Saltation threshold reduction due to the electrostatic agglomeration of fine particles

Particles between 80 and 110 microns in diameter are the most easily moved by the wind. As the particle size decreases below 60 microns, they are increasingly more difficult to move by surface winds, and a number of experiments were performed in an attempt to reduce the required wind velocity. These include: (1) the bombardment of a bed of fine particles by particles near the optimum size, the larger particles kicking the fine particles into the windstream where they are entrained; and (2) the electrostatic agglomeration of fine particles into sizes more easily saltated. The results of these experiments are discussed

Experimental study on fluidization of micronic powders

The fluidization behavior of yttrium oxide (Y2O3) powders of high density and micronic diameter belonging to the group C of Geldart’s classification has been investigated. Large interparticle forces lead to bed cracking, slugging and channelling, and cause the powder not to fluidize consistently. Different fluidization technologies have been tested, such as mechanical agitated fluidization, vibrated fluidization and addition of easyto-fluidize large particles to fine particles. The quality of fluidization has been studied through pressure drop diagrams for decreasing gas velocities and for various fixed bed heights to column diameter ratios. In the case of stirred fluidization, several stirrer geometries have been tested (helix, turbine, etc.). However, the fluidization has not been satisfactory. By adding larger particles to fine powders, convenient fluidization conditions have been obtained. An inertia effect proportional to the initial bed weight seems to contribute to fluidization. Some evaluation of interparticle forces governing the tested mixture of fine/large particles has been performed by studying the influence of mass percentage of fine particles on the Hausner ratio and the angle of repose. Fluidization under vibration allows to partly overcome the adhesion forces between powders. The fluidization behavior has been improved for the highest vibration strengths

Fluidized reduction of oxides on fine metal powders without sintering

In the process of reducing extremely fine metal particles (av. particle size or = 1000 angstroms) covered with an oxide layer, the metal particles are fluidized by a gas flow contg. H, heated, and reduced. The method uniformly and easily reduces surface oxide layers of the extremely fine metal particles without causing sintering. The metal particles are useful for magnetic recording materials, conductive paste, powder metallurgy materials, chem. reagents, and catalysts

Fine-mesh screen made by simplified method

Strong fine-mesh screens are fabricated by a method involving uniform distribution of fine ferromagnetic particles on a nonmagnetic plate. Such screens are commonly used for grids in electron tubes and ion devices

Surface treatment for valve seats

Valve with embedded fine particles of diamond in the metal surface of the valve seat resists galling, corrosion, erosion, and cold welding. Diamond powder has an average particle diameter of 0.01 micron and is used with a standard fine diamond polishing compound

New Physics and the Proton Radius Problem

Background: The recent disagreement between the proton charge radius extracted from Lamb shift measurements of muonic and electronic hydrogen invites speculation that new physics may be to blame. Several proposals have been made for new particles that account for both the Lamb shift and the muon anomalous moment discrepancies. Purpose: We explore the possibility that new particles' couplings to the muon can be fine-tuned to account for all experimental constraints. Method: We consider two fine-tuned models, the first involving new particles with scalar and pseudoscalar couplings, and the second involving new particles with vector and axial couplings. The couplings are constrained by the Lamb shift and muon magnetic moments measurements while mass constraints are obtained by kaon decay rate data. Results: For the scalar-pseudoscalar model, masses between 100 to 200 MeV are not allowed. For the vector model, masses below about 200 MeV are not allowed. The strength of the couplings for both models approach that of electrodynamics for particle masses of about 2 GeV. Conclusions: New physics with fine tuned couplings may be entertained as a possible explanation for the Lamb shift discrepancy.Comment: 6 pages, 6 figures, v2 contains revised comment on competing model of Lamb Shift discrepanc

Ferromagnetic feature from Mn near room temperature in the fine particles of GdMn2Ge2 and TbMn2Ge2

The magnetization behaviors of GdMn2Ge2 and TbMn2Ge2 in the bulk and in the fine particles obtained by high-energy ball-milling are compared. Pronounced modificayions in the spontaneous, remnent and high-field magnetization in the fine particle form, attributable to Mn are observed. The results indicate that the antiferromagnetism of Mn sub-lattice known for the bulk form in the range 100-300 K gets weakened in favor of ferromagnetism in the fine particles. On the basis of this observation, we infer that there are other factors like size (and possibly defects) also play a role to decide the exact nature of magnetic ordering of Mn in this ternary family of compounds, contrasting the traditionally held view that the basal plane Mn-Mn distance is the crucial controlling parameter.Comment: Communicated for publication on 2nd January 201

Fluorescent particles enable visualization of gas flow

Fluorescent particles enable visualization of the flow patterns of gases at slow velocities. Through a transparent section in the gas line, a camera views the visible light emitted by the particles carried by the gas stream. Fine definition of the particle tracks are obtained at slow camera shutter speeds

Resolving infall caustics in dark matter halos

We have found that the phase-space of a dark matter particles assembling a galactic halo in cosmological N-body simulations has well defined fine grained structure. Recently accreted particles form distinctive velocity streams with high density contrast. For fixed observer position these streams lead to peaks in velocity distribution. Overall structure is close to that emerging in the secondary infall model.Comment: 7 pages, 5 figure