Investigation of the propagation of an ultrasound pulse in a dispersed fractal medium

Results are presented of an experimental determination of the fractal parameters of crushed sand particles. Results of measurements of the propagation of an acoustic pulse through a mass of sand having various degrees of dispersion are used to determine the fractional exponent in the dependence of the propagation velocity on the ultrasound wavelength. A wave equation in fractional derivatives is proposed to describe the propagation of ultrasonic waves in a dispersed medium. Pis’ma Zh. Tekh. Fiz. 25, 14–18 (June 12, 1999)     

Pair production in counterpropagating electron and laser beams

An analysis is made of the collision between a high-energy electron beam and laser radiation. It is shown that when the electron energy is 800 GeV and the laser pulse has an intensity of 10²⁰ W/cm², a wavelength of 248 nm, and a duration of 300 fs, a single seed electron produces 60 electrons and positrons. Pis’ma Zh. Tekh. Fiz. 23, 72–75 (July 26, 1997)     

Influence of the stark effect on the resonance excitation transfer between quantum dots

The resonance energy transfer between exciton states in a system comprised of two semiconductor quantum dots is studied theoretically. A model Hamiltonian is constructed to describe the influence of the laser pulse, Coulomb interaction, the static Stark effect, and the relaxation of exciton states on the dynamics of the system. Specific calculations of the efficiency of energy transfer under different excitation conditions and different positions of energy levels are exemplified. It is shown that the transfer process can be controlled by shifting the levels in a constant electric field.     

Prospects for Using Nuclear Power Systems in Commercial Ships in Northern Russia

The experience gained over many years of operating nuclear-powered ice breakers in conquering the northern sea route is described. The conditions which must be met for year-round navigation of cargo ships in the Arctic are presented. For such navigation to be realistic, it must be profitable and Russian national interests in the region must be protected in accordance with the Maritime Policy of the Russian Federation for the period up to 2020. Information is also given concerning the technical status of operating nuclear-powered ice breakers and the characteristics of ice breakers and new-generation nuclear power systems.     

Blocking of group automata. II. Mutual interlocking

Groups of automata formed by mutually interlocking connections of permutation automata are considered. Groups of maximal mutually interlocking connections of any permutation automata are found. The notion of simulation of a finite automaton by a semigroup of transactions of another automaton is introduced. An algorithm for construction of the model of finite permutation automaton using mutually interlocking connections of permutation triggers is given.     

Condensation of a vapor mixture in the absence of noncondensing gases

Experimental data obtained for film and mixed condensation of saturated air vapors (N₂, O₂, Ar) [1] is compared with the results of studies [11–13] of the condensation of pure saturated water vapors.     

Construction of Simple Path Graphs in Transport Networks: I. General Solutions and Examples

Journal of Computer and Systems Sciences International - The calculation of the set of all simple paths connecting two vertices of an undirected graph is considered. The more general problems of...     

Blocking of group automata. I. One-sided interlocking

The concepts of restraining and interlocking connections of the set of automata are introduced. These concepts are used to define the concept of commutation automaton which serves as the mathematical model of switching dynamics in electrical networks regulated by the rules of switching technology. One-sided and mutual automata interlockings are determined. The structure of groups of one-sided interlocking connections of permutation automata is studied.