传统的基于有限元的建模和计算方法在中高频条件下得出的结果不精确,因此,整流罩在中高频条件下结构振动、声辐射以及声振耦合等问题,可以用统计能量分析(SEA)方法和有限元-统计能量分析(FE-SEA)法进行分析。通过ESI VA ONE软件建立整...传统的基于有限元的建模和计算方法在中高频条件下得出的结果不精确,因此,整流罩在中高频条件下结构振动、声辐射以及声振耦合等问题,可以用统计能量分析(SEA)方法和有限元-统计能量分析(FE-SEA)法进行分析。通过ESI VA ONE软件建立整流罩的结构FE模型以及划分内部声腔子系统,分析不同子系统在声振条件下内部声压级的大小。仿真结果表明在声振耦合条件下,整流罩的声腔子系统在不同的部位声压级大小不同,以及声压级大小随频率变化。展开更多
Sliding electrical contact is a common phenomenon in electrical equipment and affects performance.In this paper,the mechanism of sliding electric contact pair transition and the moment when transition occurs are inves...Sliding electrical contact is a common phenomenon in electrical equipment and affects performance.In this paper,the mechanism of sliding electric contact pair transition and the moment when transition occurs are investigated using the railgun as an example.Transition is the phenomenon where the contact between the armature and rails changes from solid-solid contact to solid-arc-solid contact.In this paper,the finite element-boundary element coupling method(FE-BE method)is used to simulate the process of armature movement.Then,the force,thermal,and electrical parameters on the armature/rail contact surface are analyzed to explore the development of contact separation.Finally,the occurrence of the transition is judged based on the Townsend discharge model(improved by Rogowski).A Small-caliber railgun firing test was carried out to validate the methodology presented in this paper.Results show that the drop edge of the current will result in the armature/rail not being able to make full contact,and the contact gap may break down,leading to a sharp increase in contact resistance and deterioration of railgun performance.Judging the occurrence of transition based on the evolution of the contact gap and the Townsend discharge model is reliable.The research provides new ideas for studying railgun transition and sliding electric contact failure.展开更多
The effects of the calorimetric buffer solutions were investigated while the two colorimetric reactions of AI-ferron complex and Fe-ferron complex occurred individually, and the effects of the testing wavelength and t...The effects of the calorimetric buffer solutions were investigated while the two colorimetric reactions of AI-ferron complex and Fe-ferron complex occurred individually, and the effects of the testing wavelength and the pH of the solutions were also investigated. A timed complexatian colorimetric analysis method of Al-Fe-ferron in view of the total concentration of {AI + Fe} was then established to determine the species distribution of polymeric Al-Fe. The testing wavelength was recommended at 362 net and the testing pH value was 5. With a comparison of the ratios of n(Al)/n(Fe), the standard adsorption curves of the polymeric Al-Fe solutions were derived from the experimental results. Furthermore, the solutions' composition were carious in both the molar n(Al)/n(Fe) ratios, i.e. 0/0, 5/5, 9/1 and 0/10, and the concentrations associated with the total ( Al + Fe which ranged from 10(-5) to 10(-4) mol/L..展开更多
In this work,we have presented a spin-coating method to produce thin films started with pure BiCrO3（BCO）and ended up with BiFeO3（BFO）by increasing x values in the（BiFeO3）x-（BiCrO3）1-x composites.All the produc...In this work,we have presented a spin-coating method to produce thin films started with pure BiCrO3（BCO）and ended up with BiFeO3（BFO）by increasing x values in the（BiFeO3）x-（BiCrO3）1-x composites.All the produced thin films have been crystallized at the annealing temperatures of 400 ℃ for 0.5 h.The XRD and EDAX spectrums give insight that the two crystal phases related to BCO and BFO stayed together within the thin film matrices.SEM analysis showed that the prepared composite had macroporous morphology with interconnected pores and its width（size）decreased with increasing x values.The strong correlations are observed among the microstructure,dielectric,ferroelectric,ferromagnetic properties and Fe concentration.Among all composites,the composition of 0.75 shows an attractive magnetization,polarization,switching and improved dielectric behaviors at room temperature.Significant increase in the multiferroic characteristics of 0.75 composition is due to arise of lower leakage current by causing reduction in oxygen vacancy density,and enhancement of super-exchange magnetic interaction between Fe3＋ and Cr3＋ at BFO/BCO interface layers.Our result shows that the thin layer on Pt（111）/Ti/SiO2/Si substrate possesses simultaneously improved ferroelectric and ferromagnetic properties which make an inaccessible potential application for nonvolatile ferroelectric memories.展开更多
