Global Analysis of the Flows of Fluids with Pressure-Dependent Viscosities

 To describe the flows of fluids over a wide range of pressures, it is necessary to take into account the fact that the viscosity of the fluid depends on the pressure. That the viscosity depends on the pressure has been verified by numerous careful experiments. While the existence of solutions local-in-time to the equations governing the flows of such fluids are available for small, special data and rather unrealistic dependence of the viscosity on the pressure, no global existence results are in place. Our interest here is to establish the existence of weak solutions for spatially periodic three-dimensional flows that are global in time, for a large class of physically meaningful viscosity-pressure relationships. (Accepted May 1, 2002) Published online November 15, 2002 Communicated by S. S. ANTMAN     

Grating-lens dispersive delay line

For problems of control and compression of pulses in picoseconds time scale a dispersive delay line based on control of spectral phase of radiation in a device consisting of diffraction grating and lenses is proposed and tested.     

Electronic states in the valence band of a cylindrical ZnSe quantum dot

Electronic states in the valence band of a cylindrical ZnSe quantum dot are studied with allowance for the valence band mixing. Dependences of the wave functions and energy levels on the quantum dot radius are calculated. The influence of a magnetic field parallel to the quantum dot radius on the energy levels is also considered.     

Effect of hydrostatic pressure and temperature on the electronic states in InAs/GaAs cylindrical double quantum dots

The effect of hydrostatic pressure and temperature on the electronic states in vertically coupled InAs/GaAs cylindrical double quantum dots is considered. The problem is solved using the effective mass method and the adiabatic approximation. Dependences of the electron energy on the pressure and temperature are studied for different values of geometric parameters of the structure.     

Effect of interdiffusion of In and Al atoms on excitonic states in In<Subscript>x</Subscript>Ga<Subscript>1−x</Subscript>As/Al<Subscript>y</Subscript>Ga<Subscript>1−y</Subscript>As quantum dots

The effect of interdiffusion of aluminum and indium atoms on the exciton emission energy and binding energy in In_xGa_1?xAs/Al_yGa_1?yAs quantum dots is studied. It is shown that the emission energy increases monotonically with increasing diffusion length, while the binding energy has a maximum.     

Polaronic shift of the Wannier-Mott exciton binding energy in a quantum wire with allowance for the phonon confinement effect

Within the framework of the Li-Low-Pines model the interaction of a Wannier-Mott exciton with polar optical phonons in a cylindrical semiconductor wire is studied, taking into account the phonon confinement effect. An analytical expression for the exciton binding energy with allowance for the polaronic effect is obtained. Numerical calculations of the binding energy are carried out for AlAs/GaAs/AlAs and ZnSe/CdSe/ZnSe wires with a various degree of polarity of quantum wire materials. The polaronic shift of the binding energy of light and heavy hole excitons is calculated.     

Electron–phonon effect on the ground-state binding energy of hydrogenic impurity in quantum-well wire in presence of an electric field

The hydrogenic impurity binding energy in rectangular quantum well wire including both barriers of finite height and an applied electric field are studied. The polaron effects on the ground-state binding energy in electric field are investigated by means of Landau-Pekar variation technique. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied electric field and the position of the impurity. Our calculations are compared with previous results in quantum wires of comparable dimensions.     

Finite Genome Length Corrections for the Mean Fitness and Gene Probabilities in Evolution Models

Using the Hamilton–Jacobi equation approach to study genomes of length L, we obtain 1/L corrections for the steady state population distributions and mean fitness functions for horizontal gene transfer model, as well as for the diploid evolution model with general fitness landscapes. Our numerical solutions confirm the obtained analytic equations. Our method could be applied to the general case of nonlinear Markov models.     

Effect of interdiffusion on band structure and intersubband absorption coefficient of GaAs/GaAlAs double quantum well

The influence of Ga and Al atoms interdiffusion on the band structure and absorption coefficient of coupled double quantum wells are investigated on the basis of a potential composed of four modified Wood–Saxon potentials. Wave functions of the real potential are expressed as a superposition of the stationary state wave functions of the “basal” potential. It is shown that interdiffusion leads to the smearing of the rectangular profile of the potential and to the disappearance of the barrier between the wells, as a result of which, the degradation of doublet character of the electron energetic spectrum is observed. It is also shown that interdiffusion leads to the significant change in oscillator strength and in the enhancement of the thermal stability of the absorption spectrum of the considered heterostructure.     

Effect of In and Al interdiffusion on electron states and light absorption in InxGa1? x As/AlyGa1? y As quantum dots

A new method of theoretical investigation of the interdiffusion effect on electron states in quantum dots is proposed. The main point of the method is the replacement of the “veritable” confining potential formed due to the diffusion by a model potential, for which the Schr?dinger equation solutions and the energy spectrum are known. In the framework of the proposed method we calculate the positions of edges of the conduction and heavy hole bands and the absorption coefficient of interband transitions depending on the diffusion length in spherical In_xGa_1−x As/Al_yGa_1−y As quantum dots, using the Wood-Saxon potential as a model one. Original Russian Text ? V.N. Mughnetsyan, A.A. Kirakosyan, 2007, published in Izvestiya NAN Armenii, Fizika, 2007, Vol. 42, No. 2, pp. 83–91.