The mechanisms and kinetics of the gas phase reactions that the hydrogen atom in formyl fluoride (FCHO) abstracted by OH in the presence of water, formic acid (FA), or sulfuric acid (SA) are theoretically invest...The mechanisms and kinetics of the gas phase reactions that the hydrogen atom in formyl fluoride (FCHO) abstracted by OH in the presence of water, formic acid (FA), or sulfuric acid (SA) are theoretically investigated at the CCSD(T)/6-311++G(3df, 3pd)//MO6-2X/6- 311++G(3df, 3pd) level of theory. The calculated results show that the barriers of the transition states involving catalysts are lowered to -2.89, -6.25, and -7.76 kcal/mol from 3.64 kcal/mol with respect to the separate reactants, respectively, which reflects that those catalysts play an important role in reducing the barrier of the hydrogen abstraction reaction of FCHO with OH. Additionally, using conventional transition state theory with Eckart tun- neling correction, the kinetic data demonstrate that the entrance channel X…FCHO+OH (X=H2O, FA, or SA) is significantly more favorable than the pathway X…OH+FCHO. More- over, the rate constants of the reactions of FCHO with OH radical with H2O, FA, or SA introduced are computed to be smaller than that of the naked OH+FCHO reaction because the concentration of the formed X…FCHO or X…OH complex is quite low in the atmosphere.展开更多
The kinetics of reductive leaching of manganese from a low-grade manganese oxide ore were studied using cellulose as reductant in dilute sulfuric acid medium.It was found that when the stirring speed was higher than 2...The kinetics of reductive leaching of manganese from a low-grade manganese oxide ore were studied using cellulose as reductant in dilute sulfuric acid medium.It was found that when the stirring speed was higher than 200 r/min,the effect of gas film diffusion on manganese extraction efficiency could be neglected,and the kinetic behavior was investigated under the condition of elimination of external diffusion influence on the leaching process.Effects of leaching temperature,mass ratio of cellulose and ore,and the sulfuric acid concentration on manganese extraction efficiency were discussed.The kinetic data were analyzed based on the shrinking core model,which indicated that the leaching process was dominated by both ash layer diffusion and chemical reaction at the initial stage,with the progress of leaching reaction,the rate-controlling step switched to the ash layer diffusion.It was also concluded that the sulfuric acid concentration had the most significant influence on the leaching rate,the reaction orders with respect to the sulfuric acid concentration were 2.102 in the first 60 min,and 3.642 in the later 90 min,while the reaction orders for mass ratio of cellulose and ore were 0.660 and 0.724,respectively.An Arrhenius relationship was used to relate the temperature to the rate of leaching,from which apparent activation energies were calculated to be 46.487 kJ/mol and 62.290 kJ/mol at the two stages,respectively.Finally,the overall leaching rate equations for the manganese dissolution reaction with cellulose in sulphuric acid solution were developed.The morphological changes and mineralogical forms of the ore before and after the chemical treatment were discussed with the support of SEM and XRD analyses.展开更多
With great increase of mobile service in recent years,high quality of experience(QoE) is becoming a comprehensive and major goal for service provider.To unify evaluations of different services,mean opinion score(MOS) ...With great increase of mobile service in recent years,high quality of experience(QoE) is becoming a comprehensive and major goal for service provider.To unify evaluations of different services,mean opinion score(MOS) as a subjective assessment is usually adopted for accurate and convincing reflection of user perceived quality.In this paper,we consider the effect of the burst transmission of best effort(BE) traffic on the uses with real time video traffic in the same cell.We extend the rate scaling process which was initially used to shape burstiness of BE users as interference to handle the scenario that BE users act as resource competitors with video users.A power reallocation strategy between the two types of users is presented and an algorithm further improving the fairness of BE users is proposed.The simulation results demonstrate that the proposed algorithm can not only promote the QoE of both types of users,but also guarantee the fairness among users.展开更多
Dip-coating is a low-cost,high-throughput technique for the deposition of organic semiconductors over large area on various substrates.Tremendous studies have been done and many parameters such as withdrawal speed,sol...Dip-coating is a low-cost,high-throughput technique for the deposition of organic semiconductors over large area on various substrates.Tremendous studies have been done and many parameters such as withdrawal speed,solvent type and solution concentration have been investigated.However,most of the depositions were ribbons or dendritic crystals with low coverage of the substrate due to the ignorance of the critical role of dynamic solution-substrate interactions during dip-coating.In this study,meniscus angle(MA)was proposed to quantify the real-time in-situ solutionsubstrate interactions during dip-coating.By proper surface treatment of the substrate,the value of MA can be tuned and centimeter-sized,continuous and highly ordered organic semiconductor thin films were achieved.The charge transport properties of the continuous thin films were investigated by the construction of organic field-effect transistors.Maximum(average)hole mobility up to 11.9(5.1)cm2V-1s-1was obtained.The average mobility was 82%higher than that of ribbon crystals,indicating the high crystallinity of the thin films.Our work reveals the critical role of dynamic solutionsubstrate interactions during dip-coating.The ability to produce large-area,continuous and highly ordered organic semiconductor thin films by dip-coating could revival the old technique for the application in various optoelectronics.展开更多
文摘The mechanisms and kinetics of the gas phase reactions that the hydrogen atom in formyl fluoride (FCHO) abstracted by OH in the presence of water, formic acid (FA), or sulfuric acid (SA) are theoretically investigated at the CCSD(T)/6-311++G(3df, 3pd)//MO6-2X/6- 311++G(3df, 3pd) level of theory. The calculated results show that the barriers of the transition states involving catalysts are lowered to -2.89, -6.25, and -7.76 kcal/mol from 3.64 kcal/mol with respect to the separate reactants, respectively, which reflects that those catalysts play an important role in reducing the barrier of the hydrogen abstraction reaction of FCHO with OH. Additionally, using conventional transition state theory with Eckart tun- neling correction, the kinetic data demonstrate that the entrance channel X…FCHO+OH (X=H2O, FA, or SA) is significantly more favorable than the pathway X…OH+FCHO. More- over, the rate constants of the reactions of FCHO with OH radical with H2O, FA, or SA introduced are computed to be smaller than that of the naked OH+FCHO reaction because the concentration of the formed X…FCHO or X…OH complex is quite low in the atmosphere.
