Dynamic failure of dry and fully saturated limestone samples based on incubation time concept

This paper outlines the results of experimental study of the dynamic rock failure based on the comparison of dry and saturated limestone samples obtained during the dynamic compression and split tests. The tests were performed using the Kolsky method and its modifications for dynamic splitting. The mechanical data (e.g. strength, time and energy characteristics) of this material at high strain rates are obtained. It is shown that these characteristics are sensitive to the strain rate. A unified interpretation of these rate effects, based on the structural–temporal approach, is hereby presented. It is demonstrated that the temporal dependence of the dynamic compressive and split tensile strengths of dry and saturated limestone samples can be predicted by the incubation time criterion. Previously discovered possibilities to optimize (minimize) the energy input for the failure process is discussed in connection with industrial rock failure processes. It is shown that the optimal energy input value associated with critical load, which is required to initialize failure in the rock media, strongly depends on the incubation time and the impact duration. The optimal load shapes, which minimize the momentum for a single failure impact, are demonstrated. Through this investigation, a possible approach to reduce the specific energy required for rock cutting by means of high-frequency vibrations is also discussed.     

Layers obtained on aluminum by nanopowder deposition and subsequent electron beam scanning

The scanning circular rotating motion of the electron beam is used for embedding unclad TiCN nanoparticles in the aluminum matrix. The most appropriate treatment conditions for obtaining layers with significant thickness and high microhardness are reported. Layers with thickness 14–33?µm and microhardness 562–798?kg/mm², which is 16–22 times higher than the substrate microhardness, are obtained. Possible strengthening mechanisms of the layers are discussed. The layers, chemical, and phase compositions are investigated by EDX detector of SEM and XRD. The complex investigation is completed with TEM analysis. Incorporated TiCN nanoparticles are observed in the aluminum matrix. Layers with such characteristics could be convenient for details to which high surface hardness and light, soft, and plastic base metal are required.     

Self-administration of ethanol and saccharin in newborn rats: Effects on suckling plasticity.

Responsiveness to a surrogate nipple providing water, saccharin, 5% ethanol, or 10% ethanol was tested in newborn rats naive to suckling (3–5 hr old) on Postnatal Day (P) 0 and in older neonates with regular suckling experience on P1 or P2. At all ages, pups demonstrated greater nipple attachment for saccharin or 5% ethanol than for water. Intake of saccharin and 5% ethanol was high in newborns, far exceeding that of water. At P1 and P2, pups exhibited a preference for saccharin, but not for 5% ethanol. Preexposure to a nipple providing ethanol or saccharin (but not a nipple alone or fluids alone) increased subsequent responsiveness toward an empty surrogate nipple (no fluid), both 1 hr and 24 hr after preexposure. Although, during preexposure, pups responded most positively to the nipple providing saccharin, the longest time spent on an empty nipple was observed in pups preexposed to 10% ethanol. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incorporation of InAs nanostructures in a silicon matrix: growth, structure and optical properties

MBE growth and properties of InAs nanoscale islands formed on silicon are reported. Islands capped with Si emit a photoluminescence band in the 1.3 μm region. Upon annealing at increased substrate temperature, extensive interdiffusion leads to the formation of an InAs solid solution in the Si cap layer. Additionally, InAs-enriched regions with extensions of 6 nm, exhibiting two kinds of ordering, are observed. The ordering of InAs molecules occurs, respectively, in (101) and planes inclined to (110) and planes parallel to the [001] growth direction.     

Experimental determination of parameters of laser-generated lamb waves

The process of laser generation of Lamb wave pulses in a ferromagnet by the evaporation mechanism has been studied experimentally. The results can be recommended for developing methods and tools for testing thin-wall metal items.     

Mathematical model of plasma heating for quenching

A mathematical model that makes it possible to determine the main laws of surface heating of a large steel part by a high-enthalpy plasma jet with the aim of optimizing the technology of surface plasma hardening of wheel pairs of rolling stock is suggested. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 29–31, May, 1999.     

Mass-spectrometric study of the electron-beam-stimulated conversion of sulfur dioxide

The dynamics of electron-beam-stimulated conversion of sulfur dioxide into ammonium sulfate has been studied using a highly sensitive, fast-response time-of-flight mass spectrometer of the reflectron type. The conversion of various gas mixtures containing SO₂, CO₂, O₂, N₂, and Ar in the presence of an ammonia and water vapor was carried out in a reactor with a volume of 0.04 m³. Optimum conditions for the electron-beam-stimulated conversion of SO₂ are determined. The reaction product ((NH₄)₂SO₄) is a valuable nitrogenous fertilizer.     

A model of coupled resonators for calculating the electromagnetic wave diffraction on planar one-dimensional Bragg gratings

The problem of excitation of a one-dimensional planar Bragg grating is studied. A model of coupled resonators is proposed for investigating the diffraction of electromagnetic waves on a waveguide surface with arbitrary corrugation profile. The model is based on the strict relationships derived from a solution to a two-dimensional boundary problem for the Helmholtz equation. A particular form of equations is presented for the case of a rectangular corrugation of plates in the grating.