WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653

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End date: 2009Publisher: search.filters.publisher.Elsevier Science Bv

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  • Article
    Citation - WoS: 49
    Citation - Scopus: 51
    Multidetermination of Thiamine Hcl and Pyridoxine Hcl in Their Mixture Using Continuous Daubechies and Biorthogonal Wavelet Analysis
    (Elsevier Science Bv, 2003) Baleanu, D; Dinç, E
    A new graphical method based on the one-dimensional wavelet transform (WT) was proposed and tested on mixture of thiamine hydrochloride (THI) and pyridoxine hydrochloride (PYR) in the presence of strongly overlapping signals. We selected from the data of the UV-VIS absorption spectra a signal consisting of 1150 points corresponding to the concentration range 8-32 mg ml(-1) for each vitamin and we subjected it to Daubechies8 (DAUB8) and Biorthogonal6.8 (BIOR6.8) wavelet transforms. Since the peaks of the transformed signals were bigger than original ones a zero crossing method was applied to obtain the calibration graphs. In addition, the validity of Beer-Lambert law was assumed for the transformed signals. An appropriate scale setting was choosing to obtain an alternative calibration for each method. MATLAB 6.5 software was used for one-dimensional wavelet analysis and the basic concepts about wavelet method were given. The obtained results were successfully compared among each other as well as with those obtained by other literature methods. The method developed in this paper is rapid, easy to apply, not expensive and it is suitable for analyzing of the overlapping signals of compounds in their mixtures without any chemical pre-treatment. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Conference Object
    Citation - WoS: 3
    Citation - Scopus: 5
    Reactivity of the Nin(T) (N=54,55,56) Clusters With D2(V,j) Molecule: Molecular Dynamics Simulations
    (Elsevier Science Bv, 2004) Özçelik, S; Güvenç, ZB; Durmus, P; Jellinek, J
    The reactive channel of the D(2) (v, j) + Ni(n) (T) (n = 54, 55, 56) collision system is studied via quasiclassical molecular dynamics simulations. The cluster is described using an embedded-atom potential, and the interaction between the molecule and the cluster is modeled by a LEPS (London-Eyring-Polanyi-Sato) potential energy function. Dissociative chemisorption probabilities are computed as functions of the impact parameter and the collision energy, and are used to evaluate the reaction cross-sections. Effects of the initial rovibrational states of the molecule and the temperatures of the clusters on the reactive channel are analyzed. Reaction rate constants are also computed and compared with those measured experimentally. (C) 2004 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    Molecule-Surface Interaction: Dissociative Chemisorption of a D2 (V=0, J=0) Molecule on Rigid Low Index Ni Surfaces
    (Elsevier Science Bv, 2004) Böyükata, M; Güvenç, ZB
    D(2) + Ni-surface collision system has been studied by a quasiclassical molecular dynamic simulation method. Dissociative adsorption of a D(2) molecule on rigid Ni(1 0 0), Ni(1 1 0) and Ni(1 1 1) surfaces are investigated. Interactions between the molecule and Ni surfaces were described by a LEPS potential. The contour plots of the LEPS function is presented as functions of the distances between the center of mass of the D(2) and surface, and between the two deuterium atoms (D-D) for topologically different sites of the surfaces. Dissociative chemisorption probabilities of the D(2) (nu = 0, j = 0) molecule on various sites of the surfaces are presented for different translation energies between 0.001 and 1.0 eV. The probabilities obtained at each collision site have unique behavior. At low collision energies indirect processes enhance the reactivity. The results are compared with the available studies. The physical mechanisms underlying the results are discussed. (C) 2004 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Almost Autonomous Training of Mixtures of Principal Component Analyzers
    (Elsevier Science Bv, 2004) Musa, MEM; de Ridder, D; Duin, RPW; Atalay, V
    In recent years, a number of mixtures of local PCA models have been proposed. Most of these models require the user to set the number of submodels (local models) in the mixture and the dimensionality of the submodels (i.e., number of PC's) as well. To make the model free of these parameters, we propose a greedy expectation-maximization algorithm to find a suboptimal number of submodels. For a given retained variance ratio, the proposed algorithm estimates for each submodel the dimensionality that retains this given variability ratio. We test the proposed method on two different classification problems: handwritten digit recognition and 2-class ionosphere data classification. The results show that the proposed method has a good performance. (C) 2004 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 11
    Dualisation of the Symmetric Space Sigma Model With Couplings
    (Elsevier Science Bv, 2005) Dereli, T; Yilmaz, NT
    The first-order formulation of the G/K symmetric space sigma model of the scalar cosets of the supergravity theories is discussed when there is coupling of (m - 1)-form matter fields. The Lie superalgebra which enables the dualized coset formulation is constructed for a general scalar coset G/K with matter coupling where G is a non-compact real form of a semi-simple Lie group and K is its maximal compact subgroup. (C) 2004 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 72
    Citation - Scopus: 81
    An Application of Derivative and Continuous Wavelet Transforms To the Overlapping Ratio Spectra for the Quantitative Multiresolution of a Ternary Mixture of Paracetamol, Acetylsalicylic Acid and Caffeine in Tablets
    (Elsevier Science Bv, 2005) Özdemir, A; Baleanu, D; Dinç, E
    Quantitative multi resolution of tablets and ternary mixtures of paracetamol (PAR), acetylsalicylic acid (ASP) and caffeine (CAF) having strongly overlapping spectra was accomplished by two graphical transform methods as ratio spectra first derivative-zero crossing and ratio spectra-continuous wavelet transform-zero crossing (ratio spectra CWT-zero crossing) methods. In this study, ratio spectra derivative-zero crossing and ratio spectra CWT-zero crossing methods are based on the use of transformed signals of the ratio spectra and their calibration graphs were obtained by measuring the dA/dlambda and CWT amplitudes of the ratio spectra corresponding to zero crossing points. For the comparison purpose. PLS calibration method was applied to predict the content of the same mixtures containing the subject active Compounds. The obtained calibrations were tested by using the synthetic mixtures and standard addition technique and they applied to the simultaneous determination of PAR, ASP and CAF in commercial pharmaceutical preparation. The obtained results were statistically compared with each other as well as those obtained by HPLC method and they showed good agreement. (C) 2004 Published by Elsevier B.V.
