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21.
Hafid Anane Soufiane El Houssame Abdelali El Guerraze Abdeladim Guermoune Abderrahim Boutalib Abedellah Jarid Ignacio Nebot-Gil Francisco Tomás 《Central European Journal of Chemistry》2008,6(3):400-403
The complexation energies of H3BNHnCl3−n (n= 3-0) complexes and the proton affinities of NHnCl3−n compounds have been computed at the G2(MP2) level of theory. G2(MP2) results show that the successive chlorine substitution
on the ammonia decreases both the basicity of the NHnCl3−n ligands and the stability of H3BNHnCl3−n complexes. The findings are interpreted in terms of the rehybridisation of the nitrogen lone-pair orbital. The NBO partitioning
scheme shows that the variation of the N-H and N-Cl bond lengths, upon complexation, is due to variation of “s” character
in these bonds.
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22.
Mohamed Nohair Ouafae Britel Nabil Souaf Driss Zakarya Abdelmjid Hafid Noura Mallouk 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1772-1781
We have used a new, robust model mapping technique—a Bayesian-regularized neural network—to develop a quantitative relationships model for the synthesis of the phosphocalcic hydroxyapatite by precipitation from a calcium carbonate solution and a phosphoric acid solution. This model was preformed by using a set of factors consisting on the pH of reactional medium, the Ca/P molar ratio of the reagents, reaction time, and the initial concentration of calcium. The results show that the method is robust and gives satisfied results. The Levenberg–Marquardt's algorithm implemented in the neural network Matlab's toolbox allowed a drastic improvement of the performance of the model. Very satisfactory results are then obtained by testing the validity by cross-validation technique. We have also turned our interests to the explanatory capacities of our methodology to explore the relative contribution and/or the contribution profile of the input factors by using Garson weight portioning method. 相似文献
23.
Yasmina Belaroussi Gilles Scheen Abdelhalim A. Saadi Abdelkader Taibi Djabar Maafri Bernard Nysten Noureddine Gabouze Jean-Pierre Raskin 《Surface and interface analysis : SIA》2020,52(12):1055-1060
The surface topology of porous silicon (PSi) is a relevant parameter that decides the compatibility of such substrate with CMOS process. Using standard resistivity (1–10 Ω·cm) of Si substrate to fabricate PSi-S is a low cost solution for the industry. In this paper, through an atomic force microscopy (AFM) analysis, the root mean square (RMS) roughness, the power spectral density and the correlation length were determined for different PSi layers. Furthermore, the measured hardness, Young's modulus, and stress have been made for different thicknesses of PSi: 5, 10, 50, and 200 μm. The obtained results demonstrated that very interesting properties have been achieved with the 50 μm-thick PSi-S layer with a maximum porosity around 65%, a surface roughness less than 1 nm and a hardness value of (~1 GPa). The realized results encourage the utilization the PSi-based substrate into the industry process and thus the development of a Systems-on-Chip (SoC). 相似文献
24.
Abdelhalim Ebaid 《Journal of Computational and Applied Mathematics》2011,235(8):1914-1924
Based on the Adomian decomposition method, a new analytical and numerical treatment is introduced in this research to investigate linear and non-linear singular two-point BVPs. The effectiveness of the proposed approach is verified by several linear and non-linear examples. 相似文献
25.
For a wedge-like membrane, Payne and Weinberger proved in 1960 an isoperimetric inequality for the fundamental eigenvalue which in some cases improves the classical isoperimetric inequality of Faber–Krahn. In this work, we introduce “relative torsional rigidity” for this type of membrane and prove new isoperimetric inequalities in the spirit of Saint-Venant, Pólya–Szeg?, Payne, Payne–Rayner, Chiti, and Talenti, which link the eigenvalue problem with the boundary value problem in a fundamental way. 相似文献
26.
