Dynamic tank in series modeling of direct internal reforming SOFC

A dynamic tank in series reactor model of a direct internally reforming solid oxide fuel cell is presented and validated using experimental data as well as a computational fluid dynamics (CFD) model for the spatial profiles. The effect of the flow distribution pattern at the inlet manifold on the cell performance is studied with this model. The tank in series reactor model provides a reasonable understanding of the spatio‐temporal distribution of the key parameters at a much lesser computational cost when compared to CFD methods. The predicted V–I curves agree well with the experimental data at different inlet flows and temperatures, with a difference of less than ±1.5%. In addition, comparison of the steady‐state results with two‐dimensional contours from a CFD model demonstrates the success of the adopted approach of adjusting the flow distribution pattern at the inlet boundaries of different continuous stirred tank reactor compartments. The spatial variation of the temperature of the PEN structure is captured along with the distributions of the current density and the anode activation over‐potential that strongly related to the temperature as well as the species molar fractions. It is found that, under the influence of the flow distribution pattern and reaction rates, the dynamic responses to step changes in voltage (from 0.819 to 0.84 V), fuel flow (15%) and temperature changes (30 °C), on anode side and on cathode side, highly depend on the spatial locations in the cell. In general, the inlet points attain steady state rapidly compared to other regions. Copyright © 2017 John Wiley & Sons, Ltd.     

Phytosterols in Seaweeds: An Overview on Biosynthesis to Biomedical Applications

Seaweed extracts are considered effective therapeutic alternatives to synthetic anticancer, antioxidant, and antimicrobial agents, owing to their availability, low cost, greater efficacy, eco-friendliness, and non-toxic nature. Since the bioactive constituents of seaweed, in particular, phytosterols, possess plenty of medicinal benefits over other conventional pharmaceutical agents, they have been extensively evaluated for many years. Fortunately, recent advances in phytosterol-based research have begun to unravel the evidence concerning these important processes and to endow the field with the understanding and identification of the potential contributions of seaweed-steroidal molecules that can be used as chemotherapeutic drugs. Despite the myriad of research interests in phytosterols, there is an immense need to fill the void with an up-to-date literature survey elucidating their biosynthesis, pharmacological effects, and other biomedical applications. Hence, in the present review, we summarize studies dealing with several types of seaweed to provide a comprehensive overview of the structural determination of several phytosterol molecules, their properties, biosynthetic pathways, and mechanisms of action, along with their health benefits, which could significantly contribute to the development of novel drugs and functional foods.     

Spectroscopic studies on DLC/TM (Cr,Ag, Ti,Ni) multilayers

The hydrogen-free diamond-like carbon (DLC) films with transition metal (TM = Cr, Ag, Ti, Ni) interlayer (bilayer and multilayer) were deposited on to stainless steel and silicon substrates using pulsed laser deposition technique. Secondary ion mass spectroscopy (SIMS) confirmed that the films were hydrogen free. Incorporation of chromium inter layer reduced the stress value by about 3 GPa as determined by micro Raman spectroscopy. Incorporation of the TM inter layer enhanced the photoluminescence (PL) intensity as compared to the monolithic DLC films. The optical band gap determined by spectroscopic ellipsometry for DLC/TM films was found to be in the range of 1.56–1.67 eV.     

Mart Algorithms for Circular and Helical Cone-Beam Tomography

The present work is concerned with the evaluation of the performance and the efficient implementation of multiplicative algebraic reconstruction technique (MART) to reconstruct three-dimensional (3D) objects for two different source/detector trajectories. Three types of MART algorithms are tested on a numerical phantom (Defrise), and they are implemented on a 3D X-ray system of Vikram Sarabhai Space Centre (VSSC). Circular and helical cone-beam trajectories are used. The results are compared with convolution backprojection (CBP) algorithm for each trajectory. It is found that iterative algorithms perform better than their counterpart, the transform-based CBP algorithm, whenever tomography systems are ill-conditioned due to limited views and/or noisy projection data.     

