ahmed abed - Academia.edu (original) (raw)
Papers by ahmed abed
At this stage of development of telecommunication systems, wireless networks find their increasin... more At this stage of development of telecommunication systems, wireless networks find their increasing use. However, the main limiting factor in their development is the low productivity. An analysis of existing ways to improve performance of wireless networks should be noted that the ...
The article introduces a two-index model of the distribution channels in the multiradio multichan... more The article introduces a two-index model of the distribution channels in the multiradio multichannel wireless mesh networking (MR-MC WMN) standard IEEE 802.11. The model describes the process of distribution channels in both homogeneous and in heterogeneous MR-MC WMN.
Cheminform, 2003
For Abstract see ChemInform Abstract in Full Text.
Inorganic Chemistry, 2003
Single crystals of two new osmium-containing triple perovskites, Ba 3 LiOs 2 O 9 and Ba 3 NaOs 2 ... more Single crystals of two new osmium-containing triple perovskites, Ba 3 LiOs 2 O 9 and Ba 3 NaOs 2 O 9 , were grown from reactive molten hydroxide fluxes in sealed silver tubes. They crystallize in the space group P6 3 /mmc with lattice parameters of a ) 5.8025(1) Å, c ) 14.1468(4) Å for Ba 3 LiOs 2 O 9 and a ) 5.8858(1) Å, c ) 14.3451-(5) Å for Ba 3 NaOs 2 O 9 . The magnetic susceptibility of these osmates indicates significant Os−Os coupling within the octahedra pair.
Solid State Sciences, 2001
The crystal structure of Sr4Mn2NiO9 has been refined on single crystal. This phase belongs to the... more The crystal structure of Sr4Mn2NiO9 has been refined on single crystal. This phase belongs to the series A1+x(A′xB1–x)O3 (x=1/3) related to the 2H-hexagonal perovskite. The structure contains transition metals in chains of oxide polyhedra (trigonal prisms and octahedra); neighboring chains are separated from each other by the Sr atoms. The sequence of the face sharing polyhedra along the chains is
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Acta Crystallographica Section B-structural Science, 2003
H n B 4m2n O 12m9n . This description allows the a priori derivation of a re®neable superspace mo... more H n B 4m2n O 12m9n . This description allows the a priori derivation of a re®neable superspace model that includes the superspace symmetry and crenel functions and is valid for the whole family. This model has been successfully applied to the
Acta Crystallographica Section C-crystal Structure Communications, 2002
Tetrastrontium Dimanganese Copper Nonaoxide, Sr 4 Mn 2 CuO 9 . -Single crystals of the title comp... more Tetrastrontium Dimanganese Copper Nonaoxide, Sr 4 Mn 2 CuO 9 . -Single crystals of the title compound are grown by flux synthesis from a stoichiometric mixture of SrCO 3 , Mn 2 O 3 , and CuO in the presence of K 2 CO 3 (alumina crucible, air, 1200°C, 48 h). Sr 4 Mn 2 CuO 9 crystallizes in the trigonal space group P321 with Z = 3. The structure is closely related to the hexagonal perovskite 2H and contains chains of face-sharing polyhedra with a sequence of two octahedra and one trigonal prism. -(EL ABED, A.; GAUDIN*, E.; DARRIET, J.; Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 58 (2002) 10, i138-i139; Inst. Chim. Matiere Condens. Bordeaux, CNRS, Univ. Bordeaux, F-33608 Pessac, Fr.; Eng.) -Schramke 01-009
Solid State Sciences, 2003
Cheminform, 2003
For Abstract see ChemInform Abstract in Full Text.
Acta Crystallographica Section C-crystal Structure Communications, 2001
The new oxychloride InTeO 3 Cl was synthesized from a mixture of In 2 O 3 , InCl 3 and TeO 2 . It... more The new oxychloride InTeO 3 Cl was synthesized from a mixture of In 2 O 3 , InCl 3 and TeO 2 . Its structure has been determined from single-crystal X-ray diffraction data. The structure is composed of layers separated by a van der Waals gap. The layers consist of edge-sharing chains of [InO 4 Cl 2 ] octahedra linked through [TeO 3 ] trigonal pyramids. No free Cl atoms are located between the layers.
