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Nejma F.B.,Institute Preparatoire aux Etudes dIngenieurs | Slimi K.,Institute Superieur Du Transport Et Of La Logistique
Computational Thermal Sciences | Year: 2011

The present paper deals with a numerical simulation of a combined laminar forced convection and radiation in humid air flowing between two vertical plates. The left plate is assumed to be adiabatic and humid while the second is isothermal and dry. The governing set of conservation equations are solved numerically by the classical finite-volume method, while the statistical narrow band k-correlated model (SNBCK4) and the "ray-tracing" method are used to solve the radiative coupling problem. Our numerical results are compared with the most related available published works. Satisfactory agreement was obtained between our results and those of the literature. The effects of ambient conditions, channel width, dry wall temperature, and wall emissivity are also analyzed in this study. © 2011 by Begell House, Inc.


Ben Nejma F.,Institute Preparatoire aux Etudes dIngenieurs | Slimi K.,Institute Superieur Du Transport Et Of La Logistique
High Temperatures - High Pressures | Year: 2010

This work deals with combined natural convection and radiation in a humid air flowing between two-isothermal vertical plates. The governing set of conservation equations in the dimensional form are solved numerically by the classical finite volume method. The radiative coupling problem is solved using the SNBCK4 model. Present solutions are compared with already known results from previous published works. An excellent agreement was obtained between results that validate the used computer code. It is shown that the existence of water vapor, even in small quantities, improves the heat transfer rate and increases considerably the evacuated flow rate. The influence of the wall's temperature, the duct's dimensions as well as the vapor molar fraction on the mean Nusselt number and flow rate is examined and discussed throughout this paper. © 2010 Old City Publishing, Inc.


Awali S.,French National Center for Scientific Research | Awali S.,CEA Saclay Nuclear Research Center | Awali S.,Institute Preparatoire Aux Etudes DIngenieurs | Poisson L.,French National Center for Scientific Research | And 15 more authors.
Physical Chemistry Chemical Physics | Year: 2014

This paper is a joint experimental and theoretical approach concerning a molecule deposited on a large argon cluster. The spectroscopy and the dynamics of the deposited molecule are measured using the photoelectron spectroscopy. The absorption spectrum of the deposited molecule shows two solvation sites populated in the ground state. The combined dynamics reveals that the population ratio of the two sites is reversed when the molecule is electronically excited. This work provides the timescale of the corresponding solvation dynamics. Theoretical calculation supports the interpretation. More generally, close examination of the short time dynamics (0-6 ps) of DABCO⋯Arn gives insights into the ultrafast relaxation dynamics of molecules deposited at interfaces and provides hence the time scale for deposited molecules to adapt to their neighborhoods. © 2014 the Owner Societies.


Salem F.B.,Institute Preparatoire Aux Etudes dIngenieurs | Rhouma M.B.E.H.,Institute Preparatoire Aux Etudes dIngenieurs | Spiegelman F.,CNRS Laboratory for Quantum Chemistry and Physics | Mestdagh J.-M.,French Atomic Energy Commission | Hochlaf M.,University Paris Est Creteil
Journal of Chemical Physics | Year: 2012

The electronic state properties of NaXe are investigated using ab initio methodologies and various pseudopotential approaches for comparison. The spectroscopic terms and dipole moments of the lowest electronic states up to the Na(3d) +Xe dissociation limit are determined. The difference between valence or smaller core pseudopotential on Xe is shown to be negligible and so is the difference between all-electron and valence pseudopotential completed by core-polarization treatments of Na. These calculations are used as references to test the performance of a treatment involving a zero electron pseudopotential description of xenon together with a one-electron pseudopotential description of Na. When compared with the reference calculations, the one-electron model leads to reasonable quantitative results. The potential energy curves and spectroscopic data of all Rydberg excited states of NaXe up the Na(5f)+Xe dissociation limit are determined using this method. Long distance wells and barriers in the range R = 15-40 bohrs are identified for some of the higher states with 2Σ+ symmetry. © 2012 American Institute of Physics.


PubMed | University Paris Est Creteil and Institute Preparatoire aux Etudes dIngenieurs
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2015

At present, we investigate the structure and the stability of NO(+)Arn (n 54) ionic clusters using analytical potential functions. The energy of these systems is described using additive potentials with VNO(+)Ar and VAr-Ar representing the pair potential interactions. To find the geometry of the lowest energy isomers of the NO(+)Arn clusters, we use the so-called basin hopping method of Wales et al. which combines a Monte-Carlo exploration and deformation method. The reliability of our model was checked by deriving the structures of the NO(+)Arn systems (n = 1, 2, 3 and 4) using ab initio Moller-Plesset perturbation theory up to second order (MP2) in connection with the aug-cc-pVTZ basis set. Magic numbers for sizes n = 8, 12, 18, 22, and 25 are found and they show a high relative stability. Our results reveal that a transition in the NO(+) ion coordination from 8 (square antiprism) to 12 (icosahedrons) occurs for n = 11. Examination of the stable structures of the ionic clusters demonstrates that the first solvation shell closes at n = 12. Furthermore, we found that the NO(+)Arn (n = 12-54) clusters are structurally very similar to the homogenous rare gas clusters with a polyicosahedral packing pattern. The distribution exhibits an additional magic number at n = 54, consistent with the completion of a second solvation sphere around NO(+). The effects of microsolvation of NO(+) cation in Ar clusters are also discussed. Generally, our results agree with the available experimental and theoretical findings on NO(+)Arn clusters and more generally on diatomics solvated in Ar clusters.


