Home – Home – Jornals – 2009 number 5

Thermal maturation for the top and base of the Jurassic in the West Siberian megabasin was modeled on the basis of the vitrinite reflectance (R _vt ⁰) data using mathematical modeling and computer simulations. The values of thermal maturation are found to vary within substages PC₃-MC₃² for the top (or being equivalent to PC₃-MC ₁ ² on the periphery and southern part of the basin, or to MC₂- MC₃² in the north) and PC₃-AC₃ for the base of the Jurassic (or being equivalent to PC₃-MC₂ on the periphery and southern part of the basin or MC₃¹-AC₃ in the north). Thermal maturity levels of the Jurassic in West Siberia are controlled by depths of burial and peak temperatures which the source rocks were subjected to during this period. The situation is further complicated by high heat flows superimposed on the regional background, which are observed in deep fault zones and in the proximity of numerous igneous bodies.

According to the suggested model of groundwater stratigraphy obtained on the basis of geological and groundwater data, the sedimentary cover of the western Siberian craton includes the suprasalt, salt, and subsalt groundwater units subdivided into regional and subregional reservoirs. It has been found reasonable to carry out special groundwater studies, either before or concurrently with petroleum exploration, in order to ensure supply of drinking, household, and technological waters to meet the demand of oil and gas production and to make groundwater available for oil-well pressure maintaining systems and for underground burial of waste waters.

Division of sedimentary strata according to groundwater chemistry is discussed with implications for petroleum reservoir potential. It is suggested to process multiparametric water chemistry data from West Siberia using formalized clustering techniques. The efficiency of this approach has been tested for Neocomian clinoform reservoirs with reference to regional-scale appraisal and subregional petroleum division.

Using the Chiller computer program, we performed modeling of the mechanisms of the joint transport and deposition of Au and Sb from various ore-forming solutions during the formation of Au-Sb deposits. Three models are considered by the example of the Uderei Au-Sb deposit in the Yenisei Ridge: (1) simple cooling (cooling only), (2) iso-enthalpy boiling ( P = f ( T )), and (3) solution-rock interaction (rock titration model). The behavior of Sb(III) and Au(I) in the system Au-Sb-Fe-Cu-Pb-Zn-As-H₂O-Cl-H₂S-CO₂ under hydrothermal conditions was studied. It is shown that both weakly alkaline (near-neutral) and reduced acidic Fe_aq²-enriched low-chloride high-CO₂ and high-chloride hydrothermal solutions play a crucial role in the formation of gold parageneses of Au-Sb ores.

Picroilmenite samples from five kimberlite pipes of the Yakutian kimberlite province have been studied. Point microprobe analyses of two mutually perpendicular profiles of each sample were carried out to study the compositional inhomogeneity of picroilmenite. Thermomagnetic curves were also recorded for each sample. A model for the processing of thermomagnetic curves is proposed on the basis of the relationship between the Curie point of picroilmenite and the content of the hematite end-member. The compositions determined by the thermomagnetic curves and microprobe analysis are rather similar. The conclusion has been drawn that thermomagnetic analysis can be used for the rapid determination of the picroilmenite composition. The possibilities and restrictions of this method are shown.

Bottom sediments from the central zone of the Sea of Okhotsk were preliminarily dated. The petromagnetic parameters of two groups of samples formed at cold and warm climatic stages were studied. Warm oxygen isotopic stages and substages were characterized by the coexistence of pseudo-single-domain allogenic magnetite and predominant magnetite and greigite (pyrrhotite) grains subject to biologic control. At cold stages, sediments containing a mixture of pseudo-single-domain and multidomain terrigenous magnetite particles accumulated. The petromagnetic curves agree with the normalized standard oxygen isotopic curve over the last 350 kyr of the column section.

Electromagnetic wave propagation from an induction source (a transmitter coil) in media with time-dependent conductivity and permittivity is simulated using the vector finite-element method. A special algorithm is suggested for source approximation.

The use of electrochemical effects in petroleum exploration and engineering-geological applications is discussed with reference to the Zhirnovsky oil and gas field where mobile forms of metals are 1.5-2 times above the background. Electrochemical stiffening applied to Maastrichtian shales, which are sliding planes of landslides in the Lower Volga area, increased their stiffness by a factor of 2 or more.

