Role of involutive criteria in computing Boolean Gröbner bases

In this paper, effectiveness of using four criteria in an involutive algorithm based on the Pommaret division for construction of Boolean Gröbner bases is studied. One of the results of this study is the observation that the role of the criteria in computations in Boolean rings is much less than that in computations in an ordinary ring of polynomials over the field of integers. Another conclusion of this study is that the efficiency of the second and/or third criteria is higher than that of the two others.     

A Destruction Model for an Anisogrid Composite Structure

Finite element modeling of the deformation and fracture processes in a composite anisogrid (network) structure made of carbon fiber reinforced plastic (CFRP) with different types of deformation has been performed. The anisogrid structure is based on a longitudinal set of ribs supported by diagonal sets of ribs directed at angles of about ±45° with respect to the longitudinal ribs. Based on the model of mechanical property degradation for composite material layers strength analysis of the structure has been performed taking into account the process of damage accumulation in the course of loading. The maximum destructive load is determined and the fracture pattern is obtained for each type of deformation. The determining impact of the rib-crossing zones of different directions as the foci of progressive destruction of the entire anisogrid structure is established.     

Precise measurements of holes with diameters of 0.05 to 200 mm

Conclusions Engineering enterprises which require precision measurements of holes in mass production can be guided by the following arrangement for transferring dimensions from the initial measures to the product. Reference rings made with the maximum possible precision should be certified on the BV-2007 instrument. Horizontal interferometers in conjunction with these rings should be used for certifying adjusting rings used in setting pneumatic measuring machines to size for testing holes in components. The adjusting rings for setting inside gauges are certified on horizontal optimeters. If it is necessary to raise the precision of certification, the optimeters should be set by means of reference rings certified on the horizontal interferometer. Rings intended for testing high-precision inside gauges should be certified on the horizontal interferometer by means of block gauges.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 81–84, January, 1970.     

Determination of the elastic properties of a barrier film on aluminium by Brillouin spectroscopy

The surface wave dispersion for a barrier oxide film on aluminium has been determined from surface Brillouin scattering measurements carried out on films of thicknesses of 0.2, 0.35 and 0.45 μm. The measured velocities of the generalised Rayleigh mode, the pseudo interfacial mode and of several Lamb modes conform to simulations performed for stiffening layers [1]. The longitudinal velocity and the shear velocity of the layer have been calculated from the experimental dispersion curve.     

Mechanical properties of single cells by high-frequency time-resolved acoustic microscopy

In this paper, we describe a new, high-frequency, time-resolved scanning acoustic microscope developed for studying dynamical processes in biological cells. The new acoustic microscope operates in a time-resolved mode. The center frequency is 0.86 GHz, and the pulse duration is 5 ns. With such a short pulse, layers thicker than 3 microm can be resolved. For a cell thicker than 3 microm, the front echo and the echo from the substrate can be distinguished in the signal. Positions of the first and second pulses are used to determine the local impedance of the cell modeled as a thin liquid layer that has spatial variations in its elastic properties. The low signal-to-noise ratio in the acoustical images is increased for image generation by averaging the detected radio frequency signal over 10 measurements at each scanning point. In conducting quantitative measurements of the acoustic parameters of cells, the signal can be averaged over 2000 measurements. This approach enables us to measure acoustical properties of a single HeLa cell in vivo and to derive elastic parameters of subcellular structures. The value of the sound velocity inside the cell (1534.5 +/- 33.6 m/s) appears to be only slightly higher than that of the cell medium (1501 m/s).     

The Effect of Boron on the Structure and Conductivity of Thin Films Obtained by Laser Ablation of Diamond with Deposition at 700°C

Structural features of CB_x films obtained by pulsed laser ablation of targets made of pressed diamond powder with boron-powder additions at B/C atomic ratio of x = 0.33 have been studied. The films were deposited on heated substrates, so that diffusion processes involving C and B atoms on the surface and in the volume of films were possible. Selected conditions of film deposition ensured their effective doping with boron (0.4 ≤ x ≤ 0.6). The incorporation of B atoms was accompanied by the formation of B–C chemical bonds, whereas the formation of sp² graphite bonds and their ordering in clusters with laminar packing was suppressed. The films possessed very low resistivity (~1.4 mΩ cm) at room temperature and exhibited metallic type of conductance on decreasing the temperature to 77 K.     

Acoustic microscopy of portland cement mortar aggregate/paste interfaces

We have demonstrated the use of acoustic microscopy tocharacterize hydrated Portland cement microstructure. Highfrequency (1 GHz) studies identified reaction zones aroundbubbles, ettringite formation, and effects of aggregatecomposition. Lower frequency images (200–400 MHz) have been used to characterize effects of aggregate composition oncement/grain interface. The information obtained fromacoustic microscopy complements optical and scanningelectron microscopy. We demonstrate the importance ofacoustic microscopy as an important nondestructive in situtechnique for characterization of concrete. A major, uniqueadvantage of the scanning acoustic microscope technique isits capability of penetrating into the material, whichallows us to study cracks, defects and other zones ofweakness that might be hidden below the surface.