Journal of The American Chemical Society, 2001
Single crystals of Sr 6 Rh 5 O 15 were grown from a molten potassium carbonate flux. The structur... more Single crystals of Sr 6 Rh 5 O 15 were grown from a molten potassium carbonate flux. The structure was solved by both the traditional 3-D crystallographic approach and the 4-D superspace group approach using JANA2000. Both methods produced an equivalent structure determination, thereby confirming the 4-D superspace group approach as an effective structure solution method for 3-D commensurate composite structures. Sr 6 Rh 5 O 15 corresponds to the n ) 1, m ) 1 member of the A 3n+3m A′ n B 3m+n O 9m+6n family of 2H hexagonal perovskite-related oxides. This compound is characterized by pseudo-one-dimensional polyhedral chains of four face-sharing RhO 6 octahedra followed by one RhO 6 trigonal prism. These chains in turn are separated by [Sr] ∞ chains. Magnetic measurements were carried out on oriented single crystals, and a very large magnetic anisotropy in the magnetic susceptibility was observed.
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Solid State Chemistry, 2004
Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The ... more Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The new compound, Ba12Rh9.25Ir1.75O33, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O6 octahedra and one (Rh/Ir)O6 trigonal prism. The magnetic susceptibility of Ba12Rh9.25Ir1.75O33 is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280Ω.
Journal of Solid State Chemistry, 2004
Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The ... more Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The new compound, Ba12Rh9.25Ir1.75O33, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O6 octahedra and one (Rh/Ir)O6 trigonal prism. The magnetic susceptibility of Ba12Rh9.25Ir1.75O33 is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280Ω.
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Solid State Chemistry, 2004
Single crystals of a new Ba-Rh-Ir-O oxide were grown from a molten potassium carbonate flux. The ... more Single crystals of a new Ba-Rh-Ir-O oxide were grown from a molten potassium carbonate flux. The new compound, Ba 12Rh 9.25Ir 1.75O 33, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O 6 octahedra and one (Rh/Ir)O 6 trigonal prism. The magnetic susceptibility of Ba 12Rh 9.25Ir 1.75O 33 is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280 Ω.
Cheminform, 2004
For Abstract see ChemInform Abstract in Full Text.
Journal of The American Chemical Society, 2004
Large single crystals of oxygen-deficient Sr 6 Co 5 O 15-δ compounds, i.e., Sr 6 Co 5 O 14.70 and... more Large single crystals of oxygen-deficient Sr 6 Co 5 O 15-δ compounds, i.e., Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 , were obtained by using K 2 CO 3 flux in the presence of additives of transition metal oxides. The single-crystal structure determination shows that the structures of Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 crystallize in the space group R3 h and can be described as one-dimensional face-sharing CoO 3 polyhedral chains and Sr cation chains. Unlike the other known 2H-perovskite-related oxides in which the polyhedral chains consist of octahedra (Oh) and trigonal prism (TP), the structure of Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 contain Oh and intermediate polyhedra (IP) and can be attributed to a general structure formula A 6 A ′ 2 B 3 O 15-δ , which is closely related to the known A 6 A ′ B 4 O 15 phases by shifting of a B atom and the O 3 triangle along the c axis. Further study on O3 reveals that this oxygen position splits into two independent positions, corresponding to polyhedral geometry of IP and TP, respectively. Therefore, the polyhedral chain in the structure should be more precisely described as a random composite of the 4Oh + TP and 3Oh + 2IP. This model is used to interpret the magnetic properties, although not quantitatively. The 4-D structure analysis was also conducted for both Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 with a commensurate modulated structure in a 4-D superspace group, R3 hm(00γ)0s, γ ) p/k ) 3/5. By considering the same 4-D superspace group R3 hm(00γ)0s but different t-phases, one can understand the structure relationship between Sr 6 Co 5 O 14.70 and Sr 6 Rh 5 O 15 . Gutiérrez-Puebla, E.; Monge, M. A.; Rasines, L.; Ruíz-Valero, C. J. Solid State Chem. 1994, 108, 230. (6) Fjellvåg, H.; Gulbrandsen, E.; Aasland, S.; Olsen, A.; Hauback, B. C. J. Solid State Chem. 1996, 124, 190. (7) Evain, M.; Boucher, F.; Gourdon, O.; Petricek, V.; Dusek, M.; Bezdicka, P.
At this stage of development of telecommunication systems, wireless networks find their increasin... more At this stage of development of telecommunication systems, wireless networks find their increasing use. However, the main limiting factor in their development is the low productivity. An analysis of existing ways to improve performance of wireless networks should be noted that the ...