PubMed | Tunis el Manar University, Institute Preparatoire aux Etudes dIngenieurs, King Saud University and University Paris Est Creteil
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2014

Using ab initio methodology, we studied the IO(q+) (q = 2, 3, 4) multi-charged ions. Benchmark computations on the IO(X(2)) neutral species allow validate the current procedure. For IO(2+), several potential wells were found on the ground and the electronic excited states potentials with potential barriers with respect to dissociation, where this dication can exist in the gas phase as long-lived metastable molecules. We confirm hence the recent observation of the dication by mass spectrometry. Moreover, we predict the existence of the metastable IO(3+) trication, where a shallow potential well along the IO internuclear distance is computed. This potential well supports more than 10 vibrational levels. The IO(3+) excited states are repulsive in nature, as well as the computed potentials for the IO(4+) tetracation. For the bound states, we give a set of spectroscopic parameters including excitation transition energies, equilibrium distances, harmonic and anharmonic vibrational terms, and rotational constants. At the MRCI + Q/aug-cc-pV5Z(-PP) level, the adiabatic double and triple ionization energies of IO are computed to be ~28.1 eV and ~55.0 eV, respectively.


Sole P.,Telecom ParisTech | Sole P.,King Abdulaziz University | Yemen O.,Institute Preparatoire Aux Etudes DIngenieurs
Finite Fields and their Applications | Year: 2012

We present a study of the factorization of the polynomial X m-1 in M2( F2)[X] and we determine the period of any reversible polynomial of this polynomial ring by using skew polynomial rings. These results are applied to the construction of the class of quasi-cyclic codes Ω(P) introduced by Cayrel et al. Furthermore, we present a new construction of the self dual subclass. © 2012 Elsevier Inc.


Gaied W.,University of Monastir | Ben El Hadj Rhouma M.,Institute Preparatoire Aux Etudes dIngenieurs
International Journal of Quantum Chemistry | Year: 2011

The structure and stabilities of Ca2+Arn (n = 1-24) clusters are investigated using analytical potential functions. The energy of the systems, in its ground state, is described using additive potentials with V(Ca2+-Ar) and V(Ar-Ar) representing the pair potential interactions, and many-body effects are described using the interaction between dipoles induced by the calcium ion. To find the geometry of the lowest energy isomers of Ca2+Arn clusters, we use the so-called basin-hopping method of Wales et al. We show that in the equilibrium structures of Ca 2+Arn clusters, the Ca2+ cation is always solvated by argon clusters. For n = 2, we have found a strong competition between the symmetric linear shape (D∞) and the bent isomer (C2v). The relative importance of the three-body interactions due to the presence of the induced dipoles on the Ar atoms can be inferred from the magnitude of the known Ar2 interaction, and lead to a more stabilized linear structure. The global minimum of Ca2+Ar3 is planar (D3h), but a second three-dimensional isomer with a pyramidal C 3v symmetry exists. The absolute minimum of Ca2+Ar 4 is a regular tetrahedron, and that of Ca2+Ar 6, is a regular octahedron. The particularly stable sizes with respect to their immediate neighbors were studied by calculating the second energy difference between size n and its immediate neighbors. © 2009 Wiley Periodicals, Inc.


PubMed | Institute Preparatoire aux Etudes dIngenieurs
Type: Journal Article | Journal: The Journal of chemical physics | Year: 2012

The electronic state properties of NaXe are investigated using ab initio methodologies and various pseudopotential approaches for comparison. The spectroscopic terms and dipole moments of the lowest electronic states up to the Na(3d) +Xe dissociation limit are determined. The difference between valence or smaller core pseudopotential on Xe is shown to be negligible and so is the difference between all-electron and valence pseudopotential completed by core-polarization treatments of Na. These calculations are used as references to test the performance of a treatment involving a zero electron pseudopotential description of xenon together with a one-electron pseudopotential description of Na. When compared with the reference calculations, the one-electron model leads to reasonable quantitative results. The potential energy curves and spectroscopic data of all Rydberg excited states of NaXe up the Na(5f)+Xe dissociation limit are determined using this method. Long distance wells and barriers in the range R = 15-40 bohrs are identified for some of the higher states with (2)(+) symmetry.


PubMed | CEA Saclay Nuclear Research Center and Institute Preparatoire aux Etudes dIngenieurs
Type: Journal Article | Journal: The journal of physical chemistry. A | Year: 2015

Photoabsorption spectra of KArn (n = 1-10) are simulated at temperatures ranging between 5 and 25 K. The calculations associate a Monte Carlo (MC) method to sample cluster geometries at temperature T, with a one-electron ab initio model to calculate the ground-state and excited-state energies of the cluster. The latter model replaces the K(+) core electrons and all the electrons of the Ar atoms by appropriate pseudopotentials, complemented by core polarization potentials. It also provides the necessary oscillator strengths to simulate the spectra. Global optimization by basin-hopping is used in combination with MC simulation at low temperature (5 K) to identify the most stable isomer and remarkable isomers of ground-state KArn clusters, which are stable with respect to deformations of the order of those expected with Zero Point Energy motions. The absorption spectra calculated for each of these isomers at 5 K suggest that absorption spectroscopy can probe sensitively the local environment of K atom: surface location of K with respect to a close-packed Ar moiety, number of Ar atom in close vicinity, and local symmetry about K. Simulation at increasing temperatures, up to the evaporation limit of K out of the cluster, shows the onset of large amplitude motions above 20 K, when the K atom experiences a variety of local environments.

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