Effects of citrate concentration and pH on the electrochemical reduction process of Co(Ⅱ) were investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). The results show that Co(...Effects of citrate concentration and pH on the electrochemical reduction process of Co(Ⅱ) were investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). The results show that Co(Ⅱ) is reduced into two species which are free Co2+ and [Co(C6H607)] in the solution composed of 0.05 mol/L CoS04·5H2O, 0.20 mol/L Na2SO4 and 0-0.40 mol/L C6H5O7Na3·2H2O in the pH range of 3-9. The reduction behavior depends on the pH of the solution. Co(H) is mainly reduced into the form of free Co^2+ at pH 3 and into the form of [Co(C6H6O7)] at the pH range of 4-6 in citrate solution. The [Co(C6H6O7)] is first reduced to an intermediate state and then to Co°. Adsorption of the intermediate state exists on the surface of the electrode. Co(Ⅱ) is difficult to be reduced in the solution with the pH above 7, because the existing Co(Ⅱ)-citrate complex species [Co(C6H5O7)]- and [Co(C6H4O7)]2- are more difficult to be reduced than the hydrogen ion.展开更多
With using the cone and partial ordering t heory and mixed monotone operator theory, the existence and uniqueness for solut ion of systems of non-monotone binary nonliear operator equations are discussed. And the it...With using the cone and partial ordering t heory and mixed monotone operator theory, the existence and uniqueness for solut ion of systems of non-monotone binary nonliear operator equations are discussed. And the iterative sequences which converge to solution of systems of operator e quations and the error estimates are also given. Some corresponding results for the mixed monotone operations and the unary operator equations are improved and generalized.展开更多
By using the theory of the cone and partial ordering. It is studied that the existence and uniqueness of solutions for a non-monotone binary operator equation A(x, x)= x and operator system of equations A(x,x)=x,B(x,x...By using the theory of the cone and partial ordering. It is studied that the existence and uniqueness of solutions for a non-monotone binary operator equation A(x, x)= x and operator system of equations A(x,x)=x,B(x,x)=x in Banach spaces. Where A and B can be decomposed A=A1+A2, B=B1+B2,A1 and B1 are mixed monotone, A2 and B2 are anti-mixed monotone. The results presented here improve and generalize some corresponding results of mixed monotone operator equations.展开更多
To advance hierarchical equations of motion as a standard theory for quantum dissipative dynamics, we put forward a mixed Heisenberg-SchrSdinger scheme with block-matrix implementation on efficient evaluation of nonli...To advance hierarchical equations of motion as a standard theory for quantum dissipative dynamics, we put forward a mixed Heisenberg-SchrSdinger scheme with block-matrix implementation on efficient evaluation of nonlinear optical response function. The new approach is also integrated with optimized hierarchical theory and numerical filtering algorithm. Different configurations of coherent two-dimensional spectroscopy of model excitonic dimer systems are investigated, with focusing on the effects of intermolecular transfer coupling and bi-exciton interaction.展开更多
Using the cone and partial ordering theory and mixed monotone operator theory, the existence and uniqueness of solutions for some classes of systems of nonlinear two binary operator equations in a Banach space with a ...Using the cone and partial ordering theory and mixed monotone operator theory, the existence and uniqueness of solutions for some classes of systems of nonlinear two binary operator equations in a Banach space with a partial ordering are discussed. And the error estimates that the iterative sequences converge to solutions are also given. Some relevant results of solvability of two binary operator equations and systems of operator equations are improved and generalized.展开更多
This article introduces a new chaotic system of three-dimensional quadratic autonomous ordinary differential equations, which can display different attractors with two unstable equilibrium points and four unstable equ...This article introduces a new chaotic system of three-dimensional quadratic autonomous ordinary differential equations, which can display different attractors with two unstable equilibrium points and four unstable equilibrium points respectively. Dynamical properties of this system are then studied. Furthermore, by applying the undetermined coefficient method, heteroclinic orbit of Shil'nikov's type in this system is found and the convergence of the series expansions of this heteroclinic orbit are proved in this article. The Shil'nikov's theorem guarantees that this system has Smale horseshoes and the horseshoe chaos.展开更多
