Feeder components and instrumentation for the JT-60SA magnet system

The modifying of the JT-60U magnet system to the superconducting coils is progressing as a satellite facility for ITER by both parties of Japanese government and European commission in the Broader Approach agreement. The magnet system requires current supplies of 25.7 kA for 18 TF coils and of 20 kA for 4 CS modules and 6 EF coils. The magnet system generates an average heat load of 3.2 kW at 4 K to the cryogenic system. The feeder components connected to the power supply provide current supply. The cooling pipes connected to the cryogenic system provide coolant supply. The instrumentation of the JT-60SA magnet system is used for its operation.     

Hydroxy Radical,Hexanal, and Decadienal Generation by Autocatalysts in Autoxidation of Linoleate Alone and with Eleostearate

The formation of hydroxy radicals, hexanal, and 2,4-decadienal was demonstrated from the autocatalytic dimer peroxide which had been reported by us in autoxidizing linoleate (Morita and Tokita in Lipids 41:91-95, 2006). Then, autoxidizing linoleate containing eleostearate was investigated for new autocatalytic substances. The substances obtained were identified as peroxide-linked polymers consisting of both linoleate- and eleostearate-origin units with one hydroperoxy group, and also revealed activity of hydroxy-radical generation. The background of this study is as follows: the above paper reported this autocatalytic dimer peroxide as one of the real radical generators in linoleate autoxidation; this is a peroxide-linked dimer consisting of two linoleate moieties with two hydroperoxy groups, and was much more important than the main-product hydroperoxide in autocatalytic radical supply; its proposed decomposition mechanism has suggested the generation of hydroxy radicals, hexanal, and 2,4-decadienal; on the other hand, analogy to the formation mechanism of this dimer peroxide has predicted the formation of similar polymeric products from conjugated polyene components in lipids. In this study, these two predictions were successfully verified and a discussion is presented in connection with them.     

Consideration on the Relationship Between Dielectric Breakdown Voltage and Water Content in Fatty Acid Esters

Mineral oil is commonly used as an electrical insulating oil in transformers because of its relatively high electrical insulating ability and fluidity. Considering the depletion of resources and environmental problems, however, fatty acid esters synthesized from natural plant oils are attracting attention as an environmentally friendly insulating oil. In addition, fatty acid esters such as methyl octanoate, methyl dodecanoate, 2-ethylhexyl octanoate, and 2-ethylhexyl dodecanoate have high fluidity, and also show excellent moisture tolerance against dielectric breakdown compared to mineral oil. In the present study, to clarify the reason for the superior moisture tolerance of fatty acid esters, the status of dissolved water in esters is investigated with IR spectroscopic measurements and density functional theory (DFT) calculations. It is revealed that water molecules in fatty acid esters are trapped by the ester moiety of fatty acid esters. As a result, fatty acid esters have a higher moisture tolerance against dielectric breakdown than mineral oil.     

Detection and visualization method of dynamic state transition for biological spatio-temporal imaging data

In the statistical analysis of functional brain imaging data, regression analysis and cross correlation analysis between time series data on each grid point have been widely used. The results can be graphically represented as an activation map on an anatomical image, but only activation signal, whose temporal pattern resembles the predefined reference function, can be detected. In the present study, we propose a fusion method comprising innovation approach in time series analysis and statistical test. Autoregressive (AR) models were fitted to time series data of each pixel for the range sufficiently before or after the state transition. Then, the remaining time series data were filtered using these AR parameters to obtain its innovation (filter output). The proposed method could extract brain neural activation as a phase transition of dynamics in the system without employing external information such as the reference function. The activation could be detected as temporal transitions of statistical test values. We evaluated this method by applying to optical imaging data obtained from the mammalian brain and the cardiac sino-atrial node (SAN), and demonstrated that our method can precisely detect spatio-temporal activation profiles in the brain or SAN.     

Thermoelectric properties of ternary and Al-containing quaternary Ru1−xRexSiy chimney–ladder compounds

The thermoelectric properties of ternary and Al-containing quaternary Ru_1?xRe_xSi_y chimney–ladder phases have been studied as a function of the Re concentration with the use of directionally solidified alloys. The Ru_1?xRe_xSi_y chimney–ladder phases exhibit n- and p-type semiconducting behaviors, respectively, at low and high Re concentrations, at which the X(=Si)/M(=Ru + Re) ratios are respectively, larger and smaller than those expected from the VEC (valence electron concentration) = 14 rule. The absolute values of both Seebeck coefficient and electrical resistivity increase as the extent of the deviation from the VEC = 14 rule increases, i.e. as the alloy composition deviates from that corresponding to the p–n transition (x ≈ 0.5), indicating that the carrier concentration can be controlled by changing the extent of compositional deviation from the ideal VEC = 14 composition. The highest values of the dimensionless figure of merit obtained are 0.47 for ternary (x = 0.60) and 0.56 for Al-containing quaternary alloys. The reasons for the systematic compositional deviation from the ideal VEC = 14 compositions observed for a series of chimney–ladder phases are discussed in terms of atomic packing.     

