Journal of Basic and Applied Sciences  -   Volume 8 Number 2

Some New Exact Solutions for Prescribed Vorticity Distribution of Couple Stress Fluids in the Presence of Unknown Body Force

Rana Khalid Naeem

http://dx.doi.org/10.6000/1927-5129.2012.08.02.39

Abstract: In the present paper, we indicate some new exact solutions of equations of motion for plane steady incompressible couple stress fluids flows in the presence of unknown body force for which vorticity distribution is defined by Eq. (12). All solutions involve arbitrary real constants and arbitrary real constants depending on the parameter è indicating that a large number of streamfunctions and expressions for body force can be constructed. Some streamfunctions ø are constructed for some values of parameters. The streamlines patterns of these streamfunctions are presented and discussed.

Keywords: Exact solutions, Couple stress fluid, Flows for prescribed vorticity distribution.

 

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The Effect of Grain Size on Radon Exhalation Rate in Soil Samples of Dera Ismail Khan in Pakistan

Tabassum Nasir and Nisar Ahmad

http://dx.doi.org/10.6000/1927-5129.2012.08.02.29

Abstract: Radon concentration and its exhalation rate has been measured from twenty five soil samples collected from seven different locations of Dera Ismail Khan, in the north west of Pakistan. These samples were crushed after drying and passed through sieves with different sizes of pores to get three grain sizes, £0.595 mm, 0.595-2.00 mm and 2.00-4.00 mm of soil. CR-39 based NRPB (National Radiological Protection Board) radon dosimeters have been used to measure the radon concentration and exhalation rates. The maximum average value of radon exhalation rate has found to be: (3.57±0.38) Bq m-2 hr-1 in the samples having grain size 2.00-4.00 mm and the minimum as: (2.21±0.26) Bq m-2 hr-1, in the samples with grain size £ 0.0595 mm. This indicates that the radon exhalation rate increases with the grain size. The maximum average value of radon exhalation rate has been found in samples collected from river side where soil texture is silty clay loam. The obtained values of radon exhalation rate for all the samples are well below the world average value of 57.60 Bq m-2 hr-1.

Keywords: Radon concentration, Radon exhalation rate, grain size, soil texture.

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