A new algorithm of estimating the stationary part of the background of the observed scene and its adaptation to changes in this scene and observation conditions are proposed. The algorithm is optimal in the statistical sense and employs the minimum number of statistical characteristics (moving average, variance, and median), which allows their recurrent calculation necessary for real-time implementation. The validity of the proposed method is confirmed by results of a computational experiment with real video sequences.

A possibility of increasing the resolution of photodetector arrays by doubling the spatial sampling frequency and subsequent processing of the samples obtained is considered.

An improved algorithm is proposed to calculate the mutual correlation functions (MCFs) of signals using the fast Fourier transform, the quadrature formulas of the trapezoidal method, and the Simpson method. The calculation error of MCFs is analyzed by comparing MCFs obtained for continuous finite signal samples and MCFs obtained using improved calculation algorithms for discrete signal samples. It is shown that these algorithms for calculating MCFs provide a more accurate primary estimate of MCFs. Improved calculation algorithms are described.

An algorithm of reconstruction of two-dimensional radar images in a frequency range is proposed. The algorithm is based on the property of the instrument function of separation of variables, which allows the procedure of two-dimensional reconstruction to be reduced to a two-stage procedure of one-dimensional reconstruction, thus, ensuring faster performance. A comparison with the algorithm of reconstruction in a spatial domain is presented.

The process of constructing vector fields of displacements of clouds in the atmosphere from a series of consecutive images obtained by geostationary satellites is considered. The process is based on searching for the maximum of the coefficient of mutual correlation between reference objects (targets) found in the current image of the series and their positions in the next image of the series. In addition to the transfer transformation, the target can also be subjected to transformations of rotation and scaling. Interpolation of pixels is used to increase the accuracy of computations.

The estimation of the characteristics of motion of the object controllable by means of seismic monitoring system is considered. It is assumed that the motion in a local area of space is uniform and rectilinear, and the problem is therefore reduced to estimating the coordinates of the initial point and velocity vector. The input data are measured time delay differences in receiving seismic signals by various sensors of the system. Usually, these measurements are formed as a sequential flow in real systems. The obtained estimates of the trajectory also have the form of a sequence, and their accuracy increases with increasing number of primary data. The accuracy of the proposed method are analyzed by statistical simulation.

X-ray radiography is extended by a digital image processing method for measuring the velocity vector field of metal foaming in radiographic sequences. A tensor approach coupled with interpolation using an adaptive Gaussian window is proposed. The method was successfully tested on experimental images.

Statistically optimal and neural network algorithms of joint detection and estimation of brightness difference parameters in a local observation window are synthesized for the purpose of solving the problem of object boundary extraction in digital images in the presence of noise. Comparative results on the performance of these algorithms are given.

A SynApp program is developed for studying the algorithms of processing data obtained by arrays with a synthesized aperture in passive sonar devices. Various synthesis algorithms are compared, and the best algorithm is chosen on the basis of particular criteria. Inspection of program operation with signals obtained by a real array demonstrates the efficiency of synthesis with the use of the ETAM algorithm. Application of synthesis in passive sonar devices is proved to reduce the array aperture without deterioration of the bearing quality. The effect of the changes in the array subaperture used for synthesis and the size of the synthesized aperture (number of synthesis steps) on the bearing quality is studied.

An algorithm for controlling the torque or the rotation velocity of the rotor of an induction (asynchronous) motor with vector control of flux linkages is proposed. Stability of the control loops of the torque and rotor rotation velocity is analyzed, and results of simulating the operation of the proposed algorithms are described.

The properties of adaptive control systems synthesized by the velocity vector method are considered. It is shown that the systems are characterized by different time-scale dynamics because they contain a reference model, a fast adaptor, and a derivative estimation filter. A study is made of the effect of the parameters of the reference model on the properties of systems with additive adjustment and additive and parameter adjustments. The system parameters having the most significant effect on the control are determined and recommendations are given for the choice of these parameters with the constraints on the control actions taken into account.

A precise method based on a special procedure of successive parametrization of control actions is proposed to solve boundary-value optimal control problems for distributed-parameter systems with the tolerances for deviations from the required final state of the controlled object specified in the uniform metric. The method is used to solve the time optimal control problem for an innovative technology of induction heating of massive bodies rotating in a direct current magnetic field.

