In this paper we are interested in the large time behavior of the nonlinear diffusion equationWe consider functions which allow the equation to possess traveling wave solutions. We first present an existence and uniqu...In this paper we are interested in the large time behavior of the nonlinear diffusion equationWe consider functions which allow the equation to possess traveling wave solutions. We first present an existence and uniqueness as well as some comparison principle result of generalized solutions to the Cauchy problem. Then we give for some threshold results, from which we can see that u=a is stable, while u= 0 or u=1 is unstable under some assumptions, etc.展开更多
The solid solution characteristics of Pb（B1/3Nb2/3）O3-based （B=Zn^2＋, Mg^2＋, Ni^2＋） composite ceramics prepared by two-phase mixed-sintering method were developed based on dielectric measurements. Results show ...The solid solution characteristics of Pb（B1/3Nb2/3）O3-based （B=Zn^2＋, Mg^2＋, Ni^2＋） composite ceramics prepared by two-phase mixed-sintering method were developed based on dielectric measurements. Results show that there are double dielectric peaks for PZN-based composite ceramic, implying two phases coexist. However single dielectric peak was presented in PMN- and PNN-based composite ceramics, respectively. It is indicated that obvious solid solution reaction exists during the sintering process of these two systems. The effects of B-site ion difference on the solid solution characteristics were discussed by crystal chemistry. SEM was employed to investigated the microstructures of composite ceramics. The influences of solid solution reaction on grain growth were discussed.展开更多
In this paper we consider the initial-boundary value problems for a class ofapplications, such as biomathematics and biochemistry.Applying the method ofcomposile expansion we construct the formally asymptotic solution...In this paper we consider the initial-boundary value problems for a class ofapplications, such as biomathematics and biochemistry.Applying the method ofcomposile expansion we construct the formally asymptotic solution of the problemdescribed. With the help of theory of upper and lower solutions we prove the uniformlyvalidity of the formal solution and the existence of solution of the original problem.展开更多
This study deals with the stagnation point flow of ferrofluid over a flat plate with non-linear slip boundary condition in the presence of homogeneous-heterogeneous reactions.Three kinds of ferroparticles,namely,magne...This study deals with the stagnation point flow of ferrofluid over a flat plate with non-linear slip boundary condition in the presence of homogeneous-heterogeneous reactions.Three kinds of ferroparticles,namely,magnetite(Fe_3O_4),cobalt ferrite(CoFe_2O_4) and manganese zinc ferrite(Mn-ZnFe_2O_4) are taken into account with water and kerosene as conventional base fluids.The developed model of homogeneous-heterogeneous reactions in boundary layer flow with equal and unequal diffusivities for reactant and autocatalysis is considered.The governing partial differential equations are converted into system of non-linear ordinary differential equations by mean of similarity transformations.These ordinary differential equations are integrated numerically using shooting method.The effects of pertinent parameters on velocity and concentration profiles are presented graphically and discussed.We found that in the presence of Fe_3O_4-kerosene and CoFe_2O_4-kerosene,velocity profiles increase for large values of α and β whereas there is a decrement in concentration profiles with increasing values of if and K_s.Furthermore,the comparison between non-magnetic(A1_2O_3) and magnetic Fe_3O_4 nanoparticles is given in tabular form.展开更多
The microstructure of coke has an important influence on its thermal properties.The solution loss reactions of coke in CO2 and H2O atmospheres were investigated by in situ observation.The results showed that the isotr...The microstructure of coke has an important influence on its thermal properties.The solution loss reactions of coke in CO2 and H2O atmospheres were investigated by in situ observation.The results showed that the isotropic components had a more vigorous reaction than the anisotropic components,and the solution loss reaction of the fine-grained mosaic structure was faster than that of the coarse-grained mosaic structure under the CO2 and H2O atmospheres.The coarse-grained mosaic structure and the flowing structure had a relatively higher anti-erosion ability in the CO2 atmosphere than in the H2O atmosphere,and there was no distinct difference in the solution loss of the isotropic structure under the CO2 and H2O atmospheres.The electron probe microanalysis showed that the Al-Si-Fe compounds in the carbon matrix had positive influence on the solution loss reaction of the anisotropic structure.The iron compounds were able to destroy the pore walls of coke and accelerate the solution loss rate of coke.展开更多
