An experimental study of the acousto-elastic effect in a rolled plate of steel

The acousto-elastic effect in rolled steel is studied experimentally by transmitting ultrasonic transverse waves and measuring amplitudes of reflected echoes. A Y-cut quartz transducer with a frequency 4.8 MH_z and ultrasonic flaw detection equipment are used for generation and detection of waves, and three tensile specimens with different orientations are prepared from a rolled plate so as to ascertain an important role of its slight orthotropy. At first the variation of amplitude with the transducer direction is examined in the unstressed state, and the slight orthotropy of each specimen is determined quantitatively. Then the variation of amplitude with the tensile stress is examined in the elastic range. The results depend clearly on the orientation of each specimen, and rotation of polarization direction is affirmed in the specimen with an inclination 45° against the rolling direction. Quantitative discussions about the whole experimental results give the conclusion that the acousto elastic effect in this rolled plate obeys the relations which were proposed theoretically by one of the authors.     

Enhanced oxygen barrier property of poly(ethylene oxide) films crystallite-oriented by adding cellulose single nanofibers

In this study, we investigated the influence of cellulose single nanofibers (CSNFs) added to poly(ethylene oxide) (PEO) on the microstructure and property to create high gas barrier films. The CSNF/PEO nanocomposite films were prepared by solvent casting. The PEO crystallite orientation was measured using wide-angle X-ray diffraction of the SPring-8 synchrotron radiation facility. The degree of crystallite orientation was evaluated from the reflections of the PEO (1 2 0) lattice planes to investigate quantitatively the effect of different amounts of the additive CSNFs. The crystallite orientation of PEO increased with the addition of the CSNF. Furthermore, the oxygen barrier property for each nanocomposite film was found to be higher than that of the pure PEO film. The 5 wt% addition of CSNFs was mostly effective in enhancing the PEO crystallite orientation and oxygen barrier.     

Structural Analysis of Amorphous Alloys by X-Ray Diffraction

The structure of amorphous alloys has been studied by using various techniques, such as x-ray, neutron, and electron diffraction experiments. X-ray diffraction is the most conventional of all the techniques and is based on EXAFS (extended x-ray absorption fine structure) [1-3] and AXS (anomalous x-ray scattering) [4-5] experiments, which are used for the investigation of the local environment around a species of atom. Recently, x-ray diffraction has been applied to the structural analysis of some quasicrystals [5,7]. It is, of course, hard to determine the local structure of a noncrystalline material only from ordinary x-ray diffraction experiments. However, the role of x-ray diffraction in structural analysis is still important from the viewpoint that this supplies a relatively convenient method, and the appropriate selection of a Sample makes it possible to extract the dominant atomic correlation in the material. In the present study, a conventional θ-2θ diffractometer was used with a monochrometor in the diffracted beam. First, the theoretical background is discussed, the data analysis procedure is given in detail, and error estimation in the data analysis is presented last.     

Sintering process of Y2O3-added Si3N4

The sintering process of Y₂O₃-added Si₃N₄ has been investigated by dilatometry and microstructural observations. Densification was promoted above 1440 ° C by the formation of eutectic melts in the Y₂O₃-SiO₂-Si₃N₄ triangle. However, the dilatometric curves indicated no shrinkage corresponding to the rearrangement process, despite liquid-phase sintering. The kinetic order for The Initial-stage sintering was 0.47 to 0.49. These values indicated that the phase-boundary reaction was rate controlling. The apparent activation energy (323 kJ mol^–1) was smaller than the dissociation energy for the Si-N bond (435 kJ mol^–1). ESR data and lattice strain indicated that the disordered crystalline structure of the Si₃N₄ starting powder promoted the reaction of Si₃N₄ with eutectic melts. After a period of initial-stage sintering, the formation of fibrous -Si₃N₄ grains resulted in interlocked structures to interrupt the densification.     

Highly controlled side-chain chromophore orientation in poly[N-1-(1-pyrenyl)ethyl-l-glutamines]

Poly[N⁵-(R and S)-1-(1-pyrenyl)ethyl-l-glutamines] (1 and 2) were prepared by condensation of poly(l-glutamic acid) with optically resolved amines. In solution, these polymers, 2 in particular, gave large circular dichroism (CD) indicative of exciton coupling among the side-chain pyrene chromophores. When compared with the corresponding polymer with achiral side groups, i.e. poly(1-pyrenylmethyl-l-glutamine) (3), 1 and 2 not only gave much stronger CD, but also gave much reduced excimer emission with a significant hypsochromic shift of emission maximum. The highly controlled orientation of the side-chain chromophores is apparently brought about by the specific steric interactions among the bulky chiral side chains along the helical main chain.     

