Surface tension of evaporating nanofluid droplets

Measurements of nanofluid surface tension were made using the pendant droplet method. Three different types of nanoparticles were used – laponite, silver and Fe₂O₃ – with de-ionized water (DW) as the base fluid. The reported results focus on the following categories: (1) because some nanoparticles require surfactants to form stable colloids, the individual effects of the surfactant and the particles were investigated; (2) due to evaporation of the pendant droplet, the particle concentration increases, affecting the apparent surface tension; (3) because of the evaporation process, a hysteresis was found where the evaporating droplet can only achieve lower values of surface tension than that of nanofluids at the same prepared concentrations; and (4) the Stefan equation relating the apparent surface tension and heat of evaporation was found to be inapplicable for nanofluids investigated. Comparisons with findings for sessile droplets are also discussed, pointing to additional effects of nanoparticles other than the non-equilibrium evaporation process.     

Ru@Pt core–shell nanoparticles for methanol fuel cell catalyst: Control and effects of shell composition

The present work presents a method to encapsulate pre-synthesised Ru nanoparticles (NPs) by Pt using a polyol method without capping agents at various pH values (6, 7, 8 and 10). The structural and surface properties of the catalysts were characterised using X-ray diffraction, transmission electron microscopy, CO stripping, and energy-dispersive X-ray spectroscopy. The studies suggest that the pH during encapsulation of Ru by Pt plays an important role in controlling of shell composition. A core–shell catalyst with an alloy shell was obtained at a pH of 6, whereas a monometallic Pt shell was obtained at a pH of 10. The core–shell catalysts gave higher steady-state current for methanol oxidation: 10-fold higher for alloy shells and 5-fold higher for Pt-enriched shells compared to the pure Pt catalyst. It is suggested that the highest catalytic enhancement of the core–shell catalysts is obtained through the bi-functional character that dominates the alloy shells rather than the ligand-effect-promoted Pt-enriched shells.     

Feasibility of palm‐biodiesel fuel for a direct internal reforming solid oxide fuel cell

The feasibility of a direct internal reforming (DIR) solid oxide fuel cell (SOFC) running on wet palm‐biodiesel fuel (BDF) was demonstrated. Simultaneous production of H₂‐rich syngas and electricity from BDF could be achieved. A power density of 0.32 W cm^?2 was obtained at 0.4 A cm^?2 and 800 °C under steam to carbon ratio of 3.5. Subsequent durability testing revealed that a DIR‐SOFC running on wet palm‐BDF exhibited a stable voltage of around 0.8 V at 0.2 A cm^?2 for more than 1 month with a degradation rate of approximately 15 % / 1000 h. The main cause of the degradation was an increase in the ohmic resistance. Copyright © 2012 John Wiley & Sons, Ltd.     

Detection of thermophilic Campylobacter spp. in blood-free enriched samples of inoculated foods by the polymerase chain reaction

The detection of thermophilic Campylobacter spp., as represented by Campylobacter jejuni, by the polymerase chain reaction (PCR) was investigated and compared with the selective agar isolation (SAI) method. Stationary-phase cultures of C. jejuni were inoculated into either blood-free enrichment broth (BFEB) or BFEB that contained 10% broccoli, crabmeat, mushroom, raw milk, and raw oyster rinses. Following a 48-h enrichment period, aliquots of food test portions were removed for simultaneous analysis by PCR and SAI. It was determined that the presence of charcoal and iron in the enrichment broth interfered with the PCR assay. Therefore, three DNA extraction techniques were developed and evaluated using a 16S rRNA primer pair in the PCR assay. The 50% end point (DL50) values (determined upon six initial C. jejuni spiking levels) were used to assess the frequency of isolation utilizing PCR versus SAI for the detection of this organism in the enrichment matrices. There were virtually no differences in detection of C. jejuni among enriched samples analyzed by PCR and SAI. Mean DL50 values (n = 3) for plain BFEB, broccoli, crabmeat, mushroom, raw milk, and raw oyster were, respectively, 0.02 (PCR) versus 0.01 (SAI), 0.01 versus 0.06, 0.07 versus 0.04, 0.03 versus 0.08, 0.01 versus 0.01, and 0.01 versus 0.01 CFU/5 g food. Significant variability in the detection limit of C. jejuni by PCR in the food enrichments was observed among DNA extraction techniques. Using 48-h enrichment cultures followed by PCR analysis could save 1 day of the time required for the presumptive identification of C. jejuni in suspected foods.     

CAD-Oriented Model of a Coplanar Line on a Silicon Substrate Including Eddy-Current Effects and Skin Effect

Silicon technologies are now widely used for RF applications. Due to the substrate and conductor conductivity, losses and magnetic coupling affect the signal propagation in transmission lines. We propose an equivalent scheme for a transmission line taking these phenomena into account. All the parameters are analytically extracted from measurements. The magnetic coupling, including eddy currents, are described as series elements. They are affected by skin effects. The electric losses are described as parallel elements. They depend on the different layers that the electric field lines meet.     

An optimal loading principle of burnable poisons for an OTTO refueling scheme in pebble bed HTGR cores

An optimal loading principle of burnable poisons (BPs) is proposed to eliminate the problem of an excessively high power peaking factor in once-through-then-out (OTTO) pebble bed HTGR cores. The effectiveness of the principle is confirmed through neutronic and thermal hydraulic calculations for an HTGR core with thermal power of 600 MWt. Spherical BP particles are distributed uniformly together with TRISO-coated fuel particle inside the free fuel zones of fuel pebbles to maintain constant k_∞ during burnup. The applicability of BP materials, such as B₄C, Gd₂O₃, Sm₂O₃, Eu₂O₃, Er₂O₃, CdO, and HfO₂, is investigated. Because complete BP depletion at the target burnup is required to avoid reactivity loss and extra enrichment, the four BP materials considered as applicable candidates are B₄C, Gd₂O₃, Er₂O₃, and CdO. The complete BP depletion is demonstrated by a burning fraction at the target burnup. The power density is excessively high at the core top and the power peaking factor is 4.44 when no BP is added to the fuel pebbles. Optimal BP loading reduces the power peaking factor from 4.44 to about 1.7. Because of the power peaking factor reduction, the maximum fuel temperatures are lower than the maximum permissible values of 1250 °C for normal operation and 1600 °C during a depressurization accident.