The reason that polling is often used for the last stage of mail delivery is that, although the server mail delivery agent would normally be permanently connected to the network, it does not necessarily know how to locate the client mail user agent, which may only be connected occasionally and also change network address quite often.
For example, a user with a laptop on a Wi-Fi connection may be assigned different addresses from the network DHCP server periodically and have no persistent network name.
When new mail arrives to the mail server, it does not know what address the client is currently assigned.
Lana Reddlyn, 19 Lana and Kayla have been friends …Games with manipulative or computer simulations should help them in getting the idea of how a constant proportional rate of decay is consistent with declining measures that only gradually approach zero.The mathematics of inferring backwards from measurements to age is not appropriate for most students.They need only know that such calculations are possible. 79.) In this lesson, students will be asked to simulate radioactive decay by pouring small candies, such as plain M&M's® or Skittles®, from a cup and counting which candies fall with their manufacturer's mark down or up.The exercise they will go through of predicting and successively counting the number of remaining "mark-side up" candies should help them understand that rates of decay of unstable nuclei can be measured; that the exact time that a certain nucleus will decay cannot be predicted; and that it takes a very large number of nuclei to find the rate of decay.