Atmospheric radio ducts can trap VHF/UHF radio waves and propagate them over long distances. 284.4625 MHz Japanese radio wave signal measurements show that the radio waves are propagated to Korea coastal regions when ground temperatures exceed 10C. This paper discusses the reasons for the existence of this critical temperature threshold.

In this paper there suggested is a bifurcated (or multiple) input-queued ATM switch in which a buffer for each input port is divided into multiple (m) buffer blocks, i. e. , bifurcated buffers, for enhancement of the limited throughput of the ordinary input-queued switch using a single FIFO. As the contention/arbitration rule for the bifurcated input-queued switching scheme, free and restricted contention rules are come up with and discussed. The free rule allows an input port to switch up to m cells at the cost of internal speedup. With the restricted rule, on the other hand, an input port can switch no more than one cell in a time slot so that the switch operates at the same speed as the external link speed. The throughput bound for the bifurcated input-queued switch is analyzed for both rules through the generalization of the analysis by Karol et al. The throughput bound approaches to 1.0 as m becomes large enough, irrespective of the contention/arbitration rule.