The article introduces a two-index model of the distribution channels in the multiradio multichan... more The article introduces a two-index model of the distribution channels in the multiradio multichannel wireless mesh networking (MR-MC WMN) standard IEEE 802.11. The model describes the process of distribution channels in both homogeneous and in heterogeneous MR-MC WMN.
Cheminform, 2003
For Abstract see ChemInform Abstract in Full Text.
Inorganic Chemistry, 2003
Single crystals of two new osmium-containing triple perovskites, Ba 3 LiOs 2 O 9 and Ba 3 NaOs 2 ... more Single crystals of two new osmium-containing triple perovskites, Ba 3 LiOs 2 O 9 and Ba 3 NaOs 2 O 9 , were grown from reactive molten hydroxide fluxes in sealed silver tubes. They crystallize in the space group P6 3 /mmc with lattice parameters of a ) 5.8025(1) Å, c ) 14.1468(4) Å for Ba 3 LiOs 2 O 9 and a ) 5.8858(1) Å, c ) 14.3451-(5) Å for Ba 3 NaOs 2 O 9 . The magnetic susceptibility of these osmates indicates significant Os−Os coupling within the octahedra pair.
Solid State Sciences, 2001
The crystal structure of Sr4Mn2NiO9 has been refined on single crystal. This phase belongs to the... more The crystal structure of Sr4Mn2NiO9 has been refined on single crystal. This phase belongs to the series A1+x(A′xB1–x)O3 (x=1/3) related to the 2H-hexagonal perovskite. The structure contains transition metals in chains of oxide polyhedra (trigonal prisms and octahedra); neighboring chains are separated from each other by the Sr atoms. The sequence of the face sharing polyhedra along the chains is
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Acta Crystallographica Section B-structural Science, 2003
H n B 4m2n O 12m9n . This description allows the a priori derivation of a re®neable superspace mo... more H n B 4m2n O 12m9n . This description allows the a priori derivation of a re®neable superspace model that includes the superspace symmetry and crenel functions and is valid for the whole family. This model has been successfully applied to the
Acta Crystallographica Section C-crystal Structure Communications, 2002
Tetrastrontium Dimanganese Copper Nonaoxide, Sr 4 Mn 2 CuO 9 . -Single crystals of the title comp... more Tetrastrontium Dimanganese Copper Nonaoxide, Sr 4 Mn 2 CuO 9 . -Single crystals of the title compound are grown by flux synthesis from a stoichiometric mixture of SrCO 3 , Mn 2 O 3 , and CuO in the presence of K 2 CO 3 (alumina crucible, air, 1200°C, 48 h). Sr 4 Mn 2 CuO 9 crystallizes in the trigonal space group P321 with Z = 3. The structure is closely related to the hexagonal perovskite 2H and contains chains of face-sharing polyhedra with a sequence of two octahedra and one trigonal prism. -(EL ABED, A.; GAUDIN*, E.; DARRIET, J.; Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 58 (2002) 10, i138-i139; Inst. Chim. Matiere Condens. Bordeaux, CNRS, Univ. Bordeaux, F-33608 Pessac, Fr.; Eng.) -Schramke 01-009
Solid State Sciences, 2003
Cheminform, 2003
For Abstract see ChemInform Abstract in Full Text.
Acta Crystallographica Section C-crystal Structure Communications, 2001
The new oxychloride InTeO 3 Cl was synthesized from a mixture of In 2 O 3 , InCl 3 and TeO 2 . It... more The new oxychloride InTeO 3 Cl was synthesized from a mixture of In 2 O 3 , InCl 3 and TeO 2 . Its structure has been determined from single-crystal X-ray diffraction data. The structure is composed of layers separated by a van der Waals gap. The layers consist of edge-sharing chains of [InO 4 Cl 2 ] octahedra linked through [TeO 3 ] trigonal pyramids. No free Cl atoms are located between the layers.
