1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their...1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their incredible speed of development and wide-reaching impact,mobile communications serve as the cornerstone of the Internet of Everything,profoundly reshaping human cognitive abilities and ways of thinking.Furthermore,mobile communications are altering the patterns of production and life,driving leaps in productivity quality,and strongly promot-ing innovation within human civilization.展开更多
The oviduct epithelium is the initial maternal contact site for embryos after fertilization,offering the microenviron-ment before implantation.This early gestation period is particularly sensitive to stress,which can ...The oviduct epithelium is the initial maternal contact site for embryos after fertilization,offering the microenviron-ment before implantation.This early gestation period is particularly sensitive to stress,which can cause reduced fertil-ity and reproductive disorders in mammals.Nevertheless,the local impact of elevated stress hormones on the ovi-duct epithelium has received limited attention to date,except for a few reports on polyovulatory species like mice and pigs.In this study,we focused on the effects of chronic maternal stress on cattle,given its association with infertil-ity issues in this monoovulatory species.Bovine oviduct epithelial cells(BOEC)differentiated at the air–liquid interface(ALI)were stimulated with 250 nmol/L cortisol for 1 or 3 weeks.Subsequently,they were assessed for morphology,bioelectrical properties,and gene expression related to oviduct function,glucocorticoid pathway,cortisol metabo-lism,inflammation,and apoptosis.Results revealed adverse effects of cortisol on epithelium structure,featured by deciliation,vacuole formation,and multilayering.Additionally,cortisol exposure led to an increase in transepithelial potential difference,downregulated mRNA expression of the major glucocorticoid receptor(NR3C1),upregulated the expression of cortisol-responsive genes(FKBP5,TSC22D3),and significant downregulation of oviductal glycopro-tein 1(OVGP1)and steroid receptors PGR and ESR1.The systematic comparison to a similar experiment previously performed by us in porcine oviduct epithelial cells,indicated that bovine cultures were more susceptible to elevated cortisol levels than porcine.The distinct responses between both species are likely linked to their divergence in the cortisol-induced expression changes of HSD11B2,an enzyme controlling the cellular capacity to metabolise cortisol.These findings provide insights into the species-specific reactions and reproductive consequences triggered by maternal stress.展开更多
Based on the modified Biot＇s theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences...Based on the modified Biot＇s theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences between air-saturated soils and water-saturated soils were theoretically discussed, and the theoretical formulas of reflection and transmission coefficients at an air-water interface were derived. The characteristics of propagation and attenuation of elastic waves in air-saturated soils were given and the relations among the frequency, the angle of incidence and the reflection, transmission coefficients were analyzed by using numerical methods. Numerical results show that the propagation characteristic of the wave in air-saturated soils is great different from that in water-saturated soils. The frequency and the angle of incidence can have great influences on the reflection and transmission coefficients at interface. Some new cognition about the wave propagation is obtained and the study suggests that we may carefully pay attention to the influence of air on the dynamic analysis of seismic wave.展开更多
Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductanc...Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductance to survey soil water profiles and comparing it with root distribution surveyed by soil coring and root harvesting in Changbai Mountain in 1999. The results were: (1) The profiles of soil water content were adjusted by root activity. The water content of the soil layer with abundant roots was higher. (2) When CO 2 concentration was doubled, water transport was more active at the root/soil interface and the roots were distributed into deeper layer. It was shown in this work that the method of measuring electric conductance is an inexpensive, non_destructive and relatively sensitive way for underground water transport process.展开更多
For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in t...For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.展开更多
The electronic structures and properties of electrocatalysts,which depend on the physicochemical structure and metallic element components,could significantly affect their electrocatalytic performance and their future...The electronic structures and properties of electrocatalysts,which depend on the physicochemical structure and metallic element components,could significantly affect their electrocatalytic performance and their future applications in Zn-air battery(ZAB)and overall water splitting(OWS).Here,by combining vacancies and heterogeneous interfacial engineering,three-dimensional(3D)core-shell NiCoP/NiO heterostructures with dominated oxygen vacancies have been controllably in-situ grown on carbon cloth for using as highly efficient electrocatalysts toward hydrogen and oxygen electrochemical reactions.Theoretical calculation and electrochemical results manifest that the hybridization of NiCoP core with NiO shell produces a strong synergistic electronic coupling effect.The oxygen vacancy can enable the emergence of new electronic states within the band gap,crossing the Fermi levels of the two spin components and optimizing the local electronic structure.Besides,the hierarchical core-shell NiCoP/NiO nanoarrays also endow the catalysts with multiple exposed active sites,faster mass transfer behavior,optimized electronic strutures and improved electrochemical performance during ZAB and OWS applications.