Manufacturing of greases based on deep-cleaned spent mineral and synthetic motor oils

The possibility of increasing the efficiency of utilization of spent motor oils as the dispersion medium of lubricating greases has been explored. It has been established that the removal of resins, asphaltenes, carbenes, and carboids from used mineral and synthetic motor oils makes it possible to obtain a base stock close to commercial base oils in the main characteristics. It has been proposed to use carbamide or monoethanolamine in a mixture with isopropanol. It has been found that more than 90% of the contaminants are removed from used engine oils by refining according to the methods proposed. The re-refined oils have a high margin of performance. The composition of Litol-24 and Solidol Zh grease analogues based on refined waste motor oils has been determined. The corrosion-preventing, adhesion, and strength properties of the lubricant compositions are considered. The results of bench testing of lubricant compositions in rolling bearings, which confirm their high performance properties, are presented.     

Electromagnetic processes in power transformers with vector control

One possible circuit of a power transformer with vector control is considered. Initial statements of the electromagnetic analysis of transformers are given. An algorithm for determining the voltage and current time dependences, as well as characteristics ones, is described. The dependences between the power transformer characteristics with vector control and the control parameters are shown by the example of the transformer with a nominal power of 16 MV A and nominal supply voltage of 110 kV. The conclusion is drawn that minimum power losses are present at a certain combination of control parameters. The time dependences of current and voltage power keys involved in the transformer of active converters, which result from the mathematical simulation in MATLAB and Simulink, are presented. The effectiveness of the proposed model is evaluated.     

Chemical and phase composition of nanosize oxide and passive films on Ni-Cr alloys. I. XPS studies of films obtained by alloy oxidation in air

XPS data for thin (less than 100 nm) oxide films obtained by oxidation of Ni-4 Cr and Ni-12.5 Cr alloys at 500°C (0.5 h) are discussed. Thermodynamic analysis of 3 NiO + 2 Cr = Cr₂O₃ + 3 Ni solid-phase reaction is given, in which both the Gibbs energy change in the thermochemical process and the change in the interface energy at the alloy-oxide film boundary are taken into account.     

Low temperature n-butane oxidation skeletal mechanism, based on multilevel approach

In order to reconcile an increasingly large deviation (order of magnitude) of the ignition delay time at decreasing initial temperature, computed using the prior art kinetic schemes, with the available experimental values, a new skeletal mechanism (54 species, 94 reactions) for low-temperature (500-800 K) ignition of n- butane in air based on ab initio calculations is developed. The skeletal mechanism obtained accurately reproduces n-butane combustion kinetics for the practically important ranges of pressure, temperature and fuel-air equivalence ratio, especially in the low-temperature range. The elaborated first principal skeletal chemical kinetic mechanism of n-butane oxidation was validated against available experimental results for normal and elevated initial pressure (1-15 atm) using the Chemical Work Bench code. A good agreement with experiments was shown.     

Study of Beaconing in Multihop Wireless PAN with Distributed Control

Distributed media access control (MAC) architecture has many merits to make it a favorable candidate for high-data-rate wireless personal area networks (WPANs) with physical layer (PHY) based on ultrawideband (UWB) technology. This paper focuses on the WiMedia MAC, which is the first distributed MAC for WPANs, approved as a standard. In such a MAC, all devices transmit their beacons to provide timing reference and to broadcast control and reservation information, that is, to maintain device synchronization. We investigate problems related to beacon collisions, which occur when multiple devices join a piconet almost at the same time. To join a piconet or to resolve a collision, a device chooses a slot for its beacon randomly within some window. We show that an improper slot choice scheme leads to repeated collisions, increasing the time overhead to achieve device synchronization. It also leads devices into trouble in joining and collision resolution, even into deadlocks, when devices have no chance to escape repeated collisions. We develop an analytical model to evaluate the performance of various slot choice schemes for multihop WPANs. The model is employed to compare the efficiency of these choice schemes and to optimize their parameters to achieve the best performance.     

Strength Analysis and Process Simulation of Subway Contact Rail Support Bracket of Composite Materials

An application of composites for construction of subway brackets is a very effective approach to extend their lifetime. However, this approach involves the necessity to prevent process-induced distortions of the bracket due to thermal deformation and chemical shrinkage. At present study, a process simulation has been carried out to support the design of the production tooling. The simulation was based on the application of viscoelastic model for the resin. Simulation results were verified by comparison with results of manufacturing experiments. To optimize the bracket structure the strength analysis was carried out as well.     

Stability of strengthening of laser-treated aluminum alloys

Laser treatment is one of the effective methods of strengthening the surface of parts made of aluminum alloys. In operation some of them are subjected to elevated temperatures for a long time. However, the literature contains insufficient information on the degree of weakening of the laser-affected zone (LAZ) in aluminum alloys. We investigated the microhardness of various classes of aluminum alloys strengthened with the aid of laser radiation after they had been heated.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 32–34, June, 1994.