase media of air-water are solved by the commercial finite element based COMSOL Multiphysics software. Ratios of pressure amplitudes of different sound sources in two different underwater and air coordinates are computed and analyzed against non-dimensional ratio of the source depth （D） to the sound wavelength （λ）. The obtained results are compared with the experimental data and good agreement is displayed.展开更多
To obtain carbon dioxide （CO2） flux between water-air interface of Taihu lake, monthly water samplers at 14 sites and the local meteorological data of the lake were collected and analyzed in 1998. Carbon dioxide par...To obtain carbon dioxide （CO2） flux between water-air interface of Taihu lake, monthly water samplers at 14 sites and the local meteorological data of the lake were collected and analyzed in 1998. Carbon dioxide partial pressures （pCO2） at air-water interface in the lake were calculated using alkalinity, pH, ionic strength, active coefficient, and water temperature. The carbon fluxes at different sublakes and areas were estimated by concentration gradient between water and air in consideration of Schmidt numbers of 600 and daily mean windspeed at 10 m above water surface. The results indicated that the mean values of pCO2 in Wuli Lake,Meiliang Bay, hydrophyte area, west littoral zone, riverine mouths, and the open lake areas were 1 807.8±1 071.4（mean±standard deviation）μatm （latm=1.013 25×10^5pa）, 416.3±217.0μatm, 576.5±758.8μatm, 304.2±9.43.5μatm, 1 933.6±1 144.7 μatm, and 448.5±202.6μatm, respectively. Maximum and minimum pCO2 values were found in the hypertrophic （4 053.7μatm） and the eutrophic （3.2 μatm） areas. The riverine mouth areas have the maximum fluxes （82.0±62.8 mmol/m^2a）. But there was no significant difference between eutrophic and mesotrophic areas in pCO2 and the flux of CO2. The hydrophyte area, however, has the minimum （--0.58±12.9mmol/m^2a）. In respect to CO2 equilibrium, input of the rivers will obviously influence inorganic carbon distribution in the riverine estuary. For example, the annual mean CO2 flux in Zhihugang River estuary was 19 times of that in Meiliang Bay, although the former is only a part of the latter. The sites in the body of the lake show a clear seasonal cycle with pCO2 higher than atmospheric equilibrium in winter, and much lower than atmospheric in summer due to CO2 consumption by photosynthesis. The CO2 amount of the net annual evasion that enters the atmosphere is 28.42×10^4 t/a, of which those from the west littoral zone and the open lake account for 53.8% and 36.7%, respectively.展开更多
The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structu...The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(<lambda>+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(<lambda>+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(<lambda>+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed.展开更多
Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amount of hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is...Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amount of hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750. The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water. It was shown by experimental measurement at 30.0 +/- 0.1 degreesC that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration, e.g. about 0.1 g/mL. Obviously, macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants. The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.展开更多
Given the high abundance of water in the atmosphere,the reaction of Criegee intermediates(CIs)with(H_(2)O)_(2) is considered to be the predominant removal pathway for CIs.However,recent experimental findings reported ...Given the high abundance of water in the atmosphere,the reaction of Criegee intermediates(CIs)with(H_(2)O)_(2) is considered to be the predominant removal pathway for CIs.However,recent experimental findings reported that the reactions of CIs with organic acids and carbonyls are faster than expected.At the same time,the interface behavior between CIs and carbonyls has not been reported so far.Here,the gas-phase and air-water interface behavior between Criegee intermediates and HCHO were explored by adopting high-level quantum chemical calculations and Born-Oppenheimer molecular dynamics(BOMD)simulations.Quantum chemical calculations evidence that the gas-phase reactions of CIs+HCHO are submerged energy or low energy barriers processes.The rate ratios speculate that the HCHO could be not only a significant tropospheric scavenger of CIs,but also an inhibitor in the oxidizing ability of CIs on SO_(x) in dry and highly polluted areas with abundant HCHO concentration.The reactions of CH_(2)OO with HCHO at the droplet’s surface follow a loop structure mechanism to produce i)SOZ(■),ii)BHMP(HOCH_(2)OOCH_(2)OH),and iii)HMHP(HOCH_(2)OOH).Considering the harsh reaction conditions between CIs and HCHO at the interface(i.e.,the two molecules must be sufficiently close to each other),the hydration of CIs is still their main atmospheric loss pathway.These results could help us get a better interpretation of the underlying CIs-aldehydes chemical processes in the global polluted urban atmospheres.展开更多
Photoisomerization of a new polymer: monoesters of polymaleic acid containing naphthalene-azo-anthraquinone groups in side chains at the air-water interface of a Langmuir trough wan detected by recording the developme...Photoisomerization of a new polymer: monoesters of polymaleic acid containing naphthalene-azo-anthraquinone groups in side chains at the air-water interface of a Langmuir trough wan detected by recording the development of surface pressure with time. This process wan found to be a first-order reaction and complete within several minutes.展开更多
