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241.
A piece of stainless steel 304 was thermal annealed either in a 60Co solution at 280°C, or in a He atmosphere at 300 or 600°C after being smeared with a 60Co solution. The depth profile of 60Co in SUS was determined with these samples, together with those sampled from the water cleaning system in the Japan Power Demonstration Reactor and those exposed to a high-temperature water ( ˜ 280°C) circulating OWL-loop installed in the Japan Material Testing Reactor, in order to determine the apparent values of the volume and grain boundary diffusion constants. The results have been compared with those of the previous measurements on Ni, Cr, and Fe above 500°C. A consistency has been noticed between both results at 600°C, while the present values at 280 and 300°C are much larger than those expected from the extrapolation of the previous measurements. Although this inconsistency is ascribed to the contribution of the dislocation pipe diffusion at such a low temperature, an attempt has been made to apply the present values to estimate how deep 60Co would penetrate SUS—one of the main constructing materials of the primary cooling system—in the life time of a power reactor.  相似文献   
242.
243.
In the present work, diffusion between vanadium and Cu-20 at.% Ga alloy and that between vanadium and Cu-20 at.% Si alloy were studied. An intermetallic compound, V3Ga, is formed easily by the selective diffusion of gallium from the Cu-Ga alloy to the vanadium. V5Si3 and V3Si are formed also by the selective diffusion of silicon from the Cu-Si alloy to the vanadium. Copper scarcely dissolves either in V3Ga, V5Si3 or V3Si. Copper is not effective for enhancing the formation of V3Si unlike the case of V3Ga. A large super-conducting critical current density, J c, is obtained in the V3Ga formed at temperatures below 700° C while a much smaller J c is obtained in the V3Si formed at 800° C. Changes in J c due to the heat-treatment can be interpreted by the grain growth of the compounds.  相似文献   
244.
The aim of this study was to fabricate moisture‐proof, phase‐stabilized, ammonium nitrate/potassium nitrate (AN/PN) particles, with a polymer used as the moisture‐proofing agent. The particles were prepared with a spray drying technique. Water solutions (or water dispersions) containing AN/PN and one of five different types of polymer were spray‐dried, which produced white powders with particle diameters of approximately 20–40 μm. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy indicated that each component was homogeneously distributed throughout the particles. The particles exhibited little aggregation compared to the reagent AN, even when left for 7 d or more. In addition, the moisture absorption of the particles at less than 40 % relative humidity (RH) was lower than that of the polymer‐free particles. Even under high‐moisture conditions (83 % RH), the particles did not deliquesce immediately, and they retained their original shape for 30–60 min, whereas the polymer‐free particles were transformed into droplets within 5 min.  相似文献   
245.
A linear motor that uses a finite length Halbach array as its magnetic field causes a thrust force ripple owing to end effects. In this paper, the theoretical and numerical analysis methods of the Halbach array are investigated. The results of the electromagnetic field analysis are compared to confirm the validity of the theoretical and numerical solutions. Moreover, we focus on the magnetic pole period and coil arrangement of the finite length Halbach field type linear motor to eliminate the influence of the end effects, and report the relationship with the end effects.  相似文献   
246.
The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ′ volume fraction and a finer tertiary γ′ distribution. In addition, an increase in the anti-phase-boundary energy of the γ′ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ′ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.  相似文献   
247.
Cyclic nigerosylnigerose (CNN) is produced enzymatically from starch by the combined action of 6-α-glucosyltransferase and 3-α-isomaltosyltransferase. In our previous study, α-1,6-branching chains found in the structure of amylopectin and glycogen were shown to be favorable for CNN formation by the two enzymes. Therefore, we examined whether the introduction of α-1,6-branch points into starch using the action of branching enzyme (BE) could improve the yield of CNN from starch. Thermostable BE from Geobacillus stearothermophilus TC-91 was prepared as a purified recombinant protein. Pretreatment of amylose with BE considerably increased the CNN yield from 5% to 38%. When BE acted on tapioca starch, the CNN yield was elevated from 47% to 60%. Conversely, BE treatment of waxy corn starch containing very little amylose resulted in a negligible increase in CNN yield. In addition, BE exerted a beneficial effect when starch with a lower degree of hydrolysis was used as a substrate. The present results indicate that the addition of α-1,6-glucosidic linkages to starch using BE is an effective strategy to improve the yield of CNN from starch.  相似文献   
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