The physical foundations for a new generation of compact gas lasers have been developed and new versions of active elements and cavities for planar waveguide transversely pumped CO2-lasers have been proposed.
By laser spectroscopy a multi-stage mechanism has been established of the reaction of photo-induced reversible axial ligandation of Cu-porphyrins by various oxygen-containing organic molecules, which models the biologically vital reactions in haemoproteins. The 'binding' character of the (d,d)-state and the 'quenching' character of the state with charge transfer in this process have been proved. (In cooperation with the Institute of Molecular and Atomic Physics of the ASB.)
The frequency of generation of horizontal air showers by muons and cosmic neutrinos has been calculated and an experiment on measuring these showers by means of the EASTOP device (Italy) has been proposed. The best of all the now known upper bounds on total fluxes of high-energy cosmic neutrinos have been found.
A method of measuring the complex propagation constants of the guided, leaky and plasmon modes for testing the dielectric, semiconductor and metal thin-film structures has been developed. The method is based on the analysis of the measured angular dependence of the light beam reflection ratio in the prism-film coupler.
The photostructural transformation and optical nonlinearity in azo dyes / polymer films and layers obtained by joint vacuum evaporation, diffusion and spin coating from the solution were investigated by photomodulation and waveguide refractometry. It was shown that film's photochromic characteristics depend weakly on the way of dye introduction, the concentration and aggregative state of dye molecules in the polymer. The magnitude of photoinduced refractive index change in evaporated layers (n~5 cm2/W) is by a factor 102--103 greater than that in the films obtained by traditional methods. It is also established that the evaporated films transimission band photosensitivity acquired under their irradiation in the dye absorption band is caused by its photoinduced trans-isomer.
A new approach to analysis of radiative transfer in the macrostochastic scattering media by using a dynamic causality condition was developed. It is shown that all known models of this process follow from the consideration proposed. The results obtained can be used for solving many problems of radiation and image transfer through the atmosphere and different aqueous media.
The problem has been theoretically studied of compensation for attenuation and amplification of an information digital signal in an optical fiber, both isotropic and keeping polarization owing to the effect of non-linear interaction of optical pumping radiation with substance. Estimates have been obtained of the limiting optical pumping wave power as a function of the optical-fiber circuit length, information signal decoupling coefficients, signal loss due to fiber bending caused by mechanical stress, and other factors.
The conditions for optimizing the optical fiber length by using the minimum optical pump power as a criterion have been found.
As a result of studying the degradation resistance of light-emitting diodes based on multilayered Ga1-xAlxAs structures, it has been shown that changes in the injection luminescence characteristics are caused by the type of deep levels that are present in depleted region of a p-n-junction. It has been established that the greatest drop in radiation intensity is brought about by the presence of deep levels with 0.99 eV ionization energy which, when occurring in A3B5 compounds and solid solutions, correspond to a BA++ defect identified as an antistructural defect AsGaacting as a deep donor.
A technological process has been developed for formation of polycrystalline anodic aluminium oxide having through porosity with 3 nm hole dimensions and extremely narrow size distribution, thus opening up prospects for creating the nanodispersed media. To determine the hole dimensions, use was made, for the first time for such purpose, of the method of Knudsen's flow of gases through pores whose surface was covered with monomolecular layers similar to the Langmuir--Blodget films. (In cooperation with the Institute of Physical Organic Chemistry of ASB and the Glasgov University.)
Based on the studies of the uniformity of avalanche process development in semiconductor layered systems, the design and technological features have been defined for formation of large-area avalanche photodiodes with spectral characteristics extended towards short-wavelength region. These results were used for the first time to develop, make and test detectors for nuclear research with an area of up to 1 cm2 and amplification coefficient over 1000.
New methods of transformations of a functional description of ASIC (Application-Specific Integrated Circuits) macroelements into structural ones, and methods of regular matrix structures synthesis with account of outer connections displacement on the crystal space have been developed. The methods proposed are implemented in programs and included into a prototype of the system of ASIC logic design with intensive use of graphical interface and menu-technology.
A method for a simulation of technological processes of hot pressing with crank drop forging presses and axially symmetrical forging hammers is developed. For the first time an approach for the mentioned process optimization on a base of a movement inversion and uniformness of deformed state has been proposed.
The theoretical foundation of signal and object image detection using the composition of the optimal detection approaches and the limit extension approaches of potential noise stability of the classical detection theory have been developed. On this base the totality of tools and robust algorithms allowing to extend essentially the noise stability of complex information processing systems was developed and analyzed. It is shown that the noise stability of such systems is twice as many in comparison with the well-known complex information processing systems.
Having used the Lyapunov--Krasovskii functionals theory new stability conditions are worked out for delay equations. New restrictions for the functional have allowed to extend essentially the stability conditions with respect to known ones and to unite the main directions in the stability theory, namely the Lyapunov--Krasovskii functionals method and the Lyapunov--Razumikhin functions method.
