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Enhancement of thermoelectric properties of MBE grown un-doped ZnO by thermal annealing
Khalid, Mahmood,Asghar, Muhammad,Ali, Adnan,Ajaz-Un-Nabi, M.,Arshad, M. Imran,Amin, Nasir,Hasan, M.A. Techno-Press 2015 Advances in energy research Vol.3 No.2
In this paper, we have reported an enhancement in thermoelectric properties of un-doped zinc oxide (ZnO) grown by molecular beam epitaxy (MBE) on silicon (001) substrate by annealing treatment. The grown ZnO thin films were annealed in oxygen environment at $500^{\circ}C-800^{\circ}C$, keeping a step of $100^{\circ}C$ for one hour. Room temperature Seekbeck measurements showed that Seebeck coefficient and power factor increased from 222 to $510{\mu}V/K$ and $8.8{\times}10^{-6}$ to $2.6{\times}10^{-4}Wm^{-1}K^{-2}$ as annealing temperature increased from 500 to $800^{\circ}C$ respectively. This observation was related with the improvement of crystal structure of grown films with annealing temperature. X-ray diffraction (XRD) results demonstrated that full width half maximum (FWHM) of ZnO (002) plane decreased and crystalline size increased as the annealing temperature increased. Photoluminescence study revealed that the intensity of band edge emission increased and defect emission decreased as annealing temperature increased because the density of oxygen vacancy related donor defects decreased with annealing temperature. This argument was further justified by the Hall measurements which showed a decreasing trend of carrier concentration with annealing temperature.
Exact third-order static and free vibration analyses of functionally graded porous curved beam
Mirza S. Beg,Hasan M. Khalid,Mohd Y. Yasin,L. Hadji 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.1
An exact solution based on refined third-order theory (TOT) has been presented for functionally graded porous curved beams having deep curvature. The displacement field of the refined TOT is derived by imposing the shear free conditions at the outer and inner surfaces of curved beams. The properties of the two phase composite are tailored according the power law rule and the effective properties are computed using Mori-Tanaka homogenization scheme. The equations of motion as well as consistent boundary conditions are derived using the Hamilton's principle. The curved beam stiffness coefficients (A, B, D) are obtained numerically using six-point Gauss integration scheme without compromising the accuracy due to deepness (1+z/R) terms. The porosity has been modeled assuming symmetric (even) as well as asymmetric (uneven) distributions across the cross section of curved beam. The programming has been performed in MATLAB and is validated with the results available in the literature as well as 2D finite element model developed in ABAQUS. The effect of inclusion of 1+z/R terms is studied for deflection, stresses and natural frequencies for FG curved beams of different radii of curvature. Results presented in this work will be useful for comparison of future studies.
Rajina R. Mohamed,Wahidah Hashim,Ahmad Fadzil Ismail,Khalid M.Abdilahi,Mohammad Kamrul Hasan 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.8
As the rate of internet users is increasing on a daily basis, a tremendous amount of these users are accessing online streaming websites and applications. This paper proposes a live streaming architecture that supports traffic balancing during peak times and bitrate adaptation. Rather than replicating content on multiple servers, we implemented traffic balancing by assigning a temporary regional server to manage the traffic at regional area. Bitrate adaptation at server side was also proposed and implemented to provide a fair video quality to all users. Through a few tests that has been run on the testbed, we can see the live video streaming was move seamlessly from one server to another server with an acceptable video quality among the users.