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771.
772.
Alireza Najafi Chermahini Masoud Nasr-Esfahani Zeinab Dalirnasab Hossein Abdol Dabbagh Abbas Teimouri 《Journal of Molecular Structure》2007,820(1-3):7-11
Computational calculations at B3LYP/6-31++G(d,p) level were employed in the study of the predominant tautomeric forms of 1-H and 2-H tetrazole derivatives (5-NO2, 5-CF3, 5-F, 5-H, 5-NH2, 5-OH, 5-CH3) in the gas phase and solution using PCM model. For electron withdrawing derivatives in the gas phase and solution 2-H forms are more stable and dominant form. For electron releasing groups in the gas phase and solution with low dielectric constants the 2-H form is more stable but in solvents with high dielectric constants 1-H isomer is dominant form. In addition variation of dipole moments and charges on atoms in the solvents are studied. 相似文献
773.
An implicit finite volume model in sigma coordinate system is developed to simulate two‐dimensional (2D) vertical free surface flows, deploying a non‐hydrostatic pressure distribution. The algorithm is based on a projection method which solves the complete 2D Navier–Stokes equations in two steps. First the pressure term in the momentum equations is excluded and the resultant advection–diffusion equations are solved. In the second step the continuity and the momentum equation with only the pressure terms are solved to give a block tri‐diagonal system of equation with pressure as the unknown. This system can be solved by a direct matrix solver without iteration. A new implicit treatment of non‐hydrostatic pressure, similar to the lower layers is applied to the top layer which makes the model free of any hydrostatic pressure assumption all through the water column. This treatment enables the model to evaluate both free surface elevation and wave celerity more accurately. A series of numerical tests including free‐surface flows with significant vertical accelerations and nonlinear behaviour in shoaling zone are performed. Comparison between numerical results, analytical solutions and experimental data demonstrates a satisfactory performance. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
774.
Fabrication of chain-like Mn2O3 nanostructures via thermal decomposition of manganese phthalate coordination polymers 总被引:1,自引:0,他引:1
Masoud Salavati-Niasari Fatemeh Mohandes Kamal Saberyan 《Applied Surface Science》2009,256(5):1476-1480
A novel manganese coordination polymer [Mn(Pht)(H2O)]n as a precursor was obtained by chemical precipitation involving an aqueous solution of anhydrous manganese acetate and phthalate anion as a potential O-banded ligand. Fourier transform infrared (FT-IR) results proved that phthalate anions coordinate to metal cations as a chelating bidentate ligand, making polymeric structure. The Mn2O3 nanostructures have been prepared via thermal decomposition of as-prepared manganese phthalate polymers as precursor in the presence of oleic acid (OA) and triphenylphosphine (TPP) as a stabilizer and capping. Different approaches such as FT-IR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to characterize the products. TEM images and XRD analysis indicated that the as-synthesized chain-like Mn2O3 has a crystal phase of cubic syngony with a mean size of ∼40 nm. 相似文献
775.
The goal of this study was to investigate the capability of conceptual models for correct prediction of ternary blends morphology. All existing models, including spreading coefficient, relative interfacial energy, dynamic interfacial energy (DIE), and modified DIE were employed to predict the type of morphology of the polyamide 6/poly(styrene-co-acrylonitrile)/poly(styrene-b-(ethylene-co-butylene)-b-styrene) ternary system. Various samples with different compositions were prepared and predictions of the models were compared with the experimental phase morphology of the samples based on scanning electron microscopy micrographs. Additionally, the effect of elasticity of the matrix component on the both predictions and experimental phase structures of the blends was studied. It was demonstrated that, among the available phenomenological models, the modified DIE can comprehensively represent the most correct predictions for the morphology of ternary polymer blends. 相似文献
776.
Lead sulfide (PbS) nanostructures with different morphologies and particle sizes were obtained via a simple hydrothermal reaction between lead (II) salicylate (Pb(Hsal)2) and thiourea (tu). Reaction products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV–vis) and Fourier transform infrared (FT-IR) spectroscopy. Morphology of the product, varying from star-like to dendritic, depends on the mole ratio of tu to (Pb(Hsal)2), pH, and reaction time. 相似文献
777.
Fatemeh Taghipour Masoud Mirzaei 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(3):231-247
The important role of pyrazine (pz) and its derivatives in fields such as biochemistry and pharmacology, as well as in the study of magnetic properties, is surveyed. Recognition of these properties without extensive investigations into their structural properties is not possible. This review summarizes interactions that exist between these organic compounds by themselves in the solid state, as well as those in coordination polymers with metal ions and in polyoxometalate‐based hybrids. Complexes based on pyrazine ligands can generate metal–organic framework (MOF) structures that bind polyoxometalates (POMs) through covalent and noncovalent interactions. Some biological and magnetic properties involving these compounds are considered and the effect of hydrogen bonding on their supramolecular architectures is highlighted. 相似文献
778.
Ahmadi Masoumeh Moradi Leila Sadeghzadeh Masoud 《Research on Chemical Intermediates》2018,44(12):7873-7889
Research on Chemical Intermediates - A green, rapid, mild and highly efficient pathway for the preparation of benzamide derivatives is reported. The reaction was performed through direct... 相似文献
779.
Aghili Siavash Panjepour Masoud Meratian Mahmood 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2443-2455
Journal of Thermal Analysis and Calorimetry - This study investigated the kinetic analysis of the dehydration process of boric acid (H3BO3) and its transformation into boron trioxide (B2O3) under... 相似文献
780.
An implicit 2D hydrodynamic numerical model for free surface–subsurface coupled flow problems 下载免费PDF全文
A 2‐dimensional hydrodynamic finite volume model has been proposed for simultaneous simulation of free surface and saturated porous media. The governing equations of the former are 2‐dimensional averaged in a unit width of Navier‐Stokes, whereas that of the latter are Darcy law. An efficient, simple, and stable algorithm has been proposed to track the surface elevation in Cartesian coordinate system by which the water elevation in each computational column has been computed along with the other pressure unknowns simultaneously. The surface position has not been considered to remain in a specific layer so the number of cells in each column have been variably adjusted in accordance with the water surface elevation. Performance of the coupled model has been validated against a range of hydrodynamic problems including propagation of linear short wave, seepage test, tidal oscillation in a lagoon system, gravity current, and saltwater intrusion. Comparison between numerical results, analytical solutions, and experimental data demonstrates that the model represents well the interacting surface water and ground water flow and solute transport processes. 相似文献