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81.
In this research work, an exact analytical solution for buckling of functionally graded rectangular plates subjected to non-uniformly
distributed in-plane loading acting on two opposite simply supported edges is developed. It is assumed that the plate rests
on two-parameter elastic foundation and its material properties vary through the thickness of the plate as a power function.
The neutral surface position for such plate is determined, and the classical plate theory based on exact neutral surface position
is employed to derive the governing stability equations. Considering Levy-type solution, the buckling equation reduces to
an ordinary differential equation with variable coefficients. An exact analytical solution is obtained for this equation in
the form of power series using the method of Frobenius. By considering sufficient terms in power series, the critical buckling
load of functionally graded plate with different boundary conditions is determined. The accuracy of presented results is verified
by appropriate convergence study, and the results are checked with those available in related literature. Furthermore, the
effects of power of functionally graded material, aspect ratio, foundation stiffness coefficients and in-plane loading configuration
together with different combinations of boundary conditions on the critical buckling load of functionally graded rectangular
thin plate are studied. 相似文献
82.
Martins N Mateus N Vinci D Saidi O Brigas A Bacsa J Xiao J 《Organic & biomolecular chemistry》2012,10(20):4036-4042
A new ferrocenyl oxazaphospholidine oxide 3 was synthesized together with its P-epimer 2 in the reaction of ferrocene lithium with phosphoramidite chloride 1. 3 was successfully derivatized into planar chiral 1,2-ferrocenes, including phosphine ligands, via highly diastereoselective ortho-lithiation and subsequent functionalization; these compounds display opposite planar chirality to those obtained from 2. Some of these 1,2-ferrocenes were further lithiated, allowing for the introduction of a free phosphine group at the oxazaphospholidine ring. The X-ray structures of the compounds 2 and 3 as well as those of the new 1,2-ferrocenes 4 and 7 have been determined. 相似文献
83.
The crystal structure, the 13C NMR spectroscopy and the complex impedance have been carried out on [Cd3(SCN)2Br6(C2H9N2)2]n. Crystal structure shows a 2D polymeric network built up of two crystallographically independent cadmium atoms with two different octahedral coordinations. This compound exhibits a phase transition at (T=355±2 K) which has been characterized by differential scanning calorimetry (DSC), X-rays powder diffraction, AC conductivity and dielectric measurements. Examination of 13C CP/MAS line shapes shows indirect spin–spin coupling (14N and 13C) with a dipolar coupling constant of 1339 Hz. The AC conductivity of this compound has been carried out in the temperature range 325–376 K and the frequency range from 10−2 Hz to 10 MHz. The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes. One, at low frequency side, is thermally activated due to the ionic conduction of the crystal and the other, at higher frequency side, gradually disappears when temperature reaches 355 K which is attributed to the localized dipoles in the crystal. Moreover, the temperature dependence of DC-conductivity in both phases follows the Arrhenius law and the frequency dependence of σ(ω,T) follows Jonscher's universal law. The near values of activation energies obtained from the conductivity data and impedance confirm that the transport is through the ion hopping mechanism. 相似文献
84.
A. Kashefi M. Mahdinia B. Firoozabadi M. Amirkhosravi G. Ahmadi M.S. Saidi 《Acta Mechanica Sinica》2014,30(2):259-273
This study describes a multidimensional 3D/lumped parameter(LP) model which contains appropriate inflow/outflow boundary conditions in order to model the entire human arterial trees. A new extensive LP model of the entire arterial network(48 arteries) was developed including the effect of vessel diameter tapering and the parameterization of resistance, conductor and inductor variables. A computer aided-design(CAD) algorithm was proposed to effciently handle the coupling of two or more 3D models with the LP model, and substantially lessen the coupling processing time. Realistic boundary conditions and Navier–Stokes equations in healthy and stenosed models of carotid artery bifurcation(CAB) were used to investigate the unsteady Newtonian blood flow velocity distribution in the internal carotid artery(ICA). The present simulation results agree well with previous experimental and numerical studies. The outcomes of a pure LP model and those of the coupled 3D healthy model were found to be nearly the same in both cases. Concerning the various analyzed 3D zones, the stenosis growth in the ICA was not found as a crucial factor in determining the absorbing boundary conditions.This paper demonstrates the advantages of coupling local and systemic models to comprehend physiological diseases of the cardiovascular system. 相似文献
85.
