Similar to hydraulic fracturing(HF), the coalescence and fracture of cracks are induced within a rock under the action of an ultrasonic field, known as ultrasonic fracturing(UF). Investigating UF is important in both ...Similar to hydraulic fracturing(HF), the coalescence and fracture of cracks are induced within a rock under the action of an ultrasonic field, known as ultrasonic fracturing(UF). Investigating UF is important in both hard rock drilling and oil and gas recovery. A three-dimensional internal laser-engraved crack(3D-ILC) method was introduced to prefabricate two parallel internal cracks within the samples without any damage to the surface. The samples were subjected to UF. The mechanism of UF was elucidated by analyzing the characteristics of fracture surfaces. The crack propagation path under different ultrasonic parameters was obtained by numerical simulation based on the Paris fatigue model and compared to the experimental results of UF. The results show that the 3D-ILC method is a powerful tool for UF research.Under the action of an ultrasonic field, the fracture surface shows the characteristics of beach marks and contains powder locally, indicating that the UF mechanism includes high-cycle fatigue fracture, shear and friction, and temperature load. The two internal cracks become close under UF. The numerical result obtained by the Paris fatigue model also shows the attraction of the two cracks, consistent with the test results. The 3D-ILC method provides a new tool for the experimental study of UF. Compared to the conventional numerical methods based on the analysis of stress-strain and plastic zone, numerical simulation can be a good alternative method to obtain the crack path under UF.展开更多
First it is proved that both the integral of the divergence and the Melnikov function are invariants of the C2 transformation. Then, the problem of the planar homoclinic bifurcation with codimension 3 is considered. I...First it is proved that both the integral of the divergence and the Melnikov function are invariants of the C2 transformation. Then, the problem of the planar homoclinic bifurcation with codimension 3 is considered. It is proved that, in a small neighborhood of the origin in the parameter space of a Cr (r≥5) system, there exist exactly two Cr-1 semi- stable- limit- cycle branching surfaces, and their common boundary is a unique Cr-1 three-multiple- limit-cycle branching curve. The bifurcation pictures and the asymptotic expansions of the bifurcation functions are given. The stability criterion for the homoclinic loop is also obtained when the integral of the divergence is zero. The proof of the auxiliary theorems will be presented in [16].展开更多
The uncontrolled dendrite growth and volume change of Li metal during cycling lead to a short cycle life and safety concerns for Li-metal batteries,which hinders their practical application.Herein,we report the facile...The uncontrolled dendrite growth and volume change of Li metal during cycling lead to a short cycle life and safety concerns for Li-metal batteries,which hinders their practical application.Herein,we report the facile and energy-saving production of a three-dimensional(3D)CuZn matrix decorated with in-situ formed ZnO nano seeds(ZnO NS@3D CuZn)in pores and tunnels,which can serve as an anode current collector for dendrite-free Li-metal batteries.The 3D porous framework reduced the anode current density and accommodated Li volume change during the charge/discharge process.More importantly,the lithiophilic ZnO nano seeds induced fast Li deposition into the pores and tunnels of the 3D structure to effectively confine the deposited Li.As a positive effect,the volume change and Li dendrite growth during cycling are greatly suppressed.The half-cell with the ZnO NS@3D CuZn current collector exhibited a Coulombic efficiency(CE)of above 98%for over 320 and 240 cycles at 0.5 and 1 mA·cm^(-2),respectively.The Li@ZnO NS@3D CuZn symmetric cell achieves a lifespan of over 1500 h.Moreover,the Li@ZnO NS@3D CuZn||LiFePO4 full cell achieves a superb average CE of 99.4%and a long life of 600 cycles before the capacity retention rate decays to 90%.展开更多
