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.

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Despite the fact that OFDM has numerous features, the high peak-to-average power ratio (PAPR) deems one of the challenging disadvantages face by the system in the real applications. The high PAPR limits the OFDM signal efficiency on the transmitter side. Thus many PAPR alleviation approaches have been suggested in the past. Partial transmit sequences (PTS) has been accounted as one of the successful procedures for decreasing the high PAPR; with the consideration that the computational complexity of the PTS method regarded high relatively. Moreover, improving the PAPR mitigation performance of the PTS algorithm relies upon the number of the partitioned subblocks, the number of the phase rotation vectors, and the kind of the segmentation scheme utilized. This article presents new segmentation schemes to enhance the PAPR mitigation execution without further intricacy on the system. Adjacent shifting segmentation scheme (Ad-Sh-PTS) and rows exchange of interleaving segmentation schemes (IL-Ex-PTS) are proposed depending on the two well-known segmentation schemes of adjacent partition PTS (Ad-PTS) and interleaving partition PTS (IL-PTS). The simulation demonstrates that the suggested algorithms can accomplish mitigation in PAPR preferable compared to the traditional schemes, Ad-PTS and IL-PTS schemes.

Pesticide helps to enhance agricultural production, however, it significantly affect both socio and environmental entities of a country. In Nigeria, pesticide is widely used, thus its traces have been detected in water, soil and air. Several studies have already indicated that most of the environmental ecology (air, water, and soil) in Nigeria has been contaminated by persistent organic pesticides like organochlorine and organophosphate. Other reasons of high pesticide residues present in Nigeria environment is due to inappropriate dosage applied of pesticides that leaves behind excess. However, its residues are found above safety levels in the air, water, and soil across the nation. Based on previous analysis, it is indicated that 125,000-130,000 metric ton pesticides are being applied annually in Nigeria. Despite banned of some pesticides such as dichlorodiphenyltrichloroethane-and -Hexachlorocyclohexane, they are still being used by farmers in their agricultural production. Many of the Class 1 (high extremely toxic) pesticides are still being used in developing countries like Nigeria. Hence, there is need to sensitize and educate the general public especially the end-users (farmers) particularly on management practices of pesticides. Considering these entire hazardous situations, in this article the history of pesticide used in Nigeria has been reviewed in detail. The article also discussed the effects of pesticide use in Nigerian waters, soil and on crops. The risk of residual pesticide on agricultural workers, pesticide residue risk preventive measures by the Federal Government of Nigeria, banned and restricted pesticides in Nigeria, Nigerian Government and its efforts to eliminate persistent organic pesticides in use are also reviewed in details. Key words: Organic pesticide. Organochlorine. Organophosphate. DDT. HCH. Residue. ResumoInseticidas ajudam a aumentar a produção agrícola, no entanto, afetam significativamente a sociedade e o ambiente do país. Na Nigéria, os inseticidas são amplamente utilizados, assim, seus resíduos foram detectados na água, solo e ar. Vários estudos já indicaram que a maior parte dos aspetos ecológicos ambientais (ar, água e solo) na Nigéria tenham sido contaminados por pesticidas orgânicos persistentes como os organoclorados (OCL) e organofosforados (OP). Outro motivo relacionado com a ocorrência de resíduos elevados de inseticidas presentes no meio ambiente na Nigéria é devido às dosagens inadequadas aplicadas de pesticidas que são aplicados em excesso. No entanto, seus resíduos são

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