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61.
The acid-catalyzed cyclocondensation of N,N'-bisaryl (aryl = 2-pyrimidinyl, 2-pyrazinyl and 4-nitrophenyl) methanediamines 5a-c with aqueous formaldehyde in refluxing acetonitrile leads to the formation of the corresponding 1,3,5-triaryl-1,3,5-hexa-hydrotriazines 6a-c. The stoichiometric reactions of 2-aminopyrimidine and 2-amino-pyrazine with aqueous formaldehyde in acetonitrile under reflux conditions also afforded 6a and 6b, respectively. Treatment of 2-aminopyrimidine with aqueous formaldehyde in a 3:2 ratio yielded N,N',N"-tris(2-pyrimidinyl)dimethylenetriamine (7a) as a sole product, which upon subsequent reaction with formaldehyde also afforded 6a. The reaction of N,N'-biphenylmethanediamine with formaldehyde was also investigated. 相似文献
62.
We investigate the occurrence of Shimura (special) subvarieties in the locus of Jacobians of abelian Galois covers of in and give classifications of families of such covers that give rise to Shimura subvarieties in the Torelli locus inside . Our methods are based on Moonen–Oort works as well as characteristic p techniques of Dwork and Ogus and Monodromy computations. 相似文献
63.
Davood Nori‐Shargh Abolfazl Soofi Nasrin Saroogh Farahani Farzad Deyhimi 《国际化学动力学杂志》2005,37(7):427-433
This work reports the results of a kinetic and mechanistic investigations of the addition reaction of triphenylphosphine to para‐naphtoquinone in 1,2‐dichloromethane as solvent. The order of reaction with respect to the reactants was determined using initial rate method, and the rate constant was obtained on the basis of pseudo‐first‐order method. Variable time method using Uv–Vis spectrophotometry (at 400 nm) was utilized for monitoring this addition reaction, for which the following Arrhenius equation was obtained: The resulting activation parameters Ea, ΔH#, ΔG#, and ΔS# at 300 K were 13.63, 14.42, 18.75 kcal mol?1, and ?14.54 cal mol?1K?1, respectively. The results suggest that the reaction is first order with respect to both triphenylphosphine and para‐naphthoquinone. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 427–433, 2005 相似文献
64.
This paper proposes a linear constrained model predictive control (MPC) to solve the path following problem for quadrotor unmanned aerial vehicles. In the controller, an augmented model is employed to completely eliminate the tracking error due to external disturbances imposed on the quadrotor. The proposed controller is capable of improving the trade-off between feasibility and performance of the system. By approximating the control input sequence in MPC with Laguerre function, the computational burden significantly decreases and the closed-loop performance improves. In addition, a prescribed stability procedure is applied to guarantee the asymptotic stability of the quadrotor error dynamics. Besides, the proposed method improves the numerical ill-conditioning problem in solving MPC, by modifying the position of the closed-loop system poles to lie inside the unit circle. In the simulation results, two scenarios for the quadrotor tracking problem are considered. The results demonstrate the capability and the effectiveness of the proposed control strategy in disturbance rejection, fast trajectory tracking and the quadrotor stability, while a desired performance is achieved. 相似文献
65.
Mahdi Alipour Mohammad Amin Torabi Mohammad Sareban Hadi Lashini Ehsan Sadeghi Abolfazl Fazaeli 《基于设计的结构力学与机械力学》2020,48(5):525-541
AbstractIn this article, we investigated the effect of martensite morphology on the mechanical properties and formability of dual phase steels. At first, three heat treatment cycles were subjected to a low-carbon steel to produce ferrite–martensite microstructure with martensite morphology of blocky-shaped, continuous, and fibrous. Tensile tests were then carried out so as to study mechanical properties, particularly the strength and strain hardening behavior of dual phase steels. In order to study the formability of dual phase samples, Forming Limit Diagram was obtained experimentally and numerically. Experimental forming limit diagram was obtained using Nakazima forming test, while Finite Element Method was utilized to numerically predict the forming limit diagram. The results indicated that the dual phase samples with fibrous martensite morphology had the highest tensile properties and strain rate hardening out of the three different microstructures. Blocky-shaped martensite morphology, on the other hand, had the worst mechanical properties. The study of the strain hardening behavior of dual phase sample by Kocks–Mecking-type plots, evinced two stages of strain hardening for all specimens with different microstructures: stages III and IV. The forming limit diagram of dual phase steels also proved that samples with fibrous martensite morphology had the best formability compared to other two microstructures. The simulated forming limit diagram manifested that there is a good agreement between experimental results and those obtained by FEM. 相似文献
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68.
Zahra Danesh Kaftroudi Esfandiar Rajaei Abolfazl Mazandarani 《Journal of Russian Laser Research》2014,35(2):124-137
We investigate the physics of an internal device for a high-performance, vertical-cavity surface-emitting laser operating at 1.305 μm. Experimental results are analyzed using as the simulation software a photonic-integrated-circuit simulator in 3D (PICS3D), which is a state-of-the-art 3D simulator for surface- and edge-emitting laser diodes, semiconductor optical amplifiers, and other similar active waveguide devices. The 2D/3D semiconductor equations are coupled to the optical modes in both lateral and longitudinal directions. Optical properties such as the quantum well/wire/dot optical gain and spontaneous emission rates are computed self-consistently. Careful adjustments of material parameters led to an excellent agreement between simulation and measurements. Simulation results show that the maximum output power is limited by electron leakage from quantum wells. 相似文献
69.
A facile, one-pot stereoselective synthesis of novel trans-4,5-dihydroxy-2-aryl-1,3-bis(heteroaryl)imidazolidines is achieved by a cyclocondensation reaction of 2 equiv of heteroarylamines with benzaldehyde derivatives, in the presence of guanidinium chloride as a polyfunctional organocatalyst, with aqueous glyoxal to afford the title products. This general protocol provides a wide range of new polyfunctionalized imidazolidines in good to high yields. 相似文献
70.
Elahe Sedghamiz Zahra Halfinezhad Abolfazl Shiroudi Ehsan Zahedi 《Research on Chemical Intermediates》2013,39(8):3843-3857
Adsorption of nitrogen dioxide in three different configurations on the exterior surface of C30B15N15 is studied using density functional theory calculations. To this end, we optimized the structures of raw C30B15N15 and nine NO2–C30B15N15 complexes at the B3LYP/6-31G* level of theory and then calculated chemical shielding (CS) tensors at the GIAO-B3LYP/6-311G** level for the optimized structures. The calculated chemical shielding isotropy (CSI), chemical shielding anisotropy (CSA), and orientation of CS tensors (Euler angles) reveal that the adsorption configurations (nitro, trans-nitrite, and cis-nitrite) have different effects on the electronic structure of C30B15N15. Natural atomic charges based on natural population analysis (NPA) were used to justify the changes in CSI values after gas sorption. 相似文献