Effect of Gd-Mn exchange on phase transitions in GdMn<Subscript>2</Subscript>O<Subscript>5</Subscript> induced by a strong magnetic field

Complex studies of the magnetic, magnetoelectric, and magnetoelastic properties of GdMn₂O₅ single crystals in strong pulsed magnetic fields are carried out in order to obtain additional indirect information on the character of the rare-earth and manganese spin ordering. It is shown that magnetic ordering of Gd³⁺ spins affects the manganese sublattice spin orientation and initiates new magnetic phase transitions. The observed magnetoelectric properties of the GdMn₂O₅ system are interpreted in terms of the theory of phase transitions.     

Application of adhesion coats and systems of surface modification during gluing

Technologies of preparation for gluing of surfaces from aluminum, beryllium alloys, porous materials (glass-fiber plastics and heat-protective materials), and technologies of polyimide film, rubber, and fabric gluing are described. It is shown that the application of epoxy primer, phosphatizing (mordant) coat, VK-32-200 and VK-25 phenolic-elastomer adhesives, and adhesive sublayers and primers allows one to preserve the activity of the preliminary treated adherent surface. The modification of polypropylene and polyester fiber surfaces by the coupling agents based on silanes with the aim to improve the nonwoven fabric properties is considered.     

Cold fast setting epoxy adhesive VK-93

A developed epoxy adhesive, which meets the requirements of the operational repair of aeronautical equipment, components, and aggregates, as well as repairs under field conditions, is presented. The adhesive combines rather high pot life (～40 min), which enables surfaces with large areas to be bonded, as well as high hardening velocity at normal temperature upon reaching the initial level of adhesive joints of no less than 7.0 MPa (after 5 h of hardening) and a maximal level of strength of no less than 17.5 MPa (after 24 h of hardening). These characteristics of the adhesive serve to substantially improve the technical and economic efficiency of bonding operations.     

Global properties of integrable Hamiltonian systems

This paper deals with Lagrangian bundles which are symplectic torus bundles that occur in integrable Hamiltonian systems. We review the theory of obstructions to triviality, in particular monodromy, as well as the ensuing classification problems which involve the Chern and Lagrange class. Our approach, which uses simple ideas from differential geometry and algebraic topology, reveals the fundamental role of the integer affine structure on the base space of these bundles. We provide a geometric proof of the classification of Lagrangian bundles with fixed integer affine structure by their Lagrange class.      

Adhesive composite materials based on glass and carbon fillers

Grades and physicomechanical characteristics of glass and carbon fiber-reinforced plastics based on adhesive prepregs are presented. Certain fields of application of these materials are shown.