排序方式: 共有202条查询结果,搜索用时 15 毫秒
21.
Rouhollah Heydari Mohammad Hosseini Reza Rezaeepour 《Journal of the Iranian Chemical Society》2017,14(8):1691-1698
In this study, a new device for semi-automated salt-assisted liquid–liquid extraction was designed and coupled with high-performance liquid chromatography (HPLC) to determine three aromatic hydrocarbons in aqueous samples. In order to evaluate the performance of the designed device, three aromatic hydrocarbons including 2-naphthol, naphthalene and anthracene were selected as model analytes. Sample solution, extraction solvent and salt solution using separate channels were transferred to a sample holder, respectively. These three components were mixed using a magnetic stirrer. After stirrer stopping, the aqueous and organic phases were separated and organic layer transferred to the injection loop of HPLC system. Optimization process was achieved using response surface methodology by Design-Expert software. A central composite design was used to optimize the main parameters including pH (A), stirrer time (B), organic solvent volume (C) and salt concentration (D). The limit of quantitation for 2-naphthol, naphthalene and anthracene was 15.0, 25.0 and 1.0 ng mL?1, respectively. Under the optimum conditions, obtained recoveries for three analytes were in the range of 76.0–96.2% with relative standard deviation less than 8.2%. The salt-assisted liquid–liquid extraction method using the proposed device has been successfully used for the analysis of real samples containing studied analytes in various matrices. 相似文献
22.
S.A. Mirkhani M. Vossoughi G.R. Pazuki A.A. Safekordi A. Heydari J. Akbari M. Yavari 《The Journal of chemical thermodynamics》2011,43(10):1530-1534
(Liquid + liquid) equilibrium (LLE) data for the ternary systems (heptane + toluene + 1-ethyl-3-methylpyridinium ethylsulfate) and (heptane + benzene + 1-ethyl-3-methylpyridinium ethylsulfate) were measured at T = 298.15 K and atmospheric pressure. The selectivity and aromatic distribution coefficients, calculated from the equilibrium data, were used to determine if this ionic liquid can be used as a potential extracting solvent for the separation of aromatic compounds from heptane. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations. 相似文献
23.
Mohammad HojjatSeyed Gholamreza Etemad Rouhollah BagheriJules Thibault 《Experimental Thermal and Fluid Science》2011,35(7):1351-1356
Forced convection heat transfer of non-Newtonian nanofluids in a circular tube with constant wall temperature under turbulent flow conditions was investigated experimentally. Three types of nanofluids were prepared by dispersing homogeneously γ-Al2O3, TiO2 and CuO nanoparticles into the base fluid. An aqueous solution of carboxymethyl cellulose (CMC) was used as the base fluid. Nanofluids as well as the base fluid show shear-thinning (pseudoplastic) rheological behavior. Results indicate that the convective heat transfer coefficient of nanofluids is higher than that of the base fluid. The enhancement of the convective heat transfer coefficient increases with an increase in the Peclet number and the nanoparticle concentration. The increase in the convective heat transfer coefficient of nanofluids is greater than the increase that would be observed considering strictly the increase in the effective thermal conductivity of nanofluids. Experimental data were compared to heat transfer coefficients predicted using available correlations for purely viscous non-Newtonian fluids. Results show poor agreement between experimental and predicted values. New correlation was proposed to predict successfully Nusselt numbers of non-Newtonian nanofluids as a function of Reynolds and Prandtl numbers. 相似文献
24.
Abbas Heydari 《Linear algebra and its applications》2008,429(7):1744-1757
Let H be a simple graph with n vertices and G be a sequence of n rooted graphs G1,G2,…,Gn. Godsil and McKay [C.D. Godsil, B.D. McKay, A new graph product and its spectrum, Bull. Austral. Math. Soc. 18 (1978) 21-28] defined the rooted product H(G), of H by G by identifying the root vertex of Gi with the ith vertex of H, and determined the characteristic polynomial of H(G). In this paper we prove a general result on the determinants of some special matrices and, as a corollary, determine the characteristic polynomials of adjacency and Laplacian matrices of H(G).Rojo and Soto [O. Rojo, R. Soto, The spectra of the adjacency matrix and Laplacian matrix for some balanced trees, Linear Algebra Appl. 403 (2005) 97-117] computed the characteristic polynomials and the spectrum of adjacency and Laplacian matrices of a class of balanced trees. As an application of our results, we obtain their conclusions by a simple method. 相似文献
25.
I. Yavari M. Davar-Panah M. Heydari K. Najafian A. Zonouzi 《Monatshefte für Chemie / Chemical Monthly》1996,127(8-9):963-966
Summary A one-pot synthesis of highly functionalized ketenimines by reaction of alkyl isocyanides with dialkyl acetylenedicarboxylates in presence of 1,3-diphenylpropan-1,3-dione is reported.
Ein einfacher Weg zu hochfunktionalisierten Keteniminen
Zusammenfassung Es wird eine Eintopfsynthese hochfunktionalisierter Ketenimine durch Reaktion von Isocyaniden mit Dialkylacetylendicarboxylaten in Gegenwart von 1,3-Diphenylpropan-1,2-dion beschrieben.相似文献
26.
Let R be a left Noetherian ring and ZD(R) be the set of all zero-divisors of R. In this paper, it is shown that if R \ ZD(R) is finite, then R is finite. 相似文献
27.
Elahe Yazdani Farzane Pazoki Arefe Salamatmanesh Masoume Jadidi Nejad Maryam Kazemi Miraki Akbar Heydari 《应用有机金属化学》2020,34(10):e5855
Copper supported on magnetite nanoparticles modified with environmentally friendly ligand tricine was devised for synthesis of acetamides via C–C oxidative cleavage of ketones with amines. The catalyst was characterized using different techniques, including Fourier transform infrared, X-ray diffraction, scannin electron microscopy, vibrating sample magnetometry, thermogravimetric analysis, and energy dispersive x-ray spectroscopy. The protocol showed relatively high yields of acetamide products. Furthermore, the magnetic recovery of the catalyst rendered the overall process fast and efficient. It was used in the reaction for six consecutive cycles with negligible loss of catalytic activity. This research is the first report of application of magnetic nanocatalysts for synthesis of acetamides from ketones of low activity through a C–C bond cleavage strategy. 相似文献
28.
29.
30.