Non-hookean stress-strain response and changes in crystallite orientation of carbon fibres

The non-hookean stress-strain response of carbon fibres was investigated in relation to changes in crystallite orientation with tensile stress. Various one-dimensional array models and a mosaic model were examined. Amongst these models, only the mosaic model in which the stress of the crystallites can be transmitted in both the transverse and the axial directions showed any quantitative agreement with the measured increases in the tensile modulus and the crystallite orientation with tensile stress. This suggests that deformation of the crystallites is constrained with increasing tensile stress. It was also found that the ratio of the tensile stress of the fibre to that of the crystallites is close to the crystallite volume fraction rather than the ratio of the fibre density to the crystallite density.     

Study of drive system for linear induction motor using magnetic energy recovery switch

This paper proposes a power supply suitable for driving linear induction motors. The power supply consists of a voltage source inverter (VSI) and a magnetic energy recovery switch (MERS). Circuit configuration and operation principles of the power supply are described. Power factor correction by MERS can increase the output power. Technical advantages of using MERS compared with increasing the rated voltage of VSI are discussed. Some experiments with a linear induction motor were conducted. The results confirm that MERS can reduce the capacity of the VSI or increase the output with the same VSI capacity. The number of devices and magnitude of losses are evaluated on a large‐scale drive system. A half‐bridge type of MERS is provided and discussed. The half‐bridge MERS mitigates disadvantages of using MERS. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 169(4): 65–74, 2009; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20832     

Structural analysis and transistor properties of hetero-molecular bilayers

We examined the film morphologies and transistor properties of hetero-molecular bilayer consisting of N, N’-dioctyl-3, 4, 9, 10-perylenedicarboximide (PTCDI-C₈) and quaterrylene. First, the structure and carrier conduction of PTCDI-C₈ films were studied, followed by an analysis of the carrier accumulation process in a PTCDI-C₈/quaterrylene hetero-bilayer transistor. Based on the displacement current measurement (DCM), we stress the potential of the hetero-bilayer for tuning carrier accumulation like carrier doping techniques in field-effect transistors.     

Formation of core-type macroscopic morphologies in Cu-Fe base alloys with liquid miscibility gap

The effects of alloying elements on the macroscopic morphologies in Cu-Fe base alloys were experimentally investigated. It was found that macroscopic homogeneity can be achieved by the addition of Mn, Ni, Al, or Co in the Cu-Fe base alloys, while the core-type macroscopic morphologies with Cu-rich or Fe-rich cores, which are radially separated as two layers in the inner and outer parts of the ingot solidified in the cast-iron mold, were formed by the addition of C, Cr, Mo, Nb, Si, or V. It is shown that the formation of the core-type macroscopic morphology is strongly connected with the existence of a stable miscibility gap of the liquid phase in the Cu-Fe base alloy due to the addition of alloying elements. The liquid phase with less volume fraction always forms the center part. This result can be explained by a mechanism that the minor droplets as the second phase are forced to move into the thermal center due to Marangoni motion, which is caused by the temperature dependence of interfacial energy between two liquid phases.     

Radical-induced degradation mechanism of perfluorinated polymer electrolyte membrane

The degradation mechanism induced by radicals was investigated for Nafion^®-117 by solution analysis. Nafion^® was exposed independently to three kinds of radicals, OH, H and O₂⁻ which were produced separately by γ-irradiation. Based on the eluted elements, the scission site in the membrane was analyzed. The results showed that the scission site was classified into two and these locations were closely relating to oxidative and reductive reactions. The decreasing rate of proton conductivity was more significant under the influence of reductive radicals. The progression of the unzipping reaction of main chain was suggested to be initiated by the production of tertiary carbon radical by reductive radicals such as H and O₂⁻ with the aid of OH. The structural degradation such as collapse of cluster and the cluster decomposition as well as the performance degradation was found to be initiated by such reductive radicals.     

Wide variations of plasma triglyceride concentrations in guinea pigs

Guinea pigs have varying plasma triglyceride concentrations ranging from 28 to 1392 mg/dl, with relatively uniform plasma cholesterol and phospholipid levels. To understand why the animals exhibit such wide variations of plasma triglyceride concentrations, we have explored the triglyceride hydrolyzing system by measuring tissue lipoprotein lipase activities and plasma activator for the enzyme. Lipoprotein lipase activities of epididymal adipose tissue of these animals were 759±117 (mean±SE) n moles FFA·min⁻¹·g wet tissue⁻¹, markedly low compared with those of rats. There were no relationships between plasma triglyceride concentrations and tissue lipase activities. Plasma activator for lipoprotein lipase was lacking in this animal. Guinea pigs with ascorbic acid deficiency for 2 weeks also showed marked variations of plasma triglyceride concentrations, without any changes in tissue lipoprotein lipase activities. Low adipose tissue lipoprotein lipase activities with deficient plasma activator for the enzyme suggest that the lipoprotein lipase-mediated triglyceride degradation could be impaired in this animal, and this may account for the marked variation of plasma triglyceride concentrations.     

Study of a thick target surface ionizer at INS

A surface-ionization ion source for the use of a thick target has been studied by an isotope separator on-line at INS using the ⁴⁰Ca(p,2pn)³⁸K reaction. The ionization efficiency and release time were measured for CaC₂, CaO and CaF₂ targets. The measured efficiency turned out to be about 20% both for tantalum and platinum surface ionizers. The release time was also deduced for each target at various values of temperature by measuring time distributions of the extracted radioactivity after bombarding the target for a short time.     

Volume contraction and its significance in structural formation during the thermal stabilization of acrylic fibers

The length changes of acrylic fibers during isothermal treatment at temperatures from 208°C to 270°C were measured under constant tensile stresses. In order to elucidate the relation between the length and structural changes during heat treatment, the measurements of density, the elemental composition, and the aromatization index determined from X-ray diffraction were made for the fibers heat-treated at 252°C for various periods of time. It is shown that a contraction in length which accompanied a volume contraction occurred during extended heat treatment, even when the fibers were subjected to high tensile stresses. The volume contraction is attributed to the fact that planar cyclized polymer segments, formed by additional polymerization of the nitrile side groups, are built up and construct a stacking which is denser than the original fiber structure. The orientation of the stacking of the cyclized segments was measured for the fibers heat-treated in the fixed state giving a high orientation, which is comparable to that of the fibers heat-treated under a high tensile stress giving an extension to the fibers in the initial periods of heat treatment. These results were explained by considering the interaction of external constraint and volume contraction which occurs during heat treatment.     

Combined effects of neutron irradiation and hydrogen absorption on tensile properties and fracture mode of steels for nuclear pressure vessel

The combined effect of neutron irradiation and hydrogen absorption on the mechanical properties and fracture modes are investigated for the reactor pressure vessel steels in use and pure iron. The embrittlement of the steel A533B neutron-irradiated up to 4.4 × 10¹⁹n cm⁻² (E > 1 MeV) is not accelerated by the interaction between irradiation-induced defects and hydrogen atoms. For the steel A542 and pure iron, the embrittlement due to the combined effects of the above two factors is a little larger than that of A533B, and the ductility behaviour of these materials is quite similar to that of the unirradiated hydrogen-charged specimens. The change of the tensile properties and fracture modes can reasonably be explained by the interaction between irradiation defects and hydrogen atoms. Sensitivity to the brittle fracture of the steel in use, i.e. A533B, may not be increased by the combination of the above two embrittlement factors.