Home – Home – Jornals – Journal of Mining Sciences 2017 number 1

A method of optimal output-uniform coding for a set of sources consisting of a union of a countable number of source sets is proposed. It is shown that the coding for a union of finite-memory Markov sources is asymptotically optimal. It is established that the proposed coding is weakly universal for a set of stationary sources.

The phenomenon of four-wave mixing that occurs in passive optical networks with wavelength-division multiplexing of channels has been studied.пResults of modeling the distribution of combination frequencies over the spectrum depending on the number and frequency interval between the channels are given. To suppress crosstalk between the channels at combination frequencies, it is proposed to divide the range into two bands and select a guard interval between them. The effect of combination frequencies on the signal transmission quality is considered as a function of the power level in the channels, frequency interval, and transmission length.

This paper presents the results of experimental studies of the spectral properties of layered structures consisting of two volume reflective holographic gratings separated by an optically homogeneous layer. When such structures are exposed to polychromatic light, the interference interaction of the waves formed by these gratings leads to the formation of a plurality of narrow spectral passbands. The period of arrangement of the passbands is determined by the optical thickness of the intermediate layer, and their envelope coincides with the spectral selectivity contour of one grating. The existence of this type of spectra with local passbands arranged at a periodicity 2-8 Å (in different experiments) has been experimentally confirmed. A high-resolution Ramanor U1000 spectrometer and an optical Fabry-Perot interferometer were used. It is found that the irregularities in the internal structure of the holographic gratings due to the imperfection of the recording medium substantially distort the spectral characteristics of the studied structures in comparison with their simple theoretical models: the spectrum is asymmetric and the local bandwidth is significantly less than the estimated value. Similarity between experimental data and simulation results is achieved by selecting the parameters of said irregularities.

This paper presents the results of a computer simulation of the process of measuring the parameters of MIOL-Akkord type bifocal refractive-diffractive lenses in which the central area of the diffraction element is reduced and compensation of spherical aberrations of the eye is provided. The spatial-energy characteristics of an ideal diffractive lens is preliminarily calculated using existing formulas. The simulation of the process of controlling intraocular lens parameters showed that the intensity distribution along the optical axis does not characterize the diffraction efficiency, which is the total (integrated) intensity in the beam cross section at the focus.пIt is found that due to the coupling of diffraction orders, it is difficult to measure the absolute diffraction efficiency and it is better to evaluate only the relative efficiency.

The luminescent properties of gradient activated crystals of lithium niobate with the concentration profiles of the optical centers of ytterbium and erbium ions are studied. It is shown that the spectral-luminescent properties of the gradient crystal are correlated with the concentration profiles of the optical centers of Yb^{3 +} donors and Er³⁺ acceptors.

This paper shows that the near-surface layer of a lithium niobate single layer 15 μm in depth is essentially different from the rest of the volume of the material from the standpoint of composition, structure, and mechanical properties. The pointed out difference are due to the effect of cutting, polishing, and smoothing of the lithium niobate plates, which result in an increase in the density of point defects and dislocations. The increasing density of the structural defects leads to uncontrollable changes in the conditions of the formations of waveguides and the drifting of characteristics of integrated optical circuits. The results obtained are very important for the manufacture of lithium niobate based integrated optical circuits.

This paper describes the technological approach to the implementation of quasioptical high-pass subterahertz filters with the use of high-aspect pseudometallic structures. The approach is based on microstructuring of the solid polymer layer of polymethylmethacrylate by synchrotron X-ray lithography with subsequent metallization of the entire surface of the structure. This paper also presents the example of the manufactured sample and the operational characteristics of the high-pass filter with a cut-off frequency of 0.275 THz, whose thickness is 1 mm and which was formed by hexagonally packed open-end hexangular holes separated by partitions 70 μm. The electrodynamic analysis and design basics of high-pass structures are given too.

