The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly...The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly monsoon in summer induces a clockwise circulation in the Beibu Gulf, and the density gradient induces a counter-clockwise one; but the density current is more intense than the wind- driven one in summer, espeially in surface layer. In addition, the northeasterly monsoon in winter in- duces a counter-clockwise circulation. The simulated results don't support the traditional condusion that there is a clockwise circulation in the Beibu Gulf in summer and a counter-clockwise one in winter, but support the statement that a counterclockwise circulation exists in the Beibu Gulf all year round.展开更多
In this paper, the characteristics of density current under the action of waves are described with the help of flume experiment and theoretical analysis. The study shows that turbid water under the action of the waves...In this paper, the characteristics of density current under the action of waves are described with the help of flume experiment and theoretical analysis. The study shows that turbid water under the action of the waves can present three types of motion, i. e. significant stratification, fragile stratification and strong mixing. The motion gf turbid;,ater presents significant stratification when (H/D)/root Delta rho/rho less than or equal to 4.5, generally this state is known as density current. The formulas of motion velocity, thickness, and discharge of density current moving on horizontal bottom are derived by use of basic equations such as momemtum equation, equation of energy conservation and continuity equation of fluid. The time-average velocity and the thickness of density current under the action of waves have a relationship with such parameters as relative density (Delta rho/rho), wave height (H), and water depth (D). When these parameters are determined, the time-average thickness and motion velocity of density current are also determined. The relative thickness of density current (D-t/D) decreases with the increase of Delta rho/rho and increases with the increase of H/D. On the other hand, the motion velocity of density current increases with the increase of Delta rho/rho and decreases with the increase of the relative thickness (D-t/D) of density current. It is shown that the calculated results are in agreement with those of the flume experiment.展开更多
The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-...The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.展开更多
Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5...Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.展开更多
Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of ac...Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition.Herein,we present a freestanding lamellar nanoporous Ni-Co-Mn alloy electrode(Lnp-NCM)designed by a refined variant of the“dealloying-coarsening-dealloying”protocol for highly efficient bifunctional electrocatalyst,where large porous channels distribute on the surface and small porous channels at the interlayer.With its 3D lamellar architecture regulating,the electrocatalytic properties of the electrodes with different distances between lamellas are compared,and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites.Note that the optimized sample(Lnp-NCM4)is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm^(-2)for hydrogen and oxygen evolution reactions(HER and OER),respectively.During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode,it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm^(-2)with remarkable long-term stability over 50 h.This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.展开更多
Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence...Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence of ultraviolet(UV)and electromagnetic wave radiation,the results indicate that the BAM target may undergo luminescent excitation due to collisions with electrons and ions.This led us to investigate the physical mechanism behind this plasma luminescence excitation phenomenon.A spectrometer was used to record the luminescent spectroscopy and peak light intensity.Under excitation by argon plasma,the BAM material emits a continuum spectrum from 400 nm to 550 nm,with the peak light intensity located at 462.58 nm,which is the same as the spectrum excited by UV torchlight.To identify the relationship between the plasma parameters and the luminescent intensity,Langmuir and Faraday probes were employed to determine the local plasma parameters such as electron density,electron temperature,and current density.After normalizing the peak light intensity to the plasma parameters,the most interesting point is that the current density is linearly correlated with the luminescent light intensity.To verify the repeatability and lifetime of the plasma-luminescence interaction,a 600 s lifetime test was conducted in a 200 W ICP discharge environment.The maximum difference for the peak light strength of the luminescent spectrum is 6.5%.From a voltage bias experiment and a theoretical derivation,we initially identified that bombardment by ions plays the dominant role in the luminescence excitation process,which also explains the mechanism by which the current density is proportional to the luminescence intensity.This new finding leads us to reconsider the possibility of applying this plasma luminescence phenomenon to optical plasma diagnostics.The BAM light intensity can potentially be used to predict the current density of a plasma beam for large-area two-dimensional(2D)measurements and can capture high spatial resolution in a single test.We believe that this method may lead to high-efficiency,spatially resolved plasma current density measurement.展开更多
Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance i...Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance is often limited by charge carrier recombination,resulting in unsatisfactory saturation current densities.To address this challenge,we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper.The optimal photoanode(TCO/n-p-Si/TCO/Ni)shows a remarkably low onset potential of 0.92 V vs.a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm^(-2),which is about 92.7%of the theoretical maximum(42.7 mA·cm^(-2)).In addition,the photoanode demonstrates stable operation for 60 h.Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer,enhances catalytic performance,and provides corrosion protection to the underlying substrate.Notably,the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential.These findings provide a viable pathway for fabricating highperformance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.展开更多
The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited ...The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited a high formate Faradaic efficiency(FE)of 97.45%(-0.9 V)and a large partial current density of-45.82 mA/cm^(2)(-1.2 V).The good performance benefits from the reconstruction of BiVO_(4)to generate active metal Bi sites,which results in the electron redistribution to boost the OCHO∗formation.In flow cells,near industrial current density of 183.94 mA/cm^(2)was achieved,with the FE of formate above 95%from 20mA/cm^(2)to 180mA/cm^(2).Our work provides a facily synthesized BiVO_(4)precatalyst for CO_(2)electroreduction.展开更多
A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate...A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate the equilibrium current density in a ribbon-shaped system within the AHE regime,consisting of two sets of counterpropagating channels arranged in a zebra stripes pattern.While the middle channels are susceptible to scattering,the edge channels remain relatively robust.Despite this difference,all channels exhibit the same differential current density when subjected to a differential voltage across the two ends of the ribbon.When a differential voltage is applied to both sides of the ribbon,it results in a snaking pattern of differential current density forming across it.Furthermore,in a four-terminal device comprising the ribbon and two normal leads,it is found that Hall conductance is independent of ribbon width within certain scattering strengths due to the differences in robustness between middle and edge channels.These findings disclose the details of the AHE transport in a finite-sized system under weak scattering.展开更多
Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/mo...Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures(denoted Co/Mo_(2)N)via ammonia-assisted reduction,which effectively modulating the HER performance.The optimized Co/Mo_(2)N-500,characterized by 3%tensile lattice strain,demonstrates exceptional HER activity with lower overpotentials of140 mV and 184 mV at high current density of 1000 mA cm^(-2)in alkaline freshwater and seawater electrolytes,respectively.Co/Mo_(2)N also exhibits excellent long-term durability even at a high current density of 300 mA cm^(-2),surpassing its counterparts and benchmark Pt/C catalyst.Density functional theory calculations validate that the tensile strain optimizes the d-band states,water dissociation,and hydrogen adsorption kinetics of the strained Mo_(2)N in Co/Mo_(2)N,thereby improving its catalytic efficacy.This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.展开更多
Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density o...Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.展开更多
Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique...Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique. The effects of current density on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated by energy dispersive X-ray spectroscopy（EDXS）, anode polarization curves, quasi-stationary polarization（Tafel） curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, and X-ray diffraction（XRD）. Results reveal that the composite electrode obtained at 1 A/dm2 possesses the lowest overpotential（0.610 V at 500 A/m2） for oxygen evolution, the best electrocatalytic activity, the longest service life（360 h at 40 °C in 150 g/L H2SO4 solution under 2 A/cm2）, and the lowest cell voltage（2.75 V at 500 A/m2）. Furthermore, with increasing current density, the coating exhibits grain growth and the decrease of content of Mn O2. Only a slight effect on crystalline structure is observed.展开更多
AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer betwee...AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer between GaAs layers, potential wells beside the two sides of barrier are deepened, resulting in an increase of the peak-to-valley current ratio （PVCR） and a peak current density. A special shape of collector is designed in order to reduce contact resistance and non-uniformity of the current;as a result the total chrrent density in the device is increased. The use of thin barriers is also helpful for the improvement of the PVCR and the peak current density in DBRTDs. The devices exhibit a maximum PVCR of 13.98 and a peak current density of 89kA/cm^2 at room temperature.展开更多
Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxid...Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.展开更多
Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo all...Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam(NiCo@C-NiCoMoO/NF)for water splitting.NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction(HER:39/266 mV;OER:260/390 mV)at±10 and±1000 mA cm^(−2).More importantly,in 6.0 M KOH solution at 60℃ for WE,it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h,exhibiting the potential for actual application.The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet,which not only increase the intrinsic activity and expose abundant catalytic activity sites,but also enhance its chemical and mechanical stability.This work thus could provide a promising material for industrial hydrogen production.展开更多
M 2 tide and density residual currents in the Bohai Sea were examined using the Blumberg and Mellor 3D nonlinear numerical coastal circulation model incorporating Mellor and Yamada level 2.5 turbulent closure model. T...M 2 tide and density residual currents in the Bohai Sea were examined using the Blumberg and Mellor 3D nonlinear numerical coastal circulation model incorporating Mellor and Yamada level 2.5 turbulent closure model. The tidal results showed good agreement with previous work. The model results indicated that the density residual currents are robust in summer; and that at the transition zone between well-mixed and stratified water, the horizontal velocity is high and the vertical velocity is positive.展开更多
In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed ...In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed void shapes: circular, ellipse, and cardioid. Void morphological evolution is governed by the competition between the electric field and surface capillary force. In the developed model, both the electric field and capillary force on the void's surface are solved analytically. Based on the mass conversation principle, the normal velocity on the void surface during diffusion is obtained. The void morphological evolution behavior is investigated, and a physical model is developed to predict void collapse to a crack or to split into sub-voids under electric current. It is noted that when the electric current is being applied from the horizontal direction, a circular void may either move stably along the electric current direction or collapse to a finger shape, depending on the relative magnitude of the electric current and surface capillary force. However, the elliptical-shaped void will elongate along the electric current direction and finally collapse to the finger shape. On the other hand, the cardioid-shaped void could bifurcate into two sub-voids when the electric current reaches a critical value. The theoretical predictions agree well with the experimental observations.展开更多
The α-PbO2 electrodes are prepared by anodic electrodeposition on Al/conductive coating electrode from alkaline plumbite solutions in order to investigate the effect of the different current densities on the properti...The α-PbO2 electrodes are prepared by anodic electrodeposition on Al/conductive coating electrode from alkaline plumbite solutions in order to investigate the effect of the different current densities on the properties of α-PbO2 electrodes. The physic- ochemical properties of the α-PbO2 electrodes are analyzed by using SEM, EDS, XRD, Tafel plot, linear sweep voltammetry （LSV） and A.C. impedance. A compact and uniform layer of lead dioxide ：）vas obtained at the current density of 3 mA.cm-2. A further increase in current density results in smaller particles with high porosity. EDS and XRD analyses have shown that the PbO2 deposited in alkaline conditions is highly non stoichiometric, and the PbO impurities are formed on the surface layer besides the α-PbO2. The corrosion resistance of α-PbO2 at the low current density is superior to that of the high current density. It can be attributed to a porous layer of deposited films at high current densities in aqueous Zn2＋ 50 g·L^-1, H2SO4 150 When used as anodes for oxygen evolution g·L^-1, the Al/conductive coating/α-PbO2 exhibits lower potential compared to Pb electrode. Al/conductive coating/α-PbO2 electrode with the best electrocatalytic activity was obtained at current density of 1 mA·cm^-2. The lowest roughnest factor was obtained at 1 mA·cm^-2.展开更多
