ALBERT

Description: Econometric models for the forecast of tourism demand are developed in this paper. In order to assess the long-run trends concerning principal tourism generating countries, the Johansen's maximum likelihood techniques are applied. For a better assessment of the short-run trends, the estimated error correction terms are introduced to the first difference models to estimate the short-run relationships (Error Correction Models, ECMs). Based on the results given by the ECMs, fuzzy regression models are suggested and then compared in order to provide the forecasting ability of both techniques (Fuzzy and ECMs). Finally, for the evaluation of forecasting performance, the Theil's Inequality Coefficient is applied. Content Type Journal Article Pages 245-257 DOI 10.3233/JCM-140501 Authors G. Botzoris, Department of Civil Engineering, Democritus University of Thrace, Xanthi, Greece E. Varagouli, Department of Civil Engineering, Democritus University of Thrace, Xanthi, Greece V. Profillidis, Department of Civil Engineering, Democritus University of Thrace, Xanthi, Greece B. Papadopoulos, Department of Civil Engineering, Democritus University of Thrace, Xanthi, Greece P. Lathiras, Aristotle University of Thessaloniki, Thessaloniki, Greece Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: This paper examines the natural convection in a square enclosure filled with a water-Al_{2}O_{3} nanofluid which is under the influence of an external magnetic field. The bottom wall is uniformly heated and vertical walls are linearly heated whereas the top wall is well insulated. Lattice Boltzmann method (LBM) is applied to solve the coupled equations of flow and temperature fields. This study has been carried out for the pertinent parameters in the following ranges: Rayleigh number of the base fluid, Ra=10^{3} to 10^{5}, Hartmann number varied from Ha=0 to 60, the inclination angle of the magnetic field relative to the horizontal plane γ= 0° to 180° and the solid volume fraction of the nanoparticles between ϕ=0 and 6%. The results show that the heat transfer rate increases with an increase of the Rayleigh number but it decreases with an increase of the Hartmann number. Also for Ra ⩾ 5 × 10^{4} and for the range of Hartmann number study, we note that the heat transfer and fluid flow depends strongly upon the direction of magnetic field. In addition, according the Hartmann number, it observed that the magnetic field direction controls the effects of nanoparticles. Content Type Journal Article Pages 291-313 DOI 10.3233/JCM-140503 Authors Ahmed Mahmoudi, Unité de Recherche Matériaux, Energie et Energies Renouvelables, Faculté des Sciences de Gafsa, Gafsa, Tunisie Imen Mejri, Unité de Recherche Matériaux, Energie et Energies Renouvelables, Faculté des Sciences de Gafsa, Gafsa, Tunisie Mohamed AmmarAbbassi, Unité de Recherche Matériaux, Energie et Energies Renouvelables, Faculté des Sciences de Gafsa, Gafsa, Tunisie Ahmed Omri, Unité de Recherche Matériaux, Energie et Energies Renouvelables, Faculté des Sciences de Gafsa, Gafsa, Tunisie Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: Based on Petković-Ilić-Džunić method [3], we derive a family of three-step eighth-order Steffensen type iterative methods for solving nonlinear equations. The new methods without memory use two suitable parametric functions at the second and third steps and are free from any derivatives. Per iteration the new methods require four functional evaluations, which implies that the efficiency index of the new methods is 1.682. The advantage of the new methods is that the computing speed of the new methods is faster than that of other eighth-order Steffensen type methods without memory. Numerical examples are made to show the performance of our methods and support the developed theory. Content Type Journal Article Pages 277-287 DOI 10.3233/JCM-140505 Authors Xiaofeng Wang, School of Mathematics and Physics, Bohai University, Jinzhou, Liaoning, China Tie Zhang, College of Sciences, Northeastern University, Shenyang, Liaoning, China Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: Disaggregate mode choice models estimation, which are used for evaluating the ridership share on intercity travel service and for identifying modes which will lead to an upgraded traveler's service, constitutes a critical part of evaluating alternative travel service proposals to intercity travel. The aim of this paper is to estimate the choice of mode in intercity travel demand. Disaggregate logit models are estimated by using data collected in order to investigate the passengers' behavior of the broader region under study. The final models are applicable on regional level and have statistics within acceptable region. Content Type Journal Article Pages 259-268 DOI 10.3233/JCM-140502 Authors E.G. Varagouli, Department of Civil Engineering, Democritus University of Thrace, Komotini, Greece. E-mail: evarggo@civil.duth.gr Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: In this paper, the solution of fractional Riccati differential equation by using the operational matrix of shifted Legendre polynomial is discussed. The properties of shifted Legendre polynomials together with the Caputo fractional derivative are used to reduce the problem to the solution of nonlinear algebraic equations. Also the theoretical analysis of shifted Legendre polynomial method such as convergence and error analysis has been discussed. The illustrative examples demonstrate its applicability, validity and simplicity of the approximation scheme. Content Type Journal Article Pages 229-243 DOI 10.3233/JCM-140489 Authors K. Krishnaveni, Department of Mathematics, School of Humanities and Sciences, Sastra University, Thanjavur, Tamilnadu, India K. Kannan, Department of Mathematics, School of Humanities and Sciences, Sastra University, Thanjavur, Tamilnadu, India S. Raja Balachandar, Department of Mathematics, School of Humanities and Sciences, Sastra University, Thanjavur, Tamilnadu, India Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: The basic formalism of the MR-AQCC method is presented which is basically a size extensivity corrected MR-CI procedure. The correction is applied in form of a diagonal shift which allows easy implementation of the method into any MR-CI programs and makes the calculation on excited states also possible. Accuracy of the method is discussed. To show the applicability of the method we present the first results of our systematic study on the proton transfer in 7-azaindol. We conclude that inclusion of dynamic correlation is essential to get reliable energy differences and potential energy surfaces for this process. Content Type Journal Article Pages 457-467 DOI 10.3233/JCM-2002-23-422 Authors Péter G. Szalay, Department of Theoretical Chemistry, Eötvös Loránd University Imre Berente, Department of Theoretical Chemistry, Eötvös Loránd University Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Solvent, effect in both quantum and classical calculations are accurately described by the Polarizable Continuum Model (PCM) whose electrostatic equations can be solved on the molecular surface by finite elements approximation. The GePol algorithm for the definition of finite elements molecular surface has been revisited, improved and reimplemented from scratch. We achieved linear scaling computational cost thus extending the range of applicability of the PCM approach to very large molecular systems. Content Type Journal Article Pages 469-474 DOI 10.3233/JCM-2002-23-423 Authors G. Scalmani, Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte S.Angelo, via Cintia, I-80126 Napoli, Italy N. Rega, Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte S.Angelo, via Cintia, I-80126 Napoli, Italy M. Cossi, Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte S.Angelo, via Cintia, I-80126 Napoli, Italy V. Barone, Dipartimento di Chimica, Università di Napoli “Federico II”, Complesso Universitario di Monte S.Angelo, via Cintia, I-80126 Napoli, Italy Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Isotopic separation factors of lithium ion complexed by crown-ethers are obtained from statistical mechanics. The effect of the organic arm which links the crown-ether to a silica matrix is considered. Ab initio HF/6-31+G * calculations, PM3 semiempirical calculations and hybrid quantum mechanics/molecular mechanics PM3/MM Molecular Dynamics simulations have been performed. In vacuum, it is found that 7 Li is better complexed than 6 Li by the crown-ether with or without its organic arm, in contrast to what is experimentally observed by liquid chromatography with ethanol solvent and crown-ethers grafted on silica. To model the solvent effect, some ethanol molecules are first included in the PM3 calculations to solvate the free lithium isotopes and the lithium isotopes complexed by the crown-ether. The method reproduces the observation that 6 Li isotope is more complexed than 7 Li, but the hierarchy of the experimental separation factor in the crown-ether series is not correctly recovered. The PM3/MM Molecular Dynamics simulations of the crown-ether 12C4 system show that