To investigate the corrosion degradation law and service life of reinforced concrete in various salt solution environments,reinforced concrete specimens were semi-immersed in 3%Na_(2)CO_(3)(N3-0-0),3%Na_(2)CO_(3)+3%Na...To investigate the corrosion degradation law and service life of reinforced concrete in various salt solution environments,reinforced concrete specimens were semi-immersed in 3%Na_(2)CO_(3)(N3-0-0),3%Na_(2)CO_(3)+3%NaCl(N3-Cl3-0)and 3%Na_(2)CO_(3)+3%NaCl+3%Na_(2)SO_(4)(N3-Cl3-S3)salt solutions.The electrochemical workstation was used for regular non-destructive testing,and the polarization curve and related electrochemical parameters were used as the macroscopic durability evaluation indicators,while microscopic analysis of steel bar corrosion products was performed in combination with SEM and EDS.In addition,the corrosion current density degradation model of GM(1,1)was established and compared with the modified GM(1,1)-Markov degradation model.The results showed that the prediction error of the GM(1,1)-Markov model was smaller and more accurate than that of GM(1,1).The reinforced concrete specimens in the N3-0-0,N3-Cl3-0 and N3-Cl3-S3 solutions reached the failure state in 3.08,1.67,and 2.30 years,respectively,as predicted by the GM(1,1)-Markov model.According to ESM and EDS microscopic analysis of reinforcement,carbonate had no significant effect on reinforcement corrosion,chloride ions played a dominant role in reinforcement corrosion,and sulfate ion improved concrete's resistance to chloride ion corrosion.Based on GM(1,1)-Markov model,the failure and damage of reinforced concrete in saline soil areas can be quantitatively evaluated in the whole life cycle,which provides a theoretical basis for the early maintenance or reinforcing of reinforced concrete.展开更多
By means of an equivalent invariant form of boundary conditions, the authors get the exis- tence and uniqueness of semi-global C1 solution to the mixed initial-boundary value problem for quasilinear hyperbolic systems...By means of an equivalent invariant form of boundary conditions, the authors get the exis- tence and uniqueness of semi-global C1 solution to the mixed initial-boundary value problem for quasilinear hyperbolic systems with general nonlinear boundary conditions.展开更多
Photocatalytic CO_(2)reduction driven by green solar energy could be a promising approach for the carbon neutral practice.In this work,a novel defect engineering approach was developed to form the Sn_(x)Nb_(1-x)O_(2)s...Photocatalytic CO_(2)reduction driven by green solar energy could be a promising approach for the carbon neutral practice.In this work,a novel defect engineering approach was developed to form the Sn_(x)Nb_(1-x)O_(2)solid solution by the heavy substitutional Nb-doping of SnO_(2)through a robust hydrothermal process.The detailed analysis demonstrated that the heavy substitution of Sn^(4+)by a higher valence Nb^(5+)created a more suitable band structure,a better photogenerated charge carrier separation and transfer,and stronger CO_(2)adsorption due to the presence of abundant acid centers and excess electrons on its surface.Thus,the Sn_(x)Nb_(1-x)O_(2)solid solution sample demonstrated a much better photocatalytic CO_(2)reduction performance compared to the pristine SnO_(2)sample without the need for sacrificial agent.Its photocatalytic CO_(2)reduction efficiency reached~292.47μmol/(g·h),which was 19 times that of the pristine SnO_(2)sample.Furthermore,its main photocatalytic CO_(2)reduction product was a more preferred multi-carbon(C_(2+))compound of C_(2)H_(5)OH,while that of the pristine SnO_(2)sample was a one-carbon(C1)compound of CH_(3)OH.This work demonstrated that,the heavy doping of high valence cations in metal oxides to form solid solution may enhance the photocatalytic CO_(2)reduction and modulate its reduction process,to produce more C_(2+)products.This material design strategy could be readily applied to various material systems for the exploration of high-performance photocatalysts for the solar-driven CO_(2)reduction.展开更多
