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631.
Salar Amoli H Porgam A Bashiri Sadr Z Mohanazadeh F 《Journal of chromatography. A》2006,1118(1):82-84
In this study a rapid, simultaneous analysis of V, Ni, Fe and Cu in crude oil was achieved by high performance liquid chromatography using 10 cm length reversed-phase C18 column. Since the amount of metal ions is at a very low level, in this work, solvent extraction of metals by a ligand such as 8-hydroxyquinoline from acidic media was investigated with some modification to previous procedures. Average extraction recoveries were 99, 85, 94 and 96 for V, Ni, Fe and Cu, respectively. The proposed method was successfully applied to the crude oil which was obtained from Koshk area in southern Iran. Fast analysis of metal ion in reversed-phase short column was achieved with methanol/water (55/45, v/v) and the detection limits measured as three times the background noise were obtained. Also it was shown that if small amount of 8-hydroxyquinoline was added to the mobile phase, the peak height and the peak symmetry were improved. A typical chromatogram for the separation of the 8-hydroxyquinoline complexes of V (V), Ni (II), Fe (III) and Cu (II) in crude oil was obtained in less than 4 min. 相似文献
632.
Ahmad Reza Massah Roozbeh Javad Kalbasi Anahita Shafiei 《Monatshefte für Chemie / Chemical Monthly》2012,141(10):643-652
Abstract
ZSM-5 has been modified as supported sulfuric acid (ZSM-5-SO3H) and introduced for the first time as a mild, convenient, reusable, and heterogeneous catalyst. Various types of aldehydes were efficiently converted to their 1,1-diacetates using a catalytic amount of ZSM-5-SO3H in excellent yields under solvent-free and heterogeneous conditions at room temperature. The deprotection of 1,1-diacetates has also been achieved using this novel catalyst in ethanol. The procedure is operationally simple, environmentally benign, and only a stoichiometric amount of anhydride is used. 相似文献633.
In the present paper, fundamental frequency optimization of symmetrically laminated composite plates is studied using the combination of Elitist-Genetic algorithm (E-GA) and finite strip method (FSM). The design variables are the number of layers, the fiber orientation angles, edge conditions and plate length/width ratios. The classical laminated plate theory is used to calculate the natural frequencies and the fitness function is computed with a semi-analytical finite strip method which has been developed on the basis of full energy methods. To improve the speed of the optimization process, the elitist strategy is used in the Genetic algorithm. The performance of the E-GA is also compared with the simple genetic algorithm and shows the good efficiency of the E-GA algorithm. A multi-objective optimization strategy for optimal stacking sequence of laminated box structure is also presented, with respect to the first natural frequency and critical buckling load, using the weighted summation method to demonstrate the effectiveness of the E-GA. Results are corroborated by comparing with other optimum solutions available in the literature, wherever possible. 相似文献
634.
Fazlollah Soleymani Fuad W. Khdhr Rostam K. Saeed Javad Golzarpoor 《Mathematical Methods in the Applied Sciences》2020,43(14):8192-8203
For the computation of a matrix sign function, a family of iterative methods is proposed. for some cases of the accelerator parameters, this method is proven to converge globally with higher rates of convergence. Its stability is discussed analytically as well. to illustrate the efficiency of the proposed methods from the family, several tests of various matrix sizes are considered to worked out. 相似文献
635.
636.
Javad Azizian Ali Reza Karimi Zahra Kazemizadeh Ali A. Mohammadi Mohammad R. Mohammadizadeh 《Tetrahedron letters》2005,46(36):6155-6157
11H-Indeno[1,2-b]quinoxalin-11-ones generated in situ from ninhydrin and various 1,2-phenylenediamines, catalysed by montmorillonite K10 under microwave irradiation, condense with 4-hydroxyproline to produce 11-(1H-pyrrol-1-yl)-11H-indeno[1,2-b]quinoxaline derivatives in good yields. 相似文献
637.
Mitra Ghassemzadeh Samira Bahemmat Javad Malakootikhah Bernhard Neumüller Alexander Rothenberger 《无机化学与普通化学杂志》2007,633(8):1178-1182
The reactions of AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) with 2‐hydroxybenzaldehyde (salicylaldehyde) and 4‐hydroxybenzaldehyde in methanol under reflux conditions led to the corresponding Schiff‐bases ( H2L1 and H2L2 ). The reaction of H2L1 with palladium acetate in ethanol and additional recrystallization from toluene gave the tetrameric complex [Pd(L)]4·2C7H8 ( 2 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for H2L1 at ?80 °C: space group P21/c with a = 1285.4(1), b = 707.7(1), c = 1348.2(1) pm, β = 109.32(1)°, Z = 4, R1 = 0.0328, H2L2 at ?80 °C: space group P43212 with a = 762.5(1), b = 762.5(1), c = 4038.9(2) pm, Z = 8, R1 = 0.025 and for 2 at ?103 °C: space group C2/c with a = 2862.5(6), b = 2847.6(6), c = 1727.8(4) pm, β = 105.18(3)°, Z = 8, R1 = 0.0704. 相似文献
638.
Javad Zolgharnein Hoomayon Tahmasebi Morteza Habibi Saeid Amani 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(3-4):231-234
The complexation of some alkali and alkaline earth cations with18-crown-6(18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexyl-18-crown-6 (DCY18C6), and dibenzopyridino-18-crown-6 (DBPY18C6) in a methanol solution has been studied by a competitive potentiometric titration using Ag+/Ag electrode as a probe. The stoichiometry and stability constants of the resulting complexes have been evaluated by the MINIQUAD program. The stoichiometry for all resulting complexes was 1:1. The order of stability of Ag+ complexes with desired crown ethers varied as DBPY18C6 > DCY18C6 > 18C6 > DB18C6.The stability of the resulting complexes for each of these crown ethers varies in the order ofK+ > Na+ and Ba2+ > Sr2+ > Ca2+ > Mg2+.For each of the used metal ions the major sequence of the stability constants of the resulting complexes varies as DCY18C6 > 18C6 > DB18C6 > DBPY18C6 with minor exceptions. 相似文献
639.
Issa Yavari Mehdi Adib Hamid R. Bijanzadeh Majid M. M. Sadegi Hossein Logmani-Khouzani Javad Safari 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1109-1113
Summary. A dynamic NMR effect is observed in the 13C NMR spectra of anhydrous quinophthalone (quinoline yellow) and its monohydrate in the vicinity of 47°C and 0°C, respectively,
and is attributed to a restricted rotation around the polarized carbon–carbon double bond. The free energy of activation for
this process in anhydrous quinophthalone and the monohydrate is 65±2 and 55±2 kJ · mol−1, respectively, in CDCl3.
Received September 25, 2001. Accepted (revised) November 14, 2001 相似文献
640.
The effect of a 30% variation around a mean value of thermal property values on the vulcanization of 1 and 2 cm thick rubber sheets is studied, by using a molding process at 40°C for the initial rubber and 120°C for the injected rubber. The thermal properties chosen are the diffusivity and the product of density and heat capacity. This variation in thermal properties has a slight effect on sheets 1 cm thick, but becomes significant when the thickness is 2 cm. This must be taken into account when calculating the time necessary for the state-of-cure to reach 90% at the midplane of the sheets. 相似文献