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 salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy（SFG-VS）. We clarified that the average til...The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy（SFG-VS）. We clarified that the average tilting angle of the methyl group to be u = 308 58 at the air/pure methanol surface assuming a d-function orientational distribution. Upon the addition of 3 mol/L Na I, the methyl group tilts further away from the surface normal with a new u = 418 38. This orientational change does not explain the enhancement of the SFG-VS intensities when adding Na I, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the Na I concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data.展开更多
Here we report a quantitative study of the orientational structure and motion of water molecule at the air/water interface. Analysis of Sum Frequency Generation （SFG） vibrational peak of the free O-H stretching band...Here we report a quantitative study of the orientational structure and motion of water molecule at the air/water interface. Analysis of Sum Frequency Generation （SFG） vibrational peak of the free O-H stretching band at 3700 cm^-1 in four experimental configurations showed that orientational motion of water molecule at air/water interface is libratory within a limited angular range. The free OH bond of the interracial water molecule is tilted around 33°from the interface normal and the orientational distribution or motion width is less than 15°. This picture is significantly different from the previous conclusion that the interracial water molecule orientation varies over a broad range within the ultrafast vibrational relaxation time, the only direct experimental study concluded for ultrafast and broad orient, ational motion of a liquid interface by Wei et al. （Phys. Rev. Lett. 86, 4799, （2001）） using single SFG experimental configuration.展开更多
The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions.In this research,a series of cryogenic direct shear tests for ice...The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions.In this research,a series of cryogenic direct shear tests for ice-frozen clay soil interface were conducted.Based on experimental results,a nonlinear interface structural damage model is proposed to describe the shear properties of ice-frozen clay soil interface.Firstly,the cementation and friction structural properties of frozen soil materials were analyzed,and a structural parameter of the ice-frozen clay soil interface is proposed based on the cryogenic direct shear test results.Secondly,a structural coefficient ratio is proposed to describe the structural development degree of ice-frozen clay soil interface under load,which is able to normalize the shear stress of ice-frozen clay soil interface,and the normalized data can be described by the Duncan-Chang model.Finally,the tangent stiffness of ice-frozen clay soil interface is calculated,which can be applied to the mechanics analysis of frozen soil.Also,the shear stress of ice-frozen clay soil interface calculated by the proposed model is compared with test results.展开更多
Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to...Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage,and to devise proper mitigation measures for effective pot planting in cold regions.A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil.The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature.Microscopic poromechanic effects on heat transfer behavior were ignored.The spatial domain of the problem was simplified to a 1D spherical coordinate system with variation in the radial direction.Green's function was applied to solve for the time-dependent body temperature.Experiments were conducted for validation of the theoretical model.Reasonable agreement between the theoretical predictions and experimental measurements was obtained.The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes,e.g.,thermal properties of soil,ambient temperature,and planting pot size.展开更多
The direct conversion of atmospheric CO_(2) into fuel via photocatalysis exhibits significant practical application value in advancing the carbon cycle.In this study,we established an electro-assisted photocatalytic s...The direct conversion of atmospheric CO_(2) into fuel via photocatalysis exhibits significant practical application value in advancing the carbon cycle.In this study,we established an electro-assisted photocatalytic system with dual compartments and interfaces,and coated Ag nanoparticles on the titanium nanotube arrays(TNTAs)by polydopamine modification.In the absence of sacrificial agent and alkali absorption liquid conditions,the stable,efficient and highly selective conversion of CO_(2) to CO at the gas-solid interface in ambient air was realized by photoelectric synergy.Specifically,with the assistance of potential,the CO formation rates reached 194.9μmol h^(−1) m^(−2) and 103.9μmol h^(−1) m^(−2) under ultraviolet and visible light irradiation,respectively;the corresponding CO_(2) conversion rates in ambient air were 30%and 16%,respectively.The excellent catalytic effect is mainly attributed to the formation of P–N heterojunction during the catalytic process and the surface plasmon resonance effect.Additionally,the introduction of solid agar electrolytes effectively inhibits the hydrogen evolution reaction and improves the electron utilization rate.This system promotes the development of photocatalytic technology for practical applications and provides new insights and support for the carbon cycle.展开更多
Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geolo...Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geological media.The tests were conducted at a site in the northwestern part of Singapore composed of residual soil and granitic rock.The field test aims to provide measurement data to better understand the stress wave propagation in soil/rock and along their interface.Triaxial accelerometers were used for the free field vibration monitoring.The measured results are presented and discussed,and empirical formulae for predicting peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data.Also,the ground vibration attenuation across the soil-rock interface was carefully examined,and it was found that the PPV of ground vibration was decreased by 37.2% when it travels from rock to soil in the vertical direction.展开更多
Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the labo...Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the laboratory. The mechanical properties of the soil-root with branches interface is determined through the pullout-force and root-slippage curve （F-S curve）. The results of investigating 24 Pinus tabulaeformis single roots and 55 P. tabulaeformis roots with branches demonstrated three kinds of pullout test failures： breakage failure on branching root, breakage failure on branching node, and pullout failure. The branch angle had a remarkable effect on the failure mode of the roots with branches： the maximum pullout force increased with the sum of the branch diameters and the branch angle. The peak slippage and the initial force had a positive correlation with the sum of the branch diameter. The sig- nificance test of correlation between branch angle and the initial force, however, showed they had no correlation. Branch angle and branch root diameter affect the anchorage properties between root system and soil. Therefore, it is important to investigate the anchorage mechanics of the roots with branches to understand the mechanism of root reinforcement and anchorage.展开更多
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
During the Huanghai Sea Circulation and Material Flux Expedition in Spring 1996, fco_2 in surface water and atmosphere was measured. The fco2 in surface water varied in a range from 220 to 360 uatm1) while atmospheric...During the Huanghai Sea Circulation and Material Flux Expedition in Spring 1996, fco_2 in surface water and atmosphere was measured. The fco2 in surface water varied in a range from 220 to 360 uatm1) while atmospheric concentration was nearly constant at 360μatm, showing that the Huanghai Sea surface waters were undersaturated with respect to atmospheric Co during the time of investigation. A model was developed in this study in order to estimate the Co flux at the air-sea interface. The model incorporates the time-series variations of the distributions in SST (sea surface temperature), salinity, mixed-layer depth, atmospheric fco2, gas-transfer velocity, and CZCS chlorophyll concentration in the Huanghai Sea and was calibrated with the observed fco2 data. The primary parameter affecting fco2 in surface water is the variation of SST through time. The annual fluxes of Co are estimated as 0. 033 Gt C from the sea into the atmosphere and 0. 044 Gt C from the air into sea. The Huanghai Sea, thus behaves as a CO2 sink absorbing 0. 011 Gi C of CO2 a year. which.corresponds to about 0. 5 % of global oceanic absorption capacity.展开更多
Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at so...Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at soil-water interface, were analyzed by the probit method. Growth enhancing concentration, no-observed effective concentration, minimum inhibitory concentration, the highest permissive concentration and lethal concentration100 （LCloo） were determined experimentally. The LC^o values of carbaryl, carbofuran, ziram, zineb and mancozeb in N2-fixing liquid medium were 56.2, 588.8, 0.07, 4.2 and 3.4 IJg/mL, respectively, whereas the corresponding LCloo values were 100.0, 1500.0, 0.17, 25.0 and 9.0 IJg/mL, respectively. The LC50 values of these pesticides in succession in N2-fixing agar medium were 44.7, 239.9, 0.07, 1.8 and 2.3 IJg/mL, respectively, whereas the corresponding LC100 values were 100.0, 600.0, 0.17, 10.0 and 7.0 IJg/mL, respectively. Similar results with nitrate supplemented liquid and agar media indicated that nitrate supplementation had toxicity reducing effect. The LCso and LC^oo values of toxicity in the N2-fixing liquid medium at soil-water interface were 91.2 and 200.0 IJg/mL for carbaryl, 2 317 and 6 000 pg/mL for carbofuran, 0.15 and 0.50 pg/mL for ziram, 16.4 and 50.0 pg/mL for zineb, and 7.2 and 25.0 pg/mL for mancozeb, respectively. Each LC^oo value at soil- water interface with a pesticide was significantly higher than its corresponding LCloo value at liquid/agar media. It can be concluded that, under the N2-fixing conditions, the cyanobacterium tolerated higher levels of each pesticide at soil-water interface.展开更多
Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil...Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil sample in the upper part, a series of dynamic shear tests on their interfaces were carried out. The obtained results are summarized and the main influencing factors are revealed.展开更多
Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformati...Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.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
基金supported by the National Key Research and Develop-ment Program of China(2019YFB1803400).