The forces acting on submillimeter spheres at the air-water interface are investigated theoretically and experimentally. To calculate the capillary force acting on the sphere, an iterative method is used to determine ...The forces acting on submillimeter spheres at the air-water interface are investigated theoretically and experimentally. To calculate the capillary force acting on the sphere, an iterative method is used to determine the immersing position of the liquid interface on the sphere for a given distance. Then the total forces acting on the sphere are considered. The scaling effects of the net force acting on the sphere at the air-water interface are demonstrated. For the experiments, the force-position relationship of microspheres is measured with a precise electronic balance. The results show that the evaporation of the liquid in the container affects the measuring results greatly under ambient conditions. After considering the evaporation compensation, there is a great agree- ment between the theoretical and experimental results. Obvious hysteresis phenomena of the force-distance curve during the emersion processes are also observed and explained.展开更多
High-speed planing crafts have successfully evolved through developments in the last several decades.Classical approaches such as inviscid potential flow–based methods and the empirically based Savitsky method provid...High-speed planing crafts have successfully evolved through developments in the last several decades.Classical approaches such as inviscid potential flow–based methods and the empirically based Savitsky method provide general understanding for practical design.However,sometimes such analyses suffer inaccuracies since the air–water interface effects,especially in the transition phase,are not fully accounted for.Hence,understanding the behaviour at the transition speed is of fundamental importance for the designer.The fluid forces in planing hulls are dominated by phenomena such as flow separation at various discontinuities viz.,knuckles,chines and transom,with resultant spray generation.In such cases,the application of potential theory at high speeds introduces limitations.This paper investigates the simulation of modelling of the pre-planing behaviour with a view to capturing the air–water interface effects,with validations through experiments to compare the drag,dynamic trim and wetted surface area.The paper also brings out the merits of gridding strategies to obtain reliable results especially with regard to spray generation due to the air–water interface effects.The verification and validation studies serve to authenticate the use of the multi-gridding strategies on the basis of comparisons with simulations using model tests.It emerges from the study that overset/chimera grids give better results compared with single unstructured hexahedral grids.Two overset methods are investigated to obtain reliable estimation of the dynamic trim and drag,and their ability to capture the spray resulting from the air–water interaction.The results demonstrate very close simulation of the actual flow kinematics at steady-speed conditions in terms of spray at the air–water interface,drag at the pre-planing and full planing range and dynamic trim angles.展开更多
The main objective of this work was to develop a kinetic model to describe the variation of the surface tension in an air-water interface due to the adsorption of proteins from different origins and to identify quanti...The main objective of this work was to develop a kinetic model to describe the variation of the surface tension in an air-water interface due to the adsorption of proteins from different origins and to identify quantitatively the relevant parameters, it was considered that the processes of adsorption, unfolding and reordering of the protein molecule in the interface occur simultaneously. The model used in the present work to calculate the surface tension postulates the existence of two simultaneous processes, adsorption and protein rearrangement represented with an equation of first order with two exponential components. The relevant parameter of the equation are ka and kr-the rate constants of the two first order kinetic phases that correspond to both conformational states of the protein, adsorption and rearrangement during the process of variation of the surface tension, and the amplitude parameters Aa and Ar. The results suggest that the kinetic model for the variation of the surface tension of protein solutions proposed in this work, with two simultaneous first order processes, is more appropriate than previous models to describe such variation.展开更多
A transient three-dimensional coupling model based on the compressible volume of fluid （VOF） method was developed to simulate the transport of volatile pollutants at the air-water interface. VOF is a numerical techn...A transient three-dimensional coupling model based on the compressible volume of fluid （VOF） method was developed to simulate the transport of volatile pollutants at the air-water interface. VOF is a numerical technique for locating and tracking the free surface of water flow. The relationships between Henry＇s constant, thermodynamics parameters, and the enlarged topological index were proposed for nonstandard conditions. A series of experiments and numerical simulations were performed to study the transport of benzene and carbinol. The simulation results agreed with the experimental results. Temperature had no effect on mass transfer of pollutants with low transfer free energy and high Henry＇s constant. The temporal and spatial distribution of pollutants with high transfer free energy and low Henry＇s constant was affected by temperature. The total enthalpy and total transfer free energy increased significantly with temperature, with significant fluctuations at low temperatures. The total enthalpy and total transfer free energy increased steadily without fluctuation at high temperatures.展开更多
Fabrication of anisotropic material is one of the important topics and we examined to introduce “anisotropic” nature by spreading polymer-grafted particle on the medium with polymer-reactive potential. Poly (tert-bu...Fabrication of anisotropic material is one of the important topics and we examined to introduce “anisotropic” nature by spreading polymer-grafted particle on the medium with polymer-reactive potential. Poly (tert-butyl methacrylate) (PtBMA) was polymerized from polystyrene latex (PSL) surface by ATRP to give PtBMA-grafted PSL (PSL-PtBMA). Particle monolayer was formed at air-water and air-acidic water interfaces and the monolayer characteristics were compared by π-A isotherm measurements, SEM observations, and contact angle measurements. π-A isotherms, in particular, indicates that the interaction between polymer chains become stronger by changing the subphase condition, which suggests that anisotropicparticle monolayer formation.展开更多