This paper describes the stochastic models of recombination of electrons and holes in inhomogeneous semiconductors in two-dimensional and three-dimensional cases, which were developed on the basis of discrete (cellular automation) and continuous (Monte Carlo method) approaches. The mathematical model of electron and hole recombination constructed on the basis of a system of spatially inhomogeneous nonlinear integro-differential Smoluchowski equations is described. The continuous algorithm of the Monte Carlo method and the discrete cellular automation algorithm used for the simulation of particle recombination in the semiconductors is described.

Using a tunable frequency stabilized CO₂ laser, the dependences of the unsaturated absorption coefficient in pure carbon dioxide on pressure were measured in the range 5-30 Torr, where line contours are described by the Voigt function. The absorption coefficients were measured at the center frequencies of R(8), R(22), R(34), P(22), and P(36) lines of the 10⁰0-00⁰1 transition in the temperature range 300-700 K. By means of the least squares method, the inverse problem is solved for the system of equations for absorption coefficients at different pressures in the temperature range under study. The self-broadening coefficient γ_CO2-CO2 and the probability of spontaneous emission A_ik are determined. A new formula is proposed for the dependence γ_CO2-CO2(T).

The filamentation conditions of a femtosecond laser pulse by its focusing in air are investigated experimentally and theoretically. A good agreement is observed between experimental and calculated data when neglecting the filament plasma. It is shown that at low numerical aperture (NA ≤ 2.15 x 10^-3), a Kerr nonlinearity plays a fundamental role in the formation, existence, and termination of a filament. At the initial stage, the Kerr effect leads to the beam self-focusing and emergence of the filament; at the final stage, to radiation defocusing and sharp decrease in its axial intensity due to the beam wave front distortions. In the case of aberration focusing, a spatial quasi-soliton is formed after a visible filament due to the balance between Kerr self-focusing and diffraction extending. The quasisoliton is a source of the directional white supercontinuum.

Description of the developed prototype of a remote detector of hazardous substance vapors based on a tunable ¹³С¹⁶О₂ laser is given. Results of test measurements of laser radiation transmission of organic liquid vapors (acetone, ammonia, ethanol, gasoline) are presented. The remote detection of acetone and ammonia vapors at distances up to 100 m is experimentally implemented.

The results of two-frequency lidar investigation at wavelengths of 561 and 532 nm of the atmosphere scattering are presented. The laser radiation band covers two emission lines of atomic oxygen and three emission lines of atomic nitrogen. The lines correspond to the transitions between the exited states of ions of atomic oxygen or nitrogen. The possibility of application of the lidar method for ionosphere investigations is discussed. The physical basis of this method may be the resonance scattering on upper atmosphere ions.

The spatiotemporal variability of carbon monoxide (CO) during the atmospheric blocking event over European Russia in summer of 2010 is studied using the CO measurements from satellite Atmospheric Infrared Sounder (AIRS) instrument. Total column CO data from AIRS are compared with those from the ground-based spectrometer operated at Zvenigorod Scientific Station of A.M. Obukhov Institute of Atmospheric Physics. The peculiarities of CO field evolution conditioned by the regional atmospheric circulation associated with the omega block in the presence of severe wildfires are revealed.

A three-dimensional numerical model of moist convection and formation of convective cloudiness in the Arctic atmosphere is considered. A model of mixed clouds with explicit description of liquid and ice phases is used with nonstationary equations for cloud-drop and ice-particle size distributions. The model capability in the reproduction of polar mesoscale cyclones in the Arctic atmosphere is analyzed.

A technique is developed for retrieving the vertical profile of the mass saltation flux from measurements of the saltating sand mass concentration and wind velocity in the surface air layer. The technique is based on the solution of direct and inverse problems of the saltation sand dynamics. In order to estimate the saltating sand sliding coefficient, calculation results are compared with measurements in wind channels. The conditions for the saltating sand trajectories to fall in the altitude ranges from 0.5 to 1.0 cm and from 1.0 to 2.0 cm are ascertained. The effects of the diameter, sand grain liftoff velocity and angle, and the friction velocity on the sliding coefficient are analyzed. The sliding coefficient for sand particles of 100 μm diameter is estimated for the first time.

Transfer of the solar radiation in a freely expanding spherical atomic cloud is numerically investigated. The spectral and spatial characteristics of the absorbed and scattered radiation are calculated; the influence of the expansion velocity of the medium on them are detected.

The remote sensing results of the dynamics of thermokarst lake areas are presented. The study is carried out for 29 test sites in the permafrost zone of Western Siberia and covers 35 years. It shows a trend toward a decrease in the areas of thermokarst lakes during the period under study. The time series of climatic variables (temperature and precipitation), received from reanalysis, are analyzed. It is found that an increase in the annual average temperature is accompanied by a reduction in the areas of thermokarst lakes located in the permafrost zone of Western Siberia.

Air environment pulse-periodic discharge in apokamp mode is studied. It is confirmed that the blue and red diffuse minijets (apokamps) form from the plasma discharge channel under the floating potential. It is shown that at low pressures the apokamps are units-tens of centimeters in size and possess the properties inherent to giant plasma jets (sprites, starters, and blue jets) observed in the Earth's atmosphere at altitudes of 17-100 km. Morphological, spectral, and electrophysical parameters of apokamps in various conditions are ascertained. It is found that plasma minijets are easier implementable at the positive polarity of the discharge channel. A gradual change in the color of diffuse jets with a decrease in the air pressure is demonstrated.

The results of experimental study of a gas-discharge Ne-Eu laser are presented. In this work, lasing lines, pulse shapes in europium atom and ion in the conditions of this experiment are identified. Influence of the buffer gas pressure and pulse repetition rate on the energy characteristics of the laser is ascertained; their optimal values are determined. It is shown that under optimum operating conditions for the corresponding transitions the output power is 1 W at 1759 nm line and 70 mW at 664.5 nm line.

The recovery of steady-state lasing in a CuBr laser operating in the train mode is studied with the use of a computer-based control system. The control system provided the repetitively-pulsed, train, and waiting modes. The dependences of the recovery time on the pause duration and the strorage capacitor are derived. The specific recover times are determined; their dependences on the pause duration in the train mode are analyzed. A time delay between the start of pump pulses and appearance of lasing pulses is shown. The time where lasing is absent increases in the pause duration range from 0.2 to 10 ms; this time is set to about 15 ms if a pause is equal or longer than 10 ms.

Results of research of the CuBr laser operating characteristics working in the double-pulse excitation mode with a pulse repetition rate of 50 Hz are given. The possibilities of increasing the efficiency by optimizing the parameters of the excitation pulse and matching with the impedance of the plasma formed by a dissociating pulse are considered. Laser efficiency of 2.56% at an excitation pulse with average power of 16 mW and time delay between dissociation and excitation pulses of 150 ms is received. Specific energy of the dissociating pulse reached 22 mJ/cm³; and of the exciting, 0.4 mJ/cm³. Introduction of saturation inductance into the excitation circuit provides for the maximum efficiency of 2.7%.

In this paper we discuss the evolution of the new approach to the prediction problem for nonlinear stochastic differential systems with a Poisson component. The proposed approach is based on reducing the prediction problem to the analysis of stochastic jump-diffusion systems with terminating and branching paths. The solution of the prediction problem can be approximately found by using numerical methods for solving stochastic differential equations and methods for modeling inhomogeneous Poisson flows.

We consider a strongly NP-hard problem of finding a family of disjoint subsets with given cardinalities in a finite set of points from the Euclidean space. A minimum of the sum over all required subsets of the sum of the squared distances from the elements of these subsets to their geometric centers is used as a search criterion. We have proved that if the coordinates of the input points are integer, and the space dimension and the number of required subsets are fixed (i.e. bounded by some constants), then the problem is a pseudopolynomial-time solvable one.