Porous Titania Ceramic Prepared by Mimicking Silicified Wood

A porous titania ceramic with a woodlike microstructure that was analogous to silicified wood was prepared. The production of "titanified wood" was performed using the following process: (i) introduction of titanium tetraisopropoxide into wood materials via vacuum infiltration, (ii) hydrolysis of the titanium tetraisopropoxide in the cell structure to form a titania gel, and (iii) firing at a temperature of 600°–1400°C in air. The resulting titania ceramic had the same external and internal forms of the original wood.     

Preparation of Magnesium Nitride Powder by Low-Pressure Chemical Vapor Deposition

Submcrometer-scale magnesium nitride (Mg₃N₂) powder was prepared by low-pressure chemical vapor deposition, i.e., the reaction of Mg vapor with mixed NH₃–N₂ gases at 800°C under a pressure of ∼1 kPa. The mixing ratios of NH₃–N₂ gases were 0% NH₃–100% N₂ (pure N₂), 20% NH₃–80% N₂, 40% NH₃–60% N₂, 60% NH₃–40% N₂, 80% NH₃–20% N₂, and 100% NH₃–0% N₂ (pure NH₃). The reactions between Mg vapor and NH₃–N₂ gases produced platy Mg₃N₂ particles <0.2 μm and acicular particles with long-axis length of ∼0.2 μm, whereas the reaction of Mg vapor with pure NH₃ gas produced spherical Mg₃N₂ particles with diameters of ∼0.1 μm.     

Agglomeration of magnesium oxide particles formed by the decomposition of magnesium hydroxide

Agglomeration of magnesium oxide (MgO) particles was studied by decomposing magnesium hydroxide (Mg(OH)₂). The properties of agglomerates varied according to the decomposition temperature region: (i) below 650° C, (ii) 650° C to 850° C, (iii) 850° C to 1050° C, and (iv) 1050° C to 1200°C. In region (i), the original Mg(OH)₂ frameworks or pseudomorphs remained in the powder and showed agglomeration. The strength of agglomerates containing the pesudomorphs was about 50 MPa; the primary particles in pseudomorphs are bonded chemically by the interaction of MgO and residual water. In region (ii) the pseudomorphs began to show some fragmentation: the bonding strength of these pseudomorphs reduced rapidly. In region (iii), both crystallite and primary particles were grown by the sintering; this growth may be due to an increase in contact area based on the collapse of pseudomorphs. The primary particles whose necks were grown by the sintering could be easily pulled apart by grinding. In region (iv) pore growth due to the rearrangement of primary particles caused the suppression of both densification rate and crystal growth of MgO.     

Anisotropy Effect on the Flow-Induced Instability of the Solid-Superfluid Interface

At the solid-superfluid interface of ⁴ He a Kelvin–Helmholtz type instability is expected to occur with a tangential flow. Nonlinear effect in the instability is studied with a perturbation expansion. For an isotropic interface the amplitude of the destabilized crystallization wave grows without limit, which suggests a chaotic motion. With a strong crystal anisotropy and for the surface orientation of minimum stiffness, the amplitude has a stable fixed point and a corrugated interface may be stabilized. Increasing further the anisotropy changes the type of the bifurcation from subcritical to supercritical.     

Experimental study of squirrel-caged damper structure for superconducting generator

In this paper a double-layer damper is developed which will consist of a squirrelcaged warm damper and a cylindrical cold damper as a part of a 70-MW superconducting generator development project. To evaluate the characteristics of unbalance current capability, magnetic shielding and damping for rotor swing, a one-half scale rotor model is constructed and an experimental study is made. From analysis of the experimental results, design guidelines have been developed and the FEM magnetic field analysis technique is refined. The main results are summarized as follows:

• 1 The squirrel-caged warm damper has sufficient capability against negative sequence current;
• 2 Damping characteristics can be designed to be effective near the rotor swing frequency;
• 3 Flux shielding at low frequencies corresponding to quick response excitation is sufficiently small so as not to prevent field flux change; and
• 4 Magnetic field can be analyzed by the refined FEM field analysis technique which now takes into account the effects of the rotor end region by estimating the end resistance based on the eddy current flow path.