The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi（NO3）3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffr...The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi（NO3）3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffraction and transmission electron microscopy, respectively. The results show that under the optimum condition that 300g/L Bi（NO3）3 reacts at 90℃ for 2h, the Bi2O3 powders with 60nm on the average and 99.5% in purity are obtained. The prepared nano-Bi2O3 powders contain a mixed crystal structure of monoclinic and triclinic instead of traditional structure of monoclinic α-Bi2O3. And the mixed crystal structure is stable in air. The reason for the appearance of the mixed crystal structure may be that the ionic radius ratio of Bi 3+ to O 2- changes easily during the formation of nano-Bi2O3 particles by a chemical precipitation method.展开更多
Language learning is a complex process for many reasons. First, it is closely related to linguistics. Second, language is social as it occurs within certain social contexts. And finally, it is individual. Personal cha...Language learning is a complex process for many reasons. First, it is closely related to linguistics. Second, language is social as it occurs within certain social contexts. And finally, it is individual. Personal characteristics such as experience, gender and age, attitude and aptitude, motivation, beliefs, self-confidence, and anxiety greatly influence language learning. Among these variables, motivation is considered to be one of the most important factors affecting the success of second or foreign language learning. However, the relationship between motivation and educational achievement is not quite clear. In the current literature, motivation is regarded as socially constructed, therefore as dynamic rather than static. Little research has been conducted on the motivation of Vietnamese students studying English as a compulsory curriculum component rather than as a major from a socio-cultural perspective. Understanding the relationship between student motivation and academic achievement as well as the socio-cultural factors that affect students＇ motivation will be an important contribution to motivation theory. Therefore, the situation requires longitudinal and in-depth research into student motivation, the factors affecting it during the learning process, and the relationship between student motivation and academic achievement. A mixed method approach has been chosen to meet the needs of the study. It is believed that insights in these areas will help address the issue of motivation at the Police University.展开更多
Three-layer feedforward networks have been widely used in modeling chemical engineering processes and prior-knowledge-based methods have been introduced to improve their performances.In this paper,we propose the metho...Three-layer feedforward networks have been widely used in modeling chemical engineering processes and prior-knowledge-based methods have been introduced to improve their performances.In this paper,we propose the methodology of designing better prior-knowledge-based hybrid methods by combining the existing ones. Then according to this methodology,two hybrid methods,interpolation-optimization (IO) method and interpolation penalty-function (IPF) method,are designed as examples.Finally,both methods are applied to modeling two cases in chemical engineering to investigate their effectiveness.Simulation results show that the performances of the hybrid methods are better than those of their parents.展开更多
This paper reports a simple yet efficient method for the synthesis of hierarchical TiO2-B nanowire@α-Fe2O3 nanothorn core-branch arrays based on a stepwise hydrothermal approach. The as-fabricated hybrid arrays show ...This paper reports a simple yet efficient method for the synthesis of hierarchical TiO2-B nanowire@α-Fe2O3 nanothorn core-branch arrays based on a stepwise hydrothermal approach. The as-fabricated hybrid arrays show impressive performance as a high-capacity anode for lithium-ion batteries. The key design in this study is a core-branch hybrid architecture, which not only provides large surface active sites for lithium ion insertion/extraction, but also enables fast charge transport owing to the reduced diffusion paths for both electrons and lithium ions. The peculiar combination of attributes of TiO2 （good structural stability） and Fe2O3 （large specific capacity） provides the hybrid array electrodes with several desirable electrochemical features： large reversible capacity （-800 mA.h.g^-1 for specific mass capacity and -750 μA.h-cm^-2 for specific areal＂ capacity）, good cycling stability, and high rate capability. The impressive electrochemical performance, together with the facile synthesis procedure, may provide an efficient platform to integrate the TiO2 nanowire@Fe2O3 nanothorn core-branch arrays as a three-dimensional thin film electrode for lithium-ion microbatteries.展开更多
The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wal...The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wall) are determined.Therefore its performance and efficiency is high.The analytical formulas,which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length,are used in this model.The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.展开更多
文摘The nano-Bi2O3 powders were prepared by a chemical precipitation method with Bi（NO3）3, HNO3 and NaOH as reactants. The structural characteristics and morphology of nano-Bi2O3 powders were investigated by X-ray diffraction and transmission electron microscopy, respectively. The results show that under the optimum condition that 300g/L Bi（NO3）3 reacts at 90℃ for 2h, the Bi2O3 powders with 60nm on the average and 99.5% in purity are obtained. The prepared nano-Bi2O3 powders contain a mixed crystal structure of monoclinic and triclinic instead of traditional structure of monoclinic α-Bi2O3. And the mixed crystal structure is stable in air. The reason for the appearance of the mixed crystal structure may be that the ionic radius ratio of Bi 3+ to O 2- changes easily during the formation of nano-Bi2O3 particles by a chemical precipitation method.