In this paper, the kinematics of the tsunami wave ray and the wavefront above an uneven bottom is studied. The formula to determine the wave height along a ray tube has been obtained. The exact analytical solution for the wave-ray trajectory above the parabolic bottom topography has been derived. Within the wave-ray approach this solution gives the possibility to determine the tsunami wave heights in an area with a parabolic bottom relief. The distribution of the wave-height maxima in the area with the parabolic bottom was compared to the one obtained by the numerical computation with a shallow-water model.

This paper deals with numerical simulations of a system of diffusion-reaction equations in the context of a porous medium. We start by giving a microscopic model and then an upscaled version (i.e., homogenized or continuum model) of it from previous works of the author. Since with the help of homogenization we obtain a macroscopic description of a model which is microscopically heterogeneous, via these numerical simulations we show that this macroscopic description approximates the microscopic model, which contains heterogeneities and oscillating terms at the pore scale, such as diffusion coefficients.

The dual scheme for solving a crack problem in terms of displacements is considered. The dual solution method is based on a modified Lagrangian functional. In addition, the method convergence is investigated under natural assumptions on H¹-regularity of the crack problem solution. The duality relation for the primal and dual problems has been proposed.

This paper is concerned with the semilocal convergence of a continuation method between two third-order iterative methods, namely, Halley's method and the convex acceleration of Newton's method, also known as super-Halley's method. This convergence analysis is discussed using a recurrence relations approach. This approach simplifies the analysis and leads to improved results. The convergence is established under the assumption that the second Fréchet derivative satisfies the Lipschitz continuity condition. An existence-uniqueness theorem is given. Also, a closed form of error bounds is derived in terms of a real parameter α ∈ [0,1]. Two numerical examples are worked out to demonstrate the efficiency of our approach. On comparing the existence and uniqueness region and error bounds for the solution obtained by our analysis with those obtained by using majorizing sequences [15], we observed that our analysis gives better results. Further, we observed that for particular values of α our analysis reduces to Halley's method (α = 0) and convex acceleration of Newton's method (α = 1), respectively, with improved results.

The equilibrium problem for two elastic bodies pasted together along some curve is considered. There exists a crack on a part of the curve. Nonlinear boundary conditions providing a mutual non-penetration between crack faces are set. The main objective of the paper is to construct and to approve an algorithm for the numerical solution of the equilibrium problem. The algorithm is based on the two approaches: the domain decomposition method and the Uzawa method. The numerical experiment illustrates the efficiency of the algorithm.

The main objective and inspiration in the construction of two- and three-point with memory methods is to attain the ut computational efficiency without any additional function evaluations. At this juncture, we have modified the existing fourth and eighth order without memory methods with optimal order of convergence by means of different approximations of self-accelerating parameters. The parameters are calculated by a Hermite interpolating polynomial, which accelerates the order of convergence of the without memory methods. In particular, the R-order convergence of the proposed two- and three-step with memory methods is increased from four to five and eight to ten. One more advantage of these methods is that the condition f'(x) ≠ 0 in the neighborhood of the required root, imposed on Newton's method, can be removed. Numerical comparison is also stated to confirm the theoretical results.

This paper deals with the use of a scalar product with derivatives for constructing semi-orthogonal spline-wavelets. The reduction of supports of such wavelets in comparison with classical semi-orthogonal wavelets is shown. For the splines of the 3rd degree, the algorithm of wavelet-transformation in the form of the solution to a three-diagonal system of the linear equations with strict diagonal prevalence has been obtained. The results of numerical experiments on the calculation of derivatives of a discretely set function are presented.

The generalized observations over hypocenters of the strongest mining-induced events have shown that this type of deformation occurs as movement along the existing faults. From the experimental evidence, transition of a section of a fault to meta-stable state goes with the decrease of its dynamic shearing rigidity. The alteration of the mechanical properties starts long before macroscopic movement of the fault surfaces is recorded. This effect is detectable using instruments and can be used as a foundation for a new approach to monitoring of induced earthquakes.

