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721.
In this paper the effects of temperature on theradial breathing modes(RBMs) and radial wave propagation in multiwall carbon nanotubes(MWCNTs) are investigated using a continuum model of multiple elastic isotropicshells.The van der Waals forces between tubes are simulatedas a nonlinear function of interlayer spacing of MWCNTs.The governing equations are solved using a finite elementmethod.A wide range of innermost radius-to-thickness ratioof MWCNTs is considered to enhance the investigation.Thepresented solution is verified by comparing the results withthose reported in the literature.The effects of temperature onthe van der Waals interaction coefficient between layers ofMWCNTs are examined.It is found that the variation of thevan der Waals interaction coefficient at high temperature issensible.Subsequently,variations of RBM frequencies andradial wave propagation in MWCNTs with temperatures upto 1 600 K are illustrated.It is shown that the thick MWCNTs are more sensible to temperature than the thin ones. 相似文献
722.
Sh. Hosseini Hashemi S. R. Atashipour M. Fadaee 《Archive of Applied Mechanics (Ingenieur Archiv)》2012,82(5):677-698
In this article, the governing equations of motion of thick laminated transversely isotropic plates are derived based on Reddy’s
third-order shear deformation theory. These equations are exactly converted to four uncoupled equations to study the in-plane
and out-of-plane free vibrations of thick laminated plates without any usage of approximate methods. Based on the present
analytical approach, exact Levy-type solutions are obtained for thick laminated transversely isotropic plates and, for some
boundary conditions, the exact characteristic equations hitherto not reported in the literature are given. Also, the in-plane
and out-of-plane deformed mode shapes are plotted for different boundary conditions. The present solutions can accurately
predict both the in-plane and out-of-plane natural frequencies and mode shapes of thick laminated transversely isotropic plates. 相似文献
723.
Harmonic acoustic radiation from a modally oscillating spherical source positioned at the center of a fluid-filled cylindrical cavity embedded within a fluid-saturated porous elastic formation is studied in an exact manner. The formulation utilizes the Biot theory of dynamic poroelasticity along with the cylindrical to spherical wave-field transformations, and the pertinent boundary conditions to obtain a closed-form series solution. The analytical results are illustrated with a numerical example in which the spherical source, with its polar axis oriented along the main axis of a water-filled borehole and embedded within a water-saturated Ridgefield sandstone formation, is excited in vibrational modes of various orders. The magnitude of the reflected component of acoustic pressure along the axis of the borehole for a pulsating (n = 0), an oscillating (n = 1), and also a multipole (n = 0–3) spherical source as a function of the excitation frequency is calculated and discussed for representative values of the parameters characterizing the system. Special attention is paid to the effects of source excitation frequency, size, surface velocity profile, and internal impedance as well as borehole interface permeability condition on the reflected pressure magnitudes. Limiting cases are considered and fair agreements with well-known solutions are obtained. 相似文献
724.
The proposed method is a simple process for the determination of trace amount of thallium(I) in the environmental wastewater samples by electrothermal atomic absorption spectrometry. The wastewater samples were obtained from the environment of a cement plant and subjected to a simple treatment, such as adjusting pH and masking the interfering ions, to prepare for the flotation process in which the thallium(I) content was floated as an ion-association complex using iodide and Rhodamine B at the interface of aqueous/cyclohexane layers. The floated layer was then separated and dissolved in 2 ml of a solution, which was 1% to H2SO4 and 50% to methanol, respectively. Aliquots of 10-microl of this solution were subjected to the graphite furnace to determine the thallium(I) content. The flotation process can be carried in a weak acidic medium in which the interfering effects owing to certain metal ions were eliminated by masking them as neutral citrate chelates. The dynamic range for the determination was found to be 1.0 x 10(-8) - 1.0 x 10(-7) mol l(-1). The RSD was 3.2% and the DL was 2.5 x 10(-9) mol l(-1) (calculated as 3SD of the blank). The reliability of the method is demonstrated by the analysis of a synthetic wastewater in which the recovery was found to be 94%. 相似文献
725.
A novel dithiolene ligand appended with a 4,5-diazafluorene moiety has been synthesized and used for the preparation of discrete nickel and mercury complexes and a one-dimensional polymer in the presence of sodium cations. 相似文献
726.
A nonlinear conformable time-fractional parabolic equation with exponential nonlinearity is explored, in this article. First, under the specific transformations, the time-fractional parabolic equation is changed into a nonlinear ODE of integer order, and then, the reduced equation is solved using two lately established techniques called the \({ \exp }\left( { - \varphi \left( \varepsilon \right)} \right)\)-expansion and modified Kudryashov methods. Several exact solutions in various wave forms for the nonlinear conformable time-fractional parabolic equation with exponential nonlinearity are formally constructed. 相似文献
727.
Hosseini MW 《Chemical communications (Cambridge, England)》2005,(47):5825-5829
Supramolecular synthesis, by combining molecules through non-covalent interactions, makes it possible to build up extremely sophisticated supramolecular assemblies in the solid state and offers endless architectural possibilities. 相似文献
728.
Al(2)O(3)/MeSO(3)H (AMA) was found to be an extremely efficient reagent for the conversion of aromatic aldehydes and diols to glycol monoesters. The remarkable selectivity achieved with this reagent is an attractive feature of the present method. 相似文献
729.
A new facile method for monoesterification of diols has been developed. A variety of diols, in particular oligoethylene glycols, were selectively monoesterified in excellent yields by reaction with aromatic and aliphatic acids in the presence of Al2O3/MeSO3H as a new reagent without use of any solvents. 相似文献
730.
Hossein E. Hosseini Harold W. Kroto John F. Nixon Osamu Ohashi 《Journal of organometallic chemistry》1985,296(3):351-355
The formation and subsequent reaction of the phosphaalkene CF3PCF2 obtained via dehydrofluorination of (CF3)2PH with KOH pellets at room temperature has been studied by multinuclear NMR spectroscopy. 相似文献