 567  528. Over a period of three years of experimental work on the two-phase flow of air and water, a considerable number of test sections have had to be constructed. These have always consisted of an acrylic resin tube with standardized end flanges and one or more of a variety of blocks and sleeves cemented to it. On all but a very few occasions great difficulty has been experienced in joining these items together. Whilst the Tensol No. 6 cement used has no ill effects on the flanges or blocks, its use has always been accompanied by cracking or severe surface crazing of the tube wall. 529. Germanium devices, when correctly used, are capable of essentially infinite life. It was commonly assumed in early higher temperature semiconductor work that silicon devices and those of materials, such as silicon carbide and III-V compounds would have similar life expectancy. That this is not realized in soft-soldered silicon devices is now well established. Evidence is presented to show that this limitation in life is due to fatigue rupture of the soft-soldered joints when they are subjected to cyclic thermal strees. A new hard-soldered structure is described which has been proved by long experience to eliminate fatigue failure completely. 530. Models indicate that with triphenyl phosphite in a pyramidal form the tetramethylammonium ion can be completely surrounded by the aryl groups, and the centre of positive charge of the ion lies within 3.5 A of the P-0 and C-O bonds. The extent to which this occurs with the consequent reduction in ion mobility will clearly depend, in part at least, on the degree to which the aryl groups of the particular solvent molecule have achieved a planar configuration, and this in turn muts affect the closeness of approach of the ions of the other solutes. 531. Early papers on this type of amplifier were optimistic that it would prove to be a device with very high efficiency. The present calculations show that the simple considerations on which this was based are not valid, but it is by no means certain that it will not be possible to find modes of operation which will give high efficiency. In particular the effects of space-charge forces and operation with the cyclotron frequency not equal to the signal frequency and the possibilities of various methods of maintaining synchronism have still to be explored. 532. To understand how collective motion can develop in the shell-model framework it is necessary to study configuration interaction. Therefore group-theoretical methods are used to investigate the possible classification schemes for a number of nucle-ons in mixed configurations. One particular coupling scheme which will be shown to have collective properties is described in detail. The wave functions in this scheme are seen to be very similar to those resulting from an actual shell-model calculation with configurational mixing. 567 |
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