文摘Language learning is a complex process for many reasons. First, it is closely related to linguistics. Second, language is social as it occurs within certain social contexts. And finally, it is individual. Personal characteristics such as experience, gender and age, attitude and aptitude, motivation, beliefs, self-confidence, and anxiety greatly influence language learning. Among these variables, motivation is considered to be one of the most important factors affecting the success of second or foreign language learning. However, the relationship between motivation and educational achievement is not quite clear. In the current literature, motivation is regarded as socially constructed, therefore as dynamic rather than static. Little research has been conducted on the motivation of Vietnamese students studying English as a compulsory curriculum component rather than as a major from a socio-cultural perspective. Understanding the relationship between student motivation and academic achievement as well as the socio-cultural factors that affect students＇ motivation will be an important contribution to motivation theory. Therefore, the situation requires longitudinal and in-depth research into student motivation, the factors affecting it during the learning process, and the relationship between student motivation and academic achievement. A mixed method approach has been chosen to meet the needs of the study. It is believed that insights in these areas will help address the issue of motivation at the Police University.
基金Supported by the National Natural Science Foundation of China (No. 20076041)
文摘Three-layer feedforward networks have been widely used in modeling chemical engineering processes and prior-knowledge-based methods have been introduced to improve their performances.In this paper,we propose the methodology of designing better prior-knowledge-based hybrid methods by combining the existing ones. Then according to this methodology,two hybrid methods,interpolation-optimization (IO) method and interpolation penalty-function (IPF) method,are designed as examples.Finally,both methods are applied to modeling two cases in chemical engineering to investigate their effectiveness.Simulation results show that the performances of the hybrid methods are better than those of their parents.
基金This work was supported by the National Natural Science Foundation of China （No. 51102134）, the Natural Science Foundation of Jiangsu Province （No. BK20131349）, the China Postdoctoral Science Foundation （No. 2013M530258）, and the Jiangsu Planned Projects for Postdoctoral Research Funds （No. 1202001B）.
文摘This paper reports a simple yet efficient method for the synthesis of hierarchical TiO2-B nanowire@α-Fe2O3 nanothorn core-branch arrays based on a stepwise hydrothermal approach. The as-fabricated hybrid arrays show impressive performance as a high-capacity anode for lithium-ion batteries. The key design in this study is a core-branch hybrid architecture, which not only provides large surface active sites for lithium ion insertion/extraction, but also enables fast charge transport owing to the reduced diffusion paths for both electrons and lithium ions. The peculiar combination of attributes of TiO2 （good structural stability） and Fe2O3 （large specific capacity） provides the hybrid array electrodes with several desirable electrochemical features： large reversible capacity （-800 mA.h.g^-1 for specific mass capacity and -750 μA.h-cm^-2 for specific areal＂ capacity）, good cycling stability, and high rate capability. The impressive electrochemical performance, together with the facile synthesis procedure, may provide an efficient platform to integrate the TiO2 nanowire@Fe2O3 nanothorn core-branch arrays as a three-dimensional thin film electrode for lithium-ion microbatteries.
文摘The paper presents a simplified numerical model of evaporation processes inside vertical tubes.In this model only the temperature fields in the fluid domain(the liquid or two-phase mixture) and solid domain(a tube wall) are determined.Therefore its performance and efficiency is high.The analytical formulas,which allow calculating the pressure drop and the distribution of heat transfer coefficient along the tube length,are used in this model.The energy equation for the fluid domain is solved with the Control Volume Method and for the solid domain with the Finite Element Method in order to determine the temperature field for the fluid and solid domains.
