Home – Home – Jornals – 2010 number 3

This paper considers the state and prospects for studies of the central problem of the theory and practice of automatic control-the problem of controller synthesis for systems with nonlinear plants. A crucial factor in the performance of controllers for nonlinear plants is the use of deep feedback for derivatives of the output variable, which provides localization of disturbances in fast subprocesses (against the background of the main processes) and allows the generation of the required dynamic properties

The degeneration property of dynamic multivariable control systems is considered. In this work, by degeneration for a multivariable systems is meant primarily a decrease and even a loss of its operating capacity. A technique of quantitative assessment of the tendency of multivariable control systems to degeneration was developed using a singular decomposition of criteria matrices formed on the basis of the matrix formalism of Faddeev-Leverrier algorithm, Gramian representation, matrix coefficient of the expansion of the system output vector in the derivatives of the control input vector, and with the use of the matrix formalism of Sylvester's and Lyapunov's equations.

Experimenting with large-scale, multi-agent software systems yields insight into factors that determine the capability of complex systems to operate at the edge of chaos without disintegrating. The research results are generalised and applied to the diagnosis of the failure of the global financial system.

Algorithms of constructing a fuzzy approximator of atmospheric temperature fields are considered. The consequent parameters of the fuzzy rule approximator are determined using the leastsquares method, and the antecedent parameters are determined by the genetic algorithm. Results of a numerical experiment are presented. Optimal approximator parameters are given

Maximum likelihood algorithms for estimating the area of stochastic images against a stochastic background in the presence of spatial noise are synthesized. A comparison is made of area estimation algorithms based on the additive and applicative models of interaction between the image and background. Asymptotic expressions for the characteristics of the area estimators are obtained. The effect of the difference between the statistical characteristics of the background and image on the accuracy of image area estimation is studied

A system of cluster analysis (unsupervised classification) for Earth remote sensing data is considered. The system is represented by three methods: the K-means method, the mode analysis of multidimensional histograms, and a hybrid method which combines the mode analysis of multidimensional histograms with their subsequent hierarchical grouping

This paper considers the operation algorithm of a hydrostatic level sensor in a liquid of unknown density which is based on the determination of the moment when the level crosses the pressure sensor and provides increased accuracy of density and level measurements compared to available methods. The algorithm was synthesized on the basis of the maximum likelihood method. The algorithm was analyzed and experimental data are given

The geometric and information parameters of the page-oriented holographic memory are optimized with allowance for the cross-talk influence on the recording density and on the bit error rate

Results of development and testing of a scanning system of interference lithography are presented. The system is designed to form diffractive microstructures consisting of microgratings with a specified orientation, a size of 5-10 μm, and a period ranging from 0.6 to 1.5 μm. The total writing field of the system is 300×300 mm. The system is used to study direct laser writing of microgratings on chromium and amorphous silicon films applied by the method of magnetron sputtering onto the glass substrate surfaces. The device and technology of direct writing of microgratings can be further used to form antireflective subwave coatings of optical elements and graphical microstructured identification marks for product protection and also to manufacture diffractive attenuators of laser radiation.

Splitting of orthogonally polarized radiation components at the exit of birefringent crystal prisms (BCPs) having a special structure and fabricated from uniaxial Iceland spar crystals is studied by the vector analysis method. For these prisms, the angle of splitting between the ordinary (o) and extraordinary (e) beams at the BCP exit depends linearly on the angle of incidence of a collimated laser beam onto the BCP entrance face. This dependence has the maximum slope only for two fixed orientations of the optical axis vectors a₁ and a₂ in both crystal wedges (BCP components). As a result of interference of polarized o- and e-waves, a straight-line interference pattern with a controlled and smoothly changed spatial frequency in the range from 0 to 125 periods/mm can be formed directly at the BCP exit. The BCP ability to form a sinusoidal interference pattern with the modulation depth not lower than 30% and with a varied spatial frequency at the aperture up to 30 mm makes it possible to use the BCP as a basis for creating a compact static Fourier spectrometer with the ultimate theoretical resolution λ/Δλ up to ~2000.

