A new detection method for the primary cosmic heavy nuclei by the plastic track detector CR-39

A new multiple scanning method is developed and applied to detect cosmic heavy nuclei. The plastic track detectors CR-39 exposed to cosmic heavy nuclei are over-etched in 8.0N NaOH for 94 h at 80°C. We found that the etched cones can easily be scanned on the plastic plates without using an optical microscope. The trajectories of heavy nuclei can be reconstructed with the naked eyes by superposing four or more over-etched plates. The charge detection threshold is obtained by this method, and appears to be 10. The charge resolution is estimated to be 1.0 charge units for iron nuclei. By adopting this method, the scanning time is much shortened and CR-39 plastic chamber size can easily be scaled up. The method is very useful for detecting particles with low flux intensity, like for searching magnetic monopoles or for measuring the high energy spectra of cosmic heavy nuclei.     

Swelling and mechanical properties of polyvinylalcohol hydrogels

Summary The swelling and mechanical properties of Poly(vinylalcohol) hydrogels were examined. It was found that the degree of swelling of PVA hydrogels depends on annealing temperature, but is almost independent of the initial polymer concentration. Mechanical properties of the hydrogels were also influenced by the degree of swelling. A shoulder was observed in double-logarithmic plots of stress vs. strain for the hydrogels, and became clearer as annealing temperature increased. This shoulder was closely related to the breakdown of the microcrystalline domains acting as crosslinks. Also, the shape of stress-strain curves plotted double-logarithmically for the hydrogels changed with the extension rate.     

CMP process run-to-run control to adjust margin in control limit

This paper describes a run-to-run control method based on within-wafer distribution of film-thickness and removal rate. The main feature of this method incorporates adjusting the lower and upper margin of the film-thickness after CMP. The margins represent the differences of the minimum and maximum film-thickness values from the lower and upper control limits, respectively. In order to realize this concept, (1) the removal-rate within-wafer distribution is modeled as a polygonal line profile using the results of blanket-wafer polishing, (2) the removal rate at measurement sites of the product wafer is derived from the profile to adjust for differences between product types, (3) the profile is updated with the results of product wafer polishing in the work sequence, and (4) polishing time is calculated so that it satisfies the condition wherein the margin on the upper side equals the margin on the lower side within control limits to prevent film-thickness failure due to run-to-run variations. A capability index based on the margins is suggested and actual production results are shown using this index, which indicates a 71.6% improvement in accuracy and precision.     

A plasticating model for single-screw extruders

By measuring the solid-bed transfer velocity, width and thickness under various conditions, die following results are obtained. As the result of melting, the solid bed decreases in width and thickness almost with the same rate, and the solid-bed transfer velocity is constant, while a melt layer exists between the solid bed and the screw root; also, when the phenomenon of dam-up occurs, caused by the combined effect of decreasing depth of the screw channel with tin insufficient decrease of solid-bed thickness, the transfer velocity increases proportional to the rate of decrease of channel depth. Consequently, the solid bed is considered to behave us loosely packed particles. A new plasticating model is developed by making the above results an assumption and adopting finite differential calculus with the Newton-Raphson method to obtain accurately the melting velocity, melt profile, and solid-bed temperature. Calculated values are in remarkably good agreement with the experimental values Solid-bed softening point, pressure, and screw torque are also successfully estimated.