Rapid determination of zinc in soils by laser-induced breakdown spectroscopy

The possibility of quantitative detection of trace zinc levels in soils per single laser pulse using laser-induced breakdown spectroscopy is shown. The development of laser plasma and the signal-to-noise ratio are studied when evaporating soils by the second (532 nm) and the third (355 nm) harmonics of an Nd:YAG pulse laser. The use of the third harmonics permits one to reach the zinc detection limit (18 ppm) below Occupational Exposure Limits (OEL) in soil (150 ppm) and below the mean abundance in the earth’s crust of zinc (83 ppm). This allows the use of the suggested technique for the rapid determination of soil pollution with zinc and searching for geochemical anomalies.     

Structure-phase composition and properties of mechanically alloyed high-nitrogen powder steels

The structure and properties of the Fe-21% Cr-N and Fe-18% Cr-7% Ni-0.8% Mn-0.5% C-N powder systems mechanically alloyed in nitrogen atmosphere and steels sintered from the powders in dissociated ammonia at t = 1170°C have been investigated. The thermodynamic calculations of the phase compositions of the steels are carried on the basis of searching the Gibbs integral energy minimum for the system. In comparing the obtained experimental data with the results of thermodynamic calculations for the Fe-Cr-C-N and Fe-Cr-N systems, it is found that the equilibrium phase composition is not reached. The resulted steels contain increased nitrogen quantity (1.6 to 2.1%) distributed in austenite and/or nitrides. The steels have high strength, wear and corrosion resistance.     

Thermodynamic simulation of phase equilibria in the UO<Subscript>2</Subscript>-Gd<Subscript>2</Subscript>O<Subscript>3</Subscript> system at high temperatures

Thermodynamic models of a UO₂-based melt and cubic solid solution were developed on the basis of the most accurate measurements of the UO₂-Gd₂O₃ liquidus in a range of 0–30 mol. % of Gd₂O₃. These models enabled computing the phase diagram of this system in a temperature range of 1900–3200 K for all composition varieties.     

Thermal stability of nickel structure obtained by high-pressure torsion in liquid nitrogen

Using transmission electron microscopy and durometry, the structural evolution of commercially pure nickel (99.6%) under high-pressure torsion (HPT) in liquid nitrogen and subsequent annealings in the temperature range 100–400°C has been investigated. In this nickel, at cryogenic temperature, HPT gives rise to a nanocrystalline structure with the record high microhardness (6200 MPa) and average crystallite size ～80 nm. The obtained structure is stable at room temperature and possesses a relatively low thermal stability, since recrystallization occurs at lower temperatures than after conventional deformation or HPT at room temperature.     

Effect of aging on structure and properties of quenched alloy based on orthorhombic titanium aluminide Ti2AlNb

Phase and structural transformations that occur upon the aging of a titanium alloy based on the O phase have been investigated. The formation of a special type of arrangement (zigzag or packet ensembles) of the O-phase plates that arise in the course of the β → O transformation has been detected. Using transmission electron microscopy, the multistage character of structural changes during the α₂ → O transformation has been studied, and a schematic of the occurrence of the transformation has been proposed. The microdurometric characteristics of the indicated alloy that were obtained after different aging regimes have been estimated.     

Aerodynamic design and analysis of a small-scale vertical axis wind turbine

Small-scale vertical axis wind turbines are regarded today as an attractive source of green energy, still insufficiently implemented and tested. This paper presents a fast design methodology of such a VAWT, in terms of choosing its main parameters: airfoil, rotor diameter and solidity. For obtaining generated power of each considered geometrical model at different undisturbed wind velocities and rotor angular velocities two models were used — momentum and vortex-wake model, combined with experimentally measured airfoil data (airfoil lift and drag coefficients). Even though the former model is simpler, it is the most utilized model, known to provide good results in stationary working regimes. Both models still present fairly accurate and fast tools for computation and optimization, particularly useful in the phase of conceptual design. In this research, the use of the momentum model resulted in determination of the maximal power coefficient, optimal- and minimal freestream velocity for every considered VAWT model. From these output parameters, a selection of the optimal geometric model was done, and a more detailed transient analysis and flow representation around the selected solution was obtained by the vortex-wake model. The results obtained by the two used computational models coincide satisfactorily.     

Reconstructing the Topography of Surface Defects of Ferromagnets in a Normal Magnetization Field

Russian Journal of Nondestructive Testing - The method of reconstructing the topography of defects in a ferromagnet in a normal magnetization field is considered. It is shown that with such...