Onset of transition in mixed convection of a lid-driven trapezoidal enclosure filled with water-Al2O3 nanofluid

A numerical study is carried out to investigate the transition from laminar to chaos in mixed convection heat transfer inside a lid-driven trapezoidal enclosure. In this study, the top wall is considered as isothermal cold surface, which is moving in its own plane at a constant speed, and a constant high temperature is provided at the bottom surface. The enclosure is assumed to be filled with water-Al2O3 nanofluid. The governing Navier–Stokes and thermal energy equations are expressed in non-dimensional forms and are solved using Galerkin finite element method. Attention is paid in the present study on the pure mixed convection regime at Richandson number, Ri = 1. The numerical simulations are carried out over a wide range of Reynolds (0.1 ≤ Re ≤ 103) and Grashof (0.01 ≤ Gr ≤ 106) numbers. Effects of the presence of nanofluid on the characteristics of mixed convection heat transfer are also explored. The average Nusselt numbers of the heated wall are computed to demonstrate the influence of flow parameter variations on heat transfer. The corresponding change of flow and thermal fields is visualized from the streamline and the isotherm contour plots.

Understanding welding practices on shipyards : an ethnographic study for designing an interactive robot welder

The aim of this ethnographic study was to understand welding practices in shipyard environments with the purpose of designing an interactive welding robot that can help workers with their daily job. The robot is meant to be deployed for automatic welding on jack-up rig structures. The design of the robot turns out to be a challenging task due to several problematic working conditions on the shipyard, such as dust, irregular floor, high temperature, wind variations, elevated working platforms, narrow spaces, and circular welding paths requiring a robotic arm with more than 6 degrees of freedom. Additionally, the environment is very noisy and the workers – mostly foreigners – have a very basic level of English. These two issues need to be taken into account when designing the interactive user interface for the robot. Ideally, the communication flow between the two parties involved should be as frictionless as possible. The paper presents the results of our field observations and welders’ interviews, as well as our robot design recommendation for the next project stage.

Large-volume methacrylate monolith for plasmid purification : process engineering approach to synthesis and application

The extent of exothermicity associated with the construction of large-volume methacrylate monolithic columns has somewhat obstructed the realisation of large-scale rapid biomolecule purification especially for plasmid-based products which have proven to herald future trends in biotechnology. A novel synthesis technique via a heat expulsion mechanism was employed to prepare a 40 mL methacrylate monolith with a homogeneous radial pore structure along its thickness. Radial temperature gradient was recorded to be only 1.8 °C. Maximum radial temperature recorded at the centre of the monolith was 62.3 °C, which was only 2.3 °C higher than the actual polymerisation temperature. Pore characterisation of the monolithic polymer showed unimodal pore size distributions at different radial positions with an identical modal pore size of 400 nm. Chromatographic characterisation of the polymer after functionalisation with amino groups displayed a persistent dynamic binding capacity of 15.5 mg of plasmid DNA/mL. The maximum pressure drop recorded was only 0.12 MPa at a flow rate of 10 mL/min. The polymer demonstrated rapid separation ability by fractionating Escherichia coli DH5α-pUC19 clarified lysate in only 3 min after loading. The plasmid sample collected after the fast purification process was tested to be a homogeneous supercoiled plasmid with DNA electrophoresis and restriction analysis.

Optical gas sensing properties of nanoporous Nb2O5 films

Nanoporous Nb2O5 has been previously demonstrated to be a viable electrochromic material with strong intercalation characteristics. Despite showing such promising properties, its potential for optical gas sensing applications, which involves the production of ionic species such as H+, has yet to be explored. Nanoporous Nb2O5 can accommodate a large amount of H+ ions in a process that results in an energy bandgap change of the material, which induces an optical response. Here, we demonstrate the optical hydrogen gas (H¬2) sensing capability of nanoporous anodic Nb2O5 with a large surface-to-volume ratio prepared via a high temperature anodization method. The large active surface area of the film provides enhanced pathways for efficient hydrogen adsorption and dissociation, which are facilitated by a thin layer of Pt catalyst. We show that the process of H2 sensing causes optical modulations that are investigated in terms of response magnitudes and dynamics. The optical modulations induced by the intercalation process and sensing properties of nanoporous anodic Nb2O5 shown in this work can potentially be used for future optical gas sensing systems.

