Operation of superconducting fault current limiter using vacuum interrupter driven by electromagnetic repulsion force for commutating switch

Using conventional high‐temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20315     

An important factor affecting synergism on coprocessing of Taiheiyo coal with Athabasca oil sand bitumen

A series of mixtures of Japanese subbituminous Taiheiyo coal and Athabasca oil sand bitumen (AOB) with various coal concentrations (0–100 wt%) was coprocessed in a 70 ml autoclave at 420°C for 1 h in the presence of H₂ (50 kg/cm² at room temperature) and sulfided Ni---Mo/Al₂O₂ catalyst. The mixture containing 2 wt% coal produced the largest amount of hexane soluble fraction (HS) and the smallest amount of benzene insoluble fraction (BI). Thus, a synergistic liquid production occurred for this mixture with 2 wt% coal by suppressing the retrogressive reactions which proceeded for pure AOB. The HS obtained from mixtures with 2–30 wt% showed higher H/C ratios and lower heteroatom contents than those obtained from pure AOB and the mixtures with more than 30 wt% coal. The amounts of transferable hydrogen contained in the mixtures were estimated using anthracene as a hydrogen acceptor. The mixtures with 2–10 wt% coal contained higher amounts of donor hydrogen than pure AOB. The HS yield from the various mixtures was correlated with the amount of donor hydrogens contained in the mixtures, except for the mixture with 10 wt% coal. Thus, the important factor which results in synergism is suggested to be the amount of donor hydrogens contained in the feed mixtures.     

Effect of the Chiral Center Position of an Optically Active Terminal Group on the Induction of Optical Activity in Polysilanes

Summary Polysilanes with an optically active alkoxy group, i.e., (S)-(+)-2-butoxy, (R)-(-)-2-butoxy, (S)-(-)-2-methyl-1-butoxy, and (S)-(+)-3,7-dimethyl-1-octoxy, at the terminal positions, the chiral carbon centers of which were located at the α, β, and γ positions relative to the oxygen, respectively, were prepared, and the effect of the position of chiral center of the terminal optically active group on the induction of optical activity in polysilanes was investigated. The circular dichroism (CD) spectra of these polymers showed positive Cotton signals around 340 nm at temperatures below -20 °C, but the intensities were small, indicating that the optically active groups at the terminal positions have some ability, albeit small, to induce optical activity to the polysilanes. Further, the optically active (S)-(+)-2-butoxy and (R)-(-)-2-butoxy groups did not control the helical sense direction of the polymers, despite the different chiral stimuli from the 2-butoxy groups introduced to the terminal positions. To control the helical structure of polysilanes by the use of optically active terminal groups, appropriate optically active groups are required.     

A full‐color eyewear display using planar waveguides with reflection volume holograms

Abstract— A full‐color eyewear display with over 85% see‐through transmittance with a 16° horizontal field of view was developed. Very low color crosstalk, less than 0.008 Δu′v′ uniformity, and 120% NTSC color gamut were achieved. Waveguides with two in‐ and out‐coupling reflection volume hologram elements enabled a simple configuration that has an optical engine beside the user's temples. The reflection volume hologram elements used on the waveguides realized a small thickness of 1.4 mm for each waveguide, and an out‐coupling reflection volume hologram used as an optical combiner contributed a high see‐through transmittance of 85% due to its wavelength selectivity. However, there are technical challenges in achieving a reasonable screen size and quality color images with optics that utilize holographic waveguides because holograms have large chromatic dispersions compared to conventional optical elements such as lenses and mirrors. Approaches to overcome these issues are described.     

Analysis of spatial smoothing effect of short‐term fluctuation of global solar radiation based on data including quantization error

Photovoltaic (PV) systems are attracting attention as one of the promising countermeasures against global warming and the environmental issues. However, the generation output from PV systems is generally unstable and unpredictable. Therefore, large penetration of PV systems may cause some serious impacts on power system operation, such as load frequency control, voltage regulation, etc. Estimation of the influences of PV system installation is becoming important, but it requires simultaneous multipoint solar radiation measurements. The Japan Meteorological Business Support Center has provided 1‐minute meteorological data observed in Japan, but its solar radiation data includes quantization errors. This paper proposes a regeneration method for solar radiation data including quantization errors. It also analyzes the spatial smoothing effect of global solar radiation fluctuations. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(3): 55–63, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21274     

Study on FBR core concepts to increase proliferation resistance of plutonium in LWR–FBR transition period

The possibility to enhance proliferation resistance of discharged plutonium in fast breeder reactor (FBR) has been investigated in terms of reactor core-design aspects. The provisional target for proliferation resistance measures based on Saito's attractiveness (ATTR) is defined. It is found that a few percent of plutonium loading and/or Am/Cm loading, which come from various types of spent fuel, might satisfy the provisional target with a minimum impact on the core neutronic performances. On Am/Cm loading core, decay heat constraints for fuel-handling aspects are found to be important and should be considered in design. There is not significant change on the current developing scenarios for light water reactor–FBR transition period by applying the measures based on Saito's ATTR. It is found that applying Kimura's proposal, 15% ²³⁸Pu content requires about 7% MA loading fraction both in the core and the blanket, and it only can be applied at limited case. The period to consume minor actinides is shorter than to consume plutonium.     