A criterion of asymptotic stability and absolute integrability for solutions of differential systems with linear diagonal approximation and arbitrary perturbation of higher order has been elaborated.
For representations of the classical groups over fields of characteristic p>0 with highest weights large enough with respect to p the lower bounds for the number of the Jordan blocks of size p of matrices of elements of order p have been obtained. These bounds are given in terms of linear functions of the group rank. It is also found that for problem discussed the notion of a large weight does not depend upon the group rank.
It is shown that for any e>0 an optimal solution of the planar bottleneck travelling salesman problem can not be approximated in polynomial time within factor (2-e) unless P=NP.
The convergence of a certain difference scheme to generalized solution of the first boundary problem was proved for quasilinear stationary heat conductivity equation with nonlinearity of unlimited growth.
The conforming accuracy estimates for classes of functions from W2m(W), m=1,2 are obtained.
New structural-organized self-compacting systems with regulated composition and physical-chemical properties of components being included have been created by the method of supramolecular chemistry on the basis of tetrapyrrolic compounds. By use of picosecond fluorescent experimental setup the regularities of direct energy and electron transfer have been determined in obtained triadic and pentadic complexes of porphyrins and chlorines. These systems model the primary processes in photosynthetic reaction centers in vivo and may serve as a base for creating of informational-logic devices in molecular electronics. (In cooperation with the Institute of Physics of the University of Technology Chemnitz-Zwickau, Germany.)
It has been established that the formation of electronic excited oxide molecules in the decaying laser-produced plasma is the result of the gas-phase exoenergic oxidation reaction of ground state target material atoms.
The semiclassical theory of rovibronic polarized luminescence of free complex molecules has been developed and on its basis the main intramolecular vectorial regularities of echo-transitions and the correspondent simple quantitative relations of time-delay of optically induced rotational echo as moments of molecular top rotational modes synchronization have been elaborated. The influence of molecular characteristics and rotational selection on formation of luminescence polarization, average rotational contour of vibronic band is established. It is shown that optical probing of vapor rotational anisotropy by measurements in the Q-branch of rotational contour of vibrational or vibronic bands, or by similar way excited polarized luminescence is more effective.
The effect of time delay of short microwave pulses in the vicinity of a hybrid resonance in an inhomogeneous plasma has been observed and investigated. The opportunity to use this effect for the short wave plasma oscillations diagnostics has been demonstrated.
A new type of the shape memory effect has been found in the non-stoichiometric rare earth manganites and superconducting yttrium-barium cuprate. This effect represents the jump-like restoring of the sample shape during cooling after its deformation with an external load in the temperature interval of the structural phase transformation and results from the cooperative reconstruction of the ferroelastic domain structure.
The concentration phase transition was observed in the metastable perovskites of PbZrx Ge1-xO3 solid solutions synthesized under high pressures and temperatures. These solid solutions are found to be ferroelectrics with changing character of dipole ordering depending on composition.
The character of magnetic ordering in rare-earth cuprates of RE2CuO4 (RE = Pr, Nd, Sm, Eu), being the parent materials for high temperature superconductors, has been established to be caused by the exchange interaction between the RE ions via the CuO layers, and to manifest itself in noncollinearity of magnetic moments in the Cu ions subsystem.
The continuous series of the chromium telluride -- manganese telluride solid solutions with the competitive exchange interactions has been obtained using the high-pressure technique. The concentration range of the transition from ferromagnetic to antiferromagnetic states has been determined.
An analytical theory of the first-order phase transition in the two-dimensional Ising model in a weak external field was developed, which gives the microscopic foundation for Frenkel's phenomenological droplet theory of condensation. The explicit expression for the lifetime of metastable states has been derived.
The principles of the integrated approach to definition and evaluation of criteria for structural testing of computer software were stated. The approach supposes to be based on the unit test criterion applied to every module and having the stated reliability level and further to keep that level by means of mathematically rigorous and nonredundant definition (as comparison with other ones) of strategies for integration testing of modules' systems and regression testing caused by the program modifications. The proposed test techniques have been implemented in the software tools.
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The anisotropy of nonlinearity in fiber waveguides has been shown to result in effect of self-rotation of polarization plane of linearly polarized light and fiber modes instability. The Kerr-like nonlinearity parameters area where slow mode is switched to under lower light intensity than for fast one has been found. It extends the possibility to create fiber couplers in optical processing systems.
The 'spatial amplification' units for processing 2-D optical data arrays and images were designed, created and experimentally tested. The functioning of these units is based on the phenomenon of optical bistability in nonlinear semiconductor thin-film structures. The use of 'spatial amplifier' allowed to detect the extremely weak optical signals with the power by a factor 104--105 lower than the power of noise.
Source: "Main Results of Fundamental Research.1994". Eds. A.M.Goncharenko and N.N.Kostyukovich. Academy of Sciences of Belarus, Minsk, 1995
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