排序方式: 共有7条查询结果,搜索用时 0 毫秒
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Samir Meskaldji Abdelmalik Belkhiri Lotfi Belkhiri Abdou Boucekkine Michel Ephritikhine 《Comptes Rendus Chimie》2012,15(2-3):184-191
Magnetic exchange coupling between uranium U(V) ions, in the case of the two para- and meta-imido diuranium complexes, respectively [(C5H5)3U]2(μ-1,4-N2C6H4) and [(C5H5)3U]2(μ-1,3-N2C6H4) exhibiting the 5f1-5f1 configuration, have been investigated using relativistic DFT calculations, combined with the broken symmetry (BS) approach. Using the B3LYP functional, the singlet BS state of the para complex has been found of lower energy than the high spin (HS) triplet one, in agreement with the observed antiferromagnetic character of the complex. On the contrary the BP86 functional fails to predict this magnetic property. The spin density distributions and MO analysis explain well the antiferromagnetic character of the para complex and clarify the failure of the BP86 functional. The effective participation of the 5f metal orbitals in bonding with the imido ligand plays a key role for electronic and magnetic communication between the two active U(V) 5f1 electrons. The same technique led us to explain the ferromagnetic character of the meta isomer in agreement with experiment. For both isomers the spin polarization mechanism explains well their observed magnetic behaviour. 相似文献
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Abdelmalik Moujahid Alicia d’Anjou Blanca Cases 《Chaos, solitons, and fractals》2012,45(9-10):1171-1179
This work analyzes the problem of community structure in real-world networks based on the synchronization of nonidentical coupled chaotic Rössler oscillators each one characterized by a defined natural frequency, and coupled according to a predefined network topology. The interaction scheme contemplates an uniformly increasing coupling force to simulate a society in which the association between the agents grows in time. To enhance the stability of the correlated states that could emerge from the synchronization process, we propose a parameterless mechanism that adapts the characteristic frequencies of coupled oscillators according to a dynamic connectivity matrix deduced from correlated data. We show that the characteristic frequency vector that results from the adaptation mechanism reveals the underlying community structure present in the network. 相似文献
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Structural,magnetic and thermal characterization of Fe50Se50 powders obtained by mechanical alloying
Chebli Abdelhak Djekoun Abdelmalik Suñol Joan Josep Nižňanský Daniel 《Journal of Thermal Analysis and Calorimetry》2020,140(1):53-62
Journal of Thermal Analysis and Calorimetry - In this paper, Fe50Se50 alloy powders were synthesized from pure elemental powder by mechanical allowing. The structure, microstructure, morphology,... 相似文献
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Naïma Belhaneche-Bensemra Belkacem Belaabed Abdelmalik Bedda 《Macromolecular Symposia》2002,180(1):203-216
The aim of this paper is to study the miscibility and the thermal degradation of PVC/PMMA blends. For that purpose, blends of variable compositions from 0 to 100 wt% were prepared with and without plasticizer. Their physico-chemical characterization was carried out by differential scanning calorimetric analysis (DSC) and Fourier transform infrared spectroscopy (FTIR). Their thermal degradation under nitrogen at 185°C was studied and the HCl evolved from PVC was measured by the pH method. Degraded samples were characterized, after purification, by FTIR and UV-visible spectroscopy. The DSC analysis showed polymer miscibility up to 60 wt% of PMMA. This miscibility is due to a specific interaction of hydrogen bonding type between carbonyl groups (C=O) of PMMA and hydrogen from (CHCl) groups of PVC as evidenced by FTIR analysis. On the other hand, it was found that PMMA exerted a stabilizing effect on the thermal degradation of PVC by reducing the zip dehydrochlorination and by leading to the formation of short polyenes. 相似文献
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