The modern trend of consuming mustard oil in raw, fried and cooked forms is increasing day by day in the general people irrespective of economic status in Bangladesh. But unfortunately they are not aware of the adverse effects of this oil. Because, mustard oils have been evidenced to have high level of erucic acid and erucic acid has been evidenced to be a causative agent for cardiovascular diseases. It is therefore very important to know the erucic acid level both in traditional and commercially available mustard oils in Bangladesh. The aim of the study was to investigate the fatty acid profile of the commercial mustard oil (Industrially manufactured) and ghani (traditional method of oil processing) mustard oil. After preparation of the purified fatty acid methyl esters of the above oils, Gas-Liquid Chromatographic (GLC) analysis was carried out. Results showed that the percentage of erucic acid (22:1) in the commercial and ghani mustard oils were 41.80% and 51.98% respectively. In context to percentage of erucic acid, the commercial mustard oil seemed better compared to ghani. The reasons behind this discrepancy still remains unclear but the possibility of mixed oil effects in the commercial mustard oil could be investigated in the near future. The author also established a method to partially eliminate erucic acid from mustard oil. After partially eliminate erucic acid from commercial mustard oil erucic acid reduces from 41.80% to 20.14%.
Orthogonal Frequency Division Multiplexing (OFDM) signaling has been widely used for high data rate transmission applications due to its high spectral efficiency and robustness to the frequency selective fading channels. One of the major drawbacks of the analog OFDM system is frequency shifting in every sub-carrier. That's why bit error rate increased in analog OFDM system. In this research, we want to solve the problem of the analog OFDM system by using IFFT circuit instead of the local oscillator. The IFFT circuit takes an input as frequency domain and provides output as a time domain signal for 4-QAM modulation. Basically IFFT circuit acts as a local oscillator in the analog OFDM system. The IFFT circuit only executes operation on a discrete frequency domain signal which is converted into a time domain signal by its. So no frequency shifting occurs in every sub-carrier in the digital OFDM system. As a result BER also decrease in digital OFDM system over the analog OFDM system.
Orthogonal Frequency Division Multiplexing (OFDM) is an attractive modulation technique for transmitting large amounts of digital data over radio waves. One major disadvantage of OFDM is that the time domain OFDM signal which is a sum of several sinusoids leads to high peak to average power ratio (PAPR) which leads to power inefficiency in RF section of the transmitter and increased complexity in the analog to digital and digital to analog Converter. Selected mapping (SLM) is a well-known method for reducing the PAPR in OFDM. In this paper, we have studied the performance of SLM for Different Number of Subcarriers. Simulation result shows that the PAPR is reduced significantly when the number of phase sequences is increased and PAPR is increased when the number of subcarriers is increased. It also shows that data speed increases when subcarriers increase where N-point IFFT/FFT circuit depends on N-subcarriers.
Background and Objective: In this research work, the basic digital communication system with frequency shift keying modulation technique has been implemented in MATLAB. Methods: The same sinusoidal signal in audio frequency range has been transmitted and reconstructed with the different number of quantization level and sampling rate, where sampling frequency has been taken according to the Nyquist theorem. It has been seen that reconstructed signal at low data rate has appeared with better resolution compared with the reconstructed signal at the high data rate. Results and Conclusion: In this regard, it is evident that the resolution of a reconstructed signal not only depends on data rate but it also depends on the ratio of sampling rate to quantization level. So it is required to optimize the ratio of sampling rate to quantization level before transmitting audio signal.
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