For smooth curved objects in contact with a flat interface,the propagation paths of supported surface elastic waves can be altered by the interface,thereby enhancing the characteristics of the backscattered echo retur...For smooth curved objects in contact with a flat interface,the propagation paths of supported surface elastic waves can be altered by the interface,thereby enhancing the characteristics of the backscattered echo returns.In this study,backscattering experiments are conducted on an empty stainless steel cylindrical shell that breaks through an air-water interface and is insonified from below at grazing incidence.The shell has a thickness-to-radius ratio of 5%.The frequencies of interest fall within the vicinity of and below the coincidence frequency,which corresponds to a ka range of 13.8-20.1.The experimental results demonstrate that,for the partially exposed cylindrical shell,the flexural waves can traverse the interface and circumnavigate the shell multiple times.The flexural waves experience mode transitions upon passing through the interface,existing as a0−waves below the interface and a0 waves above the interface.Simultaneously,the flexural waves undergo partial reflection each time they pass through the interface,guiding them to follow a reverse path and generating a periodic series of echo returns,which leads to the enhancement of backscattering.The shift in resonance frequency in relation to the changing exposure is analyzed and predicted using the phase matching theory.展开更多
A cross air-water interface hydroacoustic signal detection method based on microvibration detection at the air-water interface is proposed.Laser speckles modulated by water surface acoustic waves are recorded and used...A cross air-water interface hydroacoustic signal detection method based on microvibration detection at the air-water interface is proposed.Laser speckles modulated by water surface acoustic waves are recorded and used as an information carrier.Phase correlation and multichannel fusion algorithms are used to extract and enhance hydroacoustic signals.Wide frequency range(200 Hz to 20 kHz)underwater acoustic signals are detected with a frequency relative error smaller than 0.5%.Several common artificial and natural hydroacoustic signals are used as source signals and correctly reconstructed.The average intelligibility of recovered humpback whale signals evaluated with the normalized subband envelope correlation algorithm is 0.52±0.02.展开更多
Humic-like substances(HULIS),a class of macromolecular photosensitizers,are major components of light-absorbing aerosols in the atmosphere.Due to the amphiphilic nature of HULIS,they tend to appear at the air-water in...Humic-like substances(HULIS),a class of macromolecular photosensitizers,are major components of light-absorbing aerosols in the atmosphere.Due to the amphiphilic nature of HULIS,they tend to appear at the air-water interface of atmospheric water.However,there have been limited studies on the photosensitized chemistry of HULIS at the air-water interface owing to the lack of methods with high interface selectivity.Here,a unique field-induced droplet ionization mass spectrometry(FIDI-MS)technique was used to investigate the photosensitized chemistry of several samples at the air-water interface.These samples include commercially available humic acid and the PM_(2.5)sample collected during Beijing′s severe winter haze in December 2016.Ultrahigh-resolution Fourier transform-ion cyclotron resonance mass spectrometry(FT-ICR MS)was also applied to analyze the atomic compositions,the degree of unsaturation and the aromaticity of these samples.Both TypeⅠand TypeⅡphotosensitized oxidation pathways were observed,which were postulated to be dictated by the packing density of the molecules at the air-water interface.These findings reveal that the photosensitization of HULIS at the air-water interface contributes greatly to the formation of atmospheric aerosols,further advancing our understanding of the important roles played by photosensitized chemistry in the atmosphere.展开更多
Invasive as well as non-invasive neurotechnologies conceptualized to interface the central and peripheral nervous system have been probed for the past decades,which refer to electroencephalography,electrocorticography...Invasive as well as non-invasive neurotechnologies conceptualized to interface the central and peripheral nervous system have been probed for the past decades,which refer to electroencephalography,electrocorticography and microelectrode arrays.The challenges of these mentioned approaches are characterized by the bandwidth of the spatiotemporal resolution,which in turn is essential for large-area neuron recordings(Abiri et al.,2019).展开更多
The escalating global issues of water scarcity and pollution emphasize the critical need for the rapid development of efficient and eco-friendly water treatment technologies.Photoelectrocatalytic technology has emerge...The escalating global issues of water scarcity and pollution emphasize the critical need for the rapid development of efficient and eco-friendly water treatment technologies.Photoelectrocatalytic technology has emerged as a promising solution for effectively degrading refractory organic pollutants in water under light conditions.This review delves into the advancements made in the field,focusing on strategies to enhance the generation of active species by modulating the micro-interface of the photoanode.Strategies,such as morphological control,element doping,introduction of surface oxygen vacancies,and construction of heterostructures,significantly improve the separation efficiency of photogenerated charges and the generation of active species,thereby boosting the efficiency of photoelectrocatalytic performance.Furthermore,the review explores the potential applications of photoelectrocatalytic technology in organic pollutant degradation in solutions.It also outlines the current challenges and future development directions.Despite its remarkable laboratory success,practical implementation of photoelectrocatalytic technology encounters obstacles related to stability,cost-effectiveness,and operational efficiency.Future investigations need to focus on optimizing the performance of photoelectrocatalytic materials and exploring strategies for upscaling their application in real water treatment scenarios.展开更多
