Nonlinear Dynamics and Stability of a Two D.O.F. Elastic/Elasto-Plastic Model System

The local and global nonlinear dynamics of a two-degree-of-freedom model system is studied. The undeflected model consists of an inverted T formed by three rigid bars, with the tips of the two horizontal bars supported on springs. The springs exhibit an elasto-plastic response, including the Bauschinger effect. The vertical rigid bar is subjected to a conservative (dead) or non-conservative (follower) force having static and periodic components. First, the method of multiple scales is used for the analysis of the local dynamics of the system with elastic springs. The attention is focused at modal interaction phenomena in weak excitation at primary resonance and in hard sub-harmonic excitation. Three different asymptotic expansions are utilised to get a structural response for typical ranges of excitation parameters. Numerical integration of the governing equations is then performed to validate results of asymptotic analysis in each case. A full global nonlinear dynamics analysis of the elasto-plastic system is performed to reveal the role of plastic deformations in the stability of this system. Static 'force-displacement' curves are plotted and the role of plastic deformations in the destabilisation of the system is discussed. Large-amplitude non-linear oscillations of the elasto-plastic system are studied, including the influence of material hardening and of static and sinusoidal components of the applied force. A practical method is proposed for the study of a non-conservative elasto-plastic system as a non-conservative elastic system with an 'equivalent' viscous damping. This revised version was published online in July 2006 with corrections to the Cover Date.     

Homogeneous condensation in turbulent submerged isobaric jets

Turbulent isobaric vapor-air jet flows with homogeneous condensation are examined. A general system of equations, including the gas dynamic and kinetic equations, the thermodynamic relations and the equations for the turbulence model, is formulated. The moment kinetic equations valid for the free-molecular regime of drop growth in the surrounding medium are extended to other drop mass transfer regimes. The structure of the condensation shock, which includes the nucleation zone and the zone of drop growth on pre-existing nuclei, is investigated on the basis of a general asymptotic approach. Additional conditions at the nucleation and condensation shocks, the need for which follows from the requirement that the shocks be evolutionary, are obtained. Certain problems of averaging of the source terms in the moment equations are discussed, and with reference to the simple example of averaging of the frozen nucleation rate it is shown that the latter is nonzero for a mean supersaturation less than unity and that the condensation zone is displaced upstream. Condensation in a turbulent jet into which condensation-intensifying charged particles (corona discharge ions) are introduced is studied. A numerical method of analyzing homogeneous condensation in turbulent jets, which makes it possible to obtain the gas dynamic and disperse flow characteristics for various temperature conditions with allowance for the averaging of the source terms, is developed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 43–52, March–April, 1988.The authors wish to thank V. R. Kuznetsov for discussing various aspects of their work.     

Rebounding of a shaped-charge jet

The phenomenon of rebounding of a shaped-charge jet from the armour surface with small angles between the jet axis and the target surface is considered. Rebounding angles as a function of jet velocity are obtained in experiments for a copper shaped-charge jet. An engineering calculation technique is developed. The results calculated with the use of this technique are in reasonable agreement with experimental data. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 17–20, September–October, 2007.     

Phototransformations of azetidine radical cations stabilized in freonic matrices

It has been established that transformations of azetidine radical cations observed in freonic matrices under the action of light with λ = 436 nm (T = 77 K) are associated with C-N bond cleavage which corresponds to the cyclic form yielding a mixture of open distonic C-centered radical cations of the following structure: ·CH₂CH₂CH=NH ₂ ⁺      

Thermodynamic properties of nonsuperconducting Ln2CuO4 (Ln = Nd, Sm, Eu), Ho2Cu2O5 and Ln2BaCuO5 (Ln = Nd, Sm, Eu, Ho, Yb) cuprates

Thermodynamic properties of rare-earth Ln₂CuO₄ (Ln = Nd, Sm, Eu), Ho₂Cu₂O₅ and Ln₂BaCuO₅ (Ln = Nd, Sm, Eu, Ho, Yb) cuprates were determined using the electromotive force method with a fluorine-ion electrolyte in the temperature interval of 1000–1230 K. The thermodynamic data obtained by different experimental methods were compared.     

Synergistic effects of encapsulated phthalocyanine complexes in MIL-101 for the selective aerobic oxidation of tetralin

Metal phthalocyanine complexes encapsulated in MIL-101, and used as "ship-in-a-bottle" catalysts, show outstanding TONs in the aerobic oxidation of tetralin.     

(Butylsulfanyl)ethanal and 3-(Organylsulfanyl)butanal 1,1-Dimethylhydrazones

Previously unknown (butylsulfanyl)ethanal and 3-(organylsulfanyl)butanal 1,1-dimethylhydrazones were synthesized. Their reactivity toward methyl iodide was studied.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 945–953.Original Russian Text Copyright © 2005 by Sorokin, Lopyrev, Voronkov.     

Electron beam formation in an anomalous glow discharge

Scaling parameters that account for the efficient formation of electron beams in sources based on an anomalous glow discharge are considered, and the processes leading to the violation of scaling laws are analyzed. Estimates show that the working pressure range in such sources can be increased significantly. The results obtained can be used to optimize discharge regimes with required electron beam parameters. It is demonstrated that sources with plane-parallel continuous electrodes can operate at pressures as high as 100 Torr (which is one to two orders of magnitude higher than that in similar existing electron beam sources), provided that parasitic spark breakdowns at the insulator near the discharge cathode are suppressed. The sources designed can be used for direct excitation of laser working media or their preionization by soft X-rays.