Some new structures and interactions of solitons for the (2+1)-dimensional Nizhnik-Novikov-Veselov equation are revealed with the help of the idea of the bilinear method and variable separation approach. The soluti...Some new structures and interactions of solitons for the (2+1)-dimensional Nizhnik-Novikov-Veselov equation are revealed with the help of the idea of the bilinear method and variable separation approach. The solutions to describe the interactions between two dromions, between a line soliton and a y-periodic soliton, and between two y-periodic solitons are included in our results. Detailed behaviors of interaction are illustrated both analytically and in graphically. Our analysis shows that the interaction properties between two solitons are related to the form of interaction constant. The form of interaction constant and the dispersion relationship are related to the form of the seed solution (u0, v0, w0 ) in Backlund transformation.展开更多
A two-dimensional generalized Langevin equation is proposed to describe the protein conformational change, compatible to the electron transfer process governed by atomic packing density model. We assume a fractional G...A two-dimensional generalized Langevin equation is proposed to describe the protein conformational change, compatible to the electron transfer process governed by atomic packing density model. We assume a fractional Gaussian noise and a white noise through bond and through space coordinates respectively, and introduce the coupling effect coming from both fluctuations and equilibrium variances. The general expressions for autocorrelation functions of distance fluctuation and fluorescence lifetime variation are derived, based on which the exact conformational change dynamics can be evaluated with the aid of numerical Laplace inversion technique. We explicitly elaborate the short time and long time approximations. The relationship between the two-diraensional description and the one-dimensional theory is also discussed.展开更多
The resonant tunneling diode (RTD) is a kind of novel ultra-high speed and ultra-high frequency negative differential resistance nanoelectronic device. Integration of RTD and other three-terminal compound semiconducto...The resonant tunneling diode (RTD) is a kind of novel ultra-high speed and ultra-high frequency negative differential resistance nanoelectronic device. Integration of RTD and other three-terminal compound semiconductor devices is one important direction of high speed integrated circuit development. In this paper, monolithic integration technology of RTD and high electron mobility transistor (HEMT) based on GaAs substrate was discussed. A top-RTD and bottom-HEMT material structure was proposed and epitaxyed. Based on wet chemical etching, electron beam lithography, metal lift-off and air bridge technology, RTD and HEMT were fabricated on the same wafer. The peak-to-valley current ratio of RTD is 4 and the peak voltage is 0.5 V. The maximal transconductance is 120 mS/mm for a 0.25 μm gate length depletion mode HEMT. Current levels of two devices are basically suited. The results validate the feasibility of the designed integration process.展开更多
The applicability of the density rule of Pathwardhan and Kumer and the rule based on the linear isopiestic relation is studied by comparison with experimental density data in the literature. Predicted and measured val...The applicability of the density rule of Pathwardhan and Kumer and the rule based on the linear isopiestic relation is studied by comparison with experimental density data in the literature. Predicted and measured values for 18 electrolyte mixtures are compared. The two rules are good for mixtures with and without common ions, including those containing associating ions. The deviations of the rule based on the linear isopiestic relation are slightly higher for the mixtures involving very strong ion complexes, but the predictions are still quite satisfactory.The density rule of Pathwardhan and Kumer is more accurate for these mixtures. However, it is not applicable for mixtures containing non-electrolytes. The rule based on the linear isopiestic relation is extended to mixtures involving non-electrolytes. The predictions for the mixtures containing both electrolytes and non-electrolytes and the non-electrolyte mixtures are accurate. All these results indicate that this rule is a widely applicable approach.展开更多