when taking into account the effect of the organic arm, it is possible to find a separation factor in agreement with the experimental result. Content Type Journal Article Pages 451-456 DOI 10.3233/JCM-2002-23-421 Authors C. Millot, Equipe de chimie et biochimie théorique, UMR CNRS-UHP no 7565, Université Henri Poincaré – Nancy 1, Faculté des Sciences et Techniques, Boulevard des Aiguillettes, BP 239, 54506 Vandoeuvre-lès-Nancy Codex, France F. Dehez, Equipe de chimie et biochimie théorique, UMR CNRS-UHP no 7565, Université Henri Poincaré – Nancy 1, Faculté des Sciences et Techniques, Boulevard des Aiguillettes, BP 239, 54506 Vandoeuvre-lès-Nancy Codex, France Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: This paper describes the design and implementation of abiGrid, a grid-based tool to enhance the scientific collaboration among different research groups of Quantum Chemists. The goal of abiGrid is to permit the use and interchange of home-made programs, while maintaining the individuality of the different codes that, as research tools, are subjected to changes and evolution. The research activity of the partners is focused on orbital localization in a Multi-Reference context, as a necessary step towards the development of efficient methods for the treatment of large quasi-degenerate systems. Central points of the project are the design of a Common Data format, and an extensive use of the Grid technology. Content Type Journal Article Pages 417-422 DOI 10.3233/JCM-2002-23-417 Authors Elda Rossi, CINECA, via Magnanelli 6/3, 40033 Casalecchio di Reno (BO), Italy Andrew Emerson, CINECA, via Magnanelli 6/3, 40033 Casalecchio di Reno (BO), Italy Stefano Evangelisti, Laboratoire de Physique Quantique, UMR 5626, Université Paul Sabatier, 118 Route de Narbonne, 41062 Toulouse CEDEX, France Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: The gas-phase interactions of H 3 C-CH 2 -CH 3 , H 2 C=C(H)XH 3 and HC≡C-XH 3 (X=C, Si, Ge) with Cu + have been investigated through the use of B3LYP/6-311+G(2df,2p) calculations. The most stable complexes are stabilized through agostic interactions between the metal cation and the hydrogen atoms of the XH 3 group. Only when the neutral presents a C≡C triple bond the conventional π-complexes are slightly more stable than those exhibiting agostic interactions. The nature of these non-conventional bonds is analyzed in terms of the topology of the charge density and second order orbital interactions. The strength of these bonds increases with the hydride character of the XH hydrogens explaining the fact that while propene and the Si- and Ge-containing analogs have similar Cu + binding energies, ethylsilane and ethylgermane are predicted to bind Cu + much more strongly than propane. Concomitantly, a significant weakening of the X-H linkages involved in the bond reflected in a very large red shifting of the X-H stretching frequency is systematically observed. Content Type Journal Article Pages 411-416 DOI 10.3233/JCM-2002-23-416 Authors Inés Corral, Departamento do Química, C-9. Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain Otilia Mó, Departamento do Química, C-9. Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain Manuel Yáñez, Departamento do Química, C-9. Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: The resonance Raman (RR) spectra of nickel bis-dimetliylglyoxime (NiDMG) were calculated in the framework of the transform theory of RR scattering by means of the Rush and Peticolas approximation in combination with density functional theory (DFT). The 1 1 Bu and 1 1 Au excited state geometries, required by this approach, were optimised within time-dependent DFT at the B3LYP and B3P86 levels of theory, using a Newton-Raphson algorithm where the first and second derivatives of the molecular excited state energies were calculated numerically through finite difference approximations. The B3LYP ground state force field was scaled with a set of global scaling factors that correct for errors arising from the quantum chemical method and the harmonic approximation. Comparison between the experimental RR spectra of NiDMG obtained with 413 nm excitation and those calculated in resonance with the transitions to the 1 1 Bu and 1 1 Au states show a good agreement for the most intense RR bands. Content Type Journal Article Pages 405-410 DOI 10.3233/JCM-2002-23-415 Authors Maria-Andrea Mroginski, Max-Planck-Institut für Strahlenchemie, Stiftstr. 34–36, D-45470 Mülheim an der Ruhr, Germany Franz Mark, Max-Planck-Institut für Strahlenchemie, Stiftstr. 34–36, D-45470 Mülheim an der Ruhr, Germany Peter Hildebrandt, Max-Planck-Institut für Strahlenchemie, Stiftstr. 34–36, D-45470 Mülheim an der Ruhr, Germany Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Hartree-Fock and MP2 calculations for the dipole moment μ and the dipole polarizabilities of uracil, using optimized geometries, and the 6-31+G(d,p) and 6-31+G(d * ,p) (d = 0.05) basis sets, have been performed. The experimental μ of uracil is reproduced with the MP2/6-31++G(3d,3p) methodology. The calculated values of dipole polarizability α are consistent with MP2 calculations of literature. Prediction for the β first- and γ second-hyperpolarizabilities of uracil are reported. Comparison to MP2 calculations between the employed basis sets, shows that 6-31+G(d * ,p) results leads to values of the β v and γ ave that are 20 % and 42 % larger than the obtained with the standard basis set. The proposed values for these properties of uracil are 45.1 au and 12787 au, respectively. Content Type Journal Article Pages 423-430 DOI 10.3233/JCM-2002-23-418 Authors Humberto Soscún, Laboratorio de Química Inorgánica Teórica, Departamento de Química, Facultad Experimental de Ciencias, La Universidad del Zulia, Ap. 526, Grano de Oro, Módulo No.2, Maracaibo, Venezuela Elba Manrique, Laboratorio de Química Inorgánica Teórica, Departamento de Química, Facultad Experimental de Ciencias, La Universidad del Zulia, Ap. 526, Grano de Oro, Módulo No.2, Maracaibo, Venezuela Javier Hernández, Laboratorio de Química Inorgánica Teórica, Departamento de Química, Facultad Experimental de Ciencias, La Universidad del Zulia, Ap. 526, Grano de Oro, Módulo No.2, Maracaibo, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Recent, work in the field of biological photoreceptors has demonstrated that computational chemistry can be successfully applied to ultrafast photobiological problems. Here we revise the results of the photoisomerization path mapping of the protonated Schiff base of retinal: the chromophore of rhodopsin proteins. These studies have produced the two-state/two-mode model which provides a rationale for the photon-induced molecular motion in the isolated retinal chromophore. Such model represents a substantial revision of the previous models for the primary event in vision in animals and light driven proton-pumping in halobacteriae. New computational results will be presented, which model the effects of an external counterfoil on the photoisomerization paths. Energetic, electronic, stereoselectivity control and tuning-effects will be analyzed and discussed in terms of counterfoil positions. Both solution and protein experimental data are revised using the new reactivity model. Content Type Journal Article Pages 431-439 DOI 10.3233/JCM-2002-23-419 Authors Marco Garavelli, Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via Selmi 2, 40126 Bologna, Italy Fernando Bernardi, Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via Selmi 2, 40126 Bologna, Italy Alessandro Cembran, Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via Selmi 2, 40126 Bologna, Italy Massimo Olivucci, Istituto di Chimica Organica, Università di Siena, Via Aldo Moro, I-53100 Siena, Italy Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: In this paper we report the development of a new approach which can be used to improve supermolecule ab initio intermolecular potentials. It involves combining quantities obtained from low-level dimer calculations (exchange and coulomb energies) with quantities obtained from high-level monomer calculations (charge density overlaps, first-order Coulomb interaction energies and dispersion energy coefficients) in order to estimate the resulting potential energy surfaces at the high level of theory. The level of theory which can be used for both monomer and dimer calculations will increase in time. Therefore, the definitions of ‘low’ and ‘high’ level are flexible and depend on technological limitations: ‘low’ level must be computationally cheap enough to use in thousands of dimer calculations for multidimensional potential energy surfaces, and ‘high’ level is required only in a few monomer calculations. We present results for three homonuclear (He 2 , Ne 2 , Ar 2 ) and three heteronuclear (He-Ne, He-Ar, Ne-Ar) rare gas dimers using the MP2 method as the ‘low’ level of theory and the QCISD approach as the ‘high’ level. We compare the extrapolated results with the literature data available for ground state potential energy curves of these dimers. Content Type Journal Article Pages 391-397 DOI 10.3233/JCM-2002-23-413 Authors Elena