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M A Mahdi - One of the best experts on this subject based on the ideXlab platform.

  • analytical study of nonlinear phase shift through stimulated brillouin scattering in single mode fiber with the pump power Recycling Technique
    Journal of Optics, 2011
    Co-Authors: Hamid Ali Abed Alasadi, F Mahamd R Adikan, Ahmad Ashrif A Bakar, M A Mahdi
    Abstract:

    We present a theoretical study of nonlinear phase shift through stimulated Brillouin scattering in single mode optical fiber. Analytical expressions describing the nonlinear phase shift for the pump and Stokes waves in the pump power Recycling Technique have been derived. The dependence of the nonlinear phase shift on the optical fiber length, the reflectivity of the optical mirror and the frequency detuning coefficient have been analyzed for different input pump power values. We found that with the Recycling pump Technique, the nonlinear phase shift due to stimulated Brillouin scattering reduced to less than 0.1 rad for 5 km optical fiber length and 0.65 reflectivity of the optical mirror, respectively, at an input pump power equal to 30 mW.

  • analytical study of nonlinear phase shift through stimulated brillouin scattering in single mode fibre with pump power Recycling Technique
    Social Science Research Network, 2011
    Co-Authors: Hamid Ali Abed Alasadi, Ahmad Ashrif A Bakar, F R Mahamd, M A Mahdi
    Abstract:

    We present a theoretical study of nonlinear phase shift through stimulated Brillouin scattering in single mode optical fiber. Analytical expressions describing the nonlinear phase shift for the pump and Stokes waves in the pump power Recycling Technique have been derived. The dependence of the nonlinear phase shift on the optical fiber length, the reflectivity of the optical mirror and the frequency detuning coefficient have been analyzed for different input pump power values. We found that with the Recycling pump Technique, the nonlinear phase shift due to stimulated Brillouin scattering reduced to less than 0.1 rad for 5 km optical fiber length and 0.65 reflectivity of the optical mirror, respectively, at an input pump power equal to 30 mW.

  • effects of pump Recycling Technique on stimulated brillouin scattering threshold a theoretical model
    Optics Express, 2010
    Co-Authors: Hamid Ali Abed Alasadi, M H Almansoori, M Ajiya, S Hitam, M I Saripan, M A Mahdi
    Abstract:

    We develop a theoretical model that can be used to predict stimulated Brillouin scattering (SBS) threshold in optical fibers that arises through the effect of Brillouin pump Recycling Technique. Obtained simulation results from our model are in close agreement with our experimental results. The developed model utilizes single mode optical fiber of different lengths as the Brillouin gain media. For 5-km long single mode fiber, the calculated threshold power for SBS is about 16 mW for conventional Technique. This value is reduced to about 8 mW when the residual Brillouin pump is recycled at the end of the fiber. The decrement of SBS threshold is due to longer interaction lengths between Brillouin pump and Stokes wave.

  • reduction of stimulated brillouin scattering threshold through pump Recycling Technique
    Laser Physics Letters, 2009
    Co-Authors: M Ajiya, M A Mahdi, M H Almansoori, S Hitam, Y G Shee, M Mokhtar
    Abstract:

    We demonstrate a simple method of stimulated Brillouin scattering (SBS) threshold reduction through a procedure of Brillouin pump Recycling Technique. High reflectivity optical mirror was incorporated onto our experimental structure in order to recycle the forward transmitted Brillouin pump signal back into the Brillouin gain medium thereby increasing its effective gain. In a 5.0 km single mode fiber spool, our Technique reduced SBS threshold by over 48% (measured at 8.5 mW of input signal against 16.5 mW in the conventional Technique under same input signal conditions). In addition, the Stokes power was amplified to 9.2 dBm by our method against 4.3 dBm measured in the conventional Technique in the 5.0 km single mode fiber spool. Result of different lengths has proved that our Technique considerably reduced SBS threshold compared to the conventional method of SBS characterization under same pumping schemes.

Hamid Ali Abed Alasadi - One of the best experts on this subject based on the ideXlab platform.

Joost Duflou - One of the best experts on this subject based on the ideXlab platform.