In this paper two kinds of two-boson realizations of generally deformed algebras with three generators are obtained by generalizing the Jordan-Schwlnger realizations of SU(2) and SU(1,1). For each kind, a unitary ...In this paper two kinds of two-boson realizations of generally deformed algebras with three generators are obtained by generalizing the Jordan-Schwlnger realizations of SU(2) and SU(1,1). For each kind, a unitary realization and a non-unitary realizatlon, together with the properties of their acting spaces, are discussed. Similarity transformations that relate the non-unitary realizations to the unitary ones are given by solving unitarization equations.展开更多
The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by...The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by BET, XRD (X-ray diffraction), TPR (temperature programmed reduction), IR (infra-red adsorption), NH 3-TPD (temperature programmed desorption) and CO 2-TPD (temperature programmed desorption) techniques. The results showed that the surface area of catalysts decreased with increasing metal content, and the metals as well as Cu-Ni alloy co-existed on the reduced catalyst surface. There existed interaction between metal and carrier, and moreover, metal particles affected obviously the acidity and basicity of carrier. The large amount of basic sites facilitated the activation of methanol to methoxyl species and their subsequent reaction with activated carbon dioxide. The catalysts were evaluated in a continuous tubular fixed-bed micro-gaseous reactor and the catalyst with bimetal loading of 20% (by mass) had best catalytic activities. Under the conditions of 393 K, 1.1 MPa, 5 h and gas space velocity of 510 h 1 , the selectivity and yield of DMC were higher than 86.0 % and 5.0 %, respectively.展开更多
Alkanolamines are widely used in the purification of the sourgas sweetening process. During the sour gas absorption process, CO_2 significantly degrades the amine solvent and creates enormous problems for plant operat...Alkanolamines are widely used in the purification of the sourgas sweetening process. During the sour gas absorption process, CO_2 significantly degrades the amine solvent and creates enormous problems for plant operation. In this work, CO_2 induced degradation of aqueous diethanolamine(DEA) solution was conducted in a 1.25 L jacketed glass reactor that functioned as an absorber and stripper at atmospheric conditions. Pure CO_2 was bubbled through the reactor until the solution became saturated. In this study, the concentrations of DEA used were in the range of concentrations between 2 mol·L^(-1) and 4 mol·L^(-1). In the degradation experiment, six generic cycles were conducted for each run. Each cycle was configured with the absorption and desorption of carbon dioxide at 55 ℃ and 100 ℃, respectively. Samples were collected after a predetermined experimental time and analyzed by ion chromatography(IC) to identify unknown ionic degradation products(DGPs). In the IC analysis, three different columns were used for anion, cation and ion exclusion systems, which are Metrosep A Supp 5150/4.0, Metrosep C Supp 4 150/4.0 and Metrosep Organic Acids, respectively. The major identified DGPs of D01 DEA2 M, D02 DEA3 M, and D03 DEA4 M are nitrite, acetate and ammonium. Phosphate product was found in the degraded amine samples which might be due to the contamination of water or chromatographic system.展开更多
In order to investigate the rules on formation of zeolite during crystallization of titanium silicalite zeolite (TS-1) the X-ray diffractometry and Foulier transform infra-red spectrometry were applied to track the pr...In order to investigate the rules on formation of zeolite during crystallization of titanium silicalite zeolite (TS-1) the X-ray diffractometry and Foulier transform infra-red spectrometry were applied to track the process of crystallization of titanium silicalite zeolite. The research results revealed that at the initial stage of crystallization the interactions between silica gel and titania gel in the polymer blend could gradually lead to the formation of tiny crystal nuclei with complicated structure that could slowly grow up to form molecular sieves. Quite different from the conventional zeolites that use the acid sites as the catalytically active centers, the oxidative reactivity of the titanium silicalite zeolite was not proportional to its crystallinity and is associated with the oxidative centers of titanium contained in the zeolite.展开更多