Bichoutskaia, School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK Matthew P. Hodges, School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK Richard J. Wheatley, School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: First-principles computer simulations of the metcar Ti 8 C 12 allow one to identify the geometrical structure of the clusters studied experimentally. Indeed, the combination of predictive computer simulations and experimental measurements of the vibrational spectra of clusters offers a viable tool for structural identification of atomic clusters. Content Type Journal Article Pages 399-403 DOI 10.3233/JCM-2002-23-414 Authors G.K. Gueorguiev, Departamento de Fíisica da Universidade, P-3004-516 Coimbra, Portugal J.M. Pacheco, Departamento de Fíisica da Universidade de Lisboa, Complexo Interdisciplinar, Av. Prof. Gama Pinto 2, P-1649-003 Lisboa Codex, Portugal Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Variational and Perturbative CAS-SCF-type algorithms based on molecular orbitals that, preserve their physical nature during the iterative process are discussed. The methods are based on the iterative diagonalization of the one-body reduced density matrix. If localized guess orbitals are used, the locality property is kept by the final orbitals. The formalism can be used to reduce the number of active orbitals in CAS-SCF calculations on large systems, and in general to have a better control on the physical nature of the active space. The reduction from a complete to selected reference space is also possible in the case of Configuration-Interaction calculations. Content Type Journal Article Pages 385-389 DOI 10.3233/JCM-2002-23-412 Authors Celestino Angeli, Dipartimento di Chimica, Universitá di Ferrara, via Borsari 46, I-44100 Ferrara, Italy Carmen J. Calzado, Departamento de Quimica Fisica, Universidad de Sevilla - c/ Profesor Garcia Gonzalez, s/n. E-41012 Sevilla, Spain Renzo Cimiraglia, Dipartimento di Chimica, Universitá di Ferrara, via Borsari 46, I-44100 Ferrara, Italy Stefano Evangelisti, Laboratoire de Physique Quantique, UMR 5626, Université Paul Sabatier, 118, Route de Narbonne, 31062 Toulouse CEDEX, France Nathalie Guihéry, Laboratoire de Physique Quantique, UMR 5626, Université Paul Sabatier, 118, Route de Narbonne, 31062 Toulouse CEDEX, France Jean-Paul Malrieu, Laboratoire de Physique Quantique, UMR 5626, Université Paul Sabatier, 118, Route de Narbonne, 31062 Toulouse CEDEX, France Daniel Maynau, Laboratoire de Physique Quantique, UMR 5626, Université Paul Sabatier, 118, Route de Narbonne, 31062 Toulouse CEDEX, France Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: The aggregation of molecules characterized by some degree of rigidity, in amorphous systems, leads to the presence of voids that are responsible for important properties of the amorphous material. One example is the diffusion of small atoms or molecules through polymers or other materials, which is of relevance in the fabrication of materials for packaging, or for efficient gas sensors and biosensors. A second example, is the physisorption of hydrogen molecules in carbonaceous materials, of relevance for the utilization of hydrogen as a pollution-free energy carrier. In this work we present a computational study, carried out with the help of molecular mechanics and molecular dynamics simulations, of the diffusion and storage of gas particles inside samples of amorphous aggregates: in particular we concentrate on the diffusion of He into the branched structure of polypyrrole, and simulate the hydrogen storage capacity of aggregates of three-dimensional polyphenylene dendrimers. Content Type Journal Article Pages 441-449 DOI 10.3233/JCM-2002-23-420 Authors Fabrizia Negri, Universita' di Bologna, Dipartimento di Chimica ‘G. Ciamician’, Via F. Selmi, 2 40126 Bologna, Italy Emanuela Emanuele, Universita' di Bologna, Dipartimento di Chimica ‘G. Ciamician’, Via F. Selmi, 2 40126 Bologna, Italy Aurora Calabretta, Universita' di Bologna, Dipartimento di Chimica ‘G. Ciamician’, Via F. Selmi, 2 40126 Bologna, Italy Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: In this paper we describe developed grid tools for qunatum chemical and biomolecular applications. We have used Unicore infrastructure as framework for development dedicated user interface to the Gaussian98, Amber 6.0, Car-Parrinello Molecular Dynamics Code as well as interface to Protein Data Bank. The user interface is integrated with the UNICORE client based on plugin mechanism which provides general grid functionality such as single login, job submission and control mechanism. Content Type Journal Article Pages 369-375 DOI 10.3233/JCM-2002-23-410 Authors Jaroslaw Pytliński, ICM Warsaw University, Pawińskiego 5a, 02-106 Warsaw, Poland Łukasz Skorwider, ICM Warsaw University, Pawińskiego 5a, 02-106 Warsaw, Poland Valentina Huber, Research Center Jülich, D-52425 Jülich, Germany Michał Wroński, Faculty of Mathematics and Computer Science, N. Copernicus University, Chopina 12/18, 87-100 Toruń, Poland Piotr Bała, Faculty of Mathematics and Computer Science, N. Copernicus University, Chopina 12/18, 87-100 Toruń, Poland Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Time-dependent, quantum mechanical values of the reactive probability for the Li + HF(v = 0, j = 0) → LiF + H system have been calculated for a sufficiently extended interval of energy. From these values estimates of the reactive cross section were obtained using an energy shifting model. A comparison of theoretical predictions with experimental data is also given. Content Type Journal Article Pages 361-367 DOI 10.3233/JCM-2002-23-409 Authors Valentina Piermarini, Dipartimento di Chimica, Università di Perugia, Perugia, Italy Stefano Crocchianti, Dipartimento di Chimica, Università di Perugia, Perugia, Italy Antonio Laganà, Dipartimento di Chimica, Università di Perugia, Perugia, Italy Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Natural Computing is a general term referring to computing going on in nature and computing inspired by nature. When complex phenomena going on in nature are viewed as computational processes, our understanding of these phenomena and of the essence of computation is enhanced. In this way one gains valuable insights into both natural sciences and computer science. Ciliates, a very ancient group of single cell organisms, have evolved extraordinary ways of organizing, manipulating and replicating their DNA. The way that ciliates transform genes from their micronuclear (storage) form into their macronuclear (expression) form, called gene assembly, is very interesting from the computational point of view. Current research in gene assembly is an example of flourishing interdisciplinary research involving computer scientists and molecular biologists. This paper discusses (in tutorial fashion) some central ideas of this research. Content Type Journal Article Pages 343-349 DOI 10.3233/JCM-2002-23-407 Authors G. Rozenberg, Leiden Institute of Advanced Computer Science, Leiden University, The Netherlands Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: We discuss a prototype of a Problem Solving Environment for an a priori Molecular Simulator for the study of Chemical reactivity implemented on a computational Grid. The Environment is implemented using Web technologies and makes use of Freesoftware packages. Content Type Journal Article Pages 377-383 DOI 10.3233/JCM-2002-23-411 Authors Osvaldo Gervasi, Department of Mathematics and Informatics, University of Perugia, via Vanvitelli, 1, I-06124 Perugia, Italy Antonio Laganà, Department of Chemistry, University of Perugia, via Elce di Sotto, 8, I-06123 Perugia, Italy Francesco Sportolari, CASI, University of Perugia, via G.Duranti 1/A, I-06125 Perugia, Italy Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Energy minimized even-tempered basis sets for 4-component relativistic quantum chemical calculations have been derived for Kr, Xe, and Rn. In order to reach the same accuracy as previously derived double zeta basis sets, a considerably larger number of functions is needed for the even-tempered sets. The even tempered sets are also unsuited for dual family type basis sets. Content Type Journal Article Pages 335-341 DOI 10.3233/JCM-2002-23-406 Authors Knut Fægri, Laboratoire do Physique Quantique, IRSAMC, Universite Paul Sabatier, 118 Route de Narbonne, F - 31062 Toulouse CEDEX, France Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: In this paper we have reported the results of theoretical investigations at the DFT level on the mechanism of some representative organometallic reactions. In all cases the non-local hybrid B3LYP functional has been used. The reactions examined here are: (a) the cyclopropanation reactions promoted by transition metal complexes and (b) the nickel-catalyzed carbonylation reactions. In the former case we have considered in details the Simmons-Smith reaction and the cyclopropanation promoted by palladium complexes. It has been found that the active cyclopropanating reagent is always a carbenoid species [L]-M-CH 2 -X (I., X = ligands) and that the cyclopropanation promoted