Home – Home – Jornals – Advanced Search

The solution to a hydraulic fracture problem for the model of Khristianovich-Geertsma-de Klerk is obtained on the basis of the modified formulation of the problem, which, in contrast with the conventional approach, employs the particle velocity rather than the flux. This served to complement the system of ordinary differential equations, resulting after spatial discretization, with the speed equation. The complete system is solved by the Runge-Kutta method for arbitrary initial conditions.The decaying influence of the initial conditions on key characteristics of a fracture (opening and length) at the end of a treatment is established and numerically analyzed.

Based on the strength and crack resistance tests of dolerite and gabbro-diorite samples subjected to bending as a function of loading rate, it is shown that the kinetic constants of strength in Zhurkov model have the same values in the localized and nonlocalized failure modes. The tests on destruction of an organic glass sample with an edge crack yield the similar results.

The article gives the results of mathematical calculations of change in the parameters of electromagnetic signals in stratified and damaged dielectric solid model structures exposed to pulsed acoustic treatment. It is shown that the acousto-electric transformations in such structures result in transition of energy of acoustic pulses to energy of electromagnetic responses in double electric layers. The amplitude-frequency parameters of electromagnetic signals are directly connected with the characteristics of the determinate acoustic effects and with the charge state of the stratified and damaged structures.

It has been found that gold mine waste in the Amur River Area (Priamurye, Russian Far East) contain associated minerals of gold belonging in the group of useful components. In view of the complicated nature of the mine waste, it is decided on the appraisal and recovery of the associated useful components with the help of rational technologies.

The article describes the research results on evaluation of rational technological parameters for open pit mining of Oshkurkovskoe apatite deposit using Wirtigen Surface Miners. Basic relations between the surface miner capacity, ground conditions and technological factors are substantiated. The authors have constructed lag models and determined optimal design capacity of open pit mine.

The authors analyze feasibility of voltage stabilization for permanent magnet synchronous generators in independent variable-frequency power networks. The method of voltage stabilization is based on series connection of the generator and a semiconductor converter generating wattles power. Basic energy characteristics of the semiconductor converter and synchronous generator are analytically defined, frequency constraints of the proposed method are found, and rational frequency range and overall power of the system are determined.

Electrical insulation of open pit shovels has been tested. It is found that line-to-ground short circuit current in up to 1000 V network is lower than setting current of safety cut-out. The authors propose a method to improve efficiency of safety cut-out of mining shovels and drill rigs. The method is based on superimposing D/C current on three-phase network with fixed setting of cut-out operation, i.e. when a person touches live parts the electrics is cut-out owing to increase in capacitance of phase relative to ground.

The article gives new experimental data on spectral characteristics of photoluminescence of natural diamonds extracted from deep horizons of Mir and Internatsionalnaya Pipes, Republic of Sakha (Yakutia) depending on composition of basic and additional optically active structural defects in crystals and on temperature during spectrum recording, considering kinetics of luminescence. It is hypothesized on applicability of low-temperature effects to enhance efficiency of photoluminescence separation of diamond crystals.

From the analysis of information on flotation of quartz, barite, hematite and diamond spar using cationic reagents (amines), the authors show deficiency of thermodynamic approach to explain flotation results by one type of adsorption due to ion-electrostatic mechanism. The discussion offers hypothesis that says that at low pH collecting ability of a reagent is connected with hydrophobic attachment of reagent ions in adsorption layer. In alkaline range of pH, the collecting ability is conditioned by formation and precipitation of ion-molecular associates in the adsorption layer of a mineral. These types of adsorption attach particle surface which is preliminarily made hydrophobic by ion-electrostatic mechanism. These adsorption types are active at bubble-liquid interface and can go to this interface upon rupture of water film between a particle and a bubble. According to the suggested hypothesis, liquid tension in the film becomes nonuniform and a surface force arises and expels kinematic constraint for particle-bubble attachment. The analytical review of the collected test data on cationic reagents proves the suggested hypothesis. The causes of breakdown of correlation between surface pressure and collecting ability for initial conditions of flotation are explained.

Air bubble and pyrite grain attachment is studied. It is found that mineralization area on air bubble depends on pulp agitation time, potassium butyl xanthate concentration and pyrite grain size. The authors show the connection between mineralization area of air bubble and weight of mineral load. Using experimental data, it is calculated how many pyrite grains from a narrow size range attach air bubble during pulp agitation time, and the weight of these grains is estimated. Physical forces on mineral loading exerted by pyrite grains -_{0.1 + 0.071, - 0.071 + 0.044 and -0.044 + 0 mm in size on air bubble at different pulp agitation times, as well as the absolute and specific retention forces are calculated, too.}