Zinc-ion hybrid super-capacitors are regarded as promising safe energy storage systems,However,the relatively low volumetric energy density has become the main bottlenecks in practical applications of portable electro...Zinc-ion hybrid super-capacitors are regarded as promising safe energy storage systems,However,the relatively low volumetric energy density has become the main bottlenecks in practical applications of portable electronic devices,In this work,the zinc-ion hybrid super-capacitor with high volumetric energy density and superb cycle stability had been constructed which employing the high-density threedimensional graphene hydrogel as cathode and Zn foil used as anode in 1 mol/L ZnSO4 electrolyte.Benefiting from the abundant ion transport paths and the abundant active sites for graphene hydrogel with high density and porous structure,the zinc-ion hybrid super-capacitor exhibited an extremely high volumetric energy density of 118.42 Wh/L and a superb power density of 24.00 kW/L,as well as an excellent long cycle life(80% retention after 30,000 cycles at 10 A/g),which was superior to the volumetric energy density of the reported zinc-ion hybrid super-capacitors.This device,based on the fast ion adsorption/deso rption on the capacitor-type graphene cathode and reversible Zn^(2+) plating/stripping on the battery-type Zn anode,which will inspire the development of zinc-ion hybrid super-capacitor in miniaturized devices.展开更多
喷头驱动电源是压电喷头的核心部件之一。针对厚度剪切型压电喷头致动器结构特征,分析了0.11～0.32μm范围内的致动壁位移随驱动电压在20～60 V范围内近似线性增大的关系,推导出致动壁15 k Hz的谐振基频数值,结合喷墨通道＂三循环＂驱...喷头驱动电源是压电喷头的核心部件之一。针对厚度剪切型压电喷头致动器结构特征,分析了0.11～0.32μm范围内的致动壁位移随驱动电压在20～60 V范围内近似线性增大的关系,推导出致动壁15 k Hz的谐振基频数值,结合喷墨通道＂三循环＂驱动方式时序,设计了一种基于直流变换原理的开关式驱动电源,实现了32路喷墨通道分组喷射,其最大输出电压范围±60 V,正负脉宽和设置时间在15～200μs内在线可调,单路输出电流大于6 m A,脉宽最大误差小于3%。初步测试实验了该驱动电源的可行性。展开更多
On the basis of introducing the concept of urban agriculture, this paper analyses the necessity of developing urban agriculture in Huainan City as follows: it is the need of transformation and upgrading of agricultura...On the basis of introducing the concept of urban agriculture, this paper analyses the necessity of developing urban agriculture in Huainan City as follows: it is the need of transformation and upgrading of agricultural industry; it is the need of development of urban-rural integration; it is the need of sustainable urban development; it is the need of solving the issues concerning agriculture, countryside and farmers effectively. Then this paper analyses the endowment of developing urban agriculture in Huainan City. And finally the basic conception in industrial form and spatial framework is put forward, to develop urban agriculture in Huainan City.展开更多
Pseudocapacitive transition metal oxides(PTMOs)have the advantages of high areal capacitance and material density suitable for high-energy supercapacitor devices,but they are typically marred by insufficient rate perf...Pseudocapacitive transition metal oxides(PTMOs)have the advantages of high areal capacitance and material density suitable for high-energy supercapacitor devices,but they are typically marred by insufficient rate performance,which in turn deteriorates cyclic stability at high current levels.Using the example of spinel manganese oxide,herein we demonstrate that a pseudocapacitive oxide electrode of remarkable rate performance and cyclic stability may be realized by adopting oxide nanocrystallites,which are derived based on a novel solution chemistry,and carbon additive(CA)nanoparticles with highly uniform of size distributions.Precisely controlling the particle morphology and size distribution of the active material and conductive additive(CA)in the nanometer range can maximize the density of active material-CA-electrolyte three-phase contact points,thus facilitating synchronized electron and cation flow for the completion of surface faradaic reactions.The resultant Mn3O4 pseudocapacitive electrode exhibits rate capability and cycle stability,including 60%capacity retention at 60 A g-1 and no capacity fade over 100000 cycles under dynamic current densities,far superior to the state-of-the-art PTMO electrodes.The electrode design strategy is in general applicable to pseudocapacitors containing poorly conductive active materials.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 52104125, U1765204 and 51739008)