Introducing Ti_(2)AlC particles into TiAl alloys can effectively improve their strength,but this can also lead to stress concentration at the interface,resulting in the reduction of ductility.Therefore,Mn is adopted t...Introducing Ti_(2)AlC particles into TiAl alloys can effectively improve their strength,but this can also lead to stress concentration at the interface,resulting in the reduction of ductility.Therefore,Mn is adopted to synergistically improve the strength and ductility of the Ti_(2)AlC/TiAl composite through solid solution and interface manipulation.The first-principles calculation shows the Ti-Mn bonds are formed at the Ti_(2)AlC/TiAl interface after Mn doping,characterized primarily by metallic bonds with some covalent bonding.This combination preserves strength while enhancing ductility.Then,Ti_(2)AlC/TiAl-Mn composite is prepared.The Ti_(2)AlC,with an average size of 1.6μm,is uniformly distributed within the TiAl matrix.Mn doping reduces the lamellar colony size and lamellar thickness by 25.1%and 27.4%,respectively.A small quantity of Mn accumulates at the boundaries of the lamellar colonies.The Mn content must be controlled to avoid segregation,which may negatively impact performance.The yield stress,ultimate compressive stress,fracture strain,and product of strength and plasticity of the Ti_(2)AlC/TiAl-Mn composite have been increased by 5.5%,11.5%,10.4%,and 23.0%,respectively,compared to those of the Ti_(2)AlC/TiAl composite.The enhancement in strength is due to the combined effects of grain refinement,solid solution of Mn,and twining strengthening.Grain refinement and twin strengthening also can reduce stress concentration and improve ductility.In addition,at the electronic level,the Ti-Mn bond formed at the interface is contributed to the improvement of ductility.展开更多
Aqueous zinc-ion batteries(AZIBs) are regarded as one of the most promising energy conversion and storage devices.Nevertheless,side reactions and dendrite growth on the zinc metal anode hinder their widespread applica...Aqueous zinc-ion batteries(AZIBs) are regarded as one of the most promising energy conversion and storage devices.Nevertheless,side reactions and dendrite growth on the zinc metal anode hinder their widespread application.In this study,hemin was employed as a multi-functional artificial interface for the first time to inhibit the disordered growth of zinc dendrites and mitigate side reactions.Theoretical calculations indicate that hemin is preferentially adsorbed onto the zinc anode,thus blocking the interaction between the active zinc anode and electrolyte.Compared with zinc foil,the Hemin@Zn anode demonstrates enhanced corrosion resistance,a decrease in hydrogen evolution,and more orderly deposition of zinc.As expected,the symmetric cell with Hemin@Zn anode can sustain up to 4000 h at 0.2 mA/cm^(2),0.2 mAh/cm^(2).Asymmetric Zn//Cu cells exhibit an average coulombic efficiency exceeding 99.72 % during 500 cycles.Moreover,the full cell Hemin@Zn//NH_(4)V_(4)O_(10) delivers a superior capacity up to 367 m Ah/g and the discharge capacity retention reaches 124 mAh/g after 1200 cycles even at a current density of 5 A/g.This work provides a simple and effective method for constructing a robust artificial interface to promote the application of long-life AZIBs.展开更多
基金The project supported by the National Natural Science Foundation of China (Grant No.19672070)
文摘The turbulence structures near a sheared air-water interface were experimentally investigated with the hydrogen bubble visualization technique. Surface shear was imposed by an airflow over the water flow which was kept free from surface waves. Results show that the wind shear has the main influence on coherent structures under air-water interfaces. Low- and high- speed streaks form in the region close to the interface as a result of the imposed shear stress. When a certain airflow velocity is reached, “turbulent spots” appear randomly at low-speed streaks with some characteristics of hairpin vortices. At even higher shear rates, the flow near the interface is dominated primarily by intermittent bursting events. The coherent structures observed near sheared air-water interfaces show qualitative similarities with those occurring in near-wall turbulence. However, a few distinctive phenomena were also observed, including the fluctuating thickness of the instantaneous boundary layer and vertical vortices in bursting processes, which appear to be associated with the characteristics of air-water interfaces.
文摘It is the traditional belief that sound transmission from water to the air is very weak due to a large contrast between air and water impedances. Recently, the enhanced sound transmission and anomalous transparency of air-water interface have been introduced. Anomalous transparency of air-water interface states that the sound generated by a submerged shallow depth monopole point source localized at depths less than 1/10 sound wavelength, can be transmitted into the air with omni-directional pattern. The generated sound has 35 times higher power compared to the classical ray theory prediction. In this paper, sound transmission through air-water interface for a localized underwater shallow depth source is examined. To accomplish this, two-phase coupled Helmholtz wave equations in two-phase media of air-water are solved by the commercial finite element based COMSOL Multiphysics software. Ratios of pressure amplitudes of different sound sources in two different underwater and air coordinates are computed and analyzed against non-dimensional ratio of the source depth （D） to the sound wavelength （λ）. The obtained results are compared with the experimental data and good agreement is displayed.
