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Träfflista för sökning "WFRF:(Ahmad Ashfaq) srt2:(2018)"

Sökning: WFRF:(Ahmad Ashfaq) > (2018)

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1.
  • Ahmad, Ashfaq, et al. (författare)
  • Design, Fabrication, and Measurements of Extended L-Shaped Multiband Antenna for Wireless Applications
  • 2018
  • Ingår i: Applied Computational Electromagnetics Society Journal. - : Applied Computational Electromagnetics Society (ACES). - 1054-4887. ; 33:4, s. 388-393
  • Tidskriftsartikel (refereegranskat)abstract
    • This article expounds a multi-band compact shaped antenna, which is based on CPW ground plane. FR-4 with a thickness of 1.6 mm is used as a substrate for the proposed antenna. The proposed antenna is capable of operating at 1.56 GHz for (Global Positioning System), 2.45 GHz (Wireless Local Area Network) and 4.49 GHz (Aeronautical Mobile Telemetry (AMT) fixed services). The efficiency at 1.56, 2.45, and 4.49 GHz is 79.7, 76.9 and 76.7%, respectively. The VSWR of the presented antenna is less than 1.5 at all the desired resonance modes, which confirms its good impedance matching. The performance of the proposed antenna is evaluated in terms of VSWR, return loss, radiation pattern and efficiency. CST (R) MWS (R) software is used for simulations. In order to validate the simulation results, a prototype of the designed antenna is fabricated and a good agreement is found between the simulated and measured results.
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2.
  • Ali, Amjad, et al. (författare)
  • A potential electrolyte (Ce1-x CaxO2-delta) for fuel cells:Theoretical andexperimental study
  • 2018
  • Ingår i: Ceramics International. - : ELSEVIER SCI LTD. - 0272-8842 .- 1873-3956. ; 44:11, s. 12676-12683
  • Tidskriftsartikel (refereegranskat)abstract
    • First-principles calculations are performed using density function theory to explore the effects of dopant Ca in ceria (Ce1-x CaxO2-delta). The impact of oxygen vacancy on band gap and density of states is examined in doped ceria using generalized gradient approximations. Vacancy association and vacancy formation energies of the doped ceria are calculated to reveal the effect of dopant on ion conduction. The experimental study of the sample Ce0.875Ca0.125O2-delta) was performed to compare with the theoretical results. The obtained results from theoretical calculation and experimental techniques show that oxygen vacancy increases the volume, lattice constant (5.47315 angstrom) but decrease the band gap (1.72 eV) and bulk modulus. The dopant radius (1.173 angstrom) and lattice constant (5.4718 angstrom) are also calculated by equations which is close to the DFT lattice parameter. The result shows that oxygen vacancy shifts the density of states to lower energy region. Band gap is decreased due to shifting of valence states to conduction band. Vacancy formation shows a significance increase in density of states near the Fermi level. Density of states at Fermi level is proportional to the conductivity, so an increase in density of states near the Fermi level increases the conductivity. The experimental measured ionic conductivity is found to 0.095 S cm(-1) at 600 degrees C. The microstructural studies is also reported in this work.
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3.
  • Tariq, S., et al. (författare)
  • Comparative study of Ce0.80Sm0.20 Ba0.80Y0.20O3-δ (YB-SDC) electrolyte by various chemical synthesis routes
  • 2018
  • Ingår i: Results in Physics. - : Elsevier B.V.. - 2211-3797. ; 8, s. 780-784
  • Tidskriftsartikel (refereegranskat)abstract
    • Solid Oxide Fuel Cells is received a significant attention in recent years due to higher efficiency and fuel flexibility. The one of the main challenge for SOFC is to lower the operating temperature of SOFCs. Therefore, different strategies are used in order to enhance the ionic conduction of electrolyte, which can lower the overall SOFC operating temperature. The present work is focused on this strategy to enhance the electrolytic conductivity. Therefore, the ceria based composite electrolytes Ce0.80Sm0.20B0.80Y0.20O3-δ (YBSDC) are synthesized using three different approaches i.e. co-precipitation (YBSDC-1), sol-gel (YBSDC-2) and ball milling (YBSDC-3). Their crystal structures and surface morphologies are characterized through X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques, respectively. The four-probe technique is employed to measure their dc conductivities in the temperature range (300–700) °C under air atmosphere. The open circuit voltage (OCV) and current are recorded with natural gas as fuel {flow rate kept at 100 ml min−1 at 1 atm pressure} over the temperature range (300–600) °C. The electrolyte (YBSDC-1) prepared by co-precipitation technique is shown better results as compare to other two electrolytes (YBSDC-2 and YBSDC-3). The electrolyte (YBSDC-1) having maximum dc conductivity (0.096 S/cm), peak power density 224 mW cm−2 and OCV 0.94 V at 600 °C. These results show that YBSDC-1electrolyte is potential candidate for low temperature SOFCs.
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