Membrane-hydration-state detection in proton exchange membrane fuel cells using improved ambient-condition-based dynamic model

Proton-exchange-membrane fuel cells (PEMFCs) are a popular source of alternative energy because of their operational reliability and compactness. This paper presents an improved model to represent the semi-empirical voltage of PEMFCs to overcome the limitations of existing models. The proposed model considers variations in ambient conditions, such as the ambient temperature and relative humidity, to obtain the accurate output voltage that corresponds to variations in dynamic and static loads. The proposed model was developed by conducting several experiments on the Horizon PEMFC system under normal, humid, and dry ambient conditions. Subsequently, the model parameters corresponding to each case were optimised using the quantum lightning search algorithm (QLSA). Parameters demonstrating significant variations with ambient conditions were finally represented as a function of the ambient temperature and relative humidity via statistical regression analysis. The voltage obtained using the modified model was verified by conducting experiments on both the Horizon and NEXA PEMFC systems by varying the ambient temperature and relative humidity with root mean square error (RMSE) less than 0.5. As observed, the results we obtained using the modified model closely approximated those obtained using PEMFCs under various operating conditions, and in both cases, the PEMFC voltage was observed to vary with the ambient and load conditions. The inherent advantages of the proposed PEMFC model include its ability to determine the membrane-water content and water pressure inside PEMFCs. The membrane-water content provides clear indications regarding the occurrence of drying and flooding faults. Under normal conditions, this membrane water content ranges from 11 to 7 for both the Horizon and NEXA PEMFC system. The simulation results suggested using the threshold membrane-water-content level as a possible indicator of fault occurrence under extreme ambient conditions. The limits of the said threshold were observed to be useful for fault diagnosis within PEMFC systems.     

Evaluation of hidden H2-consuming pathways using metabolic flux-based analysis for a fermentative side-stream dynamic membrane bioreactor using untreated seed sludge

This study investigates the performance and hidden hydrogen consuming metabolic pathways of a fermentative side stream dynamic membrane (DM) bioreactor using flux balance analysis (FBA). The bioreactor was inoculated with untreated methanogenic seed sludge. It was found that fouling rate aggravated with increasing COD concentration (10–30 g/L) and was positively correlated to it rather than to the applied solid flux on the DM module. Due to increased fouling rate the hydraulic retention time (HRT) could not be reduced less than 0.82 ± 0.02 d. An increase in the organic loading rate (OLR) led to an increase in H₂ yield from 0.01 to 0.76 mol H₂/mol of sucrose. FBA revealed that homoacetogenesis was the main H₂-consuming pathway at lower OLRs (corresponding to 10 and 15 g COD/L), while for the OLR corresponding to 30 g COD/L, homoacetogens were suppressed. More importantly, caproic acid production pathway was identified for the first time as another H₂-consuming pathway at high OLR which was not significant at lower OLRs during fermentative dynamic membrane bioreactor operations.     

Development of ethylene glycol-Cr2AlC nanofluid for thermal management in the automotive sector

The current study is focused on the development of a novel nanofluid for efficient thermal management in the automotive sector. For this, novel Cr₂AlC-based nanofluids were prepared and its properties were compared with conventional nanofluids prepared under similar condition. h-BN, MoS₂, Al₂O₃, and Cr₂AlC powders of <60 nm were prepared by high energy ball mill and were added into the EG fluid in 0.25 and 0.50 wt%. The nanofluids were investigated for viscosity, flash point, fire point, thermal conductivity, stability, and freezing temperature. The flash and fire points of EG increase with the addition of nanocrystalline powders. The viscosity of nanofluids decreases and thermal conductivity increases with increase in temperature. Among all addition, nanofluid containing 0.50 wt% of Cr₂AlC shows maximum enhancement in the thermal conductivity and freezing temperature by 57.91% and 42.15%, respectively. It also shows a good stability up to 20 days.     

Novel sensing and joint beam and null steering based resource allocation for cross-tier interference mitigation in cognitive femtocell networks

Wireless Networks - Cognitive radios and femtocell networks are gaining much popularity due to the formers ability to carry out unlicensed transmission in licensed bands and the latter’s...     

Study of silver electrodeposition in deep eutectic solvents using atomic force microscopy

The electrodeposition of metals in ionic liquids and deep eutectic solvents leads to deposits with significantly different morphologies to those seen with aqueous solutions. The classical methods of fitting amperometric data to nucleation and growth mechanisms do not fit the data well in ionic systems and tend to focus on the short time-scale aspects of nucleation. In the current study, ex-situ AFM was used to model crystallite sizes and distributions by digitising and modelling the images. The deposition of silver from a deep eutectic solvent was chosen as it has been studied by several groups with a variety of techniques. The crystallite size data obtained from AFM and chronoamperometry for long time-scale deposition studies are compared and it is shown that the trends are similar, but there is a discrepancy in the nuclear number density of approximately an order of magnitude. The nuclear number density was found to be consistent with aqueous nucleation studies once differences in concentration and mass transport were accounted for.     

46 XX male: a case of sex reversal syndrome

Methamphetamine is an amphetamine derivative and a category II controlled substance. It is uncommonly prescribed by physicians, but is more often used illegally as a stimulant. In this case study, 3 dogs were believed maliciously poisoned. Methamphetamine was detected in the stomach contents of 1 dog. One died and 2 recovered after gastrointestinal decontamination and supportive care. The recommended treatment protocol of methamphetamine toxicosis should also include urine acidification and alpha-adrenergic blocking agents.     

Variables influencing parental perception of inherited metabolic diseases before and after genetic counselling

BACKGROUND: Sixty percent of adults has typical symptoms of gastroesophageal reflux in Chile. AIM: To report the clinical and laboratory features of patients with gastroesophageal reflux. PATIENTS AND METHODS: Five hundred thirty-four patients (255 male) with gastroesophageal reflux were included in a prospective protocol that included clinical analysis, manometry and endoscopy in all patients, barium swallow in 427, scintigraphy in 195, acid reflux test in 359, 24 h pH in 175, and differential potential of gastroesophageal mucosa in 73 patients. RESULTS: There was no correlation between the severity of symptoms and the endoscopical severity. Patients with Barret esophagus were 12 years older, were male in a greater proportion and had a higher proportion of manometrically incompetent sphincters than patients with esophageal reflux but without esophagitis or with erosive esophagitis. Severity of acid reflux, measured with 24 h pH monitoring was proportional to the endoscopical damage of the mucosa. There was a close relationship between the mucosal change limit determined with differential potentials and with endoscopy. No short esophagi were found. CONCLUSIONS: Patients with symptoms of gastroesophageal reflux must be assessed using several objective measures to determine the severity of their pathological alterations.