Two different models for the evolution of incompressible binary fluid mixtures in a three-dimensional bounded domain are considered.They consist of the 3D incompressible Navier-Stokes equations,subject to time-depende...Two different models for the evolution of incompressible binary fluid mixtures in a three-dimensional bounded domain are considered.They consist of the 3D incompressible Navier-Stokes equations,subject to time-dependent external forces and coupled with either a convective Allen-Cahn or Cahn-Hilliard equation.Such systems can be viewed as generalizations of the Navier-Stokes equations to two-phase fluids.Using the trajectory approach,the authors prove the existence of the trajectory attractor for both systems.展开更多
We study two-dimensional massive Dirac equation in circular well potential. The energies of bound states are obtained. We demonstrate the Klein paradox of this relativistic wave equation:For large enough potential dep...We study two-dimensional massive Dirac equation in circular well potential. The energies of bound states are obtained. We demonstrate the Klein paradox of this relativistic wave equation:For large enough potential depth, the bound states disappear from the spectra. Applications to graphene systems are discussed.展开更多
Based on the rapid genetic algorithm(RGA),the band gap structures of square lattices with square scatters are optimized.In the optimizing process,gene codes are used to express square scatters and the fitting function...Based on the rapid genetic algorithm(RGA),the band gap structures of square lattices with square scatters are optimized.In the optimizing process,gene codes are used to express square scatters and the fitting function adopts the relative values of the largest absolute photonic band gaps(PBGs).By changing the value of filling factor,three cell forms with large photonic band gaps are obtained.In addition,the comparison between the rapid genetic algorithm and the general genetic algorithm(GGA) is analyzed.展开更多
An accurate knowledge about phase behaviors of CH4, CO2 and their binary mixture is crucial in fields of natural gas liquefaction and refrigeration applications. In this work, two all-atom force fields of TraPPE-EH an...An accurate knowledge about phase behaviors of CH4, CO2 and their binary mixture is crucial in fields of natural gas liquefaction and refrigeration applications. In this work, two all-atom force fields of TraPPE-EH and EMP2 were used for the components CH4 and CO〉 respectively. Then the vapor-liquid equilibria (VLE) of CH4, CO2 and their binary system were calculated via the NVT- and NpT Gibbs Ensemble Monte Carlo Simulations. Meanwhile the traditional method using Equation of State (EoS) to correlate the VLE properties was also investigated. The EoSs considered in this work were three classic cubic RK, SRK, PR and another advanced molecular-based PC-SAFT equations. For pure components, both molecular simulations and the PC-SAFT EoS could obtain satisfactory predictions for all the saturated properties. However, the saturated liquid densities calculated by the cubic EoSs were not so good. It was also observed that the TraPPE-EH force field had a good representation for CH4 molecule, while the EMP2 force field was not enough accurate to represent CO2 molecules. For the mixture CH4 + CO2, SRK and PR showed the best predictions for the saturated pressure-component property, while good results were also obtained via molecular simulations and PC-SAFT EoS. It was suggested that special combining rules or binary interaction parameters were important to obtain enough accurate prediction of the mixed phase behavior. Compared with the cubic EoS, the PC-SAFT and molecular simulation method showed better adaptabilities for both the pure and mixture systems. Besides, the accurate molecular parameters used in the PC-SAFT and molecular simulations could bring about direct and deep understanding about the molecular characteristics.展开更多
The determination of initial equilibrium shapes is a common problem in research work and engineering applications related to membrane structures. Using a general structural analysis framework of the finite particle me...The determination of initial equilibrium shapes is a common problem in research work and engineering applications related to membrane structures. Using a general structural analysis framework of the finite particle method (FPM), this paper presents the first application of the FPM and a recently-developed membrane model to the shape analysis of light weight mem- branes. The FPM is rooted in vector mechanics and physical viewpoints. It discretizes the analyzed domain into a group of parti- cles linked by elements, and the motion of the free particles is directly described by Newton's second law while the constrained ones follow the prescribed paths. An efficient physical modeling procedure of handling geometric nonlinearity has been developed to evaluate the particle interaction forces. To achieve the equilibrium shape as fast as possible, an integral-form, explicit time integration scheme has been proposed for solving the equation of motion. The equilibrium shape can be obtained naturally without nonlinear iterative correction and global stiffness matrix integration. Two classical curved surfaces of tension membranes pro- duced under the uniform-stress condition are presented to verify the accuracy and efficiency of the proposed method.展开更多
