LES analysis of flow and turbulent mixing in an unsteady jet

The flow and mixing process of unsteady jets are fundamentally analyzed by large eddy simulations. The effects of nozzle velocity and turbulence intensity on the turbulent eddy structure and mixing process between the nozzle fluid and ambient fluid were investigated. The results show that a toroidal‐shaped vortex, which emerges around the jet tip, primarily accelerates the entraining flow. Also, increasing the turbulence intensity in the nozzle encourages mixing in the jet without changing the jet‐contour. Furthermore, when the rise‐up time of the initial nozzle velocity is elongated, turbulent mixing is suppressed. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 303–313, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20158     

日中の蚕书类にみる古蚕具の比较试论

日本从江户时代起、中国从周代起至唐宋,很多古籍和农蚕书记载着当时蚕具的形制,更从书中的插图以及《耕织图》,加深了对古代蚕具的认识。公元前后,日中两国蚕具大多以木、竹和芦苇为材料,形制也类似,其后因就地取材方便,向各自的方向发展,日本重视稻草的利用,固定蚕架改为活动蚕架(棚),名称也各不相同。近年日本推行高工效饲育技术,走向机械化,传统的蚕具急速消减,而中国仍保持传统的蚕具。     

Increasing the audio watermark data rate in the construction of ubiquitous acoustic spaces

We propose “Ubiquitous Acoustic Spaces,” in which each sound source can emit some address information with audio signals and allow automatic access to its related cyber space, using handheld devices such as cell phones. In order to realize this concept, we have considered three types of extraction methods: acoustic modulation, audio fingerprints, and audio watermarking. We have proposed a novel audio watermarking technique, which allows contactless asynchronous detection of embedded audio watermarks through speaker and microphone devices. However, its embedding data rate was around 10 bps, which was not sufficient for embedding generally used URL address texts. Therefore, we have extended the embedding frequency range and proposed a duplicated embedding algorithm, which uses both the previously proposed frequency division method and the temporal division method together. By these improvements, the possible embedding data rate could be extended to 61.5 bps, and we could extract watermarks through public telephone networks, even from a cell phone sound source. In this paper, we describe our improved watermark embedding and extracting algorithms, and present experimental results on watermark extraction precision under several audio signal capturing conditions. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(1): 42–51, 2008; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20758     

Improvement of bond strength of BPDA‐PDA‐type polyimide film by corona discharge treatment

Aromatic polyimide film composed of biphenyl tetracarboxylic acid dianhydride (BPDA) and p‐phenylene diamine (PDA) is a very stable polymer at high temperatures and very useful for the electronics industry. Bonding properties were improved by corona discharge treatment of this film. The chemical modification method was applied for generated functional groups, that is, carboxylic, hydroxyl, and amino groups in the gas phase, and the quantity of these functional groups was determined by X‐ray photoelectron spectroscopy. The functional groups increased with corona energy, leveling off at a specific corona energy. The bond strength of the copper foil/adhesive/polyimide film was determined. The relationship between bond strength and functional group content was analyzed by multivariate analysis. Bond strength could be sufficiently correlated with functional group quantity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3403–3408, 2006     

Effect of Particle Sizes of Starting Materials on Microstructure Development in Textured Bi0.5(Na0.5K0.5)0.5TiO3

Microstructure development in Bi_0.5(Na_0.5K_0.5)_0.5TiO₃ prepared by a reactive-templated grain growth process was dependent on the sizes of platelike Bi₄Ti₃O₁₂ (BiT) and equiaxed TiO₂ particles used as starting materials. Calcined compacts were composed of large, platelike template grains and small, equiaxed matrix grains, the sizes of which were determined by those of the BiT and TiO₂ particles, respectively. Texture was developed by the growth of template grains at the expense of matrix grains during sintering, and a new mechanism of grain growth was proposed on the basis of microstructure observation. The grain growth rate was determined by the template and matrix grain sizes, and a dense ceramic with extensive texture was obtained using small BiT and TiO₂ particles.     

Enzymatic hydrolysis of water-soluble random copolypeptides

Two component water-soluble random copolypeptides consisting of N-hydroxyethyl L-glutamine and hydrophobic L-amino acids such as L-alanine, L-leucine, L-phenylalanine, or L-valine, were prepared by carrying out aminolysis reactions with 2-amino-1-ethanol (E) on starting copolymers consisting of γ-benzyl L-glutamate (B) and the corresponding hydrophobic L-amino acid. The effects of copolymer composition and sequential distributions, as well as molecular conformations, on the rate of degradation by bromelain in a PECF at pH 7.4 and 37.0°C to simulate in vivo polymer degradation. All the samples were found to be extensively degraded by random chain fracture with bromelain. Further, the degradation data for these samples followed the Michaelis-Menten rate law, being of the first order in papain concentration. The nature of side chains and the molecular conformations are important to the rate of degradation by bromelain.     

Defect and Mixed Conductivity in Nanocrystalline Doped Cerium Oxide

The results obtained from a study on the microstructure and the electrical properties of Gd-doped CeO₂ thin films were reported. Dense, nanocrystalline films on sapphire substrates are prepared using a polymeric precursor spin coating technique. The electrical conductivity was studied as a function of temperature and oxygen activity and correlated with the grain size. For nanocrystalline Gd-doped CeO₂ thin films, the ionic conductivity increased with decreasing activation energy as the grain size decreased. A conductivity model was developed to analyze P _O2 behavior of the electrical conductivity. Using the conductivity model, the hopping energy of electron conduction and the enthalpy of oxygen vacancy formation were determined for different microstructures.     

Crystallization of nylon 6–clay hybrid by annealing under elevated pressure

Nylon 6–clay hybrid (NCH) is a molecular composite of nylon 6 and uniformly dispersed silicate layers of montmorillonite. We found that the phase with the high melting temperature (HMT phase) in the NCH annealed under elevated pressure. The melting temperature of the HMT phase was 240°C. Nylon 6 annealed under elevated pressure did not have the HMT phase. Thus, the presence of the HMT phase was characteristic of the NCH. The relative heat of fusion of the HMT phase (heat of fusion of HMT phase/heat of fusion in the pressure annealed NCH) increased with increase in pressure. High-pressure differential thermal analysis (DTA) measurement revealed that the temperature, at which the relative heat of fusion showed a maximum value, was below about 20°C of the melting temperature of the original NCH under elevated presssure. It was considered that the nylon 6 crystallite near the melting temperature and the molecular mobility under elevated pressure were necessary to the appearance to the HMT phase. © 1994 John Wiley & Sons, Inc.