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Interior permanent magnet (IPM) motors in traction applications often employ discrete rotor skewing constructions to reduce torsional excitations and back-EMF harmonics. Although skewing is very effective in reducing cogging torque, the impact on torque ripple is not well understood and can vary significantly over the operating envelope of a motor. Skewing also leads to the creation of a non-zero axial force that may compromise the bearing life if not considered. This paper introduces a holistic methodology for analyzing the effect of skewing, aiming to minimize torsional excitations, axial forces and back-EMF harmonics whilst mitigating the impact on performance and costs. Firstly, analytical models are employed for calculating cogging torque, torque ripple and axial forces. Then, 2D and 3D finite element analysis are used to incorporate the influence of non-linear material behavior. A detailed structural model of the powertrain is employed to calculate the radiated noise and identify key areas allowing a motor designer to reduce noise, vibration and harshness (NVH). A meticulous selection process for the skewing angle, the number of skew stacks and the orientation of skew stacks is developed, giving particular attention to the effect of the selected pattern on NVH in both forward and reverse rotating directions. [ABSTRACT FROM AUTHOR]

Uralian parietal and rock art (cave paintings and pictographs, or "pisanitsy") represents a unique archaeological and cultural phenomenon, comprising 90 sites stretching for more than 800 km from north to south, which date from the Paleolithic era extending into the present Holocene epoch. The identification of the nature of prehistoric colorants provides an insight into their provenance, manufacture and utilization, as well as contributing to the conservation and restoration of drawings. The studies of mineral, elemental and organic phase composition of the colorant micro-samples from the drawings of Ignatievskaya cave and Idrisovskaya II and Zmiev Kamen' pictographs (Southern and Middle Urals, Russia) discussed in the present work were carried out using a special set of microspectroscopic methods (SEM-EDS and Raman spectroscopy) offering high spatial resolution. The fatty acid composition of the organic phase was analyzed by GC–MS. The technology of colorant manufacture could have included thorough grinding and mixing of unheated hematite with an organic binder made from animal fat and a clayey extender in order to achieve the desired hue and intensity of the color. It is possible that the colorant was applied in layers (Idrisovskaya II and Zmiev Kamen' pictographs). The development of authigenic phosphate and sulfate (gypsum) mineralization, which is observed in all studied sites, as well as oxalate encrustation on the Idrisovskaya II pictograph, indicates the conditions and processes of secondary mineral formation. [ABSTRACT FROM AUTHOR]

The article provides information on industrial waste generation at enterprises of the Samara region, suitable for use as raw materials components of such heat-resistant composites as solutions, concretes, gun mixes, coatings. The research indicates rational ways of some heat-resistant binders application for utilization of mineral high-melting and heat-resistant industrial wastes. It proves that the enrichment of certain types of industrial waste, i.e. bringing the chemical composition of their components to the required state, allowed to expand the raw material base for the synthesis of heat-resistant binders and concrete in general. The use of sludge waste in the processes of synthesizing liquid phosphate binders allowed to obtain such effective binders as aluminophosphates and aluminocalciumphosphates. The research proves that application of technogenic wastes of non-ferrous metallurgy enterprises allows to receive heat-resistant materials solutions, concretes, coatings, gun mixes which characteristics are similar to their industrial analogues.

In Russian practice, the vast majority of thermal units and other industrial furnaces are still built with the use of single-piece ceramic refractories. The purpose of research was to develop a wide range of special materials suitable for repairs of any linings of thermal units. In accordance with the purpose, this paper solved the following tasks: Selecting reactive binders used in the compositions of refractory concrete capable of structural modification of any refractory lining materials; Developing impregnating-coating compositions based on reactive binders capable of forming a protective coating with high adhesive strengthen linings; Developing compositions of refractory ramming mixtures, used for the repair of large fragments of linings and having high adhesion to any refractory lining materials; Checking the effectiveness of the technology in production environment. In this paper, we used not only standard techniques but also specially designed ones, in particular, to determine the adhesion of refractory coating to the refractory lining materials. The technology of repair works consists of application of some or all of the above solutions depending on the state of worn out lining of the thermal unit. Testing was carried out on many sintering plants of Samara region where rotary kilns are operated. The use of such chemically active substances as phosphate bonds and sodium silicate solutes in special refractory repair compositions with different functional purpose, allowed increasing the durability of liners of expanded fire clay rotary kilns as a result of reparatory works. Some items from the general technological scheme of repair works to restore the linings of heating units may be used in industrial furnaces in many industries.

