A Fuzzy-Fuzzy Relation and its Application to the Clustering Technique

Behaviormetrika - In this paper we have formulated a fuzzy-fuzzy relation which is an extension of the fuzzy one, and have investigated its properties. Using some characteristic property which...     

Graphitization and sintering of coals under pressure

Anthracite from Abernant, Wales, and sub-bituminous coal from Taiheiyo, Hokkaido, were graphitized above 1500 °C at a pressure of 0.5 MPa. The graphitization occurred abruptly in a very narrow range of temperature. In association with the graphitization, sintering of the sample powder and densification were observed.     

Effect of ambient pretreatment of graphite and solvent-catalyst on diamond formation

Diamond was formed from purified natural graphite under high pressure and temperature conditions (7 G Pa, 1700° C) using a solvent-catalyst in the unary (Fe) or binary (Fe-Ti) system. The effect of an ambient pretreatment of the starting mixed powder (graphite and solvent-catalyst) was investigated in relation to the formation and grain growth of diamond. An initial desorption of adsorbed water vapour or harmful gases from the starting powder in vacuum (2 × 10^–5 torr) at higher temperatures (>400° C) was required in order to increase the conversion ratio from graphite to diamond. The subsequent ambient pretreatment at 1000° C in different atmospheres was found to affect the grain growth process of diamond. The depression of grain growth was confirmed in both cases of pretreatments in vacuum (2 × 10^–5 torr) and in an argon atmosphere (1 × 10^–3 or 760 torr). The diamond grains were discrete in the vacuum pretreatment, while a particle joining between the diamond grains was promoted in the argon pretreatment. The pretreatment in an N₂ atmosphere (1 × 10^–3 or 760 torr) tended to accelerate the grain growth of diamond.     

A High Performance AC Servo System with Permanent Magnet Synchronous Motors

A high performance ac servo system with permanent magnet synchronous motor, including a field-weakening control and a high-speed current response control of PWM inverter is proposed. For the field weakening, the d-axis armature current is adequately controlled through a microprocessor. The novel current control scheme of PWM inverter includes the motor neutral point potential stabilization and the switching carrier frequency equalization.     

Effect of a silicon sintering additive on solid state bonding of SiC to Nb

Pressureless-sintered (PLS) SiC was joined to Nb by solid state bonding in a vacuum. The joining strength of the PLS SiC/Nb joint increases to the saturated value of 108 MPa with increasing joining pressure at a joining condition of 1673 K and 7.2 ks. This saturated value of PLS SiC/Nb joint is higher than that of the reaction sintered (RS) SiC/Nb joint. The strength of SiC itself affects the strength of the SiC/Nb joint. The high stability of the intermediate phase Nb₅Si₃ in the interface at elevated temperature leads to the high heat resistance of the joint. The thickness of the intermediate phase Nb₅Si₃ in the PLS SiC/Nb system is lower than that of the RS SiC/Nb system at a constant joining time, although the activation energy, 452 kJ mol^–1, of growth for the phase in the PLS SiC/Nb system is almost the same as the RS SiC/Nb system, 456 kJ mol^–1. The rate constant of the growth for the phase in the PLS SiC/Nb system is lower than that in the RS SiC/Nb system. The excess silicon in RS SiC promotes the formation of the Nb₅Si₃ phase at the interface between SiC and Nb.     

Integrated intensity changes of X-ray diffraction lines for crystalline powders by grinding and compression. Relations between effective Debye parameter and lattice strain

The relations between the effective Debye parameter and lattice strain are investigated on some non-metallic crystalline powders, CoO, Co_0.5 Mg_0.5O, CoAl₂O₄, TiO₂, CaF₂, BaTiO₃ and graphite. The effective Debye parameter B _eff was determined from the integrated intensities of X-ray diffraction lines with different sin /-values and the lattice strain, , was determined from the half-widths of the diffraction lines. Both B _eff and increased with increase in grinding time and pressure. B _eff showed a relatively sharp increase, but tended to saturation. However, increased slowly even after prolonged grinding, and B _eff increased with increase in . When >0.2×10^–2, however, B _eff tended to a limit. The limiting values of B _eff were varied from sample to sample. An attempt was made to explain the changes of B _eff and with grinding and compression to large shear by the introduction of various defects into the structure. B _eff was found to give some information on the deformed structure of crystalline powders.     

Hydrothermal synthesis and properties of Na0.70MnO2.25 layer crystal

The single crystals of Na_0.70MnO_2.25 were hydrothermally synthesized by the reaction of MnO₂ with hydrothermal NaOH solution. The crystal of Na_0.70MnO_2.25 has the layer structure in which sodium ions are located between the sheets composed by MnO₆ octahedra. The oxygen fugacity under hydrothermal conditions was found to influence the valence of manganese ion in a grown crystal, determining the kind of crystalline phase in the NaMnO system. The chemical and physical properties of Na_0.70MnO_2.25 were measured.     

The role of alloying elements in improving the corrosion resistance of amorphous iron base alloys

X-ray photo-electron spectroscopy has been used to investigate the correlation between the compositions of a surface film and the underlying alloy and the beneficial effects of alloying elements. The addition of alloying elements less noble than iron increases the corrosion resistance in the active region by improving the protective quality of the corrosion product film in which the cations of alloying elements are significantly concentrated. Even if the passivity of alloying elements is not stable in the passive region of alloys, the alloying asists the formation of passive hydrated iron oxy-hydroxide film by decreasing the dissolution rate of alloys prior to the passive film formation. The improvement of corrosion resistance by alloying with the elements more noble than iron has been interpreted in terms of the decrease in the anodic activity of alloys.