Tree Growth Algorithm for Parameter Identification of Proton Exchange Membrane Fuel Cell Models

Demonstrating an accurate mathematical model is a mandatory issue for realistic simulation, optimization and performance evaluation of proton exchange membrane fuel cells (PEMFCs). The main goal of this study is to demonstrate a precise mathematical model of PEMFCs through estimating the optimal values of the unknown parameters of these cells. In this paper, an efficient optimization technique, namely, Tree Growth Algorithm (TGA) is applied for extracting the optimal parameters of different PEMFC stacks. The total of the squared deviations (TSD) between the experimentally measured data and the estimated ones is adopted as the objective function. The effectiveness of the developed parameter identification algorithm is validated through four case studies of commercial PEMFC stacks under various operating conditions. Moreover, comprehensive comparisons with other optimization algorithms under the same study cases are demonstrated. Statistical analysis is presented to evaluate the accuracy and reliability of the developed algorithm in solving the studied optimization problem

Low-SAR Miniaturized Handset Antenna Using EBG

Advances in wireless communications have paved the way for wide usage of mobile phones in modern society, resulting in mounting concerns surrounding its harmful radiation. Energy absorption in human biological tissues can be characterized by specific absorption rate (SAR). This value refers to the actual amount of electromagnetic energy absorbed in the biological tissues, thus a lower value of SAR indicates a lower radiation exposure risk to the human body. So, our challenge is to introduce mobile handset antennas with low SAR and operating at all mobile and wireless applications. In this chapter, novel configurations of single-element antenna are designed, simulated, fabricated, and measured. The antennas operate for most cellular applications: global system for mobile (GSM)-850/900, digital cellular system (DCS)-1800, personal communication service (PCS)-1900, universal mobile telecommunication system (UMTS)-2100, and long-term evolution (LTE) bands. The antennas also support wireless applications. The proposed antennas have a compact size and low SAR at all bands. Also, this chapter presents a comprehensive study on the performance of the antenna in the different environments. Furthermore, the antenna performance is tested in the presence of head and hand in free space and in a car. The simulation and measurement results are in good agreement

Optimal Design of Photovoltaic, Biomass, Fuel Cell, Hydrogen Tank units and Electrolyzer hybrid system for a remote area in Egypt

In this paper, a new isolated hybrid system is simulated and analyzed to obtain the optimal sizing and meet the electricity demand with cost improvement for servicing a small remote area with a peak load of 420 kW. The major configuration of this hybrid system is Photovoltaic (PV) modules, Biomass gasifier (BG), Electrolyzer units, Hydrogen Tank units (HT), and Fuel Cell (FC) system. A recent optimization algorithm, namely Mayfly Optimization Algorithm (MOA) is utilized to ensure that all load demand is met at the lowest energy cost (EC) and minimize the greenhouse gas (GHG) emissions of the proposed system. The MOA is selected as it collects the main merits of swarm intelligence and evolutionary algorithms; hence it has good convergence characteristics. To ensure the superiority of the selected MOA, the obtained results are compared with other well-known optimization algorithms, namely Sooty Tern Optimization Algorithm (STOA), Whale Optimization Algorithm (WOA), and Sine Cosine Algorithm (SCA). The results reveal that the suggested MOA achieves the best system design, achieving a stable convergence characteristic after 44 iterations. MOA yielded the best EC with 0.2106533 $/kWh, the net present cost (NPC) with 6,170,134$, the loss of power supply probability (LPSP) with 0.05993%, and GHG with 792.534 t/y

Optimal Design of Photovoltaic, Biomass, Fuel Cell, Hydrogen Tank Units and Electrolyzer Hybrid System for a Remote Area in Egypt

