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Capacitance-voltage (C-V) characteristics of a Si/C&sub60; heterojunction, i.e., a HF solution (7.3% HF+30% NH[sub 4]F) treated Si surface interfaced solid crystal of C&sub60; molecules, were measured while applying various ac frequencies. The entire C[sub 60] thin film and near-interface region of the Si wafer behaved as a depletion region, with the C – V curve showing two distinct regions: one above and one below a threshold bias voltage. Below the threshold, C –V characteristics were dependent on applied frequency, which suggests the presence of interface states that only affect capacitance at lower frequencies. This frequency dependence was analyzed by assuming a suitable equivalent circuit, and based on derived curve-fitting circuit parameters the interface states density was accordingly estimated to have a value as low as ∼ 10[sup 11]/cm² eV. Such a small density indicates that only a few lattice defects occur within the interface of the HF-treated Si surface and C&sub60; crystal. Although no frequency dependence was observed above the threshold, the C – V characteristics were found to be dependent on the width of the depletion region in Si. [ABSTRACT FROM AUTHOR]

We studied the possible application of high-TC superconducting traction transformer to railway rolling stock, and designed an iron core type two-leg 4 MVA superconducting traction transformer for Shinkansen. This traction transformer has a primary winding, four secondary windings and a tertiary winding. The four secondary windings are independent of each other. Two secondary windings are arranged around each leg of the iron core and placed inside and outside the primary and tertiary windings. In this study, we fabricated a high-TC super-conducting coil whose form and dimension are the same as those of the inner secondary winding. This coil can be used as the inner secondary winding of the experimental high TC superconducting traction transformer that will be fabricated in the future. The inner secondary winding has 96 turns and a later with eight parallel Bi2223 superconducting tapes. Transposition among the superconducting tapes is performed 15 times every six turns. We measured the voltage-current and AC loss characteristics when it was cooled in saturated and sub-cooled liquid nitrogen. [ABSTRACT FROM AUTHOR]

We fabricated two high-T[sub c] superconducting coils that simulated the winding of a traction transformer for railway rolling stock. The multi-layer solenoid coil to simulate the primary winding of the transformer had five layers with a single Bi2223 superconducting tape. The closed solenoid coil to simulate the secondary winding of the transformer had one layer with eight parallel Bi2223 superconducting tapes. We measured the voltage-current, AC loss and current sharing characteristics of these coils cooled in saturated liquid nitrogen at 77 K. As a result, we concluded that the multi-layer solenoid coil is applicable to the primary winding and the closed solenoid coil is also applicable to the secondary winding. [ABSTRACT FROM AUTHOR]

Nozzle geometry, which influences combustion gas dynamics and, therefore, sprayed particle behavior, is one of the most important parameters in the high-velocity oxygen-fuel (HVOF) thermal spray process. The nozzle geometry is also important in the cold spray method. The gas flows in the entrance convergent section of the nozzle exhibit a relatively higher temperature and are subsonic; thus, this region is most suitable for heating spray particles. In this study, numerical simulation and experiments investigated the effect of the entrance geometry of the gun nozzle on the HVOF process. The process changes inside the nozzle, as obtained by numerical simulation studies, were related to the coating properties. An Al2O3-40 mass% TiO2 powder was used for the experimental studies. The change in entrance convergent section length (rather than barrel part length or total length) of the gun nozzle had a significant effect on the deposition efficiency, microstructure, and hardness. The deposition efficiency and hardness increased as this geometry increased. On the other hand, the calculated and measured particle velocity showed a slight decrease. This effect on the HVOF process will also be applied to the nozzle design for the cold spray method. [ABSTRACT FROM AUTHOR]

The stress-concentration factor for keyways is obtained by the electroplating method of strain analysis which was recently developed in Japan. The stresses in keyways are examined under most practical conditions. The shaft to be examined is set in a boss and fixed with a key so that the torque is wholly transmitted to the test piece through the key. To obtain the limit value for a shaft twisted only through a key, the fitting is devised so as to minimize the surface friction at the fitted portion. The results are compared to those reported previously by other authors in which local effects of the key are ignored. [ABSTRACT FROM AUTHOR]

Examines the evanescent-light guiding of atoms through hollow optical fiber for optically controlled atomic deposition. Spatial distribution of the guided atom flux; Details on the control of the deposition rate; Enhancement of the guided atom flux ratio.