In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.Bu...In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.But such an approach has not been proved rigorously,and its accuracy must be carefully considered.In this paper,we discuss the problem of a sphere moving in a non-uniform flow field,on the basis of the fundamental theory of hydrodynamics.We introduce two assumptions:i)the diameter of the sphere is much smaller than the linear dimension of the flow field,and ii)the velocity of the sphere relative to the surrounding water is very small.Using these two assumptions,we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform,and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.展开更多
In this paper, the models describing the charge transfer between two sand particles due to collisions are reviewed. By comparing the experimental results and the calculated results by the models carried on an individu...In this paper, the models describing the charge transfer between two sand particles due to collisions are reviewed. By comparing the experimental results and the calculated results by the models carried on an individual particle due to a single collision, it indicates the Mosaic model is more reasonable to describe the collision charging mechanism. The Mosaic model cannot only describe the dependence of the collision charges on the relative collision speed and the particle size, but also reveal the relationship between the collision charges with the environmental temperature, the relative humidity and the material parameters, e.g., the absorption energy. Based on the Mosaic model, the model to describe the charges transfer due to multiple collisions is also developed, which can be used to calculate the charges carried by sand particles due to multiple collisions in the wind blown sand flux.展开更多
The critical size of the sand particles in liquid is determined by means of the special vibratory apparatus, and it is related to various effects on the cavitation damage. The increase of the sand size or concentratio...The critical size of the sand particles in liquid is determined by means of the special vibratory apparatus, and it is related to various effects on the cavitation damage. The increase of the sand size or concentration would aggravate the cavitation damage if their sizes are larger than this critical size, conversely, this damage would be relieved.展开更多
Fluoroalkyl end-capped vinyltrimethoxysilane oligomer</span> </div> <span style="font-family:""> <div style="text-align:justify;"> <span style="font-family:&quo...Fluoroalkyl end-capped vinyltrimethoxysilane oligomer</span> </div> <span style="font-family:""> <div style="text-align:justify;"> <span style="font-family:""><span style="font-family:Verdana;">[R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(CH</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">-CHSi(OMe)</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">: </span><i><span style="font-family:Verdana;">n</span></i><span style="font-family:Verdana;"> = 2, 3, R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;"> = CF(CF</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)OC</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">7</span></sub><span style="font-family:Verdana;">: R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">]</span></span><span style="font-family:Verdana;">,</span><span style="font-family:""><span style="font-family:Verdana;"> was applied to the facile preparation of the corresponding oligomer/sand (Ottawa </span><span style="font-family:Verdana;">sand: OS) composites [R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/OS] through the sol-gel reaction </span><span style="font-family:Verdana;">of the oligomer in the presence of micro-sized OS particles (590 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:""><span style="font-family:Verdana;"> 840 μm) under alkaline conditions at room temperature. FE-SEM (Field Emission Scanning Electron Micrograph) images showed that the obtained composites consist of the R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;"> oligomeric nanoparticles and the micro-sized </span><span style="font-family:Verdana;">OS particles. Interestingly, the R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/OS composites thus ob</span><span style="font-family:Verdana;">tained </span><span style="font-family:Verdana;">can provide the superoleophilic/superhydrophobic characteristic on the</span><span style="font-family:Verdana;"> composite surface, applying to the separation of not only the mixture of oil/water but also the W/O emulsion to isolate the transparent colorless oil. The fluorinated oligomeric OS composites were also found to be applicable to the selective removal of fluorinated aromatic compounds from </span></span><span style="font-family:Verdana;">an </span><span style="font-family:Verdana;">aqueous methanol solution. Especially, it was demonstrated that the fluorinated OS composites can supply a higher efficient and smooth separation ability for the separation of </span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">mixture of oil and water than that of the corresponding fluorinated micro-sized controlled silica gel (μ-SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">) composites (average particle size: 9.5 μm), which were prepared under similar conditions. In addition to the separation of oil/water, the fluorinated OS composites provided higher and </span></span><span style="font-family:Verdana;">more </span><span style="font-family:""><span style="font-family:Verdana;">selective removal ability for the fluorinated aromatic compounds from aqueous solutions than that of the μ-SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> composites.展开更多
Sand storm is a serious environmental threat to humans. Sand particles are transported by saltation and suspension, causing soil erosion in one place and deposition in another. In order to prevent and predict sand sto...Sand storm is a serious environmental threat to humans. Sand particles are transported by saltation and suspension, causing soil erosion in one place and deposition in another. In order to prevent and predict sand storms, the causes and the manners of particle motions must he studied in detail. In this paper a standard k-8 model is used for the gas phase simulation and the discrete element method (DEM) is used to predict the movements of particles using an in-house procedure. The data are summarized in an Eulerian-Eulerian regime after simulation to get the statistical particle Reynolds stress and particle collision stress. The results show that for the current case the Reynolds stress and the air shear stress predominate in the region 20-250 mm above the initial sand bed surface. However, in the region below 3 ram, the collision stress must be taken into account in predicting particle movement.展开更多
文摘In hydraulics,when we deal with the problem of sand particles moving relative to the surrounding water,Stokes'formula of resistance has usually been used to render the velocity of sedimentation of the particles.But such an approach has not been proved rigorously,and its accuracy must be carefully considered.In this paper,we discuss the problem of a sphere moving in a non-uniform flow field,on the basis of the fundamental theory of hydrodynamics.We introduce two assumptions:i)the diameter of the sphere is much smaller than the linear dimension of the flow field,and ii)the velocity of the sphere relative to the surrounding water is very small.Using these two assumptions,we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform,and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.