文摘Similar to hydraulic fracturing(HF), the coalescence and fracture of cracks are induced within a rock under the action of an ultrasonic field, known as ultrasonic fracturing(UF). Investigating UF is important in both hard rock drilling and oil and gas recovery. A three-dimensional internal laser-engraved crack(3D-ILC) method was introduced to prefabricate two parallel internal cracks within the samples without any damage to the surface. The samples were subjected to UF. The mechanism of UF was elucidated by analyzing the characteristics of fracture surfaces. The crack propagation path under different ultrasonic parameters was obtained by numerical simulation based on the Paris fatigue model and compared to the experimental results of UF. The results show that the 3D-ILC method is a powerful tool for UF research.Under the action of an ultrasonic field, the fracture surface shows the characteristics of beach marks and contains powder locally, indicating that the UF mechanism includes high-cycle fatigue fracture, shear and friction, and temperature load. The two internal cracks become close under UF. The numerical result obtained by the Paris fatigue model also shows the attraction of the two cracks, consistent with the test results. The 3D-ILC method provides a new tool for the experimental study of UF. Compared to the conventional numerical methods based on the analysis of stress-strain and plastic zone, numerical simulation can be a good alternative method to obtain the crack path under UF.
文摘First it is proved that both the integral of the divergence and the Melnikov function are invariants of the C2 transformation. Then, the problem of the planar homoclinic bifurcation with codimension 3 is considered. It is proved that, in a small neighborhood of the origin in the parameter space of a Cr (r≥5) system, there exist exactly two Cr-1 semi- stable- limit- cycle branching surfaces, and their common boundary is a unique Cr-1 three-multiple- limit-cycle branching curve. The bifurcation pictures and the asymptotic expansions of the bifurcation functions are given. The stability criterion for the homoclinic loop is also obtained when the integral of the divergence is zero. The proof of the auxiliary theorems will be presented in [16].
基金supported by the National Natural Science Foundation of China(No.U1904215)Natural Science Foundation of Jiangsu Province(No.BK20200044)+1 种基金Changjiang scholars program of the Ministry of Education(No.Q2018270)China Postdoctoral Science Foundation(Nos.2022M722683 and 2022M722686).
文摘The uncontrolled dendrite growth and volume change of Li metal during cycling lead to a short cycle life and safety concerns for Li-metal batteries,which hinders their practical application.Herein,we report the facile and energy-saving production of a three-dimensional(3D)CuZn matrix decorated with in-situ formed ZnO nano seeds(ZnO NS@3D CuZn)in pores and tunnels,which can serve as an anode current collector for dendrite-free Li-metal batteries.The 3D porous framework reduced the anode current density and accommodated Li volume change during the charge/discharge process.More importantly,the lithiophilic ZnO nano seeds induced fast Li deposition into the pores and tunnels of the 3D structure to effectively confine the deposited Li.As a positive effect,the volume change and Li dendrite growth during cycling are greatly suppressed.The half-cell with the ZnO NS@3D CuZn current collector exhibited a Coulombic efficiency(CE)of above 98%for over 320 and 240 cycles at 0.5 and 1 mA·cm^(-2),respectively.The Li@ZnO NS@3D CuZn symmetric cell achieves a lifespan of over 1500 h.Moreover,the Li@ZnO NS@3D CuZn||LiFePO4 full cell achieves a superb average CE of 99.4%and a long life of 600 cycles before the capacity retention rate decays to 90%.
