Recently, empirical investigations have suggested that the components of contact forces follow the exponential distribution. However, explicit expressions for the probability distribution of the corresponding force magnitude have not been known and only approximations have been used in the literature. In this note, for the first time, I provide explicit expressions for the probability distribution of the force magnitude. Both two-dimensional and three-dimensional cases are considered.

We show that channel capacity of N-transmitter M-receiver antenna systems is approximately normal for both Raleigh fading and Ricean environments whether or not antennas are correlated. We give the distribution and percentiles of capacity as a power-series in (MN)^-1/2 when M or M/N is fixed, both for the case of fixed total power transmitted and also for the case, where total power transmitted increases with N.