The synthesis of methylene diphenyl dimethylcarbamate （4,4＇-MDC） from methyl N-phenyl carbonate （MPC） and formaldehyde （HCHO） was conducted in the presence of sulfonic acid-functionalized ionic liquids （ILs） ...The synthesis of methylene diphenyl dimethylcarbamate （4,4＇-MDC） from methyl N-phenyl carbonate （MPC） and formaldehyde （HCHO） was conducted in the presence of sulfonic acid-functionalized ionic liquids （ILs） as dual solvent-catalyst. The influences of the kind of anion in the ionic liquids, reaction conditions and the recycle of the ionic liquid on 4,4＇-MDC synthesis reaction were investigated. In addition, the acid strength of ILs was de-termined by the Hammett method with UV-visible spectroscopy, and the acid strength-catalytic activity relationship was correlated. The activity estimation results showed that [HSO3-bmim]CF3SO3 was the optimal dual solvent-catalyst. Under the suitable reaction conditions of 70℃, 40 min, molar ratio of nMPC/nHCHO= 10/1 and mass ratio of WILs/WMPC = 4.5/1, the yield of 4,4＇-MDC based on HCHO was 89.9 % and the selectivity of 4,4＇-MDC with respect to MPC was 74.9%. Besides, [HSO3-bmim]CF3SO3 was reused four times after being purified and no significant loss in the catalytic activity was observed.展开更多
The generalized conditional symmetry is developed to study the variable separation for equations of type uxt = A（u,ux）uxx ＋ B（u, ux）. Complete classification of those equations which admit derivative-dependent fu...The generalized conditional symmetry is developed to study the variable separation for equations of type uxt = A（u,ux）uxx ＋ B（u, ux）. Complete classification of those equations which admit derivative-dependent functional separable solutions is obtained and some of their exact separable solutions are constructed.展开更多
The impacts of initial perturbations on the computational stability of nonlinear evolution equations for non-conservative difference schemes and non-periodic boundary conditions are studied through theoretical analysi...The impacts of initial perturbations on the computational stability of nonlinear evolution equations for non-conservative difference schemes and non-periodic boundary conditions are studied through theoretical analysis and numerical experiments for the case of onedimensional equations.The sensitivity of the difference scheme to initial values is further analyzed.The results show that the computational stability primarily depends on the form of the initial values if the difference scheme and boundary conditions are determined.Thus,the computational stability is sensitive to the initial perturbations.展开更多
Generalized Casoratian condition and Casoratian solutions of the Toda lattice are given in terms of its bilinear Bgcklund transformation. By choosing suitable Casoratian entries and parameter in the bilinear Bgcklund ...Generalized Casoratian condition and Casoratian solutions of the Toda lattice are given in terms of its bilinear Bgcklund transformation. By choosing suitable Casoratian entries and parameter in the bilinear Bgcklund transformation, we can give transformations among many kinds of solutions.展开更多
The impact of different phases of shipment （at sea and at port） on two German white wines of two vintages and the lasting effects of the temperature regimes over time was investigated. The wines were subjected to th...The impact of different phases of shipment （at sea and at port） on two German white wines of two vintages and the lasting effects of the temperature regimes over time was investigated. The wines were subjected to three temperature programs--control （15 ℃）, linear increase （15℃ steadily increasing to 45 ℃）, and diurnal fluctuation （15 ℃/40 ℃）--in both movement and non-movement conditions. The wines were analyzed for chemical, physical and sensorial changes at one and eight months post-treatment. Changes in temperature and pressure were recorded within the bottles, which correlated with the temperature programs： ＋0.04 bar/℃ in the linear increase program and ＋0.08 bar/℃ in the diurnal fluctuation program. The oxygen levels in the headspace and in the wine were monitored during all of the treatments. The oxygen development in the bottles was similar between the diurnal and linear programs, and was found to be distinctive from the control program. The chemical analysis revealed that there were significant differences related to the experimental treatments of the wines for the following parameters： tartaric acid, free sulfur dioxide, total sulfur dioxide and percent cork weight loss measurements. Difference sensory testing found very few differences. After eight months storage, significant differences were found in the Diurnal Non-movement treatment compared to Linear Non-movement and control treatments, as well as Diurnal Movement and Control treatments for the 2014 Miiller-Thurgau wine. Sensory descriptive analysis of the wines found that the wines could be differentiated by variety, but could not be distinguished according to experimental treatment after one month storage. These results indicate that wines of these types are more robust to shipping conditions than previously found.展开更多