Earth-abundant electrocatalysts for large-current-density water splitting under alkaline condition are desirable.Oxygen evolution reaction,which is a bottleneck of the overall water splitting,faces the problems of com...Earth-abundant electrocatalysts for large-current-density water splitting under alkaline condition are desirable.Oxygen evolution reaction,which is a bottleneck of the overall water splitting,faces the problems of complicated reconstruction and deficiency in rational design of active sites.Herein,we report a series of transition metal chalcogenides for alkaline OER.Among them,FeCoNi(S)displayed a low overpotential of 293 m V to deliver a current density of 500 m A cm^(-2),which is in the top level of non-precious metal based OER electrocatalysts.A combination of(ex)in situ characterizations and DFT calculation shows that Ni(Fe,Co)trimetallic oxyhydroxides were the active sites for highly-efficient OER.Furthermore,for FeCoNi(S),when used as a bifunctional catalyst for water splitting,it only required a cell voltage of 1.84 V to deliver~500 m A cm^(-2) with extraordinary long-term stability over 2000 h.This work provides the comprehension of high-efficiency,robust catalysts for OER and overall water splitting at large current densities in alkaline media.展开更多
Objective Electrophysiological examination of the ipsilateral pretectotectal projection has proved that pretectal cells elicit strong suppressive responses to the ipsilateral tectum.However,the neural mechanisms under...Objective Electrophysiological examination of the ipsilateral pretectotectal projection has proved that pretectal cells elicit strong suppressive responses to the ipsilateral tectum.However,the neural mechanisms underlying the contralateral pretectotectal prejection are still obscure.The present study aimed to examine the synaptic nature of pretectal nuclei and contralateral tectal cells,and to demonstrate the spatiotemporal pattern of neuronal activity in the 2 main brain structures. Methods Intracellular recording and current source density（CSD）analysis were used to test the complexity of neuronal mechanism of pretectotectal information transfer.Results The pretectal stimulation elicited only one type of response on the contralateral tectum,the inhibitory postsynaptic potential（IPSP）.The majority of contra-induced IPSPs were assumed to be polysynaptically driven.In the CSD analysis,only one sink with short latency was observed in each profile.The ipsilateral projection produced a prominent monosynaptic sink in layer 8 of tectum.Recipient neurons were located in layers 6 and 7 of tectum.The result confirmed former findings from ipsilateral intracellular recordings.Conclusion These results suggest the following neuronal circuit：afferents from the pretectal nuclei broadly inhibit both tectal neuron,and since no second sink occurs in tectal layers,the pretectotectal excitatory afferents probably do not extend over the whole tectum,but are within limited state.The results of intracellular recording and CSD analysis further provide evidence of how pretectal afferent activity flows within the tectal laminae.展开更多
基金This study was supported by the Youth Ocean Sience Funds of State Oceanic Administration under contract No. 97301.
文摘The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly monsoon in summer induces a clockwise circulation in the Beibu Gulf, and the density gradient induces a counter-clockwise one; but the density current is more intense than the wind- driven one in summer, espeially in surface layer. In addition, the northeasterly monsoon in winter in- duces a counter-clockwise circulation. The simulated results don't support the traditional condusion that there is a clockwise circulation in the Beibu Gulf in summer and a counter-clockwise one in winter, but support the statement that a counterclockwise circulation exists in the Beibu Gulf all year round.
文摘In this paper, the characteristics of density current under the action of waves are described with the help of flume experiment and theoretical analysis. The study shows that turbid water under the action of the waves can present three types of motion, i. e. significant stratification, fragile stratification and strong mixing. The motion gf turbid;,ater presents significant stratification when (H/D)/root Delta rho/rho less than or equal to 4.5, generally this state is known as density current. The formulas of motion velocity, thickness, and discharge of density current moving on horizontal bottom are derived by use of basic equations such as momemtum equation, equation of energy conservation and continuity equation of fluid. The time-average velocity and the thickness of density current under the action of waves have a relationship with such parameters as relative density (Delta rho/rho), wave height (H), and water depth (D). When these parameters are determined, the time-average thickness and motion velocity of density current are also determined. The relative thickness of density current (D-t/D) decreases with the increase of Delta rho/rho and increases with the increase of H/D. On the other hand, the motion velocity of density current increases with the increase of Delta rho/rho and decreases with the increase of the relative thickness (D-t/D) of density current. It is shown that the calculated results are in agreement with those of the flume experiment.
