1,721,732 research outputs found
Effect of matrix hardness on the creep properties of a 12CrMoVNb steel
No full textUsing a creep-ductile 12CrMoVNb steel, constant-load creep tests were conducted in air at 650 degrees C, and the effects of matrix hardness on the creep properties were investigated. Specimens with a matrix hardness (Rc) of 30, 25, and 20 were prepared using different tempering conditions. The creep behaviors were well described by the power-law creep equation, with the stress exponents of strain rate (n) and rupture time (chi) decreasing with matrix hardness. Rupture-time analyses showed that creep rupture occurred by the nucleation of creep cavities on second-phase particles and growth by creep flow of the surrounding matrix. A hardness decrease tends to lower the rupture time and increase the strain rate (epsilon), and the effect of hardness was quite distinct at high applied stresses due to the short creep times, but not so at low applied stresses due to elongated creep times. After 10(4) hours, there were almost no effects. The hardness decrease during the creep test was more severe for the specimens with higher hardness and was also more severe in the gage section than in the head section, the latter due to the stress-assisted diffusion in the coarsening of carbides. Microstructural examinations showed that subgrain boundaries grew during creep, and equiaxed carbide particles coarsened during the creep test, the rates of coarsening being greater for specimens with a higher hardness
EFFECTS OF WHITE, BLUE, RED-LIGHT AND DARKNESS ON PH OF THE APOPLAST IN THE SAMANEA PULVINUS
No full textX1129sciescopu
EFFECTS OF TEMPERATURE ON H+ UPTAKE AND RELEASE DURING CIRCADIAN RHYTHMIC MOVEMENTS OF EXCISED SAMANEA MOTOR ORGANS
No full textX118sciescopu
Actin filaments of guard cells are reorganized in response to light and abscisic acid
No full textWe recently showed that treatment with actin antagonists perturbed stomatal behavior in Commelina communis L. leaf epidermis and therefore suggested that dynamic changes in actin are necessary for signal responses in guard cells (M. Kim, P.K. Hepler, S.O. fun, K.-S. Ha, Y. Lee [1995] Plant Physiol 109: 1077-1084). Here we show that actin filaments of guard cells, visualized by immunofluorescence microscopy, change their distribution in response to physiological stimuli. When stomata were open under white-light illumination, actin filaments were localized in the cortex of guard cells, arranged in a pattern that radiates from the stomatal pore. In marked contrast, for guard cells of stomata closed by darkness or by abscisic acid, the actin organization was characterized by short fragments randomly oriented and diffusely labeled along the pore site. Upon abscisic acid treatment, the radial pattern of actin arrays in the illuminated guard cells began to disintegrate within a few minutes and was completely disintegrated in the majority of labeled guard cells by 60 min. Unlike actin filaments, microtubules of guard cells retained an unaltered organization under all conditions tested. These results further support the involvement of actin filaments in signal transduction pathways of guard cells.X1185sciescopu
Modelling and vibration analysis of misaligned rotor-ball bearing systems
No full textA dynamic model is derived for misaligned rotor-ball bearing systems driven through a flexible coupling by treating the reaction loads and deformations at the bearing and coupling elements as the misalignment effect. In order to verify the validity of the misaligned rotor system model, experiments are extensively carried out with a laboratory test rig. Both the experimental and simulation results agree well in that, as the angular misalignment increases, the whirling orbits tend to collapse toward a straight line and the natural frequency of the misaligned rotor system associated with the misalignment direction increases largely. It is found that the increase in natural frequency is mostly due to the increase in effective bearing moment stiffness associated with the misalignment direction. (C) 1999 Academic Press
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