High-temperature solid-state electrolyte is a key component of several important electrochemical devices,such as oxygen sensors for automobile exhaust control,solid oxide fuel cells(SOFCs) for power generation,and sol...High-temperature solid-state electrolyte is a key component of several important electrochemical devices,such as oxygen sensors for automobile exhaust control,solid oxide fuel cells(SOFCs) for power generation,and solid oxide electrolysis cells for H_(2) production from water electrolysis or CO_(2) electrochemical reduction to value-added chemicals.In particular,internal diffusion of protons or oxygen ions is a fundamental and crucial issue in the research of SOFCs,hypothetically based on either oxygen-ionconducting electrolytes or proton-conducting electrolytes.Up to now,some electrolyte materials based on fluorite or perovskite structure were found to show certain degree of dual-ion transportation capability,while in available electrolyte database,particularly in the field of SOFCs,such dual-ion conductivity was seriously overlooked.Actually,few concerns arising to the simultaneous proton and oxygen-ion conductivities in electrolyte of SOFCs inevitably induce various inadequate and confusing results in literature.Understanding dual-ion transportation behavior in electrolyte is indisputably of great importance to explain some unusual fuel cell performance as reported in literature and enrich the knowledge of solid state ionics.On the other hand,exploration of novel dual-ion conducting electrolytes will benefit the development of SOFCs.In this review,we provide a comprehensive summary of the understanding of dual-ion transportation in solid electrolyte and recent advances of dual-ion conducting SOFCs.The oxygen ion and proton conduction mechanisms at elevated temperature inside oxide-based electrolyte materials are first introduced,and then(mixed) oxygen ion and proton conduction behaviors of fluorite and perovskite-type oxides are discussed.Following on,recent advances in the development of dual-ion conducting SOFCs based on fluorite and perovskite-type single-phase or composite electrolytes,are reviewed.Finally,the challenges in the development of dual-ion conducting SOFCs are discussed and future prospects are proposed.展开更多
This paper is concerned with the spatial propagation of an SIR epidemic model with nonlocal diffusion and free boundaries describing the evolution of a disease.This model can be viewed as a nonlocal version of the fre...This paper is concerned with the spatial propagation of an SIR epidemic model with nonlocal diffusion and free boundaries describing the evolution of a disease.This model can be viewed as a nonlocal version of the free boundary problem studied by Kim et al.(An SIR epidemic model with free boundary.Nonlinear Anal RWA,2013,14:1992-2001).We first prove that this problem has a unique solution defined for all time,and then we give sufficient conditions for the disease vanishing and spreading.Our result shows that the disease will not spread if the basic reproduction number R_(0)<1,or the initial infected area h_(0),expanding ability μ and the initial datum S_(0) are all small enough when 1<R_(0)<1+d/μ_(2)+α.Furthermore,we show that if 1<R_(0)<1+d/μ_(2)+α,the disease will spread when h_(0) is large enough or h_(0) is small but μ is large enough.It is expected that the disease will always spread when R_(0)≥1+d/μ_(2)+α which is different from the local model.展开更多
Mole crickets,Gryllotalpa orientalis,have a pair of fully specialized forelegs for burrowing and employ an efficient underground excavating pattern,which provides excellent biological example for design of bionic unde...Mole crickets,Gryllotalpa orientalis,have a pair of fully specialized forelegs for burrowing and employ an efficient underground excavating pattern,which provides excellent biological example for design of bionic underground excavation equipment.In this study,the excavating pattern and kinematic features of mole crickets were obtained by using high-speed motion capture system and employing a transparent hydrogel as the analogue for soil.The two-dimensional motion characteristics of the forelegs of mole crickets during burrowing were captured and analyzed.The results show that the forelegs of the mole cricket employ a unique excavating pattern,which consists of foreword digging and horizontal expansion.We label this pattern a digging-expanding mode.An excavating cycle includes the digging and expanding motion of the forelegs,rotation caused by the midlegs and hindlegs,and forward thrust by the hindlegs.The excavating motion of the left and right forelegs is alternately carried out.This study can inspire the design of bionic tunnelling mechanisms and underground excavation equipment.展开更多
