Externalities, Tangible Externalities, and Queue Disciplines
定义了用户在服务过程中对他人施加的有形外部性，并计算了不同排队规则下预期外部性和有形外部性随服务时长的变化。
Externalities are the (marginal) costs that a user of a common resource imposes on others. We introduce the efficient measure of tangible externalities that are the costs that a user imposes on others while being served. Then, for a single server queueing system under various service disciplines, we compute the expected externalities and the expected tangible externalities conditioning on the length of the service requirement.