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81.
Mehrdad Massoudi 《Mechanics Research Communications》2011,38(5):378-381
In this paper we modify the constitutive relation derived by Reiner (1945), to describe dilatancy in wet sand, by suggesting that the shear viscosity would depend on the shear rate and the volume fraction. We then look at the flow of a saturated densely packed bed of particles (with liquid in the pores) between two horizontal flat plates. We obtain exact solutions for a very special case. 相似文献
82.
Mehrdad Lakestani 《Journal of Computational and Applied Mathematics》2011,235(11):3291-3303
An effective method based upon Legendre multiwavelets is proposed for the solution of Fredholm weakly singular integro-differential equations. The properties of Legendre multiwavelets are first given and their operational matrices of integral are constructed. These wavelets are utilized to reduce the solution of the given integro-differential equation to the solution of a sparse linear system of algebraic equations. In order to save memory requirement and computational time, a threshold procedure is applied to obtain the solution to this system of algebraic equations. Through numerical examples, performance of the present method is investigated concerning the convergence and the sparseness of the resulted matrix equation. 相似文献
83.
Abbas Mehrdad Mohammad Taghi Taghizadeh Roghieh Moladoust 《Journal of solution chemistry》2011,40(5):832-842
In this work, the intrinsic viscosities of poly(ethylene glycol) with a molar mass of 20 kg⋅mol−1 were measured in water/1-propanol solutions from 283.1 to 313.1 K. The expansion factors of the polymer chains were calculated
from the intrinsic viscosity data. The thermodynamic parameters entropy of dilution parameter, the heat of dilution parameter,
theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient were derived from the temperature
dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/1-propanol
become weaker solvents for poly(ethylene glycol) with increasing temperature. Also, the thermodynamic parameters indicate
that the solvent ability of mixed water/1-propanol for poly(ethylene glycol) is less than that of pure water. 相似文献
84.
To realize the effects of the pyridyl group on the stability, multiplicity, and geometry of isomeric pyridylcarbenes and their heavier Si and Ge analogues, a theoretical study was performed at B3LYP/6-311++G(d,p)//B3LYP/6-31G(d). The behavior of nitrogen atom was totally different in each multiplicity (singlet and triplet), structural isomer (ortho-, meta-, and para-), and divalent center (C, Si, and Ge). All pyridylcarbenes have triplet ground states, while the stable silylene and germylene analogues are singlet. The pyridyl group stabilizes both singlet and triplet states divalent centers with more pronounced effects on the singlet states in the order: carbene>germylene>silylene. While all planar species benefit from common π–p conjugative interaction of the pyridyl ring, in the ortho-isomers of 2-pyridylsilylene and 2-pyridylgermylene there is another interaction, n–p, that leads to two stable non-planar conformers. This finding is confirmed by NBO charges, calculated UV–vis spectra, philicity indices (N and ω), and isodesmic reactions. 相似文献
85.
Neshati V Matin MM Bahrami AR Iranshahi M Rassouli FB Saeinasab M 《Natural product research》2012,26(18):1724-1727
Despite widespread application of cisplatin in treatment of transitional cell carcinomas, its efficiency is far from satisfactory due to acquired drug resistance. The present study was carried out to estimate the effects of conferone, a sesquiterpene-coumarin isolated from Ferula badrakema, on increasing cisplatin cytotoxicity in 5637 cells. In order to determine conferone effects, 5637 cells were cultured in the presence of different concentrations of conferone and cisplatin in combination. The cytotoxicity and DNA damaging effects were then studied using MTT and comet assays, respectively. The results revealed that 24?h after the combination of 1?μg?mL?1 cisplatin with 32?μg?mL?1 conferone, the cytotoxicity of cisplatin was increased by 36.76%, and comet assay analyses showed that conferone could enhance the DNA damaging effects of cisplatin by 41%. 相似文献
86.
Four numerical techniques based on the linear B‐spline functions are presented for the numerical solution of the Lane–Emden equation. Some properties of the B‐spline functions are presented and are utilized to reduce the solution of the Lane–Emden equation to the solution of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the new techniques. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
87.