基金supported by the National Nature Science Foundations of China (No.21965019)the China Postdoctoral Science Foundation (No.2017M613248)+1 种基金the Natural Science Foundation of Gansu Province (No.1506 RJZA091)the Scientific Research Foundation of the Higher Education Institutions of Gansu Province (No.2015A-037)。
文摘Zinc-ion hybrid super-capacitors are regarded as promising safe energy storage systems,However,the relatively low volumetric energy density has become the main bottlenecks in practical applications of portable electronic devices,In this work,the zinc-ion hybrid super-capacitor with high volumetric energy density and superb cycle stability had been constructed which employing the high-density threedimensional graphene hydrogel as cathode and Zn foil used as anode in 1 mol/L ZnSO4 electrolyte.Benefiting from the abundant ion transport paths and the abundant active sites for graphene hydrogel with high density and porous structure,the zinc-ion hybrid super-capacitor exhibited an extremely high volumetric energy density of 118.42 Wh/L and a superb power density of 24.00 kW/L,as well as an excellent long cycle life(80% retention after 30,000 cycles at 10 A/g),which was superior to the volumetric energy density of the reported zinc-ion hybrid super-capacitors.This device,based on the fast ion adsorption/deso rption on the capacitor-type graphene cathode and reversible Zn^(2+) plating/stripping on the battery-type Zn anode,which will inspire the development of zinc-ion hybrid super-capacitor in miniaturized devices.
文摘喷头驱动电源是压电喷头的核心部件之一。针对厚度剪切型压电喷头致动器结构特征,分析了0.11～0.32μm范围内的致动壁位移随驱动电压在20～60 V范围内近似线性增大的关系,推导出致动壁15 k Hz的谐振基频数值,结合喷墨通道＂三循环＂驱动方式时序,设计了一种基于直流变换原理的开关式驱动电源,实现了32路喷墨通道分组喷射,其最大输出电压范围±60 V,正负脉宽和设置时间在15～200μs内在线可调,单路输出电流大于6 m A,脉宽最大误差小于3%。初步测试实验了该驱动电源的可行性。
文摘On the basis of introducing the concept of urban agriculture, this paper analyses the necessity of developing urban agriculture in Huainan City as follows: it is the need of transformation and upgrading of agricultural industry; it is the need of development of urban-rural integration; it is the need of sustainable urban development; it is the need of solving the issues concerning agriculture, countryside and farmers effectively. Then this paper analyses the endowment of developing urban agriculture in Huainan City. And finally the basic conception in industrial form and spatial framework is put forward, to develop urban agriculture in Huainan City.
基金financially supported by the“Advanced Research Center for Green Materials Science and Technology”from The Featured Area Research Center Program within the framework of the Higher Education Sprout Project by Ministry of Science and Technology in Taiwan under the grants of MOST-108-3017-F-002002,and also of MOST-107-2221-E-002-106-MY3,MOST-108-2119-M-002-010,MOST-107-2923-E-011-002,MOST-108-3116-F-301-001-F
文摘Pseudocapacitive transition metal oxides(PTMOs)have the advantages of high areal capacitance and material density suitable for high-energy supercapacitor devices,but they are typically marred by insufficient rate performance,which in turn deteriorates cyclic stability at high current levels.Using the example of spinel manganese oxide,herein we demonstrate that a pseudocapacitive oxide electrode of remarkable rate performance and cyclic stability may be realized by adopting oxide nanocrystallites,which are derived based on a novel solution chemistry,and carbon additive(CA)nanoparticles with highly uniform of size distributions.Precisely controlling the particle morphology and size distribution of the active material and conductive additive(CA)in the nanometer range can maximize the density of active material-CA-electrolyte three-phase contact points,thus facilitating synchronized electron and cation flow for the completion of surface faradaic reactions.The resultant Mn3O4 pseudocapacitive electrode exhibits rate capability and cycle stability,including 60%capacity retention at 60 A g-1 and no capacity fade over 100000 cycles under dynamic current densities,far superior to the state-of-the-art PTMO electrodes.The electrode design strategy is in general applicable to pseudocapacitors containing poorly conductive active materials.