The structure and functional capabilities of a digital optical microscope-profilometer capable of operating in two modes, those of micro- and nanomeasurements, are presented. The instrument operation principle is based on measuring the phase function of the wave front of light scattered by the measured surface. Software for the microscope-profilometer and its performance characteristics are considered.

A maximum likelihood algorithm for estimating the velocity vector of a moving object from its image of unknown intensity against an applicative background whose intensity may be unknown a priori was designed and analyzed.

Algorithms for modeling images with fractal characteristics based on generalized spatial frequency filtering are proposed in which the phase or sign of the amplitude of the corresponding orthogonal transformation of the original image is retained and the modulus of the amplitude decreases exponentially for the entire generalized spectrum of the image or for the integral frequency characteristic of the spectrum. For the model images, fractal measures in a spatial region are proposed, which, similarly to the integral frequency characteristic, are invariant under multiplicative reduction in scale.

An algorithm for detecting spectral peak absorption in the secondary radiation from an object containing nitrogen compounds is proposed. The algorithm is based on the statistical invariance principle and has the property of automatically adjusting to signal-noise parameters. The algorithm was tested by simulation modeling and was shown to be applicable to real secondary-radiation spectra. The algorithm and the associated experimental hardware make it possible to implement a fundamentally new method for the automatic detection of nitrogen-containing compounds.

An algorithm for estimating the state vector of controlled plants in the class of bandlimited functions with a cutoff regularizing function is proposed which is more effective and accurate than available algorithms. The effect of errors in assigning samples of the differentiated functions on the estimate quality is evaluated, and the methodical error of the algorithm is analyzed.

The problem of object selection in the presence of random geometric transformations of the observed images due to the movement of the image sensor and random atmosphere fluctuations is solved. An analytical and simplified algorithms of for solution of the problem are developed. Results of statistical investigation of the algorithms are presented.

Quantitative relations between the approximation properties of nonparametric estimates of the separation-surface equation and the nonuniformity of the distribution of the learning-sample elements between the classes are studied in a two-alternative problem of pattern recognition

Methods of the numerical solution of equations that describe the resonant interaction of polarized radiation with alkali atoms are presented. Some procedures of converting these equations to a form reducing the calculation time are given. Typical simplifying assumptions used in solving these equations are discussed. Based on comparisons of magnetic-optical resonances for Rb⁸⁷ with various simplifying assumptions, a conclusion is made on applicability of these approximations and possible inherent errors

Results of experimental studies and modeling of holographic photonic crystals (PCs) with defects of their spatial and band-gap structures and also of studying quasi-crystals are presented. Thicklayer photopolymer materials with a hybrid matrix formed on the basis of the sol-gel technology are used for PC production. A method of obtaining delocalized defects is proposed and implemented. A code is written for computer modeling of the spatial PC structure, which offers a clear idea about the appearance of the synthesized crystal and the expected spectral characteristics.

As the eye pupil decreases, the bifocal properties of the intraocular lens (IOL), which is an artificial eye lens, can be violated. To avoid it, a phase shift is introduced into the structure of the IOL diffractive component. Results of an analytical study of the light intensity distribution on the axis of a bifocal IOL for different values of the eye pupil and phase shift in the diffractive component with a focal power of 4.2 D (diopters) are presented. Because of broadening and asymmetry of the intensity distribution function arising at small pupil diameters, the foci of orders 0 (far vision) and +1 (near vision) of the bifocal IOL are demonstrated to affect each other: they come closer or farther, become separated or overlapped. The total intensity distribution may be continuous or have a dip whose magnitude depends on the pupil diameter and phase shift. It is noted that the optimal phase shift at which separation of the foci (bifocality) begins from the pupil diameter of ~0.9 mm and is not violated with further pupil expansion is 180° (π radian).