Paleolithic antiquity of parietal art in Ignatievskaya cave, Southern Ural, is supported by its subject (Late Pleistocene animals) as well as by paleontological and palynological data, and 14C dates from cultural layers associated with artistic activity (17.8−16.3 cal ka BP; association is established by finds of ochre in these layers). However, three 14C dates of charcoal motifs yielded younger, Holocene ages (7.4−6.0 cal ka BP). In this study, we constrain the age of parietal art in the cave by 230Th dating of flowstone that brackets the paintings. Flowstone did not form in the cave between c. 78 and 10 ka BP, due to widespread permafrost in northern Eurasia at that time. Our 230Th dates do not support the middle Holocene age of art in Ignatievskaya cave and are consistent with its Upper Paleolithic antiquity instead. [ABSTRACT FROM AUTHOR]

Bi4Ti3O12 is a representative of the Aurivillius family of layered perovskites. These are high‐temperature ferroelectric materials with prospects for applications in random‐access memory and are characterized by an extremely confused interaction of their structural degrees of freedom. Using group‐theoretical methods, structural distortions in the Bi4Ti3O12 high‐symmetry phase, caused by rotations of rigid octahedra and their displacements as a single unit, have been investigated, taking into account the connections between them. Within the Landau theory, a stable thermodynamic model of phase transitions with three order parameters has been constructed. It is shown that, according to the phenomenological phase diagram, the transition between the high‐temperature tetragonal phase and the low‐temperature ferroelectric can occur both directly and through intermediate states, including those observed experimentally. The role of improper ordered parameters and possible domain configurations in the structure formation of the low‐temperature ferroelectric phase are discussed. [ABSTRACT FROM AUTHOR]

Bi4Ti3O12 is a representative of the Aurivillius family of layered perovskites. These are high‐temperature ferroelectric materials with prospects for applications in random‐access memory and are characterized by an extremely confused interaction of their structural degrees of freedom. Using group‐theoretical methods, structural distortions in the Bi4Ti3O12 high‐symmetry phase, caused by rotations of rigid octahedra and their displacements as a single unit, have been investigated, taking into account the connections between them. Within the Landau theory, a stable thermodynamic model of phase transitions with three order parameters has been constructed. It is shown that, according to the phenomenological phase diagram, the transition between the high‐temperature tetragonal phase and the low‐temperature ferroelectric can occur both directly and through intermediate states, including those observed experimentally. The role of improper ordered parameters and possible domain configurations in the structure formation of the low‐temperature ferroelectric phase are discussed. [ABSTRACT FROM AUTHOR]

The spinel oxide AlV2O4 is a unique material, in which the formation of clusters is accompanied by atomic, charge and orbital ordering and a rhombohedral lattice distortion. In this work a theory of the structural phase transition in AlV2O4 is proposed. This theory is based on the study of the order‐parameter symmetry, thermodynamics, electron density distribution, crystal chemistry and mechanisms of formation of the atomic and orbital structures of the rhombohedral phase. It is established that the critical order parameter is transformed according to irreducible representation k9(τ4) (in Kovalev notation) of the space group. Knowledge of the order‐parameter symmetry allows us to show that the derived AlV2O4 rhombohedral structure is a result of displacements of all atom types and the ordering of Al atoms (1:1 order type in tetrahedral spinel sites), V atoms (1:1:6 order type in octahedral sites) and O atoms (1:1:3:3 order type), and the ordering of dxy, dxz and dyz orbitals. Application of the density functional theory showed that V atoms in the Kagomé sublattice formed separate trimers. Also, no sign of metallic bonding between separate vanadium trimers in the heptamer structure was found. The density functional theory study and the crystal chemical analysis of V—O bond lengths allowed us to assume the existence of dimers and trimers as main clusters in the structure of the AlV2O4 rhombohedral modification. The trimer model of the low‐symmetry AlV2O4 structure is proposed. Within the Landau theory of phase transitions, typical diagrams of possible phase states are built. It is shown that phase states can be changed as a first‐order phase transition close to the second order in the vicinity of tricritical points of the phase diagrams. [ABSTRACT FROM AUTHOR]

