The development of the predictive estimation of drainage waters of sulfide-containing wastes from mining industry attracts much attention. Investigation of particular objects permits the development of empirical dependences for analysis of various situations in similar technogenic systems. In this contribution, the acid and neutralization potentials of the waste rocks from the Veduginskoe and Taseevskoe gold deposits were calculated from the measured contents of sulfide sulfur and CO32–. Accelerated-leaching experiments (peroxide and dynamic) were carried out, and pH values, acidity and alkalinity (titrated and calculated), and metal (Fe, Zn, Cu, Pb, Ni, Co) concentrations were determined. The values of net acid generation potential were compared with the chemical composition of model drainage waters. The data were correlated with the physicochemical processes in the water-rock system. The value of net acid generation potential was proposed to use for estimating the chemical composition of mine waters.
This paper considers the propagation of pulsed optical Gaussian beams through a homogeneous medium under different diffraction conditions on a transmitting aperture. It is shown that for any curvature radius of the initial wave front the diffraction broadening of a pulsed beam decreases with a decrease in the pulse duration, and in the limiting case of zero pulse duration the diffraction spreading of a pulsed beam is absent.
The single (axial) filamentation regime of high-power collimated femtosecond laser radiation in the atmosphere is theoretically investigated. The effect of laser beam initial diameter on characteristics of a filament is analyzed. We consider three filament parameters: the coordinate of the filament beginning, its length and longitudinal continuity. We found that for the same initial beam power all the above characteristics of filaments show the dependence on the beam radius. As the main physical cause for this circumstance the diffraction interaction of various beam areas during the filamentation process is considered; the strength of this interaction increases as the beam widens.
Line shape data for different СО2 and H2O bands are retrieved by fitting to the available in literature experimental data on the respected continuum absorption. The obtained line shape strongly depends on spectral region, which is consistent with the main principles of the asymptotic line shape theory.
By data of a network of posts for greenhouse gases monitoring at West Siberia area the distribution of carbon dioxide is analyzed at the passage of frontal sections. To except the influence of meteorological parameters, all initial data were pre-reduced to standard conditions. It was found that in the cold season the CO2 concentration increases in the cold front rear and decreases behind the line of the warm front. In the warm season, due to augmentation of the plant vegetation, which in this period is both the source and drain of the carbonic gas, its distribution becomes opposite to the observable in the cold period. In transition periods, both summer and winter variants of CO2 distribution in zones of fronts are possible, which depends on the prehistory of the air mass, coming to the region.
This is the third in a series of papers devoted to the development of technical tools and techniques for rapid and comprehensive analysis of the ecological status of coastal waters by optical methods. The possibility of shore-based optical systems to map and to determine the dynamic characteristics of ocean eddies and internal waves are shown. The efficiency of the maximum cross-correlation method to recover the velocity field of the flow in the vortex body and the phase velocities of internal waves, using optical images of the sea surface is discussed.
The technical means for the real time control for phytoplankton by fluorescence method in coastal waters are considered. Preliminary results of the monitoring by the immersion fluorometric system for the real time measurements are given. The article discusses the possibility of using fiber optic immersible and pumped systems for integrated monitoring of coastal waters.
Relative concentration of 13CH4, 12CH4 and 13CO2, 12CO2 in the atmosphere contains information about carbon dioxide and methane emission sources. High resolution of modern ground-based IR Fourier spectrometers allows one to resolve absorption lines of different isotopologues of the trace gases in atmospheric transmittance spectra. The modeling of synthetic atmospheric transmittance spectra within 2200–11000 cm–1 spectral region has been done and good signals of 13CH4 and 13CO2 were found. Several atmospheric transmittance spectra measured with ground-based FTIR at the Ural Atmospheric Station in Kourovka and at the Institute of Environmental Physics of Bremen University during 2010–2011 have been selected and processed. This paper presents a method and first results on the remote sensing of 13CH4/12CH4(δ13CCH4) and 13CO2/12CO2(δ13CCO2) in the atmoshpere.