An optimization approach to finding the parameters of reduced-order controllers is proposed. It is shown that numerical estimation of the location of the characteristic roots in the complex plane allows the set of the roots to be divided into parts, in each of which, real coordinates for the roots are introduced. The resulting structure of the root simplex is similar to a geometrical complex. The structure of the regions and boundaries of the simplex is represented by graphs and digraphs. The roots are moved to the desired region by minimization of the same estimate of the objective function depending on the controller parameters. Critical regions are represented by reduced graphs.

A data processing method based on one variant of ternary logic, which allows considering unreliable and incomplete information, is presented. An example of practical application of the proposed method in the development of the Novosibirsk subway supervisory train control system is given.

The technical means and software of an MTSR-40 measuring and computing complex for recording fast processes are described. The functions and operating modes of this complex are considered.

A series of aromatic vinyl ethers and some compounds close to them in structure are studied by DFT (B3LYP/6-311+G(2d,p)) and MP2(full)/6-311+G(2d,p) methods. Measurements of Raman spectra are also used. The calculation of vibrational spectra of aryl vinyl ether (AVE) isomers shows that stretching vibrations ν(С=С) are most conformation sensitive. The calculated value of I(С=С) for vinyl phenyl ether more than twice exceeds the corresponding value for vinyl methyl ether. The calculated and experimental values of I(С=С) are consistent with the hypothesis about the presence of a common conjugated π-system in the molecules of substituted AVEs. Here the bridging oxygen atom provides the π,р,π-interaction.

Based on the B3LYP/6-311++G(3df,3pd) density functional method, quantum chemical calculations of the electronic structure, geometry, and thermodynamic parameters of eight isomers of nitric acid (three known isomers in the form of peroxynitrous acid ONOOH and five new isomers in the form of oxo-conformation OON(H)O) are presented in the work. The molecular structure of each isomer is characterized by a local minimum on the potential energy hypersurface of the HNO₃ molecular system and corresponds to one of its stationary states. A theoretical study of the reactivity of nitric acid oxo-isomers characterized for the first time can provide adequate explanation for experiments on the autocatalytic use of nitric acid vapors in binding molecular nitrogen. The results obtained can be a direction for developing principally new methods to bind atmospheric nitrogen and activate methane, which are fundamental problems in chemical science and technology.

Based on the 2HI4 complex taken from the PDB database, molecular docking of 17 substrates in the cytochrome P450 1A2 cavity is performed using the 3D-QSAR algorithm CiS. The arrangement of substrate molecules in the 1A2 isoform cavity is considered, the orientation of the molecular reaction centers relative to heme is analyzed, and the character of interaction between substrates and active site aminoacid residues is investigated. The structures of the modeled complexes allow us to explain metabolic pathways in demethylation reactions and some reactions of hydroxylation, which enables an application of the CiS algorithm to predict metabolic pathways.

A quantitative structure-property relationship (QSPR) model obtained by using multiple linear stepwise regression analysis, with correlation coefficient R of 0.979 for the training set and 0.951 for the validation set, was developed to predict the glass transition temperature (T_g) values of polyacrylates. Three quantum chemical descriptors (the molecular average polarizability α, the entropy S, and the lowest unoccupied molecular orbital E_LUMO) obtained directly from polyacrylates monomer structure by density function theory (DFT) calculation, were used to produce the model. The result confirmed the role that quantum chemical descriptors play in studying QSPR of glass transition temperature for polymers.

A combined gas-phase electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ, MP2/6-31G*, and MP2/cc-pVTZ) study of the structure of the 4-nitrobenzene sulfonyl chloride molecule is performed. It is found that at a temperature of 391(3) K only one conformer with C_s symmetry is present in the gas phase. The following experimental values of structural parameters are obtained: r_h1(C-H)_av = 1.086(6) Å, r_h1(C-C)_av = 1.395(3) Å, r_h1(C1-S) = 1.773(4) Å, r_h1(S=O) = 1.423(3) Å, r_h1(S-Cl) = 2.048(4) Å, r_h1(N-O) = 1.224(3) Å, r_h1(N-C4) = 1.477(3) Å, ∠(С1-S=O) = 109.0(4)°, ∠(Cl-S-O) = 106.7(2)°, ∠C1-S-Cl = 100.2(13)°, ∠O=S=O = 122.9(11)°, ∠O=N=O = 123.6(5)°. The C2-C1-S-Cl torsion angle that characterizes the position of the S-Cl bond relative to the benzene ring plane is 89(4)°. The NO₂ group lies in the benzene ring plane. Internal rotation barriers calculated by B3LYP/6-311+G** and MP2/6-31G* methods are: V₁ = 4.7 kcal/mol and 5.3 kcal/mol for the sulfonyl chloride group; V₂ = 4.9 kcal/mol and 6.0 kcal/mol for the nitro group.

