Bu-Ali Sina University

About: Bu-Ali Sina University is a education organization based out in Hamadan, Hamadān, Iran. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 4078 authors who have published 7969 publications receiving 122828 citations.

Series solutions for unsteady laminar MHD flow near forward stagnation point of an impulsively rotating and translating sphere in presence of buoyancy forces

Abstract: The similarity solution for the unsteady laminar incompressible boundary layer flow of a viscous electrically conducting fluid in stagnation point region of an impulsively rotating and translating sphere with a magnetic field and a buoyancy force gives a system of non-linear partial differential equations. These non-linear differential equations are analytically solved by applying a newly developed method, namely the homotopy analysis method (HAM). The analytic solutions of the system of non-linear differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. Graphical results are presented to investigate the influence of the magnetic parameter, buoyancy parameter and rotation parameter on the surface shear stresses and surface heat transfer. It is noted that the behavior of the HAM solution for the surface shear stresses and surface heat transfer is in good agreement with the numerical solution given in reference [H. S. Takhar, A. J. Chamkha, G. Nath, Unsteady laminar MHD flow and heat transfer in the stagnation region of an impulsively spinning and translating sphere in the presence of buoyancy forces, Heat Mass Transfer 37 (2001) 397].

The long-term compressive strength and durability properties of silica fume fiber-reinforced concrete

Abstract: The long-term compressive strength and durability properties of concrete specimens produced by incorporating polypropylene fibers and silica fume were investigated. Silica fume, a cement replacement, was used at 8% (by weight of cement) and the volume fractions of the polypropylene fibers were 0%, 0.2%, 0.3% and 0.5%. Water-binder ratios were 0.46 and 0.36. The results indicate that the inclusion of fiber and particularly silica fume into the specimens led to an increased long-term compressive strength. Electrical resistance of the silica fume specimens improved remarkably, but decreased slightly due to the fiber inclusion. Water absorption of the fiber–silica fume specimens decreased exclusively compared to the reference samples. Inclusion of fiber and silica fume into the specimens had no considerable effect on the dynamic frequency results.

Freezing tolerance and its relationship with soluble carbohydrates, proline and water content in 12 grapevine cultivars

Abstract: The objectives of this study were to compare freezing tolerance (FT) of 12 field-grown grapevine cultivars at four stages: Nov., Jan., Mar., and Apr., and to investigate the relationship between FT and soluble carbohydrates, proline and water content changes of buds during acclimation and deacclimation stages. After exposure to various freeze test temperatures bud LT50 values were estimated using electrolyte leakage and bud browning measurement. Bud FT of all cultivars studied increased with the overall trend of declining temperatures from Nov. through Jan., after which the buds began to deacclimate from Mar. and gradually lost FT in Apr.; overall LT50 means were −13.79, −21.74, −20.38, and −10.06, respectively. However, cultivars did not show alike acclimation and deacclimation rates and, for example, ‘Yaquti’, an early ripening cultivar, showed relatively higher FT in early autumn, but was one of the least hardy cultivars in later stages. In Jan. (full hardening), cultivars were classified as hardy (‘Red Sultana’, ‘Fakhri’, ‘Shahani’ and White Sultana), moderately hardy (‘Tabarzeh’, ‘Gaznei’, ‘Thompson Seedless’, Laal, ‘Sahebi’ and ‘Rishbaba’) and least hardy (‘Yaquti’ and ‘Ruby Seedless’). The pattern of soluble carbohydrates and proline changes were highly consistent with the LT50 profile. Bud water content, especially in early autumn, had a stronger correlation with FT, compared to the concentration of cytoplasmic osmoregulants. Likewise, soluble carbohydrates proved to be a superior indicator of FT, as compared to proline. Our results showed osmoregulants as well as bud water content are useful indices to screen FT in a range of grapevine germplasm resources.

Voltammetric determination of 4-nitrophenol using a glassy carbon electrode modified with a gold-ZnO-SiO 2 nanostructure

Abstract: A nanostructured material of the type Au-ZnO-SiO2 is described that consists of ZnO and gold nanoparticles (NPs) dispersed into a silica matrix and used to construct a voltammetric sensor for 4-nitrophenol. The AuNPs and ZnO NPs are anchored onto the silica network which warrants the nanostructures to be stable in various environments. It also facilitates the electron transfer between the electrolyte and the glassy carbon electrode (GCE). The properties of the nanostructure as a modifier for the GCE were investigated by energy dispersive spectrometry, X-ray diffraction spectroscopy, and transmission electron microscopy. It is shown that the nanostructure increases the surface area. Hence, the cathodic and anodic current in differential pulse voltammetry of 4-nitrophenol are considerably enhanced in comparison to a bare GCE. Under optimum conditions, the currents for oxidation and reduction are proportional to the concentration of 4-nitrophenol in the 0.05–3.5 μM and 0.01–1.2 μM concentration ranges, with 13.7 and 2.8 nM detection limits, respectively. The sensor has excellent sensitivity, fast response, long-term stability, and good reproducibility. It is perceived to be a valuable tool for monitoring 4-nitrophenol in real water samples.