Study of the Performance of Copper Coatings Formed by Electroplating and Deformation Cladding with a Flexible Tool

The results of comparative tests of copper coatings formed by electroplating and deformation cladding with a flexible tool (DGFT) under ultimate loads that cause breakage and burrs have been presented. The number of cycles of lateral bending that cause the copper coating to peel and the sample to break, as well as coefficient of sliding friction and the wear of samples during the friction of a lubricant-free spherical indenter on the flat surface of the copper-plated steel disks with substrate hardnesses of 20, 50, and 70 HRC, have been accepted as the performance standards. During the peeling test under bending, it has been found that cladded coatings were not peeled off from the basic material, even in the case when experimental samples were broken, and the peeling of coating in the samples with galvanic coatings has been observed on half of the first bending cycle. Based on the results of the tribotechnical tests, it has been found that copper coatings formed using the above technologies contribute mainly to a reduction in the coefficient of sliding friction on friction surfaces compared to samples without coatings. However, under loads that cause burrs, galvanic coatings have smaller values of the coefficient of sliding friction compared to cladded coatings.     

Fractal-like Matrices

We introduce special sparse n×n-matrices (n=2 ^k ) containing up to 3 ^k ≈n ^1.585 nonzero elements. Their structure is inherited from the famous Sierpinski triangle and is not sensitive to matrix multiplication and inversion. The arithmetical complexity of taking product or inverse of such matrices is proved to be O(n ²).     

Thermo-mechanical coupling in cylindrical bending of sandwich plates

This paper presents an exact solution of linear elasticity theory for bending of sandwich plate-like beams due to temperature difference at the plate faces. It is assumed that the heat flow is stationary. The exact solution yields the temperature profile, stress and displacement distribution across the plate thickness. The analytical results are complemented by an example of a simply-supported sandwich beam.     

Electronic properties of polymethine systems. 10. Electron structure and absorption spectra of cyanine bases

Complex quantum-chemical and spectral studies of the features of the electron structure and absorption spectra of the bases' derivatives of the symmetrical cyanine dyes are performed. It is found that moving from cationic cyanines to their neutral bases is accompanied by a drastic increase in the bond length alternation, equalizing the electron densities at atoms in the chromophore and by sharp shifting up of the molecular levels. Spectral bands in the absorption spectra of the bases are essentially wider and lower intensive and hypsochromically shifted, what is suggested to be connected with different nature of the first electron transition in the cyanine dyes and their bases.     

Mechanism of current flow in a Au-Ti-Al-Ti-n +-GaN ohmic contact in the temperature range of 4.2–300 K

The temperature dependence of the contact resistivity ρ _c (T) of Au-Ti-Al-Ti-n ⁺-GaN ohmic contacts is studied experimentally and substantiated theoretically in the temperature range T = 4.2–300 K. It is shown that the saturation portion of ρ _c (T) is observed in the low-temperature measurement region (4.2–50 K). As the temperature increases, ρ _c decreases by the exponential law. The experimental and calculated dependences ρ _c (T) are in agreement. The obtained results make it possible to conclude the field nature of the current transfer for the saturation region of ρ _c (T) and the thermal-field one, for the exponential region.     

Bounds on the Cardinality of Subspace Codes with Non-maximum Code Distance

We study subspace codes with nonmaximum code distance. As opposed to spreads, i.e., codes with the maximum subspace distance, we refer to them as nonspreads here. We consider families of nonspreads based on using the Silva–Kötter–Kschischang (SKK) subspace code construction and Gabidulin–Bossert multicomponent codes with zero prefix (MZP). We give estimates for cardinalities of nonspreads for a large number of parameters. We show that for large dimensions, the cardinalities almost attain the upper bound given by the Johnson inequality.