基金sponsored by the National Natural Science Foundation of China(Nos.5210125 and 52375422)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069,B2020208083 and E202320801).
文摘The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.
基金supported by the National Natural Science Foundation of China(Nos.52305349,52305423 and 51635005)CGN-HIT Advanced Nuclear and New Energy Research Institute(No.CGN-HIT202305).
文摘Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.
基金supported by the National Natural Science Foundation of China(No.52101251)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069 and B2020208083).
文摘Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition.Herein,we present a freestanding lamellar nanoporous Ni-Co-Mn alloy electrode(Lnp-NCM)designed by a refined variant of the“dealloying-coarsening-dealloying”protocol for highly efficient bifunctional electrocatalyst,where large porous channels distribute on the surface and small porous channels at the interlayer.With its 3D lamellar architecture regulating,the electrocatalytic properties of the electrodes with different distances between lamellas are compared,and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites.Note that the optimized sample(Lnp-NCM4)is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm^(-2)for hydrogen and oxygen evolution reactions(HER and OER),respectively.During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode,it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm^(-2)with remarkable long-term stability over 50 h.This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.
基金partly supported by National Natural Science Foundation of China(Nos.52302464 and 52177128)supported by the Key Scientific Research Project for Institutions of Higher Education of Henan Province(No.22B140002).
文摘Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence of ultraviolet(UV)and electromagnetic wave radiation,the results indicate that the BAM target may undergo luminescent excitation due to collisions with electrons and ions.This led us to investigate the physical mechanism behind this plasma luminescence excitation phenomenon.A spectrometer was used to record the luminescent spectroscopy and peak light intensity.Under excitation by argon plasma,the BAM material emits a continuum spectrum from 400 nm to 550 nm,with the peak light intensity located at 462.58 nm,which is the same as the spectrum excited by UV torchlight.To identify the relationship between the plasma parameters and the luminescent intensity,Langmuir and Faraday probes were employed to determine the local plasma parameters such as electron density,electron temperature,and current density.After normalizing the peak light intensity to the plasma parameters,the most interesting point is that the current density is linearly correlated with the luminescent light intensity.To verify the repeatability and lifetime of the plasma-luminescence interaction,a 600 s lifetime test was conducted in a 200 W ICP discharge environment.The maximum difference for the peak light strength of the luminescent spectrum is 6.5%.From a voltage bias experiment and a theoretical derivation,we initially identified that bombardment by ions plays the dominant role in the luminescence excitation process,which also explains the mechanism by which the current density is proportional to the luminescence intensity.This new finding leads us to reconsider the possibility of applying this plasma luminescence phenomenon to optical plasma diagnostics.The BAM light intensity can potentially be used to predict the current density of a plasma beam for large-area two-dimensional(2D)measurements and can capture high spatial resolution in a single test.We believe that this method may lead to high-efficiency,spatially resolved plasma current density measurement.
基金supported by Multi-Year Research Grants from the University of Macao(MYRG-GRG2023-00010-IAPME,MYRG-GRG2024-00038-IAPME,MYRG2022-00026-IAPME)the Science and Technology Development Fund(FDCT)from Macao SAR(0023/2023/AFJ,0050/2023/RIB2,006/2022/ALC,0087/2024/AFJ,0111/2022/A2).
文摘Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance is often limited by charge carrier recombination,resulting in unsatisfactory saturation current densities.To address this challenge,we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper.The optimal photoanode(TCO/n-p-Si/TCO/Ni)shows a remarkably low onset potential of 0.92 V vs.a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm^(-2),which is about 92.7%of the theoretical maximum(42.7 mA·cm^(-2)).In addition,the photoanode demonstrates stable operation for 60 h.Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer,enhances catalytic performance,and provides corrosion protection to the underlying substrate.Notably,the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential.These findings provide a viable pathway for fabricating highperformance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.
