This paper presents a closed-form algorithm for the steady-state response of elastic mecha-nisms. Based on an analytic expression of the initial conditions, the steady-state response can beobtained by just one cycle o...This paper presents a closed-form algorithm for the steady-state response of elastic mecha-nisms. Based on an analytic expression of the initial conditions, the steady-state response can beobtained by just one cycle of integration, thus the algorithm is of high efficiency. The algorithm isthen verified by comparing the computational results with the previously published experimental re-sults.展开更多
Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics d...Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere. Here we report the first measurement of the uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide. Isoprene cannot readily partition into the solution because of its high volatility and low solubility, which hinders its further liquid-phase oxidation. Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide, and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%, respectively. The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity. These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups. The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients. These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation, but for isoprene and methyl methacrylate, this process is not important in the troposphere.展开更多
To investigate the influence of initial curing conditions and exposure environments on chloride ions’migration in concrete,the specimens that were cured in different conditions and placed in several marine environmen...To investigate the influence of initial curing conditions and exposure environments on chloride ions’migration in concrete,the specimens that were cured in different conditions and placed in several marine environments were studied.The amount of chloride ions passing through the specimen’s section was monitored in the accelerated chloride migration test.The effective chloride diffusion coefficients(De)were calculated from the steadystate on the basis of Nernst-Planck’s equation.The results indicated that the initial curing conditions and the wet-dry interval of external environments have coupling influence on effective diffusion coefficient of chloride ion significantly.De reflected the density and pore connectivity of concrete.The co-effects of the initial curing condition and following exposure environment should be taken into account in durability design for concrete structure located in marine environment.展开更多
文摘This paper presents a closed-form algorithm for the steady-state response of elastic mecha-nisms. Based on an analytic expression of the initial conditions, the steady-state response can beobtained by just one cycle of integration, thus the algorithm is of high efficiency. The algorithm isthen verified by comparing the computational results with the previously published experimental re-sults.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KJCX2-EW-H01)the National Basic Research Program(973) of Ministry of Science and Technology of China (No.2011CB403401)the National Natural Science Foundation of China (No.40925016, 40830101, 21077109,41005070, 41105085)
文摘Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere. Here we report the first measurement of the uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide. Isoprene cannot readily partition into the solution because of its high volatility and low solubility, which hinders its further liquid-phase oxidation. Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide, and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%, respectively. The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity. These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups. The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients. These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation, but for isoprene and methyl methacrylate, this process is not important in the troposphere.
基金supports from JSPS–NSFC Scientific Cooperation Program(No.50538070)the National Natural Science Foundation of China(Grant No.50811140088).
文摘To investigate the influence of initial curing conditions and exposure environments on chloride ions’migration in concrete,the specimens that were cured in different conditions and placed in several marine environments were studied.The amount of chloride ions passing through the specimen’s section was monitored in the accelerated chloride migration test.The effective chloride diffusion coefficients(De)were calculated from the steadystate on the basis of Nernst-Planck’s equation.The results indicated that the initial curing conditions and the wet-dry interval of external environments have coupling influence on effective diffusion coefficient of chloride ion significantly.De reflected the density and pore connectivity of concrete.The co-effects of the initial curing condition and following exposure environment should be taken into account in durability design for concrete structure located in marine environment.
