铜阴极电解的EMD的电子微探分析

对EMD的电子微探分析(EPMA),发现有Cu的浓缩点存在,电感耦合等离子体发射光谱(ICP-AES)分析析值为0.8×10-4%.通过EPMA,可以对EMD进行微观解析.     

Material performance of age-hardened beryllium–copper alloy,CDA-C17200, in a high-pressure,gaseous hydrogen environment

In order to develop safer and more energy-efficient, hydrogen pre-cooling systems for use in hydrogen refueling stations, it is necessary to identify a high-strength metallic material with greater thermal conductivity and lower susceptibility to hydrogen embrittlement, as compared with ordinary, stable austenitic stainless steels. To accomplish this task, the hydrogen compatibility of a precipitation-hardened, high-strength, copper-based alloy was investigated by slow-strain-rate tensile (SSRT), fatigue-life, fatigue-crack-growth (FCG) and fracture toughness tests in 115-MPa hydrogen gas at room temperature. The hydrogen solubility and diffusivity of the alloy were also determined. The hydrogen solubility of the alloy was two or three orders of magnitude lower than that of austenitic stainless steels. The alloy also demonstrated absolutely no hydrogen-induced degradation of its strength properties, a factor which could contribute to the reduction of costs related to the construction and maintenance of hydrogen refueling stations, owing to the downsizing and improved cooling performance of the pre-cooling systems.     

Velocity and absorption coefficient of ultrasonic waves in molten and glassy silicates and borates

The velocity and absorption coefficient of longitudinal ultrasonic waves with 5 and 10 MHz in molten and glassy silicates and borates have been measured by means of the pulse-echo method in 300 to 1600 K. The silicate and borate were Na₂O−SiO₂, K₂O−SiO₂, PbO−SiO₂, Na₂O−B₂O₃, and PbO−B₂O₃. The velocity of sound decreased with increasing temperature and decreased rapidly near the transition temperature of glasses. The product of the one-third power of velocity of sound and the molar volume of the oxide melt was constant and independent of temperature. The absorption coefficient of ultrasonic waves in the oxide melts increased with an increase in viscosity. The absorption mechanisms of ultrasonic waves and the mean free path of phonons in the oxide melts were discussed.     

Graphite-epoxy laminates with almost null coefficient of thermal expansion under a wide range of temperature

A lamination tailoring technique is proposed in order to control a coefficient of thermal expansion of graphite-epoxy composites in a principal direction. This technique consists of two concepts of the thermoelastic invariants and the lamination parameters. The expansion free condition yields to a parabola in the feasible region of the lamination parameters. The calculated curves for a wide range of temperatures intersect almost at a point. A laminate with the lay-up construction corresponding to this point will exhibit an approximately null coefficient of thermal expansion in one direction in that temperature range. Some preliminary experimental results indicate that the present procedure is possible and promising. The tailored material will be appropriate for the space station structure.     

Design of an adaptive observer for sensorless vector control of induction machines under regenerating conditions

The objective of this investigation is to stabilize a sensorless vector control system of induction motors by means of an adaptive observer in regenerating mode at very low speed. The adaptive observer gain is designed by means of the Routh–Hurwitz criterion. It is verified by simulation and experiment that the proposed system is stable. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(4): 78–87, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10202     

Fibrous support for immobilization of enzymes. II

A series of adsorption experiments was conducted with varying initial enzyme concentrations. The observed values are compared with the results calculated from the adsorption equations based on Langmuir adsorption mechanism. The values of three parameters, adsorption equilibrium constant K_a, maximum value of adsorbed enzyme per unit mass of SFF, N, and forward adsorption rate constant k_a, were determined from Langmuir adsorption equations and experimental data. In the initial enzyme concentration range below 100 (mg enz./dL), the simulated enzyme concentration vs. time curve agreed well with observed values. However, it was found that the adsorption in the higher concentration range was slow, and the corrected forward adsorption rate constant should be employed.     

Molecular orientation behaviour of uniaxially stretched poly(vinyl chloride) film: 1. Birefringence: effect of plasticizers and draw ratio above and below Tg

In order to investigate the orientation behaviour of a non-crystalline chain polymer, plasticized and unplasticized poly(vinyl chloride) films (PVC) are chosen for investigation. The following two orientation distribution functions are postulated to calculate the second moment of the molecular orientation: (a) for the unplasticized film drawn below the glass transition temperature the distribution function derived from an affine deformation mechanism is applied; (b) for the all plasticized films or for the films drawn above the glass transition temperature a compound distribution function derived from the affine deformation mechanism and that of a rubber-like chain (Langevin model) proposed by Roe et al is applied. The parameters which are included in the distribution function, viz. the ratio of the affine part to the Langevin part, the ratio of polyene to carbonyl in a heat treated film and the segment number of the Langevin chain, can be evaluated experimentally. The intrinsic birefringences of normal and heat treated unplasticized and plasticized films are estimated theoretically on the basis of additivity of band polarizabilities. The calculated birefringences and orientation distribution functions show good agreement with measured values.     

High-speed InGaP/GaAs transistors with a sidewall base contactstructure

We have fabricated InGaP/GaAs double heterojunction bipolar transistors with a sidewall base contact structure. These transistors operate in both emitter-up and emitter-down modes. Symmetric characteristics of the cutoff frequency f_T=68 GHz and the maximum oscillation frequency f_max=31 GHz were obtained at a base-collector bias V_BC of 0 V. For emitter-down operation, f _T was found to reach a maximum of 78 GHz when the base-collector junction was forward biased at 0.9 V. The product of f _T for emitter-down operation and f_T for emitter-up operation was 5.3×10³ GHz², which is about six times that of previously reported SiGe heterojunction bipolar transistors