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21.
Journal of Thermal Analysis and Calorimetry - In this study, an experimental study on the effect of temperature and particles concentration on the dynamic viscosity of MWCNT-OH and their composites... 相似文献
22.
Alireza Pourhossein Masoud Madani Mohsen Shahlaei Kambiz Fakhri Parisa Alimohamadi Maryam Amiri 《Central European Journal of Chemistry》2009,7(3):382-387
A sensitive, simple and rapid method for ultra-trace determination of iron and manganese based on ultrasound assisted pseudodigestion
in citric acid fermentation medium samples (beet and cane molasses and raw sugar based mediums) is described. Parameters influencing
pseudo-digestion, such as sonication time, sample mass and solvent system were fully optimized. Final solutions obtained upon
sonication were analyzed by electrothermal atomic absorption spectrometry (ETAAS). The best conditions for metal pseudo-digestion
were as follows: a 25, 30 and 20 min sonication time for beet molasses, cane molasses and raw sugar based medium samples,
respectively, 0.7 g sample mass of raw sugar based samples, 0.5 g sample mass of molasses based samples and an extraction
mixture of concentrated HNO3-H2O2, in 25 mL of solvent. Analytical results obtained for the two metals by ultrasound assisted pseudo-digestion and conventional
wet digestion methods showed a good agreement. This method reduces the time required for all treatments (heating to dryness,
cooling and separation) in comparison with conventional wet digestion method. The accuracy of the method was tested by comparing
the obtained results with that of conventional wet digestion method.
相似文献
23.
Fakhri Yousefi 《Ionics》2012,18(8):769-775
In our previous paper, we extended the Tao and Mason equation of state (TM EOS) to pure ionic liquids. Here we apply TM EOS based on statistical?Cmechanical perturbation theory to binary mixtures of ionic liquids. Three temperature-dependent quantities are needed to use the equation of state: the second virial coefficient, B 2, effective van der Waals co-volume, b, and a scaling factor, ??. The second virial coefficients are calculated from a correlation that uses the normal boiling temperature and normal boiling density. ?? and b can also be calculated from the second virial coefficient by scaling. In this procedure, the number of input parameters, for calculation of B 2, ??, and b reduced from 5 (i.e., critical temperature, critical pressure, acetric factor, Boyle temperature T B, and the Boyle volume ?? B) to 2 (i.e., T bp and ?? bp). At close inspection of the deviations given in this work, the TM EOS predicts the densities with a mean AAD of 1.69%. The density of selected system obtained from the TM EOS has been compared with those calculated from perturbed-hard-sphere equation of state. Our results are in favor of the preference of the TM EOS over another equation of state. The overall average absolute deviation for 428 data points that calculated by perturbed-hard-sphere equation of state is 2.60%. 相似文献
24.
Axial rotational diffusion of rodlike polymers is important in processes such as microtubule filament sliding and flagella beating. By imaging the motion of small kinks along the backbone of chains of DNA-linked colloids, we produce a direct and systematic measurement of axial rotational diffusivity of rods both in bulk solution and near a wall. The measured diffusivities decrease linearly with the chain length, irrespective of the distance from a wall, in agreement with slender-body hydrodynamics theory. Moreover, the presence of small kinks does not affect the chain's axial diffusivity. Our system and measurements provide insights into fundamental axial diffusion processes of slender objects, which encompass a wide range of entities including biological filaments and linear polymer chains. 相似文献
25.
Sultan T. Abu-Orabi M. Adnan Atfah Ibrahim Jibril Fakhri M. Mari'i Amer Al-Sheikh Ali 《Journal of heterocyclic chemistry》1989,26(5):1461-1468
Phenyl azide 1 and several substituted benzyl azides 2a-o underwent 1,3-dipolar cycloaddition reactions with dimethyl acetylenedicarboxylate 3, phenylacetylene 4 and ethyl propiolate 5 to afford the triazoles 6-13. The reactions of these azides with ethyl propiolate were found to be completely regiospecific. 相似文献
26.
Ashkan Fakhri 《Optimization》2016,65(5):1023-1038
This paper tries to minimize the sum of a linear and a linear fractional function over a closed convex set defined by some linear and conic quadratic constraints. At first, we represent some necessary and sufficient conditions for the pseudoconvexity of the problem. For each of the conditions, under some reasonable assumptions, an appropriate second-order cone programming (SOCP) reformulation of the problem is stated and a new applicable solution procedure is proposed. Efficiency of the proposed reformulations is demonstrated by numerical experiments. Secondly, we limit our attention to binary variables and derive a sufficient condition for SOCP representability. Using the experimental results on random instances, we show that the proposed conic reformulation is more efficient in comparison with the well-known linearization technique and it produces more eligible cuts for the branch and bound algorithm. 相似文献
27.
Indirect echoes (such as stimulated echoes) are a source of signal contamination in multi-echo spin-echo T2 quantification and can lead to T2 overestimation if a conventional exponential T2 decay model is assumed. Recently, nonlinear least square fitting of a slice-resolved extended phase graph (SEPG) signal model has been shown to provide accurate T2 estimates with indirect echo compensation. However, the iterative nonlinear least square fitting is computationally expensive and the T2 map generation time is long. In this work, we present a pattern recognition T2 mapping technique based on the SEPG model that can be performed with a single pre-computed dictionary for any arbitrary echo spacing. Almost identical T2 and B1 maps were obtained from in vivo data using the proposed technique compared to conventional iterative nonlinear least square fitting, while the computation time was reduced by more than 14-fold. 相似文献
28.
Fakhri Hanieh Mahjoub Ali Reza Aghayan Hassan 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(2):449-461
Journal of Radioanalytical and Nuclear Chemistry - The presence of heavy metals in water sources have created serious environmental concerns. In this study, 10-tungsten-2-molybdophosphoric acid... 相似文献
29.
A fairly selective and sensitive spectrophotometric method for the trace determination of nitrite in aqueous solution is described. The titled ion reacts with indole in acidic medium to form a soluble pink-red product, which is measured at 530 nm. Maximum absorbance is achieved in 10 min and remains constant for about 45 min. This method is applicable to water samples containing 0–2 μg/ml with a relative error of 0.0 to–0.8%, and relative standard deviation of 0.3–0.8%, depending on the concentration level. The optimum reaction conditions affecting and related to the color reaction and interferences due to foreign ions have been studied. 相似文献
30.
Jalil Moghadasi Fakhri Yousefi Mohammad Mehdi Papari Mohammad Ali Faghihi Ali Asghar Mohsenipour 《Heat and Mass Transfer》2009,45(11):1453-1466
It is the purpose of this paper to extract unlike intermolecular potential energies of five carbon dioxide-based binary gas
mixtures including CO2–He, CO2–Ne, CO2–Ar, CO2–Kr, and CO2–Xe from viscosity data and compare the calculated potentials with other models potential energy reported in literature. Then,
dilute transport properties consisting of viscosity, diffusion coefficient, thermal diffusion factor, and thermal conductivity
of aforementioned mixtures are calculated from the calculated potential energies and compared with literature data. Rather
accurate correlations for the viscosity coefficient of afore-cited mixtures embracing the temperature range 200 K < T < 3273.15 K is reproduced from the present unlike intermolecular potentials energy. Our estimated accuracies for the viscosity
are to within ±2%. In addition, the calculated potential energies are used to present smooth correlations for other transport
properties. The accuracies of the binary diffusion coefficients are of the order of ±3%. Finally, the unlike interaction energy
and the calculated low density viscosity have been employed to calculate high density viscosities using Vesovic–Wakeham method. 相似文献