文摘1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their incredible speed of development and wide-reaching impact,mobile communications serve as the cornerstone of the Internet of Everything,profoundly reshaping human cognitive abilities and ways of thinking.Furthermore,mobile communications are altering the patterns of production and life,driving leaps in productivity quality,and strongly promot-ing innovation within human civilization.
基金German research Foundation(DFG,grant numbers:CH2321/1–1 and SCHO1231/7–1)JH has received a scholarship from the Chinese Scholarship Council(CSC No.:201908350115).
文摘The oviduct epithelium is the initial maternal contact site for embryos after fertilization,offering the microenviron-ment before implantation.This early gestation period is particularly sensitive to stress,which can cause reduced fertil-ity and reproductive disorders in mammals.Nevertheless,the local impact of elevated stress hormones on the ovi-duct epithelium has received limited attention to date,except for a few reports on polyovulatory species like mice and pigs.In this study,we focused on the effects of chronic maternal stress on cattle,given its association with infertil-ity issues in this monoovulatory species.Bovine oviduct epithelial cells(BOEC)differentiated at the air–liquid interface(ALI)were stimulated with 250 nmol/L cortisol for 1 or 3 weeks.Subsequently,they were assessed for morphology,bioelectrical properties,and gene expression related to oviduct function,glucocorticoid pathway,cortisol metabo-lism,inflammation,and apoptosis.Results revealed adverse effects of cortisol on epithelium structure,featured by deciliation,vacuole formation,and multilayering.Additionally,cortisol exposure led to an increase in transepithelial potential difference,downregulated mRNA expression of the major glucocorticoid receptor(NR3C1),upregulated the expression of cortisol-responsive genes(FKBP5,TSC22D3),and significant downregulation of oviductal glycopro-tein 1(OVGP1)and steroid receptors PGR and ESR1.The systematic comparison to a similar experiment previously performed by us in porcine oviduct epithelial cells,indicated that bovine cultures were more susceptible to elevated cortisol levels than porcine.The distinct responses between both species are likely linked to their divergence in the cortisol-induced expression changes of HSD11B2,an enzyme controlling the cellular capacity to metabolise cortisol.These findings provide insights into the species-specific reactions and reproductive consequences triggered by maternal stress.
基金National Natural Science Foundation of China (59808011).
文摘Based on the modified Biot＇s theory of two-phase porous media, a study was presented on seismic reflection and transmission coefficients at an air-water interface of saturated porous soil media. The major differences between air-saturated soils and water-saturated soils were theoretically discussed, and the theoretical formulas of reflection and transmission coefficients at an air-water interface were derived. The characteristics of propagation and attenuation of elastic waves in air-saturated soils were given and the relations among the frequency, the angle of incidence and the reflection, transmission coefficients were analyzed by using numerical methods. Numerical results show that the propagation characteristic of the wave in air-saturated soils is great different from that in water-saturated soils. The frequency and the angle of incidence can have great influences on the reflection and transmission coefficients at interface. Some new cognition about the wave propagation is obtained and the study suggests that we may carefully pay attention to the influence of air on the dynamic analysis of seismic wave.
