720 research outputs found

    Viscoelastic Behavior of Amorphous Metals

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    The viscoelastic behavior and its rate controlling process of amorphous metals have been examined by extensive experiments of tensile creep and stress relaxation using amorphous Pd-Si, Fe-P-C and Cu-Zr alloys. The differences in creep properties of amorphous and crystalline metals have also been discussed. Creep curves of all amorphous metals used may be classified into three stages of transient creep, steady-state creep and tertiary creep. The creep strain is composed of recoverable and irrecoverable components and it can be described in terms of viscoelastic elements in rheology. The steady-state creep is controlled by thermally activated process, and seems to be closely related with atomic diffusion in amorphous structure

    Crystallization Process of Iron-, Nickel-, and Cobalt-Based Amorphous Alloys Containing Silicon and Boron (Metallurgy)

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    Structural changes during heating or aging in a wide temperature range were exmained with three amorphous alloys of Fe_Si_B_, Ni_S_8B_ and Co_Si_B_ by measurements of electrical resistance, differential scanning calorie and Vickers hardness and also by transmission electron microscopy and X-ray diffraction. The results obtained are summarized as follows : (1) The crystallization process of three amorphous alloys is divided into four stages : (a) the incipient stage of crystallization where a certain short range ordering of atoms occurs, (b) the formation of primary metastable phases (MS-I), (c) the formation of secondary metastable phase (MS-II) with complex single structures, and (d) the formation of a stable phase consisting of a mixture of each equilibrium phase. The MS-I phase appears in the amorphous matrix in a manner of homogeneous nucleation and gradual growth, while the MS-II phase grows rapidly from a few nuclei and completely spreads over the amorphous matrix containing the MS-I phases. At higher temperatures, these MS-II phases transform finally to stable phases. (2) The temperature-time-transformation diagrams of three alloys were constructed. In these diagrams, distinct differences in the transformation sequence and the mode are observable in the upper and lower ranges of the critical temperature (Tx\u27). Above this boundary, crystallization by way of nucleation and growth proceeds through two metastable phases and finally to a stable phase. Below that temperature, on the other hand, progressive aging gradually changes the amorphous structure to the assembly of fine grains (about 100~200A) with a simple structure such as bcc, fcc, or hcp

    Quadrupole moments in chiral material DyFe3(BO3)4 observed by resonant x-ray diffraction

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    By means of circularly polarized x-ray beam at Dy L3 and Fe K absorption edges, the chiral structure of the electric quadrupole was investigated for a single crystal of DyFe3(BO3)4 in which both Dy and Fe ions are arranged in spiral manners. The integrated intensity of the resonant x- ray diffraction of space-group forbidden reflections 004 and 005 is interpreted within the electric dipole transitions from Dy 2p3 to 5d and Fe 1s to 4p, respectively. We have confirmed that the 2 handedness of the crystal observed at Dy L3 and Fe K edges is consistent with that observed at Dy M5 edge in the previous study. By analyzing the azimuth scans of the diffracted intensity, the electronic quadrupole moments of Dy 5d and Fe 4p are derived. The temperature profiles of the integrated intensity of 004 at the Dy L3 and the Fe K edges are similar to those of Dy-O and Fe-O bond lengths, while that at the Dy M5 edge does not. The results indicate that the helix chiral orientations of quadrupole moments due to Dy 5d and Fe 4p electrons are more strongly affected by the crystal fields than Dy 4f

    Studies on the iron metabolism of erythroblasts in various blood diseases

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    The serum iron contents and the number of sideroblasts from various patients and the radioactivity of erythroblasts from the same patients incubated with Fe55 have been observed. The results have proved that in the case with accelerated erythropoietic function like polycythemia vera and in the iron deficient state like idiopathic hypochromic anemia, the serum iron level and the number of sideroblast are lower than those in normal persons and higher in radioactivity in erythroblasts, whereas in the case with low erythropoietic function like hypoplastic anemia the former values are higher and lower in radioactivity of erythroblasts. There is an inverse correlation between the average number of stainable iron granules and the average rate of radioactive iron appearance in erythroblasts, and the observation on these factors will give an important clue for judging the utilization process of iron in each disease. The limitation of the iron uptake correlating with the hemoglobin synthesis have been discussed.</p

    Business Model Development in a Foreign Market : Case Analyses by the Expanded Dynamic Capabilities Framework

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    This study attempted to analyze two Japanese companies that were able to obtain and sustain competitive advantage in an overseas market by developing a business model (BM) that is a fit to the local market. An analytical framework expanding the dynamic capabilities( DC) framework of Teece( 2007, 2014a) particularly on how DC had influenced BM in the introduction and growth stages, which was proposed by Kimura and Chitose( 2021), was used to examine the two companies, Ito-Yokado and Shiseido. This paper identified how each BM was developed and adjusted to the changing environment, and how DC was deployed to realize BM, thus demonstrating the validity of the expanded DC framework for analyzing such company cases

    Domain Nucleation and Annihilation in Uniformly Magnetized State under Current Pulses in Narrow Ferromagnetic Wires

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    We investigate the current-driven magnetization dynamics in narrow Permalloy wires by means of Lorentz microscopy and electron holography. Current pulses are found to transform the magnetic structure in the uniformly magnetized state below the Curie temperature. A variety of magnetic states including reversed magnetic domains are randomly obtained in low probability. The dynamics of vortices found in most of observed magnetic states seems to play a key role in triggering the magnetization reversal.Comment: 11 pages, 3 figures, 1 video, to appear in Japanese Journal of Applied Physics (Express Letter