Investigation for Necessity of Dispersivity and Tortuosity in the Dusty Gas Model for a Binary Gas System in Soil

Diffusion, dispersion, and advection are important processes in multi-gas systems in soils. To date, both Fick's model and the Dusty Gas (DG) model have been used to model the movement of gases in these systems. Dispersion is included in the dispersion-advection equation with Fick's Model for the movement of gases in gas-phase of soil, yet the movement of gases in multi-component gas-soil systems is considered to be expressed more accurately by the DG model than by Fick's model. However to date, no study has investigated the necessity of considering dispersion in the Dusty Gas (DG) model. We carried out column experiments for nitrogen-methane, nitrogen-carbon dioxide, and carbon dioxide-methane binary gas systems in sandy soil, and also did simulations on the same systems using both Fick's model and the DG model. A comparison of the results of the column experiments with our simulations confirmed that there was no need to consider the dispersion in the advection-diffusion equations with the DG model when the velocity of gas was 0.05-0.4 cm/s in Toyoura sand. Furthermore, our experiments and simulations with the DG model showed that, rather than dispersion, tortuosity should be taken into account in application of the DG model to the above condition.     

Molecular Dynamics Study of Atomic Structure and Diffusion Behavior in Amorphous Silicon Nitride Containing Boron

We have performed molecular dynamics simulations of amorphous Si₃N₄ containing boron (Si-B-N). We have examined short-range atomic arrangements and self-diffusion constants of amorphous Si-B-N systems with various boron contents. Our simulations show that boron atoms are threefold coordinated by nitrogen atoms and that nitrogen atoms are bonded to both silicon and boron atoms in the amorphous network of Si-B-N. Also, the self-diffusion constant of nitrogen in Si-B-N is much decreased compared with that in amorphous Si₃N₄. This suggests that boron is important in decreasing the mobility of atoms in amorphous Si-B-N, which may explain the improved thermal stability of amorphous Si-B-N relative to amorphous Si₃N₄ observed experimentally.     

Composite of Au nanoparticles and molecularly imprinted polymer as a sensing material

A molecularly imprinted polymer with immobilized Au nanoparticles (Au-MIP) is reported as a novel type of sensing material. The sensing mechanism is based upon the variable proximity of the Au nanoparticles immobilized in the imprinted polymer, which exhibits selective binding of a given analyte accompanied by swelling that causes a blue-shift in the plasmon absorption band of the immobilized Au nanoparticles. Using adrenaline as the model analyte, it was shown that molecular imprinting effectively enhanced the sensitivity and selectivity, and accordingly, Au-MIP selectively detects the analyte at 5 microM. The combination of molecular imprinting and the Au nanoparticle-based sensing system was shown to be a general strategy for constructing sensing materials in a tailor-made fashion due to wide applicability of the imprinting technique and the independence of the sensing mechanism from the analyte recognition system.     

Synthesis and characterization of K2NiF4-type CaLnCoO4 (Ln = Sm and Gd)

K₂NiF₄-type CaLnCoO₄ (Ln = Sm and Gd) has been synthesized at 1173 or 1223 K in air using citric acid (CA) and ethylene glycol (EG). CaLnCoO₄ (Ln = Sm and Gd) has an orthorhombic structure with the space group Bmab. The average particle sizes are approximately 300 nm for CaSmCoO₄ and approximately 170 nm for CaGdCoO₄, respectively. The global instability index (GII) indicates that the crystal structure of CaGdCoO₄ is more stable than that of CaSmCoO₄. CaLnCoO₄ (Ln = Sm and Gd) is a p-type semiconductor and shows paramagnetic behavior above 5 K. The 1/χ-T curve of CaSmCoO₄ deviates from the Curie-Weiss law, whereas the 1/χ-T curve of CaGdCoO₄ follows the Curie-Weiss law in the temperature range of 5 ≤ T ≤ 300 K. From the values of the observed effective magnetic moment (μ_eff) of CaLnCoO₄ (Ln = Sm and Gd), it is considered that the spin state of the Co³⁺ ion is low.