Prediction of vortex penetration depth at thermal stratification by cavity flow in a branch pipe with closed end (effect of heat radiation condition on temperature fluctuations)

In a branch pipe with one closed end, the cavity flow penetrates into the branch pipe from the main loop and a thermal boundary layer occurs because the cavity flow is a hot fluid, but heat removal causes a colder fluid in the branch pipe. This thermal stratification may affect the structural integrity. Therefore, a pipe design standard to suppress thermal fatigue should be established. The pipe design standard consists of the maximum penetration depth L_sv and the minimum penetration depth L_sh. In order to establish an evaluation method for L_sh, a visualization test and a temperature fluctuation test were carried out. A theoretical formula for thermal stratification was introduced from the heat balance model. Then the model was used to obtain an empirical equation from the map of fluid temperature fluctuation. This method can predict the vortex penetration depth by cavity flow in horizontal branch pipes. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(1):38–55, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20135     

Hydrogen economy assessment for long-term energy systems in Japan

An assessment is made of hydrogen technology development; in particular, economy as an energy carrier, applicability for end-uses and the potential of the market in the future. Specifically, rough static cost comparisons are made on several modes of electricity transmission and hydrogen transport, and on several ways of off-peak electricity saving; including energy storage in the form of hydrogen. Then, the quantity of oil that could be saved for some representative end-use sectors if hydrogen fuel were to be introduced is discussed. Finally, a potential market is assessed, by projecting overall future energy supply/demand dynamics in Japan.     

Numerical analysis of field-effect surface passivation for solar cells

In order to investigate the influence of surface potential on the electric characteristics of solar cells, the characteristics of conventional cells and back-contact type high-efficiency silicon cells were analyzed using 2-dimensional numerical simulation, varying the surface electrical potential. The locations where surface electrical potential is controlled are the rear side in conventional cells and the front side in back-contact cells. As a result of the calculations, it was found that field-effect surface passivation yields cell characteristics equivalent to those of a cell with effective surface recombination velocity of 0 cm/s, even if the cell has a poor interface (i.e., D_it > 1.0 × 10¹¹cm⁻²eV⁻¹). It was also found that both the use of a higher resistivity wafer and — especially in p-type substrates — the formation of inversion layers causes the field-effect surface passivation to work the fullest effect. In addition, a computer simulation based on physical-parameter measurements taken from actual materials forecasts that a back-contact cell would realistically be able to exceed 25% efficiency under AM1.5 global, one-sun illumination.     

Growth of AlN Crystals on SiC Substrates by Thermal Nitridation of Al2O3

The growth of AlN crystals on c‐plane 6H–SiC substrates by thermal nitridation of Al₂O₃ pellets in the presence of graphite and ZrO₂ was demonstrated. Addition of graphite and ZrO₂ effectively accelerated the evaporation of Al₂O₃, yielding c‐axis oriented AlN films on SiC substrates. The SiC substrate was severely deteriorated at 2173 K, which produced a porous interface between the AlN film and substrate, resulting in low‐quality AlN crystals. The deterioration of SiC was successfully suppressed by introducing a pre‐deposited homo‐buffer layer, allowing two‐dimensional‐like growth of AlN. The buffer layer promoted the formation of a high‐quality AlN film. At 2173 K, the full‐width at half maximum of the X‐ray rocking curves of the (0002) and (10–10) planes of the AlN film was 360 and 425 arcsec, respectively.     

Direct observation of a local structural mechanism for dynamic arrest

The mechanism by which a liquid may become arrested, forming a glass or gel, is a long-standing problem of materials science. In particular, long-lived (energetically) locally favoured structures (LFSs), the geometry of which may prevent the system relaxing to its equilibrium state, have long been thought to play a key role in dynamical arrest. Here, we propose a definition of LFSs which we identify with a novel topological method and directly measure with experiments on a colloidal liquid-gel transition. The population of LFSs is a strong function of (effective) temperature in the ergodic liquid phase, rising sharply approaching dynamical arrest, and indeed forms a percolating network that becomes the 'arms' of the gel. Owing to the LFSs, the gel is unable to reach equilibrium, crystal-gas coexistence. Our results provide direct experimental observation of a link between local structure and dynamical arrest, and open a new perspective on a wide range of metastable materials.     

Catalytic wet oxidations of aromatic compounds over supported copper oxides

Catalytic wet oxidations of naphthalene as a model compound of persistent aromatic compounds were carried out with hydrogen peroxide in a closed autoclave lined with Teflon. CuO/Al₂O₃ and CuO/AC catalyst showed the high activity for the naphthalene oxidation with hydrogen peroxide of 1.0 mol L⁻¹ at 100 °C. Naphthalene, whose initial concentration was 1.0 g L⁻¹, was converted completely and the concentration of water-soluble organic compounds in the resultant aqueous solution was less than 25 ppm-C. In contrast, platinum, and manganese oxide, silver oxide, and ruthenium oxide catalysts consumed hydrogen peroxide preferentially. Iron and nickel oxides catalysts showed lower activity than the copper oxide catalyst. During the reaction, the intermediate organic acids were formed and then were oxidized. Simultaneously, copper species of CuO catalysts were dissolved and then were precipitated. The precipitated copper species on the catalyst support showed the catalytic activity. CuO/Al₂O₃ catalysts showed high activity for the six successive batch reactions with the treatment of sodium carbonate after the reaction to precipitate copper ions.     

Deposition of Metal Oxide Films from Metal–EDTA Complexes by Flame Spray Technique

R₂O₃ (R = Y, Eu, Er) metal oxides were synthesized from metal–ethylenediaminetetraacetic acid (EDTA) complexes using a flame spray technique. As this technique enables high deposition rates, films with thickness of several tens of micrometers were obtained. Films of yttria, europia, and erbia phase were synthesized on stainless-steel substrates with reaction assistance by H₂–O₂ combustion gas. The oxide films consisted of the desired crystalline phase with micropores. The porosity of the films was in the range of 6–15%, varying with the metal used. These results suggest that the true density of the metal oxide obtained from metal–EDTA powder through the thermal reaction process plays an important role in achieving film with the desired porosity.     

Technical note: measurement of ferritin in bovine milk and its clinical significance

A quantitative ELISA was developed for bovine milk ferritin with an assay limit of 0.16 ng/mL of bovine spleen ferritin. Ferritin-binding activity was detected in bovine milk samples, and this binding activity was inhibited by increasing ionic strength with the addition of 0.5 M (NH₄)₂SO₄. Heat treatment (60°C, 20 min) of bovine milk in the presence of 0.5 M (NH₄)₂SO₄ resulted in a 15 to 58% increase in ferritin concentrations compared with untreated samples. Although the recovery of bovine spleen ferritin added to milk was still low (55 to 90%), even in the presence of increased ionic strength with 0.5 M (NH₄)₂SO₄, recovery was improved by heat treatment at 60°C for 20 min (92 to 95%). Milk ferritin concentrations in 30 milk samples from quarters of 25 cows with mastitis (mean ± SE: 134.2 ± 28.7 ng/mL) were significantly higher than those in 17 quarter milk samples from 17 noninfected lactating cows (7.2 ± 1.2 ng/mL), suggesting that bovine milk contains putative ferritin-binding proteins that inhibit immunoassay for milk ferritin and that bovine milk ferritin is an indicator of IMI.