The fundamentals of the theory of spatiotemporal signal processing as applied to problems of ultrasonic flaw detection of articles from complexly structured materials

The basic propositions of spatiotemporal signal processing as applied to the problems of ultrasonic testing of complex-structure articles with a high attenuation of acoustic signals are considered. Different algorithms of extracting informational echo signals from white and structural noise during multichannel spatiotemporal signal processing are studied.     

The effect of vibrations of the base of a tunnel microscope on the deviation of the program motion of a probe

The resolution of a tunnel microscope is determined by the precision of operation of its control system and the possibility of using deterministic models of the interaction between the needle and substrate and the operation of the control system in the interpretation of results. Random vibrations of the microscope base cause perturbations in the needle motion and reduce the capabilities of measurement interpretation. In the considered paper, an estimate of the dependence of the amplitude of needle vibrations on the amplitude of base vibrations for certain models of microscopes is given. It is shown that, together with translational vibrations of the measurement unit, whose contribution to measurement errors is small, vibrations connected with swinging the measurement unit on an elastic suspension are communicated to the needle. For the considered devices, these vibrations are significant under a resolution of about 1 nm, which makes it necessary to take into account nondeterministic errors in interpretation of the results of scanning with nanometer resolution.     

Modifiing Effect of Zirconia Nanoparticles during Electric Arc Welding

The structure of the weld metal after welding using a flux-cored wire with the addition of 0.3% zirconia flaky nanoparticles is studied. The weld consists of an acicular ferrite. This finding can indicate that the dissociation of zirconia in an electric arc is not an obstacle to a modifying effect, which manifests itself in both the interaction of zirconium with oxygen and the surface activity of zirconium in an iron-based solidifying melt. Thus, zirconia is a modifier of both the first and second kinds for the solidifying weld metal. Excess oxygen is likely to form individual pores less than 1 μm in diameter in the weld metal; however, they only wealy affect the mechanical properties of the welded joint. These results will be used to develop electrode materials for welding pipe steels.     

Main results of the first phase of the upgrade of the SM core

The first phase of the work on checking the main assumptions of the concept for upgrading the core of the SM reactor has been completed. A full-scale reactor experiment has been performed for the purpose of creating in the reactor the conditions necessary for accelerated high-dose irradiation of materials, meeting the requirements for the fast-neutron flux density, water temperature, pressure, and composition, and making it possible to install large-diameter experimental channels and apparatus for regulating the temperature and neutron spectrum. The decrease of the fuel volume and excess reactivity are compensated by a 20% increase of the uranium content in a fuel element and by replacing the corrosion-resistant steel fuel-assembly jackets with zirconium-alloy jackets. The results of the calculations and experiments performed during the first phase have shown that the objective has been achieved-the reactor can be operated efficiently with the new arrangement of the core. The objective and problems of the second phase are formulated: increase of the neutron flux density in the experimental channels by a factor of 1.5 by increasing the power density in the core, using a fuel element with a low harmful absorption of neutrons, and equalizing the power-release distribution by using a consumable absorber. __________ Translated from Atomnaya énergiya, Vol. 102, No. 2, pp. 86–92, February, 2007.