Low-temperature spin relaxation in n-type GaAs

Low-temperature electron spin relaxation is studied by the optical orientation method in bulk n-GaAs with donor concentrations from 10^14 cm^{-3} to 5x10^17 cm^{-3}. A peculiarity related to the metal-to-insulator transition (MIT) is observed in the dependence of the spin lifetime on doping near n_D = 2x10^16 cm^{-3}. In the metallic phase, spin relaxation is governed by the Dyakonov-Perel mechanism, while in the insulator phase it is due to anisotropic exchange interaction and hyperfine interactio

Evaluation of the effectiveness of sealing the grid of wells at an oil facility

This paper discusses the use of well pattern compaction technology by drilling small-diameter wells in the conditions of the N field and identifying its effect on the oil recovery factor. An analysis of the effectiveness of the results of grid compaction by drilling using smalldiameter wells in the conditions of the N field is carried out, and an increase in the efficiency of field development by compacting the existing development grid by drilling small-diameter wells is also considered. Research methods include systems analysis methods; methods of mathematical modeling; mathematical programming; mathematical statistics; cluster analysis; numerical methods; computational experiments; database design theories

New approach to assessing the state of fish stocks on the example of bream

© 2020 Publishing House "O- Kratkoe". All rights reserved. This paper substantiates a new approach to the protection of fish resources, based on the transition from the concept of a calculated forecast of catches and quotas to a multilevel system for assessing the status of fish populations under conditions of slow flow. The main levels of the fish population monitoring system are considered. A new approach based an analysis of monitoring results of the main structural and functional population characteristics of fish, on data on the dynamics of the population size and its generations, changes in the age structure, growth rate, abundance of individuals with morphological anomalies. A new approach was tested on the example of a model species of bream (Abramis brama L.) in the Kuibyshev reservoir as a common inhabitant of different morpho-hydrological properties of reservoirs in Europe, belonging to the LC group according to the IUCN classification. An array of new scientific data has been obtained. Based on the calculation of natural mortality by approximating the population curve, taking into account the age composition of catches, it is shown that with a stable replenishment of the fishing herd, when high- and small-numbered generations enter the fishery, depending on the spawning conditions, bream stocks are not expected to be undermined. The results of the study can be used as a basis for assessing the state of fish populations, developing measures for the rational development of their reserves in conditions of unstable hydrological regime of reservoirs and weakening of control over fishing in the protection of fish resources