IN the process of forecasts, analyses and numerical treatments of the ground water resource, we often meet with various chemical reaction models. One type of them is three kinds of chemical substance M<sub>1<...IN the process of forecasts, analyses and numerical treatments of the ground water resource, we often meet with various chemical reaction models. One type of them is three kinds of chemical substance M<sub>1</sub>, M<sub>2</sub> and M<sub>3</sub> which can react with each other to produce two new kinds of other chemical compounds: （M<sub>2</sub>）<sub>n</sub> （M<sub>1</sub>）<sub>m</sub> and （M<sub>3</sub>）<sub>r</sub> （M<sub>1</sub>）<sub>κ</sub> at the same time. Usually, these reactions are irreversible and they have the following forms:展开更多
By using a 2D-coupled flow and solute transport and reaction model across the stream-to-riparian continuum,this paper systematically studied the nitrogen-cycling processes driven by a flood wave and their spatial-temp...By using a 2D-coupled flow and solute transport and reaction model across the stream-to-riparian continuum,this paper systematically studied the nitrogen-cycling processes driven by a flood wave and their spatial-temporal distributions.The influences on hyporheic nitrogen removal of different waves that vary by amplitude(A),duration(T),wave-type parameter(r)and rising duration(t_(p))were investigated.展开更多
Layered metal oxides are promising cathode materials for sodium-ion batteries(SIBs)due to their high theoretical specific capacity and wide Na^(+)diffusion channels.However,the irreversible phase transitions and catio...Layered metal oxides are promising cathode materials for sodium-ion batteries(SIBs)due to their high theoretical specific capacity and wide Na^(+)diffusion channels.However,the irreversible phase transitions and cationic/anionic redoxes cause fast capacity decay.Herein,P2-type Na_(0.67)Mg_(0.1)Mn_(0.8)Fe_(0.1)O_(2)(NMMF-1)cathode material with moderate active Fe^(3+)doping has been designed for sodium storage.Uneven Mn^(3+)/Mn^(4+)distribution is observed in NMMF-1 and the introduction of Fe^(3+)is beneficial for reducing the Mn^(3+)contents both at the surface and in the bulk to allevi-ate the Jahn-Teller effect.The moderate Fe^(3+)/Fe^(4+)redox can realize the best tradeoff between capacity and cycla-bility.Therefore,the NMMF-1 demonstrates a high capacity(174.7 mAh g^(-1)at 20 mA g^(-1))and improved cyclability(78.5%over 100 cycles)in a wide-voltage range of 1.5-4.5 V(vs.Na^(+)/Na).In-situ X-ray diffraction reveals a complete solid-solution reaction with a small volume change of 1.7%during charge/discharge processes and the charge com-pensation is disclosed in detail.This study will provide new insights into designing high-capacity and stable layered oxide cathode materials for SIBs.展开更多
Chirai sodium zincophosphate nanocrystalline has been prepared and characterized. The standard molar enthaipy of the following reaction 12Na3PO4·12H2O（s）＋ 12ZnSO4·7H2O（s）= Na12（Zn12P12O48）·12H2O...Chirai sodium zincophosphate nanocrystalline has been prepared and characterized. The standard molar enthaipy of the following reaction 12Na3PO4·12H2O（s）＋ 12ZnSO4·7H2O（s）= Na12（Zn12P12O48）·12H2O（s）＋ 12Na2SO4（s）＋216H2O（1） was determined by solution reaction calorimetric at 298.15 K, and calculated to be 33.666±0.195 kl/mol. From the results and other auxiliary quantities, the standard enthalpy of formation for sodium zincophosphate nanocrystalline was derived to be △fHm^⊙ [Na12（Zn12P12O48）·12H2O（s）, 298.15 K] =- 24268.494 ± 0.815 kJ/mol.展开更多
A carbon-coated K_(0.76)V_(0.55)Nb_(0.45)OPO_(4)(KVNP@C)polyanion material was successfully synthesized by a simple sol-gel method.The KVNP@C possesses a highly stable inorganic open-framework structure,which is hard ...A carbon-coated K_(0.76)V_(0.55)Nb_(0.45)OPO_(4)(KVNP@C)polyanion material was successfully synthesized by a simple sol-gel method.The KVNP@C possesses a highly stable inorganic open-framework structure,which is hard to be affected by the Na^(+) intercalation/deintercalation when used as an anode material for sodium-ion batteries(NIBs).The assembled KVNP@C/Na half-cell shows a capacity retention of 81.2%and an average Coulombic efficiency of 99.8%at a current density of 300 mA/g after 1500 cycles.In-situ XRD analysis reveals a single-phase solid solution reaction mechanism with a lattice expansion of 4.76%.This work sheds insights into the quest for developing novel polyanion-based anode materials for sodium-ion batteries.展开更多
文摘In this paper we are interested in the large time behavior of the nonlinear diffusion equationWe consider functions which allow the equation to possess traveling wave solutions. We first present an existence and uniqueness as well as some comparison principle result of generalized solutions to the Cauchy problem. Then we give for some threshold results, from which we can see that u=a is stable, while u= 0 or u=1 is unstable under some assumptions, etc.
