Continuous need for the optimum conversion efficiency of polymer electrolyte membrane fuel cell (PEMFC) operation has triggered varieties of advancements, namely in the thermal management engineering scope. Excellent heat dissipation is correlated with higher performance of a fuel cell, thus increasing its conversion efficiency. This study reveals the potential advancement in thermal engineering of a fuel cell cooling system with respect to nanofluid technology. Nanofluids are seen as a potential evolution of nanotechnology hybridization with the fuel cell serving as a cooling medium. The available literature on the thermophysical properties of potential nanofluids, especially on the electrical conductivity property, has been discussed. The lack of electrical conductivity data for various nanofluids in open literature was another challenge in the application of nanofluids in fuel cells. Unlike in any other thermal management system, a nanofluid in a fuel cell is dealt with using a thermoelectrically active environment. The main challenge in nanofluid adoption in fuel cells was the formulation of a suitable nanofluid coolant with heat transfer enhancement, as compared to its base fluid, but still complying with the strict limits of electrical conductivity as low as 2 S/cm and several other restrictions discussed by the researchers. It is concluded that a nanofluid in PEMFC is advantageous in terms of both heat transfer and simplification of the cooling system through radiator size reduction and potential elimination of the deionizer as compared to the current PEMFC cooling system. However, there are challenges that need to be well addressed, especially in the electrical conductivity requirement.
Abstract:The low hardness and strength of aluminum, which limits its use in many industrial applications, could be increased through the addition of nanoparticles. However, the appropriate processing method and parameters should be carefully selected in order to achieve the desired improvement in properties. In this work, aluminum was reinforced with low weight fraction (1 wt.%) of SiC nanoparticles and consolidated through spark plasma sintering. The effect of processing parameters on the densification, microstructure, and properties of the processed material was investigated. Field Emission Scanning Electron Microscope (FE-SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) facility was used to characterize the microstructure and analyze the reinforcement's distribution in sintered samples. Phases present were characterized through X-ray diffraction (XRD). A densimeter and a digital microhardness tester were used to measure the density and hardness, respectively. Compressive tests were performed using universal testing machine. A fully dense Al-1 wt.% SiC sample was obtained. Analysis of density and hardness values showed that the influence of applied pressure was more pronounced than heating rate while the influence of sintering temperature was more significant than sintering time. Within the range of parameters used, the highest values of the characterized properties were obtained at a sintering temperature of 600 °C, sintering time of 10 min, pressure of 50 MPa, and heating rate of 200 °C/min. OPEN ACCESSMetals 2015, 5 71
Summary The rate of elimination of trimethoprim in sheep, as indicated by its half‐life, was determined. The average half‐life for this drug was 43.6 + 2.27 min. and the apparent volume of distribution was 1.5 + 0.04. Estimation of the drug in tissues one hour after intravenous injection showed higher concentrations, especially in liver and kidney, than in blood plasma. The tissues of the foetus contained trimethoprim in concentrations similar to those in the plasma of the dam. Zusammenfassung Pharmakokinetik und Gewebsverteilung von Trimethoprim beim Schaf Aufgrund der Halbzeit wurde die Eliminationsrate von Trimethoprim beim Schaf bestimmt. Die Halbwertszeit betrug 43.6 + 2.27 min und das apparente Distributionsvolumen 1.5 + 0.04. Eine Stunde nach der intravenösen Injektion waren die Konzentrationen des Trimethoprims speziell in der Leber und Niere höher als im Blutplasma. Die fötalen Gewebe wiesen ähnliche Konzentrationen auf wie das Plasma des Muttertieres. Résumé Pharmacocynétique et répartition tissulaire du trimethoprim chez le mouton Le taux d'élimination du trimethoprim chez le mouton a été déterminé miné sur la base du demi‐temps de valeur. Le demi‐temps d'effet fut de 43,6 + 2,27 min. et le volume apparent de distribution de 1,5 + 0,04. Une heure après l'injection intraveineuse, les concentrations du trimethoprim furent particulièrement plus élevées dans le foie et les reins que dans le plasma sanguin. Les tissus du foetus ont montré les mêmes concentrations que celles du plasma de la mère. Resumen Farmacocinética y distribución hística de trimethoprim en la oveja En virtud del semitiempo se determinó la tasa del eliminación de trimethoprim en la oveja. El semitiempo de valor fué del orden de 43.6 + 2.27 min. y el volumen de distribución aparente era 1.5 + 0.04. Una hora después de efectuar la inyección intravenosa se apreciaron concentraciones mayores de este fármaco en el hígado y riñones que en el plasma sanguíneo. Los tejidos fetales contenían concentraciones semejantes a las plasmáticas en las madres correspondientes.
The Internet is gradually becoming part and parcel of our lives. As a result, online educational technologies are gaining more acceptance in our educational system. This is more so in higher education. However, online assessment is one aspect of online technologies that has taken time to be accepted by educators. This is primarily due to concerns related to reliability, validity and security of online assessment. This paper presents the results of a study that investigates students' perceptions of online homework that was recently introduced in our precalculus courses, as compared to conventional paper and pencil homework. Furthermore, we share some qualitative data we observed that should be useful to all mathematics educators, especially those planning to implement online homework. Some important issues related specifically to MyMathLab, which is the platform we are currently using for online homework, together with the major problems students faced in getting accustomed to the online environment will be discussed.
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