基金This research was supported by the Knowledge Innovation Project of Chinese Academy of Sciences (KZCX1-SW-01-15) and (KZCX1- SW-12)
文摘To obtain carbon dioxide （CO2） flux between water-air interface of Taihu lake, monthly water samplers at 14 sites and the local meteorological data of the lake were collected and analyzed in 1998. Carbon dioxide partial pressures （pCO2） at air-water interface in the lake were calculated using alkalinity, pH, ionic strength, active coefficient, and water temperature. The carbon fluxes at different sublakes and areas were estimated by concentration gradient between water and air in consideration of Schmidt numbers of 600 and daily mean windspeed at 10 m above water surface. The results indicated that the mean values of pCO2 in Wuli Lake,Meiliang Bay, hydrophyte area, west littoral zone, riverine mouths, and the open lake areas were 1 807.8±1 071.4（mean±standard deviation）μatm （latm=1.013 25×10^5pa）, 416.3±217.0μatm, 576.5±758.8μatm, 304.2±9.43.5μatm, 1 933.6±1 144.7 μatm, and 448.5±202.6μatm, respectively. Maximum and minimum pCO2 values were found in the hypertrophic （4 053.7μatm） and the eutrophic （3.2 μatm） areas. The riverine mouth areas have the maximum fluxes （82.0±62.8 mmol/m^2a）. But there was no significant difference between eutrophic and mesotrophic areas in pCO2 and the flux of CO2. The hydrophyte area, however, has the minimum （--0.58±12.9mmol/m^2a）. In respect to CO2 equilibrium, input of the rivers will obviously influence inorganic carbon distribution in the riverine estuary. For example, the annual mean CO2 flux in Zhihugang River estuary was 19 times of that in Meiliang Bay, although the former is only a part of the latter. The sites in the body of the lake show a clear seasonal cycle with pCO2 higher than atmospheric equilibrium in winter, and much lower than atmospheric in summer due to CO2 consumption by photosynthesis. The CO2 amount of the net annual evasion that enters the atmosphere is 28.42×10^4 t/a, of which those from the west littoral zone and the open lake account for 53.8% and 36.7%, respectively.
基金The project supported by the National Natural Science Foundation of China (19672070)
文摘The characteristics of low-speed fluid streaks occurring under sheared air-water interfaces were examined by means of hydrogen bubble visualization technique. A critical shear condition under which the streaky structure first appears was determined to be u(tau) approximate to 0.19 cm/s. The mean spanwise streak spacing increases with distance from the water surface owing to merging and bursting processes, and a linear relationship describing variation of non-dimensional spacing <(<lambda>+)over bar> versus y(+) was found essentially independent of shear stress on the interface. Values of <(<lambda>+)over bar>, however, are remarkably smaller than their counterparts in the near-wall region of turbulent boundary layers. Though low-speed streaks occur randomly in time and space, the streak spacing exhibits a lognormal probability distribution behavior. A tentative explanation concerning the formation of streaky structure is suggested, and the fact that <(<lambda>+)over bar> takes rather smaller values than that in wall turbulence is briefly discussed.
基金The project was supported by the National Natural Science Foundation of China (No.29774016).
文摘Perfluorooctanoyl modified poly(vinyl alcohol)s (FPVA) were prepared by means of substituting a small amount of hydroxyl groups on the backbone of poly(vinyl alcohol), for which the initial degree of polymerization is equal to 1750. The substitution extent, defined by the number of substituting units in a chain, for the four FPVA samples was in the range of 0.5-5 perfluorooctanoyl groups per chain. The FPVA samples with the highest substitution extent still had good solubility in water. It was shown by experimental measurement at 30.0 +/- 0.1 degreesC that the surface tension of the aqueous solution of the highest substituted FPVA decreased to 16.6 mN/m at a higher concentration, e.g. about 0.1 g/mL. Obviously, macromolecules of FPVA exhibit a very strong tendency to adsorb at the air-water interface, because the hydrophobic perfluorooctanoyl groups in FPVA have a very high surface activity as they are in small molecular fluorinated surfactants. The chain conformation of such a model polymer adsorbed on the air-water interface was also discussed.
基金support from the National Natural Science Foundation of China(Nos:22073059,42107109)the GHfund B(No:20210702)+2 种基金the Key Cultivation Project of Shaanxi University of Technology(No:SLG2101)the Funds of Graduate Innovation of Shaanxi University of Technology(No:SLGYCX2120)the State Key Laboratory of Biological Resources and Ecological Environment of Qinba Areas“City-School Co-Construction”Special Research Project(No:SXC-2110).
