Ground clutter from irregular surfaces was measured using an L-band long range air-route surveillance radar (ARSR) at very low grazing angles, between 0.13 and 0.25. It is shown that the ground clutter amplitude statistics themselves do not always follow a Weibull distribution, but rather the residual amplitude after the double canceller moving target indicator (MTI) obeys a Weibull distribution. Therefore, the unsuppressed residual ground clutter will be suppressed by means of Weibull CFAR processors.

The wiretap channel is now a fundamental model for information-theoretic security. After introduced by Wyner, Csiszár and Körner have generalized this model by adding an auxiliary random variable. Recently, Han, Endo and Sasaki have derived the exponents to evaluate the performance of wiretap channels with cost constraints on input variable plus such an auxiliary random variable. Although the constraints on two variables were expected to provide larger-valued (or tighter) exponents, some non-trivial theoretical problems had been left open. In this paper, we investigate these open problems, especially concerning the concavity property of the exponents. Furthermore, we compare the exponents derived by Han et al. with the counterparts derived by Gallager to reveal that the former approach has a significantly wider applicability in contrast with the latter one.