by palladium complexes proceeds either via a concerted mechanism or a multi-step mechanism involving palladacyclobutane intermediates. For the carbonylation reactions we have examined in details the mechanism of the insertion of a CO molecule into a nickel-carbon bond. This step corresponds to a complicated process involving either four-coordinated or five-coordinated nickel complexes. Content Type Journal Article Pages 319-333 DOI 10.3233/JCM-2002-23-405 Authors Andrea Bottoni, Dipartimento di Chimica “G.Ciamician”, Universita' di Bologna, via Selmi 2, 40126 Bologna, Italy Fernando Bernardi, Dipartimento di Chimica “G.Ciamician”, Universita' di Bologna, via Selmi 2, 40126 Bologna, Italy Gian Pietro Miscione, Dipartimento di Chimica “G.Ciamician”, Universita' di Bologna, via Selmi 2, 40126 Bologna, Italy Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: The last couple of years it lias become more and more clear that lateral interactions (interactions between adsorbates) play an important role in the kinetics of surface reactions. We work on the determination of these interactions, and on methods to predict the kinetics including these interactions. Our main method is Dynamic Monte Carlo. With this method we can simulate all reactions on a surface with between 10 4 and 10 8 reactive sites for about 10 2 -10 3 seconds. The simulations yield predictions of the kinetics that are exact for a given model of the surface reactions. As input we need rate constants (prefactors and activation energies) and lateral interactions. These are either obtained by fitting to experimental results or by calculating them using Density-Functional Theory. We use Evolutionary Computation methods to vary and optimize the kinetic parameters when fitting to experiments. Content Type Journal Article Pages 351-359 DOI 10.3233/JCM-2002-23-408 Authors A.P.J. Jansen, Schuit Institute of Catalysis, ST/SKA, Eindhoven University of Technology P. O. Box 513, 5600 MB Eindhoven, The Netherlands W.K. Offermans, Schuit Institute of Catalysis, ST/SKA, Eindhoven University of Technology P. O. Box 513, 5600 MB Eindhoven, The Netherlands Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: Ab initio Density Functional Theory calculations are presented on cyclization and hydrogen abstraction reactions of various polycyclic aromatic hydrocarbons (PAH) which are important for numerous applications. Attention is focussed on the influence of the local structure of the cluster on the reactivity of these elementary radical processes. This is done by calculating the kinetic parameters by means of Transition State Theory. For ring-closure reactions the activation energies are largely affected by the local structure of the polycyclic aromatic hydrocarbon. The variations can be explained in terms of the aromaticity of the reactants and steric hindrance between the attacking radical and the substrate. The aromaticity of the various PAHs can be efficiently probed by various magnetic properties (proton chemical shifts, magnetic susceptibilities and nuclear-independent chemical shifts (NICS)). A correlation is found between the variations in aromaticity during a chemical reaction and the reaction barrier. Reaction barriers for hydrogen abstraction reactions are quite insensitive for the local PAH structure. Variations in the preexponential factor must be attributed to the presence of low vibrational internal rotations or various bending modes in the clusters. Content Type Journal Article Pages 315-318 DOI 10.3233/JCM-2002-23-404 Authors V. Van Speybroeck, Laboratory of Theoretical Physics, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium K. Hemelsoet, Laboratory of Theoretical Physics, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium M. Waroquier, Laboratory of Theoretical Physics, Ghent University, Proeftuinstraat 86, B-9000 Gent, Belgium G.B. Marin, Laboratorium voor Petrochemische Techniek, Ghent University, Krijgslaan 286-S5, B-9000 Gent, Belgium Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 2 Journal Issue Volume 2, Number 3-4 / 2002

Description: A binary system in solid solution when is quenched at a temperature under the solubility limit, shows a structural instability that disappears when said system reaches equilibrium. In the process of reaching stability, a number of microstructural modifications or fluctuations in concentration occur, which tend to generate a decrease in the free energy of the system. Critical fluctuations arise, prompting the association of critical size clusters, from which the growth of the phases responsible for final equilibrium is produced. Such proposal falls completely under the nucleation and growth theory where the first stage – before critical fluctuation appears, occurs at nucleation, whereas the latter stage corresponds to growth and coalescence of the clusters. The evaporation and condensation theory has been adapted so that the process of phase transformation is simulated while considering different evolution pathways from solid solution to the phase of equilibrium. Because the nucleation phase is energetically unstable, it is characterized by each cluster in that stage, while every cluster in the metastable or stable growth phase is grouped via the corresponding transformed fraction, which includes every metastable or stable cluster formed for a given aging time and temperature, thus allowing phase transformation to be expressed as one equation per phase plus the nucleation equations instead of an equation per cluster of different size. This paper expands on the calculation of the problem, determining the effect of the different parameters affecting phase kinetics in the Fe-C system for very low concentrations of C. Content Type Journal Article Pages 179-194 DOI 10.3233/JCM-140495 Authors M. Gómez, Grupo de Física de Metales, Dpto. de Física, Escuela de Ciencias, Núcleo de Sucre, Universidad de Oriente, Cumaná, Venezuela N. Luiggi A., Grupo de Física de Metales, Dpto. de Física, Escuela de Ciencias, Núcleo de Sucre, Universidad de Oriente, Cumaná, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: The structure graphene has a semiconductor character, however this property can be modified by the incorporation of defects produced by desorption of carbon atoms or adsorption on the surface metals. Therefore has an importance in areas of catalysis, new generations of batteries and nanoelectronics. This work was done through a theoretical study of graphene with defects and its variation in the electrical conduction. The optimized circumcoronene formed the basis for the molecules with vacancies and doped with transition metals: Fe and Cu. Calculations were made using the B3PW91 hybrid functional theory of the density and the LANL2DZ basis set. In all forms is calculated NBO electrical charges, energy gap value, geometric parameters, electrostatic potential to the last occupied molecular orbital and determined the stability of the structures by adsorption energies for metals and the desorption for vacancy defects. All structures showed a decreasing in the gap compared to the pristine and depend on their position and the capacities of graphene in stabilize the imperfection. Content Type Journal Article Pages 207-217 DOI 10.3233/JCM-140497 Authors S. Dasilva, Laboratorio de Física de Metales, Departamento de Física, Escuela de Ciencias, Universidad de Oriente, Cumaná, Venezuela R. López-Planes, Laboratorio de Física de Metales, Departamento de Física, Escuela de Ciencias, Universidad de Oriente, Cumaná, Venezuela R. Carreño, Laboratorio de Física de Metales, Departamento de Física, Escuela de Ciencias, Universidad de Oriente, Cumaná, Venezuela E. Franco, Laboratorio de Física de Metales, Departamento de Física, Escuela de Ciencias, Universidad de Oriente, Cumaná, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: The elimination kinetics study of 2,4-dimethyl-2,4-pentanediol in gas phase at 440°C has been carried out using ab initio MP2 method with 6-31G, 6-31G(d), 6-31G(d,p), 6-31+G(d,p), 6-311G(d) and 6-311G(d,p) basis functions set to explore the possibility of determining a possible concerted process with a six-membered cyclic transition state (TS). Vibrational frequencies analysis was realized in order to confirm the reactant, TS and products structures. The nature of these chemical species is examined in terms of geometrical parameters and of the charge density on the TQAIM analysis. IRC calculations have been performed in order to verify that localized TS structure connect with the corresponding minimum stationary points of the reactant and products. With the aim of corroborating the reaction mechanics postulated by Chuchani et al. [1] in their experimental work, we present a theoretical study in order to calculate the rate constant and the activation parameters. Results from MP2/6-311G(d,p) method was found to be in better agreement with the experimental values of the A-factor Arrhenius, activation energy and, activation enthalpy. However, at these levels of theory, it was not possible to reproduce the experimental values of the rate constant and, activation entropy. Content Type Journal Article