Volumetric displays with numerous fronto-parallel planes-images stimulating eye accommodation are considered. The depth of the focal field is determined as a function of the axial intensity distribution. Results of interpolation of images between the planes are presented. It is shown that the best resolution and visual comfort are reached if the distance between the planes does not exceed the diffractive depth of focus.

A correlation method for processing dynamic light scattering patterns resulting from laser radiation propagation through solutions and suspensions is proposed which is based on spatial averaging of measurement data on the correlation functions of the intensity of light scattered by small particles

A new element of a field-controlled diffraction grating [Grating Light Valve^TM diffractive MOEMS device (GLV)] is described, which differs from known similar elements by the physical principle of operation and its structure; other distinctive features are the lower control voltage, the absence of the hysteresis, and the possibility of operation in the analog mode. Experimental characteristics of the GLV element are presented.

Possible implementations of a small-size terahertz spectrometer with a subpicosecond resolution on the basis of a femtosecond fiber laser are considered. An experimental sample of a spectrometer is fabricated. This spectrometer employs the method of optical rectification in a ZnTe nonlinear crystal and the Dember (photodiffusion) effect on the InAs semiconductor surface to generate terahertz radiation and the polarization-optical method to detect radiation. System operation is demonstrated by an example of measuring the terahertz absorption spectrum of water and determining the refractive index of the β-BBO crystal. The basic spectrometer parameters are found: spectral range, spectral resolution, and dynamic range of the terahertz spectrum amplitude.

Three-component condensation of N1-phenylthiocarbamide with salicylaldehyde and with the ether of acetoacetic acid in the presence of trifluoroacetic acid provides a productive synthesis of ethyl 9-methyl-10-phenyl-11-thioxo-8-oxa-10,12-diazatricyclo[7.3.1.0^2.7]trideca-2(7),3,5-trien-13-carboxylate I. Single crystal XRD is used to determine the crystal structure of I and to identify the conformation properties of the structures.

A new compound (pefloxacindium tetrachlorozincate(II)), C₁₇H₂₀FN₃O₃ 1-ethyl-N-methyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-methyl-1-piperazinyl)-3-quinoline carbonic acid (PefH, pefloxacin) is synthesized, and its crystal structure is determined. The crystal contains and ions. The supramolecular architecture of the crystal is analyzed

By heating in the air [НBW₁₁O₃₉]^8- with [Rh₂(CH₃COO)₄(H₂O)₂] in the excess of tungstate followed by crystallization in the presence of CsCl, a double salt of Cs₈[α-BW₁₂O₄₀][RhCl₆]·5.5H₂O is obtained and structurally characterized. Its crystal structure is determined by single crystal X-ray diffraction. The structure is ionic with Cs⁺ cations, [BW₁₂O₄₀]^5- anions with the Keggin structure, and [RhCl₆]^3- octahedral anions.

The products of the extraction treatment of Rh(III) and Pd(II) nitrate-nitrite solutions are studied. The [Rh(Thio)₆](NO₃)₃·3H₂O and [Pd(Thio)₄](NO₃)₂ complex salts are extracted and an X-ray diffraction analysis of single crystals is performed (BRUKER X8 APEX automated diffractometer, MoK_α radiation, graphite monochromator, two-dimensional CCD-detector). [Rh(Thio)₆](NO₃)₃·3H₂O crystallographic characteristics are as follows: a = 15.1857(3) Å, b = 10.7292(2) Å, c = 18.8524(4) Å, β = 105.165(1)°, P2₁/c space group, Z = 4; [Pd(Thio)₄](NO₃)₂: a = 5.8013(4) Å, b = 7.0981(5) Å, c = 11.4991(8) Å, α = 99.963(2)°, β = 101.410(2)°, γ = 102.229(2)°, P -1 space group, Z = 1.

