Sharif Digital Repository

In this paper, a general class of Eshelby-like or weighted stress tensors based on the right stretch tensor is defined as the product of a general type of Lagrangian stress tensor and a class of stretch measure. In addition, basis free relations for conjugate strains of Eshelby-like stress tensors are investigated, which are based on Hill's definition of energy conjugacy. The equations for strain tensors conjugate to Eshelby-like stress tensors are generally determined, but the case in which the conjugate strains are coaxial with the right stretch tensor is mostly investigated. © 2006 Elsevier Ltd. All rights reserved  

In this paper, nanoscale modeling of a multi-shell fullerene embedded in an elastic medium and its application to vibrational analysis is investigated. The spherical layers of the multi-shell fullerene are concentrically nested, with carbon-carbon van der Waals interactions between them. Also, the whole multi-shell fullerene is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium. The elasticity generated by the carbon-carbon bonds is assumed to be distributed isotropically over the fullerene surfaces. Following derivation of explicit equations for the motion of the multi-shell fullerene, vibrational behavior of a double-shell fullerene is analyzed and... 

In this article, the bending stiffness of a double-layered graphene sheet is investigated using a geometrically-based analytical approach. The analysis is based on the van der Waals interactions of atoms belonging to two neighboring sheets. The inter-atomic spacing between the adjacent layers is geometrically determined when the sheet is applied by a couple of moments in the opposite sides. The bending potential energy is obtained by summing up the potentials at discrete hexagons over the length and width of the sheet. It is observed that the bending stiffness of a double-layered graphene sheet does not depend on the length of the sheet and be a material property for the associated sheet.... 

In this paper, nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium is investigated and the corresponding natural frequencies and the associated modes are determined. The modeling is based on the fact that the elastic moduli of a graphene sheet in two perpendicular orientations are different, so the plate is considered to be anisotropic. The graphene layers stacking at the top of each other bond with carbon-carbon van der Waals forces between two adjacent ones. Also, the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium. © 2005 Elsevier Ltd. Al rights reserved  

In this paper, a general type of Eshelby-like stress tensor is defined which is based on the right stretch tensor and is equal to the product of a general class of strain and the corresponding conjugate stress tensor. The Eshelby-like stress tensor depending on the fact that from which side the stress tensor is multiplied by, is categorized into the right-weighted and left-weighted ones. General relations for conjugate strains of Eshelby-like stress tensors are investigated using the method, based on the definition of energy conjugacy and Hill's principal axis method  

In this paper, the bending modulus of a multi-layered graphene sheet is investigated using a geometrically based analytical approach. For this purpose, a bending potential energy is derived, based on the van der Waals interactions of atoms belonging to the two neighboring sheets of a double-layered graphene sheet. The inter-atomic spacing between the adjacent layers is determined along the line of action of the applied bending moments. The bending potential of the double-layered sheet is calculated by summing up the potentials at discrete hexagons over the length and width of the sheet. A multi-layered graphene sheet is considered as consisting of many stacking double-layers. It is observed... 

In this paper, nanoscale vibrational analysis of a multi-layered graphene sheet embedded in an elastic medium is investigated and the corresponding resonant modes and frequencies are determined. It is known that the elastic moduli of a graphene sheet in two orientations x, y are different, so the graphene sheet is assumed to be a general form of an orthotropic plate. The orthotropic sheets stacking at the top of each other bond with carbon-carbon van der Waals forces, also the whole multi-layered graphene sheet is influenced by polymer-carbon van der Waals forces from the surrounding elastic medium  

Nano sized ZnO on TiO 2 spherical core shells were prepared by using hydrothermal method. The particle size of initial TiO 2 was around 20 nm, and the specific surface area was 50 m2/gr. Different ratios of TiO 2 and ZnO applied to synthesize core shell particle. X-ray diffraction (XRD) used to phase characterization and crystalline size, scanning electron microscopy (SEM) to morphology and microstructure investigations. S. Brunauer, P. H. Emmett and E. Teller method (BET) to find specific surface area, Diffusive UV-visible-NIR spectrometry to bang gap calculations. The results indicate that powders with a shell of zinc oxide in specific range have the quantum size effect. Titanium oxide and... 

Risk aversion is a prevalent phenomenon when sufficiently large amounts are at risk. In this paper, we introduce a new prescriptive approach for coping with risk in sequential decision problems with discrete scenario space. We use Conditional Value-at-Risk (CVaR) risk measure as optimization criterion and prove that there is an explicit linear representation of the proposed model for the problem  

Treatment of dye pollution containing C.I. Acid Red 14 (AR14) by a coupled photocatalytic process was studied. Titanium dioxide, in the form of anatase and rutile, and zinc oxide, were used as photocatalysts. The investigated photocatalysts were Aldrich-produced nanopowders with crystallites of a mean size of 20-30 nm and a specific surface area of about 50 m 2/g. A comparison of TiO 2(anatase), TiO 2(rutile), TiO 2(a,r), and ZnO for the decolorization of the AR14 solution was performed. Results showed that color removal followed the decreasing order of TiO 2(a,r), ZnO > TiO 2(a,r) > TiO 2(a), ZnO > TiO 2(r), ZnO >TiO 2(a,r) > TiO 2(a) > ZnO > TiO 2(r). Response surface methodology (RSM) was... 