文摘传统的基于有限元的建模和计算方法在中高频条件下得出的结果不精确,因此,整流罩在中高频条件下结构振动、声辐射以及声振耦合等问题,可以用统计能量分析(SEA)方法和有限元-统计能量分析(FE-SEA)法进行分析。通过ESI VA ONE软件建立整流罩的结构FE模型以及划分内部声腔子系统,分析不同子系统在声振条件下内部声压级的大小。仿真结果表明在声振耦合条件下,整流罩的声腔子系统在不同的部位声压级大小不同,以及声压级大小随频率变化。
文摘Sliding electrical contact is a common phenomenon in electrical equipment and affects performance.In this paper,the mechanism of sliding electric contact pair transition and the moment when transition occurs are investigated using the railgun as an example.Transition is the phenomenon where the contact between the armature and rails changes from solid-solid contact to solid-arc-solid contact.In this paper,the finite element-boundary element coupling method(FE-BE method)is used to simulate the process of armature movement.Then,the force,thermal,and electrical parameters on the armature/rail contact surface are analyzed to explore the development of contact separation.Finally,the occurrence of the transition is judged based on the Townsend discharge model(improved by Rogowski).A Small-caliber railgun firing test was carried out to validate the methodology presented in this paper.Results show that the drop edge of the current will result in the armature/rail not being able to make full contact,and the contact gap may break down,leading to a sharp increase in contact resistance and deterioration of railgun performance.Judging the occurrence of transition based on the evolution of the contact gap and the Townsend discharge model is reliable.The research provides new ideas for studying railgun transition and sliding electric contact failure.
基金TheNationalNaturalScienceFoundationofChina (No .2 96 770 0 4)
文摘The effects of the calorimetric buffer solutions were investigated while the two colorimetric reactions of AI-ferron complex and Fe-ferron complex occurred individually, and the effects of the testing wavelength and the pH of the solutions were also investigated. A timed complexatian colorimetric analysis method of Al-Fe-ferron in view of the total concentration of {AI + Fe} was then established to determine the species distribution of polymeric Al-Fe. The testing wavelength was recommended at 362 net and the testing pH value was 5. With a comparison of the ratios of n(Al)/n(Fe), the standard adsorption curves of the polymeric Al-Fe solutions were derived from the experimental results. Furthermore, the solutions' composition were carious in both the molar n(Al)/n(Fe) ratios, i.e. 0/0, 5/5, 9/1 and 0/10, and the concentrations associated with the total ( Al + Fe which ranged from 10(-5) to 10(-4) mol/L..
基金supported by Department of Science and Technology (SB/S2/CMP- 028/2013), New Delhi, India
文摘In this work,we have presented a spin-coating method to produce thin films started with pure BiCrO3（BCO）and ended up with BiFeO3（BFO）by increasing x values in the（BiFeO3）x-（BiCrO3）1-x composites.All the produced thin films have been crystallized at the annealing temperatures of 400 ℃ for 0.5 h.The XRD and EDAX spectrums give insight that the two crystal phases related to BCO and BFO stayed together within the thin film matrices.SEM analysis showed that the prepared composite had macroporous morphology with interconnected pores and its width（size）decreased with increasing x values.The strong correlations are observed among the microstructure,dielectric,ferroelectric,ferromagnetic properties and Fe concentration.Among all composites,the composition of 0.75 shows an attractive magnetization,polarization,switching and improved dielectric behaviors at room temperature.Significant increase in the multiferroic characteristics of 0.75 composition is due to arise of lower leakage current by causing reduction in oxygen vacancy density,and enhancement of super-exchange magnetic interaction between Fe3＋ and Cr3＋ at BFO/BCO interface layers.Our result shows that the thin layer on Pt（111）/Ti/SiO2/Si substrate possesses simultaneously improved ferroelectric and ferromagnetic properties which make an inaccessible potential application for nonvolatile ferroelectric memories.