A single crystal X-ray diffraction study of the crystals of methyl 4-methyl-3,5-dioxo-1-phenyl-2-oxaspiro[5.5]undecane-4-carboxylate shows that phenyl and methoxycarbonyl substituents are in the equatorial position on the one side of the dioxopyran ring with twist boat conformation.

Single crystal X-ray diffraction is used to determine the crystal structure of 1-(4-bromo-9-methyl-11-thioxo-8-oxa-10,12-diazatricyclo[7.3.1.0^2.7]trideca-2,4,6-trien-13-yl)ethanone and identify its conformation characteristics.

Single crystal X-ray diffraction is used to determine the crystal structure of 4,5-bis-phenyl-8а-phenyl-3,4,4а,5,6,8а-hexahydro-1Н,8Н-pyrimido[4.5-d]pyrimidine-2,7-dione and identify its conformation characteristics.

The all-electron approach implemented in the CRYSTAL06 program is used along with a pseudopotential method in the pseudo-atomic orbital basis set to study the crystal structure, elastic constants and bulk moduli, the band structure and density of states for the family of silver nitrides. Calculations are performed within density functional theory with the use of local and gradient functionals to describe exchange and correlation. For the general type of the cubic lattice, all considered compounds can be put in the following order of their relative stability: AgN (rock salt structure), AgN₂ (fluorite structure), Ag₂N (cuprite structure), and Ag₃N (anti-ReO₂). It is shown that AgN, AgN₂, and Ag₂N are metals, whereas Ag₃N is a semiconductor with a band gap of 0.25 eV. Chemical bonding in these compounds has ionic and covalent components, apart from the metal one.

Quantum chemical calculations of the equilibrium structure, potential energy surface cross-sections along the nonrigid degrees of freedom of (CF₃COOAg)₂, (CHF₂COOAg)₂, (CH₂FCOOAg)₂, and (CH₃COOAg)₂ dimers and the corresponding monomers are presented. The B3LYP method with the augmented cc-pVTZ basis set for C, O, F atoms and the Stuttgart 1997 RSC basis set together with the relativistic effective potential for Ag atoms is used. It is shown that in all dimers the eight-membered ring is a rather rigid planar fragment, and the Ag atoms can be bonded with the bond order of 0.2 in dimers. Almost free rotation of acyclic groups around the C-C bond in (CH₃COOAg)₂ and (CF₃COOAg)₂ dimers transforms into a hindered one in the (CHF₂COOAg)₂ dimer, and further into the existence of syn- and anti-structures divided by a high rotation barrier in the (CH₂FCOOAg)₂ dimer. In monomers, the ratio of the internal rotation barriers is similar. With increasing number of fluorine substitution for hydrogen atoms in dimers the Ag-Ag bond length is found to increase (2.79 Å, 2.81 Å, 2.83 Å, 2.84 Å) and the ring rigidity to simultaneously decrease in the acetate-triflouroacetate series

The PRIRODA (riDFT method, BLYP functional, hf.bas basis set) and Gaussian 98 (HF method, 6-311G(d,p) basis set) programs are used to calculate the spatial and electronic structures of a number of molecules of substituted germocanes with a general formula of R,R′Ge(XCH₂CH₂)₂Y (where X = C, O, S, and Y = N, O, S). With the use of the AIM method the topological characteristics of Ge-Y donation bonds are calculated in these molecules. An analysis of the obtained data shows that up to the values of Ge-Y interatomic distances of ~2.7 Å these bonds can be considered as the intermediate type bonds. At Ge-Y distances of ~3.0 Å these bonds become ionic, therefore the Coulomb interaction between oppositely charged Ge and Y atoms mainly contributes to Ge-Y bonding.

