An Experimental Investigation of the Coagulation of Aerosol in a Tube in the Vicinity of Subharmonic Resonance

Nonlinear oscillation of aerosol in the vicinity of a resonance frequency that is twice lower than the first eigenfrequency (subharmonic resonance) is experimentally investigated in tubes with different conditions at the ends. The time dependence of the number density of aerosol droplets is determined, and the effect of the frequency and intensity of oscillation on the process of coagulation of droplets is studied. The nonmonotonic pattern of the dependence of the time of coagulation of aerosol droplets on the frequency of excitation with a minimal value at resonance is found. Ordered space-time structures (alternation of denser and looser regions of aerosol) are revealed in the visible region in the vicinity of the middle of a closed tube.     

Effect of Nb Addition on Oxidation Mechanisms of High Cr Ferritic Steel in Ar–H2–H2O

High chromium ferritic steels are being used as construction materials for interconnects in solid oxide electrolysis cells (SOEC). Addition of niobium in the range of a few tenths of a percent is suitable for increasing the high-temperature creep strength of this type of ferritic steel. In the present work, the high-temperature isothermal oxidation behavior of a niobium containing ferritic steel at 800 °C was investigated in Ar–4%H₂–4%H₂O gas simulating the service environment in an SOEC (cathode side) and compared with that of a Nb-free counterpart alloy. Gravimetric data were correlated with the results from microstructural analyses using, among others, scanning and transmission electron microscopy as well as glow discharge optical emission spectroscopy. Atom probe tomography was used for obtaining atomic-scale insight into the segregation processes in external oxides and their interfaces. The oxidation rate was substantially higher for the Nb-containing than for the Nb-free alloy. Both alloys formed double-layered oxide scales consisting of inner chromia and outer MnCr₂O₄ spinel. Additionally, a thin layer of rutile-type Nb(Ti,Cr)O₂ oxide of 200–300 nm thickness was observed at the scale–alloy interface in the Nb-containing steel. Nb addition to the alloy led to its segregation at chromia grain boundaries which affected the diffusion of Cr and other solute species such as Ti, Mn and Si.

     

Influence of absorption on nonlinear vibrations of gas in a closed pipe

We consider dissipative mechanisms involved in resonance vibrations of gas in a closed pipe. Using analysis of a resonance curve as an example, we show the existence of four regimes differing in the mechanism of dissipation. We determine their boundaries, as well as lay a foundation for the procedures used to calculate the amplitude of vibrations within these intervals. Comparison of calculating formulas with experiments conducted by various authors is made.     

Thermoacoustic effect in a resonant semiopen tube

Results are given of a theoretical and experimental study of the effect of heating the walls of a semiopen tube under conditions of acoustic resonance.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 4, pp. 615–623, October, 1982.     

Resonance gas oscillations in a tube with an open end under weakly developed turbulence

Resonance gas oscillations in a tube, one end of which has an oscillating piston and the other of which is open to the environment, are considered. A semi-empirical model of resonance oscillations in a long tube under conditions of weakly developed turbulence is constructed. The boundary condition at the open end is calculated analytically. The relations obtained are compared to experiment. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2, pp. 311–316, March–April, 1998.     

Synthesis and properties of hybrid materials obtained by in situ copolymerization of ethylene and propylene in the presence of Al2O3 nanofibers (NafenTM) on catalytic system rac‐Et(2‐MeInd)2ZrMe2/isobutylalumoxane

Nanofibers of Al₂O₃ (commercial product Nafen^TM) with characteristic length of ～100 nm and diameter of ～10 nm were used to create new hybrid materials based on copolymer of ethylene and propylene. Nanocomposites were obtained by in situ catalytic copolymerization on the system rac‐Et(2‐MeInd)₂ZrMe₂/isobutylalumoxane. Formation of the nanocomposites with uniform distribution of Nafen nanoparticles in polymer matrix was confirmed by scanning and transmission electron microscopy. According to dynamic mechanical analysis data, introduction of the nanofiller in an amount of up to 3 wt % leads to an increase in glass transition temperature by 10 °C (E″) and by 21 °C (tan δ). The nanocomposites exhibit improved physico‐mechanical properties (tensile strength and elongation at break). It is shown that the nanofiller significantly improves resistance of the nanocomposite to the thermo‐oxidative and thermal degradation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44678.     

Hybrid neural network for the adjustment of fuzzy systems when simulating tests of internal combustion engines

The use of a hybrid neural network for automatic formulation of fuzzy control rules is considered, in the testing of internal combustion engines. The topology of this network is determined. On the basis of the resulting fuzzy rules, the quality of combustion-engine control is assessed.