We study the global pressure of a one-dimensional polydisperse granular gases system for the first time, in which the size distribution of particles has the fractal characteristic and the inhomogeneity is described by...We study the global pressure of a one-dimensional polydisperse granular gases system for the first time, in which the size distribution of particles has the fractal characteristic and the inhomogeneity is described by a fractal dimension D. The particles are driven by Gaussian white noise and subject to inelastic mutual collisions. We define the global pressure P of the system as the impulse transferred across a surface in a unit of time, which has two contributions, one from the translational motion of particles and the other from the collisions. Explicit expression for the global pressure in the steady state is derived. By molecular dynamics simulations, we investigate how the inelasticity of collisions and the inhomogeneity of the particles influence the global pressure. The simulation results indicate that the restitution coefficient e and the fractal dimension D have significant effect on the pressure.展开更多
In atomic force microscopy(AFM), high-frequency components consisted in dynamic tip-sample interaction have been recently demonstrated as a promising technique for exploring more extensive material properties. Here we...In atomic force microscopy(AFM), high-frequency components consisted in dynamic tip-sample interaction have been recently demonstrated as a promising technique for exploring more extensive material properties. Here we present an exploratory study of high harmonic atomic force microscopy by force-spectroscopy and high harmonic imaging. Since these components are very weak compared to the fundamental response, we firstly designed a high harmonic cantilever by tuning the second order flexural resonance frequency to an integer 6 times of its fundamental mode(i.e. ω_2=6ω_1). Moreover, it is verified that high harmonic can discern extra features than topographies on different samples with amplitude/frequency modulation(AM/FM) dynamic AFM mode. In AM mode, the first resonance amplitude and 6 th harmonic amplitude were discussed. The 6 th harmonic is more sensitive than the first order response. In FM mode, it is noted that the decaying rate of the 6 th harmonic frequency is approximately 6 multiples to the slope of the fundamental frequency shift when the tip approaches to the surface of sample. This non-destructive method was also adopted to investigate the local interlayer coupling and intercalation in the two-dimensional graphene films tentatively.展开更多
Aircraft metal components and structures are susceptible to environmental degradation throughout their original design life and in many cases their extended lives.This paper summarizes the results of an experimental p...Aircraft metal components and structures are susceptible to environmental degradation throughout their original design life and in many cases their extended lives.This paper summarizes the results of an experimental program to evaluate the ability of Supersonic Particle Deposition(SPD),also known as cold spray,to extend the limit of validity(LOV)of aircraft structural components and to restore the structural integrity of corroded panels.In this study the potential for the SPD to seal the mechanically fastened joints and for this seal to remain intact even in the presence of multi-site damage(MSD)has been evaluated.By sealing the joint the onset of corrosion damage in the joint can be significantly retarded,possibly even eliminated,thereby dramatically extending the LOV of mechanically fastened joints.The study also shows that SPD can dramatically increase the damage tolerance of badly corroded wing skins.展开更多
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10675048 and 10604017 and Natural Science Foundation of Xianning College under Grant No. KZ0627
文摘We study the global pressure of a one-dimensional polydisperse granular gases system for the first time, in which the size distribution of particles has the fractal characteristic and the inhomogeneity is described by a fractal dimension D. The particles are driven by Gaussian white noise and subject to inelastic mutual collisions. We define the global pressure P of the system as the impulse transferred across a surface in a unit of time, which has two contributions, one from the translational motion of particles and the other from the collisions. Explicit expression for the global pressure in the steady state is derived. By molecular dynamics simulations, we investigate how the inelasticity of collisions and the inhomogeneity of the particles influence the global pressure. The simulation results indicate that the restitution coefficient e and the fractal dimension D have significant effect on the pressure.
基金supported by the Ministry of Science and Technology(MOST)of China(Grant No.2016YFA0200700)the National Natural Science Foundation of China(Grant Nos.21622304,61674045,11604063)+2 种基金Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDB-SSW-SYS031)Osaka University's International Joint Research Promotion Program(Grant Nos.J171013014,J171013007)Distinguished Technical Talents Project and Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘In atomic force microscopy(AFM), high-frequency components consisted in dynamic tip-sample interaction have been recently demonstrated as a promising technique for exploring more extensive material properties. Here we present an exploratory study of high harmonic atomic force microscopy by force-spectroscopy and high harmonic imaging. Since these components are very weak compared to the fundamental response, we firstly designed a high harmonic cantilever by tuning the second order flexural resonance frequency to an integer 6 times of its fundamental mode(i.e. ω_2=6ω_1). Moreover, it is verified that high harmonic can discern extra features than topographies on different samples with amplitude/frequency modulation(AM/FM) dynamic AFM mode. In AM mode, the first resonance amplitude and 6 th harmonic amplitude were discussed. The 6 th harmonic is more sensitive than the first order response. In FM mode, it is noted that the decaying rate of the 6 th harmonic frequency is approximately 6 multiples to the slope of the fundamental frequency shift when the tip approaches to the surface of sample. This non-destructive method was also adopted to investigate the local interlayer coupling and intercalation in the two-dimensional graphene films tentatively.
文摘Aircraft metal components and structures are susceptible to environmental degradation throughout their original design life and in many cases their extended lives.This paper summarizes the results of an experimental program to evaluate the ability of Supersonic Particle Deposition(SPD),also known as cold spray,to extend the limit of validity(LOV)of aircraft structural components and to restore the structural integrity of corroded panels.In this study the potential for the SPD to seal the mechanically fastened joints and for this seal to remain intact even in the presence of multi-site damage(MSD)has been evaluated.By sealing the joint the onset of corrosion damage in the joint can be significantly retarded,possibly even eliminated,thereby dramatically extending the LOV of mechanically fastened joints.The study also shows that SPD can dramatically increase the damage tolerance of badly corroded wing skins.