O. Mounkachi A. El Kenz E.H. Saidi 《Journal of magnetism and magnetic materials》2009,321(16):2402-2406
By ab-initio calculation we show that the (Ga,Fe)N ground state may be changed from anti-ferromagnetic to ferromagnetic by acceptor defect like Ga vacancies. The electronic structures are calculated by using the Korringa-Kohn-Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that we can increase the magnetic moment of Fe in p-type GaN by oxygen co-doping. Mechanism of exchange interactions between magnetic ions in p-type (Ga,Fe)N is also studied. The effect of external magnetic field on the electronic structure of (Ga, Fe)N and p-type (Ga, Fe)N is investigated. 相似文献
86.
S. Ben Khalifa B. Gruzza G. Bremond F. Saidi L. Bèji 《Journal of luminescence》2008,128(10):1611-1616
Porous GaAs layers were formed by electrochemical etching of p-type GaAs(1 0 0) substrates in HF solution. A surface characterization has been performed on p-type GaAs samples using X-ray photoelectron spectroscopy (XPS) technique in order to get information about the chemical composition, particularly on the surface contamination. According to the XPS spectra, the oxide layer on as-received porous GaAs substrates contains As2O3, As2O5 and Ga2O3. Large amount of oxygen is present at the surface before the surface cleaning.Compared to untreated GaAs surface, room temperature photoluminescence (PL) investigations of the porous layers reveal the presence of two PL bands: a PL peak at ∼871 nm and a “visible” PL peak at ∼650-680 nm. Both peak wavelengths and intensities varied from sample to sample depending on the treatment that the samples have undergone. The short PL wavelength at 650-680 nm of the porous layers is attributed to quantum confinement effects in GaAs nano-crystallites. The surface morphology of porous GaAs has been studied using atomic force microscopy (AFM). Nano-sized crystallites were observed on the porous GaAs surface. An estimation of the mean size of the GaAs nano-crystals obtained from effective mass theory and based on PL data was close to the lowest value obtained from the AFM results. 相似文献
87.
E. H. Saidi 《Physics letters. [Part B]》1991,260(3-4):327-332
The fundamentals of the Diff(S2) and the SDiff(S2) gauge theories are developed. It is shown that the adjoint representation of SU (∞) is described by a divergentless two-dimensional vector field defined on the sphere. The SU (∞) Yang-Mills gauge action obtained earlier by Floratos et al. is reviewed. The problem of the zero modes is solved without need of any constraint. The fundamental representations of SU (∞) and the gauge-matter couplings are discussed. 相似文献
88.
Summary A technique is described for determination of the amount of bonded phase in commercial columns. It is adapted to the determination
of the real nature and the thickness of a siloxane bonded film. Ten-centimeter samples of column are used. The method is tested
for large-bore capillary columns. Applications to kinetic studies are suggested. 相似文献
89.
Let G be a reflexive subspace of the Banach space E and let Lp(I,E) denote the space of all p-Bochner integrable functions on the interval I=[0,1] with values in E, 1p∞. Given any norm N(
,
) on R2, N nondecreasing in each coordinate on the set R2+, we prove that Lp(I,G) is N-simultaneously proximinal in Lp(I,E). Other results are also obtained. 相似文献
90.
Silica chloride has been found to be an efficient catalyst for facile tosylation of alcohols directly with p-toluenesulfonic acid in methylene chloride under reflux. The process is associated with selective tosylation of secondary alcohols over primary alcohols. 相似文献