A glance on the effects of temperature on axisymmetric dynamic behavior of multiwall carbon nanotubes

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.     

An exact analytical approach for in-plane and out-of-plane free vibration analysis of thick laminated transversely isotropic plates

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.     

Dynamic interaction of a spherical radiator in a fluid-filled cylindrical borehole within a poroelastic formation

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.     

Flotation separation and electrothermal atomic absorption spectrometric determination of thallium in wastewater samples

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%.     

Sequential generation of one-dimensional networks based on a differentiated bischelate-type ligand bearing both 4,5-diazafluorene and dithiolene units

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.     

Exact solutions of a nonlinear conformable time-fractional parabolic equation with exponential nonlinearity using reliable methods

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.     

Self-assembly and generation of complexity

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.     

Highly selective methodology for the direct conversion of aromatic aldehydes to glycol monoesters

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.     

Al2O3/MeSO3H (AMA) as a new reagent with high selective ability for monoesterification of diols

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.     

31P, 19F and 1H NMR spectroscopic study of the reaction of bis(trifluoromethyl)phosphine and solid KOH. Synthesis of the phosphaalkene CF3PCF2

The formation and subsequent reaction of the phosphaalkene CF₃PCF₂ obtained via dehydrofluorination of (CF₃)₂PH with KOH pellets at room temperature has been studied by multinuclear NMR spectroscopy.