In this paper, a new isolated hybrid system is simulated and analyzed to obtain the optimal sizing and meet the electricity demand with cost improvement for servicing a small remote area with a peak load of 420 kW. The major configuration of this hybrid system is Photovoltaic (PV) modules, Biomass gasifier (BG), Electrolyzer units, Hydrogen Tank units (HT), and Fuel Cell (FC) system. A recent optimization algorithm, namely Mayfly Optimization Algorithm (MOA) is utilized to ensure that all load demand is met at the lowest energy cost (EC) and minimize the greenhouse gas (GHG) emissions of the proposed system. The MOA is selected as it collects the main merits of swarm intelligence and evolutionary algorithms; hence it has good convergence characteristics. To ensure the superiority of the selected MOA, the obtained results are compared with other well-known optimization algorithms, namely Sooty Tern Optimization Algorithm (STOA), Whale Optimization Algorithm (WOA), and Sine Cosine Algorithm (SCA). The results reveal that the suggested MOA achieves the best system design, achieving a stable convergence characteristic after 44 iterations. MOA yielded the best EC with 0.2106533 $/kWh, the net present cost (NPC) with 6,170,134$, the loss of power supply probability (LPSP) with 0.05993%, and GHG with 792.534 t/y

Low-profile antenna system for cognitive radio in IoST CubeSat applications

Since the CubeSats have become inherently used for the Internet of space things (IoST) applications, the limited spectral band at the ultra-high frequency (UHF) and very high frequency should be efficiently utilized to be sufficient for different applications of CubeSats. Therefore, cognitive radio (CR) has been used as an enabling technology for efficient, dynamic, and flexible spectrum utilization. So, this paper proposes a low-profile antenna for cognitive radio in IoST CubeSat applications at the UHF band. The proposed antenna comprises a circularly polarized wideband (WB) semi-hexagonal slot and two narrowband (NB) frequency reconfigurable loop slots integrated into a single-layer substrate. The semi-hexagonal-shaped slot antenna is excited by two orthogonal +/−45° tapered feed lines and loaded by a capacitor in order to achieve left/right-handed circular polarization in wide bandwidth from 0.57 GHz to 0.95 GHz. In addition, two NB frequency reconfigurable slot loop-based antennas are tuned over a wide frequency band from 0.6 GHz to 1.05 GH. The antenna tuning is achieved based on a varactor diode integrated into the slot loop antenna. The two NB antennas are designed as meander loops to miniaturize the physical length and point in different directions to achieve pattern diversity. The antenna design is fabricated on FR-4 substrate, and measured results have verified the simulated results

Impact of risk factors on the timing of first postpartum venous thromboembolism: a population-based cohort study from England

For women with preeclampsia, BMI >30 kg/m2, infection, or those having cesarean delivery, VTE risk remained elevated for 6 weeks postpartum.For women with postpartum hemorrhage or preterm birth, the relative rate of VTE was only increased for the first 3 weeks postpartum.Impact on the timing of first postpartum venous thromboembolism (VTE) for women with specific risk factors is of crucial importance when planning the duration of thromboprophylaxis regimen. We observed this using a large linked primary and secondary care database containing 222 334 pregnancies resulting in live and stillbirth births between 1997 and 2010. We assessed the impact of risk factors on the timing of postpartum VTE in term of absolute rates (ARs) and incidence rate ratios (IRRs) using a Poisson regression model. Women with preeclampsia/eclampsia and postpartum acute systemic infection had the highest risk of VTE during the first 3 weeks postpartum (ARs ≥2263/100 000 person-years; IRR ≥2.5) and at 4-6 weeks postpartum (AR ≥1360; IRR ≥3.5). Women with body mass index (BMI) >30 kg/m2 or those having cesarean delivery also had elevated rates up to 6 weeks (AR ≥1425 at 1-3 weeks and ≥722 at 4-6 weeks). Women with postpartum hemorrhage or preterm birth, had significantly increased VTE rates only in the first 3 weeks (AR ≥1736; IRR ≥2). Our findings suggest that the duration of the increased VTE risk after childbirth varies based on the type of risk factors and can extend up to the first 3 to 6 weeks postpartum