Orthogonal frequency division multiplexing (OFDM) is a superior technology for the high-speed data rate of wire-line and wireless communication systems. The OFDM has many advantages over other techniques such as its high capacity and immunity against multipath fading channels. However, one of the main drawbacks of the OFDM system is the high-peak-to-average power ratio (PAPR) that leads the system to produce in-band distortion and out-of-band radiation because of the non-linearity of the high-power amplifiers. Therefore, numerous techniques have been proposed to overcome the PAPR problem such as selective mapping, partial transmit sequence (PTS), clipping, and nonlinear companding. In this paper, the PTS technique was analytically reviewed as one of the important methods to reduce the high PAPR problem. The PAPR performance and the computational complexity level are discussed in terms of modifying the PTS technique in the frequency domain, time domain and modulation stage (inverse fast Fourier transform block). Moreover, the numerical statistic comparison of the current modified-PTS methods is introduced, and the criteria for selecting the suitable modified-PTS method in the OFDM system are also given. The simulation and the numerical calculations results show that the rows exchange-interleaving PTS scheme is the best method for reducing the PAPR value with low complexly in the frequency domain, and the cooperative PTS method is the best among the modulation stage methods, while the cyclic shift sequence PTS method achieves the superior performance in PAPR reduction and computational complexity for the time domain methods.

Chemical vapour deposition (CVD) had been used to produce carbon nanotube (CNT) coated carbon fibre, referred to in this work as nano-hybrid fibres. In order to understand the gas flow behaviour inside the CVD reactor, computational fluid dynamics (CFD) has been utilised to simulate the process in a horizontal CVD reactor together with a vertical CVD reactor for comparison. For simplicity purposes, the CNT synthesis was represented by ferrocene decomposition into iron, which acts as the catalyst for CNT formation. The gas flow behaviour inside the horizontal reactor was asymmetrical in nature and seen to be dominated by recirculation effects compared with the vertical reactor, which was symmetrical and generally lacking in circulation. The impact of the gas flow characteristics on the reaction rates of the ferrocene decomposition and mass fraction of chemical species was also investigated. The kinetic rate of reaction in the horizontal reactor was found to be 2-3 orders of magnitude larger in the horizontal reactor compared with the vertical reactor. The results provide valuable insight into the best approach for producing nano-hybrid fibres in a one-step continuous process.

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The deposition of titanium dioxide, TiO2, films on ceramic tiles was studied in order to take benefit of its antimicrobial properties for suitable application in related fields. In this paper, the characteristics of TiO2 coating deposited on unglazed ceramic substrates with high surface roughness were investigated. TiO2 films were deposited several times via dip coating sol-gel technique and heat treated at 500oC for 1 hour. The coating morphologies and thickness were analyzed using Scanning electron microscope (SEM), while the crystalline phases were characterized using Glancing angle X-ray Diffraction (GAXRD). Results show that it produces coating with homogeneous morphology, thicker film and with the presence of anatase and rutile phases. It was also observed that one dipping time is sufficient to produce a continuous coating with thickness of ~ 12 μm on average.

Sol-gel dip-coating technique was utilized to prepare Ag-TiO2 coating with additive (Degussa P25) on unglazed ceramic tiles. Three different numbers of coating layers (5, 7 and 10 layers) were deposited on unglazed ceramic tiles made of waste glass. The coatings were sintered at 500 °C with the heating rate of 2 °C/min. The crystalline phase and cross sectional areas of the coatings were evaluated using GAXRD and SEM analysis, respectively. Results showed that the average thickness of the coating increased from 7 µm to 9 µm and to 12 µm for 5, 7 and 10 coating layers, correspondingly. Coating of 10 layers exhibited a high crystallinity of anatase phase, a good surface morphology without significant cracks, and a homogeneous coating compared to the 5 and 7 layers of coating, which suggested a better performance in Ag-TiO2 coating.