First-principles investigations of the MMgH3 (, Na, K, Rb, Cs) series

The structural stability of the MMgH₃ (M=Li, Na, K, Rb, Cs) series has been investigated using the density-functional projector-augmented-wave method within the generalized-gradient approximation. Among the 24 structural arrangements used as inputs for the structural optimization calculations, the experimentally known frameworks are successfully reproduced, and positional and unit-cell parameters are found to be in good agreement with the experimental findings. The crystal structure of LiMgH₃ has been predicted, the most stable arrangement being the trigonal LiTaO₃-type (R3c) structure, which contains highly distorted octahedra. The formation energy for all members of the MMgH₃ series is investigated along different reaction pathways. The electronic density of states reveals that the MMgH₃ compounds are wide-band-gap insulators. Analyses of chemical bonding in terms of charge density, charge transfer, electron-localization function, Born effective charge, and Mulliken population show that these hydrides are basically saline hydrides similar to the parent alkali-/alkaline-earth mono-/di-hydrides.     

Influence of grain refinement on hot tearing in B206 and A319 aluminum alloys

Aluminum-copper (Al-Cu) and aluminum-silicon-copper (Al-Si-Cu) alloys are among the most common aluminum casting alloys. Aluminum alloy B206 is a relatively new Al-Cu alloy with high strength and ductility at room and elevated temperatures, while A319 is an Al-Si-Cu alloy with good strength and excellent wear resistance. However, despite their advantages, when these alloys are cast via the permanent mold casting (PMC) process, they show a high susceptibility to hot tearing. Grain refinement has shown promise as a means to reducing hot tears in aluminum alloys. In this study, Ti-B grain refiner was used to investigate the effect of grain refinement on hot tearing in B206 and A319 aluminum alloys during permanent mold casting. The results suggest that Ti-B additions significantly reduced hot tearing in B206 and A319. Grain sizes were also seen to reduce significantly in both alloys with addition of Ti-B grain refiner. However, Ti-B grain refiner had a diverse effect on alloy grain morphology, as a dendritic morphology in B206 was transformed to a more globular one, while in A319, the grain structure remained dendritic.     

Experimental characterization of meso‐scale deformation mechanisms and the RVE size in plastically deformed carbon steel

The local deformation response of low carbon steel subjected to uniaxial tensile loading is investigated, and the local strain field at sub‐grain scale is obtained using high‐spatial‐resolution digital image correlation. The implemented digital image correlation method enables the observation and study of inhomogeneous deformation response at microstructural levels. Detailed local deformation mechanisms including mesoscopic slip bands are captured. Furthermore, the local information is used for the determination of representative volume element size in polycrystalline low carbon steel. To obtain the representative volume element size, we proposed and successfully implemented a strain variation method. Further, the influence of global strain on the local deformation mechanisms and representative volume element size is discussed. The challenges associated with the local strain measurement using digital image correlation are also discussed.     

Fabrication of Biogenic Silica Nanostructures from Sorghum bicolor Leaves for Food Industry Applications

Silicon - Due to the large production of sorghum, the generation of associated agricultural residues, which contain high contents of silica, is inevitable. Also, these agricultural residues are not...     

Chemical-bonding and high-pressure studies on hydrogen-storage materials

From gradient-corrected, all-electron, full-potential, density-functional calculations, including structural relaxation, it is shown that the metal-hydride series RTInH_1.333 (R=La, Ce, Pr, or Nd; T=Ni, Pd, or Pt) violate the “2-Å” rule as well as the hole-size requirement. These hydrides possess unusually short H–H separations which in the most extreme case for LaPtInH_1.333 is as short as 1.454 Å. These findings have been analyzed in terms of charge density, charge transfer, electron-localization function, crystal-orbital Hamilton population, and density of states analyses. From high-pressure studies it is predicted several successive pressure-induced structural transitions in MgH₂ within the 20 GPa range. Calculations have also shown several pressure-induced structural transitions in alkali aluminum tetrahydrides with large volume reductions at the phase-transition points and small energy differences between the ambient-pressure and subsequent high-pressure phases.     

Electrical conductivity and magnetic susceptibility of rutile type CrVNbO6, FeVNbO6 and NiV2Nb2O10

Electrical conductivity (77–300K) and magnetic susceptibility (4.2–300K) of rutile type polycrystalline samples of CrVNbO₆, FeVNbO₆ and NiV₂Nb₂O₁₀ are reported. All three compounds are n-type semiconductors with room termperature resistivities of the order of 10²–10³ ohm-cm. CrVNbO₆ shows ferromagnetic coupling in the high temperature region and orders antiferromagnetically below 10K. FeVNbO₆ trans-forms to a spin glass state below 20K. NiV₂Nb₂O₁₀ shows evidence of weak antiferromagnetic interactions. The transport properties of the compounds are discussed in terms of structural properties and unpaired d electrons present on the respective transition metal ions.