Diffusion studies in the β (B2), β′ (bcc), and γ (fcc) Fe-Ni-Al alloys at 1000 °C

Diffusion studies were carried out in the Fe-Ni-Al system at 1000 °C with solid-solid diffusion couples assembled with β (B₂), β′ (bcc), and γ (fcc) single-phase alloys for the development of diffusion structures, diffusion paths, and for the determination of interdiffusion and intrinsic diffusion coefficients. The diffusion structures were examined by optical and scanning electron microscopy, and the concentration profiles were determined by electron microprobe analysis. Diffusion couples included several series of β vs γ and β′ vs γ diffusion couples characterized by a common terminal alloy bonded to several terminal alloys with varying compositions. The development of planar and nonplanar interfaces, as well as two-phase layers, as observed in various couples, were related to the diffusion paths. The interdiffusion fluxes of individual components were calculated directly from the experimental concentration profiles, and the diffusional interactions among components were examined in the light of zero-flux planes (ZFPs) and flux reversals, which were identified in several couples. Ternary interdiffusion coefficients ( (i, j = Al, Ni)), with Fe considered as the dependent concentration variable, were evaluated at composition points of the intersection of diffusion paths of single-phase couples and of multiphase couples that developed planar interfaces. The interdiffusion coefficients were the largest in magnitude for the β′ alloys, especially near the β/β′ miscibility gap, and decreased for the β and γ alloys. In the β and γ phases, the main interdiffusion coefficient for Al was larger than those for Ni and Fe. Also, Fe interdiffused faster than Ni in the Fe-rich β and β′ phases. The cross-interdiffusion coefficients ( and ) were negative in all three phases. In general, the coefficients were larger in magnitude than the coefficients; however, the magnitude of was greater than that of near the β/(β + γ) phase boundary on the ternary isotherm. In the β phase, the magnitude of (i, j=Al, Ni) coefficients increased over 1 to 2 orders of magnitude with a decrease in the Al concentration and increase in the Fe/Ni concentration ratio. Interdiffusion coefficients, extrapolated from the ternary coefficients for binary alloys, were consistent with those in literature. Intrinsic diffusion coefficients were also determined at selected compositions. In addition, tracer diffusion coefficients were estimated for the binary Fe-Al and Ni-Al alloys at selected compositions, from an extrapolation of ternary interdiffusion coefficients.     

Scanning electron microscopic observation on the equatorial region of the rat intrafusal muscle fibres, especially on the subsarcolemmal sarcoplasmic reticulum

We examined intracellular structures in the equatorial region of the muscle spindles of rat soleus muscles by scanning electron microscopy, paying particular attention to the ultrastructure of the sarcoplasmic reticulum (SR) beneath the sarcolemma. The subsarcolemmal SR was more developed in nuclear chain fibres than in nuclear bag fibres as was reported in the sleeve and extracapsular regions. In addition, the subsarcolemmal SR of the chain fibre formed a fenestrated sheet, whereas that of the bag fibre organized a layer of fenestrated bands beneath the sarcolemma where the sensory nerve endings are associated. No T-tubules were discerned in the subsarcolemmal SR of both fibres, which may be concerned with the little contraction of the equatorial region.     

Phase-field investigation of multicomponent diffusion in single-phase and two-phase diffusion couples

Interdiffusion in hypothetical ternary single-phase and two-phase diffusion couples are examined using a phase-field model by numerically solving the nonlinear Cahn-Hilliard and Ginzburg-Landau equations. For diffusion couples assembled with a regular single-phase solution, constant chemical mobilities were used to examine the development of concentration profiles including uphill diffusion and zero-flux plane. Zero-flux plane for a component was observed to develop for a diffusion couple at the composition that corresponds to the activity of that component in one of the terminal alloys. Experimental thermodynamic parameters and composition-dependent chemical mobilities were used to examine the morphological evolution of the interphase boundary in solid-to-solid, two-phase diffusion couples. Instability at the interphase boundary was introduced initially (t=0) by a small compositional fluctuation at the diffuse interface, and its evolution varied largely as a function of terminal alloys and related composition-dependent chemical mobility. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.     

COMPUTATION OF THE FLOW FIELD IN A RECIRCULATING TURBULENT GAS JET

As part of an overall investigation of flash-smelting processes, numerical computations were performed for the turbulent recirculating flow field of a gas jet in a confined cylindrical system. The two-equation (k - e) model was used to describe turbulence. The two-dimensional elliptic partial differential equations cast into finite difference forms were solved by the TEACH code (Gosman and Pun, 1973), and the pressure field was computed by the SIMPLER method (Patankar, 1980). Various correlations for the dissipation rate of turbulent kinetic energy at the inlet were tested, and the relation yielding the best results was obtained as E= C_μK^1.5/(0.015d_e where d_e = 4 x hydraulic radius. Extensive comparisons have been made between the computed results using the proposed form of e at the inlet and experimental data taken from the literature. Much better predictions than previously possible have been obtained     

Storage of multiple holograms of equal diffraction efficiency in a phase-code multiplexing system

Computer simulations of 8-, 32-, and 128-bit phase-code multiplexing systems are presented, and exposure schedules are obtained numerically for equal diffraction efficiency. An analytic prediction of the exposure schedule is derived as a double exponential function that can be applied to the three different systems for variation of diffraction efficiency of less than +/- 13.5%. Eight holograms were experimentally recorded in a BaTiO3 crystal according to our exposure schedule and also to conventional schedules, which had originally been derived for an angle-multiplexing system. It is shown that the experimental data agree well with the computer simulations.     

A study on the student pilot's mental workload due to personality types of both instructor and student

The main purpose of this paper is to provide the ideal flight crew combination for instructor and student pilots in order to enhance the flight training effects based on Myers Briggs Type Indicator (MBTI) theory. In addition to personality, various levels of flight difficulty are considered in order to investigate their potential interaction effect in terms of student pilots' mental workload measured in heart rate, altitude deviation, NASA-TLX (Task Load Index) and subjective degree of personality harmony. Based on an experiment performed in a real flight situation, we found significant effects of personality combinations in terms of all four outcome measures. Both group C types of instructors and students who are concrete, realistic and have mechanical skills turn out to be the ideal flight crew combination. A structural equation model, fitted to analyse causality among the four response variables, implied that as the heart rate increased, the altitude deviation increased. In addition, as the altitude deviation and personality harmony increased, NASA-TLX increased. The results of this study are expected to provide a theoretical basis for manning the flight crew combinations and thereby enhancing the efficiency of flight training.     

Controlled crystallization and characterization of cordierite glass-ceramics for magnetic memory disk substrate

Glass-ceramics containing cordierite (2MgO-2Al₂O₃-5SiO₂) as a crystal phase based on the glasses in the system MgO-Al₂O₃-SiO₂ were investigated for the application to magnetic disk substrate for higher storage capacity. Parent glasses were prepared with CeO₂ addition as a flux and were crystallized by a controlled 2-step heat treatment The maximum nucleation and crystal growth rates were 2.4 × 10⁹/mm³ · hr at 800 °C and 0.3 m/hr at 915°C respectively. Only - cordierite was precipitated after heat-treatment. After nucleation at 800 °C for 5 hours prior to crystallization at 915 °C for 1 hour, the resulting crystal volume fraction and crystal size were 17.6% and 0.3 m, respectively. Heat-treated specimens through the above condition showed the optimum properties for magnetic memory disk substrates as follows.; Bending strength of 192 MPa, Vickers hardness of 642.1 kg/mm², thermal expansion coefficient of 39 × 10^–7/K and surface roughness of 27 Å.