Pages 195-205 DOI 10.3233/JCM-140496 Authors E. Echeverría, Lab de Química Computacional, Dpto de Química, Facultad de Ciencias y Tecnología, Universidad de Carabobo, Valencia, Venezuela J.A. Guaregua, Lab de Química Computacional, Dpto de Química, Facultad de Ciencias y Tecnología, Universidad de Carabobo, Valencia, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: The effect of the pre-adsorption of sulfur on the hexagonal-Mo_{2}C-(001) surface in the hydrodechlorination (HDC) reaction of chlorobenzene was studied using density functional theory (DFT) calculations. The results related with the coordination modes and the adsorption energies of the aromatic molecule suggest that the main effect of the sulfur incorporation into the surface is to lead towards a weaker chlorobenzene adsorption that will benefit the continuity of the catalytic cycle and therefore to avoid the carbonization and chlorination of the catalyst. The study of the HDC mechanism was also performed and two different reaction paths were considered. The calculated energy barriers indicate that both mechanisms may occur at the normal reaction temperature (350°C). These latter approaches involve new roles of the superficial sulfur as atomic or radical hydrogen scavenger for the S-Hformation and as a precursor of the σ chlorobenzene coordination, necessary for effective hydrogenation in the proposed mechanisms. Content Type Journal Article Pages 169-177 DOI 10.3233/JCM-140494 Authors Milagros Velásquez, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Alba B. Vidal, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Anelisse Bastardo, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Raquel del Toro, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Jesús Rodríguez, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Rafael Añez, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Paulino Betancourt, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Joaquín Brito, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Yosslen Aray, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela David S. Coll, Instituto Venezolano de Investigaciones Científicas,Centro de Química, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: This paper deals with the problem of evaluating the predictive and extrapolative ability of QSPR models by using the PaDEL-descriptor software. In this sense, the selections of training and external data sets were modified considering the molecular weight. Two criteria were used to evaluate the extapolative ability: high correlation factor (R^{2}) (criterion I) and positive ΔR^{2} and high R^{2} (criterion II). Based on internal and external validation, it is shown that criterion II has a better performance than criterion I. Other selection criteria were found by considering the maximum square correlation coefficient (Q_{ext}^2) or the minimum standard deviation (σ_{ext}) for the external set with high R^{2} values. These facts are supported by a systematic variation of the correlation factor (VCF) and the variation of correlation coefficients (VCC), as analysis tools proposed in this article. The methodology was successfully applied to critical temperature (Tc) estimation of linear alkanes and aromatic compounds, considering extrapolation to the heaviest compounds. Descriptors obtained for studied cases, using the criterion II, are in some way in agreement with group contribution and QSPR methods from literature. Content Type Journal Article Pages 155-167 DOI 10.3233/JCM-140493 Authors Alexander R. Peraza, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Laura Rojas, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Carín Bolívar, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Fernando Ruette, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: The objective of this contribution was to explore the effect of thermodynamic model selection on predicting the solubility of hydrogen in Pyrolysis Gasoline (PYGAS). In order to do this, different combinations of cubic equations of state (EOS), cohesion functions and mixing rules were compared, using both own algorithms and those implemented in the PRO/II 8.0 process simulation software. The models were selected following the recommendations made by some authors for H_{2} + hydrocarbons systems similar to the studied here. The cubic EOS of Redlich-Kwong (RK) and Peng-Robinson (PR) were considered using: five different cohesion functions, and the classical quadratic mixing rule (CQMR) with five single correlations to estimate the binary interaction parameters (BIP). Additionally, the system was simulated with PRO/II employing the Panagiotopoulos-Reid Modified (PA-RE-Mod) and the modified PA-RE mixing rule implemented by SimSci. The results were validated with experimental data reported in the literature for four temperatures 298 K, 313 K, 323 K, 343 K and pressures up to 6 MPa. The model composed by the RK EOS, Soave (1993) cohesion function, the CQMR with the BIP calculated with the Gray et al. correlation is the recommended selection to predict the solubility of H_{2} in PYGAS, under the considered conditions, with a 3.1% AARD (average absolute relative deviation). Content Type Journal Article Pages 137-153 DOI 10.3233/JCM-140492 Authors Mixef Rojas, Coordinación de Ingeniería Química, Universidad Simón Bolívar, Caracas, Venezuela Freddy Figueira, Grupo TADiP, Departamento de Termodinámica y Fenómenos de Transferencia, Universidad Simón Bolívar, Caracas, Venezuela Susana Zeppieri, Grupo de Fenómenos de Transporte GFT-10, Departamento de Termodinámica y Fenómenos de Transferencia, Universidad Simón Bolívar, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: Content Type Journal Article Category Editorial Pages 1-2 DOI 10.3233/JCM-140499 Authors Fernando Ruette, Centro de Química, Instituto Venezolano de Investigaciones Científicas, IVIC, Caracas, Venezuela Anibal Sierralta, Centro de Química, Instituto Venezolano de Investigaciones Científicas, IVIC, Caracas, Venezuela Morella Sánchez, Centro de Química, Instituto Venezolano de Investigaciones Científicas, IVIC, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: Quantum chemistry calculations were done, using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on Au_{5}/SAPO-11, Au_{6}/SAPO-11, CO-Au_{5}/SAPO-11 and CO-Au_{6}/SAPO-11 aggregates to analyze the geometries of small clusters of Au_{5} and Au_{6} on SAPO-11 support. Au_{5} cluster presents a pentagonal structure in Au_{5}/SAPO-11. Au_{6} aggregate shows a "multi triangular" structure (as from a trapezoidal "W shaped" Au_{5}) in Au_{6}/SAPO-11. Au_{5} is also obtained as an "X shaped" structure. Similarly another Au_{6} aggregate configuration is obtained also multi triangular but as from X shape Au_{5} cluster. The CO interaction with Au_{5} and Au_{6}/SAPO-11 is studied. The formation energy ΔE_{F} of the aggregates, the CO adsorption energy ΔE_{ads} on them and CO frequency are presented. Content Type Journal Article Pages 45-52 DOI 10.3233/JCM-130483 Authors Beulah Griffe, Labs. Química Computacional y Fisicoquímica de Superficies, Centro de Química, IVIC, Caracas, Venezuela Joaquín L. Brito, Labs. Química Computacional y Fisicoquímica de Superficies, Centro de Química, IVIC, Caracas, Venezuela Anibal Sierraalta, Labs. Química Computacional y Fisicoquímica de Superficies, Centro de Química, IVIC, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: In this paper we study the manifestations of cooperative effects in the formation of supramolecular synthons observed in some thiohydantoin derivatives crystals. Energetic and structural properties were analyzed from the fully optimized clusters employing a DFT/B3LYP level of calculations, which reproduce the main features of the stereochemistry and geometries of the synthons exhibited by reported crystalline structures. The calculations performed in this work have also evidenced that the cluster stabilization is mainly due to the existence of strong cooperative effects, which display energetic as well as geometrical manifestations. The stabilization energy and stabilization energy per monomer, that comprises all the intermolecular interactions between the individual molecules that form the clusters, were computed, showing that the supramolecular clusters of 5-sec-butyl-2-tioxoimidazolidin-4-one is less stable than the compound 5-isopropyl-2-tioxoimidazolidin-4-one by 1.16 Kcal/mol. Finally, through this work it has been also evidenced the need of employing large basis sets, including polarization and diffuse effects, in order to properly model all the interactions existing in systems bonded by weak interactions. Content Type Journal Article Pages 5-16 DOI 10.3233/JCM-140480 Authors Luis E. Seijas, Laboratorio de Procesos Dinámicos en Química, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida, Venezuela Rafael Almeida, Laboratorio de Procesos Dinámicos en Química, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida, Venezuela Asiloé J. Mora, Laboratorio de Cristalografía, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida, Venezuela Gerzon E. Delgado, Laboratorio de