Search results for "Model theory"
showing 10 items of 681 documents
F-contractions of Hardy–Rogers-type and application to multistage decision
2016
We prove fixed point theorems for F-contractions of Hardy–Rogers type involving self-mappings defined on metric spaces and ordered metric spaces. An example and an application to multistage decision processes are given to show the usability of the obtained theorems.
A comprehensive probabilistic analysis of approximate SIR‐type epidemiological models via full randomized discrete‐time Markov chain formulation with…
2020
Spanish Ministerio de Economia y Competitividad, Grant/Award Number: MTM2017-89664-P; Generalitat Valenciana, Grant/Award Number: APOSTD/2019/128; Ministerio de Economia y Competitividad, Grant/Award Number: MTM2017-89664-P
Jakimovski–Leviatan operators of Kantorovich type involving multiple Appell polynomials
2019
Abstract The purpose of the present paper is to obtain the degree of approximation in terms of a Lipschitz type maximal function for the Kantorovich type modification of Jakimovski–Leviatan operators based on multiple Appell polynomials. Also, we study the rate of approximation of these operators in a weighted space of polynomial growth and for functions having a derivative of bounded variation. A Voronvskaja type theorem is obtained. Further, we illustrate the convergence of these operators for certain functions through tables and figures using the Maple algorithm and, by a numerical example, we show that our Kantorovich type operator involving multiple Appell polynomials yields a better r…
The uniform convergence of a double sequence of functions at a point and Korovkin-type approximation theorems
2020
Abstract In this paper, we introduce an interesting kind of convergence for a double sequence called the uniform convergence at a point. We give an example and demonstrate a Korovkin-type approximation theorem for a double sequence of functions using the uniform convergence at a point. Then we show that our result is stronger than the Korovkin theorem given by Volkov and present several graphs. Finally, in the last section, we compute the rate of convergence.
Molecular dynamics simulations of nanometric metallic multilayers: Reactivity of the Ni-Al system
2011
The reactivity of a layered Ni-Al-Ni system is studied by means of molecular dynamics simulations, using an embedded-atom method type potential. The system, made of an fcc-Al layer embedded in fcc-Ni, is initially thermalized at the fixed temperature of 600 K. The early interdiffusion of Ni and Al at interfaces is followed by the massive diffusion of Ni in the Al layer and by the spontaneous phase formation of $B2$-NiAl. The solid-state reaction is associated with a rapid system heating, which further enhances the diffusion processes. For longer times, the system may partly lose some its $B2$-NiAl microstructure in favor of the formation of $L{1}_{2}$-${\mathrm{Ni}}_{3}\mathrm{Al}$. This st…
The ${JV}$ -Characteristic of Intermediate Band Solar Cells With Overlapping Absorption Coefficients
2017
An analytic expression for the $\textit {JV}$ -characteristic of intermediate band (IB) solar cells with overlapping absorption coefficients is derived. The characteristic contains six voltage-independent parameters that are calculated from material properties, cell properties, and external conditions. Combined with exponential functions containing the cell voltage, these describe the full $\textit {JV}$ -characteristic. Expressions are also derived for the short-circuit current and open-circuit voltage. The model represents a major simplification compared with the existing model for this type of devices. The simplicity will facilitate the understanding of the operation of such cells. Furth…
Model building on the non-factorisable type IIA T6/(Z4×ΩR) orientifold
2016
We construct global semi-realistic supersymmetric models with intersecting D6-branes on the non-factorisable orientifold . The non-factorisable structure gives rise to differences compared to the factorisable case: additional conditions for the three-cycles to be Lagrangian and extra constraints on the wrapping numbers for building fractional cycles.
A decacobalt(ii) cluster with triple-sandwich structure obtained by partial reductive hydrolysis of a pentacobalt(ii/iii) Weakley-type polyoxometalat…
2016
Partial reductive hydrolysis of a penta-CoII/III cluster [CoII4(H2O)2(CoIIIW9O34)(PW9O34)]12− (1) leads to the formation of [Co2{Co3(H2O)(Co(OH)2W7O26)(PW9O34)}2]22− (2). This polyoxometalate is made up of two capping [PW9O34]9− units and two bridging [W7O26]10− units that assemble to encapsulate a novel deca-CoII cluster core comprising octahedral and tetrahedral CoII ions.
Cobalt Clusters with Cubane-Type Topologies Based on Trivacant Polyoxometalate Ligands.
2016
Four novel cobalt-substituted polyoxometalates having cobalt cores exhibiting cubane or dicubane topologies have been synthesized and characterized by IR, elemental analysis, electrochemistry, UV-vis spectroscopy, X-ray single-crystal analysis, and magnetic studies. The tetracobalt(II)-substituted polyoxometalate [Co4(OH)3(H2O)6(PW9O34)](4-) (1) consists of a trilacunary [B-α-PW9O34](9-) unit which accommodates a cubane-like {Co(II)4O4} core. In the heptacobalt(II,III)-containing polyoxometalates [Co7(OH)6(H2O)6(PW9O34)2](9-) (2), [Co7(OH)6(H2O)4(PW9O34)2]n(9n-) (3), and [Co7(OH)6(H2O)6(P2W15O56)2](15-) (4), dicubane-like {Co(II)6Co(III)O8} cores are encapsulated between two heptadentate [B…
Joint interpretation of seismic refraction tomography and electrical resistivity tomography by cluster analysis to detect buried cavities
2020
Abstract In the last few years, the geophysical methods of seismic refraction tomography (SRT) and electrical resistivity tomography (ERT) are among the most used geophysical techniques for the reconstruction of subsoil geometries, for the investigation of underground cavities and also for the archaeological prospecting. However, the main disadvantage of each geophysical method is the difficulty of final interpretation of the data. In order to eliminate artifacts and generally improve the reliability and accuracy of geophysical interpretation, it is useful to perform a joint approach of different geophysical methods, also introducing the a priori information. In this work, it is shown the i…