基金financially supported by the Fundamental Research Funds for the Central Universities of Central South University(No.2022ZZTS0579).
文摘The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited a high formate Faradaic efficiency(FE)of 97.45%(-0.9 V)and a large partial current density of-45.82 mA/cm^(2)(-1.2 V).The good performance benefits from the reconstruction of BiVO_(4)to generate active metal Bi sites,which results in the electron redistribution to boost the OCHO∗formation.In flow cells,near industrial current density of 183.94 mA/cm^(2)was achieved,with the FE of formate above 95%from 20mA/cm^(2)to 180mA/cm^(2).Our work provides a facily synthesized BiVO_(4)precatalyst for CO_(2)electroreduction.
基金supported by the National Natural Science Foundation of China(Grant No.12304062)supported by the National Natural Science Foundation of China(Grant No.12074107)+1 种基金the Program of Outstanding Young and Middle-aged Scientific and Technological Innovation Teams of Colleges and Universities in Hubei Province(Grant No.T2020001)the Innovation Group Project of the Natural Science Foundation of Hubei Province of China(Grant No.2022CFA012)。
文摘A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate the equilibrium current density in a ribbon-shaped system within the AHE regime,consisting of two sets of counterpropagating channels arranged in a zebra stripes pattern.While the middle channels are susceptible to scattering,the edge channels remain relatively robust.Despite this difference,all channels exhibit the same differential current density when subjected to a differential voltage across the two ends of the ribbon.When a differential voltage is applied to both sides of the ribbon,it results in a snaking pattern of differential current density forming across it.Furthermore,in a four-terminal device comprising the ribbon and two normal leads,it is found that Hall conductance is independent of ribbon width within certain scattering strengths due to the differences in robustness between middle and edge channels.These findings disclose the details of the AHE transport in a finite-sized system under weak scattering.
基金supported by the Hunan Joint International Laboratory of Advanced Materials and Technology for Clean Energy(2020CB1007)Fundamental Research Funds for the Central Universities and Guangxi Key Laboratory of Information Materials and Guilin University of Electronic Technology,China(231002-K)+4 种基金Natural Science Foundation of Guangxi Zhuang Autonomous Region(2022GXNSFAA035467)Guangxi Science and Technology Program(Guike AD21220067)National Natural Science Foundation of China(22369002)Nationally Funded Postdoctoral Researcher Program(GZC20230756)China Postdoctoral Science Foundation(2024M750858)。
文摘Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures(denoted Co/Mo_(2)N)via ammonia-assisted reduction,which effectively modulating the HER performance.The optimized Co/Mo_(2)N-500,characterized by 3%tensile lattice strain,demonstrates exceptional HER activity with lower overpotentials of140 mV and 184 mV at high current density of 1000 mA cm^(-2)in alkaline freshwater and seawater electrolytes,respectively.Co/Mo_(2)N also exhibits excellent long-term durability even at a high current density of 300 mA cm^(-2),surpassing its counterparts and benchmark Pt/C catalyst.Density functional theory calculations validate that the tensile strain optimizes the d-band states,water dissociation,and hydrogen adsorption kinetics of the strained Mo_(2)N in Co/Mo_(2)N,thereby improving its catalytic efficacy.This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.