Cristalografía, Departamento de Química, Facultad de Ciencias, Universidad de Los Andes, Mérida, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: The additament of an impurity to a metal matrix generates a shift in the local electron density of states due to a change in the local electric potential so that an electron or electron beam will be scattered upon interaction with the ensuing potential, causing its wave function measured at a distance far removed from the source to show a quantum phase change. This phenomenon, reflected in Friedel's law, permits to relate the quantum phase shifts with both the density of states at the Fermi level and the transport properties of the system. This work calculates the electric resistivity of nanometric clusters in an aluminiumsupercell, emulating the formation of Guinier-Preston zones during pre-precipitation in an Al-Zn alloy. The density of states is evaluated each time a new atom of solute is added to the Al supercell using the ab initio method of the Density Functional Theory or DFT in its GGA and LDA approximations via the Dmol^{3} package of Materials Studio Software. A resistivity anomaly is obtained when, in concordance with literature reports for diluted AlZn alloys, the supercell contains 25 atoms, thus confirming that the electric resistivity anomaly during cluster formation is a consequence of both density of states variations and quantum transitions at the Fermi Level for a nanometric size in particular. The results are contrasted with those obtained via the transport equation. Content Type Journal Article Pages 29-43 DOI 10.3233/JCM-140482 Authors Diego Subero, Grupo Física de Metales, Dpto de Física, Núcleo de Sucre Cumaná, Universidad de Oriente, Venezuela Ney Luiggi, Grupo Física de Metales, Dpto de Física, Núcleo de Sucre Cumaná, Universidad de Oriente, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: A three-phase fixed-bed reactor for selective hydrogenation of butadiene in liquid phase with toluene as solvent is modeled using published kinetics. Thermodynamic and transport properties are estimated from models and correlations available in the literature. The model incorporates momentum and energy balances and mass transfer resistances. The results show that use of toluene increases the yield of cis-butane and trans-butane isomers by comparison with a previous study by Bressa et al. where a solvent was not included. The effects of temperature, pressure, hydrogen/butadiene ratio and toluene/feed ratio on the reactor performance are studied. A temperature rise of 37.8 K and a pressure drop of 100 kPa are predicted for a reactor 1 m in length and 0.58 m in diameter using a typical feed composition. Greater reactor lengths result in complete vaporization of the reacting mixture. This vaporization effect can be controlled by increasing the inlet pressure and toluene/feed ratio, and by decreasing the inlet temperature and hydrogen/butadiene ratio. The effect of inlet hydrogen/butadiene ratio is found to be negligible, whereas a rise in inlet temperature rise has a significant effect on the conversions and yields for the same reactor length. Finally, it was found that the yield of 1-butene increases with increasing inlet solvent/feed ratio and pressure. Content Type Journal Article Pages 103-119 DOI 10.3233/JCM-140488 Authors D.E. Pérez Vilela, Thermodynamics and Transport Phenomena Department, Simón Bolívar University, Caracas, Venezuela C. Olivera Fuentes, Thermodynamics and Transport Phenomena Department, Simón Bolívar University, Caracas, Venezuela S. Curbelo, Thermodynamics and Transport Phenomena Department, Simón Bolívar University, Caracas, Venezuela M.J. Rodríguez, Thermodynamics and Transport Phenomena Department, Simón Bolívar University, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: This paper implements a digital algorithm that allows the segmentation and skeletonization of digital images, this method is particularly important in the processing of retinographies where fundus analysis enables early detection of diseases such as diabetic retinopathy. The algorithm implemented using the Fourier transforms of two-dimensional Gabor and with the aid of conventional filters. The performance of the algorithm implemented under the Matlab mathematical platform has been compared with conventional methods resulting in obtaining filtered images with better contrast and higher resolution. Content Type Journal Article Pages 219-225 DOI 10.3233/JCM-140498 Authors Ronald Perez, Guajira University, Riohacha, Colombia William Lasso, Popular University of Cesar, Cesar, Colombia Carlos Jimenez, Applied Mathematics Group (GIMA), Guajira University, Riohacha, Colombia Lorenzo Mattos, Optics and Informatics Group (LOI), Popular University of Cesar, Cesar, Colombia Cesar O. Torres, Optics and Informatics Group (LOI), Popular University of Cesar, Cesar, Colombia Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: In this work, we study the interaction between OH radicals with black carbon (BC) modeled by a coronene molecule by means of quantum chemistry calculations MOPAC, DeMon-nano, DeMon2K packages with the purpose of understand the aging process of this material. Results show that strong OH radical adsorption is preferred on border sites than on center ones, independently of the theoretical method employed. Results of potential energy curves for OH adsorption show that a chemisorption state may occur with small barrier slower than 3.2 kcal/mol. At the center site a physisorbed state may take place. Once OH chemisorption happens, a dipole moment is created and the hydrophobic coronene surface is transformed to hydrophilic. For that reason water molecules are stabilized in the hydroxylated coronene surface by O^{…}H interactions. Chemisorption of many OH radicals, especially at edge sites, produces coronene hydroxylation that after subsequent OH attacks would lead to H abstractions directly from coronene and from chemisorbed OH. The last feature yield a C-C bond breaking at the coronene edge and the formation of hydroxyl and carboxylic groups. Both reactions were confirmed with DFT calculations using coordinates obtained by PM6. Small reaction barriers in both processes were found. From these preliminary results, it is concluded that a detailed modeling of OH interactions with a coronene molecule may shed some light in the formation of volatile oxygenate compounds and therefore the BC aging in the atmosphere. Content Type Journal Article Pages 81-91 DOI 10.3233/JCM-140486 Authors Laura Rojas, Laboratorio de Química Computacional, Centro de Química, IVIC, Caracas, Venezuela Tibisay Pérez, Laboratorio de Química Atmosférica, Centro de Química, IVIC, Caracas, Venezuela Loreto Donoso, Laboratorio de Química Atmosférica, Centro de Química, IVIC, Caracas, Venezuela Alexander Peraza, Laboratorio de Química Computacional, Centro de Química, IVIC, Caracas, Venezuela Fernando Ruette, Laboratorio de Química Computacional, Centro de Química, IVIC, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: The electronic properties of Al-Ti intermetallics are receiving great attention in the specialized literature because these alloys present excellent mechanical performance at high temperatures. This consideration prompted our DFT-LDA and DFT-GGA ab initio study on electronic band structures, density of states, contour plots, Fermi Surface, Bulk modulus, and cohesive energy of intermetallics Al_{3}Ti, AlTi, and AlTi_{3} using the FP-LAPW method. The band structure confirms their electrical conductivity, AlTi_{3} featuring a highly localized band associated to Ti 3d electrons around the Fermi level, not observed in the others. The DOS around the Fermi level is dominated by interactions between Al 3p and Ti 3d orbitals, whereas Al 3s and Ti 3d orbital interactions prevail in the regions of low and high energies, respectively. The density pseudogap in AlTi_{3} is located very close to the Fermi Level, granting a greater structural stability to this system. The Fermi Surface of these intermetallics, for which the authors found no previous reference in the literature, is reported. The difference in density distribution for the LDA and GGA methods is reflected in the contour plots. The Bulk modulus and cohesive energy values reported are in agreement with those reported in the literature. Content Type Journal Article Pages 53-71 DOI 10.3233/JCM-130484 Authors F. Pabel J. Machado, Grupo de Física de Metales, Dpto. de Física, Escuela de Ciencias, Núcleo de Sucre, Universidad de Oriente, Venezuela. E-mail: p.j.001@hotmail.com, nluiggi51@gmail.com Ney Luiggi A., Grupo de Física de Metales, Dpto. de Física, Escuela de Ciencias, Núcleo de Sucre, Universidad de Oriente, Venezuela. E-mail: p.j.001@hotmail.com, nluiggi51@gmail.com Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: We theoretically study the impact of an external noise on a kinetic mean-field model for the bistable catalytic CO oxidation on Pd(111) surfaces. A spatially homogeneous Gaussian white noise is imposed on the fraction of CO in the constant gas flow directed at the surface and the resulting stochastic system is