Cn/ log n, 其中 C 与 n 无关. 另外, 本文给出集中不等式 P(|W n − E(W n)| t √ n/ log n) C 1 e −C2t .

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Abstract-This paper focuses on the problem of modeling the correspondence pattern for ordinary people. Suppose that letters arrive at a rate and answered at a rate . Furthermore, we assume that, for a constant T, and the remains are answered in last in first out order. Let be the waiting time of the n-th answered letter. It is proved that converges weekly to , a non-negative random variable which possesses a density with power-law tail when = and with exponential otherwise. Note that this may provide a reasonable explanation to the phenomenon reported by Oliveira and Barabási in [16].