A microbial fuel cell(MFC)is a novel promising technology for simultaneous renewable electricity generation and wastewater treatment.Three non-comparable objectives,i.e.power density,attainable current density and was...A microbial fuel cell(MFC)is a novel promising technology for simultaneous renewable electricity generation and wastewater treatment.Three non-comparable objectives,i.e.power density,attainable current density and waste removal ratio,are often conflicting.A thorough understanding of the relationship among these three conflicting objectives can be greatly helpful to assist in optimal operation of MFC system.In this study,a multiobjective genetic algorithm is used to simultaneously maximizing power density,attainable current density and waste removal ratio based on a mathematical model for an acetate two-chamber MFC.Moreover,the level diagrams method is utilized to aid in graphical visualization of Pareto front and decision making.Three biobjective optimization problems and one three-objective optimization problem are thoroughly investigated.The obtained Pareto fronts illustrate the complex relationships among these three objectives,which is helpful for final decision support.Therefore,the integrated methodology of a multi-objective genetic algorithm and a graphical visualization technique provides a promising tool for the optimal operation of MFCs by simultaneously considering multiple conflicting objectives.展开更多
The meta-instable state(MIS)is the final stage before fault instability during stick-slip movement.Thus,identification of MIS is of great significance for assessing earthquake hazard in fault zones.A rock sample with ...The meta-instable state(MIS)is the final stage before fault instability during stick-slip movement.Thus,identification of MIS is of great significance for assessing earthquake hazard in fault zones.A rock sample with a precut planar fault was loaded on a horizontally biaxial servo-controlled press machine to create stick-slip conditions.Digital images of the sample surface were taken by a high-speed camera at a rate of 1000 frames per second during the stick-slip motion and processed using a 2D digital image correlation method to obtain the displacement field.We define a synergism coefficient that describes the relative dispersion of the accumulative fault slip.The results reveal that:(1)a local pre-slip area spreads very slowly along the fault before the MIS develops.It extends at a higher but still slow speed during meta-instable state I(MIS-I).During the final^1.5%of MIS,in meta-instable state II(MIS-II),the local pre-slip area first extends at a speed of^0.9 m/s,and then expands out of the observed image area at a very high speed.These results indicate that the local pre-slip area transforms from a state of quasi-static extension in MIS-I to quasi-dynamic extension in MIS-II.(2)The synergism coefficient of the fault slip decreases to half of its original value in MIS-I and to a quarter of its original value in MIS-II.This continuous decrease of synergism coefficient indicates that the strengthening of fault slip synergism is a characteristic of MIS.(3)Furthermore,the unstable sliding stage includes three sliding processes:initial-,fast-,and adjusted-sliding.There are two pauses between the three sliding processes.展开更多
基金Supported by the National Natural Science Foundation of China(21576163)the Major State Basic Research Development Program of China(2014CB239703)+1 种基金the Science and Technology Commission of Shanghai Municipality(14DZ2250800)the Project-sponsored by SRF for ROCS,SEM
文摘A microbial fuel cell(MFC)is a novel promising technology for simultaneous renewable electricity generation and wastewater treatment.Three non-comparable objectives,i.e.power density,attainable current density and waste removal ratio,are often conflicting.A thorough understanding of the relationship among these three conflicting objectives can be greatly helpful to assist in optimal operation of MFC system.In this study,a multiobjective genetic algorithm is used to simultaneously maximizing power density,attainable current density and waste removal ratio based on a mathematical model for an acetate two-chamber MFC.Moreover,the level diagrams method is utilized to aid in graphical visualization of Pareto front and decision making.Three biobjective optimization problems and one three-objective optimization problem are thoroughly investigated.The obtained Pareto fronts illustrate the complex relationships among these three objectives,which is helpful for final decision support.Therefore,the integrated methodology of a multi-objective genetic algorithm and a graphical visualization technique provides a promising tool for the optimal operation of MFCs by simultaneously considering multiple conflicting objectives.
基金supported by the National Natural Science Foundation of China(Grant No.41172180)Basic Research Funds from the Institute of Geology,China Earthquake Administration(Grant No.IGCEA1203)
文摘The meta-instable state(MIS)is the final stage before fault instability during stick-slip movement.Thus,identification of MIS is of great significance for assessing earthquake hazard in fault zones.A rock sample with a precut planar fault was loaded on a horizontally biaxial servo-controlled press machine to create stick-slip conditions.Digital images of the sample surface were taken by a high-speed camera at a rate of 1000 frames per second during the stick-slip motion and processed using a 2D digital image correlation method to obtain the displacement field.We define a synergism coefficient that describes the relative dispersion of the accumulative fault slip.The results reveal that:(1)a local pre-slip area spreads very slowly along the fault before the MIS develops.It extends at a higher but still slow speed during meta-instable state I(MIS-I).During the final^1.5%of MIS,in meta-instable state II(MIS-II),the local pre-slip area first extends at a speed of^0.9 m/s,and then expands out of the observed image area at a very high speed.These results indicate that the local pre-slip area transforms from a state of quasi-static extension in MIS-I to quasi-dynamic extension in MIS-II.(2)The synergism coefficient of the fault slip decreases to half of its original value in MIS-I and to a quarter of its original value in MIS-II.This continuous decrease of synergism coefficient indicates that the strengthening of fault slip synergism is a characteristic of MIS.(3)Furthermore,the unstable sliding stage includes three sliding processes:initial-,fast-,and adjusted-sliding.There are two pauses between the three sliding processes.
