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Islamabad, Pakistan

Masood W.,National Center for Physics | Rizvi H.,PO Nilore | Siddiq M.,National Center for Physics
Astrophysics and Space Science | Year: 2012

Nonlinear electrostatic waves in dense dissipative magnetized electron-positron-ion (e-p-i) plasmas are investigated employing the quantum hydrodynamic model. In this regard, Zakharov Kuznetsov Burgers (ZKB) equation is derived in dense plasmas using the small amplitude perturbation expansion method. It is observed that obliqueness, positron concentration, kinematic viscosity, and the ambient magnetic field significantly alter the structure of nonlinear quantum ion acoustic waves in dense dissipative e-p-i magnetoplasmas. The present study may be useful to understand the nonlinear propagation characteristics of electrostatic shock structures in dense astrophysical systems where the quantum effects are expected to dominate. © 2011 Springer Science+Business Media B.V. Source


Ali N.,International Islamic University, Islamabad | Javid K.,International Islamic University, Islamabad | Sajid M.,PO Nilore | Hayat T.,Quaid-i-Azam University | Hayat T.,King Abdulaziz University
Meccanica | Year: 2015

The main objective of this paper is to investigate boundary layer character of the velocity in peristaltic flow of a Sisko fluid in a curved channel under the influence of strong imposed radial magnetic field. The Sisko fluid model falls in the category of generalized Newtonian fluid models. The constitutive equation of Sisko model is described in terms of three material constants namely; power-law index (n), infinite shear rate viscosity (a) and consistency index (b). This model is capable of predicting shear-thinning and shear-thickening effects for n < 1 and n > 1, respectively. The equation governing the flow is first derived under the assumptions of long wavelength and low Reynolds number, and then made dimensionless by defining appropriate parameters. In dimensionless form it contains three dimensionless parameters namely; generalized ratio of infinite-shear rate viscosity to consistency index, power-law index and Hartmann number characterizing strength of the imposed magnetic field. It is found that the governing equation of flow becomes singular for large values of Hartmann number. Asymptotic solutions representing flow velocity at large values of Hartmann number are reported for two specific values of power-law index (namely n = 1 and n = 1/2) using singular perturbation technique. The flow velocity in either case exhibits qualitatively similar behavior. In fact, it exhibits boundary layer character i.e., it varies sharply in thin layer near the walls and varies linearly over rest of the cross-sections. This is contrary to what that is observed for flow velocity in straight channel (where except in thin layer near the channel walls the velocity over rest of the cross-section is uniform). The estimates of boundary layer thickness at upper and lower walls in either case are different. Moreover, the boundary layer thickness in either case is found to be inversely proportional to the Hartmann number. © 2015 Springer Science+Business Media Dordrecht Source


Mahmood S.,PO Nilore | Mahmood S.,Quaid-i-Azam University | Saleem H.,Quaid-i-Azam University
AIP Conference Proceedings | Year: 2011

Solitary inertial Alfvén wave in the presence of positively and negatively charged dust particles is studied. It is found that electron density dips are formed in the super Alfvénic region and wave amplitude is increased for the case of negatively charged dust particles in comparison with positively charged dust particles in electron-ion plasmas. © 2011 American Institute of Physics. Source


Javid K.,International Islamic University, Islamabad | Ali N.,International Islamic University, Islamabad | Sajid M.,PO Nilore
Meccanica | Year: 2015

We have analyzed peristaltic flow of an Oldroyd-B fluid in a curved channel. Assuming the flow to be incompressible, laminar and two-dimensional, the governing partial differential equations are reduced under long wavelength and low Reynolds number approximations into a single nonlinear ordinary differential equation in the stream function. Matlab built-in routine bvp4c is utilized to solve this nonlinear ordinary differential equation. The solution thus obtained is used to investigate the effects of curvature of the channel and Weissenberg number on important phenomena of pumping and trapping associated with peristaltic motion. It is found that for small values of Weissenberg number, the effects of curvature are dominant. However, for large values of Weissenberg number, viscoelastic effects counteract the effects of curvature and help the flow velocity and circulating bolus of fluid to regain their symmetry. © 2015 Springer Science+Business Media Dordrecht Source


Tabata M.,Saga University | Shono A.,Kankyo Anetos Co. | Ghaffar A.,PO Nilore
Journal of Material Cycles and Waste Management | Year: 2016

A supernatant solution, obtained after immobilization of heavy metals involved in fly ashes by a solution of sulfur and calcium hydroxide, was re-used for immobilization of heavy metals and decomposition of asbestos in construction materials. Asbestos was decomposed to more than 99.9 % by mixing it with the supernatant in a ball mill at room temperature. The decomposition of asbestos was confirmed by X-ray diffraction (XRD), a phase contrast microscope after staining the asbestos with solutions of different diffractive indexes and a scanning electron microscope. XRD indicated complete disappearance of specific main peaks of asbestos: chrysotile, crocidolite, amosite and tremolite. Heavy metals such as chromium(VI) and lead(II) in fly ashes were completely immobilized by the supernatant. It is the first time that a solution obtained after the treatment of wasted fly ash is recycled for decomposition of hazardous waste materials such as asbestos. © 2016 Springer Japan Source

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