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Ali N.,International Islamic University, Islamabad | Javid K.,International Islamic University, Islamabad | Sajid M.,P.O. 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

Javid K.,International Islamic University, Islamabad | Ali N.,International Islamic University, Islamabad | Sajid M.,P.O. 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

Siddiqa S.,COMSATS Institute of Information Technology | Begum N.,TU Dortmund | Hossain M.A.,University of Dhaka | Mustafa N.,P.O. Nilore | Gorla R.S.R.,Purdue University
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2016

In this paper numerical solutions of a two-phase natural convection dusty fluid flow are presented. The two-phase particulate suspension is investigated along a vertical cone by keeping variable viscosity and thermal conductivity of the carrier phase. Comprehensive flow formations of the gas and particle phases are given with the aim to predict the behavior of heat transport across the heated cone. The influence of (1) air with particles, (2) water with particles and (3) oil with particles are shown on shear stress coefficient and heat transfer coefficient. It is recorded that sufficient increment in heat transport rate can be achieved by loading the dust particles in the air. Further, distribution of velocity and temperature of both the carrier phase and the particle phase are shown graphically for the pure fluid (air, water) as well as for the fluid with particles (air-metal and water-metal particle mixture). © 2016 Springer-Verlag Berlin Heidelberg

Masood W.,P.O. Nilore | Ahmad A.,P.O. Nilore | Ahmad A.,National Center for Physics | Ahmad A.,COMSATS Institute of Information Technology
Astrophysics and Space Science | Year: 2012

Linear dispersion characteristics of the coupled drift acoustic modes are investigated in inhomogeneous dusty magnetoplasmas both when the dust is considered immobile and when the dust dynamics is taken into account in the presence of nonthermal population of electrons and ions. In this regard, Cairns and Kappa distributed electrons and ions are considered. It is found that the nonthermal distributions affect the phase velocities and the fundamental scalelengths of the plasma. It is found that for both the ion and dust dynamics driven waves, the phase velocities are highest for Cairns, intermediate for Kappa, whereas they are minimum for the Maxwellian distributed electrons. The work presented here may be useful to understand the low frequency electrostatic modes in inhomogeneous dusty plasmas such as those found in planetary environments. © 2012 Springer Science+Business Media B.V.

Masood W.,National Center for Physics | Rizvi H.,P.O. 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.

Hasnain H.,P.O. Nilore | Masood W.,COMSATS Institute of Information Technology | Masood W.,National Center for Physics | Mahmood A.,National Institute of Lasers and Optronics
Physica Scripta | Year: 2015

Linear and nonlinear propagation of coupled dust drift acoustic waves are investigated in the presence of a kappa distributed ion population and Boltzmannian electrons. It is observed that the frequency of the dust drift acoustic wave decreases by increasing the kappa value. Using the drift approximation, a nonlinear equation is derived for the dust drift acoustic shock wave that reduces to a Kadomtsev-Petviashvili-Burgers (KPB)-like equation in the comoving frame of reference. It is found that the nonlinear structure of dust drift acoustic shock waves modifies in the presence of increasing values of kappa, dust number density, ambient magnetic field, and the dust neutral collision frequency. Interestingly, it is found that the non-Maxwellian ion population modifies the scale lengths over which the nonlinear structures are formed. The results obtained are applied in Saturns magnetosphere, where the non-Maxwellian distribution of particles has been reported by several satellite missions. © 2015 The Royal Swedish Academy of Sciences.

Khan N.A.,Quaid-i-Azam University | Khan A.S.,Quaid-i-Azam University | Khan M.N.,P.O. Nilore | Rahim M.,Hazara University | Hassan N.,Hazara University
Journal of Materials Science: Materials in Electronics | Year: 2016

YBa2(Cu3−xTix)O7−δ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) superconductors are synthesized at 900 °C by solid state reaction method. The superconducting properties of the samples are studied by X-ray diffraction, resistivity, AC-susceptibility and Fourier transform infrared spectroscopy (FTIR) absorption measurements. These samples have shown orthorhombic crystal structure and the cell parameters slightly increase for higher Ti-contents. The Tc(R = 0), the onset temperature and magnitude of diamagnetism are suppressed with increasing Ti-doping. A new in-chain [Ti–O–Cu(1)] oxygen vibration mode appears around 551 cm−1 in the FTIR spectra which grows in intensity with increased Ti-doping. The peak position of the CuO2 planar oxygen mode is not affected with the doping of Ti showing that Ti is doped at the in-chain-copper Cu(1) sites in the unit cell. The fluctuation induced conductivity analyses reveals that despite an increase in the parameters such as ξc, VF, and inter-layer coupling J, the critical temperature and superconductor volume fraction are suppressed. It shows that the doped Ti-atoms most likely induce anharmonic oscillations which may suppress the density of phonon population and hence the superconductivity. It can also be witnessed in the decreased phase relaxation time of the carriers with increasing Ti-doping. These studies stress on the essential role of soft phonons in the mechanism of high Tc superconductivity in YBa2(Cu3−xTix)O7−δ superconductors. © 2016 Springer Science+Business Media New York

Mahmood S.,P.O. 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.

Tabata M.,Saga University | Shono A.,Kankyo Anetos Co. | Ghaffar A.,P.O 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

Zeb J.,P.O. Nilore | Wasim M.,P.O. Nilore | Rashid A.,P.O. Nilore | Arshed W.,P.O. Nilore
Journal of Radioanalytical and Nuclear Chemistry | Year: 2015

This study presents survey of gamma radiation exposure around Pakistan Institute of Nuclear Science and Technology (PINSTECH). PINSTECH hosts two research reactors, two isotope production plants and several radiochemistry laboratories. Dose measurement was performed in thirty villages around PINSTECH. The average outdoor absorbed dose rate in air was 59 ± 16 nGy h−1. The average annual outdoor dose rate due to terrestrial gamma-rays was 71.4 ± 20.0 μSv y−1. The annual collective effective dose equivalent was 415 man-Sv and the estimated excess life-time cancer risk was 7.3 × 10−4. The study revealed that inhabitants living in the area surrounding PINSTECH were radiologically safe. © 2015 Akadémiai Kiadó, Budapest, Hungary

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