基金Project(200800560002)supported by the Ph.D.Programs Foundation of Ministry of Education of China
文摘Effects of citrate concentration and pH on the electrochemical reduction process of Co(Ⅱ) were investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS). The results show that Co(Ⅱ) is reduced into two species which are free Co2+ and [Co(C6H607)] in the solution composed of 0.05 mol/L CoS04·5H2O, 0.20 mol/L Na2SO4 and 0-0.40 mol/L C6H5O7Na3·2H2O in the pH range of 3-9. The reduction behavior depends on the pH of the solution. Co(H) is mainly reduced into the form of free Co^2+ at pH 3 and into the form of [Co(C6H6O7)] at the pH range of 4-6 in citrate solution. The [Co(C6H6O7)] is first reduced to an intermediate state and then to Co°. Adsorption of the intermediate state exists on the surface of the electrode. Co(Ⅱ) is difficult to be reduced in the solution with the pH above 7, because the existing Co(Ⅱ)-citrate complex species [Co(C6H5O7)]- and [Co(C6H4O7)]2- are more difficult to be reduced than the hydrogen ion.
文摘With using the cone and partial ordering t heory and mixed monotone operator theory, the existence and uniqueness for solut ion of systems of non-monotone binary nonliear operator equations are discussed. And the iterative sequences which converge to solution of systems of operator e quations and the error estimates are also given. Some corresponding results for the mixed monotone operations and the unary operator equations are improved and generalized.
基金Supported by the Scientific Research Foundation of Henan Provincial Education Com mittee(1999110018)
文摘By using the theory of the cone and partial ordering. It is studied that the existence and uniqueness of solutions for a non-monotone binary operator equation A(x, x)= x and operator system of equations A(x,x)=x,B(x,x)=x in Banach spaces. Where A and B can be decomposed A=A1+A2, B=B1+B2,A1 and B1 are mixed monotone, A2 and B2 are anti-mixed monotone. The results presented here improve and generalize some corresponding results of mixed monotone operator equations.
基金This work was supported by the National Natural Science Foundation of China (No.21033008 and No.21073169)the National Basic Research Program of China (No.2010CB923300 and No.2011CB921400)and the Hong Kong RGC (No.604709) and UGC (AoE/P04/08-2) is gratefully acknowledged.
文摘To advance hierarchical equations of motion as a standard theory for quantum dissipative dynamics, we put forward a mixed Heisenberg-SchrSdinger scheme with block-matrix implementation on efficient evaluation of nonlinear optical response function. The new approach is also integrated with optimized hierarchical theory and numerical filtering algorithm. Different configurations of coherent two-dimensional spectroscopy of model excitonic dimer systems are investigated, with focusing on the effects of intermolecular transfer coupling and bi-exciton interaction.
基金Supported by the Important Science Foundation of Henan Education Commission(2000110019)Supported by the Natural Science Foundation of Shangqiu(200211125)
文摘Using the cone and partial ordering theory and mixed monotone operator theory, the existence and uniqueness of solutions for some classes of systems of nonlinear two binary operator equations in a Banach space with a partial ordering are discussed. And the error estimates that the iterative sequences converge to solutions are also given. Some relevant results of solvability of two binary operator equations and systems of operator equations are improved and generalized.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 60074034 and 70271068
文摘This article introduces a new chaotic system of three-dimensional quadratic autonomous ordinary differential equations, which can display different attractors with two unstable equilibrium points and four unstable equilibrium points respectively. Dynamical properties of this system are then studied. Furthermore, by applying the undetermined coefficient method, heteroclinic orbit of Shil'nikov's type in this system is found and the convergence of the series expansions of this heteroclinic orbit are proved in this article. The Shil'nikov's theorem guarantees that this system has Smale horseshoes and the horseshoe chaos.
