Electrical and thermoelectric properties of <Emphasis Type="Italic">p</Emphasis>-Ag<Subscript>2</Subscript>Te in the β phase

The conductivity σ, Hall coefficient R, and thermoelectric power α₀ of p-Ag₂Te were studied in the temperature range of 300–550 K. Inconsistency between the signs of R and α₀ was observed at 420–550 K. These results are interpreted within the two-phase model with spherical constant energy surfaces. It is established that the inconsistency between the R and α₀ signs is due to the emergence of the scattering mechanisms with the parameters r_0ac, r₀₀, and r_0d an increase of about 50% in the ratio of the effective electron and hole masses as a result of the transition α → β.     

A study of the domain structure of ferrites in the vicinity of the compensation point by Mössbauer spectroscopy

A single-crystal sample of gadolinium ferrite garnet Gd₃Fe₅O₁₂ was studied by Mössbauer spectroscopy near compensation point T _cm (T _cm = 286 K). The relative intensities of absorption lines in ⁵⁷Fe Mössbauer spectra allow it to be concluded that the domain sizes in ferrite grow with the temperature approaching T _cm, with domain structure in the sample disappearing at compensation point T _cm.     

Comment on ‘Persistent inputs and the standard H2-multivariable control problem’ by K. Park and J.J. Bongiorno Jr

It is necessary to welcome the publication of the paper by Park and Bongiorno Jr (Park, K. and Bongiorno Jr, J.J. (2009 Park, K and Bongiorno Jr, JJ. 2009. Persistent Inputs and the Standard H₂-multivariable Control Problem. International Journal of Control, 82: 2002–2012. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), ‘Persistent Inputs and the Standard H₂-multivariable Control Problem’, International Journal of Control, 82, 2002–2012) in which the special cases in H₂-optimisation problems are considered. However, for correct orientation of readers we would like to note some publications which, in our opinion, are connected to a problem given by Park and Bongiorno Jr (2009 Park, K and Bongiorno Jr, JJ. 2009. Persistent Inputs and the Standard H₂-multivariable Control Problem. International Journal of Control, 82: 2002–2012. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]), but are absent there.     

Optimal control of process of pyrolysis of paraffinic hydrocarbons C2-C4 and their mixtures

This paper describes the scheme that has been developed for the optimal control of the process of pyrolysis for different types of hydrocarbon feedstock in the four-flow pyrolysis furnace at the Sumgait Ethylene-Polyethylene plant; the scheme is based on the use of a complex parameter of the process, i.e., the pyrolysis intensity function. The algorithm for this control has been constructed. In the paper, the results of optimal control of the process of propane pyrolysis, ethane pyrolysis, and pyrolysis of ethane together with the butane-butylene fraction are presented in accordance with the scheme being developed using the intensity function that corresponds to each process. Optimal values of the intensity function were found from the results of calculations carried out using the mathematical model of each process. The extended expression for the intensity function has been formulated and, with its use, it is possible to control the process both in the case of the change in the flows of feedstock and steam and the change in the inlet temperature, as well as in the case of the change in the feedstock composition.     

High-voltage solar elements based on polycrystalline silicon

Problems connected with developing designs of high-voltage solar elements (SE) with vertical p- n transitions on the basis of polycrystalline silicon and also the results of analysis of new experimental data are considered. The photoelectric characteristics of SE with unilateral and bilateral illumination are presented. The prospects of using these SE in solar modules with parabolic-spherical and parabolic-cylindrical radiation concentrators are discussed.     

Hyperfine structure of magnetic-resonance electrical conductivity of doped polydiacetylene

Magnetic resonance with a hyperfine structure which can be detected from the electrical conductivity has been observed in iodine-doped polydiacetylene films. This resonance is attributable to transitions between Zeeman levels in the spin-dependent carrier transfer process in a system of localized paramagnetic centers. Pis’ma Zh. Tekh. Fiz. 25, 86–90 (December 12, 1999)