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.     

Stability of imperfect conical shells with helical reinforcement

The article explains a method of numerical calculation of the stability of imperfect conical shells with helical reinforcement under uniform external pressure. It also investigates the effect of the amplitude of local initial imperfections on the critical loads.Translated from Problemy Prochnosti, No. 12, pp. 67–69, December, 1991.     

Stability of Circular Cylindrical Shells with a Single Local Dent

The theoretical-and-experimental investigation has been performed on the stability of smooth cylindrical shells of steel with a single local dent. All the shells manufactured using the same process were tested with the fulfillment of identical conditions for observations and measurements. Theoretical calculations were carried out by the mesh method with the use of the nonlinear theory of shells. A comparison of the experimental and theoretical values of the critical loads has been made. The theoretical-and-experimental approach proposed enables one to evaluate the quality of shells by studying local dents and other specific imperfections.     

Electrophysical Characteristics of a Posistor Block

The influence of the parameters of posistor elements and the conditions of their heat exchange on the electrical and dynamic characteristics of a posistor block have been investigated. Good agreement between calculation results and experimental data has been established.     

Terahertz radiation generation in multilayer quantum-cascade heterostructures

I–V and radiative characteristics of multilayer quantum-cascade GaAs/AlGaAs heterostructures with a double metal waveguide are investigated. The I–V characteristics typical of the quantum-cascade lasers are seen. The observed threshold-intensity growth and narrow radiation spectrum are characteristic of laser generation. The measured radiation frequency was found to be about 3 THz, which coincides with the calculated value. Thus, fully domestic terahertz quantum-cascade lasers are demonstrated for the first time.     

A digital colorimetric analyzer for chemical measurements on the basis of polymeric optodes

A digital colorimetric analytical instrument is described that allows one to determine the concentrations of substances in solutions using transparent polymeric optodes, which are able to change their color depending on a reagent and the determined-substance content. The structural and functional diagrams of the instrument that operates under the control of a LabVIEW-based program are presented. The instrumental error of the analyzer is within 1%. The instrument operation was demonstrated by the example of determining the cobalt content in drinking water, which was taken from an outdoor water pump. The metrological characteristics of the instrument are not worse than those implemented with the standard solid-phase spectrophotometry method. The instrument can be used in the industrial, environmental, clinical, and other kinds of monitoring, where the rapid determination of the concentrations of various substances is required.     

Investigation of Stimulated Emission from HgTe/CdHgTe Quantum-Well Heterostructures in the 3–5 μm Atmospheric Transparency Window

Semiconductors - Stimulated emission based on interband transitions depending on the pumping wavelength is studied for heterostructures with Hg(Cd)Te/CdHgTe quantum wells in the wavelength region...     

Electrical erosion of W(Mo)-Cu composition in electrospark machining a hard alloy in a carbon-bearing liquid. II. Concentration dependence of wear and removal rate

Conclusions The concentration dependences of relative wear and productivity of the tungsten-copper and molybdenum-pseudoalloys in electrospark machining VK20 hard alloy were constructed. These dependences are characterized by the extreme values and are explained by the mechanism of their erosion (described in report 1) in the carbon-bearing liquid with an allowance made for the formation of a mixture of refractory metal and its carbide on the working surface.Translated from Poroshkovaya Metallurgiya, No. 2(302), pp. 78–81, February, 1988.