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Reshak A.H.,University of South Bohemia | Reshak A.H.,University Malaysia Perlis | Kamarudin H.,University Malaysia Perlis | Kityk I.V.,Czestochowa University of Technology | And 2 more authors.
Journal of Physical Chemistry B | Year: 2012

Linear and nonlinear optical susceptibility dispersion and hyperpolarizability of C11H8N2O, o-methoxydicyanovinylbenzene, crystals were performed by means of density functional theory (DFT). The exchange and correlation potential was described within a framework of the local density approximation (CA-LDA) and gradient approximation (GGA) based on exchange-correlation energy optimization to calculate the total energy. Engel-Vosko generalized gradient approximation (EV-GGA) and the modified Becke-Johnson potential (mBJ) were used for the electronic crystal structure and optical susceptibility dispersion calculations. We have established systematically increasing energy gap from 2.25 eV (LDA), 2.34 eV (GGA), 2.50 eV (EVGGA), and 2.96 eV (mBJ). The crystal possesses a direct band gap which is an important key factor to make the crystal optically active with high linear and nonlinear optical susceptibilities and hyperpolarizability. Additionally, the studied crystal has a considerable anisotropy of birefringence which is necessary for phase matching conditions during the optical second harmonicexperiments. We have found that the theoretically evaluated second harmonic generation achieves about 5.8 × 10-8 esu in good agreement with the experimental value (4.9 × 10-8 esu). Additionally, we have found that our calculated value of β222 is about 2.3 × 10-30 esu at zero energy and 6.6 × 10-30 esu at λ = 1.064 μm. We should emphasize that our calculated value of β222 (6.60 × 10-30 esu at λ = 1.064 μm) shows better agreement with the experimental data (5.04 × 10-30 esu at λ = 1.064 μm) than other calculations. © 2012 American Chemical Society. Source

Brenych Y.,European University at Kiev
2013 12th International Conference: The Experience of Designing and Application of CAD Systems in Microelectronics, CADSM 2013 | Year: 2013

The K-Winner-Take-All (KWTA) classifier is presented in this article. Its architecture is demonstrated. The basic steps of KWTA classifier are described. Its algorithm is presented. The KWTA structure is demonstrated. Its advantages and limitations are analyzed. © 2013 Lviv Polytechnic Natl Univ. Source

Khyzhun O.Y.,Ukrainian Academy of Sciences | Ocheretova V.A.,Kharkiv Polytechnic Institute | Fedorchuk A.O.,Lviv National University of Veterinary Medicine and Biotechnologies | Parasyuk O.V.,European University at Kiev
Optical Materials | Year: 2014

We report on studies of the electronic structure of Ag 2CdSnS4 single crystal grown by the horizontal gradient freeze technique. For the crystal under consideration, X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces have been measured. The present X-ray photoelectron spectroscopy (XPS) results indicate that Ag2CdSnS4 single crystal surface is very rigid with respect to Ar+ ion-irradiation. In particular, Ar+ bombardment of the single crystal surface does not induce any significant changes of values of the binding energies of core-level electrons as well as the energy distribution of electronic states within the valence-band region. The Ar+ bombardment does not change the elemental stoichiometry of the Ag2CdSnS4 surface. For the Ag2CdSnS4 compound, the X-ray emission bands representing the energy distribution of the valence Ag d, Cd d and S p states were recorded and compared on a common energy scale with the XPS valence-band spectrum. Results of such a comparison indicate that the S 3p states contribute predominantly in the upper and central portions of the valence band of the Ag2CdSnS4 single crystal. In addition, our data reveal that the Ag 4d and Cd 4d states contribute mainly in the central portion and at the bottom of the valence band, respectively. © 2014 Elsevier B.V. All rights reserved. Source

Khyzhun O.Y.,Ukrainian Academy of Sciences | Bekenev V.L.,Ukrainian Academy of Sciences | Denysyuk N.M.,Ukrainian Academy of Sciences | Parasyuk O.V.,European University at Kiev | Fedorchuk A.O.,Lviv National University of Veterinary Medicine and Biotechnologies
Journal of Alloys and Compounds | Year: 2014

We report on first-principles calculations of total and partial densities of states of atoms constituting TlPb2Cl5 using the full potential linearized augmented plane wave (FP-LAPW) method. The calculations reveal that the valence band of TlPb2Cl5 is dominated by contributions of the Cl 3p-like states, which contribute mainly at the top of the valence band with also significant contributions throughout the whole valence-band region. In addition, the bottom of the conduction band of TlPb 2Cl5 is composed mainly of contributions of the unoccupied Pb 6p-like states. Our FP-LAPW data indicate that the TlPb2Cl 5 compound is an indirect-gap material with band gap of 3.42 eV. The X-ray photoelectron core-level and valence-band spectra for pristine and Ar + ion-irradiated surfaces of a TlPb2Cl5 polycrystalline sample were measured. The measurements reveal high chemical stability and confirm experimentally the low hygroscopicity of TlPb 2Cl5 surface. © 2013 Elsevier B.V. All rights reserved. Source

Rachkovsky V.P.,European University at Kiev
Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu | Year: 2013

Purpose: To calculate the resistance of the massif around the mine working during development of diamond deposits. Methodology: By the method of mathematical modeling we have determined the stability of the equilibrium state of the bottom of stope in vertical opening located in kimberlite rock taking into account the equilibrium of the infinite space of the cavity under the load at a depth of 1000 meters. Findings: We have created the model of the cylindrical vertical opening stability and determined appearance of local critical pressure in the surrounding massif during its deformation. The system of diamond deposits mining with ore shrinkage in mined-out spaces. Originality: We have created a combination of axisymmetric computational model blocks of stress state of the cylindrical stope with axial compression and external pressure determining the stability of the kimberlite rock. Practical value: We have developed the methodology of substantiation of geotechnology parameters of mining of Ukrainian kimberlite deposits and guidelines for assessment of technologic parameters of stopes in kimberlite pipes. Source

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