Direct modulation characteristics of GaInAsP/InP d.h. lasers with various stripe widths measured by sharp-pulse method

The direct modulation characteristics of GaInAsP/InP d.h. lasers emitting at 1.3 ?m with various stripe widths were measured by the proposed sharp-pulse method. As a result, a flat modulation frequency response up to 1.9 GHz was observed in a laser diode with 5 ?m stripe width.     

Basic experiments during loss of vacuum event (LOVE) in fusion experimental reactor

If a loss of vacuum event (LOVE) occurs due to damage of the vacuum vessel of a nuclear fusion experimental reactor, some chemical reactions such as a graphic oxidation and a buoyancy-driven exchange flow take place after equalization of the gas pressure between the inside and outside of the vacuum vessel. The graphite oxidation would generate inflammable carbon monoxide and release tritium retained in the graphite. The exchange flow through the breaches may transport the carbon monoxide and tritium out of the vacuum vessel. To add confidence to the safety evaluations and analyses, it is important to grasp the basic phenomena such as the exchange flow and the graphite oxidation. Experiments of the exchange flow and the graphite oxidation were carried out to obtain the exchange flow rate and the rate constant for the carbon monoxide combustion, respectively. These experimental results were compared with existing correlations. We plan a scaled-model test and a full-scale model test for the LOVE.     

NONDESTRUCTIVE MEASUREMENT OF MOISTURE DIFFUSION COEFFICIENT IN WOOD DRYING

The computer tomography(CT image of wood was analyzed to estimate the moisture content from CT number. Comparing moisture contents, densities and CT numbers, moisture distributions were nondestructively determined by CT numbers detected with the scanner.

By periodically measuring CT images of the same cross section of specimens in drying, change of moisture distribution was computed. The coefficients of moisture movement at given positions inside the specimen were directly calculated from Fick's Law with known values of moisture content change, distance and drying time.

The diffiion coeficient was described as a function of various driving forces of moisture content, partial vapor pressure and chemical potential of moisture in wood. The results were comparable to data in the literature. Furthermore, it is shown that diffusion coefficients based on moisture content varies as a curve with the maximum value at about 15% m.c. during drying, and that the moisture content is actually adaptable to the driving force for moisture movement in wood because of capability over wide moisture content range.     

Radioactivation of structural material of the superconducting magnet for a fusion reactor

Radioactivation of five types of candidate steel alloys for the structural materials of superconducting toroidal field coils (TFC) of a D-T fusion reactor has been comparatively studied. As a result, the use of a high Mn steel in place of 316 SS is shown to reduce the dose rate at the He vessel of the TFC to ～ 1/3 the value with 316 SS at 1 day after shutdown, and to ～ 1/1000 at 10 years after shutdown. These reductions are mostly caused by the 0.28 wt% Co assumed to be included in 316 SS but none in the high Mn steel. Newly defined dose rate sensitivities of constituent elements are shown to be useful in identifying the cause of dose rate change brought on by the steel composition change. They can also be utilized in estimating the dose rate change brought on by the replacement of 316 SS with any new steel alloy with similar composition.     

Novel Perovskite-Type Oxide Catalysts for Dehydrogenation of Ethylbenzene to Styrene

We investigated novel LaMnOx perovskite-oxide (ABO₃) catalysts for effective catalytic dehydrogenation of ethylbenzene to produce styrene monomer. Comparison with industrial Fe–K catalyst, our La_0.8Ba_0.2Mn_0.6Fe_0.4O_3-δ catalyst showed higher activity. Results show that the A-site in perovskite-type oxides affected catalytic dehydrogenation activities and that the B-site affected stability of the activities.     

