Stress relaxation in InGaAsP/InP heterostructures for 1064-nm laser radiation converters

Technical Physics Letters - Specific features of mechanical-stress relaxation in InGaAsP/InP heterostructures for 1064 nm laser radiation converters have been studied. It is established that stress...     

Beyond-design-basis regimes of uranium stripping and of carbonate regeneration of the solvent

Beyond-design-basis regimes of centrifugal contactors for U stripping and of mixer–settlers for carbonate regeneration of the solvent, 30% TBP in Isopar M, were studied from the viewpoint of the influence of incomplete uranium stripping on the phase stability of the extraction system in the step of the carbonate scrubbing of the solvent. Dynamic relationship between these two operations was determined. A mathematical model of uranium stripping at stepwise–20% deviation from the nominal value was developed and verified; it was shown that the beyond-design-basis regime develops in such apparatuses within 4 h at the total trial time longer than 8 h. The mathematical relationships obtained were used in the development of software for calculating transient processes that occur when the stream parameters in the course of carbonate regeneration of the solvent change. The beyond-design-basis regime of the solvent regeneration was found to have two regions: region of stoichiometric excess of carbonate ions over uranyl ions with the risk of precipitation and region of excess of uranyl ions over carbonate ions with acidification of the unit and uranium breakthrough with the recycled solvent. The conditions of the tests performed correspond to the second region.     

Interaction of thorium and plutonium with pertechnetic acid in the course of extraction from nitric acid solutions with tributyl phosphate in diluent and its mathematical description

Databases on the coextraction of Th or Pu with Tc into 30% TBP in hydrocarbon diluent at 25°С are presented. The coextraction leads to mutual enhancement of the extraction of all the elements. The interactions in the system are described within the framework of a new approach to modeling, using the previously suggested and additional equations of concurrently occurring chemical reactions. The apparent equilibrium constants of these reactions are calculated.     

Optimal materials for the manufacture of metal-cutting machines

With the goal of improving machine-tool design, attention focuses on the possibility of manufacturing the components of metal-cutting machines from effective new nonmetallic materials that not only meet all the current requirements on such machines but also in most cases improve their performance. The best results are obtained with metal–concrete structures in which the nonmetallic binder consists of modified cement with chemically active additives. Results from materials science are compared with multiyear production tests of metal-cutting machines based on metal–concrete components, which are characterized by stable performance over time. On that basis, an effective new approach is proposed for the modernization of machine tools at the end of their effective working life, without replacing the fundamental structures. The design of the basic structures is analyzed. The production of metal–concrete components in a specialized department of the manufacturing plant is recommended.     

Features of the spin-lattice relaxation of nuclear spins 63,65Cu in the CuAlO2 semiconductor compound

The results of studying the nuclear spin-lattice relaxation of the nuclear spins of ^63,65Cu in the CuAlO₂ semiconductor compound (T = 77, 300 K) by the method of nuclear quadrupole resonance of Cu are presented. The relaxation rates in the CuAlO₂ compound contain contributions from the magnetic and quadrupole relaxation mechanisms. The magnetic contribution to the relaxation rate is caused by hyperfine magnetic fields of mobile holes. Comparison of the magnetic contribution to the relaxation rate with electrical conductivity made it possible to estimate the carrier concentration and mobility.     

Carbon and sulfur isotopes as geochemical keys to the origin of petroleum

A possible abiogenic origin for oil structures is indicated by the carbon and sulfur isotope ratios in crude oil, oil components, and other natural systems. Oils are enriched in the ³⁴S isotope as the sulfur content decreases, which provides indirect evidence for an increase in the contribution of biomaterial to oil as the sizes of oil pools decrease. Translated from Khimiya i Tekhnologiya Topliv i Masel, No.3, pp. 36 – 38, May – June, 2009.