Ibrahim Abdelhalim AhmedGuido Kastner Hans Reuter Dietrich Schultze 《Journal of organometallic chemistry》2002,649(2):147-151
Reaction of (CH3)2SnF2 with two equivalents of KF in aqueous medium leads to the formation of the complex salt K2[(CH3)2SnF4]·2H2O (1). Its crystal structure was determined by single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group C2 (No. 5) with the lattice parameters a=9.265(1), b=7.556(1), c=7.076(1) Å; β=98.21(1)° and Z=2. The structure is characterized by the anion [(CH3)2SnF4]2− in which the tin atom adopts a slightly distorted octahedral coordination, with the methyl groups in trans position. The potassium cations are pentacoordinated from three fluorine atoms and the oxygen atoms of two water molecules in the form of a distorted square pyramid. In addition, the thermal behavior of the compound was studied with the aid of TG/DSC-measurements coupled with MS, revealing that the dehydration of 1 takes place at 75 °C, with an enthalpy of 57.79 kJ mol−1, and that it decomposes without melting in two further endothermic steps to undetermined phases in the system KF-SnF2-SnF4 and free carbon (∼0.1%). 相似文献
27.
Hafid Sayah 《Comptes Rendus Mecanique》2004,332(2):161-168
The differential inclusion describing the quasi-static motion of a supple, homogeneous and inextensible string on a horizontal plane with dry friction (Coulomb's law) is a one dimensional evolution model of a continuous medium, with non-linear geometry, obeying a “plastic-rigid” law. With a view to numerical simulation, we treat the discrete case: the string is assimilated to a chain constituted by rigid rods perfectly articulated around ball-joints. We give variational formulation of the problem and prove existence and uniqueness of solutions. We construct an algorithm that describes the instantaneous solutions when the initial configuration of the string is given. Then, some examples are treated. To cite this article: H. Sayah, C. R. Mecanique 332 (2004). 相似文献
28.
Salah Daoud Abdelhakim Latreche Abdelhalim Bencheikh 《Crystal Research and Technology》2016,51(1):115-116
In the present work, we have readjusted some empirical parameters obtained by Kumar et al. in their work which contains some numerical errors. 相似文献
29.
Abdelhalim Ebaid 《Applied Mathematical Modelling》2011,35(3):1231-1239
The projectile motion is examined by means of the fractional calculus. The fractional differential equations of the projectile motion are introduced by generalizing Newton’s second law and Caputo’s fractional derivative is considered to use the physical initial conditions. In the absence of air resistance it is found that at certain conditions, the range and the maximum height of the projectile obtained by using the fractional calculus give the same results of the classical calculus. It is also found that, unlike the classical projectile motion, the launching angle that maximizes the horizontal range is a function of the arbitrary order of the fractional derivative α. Moreover, in a resistant medium, the parametric equations are expressed in terms of Mittag-Leffler function and the results agree with those of the classical projectile as α → 2. Moreover, the trajectories of the projectile are discussed in graphs and compared with those of the classical calculus. In order to explore the validity of modelling the projectile motion by the fractional approach, we compared our results with the experimental data of mortar. 相似文献
30.
Saliha Loughmari Abderrafia Hafid Aicha Bouazza Abdelaziz El Bouadili Philippe Zinck Marc Visseaux 《Journal of polymer science. Part A, Polymer chemistry》2012,50(14):2898-2905
Polymerization of β‐myrcene with neodymium borohydride‐based coordination catalysts is very efficient, affording poly‐β‐myrcene (polymyrcene, PMy) with high selectivity. With stoichiometric amounts of n‐butylethyl magnesium (BEM) as co‐catalyst, good control over macromolecular data along with cis‐stereoselectivity up to 98.5%, are obtained. In the presence of excess BEM, high level of transfer reactions efficiency between neodymium and magnesium is clearly evidenced whereas the selectivity switches to 3,4‐rich. Combining the neodymium pre‐catalyst with triisobutyl aluminum in the presence of a boron activator affords PMy in good yield, but the polymer material displays low solubility, likely due to the occurrence of crosslinking. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献