文摘Given the high abundance of water in the atmosphere,the reaction of Criegee intermediates(CIs)with(H_(2)O)_(2) is considered to be the predominant removal pathway for CIs.However,recent experimental findings reported that the reactions of CIs with organic acids and carbonyls are faster than expected.At the same time,the interface behavior between CIs and carbonyls has not been reported so far.Here,the gas-phase and air-water interface behavior between Criegee intermediates and HCHO were explored by adopting high-level quantum chemical calculations and Born-Oppenheimer molecular dynamics(BOMD)simulations.Quantum chemical calculations evidence that the gas-phase reactions of CIs+HCHO are submerged energy or low energy barriers processes.The rate ratios speculate that the HCHO could be not only a significant tropospheric scavenger of CIs,but also an inhibitor in the oxidizing ability of CIs on SO_(x) in dry and highly polluted areas with abundant HCHO concentration.The reactions of CH_(2)OO with HCHO at the droplet’s surface follow a loop structure mechanism to produce i)SOZ(■),ii)BHMP(HOCH_(2)OOCH_(2)OH),and iii)HMHP(HOCH_(2)OOH).Considering the harsh reaction conditions between CIs and HCHO at the interface(i.e.,the two molecules must be sufficiently close to each other),the hydration of CIs is still their main atmospheric loss pathway.These results could help us get a better interpretation of the underlying CIs-aldehydes chemical processes in the global polluted urban atmospheres.
文摘Photoisomerization of a new polymer: monoesters of polymaleic acid containing naphthalene-azo-anthraquinone groups in side chains at the air-water interface of a Langmuir trough wan detected by recording the development of surface pressure with time. This process wan found to be a first-order reaction and complete within several minutes.
基金Supported by the National Natural Science Foundation of China under Grant No 61005072the Self-Planned Task of State Key Laboratory of Robotics and System under Grant Nos SKLRS201501A04 and SKLRS201301A01
文摘The forces acting on submillimeter spheres at the air-water interface are investigated theoretically and experimentally. To calculate the capillary force acting on the sphere, an iterative method is used to determine the immersing position of the liquid interface on the sphere for a given distance. Then the total forces acting on the sphere are considered. The scaling effects of the net force acting on the sphere at the air-water interface are demonstrated. For the experiments, the force-position relationship of microspheres is measured with a precise electronic balance. The results show that the evaporation of the liquid in the container affects the measuring results greatly under ambient conditions. After considering the evaporation compensation, there is a great agree- ment between the theoretical and experimental results. Obvious hysteresis phenomena of the force-distance curve during the emersion processes are also observed and explained.
文摘High-speed planing crafts have successfully evolved through developments in the last several decades.Classical approaches such as inviscid potential flow–based methods and the empirically based Savitsky method provide general understanding for practical design.However,sometimes such analyses suffer inaccuracies since the air–water interface effects,especially in the transition phase,are not fully accounted for.Hence,understanding the behaviour at the transition speed is of fundamental importance for the designer.The fluid forces in planing hulls are dominated by phenomena such as flow separation at various discontinuities viz.,knuckles,chines and transom,with resultant spray generation.In such cases,the application of potential theory at high speeds introduces limitations.This paper investigates the simulation of modelling of the pre-planing behaviour with a view to capturing the air–water interface effects,with validations through experiments to compare the drag,dynamic trim and wetted surface area.The paper also brings out the merits of gridding strategies to obtain reliable results especially with regard to spray generation due to the air–water interface effects.The verification and validation studies serve to authenticate the use of the multi-gridding strategies on the basis of comparisons with simulations using model tests.It emerges from the study that overset/chimera grids give better results compared with single unstructured hexahedral grids.Two overset methods are investigated to obtain reliable estimation of the dynamic trim and drag,and their ability to capture the spray resulting from the air–water interaction.The results demonstrate very close simulation of the actual flow kinematics at steady-speed conditions in terms of spray at the air–water interface,drag at the pre-planing and full planing range and dynamic trim angles.
文摘The main objective of this work was to develop a kinetic model to describe the variation of the surface tension in an air-water interface due to the adsorption of proteins from different origins and to identify quantitatively the relevant parameters, it was considered that the processes of adsorption, unfolding and reordering of the protein molecule in the interface occur simultaneously. The model used in the present work to calculate the surface tension postulates the existence of two simultaneous processes, adsorption and protein rearrangement represented with an equation of first order with two exponential components. The relevant parameter of the equation are ka and kr-the rate constants of the two first order kinetic phases that correspond to both conformational states of the protein, adsorption and rearrangement during the process of variation of the surface tension, and the amplitude parameters Aa and Ar. The results suggest that the kinetic model for the variation of the surface tension of protein solutions proposed in this work, with two simultaneous first order processes, is more appropriate than previous models to describe such variation.
