On Variational and PDE‐Based Distance Function Approximations

In this paper, we deal with the problem of computing the distance to a surface (a curve in two dimensional) and consider several distance function approximation methods which are based on solving partial differential equations (PDEs) and finding solutions to variational problems. In particular, we deal with distance function estimation methods related to the Poisson‐like equations and generalized double‐layer potentials. Our numerical experiments are backed by novel theoretical results and demonstrate efficiency of the considered PDE‐based distance function approximations.     

Optical and electrical properties of thin carbide-containing films on silicon

The optical and electrical properties of thin carbide-containing films grown using a new promising method on silicon wafers have been experimentally studied. The results of electron diffraction measurements, the current-voltage characteristics measured in the dark and under illumination, the photo emf as a function of the excitation level, and the photoresponse spectrum are presented. The proposed thin-film system is a promising material for optoelectronics.     

A correction method for dynamic model calculations using observational data and its application in oceanography

A new data assimilation method for the correction of model calculations is developed and applied. The method is based on the least resistance principle and uses the theory of diffusion-type stochastic processes and stochastic differential equations. Application of the method requires solving a system of linear equations that is derived from this principle. The system can be considered as a generalization of the well-known Kalman scheme taking the model’s dynamics into account. The method is applied to the numerical experiments with the HYbrid Coordinate Ocean Model (HYCOM) and Archiving, Validating, and Interpolating Satellite Ocean (AVISO) data for the Atlantic. The skill of the method is assessed using the results of the experiments. The model’s output is compared with the twin experiments, namely, the model calculations without assimilation, which confirms the consistency and robustness of the proposed method.     

Diagnostic investigation of the damaged reactor at Chernobyl

Conclusion The lessons of the accident at Chernobyl' should be used to the maximum extent in a critical scrutiny both of plans for the development of nuclear energy and of the guarantees of its safety. In this matter, the work performed on the "Cover" structure should play a major role, permitting one to more precisely limit the development of a severe accident, to control the behavior of the fuel, and to guide the building of structures in extreme situations. Experience accumulates the creation of control and diagnostics systems, warnings, the acceptance of solutions for projected accidents, and develops a data bank.In conclusion, the authors offer thanks to all the participants in the diagnosis work on the "Cover" structure.Translated from Atomnaya Énergiya, Vol. 68, No. 5, pp. 355–359, May, 1990.     

Some specific features of wire-bridge blowout in various media

We have shown that the chemical redox properties of an ambient medium in which there is a wire bridge from a high-ohmic alloy can exert, under some conditions, a strong effect on bridge heating by the electric current at a stage close to its fracture (blowout), thus promoting or hindering the occurrence of an additional stage of heating of the already melted bridge. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 1, pp. 111–116, January–February, 1998.     

Effects of a Metal–Insulator–Metal Contact on the Antenna in a Radar Monitoring System

Theoretical and experimental studies have been performed on the scattering by a horn antenna containing a metal–insulator–metal contact having a nonlinear voltage–current characteristic, which lies at the flange joint between the waveguide components. The effects of the contact are examined as regards the performance of the radar antenna system.     

EFFECTIVE DIFFUSION COEFFICIENT OF ACTIVE SOLVENTS IN COMPOSITE POLYMERIC MATERIALS

A method and a device for determination of the effective diffusion coefficient of active solvents in composite polymeric materials (CPM) based on cellulose derivatives are proposed and examined. This method accounts for anomalous mass transfer phenomena, considerable shrinkage and changes of sorption capacity of the CPM specimen allowing selection of the rational technological regime. Results of experimental studies on diffusion of acetone and ethanol in cellulose nitrate with various degrees of substitution are given as examples.