analyzed by a set of Langevin equations. Using an adiabatic elimination technique, we are able to analyze the interplay between the noise and the kinetic bistability reported for this surface reaction in recent experimental studies. The analytical results predict a strong impact on the bistability phase diagram. The stochastic effects are analyzed by computing stationary solutions of the probability distribution functions and the transition times between the active and inactive states of the bistable region. We also introduce an effective potential description that allows us to analyze the impact of noise. Content Type Journal Article Pages 17-28 DOI 10.3233/JCM-130481 Authors Miguel Pineda, Department of Physics, Universidad Simón Bolívar, Caracas, Venezuela Raúl Toral, Instituto de Física Interdisciplinar y Sistemas Complejos (CSIC-UIB), Palma de Mallorca, Spain Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: We apply kinetic Monte Carlo simulations to study the catalytic oxidation of CO on a surface in the presence of contaminants in the gas phase. The dynamic behavior of the process is simulated by models based on the Ziff-Gulari-Barshad model (ZGB). We analyze three ways in which the entrance mechanism of the oxygen atoms can be modified such that the unphysical oxygen poisoned phase that characterizes the ZGB model disappears. We study the behavior of these models in the presence of impurities in the gas phase. Once on the surface, the impurities cannot be desorbed and do not react. We calculate the phase diagrams of the three cases for different percentages of impurities and study the behavior of the CO_2 production. We found that the non-desorbing impurities have the effect of eliminating the discontinuous phase transition to a CO poisoned phase, and that in the steady state there is no production of CO_2. However in the transient phase there can be an important CO_2 production that depends on the model. Content Type Journal Article Pages 73-80 DOI 10.3233/JCM-140485 Authors G.M. Buendía, Department of Physics, Universidad Simón Bolívar, Caracas, Venezuela G.A. Elcure, Department of Physics, Universidad Simón Bolívar, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: A detailed study of the interactions leading to stabilization of the NH_{3}(H_{2}O)_{n =1,2} clusters is presented in this work. The Potential Energy Surface for the trimers was explored using an adapted version of the simulated annealing optimization procedure that produced cluster candidate structures that were further optimized, refined, and characterized at the MP2/6–311++G(d, p) level. Our results indicate that hydrogen bonding of the N…H type is stronger and more covalent than of the O…H type. We provide evidence that suggests that the topological complexity of the electron distributions is directly correlated with cluster stability and that most of the stabilization energy originates in electrostatic and exchange contributions. Our calculated trimerization enthalpy, ΔH^°_{298} −41.75 kJ/mol, is in excellent agreement with the experimental enthalpy of adsorption of NH_{3} into surface water, reported to be − (41 ± 5) kJ/mol. Content Type Journal Article Pages 93-102 DOI 10.3233/JCM-140487 Authors Doris Guerra, Grupo de Química – Física Teórica, Instituto de Química, Universidad de Antioquia, Medellín, Colombia Jorge David, Escuela de Ciencias y Humanidades, Departamento de Ciencias Básicas, Universidad Eafit, Medellín, Colombia Albeiro Restrepo, Grupo de Química – Física Teórica, Instituto de Química, Universidad de Antioquia, Medellín, Colombia Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: In this study, we carried out two-layer ONIOM(DFT:MM) calculations to determine the adsorption enthalpies and vibrational frequencies of NO and CO molecules, on palladium exchanged zeolite (Pd/ZSM-5) catalyst. The results reveal that the local Al distribution near to Pd^{+2} influence the stretching frequencies as well as the adsorption enthalpies. The nine possible Al distributions studied can be gathered in two groups. One responsible for high CO and NO frequencies (ε_{CO}= 2146 cm^{-1} and ε_{NO}= 1880 cm^{-1}) and the other one responsible for the low frequencies (ε_{CO} = 2127 cm^{-1} and ε_{NO}= 1840 cm^{-1}). In general, the adsorption enthalpy of the CO is similar to the NO therefore; there is not a preferential adsorption of CO over the NO molecule. Content Type Journal Article Pages 121-130 DOI 10.3233/JCM-140490 Authors Anibal Sierraalta, Laboratorio de Química Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Rafael Añez, Laboratorio de Química Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Dianela Rincón, Laboratorio de Química Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: In this paper we introduce AIM-UC, a free application that allows to create graphs related to Quantum Theory of Atoms in Molecules (QTAIM). The input data are files that contain 3D grid of electron density, in some known formats: CUBE from gaussian, grd from DMol and CHGCAR from VASP. Also it supports wave function files from AIMPAC. The application calculates 2D regular grids (electron densities and its laplacians) in a plane positioned by the user. By using bicubic interpolation and the Newton-Raphson method, the critical points at the plane can be calculated, and the gradient field and molecular graph can also be generated using the Cash-Karp Runge-Kutta method. It also permits plotting the electron density and its negative laplacian on the selected plane. Moreover, for both 2D grids, it is possible to calculate the contour maps using the "Marching Squares" algorithm. This application also permits finding the critical points in the 3D space. The output consist of plain text files and images in PNG, BMP and EPS (encapsulated post script) formats. AIM-UC was programmed in C++, using the GUI toolkit FLTK (fast light toolkit) and OpenGL (open graphic library). Content Type Journal Article Pages 131-136 DOI 10.3233/JCM-140491 Authors D. Vega, Laboratorio de Química Computacional, FACYT, Universidad de Carabobo, Bárbula, Edo. Carabobo, Venezuela D. Almeida, Laboratorio de Química Computacional, FACYT, Universidad de Carabobo, Bárbula, Edo. Carabobo, Venezuela Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 1-3 / 2014

Description: Virtual bioactive molecular design is an important part of modern drug discovery projects. In this regard, molecular docking may be looked upon as a well established in silico approach in structure-based hit/lead development. Stereoelectronic complementary fit of a bioactive ligand with its receptor may be predicted by molecular docking. Generally docking simulations are compromised of two principal steps; search algorithm and a scoring function. Search algorithms explore the ligand-receptor configurational space while scoring functions apply molecular mechanic force fields to estimate the free binding energies of various ligand-enzyme poses. In the present contribution, a new probability factor (PF) was proposed that could successfully enhance the predictability of AutoDock4.2 scoring function with regard to FRET-based BACE-1 inhibitory activities of some organic small molecules. BACE-1 or beta site amyloid precursor protein cleaving enzyme is a major therapeutic target for Alzheimer disease due to its determinant role in pathogenesis of the disease. Content Type Journal Article Pages 315-325 DOI 10.3233/JCM-140506 Authors Nima Razzaghi-Asl, Department of Medicinal Chemistry, School of Pharmacy, Ardabil University of Medical Sciences, Ardabil, Iran Bahram Hemmateenejad, Chemistry Department, Shiraz University, Shiraz, Iran Ahmad Ebadi, Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Sara Shahabipour, Department of Medicinal Chemistry, School of Pharmacy, Ardabil University of Medical Sciences, Ardabil, Iran Ramin Miri, Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: The main goal of this article is to demonstrate the use of the Reduced Differential Transform Method (RDTM). This method has been applied directly without using bilinear forms, Wronskian, or inverse scattering method. Also it is worth pointing out that if the terms of the series increase, the RDTM provides better convergence to the analytical solution. In this paper, this method is used for solving nonlinear coupled MKdV equation with given initial conditions having arbitrary constants. The numerical solutions obtained by RDTM are compared with the known exact solutions by fixing the arbitrary constants and with Adomian Decomposition Method (ADM) in tables as well as in figures. Content Type Journal Article Pages 269-275 DOI 10.3233/JCM-140504 Authors Amit Tomar, Department of Mathematics, DIT University, Dehradun, India Rajan Arora, Department of Applied Science and Engineering, Indian Institute of Technology Roorkee, India Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 14 Journal Issue Volume 14, Number 4-5 / 2014

