The method of multifrequency near-field acoustical tomography of bulk inhomogeneities of the sea bottom

In this work, we propose a method of near-field acoustical multi-frequency coherent tomography of spatially localized inhomogeneities of the shallow-sea bottom. In the framework of the developed method, two-dimensional spatial scanning of the radiating-receiving system along the bottom over the region of location of the inhomogeneities is performed at multiple frequencies. Using the Born approximation, the initial three-dimensional integral equation for the scattered field is reduced to one-dimensional Fredholm equation of the first kind with respect to the depth profile of the transverse spatial spectrum of the inhomogeneities. In the solution of this integral equation for each pair of spectral components, we use the method of generalized residual and obtain the sought three-dimensinal distribution via the inverse Fourier transform of the reconstructed spectrum. Results of numerical simulation of the tomography scheme and visualized inhomogeneities of shallow-sea bottom are presented.     

Elemental composition of fine particulate matter (PM2.5) in Skopje,FYR of Macedonia

Aerosol samples were collected at an urban background site in Skopje, Former Yugoslavic Republic of Macedonia, during four measurement campaigns from December 2006 to October 2007. An impactor was used to collect particulate matter (PM_2.5) aerosol particles and the samples were analyzed for the concentrations of particulate mass, black carbon (BC), and 17 elements. The 12‐h average PM_2.5 concentrations varied in the range 10–140 µg m^?3 with the highest concentrations measured during wintertime pollution episodes and during the summer period. Pair‐wise correlations and crustal enrichment were studied and the data set was analyzed by factor analysis and positive matrix factorization. Major aerosol components were identified as mineral dust (main observed tracers Si, K, Ca, Ti, Fe, Sr, and Rb), combustion (BC, S, K, V, and Ni), traffic‐related aerosol (Pb and Zn), and secondary sulfate combined with mineral dust. Combustion sources dominated during wintertime and were likely due to heavy oil combustion, biomass burning, and other industrial activities within the city area. Mineral dust was observed throughout the year, but the concentrations peaked during the unusually hot and dry summer of 2007. It is concluded that Skopje suffers from serious air pollution due to central and residential heating, the transport sector, and industrial activities within the city, and contributions from mineral dust increase the PM_2.5 concentrations under dry periods. Topography and meteorological conditions aggravate the problems and make the air quality comparable with the conditions in other highly polluted cities in Southern Europe and worldwide. Copyright © 2011 John Wiley & Sons, Ltd.     

Wake effect in doped graphene due to moving external charge

We use the dielectric-response formalism to evaluate the induced density of charge carriers in supported graphene due to an external moving charged particle in terms of its velocity and distance from graphene for several equilibrium charge carrier densities due to graphene doping. We show that, when the particle speed exceeds a threshold value, an oscillatory wake effect develops in the induced charge density trailing the particle. Strong effects are observed in the wake pattern due to finite size of the graphene–substrate gap, as well as due to strong coupling effects, and plasmon damping of graphene?s π electrons.     

Influence of Basic Red 1 dye adsorption on thermal stability of Na-clinoptilolite and Na-bentonite

Influence of physically adsorbed basic red 1 (BR1) dye on the physicochemical properties of natural zeolite (clinoptilolite) and clay (bentonite) was compared using adsorption, FTIR, and TG/DTA methods. A larger adsorption of the dye was observed for bentonite (0.143 mmol/g) than for clinoptilolite (0.0614 mmol/g) per gram of an adsorbent. However, the adsorption values are the same per surface unit (1.8 μmol/m²). The result (per gram) is due to location of dye molecules in interlayer and interparticle space of bentonite with much larger specific surface area than that of clinoptilolite. The dye adsorption leads to a decrease in the specific surface area and the pore volume of both minerals. The adsorption changes also a character of active sites and thermal stability. A TG study shows that the dye adsorption on bentonite changes adsorbed water amounts, weight loss, and decomposition temperature. In the case of zeolite, the dye adsorption insignificantly influences the thermal stability. The dehydration energy distributions calculated from the Q-TG and Q-DTG data demonstrate a complex mechanism of water thermodesorption and the influence of adsorbed dye on this process.     

Grain-boundary dislocation climb and diffusion in nanocrystalline solids

The effect of grain-boundary dislocation transformations on diffusion in nanocrystalline solids is discussed. A theoretical model describing the enhancement of diffusion processes associated with the climb of grain-boundary dislocations in nanocrystalline solids is developed.     

Assessment of coal and ash environmental impact with the use of gamma- and X-ray spectrometry

Gamma-ray spectrometry (GS), energy dispersive X-ray fluorescence (EDXRF) analysis methods and wavelength dispersive X-ray fluorescence (WDXRF) were applied for the studies of some coal components, e.g., sulphur, light and heavy metal element concentrations and naturally occurring radioactive isotope contents. Hundred fifty coal samples originating mostly from eight different coal mines from Upper Silesian Coal Basin and 150 samples of ash obtained from these coal samples in laboratory by total combustion at final temperature of 820°C, were analyzed. Such comparitive analyses can be helpful in selection of most suitable kind of coal for burning in electrical power and heat plants to minimize the environmental pollution.     

Activation and structural and adsorption features of activated carbons with highly developed micro-, meso- and macroporosity

Three sets of activated carbons (ACs) were prepared with the same precursor but activated differently (by CO₂ or water vapour) with various burn-off levels. The ACs demonstrate increased deviation of the pore shape from the slitshaped model with increasing burn-off and contributions of pores of different sizes depending on the activation type. Significant re-arrangement of adsorption complexes, especially of the Van der Waals type characteristic for nonpolar or weakly polar adsorbates (H₂, CH₄, CH₂Cl₂, CHCl₃), occurs in both micropores and mesopores of ACs with decreasing temperature. The behaviour of their mixtures with water and DMSO can strongly differ from that of individual adsorbates.     

Solvation microdynamics of the Gd(3+) ion in 4-methyl-<Emphasis Type="Italic">N</Emphasis>-butylpyridinium tetrafluoroborate as probed by <Superscript>19</Superscript>F NMR and EPR

The solvation dynamics of the Gd(3+) ion in the ionic liquid 4-methyl-N-butylpyridinium tetrafluoroborate was studied by ¹⁹F NMR and EPR.     

On the Newton-Kantorovich method inK-normed spaces

Nondifferentiable operator equations in spaces equipped with aK-norm — map taking values in the cone of an ordered Banach space — are studied. The majorant method is used to derive the convergence of a modified sequence of Newton-Kantorovich approximations.