A NOTE ON THE REDUCED EFFICIENCY OF THE INDUSTRIAL CYCLONE

In this paper a theoretical investigation into the basis of the reduced efficiency of a conical cyclone is performed. By considering the flow in a region where viscosity is unimportant an analytical solution to the problem is obtained. From this model the performance of the cyclone is evaluated and this can be expressed in terms of three operating and design parameters. One of these parameters is the split ratio, that is the proportion of the volume of fluid entering the cyclone which goes to the underflow. It is demonstrated mathematically that the empirical formula for the reduced efficiency at present in common use is a very good absolute measure of the separating ability of a cyclone.     

Formation of carbon nanofibers via carbon monoxide disproportionation

Experimental results suggesting that carbon nanofibers are formed from amorphous carbon released at several compact active sites are reported. It was shown that the sites in question are catalyst crystal lattice defects formed at the crystallite contact boundaries.     

Explosion of a cylindrical charge above a rigid surface

We investigated the explosion of a cylindrical charge, which lies on a rigid surface or is positioned at some height above it. The explosion is modeled by the jump between the background and the region occupied by gas at a high pressure, density, and temperature. In an analogous formulation, the explosion from the Tunguska meteorite impact [1–4] was modeled by spherical and cylindrical explosive waves which consider the gravitational back pressure. Explosions from charges with nontraditional shapes have been studied [5–8]. Reflections of an explosive wave from a point charge from a rigid surface have been examined [9–10]. A more complete review of investigations on the spatial effects of forming propagating explosive waves can be found in [11].Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 131–134, November–December, 1991     

An algorithm for deducing an effective sieve residue from the rate of powder passage through a sieve

The effect of non-ideal aperture distribution of a sieving surface on the sieve residue has been the object of many experimental studies. Unfortunately, the sieving kinetics of many sieving techniques do not result in a simple probability relationship between the size distribution function of the powder and the sieve aperture distribution function. If one specifies a certain type of sieving kinetics, then one can apply probability theory to the rate of movement of powder through the sieve and the size aperture distribution function of the sieve. Under such specified sieving conditions it can be shown that it is possible to deduce a size characteristic parameter of the powder being sieved, which in this publication is described as the kinetic residue of the sieve. An algorithm for the automatic computation of the kinetic residue from the rate of powder sieving is described. The possible implementation of this algorithm to automate sieve analysis is explored.     

The Determination of Surface Development in Cement Pastes by Nuclear Magnetic Resonance

Pulsed proton NMR was used to determine the specific surface of hydrating cement pastes. The method is based on the fact that the measured proton spin-lattice relaxation rate (l/ T₁ ) of water in cement pastes is (in view of the fast exchange between water molecules in the adsorbed and bulk phase) proportional to the fraction of water molecules covering the solid surface and thus proportional to the NMR surface of the newly grown hydration products. In general, the method can be used for powders, fibrous and porous materials in contact with liquid water, or other fluids containing protons.     

Formation and surface properties of electron-emissive coatings IV. DTA,ETA and dilatometry studies on some alkaline–earth hydroxides

The decomposition under vacuum of the hydroxides of calcium, strontium and barium was investigated by differential thermal analysis (DTA), electrothermal analysis (ETA) and dilatometry. The results suggest that the rate of sintering of calcium oxide is initially governed by the formation of a pseudo-hydroxide lattice; rapid sintering occurs only after conversion of this to the true oxide. Compacts of the oxides of strontium and barium show a remarkable resistance to sintering at temperatures up to 1000°. It is proposed that the sintering may have been inhibited by the presence of trace amounts of calcium oxide and strontium oxide formed by decomposition of impurities present in the samples of strontium and barium hydroxides, respectively.     

Aspects of making a superconducting yttrium ceramic by self-propagating high-temperature synthesis

Macrokinjetic features are considered for the combustion in oxygen of BaO₂–Cu–Y₂O₃ mixtures, which produces the high-temperature superconductor yttrium barium cuprate YBa₂Cu₃O_7–x. Studies have been made on how the initial temperature affects the combustion temperature and rate, and the critical temperature for self-ignition has been determined. Ultrasonic activation of the initial powders has an advantageous effect on the product quality. Thermal analysis has been applied to the activated mixtures, which indicates the reason for the rise in burning wave propagation rate and increase in conversion to the superconducting phase.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 62–67, March–April, 1993.     

A comparison of some approaches to classification problems,and possibilities to construct optimal solutions efficiently

We consider sequential linear (binary) classifiers for the case of many classes along with the linear classifiers based on determining the maximum discriminant function. It is shown that the capabilities of sequential binary classifiers are wider than those of linear classifiers. For the case of linearly non-separable training samples there are considered approaches based on minimizing the margin of misclassification and minimizing empirical risk. It is shown that problem of minimizing the margin of misclassification is polynomially solvable for a certain choice of the norm in the feature space. A refined model of the empirical risk minimization problem and its continuous relaxation are considered, a comparison with the mathematical model of SVM is done. The results of numerical experiments comparing different approaches are discussed.     

Interfacial pH measurement during the reduction of dissolved oxygen in a submerged impinging jet cell

A pH sensor-grid assembly is used in a submerged impinging jet cell to measure the interfacial pH during the reduction of dissolved oxygen in well controlled flow conditions. Experiments were performed in a 0.5m K2SO4 solution with and without carbonate ions. In each case a good agreement between experiment and theory is found. In particular it was confirmed that, in the absence of chemical reaction and for a totally mass transport controlled oxygen reduction reaction, stirring has no influence on the interfacial pH.     

Scale effect in high-rate (spall) failure

Experimental results on the spall strength of copper in which the scale of the system was changed by a factor of ten show that the scale effect for high-rate one-dimensional strain depends on energy. The spall energy per unit surface area for failure increases with time. Arzamas-16. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 88–93, November–December, 1993.