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101.
Hamid Rabah Jacques Guillin Annie Cereze-Ducouret Jean-Marc Greneche Daniel Talham Kamel Boukheddaden Jorge Linares François Varret 《Hyperfine Interactions》1993,77(1):51-66
We have studied by absorption Mössbauer spectroscopy, some bridged derivatives of biferrocene, unoxidized (FeII– FeII) and mono-oxidized (FeII – FeIII). The mixed-valence species exhibits a quasi-delocalized behavior at the Mössbauer timescale (~ 10?8 s), with a splitting of the lines which is interpreted in terms of a partial valence trapping. This in turn reveals intramolecular properties at variance from those of the unbridged cation. SCC-Xα MO calculations have been performed; they correctly reproduce the measured quadruple splittings and provide evidence that the HOMO of the mixed-valence complex is of \(d_{xy} ,d_{x^2 - y^2 } \) type. Some consequences on the mixed-valence properties are discussed. 相似文献
102.
A. R. Greenberg Ihab Kamel 《Journal of polymer science. Part A, Polymer chemistry》1977,15(9):2137-2149
The kinetics of anhydride formation of poly(acrylic acid) (PAA) in porous PAA–alumina composites have been investigated by using a thermogravimetric technique (TGA). Three distinct reaction peaks at 200°C (I), 250°C (II), and 390°C (III) were identified in the dynamic TGA thermogram. These peaks were attributed to bound water removal (I), anhydride formation (II), and polymer degradation (III). The kinetics of the anhydride reaction were studied in a temperature range of 220–240°C and found to follow a second-order mechanism with an activation energy of approximately 38 kcal/mole. In addition, the bound water was found to inhibit the onset of anhydride formation. The degree of conversion to anhydride was correlated with the equilibrium swelling level attained by the composite in water. 相似文献
103.
Mixtures of heavy aromatics with high aliphatics are important in the formation of asphaltenes in the oil industry.This work reports binary solid-liquid equilibria for naphtalene + eicosane, +pentacosane, +hexatriacontane mixtures by differential scanning calorimetry. Results are compared with those from modified UNIFAC (Larsen and Gmehling versions) and ideal predictions. Finally, we determine the purity according to van’t Hoff equation. Results are in good agreement with values given by ultraviolet spectrophotometry. 相似文献
104.
The synthesis of mononuclear cobalt(II/III) complexes with two different ligands (complex 2: [Co(valp)2(2,9‐dmp)] and complex 3: [Co(valp)2(H2O)(1,10‐phen)]) was investigated and the characterization of both complexes was achieved using IR, UV–Vis, and single crystal X‐ray diffraction. Using single crystal X‐ray diffraction, the crystal structure of each of the complexes was determined. Additionally, the biological activity of these complexes was studied in five gram‐positive and four gram‐negative bacterial strains. Whereas in all gram‐negative bacteria tested, cobalt valproate complexes did not show any anti‐bacterial activity, both complexes had effects on gram positive bacteria. Complex 2 demonstrated good anti‐bacterial activity against all gram‐positive bacteria with inhibition zone diameter (IZD) ranging between 15–28 mm. Complex 3 exhibited low inhibition activity against all gram‐positive bacteria except E. faecalis with IZD ranging between 11.3–13.7 mm. Moreover, as an indication of its uses as industrial catalyst, the rate of bis(p‐nitrophenyl) phosphate (BNPP) hydrolysis when catalyzed by these complexes was measured at different temperatures, concentrations and pH. Complex 2 proved to be a better catalyst to induce the hydrolysis of BNPP. 相似文献
105.
Laser welding is an important joining process for magnesium alloys. These materials are being increasingly used in different applications such as in aerospace, aircraft, automotive, electronics, etc. To date, carbon dioxide (CO2) neodymium-doped yttrium aluminum garnet (Nd:YAG) and the high power diode laser have been extensively used to investigate the weldability of magnesium alloys. The present work describes an analytical thermal model for the weldability of magnesium alloys (WE43) using an industrial (CO2) laser source. The main target of the project is to present to the industrial community a simple and rapid tool for the determination of the penetration depth and the bead width as a function of both the incident laser power and welding speed. The proposed model is based on the Davis thermal approach, largely considered for the characterization of the average radius of the liquid zone, aiming at predicting the joint shape. Moreover, since during the welding process considered in this study, a protecting gas is used to avoid joint oxidation, both thermal convection and radiation phenomena in the welding area have been estimated and introduced in our model for a better characterization of the welding process. The obtained results have been compared to the experimental ones and a satisfactory correlation has been observed, indicating the reliability of the model developed in this study. 相似文献
106.
Fuzzy Almost Quadratic Functions 总被引:1,自引:0,他引:1
107.
Abdelmalek Zahra Khan Sami Ullah Waqas Hassan Al-Khaled Kamel Tlili Iskander 《Journal of Thermal Analysis and Calorimetry》2021,144(5):1639-1654
Journal of Thermal Analysis and Calorimetry - The revolution in nanotechnology has made new developments toward enhancement of energy resources which play a substantial role in the growth of... 相似文献
108.
Tabti Hadja Alia Adjdir Mehdi Ammam Abdelkader Mdjahed Baghdad Guezzen Brahim Ramdani Amina Benddedouche Choukry Kamel Bouchikhi Noria Chami Nadir 《Research on Chemical Intermediates》2020,46(12):5377-5390
Research on Chemical Intermediates - A range of Cu-LDHs has been synthesized by co-precipitation using metal nitrate precursors and sodium carbonate under varying molar ratios Cu/Al... 相似文献
109.
Lakaour Lamia Aïssani Djamil Adel-Aissanou Karima Barkaoui Kamel 《Methodology and Computing in Applied Probability》2019,21(4):1395-1406
Methodology and Computing in Applied Probability - In this paper, an M/M/1 retrial queue with collisions and transmission errors is considered. The collision may occur when a primary arriving... 相似文献
110.
Kamel Hamdache 《偏微分方程通讯》2013,38(7):813-845
This work is concerned by the initial and boundary value problem for the Boltzmann equation. Existence in the large and asymptotic behaviour results are proved for small data and general reemission laws. The colisional kernel satisfies the cut—off angular hypothesesand, the intermolecular potential is such that 7/3 <s≤∞ for the Dirichlet case and 7/3 <s≤5for the general case Mot—clés: Equation de Boltzmann— Problèmes aux limites intérieurs et extérieurs — Gaz raréfiés —Condition aux limites de Dirichlet— Conditions aux limites non lináeaires— Existence globale de petites solutions 相似文献