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- 저자 : Ali K. Abed (검색결과 2 건)
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Aly, I.H.M.,Abed Alrahim Mohammed, L.,Al-Meer, S.,Elsaid, K.,Barakat, N.A.M. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.10
In this study, novel composites consisting of electrospun titanium dioxide (TiO<SUB>2</SUB>) nanofibers incorporated into high-purity wollastonite glass ceramics were prepared as materials for use in hard tissue engineering applications. These materials were characterized and investigated by means of physical, mechanical and in vitro studies. The proposed composite showed greater densification and better mechanical characteristics compared to pure wollastonite. The influence of densification temperature and TiO<SUB>2</SUB> content was investigated. Typically, TiO<SUB>2</SUB>/wollastonite composites having 0, 10, 20 and 30wt% metal oxide nanofibers were sintered at 900, 1100 and 1250<SUP>o</SUP>C. The results indicated that increasing TiO<SUB>2</SUB> nanofibers content leads to increase the bulk density, compressive strength and microhardness with negligible, high and moderate influence for the densification temperature, respectively. While porosity and water adsorption capacity decreased with increasing the metal oxide nanofibers with a considerable impact for the sintering temperature in both properties. Moreover, bone-like apatite formed on the surface of wollastonite and wollastonite/TiO<SUB>2</SUB> nanofibers soaked in simulated body fluid (SBF). All these results show that the inclusion of TiO<SUB>2</SUB> nanofibers improved the characteristics of wollastonite while preserving its in vitro bioactivity; hence, the proposed composite may be used as a bone substitute in high load bearing sites.
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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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