基金Funded by National Natural Science Foundation of China(No.52178216)Gansu Provincial Science and Technology Programme(No.23JRRA813)。
文摘To investigate the corrosion degradation law and service life of reinforced concrete in various salt solution environments,reinforced concrete specimens were semi-immersed in 3%Na_(2)CO_(3)(N3-0-0),3%Na_(2)CO_(3)+3%NaCl(N3-Cl3-0)and 3%Na_(2)CO_(3)+3%NaCl+3%Na_(2)SO_(4)(N3-Cl3-S3)salt solutions.The electrochemical workstation was used for regular non-destructive testing,and the polarization curve and related electrochemical parameters were used as the macroscopic durability evaluation indicators,while microscopic analysis of steel bar corrosion products was performed in combination with SEM and EDS.In addition,the corrosion current density degradation model of GM(1,1)was established and compared with the modified GM(1,1)-Markov degradation model.The results showed that the prediction error of the GM(1,1)-Markov model was smaller and more accurate than that of GM(1,1).The reinforced concrete specimens in the N3-0-0,N3-Cl3-0 and N3-Cl3-S3 solutions reached the failure state in 3.08,1.67,and 2.30 years,respectively,as predicted by the GM(1,1)-Markov model.According to ESM and EDS microscopic analysis of reinforcement,carbonate had no significant effect on reinforcement corrosion,chloride ions played a dominant role in reinforcement corrosion,and sulfate ion improved concrete's resistance to chloride ion corrosion.Based on GM(1,1)-Markov model,the failure and damage of reinforced concrete in saline soil areas can be quantitatively evaluated in the whole life cycle,which provides a theoretical basis for the early maintenance or reinforcing of reinforced concrete.
基金National Science foundation of China(10671126)Shanghai Higher Education Outstanding Young Professor(sdl07038)Doctor foundation of Shanghai University of Electric Power(F06028).
基金the Special Funds for Major State Basic Research Projects of China.
文摘By means of an equivalent invariant form of boundary conditions, the authors get the exis- tence and uniqueness of semi-global C1 solution to the mixed initial-boundary value problem for quasilinear hyperbolic systems with general nonlinear boundary conditions.
基金This study was supported by the National Natural Science Foundation of China(Grant No.51902271)the Fundamental Research Funds for the Central Universities(Grant Nos.2682020CX07,2682020CX08,and 2682021CX116)Sichuan Science and Technology Program(Grant Nos.2020YJ0072,2020YJ0259,and 2021YFH0163)。
文摘Photocatalytic CO_(2)reduction driven by green solar energy could be a promising approach for the carbon neutral practice.In this work,a novel defect engineering approach was developed to form the Sn_(x)Nb_(1-x)O_(2)solid solution by the heavy substitutional Nb-doping of SnO_(2)through a robust hydrothermal process.The detailed analysis demonstrated that the heavy substitution of Sn^(4+)by a higher valence Nb^(5+)created a more suitable band structure,a better photogenerated charge carrier separation and transfer,and stronger CO_(2)adsorption due to the presence of abundant acid centers and excess electrons on its surface.Thus,the Sn_(x)Nb_(1-x)O_(2)solid solution sample demonstrated a much better photocatalytic CO_(2)reduction performance compared to the pristine SnO_(2)sample without the need for sacrificial agent.Its photocatalytic CO_(2)reduction efficiency reached~292.47μmol/(g·h),which was 19 times that of the pristine SnO_(2)sample.Furthermore,its main photocatalytic CO_(2)reduction product was a more preferred multi-carbon(C_(2+))compound of C_(2)H_(5)OH,while that of the pristine SnO_(2)sample was a one-carbon(C1)compound of CH_(3)OH.This work demonstrated that,the heavy doping of high valence cations in metal oxides to form solid solution may enhance the photocatalytic CO_(2)reduction and modulate its reduction process,to produce more C_(2+)products.This material design strategy could be readily applied to various material systems for the exploration of high-performance photocatalysts for the solar-driven CO_(2)reduction.
