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Your search keyword '"Farhan, A.M."' showing total 8 results
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8 results on '"Farhan, A.M."'

5. Laser processing of dry, wet and immersed polyamide nanofiber nonwovens with different laser sources

Author

Götze, M., Farhan, A.M., Kürbitz, T., Krimig, O., Henning, S., Heilmann, A., Hillrichs, G., and Publica

Subjects
nanofiber scaffold, femtosecond laser, tissue engineering, laser ablation, polyamide nanofibers, picosecond laser, electrospinning
Abstract

Electrospun nanofiber scaffolds of different polymers are used in tissue engineering to mimic the extracellular matrices with favourable conditions for cell growth and proliferation. Structures such as cavities, holes and cuts in the scaffolds can be used to optimize cell growth. We investigated the influence of different laser sources used for direct laser writing on the cutting and structuring quality of electrospun polyamide nonwovens. Ablation thresholds and rates were determined. Because of different approaches in cell colonization with scaffolds, the investigations were carried out on dry, wet and immersed nonwovens. The results show that femto- and picosecond lasers are very well suited for processing of dry nonwovens. Processing with green wavelengths is more effective and leads to similar minimum feature sizes than in the ultraviolet range. Ablation rates up to 8000 µm³/pulse were obtained which are about a factor of 100 higher than those for polyamide bulk material. Nanosecond UV lasers produced structures of reduced quality. Excimer lasers at 193 nm offer a possible alternative for large-area structures when operated at low fluences. Processing of wet and immersed nanofibers is possible with smaller processing speed and with a slightly degraded quality.

Published
2017

7. Effect of the non-homogenity on the composite infinite cylinder of orthotropic material

Author

Abd-Alla, A.M. and Farhan, A.M.

Subjects
*DENSITY, *NUMERICAL analysis, *PROPERTIES of matter, *HOMOGENEITY
Abstract

Abstract: In this Letter, the solution of non-homogeneous orthotropic elastic cylinder for plane strain problems is developed. The dynamical problem of an orthotropic cylinder containing: (i) an isotropic core and (ii) a rigid core are considered. The elastic constants and density are taken as a power function of the radial coordinate. Analytical expressions for the component of the displacement and the components of the stresses in different cases are obtained. The numerical calculations are carried out for the component of displacement and the components of the stresses through the radial of the cylinder. The results indicate that the effect of inhomogeneity is very pronounced. Those cases have been illustrated and discussed by figures. [Copyright &y& Elsevier]

Published
2008
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8. Effect of the non-homogenity on the composite infinite cylinder of isotropic material

Author

Abd-Alla, A.M., Nofal, T.A., and Farhan, A.M.

Subjects
*ASYMPTOTIC homogenization, *ENGINE cylinders, *BOUNDARY value problems, *NUMERICAL calculations
Abstract

Abstract: The aim of the present Letter is to investigate the effect of non-homogeneous on the stresses in composite cylinder of isotropic material subject to certain boundary conditions. The dynamical problem of an isotropic cylinder containing: (i) an isotropic core and (ii) a rigid core are considered. The elastic constants and density are taken as a power function of the radial coordinate. Analytical expressions for the component of the displacement and the components of the stresses in different cases are obtained. The numerical calculations are carried out for the component of displacement and the components of the stresses through the radial of the cylinder. The results indicate that the effect of inhomogeneity is very pronounced. Those cases have been illustrated and discussed by figures. [Copyright &y& Elsevier]

Published
2008
Full Text
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