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101.
Hasna Jerbi Mourad Hidouri Mohamed Rzeigui Mongi Ben Amara 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(3):i17-i20
A new phosphate, sodium calcium magnesium tetrakis(phosphate), Na8Ca1.5Mg12.5(PO4)12, has been synthesized by a flux method. Its novel structure consists of MgOx (x = 5 and 6) polyhedra and MO7 (M = Mg or Na) octahedra linked directly through common corners or edges to form a rigid three‐dimensional skeleton, reinforced by corner‐sharing between identical Mg12MO48 units. The connection of these units by the PO4 tetrahedra induces cavities and crossing tunnels where the Na+ and Ca2+ cations are located. This structural model was supported by a 31P NMR spectroscopy study which confirmed the existence of 12 crystallographically independent sites for the P atoms. 相似文献
102.
M. Amara R. M. Gal ra P. Morin T. Veres P. Burlet 《Journal of magnetism and magnetic materials》1994,130(1-3):127-132
Among the AuCu3-type RIn3 series where R is a rare earth, the NdIn3 compound presents a complex magnetic phase diagram. In this compound, which orders antiferromagnetically at TN = 5.9 K, three magnetic phases are separated by two sharp first-order transitions. The phase diagrams, determined for the main crystallographic directions, by magnetization measurements in fields up to 7 T show a strong dependence of the transition temperatures. In order to determine the actual magnetic structures in NdIn3, a neutron diffraction experiment has been performed on a single crystal under magnetic field. It shows that the magnetic structures are collinear (single q) with the magnetic moments aligned along the fourfold axis. They clearly evidence the existence of two incommensurate phases with q = (1/2, 1/2, τ): for TN T 5.5 K, τ1 ≈ 0.037 2π/a and the structure is sine-wave modulated, for 5.5 K > T > 4.7 K, τ2 = 0.017 2π/a and the structure squares up. Below 4.7 K the q = (1/2, 1/2, 0) commensurate structure is stabilized. 相似文献
103.
104.
This paper deals with a posteriori estimates for the finite element solution of the Stokes problem in stream function and vorticity formulation. For two different
discretizations, we propose error indicators and we prove estimates in order to compare them with the local error. In a second
step, these results are extended to the Navier-Stokes equations.
Received March 25, 1996 / Revised version received April 7, 1997 相似文献
105.
M. Mekhnache A. Drici L. Saad Hamideche H. Benzarouk A. Amara L. Cattin J.C. Bernède M. Guerioune 《Superlattices and Microstructures》2011
ZnO thin films were deposited on glass, ITO (In2O3; Sn) and on ZnO:Al coated glass by spray pyrolysis. The substrates were heated at 350 °C. Structural characterization by X-ray diffraction (XRD) measurements shows that films crystallize in hexagonal structure with a preferential orientation along (0 0 2) direction. XRD peak-shift analysis revealed that films deposited on glass substrate (−0.173) were compressive, however, films deposited onto ITO (0.691) and on ZnO:Al (0.345) were tensile. Scanning electron microscopies (SEM) show that the morphologies of surface are porous in the form of nanopillars. The transmittance spectra indicated that the films of ZnO/ITO/glass and ZnO/ZnO:Al/glass exhibit a transmittance around 80% in the visible region. An empirical relationship modeled by theoretical numerical models has been presented for estimating refractive indices (n) relative to energy gap. All models indicate that the refractive index deceases with increasing energy band gap (Eg). 相似文献
106.
Maddouri Kamel Azzouzi Faiçal Triki Houria Bouguerra Abdesselam Amara Korba Sabiha 《Nonlinear dynamics》2021,103(3):2793-2803
Nonlinear Dynamics - We investigate the inhomogeneous higher-order nonlinear Schrödinger (INHLS) equation including cubic–quintic–septic (CQS) nonlinear terms and gain or loss with... 相似文献
107.
108.
109.
A systematic study of the effect of an electric field on the critical temperature of a pure fluid is made for the first time to our knowledge. An ac electric field is applied to a spherical capacitor filled with SF6 at its critical density, while the temperature is slowly ramped down through its critical temperature T(c). By continuously observing the light transmission through the fluid during the temperature ramp, a shift in T(c), DeltaT(c), is found at various electric fields. By shining the light vertically through the fluid, we utilize the density gradient induced by the fluid's weight to compensate for the effects of density changes from electrostriction. This technique effectively keeps the system at constant critical density with respect to the observation of T(c). We observe an increase in T(c) as expected from thermodynamic stability and renormalization group theory, but quantitatively larger by an order of magnitude. 相似文献
110.
The influence of power ultrasound on the growth rate of potash alum was investigated. The experiments on growth of potash alum crystals were carried out in a stirred double jacket tank in silent conditions as well as in the presence of power ultrasound (20 kHz) at 32 degrees C, with different initial crystal sizes. It was observed that the mass growth rate of potash alum was faster under ultrasound compared to that under silent conditions. The shape was not modified by ultrasound but the size of crystals, which are grown under ultrasound, are smaller and with higher density compared to those grown under silent conditions. 相似文献