Biodiesel from green energy source is gaining tremendous attention for ecofriendly and economically aspect. In this investigation, a two-step process was developed for the production of biodiesel from microalgae Spirulina maxima and determined best operating conditions for the steps. In the first stage, acid esterification was conducted to lessen acid value (AV) from 10.66 to 0.51 mgKOH/g of the feedstock and optimal conditions for maximum esterified oil yielding were found at molar ratio 12:1, temperature 60 C, 1% (wt%) H 2 SO 4 , and mixing intensity 400 rpm for a reaction time of 90 min. The second stage alkali transesterification was carried out for maximum biodiesel yielding (86.1%) and optimal conditions were found at molar ratio 9:1, temperature 65 C, mixing intensity 600 rpm, catalyst concentration 0.75% (wt%) KOH for a reaction time of 20 min. Biodiesel were analyzed according to ASTM standards and results were within standards limit. Results will helpful to produce third generation algal biodiesel from microalgae Spirulina maxima in an efficient manner.
SummaryIn this paper, a human skull‐shaped miniaturized super wideband microstrip monopole antenna is presented. The shape of the microstrip radiator is optimized and designed by combining different sizes of semicircular‐ and rectangular‐shaped radiating elements along with a microstrip feed line. On the other hand, a defected ground structure as the ground is placed at the opposite side of the radiator, which is fabricated on Rogers 5880 substrate. The electrical length of the proposed antenna is 0.240 × 0.200 × 0.016 λ at 3 GHz. The CST microwave studio is used for all the required simulations regarding antenna prototype design and optimization. The complete outcomes demonstrate that the proposed miniaturized antenna has a bandwidth of 24.5 GHz (3 to 27.5 GHz) having a radiation pattern in the form of nearly omnidirectional. The measured fractional bandwidth of the antenna is 160.66%, and the bandwidth dimension ratio is 3346.99, which is the highest among the literature review. The maximum calculated gain and efficiency are 6.3 dBi and 93%, respectively. For the time domain analysis, the antenna shows a decent performance in terms of the system group delay and fidelity factor. The numerical and experimental data are investigated throughout the study, which represents that the proposed antenna is suitable for short‐distance wireless communication like wireless local area network/Wi‐Fi/Worldwide Interoperability for Microwave Access (WiMAX)/ultra‐wideband and some other applications.
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