Formation of the block structure during growth of basal-plane-faceted sapphire ribbons with different widths

The defect structure of basal-plane-faceted sapphire ribbons 10, 30, and 50 mm wide is investigated. It is shown that the high density of blocks in these crystals is associated with the specific features of the plastic deformation of the crystals with this orientation during crystal growth. In the basal-plane-faceted ribbons, the plastic deformation begins with the slip in the prismatic system. Dislocations of this system form characteristic low-angle boundaries, which then transform into block boundaries. It is revealed that the slip in the easiest basal system, which is characteristic of ribbons with all other orientations, is impossible because of the geometric constraints. Block-free basal-plane-faceted ribbons 50 mm wide are produced by decreasing thermal stresses in growing crystals.     

Stabilization of uncertain systems on rings

M. V. Lomonosov Moscow State University. Translated from Matematicheskoe Modelirovanie. Published by Moscow University, Moscow, 1993, pp. 279–295.     

Determination of the modulus of elasticity of the amorphous regions of chemical fibers

A method of calculating the orientation index and modulus of elasticity of the elements of a two-phase fiber model is presented. The effect of orientational drawing on the variation of these characteristics has been investigated for nylon [capron] fibers.Mekhanika Polimerov, Vol. 3, No. 3, pp. 409–412, 1967     

New gravitational experiment with ultracold neutrons

The results of a new neutron gravitation experiment are reported. The change in the energy of a neutron falling to a known height in the Earth’s gravitational field is compensated by an energy quantum ?Θ transferred to the neutron as a result of the phase modulation of the neutron wave. A phase diffraction grating moving across the direction of the propagation of the neutron wave is used as a modulator. The experiment has been carried out with ultracold neutrons Interference filters, neutron analogues of Fabry-Perot interferometers, are used for the spectrometry of ultracold neutrons. The force m _g g _n acting on the neutron in the Earth’s gravitational field has been measured with an accuracy of about 0.2%.     

Simultaneous stabilization of linear plants by a low order controller

We consider simultaneous stabilization of linear scalar stationary plants of second order and derive an easily verified necessary condition of simultaneous stabilization, as well as a sufficient condition that leads to a constructive algorithm for a stabilizing controller. The existence of a stabilizing controller is established in the parametric polynomial space by a method that finds the stability radii of polynomials.     

Biological-like vesicular structures self-assembled from DNA-block copolymers

The polymer modification of short nucleotide sequences has been achieved for future use as self-assembled biologically active structures with sizes in the nanometre range. Co-assembly of the resulting DNA-based amphiphilic block copolymers with native proteins demonstrates the self-assembly of biological-like vesicular structures.     

The potential and vortex traces of a tsunamigenic earthquake in the ocean

An equation system that describes the potential and vortex residual hydrodynamical fields that emerge in the rotating ocean during tsunami generation by co-seismic deformations of the bottom was obtained in terms of linear long-wave theory. For the model case of a cylindrically symmetrical deformation of the bottom, a completely analytical solution was found. On the basis of this solution, the structure of residual fields was analyzed and estimates of the residual horizontal displacements of water particles, of the speed of the vortex current, and of the energy of a geostrophic vortex were obtained under typical tsunami source conditions.     

Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.