基金National Natural Science Foundation of China(Grants 51435008,11472122 and 11272139)。
文摘In this paper, the models describing the charge transfer between two sand particles due to collisions are reviewed. By comparing the experimental results and the calculated results by the models carried on an individual particle due to a single collision, it indicates the Mosaic model is more reasonable to describe the collision charging mechanism. The Mosaic model cannot only describe the dependence of the collision charges on the relative collision speed and the particle size, but also reveal the relationship between the collision charges with the environmental temperature, the relative humidity and the material parameters, e.g., the absorption energy. Based on the Mosaic model, the model to describe the charges transfer due to multiple collisions is also developed, which can be used to calculate the charges carried by sand particles due to multiple collisions in the wind blown sand flux.
文摘The critical size of the sand particles in liquid is determined by means of the special vibratory apparatus, and it is related to various effects on the cavitation damage. The increase of the sand size or concentration would aggravate the cavitation damage if their sizes are larger than this critical size, conversely, this damage would be relieved.
文摘Fluoroalkyl end-capped vinyltrimethoxysilane oligomer</span> </div> <span style="font-family:""> <div style="text-align:justify;"> <span style="font-family:""><span style="font-family:Verdana;">[R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(CH</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">-CHSi(OMe)</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">: </span><i><span style="font-family:Verdana;">n</span></i><span style="font-family:Verdana;"> = 2, 3, R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;"> = CF(CF</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">)OC</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">7</span></sub><span style="font-family:Verdana;">: R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">]</span></span><span style="font-family:Verdana;">,</span><span style="font-family:""><span style="font-family:Verdana;"> was applied to the facile preparation of the corresponding oligomer/sand (Ottawa </span><span style="font-family:Verdana;">sand: OS) composites [R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/OS] through the sol-gel reaction </span><span style="font-family:Verdana;">of the oligomer in the presence of micro-sized OS particles (590 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:""><span style="font-family:Verdana;"> 840 μm) under alkaline conditions at room temperature. FE-SEM (Field Emission Scanning Electron Micrograph) images showed that the obtained composites consist of the R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;"> oligomeric nanoparticles and the micro-sized </span><span style="font-family:Verdana;">OS particles. Interestingly, the R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">-(VM-SiO</span><sub><span style="font-family:Verdana;">3/2</span></sub><span style="font-family:Verdana;">)</span><i><sub><span style="font-family:Verdana;">n</span></sub></i><span style="font-family:Verdana;">-R</span><sub><span style="font-family:Verdana;">F</span></sub><span style="font-family:Verdana;">/OS composites thus ob</span><span style="font-family:Verdana;">tained </span><span style="font-family:Verdana;">can provide the superoleophilic/superhydrophobic characteristic on the</span><span style="font-family:Verdana;"> composite surface, applying to the separation of not only the mixture of oil/water but also the W/O emulsion to isolate the transparent colorless oil. The fluorinated oligomeric OS composites were also found to be applicable to the selective removal of fluorinated aromatic compounds from </span></span><span style="font-family:Verdana;">an </span><span style="font-family:Verdana;">aqueous methanol solution. Especially, it was demonstrated that the fluorinated OS composites can supply a higher efficient and smooth separation ability for the separation of </span><span style="font-family:Verdana;">the </span><span style="font-family:""><span style="font-family:Verdana;">mixture of oil and water than that of the corresponding fluorinated micro-sized controlled silica gel (μ-SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">) composites (average particle size: 9.5 μm), which were prepared under similar conditions. In addition to the separation of oil/water, the fluorinated OS composites provided higher and </span></span><span style="font-family:Verdana;">more </span><span style="font-family:""><span style="font-family:Verdana;">selective removal ability for the fluorinated aromatic compounds from aqueous solutions than that of the μ-SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> composites.
基金supported by the National Natural Science Foundation of China(Grant No.10532030)the CAS Innovation Program
文摘Sand storm is a serious environmental threat to humans. Sand particles are transported by saltation and suspension, causing soil erosion in one place and deposition in another. In order to prevent and predict sand storms, the causes and the manners of particle motions must he studied in detail. In this paper a standard k-8 model is used for the gas phase simulation and the discrete element method (DEM) is used to predict the movements of particles using an in-house procedure. The data are summarized in an Eulerian-Eulerian regime after simulation to get the statistical particle Reynolds stress and particle collision stress. The results show that for the current case the Reynolds stress and the air shear stress predominate in the region 20-250 mm above the initial sand bed surface. However, in the region below 3 ram, the collision stress must be taken into account in predicting particle movement.