基金supported by the National Natural Science Foundation of China(Grant No.51109106)the Natural Science Foundation of Jiangsu Province(Grant No.BK20130946)the Qing Lan Project of Jiangsu Province
文摘A transient three-dimensional coupling model based on the compressible volume of fluid （VOF） method was developed to simulate the transport of volatile pollutants at the air-water interface. VOF is a numerical technique for locating and tracking the free surface of water flow. The relationships between Henry＇s constant, thermodynamics parameters, and the enlarged topological index were proposed for nonstandard conditions. A series of experiments and numerical simulations were performed to study the transport of benzene and carbinol. The simulation results agreed with the experimental results. Temperature had no effect on mass transfer of pollutants with low transfer free energy and high Henry＇s constant. The temporal and spatial distribution of pollutants with high transfer free energy and low Henry＇s constant was affected by temperature. The total enthalpy and total transfer free energy increased significantly with temperature, with significant fluctuations at low temperatures. The total enthalpy and total transfer free energy increased steadily without fluctuation at high temperatures.
基金This work was financially supported by a grant-in-aid(No.19750099,24850015)from JSPS.
文摘Fabrication of anisotropic material is one of the important topics and we examined to introduce “anisotropic” nature by spreading polymer-grafted particle on the medium with polymer-reactive potential. Poly (tert-butyl methacrylate) (PtBMA) was polymerized from polystyrene latex (PSL) surface by ATRP to give PtBMA-grafted PSL (PSL-PtBMA). Particle monolayer was formed at air-water and air-acidic water interfaces and the monolayer characteristics were compared by π-A isotherm measurements, SEM observations, and contact angle measurements. π-A isotherms, in particular, indicates that the interaction between polymer chains become stronger by changing the subphase condition, which suggests that anisotropicparticle monolayer formation.
文摘For smooth curved objects in contact with a flat interface,the propagation paths of supported surface elastic waves can be altered by the interface,thereby enhancing the characteristics of the backscattered echo returns.In this study,backscattering experiments are conducted on an empty stainless steel cylindrical shell that breaks through an air-water interface and is insonified from below at grazing incidence.The shell has a thickness-to-radius ratio of 5%.The frequencies of interest fall within the vicinity of and below the coincidence frequency,which corresponds to a ka range of 13.8-20.1.The experimental results demonstrate that,for the partially exposed cylindrical shell,the flexural waves can traverse the interface and circumnavigate the shell multiple times.The flexural waves experience mode transitions upon passing through the interface,existing as a0−waves below the interface and a0 waves above the interface.Simultaneously,the flexural waves undergo partial reflection each time they pass through the interface,guiding them to follow a reverse path and generating a periodic series of echo returns,which leads to the enhancement of backscattering.The shift in resonance frequency in relation to the changing exposure is analyzed and predicted using the phase matching theory.
基金supported by the Natural National Science Foundation of China(No.61975167)。
文摘A cross air-water interface hydroacoustic signal detection method based on microvibration detection at the air-water interface is proposed.Laser speckles modulated by water surface acoustic waves are recorded and used as an information carrier.Phase correlation and multichannel fusion algorithms are used to extract and enhance hydroacoustic signals.Wide frequency range(200 Hz to 20 kHz)underwater acoustic signals are detected with a frequency relative error smaller than 0.5%.Several common artificial and natural hydroacoustic signals are used as source signals and correctly reconstructed.The average intelligibility of recovered humpback whale signals evaluated with the normalized subband envelope correlation algorithm is 0.52±0.02.
基金the National Natural Science Foundation of China(42221001)the National Natural Science Foundation of China(22325402,22174073)+4 种基金the National Key R&D Program of China(2023YFE0124200)the Natural Science Foundation of Tianjin City(21JCJQJC00010)the Natural Science Foundation of Tianjin City(23ZYJDSS00030)the Nankai Cangzhou Chemistry(NCC)Fund(NCC2022PY05)the Haihe Laboratory of Sustainable Chemical Transformations and the Frontiers Science Center for New Organic Matter at Nankai University(63181206)。
文摘Humic-like substances(HULIS),a class of macromolecular photosensitizers,are major components of light-absorbing aerosols in the atmosphere.Due to the amphiphilic nature of HULIS,they tend to appear at the air-water interface of atmospheric water.However,there have been limited studies on the photosensitized chemistry of HULIS at the air-water interface owing to the lack of methods with high interface selectivity.Here,a unique field-induced droplet ionization mass spectrometry(FIDI-MS)technique was used to investigate the photosensitized chemistry of several samples at the air-water interface.These samples include commercially available humic acid and the PM_(2.5)sample collected during Beijing′s severe winter haze in December 2016.Ultrahigh-resolution Fourier transform-ion cyclotron resonance mass spectrometry(FT-ICR MS)was also applied to analyze the atomic compositions,the degree of unsaturation and the aromaticity of these samples.Both TypeⅠand TypeⅡphotosensitized oxidation pathways were observed,which were postulated to be dictated by the packing density of the molecules at the air-water interface.These findings reveal that the photosensitization of HULIS at the air-water interface contributes greatly to the formation of atmospheric aerosols,further advancing our understanding of the important roles played by photosensitized chemistry in the atmosphere.
文摘Invasive as well as non-invasive neurotechnologies conceptualized to interface the central and peripheral nervous system have been probed for the past decades,which refer to electroencephalography,electrocorticography and microelectrode arrays.The challenges of these mentioned approaches are characterized by the bandwidth of the spatiotemporal resolution,which in turn is essential for large-area neuron recordings(Abiri et al.,2019).
