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Quetta, Pakistan

Rahman S.U.,UET Taxila | Ellahi R.,FBAS | Ellahi R.,University of California at Riverside | Nadeem S.,Quaid-i-Azam University | Zia Q.M.Z.,COMSATS Institute of Information Technology
Journal of Molecular Liquids | Year: 2016

This study examines the effects of nanoparticles for the blood flow of Jeffrey fluid in tapered artery with stenosis. The slip effects along with permeable nature of the arterial wall in the presence of convection are also taken into account. Mathematical modeling is based upon continuity, momentum and energy equations. This analysis is carried out under the constraints of mild stenosis. Closed form solutions for velocity and concentration are obtained. Numerical integration is used to analyze the novel features of flow impedance, pressure rise and stream function. Effects of pertinent parameters such as Brownian diffusion coefficient, thermospheric diffusion parameter, Grashof number and material constant of Jeffrey fluid on velocity, temperature and concentration are discussed through graphs. © 2016 Elsevier B.V. All rights reserved. Source

Imtiaz H.,UET Taxila | Mahfouz F.M.,Menoufia University
CMES - Computer Modeling in Engineering and Sciences | Year: 2015

This paper investigates numerically the conjugate heat transfer in a concentric enclosure that is formed between two concentric cylinders and filled with micropolar fluid. The wall of inner cylinder is considerably thick, while the wall of outer cylinder is very thin. The inner cylinder is heated from inner side through constant heat flux, whereas the outer cylinder is cooled and maintained at constant temperature. The induced buoyancy driven flow and associated conjugate heat transfer are predicted numerically by solving flow and energy governing equations considering a combination of finite difference and Fourier spectral methods. The study investigates the effect of controlling parameters on both flow and thermal fields, keeping focus on inner wall temperature. The controlling parameters are Rayleigh number Ra, dimensionless thickness of inner wall, inner cylinder fluid thermal conductivity ratio Kr, and material parameters of micropolar fluid (λ, B and D). The study shows that the steady dimensionless mean inner wall temperature φI decreases with increase in Kr and Ra, and decrease in the vortex viscosity D. The study also shows that the increase in thickness of inner wall at Kr < 1 leads to increase in steady φI . While in case of Kr > 1, for a given value of Ra and D, φI assumes maximum value at certain thickness of inner wall. In general, the study demonstrates that, for same geometrical and flow parameters, φI is more in case of micropolar fluids as compared to Newtonian fluids. Copyright © 2015 Tech Science Press. Source

Imtiaz H.,UET Taxila | Mahfouz F.M.,Menoufia University
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2014

This paper investigates numerically the conjugate heat transfer in an annulus between two concentric cylinders. The annulus contains micropolar fluid and is heated isothermally from its inner wall. The effect of Rayleigh number, thickness of inner wall, inner wall-fluid thermal conductivity ratio, and material parameters of micropolar fluid on heat transfer rate within the annulus has been investigated. The study has shown that for low Rayleigh number regimes and for thermal conductivity of the inner wall greater than that of the fluid, the increase of inner wall thickness increases the heat transfer rate through the annulus and vice versa. While for convection dominating regimes Ra ≥ 104 the increase of inner wall thickness decreases the heat transfer rate. Moreover, the study has shown that for fixed geometrical and flow parameters the heat transfer decreases in case of micropolar fluids in comparison with that of Newtonian fluids. © 2013 Springer-Verlag Berlin Heidelberg. Source

Jalil A.,CESAT | Yousaf H.,CESAT | Baig M.I.,UET Taxila
Proceedings of 2016 13th International Bhurban Conference on Applied Sciences and Technology, IBCAST 2016 | Year: 2016

In radar the reflected signal is received by the antenna which is amplified, down converted and then the required signal is extracted (video signal). The video signal is then passed through Moving Target Indicator (MTI) processor which suppresses clutter. The post-MTI data is passed through Constant False Alarm Rate (CFAR) processor which qualifies echoes as targets or otherwise. The role of CFAR processor is to determine a threshold, above which any return can be considered to be from target. If this threshold is too low, more targets will be detected at the expense of more false alarms. Conversely, if the threshold is set too high, then fewer targets will be detected but the number of false alarms will be less. The distribution of the clutter can be approximated by certain probability distribution functions, where each medium follows a different probability distribution. We shall investigate important CFAR processing techniques in Gaussian noise and Rayleigh clutter. The threshold is set adaptive, that is the threshold is raised or lowered, to maintain a required Probability of False Alarm (PFA). This paper discusses various CFAR processing techniques, by applying them to raw video of real radar, analyzing advantages and disadvantages of each technique. © 2016 IEEE. Source

Arshad A.,National University of Sciences and Technology | Hashim N.H.,UET Taxila
International Journal of Environmental Research | Year: 2012

Two UASB reactors R-I and R-II, each of 10liters capacity, made up of acryl material were operated parallel and continuously for a period of 220 days, using actual effluent of the NSSC pulp and paper mill, at mesophilic temperature and neutral pH. The main objective was to investigate the treatability performance of the reactors at varying OLR and HRT in terms of TOC and lignin removal. The reactor R-I was used by conventional procedure, whereas, for the reactor R-II methanol and activated carbon was added to supplement its efficiency. Corresponding to an optimum OLR of 4.5kg/m3-day and HRT of 18hrs, the reactor R-II gives 69% TOC and 60% lignin removal. But, in the reactor R-I at same operating conditions, only 56% TOC and 51% lignin removal was noticed. However, the biogas yield in the reactor R-I was noticed relatively more than in the R-II. The biogas yield observed was 0.28m3/kg-CODrem and 0.18m3/kg-CODrem in the reactor R-I and R-II, respectively, with 56-58% methane content in both the reactors. The average VFAs concentration observed in the reactor R-I and R-II is 360mg/L and 230mg/L, respectively. The results of this study suggest that the use of methanol and activated carbon to enhance the treatability efficiency of the UASB reactor is a viable option for the treatment of NSSC pulping effluent. Source

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