The present paper deals with a multiobjective optimization of truss topology by either Sequential Linear Programming （SLP） method or Linear Programming （LP） method. The ground structure approach is often used to s...The present paper deals with a multiobjective optimization of truss topology by either Sequential Linear Programming （SLP） method or Linear Programming （LP） method. The ground structure approach is often used to solve this kind of design problems. In this paper, the topology optimization is formulated as a Multiobjective Optimization Problem （MOP）, which is to find the cross-sectional area of truss members, such that both the total volume of members and the weighted mean compliance are minimized. Based upon the Karush-Kuhn-Tucker conditions （the optimality condition）, the Pareto optimal front of this problem can be obtained theoretically. The truss topology optimization under multiple load cases can be solved by the SLP. On the other hand, the LP such as the Simplex method or the interior point method can be applied to find one of the Pareto optimal solutions of the MOP under single load case. The applications of either the SLP or the LP are illustrated in numerical examples with discussion on characteristics of design results.展开更多
This paper, we discuss a class of second order nonlinear neutral differential equations with variable coefficients and variable deviations， Sharp conditions are established for all bounded solutions of the equations ...This paper, we discuss a class of second order nonlinear neutral differential equations with variable coefficients and variable deviations， Sharp conditions are established for all bounded solutions of the equations to be oscillatory， Linearized oscillation criteria of the equations are also given，展开更多
The dynamical behaviors of a two-species discrete ratio-dependent predator-prey sys- tem are considered. Some sufficient conditions for the local stability of the equilibria is obtained by using the linearization meth...The dynamical behaviors of a two-species discrete ratio-dependent predator-prey sys- tem are considered. Some sufficient conditions for the local stability of the equilibria is obtained by using the linearization method. Further, we also obtain a new sufficient condition to ensure that the positive equilibrium is globally asymptotically stable by using an iteration scheme and the comparison principle of difference equations, which generalizes what paper [G. Chen, Z. Teng and Z. Hu, Analysis of stability for a discrete ratio-dependent predator-prey system, Indian J. Pure Appl. Math. 42（1） （2011） 1-26] has done. The method given in this paper is new and very resultful comparing with papers [H. F. Huo and W. T. Li, Existence and global stability of periodic solutions of a discrete predator--prey system with delays, Appl. Math. Comput. 153 （2004） 337-351; X. Liao, S. Zhou and Y. Chen, On permanence and global stability in a general Gilpin- Ayala competition predator prey discrete system, Appl. Math. Comput. 190 （2007） 500-509] and it can also be applied to study the global asymptotic stability for general multiple species discrete population systems. At the end of this paper, we present an open question.展开更多
基金Supported by the National Natural Science Foundation of China （20576025）. the National Key Basic Project of China （2005CCA06100）, the Science and Technological Research and Development Project of Hebei Province （07215602D） and the Natural Science Foundation of Hebei Province 032007000010）.
文摘The synthesis of methylene diphenyl dimethylcarbamate （4,4＇-MDC） from methyl N-phenyl carbonate （MPC） and formaldehyde （HCHO） was conducted in the presence of sulfonic acid-functionalized ionic liquids （ILs） as dual solvent-catalyst. The influences of the kind of anion in the ionic liquids, reaction conditions and the recycle of the ionic liquid on 4,4＇-MDC synthesis reaction were investigated. In addition, the acid strength of ILs was de-termined by the Hammett method with UV-visible spectroscopy, and the acid strength-catalytic activity relationship was correlated. The activity estimation results showed that [HSO3-bmim]CF3SO3 was the optimal dual solvent-catalyst. Under the suitable reaction conditions of 70℃, 40 min, molar ratio of nMPC/nHCHO= 10/1 and mass ratio of WILs/WMPC = 4.5/1, the yield of 4,4＇-MDC based on HCHO was 89.9 % and the selectivity of 4,4＇-MDC with respect to MPC was 74.9%. Besides, [HSO3-bmim]CF3SO3 was reused four times after being purified and no significant loss in the catalytic activity was observed.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10371098, 10447007, aria 10475055, the Natural Science Foundation of Shaanxi Province of China under Grant No. 2005A13, and the Special Research Project of Educational Department of Shaanxi Province under Grant No. 03JK060
文摘The generalized conditional symmetry is developed to study the variable separation for equations of type uxt = A（u,ux）uxx ＋ B（u, ux）. Complete classification of those equations which admit derivative-dependent functional separable solutions is obtained and some of their exact separable solutions are constructed.