基金The project supported by the State Key Laboratory of 0il/Gas Reservoir Geology and Exploitation "PLN0402"The authors would like to thank Prof.Sen-Yue Lou for helpful discussions.
文摘Some new structures and interactions of solitons for the (2+1)-dimensional Nizhnik-Novikov-Veselov equation are revealed with the help of the idea of the bilinear method and variable separation approach. The solutions to describe the interactions between two dromions, between a line soliton and a y-periodic soliton, and between two y-periodic solitons are included in our results. Detailed behaviors of interaction are illustrated both analytically and in graphically. Our analysis shows that the interaction properties between two solitons are related to the form of interaction constant. The form of interaction constant and the dispersion relationship are related to the form of the seed solution (u0, v0, w0 ) in Backlund transformation.
基金This work was supported by the National Natural Science Foundation of China (No.20973119 and No.21033008).
文摘A two-dimensional generalized Langevin equation is proposed to describe the protein conformational change, compatible to the electron transfer process governed by atomic packing density model. We assume a fractional Gaussian noise and a white noise through bond and through space coordinates respectively, and introduce the coupling effect coming from both fluctuations and equilibrium variances. The general expressions for autocorrelation functions of distance fluctuation and fluorescence lifetime variation are derived, based on which the exact conformational change dynamics can be evaluated with the aid of numerical Laplace inversion technique. We explicitly elaborate the short time and long time approximations. The relationship between the two-diraensional description and the one-dimensional theory is also discussed.
基金Supported by Funds of National Defense Technology Key Laboratory (NO.9140C060203060C0603)China Postdoctoral Science Foundation(NO.20060400189) .
文摘The resonant tunneling diode (RTD) is a kind of novel ultra-high speed and ultra-high frequency negative differential resistance nanoelectronic device. Integration of RTD and other three-terminal compound semiconductor devices is one important direction of high speed integrated circuit development. In this paper, monolithic integration technology of RTD and high electron mobility transistor (HEMT) based on GaAs substrate was discussed. A top-RTD and bottom-HEMT material structure was proposed and epitaxyed. Based on wet chemical etching, electron beam lithography, metal lift-off and air bridge technology, RTD and HEMT were fabricated on the same wafer. The peak-to-valley current ratio of RTD is 4 and the peak voltage is 0.5 V. The maximal transconductance is 120 mS/mm for a 0.25 μm gate length depletion mode HEMT. Current levels of two devices are basically suited. The results validate the feasibility of the designed integration process.
基金Supported by the Science Foundation of University of Petroleum (No. ZX9903), the Open Science Foundation of the State Key Laboratory of Heavy Oil Processing (No. 200005), and the National Natural Science Foundation of China (No. 20006010).
文摘The applicability of the density rule of Pathwardhan and Kumer and the rule based on the linear isopiestic relation is studied by comparison with experimental density data in the literature. Predicted and measured values for 18 electrolyte mixtures are compared. The two rules are good for mixtures with and without common ions, including those containing associating ions. The deviations of the rule based on the linear isopiestic relation are slightly higher for the mixtures involving very strong ion complexes, but the predictions are still quite satisfactory.The density rule of Pathwardhan and Kumer is more accurate for these mixtures. However, it is not applicable for mixtures containing non-electrolytes. The rule based on the linear isopiestic relation is extended to mixtures involving non-electrolytes. The predictions for the mixtures containing both electrolytes and non-electrolytes and the non-electrolyte mixtures are accurate. All these results indicate that this rule is a widely applicable approach.
基金The project supported by National Natural Science Foundations of China under Grant Nos. 10275038 and 60635040, and partly by the State Key Research Development Program under Grant No. G2000077400
文摘In this paper two kinds of two-boson realizations of generally deformed algebras with three generators are obtained by generalizing the Jordan-Schwlnger realizations of SU(2) and SU(1,1). For each kind, a unitary realization and a non-unitary realizatlon, together with the properties of their acting spaces, are discussed. Similarity transformations that relate the non-unitary realizations to the unitary ones are given by solving unitarization equations.
