Browsing by Subject "Gradient methods"

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    The investigation of fluorine substitution in difluoroanilines with focus on 2,6-difluoroaniline by spectroscopic methods, density functional theory approach, and molecular docking
    (Elsevier B.V., 2019) Kose E.; Bardak F.; Atac A.
    In this study, the spectroscopic features and reactive nature of difluoroanilines, with special attention on 2,6-difluoroaniline (2,6-DFA), are explored thoroughly to gain insight into the effect of fluorine substitution in aniline derivatives. The quantum chemically obtained spectral properties including Fourier transform infrared, Raman, ultraviolet, and 1H and 13C nuclear magnetic resonance spectra were obtained by using Density Functional Theory (DFT) calculations at B3LYP/6-311++G(d,p) level of theory, and given along with the ones measured experimentally. The reactivity characteristics such as Fukui descriptor, electrostatic potential, and electronegativity were defined based on electron density generated theoretically. The position of fluorine substitution does not significantly alter the amide group reactivity making all difluoroanilines compatible to each other in terms of the reactivity. The time-dependent DFT was used to calculate the electronic properties such as excitation energies, maximum wavelengths, oscillator strengths, and molecular orbitals energies, and given along with the density of state diagrams. The intramolecular interactions were mapped by reduced density gradient method to reveal possible fluorine influence on the amide group and its reactivity, and the strongest van der Waals interactions in 2,6-DFA were observed. Besides, the thermodynamic and nonlinear optical properties of the title molecule were also investigated. The 2,6-DFA molecule seems to be appealing for multidisciplinary studies about the relevant nonlinear optical properties. To explore the binding capability of 2,6-DFA and see the influence of fluorine substitution in difluoroanilines, molecular docking was performed on a model enzyme structure of T4 lysozyme. Ligand-enzyme binding energies of 2,6-DFA is nearly the same with that of 2,5 DFA and 3,5 DFA at the same binding site which differs from the remaining derivatives. © 2019 Elsevier B.V.
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    External field intensity and wavelength dependency from IR to deep UV of linear and nonlinear optical properties of 1-butyl-3-methylimidazolium dicyanamide ionic liquid
    (Elsevier B.V., 2023) Bardak F.; Bardak C.
    The electronic structure, inter-ionic interactions and charge transfer, polarizability, and first-order and second-order hyperpolarizabilities of 1-butyl-3-methylimidazolium dicyanamide ionic liquid have been explored via modeling at M06-2X/6-311++G(d,p) level of theory. External field intensity dependence of electronic properties was investigated by utilization of field intensity from 0.0001 to 0.002 au applied in the direction of anion-cation. Interionic interactions have been characterized through the reduced density gradient method to reveal and distinguish hydrogen bonding and other non-covalent interactions. Extraordinary bonding interactions were observed between the anion and ring system of the cation. Electronic excitation characteristics were analyzed based on the inter-fragment charge transfer method to distinguish charge transfer contributions from local excitations. Static and dynamic nonlinear optical parameters namely the total dipole moment μ, the mean polarizability α(0,0) and α(−ω; ω), the anisotropy of polarizability Δα(0,0) and Δα(−ω; ω) the first hyperpolarizability in the direction of dipole moment β(0,0,0), β(−ω; ω,0), and β (−2ω; ω,ω), the average second hyperpolarizability γ(0;0,0,0), γ(−ω; ω,0,0) and γ(−2ω; ω,ω,0) have been calculated for specific laser wavelengths corresponding to the UV, visible, and infrared region. Thus, a novel way of mapping the field intensity and wavelength dependence of NLO properties was achieved. The hyperpolarizability calculations indicate that 1-butyl-3-methylimidazolium dicyanamide has a significant potential to be used in electro-optics Pockels effect, second-harmonic generation, and electro-optical Kerr effect applications. NLO property maps indicate that the wavelength dependence in the IR and visible region is almost ignorable when compared with that of the UV region where the first hyperpolarizabilities can increase by ten thousand and the second hyperpolarizabilities can reach up to ten billion times. © 2023 Elsevier B.V.
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    A novel hybrid multilayer perceptron neural network with improved grey wolf optimizer
    (Springer Science and Business Media Deutschland GmbH, 2023) Altay O.; Varol Altay E.
    The multilayer perceptron (MLP), a type of feed-forward neural network, is widely used in various artificial intelligence problems in the literature. Backpropagation is the most common learning method used in MLPs. The gradient-based backpropagation method, which is one of the classical methods, has some disadvantages such as entrapment in local minima, convergence speed, and initialization sensitivity. To eliminate or minimize these disadvantages, there are many studies in the literature that use metaheuristic optimization methods instead of classical methods. These methods are constantly being developed. One of these is an improved grey wolf optimizer (IMP-GWO) proposed to eliminate the disadvantages of the grey wolf optimizer (GWO), which suffers from a lack of search agent diversity, premature convergence, and imbalance between exploitation and exploration. In this study, a new hybrid method, IMP-GWO-MLP, machine learning method was designed for the first time by combining IMP-GWO and MLP. IMP-GWO was used to determine the weight and bias values, which are the most challenging parts of the MLP training phase. The proposed IMP-GWO-MLP was applied to 20 datasets consisting of three different approximations, eight regression problems, and nine classification problems. The results obtained have been suggested in the literature and compared with the gradient descent-based MLP, commonly used GWO, particle swarm optimization, whale optimization algorithm, ant lion algorithm, and genetic algorithm-based MLP methods. The experimental results show that the proposed method is superior to other state-of-the-art methods in the literature. In addition, it is thought that the proposed method can be modeled with high success in real-world problems. © 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.