A general discrete hub network model that accounts for fixed, capacity, and operating/congestion costs on links and at hubs, with both economies and diseconomies of scale, selects hubs and links, determines their capacities, and assigns O-D flows over paths, while minimizing all system costs. Initially formulated as a mixed-integer non-linear program, the model is transformed into a mixed-integ...

Surrogate Branching (SB) methods in mixed integer optimization provide a staged parametric relaxation of customary branching methods used in branch-and-bound and branch-and-cut algorithms. SB methods operate by forming surrogate constraints composed of non-negative linear combinations of component inequalities of three types: (1) ordinary branching inequalities, (2) redundant inequalities invol...