基金Projects(51004056,51004057)supported by the National Natural Science Foundation of ChinaProject(KKZ6201152009)supported by the Opening Foundation of Key Laboratory of Inorganic Coating Materials,Chinese Academy of Sciences+2 种基金Project(2010ZC052)supported by the Applied Basic Research Foundation of Yunnan Province,ChinaProject(20125314110011)supported by the Specialized Research Fund for the Doctoral Program of Higher Education,ChinaProject(2010247)supported by Analysis&Testing Foundation of Kunming University of Science and Technology,China
文摘Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique. The effects of current density on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated by energy dispersive X-ray spectroscopy（EDXS）, anode polarization curves, quasi-stationary polarization（Tafel） curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, and X-ray diffraction（XRD）. Results reveal that the composite electrode obtained at 1 A/dm2 possesses the lowest overpotential（0.610 V at 500 A/m2） for oxygen evolution, the best electrocatalytic activity, the longest service life（360 h at 40 °C in 150 g/L H2SO4 solution under 2 A/cm2）, and the lowest cell voltage（2.75 V at 500 A/m2）. Furthermore, with increasing current density, the coating exhibits grain growth and the decrease of content of Mn O2. Only a slight effect on crystalline structure is observed.
文摘AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer between GaAs layers, potential wells beside the two sides of barrier are deepened, resulting in an increase of the peak-to-valley current ratio （PVCR） and a peak current density. A special shape of collector is designed in order to reduce contact resistance and non-uniformity of the current;as a result the total chrrent density in the device is increased. The use of thin barriers is also helpful for the improvement of the PVCR and the peak current density in DBRTDs. The devices exhibit a maximum PVCR of 13.98 and a peak current density of 89kA/cm^2 at room temperature.
基金Project(20080505)supported by Science and Technology Department of Jilin Province,China
文摘Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.
基金supported by the National Natural Science Foundation of China(21872040)the Hundred Talents Program of Guangxi Universitiesthe Excellent Scholars and Innovation Team of Guangxi Universities。
文摘Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam(NiCo@C-NiCoMoO/NF)for water splitting.NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction(HER:39/266 mV;OER:260/390 mV)at±10 and±1000 mA cm^(−2).More importantly,in 6.0 M KOH solution at 60℃ for WE,it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h,exhibiting the potential for actual application.The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet,which not only increase the intrinsic activity and expose abundant catalytic activity sites,but also enhance its chemical and mechanical stability.This work thus could provide a promising material for industrial hydrogen production.
文摘M 2 tide and density residual currents in the Bohai Sea were examined using the Blumberg and Mellor 3D nonlinear numerical coastal circulation model incorporating Mellor and Yamada level 2.5 turbulent closure model. The tidal results showed good agreement with previous work. The model results indicated that the density residual currents are robust in summer; and that at the transition zone between well-mixed and stratified water, the horizontal velocity is high and the vertical velocity is positive.
基金supported by the National Natural Science Foundation of China (Grant 11572249)the Aerospace Technology Foundation (Grant N2014KC0068)the Aeronautical Science Foundation of China (Grant N2014KC0073)
文摘In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed void shapes: circular, ellipse, and cardioid. Void morphological evolution is governed by the competition between the electric field and surface capillary force. In the developed model, both the electric field and capillary force on the void's surface are solved analytically. Based on the mass conversation principle, the normal velocity on the void surface during diffusion is obtained. The void morphological evolution behavior is investigated, and a physical model is developed to predict void collapse to a crack or to split into sub-voids under electric current. It is noted that when the electric current is being applied from the horizontal direction, a circular void may either move stably along the electric current direction or collapse to a finger shape, depending on the relative magnitude of the electric current and surface capillary force. However, the elliptical-shaped void will elongate along the electric current direction and finally collapse to the finger shape. On the other hand, the cardioid-shaped void could bifurcate into two sub-voids when the electric current reaches a critical value. The theoretical predictions agree well with the experimental observations.