基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry(2005)
文摘The solid solution characteristics of Pb（B1/3Nb2/3）O3-based （B=Zn^2＋, Mg^2＋, Ni^2＋） composite ceramics prepared by two-phase mixed-sintering method were developed based on dielectric measurements. Results show that there are double dielectric peaks for PZN-based composite ceramic, implying two phases coexist. However single dielectric peak was presented in PMN- and PNN-based composite ceramics, respectively. It is indicated that obvious solid solution reaction exists during the sintering process of these two systems. The effects of B-site ion difference on the solid solution characteristics were discussed by crystal chemistry. SEM was employed to investigated the microstructures of composite ceramics. The influences of solid solution reaction on grain growth were discussed.
文摘In this paper we consider the initial-boundary value problems for a class ofapplications, such as biomathematics and biochemistry.Applying the method ofcomposile expansion we construct the formally asymptotic solution of the problemdescribed. With the help of theory of upper and lower solutions we prove the uniformlyvalidity of the formal solution and the existence of solution of the original problem.
文摘This study deals with the stagnation point flow of ferrofluid over a flat plate with non-linear slip boundary condition in the presence of homogeneous-heterogeneous reactions.Three kinds of ferroparticles,namely,magnetite(Fe_3O_4),cobalt ferrite(CoFe_2O_4) and manganese zinc ferrite(Mn-ZnFe_2O_4) are taken into account with water and kerosene as conventional base fluids.The developed model of homogeneous-heterogeneous reactions in boundary layer flow with equal and unequal diffusivities for reactant and autocatalysis is considered.The governing partial differential equations are converted into system of non-linear ordinary differential equations by mean of similarity transformations.These ordinary differential equations are integrated numerically using shooting method.The effects of pertinent parameters on velocity and concentration profiles are presented graphically and discussed.We found that in the presence of Fe_3O_4-kerosene and CoFe_2O_4-kerosene,velocity profiles increase for large values of α and β whereas there is a decrement in concentration profiles with increasing values of if and K_s.Furthermore,the comparison between non-magnetic(A1_2O_3) and magnetic Fe_3O_4 nanoparticles is given in tabular form.
基金This study was conducted with financial support from the National Natural Science Foundation of China(No.51574023).
文摘The microstructure of coke has an important influence on its thermal properties.The solution loss reactions of coke in CO2 and H2O atmospheres were investigated by in situ observation.The results showed that the isotropic components had a more vigorous reaction than the anisotropic components,and the solution loss reaction of the fine-grained mosaic structure was faster than that of the coarse-grained mosaic structure under the CO2 and H2O atmospheres.The coarse-grained mosaic structure and the flowing structure had a relatively higher anti-erosion ability in the CO2 atmosphere than in the H2O atmosphere,and there was no distinct difference in the solution loss of the isotropic structure under the CO2 and H2O atmospheres.The electron probe microanalysis showed that the Al-Si-Fe compounds in the carbon matrix had positive influence on the solution loss reaction of the anisotropic structure.The iron compounds were able to destroy the pore walls of coke and accelerate the solution loss rate of coke.