Description: Consider a planar annulus. A result of Ramm and Shivakumar states that as the inner circle moves toward the outer circle, the principal Dirichlet eigenvalue of the Laplacian decreases. Numerical experiments in that paper clearly verify this result. The purpose of this short note is to fill in a small gap in that paper: the numerical calculation of the principal eigenvalue when the two circles touch. This is a non-trivial numerical problem because the domain has a cusp which is a strong singularity. Adaptive finite element methods have difficulty converging in the presence of such singularities. Our method is to perform a transformation taking the domain to a rectangle, where it is relatively straightforward to compute the principal eigenvalue. We also calculate the minimal (non-zero) eigenvalue of the Neumann problem. Numerically, the Neumann eigenvalue has no such monotonicity property. Content Type Journal Article Pages 433-437 DOI 10.3233/JCM-130479 Authors S.H. Lui, Department of Mathematics, University of Manitoba, Winnipeg, Manitoba, R3T 2N2, Canada. E-mail: luish@cc.umanitoba.ca Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 13 Journal Issue Volume 13, Number 5-6 / 2013

Description: We show simulation techniques that enable to computationally bridge from the atomistic up to the mesoscopic scale. To evaluate the efficiency, we use a phase-field method to simulate symmetric thermal dendrites and start the computation at an early stage of solidification related to nucleation. The early structures are taken from the molecular dynamics method. The proposed techniques allow to simulate three dimensional dendrites from the state of nuclei (≈ 50 Å) up to a size proportional to μ m where ternary side-arms start to grow. Content Type Journal Article Pages 441-454 DOI 10.3233/JCM-130476 Authors Marco Berghoff, Institute of Applied Materials, Karlsruhe Institute of Technology, Karlsruhe, Germany Michael Selzer, Institute of Applied Materials, Karlsruhe Institute of Technology, Karlsruhe, Germany Abhik Choudhury, Institute of Applied Materials, Karlsruhe Institute of Technology, Karlsruhe, Germany Britta Nestler, Institute of Applied Materials, Karlsruhe Institute of Technology, Karlsruhe, Germany Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 13 Journal Issue Volume 13, Number 5-6 / 2013

Description: To obtain the maximum drag profiles for the surface of an object located in unsteady flow, a shape optimization algorithm based on an adjoint method is presented. The adjoint method is based on the Lagrange multiplier method. Using a first variation of the Lagrange function, stationary conditions can be derived. These conditions consist of state equations, adjoint equations, and sensitivity equations with boundary conditions. The sensitivity equations are derived based on the shape derivative and the material derivative. To achieve the optimal shape based on these stationary conditions, a smoothing technique, a constant volume technique, a node relocation technique, the SUPG/PSPG stabilized method, and the GPBi-CG solver are implemented in the shape optimization algorithm. Using this algorithm, under Stokes flow, we can obtain the Pironneau's result found in the literature (where the optimal shape is of the rugby ball type). Under unsteady flow (i.e. for a Reynolds number of 1000), this algorithm can also construct an optimal shape. Compared an initial cylindrical shape, the drag of the optimal shape under constant volume can be increased by about 218% in the case of a Reynolds number of 1000. Content Type Journal Article Pages 461-497 DOI 10.3233/JCM-130478 Authors Kazunori Shinohara, Japan Aerospace Exploration Agency (JAXA), JAXA's Engineering Digital Innovation Center (JEDI), 3-1-1 Yoshinodai, Chuuou, Sagamihara Kanagawa 252 5210, Japan. E-mail: shinohara@06.alumni.u-tokyo.ac.jp Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 13 Journal Issue Volume 13, Number 5-6 / 2013

Description: Parastatistical macroscopic classical systems with distinguishable states (cells) and arranged state occupation (IDA-systems) are considered. In one-dimensional case (IDA1-systems) they are shown to be equivalent to the systems with indistinguishable elements and states (II-systems). In two-dimensional case (IDA2-systems) they require special approach. Their microscopic states are associated with one- and two-dimensional Young diagrams, respectively. Macroscopic states are defined as neighbourhoods of microscopic ones. Explicit expressions for probabilities and entropies of macroscopic states are derived. Analysis of equilibrium states reveals shell-type mechanism of growth for IDA-systems. Content Type Journal Article Pages 501-516 DOI 10.3233/JCM-130474 Authors D.L. Dorofeev, Department of Mathematical Physics, Voronezh State University, Voronezh, Russia A.E. Popova, Department of Mathematical Physics, Voronezh State University, Voronezh, Russia S.V. Elfimov, Department of Mathematical Physics, Voronezh State University, Voronezh, Russia Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 13 Journal Issue Volume 13, Number 5-6 / 2013

Description: We make an endeavor to study and analyze the effect of surface roughness on the performance of a magnetic fluid based squeeze film between conical plates. The lubricant used here is a magnetic fluid and the external magnetic field is oblique to the lower plate. The bearing surfaces are assumed to be transversely rough. The roughness of the bearing surface is modeled by a stochastic random variable with non-zero mean variance and skew-ness. The associated Reynolds' equation is solved with appropriate boundary conditions to get the pressure distribution, which is, then used to obtain the expression for load carrying capacity leading to the computation of the response time. The results are presented graphically as well as in tabular form. It is noticed that although the bearing suffers owing to transverse surface roughness, the load carrying capacity registers an increase in the case of negatively skewed roughness. Even the negative variance causes an increase in the load carrying capacity. It is observed that the reduction in the load carrying capacity induced by the porosity and the standard deviation can be neutralized up to certain extent by the positive effect of the magnetization parameter μ^* with suitable values of the semi-vertical angle ω in the case of negatively skewed roughness. A close scrutiny of some of the results presented graphically makes it clear that the positive effect of variance dominates the effect of the skew-ness whose impact is slightly better than that of the magnetization parameter. It is needless to say that the performance of the rough bearing with the magnetic fluid lubricant is definitely better than the one with conventional lubricant. This article reveals that there is a scope for enhancing the performance of the bearing system considerably by choosing a suitable combination of the magnetization parameter and semi-vertical angle of the cone in the case of negatively skewed roughness especially when negative variance is involved. Content Type Journal Article Pages 419-432 DOI 10.3233/JCM-130475 Authors G.M. Deheri, Department of Mathematics, Sardar Patel University, Vallabh Vidyanagar, Gujarat, India Rakesh M. Patel, Department of Mathematics, Gujarat Arts and Science College, Ahmedabad, Gujarat, India H.C. Patel, Scientific Officer, Gujarat Council on Science and Technology, Gandhinagar, Gujarat, India Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 13 Journal Issue Volume 13, Number 5-6 / 2013

Description: Three-party key exchange protocol is one of the most essential cryptographic technique in the secure communication areas. In this protocol, two clients, each shares a human-memorable password, working with a trusted server, can agree a secure session key. Recently, Lu and Cao proposed a new simple three-party key exchange (S-3PAKE) protocol and claimed that it is not only very simple and efficient, but also can survive against various known attacks. However, Nam et al. pointed out that S-3PAKE is vulnerable to both off-line password guessing attack and undetectable on-line password guessing attack. Based on their finding, Nam et al. proposed an improved method to resolve this weakness. They further claimed that so far no off-line password guessing attack has been successful against their proposed protocol. In this paper, we demonstrate that Nam et al.'s improved protocol, unfortunately, is still vulnerable to an undetectable on-line password guessing attack. We therefore propose a simple and powerful method to address this issue. Which results in an improved three-party key exchange protocol that can protect against an undetectable on-line password guessing attack. Content Type Journal Article Pages 455-460 DOI 10.3233/JCM-130477 Authors Cheng-Chi Lee, Department of Library and Information Science, Fu Jen Catholic University, New Taipei City, Taiwan Chun-Ta Li, Department of Information Management, Tainan University of Technology, Tainan, Taiwan Rui-Xiang Chang, Department of Photonics and Communication Engineering, Asia University, Taichung, Taiwan Journal Journal of Computational Methods in Science and Engineering Online ISSN 1875-8983 Print ISSN 1472-7978 Journal Volume Volume 13 Journal Issue Volume 13, Number 5-6 / 2013