文摘Water transport at the root/soil interface of 1 year old Pinus sylvestris Linn. var. sylvestriformis (Takenouchi) Cheng et C. D. Chu seedlings under CO 2 doubling was studied by measuring soil electric conductance to survey soil water profiles and comparing it with root distribution surveyed by soil coring and root harvesting in Changbai Mountain in 1999. The results were: (1) The profiles of soil water content were adjusted by root activity. The water content of the soil layer with abundant roots was higher. (2) When CO 2 concentration was doubled, water transport was more active at the root/soil interface and the roots were distributed into deeper layer. It was shown in this work that the method of measuring electric conductance is an inexpensive, non_destructive and relatively sensitive way for underground water transport process.
文摘For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.
基金financially supported by the National Natural Science Foundation of China(No.22179014,21603019)program for the Hundred Talents Program of Chongqing University。
文摘The electronic structures and properties of electrocatalysts,which depend on the physicochemical structure and metallic element components,could significantly affect their electrocatalytic performance and their future applications in Zn-air battery(ZAB)and overall water splitting(OWS).Here,by combining vacancies and heterogeneous interfacial engineering,three-dimensional(3D)core-shell NiCoP/NiO heterostructures with dominated oxygen vacancies have been controllably in-situ grown on carbon cloth for using as highly efficient electrocatalysts toward hydrogen and oxygen electrochemical reactions.Theoretical calculation and electrochemical results manifest that the hybridization of NiCoP core with NiO shell produces a strong synergistic electronic coupling effect.The oxygen vacancy can enable the emergence of new electronic states within the band gap,crossing the Fermi levels of the two spin components and optimizing the local electronic structure.Besides,the hierarchical core-shell NiCoP/NiO nanoarrays also endow the catalysts with multiple exposed active sites,faster mass transfer behavior,optimized electronic strutures and improved electrochemical performance during ZAB and OWS applications.
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.
基金supported by the National Natural Science Foundation of China (Nos. 21227802, 21303216 and 21473217)
文摘The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy（SFG-VS）. We clarified that the average tilting angle of the methyl group to be u = 308 58 at the air/pure methanol surface assuming a d-function orientational distribution. Upon the addition of 3 mol/L Na I, the methyl group tilts further away from the surface normal with a new u = 418 38. This orientational change does not explain the enhancement of the SFG-VS intensities when adding Na I, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the Na I concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data.
基金This work was supported by Chines Academy of Scieuces（No.CMS-cx200305）,National Natural Science Foundation of China（NSFC No.20425309,No.20573117）and Chinese Ministry of Science and Technology （M0ST No.G1999075305）.
文摘Here we report a quantitative study of the orientational structure and motion of water molecule at the air/water interface. Analysis of Sum Frequency Generation （SFG） vibrational peak of the free O-H stretching band at 3700 cm^-1 in four experimental configurations showed that orientational motion of water molecule at air/water interface is libratory within a limited angular range. The free OH bond of the interracial water molecule is tilted around 33°from the interface normal and the orientational distribution or motion width is less than 15°. This picture is significantly different from the previous conclusion that the interracial water molecule orientation varies over a broad range within the ultrafast vibrational relaxation time, the only direct experimental study concluded for ultrafast and broad orient, ational motion of a liquid interface by Wei et al. （Phys. Rev. Lett. 86, 4799, （2001）） using single SFG experimental configuration.
基金supported the National Key Research and Development Program of China(Nos.2016YFE0202400,2018YFC1505306)the National Natural Science Foundation of China(No.41971076)the State Key Laboratory of Road Engineering Safety and Health in Cold and High-altitude Regions(No.YGY2017KYPT-04)。
文摘The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions.In this research,a series of cryogenic direct shear tests for ice-frozen clay soil interface were conducted.Based on experimental results,a nonlinear interface structural damage model is proposed to describe the shear properties of ice-frozen clay soil interface.Firstly,the cementation and friction structural properties of frozen soil materials were analyzed,and a structural parameter of the ice-frozen clay soil interface is proposed based on the cryogenic direct shear test results.Secondly,a structural coefficient ratio is proposed to describe the structural development degree of ice-frozen clay soil interface under load,which is able to normalize the shear stress of ice-frozen clay soil interface,and the normalized data can be described by the Duncan-Chang model.Finally,the tangent stiffness of ice-frozen clay soil interface is calculated,which can be applied to the mechanics analysis of frozen soil.Also,the shear stress of ice-frozen clay soil interface calculated by the proposed model is compared with test results.