基金supported by the Australian Research Council Discovery Projects(DP150104365 and DP160104835)the financial support by the China Scholarship Council(201808340038) for his visiting at Curtin University,Australiathe ARC Discovery Early Career Researcher Award(DE180100773)。
文摘High-temperature solid-state electrolyte is a key component of several important electrochemical devices,such as oxygen sensors for automobile exhaust control,solid oxide fuel cells(SOFCs) for power generation,and solid oxide electrolysis cells for H_(2) production from water electrolysis or CO_(2) electrochemical reduction to value-added chemicals.In particular,internal diffusion of protons or oxygen ions is a fundamental and crucial issue in the research of SOFCs,hypothetically based on either oxygen-ionconducting electrolytes or proton-conducting electrolytes.Up to now,some electrolyte materials based on fluorite or perovskite structure were found to show certain degree of dual-ion transportation capability,while in available electrolyte database,particularly in the field of SOFCs,such dual-ion conductivity was seriously overlooked.Actually,few concerns arising to the simultaneous proton and oxygen-ion conductivities in electrolyte of SOFCs inevitably induce various inadequate and confusing results in literature.Understanding dual-ion transportation behavior in electrolyte is indisputably of great importance to explain some unusual fuel cell performance as reported in literature and enrich the knowledge of solid state ionics.On the other hand,exploration of novel dual-ion conducting electrolytes will benefit the development of SOFCs.In this review,we provide a comprehensive summary of the understanding of dual-ion transportation in solid electrolyte and recent advances of dual-ion conducting SOFCs.The oxygen ion and proton conduction mechanisms at elevated temperature inside oxide-based electrolyte materials are first introduced,and then(mixed) oxygen ion and proton conduction behaviors of fluorite and perovskite-type oxides are discussed.Following on,recent advances in the development of dual-ion conducting SOFCs based on fluorite and perovskite-type single-phase or composite electrolytes,are reviewed.Finally,the challenges in the development of dual-ion conducting SOFCs are discussed and future prospects are proposed.
基金Zhao was supported by a scholarship from the China Scholarship Council,Li was partially supported by NSF of China(11731005)Cao was partially supported by NSF of China(11901264).
文摘This paper is concerned with the spatial propagation of an SIR epidemic model with nonlocal diffusion and free boundaries describing the evolution of a disease.This model can be viewed as a nonlocal version of the free boundary problem studied by Kim et al.(An SIR epidemic model with free boundary.Nonlinear Anal RWA,2013,14:1992-2001).We first prove that this problem has a unique solution defined for all time,and then we give sufficient conditions for the disease vanishing and spreading.Our result shows that the disease will not spread if the basic reproduction number R_(0)<1,or the initial infected area h_(0),expanding ability μ and the initial datum S_(0) are all small enough when 1<R_(0)<1+d/μ_(2)+α.Furthermore,we show that if 1<R_(0)<1+d/μ_(2)+α,the disease will spread when h_(0) is large enough or h_(0) is small but μ is large enough.It is expected that the disease will always spread when R_(0)≥1+d/μ_(2)+α which is different from the local model.
基金the National Natural Science Foundation of China(Grant Nos.51405341 and 51505332)the Tianjin Research Program of Application Foundation and Advanced Technology(Grant Nos.15JCYBJC19300,15JCQNJC06900,14ZCDSYOOO10 and 16JCZDJC35900).
文摘Mole crickets,Gryllotalpa orientalis,have a pair of fully specialized forelegs for burrowing and employ an efficient underground excavating pattern,which provides excellent biological example for design of bionic underground excavation equipment.In this study,the excavating pattern and kinematic features of mole crickets were obtained by using high-speed motion capture system and employing a transparent hydrogel as the analogue for soil.The two-dimensional motion characteristics of the forelegs of mole crickets during burrowing were captured and analyzed.The results show that the forelegs of the mole cricket employ a unique excavating pattern,which consists of foreword digging and horizontal expansion.We label this pattern a digging-expanding mode.An excavating cycle includes the digging and expanding motion of the forelegs,rotation caused by the midlegs and hindlegs,and forward thrust by the hindlegs.The excavating motion of the left and right forelegs is alternately carried out.This study can inspire the design of bionic tunnelling mechanisms and underground excavation equipment.
