Waveguide probe structures for a multilayer magnetodielectric: An inverse problem

Direct and inverse problems are considered for diffraction by an open end of a rectangular waveguide (RW) with a flange that adjoins a piecewise inhomogeneous planar layered lossy medium. Also considered are similar diffraction problems for a junction of an RW and a rectangular resonator filled with a multilayer medium and a junction of two RWs, one of which contains a multilayer plate. Such open and shielded waveguide probe structures (WPSs) are used for determination and nondestructive testing of parameters of multilayer samples. The direct problem is formulated on the basis of admittance and impedance algorithms with consideration for losses existing in the medium, flange, and screens. In this case, the approximation of the given aperture field allows obtainment of explicit solutions for open and shielded WPSs in the form of integrals. Solution of the inverse problem that lies in determining thicknesses, permittivities, and permeabilities of the layers from measured values of the magnitude of the reflection coefficient is obtained by minimizing the corresponding least-squares error and by constructing artificial neural networks. In order to increase the accuracy, it is proposed to use a two-port of errors and perform measurements for several positions of the sample with respect to the flange and different impedance conditions behind the sample.     

Magnet Safety Assessment for ITER

The ITER magnet system consists of structurally linked sets of toroidal (TF) and poloidal (PF) field coils, central solenoid (CS), and various support structures. The coils are superconducting, force flow Helium cooled with a Kapton-Glass-Epoxy multilayer insulation system. The stored magnetic energy is about 100GJ in the TF system and 20GJ in the PF-CS. Coils and structure are maintained at 4 K by enclosing them in a vacuum cryostat. The cryostat, comprising an outer envelope to the magnets, forms most of the second radioactivity confinement barrier. The inner primary barrier is formed by the vacuum vessel, its ports and their extensions. To keep the machine size within acceptable bounds, it is essential that the magnets are in close proximity to both of the nuclear confinement barriers. The objective of the magnet design is that, although local damage to one of the barriers may occur in very exceptional circumstances, large scale magnet structural or thermal failure leading to simultaneous breaching of both barriers is not credible. Magnet accidents fall into three categories: thermal (which includes arcing arising from insulation failure and local overheating due to discharge failure in the event of a superconductor quench), structural (which includes component mechanical failure arising from material inadequacies, design errors and exceptional force patterns arising from coil shorts or control failures), and fluid (Helium release due to cooling line failure). After a preliminary survey to select initial faults conceivable within the present design, these faults are systematically analyzed to provide an assessment of the damage potential. The results of this damage assessment together with an assessment of the reliability of the monitoring and protective systems, shows that the magnets can operate with the required safety condition.     

The spatial scales of heterogeneities in the direct-current discharge stream

The results of a calculational-experimental investigation of spatial scale heterogeneities in a gas stream with direct-current discharge are presented. The numerical modeling was made within the framework of the Navier-Stokes equations with a distributed source of input energy density in a gas. The experimental study was conducted by the Talbot-interferometry method. The Shtrel number was used as the criterion of the optical homogeneity of the stream.St. Petersburg Institute of Mechanics. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 6, pp. 820–824, June, 1992.     

Use of special-purpose bulk activity measures in monitoring raw materials and environmental objects

Mendeleev All-Union Metrology Research Institute. Translated from Atomnaya Énergiya, Vol. 73, No. 5, pp. 393–397, November 1992.     

Essential shortcomings of Tafel equations in describing electrochemical dissolution kinetics of a solid electrode

A simplified topokinetic dissolution model of a solid taking into account the correlation between the dissolution rate and the atomic surface topography enables one to interpret a linear (in semilogarithmic coordinates) segment of the steady-state curves of the active anodic dissolution of metals. Its slope corresponds to the product of a concentration of kinks and the elementary reaction rate, both of which exponentially depend on the potential, rather than a simple (Tafel) elementary rate of the atom dissolution at a semi-crystal kink. Original Russian Text ? Yu.V. Alekseev, G.Yu. Alekseev, V.A. Bityurin, A.V. Plaskeev, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 6, pp. 568–573.     

Testing procedure and results of tests performed on a VVÉR-1000 fuel assembly fragment in a MIR channel for a maximum anticipated accident

The testing procedure and the results of tests performed on a 19-element fragment of a VVéR-1000 fuel assembly in the channel of a MIR reactor under conditions of the second and third stage of a maximum anticipated accident are presented. The state arising in the reactor core with an uncompensated leak arising in the first cooling loop when a pipeline with the maximum diameter bursts (large leak) is studied in the experiment. In each case study, superheated steam cools the top part of the fuel elements. The main goal of the tests is to obtain data on the distortion of fuel-element cladding under tensile stresses. __________ Translated from Atomnaya énergiya, Vol. 103, No. 5, pp. 286–291, November, 2007.