基金Supported by the National High Technology Research and Development Program of China (2008AA03Z3472294,2009AA302410)the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (2010)+1 种基金the Guangdong Province Sci & Tech Bureau (2006B12401006, 2008A080800024)the Chinese Universities Basic Research Founding
文摘The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by BET, XRD (X-ray diffraction), TPR (temperature programmed reduction), IR (infra-red adsorption), NH 3-TPD (temperature programmed desorption) and CO 2-TPD (temperature programmed desorption) techniques. The results showed that the surface area of catalysts decreased with increasing metal content, and the metals as well as Cu-Ni alloy co-existed on the reduced catalyst surface. There existed interaction between metal and carrier, and moreover, metal particles affected obviously the acidity and basicity of carrier. The large amount of basic sites facilitated the activation of methanol to methoxyl species and their subsequent reaction with activated carbon dioxide. The catalysts were evaluated in a continuous tubular fixed-bed micro-gaseous reactor and the catalyst with bimetal loading of 20% (by mass) had best catalytic activities. Under the conditions of 393 K, 1.1 MPa, 5 h and gas space velocity of 510 h 1 , the selectivity and yield of DMC were higher than 86.0 % and 5.0 %, respectively.
基金the Ministry of Science,Technology and Innovation,Malaysia(MOSTI),for funding the project:RG003/09AET as well as the University of Malaya for allowing full access to several key laboratories to perform experimental work
文摘Alkanolamines are widely used in the purification of the sourgas sweetening process. During the sour gas absorption process, CO_2 significantly degrades the amine solvent and creates enormous problems for plant operation. In this work, CO_2 induced degradation of aqueous diethanolamine(DEA) solution was conducted in a 1.25 L jacketed glass reactor that functioned as an absorber and stripper at atmospheric conditions. Pure CO_2 was bubbled through the reactor until the solution became saturated. In this study, the concentrations of DEA used were in the range of concentrations between 2 mol·L^(-1) and 4 mol·L^(-1). In the degradation experiment, six generic cycles were conducted for each run. Each cycle was configured with the absorption and desorption of carbon dioxide at 55 ℃ and 100 ℃, respectively. Samples were collected after a predetermined experimental time and analyzed by ion chromatography(IC) to identify unknown ionic degradation products(DGPs). In the IC analysis, three different columns were used for anion, cation and ion exclusion systems, which are Metrosep A Supp 5150/4.0, Metrosep C Supp 4 150/4.0 and Metrosep Organic Acids, respectively. The major identified DGPs of D01 DEA2 M, D02 DEA3 M, and D03 DEA4 M are nitrite, acetate and ammonium. Phosphate product was found in the degraded amine samples which might be due to the contamination of water or chromatographic system.
基金supported by the NationalScience Foundation of China(2006CB202508)wewould like to extend our heartfelt thanks to the RIPP’s labo-ratories engaging in XRD and FT-IR analyses for theirenergetical support and warm assistance provided to thisresearch work.
文摘In order to investigate the rules on formation of zeolite during crystallization of titanium silicalite zeolite (TS-1) the X-ray diffractometry and Foulier transform infra-red spectrometry were applied to track the process of crystallization of titanium silicalite zeolite. The research results revealed that at the initial stage of crystallization the interactions between silica gel and titania gel in the polymer blend could gradually lead to the formation of tiny crystal nuclei with complicated structure that could slowly grow up to form molecular sieves. Quite different from the conventional zeolites that use the acid sites as the catalytically active centers, the oxidative reactivity of the titanium silicalite zeolite was not proportional to its crystallinity and is associated with the oxidative centers of titanium contained in the zeolite.