First-principle engineering magnetism in low-dimensional boron nitride materials

Nanotubes and nanosheets are low-dimensional nanomaterials with unique properties that can be exploited for numerous applications. This book offers a complete overview of their structure, properties, development, modeling approaches, and practical use. It focuses attention on boron nitride (BN) nanotubes, which have had major interest given their special high-temperature properties, as well as graphene nanosheets, BN nanosheets, and metal oxide nanosheets. Key topics include surface functionalization of nanotubes for composite applications, wetting property changes for biocompatible environments, and graphene for energy storage applications

Low δ18O zircons from the Bruneau-­Jarbidge eruptive center: A key to crustal anatexis along the track of the Yellowstone hotspot

The Bruneau-Jarbidge eruptive center (BJEC) in the central Snake River Plain, Idaho, USA consists of the Cougar Point Tuff (CPT), a series of ten, high-temperature (900-1000°C) voluminous ignimbrites produced over the explosive phase of volcanism (12.8-10.5 Ma) and more than a dozen equally high-temperature rhyolite lava flows produced during the effusive phase (10.5-8 Ma). Spot analyses by ion microprobe of oxygen isotope ratios in 210 zircons demonstrate that all of the eruptive units of the BJEC are characterized by zircon δ¹⁸O values ≤ 2.5‰, thus documenting the largest low δ¹⁸O silicic volcanic province known on Earth (>10⁴ km³). There is no evidence for voluminous normal δ¹⁸O magmatism at the BJEC that precedes generation of low δ¹⁸O magmas as there is at other volcanic centers that generate low δ¹⁸O magmas such as Heise and Yellowstone. At these younger volcanic centers of the hotspot track, such low δ¹⁸O magmas represent ~45 % and ~20% respectively of total eruptive volumes. Zircons in all BJEC tuffs and lavas studied (23 units) document strong δ¹⁸O depletion (median CPT δ¹⁸OZrc = 1.0‰, post-CPT lavas = 1.5‰) with the third member of the CPT recording an excursion to minimum δ¹⁸O values (δ¹⁸OZrc= -1.8‰) in a supereruption > 2‰ lower than other voluminous low δ¹⁸O rhyolites known worldwide (δ¹⁸OWR ≤0.9 vs. 3.4‰). Subsequent units of the CPT and lavas record a progressive recovery in δ¹⁸OZrc to ~2.5‰ over a ~ 4 m.y. interval (12 to 8 Ma). We present detailed evidence of unit-to-unit systematic patterns in O isotopic zoning in zircons (i.e. direction and magnitude of Δcore-rim), spectrum of δ¹⁸O in individual units, and zircon inheritance patterns established by re-analysis of spots for U-Th-Pb isotopes by LA-ICPMS and SHRIMP. In conjunction with mineral thermometry and magma compositions, these patterns are difficult to reconcile with the well-established model for "cannibalistic" low δ¹⁸O magma genesis at Heise and Yellowstone. We present an alternative model for the central Snake River Plain using the modeling results of Leeman et al. (2008) for ¹⁸O depletion as a function of depth in a mid-upper crustal protolith that was hydrothermally altered by infiltrating meteoric waters prior to the onset of silicic magmatism. The model proposes that BJEC silicic magmas were generated in response to the propagation of a melting front, driven by the incremental growth of a vast underlying mafic sill complex, over a ~5 m.y. interval through a crustal volume in which a vertically asymmetric δ¹⁸OWR gradient had previously developed that was sharply inflected from ~ -1 to 10‰ at mid-upper crustal depths. Within the context of the model, data from BJEC zircons are consistent with incremental melting and mixing events in roof zones of magma reservoirs that accompany surfaceward advance of the coupled mafic-silicic magmatic system.