  • Solid state Recycling of pure Mg and AZ31 Mg machining chips via spark plasma sintering
    Materials & Design, 2016
    Co-Authors: Dimos Paraskevas, Sasan Dadbakhsh, Wim Dewulf, Jef Vleugels, Kim Vanmeensel, Joost Duflou
    Abstract:

    Abstract This work investigates the applicability of spark plasma sintering (SPS) as a solid state Recycling Technique for magnesium alloy scrap. In this respect, machining chips from pure Mg and AZ31 Mg alloy ingots are chemically cleaned, cold compacted and SPSed directly into bulk specimens. It is found that SPS can successfully establish full densification and effective metallurgical bonding between chips without altering compositional constituents. This is attributed to the dynamic compaction during sintering as well as to the disruption of the chips' surface oxide film due to SPS electric current based joule heating. Apart from the successful consolidation, microstructural analysis of the initial Mg ingots, chips and SPS recycled material reveals that the SPS microstructure was finer than that of the original ingots due to significant deformation induced grain refinement during machining. As a result, the recycled materials had a higher compression and shear strength than that of the starting ingot material. The findings indicate that SPS is an effective alternative method for solid state Recycling of magnesium alloy scrap.

  • Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation
    Materials, 2014
    Co-Authors: Dimos Paraskevas, Wim Dewulf, Jef Vleugels, Kim Vanmeensel, Yelin Deng, Joost Duflou
    Abstract:

    Recently, “meltless” Recycling Techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final Recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a novel solid-state Recycling Technique. The objective is two-fold: (I) to prove the technical feasibility of this approach; and (II) to characterize the recycled samples. Aluminum (Al) alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT) analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach.

Ahmad Ashrif A Bakar - One of the best experts on this subject based on the ideXlab platform.

Dimos Paraskevas - One of the best experts on this subject based on the ideXlab platform.

  • Solid state Recycling of pure Mg and AZ31 Mg machining chips via spark plasma sintering
    Materials & Design, 2016
    Co-Authors: Dimos Paraskevas, Sasan Dadbakhsh, Wim Dewulf, Jef Vleugels, Kim Vanmeensel, Joost Duflou
    Abstract:

    Abstract This work investigates the applicability of spark plasma sintering (SPS) as a solid state Recycling Technique for magnesium alloy scrap. In this respect, machining chips from pure Mg and AZ31 Mg alloy ingots are chemically cleaned, cold compacted and SPSed directly into bulk specimens. It is found that SPS can successfully establish full densification and effective metallurgical bonding between chips without altering compositional constituents. This is attributed to the dynamic compaction during sintering as well as to the disruption of the chips' surface oxide film due to SPS electric current based joule heating. Apart from the successful consolidation, microstructural analysis of the initial Mg ingots, chips and SPS recycled material reveals that the SPS microstructure was finer than that of the original ingots due to significant deformation induced grain refinement during machining. As a result, the recycled materials had a higher compression and shear strength than that of the starting ingot material. The findings indicate that SPS is an effective alternative method for solid state Recycling of magnesium alloy scrap.

  • the use of spark plasma sintering to fabricate a two phase material from blended aluminium alloy scrap and gas atomized powder
    Procedia CIRP, 2015
    Co-Authors: Dimos Paraskevas, Wim Dewulf, Jef Vleugels, Kim Vanmeensel, Joos Duflou
    Abstract:

    Abstract Recently innovative solid state / ‘meltless’ Recycling Techniques have been developed and proposed for the consolidation of aluminium alloy scrap, aiming both at energy and material savings by eliminating the melting step. In this context, a powder metallurgy route is examined as a solid state Recycling Technique for the fabrication of a two-phase material via Spark Plasma Sintering. By mixing aluminium atomized powder and machining chips of the same alloy, a two-phase material was produced, where the powder phase acts as a binder/matrix for the Al scrap. Hardness, density, compression testing along with microstructural and computed tomography analysis of the densified Al 6061 alloy are presented.

  • Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation
    Materials, 2014
    Co-Authors: Dimos Paraskevas, Wim Dewulf, Jef Vleugels, Kim Vanmeensel, Yelin Deng, Joost Duflou
    Abstract:

    Recently, “meltless” Recycling Techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final Recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a novel solid-state Recycling Technique. The objective is two-fold: (I) to prove the technical feasibility of this approach; and (II) to characterize the recycled samples. Aluminum (Al) alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT) analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach.