The effect of high-frequency vibrations on the load bearing capacity of tubular models in complex states of stress

The article presents the results of investigations of the resistance to plastic deformation of specimens of steel 40Kh, alloy D16, and copper Ml loaded by a complex arrangement by high-frequency vibrations of different intensity, internal pressure, and subjected to torsion within a wide range of rates; this made it possible to evaluate the load bearing capacity of structural elements with the highest reliability.Translated from Problemy Prochnosti, No. 3, pp. 27–30, March, 1991.     

Interrelationship between the properties of powders,the pressing and sintering conditions,and the structure of porous niobium III. The porous structure of material of sintered niobium powders

Conclusions In the initial stage of sintering of high-porosity compacts of niobium powder the average pore size increases, the fine pores disappear, and coarser pores than in the original compacts appear.There is a linear relationship between average pore radius and the total volume of pores for similar sintering conditions.The relationship between open and closed porosity after sintering is determined completely by the total porosity and does not depend upon sintering conditions.In sintering of high porosity specimens of dispersed niobium powders zonal isolation of the particles occurs.Translated from Poroshkovaya Metallurgiya, No. 7(331), pp. 23–28, July, 1990.     

An automated device for manufacturing microneedles of iterated shape

A computer-controlled device allows for obtaining metallic microneedles with a vertex radius of ∼10 nm from wire bars by using the electropolishing technique. The microneedles have a highly reproducible shape and a nondisturbed interior microstructure of bars. The essence of the method consists in terminating the process at an optimal instant determined from the time dependence of the electric current by using a computer program. The microneedles obtained are utilized as point electron sources, samples in field-emission microscopy, and indenters in tunneling microscopy.     

Model for controlling processes in the ladle treatment of steel

In Russia, the Bardin Central Research Institute of Metallurgy (TsNIIchermet) has used results obtained from many years of basic research to construct physicochemical models of the processes of deoxidizing, desulfurizing, alloying, and finishing steel in out-of-furnace treatments in accordance with the main chemical reactions that take place. Construction of the models has in turn made it possible to develop a series of software applications designed to solve practical problems that arise in controlling the processes which occur in ladle metallurgy.     

Adsorbed molecules form ordered structures on the surface of metals exposed to an electric field

Submonomolecular films deposited onto a metal surface in an electric field exhibit the phenomenon of self-organization. The ordering is manifested by the formation of molecular chains featuring the mass transfer. This results in the appearance of a stable dynamic network structure, which exists within a certain optimum temperature interval. It is suggested that this phenomenon is related to the electric interactions in a system of dipoles, one end of each dipole being free and another moving on the substrate surface with friction. Modeling of the evolution of this system with time qualitatively agrees with the experiment. These results can be used in high-voltage and vacuum electronics, space technologies, and nanoelectronics.     

Extraction of thorium nitrate with a binary extractant derived from trialkylbenzylammonium and higher isomeric α,α′-branched carboxylic acids

A binary extractant based on trialkylbenzylammonium and higher isomeric α,α′-branched carboxylic acids, R₄NA, was prepared. The extraction of Th(IV) nitrate with 0.52 M solutions of R₄NA and R₄NNO₃ in toluene was studied. The extraction isotherms were determined. The physicochemical and mathematical models of the Th extraction were constructed. Formation of several extractable species in the organic phase, (R₄N)₂[Th(NO₃)₆], R₄N[ThA(NO₃)₄], and (R₄N)₂[ThA₂(NO₃)₄], was established. The extraction constants were calculated. The organic phase was studied by IR spectroscopy.     

α- al(OH)3, dissolution in acid media

The dissolution rate of aluminum hydroxide in sulfuric and hydrochloric acids was studied as a function of acid concentration, solution temperature, and the hydroxide/electrolyte interfacial potential. It was found to be limited by the transfer of surface complexes from the solid phase to the solution.     

Influence of a thin layer with arbitrary conductivity on the characteristics of acoustic waves in potassium niobate

The influence of a thin layer of arbitrary conductivity on the characteristics of acoustic waves in potassium niobate is investigated theoretically. The conductivity of a thin layer on the surface of a potassium niobate crystal or plate is shown to have a significant influence on the damping and velocity not only of symmetric Lamb waves and quasi-shear-horizontal waves but also of Gulyaev-Bleustein waves. It is found that a relative change in velocity as large as 50% can be achieved for quasi-shear-horizontal waves by altering the surface conductivity. The results obtained reveal great prospects of using potassium niobate to create acoustoelectronic devices with controllable characteristics. Pis’ma Zh. Tekh. Fiz. 25, 21–26 (April 26, 1999)