Photochemical and Photophysical Processes of N-Deacetyllappaconitine and Its Monohydrobromide in Aqueous Solutions

Chemistry of Natural Compounds - The photophysical and photochemical processes of N-deacetyllappaconitine (DAL) and its hydrobromide (DAL·HBr) in aqueous solutions were investigated. Their...     

Magnetic State of Layered Cobalt Chalcogenides Co7Se8 and Co7Te8

JETP Letters - The structural and magnetic properties of the Co7Te8 layered compound have been studied for the first time using X-ray diffraction, measurements of the magnetic susceptibility, and...     

Formation of Polyhydroxyurethanes in the Reaction of Carbon Dioxide with Diepoxides and Diamines in the Presence of a Chromium Complex

Kinetics and Catalysis - Cyclic biscarbonates were synthesized from CO2 and diepoxides in the presence of a chromium(III) salen complex. The effect of the reaction conditions on the process...     

STRUCTURAL FEATURES OF HYDROGEN- BONDED ORGANIC FRAMEWORKS BASED ON NICKEL(II) 5,10,15,20-TETRAKIS(4- PHOSPHONATOPHENYL)PORPHYRINATE

Journal of Structural Chemistry - Two hydrogen-bonded organic frameworks of the composition [((CH3)2NH2)3.5(Ni-H4.5TPPP)]·DMF·H2O (1) and [((CH3)2NH2)4(Ni-H4TPPP)(H2O)3]·DMF·H2O...     

On plasticity, elastic relaxation phenomena, and a stress-strain relation which characterizes Schofield-Scott Blair media

A generalization is given of the author's theory for plasticity phenomena. The theory includes the possibility of both stress and strain relaxation in the preplastic range. Methods of non-equilibrium thermodynamics are used. The plasticity phenomenon is explained by introducing a physical assumption concerning the phenomenological coefficients. A yield function is proposed which includes the Bauschinger effect and strain hardening. If the free energy f has the form f=f ⁽¹⁾+f ⁽²⁾, where f ⁽¹⁾ is a function of the temperature and the elastic strains and f ⁽²⁾ is a function of the temperature and the inelastic strains, and if cross effects between the plastic flow and elastic relaxation phenomena may be neglected, the proposed yield function is such that the derivative with respect to time of the deviator of the plastic strain tensor is given by , where Φ is the yield function, ταβ is the mechanical stress tensor, and η is a coefficient which vanishes in the preplastic range. If the equations of state may be linearized the proposed yield function reduces to a function which is analogous to a yield function proposed by Freudenthal. If the plastic flow phenomenon is not associated with changes in the microscopic structure of the medium the proposed yield function reduces to the Von Mises function. It follows from the theory that in a first approximation elastic relaxation phenomena in the preplastic range may be described by the equation for Poynting-Thomson media (standard linear solids). An equation which characterizes Schofield-Scott Blair media is also derived from the developed theory.     

Étude du comportement viscoélastique du polycarbonate de bisphénol-A partiellement cristallisé

Résumé On étudie dans cet article un procédé pour obtenir des polycarbonates de bisphénol-A de divers taux de cristallinité. On détermine la variation thermique du module-(10 sec) et la résistance au choc des ces polymères. On étudie également l'influence du recuit sur les propriétés mécaniques.

---

Summary This paper describes a procedure to obtain polycarbonate of bisphenol A samples of various degrees of crystallinity. The modulus-temperature curves and the impact strength of these materials are investigated. The results show the importance of the annealing procedure on the mechanical properties of these systems.

     

Interaction of a turbulent wake with the outer flow

The integral methods of boundary-layer theory are used to examine the interaction of a turbulent wake with the outer flow for the example of planar flow.In contrast with the known Crocco-Lees theory [1], the turbulent layer in the gas is described with the aid of an appropriate family of velocity profiles rather than by means of a Dorodnitsyn-type transformation of the incompressible turbulent layer. The selection of the simplest among the possible systems of first order interaction equations is justified; this system reduces to a single differential equation and an estimate is given of the influence of the arbitrariness in the equation selection on the final results.The hydrodynamic meaning of the singular and nonsingular integral curves and the singular point of the interaction equation is clarified on the basis of an examination of the interaction of compression and rarefaction waves in the outer supersonic stream with the wake. The effect of blowing (suction) and the initial boundary layer on the base pressure and the supersonic interaction flow as a whole is examined on the basis of the integral conditions for the splicing of the interaction flow with the isobaric mixing flow behind the corner. It is shown that, with proper selection of the single constant in the turbulent viscosity formula, the computational results are in satisfactory agreement with experiment.In conclusion, the authors wish to thank G. G. Chernyi for helpful discussions of the study, and L. V. Kapranova and Z. A. Donskova for assistance in the calculations.     

Material laws as a basis for simulation models for the calculation of wheel-soil interaction examination using the finite element method

It is the purpose of this article to present the material laws of the soil in such a way that the complex nature of load cycle and deformation paths are sufficiently taken into account. As an important new aspect, not only the so-called failure strength, but also the deformation-dependent stress behavior prior to failure is considered. Such a formulation of the material behavior is espeically well suited as a basis for modelling of the interaction between the tire or track and the soil. The presentation of the material behavior give here is applied in a numeric simulation model of the tire-soil interaction, in order to determine both drawbar pull and soil deformations. The results correspond well to values obtained from mobility tests.     

Influence of second-order boundary layer effects in hypersonic flow over slender blunt cones

The aim of this study is to determine the influence of second-order effects in the aggregate on supersonic axisymmetric flow over slender blunt cones and also to determine the region of applicability of approximate methods of taking into account the strongest of these second-order effects — entropy layer absorption. A system of complete viscous shock layer equations containing all the terms of the gas dynamic Euler equations and all the second-order terms of asymptotic boundary layer theory is chosen as the gas-dynamic model. Within the calculation domain the problem is solved in a unified manner.Translated from Izvestiya Rossiiskoi Akademii Nauk, Meknanika Zhidkosti i Gaza, No.4, pp. 129–134, July–August, 1992.     

Motion of bed-loads under the influence of flow of a liquid

Equations are obtained for the motion of a water-soil mixture in the layer next to the base. The water-soil mixture is modeled by means of a viscous-friable medium, and the acceleration of the mixture is assumed to be small and is not taken into account. The validity of the equations is confirmed by the experimental data for the following characteristics of uniform motion of a flow: for the speed of the start of particles touching on an even bed and with allowance for inclines of a bed, and also for the flow rate of loads on an even bed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 182–185.The author is grateful to A. G. Kulikovskii, V. Ya. Shkadov, and M. É. Églit for discussing the results of the study.