The project of the eye-safe High Spectral Resolution Lidar with a wavelength of 532 nm is proposed. Absolute calibration is provided by the molecular channel with iodine cell cavity for filtration of the aerosol signal. Transmitter has a laser beam expansion via receiving telescope to have a design with high thermo-mechanical stability to install small field-of-view and substantially reduce background sky noise. A detailed optical diagram of the transceiver is provided by the transmitter and receiver located on different sides of the optical bench. Characteristics of the laser and the system are given. Calculated lidar returns and errors of measurements are estimated. To have ten percent accuracy in troposphere, the aerosol backscattering and optical depth time of averaging should be from ten seconds to one minute. Proposed system must run continuously and be unattended.
Specular reflection is a bright spot of intensity observed when light is reflected by cirrus clouds, snow blankets, and wavy water surfaces. The analytical expressions, which combine specular scattering on particulate media and rough surfaces, are obtained. The conditions, which allow the identification of the scattering media from the differential cross-section, have been determined for remote sensing applications.
The experimental results on remote detection of vapor of a number of chemical compounds in the atmosphere using the Raman lidar system with the narrow line eximer KrF laser and multichannel spectrum analyzer, based on diffraction spectrograph and intensified CCD camera, are presented. The sensitivity evaluation of the system with sensing range 6–10 m is given. Using additional suppression of the intense Raman bands of the molecules N2 and O2 the threshold of detection of 1 ppm is reached. The experimentally registered bands of the overtones of oxygen and nitrogen in the Raman spectrum of the atmosphere are demonstrated. The absence of the fluorescence and the Raman signals overlapping is confirmed experimentally.
The paper examines the response of the upper atmosphere parameters to the unique geomagnetic storm on January 21, 2005 at middle latitudes. Measurement data of the OI 630 and OI 557.7 nm airglow intensities, the magnetospheric pulsations and ionospheric parameter variations obtained for the Eastern Siberia region (52 N, 103 E) are used for the analysis. Penetration of the global electric field into middle latitudes, geomagnetic pulsations with periods ranging from 0.2 to 1000 s, radio wave absorption in the D ionospheric region, the occurrence of sporadic auroral-type Es formations at altitudes of 140–200 km, and an increase in the intensity of the atmospheric 630 and 557.7 nm emission were observed during this storm. It has been suggested that, in this case, the disturbance of the mid-latitude upper atmosphere parameters might have been resulted from precipitations of energetic charged particles into the ionosphere. These precipitations took place during magnetosphere compression under the influence of enhanced dynamic pressure of the solar wind.
The features of application the low-angle laser light scattering method for study of the pulse formation of aerosol media are discussed. A modification of the measuring system, which allows the study of a cloud simulated in the laboratory conditions, almost from the time after its formation was proposed.
In atmospheric pressure air formation and decay of diffuse "channels" of corona discharge, as well as optical and X-ray radiation were investigated. Modulate pulses (~ 290 kHz) of high voltage (~ 250 kV) with duration of 10 ms was used. A soft X-ray radiation was obtained from corona discharge. In the area of diffuse “channel” and at a distance from the plasma channel the bright glowing points was registred. It was determined that on diffuse “channels” bends appear, the length of which is increased by the end of the pulse voltage
This paper considers the problem of the possible equilibrium configurations of the free surface of a perfectly conducting fluid deformed by a nonuniform magnetic field. A family of exact solutions of the problem is obtained using conformal mappings; equilibrium is achieved due to the balance of capillary and magnetic pressures. According to these solution, the surface strain amplitude increases with increasing current and the hole is transformed into a two-dimensional bubble covering the linear conductor.
G. Hussaina, A. Hameedb, J. G. Hetheringtonb, A. Q. Malika, K. Sanaullaha
Keywords: velocity, yield stress, pressure, compression, divergence, stability
Hydrocode simulations are carried out using Ansys Autodyn (version 11.0) to study the effects of the liner material (mild steel, copper, armco iron, tantalum, and aluminum) on the shape, velocity, traveled distance, pressure, internal energy, temperature, divergence orstability, density, compression, and length-to-diameter ratio of explosively formed projectiles. These parameters are determined at the instants of the maximum as well as stable velocity during the flight towards the target. The results of these parameters present the potential capability of each liner material used to fabricate explosively formed projectiles. An experimental analysis is performed to study the velocity status and the length-to-diameter ratio of explosively formed projectiles.