This article presents a novel identification approach which can deal with nonlinear and time-varying characteristics of complex dynamic systems, especially an aerial vehicle in the entire flight envelope. A set of local sub-models are first developed at different operating points of the system, and subsequently a self-organizing multi-model ensemble is introduced to aggregate the outputs of the local models as a single model. The number of employed local models in the proposed multi-model ensemble is optimized using a novel self-organizing approach. Also, wavelet neural networks, which combine both the universal approximation property of neural networks and the wavelet decomposition... 

L-tryptophan functionalized AgNPs were successfully fabricated using a one-pot synthesis method and assessed as a colorimetric probe for rapid and accurate determination of Mg2+ ions. The developed sensor showed a selective response towards Mg2+ with no interference from Ca2+ in the wide concentration range of 1–200 µM. The sensor's response was optimized in the pH range of 9–10, which can be attributed to the protonation of amine groups and their interaction with Mg2+ ions. The stability and selectivity of the sensor were examined in different salt (NaCl) and other metal ions, respectively. The L-tryptophan-AgNPs sensor detected Mg2+ with the limit of detection of 3 µM, which is way lower... 

Graphitic carbon nitride (g-CN) is a promising metal-free catalyst for environmental remediation. However, its practical applications have been limited due to insufficient solar-light responsivity. Hetero-element doping and the construction of heterostructures, comprised of g-CN and other band-matched semiconductors could be considered to overcome these drawbacks. In the present work, a series of 2D/3D heterostructures comprised of a few layers of boron-doped g-CN (B-CN) anchored on sea urchin-like Bi2S3 (BS) particles (B-CN@BS) were successfully synthesized. The catalytic performances of B-CN@BS composites were assessed for the photo-reduction of Cr(VI) and in-situ generation of H2O2 under... 

To evaluate the propulsion system capabilities of a Flapping Micro Air Vehicle (FMAV), a new aeroelastic model of a typical flexible FMAV is developed, utilizing the Euler-Bernoulli torsion beam and quasi steady aerodynamic model. The new model accounts for all existing complex interactions between the mass, inertia, elastic properties, aerodynamic loading, flapping amplitude and frequency of the FMAV, as well as the effects of several geometric and design parameters. To validate the proposed theoretical model, a typical FMAV, as well as an instrumented test stand for the online measurement of forces, flapping angle and power consumption, has been constructed. The experimental results are... 

The graphitic carbon nitride/tin oxide (g-C3N4/SnO2) nanocomposite synthesized under microwave irradiation was used for adsorptive removal of sulfur-containing dibenzothiophene (DBT) from Tehran vehicular gasoline. High-resolution transmission electron microscopy, X-ray powder diffraction, energy dispersive X-ray spectroscopy, Brunauer-Emmett-Teller, Fourier-transform infrared spectroscopy, and field emission scanning electron microscopy techniques determined the adsorbent characteristics, and gas chromatography with a flame ionization detector determined the DBT concentration of the samples. Application of the experimental data into the solid/fluid kinetic models indicated a chemisorption... 

The geometry structures of hexa-coordinated [NiLX]X complexes (X = Cl -, Br-, I-) {L = 8,9,18,19-tetrahydro-7H,17H- dibenzo[f,o] [1,5,9,13]dioxadiaza cyclohexadecine-8,18-diol} are optimized by density functional theory (DFT) using B3LYP/LANL2DZ. The calculated geometric parameters are in good agreement with the corresponding experimental values. Calculation results about these complexes show that dipole moment decreases, and the energy levels of HOMOs descend from iodo-complex to chloro-complex. The energy levels of HOMOs descend gently from iodo-complex to chloro-complex, while the energy levels of LUMOs in the present complexes are almost similar; therefore the energy gapes between HOMOs... 

The granular activated carbon (GAC) was used as an adsorbent for its ability to remove haloacetic acids (HAAs) from drinking water by batch and column experiments. Various thermodynamic parameters, such as ΔG°, ΔH° and ΔS° have been calculated. The thermodynamics of HAAs onto GAC system indicates spontaneous and exothermic nature of the process. The ability of GAC to adsorb HAAs in a fixed bed column was investigated as well. The effect of operating parameters such as flow rate and inlet HAAs concentration on the sorption characteristics of GAC was investigated. The total adsorbed quantities, equilibrium uptakes and total removal percents of HAAs related to the effluent volumes were... 

Conventional features for speech recognition have not been evaluated in terms of importance in human speech recognition. In this paper a method for extracting important features in an interactive process has been introduced. This method can be used as an aid for experts in an ASR expert system. It has also been shown, as an application of our method, how an expert might find out the distinguishing features between "m" and "n". As another use, it has been illustrated that how our method could be used to check the sufficiency of information in the quantized filter-bank for speech recognition  

The energy supply system of Uzbekistan is not well positioned to meet the rapidly rising domestic energy demand of this country. Uzbekistan's current energy supply system is outdated and has very low diversity, as most of its energy comes from natural gas. In addition to producing immense amounts of greenhouse gas and environmental pollution, this situation is untenable considering the eventual depletion of fossil fuel reserves of this country. Uzbekistan's renewable energy sector is highly undeveloped, a situation that can be attributed to the lack of coherent policies for the advancement of renewable power and the low price of natural gas. However, this country has significant untapped...