Determination of the temperature of a moving yarn

Conclusions A mathematical model has been proposed for the process of heat-exchange between yarn and heating chamber which permits one, with reasonable accuracy, to describe the yarn temperature distribution over the length of the heater and beyond its limits. This model affords the possibility of calculating the amount of heat carried off by the yarn from the heating chamber and to estimate heat losses into the environment, and, consequently, to select the most economical heater.By connecting up the dynamics of yarn heating with yarn properties, the mathematical model developed permits one to calculate the optimum temperature profile in a heating chamber. Using this model, one can transfer the optimum conditions for heat-stretching yarns to other temperature-time levels.Translated from Khimicheskie Volokna, No. 2, pp. 54–56, March–April, 1989.     

Wannier-Mott excitons in semiconductors with a superlattice

The effect of the motion of a Wannier-Mott exciton in semiconductors with a superlattice formed by heterojunctions on the exciton binding energy and wave function is analyzed. This effect arises as a result of the fact that the dispersion laws of the electron and hole that form an exciton in a superlattice differ from the quadratic law. The investigated one-dimensional superlattice consists of alternating semiconductor layers with different energy positions of the conduction and valence bands, i.e., with one-dimensional wells and barriers. The exciton state in a superlattice consisting of quantum dots is analyzed. It is demonstrated that the closer the electron and hole effective masses, the greater the dependence of the binding energy on the exciton quasi-momentum. The possibility of replacing the tunneling excitation transfer between superlattice cells with the dipole-dipole one at certain exciton quasi-wave vector values is investigated.

     

Holes localized in nanostructures in an external magnetic field: g-factor and mixing of states

Semiconductors - The energy spectrum and wave functions of holes in the valence band in semiconductor nanosystems, including quantum wells, quantum wires, and quantum dots, in an external magnetic...     

Exciton dephasing and absorption line shape in semiconductor quantum dots

The homogeneous broadening of exciton absorption spectral lines in semiconductor quantum dots (QDs) in the strong confinement regime is studied theoretically. It is shown that the term linear in nuclear displacements in the difference of the phonon Hamiltonians of the ground and optically excited states does not lead to the zero-phonon line (ZPL) broadening. The ZPL width is contributed by the term quadratic in nuclear displacements associated with short-living optical phonons. This contribution is estimated for CdSe nanocrystals (NCs) and found to be much less than the linewidth observed in recent experiments. We conclude that the experimentally observed linewidth is due to the longitudinal lifetime associated with the exciton relaxation to the dark state. The shape of spectral wings originating from the exciton interaction with long-living acoustic phonons is studied at various temperatures for a CdSe NC embedded in a glass matrix.     

Some algorithms for treatment of information in automatic control systems for technological processes

Conclusions Questions in the selection of optimum algorithms for filtration, extrapolation, and interpolation in an ACS TP have been examined.Procedures have been proposed for estimating optimum values for the sampling period and filter parameters from measured signal values.Results of this work have been introduced into the ACS TP for viscose tire cord manufacture at the Svetlogorodsk Khimvolokno PO.Translated from Khimicheskie Volokna, No. 1, pp. 24–27, January–February, 1987.     

Heat transfer in a plasmochemical reactor

An empirical method is proposed for calculating heat transfer in the channel in a plasmochemical reactor when the reagents are input via a system of holes in the wall.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 1, pp. 71–74, January, 1989.     

The binding energy of excitons and <Emphasis Type="Italic">X</Emphasis><Superscript>+</Superscript> and <Emphasis Type="Italic">X</Emphasis><Superscript>−</Superscript> trions in one-dimensional systems

The exciton and trion states in semiconductor quantum wires are treated by the variational method. Simple trial functions provide an adequate precision of the calculation over a wide region of wire radii, with an arbitrary relation between the effective masses of charge carriers. The precision of the results obtained by the variational method is checked by numerical diagonalization of the Hamiltonian of excitons and positively and negatively charged trions. The asymptotic behavior of the binding energies of excitons and trions in narrow quantum wires is established in the analytical form. The structure of the excited X ⁺ trion states is analyzed in the context of the adiabatic approximation.     

Kinetics of heat and mass transfer between a sprayed solution and a hot gas flow

A two-zone mathematical model is given for the process of moisture evaporation from a sprayed solution and crystallization of the salt. The computer calculations are compared with the results of experimental work.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 5, pp. 797–804, May, 1984.