Strength and fracture behaviour of diffusion bonded joints in Al-Li (8090) alloy

Peel strengths at room temperature and under superplastic forming conditions at 530 °C were measured for diffusion-bonded joints in Al-Li 8090 alloy sheet. The bonds were made in the solid state, or via a transient liquid phase using interlayers. The effect of strain rate, sheet thickness and heat treatment were investigated. The significance of these results for the testing of DB joints and for their use in DB/SPF structures is discussed.     

Determination of the power density of pulsed focussed laser radiation

Translated from Izmeritel'naya Tekhnika, No. 3, pp. 33–34, March, 1992.     

Computation of laminar flow in mixed turbulent convection and its influence on heat transfer

Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 3, pp. 366–372, March, 1992.     

Finite data performance analysis of MVDR beamformer with andwithout spatial smoothing

The finite-data performance of a minimum-variance distortionless response (MVDR) beamformer is analyzed with and without spatial smoothing, using first-order perturbation theory. In particular, expressions are developed for the mean values of the power gain in any direction of interest, the output power, and the norm of the weight-error vector, as a function of the number of snapshots and the number of smoothing steps. It is shown that, in general, the smoothing, in addition to decorrelating the sources, can alleviate the effects of finite-data perturbations. The above expressions are reduced to the case in which no spatial smoothing is used. These expressions are valid for an arbitrary array and for arbitrarily correlated signals. For this case, an expression for the variance of the power gain is also developed. For a single interference case it is shown explicitly how the SNR, spacing of the interference from the desired signal and the correlation between them influence the beamformer performance. Simulations verify the usefulness of the theoretical expressions     

Distinctive aspects of the physics and thermal physics of the igrit reactor

Translated from Atomnaya Énergiya, Vol. 73, No. 5, pp. 350–354, November, 1992.     

Evolution of the capillary network in a reactive powder concrete during hydration process

Ultrasonic waves in echographic mode, combined with autogenous shrinkage measurements, were used to study the evolution of the capillary network of reactive powder concrete (RPC) from the time after the mixing. Two characteristic porous classes have been identified: the first, between 10 and 20 nm, begins when the material reaches its solid hyperstatic state, and the second about 1 or 2 nm. The first class is associated with the porous space between the C-S-H hydrate clusters and the second with the internal porosity of the hydrate. The evolution of the active capillary radius as a function of the degree of hydration allows us to understand the strong interaction between the capillary network size and the chemical activity given by the dissipated calorimetric power curve. Indeed, the maximum point of the chemical activity marks the transition of the first class of pores to the second one. Finally, measurements of electrical conductivity through RPC samples show that after the maximum of the dissipated power, the curve of this electrical conductivity presents the same evolution as the capillary radius. As the electrical conductivity clearly depends on the evolution of the capillary network, the similarity between the results confirms our analysis in pore classes.     

Phase Transformations in Martensitic Steels Tested for High-Temperature Fatigue

The method of layer-by-layer physicochemical analysis is used to study phase transformations in chromium-nickel steels of martensitic class after high-cycle fatigue tests and after thermal exposure at similar temperature and time conditions. The Laves phase is shown to be distributed nonuniformly over the cross section of specimens tested for fatigue resistance. The results of the tests are used to correct phase compositions.     

Influence of the intensity of gg irradiation on the photoluminescence of GaAs:Te

The influence of gg irradiation (⁶⁰Co) of various intensities (P _γ≈1.7−7.5kGR/h) on the photoluminescence of GaAs:Te single crystals [n ₀=(1.2–2.3×10¹⁸ cm⁻³] is investigated. Together with the known photoluminescence impurity bands (hν _max≈1.2 eV and/or hν _max≈1.35 eV) and edge band (hν _max≈1.51 eV), new bands are also observed in the spectra at hν _max≈1.3 eV and hν _max≈1.48 eV. The observed effects are attributed to radiation-stimulated ordering of the donor impurity and deep impurity centers. Fiz. Tekh. Poluprovodn. 32, 38–39 (January 1998)     

On the Yustova threshold plates

A response to criticism of threshold plates for the study of color vision developed at the Mendeleev All-Russia Research Institute of Metrology and published in 1994 is presented. The critics base their conclusions on colorimetric testing and the examination of the plates. In response to the article by M. V. Danilova and J. D. Mollon [4]. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 37–39, January, 2007.