Photoanodic response of iron oxide electrode in aqueous solution and its application to Pb removal under visible light irradiation

The iron oxide electrode was prepared from thermal oxidation of iron at 600 °C for 3 h in air atmosphere. This electrode with the structure of Fe₃O₄ and α-Fe₂O₃ showed the response of photoanodic current to the light with wavelength shorter than 600 nm. The band gap energy of this electrode was 1.99 eV. The onset potential of distinct steady photocurrent and also the flatband potential were 0.80 and 0.09 V vs. Ag/AgCl, respectively, in 0.1 M HNO₃ aqueous solution. The cell consisting of the iron oxide photoanode in HNO₃-Pb(NO₃)₂ and the graphite cathode in H₂SO₄-Ce(SO₄)₂ caused the PbO₂ deposit on the surface of the former electrode due to visible light irradiation without application of voltage. By holding the potential of this electrode at more positive value than 0.90 V, the photoanodic removal rate of Pb²⁺ in HNO₃-Pb(NO₃)₂ solution was higher than that observed when Ce⁴⁺ was used as electron acceptor.     

First plasma experiment on spherical tokamak device UTST

The UTST (University of Tokyo Spherical Tokamak) device was constructed for the purpose of exploring the formation of ultrahigh‐beta ST (spherical tokamak) plasma using the double null plasma merging method. When two plasmas merge together to form a single plasma, magnetic field lines reconnect, and magnetic field energy is converted to plasma kinetic energy, increasing the plasma beta. Merging start‐up has been demonstrated in the TS‐3/4, START, and MAST devices using coils inside the vacuum vessel, and the TS‐3 plasma obtained a 50% beta. In order to demonstrate start‐up in a more reactor‐relevant situation, UTST has all poloidal field (PF) coils outside the vacuum vessel. The first plasma experiment on the UTST was begun in December 2007. In the results, the plasma obtained 10 kA by using only the outer PF coils and a single ST was generated in the lower area (z = –0.3 to –1.0 m) close to a washer gun. This result suggests that another washer gun on the top of the UTST can allow the generation of ST in the upper area and merging start‐up by using outer PF coils. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(2): 20–26, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21216     

Stable repeated-batch production of recombinant dye-decolorizing peroxidase (rDyP) from Aspergillus oryzae

Recombinant Aspergillus oryzae expressing a dye-decolorizing peroxidase gene (dyp) was cultivated for repeated-batch production of recombinant dye-decolorizing peroxidase (rDyP) using maltose as a carbon source. High-level rDyP activity in limitation of carbon and nitrogen sources was maintained stably for 26 cycles of repeated 1-d batches of A. oryzae pellets without any additional pH control. Cultures maintained at 4 degrees C for 20 d resumed rDyP production following a single day of incubation. One liter filtrated crude rDyP containing 4600 U rDyP decolorized 5.07 g RBBR at the apparent decolorization rate of 17.7 mg l(-1) min(-1).     

Adaptation to climate change and conservation of biodiversity using green infrastructure

In recent years, we have experienced mega‐flood disasters in Japan due to climate change. In the last century, we have been building disaster prevention infrastructure (artificial levees and dams, referred to as “grey infrastructure”) to protect human lives and assets from floods, but these hard protective measures will not function against mega‐floods. Moreover, in a drastically depopulating society such as that in Japan, farmland abandonment prevails, and it will be more difficult to maintain grey infrastructure with a limited tax income. In this study, we propose the introduction of green infrastructure (GI) as an adaptation strategy for climate change. If we can use abandoned farmlands as GI, they may function to reduce disaster risks and provide habitats for various organisms that are adapted to wetland environments. First, we present a conceptual framework for disaster prevention using a hybrid of GI and conventional grey infrastructure. In this combination, the fundamental GI, composed of forests and wetlands in the catchment (GI‐1) and additional multilevel GIs such as flood control basins that function when floodwater exceeds the planning level (GI‐2) are introduced. We evaluated the flood attenuation function (GI‐1) of the Kushiro Wetland using a hydrological model and developed a methodology for selecting suitable locations of GI‐2, considering flood risk, biodiversity and the distribution of abandoned farmlands, which represent social and economic costs. The results indicated that the Kushiro Wetland acts as a large natural reservoir that attenuates the hydrological peak discharge during floods and suitable locations for introducing GI‐2 are concentrated in floodplain areas developing in the downstream reaches of large rivers. Finally, we discussed the network structure of GI‐1 as a hub and GI‐2 as a dispersal site for conservation of the Red‐crowned Crane, one of the symbolic species of Japan.