An ab initio quantum chemical study (MP2/6-311++G**//B3LYP/6-31+G*) of a number of possible interactions is performed for the gas phase system of acetylene-potassium hydroxide-dimethylsulfoxide(DMSO)-methanol and with regard to the solvent effect within the continuum model. Key structures in the vinylation reaction are shown to be methoxide ion complexes with the alkali metal hydroxide and acetylene molecules. The formation of these complexes results in the activation of the acetylene molecule and an increase in the nucleophilicity of the methoxide ion. In the С₂Н₂/CH₃OH/KOH/DMSO reaction system, a proton exchange between the acetylene molecule and the anionic nucleophile ([OH]^- and [CH₃O]^-) is freely performed with the formation of systems with ethynide ions, whereas the thermodynamically preferable formation of vinyl alcohol or methyl vinyl ether is determined by a barrier of 20 kcal/mol

Molecular structure and vibrational spectra of 1,2-tetramethylenediborane (B₂C₄H₁₂), 1,2:1,2-bis(tetramethylene)diborane (B₂C₈H₁₈), 1,1-tetramethylenediborane (B₂C₄H₁₂) and 1,1:2,2-bis(tetramethylene)diborane (B₂C₈H₁₈), have been studied using quantum computational density functional B3LYP and B3PW91 methods and 6-31G*, 6-31G** and 6-31++G** basis sets. Natural bond orbital analyses have been carried out to study in detail the nature of the B-C, C-C and B-H bonds in these molecules. This study showed that all these compounds are thermodynamically stable in the gas phase, but bicyclic structures are more stable than monocyclic structures.

In the anharmonic approximation the intensities of fundamental, overtone, and combined absorption bands are calculated in the range fr om 100 cm^-1 to 4000 cm^-1 for a series of alkanes, nitriles, amines, and nitroalkanes. The first and second derivatives of the molecular dipole moment are calculated by quantum chemical methods in the ab initio approximation using the MP2/6-31G(1d) basis set. Overtones and combined frequencies are found to make a significant contribution (5-20%) to the total absorption. The spectral distribution of this contribution depends on the molecular structure. For nitriles and amines significant absorption of the overtones and combined frequencies is observed in the same regions wh ere fundamental absorption bands characteristic of these compounds are located.

Vibrational spectra of the adenine-uracil complementary pair of nucleic acid bases (NAB) in the isolated state are calculated in the B3LYP/6-311++G(d,p) approximation and analyzed. The hydrogen bonding effect on frequency positions and intensities of normal vibrations of NAB pairs is shown in comparison with isolated uracil and adenine molecules.

¹⁹F NMR and DFT methods are used to study the electronic structure and chemical bonding of titanyl ions in pentafluoro titanyl complexes (NH₄)₃TiOF₅ and Rb₂KTiOF₅. The experimental values of the anisotropy of ¹⁹F NMR chemical shifts (CSs) are shown to be consistent with the calculated parameters within the DFT method. At normal temperatures orientational disordering of octahedral [TiOF₅]^3- anions occurs, fluorine atoms steadily occupying cis- and trans-positions with respect to the О^2- ion. In both complexes, trans-position is not fully occupied; the occupation ratio does not exceed ~4:0.9. When the temperature is decreased to 150 K, the value of the CS anisotropy of the fluorine atom resonance line in trans-position is found to be smaller than the dipole-dipole broadening, whereas the line from fluorine atoms in cis-positions transforms into an asymmetric broad line characterized by the triaxial anisotropy of the CS tensor. It is shown that the found anisotropy corresponds to violation of the axial symmetry of Ti-F_cis bonds because of strong delocalization of the electron density of Ti-O bonds in the titanyl ion.

In a group of natural marine apatites Ca₅(PO₄)₃(F, OH), organic H₃, H₂-R, HOHR, (CH₃)₂-R, and radicals are identified by EPR. The relation between the EPR spectra of the observed organic radicals, the valence form, and the structural location of impurity vanadium ions (V⁴⁺ (VO²⁺) on the Ca²⁺ II site or V⁵⁺ (VO₄)^3- → (PO₄)^3-) is established. The structure of organic radicals correlates with the type of organic matter in the sample under analysis: sapropelic or humic, depending on the climatic conditions of mineral genesis