Effect of mechanical activation on the properties of natural zeolites

We have examined the effect of mechanical activation on the Sr²⁺ and Cu²⁺ ion exchange selectivity of Russian natural zeolites: clinoptilolite-containing tuffs and chabazite concentrates. We have studied their structural changes and thermal properties and determined the specific surface area and porosity of the mechanically activated zeolites. At specific milling energies below 0.5–0.7 kJ/g, the dominant process is disintegration of zeolite particles and changes in their bulk porosity. At higher milling energies, amorphization prevails. Our results demonstrate that, in the initial stage of activation, one can markedly raise the Sr²⁺ selectivity of some zeolites (e.g., by 16 times for Shivyrtuiskoe clinoptilolites and by 300 times for chabazite) and increase the Cu²⁺ selectivity (by 40 to 100 times), which will persist at high specific milling energies.     

The effect of treatment in a pulsed magnetic field on the kinetics of oxidation of indium phosphide crystals

It is demonstrated that preliminary treatment of semiconductors (for example, indium phosphide) in a pulsed magnetic field can increase the rate of surface chemical reactions (in particular, oxidation).     

Chemical Processing of Low-Grade Bauxites on the Basis of Activation Grinding. Part I: Development of Deferrization Method for Bauxites of the Bokson Deposit

The process of leaching iron oxides from bauxites of the Bokson deposit by hydrochloric acid solutions is investigated. It is shown that iron extraction into solution depends considerably on the temperature and concentration of acid. The optimum parameters are established for the production of iron-free concentrates from bauxites, including the use of fine grinding.     

Beneficiation and Physico-Chemical Properties of Chabasite as One of the Perspective Types of Transbaikalia Zeolites

A scheme is proposed for concentration of zeolite-bearing basaltoids of the Margintuisk volcanic field of Transbaikalia, and a comparative investigation into physico-chemical and adsorption properties of synthetic and natural chabasite recovered from the basalts is conducted. It is shown that the chabasite concentrate extraction is possible with the use of sufficiently simple scheme of electromagnetic concentration. It is established that despite some differences in physico-chemical characteristics, the adsorption properties of natural chabasite are not inferior to the properties of synthetic analog.     

Flotation behavior of sulfides on mechanical activation

Mechanical activation during grinding affects the flotability of pyrite, arsenopyrite, and galena. It is established that the S, Fe, and As atoms at the surfaces of the initial materials are mainly in the oxidized state. The transformations occurring on the surfaces of mechanically activated sulfide minerals are the cause of the changes in flotability. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 102–106, January–February, 2000     

Simulation of Monotone Failures of a System with Different Orders of Smallness of Random Variables That Determine Its Functioning

The probability of monotone failure of a system in a given time interval is investigated. A method of accelerated simulation based on the small parameter method and stratified sampling is proposed. Conditions are established under which estimates have a bounded mean-square error. A numerical example is considered.__________Translated from Kibernetika i Sistemnyi Analiz, No. 1, pp. 128–137, January–February 2005.     

Estimation of Stationary Loss Probability in a Queuing System with Recurrent Input Flows

A multiserver queuing system with recurrent input flows is considered. A fast simulation method is proposed for evaluation of stationary loss probability. It is based on the joint use of importance sampling and the central limit theorem. The estimates are asymptotically unbiased. Two examples demonstrate high accuracy of the estimates.     

Estimating the deviation of steady-state probabilities of system GI / G / m / r from state probabilities of system M / M / m / r by analytical-statistical method

An algorithm is proposed to model “corrections” to characteristics of a general model where exponential distributions are substituted with nonexponential ones. This algorithm is used to evaluate the deviation of steady-state probabilities of system GI/G/m/r from steady-state probabilities of system M/M/m/r. A numerical example is given.     

The adaptive algorithm of information unmistakable embedding into digital images based on the discrete Fourier transformation

Multimedia Tools and Applications - Many effective methods of the data embedding into digital images are based on the frequency transformations. However use of similar transformations is connected...