Influence of ash deposits on the heat resistance of materials for gas turbine engine blades

Leningrad. Translated from Problemy Prochnosti, No. 1, pp. 71–76, January, 1989.     

Criteria for evaluation of the hardening factor of machine parts

V. Ya. Chubar' Zaporozhe Machine Building Institute. Translated from Problemy Prochnosti, No. 3, pp. 62–65, March, 1989.     

Optical properties of graphite-like carbon films

A model of the electronic structure of graphite-like carbon films, describing the semiconductor properties of this material, is presented. Spectra of optical constants of microcrystalline carbon films in the region λ = 0.4–8.0 μm were studied by the spectral ellipsometry and IR reflection methods. A number of distinctive features of the spectra, associated with both the appearance of C---C- and C---H_n-type bonds and direct energy gaps, were found. Analysis of the optical data using the proposed model makes possible a common interpretation of our results and literature data. Values of a parameter Θ, which is an averaged qualitative parameter of structural distortions within carbon microcrystallites as compared with crystalline graphite, are determined from comparison of theoretical results and experimental data.     

Electrical conductivity of ferroelectric sodium vanadate,rubidium vanadate,cesium vanadate and their solid solutions

The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO₃, RbVO₃ and CsVO₃, increase in d.c. conductivity is observed in the ferroelectric region while nonlinearities are observed above transition temperatures. In solid solutions, the activation energy in the paraelectric state is higher than that in the ferroelectric state and depends upon sodium concentration.     

Strength of small-scale spherical shells formed from pressed glass elements

Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Sumy Branch, Khar'kov Polytechnic Institute. Translated from Problemy Prochnosti, No. 8, pp. 102–104, August, 1989.     

Ultra-strong, well-apodised Bragg gratings in chalcogenide rib waveguides

The first ultra-strong, near-perfect, raised-apodised Bragg gratings in As/sub 2/S/sub 3/ chalcogenide rib waveguides using /spl lambda/=532 nm light and a modified Sagnac holographic writing setup are demonstrated. Good agreement is achieved between the experimental results and the numerical modelling of the gratings using the transfer matrix analysis for thin film structures.     

Effect of orienting fields on agglomeration in dilute dispersions of magnetic fine particles

Static light scattering was used to investigate dilute dispersions of fine gamma -Fe/sub 2/O/sub 3/ magnetic particles. The particles were acicular and on average 0.39 mu m long and 0.056 mu m in diameter. They were dispersed in organic solvents at concentrations of approximately 10/sup -4/ vol%, corresponding to an average interparticle separation of 9 mu m. Computer programs using a coupled dipole algorithm to predict the scattering from the particles were written. Experimental results do not agree with computer calculations of the light scattering from single particles, but are consistent with scattering from thick ropelike agglomerates of particles. The size of these agglomerates was estimated after 10 s to be less than 100 particles, while the thickness of the ropes is at least 5 particles.<>     

Shear strength of lead,tin, copper,aluminum., corundum,and fluoroplastic-4 behind a shock wave

On the basis of the results of measurements in the pressure range 3.5–11 GPa for the shear strength of a number of shock-compressed substances carried out taking account of the completion of relaxation processes and establishment of pressure equilibrium the divergence is explained in results published previously for measurements of the dynamic yield point for highly ductile metals of the lead and tin type.Translated from Problemy Prochnosti, No. 10, pp. 50–54, October, 1991.     

Calculation of stress concentration in the manipulator element using a combined finite and boundary element method

Elastic stress concentration in a manipulator element is calculated within the framework of the two-dimensional stressed state model. The purpose here is to make recommendations for selecting the radius of joining of the beam parts of the element based on analysis of maximum stresses in the stress concentration zone. Combination of the finite element and boundary element methods is proposed for solving the problem. A coarse finite element subdivision is used for the initial calculation for the entire element. Then, the solution is refined by using boundary elements in the identified zone. Comparison of calculation results with solutions obtained by the finite element and boundary element methods points to the effectiveness of the proposed algorithm for stress concentration calculations.Translated from Problemy Prochnosti, No. 6, pp. 72–74, June, 1991.     

ESD–RF co-design methodology for the state of the art RF-CMOS blocks

This paper describes an approach to design ESD protection for integrated low noise amplifier (LNA) circuits used in narrowband transceiver front-ends. The RF constraints on the implementation of ESD protection devices are relaxed by co-designing the RF and the ESD blocks, considering them as one single circuit to optimise. The method is applied for the design of 0.25 μm CMOS LNA. Circuit protection levels higher than 3 kV HBM stress are achieved using conventional highly capacitive ggNMOS snapback devices. The methodology can be extended to other RF-CMOS circuits requiring ESD protection by merging the ESD devices in the functionality of the corresponding matching blocks.