Synthesis and antioxidant activity of novel amphipathic derivatives of tea polyphenol

Hydrophobic derivatives of a tea polyphenol have been synthesized. 6, 8-Bis(octylthiomethyl)-epigallocatechin 3-O-gallate, 6, 8-bis(octylthiomethyl)-4 beta-(2-hydroxyethylthio)epigallocatechin 3-O-gallate and epigallocatechin 3-O-[4-O-(N-octadecylcarbamoyl)gallate] showed strong inhibition activity against lipid peroxidation of liposome caused by both lipid-soluble and water-soluble radical generators.     

Bi-based electrochromic cell with mediator for white/black imaging

We studied electrochemical properties of bismuth deposit, which showed reversible color change from colorless clear to black by electrochemical reaction, toward paper-like electronic imaging device. Bismuth salt in an electrolyte solution is colorless clear, but turned to black by the electrodeposition on an electrode. Namely, bismuth ion (Bi³⁺) dissolved in the electrolyte solution (colorless clear) is electrochemically reduced on the electrode to deposit the Bi metal showing black color. The Bi deposit on the electrode is electrochemically oxidized to dissolve the deposit into the solution. These processes enable the color change between colorless clear and black. However, the stability of the switching between colorless and black state is not sufficient due to less electroactivity of bismuth deposit. To improve the switching stability of the present electrochromic cell, various mediators were employed to add into the electrolyte solution. Reversible white/black display cell has been successfully demonstrated.     

Propagation of weak pressure waves against two parallel subsonic streams

In this paper, the characteristics of a pressure wave propagating against two parallel subsonic streams in a constant-area straight duct are investigated by one-dimensional analysis, two-dimensional numerical simulation, and experiments. Computations have been carried out by the two-dimensional Euler Equations using the Chakravarthy-Osher-type TVD scheme. Optical observations by the schlieren method as well as wall pressure measurements have been performed to clarify both the structure and the propagation velocity of pressure waves. The results show that the pressure wave propagating against the streams changes into a bifurcated pressure wave and the bifurcation occurs in the low speed streams. It is also found that the propagation velocity of the pressure wave obtained by the analysis and computation agrees well with the present experimental data.     

SUPERHEATED STEAM DRYING OF SINTERED SPHERES OF GLASS BEADS UNDER VACUUM

Drying of sintered spheres of coarse glass beads with a wide sintering range in superheated steam under vacuum was studied.

In samples with sintered angles of 7.5° -27°, the experimental normalized drying rates in superheated steam at pressures of 7.3-7.9mmHg were smaller than those for 56.0-767.6 mmHg in the vicinity of the critical moisture cotents for 56.0-767.6GmmHg. As reported in an earlier paper, there were     

Rescue mission of Ryounkaku Tower in Great Kanto Earthquake; travelling back in time to 1923 to apply the latest aseismic technologies

In 1890, a twelve-story octagonal sight-seeing tower was constructed as a high rise building in Tokyo Asakusa Park. In 1923, however, the top of the tower from the eighth floor up collapsed due to the Great Kanto Earthquake. In order to raise public interest in disaster prevention, we performed as a virtual experiment a conceptual attempt to save the tower without fundamentally changing its architectural characteristics by applying the most advanced structural control techniques. In the simulation, the top of the tower from the eighth floor experienced, almost exactly as described in historical record, a shear fracture during the initial period of principal shock. The modified Ryounkaku Tower would have ensured a comfortable margin of safety even against earthquakes more severe than the Great Kanto Earthquake in 1923.     