The spinel oxide AlV2O4 is a unique material, in which the formation of clusters is accompanied by atomic, charge and orbital ordering and a rhombohedral lattice distortion. In this work a theory of the structural phase transition in AlV2O4 is proposed. This theory is based on the study of the order‐parameter symmetry, thermodynamics, electron density distribution, crystal chemistry and mechanisms of formation of the atomic and orbital structures of the rhombohedral phase. It is established that the critical order parameter is transformed according to irreducible representation k9(τ4) (in Kovalev notation) of the space group. Knowledge of the order‐parameter symmetry allows us to show that the derived AlV2O4 rhombohedral structure is a result of displacements of all atom types and the ordering of Al atoms (1:1 order type in tetrahedral spinel sites), V atoms (1:1:6 order type in octahedral sites) and O atoms (1:1:3:3 order type), and the ordering of dxy, dxz and dyz orbitals. Application of the density functional theory showed that V atoms in the Kagomé sublattice formed separate trimers. Also, no sign of metallic bonding between separate vanadium trimers in the heptamer structure was found. The density functional theory study and the crystal chemical analysis of V—O bond lengths allowed us to assume the existence of dimers and trimers as main clusters in the structure of the AlV2O4 rhombohedral modification. The trimer model of the low‐symmetry AlV2O4 structure is proposed. Within the Landau theory of phase transitions, typical diagrams of possible phase states are built. It is shown that phase states can be changed as a first‐order phase transition close to the second order in the vicinity of tricritical points of the phase diagrams. [ABSTRACT FROM AUTHOR]

Polarized Raman spectra of the epitaxial Ba0.4Sr0.6TiO3 film grown on MgO substrate with thickness of 600 nm were studied in a broad temperature range of 80-600 K and the phase transition from paraelectric to tetragonal ferroelectric phase was observed at about 500 K. This critical temperature is substantially higher than that calculated from the lattice-mismatch strain theory. In addition, the predicted from the theory low-temperature orthorhombic and rhombohedral phases were not observed. We ascribe the strengthening of the tetragonal ferroelectric phase to the effect of the interface-induced build-in electric field resulted from the interface-accumulated charges. [ABSTRACT FROM AUTHOR]

The theory of structural phase transition in CuTi2S4 is proposed. The symmetry of order parameters, thermodynamics and the mechanism of the atomic structure formation of the rhombohedral Cu–Ti–thiospinel have been studied. The critical order parameter inducing the phase transition has been found. Within the Landau theory of phase transitions, it is shown that the phase state may change from the high-symmetry cubic disordered Fd3̅m phase to the low-symmetry ordered rhombohedral R3̅m phase as a result of phase transition of the first order close to the second order. It is shown that the rhombohedral structure of CuTi2S4 is formed as a result of the displacements of all types of atoms and the ordering of Cu-atoms (1 : 1 order type in tetrahedral spinel sites), Ti-atoms (1 : 1 : 6 order type in octahedral spinel sites), and S-atoms (1 : 1 : 3 : 3 order type). The Cu- and Ti-atoms form metal nanoclusters which are named a “bunch” of dimers. The “bunch” of dimers in CuTi2S4 is a new type of self-organization of atoms in frustrated spinel-like structures. It is shown that Ti-atoms also form other types of metal nanoclusters: trimers and tetrahedra. [ABSTRACT FROM AUTHOR]