基金Project(No.10206014)supported by Research Grant Council Direct Allocation Fund from the University of Hong Kong,China
文摘Soil in a cold region is subject to frequent freezing and thawing cycles.Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture.It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage,and to devise proper mitigation measures for effective pot planting in cold regions.A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil.The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature.Microscopic poromechanic effects on heat transfer behavior were ignored.The spatial domain of the problem was simplified to a 1D spherical coordinate system with variation in the radial direction.Green's function was applied to solve for the time-dependent body temperature.Experiments were conducted for validation of the theoretical model.Reasonable agreement between the theoretical predictions and experimental measurements was obtained.The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes,e.g.,thermal properties of soil,ambient temperature,and planting pot size.
文摘The direct conversion of atmospheric CO_(2) into fuel via photocatalysis exhibits significant practical application value in advancing the carbon cycle.In this study,we established an electro-assisted photocatalytic system with dual compartments and interfaces,and coated Ag nanoparticles on the titanium nanotube arrays(TNTAs)by polydopamine modification.In the absence of sacrificial agent and alkali absorption liquid conditions,the stable,efficient and highly selective conversion of CO_(2) to CO at the gas-solid interface in ambient air was realized by photoelectric synergy.Specifically,with the assistance of potential,the CO formation rates reached 194.9μmol h^(−1) m^(−2) and 103.9μmol h^(−1) m^(−2) under ultraviolet and visible light irradiation,respectively;the corresponding CO_(2) conversion rates in ambient air were 30%and 16%,respectively.The excellent catalytic effect is mainly attributed to the formation of P–N heterojunction during the catalytic process and the surface plasmon resonance effect.Additionally,the introduction of solid agar electrolytes effectively inhibits the hydrogen evolution reaction and improves the electron utilization rate.This system promotes the development of photocatalytic technology for practical applications and provides new insights and support for the carbon cycle.
基金supported by the Land and Liveability National Innovation Challenge under L2 NIC Award No. L2NICCFP1-2013-1
文摘Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geological media.The tests were conducted at a site in the northwestern part of Singapore composed of residual soil and granitic rock.The field test aims to provide measurement data to better understand the stress wave propagation in soil/rock and along their interface.Triaxial accelerometers were used for the free field vibration monitoring.The measured results are presented and discussed,and empirical formulae for predicting peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data.Also,the ground vibration attenuation across the soil-rock interface was carefully examined,and it was found that the PPV of ground vibration was decreased by 37.2% when it travels from rock to soil in the vertical direction.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.YX2010-20)the National Natural Science Foundation of China(No.31570708,No.30901162)the Open Projects Foundation of Key Laboratory of Soil and Water Conservation&Desertification Combat(Beijing Forestry University),Ministry of Education of China(No.201002)
文摘Roots play an important role in stabilizing and strengthening soil. This article aims to study the mechanical properties of the interface between soil and roots with branches, using the pullout test method in the laboratory. The mechanical properties of the soil-root with branches interface is determined through the pullout-force and root-slippage curve （F-S curve）. The results of investigating 24 Pinus tabulaeformis single roots and 55 P. tabulaeformis roots with branches demonstrated three kinds of pullout test failures： breakage failure on branching root, breakage failure on branching node, and pullout failure. The branch angle had a remarkable effect on the failure mode of the roots with branches： the maximum pullout force increased with the sum of the branch diameters and the branch angle. The peak slippage and the initial force had a positive correlation with the sum of the branch diameter. The sig- nificance test of correlation between branch angle and the initial force, however, showed they had no correlation. Branch angle and branch root diameter affect the anchorage properties between root system and soil. Therefore, it is important to investigate the anchorage mechanics of the roots with branches to understand the mechanism of root reinforcement and anchorage.
