Spray-drying of alumina powder for APS: effect of slurry properties and drying conditions upon particle size and morphology of feedstock

In this paper, effects of variables concerning slurry properties and drying conditions on the particle size and morphology of feedstock were discussed. The results indicated that, the increase of powder loading increased D ₅₀ and volume content but reduced recovery rate slightly. Other variables, such as inlet temperature, showed a maximum on the desired property. The particle size of resulting feedstock increased with the rise of feeding rate of slurry, however, decreased with the increase of atomization pressure based on the premise that atomization pressure was enough to force slurry to form the liquid membrane. For preparation of spherical feedstock, optimized variables were as follows: 60 wt.% powder in slurry, 2 wt.% PVA in slurry, inlet temperature of 60°C, atomization pressure of 13 × 10³ KPa and feeding rate of 12 ml min^?1. The volume content of feedstocks with 10–45 μm was above 65% and for D ₅₀ it was 15·42 μm. In addition, according to the heat and mass transfer equation, the drying mechanism was established, which was well in agreement with the experimental results.     

Analysis of the diametral compression method for determining the tensile strength of transparent magnesium aluminate spinel

Attempts were made to determine the inherent tensile strength of a coarse-grained, hot-pressed magnesium aluminate spinel (MgAl₂O₄) using the diametral compression test. Thick (9.6 mm) disk specimens were machined from a large (356 mm square) plate of spinel. Two pairs of tungsten carbide (WC) platens, one with flat surfaces and the other with a 20° half-arc and radius matched to the disk diameter, were used to transfer the applied load. Specimens tested using the platens with the matched radius had strength values almost 50% higher than those tested using flat platens. Images of the fracture process captured using a high-speed camera showed that irrespective of the type of platens used, fracture consistently initiated at the loading interface, resulting in an invalid test. These results show that the diametral compression test method is not appropriate for determining the tensile strength of this spinel and it raises concerns about the applicability of the method for any advanced ceramic.     

Regularizing the problem of monitoring the technical state of complex technical objects using program complexes for fuzzy conditional inference systems

Regularizing the problem of monitoring the technical state of complex technical objects in emergencies through drawing on additional semantic information is illustrated for a specific example.     

On the 25th anniversary of the disaster at the chernobyl nuclear power plant

The participation of experts from the Gosstandart system in efforts to remediate the consequences of the disaster at the Chernobyl Nuclear Power plant and some results of this work are discussed.     

A procedure for estimating the statistical characteristics of streams of hacker attacks. The structure and determination of their fundamental properties

A procedure for estimating the statistical characteristics of ordinary streams of random events is proposed. This procedure was used to investigate the characteristics of hacker phishing attacks in the period from December 2008 to October 2010. A comparative investigation of the monthly dynamics of phishing attacks and attacks using malicious software, recorded in 2009, is described.     

A system approach to the description of the properties of the ITS-90

The use of a system approach to describe the properties of the International Temperature Scale (ITS-90) is proposed. A model is presented which enables the error of the difference between the ITS-90 and the thermodynamic scale to be estimated. The possibility of estimating the static chaos of the results of temperature measurements is considered.     

Electric conductivity of metal-dielectric-metal structures with dielectric layer formed by spherical metal oxide nanoparticles

The electrical properties of metal-dielectric-metal (MDM) structures with the dielectric layer representing a monolayer of spherical Al₂O₃ or ZrO₂ oxide nanoparticles have been studied. It is established that these heterogeneous structures exhibit electric conductivity according to the mechanism for which the differential resistance dU/dI is negative and reversibly approaches zero with increasing current I. The electric conductivity strongly depends on the polarity of the applied voltage U, provided that electrodes are made of basically different metals or the same metal with different surface conditions. The mechanism of the electric conductivity in the given MDM structure depends on the diameter of nanoparticles in the dielectric layer.     

Secondary diffraction of diffracted Gaussian beam of laser radiation

The diffraction of a narrow Gaussian beam of laser radiation on mutually perpendicular edges of crossed, superimposed sharp wedge-shaped blades (safety razors) has been studied. The diffraction pattern observed on a flat screen behind the blades comprises a very bright central spot, which exhibits the structure of a “light network” with rectangular cells, and four groups of narrow bright bands that expand from the central spot toward the periphery and form a rectangular cross. The spatial frequency of light-field modulation on the screen can be controlled by varying the distance from the blades to screen.     

Thermal parameters of centrifugal induction deposition of powder coatings

An engineering method of calculation of the thermal parameters of centrifugal induction sintering of a powder onto the surface of a workpiece with allowance for the geometric, thermophysical, and electrophysical parameters of the workpiece and the powder layer and for the convective and radiative heating of the exterior surface of the workpiece has been developed. A system for control of the temperature of the workpiece in the process of centrifugal induction sintering of the powder coating onto it has been developed.