文摘IN the process of forecasts, analyses and numerical treatments of the ground water resource, we often meet with various chemical reaction models. One type of them is three kinds of chemical substance M<sub>1</sub>, M<sub>2</sub> and M<sub>3</sub> which can react with each other to produce two new kinds of other chemical compounds: （M<sub>2</sub>）<sub>n</sub> （M<sub>1</sub>）<sub>m</sub> and （M<sub>3</sub>）<sub>r</sub> （M<sub>1</sub>）<sub>κ</sub> at the same time. Usually, these reactions are irreversible and they have the following forms:
基金supported by the National Research Foundation of Korea(NRF),funded by the Korea government(MSIT)(No.NRF-2015R1A4A1041105)partly funded by the key project of Nanjing Hydraulic Research Institute(NHRI)(No.Y919005).
文摘By using a 2D-coupled flow and solute transport and reaction model across the stream-to-riparian continuum,this paper systematically studied the nitrogen-cycling processes driven by a flood wave and their spatial-temporal distributions.The influences on hyporheic nitrogen removal of different waves that vary by amplitude(A),duration(T),wave-type parameter(r)and rising duration(t_(p))were investigated.
基金supported by the National Natural Science Foundation of China(U23A20684)Independent Innovation Project of Hubei Longzhong Laboratory(2022ZZ-18).
文摘Layered metal oxides are promising cathode materials for sodium-ion batteries(SIBs)due to their high theoretical specific capacity and wide Na^(+)diffusion channels.However,the irreversible phase transitions and cationic/anionic redoxes cause fast capacity decay.Herein,P2-type Na_(0.67)Mg_(0.1)Mn_(0.8)Fe_(0.1)O_(2)(NMMF-1)cathode material with moderate active Fe^(3+)doping has been designed for sodium storage.Uneven Mn^(3+)/Mn^(4+)distribution is observed in NMMF-1 and the introduction of Fe^(3+)is beneficial for reducing the Mn^(3+)contents both at the surface and in the bulk to allevi-ate the Jahn-Teller effect.The moderate Fe^(3+)/Fe^(4+)redox can realize the best tradeoff between capacity and cycla-bility.Therefore,the NMMF-1 demonstrates a high capacity(174.7 mAh g^(-1)at 20 mA g^(-1))and improved cyclability(78.5%over 100 cycles)in a wide-voltage range of 1.5-4.5 V(vs.Na^(+)/Na).In-situ X-ray diffraction reveals a complete solid-solution reaction with a small volume change of 1.7%during charge/discharge processes and the charge com-pensation is disclosed in detail.This study will provide new insights into designing high-capacity and stable layered oxide cathode materials for SIBs.
文摘Chirai sodium zincophosphate nanocrystalline has been prepared and characterized. The standard molar enthaipy of the following reaction 12Na3PO4·12H2O（s）＋ 12ZnSO4·7H2O（s）= Na12（Zn12P12O48）·12H2O（s）＋ 12Na2SO4（s）＋216H2O（1） was determined by solution reaction calorimetric at 298.15 K, and calculated to be 33.666±0.195 kl/mol. From the results and other auxiliary quantities, the standard enthalpy of formation for sodium zincophosphate nanocrystalline was derived to be △fHm^⊙ [Na12（Zn12P12O48）·12H2O（s）, 298.15 K] =- 24268.494 ± 0.815 kJ/mol.
基金This project was supported by the National Natural Science Foundation of China(No.21771180)。
文摘A carbon-coated K_(0.76)V_(0.55)Nb_(0.45)OPO_(4)(KVNP@C)polyanion material was successfully synthesized by a simple sol-gel method.The KVNP@C possesses a highly stable inorganic open-framework structure,which is hard to be affected by the Na^(+) intercalation/deintercalation when used as an anode material for sodium-ion batteries(NIBs).The assembled KVNP@C/Na half-cell shows a capacity retention of 81.2%and an average Coulombic efficiency of 99.8%at a current density of 300 mA/g after 1500 cycles.In-situ XRD analysis reveals a single-phase solid solution reaction mechanism with a lattice expansion of 4.76%.This work sheds insights into the quest for developing novel polyanion-based anode materials for sodium-ion batteries.