基金supported by the"Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues"of the Chinese Academy of Sciences (Grant No.XDA01020304)
文摘The impacts of initial perturbations on the computational stability of nonlinear evolution equations for non-conservative difference schemes and non-periodic boundary conditions are studied through theoretical analysis and numerical experiments for the case of onedimensional equations.The sensitivity of the difference scheme to initial values is further analyzed.The results show that the computational stability primarily depends on the form of the initial values if the difference scheme and boundary conditions are determined.Thus,the computational stability is sensitive to the initial perturbations.
基金Supported by National Natural Science Foundation of China under Grant No. 10671121Shanghai Leading Academic Discipline Project under Grant No. J50101
文摘Generalized Casoratian condition and Casoratian solutions of the Toda lattice are given in terms of its bilinear Bgcklund transformation. By choosing suitable Casoratian entries and parameter in the bilinear Bgcklund transformation, we can give transformations among many kinds of solutions.
文摘The impact of different phases of shipment （at sea and at port） on two German white wines of two vintages and the lasting effects of the temperature regimes over time was investigated. The wines were subjected to three temperature programs--control （15 ℃）, linear increase （15℃ steadily increasing to 45 ℃）, and diurnal fluctuation （15 ℃/40 ℃）--in both movement and non-movement conditions. The wines were analyzed for chemical, physical and sensorial changes at one and eight months post-treatment. Changes in temperature and pressure were recorded within the bottles, which correlated with the temperature programs： ＋0.04 bar/℃ in the linear increase program and ＋0.08 bar/℃ in the diurnal fluctuation program. The oxygen levels in the headspace and in the wine were monitored during all of the treatments. The oxygen development in the bottles was similar between the diurnal and linear programs, and was found to be distinctive from the control program. The chemical analysis revealed that there were significant differences related to the experimental treatments of the wines for the following parameters： tartaric acid, free sulfur dioxide, total sulfur dioxide and percent cork weight loss measurements. Difference sensory testing found very few differences. After eight months storage, significant differences were found in the Diurnal Non-movement treatment compared to Linear Non-movement and control treatments, as well as Diurnal Movement and Control treatments for the 2014 Miiller-Thurgau wine. Sensory descriptive analysis of the wines found that the wines could be differentiated by variety, but could not be distinguished according to experimental treatment after one month storage. These results indicate that wines of these types are more robust to shipping conditions than previously found.
文摘The present paper deals with a multiobjective optimization of truss topology by either Sequential Linear Programming （SLP） method or Linear Programming （LP） method. The ground structure approach is often used to solve this kind of design problems. In this paper, the topology optimization is formulated as a Multiobjective Optimization Problem （MOP）, which is to find the cross-sectional area of truss members, such that both the total volume of members and the weighted mean compliance are minimized. Based upon the Karush-Kuhn-Tucker conditions （the optimality condition）, the Pareto optimal front of this problem can be obtained theoretically. The truss topology optimization under multiple load cases can be solved by the SLP. On the other hand, the LP such as the Simplex method or the interior point method can be applied to find one of the Pareto optimal solutions of the MOP under single load case. The applications of either the SLP or the LP are illustrated in numerical examples with discussion on characteristics of design results.
文摘This paper, we discuss a class of second order nonlinear neutral differential equations with variable coefficients and variable deviations， Sharp conditions are established for all bounded solutions of the equations to be oscillatory， Linearized oscillation criteria of the equations are also given，
文摘The dynamical behaviors of a two-species discrete ratio-dependent predator-prey sys- tem are considered. Some sufficient conditions for the local stability of the equilibria is obtained by using the linearization method. Further, we also obtain a new sufficient condition to ensure that the positive equilibrium is globally asymptotically stable by using an iteration scheme and the comparison principle of difference equations, which generalizes what paper [G. Chen, Z. Teng and Z. Hu, Analysis of stability for a discrete ratio-dependent predator-prey system, Indian J. Pure Appl. Math. 42（1） （2011） 1-26] has done. The method given in this paper is new and very resultful comparing with papers [H. F. Huo and W. T. Li, Existence and global stability of periodic solutions of a discrete predator--prey system with delays, Appl. Math. Comput. 153 （2004） 337-351; X. Liao, S. Zhou and Y. Chen, On permanence and global stability in a general Gilpin- Ayala competition predator prey discrete system, Appl. Math. Comput. 190 （2007） 500-509] and it can also be applied to study the global asymptotic stability for general multiple species discrete population systems. At the end of this paper, we present an open question.