基金Project(2010FJ1011)supported by the Major Project of Science and Technology of Hunan Province,China
文摘The kinetics of reductive leaching of manganese from a low-grade manganese oxide ore were studied using cellulose as reductant in dilute sulfuric acid medium.It was found that when the stirring speed was higher than 200 r/min,the effect of gas film diffusion on manganese extraction efficiency could be neglected,and the kinetic behavior was investigated under the condition of elimination of external diffusion influence on the leaching process.Effects of leaching temperature,mass ratio of cellulose and ore,and the sulfuric acid concentration on manganese extraction efficiency were discussed.The kinetic data were analyzed based on the shrinking core model,which indicated that the leaching process was dominated by both ash layer diffusion and chemical reaction at the initial stage,with the progress of leaching reaction,the rate-controlling step switched to the ash layer diffusion.It was also concluded that the sulfuric acid concentration had the most significant influence on the leaching rate,the reaction orders with respect to the sulfuric acid concentration were 2.102 in the first 60 min,and 3.642 in the later 90 min,while the reaction orders for mass ratio of cellulose and ore were 0.660 and 0.724,respectively.An Arrhenius relationship was used to relate the temperature to the rate of leaching,from which apparent activation energies were calculated to be 46.487 kJ/mol and 62.290 kJ/mol at the two stages,respectively.Finally,the overall leaching rate equations for the manganese dissolution reaction with cellulose in sulphuric acid solution were developed.The morphological changes and mineralogical forms of the ore before and after the chemical treatment were discussed with the support of SEM and XRD analyses.
基金supported by China National S&T Major Project 2013ZX03003002003Beijing Natural Science Foundation No.4152047+1 种基金the 863 project No.2014AA01A701111 Project of China under Grant B14010
文摘With great increase of mobile service in recent years,high quality of experience(QoE) is becoming a comprehensive and major goal for service provider.To unify evaluations of different services,mean opinion score(MOS) as a subjective assessment is usually adopted for accurate and convincing reflection of user perceived quality.In this paper,we consider the effect of the burst transmission of best effort(BE) traffic on the uses with real time video traffic in the same cell.We extend the rate scaling process which was initially used to shape burstiness of BE users as interference to handle the scenario that BE users act as resource competitors with video users.A power reallocation strategy between the two types of users is presented and an algorithm further improving the fairness of BE users is proposed.The simulation results demonstrate that the proposed algorithm can not only promote the QoE of both types of users,but also guarantee the fairness among users.
基金financial support from the National Natural Science Foundation of China(51873148,61674116 and 51633006)the Ministry of Science and Technology of China(2016YFA0202302)the Natural Science Foundation of Tianjin(18JC-YBJC18400)。
文摘Dip-coating is a low-cost,high-throughput technique for the deposition of organic semiconductors over large area on various substrates.Tremendous studies have been done and many parameters such as withdrawal speed,solvent type and solution concentration have been investigated.However,most of the depositions were ribbons or dendritic crystals with low coverage of the substrate due to the ignorance of the critical role of dynamic solution-substrate interactions during dip-coating.In this study,meniscus angle(MA)was proposed to quantify the real-time in-situ solutionsubstrate interactions during dip-coating.By proper surface treatment of the substrate,the value of MA can be tuned and centimeter-sized,continuous and highly ordered organic semiconductor thin films were achieved.The charge transport properties of the continuous thin films were investigated by the construction of organic field-effect transistors.Maximum(average)hole mobility up to 11.9(5.1)cm2V-1s-1was obtained.The average mobility was 82%higher than that of ribbon crystals,indicating the high crystallinity of the thin films.Our work reveals the critical role of dynamic solutionsubstrate interactions during dip-coating.The ability to produce large-area,continuous and highly ordered organic semiconductor thin films by dip-coating could revival the old technique for the application in various optoelectronics.