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- 저자 : Ahmed K. Abed (검색결과 2 건)
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Ahmed K. Abed,Riyadh Mansoor,Ali K. Abed 한국통신학회 2022 ICT Express Vol.8 No.1
Orthogonal Frequency Division Multiplexing (OFDM) is the best choice for wireless and wired high data rate communications. The OFDM system has many advantages such as high spectral efficiency, robustness to channel fading, and immunity to impulse interference. However, it has a main drawback, which is the Peak to Average Power Ratio (PAPR). Selecting Mapping (SLM) and Partial Transmit Sequences (PTS) are the two essential techniques for reducing the PAPR; however, they need to send side information to indicate how the transmitter generates signals. In this paper, Particle Swarm Optimization (PSO)-based dummy sub-carriers are inserted with the data to reduce PAPR without transmitting side information. The incorporation of PSO-based Dummy Sub-carriers Insertion (DSI) method on this system is performed by measuring the PAPR at the IFFT output (Inverse Fast Fourier Transform) after adding 6 adaptive sub-carrier sequences to the input data of IFFT. The PSO-based dummy algorithm decides to send the data once the PAPR of this data sequence and dummy sub-carrier is under a specific threshold. Using MATLAB as a mathematical simulation tool, simulation results are presented for a standard OFDM network model. The network model has been simulated in an Additive White Gaussian Noise (AWGN) channel environment to investigate PAPR and Bit-Error Rate (BER) performance. The simulation results show that the dummy sequence based on PSO reduces PAPR down to 4 dB compared to a conventional OFDM system and down to 3 dB compared with the clipping technique for the same BER performance.
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Evaluation of cellulose acetate membrane with carbon nanotubes additives
L.A. Nezam El-Din,A. El-Gendi,N. Ismail,K.A. Abed,Awd I. Ahmed 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.26 No.-
Cellulose acetate (CA)/carbon nano tubes (CNT) membranes were prepared using phase inversion method by dispersing different ratio of carbon nano-materials in CA casting solution. Different polymer to solvent ratios examined for enhancement of membrane desalination. The influence of differentiation in CA and CNT ratio on the morphology and thermal stability were investigated using scanning electron microscopy and thermogravimetric analysis (TGA). Also, Permeation performance of the prepared membranes was evaluated. Morphology results showed that CA membrane porosity decreased with increasing polymer ratio. The membranes pure water flux was increased by the addition of nano-carbon materials. The optimum polymer to solvent ratio for accepted desalination performance was 25:75. The presence of carbon nanotubes (CNT) in the optimum membrane enhanced the salt rejection markedly to 96% as well as the pure water flux has been improved. The optimum membrane in the presence of CNT has convenient thermal stability with accepted water content percent and swelling percent.
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