S. V. Meleshko, O. Sumrum, E. Schulz
Keywords: stochastic equations, equations of gas dynamics, Navier–Stokes equations, group analysis, invariant solutions
Group analysis is used to study stochastic equations of fluid dynamics. Determining equations for admitted Lie groups of transformation involving independent and dependent variables and Wiener processes are obtained. It is shown that, as in the case of deterministic differential equations, admitted groups make it possible to reduce invariant solutions of stochastic differential equations to solutions with a smaller number of independent variables.
A weakly nonlinear oscillator is modeled by a differential equation. A superharmonic resonance system can have a saddle-node bifurcation, with a jumping transition from one state to another. To control the jumping phenomena and the unstable region of the nonlinear oscillator, a combination of feedback controllers is designed. Bifurcation control equations are derived by using the method of multiple scales. Furthermore, by performing numerical simulations and by comparing the responses of the uncontrolled system and the controlled system, we clarify that a good controller can be obtained by changing the feedback control gain. Also, it is found that the linear feedback gain can delay the occurrence of saddle-node bifurcations, while the nonlinear feedback gain can eliminate saddle-node bifurcations. Feasible ways of further research of saddle-node bifurcations are provided. Finally, we show that an appropriate nonlinear feedback control gain can suppress the amplitude of the steady-state response.
In this paper, we study exact solutions of the Navier–Stokes equations for a layer between parallel plates, the distance between which varies according to an arbitrary power law and whose boundary has a no-slip condition, are under study. A solution in the form of a power series of the Reynolds number is obtained. Comparison with the exact solutions is performed, and high accuracy of expansions for Reynolds numbers Re = 1÷10 is shown. An accurate estimate of the error of the Reynolds thin layer approximation is obtained.
The problem of linear perturbations of the sandy bottom in a rectangular channel with a heavy incompressible fluid is formulated. The turbulent viscosity of the flow is defined as a drag coefficient function, and the hydrodynamic equations are written in the long-wave Boussinesq approximation. In the expression for the hydrostatic pressure, a correction is applied to the Boussinesq approximation that changes the sediment discharge. The problem of the development of bottom perturbations is solved taking into account the modified formula of sediment discharge, resulting in analytical expressions for the velocity of bottom perturbations and the wavelength of the fastest-growing bottom perturbations at small Froude numbers.
An analysis is performed to study a laminar boundary layer flow over a porous flat plate with injection or suction imposed at the wall. The basic equations of this problem are reduced to a system of nonlinear ordinary differential equations by means of appropriate transformations. These equations are solved analytically by the optimal homotopy asymptotic method (OHAM), and the solutions are compared with the numerical solution (NS). The effect of uniform suction/injection on the heat transfer and velocity profile is discussed. A constant surface temperature in thermal boundary conditions is used for the horizontal flat plate.
A problem of wave dynamics of internal gravity waves in a variable-depth stratified medium is considered. By using a modified method of geometrical optics (vertical modes–horizontal rays), wave modes of higher approximations of asymptotic solutions are constructed. It is demonstrated that the main contributions to the solution in real stratified media are made by the first terms of the corresponding asymptotic presentations.
The reflection and transmission of harmonic waves and waves of finite duration through the boundary of the perforated zone of a cased wellbore filled with a fluid are studied. A model of the plane fluid flow in the well (in a quasi-one-dimensional approximation) and filtration absorption of the fluid by the porous medium surrounding the well is proposed. The effect of the quality of the perforation (length of perforation tunnels) on the evolution of the waves reflected from the boundary of the perforated zone of the well is studied.
Conditions of unstable equilibrium of single-layer islands of the adsorbate and empty adsorption vacancies are studied. An analog of the Kelvin–Thomson effect for these islands is found. Appropriate corrections are made in the classical theory of nucleation.
M. A. A. Mahmoud, A. M. Megahed
Keywords: non-Newtonian fluid, mixed convection, porous medium, thermal radiation, thermal diffusion and diffusion-thermo effects
Thermal radiation, thermal diffusion, and diffusion-thermo effects on heat and mass transfer by mixed convection of non-Newtonian power-law fluids over a vertical permeable surface embedded in a saturated porous medium are investigated. The governing equations describing the problem are non-dimensionalized and transformed into a non-similar form. The transformed equations are solved by using the local non-similarity method combined with the shooting technique. The effects of the physical parameters of the problem on the fluid temperature and concentration are illustrated graphically and analyzed. Also, the effects of the pertinent parameters on the local Nusselt number and the local Sherwood number are presented.
