Theoretical investigation of the hydrogen abstraction reaction of the OH radical with CH3CHF2 (HFC152-a): a dual level direct density functional theory dynamics study

The hydrogen abstraction reaction of the OH radical with CH(3)CHF(2) (HFC152-a) has been studied theoretically over a wide temperature range, 200-3000 K. Two different reactive sites of the molecule, CH(3) and CHF(2) groups have been investigated precisely, and results confirm that CHF(2) position of the molecule is a highly reactive site. In this study, three recently developed hybrid density functional theories, namely, MPWB1K, MPW1B95, and MPW1K, are used. The MPWB1K/6-31+G(d,p) method gives the best result for kinetic calculations, including barrier heights, reaction path information and geometry of transition state structures and other stationary points. To refine the barrier height of each channel, a single point energy calculation was performed in MPWB1K/MG3S method. The obtained rate constants by dual level direct dynamics with the interpolated single point energy method (VTST-ISPE) using DFT quantum computational methods, are consistent with available experimental data. The canonical variational transition state theory (CVT) with the zero-curvature and also the small-curvature tunneling correction methods is used to calculate the rate constants. Over the temperature range 200-3000 K, the variation effect, tunneling contribution, branching ratio of each channel are calculated. The rate constants and their temperature dependency in the form of a fitted three-parameter Arrhenius expression are k(1)(T) = 2.00 x 10(-19)(T)(2.24) exp(-1273/T), k(2)(T) = 1.95 x 10(-19)(T)(2.46) exp(-2374/T), and k(T) = 3.13 x 10(-19)(T)(2.47) exp(- 1694/T) cm(3) molecule(-1) s(-1). For the H abstraction from the CHF(2) group, a nonclassical reflection effect is detected as a dominant quantum effect.     

Normal forms application for studying solitary wave solutions of non-integrable evolution systems

In this paper the problem of obtaining soliton-like solutions to the non-integrable evolution system is discussed. Self-similarity methods together with the normal forms technique are shown to provide significant information on the possibility that such solutions appear. Qualitative investigations, backed by the numerical simulation, are applied to a reactive hydrodynamic model. It is evidenced that this model has a one-parameter family of solitary wave solutions. In addition, the expressions for coefficients of the normal form, corresponding to dynamic systems with (0,±iΩ) degeneracy of the linear parts, are obtained.     

Numerical study of laminar pulsed impinging jet on the metallic foam blocks using the local thermal non-equilibrium model

Journal of Thermal Analysis and Calorimetry - In this study, thermal performance of an impingement jet with the presence of porous block is numerically investigated. The study is comprised of two...     

Dirac particle in generalized Pöschl–Teller field including a Coulomb‐like tensor coupling: super‐symmetric solution

In the presence of pseudo‐spin (p‐spin) and spin symmetries, we use the super‐symmetric formalism to solve the Dirac equation with the generalized Pöschl–Teller potential including the Coulomb‐like tensor interaction with any arbitrary spin‐orbit quantum number κ.. Using the Greene–Aldrich usual approximation scheme to deal with pseudo‐centrifugal or centrifugal rotational kinetic energy l (l + 1) ∕ r² or , we obtain the Pseudo‐spin and spin‐symmetric energy eigenvalue equation and the normalized upper and lower components of the radial wave functions in closed form. The presence of the tensor coupling interaction removes the degeneracy in the p‐spin and spin doublets. Copyright © 2013 John Wiley & Sons, Ltd.     

Creation of cluster state of four ions in ion-trap system by individual addressing

The cluster state is a special, highly entangled quantum state that forms the universal resource, on which measurement-based quantum computation can be performed. In this study, a new scheme is presented for creating four-ions cluster state in ion-trap system. This scheme is based on resonant sideband excitation in which the population is transferred to target states by precise control of pulse area. Meanwhile, the scheme is consist of combination of elementary stages belonging to a universal set whereby cluster state has been created in five interaction stages by individually addressed ions with red- or blue-sideband resonance laser pulses. The paper studies the population transfer of the system by numerical solutions of the master equation, considering the effect of decoherence channels due to dissipation in the phonon modes. The presented scheme does not require control of the turn-off ratio and time delay among pulses.     

Centers on center manifolds in the Lü system

We confirm a conjecture of Mello and Coelho [Phys. Lett. A 373 (2009) 1116] concerning the existence of centers on local center manifolds at equilibria of the Lü system of differential equations on R³. Our proof shows that the local center manifolds are algebraic ruled surfaces, and are unique.     

On the coupling of the homotopy perturbation method and Laplace transformation

In this paper, a Laplace homotopy perturbation method is employed for solving one-dimensional non-homogeneous partial differential equations with a variable coefficient. This method is a combination of the Laplace transform and the Homotopy Perturbation Method (LHPM). LHPM presents an accurate methodology to solve non-homogeneous partial differential equations with a variable coefficient. The aim of using the Laplace transform is to overcome the deficiency that is mainly caused by unsatisfied conditions in other semi-analytical methods such as HPM, VIM, and ADM. The approximate solutions obtained by means of LHPM in a wide range of the problem’s domain were compared with those results obtained from the actual solutions, the Homotopy Perturbation Method (HPM) and the finite element method. The comparison shows a precise agreement between the results, and introduces this new method as an applicable one which it needs fewer computations and is much easier and more convenient than others, so it can be widely used in engineering too.