Effects of aspect ratio on mixed convection in a horizontal rectangular duct with heated and cooled side walls

This paper describes the effect of aspect ratio on mixed convection in a horizontal rectangular duct with heated and cooled side walls numerically and experimentally. In the numerical analysis, fluid flow and temperature distributions for Ri=1.61, Pr=6.99, Re=100 and aspect ratio, Ar=0.2–10, were obtained by solving dimensionless governing equations using the SIMPLE procedure. The QUICK scheme was applied to the convective term of these equations. In the experimental analysis, the flow behavior for A_r=0.5–2 was visualized by the dye‐injection method. Numerical results showed that the swirl flow was generated along the flow direction, and its pitch length was influenced by A_r. The pitch length was the shortest when A_r=0.5–1, and this tendency was the same in numerical results and experimental results. The heat transfer behavior was also discussed corresponding to the flow, and the heat transfer ratio was highest at A_r=1 in 0.2 ≤ A_r ≤ 10. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20391     

Ubiquitous Experience Media

We exploit recorded activities as a good source of human-human and human-robot communication for sharing experience, memory, and knowledge. In particular, we're interested in audiovisual, ubiquitous, and wearable-experience-capturing technology as interaction-grounded lifelong tools. We've developed several devices - such as a wearable interaction tracker - that facilitate an indexed recording of human experiences     

Thermal Conductivity of β-Si3N4: III, Effect of Rare-Earth (RE = La, Nd, Gd, Y, Yb, and Sc) Oxide Additives

β-Si₃N₄ ceramics sintered with a series of rare-earth (RE = La, Nd, Gd, Y, Yb and Sc) oxide additives were fabricated by hot pressing and subsequent annealing. Their microstructures, lattice oxygen contents, and thermal conductivities were evaluated. Mean grain size increased, while lattice oxygen content decreased, and hence, thermal conductivity increased with decreasing ionic radius of the rare-earth element. In all cases, a marked change was observed in the order of ionic radius from La to Nd to Gd, and a little change was observed below them. Rare-earth oxide additives significantly influenced the thermal conductivity of β-Si₃N₄, unlike in the case of AlN.     

Influence of Aluminum–Oxygen–Yttrium Solid Solution on the Aqueous Tribological Behavior of Silicon Nitride

To investigate the influence of crystal structure and solid solutions of certain elements in Si₃N₄ on aqueous tribological properties, seven specimens were fabricated. Solid solutions of aluminum and oxygen made the friction coefficient and wear increase in both α-type and β-type crystal structures. In particular, α-SiAlON, in which yttrium is also incorporated into the α-Si₃N₄ lattice, showed a higher friction coefficient and wear than other specimens containing the same concentration of Al or O.     

Fabrication of Textured Alumina by High-Temperature Deformation

Texture formation via high-temperature deformation in sintered alumina was investigated. Fine-grained, normal-purity-alumina sintered bodies deformed under stresses up to 80 MPa in a temperature range of 1200°–1300°C. Fine, disklike grains formed in the equiaxial fine-grained matrix during high-temperature deformation and aligned unidirectionally via material flow during deformation. Highly textured sintered alumina bodies were obtained via high-temperature deformation and further annealing.     

Influence of Silica and Aluminum Contents on Sintering of and Grain Growth in 6H-SiC Powders

To clarify the influence of impurities on the sintering of SiC powder, three 6H-SiC powder samples—with different levels of SiO₂ and aluminum impurities—were sintered with additions of boron and carbon. The densification, grain growth, and transformation of 6H-SiC during sintering were studied qualitatively. The powder that contained the most SiO₂ required the greatest amount of boron additive for complete densification. SiO₂ apparently reacted with the boron additive and was consumed during sintering. The powder with the greater aluminum impurity level exhibited partial transformation of 6H-SiC to 4H-SiC, and the sintered SiC from this powder had elongated grains. The partial transformation in the SiC crystal accelerated non-equiaxial grain growth.     

