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131.
Hasan Nemati Kurosh Sedighi Mohammad Mohammadi Pirouz Ehsan Fattahi 《International Journal of Computational Fluid Dynamics》2013,27(3-4):83-94
A numerical investigation of the two-dimensional laminar flow around side-by-side rotating circular cylinders using Lattice Boltzmann method is conducted. The effects of variation of rotational speed ratio β and different gap spacings g* at Reynolds number of 100 are studied. A various range of rotational speed ratio 0 ≤ β ≤ 2 for four different gap spacings of 3, 1.5, 0.7 and 0.2 are investigated. Flow conditions and its characteristics, such as lift and drag coefficients and Strouhal number, is studied. The results indicated that as β increases, the flow changes its condition from periodic to steady after a critical rotational speed. Results also indicated that variation of the gap spacing and rotational speed has significant effect on wake pattern. Wake pattern in turn has significant effect on the Strouhal number. Finally, the result is compared with experimental and other numerical data. 相似文献
132.
Ali Nemati Hayati Mohammad Mehdi Ahmadi Soheil Mohammadi 《Transport in Porous Media》2012,93(1):13-27
Analytical solution of shock wave propagation in pure gas in a shock tube is usually addressed in gas dynamics. However, such
a solution for granular media is complex due to the inclusion of parameters relating to particles configuration within the
medium, which affect the balance equations. In this article, an analytical solution for isothermal shock wave propagation
in an isotropic homogenous rigid granular material is presented, and a closed-form solution is obtained for the case of weak
shock waves. Fluid mass and momentum equations are first written in wave and (mathematical) non-conservation forms. Afterwards
by redefining the sound speed of the gas flowing inside the pores, an analytical solution is obtained using the classical
method of characteristics, followed by Taylor’s series expansion based on the assumption of weak flow which finally led to
explicit functions for velocity, density and pressure. The solution enables plotting gas velocity, density and pressure variations
in the porous medium, which is of high interest in the design of granular shock isolators. 相似文献
133.
Saber Mohammadi Mohsen Masihi Mohammad Hossein Ghazanfari 《Transport in Porous Media》2012,91(3):973-998
Many heavy oil reservoirs contain discontinuous shales which act as barriers or baffles to flow. However, there is a lack
of fundamental understanding about how the shale geometrical characteristics affect the reservoir performance, especially
during polymer flooding of heavy oils. In this study, a series of polymer injection processes have been performed on five-spot
glass micromodels with different shale geometrical characteristics that are initially saturated with the heavy oil. The available
geological characteristics from one of the Iranian oilfields were considered for the construction of the flow patterns by
using a controlled-laser technology. Oil recoveries as a function of pore volumes of injected fluid were determined from analysis
of continuously recorded images during the experiments. We observed a clear bypassing of displacing fluid which results in
premature breakthrough of injected fluid due to the shale streaks. Moreover, the results showed a decrease of oil recovery
when shales’ orientation, length, spacing, distance of the shale from production well, and density of shales increased. In
contrast, an increase of shale discontinuity or distance of the shale streak from the injection well increased oil recovery.
The obtained experimental data have also been used for developing and validating a numerical model where good matching performance
has been observed between our experimental observations and simulation results. Finally, the role of connate water saturation
during polymer flooding in systems containing flow barriers has been illustrated using pore level visualizations. The microscopic
observations confirmed that besides the effect of shale streaks as heterogeneity in porous medium, when connate water is present,
the trapped water demonstrates another source of disturbance and causes additional perturbations to the displacement interface
leading to more irregular fingering patterns especially behind the shale streaks and also causes a reduction of ultimate oil
recovery. This study reveals the application of glass micromodel experiments for studying the effects of barriers on oil recovery
and flow patterns during EOR processes and also may provide a set of benchmark data for recovery of oil by immiscible polymer
flood around discontinuous shales. 相似文献
134.
By applying non-equilibrium Green's functions (NEGF) in combination with tight-binding (TB) model, we investigate and compare the electronic transport properties of perfect and defected bilayer armchair graphene nanoribbons (BAGNRs) under finite bias. Two typical defects which are placed in the middle of top layer (i.e. single vacancy (SV) and stone wale (SW) defects) are examined. The results reveal that in both perfect and defected bilayers, the maximum current refers to β-AB, AA and α-AB stacking orders, respectively, since the intermolecular interactions are stronger in them. Moreover it is observed that a SV decreases the current in all stacking orders, but the effects of a SW defect is nearly unpredictable. Besides, we introduced a sequential switching behavior and the effects of defects on the switching performance is studied as well. We found that a SW defect can significantly improve the switching behavior of a bilayer system. Transmission spectrum, band structure, molecular energy spectrum and molecular projected self-consistent Hamiltonian (MPSH) are analyzed subsequently to understand the electronic transport properties of these bilayer devices which can be used in developing nano-scale bilayer systems. 相似文献
135.
