The paper introduces author's job on realization of continuous attribute discretization based on languagefield theory that Prof. Yang put forward. It applies a new algorithm of seeking border values and its increm...The paper introduces author's job on realization of continuous attribute discretization based on languagefield theory that Prof. Yang put forward. It applies a new algorithm of seeking border values and its incremental onerather than seeking boundary ones that is a difficulty. The theory of the algorithm is self-contained, and its realiza-tion is simple. And the paper introduces simply four thoughts about defining language values and then discretizing fornon-numerical value that author already realized in KDD * .展开更多
A series of first-principle calculations were carried out to study the reaction pathways for alkaline hydrolysis of formamide. A hybrid supermolecule-polarizable continuum approach based on a recently developed Fully ...A series of first-principle calculations were carried out to study the reaction pathways for alkaline hydrolysis of formamide. A hybrid supermolecule-polarizable continuum approach based on a recently developed Fully Polarizable Continuum Model (FPCM) was used to account for solvent effects on the reaction process and free energy barriers in aqueous solution. Four solvent water molecules were explicitly included in the supermolecular reaction coordinate calculations; the remaining solvent water was modeled as a polarizable dielectric continuum surrounding the supermolecular reaction system. The calculations indicate that the alkaline amide hydrolysis consists of two reaction steps, i.e. the formation of the tetrahedral intermediate and the decomposition of the tetrahedral intermediate. Considering hybrid supermolecule in the reaction, the second step involved a water-assisted proton transfer during the decomposition of the tetrahedral intermediate. The direct participation of the solvent water molecule in the proton-transfer process significantly drops the energy barrier for the decomposition of the tetrahedral intermediate. Thus, the free energy barrier calculated for the decomposition of the tetrahedral intermediate through the water-assisted proton transfer becomes lower than the free energy barrier for the formation of the tetrahedral intermediate. The calculations demonstrate the important effect of solvent hydrogen bonding on energy barriers. The favorable pathway involving water-assisted proton transfer and the free energy barriers calculated using the hybrid supermolecule-polarizable continuum approach, including both the hydrogen-bonding effects and the remaining bulk solvent effects, are in good agreement with the available experimental data.展开更多
To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance asses...To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.展开更多
文摘The paper introduces author's job on realization of continuous attribute discretization based on languagefield theory that Prof. Yang put forward. It applies a new algorithm of seeking border values and its incremental onerather than seeking boundary ones that is a difficulty. The theory of the algorithm is self-contained, and its realiza-tion is simple. And the paper introduces simply four thoughts about defining language values and then discretizing fornon-numerical value that author already realized in KDD * .
文摘A series of first-principle calculations were carried out to study the reaction pathways for alkaline hydrolysis of formamide. A hybrid supermolecule-polarizable continuum approach based on a recently developed Fully Polarizable Continuum Model (FPCM) was used to account for solvent effects on the reaction process and free energy barriers in aqueous solution. Four solvent water molecules were explicitly included in the supermolecular reaction coordinate calculations; the remaining solvent water was modeled as a polarizable dielectric continuum surrounding the supermolecular reaction system. The calculations indicate that the alkaline amide hydrolysis consists of two reaction steps, i.e. the formation of the tetrahedral intermediate and the decomposition of the tetrahedral intermediate. Considering hybrid supermolecule in the reaction, the second step involved a water-assisted proton transfer during the decomposition of the tetrahedral intermediate. The direct participation of the solvent water molecule in the proton-transfer process significantly drops the energy barrier for the decomposition of the tetrahedral intermediate. Thus, the free energy barrier calculated for the decomposition of the tetrahedral intermediate through the water-assisted proton transfer becomes lower than the free energy barrier for the formation of the tetrahedral intermediate. The calculations demonstrate the important effect of solvent hydrogen bonding on energy barriers. The favorable pathway involving water-assisted proton transfer and the free energy barriers calculated using the hybrid supermolecule-polarizable continuum approach, including both the hydrogen-bonding effects and the remaining bulk solvent effects, are in good agreement with the available experimental data.
基金Project(2006.318.223.02-01) supported by the Ministry of Transportation and Communications through the Scientific and Technological Funds of ChinaProject(2007AA11Z104) supported by the High Technology Research and Development of ChinaProject(20090072110045) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘To accurately evaluate the degradation process of prestressed concrete continuous bridges exposed to aggressive environments in life-cycle,a finite element-based approach with respect to the lifetime performance assessment of concrete bridges was proposed.The existing assessment methods were firstly introduced and compared.Some essential mechanics problems involved in the degradation process,such as the deterioration of materials properties,the reduction of sectional areas and the variation of overall structural performance caused by the first two problems,were investigated and solved.A computer program named CBDAS(Concrete Bridge Durability Analysis System) was written to perform the above-metioned approach.Finally,the degradation process of a prestressed concrete continuous bridge under chloride penetration was discussed.The results show that the concrete normal stress for serviceability limit state exceeds the threshold value after 60 a,but the various performance indicators at ultimate limit state are consistently in the allowable level during service life.Therefore,in the case of prestressed concrete bridges,the serviceability limit state is more possible to have durability problems in life-cycle;however,the performance indicators at ultimate limit state can satisfy the requirements.