L-Seryl-L-histidine dipeptide is of scientific interest mainly because of its various biological activities. In this paper, the lowest energy structure of the dipeptide was determined by molecular modeling, and further validated by quantum chemistry calculations and ¹H NMR spectroscopy.

Monte Carlo simulation of caffeine aqueous solutions containing a superhelical В-DNA fragment is performed using parallel computing. The binding sites of caffeine molecules with DNA were identified as well as the most probable structures of the resultant complexes. The degrees of caffeine molecule association in aqueous solutions with different concentrations were estimated and the main configuration types of molecular aggregates were revealed.

Many mercury-containing minerals belonging to the class of sulfides and sulfosalts are based on a highly symmetric sphalerite type structure (ZnS), where both components occupy sites with high point symmetry providing stable orientation of directed interatomic interactions. Some structures of natural compounds of this type are used to demonstrate that the geometric matrix of cations and anions tends to be preserved during variation of the chemical composition caused by migration of elements under natural conditions. The fundamental laws of crystal formation are confirmed: the governing role of the families of close packed (crystallographic) planes, the independence of ordering of different types of atoms, the tendency of sulfur atoms to mirror plane symmetry, and the trend to cluster formation in the development of crystal structures, as exemplified by [As₄S₁₂]^12-, [(Cs,Tl)S₁₂]^23-, [Tl₂S₁₂]^22- atomic groups.

Using Voronoi-Dirichlet (VD) polyhedra and the method of overlapping spheres, we analyze the coordination of 714 crystallographically different vanadium atoms in the structure of compounds containing VO_n polyhedra. Vanadium atoms are found to be bonded to 4, 5, 6, or 7 oxygen atoms. The effect of the valence state and coordination number of vanadium atoms on the main parameters of their VD polyhedra is considered. A unified linear dependence between the solid angles of VD polyhedron faces corresponding to V-O bonds and the respective interatomic distances varying in a range of 1.55 Å to 2.79 Å is stated to exist. It is shown that the parameters of VD polyhedra can be used to determine the valence state of vanadium atoms.

The known methods to determine the surface areas of molecules are discussed and a new method is proposed based on the molecule representation in the form of a molecular Voronoi-Dirichlet polyhedron. A linear correlation is found between the surface areas of molecules calculated using the molecular Voronoi-Dirichlet polyhedra and determined by the already known methods. The efficiency of the use of molecular Voronoi-Dirichlet polyhedra for the analysis of intermolecular interactions in crystal structures is demonstrated by concrete examples.

Using X-ray diffraction the presence of two phases of 1-fluorosilatrane (FSa) is stated and the specific features of their spatial structure are studied. Phase transition occurs at 156-158 K and is characterized by low energy. In the low-temperature phase, four crystallographically independent molecules are ordered, while in the high-temperature phase one of two independent molecules has disordered carbon β-atoms. A quantum chemical analysis of crystal packing in the low-temperature FSa phase is performed. The estimated value of the coordination N→Si bond strength in the crystal is 29.2 kcal/mol. The charge distribution indicates the localization of valence electron density around the O₃SiF fragment.