Electrochemical conditions for environment-assisted cracking of 6061 Al alloy

We have investigated the influence of electrochemical conditions on environment-assisted cracking (EAC) of 6061 aluminum alloy in acidic chloride solutions. An EAC test was conducted by means of potential-controlled slow strain rate technique. In addition, thermal desorption spectroscopy (TDS) was employed to determine amount of hydrogen absorbed in the specimens under the same electrochemical conditions as those in the EAC tests. As a result, almost no EAC and very small amount of hydrogen absorption were found in a potential range lower than the film breakdown potential, while the higher potential induced severer EAC and much larger hydrogen absorption. The specimen pre-immersed in the chloride solution of pH 1, which derived voluntary breakdown of the oxide film, suffered preferential grain boundary attack. When the tensile test was conducted in air for the specimen with pre-immersion, the fracture strain became slightly smaller than that without pre-immersion. Moreover, the fracture strain drastically decreased and deep cracks was observed, namely the EAC occurred, when the pre-immersed specimen was examined by the EAC test under the cathodic condition which induced no EAC and very small hydrogen absorption for the specimen without pre-immersion.     

Spectroscopic study of polytoluidines in the UV-visible and IR regions

Electropolymerization of o-toluidine(o-methylaniline) and m-toluidine was carried out in acidic aqueous solution, and UV-visible and IR spectra of the resulting polymer films were obtained at various electric potentials and pHs. In Na₂SO₄ aqueous solution, poly(o-toluidine) gave considerably different UV-visible spectra from polyaniline, whereas, in HCl (pH ～ 0), the spectra of poly(o-toluidine) changed in the same way as polyaniline when the potential was varied. This spectral change depended also on counterion. This suggests that the intermediate state (radical cation) of poly(o-toluidine) is unstable in a neutral solution especially when a large counter ion exists, which is contrast to polyaniline. The dependency of the FT-IR spectra of poly(o-toluidine) on the potential and pH supported also the above result of UV-visible spectra. From both UV-visible and IR spectra under various conditions, it was found that o-toluidine and m-toluidine give the same polymer.     

2.5kA/1.2kV两单元IGBT模块

介绍一种工业用2.5 kA/1.2 kV两单元IGBT模块.在该大电流器件中,P端到N端的内部连线电感非常小.半导体硅片的巧妙布局有效地提高了模块的散热能力,采用铝底板直接连接绝缘基板来提高热循环能力.对于这种底板面积较大的器件,为了获得更好的底板和散热片之间的热接触.底板被分成几段.2.5 kA/1.2 kV两单元IGBT模块的封装同样适用于1.8 kA/1.7 V两单元IGBT模块.     

Depth sizing of partial-contact stress corrosion cracks from ECT signals

A partial-contact stress corrosion crack (SCC) is electrically modeled as a crack region with non-zero conductivity in eddy current testing (ECT). This partial-contact effect is excluded by an optimally designed crack-conductivity-insensitive depth characterization signal function (DCSF), and consequently the master curves obtained from electric-discharge machining (EDM) notches can be utilized directly in the depth sizing of SCCs. Furthermore, a crack conductivity independent artificial neural network (ANN) is constructed so that the entire depth profile can be reconstructed regardless of the crack conductivity. These two approaches are numerically validated and applied to the characterization of SCCs in SUS304 from measurement ECT signals. The average depth of each SCC is fast estimated from the DCSF, and the detailed depth profile is reconstructed from ANN. The ECT depth-sizing results show reasonable agreement with UT-TOFD measurement.     

Effect of glycerol on micro/nano structures of catalyst layers in polymer electrolyte membrane fuel cells

Effect of glycerol in catalyst ink on the micro/nano structures of polymer electrolyte membrane fuel cells (PEMFCs) catalyst layers was investigated. Catalyst layers were fabricated by the decal method for various mass ratios of glycerol to carbon in the catalyst ink r_gc (=m_g/m_c) from 0 to 20, and thus change the micro/nano structures of catalyst layer. The structures were evaluated by measuring the pore size with a mercury porosimeter and by observing the surface with a field emission scanning electron microscope (FE-SEM). At r_gc < 5, although the residual glycerol was almost zero, the cell performance decreased with decreasing r_gc, suggesting that the structure of the catalyst layers significantly depended on r_gc. At r_gc > 5, the remaining glycerol was proportional to r_gc. Because remaining glycerol blocks the pores and reduces the reaction sites, the cell performance decreased with increasing r_gc. If the remaining glycerol is removed by steam water, the performance is improved to the same level of the maximum performance for not steamed MEAs.