Journal of The American Chemical Society, 2001
Single crystals of Sr 6 Rh 5 O 15 were grown from a molten potassium carbonate flux. The structur... more Single crystals of Sr 6 Rh 5 O 15 were grown from a molten potassium carbonate flux. The structure was solved by both the traditional 3-D crystallographic approach and the 4-D superspace group approach using JANA2000. Both methods produced an equivalent structure determination, thereby confirming the 4-D superspace group approach as an effective structure solution method for 3-D commensurate composite structures. Sr 6 Rh 5 O 15 corresponds to the n ) 1, m ) 1 member of the A 3n+3m A′ n B 3m+n O 9m+6n family of 2H hexagonal perovskite-related oxides. This compound is characterized by pseudo-one-dimensional polyhedral chains of four face-sharing RhO 6 octahedra followed by one RhO 6 trigonal prism. These chains in turn are separated by [Sr] ∞ chains. Magnetic measurements were carried out on oriented single crystals, and a very large magnetic anisotropy in the magnetic susceptibility was observed.
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Solid State Chemistry, 2004
Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The ... more Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The new compound, Ba12Rh9.25Ir1.75O33, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O6 octahedra and one (Rh/Ir)O6 trigonal prism. The magnetic susceptibility of Ba12Rh9.25Ir1.75O33 is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280Ω.
Journal of Solid State Chemistry, 2004
Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The ... more Single crystals of a new Ba–Rh–Ir–O oxide were grown from a molten potassium carbonate flux. The new compound, Ba12Rh9.25Ir1.75O33, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O6 octahedra and one (Rh/Ir)O6 trigonal prism. The magnetic susceptibility of Ba12Rh9.25Ir1.75O33 is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280Ω.
Cheminform, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Journal of Solid State Chemistry, 2004
Single crystals of a new Ba-Rh-Ir-O oxide were grown from a molten potassium carbonate flux. The ... more Single crystals of a new Ba-Rh-Ir-O oxide were grown from a molten potassium carbonate flux. The new compound, Ba 12Rh 9.25Ir 1.75O 33, is structurally related to the 2H-hexagonal perovskite structure and contains pseudo one-dimensional chains of alternating units of ten face-sharing (Rh/Ir)O 6 octahedra and one (Rh/Ir)O 6 trigonal prism. The magnetic susceptibility of Ba 12Rh 9.25Ir 1.75O 33 is featureless, indicating the absence of magnetic order. The oxide is a semiconductor with a room temperature resistance of 280 Ω.
Cheminform, 2004
For Abstract see ChemInform Abstract in Full Text.
Journal of The American Chemical Society, 2004
Large single crystals of oxygen-deficient Sr 6 Co 5 O 15-δ compounds, i.e., Sr 6 Co 5 O 14.70 and... more Large single crystals of oxygen-deficient Sr 6 Co 5 O 15-δ compounds, i.e., Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 , were obtained by using K 2 CO 3 flux in the presence of additives of transition metal oxides. The single-crystal structure determination shows that the structures of Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 crystallize in the space group R3 h and can be described as one-dimensional face-sharing CoO 3 polyhedral chains and Sr cation chains. Unlike the other known 2H-perovskite-related oxides in which the polyhedral chains consist of octahedra (Oh) and trigonal prism (TP), the structure of Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 contain Oh and intermediate polyhedra (IP) and can be attributed to a general structure formula A 6 A ′ 2 B 3 O 15-δ , which is closely related to the known A 6 A ′ B 4 O 15 phases by shifting of a B atom and the O 3 triangle along the c axis. Further study on O3 reveals that this oxygen position splits into two independent positions, corresponding to polyhedral geometry of IP and TP, respectively. Therefore, the polyhedral chain in the structure should be more precisely described as a random composite of the 4Oh + TP and 3Oh + 2IP. This model is used to interpret the magnetic properties, although not quantitatively. The 4-D structure analysis was also conducted for both Sr 6 Co 5 O 14.70 and Sr 6 Co 4.9 Ni 0.1 O 14.36 with a commensurate modulated structure in a 4-D superspace group, R3 hm(00γ)0s, γ ) p/k ) 3/5. By considering the same 4-D superspace group R3 hm(00γ)0s but different t-phases, one can understand the structure relationship between Sr 6 Co 5 O 14.70 and Sr 6 Rh 5 O 15 . Gutiérrez-Puebla, E.; Monge, M. A.; Rasines, L.; Ruíz-Valero, C. J. Solid State Chem. 1994, 108, 230. (6) Fjellvåg, H.; Gulbrandsen, E.; Aasland, S.; Olsen, A.; Hauback, B. C. J. Solid State Chem. 1996, 124, 190. (7) Evain, M.; Boucher, F.; Gourdon, O.; Petricek, V.; Dusek, M.; Bezdicka, P.