Calculation of Thermobimetallic Releases of Circuit Breakers with Indirect Heating for Currents from 63 to 250 A

Thermal releases based on thermobimetallic elements (TBEs) form the current-dependent part of the protective characteristic of a circuit breaker. The design of a mechanism of free releasing and the characteristics of a thermobimetallic element are analyzed. The operating condition for the thermal release is formulated, which is based on comparison of the mechanical characteristics of an actuator and thermomechanical characteristic of TBEs. Experimental studies of thermobimetallic releases, which are analogues of the breakers to be developed, were carried out. Taking into account the results of these experiments, a design procedure of thermobimetallic release was developed, which is applicable for all types of TBE heating (direct, indirect, combined). The procedure makes it possible to determine the geometrical dimensions of a TBE and the methods of its heating, as well as the operating temperature of release depending on the rated current of the breaker. It has been noted that, to provide the possibility of operating current adjusting, as well as for reliable operation of circuit breakers under vibration and shock conditions, it is necessary to provide for the free running of TBE during design. Comparison of design and experimental data showed the accuracy of procedure, which is acceptable for practical calculations.     

MBE-grown nanoheterostructures with increased electron mobility

Multilayered nitride heterostructures AlN/AlGaN/GaN/AlGaN are grown using a Nanofab-100 multichamber domestic complex involving a STE3N3 specialized installation of molecular beam epitaxy. The obtained heterostructures have high structural quality, smooth morphology, and a low dislocation density, which demonstrates the high potential of the nanotechnological complex.     

Investigation of the influence of the initial state of powder,pore-forming additions,and U<Subscript>3</Subscript>O<Subscript>8</Subscript> on the microstructure and strength of fuel pellets

It is shown that the initial state of uranium dioxide powder has no effect on the density, microstructure, and strength of pellets. Pore-forming agents and U₃O₈ used in fabrication lower the pellet strength because their particles are not spherical. To increase pellet strength, it is recommended that U₃O₈ be subjected to special processing to spheroidize the particles before mixing for uranium dioxide powder.     

Results from tests of the P-67 boiler used as part of a 800-MW power unit

Results from the balance tests of a retrofitted P-67 boiler carried out in the period 2006–2008 are presented. The tests involved assessment of the change with time of the heating-surface thermal efficiency coefficients in running the power unit at its base loads in the range 740–800 MW, with seven to eight coarsegrinding mills switched into operation, with the open and closed gate values installed in the channels supplying air-powder mixture to the fourth-tier burners, and with the fraction of air supplied for lower blasting equal to 5–7% and that for the startup burners, 2%. The combined cleaning system operated in its design mode with additional blowing operations according to special control signals. The furnace waterwalls and the convective shaft surfaces were subjected to mechanical cleaning every year during current repairs.     

Express method of the quantitative determination of nitrites by computer colorimetry using new reagent compositions

The possibilities of using new reagent compositions based on diazo and azo dyestuff components that contain sulfonic groups are considered to determine nitrites in the presence of the contents of chlorides. New reagent compositions based on 1-hydroxynaphthalene-3,6-disulfonic acid in combination with 2,6- nitroorthanilic and 2,6-dichlorosulfanilic acids have been used to create indicator powders and indicator papers for the quantitative test determination of nitrite ions. Test methods based on sustainable indicator powders and indicator papers have been developed with the use of the ilPro portable spectrophotometer and PlustekSmartPhoto P60 compact mobile scanner combined with the Vuescan universal scan program. It has been shown that the sensitivity of the visual determination of nitrites in liquids using indicator papers is 0.5 mg/L. The sensitivity of the test method that uses indicator papers, the PlustekSmartPhoto P60 mobile scanner, and the ilPro portable spectrophotometer is 0.2 mg/L. Upon using the indicator powder and i1Pro portable spectrophotometer, the range of defined concentrations of nitrite ions is 0.01–5 mg/L.     

Measuring the mechanical recoil impulse of a polymeric target upon impact of a high power electron beam

A method for measuring the mechanical recoil impulse of a target produced by the relativistic electron beam of the Calamary accelerator is described. A detector based on a piezoelectric sensor is used in measurements. Results of measurements are presented for the mechanical recoil impulse produced by the relativistic electron beam with an energy as high as 300 keV, a current of up to 30 kA, and a duration of ~100 ns that is incident on an epoxy target. The energy flux density on the target surface is varied in the range of 1–10 GW/cm². The maximum measured impulse value is 0.32 N · s at an energy flux density of 10 GW/cm² (an energy fluence of 810 J/cm2).     

The stability of a balloon support subjected to blasting

Journal of Mining Science -     

Conditions for obtaining ultrafiltration membranes from a solution of polyacrylonitrile in dimethylformamide in the presence of formamide

The possibility to obtain ultrafiltration polyacrylonitrile terpolymer membranes in the presence of formamide in dimethylformamide polymer solution was studied. Correlation between the changes in viscosity and rheological characteristics of the polymer solutions, on the one hand, and the equivalent pore radii, efficiency, and selectivity of membranes, on the other hand, were found. The concentration of formamide was varied from 0 to 4 mass %. The dynamic characteristics of the membranes were determined with regard to calibrators having different molecular weight. © 1996 John Wiley & Sons, Inc.     

Prediction of Ferroalloy Properties for Expert Evaluation of the Efficiency of their Use During Addition to Steel in a Ladle Furnace Unit

Metallurgist - A procedure is developed for calculating criteria for estimation and evaluation of chemical and structural micro-inhomogeneity of ferroalloy production melts. Models are proposed for...