V. G. Bazhenov, V. K. Lomunov, S. L. Osetrov, E. V. Pavlenkova
Keywords: cylindrical shell, tension, experimental and computational approach, true strain diagrams, edge effects, stability, plastic strain localization, neck
An experimental and computational method of constructing true strain diagrams of steel tubular specimens under tension to rupture at large deformations is developed. Experimental and theoretical studies were performed to investigate the effect of the geometric parameters of cylindrical shells, initial imperfections of the geometry, and edge effects on strain localization, the point of necking, and the critical loads.
This paper considers the basic laws of localized plastic flow in solids obtained from an experimentally established relation invariant for plastic and elastic deformation that determine the propagation velocities of localized plasticity autowaves, the dispersion of these waves, and the dependence of the autowave length on the grain size. The relationship of the equations of localized plasticity and the equations of dislocation dynamics is established.
I. E. Gerasimov, D. A. Knyazkov, S. A. Yakimov, T. A. Bolshova, A. G. Shmakov, O. P. Korobeinichev
Keywords: ethylene flame, ethanol, molecular beam mass spectrometry, flame structure, formation of soot precursors
The effect of the addition of ethanol (EtOH) to the initial combustible mixture on the concentration of various compounds, in particular, those preceding the formation of polyaromatic hydrocarbons in a fuel-rich (equivalence ratio of fuel f = 1.7) flat premixed ethylene/oxygen/argon flame at atmospheric pressure was studied experimentally and by numerical modeling using a detailed mechanism of chemical reactions. Concentrations of various stable and labile species, including reactants, major combustion products, and intermediates in C2H4/O2/Ar and C2H4/EtOH/O2/Ar flames were measured along the height above the burner using molecular beam mass spectrometry. Experimental mole fraction profiles were compared with those calculated using the previously proposed mechanisms of chemical reactions. This mechanism was analyzed to determine the cause of the ethanol effect on the flame concentration of propargyl, the main precursor of polyaromatic hydrocarbons.
A new method is proposed to organize the working process in the combustion chamber of a scramjet. The flow velocity in the combustor is maintained close to the velocity of sound. In a constant-area channel, this situation is achieved by organizing combustion in a pulsed wave structure of the pseudo-shock type whose position is determined by parameters of the external thermal-gas-dynamic pulsed-periodic action on the flow. In the channel part with a variable cross section, the mean Mach number close to unity is maintained by choosing an appropriate degree of combustor expansion and appropriate places of fuel injection. The pulsed mode assists in improvement of fuel–air mixing and in reduction of the combustion zone length. The main advantage of this method is the high efficiency of the process determined by the minimum loss of the total pressure and the maximum increase in temperature. Experimental results are given to confirm the possibility of realization of the pulsed combustion mode.
Effects of the recession of the central air jet on the visible flame height, necking zone, and luminosity of a turbulent compressed natural gas–air inverse diffusion flame in a coaxial burner are investigated in this experimental study. The inner circular tube of the coaxial burner is recessed by 0.25da, 0.5da, and 1.0da, where da is the central tube inner diameter. From the visual observation, the flame height and the necking zone height are observed to decrease exponentially with the air jet Reynolds number with no recession of the central air jet. However, only a marginal reduction in the visible flame height is observed with an increase in the recession height of the air jet as compared to the necking zone height. Interestingly, the necking zone at the flame base disappears beyond the critical recession height of the central jet. Moreover, the recession is found to be effective in eradicating the fuel rich zone and soot ring at the flame base of turbulent compressed natural gas inverse diffusion flame at lower air jet Reynolds numbers.
Based on experimental data on the conditions of spontaneous self-ignition of titanium alloys in a mixture of oxygen and nitrogen and water vapor, an equation was derived that relates the critical temperature of ignition of titanium alloys at fracture with partial pressures of oxygen and diluent in the mixture. In the derivation of the equation, it was assumed that the limiting stage of interaction is the dissociative chemical adsorption of the reactants on the active sites of the juvenile metal surface. The calculation results were compared with experimental data on the critical pressure of ignition of titanium alloys performed under various conditions.
