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931.
Suneela Arif Iftikhar Ahmad Bin Amin 《International journal of quantum chemistry》2012,112(3):882-888
Results of Co and Ni substituted AlN in the zinc blende phase are presented. For spin up states, the hybridized N‐2p and Co/Ni‐3d states form the valance bands with a bandgap around the Fermi level for both materials, while in the case of the spin down states, the hybridized states cross the Fermi level and hence show metallic nature. It is found that, Al0.75Co0.25N and Al0.75Ni0.25N are ferromagnetic materials with magnetic moments of 4 μB and 3 μB, respectively. The integer magnetic moments and the full spin polarization at the Fermi level make these compounds half‐metallic semiconductors. Furthermore it is also found that the interaction with the N‐2p state splits the 5‐fold degenerate Co/Ni‐3d states into t2g and eg states. The t2g states are located at higher energies than the eg states caused by the tetrahedral symmetry of these compounds. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
932.
This paper studies a nonlinear Langevin equation involving two fractional orders α∈(0,1] and β∈(1,2] with three-point boundary conditions. The contraction mapping principle and Krasnoselskii’s fixed point theorem are applied to prove the existence of solutions for the problem. The existence results for a three-point third-order nonlocal boundary value problem of nonlinear ordinary differential equations follow as a special case of our results. Some illustrative examples are also discussed. 相似文献
933.
In this work,three-dimensional molecular dynamics simulation is carried out to elucidate the nanoindentation behaviour of single crystal Ni.The substrate indenter system is modelled using hybrid interatomic potentials including the manybody potential(embedded atom method) and two-body Morse potential.The spherical indenter is chosen,and the simulation is performed for different loading rates from 10 m/s to 200 m/s.Results show that the maximum indentation load and hardness of the system increase with the increase of velocity.The effect of indenter size on the nanoindentation response is also analysed.It is found that the maximum indentation load is higher for the large indenter whereas the hardness is higher for the smaller indenter.Dynamic nanoindentation is carried out to investigate the behaviour of Ni substrate to multiple loading-unloading cycles.It is observed from the results that the increase in the number of loading unloading cycles reduces the maximum load and hardness of the Ni substrate.This is attributed to the decrease in recovery force due to defects and dislocations produced after each indentation cycle. 相似文献
934.
The problem of steady laminar mixed convection boundary layer flow of an incompressible viscous fluid along vertical moving
thin needles with variable heat flux for both assisting and opposing flow cases is theoretically considered in this paper.
The governing boundary layer equations are first transformed into non-dimensional forms. The curvature effects are incorporated
into the analysis whereas the pressure variation in the axial direction has been neglected. These equations are then transformed
into similarity equations using the similarity variables, which are solved numerically using an implicit finite-difference
scheme known as the Keller-box method. The solutions are obtained for a blunt-nosed needle (m = 0). Numerical calculations are carried out for various values of the dimensionless parameters of the problem, which include
the mixed convection parameter λ, the Prandtl number Pr and the parameter a representing the needle size. It is shown from the numerical results that the skin friction coefficient, the surface (wall)
temperature and the velocity and temperature profiles are significantly influenced by these parameters. The results are presented
in graphical form and are discussed in detail. 相似文献
935.
The equations governing plane steady-state flow in heterogeneous porous body containing cracks are presented first. Then,
a general transformation lemma is presented which allows extending a particular solution obtained for a given flow problem
to another configuration with different geometry, behaviour and boundary conditions. An existing potential solution in terms
of discharges along the cracks, established by Liolios and Exadaktylos (J Solids Struct 43:3960–3982, 2006) for non-intersecting
cracks in isotropic matrix, is extended to intersecting cracks in anisotropic matrix. The basic problem of a single straight
crack in an infinite body submitted to a pressure gradient at infinity is then investigated and a closed-form solution is
presented for the case of void cracks (infinite conductivity), as well as a semi-analytical solution for the case of cracks
with Poiseuille type conductivity. These solutions, derived first for an isotropic matrix, are then extended to anisotropic
matrices using the general transformation lemma. Finally, using the solution obtained for a single crack, a closed-form estimation
of the effective permeability of micro-cracked porous materials with weak crack density is derived from a self-consistent
upscaling scheme. 相似文献
936.
Ashfaque H. Bokhari Ahmad Y. Al Dweik A. H. Kara F. D. Zaman 《Nonlinear dynamics》2010,62(1-2):127-138
In this paper the (2+1)-nonlinear diffusion equation u t ?div(f(u)grad u)=0 with variable diffusivity is considered. Using the Lie method, a complete symmetry classification of the equation is presented. Reductions, via two-dimensional Lie subalgebras of the equation, to first- or second-order ordinary differential equations are given. In a few interesting cases exact solutions are presented. 相似文献
937.
Pot experiments were conducted to study the efficacy of a slow sulfur-releasing fertilizer, sulfur glass fritz (SGF 1), on
growth, photosynthesis, and sulfur, and nitrogen assimilation potentials of brown mustard (Brassica juncea L. Czern. & Coss. cv. Pusa Jaikisan). Growth as indicated by biomass accumulation slowed down in response to the application
of sulfur glass fritz. A similar trend was observed in the case of photosynthesis rate. The activity of two marker enzymes,
ATP-sulfurylase and nitrate reductase, showed very low levels of activity, indicating poor assimilation of sulfur and nitrogen
by the plant under sulfur glass fritz. It is therefore concluded that the release of sulfur by sulfur glass fritz is too slow
and that the initial nonavailability of sulfur to the plants could lead to suboptimization of both sulfur- and nitrogen-assimilating
enzymes. These factors may contribute to low rates of photosynthesis and poor growth. 相似文献
938.
939.
Masood Parvez Jehan Ara Viqar Sultana Rashida Qasim Viqar Uddin Ahmad 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):e96-e97
The crystal structure of caulerpin (dimethyl 6,13‐dihydrodibenzo[b,i]phenazine‐5,12‐dicarboxylate, C24H18N2O4), an indole alkaloid, reported in space group Cc with an acute β angle, has been redetermined in the correct space group, C2/c. The molecule has twofold crystallographic symmetry and is composed of two essentially planar indole groups fused to an eight‐membered cyclooctatetraene ring which adopts a boat conformation. The molecular dimensions are normal. The structure is stabilized by intermolecular and intramolecular interactions involving the indole N—H atom and carbonyl O atom [N?O 3.211 (4) and 2.836 (4) Å]. 相似文献
940.
Ahmad Pouya 《European Journal of Mechanics - A/Solids》2000,19(6):1015
Rock salt is considered as a pure aggregate of halite (mineral NaCl) crystals and its behaviour is investigated by a micro–macro approach. The behaviour of the polycrystalline aggregate is deduced from the properties of the constituent halite crystals. A model for the elastoplastic behaviour of halite crystal has been deduced from experimental data available in the literature. The basic equations of the micro–macro model for the polycrystalline medium and the calculation method are then presented and the elastoplastic behaviour of rock salt is investigated by this method. The hardening effects obtained for the polycrystal are found to be very different from those obtained for FCC metal polycrystals. The differences are explained as a consequence of differences of families of glide systems in these crystals. Finally, the internal stresses in the polycrystal are studied in order to elucidate the origin of cracking and damage of the rock salt. 相似文献