基金supported by the Italian MIUR-PRIN Research Project 2008 "Transizioni di fase,isteresi e scale multiple"
文摘Two different models for the evolution of incompressible binary fluid mixtures in a three-dimensional bounded domain are considered.They consist of the 3D incompressible Navier-Stokes equations,subject to time-dependent external forces and coupled with either a convective Allen-Cahn or Cahn-Hilliard equation.Such systems can be viewed as generalizations of the Navier-Stokes equations to two-phase fluids.Using the trajectory approach,the authors prove the existence of the trajectory attractor for both systems.
基金Supported by the Fundamental Research Funds for the Central Universitiesthe National Natural Science Foundation of China under Grant No.10904111
文摘We study two-dimensional massive Dirac equation in circular well potential. The energies of bound states are obtained. We demonstrate the Klein paradox of this relativistic wave equation:For large enough potential depth, the bound states disappear from the spectra. Applications to graphene systems are discussed.
基金supported by the Natural Science Collaborating Foundation of Jiaying College and Meizhou Science and Techonolgy Bureau(No. 2009KJ08)
文摘Based on the rapid genetic algorithm(RGA),the band gap structures of square lattices with square scatters are optimized.In the optimizing process,gene codes are used to express square scatters and the fitting function adopts the relative values of the largest absolute photonic band gaps(PBGs).By changing the value of filling factor,three cell forms with large photonic band gaps are obtained.In addition,the comparison between the rapid genetic algorithm and the general genetic algorithm(GGA) is analyzed.
基金The National Natural Science Foundation of China(Grant No.51376188)The National Basic Research Program of China("973"Project)(Grant No.2011CB710701)
文摘An accurate knowledge about phase behaviors of CH4, CO2 and their binary mixture is crucial in fields of natural gas liquefaction and refrigeration applications. In this work, two all-atom force fields of TraPPE-EH and EMP2 were used for the components CH4 and CO〉 respectively. Then the vapor-liquid equilibria (VLE) of CH4, CO2 and their binary system were calculated via the NVT- and NpT Gibbs Ensemble Monte Carlo Simulations. Meanwhile the traditional method using Equation of State (EoS) to correlate the VLE properties was also investigated. The EoSs considered in this work were three classic cubic RK, SRK, PR and another advanced molecular-based PC-SAFT equations. For pure components, both molecular simulations and the PC-SAFT EoS could obtain satisfactory predictions for all the saturated properties. However, the saturated liquid densities calculated by the cubic EoSs were not so good. It was also observed that the TraPPE-EH force field had a good representation for CH4 molecule, while the EMP2 force field was not enough accurate to represent CO2 molecules. For the mixture CH4 + CO2, SRK and PR showed the best predictions for the saturated pressure-component property, while good results were also obtained via molecular simulations and PC-SAFT EoS. It was suggested that special combining rules or binary interaction parameters were important to obtain enough accurate prediction of the mixed phase behavior. Compared with the cubic EoS, the PC-SAFT and molecular simulation method showed better adaptabilities for both the pure and mixture systems. Besides, the accurate molecular parameters used in the PC-SAFT and molecular simulations could bring about direct and deep understanding about the molecular characteristics.
基金Project supported by the National Natural Science Foundation of China (Nos. 51025858 and 51178415)
文摘The determination of initial equilibrium shapes is a common problem in research work and engineering applications related to membrane structures. Using a general structural analysis framework of the finite particle method (FPM), this paper presents the first application of the FPM and a recently-developed membrane model to the shape analysis of light weight mem- branes. The FPM is rooted in vector mechanics and physical viewpoints. It discretizes the analyzed domain into a group of parti- cles linked by elements, and the motion of the free particles is directly described by Newton's second law while the constrained ones follow the prescribed paths. An efficient physical modeling procedure of handling geometric nonlinearity has been developed to evaluate the particle interaction forces. To achieve the equilibrium shape as fast as possible, an integral-form, explicit time integration scheme has been proposed for solving the equation of motion. The equilibrium shape can be obtained naturally without nonlinear iterative correction and global stiffness matrix integration. Two classical curved surfaces of tension membranes pro- duced under the uniform-stress condition are presented to verify the accuracy and efficiency of the proposed method.