The inhibitory effect of non-steroidal anti-inflammatory drugs (NSAIDs) on the monophenolase and diphenolase activities of mushroom tyrosinase

In the present work, we investigated the effect of non-steroidal anti-inflammatory drugs (NSAIDs) on the monophenolase and diphenolase activity of mushroom tyrosinase. The results showed that diflunisal and indomethacin inhibited both monophenolase and diphenolase activity. For monophenolase activity, the lag time was extended in the presence of diflunisal. In the presence of indomethacin, the lag time did not change. IC(50) values of monophenolase activity were estimated to be 0.112 mM (diflunisal) and 1.78 mM (indomethacin). Kinetic studies of monophenolase activity revealed that both diflunisal and indomethacin were non-competitive inhibitors. For diphenolase activity, IC(50) values were estimated to be 0.197 mM (diflunisal) and 0.509 mM (indomethacin). Diflunisal and indomethacin were also found to be non-competitive diphenolase inhibitors.     

Effect of Grain Size on the Thermal Conductivity of Si3N4

Polycrystalline Si₃N₄ samples with different grain-size distributions and a nearly constant volume content of grain-boundary phase (6.3 vol%) were fabricated by hot-pressing at 1800°C and subsequent HIP sintering at 2400°C. The HIP treatment of hot-pressed Si₃N₄ resulted in the formation of a large amount of ß-Si₃N₄ grains ∼10 µm in diameter and ∼50 µm long, and the elimination of smaller matrix grains. The room-temperature thermal conductivities of the HIPed Si₃N₄ materials were 80 and 102 Wm⁻¹K⁻¹, respectively, in the directions parallel and perpendicular to the hot-pressing axis. These values are slightly higher than those obtained for hot-pressed samples (78 and 93 Wm⁻¹K⁻¹). The calculated phonon mean free path of sintered Si₃N₄ was ∼20 nm at room temperature, which is very small as compared to the grain size. Experimental observations and theoretical calculations showed that the thermal conductivity of Si₃N₄ at room temperature is independent of grain size, but is controlled by the internal defect structure of the grains such as point defects and dislocations.     

Growth of calcium phosphate on ion-exchange resins pre-saturated with calcium or hydrogenphosphate ions: an SEM/EDX and XPS study

Calcium phosphate formed on the surfaces of ion-exchange resins pre-saturated with either Ca²⁺ or HPO₄ ^2- ions has been studied using a combination of scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). Calcium phosphate was formed at a temperature of 36.5°C via two methods. On Ca²⁺ or HPO₄ ^2--saturated resins, 1.5xSBF (simulated body fluid) solution was used while on Ca²⁺-saturated resins only, a novel biomimetic growth medium using the alkaline phosphatase-catalysed hydrolysis reaction of disodium p-nitrophenylphosphate as a source of inorganic phosphate was employed. SEM micrographs showed that the use of 1.5xSBF growth medium solution led to extensive coverage of the resins with calcium phosphate. In contrast, calcium phosphate coatings formed via the alkaline phosphatase-catalysed reaction were of a more variable quality whose morphology could be influenced by adding albumin and collagen to the growth medium. Average Ca:P ratios determined by EDX for coatings formed from the 1.5xSBF growth medium were in the range 1.62–1.74 suggesting that hydroxyapatite had formed. In contrast, Ca:P ratios for the calcium phosphate compounds formed on resins from the alkaline phosphatase reaction were lower at 1.50 suggesting that calcium-deficient hydroxyapatite had formed which was confirmed by inductively coupled plasma (ICP) analysis and X-ray diffraction of isolated amorphous and crystallized powder samples, respectively. Evidence from X-ray photoelectron studies supports a mechanism of formation of the coatings which involves diffusion of the ion out of the interior of the resin to create a high local concentration at the surface thus stimulating precipitation of the coating material on the resin beads.