基金supported by the Author of National Excellent Doctoral Dissertation of China (No.20050053)Analysis and Measurement Research Fund(2007-21) of Kunming University of Science and Technology
文摘The α-PbO2 electrodes are prepared by anodic electrodeposition on Al/conductive coating electrode from alkaline plumbite solutions in order to investigate the effect of the different current densities on the properties of α-PbO2 electrodes. The physic- ochemical properties of the α-PbO2 electrodes are analyzed by using SEM, EDS, XRD, Tafel plot, linear sweep voltammetry （LSV） and A.C. impedance. A compact and uniform layer of lead dioxide ：）vas obtained at the current density of 3 mA.cm-2. A further increase in current density results in smaller particles with high porosity. EDS and XRD analyses have shown that the PbO2 deposited in alkaline conditions is highly non stoichiometric, and the PbO impurities are formed on the surface layer besides the α-PbO2. The corrosion resistance of α-PbO2 at the low current density is superior to that of the high current density. It can be attributed to a porous layer of deposited films at high current densities in aqueous Zn2＋ 50 g·L^-1, H2SO4 150 When used as anodes for oxygen evolution g·L^-1, the Al/conductive coating/α-PbO2 exhibits lower potential compared to Pb electrode. Al/conductive coating/α-PbO2 electrode with the best electrocatalytic activity was obtained at current density of 1 mA·cm^-2. The lowest roughnest factor was obtained at 1 mA·cm^-2.
基金the financial support from the Hunan Provincial Science and Technology Plan Project(No.2020JJ4710)the Hunan Key Laboratory of Two-Dimensional Materials(No.2018TP1010)+1 种基金the postdoctoral research funding plan in Central South University(No.140050022)the support from National Natural Science Foundation of China(No.12004439)。
文摘Earth-abundant electrocatalysts for large-current-density water splitting under alkaline condition are desirable.Oxygen evolution reaction,which is a bottleneck of the overall water splitting,faces the problems of complicated reconstruction and deficiency in rational design of active sites.Herein,we report a series of transition metal chalcogenides for alkaline OER.Among them,FeCoNi(S)displayed a low overpotential of 293 m V to deliver a current density of 500 m A cm^(-2),which is in the top level of non-precious metal based OER electrocatalysts.A combination of(ex)in situ characterizations and DFT calculation shows that Ni(Fe,Co)trimetallic oxyhydroxides were the active sites for highly-efficient OER.Furthermore,for FeCoNi(S),when used as a bifunctional catalyst for water splitting,it only required a cell voltage of 1.84 V to deliver~500 m A cm^(-2) with extraordinary long-term stability over 2000 h.This work provides the comprehension of high-efficiency,robust catalysts for OER and overall water splitting at large current densities in alkaline media.
基金supported by the 21st Century program,Committee of Education of Japan at the Kyushu Institute of Technology,and the Health Bureau of Shangdong Province,China
文摘Objective Electrophysiological examination of the ipsilateral pretectotectal projection has proved that pretectal cells elicit strong suppressive responses to the ipsilateral tectum.However,the neural mechanisms underlying the contralateral pretectotectal prejection are still obscure.The present study aimed to examine the synaptic nature of pretectal nuclei and contralateral tectal cells,and to demonstrate the spatiotemporal pattern of neuronal activity in the 2 main brain structures. Methods Intracellular recording and current source density（CSD）analysis were used to test the complexity of neuronal mechanism of pretectotectal information transfer.Results The pretectal stimulation elicited only one type of response on the contralateral tectum,the inhibitory postsynaptic potential（IPSP）.The majority of contra-induced IPSPs were assumed to be polysynaptically driven.In the CSD analysis,only one sink with short latency was observed in each profile.The ipsilateral projection produced a prominent monosynaptic sink in layer 8 of tectum.Recipient neurons were located in layers 6 and 7 of tectum.The result confirmed former findings from ipsilateral intracellular recordings.Conclusion These results suggest the following neuronal circuit：afferents from the pretectal nuclei broadly inhibit both tectal neuron,and since no second sink occurs in tectal layers,the pretectotectal excitatory afferents probably do not extend over the whole tectum,but are within limited state.The results of intracellular recording and CSD analysis further provide evidence of how pretectal afferent activity flows within the tectal laminae.
