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91.
Hadi Beiginejad Davood Nematollahi Sadegh Khazalpour 《Journal of the Iranian Chemical Society》2017,14(4):873-882
Electrochemical oxidations of 4-methylcatechol (1), 4-tert-butylcatechol (5) and catechol (7) in the presence of different nucleophiles have been investigated both experimentally and theoretically. Experimental results have been obtained by means of cyclic voltammetry and controlled-potential coulometry. Also the theoretical results were calculated at DFT (B3LYP) level of theory and 6–311+G (p, d) basis set. The calculated results indicate that oxidation potential of catechols (1, 5, 7) and their substituted species are directly dependent on the ?G tot, and continuance of reactions during electrolysis is dependent on ?G tot of produced species on the surface of electrode. The current study indicates that theoretical studies along with empirical research can be useful in displaying electrochemical reaction mechanisms. 相似文献
92.
Maziar Dehghan Mohammad Sadegh Valipour Seyfollah Saedodin 《Transport in Porous Media》2014,102(2):139-152
This study focuses analytically on the local thermal non-equilibrium (LTNE) effects in the developed region of forced convection in a saturated porous medium bounded by isothermal parallel-plates. The flow in the channel is described by the Brinkman–Forchheimer-extended Darcy equation and the LTNE effects are accounted by utilizing the two-equation model. Profiles describing the velocity field obtained by perturbation techniques are used to find the temperature distributions by the successive approximation method. A fundamental relation for the temperature difference between the fluid and solid phases (the LTNE intensity) is established based on a perturbation analysis. It is found that the LTNE intensity ( $\Delta \textit{NE}$ ) is proportional to the product of the normalized velocity and the dimensionless temperature at LTE condition. Also, it depends on the conductivity ratio, Da number, and the porosity of the medium. The intensity of LTNE condition ( $\Delta \textit{NE}$ ) is maximum at the middle of the channel and decreases smoothly to zero by moving to the wall. Finally, the established relation for the intensity of LTNE condition is simple and fundamental for estimating the importance of LTNE condition and validation of numerical simulation results. 相似文献
93.
In this numerical study, we present and demonstrate a compact, electrical plasmonic beam-steering device composed of anisotropic material. The splitting angle can be modulated by the external electric or magnetic field. The physical principle of this phenomenon is evaluated from the phase of surface plasmon polaritons and Fabry-Perot (F-P) resonance in slits. Our numerical simulations with finite-difference time-domain (FDTD) technique reveals that wide-angle (±27°) beam steering can be achieved. Moreover, the efficiency increases when increasing the steering angle. A special characteristic of the presented structure gives an opportunity to be used as an efficient element in a high integrated optical device for miniaturization and tuning purposes. 相似文献
94.
Ali Azadeh Mohamad Sadegh Sangari Alireza Shamekhi Amiri 《Applied Mathematical Modelling》2012,36(4):1455-1464
Implementing efficient inspection policies is much important for the organizations to reduce quality related costs. In this paper, a particle swarm optimization (PSO) algorithm is proposed to determine the optimal inspection policy in serial multi-stage processes. The policy consists of three decision parameters to be optimized; i.e. the stages in which inspection occurs, tolerance of inspection, and size of sample to inspect. Total inspection cost is adopted as the performance measure of the algorithm. A numerical example is investigated in two phases, i.e. fixed sample size and sample size as a decision parameter, to ensure the practicality and validity of the proposed PSO algorithm. It is shown that PSO gives better results in comparison with two other algorithms proposed by earlier works. 相似文献
95.
A theoretical study on first protonation step of a series of triazacycloalkanes with general formula {([X]aneN3, X = 9–12)} (X = 9, L222; X = 10, L223; X = 11, L233; X = 12, L333) is reported. The geometry of all ligands and their monoprotonated forms were fully optimized at both the Hartree–Fock and DFT (B3LYP) levels of theory using 6-31+G* basis set. Then the first proton macroaffinities were calculated from the proton microaffinities according to defined equations. It is shown that there are good correlations between the calculated gas-phase first proton macroaffinities of these ligands with their protonation constants in solution. 相似文献
96.
