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171.
In this paper transient thermal stresses in a thick hollow cylinder with finite length made of two-dimensional functionally
graded material (2D-FGM) based on classical theory of thermoelasticity are considered. The volume fraction distribution of
materials, geometry and thermal load are assumed to be axisymmetric but not uniform along the axial direction. The finite
element method with graded material properties within each element is used to model the structure. Temperature, displacements
and stress distributions through the cylinder at different times are investigated. Also the effects of variation of material
distribution in two radial and axial directions on the thermal stress distribution and time responses are studied. The achieved
results show that using 2D-FGM leads to a more flexible design so that time responses of structure, maximum amplitude of stresses
and uniformity of stress distributions can be modified to a required manner by selecting suitable material distribution profiles
in two directions. 相似文献
172.
In this paper we develop the Banach contraction principle and Kannan fixed point theorem on generalized cone metric spaces.We prove a version of Suzuki and Kannan type generalizations of fixed point theorems in generalized cone metric spaces. 相似文献
173.
We present an analytic theory of the pair distribution function and the ground-state energy in a two-dimensional (2D) electron gas with an arbitrary degree of spin polarization. Our approach involves the solution of a zero-energy scattering Schrödinger equation with an effective potential which includes a Fermi term from exchange and kinetic energy and a Bose-like term from Jastrow-Feenberg correlations. The form of the latter is assessed from an analysis of data on a 2D gas of charged bosons. We obtain excellent agreement with data from quantum Monte Carlo studies of the 2D electron gas. In particular, our results for the correlation energy show a quantum phase transition occurring at coupling strength rs≈24 from the paramagnetic to the fully spin-polarized fluid. 相似文献
174.
We introduce the notions of “t-extending modules,” and “t-Baer modules,” which are generalizations of extending modules. The second notion is also a generalization of nonsingular Baer modules. We show that a homomorphic image (hence a direct summand) of a t-extending module and a direct summand of a t-Baer module inherits the property. It is shown that a module M is t-extending if and only if M is t-Baer and t-cononsingular. The rings for which every free right module is t-extending are called right Σ-t-extending. The class of right Σ-t-extending rings properly contains the class of right Σ-extending rings. Among other equivalent conditions for such rings, it is shown that a ring R is right Σ-t-extending, if and only if, every right R-module is t-extending, if and only if, every right R-module is t-Baer, if and only if, every nonsingular right R-module is projective. Moreover, it is proved that for a ring R, every free right R-module is t-Baer if and only if Z 2(R R ) is a direct summand of R and every submodule of a direct product of nonsingular projective R-modules is projective. 相似文献
175.
Six new photosensitive and optically active poly(amide-imide)s 8a–8f with good inherent viscosities based on dibenzalacetone moiety were synthesized from the direct polycondensation reaction of N-Trimellitylimido-L-amino acids 3a–3f with 2,5-bis(4-aminobenzylidene)cyclopentanone 7 by two different methods such as direct polycondensation in a medium consisting of N-methyl-2-pyrrolidone/triphenyl phosphite/calcium chloride/pyridine and direct polycondensation in a tosyl chloride/pyridine (py)/N,N-dimethylformamide system. Diamine 7 was synthesized by using a two-step reaction. At first 2,5-bis(4-nitrobenzylidene)cyclopentanone 6 was prepared from the reaction of two equimolars 4-nitrobenzaldehyde 5 and one equimolar cyclopentanone 4 and dinitro compound 6 was reduced by using Na2S. Also N-trimellitylimido-L-amino acids 3a–3f were synthesized by the condensation reaction of trimellitic anhydride 1 with two equimolars of various L-amino acids 2a–2f in an acetic acid solution. The polymerization reactions produced a series of photosensitive and optically active poly(amide-imide)s with high yield and good inherent viscosity. The resulted polymers were fully characterized by means of FTIR and 1H-NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation, solubility tests, UV-VIS spectroscopy, differential scanning calorimeter, thermogravimetric analysis, and derivative of thermogravimetric. These macromolecules exhibited maximum UV-VIS absorption at around 395 and 265 nm in a N,N-dimethylformamide solution. 相似文献
176.
177.
Zolfigol MA Khazaei A Moosavi-Zare AR Zare A Kruger HG Asgari Z Khakyzadeh V Kazem-Rostami M 《The Journal of organic chemistry》2012,77(7):3640-3645
3-Methyl-1-sulfonic acid imidazolium nitrate ([Msim]NO(3)) as a new Br?nsted acidic ionic liquid and nitrating agent was prepared and used for the efficient nitration of aromatic compounds (even aniline derivatives). The dramatic effect of this reagent by in situ generation of nitrogen dioxide as a radical on aromatic compounds to give nitroarenes has been studied. 相似文献
178.
Abdolkarim Zare Maria Merajoddin Fereshteh Abi Ahmad Reza Moosavi‐Zare Mohammad Mokhlesi Mohammad Ali Zolfigol Zhila Asgari Vahid Khakyzadeh Alireza Hasaninejad Ali Khalafi‐Nezhad Abolfath Parhami 《中国化学会会志》2012,59(7):860-865
Trityl chloride (triphenylmethyl chloride, TrCl, Ph3CCl) is utilized as an efficient and homogeneous organocatalyst for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes from β‐naphthol and arylaldehydes under solvent‐free conditions. Moreover, a plausible mechanism is suggested based on the literature and on in situ formation of trityl carbocation with inherent instability during the reaction. 相似文献
179.
Mohammad Sadegh Asgari 《Proceedings Mathematical Sciences》2009,119(3):369-382
In this article, we give new characterizations of fusion frames, on the properties of their synthesis operators, on the behavior
of fusion frames under bounded operators with closed range, and on erasures of subspaces of fusion frames. Furthermore we
show that every fusion frame is the image of an orthonormal fusion basis under a bounded surjective operator. 相似文献