The hierarchical hub location problem is encountered three-level network that is applied in production-distribution system, education system, emergency medical services, telecommunication network, etc. This paper addresses the hierarchical hub covering problem with single assignment accounting for mandatory dispersion of central hubs restriction as a special case. This formulation with incorpor...

in this paper, we study the network location problem for two congestible facilities, considering impatient customers. we suppose that when a customer arrives his/her corresponding facility and faces a queue with the size more than a predetermined threshold, the customer decides not to join the queue but to go to the closest facility to current facility. in the second facility, if the queue size...