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Beya Haouas Taieb Saied Hanen Ayari Youssef Arfaoui Mohamed Lamine Benkhoud Khaled Boujlel 《Journal of Sulfur Chemistry》2016,37(4):391-400
Electrogenerated cyanomethylanions obtained by reduction of dry acetonitrile at a steel grid cathode were used to promote the addition of ethyl bromoacetate to thiourea derivatives. The reaction yields the corresponding 2-imino-1,3-thiazolidin-4-one. The reaction pathway was discussed based on the kinetic and thermodynamic data obtained by computational methods. In addition, the biological activity of these new compounds was also investigated. 相似文献
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Beya K. Pintelon R. Schoukens J. Lataire P. Guillaume P. Mpanda-Mabwe B. Delhaye M. 《Energy Conversion, IEEE Transaction on》1994,9(2):270-280
This paper describes a newly developed measurement and identification technique for synchronous machine parameters. The first part presents a technique to generate periodic broadband power signals with a controllable amplitude spectrum using a classic rectifier bridge. These signals are well suited to measure the frequency response function of large power systems using the fast Fourier transform. The broadband measurements are compared with the classical mono frequency measurements. The second part presents a frequency domain identification method taking into account the uncertainty on all the current and voltage measurements, and giving a confidence interval on the estimated synchronous machine parameters. As an illustration the d- and q-axis model of a 1.905 kVA/220 V micro-machine is identified 相似文献
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Electrochemical study of N-thioamidoimidates 1 is carried out in non-aqueous solvent at platinum electrodes by means of cyclic voltammetry at different scan rates. A mechanistic investigation shows that the oxidation of the NH bond of these substrates leads, during macroscale electrolysis, to oxadiazole-3-thione 2 with satisfactory yields according to an ECE mechanism. On the other hand, the rate of deprotonation kH and the standard oxidation potential of the N-thioamidoimidate cation radical/N-thioamidoimidate couple were derived directly and indirectly by the use of the homogenous redox catalysis. The perfect agreement of the predicted kinetic with the experiment data both under homogeneous and heterogeneous electron transfer provides further support for the ECE mechanism. 相似文献
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The problem of two-dimensional natural convection flow of a dielectric fluid in a square inclined enclosure with a fin placed on the hot wall is investigated numerically. The fin thickness and length are 1/10 and 1/2 of the enclosure side, respectively. The Rayleigh number is varied from 103 to 5 × 105 and the solid to fluid thermal conductivity ratio is fixed at 103. The enclosure tilt or inclination angle is varied from 0° to 90°. The streamlines and isotherms within the enclosure are produced and the heat transfer is calculated. It is found that for 2.5 × 104 ≤ Ra ≤ 2.5 × 105, the average Nusselt number is maximum when γ = 0° and minimum when γ = 90°. For Ra = 5 × 105, the values of enclosure tilt angle for which the average Nusselt number is maximum or minimum are completely different due to the transition to unsteady state. In this case, the maximum heat transfer is obtained for γ = 60°, while the minimum heat transfer is predicted for γ = 0°. Monomial correlations relating the average Nusselt number with the different values of the Rayleigh number from 104 to 105 are determined for two different angles, γ = 0° and γ = 90°. 相似文献
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四元磷酸盐玻璃的 Raman 光谱和 AlO_6丰度变化的研究表明,玻璃的离子电导率主要由活动离子 Na~ 的总数决定,Na_2O 含量越高,其电导率也越高;但是,玻璃结构对电导率也有一定影响。由 AlO_4四面体和(Al—O—P)~-基团构成结构网络的某些 Na_2O—Al_2O_3—P_2O_5玻璃有较高的离子电导率。当以 MgO 替代玻璃中的 Al_2O_3时,由于MgO 只起网络修饰体作用,电导率是单调下降的。以 SiO_2替代 Al_2O_3时,情况有所不同。由于 SiO_2可能兼起网络形成体和修饰体的作用,无疑使玻璃结构变得复杂了。只有在参与网络的 SiO_2达到相当量的情况下,才有希望提高玻璃的电导率。外加 SiO_2到 Na_2O—Al_2O_2—P_2O_5玻璃内,导致玻璃中的 Na~ 离子的相对量降低,所以其电导率总是下降的。 相似文献
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Nader Ben Cheikh Brahim Ben Beya Taieb Lili 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(2):131-151
A computational procedure is presented with an accelerated full-multigrid scheme for an efficient modeling of time-dependent buoyancy-driven flows. The smoother is the iterative red-and-black successive overrelaxation (RBSOR) scheme. In order to improve the convergence, an acceleration parameter, Γ, is implemented in the classical full-multigrid procedure. It is shown that an optimal value of Γ = 3.75 minimizes the number of iterations needed for convergence. Numerical results are presented and compared with available investigations for an 8:1 differentially heated enclosure and a square heated cavity. Solutions for Prandtl number Pr = 0.71, Rayleigh number Ra = 3.4 × 105 for the 8:1 heated enclosure, and 105 ≤ Ra ≤ 109 for the square cavity are presented and show excellent agreement. 相似文献
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In the present work, we investigate numerically the natural convection flow in 3D cubic enclosure tilted at an angle (γ) with respect to the vertical position. The enclosure is heated and cooled from the two opposite walls while the remaining walls are adiabatic. The numerical procedure adopted in this analysis yield consistent performance over a wide range of parameters. Simulations have been carried out for Rayleigh numbers Ra ranging from 103 to 1.3 × 105, Prandtl number, Pr, (0.71 ≤ Pr ≤ 75) and inclination angle γ (0° ≤ γ ≤ 90°). Particular attention is focused on the three-dimensional steady effects that can arise in such configuration that seem to be unknown in the literature, even for relatively small values of the Rayleigh number. The 3D flow characteristics and thermal fields are analyzed in terms of streamlines, isotherms and Nusselt numbers. A periodic behavior of the 3D flow has been observed at Ra = 8.5 × 104 with a fundamental frequency of 8.27. The Hopf bifurcation is localized. In addition, time-dependent solutions reveal that the flow characteristics depend on the inclination angle γ. The effects of Prandtl number on heat transfer and fluid flow is significant for Pr ≥ 6. 相似文献
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