The title complexes, K₂[Eu^III(dtpa)(H₂O)]·5H₂O (H₅dtpa = diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid), Na₂[Tb^III(Httha)]·6H₂O (H₆ttha = triethylenetetramine-N,N,N′,N′,N″,N″-hexaacetic acid), were prepared, and their compositions and structures were determined by elemental analyses and single-crystal X-ray diffraction techniques. The crystal of K₂[Eu^III(dtpa)(H₂O)]·5H₂O belongs to triclinic crystal system and P space group. The crystal data are as follows: a = 8.3540(17) Å, b = 10.147(2) Å, c = 15.059(3) Å, α = 84.63(3)°, β = 82.02(3)°, γ = 83.96(3)°, V = 1253.1(4) ų, Z = 2, R = 0.0325 and wR = 0.1013 for 4407 observed reflections with I ≥ 2σ(I). The [Eu^III(dtpa)(H₂O)]^2- has a nine-coordinate pseudo-monocapped square antiprismatic structure, in which the nine coordinate atoms, three N and six O are from one dtpa ligand and one water molecule. The crystal of the Na₂[Tb^III(Httha)]·6H₂O belongs to monoclinic system and P2₁/c space group. The crystal data are as follows: a = 10.3976(10) Å, b = 12.7908(13) Å, c = 23.199(2) Å, β = 90.914(2)°, V = = 3084.9(5) ų, Z = 4, R = 0.0309 and wR = 0.0704 for 5429 observed reflections with I ≥ ≥ 2σ(I). In the [Tb^III(Httha)]^2-, the Tb³⁺ ion is nine-coordinated yielding a pseudo-monocapped square antiprismatic conformation, in which the ttha ligand coordinates to the central Tb³⁺ ion with four N atoms and five O atoms. There is a free non-coordinate carboxyl group (-CH₂COOH) that can be modified by some biological molecules having target function.

By the ¹Н NMR and Raman spectroscopy data it is shown that in the porous inclusion compound of Zn₂(C₈H₄O₄)₂[(N₂(CH₂)₆))]·n(CH₃)₂CO (n ≈ 0-4.7) acetone molecules exist in two structural forms: ketonic (CH₃)₂CO, for which the ¹Н NMR chemical shift value is δ^ket = 0.8 ppm, and enolic CH₃C(OН)=CH₂, for which δ^en(ОН) = 11 ppm, δ^en(CH₂) = 8.9 ppm, and δ^en(CH₃) = 1.6 ppm are found, the average value over three proton sites being 〈δ^en〉 = 5.6 ppm. A sharp difference in chemical shift values for the keto and enol forms of acetone in the inclusion compounds can be assigned to the effect of structural chemical conditions in two types of adsorption centers.

The previously proposed method of the integrated interpretation of mass-spectrometric and chromatographic data is applied to compounds with a branched carbon skeleton, namely, hydrocarbons containing tert-butyl groups. We estimate the increments of chromatographic retention indices for a hypothetical (СН₃)₃С → СН₃ transformation and determine the factors affecting their value. Several simple mass spectral characteristics are recommended to reveal tert-butyl groups in the structure of analyte molecules; however, one of the most informative criterion is to estimate the total number of carbon skeleton branches based on the homological increments of retention indices. The work shows high efficiency of the identification method proposed when the analytical and reference data are scarce.

Some projection conversions of molecular structures containing a loop of elements with a topological model in the form of a knot are studied. We describe a graph representation of knot diagrams and inversion algorithms for points in the knot projection to obtain various projections.

In order to determine the features of the structure of double complex salts (DCSs) of [Cr(NH₃)₅Cl]×
[MCl₄]·nH₂O, where M = Pd, Pt, n = 0, 1, the DCS solid solutions of palladium and platinum with isostructural DCSs containing the chloropentaammine rhodium cation, [Cr(NH₃)₅Cl]_x[Rh(NH₃)₅Cl]_1-x× [MCl₄]·nH₂O, where x = 0.01-0.2, are synthesized and studied by the EPR method. DCSs with the isostructural chloropentaammine rhodium cation are used as a diluter for magneto concentrated systems. It is shown that DCS of platinum and anhydrous DCS of palladium have the identical environment of chromium ions. The EPR spectra of chromium ions for these compounds are described by the following spin Hamiltonian parameters: S = 3/2, g_xx = 1.987, g_yy = 1.987, g_zz = 1.985, D = 1660 Gs, E = 235 Gs. For the palladium complex containing crystalline water, the EPR spectra of chromium ions are described by the parameters: S = 3/2, g_xx = 1.984, g_yy = 1.984, g_zz = 1.984, D = 1060 Gs, E = 350 Gs. A decrease in the crystal field parameters for the aqueous palladium complex is caused by a redistribution of the electron density to the oxygen atom in the second sphere of the chromium ion environment.

Chemical vapor deposition is used to obtain Ir and Ir-Al₂O₃ coatings with a thickness of up to 5 μm and growth rate of 2.5 μm/h on steel substrates previously covered with an alumina layer. Tris-acetylacetonates of Ir(III) and Al(III) are used as precursors. The deposition process is carried out at the atmospheric pressure in the presence of hydrogen. The coatings obtained are studied by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. A dependence of the structure and composition of coatings on their preparation conditions is found.