We combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magnetoresistance(GMR) in magnetic granular composites.The composite is ...We combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magnetoresistance(GMR) in magnetic granular composites.The composite is composed of small magnetic granules (such as Co) embedded in an immiscible nonmagnetic metallic matrix (such as Ag).We consider the influence of granule size and concentration respectively.Firstly,granules have a distribution in size,resulting in superparamagnetic(SPM) granules and ferromagnetic granules which have different contributions to conductance.Secondly,the effective surface scattering is changed with the changes of concentration.The calculated result of GMR is in agreement with theexperimental data.展开更多
We present a model of non-uniform granular gases in one-dimensional case, whose granularity distribution has the fractal characteristic. We have studied the nonequilibrium properties of the system by means of Monte Ca...We present a model of non-uniform granular gases in one-dimensional case, whose granularity distribution has the fractal characteristic. We have studied the nonequilibrium properties of the system by means of Monte Carlo method. When the typical relaxation time T of the Brownian process is greater than the mean collision time To, the energy evolution of the system exponentially decays, with a tendency to achieve a stable asymptotic value, and the system finally reaches a nonequilibrium steady state in which the velocity distribution strongly deviates from the Gaussian one. Three other aspects have also been studied for the steady state： the visualized change of the particle density, the entropy of the system and the correlations in the velocity of particles. And the results of simulations indicate that the system has strong spatial clustering; Furthermore, the influence of the inelasticity and inhomogeneity on dynamic behaviors have also been extensively investigated, especially the dependence of the entropy and the correlations in the velocity of particles on the restitute coefficient e and the fractal dimension D.展开更多
A model for incipient movement of sediment in rolling pattern was established. In this model, the starting of sediment particles under low transport rate, the exposure degree of sediment, the lateral slope of water su...A model for incipient movement of sediment in rolling pattern was established. In this model, the starting of sediment particles under low transport rate, the exposure degree of sediment, the lateral slope of water surface and the effect of transverse circulating current induced by the hydraulic structure of bend flow were fully considered. A theoretical formula for the incipient velocity of non-cohesive and non-uniform sediment in sloping river bends was developed. The results from the theoretical formula compared well with the experimental data.展开更多
Drying of colloidal droplets often develops versatile depositions.We study the drying deposition of both colloidal droplets containing silica nanoparticles and the silica colloidal droplets with polyethylene oxide(PEO...Drying of colloidal droplets often develops versatile depositions.We study the drying deposition of both colloidal droplets containing silica nanoparticles and the silica colloidal droplets with polyethylene oxide(PEO) additives.We focus on the effect of polymer additives on the deposition formation and the cracking dynamics by using in-situ microscope observation.With PEO additives,a transition from ring-like deposition to uniform deposition is observed,and the cracking dynamics is greatly reduced.The PEO additives enhance the adsorption of particles at the air-water interface,thus forming the network structure at the interface which blocks the outward capillary flow.This contributes to the uniform deposition.Meanwhile,the multi-distribution of the aggregates size enhances the non-homogeneity of the drying film and consequently results in multi-nucleation of cracks.This reduces the stress accumulation that drives the crack propagation and may be responsible for the sluggish cracking dynamics.展开更多
We introduce a non-uniform gravity-like force field to control the granular flow state in a quasi-one- dimensional system, and study the system by the molecular dynamics simulation. We find that the granular flow unde...We introduce a non-uniform gravity-like force field to control the granular flow state in a quasi-one- dimensional system, and study the system by the molecular dynamics simulation. We find that the granular flow under non-uniform force field can be well described by a density wave with fixed time period if a fixed partiele number condition is used. The base frequency of the density wave does not depend on the position of the flow, while both the average density and oseillation amplitude of the flow vary continuously with the position. The formation of the density wave results from the aggregation of the granules in the decelerated region and the feed-back mechanism in the fixed particle number condition.展开更多
文摘We combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magnetoresistance(GMR) in magnetic granular composites.The composite is composed of small magnetic granules (such as Co) embedded in an immiscible nonmagnetic metallic matrix (such as Ag).We consider the influence of granule size and concentration respectively.Firstly,granules have a distribution in size,resulting in superparamagnetic(SPM) granules and ferromagnetic granules which have different contributions to conductance.Secondly,the effective surface scattering is changed with the changes of concentration.The calculated result of GMR is in agreement with theexperimental data.