Flame height behavior from multi-fire sources

The flame height behavior of merged or inclined flames from two rectangular fire sources in a parallel configuration and from three and four circular pools of 120 mm diameter in a symmetrical configuration were studied experimentally. A rectangular gas diffusion burner, 20 mm × 400 mm or 20 mm × 800 mm was used as line fire sources. Propane gas gave 9.5–57 kW per meter for each burner. Hexane was utilized for the flame merging test using circular pool fires. The height of the flame tip when merged or inclined due to interaction of the flames and|or convective flow was estimated from picture analysis of 300 successive frames of video-recorded data. The flame extension behavior was expressed in dimensionless form as L/L_m = (f_s)^2/5 for square pool fires and L/L_m = (f₁)^2/3 for rectangular fires. The correction factors of f_s and f₁ are f_s = (nD² + S²) / n(D² + S²) and f₁ = (2DW + S²) / 2(DW + S²), respectively. When a rectangular or a circular fire source approaches the wall, the same correlation on flame extension behavior was obtained and simulated successfully considering an imaginary fire source inside a wall.     

Study on dependence of AC transport current losses in YBCO‐coated conductors on distribution of critical current density and n value

We measured AC transport current losses in three kinds of thin‐film YBCO‐coated conductors made by different processes. The results showed that the loss characteristics were different and that some of the conductors did not follow the Norris strip model which is generally believed to well explain the loss characteristics of YBCO conductors. In the paper, an analytical model in which distribution of critical current density and n value of the conductor are taken into consideration is proposed to describe the AC transport current loss characteristics more generally than the Norris strip and elliptical models. It is shown that the analytical model explains well the measured loss characteristics of the three kinds of conductors. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 26–38, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20056     

Photo-induced magnetism in La0.5Pr0.5CrO3

In a perovskite-type chromite La_0.5Pr_0.5CrO₃, we studied the photo-induced electron-spin resonance (ESR). During the illumination of near-infrared light, the photo-induced and transient magnetization is temperature dependent with the characteristic thermal activation energy of 130 meV below the spin-canted antiferromagnetic transition temperature 261 K. At room temperature the photo-induced ESR intensity is remarkably enhanced. We interpret this is coming from the photo-excited electronic state in chromite. By analogy with the manganites, we suspect that the irradiated photons excite the t_2g electrons to the e_g state in Cr³⁺ (3d³). This kind of excitation may cause a creation of novel transient magnetic order than canted antiferromagnetism. The present results may open up an intriguing collective photo-induced magnetism, the creation and control of spin and spin-polarization dependent transport with near-infrared light illumination.     

Epitaxial PbZrxTi1−xO3 Ferroelectric Bilayers with Giant Electromechanical Properties

Giant electromechanical response viaferroelastic domain switching is achieved in epitaxial (001) ferroelectric tetragonal (T) PbZr_0.3Ti_0.7O₃/rhombohedral (R) PbZr_0.55Ti_0.45O₃ bilayers, grown on La_0.67Sr_0.33MnO₃ buffered SrTiO₃ substrates. X‐ray diffraction and transmission electron microscopy show that the domain structure of the T films is tuned as a function of its thickness, from a fully a₁/a₂‐domains (30 nm thick T layer) to a three domain stress‐free c/a₁/c/a₂ polytwin state (100 nm thick T layer). A large switchable polarization is found up to 65 μC cm⁻². Quantitative piezoelectric force microscopy reveals enhanced piezoelectric coefficients, with d₃₃ coefficients ranging from 250 to 350 pm V⁻¹, which is up to seven times higher than the nominal PbZr_xTi_1−xO₃ thin film values. These are attributed to the motion of nanoscale ferroelastic domains. Fatigue testing proves that these domains are reversible and repeatable up to 10⁷ cycles. In‐situ X‐ray synchrotron measurements reveal that the ferroelastic domain switching is promoted by a pulsating strain effect imposed by the R layer. The study reports a fundamental understanding of the origin of giant piezoelectric coefficients in epitaxial ferroelectric bilayers.