Anodic Dissolution of Nickel from the Individual and NiZn Intermetallic Phases in Acidic Sulfate Solutions. II. NiZn Intermetallic Compound

Comparative investigation of the anodic behavior of nickel in its own phase and in NiZn intermetallic compound in acidic sulfate solutions showed that the kinetics of anodic process is the same in both cases, but the partial anodic curve and the passivation potentials of nickel in NiZn phase are shifted in the negative direction by 140 mV. The passivation current is larger, and the dissolution rate of nickel from NiZn phase at the cathodic polarization is higher. The peculiarity of the behavior of nickel in NiZn phase is related to the activity of surface nickel atoms and the increase in the number of active sites of anodic dissolution. It is shown that introducing an electrochemically negative metal into an alloy can, under certain conditions, facilitate the passivation of the latter irrespective of the passivability of the former.     

Peculiarities of electroplating tantalum coatings from fluoride melts

Electroplating tantalum coatings on molybdenum, copper, and steel is studied. The effects of various factors (the composition of a fluoride bath, its temperature, current density, and the electric charge spent) on the electrocrystallization of the deposit, its roughness, the degree of dendrite formation, current efficiency, and a possibility to plate multilayer coatings and produce tantalum wares by electrotyping are investigated. To compare the characteristics of the coatings, the studies in a standard chloride-fluoride salt system containing potassium fluorotantalate (K₂TaF₇) were also carried out under similar conditions. Original Russian Text ? V.A. Pavlovskii, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 3, pp. 303–306.     

Tendency of steels 10KhSND and 09G2S towards brittle failure

Conclusions The tendency towards brittle failure of low-alloy steels type 10KhSND and 09G2S at low temperatures depends on the supply condition. The highest resistance to brittle failure occurs for steel after temper hardening, i.e., quenching and high-temperature tempering. A changeover into a brittle condition for temper hardened steels of the test melts commences at –60°C, and for hot-rolled steels it commences at –40°C."Kompozit." Scientific-Production Organization. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 14–16, May, 1993.     

Interrelation of families of points of high order on the Edwards curve over a prime field

We propose a modification of the addition law on the Edwards curve over a prime field. We prove three theorems on properties of coordinates of high-order points and on a degenerate pair of twisted curves. We propose an algorithm for reconstructing all unknown points kP of the Edwards curve when only 1/8 of the points are known.     

A model for generation of directed graphs of information by the directed graph of metainformation for a two-level model of information units with a complex structure

A model for generation of directed graphs of information by the directed graph of metainformation for a two-level connected directed graph model of information units is described. It can be used as a basis in computer tools for editing information with a complex structure with different levels of abstraction and invariance to technological spaces (subject domains) in a common conceptual framework for carriers of this information, making it unnecessary to organize specialized training for these carriers or to involve professional intermediaries.     

Increase of the speed of operation of scalar neural network tree when solving the nearest neighbor search problem in binary space of large dimension

In the binary space of large dimension we analyze the nearest neighbor search problem where the required point is a distorted version of one of the patterns. Previously it was shown that the only algorithms able to solve the set problem are the exhaustive search and the neural network search tree. For the given problem the speed of operation of the last algorithm is dozens of times larger comparing with the exhaustive search. Moreover, in the case of large dimensions the neural network tree can be regarded as an accurate algorithm since the probability of its error is so small that cannot be measured. In the present publication, we propose a modification of the scalar neural network tree allowing the speeding of the algorithm’s operation up to hundred times without losses in its reliability.     

Modeling Close Packing of 3D Objects

The paper represents the concept of Φ-functions and quasi Φ-functions as an efficient tool for mathematical modeling of three-dimensional packing problems for convex geometrical objects with continuous translations and rotations. A mathematical model of close packing of convex geometrical objects is formulated and its basic properties are considered. A solution method is proposed, which includes the following stages: constructing initial points, computing local extrema, and passing from one local minimum to another. The solution approach is efficient to solve optimization packing problems. Numerical examples are given.     

Mathematical modeling of the dynamics of anomalous migration fields within the framework of the model of distributed order

The authors perform mathematical modeling of the dynamics of a locally nonequilibrium (in time) geomigration process in a geoporous medium saturated with a salt solution, on the basis of a sub-diffusion model described by a distributed-order system of equations.