The critical point (Kc) of the two-layer Ising model on the Kagome lattice has been calculated with a high precision, using the probabilistic cellular automata with the Glauber algorithm. The critical point is calculated for different values of the inter- and intra-layer couplings (K1≠K2≠K3≠Kz), where K1, K2 and K3 are the nearest-neighbor interactions within each layer in the 1, 2 and 3 directions, respectively, and Kz is the intralayer coupling. A general ansatz equation for the critical point is given as a function of the inter- and intra-layer interactions, ξ=K3/K1,σ=K2/K1 and ω=Kz/K1 for the one- and two-layer Ising models on the Kagome lattice. 相似文献
88.
Lili Zhang Mehrdad Negahban 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2012,63(6):1143-1176
We study the theory of propagation of infinitesimal thermo-mechanical waves in a special class of nonlinear viscoelastic materials under homogeneous and inhomogeneous finite static and time-varying deformations. These results are based on a thermodynamically consistent finite-deformation nonlinear viscoelastic model that reduces to a general linear viscoelastic model of integral form. On a thermo-mechanically deforming body, we impose a thermo-mechanical perturbation history and obtain the equations to solve for the perturbation parameters from the constitutive model and the balance laws. We use these equations to study the characteristics of different perturbations. We develop the special equations for both time-harmonic and time-damping plane waves for homogeneous pre-loads. 相似文献
89.
Amir A. Mehrdad Sharif Ali M. Astaraki Parviz Aberoomand Azar Saeed Abedini Khorrami Shahram Moradi 《Arabian Journal of Chemistry》2012,5(1):41-44
The effect of NaCl and Na2SO4 concentrations in aqueous phase on the phase inversion temperature (PIT) in nanoemulsions of water/Brij30/n-hexadecane system has been studied separately, and then compared. The variation of conductivity with temperature was measured by Cyber Scan PC510 conductivity meter for emulsions with 20 wt% hexadecane and 8 wt% Brij30 concentration and different concentrations of NaCl and Na2SO4 in aqueous phase. The results showed that with increasing concentrations of NaCl and Na2SO4 in aqueous phase, the PIT of nanoemulsions decreases. The effect of the elevation of concentration on the decrease of PIT was more for Na2SO4 in aqueous phase than NaCl with equal concentrations. 相似文献
90.
Mehrdad Pourayoubi Jerry P. Jasinski Samad Shoghpour Bayraq Hossein Eshghi Amanda C. Keeley Giuseppe Bruno Hadi Amiri Rudbari 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(10):o399-o404
In the phosphoric triamides N,N,N′,N′‐tetrabenzyl‐N′′‐(2‐chloro‐2,2‐difluoroacetyl)phosphoric triamide, C30H29ClF2N3O2P, (I), N,N,N′,N′‐tetrabenzyl‐N′′‐(3‐fluorobenzoyl)phosphoric triamide, C35H33FN3O2P, (II), and N,N,N′,N′‐tetrabenzyl‐N′′‐(3,5‐difluorobenzoyl)phosphoric triamide, C35H32F2N3O2P, (III), the tertiary N atoms of the dibenzylamido groups have sp2 character with minimal deviation from planarity. The sums of the three bond angles about the N atoms in (I)–(III) deviate by less than 8° from the planar value of 360°. The geometries of the tertiary N atoms in all phosphoric triamides with C(O)NHP(O)[N]2 skeletons deposited in the Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B 58 , 380–388] have been examined and the bond‐angle sums at the two tertiary N atoms (SUM1 and SUM2) and the parameter ΔSUM (= SUM1 − SUM2) considered. It was found that in compounds with a considerable ΔSUM value, the more pyramidal N atoms are usually oriented so that the corresponding lone electron pair is anti with respect to the P=O group. In (I), (II) and (III), the phosphoryl and carbonyl groups, separated by an N atom, are anti with respect to each other. In the C(O)NHP(O) fragment of (I)–(III), the P—N bond is longer and the O—P—N angle is contracted compared with the other two P—N bonds and the O—P—N angles in the molecules. These effects are also seen in analogous compounds deposited in the CSD. Compounds with [C(O)NH]P(O)[N]X (X≠ N), such as compounds with a [C(O)NH]P(O)[N][O] skeleton, have not been considered here. Also, compounds with a [C(O)NH]2P(O)[N] fragment have not been reported to date. In the crystal structures of all three title compounds, adjacent molecules are linked via pairs of P=O...H—N hydrogen bonds, forming dimers with Ci symmetry. 相似文献