基金financially supported by the National Natural Science Foundation of China (No.52100076)the Fundamental Research Funds for the Central Universities (No.2023MS064)。
文摘The escalating global issues of water scarcity and pollution emphasize the critical need for the rapid development of efficient and eco-friendly water treatment technologies.Photoelectrocatalytic technology has emerged as a promising solution for effectively degrading refractory organic pollutants in water under light conditions.This review delves into the advancements made in the field,focusing on strategies to enhance the generation of active species by modulating the micro-interface of the photoanode.Strategies,such as morphological control,element doping,introduction of surface oxygen vacancies,and construction of heterostructures,significantly improve the separation efficiency of photogenerated charges and the generation of active species,thereby boosting the efficiency of photoelectrocatalytic performance.Furthermore,the review explores the potential applications of photoelectrocatalytic technology in organic pollutant degradation in solutions.It also outlines the current challenges and future development directions.Despite its remarkable laboratory success,practical implementation of photoelectrocatalytic technology encounters obstacles related to stability,cost-effectiveness,and operational efficiency.Future investigations need to focus on optimizing the performance of photoelectrocatalytic materials and exploring strategies for upscaling their application in real water treatment scenarios.
基金supported by the National Natural Science Foundation of China(Nos.52371031 and 52574435)the Science and Technology Development Program of Jilin Province,China(No.20250102103JC)+2 种基金the Science and Technology Development Program of Changchun City,China(No.23JQ03)Changbaishan Laboratory,China(No.CBS2025004-03)the Undergraduate Innovation Fund of Jilin University,China(No.S202410183310).
文摘Introducing Ti_(2)AlC particles into TiAl alloys can effectively improve their strength,but this can also lead to stress concentration at the interface,resulting in the reduction of ductility.Therefore,Mn is adopted to synergistically improve the strength and ductility of the Ti_(2)AlC/TiAl composite through solid solution and interface manipulation.The first-principles calculation shows the Ti-Mn bonds are formed at the Ti_(2)AlC/TiAl interface after Mn doping,characterized primarily by metallic bonds with some covalent bonding.This combination preserves strength while enhancing ductility.Then,Ti_(2)AlC/TiAl-Mn composite is prepared.The Ti_(2)AlC,with an average size of 1.6μm,is uniformly distributed within the TiAl matrix.Mn doping reduces the lamellar colony size and lamellar thickness by 25.1%and 27.4%,respectively.A small quantity of Mn accumulates at the boundaries of the lamellar colonies.The Mn content must be controlled to avoid segregation,which may negatively impact performance.The yield stress,ultimate compressive stress,fracture strain,and product of strength and plasticity of the Ti_(2)AlC/TiAl-Mn composite have been increased by 5.5%,11.5%,10.4%,and 23.0%,respectively,compared to those of the Ti_(2)AlC/TiAl composite.The enhancement in strength is due to the combined effects of grain refinement,solid solution of Mn,and twining strengthening.Grain refinement and twin strengthening also can reduce stress concentration and improve ductility.In addition,at the electronic level,the Ti-Mn bond formed at the interface is contributed to the improvement of ductility.
基金financially supported by the National Natural Science Foundation of China (No.52372188)Natural Science Foundation of Henan (Nos.242300421625,252300421333)+4 种基金CAS Henan Industrial Technology Innovation & Incubation Center (No.2024121)Key Scientific Research Project of Education Department of Henan Province (Nos.22A150042,23A150038,and 24A150019)2023 Introduction of studying abroad talent programthe China Postdoctoral Science Foundation (No.2019 M652546)Key Project of Science and Technology of Henan Province (No.252102240007)。
文摘Aqueous zinc-ion batteries(AZIBs) are regarded as one of the most promising energy conversion and storage devices.Nevertheless,side reactions and dendrite growth on the zinc metal anode hinder their widespread application.In this study,hemin was employed as a multi-functional artificial interface for the first time to inhibit the disordered growth of zinc dendrites and mitigate side reactions.Theoretical calculations indicate that hemin is preferentially adsorbed onto the zinc anode,thus blocking the interaction between the active zinc anode and electrolyte.Compared with zinc foil,the Hemin@Zn anode demonstrates enhanced corrosion resistance,a decrease in hydrogen evolution,and more orderly deposition of zinc.As expected,the symmetric cell with Hemin@Zn anode can sustain up to 4000 h at 0.2 mA/cm^(2),0.2 mAh/cm^(2).Asymmetric Zn//Cu cells exhibit an average coulombic efficiency exceeding 99.72 % during 500 cycles.Moreover,the full cell Hemin@Zn//NH_(4)V_(4)O_(10) delivers a superior capacity up to 367 m Ah/g and the discharge capacity retention reaches 124 mAh/g after 1200 cycles even at a current density of 5 A/g.This work provides a simple and effective method for constructing a robust artificial interface to promote the application of long-life AZIBs.