E. A. Lebedeva, I. L Tutubalina, V. A. Val'tsifer, V. N. Strel'nikov, S. A. Astaf'eva, I. V. Beketov
Keywords: energetic condensed systems, combustion products, agglomeration, nanoaluminum, protective coating, aluminum carbide
Thermodynamic analysis of aluminum-containing energetic condensed systems was performed. It was shown that the replacement of aluminum by aluminum carbide led to a decrease in the amount of the condensed phase in the combustion products and a reduction in the specific impulse. The particle size distribution of the condensed phase of samples of energetic condensed systems containing different amounts of aluminum particles coated with aluminum carbide was studied experimentally. It was found that replacing aluminum with a particle size of 18–20 mm nanosized aluminum halved the maximum size of condensed-phase agglomerates of the combustion products.
A criterion for the initiation of explosives with a melting point below the ignition temperature by a short laser pulse is obtained. The criterion obtained is in good agreement with numerical solutions of the heat conduction equation in the cylindrical coordinate system. This criterion made it possible to explain experiments on the initiation of PETN from an open surface by a laser pulse in the range of transparency with variation in the diameter of the light beam. The calculation results coincided with the experiment α = 0.065 cm–1 and the Fresnel reflection coefficient.
V. G. Kriger, A. V. Kalenskii, A. A. Zvekov, I. Yu. Zykov, B. P. Aduev
Keywords: теория Ми, energetic materials, laser initiation, microhotspot model of thermal explosion, Mie theory
The efficiency of light absorption by inclusions of various metals in transparent media is calculated using as an example silver azide, lead, and PETN. It is shown that the absorption efficiency, along with the laser pulse energy density, has a decisive influence on the maximum temperature of heating of the inclusion. Dependences of the maximum heating temperature on the radius of the inclusions are plotted for a pulse duration of ~30 ns. Asymptotic expressions are obtained for the dependence of the maximum heating temperature on the pulse duration for an ensemble of inclusions.
This paper presents the results of experimental studies of detonation transmission through high-modulus powder materials. The features of the process related to the properties of such dispersed media and the prospects for their use in protective devices are discussed.
With the aim to improve the impact initiation capability of a rod-like jet, this paper presents the influence of an axially asymmetric shaped charge on the jet studied by means of numerical simulations. According to Held's initiation criterion, the impact initiation capability of the jet is affected by the jet tip velocity and diameter. The detonation radius over the longitudinal axis, restricted by the charge radius over the same axis, affects the detonation wave in the charge, the force acting on the liner, and, therefore, the jet velocity and shape. Based on these laws, the structure of the axially asymmetric charge is optimized. Compared with axisymmetric jets, axially asymmetric rod-like jets possess a higher impact initiation capability.
This study presents the problem of achieving multimode penetrator conversion. By using the same shaped charge and by changing the position of point initiation, the trial demonstrates two types of the penetrator, which are the explosively formed penetrator (EFP) and the rod-shaped EFP. Compared with the EFP, the penetration depth of the rod-shaped EFP is 2.17 times higher, and the penetration aperture only decreases by 31.8%.
High-concentration nitrogen-doped titania is obtained by detonation-driven flyer impacting on mixtures of TiO2 and different nitrogen precursors. XRD, IR, and XPS spectra are employed to characterize the phase composition, surface absorption, and N-doping concentration of recovered samples. The N-doping concentration is affected by doping nitrogen resources, initial content of doping nitrogen resources, and flyer velocity. A high nitrogen concentration of 13.6 at.% is achieved by shock loading of the mixture of P25 TiO2 and 10 wt.% dicyandiamide (C2N4H4) at 3.37 km/s. A possible shock doping mechanism is discussed.
V. S. Teslenko, A. P. Drozhzhin, P. N. Medvedev, V. I. Manzhalei
Keywords: electric explosion of an electrolyte, discharge in a gas, breakdown in a vapor–gas medium, initiation of combustion
Initiation of combustion of a stoichiometric propane–oxygen mixture in a bubble located in an electrolyte near a dielectric or metallic wall is performed in experiments. It is demonstrated that combustion in the bubble is initiated by an electric explosion-breakdown of a thin electrolyte layer along the bubble boundary.
Combustion of ferroalloy powders in a nitrogen-containing gas flow produces nitrogen-containing ligatures in the form of separate unbonded granules at a pressure close to atmospheric pressure.