Behrooz Mirza Somayeh Soleimani‐Amiri Maziar Mirza 《Journal of Physical Organic Chemistry》2018,31(2)
Density functional theory (DFT) calculations introduced triplet ground states for [6]n SiC‐cyclacenes and ‐acenes with alternate silabenzene rings including silicon atoms in 2 opposite edges (n = 6, 8, 10, 12). The singlet‐triplet energy gap (ΔE(S‐T)), binding energy per atom (BE/n), and NBO calculation with very small band gap (ΔELUMO‐HOMO) confirmed the triplet ground states. In contrast to polyacenes, the singlet [6]n SiC‐cyclacenes displayed more stability improvement than triplets, through n increasing. This may open the way for synthesis of larger stable [6]n SiC‐cyclacenes. The ΔE(S‐T), BE/n, and the strain energy through homodesmic equations indicated more stability for larger [6]n SiC‐cyclacenes, which was more noticeable in singlet states. Cyclacenes and acenes with high conductivity and full point charge were introduced as suitable candidates for hydrogen storage. 相似文献
136.
Ali Asghar Mohammadi Salman Taheri Arman Amini Reza Ahdenov 《Molecular diversity》2018,22(4):999-1006
Triamide derivatives have been synthesized in good yields in a novel, one-pot, five-component, and efficient process by the reaction of Z-oxazolone, water, primary amines, aldehydes, isocyanides, in the presence of catalytic amount of KAl(SO4)2·12H2O (alum) as a non-toxic, reusable, inexpensive, and easily available reagent via Ugi reaction in aqueous solution. 相似文献
137.
Mahya Mohammadi Ahmad Sheykhi Mahdi Kord Zangeneh 《The European Physical Journal C - Particles and Fields》2018,78(12):984
We analytically and numerically study the properties of one-dimensional holographic p-wave superconductors in the presence of backreaction. We employ the Sturm–Liouville eigenvalue problem for the analytical calculation and the shooting method for the numerical investigations. We apply the \(\hbox {AdS}_{{3}}\)/\(\hbox {CFT}_{{2}}\) correspondence and determine the relation between the critical temperature \(T_{c}\) and the chemical potential \(\mu \) for different values of the mass m of a charged spin-1 field \(\rho _{\mu }\) and backreacting parameters. We observe that the data of both analytical and numerical studies are in good agreement. We find that increasing the backreaction and the mass parameter causes the greater values for \({T_{c}}/{\mu }\). Thus, it makes the condensation harder to form. In addition, the analytical and numerical approaches show that the value of the critical exponent \( \beta \) is 1 / 2, which is the same as in the mean field theory. Moreover, both methods confirm the existence of a second order phase transition. 相似文献
138.
Z. Jahangiri Tazekand M. Mohseni M. A. Mohammadi H. Sabri 《Brazilian Journal of Physics》2018,48(3):266-280
In this paper, we have considered the energy spectra, quadrupole transition probabilities, energy surface, charge radii, and quadrupole moment of the190Hg nucleus to describe the interplay between phase transitions and configuration mixing of intruder excitations. To this aim, we have used four different formalisms: (i) interacting boson model including configuration mixing, (ii) Z(5) critical symmetry, (iii) U(6)-based transitional Hamiltonian, and (iv) a transitional interacting boson model Hamiltonian in both interacting boson model (IBM)-1 and IBM-2 versions which are based on affine \( \widehat{SU\left(1,1\right)} \) Lie algebra. Results show the advantages of configuration mixing and transitional Hamiltonians, in particular IBM-2 formalism, to reproduce the experimental counterparts when the weight of spherical symmetry increased. 相似文献
139.
Fatemeh Sheikholeslami-Farahani Daryoush Zareyee Marziyeh Mohammadi Mahboubeh Ghasemian Samira Soltani 《Phosphorus, sulfur, and silicon and the related elements》2016,191(10):1334-1338
A series of polysubstituted cyclopentadienephosphonate derivatives were synthesized via one-pot multicomponent reactions of primary amines and phosphites with activated acetylenic compounds in water as the solvent at room temperature.Particularly valuable features of this method include high yields of products, broad substrate scope, short reaction time and a straightforward procedure. 相似文献
140.
Mohammad Bagher Majnooni Bahareh Mohammadi Ronak Jalili Gholamreza Bahrami 《液相色谱法及相关技术杂志》2016,39(19-20):877-881
A new high-performance liquid chromatographic method is described for the determination of fatty acids in seed oils. The method was based on precolumn derivatization with 9-fluorenylmethyl chloroformate as a labeling agent and fluorescence detection. Fatty acids were extracted from the samples and subjected to derivatization with the reagent at 60°C for 10?min. The chromatographic separation of 14 fatty acids (C10–C22) was achieved on a combined loading compression octadecyl sulfate (CLC-ODS) column with a run time of 30?min. Three-step gradient elution of a mobile phase consisted of acetonitrile and water was used, and the signal was monitored at excitation and emission wavelengths of 265 and 315?nm, respectively. The method indicated favorable sensitivity and reproducibility for fatty acids’ derivatives. The detection limits, at a signal-to-noise ratio of 3, were 0.01–0.05?µg/ml and relative standard deviations (RSDs) were less than 0.27%. Excellent linear responses were observed with coefficients of 0.9995. This method was applied to quantify fatty acids in white, brown, and black sesame seeds’ oil. 相似文献