Toughness and toughening mechanisms of porous thin films

Toughness is the ability of a material to deform plastically and to absorb energy before fracture. The first of its kind, this book covers the most recent developments in the toughening of hard coatings and the methodologies for measuring the toughness of thin films and coatings. The book looks at the present status of toughness for coatings and discusses high-temperature nanocomposite coatings, porous thin films, laser treated surface layers, cracking resistance, indentation techniques, sliding contact fracture, IPN hybrid composites for protection, and adhesion strength.

Carbon concentration dependent grain growth of Cu2ZnSnS4thin films

Organic solvents are commonly used in ink precursors of Cu2ZnSnS4 (CZTS) nanocrystals to make thin films for applications such as solar cells. However, the traces of carbon residual left behind by the organic solvents after high-temperature annealing is generally considered to restrict the growth of nanocrystals to form large grains. This work reported the first systematic study on the influence of carbon content of organic solvents on the grain growth of CZTS nanomaterial during high temperature sulfurization annealing. Solvents with carbon atom per molecule varying from 3 to 10 were used to made ink of CZTS nanocrystals for thin film deposition. It has been found that, after high temperature sulfurization annealing, a bilayer structure was formed in the CZTS film using organic solvent containing 3 carbon atoms per solvent molecule based on glycerol and 1,3-propanediol. The top layer consisted of closelypacked large grains and the bottom layer was made of as-synthesized nanoparticles. In contrast, the CZTS film made with the solvent molecule with more carbon atoms including 1,5-pentanediol (5 carbon atoms) and 1,7-heptanediol (7 carbon atoms) consisted of nanoparticles embedded with large crystals. It is believed that the carbon residues left behind by the organic solvents affected the necking of CZTS nanocrystals to form large grains through influencing the surface property of nanocrystals. Furthermore, it has also been observed that the solvent affected the thickness of MoS2 layer which was formed between CZTS and Mo substrate. A thinner MoS2 film (50 nm) was obtained with the slurry using carbon-rich terpineol as solvent whereas the thickest MoS2 (350 nm) was obtained with the film made from 1,3-propanediol based solvent. The evaluation of the photoactivity of the CZTS thin films has demonstrated that a higher photocurrent was generated with the film containing more large grains.

Changes in lycopene and beta carotene contents in aril and oil of gac fruit during storage

Gac fruits were physically measured and stored under ambient conditions for up to 2 weeks to observe changes in carotenoid contents (lycopene and beta carotene) in its aril. Initial concentrations in the aril of lycopene were from 2.378 mg/g fresh weight (FW) to 3.728 mg/g FW and those of beta carotene were from 0.257 to 0.379 mg/g FW. Carotenoid concentrations in the aril remained stable after 1 week but sharply declined after 2 weeks of storage. Gac oil, pressed from gac aril, has similar concentrations of lycopene and beta carotene (2.436 and 2.592 mg/g, respectively). Oil was treated with 0.02% of butylated hydroxytoluene, or with a stream of nitrogen or untreated then stored in the dark for up to 15 or 19 weeks under different temperatures (5 °C, ambient, 45 and 60 °C). Lycopene and beta carotene in control gac oil degraded following the first-order kinetic model. The degradation rate of lycopene and beta carotene in the treated oil samples were lower than that in the control oil but the first-order kinetic was not always followed. However, both lycopene and beta carotene degraded quickly in gac oil with the first-order kinetic under high temperature conditions (45 and 60 °C) regardless of the treatments used. © 2009 Elsevier Ltd. All rights reserved.

In situ reaction furnace for real-time XRD studies

The new furnace at the Materials Characterization by X-ray Diffraction beamline at Elettra has been designed for powder diffraction measurements at high temperature (up to 1373 K at the present state). Around the measurement region the geometry of the radiative heating element assures a negligible temperature gradient along the capillary and can accommodate either powder samples in capillary or small flat samples. A double capillary holder allows flow-through of gas in the inner sample capillary while the outer one serves as the reaction chamber. The furnace is coupled to a translating curved imaging-plate detector, allowing the collection of diffraction patterns up to 2[theta] [asymptotically equal to] 130°.