Qualitative Analysis of Relationship between Refractive Index and Atomic Parameters of Solid Materials

The refractive index is one of the important parameters describing the optical properties of solid materials. However, it is difficult to obtain a quantitative relation between the refractive index and the structure and composition of materials. A qualitative relation between the refractive index and some atomic parameters of materials was proposed and demonstrated by some oxide optical crystals. A parameter P=r~-/F=r~-/(r~+ΔxD) is defined, in which Δx is the difference of the electronegativities between cations and anions in the materials and r~+ and r~- are the radii of cations and anions respectively. On the other hand, the factor D was introduced to describe the effect of mass difference of the ions. It is demonstrated by both theoretical discussion and experimental data that refractive index is a decreasing function of parameter P. The relation may be useful for the investigation of optical materials.

A NEW FORMULA FOR CALCULATING THE DENSITY OF METALS FROM THEIR ATOMIC STRUCUTURE PARAMETERS

Bused on the consideration o (?) mass and volume of one atom, a new formula tor calculating the density of simple metal substance from their atomic structure parameters is established. The densities of 66 metals in the periodic table were calculated from this formula. The calculated results are in agreement with the measured values reported in literature. The advantage of the present formula over the others is brie fly discussed.

Effects of atomization parameters of dust removal nozzles on the de-dusting results for different dust sources

In order to obtain appropriate spray pressure and enhance the spraying and dust removal efficiency, various factors including the dust characteristics, nozzle spraying angle, effective spraying range, water consumption and droplet size are taken into account. The dust characteristics from different mines and atomization parameters of different pressure nozzles were measured. It was found that the internal pressure of coal cutters and roadheaders should be kept at 2 MPa, which could ensure large droplet size, large spraying angle and low water consumption and hence realizing a large-area covering and capture for large particle dusts. However, the external spray pressure should be kept at 4 MPa for smaller droplet size and longer effective spraying range, leading to effective dust removal in the operator zone. The spray pressure of support moving, drawing opening, and stage loader on a fully mechanized caving face and stage loader on a fully mechanized driving face should be kept at 8 MPa, under which the nozzles have long effective spraying range, high water flow and small droplet size for the rapid capture of instantaneous, high-concentration and small size dust groups. From the applications on the caving and driving faces in the coal mines, it is indicated that the optimization of spray pressure in different spraying positions could effectively enhance dust removal efficiency. Selecting appropriate nozzles according to the dust characteristics at different positions is also favorable for dust removal efficiency. With the selected nozzles under optimal pressures, the removal rates of both total dust and respirable dust could reach over70%, showing a significant de-dusting effect.

An improved theoretical formulation for Sauter mean diameter of pressure-swirl atomizers using geometrical parameters of atomization

This study discusses the development of a mathematical model that is capable ofpredicting the drop size mean diameter of the spray generated by a pressure swirl atomizer,considering the effects of the liquid’s viscosity and the geometrical parameters of this typeof injector, as well as the angle of incidence of the inlet channels (j and b) and atomizationparameters (k, 8), obtained from hyperbolic relations. Additionally, this model investigatesthe phenomena of rupture and stability that are observed in the conical liquid film, in whichthe importance of a new geometrical parameter of atomization, “8”, which immediately influences the drop size diameter of the spray, should be highlighted. The results that are obtainedusing this model are compared with analytical results of Couto, Wang and Lefebvre, Jasuja,Radcliffe and Lefebvre, experimental results and numerics (Hollow cone atomization model),using the Ansys Fluent software for the validation and consistency of the model proposed in Rivas (2015). This model yields good approximations as compared to that yielded using otheralternative mathematical models, demonstrating that the new atomization geometric parameter“8” is an “adjustment” factor that exhibits considerable significance while designing pressureswirl atomizers according to the required SMD. Furthermore, this model is easy to use, withreliable results, and has the advantage of saving computational time.