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During the Huanghai Sea Circulation and Material Flux Expedition in Spring 1996, fco_2 in surface water and atmosphere was measured. The fco2 in surface water varied in a range from 220 to 360 uatm1) while atmospheric concentration was nearly constant at 360μatm, showing that the Huanghai Sea surface waters were undersaturated with respect to atmospheric Co during the time of investigation. A model was developed in this study in order to estimate the Co flux at the air-sea interface. The model incorporates the time-series variations of the distributions in SST (sea surface temperature), salinity, mixed-layer depth, atmospheric fco2, gas-transfer velocity, and CZCS chlorophyll concentration in the Huanghai Sea and was calibrated with the observed fco2 data. The primary parameter affecting fco2 in surface water is the variation of SST through time. The annual fluxes of Co are estimated as 0. 033 Gt C from the sea into the atmosphere and 0. 044 Gt C from the air into sea. The Huanghai Sea, thus behaves as a CO2 sink absorbing 0. 011 Gi C of CO2 a year. which.corresponds to about 0. 5 % of global oceanic absorption capacity.
基金supported by an ES project on ‘Cyanobacteria’ (Grant No.21 (0859)/11/EMR-II),from Council of Scientific and Industrial Research (CSIR),New Delhi,India
文摘Toxicity-data of two carbamate insecticides, carbaryl and carbofuran, and three fungicides, ziram, zineb and mancozeb with rice-field N2-fixing cyanobacterium Cylindrospermum sp., obtained by in vitro growth and at soil-water interface, were analyzed by the probit method. Growth enhancing concentration, no-observed effective concentration, minimum inhibitory concentration, the highest permissive concentration and lethal concentration100 （LCloo） were determined experimentally. The LC^o values of carbaryl, carbofuran, ziram, zineb and mancozeb in N2-fixing liquid medium were 56.2, 588.8, 0.07, 4.2 and 3.4 IJg/mL, respectively, whereas the corresponding LCloo values were 100.0, 1500.0, 0.17, 25.0 and 9.0 IJg/mL, respectively. The LC50 values of these pesticides in succession in N2-fixing agar medium were 44.7, 239.9, 0.07, 1.8 and 2.3 IJg/mL, respectively, whereas the corresponding LC100 values were 100.0, 600.0, 0.17, 10.0 and 7.0 IJg/mL, respectively. Similar results with nitrate supplemented liquid and agar media indicated that nitrate supplementation had toxicity reducing effect. The LCso and LC^oo values of toxicity in the N2-fixing liquid medium at soil-water interface were 91.2 and 200.0 IJg/mL for carbaryl, 2 317 and 6 000 pg/mL for carbofuran, 0.15 and 0.50 pg/mL for ziram, 16.4 and 50.0 pg/mL for zineb, and 7.2 and 25.0 pg/mL for mancozeb, respectively. Each LC^oo value at soil- water interface with a pesticide was significantly higher than its corresponding LCloo value at liquid/agar media. It can be concluded that, under the N2-fixing conditions, the cyanobacterium tolerated higher levels of each pesticide at soil-water interface.
基金supported by the National Natural Science Foundation of China (Grant No. 41171064)the National Basic Research Program of China (973 Program Grant No. 2012CB026104)
文摘Using newly developed dynamic shearing devices, the dynamic sheafing strength of frozen soil-conerete interface was studied experimentally. By placing concrete blocks in the lower half of the shear box and frozen soil sample in the upper part, a series of dynamic shear tests on their interfaces were carried out. The obtained results are summarized and the main influencing factors are revealed.
基金the National Key Research and Development Program of China(Grant No.2023YFF1303501)the National Science Fund for Distinguished Young Scholars of China(Grant No.42225702)the Open Fund of State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201814).
文摘Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction.Optical frequency domain reflectometry(OFDR)based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas,where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy.In this paper,a series of pullout tests were conducted on fiber optic(FO)cables embedded in the frozen soil to investigate the cable‒soil interface behavior.An experimental study was performed on interaction effects,particularly focused on the water content of unfrozen soil,freezing duration,and differential distribution of water content in frozen soil.The highresolution axial strains of FO cables were obtained using a sensing interrogator,and were used to calculate the interface shear stress.The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models.Three freezing periods,correlating with the phase change process between ice and water,were analyzed.The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times.A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information.Additionally,the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements.This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil,which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.
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.