Among all properties of reservoir rocks, permeability is an important parameter which is typically measured from core samples in the laboratory. Due to limitations of core drilling all over a reservoir, simulation of rock porous media is demanded to explore more scenarios not seen in the available data. One of the most accurate methods is cross correlation based simulation (CCSIM) which recently has broadly applied in geoscience and porous media. The purpose of this study is producing realizations with the same permeability trend to a real sample. Berea sandstone sample is selected for this aim. Permeability results, extracted from smaller sub-samples of the original sample, showed that classic Kozeny–Carman permeability trend is not suitable for this sample. One reason can be due to lack of including geometrical and fractal properties of pore-space distribution in this equation. Thus, a general trend based on fractal dimensions of pore-space and tortuosity of the Berea sample is applied in this paper. Results show that direct 3D stochastic modeling of porous media preserves porous structure and fractal behavior of rock. On the other hand, using only 2D images for constructing the 3D pore structures does not reproduce the measured experimental permeability. For this aim, a hierarchical sampling is implemented in two and three steps using both 2D and 3D stochastic modeling. Results showed that two-step sampling is not suitable enough, while the utilized three-step sampling occurs to be show excellent performance by which different models of porous media with the same permeability trend as the Berea sandstone sample can be generated. 相似文献
97.
Freidon Amini Mohammad Sadegh Shahidzadeh 《Archive of Applied Mechanics (Ingenieur Archiv)》2010,80(3):255-269
In this research, a sensitivity approach to finite element model updating is used to determine stiffness reduction factors
from measured structural response. The used method causes a set of nonlinear ill-conditioned equations that need to be linearized
and regularized in order to find the solution. A new approach to solve the problem is presented using variable regularization
parameter. Utilization of variable regularization parameter eliminates dependency on the number of iterations and prevents
the loss of regularization effect due to iterations. A new stopping criteria is used which is based on the difference between
mean and variance of last iterations. Furthermore the results show that using wavelet transform to update the model yields
better results than modal parameters. Expedient performance of the proposed method is shown through a numerical simulation. 相似文献
98.
S. Sadegh Hassani M. R. Ghasemi M. Rashidzadeh Z. Sobat 《Crystal Research and Technology》2009,44(9):948-952
Ethylene oxide catalyst is a high metal loading catalyst, in which silver crystals is impregnated on α‐Al2O3 support. In this type of catalyst, metal dispersion plays an important role on catalyst selectivity for desired products. In this work, silver nitrate and silver oxide together with oxalic and lactic acid as the raw materials were used with different impregnation techniques to make catalysts with high silver content and dispersion. It is also known that the use of promoters affect the metal dispersion on the catalyst support and for that cesium was used as the promoter to improve the silver crystal dispersion. Physical and chemical characteristics of the prepared catalysts, i.e., surface area, pore volume, silver content, nano‐sized silver crystals and their dispersion were measured using BET method, Atomic Absorption Spectroscopy, X‐ray diffraction and TEM. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
99.
We use some fractal analysis methods to study river flow fluctuations. The result of the Multifractal Detrended Fluctuation Analysis (MF-DFA) shows that there are two crossover timescales at s1×∼12 and s2×∼130 months in the fluctuation function. We discuss how the existence of the crossover timescales are related to a sinusoidal trend. The first crossover is due to the seasonal trend and the value of second one is approximately equal to the well-known cycle of sun activity. Using Fourier Detrended Fluctuation Analysis, the sinusoidal trend is eliminated. The values of Hurst exponents of the runoff water of rivers without the sinusoidal trend show a long-range correlation behavior. For the Daugava river, the value of Hurst exponent is 0.52±0.01 and also we find that these fluctuations have multifractal nature. Comparing the MF-DFA results for the remaining data set of Daugava river to those for shuffled and surrogate series, we conclude that its multifractal nature is almost entirely due to the broadness of probability density function. 相似文献
100.
Yousef Shafieyan Shahriar Sharifi Mohammad Imani Mohammad Ali Shokrgozar Neda Aboudzadeh Mohammad Atai 《先进技术聚合物》2011,22(12):2182-2190
Fabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and 1H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献