  • Article
    Citation - WoS: 51
    Citation - Scopus: 56
    Comparative Study of the Continuous Wavelet Transform, Derivative and Partial Least Squares Methods Applied To the Overlapping Spectra for the Simultaneous Quantitative Resolution of Ascorbic Acid and Acetylsalicylic Acid in Effervescent Tablets
    (Elsevier Science Bv, 2005) Ozdemir, A; Baleanu, D; Dinç, E
    The simultaneous spectrophotometric determination of ascorbic acid (AA) and acetylsalicylic acid (ASA) in effervescent tablets in the presence of the overlapping spectra was accomplished by the continuous wavelet transform (CWT), derivative spectrophotometry (DS) and partial least squares (PLS) approaches without using any chemical pre-treatment. CWT and DS calibration equations for AA and ASA were obtained by measuring the CWT and DS amplitudes corresponding to zero-crossing points of spectra obtained by plotting continuous wavelet coefficients and first-derivative absorbance values versus the wavelengths, respectively. The PLS calibration was constructed by using the concentration set and its full absorbance data consisting of 850 points from 220 to 305 urn in the range of 210-310 nun. These three methods were tested by analyzing the synthetic mixtures of the above drugs and they were applied to the real samples containing two commercial pharmaceutical preparations of subjected drugs. A comparative study was carried out by using the experimental results obtained from three analytical methodologies and precise and accurate results were obtained. (c) 2004 Published by Elsevier B.V.
  • Conference Object
    Citation - WoS: 14
    Citation - Scopus: 13
    Structures and Energetics of Pd21-Pd55 Clusters
    (Elsevier Science Bv, 2003) Karabacak, M; Özçelik, S; Güvenç, ZB
    Using molecular dynamics and thermal quenching simulations the stable geometrical structures and energies of Pd-n (n = 21-55) clusters are identified. The interaction between the cluster atoms is modeled by an embedded-atom (EA) potential energy surface, Voter and Chen's version. The stable geometrical structures and their minimum energies are obtained from 500 phase space coordinates generated along high-energy trajectories. The internal energies (about T = 2500 K) are above the melting temperature of the Pd-n clusters. The thermal quenching technique is employed to remove slowly the internal kinetic energy of the clusters. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones. Stability of the clusters is examined by the first and the second energy differences. The average bond lengths are obtained and analyzed as a function of the size of the clusters. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Conference Object
    Citation - WoS: 30
    Citation - Scopus: 31
    Structures and Melting of Cun (N=13, 14, 19, 55, 56) Clusters
    (Elsevier Science Bv, 2003) Özçelik, S; Güvenç, ZB
    Constant-energy molecular dynamics simulation was utilized to study the most stable geometrical structures, binding energy, melting, phase changes of Cu-n (n = 13, 14, 19, 55, 56) clusters. These sizes form shell and near shell structures. The cohesion of clusters is modeled by an embedded-atom potential, which contains many-body atomic interaction terms. Phase space coordinates which are generated along high-energy trajectories are used as the initial configurations (500 independent configurations) for thermal quenching in order to obtain the most stable isomers. The melting temperatures of the clusters are estimated. The melting-like transition is described in terms of relative root-mean-square bond-length fluctuations, specific heats, and caloric curves. (C) 2003 Elsevier Science B.V. All rights reserved.
  • Conference Object
    Citation - WoS: 36
    Citation - Scopus: 30
    Structures and Energetics of Pdn (n=2-20) Clusters Using an Embedded-Atom Model Potential
    (Elsevier Science Bv, 2002) Karabacak, M; Özçelik, S; Güvenç, ZB
    We have studied the structure and energetics of the stable isomers of Pd(n) (n = 2-20) clusters by using molecular dynamics and slow-quenching techniques. Cohesion of the clusters is modeled by an embedded-atom potential due to Voter and Chen, which contains many-body atomic interactions. The isomers' statistics are obtained from 10000 independent initial configurations, which have been generated along a high-energy trajectory (the chosen energy value is high enough to melt the cluster). The internal kinetic energy of these initial conditions is removed slowly. Because of this slow minimization process the locally stable isomers are separated from those meta-stable ones. Probabilities belonging to sampling the basins of attractions of each isomer are computed, and compared with each other. Furthermore, the spectrum, which is formed by isomers' energies, is analyzed. (C) 2002 Published by Elsevier Science B.V.