基金The project supported by National Natural Science of China under Grant No. 10675408 and Natural Science Foundation of Xianning College under Grant No. KZ0627
文摘We present a model of non-uniform granular gases in one-dimensional case, whose granularity distribution has the fractal characteristic. We have studied the nonequilibrium properties of the system by means of Monte Carlo method. When the typical relaxation time T of the Brownian process is greater than the mean collision time To, the energy evolution of the system exponentially decays, with a tendency to achieve a stable asymptotic value, and the system finally reaches a nonequilibrium steady state in which the velocity distribution strongly deviates from the Gaussian one. Three other aspects have also been studied for the steady state： the visualized change of the particle density, the entropy of the system and the correlations in the velocity of particles. And the results of simulations indicate that the system has strong spatial clustering; Furthermore, the influence of the inelasticity and inhomogeneity on dynamic behaviors have also been extensively investigated, especially the dependence of the entropy and the correlations in the velocity of particles on the restitute coefficient e and the fractal dimension D.
基金Supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.51021004)the National Natural Science Foundation of China(No.50979066 and No.51009105)the Natural Science Foundation of Tianjin(No.12JCQNJC05600)
文摘A model for incipient movement of sediment in rolling pattern was established. In this model, the starting of sediment particles under low transport rate, the exposure degree of sediment, the lateral slope of water surface and the effect of transverse circulating current induced by the hydraulic structure of bend flow were fully considered. A theoretical formula for the incipient velocity of non-cohesive and non-uniform sediment in sloping river bends was developed. The results from the theoretical formula compared well with the experimental data.
基金supported by the National Natural Science Foundation of China (Grant No.51103117)Shaanxi Provincial Natural Science Foundation (Grant No.2012JQ1016)+2 种基金NPU Foundation for Fundamental Research (Grant Nos.JCY20130147 and JC201125)Specialized Research Fund for the Doctoral Program of Higher Education (Grant No.20126102120058)the Research Fund of the State Key Laboratory of Solidification Processing in NWPU (Grant No.SKLSP201217)
文摘Drying of colloidal droplets often develops versatile depositions.We study the drying deposition of both colloidal droplets containing silica nanoparticles and the silica colloidal droplets with polyethylene oxide(PEO) additives.We focus on the effect of polymer additives on the deposition formation and the cracking dynamics by using in-situ microscope observation.With PEO additives,a transition from ring-like deposition to uniform deposition is observed,and the cracking dynamics is greatly reduced.The PEO additives enhance the adsorption of particles at the air-water interface,thus forming the network structure at the interface which blocks the outward capillary flow.This contributes to the uniform deposition.Meanwhile,the multi-distribution of the aggregates size enhances the non-homogeneity of the drying film and consequently results in multi-nucleation of cracks.This reduces the stress accumulation that drives the crack propagation and may be responsible for the sluggish cracking dynamics.
基金Supported by the National Basic Research Program of China under Grant No.2009CB930800by the National Natural Science Foundation of China under Grant Nos.10875166 and 11274355
文摘We introduce a non-uniform gravity-like force field to control the granular flow state in a quasi-one- dimensional system, and study the system by the molecular dynamics simulation. We find that the granular flow under non-uniform force field can be well described by a density wave with fixed time period if a fixed partiele number condition is used. The base frequency of the density wave does not depend on the position of the flow, while both the average density and oseillation amplitude of the flow vary continuously with the position. The formation of the density wave results from the aggregation of the granules in the decelerated region and the feed-back mechanism in the fixed particle number condition.