The authors use mathematical model of structurally inhomogeneous rocks to describe the property of rocks to accumulate and release potential elastic energy. The finite element algorithm and bundled software are developed to solve plane boundary-value geomechanical problems. The article presents calculations of deformation of self-stress rock specimens. It is shown that the deformation curve depends both on the elastoplastic properties of the specimens and on their natural self-balanced stresses. Depending on sign, the stresses can either increase or decrease the limit load under which the specimens fail.

This paper presents one strain gradient model of zonal disintegration of rock mass near deep level tunnel. The governing equations and boundary conditions of the model are established. Numerical methods (quasi-Newton method and shooting method) are adopted to solve the obtained fourth-order equilibrium equations with higher order boundary conditions in terms of displacement. The stress field in elastic and plastic zones is obtained. The effects of model parameters on stresses distribution in surrounding the tunnel rock mass are examined. The necessary conditions for the formation of zonal disintegration are elucidated.

The authors propose methods and means to monitor deformation and subsidence of ore crown under mining of open-pit bottom reserves by room-and-pillar system with solidifying backfill in Mir Mine, Alrosa. The article describes layout and data of geomechanical monitoring. The mechanism of ore subsidence at the lower boundary of the safety pillar is determined.

The calculations of stress state and failure of rock mass in the vicinity of longwall in a coal bed with the high gas content in Polysaevskaya Mine, SUEK-Kuzbass, are described. The effect of the mining depth and coalbed gas pressure on the geomechanical situation in the longwall is illustrated. The authors discuss scenarios of directed crack formation in front of the longwall.

Roughness of the main crack surface is an assessment criterion for stress state of geomaterials for the quantitative connection has been found between the crack roughness and stress state of geomaterials. Roughness reduces with an increase in the maximum normal stresses in the zone of failure (the area of the maximum shear stresses). Based on this regularity, the method has been developed to assess stresses using the crack surface roughness in geomaterials.

Numerous abandoned workings, mostly tunnel ones, are present in post shallow mining areas. With time, timber roof supports have been degraded and lost their bearing capacity, while excavations lost stability. The loss of stability of an excavation and its failure is often a cause of sinkholes formation at the surface, sometimes even many years after mining activities were discontinued. Such instances pose a threat to buildings and their users-to public safety. A prediction saying that the probability of sinkhole formation is greater than 0 and smaller than 1 is ambiguous and does not allow making right decisions about the use of land. Therefore, it seems advisable to provide a simple algorithm that would allow to deterministically calculate whether a sinkhole is to be formed or not. This paper presents a method of predicting the probability of sinkhole formation based on Salustowicz’s theory as well as its practical application using a computer program. It should be borne in mind, however, that there are other factors influencing the probability of sinkholes formation, which cannot be taken into account in a mathematical model. These factors include non-mining phenomena, such as suffosion, load imposed on land, vibrations caused by movement of heavy-duty vehicles and other.

Under numerical investigation is propagation of surface pendulum waves in 3D block medium. The medium is modeled by 3D lattice of masses connected with elastic spring connections and viscous dampers. The surface pin vertical pulsed loading is considered. The displacements and velocities of the surface masses are calculated. The numerical results obtained for the block medium are compared with the similar data on elastic medium and in situ experiments carried out by other researchers.

The authors give an assessment of the effect exerted by blasting on the intensity of geodynamic and seismic events. The key regularities of distribution of shocks under blasting of rock blocks are found. The scope of the experimental research embraces determination of seismic velocities on the ground surface in mining area in Gornaya Shoria.

The article reports basic design parameters of open pit mines of Alrosa, as well as criteria and factors that govern the choice of production capacity of an open pit diamond mine under conditions of permafrost. The analytical relations and tables to calculate open pit mine life are presented, and the influence of the rate of the downward advance of an open pit mine on its capacity is demonstrated. The authors formulate key provisions for a paragraph of the national standard of RF enabling systematization of approaches to optimization of open diamond mining parameters.